,illustration3 ,,fig4 #a4--;,construction of ,peck's ,run ,sewer1 ,baltimore1 ,maryland4 ,frontispiece4 ,,sewerage ,,and ,,sewage ,,treatment ,,by ,,harold ,e4 ,,babbitt1 ,m4,s4 ,assistant ,professor1 ,municipal and ,sanitary ,engineering1 ,university of ,illinois2 ,associate ,member ,american ,society of ,civil ,engineers ,,new ,,york ,,john ,,wiley ,,sons1 ,,inc4 ,,london3 ,,chapman ,,hall1 ,,limited #aibb ,copyright1 #aibb1 by ,,harold ,e4 ,,babbitt1 ,m4,s4 ,,press ,,of ,,braunworth ,,co4 ,,book ,,manufacturers ,,brooklyn1 ,n4 ,y4 ---------------------------------------- -------------------------------- ,,preface ,this book is a development of class-room and lecture notes prepared by the author for use in his classes at the ,university of ,illinois4 ,he has found such notes necessary1 since among the many books dealing with sewerage and sewage treatment he has found none suitable as a text-book designed to cover the entire subject4 ,the need for a single book of the character described has been expressed by engineers in practice1 and by students and teachers for use in the class-room4 ,this book has been prepared to meet both these needs4 ,it is hoped that the searching questions propounded by students in using the original notes1 and the suggestions and criticisms of engineers and teachers who have read the manuscript1 have resulted in a text which can be readily understood4 ,the ground covered includes an exposition of the principles and methods for the designing1 construction and maintenance of sewerage works1 and also of the treatment of sewage4 ,in covering so wide a field the author has deemed it necessary to include some chapters which might equally well appear in works on other branches of engineering1 such as the chapter on ,pumps and ,pumping ,stations4 ,special stress has been laid on the fundamentals of the subject rather than the details of practice1 although illustrations have been drawn freely from practical work4 ,the quotation of expert opinions which may be in controversy1 or the citation of examples of different methods of accomplishing the same thing1 has been avoided when possible in order to simplify explanations and to avoid confusing the beginner4 ,the work is to some extent a compilation of notes and quotations which have been collected by the author during years of study and teaching the subject4 ,credit has been given wherever due1 and at the same time references have pointed out the original sources whenever possible4 ,these references1 which have been supplemented by brief bibliographies at the end of certain chapters1 will be useful to the student and engineer interested in further study4 ,occasionally the original reference has been lost or the phraseology of a quotation has been so altered by class-room use1 as to make it impossible to trace the original source1 so that in some few instances full credit may be lacking4 ,the author is indebted to many of his friends for their criticisms and suggestions in the preparation of the manuscript2 but he desires particularly to acknowledge the assistance of ,professor ,a4 ,n4 ,talbot1 ,professor of ,municipal and ,sanitary ,engineering at the ,university of ,illinois1 and of ,professor ,m4 ,l4 ,enger1 ,professor of ,mechanics and ,hydraulics at the ,university of ,illinois1 in the entire work2 also that of ,mr4 ,t4 ,d4 ,pitts1 ,principal ,assistant ,engineer of the ,baltimore ,sewerage ,commission during the construction of the ,baltimore sewers1 for his suggestions on the first half of the book2 and to ,mr4 ,paul ,hansen1 consulting engineer1 of ,chicago1 and to ,mr4 ,langdon ,pearse1 ,sanitary ,engineer of the ,sanitary ,district of ,chicago1 for their help on the section covering the treatment of sewage2 and to ,professor ,edward ,bartow1 ,professor of ,chemistry at the ,university of ,iowa1 for his review of the chapter on ,activated ,sludge2 in general his thanks are due to all others who have furnished suggestions1 illustrations1 or quotations1 acknowledgments of which have been included in the text4 ,h4 ,e4 ,b4 ,,urbana1 ,,illinois1 #aibb4 ,,table ,,of ,,contents ,,chapter ,i ,,introduction ,,pages #a4 ,sewerage and the ,sanitary ,engineer4 #b4 ,historical4 #c4 ,methods of ,collection4 #d4 ,methods of ,disposal4 #e4 ,methods of ,treatment4 #f4 ,definitions4 #a-h ,,chapter ,,ii ,,work ,,preliminary ,,to ,,design #g4 ,division of ,work4 #h4 ,preliminary4 #i4 ,estimate of cost4 ,,methods ,,of ,,financing4 #aj4 ,bond ,issues4 #aa4 ,special ,assessment4 #ab4 ,general ,taxation4 #ac4 ,private ,capital4 ,,preliminary ,,work4 #ad4 ,preparing for ,design4 #ae4 ,underground ,surveys4 #af4 ,borings4 #i-bc ,,chapter ,,iii ,,quantity ,,of ,,sewage #ag4 ,dry ,weather ,flow4 #ah4 ,methods for ,predicting ,population4 #ai4 ,extent of ,prediction4 #bj4 ,sources of ,information on ,population4 #ba4 ,density of ,population4 #bb4 ,changes in ,area4 #bc4 ,relation between ,population and ,sewage ,flow4 #bd4 ,character of ,district4 #be4 ,fluctuations in ,rate of ,sewage ,flow4 #bf4 ,effect of ,ground ,water4 #bg4 ,rsum of ,method for ,determination of ,quantity of ,dry weather ,sewage4 ,,quantity ,,of ,,storm ,,water4 #bh4 ,the ,rational ,method4 #bi4 ,rate of ,rainfall4 #cj4 ,time of ,concentration4 #ca4 ,character of ,surface4 #cb4 ,empirical ,formulas4 #cc4 ,extent and ,intensity of ,storms4 #bd-ej ,,chapter ,,iv ,,hydraulics ,,of ,,sewers #cd4 ,principles4 #ce4 ,formulas4 #cf4 ,solution of ,formulas4 #cg4 ,use of ,diagrams4 #ch4 ,flow in ,circular ,pipes ,partly ,full4 #ci4 ,sections ,other than ,circular4 #dj4 ,non-,uniform ,flow4 #ea-gg ,,chapter ,v ,,design ,,of ,,sewerage ,,systems #da4 ,the ,plan4 #db4 ,preliminary ,map4 #dc4 ,layout of the ,separate ,system4 #dd4 ,location and ,numbering of ,manholes4 #de4 ,drainage ,areas4 #df4 ,quantity of ,sewage4 #dg4 ,surface ,profile4 #dh4 ,slope and ,diameter of ,sewers4 #di4 ,the ,sewer ,profile4 ,,design ,,of ,a ,,storm-,,water ,,sewer ,,system4 #ej4 ,planning the ,system4 #ea4 ,location of ,street ,inlets4 #eb4 ,drainage ,areas4 #ec4 ,computation of ,flood ,flow by ,mc,math ,formula4 #ed4 ,computation of ,flood ,flow by ,rational ,method4 #gh-ih ,,chapter ,,vi ,,appurtenances #ee4 ,general4 #ef4 ,manholes4 #eg4 ,lampholes4 #eh4 ,street ,inlets4 #ei4 ,catch-basins4 #fj4 ,grease ,traps4 #fa4 ,flush-tanks4 #fb4 ,siphons4 #fc4 ,regulators4 #fd4 ,junctions4 #fe4 ,outlets4 #ff4 ,foundations4 #fg4 ,underdrains4 #ii-abf ,,chapter ,,vii ,,pumps ,,and ,,pumping ,,stations #fh4 ,need4 #fi4 ,reliability4 #gj4 ,equipment4 #ga4 ,the ,building4 #gb4 ,capacity of ,pumps4 #gc4 ,capacity of ,receiving ,well4 #gd4 ,types of ,pumping ,machinery4 #ge4 ,sizes and ,descriptions of ,pumps4 #gf4 ,definitions of ,duties and ,efficiency4 #gg4 ,details of ,centrifugal ,pumps4 #gh4 ,centrifugal ,pump ,characteristics4 #gi4 ,setting of ,centrifugal ,pumps4 #hj4 ,steam ,pumps and ,pumping ,engines4 #ha4 ,steam ,turbines4 #hb4 ,steam ,boilers4 #hc4 ,air ,ejectors4 #hd4 ,electric ,motors4 #he4 ,internal ,combustion ,engines4 #hf4 ,selection of ,pumping ,machinery4 #hg4 ,costs of ,pumping ,machinery4 #hh4 ,cost ,comparisons of ,different ,designs4 #hi4 ,number and ,capacity of ,pumping ,units4 #abg-afc ,,chapter ,,viii ,,materials ,,for ,,sewers #ij4 ,materials4 #ia4 ,vitrified ,clay ,pipe4 #ib4 ,cement and ,concrete ,pipe4 #ic4 ,proportioning of ,concrete4 #id4 ,waterproofing of ,concrete4 #ie4 ,mixing and ,placing ,concrete4 #if4 ,sewer ,brick4 #ig4 ,vitrified ,clay ,sewer ,block4 #ih4 ,cast ,iron1 ,steel1 and ,wood4 #afd-aic ,,chapter ,,ix ,,design ,,of ,,the ,,sewer ,,ring #ii4 ,stresses in ,buried ,pipe4 #ajj4 ,design of ,steel ,pipe4 #aja4 ,design of ,wood ,stave ,pipe4 #ajb4 ,external ,loads on ,buried ,pipe4 #ajc4 ,stresses in ,circular ,ring4 #ajd4 ,analysis of ,sewer ,arches4 #aje4 ,reinforced ,concrete ,sewer ,design4 #aid-baj ,,chapter ,x ,,contracts ,,and ,,specifications #ajf4 ,importance of the ,subject4 #ajg4 ,scope of the ,subject4 #ajh4 ,types of ,contracts4 #aji4 ,the ,agreement4 #aaj4 ,the ,advertisement4 #aaa4 ,information and ,instructions for ,bidders4 #aab4 ,proposal4 #aac4 ,general ,specifications4 #aad4 ,technical ,specifications4 #aae4 ,special ,specifications4 #aaf4 ,the ,contract4 #aag4 ,the ,bond4 #baa-bcb ,,chapter ,,xi ,,construction #aah4 ,elements4 ,,work ,,of ,,the ,,engineer4 #aai4 ,duties4 #abj4 ,inspection4 #aba4 ,interpretation of ,contract4 #abb4 ,unexpected ,situations4 #abc4 ,cost ,data and ,estimates4 #abd4 ,progress ,reports4 #abe4 ,records4 ,,excavation4 #abf4 ,specifications4 #abg4 ,hand ,excavation4 #abh4 ,machine ,excavation4 #abi4 ,types of ,machines4 #acj4 ,continuous ,bucket ,excavators4 #aca4 ,cableway and ,trestle ,excavators4 #acb4 ,tower ,cableways4 #acc4 ,steam ,shovels4 #acd4 ,drag ,line and ,bucket ,excavators4 #ace4 ,excavation in ,quicksand4 #acf4 ,pumping and ,drainage4 #acg4 ,trench ,pump4 #ach4 ,diaphragm ,pump4 #aci4 ,jet ,pump4 #adj4 ,steam ,vacuum ,pumps4 #ada4 ,centrifugal and ,reciprocating ,pumps4 #adb4 ,well ,points4 #adc4 ,rock ,excavation4 #add4 ,power ,drilling4 #ade4 ,steam or ,air for ,power4 #adf4 ,depth of ,drill ,hole4 #adg4 ,diameter of ,drill ,hole4 #adh4 ,spacing of ,drill ,holes4 ,,sheeting ,,and ,,bracing4 #adi4 ,purposes and ,types4 #aej4 ,stay ,bracing4 #aea4 ,skeleton ,sheeting4 #aeb4 ,poling ,boards4 #aec4 ,box ,sheeting4 #aed4 ,vertical ,sheeting4 #aee4 ,pulling ,wood ,sheeting4 #aef4 ,earth ,pressures4 #aeg4 ,design of ,sheeting and ,bracing4 #aeh4 ,steel ,sheet ,piling4 ,,line ,,and ,,grade4 #aei4 ,locating the ,trench4 #afj4 ,final ,line and ,grade4 #afa4 ,transferring ,grade and ,line to the ,pipe4 #afb4 ,line and ,grade in ,tunnel4 ,,tunnelling4 #afc4 ,depth4 #afd4 ,shafts4 #afe4 ,timbering4 #aff4 ,shields4 #afg4 ,tunnel ,machines4 #afh4 ,rock ,tunnels4 #afi4 ,ventilation4 #agj4 ,compressed ,air4 ,,explosives ,,and ,,blasting4 #aga4 ,requirements4 #agb4 ,types of ,explosives4 #agc4 ,permissible ,explosives4 #agd4 ,strength4 #age4 ,fuses and ,detonators4 #agf4 ,care in ,handling4 #agg4 ,priming1 ,loading1 and ,firing4 #agh4 ,quantity of ,explosive4 ,,pipe ,,sewers4 #agi4 ,the ,trench ,bottom4 #ahj4 ,laying ,pipe4 #aha4 ,joints4 #ahb4 ,labor and ,progress4 ,,brick ,,and ,,block ,,sewers4 #ahc4 ,the ,invert4 #ahd4 ,the ,arch4 #ahe4 ,block ,sewers4 #ahf4 ,organization4 #ahg4 ,rate of ,progress4 ,,concrete ,,sewers4 #ahh4 ,construction in ,open ,cut4 #ahi4 ,construction in ,tunnels4 #aij4 ,materials for ,forms4 #aia4 ,design of ,forms4 #aib4 ,wooden ,forms4 #aic4 ,steel-lined ,wooden ,forms4 #aid4 ,steel ,forms4 #aie4 ,reinforcement4 #aif4 ,cost of ,concrete ,sewers4 ,,backfilling4 #aig4 ,method4 #bcc-cca ,,chapter ,,xii ,,maintenance ,,of ,,sewers #aih4 ,work ,involved4 #aii4 ,causes of ,troubles4 #bjj4 ,inspection4 #bja4 ,repairs4 #bjb4 ,cleaning of ,sewers4 #bjc4 ,flushing ,sewers4 #bjd4 ,cleaning ,catch-basins4 #bje4 ,protection of ,sewers4 #bjf4 ,explosions in ,sewers4 #bjg4 ,valuation of ,sewers4 #ccb-cea ,,chapter ,,xiii ,,composition ,,and ,,properties ,,of ,,sewage #bjh4 ,physical ,characteristics4 #bji4 ,chemical ,composition4 #baj4 ,significance of ,chemical ,constituents4 #baa4 ,sewage ,bacteria4 #bab4 ,organic ,life in ,sewage4 #bac4 ,decomposition of ,sewage4 #bad4 ,the ,nitrogen ,cycle4 #bae4 ,plankton and ,macroscopic ,organisms4 #baf4 ,variations in the ,quality of ,sewage4 #bag4 ,sewage ,disposal4 #bah4 ,methods of ,sewage ,treatment4 #ceb-cga ,,chapter ,,xiv ,,disposal ,,by ,,dilution #bai4 ,definition4 #bbj4 ,conditions ,required for ,success4 #bba4 ,self-purification of ,running ,streams4 #bbb4 ,self-purification of ,lakes4 #bbc4 ,dilution in ,salt ,water4 #bbd4 ,quantity of ,diluting ,water ,needed4 #bbe4 ,governmental ,control4 #bbf4 ,preliminary ,treatment4 #bbg4 ,preliminary ,investigations4 #cgb-chb ,,chapter ,,xv ,,screening ,,and ,,sedimentation #bbh4 ,purpose4 #bbi4 ,types of ,screens4 #bcj4 ,sizes of ,openings4 #bca4 ,design of ,fixed and ,movable ,screens4 ,,plain ,,sedimentation4 #bcb4 ,theory of ,sedimentation4 #bcc4 ,types of ,sedimentation ,basins4 #bcd4 ,limiting ,velocities4 #bce4 ,quantity and ,character of ,grit4 #bcf4 ,dimensions of ,grit ,chambers4 #bcg4 ,existing ,grit ,chambers4 #bch4 ,number of ,grit ,chambers4 #bci4 ,quantity and ,characteristics of ,sludge from ,plain ,sedimentation4 #bdj4 ,dimensions of ,sedimentation ,basins4 ,,chemical ,,precipitation4 #bda4 ,the ,process4 #bdb4 ,chemicals4 #bdc4 ,preparation and ,addition of ,chemicals4 #bdd4 ,results4 #chc-dji ,,chapter ,,xvi ,,septicization #bde4 ,the ,process4 #bdf4 ,the ,septic ,tank4 #bdg4 ,results of ,septic ,action4 #bdh4 ,design of ,septic ,tanks4 #bdi4 ,imhoff ,tanks4 #bej4 ,design of ,imhoff ,tanks4 #bea4 ,imhoff ,tank ,results4 #beb4 ,status of ,imhoff ,tanks4 #bec4 ,operation of ,imhoff ,tanks4 #bed4 ,other ,tanks4 #daj-dcj ,,chapter ,,xvii ,,filtration ,,and ,,irrigation #bee4 ,theory4 #bef4 ,the ,contact ,bed4 #beg4 ,the ,trickling ,filter4 #beh4 ,intermittent ,sand ,filter4 #bei4 ,cost of ,filtration4 ,,irrigation4 #bfj4 ,the ,process4 #bfa4 ,status4 #bfb4 ,preparation and ,operation4 #bfc4 ,sanitary ,aspects4 #bfd4 ,the ,crop4 #dca-dfd ,,chapter ,,xviii ,,activated ,,sludge #bfe4 ,the ,process4 #bff4 ,composition4 #bfg4 ,advantages and ,disadvantages4 #bfh4 ,historical4 #bfi4 ,aration ,tank4 #bgj4 ,sedimentation ,tank4 #bga4 ,rearation ,tank4 #bgb4 ,air ,distribution4 #bgc4 ,obtaining ,activated ,sludge4 #bgd4 ,cost4 #dfe-dgi ,,chapter ,,xix ,,acid ,,precipitation1 ,,lime ,,and ,,electricity1 ,,and ,,disinfection #bge4 ,the ,miles ,acid ,process4 ,,electrolytic ,,treatment4 #bgf4 ,the ,process4 ,,disinfection4 #bgg4 ,disinfection of ,sewage4 #dhb-dic ,,chapter ,,xx ,,sludge #bgh4 ,methods of ,disposal4 #bgi4 ,lagooning4 #bhj4 ,dilution4 #bha4 ,burial4 #bhb4 ,drying4 #die-eje ,,chapter ,,xxi ,,automatic ,,dosing ,,devices #bhc4 ,types4 #bhd4 ,operation4 #bhe4 ,three ,alternating ,siphons4 #bhf4 ,four or ,more ,alternating ,siphons4 #bhg4 ,timed ,siphons4 #bhh4 ,multiple ,alternating and ,timed ,siphons4 #ejf-eab ,,sewerage ,,and ,,sewage ,,treatment ,,chapter ,i ,,introduction #a4 ,sewerage and the ,sanitary ,engineer4--,present day conceptions of sanitation are based on the scientific discoveries which have resulted so much in the increased comfort and safety of human life during the past century1 in the increase of our material possessions1 and the extent of our knowledge4 ,the danger to health in the accumulation of filth1 the spreading of disease by various agents1 the germ theory of disease1 and other important principles of sanitation can be counted among the more recent scientific discoveries and pronouncements4 ,experience has shown1 and continues to show1 that the increase of population may be inhibited by accumulations of human waste in populous districts4 ,the removal of these wastes is therefore essential to the existence of our modern cities4 ,the greatest need of a modern city is its water supply4 ,without it city life would be impossible4 ,the next most important need is the removal of waste matters1 particularly wastes containing human excreta or the germs of disease4 ,to exist without street lights1 pavements1 street cars1 telephones1 and the many other attributes of modern city life might be possible1 although uncomfortable4 ,to exist in a large city without either water or sewerage would be impossible4 ,the service rendered by the sanitary engineer to the large municipality is indispensable4 ,in addition to the service necessary to the maintenance of life in large cities1 the sanitary engineer serves the smaller city1 the rural community1 the isolated institution1 and the private estate with sanitary conveniences which make possible comfortable existence in them1 and which are frequently considered as of paramount necessity4 ,training for service in municipal sanitation is training for a service which has a more direct beneficial effect on humanity than any other engineering work1 or any other profession4 ,w4 ,p4 ,gerhard states3 ,a ,sanitary ,engineer is an engineer who carries out those works of civil engineering which have for their object3 7a7 ,the promotion of the public and individual health2 7b7 ,the remedying of insanitary conditions2 7c7 ,the prevention of epidemic diseases4 ,a well-educated sanitary engineer should have a thorough knowledge of general civil engineering1 of architecture1 and of sanitary science4 ,the practice of the sanitary engineer embraces water supply1 sewerage1 and sewage and garbage disposal for cities and for single buildings2 the prevention of river pollution1 the improvement of polluted water supplies2 street paving and street cleaning1 municipal sanitation1 city improvement plans1 the laying out of cities1 the preparation of sanitary surveys1 the regulation of noxious trades1 disinfection1 cremation1 and the sanitation of buildings4 ,the need of the work of the sanitary engineer in the provision of sewers and drains is thrust upon us in our daily experience by the clogging of sewers1 the flooding of streets by heavy rains1 filthy conditions in unsewered districts1 increased values of property and improved conditions of living in sewered districts1 and in many other ways4 ,the increasing demand for sewerage and the amount of money expended on sewer construction is indicated by the information given in ,table ,i4 #b4 ,historical4--,an ordinance passed by the ,roman ,senate in the name of the ,emperor about ,a4,d4 #hj1 states3 ,i desire that nobody shall conduct away any excess water without having received my permission or that of my representatives2 for it is necessary that a part of the supply flowing from the delivery tanks shall be utilized not only for cleaning our city1 but also for flushing the sewers4#a ,neither the sewers mentioned nor the distributing pipes of the public water supply were connected to individual residences4 ,the contributions to the sewers came from the ground and the street surface4 ,the streets were the receptacles of liquid and solid wastes and were often little more than open sewers4 ,a promenade after dark in an ancient1 medieval1 or early modern city was accompanied not only by the underfoot dangers of an uneven pavement or an encounter with a footpad1 but with the overhead danger from the emptying of slops into the streets from the upper windows4 ,sewers were used for the collection of surface water2 the discharge of fecal matter into them was prohibited4 ,the problem of the collection of sewage remained unsolved until the ,nineteenth ,century4 ,,table #a ,,population ,,tributary ,,to ,,sewerage ,,systems #aijeb #aiaec #aibjd ,population discharging raw sewage into the sea or tidal estuaries #f1ejj1jjj #h1ejj1jjj ,population discharging raw sewage into inland streams or lakes #bj1djj1jjjbf1djj1jjj ,population connected to systems where sewage is treated in some way #a1ajj1jjj #f1ijj1jjj ,population connected with sewerage systems #bh1jjj1jjjda1hjj1jjjdf1cjj1jjj ,the development of the ,london sewers was commenced early in the ,nineteenth ,century4 ,the sewerage system of ,hamburg1 ,germany1 was laid out in #ahdb by ,lindley1 an ,english engineer who with other ,english engineers performed similar work in other ,german cities because of their earlier experience in ,english communities4 ,berlin's present system dates from #ahfj4 ,the construction of storm-water drains in ,paris dates from #affc4e ,they were intended only as street drains but are now included in the comprehensive system of the city4 ,the first comprehensive sewerage system in the ,united ,states was designed by ,e4 ,s4 ,chesbrough for the ,city of ,chicago in #ahee4 ,previous to this time sewers had been installed in an indifferent manner and without definite plan4 ,the installation of a comprehensive sewerage system in ,baltimore in #aiae marks the completion of installation of sewerage systems in all large ,american cities4 ,in the early days of sewerage design it was considered unsafe to discharge domestic wastes into the sewers as the concentration of so much sewage was expected to create great nuisances and dangers to health4 ,that the fear that the concentration of large quantities of sewage would create a nuisance was not ill founded is proven by the conditions on the ,thames at ,london in #aheh-ei4 ,dr4 ,budd states3#f ,for the first time in the history of man1 the sewage of nearly three millions of people had been brought to seethe and ferment under a burning sun in one vast open cloaca lying in their midst4 ,the result we all know4 ,stench so foul we may well believe had never before ascended to pollute this lower air4 ,never before at least had a stink risen to the height of an historic event4444 ,for months together the topic almost monopolized the public prints4444 #8,india is in revolt and the ,thames stinks' were the two great facts coupled together by a distinguished foreign writer1 to mark the climax of a national humiliation4#g ,the problem of sewage disposal followed the more or less successful solutions of the problem of sewage collection4 ,in ,england the ,british ,royal ,commission on ,sewage ,disposal was appointed in #aheg and issued its first report in #ahfe4 ,the first studies in the ,united ,states were started in #ahhg by the establishment of an experiment station at ,lawrence1 ,massachusetts1 where valuable work has been done4 ,the station is under the ,state ,board of ,health1 which issued its first report containing the results of the work at the station1 in #ahij4 ,various methods of sewage treatment preparatory to disposal have been devised from time to time4 ,some have fallen into disuse1 such as the ,a4 ,b4 ,c4 7alum1 blood and clay7 process1 and others have taken a permanent place1 such as the septic tank4 ,the unsolved problems of sewage collection1 and the number of persons still unserved by sewerage and sewage disposal opens a wide field to the study and construction of sewerage works4 #c4 ,methods of ,collection4--,the method of collection which involves the removal of night soil from a privy vault1 the pail system which involves the collection of buckets of human excreta from closets and homes1 indoor chemical closets1 and other makeshift methods of collection are of extreme importance where no sewers exist1 but they are not properly considered as sewerage systems or sewerage works4 ,these methods of collection are generally confined to rural districts and to outlying parts of urban communities4 ,they require constant attention for their proper conduct and little skill for their installation1 the principal requirements being to make the receptacles fly-proof4 ,the pneumatic system was introduced by ,liernur1 a ,dutch engineer4#h ,it is used in parts of a few cities in ,europe1 but it is not capable of use on a large scale4 ,it consists of a system of air-tight pipes1 connecting water closets1 kitchen sinks1 etc41 with a central pumping station at which an air-tight tank is provided from which the air is partly exhausted4 ,as little water as possible is allowed to mix with the fecal matter and other wastes in order not to overtax the system4 ,solid and liquid wastes are drawn to the central station when the waste valve on the plumbing fixture is opened4 ,the collection of sewage in a system of pipes through which it is conducted by the buoyant effect and scouring velocity of water is known as the water-carriage system4 ,this is the only method of sewage collection in general use in urban communities4 ,in this system solid and liquid wastes are so highly diluted with water as either to float or to be suspended therein4 ,the mixture resulting from this high dilution follows the laws of hydraulics as applied to pure water1 or water containing suspended matter4 ,it will flow freely through properly designed conduits and will concentrate the sewage wastes at the point of ultimate disposal4 #d4 ,methods of ,disposal4--,sewage is disposed of by dilution in water1 by treatment on land1 or occasionally by discharging it into channels that contain no diluting water4 ,some form of treatment to prepare sewage for ultimate disposal is frequently necessary and will undoubtedly be required in a comparatively short time for all sewage discharged into watercourses4 ,the solid matters removed by treatment may be buried1 burned1 dumped into water1 or used as a fertilizer4 ,if the volume of diluting water1 or the area and character of land used for disposal are not as they should be1 a nuisance will be created4 ,the aim of all methods of sewage treatment has so far been to produce an effluent which could be disposed of without nuisance and in certain exceptional cases to protect public water supplies from pollution4 ,financial returns have been sought only as a secondary consideration4 ,a few sewage farms and irrigation projects might be considered as exceptions to this as the value of the water in the sewage as an irrigant has been the primary incentive to the promotion of the farm4 ,it is to be remembered that since the aim of all sewage treatment is to produce an effluent that can be disposed of without causing a nuisance1 the simplest process by which this result can be attained under the conditions presented is the process to be adopted4 ,no attempt is made to purify sewage completely1 or on a practical scale to make drinking water4 #e4 ,methods of ,treatment4--,screening and sedimentation are the primary methods for the treatment of sewage4 ,by these methods a portion of the floating and settleable solids are removed1 preventing the formation of unsightly scum and putrefying sludge banks4 ,chemicals are sometimes added to the sewage to form a heavy flocculent precipitate which hastens sedimentation of the solid matters in the sewage4 ,the process in these methods is mechanical and the solid matters removed from the sewage must be disposed of by other methods than dilution with the sewage effluent4 ,more complete methods of treatment are dependent on biologic action4 ,under these methods of treatment complete stabilization of the effluent is approached1 and in the most complete treatment an effluent is produced which is clear1 sparkling1 non-odorous1 non-putrescible1 and sterile4 ,sterilization of sewage1 usually with chlorine or some of its compounds1 has been used1 not to reduce the amount of diluting water necessary1 but to reduce the number of pathogenic germs and to minimize the danger of the transmission of disease4 #f4 ,definitions4--,sewage and sewerage are not synonymous terms although frequently confused4 ,sewage is the spent water supply of a community containing the waste from domestic1 industrial or commercial use1 and such surface and ground water as may enter the sewer4#i ,sewerage is the name of the system of conduits and appurtenances designed to carry off the sewage4 ,it is also used to indicate anything pertaining to sewers4 ,a difference is made between sanitary sewage1 storm sewage1 and industrial wastes4 ,sanitary sewage1 sometimes called domestic sewage1 is the liquid wastes discharged from residences or institutions1 and contains water closet1 laundry and kitchen wastes4 ,storm sewage is the surface run-off which reaches the sewers during and immediately after a storm4 ,industrial wastes are the liquid waste products discharged from industrial plants4 ,a sewer is a conduit used for conveying sewage4 ,the names of the conduits through which sewage may flow are3 ,soil ,stack4--,a vertical pipe in a building through which waste water containing fecal matter or urine is allowed to flow4 ,waste ,pipe4--,a vertical pipe in a building through which waste water containing no fecal matter is allowed to flow4 ,house ,drain4--,the approximately horizontal portion of a house drainage system which conveys the drainage from the soil stack or waste pipe to the point of discharge from the building4 ,house ,sewer4--,the pipe which leads from the outside wall of the building to the sewer in the street4 ,lateral ,sewer4--,the smallest branch in a sewerage system1 exclusive of the house sewers4 ,sub-main or ,branch ,sewer4--,a sewer from which the sewage from two or more laterals is discharged4#aj ,main or ,trunk ,sewer4--,a sewer into which the sewage from two or more sub-main or branch sewers is discharged4#aa ,intercepting ,sewer4--,a sewer generally laid transversely to a sewerage system to intercept some portion or all of the sewage collected by the system4 ,relief ,sewer4--,a sewer intended to carry a portion of the flow from a district already provided with sewers of insufficient capacity and thus preventing overtaxing the latter4#ab ,outfall ,sewer4--,that portion of a main or trunk sewer below all branches4 ,flushing ,sewer4--,a conduit through which water is conveyed for flushing portions of a sewerage system4 ,force ,main4--,a conduit through which sewage is pumped under pressure4 ,,chapter ,,ii ,,work ,,preliminary ,,to ,,design #g4 ,division of ,work4--,engineering work on sewerage can be divided into four parts1 namely3 preliminary1 design1 construction and maintenance4 ,an engineer may be engaged during any one or all of these periods on the same sewerage system1 and should therefore be acquainted with his duties during each period4 #h4 ,preliminary4--,the demand for sewerage normally follows the installation or extension of the public water supply4 ,it may be caused by3 a lack of drainage on some otherwise desirable tract of real estate2 from a public realization of unpleasant or unhealthful conditions in a built-up district2 or through the realization by the municipal administration of the necessity for caring for the future4 ,in whatever way the demand may be created the engineer should take an active part in the promotion of the work4 ,the engineer's duties during the preliminary period are3 to make a study of the possible methods by which the demand for sewerage can be satisfied2 to present the results of this study in the form of a report to the committee or organization responsible for the promotion of the work2 and so to familiarize himself with the conditions affecting the installation of the proposed plans as to be able to answer all inquiries concerning them4 ,this work will require the general qualities of character1 judgment1 efficiency and the understanding of men in addressing interested persons individually and collectively on the features of the proposed plans1 and the exercise of engineering technique in the survey and the drawing of the plans4 ,the engineer should assure himself that all legal requirements in the drawing of petitions1 advertising1 permits1 etc41 have been complied with4 ,this requires some knowledge of national1 state1 and local laws4 ,although none the less essential their description is not within the scope of this book4 ,the engineer's preliminary report should contain a section devoted to the feasibility of one or more plans which may be explained in more or less detail with a statement of the cost and advantages of each4 ,a conclusion should be reached as to the most desirable plan and a recommendation made that this plan be installed4 ,other sections of the report may be devoted to a history of the growing demand1 a description of the conditions necessitating sewerage1 possible methods of financing1 and such other subjects as may be pertinent4 ,the making of the preliminary plan and the design of sewerage works are described in subsequent chapters4 #i4 ,estimate of ,cost4--,in making an estimate of cost the information should be presented in a readable and easily comprehended manner4 ,it is necessary that the items be clearly defined and that all items be included4 ,the method of determining the costs of doubtful items such as depreciation1 interest charges1 labor1 etc41 and the probability of the fluctuation of the costs of certain items should be explained4 ,the engineer's estimate may be divided somewhat as follows3 ,labor4 ,material4 ,overhead4 ,this may include construction plant1 office expense1 supervision1 bond1 interest on borrowed capital1 insurance1 transportation1 etc4 ,the amount of the item is seldom less than #ae per cent and is usually over #bj per cent of the contract price4 ,contingencies4 ,this allowance is usually #aj to #ae per cent of the contract price4 ,profit4 ,this should be from #e to #aj per cent of the sum of the four preceding items4 ,the contract price is the sum of these items4 ,to this may be added3 ,engineering4 #b to #e per cent of the contract price4 ,extra ,work4 ,zero to #ae per cent of the contract price2 dependent on the character of the work1 the completeness of the preliminary information1 the completeness of the plans1 etc4 ,legal expense4 ,purchase of land1 rights of way1 etc41 etc4 ,the cost of the sewer may be stated as so much per linear foot for different sizes of pipe1 including all appurtenances such as manholes1 catch-basins1 etc41 or the items may be separated in great detail somewhat as follows3 ,earth excavation1 per cu4 yd4 ,rock excavation1 per cu4 yd4 ,backfill1 per cu4 yd4 ,brick manholes1 #c feet by #d feet1 per foot of depth4 ,vitrified sewer pipe with cement joints1 in place1 444 inches in diameter1 #j to #f feet deep #f to #h feet deep #h to #aj feet deep ,repaving1 macadam per sq4 yd4 asphalt per sq4 yd4 ,flush-tanks1 444 gal4 capacity1 per tank4 ,service pipes to flush-tanks1 per linear foot41 etc41 etc4 ,these methods represent the two extremes of presenting cost estimates4 ,each method1 or modification thereof1 may have its use1 dependent on circumstances4 ,reliable cost data are difficult to obtain4 ,lists of prices of materials and labor are published in certain engineering and trade periodicals4 ,the ,handbook of ,cost ,data by ,h4 ,p4 ,gillette contains lists of the amount of material and labor used on certain specific jobs and types of construction4 ,the price of labor and materials on the local market can be obtained from the local ,chamber of ,commerce1 contractors and other employers of labor1 and dealers in the desired commodities4 ,contract prices for sewerage work published in the construction news sections of engineering periodicals may be a guide to the judgment of the probable cost of proposed work1 but are generally dangerous to rely upon as full details are lacking in the description of the work4 ,a wide experience in the collection and use of cost data is the desirable qualification for making estimates of cost4 ,it is possessed by few and is not an infallible aid to the judgment4 ,having completed the design and summary of the bills of material and labor necessary for each structure or portion of the sewerage system1 the product of the unit cost and the amount of each item plus an allowance for overhead will equal the cost of the item4 ,the total cost will be the sum of the costs of each item4 ,the items should be so grouped that the cost of the different portions of the system are separated in order that the effect on the total cost resulting from different combinations of items or the omission of any one item may be readily computed4 ,a method for estimating the approximate cost of sewers1 devised by ,w4 ,g4 ,kirchoffer#ac depends upon the use of the diagram shown in ,fig4 #b4 ,the factors for local conditions are shown in ,table #b4 ,for example1 let it be required to find the cost of a #ae-;inch vitrified pipe sewer at a depth of #i feet1 if the unit costs of labor and material and the conditions are the same as shown in ,table #c4 ,illustration3 ,,fig4 #b4--;,diagram for ,estimating the ,cost of ,sewers4 ,eng4 ,news1 ,vol4 #gf1 p4 #gha4 ,solution ,first3 ,to find the factor depending on local conditions1 enter the diagram at the #aj-;inch diameter and continue down until the intersection with the depth of trench at #h4b feet is found4 ,now go diagonally parallel to lines running from left to right upwards to the intersection with the vertical line through a cost of #de cents per foot4 ,the diagonal line running from left to right downwards through this intersection corresponds to a factor of about #aa4 ,,table #b ,,factors ,,for ,,costs ,,of ,,sewers ,,to ,,be ,,used ,,with ,,figure #b ,character of ,material ,factor ,clay1 gravel and boulders1 ,medford #bb-bf ,mostly sand1 deep trenches sheeted4 ,wages medium4 ,richland ,center4 #ba-bb ,sandy clay4 ,wages medium4 ,labor conditions good at ,kiel4 #ae-bj ,sand4 ,sandy clay1 some water4 ,labor conditions good4 ,pipe prices medium at ,manston4 #ad-bj ,gravelly clay1 th laid in concrete at ,burlington4 #ac-bb ,sandy clay1 some water1 sheeting at ,la ,farge4 #ag-bc ,sand with water4 #bj ,gravel and boulders4 ,high wages4 #bf ,clay soil4 ,good digging4 #ag ,sandy clay4 ,some water4 #bc ,clay #b miles inland4 ,laborers boarded at sanitarium1 ,wales #ce ,clay1 gravel and boulders at ,plymouth4 #bj-bg ,sand1 clay and good digging at ,lake ,mills4 #af-ai ,red clay4 ,machine work at ,north ,milwaukee4 #bj-bd ,good digging4 ,wages medium at ,west ,salem4 #ag-ai ,sandy soil1 bracing only required4 ,no water4 ,wages and pipe medium4 #ad ,red sticky clay4 #bd ,good digging in any soil4 ,work scarce4 #ae ,red clay4 ,no bracing4 #bj ,work inland from railroad4 ,boarding laborers and other expenses4 #ce ,second3 ,to find the cost of #ae-;inch pipe at a depth of #i4j feet1 enter the diagram at a diameter of #ae inches and continue down until the intersection with a depth of trench at #i feet is found4 ,now go diagonally parallel to lines running from left to right upwards to the intersection with the diagonal line running from left to right downwards corresponding to the factor of #aa found above4 ,the vertical line passing through this point shows the cost to be #fg cents per foot4 ,,table #c ,,cost ,,of ,,sewer ,,construction ,,at ,,atlantic1 ,,iowa 7,from ,gillette's ,handbook of ,cost ,data7 ,material3 ,clay1 not difficult to spade and requiring little or no bracing and practically no pumping4 ,all hand work except backfill which was done by team and scraper4 ,depth of trench averaged #h4b feet2 width #cj inches4 ,diameter of pipe #aj inches4 ,item ,wage1,cost1 ,cents,cents per per ,hour ,foot4 ,pipe4 #j4bj ,hauling team and driver4 #cj 4#jjc ,hauling4 ,man helping4 #ag 4#jja ,cement and sand4 4#jjf ,pipe layers4 #bb 4#jad ,pipe layer's helper4 #ag 4#jad ,trenching4 ,top men4 #ag 4#jbg ,trenching4 ,bottom men4 #ag 4#acj ,trenching4 ,scaffold men4 #ag 4#jjb ,trenching4 ,bracing men4 #ag 4#jjb ,backfilling4 ,shovel4 #ag 4#jaj ,backfilling4 ,team and scraper4 #cj 4#jjh ,backfilling4 ,man and scraper4 #ag 4#jje ,water boy4 #aj 4#jjf ,foreman4 #cj 4#jbb ,total4 4#dej ,,methods ,,of ,,financing ,the construction of sewerage works may be paid for by the issue of municipal bonds1 by special assessment1 by funds available from the general taxes1 or by private enterprise4 #aj4 ,bond ,issues4--,a municipal bond is a promise by the municipality to pay the face value of the bond to the holder at a certain specified time1 with interest at a stipulated rate during the interim4 ,the security on the bond is the taxable property in the municipality4 ,the legal restrictions thrown around municipal bond issues1 the value of the taxable property in the municipality1 all of which may be used as security for municipal bonds1 and the fact that a municipality can be sued in case of default1 make municipal bonds desirable and provide a good market for their sale4 ,the funds available from a municipal bond issue are limited by the amount that the legal limit is in excess of the outstanding issues4 ,the legal limit varies in different states from about #e to #ae per cent of the assessed value of the property in the municipality4 ,in some cases the amount available from municipal bonds has been increased by forming a municipality within a municipality such as a sanitary district1 a park district1 a drainage district1 etc41 which comprises a large portion or all of an existing municipal corporation4 ,this case is well illustrated in some parts of the ,city of ,chicago where the municipal taxing powers are shared by the ,city government1 the ,sanitary ,district1 and ,park ,commissioners4 ,the right to create a new municipal corporation must be granted by the state legislature4 ,knowledge of fixed bonds1 serial bonds1 life of bonds1 sinking funds1 etc4 is an important part of an engineer's education4#ad ,bond issues must usually be presented to the voters for approval at an election4 ,if approved1 and other legal procedure has been followed1 the bonds may be bought by some of the many bonding houses1 or by private individuals1 and the money is immediately available for construction4 ,the bonds are redeemed by general taxation spread over the period of the issue4 #aa4 ,special ,assessment4--,a special assessment is levied against property benefited directly by the structure being paid for4 ,special assessments are used for the payment for the construction of lateral sewers which are a direct benefit to separate districts but are without general benefit to the city4 ,in case the construction of an outfall sewer or the erection of a treatment plant1 which may be of some general benefit1 is necessary to care for a separate district1 a part of the expense may be borne by funds available from general taxation4 ,the legal procedure for the raising of funds by special assessment and the purpose to which the funds so raised may be applied are stipulated in great detail in different states and their directions must be followed implicitly4 ,illinois procedure1 which is similar to that in some other states1 is as follows3 a meeting of the interested property owners is called by a committee or board of the municipal government1 as the result of a petition by interested persons or through the independent action of the ,board4 ,at this preliminary meeting or public hearing arguments for and against the proposed improvement are heard4 ,the engineer is present at this meeting to answer questions and to advise concerning the engineering features of the plan4 ,if approval is given by the ,board the plan and specifications are prepared complete in every detail and incorporated in an ordinance which is presented to the legislative branch of the city government for passage4 ,if the project is adopted it is taken to the county court4 ,an assessment roll is prepared by a commissioner appointed by the court4 ,this roll shows the amount to be assessed against each piece of property benefited4 ,a hearing is then held in the county court at which the owner of any assessed property may voice objections to the continuation of the project4 ,the project may be thrown out of court for many different reasons1 such as the misspelling of a street name1 an error in an elevation1 an error in the description of a pavement1 but most important of all is definite proof that the benefit is not equal to the assessment4 ,the many minor irregularities which may nullify the procedure in a special assessment differ in different states and in different courts in the same state1 but in general no court can approve an assessment greater than the benefits given4 ,after the project has passed through the county court and the assessment roll has been approved1 bonds may be issued for the payment of the contractor4 ,special assessment bonds are liens against the property assessed and have not the same security as a general municipal bond4 ,for this reason a city which has reached its legal limit of municipal bond issues can still pay for work by special assessment4 ,the funds available from special assessments are limited only by the benefit to the property assessed4 ,the amount of the benefit is difficult to fix and may lead to much controversy4 ,it should not exceed the amount demanded for similar work in other localities1 unless unusual and well-understood reasons can be given4 #ab4 ,general ,taxation4--,in paying for public improvements by general taxation the money is taken from the general municipal funds which have been apportioned for that purpose by the legislative department of the municipal government4 ,this method of raising funds for sewerage construction is seldom used unless the political situation is unfavorable to the success of a bond issue or special assessment and the need for the improvement is great4 ,it is usually difficult to appropriate sufficient funds for new construction as the general tax is apportioned to support only the operating expenses of the city1 and statutory provisions limit the amount of tax which can be levied4 #ac4 ,private ,capital4--,private capital has been used for financing sewerage works in some cases because of the aversion of the public in some cities to the payment of a tax for the negative service performed by a sewer4 ,sewers are buried1 unseen1 and frequently forgotten1 but knowledge of their necessity has spread and the number of privately owned sewerage works is diminishing because of the better service which can be provided by the municipality4 ,franchises are granted to private companies for the construction of sewers only after the city has exhausted other methods for the raising of capital4 ,the return on the private capital invested is received from a rental paid by the city1 or paid directly by the users of the system1 an initial payment usually being demanded for connection to the system4 ,to be successful the enterprise must be popular and must fill a great need4 ,this method of financing sewerage works is seldom employed as favorable conditions are not common4 ,,preliminary ,,work #ad4 ,preparing for ,design4--,methods for the design of sewerage systems are given in ,chapter ,v4 ,before the design is made certain information is essential4 ,a survey must be made from which the preliminary map can be prepared as described in ,art4 #db4 ,other necessary information which is the basis of subsequent estimates of the quantity of sewage to be cared for must be obtained by a study of rates of water consumption and the density and growth of population1 the measurement of the discharge from existing sewers1 and the compilation of rainfall and run-off data4 ,if no rainfall data are available estimates must be made from the nearest available data4 ,observations of rainfall or run-off for periods of less than #aj to #bj years are likely to be misleading4 ,methods for gathering and using this information are explained in subsequent chapters4 ,underground surveys are desirable along the lines of the proposed sewers to learn of obstructions1 difficult excavation and other conditions which may be met4 ,all such data are seldom gathered except for sewerage systems involving the expenditure of a large amount of money4 ,for construction in small towns or small extensions to an existing system the funds are usually insufficient for extensive preliminary investigation4 ,the saving in this respect is paid unknowingly to the contractor as compensation for the risk in bidding without complete information4 #ae4 ,underground ,surveys4--,these may be more or less extensive dependent on the character of the district in which construction is to take place4 ,in built-up districts the survey should be more thorough than in sparsely settled districts where only the character of the excavated material is of interest and no obstructions are to be met4 ,underground surveys furnish to the engineer and to prospective bidders on contract work information on which the design and estimate of cost and the contractor's bid may be based and without which no intelligent work can be done4 ,by removing much of the uncertainty of the conditions to be met in the construction of the sewer1 the design can be made more economical and the contractor's bid should be markedly lower1 sufficiently so to repay more than the expense of the survey4 ,the information to be obtained consists of the location of the ground-water level1 and the location and sizes of water1 gas1 and sewer pipes1 telephone and electric conduits1 street-car tracks1 steam pipes1 and all other structures which may in any way interfere with subsurface construction4 ,these structures should be located by reference to some permanent point on the surface4 ,the elevation of the top of the pipes1 except sewers1 rather than the depth of cover should be recorded1 as the depth of cover is subject to change4 ,the elevation of sewers should be given to the invert rather than to the top of the pipe4 ,a portion of the map of the subsurface conditions at ,washington1 ,d4 ,c41 is shown in ,fig4 #c4 ,many of the dimensions and notations are not shown to avoid confusion on this small reproduction4#ae ,colors are generally used instead of different forms of cross hatching to show the different classes of pipe and structures4 ,in addition to a record of the underground structures the character of the ground and the pavement should be recorded4 ,a comprehensive underground survey is seldom available nor does time usually permit its being made preliminary to the design of a sewerage system4 ,the character of the material through which the sewer is to pass should be determined in all cases4 ,illustration3 ,,fig4 #c4--,record ,map of ,underground ,structures1 ,washington1 ,d4 ,c4 ,eng4 ,record1 ,vol4 #gd1 p4 #bfc4 ,the various subsurface lines are differentiated by colors as follows3 ,a--,sewers1 vermilion4 ,b--,water mains1 blue4 ,c--,potomac ,electric ,power ,co41 carmine4 ,d--,washington ,railway and ,electric ,co41 carmine4 ,e--,capital ,traction ,co41 violet4 ,f--,chesapeake and ,potomac ,telephone ,co41 green4 ,g--,washington ,gas ,light ,co41 green4 ,h--,western ,union ,telegraph ,co41 orange4 ,i--,postal ,telegraph ,co41 orange4 ,k--,private vaults1 black4 ,l--,city ,electric ,co41 yellow4 ,illustration3 ,,fig4 #d4 ,punch ,drill4 ,underground pipes and structures are located by excavations1 which may be quite extensive in some cases4 ,their position is fixed by measurements referred to manholes and other underground structures which are somewhat permanent in position4 ,a city engineer should grasp every opportunity to record underground structures when excavations are made in the streets4 ,the character of the material through which the sewer is to pass is determined by borings4 #af4 ,borings4--,methods used for the investigation of subsurface conditions preliminary to sewer construction are3 punch drilling1 boring with earth auger1 jet boring1 wash boring1 percussion drilling1 abrasive drilling1 and hydraulic drilling4 ,the last three methods named are used only for unusually deep borings or in rock4 ,punch drills are of two sorts4 ,the simplest punch drill consists of an iron rod of an inch to #a inch in diameter1 in sections about #d feet long4 ,one section is sharpened at one end and threaded at the other so that the next section can be screwed into it without increasing the diameter of the rod1 as shown in ,fig4 #d4 ,the drill is driven by a sledge striking upon a piece of wood held at the top of the drill to prevent injury to the threads4 ,the drill should be turned as it is driven to prevent sticking4 ,it is pulled out by a hook and lever as shown in ,fig4 #e4 ,it is useful in soft ground for soundings up to #h to #ab feet in depth4 ,another form of punch drill described by ,a4 ,c4 ,veatch#af consists of a cylinder of steel or iron1 one to two feet long split along one side and slightly spread4 ,the lower portion is very slightly expanded and tempered into a cutting edge4 ,in use it is attached to a rope or wooden poles and lifted and dropped in the hole by means of a rope given a few turns about a windlass or drum4 ,by this process the material is forced up into the bit1 slightly springs it1 and so is held4 ,when the bit is filled it is raised to the surface and emptied4 ,much deeper holes can be made with this than with the sharpened solid rod4 ,illustration3 ,,fig4 #e4--,lever for ,pulling ,punch ,drill4 ,illustration3 ,,fig4 #f4--;,earth ,augers4 ,types of earth augers about #a-;inches in diameter are shown in ,fig4 #f4 ,they are screwed on to the end of a section of the pipe or rod and as the hole is deepened successive lengths of pipe or rod are added4 ,the device is operated by two men4 ,it is pulled by straight lifting or with the assistance of a link and lever similar to that shown in ,fig4 #e4 ,the device is suitable for soft earth or sand free from stones1 and can be used for holes #ae to #be feet in depth4 ,for deeper holes a block and tackle should be used for lifting the auger from the hole4 ,it is not suitable for holes deeper than about #ce feet4 ,in the jetting method water is led into the hole through a -inch or #a-;inch pipe1 and forced downward through the drill bit or nozzle against the bottom of the hole4 ,the complete equipment is shown in ,fig4 #g4ag ,it is not always necessary to case the hole as shown in the figure as the muddy water and the vibration of the pipe puddle the sides so that they will stand alone4 ,the jet pipe may be churned in the hole by a rope passing over a block and a revolving drum4 ,in suitable soft materials such as clay1 sand1 or gravel1 holes can be bored to a depth of #ajj feet and samples collected of the material removed4 ,an objection to the method is the difficulty of obtaining sufficient water4 ,illustration3 ,,fig4 #g4--;,jetting ,outfit4 ,u4 ,s4 ,geological ,survey1 ,water ,supply ,paper1 ,no4 #beg #a4 ,simple ,jetting ,outfit4 #b4 ,jetting ,process4 #c4 ,common ,jetting ,drill4 #d;a and #d;b4 ,expansion ,bit or ,paddy4 #e4 ,drive ,shoe4 ,methods of drilling in rock up to depths of #bj feet are described in ,chapter ,,xi under ,rock ,drilling4 ,for deeper holes percussion1 abrasive1 or hydraulic methods as used for deep well drilling must be employed4 ,,chapter ,,iii ,,quantity ,,of ,,sewage #ag4 ,dry weather ,flow4--,estimates of the quantity of sewage flow to be expected are ordinarily based on the population1 the character of the district1 the rate of water consumption1 and the probable ground-water flow4 ,future conditions are estimated and provided for1 as the sewers should have sufficient capacity to care for the sewage delivered to them during their period of usefulness4 #ah4 ,methods for ,predicting ,population4--,methods for the prediction of future population are given in the following paragraphs4 ,the method of graphical extension4 ,this is the quickest and most simple of all4 ,in this method a curve is plotted on rectangular coordinates to any convenient scale1 with population as ordinates and years as abscissas4 ,the curve is extended into the future by judgment of its general tendency4 ,an example is given of the determination of the population of ,urbana1 ,illinois1 in #aiej4 ,table #d contains the population statistics which have been plotted on line ,a in ,fig4 #h and extended to #aiej4 ,the probable population in #aiej is shown by this line to be about #ba1jjj4 ,the method of geometrical progression4 ,in this method the rate of increase during the past few years or decades is assumed to be constant and this rate is applied to the present population to forecast the population in the future4 ,for example the rate of increase of population in ,urbana for the past #g decades has varied widely1 but indications are that for the next few decades it will be about #bj per cent4 ,applying this rate from #aibj to #aiej the population in #aiej is shown to be about #ag1hjj4 ,it is evident that this method may lead to serious error as insufficient information is given in the table to make possible the selection of the proper rate of increase4 ,,table #d ,,population ,,studies ,urbana1 ,illinois ,year,population,absolute,per ,cent ,increase,increase for ,eachfor ,each ,decade ,decade #ahej #baj #ahfj #b1jch #ahbh #he4f #ahgj #b1bgg #bci #aj4e #ahhj #b1idb #ffe #bb4f #ahij #c1eaa #efi #af4b #aijj #e1gbh #bbag #ch4g #aiaj #h1bde #beag #cj4e #aibj #aj1bcj #aihe #ai4d ,population of ,year,decatur,danville,champaign,kankake e,peoria,bloomington ,ann1 ,arbor ,michigan #ahej #gcf #e1jie #a1eid #ahfj #c1hci #a1fcb #a1gbg #b1ihdad1jde #g1jge #e1jig #ahgj #g1afa #d1gea #d1fbe #e1ahibb1hdi #ad1eij #g1cfh #ahhj #i1edg #g1gcc #e1ajc #e1feabi1bei #ag1ahj #h1jfa #ahij #af1hda #aa1dia #e1hci #i1jbeda1jbd #bj1dhd #i1dca #aijj #bj1ged #af1ced #i1jih #ac1eieef1ajj #bc1bhf #ad1eji #aiaj #ca1adj #bg1hga #ab1dba #ac1ihfff1iej #be1ghf #ad1hag #aibj #dc1hah #cc1gej #ae1hgc #af1gbagf1aba #bh1fch #ai1eaf ,illustration3 ,,fig4 #h4--;,diagram ,showing ,methods for ,estimating ,future ,population4 ,the method of utilizing a decreasing rate of increase4 ,this method attempts to correct the error in the assumption of a constant rate of increase4 ,after a certain period of growth1 as the age of a city increases its rate of increase diminishes4 ,in applying this knowledge to a prediction of the future population of a city the population curve is plotted1 as in the graphical method and a straight line representing a constant rate or increase is drawn tangent to the curve at its end4 ,the curve is then extended at a flatter rate in accordance with the rate of change of a similar nearby larger city4 ,this method has not been applied to any of the cities included in ,table #d1 as none has reached that limiting period where the rate of increase has begun to diminish4 ,the method of utilizing an arithmetical rate of increase4 ,this method allows for the error of the geometrical progression which tends to give too large results for old and slow-growing cities4 ,this method generally gives results that are too low4 ,the absolute increase in the population during the past decade or other period is assumed to continue throughout the period of prediction4 ,applying this method to the same case1 the increase in the population during the past decade was #b1jjj4 ,adding three times this amount to the population in #aibj1 the population of ,urbana in #aiej will be about #af1jjj4 ,the method involving the graphical comparison with other cities with similar characteristics4 ,in this method population curves of a number of cities larger than ,urbana but having similar characteristics1 are plotted with years as abscissas and population as ordinates1 with the present population of ,urbana as the origin of coordinates4 ,the population curve for ,urbana is first plotted4 ,it will lie entirely in the third quadrant as shown by the heavy full line in ,fig4 #h4 ,the population curves of some larger cities are then plotted in such a manner that each curve passes through the origin at the time their population was the same as that of the present population of ,urbana4 ,these curves lie in the first and third quadrants4 ,the population curve of the city in question is then extended to conform with the curves of older cities in the most probable manner as dictated by judgment4 ,such a series of plots has been made in ,fig4 #h4 ,the results indicate that the population of ,urbana in #aiej will be about #be1ejj4 ,the last method described will give the most probable result as it is the most rational4 ,for quick approximations the geometrical progression is used4 ,the arithmetical progression is useful only as an approximate estimate for old cities4 #ai4 ,extent of ,prediction4--,the period for which a sewerage system should be designed is such that each generation bears its share of the cost of the system4 ,it is unfair to the present generation to build and pay for an extensive system that will not be utilized for #be years4 ,it is likewise unfair to the next generation to construct a system sufficient to comply with present needs only1 and to postpone the payment for it by a long term bond issue4 ,an ideal solution would be to plan a system which would satisfy present and future needs and to construct only those portions which would be useful during the period of the bond issue4 ,unfortunately this solution is not practical1 because1 #ast1 it is less expensive to construct portions of the system such as the outfall1 the treatment plant1 etc41 to care for conditions in advance of present needs1 and #bnd1 the life of practically all portions of a sewerage system is greater than the legal or customary time limit on bond issues4 ,a compromise between the practical and the ideal is reached by the design of a complete system to fulfill all probable demands1 and the construction of such portions as are needed now in accordance with this plan4 ,the payment should be made by bond issues with as long life as is financially or legally practical1 but which should not exceed the life of the improvement4 ,the prediction of the population should therefore be made such that a comprehensive system can be designed with intelligence4 ,practice has seldom called for predictions more than #ej years in the future4 #bj4 ,sources of ,information on ,population4--,the ,united ,states decennial census furnishes the most complete information on population4 ,unfortunately it becomes somewhat old towards the end of a decade4 ,more recent information can be obtained from local sources4 ,practically every community takes an annual school census the accuracy of which is fairly reliable4 ,the general tendencies of the population to change can be learned by a study of the post office records showing the amount of mail matter handled at various periods4 ,local chambers of commerce and newspapers attempt to keep records of population1 but they are often inaccurate4 ,another source of information is the gross receipts of public service companies1 such as street railways1 water1 gas1 electricity1 telephone1 etc4 ,the population can be assumed to have increased almost directly as their receipts1 with proper allowance for change in rates1 character of management1 and other factors4 #ba4 ,density of ,population4--,so far the study of population has been confined to the entire city4 ,it is frequently necessary to predict the population of a district or small section of a city4 ,a direct census may be taken1 or more frequently its population is determined by estimating its density based on a comparison with similar districts of known density1 and multiplying this density by the area of the district4 ,in determining the density1 statistics of the population of the entire city will be helpful but are insufficient for such a problem4 ,a special census of the area involved would be conclusive but is generally considered too expensive4 ,a count of the number of buildings in the district can be made quickly1 and the density determined by approximating the number of persons per building4 ,statistics of the population of various districts together with a description of the character of the district are given in ,table #e4 ,illustration3 ,,fig4 #i4--;,density1 ,area1 and ,population1 ,cincinnati1 ,ohio4 #ahej to #aiej4 ,,table #e ,,densities ,,of ,,population ,city ,character of ,district ,area1 ,density ,acres per ,acre ,philadelphia,thomas ,run4 ,residential4 ,mostly pairs of two and three-story houses4 #abjd acres settled4 #a1hdj #ei ,pine ,street4 ,residential4 ,mostly solid four to six-story houses4 #aef acres settled4 #afj #ig ,shunk ,street4 ,residential4 ,mostly pairs of two and three-story houses4 #eci acres settled4 #eci #aai ,lombard ,street4 ,tenements and hotels1 #ade acres settled4 #adg #aac ,york ,street4 ,residential and manufacturing4 #ced acres settled4 #ceh #id ,new ,york ,residential4 ,three-story dwellings with ,city #ah-;foot frontage1 and four-story flats with #bj-;foot frontage4 #ajj ,residential4 ,five-story flats4 #ebj-fgj ,residential4 ,six-story flats4 #hjj-ajjj ,residential4 ,six-story apartments4 ,high class4 #cjj ,chicago #ast ,ward4 ,retail and commercial4 ,the 8,loop04 #a1ddj #bj4e #b;d ,ward4 ,commercial and low-class residential solidly built up4 #hjj #ec4e #c;d ,ward4 ,low-class residential4 #ifj #dh4a #eth ,ward4 ,industrial4 ,some low-class residences4 ,not solidly built up4 #b1bdj #be4ea #fth ,ward4 ,residential4 ,four and five-story apartments4 ,a few detached residences4 #a1fjj #dg4j #gth ,ward4 ,same as ,ward #f4 ,not solidly built up4 ,contains a large park4 #d1afj #ba4g #hth ,ward4 ,industrial4 ,sparsely settled4 #ac1fbd #d4h #ith ,ward4 ,industrial and low-class residential4 ,solidly built up4 #fdj #gj4j #ajth ,ward4 ,same as ,ward #i4 #fdj #hj4h #acth ,ward4 ,low-class residential4 ,solidly built with three and four-story flats4 #f1ajj #cf4g #afth ,ward4 ,middle-class residential4 ,some industries4 ,well built up4 #hjj #ha4e #aith ,ward4 ,industrial and commercial4 ,some low-class residences4 #fdj #ij4g #bjth ,ward4 ,low-class residential4 ,some industries4 ,entirely built up4 #hjj #gg4a #bast ,ward4 ,industrial4 ,entirely built up4 #ifj #di4i #bc;d ,ward4 ,industrial and residential4 #hjj #ee4d #bdth ,ward4 ,residential apartment houses and middle-class residences4 #a1abj #df4h #beth ,ward4 ,residential4 ,high-class apartments4 ,wealthy homes4 ,contains a large park4 #d1afj #bd4j #bfth ,ward4 ,residential4 ,middle-class homes and apartments4 ,fairly well built up4 #d1fdj #af4a #bgth ,ward4 ,residential4 ,sparsely settled4 #bj1dhj #e4e #bith ,ward4 ,low-class residential4 ,two-story frame houses4 8,back of the ,yards04 #f1djj #ab4h #cjth ,ward4 ,the ,stock ,yards4 #a1bhj #dj4a #cb;d ,ward4 ,scattered residences4 #h1dhj #h4c #cc;d ,ward4 ,scattered residences4 #ab1idd #e4e #ceth ,ward4 ,scattered residences4 #d1ifj #ab4j ,general ,the most crowded conditions with average five-story and higher1 contiguous buildings in poor class districts4 #gej-ajjj ,five and six-story contiguous flat buildings4 #ejj-gej ,six-story high-class apartments4 #cjj-ejj ,three and four-story dwellings1 business blocks and industrial establishments4 ,closely built up4 #ajj-cjj ,separate residences1 #ej to #ge-;foot fronts1 commercial districts1 moderately well built up4 #ej-ajj ,sparsely settled districts and scattered frame dwellings for individual families4 #j-ej ,the density of population in ,cincinnati from #ahej to #aiac with predictions to #aiej is given in ,fig4 #i4ah ,this shows the densities for the entire city and is illustrative of the manner in which future conditions were predicted for the design of an intercepting sewer4 ,the data given in ,table #e are of value in estimating the densities of population in various districts4 ,the ,committee on ,city ,plan of the ,board of ,estimate and ,apportionment of ,new ,york ,city obtained some valuable information on this point1 especially in ,manhattan4 ,three-story dwellings with #ah-;foot frontage1 or four-story flats with #bj-;foot frontage1 presumably contiguous1 were found to hold #ajj persons to the acre4 ,five-story flats held #ebj to #fgj persons per acre4 ,six-story flats held #hjj to #a1jjj persons per acre1 and high-class six-story apartments held less than #cjj per acre4 #bb4 ,changes in ,area4--,in order to determine the probable extent of a proposed sewerage system it is important to estimate the changes in the area of a city as well as the changes in the population4 ,with the same population and an increased area the quantity of sewage will be increased because of the larger amount of ground water which will enter the sewers4 ,predictions of the area of a city are less accurate than predictions of population because the factors affecting changes cannot be so easily predicted4 ,an area curve plotted against time would be helpful in guiding the judgment1 but its extension into the future based on past occurrences would be futile4 ,a knowledge of the city1 its political tendencies1 possibilities of extension1 and other factors must be weighed and judged4 ,the engineer1 if he is ignorant of the city for which he is making provision1 is dependent upon the testimony of real estate men1 business men and others acquainted with the local situation4 #bc4 ,relation between ,population and ,sewage ,flow4--,the amount of sewage discharged into a sewerage system is generally equal to the amount of water supplied to a community1 exclusive of ground water4 ,the entire public water supply does not reach the sewers1 but the losses due to leakage1 lawn sprinkling1 manufacturing processes1 etc41 are made up by additions from private water supplies1 surface drainage1 etc4 ,the estimated quantity of water used but which did not reach the sewers in ,cincinnati is shown in ,table #f4 ,the amount shown represents #ch per cent of the total consumption4 ,unless direct observations have been made on existing sewers or other factors are known which will affect the relation between water supply and sewage1 the average sewage flow exclusive of ground water1 should be taken as the average rate of water consumption4 ,experience has shown that water consumption increases after the installation of sewers4 ,,table #f ,,estimated ,,quantity ,,of ,,water ,,used ,,but ,,not ,,discharged ,,into ,,the ,,sewers ,,in ,,cincinnati ,expressed in gallons per capita per day1 and based on a total consumption of #abe to #aej gallons per capita per day4 ,steam railroads4 #f to #g ,street sprinklers4 #f to #g ,consumers not sewered4 #i to #aj ,manufacturing and mechanical4 #f to #g ,lawn sprinklers4 #c to #c ,leakage4 #ah to #ba ,the public water supply is generally installed before the sewerage system4 ,by collecting statistics on the rate of supply of water a fair prediction can be made of the quantity of sewage which must be cared for4 ,the rate of water supply varies widely in different cities4 ,it is controlled by many factors such as meters1 cost and availability of water1 quality of water1 climate1 population1 etc4 ,in ,american cities a rough average of consumption is #ajj gallons per capita per day4 ,other factors being equal the rate of consumption after meters have been installed will be about one-half the rate before the meters were installed4 ,low cost1 good quantity and good quality will increase the rate of consumption1 and the rate will increase slowly with increasing population4 ,statistics of rates of water consumption are given in ,table #g4 #bd4 ,character of ,district4--,the various sections of a city are classified as commercial1 industrial1 or residential4 ,the residential districts can be subdivided into sparsely populated1 moderately populated1 crowded1 wealthy1 poor1 etc4 ,commercial districts may be either retail stores1 office buildings1 or wholesale houses4 ,industrial districts may be either large factories1 foundries1 etc41 or they may be made up of small industries housed in loft buildings4 ,in cities of less than #cj1jjj population the refinement of such subdivisions is generally unnecessary in the study of sewage flow1 all districts being considered the same4 ,the data given in ,tables #h and #i indicate the difference to be found in different districts of large cities4 ,the ,milwaukee data are presented in a form available for estimates on different bases4 ,these data are shown in ,table #aj4 ,,table #g ,,rates ,,of ,,water ,,consumption ,from ,journals of ,american and ,new ,england ,water ,works ,associations ,city ,population ,per ,cent ,consumption1 in ,metered ,gal4 per ,thousands ,capita per ,day ,tacoma1 ,wash4 #ajj #aa4f #dfj ,buffalo1 ,n4 ,y4 #dej #d4i #caj ,cheyenne1 ,wyo4 #ac #bgj ,erie1 ,pa4 #gb #c4j #aih ,philadelphia1 ,pa4 #afaa #d4f #ahj ,st4 ,catherines1 ,ont4 #ag #c4b #afj ,port ,arthur1 ,ont4 #ah #ad4g #ade ,ogdensburg1 ,n4 ,y4 #ah #j4b #adj ,los ,angeles1 ,cal4 #eaf #gg4i #adj ,wilmington1 ,del4 #ib #dc4g #abe ,lancaster ,pa4 #fj #cd4f #abj ,richmond1 ,va4 #abj #ge4b #aae ,st4 ,louis1 ,mo4 #gcj #f4g #aaj ,springfield1 ,mass4 #ajj #id4d #aaj ,keokuk1 ,ia4 #ad #fd4e #aje ,jefferson ,city1 ,mo4 #ac4e #cd4d #ajj ,muncie1 ,ind4 #cj #bc4h #ie ,burlington1 ,ia4 #bd #d4e #ij ,council ,bluffs1 ,ia4 #cb #ge4e #hj ,san ,diego1 ,cal4 #he #ajj #hj ,monroe1 ,wis4 #c #ajj #hj ,yazoo ,city1 ,miss4 #g #hd4a #ge ,oak ,park1 ,illinois4 #bf #ajj #gj ,portsmouth1 ,va4 #ge #h4a #fe ,new ,orleans1 ,la4 #cfj #ii4g #fj ,rockford1 ,ill4 #ec #ic4j #ee ,fort ,dodge1 ,ia4 #bj #if4j #ej ,manchester1 ,vt4 #a4e #fi4j #de ,woonsocket1 ,r4 ,i4 #dg4e #ie4f #ce ,attempts have been made to express the rate of sewage flow in different units other than in gallons per capita per day4 ,a unit in terms of gallons per square foot of floor area tributary has been suggested for commercial and industrial districts4 ,it has not been generally adopted4 ,the rates of flow in ,new ,york ,city as reported in this unit by ,w4 ,s4 ,mc,grane are given in ,table #aa4 ,the most successful way to predict the flow from commercial or industrial districts is to study the character of the district's activities and to base the prediction on the quantity of water demanded by the commerce and industry of the district affected4 #be4 ,fluctuations in ,rate of ,sewage ,flow4--,the rate of flow of sewage from any district varies with the season of the year1 the day of the week1 and the hour of the day4 ,the maximum and minimum rates of sewage flow are the controlling factors in the design of sewers4 ,the sewers must be of sufficient capacity to carry the maximum load which may be put upon them1 and they must be on such a grade that deposits will not occur during periods of minimum flow4 ,the maximum and minimum rates of flow are usually expressed as percentages of the average rate of flow4 ,,table #h ,,sewage ,,flow ,,from ,,different ,,classes ,,of ,,districts ,arranged from data by ,kenneth ,allen in ,municipal ,engineer's ,journal1 ,feb41 #aiah4 ,district ,gallons,gallons per per ,capita ,acre per ,dayper ,day ,buffalo1 ,n4 ,y4 ,from ,report of ,international ,joint ,commission on the ,pollution of ,boundary ,waters3 ,industrial3 ,metal and automobile plants4 ,maximum4 #ac1jjj ,industrial3 ,meat packing1 chemical and soap4 #af1jjj ,commercial3 ,hotels1 stores and office buildings4 #fj1jjj ,domestic3 ,average4 #hj ,domestic3 ,apartment houses4 #adg ,domestic3 ,first-class dwellings4 #abi ,domestic3 ,middle-class dwellings4 #ha ,domestic3 ,lowest-class dwellings4 #ce4e ,cincinnati1 ,ohio4 #aiac ,report on ,sewerage ,plan3 ,industrial1 in addition to residential and ground water4 #i1jjj ,commercial1 in addition to residential and ground water4 #dj1jjj ,domestic4 #ace ,detroit1 ,mich43 ,domestic4 #bbh ,industrial1 in addition to residential and ground water4 #ab1jjj ,commercial1 in addition to residential and ground water4 #ej1jjj ,milwaukee1 ,wis4 #aiae ,report of ,sewerage ,commission3 ,industrial1 maximum4 #ha #af1fjj ,industrial1 average4 #ca #h1cjj ,commercial1 maximum4 #fj1ejj ,commercial1 average4 #cg1djj ,wholesale commercial1 maximum4 #bj1jjj ,wholesale commercial1 average4 #i1fej ,,table #i ,,observed ,,water ,,consumption ,,in ,,different ,,classes ,,of ,,districts ,,in ,,new ,,york ,,city ,from data by ,kenneth ,allen in ,municipal ,engineers ,journal1 for #aiah ,hotels ,daily ,cons4 ,tenements ,daily ,cons4 ,office and ,daily ,cons4 ,gals4 per ,gals4 per ,loft ,gals4 per #ajjj ,sq4 ,ft4 #ajjj ,sq4 ,ft4 ,buildings #ajjj ,sq4 ,ft4 ,floor ,area ,floor ,area ,floor ,area ,building ,max4#ai;,avg4 ,location ,max4#ai;,avg4 ,building ,max4#ai;,avg4 ,hotel #ghth-#gith ,mc,graw ,biltmore4 ,st4 and ,bldg4 #dgj #cfh ,b'way4 #bef #aib #cji #bjf ,hotel #daj ,e4 ,n4 ,y4 ,mc,alpin4 #feth ,st4 ,telephone #gec #fid #cej #bie ,bldg4 #aid ,hotel ,plaza4 #cjth ,st4 ,met4 ,life and ,bldg4 ,madison #fcj #egh ,ave #cjf #ahh #bef ,hotel ,waldorf #bg ,lewis #db;d ,st4 ,astoria4 #fah #dhb ,st4 #cjg #bej ,bldg #bga ,hotel ,astor4 #beh ,municipal ,delancey ,bldg4 #gcb #dib ,st4 #bfg #bbf #aah ,hotel ,equitable ,vanderbilt4 #fjd #ede ,bldg4 #cff #bfh ,average #fcd #ebf ,average #big #bcj ,average #cch #bai ,,table #aj ,,sewage ,,flow ,,from ,,different ,,classes ,,of ,,districts ,,based ,,on #aiae ,,report ,,of ,,milwaukee ,,sewerage ,,commission ,ratio of maximum to average rate for department store district4 #a4gee ,ratio of maximum to average rate for hotel district4 #a4fe ,ratio of maximum to average rate for office building district4 #a4ea ,ratio of maximum to average rate for wholesale commercial district4 #b4a ------------------------ ,average and maximum gallons per thousand square feet of floor area3 ,avg4 ,max4 ------------------------ ,for department store district4 #bcb #djg ,for office building district4 #eda #hia ,for wholesale commercial district4 #afd #cdd ,for all districts except wholesale commercial4 #cha #fah ,average and maximum gallons per day3 ,for all districts except wholesale commercial4 #ag1gjjbi1hjj ,for wholesale commercial district4 #i1fejbj1jjj ,,table #aa ,,rates ,,of ,,consumption ,,predicted ,,for ,,different ,,districts ,,in ,,new ,,york ,,city ,net ,bldg4 ,observed,observed ,area in ,sq4 ,avg4 ,cons4 in,cons4 in,predicted ,district ,ft4 per ,number g4p4d4 g4p4d4 ,mean ,acre for of per #ajjjper #ajjj ,cons4 ,ultimate ,floors,sq4 ,ft4 ,sq4 ,ft4 ,consumption ,max4 ,avg4 ,hotel and #bd1hjj #ae #fcd #ebf #ejj midtown4 ,midtown and #bd1hjj #ae #cch #bai #cjj financial4 ,east and ,west of #bd1hjj #aj #big #bcj #cjj midtown4 ,apartment1 #eith to #bj1djj #g #bcj #cjj #aeeth ,sts4 ,manhattan north of #bj1djj #e #bcj #cjj #aeeth ,st4 ,predicted,predicted,predicted,measured, measured ,mean in ,dry ,max4 ,dry ,avg4 ,dry,max4 ,dry ,district ,million ,weather ,weather ,weather ,weather ,gals4 per ,flow1 ,flow1 ,flow1 ,flow1 ,acre per c4f4s4 c4f4s4 c4f4s4 c4f4s4 ,day per ,acre per ,acre per ,acreper ,acre ,hotel and 4#bj 4#bi 4#cd #a4jd 4#adf midtown4 ,midtown and 4#ab 4#ah 4#bc 4#jgh 4#aaj financial4 ,east and ,west of 4#jgd 4#ab 4#ae 4#jeg 4#jig midtown4 ,apartment1 #eith to 4#jdc 4#jf 4#ji #aeeth ,sts4 ,manhattan north of 4#jca 4#je 4#jh #aeeth ,st4 ,midtown district consists of department stores1 large railroad terminals1 industrial and loft buildings1 and sky-scraper office buildings4 ,it is difficult to set any definite figure for the percentage which the maximum rate of flow is of the average4 ,fluctuations above and below the average are greater the smaller the tributary population4 ,this relation can be expressed empirically as ,m #ejj,p1 in which ,m represents the per cent which the maximum flow is of the average1 and ,p represents the tributary population in thousands4 ,the expression should not be used for populations below #a1jjj nor above #a1jjj1jjj4 ,having determined the expected average flow of sewage by a study of the population1 water consumption1 etc41 the maximum quantity of sewage is determined by multiplying the average flow by the per cent which the maximum is of the average4 ,in this connection ,w4 ,g4 ,harmon#bj offers the relation ,m #a #ad7d 7,p771 which was used in the design of the ,ten ,mile ,creek intercepting sewer at ,toledo1 ,ohio4 ,for rough estimates and for comparative purposes the ratio of the average to the minimum flow can be taken the same as the ratio of the maximum to the average flow1 unless direct gaugings or other information show it to be otherwise4 ,illustration3 ,fig4 #aj4--;,daily and ,hourly ,variations of ,sewage ,flow4 #a4 ,toledo1 ,o42 ,manufacturing average4 #b4 ,toledo1 ,o42 ,manufacturing1 ,monday4 #c4 ,toledo1 ,o42 ,manufacturing1 ,sunday4 #d4 ,toledo1 ,o42 ,residential1 average4 #e4 ,toledo1 ,o42 ,residential1 ,monday4 #f4 ,toledo1 ,o42 ,residential1 ,sunday4 #g4 ,cincinnati1 ,o41 ,industrial1 average4 #h4 ,cincinnati1 ,o42 ,residential1 average4 #i4 ,cincinnati1 ,o42 ,commercial1 average4 #aj4 ,average of #g cities4 ,the fluctuations of flow in commercial and industrial districts are so different from those in residential districts that the formulas given should not be used in the design of sewers other than those draining residential areas4 ,it is reasonable to suppose that fluctuations in rates of flow from industrial districts are dependent upon the character of the tributary industries4 ,a study of these industries will give valuable light on the maximum and minimum rates at which sewage will be delivered to the sewers4 ,hourly1 daily1 and seasonal fluctuations in rates of sewage flow are of interest in the design of pumping stations to give knowledge of the rates at which the pumps must operate at various periods4 ,the fluctuations in rates of sewage flow during various hours and days in different cities and districts are shown in ,fig4 #aj4 ,fluctuations in rate of flow of sewage lag behind fluctuations in rate of water consumption1 the time being dependent on the distance through which the wave of change must travel in the sewer4 #bf4 ,effect of ,ground ,water4--,sewers are seldom laid with water-tight joints4 ,since they usually lie below the ground water level it is inevitable that a certain amount of ground water will enter4 ,various units have been suggested for the expression of the inflow of ground water in an attempt to include all of the many factors4 ,some of these units are3 gallons per acre drained by the sewer per day1 gallons per mile of pipe per day1 gallons per inch diameter per mile of pipe per day1 etc4 ,since the ground water enters pipe sewers at the joints1 the longer the joints the greater the probability of the entrance of ground water4 ,the last unit is therefore the most logical but the accuracy of the result is scarcely worthy of such refinement and the unit usually adopted is gallons per mile of pipe per day4 ,no definite figure can be given for the amount of ground water to be expected in sewers since the character of the soil and the ground water pressure must be considered4 ,relatively normal infiltration may be found from #e1jjj to #hj1jjj gallons per mile of pipe per day4 ,the minimum is seldom reached in wet ground and the maximum is frequently exceeded4 ,table #ab shows the amount of ground water measured in various sewers as given by ,brooks4#ba #bg4 ,rsum of ,method for ,determination of ,quantity of ,dry weather ,sewage4--,the steps in the determination of the quantity of sewage are3 determine the period in the future for which the sewers are to be designed2 estimate the population and tributary area at the end of this period2 estimate the rate of water consumption and assume the sewage flow to equal the water consumption2 determine the maximum and minimum rates of sewage flow2 and finally1 estimate the maximum rate of ground water seepage and add it to the maximum rate of sewage flow to give the total quantity of sewage to be carried by the proposed sewers4 ,,table #ab ,,data ,,on ,,the ,,infiltration ,,of ,,ground ,,water ,,into ,,sewers ,abstracted from paper by ,j4 ,n4 ,brooks in ,transactions ,am4 ,society of ,civil ,engineers1 ,vol4 #gf1 p4 #aiji4 ,place ,diam- eter ,wet ,avg4 or ,trench1 ,head ,char- ,dimen- ,per of acter sions ,cent of,ground of in ,mate- ,total ,water1,sub- ,shape,inchesrial ,length ,fee grade ,gallons per #bd ,hours ,per ,inch ,diam- eter ,per ,per ,foot ,mile of of ,per ,mile ,joint ,pipe of ,pipe ,boston1 #h to ,mass4 ,circ4 #cf ,v4,p4 #b4f #a1hah #dj1jjj ,east ,orange1 ,n4 ,j4 #aj ,q4 #bb1djj ,east ,orange1 #h to ,n4 ,j4 #bd ,v4,p4 #j4h #edj #h1fej ,joint trunk sewer1 ,new ,g4 ,jersey ,q4 #be1jjj ,rogers ,park1 ,ill4 #f #j4c #bjg #a1bdj ,altoona1 ,pa4 #cj #e4j #b1hij #hf1eib ,concord1 ,mass4 #ah #h #dc1jjj ,malden1 ,mass4 ,circ4 ,v4,p4 #fj #ej1jjj ,westboro1 ,mass4 #ae ,v4,p4 #ajj #hh1ajja1cbj1cjj ,fond du ,lac1 ,wis4,circ4 #bd ,v4,p4 #ajj #e ,c4 #a4e #a1jaj #bd1cgj ,east ,orange1 #aj to ,n4 ,j4 ,circ4 #bd ,v4,p4 #ajj #d4g #b1edj #dc1bej ,ocean ,grove1 ,n4 #d to ,j4 ,circ4 #ab ,v4,p4 #ajj #c,s4,c4 #b4g #a1hij #ae1abf ,ocean ,grove1 ,n4 #d to ,j4 ,circ4 #ab ,v4,p4 #ajj #d,s4,c4 #g4i #e1dhj #dc1gfd ,east ,orange1 #bd ,n4 ,j4 ,rect4 #cf ,brick #ajj #egj1jjj ,westboro1 ,mass4 ,brick #dae1hej ,altoona1 #cc ,b4 ,pa4 ,rect4 #dd ,c4 #e1cij #bfd1jjj ,columbus1 #db ,con- ,ohio4 ,h4,s4 #db crete #abj #f1cdj ,bronx ,valley1 #dd to ,con- ,n4 ,y4 ,circ4 #gb crete ,g4 #abc #g1bff ,cincinnati1 ,estimated in design4 ,data not ,ohio4 from ,brooks #fg1ejj ,milwaukee1 ,residential districts1 gals4 per acre per #adfj to ,wis4 day4 ,not taken from ,brooks #bbjj ,abbreviations3 ,h4,s4 horseshoe shaped2 ,b4 ,c ,brick and concrete2 ,v4,p4 vitrified pipe2 ,g4 gravel2 ,q4 quicksand2 ,s4 ,c4 sand clay2 ,c4 clay4 ,,quantity ,,of ,,storm ,,water #bh4 ,the ,rational ,method4--,the water which falls during a storm must be removed rapidly in order to prevent the flooding of streets and basements1 and other damages4 ,the quantity of water to be cared for is dependent upon3 the rate of rainfall1 the character and slope of the surface1 and the area to be drained4 ,all methods for the determination of storm-water run-off1 whether rational or empirical1 depend upon these factors4 ,the so-called ,rational ,method can be expressed algebraically1 as1 ,q ,,air1 in which ,q rate of run-off in cubic feet per second2 ,a area to be drained expressed in acres2 ,i percentage imperviousness of the area2 ,r maximum average rate of rainfall over the entire drainage area1 expressed in inches per hour1 which may occur during the time of concentration4 ,the area to be drained is determined by a survey4 ,a discussion of ,r and ,i follows in the next two sections4 ,an example of the use of the ,rational ,method is given on page #ie4 #bi4 ,rate of ,rainfall4--,rainfall observations have been made over a long period of time by ,united ,states ,weather ,bureau observers and others4 ,continuous records are available in a few places in this country showing rainfall observations covering more than a century4 ,such records have been the bases for a number of empirical formulas for expressing the probable maximum rate of rainfall in inches per hour1 having given the duration of the storm4 ,table #ac is a collection of these formulas with a statement as to the conditions under which each formula is applicable4 ,the formula most suitable to the problem in hand should be selected for its solution4#bb ,,table #ac ,,rainfall ,,formulas ,name of ,conditions for which ,formula ,originator ,formula is ,suitable ,e4 ,s4 ,dorr i #aej7t #cj7 ,a4 ,n4 ,talbot,maximum storms in ,easterni #cfj7t #cj7 ,united ,states ,a4 ,n4 ,talbot,ordinary storms in i #aje7t #ae7 ,eastern ,united ,states ,emil ,heavy rainfall near ,new i #abj7t #bj71 etc4 ,kuichling ,york ,city ,l4 ,j4 ,le ,for ,san ,francisco4 ,see ,t4 ,conte ,a4 ,s4 ,c4 ,e4 v4 #ed1 p4 i #gt #aih ,sherman ,maximum for ,boston1 ,mass4i #be4abt4#fhg ,sherman ,extraordinary for ,boston1i #aht ,mass4 ,webster ,ordinary for i #abt#j4f ,philadelphia1 ,pa4 ,ordinary storms for ,hendrick ,baltimore4 ,eng4 i #aje7t #aj7 ,cont41 ,aug4 #i4 #aiaa ,j4 de ,ordinary storms for i #afc7t #bg7 ,bruyn-,kops ,savannah1 ,ga4 ,c4 ,d4 ,hill ,for ,chicago1 ,ill4 i #abj7t #ae7 ,metcalf and ,louisville1 ,ky4 ,am4 ,sew4 i #adt ,eddy ,prac41 ,vol ,i4 ,w4 ,w4 ,horner,st4 ,louis1 ,mo4 ,eng4 ,news1i #ef7t #e74he ,sept4 #bi1 #aiaj ,r4 ,a4 ,for ,spokane1 ,wash4 ,eng4 i #bc4ib7t #b4ae7 #j4aed ,brackenbuy ,record1 ,aug4 #aj1 #aiab ,metcalf and ,new ,orleans i #ait ,eddy ,metcalf and ,for ,denver1 ,colo4 i #hd7t #d7 ,eddy ,central ,park1 ,n4 ,y4 ,kenneth #ea-,year ,record4 ,eng4 i #djj7bt #dj7bc ,allen ,news-,record1 ,april #g1 #aiba1 p4 #ehh #cj4 ,time of ,concentration4--,by the time of concentration is meant the longest time without unreasonable delay that will be required for a drop of water#bd to flow from the upper limit of a drainage area to the outlet4 ,assuming a rainfall to start suddenly and to continue at a constant rate and to be evenly distributed over a drainage area of #ajj per cent imperviousness and even slope towards one point1 the rate of run-off would increase constantly until the drop of water from the upper limit of the area reached the outlet1 after which the rate of run-off would remain constant4 ,in nature the rate of rainfall is not constant4 ,the shorter the duration of a storm the greater the intensity of rainfall4 ,therefore the maximum run-off during a storm will occur at the moment when the upper limit of the area has commenced to contribute4 ,from that time on the rate of run-off will decrease4 ,the time of concentration can be measured fairly well by observing the moment of the commencement of a rainfall1 and the time of maximum run-off from an area on which the rain is falling4 ,a prediction of the time of concentration is more or less guess work4 ,as the result of measurements some engineers assume the time of concentration on a city block built up with impervious roofs and walks1 and on a moderate slope1 is about #e to #aj minutes4 ,this is used as a basis for the judgment of the time of concentration on other areas4 ,for relatively large drainage areas such a method cannot be used4 ,the procedure is to measure the length of flow through the drainage channels of the area1 to assume the velocity of the flood crest through these channels and thus to determine the time of concentration4 ,table #ad shows the flood crest velocities in various streams of the ,ohio ,river ,basin under flood conditions4 ,the velocity over the surface of the ground may be approximated by the use of the formula#be ,v #b1jjj;,i7,s71 in which ,v the velocity of flow over the surface of the ground in feet per minute2 ,i the percentage imperviousness of the ground2 ,s the slope of the ground4 ,for areas up to #ajj acres where natural drainage channels are not existent this formula will give more satisfactory results than guesses based on the time of concentration of certain known areas4 ,having determined the time of concentration1 the rate of rainfall ,r to be used in the ,rational ,method is found by substitution in some one of the rainfall formulas given in ,table #ac4 ,,table #ad ,,flood ,,crest ,,velocities ,,in ,,ohio ,,river ,,basin ,,in ,,march1 #aiac ,from ,table #ab4 ,u4 ,s4 ,g4 ,s41 ,water ,supply ,paper4 ,no4 #ccd ,river ,stations ,distance ,distance of ,velocity ,velocity ,distanceto ,mouth ,lower ,station between from ,time between of below ,stations1,pittsburgh1between ,stations ,river1 ,starting-point1,miles per ,miles per ,stations in ,miles ,miles ,miles ,hour ,hour in ,hours ,ohio ,pittsburgh1 ,pa41 to ,wheeling1 ,w4 ,va4 #ij #ifg #ij #i4j #i4j #aj4j ,ohio ,wheeling1 ,w4 ,va41 to ,marietta1 ,ohio #hb #hgg #agb #e4i #g4b #ad ,ohio ,marietta1 ,ohio1 to ,parkersburg1 ,w4 ,va4 #ab #gie #ahd #j4i #d4h #ad ,ohio ,parkersburg to ,point ,pleasant1 ,w4 ,va4 #hj #ghc #bfd #f4g #e4c #ab ,ohio ,point ,pleasant to ,huntington1 ,w4 ,va4 #dd #gjc #cjh #aa4j #e4g #d ,ohio ,huntington to ,catlettsburg1 ,w4 ,va4 #i #fei #cag #j4h #d4a #aa ,ohio ,catlettsburg1 ,w4 ,va41 to ,portsmouth1 ,ohio #ch #fej #cee #e4j ,ohio ,portsmouth ,ohio1 to ,maysville1 ,ky4 #eb #fab #djg #e4b #e4j #aj ,ohio ,maysville1 ,ky41 to ,cincinnati1 ,ohio #fa #efj #dfh #f4h #e4b #i ,ohio ,cincinnati1 ,ohio1 to ,louisville1 ,ky4 #acf #dii #fjd #aa4d #e4i #ab ,ohio ,louisville1 ,ky41 to ,evansville1 ,ind4 #ahc #cfc #ghg #a4i #e4c #if ,ohio ,evansville1 ,ind41 to ,mt4 ,vernon ,ind4 #cf #ahj #hbc #i4j #e4c #d ,ohio ,mt4 ,vernon1 ,ind41 to ,paducah1 ,ky4 #aja #add #ibd #b4a #d4f #dh ,ohio ,paducah1 ,ky4 to ,cairo1 ,ill4 #dc #dc #ifg #b4i #d4b #ae ,monongahela,fairmont1 ,w4 ,va41 to ,lock ,no4 #b ,pa4 7,upper7 #ajg #aai #ajg #f4g #af ,little ,creston1 ,w4 ,kanawha ,va41 to ,dam4 ,no4 #d ,w4 ,va4 7,upper7 #af #dh #af #af4j #a ,new ,radford1 ,w4 ,va41 to ,hinton1 ,w4 ,va4 #gh #aci #gh #c4j #bf ,kanawha ,kanawha ,falls1 ,w4 ,va4 to ,charleston1 ,w4 ,va4 #cg #ie #cg #b4f #ad ,scioto ,columbus1 ,ohio1 to ,chillicothe1 ,ohio #eb #aaj #eb #d4g #aa ,miami ,dayton1 ,ohio1 to ,hamilton1 ,ohio #dd #gg #dd #ad4g #c ,kentucky ,highbridge1 ,ky41 to ,frankfort1 ,ky4 #eb #aag #eb #e4b #aj ,cumberland ,celina1 ,tenn4 to ,nashville1 ,tenn4 #aij #chc #aij #b4i #fd4e ,tennessee ,knoxville to ,chattanooga1 ,tenn4 #ahc #fce #ahc #c4b #eg ,,note4--,the velocities shown are the velocities of the crest of the flood wave and are not the average velocity of the flow of the river4 ,the velocity of the crest of the flood wave should be used in determining the time of concentration4 ,the flood crest velocity is slower then that of the river because of the storage in the river basin4 #ca4 ,character of ,surface4--,the proportion of total rainfall which will reach the sewers depends on the relative porosity1 or imperviousness1 and the slope of the surface4 ,absolutely impervious surfaces such as asphalt pavements or roofs of buildings will give nearly #ajj per cent run-off regardless of the slope1 after the surfaces have become thoroughly wet4 ,for unpaved streets1 lawns1 and gardens the steeper the slope the greater the per cent of run-off4 ,when the ground is already water soaked or is frozen the per cent of run-off is high1 and in the event of a warm rain on snow covered or frozen ground1 the run-off may be greater than the rainfall4 ,the run-off during the flood of ,march1 #aiac1 at ,columbus1 ,ohio1 was over #ajj per cent of the rainfall4 ,table #aebf shows the relative imperviousness of various types of surfaces when dry and on low slopes4 ,the estimates for relative imperviousness used in the design of the ,cincinnati intercepter are given in ,table #af4 ,,table #ae ,,values ,,of ,,relative ,,imperviousness ,roof surfaces assumed to be water-tight #j4gj- #j4ie ,asphalt pavements in good order 4#he- 4#ij ,stone1 brick1 and wood-block pavements with tightly cemented joints 4#ge- 4#he ,the same with open or uncemented joints 4#ej- 4#gj ,inferior block pavements with open joints 4#dj- 4#ej ,macadamized roadways 4#be- 4#fj ,gravel roadways and walks 4#ae- 4#cj ,unpaved surfaces1 railroad yards1 and vacant lots 4#aj- 4#cj ,parks1 gardens1 lawns1 and meadows1 depending on surface slope and character of subsoil 4#je- 4#be ,wooded areas or forest land1 depending on surface slope and character of subsoil 4#ja- 4#bj ,most densely populated or built up portion of a city 4#gj- 4#ij ,,table #af ,,coefficients ,,of ,,imperviousness ,,used ,,in ,,the ,,design ,,of ,,the ,,cincinnati ,,sewers ,character of ,residential1 ,improvement #bia4a ,a4 #bj per ,acre1 ,middle ,class1 ,detached ,dwellings1 ,yellow and ,combined ,tenement ,blue ,clay and ,industrial4 ,overlying ,typical ,commercial ,area1 #cj4d #ce4f ,a41 #ee per ,beds of ,a4 ,none ,undeveloped4 ,sand and ,acre4 ,clay1 ,sand ,shale and ,gravel and ,gravel ,sandstone ,area ,equivalent ,area ,per in ,per ,imp4 ,area1 in ,per ,cent #ajjj's,cent ,i1 #ajjj's #ajjj's,cent ,i1 of ,i1 ,square,total,esti- ,square ,square,total,esti-,total,esti- ,feet ,area mated ,feet ,feet ,area mated,area mated ,roofs3 ,public and commercial #hha4b #ff4e #j4ij #gic4j #ff4h #d4c #j4dj #d4h #j4dj ,residences #bhi4b #ah4f 4#ij #ac4a 4#ij ,barns and sheds #gi4b #e4a 4#ge #a4d 4#ge ,interior ,walks3 ,brick #g4e #j4f 4#dj #c4j #ce4f #b4c 4#dj #j4f 4#dj ,cement #aj4j #j4g 4#ge #g4e #bb4f #a4e 4#ge #b4f 4#ge ,street ,walks3 ,brick #f4a #j4e 4#dj #b4d #dh4b #c4a 4#dj #a4j 4#dj ,cement #aci4c #aj4e 4#ge #ajd4e #gh4a #e4j 4#ge #c4d 4#ge ,street ,pavements3 ,asphalt1 brick1 wood block #ade4e #aa4j 4#he #abc4g #e4j 4#he ,granite block #aaa4d #h4d 4#ge #hc4f #a4j 4#ge ,macadam and cobble #bc4b #a4h 4#dj #i4c #bch4f #ae4d 4#dj #d4h 4#dj ,granite and poor macadam #j4d 4#bj ,unimproved yards and lawns3 #fib4d #dd4g 4#ae ,tributary to paved gutters #eg4a 4#ae ,not tributary to paved gutters #g4i 4#aj ,total #acbd4bajj4j #aabg4jaeej4gajj4j #ajj4j ,impervious coefficient for the district #he4a #dd4d #ce4i ,c4 ,e4 ,gregory#bg states that ,i1 in the expression ,q ,,air is a function of the time of concentration or the duration of the storm4 ,if t represents the time of concentration and ,t represents the duration of the storm1 then when ,t is less than t ,i #j4aget1 but when ,t is greater than t1 ,i #j4aget7,t#d_/c 7,t t7#d_/c74 ,gregory condenses ,kuichling's rules with regard to the per cent run-off1 as follows3 #a4 ,the per cent of rainfall discharged from any given drainage area is nearly constant for heavy rains lasting equal periods of time4 #b4 ,this per cent varies directly with the area of impervious surface4 #c4 ,this per cent increases rapidly and directly or uniformly with the duration of the maximum intensity of the rainfall until a period is reached which is equal to the time required for the concentration of the drainage waters from the entire area at the point of observation1 but if the rainfall continues at the same intensity for a longer period this per cent will continue to increase at a much smaller rate4 #d4 ,this per cent becomes larger when a moderate rain has immediately preceded a heavy shower on a partially permeable territory4 ,gregory's formulas have not been generally accepted and are not widely used in practice4 ,marston stated3#bh ,all that engineers are at present1 warranted in doing is to make some deduction from #ajj per cent run-off 444 the deduction 444 being at present left to the engineer in view of his general knowledge and his familiarity with local conditions4 ,burger states#bi in the same connection3 ,in its application there will usually be as many results 7differing widely from each other7 as the number of men using it4 ,in spite of these objections the ,rational ,method is in more favor with engineers than any other method4 #cb4 ,empirical ,formulas4--,the difficulty of determining run-off with accuracy has led to the production by engineers of many empirical formulas for their own use4 ,some of these formulas have attracted wide attention and have been used extensively1 in some cases under conditions to which they are not applicable4 ,in general these formulas are expressions for the run-off in terms of the area drained1 the relative imperviousness1 the slope of the land1 and the rate of rainfall4 ,the ,burkli-,ziegler formula1 devised by a ,swiss engineer for ,swiss conditions and introduced into the ,united ,states by ,rudolph ,hering1 was one of the earliest of the empirical formulas to attract attention in this country4 ,it has been used extensively in the form ,q ,ci,a7,s,a71 in which,q the run-off in cubic feet per second2 i the maximum rate of rainfall in inches per hour over the entire area4 ,this is determined only by experience in the particular locality1 and is usually taken at from #a to #c inches per hour2 ,s the slope of the ground surface in feet per thousand1 ,a the area in acres2 ,c an expression for the character of the ground surface1 or relative imperviousness4 ,in this form of the expression ,c is recommended as #j4g4 ,the ,mc,math formula was developed for ,st4 ,louis conditions and was first published in ,transactions of the ,american ,society of ,civil ,engineers1 ,vol4 #af1 #ahhg1 p4 #ahc4 ,using the same notation as above1 the formula is1 ,q ,ci,a7,s,a71 ,mc,math recommended the use of ,c equal to #j4ge1 i as #b4ge inches per hour1 and ,s equal to #ae4 ,the formula has been extended for use with all values of ,c1 i1 ,s1 and ,a ordinarily met in sewerage practice4 ,fig4 #aa is presented as an aid to the rapid solution of the formula4 ,illustration3 ,,fig4 #aa4--;,diagram for the ,solution of ,mc,math's ,formula1 ,q ,aci,s,a4 ,other formulas have been devised which are more applicable to drainage areas of more than #a1jjj acres4#cj ,such areas are met in the design of sewers to enclose existing stream channels draining large areas4 ,kuichling's formulas1 published in #aija in the report of the ,new ,york ,state ,barge ,canal1 were devised for areas greater than #ajj square miles4 ,the following modification of these formulas for ordinary storms on smaller areas was published for the first time in ,american ,sewerage ,practice1 ,volume ,i1 by ,metcalf and ,eddy3 ,q #be1jjj7;,a #abe7 #ae4 ,illustration3 ,,fig4 #ab4--;,comparison of ,empirical ,run-off ,formulas4 ,it is to be noted that the only factor taken into consideration is the area of the watershed4 ,it is obvious that other factors such as the rate of rainfall1 slope1 imperviousness1 etc41 will have a marked effect on the run-off4 ,there are other run-off formulas devised for particular conditions1 some of which are of as general applicability as those quoted4 ,two formulas which are frequently quoted are3 ,fanning's1 ,q #bjj,m and ,talbot's ,q #ejj,m1 in which ,m is the area of the watershed in square miles4 ,a comprehensive treatment of the subject is given in ,american ,sewerage ,practice1 ,vol4 ,i1 by ,metcalf and ,eddy4 ,a comparison of the results obtained by the application of a few formulas to the same conditions is shown graphically in ,fig4 #ab4 ,it is to be noted that the divergence between the smallest and largest results is over #ajj per cent4 ,as these formulas are not all applicable to the same conditions1 the differences shown are due partially to an extension of some of them beyond the limits for which they were prepared4 #cc4 ,extent and ,intensity of ,storms4--,in the design of storm sewers it is necessary to decide how heavy a storm must be provided for4 ,the very heaviest storms occur infrequently4 ,to build a sewer capable of caring for all storms would involve a prohibitive expense over the investment necessary to care for the ordinary heavy storms encountered annually or once in a decade4 ,this extra investment would lie idle for a long period entailing a considerable interest charge for which no return is easily seen4 ,the alternative is to construct only for such heavy storms as are of ordinary occurrence and to allow the sewers to overflow on exceptional occasions4 ,the result will be a more frequent use of the sewerage system to its capacity1 a saving in the cost of the system1 and an occasional flooding of the district in excessive storms4 ,the amount of damage caused by inundations must be balanced against the extra cost of a sewerage system to avoid the damage4 ,a municipality which does not provide adequate storm drainage is liable1 under certain circumstances1 for damages occasioned by this neglect4 ,it is not liable if no drainage exists1 nor is it liable if the storm is of such unusual character as to be classed legally as an act of ,god4 ,kuichling's studies of the probabilities of the occurrence of heavy storms are published in ,transactions of the ,american ,society of ,civil ,engineers1 ,vol4 #ed1 #aije1 p4 #aib4 ,information on the extent of rain storms is given by ,francis in ,vol4 #g1 #ahgh1 p4 #bbd1 of the same publication4 ,kuichling expresses the intensity of storms which will occur1 once in #aj years as i #aje7t #bj71 once in #ae years as i #abj7t #bj71 in which i is the intensity of rainfall in inches per hour and t is the duration of the storm in minutes4 ,,chapter ,,iv ,,the ,,hydraulics ,,of ,,sewers #cd4 ,principles4--,the hydraulics of sewers deals with the application of the laws of hydraulics to the flow of water through conduits and open channels4 ,in so far as its hydraulic properties are concerned the characteristics of sewage are so similar to those of water that the same physical laws are applicable to both4 ,in general it is assumed that the energy lost due to friction between the liquid and the sides of the channel varies as some function of the velocity1 usually the square1 and that the total energy passing any section of the stream differs from the energy passing any other section only by the loss of energy due to friction4 ,the general expression for the flow of sewage would then be1 h 7f7,vn1 in which h is the head or energy lost between any two sections1 and ,v is the average velocity of flow between these sections4 ,it is to be noted in this general expression that the quantity and rate of flow past all sections is assumed to be constant4 ,this condition is known as steady flow4 ,problems are encountered in sewerage design which involve conditions of unsteady flow1 and methods of solution of them have been developed based on modifications of this general expression4 ,the average velocity of flow is computed by dividing the rate 7quantity7 of flow past any section by the cross-sectional area of the stream at that section4 ,this does not represent the true velocity at any particular point in the stream1 as the velocity near the center is faster than that near the sides of the channel4 ,the distribution of velocities in a closed circular channel is somewhat in the form of a paraboloid superimposed on a cylinder4 ,the laws of flow are expressed as formulas the constants of which have been determined by experiment4 ,it has been found that these constants depend on the character of the material forming the channel and the hydraulic radius4 ,the hydraulic radius is defined as the ratio of the cross-sectional area of the stream to the length of the wetted perimeter1 or line of contact between the liquid and the channel1 exclusive of the horizontal line between the air and the liquid4 #ce4 ,formulas4--,the loss of head due to friction caused by flow through circular pipes flowing full as expressed by ,darcy is1 h f7ld7 7,v#bb;g71 in which h is the head lost due to friction in the distance l1 ,v is the velocity of flow1 g is the acceleration due to gravity1 and f is a factor dependent on d and the material of which the pipe is made4 ,a formula for f expressed by ,darcy as the result of experiments on cast-iron pipe is1 f #j4jaii #j4jjaff;d1 in which d is the diameter in feet4 ,in using the formula with this factor the units used must be feet and seconds4 ,another form of the same expression is known as the ,chezy formula4 ,it is an algebraic transformation of the ,darcy formula1 but in the form shown here1 by the use of the hydraulic radius1 it is made applicable to any shape of conduit either full or partly full4 ,the ,chezy formula is1 ,v ,c7,,rs71 in which ,r is the hydraulic radius1 ,s the slope ratio of the hydraulic gradient1 and ,c a factor similar to f in the ,darcy formula4 ,kutter's formula was derived by the ,swiss engineers1 ,ganguillet and ,kutter1 as the result of a series of experimental observations4 ,it was introduced into the ,united ,states by ,rudolph ,hering and its derivation is given in ,hering and ,trautwine's translation of 8,the ,flow of ,water in ,open ,channels by ,ganguillet and ,kutter40 ,in ,english units it is1 ,v 7#a4ha_/n #da4fg 4#jjbh_/,s7_/7#a 7n_/,r77#da4fg 74#jjbh_/,s7777,,rs71 in which n is a factor expressing the character of the surface of the conduit and the other notation is as in the ,chezy formula4 ,v is the velocity in feet per second1 ,s is the slope ratio1 and ,r the hydraulic radius in feet4 ,the values of n to be used in all cases are not agreed upon1 but in general the values shown below are used in practice4 ,,values ,,of n ,,in ,,kutter',s ,,formula n ,,character ,,of ,,the ,,materials #j4jji ,well-planed timber4 #j4jaj ,neat cement or very smooth pipe4 #j4jab ,unplaned timber4 ,best concrete4 ,smooth masonry or brickwork1 or concrete sewers under ordinary #j4jac conditions4 #j4jae ,vitrified pipe or ordinary brickwork4 #j4jag ,rubble masonry or rough brickwork4 #j4jbj ,smooth earth4 #j4jce #j4jcj ,rough channels overgrown with grass4 #j4jej ,kutter's formula is of general application to all classes of material and to all shapes of conduits4 ,it is the most generally used formula in sewerage design4 ,the cumbersomeness of ,kutter's formula is caused somewhat by the attempt to allow for the effect of the low slopes of the ,mississippi ,river experiments on the coefficients4 ,the correctness of these experiments has not been well established and the slopes are so flat that the omission of the term #j4jjbh,s will have no appreciable effect on the value of ,v ordinarily used in sewer design4 ,the difference between the value of ,v determined by the omission of this term and the value of ,v found by including it is less than #a per cent for all slopes greater than #a in #a1jjj for #h inch pipe 7,r #j4afg feet74 ,as the diameter of the pipe or the hydraulic radius of the channel increases up to a diameter of #ac4jb feet 7,r #c4bh feet71 the difference becomes less and at this value of ,r there is no difference whether the slope is included or not4 ,for larger pipes the difference increases slowly4 ,for a #af foot pipe 7,r #d feet7 on a slope of #a in #a1jjj the difference is less than #j4b per cent1 and on a slope of #a in #aj1jjj the difference is approximately #a per cent4 ,flatter slopes than these are seldom used in sewer design1 except for very large sewers where careful determinations of the hydraulic slope are necessary4 ,it is therefore safe in sewer design to use ,kutter's formula in the modified form shown below in which the term 74#jjbh7,s has been omitted4 ,v 7#a4ha #da4fgn7,r,s_/n7,r #da4fgn74 ,bazin's formula is ,v 7,,rs7_/7 _/d7 in which and are constants for different classes of material4 ,for cast-iron pipe is #j4jjjjggbf and is #j4jjjjjfdg4 ,this formula is seldom used in sewerage design4 ,exponential formulas have been developed as the result of experiments which have demonstrated that ,v does not vary as the one-half power of ,r and ,s but that the relation should be expressed as1 ,v ,,crp,sq1 in which p and q are constants and ,c is a factor dependent on the character of the material4 ,the various formulas coming under this classification have been given the names of the experimenters proposing them4 ,examples of these formulas are3 ,flamant's1 in ,english units1 for new cast-iron pipe1 which is1 ,v #bcb,r4#gae,s4#egb1 and ,lamp's for the same material which is1 ,v #bjc4c,r4#fid,s4#eee4 ,these formulas are useful only for the material to which they apply1 but they can be used for conduits of any shape4 ,a4 ,v4 ,saph and ,e4 ,w4 ,schoder have shown#ca that the general formula for all materials lies between the limits1 ,v 7#ic to #adb7,s4#ej to 4#ee,r4#fc to 4#fi4 ,hazen and ,williams' formula is in the form1 ,v #a4ca;,,cr4#fc,s4#ed1 in which ,c is a factor dependent on the character of the material of the conduit4 ,the values of ,c as given by ,hazen and ,williams are1 ,c ,,character ,,of ,,material #ie ,steel pipe under future conditions4 7,riveted steel47 ,cast iron under ordinary future conditions and brick #ajj sewers in good condition4 #aaj ,new riveted steel1 and cement pipe4 #abj ,smooth wood or masonry conduits under ordinary conditions4 ,masonry conduits after some time and for very smooth pipes such as glass1 brass1 lead1 etc41 when old1 and for new #acj cast-iron pipe under ordinary conditions4 ,this formula is of as general application as ,kutter's formula and is easier of solution1 but being more recently in the field and because of the ease of the solution of ,kutter's formula by diagrams it is not in such general use4 ,exponential formulas are used more in waterworks than in sewerage practice4 ,manning's formula is in the form1 ,v #a4dhfn,r,s in which n is the same as for ,kutter's formula4 ,charts for the solution of ,manning's formula are given in ,eng4 ,news-,record1 ,vol4 #he1 #aibj1 p4 #hcg4 #cf4 ,solution of ,formulas4--,the solution of even the simplest of these formulas1 such as ,flamant's1 is laborious because of the exponents involved4 ,darcy's and ,kutter's formulas are even more cumbersome because of the character of the coefficient4 ,the labor involved in the solution of these formulas has resulted in the development of a number of diagrams and other short cuts4 ,since each formula involves three or more variables it cannot be represented by a single straight line on rectangular coordinate paper4 ,the simplest form of diagram for the solution of three or more variables is the nomograph1 an example of which is shown in ,fig4 #ac for the solution of ,flamant's formula4 ,a straight-edge placed on any two points of the scales of two different vertical lines will cross the other line at a point on the scale corresponding to its correct value in the formula4 ,such a diagram is in common use for the solution of problems for the flow of water in cast-iron pipe4 ,illustration3 ,,fig4 #ac4--;,diagram for the ,solution of ,flamant's ,formula for the ,flow of ,water in ,cast-iron ,pipe4 ,fig4 #ad has been prepared to simplify the solution of ,hazen and ,williams' formula4 ,the scales of slope for different classes of material are shown on vertical lines to the left of the slope line4 ,for use these scales must be projected horizontally on the slope line4 ,the scales for other factors are shown on independent reference lines4 ,for example let it be required to find the loss of head in a #ab inch pipe carrying #a cubic foot per second when the coefficient of roughness is #ajj4 ,a straight-edge placed at #a4j cubic feet per second on the quantity scale1 and #ab inches on the diameter scale crosses the slope line at 4#jjjib opposite the slope scale for c #ajj4 ,it crosses the velocity line at #a4ca feet per second4 ,kutter's formula is the most commonly used for sewer design and has been generally accepted as a standard in spite of its cumbersomeness4 ,fig4 #ae is a graphical solution of ,kutter's formula for small pipes1 and ,fig4 #af for larger pipes4 ,the diagrams are drawn on the nomographic principle and give solutions for a wide range of materials1 but they are specially prepared for the solution of problems in which n 4#jae4 ,in their preparation the effect of the slope on the coefficient has been neglected4 ,fig4 #ag is drawn on ordinary rectangular coordinate paper and can be used only for the solution of problems in which n 4#jae4 ,both diagrams are given for practice in the use of the different types4 ,illustration3 ,,fig4 #ad4--;,diagram for the ,solution of ,hazen and ,williams' ,formula4 ,illustration3 ,,fig4 #ae4--;,diagram for the ,solution of ,kutter's ,formula4 ,for values of n between #j4jaj and #j4jbj4 ,specially arranged for n #j4jae4 ,values of ,q from #j4a to #aj second-feet4 ,illustration3 ,,fig4 #af4--;,diagram for the ,solution of ,kutter's ,formula4 ,for values of n between #j4jaj and #j4jbj4 ,specially arranged for n #j4jae4 ,values of ,q from #aj to #a1jjj second-feet4 ,illustration3 ,,fig4 #ag4--;,diagram for the ,solution of ,kutter's ,formula4 ,illustration3 ,,fig4 #ah4--;,conversion ,factors for ,kutter's ,formula4 ,in ,figs4 #ae and #af the diameter scales are varied for different values of the roughness coefficient n4 ,the velocity scale is shown only for a value of n 4#jae4 ,the velocity for other values of n can be determined by the method given in the following paragraphs4 #cg4 ,use of ,diagrams4--,there are five factors in ,kutter's formula3 n1 ,q1 ,v1 d 7or ,r71 and ,s4 ,if any three of these are given the other two can be determined1 except when the three given are ,q1 ,v1 and d4 ,these three are related in the form ,q ,,av1 which is independent of slope or the character of the material4 ,there are only nine different combinations possible with these five factors1 which will be met in the solution of ,kutter's formula4 ,the solution of the problems by means of the diagrams is simple when the data given include n 4#jae4 ,for other given values of n the solution is more complicated4 ,results of the solution of types of each of the nine problems are given in ,table #ag and the explanatory text below4 ,if n is given and is equal to 4#jae1 the solution is simple4 ,for example in ,table #ag case #a1 example #a2 to be solved on ,fig4 #ae4 ,place a straight-edge at #a4j on the ,q line and at #f inches on the diameter line for n 4#jae4 ,the slope and the velocity will be found at the intersection of the straight-edge with these respective scales4 ,all problems in which n is given as 4#jae and the solution for which falls within the limits of ,fig4 #ae or #af should be solved by placing a straight-edge on the two known scales and reading the two unknown results at the intersection of the straight-edge and the remaining scales4 ,for example in case #a1 example #b find the intersection of the horizontal line representing ,q #ajj with the sloping diameter line representing d #dh inches4 ,the vertical slope line passing through this point represents ,s 4#jjfe and the sloping velocity line passing through this point represents #h4e feet per second4 ,in general problems in which n 4#jae1 can be solved on ,fig4 #ag by finding the intersection of the two lines representing the given data1 and reading the values of the remaining variables represented by the other two lines passing through this point4 ,,table #ag ,,solutions ,,of ,,problems ,,by ,,kutter',s ,,formula ,case ,example ,given ,found n ,q ,v d ,s n ,q ,v d ,s #a #a #j4jae #a4j #b4e #f #e4j #j4jege #a #b 4#jaeajj4j #h4e 4#jjfe #a #c 4#jbj #a4j #f #e4j 4#ac #a #d 4#jbjajj4j #dh #h4e 4#jabe #b #a 4#jae #e4j #j4jjjc #a4b #bh #b #b 4#jaj #e4j 4#jjjc #a4g #bc4e #c #a 4#jae #ah4jjb #d4jb4be #c #b 4#jah #ah4jjjh #b4ja4a #d #a 4#jae #b4j #b4e #ab 4#jjdge #d #b 4#jaa #b4j #b4e #ab 4#jjbb #e #a 4#jae #e4j #cf #ce4j 4#jjch #f #a 4#jah #e4j 4#jja #ahe4j #hj #g #a #c4j #ah4jjb #j4jai #a4g #g #b #ej4j #cf4jje 4#jab #g4j #h #a #f4j #b4e 4#jjc 4#jah #ba #i #a #d4b #ff4jjjei 4#jaaajj4j ,if n is given and is not equal to 4#jae the solution is not so simple4 ,in ,fig4 #ae and #af the diagram is so drawn that the position of the diameter scales for all values of n is fixed on the vertical 8diameter0 line4 ,the scales of diameter change for each value of n4 ,these scales of diameter are shown for each value of n from 4#jaj to 4#jbj on vertical lines to the left of the 8diameter0 line4 ,for use1 the proper diameter scale for any given value of n must be projected horizontally upon the vertical 8diameter0 line4 ,the velocity can be determined on ,fig4 #ae and #af1 only when the diameter has been determined and then only when the diameter scale for n equal 4#jae is used1 since the only scale shown for velocity is for n 4#jae4 ,for example1 in ,case #a1 ,example #c there are given n 4#jbj1 ,q1 and d4 ,find the intersection of the vertical line for n 4#jbj with the sloping diameter line for d #f inches4 ,project the intersection horizontally to the right to the vertical 8diameter0 line4 ,place a straight-edge at this point and at ,q #a4j on the quantity scale4 ,the required value of ,s is read at the intersection of the straight-edge and the slope scale and is equal to #j4ac4 ,the intersection of the straight-edge in this position with the velocity scale is not the required value of the velocity since the velocity scale is made out for n 4#jae and not 4#jbj4 ,it is necessary to change the position of the straight-edge so that it may lie on ,q equal #a4j and on d equal #f inches for n equal 4#jae4 ,the value of ,v is shown in this position as #e feet per second4 ,the reverse process for ,fig4 #ae and #af is illustrated by ,case #d1 ,example #b in which n 4#jaa and ,q and ,v are also given4 ,when ,q and ,v are given the value of d is fixed independent of all other factors4 ,therefore the value of d can be read from the scale with n 4#jae and is found to be #ab inches4 ,now find the value of d #ab inches on the scale for n 4#jaa and project on to the 8diameter0 line4 ,place the straight-edge at this point and at ,q #b4 ,the required slope is read as 4#jjbb4 ,fig4 #ag is prepared for the solution of problems in which n 4#jae only4 ,for problems in which n has some other value it is necessary to transform the data to equivalent conditions in which n 4#jae4 ,this is done by means of the conversion factors shown in ,fig4 #ah4 ,the given slope or velocity is multiplied by the proper factor to convert from or to the value of n 4#jae4 ,for example in ,case #a1 ,example #d there are given n 4#jbj1 ,q1 and d4 ,with ,q and d given the value of ,v can be read from ,fig4 #ag without conversion4 ,the corresponding value of ,s for n 4#jae is 4#jjfe4 ,it is now necessary to use the transformation diagram ,fig4 #ah4 ,the hydraulic radius of the given pipe is one foot4 ,on ,fig4 #ah at the intersection of the slope line for ,r #a4j foot and n 4#jbj the value of the factor is read as #a4ib4 ,since the given n is for rougher material than that represented by n 4#jae the required slope must be greater than for n 4#jae to give the same velocity4 ,it is therefore necessary to multiply 4#jjfe #a4ib and the required slope is 4#jabe4 ,in ,case #f1 ,example #a there are given n 4#jah1 d1 and ,s4 ,the remaining factors are to be solved by ,fig4 #ag4 ,solve first as though n 4#jae in order to find an approximate value of d or ,r4 ,in this case it is evident that d is greater than #eg inches4 ,the value of ,r is therefore about #a4be4 ,referring to ,fig4 #ah the conversion factor for the slope for n 4#jah is about #a4eb4 ,since the given slope for n 4#jah is 4#jja1 for an equal velocity and for n 4#jae the slope should be less4 ,therefore in reading ,fig4 #ag it is necessary to use a slope of 4#jjaa4eb 4#jjjff4 ,the diameter is found to be about #hj inches4 ,since this is nearer to the correct diameter the value of the conversion factor must be corrected for this approximation4 ,the hydraulic radius for an #hj inch pipe is #a4fg feet1 and the conversion factor from ,fig4 #ah is about #a4dh4 ,the slope for n 4#jae should be therefore 4#jjaa4dh 4#jjjfge and from ,fig4 #ag the required diameter and quantity are read as #hj inches and #ahe second-feet1 respectively4 ,if n is not given but must be solved for1 the solution on ,fig4 #ae and #af is relatively simple4 ,the desired value of n is read at the intersection of the sloping diameter line representing the known diameter and the horizontal projection of the intersection of the straight-edge with the vertical 8diameter0 line4 ,for example in ,case #g1 ,example #a there are given ,q1 d1 and ,s4 ,lay the straight-edge on the given values of ,q #c and ,s 4#jjb4 ,at the point where the straight-edge crosses the vertical 8diameter0 line project a horizontal line to the sloping diameter line for d #ah inches4 ,the vertical line passing through this point represents a value of n 4#jai4 ,in order to find the value of ,v lay the straight-edge on ,q #c and d #ah inches for n 4#jae4 ,the value of ,v is read as #a4g4 ,a slightly different condition is illustrated in the solution of ,case #h1 ,example #a in which ,q1 ,v and ,s are given4 ,determine first the value of d as though n 4#jae4 ,then proceed to determine n as in the preceding examples4 ,the solution for an unknown value of n on ,fig4 #ag is not so simple4 ,it must be determined by working backwards from the conversion factor4 ,for example in ,case #g1 ,example #b there are given ,q1 d1 and ,s4 ,the value of ,v is read directly as though n 4#jae as #g feet per second4 ,the value of ,s read for n 4#jae is 4#jjge4 ,but the given slope is 4#jje4 ,since the given slope is flatter than that for n 4#jae the conversion factor is less than unity and is therefore 4#jje4jjge #j4fg4 ,with this value of the conversion factor and the value of ,r given as #j4ge the value of n is read from ,fig4 #ah as slightly greater than 4#jab4 #ch4 ,flow in ,circular ,pipes ,partly ,full4--,the preceding examples have involved the flow in circular pipes completely filled4 ,the same methods of solution can be used for pipes flowing partly full except that the hydraulic radius of the wetted section is used instead of the diameter of the pipe4 ,diagrams are used to save labor in finding the hydraulic radius and the other hydraulic elements of conduits flowing partly full4 ,the hydraulic elements of a conduit for any depth of flow are3 7a7 ,the hydraulic radius1 7b7 the area1 7c7 the velocity of flow1 and 7d7 the quantity or rate of discharge4 ,the velocity and quantity when partly full as expressed in terms of the velocity and quantity when full as calculated by ,kutter's formula will vary slightly with different diameters1 slopes and coefficients of roughness4 ,the other elements are constant for all conditions for the same type of cross-section4 ,the hydraulic elements for all depths of a circular section for two different diameters and slopes are shown in ,fig4 #ai4 ,the differences between the velocity and quantity under the different conditions are shown to be slight1 and in practice allowance is seldom made for this discrepancy4 ,in the solution of a problem involving part full flow in a circular conduit the method followed is to solve the problem as though it were for full flow conditions and then to convert to partial flow conditions by means of ,fig4 #ai1 or to convert from partial flow conditions to full flow conditions and solve as in the preceding section4 ,for example let it be required to determine the quantity of flow in a #ab-;inch diameter pipe with n 4#jae when on a slope of 4#jje and the depth of flow is #c inches4 ,first find the quantity for full flow4 ,from ,fig4 #ae this is #b4j cubic feet per second4 ,the depth of flow of #c inches is one-fourth or #j4be of the full depth of #ab inches4 ,from ,fig4 #ai1 running horizontally on the #j4be depth line to meet the quantity curve1 the proportionate quantity at this depth is found to be on the #j4ac vertical line1 and the quantity of flow is therefore #b #j4ac #j4bf cubic feet per second4 ,illustration3 ,,fig4 #ai4--;,hydraulic ,elements of ,circular ,sections4 d #ab #j s 4#jjjd n 4#jae d #a #j s 4#ja n 4#jac ,another problem1 involving the reversal of this process is illustrated by the following example3 ,let it be required to determine the diameter and full capacity of a vitrified pipe sewer on a grade of #j4jjb if the velocity of flow is #c4j feet per second when the sewer is discharging at #cj per cent of its full capacity1 the depth of flow being #ab inches4 ,from ,fig4 #ai the depth of flow when the sewer is carrying #cj per cent of its full capacity is #j4ch of its full depth4 ,since the partial depth is #ab inches the full diameter is #ab4jch #ca4f inches4 ,the velocity of flow at #ch per cent depth is #hf per cent of the full velocity4 ,since the velocity given is #c4j feet per second1 the full velocity is #c4j4hf #c4e feet per second4 ,with a full velocity of #c4e feet per second and a diameter of #ca4f inches from ,fig4 #af the full capacity of the sewer is #ah cubic feet per second4 #ci4 ,sections ,other than ,circular4--,the ordinary shape used for small sewers is circular4 ,the difficulty of constructing large sewers in a circular shape1 special conditions of construction such as small head room1 soft foundations1 etc41 or widely fluctuating conditions of flow have led to the development of other shapes4 ,for conduits flowing full at all times a circular section will carry more water with the same loss of head than any other section under the same conditions4 ,in any section the smaller the flow the slower the velocity1 an undesirable condition4 ,the ideal section for fluctuating flows would be one that would give the same velocity of flow for all quantities4 ,such a section is yet to be developed4 ,sections have been developed that will give relatively higher velocities for small quantities of flow than are given by a circular section4 ,the best known of these sections is the egg shape1 the proportions and hydraulic elements of which are shown in ,fig4 #bj4 ,other shapes that have the same property1 but which were not developed for the same purpose are the rectangular1 the ,u-shape1 and the section with a cunette4 ,the egg-shaped section has been more widely used than any other special section4 ,it is1 however1 more difficult and expensive to build under certain conditions1 and has a smaller capacity when full than a circular sewer of the same area of cross-section4 ,various sections are illustrated in ,fig4 #bb and #bc4 ,the ,u-shaped section is suitable where the cover is small1 or close under obstructions where a flat top is desirable and the fluctuations of flow are so great as to make advantageous a special shape to increase the velocity of low flows4 ,the proportions of a ,u-shaped section are shown in ,fig4 #bc 7#f74 ,other sections used for the same purpose are the semicircular and special forms of the rectangular section4 ,the proportions and the hydraulic elements of the square-shaped section are shown in ,fig4 #ba4 ,this is useful under low heads where a flat roof is required to carry heavy loads1 and the fluctuations of flow are not large4 ,sections with cunettes have not been standardized4 ,a cunette is a small channel in the bottom of a sewer to concentrate the low flows1 as shown in ,fig4 #bb 7#g74 ,a cunette can be used in any shape of sewer4 ,illustration3 ,,fig4 #bj4--;,hydraulic ,elements of an ,egg-shaped ,section4 d #f #j s 4#jjjfe n 4#jae ,illustration3 ,,fig4 #ba4--;,hydraulic ,elements of a ,square ,section4 d #aj #j s 4#jjjd n 4#jae ,sections developed mainly because of the greater ease of construction under certain conditions are the basket handle1 the gothic1 the catenary1 and the horse shoe4 ,some of these shapes are shown in ,fig4 #bb and #bc4 ,they are suitable for large sewers on soft foundations1 where it is desirable to build the sewer in three portions1 such as invert1 side walls1 and arch4 ,they are also suitable for construction in tunnels where the shape of the sewer conforms to the shape of the timbering1 or in open cut work where the shape of the forms are easier to support4 ,problems of flow in all sections can be solved by determining the hydraulic radius involved1 and substituting directly in the desired formula1 or by the use of one of the diagrams after converting to the equivalent circular diameter4 ,the determination of the hydraulic radius of these special sections is laborious1 and hence other less difficult methods are followed4 ,problems are more commonly solved by converting the given data into an equivalent circular sewer1 solving for the elements of this circular sewer and then reconverting into the original terms1 or by working in the other direction4 ,the hydraulic elements of various sections when full are given in ,table #ah4 ,,table #ah ,,hydraulic ,,elements ,,of ,,sewer ,,sections4 ,,sewers ,,flowing ,,full4 ,section ,area in ,terms ,hydraulic ,vert4 ,dia4 ,source ,vertical ,radius in ,d in ,terms ,diameter terms of of ,dia4 d ,squared ,d#b,vertical ,dia4of ,equivalent ,d ,circular ,section ,circular #j4ghed #j4bej #a4jjj ,egg #j4eaej 4#aicaa4bie ,eng4 ,record1 ,vol4 #gb3 #fjh ,ovoid #j4efej 4#bjgja4bjh ,eng4 ,record1 ,vol4 #gb3 #fjh ,semi-elliptical #j4hagf 4#bdhga4jda ,eng4 ,news1 ,vol4 #ga3 #eeb ,catenary #j4ffbe 4#bbcga4aage ,eng4 ,record1 ,vol4 #gb3 #fjh ,horseshoe #j4hdgb 4#becfj4ihe ,eng4 ,record1 ,vol4 #gb3 #fjh ,basket handle #j4hcac 4#beecj4igi ,eng4 ,record1 ,vol4 #gb3 #fjh ,rectangular #a4cabe 4#bhfej4gifh ,hydraulic ,dgms4 and ,tbls4 ,garrett ,square 7#c sides #a4jjjj 4#ccc #j4gejj ,eng4 ,record1 wet7 ,vol4 #gb3 #fjh ,square 7#d sides #a4jjjj 4#bej #a4jjjj ,eng4 ,record1 wet7 ,vol4 #gb3 #fjh ,illustration3 #a4 ,standard ,egg-shaped ,section1 ,north ,shore ,intercepter1 ,chicago1 ,illinois4 ,illustration3 #b4 ,rectangular ,section1 ,omaha1 ,nebraska1 ,eng4 ,contracting1 ,vol4 #df1 p4 #di4 ,illustration3 #c4 ,trench in firm ground4 #d4 ,trench in ,rock4 ,,note4--,underdrains and ,wedges to be used only when ,ordered by the ,engineer4 ,illustration3 #g4 ,brick and ,concrete ,sewer showing cunette4 ,illustration3 #e4 ,soft ,foundation4 #f4 ,wet ground4 ,illustration3 #h4 ,brick and ,concrete ,sewer1 ,evanston1 ,ill41 ,eng4 ,contracting1 ,vol4 #df1 p4 #bbg4 ,,fig4 #bb4 ,illustration #a4 ,tunnel ,sections4 #b4 ,open ,cut ,sections4 ,type ,a4 ,type ,b4 ,type ,c4 ,type ,d4 ,where ,rock ,where ,rock ,where ,rock ,where ,rock #af #f ,where ,rock is more is more is between drops below ,sewer4 #be is above than #af than #g ,springing ,springing ,fill ,springing above and less ,line and #g ,line on ,line ,springing than #af above either ,line4 above ,springing ,side4 ,springing ,line on ,line on both ,sides4 both ,sides4 ,mill ,creek ,sewer1 ,st4 ,louis1 ,eng4 ,record1 ,vol4 #gj1 pp4 #dcd1 #dce4 ,illustration3 #c4 ,circular ,concrete ,section in ,soft and ,hard ,ground1 ,eng4 ,record1 ,vol4 #ei1 p4 #egj4 ,illustration3 #d4 ,semi-,elliptical ,section1 ,louisville1 ,ky41 ,eng4 ,news1 ,vol4 #fb1 p4 #daf4 ,illustration3 #e4 ,reinforced ,concrete ,sewer1 ,harlem ,creek1 ,st4 ,louis1 ,eng4 ,news1 ,vol4 #fj1 p4 #aca4 ,illustration3 #f4 ,u-,shaped ,section1 ,san ,francisco1 ,eng4 ,news1 ,vol4 #gc1 p4 #caj4 ,,fig4 #bc4 ,equivalent sections are sections of the same capacity for the same slope and coefficient of roughness4 ,they have not necessarily the same dimensions1 shape1 nor area4 ,the diameter of the equivalent circular section in terms of the diameter of each special section shown is given in ,table #ah4 ,the inside height of a sewer is spoken of as its diameter4 ,for example let it be required to determine the rate of flow in a #ed-;inch egg-shaped sewer on a slope of #j4jja when n 4#jae4 ,first convert to the equivalent circle4 ,from ,table #ah the diameter of the equivalent circle is #aa4bie times the diameter of the egg-shaped sewer1 which becomes in this case #dc inches4 ,from ,fig4 #af the capacity of a circular sewer of this diameter with ,s #j4jja and n 4#jae is #bh cubic feet per second1 which by definition is the flow in the egg-shaped sewer4 ,as an example of the reverse process let it be required to find the velocity of flow in an egg-shaped sewer flowing full and equivalent to a #dh-;inch circular sewer4 ,both sewers are on a slope of #j4jje and have a roughness coefficient of n 4#jae4 ,it is first necessary to find the quantity of flow in the circular sewer1 which by definition is the quantity of flow in the equivalent egg-shaped sewer4 ,the velocity of flow in the egg-shaped sewer is found by dividing this quantity by the area of the egg-shaped section4 ,as read from the diagram the quantity of flow is #ij cubic feet per second4 ,from ,table #ah the area of the egg-shaped sewer is #j4ea;,d#b where ,d is the diameter of the egg-shaped sewer1 and ,d #a4bie;d where d is the diameter of the equivalent circular sewer4 ,therefore the area equals 7#j4ea7 7#a4bie #d7b #ac4e square feet and the velocity of flow is #ijac4e #f4g feet per second4 ,this is slightly less than the velocity in the circular section4 ,some lines for egg-shaped sewers have been shown on ,fig4 #ag by which solutions can be made directly4 ,for other shapes1 and for sizes of egg-shaped sewers not found on ,fig4 #ag the preceding method or the original formula must be used for solution4 ,problems in partial flow in special sections are solved similarly to partial flow in circular sections1 by converting first to the conditions of full flow or by working in the opposite direction4 #dj4 ,non-uniform ,flow4--,in the preceding articles it is assumed that the mean velocity and the rate of flow past all sections are constant4 ,this condition is known as steady1 uniform flow4 ,in this article it will be assumed that conditions of steady non-uniform flow exist1 that is1 the rate of flow past all sections is constant1 but the velocity of flow past these sections is different for different sections4 ,under such conditions the surface of the stream is not parallel to the invert of the channel4 ,if the velocity of flow is increasing down stream the surface curve is known as the drop-down curve4 ,if the velocity of flow is decreasing down stream the surface curve is known as the backwater curve4 ,the hydraulic jump represents a condition of non-uniform flow in which the velocity of flow decreases down stream in such a manner that the surface of the stream stands normal to the invert of the channel at the point where the change in velocity occurs4 ,above and below this point conditions of uniform flow may exist4 ,conditions of non-uniform flow exist at the outlet of all sewers1 except under the unusual conditions where the depth of flow in the sewer under conditions of steady1 uniform flow with the given rate of discharge would raise the surface of water in the sewer1 at the point of discharge1 to the same elevation as the surface of the body of water into which discharge is taking place4 ,by an application of the principles of non-uniform flow to the design of outfall sewers1 smaller sewers1 steeper grades1 greater depth of cover1 and other advantages can be obtained4 ,the backwater curve is caused by an obstruction in the sewer1 by a flattening of the slope of the invert1 or by allowing the sewer to discharge into a body of water whose surface elevation would be above the surface of the water in the sewer1 at the point of discharge1 under conditions of steady1 uniform flow with the given rate of discharge4 ,the drop-down curve is caused by a sudden steepening of the slope of the invert2 by allowing a free discharge2 or by allowing a discharge into a body of water whose surface elevation would be below the surface of the water in the sewer1 at the point of discharge1 under conditions of steady1 uniform flow with the given rate of discharge4 ,the last described condition is common at the outlet of many sewers1 hence the common occurrence of the drop-down curve4 ,the hydraulic jump is a phenomenon which is seldom considered in sewer design4 ,if not guarded against it may cause trouble at overflow weirs and at other control devices1 in grit chambers1 and at unexpected places4 ,the causes of the hydraulic jump are sufficiently well understood to permit designs that will avoid its occurrence1 but if it is allowed to occur the exact place of the occurrence of the jump and its height are difficult1 if not impossible1 to determine under the present state of knowledge concerning them4 ,the hydraulic jump will occur when a high velocity of flow is interrupted by an obstruction in the channel1 by a change in grade of the invert1 or the approach of the velocity to the 8critical0 velocity4 ,the 8critical0 velocity is equal to 7gh71 where h is the depth of flow and g is the acceleration due to gravity4 ,the velocity in the channel above the jump must be greater than 7gh#a71 where h#a is the depth of flow in the channel above the jump4 ,the velocity in the channel below the jump must be greater than 7gh#b71 where h#b is the depth of flow below the jump4 ,the jump will not take place unless the slope of the invert of the channel is greater than g,c#b1;in which ,c is the coefficient in the ,chezy formula4 ,with this information it is possible to avoid the jump by slowing down the velocity by the installation of drop manholes1 flight sewers1 or by other expedients4 ,the shape of the drop-down curve can be expressed1 in some cases1 by mathematical formulas of more or less simplicity1 dependent on the shape of the conduit4 ,the formula for a circular conduit is complicated4 ,due to the assumptions which must be made in the deduction of these formulas1 the results obtained by their use are of no greater value than those obtained by approximate methods4 ,a method for the determination of the drop-down curve is given by ,c4 ,d4 ,hill4#cb ,in this method it is necessary that the rate of flow past all sections shall be the same2 that the depth of submergence at the outlet shall be known2 and that the depth of flow at some unknown distance up the stream shall be assumed4 ,the shape and material of construction of the sewer and the slope of the invert should also be known4 ,the problem is then to determine the distance between cross-sections1 one where the depth of flow is known1 and the other where the depth of flow has been assumed4 ,this distance can be expressed as follows3 ,l 77d#b d#a7 7,h#a ,h#b777,s ,s#a7 7d ,h7,s1 in which ,l the distance between cross-sections2 d#a the depth of flow at the lower section2 d#b the depth of flow at the upper section2 ,h#a the velocity head at the lower section2 ,h#b the velocity head at the upper section2 ,s the hydraulic slope of the stream surface2 ,s#a the slope of the invert of the sewer4 ,in order to solve such problems with a satisfactory degree of accuracy the difference between d#a and d#b should be taken sufficiently small to divide the entire length of the sewer to be investigated into a large number of sections4 ,the solution of the problem requires the determination of the wetted area1 the hydraulic radius1 and other hydraulic elements at many sections4 ,the labor involved can be simplified by the use of diagrams1 such as ,fig4 #ai1 or by specially prepared diagrams such as those accompanying the original article by ,c4 ,d4 ,hill4 ,the solution of the problem can be simplified by tabulating the computations as follows3 ,,drop-,,down ,,curve ,,computation ,,sheet ,uniform discharge4 ,varying depth ,d ,q ,a ,v ,q,a ,s#a ,l 7d#a ,h#a7,s#a #a #b #c #d #e #f #g #h #i #aj #aa #ab #ac ,depth ,r,h,h#a;d#a,v,s,s#a,l ,elevation ,h#a ,ddd#a ,sewer,w4 ,l4 ,at the head of the computation sheet should be recorded the diameter of the sewer in feet1 the assumed volume of flow1 the area of the full cross-section of the sewer1 the velocity of the assumed volume flowing through the full bore of the sewer1 and the gradient or slope of the invert4 ,in the #ast column enter the assumed depth in decimal parts of the diameter for each cross-section2 in the #bnd column enter the same depth in feet2 in the #crd column enter the difference in feet between the successive cross-sections2 in the #dth column enter the hydraulic radius corresponding to the depth at each cross-section2 in the #hth column enter the velocity1 equal to the volume divided by the wetted area1 for each cross-section2 in the #eth column enter the corresponding velocity head2 in the #fth column enter the difference between the velocity heads at successive cross-sections2 in the #gth column enter the difference between the quantities in the third and in the sixth columns2 in the #ith column enter the hydraulic slope corresponding to the velocity and hydraulic radius of each cross-section2 in the #ajth column enter the difference between the hydraulic slope and the slope or gradient of the sewer2 in the #aath column enter the computed distance between successive cross-sections2 in the #abth column enter the elevation of the bottom of the sewer at each cross-section2 and in the #acth column enter the corresponding elevation of the surface of the water4 ,the table should be filled in until the distance to the required section is determined1 or if the distance is known1 it should be filled in until the depth of flow with the assumed rate of discharge has been checked4 ,if only the depth of flow at some section is known and it is required to know the maximum rate of flow with a free discharge1 or a discharge with a submergence at the outlet less than the depth of flow with the maximum rate of discharge1 it is necessary to make a preliminary estimate of the maximum rate of flow in order to fill in the quantity ,q at the head of the table4 ,the procedure should be as follows3 #ast4 ,assume a depth of flow at the outlet4 #bnd4 ,compute the area 7,a7 and the hydraulic radius 7,r7 at the known section and at the outlet4 #crd4 ,determine the area and the hydraulic radius half way between these two sections as the mean of the areas and the hydraulic radii of the two sections4 #dth4 ,determine the rate of flow through the sewer from the condition that the difference in head at the two sections is the head lost due to friction caused by the average velocity of flow between the sections 7equals 7l,v#b77;,c#b,r77 plus the gain in velocity head 7equals ,v#bb 7,v#ab77b;g771 which then combined and transposed result in the expression3 ,q ,,aa#a;,a#b 7#b,rgh7#b;,a#ab;,a#bb;gl 7,a#a ,a#b77;,a#b;,c#b,r777 in which ,q rate of flow2 ,a the area determined in the #crd step2 ,a#a the area at the upper cross-section2 ,a#b the area at the lower cross-section2 ,c the coefficient in the ,chezy formula2 g the acceleration due to gravity2 h the difference in elevation of the surface of the stream at the two cross-sections2 l the distance between the cross-sections2 ,r the hydraulic radius determined in the third step4 #eth4 ,continue this process by assuming different depths at the outlet until the maximum rate of discharge has been found by trial4 ,with this rate of discharge and depth of flow at the outlet1 the depth of flow at the known section can be checked4 ,if appreciably in error a correction should be made by the assumption of a different depth of flow at the outlet4 ,the approximate character of the method is scarcely worthy of the refinement in the results which will be obtained by checking back for the depth of flow at the known section4 ,it will be sufficiently accurate to assume the rate of flow obtained by trial from the preceding expression1 as the maximum rate of discharge from the sewer4 ,,chapter ,v ,,design ,,of ,,sewerage ,,systems #da4 ,the ,plan4--,good practice demands that a comprehensive plan for a sewerage system be provided for the needs of a community for the entire extent of its probable future growth1 and that sewers be constructed as needed in accordance with this plan4 ,sewerage systems may be laid out on any one of three systems3 separate1 storm1 or combined4 ,a separate system of sewers is one in which only sanitary sewage or industrial wastes or both are allowed to flow4 ,storm sewers carry only surface drainage1 exclusive of sanitary sewage4 ,combined sewers carry both sanitary and storm sewage4 ,the use of a combined or a separate system of sewerage is a question of expediency4 ,portions of the same system may be either separate1 combined1 or storm sewers4 ,some conditions favorable to the adoption of the separate system are where3 a4 ,the sanitary sewage must be concentrated at one outlet1 such as at a treatment plant1 and other outlets are available for the storm drainage4 b4 ,the topography is flat necessitating deep excavation and steeper grades for the larger combined sewers4 c4 ,the sanitary sewers must be placed materially deeper than the necessary depth for the storm-water drains4 d4 ,the sewers are to be laid in rock1 necessitating more difficult excavation for the larger combined sewers4 e4 ,an existing sewerage system can be used to convey the dry weather flow1 but is not large enough for the storm sewage4 f4 ,the city finances are such that the greater cost of the combined system cannot be met and sanitary drainage is imperative4 g4 ,the district to be sewered is an old residential section where property values are not increasing and the assessment must be kept down4 ,some additional points given in a report by ,alvord and ,burdick to the city of ,billings1 ,montana1 are3 ,the separate system of sewerage should be used1 where3 #ast4 ,storm water does not require extensive underground removal1 or where it can be concentrated in a few shallow underground channels4 #bnd4 ,drainage areas are short and steep facilitating rapid flow of water over street surfaces to the natural water courses4 #crd4 ,the sanitary sewage must be pumped4 #dth4 ,sewers are being built in advance of the city's development to encourage its growth4 #eth4 ,the existing sewer is laid at grades unsuitable for sanitary sewage1 it can be used as a storm sewer4 ,a combined system must be relatively larger than a separate storm sewer as the latter may overflow on exceptional occasions1 but the former never4 ,a combined system of sewerage should be used where3 #ast4 ,it is evident that storm and sanitary sewerage must be provided soon4 #bnd4 ,both sanitary and storm sewage must be pumped4 #crd4 ,the district is densely built up4 #db4 ,preliminary ,map4--,the first step in the design of a sewerage system is the preparation of a map of the district to be served within the limits of its probable growth4 ,the map should be on a scale of at least #bjj feet to the inch in the built up sections or other areas where it is anticipated that sewers may be built1 and where much detail is to be shown a scale as large as #dj feet to the inch may have to be used4 ,the adoption of so large a scale will usually necessitate the division of the city or sewer district into sections4 ,a key map should be drawn to such a scale that the various sections represented by separate drawings can all be shown upon it4 ,in preparing the enlarged portions of the map it is not necessary to include these portions of the city in which it is improbable that sewers will be constructed1 such as parks and cemeteries4 ,the contour interval should depend on the character of the district and the slope of the land4 ,in those sections drawn to a scale of #bjj feet to the inch for slopes over #e per cent1 the contour interval need not be closer than #aj feet4 ,for slopes between #a and #e per cent the contour interval should be #e feet4 ,for flatter slopes the interval should not exceed #b feet1 and a one foot interval is sometimes desirable4 ,in general the horizontal distances between contours should not exceed #djj feet and they should be close enough to show important features of the natural drainage4 ,elevations should also be given at street intersections1 and at abrupt changes in grade4 ,for portions of the map on a smaller scale the contours need be sufficiently close to show only the drainage lines and the general slope of the land4 ,the following may be shown on the preliminary map3 the elevation of lots and cellars2 the character of the built up districts1 whether cheap frame residences1 flat-roof buildings1 manufacturing plants1 etc42 property lines2 width of streets between property lines and between curb lines2 the width and character of the sidewalks and pavements2 street car and railroad tracks2 existing underground structures such as sewers1 water pipes1 telephone conduits1 etc42 the location of important structures which may have a bearing on the design of the sewers such as bridges1 railroad tunnels1 deep cuts1 culverts1 etc42 and the location of possible sewer outlets and the sites for sewage disposal plants4 ,fig4 #bd shows a preliminary map for a section of a city1 on which the necessary information has been entered4 ,the map is made from survey notes4 ,all streets are paved with brick4 ,the alleys are unpaved4 ,the entire section is built up with high-class detached residences averaging one to each lot4 ,the lots vary from #a to #c feet above the elevation of the street4 #dc4 ,layout of the ,separate ,system4--,upon completion of the preliminary map a tentative plan of the system is laid out4 ,the lines of the sewer pipe are drawn in pencil1 usually along the center line of the street or alley in such a manner that a sewer will be provided within #ej feet or less of every lot4 ,the location of the sewers should be such as to give the most desirable combination of low cost1 short house connections1 proper depth for cellar drainage1 and avoidance of paved streets4 ,some dispute arises among engineers as to the advisability of placing pipes in alleys1 although there is less opposition to so placing sewers than any other utility conduit4 ,the principal advantage in placing sewers in alleys is to avoid disturbing the pavement of the street1 but if both street and alley are paved it is usually more economical to place the sewer in the street as the house connections will be shorter4 ,on boulevards and other wide streets such as ,meridian ,avenue in ,fig4 #bd1 the sewers are placed in the parking on each side of the street1 rather than to disturb the pavement and lay long house connections to the center of the street4 ,all pipes should be made to slope1 where possible1 in the direction of the natural slope of the ground4 ,the preliminary layout of the system is shown in ,fig4 #bd4 ,the lowest point in the portion of the system shown is in the alley between ,alabama and ,tennessee ,streets4 ,the flow in all pipes is towards this point1 and only one pipe drains away from any junction1 except that more than one pipe may drain from a terminal manhole on a summit4 #dd4 ,location and ,numbering of ,manholes4--,manholes are next located on the pipes of this tentative layout4 ,good practice calls for the location of a manhole at every change in direction1 grade1 elevation1 or size of pipe1 except in sewers #fj inches in diameter or larger4 ,the manholes should not be more than #cjj to #ejj feet apart1 and preferably as close as #bjj to #cjj feet4 ,in sewers too small for a man to enter the distance is fixed by the length of sewer rods which can be worked successfully4 ,in the larger sewers the distances are sometimes made greater but inadvisedly so1 since quick means of escape should be provided for workmen from a sudden rise of water in the sewer1 or the effect of an asphyxiating gas4 ,in the preliminary layout the manholes are located at pipe intersections1 changes in direction1 and not over #cjj to #ejj feet apart on long straight runs at convenient points such as opposite street intersections where other sewers may enter4 ,no standard system of manhole numbering has been adopted4 ,a system which avoids confusion and is subject to unlimited extension is to number the manholes consecutively upwards from the outlet1 beginning a new series of numbers prefixed by some index number or letter for each branch or lateral4 ,this system has been followed with the manholes on ,fig4 #bd4 ,illustration3 ,,fig4 #bd4--,typical ,map ,used in the ,design of a ,separate ,sewer ,system4 ,illustration3 ,,fig4 #be4--,typical ,map ,used in the ,design of a ,storm ,sewer ,system4 #de4 ,drainage ,areas4--,the quantity of dry weather sewage is determined by the population rather than the topography4 ,lot lines and street intersections or other artificial lines marking the boundaries between districts are therefore taken as watershed lines for sanitary sewers4 ,the quantity of sewage to be carried and the available slope are the determining factors in fixing the diameter of the sewer4 ,since there may be no change in diameter or slope between manholes the quantity of sewage delivered by a sewer into any manhole will determine the diameter of the sewer between it and the next manhole above4 ,in order to determine the additional amount contributed between manholes a line is drawn around the drainage area tributary to each manhole4 ,this line generally follows property lines and the center lines of streets or alleys1 its position being such that it includes all the area draining into one manhole1 and excludes all areas draining elsewhere4 ,an entire lot is usually assumed to lie within the drainage area into which the building on the lot drains4 ,in laying out these areas it is best to commence at the upper end of a lateral and work down to a junction4 ,then start again at the upper end of another lateral entering this junction1 and continue thus until the map has been covered4 ,the areas are given the same numbers as the manholes into which they drain4 ,the dividing lines for the drainage areas on ,fig4 #bd are shown as dot and dash lines1 and the areas enclosed are appropriately numbered4 ,if more than one sewer drains into the same manhole the area should be subdivided so that each subdivision encloses only the area contributing through one sewer4 ,such a condition is shown at manhole ,c#b4 ,the areas are designated by subletters or symbols corresponding to the symbol used for the sewer into which they drain4 ,for example1 the two areas contributing to manhole ,c#b are lettered ,c#b,k and ,c#b;,d4 ,the sewer from manhole ,c#c to ,c#b receives no addition1 it being assumed that all the lots adjacent to it drain into the sewer on the alley4 ,there is therefore no area ,c#b4 ,likewise there is no area ,a#a;,c4 #df4 ,quantity of ,sewage4--,the remaining work in the computation of the quantity of sewage is best kept in order by a tabulation4 ,table #ai shows the computations for the sewers discharging from the east into manhole ,no4 #adb4 ,the computation should begin at the upper end of a lateral1 continue to a junction1 and then start again at the upper end of another lateral entering this junction4 ,each line in the table should be filled in completely from left to right before proceeding with the computations on the next line4 ,in the illustrative solution in ,table #ai1 computations for quantity have not been made between manholes where it was apparent that there would be an insufficient additional quantity to necessitate a change in the size of the pipe4 ,in making these computations the assumptions of quantity and other factors given below indicate the sort of assumptions which must be made1 based on such studies as are given in ,chapter ,,iii4 ,the density of population was taken as #bj persons per acre1 the assumption being based on the census and the character of the district4 ,the average sanitary sewage flow was taken as #ajj gallons per capita per day4 ,the per cent which the maximum dry weather flow is of the average was taken as ,m #ejj,p1 in which ,p is the population in thousands4 ,the per cent is not to exceed #ejj nor to be less than #aej4 ,the rate of infiltration of ground water was assumed as #ej1jjj gallons per mile of pipe per day4 ,in the first line of ,table #ai1 the entries in columns 7#a7 to 7#f7 are self-explanatory4 ,there are no entries in columns 7#g7 to 7#aj71 as no additional sewage is contributed between manholes #c4e and #c4d4 ,in column 7#aa71 #bbej persons are recorded as the number tributary to manhole ,no4 #c4e in the district to the north and west4 ,these people contribute an average of #ajj gallons per person per day1 or a total of #j4cdf second foot4 ,this quantity is entered in column 7#ac74 ,the figure in column 7#ad7 is obtained from the expression ,m 7#ejj7,p4 ,column 7#ae7 is 4#ja of the product of columns 7#ac7 and 7#ad74 ,column 7#af7 is the product of the length of pipe between manholes #c4e and #c4d1 and the ground water unit reduced to cubic feet per second4 ,column 7#ag7 is the sum of column 7#af71 and all of the ground water tributary to manhole #c4e1 which is not recorded in the table4 ,column 7#ah7 is the sum of columns 7#ae7 and 7#ag74 ,no new principle is represented in the second and third lines4 ,in the fourth line the first #aj columns need no further explanation4 ,the 7#aath7 column is the sum of the 7#ajth7 column1 and the 7#aath7 column in the third line4 ,it represents the total number of persons tributary to manhole #c4d on lateral ,no4 #h4 ,column 7#ac7 in the fourth line is the sum of column 7#ac7 in the third line and the 7#abth7 column in the fourth line1 and the 7#aeth7 column in the fourth line is the product of the #b preceding columns in the fourth line4 ,note that in no case is the figure in column 7#ae7 the sum of any previous figures in column 7#ae74 ,with this introduction the student should be able to check the remaining figures in the table1 and should compute the quantity of sewage entering manhole ,no4 #adb from the west1 making reasonable assumptions for the tributary quantities from beyond the limits of the map4 ,,table #ai ,,computations ,,for ,,quantity ,,of ,,sewage ,,for ,a ,,separate ,,sewerage ,,system ,on ,street ,from ,to ,street ,from ,to ,length,mark of,area1 ,street ,manhole,manhole ,feet ,added ,acres ,areas ,nebraska ,map margin,alley ,s4 #c4e #c4d #cch ,st4 ,grant ,st4 ,alley ,s4 ,railroad ,e4 of #h4c #h4b #cbh #h4b #b4g of ,grant ,missouri ,st4 ,st4 ,alley ,s4 ,e4 of ,e4 of #h4b #h4a #cee #h4a #c4da of ,grant ,missouri ,kansas ,st4 ,st4 ,st4 ,alley ,s4 ,e4 of ,nebraska #h4a #c4d #cdjc4dh #b4fh of ,grant ,kansas ,st4 ,st4 ,st4 ,nebraska ,alley ,s4 ,alley ,s4 #c4d #c4c #chj ,st4 of ,grant of ,st4 ,meridian #g4a ,alley ,s4 ,railroad ,nebraska #g4b #c4c #hjjc4cg #g4ad of ,st4 ,meridian ,nebraska ,alley ,s4 ,alley ,s4 #c4c #c4b #cjd ,st4 of of ,smith ,meridian ,av4 #f4a ,alley ,s4 ,railroad ,nebraska #f4b #c4b #fjic4bf #c4hb of ,smith ,st4 ,ave4 ,nebraska ,alley ,s4 ,s4 of #c4b #c4a #cjj ,st4 of ,smith ,cordovez ,ave4 ,st4 ,s4 of ,railroad ,nebraska #d4a #c4a #dajc4ad #c4aj ,cordovez ,st4 ,st4 ,s4 of ,map margin,nebraska #e4a #c4a #chjc4ae #b4fi ,cordovez ,st4 ,st4 ,nebraska ,s4 of ,long ,st4 #c4a #adh #agb ,st4 ,cordovez ,st4 ,long ,st4 ,map margin,nebraska #adi #adh #chj #adh #a4ec ,st4 ,long ,st4 ,nebraska ,n4 #adh #adg #dib ,st4 ,carolina ,st4 ,long ,st4 ,n4 ,georgia #adg #adf #dcj ,carolina ,st4 ,st4 ,long ,st4 ,georgia ,harris ,st4 #adf #ade #dai #adf #j4ha ,st4 #b4a ,long ,st4 ,harris ,st4,tennessee #ade #adc #gbeadc-ade #f4f ,st4 ,column ,no4 7#b7 7#c7 7#d7 7#e7 7#f7 7#g7 7#h7 7#a7 ,on ,street ,from ,to ,street ,population,number ,total ,avg4 ,street per ,acre of ,persons ,sanitary ,persons,tributary ,flow1 ,c4,f4,s4 ,nebraska ,map margin,alley ,s4 #bbej #j4jjjj ,st4 ,grant ,st4 ,alley ,s4 ,railroad ,e4 of #bj #ed #ed 4#jjhd of ,grant ,missouri ,st4 ,st4 ,alley ,s4 ,e4 of ,e4 of #bj #fh #abb 4#jajf of ,grant ,missouri ,kansas ,st4 ,st4 ,st4 ,alley ,s4 ,e4 of ,nebraska #bj #ed #agf 4#jjhd of ,grant ,kansas ,st4 ,st4 ,st4 ,nebraska ,alley ,s4 ,alley ,s4 #bdbh 4#jjjj ,st4 of ,grant of ,st4 ,meridian ,alley ,s4 ,railroad ,nebraska #bj #adb #adb 4#jbba of ,st4 ,meridian ,nebraska ,alley ,s4 ,alley ,s4 #befh 4#jjjj ,st4 of of ,smith ,meridian ,av4 ,alley ,s4 ,railroad ,nebraska #bj #gf #gf 4#jaai of ,smith ,st4 ,ave4 ,nebraska ,alley ,s4 ,s4 of #bfdd 4#jjjj ,st4 of ,smith ,cordovez ,ave4 ,st4 ,s4 of ,railroad ,nebraska #bj #fb #fb 4#jjif ,cordovez ,st4 ,st4 ,s4 of ,map margin,nebraska #bj #ed #ed 4#jjhd ,cordovez ,st4 ,st4 ,nebraska ,s4 of ,long ,st4 #bgfj 4#jjjj ,st4 ,cordovez ,st4 ,long ,st4 ,map margin,nebraska #bj #ca #ca 4#jjdh ,st4 ,long ,st4 ,nebraska ,n4 #bgia 4#jjjj ,st4 ,carolina ,st4 ,long ,st4 ,n4 ,georgia #bgiaa4jjjcc ,carolina ,st4 ,st4 ,long ,st4 ,georgia ,harris ,st4 #bj #af #bhjg 4#jjbe ,st4 ,long ,st4 ,harris ,st4,tennessee #bj #acb #bicf 4#jbje ,st4 ,column ,no4 7#b7 7#c7 7#i7 7#aj7 7#aa7 7#ab7 7#a7 ,on ,street ,from ,to ,street ,cumulative,per cent ,total ,street ,avg4 ,max4 ,max4 ,sanitary ,sanitary,sanitary1 ,flow1 is of ,c4,f4,s4 ,c4,f4,s4 ,average ,nebraska ,map margin,alley ,s4 #j4cdf #dbe #a4dg ,st4 ,grant ,st4 ,alley ,s4 ,railroad ,e4 of 4#jjhd #ejj #j4jda of ,grant ,missouri ,st4 ,st4 ,alley ,s4 ,e4 of ,e4 of 4#jaij #ejj #j4jie of ,grant ,missouri ,kansas ,st4 ,st4 ,st4 ,alley ,s4 ,e4 of ,nebraska 4#jbgd #ejj #j4acg of ,grant ,kansas ,st4 ,st4 ,st4 ,nebraska ,alley ,s4 ,alley ,s4 4#cgc #dbc #a4eh ,st4 of ,grant of ,st4 ,meridian ,alley ,s4 ,railroad ,nebraska 4#jbba #ejj #j4aaa of ,st4 ,meridian ,nebraska ,alley ,s4 ,alley ,s4 4#cie #dad #a4fc ,st4 of of ,smith ,meridian ,av4 ,alley ,s4 ,railroad ,nebraska 4#jaai #ejj #j4jfj of ,smith ,st4 ,ave4 ,nebraska ,alley ,s4 ,s4 of 4#djg #dad #a4fh ,st4 of ,smith ,cordovez ,ave4 ,st4 ,s4 of ,railroad ,nebraska 4#jjif #ejj #j4jdh ,cordovez ,st4 ,st4 ,s4 of ,map margin,nebraska 4#jjhd #ejj #j4jdb ,cordovez ,st4 ,st4 ,nebraska ,s4 of ,long ,st4 4#dbe #dji #a4gd ,st4 ,cordovez ,st4 ,long ,st4 ,map margin,nebraska 4#jjdh #ejj #j4jbd ,st4 ,long ,st4 ,nebraska ,n4 4#dcj #dji #a4gf ,st4 ,carolina ,st4 ,long ,st4 ,n4 ,georgia 4#dcj #dji #a4gf ,carolina ,st4 ,st4 ,long ,st4 ,georgia ,harris ,st4 4#dcc #djg #a4gf ,st4 ,long ,st4 ,harris ,st4,tennessee 4#ded #djc #a4hc ,st4 ,column ,no4 7#b7 7#c7 7#ac7 7#ad7 7#ae7 7#a7 ,on ,street ,from ,to ,street ,increment,cumulative,total ,line ,street of ,ground ,ground ,flow1 ,number ,water1 ,water1 ,c4,f4,s4 ,c4,f4,s4 ,c4,f4,s4 ,nebraska ,map margin,alley ,s4 #j4jje #j4jahg #a4ff #a ,st4 ,grant ,st4 ,alley ,s4 ,railroad ,e4 of 4#jjdh 4#jjdh #j4jdf #b of ,grant ,missouri ,st4 ,st4 ,alley ,s4 ,e4 of ,e4 of 4#jjeb 4#jaj #j4aje #c of ,grant ,missouri ,kansas ,st4 ,st4 ,st4 ,alley ,s4 ,e4 of ,nebraska 4#jjej 4#jae #j4aeb #d of ,grant ,kansas ,st4 ,st4 ,st4 ,nebraska ,alley ,s4 ,alley ,s4 4#jjeh 4#bjh #a4gi #e ,st4 of ,grant of ,st4 ,meridian ,alley ,s4 ,railroad ,nebraska 4#jaag 4#jaag #j4abc #f of ,st4 ,meridian ,nebraska ,alley ,s4 ,alley ,s4 4#jjde 4#bbd #a4he #g ,st4 of of ,smith ,meridian ,av4 ,alley ,s4 ,railroad ,nebraska 4#jjhi 4#jjhi #j4jfi #h of ,smith ,st4 ,ave4 ,nebraska ,alley ,s4 ,s4 of 4#jjdd 4#bcg #a4ib #i ,st4 of ,smith ,cordovez ,ave4 ,st4 ,s4 of ,railroad ,nebraska 4#jjf 4#jjf #j4jed #aj ,cordovez ,st4 ,st4 ,s4 of ,map margin,nebraska 4#jjef 4#jjef #j4jdh #aa ,cordovez ,st4 ,st4 ,nebraska ,s4 of ,long ,st4 4#jjbe 4#bea #a4ii #ab ,st4 ,cordovez ,st4 ,long ,st4 ,map margin,nebraska 4#jjef 4#jjef #j4jcj #ac ,st4 ,long ,st4 ,nebraska ,n4 4#jjgb 4#bfd #b4jb #ad ,st4 ,carolina ,st4 ,long ,st4 ,n4 ,georgia 4#jjfd #a4bg #c4jc #ae ,carolina ,st4 ,st4 ,long ,st4 ,georgia ,harris ,st4 4#jjfa #a4bh #c4jd #af ,st4 ,long ,st4 ,harris ,st4,tennessee 4#jbd #a4cj #c4ac #ag ,st4 ,column ,no4 7#b7 7#c7 7#af7 7#ag7 7#ah7 7#a7 ,,table #bj ,,computations ,,for ,,slope ,,and ,,diameter ,,of ,,pipes ,,for ,a ,,separate ,,sewerage ,,system ,on ,street ,from ,to ,street ,from ,to ,length,el4 of ,surface ,street ,manhole,manhole ,feet ,upper ,lower ,manhole,manhole ,nebraska ,map margin,alley ,s4 #c4e #c4d #cch #aje4h #ajb4d ,st4 ,grant ,st4 ,alley ,s4 ,railroad ,e4 of #h4c #h4b #cbh #aac4e #aab4j of ,grant ,missouri ,st4 ,st4 ,alley ,s4 ,e4 of ,e4 of #h4b #h4a #cee #aab4j #ajg4g of ,grant ,missouri ,kansas ,st4 ,st4 ,st4 ,alley ,s4 ,e4 of ,nebraska #h4a #c4d #cdj #ajg4g #ajb4d of ,grant ,kansas ,st4 ,st4 ,st4 ,nebraska ,alley ,s4 ,alley ,s4 #c4d #c4c #chj #ajb4d #ajj4g ,st4 of ,grant of ,st4 ,meridian ,alley ,s4 ,railroad ,kansas ,st4 #g4b #g4a #djj #aaa4h #ajg4j of ,meridian ,alley ,s4 ,kansas ,st4,nebraska #g4a #c4c #djj #ajg4j #ajj4g of ,st4 ,meridian ,nebraska ,alley ,s4 ,alley ,s4 #c4c #c4b #cjd #ajj4g #ii4c ,st4 of of ,smith ,meridian ,av4 ,alley ,s4 ,railroad ,east of #f4b #f4a #cje #aji4c #aje4c of ,smith ,kansas ,ave4 ,st4 ,alley ,s4 ,east of ,nebraska #f4a #c4b #cjd #aje4c #ii4c of ,smith ,kansas ,st4 ,ave4 ,st4 ,nebraska ,alley ,s4 ,s4 of #c4b #c4a #cjj #ii4c #aja4a ,st4 of ,smith ,cordovez ,ave4 ,st4 ,s4 of ,railroad ,nebraska #d4a #c4a #daj #ajj4h #aja4a ,cordovez ,st4 ,st4 ,s4 of ,map margin,nebraska #e4a #c4a #chj #ajd4f #aja4a ,cordovez ,st4 ,st4 ,nebraska ,s4 of ,long ,st4 #c4a #adh #agb #aja4a #ih4g ,st4 ,cordovez ,st4 ,long ,st4 ,map margin,nebraska #adi #adh #chj #ajc4h #ih4g ,st4 ,long ,st4 ,nebraska ,n4 #adh #adg #dib #ih4g #ajc4h ,st4 ,carolina ,st4 ,long ,st4 ,n4 ,georgia #adg #adf #dcj #ajc4h #ii4a ,carolina ,st4 ,st4 ,long ,st4 ,georgia ,harris ,st4 #adf #ade #dai #ii4a #if4i ,st4 ,alley ,s4 ,end of ,harris ,st4 #b4b #b4a #cej #aje4b #ih4a of ,janis ,janis ,st4 ,st4 ,harris ,st4,alley ,n4 ,long ,st4 #b4a #ade #ace #ih4a #if4i of ,janis ,st4 ,long ,st4 ,harris ,st4,kentucky #ade #add #beh #if4i #id4d ,st4 ,long ,st4 ,kentucky ,tennessee #add #adc #bhb #id4d #ic4f ,st4 ,st4 ,tarbell ,harris ,st4,long ,st4 #a4a #adc #dag #ih4g #ib4f ,ave4 ,long ,st4 ,tennessee ,alley ,w4 #adc #adb #ahe #ib4f #ib4c ,st4 of ,tenn4 ,st4 ,column ,no4 7#b7 7#c7 7#d7 7#e7 7#f7 7#g7 7#h7 7#a7 ,on ,street ,from ,to ,street ,total ,slope ,dia4 ,velocity,capacity ,street ,flow1 of when when ,c4,f4,s4 ,pipe1 ,full1 ,full1 ,inches,ft4 per ,second ,second ,feet ,nebraska ,map margin,alley ,s4 #a4ffj4jajh #aj #c4be #a4gh ,st4 ,grant ,st4 ,alley ,s4 ,railroad ,e4 of #j4jdf4jjege #h #b4jj #j4ga of ,grant ,missouri ,st4 ,st4 ,alley ,s4 ,e4 of ,e4 of #j4aje 4#jaaj #h #b4gh #j4ih of ,grant ,missouri ,kansas ,st4 ,st4 ,st4 ,alley ,s4 ,e4 of ,nebraska #j4aeb 4#jaef #h #c4bg #a4ah of ,grant ,kansas ,st4 ,st4 ,st4 ,nebraska ,alley ,s4 ,alley ,s4 #a4gi4jjche #ab #b4bh #a4gi ,st4 of ,grant of ,st4 ,meridian ,alley ,s4 ,railroad ,kansas ,st4 4#jabj #h #b4ij #a4jc of ,meridian ,alley ,s4 ,kansas ,st4,nebraska #j4abc 4#jaeg #h #c4bh #a4ah of ,st4 ,meridian ,nebraska ,alley ,s4 ,alley ,s4 #a4he 4#jjdb #ab #b4cf #a4he ,st4 of of ,smith ,meridian ,av4 ,alley ,s4 ,railroad ,east of 4#jaca #h #c4jj #a4jh of ,smith ,kansas ,ave4 ,st4 ,alley ,s4 ,east of ,nebraska #j4jfi 4#jaig #h #c4gj #a4cb of ,smith ,kansas ,st4 ,ave4 ,st4 ,nebraska ,alley ,s4 ,s4 of #a4ib4jjbac #ae #b4jj #b4de ,st4 of ,smith ,cordovez ,ave4 ,st4 ,s4 of ,railroad ,nebraska 4#jjegd #h #b4jj #j4ga ,cordovez ,st4 ,st4 ,s4 of ,map margin,nebraska #j4jed4jjhed #h #b4df #j4hg ,cordovez ,st4 ,st4 ,nebraska ,s4 of ,long ,st4 #a4ii4jjbac #ae #b4jj #b4de ,st4 ,cordovez ,st4 ,long ,st4 ,map margin,nebraska #j4jcj 4#jacd #h #c4jd #a4jh ,st4 ,long ,st4 ,nebraska ,n4 #b4jb4jjbac #ae #b4jj #b4de ,st4 ,carolina ,st4 ,long ,st4 ,n4 ,georgia #c4jc 4#jjaf #ah #b4jj #c4ej ,carolina ,st4 ,st4 ,long ,st4 ,georgia ,harris ,st4 #c4jd 4#jjaf #ah #b4jj #c4ej ,st4 ,alley ,s4 ,end of ,harris ,st4 4#jbjc #h #c4gh #a4ce of ,janis ,janis ,st4 ,st4 ,harris ,st4,alley ,n4 ,long ,st4 4#jjhh #h #b4ec #j4hi of ,janis ,st4 ,long ,st4 ,harris ,st4,kentucky 4#jjcec #ah #b4ih #e4bj ,st4 ,long ,st4 ,kentucky ,tennessee 4#jjfce #ah #d4jj #g4jj ,st4 ,st4 ,tarbell ,harris ,st4,long ,st4 4#jadf #h #c4ah #a4ad ,ave4 ,long ,st4 ,tennessee ,alley ,w4 #c4ac 4#jjaf #ah #b4jj #c4ej ,st4 of ,tenn4 ,st4 ,column ,no4 7#b7 7#c7 7#i7 7#aj7 7#aa7 7#ab7 7#ac7 7#a7 ,on ,street ,from ,to ,street ,el4 of ,invert ,line ,street ,number ,upper ,lower ,manhole,manhole ,nebraska ,map margin,alley ,s4 #ig4hj #id4dj #a ,st4 ,grant ,st4 ,alley ,s4 ,railroad ,e4 of #aje4ej #ajc4fb #b of ,grant ,missouri ,st4 ,st4 ,alley ,s4 ,e4 of ,e4 of #ajc4fa #ii4gj #c of ,grant ,missouri ,kansas ,st4 ,st4 ,st4 ,alley ,s4 ,e4 of ,nebraska #ii4fi #id4dj #d of ,grant ,kansas ,st4 ,st4 ,st4 ,nebraska ,alley ,s4 ,alley ,s4 #id4jg #ib4fa #e ,st4 of ,grant of ,st4 ,meridian ,alley ,s4 ,railroad ,kansas ,st4 #ajc4hj #ii4jj #f of ,meridian ,alley ,s4 ,kansas ,st4,nebraska #ih4ii #ib4gj #g of ,st4 ,meridian ,nebraska ,alley ,s4 ,alley ,s4 #ib4cg #ia4ji #h ,st4 of of ,smith ,meridian ,av4 ,alley ,s4 ,railroad ,east of #aja4cj #ig4cj #i of ,smith ,kansas ,ave4 ,st4 ,alley ,s4 ,east of ,nebraska #ig4bi #ia4cj #aj of ,smith ,kansas ,st4 ,ave4 ,st4 ,nebraska ,alley ,s4 ,s4 of #ij4hd #ij4bj #aa ,st4 of ,smith ,cordovez ,ave4 ,st4 ,s4 of ,railroad ,nebraska #ib4hj #ij4fb #ab ,cordovez ,st4 ,st4 ,s4 of ,map margin,nebraska #if4fj #ic4aj #ac ,cordovez ,st4 ,st4 ,nebraska ,s4 of ,long ,st4 #ij4jd #hi4hg #ad ,st4 ,cordovez ,st4 ,long ,st4 ,map margin,nebraska #ie4hj #ij4gj #ae ,st4 ,long ,st4 ,nebraska ,n4 #hi4hf #hh4id #af ,st4 ,carolina ,st4 ,long ,st4 ,n4 ,georgia #hh4fi #hh4jj #ag ,carolina ,st4 ,st4 ,long ,st4 ,georgia ,harris ,st4 #hg4ii #hg4cb #ah ,st4 ,alley ,s4 ,end of ,harris ,st4 #ig4bj #ij4aj #ai of ,janis ,janis ,st4 ,st4 ,harris ,st4,alley ,n4 ,long ,st4 #ij4ji #hh4ij #bj of ,janis ,st4 ,long ,st4 ,harris ,st4,kentucky #hg4ca #hf4dj #ba ,st4 ,long ,st4 ,kentucky ,tennessee #hf4ci #hd4fj #bb ,st4 ,st4 ,tarbell ,harris ,st4,long ,st4 #ij4gj #hd4fj #bc ,ave4 ,long ,st4 ,tennessee ,alley ,w4 #hc4gg #hc4dg #bd ,st4 of ,tenn4 ,st4 ,column ,no4 7#b7 7#c7 7#ad7 7#ae7 7#a7 #dg4 ,surface ,profile4--,a profile of the surface of the ground along the proposed lines of the sewers should be drawn after the completion of the computations for quantity4 ,an example of a profile is shown in ,fig4 #bf for the line between manholes ,no4 #c4e and ,no4 #adg4 ,the vertical scale should be at least #aj times the horizontal4 ,a horizontal scale of #a inch to #bjj feet can be used where not much detail is to be shown1 but a scale of one #a to #ajj feet is more common and more satisfactory and even one inch to #aj feet has been used4 ,the information to be given and the method of showing it are illustrated on ,fig4 #bf4 ,the profile should show the character of the material to be passed through and the location of underground obstacles which may be encountered4 ,the method of obtaining this information is taken up in ,chapter ,,ii4 ,the collection of the information should be completed as far as possible previous to design1 and borings and other investigations made as soon as the tentative routes for the sewers have been selected4 #dh4 ,slope and ,diameter of ,sewers4--,after the quantity of sewage to be carried has been determined1 and the profile of the ground surface has been drawn1 it is possible to determine the slope and diameter of the sewer4 ,a table such as ,no4 #bj is made up somewhat similar to ,no4 #ai1 or which may be an extension of ,table #ai since the first #f columns in both tables are the same4 ,the elevation of the surface at the upper and lower manholes is read from the profile4 ,the depth of the sewer below the ground surface is first determined4 ,sewers should be sufficiently deep to drain cellars of ordinary depth4 ,in residential districts cellars are seldom more than #e feet below the ground surface4 ,to this depth must be added the drop necessary for the grade of the house sewer4 ,six-inch pipe laid on a minimum grade of #a4fg per cent is a common size and slope restriction for house drains or sewers4 ,an additional #ab inches should be allowed for the bends in the pipe and the depth of the pipe under the cellar floor4 ,where the elevation of the street and lots is about the same1 and the street is not over #hj feet in width between property lines1 a minimum depth of #h feet to the invert of sewers1 #bd inches or less in diameter is satisfactory4 ,this is on the assumption that the axes of the house drain and the sewer intersect4 ,for larger pipes the depth should be increased so that when the street sewer is flowing full1 sewage will not back up into the cellars or for any great distance into the tributary pipes4 ,illustration3 ,,fig4 #bf4--,typical ,profile ,used in the ,design of a ,separate ,sewer ,system4 ,the grade or slope at which a sewer shall be may be fixed by3 the slope of the ground surface2 the minimum permissible self-cleansing velocity2 a combination of diameter1 velocity1 and quantity2 or the maximum permissible velocity of flow4 ,sewers are laid either parallel to the ground surface where the slope is sufficient or where possible without coming too near the surface they are laid on a flatter grade to avoid unnecessary excavation4 ,the minimum permissible slope is fixed by the minimum permissible velocity4 ,the velocity of flow in a sewer should be sufficient to prevent the sedimentation of sludge and light mineral matter4 ,such a velocity is in the neighborhood of #a foot per second4 ,since sewers seldom flow full this velocity should be available under ordinary conditions of dry weather flow4 ,the minimum velocity when full should therefore be about #b feet per second4 ,under this condition1 the velocity of #a foot per second is not reached until the sewer is less than #ah per cent full4 ,the velocity in small sewers should be made somewhat faster than in large sewers since the velocity of flow for small depths in small pipes is less than for the same proportionate depth in large pipes4 ,the maximum permissible velocity of flow is fixed at about #aj feet per second in order to avoid excessive erosion of the invert4 ,if the sewer is carefully laid this limit may be exceeded in sanitary sewers4 ,the method for determining the grade and diameter of sewers is best explained through an illustrative problem which is worked out in ,table #bj for the profile shown on ,fig4 #bf4 ,the figures are inserted in the table from left to right in each line1 one line being completed before the next one is commenced4 ,the headings in the first #f columns are self-explanatory4 ,the elevations of the surface at the upper and lower manholes are read from the profile4 ,the total flow is read from column 7#ah7 in ,table #ai4 ,the slope of the ground surface is then computed1 and with the quantity1 slope1 and coefficient of roughness1 the diameter of the pipe and the velocity of flow are read from ,fig4 #ae4 ,the following conditions may arise3 7#a7 ,the diameter required is less than #h inches4 ,use a diameter of #h inches as experience has shown that the use of smaller diameters is unsatisfactory4 7#b7 ,the velocity of flow when the sewer is full is less than #b feet per second4 ,increase the slope until the velocity when full is #b feet per second4 7#c7 ,the diameter of the pipe required is not one of the commercial sizes shown in ,fig4 #ae4 ,use the next largest commercial size4 7#d7 ,the slope of the ground surface is steeper than necessary to maintain the required minimum velocity and the upper end of the sewer is deeper than the required minimum depth4 ,place the sewer on the minimum permissible grade1 or upon such a grade that its lower end will be at the minimum permissible depth4 7#e7 ,the slope of the ground surface is so steep as to make the velocity of flow greater than the maximum rate permissible4 ,reduce the grade by deepening the sewer at the upper manhole and using a drop manhole at this point4 ,it is not permissible to use a pipe larger than that called for by the above conditions4 ,this is attempted sometimes in order to reduce the grade and thereby save excavation1 under the rule of a minimum velocity of #b feet per second when full4 ,it is better to use the smaller pipe on the flat grade as the quantity of sewage is insufficient to fill the larger sewer and the minimum permissible velocity is more quickly reached4 ,having determined the slope1 the diameter1 and the capacity of the pipe to be used1 these values are entered in the table4 ,the elevations of the invert of the pipe at the upper and lower manholes are next computed and entered in the table4 ,this method is followed until all of the diameters1 slopes1 and elevations have been determined4 ,the slopes are computed from center to center of manholes1 but an extra allowance of #j4ja of a foot is allowed by some designers for the increased loss in head in passing through the manhole4 ,when it becomes necessary to increase the diameter of the sewer the top of the outgoing sewer is placed at the same elevation or below the top of the lowest incoming sewer4 ,no extra allowance is made to compensate for loss in head in the manhole in this case4 ,this case is illustrated in columns 7#ad7 and 7#ae7 in lines 7#af7 and 7#ag7 of ,table #bj4 ,all of the conditions listed above are illustrated in ,table #bj1 except the condition for a velocity greater than #aj feet per second4 ,the first condition is met at the head of practically every lateral1 and is illustrated in the second line4 ,the second condition is also illustrated in the second line4 ,the slope of the ground surface is #j4jjdf1 which gives a velocity of only #a4h feet per second in an #h-;inch pipe4 ,the slope is therefore increased to #j4jjege1 on which the full velocity is #b feet per second4 ,the third condition is met in the first line4 ,the diameter called for to carry #a4ff cubic feet per second on a slope of #j4jajh is slightly less than #aj inches4 ,a #aj-;inch pipe is therefore used and its full capacity and velocity are recorded4 ,the fourth condition is illustrated in the fourteenth line4 ,the cut at manhole ,no4 #c4a is #aa4a feet4 ,the slope of the ground is #j4jad1 much steeper than is necessary to maintain the minimum velocity in a #ae-;inch pipe4 ,the pipe is therefore placed on the minimum permissible slope1 and excavation is saved4 ,the student should check the figures in ,table #bj and be sure that they are understood before an attempt is made to make a design independently4 #di4 ,the ,sewer ,profile4--,the profile is next completed as shown in ,fig4 #bf1 the pipe line being drawn in as the computations are made4 ,the cut is recorded to the nearest th of a foot at each manhole1 or change in grade4 ,it should not be given elsewhere as it invites controversy with the contractor4 ,the cut is the difference of the elevation of the invert of the lowest pipe in the trench at the point in question1 and the surface of the ground4 ,the stationing should be shown to the nearest th of a foot4 ,it should commence at #j #jj at the outlet and increase up the sewer4 ,the station of any point on the sewer may show the distance from it to the outlet1 or a new system of stationing may be commenced at important junctions or at each junction4 ,elevations of the surface of the ground should be shown to the nearest th of a foot1 and the invert elevation to the nearest #a_/ajjth of a foot4 ,only the main line sewer is shown in profile in ,fig4 #bf4 ,the profiles of the laterals computed in ,table #bj1 have not been shown4 ,the approximate location of all house inlets are shown on the profile and located exactly1 and are made a matter of record during construction4 ,,design ,,of ,a ,,storm ,,water ,,sewer ,,system #ej4 ,planning the ,system4--,storm sewer systems are seldom as extensive as separate or combined sewer systems1 since storm sewage can be discharged into the nearest suitable point in a flowing stream or other drainage channel1 whereas dry weather or combined sewage must be conducted to some point where its discharge will be inoffensive4 ,the need of a comprehensive general plan of a storm sewer system is quite as great1 however1 as for a separate system4 ,the haphazard construction of sewers at the points most needed for the moment results in the duplication of forgotten drains1 expense in increasing the capacity of inadequate sewers1 and difficult construction due to underground structures thoughtlessly located4 ,a comprehensive plan permits the construction of sewers where they are needed as they are required1 and enables all probable future needs to be cared for at a minimum of expense4 ,the same preliminary survey1 map1 and underground information are necessary for the design of a storm sewer system as for a separate sewer system4 ,the map shown on ,fig4 #be has been used for the design of a storm-water sewer system4 ,the steps in the design of a storm-water sewer system are3 #ast4 ,note the most advantageous points to locate the inlets and lay out the system to drain these inlets4 #bnd4 ,determine the required capacity of the sewers by a study of the run-off from the different drainage areas4 #crd4 ,draw the profile and compute the diameter and slope of the pipes required4 #ea4 ,location of ,street ,inlets4--,the location of storm sewers is determined mainly by the desirable location of the street inlets4 ,the inlets must therefore be located before the system can be planned4 ,in general the inlets should be located so that no water will flow across a street or sidewalk1 in order to reach the sewer4 ,this requires that inlets be placed on the high corners at street intersections1 in depressions between street intersections1 and at sufficiently frequent intervals that the gutters may not be overloaded4 ,city blocks are seldom so long as to necessitate the location of inlets between crossings solely on account of inadequate gutter capacity4 ,the capacity of a gutter can be computed approximately by the application of ,kutter's formula4 ,inlet capacities are discussed in ,chapter ,,vi4 ,when the area drained is sufficiently large to tax the capacity of the gutter or inlet1 an inlet should be installed regardless of the location of the street intersections4 ,the street inlets are located on the map as shown in ,fig4 #be4 ,the sewer lines are then located so as to make the length of pipe to pass near to all inlets a minimum4 ,storm sewers are seldom placed near the center of a street because of the frequent crowded condition on this line4 #eb4 ,drainage ,areas4--,the outline of a drainage area is drawn so that all water falling within the area outlined will enter the same inlet1 and water falling on any point beyond the outline will enter some other inlet4 ,this requires that the outline follow true drainage lines rather than the artificial land divisions used in locating the drainage lines in the design of sanitary sewers4 ,the drainage lines are determined by pavement slopes1 location of downspouts1 paved or unpaved yards1 grading of lawns and the many other features of the natural drainage which are altered by the building up of a city4 ,the location of the drainage lines is fixed as the result of a study of local conditions4 ,the watershed or drainage lines are shown on ,fig4 #be by means of dot and dash lines4 ,a drainage line passes down the middle of each street because the crown of the street throws the water to either side and directs it to different inlets4 ,a watershed line is drawn about #ej feet west of such streets as ,kentucky ,st41 ,florida ,st41 etc41 because the downspouts from the houses on those streets discharge or will discharge into the street on which they face4 ,the location of any watershed line within #bj feet more or less is1 in most cases1 a matter of judgment rather than exactness4 ,each area is given an identifying number or mark which is useful only in design4 ,it usually corresponds to the inlet number4 #ec4 ,computation of ,flood ,flow by ,mc,math ,formula4--,mc,math's ,formula is used as an example of the method pursued when an empirical formula is adopted for the computation of run-off1 and because of its frequent use in practice4 ,other formulas may be more satisfactory under favorable conditions4 ,computations should be kept in order by a tabulation such as is shown in ,table #ba1 in which the quantity of storm flow discharged from the sewer at the foot of ,tennessee ,st41 on ,fig4 #be1 has been computed by means of the ,mc,math ,formula1 using the constants suggested for ,st4 ,louis conditions1 i #b4ge1 and c #j4ge4 ,the solutions of the formula have been made by means of ,fig4 #aa4 ,the column headings in the ,table are explanatory of the figures as recorded4 ,the computation should begin at the upper end of a lateral1 proceed to the first junction and then return to the head of another lateral tributary to this junction4 ,they should be continued in the same manner until all tributary areas have been covered4 ,special computations will be necessary for the determination of the maximum quantity of storm water entering each inlet to avoid the flooding of an inlet or gutter4 ,these computations have not been shown as they are so easily made by the application of ,mc,math's ,formula to each area concerned4 ,the determination of the average slope ratio is a matter of judgment1 based on the average natural slope of the surface of the ground and an estimate of the probable future conditions4 #ed4 ,computation of ,flood ,flow by ,rational ,method4--,the rational method for the computation of storm-water run-off is described in ,chapter ,,iii4 ,an example of its application to storm sewer design is given here for the district shown in ,fig4 #be4cd ,the computations are shown in ,table #ba4 ,as in the preceding designs the table has been filled in from left to right and line by line4 ,computations have started at the upper end of laterals tributary to each junction4 ,the column headed ,i represents the imperviousness factor in the expression ,q ,,air4 ,it is based on judgment guided by the constants given in ,chapter ,,iii concerning imperviousness4 ,the column headed 8,equivalent #ajj per cent ,i acres0 is the product of the two preceding columns4 ,it reduces all areas to the same terms so that they can be added for entry in the column headed 8,total #ajj per cent ,i acres40 ,it may be necessary to record the values for this column on several lines where the imperviousnesses of the tributary areas are different4 ,this condition is illustrated in the last line of the table1 for the length of sewer nearest the outlet4 ,in the preceding lines the imperviousness recorded represents an average for all the tributary areas4 ,,table #ba ,,computations ,,for ,,the ,,quantity ,,of ,,storm ,,sewage ,,at ,,the ,,foot ,,of ,,tennessee ,,street ,,on ,,figure #be ,on ,street ,from ,to ,street ,identifying ,by ,mc,math's ,formula ,street ,number of ,acres ,drained ,additional ,total ,slope ,run ,acres ,acres of ,off in ,drained ,drained,surface,c4,f4,s4 ,state ,n4 ,s4 #ia and #ib #b4ce #b4ce #j4jje #e4e ,carolina ,carolina ,state ,s4 ,georgia #hh1 #hi and #c4j #e4ce 4#jje #aj4h ,carolina #ij ,state ,georgia ,florida #he1 #hf and #c4j #h4ce 4#jjg #af4e #hg ,state ,florida ,kentucky #ha1 #hc and #c4j #aa4ce 4#jji #bb4j #hd ,state ,kentucky ,tennessee #gi1 #hj and #c4j #ad4ce 4#jaj #bh4j #hb ,state ,texas ,louisiana #gf and #c4h #c4h 4#jje #h4c others ,state ,louisiana ,alabama #gc1 #gd and #c4g #g4e 4#jjg #ae4j #ge ,state ,alabama ,tennessee #gj1 #ga and #c4j #aj4e 4#jjf #ai4j #gb ,tennessee,state ,talon #fh1 #fi1 #gg #d4c #bi4ae 4#ae #eb and #gh ,talon ,albemarle ,tennessee #fe1 #ff and #b4h #b4h 4#jah #h4d #fg ,tennessee,talon ,burnside #fd and #j4g #bi4he 4#ae #ee #fd;a ,burnside ,n4 ,s4 #eg1 #eh and #b4hd #b4hd 4#jjh #g4b ,carolina ,carolina #ei ,burnside ,s4 ,georgia #ed1 #ee and #c4hh #f4gb 4#jaj #ad4i ,carolina #ef ,burnside ,georgia ,florida #ej1 #eb and #c4hh #aj4fj 4#jab #bb #ec ,burnside ,florida ,kentucky #dg1 #dh and #c4hh #ad4dh 4#jac #cj #ea ,burnside ,kentucky ,tennessee #dd1 #de and #c4hh #ah4cf 4#jac #cf #df ,tennessee,burnside ,elm #db and #dc #b4hd #ea4je 4#jae #hb ,elm ,above ,chetwood ,included in next line below ,chetwood ,elm ,chetwood ,albemarle #ca1 #cb and #b4ge #b4ge 4#jjg #g4j #cc ,elm ,albemarle ,tennessee #bg1 #bh1 #bi #e4ge #h4ej 4#jaf #bj and #cj ,tennessee,elm ,varennes #be1 #bf and #b4fb #fb4ag 4#jag #ajj #da ,varennes ,s4 ,georgia #ag1 #ah and #c4ag #c4ag 4#jaj #h4c ,carolina #ai ,varennes ,georgia ,florida #ad1 #ae and #c4ag #f4cd 4#jaa #ad4e #af ,varennes ,florida ,kentucky #aa1 #ab and #c4ag #i4ea 4#jac #ba #ac ,varennes ,kentucky ,tennessee #h1 #i and #ajc4ag #ab4fh 4#jac #bf ,tennessee,varennes ,boulevard #f and #g #b4cb #gg4ag 4#jag #abj ,tennessee,boulevard ,outlet #a1 #b1 #c1 #d1d4gb #ha4hi 4#jag #abb and #e ,on ,street ,from ,to ,street ,by ,rational ,method ,street ,area1 ,i ,equivalent,total ,time of ,acres #ajj ,per #ajj ,concentration1 ,cent ,i ,per ,minutes ,acres ,cent ,i ,acres ,state ,n4 ,s4 #b4ce #j4ej #a4ag #a4ag #g4j ,carolina ,carolina ,state ,s4 ,georgia #c4jj 4#ej #a4ej #b4fg #h4a ,carolina ,state ,georgia ,florida #c4jj 4#ej #a4ej #d4ag #i4j ,state ,florida ,kentucky #c4jj 4#ej #a4ej #e4fg #i4i ,state ,kentucky ,tennessee #c4jj 4#ej #a4ej #g4ag #aj4g ,state ,texas ,louisiana #c4hj 4#ce #a4cc #a4cc #aj4j ,state ,louisiana ,alabama #c4gj 4#dj #a4dh #b4ha #aa4i ,state ,alabama ,tennessee #c4jj 4#de #a4ce #d4af #ab4i ,tennessee,state ,talon #d4cj 4#ej #b4aeac4dh #ad4e ,talon ,albemarle ,tennessee #b4hj 4#dj #a4ab #a4ab #h4j ,tennessee,talon ,burnside #j4gj 4#bj #j4adad4gd #ae4c ,burnside ,n4 ,s4 #b4hd 4#ee #a4ef #a4ef #aj4j ,carolina ,carolina ,burnside ,s4 ,georgia #c4hh 4#ee #b4ac #c4fi #aa4a ,carolina ,burnside ,georgia ,florida #c4hh 4#ee #b4ac #e4hb #ab4b ,burnside ,florida ,kentucky #c4hh 4#ee #b4ac #g4ie #ac4a ,burnside ,kentucky ,tennessee #c4hh 4#ee #b4acaj4jh #ac4h ,tennessee,burnside ,elm #b4hd 4#de #b4bhbf4aj #ae4g ,elm ,above ,chetwood ,chetwood ,elm ,chetwood ,albemarle #b4ge 4#dj #a4aj #a4aj #h4j ,elm ,albemarle ,tennessee #e4ge 4#de #b4ei #c4fi #i4e ,tennessee,elm ,varennes #b4fb 4#ej #a4cacj4jj #af4b ,varennes ,s4 ,georgia #c4ag 4#ee #a4gd #a4gd #i4j ,carolina ,varennes ,georgia ,florida #c4ag 4#ee #a4gd #c4dh #i4i ,varennes ,florida ,kentucky #c4ag 4#ee #a4gd #e4bb #aj4h ,varennes ,kentucky ,tennessee #c4ag 4#ee #a4gd #f4if #aa4d ,tennessee,varennes ,boulevard #b4cb 4#ee #a4bhcb4hd #af4e ,tennessee,boulevard ,outlet #j4ah 4#hj #j4ad ,area ,no4 #a #a4ch 4#ej #j4fi ,area ,no4 #b #b4hj 4#ee #a4ed ,areas ,no4 #c and #d #j4cf 4#ge #j4bgce4dh #af4i ,on ,street ,from ,to ,street ,by ,rational ,method ,line ,street ,number ,r,q ,s ,v ,sewer ,time ,length1 in ,feet ,sewer ,state ,n4 ,s4 #d4h #e4fj4jaa #d4f #cjj #a4a #a ,carolina ,carolina ,state ,s4 ,georgia #d4fab4b 4#jaj #e4e #cjj #j4i #b ,carolina ,state ,georgia ,florida #d4dah4c 4#jab #e4h #cjj #j4i #c ,state ,florida ,kentucky #d4bbc4i 4#jji #f4j #cjj #j4h #d ,state ,kentucky ,tennessee #d4abi4c 4#jji #f4b #cjj #j4h #e ,state ,texas ,louisiana #d4b #e4f 4#jji #c4b #cgj #a4i #f ,state ,louisiana ,alabama #c4iaa4j 4#jaa #e4b #cjj #a4j #g ,state ,alabama ,tennessee #c4hae4h 4#jjb #c4b #cjj #a4f #h ,tennessee,state ,talon #c4fdh4e 4#jai #i4h #dej #j4h #i ,talon ,albemarle ,tennessee #d4f #e4b 4#jjd #c4j #baj #a4b #aj ,tennessee,talon ,burnside #c4eea4e 4#jjf #e4j #abj #j4d #aa ,burnside ,n4 ,s4 #d4b #f4e 4#jjh #d4e #cjj #a4a #ab ,carolina ,carolina ,burnside ,s4 ,georgia #d4jad4h 4#jjg #d4g #cjj #a4a #ac ,carolina ,burnside ,georgia ,florida #c4ibb4g 4#jaa #e4h #cjj #j4i #ad ,burnside ,florida ,kentucky #c4gbi4d 4#jaf #g4e #cjj #j4g #ae ,burnside ,kentucky ,tennessee #c4gcg4c 4#jai #i4b #cjj #j4e #af ,tennessee,burnside ,elm #c4dhh4h 4#jaeaj4b #bhj4 #j4e #ag ,elm ,above ,chetwood #ah ,chetwood ,elm ,chetwood ,albemarle #d4f #e4a 4#jbj #e4c #dhj #a4e #ai ,elm ,albemarle ,tennessee #d4cae4h 4#jab #f4a #daj #a4a #bj ,tennessee,elm ,varennes #c4d #ajb 4#jabaj4b #ahj #j4c #ba ,varennes ,s4 ,georgia #d4d #g4g 4#jab #e4b #bgj #j4i #bb ,carolina ,varennes ,georgia ,florida #d4bad4e 4#jaj #e4g #cjj #j4i #bc ,varennes ,florida ,kentucky #d4aba4d 4#jag #g4g #cjj #j4f #bd ,varennes ,kentucky ,tennessee #d4jbg4h 4#jae #g4h #cjj #j4f #be ,tennessee,varennes ,boulevard #c4c #ajh 4#jabaj4b #bcj #j4d #bf ,tennessee,boulevard ,outlet #bg #bh #bi #c4c #aag;,areas ,no4 #a-e inclusive #cj ,the time of concentration in minutes is assumed by judgment for the first area4 ,for all subsequent areas it is the sum of the time of concentration for the area or areas tributary to the inlet next above and the time of flow in the sewer from the inlet next above to the inlet in question4 ,for example1 in line #b the time #h4a minutes is the sum of #g4j minutes time of concentration to the inlet at the corner of ,state and ,north ,carolina ,st41 and the time of flow of #a4a minute in the sewer on ,state ,st4 from ,north ,carolina ,st4 to ,south ,carolina ,st4 ,where two sewers are converging as at the corner of ,varennes ,road and ,tennessee ,st4 the longest time is taken4 ,for example1 the time of concentration down ,varennes ,road to ,tennessee ,st4 is shown in line #be as #aa4d #j4f #ab4j minutes4 ,the time to the same point down ,tennessee ,st4 is shown in line #ba as #af4b #j4c #af4e minutes4 ,this time is therefore used in line #bf4 ,r1 the rate of rainfall in inches per hour is determined by ,talbot's formula4 ,q1 is in cubic feet per second and is the product of the #hth and #ajth columns4 ,since the #hth column is the sum of the products of the #eth and the #fth columns for the lines representing tributary areas1 then the #aath column is the product of ,a1 ,i1 and ,r4 ,s1 is the slope on which it is assumed that the sewer will be laid4 ,it is usually assumed as parallel to the ground surface unless the velocity for this slope becomes less than #b feet per second4 ,in such a case the slope is taken as one which will cause this velocity4 ,v1 the velocity in feet per second1 is computed from diagrams for the solution of ,kutter's formula4 ,the length in feet is scaled from the map as the distance between inlets or groups of inlets1 and the time is the length in feet divided by the velocity in feet per minute4 ,having computed the quantity of flow to be carried in the sewer1 the design is completed by drawing the profile and computing the diameters and slopes by the same method as used in the design of separate sewers4 ,,chapter ,,vi ,,appurtenances #ee4 ,general4--,the appurtenances to a sewerage system are those devices which1 in addition to the pipes and conduits1 are essential to or are of assistance in the operation of the system4 ,under this heading are included such structures and devices as3 manholes1 lampholes1 flush-tanks1 catch-basins1 street inlets1 regulators1 siphons1 junctions1 outlets1 grease traps1 foundations and underdrains4 #ef4 ,manholes4--,a manhole is an opening constructed in a sewer1 of sufficient size to permit a man to gain access to the sewer4 ,manholes are the most common appurtenances to sewerage systems and are used to permit inspection and the removal of obstructions from the pipes4 ,the details of the ,baltimore standard manholes are shown in ,fig4 #bg and a manhole on a large sewer in ,omaha is shown in ,fig4 #bh4 ,the features of these designs which should be noted are the size of the opening and working space1 and the strength of the structure4 ,manhole openings are seldom made less than #bj inches in diameter and openings #bd inches in diameter are preferable4 ,a man can pass through any opening that he can get his hips through provided he can bend his knees and twist his shoulders immediately on passing the hole4 ,for this reason the manhole should widen out rapidly immediately below the opening1 as shown in ,fig4 #bg and #ch4 ,the walls of the manhole may be built either of brick or of concrete4 ,brick is more commonly used1 as the forms necessary for concrete make the work more expensive unless they can be used a number of times4 ,the walls of the manhole should be at least #h inches thick4 ,greater thicknesses are used in treacherous soils and for deep manholes1 or to exclude moisture4 ,a rough expression for the thickness of the walls of a brick manhole more than #ab feet deep in ordinary firm material is t d#b #b1 in which t is the thickness in inches and d is the depth in feet4 ,the thickness of brick walls may be changed every #e to #aj feet or so4 ,concrete walls may be built thinner than brick walls4 ,illustration3 ,,fig4 #bg4--;,baltimore ,standard ,manhole ,details4 ,the bottoms of brick manholes are frequently made of concrete as shown in ,fig4 #bg4 ,the floor slopes towards the center and is constructed so that the sewage flows in a half round or ,u-shaped channel of greater capacity than the tributary sewers4 ,the sides of the channel should be high enough to prevent the overflow of sewage onto the sloping floor1 which should have a pitch of about one vertical to #aj or #ab horizontal4 ,in manholes where two or more sewers join at approximately the same level the channels in the bottom should join with smooth easy curves4 ,where the inlet and outlet pipes are not of the same diameter the tops of the pipes should ordinarily be placed at the same elevation to prevent back flow in the smaller pipes when the larger pipes are flowing full4 ,the dimensions of the manhole should not be less than #c feet wide by #d feet long for a height of at least #d feet1 when built in the form of an ellipse1 or #d feet in diameter when built circular4 ,no standard method for the reduction of the diameter of the manhole near the top is observed1 the rate being more or less dependent on the depth of the manhole4 ,the use of sloping sides above the frost line is desirable as such a form is more resistant to heaving by frost action4 ,for sewers up to #dh inches in diameter the manhole is usually centered over the intersection of the pipes and has a special foundation4 ,for larger sewers the manhole walls spring from the walls of the sewer as shown in ,fig4 #bh4 ,illustration3 ,,fig4 #bh4--;,details of a ,manhole and a ,well ,hole4 ,in the case of a decided drop in the elevation of a sewer1 or of a tributary sewer appreciably higher than an outlet in any manhole1 the sewage is allowed to drop vertically at the manhole1 hence the name drop manhole4 ,the ,baltimore standard drop manhole is shown in ,fig4 #bg4 ,a well hole is an unusually deep drop manhole in which the force of the vertical drop of sewage is broken by a series of baffle plates1 or by a sump at the bottom of the well hole4 ,fig4 #bh shows a well hole at ,st4 ,paul1 ,minn4 ,the use of drop manholes can be avoided in large sewers by the construction of a flight of steps or flight sewer as shown in ,fig4 #bi1 which allows the use of a steep grade and serves to break the velocity of the sewage4 ,the specifications of the ,sanitary ,district of ,chicago1 covering the construction of manhole covers and frames are3 ,all castings shall be of tough1 close grained1 gray iron1 free from blow holes1 shrinkage and cold shuts1 and sound1 smooth1 clean and free from blisters and all defects4 ,all castings shall be made accurately to dimensions to be furnished and shall be planed where marked or where otherwise necessary to secure perfectly flat and true surfaces4 ,allowance shall be made in the patterns so that the specified thickness shall not be reduced4 ,all castings shall be thoroughly cleaned and painted before rusting begins and before leaving the shop with two coats of high grade asphaltum or any other varnish that the ,engineer may direct4 ,after the castings have been placed in a satisfactory manner1 all foreign adhering substances shall be removed and the castings given one additional coat of asphaltum4 ,no castings shall be accepted the weight of which shall be less than that due to its dimensions by more than #e per cent4 ,illustration3 ,,fig4 #bi4--;,flight ,sewer at ,baltimore4 ,eng4 ,record1 ,vol4 #ei1 p4 #afa4 ,illustration3 ,,fig4 #cj4--;,baltimore ,standard ,manhole ,frame and ,cover4 ,the weights of frames and covers in use vary from #bjj to #fjj pounds1 the weight of the frame being about #e times that of the cover4 ,the lightest weights are used where no traffic other than an occasional pedestrian will pass over the manhole4 ,frames and covers weighing about #djj pounds are commonly used on residential streets1 whereas #fjj pound frames and covers are desirable in streets on which the traffic is heavy4 ,the frames should be so designed that the pavement will rest firmly against it and wear at the same rate as the surrounding street surface4 ,experience has shown that vertical sides should be used for the outside of the frame to approach this condition1 and that the frame should not be less than #h inches high4 ,the cover should be roughened in some desirable pattern as shown in ,fig4 #cj4 ,smooth covers become dangerously slippery4 ,where the ventilation of the sewers is not satisfactory the manhole covers are sometimes perforated4 ,this is undesirable from other points of view as the rising odors and vapors are obnoxious at the surface and the entering dirt and water are detrimental to the operation of the sewer4 ,the stealing and destruction of manhole covers and the unauthorized entering of sewers has occasionally required the locking of the covers to the frame when in place4 ,the locks commonly used consist of a tumbler which falls into place when the manhole is closed1 and which can be opened only by a special wrench or hook4 ,adjustable frames are sometimes used where the street grade is settling1 or may be raised in order that the elevation of the top of the cover may be made to conform to that of the street surface1 without reconstructing the top of the manhole4 ,one type of adjustable cover is shown in ,fig4 #ca4 ,manhole covers should be so marked that the sanitary sewer can be distinguished from the storm-water sewer1 and both from the telephone conduit1 etc4 ,illustration3 ,,fig4 #ca4--;,adjustable ,manhole ,frame and ,cover4 ,iron steps are set into the walls of the manhole about #ae inches apart vertically to allow entrance and exit to and from the manhole4 ,galvanized iron is preferable to unprotected metal as the action of rust is particularly rapid in the moist air of the sewer4 ,one type of these manhole steps is shown in ,fig4 #bg4 ,the steps should have a firm grip in the wall as a loose step is a source of danger4 ,illustration3 ,,fig4 #cb4--;,baltimore ,standard ,lamphole4 #eg4 ,lampholes4--,a lamphole is an opening from the surface of the ground into a sewer1 large enough to permit the lowering of a lantern into the sewer4 ,lampholes are used in the place of manholes to permit the inspection or the flushing of sewers1 and to avoid the expense of a manhole4 ,they are located from #cjj to #djj feet from the nearest manhole in such a manner that a lamp lowered in the lamp hole can be seen from the two nearest manholes4 ,lampholes should be constructed of #h- to #ab-;inch tile or cast-iron pipe4 ,the lower section should be a cast-iron ,t on a firm foundation1 but if constructed of tile it should be reinforced with concrete to take up the weight of the shaft4 ,the details of the ,baltimore standard lamphole are shown in ,fig4 #cb4 ,lampholes are not commonly used on sewerage systems on account of their lack of real usefulness and the troubles encountered by breaking of the pipe below the shaft4 #eh4 ,street ,inlets4--,a street inlet is an opening in the gutter through which storm water gains access to the sewer4 ,the types used in different cities vary widely4 ,details of an inlet in successful use are shown in ,fig4 #cc4 ,the figure shows also a common form of connection to the sewer4 ,a water-seal trap is sometimes used to prevent the escape of odors from the sewer4 ,care must be taken in design that such traps do not freeze in winter nor dry out in summer1 although it is not always possible to prevent these contingencies4 ,illustration3 ,,fig4 #cc4--;,details of an ,untrapped ,street ,inlet1 without ,catch-,basin4 ,the important features to be observed in the design of a street inlet are3 height and length of opening1 character of grating1 and location4 ,the general location of inlets is discussed in ,chapter ,v4 ,the clear height of opening commonly used is from #e to #f inches1 with a clear length of #bd to #cj inches or longer4 ,inlets of this size have given satisfaction on paved streets with moderate slopes1 where the drainage area is not greater than #aj1jjj to #ab1jjj square feet of pavement4 ,w4 ,w4 ,horner states3#ce ,the ,st4 ,louis type of inlet 8old0 style was a vertical opening in the curb #h inches high and #d feet in length with a horizontal bar making the net opening about #e inches4 ,it has a broad sill extending under the sidewalk4 ,the 8new0 style inlet is #d feet long with a clear opening of #f inches and no bar4 ,the sill is done away with and the opening drops down directly from the curb4 ,tests were made of the capacity of this inlet on pavements on different slopes with sumps of depths varying from #j to #f inches in front of the inlet1 extending out #c feet from the gutter1 and returning to the elevation of the gutter at a slope of #c inches to the foot4 ,the results of these tests are shown in ,table #bb4 ,the capacity of the inlet is expressed as the amount of water entering just before some water begins to lap past4 ,if a large amount of water is allowed to flow past much more water will enter the inlet thus furnishing a factor of safety for large storms4 ,it was noted that by beginning the rise in the pavement about opposite the middle of the inlet the capacity of the inlet was increased from #bj to #ej per cent4 ,,table #bb ,,capacities ,,of ,,st4 ,,louis ,,street ,,inlets ,from tests by ,w4 ,w4 ,horner4 ,cubic feet per second ,slope in #j4db #a4e ,per ,ct4 ,depth of #j4j #b #d #f #j #b #d #f ,sump1 ,inches ,capacity1 #a4bg old style ,capacity1 #j4a #j4e #a4e #b4ej4jh #j4d #a4a #b4a new style ,slope in #b4he #d4e ,per ,ct4 ,depth of #j #b #d #f #j #b #d #f ,sump1 ,inches ,capacity1#j4jcj4bej4gha4di old style ,capacity1#j4jcj4bhj4hga4fbj4jbj4aej4de #a4j new style ,gratings with horizontal bars will admit more water than gratings with vertical bars1 but they will also admit more rubbish such as sticks1 papers1 leaves1 etc41 which serve to clog the sewers4 ,vertical barred gratings and gratings in the bottom of the gutter clog more quickly than other types4 ,in the selection of the type of grating to be used a decision must be made as to whether it is more desirable to clean the sewer or catch-basin1 or to flood the street as a result of clogged inlets4 ,where catch-basins are used or the sewers are large1 horizontal bars are more satisfactory4 ,the openings between bars should be small enough to prevent the entrance of a horse's hoof or objects of sufficient size to clog the sewer4 ,four inches in the clear for vertical openings and #f inches for horizontal openings are reasonable sizes4 ,the location of the inlets at the intersection of the two curb lines at a corner results in a lower first cost but on heavily traveled streets this may result in a higher maintenance cost than for other locations because of the concentration of traffic at street corners1 hammering the inlet casting out of shape or position4 ,vehicles making short turns will tend to climb the curb and will intensify the wear upon the inlet4 ,these objections can be overcome by the use of two inlets at each corner1 set back far enough from the curb intersection to avoid interference with the cross-walks4 ,this also makes it possible to raise the cross-walks without the use of gutters under them4 ,the size of the pipe from the inlet to the catch-basin or sewer should be large enough to care for all of the water which may enter the inlet4 ,as the capacity of the inlet is seldom known with accuracy and the capacity of the pipe is difficult of determination1 it has become customary to use a #aj-;inch or a #ab-;inch connecting pipe for each ordinary independent inlet4 #ei4 ,catch-basins4--,catch-basins are used to interrupt the velocity of sewage before entering the sewer1 causing the deposition of suspended grit and sludge and the detention of floating rubbish which might enter and clog the sewer4 ,a separate catch-basin may be used for each inlet1 or to save expense1 the pipes from several inlets may discharge into one catch-basin4 ,illustration3 ,,fig4 #cd4--;,catch-basin4 ,outlets are not always trapped4 ,the types in successful use are extremely varied1 but the distinguishing feature of all is an outlet located above the floor of the basin4 ,a common form of catch-basin is shown in ,fig4 #cd4 ,it is constructed similar to a manhole with a diameter of about #d or #d feet and a depth of retained water from #c to #d feet4 ,catch-basins of this size will care for the sewage from the inlets at the four corners of a street intersection1 each draining a city block4 ,in unusual situations it may be necessary to install a larger basin1 but too large a catch-basin is less desirable than one which is too small1 as the former stinks and the latter is useless4 ,traps are sometimes used to prevent the escape of odors from the sewer into the street1 but odors are often created in the catch-basins themselves4 ,some engineers arrange the trap so that it can be opened for observation down the sewer as in ,fig4 #cd1 thus combining the advantages of a manhole with the catch-basin4 ,the use of catch-basins is objectionable because3 they furnish a breeding place for mosquitoes and other flying insects2 the septic action in them produces offensive odors2 if on a combined sewer they permit the escape of offensive odors in dry weather when the water seal in the trap has evaporated2 and the freezing of the water seal in the trap prevents the entrance of water to the sewer4 ,the sole advantage lies in the prevention of the clogging of the sewers1 but this may be sufficient to overbalance all of the disadvantages4 ,in general catch-basins should be provided on paved streets which are cleaned by flushing the material into the sewers1 or where the drainage is from an unimproved or macadamized street1 sandy country1 or into sewers in which the velocity of flow is less than #b feet per second4 ,illustration3 ,,fig4 #ce4--;,diagrammatic ,section through a ,grease ,trap4 #fj4 ,grease ,traps4--,the presence of grease in sewers results in the formation of incrustations which are difficult to remove and which cause a material loss in the capacity of the sewer4 ,the presence of oil and gasoline has resulted in violent and destructive explosions as is described in ,chapter ,,xii4 ,a type of grease trap used on the drains from hotels1 restaurants1 or other large grease producing industries is shown in ,fig4 #ce4 ,the trap is similar to a catch-basin except that it is too small for a man to enter1 and the outlet is necessarily trapped in order to prevent the escape of grease4 ,the details of a gasoline and oil separator approved by the ,new ,york ,city ,fire ,department are shown in ,fig4 #cf4cf ,illustration3 ,,fig4 #cf4--;,gasoline and ,oil ,separator4 #fa4 ,flush-,tanks4--,these are devices to hold water used in flushing sewers4 ,they are required only on sanitary and combined sewers4 ,their use tends to prevent the clogging of sewers laid on flat grades and permits flatter grades in construction than could otherwise be adopted4 ,flush-tanks may be operated either by hand or automatically4 ,automatic operation is more common than hand operation4 ,the hand-operated tanks are similar to manholes so arranged that the inlet and outlet sewers can be plugged while the manhole or tank is being filled with water either from a hose or a special service connection4 ,when sufficient water has been accumulated the outlet is opened and the sewer is flushed by the rush of water4 ,a sluice gate1 flap valve1 or a specially fitted board is sufficient to fit over the mouth of the inlet and outlet during the filling of the tank4 ,such an arrangement has the advantage of being cheap1 simple1 and satisfactory1 though somewhat crude4 ,in some cases water is run into the tank at the same rate that it is discharged through the open outlet1 maintaining a depth of #d or #e feet in the tank until the water passing the manhole below runs clean4 ,the volume of water required by this method is large4 ,flushing water under a relatively high head is sometimes obtained by the use of tank wagons which are quickly emptied into the sewer through a canvas pipe dropped down a manhole4 ,in all such cases if not well constructed the manhole is subject to caving due to the rush of water around the outlet4 ,precautions should be taken to minimize this danger by limiting the depth of water which may be accumulated4 ,this can be done by constructing an overflow at a height of #d or #e feet above the bottom of the manhole1 discharging into the sewer through an outside drain4 ,automatic flush-tanks are constructed similar to a manhole1 but special care should be taken to make them water-tight4 ,the apparatus for providing the automatic discharge may operate either with or without moving parts1 the latter being preferable as they require less attention and are not so liable to get out of order4 ,an automatic flush-tank of the ,miller type is shown in ,fig4 #cg4 ,it is a patented device manufactured by the ,pacific ,flush ,tank ,company4 ,the small pipe at the left is a service connection to the water main4 ,water is allowed to flow continuously into the tank at such a rate as to fill it in the required interval between discharges4 ,the tanks are discharged as nearly once a day as it is practicable to regulate them4 ,the rate of flow into the tank is determined by trial and varies to some extent with the water pressure4 ,the regulator shown in the figure is desirable as the continuous flow through the ordinary cock soon wears it away4 ,some waters will cause deposits to form in the small passages of the cocks or regulators1 thus cutting off the flow4 ,illustration3 ,,fig4 #cg4--;,automatic ,flush-,tank4 ,pacific ,flush ,tank ,co4 ,the tank operates as follows3 when the water rising in the tank reaches the bottom of the bell1 air is trapped in the bell and prevented from escaping through the main trap by the water at ,a4 ,as the water continues to rise in the tank the air in the bell is compressed1 the water level at ,a is driven down and water trickles from the siphon at ,c4 ,the height of the water in the tank above the level of the water in the bell is equal at all times to the height of ,c above the lowering position of ,a4 ,when ,a reaches the position of ,b a small amount of air is released through the short leg of the trap and a corresponding volume of water enters the bell4 ,the head of water above the bell then becomes greater than the head of water in the short leg of the trap1 which results in the discharge of all of the air in the long leg of the trap and the rapid discharge of the water in the tank through the siphon4 ,the discharge is continued until the siphonic action is broken by the admission of air when the water level in the tank is lowered to the bottom of the bell4 ,the size of the siphons is fixed by the diameter of the leg of the siphon4 ,table #bc shows the capacity and size of sewers for which the different sizes of siphons are recommended by the manufacturers4#cg ,,table #bc ,,sizes ,,of ,,siphons ,,to ,,be ,,used ,,with ,,automatic ,,flush-,,tanks ,height of ,diameter of ,total the ,tank at the ,discharge ,average ,discharge ,diameter ,discharge for ,one ,rate of ,diameter of ,line above of ,siphon ,line in ,flush in ,discharge ,sewer in the ,edge of in ,inches ,feet ,gallons in ,sec4-ft4 ,inches the ,bell #d #c #fj #j4ce #d to #fa ft4 #b in4 #e #c #ajj #j4gc #f to #ha ft4 #aa in4 #f #d #bdj #a4jf #h to #ajb ft4 #f in4 #h #d #bhj #b4ab #ab to #aeb ft4 #aa in4 ,when flush-tanks are placed at the upper end of laterals provision should be made for inspecting and cleaning the sewer by the construction of a separate manhole1 or by combining the features of a manhole and a flush-tank in the same structure4 ,such a combination is shown in ,fig4 #ch from a design by ,alexander ,potter4 ,except under unusual conditions flush-tanks are used only on separate sewers4 ,they should be placed at the upper end of laterals in which the velocity of flow when full is less than #b to #d feet per second4 ,the capacity of the tank or the volume of the dose is dependent on the diameter and slope of the sewer4 ,the most effective flush is obtained by a volume of water traveling at a high velocity and completely filling the sewer4 ,a large volume allowed to run slowly through the sewer will have but little if any flushing action4 ,data on the quantity of flushing water needed are given in ,table #bd4ch ,as the result of a series of experiments conducted by ,prof4 ,h4 ,n4 ,ogden on the flushing of sewers1#ci the conclusion was reached that the effect of a flush of about #cjj gallons in an #h-;inch sewer on a grade less than #a per cent would not be effective beyond #hjj to #a1jjj feet1 but that on steeper grades much smaller quantities of water would produce equally good results4 ,illustration3 ,,fig4 #ch4--;,automatic ,flush-,tank and ,manhole4 ,miller-,potter ,design4 ,pacific ,flush ,tank ,co4 ,,table #bd ,,gallons ,,of ,,water ,,needed ,,for ,,flushing ,,sewers ,slope ,diameter of ,sewer in ,inches #h #aj #ab #j4jje #hj #ij #ajj 4#jjge #ee #fe #hj 4#ja #de #ee #gj 4#jb #bj #cj #ce 4#jc #ae #bj #bd ,engineers do not agree upon the advisability of the use of automatic flush-tanks1 some believing that they are a needless expense that can be avoided by hand flushing1 and others feeling that a flush-tank should be placed at the upper end of every lateral4 ,these diverse opinions are the result of different experiences in different cities4 #fb4 ,siphons4--,there are two forms of siphons used in sewerage practice1 a true siphon and an inverted siphon4 ,a true siphon is a bent tube through which liquid will flow at a pressure less than atmospheric1 first upwards and then downwards1 entering and leaving at atmospheric pressure4 ,an inverted siphon is a bent tube through which liquid will flow at a pressure greater than atmospheric first downwards and then upwards1 entering and leaving at atmospheric pressure4 ,in sewerage practice the word siphon refers to an inverted siphon unless otherwise qualified4 ,siphons1 both true and inverted1 are used in sewerage systems to pass above or below obstacles4 ,true siphons are seldom used as they must be kept constantly filled with liquid4#dj ,accumulated gas must be removed in order to prevent the breaking of the siphon which results in the cessation of flow4 ,by the breaking of a true siphon is meant the stoppage of siphonic action due to the accumulation of air or gas at the peak of the siphon4 ,since the rate of flow of sewage fluctuates widely it is extremely difficult to control the flow so that a true siphon may be completely filled with liquid at all times4 ,in the design of inverted siphons care must be taken to prevent sedimentation1 and to permit inspection and cleaning4 ,sedimentation is prevented by maintaining a velocity greater than a fixed minimum1 usually taken at about #b feet per second4 ,this minimum is attained by providing a number of channels4 ,the smallest channel is designed to convey the least expected flow at the minimum velocity4 ,each of the other channels is made as small as possible1 within the limits of economy and simplicity1 in order that the minimum velocity shall be exceeded quickly after flow has commenced in them4 ,the last channel or channels to be filled are made somewhat larger1 because the sewage conveyed in them contains less settleable matter than is contained in the more concentrated dry weather flow4 ,the type of siphon used in ,new ,york to pass under the subway is shown in ,fig4 #ci4 ,note should be taken of the clean-out manhole provided on the #ad-;inch pipe4 ,the other pipes are large enough for a man to enter and clean4 ,illustration3 ,,fig4 #ci4--,sewer ,siphon under ,new ,york ,subway4 ,eng4 ,news ,vol4 #gf1 p4 #ddc4 ,the computations involved in the design of a siphon are illustrated in the following example1 in which it is desired to construct a siphon to pass under the railway cut shown in ,fig4 #dj4 ,the first step is to determine the limiting diameter and slope of the smallest pipe in the siphon4 ,one-sixth of the capacity of the #f-;foot approach sewer or #ai cubic feet per second will be assumed as the minimum flow4 ,the diameter of the pipe necessary to carry #ai cubic feet per second at a velocity of #b feet per second is #db inches4 ,the hydraulic gradient should have a slope of #j4jjje if the material used has a roughness coefficient of 4#jae4 ,this is the minimum permissible slope of the siphon4 ,the selection of a steeper slope will necessitate the laying of the sewer at a greater depth1 and will permit the use of smaller pipes for the siphon4 ,the selection of the exact slope must then be based on judgment with the minimum limitation above placed4 ,the slope will be arbitrarily selected as #j4jja1 the same as that of the approach sewer4 ,the diameter of the dry weather pipe will therefore be #cf inches1 with a capacity of #ah second-feet1 which is approximately the assumed dry weather flow4 ,the velocity of flow will be #b4e feet per second4 ,the length of flow along the siphon is #aej feet4 ,illustration3 ,,fig4 #dj4--;,diagram for the ,design of an ,inverted ,siphon4 ,the next step should be the determination of the elevation at the lower end of the #cf-;inch pipe4 ,this is done by multiplying the assumed grade by the equivalent length of straight pipe1 and subtracting the product from the elevation at the upper end4 ,the length of straight pipe which will give the same loss of head as the siphon is called the equivalent pipe4 ,it is determined as follows3 ,first1 determine the head loss at entrance4 ,this will vary between nothing and one velocity head1 dependent on the arrangement at the entrance4#da ,the length of straight pipe which will give this same loss can be computed from the expression l h,s1 using for ,s the assumed slope of the hydraulic gradient4 ,second1 determine the head loss due to the bends1 ,this is determined from the expression h 7fl77d7 7,v#b77b;g7 in which h the head loss in the bend2 l the length of the bend2 d the diameter of the pipe2 v the average velocity of flow2 g the acceleration due to gravity2 f a factor dependent on the radius 7,r7 of the bend and d4 ,the relation between f1 ,r1 and d1 for #ij bends is shown as follows3#db ,rd #bd #af #aj #f #d #b4d f #j4jcf #j4jcg #j4jdg #j4jfj #j4jfb #j4jgb ,after the head loss has been determined1 the equivalent length of straight pipe is determined as above4 ,third4 ,the equivalent length of pipe will be the sum of the actual length of pipe and the equivalent lengths as found above4 ,in the problem in hand the head lost at the entrance will be assumed as one-third of a velocity head1 or #j4jcbd foot4 ,with the assumed slope of #j4jja this is equivalent to #cb feet of pipe4 ,the radius of the bend is about #bj feet and the length for a #de central angle is about #af feet4 ,the head loss for this angle will probably be a little more than one-half that for a #ij angle4 ,the expression will therefore be taken as about #j4b7,v#b77b;g7 and for two bends is equivalent to about #dj feet of pipe4 ,the equivalent length of pipe is therefore #aej #cb #dj #bbb feet4 ,the elevation at the lower end should therefore be3 the elevation at the upper end1 #ib4jg #bbb 4#jja #ia4he4 ,the diameters of the remaining pipes in the siphon are determined so that the sewage in the approach sewer is backed up as little as is consistent with good judgment before each pipe comes into action4 ,this is done satisfactorily by a method of cut and try4 ,let it be assumed that the siphon will be composed of three pipes3 the dry weather pipe taking #ah second-feet1 the second pipe taking #bh second-feet1 and the third pipe taking the remaining #gj second-feet4 ,the diameters of the two larger pipes on the assumed slope of #j4jja will therefore be #db inches and #fj inches respectively4 ,other combinations might be used which would be equally satisfactory4 ,there are many methods by which the sewage can be diverted into the different channels of the siphon4 ,for example1 the openings into the different pipes may be placed at the same elevation1 and the sewage allowed to enter them in turn through automatically or hand-controlled gates1 or in another method of control the openings may be placed at such elevations that when the capacity of one pipe has been exceeded the sewage will flow into the next largest pipe as shown in ,fig4 #dj4 ,the outlets from the different pipes are ordinarily placed at the same elevation1 thus leaving each pipe standing full of sewage4 ,stop planks should be provided at the outlet in order that the pipes may be pumped out for cleaning4 ,the objection to this arrangement is that the larger pipes may operate at a velocity less than #b feet per second1 and they will be standing full of sewage which might become septic4 ,however1 as they will take nothing but the storm flow near the top of the sewer no difficulty should be encountered from sedimentation in them1 and all are large enough for a man to enter for inspection or cleaning4 ,illustration3 ,,fig4 #da4--;,coffin ,sewer ,regulator4 #fc4 ,regulators4--,regulators are commonly used to divert the direction of flow of sewage in order to prevent the overcharging of a sewer or to regulate the flow to a treatment plant4 ,sewer regulators are of two types1 those with moving parts and those without moving parts4 ,an example of the moving part type is shown in ,fig4 #da4 ,in this type as the sewage rises the float closes the gate to the inlet sewer1 thus preventing the entrance of sewage under head from the larger sewer4 ,there are many variations in the details of float controlled regulators1 but the principle of operation is similar in all4 ,these regulators can be adjusted to fix the maximum rate of flow to a relief channel or sewage treatment plant1 or during times of storm to cut off the outlet to the dry weather channel4 ,another form of the moving part type is shown in ,fig4 #db4dc ,it has been used extensively by the ,milwaukee ,sewerage ,commission4 ,in its operation the dry weather flow is diverted by the dam into the intercepter4 ,it passes under the movable gate on its way to the treatment plant4 ,as the flow increases the dam is overtopped and flood waters are discharged down the storm channel4 ,the movable gate is hung on a pivot placed below center4 ,as the water rises in the intercepter1 the pressure against the upper portion of the gate becomes greater than that against the lower portion1 and the gate closes4 ,an opening is left at the bottom to allow an amount of sewage equal to the dry weather flow to escape beneath the gate to prevent clogging or sedimentation in the intercepter channel4 ,objections to all moving part regulators are their need of attention and liability to become clogged4 ,illustration3 ,,fig4 #db4--,moving ,part ,regulator without ,float4 ,illustration3 ,,fig4 #dc4--,leaping ,weir at ,danville1 ,illinois4 ,illustration3 ,,fig4 #dd4--,overflow ,weir at ,san ,francisco4 ,eng4 ,news1 ,vol4 #gc1 p4 #cjg4 ,illustration3 ,,fig4 #de4--,overflow ,weir in ,action4 ,shadow of steel knife edge which forms the lip of the weir can be seen through the falling sewage4 ,the overflow weir and the leaping weir have no moving parts and are used for the regulation of the flow in sewers4 ,a leaping weir is formed by a gap in the invert of a sewer through which the dry weather flow will fall and over which a portion or all of the storm flow will leap4 ,one form of leaping weir is shown in ,fig4 #dc4 ,an overflow weir is formed by an opening in the side of a sewer high enough to permit the discharge of excess flow into a relief channel4 ,a weir at ,san ,francisco is shown in ,fig4 #dd4 ,a series of tests were run on leaping weirs and overflow weirs in the hydraulic laboratory of the ,university of ,illinois4 ,the type of leaping weir tested was formed by the smooth spigot end of a standard vitrified sewer pipe4 ,the overflow weirs were formed by a steel knife edge in the side of the pipe parallel to its axis as shown in ,fig4 #de4 ,tests were made in #ah-;inch and #bd-;inch pipes on various slopes from #j4jah to #j4jje1 for both leaping weirs and overflow weirs4 ,the overflow weirs were varied in length from #af inches to #db inches and were placed at various heights from #be per cent to #ej per cent of the diameter above the invert of the sewer4 ,as the result of the observations the following formulas were developed4 ,for the leaping weir the expressions for the coordinates of the curve of the surfaces of the falling stream1 are3 ,for the outside surface x #j4ec,v y#dg ,for the inside surface x #j4cj,v#dg y in which x and y are the coordinates4 ,the origin is in the upper surface of the stream vertically above the end of the invert of the pipe4 ,the ordinate y is measured vertically downwards4 ,v is the velocity of approach in feet per second4 ,these expressions are applicable to any diameter of sewer up to #aj or #ae feet4 ,they should not be used for depths of flow greater than about #ad inches2 nor for slopes of more than #be per #a1jjj2 nor for velocities less than #a foot per second nor more than #aj feet per second4 ,the expression for the ordinate of the inside curve is not good for less than #f inches nor more than #e feet4 ,the expression for the ordinate of the outside curve is limited to values between the origin and #e feet below it4 ,the expression for the length of an overflow weir of the type shown in ,fig4 #de1 necessary to discharge a given quantity1 is in the form1 l #b4c,vd log h#a;h#b in which l the length of the weir in feet2 ,v the velocity of approach in feet per second2 d the diameter of the pipe in feet2 h#a the head of water on the upper end of the weir2 h#b the head of water on the lower end of the weir4 ,in the design of an overflow weir by this formula the height of the weir above the invert of the sewer and the flow over the weir should be determined arbitrarily4 ,the height should be subtracted from the computed depth of water above the weir to determine the value of h#a4 ,the difference between the flow over the weir and the flow above the weir will represent the rate of flow in the sewer below the weir4 ,the value of h#b can then be computed as the difference in the depth of flow below the weir and the height of the weir above the invert4 ,the value of ,v is computed from ,kutter's formula4 ,the length of the weir is determined by substituting these values in the formula4 #fd4 ,junctions4--,at the junction of two or more sewers the elevation of the inverts should be such that the normal flow lines are at the same elevation in all sewers4 ,the sewers should approach the junction on a steep grade to prevent sewage backing up in one when the other is flowing full4 ,the velocity of flow at the junction should not be decreased and turbulence should be avoided in order to prevent sedimentation and loss of head4 ,the junction should be effected on smooth easy curves with radii at least five times the diameter of the sewer where possible4 ,curves with short radii cause backing up of sewage thus reducing the capacity of the sewers4 ,the terms bellmouth or trumpet arch are sometimes applied to the junction of sewers large enough to be entered by a man4 ,in small sewers the ,y branches and special junctions are manufactured so that the center lines of the pipes intersect1 and the junctions of mains and laterals are made in manholes4 ,in the construction of a bellmouth the arch is carried over all the sewers4 ,a manhole should be constructed at these junctions as clogging frequently occurs there1 due to swirling and back eddies which cannot be avoided4 #fe4 ,outlets4--,the outlets to a sewerage system discharging into a swiftly running stream must be protected against wash and floating debris4 ,in a stream or other body of water subject to wide variations in elevation the backing up of the sewage during high water should be avoided4 ,where tidal flats or low ground about the outlet may be alternately submerged and uncovered the discharge should always be into swiftly running water4 ,in quiescent bodies of water such as lakes and harbors1 and in rivers where the dilution is low1 and in many other cases1 the sewer outlet should be submerged4 ,illustration3 ,,fig4 #df4--,tide ,gate4 ,outlets are protected against wash and the impact of debris by the construction of deep foundations and heavy protecting walls4 ,although the construction of an outlet in a slow current or a back eddy would avoid danger from wash and debris1 the discharge of the sewage into the most rapid current possible aids in the prevention of a local nuisance4 ,a row of batter piles on the upstream or exposed side of the sewer is desirable1 or it may be necessary to construct a break-water to prevent the wash of the current from dislodging the pipe4 ,these break-waters are low dams of wood or broken stone1 more or less loosely thrown together4 ,the backing up of water into the sewer can be prevented by constructing the sewer above the outlet on a steep grade4 ,where this is not possible the use of tide gates will be helpful4 ,a tide gate1 one form of which is shown in ,fig4 #df1 is a special form of check valve placed on the end of the sewer4 ,illustration3 ,,fig4 #dg4--,sewer ,outlet on a ,trestle4 ,eng4 ,news1 ,vol4 #di1 p4 #i4 ,sewer outlets are sometimes constructed on long trestles in order to reach deep or running water4 ,such a trestle is shown in ,fig4 #dg4 ,in ,boston the outlet sewers are submerged under the harbor and discharge through outlets well out in the tidal currents4 ,the sewage is discharged under pressure and the pumps are operated at some of the stations only at such times as the tidal currents will carry the sewage away from the harbor4 ,it is not always necessary in a combined sewerage system to carry the storm flow to a distant submerged outlet4 ,a double outlet can be constructed as shown in ,fig4 #dh in which the dry weather flow is carried to the channel in a submerged sewer and the storm flow is discharged on the bank4#dd ,cast-iron pipe should be used for submerged outlets as the sewer is subject to disturbance by the currents1 anchors1 ice1 and other causes4 ,illustration3 ,,fig4 #dh4--;,dry ,weather and ,storm ,sewer ,outlet at ,minneapolis1 ,minnesota4 ,eng4 ,record1 ,vol4 #fc1 p4 #chc4 #ff4 ,foundations4--,sewers constructed in firm dry soil require no special foundation to distribute the weight over the supporting medium4 ,in soft materials the lower half of the sewer ring may be spread as shown in ,fig4 #bb1 and in rock the pressures on sewer pipes are evenly distributed by a cushion of sand4 ,in wet ground such as quicksand1 mud1 swamp land1 etc41 a foundation must be constructed if the water cannot be drained off4 ,the permissible intensities of pressure on foundations in various classes of material allowed by the building codes in different cities are given in ,table #be4 ,these figures are based on the assumption that the material is restrained laterally1 which is generally the condition in sewer construction4 ,in the softer materials it becomes necessary to spread the foundations not only to reduce the intensity of pressure1 but also to care for the thrust of the sewer arch4 ,the arch thrust may be found by one of the methods of arch analysis1 and the haunches spread to care for this1 or the sewer invert may be transversally reinforced to assist in caring for this action4 ,some sewer sections in hard and soft material are shown in ,fig4 #bb and #bc4 ,,table #be ,,allowable ,,bearing ,,value ,,on ,,soils ,,in ,,various ,,cities ,from ,proc4 ,am4 ,soc4 ,civil ,engrs41 ,vol4 #df1 #aibj1 p4 #ijf ,quicksand and alluvial to #a ton per sq4 ft4 for ,providence1 ,r4 ,i41 soil ton per sq4 ft4 for #f cities ,soft clay #a ton per sq4 ft4 for #bg cities1 ton per sq4 ft4 for ,new ,orleans1 #b to #c tons for ,providence1 ,r4 ,i4 ,moderately dry clay and #b tons for #g cities1 #a to #b for ,chicago1 #b fine sand1 clean and tons for ,louisville1 #b to #d tons for dry ,providence1 #c tons for ,grand ,rapids and ,los ,angeles ,clay and sand in #b tons for #ai cities1 #a to #b for ,chicago1 #c alternate layers to #e tons for ,providence ,firm and dry loam or #c tons for #bd cities1 #b tons for #b cities1 #b clay1 or hard dry clay to #c tons for ,atlanta1 #c tons for or fine sand ,philadelphia1 #d tons for #f cities ,compact coarse sand1 #d tons for #be cities1 #c tons for ,buffalo1 #c stiff gravel or natural to #d tons for ,atlanta1 #d to #e tons for earth ,cincinnati1 #e tons for ,denver1 #d to #f tons for #c cities1 #f tons for ,rochester1 ,n4 ,y4 ,coarse gravel1 stratified#f tons for #c cities1 #e tons for #b cities1 #h stone and clay1 or rock tons for #a city inferior to best brick masonry ,gravel and sand well #h tons for #e cities1 #f tons for #b cities1 #h cemented to #aj tons for #a city ,good hard pan or hard #aj tons for #d cities1 #f tons for #b cities1 #h shale tons for #a city ,good hard pan or hard #h tons for #a city1 #aj to #ae tons for #a city1 shale unexposed to air1 #ab to #ah tons for #a city frost or water ,very hard native bed rock#bj tons for #e cities1 #ae tons for #a city1 #aj tons for #a city1 #be to #ej tons for #a city ,rock under caisson #bd tons for ,baltimore1 #be tons for ,cleveland ,on soft foundations such as swamps or for outfalls on the muck bottom of rivers the sewer may be carried on a platform4 ,for small sewers #b-;inch planks1 #b to #d feet longer than the diameter of the pipe are laid across the trench1 and the sewer rests directly upon them4 ,for large sewers imposing a heavy concentrated load1 a pile foundation should be constructed4 ,the foundation may consist of piles alone1 pile bents1 or a wooden platform supported on pile bents4 ,the load which can be carried by a pile is determined with accuracy only by driving a test pile and placing a load on it4 ,where piles do not penetrate to a firm stratum the load they will support can be determined by any one of the various formulas1 either theoretical or empirical1 which have been devised4 ,probably the best known of these formulas are the so-called ,engineering ,news formulas one of which is3 ,p #b,wh7,s #a7 for a pile driven by a drop hammer1 in which ,p the safe load on the pile in pounds4 ,the factor of safety is #f2 ,w the weight of the hammer in pounds2 h the fall of the hammer in feet2 ,s the penetration of the pile in inches at the last driving blow4 ,the blow is assumed to be driven on sound wood without rebound of the hammer4 ,reference should be made to engineering handbooks for other forms of pile formulas4 ,the accuracy of all of these formulas is not of a high degree4 ,the piles are driven at about #b to #d feet centers1 to a depth of from #h to #bj feet1 unless hard bottom is struck at a lesser depth4 ,the butt diameter of the piles used for the smallest sewers is about #f to #h inches4 ,if bents are used1 #b or #c piles are driven in a row across the line of the sewer and are capped with a timber4 ,for brick1 block1 pipe1 and some concrete sewers1 a wooden platform must be constructed between the pile bents for the support of the sewer4 #fg4 ,underdrains4--,the construction of special foundations can sometimes be avoided by laying drains under the sewers1 thus removing the water held in the soil4 ,the laying of the underdrains facilitates the construction of the sewer and reduces the amount of ground water entering the sewer4 ,the underdrains usually consist of #f- or #h-;inch vitrified tile laid with open joints from #a to #b feet below the bottom of the sewer as shown in ,fig4 #a4 ,if the sewers are large1 parallel lines of drains may be laid beneath them4 ,an observation hole should be constructed from the bottom of the manhole to each underdrain4 ,this hole usually consists of a #f- or #h-;inch pipe1 embedded in concrete1 connected to the drain and open at the top4 ,it is too small to permit effective cleaning of the underdrains1 which are usually neglected after construction1 and which as a result clog and cease to function4 ,since the principal period of usefulness of the drains is during construction1 their stoppage after the work is completed is not serious4 ,the hollow tile used in vitrified block sewers serve as underdrains after construction1 but are of little or no assistance to the draining of the trench during construction4 ,,chapter ,,vii ,,pumps ,,and ,,pumping ,,stations #fh4 ,need4--,in the design of a sewerage system it is occasionally necessary to concentrate the sewage of a low-lying district at some convenient point from which it must be lifted by pumps4 ,in the construction of sewers in flat topography the grade required to cause proper velocity of sewage flow necessitates deep excavation4 ,it is sometimes less expensive to raise the sewage by pumping than to continue the construction of the sewers with deep excavation4 ,in the operation of a sewage-treatment plant a certain amount of head is necessary4 ,if the sewage is delivered to the plant at a depth too great to make possible the utilization of gravity for the required head1 pumps must be installed to lift the sewage4 ,in the construction of large office buildings1 business blocks1 etc41 the sub-basements are frequently constructed below the sewer level4 ,the sewage and other drainage from the low portion of the building must therefore be removed by pumping4 ,because pumps are often an essential part of a sewerage system1 their details should be understood by the engineer who must write the specifications under which they are purchased and installed4 #fi4 ,reliability4--,if the only outlet from a sewerage system is through a pumping station1 the inability of the pumps to handle all of the sewage delivered to them may so back up the sewage as to flood streets and basements1 endangering lives and health and destroying property4 ,such an occurrence should be guarded against by providing sufficient pumping capacity and machinery of the greatest reliability4 #gj4 ,equipment4--,the equipment of a sewage pumping station1 in addition to pumping machinery1 may include a grit chamber1 a screen1 and a receiving well4 ,the grit chamber and screen are necessary to protect the pumps from wear and clogging4 ,grit chambers are not necessary in sewage devoid of gritty matter1 such as the average domestic sewage1 unless reciprocating pumps are used4 ,sufficient gritty matter is found in average domestic sewage to have an undesirable effect on reciprocating pumps4 ,receiving wells are used in small pumping stations where the capacity of the pumps is greater than the average rate of sewage flow4 ,the pumps are then operated intermittently1 the pumps standing idle during the time that the receiving well is filling4 ,except for a few types of pumps of which the valve openings are unsuitable1 any machine capable of pumping water is capable of pumping sewage which has been properly screened4 ,the principles of sewage pumps are then similar to principles of water pumps4 ,the conditions under which these principles are applied differ but slightly in the character of the liquid1 and a smaller range of discharge pressures4 ,pumps with large passages1 discharging under low heads are more commonly found among sewage pumps4 ,illustration3 ,,fig4 #di4--;,calumet ,sewage ,pumping ,station1 ,chicago1 ,illinois4 #ga4 ,the ,building4--,the pumping station should1 if possible1 be of pleasing design and should be surrounded by attractive grounds4 ,the ,calumet ,sewage ,pumping ,station in ,chicago is shown in ,fig4 #di4 ,its architecture is pleasing particularly in contrast with its location and immediate surroundings4 ,such structures tend to remove the popular prejudice from sewerage and to arouse interest in sewerage questions4 ,service to the public is of value4 ,it can be rendered more easily by arousing public interest and cooperation by the erection of attractive structures1 than by feeding popular prejudice by the construction of miserable eyesores4 #gb4 ,capacity of ,pumps4--,the capacity of the pumping equipment should be sufficient to care for the maximum quantity of sewage delivered to it1 with the largest pumping unit shut down1 and the provision of such additional capacity as1 in the opinion of the designer1 will provide the necessary factor of safety4 ,pumps can usually be operated under more or less overload4 ,power pumps and centrifugal pumps driven by constant speed electric motors have no overload capacity4 ,a power pump or a centrifugal pump may be overloaded up to the maximum horse-power of any variable speed motor or steam engine driving it1 provided the pump has been designed to permit it4 ,direct-acting steam pumps which are designed for proper piston speed and valve action at normal loads1 can carry a #ej per cent overload for short periods1 although the strain on the pump is great4 ,they will carry a #bj to #be per cent overload for about eight hours with less vibration and strain4 ,the use of pumps capable of working at an appreciable overload is somewhat of an additional factor of safety1 but the overload factor should not be taken into consideration in determining the capacity of the pumping equipment4 ,the load on a pumping station consists of the quantity of sewage to be pumped and the height it must be lifted4 ,variations in the quantity are discussed in ,chapter ,,iii4 ,the head against which the pumps must operate fluctuates with the level in the tributary sewer or pump well1 and in the discharge conduit4 ,for a free discharge or discharge into a short force main the greater the rate of sewage flow the smaller the lift1 as the depth of flow in the tributary sewer increases more rapidly than that in the discharge conduit4 ,if the discharge is into a large body of water or under other conditions where the discharge head is approximately constant1 the fluctuations in total head should not exceed the diameter of the tributary sewer4 ,such fluctuations are of minor importance in the operation of direct-acting steam pumps1 but may be of great importance in the operation of centrifugal pumps1 as is brought out in ,art4 #gh4 #gc4 ,capacity of ,receiving ,well4--,the use of receiving wells is restricted to small installations which require1 in addition to the standby unit1 only one pump1 the capacity of which is equal to the maximum rate of sewage flow4 ,when the receiving well has been pumped dry the pump stops1 allowing the well to fill again4 ,although the use of a large receiving well1 or an equalizing reservoir1 for a large pumping station would permit the operation of the pumps under more economical conditions1 the storage of sewage for the length of time required would not be feasible4 ,the sewage would probably become septic1 creating odors and corroding the pumps4 ,the extra cost of the reservoir might not compensate for the saving in the capacity and operation of the pumps4 ,the capacity of the receiving well should be so designed that the pump when operating will be working at its maximum capacity1 and the period of rest during conditions of average rate of flow should be in the neighborhood of #ae to #bj minutes4 ,for example1 assume an average rate of flow of #b cubic feet per second1 with a maximum rate of double this amount4 ,the pump should have a capacity of #d cubic feet per second1 and if the receiving well is to be filled in #ae minutes by the average rate of sewage flow its capacity should be #ae #e #fj #g4e or #ad1jjj gallons4 ,under these circumstances the pump will operate #ae minutes and rest #ae minutes1 during average conditions of flow4 #gd4 ,types of ,pumping ,machinery4--,the two principal types of pumping machines for lifting sewage are centrifugal pumps and reciprocating pumps4 ,a centrifugal pump is1 in general1 any pump which raises a liquid by the centrifugal force created by a wheel1 called the impeller1 revolving in a tight casing1 as shown in ,fig4 #ej4 ,a reciprocating pump is one in which there is a periodic reversal of motion of the parts of the pump4 ,centrifugal pumps are sometimes classified as volute pumps and turbine pumps4 ,a volute pump is a centrifugal pump with a spiral casing into which the water is discharged from the impeller with the same velocity at all points around the circumference1 as shown in ,fig4 #ea4 ,a turbine pump is a centrifugal pump in which the water is discharged from the impeller through guide passages into a collecting chamber1 in such a manner as to prevent loss of energy in changing from kinetic head to pressure head4 ,a turbine pump is shown in section in ,fig4 #ea4 ,centrifugal pumps are sometimes classified as single stage and multi-stage4 ,a centrifugal pump from which the water is discharged at the pressure created by a single impeller is called a single-stage pump4 ,if the water in the pump is discharged from one impeller into the suction of another impeller the pump is known as a multi-stage pump4 ,the number of impellers operating at different pressures determines the number of stages of the pump4 ,a three-stage pump is shown in ,fig4 #eb4 ,illustration3 ,,fig4 #ej4--,section through de ,laval ,single-,stage1 ,double ,suction ,centrifugal ,pump4 #cge ,lubricating ring4 #chj ,oil hole cap4 #chc ,oil drain tube4 #djd ,shaft sleeve lock nut4 #ddj ,driving coupling4 #dda ,driven coupling4 #ddc ,coupling check nut4 #dej ,coupling bolt4 #dea ,coupling bolt nut4 #deb ,coupling rubber4 #dec ,coupling rubber steel tube4 #ejj ,pump case4 #eej ,bearing bracket cap4 #eea ,bearing4 #eeb ,shaft4 #eec ,shaft sleeve1 right hand thread4 ,,pw ,impeller4 #eed ,shaft sleeve1 left hand thread4 #eee ,shaft stop collar1 inner4 #eee-a ,shaft stop collar1 outer4 #eef ,guide ring4 #efj ,packing gland4 #efc ,bearing4 #efg,r ,impeller protecting ring1 right hand thread4 #efg,l ,impeller protecting ring1 left hand thread4 #ehc ,pump case protecting ring4 #efg ,labyrinth packing4 #ehc ,labyrinth packing4 #fjj ,pump case cover4 #fib ,impeller key4 #hae ,bearing bracket1 outer4 #hae-a ,bearing bracket1 inner4 ,illustration3 ,,fig4 #ea4--,types of ,centrifugal ,pumps4 ,illustration3 ,,fig4 #eb4--,section of a ,multi-,stage ,centrifugal ,pump4 ,courtesy ,de,laval ,steam ,turbine ,co4 ,reciprocating pumps are generally driven by steam and are either direct-acting1 or of the crank-and-fly-wheel type4 ,power pumps are reciprocating machines which may be driven by any form of motor1 to which they are connected by belt1 chain or shaft4 ,a ,deming triplex power pump is shown in ,fig4 #ec4 ,power pumps can be used only where the character of the sewage will not clog the valves nor corrode the pump4 ,a direct-acting steam pump is one in which the steam and water cylinders are in the same straight line and the steam is used at full boiler pressure throughout the full length of the stroke4 ,the crank-and-fly-wheel type of pumping engine permits the use of steam expansively during a part of the stroke1 the energy stored in the flywheel carrying the machine through the remainder of the stroke4 ,reciprocating pumps are sometimes classified as plunger pumps and piston pumps4 ,in the action of a plunger pump the water is expelled from the water cylinder1 by the action of a plunger which only partly fills the water cylinder1 as shown in ,figs4 #ed and #ee4 ,in a piston pump the water is expelled from the water cylinder by the action of a piston which completely fills the water cylinder1 as shown in ,fig4 #fc1 which illustrates a direct-acting piston pump4 ,illustration3 ,,fig4 #ec4--,triplex ,power ,pump4 ,courtesy1 ,the ,deming ,co4 ,plungers are better than pistons for pumping sewage as the wear between the pistons and the inside face of the cylinder soon reduces the efficiency of the pump4 ,outside packed plungers are better than the inside packed type because the packing can be taken up without stopping the pump and the leakage from the pump is visible at all times4 ,outside packed pumps are more expensive in first cost1 but are easier to maintain and have a longer life than piston pumps4 ,illustration3 ,,fig4 #ed4--,water ,end of ,inside ,center-,packed ,plunger ,pump4 ,in selecting a pump to perform certain work the size of the water cylinder and the speed of the travel of the piston should be investigated to insure proper capacity4 ,the average linear travel of the piston for slow speed pumps is estimated at about #ajj feet per minute1 dependent on the length of stroke and the valve area4 ,for short strokes and small valve areas the speed may be as low as #dj feet per minute1 and for long stroke fire pumps with large valves the piston can be operated at a speed of #bjj feet per minute4#de ,vertical1 triple-expansion1 crank-and-fly-wheel1 outside packed plunger pumps with flap valves can be operated at speeds of #bjj feet per minute when lifting sewage1 and when equipped with mechanically operated valves and lifting water they can be run at speeds of #djj to #ejj feet per minute4 ,the speed of travel multiplied by the volume of piston or plunger displacement1 with proper allowance for slippage1 will give the capacity of the pump4 ,the slippage allowance may be from #c to #h per cent for the best pumps1 and for pumps in poor conditions it may be a high as #cj to #dj per cent4 ,illustration3 ,,fig4 #ee--,water ,end of ,outside ,center-,packed ,plunger ,pump4 ,courtesy ,allis-,chalmers ,co4 ,there are two types of ejector pumps used for lifting sewage4 ,one of these depends on the vacuum created by the velocity of a stream of water or steam passing through a small nozzle4 ,the operation of this pump is described in ,art4 #aci and it is illustrated in ,fig4 #ig4 ,the other type of ejector pump is known as the compressed-air ejector4 ,it is operated by means of compressed air which is turned into a receptacle containing sewage4 ,the details of this type are explained in ,art4 #hc and are illustrated in ,fig4 #fh4 #ge4 ,sizes and ,description of ,pumps4--,the size of a centrifugal pump is expressed as the diameter of the discharge pipe in inches4 ,it has nothing to do with the head for which the pump is suited4 ,on the assumption of a velocity of flow of #aj feet per second through the discharge pipe the capacity of the pump can be approximated4 ,the size of a reciprocating pump involves the expression of the diameters of the steam cylinders1 the water cylinder1 and the length of the stroke in inches1 in the order named1 beginning with the steam cylinder with the highest pressure4 ,a complete description of a steam pumping engine might be2 compound1 duplex1 horizontal1 condensing1 crank-and-fly-wheel1 outside-center-packed1 #ab #bd #ah #bd pump4 ,the word compound means that there are a high-pressure and a low-pressure steam cylinder2 the word duplex means that there are two of each of these cylinders2 the word horizontal means that the axes of these cylinders are in a horizontal plane2 the word condensing means that the steam is discharged from the low-pressure cylinders into a condenser2 the name crank-and-fly-wheel is self-explanatory2 the name outside-center-packed means that the water cylinder is divided into two portions between which the plunger is exposed to the atmosphere1 and that the packing rings are on the outside of the two portions of the cylinder as shown in ,fig4 #ee2 the figures shown mean that the high-pressure steam cylinder is #ab inches in diameter1 the low-pressure #bd inches in diameter1 the water cylinder is #ah inches in diameter1 and the stroke of the pump is #bd inches4 #gf4 ,definitions of ,duty and ,efficiency4--,the duty of a pump is the number of foot-pounds of work done by the pump per million ,b4,t4,u41 per thousand pounds of steam1 or per hundred pounds of coal1 consumed in performing the work4 ,these units are only approximately equal as #ajj pounds of coal or #a1jjj pounds of steam do not always contain the same number of ,b4,t4,u4 and may only approximately equal #a1jjj1jjj ,b4,t4,u4 ,since #a1jjj1jjj ,b4,t4,u4 are equal to #ggh1jjj1jjj foot-pounds of work1 a pump with a duty of #ggh1jjj1jjj will have an efficiency of #ajj per cent4 ,the efficiency of a pump is therefore its duty based on ,b4,t4,u4 divided by #ggh1jjj1jjj4 ,the efficiencies or duties of various types of pumps are given in ,table #bf4df ,,table #bf ,,approximate ,,duties ,,of ,,steam ,,pumps ,small duplex1 non-condensing #aj1jjj1jjj ,large duplex1 non-condensing #be1jjj1jjj ,small simple1 flywheel1 condensing #ej1jjj1jjj ,large simple1 flywheel1 condensing #fe1jjj1jjj ,small compound1 flywheel1 condensing #fe1jjj1jjj ,large compound1 flywheel1 condensing #abj1jjj1jjj ,small triple1 flywheel1 condensing #aej1jjj1jjj ,large triple1 flywheel1 condensing #afe1jjj1jjj #gg4 ,details of ,centrifugal ,pumps4--,a section of a centrifugal pump with the names of the parts marked thereon is shown in ,fig4 #ej4 ,among the important parts which require the attention of the purchaser are3 the impeller 7,,pw71 the impeller packing rings 7#efg ,r ,l71 the bearings 7#eea1 #efc71 the thrust bearings 7#eee-a71 the shaft 7#eeb71 and the shaft coupling 7#ddj74 ,the impeller should be of bronze1 gun metal1 or other alloy1 because there is no rusting or roughening of the surface1 and the efficiency does not fall with age4 ,normal fresh sewage is not corrosive1 but septic sewage and sludge are usually so corrosive that iron parts cannot be used with success in contact with them4 ,the impeller should be machined and polished to reduce the friction with the liquid4 ,impellers are made either closed or open1 i4e41 either with or without plates on the sides connecting the blades to avoid the friction of the liquid against the side of the casing4 ,the closed type of impeller is shown in ,fig4 #ej4 ,closed impellers are slightly more expensive1 but generally give better service and higher efficiencies than the open type4 ,single impeller pumps should have an inlet on each side of the impeller to aid in balancing the machine1 unless the plane of the impeller is to be horizontal when operating4 ,multi-impeller pumps usually have single inlet openings for each impeller4 ,vibration in the pump is sometimes caused by an unbalanced impeller4 ,the moving parts may be balanced at one speed and unbalanced at another4 ,to determine if the moving parts are balanced the pump should be run free at different speeds and the amount of vibration observed4 ,if the impeller is removed from the pump its balance when at rest can be studied by resting it on horizontal knife edges4 ,if there is a tendency to rotate in any direction from any position the impeller is not perfectly balanced4 ,packing rings are used to prevent the escape of water from the discharge chamber back into the suction chamber4 ,these rings should be made of the same material as the impeller4 ,labyrinth type rings1 as shown in ,fig4 #ej1 are sometimes used as the long tortuous passages are efficient in preventing leakage4 ,the bearings must be carefully made because of the high speed of the pump4 ,they are usually made of cast iron with babbitt lining4 ,they should be placed on the ends of the shaft on the outside of the pump casing1 as shown in ,fig4 #ej1 and should be split horizontally so as to be easily renewed4 ,exterior bearings are oil lubricated by means of ring or chain oilers with deep oil wells4 ,where interior bearings are necessary1 because of the length of the shaft1 they should be made of hard brass and should be water lubricated4 ,illustration3 ,,fig4 #ef4--,marine ,type ,thrust ,bearing4 ,courtesy1 ,de,laval ,steam ,turbine ,co4 ,thrust bearings or thrust balancing devices are used to take up the end thrust which occurs in even the best designed pumps4 ,to overcome this pumps are designed with double suction1 opposed impellers1 or two pumps with their impellers opposed may be placed on the same shaft4 ,due to inequalities in wear1 workmanship or other conditions1 end thrust will occur and must be cared for4 ,various types of thrust bearings are in successful use1 such as3 the piston1 ball1 roller or marine types4 ,the marine type thrust bearing is shown in ,fig4 #ef4 ,the piston type of hydraulic balancing device is shown in ,fig4 #eg4 ,in the figure ,a represents the impeller1 and ,b a piston fixed to the shaft and revolving with it4 ,there is a passage for water through the openings 7#a71 7#b71 and 7#c7 leading from the impeller chamber to the atmosphere or to the suction of the pump4 ,if the impeller tends to move to the right opening 7#a7 is closed resulting in pressure on the right of the impeller forcing it to the left4 ,if the impeller moves to the left 7#a7 is opened thus transmitting pressure to the piston ,b forcing the impeller to the right4 ,the flange ,c is not essential1 but is advantageous in pumps handling gritty matter4 ,as the channel 7#b7 wears larger the pressure against the piston decreases allowing it to move to the left4 ,this partially closes 7#c7 building up the pressure again4 ,illustration3 ,,fig4 #eg4--,piston ,type of ,thrust ,balancing ,device4 ,flexible shaft couplings should be used if the shaft of the driving motor and the pump are in the same line1 as direct alignment is difficult to obtain or to maintain4 ,where connected to steam turbines1 reduction gearing and rigid couplings are usually used on sewage pumps to obtain slow speed and permit large passages4 ,flexible couplings are of various types1 one of which is shown in ,fig4 #ej4 ,a rigid coupling would be formed by bolting the flanges firmly together4 ,shaft couplings are usually not necessary where the pump is driven by belt connection to the engine or motor1 or where the pump and pulley rest on only two bearings4 ,the stuffing box shown in ,fig4 #ej is packed loosely with two layers of hemp between which is a lantern gland1 in order to permit a small amount of leakage4 ,a drip box is placed below this gland to catch the leakage and return it to the pump4 ,the leakage is permitted as it aids in lubrication and the tightening of the gland will cause binding of the shaft4 ,the gland on the suction side of the pump should be connected by a small pipe to the discharge chamber in order to keep a constant supply of water for lubrication and to prevent the entrance of air to the suction end of the pump4 #gh4 ,centrifugal ,pump ,characteristics4--,the capacity of a centrifugal pump is fixed by the size and type of its impeller and by the speed of revolution4 ,roughly1 the capacity of a pump1 for maximum efficiency1 varies directly as the speed of revolution1 the discharge pressure varies as the square of the speed1 and the power varies as the cube of the speed4 ,these relations are found not to hold exactly in tests because of internal hydraulic friction in the pump4 ,the characteristic curves for a centrifugal pump1 or the so-called pump characteristics1 are represented graphically by the relation between quantity and efficiency1 quantity and power necessary to drive1 and quantity and head1 all at the same speed4 ,the quantities are plotted as abscissas in every case4 ,the curve whose ordinates are head and whose abscissas are quantities is known as 8the characteristic40 ,the curve showing the relation between quantities and speeds is sometimes included among the characteristics4 ,characteristics of pumps with different styles of impellers are shown in ,fig4 #eh4 ,fig4 #ei shows the characteristics of a pump run at different speeds1 the efficiencies at these speeds when pumping at different rates1 and the maximum efficiency at different speeds4 ,it is to be noted that the information given in this figure is more extensive than that in ,fig4 #eh4 ,the operating conditions under any head1 rate of discharge1 and speed are given4 ,the curves of constant speed are parallel1 and their distances apart vary as the square of the speed4 ,the line of maximum efficiency is approximately a parabola4 ,illustration3 ,,fig4 #eh4--;,characteristics of ,centrifugal ,pumps with ,different ,styles of ,impellers at ,constant ,speed4 ,a study of the characteristics of any particular pump should be made with a view to its selection for the load and conditions under which it is to be used4 ,among the important things to be considered in the selection of a centrifugal pump for the expected conditions of load are3 the capacity required1 the maximum and minimum total head to be pumped against1 the maximum variations in suction and discharge heads1 and the nature of the drive4 ,for example1 the pump1 whose characteristics are shown in ,fig4 #ei1 should be operated at about #hjj revolutions per minute4 ,under total heads between #dj and #ej feet1 the discharge for the best efficiency will vary between #fjj and #fgj gallons per minute4 ,illustration3 ,,fig4 #ei4--;,efficiency and ,characteristic ,curves of a ,centrifugal ,pump at ,different ,speeds4 ,illustration3 ,,fig4 #fj4--;,efficiencies of ,centrifugal ,pumps4 ,the efficiencies of centrifugal pumps increase with their capacities as is shown approximately in ,fig4 #fj4 #gi4 ,setting of ,centrifugal ,pumps4--,in setting a centrifugal pump1 care should be taken to provide a firm foundation to hold the shafts of the pump and the electric motor or the reduction gearing in good alignment1 or to prevent the pump from being displaced by the pull of a belt4 ,it is desirable that the foundation be level4 ,centrifugal pumps should be set submerged for small pumping stations automatically controlled4 ,sludge pumps must be set submerged as otherwise they will not prime successfully4 ,provision should be made by which the pump can be lifted from the sewage1 or sludge1 for inspection and repair4 ,in many cases the pump can be made self-priming by setting it in a dry1 water-tight vault below the low level of sewage flow4 ,where possible it is desirable not to set the pump submerged as it will receive better care when easily accessible4 ,illustration3 ,,fig4 #fa4--;,centrifugal ,pump in ,manhole at ,duluth1 ,minn4 ,eng4 ,contracting1 ,vol4 #dc1 #aiae1 p4 #caj4 ,the suction pipe should be free from vertical bends where air might collect and should be straight for at least #ah to #bd inches from the pump casing4 ,an elbow on the suction pipe1 attached directly to the casing of the pump gives a lower efficiency than a suction pipe with a short straight run4 ,centrifugal pumps will operate with as high a suction lift as reciprocating pumps1 but at the start they must be primed and some provision must be made for priming them4 ,the suction pipe should be equipped with foot valves to hold the priming1 or some method may be provided for exhausting the air from the suction pipe4 ,the foot valves should be so installed as to form no appreciable obstruction to the flow of water4 ,they should have an area of opening at least #ej per cent greater than the cross-section of the suction pipe4 ,a strainer on the suction pipe is undesirable as it becomes clogged and is usually in an inaccessible position for cleaning4 ,a screen should be placed at the entrance to the suction well to prevent the entrance of objects that are likely to clog the pump4 ,a gate-valve and a check-valve should be provided on the discharge pipe1 the former to assist in controlling the rate of discharge and the latter to prevent back flow into the pump when it is not operating4 ,centrifugal pumps are well adapted to service in either large or small units4 ,an installation in a manhole at ,park ,point1 ,duluth1 is shown in ,fig4 #fa4 ,this station is controlled by an automatic electric device which is operated by a float in the suction pit4 ,such automatic control is an added advantage of the use of electrically driven centrifugal pumps4 ,the ,calumet ,pumping ,station in ,chicago1 shown in ,fig4 #di1 has a capacity of approximately #a1jjj cubic feet per second4 ,the simplicity of the layout of this station is shown in ,fig4 #fb4 ,illustration3 ,,fig4 #fb4--;,interior ,arrangement of the ,calumet ,sewage ,pumping ,station1 ,chicago4 ,eng4 ,news-,record1 ,vol4 #he1 #aibj1 p4 #hgb4 #hj4 ,steam ,pumps and ,pumping ,engines4--,the direct-acting steam pump1 one type of which is shown in ,fig4 #fc1 is adapted to pumping sewage the character of which will not corrode or clog the valves4 ,in this form of pump it is necessary to utilize the steam at full pressure throughout the entire length of the stroke1 which results in high steam consumption4 ,a flywheel permits the use of steam expansively during a part of the stroke1 thus increasing the economy of operation4 ,other devices used for the same purpose are known as compensators4 ,they are not in general use4 ,steam engines are classified in many different ways1 for example2 according to the type of valve gear1 as1 plain slide valve1 ,corliss1 ,lentz1 etc42 or according to the number of steam expansions1 as1 simple1 compound1 triple-expansion1 etc42 or according to the efficiency of the machine as low duty or high duty2 or as ,illustration3 ,,fig4 #fc4--,section of ,duplex ,piston ,steam ,pump4 ,courtesy1 ,the ,john ,h4 ,mc,gowan ,co4 ,,steam ,,end #b ,steam cylinder and housing combined4 #h ,steam piston head4 #i ,steam piston follower4 #aj ,steam piston inside ring4 #aa ,steam piston outside ring 7#b74 #ab ,steam cylinder head4 #ad ,steam chest4 #af ,steam chest cover4 #ag ,steam slide valve4 #ah ,steam valve rod4 #bj ,steam valve rod1 pin and nut4 #bb ,steam valve rod1 collar and set screw4 #bc ,steam valve rod1 stuffing box4 #bd ,steam valve rod1 stuffing box1 nut and gland4 #ch ,piston rod4 #dg ,piston rod stuffing box4 #dh ,piston rod1 stuffing box1 nut and gland4 #di ,valve gear stand4 #ea ,long valve crank and shaft4 #eb ,short valve crank and shaft4 ,,pump ,,end #aae ,pump body4 #abg ,brass liner4 #abi ,water piston head4 #acj ,water piston follower4 #acg ,cylinder head4 #aci ,valve plate4 #adj ,cap4 #aeb ,suction flange4 #afa ,discharge flange4 #afb ,valve seat1 suction or discharge4 #afc ,valve1 suction or discharge4 #afd ,suction valve spring4 #afg ,discharge valve spring4 #afh ,valve plate1 suction or discharge4 #afi ,valve stem1 suction or discharge4 ,,steam ,,end #ee ,crank pin4 #ef ,valve rod link4 #fa ,long rocker arm4 #fb ,short rocker arm4 #fc ,rocker arm wiper4 #fi ,cross head4 condensing or non-condensing1 etc4 ,throttling engines or automatic engines refer to the method of control of the steam by the governor4 ,in throttling engines the governor controls the amount of opening of the throttle valve1 in automatic engines the governor controls the position of the cut-off4 ,the simple slide valve1 low-duty1 non-condensing1 throttling engine1 is the lowest in first cost and the most expensive in the consumption of fuel4 ,the triple-expansion ,corliss1 or the non-releasing ,corliss1 high-duty pumping engine is the most expensive in first cost but consumes less steam for the power delivered than any other form of reciprocating engine4 ,for pumps of very small capacity the cost of fuel is not so important an item as the first cost of the machine4 ,for this reason and because of the lower cost of attendance low-duty pumps are more frequently found in small pumping stations4 ,illustration3 ,,fig4 #fd4--;,diagram ,showing ,rates of ,steam ,consumption for ,different ,size ,units under ,different ,loads4 ,,table #bg ,,water ,,rates ,,of ,,prime ,,movers ,,at ,,full ,,and ,,part ,,loads ,type of ,engine ,boiler ,power1 ,press4 ,k4,w4 ,per ,cent of ,full ,load ,lbs4 #be #ej #ge #ajj #abe ,single cylinder1 high speed1 #ajj to non-condensing #be #cc #bgbf4c #bg4jbg4e #aej #bej #dbcg4e #ce #cd4jcd4j ,automatic1 flat four valve1 #ajj to high speed #aej #cb #cj #bf4ebi4j #abe #bej #cc #ca #bhcj4j ,tandem compound condensing1 #ajj to high speed #abe #bc #ai #ag #ah #aej #be #bj #ai4e #ba ,cross compound1 condensing1 #abe high speed #cj #bf #bd #bcbc4e ,cross compound1 non-condensing1 #abe high speed #ci #ca #bg #bfbg4e ,single cylinder ,corliss1 #ajj condensing #abjbc4gbj4d #ai #ah4eai4j #ejjbf4cbb4hba4c #bj4hba4c #abe ,compound ,corliss1 condensing #af4e #adab4e #ab4aab4e #ajj #bb4b #aiag4j #af4eag4j #aej ,single cylinder1 rotary four #ajj valve1 non-condensing #gebf4bbb4cba4c #ba4fbb4h #djjce4jbg4bbf4d #bf4jbf4h #ahj ,rotary four valve1 tandem #ajj compound non-condensing #abecb4jbb4j #bjah4beah4e #fjjdj4jbh4cbc4b #bb4ebb4g #aej ,cross compound1 non-condensing #ajj rotary four valve #abe #be #baai4a #ah4eai4j #fjjci4d #bhbb4c #bj4fbj4g #aej ,single cylinder1 poppett valve1 #ajj non-condensing #abjbb4gbj4eai4g #ai4abj4a #fjjbh4ebf4jbe4j #bd4cbe4e #aej ,single cylinder1 poppett valve1 #ajj condensing #abjah4eaf4gaf4a #ae4faf4d #fjjbd4fbb4cba4d #bj4hba4i #aej ,compound condensing1 poppett #ajj valve #bjjad4bac4jab4e #ab4bab4i #abjjah4daf4iaf4c #ae4iaf4h #aej ,uniflow #abead4fac4gac4d #ac4dac4c #aej #fjjae4jad4cac4g #ac4ead4j ,steam turbines1 condensing1 #abe ,allis-,chalmers #cjj #bd #ag #afjaf4e #bjjj #ca4ibf4c #bc4hbc4j #age ,steam turbines1 condensing1 #abe ,westinghouse #cjj #ac4gab4h #ab4bab4f #bjjj #ah4baf4i #af4baf4h #age ,steam turbines1 high pressure1 non-con41 #ab to #cf wheel1 #d to #h #ajjj to #cfjj ,r4,p4,m4 stages #bh #e #aaf4e ,ditto4 ,condensing1 #bf-;inch #ag #c #aab4j ,the steam consumption per indicated horse-power1 better known as the water rate of the engine1 for various types of engines at full and at part load is shown in ,fig4 #fd4 ,the steam consumption of other types at full load is shown in ,table #bg4 ,the indicated horse-power 7,i4,h4,p47 of a steam engine is the product of the mean effective pressure 7,m4,e4,p471 the area of the steam pistons1 the length of the stroke1 and the number of strokes per unit of time4 ,a common form of this expression is1 ,i4,h4,p ,,plan#cc1jjj1 in which ,p the ,m4,e4,p4 in pounds per square inch2 ,l the length of the stroke in inches2 ,a the sum of the areas of the pistons in square inches2 ,n the number of revolutions per minute4 ,the ,i4,h4,p4 multiplied by the mechanical efficiency of the machine will give the brake or water horse-power1 that is1 the horse-power delivered by the machine4 ,the product of the ,m4,e4,p41 the sum of the areas of the steam pistons and the mechanical efficiency of the machine1 should equal the product of the total head of water pumped against expressed in pounds per square inch and the sum of the areas of the water pistons or plungers4 ,the ,m4,e4,p4 is determined from indicator cards taken from the steam cylinders during operation4 ,these cards show the steam pressure on the head and crank ends of each cylinder at all points during the stroke4 #ha4 ,steam ,turbines4--,among the advantages in the use of steam turbines as compared with reciprocating steam engines for driving centrifugal pumps are their simplicity of operation1 the small floor space needed1 their freedom from vibration requiring a relatively light foundation1 and their ability to operate successfully and economically either condensing or non-condensing under varying steam pressure4 ,they can be operated with steam at atmospheric or low pressure1 thus taking the exhaust from other engines4 ,the greatest economy of operation for the turbine alone will be obtained by operating with high pressure1 superheated steam and with a vacuum of #bh inches4 ,in large units the economy of operation of steam turbines is equal to that of the best type of reciprocating engines4 ,in order to develop the highest economy turbines are operated at speeds from about #c1fjj to #aj1jjj r4p4m4 or greater1 the smaller turbines operating at the higher speeds4 ,as these speeds are usually too great for the operation of centrifugal pumps for lifting sewage1 reduction gears must be introduced between the turbine and the pump4 ,although the best form of spiral-cut reduction gears may obtain efficiencies of #ie to #ih per cent1 or even higher1 their use1 particularly in small units1 is an undesirable feature of the steam turbine for driving pumps4 ,the steam consumption of ,de,laval turbines of different powers1 and the steam consumption of a #dej horse-power ,de,laval turbine at different loads are shown in ,fig4 #fd4 ,some steam consumptions of other turbines are recorded in ,table #bg4 ,it is to be noted that the steam consumption of the #dej horse-power turbine at part loads is not markedly greater than that at full loads4 ,this is an advantage of steam turbines as compared with reciprocating engines4 ,the steam consumption of any turbine is dependent on the conditions of operation and is lower the higher the vacuum into which the exhaust takes place4 ,illustration3 ,,fig4 #fe4--,the ,de,laval ,trade ,mark1 ,illustrating the ,principle of the ,de,laval ,steam ,turbine4 ,courtesy1 ,de,laval ,steam ,turbine ,co4 ,there are two types of turbines in general use1 the single stage or impulse machines1 and the compound or reaction type4 ,the ,de,laval is a well-known make of the single stage or impulse type4 ,the principle of its operation is indicated in ,fig4 #fe1 which is the trade mark of the ,de,laval ,steam ,turbine ,co4 ,the energy of the steam is transmitted to the wheel due to the high velocity of the steam impinging against the vanes4 ,in the compound or reaction type of machine the steam expands from one stage to the next imparting its energy to the wheel by virtue of its expansion in the passages of the turbine4 ,for this reason the single-stage or impulse type is operated at higher speeds than the compound or reaction machines4 #hb4 ,steam ,boilers4--,among the important points to be considered in the selection of a steam boiler for a sewage pumping station are3 the necessary power2 the quality of the feed water2 the available floor space2 the steam pressure to be carried2 and the quality and character of the fuel4 ,tubular boilers of the type shown in ,fig4 #ff1 are lower in first cost than other types of boilers4 ,they are not ordinarily built in units larger than #bej to #cjj horse-power and where more power is desired a number of units must be used4 ,they are objectionable because of the relatively large floor space required1 and because of their relatively poor economy of operation4 ,the efficiencies of water-tube boilers of different types are given in ,table #bh4 ,large power units of the water-tube type1 as shown in ,fig4 #fg1 although more expensive in first cost1 require less floor space4 ,almost any desired steam pressure can be obtained from either type but water-tube boilers are more commonly used for high pressures4 ,the grate or stoker can be arranged to burn almost any kind of fuel under either water-tube or fire-tube boilers4 ,the use of poor quality of water in water-tube boilers is undesirable as the tubes are more likely to become clogged than the larger passages of the fire-tube boilers4 ,if necessary1 a feed-water purification plant should be installed1 as it is usually cheaper to take the impurities out of the water than to take the scale out of the boiler4 ,illustration3 ,,fig4 #ff4--;,horizontal ,fire-tube ,boiler4 ,illustration3 ,,fig4 #fg4--;,babcock and ,wilcox ,water-tube ,boiler4 ,not less than two boiler units should be used in any power station1 regardless of the demands for power1 and if the feed water is bad1 three or even four units should be provided1 as two units may be down at any time4 ,an appreciable factor of safety is provided by the ability of a boiler to be operated at #cj to #ej per cent overload1 if sufficient draft is available1 but with resulting reduction in the economy of operation4 ,the number of units provided should be such that the maximum load on the pumping station can be carried with at least one in every #f units or less1 out of service for repairs or other cause4 ,,table #bh ,,efficiencies ,,of ,,steam ,,boilers ,from ,marks' ,mechanical ,engineer's ,handbook ,type ,horse-power ,furnace ,evap4 from and at ,b4,t4,u4 #bab ,combined ,sq4 ,per ,cent per per ,efficiency ,ft4 of ,rated ,lb4 ,lb4 of ,boiler ,grate ,capacity ,dry ,dry and ,area ,d'v'l'd ,coal ,coal ,furnace ,babcock #cjj;,hand-fired ,wilcox #hd #aah4gaa1iab #h4ha #ga4h ,babcock #fdj;,hand-fired ,wilcox #aah #aba4ead1fjb #aj4hc #gb4j ,stirling #aabh;,b4 ,w4 chain grate #ahg #aih4cab1acj #i4ea #gf4a ,rust #cce;,hand-fired #fh #baj4eac1bjb #i4db #fh4i ,heine #djj;,green chain grate #hc4e #abc4haa1fjh #h4gi #gc4e ,maximum efficiency recorded #hc ,the steam delivered by a boiler is the basis of the measurement of its capacity or power4 ,a boiler horse-power is the delivery of #cc1cbj ,b4,t4,u4 per hour4 ,it is approximately equal to the raising of #cj pounds of water per hour from a temperature of #ajj ,fahrenheit1 to steam at a pressure of #gj pounds per square inch1 or to #cd pounds of water per hour changed to steam from and at #bab ,fahrenheit1 at atmospheric pressure4 ,the horse-power of a boiler is sometimes approximated by the area of its grate or heating surface4 ,such a method of measuring has a low degree of accuracy on account of the variations in the quality of the fuel1 and the rate of combustion4 ,for example1 the rate of combustion under a locomotive boiler is high and there is less than th of a square foot of grate area and about #d4e square feet of heating surface per boiler horse-power4 ,the ,scotch ,marine type of boiler used on steam ships1 has slightly more grate area and slightly less heating surface than the locomotive type of boiler1 because the rate of combustion is lower4 ,stationary water-tube boilers may have #b to #c times as much grate area and heating surface per horse-power as is found in locomotive boilers4 ,if a poor type of fuel is to be used the area of the grate should be increased about inversely as the heat content of the fuel4 ,the approximate heat content of various types of fuels is shown in ,table #bi4 ,,table #bi ,,approximate ,,heat ,,value ,,of ,,fuels ,fuel ,pounds of ,water ,evaporated from and at #bab ,f4 ,all heat ,b4,t4,u4 per ,pound utilized ,anthracite #ac1ejj #ad4j ,semi-bituminous1 ,pennsylvania #ae1jjj #ae4e ,semi-bituminous1 best1 ,west ,virginia #ae1jjj #ae4h ,bituminous1 best1 ,pennsylvania #ad1dej #ae4j ,bituminous1 poor1 ,illinois #aj1ejj #aj4i ,lignite1 best1 ,utah #aa1jjj #aa4d ,lignite1 poor1 ,oregon #h1ejj #h4h ,wood1 best oak #i1cjj #i4f ,wood1 poor ash #h1ejj #h4h #hc4 ,air ,ejectors4--,the ,ansonia compressed-air sewage ejector is shown in ,fig4 #fh4 ,in its operation1 sewage enters the reservoir through the inlet pipe at the right1 the air displaced being expelled slowly through the air valve marked ,b4 ,the rising sewage lifts the float which actuates the balanced piston valve in the pipe above the reservoir when the reservoir fills4 ,the lifting of the valve admits compressed air to the reservoir4 ,the air pressure closes valve ,a and the inlet valve at the right1 and ejects the sewage through the discharge pipe at the left4 ,as the float drops with the descending sewage it shuts off the air supply and opens the air exhaust through the small pipe at the top center4 ,sewage is prevented from flowing back into the reservoir by the check valve in the discharge pipe4 ,other ejectors operating on a similar principle are the ,ellis1 the ,pacific1 the ,priestmann and the ,shone4 #hd4 ,electric ,motors4--,the most common form of alternating current electric motor used for driving sewage pumps where continuous operation and steady loads are met is the squirrel-cage polyphase induction motor4 ,these motors operate at a nearly constant speed which should be selected to develop the maximum efficiency of the pump and motor set4 ,while ,fig4 #ei shows the best efficiency under varying heads to be obtained with variable speed1 the advantages of cost1 attention1 and availability make the use of a constant speed motor common4#dg ,this type of motor is undesirable where stopping and starting are frequent because it has a relatively small starting torque and it requires a large starting current4 ,such motors can be constructed in small sizes for high starting torques by increasing the resistance of the rotor1 but at the expense of the efficiency of operation4 ,illustration3 ,,fig4 #fh4--;,ansonia ,compressed-,air ,sewage ,ejector4 ,alternating current motors are more generally used than direct-current motors because of the greater economy of transmission of alternating current1 but where direct current is available constant speed shunt wound motors should be adopted4 ,in the selection of a motor to drive a centrifugal pump it is important that the motor have not only the requisite power1 but that its speed will develop the maximum efficiency from the pump and motor combined4 ,if the pump and motor operate on the same shaft the speed of the two machines must be the same4 ,if the two are belt connected1 the size of the pulleys may be selected so as to give the required speed4 ,if the motor is to be connected to a power pump an adequate automatic pressure relief valve should be provided on the discharge pipe from the pump1 to prevent the overloading of the motor or bursting of the pump in case of a sudden stoppage in the pipe4 ,the motor must be selected to suit the conditions of voltage1 cycle1 and phase on the line4 ,transformers are available to step the voltage up or down to practically any value4 ,rotary converters are used to change direct to alternating current or vice versa4 #he4 ,internal ,combustion ,engines4--,internal combustion engines are used for driving pumps4 ,units are available in size from fractions of #a horse-power to #b1jjj horse-power or more1 although the use of the larger sizes is exceptional4 ,these engines are not commonly used for sewage pumping but when used they are ordinarily belt connected to a centrifugal pump1 or to an electric generator which in turn drives electric motors which operate centrifugal pumps4 ,this type of engine is more commonly adapted to small loads1 although not entirely confined to this field1 as they serve admirably as emergency units to supplement an electrically equipped pumping station4 ,the fuel efficiency of internal combustion engines is higher than for steam engines as is indicated in ,table #cj1 but the fuel is more expensive4 ,the four-cycle gas engine shown in ,fig4 #fi is the type most commonly used4 ,its horse-power is the product of3 the mean effective pressure1 the length of the stroke1 the area of the piston1 and the number of explosions per second divided by #eej4 ,the ,m4,e4,p4 is dependent on the character of the fuel used and the compression of the gas before ignition4 ,producer gas will furnish mean effective pressures between #fj and #gj pounds per square inch1 natural gas and gasoline1 #he to #ij pounds per square inch1 and alcohol from #ie to #aaj pounds per square inch4 ,,table #cj ,,comparative ,,fuel ,,costs ,,for ,,prime ,,movers ,type of ,engine ,quantity of ,cost of ,fuel in ,fuel per ,h4,p4 ,cents per ,hour ,horse-power ,hour ,reciprocating steam engines1 simple1 #ba to #h lb4 #d4b to #a4f non-condensing1 #be to #bjj ,h4,p4 coal ,triple condensing1 #bjjj to #aj1jjj #b4c to #a4i lb4 #j4df to #j4cg ,h4,p4 coal ,steam turbines1 high pressure1 non-condensing1 #bjj to #ejj ,k4,w4 #f4e to #d4b lb4 #a4c to #j4hf coal #ejj to #cjjj ,k4,w4 #b4f to #a4i lb4 #j4eb to #j4cg coal ,condensing #ejjj to #bj1jjj ,k4,w4 #a4h to #a4dc lb4 #j4cf to #j4bh coal ,gas engines ,natural gas1 #ej to #bjj ,h4,p4 #ai to #aa cu4 ft4 ,producer gas1 #ej to #bjj ,h4,p4 #b to #a4e cu4 ft4 ,illuminating gas1 #aj to #ge ,h4,p4 #bf to #ai cu4 #b4a to #a4e ft4 ,gasoline1 #aj to #ge ,h4,p4 #a4e to #j4h #e4f to #c4j pints ,oil engines1 #ajj to #ejj ,h4,p4 #a4a to #j4ge lb4 oil ,,note4--,coal assumed at #d4jj per ton1 illuminating gas at #hj cents per thousand cubic feet1 and gasoline at #cj cents per gallon4 ,illustration3 ,,fig4 #fi4--;,bessemer ,oil ,engine4 ,twin ,cylinder1 ,valve ,side4 ,the ,diesel ,engine is the most efficient of internal combustion engines4 ,the original aim of the inventor1 ,dr4 ,rudolph ,diesel1 was to avoid the explosive effect of the ordinary internal combustion engine by injecting a fuel into air so highly compressed that its heat would ignite the fuel1 causing slow combustion of the fuel thus utilizing its energy to a greater extent4 ,the fuel and air were to be so proportioned as to require no cooling4 ,although the ideal condition has not been attained1 the heat efficiency of ,diesel engines is high4 ,they will consume from #j4c to #j4e of a pound of oil 7containing #ah1jjj ,b4,t4,u4 per pound7 per brake horse-power hour1 giving an effective heat efficiency of #be to #cj per cent4 ,although not now in extensive use in the ,united ,states it is probable that this engine will be more generally adopted for conditions suitable for internal combustion engines4 #hf4 ,selection of ,pumping ,machinery4--,centrifugal pumps are particularly adapted to the lifting of sewage because of their large passages1 and their lack of valves4 ,the low lifts1 nearly constant head1 and the possibility of equalizing the load by means of reservoirs are particularly suited to efficient operation of centrifugal pumps4 ,they require less floor space than reciprocating pumps of the same capacity1 and because of their freedom from vibration they do not demand so heavy a foundation4 ,the discharge from the pump is continuous thus relieving the piping from vibration4 ,in case of emergency the discharge valve can be shut off without shutting down the pump1 an important point in 8fool proof0 operation4 ,volute pumps are better adapted to pumping sewage as their passages are more free and they are better suited to the low lifts met4 ,gritty and solid matter will cause wear on the diffusion vanes of turbine pumps in spite of the most careful design4 ,although turbine pumps can possibly be built with higher efficiency than volute pumps1 their efficiency at part load falls rapidly and the fluctuations of sewage flow are sufficient to affect the economy of operation4 ,turbine pumps are more expensive and heavier than volute pumps on account of the increased size necessitated by the diffusion vanes4 ,multi-stage pumps are used for high lifts and are seldom if ever required in sewage pumping4 ,as ordinarily manufactured1 each stage is good for an additional #dj to #ajj pounds pressure1 but wide variations in the limiting pressures between stages are to be found4 ,reciprocating plunger pumps are sometimes used for sewage pumping where the character of the sewage is such that the valves will not be clogged nor parts of the pump corroded4 ,these pumps are seldom used in small installations or for low lifts4 ,they are not adapted to automatic or long distance control as are electrically driven centrifugal pumps4 ,the use of reciprocating pumps for sewage pumping is practically restricted to very large pumping stations with capacities in the neighborhood of #ej1jjj1jjj gallons per day or more4 ,steam-driven pumps are the most common of the reciprocating type1 but power pumps are sometimes used in special cases for small installations and may be driven by either a steam or gas engine or an electric motor4 ,compressed air ejectors1 as described in ,art4 #hc are used for lifting sewage and other drainage from the basement of buildings below the sewer level4 ,centrifugal pumps electrically driven are1 as a rule1 the most satisfactory for sewage pumping4 ,electric drive lends itself to control by automatic devices1 which are particularly convenient in small pumping stations4 ,the control can be arranged so that the pump is operated only at full load and high efficiency1 and when not operating no power is being consumed1 as is not the case with a steam pump where steam pressure must be maintained at all times4 ,the electric driven pump is thrown into operation by a float controlled switch which is closed when the reservoir fills1 and opens when the pump has emptied the reservoir4 ,the choice between steam and electric power for large pumping stations is a matter of relative reliability and economy4 ,the selection of the proper type of pump1 whether reciprocating or otherwise1 requires some experience in the consideration of the factors involved4 ,fig4 #gj is of some assistance4 ,in discussing this figure1 ,chester states3 8,fig4 #gj attempts to represent graphically1 the writer's ideas under general conditions1 of the machines that should be selected for certain capacities for both principal engine and alternate and the station duty they may be expected to produce1 but you must realize that this intends the principal engine doing at least #ij per cent of the work and that the head1 the cost of coal1 the load factor1 the cost of real estate 444 the boiler pressure1 and the space available1 and finally 444 the funds available1 are factors which may shift both the horizontal and curved lines4 ,in the field of low service pumps of #aj1jjj1jjj capacity or over1 the centrifugal pump reigns supreme1 and for constant low heads of #bj1jjj1jjj capacity or over the turbine driven centrifugal usurps the field40 ,a reciprocating pump of any type would have to be specially built for pumping sewage not carefully screened or otherwise treated1 as the valves1 ordinarily used in such pumps for lifting water1 would clog4 ,the vertical triple-expansion pumping engine with special valves and for large installations1 and the centrifugal pump for large or small installations are the only suitable types for pumping sewage4 ,with steam turbine or electric drive the centrifugal has the field to itself4 ,illustration3 ,,fig4 #gj4--;,expectancy ,curves for ,pumping ,engines ,working against a ,pressure of #ajj ,pounds per ,square ,inch4 ,j4 ,n4 ,chester1 ,journal ,am4 ,water ,works ,ass'n1 ,vol4 #c1 #aiaf1 p4 #dic4 #hg4 ,costs of ,pumping ,machinery4--,the cost of pumping machinery can not be stated accurately as the many factors involved vary with the fluctuations in the prices of raw materials1 transportation1 labor1 etc4 ,the actual purchase price of machinery can be found accurately only from the seller4 ,the costs given in this chapter are useful principally for comparative purposes and for exercise in the making of estimates4 ,the costs of complete pumping stations are shown in ,table #ca4dh ,these figures represent costs in #aiaa4 ,,table #ca ,,costs ,,of ,,complete ,,pumping ,,stations ,these costs include the best type of triple-expansion engines1 high-pressure boilers1 brick or inexpensive stone building with slate roof1 chimney and intake4 ,cost of land is not included4 ,discharge ,horse-power per ,pressure1 ,lbs4 ,million ,gals4 ,cost1 ,dollars per,cost1 ,dollars per per ,sq4 ,in4 ,pumped ,horse-power ,million ,gallons #cj #ab #efb #f1gej #dj #af #dch #g1jjj #ej #bj #cfb #g1bej #fj #bd #cab #g1ejj #gj #bh #bgg #g1gej #hj #cb #bej #h1jjj #ij #cf #bbi #h1bej #ajj #dj #bac #h1ejj #aaj #dd #bjj #h1gej #abj #dh #ahg #i1jjj #acj #eb #aib #aj1jjj #hh4 ,cost ,comparisons of ,different ,designs4--,in the design of a pumping station and its equipment the relative costs of different designs should be compared1 and the least expensive design selected1 due consideration being given to serviceability1 reliability1 and other factors without definite financial value4 ,in comparing the costs of different types of machinery1 all items in connection with the pumping station should be considered4 ,for example1 the cost of an electrically driven centrifugal pump and equipment may be less than the total cost of a steam driven reciprocating pump and equipment because of the saving in the cost of boilers1 boiler house1 etc41 but a comparison of the capitalized cost of the two might show in favor of the reciprocating steam pump because of the lower cost of operation4 ,the total cost of a plant1 or any portion thereof1 may be considered as made up of three parts3 7#a7 ,the first cost1 7#b7 operation and maintenance and1 7#c7 renewal4 ,the total cost ,s can be expressed as ,s ,c ,or ,r1 in which ,c the first cost2 ,o the annual expenditure for operation and maintenance2 ,r the amount set aside to cover renewal2 r the rate of interest4 ,s is called the capitalized cost of a plant4 ,the annual payment necessary to perpetuate a plant is ,a ,sr ,cr ,o ,rr4 ,the value of ,r is useful when expressed in terms of the life of the plant or machine and the current rate of interest4 ,it is sometimes called the depreciation factor or capitalized depreciation4 ,if it is borne in mind that ,r is the amount to be set aside at compound interest for the life of the plant1 at the end of which time the accrued interest should be sufficient to renew the plant1 it is evident that ,r7#a ,r7n ,r ,c or ,r ,c77#ar7n #a7 in which n is the period of usefulness1 or life of the plant1 expressed in years1 no allowance being made for scrap value4 ,a comparison of the annual expense of three different plants is shown in ,table #cb4 ,it is evident from this comparison that the machinery with the least first cost is not always the least expensive when all items are considered4 ,a sinking fund is a sum of money to which additions are made annually for the purpose of renewing a plant at the expiration of its period of usefulness4 ,the annual payment into the sinking fund is equivalent to the term ,rr in the expression for annual cost1 or in terms of ,c1 r1 and n1 the annual payment is ,cr77#a r7n #a74 ,it is the same as the capitalized depreciation multiplied by the rate of interest4 ,the expression r77#a r7n #a7 is sometimes called the rate of depreciation4 ,the present worth of a machine is the difference between its first cost and the present value of the sinking fund4 ,if m represents the present age of a plant in years1 then the present worth is ,p ,c7#a - 77#a r7n #a777a r7m #a774 ,,table #cb ,,comparison ,,of ,,costs ,,of ,,three ,,different ,,pumping ,,stations4 ,,nominal ,,capacity ,,thirty ,,million ,,gallons ,,per ,,day ,,raised ,,thirty ,,feet ,equipment ,plant ,a ,one ,acre of ,land4 ,brick ,building1 ,steel ,trussed ,roof1 ,slate ,covered4 ,cross ,compound ,condensing ,horizontal ,pumping ,engine ,annual ,years of ,sinking ,total ,payment,usefulness ,fund on ,payment ,first ,cost ,land #ajj #j #ajj ,permanent #aahh #ej #ajhj #b1bfj ,structures#di ,pumps and #ddj #ae #dce #hge ,machinery ,boilers #bhj #aj #ddf #gbf ,labor #ad1jjj ,fuel #e1ejj ,repairs1 etc4 #dhj ,total #bc1ida ,equipment ,plant ,b ,one ,acre of ,land4 ,brick ,building4 ,steel ,trussed ,roof1 ,slate ,covered4 ,compound ,condensing ,low ,duty ,horizontal ,pumping ,engine ,annual ,years of ,sinking ,total ,payment,usefulness ,fund on ,payment ,first ,cost ,land #ajj #j #ajj ,permanent #aahj #ej #ajhj #b1bfj ,structures#di ,pumps and #cij #ae #cie #ghe ,machinery ,boilers #beb #aj #djj #feb ,labor #ad1jjj ,fuel #g1bjj ,repairs1 etc4 #djj ,total #be1dig ,equipment ,plant ,c ,one ,acre of ,land4 ,frame ,building1 ,shingle ,roof4 ,compound ,duplex ,non-,condensing ,pumping ,engine4 ,annual ,years of ,sinking ,total ,payment,usefulness ,fund on ,payment ,first ,cost ,land #ajj #j #ajj ,permanent #haj #ej #gge #a1ehe ,structures#di ,pumps and #cfj #ae #ceb #gab ,machinery ,boilers #cjh #aj #dij #gih ,labor #ad1jjj ,fuel #h1bjj ,repairs1 etc4 #eej ,total #be1ide ,where straight-line depreciation is spoken of it is assumed that the worth of a machine depreciates an equal part of its first cost each year4 ,for example1 if the life of a plant is assumed to be #bj years1 straight-line depreciation will assume that the plant loses #a_/bj of its original value annually4 ,the present worth of a plant under this assumption would be the product of its first cost and the ratio between its remaining life and its total life4 ,this method of estimating depreciation and worth is frequently used1 particularly for short-lived plants and for simplicity in bookkeeping1 but it is less logical than the method given above4 #hi4 ,number and ,capacity of ,pumping ,units4--,in order to select the number and capacity of pumping units for the best economy1 a comparison of the costs of different combinations of units should be made and the most economical combination determined by trial4 ,the principles outlined in the preceding articles should be observed in making these comparisons4 ,in a steam pumping station1 when the number of units operating is less than the average daily maximum for the period1 steam must nevertheless be kept on a sufficient number of boilers to operate the maximum number of pumps4 ,this1 and corresponding standby losses must not be overlooked1 as they may show that a smaller number of larger units is ultimately more economical4 ,,table #cc ,,summary ,,of ,,fluctuations ,,of ,,sewage ,,flow ,,at ,a ,,proposed ,,pumping ,,station ,number of ,days ,flow in ,thousand ,loads ,occurred in ,gallons per ,one ,year ,minute ,lift in ,feet ,horse-power #a #bic #f4j #dej #h #afc #h4f #ced #ae #aai #aj4j #cjj #ah #ajf #aj4f #bhd #bc #hh #aa4b #bdi #ca #fi #ab4b #baa #cb #fe #ab4d #bjd #de #ea #ac4d #agc #da #ej #ac4e #afi #cj #de #ac4h #aeh #bh #dd #ac4i #aed #bc #dj #ad4b #adc #ba #ch #ad4d #acg #ah #ce #ad4f #abi #ab #bi #ae4j #aaa #h #bd #ae4f #ie #e #bj #af4j #gi #c #af #af4e #fe #b #ad #af4h #eh #a #f4e #ah4j #bi ,total horse-power days for one year1 #ajb1jjj4 ,average load in horse-power1 #bhj4 ,,table #cd ,,possible ,,combinations ,,of ,,five ,,pumping ,,units ,,to ,,care ,,for ,,the ,,loads ,,shown ,,in ,,table #ccej #dj ,horse-power ,load ,type #aea ,per ,cent,pounds ,load in ,pounds,number ,total of ,rated,steam ,horse-power,steam1of ,days ,load ,capacity per ,units ,load is,carried ,h4,p4 #aj1jjj;,carried on ,hour ,poundsin ,year these ,days in ,h4,p4 #aea #de #fj4d #f4e #a #fha #abj #dd #dh #dj4e #h #edb #ajb #de #dj4h #ff4a #ae #deh #if #de #ch4d #gd4h #ah #dcd #ih #de #ci4b #ig4e #bc #cha #ca #cbb #cb #cab #de #bfd #da #beh #aja #de #dj4d #aca #cj #bdb #ih #de #ci4b #aai #bh #bce #bc #bah #ba #baj #ah #aih #ab #agj #ajd #de #da4f #bj4i #h #ade #e #aba #c #ajj #ii #de #ci4f #h4e #b #hi #aac #dd #de4b #d4h #a #de -------- ,sub-total #eif4f ,grand total in pounds1 #fe1gjj1jjj #ej ,horse-power ,load ,type #aea ,per ,cent,pounds ,load in ,pounds,number ,total of ,rated,steam ,horse-power,steam1of ,days ,load ,capacity per ,units ,load is,carried ,h4,p4 #aj1jjj;,carried on ,hour ,poundsin ,year these ,days in ,h4,p4 #aea #de #ge4e #h4b #a #fha #abj #dd #fj4j #ej4g #h #edb #ajb #de #ea4j #hb4g #ae #deh #ij #de #dh4j #ic4e #ah #dcd #ih #de #di4j #abb4j #bc #cha #ajd #de #eb4j #agd4e #ca #cbb #aja #de #ej4e #agd4h #cb #cab #de #bfd #ajc #de #ea4e #bbh #da #beh #cj #bdb #bh #bce #bc #bah #ba #baj #ah #aih #ab #agj #h #ade #aji #dd #ed4e #bh4h #e #aba #c #ajj #ii #de #di4e #aj4g #b #hi #a #de -------- #igc4i #fj ,horse-power ,load ,type #aea ,per ,cent,pounds ,load in ,pounds,number ,total of ,rated,steam ,horse-power,steam1of ,days ,load ,capacity per ,units ,load is,carried ,h4,p4 #aj1jjj;,carried on ,hour ,poundsin ,year these ,days in ,h4,p4 #aea #de #ij4f #i4h #a #fha #abj #dd #gb4j #fj4h #h #edb #ajb #de #fa4b #ii4b #ae #deh #if #de #eg4f #aab #ah #dcd #bc #cha #ajd #de #fb4d #bji4j #ca #cbb #aja #de #fj4f #baj #cb #cab #ajb #de #fa4b #cbe #de #bfd #da #beh #cj #bdb #bh #bce #bc #bah #ba #baj #ah #aih #ajf #de #fc4f #acg #ab #agj #h #ade #aji #dd #fe4d #cd4e #e #aba #c #ajj #b #hi #a #de -------- #aaig4c #ajj ,horse-power ,load ,type #dea ,per ,cent,pounds ,load in ,pounds,number ,total of ,rated,steam ,horse-power,steam1of ,days ,load ,capacity per ,units ,load is,carried ,h4,p4 #aj1jjj;,carried on ,hour ,poundsin ,year these ,days in ,h4,p4 #aea #bh #aea #aj4b #a #fha #abj #be #abj #eg4e #h #edb #ajb #be #ajb #fb4e #ae #deh #if #be #if #ajc4h #ah #dcd #ih #be #ih #ace4a #bc #cha #ca #cbb #cb #cab #de #bfd #da #beh #cj #bdb #bh #bce #bc #bah #ba #baj #ah #aih #ajf #be #ajf #gf4e #ab #agj #ajd #be #ajd #bi4a #h #ade #e #aba #ajj #be #ajj #cb4d #c #ajj #b #hi #a #de -------- #ejg4a #bjj ,horse-power ,load ,type #eea ,per ,cent,pounds ,load in ,pounds,number ,total of ,rated,steam ,horse-power,steam1of ,days ,load ,capacity per ,units ,load is,carried ,h4,p4 #aj1jjj;,carried on ,hour ,poundsin ,year these ,days in ,h4,p4 #aea #bc #cjb #af4g #a #fha #abj #bj #bdj #ib4j #h #edb #ajb #bj #bjd #adg #ae #deh #if #bj #aib #aff #ah #dcd #ih #bj #aif #baf #bc #cha #ajd #bj #bjh #cji4e #ca #cbb #aja #bj #bjb #caj #cb #cab #ajb #bj #bjd #dha #de #bfd #ajc #bj #bjf #dje #da #beh #aja #bj #bjb #bia #cj #bdb #ih #bj #aif #bfd #bh #bce #aji #bj #bah #bda #bc #bah #aje #bj #baj #bab #ba #baj #ii #bj #aih #aga #ah #aih #ab #agj #h #ade #e #aba #c #ajj #b #hi #a #de -------- #ccbb4b ,,table #ce ,,financial ,,comparison ,,of ,,pumping ,,equipments ,the loads to be cared for are shown in ,table #cd4 ,an emergency unit is supplied to bring the overload capacity of the plant1 less the largest unit1 equal to the maximum load on the plant4 ,no unit will be overloaded more than fifty per cent of its rated capacity4 ,number of ,units ,exclusive of ,emergency ,unit #e #d #c #b #a ,capacity #dj h4p41 and ,type of ,type #a ,units #ej h4p41 #ej h4p41 ,type #a ,type #a #fj h4p41 #ajj h4p41 #ej h4p41 ,type #a ,type #d ,type #a #ajj h4p41 #abe h4p41 #aej h4p41 #bjj h4p41 ,type #d ,type #d ,type #e ,type #e #bjj h4p41 #age h4p41 #bej h4p41 #bej h4p41 #dej h4p41 ,type #e ,type #e ,type #f ,type #f ,type #g ,emergency ,unit1 ,capacity #bjj h4p41 #age h4p41 #bej h4p41 #bej h4p41 #dej h4p41 and ,type ,type #e ,type #e ,type #f ,type #f ,type #g ,annual payments1 ,dollars ,first cost of pumps #a1efj #a1ffj #a1dhj #a1ddj #a1ejj ,renewal of pumps #a1cdj #a1dcj #a1bgj #a1bdj #a1bij ,first cost1 boilers #a1jbd #a1jhi #a1abe #a1aae #a1daj ,renewal1 boilers #hjj #ice #iff #ieh #a1baj ,fuel #ac1adj #aa1hfj #aj1dij #i1dbj #i1djj ,repairs1 oil1 etc4 #b1jjj #a1hjj #a1ejj #a1cjj #a1bjj ,labor #ce1jjj #ca1ejj #bi1ejj #bg1jjj #bg1jjj ,emergency unit4 ,first cost #fdj #efj #hjj #hjj #a1ejj ,emergency unit4 ,renewal #eej #dhj #fij #fij #a1bij ,total #ef1acd #ea1cad #dg1hba #dc1ifc #de1hjj ,type #a4 ,simple duplex1 non-condensing1 horizontal4 ,type #d4 ,compound condensing low duty horizontal4 ,type #e4 ,low duty1 triple1 condensing1 horizontal4 ,type #f4 ,cross compound1 condensing1 horizontal4 ,type #g4 ,high duty1 triple1 condensing1 vertical4 ,for example1 the sewage flow expected at a proposed pumping station is shown in ,table #cc4 ,the steps involved in the selection of the number and capacity of pumping units to care for these quantities are as follows3 7#a7 ,determine the rated capacity of the equipment to be provided4 ,in this case the capacity will be taken as #dej horse-power1 which is the maximum load to be placed on the pumps4 7#b7 ,select any number of units of such different types and capacities as are available for comparison1 and arrange them in different combinations so that each unit will operate as nearly as possible at its rated capacity4 ,the work involved in such a study for #e units is shown in ,table #cd4 ,the weight of steam consumed per indicated horse-power hour corresponding to the per cent of the rated capacity at which the unit is operating is read from ,fig4 #fd or other data4 7#c7 ,repeat this step for other numbers and types of units4 7#d7 ,prepare a table showing the annual costs of combinations of different numbers and types of units as shown for this example in ,table #ce4 ,the figures in ,table #ce show that the least expensive of the combinations of the units studied is one #bjj horse-power unit1 and one #bej horse-power unit1 with a #bej horse-power unit in reserve4 ,it is to be noted that a reserve unit has been provided in each combination1 the capacity of which is equal to that of the largest unit of the combination4 ,,chapter ,,viii ,,materials ,,for ,,sewers #ij4 ,materials4--,the materials most commonly used for the manufacture of sewer pipe are vitrified clay and concrete4 ,cast iron1 steel1 and wood are also used1 but only under special conditions4 ,for pipes built in the trench1 concrete1 concrete blocks1 brick1 and vitrified clay blocks are used4 ,concrete is being used to-day more than bricks or blocks because it is cheaper4 ,a decade or more ago all large sewers were built of bricks4 ,vitrified clay and concrete are used for manufactured pipe #db inches and less in diameter4 ,concrete is used almost exclusively for larger sizes of pipe1 particularly for pipe constructed in place1 although a brick invert lining is advisable when high velocities of flow are expected4 ,the character of the external load1 the velocity of flow and the quality of sewage are important factors in determining the material to be used in the construction of sewers4 ,reinforced concrete should be used for large sewers near the surface subjected to heavy moving loads4 ,a high velocity of flow with erosive suspended matter demand a brick wearing surface on the invert4 ,many engineers consider concrete less suitable than vitrified clay or brick for conveying septic sewage or acid industrial wastes1 as concrete deteriorates more rapidly under such conditions4 ,concrete should be used on soft yielding foundations1 whereas a hard compact earth1 which can be cut to the form of the sewer1 is suitable to the use of brick or concrete4 ,cast-iron pipe with lead joints is used for sewers flowing under pressure1 or where movements of the soil are to be expected4 ,if the sewage is not flowing under pressure1 cement joints are sometimes used in the cast-iron pipe4 ,movements of the soil are to be expected on side hills1 under railroad tracks1 etc4 ,steel pipe is used on long outfalls or under other conditions where external loads are light and the cost is less than for other materials4 ,because of the thin plates used and the liability to corrosion steel is not frequently used4 ,it should never be deeply buried nor externally loaded because of its weakness in resisting such forces4 ,like wood pipe1 its lightness is favorable to use on bridges1 but the greater heat conductivity of steel than wood necessitates protection against freezing in exposed positions4 ,wood is preferable only where the economy of its use is pronounced and the pipe is running full at all times4 ,it is desirable that the wood pipe should be always submerged as the life of alternately wet and dry wood is short4 ,corrugated galvanized iron and unglazed tile have been used for sewers1 but usually only in emergencies or as a makeshift4 ,corrugated iron is not suitable on account of its roughness and liability to corrosion1 and unglazed tile because of its lack of strength4 ,illustration3 ,,fig4 #ga4--;,diagrammatic ,section through ,clay-pipe ,press4 #ia4 ,vitrified ,clay ,pipe4--,in general the physical and chemical qualities of clays before burning are not sufficient to cause their condemnation or approval by the engineer1 as their behavior in the furnace is quite individual and depends greatly on the manner in which they are fired4 ,the engineer is interested in the result and writes his specifications accordingly4 ,in the manufacture of clay pipe1 the clay as excavated is taken to a mill and ground while dry1 to as fine a condition as possible4 ,it is then sent to storage bins from which it is taken for wet grinding and tempering4 ,in this process the clay is mixed with water to the proper degree of plasticity4 ,a variation of #a to #a per cent in the moisture content will mean failure4 ,too wet a mixture will not have sufficient strength to maintain its shape in the kiln4 ,too dry a mixture will show laminations as it is pressed through the discs4 ,a press used in the manufacture of clay pipe is shown in cross-section in ,fig4 #ga4 ,with the piston heads in the steam and mud cylinders at their extreme upward positions1 the mud cylinder is filled with clay of the proper consistency4 ,steam is then turned into the steam cylinder under pressure and the clay is squeezed into the space between the inner and outer shells of the die and mandrel to form the hub of the pipe4 ,the pressure on the clay may be from #bej to #fjj pounds per square inch4 ,when clay appears at the holes1 marked hh at the bottom of the mud cylinder1 the bottom plate and the center portion of the die are removed and the remainder or straight portion of the pipe is formed by squeezing the clay between the mandrel and the outer wall of the die4 ,a completely formed pipe can be seen issuing from the press in ,fig4 #gb4 ,any sized pipe that is desired can be formed from the same press by changing the size of the dies and mandrel4 ,illustration3 ,,fig4 #gb4--;,clay-pipe ,press4 ,courtesy1 ,blackmer and ,post ,manufacturing ,co4 ,curved pipes are made in two ways--by bending directly as they issue from the press1 or by shaping by hand in plaster of paris molds4 ,junctions are made by cutting the branch pipe to the shape of the outside of the main pipe1 fastening the branch in place with soft clay and then cutting out the wall of the main pipe the size of the branch4 ,special fittings are usually made by hand in plaster molds4 ,after being pressed into shape the pipes are taken to a steam-heated drying room where a constant temperature is maintained in order to prevent cracking of the pipes4 ,they remain in the drying room from #c to #aj days until dry1 when they are taken to the kilns4 ,if taken to the kilns when moist blisters will be produced4 ,the dried pipes are piled carefully in the kiln so that heat and weight may be as evenly distributed as possible1 and the fire is then started in the kiln4 ,the process of burning can be roughly divided into five stages3 #ast4 ,water smoking1 which lasts about #gb hours during which the temperature is raised gradually to #cej degrees ,fahrenheit4 #bnd4 ,heating1 during which the temperature is raised to #hjj degrees ,fahrenheit in #bd hours4 #crd4 ,oxidation1 during which the temperature is raised to #a1djj degrees ,fahrenheit in #hd hours4 #dth4 ,vitrification1 in which the temperature is raised to #b1ajj degrees ,fahrenheit in #dh hours1 and finally1 #eth4 ,glazing1 during which the temperature is unchanged but salt 7,na,cl7 is thrown in and allowed to burn4 ,oxidation must be complete before vitrification is started as otherwise blisters will be raised due to imprisoned carbon dioxide4 ,the important points in vitrification are to make the required temperature within a reasonable time and to maintain a uniform distribution of heat throughout the kiln4 ,when vitrification is complete as shown by a glassy fracture of a broken sample taken from the kiln1 glazing is accomplished by throwing a shovelful of salt on the hottest part of the fire4 ,about five to six applications of salt from two to three hours apart may be needed4 ,the kiln is then allowed to cool and the manufacture of the pipe is complete4 ,the completeness of vitrification is indicated by the amount of water that the finished pipe will absorb4 ,completely vitrified pipe will absorb no moisture4 ,soft-burned pipe may absorb as much as #ae per cent moisture4 ,vitrified clay blocks are made of the same material and in the same manner as vitrified clay pipe4 ,the following data on vitrified pipe have been abstracted from the specifications for vitrified pipe adopted by the ,american ,society for ,testing ,materials4 ,pipes shall be subject to rejection on account of the following3 7a7 ,variation in any dimension exceeding the permissible variations given in ,table #cf4 7b7 ,fracture or cracks passing through the shell or hub1 except that a single crack at either end of a pipe not exceeding #b inches in length or a single fracture in the hub not exceeding #c inches in width nor #b inches in length will not be deemed cause for rejection unless these defects exist in more than #e per cent of the entire shipment or delivery4 7c7 ,blisters or where the glazing is broken or which exceed #c inches in diameter1 or which project more than inch above the surface4 7d7 ,laminations which indicate extended voids in the pipe material4 7e7 ,fire cracks or hair cracks sufficient to impair the strength1 durability or serviceability of the pipe4 7f7 ,variations of more than inch per linear foot in alignment of a pipe intended to be straight4 7g7 ,glaze which does not fully cover and protect all parts of the shell and ends except those exempted in ,sect4 #ca4 ,also glaze which is not equal to best salt glaze4 7h7 ,failure to give a clear ringing sound when placed on end and dry tapped with a light hammer4 7i7 ,insecure attachment of branches or spurs4 ,workmanship and ,finish 7#bi7 ,pipes shall be substantially free from fractures1 large or deep cracks and blisters1 laminations and surface roughness4 7#ca7 ,the glaze shall consist of a continuous layer of bright or semi-bright glass substantially free from coarse blisters and pimples4444 ,not more than #aj per cent of the inner surface of any pipe barrel shall be bare of glaze except the hub1 where it may be entirely absent4 ,glazing will not be required on the outer surface of the barrel at the spigot end for a distance from the end equal to the specified depth of the socket for the corresponding size of pipe4 ,where glazing is required there shall be absence of any well defined network of crazing lines or hair cracks4 7#cb7 ,the ends of the pipe shall be square with their longitudinal axis4 7#cc7 ,special shapes shall have a plain spigot end and a hub end corresponding in all respects with the dimensions specified for pipes of the corresponding internal diameter4 ,,table #cf ,,properties ,,of ,,clay ,,sewer ,,pipe ,abstracts from ,tentative ,specifications of the ,american ,society for ,testing ,materials ,internal ,minimum ,maximum ,laying ,diameter,depth ,taper ,minimum ,diameter1,crushing ,absorption1length1 of of of ,thickness ,inches ,strength1 ,per ,cent ,feet ,inside ,socket,socket of ,pounds of ,inches ,barrel4 per ,socket1 ,inches ,linear ,inches ,foot4 ,see ,note #b #f #adcj #e #b1 #b1 #h #b #a 3 #bj #c #h #adcj #e #b1 #b1 #aj #b #a 3 #bj #c #aj #aegj #e #b1 #b1 #ac #b #a 3 #bj #c #ab #agaj #e #b1 #b1 #ae #b #a 3 #bj #a #c #ae #aifj #e #b1 #b1 #ah #b #a 3 #bj #a #c #ah #bbjj #e #b1 #b1 #bb #c #a 3 #bj #a #c #ba #beij #e #b1 #b1 #bf #c #a 3 #bj #a #c #bd #cjgj #e #b1 #b1 #bi #c #a 3 #bj #b #c #bg #ccgj #e #c #cc #c #a 3 #bj #b #cj #cfij #e #c #cg #c #a 3 #bj #b #cc #cicj #e #c #dj #d #a 3 #bj #b #cf #ddjj #e #c #dd #d #a 3 #bj #b #ci #dgaj #e #c #dg #d #a 3 #bj #b #db #ejcj #e #c #ea #d #a 3 #bj #c ,internal ,permissible ,variations ,number ,diameter1 of ,inches ,scorings on ,spigot and ,socket ,inch ,deep ,length1 ,internal ,length ,depth ,thickness ,inches ,diameter1 of ,two of of 7-71 ,inches ,opposite,socket1 ,barrel1 per ,sides1 ,inches ,inches ,foot ,inches 7-7 7-7 ,spigot,socket 77 77 #f #c_/af #a_/af #b #h #e_/af #a_/af #b #aj #e_/af #a_/af #b #ab #e_/af #a_/af #b #ae #e_/af #c_/cb #c #ah #g_/af #c_/af #c_/cb #c #ba #g_/af #c_/af #c #bd #i_/af #d #bg #aa_/af #d #cj #aa_/af #d #cc #ac_/af #c_/af #e #cf #ac_/af #c_/af #e #ci #ac_/af #c_/af #e #db #ac_/af #c_/af #e ,,note #a4 ,for methods of making tests see ,proc4 ,am4 ,soc4 for ,testing ,materials4 ,,note #b4 ,concentrated load at end of vertical diameter4 7a7 ,slants shall have their spigot ends cut at an angle of approximately #de degrees with the longitudinal axis4 7b7 ,curves shall be at angles of #ij1 #de1 #bb1 and #aa degrees as required4 ,they shall conform substantially to the curvature specified4 7c7 444 ,all branches shall terminate in sockets4 ,illustration3 ,,fig4 #gc4--,standard ,clay ,pipe ,specials4 ,courtesy1 ,blackmer and ,post ,manufacturing ,co4 ,in ,fig4 #gc are shown the various forms of vitrified pipe and specials which are ordinarily available on the market4 ,the life of vitrified clay sewers and some observations on the results of the inspection of the sewers in ,manhattan are discussed in ,chapter ,,xii4 ,the strength of vitrified sewer pipes is shown in ,table #cg4 ,,table #cg ,,strength ,,of ,,sewer ,,pipe ,strength in pounds per linear foot to carry loads from ditch filling material such as ordinary sand and thoroughly wet clay1 with the under side of the pipe bedded #fj to #ij by ordinary good methods4 ,from ,proc4 ,am4 ,society for ,testing ,materials1 ,vol4 #bj1 #aibj1 page #fjd4 ,height of ,fill ,above ,top of ,pipe1 ,feet ,breadth of the ,ditch a ,little ,below the ,top of the ,pipe #a ,foot #b ,feet #c ,feet #d ,feet #e ,feet ,ditch ,filling ,material sand clay sand clay sand clay sand clay sand clay #b #bfe #bhj #fae #fce #igj #iij #accj #a1cej #a1fij #a1gaj #d #djj #dej #ajee #aabe #agde #ahbe #bdee #b1ece #c1afe #c1bej #f #dgj #ede #acgj #aejj #bcgj #bebe #cdje #c1ege #d1dfj #d1gdj #h #eje #fje #afjj #agij #bhge #caae #dbae #d1die #e1eie #e1hij #aj #ebe #fdj #agfe #bjae #cbge #cfaj #dijj #e1bie #f1eij #g1jbj #ab #ece #ffj #ahhj #bahe #cfjj #djcj #edhe #f1jjj #g1dfj #h1jce #ad #edj #fge #aife #bcbj #chee #dchj #eige #f1fbj #h1bbe #h1iej #af #ede #fhj #bjbe #bdbe #djfe #dfge #fcie #g1afe #h1hij #i1gge #ah #ede #fhe #bjgj #beje #dbcj #dibj #fgej #g1fcj #i1dhjaj1ebj #bj #ede #fij #bajj #befe #dcfe #eacj #gjej #h1jfj #i1iieaa1aij #bb #ede #fij #babe #bfaj #ddgj #ecje #gcje #h1dbeaj1ddeaa1gie #bd #ede #fij #badj #bfde #defj #edde #gebe #h1gejaj1hdjab1cdj #bf #ede #fij #baej #bfge #dfcj #eege #ggje #i1jceaa1aheab1hcj #bh #ede #fij #bafj #bfie #dfhe #efhj #ghfj #i1bhjaa1dijac1bgj #cj #ede #fij #bafe #bgae #dgbe #egfe #giij #i1ejjaa1geeac1fgj ,very great #ede #fij #bahj #bggj #diaj #fbcj #hgbeaa1jgeac1fceag1cje #ib4 ,cement and ,concrete ,pipe4--,although there is no general recognition of a difference between cement and concrete pipe1 there is a tendency to term manufactured pipe of small diameter cement pipe1 and large pipes or pipes constructed in place1 concrete pipe4 ,cement1 unlike clay1 is used in the manufacture of pipe in the field or by more or less unskilled operators in 8one man0 plants4 ,great care should be used in the selection of cement1 aggregate1 and reinforcement for precast cement pipe since the shocks to which it is subjected in transit are more liable to rupture it than the heavier but steadier loads imposed on it in the trench4 ,the ,united ,states ,government1 various scientific and engineering societies1 and other interested organizations have collaborated in the preparation of specifications for cement and cement tests4 ,these specifications can be found in ,trans4 ,am4 ,soc4 ,civil ,engineers1 ,vol4 #hb1 #aiah1 p4 #aff1 and in other publications4 ,the following abstracts have been taken from the proposed tentative specifications for ,concrete ,aggregates1 of the ,am4 ,society for ,testing ,materials1 issued ,june #ba1 #aiba3 #a4 ,fine aggregate shall consist of sand1 stone screenings1 or other inert materials with similar characteristics1 or a combination thereof1 having clean1 hard1 strong1 durable uncoated grains1 free from injurious amounts of dust1 lumps1 soft or flaky particles1 shale1 alkali1 organic matter1 loam or other deleterious substances4 #b4 ,fine aggregates shall preferably be graded from fine to coarse1 with the coarser particles predominating1 within the following limits3 ,passing ,no4 #d sieve #ajj per cent ,passing ,no4 #ej sieve1 not more than #ej per cent ,weight removed by elutriation test1 not more than #c per cent ,sieves shall conform to the ,u4 ,s4 ,bureau of ,standards specifications for sieves4 #c4 ,the fine aggregate shall be tested in combination with the coarse aggregate and the cement with which it is to be used and in the proportions1 including water1 in which they are to be used on the work1 in accordance with the requirements specified in ,section #f4444 #g4 ,coarse aggregate shall consist of crushed stone1 gravel or other approved inert materials with similar characteristics1 or a combination thereof1 having clean1 hard1 strong1 durable1 uncoated pieces free from injurious amounts of soft1 friable1 thin1 elongated or laminated pieces1 alkali1 organic or other deleterious matter4 99 99 99 99 99 ,the following ,table indicates desirable gradings1 in percentages1 for coarse aggregate for certain maximum sizes4 ,,gradings ,,of ,,coarse ,,aggregates ,maximum ,circular ,openings1 ,inches ,passing ,screen ,size of ,having ,circular ,aggregate ,openings ,inch in ,inches diameter1 not more than #c #b #b #a #a #a #c #ajj #dj-ge #ae per cent #b #ajj #dj-ge #ae per cent #b #ajj #dj-ge #ae per cent #a #ajj #dj-ge #ae per cent #a #ajj #ce-gj #ae per cent #a #ajj #dj-ge #ae per cent #ajj #ae per cent ,the manufacture of small size cement pipe requires relatively more skill than equipment4 ,as a result great care must be observed in the inspection of cement pipe and in the enforcement of specifications4 ,for large size concrete pipe and reinforced concrete pipe the difficulty of holding the pipe together during transportation and lowering into the trench aid in insuring a good product4 ,cement pipe is made by ramming a mixture of cement1 sand1 and water into a cylindrical mold and allowing it to stand until set4 ,the mold is then removed and the pipe stands for a further period of time to become cured4 ,the selection and proportion of materials1 the amount of water1 the method of ramming1 the period of setting1 the length of time of curing1 and the control of moisture and temperature during this period are of great importance in the resulting product4 ,e4 ,s4 ,hanson#eb states that the most conservative engineers recommend a mixture of one sack of cement to #b cubic feet of aggregate measured as loosely thrown into the measuring box4 ,in making up the aggregate1 clean gravel or broken stone up to inch in size is used4 ,the ,american ,concrete ,institute recommends that #ajj per cent pass a -inch screen1 #gj per cent a -inch screen1 #ej per cent a ,no4 #aj1 #dj per cent a ,no4 #bj1 #cj per cent a ,no4 #cj1 and #bj per cent a ,no4 #dj4 ,the materials should be carefully graded by experiment and not guessed at1 as the behavior of all aggregates is not the same4 ,too coarse an aggregate is difficult to handle in manufacturing4 ,it causes loss of pipe when the jacket or mold is removed and results in rough pipe1 stone pockets1 and pin holes through which water spurts when pressure tests are applied4 ,too fine an aggregate causes loss of strength and with ordinary mixtures tends to produce a pipe which will show seepage under internal pressure tests4 ,the amount of water in the mixture will vary1 from #ae to #bj per cent4 ,the mixture should appear dry but should ball in the hand under some pressure4 ,illustration3 ,,fig4 #gd4--;,details of #bd-;,inch ,concrete ,pipe ,form4 ,the mixture can be rammed into the molds by hand or machine4 ,a machine-made pipe is preferable as it produces a more even and stronger product4 ,there are two types of machines for this purpose4 ,one type consists of a number of tamping feet which deliver about #bjj blows to the minute with a pressure of about #hjj pounds per square inch of area exposed4 ,in the other type a revolving core is drawn through the pipe1 packing and polishing the concrete as it is pulled through1 with special provision for packing the bell of the pipe4 ,the tamping machines can make #a1ejj feet of small size pipe to #cjj feet of #bd-;inch pipe in a day4 ,machines of the second type can make #gej feet of #h-;inch to #bjj feet of #cj-;inch pipe in #cj-;inch lengths in #i hours4 ,the inside and outside forms for a #bd-;inch pipe are shown in ,fig4 #gd as used with the tamping machines4 ,the forms are swabbed with oil before being filled in order to facilitate their removal4 ,in making a ,y-branch or other special1 a hole is cut in the pipe or mold the size of the joining pipe which is then set in place and the joint wiped smooth with cement4 ,,table #ch ,,properties ,,of ,,cement ,,concrete ,,sewer ,,pipe #aiag ,specifications of ,american ,society for ,testing ,materials1 with ,subsequent ,revisions ,laying ,diameter,normal ,depth ,taper ,minimum ,length1 at ,annular of of ,thickness ,feet ,inside ,space1 ,socket1,socket of of ,inches ,inches ,barrel1 ,socket1 ,inches ,inches ,internal ,diameter1 ,inches #b1 #b1 #h #b #a 3 #bj #f #c #b1 #b1 #aa #b #a 3 #bj #h #c #b1 #b1 #ac #b #a 3 #bj #aj #c #b1 #b1 #ae #b #a 3 #bj #a #ab #c #b1 #b1 #ai #b #a 3 #bj #a #ae #c #b1 #b1 #bb #b #a 3 #bj #a #ah #c #b1 #b1 #bf #b #a 3 #bj #a #ba #c #b1 #b1 #cj #c #a 3 #bj #b #bd #c #bg #c #cd #c #a 3 #bj #b #cj #c #ch #a #c #a 3 #bj #b #cc #c #da #a #d #a 3 #bj #b #cf #c #de #a #d #a 3 #bj #c #ci #c #di #a #d #a 3 #bj #c #db #c #ec #a #d #a 3 #bj #c ,limits of ,permissible ,variations ,minimum ,maximum ,crushing ,absorption1 ,strength1 ,per ,cent ,pounds per ,linear ,internal ,foot at ,diameter1 ,end of ,inches ,diameter ,length1 ,internal ,depth ,thickness ,inch ,diameter1 of ,hubof ,barrel per ,inches 7-7 7-7 ,foot ,inches ,inches 7-7 ,spigot,socket 77 77 #c_/af #c_/af #a_/af #adcj #h #f #a_/af #adcj #h #h #a_/af #aegj #h #aj #a_/af #aiaj #h #ab #c_/cb #aifj #h #ae #c_/cb #bbjj #h #ah #e_/af #e_/af #beij #h #ba #e_/af #e_/af #cjgj #h #bd #bg #e_/af #ccgj #h #cj #cfij #h #cc #c_/af #cicj #h #cf #c_/af #ddjj #h #ci #c_/af #dgaj #h #db #c_/af #ejcj #h ,after the removal of the mold the pipe may be cured by the water or the steam process4 ,hanson states3 ,by the former the pipe are simply set on the floor of the plant and as soon as they are sufficiently strong so that they can be sprinkled with water without falling down2 sprinkling is commenced and continued at such intervals for #f or #g days that the pipe will be moist at all times4 ,this is a slower process than steam curing4 ,it is also less uniform and less subject to control than where the product is cured by steam4 ,in the steam process the pipe is exposed to low-pressure steam with plenty of moisture in a closed receptacle for #bd hours1 or until hardened4 ,it has been found by tests that pipes sprinkled for #bh days are as strong as steam-cured pipes4 ,the dimensions of cement concrete sewer pipe as recommended by the ,am4 ,society for ,testing ,materials are shown in ,table #ch4 ,the following has been abstracted from the description of the manufacture of one form of concrete pipe by ,g4 ,c4 ,bartram4#ec ,all pipe are manufactured in #d-;foot lengths near the site at which they are to be installed because of their great weight1 for example1 #cf-;inch pipe weighs one ton4 ,the plant for the manufacture of the pipe consists of cast-iron bottom and top rings for each size to be used on the job1 and inside and outside steel casings4 ,there are three bases for each steel casing as the pipes stand on the bases for #gb hours and the steel casing remains on for only #bd hours after the concrete has been poured4 ,the pipes are then lifted off the bases and stored for aging4 ,the pipes are cast with the spigot end up4 ,the concrete is ordinarily mixed in the proportions of #a 3 #b 3 #d4 ,the materials are placed in the mixer in the following order3 first1 the stone1 then the sand1 then the cement1 and finally the water4 ,sufficient water is added to make the concrete flow freely4 ,in cold weather or for a hurry-up job the molds are covered with canvas and are steamed for #b or #c hours immediately after the concrete is poured4 ,the molds are then removed but the pipe should be steamed before use4 ,otherwise they are allowed to stand #gb hours1 as explained above4 ,in cold weather the steam is used to prevent freezing and not to hasten the completion of the pipe4 ,illustration3 ,,fig4 #ge4--,triangle ,mesh ,reinforced ,concrete ,pipe4 ,as made by the ,am4 ,concrete ,pipe and ,pile ,co41 ,chicago4 ,illustration3 ,,fig4 #gf4--,methods of ,joining and ,reinforcing ,concrete ,pipe4 ,one layer or ring of reinforcement is used for sizes from #bd to #dh inches and two layers or rings for larger pipe4 ,a type of reinforcement sometimes used is the ,american ,steel and ,wire ,company's ,triangular ,mesh1 an illustration of which is shown in ,fig4 #ge4 ,the wire mesh is cut to fit and is placed in a slot in the cast-iron base4 ,the slot is then filled with sand so that the concrete cannot enter1 thus leaving a portion of the reinforcement exposed4 ,the inside reinforcement extends through and out of the spigot of the completed pipe4 ,in the trench the two reinforcements overlap in the key-shaped space left on the inside of the pipe by the design of the bell and spigot4 ,this space is shown in ,fig4 #gf ,a4 ,when the pipe is placed in the trench the key-shaped space is plastered with mortar and a piece is knocked out of the bell to receive the grout with which the joint is closed4 ,a spring steel band is then put on the outside of the joint and grout poured into the hole at the top4 ,the band is removed as soon as the joint materials have set4 ,the rules for the reinforcement of concrete pipe recommended in ,volume ,,xv1 #aiai1 of the ,transactions of the ,concrete ,institute are as follows3 ,no reinforcement is approved for pipe between #cj and #fj inches in diameter or in rock or hard soils4 ,for pipe #cf inches in diameter or less the minimum thickness of shell shall be #e inches4 ,for #fj-;inch pipe the minimum thickness shall be #g inches with intermediate sizes in proportion4 ,reinforcement for circular pipe shall consist of one or two rings of circular wire fabric or rods of the areas shown in ,table #ci4 ,all sewers near the surface and subject to vibration should be reinforced4 ,for sewers #f feet or less in diameter the reinforcement should consist of at least of #a per cent of the area of the concrete4 ,it should be placed near the inside at the crown and near the outside at the haunches4 ,if large horizontal pressures are expected the pipe should be reinforced for these reverse stresses1 which involves placing the reinforcement near the outside at the crown and near the inside at the haunches4 ,the minimum thickness of the walls of sewers greater than #f feet in diameter with flat bottom and arch1 with or without side walls1 should be #h inches4 ,,table #ci ,,reinforcement ,,for ,,circular ,,concrete ,,sewer ,,pipe 7,see ,vol4 ,,xv1 ,proceedings ,am4 ,concrete ,institute7 ,diameter in ,minimum ,thickness ,number of ,rings ,cross ,sectional ,inches of ,shell in ,area of ,each ,ring ,inches #bd #c #a 4#jeh #bg #c #a 4#jfh #cj #c #a 4#jhj #cc #d #a 4#ajg #cf #d #a 4#adf #ci #d #a 4#adf #db #d #a 4#aec #dh #e #b 4#ajg #ed #e #b 4#abc #fj #f #b 4#adf #ff #f #b 4#afh #gb #g #b 4#ahj #hd #h #b 4#bjh #if #i #b 4#bde ,three methods for the reinforcement of concrete sewers are shown in ,fig4 #gf ,b4 #ic4 ,proportioning of ,concrete4--,in the proportioning of concrete questions of strength1 of permeability1 and of workability#ed may need consideration4 ,all of these qualities are affected by the amount of cement1 the nature and gradation and relative proportions of the fine and the coarse aggregate1 and the amount of mixing water used4 ,other things being equal the strength varies with the amount of cement put into the concrete4 ,for the same amount of cement and the same consistency of the mixture1 the strength increases with increased density of concrete 7that is1 with decreased voids71 and the effort should be made so to proportion the fine and coarse aggregates as to produce the densest concrete 7least voids7 with the aggregates available4 ,for the same consistency1 the strength then will vary with the ratio of the amount of cement to the amount of the voids4 ,so far as the mixing water is concerned1 the greatest strength in the concrete will be attained at a rather dry mix2 that which produces the least volume of concrete4 ,the addition of more water results in a concrete of less strength2 #dj per cent more water may give a concrete of less than half the normal strength4 ,the reduction in strength is then very marked for the wetter mixes1 and the water content used is a feature of considerable importance in the design of concrete mixtures4 ,permeability is affected by the same elements as strength1 but the size and discontinuity of the pores have a greater influence4 ,workability is an important quality2 in some respects it will have to be obtained at the expense of strength4 ,increasing the amount of mixing water increases the workability of the mixtures1 with a resulting decrease in strength which may have to be accepted or else overcome by increasing the cement in the mix4 ,an excess of water is often used unnecessarily through ignorance of the injurious results4 ,a high proportion of coarse aggregate1 up to a certain limit1 will give concrete of high strength1 but the mixture will be harsh-working and not easy to place4 ,lower proportions of coarse aggregate will give greater workability and better uniformity of product1 the latter being an important matter4 ,it is apparent that the degree of workability of the mixture needed will depend upon the nature of the construction--for a pavement where the concrete will receive substantial tamping or working the water content may be much less than that which may need to be used in placing concrete around reinforcement in narrow members1 or where little tamping or spading can be done4 ,the nature of the work will affect the standard of consistency to be specified4 ,the proportioning of the concrete should then be dependent upon the needs of the structure and the manner of placing the concrete4 ,the proportions selected should be carefully adhered to and especially should care be taken to see that the right quantity of mixing water is used4 ,the materials are commonly measured volumetrically 7by bulk74 ,because of the variations which are introduced by volumetric measurement of the materials by the presence of varying degrees of moisture1 measurements by weight would be more accurate1 but these would also be affected by differences in the specific gravity of the materials4 ,the methods of measuring1 the allowance for moisture1 as well as the proportions of the materials1 should be specified4 ,the methods for proportioning concrete are3 7#a7 ,arbitrarily selected proportions4 7#b7 ,proportions based on minimum voids4 7#c7 ,proportions based on trial mixtures4 7#d7 ,proportions based on a sieve analysis curve4 7#e7 ,proportions based on the surface area of the aggregates4 7#f7 ,proportions based on the water-cement ratio and the fineness modulus4 7#g7 ,proportions based on mortar-voids and cement-voids ratio4 ,arbitrarily selected proportions are in quite general use2 they are intended to apply to the materials most commonly used in the vicinity of the work4 ,the most common practice is to use twice as great a volume of coarse aggregate as fine aggregate1 as for instance #a part cement1 #b parts fine aggregate1 and #d parts coarse aggregate4 ,decreasing the ratio of coarse aggregate to fine aggregate may give a more easily worked mix or require relatively less water for a given workability1 and in some cases it will be proper to increase this ratio and thus secure an increase of strength4 ,judgment and experience with given materials may warrant changes from a stated ratio4 ,the proportions are now frequently given as one part cement to a certain number of parts of the mixed aggregate1 leaving the proportions of the fine to coarse to be determined otherwise1 since small variations in the relation of these will not greatly affect the strength4 ,proportions in common use are3#ee ,mortar for ,laying brick and stone masonry from #a 3 #j to #a 3 #c ,filling joints in sewer pipe #a 3 #j to #a 3 #b ,surfaces1 floors1 sidewalks1 pavements #a 3 #j to #a 3 #b ,waterproof linings #a 3 #j to #a 3 #b ,cement1 bricks1 and blocks #a 3 #b to #a 3 #d ,concrete for ,gravity retaining walls1 heavy foundations1 structures needing mass more than strength from #a 3 #c 3 #f to #a 3 #d 3 #h ,retaining walls1 piers1 sewers1 pavements1 foundations1 and work requiring strength4 7,compressive strength in #bh days1 #a1ejj to #b1jjj pounds per square inch7 from #a 3 #b 3 #d to #a 3 #c 3 #f ,floors1 beams1 pavements1 reinforced concrete1 arch bridges1 low-pressure tanks4 7,compressive strength in #bh days1 #b1jjj to #c1jjj pounds per square inch7 from #a 3 #a 3 #c to #a 3 #b 3 #d ,reinforced concrete columns1 conduit pipe1 impervious concrete4 7,compressive strength in #bh days1 #c1jjj to #d1jjj pounds per square inch7 from #a 3 #a 3 #b to #a 3 #a 3 #c ,the usual method of proportioning based on minimum voids is to assume that the particles of fine aggregate should fill the voids in the coarse aggregate and that the particles of the cement will fill the voids in the fine aggregate4 ,about #e to #aj per cent additional fine aggregate is generally added to push the particles of the coarse aggregate apart and thus give a more easily worked concrete and one freer from void spaces4 ,this method is inaccurate1 principally because of the effect of the moisture on the volume of the voids1 and because the effect on the volume by the addition of water is unknown4 ,trial mixtures may be made by carefully weighing each of the ingredients and then combining them to give a workable concrete4 ,using a given amount of cement1 the proportion of ingredients1 of the same total weight1 which will give the least volume and therefore the densest concrete is adopted4 ,when making the comparison the consistency of the mixes must be maintained constant4 ,proportioning may be based on an ideal sieve analysis curve of the mixed cement and aggregates4 ,the sieve analysis of the aggregates is made by screening a predetermined weight of the sample through a series of #e to #h sieves graded in size from slightly below the size of the largest particle to slightly above the smallest particle of the aggregate4 ,the analysis is then expressed in the form of a curve4 ,the ideal curve1 according to ,fuller1#ef is shown in ,fig4 #gg4 ,illustration3 ,,fig4 #gg4--;,gravel ,analysis4 ,the dotted line indicates the ideal combination of the coarse and fine portions4 ,the heavy full line indicates the combination attained4 ,the method of proportioning concrete by surface areas is based on the theory that the strength of a concrete depends on the amount of cement used in proportion to the surface area of the aggregates4#eg ,the proportioning of concrete on the basis of a water-cement ratio and a fineness modulus was introduced by ,prof4 ,d4 ,a4 ,abrams4#eh ,it is based on the theory that with fixed conditions of aggregate1 moisture1 etc41 the ratio of water to cement determines the strength of the concrete4 ,a method of proportioning concrete by determining experimentally the voids in mortars made up with a given amount of sand and definite proportions of cement1 and then calculating the voids in the concrete made up by adding a definite amount of coarse aggregate to the mixture1 has been developed4#ei ,the method is based on the theory that the strength of the concrete is a known function of the ratio of the volume of cement to the volume of the voids in the concrete4 ,the effect of varying the proportion of the ingredients1 including an increase in the amount of mixing water beyond that required to give the densest mixture1 may be found by the method1 and a comparison may be made of results obtainable with different classes of fine and coarse aggregates4 ,arbitrarily selected proportions1 proportions based on voids1 and proportions based on trial mixtures are usually satisfactory for small jobs where the amount of materials involved is not large4 ,where the saving in materials will permit1 more accurate methods should be used4 ,the methods can be studied more fully by reference to the original articles quoted in the footnotes1 or to the following texts3 ,materials of ,construction1 ,johnson1 #eth ,edition1 #aiah4 ,materials of ,engineering1 ,h4 ,f4 ,moore1 #b;d ,edition1 #aibj4 ,masonry ,construction1 ,i4 ,o4 ,baker1 #ajth ,edition1 #aiab4 ,concrete ,engineer's ,handbook1 ,hool and ,johnson1 #aiah4 ,concrete1 ,plain and ,reinforced1 ,taylor and ,thompson1 #aiaf4 #id4 ,waterproofing ,concrete4--,the waterproofing of concrete is most satisfactorily done by making dense mixtures4 ,in practice such substances as hydrated lime1 clay1 alum and soap1 and proprietary compounds such as ,ceresit1 ,medusa1 etc41 are frequently mixed with the concrete under the theory that these very fine substances will fill any remaining voids and render the concrete impervious4 ,the specifications of the ,joint ,committee issued on ,june #d1 #aiba1 are much briefer and contain less detailed instruction than those issued earlier4#fj ,the earlier instructions follow4 ,many expedients have been resorted to for making concrete impervious to water4 ,experience shows1 however1 that when mortar or concrete is proportioned to obtain the greatest practicable density and is mixed to the proper consistency1 the resulting mortar or concrete is impervious under moderate pressure4 ,on the other hand concrete of dry consistency is more or less pervious to water1 and1 though compounds of various kinds have been mixed with the concrete or applied as a wash to the surface1 in an effort to offset this defect1 these expedients have generally been disappointing1 for the reason that many of these compounds have at best but temporary value1 and in time lose their power of imparting impermeability to the concrete4 ,in the case of subways1 long retaining walls1 and reservoirs1 provided the concrete itself is impervious1 cracks may be so reduced1 by horizontal and vertical reinforcement properly proportioned and located1 that they will be too minute to permit leakage1 or will be closed by infiltration of silt4 ,asphaltic or coal tar preparations applied either as a mastic or as a coating on felt cloth or fabric1 are used for waterproofing1 and should be proof against injury by liquids or gases4 ,for retaining and similar walls in direct contact with the earth1 the application of one or two coatings of hot coal tar pitch1 following a painting with a thin wash of coal tar dissolved in benzol1 to the thoroughly dried surface of concrete is an efficient method of preventing the penetration of moisture from the earth4 ,tar paper and asphaltic compounds are not often used in sewer work as absolute imperviousness is seldom necessary4 #ie4 ,mixing and ,placing ,concrete4--,careful workmanship is desirable in the mixing and placing of concrete in sewers since water-tight construction is desired4 ,because of the difficulty of inspecting concrete in wet1 dark and crowded excavations1 and the careless habits of workmen experienced in concrete sewer construction1 the highest class of concrete work cannot be expected4 ,the situation is met by designing thick walls as shown in the sections illustrated in ,fig4 #bb and #bc4 ,in the report of the ,joint ,committee on ,concrete and ,reinforced ,concrete in ,transactions of the ,american ,society of ,civil ,engineers for #aiag1 on page #aaja the recommendation is made concerning the mixing and placing of concrete as follows3#fa ,the mixing of concrete should be thorough and should continue until the mass is uniform in color and is homogeneous4 ,as the maximum density and greatest strength of a given mixture depends largely on thorough and complete mixing1 it is essential that this part of the work should receive special attention and care4 ,inasmuch as it is difficult to determine by visual inspection whether the concrete is uniformly mixed1 especially where aggregates having the color of cement are used1 it is essential that the mixing should occupy a definite period of time4 ,the minimum time will depend on whether the mixing is done by machine or hand4 7a7 ,measuring ,ingredients3 ,methods of measurement of the various ingredients should be used which will secure at all times separate and uniform measurements of cement1 fine aggregate1 coarse aggregate and water4 7b7 ,machine ,mixing3 ,the mixing should be done in a batch machine mixer of a type which will insure the uniform distribution of the materials throughout the mass1 and should continue for the minimum time of #a minutes after all the ingredients are assembled in the mixer4 ,for mixers of #b or more cubic yards capacity1 the minimum time of mixing should be #b minutes4 ,since the strength of the concrete is dependent on thorough mixing1 a longer time than this minimum is preferable4 ,it is desirable to have the mixer equipped with an attachment for automatically locking the discharging device so as to prevent the emptying of the mixer until all the materials have been mixed together for the minimum time required after they are assembled in the mixer4 ,means should be provided to prevent aggregates being added after the mixing has commenced4 ,the mixer should also be equipped with water storage1 and an automatic measuring device which can be locked if desired4 ,it is also desirable to equip the mixer with a device recording the revolutions of the drum4 ,the number of revolutions should be so regulated as to give at the periphery of the drum a uniform speed4 ,about #bjj feet per minute seems to be the best speed in the present state of the art4 7c7 ,hand ,mixing3 ,hand mixing should be done on a water-tight platform and especial precautions taken after the water has been added1 to turn all the ingredients together at least #f times1 and until the mass is homogeneous in appearance and color4 7d7 ,consistency3 ,the materials should be mixed wet enough to produce a concrete of such a consistency as will flow sluggishly into the forms and about the metal reinforcement when used1 and which at the same time can be conveyed from the mixer to the forms without separation of the coarse aggregate from the mortar4 ,the quantity of water is of the greatest importance in securing concrete of maximum strength and density2 too much water is as objectionable as too little4 7e7 ,retempering3 ,the remixing of concrete and mortar that has partly reset should not be permitted4 ,placing ,concrete 7a7 ,methods3 ,concrete after the completion of the mixing should be conveyed rapidly to the place of final deposit2 under no circumstances should concrete be used that has partly set4 ,concrete should be deposited in such a manner as will permit the most thorough compacting such as can be obtained by working with a straight shovel or slicing tool kept moving up and down until all the ingredients are in their proper place4 ,special care should be exercised to prevent the formation of laitance2 where laitance has formed it should be removed1 since it lacks strength and prevents a proper bond in the concrete4 ,care should be taken that the forms are substantial and thoroughly wetted 7except in freezing weather7 or oiled1 and that the space to be occupied by the concrete is free from all debris4 ,when the placing of concrete is suspended1 all necessary grooves for joining future work should be made before the concrete has set4 ,when work is resumed concrete previously placed should be roughened1 cleansed of foreign material and laitance1 thoroughly wetted and then slushed with a mortar consisting of one part ,portland cement and not more than #b parts of fine aggregate4 ,the surfaces of concrete exposed to premature drying should be kept covered and wet for at least #g days4 ,where concrete is conveyed by spouting1 the plant should be of such a size and design as to insure a practically continuous stream in the spout4 ,the angle of the spout with the horizontal should be such as to allow the concrete to flow without separation of the ingredients2 in general an angle of about #bg degrees or #a vertical to #b horizontal is good practice4 ,the spout should be thoroughly flushed with water before and after each run4 ,the delivery from the spout should be as close as possible from the point of deposit4 ,where the discharge must be intermittent1 a hopper should be provided at the bottom4 ,spouting through a vertical pipe is satisfactory when the flow is continuous2 when it is checked and discontinuous it is highly objectionable unless the flow is checked by baffle plates4 7b7 ,freezing ,weather3 ,concrete should not be mixed or deposited at a freezing temperature1 unless special precautions are taken to prevent the use of materials covered with ice crystals or containing frost1 and to prevent the concrete from freezing before it has set and sufficiently hardened4 ,as the coarse aggregate forms the greater portion of the concrete1 it is particularly important that this material be warmed to well above the freezing point4 ,the enclosing of a structure and the warming of a space inside the enclosure is recommended1 but the use of salt to lower the freezing point is not recommended4 7c7 ,rubble ,concrete3 ,where the concrete is to be deposited in massive work1 its value may be improved and its cost materially reduced by the use of clean stones saturated with water1 thoroughly embedded in and completely surrounded by concrete4 7d7 ,under ,water3 ,in placing concrete under water1 it is essential to maintain still water at the place of deposit4 ,with careful inspection the use of tremies1 properly designed and operated1 is a satisfactory method of placing concrete through water4 ,the concrete should be mixed very wet 7more so than is ordinarily permissible7 so that it will flow readily through the tremie and into place with practically a level surface4 ,the coarse aggregate should be smaller than ordinarily used and never more than one inch in diameter4 ,the use of gravel facilitates the mixing and assists the flow4 ,the mouth of the tremie should be buried in the concrete so that it is at all times entirely sealed and the surrounding water prevented from forcing itself into the tremie4 ,the concrete will then discharge without coming in contact with the water4 ,the tremie should be suspended so that it can be lowered quickly when it is necessary either to choke off or to prevent too rapid flow4 ,the lateral flow preferably should not be over #ae feet4 ,the flow should be continuous in order to produce a monolithic mass and to prevent the formation of laitance in the interior4 ,in case the flow is interrupted it is important that all laitance be removed before proceeding with the work4 ,in large structures it may be necessary to divide the mass of concrete into several small compartments or units to permit the continuous filling of each one4 ,with proper care it is possible in this manner to obtain as good results under water as in the air4 ,a less desirable method is the use of the drop bottom bucket4 ,where this method is used the bottom of the bucket should be released when in contact with the surface of the place of deposit4 ,concrete sewers should be constructed in longitudinal sections in a continuous operation without interruption for the entire invert1 side walls1 or arch4 ,in pouring the concrete it should be kept level in the forms and should rise evenly on each side of the sewer4 ,all rough places in the concrete should be finished smooth by brushing with a grout of neat cement and water and honeycombs should be filled with neat cement or a one-to-one mortar4 #if4 ,sewer ,brick4--,the quality of brick used in sewers is seldom specified with the minute care that is taken in the specifications for concrete1 iron1 and certain other materials of construction1 as inferior materials in brick are more easily detected4 ,the specifications of the ,baltimore ,sewerage ,commission for sewer brick are3 ,sewer brick shall be whole1 new bricks of the best quality1 of uniform standard size1 with straight and parallel edges and square corners3 they shall be of compact texture1 burned hard and entirely through1 free from injurious cracks and flaws1 tough and strong1 and shall have a clear ring when struck together4 ,the sides1 ends and faces of all bricks shall be plane surfaces at right angles and parallel to each other4 ,bricks of any one make shall not vary more than #a_/afth of an inch in thickness1 nor more than #ath of an inch in width or length1 from the average of the samples submitted for approval4 ,the truest bricks shall be used in the face of the masonry and the exposed surfaces shall be true and smooth planes4 ,all bricks delivered for use shall be culled by the ,contractor when required4 ,no brick thrown out in the culling shall be used in any work done under any contract of the ,sewerage ,commission1 except that the best of the culls may be used in manholes1 above the level of the top of the sewer1 if permitted by the ,engineer4 ,the average amount of water absorbed by the bricks1 after being thoroughly dried and then immersed for #bd hours1 shall not exceed #f per cent4 ,all bricks shall be uniform in quality and percentage of absorption4 ,whenever vitrified bricks are required in the invert of the sewer1 they shall be smooth1 hard1 tough1 and of such durability as will fit them for this use4 ,they shall be of standard size1 well and uniformly burned1 thoroughly vitrified throughout1 and free from warps1 cracks1 and other defects4 ,the surfaces and edges shall be true and straight and the corners sharp and square4 ,they shall be in every respect satisfactory to the ,engineer1 and in all respects equal to the sample in the office of the ,engineer4 ,the remaining paragraphs of the specifications deal with the manner in which samples shall be submitted and the necessity for conformity between the samples submitted and the bricks used4 ,a common size of brick in use for sewers is #b #d #h inches1 but the variations in size are many4 ,the bricks in use on any one job should be as near the same size as possible as the extra mortar filling necessary to make up for small brick detracts from the strength of the sewer4 ,small brick are undesirable as the cost of laying small and large bricks is the same1 but the thickness of the finished sewer is less4 ,sewer brick should not absorb more than #aj to #bj per cent moisture by volume1 in #bd hours2 except the special paving brick used to prevent erosion at the invert which should absorb less than #e per cent moisture4 #ig4 ,vitrified ,sewer ,block4--,blocks and bricks are manufactured in a manner similar to the manufacture of vitrified sewer pipe described in ,art4 #ia4 ,j4 ,m4 ,egan describes two types of sewer blocks#fb as follows3 ,there are on the market two designs of blocks1 one being a single-ring block and the other a double-ring block4 ,the former has a ship-lap joint on the ends and a tongue-and-groove joint on the sides4 ,in the double block the laps and joints are made in the construction of the sewer and the blocks are placed one on top of the other as in a two ring brick sewer4 ,the blocks are hollow longitudinally with web braces4 ,they are made for sewers from #cj inches to #ajh inches in diameter and weigh from #dj to #abj pounds4 ,they are #ah inches to #bd inches long1 #i to #ae inches wide1 and #e to #aj inches thick4 ,short lengths are made for convenience in construction and for use on sharp curves4 ,special blocks are made for connections and junctions4 ,a special block is also made for inverts1 which has occasionally been used with brick sewers to avoid the difficulty of constructing with brick at this point4 ,such blocks are objectionable1 as they leave a line of weakness along the longitudinal joint so formed4 ,they are not used frequently in present day practice4 ,vitrified blocks are generally cheaper than bricks1 but they do not make so strong a structure4 ,in some cases it is possible to lay vitrified block without the expense of high-priced bricklayers1 thus saving on the cost of the sewer and obtaining a conduit with a smoother interior finish4 #ih4 ,cast ,iron1 ,steel1 and ,wood4--,cast iron1 steel1 and wood pipe belong more to the field of waterworks than of sewerage1 as they are not extensively used in the construction of sewers4 ,there are1 however1 some special conditions under which these materials may be serviceable4 ,the iron used in cast-iron pipe for sewers1 and in castings for manhole covers1 inlet frames1 etc41 is seldom carefully or definitely specified4 ,the standard specifications of the ,american ,water ,works ,association with regard to the quality of iron for water pipe are3 ,all pipe and special castings shall be made of cast iron of good quality and of such character as shall make the metal of the castings strong1 tough1 and of even grain and soft enough to satisfactorily admit of drilling and cutting4 ,the metal shall be made without the admixture of cinder iron or other inferior metal1 and shall be remelted in a cupola or air furnace4 ,the specifications of the ,sanitary ,district of ,chicago for the quality of iron to be used in manhole covers1 etc41 are given on page #aja4 ,although sewer pipes are not ordinarily subjected to internal pressure1 cast-iron pipe for sewers should be as heavy or heavier than water pipe to resist the corrosive action of the sewage and the external stresses that are to be imposed upon it4 ,the sizes and details of standard cast-iron pipe used for both water works and sewerage can be found in specification of the ,american and ,new ,england ,water ,works ,associations4 ,the quality of steel used for reinforcing concrete should be carefully specified because of the possibility of the substitution of inferior material4 ,the specifications for 8,billet ,steel ,concrete ,reinforcement ,bars10 of the ,american ,society for ,testing ,materials#fc are the standard for engineering practice1 or the following specifications may be used3 ,all reinforcement shall be free from excessive rust1 scale1 paint1 or coatings of any character which will tend to destroy the bond4 ,the bars shall be rolled from new billets4 ,no rerolled material will be accepted4 ,all reinforcement bars shall develop an ultimate tensile strength of not less than #gj1jjj pounds per square inch4 ,the test specimen shall bend cold around a pin1 whose diameter is two times the thickness of the bar1 #ahj degrees without cracking on the outside portion4 ,the reinforcing bars shall in all respects fulfill the requirements of the standard specifications of the ,american ,society for ,testing ,materials for ,billet ,steel ,concrete ,reinforcing ,bars serial designation ,a #ae-ad4 ,the steel used in pipe should be a soft1 open-hearth steel with an ultimate tensile strength of #fj1jjj pounds per square inch1 an elastic limit of #cj1jjj pounds per square inch1 an elongation in #h inches before fracture between #bb and #be per cent1 and a reduction in area before fracture of #ej per cent4 ,the working strength of the steel is taken at #af1jjj to #bj1jjj pounds per square inch in tension1 #aj1jjj to #ab1jjj pounds per square inch in shear1 and #bj1jjj to #bd1jjj pounds per square inch in bearing4 ,a liberal allowance should be made for corrosion4 ,the standard specifications for ,open-,hearth ,boiler ,plate and ,rivet ,steel of the ,american ,society for ,testing ,materials1 ,aug4 #af1 #aiai1 include 8flange steel10 which is suitable for the manufacture of plates1 and extra soft steel which is suitable for rivets4 ,steel pipe should be coated both inside and out to protect it against corrosion4 ,the various proprietary coatings are mainly coal tar pitches1 or mixtures of coal tar pitch and asphalt4 ,a coal tar pitch is a distillate of coal tar from which the naphtha has been removed and to which about one per cent of heavy linseed oil has been added4 ,the coating is applied to the pipe at a temperature of about #cjj degrees ,fahrenheit1 by dipping hot pipe in the heated coating material4 ,the pipe should be carefully cleaned and all rust and scale removed before it is dipped4 ,in some cases the steel is pickled before dipping4 ,this consists in rolling the cold plates to a short radius to loosen the scale1 heating them to about #abe degrees1 and dipping them in a warm #e per cent acid solution for about #c minutes1 and finally rinsing in a weakly basic wash water4 ,the woods commonly used for the manufacture of wood pipe are spruce1 ,oregon fir1 ,douglas fir1 and ,california redwood4 ,wood pipe lines have been constructed of other kinds of lumber but only in more or less unusual conditions4 ,the following has been abstracted from the specifications for ,california redwood given by ,j4 ,f4 ,partridge4#fd ,the staves shall be of clear1 air-dried1 ,california redwood1 seasoned at least one year in the open air1 and shall be free from knots 7except small knots appearing on one face only71 sap1 dry rot1 wind shakes1 pitch1 pitch seams1 pitch pockets1 or other defects which would materially impair their strength or durability4 ,the sides of the staves shall be milled to conform to the inside and outside radii of the pipe2 and the edges shall be beveled to true radial planes4 ,the staves shall be milled from stock sizes of lumber1 the net finished thickness of the stave1 for the various diameters of pipe1 shall be as given in ,table #dj4 ,the ends shall be cut square and slotted to receive the metallic tongues which form the butt joints4 ,the slots shall appear in the same position on each stave1 and shall be cut to make a tight fit with the tongues in all directions4 ,the staves shall have an average length of at least #ae ft4 #f in4 and not more than one per cent shall have a length of less than #i ft4 #f in4 ,staves shorter than #h ft4 will not be accepted4 ,the bands shall be spaced on the pipe with a factor of safety of at least four1 and shall consist of round1 mild steel rods1 connected with malleable iron shoes4 ,either open-hearth or ,bessemer steel may be used4444 ,the ultimate strength shall be from #ee1jjj to #fe1jjj lb4 per sq4 in4 ,the original reference should be consulted for complete details and for specifications for various kinds of wood and classes of pipe4 ,the discussion following the specifications is of value4 ,machine-made wood pipe is superior to stave pipe put together in the field4 ,it is seldom manufactured in sizes large enough for use in sewers1 which results in the almost exclusive use of field constructed stave pipe4 ,the steel bands used to hold the staves together should be coated similarly to steel plates4 ,all lumber1 except ,california redwood should receive a preservative coating of creosote#fe or other material4 ,one of the best methods of preserving the wood is to keep it submerged and to maintain the pipe under internal pressure4 ,,table #dj ,,details ,,of ,,design ,,for ,,continuous ,,stave ,,wood ,,pipe ,,classes ,a1 ,b1 ,,and ,c 7,by ,j4 ,f4 ,partridge1 ,trans4 ,a4 ,s4 ,c4 ,e41 ,vol4 #hb1 page #dfa7 ,stave ,stock ,size ,size of ,top ,width ,spacing of ,thickness1 of ,lumber1 ,band1 of ,staves1 ,bands for ,diameter1 ,standard1 ,inches ,inches ,standard1 #ajj ,feet ,inches ,inches ,inches ,head #ab #a #b #d #c4ef #f4ch #ah #a-g_/af #b #d #g_/af #c4ff #e4gf #bd #a-g_/af #b #d #g_/af #c4gj #d4cd #cj #a #b #f #e4dh #d4ec #cf #a-i_/af #b #f #e4fb #c4gg #db #a #b #f #e4ea #c4bc #a #b #f or #e4fj #b4hd or #dh #d4da #fj #b #c #f #e4ef #c4ed #c #d #f or #e4fi #b4ie or #gb #d4bd #hd #c #d #f #e4fe #c4fc #abj #c #d #f #e4fh #b4ed #c #d #f or #e4fd #b4ab or #add #b4hi ,,chapter ,,ix ,,design ,,of ,,the ,,sewer ,,ring #ii4 ,stresses in ,buried ,pipe4--,the stresses which sewer pipe should be designed to resist are3 internal bursting pressure1 for sewers flowing under pressure2 stresses due to handling1 for precast pipe2 temperature stresses2 and external loads4 ,the latter is by far the most important and frequently is the only stress considered in design4 ,the thickness of a pipe to resist internal stress should be 7,,pr7ft1 in which ,p the intensity of internal pressure2 ,r the radius of the inside of the pipe1 and ft the unit-strength of the material in tension ,the derivation of this expression is simple4 ,the stresses due to handling cannot be computed and are cared for by a thickness of material dictated by experience4 ,these thicknesses are given for vitrified clay and cement pipe in the specifications in the preceding chapter4 ,temperature stresses are not allowed for in the design of the pipe ring1 but allowance must be made for them in long rigid pipe lines exposed to wide variations in temperature4 ,such a condition seldom exists in sewerage works4 ,the external forces are ordinarily the controlling features in the design of sewer rings4 ,the simplest problems arise in the design of a circular pipe4 ,if the external loading is uniform about the circumference of the pipe the internal stresses will all be compression4 ,almost all other forms of loading will cause bending moments resulting in tension and compression in different parts of the pipe4 ,the maximum bending is caused by two concentrated loads diametrically opposed4 ,as such a condition is extreme it is not cared for in ordinary design1 but a loading between this condition and perfect distribution is assumed1 as explained in ,art4 #ajc4 #ajj4 ,design of ,steel ,pipe4--,the stresses which may occur in steel sewer pipes are commonly caused by the internal or bursting pressure of the contained liquid4 ,occasionally a steel pipe may be used as a bridge or as a stressed member of a bridge1 but steel pipes should not be used to withstand compression normal to the axis4 ,in order to avoid such stresses the bursting tensile stresses should exceed the external compressive stresses4 ,such a condition in design requires that buried pipes shall never be emptied1 a condition that cannot always be fulfilled4 ,precaution should be taken1 by the installation of proper valves1 to prevent the emptying of the pipe at so rapid a rate that a vacuum is created resulting in the collapse of the pipe4 ,steel pipes are ordinarily made of plates curved to the proper diameter1 the edges being held together by rivets4 ,the design of the pipe consists in the determination of the thickness of the plate and the design of the riveted joint4 ,the longitudinal joint and the thickness of the plate are first designed4 ,the design of the joint consists in determining the diameter and pitch of the rivets and the thickness of the plate so that the full strength of the uncut metal shall be developed as nearly as possible under bearing1 tearing1 and shearing4 ,this is done by making the efficiency of the joint the same under all stresses4 ,the efficiency of the joint is the ratio of the strength of the joint under any kind of stress to the strength in tension of the unpunched plate4 ,properties of riveted joints are given in ,table #da4 ,the diameter of the rivet holes should be computed as #a_/af of an inch larger than the diameter of the rivets4 ,rivets and plates should be designed for the nearest or next largest commercial size1 and a generous allowance for corrosion should be made in determining the thickness of the plate4 ,the distance from the edge of the plate to the side of the rivet should not be less than #a times the diameter of the rivet4 ,the unit-strengths of the metal are given in the preceding chapter4 ,the transverse joint must be designed empirically as the stresses in it are indeterminate4 ,the common form of joint for pipes less than #dh inches in diameter is a single-riveted lap joint1 and for larger pipes or for pipes exposed to unusual stresses1 a double riveted lap joint is used4 ,the same size rivets are used as in the longitudinal joint4 ,the maximum permissible distance between rivets should be used in the transverse joint4 ,,table #da ,,properties ,,of ,,riveted ,,joints 7,chicago ,bridge and ,iron ,works7 ,type of ,joint ,thickness,diameter ,pitch1 ,efficiency,thickness ,plate1 of ,inches of ,joint1 ,butt ,inch ,rivet1 ,per ,cent ,plate1 ,inch ,inches ,single-riveted lap #a4hh #di #b4be #ej #e_/af #b4fc #ej ,double riveted lap #b4ej #gj #e_/af #c4jj #ga #c4dj #ga ,triple riveted lap #b4ci #gd #e_/af #b4if #gd #c4ec #ge #g_/af #d4ji #gf ,quadruple riveted lap #c4bj #gg #g_/af #c4ij #gh ,double riveted butt #c4fb #gb #i_/af #c4fb #gb #c4fb #gb #aa_/af #c4fb #gb #g_/af #a #d4ab #gc #g_/af #a #c4hb #ga #a #a #c4dh #fh #i_/af ,triple riveted butt #d4id #hj #a #e4fb #hj #i_/af #a #e4af #gh #i_/af #a #a #d4ff #gf #i_/af ,quadruple riveted butt #a #g4ac #hd #a #f4ea #hc #aa_/af #a #a #e4hd #ha ,pipes used as compression members of a bridge are stiffened by riveting standard rolled steel sections longitudinally on the pipe4 ,illustration3 ,,fig4 #gh4--,lock ,bar ,pipe4 ,lock ,bar ,pipe is a steel pipe with a special form of joint made by the ,east ,jersey ,pipe ,corporation4 ,it is arranged as shown in ,fig4 #gh and has the advantage of developing the full strength of the plate4 ,it is equivalent to a joint with #ajj per cent efficiency1 which permits the use of thinner plates4 #aja4 ,design of ,wood ,stave ,pipe4--,in the design of wood stave pipe#ff the entire bursting pressure is taken up by steel bands wrapped around the outside of wood staves which make up the shell of the pipe4 ,the pipe is not designed to resist external loads except those which may be overcome by the internal pressure in the pipe4 ,the thickness of the staves is fixed by experience4 ,the sizes of staves and bands recommended by ,j4 ,f4 ,partridge#fg are given in ,table #dj4 ,the size of the steel bands can be determined from the expression2 ,s ,cr7,r t7 in which ,s the total stress in the band2 ,r the radius of the inside of the pipe2 t the thickness of the stave2 r the area of bearing per unit length of the band on the wood4 ,for circular bands it is assumed as the radius of the band2 ,c the crushing strength of wood1 usually taken at #fej pounds per sq4 in4 ,the preceding expression can be derived easily by the application of the laws of mechanics1 and from it the expression for the distance between bands follows logically4 ,it is1 p ,s7,,pr kt7 in which ,s the strength of the band2 p the distance between bands2 ,p the intensity of bursting pressure in the pipe2 ,r the radius of the inside of the pipe2 t the thickness of the staves2 k the swelling strength of wood1 usually taken at #ajj pounds per sq4 in4 ,illustration3 ,,fig4 #gi4--,shoe for ,wood ,stave ,pipe4 ,transverse joints between staves are closed by inserting metal strips between them1 or by shaping the edges irregularly so that they fit closely together with an irregular joint4 ,transverse joints between all staves at any one point are avoided by splitting the joints between staves4 ,longitudinal joints between staves are usually made smooth and are closed by steel bands which are drawn tight about the pipe by inserting the ends in coupling shoes as shown in ,fig4 #gi4 ,illustration3 ,,fig4 #hj4--;,b in ,formula ,w ,cw,b#b #ajb4 ,external ,loads on ,buried ,pipe4--,prof4 ,anston ,marston and ,h4 ,c4 ,anderson published#fh the results of a series of experiments on the loads on buried pipes which are of extreme value in the design of sewer pipe4 ,the load on the pipe is given by the empirical expression ,w ,cw,b#b1 in which w is the weight of the backfilling material in pounds per cubic foot1 ,b is the width of the trench in feet at the elevation of the end of a radius making an angle of #de degrees upwards with the horizontal diameter of the pipe as illustrated in ,fig4 #hj1 and ,c is a coefficient dependent on the character of the backfill and the ratio of the width to the depth of the trench4 ,values of ,c are given in ,table #db4 ,the weights of various classes of backfilling are given in ,table #dc4 ,,table #db ,,approximate ,,safe ,,working ,,values ,,of ,c ,,in ,,the ,,expression ,w ,cw,b#b ,from ,bulletin ,no4 #ca of the ,engineering ,experiment ,station1 ,iowa ,state ,college of ,agriculture4 ,ratio of ,depth ,approximate ,values of ,c to ,width ,damp ,top ,soil ,saturated ,top ,damp ,yellow ,saturated and ,dry and ,soil ,clay ,yellow ,clay ,wet ,sand #j4e #j4df #j4dg #j4dg #j4dh #a4j #j4ce #j4hf #j4hh #j4ij #a4f #a4af #a4ba #a4be #a4bg #c4j #a4dg #a4ea #a4ef #a4fb #b4f #a4gj #a4gg #a4hc #a4ia #c4j #a4ij #a4ii #b4jh #b4ai #c4f #b4jh #b4ah #b4bh #b4dc #d4j #b4bb #b4ce #b4dg #b4fe #d4f #b4cd #b4di #b4fc #b4he #f4j #b4de #b4fa #b4gh #c4jb #f4e #b4ed #b4gb #b4ij #c4ah #f4j #b4fa #b4ha #c4ja #c4cb #f4f #b4fh #b4hi #c4aa #c4dd #g4j #b4gc #b4ie #c4ai #c4ee #g4e #b4gh #c4ja #c4bg #c4ff #h4j #b4hb #c4jf #c4cc #c4gd #h4e #b4he #c4aj #c4ci #c4hb #i4j #b4hh #c4ad #c4dd #c4hi #i4e #b4ij #c4ah #c4dh #c4if #aj4j #b4ib #c4bj #c4eb #d4ja #aa4j #b4ie #c4be #c4eh #d4aa #ab4j #b4ig #c4bh #c4fc #d4ai #ac4j #b4ii #c4ca #c4fg #d4be #ad4j #c4jj #c4cc #c4gj #d4cj #ae4j #c4ja #c4cd #c4gb #d4cd #c4jc #c4ch #c4gi #d4ej ,,table #dc ,,approximate ,,weights ,,of ,,ditch ,,filling ,,material ,,to ,,be ,,used ,,in ,,the ,,expression ,w ,cw,b#bfi ,ditch ,filling ,pounds per ,cubic ,foot ,partly compacted top soil 7damp7 #ij ,saturated top soil #aaj ,partly compacted damp yellow clay #ajj ,saturated yellow clay #acj ,dry sand #ajj ,wet sand #abj ,where surface loads are to be carried on the sewer trench the proper proportion of the load to be carried by the sewer is determined by the expression ,lp ,,cl1 in which ,lp is the equivalent backfill load per unit length of the trench1 ,l is the surface load per unit length of the trench1 and ,c is a coefficient in which allowance is made for the character of the backfilling1 the ratio of depth to width of trench1 and the character of the load1 whether long or short4 ,a long load is a load extending along the length of the trench such as a pile of building material4 ,a short load is one extending across the trench and for only a short distance along it1 such as that caused by a street car or road roller crossing the trench4 ,values of ,c are given in ,table #dd for long loads1 and in ,table #de for short loads4 ,values of long and short loads occasionally met in practice are given in ,tables #df and #dg respectively4 ,,table #dd ,,ratio ,,of ,,load ,,on ,,pipe ,,to ,,long ,,load ,,on ,,trench#gj ,ratio of ,depth,sand and ,damp ,saturated ,top ,damp ,yellow ,saturated to ,width ,top ,soil ,soil ,clay ,yellow ,clay #j4j #a4jj #a4jj #a4jj #a4jj #j4e #j4he #j4hf #j4hh #j4hi #a4j #j4gb #j4ge #j4gg #j4hj #a4e #j4fa #j4fd #j4fg #j4gb #b4j #j4eb #j4ec #j4ei #j4fd #b4e #j4dd #j4dh #j4eb #j4eg #c4j #j4cg #j4da #j4de #j4ea #d4j #j4bg #j4ca #j4ce #j4da #e4j #j4ai #j4bc #j4bg #j4cc #f4j #j4ad #j4ag #j4bj #j4bf #h4j #j4jg #j4ji #j4ab #j4ag #aj4j #j4jd #j4je #j4jg #j4aa ,for example1 let it be desired to determine the load on a #gb-;inch concrete sewer with a #i-;inch shell under the following conditions3 depth of backfill over the top of the pipe1 #ae feet2 character of backfill1 saturated yellow clay2 superimposed load1 pile of building brick #f feet high4 ,the ratio of the depth of backfill to the width of the trench is #ae #i or #a4fg4 ,the coefficient in the expression ,cw,b#b is #a4ci1 from ,table #db4 ,the weight of saturated yellow clay is #acj pounds per cubic foot1 from ,table #dc4 ,therefore the load per foot length of the sewer due to the backfill is3 ,w ,cw,b#b #a4ci #acj #ha #ad1fjj pounds4 ,,table #de ,,ratio ,,of ,,load ,,on ,,pipe ,,to ,,short ,,load ,,on ,,trench#ga ,ratio of ,height to ,width of ,sand and ,damp ,saturated ,top ,damp ,yellow ,saturated ,trench ,top ,soil ,soil ,clay ,yellow ,clay ,length of ,load ,equal to ,width ,width ,width ,width ,width ,width ,width ,width of of of of of of of of ,trench ,trench ,trench ,trench ,trench ,trench ,trench ,trench #j4j #a4jj #a4jj #a4jj #a4jj #a4jj #a4jj #a4jj #a4jj #j4e #j4gg #j4ab #j4gh #j4ac #j4gi #j4ac #j4ha #j4ac #a4j #j4ei #j4jb #j4fa #j4jb #j4fc #j4jb #j4ff #j4jb #a4e #j4df #j4dh #j4ea #j4ed #b4j #j4ce #j4ch #j4dj #j4dd #b4e #j4bg #j4bi #j4cb #j4ce #c4j #j4ba #j4bc #j4be #j4bi #d4j #j #ab #j4ab #j4af #j4ai #e4j #j4jg #j4ji #j4aj #j4ac #f4j #j4jd #j4je #j4jf #j4jh #h4j #j4jb #j4jb #j4jc #j4jd #aj4j #j4ja #j4ja #j4ja #j4jb ,,table #df ,,weights ,,or ,,common ,,building ,,material ,,when ,,piled ,,for ,,storage4 ,,pounds ,,per ,,cubic ,,foot ,brick #abj ,cement #ij ,sand #ij ,broken stone #aej ,lumber #ce ,granite paving #afj ,coal #ej ,pig iron #djj ,the pressure of the pile of brick per square foot of trench area is1 from ,table #df1 #abj #f #gbj pounds per square foot4 ,the value of ,c from ,table #dd1 is about #j4gj4 ,therefore ,lp is #j4g #i #gbj #decf pounds4 ,the equivalent depth of backfill weighing #acj pounds per cubic foot is 7#decf7acj #i #c4hh foot4 ,the total equivalent depth of backfill is therefore #c4hh #ae #ah4hh feet4 ,the ratio of depth to width is #ah4hhi #b4ih4 ,the coefficient ,c in the expression ,w ,cw,b#b is #b4ag4 ,the total load per foot length of sewer is therefore ,w #b4ag #acj #ha #bb1hjj pounds4 ,,table #dg ,,weights ,,of ,,short ,,loads ,,on ,,sewer ,,trenches 7,adapted from ,specifications of the ,american ,bridge ,company for ,bridges7 ,street railways1 heavy ,a load of #bd tons on #b axles on #aj foot centers4 ,street railways1 light ,a load of #ah tons on #b axles on #aj foot centers4 ,for city streets1 heavy ,a load of #bd tons on #b axles #aj feet traffic apart and #e foot gage4 ,for city streets1 moderate ,a load of #ab tons on #b axles #aj feet traffic apart and #e foot gage4 ,for city streets1 light ,a load of #f tons on #b axles #aj feet traffic or country roads apart and #e foot gage4 ,road rollers ,total weight #cj1jjj pounds4 ,weight on front wheel1 #ab1jjj pounds1 and on each of two rear wheels1 #i1jjj pounds4 ,width of front wheel1 #d feet and of each of two rear wheels #bj inches4 ,distance between front and rear axles #aa feet4 ,gage of rear wheels1 #e feet1 c4 to c4 #ajc4 ,stresses in ,circular ,ring--,in ,fig4 #ha;a the loads shown indicate the distribution ordinarily assumed in sewer design1 the forces being uniformly distributed across the diameter4 ,to find the bending moment in the pipe caused by this loading1 let ab in ,fig4 #ha;b represent a section of a pipe loaded with equally distributed horizontal and vertical forces4 ,then the vertical component on a strip of differential length ds is wds cos and the horizontal component is wds sin and resolving1 the resultant normal to the surface is wds1 in which w is the intensity per unit length of the horizontal and vertical forces and is the angle which the tangent to ds makes with the horizontal4 ,thus the loading of the nature shown in ,fig4 #ha;b is equivalent to a loading of equally distributed normal forces which give no moment in the ring4 ,illustration3 ,,fig4 #ha4--;,distribution of ,stresses on ,buried ,pipe4 ,considering a ring subjected to vertical forces only1 the moments will be as shown in ,fig4 #ha;c and if loaded with horizontal forces only1 the moments will be as shown in ,fig4 #ha;d4 ,because of the symmetry of the figure1 moment 7#a7 equals moment 7#d7 but is opposite in direction and moment 7#b7 equals moment 7#c7 but is opposite in direction4 ,when the horizontal and vertical forces are combined on the same ring as in ,fig4 #ha;b these moments cancel each other as has been proven4 ,therefore moment 7#a7 equals moment 7#b7 and moment 7#c7 equals moment 7#d74 ,then in ,fig4 #ha;e1 ,ma ,mb4 ,now ,m ,o for conditions of equilibrium1 therefore ,ma ,mb 7,w#b77;d#d7 ,o and solving ,ma 7,wd7#af4 ,this moment occurs at the ends of the horizontal and vertical diameters and causes tension on the inside of the pipe at the top and on the outside at the ends of the horizontal diameter4 ,there will also be compression at each end of the horizontal diameter equal to one-half of the total load on the pipe4 ,if the material of the pipe is homogeneous1 the maximum fiber stress f can be found through the expression f 7,my7,i ,p,a in which ,m is the bending moment1 y is the distance from the neutral axis to the extreme fiber of a cross-section of the shell of the pipe of unit length1 ,i is the moment of inertia of this cross-section about its neutral axis1 ,p is one-half the total load on the pipe1 and ,a is the area of the cross-section4 ,for reinforced concrete1 the standard formulas should be used with this expression for ,m4 ,the stresses in a circular ring subjected to other distributions of loads are shown in ,table #dh4 ,an exhaustive study of the stresses in circular rings was published by ,prof4 ,a4 ,n4 ,talbot in ,bulletin ,no4 #bb of the ,engineering ,experiment ,station at the ,university of ,illinois1 #aijh4 ,,table #dh ,,maximum ,,stress ,,in ,,flexible ,,rings ,,due ,,to ,,different ,,loadings 7,from ,marston7 ,symmetrical ,moment at ,crown ,moment at ,end ,compressive ,vertical ,loadings of ,sewer of ,horizontal ,thrust at ,diameter ,crown ,character ,width ,concentrated #j 4#cah,r,w_/#ab- 4#ahb,r,w_/#ab #j4jjj ,uniform #fj 4#bjg,r,w_/#ab- 4#afh,r,w_/#ab #j4jjj ,uniform #ij 4#afi,r,w_/#ab- 4#aed,r,w_/#ab #j4jjj ,uniform #ahj 4#abe,r,w_/#ab- 4#abe,r,w_/#ab #j4jjj ,symmetrical ,compressive ,shear at ,shear at ,vertical ,loadings ,thrust at ,crown ,end of ,end of ,horizontal ,horizontal ,diameter ,diameter ,character ,width ,concentrated #j 4#ejj,w_/#abj4ejj,w_/#ab #j4jjj ,uniform #fj 4#ejj,w_/#abj4jjj,w_/#ab #j4jjj ,uniform #ij 4#ejj,w_/#abj4jjj,w_/#ab #j4jjj ,uniform #ahj 4#ejj,w_/#abj4jjj,w_/#ab #j4jjj ,r the radius of the pipe1 ,w total weight of ditch filling and superimposed load plus of the weight of the pipe itself 7usually neglected71 expressed in pounds per foot length of pipe4 ,moments are inch-pounds per inch length of pipe4 ,shears and thrusts are in pounds per inch length of pipe4 #ajd4 ,analysis of ,sewer ,arches4--,the preceding method for the determination of the stresses in a sewer ring has referred only to a circular pipe uniformly loaded4 ,other methods must be used if the pipe is not circular or the load is not uniformly distributed4 ,the simplest method1 is the static or so-called vouissoir method4 ,in this method the arch is assumed to be fixed at both ends1 presumably at the springing line or line of intersection between the inside face of the arch and the abutment1 and it is so designed that the resultant of all the forces acting on any section shall lie within the middle third of that section4 ,illustration3 ,,fig4 #hb4--,voussoir ,arch ,analysis4 ,illustration3 ,,fig4 #hc4--;,force ,polygon for ,voussoir ,arch ,analysis4 ,to design an unreinforced sewer arch by the vouissoir method1 a desired arch is drawn to scale in apparently good proportions for the loadings anticipated4 ,the arch is then divided into any number of sections of equal or approximately equal length called vouissoirs1 and the line of action of the resultant load1 including the weight of the vouissoir is drawn above each vouissoir as shown in ,fig4 #hb4 ,the forces are assumed to act as shown in the figure4 ,in symmetrically loaded sewer arches there is no vertical reaction at the crown4 ,the resultant ,r is assumed to act at the lower middle third of the skewback1 which is the inclined joint between the arch and the abutment4 ,the upper horizontal force ,h is assumed to act at the upper middle third of the middle or crown section4 ,the magnitude of ,h is computed by equating the sum of the moments of all forces about the point of application of ,r at the skewback to zero1 and solving4 ,the force polygon is then drawn as shown in ,fig4 #hc1 and the equilibrium polygon is completed in ,fig4 #hb with its rays parallel to the corresponding strings drawn from the end of ,h as origin in ,fig4 #hc4 ,if the equilibrium polygon line1 called the resistance line1 lies wholly within the middle third of each vouissoir1 the arch is satisfactory to support the assumed load without reinforcement4 ,if any portion of the resistance line lies outside of the middle third1 an attempt should be made to find a resistance line which lies wholly within the middle third4 ,the true resistance line is that which deviates the least from the neutral axis of the arch4 ,to approximate more nearly the true resistance line find two points at which the resistance line already drawn deviates the most from the neutral axis of the arch4 ,select points ,m and ,n on these joints1 ,m being nearer the crown than ,n4 ,then let ,w#a and ,w#b be the sum of all the loads between the crown and ,m and ,n respectively1 y represent the vertical distance from the crown to ,n1 and y represent the vertical distance between ,m and ,n1 and x#a and x#b represent the horizontal distance from ,w#a and ,w#b to ,m and ,n respectively4 ,then the horizontal thrust1 ,h1 and a1 the distance from the crown to the point of application of ,h1 are1 ,h 77,w#bx#b ,w#ax#a77y1 a y 7,w#bx#b7;,h4#gb ,a resistance line should be drawn with this new horizontal thrust4 ,if no resistance line can be found lying wholly within the middle third1 new sections should be designed until a resistance line can be drawn lying wholly within the middle third--unless the arch is to be reinforced4 ,a number of satisfactory arches should be designed and the easiest one to build should be selected4 ,this method is limited in its application to sewer arches with rigid side walls and it cannot be extended to include the invert4 ,although an approximate method it is accurate within less than #aj per cent of the true stresses and is usually quite close4 ,illustration3 ,,fig4 #hd4--,method for ,dividing ,arch into ,proportion ,i,s4 ,the elastic method for the design of arches locates the true line of resistance without approximations and is more accurate though not so simple to apply as the static or vouissoir method4 ,in this method a desired form of arch is drawn as in the static method and subdivided into vouissoirs so that the distance ,s along the neutral axis between joints is such that the ratio ,i,s shall be the same for all vouissoirs4 ,i is the average of the moments of inertia of the surfaces of the two limiting joints about the neutral axis4 ,if the thickness of the arch is constant the distance between joints will be the same4 ,the method for dividing the arch into sections such that the ratio ,i,s shall be a constant#gc is as follows3 divide the half arch axis into any number of equal parts2 measure the radial depth at each point of division2 lay off the length of the arch axis to scale on a straight line2 divide this line into the same number of equal parts as the half arch1 as shown in ,fig4 #hd2 at each point erect a perpendicular equal in length by scale to the moment of inertia at the corresponding point on the arch section2 draw a smooth curve through the tops of these lines2 draw a line ab at any slope from the center of the original straight line to the curve1 and then a line bc back to the straight line to form an isosceles triangle abc2 continue forming these triangles in a similar manner thus dividing the original straight line in the required ratio4 ,the distance between joints is represented by the bases of the triangles4 ,by construction the altitude of the triangle represents the average moment of inertia between the two limiting joints4 ,the base of each isosceles triangle is ,s1 and ,i,s tan in which is the base angle of all the isosceles triangles4 ,illustration3 ,,fig4 #he4--;,elastic ,arch ,analysis4 ,the following steps in the procedure are taken from the second edition of the ,american ,civil ,engineers ,pocket ,book1 p4 #fcd3 ,in ,fig4 #he let the middle points of the joints be marked #a1 #b1 #c1 etc4 and the coordinates x and y from the crown be found for each by computation or measurement4 ,for a load ,w placed at one of these points1 let z denote the distance from it1 toward the nearest skewback1 to another middle point4 ,let zx be the sum of the products of all the values of z by the corresponding x1 and zy be the sum of all the products of z by the corresponding y2 that is1 each z in the last two summations is multiplied by the x or y of the point back of ,w which corresponds to z4 ,for a single load ,w on the left semi-arch of ,fig4 #he the following formulas are deduced from the elastic theory1 n being the number of parts into which the semi-arch is divided4 ,horizontal thrust1 ,h 7,w#b77nzy yz77ny#b 7y7#b7 7#a7 ,moment at ,crown1 ,m#j 7,wz ,hy7n 7#b7 ,shear at ,crown1 ,v#j 7,wzx7x#b 7#c7 ,for symmetrical loading such as ,w on the left and ,w on the right the horizontal thrust and crown moment due to both loads are double those found by the above formulas1 while the crown shear ,v#j is zero4 ,for several loads unsymmetrically placed the formulas are to be applied to each in succession and the results added algebraically1 the value of ,v#j being taken as negative for the left semi-arch and positive for the right semi-arch4 ,for any joint whose middle point is at a distance x from the crown ,m ,m#j ,hy ,v#jx ,wz1 ,v ,v#j ,w1 where ,w is the sum of all the loads between the joint and the crown and ,wz is the sum of the moments of those loads with respect to the middle of the joint4 ,the components of the resultant thrust normal and parallel to the joints are1 ,n ,h cos ,v sin 1 ,f ,h sin ,v cos 1 in which is the angle which the plane of the joint makes with the vertical4 ,the distances from the neutral axis to the resistance line are1 at the crown1 e#j ,m#j;,h1 at the joint1 e ,m,n4 ,the resistance line should be located as in the vouissoir method and if not within the middle third a new design should be studied4 #aje4 ,reinforced ,concrete ,sewer ,design4--,the method to be followed in the design of reinforced concrete arches is similar except that the moment of inertia should include both the concrete and the steel1 that is1 ,i ,ic n,is1 in which ,i is the moment of inertia to be employed1 ,ic is the moment of inertia of the concrete1 ,is is the moment of inertia of the steel1 and n is the ratio of their moduli of elasticity1 generally taken as #ae4 ,all of the moments of inertia are referred to the neutral axis of the beam4 ,the reinforcement called for in precast circular pipes is given in ,table #ci4 ,sewers cast in place are ordinarily designed to avoid reinforcement1 except where the depth of cover is small and the sewer may be subjected to superimposed loads4 ,concrete sewers are sometimes reinforced longitudinally1 with expansion joints from #cj to #ej feet apart4 ,this reinforcement is to reduce the size of expansion and contraction cracks by distributing them over the length of a section4 ,the pipe is divided into sections to concentrate motion due to expansion or contraction at definite points where it can be cared for4 ,the amount of longitudinal reinforcement to be used is a matter of judgment4 ,it varies in practice from #j4a to #j4d per cent of the area of the section4 ,since the coefficients of expansion of concrete and of steel are nearly the same1 movements of the structure are as important as the stresses due to changes in temperature4 ,because of the uncertain and difficult conditions under which concrete sewers are frequently constructed it is advisable to specify the best grade of concrete and not to stress the concrete over #dej pounds per square inch in compression1 with no allowable stress in tension4 ,the concrete covering of reinforcing steel should be thicker than is ordinarily used for concrete building design1 because of the possibility of poor concrete allowing the sewage to gain access to the steel1 resulting in more rapid deterioration than would be caused by exposure to the atmosphere4 ,a minimum covering of about #b inches is advisable1 except in very thin sections not in contact with the sewage4 ,a minimum thickness of concrete of about #i inches is frequently used in design1 although crown thicknesses of #d inches have been used with success4 ,greater thicknesses should be used near the surface1 particularly in locations subjected to heavy or moving loads4 ,brick linings are often provided for the invert where moderately high velocities of about #aj feet per second when flowing full are to be expected4 ,for velocities in the neighborhood of #bj feet per second the invert should be lined with the best quality vitrified brick4 ,although concrete may erode no faster than brick under the same conditions1 brick linings are more easily replaced and at a smaller expense4 ,,chapter ,x ,,contracts ,,and ,,specifications #ajf4 ,importance of the ,subject4--,sewers may be constructed by day labor or by contract4 ,under the day labor plan a city official or commission is charged with the purchase of material1 the hiring and firing of employees1 and the management of the work4 ,under the contract system a private individual or company contracts to supply all the material and labor necessary for the completion of the work4 ,under the day labor plan all persons engaged are 8working for the ,city40 ,there is not the same sense of individual responsibility1 the same incentive to economize1 the same feeling of loyalty that is inspired by work under the personality of a contractor4 ,under either the day labor or contract plan unscrupulous politics are likely to enter into the relations of the employees of the city and the city officials or between the contractor and the city officials4 ,neither the day labor nor the contract plan offer a sure cure for unscrupulous political misdealings4 ,under the contract plan the contractor is led to keep his bid as low as possible1 realizing the competition of other bidders1 and during construction he will obtain greater efficiency from his labor because of their realization of the different conditions under which they are working4 ,in some states and cities it is illegal for the municipality to do sewer construction except under the contract method4 ,the contract method is therefore used in the majority of cases1 and it is to the interest of the engineer that he be acquainted with the essentials of contracts and specifications necessary for the proper prosecution of sewer construction4 #ajg4 ,scope of ,subject4--,the making of a contract is one of the most common episodes of every day life4 ,the contract may be an informal verbal agreement to meet at a certain place at a certain time1 or it may be a formal document hedged about by confusing legal phraseology and bearing varieties of penalties and dire consequences in the event of its breach4 ,the purpose of this chapter is to explain only those general features of an engineering contract which have particular bearing upon sewerage construction4 ,only the most essential points can be touched in the limited space available to this subject1 it being presumed that the engineer is previously grounded in the principles of business law4#gd #ajh4 ,types of ,contracts4--,contracts are known as lump sum1 cost-plus1 unit-price1 and by other titles indicating the method of payment4 ,a lump sum contract is one in which a stated amount is fixed upon1 before the execution of the contract1 to be paid for all the work to be done and materials to be furnished under the contract4 ,such an arrangement is not advisable for a sewer contract1 as the cautious contractor will bid high enough to protect himself in the event of any probable emergency4 ,the principal must therefore pay whether the emergency or unforeseen difficulty is met or not4 ,the advantage of this type of payment is that the principal knows exactly the cost of the work to him before construction is commenced4 ,cost-plus contracts are those in which the cost of the work to the contractor is to be paid by the principal1 plus1 7a7 a fixed sum of money1 7b7 a percentage of the cost of the work1 7c7 a percentage of the cost of the work but with a fixed limit1 7d7 a percentage of the difference between the cost of the work and some fixed sum1 or other variations of this principle4 ,such contracts have the advantage that the principal assumes all the risk in construction and therefore pays for only those contingencies which actually arise4 ,except for the last named form1 they have the disadvantage that there is little or no incentive for the contractor to keep the cost of the work down4 ,they are most successful where the contractor can be selected by the principal1 but where it is necessary to let contracts to the lowest bidder1 the 8cost-plus0 contract is not easily managed4 ,in most states a municipality cannot make a cost-plus contract4 ,a unit-price contract is one in which the amount to be paid is fixed in proportion to the amount of work done or materials supplied4 ,this type of contract is the most suitable for sewer construction for a municipality where the contract must be let to the lowest bidder4 ,the contractor is protected in the event of many unforeseen emergencies and the principal is protected against a raise in bids to cover such emergencies and against increase in the cost of the work in order to increase the profits under a 8cost-plus0 contract4 ,it is sometimes desirable for the principal to furnish a portion of the materials1 the bidders being notified beforehand that this material will be furnished4 ,in this manner the quality of material is assured1 contractors with the necessary skill but small capital may be attracted to bid1 and uncertainties in the procuring of materials is eliminated4 #aji4 ,the ,agreement4--,a contract is an agreement between two or more interested parties to do a certain thing4 ,a contract for the construction of a sewer is an agreement between a municipality or individual desiring sewerage facilities and a company or individual engaged in the construction of sewers4 ,the latter promises to construct a sewer in return for which the former promises to pay a certain amount of money4 ,the various portions of the agreement which are bound together as the complete contract are3 ,i4 ,the ,advertisement1 ,,ii4 ,information and ,instructions for ,bidders1 ,,iii4 ,proposal1 ,,iv4 ,general ,specifications1 ,v4 ,technical ,specifications1 ,,vi4 ,special ,specifications1 ,,vii4 ,contract1 ,,viii4 ,bond1 and ,,ix4 ,contract ,drawings4 ,these should be fastened together in pamphlet form and constitute the complete instrument called the contract4 ,no binding contract and specifications can be drawn upon logical deductions alone as legal precedent and tried methods must be followed to insure success4 ,to draw up an original contract requires the combined knowledge of an engineer and a lawyer4 ,the engineer of to-day writes his specifications by copying copiously from specifications used on work which has been completed successfully4 ,in order that selections may be made with judgment and discrimination some examples have been selected from existing published specifications and contracts4 #aaj4 ,the ,advertisement4--,this should contain3 7#a7 ,a heading indicating the type of work1 7#b7 ,a statement as to when1 where and how bids will be received and opened1 7#c7 ,a brief description of the character and amount of work to be done1 7#d7 ,the method of payment1 7#e7 ,the conditions under which further information can be obtained1 7#f7 ,a statement as to the amount of money which must be deposited with the bid1 and 7#g7 ,any other pertinent facts concerning the work4#ge ,an example of an advertisement follows2 ,sewer ,construction ,construction ,turkey ,creek ,sewer ,kansas ,city1 ,missouri4 ,bids for the construction of the ,turkey ,creek ,sewer1 two sewage pumping stations to be used in connection therewith1 and certain laterals and extensions of existing sewers thereto1 for ,kansas ,city1 ,missouri1 will be received up to #b p4m4 ,august #ai1 #aiai1 at the office of the ,board of ,public ,works1 ,city ,hall1 ,kansas ,city1 ,missouri4 ,the main sewer will be about one and one-fifth miles long1 and the laterals and extensions about three and one-half miles3 the main sewer will be constructed of reinforced concrete1 the laterals and extensions will consist of concrete1 segment blocks1 and clay pipe4 ,this work is estimated to cost from #a1ejj1jjj to #a1gej1jjj4 ,payment for the work will be made in four year special tax bills1 bearing #g per cent interest1 payable one-fourth each year4 ,time #fjj working days1 barring strikes1 bad weather1 etc4 ,bidders are required to deposit #ae1jjj in cash or a certified check with bid1 to insure signing of contract when let4 ,same to be returned on execution of the contract or rejection of bid4 ,complete plans and specifications for the work may be had and all information obtained by seeing or writing to ,a4 ,d4 ,ludlow1 ,engineer of ,sewers1 ,city ,hall1 ,kansas ,city1 ,missouri4 ,twenty-five 7#be4jj7 ,dollars will be required to be deposited for a set of the plans1 but #bj4jj thereof will be refunded upon return of the plans in good condition4 ,,board ,,of ,,public ,,works1 ,kansas ,city1 ,missouri1 by ,f4 ,e4 ,mc,cabe1 ,secretary4 ,there are usually legal restrictions which require that the advertisement be inserted a certain number of times in specified newspapers or other advertising mediums before the opening of bids4 ,if the contract is of sufficient size to attract outside contractors1 the advertisement should be inserted in engineering and contracting journals of wide circulation4 ,although the advertisement appears separately from the other portions of the contract1 a copy is usually bound in as the first page of the pamphlet containing the contract and specifications and is made an integral part thereof4 #aaa4 ,information and ,instructions for ,bidders4--,this is somewhat on the order of an introduction to the pamphlet in which the specifications1 contract1 and contract drawings are published4 ,as examples of the type of information and instructions given to prospective bidders the abstracts below have been taken from the 8,contract1 ,specifications1 ,bond1 and ,proposal for the ,north ,shore ,sanitary ,intercepting ,sewer0 by the ,sanitary ,district of ,chicago4 ,the information and instructions to bidders can be divided into the following sections3 #ast4 ,examination of ,site1 #bnd4 ,character and ,quantity of ,work1 #crd4 ,qualification for ,bidding1 #dth4 ,instructions for ,making out ,proposal1 #eth4 ,certified ,check1 and #fth4 ,rejection of ,bids4 ,,requirements ,,for ,,bidding ,,and ,,instructions ,,to ,,bidders ,bidders are required to submit their bids upon the following express conditions3 ,bidders must carefully examine the entire sites of the work and the adjacent premises1 and the various means of approach to the sites1 and shall make all necessary investigations to inform themselves thoroughly as to the facilities for delivering and handling materials at the sites and to inform themselves thoroughly as to all the difficulties that may be involved in the complete execution of all work under the attached contract in accordance with the specifications hereto attached4 ,bidders are also required to examine all maps1 plans1 and data mentioned in the specifications1 contract or proposal as being on file in the office of the ,chief ,engineer1 for examination by bidders4 ,no plea of ignorance of conditions that exist or that may hereafter exist or of conditions or difficulties that may be encountered in the execution of the work under this contract1 as the result of a failure to make the necessary examinations and investigations1 will be accepted as an excuse for any failure or omission on the part of the ,contractor to fulfill in every detail all of the requirements of said contract1 specifications and plans1 or will be accepted as a basis for any claims whatsoever for extra compensation4 ,upon application all information in the possession of the ,chief ,engineer will be shown to bidders1 but the correctness of such information will not be guaranteed by the ,sanitary ,district4 ,the following schedule of quantities1 although stated with as much accuracy as is possible in advance1 is approximate only1 and is assumed solely for the purpose of comparing bids4 ,then follows an itemized schedule of the quantity of work to be done after which comes the following3 ,bidders must determine for themselves the quantities of work that will be required1 by such means as they may prefer1 and shall assume all risks as to variations in the quantities of the different classes of work actually furnished under the contract4 ,bidders shall not at any time after the submission of this proposal1 dispute or complain of the aforesaid schedules of quantities or assert that there was any misunderstanding in regard to the amount or the character of the work to be done1 and shall not make any claims for damages or for loss of profits because of a difference between the quantities of the various classes of work assumed for comparison of bids and the quantities of work actually performed4 ,proposals that contain any omissions1 erasures1 or alterations1 conditions or items not called for in the contract and plans attached hereto1 or that contain irregularities of any kind1 will be rejected as informal4 ,bids manifestly unbalanced will not be considered in awarding the contract4#gf ,no bid will be accepted unless the party making it shall furnish evidence satisfactory to the ,board of ,trustees of the ,sanitary ,district of ,chicago of his experience and familiarity with work of the character specified and of his financial ability to successfully and properly prosecute the proposed work to completion within the specified time4 ,each bid shall be accompanied by a certified check1 or cash1 to the amount of ten 7#aj7 per cent of the total amount of said bid figured on the quantities given herewith1 the lowest alternative total being allowed4 ,said amounts deposited with bids1 shall be held until all of the bids have been canvassed and the contract awarded and signed4 ,the return of said check or cash to the bidder to whom the contract for said work is awarded will be conditioned upon his appearing and executing a contract for the work so awarded and giving bond satisfactory to said ,board of ,trustees1 for the fulfillment of each contract in the amount of fifty 7#ej7 per cent of the amount of each contract4 ,the said ,board of ,trustees reserves the right to reject any or all bids4 ,accompanying the contract form are plans which1 together with the specifications1 show the work on which said tenders are to be made4 ,the proposal must not be detached herefrom or from the contract by any bidder when submitting a bid4 #aab4 ,proposal4--,the proposal is a blank printed form on which the bidder is required to enter the prices for which he proposes to do the work4 ,the proposal blank is necessary in order that the bids may be sufficiently uniform for proper comparison4 ,sewers are often paid for1 particularly for small sizes1 per foot of completed sewer as measured along the center line of the pipe parallel to the surface of the ground with the exterior length of manholes and other structures deducted4 ,sometimes1 under other conditions1 a different rate is allowed for each additional two feet of depth of sewer1 and special structures1 such as manholes1 catch-basins1 flush-tanks1 etc41 are paid for at a unit price according to the depth4 ,water connections to flush-tanks are paid for per foot of length of service pipe laid4 ,in especially large or difficult work1 materials are paid for at a unit-price1 for example1 per cubic yard of excavation1 per cubic yard of concrete1 per thousand feet board measure of lumber1 etc4 ,the following example is taken from the contract for the ,north ,shore ,intercepting ,sewer previously quoted1 to indicate the type of ,proposal used3 ,,proposal ,,for ,,the ,,construction ,,of ,,the ,,north ,,shore ,,intercepting ,,sewer ,to the ,honorable1 the ,president and the ,board of ,trustees of the ,sanitary ,district of ,chicago3 ,gentlemen3,the undersigned hereby certi that ha examined the specifications and form of contract and the accompanying plans for the construction of the ,north ,shore ,intercepting sewer1 and ha also examined the premises at and adjacent to the sites of the proposed work1 as herein described1 and the means of approach to the said sites4 ,the undersigned ha also examined the foregoing 8,requirements for ,bidding and ,instructions to ,bidders0 and propose to do all the work called for in said specifications and contract1 and shown on said plans1 and to furnish all materials1 tools1 labor and all appliances and appurtenances necessary to the full completion of said work at the rates and prices for said work as follows1 towit3 7#a;a7 ,for six 7#f7 by nine 7#i7 foot concrete sewer1 complete in place1 as specified1 the sum of ,dollars and cents 7 7 per linear foot4 7#f;a7 ,for manholes1 concrete1 complete in place1 as specified the sum of ,dollars and cents 7 7 each4 ,the following plans showing the work to be performed in accordance with the attached specifications1 have been examined by the undersigned in preparing the foregoing proposal1 to-wit3 ,in accordance with the requirements set forth in the attached ,information and ,instructions for ,bidders1 there is deposited herewith the sum of ,dollars and cents 7 7 which under the terms therein mentioned entitle to bid on said work1 the said sum to be refunded to upon the faithful performance of all conditions set forth in the ,information and ,instructions for ,bidders4 ,name ,address ,blanks are provided for each item4 ,no place is left at the end for a summary4 ,the proposal ends with an acknowledgment that the contract has been examined completely and all preliminary directions therein have been complied with4 ,a blank is prepared for inserting the amount of the required certified check1 and finally for the signature of the bidders4 #aac4 ,general ,specifications4--,the specifications1 both general and technical1 are occasionally incorporated in the contract form1 but more frequently they are printed separately and are bound in the pamphlet preceding the contract4 ,the general specifications relate to the conditions under which all work must be performed and are as applicable to the construction of a pumping station as to the smallest lateral1 unless otherwise specified4 ,it is not possible to include a complete set of ,general ,specifications in the limited space of this text1 but the more important specifications will be emphasized by examples taken from specifications in use4#gg ,the subjects covered in ,general ,specifications are3 7#a7 ,definitions of doubtful terms4 7#b7 ,the ,engineer to settle disputes4 7#c7 ,duties of the ,engineer4 7#d7 ,duties of the ,contractor4 7#e7 ,hours and days of work4 7#f7 ,no work to be done in the absence of an inspector4 7#g7 ,contractor to be represented at all times4 7#h7 ,time of commencing and completing the work4 7#i7 ,liquidated damages for delay in completion4 7#aj7 ,the ,city may change the plans4 7#aa7 ,the ,city may increase the amount of the work4 7#ab7 ,inspection and its conduct4 7#ac7 ,the ,contractor to be acquainted with laws relating to the work4 7#ad7 ,contractor responsible for damages to persons or property4 7#ae7 ,city to be protected against patent claims4 7#af7 ,abandonment of contract and its remedy4 7#ag7 ,estimates of work done and moneys due4 7#ah7 ,payments for extra work4 7#ai7 ,character of workmen to be employed4 7#bj7 ,city may reserve a sum for repairs during stipulated term after completion4 7#ba7 ,city may use money due ,contractor to pay claims for labor or materials used on the work and not paid for by the ,contractor4 7#bb7 ,the ,contractor shall have no claim for damages on account of delay or unforeseen difficulties4 7#bc7 ,the ,contractor may not assign nor sublet the contract without the ,city's consent4 7#bd7 ,cleaning up after completion4 7#be7 ,the ,contractor's relations to other contractors4 7#bf7 ,the portions composing the contract4 ,the following examples cover the subjects named in the preceding titles3 #a4 ,definitions4 ,the word ,engineer whenever not qualified shall mean the ,chief ,engineer of the ,commission1 acting either directly or through his properly authorized agents1 such agents acting severally within the scope of the particular duties entrusted to them4 ,this article may include words that may be in dispute or ambiguous such as3 ,board of ,trustees1 ,elevation1 ,city1 ,contractor1 ,rock1 ,earth1 etc41 etc4 #b4 ,disputes4 ,to prevent disputes and litigations1 the ,engineer shall in all cases determine the amount1 quality1 and acceptability of the work which is to be paid for under the contract2 shall decide all questions in relation to said work and the performance thereof1 and shall in all cases decide every question which may arise relative to the fulfillment of the contract on the part of the ,contractor4 ,his determination1 decision and estimate shall be final and conclusive1 and in case any question shall arise between the parties touching the contract1 such determination1 decision1 and estimate shall be a condition precedent to the right of the ,contractor to receive any moneys under the contract4 #c4 ,duties of the ,engineer4 ,the ,engineer shall make all necessary explanations as to the meaning and intentions of the specifications and shall give all orders and directions1 either contemplated therein or thereby1 or in every case in which a difficulty or unforeseen condition shall arise in the performance of the work4 ,should there be any discrepancies in or between1 or should any misunderstanding arise as to the import of anything contained in the plans and specifications1 the decision of the ,engineer shall be final and binding4 ,any errors or omissions in plans and specifications may be corrected by the ,engineer1 when such corrections are necessary for the proper fulfillment of their intentions as construed by him4 #d4 ,duties of the ,contractor4 ,the ,contractor shall do all the work and furnish all the labor1 materials1 tools and appliances necessary or proper for performing and completing the work required by the contract1 in the manner called for by the specifications1 and within the contract time4 ,he shall complete the entire work at the prices agreed upon and fixed therefor to the satisfaction of the ,commission and its ,chief ,engineer and in accordance with the specifications1 the drawings1 and such detailed drawings as may be furnished from time to time1 together with such extra work as may be required for the performance of which written orders may be given and received as hereinafter provided4 ,the ,contractor shall place sufficient lights on or near the work and keep them burning from twilight to sunrise2 shall erect suitable railings1 fences or other protections about all open trenches1 and provide all watchmen on the work1 by day or night1 that may be necessary for the public safety4 ,the ,contractor shall1 upon notice from the ,engineer that he has not satisfactorily complied with the foregoing requirements1 immediately take such methods and provide such means and labor to comply therewith as the ,engineer may direct1 but the ,contractor shall not be relieved of this obligation under the contract by any such notice or directions given by the ,engineer1 or by neglect1 failure1 or refusal on the part of the ,engineer to give such notice and directions4 ,the ,contractor shall furnish such stakes and the necessary labor for driving them as may be required by the ,engineer4 ,he shall maintain the stakes when set1 with reasonable diligence1 and stakes misplaced due to the carelessness of the ,contractor or his workmen shall be reset under the direction of the ,engineer1 at the ,contractor's expense4 #e4 ,night1 ,sunday1 and ,holiday ,work3#gh ,no night1 ,sunday1 nor holiday work requiring the presence of an engineer or inspector will be permitted except in case of emergency1 and then only to such an extent as is absolutely necessary and with the written permission of the ,engineer2 provided that this clause shall not operate in the case of a gang organized for regular and continuous night1 ,sunday1 or holiday work4 #f4 ,absence of ,engineer or ,inspector4 ,any work done without lines1 levels1 and instructions having been given by the ,engineer or without the supervision of an assistant or inspector1 will not be estimated or paid for except when such work is authorized by the ,engineer in writing4 ,work so done may be ordered removed and replaced at the ,contractor's sole cost and expense4 #g4 ,absence of ,contractor4 ,during the absence of the ,contractor he shall at all times have a duly authorized representative on the work4 ,the ,contractor shall give written notice to the ,commission of the name and address of said representative and shall state where and how such representative can be reached1 at any and all hours1 whether by day or night4 ,whenever the ,contractor or his representative is not present at any place on the work where it may be necessary to give orders or directions1 such orders or directions will be given by the ,engineer and they shall be received and promptly obeyed by the superintendent or foreman who may have immediate charge of the particular work in relation to which the order may be given4 #h4 ,commencing ,work4 ,the ,contractor agrees to begin the work covered by this contract within ---- days of the execution of the contract and to prosecute the same with all due diligence and to entirely complete the work within ---- days4 ,it is understood and agreed that time is of the essence of this contract1 and that a failure on the part of the ,contractor to complete the work herein specified within the time specified will result in great loss and damage to said ,sanitary ,district and that on account of the peculiar nature of such loss it is difficult1 if not impossible1 to accurately ascertain and definitely determine the amount thereof4 #i4 ,liquidated ,damages4 ,it is therefore covenanted and agreed that in case the said ,contractor shall fail or neglect to complete the work herein specified on or before the date hereinbefore fixed for completion1 the said ,contractor shall and will pay the said ,sanitary ,district the sum of ---- ,dollars for each and every day the ,contractor shall be in default in the time of completion of this contract4 ,said sum of ---- ,dollars per day is hereby agreed upon1 fixed and determined by the parties hereto as the liquidated damages which said ,sanitary ,district will suffer by reason of such defaults1 and not by way of a penalty4 #aj4 ,changes in ,plans4 ,the ,board reserves the right to change the alignment1 grade1 form1 length1 dimensions or materials of the sewers or any of their appurtenances1 whenever any condition or obstructions are met that render such changes desirable or necessary4 ,in case the alterations thus ordered make the work less expensive to the ,contractor a proper deduction shall be made from the contract prices and the ,contractor shall have no claim on this account for damages or for anticipated profits on the work that may be dispensed with4 ,in case such alterations make the work more expensive1 a proper addition shall be made to the contract prices4 ,any deduction or addition as aforesaid shall be determined and fixed by the ,engineer4 #aa4 ,extensions and ,additions4 ,in the event that any material alterations or additions are made as herein specified which in the opinion of the ,engineer will require additional time for execution of all the work under this contract1 then1 in that case the time of completion of the work shall be extended by such a period or periods of time as may be fixed by said ,engineer and his decision shall be final and binding upon both parties hereto1 provided that in such case the ,contractor1 within four 7#d7 days after being notified in writing of such alterations and additions1 shall request in writing an extension of time1 but the provisions of this paragraph shall not otherwise alter the provisions of this contract with reference to liquidated damages1 and the said ,contractor shall not be entitled to any damages or compensation from the said ,sanitary ,district on account of such additional time required for the execution of the work4 #ab4 ,inspection4 ,all materials of whatsoever kind to be used in the work shall be subject to the inspection and approval of the ,engineer and shall be subject to constant inspection before acceptance4 ,any imperfect work that may be discovered before its final acceptance shall be corrected immediately1 and any unsatisfactory materials used in the work or delivered at the site shall be rejected and removed on the requirement of the ,engineer4 ,the inspection of any work shall not relieve the ,contractor of any of his obligations to perform proper and satisfactory work as herein specified1 and all work which1 during the progress and before the final acceptance1 may become damaged from any cause1 shall be removed and replaced by good and satisfactory work without extra charge therefor4 ,the ,engineer and his assistants shall have at all times free access to every part of the work and to all points where material to be used in the work is manufactured1 procured or stored and shall be allowed to examine any material furnished for use in the work under this contract4 ,all inspection of any and all material furnished for use in work to be performed under this contract shall be made at the site of the work after the delivery of the material1 provided1 that1 if requested by the ,contractor the ,engineer may at his option perform1 or have performed1 inspection of materials at points other than the site of the work4 ,in any such case the ,contractor shall pay the ,sanitary ,district the extra cost of such inspection1 including the necessary expenses of the inspector for the extra time expended in performing any such inspection at said other points4 #ac4 ,legal ,requirements4 ,the ,contractor shall keep himself fully informed of all existing and future national and state laws and local ordinances and regulations in any manner affecting those engaged or employed in the work1 or the materials used in the work1 or of all such orders and degrees of bodies or tribunals having any jurisdiction or authority over the same1 and shall protect and indemnify the party of the first part against any claim or liability arising from or based on the violation of such law1 ordinance1 regulation1 order or decree1 whether by himself or his employees4 #ad4 ,damages4 ,if any damage shall be done by the ,contractor or by any person or persons in his employ to the owner or occupants of any land or to any real or personal property adjoining1 or in the vicinity of the work herein contracted to be done or to the property of a neighboring contractor the ,engineer shall have the right to estimate the amount of said damage and to cause the ,sanitary ,district to pay the same to the said owner1 occupant1 or contractor1 and the amount so paid shall be deducted from the money due said ,contractor under this contract4 ,said ,contractor covenants and agrees to pay all damages for any personal injury sustained by any person growing out of any act or doing of himself or his employees that is in the nature of a legal liability1 and he hereby agrees to indemnify and save the ,sanitary ,district harmless against all suits or actions of every name and description brought against said ,sanitary ,district1 for or on account of any such injuries1 or such damages received or sustained by any person or persons2 and the said ,contractor further agrees that so much of the money due to him under this contract1 as shall be considered necessary by the ,board of ,trustees of said ,sanitary ,district1 may be retained by the ,sanitary ,district until such suit or claim for damages shall have been settled1 and evidence to that effect shall have been furnished to the satisfaction of said ,board of ,trustees4 #ae4 ,patents4 ,it is further agreed that the ,contractor shall indemnify1 keep and save harmless said ,sanitary ,district from all liabilities1 judgments1 costs1 damages and expenses which may in any wise come against said ,sanitary ,district1 or which may be the result of an infringement of any patent by reason of the use of any materials1 machinery1 devices1 apparatus1 or process furnished or used in the performance of this contract1 or by reason of the use of designs furnished by the ,contractor and accepted by the ,sanitary ,district1 and in the event of any claim or suit or action at law or in equity of any kind whatsoever being made or brought against said ,sanitary ,district1 then the ,sanitary ,district shall have the right to retain a sufficient amount of money in the same manner and upon the conditions as hereinafter specified4 #af4 ,abandonment of ,contract4 ,if the work to be done under the contract shall be abandoned by the ,contractor1 or if at any time the ,engineer shall be of the opinion1 and shall so certify1 in writing1 to the ,commission1 that the performance of the contract is unnecessarily or unreasonably delayed1 or that the ,contractor is willfully violating any of the conditions of the specifications1 or is executing the same in bad faith1 or not in accordance with the terms thereof1 or if the work be not fully completed within the time named in the contract for its completion1 the ,commission may notify the ,contractor to discontinue all work thereunder1 or any part thereof1 by a written notice served upon the ,contractor1 as herein provided2 and thereupon the ,contractor shall discontinue the work1 or such part thereof1 and the ,commission shall thereupon have the power to contract for the completion of said work in the manner prescribed by law1 or to procure and furnish all necessary materials1 animals1 machinery1 tools and appliances1 and to place such and so many persons as it may deem advisable to work at and complete the work described in the specifications1 or such part thereof1 and to charge the entire cost and expense thereof to the ,contractor4 ,and for such completion of the work or any part thereof1 the ,commission may for itself or its contractors1 take possession of and use or cause to be used any or all such materials1 animals1 machinery1 tools and implements of every description as may be found on the line of the said work4 ,the cost and expense so charged shall be deducted from1 and paid by the ,city out of such moneys as may be due or may become due to the ,contractor1 under and by virtue of the contract4 ,in case such expense shall exceed the amount which would have been payable under the contract1 if the same had been completed by the ,contractor1 he shall pay the amount of such excess to the ,city4 ,when any particular part of the work is being carried on by the ,commission1 by contract or otherwise1 under the provisions of this clause of the contract1 the ,contractor shall continue the remainder of the work in conformity with the terms of his contract1 and in such manner as in no wise to hinder or interfere with the persons or workmen employed by the ,commission by contract or otherwise as above provided1 to do any part of the work or to complete the same under the provisions hereof4 #ag4 ,estimates4 ,the ,engineer shall from time to time as the work progresses1 on or about the last day of each month1 make in writing an estimate1 such as he shall believe to be just and fair1 of the amount and value of the work done and the materials incorporated into the work by the ,contractor under the specifications1 provided however that no such estimate shall be required to be made when1 in the judgment of the ,engineer the total value of the work done and the materials incorporated into the work since the last preceding estimate is less than ---- dollars4 ,such estimates shall not be required to be made by strict measurements1 but they may be approximate only4 ,the ,contractor shall not be entitled to demand from the ,commission as a right1 a detailed statement of the measurements or quantities entering into the several items of the monthly estimates1 but he will be given such opportunities and facilities to verify the estimates as may be deemed reasonable by the ,commission4 ,when in the opinion of the ,engineer1 the ,contractor shall have completely performed the contract on his part1 the ,engineer shall make a final estimate1 based on actual measurements1 of the whole amount of the work under and according to the terms of the contract1 and shall certify to the ,commission in writing1 the amount of the final estimate at the completion of the work4 ,after the completion of the work the ,city shall pay to the ,contractor the amount remaining after deducting from the total amount or value of the work1 as stated in the final estimate1 all such sums as have theretofore been paid to the ,contractor under any of the provisions of the contract1 except such sums as may have been paid for extra work1 and also any sum or all sums of money which by the terms thereof the ,city is or may be authorized to reserve or retain2 provided that nothing therein contained shall affect the right of the ,city1 hereby reserved1 to reject the whole or any portion of the aforesaid work1 should the said certificate be found or known to be inconsistent with the terms of the contract or otherwise improperly given4 ,all monthly estimates upon which partial payments have been made1 being merely estimates1 shall be subject to correction in the final estimate1 which final estimate may be made without notice thereof to the ,contractor1 or of the measurements upon which it is based4 #ah4 ,extra ,work4 ,the ,contractor shall do any work not herein otherwise provided for1 when and as ordered in writing by the ,engineer or his agents specially authorized thereto in writing1 and shall when requested by the ,engineer so to do1 furnish itemized statements of the cost of the work ordered and give the ,engineer access to accounts1 bills1 vouchers1 etc4 relating thereto4 ,if the ,contractor claims compensation for extra work not ordered as aforesaid1 or for any damages sustained1 he shall within one week after the beginning of any such work or the sustaining of any such damage1 make a written statement of the nature of the work performed or the damage sustained1 to the ,engineer1 and shall1 on or before the fifteenth day of the month succeeding that in which any such extra work shall have been done or any such damage shall have been sustained1 file with the ,engineer an itemized statement of the details and amount of any such work or damage2 and unless such statement shall be made as so required1 his claim for compensation shall be forfeited and he shall not be entitled to payment on account of any such work or damage4 ,for all such extra work the ,contractor shall receive the reasonable cost of said work1 plus fifteen 7#ae7 per cent of said cost4 #ai4 ,competent ,employees4 ,the ,contractor shall employ only competent skillful men to do the work2 and whenever the ,engineer shall notify the ,contractor1 in writing1 that any man employed on the work is1 in his opinion unsatisfactory1 such man shall be discharged from the work and shall not again be employed on it1 except with the consent of the ,engineer4 #bj4 ,money ,retained4 ,upon the completion of the work and its acceptance by the ,city1 the ,city shall reserve and retain five 7#e7 per cent of the total value of the work done under the contract as shown by the final estimate1 over and above any and all other reservations which the city by the terms thereof is entitled or required to retain and shall hold the said five 7#e7 per cent for a period of nine 7#i7 months from and after the date of completion and acceptance1 and the ,city shall be authorized to apply such part of said five 7#e7 per cent so retained to any and all costs of repairs and renewals as may become necessary during such period of nine 7#i7 months1 due to improper work done or materials furnished by the ,contractor1 if the ,contractor shall fail to make such repairs or renewals within twenty-four 7#bd7 hours after receiving notice from the ,city so to do4 ,upon the expiration of said nine 7#i7 months from and after the completion and acceptance of the work1 the ,city shall pay to the ,contractor the said five 7#e7 per cent hereby retained1 less such sums as may have been retained hereunder4 #ba4 ,unpaid ,claims against ,contractor4 ,the ,contractor shall furnish the ,city with satisfactory evidence that all persons who have done work or furnished materials under the contract1 and have given written notices to the ,city1 before and within ten 7#aj7 days after the final completion and acceptance of the whole work under the contract1 that any balance for such work or materials is due and unpaid1 have been fully paid or satisfactorily secured4 ,and in case such evidence is not furnished as aforesaid1 such amount as may be necessary to meet the claims of the persons aforesaid shall be fully discharged or such notices withdrawn4 #bb4 ,delays and ,difficulties4 ,the ,contractor shall not be entitled to any claims for damages on account of postponement or delay in the work occasioned by forces beyond the control of the ,city1 nor for postponement or delay in the work where ten 7#aj7 days written notice has been given the ,contractor of such postponement or delay1 nor where unforeseen difficulties are encountered in the prosecution of the work4 ,in the event of a postponement or delay ordered in writing by the ,city the time of completion of the contract shall be extended a number of days equal to the number of days that the work has been postponed or delayed4 #bc4 ,assignment of ,contract4 ,the ,contractor shall not assign by power of attorney or otherwise1 nor sublet the work or any part thereof1 without the previous written consent of the party of the first part1 and shall not either legally nor equitably assign any of the moneys payable under this agreement or his claim thereto unless by and with the consent of the party of the first part4 #bd4 ,cleaning ,up4 ,on or before the completion of the work1 the ,contractor shall1 without charge therefor1 tear down and remove all buildings and other structures built by him1 shall remove all rubbish of all kinds from any grounds which he has occupied1 and shall leave the line of the work in a clean and neat condition4 #be4 ,access to ,work and ,other ,contractors4 ,the ,commission and its engineers1 agents and employees may at any time and for any purpose enter upon the work and the premises used by the ,contractor1 and the ,contractor shall provide proper and safe facilities therefor4 ,other contractors of the ,commission may also when so authorized by the ,engineer1 enter upon the work and the premises used by the ,contractor for all the purposes which may be required by their contracts4 ,any differences or conflicts which may arise between this ,contractor and other contractors of the ,commission in regard to their work shall be adjusted and determined by the ,engineer4 #bf4 ,the ,contract4 ,it is understood and agreed by the ,city and the ,contractor that the terms of this contract are embodied and included in the ,advertisement1 ,information and ,instructions to ,bidders1 ,proposal1 ,specifications of every nature1 the ,bond and the contract drawings hereto attached4 ,these few articles have been given as examples of some of the essential subjects to be treated in general specifications4 ,it is to be understood that these examples do not represent a complete set of general specifications and items have been omitted the absence of which in a complete contract might be injurious to the successful completion of the work4 #aad4 ,technical ,specifications4--,these ordinarily follow the general specifications and have to do with the quality of materials1 the manner of putting them together1 and the method of doing the work4 ,the subject headings in the ,technical ,specifications on the ,baltimore ,sewerage ,commission are3 ,excavation ,tunneling ,rock ,excavation ,sheeting ,sheet ,piling ,sheeting and ,bracing ,piles ,blasting ,pumping and ,drainage ,foundations ,refilling ,repaving ,underdrains ,buildings ,inlets and ,catch-,basins ,cement ,mortar ,concrete ,brick ,masonry ,reinforced ,concrete ,vitrified ,pipe ,concrete and ,brick ,sewers ,vitrified ,pipe ,sewers and ,drains ,manholes ,iron ,castings ,house ,connections ,obstructions ,fences ,flush-,tanks ,each of these subjects is treated in the appropriate section of this book4 ,an important part of each section of the technical specifications is the clause providing for the method of payment for the work specified4 ,this is usually the last clause in the section4 ,for example1 the last clause in the ,baltimore ,specifications relating to ,rock ,excavation1 is3 8,payment will be made for the number of cubic yards of rock measured and allowed as above specified at the price of four dollars and fifty cents 7#d4ej7 per cu4 yd41 measured in place4 ,payment for rock excavation will be made in addition to the prices bid for excavation40 #aae4 ,special ,specifications4--,these have to do with problems1 methods of construction1 or materials peculiar to certain contracts or certain portions of the work4 ,it frequently occurs that the construction of sewerage works will be let out under a number of contracts1 or bids will be called for on different alternatives to which the entire ,advertisement1 ,information and ,instructions for ,bidders1 ,proposal1 and ,general ,specifications are applicable4 ,the special specifications will apply only to the contract in question1 e4g41 in some work done under the direction of the author1 the sewer on one contract came within twelve inches of the surface of a highway4 ,the special specification relating to this piece of construction1 was3 8,where crossing under the ,chicago ,road the pipe sewer shall be embedded in concrete as shown on the contract drawings4 ,the concrete for this purpose shall be mixed in the proportions of one 7#a7 part cement1 three 7#c7 parts fine aggregate1 and six 7#f7 parts coarse aggregate4 ,payment for the concrete so used will be made at the unit price stated in the accompanying ,proposal40 ,in order to avoid confusion the special specifications are either incorporated directly in the ,contract form1 or follow the ,technical ,specifications and are grouped according to the contracts to which they apply4 #aaf4 ,the ,contract4--,the contract is a brief instrument which includes a simple statement of the obligations of each party involved4 ,the following is an example of a form in successful use3 ,,contract ,this agreement made and entered into this day of in the year one thousand nine hundred and by and between the ,city of by its duly constituted or elected authorities herein acting for the ,city of without personal liability to themselves1 party of the first part1 hereinafter designated as the ,city1 and party of the second part hereinafter designated as the ,contractor4 ,,witnesseth1 that the parties to these presents each in consideration of the undertakings1 promises and agreements on the part of the other herein contained1 have undertaken1 promised and agreed1 and do hereby undertake1 promise and agree1 the party of the first part for itself1 its successors and assigns1 and the part of the second part for and heirs1 executors1 administrators and assigns as follows1 to-wit3 ,art4 ,i4 ,to be bounden by all the articles of the ,general1 ,technical1 and ,special ,specifications applicable1 and by the terms of the ,advertisement1 ,information and ,instructions for ,bidders1 ,proposal and ,contract ,drawings hereto attached1 and which are understood and acknowledged to be an integral part of this contract4 ,art4 ,,ii4 ,the work to be completed under this contract is ,art4 ,,iii4 ,the ,city shall pay and the ,contractor shall receive as full compensation for everything furnished and done by the ,contractor under this contract1 including all work required but not specifically mentioned in the following items1 and also for all loss or damage arising from the nature of the work aforesaid1 or from the action of the elements1 or from any unforeseen obstruction or difficulty encountered in the prosecution of the work and for well and faithfully completing the work as herein provided1 as follows3 ,then follows a copy of the ,proposal with the prices bid4 ,the contract closes with the final clause3 ,in witness whereof the said ,city of 1 party of the first part have hereunto set their hands and seals1 and the ,contractor has also hereunto set his hand and seal and the party of the first part and the ,contractor have executed this agreement in duplicate1 one part to remain with the party of the first part and one to be delivered to the ,contractor this day of in the year one thousand nine hundred and ,city of ,contractor #aag4 ,the ,bond4--,the bond called for in the ,information and ,instructions for ,bidders is bound in the pamphlet following the ,contract4 ,no uniform practice is followed in the amount of the bond required4 ,it varies from #ej to #ajj per cent of the contract price and may be stated as a lump sum before the contract price is known4 ,there is a possibility that the ,contractor may fail before he has commenced work and the ,city may be unable to procure another contractor to take up the work4 ,the ,city should then be protected by a #ajj per cent bond4 ,such a contingency is remote4 ,the ,contractor seldom fails until work is well under way1 and other contractors are usually available1 although the failure of one contractor tends to increase the bids of other contractors for the same work4 ,in fixing the amount of the bond the judgment of the ,engineer is called into play in order that the amount may be as low as possible in fairness to the ,contractor1 and high enough to protect the interests to the ,city4 ,by reducing the amount of the bond the expense to the ,city is also reduced as the ,city ultimately must pay its cost4 ,upon the acceptance of the bond and the execution of the ,contract1 the ,engineer's duties take him out of the designing office and into the construction field4 ,,chapter ,,xi ,,construction #aah4 ,elements4--,the principal elements in construction are3 labor1 materials1 tools1 and transportation4 ,the lack of or inadequateness of any one of these detracts from the effectiveness of the others4 ,the engineer should assure himself of the completeness of his plans or those of the contractor on each of these points4 ,the disposition of labor and the handling of materials to obtain the largest amount of good with the least expenditure of money and effort are problems which must be solved by the engineer or the contractor during construction4 ,,work ,,of ,,the ,,engineer #aai4 ,duties4--,the duties of the engineer during construction consist in giving lines and grades2 inspecting materials2 interpreting the contract1 specifications and drawings2 making decisions when unexpected conditions are encountered2 making estimates of work done2 collecting cost data2 making progress reports2 keeping records2 and in guarding the interests of the ,city4 #abj4 ,inspection4--,in the inspection of workmanship and materials1 the engineer is assisted by a corps of inspectors and assistants who act under his direction4 ,the duties of the inspector are to be present at all times that work is in progress and to act for the engineer in enforcing the terms of the contract1 the details of the drawings1 and the tests applicable to the workmanship and materials that he is delegated to inspect4 ,he should have a copy of the contract1 or that portion of it which pertains to his work1 available at all times4 ,he should examine all materials as they are delivered on the job and see that rejected materials are removed at once4 ,an ordinary recourse of some foremen will be to place rejected material to one side until a brief absence of the inspector will present the opportunity for the use of the rejected material4 ,the methods to be followed in the inspection of materials and workmanship should be such as to discover discrepancies between the specifications and the materials delivered or the work done4 ,other duties of the inspector are3 to record the location of house connections or to drive a stake over them for subsequent location by the engineer2 to see that plugs are put in the branches left for future house connections2 to inspect the workmanship in the making of joints in pipe sewers2 to protect the line and grade stakes from displacement2 to check the size1 depth1 and grade of sewers and elevations of special structures1 etc4 ,dishonest and unscrupulous workmen have many tricks to get by the inspector4 ,these tricks are best learned by experience as no academic list can impress them properly on the memory4 ,the position of the inspector is not always enviable4 ,he must hold the respect of the workmen1 of the contractor1 and of the engineer4 ,to do this he must not be unreasonable or arbitrary in his decisions1 but when a decision is once made he must be firm in following up its enforcement4 ,he must be careful not to give directions whose fulfillment he cannot enforce1 nor for which he cannot give adequate reason to his superiors4 ,his integrity must never be questioned4 ,he must not allow himself to become under obligations to the contractor by the acceptance of favors he cannot return except at the expense of his employer1 yet at the same time he must not appear priggish by the refusal of all favors or social invitations4 ,in brief he must be friendly without being intimate1 independent without being aloof1 and firm without being arbitrary4 ,the engineer must support his inspectors in their decisions or discharge them if he cannot4 #aba4 ,interpretation of ,contract4--,in interpreting the contract1 specifications and drawings1 the engineer is supposedly an impartial arbiter between the interests of the city and the contractor4 ,his decisions1 as to the meaning of the contract1 must be founded on his engineering judgment1 and should aim to produce the best results without demanding more from the contractor than1 in his honest opinion1 it is the intention of the contract to demand4 ,however conscientiously he may attempt to remain impartial1 and in spite of the honesty of the contractor1 his position1 as an employee of the city will almost invariably cause him to favor the city in his decisions on close points4 ,the experienced contractor knows this and fixes his bid accordingly1 the personality of the engineer sometimes acting as an important factor in the amount of the bid4 ,the situation arises through the character of the contract1 and not through a lack of moral integrity on the part of anyone concerned4 #abb4 ,unexpected ,situations4--,when unexpected or uncertain conditions are encountered in construction the engineer should visit the spot at once and should advise or direct1 according to the terms of the contract1 the procedure to be followed4 ,such conditions may be the encountering of other pipes1 quicksand1 rock1 etc4 ,each case is a problem in itself4 ,water1 gas1 telephone and electric wire conduits can be moved above or below the sewer being constructed with comparative ease4 ,other sewers1 if smaller1 may be permitted to flow temporarily across the line of the sewer under construction and finally discharge into the completed sewer1 or one sewer must be made to pass under the other1 either as an inverted siphon or by changing the grade of one of the sewers4 ,rock1 or other material for which a special rate of payment is allowed1 must be measured as soon as uncovered in order to avoid delaying the work or losing the record of the amount removed4 ,when quicksand is met special precautions must be taken to safeguard the sewer foundation and to insure that the sewer will remain in place until after the backfilling is completed4 ,these precautions are described in ,art4 #ace4 #abc4 ,cost ,data and ,estimates4--,cost account keeping and the making of monthly or other estimates are closely connected4 ,cost accounts are of value in estimating the amount of work done to date1 and in making preliminary estimates of the cost of similar work4 ,although the engineer is not always required to keep such accounts1 they are usually of sufficient value to pay for the labor of keeping them4 ,under some contracts the contractor's accounts are open to examination by the engineer4 ,usually1 however1 he must depend on reports from the inspectors for information concerning the man-hours required on different pieces of work1 and on his own measurements of materials used and his knowledge of their unit costs1 in order to make up an estimate of total cost4 ,the measurement of a completed structure and a summary of the materials used in its construction may act as a check on the use of proper materials as called for in the contract4 ,for example1 if it is known that #b1jjj bricks are required for the construction of a manhole and if only #ae1jjj have been used in the construction of ten manholes1 it is probable that some or all of the manholes have been skimped4 ,similar conditions may show in the proportions of concrete1 backfilling in tunnels1 sheeting to be left in place1 etc4 ,the statement of a few principles of cost accounting1 and the illustration of a few blanks in use should be sufficiently suggestive to lead a resourceful engineer in the right direction4#gi ,costs should be divided into four general classifications3 labor1 materials1 equipment1 and overhead4 ,labor should be subdivided under its several different classifications arranged in accordance with rates of pay4 ,the number of laborers under each classification and the amount of work done per day should be recorded4 ,fig4 #hf is an example of a form which may be used for such a purpose4 ,illustration3 ,,fig4 #hf4--;,foreman's ,daily ,payroll ,report4 ,from ,engineering and ,contracting1 #aijg4 ,materials may be recorded as they are delivered on the job1 as they are used1 or in both cases4 ,measurements are usually easier to make at the time of delivery1 but records made at the time materials are used are more serviceable4 ,for example1 #ajj barrels of cement may be delivered on a job in ,november1 #ej of them are used before the job freezes up and the other #ej are held over until spring4 ,it would be misleading to charge #ajj barrels used in ,november4 ,fig4 #hg is a form in use for an inspector's report on materials4 ,the total cost must be made up in the office from these records and a knowledge of unit costs4 ,illustration3 ,,fig4 #hg4--;,foreman's ,daily ,material ,report4 ,from ,engineering and ,contracting1 #aijg4 ,equipment consists of tools1 animals1 machinery1 and apparatus used in construction4 ,only equipment that is actually used should be charged to the job and a credit should be made at the completion of the job for the fair value of the equipment remaining after the completion of the work4 ,overhead charges include the expense of the office force1 superintendence1 and miscellaneous items such as insurance1 rent1 transportation1 etc41 which cannot be charged to any particular portion of the work but are equally applicable to all portions4 ,it happens frequently that many jobs are handled in the same main office4 ,the division of overhead becomes more difficult and is frequently arranged on an arbitrary basis1 e4g41 each job may be charged the proportion of overhead that its contract price bears to the total contract prices being performed under that office4 ,this rule may be modified when it becomes evident that some job is taking distinctly more than its share of the overhead4 ,estimates of work done in any period can be made with the above data in hand by subtracting the total costs of the work up to the beginning of the period from the total costs up to the end of the period4 ,fig4 #hh shows a sample blank from the final estimate sheets used at ,scarsdale1 ,n4 ,y4 #abd4 ,progress ,reports4#hj--,these are kept by the engineer in order that he may see that the work is progressing as called for in the contract1 and any portion which is lagging behind without reason may be pushed4 ,such reports are most useful when the information is expressed graphically1 as the eye quickly catches points where the work is falling behind schedule4 #abe4 ,records4--,the contract drawings are supposed to show exactly where and how construction is to be done4 ,due to unexpected contingencies changes occur1 of which a record should be made and preserved4 ,these records may be kept in a form similar to the contract drawings1 or if the changes are not extensive1 they can be recorded on the original contract drawings4 ,the location of house and other connections should be recorded in a separate note book available for immediate consultation4 ,the engineer should keep a diary of the work in which are recorded events of ordinary routine as well as those of special interest and importance4 ,this diary should be illustrated by photographs showing the condition of the streets before and after construction1 methods of construction1 accidents1 etc4 ,such accounts are of great value in defending subsequent litigation and their existence sometimes prevents litigation4 ,a contractor may wait a year or so after the completion of a piece of work until the engineer and other city officials have broken their connection with the city4 ,suit is then brought against the city and unless good records are available the administration may be forced to buy the claimant off or may elect to enter court1 only to be beaten4 ,illustration3 ,,fig4 #hh4--,samples of ,cost ,record ,forms4 ,from ,engineering and ,contracting1 #aiji4 ,excavation #abf4 ,specifications4--,the following abstracts have been taken from the specifications on ,excavation by the ,baltimore ,sewerage ,commission as illustrative of good practice4 ,in conducting the work the contractor shall3 444 remove all paving1 or grub and clear the surface over the trench1 whenever it may be necessary and shall remove all surface materials of whatever nature or kind4 ,he shall properly classify the materials removed1 separating them as required by the ,engineer2 and shall properly store1 guard1 and preserve such as may be required for future use in backfilling1 surfacing1 repaving or otherwise4 ,all macadam material removed shall be separated and graded into such sizes as the ,engineer may direct and materials of different sizes shall be kept separate from each other and from any and all other materials4 ,all the curb1 gutter1 and flag-stones and all paving material which may be removed1 together with all rock1 earth and sand taken from the trenches shall be stored in such parts of the carriageway or such other suitable place1 and in such manner as the ,engineer may approve4 ,the ,contractor shall be responsible for the loss of or damage to curb1 gutter and flag-stones and to paving material because of careless removal or wasteful storage1 disposal1 or use of the same4 444 ,when so directed by the ,engineer the bottom of the trench shall be excavated to the exact form of the lower half of the sewer or of the foundation under the sewer4 ,the bottom width of the trench for a brick or concrete sewer shall be 444 not less in any case than the overall width of the sewer1 as shown on the plans4 ,in case the trench is sheeted this minimum width will be measured between the interior faces of the sheeting as driven1 but in no case shall bracing1 stringers1 or waling strips be left within any portion of the masonry of the sewer except by permission of the ,engineer2 and such braces1 stringers and waling strips shall not1 in any case1 be allowed to remain within the neat lines of the masonry as shown on the plans4 ,in case that the distance between faces of the sheeting is less than that called for by the width of the sewer to be laid in the trench1 the ,engineer may direct the sheeting to be drawn and redriven1 or otherwise changed and altered2 or he may direct that the sewer be reinforced in such manner and to such an extent as he may deem necessary without compensation to the ,contractor1 even though such narrower trench was not caused by negligence or other fault on the part of the ,contractor4 ,trenches for vitrified pipe shall be at all points at least six inches wider in the clear on each side than the greatest external width of the sewer1 measured over the hubs of the pipe4444 ,bell holes shall be excavated in the bottoms of trenches for vitrified pipe sewers wherever necessary4 ,not more than three hundred feet of trench shall be opened at any one time or place in advance of the completed building of the sewer1 unless by written permission of the ,engineer and for a distance therein specified4444 ,the excavation of the trench shall be fully completed at least twenty feet in advance of the construction of the invert1 unless otherwise ordered4 ,during the progress of construction the ,contractor will be required to preserve from obstruction all fire hydrants and the carriageway on each side of the line of the work4 ,the streets1 cross-walks1 and sidewalks shall be kept clean1 clear1 and free for the passage of carts1 wagons1 carriages and street or steam railway cars1 or pedestrians1 unless otherwise authorized by special permission in writing from the ,engineer4 ,in all cases a straight and continuous passageway on the sidewalks and over the cross walks of not less than three feet in width shall be preserved free from all obstruction4 ,where any cross walk is cut by the trench it shall be temporarily replaced by a timber bridge at least three feet wide1 with side railings1 at the ,contractor's expense4 ,the placing of planks across the trench without proper means of connection or fastenings1 or pipe or other material1 or the using of any other makeshift in place of properly constructed bridges1 will not be permitted4 ,this is equally applicable to certain wagon bridges to be fixed upon by the ,engineer1 on the basis of traffic requirements4 ,in streets that are important thoroughfares or in narrow streets the material excavated from the first one hundred feet of any opening or from such additional length as may be required1 shall upon the order of the ,engineer1 be removed by the ,contractor1 as soon as excavated4 ,the material subsequently excavated shall be used to refill the trench where the sewer has been built4 ,the preceding specifications are applicable to open-trench excavation4 ,rigid restrictions are placed about tunneling because of the greater difficulty of doing good work1 the greater danger to life and property and the possibility of later surface subsidence if the backfilling is done improperly4 ,a common clause in specifications is3 ,all excavations for sewers and their appurtenances shall be made in open trenches unless written permission to excavate in tunnel shall be given by the ,engineer4 #abg4 ,hand ,excavation4--,earth excavation by pick and shovel is the simplest and most primitive mode of excavation4 ,only small jobs are handled in this manner in order to save the investment necessary in machines or the expense of hiring and moving one to the work4 ,the tools used in the hand excavation of trenches are3 picks1 pickaxes1 long-handled and short-handled pointed shovels1 square-edged long- and short-handled shovels1 scoop shovels1 axes1 crowbars1 rock drills1 mauls1 sledges1 etc4 ,the excavating gangs are divided up into units of #bj to #ej men under one foreman or straw boss1 and among the men may be a few higher priced laborers who set the pace for the others4 ,each laborer on excavation should be provided with a shovel1 the style being dependent on the character of the material being excavated and the depth of the trench4 ,in stiff material and deep trenches requiring the lifting of the material in the shovel1 long-handled pointed shovels should be used4 ,in loose sandy material loaded directly into buckets short-handled1 square pointed shovels are satisfactory4 ,picks are used in cemented gravels or where hard obstructions prevent cutting down with the edge of the shovel4 ,very stiff but not hard material can be cut out in chunks with a pickaxe and thrown from the trench or into a bucket with a scoop shovel4 ,scoop shovels are also useful in wet running quicksand4 ,the number of picks1 axes1 crowbars1 and other tools must be proportioned according to the material being excavated4 ,under the worst conditions of excavation in a hard cemented gravel it may be necessary to provide each man with a pick as well as a shovel1 whereas in sand only a shovel is necessary4 ,two or three crowbars1 axes1 a length of chain1 two or three screw jacks1 etc41 are provided per gang in case of an unexpected encounter with an obstruction in the trench1 such as a boulder1 a tree stump1 a length of pipe1 etc4 ,in laying out the work the foreman marks the outlines of the trench on the ground by means of a scratch made with a pick1 chalk marks1 tape1 or other devices4 ,these marks are measured from offset or center stakes set by the engineer4 ,center stakes are less conducive to error but are more likely to be disturbed before use than are offset stakes1 but careless foremen make more errors with offset than with center stakes4 ,the inspector should assist or be present at the laying out of the trench4 ,after the trench has been laid out each laborer should be given a certain specific portion of it to dig and this portion is marked out on the ground4 ,in this way a check can be kept upon the performance of each laborer and the knowledge of this fact tends to a uniformly better performance4 ,the amount of work that can be performed by one man with a pick and shovel is as shown in ,table #di4 ,some men may exceed these rates1 many will not attain them4 ,the allotted task must be gaged on the character of the ground in order that the tasks may be equal and a spirit of competition fostered4 ,the hard worker will set the pace for the lazy man4 ,some contractors have adopted the expedient of dismissing laborers for the day as soon as the allotted task is done4 ,,table #di ,,amount ,,of ,,material ,,moved ,,by ,,one ,,man ,,with ,a ,,pick ,,and ,,shovel 7,from ,h4 ,p4 ,gillette7 ,material ,cubic ,yard per hour ,hardpan #j4cc ,common earth #j4h to #a4b ,stiff clay #j4he ,clay #a4jj ,sand #a4be ,sandy soil #j4h to #a4b ,clayey earth #a4c ,sandy soil 7frozen7 #j4ge ,the opening of the trench may be facilitated by breaking ground with a plow4 ,in hard ground or on paved roads it may be necessary to cut through the surface crust with a hammer and drill1 although in some cases a plow can be used successfully4 ,frozen ground can be thawed by building fires along the line of the trench1 or greater economy may be achieved by placing steam pipes along the surface with perforations about every #ah inches and either boxing them on the top and sides or burying them in the frozen earth with a covering of sand4 ,another arrangement is to blow steam into a line of bottomless boxes in which each box is about #h feet long4 ,holes are left in the top of the boxes into which the pipe is shoved1 and after its withdrawal the holes are covered4 ,blasting of frozen earth is sometimes successful but cannot be resorted to in built up districts where it is unsafe unless properly controlled4 ,once the frost crust is broken through it can be attacked from below and frequently broken down by undermining4 ,a laborer cannot dig and raise the earth much more than to the height of his head1 and preferably not quite so high1 without tiring quickly4 ,after the trench has passed a depth of #d feet he cannot throw the earth clear of the trench4 ,an additional laborer is needed then at the surface to throw the earth back4 ,he should shovel the earth from a board platform placed at the edge of the trench as a protection to the bank4 ,when the trench passes the #f-;foot depth a staging is put in about #d feet from the top on which the lowest laborer piles his materials4 ,it is then passed up to the surface by a second laborer on the staging1 and a third laborer on the surface throws the material back clear of the trench4 ,stagings are put in about every #e or #f feet for the full depth of the trench4 ,when the trench has come within half the diameter of the pipe of the final grade1 if the material is sufficiently firm1 the remainder of the trench should be cut to conform to the shape of the lower half of the outside of the pipe1 with proper enlargements for each bell4 #abh4 ,machine ,excavation4--,on work of moderately large magnitude excavation by machine is cheaper than by pick and shovel alone4 ,in comparing the cost of excavation by the two methods all items such as sheeting1 pipe laying1 backfilling1 etc41 should be included1 since these items will be affected by the method of excavation4 ,the cost of setting up and reshipping the machine must be included as this is frequently the item on which the use of the machine depends4 ,because of the cost of setting up and shipping1 which must be distributed over the total number of yards excavated1 the cost per cubic yard of excavating by machine varies with the number of cubic yards excavated4 ,the point of economy in the use of a machine is reached when the cost by hand and by machine are equal4 ,for all work of greater magnitude1 excavation by machine will prove cheaper4#ha ,items favoring the use of machinery which may cause its adoption for small jobs are3 its greater speed1 reliability1 ease in handling1 economy in sheeting1 economy in labor1 and small amount of space needed making it useful in crowded streets4 ,continuous bucket machines1 drag lines1 and occasionally steam shovels are not adapted to conditions where rocks1 pipes and other underground obstacles are frequently met4 ,the following problem is an example of the work necessary in making a comparison of the relative economy of machine and hand excavation3 ,it is assumed that a man can excavate #ae feet of trench #cj inches wide and #h feet deep in #aj hours4 ,he receives #ee cents per hour for his work4 ,a machine costing #aj1jjj has a life of #f years4 ,it can be kept busy #aej days in the year4 ,when operating it costs #a4be per hour for the operator1 fuel and repairs4 ,it will excavate #hjj linear feet of #cj inch trench to a depth of #h feet in #aj hours4 ,it is assumed that capital is worth #aj per cent on such a venture and that the sinking fund will draw #aj per cent4 ,if the cost of moving and setting up the machine is #a1hjj1 how many cubic yards of excavation must there be to make excavation by machine economical8 ,costs of sheeting1 pumping1 etc41 are assumed to be the same for machine or hand work4 ,solution4--,for hand work the man excavated #a4aa cubic yard per hour at #ee cents4 ,the relative cost of hand excavation is then #ej cents per cubic yard4 ,the cost of machine work will be divided into3 interest on first cost2 operation and repairs2 and sinking fund for renewal4 ,the interest on the first cost of #aj1jjj at #aj per cent is #a1jjj per year4 ,the machine works #a1ejj hours in the year4 ,therefore the cost per hour is #j4fg4 ,the sinking fund payment1 as found from sinking fund tables or the accumulation of #aj1jjj in4 #f years1 is #a1cjj per year or per hour for #a1ejj hours is #j4hg4 ,the cost of operation per hour is given as #a4be4 ,the total cost per hour is therefore #b4gi4 ,the machine excavated #ei4c cubic yards per hour which makes the cost1 exclusive of moving1 equal to #j4dg per cubic yard4 ,in order to equalize the cost of machine and hand excavation the cost of moving the machine must be divided among a sufficient number of cubic yards so that the cost per cubic yard shall be #c cents4 ,the cost of moving is given as #a1hjj4 ,this amount divided among #fj1jjj cubic yards equals #c cents per cubic yard4 ,therefore the job must provide at least #fj1jjj cubic yards of excavation in order that the use of the machine shall be justifiable from the viewpoint of economy alone4 #abi4 ,types of ,machines4--,machines particularly adapted to the excavation of sewer and water pipe trenches are of four types3 7#a7 continuous bucket excavators2 7#b7 overhead cableway or track excavators2 7#c7 steam shovels2 and 7#d7 boom and bucket excavators4 ,other types of excavating machinery can be used for sewer trenches under special conditions4 ,machines are ordinarily limited to a minimum width of trench of #bb inches4 ,between widths of #bb inches and #cf inches the limit of depth for the first class of machines is about #be feet4 ,for other types of machines there is no definite limit1 though the economical depth for open cut work seldom exceeds #dj feet4 #acj4 ,continuous ,bucket ,excavators4--,continuous bucket excavators are of the types shown in ,figs4 #hi and #ij4 ,the buckets which do the digging and raising of the earth may be supported on a wheel as in ,fig4 #hi or on an endless chain as in ,fig4 #ij4 ,the support of the wheel or endless chain can be raised or lowered at the will of the operator so as to keep the trench as close to grade as can be done by hand work4 ,in some machines the shape of the buckets can be made such as to cut the bottom of the trench1 in suitable material1 to the shape of the sewer invert4 ,in operation1 the buckets are at the rear of the machine and revolve so that at the lowest point in their path they are traveling forward4 ,the excavated material is dropped on to a continuous belt which throws it on the ground clear of the trench1 into dump wagons1 or on to another continuous belt running parallel with the trench to the backfiller1 by means of which the excavated material is thrown directly into the backfill without rehandling4 ,the body of the machine supporting the engine travels on wheels ahead of the excavation and is kept in line by means of the pivoted front axle4 ,when obstacles are encountered the excavating wheel or chain is raised to pass over the obstacle1 and allowed to dig itself in on the other side4 ,illustration3 ,,fig4 #hi4--;,buckeye ,wheel ,excavator4 ,courtesy1 ,buckeye ,traction ,ditcher ,co4 ,illustration3 ,,fig4 #ij4--;,buckeye ,endless-chain ,excavator4 ,courtesy1 ,buckeye ,traction ,ditcher ,co4 ,illustration3 ,,fig4 #ia4--,movable ,sheeting ,fastened to ,traction ,ditcher4 ,from ,eng4 ,news-,record1 ,vol4 #hb1 #aiai1 p4 #gdj4 ,wheel excavators are not adapted to the excavation of sewer trenches over #c to #d feet in width and #f to #h feet in depth4 ,the endless-chain excavators are suitable for depths of #be feet with widths from #bb to #gb inches1 and due to the arrangement permitting buckets to be moved sideways they will cut trenches of different widths with the same size buckets4 ,this is an advantage where there are to be irregularities in the width of the trench such as for manholes or changes in size of pipe4 ,with excavating machines pipe can be laid within #c feet of the moving buckets and the trench backfilled immediately1 thus making an appreciable saving in the amount of sheeting4 ,in the construction of trenches for drain tile at ,garden ,prairie1 ,illinois1 the sheeting was built in the form of a box or shield fastened to the rear of the machine and pulled along after it as is shown in ,fig4 #ia4 ,the performance of this type of excavating machine under suitable conditions is large4 ,a remarkable record was made by ,ryan and ,co4 in ,chicago1#hb with an excavating machine4 #acch feet of #cb-;inch trench were excavated to an average depth of #h feet in #g hours1 or an average of #afj cubic yards per hour4 ,more could have been accomplished if it had not been for delays in supplies4 ,another crew at ,greeley1 ,colorado1#hc with a ,buckeye endless-chain ditcher weighing #ag tons and costing #ebjj1 averaged #bcb cubic yards per day for #cjj days1 and the cost was #aj4g cents per cubic yard4 ,a #ae-ton ,austin excavator can be expected to remove #cjj to #ejj cubic yards per day4 ,the cost of operation of the machines is made up of items listed in ,table #ej4 ,the figures given are merely suggestive4 ,,table #ej ,,cost ,,of ,,operating ,,ditching ,,machine ,per ,day ,total ,labor3 #a ,operator at #aej per month #f4jj #a ,assistant ,operator at #abj per month #d4jj #d laborers at #d4jj per day #af4jj ------------ #bf4jj ,fuel3 #bj ,gallons of gasoline at #bh cents #e4fj #e4fj ,miscellaneous3 ,oil1 waste1 etc4 #a4bj ,repairs and maintenance #aj4jj ,interest1 #f per cent on #aj1jjj for #aej days #d4jj ,depreciation1 #bjj working days per year and an #h year life #aa4aa #bf4ca ------------------------ ,total cost per day #eg4ia ,,table #ea ,,comparison ,,of ,,cost ,,of ,,hand ,,excavation ,,and ,,machine ,,excavation ,,with ,,continuous-,,bucket ,,excavator ,hand ,work ,per ,machine ,work ,per ,day1 ,day1 ,dollars ,dollars ,foreman #d4jj;,engineer #d4jj ,timberman #c4jj;,fireman #b4ej ,helper #b4ej;,coal #e4jj #d ,laborers at #b4jj #hj4jj,team #d4jj ,foreman #d4jj ,pipe layer #c4jj ,helper #b4ej #b ,teams backfilling #h4jj #b ,helpers #d4jj ,interest1 depreciation and repairs #aj4jj ------------ ------------ ,total #ie4jj ,total #ed4ej ,in making a comparison of the cost of hand and machine excavation the figures given in ,table #ea are from 8,excavating ,machinery0 by ,mc,daniel1 who quotes the cost of machine excavation from the manufacturers of the ,parsons machine issued as the result of several years' experience with their excavator4 ,in the comparison the hand crew is assumed to dig #cae linear feet of trench #bh inches wide by #ab feet deep in a day of #aj hours4 ,this assumes that each man will excavate #g cubic yards per day4 ,the machine is assumed to excavate #bej feet of the same trench4 ,the comparison indicates that an excavator will work at about #ej per cent of the cost of hand excavation1 if the cost of moving the machine is not included4 ,illustration3 ,,fig4 #ib4--;,carson ,excavating ,machine on ,trench ,excavation in ,south ,milwaukee4 ,courtesy1 ,mr4 ,c4 ,f4 ,henning4 #aca4 ,cableway and ,trestle ,excavators4--,cableway and trestle excavators are most suitable for deep trenches and crowded conditions4 ,they should not be used for trenches much less than #h feet in depth4 ,they differ from the continuous bucket excavators in that the actual dislodgment of the material is done by pick and shovel1 the excavated material being thrown by hand into the buckets of the machine4 ,a machine of the ,carson type is shown in ,fig4 #ib4 ,the machine consists of a series of demountable frames held together by cross braces and struts to form a semirigid structure4 ,an ,i beam or channel extending the length of the machine is hung closely below the top of the struts4 ,the lower flange of this beam serves as a track for the carriages which carry the buckets4 ,all the carriages are attached to each other and to an endless cable leading to a drum on the engine4 ,this cable serves to move the buckets along the trench4 ,the buckets are attached to another cable which is wound around another drum on the engine and serves to lower or raise all the buckets at the same time4 ,in operation there are always at least two buckets for each carriage1 one in the trench being filled and the other on the machine being dumped4 ,there should be a surplus of buckets to replace those needing repairs4 ,the machines may be from #bjj to #cej feet in length1 and the number of buckets which can be lifted at one time varies from one to a dozen or more4 ,on trenches over #e to #f feet in width a double line of buckets is sometimes used4 ,the entire machine rests on rollers and straddles the trench4 ,it is moved along the trench by its own power1 either by gearing or chains attached to the wheels1 or by a cable attached to a dead-man ahead4 ,the ,potter trench machine differs from the ,carson in that only #b buckets are used at a time and these are carried on a car which travels on a track on top of the trestle4 ,the movement of the buckets and the car are controlled by #b dump men who ride on the car and who can raise or lower the buckets independently4 ,the organization needed to operate these machines is3 a lockman who locks and unlocks the buckets on the cable1 a dumper1 as many shovelers as there are buckets on the machine1 and an engineman who is usually his own fireman4 ,from #ej to #djj cubic yards of material can be excavated in a day with one of these machines1 dependent on the character of the material and the depth of the trench4 ,h4 ,p4 ,gillette in his ,handbook of ,cost ,data reports that about #aij cubic yards were excavated per day with a ,potter machine4 ,the machine was #cgj feet long4 ,six -yard buckets were used1 #d in the trench and #b on the carrier4 ,the trench was #aj feet wide and #ah feet deep in wet sand and soft blue clay4 ,the organization consisted of an engineman1 a fireman1 #b dumpmen on the carrier1 and from #ag to #ba excavating laborers depending on the kind and the amount of the excavation4 ,in general the capacity of such machines is limited by the amount of material which can be shoveled into them by hand4 #acb4 ,tower ,cableways4--,these are essentially of the same class as the trestle cableway machines4 ,they differ in that the carriage supporting the buckets travels on a cable suspended between #b towers instead of on a track supported on a trestle4 ,as a rule only one bucket is handled in the machine at a time4 ,they are used in sewer work only in exceptional cases as the towers must be taken down and re-erected each time that there is an advance in the trench greater than the distance between the towers4 #acc4 ,steam ,shovels4--,the use of steam shovels for the excavation of sewer trenches is becoming more prevalent because of their growing dependability and durability as compared with other machines1 their adaptability for small trenches1 and the relatively large number of widely different uses to which they can be put4 ,in excavating a trench the shovel straddles the trench and runs on tractors1 wheels1 or rollers on either side of it4 ,the shovel cuts the trench ahead of it4 ,as a result it is difficult to set sheeting and bracing close to the end of the trench while the shovel is operating4 ,steam shovels are therefore not suitable for excavation in unstable material1 unless the sheeting is driven ahead of the excavation4 ,it is only in the softest ground that ordinary wood sheeting can be driven ahead of the excavation4 ,steel sheet piling is more suitable for such use4 ,fig4 #ichd shows a shovel at work on a trench in ,evanston1 ,illinois4 ,shovels are equipped with extra long dipper handles to adapt them to trench excavation4 ,the dipper handle in the picture is longer than the standard for this type of machine4 ,the method of supporting the shovel can be seen in the picture under the machine and the method of bracing and of finishing the trench by hand work are also shown4 ,the excavated material is taken out in the shovel and dropped on the bank or into wagons4 ,the limiting depth to which trenches can be excavated by steam shovels is about #bj to #be feet1 where the trench is too narrow for the shovel to enter4 ,wider trenches are cut in steps of about #ae feet1 the shovel working in the trench for additional depths4 ,shovels are now made to cut trenches as narrow as a man can enter to lay pipe4 ,the greatest width that can be cut from one position of the shovel is from #ae to #dj feet1 dependent on the size of the shovel4 ,occasionally a combination of a drag line and a steam shovel can be used1 as on the construction of the ,calumet sewer in ,chicago4 ,on this work the first step was cut by a steam shovel4 ,it was followed by a drag line resting on the step thus prepared1 and excavating the remaining distance to grade4 ,the depth of the trench in this work averaged about #be to #cj feet4 ,illustration3 ,,fig4 #ic4--,steam ,shovel at ,work on ,sewer ,trench for ,north ,shore ,intercepting ,sewer1 ,evanston1 ,illinois4 ,steam shovels are rated according to their tonnage and the capacity of the dipper in cubic yards4 ,both are necessary as the size of the dipper is varied for the same weight of machine1 dependent on the character of the material being excavated4 ,for rock the dipper is made smaller than for sand4 ,gillette in his ,hand ,book of ,cost ,data gives the coal and water consumption of steam shovels as shown in ,table #eb4 ,the performance of steam shovels is recorded in ,table #ec4 ,the conditions of the work have a marked effect on the output of the shovel4 ,a shovel in a thorough cut1 i4e41 in a trench just wide enough for the shovel to turn #ahj degrees but too narrow to run cars or wagons along side of it1 will perform less than one-half of the work that it can perform in a side cut1 i4e41 where the cars can be run along side the shovel which turns less than #ij degrees4 ,,table #eb ,,coal ,,and ,,water ,,consumption ,,by ,,steam ,,shovels 7,from ,handbook of ,cost ,data1 by ,h4 ,p4 ,gillette7 ,weight in tons #ce #de #ee #fe #ge #ij ,dipper1 cubic yards #a #a #a #b #b #c ,coal1 tons per #aj hour day #a #a #a #b #b ,water1 gallons per #aj hour day #aejj #bjjj #bejj #cjjj #djjj #dejj ,,table #ec ,,performance ,,by ,,steam ,,shovels ,weight,dipper,depth ,width #aj-;,hour ,cost ,authority ,remarks in ,cubic of of ,cut ,performance in ,tons ,yards ,cut1 ,cents1 ,feet per ,cubic ,yard #be #a #i #cf in4 #he #bb4f ,r4 ,t4 ,dana #a ,eng4 ,rec41 #fi3eha #be #a #h #ce in4 #if #bc4e do4 #b #gj #b #bf #af ft4 #efi #f4g do4 #c #cj #a #ae-ah #fj in4 #cjj ,a4 ,b4 ,mc,daniel #d ,excavating ,machinery #ae #ad #acd ft4 #djj ,eng4 ,cont'r1 #e #h-be-ji #h #cf ,very #af yd4 cars ,marion ,steam #f wide ,shovel ,co4 #ee #bif ,h4 ,p4 #g ,gillette's ,cost ,data #fe #b #bhj do4 ,greater #gjj #cj4f ,g4 ,c4 ,d4 #h than #gh ,lenth1 ,eng4 in4 ,news-,record1 #he3bb ,remarks3 #a4 ,one runner at #e4jj1 one fireman at #b4ca1 two laborers at #a4gj each1 supplies at #d4ej1 and interest and depreciation on #bjj days per year1 #d4jj4 ,total per day1 #ai4ba4 ,material1 clay and gravel4 #b4 ,average of #aa jobs with the same shovel4 #c4 ,cost per day1 one runner at #e4jj1 one crane-man at #c4fj1 one fireman at #b4jj1 #g roller men at #a4ej each1 supplies #i4jj and interest and depreciation on #ijjj at #bjj days per year #h4jj4 ,total1 #ch4aj4 #d4 ,hard clay4 #e4 ,stiff clay for the basement of a building in ,chicago4 #f4 ,stripping ore4 ,this is a maximum record4 ,the average was about three hundred and twenty #af cubic yard cars per day4 #g4 ,blasted mica-schist4 #h4 ,general average4 #acd4 ,drag ,line and ,bucket ,excavators4--,a drag line excavator is shown in ,fig4 #id4 ,the back of the bucket is attached to a drum on the engine by means of a cable passing over the wheel in the end of the long boom4 ,the front of the bucket is attached by another cable directly to another drum on the engine4 ,in operation the bucket is raised by its rear end and dropped out to the extremity of the boom4 ,it is then dragged over the ground towards the machine1 digging itself in at the same time4 ,when filled the bucket is raised by tightening up on the two cables1 swung to one side by means of the movable boom1 and dumped4 ,illustration3 ,,fig4 #id4--;,drag ,line at ,work on ,trench for ,drain ,tile4 ,drag line excavators will perform as much work as steam shovels under favorable conditions4 ,they are less expensive in first cost and operation1 and are equally reliable but they are not adapted to the more difficult situations where steam shovels can be used to advantage4 ,drag lines are suitable only for relatively wide trenches in material requiring no bracing1 and in a locality where relatively long stretches of trench can be opened at one time4 ,the bucket excavator differs from the drag line in that the bucket can be lifted vertically only and the types of buckets used in the two types of machine are different4 ,the bucket may be self filling of the orange-peel or clam-shell type1 or a cylindrical container which must be filled by hand4 ,a drag line can be easily converted into a boom and bucket excavator4 ,boom and bucket excavators are well adapted to use in deep1 closely braced trenches and shafts4 #ace4 ,excavation in ,quicksand4#he--;,a sand or other granular material in which there is sufficient upward flow of ground water to lift it1 is known as quicksand4 ,its most important property1 from the viewpoint of sewer construction1 is its inability to support any weight unless the sand is so confined as to prevent flowing of the sand1 or unless the water is removed from the sand4 ,excavation in quicksand is troublesome and expensive and is frequently dangerous4 ,the material will flow sluggishly as a liquid1 it cannot be pumped easily1 and its excavation causes the sides of the trench to fall in or the bottom to rise4 ,the foundations of nearby structures may be undermined1 causing collapse and serious damage4 ,these conditions may arise even after the backfilling has been placed unless proper care has been taken4 ,the greatest safeguard against such dangers is not only to exercise care in the backfilling to see that it is compactly tamped and placed1 but to leave all sheeting in position after the completion of the work4 ,the ordinary method of combating quicksand and in conducting work in wet trenches is to drive water-tight sheeting #b or #c feet below the bottom of the trench1 and to dewater the sand by pumping4 ,when dry it can be excavated relatively easily4 ,a more primitive but equally successful method is to throw straw1 brickbats1 ashes1 or other filling material into the trench in order to hold the excavation once made1 or this may supplement the attempts at pumping1 or the wet sand may be bailed out in buckets4 ,successful excavation in quicksand requires experience1 resourcefulness4 and a careful watch for unexpected developments4 ,the well points described in ,art4 #adb are used for dewatering quicksand4 #acf4 ,pumping and ,drainage4--,ground water is to be expected in nearly all sewer construction and provision should be made for its care4 ,where geological conditions are well known or where previous excavations have been made and it is known that no ground water exists it may be safe to make no provision for encountering ground water4 ,where ground water is to be expected the amount must remain uncertain within certain rather wide limits until actually encountered4 ,in order to avoid the necessity for pumping1 or working in wet trenches it is sometimes possible to build the sewer from the low end upwards and to drain the trench into the new sewer4 ,the wettest trenches are the most difficult to drain in this manner as the material is usually soft and the water so laden with sediment as to threaten the clogging of the sewer4 ,it is undesirable to run water through the pipes until the cement in the joints has set4 ,this necessitates damming up the trench for a period which may be so long as to flood the trench or delay the progress of the work4 ,if it is not possible to drain the trench through the sewer already constructed the amount of water to be pumped can be reduced by the use of tight sheeting4 ,illustration3 ,,fig4 #ie4 ,improvised ,trench ,pump4 ,pumps for dewatering trenches must be proof against injury by sand1 mud1 and other solids in the water4 ,for this purpose pumps with wide passages and without valves or packed joints are desirable4 ,the types of pumps used are3 simple flap valve pumps improvised on the job1 diaphragm pumps1 jet pumps1 steam vacuum pumps1 centrifugal pumps1 and reciprocating pumps4 ,all are of the simplest of their type and little attention is paid to the economy of operation because of the temporary nature of their service4 #acg4 ,trench ,pump4--,a simple pump which can be improvised on the job is shown in section in ,fig4 #ie4 ,its capacity is about #bj gallons per minute but its operation is backaching work4 ,it is inexpensive1 quickly put together and may be a help in an emergency4 ,it is to be noted that the passages are large and straight1 that there are no packed joints1 and that the velocity of flow is so small that it is not liable to clogging by picking up small objects4 ,illustration3 ,,fig4 #if4--;,diaphragm ,pump ,courtesy1 ,edson ,manufacturing ,co4 #ach4 ,diaphragm ,pump4--,the type of pump shown in ,fig4 #if is the most common in use for draining small quantities of water from excavations4 ,it is known as the diaphragm pump from the large rubber diaphragm on which the operation depends4 ,the pump is made of a short cast-iron cylinder1 divided by the rubber diaphragm or disk to the center of which the handle is connected4 ,the valve is shown at the center of the disk4 ,as the diaphragm is lifted the valve remains closed1 creating a partial vacuum in the suction pipe and at the same time discharging the water which passed through the valve on the previous down stroke4 ,when the valve is lowered the foot valve on the suction pipe closes1 holding the water in place1 and the valve in the pump opens allowing the water to flow out on top of the disk to be discharged on the next up stroke4 ,table #ed shows the capacities of some diaphragm pumps as rated by the manufacturers4 ,the smaller sizes are the more frequently used and are equipped with a #c-;inch suction hose with strainer and foot valve4 ,they are not adapted to suction lifts over #aj to #ab feet4 ,where greater lifts are necessary one pump may discharge into a tub in which the foot valve of a higher pump is submerged4 ,,table #ed ,,capacities ,,of ,,diaphragm ,,pumps ,diameter of ,diameter of ,length of ,stroke ,capacity per ,cylinder1 ,inches ,suction1 ,inches in ,inches ,stroke1 ,gallons #f #c #d #j4di #h #d #f #a4dg #ihf #b #j4ge #abhf #c #a4be ,power driven by #a horse-power #abhf engine #j4ehhg ,illustration3 ,,fig4 #ig4--,mc,gowan ,steam ,jet ,pump4 ,courtesy1 ,the ,john ,h4 ,mc,gowan ,co4 #aci4 ,jet ,pump4--,the simplicity of the parts of the jet pump is shown in ,fig4 #ig4 ,it has a distinct advantage over pumps containing valves and moving parts in that there are no obstructions offered to the passage of solids as well as liquids through the pump4 ,it is not economical in the use of steam1 however4 ,it operates by means of a steam jet entering a pipe at high velocity through a nozzle4 ,this action causes a vacuum which will lift water from #f to #aj feet4 ,the lower the suction lift1 however1 the greater the efficiency of the work4 ,the sizes and capacities of jet pumps as manufactured by the ,j4 ,h4 ,mc,gowan ,co4 are shown in ,table #ee4 ,,table #ee ,,capacities ,,of ,,jet ,,pumps 7,j4 ,h4 ,mc,gowan ,co47 ,size of ,pump ,capacity1 ,approximate and ,suction ,discharge ,steam ,pipe1 ,gallons per ,horse-power ,pipe1 ,inches ,pipe1 ,inches ,inches ,minute ,required #h #b #a #ae #c #a #a #bj #d #a #a #cj #f #b #a #dj #h #b #b #a #ej #aj #c #b #a #fj #ae #d #c #a #he #be #adj4 ,steam ,vacuum ,pumps4--,this type of pump depends on the condensation of steam in a closed chamber to create a vacuum which lifts water into the chamber previously occupied by the steam and from which the water is ejected by the admission of more steam4 ,the best known pumps of this type are the ,pulsometer1 manufactured by the ,pulsometer ,steam ,pump ,co41 the ,emerson1 manufactured by the ,emerson ,pump and ,valve ,co41 and the ,nye ,pump1 manufactured by the ,nye ,steam ,pump and ,machinery ,co4 ,illustration3 ,,fig4 #ih4--,pulsometer ,steam ,vacuum ,pump4 ,a section of a ,pulsometer is shown in ,fig4 #ih4 ,it consists of two bottle-shaped chambers ,a and ,b with their necks communicating at the top and each opening into the outlet chamber ,o through a check valve4 ,steam is admitted at the top and enters chamber ,a or ,b according to the position of the steam valve ,c as shown4 ,this steam valve is a ball which is free to roll either to the right or left and forms a steam-tight joint with whichever seat it rests upon4 ,in normal operation chamber ,a would be filled with water as the steam enters the cylinder4 ,at the same time a check valve at the top opens to admit a small quantity of air which forms a cushion insulating the steam from the water1 reduces the condensation of the steam1 and serves as a cushion for the incoming water on the opposite stroke4 ,the pressure of the steam depresses the surface of the water without agitation and forces the water through the check valve ,f into the discharge chamber ,o4 ,when the water falls to the level of the discharge chamber the even surface is broken up and the intimate contact of the steam and water condenses the former instantaneously4 ,this forms a vacuum in chamber ,a which1 assisted by a slight upward pressure in chamber ,b caused by the incoming water1 immediately pulls the ball ,c over to the other seat and directs the steam into chamber ,b4 ,the vacuum in chamber ,a now draws up a new charge of water through the suction pipe into the chamber4 ,illustration3 ,,fig4 #ii4--;,emerson ,steam ,vacuum ,pump4 ,a section of the ,emerson pump is shown in ,fig4 #ii4 ,the pump consists of two vertical cylinders ,b and ,c4 ,each chamber has a suction valve ,l at the bottom1 opening upward from a common chamber from which the discharge pipe ,u extends4 ,on the top of each chamber is a baffle plate ,g which operates to distribute the steam evenly to the two chambers and to prevent it from agitating the surface of the water in the chambers4 ,a condenser nozzle ,f is connected with the bottom of the opposite chamber by a pipe into which a check valve opens upward4 ,as the pressure in the chamber alternates water will be injected through ,f into the opposite chamber and condense the steam therein1 promptly forming a vacuum4 ,an air valve ,p admits a small quantity of air while the chamber is filling with water1 the air acting as an insulating cushion as in the ,pulsometer4 ,valve ,o1 just above the top connection ,s is used to regulate the amount of steam that enters the pump4 ,the top connection ,s has two ports1 one leading to each chamber4 ,an oscillating valve enclosed in it admits the steam through these ports to the two chambers alternately4 ,this valve is driven by a small three-cylinder engine1 the crank shaft of which extends into the top connection in the center of the bearing on which the valve oscillates4 ,a positive geared connection is made between the valve and the engine and so arranged that the engine will run faster than the valve4 ,the action of these pumps consists of alternately filling and emptying the two chambers4 ,they will continue operation without attention or lubrication so long as the steam is turned on4 ,in view of the simplicity of their operation and make-up1 their ability to handle liquids heavily charged with solids1 and their reasonable steam consumption these pumps are widely used for pumping water in construction work4 ,they have an added advantage that no foundation or setting is required for them as they can be hung by a chain from any available support4 ,these pumps are manufactured in sizes varying from #be to #bejj gallons per minute at a #be-;foot head1 and with a steam consumption of about #aej pounds per horse-power hour4 ,they reduce about #d per cent in capacity for each #aj feet of additional lift4 ,they will operate satisfactorily between heads of #e to #aej feet1 with a suction lift not to exceed #ae feet4 ,lower suction lifts are desirable and the best operation is obtained when the pump is partly submerged4 ,the steam pressure should be balanced against the total head4 ,it varies from #ej to #ge pounds for lifts up to #ej feet1 and increases proportionally for higher lifts4 ,the dryer the steam the lower the necessary boiler pressure4 #ada4 ,centrifugal and ,reciprocating ,pumps4--,the details of these pumps1 their adaptability to various conditions1 and their capacities are given in ,chapter ,,vii4 ,the centrifugal is better adapted to trench pumping as it is not so affected by water containing sand and grit1 but for clear water1 high suction lifts and fairly permanent installations1 reciprocating pumps can be used with satisfaction4 #adb4 ,well ,points4--,in dewatering quicksand a method frequently attended with success is to drive a number of well points into the sand and connect them all to a single pump4 ,figure #ajj shows a well point system used on sewer work in ,indiana4 ,the well points are #c feet apart and are connected to a #b-;inch header which in turn is connected to six ,nye pumps1 each with a capacity of #bjj gallons per minute for a lift of #ej feet4 ,the number and size of well points and pumps to use will depend on conditions as met on the job4 ,on a piece of work in ,atlantic ,city#hh the equipment consisted of two complete outfits each comprising one hundred #a inch by #cf-;inch ,no4 #fj well points1 one hundred #f-;foot lengths of rubber hose1 about #fjj feet of suction main1 one hundred valved ,t connections1 and a #g #h-;inch ,gould ,triplex ,pump with a capacity of #bjj gallons per minute1 belted to a #g horse-power motor4 ,illustration3 ,,fig4 #ajj4--,well ,points ,pumped by ,nye ,steam ,vacuum ,pump4 #adc4 ,rock ,excavation4--,a common definition of rock used in specifications is3 whenever the word ,rock is used as the name of an excavated material it shall mean the ledge material removed or to be removed properly by channeling1 wedging1 barring1 or blasting2 boulders having a volume of #i 7this volume may be varied7 cubic feet or more1 and any excavated masonry4 ,no soft disintegrated rock which can be removed with a pick1 nor loose shale1 nor previously blasted material1 nor material which may have fallen into the trench will be measured or allowed as rock4 ,channeling consists in cutting long narrow channels in the rock to free the sides of large blocks of stone4 ,the block is then loosened by driving in wedges or it is pried loose with bars4 ,it is a method used more frequently in quarrying than in trench excavation where it is not necessary to preserve the stone intact4 ,in blasting1 a hole is drilled in the rock1 and is loaded with an explosive which when fired shatters the rock and loosens it from its position4 ,illustration3 ,,fig4 #aja4--,plug and ,feathers for ,splitting ,rock4 ,in drilling rock by hand the drill is manipulated by one man who holds it and turns it in the hole with one hand while striking it with a hammer weighing about #d pounds held in the other hand1 or one man may hold and turn the drill while one or two others strike it with heavier hammers4 ,in churn drilling a heavy drill is raised and dropped in the hole1 the force of the blow developing from the weight of the falling drill4 ,hand drills are steel bars of a length suitable for the depth of the hole1 with the cutting edge widened and sharpened to an angle as sharp as can be used without breaking4 ,the drill bar is usually about th of an inch smaller than the diameter of the face of the drill4 ,wedges used are called plugs and feathers4 ,they are shown in ,fig4 #aja which shows also the method of their use4 ,the feathers are wedges with one round and one flat face on which the flat faces of the plug slide4 #add4 ,power ,drilling4--,in power drilling the drill is driven by a reciprocating machine which either strikes and turns the drill in the hole1 or lifts and turns it as in churn drilling1 or the drill may be driven by a rotary machine which is revolved by compressed air1 steam1 or electricity4 ,there are many different types of machines suitable for drilling in the different classes of material encountered and for utilizing the various forms of power available4 ,a jack hammer drill is shown in ,fig4 #ajb4 ,in its lightest form the drill weighs about #bj pounds and is capable of drilling -inch holes to a depth of #d feet4 ,heavier machines are available for drilling larger and deeper holes4 ,the same machine can be adapted to the use of steam or compressed air4 ,when in use the point of the drill is placed against the rock and a pressure on the handle opens a valve admitting air or steam4 ,the piston is caused to reciprocate in the cylinder1 striking the head of the drill at each stroke4 ,the drill is revolved in the hole by hand or by a mechanism in the machine4 ,a hollow drill can be used by means of which the operator admits air or steam to the hole1 thus blowing it out and keeping it clean4 ,these machines have the advantage of small size1 portability and simplicity4 ,they can be easily and quickly set up and the drills can be changed rapidly4 ,their undesirable features are the vibration transmitted to the operator and the dust raised in the trench4 ,illustration3 ,,fig4 #ajb4--;,jack ,hammer ,rock ,drill4 ,illustration3 ,,fig4 #ajc4--,tripod ,drill4 ,a type of drill heavier and larger than the jack hammer drill is shown in ,fig4 #ajc4 ,it requires some form of support such as a tripod1 or in tunnel work it can be braced against the roof or sides4 ,some data on steam and air drills are given in ,table #ef4 ,the effect of the length of the transmission pipe1 temperature of the outside air1 pressure at the boiler or compressor1 etc41 will have a marked effect on the amount of steam or air to be delivered to the drill4 ,compressed air is affected more than steam by these outside factors1 but it has an advantage in that as it loses in pressure it increases in volume so that the loss of power is not so marked4 ,gillette states3 ,we may assume that a cubic foot of steam will do practically the same work in a drill as a cubic foot of compressed air at the same pressure1 because neither the steam nor the air acts expansively to any great extent in a drill cylinder1 due to the late cut-off4 ,this being so 444 one pound of steam is equivalent to nearly #cj cubic feet of free air 444 all at the same pressure of #ge pounds per square inch4 ,if a drill consumes at the rate of #ajj cubic feet of free air per minute 444 it would therefore consume #bdj pounds of steam 7at #ge pounds pressure7 per hour4444 ,where not more than three or four drills are to be operated1 probably no power can equal compressed air generated by gasoline4 ,it will require #ab horse-power to compress air for each drill1 hence #a gallons of gasoline will be required per hour per drill while actually drilling4 ,,table #ef ,,data ,,on ,,rock ,,drills 7,from ,h4 ,p4 ,gillette7 ,diameter of cylinder in inches #b #b #b #c #c #c ,length of stroke in inches #e #f #f #f #f #g ,length of drill from end of crank to end of piston #cf #dc #ej #ej #ej #eb ,depth of hole drilled without change of bit1 inches #ae #bj #bd #bd #bd #bd ,diameter of supply inlet4 ,standard pipe1 inches #a #a #a ,approximate strokes per minute with #fj pound pressure at the drill #ejj #dej #cge #cej #cbe #cjj ,depth of vertical hole each machine will drill easily1 feet #f #h #aj #ad #af #bj ,diameter of holes drilled1 inches to #a as desired ,diameter of octagon steel1 inches to to #a to#a to#a to#a to #a #a #a #a #a ,best size of boiler to give plenty of steam at high pressure1 horse-power #f #h #h #i #aj #ab ,best size of supply pipe to carry steam #ajj to #bjj feet1 inches #a #a #a ,weight of drill unmounted1 with wrenches and fittings1 hot boxed1 pounds #abh #aij #bfe #cae #che #cij ,weight of tripod1 without weights1 not boxed1 pounds #hj #afj #afj #afj #baj #bge ,weight of holding down weights1 not boxed1 pounds #abj #bgj #bgj #bhe #ccj #cge ,cubic feet of free air per minute required to run one drill at #ajj pounds #ib #ajd #abf #adf #aed #afj ,for more than one drill1 multiply the value in the above line by the following factors3 ,for #b drills1 #a4h2 #e by #d4a2 #aj by #g4a2 #ae by #i4e2 #bj by #aa4g2 #cj by #ae4h2 #dj by #ba4d2 #gj by #cc4b4 ,since gasoline air compressors are self regulating1 when the drill is not using air very little gasoline is burned by the gasoline engine driving the compressor4 ,a gasoline compressor possesses other very important economic advantages over a small steam-driven plant4 ,first1 there is the saving in wages of firemen and second1 there is the saving in hauling and pumping of water and the hauling of fuel4 ,the cost of gasoline is often less than the cost of coal for operating a small plant4 ,an electric drill#hi operated on the principle of the solenoid does away with motor1 valves1 pipes1 vapor1 freezing1 and other difficulties attendant on the use of steam or air4 ,the rates of drilling in different classes of rock are shown in ,table #eg4 ,frequent changes of drills and relocation of tripods will materially reduce the performance of a drill1 for as much as #de minutes may be lost in making a new set up4 ,in this the jack hammer drills show their advantage as no time is lost in a set up4 ,,table #eg ,,rates ,,of ,,rock ,,drilling ,rates in ,feet per ,ten-hour ,shift4 ,vertical ,holes #aj-bj ,feet ,deep4 7,from ,gillette7 ,hard ,adirondack granite #dh ,maine and ,massachusetts granite #de-ej ,mica-schist of ,new ,york ,city4 ,possible #fj-gj ,mica-schist of ,new ,york ,city4 ,average #dj-ej ,hard1 ,hudson ,river trap rock #dj ,soft red sand stone of ,northern ,new ,jersey #ij ,hard limestone near ,rochester1 ,n4 ,y #gj ,limestone of ,chicago ,drainage ,canal #gj-hj ,douglass1 ,indiana1 syenite4 ,difficult set ups #cf ,canadian granite on ,grand ,trunk ,r4 ,r #cj ,windmill point1 ,ontario limestone3 #c-;inch drills #ge #b-;inch drills #fj #b-;inch drills #cg #ade4 ,steam or ,air for ,power4--,the choice between steam or air is dependent on the conditions of the work4 ,steam is undesirable in tunnels on account of the heat produced4 ,in open cut work it is at a disadvantage because of the loss of power due to radiation from the hose or pipe4 ,the life of the hose is not so long as when air is used1 escaping steam causes clouds of vapor which obscure the work1 and serious burns may occur due to hot water thrown from the exhaust4 ,it is advantageous since leaks may be easily discovered and remedied1 it requires less machinery than air1 and it is sometimes less expensive4 ,with compressed air1 gasoline or electric motors can be used for operating the compressors4 ,,table #eh ,,rock ,,blasting 7,from ,gillette7 ,character of ,powder ,used per ,hole ,distance ,distance ,material ,depth of ,back of ,hole to ,hole1 ,face1 ,hole1 ,feet feet feet ,limestone of ,chicago#dj per cent dynamite ,drainage ,canal #ab #h #h ,sandstone #bjj pounds black powder #bj #ah #ad ,granite #b pounds #fj per cent dynamite #ab #a #d to #e ,pit mining1 ,treadwell1 ,mine1 ,alaska #ab #b #f #adf4 ,depth of ,drill ,hole4--,the depth of the hole is dependent on the character of the work4 ,the deepest holes can be used in open cut work where the shattered rock is to be removed by steam shovel4 ,the face can be made #aj to #ae feet high4 ,the depth of the hole in center cut tunnel facings are from #f to #aj or even #ab feet4 ,in the bench the depth is equal to the height of the bench4 ,in narrow trenches where the rock is to be removed by derrick or thrown into a bucket by hand1 the hole should be sufficiently deep to shatter the rock to a depth of at least #f inches below the finished sewer4 ,frequently shooting to this depth at one shot cannot be done due to the built up condition of the neighborhood or other local factors4 ,the depth of the hole in trench work should not much exceed the distance between holes4 ,deep holes are usually desirable as a matter of economy in saving frequent set ups1 but the holes cannot be made much over #bj feet in depth without increasing the friction on the drill to a prohibitive amount4 #adg4 ,diameter of ,drill ,hole4--,the diameter of the hole should be such as to take the desired size of explosive cartridge4 ,the common sizes of dynamite cartridges are from inch to #b inches in diameter4 ,in drilling1 the diameter of the hole is reduced about one-eighth of an inch at a time as the drill begins to stick4 ,this reduction should be allowed for1 and experience is the best guide for the size of the hole at the start4 ,in general the softer or more faulty or seamy the rock1 the more frequent the necessary reductions in size of bit4#ij ,for hard homogeneous rock the holes can be drilled #aj feet or more without changing the size of the drill bit4 #adh4 ,spacing of ,drill ,holes4--,the spacing of holes in open cut excavation is commonly equal to the depth of the hole4 ,the character of the material being excavated has much to do with the spacing of the holes4 ,the spacing1 diameter and depth of holes used on some jobs is shown in ,table #eh4 ,gillette states3 ,it is obviously impossible to lay down any hard and fast rule for drill holes4 ,in stratified rock that is friable1 and in traps that are full of natural joints and seams1 it is often possible to space the holes a distance apart somewhat greater than their depth1 and still break the rock to comparatively small sizes upon blasting4 ,in tough granite1 gneiss1 syenite1 and in trap where joints are few and far between1 the holes may have to be spaced #c to #h feet apart regardless of their depth for with wider spacing the blocks thrown down will be too large to handle with ordinary appliances4 ,since in shallow excavations the holes can seldom be much further apart than one to one and one-half times their depth we see that the cost of drilling per cubic yard increases very rapidly the shallower the excavation4 ,furthermore the cost of drilling a foot of hole is much increased where frequent shifting of the drill tripod is necessary4 ,the common practice in placing drill holes is to put down holes in pairs1 one hole on each side of the proposed trench2 and if the trench is wide one or more holes are drilled between these two side holes#ia but in narrow trench work1 such as for a #ab-;inch pipe1 one hole in the middle of the trench will usually prove sufficient4 ,the holes are spaced about #c feet apart longitudinally4 ,after the holes have been completed they should be plugged to keep out dirt and water4 ,,sheeting ,,and ,,bracing #adi4 ,purposes and ,types4--,sheeting and bracing are used in trenching to prevent caving of the banks and to prevent or retard the entrance of ground water4 ,the different methods of placing wooden sheeting are called stay bracing1 skeleton sheeting1 poling boards1 box sheeting1 and vertical sheeting4 ,steel sheeting is usually driven to secure water-tightness and if braced the bracing is similar to the form used for vertical wooden sheeting4 #aej4 ,stay ,bracing4--,this consists of boards placed vertically against the sides of the trench and held in position by cross braces which are wedged in place4 ,the purpose of the board against the side of the trench is to prevent the cross brace from sinking into the earth4 ,the boards should be from #a #d inches to #b #f inches and #c to #d feet long4 ,the cross braces should not be less than #b #d inches for the narrowest trenches and larger sizes should be used for wider trenches4 ,the spacing between the cross braces is dependent on the character of the trench and the judgment of the foreman4 ,stay bracing is used as a precautionary measure in relatively shallow trenches with sides of stiff clay or other cohesive material4 ,it should not be used where a tendency towards caving is pronounced4 ,stay bracing is dangerous in trenches where sliding has commenced as it gives a false sense of security4 ,the boards and cross braces are placed in position after the trench has been excavated4 #aea4 ,skeleton ,sheeting4--,this consists of rangers and braces with a piece of vertical sheeting behind each brace4 ,a section of skeleton sheeting is shown in ,fig4 #ajd with the names of the different pieces marked on them4 ,this form of sheeting is used in uncertain soils which apparently require only slight support1 but may show a tendency to cave with but little warning4 ,when the warning is given vertical sheeting can be quickly driven behind the rangers and additional braces placed if necessary4 ,the sizes of pieces1 spacing and method of placing should be the same as for complete vertical sheeting in order that this may be placed if necessary4 #aeb4 ,poling ,boards4--,these are planks placed vertically against the sides of the trench and held in place by rangers and braces4 ,they differ from vertical sheeting in that the poling board is about #c or #d feet long4 ,it is placed after the trench has been excavated2 not driven down with the excavation like vertical sheeting4 ,an arrangement of poling boards is shown in ,fig4 #aje4 ,this type of support is used in material that will stand unsupported for from #c to #d feet in height4 ,its advantages lie in that no driving is necessary1 thus saving the trench from jarring2 no sheeting is sticking above the sides of the trench to interfere with the excavation2 and only short planks are necessary4 ,illustration3 ,,fig4 #ajd4--,skeleton ,sheeting4 ,illustration3 ,,fig4 #aje4--,poling ,boards4 ,showing ,different ,types of ,cross ,bracing4 ,the method of placing poling boards is as follows3 ,excavate the trench as far as the cohesion of the bank will permit4 ,poling boards1 #a inch to #b inch planks1 #f inches or more in width1 are then stood on end at the desired intervals along each side of the trench for the length of one ranger4 ,the poling boards may be held in place by one or two rangers4 ,two are safer than one but may not always be necessary4 ,if one ranger is to be used it is placed at the center of the poling board4 ,after the poling boards are in position the rangers are laid in the trench and the cross braces are cut to fit4 ,if wedges are to be used for tightening the cross braces1 the cross braces are cut about #b inches short4 ,if jacks are to be used the braces are cut short enough to accommodate the jacks when closed1 or adjustable trench braces may be used as shown in ,fig4 #ajf4 ,the use of extension braces saves the labor of fitting wooden braces4 ,with everything in readiness in the trench1 the cross brace is pressed against the ranger which is thus held in place4 ,the wedge or jack is then tightened holding the poling boards and cross brace in position4 ,illustration3 ,,fig4 #ajf4--;,box ,sheeting4 ,showing ,different ,types of ,cross ,bracing4 #aec4 ,box ,sheeting4--,box sheeting is composed of horizontal planks held in position against the sides of the trench by vertical pieces supported by braces extending across the trench4 ,the arrangement of planks and braces for box sheeting is shown in ,fig4 #ajf4 ,this type of sheeting is used in material not sufficiently cohesive to permit the use of poling boards1 and under such conditions that it is inadvisable to use vertical sheeting which protrudes above the sides of the trench while being driven4 ,this sheeting is put in position as the trench is excavated4 ,no more of the excavation than the width of three or four planks need be unsupported at any one time4 ,in placing the sheeting the trench is excavated for a depth of #ab to #bd inches4 ,three or four planks are then placed against the sides of the trench and are caught in position by a vertical brace which is in turn supported by a horizontal cross brace4 ,illustration3 ,,fig4 #ajg4--,vertical ,sheeting4 #aed4 ,vertical ,sheeting4--,this is the most complete and the strongest of the methods for sheeting a trench4 ,it consists of a system of rangers and cross braces so arranged as to support a solid wall of vertical planks against the sides of the trench4 ,an arrangement of complete vertical sheeting is shown in ,fig4 #ajg4 ,this type can be made nearly water-tight by the use of matched boards1 ,wakefield piling1 steel piling1 etc4 ,wakefield piling is made up of three planks of the same width and usually the same thickness4 ,they are nailed together so that the two outside planks protrude beyond the inside one on one side1 and the inside one protrudes beyond the two outside ones on the other side as shown in ,fig4 #ajh4 ,the protruding inside plank forms a tongue which fits into the groove formed by the protruding outside planks of the adjacent pile4 ,illustration3 ,,fig4 #ajh4--,wakefield ,sheet ,piling4 ,illustration3 ,,fig4 #aji4 ,section through ,malleable ,steel ,driving ,cap4 ,in placing vertical sheeting the trench is excavated as far as it is safe below the surface4 ,blocks of the same thickness as the sheeting are then placed against the bank at the middle and at the ends of two rangers on opposite sides of the trench4 ,the ranger rest against blocks1 and are held away from the sides of the trench by them4 ,cross braces are next tightened into position opposite the blocks to hold the rangers in place4 ,after the skeleton sheeting is in place the planks forming the vertical sheeting are put in position with a chisel edge cut on the lower end of the plank1 with the flat side against the bank4 ,the planks should be driven with a maul1 the edge of the plank following closely behind the excavation4 ,in relatively dry work the driving of the plank is facilitated by excavating beneath the edge as it is driven4 ,the upper end of the sheeting should be protected by a malleable steel or iron cap to prevent brooming of the lumber4 ,a cap is shown in ,fig4 #aji4 ,a sledge hammer may be used for driving when the lumber is protected4 ,if the sheeting is to start at the surface and is to be driven by hand1 the first length should not exceed #d feet unless a platform is erected for the driver4 ,succeeding lengths may be longer1 the driver standing on planks supported on the cross braces in the trench4 ,steam hammers and pile drivers are sometimes used for driving sheeting4 ,the framework of the sheeting should be placed with a cross brace for each end of each ranger and a cross brace for the middle of each ranger4 ,if the ends of two rangers rest on the same cross brace an accident displacing one ranger will be passed on to the next and might cause a progressive collapse of a length of trench1 whereas the movement of an independently supported ranger should have no effect on another ranger4 ,the cross braces should have horizontal cleats nailed on top of them as shown in ,fig4 #ajg to prevent the braces from being knocked out of place by falling objects4 ,in driving vertical sheeting a vacant place will be left behind each cross brace corresponding to the original block placed to hold the ranger away from the bank4 ,this is an undesirable feature in the use of vertical sheeting4 ,it is ordinarily remedied by slipping in planks the width of the slot and wedging or nailing them against the convenient cross bracing4 ,in extremely wet trenches1 after all other pieces of vertical sheeting are in place1 the original cleat behind the cross brace can be knocked out and a piece of sheeting slipped into this opening and driven4 ,care must be taken in this event not to drive the rangers down when driving the sheeting4 ,if the bracing begins to drop1 it should be supported by vertical pieces between the rangers and resting on a sill at the bottom of the trench4 ,illustration3 ,,fig4 #aaj4--,steel ,clamp for ,pulling ,wood ,sheeting4 #aee4 ,pulling ,wood ,sheeting4--,wood sheeting is pulled after the completion of the trench by a device shown in ,fig4 #aaj4 ,in wet trenches where the removal of the sheeting would permit a movement of the banks1 resulting in danger to the sewer or other structures1 the sheeting should be left in place in the trench4 ,if sufficient saving can be made the sheeting is cut off in the trench immediately above the danger line1 usually the ground water line4 ,the cutting is done with an axe or by a power driven saw devised for the purpose4 #aef4 ,earth ,pressures4#ib--,the various theories of earth pressure are so conflicting in their conclusions as to be confusing4 ,rankine's theory1 the most frequently used1 assumes that the pressure increases with the depth1 whereas ,meem's theory#ic leads to an opposite conclusion4 ,the discussion following ,meem's article is very illuminating4 ,it indicates that no matter how good the theory1 practical experience together with the use of generous sizes and close spacing are the best guides for bracing trenches and coffer dams4 ,all are not possessed with the desired practical experience and some basis on which to commence work is essential4 ,another factor affecting computations of sizes based on theory is the tendency in practice to use the same size material for rangers and braces on any one job for all except very deep trenches and other special cases4 ,occasionally where there is an independent brace for each end of each ranger1 the brace is made thinner1 but is of the same depth as the ranger4 ,the application of ,rankine's theory of earth pressure to the computation of the sizes of rangers and braces will be shown4 ,his formula for the active earth pressure against a retaining wall is3 ,p wh cos 7cos 7cos#b cos#b 777cos 7cos#b cos#b 77 in which w the weight of earth in pounds per cubic foot2 h depth in feet at point at which pressure is to be determined2 the angle of surcharge1 or the angle which the surface makes with the horizontal2 the angle of repose of the earth4 ,usually taken as #cc-da #a horizontal to #a vertical2 ,p the intensity of pressure in pounds per square foot on a vertical plane in a direction parallel to the surface of the ground4 ,in studying the pressures for trenches the surface of the ground will be assumed as horizontal and the formula reduces to ,p 7#a sin 77#a sin 7wh4 #aeg4 ,design of ,sheeting and ,bracing4--,the trench shown in ,fig4 #aaa is assumed to be constructed in moist sand weighing #aaj pounds per cubic foot1 with an angle of repose of #cj degrees4 ,the material used for sheeting and bracing is yellow pine4 ,the steps taken in the design of the sheeting and bracing for this trench are as follows3 ,illustration3 ,,fig4 #aaa4--;,diagram for the ,design of ,wood ,sheeting4 #a4 ,earth ,pressure4--,substituting the units given in the data1 in ,rankine's formula for earth pressures1 ,p #cf4g;h4 ,because the earth has been freshly cut and will not be kept open long enough to break up the cohesiveness of the banks it is customary to reduce the assumed pressure by dividing by #b1 #c1 or #d1 according to the natural cohesiveness of the material4 ,the cohesiveness of sand is not great1 therefore the pressure will be assumed as one-half of the amount given by the formula1 or p #ah;h4 #b4 ,thickness of ,sheeting and ,spacing of ,rangers4--,it is desirable to use the same thickness of sheeting throughout the depth of the trench4 ,computations should therefore be commenced at the bottom of the trench where the pressures are the greatest and the thickest sheeting will be required4 ,it is necessary to determine by trial a spacing for the rangers and a thickness of sheeting so that the sheeting is stressed to its full working strength4 ,having determined the thickness of the sheeting at the bottom1 the remainder of the computations consists in determining the spacing of the rangers4 ,in the example the lower ranger will be assumed as #c feet from the bottom of the trench and the distance to the next ranger as #d feet4 ,the intensity of pressure at #bb feet #i inches is #dji4e pounds per square foot4 ,the intensity of pressure at #bf feet #i inches is #dha4e pounds per square foot4 ,the distribution of pressures is shown by the diagram on ,fig4 #aaa4 ,the maximum bending moment is slightly below the point midway between the rangers and for a #ab-;inch strip is #aj1ejj inch-pounds4 ,assuming #c inch sheeting the maximum fiber stress is3 f ,mc,i 7#aj1djj #a4e #ab7ab #bg #efh pounds per square inch4 ,the working strength of yellow pine as given in ,table #ei1 is #abjj pounds per square inch4 ,thinner sheeting should therefore be used4 ,,table #ei ,,working ,,unit ,,stresses ,,for ,,timber ,the most used value in the ,building ,codes of ,baltimore1 ,boston1 ,cincinnati1 ,chicago1 ,district of ,columbia1 and ,new ,york ,city ,wood ,shear ,shear ,with ,across ,compression,transverse,grain1,grain1 ,tension1,compression ,across ,bending1 lb4 lb4 lb4 sq4 ,with ,grain1,grain1 lb4 lb4 sq4 sq4 sq4 in4 lb4 sq4 in4 sq4 in4 in4 in4 in4 ,yellow pine #abjj #ajjj #fjj #abjj #gj #ejj ,white pine #hjj #hjj #djj #hjj #dj #bej ,spruce and ,va4 pine4 #hjj #hjj #djj #hjj #ej #cbj ,oak #ajjj #ijj #hjj #ajjj #ajj #fjj ,hemlock #fjj #ejj #ejj #fjj #dj #bge ,chestnut #fjj #ejj #ajjj #hjj #aej ,locust #abjj #ajjj #abjj #ajj #gbj ,as published in ,american ,civil ,engineers ,pocket ,book4 ,assuming #b-;inch sheeting1 the fiber stress is #a1cjj pounds per square inch4 ,this stress is too large4 ,by reducing the ranger spacing slightly the stress can be brought within the required limits4 ,assuming a ranger spacing of #c feet #i inches the depth to the upper ranger is changed to #bc feet and the maximum stress in the #b-;inch sheeting becomes #a1adj pounds per square inch1 a satisfactory result4 ,the results for the computations for the other ranger spacings are shown in ,table #fj4 ,the spacing of the rangers at the sheeting junctions is controlled by convenience and is not computed so long as it is obviously safe4 #c4 ,size of ,rangers4--,the rangers will be assumed as #af feet long with two end cross braces and one intermediate cross brace for each ranger4 ,starting as before at the bottom of the trench4 ,the area of the panel below the ranger and between cross braces is #bd square feet4 ,the average intensity of pressure is #bh4be #ah #ejh4e pounds per square inch4 ,the load transmitted to the ranger is #f1jjj pounds4 ,similarly the load transmitted to the ranger from the panel above is #f1hij pounds4 ,the total distributed load on the ranger is #ab1hij pounds4 ,if b is the vertical dimension of the ranger and d is the horizontal dimension in inches1 then from the beam theory1 using f as #a1bjj pounds per square inch1 bd#b ,m#bjj1 in which ,m is expressed in inch-pounds4 ,the maximum bending moment is 7,wl7#h #ab1bjj #h #abh #aee1jjj inch-pounds ,therefore1 bd#b #gge4 ,an #h #aj inch beam will fulfill the conditions closely4 ,substituting these dimensions in the beam formula f 7,mc7,i 7#aee1jjj #e #ab7h #ajjj #a1afj pounds per square inch tension in outer fiber4 ,the results of the computations for other rangers are shown in ,table #fj4 #d4 ,size of ,cross ,braces4--,the cross braces act as columns4 ,the dimensions of the cross braces are determined by trial in such a manner that the vertical dimension of the brace is equal to the vertical dimension of the ranger and the compressive stress in pounds per square inch is computed from the expression1 ,s ,s#a7a l7#fj;d771#id ,,table #fj ,,computations ,,for ,,sheeting ,,and ,,bracing ,,for ,,trench ,,shown ,,in ,,fig4 #aaa ,material is moist sand weighing #aaj pounds per cubic foot1 with an angle of repose of #cj4 ,lumber is yellow pine1 with working stress as given in ,table #ei4 ,working stresses for columns given as ,s7#a l7#fj;d774 ,sheeting #b inches #ab ,inches ,cross ,braces ,maximum ,fiber ,stress1 ,actual ,allowable ,maximum ,pounds ,intensity1,intensity1 ,bending per ,total ,pounds per,pounds per ,moment1 ,square ,depth and ,load1 ,size1 ,square ,square ,depth ,inch-,pounds ,inch ,description,pounds,inches ,inch ,inch end at #bf #bc-bf4ge #iajj #aadj #i #f1dde #d #h #bjb #ghd int4 at #bf #ai-bc #hhjj #aajj #iab1hij #d #h #djc #ghd end at #bc #ac-ag4e #heej #ajgj #j #f1cic #d #h #bjj #ghd int4 at #bc #h-ac #gafj #ijj #jab1ghe #d #h #djj #ghd end at #ai #j-f #cjjj #cge #j #c1icj #d #h #abc #ghd int4 at #ai #j #g1hfj #d #h #bdj #ghd end at #ag #f #c1eff #d #h #aab #fhd int4 at #ag #f #g1acb #d #h #bbd #fhd end at #ac #j #d1che #d #h #acg #fhd int4 at #ac #j #h1ggj #d #h #bgd #fhd end at #h #j #b1bgj #d #f #if #fhg int4 at #h #j #d1edj #d #f #ahi #ffg end at #f #j #a1cdd #d #f #fj #ehd int4 at #f #j #b1fhg #d #f #aab #ehd end at #j #j #dcb #d #f #ah #ehd int4 at #j #j #hfc #d #f #cf #ehd ,rangers ,area of ,intensity ,panel of ,maximum ,below ,pressure1 ,maximum ,stress this ,pounds ,total ,bending ,pounds ,depth1 per ,load ,moment in per ,square ,square in ,load ,transmitted to ,size1 ,thousand ,square ,depth ,feet ,inch ,poundsthe ,ranger from the ,inches,inch-,pounds ,inch ,panel ,panel ,both ,below ,above ,panels #bf #i #bd #ejh4eab1bjj #fjjj #fhijab1hijh #aj #aee #aafj #bc #j #cj #ddhac1ddj #fede #fbdjab1gheh #aj #aec #aaej #ai #j #cb #cghab1ajj #ehfj #bjjj #g1hfjh #aj #id4c #gjh #ag #f #ab #cbh4e #c1idb #aidb #eaij #g1acbh #aj #he4f #fcf #ac #j #cf #bgd4e #i1hhj #dfij #djhj #h1ggjh #aj #aje #gij #h #j #dj #ahi #g1efj #cdhj #ajfj #d1edjf #h #ed4d #hej #f #j #af #abf #b1jbj #ifj #agbg #b1fhgf #h #cb4b #ejc #j #j #dh #ed #b1eij #hfc #j #hfcf #h #aj4d #afa in which ,s permissible crushing across the grain in a column whose length is greater than #ae diameters2 ,s#a unit working compressive strength of wood2 l length of the column2 d smallest dimension of the column2 l and d are in the same units4 ,the lower intermediate cross brace supports a length of #h feet of the lower ranger on which the load has been found to be #ab1hij pounds4 ,the load on the end cross brace for the same ranger is one-half of this or #f1dde pounds4 ,the length of each brace is #d feet #d inches4 ,from ,table #ei1 ,s#a is #a1jjj pounds per square inch4 ,from the column formula1 ,s is #ghd pounds per square inch4 ,a #d #h inch cross brace is the smallest that is feasible4 ,this is stressed only #ab1hij pounds or #djc pounds per square inch1 which is well within the permissible limits4 ,the results of the other computations for cross braces are shown in ,table #fj4 #aeh4 ,steel ,sheet ,piling4--,this is coming into more general use with the increased cost of lumber and better acquaintance with its superiority over wood under many conditions4 ,although its first cost is higher than that of wood1 the fact that with proper care it can be used almost an indefinite number of times renders it economical to contractors who may have an opportunity to make repeated use of it4 ,the life of good yellow pine sheeting with the best of care may be as much as three or four seasons4 ,with no particular care it will be destroyed at the first using4 ,fig4 #aab shows various sections of steel piling used for trench sheeting4 ,these forms are practically water-tight and aid materially in maintaining dry trenches4 ,the piling can be made water tight by slipping a piece of soft wood between the steel sections when they are being driven1 or by pouring in between the piles some dry material which will swell when wet4 ,the piling is generally driven by a steam hammer and is pulled by attaching a ring through a bolt hole in the pile1 or by grasping the pile with a clutch that tightens its grasp as the pull increases4 ,an inverted steam hammer attached to the pile is sometimes used in pulling it4 ,the impulses of the hammer together with a steady pull on the cable serve to drag out the most stubborn piece of piling4 ,illustration3 ,,fig4 #aab4--,sections of ,lackawanna ,steel ,sheet ,piling4 ,,line ,,and ,,grade #aei4 ,locating the ,trench4--,in order to locate a trench a line of stakes should be driven at about #ej-;foot intervals along the center line of the proposed sewer before excavation is commenced4 ,reference stakes or reference points to this line are located at some fixed offset or easily described point1 or the stakes marking the center line of the trench may be driven at some constant offset distance one side of the trench1 in order to avoid danger of loss or disturbance of the stakes4 ,grade or cut is seldom marked on the line of preliminary stakes1 although the approximate cut may be indicated4 ,for hand excavation the foreman lays out the trench from these stakes4 ,in machine work the operator guides the machine so as to follow the line of the stakes4 #afj4 ,final ,line and ,grade4--,after the excavation of the trench has proceeded to within a foot or two of the final depth1 the grade and line are transferred to markers supported over the center of the trench4 ,the markers are horizontal boards spanning the trench and held in position either by nails driven into stakes at the side of the trench1 by nails driven into the sheeting1 or by weights holding the boards on the ground4 ,two stakes driven in the ground at the side of the trench as shown in ,fig4 #aac are the common method of support4 ,if the banks are too weak to stand under the jarring of the driving of the stakes1 or pavement or other causes prevent their use the horizontal cross piece may be weighted down by bricks or a bank of earth4 ,the cross pieces are located about every #be feet along the trench and at any convenient distance above the surface of the ground4 ,the nearer the ground the stronger the support but the greater the interference with work in the trench4 ,the center line of the sewer is marked on the cross pieces after they are set1 and vertical struts are nailed on them with one edge of the strut straight1 vertical1 and on the center line as shown in ,fig4 #a4 ,the corresponding edge should be used on all struts in order to avoid confusion4 ,the edge is placed in a vertical position by means of a plumb bob or carpenter's level4 ,illustration3 ,,fig4 #aac4--,methods for the ,support of the ,grade ,line4 ,the cut to the invert of the sewer is recorded to an even number of feet where practicable by driving a nail in the upright strut so that the top edge of the nail is at the desired elevation above the sewer1 or the upright is nailed with its top at the proper number of feet above the sewer invert4 ,the cut is marked on the upright in feet1 tenths1 and hundredths from the recorded point to the elevation of the invert4 ,the inspector should watch these grade markers with care by sighting back along them to see that they are in line and have not moved4 ,in quicksand or caving material the marks may move during the setting of the pipes and the levelman should be on the job constantly4 ,when excavation is being done by machine the depth of the excavation is controlled by the operator who maintains a sighting rod on the machine in line with the grade marks on the uprights4 ,illustration3 ,,fig4 #aad4--;,diagram ,showing the ,use of the ,grade ,rod for ,fixing the ,elevation of a ,sewer4 #afa4 ,transferring ,grade and ,line to the ,pipe4--,in transferring grade and line to the sewer a light strong string is stretched tightly from nail to nail on the uprights marking the line and grade4 ,a rod with a right angle projection at the lower end1 as shown in ,fig4 #aad1 is marked with chalk or a notch at such a distance from the end that when the mark is held on the grade cord the lower portion of the rod which projects into the pipe will rest on the invert4 ,the pipe is placed in line by hanging a plumb bob so that the plumb bob string touches the grade and center line cord4 ,these marks are taken only as frequently as may be necessary to keep the sewer in line4 ,an experienced workman can maintain the line by eye for considerable distances4 ,measurements should never be taken to the top of the pipe in order to determine position and grade as the variations in the diameter of the pipe may cause appreciable errors4 ,the position and elevation of the forms for brick1 concrete1 and unit block sewers are located by reference to the grade line1 or they may be placed under the immediate direction of the survey party1 or by specially located stakes4 ,for large sewers requiring deep and wide excavation the grade and line stakes are driven in the bottom of the trench about a foot above the finished grade4 ,this requires the constant presence of an engineer who is usually available on work of such magnitude4 #afb4 ,line and ,grade in ,tunnel4--,in tunnels1 line and grade are given by nails driven in the roof1 the progress of excavation or the shield being followed by eye and the forms set by direct measurement to the nails4 ,,tunneling #afc4 ,depth4--,the depth at which it becomes economical to tunnel depends mainly upon the character of the material to be excavated and on the surface conditions4 ,in soft dry material with unobstructed working space at the surface1 open cut may be desirable to depths as great as #ce or #dj feet4 ,tunnels are cut in rock at depths of #ae feet or less4 ,in some very wet and running quicksand encountered in the construction of sewers for the ,sanitary ,district of ,chicago it was found economical to tunnel at depths of #bj feet and less4 ,crowded conditions on the surface1 expensive pavements1 or extensive underground structures near the surface may make it advantageous to tunnel at shallower depths than would otherwise be economical4 ,winter is the best season for tunneling as the workmen are protected from the elements and labor is more plentiful4 #afd4 ,shafts4--,in sinking a shaft in soft material1 the excavation is usually done by hand1 the material being thrown into a bucket which is hoisted to the surface and dumped4 ,the size of the shaft is independent of the size of the sewer and depends principally on the machinery which it is necessary to lower into the tunnel4 ,ordinarily a shaft #f feet in the clear is satisfactory4 ,a method of timbering a shaft is shown in ,fig4 #aae4 ,because of the timbering the shaft must be started sufficiently large at the top to finish with the desired dimensions at the bottom4 ,this excess size is sometimes obviated by driving the sheeting at an angle to maintain the same size of shaft from top to bottom4 ,in timbering a shaft as shown in ,fig4 #aae the upper frame is staked securely in position at the surface of the ground4 ,this frame is composed of timbers fastened together in the form of a square with the ends of the timbers extending about #ab inches on all sides4 ,the protruding ends are used to hold the frame in position4 ,excavation is begun inside the frame1 and sheeting is driven around the outside of it as excavation progresses4 ,only two or three men can work advantageously at one time in these small shafts4 ,the second frame is made up of the same size timbers1 but all are cut off flush with the outside of the square4 ,the outside dimensions of this frame are such as to allow sheeting to be slipped in between it and the sheeting already driven4 ,the frame is lowered into position and supported from the upper frame by vertical struts nailed to it4 ,the lower end of the sheeting already driven is held out from the lower frame by blocks of the thickness of the next length of sheeting4 ,these blocks are removed as the next length of sheeting is placed and driven4 ,the driving of the sheeting is facilitated by excavating beneath it as it descends4 ,illustration3 ,,fig4 #aae4--,section of ,shaft ,timbering4 ,abbot1 ,journal ,western ,society of ,engineers1 ,vol4 #bb4 ,the sizes of sheeting and timbering should be computed on the same basis as that for trench sheeting except that for depths greater than #cj to #ce feet ,rankine's ,theory is not applicable and judgment must be relied on for computing the sizes for deep shafts4 ,in stiff dry material the pressures will change very little as the depth increases4 ,sheeting is needed in shaft excavation in rock only to protect the workmen from falling fragments1 but in sand1 particularly in quicksand and in wet ground1 the pressures increase directly with the depth and the sheeting should be computed accordingly4 ,care must be taken to prevent the formation of cavities behind the sheeting1 to fill them if formed1 and to see that all pieces of the sheeting and bracing have a firm bearing4 ,it is difficult to prevent the collapse of the shaft once the movement of earth against the sheeting has commenced4 ,shafts are also sunk in soft ground by constructing a concrete or metal shell resting on a cutting shoe on the surface4 ,the material inside is dug out and the shell sinks of its own or added weight4 ,the first section of the shell may be from #e to #aj feet long4 ,as this section sinks other sections are added4 ,this is called the caisson method4 ,it is advantageous in wet ground and when the shafts are to be left as a permanent manhole4 ,if a permanent shaft is to be left in an excavation being braced with wood1 the permanent lining should follow within #bj to #cj feet of the shaft excavation4 ,this is done to avoid the difficulty of maintaining a great length of temporary wood shaft with the danger of collapse1 or of blocks or other objects falling on the workers below4 ,the distance between shafts is controlled by the depth and size of the tunnel1 surface conditions1 and the character of the material being tunneled4 ,except where surface conditions are crowded the shallower the cover to the tunnel the more frequent the shafts4 ,the advantage of frequent shafts lies in the possibility of removing excavated material from the tunnel promptly1 and in making ventilation of the tunnel easier4 ,the saving made by the construction of numerous shafts must be balanced against the extra cost of the shafts4 ,for the shallowest tunnels the shafts are seldom placed closer than every #ejj feet4 #afe4 ,timbering4--,after the shaft has been excavated to the proper grade the tunnel is struck out either by cutting through the wooden sheeting or by removing portions of the caisson lining4 ,practically all tunnels except those in solid rock must be framed to some extent4 ,some of the types of frames used in tunnel construction are shown in ,fig4 #aaf4 ,different combinations of these may be used in different classes of materials4 ,in solid rock which remains firm on exposure no timbering is necessary4 ,where the roof only need be supported and the sides are strong enough to be used for support1 a timber 8hitch0 or frame supported on the sides of the tunnel may be used4 ,this is suitable for loose rock roofs with solid rock sides4 ,timbering such as is shown in the lower left hand corner of ,fig4 #aaf becomes necessary in extremely soft1 wet1 or swelling material1 where the bottom and sides as well as the roof tend to push in4 ,the remaining frame in ,fig4 #aaf shows a form frequently used and lying between the two extremes indicated4 ,in wet tunnels a channel may be cut in the bottom below the sill for drainage purposes as shown in this form4 ,the needle beam method of timbering is also shown in ,fig4 #aaf4 ,this method of timbering is used mainly near the heading because of the speed and ease with which it can be installed1 but it is undesirable because of the space occupied4 ,the distance between frames is dependent on the size of the tunnel and the character of the material4 ,it is seldom greater than #f feet and the frames are sometimes placed touching each other4 ,the size of the timbering is a matter of experience and is generally determined by the judgment of the responsible person in charge of the construction as the result of observation during the progress of the work4 ,the sheeting between frames is called poling boards1 or spiling or lagging according as it is sharpened and driven ahead of the excavation or placed after the excavation has progressed4 ,the horizontal strips placed between the frames to keep them apart are called wales4 ,illustration3 ,,fig4 #aaf4--,types of ,frames and ,timbering for ,tunnels4 ,in cutting out from the shaft in soft materials requiring support1 where the width of the tunnel is the same or smaller than that of the shaft1 a frame with a maximum width four thicknesses of sheeting less than the width of the tunnel is set up against the lining of the shaft4 ,the vertical side pieces of the tunnel frame rest on the bottom frame of the shaft as a sill and are securely wedged into position4 ,as the lining of the shaft at the top is cut away the top poling boards of the tunnel are slipped in between the cap of the first tunnel frame and the shaft frame immediately above it4 ,the poling boards are driven with an upward pitch so that there may be room to slip the second length of boards between the next tunnel frame and the first length of boards4 ,the placing of the side sheeting follows in a similar manner4 ,excavation is then started and the poling boards driven to keep pace with it4 ,the next frame is placed in position and the previous sheeting or boards wedged out a sufficient distance to allow the advance lining to be slipped in when the wedges are removed4 ,waling pieces are nailed firmly between the frames to hold them in position4 ,the various phases in the driving of a #ab-;foot sewer tunnel in ,seattle are shown in ,fig4 #aag4 ,illustration3 ,,fig4 #aag4--,stages of ,sewer ,tunneling4 ,eng4 ,record1 ,vol4 #fi1 #aiad1 p4 #aie4 ,in soft or running material it may be necessary to protect the face of the tunnel by horizontal boards1 called breast boards1 wedged back to the last frame placed4 ,the excavation is performed by removing one board at a time1 excavating behind it and then replacing it in the advance position4 ,the advance is made from the top downwards4 ,this represents the method pursued in the most difficult material where wooden sheeting without a shield is used4 ,the timbering during the advance may be modified in any manner that the character of the material will permit4 ,the timbering may lag behind the excavation a distance of two or more frames1 or it may be omitted altogether4 ,heavier timbering may be necessary in soft1 slipping or shattered rock4 ,illustration3 ,,fig4 #aah4--,shield for ,driving ,milwaukee ,sewer ,tunnel4 ,eng4 ,news-,record1 ,vol4 #hj1 #aiah1 p4 #ffi4 #aff4 ,shields4--,shields are used in tunneling in soft wet material and are particularly suitable for work under air pressure4 ,they are used in rock tunnels where water is anticipated or air pressure is used4 ,the shields often save the expense and difficulty of timbering as the masonry of the sewer follows closely behind the shield4 ,fig4 #aah shows the arrangement for a shield for tunneling in soft material in the construction of the ,milwaukee sewers4 ,the shield has an exterior diameter of #i feet #d inches and an overall length of #i feet #h inches4 ,the cutting edge section is #bj inches long4 ,the shell is made of one inch plate to the back of the jack chambers and one-half inch plate in the tail4 ,the shield is driven by ten #fj-ton hydraulic jacks4 ,the jacks are shown in position in the figure4 ,these jacks rest against the finished tunnel lining and serve to consolidate it at the same time that they push the shield into the material to be excavated4 ,the face of the tunnel is cut with a pick and shovel while the jacks are removed one at a time and a new ring of lining is put in place4 ,the lining may be temporary timbering to receive the thrust of the jacks1 but it is usually desirable that the permanent lining follow immediately behind the shield4 ,since the shield is larger than the outside of the lining the space left by its passage should be grouted immediately after it has passed4 #afg4 ,tunnel ,machines4--,tunnel machines have been used successfully on sewer tunnels in soft materials1 but not in rock4#ie ,the machines are of different types1 but in general consist of a revolving cutting head1 equipped with knives1 and driven by an electric motor4 ,the bearing on which the shaft for the cutting head rests is supported against the sides of the tunnel4 ,the muck is carried away by means of a conveyor and dumped into muck cars without rehandling4 ,rapid progress can be made with these machines in suitable conditions4 ,illustration3 ,,fig4 #aai4--,method of ,drilling and ,loading ,rock ,tunnel ,face4 ,courtesy1 ,aetna ,power ,co4 #afh4 ,rock ,tunnels4--,tunnels in rock are advanced by drilling into the face as shown in diagrammatic form in ,fig4 #aai4 ,the holes near the center are driven in at an angle towards the center and to depths from #f to #ae feet4 ,the harder the rock the greater the angle with the tunnel4 ,this is called the center cut4 ,other holes are driven near the outer edge of the tunnel and parallel to its axis4 ,when fired1 the wedge of rock between the center cut holes is thrown back into the tunnel and a delayed explosion then throws the sides into the hole thus made4 ,a final delay thrusting shot throws the muck so formed away from the face of the tunnel4 ,for tunnels up to #f or #h feet in height the entire bore is cut out in this fashion4 ,for larger tunnels1 the upper portion called the heading1 is taken out in this way1 and the remainder1 called the bench1 is taken out by drilling and blowing holes normal to the axis of the tunnel4 ,the amount of powder necessary in the bench holes is much less than that required in the heading4 #afi4 ,ventilation4--,no tunnel more than #ej feet long should be built without ventilation4 ,a fair amount of air for ordinary conditions is #ge cubic feet of free air per minute per person in the tunnel1 and double this amount for each animal4 ,where explosive gases are met1 or under conditions where the tunnel is hot1 five or six times as much air may be needed in order to cool the tunnel or to dilute the gases4 ,in order that the air may be fresh and cool at the face of the tunnel where work is going on it should be conducted to the tunnel face in a pipe and blown out into the tunnel4 ,immediately following a blast at the face the current should be reversed so as to draw the poisonous gases out of the tunnel through the duct4 ,the high pressure air line leading to the drills should be opened at the same time to create a current towards the face in order to accelerate the clearing of the air at the heading4 ,the capacity of the air machines should be sufficient to exhaust four times the volume of the gases created by the explosion1 in #ae minutes4 ,this will ordinarily call for a capacity of about #d1jjj cubic feet of free air per minute4 ,if the same blower is to be used for exhausting the gases as for ventilation while work is going on1 it should have a high overload capacity to care for this situation4 ,the air line should be arranged to allow for reversal of flow4 ,the diameter of the air pipe should be determined by a study of the saving of the cost and operation of the air equipment compared to the increased cost of a larger pipe line4 ,other factors affecting the size of the pipe line to be used are3 the available space in the tunnel1 the temporary character of the installation1 the use of the exhaust from high-pressure air machines for the purpose of ventilation1 etc4 ,cast-iron1 spiral-riveted galvanized sheet iron1 and canvas pipes have been used for conducting low-pressure ventilating air4 ,ventilation in tunnels working under air pressure is supplied from the compressors1 and the air is delivered near the face of the heading1 except that being used in the locks4 ,in tunnels using air drills1 the air for the drills is conducted through a separate pipe as it is not economical to compress the ventilating air to the pressure necessary to operate the drills4 #agj4 ,compressed ,air4--,compressed air is used in tunnel work to prevent the entrance of water into the tunnel and to keep the work dry4 ,the pressure of air used is closely that of the pressure of the ground water but in a large tunnel or a tunnel with a weak roof the pressure may be somewhat lower on account of the danger of blowing through the roof4 ,it is evident that the water pressure cannot be balanced at the top and the bottom of the tunnel4 ,to balance it at the bottom makes a blow out near the top more probable4 ,to balance the pressure at the top may leave the bottom wet4 ,judgment and care must be exercised during construction and if the pressure is balanced at or near the bottom the roof must be carefully guarded by grouting and puddling with clay1 or the surface1 particularly if under water1 may be covered with a clay bank4 ,if the cavities in the tunnel lining are large1 sawdust can be mixed with the grout to advantage1 the mixture being pumped through holes in the roof by hand or power operated force pumps4 8,blows0 must be carefully guarded against as they endanger the lives of the workmen and threaten the loss of the tunnel4 ,the pressure and volume of air supplied for some large subaqueous tunnels is shown in ,table #fa4 ,labor under compressed air is arduous and dangerous with the best of safeguards4#if ,pressure more than about #dc pounds per square inch cannot be used and at this high pressure men cannot work more than four hours at a time4 ,little or no distress is noted at pressures less than #ae pounds4 ,,table #fa ,,volume ,,and ,,pressure ,,of ,,compressed ,,air ,,in ,,tunnels 7,american ,civil ,engineers ,pocket ,book7 ,tunnel ,maximum ,average ,conditions and ,cubic ,maximum ,air ,air ,feet of ,free ,air per ,distance ,pressure1,pressure1 ,minute ,high ,pounds ,pounds ,water to,minimum per per ,invert1 ,cover ,square ,square ,feet in ,feet ,inch ,inch ,city and ,in water bearing-sand4 ,south #affj cubic feet per ,london minute per face4 ,when grouted #ajjj to #acjj cubic feet per minute #cd #db #ae per face ,blackwall #aj1jjj cubic feet per minute per face in open ballast for some #hj #e #cg #ce time ,baker ,st4 ,in gravel1 #ccjj cubic and feet of air per ,waterloo minute per face4 ,parallel tunnel #afej cubic feet per min4 #gj #ah #ce #bh per face ,greenwich ,average #hc4e per man per minute4 ,never #gj #cj #bh #bj less than #ff4g ,battery1 ,in sand4 ,two working ,east faces4 ,maximum #cb1jjj ,river4 ,n4 ,y4 #id #ab #db #bf ,east ,maximum for one face ,river1 #be1jjj cubic feet per ,n4 ,y41 minute for #bd hours4 ,penn4 ,capacity of plant for ,r4,r4 #h faces1 #hj1djj cubic #ic #h #db #bg feet per minute ,north ,maximum in gravel ,river1 #aj1jjj cubic feet per ,n4 ,y41 man per hour4 ,penn4 ,generally ranged ,r4,r4 #ih #bj #cg #bf between #aejj and #ejjj ,entrance and exit to the tunnel are gained through air locks4 ,these are sheet iron cylinders concreted into the lining of the tunnel or shaft4 ,air-tight iron doors are provided at both ends1 which open inwards towards the tunnel4 ,on entering the lock from the outside the door to the tunnel is found tightly closed4 ,the outside door is then closed by hand1 the air valve is opened and air is admitted to the lock until the pressure on the lock side of the tunnel door equalizes that on the tunnel side and the tunnel door is swung open by hand4 ,when the lock is open to the tunnel the pressure in the tunnel keeps the outside door closed4 ,in order to leave the tunnel the process is reversed4 ,materials are passed through the lock by the lock tender or tenders who pass through the lock with the material if the pressure is low1 or who manipulate the air outside of the lock if the pressure is high4 ,if pressures of #cj to #dj pounds are being used1 two or even three locks may be necessary4 ,,explosives ,,and ,,blasting#ig #aga4 ,requirements4--,the desirable features in an explosive to be used in trenching and tunneling in rock are3 7#a7 stability in make up so as not to deteriorate in strength or to become dangerous during storage1 7#b7 imperviousness to ordinary variations in temperature and moisture1 7#c7 insensibility to ordinary shocks received in transportation and handling1 7#d7 not too difficult of detonation1 7#e7 convenient form for transportation and loading and for making up charges of different weights1 7#f7 the non-formation of poisonous gases when fired1 7#g7 imperviousness to water and usefulness in wet holes1 7#h7 power without bulk1 etc4 #agb4 ,types of ,explosives4--,explosives which fill some or all these requirements can be divided into two classes1 deflagrating and detonating4 ,a deflagration is an explosion transmitted progressively from grain to grain4 ,a detonation is a sudden disruption caused by synchronous vibrations of a wave-like character4 ,the deflagrating explosives are represented by gun-powders and contractors' powders4 ,they must be carefully tamped in the hole to develop their full power and they must be ignited by a fuse or flame4 ,they are valueless in water or moist holes4 ,these powders are used mainly for loosening frozen earth1 soft sandstone1 cemented gravels and similar materials where a thrusting action rather than a disruption is desired4 ,the detonating explosives are most commonly represented by the dynamites4 ,these are exploded by a shock usually caused by another explosive which has been ignited by a fuse or electric spark1 and which is known as the 8detonator40 ,detonating explosives are more powerful than deflagrating explosives and are used in all but the softest materials4 ,gunpowder4--,this is a mechanical mixture of sulphur1 charcoal1 and saltpeter generally in the proportions of #aj parts sulphur1 #ae parts charcoal1 and #ge parts saltpeter 7sodium nitrate74 ,it weighs about #fb pounds per cubic foot and produces about #bhj times its own volume in gas at a pressure of #d4fh tons per square inch at a temperature of #cb degrees ,f41 which amounts to a pressure of approximately #ch tons per square inch at the temperature of explosion of #d1jjj degrees ,f4 ,blasting ,powder4--,this is a mixture of #ai parts sulphur1 #ae parts charcoal1 and #ff parts saltpeter4 ,these powders are made in different size angular polished grains1 from the size of a pin head to sizes just passing a to inch hole4 ,the larger the grains the slower the action of the powder4 ,nitro-,substitution ,compounds4--,these compounds are formed by the action of nitric acid on hydrocarbons4 ,triton1 ,t4,n4,t41 or trinitrotoluene1 made famous during the war1 is an example of these compounds4 ,it is made by the successive nitration of toluene1 a coal tar derivative4 ,it melts at #hj degrees ,c41 is very stable1 and is of great explosive strength4 ,it is manufactured in a convenient form1 being compressed into blocks about #b inches square by about #d inches long with a specific gravity of about #a4e4 ,the blocks are usually copper plated to protect the ,t4,n4,t4 from moisture4 ,the more dense it is the less its sensitiveness4 ,it is also put up in crystalline form in cartridges like dynamite1 in which condition it is practically equal to #dj per cent dynamite4 ,it can be cut with a knife1 pounded with a hammer1 and will burn freely and slowly in small quantities in the open air without exploding4 ,it is suitable for all but the hardest rocks4 ,it creates poisonous gases on detonation which are quickly dissipated in the open air but which render it unsuitable for use in tunnel work4 ,nitro-glycerine4--,this is formed by the action of nitric and sulphuric acids on animal compounds such as gelatine or glycerine4 ,nitro-glycerine is a yellowish1 oily1 highly unstable explosive liquid with a specific gravity of about #a4f4 ,it will burn quietly when ignited in the open air4 ,it will freeze at #da degrees ,f41 and will explode at #chh degrees ,f41 or on concussion at a lower temperature4 ,it develops about #a1ejj times its volume in gas1 which due to the heat of combustion is increased to about #aj1jjj times its volume4 ,it is a very dangerous explosive to handle1 and is unsuitable for use in the liquid form4 ,blasting ,gelatine4--,this is made by soaking guncotton in nitro-glycerine4 ,gelatine dynamite is a combination of blasting gelatine and an absorbent4 ,forcite is a gelatine dynamite in which the blasting gelatine1 forming #ej per cent of the compound1 contains #ij per cent nitro-glycerine and #b per cent guncotton2 and the absorbent1 forming the other #ej per cent of the compound1 contains #gf per cent of sodium nitrate1 #c per cent sulphur1 #bj per cent of wood tar1 and #a per cent of wood pulp4 ,blasting gelatine is packed in a jelly-like mass in metal lined wooden boxes4 ,it is less sensitive than straight dynamite and is one of the most powerful explosives known4 ,it can be made up to equal #ajj per cent dynamite4 ,it is suitable for use in the hardest rocks and for subaqueous work as it is not affected by moisture4 ,it is suitable for use in tunnels as the amount of carbon monoxide1 peroxide of nitrogen1 hydrogen sulphide and other dangerous gases is comparatively low when fully detonated4 ,gelatine dynamite#ih is sold as #cj per cent to #gj per cent dynamite1 the actual percentage of nitro-glycerine being less than the nominal quantity given4 ,dynamite4--,the dynamites are made by soaking nitro-glycerine in some absorbent4 ,if the absorbent is some neutral substance such as infusorial earth the combination is known as a true dynamite4 ,the false or active dynamites are those in which the absorbent is also an explosive compound4 ,the false dynamites form the best known contractors' explosives4 ,among the materials mixed with the nitro-glycerine are3 magnesium carbonate1 sulphur1 wood meal1 wood pulp1 wood fiber1 wood tar1 nut galls1 kieselguhr1 sawdust1 resin1 pitch1 sugar1 charcoal1 and guncotton4 ,the strength of dynamites is noted by the per cent of nitro-glycerine and nitro substitutes contained4 ,dualin and ,hercules powder both contain #dj per cent nitro-glycerine4 ,dualin contains #cj per cent sawdust and #cj per cent potassium nitrate1 but the ,hercules powder1 which is stronger1 contains #af per cent sugar1 #c per cent potassium chlorate1 #ca per cent potassium nitrate1 and #aj per cent magnesium carbonate4 ,dynamite is the most common explosive used on construction work4 ,it is supplied in cylindrical sticks wrapped in paper1 the diameter of the sticks varying between and #b inches4 ,they are about #h inches long4 ,forty per cent dynamite is the common strength found on the market4 ,it is suitable for ordinary work in all but very hard rocks or very soft material4 ,direct contact with water separates the nitro-glycerine from the base and is dangerous when the explosive is used in wet places unless it is fired immediately after the hole is loaded4 ,it freezes at about #db degrees ,f41 or at even higher temperatures and in the frozen state it is highly dangerous1 requiring powerful detonators for firing1 but exploding spontaneously from a slight jar1 or the breaking of the stick4 ,special low-freezing dynamites are made that will not freeze above #ce degrees ,f4 ,ammonia ,compounds4--,ammonia dynamite is a combination of nitro-glycerine1 ammonium nitrate and such other ingredients as sodium nitrate1 calcium carbonate and combustible material4 ,this form of explosive is advantageous for underground work because1 like gelatine dynamite1 its explosion does not create large quantities of poisonous gases4 ,it has a low freezing point and is relatively low in cost4 ,it is seriously affected by moisture1 however1 and can not be used in wet places4 ,ammonium nitrate explosives which do not contain nitro-glycerine include #gj per cent to #ie per cent ammonium nitrate and some combustible material4 ,ammonal is a special type of this class formed by a mixture of ammonium nitrate1 aluminum1 and triton4 ,all of these explosives are deliquescent1 insensitive to shock1 and are cheaper than the dynamites4 #agc4 ,permissible ,explosives4--,as specified by the ,united ,states ,bureau of ,mines explosives whose rapidity1 detonation1 and temperature of explosion will not ignite explosive mixtures of pit gases and air are known as permissible explosives4 ,they include nitrate explosives1 ammonia dynamite1 and others4 ,gunpowder1 triton1 picric acid1 blasting gelatine1 dynamite1 guncotton1 etc41 are not classed as permissible explosives4 #agd4 ,strength4--,the relative weights for equal strength of various explosives are given in ,table #fb4 ,,table #fb ,,relative ,,weights ,,of ,,explosives ,,with ,,the ,,same ,,strength ,,as ,a ,,unit ,,weight ,,of #dj ,,per ,,cent ,,dynamite ,explosive ,relative ,weight ,picric acid #j4hf ,gun powder 7well tamped7 #c4aj ,straight dynamite1 #ae #a4de ,straight dynamite1 #bj #a4cc ,straight dynamite1 #be #a4bh ,straight dynamite1 #cj #a4ah ,straight dynamite1 #ce #a4jg ,straight dynamite1 #dj #a4jj ,straight dynamite1 #de #j4ic ,straight dynamite1 #ej #j4hf ,straight dynamite1 #ee #j4hc ,straight dynamite1 #fj #j4gh ,low-freezing dynamites are the same as straight dynamites ,smokeless powder1 well tamped #j4gd ,triton #j4hf ,blasting gelatine #j4dc ,gelatine dynamite1 #cj #a4bh ,gelatine dynamite1 #ce #a4ba ,gelatine dynamite1 #dj #a4ad ,gelatine dynamite1 #ej #a4jd ,gelatine dynamite1 #ee #j4ig ,gelatine dynamite1 #fj #j4ij ,gelatine dynamite1 #gj #j4hc ,ammonia dynamites are the same as gelatine dynamites4 ,chlorates 7sprengle7 ,rack-a-rock #a4cc ,guncotton #j4gb #age4 ,fuses and ,detonators4--,the explosion of gunpowder and other deflagrating explosives is caused by the direct application of a flame led to the charge by a powder fuse1 or they may be fired by a blasting cap which is itself exploded by the heat from a fuse or an electric spark4 ,the powder fuse is a cord made up of a train of powder securely wrapped in a number of thicknesses of woven cotton or linen threads and usually made waterproof4 ,ordinary fuse burns at about #b feet per minute but there may be wide variations from this rate due to the quality of the fuse1 moisture1 temperature1 or pressure4 ,moisture tends to retard the rate1 pressure to increase it4 ,instantaneous fuse will burn at about #abj feet per second4 ,it is distinguished from the ordinary safety fuse both by eye and touch due to the rough red braid with which it is covered4 ,it is used in firing a number of charges simultaneously4 ,powder fuses are lighted by the application of a flame or smoldering torch to the freshly cut or opened end exposing the powder grains4 ,cordeau ,bickford is lead tubing filled with triton1 in which the flame travels at about #ag1jjj feet per second4 ,this is also used for igniting charges simultaneously4 ,the detonation of an explosive is caused by the shock or heat of the explosion of a more sensitive substance which has been exploded by a powder fuse or electric spark4 ,the common method of detonating explosive charges is by the firing of a blasting cap4 ,these caps are copper cylinders1 closed at one end1 about #a inches long and to of an inch in diameter1 or larger4 ,they contain a mixture of about #he per cent fulminate of mercury and #ae per cent potassium chlorate held in place by a wad of shellac1 collodion1 or paper4 ,the strength of detonators is based on the weight of fulminate of mercury and is designated as shown in ,table #fc4 ,,table #fc ,,strength ,,of ,,blasting ,,caps ,blasting ,cap1 ,commercial ,grade ,grains ,fulminate of ,mercury #c,x or ,triple #h4c #d,x or ,quadruple #aj4j #e,x or ,quintuple #ab4c #f,x or ,sextuple #ae4d #g,x or ,number #bj #bc4a #h,x or ,number #cj #cj4i ,single strength #ab4c ,double strength #ae4d ,triple strength #bc4a ,quadruple strength #cj4i ,the force of the explosion is markedly affected by the strength of the caps1 the effect being greater for low-grade powders4 ,for #dj per cent dynamite the explosion caused by a #e,x cap is #ae per cent stronger than that caused by a #c,x cap4 ,for #fj per cent dynamite the difference is only #f per cent4 ,the deterioration of the caps will reduce the strength of an explosion noticeably4 ,with straight dynamite1 #c,x caps are generally used1 but with gelatine dynamite #f,x or heavier caps must be used4 ,caps may be tested by exploding them in a confined space and noting the report and the effect on the shell4 ,a full strength cap will tear the shell into minute pieces1 while a deteriorated cap will merely tear it into three or four large pieces4 ,an ordinary blasting cap is shown in ,fig4 #abj together with other equipment for blasting4 ,firing by electricity is generally safer and more satisfactory than by the use of ordinary caps and powder fuses4 ,the explosion is more certain and its exact time is under the control of the operator4 ,fig4 #aba shows a section through an electric blasting cap or detonator1 commonly called an electric fuse4 ,delayed action electric detonators are made by inserting a slow-burning substance between the platinum bridge and the detonating substance4 ,the time of delay is controlled by the depth of the slow-burning substance4 ,delayed action detonators are useful in tunnel work where it is desired to explode the charge in three or four stages in order that the debris from one charge may be out of the way of the following1 and that the forces of the explosions may not serve to nullify each other4 ,illustration3 ,,fig4 #abj4--;,blasting ,supplies4 ,courtesy1 ,aetna ,powder ,co4 #agf4 ,care in ,handling4--,some of the don'ts in the handling of explosives recommended by the ,u4 ,s4 ,army ,engineer ,field ,manual are3 in the use of nitro-glycerine explosives of all kinds-- 7a7 ,don't store detonators with explosives4 ,detonators should be kept by themselves4 7b7 ,don't open packages of explosives in a store house4 7c7 ,don't open packages of explosives with a nail puller1 pick or chisel4 ,packages should be opened with a hard wood wedge and mallet1 outside of the magazine and at some distance from it4 7d7 ,don't store explosives in a hot or damp place4 ,all explosives spoil rapidly if so stored4 7e7 ,don't store explosives containing nitro-glycerine so that the cartridges stand on end4 ,the nitro-glycerine is more likely to leak from the cartridges when they stand on end than it is when they lie on their sides4 7f7 ,don't use explosives that are frozen or partly frozen4 ,the charge may not explode completely and serious accidents may result4 ,if the explosion is not complete the full strength of the charge is not exerted and larger quantities of harmful gases are given off4 ,illustration3 ,,fig4 #aba4--;,electric ,fuse4 ,full size4 7g7 ,don't thaw frozen explosives in front of an open fire1 nor in a stove1 nor over a lamp1 nor near a boiler1 nor near steam pipes1 nor by placing cartridges in hot water4 ,use a commercial or improvised thawer4 7h7 ,don't put hot water or steam pipes in a magazine for thawing purposes4 7i7 ,don't carry detonators and explosives in the same package4 ,detonators are extremely sensitive to heat1 friction1 or blows of any kind4 7j7 ,don't handle detonators or explosives near an open flame4 7k7 ,don't expose detonators or explosives to direct sunlight for any length of time4 ,such exposure may increase the danger in their use4 7l7 ,don't open a package of explosives until ready to use the explosive1 then use it promptly4 7m7 ,don't handle explosives carelessly4 ,they are all sensitive to blows1 friction1 and fire4 7n7 ,don't crimp a detonator 7blasting cap7 around a fuse with the teeth4 ,use a cap crimper1 which is supplied for this purpose4 7o7 ,don't economize by using a short length of fuse4 7p7 ,don't return to a charge for at least one-half hour after a miss fire4 ,hang fires are likely to happen4 7q7 ,don't attempt to draw nor to dig out the charge in case of a miss fire4 ,some of the positive rules in connection with the handling of explosives are3 build the magazine on an earth foundation remote from any other structures1 protect it with earth embankments that will direct the force of the explosion upwards1 and build it of materials that will supply as few missiles as possible4 ,hollow tile brick1 double-walled galvanized iron filled with sand1 and similar constructions are satisfactory4 ,the magazine may be heated by steam or hot-water pipes so located that explosives cannot come in contact with them1 or by a cluster of incandescent bulbs1 but if the explosives become frozen they must not be thawed out by turning on the steam or hot water4 ,if powder or nitro-glycerine is dropped on the floor the magazine should be emptied1 washed out with a hose and spots of nitro-glycerine scrubbed with a brush and a mixture of gallon of wood alcohol1 gallon of water and #b pounds of sodium sulphide4 ,frozen explosives may be thawed by spreading out on special shelves in a warm thaw house--not in the magazine proper1 by burying in a manure pile so that the explosive may not become moistened1 or more commonly by heating slowly in a water bath4 ,this is a dry kettle in which the explosives are placed and covered4 ,the kettle is then put in another containing water which is heated gently to about #abj degrees ,f4 ,it should not be boiled4 ,in case of a miss fire1 instead of digging out the old charge put a new charge on top of the old and fire the two simultaneously4 #agg4 ,priming1 ,loading1 and ,firing4--,priming is the act of placing the cap or detonator in the cartridge of explosive4 ,the primer is either the cap or the cap and cartridge which are to be detonated by the fuse4 ,if a cap and safety fuse are to be used the paper at the upper end of the cartridge is opened1 a hole is poked in the explosive with the finger or a piece of wood1 the cap and the attached fuse are pushed into the hole and gently embedded in the explosive so that the end of the cap is exposed sufficiently to prevent the fuse from igniting the dynamite directly4 ,the paper is then folded up and tied firmly around the fuse with a piece of string4 ,the result is shown in ,fig4 #abb4 ,illustration3 ,,fig4 #abb4--;,dynamite ,cartridge1 ,safety ,fuse1 and ,cap4 ,in placing the fuse in the cap the end of the fuse is cut off square1 and inserted in the open end of the cap1 care being taken not to spill the loose grains of powder or to grind the fuse down on top of the cap4 ,when the fuse is shoved firmly into place the upper portion of the copper cap is pressed or crimped with the cap crimpers shown in ,fig4 #abj4 ,the number of primers to be used is dependent on the size and location of the charge1 but in practically all sewer work only one primer is used to each hole4 ,in bulky charges the primer should be placed near the center of the charge and the fuse so protected that it will not ignite the charge prematurely4 ,in drill holes the primer is put in last with the cap end down4 ,in loading a hole1 it is first pumped and cleaned out4 ,this can be done satisfactorily with the end of a stick frayed out into a broom4 ,cartridges which very nearly fill the hole are dropped in one at a time and are pressed firmly together1 with a light wooden tamping bar4 ,they should not be pounded4 ,after the primer is placed1 a wad of clay or similar material is pressed gently into the hole against it and the hole is then filled with well-tamped clay4 ,in tunnel work tamping is not so essential as an overcharge of powder is usually used and the time of tamping1 which is worth more than two or three sticks of dynamite1 is saved4 ,in handling bulk explosives1 such as gunpowder1 they are poured into the hole1 the fuse is set in the upper portion and the remainder of the hole is tamped with clay as for dynamite cartridges4 ,illustration3 ,,fig4 #abc4--,methods for ,cutting ,safety ,fuse for ,splicing4 ,if a large number of charges are to be fired simultaneously with a safety fuse1 the length of the fuse to each charge should be made equal or a safety fuse used to a common center and approximately equal lengths of instantaneous fuse or ,cordeau ,bickford used from there to the charge4 ,in splicing the fuses for such connections they are cut diagonally as shown in ,fig4 #abc and bound together firmly with tape4 ,electric connections are particularly advantageous under such conditions as they avoid the dangers incidental to spliced fuses and are less expensive4 ,in tunnel work simultaneous electric detonation is not desirable as the holes should be fired progressively3 #ast1 the cuts2 #bnd1 the relievers2 #crd1 the backs2 #dth1 the sides2 and #eth1 the lifters4 ,different lengths of safety fuse1 or delayed action electric fuses can be used for these delay shots4 ,in igniting a safety fuse an open flame such as that furnished by a match or candle is the most satisfactory4 ,for electric fuses the current is generated by a magneto shown in ,fig4 #abj4 ,pressing vigorously down on the handle closes the circuit and generates an electric current which heats the platinum bridges and explodes the charges4 ,for the small number of charges used in ordinary construction they are connected in series so that if there is a broken connection anywhere no charge will be exploded4 ,if many charges are to be fired and a line circuit is to be used1 the final connection should not be made until just before the charge is to be fired in order to obviate the danger of stray currents firing the charge prematurely4 ,care should be taken to see that all connections are good and that there are no broken wires on the line4 #agh4 ,quantity of ,explosive4--,the quantity of explosive to be used can be determined satisfactorily only by experience on the job in question1 as the factors affecting the necessary quantity are so diverse4 ,the figures in ,table #fd indicate the relative amounts needed under different conditions4 ,,table #fd ,,quantities ,,of ,,explosives ,kind of ,drift ,feet#ii;,black#ii;,dynamite#ii1;,grade of ,rock in of ,hole ,powder1 ,pounds ,dynamite1 ,remarks ,feet ,pounds ,per ,cent ,limestone1 ,chicago #ab #j4dj #j4ge #dj;,gillette ,drainage ,canal ,limestone for #f #a4jj #j4gj #dj;,gillette crushing ,limestone for #bj #j4cg #ej;,gillette cement ,limestone1 holes #ae #j4dj #j4bf #ej;,gillette sprung ,sandstone1 #bj #j4aj #a4j #j4aj #dj;,gillette side cut ,sandstone1 thorough #bj #j4bj #b4j #j4bj #dj;,gillette cut ,shale1 soft #bd #j4jh #j4g #j4jc #dj;,gillette4 side cut ,open cut ,shale1 hard thorough #bd #j4bj #a4e #j4aj #dj;,gillette cut ,granite for #af #a4cf #j4bj #fj;,gillette rubble ,gneiss1 ,new #ab #a4cc #j4fj #dj;,gillette ,york ,city ,gneiss1 ,new #ad #j4fc #j4ej #dj;,gillette ,york ,city ,syenite1 ,treadwell #ab #a4gj #j4fg #dj;,gillette ,mine ,magnetic #ab #j4cb #j4dd #eb;,gillette iron ore ,trap1 seamy #ad #j4ce #j4bj #ge;,gillette ,trap1 #ag #a4jj #j4gj #dj;,gillette massive #ej ,granite1 dynamite ,grand #be #j4aj #j4hj #ej used to ,trunk spring holes ,clay1 rock and ,tunnel #a4jj ,gypsum ,grade varied at ,hard shale ,tunnel #b4jg #de1 at #fj1 some at #ajj ,hard rocky ,tunnel #a4fj #c4eg slate ,hard rocky ,tunnel #a4df #c4eg slate ,mill ,creek ,mun4 sewer1 ,tunnel #d4jj #fj ,eng'g4 ,st4 ,louis ,vol4 #eb1 p4 #ad ,,pipe ,,sewers #agi4 ,the ,trench ,bottom4--,it is customary to dig the bottom of the trench to conform to the shape of the lower #de degrees to #ij degrees of the sewer if the character of the material will allow such construction4 ,in soft material which will not hold its shape the sewer may be encased in concrete or a concrete cradle may be prepared for the pipe4 ,in rock the trench is excavated to about #f inches below grade and refilled with well-tamped earth so as to form a cradle giving bearing to #fj to #ij degrees of the pipe circumference4 ,for large sewers to be constructed in the trench special foundations are sometimes built4 #ahj4 ,laying ,pipe4--,before the pipe is lowered into the trench the sections which are to be adjacent should be fitted together on the surface and the relative positions marked by chalk so that the same position can be obtained in the trench4 ,small pipes are lowered into the trench and swung into position on a hook as shown in ,fig4 #abd4 ,pipes up to #ae or #ah inches in diameter can be handled by the pipe layer and helper in the trench without assistance4 ,heavier pipes may be lowered into the trench by passing ropes around each end of the pipe4 ,one end of the rope is fastened at the surface and the ropes are paid out by the men at the surface as the pipe is lowered4 ,if the pipes have been fitted together and marked at the surface it is undesirable to use this method of lowering as the position in which the pipes arrive in the bottom of the trench can not be easily predicted4 ,a cradle may be used for shoving the pipe into position as is shown in ,fig4 #abe4 ,illustration3 ,,fig4 #abd4--;,hook for ,lowering and ,placing ,sewer ,pipe4 ,illustration3 ,,fig4 #abe4--;,cradle for ,placing ,sewer ,pipe4 ,pipes above #bd to #bg inches in diameter are too large to be handled from the side of the trench4 ,a hook as shown in ,fig4 #abd is placed in the pipe so that it will be in the proper position when lowered4 ,it is raised by a rope passing through a block at the peak of a stiff-legged derrick which spans the trench1 or by a crane4 ,if a derrick is used the rope passes to a windlass on the opposite side of the trench from the pipe4 ,mechanical power may be used for raising pipes too heavy to be raised by hand4 ,the pipe is then lowered and swung into position while supported from the derrick4 ,excessive swinging is prevented by holding back on the guide rope as the pipe is raised and lowered4 ,pipes are usually laid with the bell end up grade as it is easier to fit the succeeding pipe into the bell so laid and to make the joint1 particularly on steep grades4 ,the ,baltimore specifications state3 ,the ends of the pipe shall abut against each other in such a manner that there shall be no shoulder or unevenness of any kind along the inside of the bottom half of the sewer or drain4 ,special care should be taken that the pipe are well bedded on a solid foundation4444 ,the trenches where pipe laying is in progress shall be kept dry1 and no pipe shall be laid in water or upon a wet bed unless especially allowed in writing by the ,engineer4 ,as the pipe are laid throughout the work they must be thoroughly cleaned and protected from dirt and water1 no water being allowed to flow in them in any case during the construction except such as may be permitted in writing by the ,engineer4 ,no length of pipe shall be laid until the preceding length has been thoroughly embedded and secured in place1 so as to prevent any movement or disturbance of the finished joint4 ,the mouth of the pipe shall be provided with a board or stopper1 carefully fitted to the pipe1 to prevent all earth and any other substances from washing in4 #aha4 ,joints4--,pipes may be laid with open joints1 mortar joints1 cement joints1 or poured joints4 ,open joints are used for storm sewers in dry ground close to the surface4 ,mortar and cement joints are commonly used on all sewers except in special cases4 ,cement joints are more carefully made than mortar joints and result in a greater percentage of water-tight joints4 ,poured joints are used in wet trenches where it is necessary to exclude ground water from the sewer4 ,a specification used in some cities for open joints is3 ,pipes laid with open joints are to be laid with their inverts in the same straight line and shall be firmly bedded throughout their length on the bottom of the trench4 ,no cement or mortar is to be used in the joints4 ,not more than inch shall be left between the spigot end of the pipe and the shoulder of the hub of the pipe into which it fits4 ,the joints shall be surrounded with cheese cloth1 burlap1 broken pipe1 gravel or broken stone4 ,the purpose of the cheese cloth1 etc41 is to prevent fine earth from sifting into the pipe until the cheese cloth or other material has rotted away1 by which time the earth has become arched over the opening4 ,mortar joints are specified by ,metcalf and ,eddy as follows3 ,before a pipe is laid the lower part of the bell of the preceding pipe shall be plastered on the inside with stiff mortar of equal parts of ,portland cement and sand1 of sufficient thickness to bring the inner bottoms of the abutting pipe flush and even4 ,after the pipe is laid the remainder of the bell shall be thoroughly filled with similar mortar and the joint wiped inside and finished to a smooth bevel outside4 ,in some work a wood block or a stone is embedded in the mortar at the bottom of the joint to bring the spigot in place concentric with the next pipe4 ,cement joints are specified in the ,baltimore specifications as follows3 ,cement joints shall be made with a narrow gasket of hemp or jute and cement mortar1 and special care shall be taken to secure tight joints4 ,the gasket shall be soaked in ,portland cement grout and then carefully inserted between the bell and the spigot1 and well calked with suitable hardwood or iron calking tools4 ,it shall be in one continuous piece for each joint1 and of such thickness as to bring the inverts of the two pipes smooth and even4 ,the remainder of the joint shall be filled with cement mortar all around1 on the bottom1 top and sides1 applied by hand with rubber mittens1 well pressed into the annular space and beveled off from the outer edge of the bell to a distance of two inches therefrom1 or to an angle of #de degrees4 ,the inside of each joint shall be thoroughly cleansed of all surplus mortar that may squeeze out in making the joint2 and to accomplish this some suitable scraper or follower1 or form shall be provided and always used immediately after each joint is finished4 ,cement joints so made1 form the most satisfactory joint for ordinary conditions and are the most frequently used4 ,they are not always water-tight and can be penetrated by roots4 ,some roots are able to penetrate holes of almost microscopic size and to form growths in the sewer or to split the joints4 ,poured joints are made by pouring some jointing compound1 while in a fluid state1 into the joint in which it hardens1 thus sealing the joint4 ,water-tightness in sewer lines to exclude ground water has also been attempted by using the ordinary cement joint and surrounding the pipe with a layer of cement or concrete4 ,this has not always been successful as it is difficult to obtain the proper class of workmanship in wet sewer trenches4 ,the requisite qualities of a poured jointing material are3 7#a7 ,it should make a joint proof against the entrance of water and roots4 7#b7 ,it should be inexpensive4 7#c7 ,it should have a long life4 7#d7 ,it should not deteriorate in sewage which may be either acid or alkaline4 7#e7 ,it should adhere to the surface of the pipe4 7#f7 ,it should run at a temperature below about #djj ,f41 as too high temperatures will crack the pipe4 7#g7 ,it should neither melt nor soften at temperatures below #bej ,f4 in order to maintain the joint if hot liquids are poured into the sewer4 7#h7 ,it should be elastic enough to permit slight movements of the pipes4 7#i7 ,it should not require great skill in using as it must be handled ordinarily by unskilled workers4 ,the materials used for poured joints are3 cement grout2 sulphur and sand2 and asphalt or some bituminous compound made of vulcanized linseed oil1 clay1 and other substances the resulting mixture having the appearance of vulcanized rubber or coal tar4 ,the bituminous materials most nearly approach the ideal conditions4 ,cement grout is made up of pure cement and water mixed into a soupy consistency4 ,its main advantages are its cheapness and ease in handling in wet trenches or difficult situations4 ,the result is no better than a well made cement joint4 ,there is no elasticity to the joint and a movement of the pipe will break it4 ,sulphur and sand are inexpensive1 comparatively easy to handle1 and make an absolutely water-tight and rigid joint which is stronger than the pipe itself4 ,it frequently results in the cracking of the pipe and is objected to by some engineers on that account4 ,in making the mixture1 powdered sulphur and very fine sand are mixed in equal proportions4 ,it is essential that the sand be fine so that it will mix well with the sulphur and not precipitate out when the sulphur is melted4 ,ninety per cent of the sand should pass a ,no4 #ajj sieve and #ej per cent should pass a ,no4 #bjj sieve4 ,the mixture melts at about #bfj ,f4 and does not soften at lower temperatures4 ,for making a joint in an #h inch pipe about #a pounds of sulphur1 #a pounds of sand1 pound of jute1 and #j4d pound of pitch are used4 ,the pitch is used to paint the surface of the joint while still hot in order to close up any possible cracks4 ,among the better known of the bituminous joint compounds are3 8,g4,k40 ,compound made by the ,atlas ,company1 ,mertztown1 ,pa41 ,jointite and ,filtite1 manufactured by the ,pacific ,flush ,tank ,co41 ,chicago and ,new ,york1 and some of the products of the ,warren ,brothers ,co41 ,boston4 ,these compounds fill nearly all of the ideal conditions except as to cost and ease in handling4 ,they are somewhat expensive and if overheated or heated too long become carbonized and brittle4 ,in cold weather they do not stick to the pipe well unless the pipe is heated before the joint is poured4 ,on some work joints have been poured under water with these compounds1 but success is doubtful without skillful handling4 ,an overheated compound will make steam in the joint causing explosions which will blow the joint clean1 and an underheated compound will harden before the joint is completed4 ,the materials should be heated in an iron kettle over a gasoline furnace or other controllable fire1 until they just commence to bubble and are of the consistency of a thin sirup4 ,only a sufficient quantity of material for immediate use should be prepared and it should be used within #aj to #ae minutes after it has become properly heated4 ,the ladle used should be large enough to pour the entire joint without refilling4 ,there are other important points to be considered in pouring joints which can be learned best by experience4 ,the quantity of material necessary for making these joints1 as announced by the manufacturers1 is shown in ,table #fe4 ,,table #fe ,,quantity ,,of ,,compound ,,needed ,,for ,,poured ,,joints ,diameter of ,pipe1 in ,quantity of ,material in ,pounds per ,joint ,inches ,standard ,socket ,deep and ,wide ,socket ,jointite ,filtite ,g4 ,k4 ,jointite ,filtite ,g4 ,k4 #f #j4hb #j4gb #j4db #a4df #a4bh #j4gb #h #a4jf #j4ie #j4gc #a4hb #a4fj #a4be #aj #a4cj #a4ae #j4hi #b4bf #a4ih #a4eb #ab #b4jh #a4hb #a4db #b4fe #b4cb #a4hj #ae #b4eb #b4bj #a4gd #c4bj #b4hj #b4bj #ah #c4jb #b4fd #b4eh #c4ge #c4bi #c4be #bj #c4dd #c4jj #b4hf #d4cj #c4gh #c #fj #bb #c4fb #c4af #c4ac #d4fb #d4jg #c4ig #bd #d4jc #c4ej #c4da #d4ia #d4ca #d4bg ,in making a poured joint the pipes are first lined up in position4 ,a hemp or oakum gasket is forced into the joint to fill a space of about of an inch4 ,an asbestos or other non-combustible gasket such as a rubber hose smeared with clay is forced about inch into the opening between the bell and the spigot and the compound is poured down one side of the pipe through a hole broken in the bell1 until it appears on the other side1 and the hole is filled4 ,occasionally the non-combustible gasket is wrapped tightly around the spigot of the pipe and pressed or tied firmly to the bell4 ,in pouring cement grout joints a paper gasket is used which is held to the bell and spigot by draw strings4 ,greater speed in construction and economy in the use of materials are obtained by joining two or three lengths of pipe on the bank and lowering them into the trench as a unit4 ,the pipes are set in a vertical position on the bank with the bell end up1 one length resting in the other4 ,the joint is calked with hemp and poured without the use of the gasket4 ,the joint should always be poured immediately after being calked so that the hemp can not become water soaked4 ,the asbestos gasket should be removed as soon as possible after the joint is poured in order to prevent sticking with resultant danger of breaking of the joint when attempting to pull the gasket free4 ,one man can pour about #cc eight-inch joints1 and two men can complete about #bf twelve-inch joints per hour on the bank where conditions are more or less fixed4 #ahb4 ,labor and ,progress4--,the labor required for the laying of pipe sewers1 exclusive of excavation1 bracing and backfilling1 consists of pipe layers and helpers4 ,for pipes #bd to #bg inches in diameter or smaller one pipe layer and one or more helpers are necessary1 dependent on the size of the pipe and the depth of the trench4 ,for larger pipes two pipe layers can work economically each working on one-half of the pipe and making half of the joint4 ,the speed of pipe laying is ordinarily limited by the speed of the excavation1 but on a job in ,topeka1 ,kan41#ajj where the average day's progress with a machine excavator was #bjj to #ejj feet of trench per day1 the pace was limited by the speed of the pipe laying gang4 ,this gang consisted of two pipe layers in the trench and two helpers on the surface4 ,the sizes of pipes handled were from #h to #bg inches4 ,,brick ,,and ,,block ,,sewers #ahc4 ,the ,invert4--,in good firm ground the excavation is cut to the shape of the sewer and the bricks are laid directly on the ground1 being embedded in a thick layer of mortar4 ,after the foundation has been prepared and before the bricks are laid1 two wooden templates1 called profiles1 are prepared1 similar to that shown in ,fig4 #abf1 to conform to the shape of the inside and outside of the sewer4 ,each course of bricks is represented by a row of nails in the profile and each nail corresponds to a joint in the row4 ,the two profiles are set true to line and grade4 ,a cord is stretched tightly between the two lowest nails on opposite templates and a row of bricks is laid4 ,the bricks are laid radially and on edge with their long dimension parallel to the axis of the sewer and with one edge just touching the string4 ,as each one or two or three rows are completed the guide line is moved up to the next nails4 ,when the bricks are laid on the ground all but large depressions are filled in with tamped sand or mortar by the masons4 ,approximately the same number of rows of bricks is kept completed on either side of the center line4 ,the succeeding courses follow within three to five rows of each other1 the only bond between courses being the mortar joint4 ,this is called row lock bond and with few exceptions has been used on all brick sewers in the ,united ,states4 ,as the sides of the sewer become higher during the construction1 platforms must be built for the masons4 ,these platforms are built of wood and rest directly on the green brickwork4 ,they should be designed to spread the load as much as possible4 ,the brickwork of the invert is continued up in this way to the springing line4 ,as soon as one section is completed one profile is moved #aj to #bj feet ahead along the trench according to the standard length of sections1 and set in position4 ,the line is then strung from it to nails driven or pushed into the cement joints of the last completed section4 ,between work done on separate days the bricks are racked back in courses to provide a satisfactory bond4 ,illustration3 ,,fig4 #abf4--,profile for ,brick ,sewers4 ,in ground too soft to support the brickwork directly a cradle is prepared by placing profiles in position in the sewer and nailing #b-;inch planks to these profiles1 first firmly tamping earth under the planks4 ,the bricks are laid in this cradle in a manner similar to that explained for sewers with a firm foundation4 ,in still softer ground it may be necessary to construct a concrete cradle to support the bricks4 #ahd4 ,the ,arch4--,the arch centering consists of a wooden form made up of wooden ribs as shown in ,fig4 #abg4 ,the center conforms to the shape of the inside of the arch with allowance for the thickness of the lagging4 ,the lagging is nailed on the ribs in straight strips parallel to the axis of the sewer4 ,the center is supported on triangular struts resting against the sides and on the bottom of the sewer and is lifted into position by wedges driven between it and the support4 ,the centers may be placed immediately after the completion of the invert1 or a day or two may be allowed to pass to give the invert an opportunity to set4 ,after the centers are fixed in place the arch brick are carried up evenly on each side and are pounded firmly into place4 ,the center is usually1 but not always 8struck0 immediately1 and the arch brick are cleaned and pointed up from the inside4 ,the outside is covered with a layer of to of an inch of cement mortar and may be backfilled to the top of the arch in order to maintain the moisture of the mortar during setting and to press the bricks of the arch together firmly4 ,the centers are sometimes made collapsible so that they can be carried or rolled through the finished brickwork to the advanced position4 ,in 8striking0 the centers the wedges are removed and the wings folded in4 ,illustration3 ,,fig4 #abg4--;,centering for ,brick ,sewer4 ,in tunneling1 the invert of the sewer is constructed in the same fashion as for open cut work4 ,the arch centering is made in short sections and the bricks are put in position by reaching in over the end of the centering4 ,all of the timbering of the tunnel is removed except the poling boards or lagging against which the bricks or mortar are tightly pressed1 the boards being bricked in permanently4 #ahe4 ,block ,sewers4--,sewers made of unit blocks of concrete or vitrified clay are constructed in a similar manner to brick sewers4 ,fig4 #abh shows the construction of a block sewer at ,clinton1 ,iowa4 ,in this sewer there are two rings2 an inside one of solid blocks and an outside one of hollow blocks4 ,block sewers do not demand the skill in construction that is demanded by brick sewers1 as the blocks are so cast that the joints are radial1 whereas only experienced masons can lay bricks radially4 ,illustration3 ,,fig4 #abh4--,segmental ,block ,sewer at ,clinton1 ,iowa4 #ahf4 ,organization4--,the number of men employed on a brick or block sewer is proportioned according to the size of the sewer and the working conditions4 ,the number of men working on different tasks usually bears the same ratio to the number of masons employed1 regardless of the size of the work4 ,these proportions are shown for different jobs1 in ,table #ff4 ,,table #ff ,,organizations ,,for ,,the ,,construction ,,of ,,brick ,,and ,,block ,,sewers #hd- to ,general ,ratio #ae-;foot1#ff-;inch #hd-;inch #ajh-;inch #db-;inch ,type of ,work on ,basis of #e-ring ,circular,circular ,sewer ,lock-,joint ,four ,brick ,brick1 ,brick1 ,brick1 ,brick in,tile ,block ,layers ,chicago ,gary ,gary ,detroit ,tunnel ,foreman #a #a #a #a #a #a ,brick layers #d #ab #f #f #e #b ,helpers #b #aa #c #c #a ,scaffold men #b #ba #c ,brick tossers #b #g #ae #b ,brick #b #b #b carriers ,cement mixers #b #f #f #e #a ,cement #b #aj #h carriers ,form setters #a #c #c ,laborers #a #h #ai #c #ad #g ,municipal ,source of ,engineering1 ,h4 ,p4 ,gillette1 ,handbook of ,cost ,data ,information ,vol4 #ed1 p4 #bbh #ahg4 ,rate of ,progress4--,in a general way it can be assumed that the laying of #a1jjj bricks will require #c hours of the time of one mason1 #aj man-hours for helpers and laborers1 #b barrels of cement1 #j4f cubic yard of sand1 and about #aj feet board measure of centering4 ,one thousand bricks will make about #b cubic yards of brickwork4 ,to the costs1 as estimated on the basis of materials and labor1 must be added about #ae per cent for overhead and an additional amount for the contractor's profit4 ,the number of bricks required in various size sewers is shown in ,table #fg4 ,a mason can lay more bricks per hour in a large sewer than in a small one as there is a smaller percentage of face work1 there is more room to work1 and it is easier to lay the bricks radially4 ,the number of bricks laid and the rate of progress on various jobs are shown in ,table #fh4 ,,table #fg ,,brick ,,masonry ,,in ,,circular ,,sewers4 ,,cubic ,,yards ,,per ,,linear ,,foot 7,from ,h4 ,p4 ,gillette7 ,diameter1 ,one ,ring ,two ,ring ,three ring ,feet and ,inches 7#d ,inches7 7#i ,inches7 7#ac ,inches7 #b #j #j4ajc #j4bdj #b #f #j4abe #j4bhj #c #j #j4adg #j4cbg #c #f #j4afi #j4cga #d #j #j4aia #j4dae #d #f #j4bac #j4deh #e #j #j4bcd #j4eja #j4hjb #e #f #j4bef #j4ede #j4hfg #f #j #j4bgh #j4ehi #j4icc #f #f #j4fcc #a4jjj #g #j #j4fgg #a4jfc #g #f #j4gbj #a4abh #h #j #j4gfc #a4aic #h #f #j4hjg #a4bfj #i #j #j4hea #a4cbe #i #f #j4hie #a4cij #aj #j #j4ich #a4def ,,concrete ,,sewers #ahh4 ,construction in ,open ,cut4--,in the construction of sewer pipe of cement and concrete one of two methods may be employed2 #ast1 to manufacture the pipe in a plant at some distance from the place of final use1 or #bnd1 to manufacture the pipe in place4 ,the methods of the manufacture of cement and concrete pipe which are to be transported to the place of use are treated in ,chapter ,,viii4 ,the process of constructing the pipes in place is ordinarily used for pipes #dh inches or more in diameter4 ,for smaller sizes1 brick1 vitrified clay1 and precast cement pipes are usually more economical4 ,the preparation of the foundation of a concrete sewer is similar to that for a brick sewer4 ,if the ground is suitable the trench is shaped to the outside form of the sewer and the concrete poured directly on it4 ,in soft material which would give poor support to a sewer with a rounded exterior1 the bottom of the trench is cut horizontal and a concrete cradle of poorer quality than that in the finished sewer is poured on the soft ground1 on a board platform1 on piles1 or on cribbing supported on piles4 ,if the invert of the sewer is so flat that the concrete will stand without an inside form the shape of the invert is obtained by a screed or straight-edge which is passed over the surface of the concrete and guided on two centers1 or on one center and the face of the finished work4 ,the construction of a flat invert sewer at ,baltimore is shown in ,fig4 #a4 ,the center for the concrete is shown in the foreground4 ,when the concrete for the next section is poured it will be smoothed to shape by a screed or straight-edge resting on the face of the finished concrete and the center4 ,the center is shaped to conform to that of the finished concrete4 ,it is firmly staked in position and acts as a bulkhead for the concrete as it is poured1 as well as a guide for the screed4 ,,table #fh ,,rate ,,of ,,progress ,,on ,,brick ,,sewer ,,construction 7,based on #h-;hour day7 ,bricks ,diameter ,number,number per ,number of ,sewer ,shape ,rings1,masons,mason ,laborers ,brick per ,day #g #j;,circular #h #aa and #b #f #dgaj #ci ,oval #d #j;,circular #b #c #bejj #c arch #f #h;,circular #a #ah #fb invert #a arch #b #i;,egg #b #b #c invert #e #f;,circular #b #f #degj #ce #f #f;,circular #d #dhjj #b #i;,circular #b #b #bjhj #e #af #j;,circular #e #h #e cu4 yd4 #af #j;,circular #e #ab #gj-ge #c #f;,egg #bcjj #i #f;,circular #cjjj #c #f;,circularblocks #b #ac ,diameter ,feet of ,sewer,progress ,location ,authority ,remarks per ,day #g #j #h #aa #fj;,gary ,gillette #i-;hour day ,metcalf ,general #d #j #cf and average ,eddy ,concrete #f #h ,denver ,gillette invert ,eng4 ,springfield1 ,con41 #b #i ,mass4 ,jan4 #af1 #aijg #e #f #aaj;,gary ,gillette #f #f ,gillette ,exceptional speed ,tunnel #b #i #ac4i,syracuse ,gillette #ab-;hour day #af #j #bb;,chicago ,gillette ,first year #af #j #ce;,chicago ,gillette ,second year #c #f ,st4 ,louis ,gillette #i #f #ab4e;,chicago ,h4 ,r4 ,abbott ,lock joint #c #f #cj and tile4 #aj-;hour day ,if inside forms are to be used they are made as units in lengths of #ab or #af feet for wooden forms1 and #e feet for steel forms4 ,the inside form is supported by precast concrete blocks placed under it and which are concreted into the sewer4 ,it is held in position by cleats nailed to the outside form1 to the sheeting1 or wedged against the outside of the trench4 ,in some cases1 particularly where steel forms are used1 the inside form is hung by chains from braces across the trench as is shown in ,fig4 #abi4 ,the form is easily brought to proper grade by adjustment of the turnbuckles and is then wedged into position to prevent movement either sideways or upwards during the pouring of the concrete4 ,it may be necessary to weight the forms down to prevent flotation4 ,cross bracing in the trench which interferes with the placing of the form is removed and the braces are placed against the form until the concrete is poured4 ,they are removed immediately in advance of the rising concrete4 ,illustration3 ,,fig4 #abi4--;,blaw ,standard ,half ,round ,sewer ,form1 ,suspended from ,overhead ,support4 ,courtesy1 ,blaw ,steel ,form ,co4 ,the sewer section may be built as a monolith1 in two parts1 or in three parts4 ,in casting the sewer as a monolith the complete full round inside form is fixed in place by concrete blocks and wires4 ,the full round outside form is completed as far as possible without interfering too much with the placing and tamping of the concrete4 ,the concrete is poured from the top1 being kept at the same height on each side of the form1 and tamped while being poured4 ,the remaining panels of the outside form are placed in position as the concrete rises to them4 ,an opening is left at the top of the outside arch forms which is of such a width that the concrete will stand without support4 ,the casting of sewers as a monolith is difficult and is usually undesirable because of the uncertainty of the quality of the work4 ,it has the advantage1 however1 of eliminating longitudinal working joints in the sewers which may allow the entrance of water or act as a line of weakness4 ,illustration3 ,,fig4 #acj4--;,construction ,joints for ,concrete ,sewers4 ,if the sewer is to be cast in two sections the invert is poured to the springing line or higher4 ,a triangular or rectangular timber is set in the top of the wet concrete as shown in ,fig4 #acj4 ,when the concrete has set the timber is removed and the groove thus left forms a working joint with the arch4 ,after the invert concrete has set1 the arch centering is placed and the arch is completed4 ,this is the most common method for the construction of medium-sized circular sewers4 ,large sewers with relatively flat bottoms are poured in two or three sections4 ,first the invert is poured without forms and is shaped with a screed4 ,about #f inches of vertical wall is poured at the same time4 ,this acts as a support for the side-wall forms4 ,the side walls reach to the springing line of the arch and are poured after the invert has set4 ,at the third pouring the arch is completed4 ,the sewer shown in ,fig4 #a is being poured in two steps1 as the side walls are so low that they are poured at the same time as the invert4 ,a transverse working joint similar to one of the types used in ,fig4 #acj is set between each day's work4 ,the length of the form used and the capacity of the plant should be adjusted so that one complete unit of invert1 side wall1 or arch can be poured in one operation4 ,the forms are left in place until the concrete has set4 ,invert and side-wall forms are generally left in position for at least two days1 and in cold weather longer4 ,the arch forms are left in place for double this time4 ,for example if #bj feet of invert and arch can be poured in a day1 #fj feet of invert form and #ajj feet of arch form will be required4 ,as the forms are released they must be moved forward through those in place4 ,for this reason collapsible or demountable forms are necessary and steel forms are advantageous4 ,wooden arch forms are sometimes dismantled and carried forward in sections1 but are preferably designed to collapse as shown in ,fig4 #aca1 so that they can be pulled through on rollers or a carriage4 #ahi4 ,construction in ,tunnels4--,in tunnels the invert and side walls are constructed in the same manner as for open cut work4 ,the tunneling1 which acts as the outside form1 is concreted permanently in place4 ,the concreting of a tunnel by hand is shown in ,fig4 #acb4 ,if the work is to be done by hand the concrete is thrown in between the ribs of the arch centering and behind the plates or lagging1 which are set in advance of the rising concrete4 ,the lagging plates are #e feet long which makes it possible to throw the concrete in place at the arch1 and to tamp it in place from the end4 ,a bulkhead and a well-greased joint timber are placed in position as the concrete rises4 ,illustration3 ,,fig4 #aca4--,section through a ,collapsible ,wood ,form4 ,pneumatic transmission of concrete is also used for filling the arch forms as well as the side walls and invert forms4 ,in using this method the mixer may be placed at the surface or at the bottom of the shaft or other convenient permanent location which may be some distance from the form4 ,the mixture is discharged into a pipe line through which it is blown by air to the forms4 ,the starting pressure of about #hj pounds per square inch can be reduced after flow has commenced4 ,in constructing the ,st4 ,louis ,water ,works tunnel the compressor equipment for moving the concrete had a capacity of #a1fjj cubic feet per minute at a pressure of #aaj pounds4 ,the tunnel is horseshoe shaped1 #h feet in height and with walls varying from #i to #bj inches in thickness4 ,the extreme travel of the concrete was #a1ajj feet in an #h inch pipe4 ,the amount of air consumed at #aaj pounds varied from #a4b to #a4g cubic feet of free air per linear foot of pipe4 ,by the time the batch had been discharged the pressure had reduced to #be to #dj pounds1 depending on the length of the pipe4 ,it is reported that a #f-;inch pipe line would probably have given better results4 ,illustration3 ,,fig4 #acb4--,ogier's ,run ,intercepting ,storm-,water ,drain1 ,baltimore1 ,maryland4 ,placing concrete in ,arch4 ,the steel lagging of the forms is carried up in sections as the concrete is deposited4 ,the drain is horseshoe shaped1 and is #ab feet #c inches high and #ab feet #c inches wide4 ,the end of the concrete conveying pipe is provided with a flexible joint the simplest form of which can be made by slipping a section of pipe of larger diameter over the end of the transmission line4 ,the concrete is deposited directly on the invert or into the side-wall forms and can be blown into the arch forms for #bj to #be feet4 #aij4 ,materials for ,forms4--,the materials used in forms for concrete sewers are3 wood1 wood with steel lining1 and steel alone4 ,the first cost of wood forms is lower than that of steel but their life is relatively short4 ,if the forms are to be used a number of times steel is more economical4 ,with proper care and repairs steel forms will outlast any other material4 ,because of the increasing price of lumber and improvements in steel forms1 wood forms are not frequently used4 ,a common type of specification under which forms are used is3 ,the material of the forms shall be of sufficient thickness and the frames holding the forms shall be of sufficient strength so that the forms shall be unyielding during the process of filling4 ,the face of the form next to the concrete shall be smooth4 ,if wooden forms are used the planking forming the lining shall invariably be fastened to the studding in horizontal lines1 the ends of these planks shall be neatly butted against each other1 and the inner surface of the form shall be as nearly as possible perfectly smooth1 without crevices or offsets between the ends of adjacent planks4 ,where forms are used a second time1 they shall be freshly jointed so as to make a perfectly smooth finish to the concrete4 ,all forms shall be water-tight and shall be wetted before using4 ,any material in contact with wet concrete should be oiled or greased beforehand in order to prevent adherence to the concrete4 #aia4 ,design of ,forms4--,the design of forms for reinforced concrete work requires some knowledge of the strength of materials and the theories of beams1 columns1 and arches4 ,forms can be constructed without such knowledge but that they will be both economical and adequate is an improbability4 ,the ordinary beam and column formulas are applicable to the design of forms4 ,the maximum bending moment for sheeting and ribs is taken as 7wl#b7h1 where w is the load per unit length1 and l is the length between supports4 ,sanford ,thompson recommends that the deflection be calculated as 7wl#c77abh;,,ei71 in which ,e is the modulus of elasticity of the material1 and ,i is the moment of inertia of the cross-section referred to the neutral axis4 ,the horizontal pressure of the concrete against the forms has been expressed empirically by ,e4 ,b4 ,smith1#aja as ,p ,h#j4b,r#j4c #abj;,c #j4c,s in which ,p lateral pressure in pounds per square inch2 ,r rate of filling forms in feet per hour2 ,h head of fill4 ,ordinarily taken as ,r1 but in cold weather or when continuously agitated it may be as high as ,r2 ,c ratio1 by volume1 of cement to aggregate2 ,s consistency in inches of slump4 ,earlier investigators have usually concluded that the pressures were equal to those caused by a liquid weighing #add pounds per cubic foot1 but the tests of the ,united ,states ,bureau of ,public ,roads1 from which the above formula was devised1 show the pressures to be decidedly below this amount under certain conditions4 ,illustration3 ,,fig4 #acc4--;,centering for ,large ,forms4 ,with these units and formulas the design of the lagging becomes a matter of substitution in1 and the solution of1 the equations produced4#ajb ,the forces acting on the ribs are indeterminate4 ,no more satisfactory design can be made for the ribs than to follow successful practice1 or what is seldom done1 to determine the stresses in the forms by the application of one of the theories for the solution of arch stresses4 ,the sizes of the lumber used in the ribs varies from #a #f inches to #b #aj inches1 depending on the size of the sewer4 ,if vertical posts are used at the ends to support the arch forms they are computed as columns taking the full weight of the arch4 ,if the span is so wide that radial supports are used as shown in ,fig4 #acc the load at the center is assumed as one-fourth of the weight of the arch4 #aib4 ,wooden ,forms4--,norway and ,southern pine1 spruce1 and fir are satisfactory for form construction4 ,white pine is satisfactory but is generally too expensive4 ,the hard woods are too difficult to work4 ,the lumber should be only partly dried as kiln-dried lumber swells too much when it is moistened1 warping the forms out of shape or crushing the lagging at the joints4 ,green lumber must be kept moist constantly to prevent warping before use and when it is used it does not swell enough to close the cracks4 ,the lumber should be dressed on the face next to the concrete and at the ends4 ,either beveled or matched lumber may be used for lagging4 ,the joint made by beveled lumber shown in ,fig4 #acd is cheaper but less satisfactory than a tongued and grooved joint4 ,illustration3 ,,fig4 #acd4--;,beveled ,joint for ,wood ,fords4 ,illustration3 ,,fig4 #ace4--;,collapsible ,wooden ,invert ,form for ,concrete ,sewers4 ,illustration3 ,,fig4 #acf4--,support for ,arch ,centering4 ,illustration3 ,,fig4 #acg4--,wooden ,forms ,used in ,tunnel1 ,north ,shore ,sewer1 ,sanitary ,district of ,chicago4 ,journal ,western ,society of ,engineers1 ,vol4 #bb1 p4 #che4 ,types of wooden forms are shown in ,figs4 #ace and #acf for use in sewers to be built as monoliths or in two portions4 ,fig4 #acg shows the details of a built-up wooden form used in tunnel work for a #db inch egg-shaped sewer4 #aic4 ,steel-lined ,wooden ,forms4--,sheet metal linings are sometimes used on wooden forms4 ,they permit the use of cheaper undressed lumber1 demand less care in the joining of the lagging1 and when in good condition give a smooth surface to the finished concrete4 ,their use has frequently been found unsatisfactory and more expensive than well-constructed wooden forms because of the difficulty of preventing warping and crinkling of the metal lining and in keeping the ends fastened down so that they will not curl4 ,sheet steel or iron of ,no4 #ah or #bj gage 7#j4je to #j4jcge of an inch7 weighing #b to #a pounds per square foot is ordinarily used for the lining4 ,illustration3 ,,fig4 #ach4--;,blaw ,standard ,full ,round ,telescopic ,sewer ,forms1 ,showing ,knocked-,down ,sections ,loaded on a ,truck4 ,courtesy1 ,blaw ,steel ,form ,co4 #aid4 ,steel ,forms4--,these are simple1 light1 durable1 and easy to handle4 ,the engineer is seldom called upon to design these forms as the types most frequently used are manufactured by the patentees and are furnished to the contractor at a fixed rental per foot of form1 exclusive of freight and hauling from the point of manufacture4 ,the forms can be made in any shape desired1 the ordinary stock shapes such as the circular forms being the least expensive4 ,the smaller circular forms are adjustable within about #c inches to different diameters so that the same form can be used for two sizes of sewers4 ,the same form can be used for arch and invert in circular sewers4 ,fig4 #ach shows the collapsible circular forms and the manner in which they are pulled through those still in position4 ,fig4 #abi shows a half round steel form swung in position by chains and turnbuckles from the trench bracing1 and ,fig4 #aci shows the free unobstructed working space in the interior of some large steel forms4 ,illustration3 ,,fig4 #aci4--;,interior of ,steel ,forms for ,calumet ,sewer1 ,chicago4 ,sewer is #af feet wide4 ,note absence of obstructions4 ,courtesy1 ,hydraulic ,steelcraft ,co4 #aie4 ,reinforcement4--,it is essential that the reinforcement be held firmly in place during the pouring of the concrete4 ,a section of reinforcement misplaced during construction may serve no useful purpose and result in the collapse of the sewer4 ,in sewer construction a few longitudinal bars may be laid in order that the transverse bars may be wired to them and held in position by notches in the centering and in fastenings to bars protruding from the finished work4 ,this construction is shown in ,fig4 #a4 ,the network of reinforcement is held up from the bottom of the trench by notched boards which are removed as the concrete reaches them1 or better by stones or concrete blocks which are concreted in4 ,sometimes the reinforcement is laid on top of the freshly poured portion of the concrete the surface of which is at the proper distance from the finished face of the work4 ,this method has the advantage of not requiring any special support for the reinforcement1 but it is undesirable because of the resulting irregularity in the reinforcement spacing and position4 ,in the side walls the position of the reinforcement is fixed by wires or metal strips which are fastened to the outside forms or to stakes driven into the ground4 ,wires are then fastened to the reinforcement bars and are drawn through holes in the forms and twisted tight4 ,when the forms are removed the wires or strips are cut leaving a short portion protruding from the face of the wall4 ,the reinforcing steel from the invert should protrude into the arch or the side walls for a distance of about #dj diameters in order to provide good bond between the sections4 ,the protruding ends are used as fastenings for the new reinforcement4 ,the arch steel may be supported above the forms by specially designed metal supports1 by small stones or concrete blocks which are concreted into the finished work2 or by notched strips of wood which are removed as the concrete approaches them4 ,strips of wood are not satisfactory because they are sometimes carelessly left in place in the concrete resulting in a line of weakness in the structure4 ,metal chairs are the most secure supports4 ,they are fastened to the forms and the bars are wired to the chairs4 ,in some instances the entire reinforcement has been formed of one or two bars which are fastened into position as a complete ring4 ,this results in a better bond in the reinforcement1 requires less fastening and trouble in handling1 but is in the way during the pouring of the concrete and interferes with the handling of the forms4 #aif4 ,costs of ,concrete ,sewers4--,under present day conditions a general statement of the costs of an engineering structure can not be given with accuracy4 ,only the items of labor1 materials1 and transportation that go to make up the cost can be estimated quantitively1 and the total cost computed by multiplying the amount of each item by its proper unit cost obtained from the market quotations4 ,a summary of some of the items that go to make up the cost of a concrete sewer and the relative amount of these items on different jobs is given in ,tables #fi and #gj4 ,,table #fi ,,division ,,of ,,labor ,,costs ,,for ,,the ,,construction ,,of #if-;,,inch ,,circular ,,concrete ,,sewer ,classification of ,labor ,classification of ,work ,task or ,title ,total ,type of ,work ,number of dollars per ,dollars per men day foot ,superintendent #a #f4jj;,excavation #a4hj ,engineman ,sheeting and #a #c4ej bracing #j4eh ,hoister ,bottom plank 7engineman7 #a #b4jj #j4ag ,tag-men #b #c4cj,pulling sheeting #j4de ,earth diggers #aj #af4ej;,backfilling #j4cc ,on dump cars ,making and #b #c4cj placing invert #a4ag ,carpenter on ,making and bracing #b #c4jj placing arch #a4ed ,carpenters' ,laying brick in helpers #b #c4cj invert #j4bi ,laying bottom #b #c4cj ,moving pumps1 ,bending and etc4 placing steel #b #c4cj in arch #j4bj ,pulling sheeting #c #e4be ,mixing and ,bending and placing placing steel concrete #af #bf4dj in invert #j4ji ,on steel forms ,moving forms and #c #e4be centers #j4fb ,water boy ,watchmen1 water #a #a4jj boy1 etc4 #j4fb ,coal and oil #e4jj ---------- ---------- ,total #ij4dj ,total #g4hf ,,notes4--,trench was #ab feet wide and of various depths4 ,at depth of #ab feet the cost of excavation was #a4fa per foot4 ,from ,engineering and ,contracting1 ,vol4 #dg1 p4 #aeg4 ,,backfilling #aig4 ,methods4--,careful backfilling is necessary to prevent the displacement of the newly laid pipe and to avoid subsequent settlement at the surface resulting in uneven street surfaces and dangers to foundations and other structures4 ,the backfilling should commence as soon as the cement in the joints or in the sewer has obtained its initial set4 ,clay1 sand1 rock dust1 or other fine compactible material is then packed by hand under and around the pipe and rammed with a shovel and light tamper4 ,this method of filling is continued up to the top of the pipe4 ,the backfill should rise evenly on both sides of the pipe and tamping should be continuous during the placing of the backfill4 ,for the next #b feet of depth the backfill should be placed with a shovel so as not to disturb the pipe1 and should be tamped while being placed1 but no tamping should be done within #f inches of the crown of the sewer4 ,the tamping should become progressively heavier as the depth of the backfill increases4 ,generally one man tamping is provided for each man shoveling4 ,,table #gj ,,division ,,of ,,costs ,,for ,,the ,,construction ,,of ,,concrete ,,sewers ,gillette's ,handbook of ,cost ,data4 ,item ,location ,fond du ,south ,lac ,bend ,wilmington ,richmond1 ,indiana ,diameter in inches #cj #ff #ec #ed #dh #db ,shape circular circularhorseshoe circularcircularcircular ,plain or reinforced plain rein4 rein4 rein4 rein4 rein4 ,cubic yards per foot #j4aa #j4eid #j4cg #e shell#e shell#d shell ,daily progress1 feet #dg #bd to #cf ,cost per foot1 dollars #a4bj #d4dj #b4ig #a4ce #a4jh #j4ia ,per cent of total cost3 ,labor #ci4jajc #cc4e #cc4j #ag4a ,tools #a4e #aa4e ,sand and gravel #ab4d #ae4e #ah4i #ai4c ,lumber #j4i ,water #j4g #aa4e ,reinforcing #j4j #ad4e #bb4c ,cement #bc4j #bj4j #bg4e #cb4jajd ,frost prevention #b4j ,forms #ab4e #h4j #f4a #i4c ,engineering #h4j ,length of day1 hours #h #aj ,year of construction #aijh #aijf ,pre-war conditions ,above a point #b feet above the top of the sewer the method pursued and the care observed in backfilling will depend on the character of the backfilling material and the location of the sewer4 ,if the sewer is in a paved street the backfill is spread in layers #f inches thick and tamped with rammers weighing about #dj pounds with a surface of about #cj square inches4 ,one man tamping for each man shoveling is frequently specified4 ,if no pavement is to be laid but it is required that the finished surface shall be smooth1 slightly less care need be taken and only one man tamping is specified for each two men shoveling4 ,on paved streets a reinforced concrete slab with a bearing of at least #ab inches on the undisturbed sides of the trench may be designed to support the pavement and its loads4 ,this is of great help in preventing the unsightly appearance and roughness due to an improperly backfilled trench4 ,on unpaved streets the backfill is crowned over the trench to a depth of about #f inches and then rolled smooth by a road roller4 ,in open fields1 in side ditches1 or in locations where obstruction to traffic or unsightliness need not be considered1 after the first #b feet of backfill have been placed with proper care1 the remainder is scraped or thrown into the trench by hand or machine1 care being taken not to drop the material so far as to disturb the sewer4 ,if the top of the sewer1 manhole1 or other structure comes close to or above the surface of the ground1 an earth embankment should be built at least #c feet thick over and around the structure4 ,the embankment should have side slopes of at least #a on #a and should be tamped to a smooth and even finish4 ,if sheeting is to be withdrawn from the trench it should be withdrawn immediately ahead of the backfilling1 and in trenches subject to caving it may be pulled as the backfilling rises4 ,puddling is a process of backfilling in which the trench is filled with water before the filling material is thrown in4 ,it avoids the necessity for tamping and can be used satisfactorily with materials that will drain well and will not shrink on drying4 ,sand and gravel are suitable materials for puddling1 heavy clay is unsatisfactory4 ,puddling should not be resorted to before the first #b feet of backfill has been carefully placed4 ,more compact work can be obtained by tamping than with puddling4 ,frozen earth1 rubbish1 old lumber1 and similar materials should not be used where a permanent finished surface is desired as these will decompose or soften resulting in settlement4 ,rocks may be thrown in the backfill if not dropped too far and the earth is carefully tamped around and over them4 ,in rock trenches fine materials such as loam1 clay1 sand1 etc41 must be provided for the backfilling of the first portion of the trench for #b feet over the top of the pipe4 ,more clay can generally be packed in an excavation than was taken out of it1 but sand and gravel occupy more space than originally even when carefully tamped4 ,tamping machines have not come into general use4 ,one type of machine sometimes used consists of a gasoline engine which raises and drops a weighted rod4 ,the rod can be swung back and forth across the trench while the apparatus is being pushed along4 ,it is claimed that two men operating the machine can do the work of six to ten men tamping by hand4 ,the machine delivers #ej to #fj blows per minute1 with a #b foot drop of the #hj to #ij pound tamping head4 ,backfilling in tunnels is usually difficult because of the small space available in which to work4 ,ordinarily the timbering is left in place and concrete is thrown in from the end of the pipe between the outside of the pipe and the tunnel walls and roof4 ,if vitrified pipe is used in the tunnel1 the backfilling is done with selected clayey material which is packed into place around the pipe by workmen with long tamping tools4 ,the backfilling should be done with care under the supervision of a vigilant inspector in order that subsequent settlement of the surface may be prevented4 ,,chapter ,,xii ,,maintenance ,,of ,,sewers #aih4 ,work ,involved4--,the principal effort in maintaining sewers is to keep them clean and unobstructed4 ,a sewerage system1 although buried1 cannot be forgotten as it will not care for itself1 but becoming clogged will force itself on the attention of the community4 ,besides the cleaning and repairing of sewers and the making of inspections for determining the necessity for this work1 ordinances should be prepared and enforced for the purpose of protecting the sewers from abuse4 ,inspections to determine the amount of the depreciation of sewers with a view towards possible renewal1 or to determine the capacity of a sewer in relation to the load imposed upon it are sometimes necessary4 ,the valuation of the sewerage system as an item in the inventory of city property may be assigned to the engineer in charge of sewer maintenance4 ,the work involved in the inspection and cleaning of sewers in ,new ,york ,city for the year ending ,may1 #aiad1 included the removal of #bb1fhg cubic yards of material from catch-basins1 and #ad1hbf catch-basin cleanings4 ,this made an average of two and one-half cleanings per catch-basin per year1 or #a cubic yards removed at each cleaning4 ,the #f1dcb catch-basins were inspected #ga1hij times4 ,there were #d1aab cubic yards of material removed from #eag miles of sewers1 or about #h cubic yards per mile4 ,inspection of #aid miles of brick sewers were made1 #d4d miles were flushed1 and #bg miles were cleaned4 ,inspections of #aih miles of pipe sewers were made1 #hj miles were examined more closely1 #cg miles were flushed1 and #ia miles were cleaned4 ,the field organization for this work consisted of #ag foremen1 #h assistant foremen1 #bi laborers1 #ga cleaners1 #ac mechanics1 #g inspectors of construction1 #c inspectors of sewer connections1 #ac horses and wagons1 and #bh horses and carts4#aje #aii4 ,causes of ,troubles4--,the complaints most frequently received about sewers are caused by clogging1 breakage of pipes1 and bad odors4 ,sewers become clogged by the deposition of sand and other detritus which results in the formation of pools in which organic matter deposits1 aggravating the clogged condition of the sewers and causing the odors complained of4 ,grease is a prolific cause of trouble4 ,it is discharged into the sewer in hot wastes1 and becoming cooled1 deposits in thick layers which may effectively block the sewer if not removed4 ,it can be prevented from entering the sewers by the installation of grease traps as described in ,chapter ,,vi4 ,the periodic cleaning of these traps is as important as their installation4 ,tree roots are troublesome1 particularly in small pipe sewers in residential districts4 ,roots of the ,north ,carolina poplar1 silver leaf poplar1 willow1 elm1 and other trees will enter the sewer through minute holes and may fill the sewer barrel completely if not cut away in time4 ,fungus growths occasionally cause trouble in sewers by forming a network of tendrils that catches floating objects and builds a barricade across the sewer4 ,difficulties from fungus growths are not common1 but constant attention must be given to the removal of grit1 grease1 and roots4 ,tarry deposits from gas-manufacturing plants are occasionally a cause of trouble1 as they cement the detritus already deposited into a tough and gummy mass that clings tenaciously to the sewer4 ,broken sewers are caused by excessive superimposed loads1 undermining1 and progressive deterioration4 ,the changing character of a district may result in a change of street grade1 an increase in the weight of traffic1 or in the construction of other structures causing loads upon the sewer for which it was not designed4 ,the presence of corrosive acids or gases may cause the deterioration of the material of the sewer4 #bjj4 ,inspection4--,the maintenance of a sewerage system is usually placed under the direction of a sewer department4 ,in the organization of the work of this department no regular routine of inspection of all sewers need be followed ordinarily4 ,attention should be given regularly to those sewers that are known to give trouble1 whereas the less troublesome sewers need not be inspected more frequently than once a year1 preferably during the winter when labor is easier to obtain4 ,the routine inspection of sewers too small to enter is made by an examination at the manhole4 ,if the water is running as freely at one manhole as at the next manhole above1 it is assumed that the sewer between the manholes is clean and no further inspection need be given unless there is some other reason to suspect clogging between manholes4 ,if the sewage is backed up in a manhole it indicates that there is an obstruction in the sewer below4 ,if the sewage in a manhole is flowing sluggishly and is covered with scum it is an indication of clogging1 slow velocity and septic action in the sewer4 ,sludge banks on the sloping bottom of the manhole or signs of sewage high upon the walls indicate an occasional flooding of the sewer due to inadequate capacity or clogging4 ,illustration3 ,,fig4 #adj4--;,inspecting ,sewers with ,reflected ,sunlight4 ,if any of the signs observed indicate that the sewer is clogged1 the manhole should be entered and the sewer more carefully inspected4 ,such inspection may be made with the aid of mirrors as shown in ,fig4 #adj or with a periscope device as shown in ,fig4 #ada4 ,sunlight is more brilliant than the electric lamp shown in ,fig4 #ada1 but the mirror in the manhole directs the sunlight into the eyes of the observer1 dazzling him and preventing a good view of the sides of the sewer4 ,the observers' eyes can be protected against the direct rays of the electric light1 which can be projected against the sides of the pipe by proper shades and reflectors4 ,it is possible with this device to locate house connection1 stoppages1 breaks of the pipe1 and to determine fairly accurately the condition of the sewer without discomfort to the observers4 ,sewers that are large enough to enter should be inspected by walking through them where possible4 ,the inspection should be conducted by cleaning off the sewer surface in spots with a small broom1 and examining the brick wall for loose bricks1 loose cement or cement lost from the joints1 open joints1 broken bond1 eroded invert1 and such other items as may cause trouble4 ,an inspection in storm sewers is sometimes of value in detecting the presence of forbidden house connections4 ,illustration3 ,,fig4 #ada4--;,inspecting ,sewers with ,periscope and ,electric ,light4 ,the ,g-,k ,system4 ,certain precautions should be taken before entering sewers or manholes4 ,if a distinct odor of gasoline is evident the sewer should be ventilated as well as possible by leaving a number of manhole covers open along the line until the odor of gasoline has disappeared4 ,the strength of gasoline odor above which it is unsafe to enter a sewer is a matter of experience possessed by few4 ,a slight odor of gasoline is evident in many sewers and indicates no special danger4 ,a discussion of the amount of gasoline necessary to create explosive conditions is given in ,art4 #bjf4 ,in making observations of the odor it should also be noted whether air is entering or leaving the manhole4 ,the presence of gasoline cannot be detected at a manhole into which air is entering4 ,as soon as it is considered that the odors from a sewer indicate the absence of an explosive mixture1 a lighted lantern or other open flame should be lowered into the manhole to test the presence of oxygen4 ,carbon monoxide or other asphyxiating gases may accumulate in the sewer1 and if present will extinguish the flame4 ,if the flame burns brilliantly the sewer is probably safe to enter1 but if conditions are unknown or uncertain1 the man entering should wear a life belt attached to a rope and tended by a man at the surface4 ,asphyxiating or explosive gases are sometimes run into without warning due to their lack of odor1 or the presence of stronger odors in the sewer4 ,breathing masks and electric lamps are precautions against these dangers1 the masks being ready for use only when actually needed4 ,more deaths have occurred in sewers due to asphyxiating gases than by explosions1 as the average sewer explosion is of insufficient violence to do great damage1 although on occasion1 extremely violent explosions have occurred4 ,during inspections of sewers there should always be at least one man at the surface to call help in case of accident and the inspecting party should consist of at least two men4 ,it must not be felt that entering sewers is fraught with great danger1 as it is perfectly safe to enter the average sewer4 ,the air is not unpleasant and no discomfort is felt1 but conditions are such that unexpected situations may arise for which the man in the sewer should be prepared4 ,it is therefore wise to take certain precautions4 ,these may indicate to the uninitiated1 a greater danger than actually exists4 ,the inspection of sewers should include the inspection of the flush-tanks1 control devices1 grit chambers1 and other appurtenances4 ,a common difficulty found with flush-tanks is that the tank is 8drooling10 that is to say the water is trickling out of the siphon as fast as it is entering the tank1 and the intermittency of the discharge has ceased4 ,if1 when the tank is first inspected the water is about at the level of the top of the bell it is probable that the siphon is drooling4 ,a mark should be made at the elevation of the water surface and the tank inspected again in the course of an hour or more4 ,if the water level is unchanged the siphon is drooling4 ,this may be caused by the clogging of the snift hole or by a rag or other obstacle hanging over the siphon which permits water to pass before the air has been exhausted1 or a misplacement of the cap over the siphon1 or other difficulty which may be recognized when the principle on which the siphon operates is understood4 ,occasionally it is discovered that an over zealous water department has shut off the service4 ,control devices1 such as leaping or overflow weirs1 automatic valves1 etc41 may become clogged and cease to operate satisfactorily4 ,they should be inspected frequently1 dependent upon their importance and the frequency with which they have been found to be inoperative4 ,an inspection will reveal the obstacle which should be removed4 ,floats should be examined for loss of buoyancy or leaks rendering them useless4 ,grit and screen chambers should be examined for sludge deposits4 ,catch-basins on storm sewers are a frequent cause of trouble and need more or less frequent cleaning4 ,cleanings are more important than inspections for catch-basins for if they are operating properly they are usually in need of cleaning after every storm of any magnitude1 and a regular schedule of cleaning should be maintained4 ,a record should be kept of all inspections made4 ,it should include an account of the inspection1 its date1 the conditions found1 by whom made and the remedies taken to effect repairs4 #bja4 ,repairs4--,common repairs to sewerage systems consist in replacing street inlets or catch-basin covers broken by traffic2 raising or lowering catch-basin or manhole heads to compensate for the sinking of the manhole or the wear of the pavement2 replacing of broken pipes1 loosened bricks or mortar which has dropped out2 and other miscellaneous repairs as the necessity may arise4 ,connections from private drains are a source of trouble because either the sewer or the drain has broken due to careless work or the settlement of the foundation or the backfill4 #bjb4 ,cleaning ,sewers4--,sewers too small to enter are cleaned by thrusting rods or by dragging through them some one of the various instruments available4 ,the common sewer rod shown in ,fig4 #adb is a hickory stick1 or light metal rod1 #c or #d feet long1 on the end of which is a coupling which cannot come undone in the sewer4 ,sections of the rod are joined in the manhole and pushed down the sewer until the obstruction is reached and dislodged4 ,occasionally pieces of pipe screwed together are used with success4 ,the end section may be fitted with a special cutting shoe for dislodging obstructions4 ,in extreme cases these rods may be pushed #djj to #ejj feet1 but are more effective at shorter distances4 ,obstructions may be dislodged by shoving a fire hose1 which is discharging water under high pressure through a small nozzle1 down the sewer toward the obstruction4 ,the water pressure stiffens the hose1 which1 together with the support from the sides of the conduit1 make it possible to push the hose in for effective work #ajj feet or more from the manhole4 ,a strip of flexible steel about inch thick and #a to #b inches wide is useful for 8rodding0 a short length of crooked sewer4 ,illustration3 ,,fig4 #adb4--,sewer ,rods ,sewers are seldom so clogged that no channel whatever remains4 ,as a sewer becomes more and more clogged1 the passage becomes smaller1 thereby increasing the velocity of flow of the sewage around the obstruction and maintaining a passageway by erosion4 ,this phenomenon has been taken advantage of in the cleaning of sewers by 8pills40 ,these consist of a series of light hollow balls varying in size4 ,one of the smaller balls is put into the sewer at a manhole4 ,when the ball strikes an obstruction it is caught and jammed against the roof of the sewer4 ,the sewage is backed up and seeks an outlet around the ball1 thus clearing a channel and washing the ball along with it4 ,the ball is caught at the next manhole below4 ,a net should be placed for catching the ball and a small dam to prevent the dislodged detritus from passing down into the next length of pipe4 ,the feeding of the balls into the sewer is continued1 using larger and larger sizes1 until the sewer is clean4 ,this method is particularly useful for the removal of sludge deposits1 but it is not effective against roots and grease4 ,the balls should be sufficiently light to float4 ,hollow metal balls are better than heavier wooden ones4 ,illustration3 ,,fig4 #adc4--;,cable and ,windlass ,method of ,cleaning ,sewers4 ,the cable is held to the bottom of the sewer by bracing a #b x #d upright in the sewer1 with a snatch block attached4 ,a trailer is attached to the scoop to prevent loss of material4 ,plows and other scraping instruments are dragged through pipe sewers to loosen banks of sludge and detritus and to cut roots or dislodge obstructions4 ,one form of plow consists of a scoop#ajf similar to a grocer's sugar scoop1 which is pushed or dragged up a sewer against the direction of flow4 ,as fast as the scoop is filled it is drawn back and emptied4 ,the method of dragging this through a sewer is indicated in ,fig4 #adc4 ,at ,atlantic ,city the crew operating the scoop comprises five men1 two are at work in each manhole and one on the surface to warn traffic and wait on the men in the manholes4 ,the outfit of tools is contained in a hand-drawn tool box and includes sewer rods1 metal scoops for all sizes of sewers1 picks1 shovels1 hatchets1 chisels1 lanterns1 grease and root cutters1 etc41 and two winches with from #djj to #fjj feet of -inch wire cable4 ,illustration3 ,,fig4 #add4--,sewer ,cleaning ,device4 ,eng4 ,news1 ,vol4 #db1 #ahii1 p4 #cbh4 ,illustration3 ,,fig4 #ade4--,tools for ,cleaning ,sewers4 ,illustration3 ,,fig4 #adf4--,turbine ,sewer ,machine ,connected to ,forcing ,jack4 ,the forcing jack is used when windlass and cable cannot be used4 ,courtesy1 ,the ,turbine ,sewer ,machine ,co4 ,another form of plow or drag consists of a set of hooks or teeth hinged to a central bar as shown in ,fig4 #add4 ,a root cutter and grease scraper in the form of a spiral spring with sharpened edges1 and other tools for cleaning sewers are shown in ,fig4 #ade4 ,a turbine sewer cleaner shown in ,fig4 #adf consists of a set of cutting blades which are revolved by a hydraulic motor of about #c horse-power under an operating pressure of about #fj pounds per square inch4 ,the turbine is attached to a standard fire hose and is pushed through the sewer by utilizing the stiffness of the hose1 or by rods attached to a pushing jack as shown in the figure4 ,this machine was invented and patented by ,w4 ,a4 ,stevenson in #aiad4 ,its performance is excellent4 ,the blades revolve at about #fjj ,r4,p4,m41 cutting roots and grease4 ,the revolving blades and the escaping water also serve to loosen and stir up the deposits and the forward helical motion imparted to the water is useful in pushing the material ahead of the machine and in scrubbing the walls of the sewer4 ,in ,milwaukee four men with the machine cleaned #cai feet of #ab-;inch sewer in #af hours1 and in ,kansas ,city #g1hja feet of sewers were cleaned in #ad days4 ,sewers large enough to enter may be cleaned by hand4 ,the materials to be removed are shoveled into buckets which are carried or floated to manholes1 raised to the surface and dumped4 ,in very large sewers temporary tracks have been laid and small cars pushed to the manhole for the removal of the material4 ,hydraulic sand ejectors may also be used for the removal of deposits1 similar to the steam ejector pump shown in ,fig4 #ig4 ,the water enters the apparatus at high velocity1 under a pressure of about #fj pounds per square inch1 leaps a gap in the machine from a nozzle to a funnel-shaped guide leading to the discharge pipe4 ,the suction pipe of the machine leads to the chamber in which the leap is made4 ,in leaping this gap the water creates a vacuum that is sufficient to remove the uncemented detritus large enough to pass through the machine1 and will lift small stones to a height of #aj to #ab feet4 ,occasionally barricades of logs1 tree branches1 rope1 leaves1 and other obstructions which have piled up against some inward projecting portion of the sewer1 must be removed by hand either by cutting with an axe or by pulling them out4 ,projections from the sides of sewers are objectionable because of their tendency to catch obstacles and form barricades4 ,little authentic information on the cost of cleaning sewers is available4 ,a permanent sewer organization is maintained by many cities4 ,the division of their time between repairs1 cleaning1 and other duties is seldom made a matter of record4 ,from data published in ,public ,works#ajg it is probable that the cost varies from #c to #ae per cubic yard of material removed4 ,from the information in ,vol4 ,,ii of 8,american ,sewerage ,practice0 by ,metcalf and ,eddy the combined cost of cleaning and flushing will vary between #aj and #dj per mile2 the expense of either flushing or cleaning alone being about one-half of this4 #bjc4 ,flushing ,sewers4--,sewers can sometimes be cleaned or kept clean by flushing4 ,flushing may be automatic and frequent1 or hand flushing may be resorted to at intervals to remove accumulated deposits4 ,automatic flush-tanks1 flushing manholes1 a fire hose1 a connection to a water main1 a temporary fixed dam1 a moving dam1 and other methods are used in flushing sewers4 ,the design1 operation1 and results obtained from the use of automatic flush-tanks and flushing manholes are discussed in ,chapter ,,vi4 ,the method in use for cleaning a sewer by thrusting a fire hose down it can also be used for flushing sewers4 ,it is an inexpensive and fairly satisfactory method4 ,there is1 however1 some danger of displacing the sewer pipe because of the high velocity of the water4 ,an easier and safer but less effective method is to allow water to enter at the manhole and flow down the sewer by gravity4 ,direct connections to the water mains are sometimes opened for the same purpose4 ,sewers are sometimes flushed by the construction of a temporary dam across the sewer1 causing the sewage to back up4 ,when the sewer is half to three-quarters full the dam is suddenly removed and the accumulated sewage allowed to rush down the sewer1 thus flushing it out4 ,the dam may be made of sand bags1 boards fitted to the sewer1 or a combination of boards and bags4 ,the expense of equipment for flushing by this method is less than that by any other method1 but the results obtained are not always desirable4 ,below the dam the results compare favorably with those obtained by other methods1 but above the dam the stoppage of the flow of the sewage may cause depositions of greater quantities of material than have been flushed out below4 ,a time should be chosen for the application of this method when the sewage is comparatively weak and free from suspended matter4 ,the most convenient place for the construction of a dam is at a manhole in order that the operator may be clear of the rush of sewage when the dam is removed4 ,movable dams or scrapers are useful in cleaning sewers of a moderate size1 but are of little value in small sewers4 ,the scraper fits loosely against the sides of the sewer and is pushed forward by the pressure of the sewage accumulated behind it4 ,the iron-shod sides of the dam serve to scrape grease and growths attached to the sewer and to stir up sand and sludge deposited on the bottom4 ,the high velocity of the sewage escaping around the sides of the dam aids in cleaning and scrubbing the sewer4 ,a natural watercourse may be diverted into the sewer if topographical conditions permit1 or where sewers discharge into the sea below high tide a gate may be closed during the flood and held closed until the ebb4 ,the rush of sewage on the opening of the gate serves to flush the sewers and stir up the sludge deposited during high tide4 ,other methods of flushing sewers may be used dependent on the local conditions and the ingenuity of the engineer or foreman in charge4 ,in some sewers it is not necessary to remove the clogging material from the sewer4 ,it is sufficient to flush and push it along until it is picked up and carried away by higher velocities caused by steeper grades or larger amounts of sewage4 #bjd4 ,cleaning ,catch-basins4#ajh--;,catch-basins have no reason for existence if they are not kept clean4 ,their purpose is to catch undesirable settling solids and to prevent them from entering the sewers1 on the theory that it is cheaper to clean a catch-basin than it is to clean a sewer4 ,if the cleaning of storm sewers below some inlet to which no catch-basin is attached becomes burdensome1 the engineer in charge of maintenance should install an adequate catch-basin and keep it clean4 ,catch-basins are cleaned by hand1 suction pumps1 and grab buckets4 ,in cleaning by hand the accumulated water and sludge are removed by a bucket or dipper and dumped into a wagon from which the surplus settled water is allowed to run back into the sewer4 ,the grit at the bottom of the catch-basin is removed by shoveling it into buckets which are then hoisted to the surface and emptied4 ,suction pumps in use for cleaning catch-basins are of the hydraulic eductor type4 ,the eductor works on the principle of the steam pump shown in ,fig4 #ig1 except that water is used instead of steam4 ,the material removed may be discharged into settling basins constructed in the street1 or may be discharged directly into wagons4#aji ,in ,chicago a special motor-driven apparatus is used4 ,this consists of a #e-yard body on a #e-ton truck1 and a centrifugal pump driven by the truck motor4 ,in use1 the truck1 about half filled with water1 drives up to the catch-basin1 the eductor pipe is lowered and water pumped from the truck into the eductor and back into the truck again1 together with the contents of the catch-basin4 ,the surplus water drains back into the sewer4 ,the ,chicago ,bureau of ,sewers reports a truck so equipped to have cleaned #ajac catch-basins1 removing #agfc cubic yards of material1 and running #achj miles1 during the months of ,august1 ,september and ,october1 #aiag4 ,the cost1 including all items of depreciation1 wages1 repairs1 etc41 was #a1cic4hi4 ,orange-peel buckets1 about #bj inches in diameter1 operated by hand or by the motor of a #c to #e-ton truck with a water-tight body1 are used for cleaning catch-basins in some cities4 ,catch-basins in unpaved streets and on steep sandy slopes should be cleaned after every storm of consequence4 ,basins which serve to catch only the grit from pavement washings require cleaning about two or three times per year1 and from one to three cubic yards of material are removed at each cleaning4 ,the cost of cleaning ordinary catch-basins by hand may vary from #ae to #be1 but with the use of eductors or orange-peel buckets the cost is somewhat lower4 ,in ,seattle the cost of cleaning large detritus basins by hand is said#aaj to vary from #de to #fj4 ,with the use of eductors this cost has been reduced to one-third or one-fifth the cost of cleaning by hand4 #bje4 ,protection of ,sewers4#aaa--;,city ordinances should be wisely drawn and strictly enforced for the protection of sewers against abuse and destruction4 ,the requirements of some city ordinances are given in the following paragraphs4 ,washington1 ,d4 ,c41#aab sewer ordinances provide that3 ,no person shall make or maintain any connection with any public sewer or appurtenance thereof whereby there may be conveyed into the same any hot1 suffocating1 corrosive1 inflammable or explosive liquid1 gas1 vapor1 substance or material of any kind 444 provided that the provisions of this act shall not apply to water from ordinary hot water boilers or residences4 ,the following extracts from the ordinances of ,indianapolis are typical of those from many cities3 #biej4 ,no connection shall be made with any public sewer without the written permission of the ,committee on ,sewers and the ,sewerage ,engineer4 #biec4 ,no person shall be authorized to do the work of making connections until he has furnished a satisfactory certificate that he is qualified for the duties4 ,he shall also file bond for not less than #a1jjj that he will indemnify the ,city from all loss or damage that may result from his work and that he will do the work in conformity to the rules and regulations established by the ,city ,council4 #biee4 ,it shall be unlawful for any person to allow premises connected to the sewers or drains to remain without good fixtures so attached as to allow a sufficiency of water to be applied to keep the same unobstructed4 #bief4 ,no butcher's offal or garbage1 or dead animals1 or obstructions of any kind shall be thrown in any receiving basin or sewer in penalty not greater than #ajj4 ,any person injuring1 breaking1 or removing any portion of any receiving basin1 manhole cover1 etc41 shall be fined not more than #ajj4 #bifb4 ,no person shall drain the contents of any cesspool or privy vault into any sewer without the permission of the ,common ,council4 ,the ,cleveland ordinances are similar and contain the following in addition3 #abea4 ,rule #d4 ,all connections with the main or branch sewers shall be made at the regular connections or junctions built into the same1 except by special permit4 ,rule #af4 ,no steam pipe1 nor the exhaust1 nor the blow off from any steam engine shall be connected with any sewer4 ,evanston1 ,illinois1 protects its sewers against the additions of grease and other undesirable substances as follows3 #addd4 ,it is unlawful for any person to use any sewer or appurtenance to the sewerage system in any manner contrary to the orders of the ,commissioner of ,public ,works4 #addf4 ,wastes from any kitchen sinks1 floor drains1 or other fixtures likely to contain greasy matter from hotels1 certain apartment houses1 boarding houses1 restaurants1 butcher shops1 packing houses1 lard rendering establishments1 bakeries1 laundries1 cleaning establishments1 garages1 stables1 yard and floor drains1 and drains from gravel roofs shall be made through intervening receiving basins constructed as prescribed in par4 ,,viii of this code4 ,receiving basins suitable for the work required in the code are illustrated in ,chapter ,,vi4 #bjf4 ,explosions in ,sewers4--,disastrous explosions in sewers were first recorded about #ahhf4aac ,up to about #aije explosions were infrequent and were considered as unavoidable accidents and so rare as to be unworthy of study4 ,for a decade or more after #aije explosions occurred with increasing violence and frequency causing destruction of property1 but by some freakish chance1 but little loss of life4 ,a violent and destructive explosion occurred in ,pittsburgh on ,nov4 #be1 #aiac1aad and another on ,march #ab1 #aiaf4 ,the property damage amounted to #cjj1jjj to #ejj1jjj on each occasion1 but there was no loss of life4 ,two miles of pavement were ripped up1 gas1 water1 and other sewer pipes were broken1 buildings collapsed and the streets were flooded4 ,the streets were rendered unserviceable for long periods during the expensive repairs that were necessary4 ,in recent years the number of explosions in sewers has been smaller1 due probably to the gain in knowledge of the causes and intelligent methods of prevention4 ,the three principal causes of explosions in sewers are3 gasoline vapor1 illuminating gas1 and calcium carbide4 ,it is probable that gasoline vapor is by far the most troublesome4 ,explosions caused by these gases are not so violent as those caused by dynamite or other high explosives1 as the volume of gas and the temperature generated are much less4 ,the violence of sewer explosions may be increased somewhat by the sudden pressures that are put upon them4 ,gasoline finds its way into sewers from garages and cleaning establishments4 ,a mixture of #a per cent gasoline vapor and air may be explosive4 ,it needs only the stray spark of an electric current1 a lighted match1 or a cigar thrown into the sewer to cause the explosion4 ,as the result of a series of experiments on #b1gjf feet of #h-;foot sewer1 ,burrell and ,boyd conclude4#aae ,one gallon of gasoline if entirely vaporized produces about #cb cubic feet of vapor at ordinary temperature and pressure4 ,if #a per cent be adopted as the low explosive limit of mixtures of gasoline vapor and air1 #ee gallons or a barrel of gasoline would produce enough vapor to render explosive the mixture in #a1ijj feet of #i foot sewer provided the gasoline and the air were perfectly mixed4 ,many different factors1 however1 govern explosibility1 such as3 size of the sewer1 velocity of the sewage1 temperature of the sewer1 volatility and rate of inflow of the gasoline4 ,only under identical conditions of tests would duplicate results be obtained4 ,a large amount of gasoline poured in at one time is less dangerous than the same amount allowed to run in slowly4 ,with a velocity of flow of about #f feet per second it was evident that #ee gallons of gasoline poured all at once into a manhole rendered the air explosive only a few minutes 7less than #aj7 at any particular point4 ,with the same amount of gasoline run in at the rate of #e gallons per minute1 an explosive flame would have swept along the sewer if ignited #ae minutes after the gasoline had been dumped4 ,with a slow velocity of flow and a submerged outlet the gasoline vapor being heavier than air accumulated at one point and extremely explosive conditions could result from a small amount of gasoline4 ,comparatively rich explosive mixtures were found #e hours after the gasoline had been discharged4 ,high-test gasoline is much more dangerous than the naphtha used in cleaning establishments1 yet on account of the large quantity of waste naphtha the sewage from cleaning establishments may be very dangerous4 ,illuminating gas is not so dangerous as gasoline vapor as it is lighter than air and it is more likely to escape from the sewer than to accumulate in it4 ,it requires about one part of illuminating gas to seven parts of air to produce an explosive mixture4 ,calcium carbide is dangerous because it is self igniting4 ,the heat of the generation of gas is sufficient to ignite the explosive mixture4 ,the gases are highly explosive and cause a relatively powerful explosion4 ,fortunately large amounts of this material seldom reach a sewer1 the gas being generated in garage drains or traps and escaping in the atmosphere4 ,a hydrocarbon oil used by railroads in preventing the freezing of switches1 if allowed to reach the sewers1 may cause explosions therein4#aaf ,the oil crystallizes and in this form it is soluble in water4 ,it will thus pass traps and on volatilization will produce explosive mixtures4 ,methane1 generated by the decomposition of organic matter1 is a feebly explosive gas occasionally found in sewers4 ,its presence may add to the strength of other explosive mixtures4 ,sewer explosions may be prevented by the building of proper forms of intercepting basins to prevent the entrance of gasoline and calcium carbide gases1 and by ventilation to dilute the explosive mixtures which may be made up in the sewer4 ,there are no practical means to predict when an explosion is about to occur1 and after an explosion has occurred it is difficult to determine the cause as all evidence is usually destroyed4 #bjg4 ,valuation of ,sewers4--,the necessity for the valuation of a sewerage system may arise from the legal provisions in some states limiting the amount of outstanding bonds which may be issued by a municipality to a certain percentage of the present worth of municipal property4 ,the investment in the sewerage system is usually great and forms a large portion of the ,city's tangible property4 ,it may be desirable also to determine the depreciation of the sewers with a view towards their renewal4 ,the most valuable work on the valuation of sewers has been done in ,new ,york ,city#aag by the engineers of the ,sewer ,department4 ,the committee of engineers appointed to do the work recommended3 7#a7 that the original cost be made the basis of valuation1 and that 7#b71 in fixing this cost the cost of pavement should be omitted or at most the cost of a cheap 7cobblestone7 pavement should be included4 ,trenches previously excavated in rock were considered as undepreciated assets4 ,the present worth of sewers depends on many factors aside from the effects of age1 such as the care exercised in the original construction1 the material used1 the kind and quantity of sewage carried1 the care taken in maintenance1 and finally the injury caused by the careless building of adjoining substructures4 ,during the progress of the inspections the examination of brick sewers1 due to their accessibility1 yielded better results than the examination of pipe sewers4 ,the routine of the examination of the brick sewers consisted in cleaning off the bricks with a short broom1 tapping the brick with a light hammer to determine solidity1 and testing the cement joints by scraping with a chisel4 ,in addition1 measurements of height and width were taken every #cj feet4 ,the bricks in the invert at and below the flow line were examined for wear4 ,a study of the reports of these examinations disclosed that the following defects were noticeable3 #a4 ,cement partly out at water line4 #b4 ,cement partly out above water line4 #c4 ,depressed arch and sewer slightly spread4 #d4 ,large open joints4 #e4 ,loose brick4 #f4 ,bond of brick broken4 #g4 ,distorted sides1 uneven bottom1 joints out of line4 ,illustration3 ,,fig4 #adg4--;,diagrams used in ,estimating ,depreciation of ,brick ,sewers ,due to ,age1 ,manhattan ,borough1 ,new ,york ,city4 a4 ,proportionate deterioration from various causes4 b4 ,percentage of depreciation based on examination of sewers1 use of deterioration curve 7,fig4 a71 and age of sewers examined4 ,eng4 ,news1 ,vol4 #ga1 p4 #hd4 ,inspection of pipe sewers from manholes1 the pipe being illuminated by floating candles1 was found to be unsatisfactory4 ,reliance was placed on the reports of men experienced in making connections and repairs to the sewers4 ,early pipe sewers in ,new ,york were laid directly on the bottom of the trench4 ,under these circumstances a small leak at a joint was sufficient to wash the earth away and to drop the pipe1 causing serious conditions along the line4 ,no wear or deterioration of pipe sewers were noted1 the only defects being cracking of the pipes at the center line due to poor foundation and to defects in the pipe itself4 ,illustration3 ,,fig4 #adh4--;,diagram ,showing ,rate of ,depreciation of ,pipe ,sewers4 ,eng4 ,news1 ,vol4 #ga1 p4 #hf4 ,the depreciation of brick sewers as studied in ,new ,york1 is shown graphically in ,fig4 #adg4 ,at zero the sewer is in good condition and at #ajj it is in such a state of dilapidation as to require instant rebuilding4 ,repairs are not considered economical in this condition4 ,in the preparation of this diagram each condition on the list above was given a certain number of points1 which when added together represented the state of depreciation of the sewer4 ,these sums were plotted as ordinates and the corresponding ages of the sewer were plotted as abscissas4 ,the various points were taken cumulatively1 and where the bond of the brickwork was broken 7given a value of #gb7 plus other defects gave a total of #afd the sewer was considered as valueless and not worth repair4 ,the scale of #afd was later reduced to a percentage basis as shown on the right of the figure4 ,fig4 #adh shows a similar diagram for the depreciation of pipe sewers4 ,it was concluded that the life of a brick sewer in ,new ,york is #fd years4 ,some of the sewers examined were over #bjj years old4 ,the total original cost of #dhc miles of brick1 pipe and wood sewers was figured as #bc1hhj1jjj with a present worth of #ah1ffe1jjj and an average annual depreciation of #b4b per cent4 ,in figuring these amounts no account was taken of obsolescence4 ,the deterioration of catch-basins proceeded at about the same rate as for brick sewers4 ,,chapter ,,xiii ,,composition ,,and ,,properties ,,of ,,sewage #bjh4 ,physical ,characteristics4--,sewage is the spent water supply of a community containing the wastes from domestic1 industrial1 or commercial use1 and such surface and ground water as may enter the sewer4#aah ,sewages are classed as3 domestic sewage1 industrial waste1 storm water1 surface water1 street wash1 and ground water4 ,domestic sewage is the liquid discharged from residences or institutions and contains water closet1 laundry1 and kitchen wastes4 ,it is sometimes called sanitary sewage4 ,industrial sewage is the liquid waste resulting from processes employed in industrial establishments4 ,storm water is that part of the rainfall which runs over the surface of the ground during a storm and for such a short period following a storm as the flow exceeds the normal and ordinary run-off4 ,surface water is that part of the rainfall which runs over the surface of the ground some time after a storm4 ,street wash is the liquid flowing on or from the street surface4 ,ground water is water standing in or flowing through the ground below its surface4 ,ordinary fresh sewage is gray in color1 somewhat of the appearance of soapy dish water4 ,it contains particles of suspended matter which are visible to the naked eye4 ,if the sewage is fresh the character of some of the suspended matter can be distinguished as3 matches1 bits of paper1 fecal matter1 rags1 etc4 ,the amount of suspended matter in sewage is small1 so small as to have no practical effect on the specific gravity of the liquid nor to necessitate the modification of hydraulic formulas developed for application to the flow of water4 ,the total suspended matter in a normal strong domestic sewage is about #ejj parts per #a1jjj1jjj4 ,it is represented graphically in ,fig4 #adi4 ,the quantity of organic or volatile suspended matter is about #bjj parts per #a1jjj1jjj4 ,it is shown graphically in the smaller cube in ,fig4 #adi4 ,illustration3 ,,fig4 #adi4--;,graphical ,representation of ,relative ,volumes of ,liquids and ,solids in ,sewage4 ,the odor of fresh sewage is faint and not necessarily unpleasant4 ,it has a slightly pungent odor1 somewhat like a damp unventilated cellar4 ,occasionally the odor of gasoline1 or some other predominating waste matter may hide all other odors4 ,stale sewage is black and gives off nauseating odors of hydrogen sulphide and other gases4 ,if the sewage is so stale as to become septic1 bubbles of gas will be seen breaking the surface and a black or gray scum may be present4 ,before the ,south ,branch of the ,chicago ,river was cleaned up and flushed this scum became so thick in places1 particularly in that portion of the ,stock ,yards where the river became known as ,bubbly ,creek1 that it is said that weeds and small bushes sprouted in it1 and chickens and small animals ran across its surface4 ,a physical analysis of sewage should include an observation of its appearance1 and a determination of its temperature1 turbidity1 color1 and odor1 both hot and cold4 ,the temperature is useful in indicating certain of the antecedents of the sewage1 its effect on certain forms of bacterial life1 and its effect on the possible content of dissolved gases4 ,temperatures higher than normal are indicative of the presence of trades wastes discharged while hot into the sewers4 ,a low temperature may indicate the presence of ground water4 ,if the temperature is much over #dj ,c4 bacterial action will be inhibited and the content of dissolved gases will be reduced4 ,turbidity1 color1 and odor determinations may be of value in the control of treatment devices1 or to indicate the presence of certain trades wastes1 which give typical reactions4 ,since all normal sewages are high in color and turbidity1 the relative amounts of these two constituents in two different sewages has little significance regarding the relative strengths of the two sewages or the proper method of treating them4 ,a fresh domestic sewage should have no highly offensive odor4 ,the presence of certain trades wastes can be detected sometimes in fresh sewages1 and a stale sewage may sometimes be recognized by its odor4 ,sewage is a liability to the community producing it4 ,although some substances of value can be obtained from sewage#aai the cost of the processes usually exceed the value of the substances obtained4 ,where it becomes necessary to treat sewage the value of these substances may be helpful in defraying the cost of treatment4 #bji4 ,chemical ,composition4--,sewage is composed of mineral and organic compounds which are either in solution or are suspended in water4 ,in making a standard chemical analysis of sewage only those chemical radicals and elements are determined which are indicative of certain important constituents4 ,neither a complete qualitative nor quantitative analysis is made4 ,a sewage analysis will not show1 therefore1 the number of grams of sodium chloride present or any other constituent4 ,a complete standard sanitary chemical analysis will report the constituents as named in the first column of ,table #ga4 ,the quantities of these materials found in average strong1 medium and weak sewages are also shown in this table4 ,these values are not intended as fixed boundaries between sewages of different strengths4 ,they are presented merely as a guide to the interpretation of sewage analyses4 ,the principal objects of a chemical analysis of sewage are to determine its strength and its state of decomposition4 ,the influents and effluents of a sewage treatment device are analyzed to aid in the control of the device and to gain information concerning the effect of the treatment4 ,chemical and other analyses1 in connection with the desired conditions after disposal1 will indicate the extent of treatment which may be required4 ,the standard methods of water and sewage analysis adopted by the ,american ,public ,health ,association have been generally accepted by sanitarians4 ,these uniform methods make possible comparisons of the results obtained by laboratories working according to these standards4 ,,chemical ,,analysis ,,of ,,sewages 7,parts per million7 ,from ,report on ,industrial ,wastes from the ,stock ,yards and ,packingtown1 ,chicago by the ,sanitary ,district of ,chicago in #aiba1 page #bca4 ,waterbury1 ,boston ,columbus ,conn41 ,typical ,analyses #aije-g #aijd-e #aije-f ,strong,medium,weak ,nitrogen as ,organic ,nitrogen #ce #bj #aj #i4a #i4j #ad4h ,free ,ammonia #ej #cj #ae #ac4i #aa4j #g4h ,nitrites #j4aj #j4je #j4j #j4j #j4ji #j4ad ,nitrates #j4dj #j4bj #j4a #j4bj #j4bj #a4eb ,oxygen consumed #ge #ej #cjefabj #eaaba #dfabj ,oxygen demand #cjj #bjj #ajj ,chlorine #age #ajj #ae #bcjj #fe #dh ,suspended matter #ejj #cjj #aej #ace #bji #afe ,volatile #ia #gi #aae ,fixed #dd #acj #ej ,alkalinity #bjj #ajj #ej #abe #cej #da ,fats #dj #bj #be #bf ,chicago1 ,center ,chicago1 ,avenue4 ,gloversville1,worcester1 #cith ,st4 ,industrial4 ,n4 ,y4 ,mass4 ,residential,day ,sewage #aijh-i #aijh #aiji-ab #aiac ,nitrogen as ,organic ,nitrogen #bc4j #g4h #gi ,free ,ammonia #ab4j #bb4b #i4a #bb ,nitrites #j4ch #j4aj #j4di ,nitrates #j4hh #j4cc #c4jd ,oxygen consumed #ieabj #aag #dc #bfh ,oxygen demand ,chlorine #aeh #eg #dj #aajj ,suspended matter #djf #beh #add #fje ,volatile #bbi #aff #ij #df ,fixed #agg #ib #ed #add ,alkalinity #bcc #bab #bia ,fats #dh #bcabb #aihabc #baj4 ,significance of ,chemical ,constituents4--,organic nitrogen and free ammonia taken together are an index of the organic matter in the sewage4 ,organic nitrogen includes all of the nitrogen present with the exception of that in the form of ammonia1 nitrites1 and nitrates4 ,free ammonia or ammonia nitrogen is the result of bacterial decomposition of organic matter4 ,a fresh cold sewage should be relatively high in organic nitrogen and low in free ammonia4 ,a stale warm sewage should be relatively high in free ammonia and low in organic nitrogen4 ,the sum of the two should be unchanged in the same sewage4 ,nitrites 7,,rno#b7 and nitrates 7,,rno#c7abd are found in fresh sewages only in concentrations of less than one part per million4 ,in well-oxidized effluents from treatment plants the concentration will probably be much higher4 ,nitrates contain one more atom of oxygen than nitrites4 ,they represent the most stable form of nitrogenous matter in sewage4 ,nitrites are not stable and are reduced to ammonias or are oxidized to nitrates4 ,their presence indicates a process of change4 ,they are not found in large quantities in raw sewage because their formation requires oxygen which must be absorbed from some other source than the sewage4 ,in an ordinary sewer or sluggishly flowing open stream this absorption cannot take place from the atmosphere with sufficient rapidity to supply the necessary oxygen4 ,oxygen consumed is an index of the amount of carbonaceous matter readily oxidizable by potassium permanganate4 ,it does not indicate the total quantity of any particular constituent1 but it is the most useful index of carbonaceous matter4 ,carbonaceous matter is usually difficult of treatment and a high oxygen consumed is indicative of a sewage difficult to care for4 ,the amount of oxygen consumed1 as expressed in the analysis1 is dependent on the amount of oxidizable carbonaceous matter present1 the oxidizing agent used1 and the time and temperature of contact of the sewage and the oxidizing agent4 ,it is essential therefore that the test be conducted according to some standard method1 since the results are of value only as compared with results obtained under similar conditions4 ,total solids 7residue on evaporation7 are an index of the strength of the sewage4 ,they are made up of organic and inorganic substances4 ,the inorganic substances include sand1 clay1 and oxides of iron and aluminum1 which are usually insoluble1 and chlorides1 carbonates1 sulphates and phosphates1 which are usually soluble4 ,the insoluble inorganic substances are undesirable in sewage because of their sediment forming properties which result in the clogging of sewers1 treatment plants1 pumps1 and stream beds4 ,the soluble inorganic substances are generally harmless and cause no nuisance1 except that the presence of sulphur may permit the formation of hydrogen sulphide1 which has a highly offensive odor4 ,the organic substances are3 carbohydrates1 fats1 and soaps1 which are carbonaceous and are difficult of removal by biological processes2 and the nitrogenous substances such as urea1 proteins1 amines1 and amino acids4 ,the inorganic and organic substances may be either in solution or suspension or in a colloidal condition4 ,volatile solids are used as an index of the organic matter present1 as it is assumed that the organic matter is more easily volatilized than the inorganic matter4 ,the amount of volatile inorganic matter present is usually so small as to be negligible4 ,fixed solids are reported as the difference between the total and volatile solids4 ,they are therefore representative of the amount of inorganic matter present4 ,suspended matter is the undissolved portion of the total solids4 ,high volatile suspended matter is an indication of offensive qualities in the nature of putrefying organic matter1 whereas fixed suspended matter is indicative of inoffensive inorganic matter4 ,it is difficult to obtain a sample of sewage which will represent the amount of suspended matter in the sewage1 since a sample taken from near the surface will contain less inorganic matter and grit than a sample taken near the bottom4 ,settling solids are indicative of the sludge forming properties of the sewage and of the probable degree of success of treatment by plain sedimentation4 ,volatile settling solids indicate the property of the formation of offensive putrefying sludge banks4 ,there is no chemical test which will indicate the scum-forming properties of sewage4 ,fixed settling solids indicate the presence of inorganic matter1 probably gritty material such as sand1 clay1 iron oxide1 etc4 ,colloidal matter is material which is too finely divided to be removed by filtration or sedimentation1 yet is not held in solution4 ,it can sometimes be removed by violent agitation in the presence of a flocculent precipitate1 as in the treatment with activated sludge1 or by the flocculent precipitate alone1 as in chemical precipitation1 or by the acidulation of the sewage so as to precipitate the colloids4 ,colloidal matter is probably the result of the constant abrasion of finely divided suspended matter while flowing through the sewer or other channel4 ,high colloidal matter may therefore indicate a stale sewage1 or the presence of a particular trades waste4 ,colloids are difficult of removal4 ,for this reason1 where sewage is to be treated1 turbulence in the tributary channels should be avoided4 ,alkalinity may indicate the possibility of success of the biologic treatment of sewage1 since bacterial life flourishes better in a slightly alkaline than in a slightly acid sewage4 ,within the normal limits of the amount of alkalinity in sewage the exact amount has little significance in sewage analyses4 ,sewages are normally slightly alkaline4 ,an abnormal alkalinity or acidity may indicate the presence of certain trades wastes necessitating special methods of treatment4 ,a method of sewage treatment may be successful without changing the amount of alkalinity in the sewage since the amount of alkalinity is not inherently an objection4 ,chlorine1 in the form of sodium chloride1 is an inorganic substance found in the urine of man and animals4 ,the amount of chlorine above the normal chlorine content of pure waters in the district is used as an index of the strength of the sewage4 ,the chlorine content may be affected by certain trades wastes such as ice-cream factories1 meat-salting plants1 etc41 which will increase the amount of chlorine materially4 ,since chlorine is an inorganic substance which is in solution it is not affected by biological processes nor sedimentation4 ,its diminution in a treatment plant or in a flowing stream is indicative of dilution and the reduction of chlorine will be approximately proportional to the amount of dilution4 ,fats have a recoverable market value when present in sufficient quantity to be skimmed off the surface of the sewage4 ,ordinarily fats are an undesirable constituent of sewage as they precipitate on and clog the interstices in filtering material1 they form objectionable scum in tanks and streams1 and they are acted on very slowly by biological processes of sewage treatment4 ,although fats are carbonaceous matter they are not indicated by the oxygen consumed test because they are not easily oxidized4 ,they are therefore determined in another manner2 by evaporation of the liquid and extracting the fats from the residue by dissolving them in ether4 ,relative stability and bio-chemical oxygen demand are the most important tests indicating the putrefying characteristics of sewage4 ,since stability and putrescibility have opposite meanings the relative stability test is sometimes called the putrescibility test4 ,the relative stability of a sewage is an expression for the amount of oxygen present in terms of the amount required for complete stability4 ,a relative stability of #ge signifies that the sample examined contains a supply of available oxygen equal to #ge per cent of the amount of oxygen which it requires in order to become perfectly stable4 ,the available oxygen is approximately equivalent to the dissolved oxygen plus the available oxygen of nitrate and nitrite4#abe ,,table #gb ,,relative ,,stability ,,numbers ,time ,required for ,decolorization at #bj ,c4 ,days ,relative ,stability ,number #j4e #aa #a4j #ba #a4e #cj #b4j #cg #b4e #dd #c4j #ej #d4jabf #fj #e4j #fh #f4j #ge #g4j #hj #h4j #hd #i4j #hg #aj4j #ij #aa4j #ib #ab4j #id #ac4j #ie #ad4j #if #af4j #ig #ah4j #ih #bj4j #ij ,the relative stability numbers1 given in ,table #gb1 are computed from the expression1 ,s #ajj7a #j4gidt7 in which ,s is the stability number and t is the time in days that the sample has been incubated at #bj ,c4 ,the bio-chemical oxygen demand is more directly an index of the consumption of available oxygen by the biological and chemical changes which take place in the decomposition of sewage or polluted water4 ,as such it is a more valuable1 though less easily performed test than the test of relative stability4 ,the methods for the determination of the relative stability and the bio-chemical oxygen demand are given to show more clearly what these tests represent4 ,the procedure in the relative stability test is to add #j4d c4c4 of a standard solution of methylene blue to #aej c4c4 of the sample4 ,the mixture is then allowed to stand in a completely filled and tightly stoppered bottle at #bj ,c4 for #bj days or until the blue fades out due to the exhaustion of the available oxygen4 ,there are three methods in use for the determination of the bio-chemical oxygen demand2#abg the relative stability method1 the excess nitrate method1 and the excess oxygen method4 ,in the relative stability method the sample to be treated should have a relative stability of at least #ej4 ,if it is lower than this the sample should be diluted with water containing oxygen until the relative stability has been raised to or above this point4 ,the oxygen demand in parts per million is then expressed as ,o 77#a ,p7,o7,,rp1#abh in which ,o is the oxygen demand1 ,o is the initial oxygen in parts per million 7p4p4m47 in the diluting water or sewage1 ,p is the proportion of sewage in the mixture expressed as a ratio1 and ,r is the relative stability of the mixture expressed as a decimal4 ,for the effluents from sewage treatment plants1 polluted waters1 and similar liquids1 the total available oxygen expressed as the sum of the dissolved oxygen1 nitrites1 and nitrates1 divided by the relative stability expressed as a decimal will give the bio-chemical oxygen demand4 ,the excess nitrate method requires the determination of the total oxygen available as dissolved oxygen1 nitrites1 and nitrates and the addition of a sufficient amount of oxygen in the form of sodium nitrate to prevent the exhaustion of oxygen during a #aj-;day period of incubation4 ,at the end of the period the total available oxygen is again determined4 ,the difference between the original and the final oxygen content represents the bio-chemical oxygen demand4 ,the excess oxygen test requires the determination of the total available oxygen as before1 and the addition of a sufficient amount of oxygen1 in the form of dissolved oxygen in the diluting water1 to prevent exhaustion of the oxygen in a #aj-;day period of incubation4 ,the difference between the original and final oxygen content represents the bio-chemical oxygen demand4 ,theriault concludes as a result of his tests1 that the relative stability and excess nitrate methods are open to objections but that the excess oxygen method yields very accurate and consistent results with as little or less labor than is required by other methods4 ,dissolved oxygen represents what its name implies1 the amount of oxygen 7,o#b7 which is dissolved in the liquid4 ,normal sewage contains no dissolved oxygen unless it is unusually fresh4 ,it is well1 if possible1 to treat a sewage before the original dissolved oxygen has been exhausted4 ,normal pure surface water contains all of the oxygen which it is capable of dissolving1 as shown in ,table #gc4 ,the presence of a smaller amount of oxygen than is shown in this table indicates the presence of organic matter in the process of oxidation1 which may be in such quantities as ultimately to reduce the oxygen content to zero4 ,normal pure ground waters may be deficient in dissolved oxygen because of the absence of available oxygen for solution4 ,the presence of certain oxygen-producing organisms in polluted or otherwise potable surface waters may cause a supersaturation with oxygen however4 ,the dissolved-oxygen test for polluted water is probably the most significant of all tests4 ,if dissolved oxygen is found in a polluted water it means that putrefactive odors will not occur1 since putrefaction cannot begin in the presence of oxygen4 ,it is possible for different strata in a body of water to have different quantities of dissolved oxygen1 and putrefaction may be proceeding in the lower strata before the oxygen is exhausted from the upper strata4 ,the oxygen content of a river water will indicate the ability of the river to receive sewage without resulting in a nuisance4 ,,table #gc ,,solubility ,,of ,,oxygen ,,in ,,water ,under an atmospheric pressure of #gfj mm4 of mercury1 the atmosphere containing #bj4i per cent of oxygen4 ,temperature1 degrees ,c ,oxygen in parts per million #j #ad4fb #a #ad4bc #b #ac4hd #c #ac4dh #d #ac4ac #e #ab4h #f #ab4dh #g #ab4ag #h #aa4hg #i #aa4ei #aj #aa4cc #aa #aa4jh #ab #aj4hc #ac #aj4f #ad #aj4cg #ae #aj4ae #af #i4ie #ag #i4gd #ah #i4ed #ai #i4ce #bj #i4ag #ba #h4ii #bb #h4hc #bc #h4fh #bd #h4ec #be #h4ch #bf #h4bb #bg #h4jg #bh #g4ib #bi #g4gg #cj #g4fc #baa4 ,sewage ,bacteria4--,a slight knowledge of the nature of bacteria is necessary in order that the biological changes which occur in the treatment of sewage may be understood4 ,bacteria are living organisms which are so small that it is difficult or impossible to study them either with the eye alone or with the aid of powerful microscopes4 ,they are studied by means of cultures1 stains1 and certain characteristic phenomena such as the production of a gas1 the production of a red colony on litmus lactose agar1 etc4 ,bacteria occur in three forms3 spherical1 called coccus2 cylindrical1 called bacillus2 and spiral1 called spirillum4 ,in size they vary from the largest at about #aaj1jjj of an inch to sizes so small as to be invisible under the most powerful microscope4 ,an ordinary size is #abe1jjj of an inch4 ,the cylindrical or rod bacteria are about four times as long as they are wide4 ,some bacteria possess the power of motion due to the presence of flagella or hairs which can be moved and cause the cell to progress at a rate as high as #ah cm4 per hour1 but usually the rate is very much less than this4 ,the composition of the bacterial cell has never been definitely determined4 ,bacteria are unicellular plants4 ,they possess no digestive organs and apparently obtain their food by absorption from the surrounding media4 ,reproduction is by the division of the cell into two approximately equal portions4 ,this reproduction may occur as frequently as once every half hour and if unchecked would quickly mount to unimaginable numbers4 ,the natural cause limiting the growth of bacteria is the generation by the bacterium of certain substances such as the amino acids1 which are injurious to cell life4 ,the exhaustion of the food supply is not considered as an important cause of inhibition of multiplication4 ,the products of growth of one species of bacteria may be helpful or harmful to other forms4 ,where the products are helpful the effect is known as symbiosis1 and where harmful the effect is known as antibiosis4 ,in sewage the presence of both arobic and anarobic bacteria is usually mutually helpful and the condition is an example of symbiosis4 ,the arobes1 sometimes called obligatory arobes1 are bacteria which demand available oxygen for their growth4 ,the anarobes1 or obligatory anarobes1 can grow only in the absence of oxygen4 ,there are other forms that are known as facultative anarobes 7or arobes7 whose growth is independent of the presence or absence of oxygen4 ,spores are formed by some bacteria when they are subjected to an unfavorable environment such as high temperatures1 the absence of food1 the absence of moisture1 etc4 ,spores are cells in which growth and animation are suspended but the life of the cell is carried on through the unsuitable period1 somewhat similar to the condition in a plant seed4 #bab4 ,organic ,life in ,sewage4--,living organisms1 both plants and animals1 exist in sewage4 ,bacteria are the smallest of these organisms4 ,others1 which can be studied easily under the microscope or can be seen with difficulty by the naked eye but which do not require special cultures for their study1 are classed as microscopic organisms or plankton4 ,organisms which are large enough to be studied without the aid of a microscope or special cultures are classed as macroscopic4 ,the part taken in the biolysis of sewage by macroscopic organisms belonging to the animal kingdom1 such as birds1 fish1 insects1 rodents1 etc41 which feed upon substances in the sewage is so inconsequential as to be of no importance4 ,both plants and animals are found among the macroscopic organisms4 ,organisms in sewage may be either harmful1 harmless1 or beneficial4 ,from the viewpoint of mankind the harmful organisms are the pathogenic bacteria4 ,their condition of life in sewage is not normal and in general their existence therein is of short duration4 ,it may be of sufficient length1 however1 to permit the transmission of disease4 ,the diseases which can be transmitted by sewage are only those that are contracted through the alimentary canal1 such as typhoid fever1 dysentery1 cholera1 etc4 ,diseases are not commonly contracted by contact of sewage with the skin nor by breathing the air of sewers4 ,it is safe to work in and around sewage so long as the sewage is kept out of the mouth1 and asphyxiating or toxic gases are avoided4 ,the beneficial organisms in sewage are those on which dependence is placed for the success of certain methods of treatment4 ,these organisms have not all been isolated or identified4 ,the total number of bacteria in a sample of sewage has little or no significance4 ,in a normal sewage the number may be between #b1jjj1jjj and #bj1jjj1jjj per c4c4 and because of the extreme rapidity of multiplication of bacteria a sample showing a count of #a1jjj1jjj per c4c4 on the first analysis may show #d to #e times as many #c or #d hours later4 ,a bacterial analysis of sewage is ordinarily of little or no value1 since pathogenic organisms are practically certain to be present1 there is no interest in the harmless organisms1 and the helpful nitrifying and arobic bacteria will not grow on ordinary laboratory media4 ,occasionally the presence of certain bacteria may indicate the presence of certain trades wastes4 ,in general1 the total bacterial count1 as sometimes reported1 represents only the number of bacteria which have grown under the conditions provided4 ,it bears no relation to the total number of bacteria in the sample4 ,the presence of bacteria in sewage is of great importance however1 as practically all methods of treatment depend on bacterial action1 and all sewages which do not contain deleterious trades wastes1 contain or will support the necessary bacteria for their successful treatment1 if properly developed4 #bac4 ,decomposition of ,sewage4--,if a glass container be filled with sewage and allowed to stand1 open to the air1 a black sediment will appear after a short time1 a greasy scum may rise to the surface1 and offensive odors will be given off4 ,this condition will persist for several weeks1 after which the liquid will become clear and odorless4 ,the sewage has been decomposed and is now in a stable condition4 ,the decomposition of sewage is brought about by bacterial action the exact nature of which is uncertain4 ,it#abi is well established that many of the chemical effects wrought by bacteria1 as by other living cells1 are due1 not to the direct action of the protoplasm1 but to the intervention of soluble ferments or enzymes4 ,enzymes are soluble ferments produced by the growth of the bacterial cell4 ,in#acj many cases the enzymes diffuse out from the cell and exert their effort on the ambient substances 444 in others the enzyme action occurs within the cell and the products pass out1 7for example7 444 the alcohol-producing enzymes of the yeast cell act upon sugar within the cell1 the resulting alcohol and carbon dioxide being ejected4 ,other chemical effects may be brought about by the direct action of the living cells1 but this has never been well established4 ,metabolism is the life process of living cells by which they absorb their food and convert it into energy and other products4 ,it is the metabolism of bacterial growth that in itself or by the production of enzymes hastens the putrefactive or oxidizing stages of the organic cycles in sewage treatment4 ,bacteria can assimilate only liquid food since they have no digestive tract through which solid food can enter4 ,the surrounding solids are dissolved by the action of the enzymes1 the resulting solution diffusing through the chromatin or outer skin1 and being digested throughout the interior cytoplasm4 ,bacteria are sometimes classified as parasites and saprophytes4 ,the parasites live only on the growing cells of other plant or animal life4 ,the saprophytes obtain their food only from the life products of living organisms and do not exist at the expense of the organisms themselves4 ,facultative saprophytes 7or parasites7 may exist on either living or dead tissue4 ,the decomposition of sewage may be divided into anarobic and arobic stages4 ,these conditions are usually1 but not always1 distinctly separate4 ,the growth of certain forms of bacteria is concurrent1 while the growth of other forms is dependent on the results of the life processes of other bacteria in the early stages of decomposition4 ,when sewage is very fresh it contains some oxygen4 ,this oxygen is quickly exhausted so that the first important step in the decomposition of sewage is carried on under anarobic conditions4 ,this is accompanied by the creation of foul odors of organic substances1 ammonia1 hydrogen sulphide1 etc42 other odorless gases such as carbon dioxide1 hydrogen1 and marsh gas1 the latter being inflammable and explosive2 and other complicated compounds4 ,an exception to the rule that putrefaction takes place only in the absence of oxygen is the production of other foul-smelling substances by the putrefactive activity of obligatory and facultative arobes4 ,hydrogen sulphide may be produced apparently in the presence of oxygen the action which takes place not being thoroughly understood4 ,the biolysis of sewage is the term applied to the changes through which its organic constituents pass due to the metabolism of bacterial life4 ,organic matter is composed almost exclusively of the four elements3 carbon1 oxygen1 hydrogen1 and nitrogen 7,,cohn7 and sometimes in addition sulphur and phosphorus4 ,the organic constituents of sewage can be divided into the proteins1 carbohydrates1 and fats4 ,the proteins are principally constituents of animal tissue1 but they are also found in the seeds of plants4 ,the principal distinguishing characteristic of the proteins is the possession of between #ae and #af per cent of nitrogen4 ,to this group belong the albumens and casein4 ,the carbohydrates are organic compounds in which the ratio of hydrogen to oxygen is the same as in water1 and the number of carbon atoms is #f or a multiple of #f4 ,to this group belong the sugars1 starches and celluloses4 ,the fats are salts formed1 together with water1 by the combination of the fatty acids with the tri-acid base glycerol4 ,the more common fats are stearin1 palmatin1 olein1 and butyrine4 ,the soaps are mineral salts of the fatty acids formed by replacing the weak base glycerol with some of the stronger alkalies4 ,the first state in the biolysis of sewage is marked by the rapid disappearance of the available oxygen present in the water mixed with organic matter to form sewage4 ,in this state the urea1 ammonia1 and other products of digestive or putrefactive decomposition are partially oxidized and in this oxidation the available oxygen present is rapidly consumed1 the conditions in the sewage becoming anarobic4 ,the second state is putrefaction in which the action is under anarobic conditions4 ,the proteins are broken down to form urea1 ammonia1 the foul-smelling mercaptans1 hydrogen sulphide1 etc41 and fatty and aromatic acids4 ,the carbohydrates are broken down into their original fatty acid1 water1 carbon dioxide1 hydrogen1 methane1 and other substances4 ,cellulose is also broken down but much more slowly4 ,the fats and soaps are affected somewhat similarly to the hydrocarbons and are broken down to form the original acids of their make up together with carbon dioxide1 hydrogen1 methane1 etc4 ,the bacterial action on fats and soaps is much slower than on the proteins1 and the active biological agents in the biolysis of the hydrocarbons1 fats1 and soaps are not so closely confined to anarobes as in the biolysis of the proteins4 ,the third state in the biolysis of sewage is the oxidation or nitrification of the products of decomposition resulting from the putrefactive state4 ,the products of decomposition are converted to nitrites and nitrates1 which are in a stable condition and are available for plant food4 ,it must be understood that the various states may be coexistent but that the conditions of the different states predominate approximately in the order stated4 ,in the biolysis of sewage there is no destruction of matter4 ,the same elements exist in the same amount as at the start of the biolytic action4 #bad4 ,the ,nitrogen ,cycle4--,nitrogen is an element that is found in all organic compounds4 ,its presence is necessary to all plant and animal life4 ,the nitrogenous compounds are most readily attacked by bacterial action in sewage treatment4 ,the non-nitrogenous substances such as soaps and fats1 and the inorganic compounds are more slowly affected by bacterial action alone4 ,the element nitrogen passes through a course of events from life to death and back to life again that is known as the ,nitrogen ,cycle4 ,it is typical of the cycles through which all of the organic elements pass4 ,upon the death of a plant or animal1 decomposition sets in accompanied by the formation of urea which is broken down into ammonia4 ,this is known as the putrefactive stage of the ,nitrogen ,cycle4 ,the next state is nitrification in which the compounds of ammonia are oxidized to nitrites and nitrates1 and are thus prepared for plant food4 ,in the state of plant life the nitrites and nitrates are denitrified so as to be available as a plant or animal food4 ,the highest state of the ,nitrogen ,cycle is animal life1 in which nitrogen is a part of the living animal substance or is charged from protein to urea1 ammonia1 etc41 by the functions of life in the animal4 ,upon the death of this animal organism the cycle is repeated4 ,the ,nitrogen ,cycle1 like the cycle of ,life and ,death1 is purely an ideal condition as in nature there are many short circuits and back currents which prevent the continuous progression of the cycle4 ,the conception of this cycle is an aid1 however1 in understanding the processes of sewage treatment4 #bae4 ,plankton and ,macroscopic ,organisms4--,in general the part played by these organisms in the biolysis of sewage is not sufficiently well understood to aid in the selection of methods of sewage treatment involving their activities4 ,the presence in bodies of water receiving sewage1 of certain plankton which are known to exist only when putrefaction is not imminent1 indicates that the body of water into which the discharge of sewage is occurring is not being overtaxed4 ,the control of sewage treatment plant effluents so as to avoid the poisoning of fish life or the contamination of shell fish is likewise important4 ,the study of plankton and macroscopic life in the treatment of sewage is an open field for research4 #baf4 ,variations in the ,quality of ,sewage4--,the quality of sewage varies with the hour of the day and the season of the year4 ,some of the causes of these variations are3 changes in the amount of diluting water due to the inflow of storm water or flushing of the streets or sewers2 variations in domestic activities such as the suspension of contributions of organic wastes during the night1 ,monday's wash1 etc42 characteristics of different industries which discharge different kinds of wastes according to the stage of the manufacturing process1 etc4 ,in general night sewage is markedly weaker than day sewage in both domestic and industrial wastes1 but in specific cases the varying strength depends entirely upon the characteristics of the district4 ,some analyses are given in ,table #gd1 which emphasize these points4 ,,table #gd ,,sewage ,,analyses ,,showing ,,hourly1 ,,daily1 ,,and ,,seasonal ,,variations ,,in ,,quality ,place ,time ,suspended ,remarks ,reference ,nitrogen ,total,chlorine ,matter ,marion1 ,ohio,mid't-noon1 ,industrial #a #e-ba-jf4 #de #ec #aij ,noon-mid't ,domestic #a #e-ba-jf4 #cg #id #acc ,westerville1,day college #a ,ohio #aj4b #gf #aah town ,night #b4f #gd #da #a ,columbus1 #aijd-aije ,ohio ,mid't to #b #b a4m4 #d4f #ej #aca #b a4m4 to #d #b a4m4 #c4j #eb #ie #d a4m4 to #f #b a4m4 #b4c #ea #hc #f a4m4 to #h #b a4m4 #b4g #dh #hc #h a4m4 to #aj #b a4m4 #af4c #ff #dgf #aj a4m4 to #b noon #aa4d #ajj #cbd ,noon to #b #b p4m4 #aa4c #hf #bdf #b p4m4 to #d #b p4m4 #ab4c #gh #bdf #d p4m4 to #f #b p4m4 #bb4j #gh #cfh #f p4m4 to #h #b p4m4 #h4b #ga #bji #h p4m4 to #aj #b p4m4 #g4h #hj #abj #aj p4m4 to #b mid't #f4b #ef #aag ,center ,ave41,mid't to #c #c ,chicago4 a4m4 #abc #d a4m4 to #g #c p4m4 #caf #h a4m4 to #aa #c p4m4 #fjh ,noon to #c #c p4m4 #ghe #d p4m4 to #g #c p4m4 #gag #h p4m4 to #aa #c p4m4 #bhg ,columbus1 ,sunday #b ,ohio #f4g #ee #heh ,monday #i4a #ff #ajdh #b ,tuesday #i4d #fi #ajbd #b ,wednesday #i4f #fh #ajje #b ,thursday #i4b #ff #iij #b ,friday #i4b #fg #ajah #b ,saturday #i4c #fg #ajaf #b ,baltimore1 ,aug4 #a to #d #aijg-aijh ,sept4 #a #af4j #bdf ,sept4 #d to #d ,oct4 #c #ai4j #aij ,oct4 #f to #d ,nov4 #d #bj4j #ahh ,nov4 #ae to #d ,nov4 #bi #bj4j #afd ,dec4 #c to #d ,dec4 #bi #bj4j #abc ,jan4 #f to #d ,jan4 #ba #ai4j #abg ,feb4 #b to #d ,feb4 #bf #bj4j #adi ,feb4 #bi to #d ,mar4 #bd #bh4j #bgd ,mar4 #bg to #d ,april #bi #be4j #afe ,april #cj to #d ,may #bf #ai4j #ajd ,june #h to #d ,july #aa #ae4j #hh ,july #ac to #d ,aug4 #h #i4e #abd ,references3 #a4 #aijh ,report of the ,ohio ,state ,board of ,health4 #b4 ,report on ,sewage ,purification at ,columbus1 ,ohio1 by ,g4 ,a4 ,johnson1 #aije4 #c4 ,report on ,industrial ,wastes from the ,stock ,yards and ,packingtown in ,chicago1 by the ,sanitary ,district of ,chicago4 #aiba4 #d4 ,report of the ,baltimore ,sewerage ,commission1 #aiaa4 #bag4 ,sewage ,disposal4--,previous to the development of the water-carriage method for removing human excreta and other liquid wastes the solid matter was disposed of by burial and the liquid wastes were allowed to seep into the ground or to run away over its surface4 ,following the development of the water-carriage system1 which necessitated the development of sewers1 the problem of ultimate disposal was rendered more serious by the concentration of human excreta together with a large volume of water4 ,the unthinking citizen believes the problem of sewage disposal is solved when the toilet is flushed or the bath tub is drained4 ,the problem may more truly be said to commence at this point4 ,it would appear that the simplest method of disposal of sewage would be to discharge it into the nearest water course4 ,unfortunately the nature of sewage is such that it may be either highly offensive to the senses or dangerous to health or both1 when discharged in this manner4 ,only the most fortunate communities are favored with a body of water of sufficient size to receive sewage without creating a nuisance4 ,the problems of sewage disposal are to prevent nuisances causing offense to sight and smell2 to prevent the clogging of channels2 to protect pumping machinery2 to protect public water supplies2 to protect fish life2 to prevent the contamination of shell fish2 to recover valuable constituents of the sewage2 to enrich and to irrigate the soil2 to safeguard bathing and boating2 for other minor purposes2 and in some cases to comply with the law4 ,sewage may be treated to attain one or more of these objects by methods of treatment varying as widely as the objects to be attained4 #bah4 ,methods of ,sewage ,treatment4--,in studying the subject of sewage treatment it must be borne in mind that it is impossible to destroy any of the elements present4 ,they may be removed from the mixture only by gasification1 straining or sedimentation4 ,their chemical combinations may be so changed1 however1 as to result in different substances than those introduced to the treatment plant4 ,it is with these chemical changes that the student of sewage treatment is interested4 ,the methods of sewage treatment can be classified as mechanical1 chemical and biological4 ,these classifications are not separated by rigid lines but may overlap in certain treatment devices or methods4 ,mechanical methods of treatment are exemplified by sedimentation1 and screening4 ,chemical precipitation and sterilization are examples of chemical methods4 ,the biological methods1 the most important of all1 include dilution1 septicization1 filtration1 sewage farming1 activated sludge1 etc4 ,if for any reason it is desired to treat sewage by more than one of these methods the procedure should follow as nearly as possible the order of the occurrence of the phenomena in the natural biolysis of sewage4 ,for example1 in one treatment plant the sewage would first pass through a grit chamber where the coarse sediment would be removed1 then through a screen where the floating matter and coarse suspended matter would be removed1 then to a sedimentation basin where some finer suspended matter might settle out1 then to a digestive tank where the solid matter deposited would be worked upon by bacterial action and partially liquefied4 ,simultaneous to the liquefaction of the deposited solid matter the liquid effluent from the digestive tank might proceed to an arating device to expedite oxidation1 then to an arobic filter1 and finally to disposal by dilution4 ,,chapter ,,xiv ,,disposal ,,by ,,dilution #bai4 ,definition4--,disposal of sewage by dilution is the discharge of raw sewage or the effluent from a treatment plant into a body of water of sufficient size to prevent offense to the senses of sight and smell1 and to avoid danger to the public health4 #bbj4 ,conditions ,required for ,success4--,among the desired conditions for successful disposal by dilution are3 adequate currents to prevent sedimentation and to carry the sewage away from all habitations before putrefaction sets in1 or sufficient diluting water high in dissolved oxygen to prevent putrefaction2 a fresh or non-septic sewage2 absence of floating or rapidly settling solids1 grease or oil2 and absence of back eddies or quiet pools favorable to sedimentation in the stream into which disposal is taking place4 ,the conditions which should be prevented are3 offensive odors due to sludge banks1 the rise of septic gases1 and unsightly floating or suspended matter4 ,in some instances the pollution of the receiving body of water is undesirable and the sewage must be freed from pathogenic organisms and the danger of aftergrowths minimized before disposal4 ,such conditions are typified at ,baltimore1 where the sewage is discharged into ,back ,bay1 an arm of ,chesapeake ,bay4 ,one of the important industries of the state of ,maryland is the cultivation of oysters4 ,the pollution of the ,bay was therefore so objectionable that careful treatment of the ,baltimore sewage has been a necessary preliminary to final disposal by dilution4 ,it is unwise to draw public water supplies1 without treatment1 from a stream receiving a sewage effluent1 no matter how careful or thorough the treatment of the sewage4 ,the treatment of the sewage is a safeguard1 and lightens the load on the water purification plant1 but under no considerations can it be depended upon to protect the community consuming the diluted effluent4 ,the sewer outlet should be located well out in the current of the stream1 lake1 or harbor4 ,deeply submerged outlets are usually better than an outlet at the surface1 as a better mixture of the sewage and water is obtained4 ,the discharge of sewage into a body of water of which the surface level changes1 alternately covering and exposing large areas of the bottom is unwise1 as the sludge which is deposited during inundation will cause offensive odors when uncovered4 ,such conditions must be carefully guarded against when selecting a point of disposal in tidal estuaries because of the frequent fluctuations in level4 #bba4 ,self-,purification of ,running ,streams4--,the self-purification of running streams is due to dilution1 sedimentation1 and oxidation4 ,the action is physical1 chemical1 and biological4 ,when putrescible organic matter is discharged into water the offensive character of the organic matter is minimized by dilution4 ,if the dilution is sufficiently great1 it alone may be sufficient to prevent all nuisance4 ,the oxidation of the organic matter commences immediately on its discharge into the diluting water due to the growth and activity of nitrifying and other oxidizing organisms and to a slight degree to direct chemical reaction4 ,so long as there is sufficient oxygen present in the water septic conditions will not exist and offensive odors will be absent4 ,when the organic matter is completely nitrified or oxidized there will be no further demand on the oxygen content of the stream and the stream will be said to have purified itself4 ,at the same time that this oxidation is going on some of the organic matter will be settling due to the action of sedimentation4 ,if oxidation is completed before the matter has settled on the bottom the result will be an inoffensive silting up of the river4 ,if oxidation is not complete1 however1 the result will be offensive putrefying sludge banks which may send their stinks up through the superimposed layers of clean water to pollute the surrounding atmosphere4 ,the most important condition for the successful self-purification of a stream is an initial quantity of dissolved oxygen to oxidize all of the organic matter contributed to it1 or the addition of sufficient oxygen subsequent to the contribution of sewage to complete the oxidation4 ,oxygen may be added through the dilution received from tributaries1 through aration over falls and rapids1 or by quiescent absorption from the atmosphere4 ,the rapidity of self-purification is dependent on the character of the organic matter1 the presence of available oxygen1 the rate of rearation1 temperature1 sedimentation1 and the velocity of the current4 ,sluggish streams are more likely to purify themselves in a shorter distance and rapidly flowing turbulent streams are more likely to purify themselves in a shorter time1 other conditions being equal4 ,although the absorption of oxygen by a stream whose surface is broken is more rapid than through a smooth unbroken surface1 the growth of alg1 biological activity1 the effect of sunlight1 and sedimentation are more potent factors and have a greater effect in sluggish streams than the slightly more rapid absorption of oxygen in a turbulent stream4 ,it is frequently more advantageous to discharge sewage into a swiftly moving stream1 however1 regardless of the conditions of self-purification1 as the undesirable conditions which may result occur far from the point of disposal and may be offensive to no one4 ,the sewage from a population of about #c1jjj1jjj persons residing in and about ,chicago is discharged into the ,chicago ,drainage ,canal4 ,it ultimately reaches tide water through the ,des ,plaines1 the ,illinois1 and the ,mississippi ,rivers4 ,the action occurring in these channels is one of the best illustrations known of the self-purification of a stream4 ,in ,table #ge are shown the results of analyses of samples taken at various points below the mouth of the ,chicago ,river where the diluting water from ,lake ,michigan enters1 to ,grafton1 ,illinois1 at the junction of the ,illinois and ,mississippi ,rivers about #dj miles above ,st4 ,louis4 ,the effect of the physical characteristics of the stream on its chemical composition is well illustrated in this table4 ,the rise in the chlorine content between ,lake ,michigan and the entrance to the ,drainage ,canal is a measure of the addition of sewage4 ,since the chlorine is an inorganic substance which is not affected by biologic action1 its loss in concentration in the lower reaches of the rivers is due to dilution by tributaries and sedimentation1 e4g41 between the end of the canal at ,lockport and the sampling point at ,joliet1 the entrance of the ,des ,plaines ,river reduces the concentration of chlorine from #abd4e to #da4e parts per million4 ,the entrance of the ,kankakee ,river at ,dresden ,heights further reduces the chlorine to #bd4e p4p4m4 ,the increase of albuminoid and ammonia nitrogen accompanied by a decrease in nitrites and nitrates1 between the upper end of the canal at ,bridgeport and its lower end at ,lockport indicates the reducing action proceeding therein4 ,the oxidizing action over the various dams and the effect of dilution with water containing oxygen is shown between miles #cd and #ch1 at mile #gi1 and at mile #bid4 ,the excellent effect of quiescent sedimentation and aration in ,peoria ,lakes is shown between miles #ade1 #afa and #afe4 ,,table #ge ,,analyses ,,of ,,chicago1 ,,des ,,plaines ,,and ,,illinois ,,rivers 7,parts per million7 ,sampling ,distance,january-,june1 #aijj1 from 8,sewage ,disposal10 by ,point in ,miles ,kinnicutt1 ,winslow and ,pratt from ,lake ,michigan ,chlorine ,ammonia,albuminoid,nitrates,nitrates ,nitrogen ,nitrogen ,lake #j #c4j #j4jc #fj4ac #j4jjb #j4jjh ,michigan ,canal1 #e #if4f #h4je #b4je 4#jba 4#jgd ,bridgeport ,canal1 #cd #abd4e #aj4ij #b4jg 4#jac 4#jff ,lockport ,joliet #ch #da4e #d4bb #j4hc 4#jba 4#jhf ,dresden #eb ,heights ,dresden #eb ,heights ,morris #fb #bd4e #b4df 4#fj 4#jge 4#dbd ,marseilles #gi ,marseilles #gi ,ottawa #he #ae4c #a4ee 4#da 4#aig 4#iff ,la ,salle #ajj #ag4e #a4je 4#dc 4#aji 4#igi ,henry #abi #ac4c 4#ib 4#ch 4#ajb 4#hjj ,chillicothe #ade ,averyville #afa #ac4e 4#ha 4#cg 4#jjd #a4aej ,wesley #afe #ab4j 4#eg 4#da 4#jhc #a4jc ,pekin #age #ab4c 4#gj 4#dc 4#jfj 4#iij ,havana #bje #aa4b 4#fj 4#cf 4#jfe 4#egj ,beardstown #bcg #aj4g 4#fi 4#dd 4#ajf 4#fhe ,la ,grange #bdi ,kampsville #bid #aa4c 4#ff 4#dd 4#jdd 4#hgj ,kampsville #bid ,grafton #cbe #i4h 4#df 4#db 4#jca #a4jf ,grafton #cbe ,sampling ,dissolved ,oxygen ,remarks ,point ,jan4 ,july ,nov4 #cj-;,feb4 #h-ae #ab-ai1 #b1 #aiab #aiab #aiab ,lake #ad4a #aj4h,typical ,michigan chemical analysis ,canal1 #f4i,kedzie ,bridgeport ,avenue ,canal1 #i4i #a4g;,above dam ,lockport ,joliet #a4d #e4f;,aration over dam4 ,dilution by ,des ,plaines ,river ,dresden #a4j #d4a;,des ,plaines ,heights ,river ,dresden #aj4d,kankakee ,heights ,river ,morris #g4h #e4g;,illinois ,river ,marseilles #e4g #j4f #f4h;,above dam ,marseilles #h4b #d4e #i4c;,below dam ,ottawa #aj4j #h4a ,la ,salle #e4d #g4h ,henry #g4i ,chillicothe #c4d #a4e #e4i;,above ,peoria ,lakes ,averyville #c4c #h4b #h4i;,below ,peoria ,lakes ,wesley #g4a;,below ,peoria ,pekin #d4i #c4b #h4i ,havana #d4h #h4h ,beardstown #f4e #i4a ,la ,grange #d4a #i4d;,below dam ,kampsville #d4a #aj4j;,above dam ,kampsville #d4f #aj4j;,below dam ,grafton #f4f #d4g #aj4d;,illinois ,river ,grafton #g4c #ab4j,mississippi ,river #bbb4 ,self-,purification of ,lakes4--,sewage may be disposed of into lakes with as great success as into running streams if conditions exist which are favorable to self-purification4 ,lakes and rivers purify themselves from the same causes2 oxidation1 sedimentation1 etc41 but in the former the currents are much less pronounced and may be entirely absent4 ,in shallow lakes 7#bj feet or less in depth7 dependence must be placed on horizontal currents and the stirring action of the wind to keep the water in motion in order that the sewage and the diluting water may be mixed4 ,in deeper bodies of water1 currents induced by the wind are helpful but entire dependence need not be placed upon them4 ,vertical currents1 and the seasonal turnovers in the spring and fall completely mix the waters of the lake above those layers of water whose temperature never rises higher than #d ,c4 ,in the early winter the cold air cools the surface waters of a lake4 ,the cooling increases the density of the surface water causing it to sink1 and allowing the warmer layers below to rise and become cooled4 ,after the temperature of the entire lake has reached #d ,c4 the vertical currents induced by temperature cease1 as continued cooling decreases the density of the surface water maintaining the same layer at the surface4 ,in the spring as the temperature of the surface water rises to #d ,c4 and above it becomes heavier and drops through the colder water below causing vertical currents4 ,these phenomena are known as the fall and spring turnovers4 ,the former is more pronounced4 ,these turnovers are effective in assisting in the self-purification of lakes4 #bbc4 ,dilution in ,salt ,water4--,the oxygen content in salt water is about #bj per cent less than in fresh water at the same temperature4 ,the greater content of matter in solution in salt water reduces its capacity to absorb many sewage solids4 ,this1 together with the chemical reaction between the constituents of the salt water and those of the sewage serve to precipitate some of the sewage solids and to form offensive sludge banks4 ,the evidence of the action which takes place in the absorption of oxygen from the atmosphere by salt water and its effect on dissolved sewage solids is conflicting1 but in general fresh water is a better diluting medium than salt water4 ,black and ,phelps have made valuable studies of the relative rates of absorption of oxygen from the air by fresh and salt water4 ,the results of their experiments are published in a ,report to the ,board of ,estimate and ,apportionment of ,n4 ,y4 ,city1 made ,march #bc1 #aiaa4aca ,concerning these rates they conclude3 ,therefore there is no reason to believe that the rearation of salt water follows any other laws than those we have determined mathematically and experimentally for fresh water4 ,in the absence of fuller information on the effect of increased viscosity upon the diffusion coefficient1 it can only be stated that the rate of rearation of salt water is less than that of fresh water1 in proportion to the respective solubilities of oxygen in the two waters1 and still less1 but to an unknown extent1 by reason of the greater viscosity and consequent small value of the diffusion coefficient4 #bbd4 ,quantity of ,diluting ,water ,needed4--,in a large majority of the problems of disposal of sewage by dilution it is not necessary to add sufficient diluting water to oxidize completely all organic matter present4 ,ordinarily it is sufficient to prevent putrefactive conditions until the flow of the stream1 lake1 or tidal current1 has reached some large body of diluting water or where putrefaction is no longer a nuisance4 ,it is never desirable to allow the oxygen content of a stream to be exhausted as putrescible conditions will exist locally before exhaustion is complete4 ,the exact point to which oxygen can be reduced in safety is in some dispute4 ,black and ,phelps have assumed #gj per cent of saturation as the allowable limit2 ,fuller has placed it at #cj per cent2 ,kinnicutt1 ,winslow1 and ,pratt have placed it at #ej per cent4 ,since the reaction between the oxygen and the organic matter is quantitative1 others have placed the limit in terms of parts per million of oxygen4 ,wisner1#acb has recommended a minimum of #b4e p4p4m4 as the limit for the sustenance of fish life1 which is not far from ,fuller's limit for hot-weather conditions4 ,formulas of various types have been devised to express the rate of absorption of oxygen with a given quantity of diluting water which is mixed with a given quantity and quality of sewage4 ,the quantity of sewage is sometimes expressed in terms of the tributary population or in other ways4 ,knowing the rate at which oxygen is exhausted and the velocity of flow of the stream1 the point at which the oxygen will be reduced to the limit allowed is easily determined4 ,the accuracy of none of these formulas has been proven1 and their use1 without an understanding of the effect of local conditions1 may lead to error4 ,they may be used as a check on the bio-chemical oxygen demand determinations1 which should be conclusive4 ,the following formula1 based on the work of ,black and ,phelps1 is a guide to the amount of sewage which can be added to a stream without causing a nuisance4 ,it is3 ,c 7log7,o,o77kt1 in which ,c per cent of sewage allowed in the water2 ,o per cent of saturation or the p4p4m4 of oxygen in the mixture at the time of dilution2 ,o per cent of saturation or the p4p4m4 of oxygen in the stream after period of flow to point beyond which no nuisance can be expected2 t time in hours required for the stream to flow to this point2 k constant determined by test determinations of the factors in the following expression3 k 7log7,o#a,o#a77;,c#at#a1 in which ,o#a per cent of saturation or the p4p4m4 of oxygen in the diluting water before mixing with the sewage2 ,o#a per cent of saturation or the p4p4m4 of oxygen in an artificial mixture made in the laboratory1 after t#a hours of incubation2 ,c#a per cent of sewage in the mixture2 t#a number of hours of incubation of the mixture of sewage and diluting water under laboratory conditions4 ,in the solution of these formulas it is desired to determine the permissible amount of sewage to discharge into a given quantity of diluting water4 ,this value is expressed by ,c in the first equation4 ,in solving this equation3 ,o is determined by laboratory tests and should represent the conditions to be expected during various seasons of the year2 ,o is determined by judgment4 ,it may be #cj per cent or #ej per cent or more as previously explained2 t is determined by float tests or other measurements of the stream flow2 k is determined by laboratory tests in which mixtures of various strengths are incubated for various periods of time4 ,different values of k will be obtained for different characteristics of the sewage2 but for the same sewage the value of k should be unchanged for different periods of incubation4 ,rideal devised the formula3#acc ,,xo ,c7,m ,n7,s in which ,x flow of the stream expressed in second-feet2 ,o grams of free oxygen in one cubic foot of water2 ,s rate of sewage discharge in second-feet2 ,m grams of oxygen required to consume the organic matter in one cubic foot of diluted sewage as determined by the permanganate test with #d hours boiling2 ,n grams of oxygen available in the nitrites and nitrates in one cubic foot of diluted sewage2 ,c ratio between the amount of oxygen in the stream and that required to prevent putrefaction4 ,where ,c is equal to or greater than one1 satisfactory conditions have been attained4 ,in using this formula it is necessary to make analyses of trial mixtures of sewage and water until the correct mixture has been found4 ,hazen's formula is3#acd ,d x,s #dm,o1 in which ,d dilution ratio2 x volume of water2 ,s volume of sewage2 m result of the oxygen consumed test expressed in p4p4m4 after #e minutes1 boiling with potassium permanganate2 ,o amount of dissolved oxygen in the diluting water expressed in p4p4m4 ,for comparison with ,rideal's formula the factor of #g should be used instead of #d to allow for the increased time of boiling4 ,since the amount of oxygen needed is dependent on the amount of organic matter in the sewage rather than the total volume of the sewage1 and since the amount of organic matter is closely proportional to the population1 the amount of diluting water has sometimes been expressed in terms of the population4 ,hering's recommendation for the quantity of diluting water necessary for ,chicago sewage was #c4c cubic feet of water per second per thousand population4 ,experience has proven this to be too small4 ,between a minimum limit of #b second-feet and a maximum of #h second-feet of diluting water per thousand population the success of dilution is uncertain4 ,above this limit success is practically assured and below this limit failure can be expected4 ,even with these carefully devised formulas and empirical guides1 the factors of rearation1 dilution1 sedimentation1 temperature1 etc41 may have so great an effect as to vitiate the conclusions4 ,as shown in ,table #ge dilution in winter is far more successful than in summer4 ,the lower temperatures so reduce the activity of the putrefying organisms that consumption of oxygen is greatly retarded4 #bbe4 ,governmental ,control4--,a comprehensive discussion of the legal principles governing the pollution of inland waters is contained in 8,a ,review of the ,laws ,forbidding the ,pollution of ,inland ,waters10 by ,e4 ,b4 ,goodell1 published by the ,united ,states ,geological ,survey in #aije1 as ,water ,supply ,paper ,no4 #aeb4 ,the disposal of sewage by dilution is subject to statutory limitations in many states4 ,the enforcement of these laws is usually in the hands of the state board of health1 which is frequently given discretionary powers to recommend and sometimes to enforce measures for the abatement of an actual or potential nuisance4 ,such recommendations usually take the form of a specification of certain forms of treatment preliminary to disposal by dilution4 ,no project for the disposal of sewage by dilution should be consummated until the local1 state1 national1 and in the case of boundary waters1 international laws have been complied with4 ,the attitude of the courts in different states has not been uniform4 ,little guidance can be taken from the personal feeling of the persons immediately interested4 ,the opinion of the riparian owner #e miles down stream may differ materially from the popular will of the voters of a city1 and it is likely to receive a more favorable hearing from the court4 ,statutes and legal precedents are the safest guides4 #bbf4 ,preliminary ,treatment4--,if the sewage to be disposed of by dilution contains unsightly floating matter1 oil1 or grease1 no amount of oxygen in the diluting water will prevent a nuisance to sight1 or the formation of putrefying sludge banks4 ,under such conditions it will be necessary to introduce screens or sedimentation basins1 or both1 in order to remove the floating and the settling solids4 ,biologic tanks1 filtration1 or other methods of treatment may be necessary for the removal of other undesirable constituents4 #bbg4 ,preliminary ,investigations4--,before adopting disposal of sewage by dilution without preliminary treatment1 or before considering the proper form of treatment necessary to render disposal by dilution successful1 a study should be made of the character of the body of water into which the sewage or effluent is to be discharged4 ,this study should include3 measurements of the quantity of water available at all seasons of the year2 analyses of the diluting water to determine particularly the available dissolved oxygen2 observations of the velocity and direction of currents1 and the effect of winds thereon2 a study of the effect on public water supplies1 bathing beaches1 fish life1 etc4 ,good judgment1 aided by the proper interpretation of such information should lead to the most desirable location for the sewer outlet4 ,if preliminary treatment is found to be necessary tests should be made to determine the necessary extent and thoroughness of the treatment4 ,,chapter ,,xv ,,screening ,,and ,,sedimentation #bbh4 ,purpose4--,the first step in the treatment of sewage is usually that of coarse screening in order to remove the larger particles of floating or suspended matter4 ,screens and sedimentation basins are used to prevent the clogging of sewers1 channels1 and treatment plants2 to avoid clogging of and injuries to machinery2 to overcome the accumulation of putrefying sludge banks2 to minimize the absorption of oxygen in diluting water2 and to intercept unsightly floating matter4 ,by the plain sedimentation of sewage is meant the removal of suspended matter by quiescent subsidence unaffected by septic action or the addition of chemicals or other precipitants4 ,in order to prevent septic action plain sedimentation tanks must be cleaned as frequently as once or twice a week in warm weather but not quite so often in cold weather4 ,fine screening may take the place of sedimentation where insufficient space is available for sedimentation tanks1 and it is desired to remove only a small portion of the suspended matter4 ,recent ,american practice has tended to restrict the field of fine screening to treatment requiring less than #aj per cent removal of suspended matter1 thus eliminating screens from the field covered by plain sedimentation tanks4 ,the practice is well expressed by ,potter1 who states3#ace ,where a high degree of purification is sought1 the use of fine screens is of doubtful value4 ,a modern settling tank will give better results and at a less cost for a given degree of purification4 ,a settled liquid is also superior to a screened liquid for subsequent biological treatment in filters4444 ,again the storing of large quantities of screenings must necessarily be more objectionable than the storing of the digested sludge of a modern settling tank4 ,illustration3 ,,fig4 #aej4--,types of ,moving ,screens4 ,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #gh1 #aiae1 p4 #hic4 #bbi4 ,types of ,screens4--,the definitions of some types of screens as proposed by the ,american ,public ,health ,association follow3 ,a bar screen is composed of parallel bars or rods4 ,a mesh screen is composed of a fabric1 usually wire4 ,a grating consists of #b sets of parallel bars in the same plane in sets intersecting at right angles4 ,a band screen consists of an endless perforated band or belt which passes over upper and lower rollers4 ,a perforated plate screen is made of an endless band of perforated plates similar to a band screen4 ,a wing screen has radial vanes uniformly spaced which rotate on a horizontal axis4 ,a disc screen consists of a circular perforated disc with or without a central truncated cone of similar material mounted in the center4 ,the ,reinsch ,wurl screen is the best known type of disc screen4 ,a cage screen#acf consists of a rectangular box made up of parallel bars with the upstream side of the box or cage omitted4 ,allen#acg gives the following definitions3 ,a drum screen is a cylinder or cone of perforated plates or wire mesh which rotates on a horizontal axis4 ,a shovel vane screen is similar to a wing screen with semicircular wings and a different method of removing the screenings4 ,examples of a band screen1 a wing screen1 a shovel vane screen1 a drum screen and a disc screen are shown in ,fig4 #aej4 ,a bar screen is shown in ,fig4 #aea and a cage screen is shown in ,fig4 #aeb4 ,illustration3 ,,fig4 #aea4--,sketch of a ,bar ,screen4 ,illustration3 ,,fig4 #aeb4--,sketch of a ,cage ,screen4 ,screens can be classed as fixed1 movable1 or moving4 ,fixed screens are permanently set in position and must be cleaned by rakes or teeth that are pulled between the bars4 ,movable screens are stationary when in operation1 but are lifted from the sewage for the purpose of cleaning4 ,moving screens are in continuous motion when in operation and are cleaned while in motion4 ,fixed bar screens may be set either vertical1 inclined1 or horizontal4 ,movable screens with a cage or box at the bottom are sometimes used4 ,the box should be of solid material to prevent the forcing of screenings through it when the screen is being raised for cleaning4 ,a mesh screen should be used only under special circumstances because of the difficulty in cleaning4 ,screens which must be raised from the sewage for cleaning should be arranged in pairs in order that one may be working when the other is being cleaned4 ,movable screens are undesirable for small plants because the labor involved in raising and lowering is greater than in cleaning with a rake and the screens are more likely to be neglected4 ,in a large plant rakes operated by hand are too small for cleaning the screens4 ,a fixed screen is sometimes used with moving teeth fastened to endless chains4 ,the teeth pass between the parallel bars and comb out the screenings4 ,if the screen chamber in a small plant is too deep for accessibility a movable cage or box screen may be desirable4 ,moving screens are generally of fine mesh or perforated plates4 ,they are kept moving in order to allow continuous cleaning4 ,they are cleaned by brushes or by jets of air1 water1 or steam4 #bcj4 ,sizes of ,openings4--,the area or size of the opening of a screen is dependent upon the character of the sewage to be treated and upon the object to be attained4 ,large screens1 with openings between #a inches and #f inches are used to protect centrifugal pumps1 tanks1 automatic dosing devices1 conduits1 and gate valves from large objects such as pieces of timber1 dead animals1 etc41 which are found in sewage4 ,the quantity of material removed is variable1 and is usually small4 ,medium-size screens with openings from inch to #a inches are used to prepare sewage for passage through reciprocating pumps1 complex dosing apparatus1 contact beds1 and sand filters4 ,the amount of material removed varies from #j4e to #aj cubic feet per million gallons of sewage treated1 dependent on the character of the sewage and the size of the screen4 ,screenings before drying contain #ge to #ij per cent moisture and weigh #dj to #ej pounds per cubic foot4 ,at times the amount removed may vary widely from the limits stated4 ,schaetzle and ,davis#ach state3 ,screenings differ greatly both in amount and character4444 ,the amount varies with the days of the week as well as during the course of the day4 ,it reaches its maximum about noon or shortly before and commences to disappear about midnight1 reaching a minimum about #d or #e a4m4 ,the material is almost wholly organic and consists of scraps of vegetables or fruit1 cloth1 hair1 wood1 paper and lumps of fecal matter4 ,the amount varies so widely that it is impossible to state just what to expect any definite size screen to remove4 ,the amount of water contained is small compared with that in the sludge in sedimentation basins and amounts to from #gj per cent to #hj per cent4 ,on account of its organic origin it is highly putrescible4 ,medium-size screens are sometimes placed close together with the bars of the one opposite the openings in the other1 thus approaching a fine screen4 ,fine screens vary in size of opening from inch to #ej openings per linear inch or #b1ejj per square inch4 ,they are used for removing solids preparatory to disposal by dilution1 to protect sprinkling filters1 complex dosing apparatus1 sand filters1 sewage farms1 and to prevent the formation of scum in subsequent tank treatment4 ,in general1 fine screens will remove from #j4a to #a cubic yard of wet material per million gallons of sewage treated4 ,the wet screenings will contain about #ge per cent moisture and will weigh about #fj pounds per cubic foot4 ,the dry weight of the screenings will therefore be about #aj to #djj pounds per million gallons of sewage treated4 ,the effect of the removal of this amount of material is usually not detectable by methods of chemical analysis1 the amount of suspended matter before and after screening being found unchanged4 ,in his conclusions on the discussion of the results to be expected from fine screens1 ,allen states3#aci ,with openings not more than #j4a inch in size1 fine screening should remove at least #cj per cent of the suspended solids and #bj per cent of the suspended organic solids from ordinary domestic sewage1 or #j4a cubic yard of screenings1 containing #ge per cent water per thousand population daily4 ,the effect of the use of different size openings under the same conditions is shown in ,fig4 #aec4adj ,some data covering the amount of material removed by screening are given in ,table #gf4 ,more extensive data are given in ,volume ,,iii of 8,american ,sewerage ,practice0 by ,metcalf and ,eddy4 ,,table #gf ,,data ,,on ,,screens 7,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #gh1 ,page #idb7 ,type of ,location ,clear ,screenings ,screen ,opening1 in ,inches ,per ,million ,per #ajjj ,gallons1 ,population y ,cubic ,daily1 ,yard y ,cubic t ,tons ,yard t ,tons ,band ,hamburg #j4f #j4cdy #j4jahy ,gttingen #j4d #j4cey #j4jbfy ,sutton #j4cgeada #j4fy ,chicago #b4d-c4at ,wing ,frankfort #j4dj #j4gy #j4jdjy ,elberfeld #j4dj #a4aey #j4jecy ,stralsund #j4bj #j4jgiy ,wiesbaden #j4fj #a4ay #j4jccy ,shovel ,strassburg #j4aj #a4fy #j4jdcy vane ,gleiwitz #j4ab #j4aiby ,temesvar #j4ab #j4i-a4gy #j4jfg-4accy ,drum ,bromberg #j4jh #d4get ,mainz ,note #f #j4eby ,trier #j4aj #j4ci-j4dby #j4acy ,osnabruck #j4jh #c4b-d4jy #j4jh-4ajy ,weand ,reading1 #cfada #a4jy ,pa4 ,brockton #cfada #a4dt ,reinsch,dresden #j4jh #j4igt #j4jiy ,wurl ,type of,per ,cent,horse-,power ,cost of ,remarks ,screen ,moisture,per ,screen ,operation ,per ,million ,gallons1 ,dollars ,band #hg #b4e ,note #a #b4j #gi ,stock ,yard ,wing #e4j ,note #b #ge ,note #c #d4e hand power #a4fd ,note #d ,shovel #hi4c #c4ce ,note #e vane #j4ij #fj-gj small ,drum #dj-fj #b4de ,experimental #ge #e4b-f4h #j4hi-c4db #ej-fj #b4da ,experimental #i4jj ,note #g ,weand #hi4e #b4j #a4jj ,reinsch #hd #b4e 4#cbe-a4gf ,wurl ,notes3--#a4 ,after removal of this volume of grit4 #b4 ,after removal of #af per cent by the grit chamber4 #c4 ,including #j4f cubic yard grit per million gallons4 #d4 ,after passing #a4f inch bar screen4 #e4 ,after removal of #j4acb cubic yard grit and coarse screenings per #ajjj population4 #f4 #j4ab1 #j4jd-j4jh4 #g4 ,before removal of #j4d cubic yard grit per million gallons4 ,illustration3 ,,fig4 #aec4--,screenings ,collected on ,different ,sized ,openings4 #aiba ,report on ,industrial ,wastes ,disposal1 ,union ,stock ,yards ,district1 ,chicago1 ,illinois1 to the ,sanitary ,district of ,chicago4 #bca4 ,design of ,fixed and ,movable ,screens4--,the determination of the size of the opening is the first step in the design of a sewage screen4 ,this is followed by the computation of the net area of openings in the screen4 ,the final steps are the determination of the overall dimensions of the screen2 the size of the bar1 wire1 or support2 and the dimensions of the screen chamber4 ,the net area of openings is fixed by the permissible velocity of flow through the screen and the quantity of sewage to be treated4 ,in determining the velocity of flow the general principle should be followed that the velocity should not be reduced sufficiently to allow sedimentation in the screen chamber4 ,the velocity of grit bearing sewage in passing through coarse screens should not be reduced below #b or #c feet per second4 ,if the sewage contains no grit1 or the screen is placed below a grit chamber the velocity through a medium or fine screen should be from to #a feet per minute4 ,the velocity through the screen in a direction normal to the plane of the screen can be reduced without reducing the horizontal velocity of the sewage by placing the screen in a sloping position4 ,the final steps are the design of the screen bar and the determination of the dimensions of the screen and of the screen chamber4 ,the size of the bar in a bar screen1 or as a support to a wire mesh1 is dependent on the unsupported length of the bar4 ,the stresses in the bars are the results of impact and bending1 caused by cleaning1 and of the load due to the backing up of the sewage when the screen is clogged4 ,allowance should be made for a head of #b or #c feet of sewage against the screen4 ,a generous allowance should be made in addition for the indeterminate stresses due to cleaning4 ,the screen should be supported only at the top and bottom1 as intermediate supports in a bar screen are undesirable unless they are so arranged as not to interfere with the teeth of the cleaning devices4 ,fixed screens should be placed at an angle between #cj and #fj with the horizontal1 with the direction of slope such that the screenings are caught on the upper portion of the screen4 ,a small slope is desirable in order to obtain a low velocity through the screen4 ,the slope is limited since the smaller the slope the longer the bars of the screen and the greater the difficulty of hand cleaning4 ,small slopes will tend to make the screens self cleaning4 ,as the screen clogs1 the increasing head of sewage will push the accumulated screenings up the screen4 ,the use of flat screens in a vertical position is not desirable because of the difficulty of cleaning and the accumulation of material at inaccessible points4 ,if a flat screen is placed in a horizontal position with the flow of sewage downward difficulties are encountered in cleaning and solid matter is forced through the screen as clogging increases4 ,an upward flow through a horizontal screen is undesirable as the material is caught in a position inaccessible for cleaning4 ,movable screens are more easily handled when placed in a vertical position4 ,in the construction of small screens1 round bars are sometimes used where the unsupported length of the bar is less than #c or #d feet4 ,they are not recommended1 however1 as the efficient area and the amount of material removed by the screen are diminished4 ,bars which produce openings with the larger end upstream are undesirable as particles become wedged in the screen1 and are either forced through or become difficult to remove4#adb ,rectangular bars are easily obtained and give satisfactory service except where they are of insufficient strength laterally4 ,for greater lateral thickness a pear-shaped bar is sometimes used1 with the thicker side upstream4 ,fine mesh screens or perforated plates are supported on grids or parallel bars of stronger material designed to take up the heavy stresses on the screen4 ,the dimensions of the bar may be selected arbitrarily4 ,the length and width of the screen are fixed to give desirable dimensions to the screen chamber and to give the necessary net opening in the screen4 ,the width of the screen chamber and the screen should be the same4 ,the screen chamber should be sufficiently long to prevent swirling and eddying around the screen4 ,if the dimensions thus fixed permit an undesirable1 velocity in the screen chamber they should be changed4 ,a sufficient length of screen should be allowed to project above the sewage for the accumulation of screenings4 ,the bars may be carried up and bent over at the top as shown in ,fig4 #aea to simplify the removal of screenings4 ,coarse screens are usually placed above all other portions of a treatment plant4 ,they may be followed by grit chambers or finer screens4 ,coarse screens are occasionally placed as a protection above medium or fine screens4 ,in sewage containing grit the smaller screens are sometimes placed below the grit chamber4 ,it is desirable to provide some means of diverting the sewage from a screen chamber to allow of repairs to the screen and the cleaning of the chamber4 ,screen chambers are sometimes designed in duplicate to allow for the cleaning of one while the other is operating4 ,,plain ,,sedimentation #bcb4 ,theory of ,sedimentation4--,sedimentation takes place in sewage because some particles of suspended matter have a greater specific gravity than that of water4 ,all particles do not settle at the same rate4 ,since the weights of particles vary as the cubes of their diameters1 whereas the surface areas 7upon which the action of the water takes place7 vary only as the squares of the diameters1 the amount of the skin friction on small particles is proportionally greater than that on large particles1 because of the relatively greater surface area compared to their weight4 ,as a result the smaller particles settle more slowly4 ,the velocity of sedimentation of large particles has been found to vary about as the diameter and of small particles as the square root of the diameter4 ,the change takes place at a size of about #j4ja mm4 ,sedimentation is accomplished by so retarding the velocity of flow of a liquid that the settling particles will be given the opportunity to settle out4 ,the slowing down of the velocity is accomplished by passing the sewage through a chamber of greater cross-sectional area than the conduit from which it came4 ,the time that the sewage is in this chamber is called the period of retention4 ,although the shape of a basin1 the arrangement of the baffles and other details have a marked effect on the results of sedimentation1 the controlling factors are the period of retention and the velocity of flow4 ,another factor affecting the efficiency of the process is the quality of the sewage4 ,usually the greater the amount of sediment in the sewage the greater the per cent of suspended matter removed4 ,a method for the determination of the proper period of sedimentation has been developed by ,hazen in ,transactions of the ,american ,society of ,civil ,engineers1 ,volume #ec1 #aijd1 page #de4 ,the results of his studies are summarized in ,fig4 #aed which shows the per cent of sediment remaining in a treated water after a certain period of retention4 ,this period of retention is expressed in terms of the hydraulic coefficient#adc of the smallest size particle to be removed4 ,table #gg shows the hydraulic coefficients of various particles4 ,in ,fig4 #aed a represents the period of retention and t the time that it would take a particle to fall to the bottom of the basin4 ,the different lines of the diagram represent the results to be expected by various arrangements of settling basins4 ,the meaning of these lines is given in ,table #gh4 ,,table #gg ,,hydraulic ,,values ,,of ,,settling ,,particles ,,in ,,millimeters ,,per ,,second ,diameter in mm4 ,hydraulic ,value #a4jj #ajj #j4hj #hc #j4fj #fc #j4ej #ec #j4dj #db #j4cj #cb #j4bj #ba #j4ae #ae #j4aj #h #j4jh #f #j4jf #c4h #j4je #b4i #j4jd #b4a #j4jc #a4c #j4jb #j4fb #j4jae #j4ce #j4jaj #j4aed #j4jjh #j4jih #j4jjf #j4jee #j4jje #j4jche #j4jjd #j4jbdg #j4jjc #j4jach #j4jjb #j4jjfb #j4jjae #j4jjce #j4jja #j4jjaed #j4jjja #j4jjjjaed ,an example will be given to illustrate the method of using the diagram and tables to determine the size of a sedimentation basin to perform certain required work4 ,let it be required to determine the period of retention in a continuously operated sedimentation basin with good baffling1 corresponding to two properly baffled sedimentation basins in series4 ,the basins are to remove #fj per cent of the finest particles which are to have a size of 4#ja mm4 ,the quantity to be treated daily is #c1jjj1jjj gallons4 #ast4 ,entering ,table #gg1 we find that the hydraulic value of the finest particles is 4#aed mm4 per second4 #b;d4 ,since we wish to remove #fj per cent of the finest particles1 #dj per cent will remain4 ,since ,fig4 #aed shows the per cent remaining after the time at we enter ,fig4 #aed at #dj per cent on the ordinates and run horizontally until we encounter ,line #d corresponding to good baffling in ,table #gh4 ,we then run down vertically from this intersection and find that the ratio of at is #a4j4 ,then a equals t1 which means that the period of retention should equal the time that it takes a particle #j4ja mm4 in diameter to drop from the top to the bottom of the basin4 ,since this depends on the depth of the basin it is necessary to determine the depth before the other dimensions of the basin can be fixed4 ,although this method is seldom used in practice for the final design of a sedimentation basin1 it is a guide to judgment and can be used to supplement the data obtained from tests4 ,illustration3 ,,fig4 #aed4--;,hazen's ,diagram1 ,showing the ,relation between the ,time of ,settling and the ,period of ,retention in ,various ,types of ,sedimentation ,basins4 ,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #ec1 #aijd1 p4 #de4 ,,table #gh ,,comparison ,,of ,,different ,,arrangements ,,of ,,settling ,,basins 7,from ,hazen7 ,description of ,basins ,line in ,fig4 ,values of #aed at4 ,per ,cent of ,matter ,removed #ej #gd #hg4e ,theoretical maximum4 ,cannot be reached4 ,a #j4ej #j4gej4hge ,surface skimming4 ,rockner ,roth system4 ,b #j4ed #j4ih #a4cg ,intermittent basins1 reckoned on time of ,c service only4 #j4fc #a4bf #a4hi ,continuous basin4 ,theoretical limit4 ,d #j4fi #a4ch #b4jh ,close approximation to the above4 #af #j4ga #a4de #b4bc ,very well baffled basin4 #h #j4gc #a4fb #b4cg ,good baffling4 #d #j4gf #a4ff #b4ge ,two basins1 tandem4 #b #j4hb #b4jj #c4gj ,one long basin1 well controlled4 #a4e #j4ij #b4cd #d4ej ,intermittent basin in service half time4 ,e #a4bf #b4ej #c4hj ,one basin1 continuous4 #a #a4j #c4jj #g4jj ,the design of sedimentation basins should be based on experimental observations made upon the quantity of sediment removed at certain rates of flow and periods of retention in different types of basins4 ,hazen's mathematical analysis is serviceable in making preliminary estimates and in checking the results4 ,the shape of the tank1 period of retention and rate of flow producing the most desirable results should be duplicated with the expectation of obtaining similar results or results but slightly modified from those obtained in the tests4 ,this is the most satisfactory method of determining the proper period of retention4 #bcc4 ,types of ,sedimentation ,basins4--,a sedimentation basin is a tank for the removal of suspended matter either by quiescent settlement or by continuous flow at such a velocity and time of retention as to allow deposition of suspended matter4#add ,the difference between sedimentation tanks and other forms of tank treatment is that no chemical or biological action is depended on for the successful operation of the tank4 ,sedimentation tanks may be divided into two classes1 grit chambers and plain sedimentation basins4 ,a grit chamber is a chamber or enlarged channel in which the velocity of flow is so controlled that only heavy solids1 such as grit and sand1 are deposited while the lighter organic solids are carried forward in suspension4 ,if the velocity of flow is more than about one foot per second1 the tank is a grit chamber and below this velocity it is a plain sedimentation basin4 ,there are six general types of plain sedimentation basins3 #ast4 ,rectangular flat-bottom tanks operated on the continuous-flow principle4 #bnd4 ,rectangular flat-bottom tanks operated on the fill and draw principle4 #crd4 ,rectangular or circular hopper-bottom tanks operated on the continuous-flow principle1 with horizontal flow4 #dth4 ,rectangular or circular hopper-bottom tanks operated on the fill and draw principle1 with horizontal flow4 #eth4 ,rectangular or circular hopper-bottom tanks operated on the continuous-flow principle with vertical flow4 #fth4 ,circular hopper-bottom tanks operated on the continuous-flow principle with radial flow4 ,,table #gi ,,critical ,,velocities ,,for ,,the ,,transportation ,,of ,,debris ,sedimentation will not ,occur at ,higher ,velocities ,diameter of,critical ,velocity1 ,feet per ,second4 ,size of ,screen or ,particle in ,number of ,meshes per ,millimeters ,inch ,specific ,gravity #a4e #b4j #c4j #e4j #j4jaj #j4ac #j4bj #j4bb #j4bh #j4jej #j4bc #j4cd #j4ci #j4ej ,more than #bjj #j4ajj #j4cj #j4db #j4ej #j4fe ,more than #aej #j4ejj #j4ee #j4gc #j4ia #a4ae ,more than #bh #a4j #j4ga #j4ib #a4ah #a4ej ,more than #ad #a4be #j4gg #a4jj #a4cj #a4fj #b4j #j4ib #a4bj #a4ej #a4ij ,more than #aj #e4j #a4cj #a4gj #b4bj #b4fj ,more than #d #aj #a4gj #b4bj #b4h #c4d ,diameter in ,millimeters for a ,velocity of #a ,foot per ,second #b4e #a4be #j4fe #j4cb #bcd4 ,limiting ,velocities4--,sand1 clay1 bits of metal and other particles of mineral matter will commence to deposit in appreciable quantities when the velocity of flow falls below #c feet per second4 ,the amount deposited will increase as the velocity decreases4 ,in ,table #gi are given the approximate horizontal velocities at which certain size particles of mineral matter will deposit4 ,at a velocity of about one foot per second organic matter will commence to deposit4 ,it will be noticed by interpolation in ,table #gi1ade that particles with the same specific gravity as sand 7#b4f71 larger than one mm4 in diameter will deposit at a velocity of about one foot per second or less1 and that smaller and lighter particles will not deposit at velocity of one foot per second or greater4 ,it will also be noticed that a velocity of one foot per minute is sufficiently slow to permit the deposit of the smallest and lightest particles4 ,for this reason velocities of #a or #b or even #c feet per second have been adopted as the velocities in grit chambers and velocities less than #a foot per minute in plain sedimentation basins4 #bce4 ,quantity and ,character of ,grit4--,the amount of material deposited in grit chambers varies approximately between #j4aj and #j4ej cubic yard per million gallons4 ,it is to be noted that grit chambers are used only for combined and storm sewage and for certain industrial wastes4 ,they are unnecessary for ordinary domestic sewage4 ,the material deposited in grit chambers operating with a velocity greater than one foot per second is non-putrescible1 inorganic1 and inoffensive4 ,it can be used for filling1 for making paths and roadways1 or as a filtering material for sludge drying beds4 ,an analysis of a typical grit chamber sludge is shown in ,table #hj4 ,,table #hj ,,analysis ,,of ,,grit ,,chamber ,,sludge ,velocity ,specific ,per ,cent ,calculated to ,dry ,weight1 ,per ,cent ,feet per ,gravity ,moisture ,second ,nitrogen ,fixed ,miscellaneous ,matter #a4j #a4e #de #bj #gh #b #bcf4 ,dimensions of ,grit ,chambers4--,the quantity of sewage to be treated and the amount and character of the settling solids which it contains should be determined by measurement and analysis1 and the amount of settling solids to be removed should be determined by a study of the desired conditions of disposal1 in order that a grit chamber that will accomplish the desired results may be designed4 ,the period of retention and the velocity of flow are the controlling features in the successful operation of any grit chamber4 ,these should be determined by experiment or as the result of experience4 ,where neither are available1 ,hazen's method can be followed or a decision made based on a study of other grit chambers4 ,in general1 the period of retention in grit chambers is from #cj to #ij seconds1 and the velocity of flow is about one foot per second4 ,after having determined the quantity of sewage to be treated1 the quantity of grit to be stored between cleanings1 the period of retention1 the arrangement of the chambers1 and the velocity of flow to be used1 the overall dimensions of the chambers are computed4 ,the capacity of the chamber is fixed as the sum of the quantity of sewage to be treated during the period of retention and the required storage capacity for grit accumulated between cleanings4 ,the length of the chamber is fixed as the product of the velocity of flow and the period of retention4 ,the cross-sectional area of the portion of the chamber devoted to sedimentation is fixed as the quotient of the quantity of flow of sewage per unit time and the velocity of flow4 ,only the relation between the width and depth of the portion devoted to sedimentation and the portion devoted to the storage of grit remain to be determined4 ,these should be so designed as to give the greatest economy of construction commensurate with the required results4 ,they will be affected by the local conditions such as topography1 available space1 difficulties of excavation1 etc4 ,common depths in use lie between #h and #ab feet1 although wide variations can be found4 ,a study of the proportions of existing grit chambers will be of assistance in the design of other basins4 #bcg4 ,existing ,grit ,chambers4--,the details of some typical grit chambers are shown in ,figs4 #aee and #aef4 ,the grit chamber at the foot of #ehth ,street1 in ,cleveland1 ,ohio1 is shown in ,fig4 #aee4 ,the special feature of this structure is the shape of the sedimentation basin1 the bottom of which is formed by sloping steel plates forming a #f-;inch longitudinal slot above the grit storage chamber4 ,flows between #h1jjj1jjj and #af1jjj1jjj gallons per day are controlled by the outlet weir so that the velocity of flow remains at one foot per second4 ,this is accomplished by increasing the depth of flow in the same ratio as the increase in the rate of flow4 ,the bottoms of the two chambers differ1 one having a special hopper for grit and the other a flat bottom4 ,this is due to the method of cleaning the chambers1 it being necessary in the one with a flat bottom to shut off the flow when removing the grit while in the one with the hopper bottom it is hoped to remove the grit by the use of sand ejectors without stopping the sewage flow4 ,the details of the chamber at ,hamilton1 ,ontario1 are shown in ,fig4 #aef4 ,in studying these drawings the following features should be noted3 #ast1 the smooth curves in the channel to prevent eddies1 undue deposition of organic matter1 and difficulties in cleaning2 #bnd1 the hopper in the upper end of the grit storage chamber and the slope of the bottom of at least #a3bj2 and #crd1 the simplicity of the inlet and outlet devices which may be either stop planks or cast-iron sluice gates4 ,illustration3 ,,fig4 #aee4--;,grit ,chamber at ,cleveland1 ,ohio4 ,eng4 ,record1 ,vol4 #gc1 #aiaf1 p4 #dji4 ,illustration3 ,,fig4 #aef4--;,grit ,chamber at ,hamilton1 ,ontario4 ,eng4 ,news1 ,vol4 #gc1 #aiae1 p4 #dbe4 ,the drawings shown are merely representative of some satisfactory types4 ,the number and variety of grit chambers in existence is great4 ,in designing grit chambers consideration must be given to the method of cleaning4 ,they are ordinarily cleaned by such methods as have been described for the cleaning of catch-basins in ,chapter ,,xii4 ,continuous bucket scrapers similar to excavating machines are sometimes used for the cleaning of large grit chambers4 ,the period between cleanings is variable4 ,the design should be such as not to require more frequent cleanings than twice a month under the worst conditions4 ,the fluctuations in quality and quantity of grit will vary the period between cleanings4 #bch4 ,number of ,grit ,chambers4--,the period of retention in grit chambers is so short and the velocity of flow so near the maximum and minimum limitations that the wide fluctuations in the rate of discharge in storm and combined sewers necessitates the construction of a number of chambers which should be operated in parallel in order to maintain the velocity between the proper limits4 ,unless arrangements are made permitting the cleaning of grit chambers during operation1 more than one grit chamber should be installed in order that when one is being cleaned the others may be in operation4 ,the number of grit chambers must be determined by the desired conditions of operation and the cost of construction4 ,the larger the number of basins the more nearly the flow in any one basin can be maintained constant1 but the more expensive the construction4 ,the increase in velocity of flow with increasing quantity is dependent on the outlet arrangements4 ,in a shallow chamber with vertical sides and a standard sharp-crested rectangular weir at the outlet the velocity will vary approximately as the cube root of the rate of flow4 ,similarly if the outlet is a ,v notch the velocity will vary as the fifth root of the rate of flow4 ,in all cases the deeper the basin the more nearly the velocity varies directly as the rate of flow4 ,the outlet weir can be arranged as at ,cleveland1 so that the velocity remains constant for all rates of flow within certain limits4 ,it is seldom that more than three grit chambers are necessary to care for the fluctuations in flow4 #bci4 ,quantity and ,characteristics of ,sludge from ,plain ,sedimentation4--,the sludge removed from plain sedimentation basins is slimy1 offensive1 not easily dried1 and is highly putrescible and odoriferous4 ,it contains about #ij per cent moisture and has a specific gravity from #a4ja to #a4je4 ,the amount removed varies between #b and #e cubic yards per million gallons of sewage4 ,the percentage of suspended matter removed varies between #bj and #fj4 ,the total amount removed and the percentage removal depend on the character of the sewage1 the type of basin1 and the period of detention4 #bdj4 ,dimensions of ,sedimentation ,basins4--,the dimensions of a sedimentation basin are determined by a method similar to the one given for the determination of the dimensions of a grit chamber in ,art4 #bcf4 ,the capacity of the basin is first fixed upon to give the required period of sedimentation and sludge storage capacity4 ,the length of the basin is the product of the velocity and the period of retention4 ,the length1 width1 and depth of the basin are normally fixed by considerations of economy and the limitations of the local conditions1 such as available area1 topography1 foundations1 etc41 and examples of good practice4 ,a study of basins in use shows the relation between length and width to vary normally between #b3a and #d3a4 ,widths greater than #cj to #ej feet are undesirable because of the danger of cross currents and back eddies which will reduce the efficiency of the sedimentation4 ,depths used in practice vary too widely to act as guides for any particular design4 ,theoretically the shallower the basin the better the result4 ,tanks abroad have been built as shallow as #c feet and some in this country as deep as #af feet4 ,the economical dimensions can be determined by trial or by calculus4 ,they will serve as a guide in the adoption of the final dimensions4 ,the method to be pursued in determining the economical dimensions of any engineering structure are3 ,i4 ,express the total cost of the structure in terms of as few variables as possible4 ,,ii4 ,express all of the variables in terms of any one and rewrite the expression for the total cost in terms of this one variable4 ,,iii4 ,equate the first derivative of the expression with regard to this variable to zero and solve for the variable4 ,the result will be the economical value of the variable4 ,the values of the other variables can be computed from the relations already expressed4 ,illustration3 ,,fig4 #aeg4--;,diagram for the ,computation of ,economical ,basin ,dimensions4 ,for example1 let it be desired to determine the dimensions of two continuous-flow sedimentation basins as shown in ,fig4 #aeg1 in which the period of retention in each is to be #b hours1 the velocity of flow is not to exceed one foot per second1 and the sludge accumulated will be #c cubic yards per million gallons of sewage treated4 ,the quantity of sewage to be treated is #ah1jjj1jjj gallons per day4 ,the shortest time between cleanings will be #b weeks4 ,the capacity of each basin must be #b_/bd of #ah1jjj1jjj gallons1 or #bjj1jjj cubic feet in order to allow a period of retention of #b hours4 ,to this volume should be added sufficient capacity to allow for the #b weeks of sludge storage between cleanings4 ,when a basin is being cleaned the load must be put on the remaining basins4 ,then if ,q represents the rate of accumulation of sludge per day1 n represents the number of days between cleanings1 m represents the number of basins1 and ,s the sludge capacity of one basin1 then ,s 7,q7n #a77m ,q7m #a7 ,the sludge storage capacity for the example given will be approximately #aa1jjj cubic feet4 ,in expressing the total cost of the basins let h the depth in feet4 l the length in feet4 b the width in feet4 ,the cost of land1 floor1 etc41 per square foot p dollars4 ,the cost of wall per foot length qh#b dollars4 ,the cost of pipes1 valves and appurtenances ,p dollars4 ,then the total cost ,c 7#cl #d;b7qh#b #bplb ,p4 ,it is now necessary to express the three variables b1 l1 and h1 in terms of one of them4 ,from the relation ,q #b;blh it is possible to rewrite the expression for the total cost as3 ,c 7#c,q7#b;bh7 #d;b7qh#b 7p,q7h ,p4 ,c 7#cl #b,q7lh77qh#b 7p,q7h ,p4 ,holding h constant and differentiating with regard to b in the first expression and with regard to l in the second expression1 equating to zero and solving we get3 b 77#c,q77#h;h77 and l 77#b,q77#c;h774 ,the economical relation between b and l is therefore b #j4gel regardless of the value of h4 ,substituting these values of l and b in the original expression for the total cost1 it becomes ,c 7#c77b,q77#c;h77 #d77c,q77#h;h777qh#b 7p,q7h ,p4 ,differentiating with regard to h1 equating to zero1 and solving h #j4de77p,q7q74 ,in the example given if q #j4b and p #a4j then h #aa4f feet1 b #abj feet and l #afj feet4 ,since these are reasonable dimensions and in accord with good practice they should be used1 unless other conditions are unsuitable or the velocity of flow is too great4 ,a width of channel of #abj feet as compared to a length of #afj feet is conducive to a poor distribution of velocity across the basin4 ,a ratio of width to length of about #a3d is desirable4 ,in this case1 by the use of three baffles parallel to the length of the basin1 thus dividing it into channels #dj feet wide and #aa4f feet deep1 the ratio of width to length is changed to #a3d and the velocity will be increased only to #j4jf foot per second or #c4f feet per minute1 which is a reasonable velocity4 ,it could be reduced by increasing the spacing of the baffles or the depth of the chamber4 ,complicated baffling is undesirable4 ,two or three overflow baffles may be used to permit quiescent sedimentation in the space thus formed1 and hanging baffles may be placed before the inlet and outlet to break up surface currents1 or to prevent the movement of scum4 ,the hanging baffles should not extend more than #ab to #ah inches below the water surface4 ,the inlet and outlet are sometimes arranged to permit the reversal of flow1 and the connecting channels between basins to allow the operation of any number of basins in series or in parallel1 although such arrangements are more important in water purification4 ,sewage should enter and leave at the top of the basin4 ,illustration3 ,,fig4 #aeh4--,section through a ,dortmund ,tank4 ,depth #bj to #cj feet4 ,cleaning is facilitated by the location of a central gutter in the bottom of the basin with the slope of the bottom of the basin towards the gutter from #a3be to #a3hj or steeper4 ,a pipe1 #b inches or larger in diameter1 containing water under pressure with connections for hose placed at frequent intervals is a useful adjunct in flushing the sludge from the sedimentation basins4 ,for equal capacity1 deep vertical flow tanks are more expensive and difficult to construct than the shallower rectangular type4 ,deep tanks are advantageous1 however1 in that sludge can sometimes be removed by gravity or by pumping without stopping the operation of the tank4 ,they will also operate successfully with shorter periods of detention and higher velocities4 ,the upward velocity should not be greater than the velocity of sedimentation of the smallest particle to be removed4 ,the efficiency of sedimentation in them will be increased by the sedimentation of the larger particles which drag some of the smaller particles down with them4 ,the ,dortmund tank shown in ,fig4 #aeh is an example of this type4 ,ordinarily it is not necessary to roof sedimentation basins as the odors created are not strong1 and difficulties with ice are seldom serious4 ,,chemical ,,precipitation #bda4 ,the ,process4--,chemical precipitation consists in adding to the sewage such chemicals as will1 by reaction with each other and the constituents of the sewage1 produce a flocculent precipitate and thus hasten sedimentation4 ,the advantages of this process over plain sedimentation are a more rapid and thorough removal of suspended matter4 ,its disadvantages include the accumulation of a large amount of sludge1 the necessity for skilled attendance1 and the expense of chemicals4 ,the process is not in extensive use as the conditions under which the advantages outweigh the disadvantages are unusual4 ,sewage containing large quantities of substances which will react with a small amount of an added chemical to produce the required precipitate are the most favorable for this method of treatment4 ,chemical precipitation accomplishes the same result as plain sedimentation1 although the effluent from the chemically precipitated sewage may be of better quality than that from a plain sedimentation basin4 #bdb4 ,chemicals4--,lime is practically the only chemical used for the precipitation of the solid matter in sewage4 ,commercial lime used for precipitation consists of calcium oxide 7,ca,o71 with large quantities of impurities4 ,it should be stored in a dry place and protected from undue exposure to the air to prevent the formation of calcium carbonate 7,ca,c,o#c71 the formation of which is commonly known as air slacking4 ,the active work in the formation of the precipitate is performed by the lime 7,ca,o7 or calcium hydroxide 7,ca7,,oh7#b74 ,the lime should therefore be purchased on the basis of available ,ca,o1 which may be as low as #aj to #ae per cent in some commercial products4 ,the amount of lime necessary depends on the quality of the sewage1 the period of retention in the sedimentation basin1 the method of application1 the required results1 and other less easily measured factors4 ,full scale tests for the amount of lime needed to produce certain results are the most satisfactory4 ,in practice the amount of lime necessary when lime alone is used as a precipitant has been found to be about #ae grains per gallon4 ,this may be markedly different1 dependent on the quality of the sewage4 ,for acid sewages1 lime alone is not suitable as a precipitant since it is necessary to add sufficient lime to neutralize the sewage before the calcium carbonate will be precipitated4 ,the use of copperas 7,fe,s,o#d7 together with lime1 leads to economy in the use of chemicals as the flocculent precipitate of ferrous hydroxide 7,fe7,,oh7#b7 is more voluminous than the precipitate of calcium carbonate4 ,this is commonly known as the lime and iron process4 ,the presence of iron in certain trade wastes may reduce the cost of chemical precipitation1 as the necessary amount of copperas is reduced4 ,where #ae grains of lime alone will be needed per gallon of sewage1 the total amount of chemicals used will be reduced to #h to #aj grains per gallon with the use of lime and iron4 ,this combination is less expensive than the use of lime alone1 and is even cheaper where the iron is already present in the sewage4 ,such a condition is well illustrated by the sewage at ,worcester1 ,mass41 where the oldest and best known chemical precipitation plant in the ,united ,states is located4 ,the amount of lime used at this plant has varied between #f and #aj grains per gallon of sewage1 the normal amount being about #g grains4 ,no iron is added because of the amount already in solution4 ,the results of a series of experiments on the chemical precipitation of sewage by ,allen ,hazen1 are given in the #ahij ,report of the ,massachusetts ,state ,board of ,health1 on p4 #gcg of the volume on the ,purification of ,water and ,sewage4 ,hazen concludes as the result of his experiments3 concerning lime1 ,there is a certain definite amount of lime 444 which gives as good or better results than either more or less4 ,this amount is that which exactly suffices to form normal carbonates with all the carbonic acid of the sewage4 ,this amount can be determined in a few minutes by simple titration4 ,concerning lime and iron 7copperas7 he states3 ,ordinary house sewage is not sufficiently alkaline to precipitate copperas1 and a small amount of lime must be added to obtain good results4 ,the quantity of lime required depends both upon the composition of the sewage and the amount of copperas used1 and can be calculated from titration of the sewage4 ,very imperfect results are obtained from too little lime1 and1 when too much is used1 the excess is wasted1 the result being the same as with a smaller quantity4 ,in precipitation by ferric sulphate and crude alum1 the addition of lime was found unnecessary1 as ordinary sewage contains enough alkali to decompose these salts4 ,within reasonable limits the more of these precipitants used the better is the result1 but with very large quantities the improvement does not compare with the increased cost4 ,using equal values of different precipitants1 applied under the most favorable conditions for each1 upon the same sewage1 the best results were obtained from ferric sulphate4 ,nearly as good results were obtained from copperas and lime used together1 while lime and alum each gave somewhat inferior effluents4444 ,when lime is used there is always so much lime left in solution that it is doubtful if its use would ever be found satisfactory except in case of an acid sewage4 ,it is quite impossible to obtain effluents by chemical precipitation which will compare in organic purity with those obtained by intermittent filtration through sand4 ,it is possible to remove from one-half to two-thirds of the organic matter by precipitation 444 and it seems probable that 444 a result may be obtained which will effectually prevent a public nuisance4 #bdc4 ,preparation and ,addition of ,chemicals4--,lime is not readily soluble in water4 ,therefore1 it is not best to add the lime as a powder to the sewage1 but to form a milk of lime1 that is1 a supersaturated solution containing from #b1jjj to #d1jjj grains per gallon1 although dry slaked lime has sometimes been applied directly4 ,the solution is prepared in tanks in a quantity sufficient for some part of the day's run1 commonly sufficient to last through one shift of #h or #aj hours4 ,the lime is prepared by placing the amount necessary to fill one storage tank into a slaking tank containing some cold water4 ,sufficient water is added to keep the solution just at the boiling point1 or steam may be added to make it boil4 ,after slaking1 it is run into the milk-of-lime solution tank and sufficient water added to bring to the proper strength4 ,the milk of lime is added in measured quantities1 being controlled by a variable head on a fixed orifice or weir1 so that it may be varied with the amount of sewage flowing through the plant4 ,the amount of lime to be added is determined by titration with phenolphthalein1 experience indicating the color to be obtained when the proper amount of lime has been added4 ,the use of either copperas or alum has been so rare1 for the precipitation of sewage1 that a description of the methods of handling these chemicals as a sewage precipitant is not warranted4 ,an excellent description of the methods of handling these chemicals in water purification will be found in 8,water ,purification0 by ,ellms4 ,,table #ha ,,results ,,of ,,chemical ,,precipitation ,,at ,,worcester1 ,,massachusetts#adf #aijj #aiaj #aibj ,amount of sewage treated1 million #d1gha #e1cag #h1hic gallons ,amount of sewage chemically treated1 #c1fej #c1egd #g1cjj million gallons ,gallons of wet sludge per million #d1dej #d1ahe gallons of sewage treated ,per cent of solids in sludge #d4db #h4bj #d4fdadg ,tons of solids #g1bid #d1ahb #f1dcaadg ,pounds of lime added per million #iiiadh #gfbadg #ecd gallons of sewage pumped ,per cent of organic matter removed3 ,by albuminoid ammonia3 ,total #eb4gadi #eh4d #ea4i ,suspended #ij4jadi #hh4g #hc4f ,by oxygen consumed3 ,total #fb4hadi #fa4a #fb4e ,suspended #hf4fadi #hi4g #hf4b #bdd4 ,results4--,the results of ,hazen's experiments indicate that a greater amount of suspended matter can be removed in the same time by chemical precipitation than by plain sedimentation4 ,the percentage of removal of suspended matter may be as high as #hj to #ij per cent with a period of retention of #f to #h hours and the addition of a proper amount of chemical4 ,that the method is not always a success is shown by the results of some tests at ,canton1 ,ohio4#aej ,the report states3 444 lime treatment removes about #ej per cent of the suspended matter1 and in the main about #ej per cent of the organic matter4444 ,these data are instructive as indicating that the addition of lime to the ,canton sewage in quantities as previously stated does not materially improve the character of the resulting effluent over and above that which could be produced by plain sedimentation alone4 ,the plant at ,worcester1 ,mass41 is the largest in the ,united ,states and information from it is of value4 ,a summary of the results at ,worcester for #aijj1 #aiaj1 and #aibj are shown in ,table #ha4 ,,chapter ,,xvi ,,septicization #bde4 ,the ,process4--,septic action is a biological process caused by the activity of obligatory or facultative anarobes as the result of which certain organic compounds are reduced from higher to lower conditions of oxidation1 some of the solid organic substances are rendered soluble1 and a quantity of gas is given off4 ,among these gases are3 methane1 hydrogen sulphide1 and ammonia4 ,the biologic process in the septic tank represents the downward portion of the cycle of life and death1 in which complex organic compounds are reduced to a more simple condition available as food for low forms of plant life4 ,the disposal of sewage by septic action1 when introduced1 promised the solution of all problems in sewage treatment4 ,septic action is now better understood1 and it is known that some of the early claims were unfounded4 ,the principal advantage of septic action in sewage treatment is the relatively small amount of sludge which must be cared for compared to that produced by a plain sedimentation tank4 ,the sludge from a septic tank may be #be to #cj per cent and in some cases #dj per cent less in weight1 and #ge to #hj per cent less in volume than the sludge from a plain sedimentation tank4 ,the most important results of septic action and the greatest septic activity occur in the deposited organic matter or sludge4 ,the biologic changes due to septic action which occur in the liquid portion of the tank contents are of little or no importance4 ,the installation of a septic tank1 although it may fail to prevent the nuisance calling for abatement1 has a remarkable psychological effect in stilling complaints4 ,among other advantages are the comparative inexpensiveness of the tanks and the small amount of attention and skilled attendance required4 ,the tanks need cleaning once in #f months to a year4 ,if properly designed no other attention is necessary4 ,the septic tank has fallen into some disrepute because of the better results obtainable by other methods1 the occasional discharge of effluents worse than the influent1 the occasional discharge of sludge in the effluent caused by too violent septic boiling1 and on account of patent litigation4 ,this last difficulty has been overcome as the ,cameron patents expired in #aiaf4 ,occasionally the odors given off by the septic process are highly objectionable and are carried for a long distance4 ,these odors can be controlled to a large extent by housing the tanks4 ,over-septicization must be guarded against as an over-septicized effluent is more difficult of further treatment or of disposal than a comparatively fresh1 untreated sewage4 ,an over-septicized or stale sewage is indicated by the presence of large quantities of ammonias1 either free or albuminoid1 frequently accompanied by hydrogen sulphide and other foul-smelling gases4 ,the oxygen demand in an over-septicized sewage is greater than that in a fresh or more carefully treated sewage4 #bdf4 ,the ,septic ,tank4--,a septic tank is a horizontal1 continuous-flow1 one-story sedimentation tank through which sewage is allowed to flow slowly to permit suspended matter to settle to the bottom where it is retained until anarobic decomposition is established1 resulting in the changing of some of the suspended organic matter into liquid and gaseous substances1 and a consequent reduction in the quantity of sludge to be disposed of4#aea ,it is to be noted that a continuous flow is essential to a septic tank4 ,small tanks containing stagnant household sewage are called cesspools1 although sometimes erroneously spoken of as septic tanks4 ,septic and sedimentation tanks differ in their method of operation only in the period of storage and the frequency of cleaning4 ,the period of flow in a septic tank is longer and it is cleaned less frequently4 ,the results obtained by the two processes differ widely4 ,a septic tank can be converted into a sedimentation tank1 or vice versa1 by changing the method of operation1 no constructional features requiring alteration4 ,the purpose of the tank is to store the sludge for such a period of time that partial liquefaction of the sludge may take place1 and thus minimize the difficulty of sludge disposal4 ,for this reason the sludge storage capacity of a septic tank is sometimes greater than would be necessary for a plain sedimentation tank4 ,,table #hb ,,efficiencies ,,and ,,performance ,,of ,,septic ,,tank ,,at ,,columbus1 ,,ohio 7,report of ,sewage ,purification1 by ,g4 ,a4 ,johnson1 ,nov4 #aj1 #aije7 ,month1 ,aug4,sept4,oct4,nov4,dec4,jan4,feb4,mar ch,april,may,june,avg4 #aijd-aije ,temperature1 degrees ,f4 ,influent #fi #gj #fe #fj #ed #ea #dh #ej #eg #fa #fg ,effluent #fi #fh #fd #ei #eb #dh #de #di #eg #fb #fh ,oxygen consumed1 parts per million3 ,influent #di #ej #eb #dg #dc #ea #dd #dg #ec #cc #dj #dg ,effluent #dj #cf #dj #ci #cg #ce #cg #ci #ej #cd #cc #ch ,per cent #ah #bh #bc #ae #af #ca #af #ag #f -#c #ah #ai removal ,organic nitrogen1 parts per million3 ,influent #f4e #h4b #i4c #h4d #h4h #h4e #f4g #f4d #g4i #f4af4g #g4h ,effluent #g4c #e4e #f4j #g4d #h4b #g4j #e4d #e4e #e4b ,per cent -#ab #cb #ce #ab #g #ah #ai #ad #be #cj #ai #ai removal ,free ammonia1 parts per million3 ,influent #i4g #ab4b #ab4daf4cad4gaj4hh4c #i4i #ab4c #f4ih4c #aa4g ,effluent #aj4eaa4e #ab4dag4bad4caa4ah4i #aj4g #ad4i #i4jh4g #ab4a ,per cent -#h #f #j -#f #c -#c -#g -#h -#ba -#bc -#e -#c removal ,residue on ,evaporation1 parts per million3 ,total3 ,influent #iij #ieb #iic #ifa #ihi #idi #hij #hej #ajfg #iabide #idf ,effluent #ice #hia #hic #iaf #ibe #hhf #hdc #ghb #hie #hjjhce #hgc ,per cent #f #f #aj #e #f #f #e #h #af #ab #ab #h removal ,volatile3 ,influent #bca #ahd #afb #age #aef #afg #aef #afh #bab #abbafb #aff ,effluent #bjf #afj #abi #adh #acg #acg #acd #acg #adg #ajcadd #aci ,per cent #aa #ac #bj #ae #ab #ah #ad #ah #ca #af #aa #af removal ,mineral3 ,influent #gei #gfh #hca #ghf #hcc #ghb #gcd #fhb #hee #gjjghc #ghj ,effluent #gbi #gca #gfd #gfh #ghh #gdi #gji #fde #gdh #figfia #gcd ,per cent #d #e #h #b #e #d #c #e #aa #a #ab #f removal ,cubic yards #j4aja4bda4jia4agj4fej4fc #j4eg #a4cd wet sludge per million gallons3 ,per cent removal of suspended matter3 ,total #ei #ed #ef #ea #db #dh #cb #dg #ef #fg #ec #ej ,volatile #fj #da #dh #eb #dd #ee #dg #dg #fb #hj #ae #dh ,fixed #ge #fe #fj #ea #dj #ch #ai #dh #ec #fd #fg #ea ,gas evolved1 #bi #ad #da #ej cubic feet per day3 #bdg4 ,results of ,septic ,action4--,the results obtained from the septic tanks at the ,columbus ,sewage ,experiment ,station are given in ,table #hb4 ,the effluent is higher than the influent in free ammonia1 but the reduction of other constituents1 particularly suspended matter1 is marked4 ,septic action is sensitive to temperature changes1 and to certain constituents of the incoming sewage4 ,cold weather or an acid influent will inhibit septicization4 ,in winter the liquefaction of sludge may practically cease1 whereas in summer liquefaction may exceed deposition4 ,the amount of gas generated is a measure of the relative amount of septic action4 ,the rapid generation of gas in warm weather disturbs the settled sludge and may cause a deterioration of the quality of the effluent because of the presence of decomposed sludge4 ,the results in ,table #hb show the effect of cold weather on the process4 ,in warm weather the violent ebullition of gas sometimes causes the discharge of sludge in the effluent1 resulting in a liquid more difficult of disposal than the incoming sewage4 ,since septic action is dependent on the presence of certain forms of bacteria1 where these are absent there will be no septic action4 ,sewage generally contains the forms of bacteria necessary for this action but it has occasionally been found necessary to seed new tanks in order to start septic action4 ,the sludge from septic tanks is usually black1 with a slight odor1 though in some cases this odor may be highly offensive4 ,the sludge will flow sluggishly4 ,it can be pumped by centrifugal pumps and it will flow through pipes and channels4 ,it has a moisture content of about #ij per cent and a specific gravity of about #a4jc4 ,it is dried with difficulty on open-air drying beds1 and it is worthless as a fertilizer4 ,the composition of some septic sludges are shown in ,table #hc4 #bdh4 ,design of ,septic ,tanks4--,the sedimentation chambers of a septic tank are designed on the same principles as the sedimentation basins described in ,art4 #bdj4 ,the velocity of flow should not exceed one foot per minute4 ,the channels should be straight and free from obstructions causing back eddies4 ,the ratio of length to width of channel should be between #b 3 #a to #d 3 #a with a width not exceeding #ej feet1 and desirably narrower4 ,the depths used vary between #e and #aj feet1 exclusive of the sludge storage capacity4 ,hanging baffles should be placed1 one before the inlet and the other in front of the outlet1 so as to distribute the incoming sewage over the tank1 and to prevent scum from passing into the outlet4 ,the baffles should hang about #ab inches below the surface of the sewage4 ,intermediate baffles are sometimes desirable to prevent the movement of sludge or scum towards the outlet4 ,the placing of baffles must be considered carefully as injudicious baffling may lessen the effectiveness of a tank by so concentrating the currents as to prevent sedimentation or the accumulation of sludge4 ,baffles should be built of concrete or brick1 as wood or metal in contact with septic sewage deteriorates rapidly4 ,in designing the sludge storage chambers it may be assumed that one-half of the organic matter and none of the mineral matter will be liquefied or gasified4 ,the net storage volume allowed is about #b to #c cubic yards per million gallons of sewage treated4 ,variations between #j4a and #aj4j cubic yards have been recorded1 however4 ,if grit is carried in the sewage to be treated1 it should be removed by the installation of a grit chamber before the sewage enters the septic tank4 ,,table #hc ,,analysis ,,of ,,tank ,,sludges ,place ,specific,per ,cent ,per ,cent in ,terms of ,dry ,gravity ,moisture ,matter ,volatile,fixed,nitrogen,fat ,mansfield1 #a4aa #hj4h ,o4 ,chicago1 #a4jc #ij #dj #fj #a4i #g4j ,ill4 ,columbus1 #a4ji #hc4c #d4d #af4g #j4bej4id ,o4 ,atlanta1 #a4jb #hg4a #ci4a #fj4i #a4bef4aa ,ga4 ,baltimore1 #a4jb #ia4i #ff4b #b4ded4jb ,md4 ,baltimore1 #a4jb #ib4d #fb4g #b4ge ,md4 ,baltimore1 #gi4b #gc4h #b4fdi4jj ,md4 ,baltimore1 #ib4d #eh4j #c4ai ,md4 ,place ,cubic ,pounds ,kind of ,reference ,yard per per ,sludge ,million ,million ,gallons1,gallons1 ,wet ,dry ,mansfield1 ,septic #aijh ,report1 ,o4 ,state ,board of ,health ,chicago1 #a4j #bjj,septic ,ill4 #a4e #cjj ,columbus1 ,septic ,g4 ,a4 ,o4 ,johnson #aije ,report ,atlanta1 ,imhoff ,eng4 ,rec41 ,ga4 ,v4 #gb1 #aiae1 p4 #d ,baltimore1 ,digestion,eng4 ,md4 ,tank ,news-,rec41 ,v4 #hg1 #aiba1 p4 #ih ,baltimore1 ,imhoff do4 ,md4 ,baltimore1 ,raw do4 ,md4 ,sludge ,baltimore1 ,settling do4 ,md4 ,basin ,two or more tanks should be constructed to allow for the shut down of one for cleaning and to increase the elasticity of the plant4 ,the number of tanks to be used is dependent on the total quantity of sewage and the fluctuations in rate of flow4 ,an average period of retention of about #i to #aj hours with a minimum period of #f hours during maximum flow is a fair average to be assumed for design4 ,the period of retention should not exceed about #bd hours1 as the sewage may become over-septicized4 ,the sludge storage period should be from #f to #ab months4 ,a cover is not necessary to the successful operation of a septic tank4 ,covers are sometimes used with success1 however1 in reducing the dissemination of odors from the tank4 ,they are also useful in retaining the heat of the sewage in cold weather and thus aid in promoting bacterial activity4 ,types of covers vary from a building erected over the tank to a flat slab set close to the surface of the sewage4 ,in the design of a cover1 good ventilation should be provided to permit the escape of the gases1 and easy access should be provided for cleaning4 ,tightly covered tanks or tanks with too little ventilation have resulted in serious explosions1 as at ,saratoga ,springs in #aijf and at ,florenceville1 ,n4 ,c41 in #aiae4aeb ,the sludge may be removed through drains in the bottom of the tank as described for sedimentation basins1 or where such drains are not feasible the sludge and sewage are pumped out4 ,for this purpose a pump may be installed permanently at the tank1 or for small tanks portable pumps are sometimes used4 ,septic tanks should be cleaned as infrequently as possible without permitting the overflow of sludge into the effluent4 ,the less frequent the cleaning the less the amount of sludge removed since digestion is continuous throughout the sludge4 ,it is necessary to clean when the tank becomes so filled with sludge1 that the period of retention is materially reduced1 or sludge is being carried over into the effluent4 ,the details of the septic tank at ,champaign1 ,illinois1 are shown in ,fig4 #aei4 ,this tank was designed by ,prof4 ,a4 ,n4 ,talbot1 and was put in service on ,nov4 #a1 #ahig4 ,it was among the first of such tanks to be installed in the ,united ,states4 ,the tank shown in ,fig4 #aei is an example of present day practice in single-story septic tank design4 ,illustration3 ,,fig4 #aei4--,septic ,tank at ,champaign1 ,illinois4 ,illustration3 ,,fig4 #afj4--;,design for a ,residential ,septic ,tank for a ,family of ,ten4 ,illinois ,state ,board of ,health4 ,small septic tanks for rural homes of #e to #ae persons1 or on a slightly larger scale for country schools and small institutions1 are little more than glorified cesspools4 ,nevertheless much attention has been given to the construction of such tanks by the ,national ,government and by state boards of health4#aec ,the recommendations of some of these boards have been compiled in ,table #hd4 ,a typical method for the construction of such tanks1 as recommended by the ,illinois ,state ,board of ,health1 is shown in ,fig4 #afj4 ,a subsurface filter1 into which the effluent is discharged1 is an important adjunct where no adequate stream is available to receive the discharge from the tank4 ,,table #hd ,,capacities ,,of ,,septic ,,tanks ,,for ,,small ,,installations ,rule ,number1 ,capacity1,period of ,remarks ,recommended by ,persons ,gallons ,retention ,state ,board of per ,health ,person ,wisconsin #cj #bd hours ,ohio #d to #aj #ej ,not less than #efj gallons ,kentucky #bd to #dh ,not more than #e feet hours deep ,texas #bd hours ,illinois #de #bd hours ,u4,s4 ,dept4 #dj #bd hours #be per cent additional ,agriculture4 capacity for sludge ,north ,carolina,large ,schools #ae ,not less than #ejj gallons ,north ,carolina #bj pupils #be ,north ,carolina,medium ,school #bj ,north ,carolina ,homes #be to #cj #bdi4 ,imhoff ,tanks4--,in the discussion of septic tanks it has been brought out that one of the objections to their use is the unloading of sludge into the effluent which occasionally causes a greater amount of suspended matter in the effluent than in the influent4 ,the ,imhoff tank is a form of septic tank so arranged that this difficulty is overcome4 ,it combines the advantages of the septic and sedimentation tanks and overcomes some of their disadvantages4 ,an ,imhoff tank is a device for the treatment of sewage1 consisting of a tank divided into #c compartments4 ,the upper compartment is called the sedimentation chamber4 ,in it the sedimentation of suspended solids causes them to drop through a slot in the bottom of the chamber to the lower compartment called the digestion chamber4 ,in this chamber the solid matter is humified by an action similar to that in a plain septic tank4 ,the generated gases escape from the digestion chamber to the surface through the third compartment called the transition or scum chamber4 ,sections of ,imhoff tanks are shown in ,fig4 #afa4 ,it is essential to the construction of an ,imhoff tank that the slot in the bottom of the sedimentation chamber does not permit the return of gases through the sedimentation chamber1 and that there be no flow in the digestion chamber4 ,illustration3 ,,fig4 #afa4--,typical ,sections through ,imhoff ,tanks4 ,eng4 ,news1 ,vol4 #ge1 p4 #ae4 ,the ,imhoff tank was invented by ,dr4 ,karl ,imhoff1 director of the ,emscher ,sewerage ,district in ,germany4 ,its design is patented in the ,united ,states1 the control of the patent being in the hands of the ,pacific ,flush ,tank ,co4 of ,chicago1 which collects the royalties which are payable when construction work begins4 ,the fee for a tank serving #ajj persons is #aj1 for #a1jjj persons is #hj and for #ajj1jjj persons is #beej4 ,the rate of the royalty reduces in proportion as the number of persons served increases4#aed ,as designed by ,imhoff and used in ,germany the tanks were of the radial flow type and quite deep4 ,the depth1 as explained by ,imhoff1 is one of the chief requirements for the successful operation of the tank4 ,as adapted to ,american practice the tanks are generally of the longitudinal flow type and are not made so deep4 ,an isometric view of a radial flow ,imhoff tank is shown in ,fig4 #afb4 ,the sewage enters at the center of the tank near the surface and flows radially outward under the scum ring and over a weir placed near the circumference of the tank4 ,one type of longitudinal flow tank is shown in isometric view in ,fig4 #afc4 ,illustration3 ,,fig4 #afb4--,sketch of ,radial ,flow ,imhoff ,tank at ,baltimore1 ,maryland4 ,eng4 ,record1 ,vol4 #gj1 p4 #e4 ,illustration3 ,,fig4 #afc4--;,isometric ,view of ,longitudinal ,flow ,imhoff ,tank at ,cleburne1 ,texas4 ,eng4 ,news1 ,vol4 #gf1 p4 #ajbi4 #bej4 ,design of ,imhoff ,tanks4--,the velocity of flow1 period of retention1 and the quantity of sewage to be treated determine the dimensions of the sedimentation chamber as in other forms of tanks4 ,the velocity of flow should not exceed one foot per minute1 with a period of retention of #b to #c hours4 ,a greater velocity than one foot per minute results in less efficient sedimentation4 ,a longer period of retention than the approximate limit set may result in a septic or stale effluent1 and a shorter period may result in loss of efficiency of sedimentation4 ,the bottom of the sedimentation chamber should slope not less than #a vertical to #a horizontal1 in order that deposited material will descend into the sludge digestion chamber4 ,provision should be made for cleaning these sloping surfaces by placing a walk on the top of the tank from which a squeegee can be handled to push down accumulated deposits4 ,it is desirable to make the material of the sides and bottom of the sedimentation chamber as smooth as possible to assist in preventing the retention of sludge in the sedimentation chamber4 ,wood1 glass1 and concrete have been used4 ,the latter is the more common and has been found to be satisfactory4 ,the length of the sedimentation chamber is fixed by the velocity of flow and the period of retention4 ,tanks are seldom built over #ajj feet in length1 however1 because of the resulting unevenness in the accumulation of sludge4 ,where longer flows are desired two or more tanks may be operated in series4 ,the width of the chamber is fixed by considerations of economy and convenience4 ,it should not be made so great as to permit cross currents4 ,in general a narrow chamber is desirable4 ,satisfactory chambers have been constructed at depths between #e and #ae feet4 ,the depth of the sedimentation chamber and the depth of the digestion chamber each equal about one-half of the total depth of the tank4 ,this should be made as deep as possible up to a limit of #cj to #ce feet1 with due consideration of the difficulties of excavation4 ,c4 ,f4 ,mebus states3#aee ,in #i of the largest representative ,united ,states installations1 the depth from the flow line to the slot varies from #aj feet #aj inches to #ac feet #f inches4 ,imhoff states1 concerning the depth of tanks3 ,deep tanks are to be preferred to shallow tanks because in them the decomposition of the sludge is improved4 ,this is so because in the deeper tanks the temperature is maintained more uniformly and because the stirring action of the rising gas bubbles is more intense4 ,the stirring action of the gas bubbles is desirable as it brings the fresh sludge more quickly under the influence of the active bacterial agents4 ,the greater pressure on the sludge in deep tanks also reduces its moisture content4 ,two or more sedimentation chambers are sometimes used over one sludge digestion chamber in order to avoid the depths called for by the sloping sides of a single sedimentation chamber4 ,an objection to multiple-flow chambers is the possibility of interchange of liquid from one chamber to another through the common digestion chamber4 ,the inlet and outlet devices should be so constructed that the direction of flow in the tank can be reversed in order that the accumulated sludge may be more evenly distributed in the hoppers of the digestion chamber4 ,the sewage should leave the sedimentation chamber over a broad crested weir in order to minimize fluctuations in the level of sewage in the tank4 ,the gases in the digesting sludge are sensitive to slight changes in pressure4 ,a lowering of the level of sewage will release compressed gas and will too violently disturb the sludge in the digestion chamber4 ,hanging baffles1 submerged #ab to #af inches and projecting #ab inches above the surface of the sewage1 should be placed in front of the inlet and outlet1 and in long tanks intermediate baffles should be placed to prevent the movement of scum or its escape into the effluent4 ,an ,imhoff tank which is operating properly should not have any scum on the surface of the sewage in the sedimentation chamber4 ,the slot or opening at the bottom of the sedimentation chamber should not be less than #f inches wide between the lips4 ,wider slots are preferable1 but too wide a slot will involve too much loss of volume in the digestion chamber4 ,one lip of the slot should project at least #c inches horizontally under the other so as to prevent the return of gases through the sedimentation chamber4 ,a triangular beam may be used as shown in ,fig4 #afa ,a4 ,this method of construction is advantageous in increasing the available capacity for sludge storage4 ,the digestion chamber should be designed to store sludge from #f to #ab months1 the longer storage periods being used for smaller installations4 ,in warm climates a shorter period may be used with success4 ,the amount of sludge that will be accumulated is as uncertain as in other forms of sewage treatment4 ,a widely quoted empirical formula1 presented in 8,sewage ,sludge0 by ,allen1 states3 ,c #aj4e ,,pd for combined sewage2 ,c #e4be ,,pd for separate sewage1 in which ,c the effective capacity of the digestion chamber in cubic feet2 ,p the population served1 expressed in thousands2 ,d the number of days of storage of sludge4 ,the effective capacity of the chamber is measured as the entire volume of the chamber approximately #ah inches below the lower lip of the slot4 ,the capacity as computed from the above formula is assumed as satisfactory for a deep tank4 ,frank and ,fries#aef recommend the increase of the capacity for shallow tanks to compensate for the decreased hydrostatic pressure4 ,in any event the formula can be no more than a guide to design4 ,no formula can be of equal value to data accumulated from tests on the sewage to be treated4 ,the ,illinois ,state ,board of ,health requires #c cubic yards of sludge digestion space per million gallons of sewage treated4 ,frank and ,fries recommend an allowance of #j4jjg cubic foot of storage per inhabitant per day for combined sewage and one-half that amount for separate sewage4 ,if this is based on #hj per cent moisture content1 the volume for other percentages of moisture can be easily computed4 ,an average figure used in the ,emscher ,district is one cubic foot capacity for each inhabitant for the combined system1 and three-fourths of this for the separate system4 ,metcalf and ,eddy#aeg recommend the following method for the determination of the sludge storage capacity3 7#a7 ,from analyses of the sewage or study of the sources ascertain the amount of suspended matter4 7#b7 ,assume1 or determine by test1 the amount which will settle in the period of detention selected1 say #fj per cent in #c hours4 7#c7 ,estimate the amount which will be digested in the sludge chamber at about #be per cent1 leaving #ge per cent to be stored4 7#d7 ,estimate the percentage moisture in the sludge conservatively1 say #he per cent4 ,the total volume of sludge can then be computed4 ,this method is more rational than the use of empirical formulas1 but because of the estimates which must be made its results will probably be of no greater accuracy than those obtained empirically4 ,the digestion chamber is made in the form of an inverted cone or pyramid with side slopes at most about #b horizontal to #a vertical and preferably much steeper without necessitating too great a depth of tank4 ,the purpose of the steep slope is to concentrate the sludge at the bottom of the hopper thus formed4 ,concrete is ordinarily used as the material of construction as a smooth surface can be obtained by proper workmanship4 ,where flat slopes have been used1 a water pipe perforated at intervals of #f to #ab inches may be placed at the top of the slopes1 and water admitted for a short time to move the sludge when the tank is being cleaned4 ,a cast-iron pipe1 #f to #h inches in diameter1 is supported in an approximately vertical position with its open lower end supported about #ab inches above the lowest point in the digestion chamber4 ,this is used for the removal of sludge4 ,a straight pipe from the bottom of the tank to a free opening in the atmosphere is desirable in order to allow the cleaning of the pipe or the loosening of sludge at the start1 and to prevent the accumulation of gas pockets4 ,the sludge is led off through an approximately horizontal branch so located that from #d to #f feet of head are available for the discharge of the sludge4 ,a valve is placed on the horizontal section of the pipe4 ,a sludge pipe is shown in ,fig4 #afb and #afc4 ,under such conditions1 when the sludge valve is opened the sludge should flow freely4 ,the hydraulic slope to insure proper sludge flow should not be less than #ab to #af per cent4 ,where it is not possible to remove the sludge by gravity an air lift is the best method of raising it4 ,the volume of the transition or scum chamber should equal about one-half that of the digestion chamber4 ,the surface area of the scum chamber exposed to the atmosphere should be #be to #cj per cent of the horizontal projection of the top of the digestion chamber4 ,some tanks have operated successfully with only #aj per cent1 but troubles from foaming can usually be anticipated unless ample area for the escape of gases has been provided4 ,all portions of the surface of the tank should be made accessible in order that scum and floating objects can be broken up or removed4 ,the gas vents should be made large enough so that access can be gained to the sludge chamber through them when the tank is empty4 ,precautions should be taken against the wrecking of the tank by high ground water when the tank is emptied4 ,with an empty tank and high ground water there is a tendency for the tank to float4 ,the flotation of the tank may be prevented by building the tank of massive concrete with a heavy concrete roof1 by underdraining the foundation1 or by the installation of valves which will open inwards when the ground water is higher than the sewage in the tank4 ,dependence should not be placed on the attendant to keep the tank full during periods of high ground water4 ,roofs are not essential to the successful operation of ,imhoff tanks4 ,they are sometimes used1 however1 as for septic tanks1 to assist in controlling the dissemination of odors1 to minimize the tendency of the sewage to freeze1 and to aid in bacterial activity4 ,in the construction of a roof1 ventilation must be provided as well as ready access to the tank for inspection1 cleaning1 and repairs4 #bea4 ,imhoff ,tank ,results4--,the ,imhoff tank has the advantage over the septic tank that it will not deliver sludge in the effluent1 except under unusual conditions4 ,the ,imhoff tank serves to digest sludge better than a septic tank and it will deliver a fresher effluent than a plain sedimentation tank4 ,imhoff sludge is more easily dried and disposed of than the sludge from either a septic or a sedimentation tank4 ,this is because it has been more thoroughly humified and contains only about #hj per cent of moisture4 ,as it comes from the tank it is almost black1 flows freely and is filled with small bubbles of gas which expand on the release of pressure from the bottom of the tank1 thus giving the sludge a porous1 sponge-like consistency which aids in drying4 ,when dry it has an inoffensive odor like garden soil1 and it can be used for filling waste land1 without further putrefaction4 ,it has not been used successfully as a fertilizer4 ,offensive odors are occasionally given off by ,imhoff tanks1 even when properly operated4 ,they also have a tendency to 8boil0 or foam4 ,the boiling may be quite violent1 forcing scum over the top of the transition chamber and sludge through the slot in the sedimentation chamber1 thus injuring the quality of the effluent4 ,the scum on the surface of the transition chamber may become so thick or so solidly frozen as to prevent the escape of gas with the result that sludge may be driven into the sedimentation chamber4 ,some chemical analyses of ,imhoff tank influents and effluents are given in ,table #hf and the analyses of some sludges from ,imhoff tanks are given in ,table #hc4 ,it is to be noted that the nitrites and nitrates are still present in the effluent1 whereas they are seldom present in the effluent from septic tanks4 ,the per cent of moisture in the ,imhoff sludge is less than that in the septic tank sludge1 and its specific gravity is higher4 ,it is heavier and more compact because of the longer time and the greater pressure it has been subjected to in the digestion chamber of the ,imhoff tank4 #beb4 ,status of ,imhoff ,tanks4--,the introduction of the ,imhoff tank into the ,united ,states1 like the introduction of the ,burkli-,ziegler ,run-,off ,formula1 and ,kutter's ,formula1 is to be credited to ,dr4 ,rudolph ,hering4 ,he advised ,dr4 ,imhoff to come to the ,united ,states to introduce his tank and gave him material aid through recommendations and introductions to engineers4 ,shortly after its introduction1 in #aijg1 the tank became very popular and installations were made in many cities4 ,this popularity was caused by a growing dissatisfaction with the septic tank1 the litigation then progressing over septic patents1 the production of inoffensive sludge1 and the promising results which had been obtained in ,germany4 ,as a result of the extended experience obtained in the use of ,imhoff tanks ,american engineers have learned that1 like all other sewage treatment devices introduced up to the present time1 the ,imhoff tank requires experienced attention for its successful operation4 ,these tanks are now being installed in the place of septic tanks1 and they are frequently used in conjunction with sprinkling filters4 #bec4 ,operation of ,imhoff ,tanks4--,the important feature in the successful operation of an ,imhoff tank is the proper control of the sludge and transition chambers4 ,during the ripening process1 which may occupy #b weeks to #c months after the start of the tank1 offensive odors may be given off1 the tank may foam violently1 and scum may boil over into the sedimentation chamber4 ,this is usually due to an acid condition in the digestion chamber which may possibly be overcome by the addition of lime4 ,a very fresh influent will have a similar effect4 ,too violent boiling is not likely to occur where the area for the escape of gas has been made large and the gas is not confined4 ,any accumulation of scum should be broken up and pushed down into the digestion chamber1 or removed from the tank4 ,the stream from a fire hose is useful in breaking up scum4 ,the side walls of the sedimentation chamber should be squeegeed as frequently as is necessary to keep them free from sludge1 which may be as often as once or twice a week4 ,material floating on the surface of the sedimentation chamber should be removed from the tank or sunk into the digestion chamber through the gas vents in the transition chamber4 ,no sludge should be removed1 except for the taking of samples1 until the tank is well ripened4 ,the ripening of the sludge can be determined by examining a sample and observing its color and odor4 ,an odorless1 black1 granular1 well humified sludge is indicative of a ripened tank4 ,after the tank has ripened1 sludge should be removed in small quantities at #b to #c-week intervals1 except in cold or rainy weather4 ,the sludge should be drawn off slowly to insure the removal of the oldest sludge at the bottom of the digestion chamber4 ,after the drawing off of the sludge has ceased the pipe should be flushed with fresh water to prevent its clogging with dried sludge in the interim until the next removal4 ,under no circumstances should all the sludge in the tank be removed at any time4 ,the removal of some sludge during foaming after ripening may reduce or stop the foaming4 ,the ripening of a tank can be hastened by adding some sludge from a tank already ripened4 ,sludge should not be allowed to accumulate within #ah inches of the slot at the bottom of the digestion chamber4 ,the elevation of the surface of the sludge can be located by lowering into the tank1 a stoppered1 wide-mouthed bottle on the end of a stick4 ,the stopper is pulled out by a string when the bottle is at some known elevation4 ,the bottle is then carefully raised and observed for the presence of sludge4 ,the process is repeated with the bottle at different elevations until the surface of the sludge has been discovered4 ,another method is to place the suction pipe of a small hand pump at known points1 successively increasing in depth1 and to pump in each position until one position is found at which sludge appears in the pump4 ,when the sludge in one portion of the digestion chamber has risen higher than in another portion1 the direction of flow in the sedimentation chamber should be reversed if possible4 ,in the ordinary routine of operation it is never necessary to shut down an ,imhoff tank4 ,sludge is removed while the tank is operating4 ,the shut down of a tank will be caused by accidents and breaks to the structure or control devices4 #bed4 ,other ,tanks4--,the ,travis ,hydrolytic ,tank represents a step in the development from the septic tank to the ,imhoff tank4 ,the ,doten tank and the ,alvord tank are recent developments1 and are somewhat similar in operation to the ,imhoff tank4 ,the ,travis ,hydrolytic ,tank when first designed differed from the later design of the ,imhoff tank in the slot between the sedimentation chamber and the digestion chamber which was not trapped against the escape of gas from the latter to the former1 and in operation a small quantity of fresh sewage was allowed to flow through the digestion chamber4 ,the tank is called a hydrolytic tank because some solids are liquefied in it4 ,the tank is mainly of historic interest as designs similar to it are rarely made to-day4 ,better results are obtained from the use of the ,imhoff tank4 ,recent developments have altered the original design of the ,travis tank so that it is hardly recognizable4 ,the ,travis tank at ,luton1 ,eng41 is shown in ,fig4 #afd4 ,the detailed description given in the ,engineering ,news in connection with this illustration shows that the governing object of the design is to separate as quickly as possible the sludge deposited by the sewage without septic action being set up4 ,to aid in the collection and settlement of flocculent matter vertical wooden grids or colloiders are used4 ,the suspended matter strikes these and forms a slimy deposit on them that in a short time slips off in pieces large enough to settle readily4 ,illustration3 ,,fig4 #afd4--,plan and ,section of ,hydrolytic ,tank at ,luton1 ,england4 ,eng4 ,news1 ,vol4 #gf1 #aiaf1 p4 #aid4 ,illustration3 ,,fig4 #afe4--;,doten ,tank for ,army ,cantonment ,sewage ,disposal4 ,eng4 ,news-,record1 ,vol4 #gi1 #aiag1 p4 #ica4 ,the ,doten tank#aeh is a single-storied1 hopper-bottomed septic tank1 views of which are shown in ,fig4 #afe4 ,it was devised by ,l4 ,s4 ,doten for army cantonments during the ,war4 ,its chief purpose was to avoid the foaming and frothing so common to ,imhoff tanks when overdosed with fresh sewage4 ,the first ,alvord tank was constructed in ,madison1 ,wis41 in #aiac4aei ,as now constructed the tank consists of three deep1 single-story compartments with hopper bottoms4 ,these compartments are arranged side by side in any one unit4 ,sewage enters at the surface of one of the compartments and is retained here during one-half of the total period of retention4 ,it leaves the first compartment over a weir and passes in a channel over the top of the intermediate compartment to the third or effluent compartment1 where it is held for the remainder of the period of detention4 ,accumulated scum and sludge are drawn off into the intermediate compartment at the will of the operator1 this compartment being used for sludge digestion only4 ,such tanks as the ,doten and the ,alvord have been used for plants receiving very fresh sewages such as is discharged from military cantonments1 in order to assist in the prevention of the foaming to be expected from an ,imhoff tank receiving such a fresh influent4 ,the tanks are suitable for small installations1 or where excavation to the depth required for an ,imhoff tank is not practicable4 ,,chapter ,,xvii ,,filtration ,,and ,,irrigation #bee4 ,theory4--,the cycle through which the elements forming organic matter pass from life to death and back to life again has been described in ,chapter ,,xiii4 ,it has been shown in ,chapter ,,xvi that septic action occupies that portion of the cycle in which the combinations of these elements are broken down or reduced to simpler forms and the lower stages of the cycle are reached4 ,the action in the filtration of sewage builds up the compounds again in a more stable form and almost complete oxidation is attained1 dependent on the thoroughness of the filtration4 ,in the filtration of sewage only the coarsest particles of suspended matter are removed by mechanical straining4 ,the success of the filtration is dependent on biologic action4 ,the desirable form of life in a filter is the so-called nitrifying bacteria which live in the interstices of the filter bed and feed upon the organic matter in the sewage4 ,anything which injures the growth of these bacteria injures the action of the filter4 ,in a properly constructed and operated filter1 all matter which enters in the influent1 leaves with the effluent1 but in a different molecular form4 ,a slight amount may be lost by evaporation and gasification but this is more than made up by the nitrogen and oxygen absorbed from the atmosphere4 ,the nitrifying action in sewage filtration is shown by the analysis of sewage passing through a trickling filter1 as given in ,tables #hf and #hg4 ,it is shown by the reduction of the content of organic nitrogen1 free ammonia1 oxygen consumed1 and the increase in nitrites1 nitrates1 and dissolved oxygen4 ,the reduction of suspended matter is interrupted periodically when the filter 8unloads40 ,the suspended matter in the effluent is then greater than in the influent4 ,the nitrifying organisms have been isolated and divided into two groups--nitrosomonas1 the nitrite formers1 and nitrobacter1 the nitrate formers4 ,experiments indicate that the growth of the nitrobacter organisms is dependent on the presence of the nitrosomonas organisms1 which are in turn dependent on the presence of the putrefactive compounds resulting from the action of putrefying bacteria4 ,the existence of these organisms is an example of symbiotic action in bacterial growth4 ,the organisms have been found to grow best on rough porous material on which their zogleal jelly can be easily deposited and affixed4 ,sewage filters were constructed to provide these ideal conditions before the action of a filter was thoroughly understood4 ,the action in irrigation is similar to that in filtration4 ,although more strictly a method of final disposal rather than preliminary treatment1 the similarity of the actions which take place1 and the grading of sand filtration into broad irrigation with no distinct line of difference has resulted in the inclusion of the discussion of irrigation in the same chapter with filtration4 #bef4 ,the ,contact ,bed4--,a contact bed is a water-tight basin filled with coarse material1 such as broken stone1 with which sewage and air are alternately placed in contact in such a manner that oxidation of the sewage is effected4 ,a contact bed has some of the features of a sedimentation tank and an oxidizing filter4 ,as such it marks a transitory step from anarobic to arobic treatment of sewage4 ,a plan and a section of a contact bed are shown in ,fig4 #aff4 ,because of its dependence on biologic action a contact bed must be ripened before a good effluent can be obtained4 ,the ripening or maturing occurs progressively during the first few weeks of operation1 the earlier stages being more rapidly developed4 ,the time required to reach such a stage of maturity that a good effluent will be developed will vary between one and six or eight weeks1 dependent on the weather and the character of the influent4 ,during the period of maturing the load on the bed should be made light4 ,the use of contact beds has been extensive where a more stable effluent than could be obtained from tank treatment has been desired1 yet the best quality of effluent was not required4 ,the sewage to undergo treatment in a contact bed should be given a preliminary treatment to remove coarse suspended matter4 ,the efficiency of the contact treatment can be increased by passing the sewage through two or three contact beds in series4 ,in double contact treatment the primary beds are filled with coarser material and operate at a more rapid rate than the secondary beds4 ,double contact gives better results than single contact1 but triple contact treatment1 though showing excellent results1 is hardly worth the extra cost4 ,an advantage which contact treatment has over all other methods of sewage filtration is that the bed can be so operated that the sewage is never exposed to view4 ,as a result the odors from well-operated contact beds are slight or are entirely absent and there should be no trouble from flying insects4 ,such a method of treatment is favorable to plants located in populous districts and to the fancies of a landscape architect4 ,another advantage of the contact bed is the small amount of head required for its operation1 which may be as low as #d to #e feet4 ,this low head consumption by a sewage filter is equaled only by the intermittent sand filter4 ,illustration3 ,,fig4 #aff4--,plan and ,section of ,treatment ,plant at ,marion1 ,ohio1 ,showing ,septic ,tank1 ,contact ,bed1 and ,sand ,filter4 #aijh ,report ,ohio ,state ,board of ,health4 ,the quality of the effluent from some contact beds is shown in ,table #he4 ,it is to be noted that nitrification has been carried to a fair degree of completion1 and that the reduction of oxygen consumed has been marked4 ,in comparison with the effluent from filters1 contact effluent contains a smaller amount of nitrogen as nitrites and nitrates1 and suspended solids4 ,contact effluent is usually clear and odorless1 but it is not stable without dilution4 ,the absence of nitrites and nitrates is sometimes advantageous as the effluent will not support vegetable growths dependent on this form of nitrogen4 ,the absence of suspended solids obviates the use of secondary sedimentation basins which are needed with trickling filters4 ,the head of #e to #h feet required for contact treatment is low in comparison to the #aj to #ae feet required for trickling filters1 but is slightly higher than the head required for intermittent sand filtration4 ,the cost of contact treatment is higher than the cost of trickling filters but is lower than the cost of intermittent sand filtration1 as shown in ,table #ij4 ,,table #he ,,quality ,,of ,,effluents ,,from ,,contact ,,beds ,report on ,sewage ,purification at ,columbus1 ,ohio1 by ,g4 ,a4 ,johnson1 #aije4 ,filter,depth1 ,size of ,rate1 ,oxygen ,nitrogen as ,feet ,material ,million,consumed in ,inches,gallons per ,acre per ,day ,organic ,free ,nitrites,nitrates ,ammonia ,parts per ,million ,a #ej4be-a4jj #j4iec #bc #c4e #h4g #j4bj #a4f ,b #ej4be-b4jj #a4ead #ba #d4j #h4d #j4ae #a4d ,c #ej4be-a4ej #a4bbb #bd #c4e #aj4h #j4aa #j4f ,d #ej4ej-a4ej #a4dje #bb #c4c #i4e #j4ac #j4i ,per ,cent ,removal of ,constituents of ,applied ,sewage ,a #ej4be-a4jj #j4iec #dh #di #aj ,b #ej4be-b4jj #a4ead #eb #dj #aa ,c #ej4be-a4ej #a4bbb #dg #ca #ab ,d #ej4ej-a4ej #a4dje #df #cg #ai ,filter,depth1 ,suspended ,matter ,dissolved ,feet ,oxygen ,total,volatile,fixed ,parts per ,million ,a #e #hcb #id #gcg #j4c ,b #e #hca #he #gdf #j4a ,c #e #hbf #ib #gcd #j4h ,d #e #haj #ia #gag #j4i ,per ,cent ,removal of ,constituents of ,applied ,sewage ,a #e #gc #gj #gf ,b #e #hj #gg #hc ,c #e #gj #gj #gj ,d #e #fg #fa #gb ,the depth of the contact bed is generally made from #d to #f feet4 ,the deeper beds are less expensive per unit of volume1 to construct1 as the cost of the underdrains and the distribution system is reduced in relation to the capacity of the filter4 ,the increased depth reduces the aration1 and the periods of filling and emptying are so increased as to limit the depths to the figures stated4 ,the other dimensions of the bed are controlled by economy and local conditions1 as the success of the contact treatment is not affected by the shape of the bed4 ,contact units are seldom constructed larger than one-half an acre in area1 as larger beds require too much time for filling and emptying4 ,a large number of small units is also undesirable because of the increased difficulty of control4 ,in general it is well to build as large units as are compatible with efficient operation1 elasticity of plant1 and which can be filled within the time allowed at the average rate of sewage flow1 or from dosing tanks in which the storage period is not so long as to produce septic conditions4 ,the interstices in a contact bed will gradually fill up1 due to the deposition of solid matter on the contact material1 the disintegration of the material1 and the presence of organic growths4 ,the period of rest allowed every five or six weeks tends to restore partially some of this lost capacity through the drying of the organic growths4 ,it is occasionally necessary to remove the material from the bed and wash it in order to restore the original capacity4 ,it may be necessary to do this three or four times a year1 in an overloaded plant1 or as infrequently as once in five or six years in a more lightly loaded bed4 ,the period is also dependent on the character of the contact material and the quality of the influent4 ,this loss of capacity may reduce the voids from an original amount of #dj to #ej per cent of voids to #aj to #ae per cent4 ,if the bed is not overloaded the loss of capacity will not increase beyond these figures4 ,the rate of filtration depends on the strength of the sewage1 the character of the contact material1 and the required effluent4 ,it should be determined for any particular plant as the result of a series of tests4 ,for the purposes of estimation and comparison the approximate rate of filtration should be taken at about #id gallons per cubic yard of filtering material per day on the basis of three complete fillings and emptyings of the tank4 ,this is equivalent to #aej1jjj gallons per acre foot of depth per day1 or for a bed #e feet deep to a rate of #gej1jjj gallons per acre per day4 ,the net rate for double or triple filtration is less than these figures1 but on each filter the rates are higher4 ,the material of the contact bed should be hard1 rough1 and angular4 ,it should be as fine as possible without causing clogging of the bed4 ,materials in successful use are3 crushed trap rock or other hard stone1 broken bricks1 slag1 coal1 etc4 ,soft crumbling materials such as coke are not suitable as the weight of the superimposed material and the movement of the sewage crushes and breaks it into fine particles which accumulate in the lower portion of the filter and clog it4 ,roughness1 porosity1 and small size are desirable1 as the greater the surface area the more rapid the deposition of material4 ,after a short time1 however1 the advantages of roughness and porosity are lost1 as the sediment soon covers all unevenness alike4 ,the minimum size of the material is limited by the tendency towards clogging4 ,the sizes in successful use vary between and of an inch1 inch being a common size4 ,the same size of material is used throughout the depth of the bed except that the upper #f inches may be composed of small white pebbles or other clean material1 which does not come in contact with the sewage and which will give an attractive appearance to the plant4 ,in double or triple contact beds #c or #d-;inch material is sometimes used for the primary beds1 and -inch material in the final bed4 ,sewage may be applied at any point on or below the surface4 ,the sewage is withdrawn from the bottom of the bed4 ,it is undesirable to have too few inlet or outlet openings as the velocity of flow about the openings will be so great as to disturb the deposit on the contact material4 ,the distribution system and the underdrains for the bed at ,marion1 ,ohio1 are shown in ,fig4 #aff4 ,the cycle of operation of a contact bed is divided into four periods4 ,a representative cycle might be3 time of filling1 one hour2 standing full1 #b hours2 emptying1 one hour2 standing empty1 #d hours4 ,the length of these periods is the result of long experience based on many tests and are an average of the conclusions reached4 ,wide variations from them may be found in different plants1 and tests may show successful results with different periods4 ,the combination of these four periods is known as the contact cycle4 ,the period of filling should be made as short as possible without disturbing the material of the bed nor washing off the accumulated deposits4 ,the sewage should not rise more rapidly than one vertical foot per minute4 ,during the contact or standing full period sedimentation and adsorption of the colloids are occurring on the area of surface exposed to the sewage4 ,this period should be of such length that septic action does not become pronounced1 and long enough to permit of thorough sedimentation4 ,the period of emptying should be made as short as possible without disturbing the bed1 on the same basis that the period of filling is determined4 ,during the period of standing empty1 air is in contact with the sediment deposited in thin layers on the contact material1 and the oxidizing activities of the filter are taking place4 ,the filter is given a rest period of one or two days every five or six weeks1 in order that it may increase its capacity and its biologic activity4 ,the control of a contact bed may be either by hand or automatic1 the latter being the more common4 ,hand control requires the constant attention of an operator and results in irregularity of operation1 whereas automatic control will require inspection not more than once a day and insures regularity of operation4 ,a number of automatic devices have been invented which give more or less satisfaction4 ,the air-locked automatic siphons1 without moving parts1 have proven satisfactory and are practically 8fool-proof40 ,the operation of these devices is explained in ,chapter ,,xxi4 #beg4 ,the ,trickling ,filter4--,a trickling or sprinkling filter is a bed of coarse1 rough1 hard material over which sewage is sprayed or otherwise distributed and allowed to trickle slowly through the filter in contact with the atmosphere4 ,a general view of a trickling filter in operation at ,baltimore is shown in ,fig4 #afg4 ,the action of the trickling filter is due to oxidation by organisms attached to the material of the filter4 ,the solid organic matter of the sewage deposited on the surface of the material1 is worked over and oxidized by the arobic bacteria1 and is discharged in the effluent in a more highly nitrified condition4 ,at times the discharge of suspended matter becomes so great that the filter is said to be unloading4 ,the action differs from that in a contact bed in that there is no period of septic or anarobic action and the filter never stands full of sewage4 ,the effluent from a trickling filter is dark1 odorless1 and is ordinarily non-putrescible4 ,analyses of typical effluents are given in ,tables #hf and #hg4 ,the unloading of the filter may occur at any time1 but is most likely to occur in the spring or in a warm period following a period of low temperatures4 ,it causes higher suspended matter in the effluent than in the influent and may render the effluent putrescible4 ,the action is marked by the discharge of solid matter which has sloughed off of the filter material and which increases the turbidity of the effluent4 ,where the diluting water is insufficient to care for the solids so carried in the effluent1 they can be removed by a #b-;hour period of sedimentation4 ,the effluent may become septic during this time1 however4 ,the nitrogen in the effluent is almost entirely in the form of nitrates1 and the percentage of saturation with dissolved oxygen is high4 ,the effluent is more highly nitrified than that from a contact bed1 and its relative stability is also higher1 thus demanding a smaller volume of diluting water4 ,illustration3 ,,fig4 #afg4--,sprinkling ,filter in ,operation in ,winter at ,baltimore4 ,the principal advantage of a trickling filter over other methods of treatment is its high rate which is from two to four times faster than a contact bed1 and about seventy times faster than an intermittent sand filter4 ,the greatest disadvantage is the head of #ab to #ae feet or more necessary for its operation4 ,sedimentation of the effluent is usually necessary to remove the settleable solids4 ,during the period of secondary sedimentation the quality of the filter effluent may deteriorate in relative stability4 ,in winter the formation of ice on the filter results in an effluent of inferior quality1 but as the diluting water can care for such an effluent at this time the condition is not detrimental to the use of the trickling filter4 ,in summer the filters sometimes give off offensive odors that can be noticed at a distance of half a mile1 and flying insects may breed in the filter in sufficient quantities to become a nuisance if preventive steps are not taken4 ,the dissemination of odors is especially marked when treating a stale or septic sewage4 ,the treatment of a fresh sewage seldom results in the creation of offensive odors4 ,,table #hf ,,analysis ,,of ,,crude ,,sewage1 ,,imhoff ,,tank1 ,,and ,,sprinkling ,,filter ,,effluents ,,at ,,atlanta1 ,,georgia 7,engineering ,record1 ,vol4 #gb1 p4 #d7 ,temperature ,parts per ,million ,fahrenheit ,nitrogen as ,oxygen ,consumed ,organic ,free ,nitrites,nitrates ,ammonia ,crude ,sewage #aiac ,maximum #gg #ae4f #ba4h #j4a #c4j #ajj4j ,minimum #fa #aj4d #af4e #j4a #a4d #gh4c ,average #gj #ab4h #ah4h #j4a #b4b #ij4f #aiad 7#g months7 ,maximum #gd #af4j #cc4d #b4c ,minimum #fj #i4e #ah4a #a4f ,average #ff #ac4d #bg4a #b4j ,imhoff ,effluent #aiac ,maximum #gh #ac4b #ba4i #j4b #c4a #fh4j ,minimum #eh #f4e #af4h #j4a #a4a #ec4a ,average #fh #i4j #bj4j #j4b #b4a #fj4a #aiad 7#g months7 ,maximum #gg #aj4c #cj4c #b4j ,minimum #ei #d4a #ah4j #a4e ,average #fe #g4g #be4i #a4h ,sprinkling ,filter ,effluent #aiac ,maximum #gi #e4f #ad4b #j4h #aa4c #cb4a ,minimum #ee #b4f #f4b #j4e #e4h #bc4f ,average #ff #c4h #i4i #j4g #h4b #bh4b #aiad 7#g months7 ,maximum #gg #h4e #bj4g #aa4b ,minimum #ee #d4d #h4h #c4f ,average #fc #e4g #ae4b #g4b ,parts per ,million ,per ,cent ,relative ,saturation,stability ,dissolved ,oxygen ,suspended ,matter ,total,volatile,fixed ,crude ,sewage #aiac ,maximum #cga #aed #afc #dg ,minimum #bbb #ih #aab #aa ,average #bhe #abf #ach #bh #aiad 7#g months7 ,maximum #dca #dh ,minimum #bgi #ab ,average #cea #cj ,imhoff ,effluent #aiac ,maximum #ij #ej #da ,minimum #ce #db #ba ,average #fh #df #cc #aiad 7#g months7 ,maximum #gc #dh ,minimum #di #cd ,average #fe #dc ,sprinkling ,filter ,effluent #aiac ,maximum #fj #ca #bh #gf #ii ,minimum #cc #bf #bh #eb #hh ,average #di #bh #bh #fd #hi #aiad 7#g months7 ,maximum #ajf #gi #ii ,minimum #dj #ee #hi ,average #fb #fe #ie ,,table #hg ,,efficiency ,,of ,,sprinkling ,,filter ,,chicago1 ,,illinois ,depth of ,filter #i feet4 ,size of stone #b in4 to #c in4 ,month ,organic ,nitrogen ,free ,ammonia ,influent1,effluent1 ,per ,influent1,effluent1 ,per ,parts per,parts per ,cent ,parts per,parts per ,cent ,million ,million ,removed ,million ,million ,removed #aiaj ,october #e4a #b4h #de #ab4j #d4f #fb ,november #e4i #b4e #eh #ab4j #e4i #ea ,december #d4f #c4j #ce #ab4j #f4i #db #aiaa ,january #f4c #d4h #bd #aa4j #g4j #cf ,february #i4j #d4h #dg #aj4j #g4b #bh ,march #h4c #c4e #eh #i4i #f4d #ce ,april #f4d #d4j #cg #h4c #c4f #fi ,may #g4f #e4d #bi #i4b #b4d #gd ,june #e4i #c4b #df #aa4j #j4f #ie ,july #f4b #d4b #cb #aa4j #a4c #hh ,month ,oxygen ,consumed ,nitrites ,influent1,effluent1 ,per ,influent1,effluent1 ,per ,parts per,parts per ,cent ,parts per,parts per ,cent ,million ,million ,removed ,million ,million ,removed #aiaj ,october #cj #ae #ej 4#ij ,november #ce #ae #eg 4#gf ,december #ci #bj #di 4#jg 4#de #f4d #aiaa ,january #db #bj #eb 4#jh 4#ae #a4i ,february #df #bj #ef 4#ji 4#ae #a4g ,march #dg #ba #ef 4#ji 4#ae #a4g ,april #ch #ba #de 4#af 4#ba #a4c ,may #cc #ca #f 4#jh 4#ch #d4h ,june #bh #af #dc 4#jj 4#cj ,july #cd #bf #bd 4#jj 4#cf ,month ,nitrates ,dissolved ,oxygen ,influent1,effluent1 ,per ,influent1,effluent1 ,per ,parts per,parts per ,cent ,parts per,parts per ,cent ,million ,million ,removed ,million ,million ,removed #aiaj ,october #g4h #j4j #h4e ,november #e4i #j4j #h4a ,december 4#ae #b4f #ag #b4j #h4d #d4b #aiaa ,january 4#bg #b4b #h4b #c4j #g4h #b4i ,february 4#ej #b4f #e4b #b4f #h4j #c4a ,march 4#cd #c4b #i4d #b4b #f4f #c4j ,april 4#ec #d4e #h4e #b4a #g4a #c4d ,may 4#ae #g4e #d4c #j4a #g4g #gg ,june 4#af #h4c #e4b #j4j #g4f ,july 4#ji #g4g #h4j #j4j #f4e ,month ,per ,cent ,suspended ,matter ,putrescible ,total ,volatile ,influent1,effluent1 ,per ,influent1,effluent1 ,per ,parts per,parts per ,cent ,parts per,parts per ,cent ,million ,million ,removed ,million ,million ,removed #aiaj ,october #j #ge #dj #dg #ed #be #ed ,november #e #fa #af #gd #eb #ae #ga ,december #ce #he #dj #ec #fj #bf #eg #aiaa ,january #ch #aab #dc #fc #fh #bi #eg ,february #bi #ajj #di #ea #fd #cb #ej ,march #bh #ajf #cg #fe #fc #bb #fe ,april #i #aac #fh #dj #ei #ce #da ,may #f #hh #aej #a4g #ed #gj #a4c ,june #a #ib #gg #ah #ef #cf #cf ,july #d #aee #acj #af #gd #fa #ah ,month ,suspended ,matter ,fixed ,influent1,effluent1 ,per ,parts per,parts per ,cent ,million ,million ,removed #aiaj ,october #ba #ae #bi ,november #i #a #hi ,december #be #ad #dd #aiaa ,january #dd #ac #gj ,february #cg #ag #ec ,march #dc #ae #fe ,april #ed #cc #ci ,may #cd #hj #b4d ,june #cf #da #a4a ,july #ha #fi #ae ,,note4--,italic figures represent increases4 ,raw sewage cannot be treated successfully on a trickling filter4 ,coarse solid particles should be screened and settled out1 in order that the distributing devices or the filter may not become clogged4 ,the effluent from an ,imhoff tank has proven to be a satisfactory influent for a trickling filter4 ,a septic tank effluent may be so stale as to be detrimental to the biologic action in the filter4 ,in the operation of a trickling filter the sewage is sprayed or otherwise distributed as evenly as possible in a fine spray or stream1 over the top of the filtering material4 ,the sewage then trickles slowly through the filter to the underdrains through which it passes to the final outlet4 ,the distribution of the sewage on the bed is intermittent in order to allow air to enter the filter with the sewage4 ,the cycle of operation should be completed in #e to #ae minutes1 with approximately equal periods of rest and distribution4 ,cycles of too great length will expose the filter to drying or freezing and will give poorer distribution throughout the filter4 ,cycles which are too short will operate successfully only with but slight variation in the rate of sewage flow4 ,in some plants it has been found advantageous to allow the filters to rest for one day in #c to #f weeks or longer1 dependent on the quality of the effluent4 ,the rate of filtration may be as high as #b1jjj1jjj gallons per acre per day1 which is equivalent to #bjj gallons per cubic yard of material per day in a bed #f feet deep4 ,this is more than double the rate permissible in a contact bed4 ,the exact rate to be used for any particular plant should be determined by tests4 ,it is dependent on the quality of the sewage to be treated1 on the depth of the bed1 the size of the filling material1 the weather1 and other minor factors4 ,the filtering material is similar to that used in a contact bed4 ,it should consist of hard1 rough1 angular material1 about #a to #b inches in size4 ,larger sizes will permit more rapid rates of filtration1 but will not produce so good an effluent4 ,smaller sizes will clog too rapidly4 ,the depth of the filter is limited by the possibility of ventilation and the strength of the filtering material to withstand crushing4 ,the deeper the bed the less the expense of the distribution and collecting system for the same volume of material1 and the more rapid the permissible rate of filtration4 ,the depths in use vary between #f and #aj feet1 with #f to #h feet as a satisfactory mean4 ,from a biologic standpoint the action of the filter seems to be proportional to the volume of the filtering material and therefore proportional to the depth of the bed1 being limited to a minimum depth of about #e feet1 below which sewage may pass through the filter without treatment4 ,the shape and other dimensions of the filter depend on the local conditions and the economy of construction4 ,the filters need not be broken up into units by water-tight dividing walls4 ,one filter can be constructed sufficient for all needs and various portions of it can be isolated as units by the manipulation of valves in the distribution system4 ,ventilation is provided by the air entrained with the sewage as it falls upon the surface4 ,if the sides of the filter are built of open stone crib work the ventilation will be greatly improved1 but it will not be possible to flood the filters to keep down flies1 and in cold climates these openings must be covered in winter to prevent freezing4 ,filters have been constructed without side walls1 the filtering material being allowed to assume its natural angle of repose4 ,this has usually been found to be more expensive than the construction of side retaining walls1 due to the unused filling material and the extra underdrains required4 ,the distribution of sewage is ordinarily effected by a system of pipes and spray nozzles as shown in ,fig4 #afh and #afi4 ,other methods of distribution have been used4 ,at ,springfield1 ,mo41#afj a moving trough from which the sewage flows continuously is drawn back and forth across the bed by means of a cable4 ,in ,england circular beds have been constructed and the sewage distributed on them through revolving perforated pipes4 ,at the ,great ,lakes ,naval ,training ,station#afa the distributing pipes in the plant1 now abandoned1 were supported above the surface of the filter4 ,the sewage fell from holes in the lower side of these pipes on to brass splash plates #ad inches above the filter4 ,it was deflected horizontally from these plates over the filter surface4 ,pipes and spray nozzles have been adopted almost universally in the ,united ,states4 ,splash plates1 traveling distributors1 and other forms of distribution have been used only in exceptional cases4 ,in a distributing system consisting of pipes and nozzles1 a network of pipes is laid out somewhat as shown in ,fig4 #afh1 in such a manner that the head loss to all points is approximately equal4 ,the number of valves required should be reduced to a minimum4 ,the pipes may be laid out with the main feeders leading from a central point and branches at right angles to them1 somewhat on the order of a spider's web1 or they may be laid out on a rectangular or gridiron system4 ,the radial system is advantageous because of the central location of the control house1 but it does not always lend itself favorably to the local conditions1 and the piping and nozzle location are not so simple4 ,the gridiron system lends itself favorably to the equalization of head losses4 ,the pipes used should be larger than would be demanded by considerations of economy alone1 both for the purpose of reduction of head loss and ease in cleaning4 ,no pipe less than #f inches in diameter should be used1 and the average velocity of flow should not exceed one foot per second4 ,cast-iron1 concrete1 or vitrified clay pipe may be used1 but cast iron is the material commonly used4 ,the system should be arranged for easy flushing and cleaning and the pipes so sloped that the entire system can be drained in case of a shut down in cold weather4 ,illustration3 ,,fig4 #afh4--,section through ,sprinkling ,filter at ,fitchburg1 ,mass41 ,showing ,distribution ,system4 ,eng4 ,record1 ,vol4 #fg1 p4 #fcd4 ,the pipes are placed far enough below the surface of the filling material so that the top of the spraying nozzle is #f to #ab inches above the surface of the filter4 ,if the pipes are placed near the surface they are accessible for repairs1 but are exposed to temperature changes4 ,if the pipes are large their presence near the surface of the filter may seriously affect the distribution of the sewage through the filter4 ,if the distributing pipes are placed near the bottom of the filter they are inaccessible for repairs and the nozzles must be connected to them by means of long riser pipes4 ,the distributing pipes should be supported by columns extending to the foundation of the filter bed1 there being a column at every pipe joint with such intermediate supports as may be required4 ,in some plants the pipes have been supported by the filtering material4 ,although slightly less expensive in first cost the practice of so supporting the pipes is poor1 as settling of the material may break the pipe or cause leaks1 and if the bed becomes clogged1 removal of the material is made more difficult4 ,valves should be placed in the distributing system in such a manner that different sets of nozzles can be cut out at will1 thus resting those portions of the filter and permitting repairs without shutting down the entire filter4 ,the spacing of the nozzles is fixed by the type and size of the nozzle1 the available head1 and the rate of filtration4 ,various types of sprinkler nozzles are shown in ,fig4 #afi and the discharge rates1 head losses1 and distances to which sewage is thrown for the ,taylor nozzles1 are shown in ,fig4 #agj4 ,nozzles are available which will throw circular1 square1 or semicircular sprays4 ,in the use of circular sprays there is necessarily some portion of the filter which is underdosed if the nozzles are placed at the corners of squares with the sprays tangent1 and there is an overdosing of other portions if the sprays are allowed to overlap so that no portion of the filter is left without a dose4 ,rectangular sprays will apparently overcome these difficulties1 but studies have shown that circular sprays with some overlapping1 and the nozzles placed at the apexes of equilateral triangles as shown in ,fig4 #agb will give as satisfactory distribution as other forms4 ,illustration3 ,,fig4 #afi4--,sprinkling ,filter ,nozzles4 ,bulletin ,no4 #c1 ,engineering ,experiment ,station1 ,purdue ,university4 ,illustration3 ,,fig4 #agj4--;,diagram ,showing the ,discharge and ,spacing of ,taylor ,nozzles4 ,the nozzles should be selected to give the best distribution1 to consume all of the head available1 and to give the proper cycle of operation4 ,the entire head available should be consumed in order that the fewest number of nozzles may be used4 ,an excellent study of the characteristics of various types of nozzles has been published in ,bulletin ,no4 #c of the ,engineering ,experiment ,station at ,purdue ,university1 #aibj4 ,as a result of the tests on the nozzles shown in ,fig4 #afi1 it was determined for all nozzles1 except ,no4 #h1 that ,q ,ca7#b;gh72 in which ,q the rate of discharge in cubic feet per second2 ,c a coefficient shown in ,table #hh2 a the net cross-sectional opening of the nozzle in square feet2 h the pressure on the nozzle in feet of water4 ,,table #hh ,,coefficients ,,of ,,discharge ,,for ,,sprinkler ,,nozzles ,,shown ,,in ,,fig4 #afi ,nozzle ,number #a #b #c #d #e #f #g ,coefficient 4#fdh 4#gef 4#fif 4#fff 4#fge 4#eih 4#efi ,it is evident that if the head on the nozzles is constant and the nozzle throws a circular spray1 the intensity of dosing at the circumference will be greater than nearer the center4 ,this difficulty is overcome by so designing the dosing tank from which the sewage is fed that the head on the nozzle and the quantity thrown will vary in such a manner that the distribution over the bed is equalized4 ,intermittent action is obtained by an automatic siphon which commences to discharge when the tank is full and empties the tank in the period allowed for dosing4 ,under such conditions the tank should discharge for a longer time at the higher heads than at the lower heads as there is more territory to be covered at the higher heads4 ,the design of the tank to do this with exactness is difficult1 and the construction of the necessary curved surfaces is expensive4 ,where a dosing tank is used for such conditions it has been found satisfactory to construct the tank with plane sides sloping at approximately #de degrees from the vertical 7or horizontal74 ,a tank with curved surfaces is shown in ,fig4 #aga4 ,the dosing siphon is usually placed in the tank as shown in the figure4 ,the head and quantity of discharge through the nozzles can be varied also by maintaining a constant depth in a dosing tank by means of a float feed valve1 and varying the head and quantity discharged to the nozzles by a butterfly valve in the main feed line1 or by the use of a ,taylor undulating valve designed for this purpose4 ,the butterfly valve is opened and closed by a cam so designed and driven at such a rate that the required distribution is obtained4 ,the ,taylor undulating valve is opened and closed at a constant rate1 the shape of the valve giving the required variations in head and discharge4 ,other methods of control have been attempted but have not been used extensively4 ,illustration3 ,,fig4 #aga4--,section of #ab-;inch ,siphon and ,dosing ,tank1 for ,king's ,park1 ,long ,island4 ,an example of the design of the nozzle layout and dosing tank for a sprinkling filter follows3 ,let it be required to determine the nozzle layout for one acre of sprinkling filters with #e feet available head on the nozzles4 ,the selection of the type of nozzle and the size of opening is a matter of judgment and experience4 ,nozzles with large openings are less liable to clog and fewer nozzles are needed than where small nozzles are used1 but the distribution of sewage is not so even as with the use of small nozzles4 ,in this example ,taylor circular spray nozzles will be selected4 ,fig4 #agj shows that a ,taylor circular spray nozzle will discharge #bb4c g4p4m4 under a head of #e feet1 and that the economical nozzle spacing will be #ae4c feet4 ,the least number of nozzles at this spacing required for a bed of one acre in area is found as follows3 ,in ,fig4 #agb1 let n equal the number of nozzles in a horizontal row1 counting half-spray nozzles as 1 and let m equal the number of rows counting rows of half-spray nozzles as half rows4#afb ,then the number of nozzles1 ,n1 equals mn1 and #ae4cm #ac4bn equals #dc1efj or mn equals #bae4 ,illustration3 ,,fig4 #agb4--,typical ,sprinkler ,nozzle ,layout4 ,the next step should be the design of the dosing tank and siphon4 ,it is possible to design a tank which will give equal distribution over equal areas of filter surface4 ,it has been found1 however1 that the expense of this refinement is unwarranted as there are a number of outside factors which tend to overcome the theoretical design4 ,the effect of wind1 unequal spacing1 and irregularities in the elevation of the nozzles have a tendency to offset refinements in the design of a dosing tank4 ,it is therefore the general practice to slope the sides of the tank at an angle of about #de degrees as previously stated4 ,the dosing tank is generally designed to have a capacity which will give a complete cycle of operation once in #ae minutes4 ,in the ordinary design the factors given are the rate of inflow and the given time of filling4 ,in the following example the time of filling will be taken as #aj minutes1 the time of emptying as #e minutes1 and the rate of flow as #a1jjj1jjj gallons per day4 ,the capacity of the tank will therefore be 7#a1jjj1jjj7bd x #f #g1jjj gallons4 ,the diameter of the siphon to be selected can be computed as follows3 ,let ,q the capacity of the tank in cubic feet2 q#a the rate of discharge of the siphon in cubic feet per second2 q#b the rate of inflow to the tank in cubic feet per second2 q the rate of emptying the tank in cubic feet per second 7q#a q#b72 ,a the cross-sectional area of the free surface of the water in the tank at any instant1 in square feet2 a the cross-sectional area of the siphon in square feet2 b the small dimension of the base of the tank in feet2 h the head of water1 in feet1 on the discharge siphon2 h#a the initial head of water1 in feet1 on the siphon2 h#b the final head of water in feet1 on the siphon2 t the time1 in seconds1 required to empty the tank1 then d,q -,adh q#a;dt q#b;dt1 and dt 7d,q7q ,adh7q#a q#b71 but q#a #j4d ,a 77#b;gh771#afc therefore t h#b;h#a -,adh7#j4d;a7#b;gh7 q#b71 but ,a #d;h#b #d;bh b#b1 therefore t h#a;h#b 77b#b #d;bh #d;h#b7;dh7#j4d;a7#b;gh7 q#b4 ,the integration of this expression is tedious4 ,its solution for siphons between #f inches and #ab inches operating under heads commencing from #c feet to #f feet1 with a time of emptying of #e minutes and time of filling of #aj minutes is given in ,fig4 #agc4 ,in the example given the rate of inflow is #a4ee sec4 feet and the head is #e feet4 ,then from ,fig4 #agc the size of the siphon to be used is #ab inches4 ,where a siphon of the size required to empty the tank in the time fixed is not available1 combinations of available sizes can sometimes be used4 ,illustration3 ,,fig4 #agc4--;,diagram for the ,determination of the ,capacities of ,dosing ,tanks for ,trickling ,filters4 ,time of emptying1 #e minutes4 ,time of filling1 #aj minutes4 ,shape of tank is a right pyramid or a truncated right pyramid with all four sides making an angle of #de degrees with the vertical4 ,all horizontal cross-sections are squares4 ,for example1 if the given head is #f feet1 and the rate of inflow is #a4d sec4 feet1 it is evident from ,fig4 #agc that a #f1cjj-;gallon dosing tank and two #h-;inch siphons will give the required cycle4 ,the method used for the design of the setting of ,taylor nozzles by the ,pacific ,flush ,tank ,co41 is less rational but more simple and probably as satisfactory4 ,in this method the steps are as follows3 7#a7 ,divide the maximum daily rate of sewage flow by #a1jjj to get the maximum minute inflow4 7#b7 ,the number of nozzles required is determined by dividing the preceding figure by #f4 ,generally a ,taylor nozzle with an orifice of of an inch will discharge about #bj g4p4m4 at the high head and about #h g4p4m4 at the low head1 and as the nozzles must have a capacity which will take care of the inflow at the low head1 the divisor #f is used as a factor of safety instead of using #h as the divisor4 7#c7 ,the type of nozzle to be used is selected from experience or as a matter of judgment4 ,circular-spray nozzles are more generally used4 7#d7 ,the spacings are determined from ,fig4 #agj4 7#e7 ,the dosing tank of the shape described is then designed4 ,the capacity is such as to give a complete cycle once every #ae minutes4 ,the method of this design is similar to that followed previously4 7#f7 ,the dosing siphons are designed so that they will have a capacity at the minimum head of from #dj to #ej per cent in excess of the maximum minute inflow1 and the draining depth of the siphon will be limited to a maximum of #e to #e feet4 ,the siphons are all made adjustable with a variation of #f inches or more on either side of the normal discharge line so that the spraying area and cycle can be varied to secure the best results4 ,the underdrainage of a trickling filter should consist of some form of false bottom such as the types shown in ,fig4 #agd4 ,where possible the underdrains should be open at both ends for the purpose of ventilation and flushing4 ,it is desirable that the drains be so arranged that a light can be seen through them in order that clogging can be easily located4 ,the drains should be placed on a slope of approximately #b in #ajj towards a main collector4 ,the length of the drains is limited by their capacity to carry the average dose from the area drained by them4 ,the main collecting conduits must be designed in accordance with the hydraulic principles given in ,chapter ,,iv4 ,no valves1 or other controlling apparatus1 are placed on the underdrains or outlets from the filter4 ,covers have been provided in winter for some trickling filters in cold climates4 ,the ,taylor sprinkling nozzle has been found to work successfully in extremely cold weather1 and it is generally accepted that the covering of filters is unnecessary1 if the filter is not to be shut down for any length of time in cold weather4 ,the operation of devices for automatically controlling the operation of a trickling filter is explained in ,chapter ,,xxi4 ,illustration3 ,,fig4 #agd4--,types of ,false ,bottoms for ,trickling ,filters4 ,eng4 ,news1 ,vol4 #gd1 p4 #e4 #beh4 ,intermittent ,sand ,filter4--,an intermittent sand filter is a specially prepared bed of sand1 or other fine grained material1 on the surface of which sewage is applied intermittently1 and from which the sewage is removed by a system of underdrains4 ,it differs from broad irrigation in the character of the material1 the care and preparation of the bed1 and the thoroughness of the underdrainage4 ,a distinctive feature of the intermittent sand filter is the quality of the effluent delivered by it4 ,in a properly designed and operated plant the effluent is clear1 colorless1 odorless1 and sparkling4 ,it is completely nitrified1 is stable and contains a high percentage of dissolved oxygen4 ,it contains no settleable solids except at widely separated periods when a small quantity may appear in the effluent4 ,the percentage removal of bacteria may be from #ih to #ii per cent4 ,some analyses of sand filter effluents are given in ,table #hi4 ,the dissolved solids1 the remaining bacteria1 and the antecedents of the effluent are the only differences between it and potable water4 ,an effluent from an intermittent sand filter is the most highly purified effluent delivered by any form of sewage treatment4 ,the effluent can be disposed of without dilution1 on account of its high stability4 ,the treatment of sewage to so high a degree is seldom required1 so that the use of intermittent filters is not common4 ,other drawbacks to their use are the relatively large area of land necessary and the difficulty of obtaining good filter sand in all localities4 ,,table #hi ,,quality ,,of ,,effluents ,,from ,,sand ,,filters 7,report on ,sewage ,purification at ,columbus1 ,ohio1 by ,g4 ,a4 ,johnson1 #aije7 ,source of ,parts per ,million ,rate of ,sample ,filtra- tion ,gallons per ,acre1 per ,day ,nitrogen as ,oxygen ,oxygen ,consumed,dissolved ,free ,albuminoid,nitrites,nitrates ,ammonia ,ammonia ,filter #aa4j #h4f #ei4 influent from grit chamber ,filter #a4ab #j4hh #j4jh #aa4e #f4i #f4c #j4jha effluent ,filter #j4ha #j4hh #j4aj #ab4f #f4e #f4b #j4aah effluent ,filter #i4g #e4d #cc4 influent from plain settling tank ,filter #j4fb #j4gg #j4aa #ad4i #f4j #h4b #j4aci effluent ,filter #j4ii #a4aj #j4aj #ab4f #g4h #f4e #j4bgd effluent ,filter #b4fa #a4ci #j4ji #i4j #i4g #c4i #j4ceg effluent ,filter #aj4g #e4f #ch4 influent from septic tank ,filter #a4fc #a4af #j4ji #aa4b #h4j #e4h #j4ceg effluent ,filter #ac4d #d4g #dj4 influent from coke strainer ,filter #b4bd #a4ce #a4jc #ad4f #aj4a #f4i #j4cgb effluent ,filter #h4f #c4f #j4ai #a4f #bd4 #j4c influent from contact bed ,filter #b4fb #a4ce #j4ca #h4a #h4c #e4h #j4eaf effluent ,filter #b4dd #b4da #j4af #i4d #ab4e #e4j #j4ebe effluent ,filter #c4dj #a4ae #j4bj #aj4i #i4g #e4b #j4ebe effluent ,filter #i4j #d4h #j4db #a4c #bg4 #c4d influent from sprinkling filter after sedimen- tation ,filter #b4ie #a4be #j4ai #g4j #h4h #c4h #j4fge effluent ,filter #d4gg #b4fc #j4ea #d4f #aa4h #b4e #j4gdi effluent ,filter #c4dg #a4fa #j4ca #g4b #aa4i #c4g #a4abi effluent ,the action in an intermittent sand filter is more complete than in other forms of filters because a greater surface is exposed to the passage of sewage by the fine sand particles1 and the sewage is in contact with the filtering material a longer time due to the lower rate of filtration and the slow velocity of flow through the filter4 ,it is essential that the sewage be applied to the bed intermittently in order that air shall be entrained in the filter4 ,the period between doses should not be so long that the filter becomes dry4 ,in the operation of an intermittent sand filter one dose per day is considered an ordinary rate of application1 although some plants operate with as many as four doses per day per filter1 and others on one dose at long and irregular intervals4 ,it is not always necessary to rest the filter for any length of time unless signs of overloading and clogging are shown4 ,the intermittent dosing action may be obtained by the action of an automatic siphon as is described in ,chapter ,,xxi4 ,the sewage is distributed on the beds through a number of openings in the sides of distributing troughs resting on the surface of the filter4 ,the sewage is withdrawn from the bottom of the filter through a system of underdrains1 into which it enters after its passage through the bed4 ,there are no control devices on the outlet1 as the rate of filtration is controlled by the action of the dosing apparatus and the rate at which sewage is delivered to it4 ,the action of the dosing apparatus should respond quickly to variations in sewage flow4 ,as the doses are applied to a sand filter1 a mat of organic matter or bacterial zoglea is formed on the surface of the bed4 ,the mat is held together by hair1 paper1 and the tenacity of the materials4 ,it may attain a thickness of to an inch before it is necessary to remove it4 ,so long as the filter is draining with sufficient rapidity this mat need not be removed1 but if the bed shows signs of clogging1 the only cleaning that may be necessary will be the rolling up of this dried mat4 ,it is believed that the greater portion of the action in the filter occurs in the upper #e to #h inches of the bed1 but occasionally the beds become so clogged that it is necessary to remove of an inch to #b inches of sand in addition to the surface mat1 or to loosen up the surface by shallow plowing or harrowing4 ,the necessity for such treatment may indicate that the filter is being overloaded as a result of which the rate of filtration should be decreased or the preliminary treatment should be improved4 ,the plowing of clogging material into the bed should be avoided as under these conditions the final condition of the bed will be worse than its condition when trouble was first observed4 ,in winter the surface of the bed should be plowed up into ridges and valleys4 ,the freezing sewage forms a roof of ice which rests on the ridges and the subsequent applications of sewage find their way into the filter through the valleys under the ice4 ,in a properly operated bed the filtering material will last indefinitely without change4 ,if a filter is operated at too high a rate1 however1 although the quality of the effluent may be satisfactory1 it will be necessary at some time to remove the sand and restore the filter4 ,the rate of filtration depends on the character of the influent1 the desired quality of the effluent1 and the depth and character of the filtering material4 ,filters can be found operating at rates of #ej1jjj gallons per acre per day and others at eight times this rate4 ,for sewage which has had some preliminary treatment1 the rate should not exceed #ajj1jjj gallons per acre per day1 whereas the rate for raw sewage should be less than this4 ,for rough estimates made without tests of the sewage in question1 the rate should not be taken at more than #a1jjj persons per acre4 ,if the preliminary treatment of the sewage has been thorough and the material of the sand filter is coarser than ordinary the rate of filtration can be high4 ,for less careful preliminary treatment and fine filtering material the rates must be reduced4 ,the sewage must undergo sufficient preliminary treatment to remove large particles of solid matter which would otherwise clog the dosing apparatus and the filter4 ,this treatment should include grit removal1 screening1 and some form of tank treatment4 ,some plants have operated successfully with a stale sewage and no preliminary treatment1 as at ,brockton1 ,mass4 ,septic tank effluent can be treated successfully on an intermittent sand filter1 but not so satisfactorily as the effluent from a tank delivering a fresh sewage4 ,the material of the filter should consist of clean1 sharp1 quartz or silica sand with an effective size#afd of #j4b to #j4d mm41 preferably about #j4be to #j4ce mm41 and a uniformity coefficient#afe of #b to #d4 ,within the limits mentioned no careful attention need be given to the size of the material4 ,natural sand found in place has been underdrained and used successfully for sewage treatment4 ,the size of the sand is fixed by the rate of filtration rather than the bacteriological action of the filter4 ,a coarse sand will permit the sewage to pass through the bed too rapidly1 and a fine sand will hold it too long or will become clogged4 ,the same size of material should be used throughout the bed1 except that a layer of gravel from #f to #ab inches thick1 graded from very small sizes to stones just passing a #b-;inch ring should be placed at the bottom to facilitate the drainage of the bed4 ,the thickness of the sand layer should not be less than #cj inches to insure complete treatment of the sewage4 ,in shallower beds the sewage might trickle through without adequate treatment4 ,beds are ordinarily made from #cj to #cf inches deep1 but when deeper layers of sand are found in place there is no set limit to the depth which may be used4 ,the shape and overall dimensions of the bed should conform to the topography of the site and the rate of filtration adopted4 ,a plan and cross-section of an intermittent sand filter showing the distribution and under drainage systems are given in ,fig4 #aff and #age4 ,the distribution system consists of a system of troughs on the surface of the filter1 laid out in a branching form1 as shown in the figure4 ,the openings in the troughs should be so located that the maximum distance from any point on the bed to the nearest opening should not exceed #bj to #cj feet4 ,if the filters are small enough1 troughs need not be used1 the sewage being distributed from one corner1 or from mid-points on the sides4 ,where troughs are used they should be supported from the bottom of the filter in order to prevent uneven settling due to the washing of the sand4 ,the openings in the troughs are made adjustable by swinging gates as shown in ,fig4 #agf1 or by other means so that after the filter is in operation the intensity of the dose on any portion of the filter can be changed4 ,the troughs may be placed with their bottoms level with the surface of the sand and with sides of sufficient height to give the required gradient to the water surface1 or they may be built up above the surface of the filter and given the required slope so that the surface of the flowing water is parallel to the bottom of the trough4 ,in either case a splash plate should be placed at each opening1 so that not less than #b feet of the surface of the sand is protected in all directions from the opening4 ,a stone or concrete slab #b to #d inches thick makes a satisfactory splash plate4 ,either wood or concrete may be used for the construction of the troughs4 ,the former is less durable1 but also less expensive in first cost4 ,the capacity of the troughs may be computed by ,kutter's formula with the quantity to be carried equal to the maximum rate of discharge of the feeding siphon1 with a reduction in size below each branch or outlet proportional to the amount which will be discharged above this point4 ,illustration3 ,,fig4 #age4--,plan and ,section of an ,intermittent ,sand ,filter ,showing ,central ,location of ,control ,house4 ,the operation of automatic devices for dosing the bed is explained in ,chapter ,,xxi4 ,the dosing tank should have a capacity sufficient to cover the bed to a depth of about #a to #c inches at one dose1 and the siphon should discharge at a rate of about one second-foot for each #e1jjj square feet of filter area4 ,a dose should disappear within #bj minutes to half an hour after it is applied to the filter4 ,with the rate stated and four applications per day to a depth of #a inch at each dose1 the rate per acre per day will be #aji1jjj gallons4 ,illustration3 ,,fig4 #agf4--;,distributing ,trough with ,adjustable ,openings4 ,the filtration of sewage through sand in a manner similar to the rapid sand filtration of water is being attempted at the ,great ,lakes ,naval ,training ,station4 ,no results of this treatment have been published and the practical success of the method has not been assured4 #bei4 ,cost of ,filtration4--,only comparative figures can be given in stating the costs of filtration1 as most data available are based on pre-war conditions1 and are therefore unreliable for present conditions4 ,the variations from the figures given may be very large but in general the relative costs have not changed4 ,the figures given in ,table #ij are suggestive of the relative costs of the different forms of filtration4 ,,table #ij ,,relative ,,costs ,,of ,,different ,,methods ,,of ,,sewage ,,treatment ,costs in ,dollars per ,million ,gallons per ,day ,form of ,treatment ,first ,cost#aff,operation and ,total ,maintenance ,coarse screens #j4bj ,fine screens #c4jj ,plain sedimentation #g4jj #c4jj #aj4jj ,chemical precipitation #bb4jjafg ,septic tank #g4jj #a4jj #h4jj ,imhoff tank #aj4jj #a4jj #aa4jj ,contact bed #h4jj #b4jj #aj4jj ,trickling filter #d4jj #b4jj #f4jj ,intermittent sand filter #ae4jj #aj4jj #be4jj ,activated sludge #f4ej #h4ej #ae4jjafh ,,irrigation #bfj4 ,the ,process4--,broad irrigation is the discharge of sewage upon the surface of the ground1 from which a part of the sewage evaporates and through which the remainder percolates1 ultimately to escape in surface drainage channels4 ,sewage farming is broad irrigation practiced with the object of raising crops4 ,broad irrigation can be accomplished successfully without the growing of crops1 but it is seldom attempted as some return and sometimes even a profit can be obtained from the crops raised4 ,broad irrigation and sewage farming differ from intermittent sand filtration in the intensity of the application of the sewage1 the method of preparing the area on which the sewage is to be treated1 and the care in operation4 ,in broad irrigation and intermittent sand filtration the paramount consideration is successful disposal of the sewage4 ,in sewage farming the paramount consideration is the growing of crops4 ,the growing of crops may be combined with irrigation and filtration1 however1 but the crop should be sacrificed to the successful disposal of the sewage4 ,the change which occurs in the characteristics of the sewage due to its filtration through the ground is the same as occurs in arobic filtration4 ,the effect on the crops is mainly that of an irrigant1 as the manurial value of the sewage is small4 #bfa4 ,status4--,the disposal of sewage by broad irrigation was practiced in ,england previous to the development of any of the more intensive biologic methods of treatment4 ,it was considered the only safe and sanitary method for the disposal of sewage1 and as a result1 areas irrigated by sewage were common throughout ,england4 ,crops were grown on these areas as a minor consideration1 and sewage farming gained some of its popularity from the apparent success of these disposal areas4 ,the success of sewage farms is due more to generous irrigation in dry years than to fertilization by sewage4 ,the sewage farms of ,paris and ,berlin are frequently cited as examples of the successful and remunerative disposal of sewage by farming in connection with broad irrigation4 ,kinnicutt1 ,winslow1 and ,pratt#afi state3 ,the ,berlin ,sewage farms offer examples of broad irrigation under better conditions 444 of #ba1jjh acres receiving sewage1 #af1feg acres were farmed by the city1 #c1ief acres were leased to farmers1 and only #cie acres were unproductive4 ,the contributing population at this time was #b1jfd1jjj and the average amount of sewage treated was #gg1jjj1jjj gallons1 giving a daily rate of treatment of about #c1gjj gallons per acre of prepared land4 ,the soil is sandy and of excellent quality4 ,a quarter of the area operated by the authorities is devoted to pasturage1 and about a third to the cultivation of cereals1 of which winter rye and oats are the most important4 ,potatoes and beets are grown in considerable amounts and a wide variety of other crops in smaller proportions4444 ,even fish ponds are made to yield a part of the revenue1 and the drains on some of the farms have been successfully stocked with breed trout4 ,the cost of the ,berlin farms to ,march #ca1 #aiaj1 was #ag1dgj1jjj1 somewhat more than half being the purchase price of the land4 ,the expenses for this year amounted to #a1cjj1che for maintenance1 and #gda1hah for interest charges4 ,the receipts were #a1bdj1ggc and there was an estimated increase of #abb1eic in value of live stock and other property4 ,the conditions at ,berlin are quoted at length to indicate the success which can accompany broad irrigation1 and as an example of what is being done abroad1 where the rainfall is light and the soil is suitable4 ,in the ,united ,states success in sewage farming has not been marked4 ,this may be due partially to the relative weakness of ,american sewages1 to the cost of labor1 to lack of satisfactory irrigation areas1 and to inattention to details4 ,an attempt was made to grow crops on the sand filters at ,brockton1 ,mass41 but it was finally abandoned as the interests of the crops and the successful treatment of the sewage could not both be satisfied4 ,at ,pullman1 ,illinois1#agj in #ahhj1 there was commenced probably the most extensive attempt at sewage farming in eastern ,united ,states4 ,the farm was a failure from the start1 because of the clay soil1 and it was subsequently abandoned4 ,sewage farming1 mainly as a subsidiary consideration to the filtration of sewage1 is practiced in a few cities in the eastern portion of the ,united ,states to-day4 ,among the cities mentioned by ,metcalf and ,eddy#aga are ,danbury1 ,conn41 and ,fostoria1 ,ohio4 ,in the western portion of the ,united ,states where water is scarce and the ground is porous1 sewage has been used as an irrigant with some success4 ,such use of sewage cannot be considered as a method of treatment since the prime consideration is the growing of crops4 ,in this process all sewage not used as an irrigant is discharged without treatment into water courses4 ,according to ,metcalf and ,eddy there were #ce cities in ,california in #aiad that were operating sewage farms4 ,among these are ,pasadena1 ,fresno1 and ,pomona4 ,other farms1 notably the pioneer farm at ,cheyenne1 ,wyo41 have been abandoned because of the local nuisance created and the lack of financial success4 #bfb4 ,preparation and ,operation4--,a porous sandy soil on a good slope and with good underdrainage is most suitable for broad irrigation4 ,impervious clay or gumbo soils are unsuitable and should not be used4 ,they become clogged at the surface1 forming pools of putrefying sewage1 or in hot weather form cracks which may permit untreated sewage to escape into the underdrains4 ,the sewage may be distributed to the irrigated area in any one of five ways which are known as3 flooding1 surface irrigation1 ridge and furrow irrigation1 filtration1 and subsurface irrigation4 ,in flooding1 sewage is applied to a level area surrounded by low dikes4 ,the depth of the dose may be from #a inch to #b feet4 ,in surface irrigation the sewage is allowed to overflow from a ditch over the surface of the ground into which it sinks or over which it flows into another ditch placed lower down4 ,this ditch conducts it to a point of disposal or to another area requiring irrigation4 ,ridge and furrow irrigation consists in plowing a field into ridges and furrows and filling the furrows with sewage while crops are grown on or between the ridges4 ,in filtration the sewage is distributed in any desired fashion on the surface and is collected by a system of underdrains after it has filtered through the soil4 ,in subsurface irrigation the sewage is applied to the land through a system of open-joint pipes laid immediately below the surface1 similarly to a system of underdrains4 ,combinations of and modifications to these methods are sometimes made4 ,underdrains may be used in connection with any of these forms of distribution4 ,the preparation of the ground consists in3 the construction of ditches or dikes to permit of any of the above described methods of application1 grading of the surface to prevent pooling1 the laying of underdrains1 and the grubbing and clearing of the land4 ,the main carriers may be excavated in open earth or earth lined with an impervious material4 ,the distribution of the sewage from the main carriers to groups of laterals may be controlled by hand-operated stop planks4 ,if the soil has a tendency to become waterlogged it may be relieved by installing underdrains at depths of #c to #f feet1 and #dj to #ajj feet apart4 ,the tile underdrains may discharge into open ditches excavated for the purpose which serve also to drain the land4 ,drains should be used where the ground water is within #d feet of the surface1 and the open ditches should be cut below the drains to keep the ground water out of them4 ,four or #f-;inch open-joint farm tile may be used for underdrains4 ,the porosity of the soil will be increased by cultivation4 ,where particular care is taken in the cultivation of the soil so that sewage can be applied at a high rate1 broad irrigation merges into the more intensive intermittent filtration through sand4 ,before being turned on to the land1 sewage should be screened and heavy-settling particles should be removed4 ,the rate of application may be increased as the intensity of the preliminary treatment is increased4 ,the rate at which sewage may be applied is dependent also on the character of the soil1 and may vary between #d1jjj and #cj1jjj gallons per acre per day1 although higher rates have been used with the effluent from treatment plants and on favorable soil4 ,the sewage should be applied intermittently in doses1 the time between doses varying between one day and two or three weeks or more1 dependent on the weather and the condition of the soil4 ,the methods of dosing vary as widely as the rates4 ,the dose may be applied continuously for one or two weeks with correspondingly long rests1 or it may be applied with frequent intermittency alternated with short rests1 interspersed with long rest periods at longer intervals of time4 ,when applying the sewage to the land the rate of application of the dose is about #aj1jjj to #aej1jjj gallons per acre per day4 ,the area under irrigation at any one time may be as much as #aj to #ae acres4 ,the rate of the application of the sewage is also dependent on the weather and may vary widely between seasons4 ,it is obvious that a rain-soaked pasture cannot receive a large dose of sewage without danger of undue flooding4 ,one of the principal difficulties with the treatment or disposal of sewage by broad irrigation is that the greatest load of sewage must be cared for in wet seasons when the ground is least able to absorb the additional moisture4 #bfc4 ,sanitary ,aspects4--,a well-operated sewage farm should cause no offense to the eye or nose1 and is not a danger to the public health4 ,in ,berlin1 a portion of the sewage farms are laid out as city parks4 ,the liquid in the drainage ditches or underdrains may be clear1 odorless1 and colorless1 high in nitrates and non-putrescible4 ,where the farm has been improperly managed or overdosed the condition may be serious from both esthetic and health considerations4 ,sewage may be spread out to pollute the atmosphere and to supply breeding places for flying insects which will spread the filth for long distances surrounding the farm4 ,the character of the crop is also a sanitary consideration4 #bfd4 ,the ,crop4--,from a sanitary viewpoint no crops which come in contact with the sewage should be cultivated on a sewage farm4 ,such products as lettuce1 strawberries1 asparagus1 potatoes1 radishes1 etc41 should not be grown4 ,grains1 fruits1 and nuts are grown successfully and as they do not come in contact with the sewage there is no sanitary objection to their cultivation in this manner4 ,italian rye grass and other forms of hay are grown with the best success as they will stand a large amount of water without injury4 ,the raising of stock is also advisable for sewage farms where hay and grain are cultivated4 ,the stock should be fed with the fodder raised on the irrigated lands and should not be allowed to graze on the crops during the time that they are being irrigated4 ,this is due as much to the danger of injury to the distributing ditches and the formation of bogs by the trampling of the cattle1 as to the danger to the health of the cattle4 ,,chapter ,,xviii ,,activated ,,sludge #bfe4 ,the ,process4--,in the treatment of sewage by the activated sludge process the sewage enters an aration tank after it has been screened and grit has been removed4 ,as it enters the aration tank it is mixed with about #cj per cent of its volume of activated sludge4 ,the sewage passes through the aration tank in about two to four hours during which time air is blown through it in finely divided bubbles4 ,the effluent from the aration tank passes to a sedimentation tank where it remains for one-half an hour to an hour to allow the sedimentation of the activated sludge4 ,the supernatant liquid from the sedimentation tank is passed to the point of final disposal4 ,a portion of the sludge removed from the tank is returned to the influent of the aration tank4 ,the remainder may be sent to any or all of the following3 the sludge drying process1 the rearation tanks1 or to some point for final disposal4 ,sections of the activated sludge plant at ,houston1 ,texas1 are shown in ,fig4 #agg4 ,the biological changes in the process occur in the aration tank4 ,these changes are dependent on the arobic organisms which are intensively cultivated in the activated sludge4 ,when placed in intimate contact with fresh sewage1 brought about by the agitation caused by the rising air1 and in the presence of an abundance of oxygen1 the organic matter is partially oxidized4 ,the putrefactive stage of the organic cycle is avoided4 ,colloids and bacteria are partially removed probably by the agitation effected in the presence of activated sludge but the exact action which takes place is not well understood4 ,illustration3 ,,fig4 #agg4--;,activated ,sludge ,plant at ,houston1 ,texas4 ,eng4 ,news1 ,vol4 #gg1 p4 #bcf4 #bff4 ,composition4--,activated sludge is the material obtained by agitating ordinary sewage with air until the sludge has assumed a flocculent appearance1 will settle quickly1 and contain arobic and facultative bacteria in such numbers that similar characteristics can be readily imparted to ordinary sewage sludge when agitated with air in the presence of activated sludge4 ,copeland described activated sludge as follows3#agb ,the sludge embodied in sewage and consisting of suspended organic solids1 including those of a colloidal nature1 when agitated with air for a sufficient period assumes a flocculent appearance very similar to small pieces of sponge4 ,arobic and facultative bacteria gather in these flocculi in immense numbers--from #ab to #ad million per c4c4--some having been strained from the sewage and others developed by natural growth4 ,among the latter are species that have the power to decompose organic matter1 especially of an albuminoid or nitrogenous nature1 setting the nitrogen free2 and others absorbing the nitrogen convert it into nitrites and nitrates4 ,these biological processes require time1 air1 and favorable environment such as suitable temperature1 food supply and sufficient agitation to distribute them throughout all parts of the sewage4 ,ardern states that the sludge differs entirely from the usual tank sludge4 ,it is inoffensive and flocculent in character4 ,the percentage of moisture is from #ie to #ii per cent4 ,american experience has generally been that the sludge does not readily separate from its moisture by treatment on fine-grain filters1 but the results in ,england and at ,milwaukee1 ,wisconsin1 are in conflict with this general experience4 ,upon standing #bd hours or more partially dried activated sludge may start to decompose accompanied by the production of offensive odors4 ,duckworth states3 ,the activated sludge at ,salford contained three times as much nitrogen1 twice as much phosphoric acid and one-half as much fatty matter as ordinary sludge4 ,,table #ia ,,composition ,,of ,,sewage1 ,,imhoff ,,sludge1 ,,and ,,activated ,,sludge ,,and ,,effluent ,,at ,,milwaukee 7,w4 ,r4 ,copeland1 ,eng4 ,news1 ,vol4 #gf1 p4 #ffe7 ,period,source of ,parts per ,million of ,sample ,test ,sus- ,nitrogen as ,nitrogen pended ,reported as ,matter ,ammonia on a ,basis of ,sludge ,dried to #aj ,per ,cent ,moisture4 ,three samples of ,sludge ,free ,albu- ,organic ,ni- ,ni- ,ammoniaminoid ,nitrogentritestrates ,ammonia ,aug41 ,sewage #bec #ad4f #g4hh #bi #j4ae #j4ac #aiae ,imhoff #aje #af4b #f4aj #bg #j4ai #j4acb4hgc4hb effluent ,activated #ad #c4h #c4ai #f #j4bi #f4jje4gad4igg4jd sludge effluent ,sept41,sewage #cjj #ac4e #h4ha #bi #j4be #j4ad #aiae ,imhoff #aaf #ae4d #g4aj #bg #j4ab #j4jic4hh effluent ,activated #h #e4g #b4bb #i #j4bd #e4jah4fii4jj sludge effluent ,these results have been roughly checked by ,american experimenters as shown in ,table #ia4agc ,in the recovery of nitrogen from sewage the activated sludge process is the most promising for satisfactory results4 ,in all other processes of sewage treatment the sludge is digested to some extent and nitrogen lost in the gases or in the soluble matter which passes off with the effluent4 ,in the activated sludge process a negligible amount of gasification and liquefaction take place and only a small amount of nitrogen passes off with the effluent as compared with the loss from the ,imhoff process as shown in ,table #ia4 ,the percentage of nitrogen in dried activated sludge is shown in ,table #ib4 ,,table #ib ,,nitrogen ,,content ,,of ,,dry ,,activated ,,sludge ,,and ,,sludge ,,from ,,other ,,processes 7,g4 ,w4 ,fuller1 ,eng4 ,news1 ,vol4 #gf1 p4 #ffg7 ,source ,per ,cent ,nitrogen ,milwaukee 7,copeland7 #d4dj ,manchester1 ,england 7,ardern7 #d4fj ,salford1 ,england 7,melling7 #c4ge ,urbana1 ,illinois 7,bartow7 #c4e to #f4d ,armour and ,co4 7,noble7 #d4f ,approximate range of all other processes #a4j to #c4j ,these figures are expressed in terms of nitrogen and not of ammonia4 ,nitrogen is only #hb per cent of the ammonia content4 ,nitrifying bacteria and other species which have the power of destroying organic matter have been isolated from the sludge4 ,an analysis of the dried sludge at ,urbana#agd showed the following results after the weight had been reduced #ie4e per cent by drying3 #f4c per cent nitrogen1 #d4jj per cent fat1 #a4dd per cent phosphorus1 and #ge per cent volatile matter or loss on ignition4 ,analyses of other domestic sewages have not shown such high contents of these desirable constituents4 ,the dewatering of activated sludge is a problem which offers serious obstacles to the successful operation of the process4 ,it is its greatest disadvantage4 ,five to ten times the volume of sludge may be produced by the activated sludge process as by an ,imhoff tank1 and the activated sludge contains a greater percentage of water4 ,according to ,copeland3 ,the best information now available points to a combination of settling and decantation as a preliminary dewatering process4 ,by this means the water will be cut down from about #ii per cent to #if per cent4 ,on passing the concentrated residue through a pressure filter the moisture can be cut down to #ge per cent4 ,the press cake can be dewatered in a heat drier to #aj per cent moisture or less4#age ,the quantity of sludge produced at ,milwaukee#agf is about #ae cubic yards per million gallons of sewage1 the sludge having about #ih per cent moisture4 ,on the basis of #aj per cent moisture it produces ton of dry sludge per million gallons of sewage treated4 ,at ,cleveland1#agg #bj cubic yards per million gallons at #ig4e per cent moisture are produced4 ,methods of drying sludge are discussed in ,chapter ,,xx4 ,chemical analyses and biological tests indicate that the fertilizing value of the sludge is appreciable4 ,professor ,c4 ,b4 ,lipman states1 as the result of a series of tests in which a sludge and a soil were incubated for one month1 as follows3#agh ,the amounts of nitrates produced in one month's incubation from the soil's own nitrogen and from the nitrogen from the sludge mixed with the soil in the ratio of one part of sludge to #ajj of soil is1 in milligrams of nitrate1 as follows3 ,anaheim soil without sludge #f4j1 with sludge #aj4j2 ,davis soil without sludge #d4b1 with sludge #ad4j2 ,oakley soil without sludge #b4b1 with sludge #d4j4 ,the effect of the sludge on plant growth is shown in ,table #ic4agi ,the results represent the growth obtained after fifteen weeks from the planting of #cj wheat seeds in each pot4 #bfg4 ,advantages and ,disadvantages4--,some of the advantages of the process are3 a clear1 sparkling1 and non-putrescible effluent is obtained2 the degree of nitrification is controllable within certain limits2 the character of the effluent can be varied to accord with the quantity and character of the diluting water available2 more than #ij per cent of the bacteria can be removed2 the cost of installation is relatively low2 and the sludge has some commercial value4 ,,table #ic ,,fertilizing ,,value ,,of ,,activated ,,sludge 7,e4 ,bartow1 ,journal ,am4 ,water ,works ,ass'n1 ,vol4 #c1 p4 #cbg7 ,cultivating ,medium ,grams ,contained in ,experimental ,pot #a #b #c #d ,white sand #ai1hbj #ai1hbj #ai1hbj #ai1hbj ,dolomite #fj #fj #fj #fj ,bone meal #f #f #f #f ,potassium sulphate #c #c #c #c ,activated sludge #j #j #bj #j ,activated sludge extracted with ,ligroin #j #j #j #bj ,dried blood #j #h4fa #j #j ,number of heads of wheat #ad #ae #bb #bc ,number of seeds #he #ahi #dia #eah ,weight of seeds1 grams #b4ch #e4bi #ac4gdh #ad4ejd ,bushels per acre1 calculated #f4bj #ac4f #ce4i #ch4g ,average length of stalk1 inches #ai4dj #bc4j #ce4d #cg4a ,weight of straw1 grams #b4be #h4be #bf4ge #bf4ba ,tons per acre1 calculated #j4ah #j4fh #b4bc #b4ah ,among the disadvantages of the process can be included1 uncertainty due to the lack of information concerning the results to be expected under all conditions1 high cost of operation under certain conditions1 the necessity for constant and skilled attendance1 and the difficulty of dewatering the sludge4 #bfh4 ,historical4--,the most notable work in the aration of sewage within recent years was that performed by ,black and ,phelps for the ,metropolitan ,sewerage ,commission of ,new ,york1 in #aiaj1ahj and by ,clark and ,gage at the ,lawrence1 ,massachusetts1 ,sewage ,experiment ,station in #aiab and #aiac4aha ,the results of these investigations showed that the treatment of sewage by forced aration might give a satisfactory effluent1 but that the time and expense in connection thereto rendered the method impractical4 ,it remained for ,messrs4 ,ardern and ,lockett of ,manchester1 ,england1 to introduce the process of the aration of sewage in the presence of activated sludge1 as a result of their connection with ,dr4 ,fowler1 who attributes his inspiration to his visit to the ,lawrence ,experiment ,station and observing the work of ,clark and ,gage4 ,ardern and ,lockett commenced their experiments in #aiac4 ,their results were published in the ,journal of the ,society of ,chemical ,industry1 ,may #cj1 #aiad1 ,vol4 #cc1 p4 #ebc4 ,shortly thereafter experiments were started at the ,university of ,illinois by ,dr4 ,edw4 ,bartow and ,mr4 ,f4 ,w4 ,mohlmann of the ,illinois ,state ,water ,survey4 ,at about the same time an experimental plant was started at ,milwaukee1 by ,t4 ,c4 ,hatton1 ,chief ,engineer of the ,milwaukee ,sewerage ,commission4 ,the ,united ,states ,public ,health ,service became actively interested in ,december1 #aiad1 and on ,february #bj1 #aiae1 announced its intention to co-operate with the ,baltimore ,sewerage ,commission in the conduct of experiments4 ,in ,may1 #aiae1 patent number #a1aci1jbd was granted to ,leslie ,c4 ,frank1 ,sanitary ,engineer of the ,u4 ,s4 ,public ,health ,service1 covering certain features of the process4 ,mr4 ,frank generously donated this patent to the public for the use of municipalities4 ,the first full sized plant for the treatment of sewage by this method was erected in ,milwaukee in ,december1 #aiae4 ,this plant had a capacity of #a1fjj1jjj gallons per day4 ,it was used for experimental purposes and is not now in use4 ,the ,champaign1 ,illinois1 septic tank1 among the first of its kind in the country1 was converted into an activated sludge tank on ,april #ac1 #aiaf4 ,the changes1 developments1 and the results obtained from these and other plants have been reported in the technical press from time to time4 #bfi4 ,aration ,tank4--,the sewage on leaving the screen and grit chamber enters the aration tank1 which is usually operated on the continuous-flow principle1 although in the early days of experimentation the fill and draw method was practiced4 ,this tank should be rectangular with a depth of about #ae feet and a width of channel not to exceed #f to #h feet4 ,such proportions allow better air and current distribution than larger tanks4 ,the bottom should be level to insure an even distribution of air4 ,the velocity of flow of sewage through the tank is usually in the neighborhood of #e feet per minute1 dependent on the length of the tank and the period of retention4 ,the period of retention is in turn dependent on the desired quality of the effluent4 ,the process is flexible and the quality of the effluent can be changed by changing the period of retention or by changing the rate of application of the air1 or both4 ,the period of retention in the aration tank is usually about #d hours4 ,the bottom of the aration tank is usually made of concrete arranged in ridges and valleys1 or small shallow hoppers1 at the bottom of which the air-diffusing devices are located1 as shown in ,fig4 #agg4 ,the inlet and outlet devices are similar to those in a plain sedimentation tank4 #bgj4 ,sedimentation ,tank4--,it is evident that as no sedimentation is permitted in the aration tank1 the settleable particles will be discharged in the effluent unless some provision is made for their detention4 ,the effluent from the aration tank is therefore run through a plain sedimentation tank1 usually with a hopper bottom1 which has been arranged to permit frequent and easy cleaning4 ,an air lift or a centrifugal sludge pump is satisfactory for this purpose4 ,another type of sedimentation tank which has been used has a smooth bottom with a slight slope towards the center4 ,a revolving scraper collects the sludge continuously1 scraping it towards the center of the tank4 ,although this arrangement gives better results than the hopper-bottom tank1 its expense has usually prevented its installation4#ahb ,the period of sedimentation in different plants varies from #cj minutes to one hour1 although the longer periods usually give the better results4 ,approximately #fe per cent of the sludge will settle in the first #aj minutes1 #hj per cent in the first #cj minutes1 and about #e per cent more in the next half hour4 ,the effluent from the sedimentation tank is ready for final disposal or if desired1 for further treatment by some other method4 ,the sludge1 or a portion of it1 is pumped back into the influent of the aration tank1 provided the sludge is in a satisfactory state of nitrification4 ,otherwise it should be pumped to the rearation tanks4 ,the remainder of the sludge which is not to be used in the process is ready for drying and final disposal4 #bga4 ,rearation ,tank4--,the purpose of the rearation or sludge aration tank is to reactivate the sludge which has gone through the aration tank4 ,during the process of the aration of the sewage in the aration tank the activated sludge may lose some of its qualities because of the deficiency of oxygen to maintain arobic conditions4 ,by blowing air through the sludge in the rearation tank these properties are returned and the sludge made available to be pumped back into the aration tank4 ,the reactivation of the sludge obviates the necessity for supplying sufficient air to the entire mass of the sewage to maintain arobic conditions1 and results in an economy in the use of air4 ,the use of mechanical agitators has also been attempted both in the rearation and the aration tanks with the expectation of saving in the use of air1 but with indifferent success4 ,it is difficult to say1 without experimentation1 what the size of the rearation tank should be1 as the necessary amount or reactivation is uncertain4 ,in the experimental plant at ,milwaukee1 there were eight units of aration tanks1 one sedimentation tank1 and two rearation tanks1 all of the same capacity and general design4 ,this represents a ration of about one rearation tank to four aration tanks4 #bgb4 ,air ,distribution4--,air is applied to the sewage at the bottom of the aration tank at a pressure in the neighborhood of #e4e to #f4j pounds per square inch1 dependent on the depth of the sewage1 the loss of head through the distributing pipes1 and the rate of application4 ,in different experimental plants the pressure has varied from #c to #cj pounds per square inch4 ,such pressures are on the line which divides the use of direct blowers for low pressures from turbo and reciprocating pressure machines for pressures above #aj pounds per square inch4 ,positive-pressure blowers or direct blowers operate on the principle of a centrifugal pump and because of the lighter specific gravity of air they rotate at a very high speed4 ,the ,nash ,hytor ,turbo ,blower consists of a rotor with a large number of long teeth slightly bent in the direction of rotation4 ,the rotor1 which has a circular circumference1 revolves in an elliptical casing4 ,at the commencement of operation the rotor and casing are partially filled with water4 ,the revolution of the rotor throws the water to the outside of the elliptical casing thus forming a partial vacuum between any two teeth as the water is thrown from near the center of the short diameter of the casing to the extremity of the long diameter of the casing4 ,air is allowed to enter through the inlet port to relieve the vacuum4 ,as the teeth pass from the long diameter to the short diameter of the ellipse1 the water again approaches the center of the rotor compressing the air trapped between the teeth and forcing it out under pressure into the exhaust pipe4 ,among the advantages of this compressor are the washing of the air1 cooling1 and ease in operation4 ,reciprocating air compressors operate similarly to direct-acting steam pumps or crank-and-fly-wheel pumps but at much higher speeds1 and they require more floor space than either of the other types4 ,fig4 #agh shows the field of serviceability of various types of air compression machinery4 ,illustration3 ,,fig4 #agh4--;,economic ,range of ,air ,compressors4 ,from ,eng4 ,news1 ,vol4 #gd1 p4 #ijf4 ,for pressures up to about #aj pounds per square inch the positive blower seems most desirable4 ,it has a low first cost and a relatively high efficiency of about #ge to #hj per cent of the power input4 ,no oil or dirt is added to the air to clog the distributing plates1 as in the reciprocating machine4 ,a disadvantage is the difficulty of varying the pressure or quantity of the output of the machine4 ,as the required pressure and volume of air increases the turbo blower becomes more and more desirable within the limits of pressure which are ordinarily used in this process4 ,for small installations the best form of power is probably the electric drive1 but when the capacity becomes such as to make turbo blowers advisable they should be driven by directly connected steam turbines4 ,the quantity of air required varies between #j4e to #f4j cubic feet per gallon of sewage1 with from #c to #f hours of aration4 ,the quantity of air depends on the degree of treatment required1 the strength of the sewage1 the depth of the tank1 and the period of aration4 ,the deeper the tank the less the amount of air needed because of the greater travel of the bubble in passing through the sewage1 but the higher the pressure at which the air must be delivered4 ,shallow tanks usually require a longer period of retention4 ,the depth of the tank then has very little to do with economy in the use of air4 ,hatton states3#ahc ,the purification of sewage obtained varies decidedly with the volume of air applied4 ,small volumes applied for #e or #f hours do as well as larger volumes applied for #c or #d hours1 but the time of aration required to obtain a like effluent does not vary directly with the volume of air applied per unit of time4 ,for instance air applied at a rate of #b cubic feet per minute purifies the sewage in less time than one cubic foot of air per minute1 but will not accomplish an equal degree of purification in half the time4 ,it has been found that although a low temperature has a deleterious effect on the process1 by the use of an additional quantity of air good results can be maintained4 ,the effect of changing the quantity of air and the period of aration are shown in ,table #id taken from ,hatton4 ,the velocity of the air in the pipes should be about #a1jjj feet per minute4 ,there should be relatively few sharp turns in the line1 and the distributing mains should be arranged without dead ends4 ,it is desirable to use as little piping as possible and at the same time to make the travel of the sewage long in order to maintain a non-settling velocity and intimate contact with the air4 ,the piping should be accessible and well provided with valves4 ,it should be non-corrodible1 particularly on the inside1 as flakes of rust will quickly clog the air diffusers4 ,it should drain to one point in order that it can be emptied when flooded1 as occasionally happens4 ,,table #id ,,effect ,,of ,,various ,,rates ,,and ,,periods ,,of ,,application ,,of ,,air ,,on ,,the ,,results ,,obtained ,,from ,,the ,,treatment ,,of ,,sewage ,,by ,,the ,,activated ,,sludge ,,process 7,milwaukee ,results7 ,time of ,cubic ,cubic ,appearance,per ,cent ,aration1 ,feet ,feet of ,settled,removal ,hours ,free ,air ,liquid ,bacteria ,air per ,per ,gallon ,minute of ,sewage #j #j #j4j ,turbid #j #a #afj #j4fg ,clear #eb #b #afj #a4cb ,clear #ha #c #afj #a4ih ,clear #ib #d #afj #b4fd ,clear #id #e #afj #c4ca ,clear #ih #b4e #ij #a4jg #ib #c #ij #a4bh #if #d #ij #a4ga #ih #d #hj #a4hb #ig4g #d #gj #a4fj #ii4f #d #df #a4fg #hh4c #d #aje #a4ge #ib4g #c #adj #a4ge #ia4b #b4e #afh #a4gd #if4g #a4hj #ih4a #a4ec #ii #a4ab #ia ,time of ,parts per ,million ,stability1 ,aration1 ,hours ,hours ,nitrogen as ,dissolved,suspended ,oxygen ,matter ,free ,nitrites,nitrates,organic ,ammonia #j #bb #j4jh #j4jh #j4jj #jjj #a #ag #j4jj #j4jd #j4cj #b #b #ae #j4ie #j4gj #a4ij #cc #c #aa #a4ge #b4hj #d4cj #abj #d #g #b4bj #e4fj #e4ij #abj #e #e #b4ej #h4bj #f4gj #abj #b4e #aa #j4je #b4jj #fi #c #i4i #j4ab #b4i #ie #d #a4h #j4ad #e4b #abj #d #a4ie #j4jh #h4e #abj #d #e4gi #j4ad #i4j #abj #d #g4ij #j4jb #b4j #fa #d #d4hf #j4cf #d4i #abj #c #i4ci #j4fj #c4j #abj #b4e #aa4b #j4cf #a4a #hd #h4e #d #aa #abj #e4gi #i4j #h #i #abj #aj4a #b4c #ad #db #gc ,,table #ie ,,comparative ,,results ,,from ,,the ,a,,ration ,,of ,,sewage ,,in ,,the ,,presence ,,of ,,activated ,,sludge ,,with ,,the ,,use ,,of ,,different ,,distributing ,,media 7,t4 ,c4 ,hatton1 ,eng4 ,record1 ,vol4 #gc1 p4 #bee7 ,diffusers ,months in ,pounds ,air1 ,per ,cent,nitrates1,stability #aiae per ,cubic ,bacteria,parts per,effluent ,square ,feet per,removed ,million in ,hours ,inch ,gallon ,filtros plate,june #a to #d4c #b4jf #ia #c4d #gh ,aug4 #ae ,air jet ,june #a to #c4e #a4id #ia #b4b #eb ,aug4 #ae ,filtros plate,nov4 #ah to #d4f #a4ga #ij #j4c #aac ,dec4 #g ,monel metal ,nov4 #ah to #c4j #a4ga #hj #j4b #fc ,dec4 #g ,it is desirable to diffuse the air in small bubbles as by this means the greatest efficiency seems to be obtained from the amount of air added4 ,a diameter #a_/af to of an inch is approximately the maximum limit for the size of an effective bubble4 ,monel metal cloth1 porous wood blocks1 open jets1 paddles1 and other forms of diffusers have been tried1 but none have given the satisfaction of the filtros plate4 ,the relative value of different types of diffusers is shown in ,table #ie taken from ,hatton4#ahd ,the ,filtros plates are a proprietary article manufactured by the ,general ,filtration ,company of ,rochester1 ,n4 ,y4 ,they are made of a quartz sand firmly cemented together and can be obtained with practically any degree of porosity1 size of pore opening or dimension of plate1 but they are made in a standard size #ab inches square by #a inches thick4 ,the frictional loss through the plate is not very great for the amount of air ordinarily used4 ,the plates are classified in accordance with the volume of air which will pass through them1 when dry1 per minute when under a pressure of #b inches of water4 ,these classes run from to #ab cubic feet of air per minute4 ,the type usually specified passes about #b cubic feet of air per minute4 ,the loss of head through these plates as tested at ,milwaukee showed an initial loss of of a pound and an additional loss of about of a pound for every cubic foot of air per minute per square foot of surface4 ,it is necessary to screen and wash the air before blowing it through the filtros plate as ordinary air is so filled with dirt as to clog the pores of the diffuser quite rapidly4 ,the area of filtros plates required in the bottom of the tank is usually expressed in terms of the free surface of the tank or as a ratio thereto4 ,in the ,urbana tests the best ratio was found to be less than #a 3 #c and more than #a 3 #i4 ,in ,milwaukee#ahe the ratio adopted is in the neighborhood of #a 3 #d or #a 3 #e4 ,at ,fort ,worth the ratio will be about #a 3 #g and at ,chicago it will be #a 3 #h4 ,the exact ratio should be determined by experiment and will depend on the construction of the tank and the character of the raw sewage and the desired effluent4 ,it is essential that the filtros plates be placed level and at the same elevation as otherwise the distribution of air will be uneven4 #bgc4 ,obtaining ,activated ,sludge4--,after a plant is once started activated sludge is generated during the process of treatment and with careful management a stock of activated sludge can be kept on hand4 ,when a plant is new1 or if shut down for such a length of time that the sludge loses its activation1 it is necessary to activate some new sludge4 ,this is done by blowing air continuously through sewage either on the fill and draw method with periodic decantations of the supernatant liquid1 or by the continuous-flow process1 but more preferably by the latter4 ,where activated sludge is to be obtained from fresh sewage alone the time required is in the neighborhood of #aj to #ad days1 and purification begins at the start4 ,an estimate of the quantity which will be obtained can not be made with accuracy4 ,after the initial quantity of sludge has been obtained activated sludge can be maintained during the process of aration of the raw sewage1 or by means of the rearation tanks previously described4 ,the volume of activated sludge present in the aration tank should be about #be per cent of the volume of the tank4 ,the volume of the sludge is measured in a somewhat arbitrary manner as the amount by volume which will settle in #cj minutes in an ordinary test tube4 ,it is found that this is almost #ij per cent of the solids settling in #d to #f hours4 #bgd4 ,cost4--,the available information on the cost of the activated sludge process is meager and unreliable4 ,the factors entering into the cost are3 the price of fuel1 the size of the plant1 the period of sedimentation1 the amount of air per gallon of sewage1 the air pressure1 and the percentage of sludge to be arated in the mixture4 ,in ,milwaukee#ahf the cost of construction is estimated at #dd1jjj per million gallons1 and #d4ge per million gallons for operation4 ,at ,houston1 ,texas1 the cost is estimated at #bd1jjj per million gallons1 exclusive of the sludge drying plant1 which may cost #dj1jjj per million gallons4 ,at ,milwaukee1 the cost of pressing the sludge is #d4hb per dry ton and of drying is #c4ic per dry ton4 ,the sludge may be sold at the normal rate of #b4ej per unit of nitrogen4 ,based on the normal value the evident profit will be #c4ge per ton4 ,the net cost of disposing of ,milwaukee sewage is estimated at #i4fd per million gallons of which #d4hi is chargeable to overhead and #d4ge to repairs1 operation and renewal4 ,in a comparison of the costs of activated sludge and ,imhoff tanks with sprinkling filters1#ahg the information given by ,eddy has been summarized in ,table #if4 ,in comparing the relative areas required for different methods of sewage treatment1 activated sludge should be allowed about #ae million gallons per acre per day on the basis of aration tanks #ae feet deep4 ,this figure represents approximately the gross area of the plants at ,milwaukee and at ,cleveland4 ,,table #if ,,comparative ,,costs ,,of ,,activated ,,sludge1 ,,and ,,of ,,imhoff ,,tanks ,,followed ,,by ,,sprinkling ,,filters 7,h4 ,p4 ,eddy1 ,eng4 ,record1 ,vol4 #gd1 p4 #eeg7 ,process ,first ,cost ,operation per,total ,annual ,cost at #d ,per per ,million ,million ,cent with ,sinking ,fund at ,gallons1 ,gallons1 #b4e ,per ,cent per ,dollars ,dollars ,million ,capita1 ,gallons1 ,dollars ,dollars ,activated #eg1ajj #bj4jj #bi4he #a4ji sludge ,imhoff tank #gh1ejj #h4ej #ba4hd #j4hj and sprinkling filter ,,references ,,and ,,bibliography ,,on ,,activated ,,sludge ,the following abbreviations will be used3 ,a4,s4 for ,activated ,sludge1 ,e4,c4 for ,engineering and ,contracting1 ,e4,n4 for ,engineering ,news1 ,e4,r4 for ,engineering ,record1 ,e4,n4,r4 for ,engineering ,news-,record1 p4 for page1 and ,v4 for volume4 ,no4 #a4 ,cooperation ,sought in ,conducting ,a4,s4 ,experiments at ,baltimore1 by ,franks and ,hendrick4 ,e4,r4 ,v4 #ga1 #aiae1 pp4 #eba1 #gbd1 and #ghd4 ,v4 #gb1 #aiae1 pp4 #bc1 and #fdj4 #b4 ,sewage ,treatment ,experiments with ,aration and ,a4,s41 by ,bartow and ,mohlman4 ,e4,n4 ,v4 #gc1 #aiae1 p4 #fdg1 and ,e4,r4 ,v4 #ga1 #aiae1 p4 #dba4 #c4 ,a4,s4 ,experiments at ,milwaukee1 ,wisconsin1 by ,hatton4 ,e4,n4 ,v4 #gd1 #aiae1 p4 #acd4 #d4 ,a4,s4 in ,america1 ,an ,editorial ,survey1 by ,baker4 ,e4,n4 ,v4 #gd1 #aiae1 p4 #afd4 #e4 ,choosing ,air ,compressors for ,a4,s41 by ,nordell1 ,e4,n4 ,v4 #gd1 #aiae1 p4 #ijd4 #f4 ,a ,year of ,a4,s4 at ,milwaukee1 by ,fuller4 ,e4,n4 ,v4 #gd1 #aiae1 p4 #aadf4 #g4 ,a4,s4 ,experiments at ,urbana4 ,e4,n4 ,v4 #gd1 #aiae1 p4 #ajig4 #h4 ,experiments on the ,a4,s4 ,process1 by ,bartow and ,mohlman4 ,e4,c4 ,v4 #dd1 #aiae1 p4 #dcc4 #i4 ,milwaukee's ,a4,s4 ,plant1 the ,pioneer ,large ,scale ,installation1 by ,hatton4 ,e4,r4 ,v4 #gb1 #aiae1 p4 #dha and ,e4,c4 ,v4 #dd1 #aiae1 p4 #cbb4 #aj4 ,a4,s4 ,experiments at ,milwaukee1 by ,hatton4 ,journal ,american ,waterworks ,association and ,proceedings ,illinois ,society of ,engineers1 #aiaf4 ,also ,e4,r4 ,v4 #gc1 #aiaf1 p4 #bee4 ,e4,c4 ,v4 #de1 #aiaf1 p4 #ajd1 and ,e4,n4 ,v4 #ge1 #aiaf1 pp4 #bfb and #cjf4 #aa4 ,a4,s4 ,defined4 ,e4,n4 ,v4 #ge1 #aiaf1 p4 #ejc1 and ,e4,n4,r4 ,v4 #hj1 #aiah1 p4 #bje4 #ab4 ,status of ,a4,s4 ,sewage ,treatment1 by ,hammond4 ,e4,n4 ,v4 #ge1 #aiaf1 p4 #gih4 #ac4 ,trial ,a4,s4 ,unit at ,cleveland1 by ,pratt4 ,e4,n4 ,v4 #ge1 #aiaf1 p4 #fga4 #ad4 ,air ,diffuser ,experience with ,a4,s4 ,e4,n4 ,v4 #gf1 #aiaf1 p4 #ajf4 #ae4 ,nitrogen from ,sewage ,sludge1 ,plain and ,activated1 by ,copeland1 ,journal ,american ,chemical ,society1 ,sept4 #bh1 #aiaf4 ,e4,n4 ,v4 #gf1 #aiaf1 p4 #ffe4 ,e4,r4 ,v4 #gd1 #aiaf1 p4 #ddd4 #af4 ,tests ,show ,a4,s4 ,process ,adapted to ,treatment of ,stock ,yards ,wastes4 ,e4,r4 ,v4 #gd1 #aiaf1 p4 #acg4 #ag4 ,aration ,suggestions for ,disposal of ,sludge1 by ,hammond4 ,journal ,american ,chemical ,society1 ,sept4 #be1 #aiaf4 ,e4,r4 ,v4 #gd1 #aiaf1 p4 #ddh4 #ah4 ,cost ,comparison of ,sewage ,treatment4 ,imhoff ,tank and ,sprinkling ,filters vs4 ,a4,s41 by ,eddy4 ,e4,r4 ,v4 #gd1 #aiaf1 p4 #eeg4 #ai4 ,large ,a4,s4 ,plant at ,milwaukee4 ,e4,n4 ,v4 #gf1 #aiaf1 p4 #fhf4 #bj4 ,a4,s4 ,novelties at ,hermosa ,beach1 ,cal4 ,e4,n4 ,v4 #gf1 #aiaf1 p4 #hij4 #ba4 ,a4,s4 ,experiments at ,university of ,illinois1 by ,bartow1 ,mohlman1 and ,schnellbach4 ,e4,n4 ,v4 #gf1 #aiaf1 p4 #igb4 #bb4 ,a4,s4 ,results at ,cleveland ,reviewed1 by ,pratt and ,gascoigne4 ,e4,n4 ,v4 #gf1 #aiaf1 pp4 #ajfa and #aabd4 #bc4 ,sewage ,treatment by ,aration and ,activation1 by ,hammond4 ,proceedings ,american ,society ,municipal ,improvements1 #aiaf4 #bd4 ,a4,s41 by ,bartow and ,mohlman1 ,proceedings ,illinois ,society of ,engineers1 #aiaf4 #be4 ,the ,latest ,method of ,sewage ,treatment1 by ,bartow4 ,journal ,american ,waterworks ,association1 ,v4 #c1 ,march1 #aiaf1 p4 #cbg4 #bf4 ,winter ,experiences with ,a4,s41 by ,copeland4 ,journal ,american ,society of ,chemical ,engineers1 ,april #ba1 #aiaf4 ,e4,c4 ,v4 #de1 #aiaf1 p4 #chf4 #bg4 ,a4,s4 ,process ,firmly ,established1 by ,hatton4 ,e4,r4 ,v4 #ge1 #aiag1 p4 #af4 #bh4 ,operate ,continuous ,flow ,a4,s4 ,plant1 by ,bartow1 ,mohlman1 and ,schnellbach4 ,e4,r4 ,v4 #ge1 #aiag1 p4 #chj4 #bi4 ,chicago ,stock ,yards ,sewage and ,a4,s41 by ,lederer4 ,journal ,american ,society of ,chemical ,engineers1 ,april #ba1 #aiaf4 ,e4,c4 ,v4 #de1 #aiaf1 p4 #chh4 #cj4 ,the ,patent ,situation ,concerning ,a4,s4 ,e4,c4 ,v4 #de1 #aiaf1 p4 #bjh4 #ca4 8,sewage ,disposal0 by ,kinnicutt1 ,winslow1 and ,pratt1 published by ,john ,wiley ,sons4 #b;d ,edition1 ,chapter #ab4 #cb4 ,a4,s4 ,tests ,made by ,california ,cities4 ,e4,n4,r4 ,v4 #gi1 #aiag1 p4 #ajji4 #cc4 ,conclusions on the ,a4,s4 ,process at ,milwaukee4 ,journal ,american ,public ,health ,association1 #aiag4 ,e4,n4,r4 ,v4 #gi1 #aiag1 p4 #hdj4 #cd4 ,dewatering ,a4,s4 at ,urbana1 by ,bartow4 ,journal ,american ,institute of ,chemical ,engineers1 #aiag4 ,e4,n4,r4 ,v4 #gi1 #aiag1 p4 #bfi4 #ce4 ,milwaukee ,air ,diffusion ,studies in ,a4,s4 ,e4,n4,r4 ,v4 #gh1 #aiag1 p4 #fbh4 #cf4 ,a4,s4 ,bibliography 7up to ,may #a1 #aiag7 by ,j4 ,e4 ,porter4 #cg4 ,air ,diffusion in ,a4,s4 ,e4,n4,r4 ,v4 #gh1 #aiag1 p4 #bee4 #ch4 ,a4,s4 ,plant at ,houston1 ,texas4 ,e4,n4 ,v4 #gg1 #aiag1 p4 #bcf1 ,e4,n4,r4 #hc1 #aiai1 p4 #ajjc1 and ,v4 #hd1 #aibj1 p4 #ge4 #ci4 ,a4,s4 ,power ,costs1 by ,requardt4 ,e4,n4 ,v4 #gg1 #aiag1 p4 #ah4 #dj4 ,a4,s4 at ,san ,marcos1 ,texas1 by ,elrod4 ,e4,n4 ,v4 #gg1 #aiag1 p4 #bdi4 #da4 ,filtros ,plates ,made the ,best ,showing in ,air ,diffuser ,tests4 ,e4,n4,r4 ,v4 #gi1 #aiag1 p4 #bfi4 #db4 ,results of ,experiments on ,a4,s41 by ,ardern and ,lockett4 ,journal ,society for ,chemical ,research1 ,v4 #cc1 ,may #cj1 #aiad1 p4 #ebc4 #dc4 ,final ,plans at ,milwaukee4 ,e4,n4,r4 ,v4 #hd1 #aibj1 p4 #iij4 #dd4 ,a4,s4 ,bibliography1 published by ,general ,filtration ,co41 ,rochester1 ,n4 ,y41 #aiba4 #de4 ,a4,s4 at ,manchester1 ,eng4 by ,ardern4 ,journal ,society ,chemical ,industry1 #aiba4 ,e4,c4 ,v4 #ee1 #aiba1 p4 #caj4 #df4 ,the ,des ,plaines ,river ,a4,s4 ,plant1 by ,pearse4 ,e4,n4,r4 ,v4 #hh1 #aibj1 p4 #aacd4 #dg4 ,sewage ,treatment by the ,dorr ,system1 by ,eagles4 ,proceedings1 ,boston ,society of ,engineers1 #aibj4 ,public ,works ,v4 #ej1 #aibj1 p4 #ec4 ,,chapter ,,xix ,,acid ,,precipitation1 ,,lime ,,and ,,electricity1 ,,and ,,disinfection #bge4 ,the ,miles ,acid ,process4--,the ,miles ,acid ,process for the treatment of sewage was devised and patented by ,g4 ,w4 ,miles4 ,it was tried experimentally at the ,calf ,pasture sewage pumping station1 ,boston1 ,mass41 #aiaa to #aiad4 ,in #aiaf it was tried experimentally at the ,massachusetts ,institute of ,technology1 and it has been tested subsequently at other places1 notably at ,new ,haven1 ,conn41 in #aiag and #aiah4 ,it is one of the most recent developments in sewage treatment and no extensive experience has been had with it4 ,the process consists in the acidification of sewage with sulphuric or sulphurous acid1 as the result of which the suspended matter and grease are precipitated and bacteria are removed4 ,the equipment required for the process consists of devices for the production of sulphur dioxide 7,,so#b71 and for feeding niter cake or other forms of acid2 subsiding basins2 sludge-handling apparatus2 sludge driers2 grease extractors2 grease stills2 and tankage driers and grinders4 ,the first step is the acidification of the sewage4 ,the period of contact with the acid is about #d hours4 ,sulphurous acid seems to give better results than sulphuric because of the ease in which it can be manufactured on the spot4 ,it seems also to be more virulent in attacking bacteria than an equal strength of sulphuric acid4 ,in experimental plants the acidulation has been accomplished in different ways such as3 by the addition of compressed sulphur dioxide from tanks2 by the addition of sulphur dioxide made from burning sulphur2 or by the roasting of iron pyrite 7,fe,s#b74 ,the acidulation precipitates most of the grease as well as the suspended matter and results in a sludge which gives some promise of commercial value4 ,in referring to the process ,r4 ,s4 ,weston states3#ahh 7#a7 ,it disinfects the sewage by reducing the numbers of bacteria from millions to hundreds per c4c4 7#b7 ,if the drying of the sludge and the extraction of the grease can be accomplished economically1 it is possible that a large part1 if not all1 of the cost of the acid treatment may be met by the sale of the grease and fertilizer recovered from the sewage4 7#c7 ,the use of so strong a deodorizer and disinfectant as sulphur dioxide would prevent the usual nuisances of treatment works4 7#d7 ,the addition of sulphur dioxide to the sewage also avoids any fly nuisance1 which is a handicap to the operation of ,imhoff tanks and trickling filters4 ,the amount of acid used varies with the quality of the sewage and the desired character of the effluent4 ,at ,bradford1 ,england1#ahi #e1ejj pounds of sulphuric acid are used per million gallons1 producing about #b1cdj pounds of grease or #j4dc pound of grease per pound of sulphuric acid4 ,at ,boston only #j4bae pound of grease were produced per pound of sulphuric acid4 ,the difference is probably due to the great difference in the amount of grease in the raw sewage4 ,in the ,east ,street sewer at ,new ,haven1 ,conn41#aij only #gjj pounds of acid are used per million gallons of sewage as the alkalinity is only #ej p4p4m4 ,this amount of acid secures an acidity of #ej p4p4m4 whereas in the ,boulevard sewer #a1acj pounds of acid had to be added to produce the same result4 ,the results obtained by the experiments conducted by the ,massachusetts ,state ,board of ,health in #aiag are shown in ,table #ig4 ,the character of the sludge from the same tests is shown in ,table #ih4 ,after acidification#aia the sewage contains bisulphites and some free sulphurous acid1 with some lime and magnesium soaps which are attacked by the acid liberating the free fatty acids4 ,part of the bisulphites and sulphurous acid are oxidized to bisulphates and sulphuric acid4 ,it was found as a result of the ,new ,haven#aia experiments that the presence of sulphur dioxide in the effluent caused an abnormal oxygen demand from the diluting water and that this difficulty could be partly overcome by the aration of the effluent after acidulation and sedimentation1 without prohibitory expense4 ,the effluent and sludge are both stable for appreciable periods of time and are suitable for disposal by dilution4 ,the character of the sludge as determined by the ,new ,haven tests#aib is shown in ,table #ii4 ,,table #ig ,,average ,,analysis ,,of ,,sewage ,,entering ,,boston ,,harbor1 ,,before ,,and ,,after ,,treatment1 ,,july #ag ,,to ,,september #bg1 #aiag 7,eng4 ,news-,record1 ,vol4 #hj1 p4 #cai7 ,sample ,parts per ,million ,bacteria1 ,millions ,ammonia ,kjeldahl ,chlorine ,oxygen ,nitrogen ,consumed ,free ,albuminoid ,total,total,diss4,total,diss4 #bj #cg ,paddock's ,island ,raw #ad4j #c4c #a4h #f4h #c4f #acd #bc4aa4hf #d4ae sewage ,settled #ab4b #a4f #a4a #c4e #b4b #ae4d ,sewage ,acidified #bj4i #e4b #c4i #aj4j #g4e unitsunits #ia and #id settled sewage ,deer ,island ,raw #bc4c #h4b #d4h #af4h #h4i #cajj #hg4cb4fc #a4ej sewage ,settled #ba4a #e4f #c4i #aj4g #g4c #fb4b sewage ,acidified #bj4i #e4b #c4i #aj4j #g4e unitsunits #he and #adg settled sewage ,calf ,pasture ,raw #ah4j #d4e #b4j #i4g #d4a #cbed #da4ba4hi #j4ih sewage ,settled #ai4a #b4c #a4d #d4i #c4c #be4h sewage ,acidified #ag4h #b4d #a4f #d4i #c4c unitsunits #adi and #bgg settled sewage ,the success of the ,miles ,acid ,process in comparison with other processes is dependent on the commercial value of the sludge produced4 ,the ,new ,haven experiments indicate that #af to #ba per cent of the grease in the sludge is unsaponifiable and seriously impairs the value of the process4 ,,table #ih ,,average ,,amount ,,of ,,sludge ,,and ,,fats ,,obtained ,,from ,,sewage ,,entering ,,boston ,,harbor ,,after ,,eighteen ,,hours ,,sedimentation ,,with ,,and ,,without ,,acidification 7,eng4 ,news-,record1 ,vol4 #hj1 p4 #cai7 ,paddock's ,island ,deer ,island ,calf ,pasture ,sedimentation ,sedimentation ,sedimentation ,plain,acidulated,plain,acidulated,plain ,acidulated ,pounds of ,,so#b #hah #aeac #aahi used per million gallons of sewage treated ,dry sludge per #ghb #iei #agji #aici #abjh #adbg million gallons ,per cent ,nitrogen in #c4aj #c4ch #c4eg #c4de #c4ah #b4hc sludge ,per cent fats in #bg4cj #bg4cjbd4fj #ai4djbd4cj #bf4cj sludge ,,table #ii ,,character ,,of ,,miles ,,acid ,,sludge ,,at ,,new ,,haven 7,eng4 ,news-,record1 ,vol4 #ha1 p4 #ajcd7 ,east ,street ,sewer ,boulevard ,sewer ,length of run in days #be #bd #dd #gj #bi ,total sewage treated1 #bfj #bci4d #djg4h #fjb4b #ade4e thousand gallons ,gallons wet sludge per #cgej #djbe #cbjj #bfjj #ecge million gallons sewage ,specific gravity #a4jfg #a4jdh #a4jed #a4jfa ,per cent moisture #hf4f #hh #hf4c #he4g #ib4e ,pounds of dry sludge per #ejc #dhc #dci #cfh #djc million gallons sewage ,ether extract1 per cent #bc4g #bd4j #bi #cb4f #cj4i dry sludge ,ether extract1 pounds per #aai #aaf #abg #abj #abd million gallons ,volatile matter1 per cent #dg4b #ea4b #eg4c #fc4h #gh4e dry sludge ,nitrogen1 per cent dry #a4f #a4f #b4d #b4j #c4j sludge ,the conclusions reached as a result of the ,new ,haven experiments are3#aic ,our experience with ,new ,haven sewage lends no color to the hope that a net financial profit can be obtained by the use of the ,miles ,acid ,process1 except with sewage of exceptionally high grease content and low alkalinity4 ,they do1 however1 suggest that for communities where clarification and disinfection are desirable--where screening would be insufficient and nitrification unnecessary--the process of acid treatment comes fairly into competition with the other processes of tank treatment1 and that it is particularly suited to dealing with sewages that contain industrial wastes1 and to use in localities where local nuisances must be avoided at all costs and where sludge disposal could be provided for only with difficulty4 ,the conclusions reached as a result of the ,chicago experiments are3#aid ,the results on hand indicate that treatment of this sewage with acid results in a somewhat greater retention of fat4 ,an apparent reduction in the oxygen demand over that resulting from plain sedimentation1 while remarkable1 is probably not real1 being simply due to a retardation of decomposition by the sterilization of the bacteria present1 the organic matter being left in solution4444 ,however1 there appears the added cost of acid treatment and the cost of recovery of the grease1 as well as the uncertainty of the price to be received for the grease recovered4 ,the cost of the treatment is estimated by ,dorr to be #ah per million gallons1 and the value of the sludge obtained from the ,boston sewage as #bd per million gallons1 giving a net margin of profit of #f per million gallons4 ,at ,new ,haven1 the total return is estimated at #g4ji per million gallons4 ,based on the production of sulphur dioxide by burning sulphur 7assumed to cost #cf per long ton7 and on drying from #he per cent to #aj per cent moisture with coal assumed to cost #g4ej per ton1 it appears that the acid treatment of sewage should be materially cheaper than either the ,imhoff treatment or fine screening under the local conditions4 ,a comparison of the cost of the treatment of the ,east ,street and the ,boulevard sewage at ,new ,haven and the ,calf ,pasture sewage in ,boston is given in ,table #ajj4 ,the cost of construction was estimated by ,dorr and ,weston in #aiai as greater than #ae1jjj per million gallons of sewage per day capacity4 ,,table #ajj ,,estimated ,,cost ,,of ,,sewage ,,treatment ,,at ,,new ,,haven ,,and ,,boston ,,by ,,three ,,different ,,processes ,cost in ,dollars per ,million ,gallons ,treated 7,engineering and ,contracting1 ,vol4 #ea1 p4 #eaj7 ,miles ,acid ,process ,imhoff ,tank and ,fine ,screens ,chlorination and ,chlorination ,east ,boul- ,calf ,east ,boul- ,calf ,east ,boul- ,streetevard,pasture,streetevard,pasture ,streetevard ,tanks and #b4dg #b4dg #b4dg #e4bh #d4dd #d4fj #d4fj ,buildings ,int4 and ,dep4 ,acid treatment #f4icaj4gd #ah4fe ,drying sludge #b4ji #b4jd #aj4cd ,degreasing #a4gh #a4ia #i4ab sludge ,superintendence #a4jf #b4fe #a4jf #j4df #a4ae #j4dg #a4ae ,labor on tanks #a4jj #a4jj #a4jj #a4bj #a4ej #a4db #b4je and screens ,disposal of #a4jj #a4jj #j4ej #j4ej sludge or screenings ,chlorination #d4je #d4je #d4je #d4je ,gross cost #ae4ejbj4ih #db4ge #aa4iiab4ad #aa4jcab4ce ,revenue #f4egaj4ff #dg4ei ,net cost #h4icaj4cb #d4hd #aa4iiab4ad #aa4jcab4ce ,,electrolytic ,,treatment #bgf4 ,the ,process4--,this process has been generally unsuccessful in the treatment of sewage and has grown into disrepute4 ,in the words of the editor of the ,engineering ,news-,record3#aie ,thirty years of experiments and demonstrations with only a few small working plants built and most of them abandoned--such in epitome is the record of the electrolytic process of sewage treatment4 ,it is probably true that the process has never received a thorough and exhaustive test on a large scale1 but the small-scale tests have not been promising of good results4 ,among the most extensive tests have been those at ,elmhurst1 ,long ,island1#aif ,decatur1 ,ill41#aig and ,easton1 ,pa4#aih ,whatever degree of popularity the method has possessed has been due possibly to the mystery and romance of 8electricity0 and to the personality of its promoters4 ,the process should1 nevertheless1 be understood by the engineer in order that it may be explained satisfactorily to the layman interested in its adoption4 ,in this process1 sometimes called the direct-oxidation process1 all grit is removed and the sewage is passed through fine screens before entering the electrolytic tank4 ,in the electrolytic tank the sewage passes in thin sheets between electrodes and an electric current is discharged through it4 ,a recent development has been the addition of lime to the sewage at some point in its passage through the electrolytic tank4 ,from the electrolytic tank the sewage flows to a sedimentation tank1 where sludge is accumulated1 and from which the liquid effluent is finally disposed of4 ,it is claimed that the action of the electricity electrolyzes the sewage1 releasing chlorine1 which acts as a powerful disinfectant4 ,the constituents of the sewage are oxidized so that the dissolved oxygen1 nitrates1 and relative stability are increased and the sludge is rendered non-putrescible4 ,it is said that the addition of lime increases the efficiency of sedimentation and enhances the effect of the electric current4 ,the results obtained by tests at ,easton1 ,pa41 are shown in ,table #aja4 ,it will be observed from this table that the combination of lime and electricity does not have a more beneficial effect than either one of them alone4 ,the amount of sludge produced by the combination is about the same as by chemical precipitation alone1 but the character of the sludge produced with electricity is less putrescible4 ,the cost of the treatment as estimated at ,elmhurst is shown in ,table #ajb4 ,as a result of the tests at ,decatur1 comparing lime alone with lime and electricity together1 ,dr4 ,ed4 ,bartow stated3 ,the purification by treatment with lime alone was greater than that obtained in several of the individual samples treated with lime and electricity4 ,,table #aja ,,comparative ,,results ,,obtained ,,from ,,the ,,treatment ,,of ,,sewage ,,by ,,lime ,,alone1 ,,electricity ,,alone1 ,,and ,,lime ,,and ,,electricity ,,combined 7,creighton and ,franklin1 ,journal of the ,franklin ,institute1 ,august1 #aiai7 ,lime and ,lime ,alone ,electricity ,electricity ,alone ,change1,change1,change1,change1,change1 ,change1 ,parts ,per ,parts ,per ,parts ,per per ,cent per ,cent per ,cent ,million ,million ,million ,chlorine #a4b #a4i #ab4c #ah4b #a4f #b4b ,nitrites #j4jad #eh4c -4#jje -#aj4j -#j4ja -#bj4j ,nitrates #j4ac #bc4f 4#jje #j4h -#j4ae -#bj4j ,ammonia -#c4c -#ah4c #j4b #a4c #j4i #f4f ,albuminoid ammonia -#c4f -#ab4a -#j4d -#a4g -#j4e -#b4c ,oxygen demand -#ac4j -#bj4e -#g4g -#h4i -#f4e -#aj4j ,dissolved oxygen #a4gh #dj4i -#j4ic -#ai4a #a4fa #dj4a ,total bacteria at #cg -#cdc -#ib4g -#cgc -#hb4d -#afe -#cg4h 7,thousands7 ,total bacteria at #bj -#fhh -#ib4g -#ajgd -#ij4a -#fce -#gj4j 7,thousands7 ,b4 ,coli 7,thousands7 -#gg4i -#ii4he -#if4c -#ib4c -#de -#ha4h ,oxygen absorbed in #e -#c4dj -#ha4f -#a4jc -#ba4 #a4bd #ca days ,,disinfection #bgg4 ,disinfection of ,sewage4--,sewage is disinfected in order to protect public water supplies1 shell fish1 and bathing beaches2 to prevent the spread of disease2 to keep down odors1 and to delay putrefaction4 ,disinfection is the treatment of sewage by which the number of bacteria is greatly reduced4 ,sterilization is the destruction of all bacterial life1 including spores4 ,ordinarily even the most destructive agents do not accomplish complete sterilization4 ,chlorine and its compounds are practically the only substances used for the disinfection of sewage4 ,the lime used in chemical precipitation1 the acid used in the ,miles ,acid ,process1 the aration in the activated sludge process1 all serve to disinfect sewage1 but are not used primarily for that purpose4 ,copper sulphate has been used as an algaecide but never on a large scale as a bactericide4#aii ,heat has been suggested1 but its high cost has prevented its practical application to the disinfection of sewage4 ,,table #ajb ,,cost ,,of ,,electrolytic ,,treatment1 ,,elmhurst1 ,,long ,,island1 ,,and ,,easton1 ,,pennsylvania ,three ,item ,one ,million ,gallon ,million ,gallon unit at unit at unit at ,easton1 ,elmhurst1,elmhurst1 ,dollars ,dollars ,dollars ,hydrated lime3 ,elmhurst1 #acjj pounds at #g4ij ton4 #ab4ef #e4ad #ae4db ,easton1 #cgbj pounds at #f4ge ton4 ,electric power electrolysis3 ,elmhurst1 #he kw-h4 at #d cents #d4ai #c4dj #i4fj ,easton1 #f4be kw-h4 at #h4je cents ,electric power1 light and agitation3 ,elmhurst1 #fj kw-h4 at #d cents #j4ej #b4dj #g4bj ,easton1 #f4be kw-h at #h4je cents ,heating #a4be ,labor and supervision #ae4jj #ab4ej #ae4jj ,maintenance1 repairs and supplies #a4ej #a4jj #c4jj ,sludge pressing and removal #e4aa #ae4cc ,total #ce4jj #bi4ee #fe4ee ,cost per million gallons #ce4jj #bi4ee #ba4he ,the action which takes place on the addition to sewage of chlorine or its compounds is not well understood4 ,the idea that the bacteria are burned up with 8nascent0 or freshly born oxygen1 has been exploded4#bjj ,likewise the idea that the toxic properties of chlorine have no effect has not been borne out by experiments4 ,it has been demonstrated1 particularly by tests on strong tannery wastes1 that the action of chlorine gas is more effective than the application of the same amount of chlorine in the form of hypochlorite4 ,all that we are certain of at present is that the greater the amount of chlorine added under the same conditions1 the greater the bactericidal effect4 ,chlorine is applied either in the form of a bleaching powder or a gas4 ,in ordinary commercial bleach 7calcium hypochlorite7 the available chlorine is about #ce to #dj per cent by weight4 ,in order to add one part per million of available chlorine to sewage it is necessary to add about #be pounds of bleaching powder or #h pounds of liquid chlorine per million gallons of sewage4 ,this can be computed as follows3 ,the molecular weight of calcium hypochlorite is #abg4j4 ,this reacts to produce two atoms of available chlorine with a molecular weight of #gj4i4 ,if the bleaching powder were pure the available chlorine would therefore represent #gj4i #abg1 or #ef per cent of its weight4 ,then to obtain one pound of chlorine it would be necessary to have #a4gi pounds of pure bleaching powder4 ,since #a1jjj1jjj gallons of water weigh approximately #h1cjj1jjj pounds1 in order to apply one part per million of chlorine to #a1jjj1jjj gallons of sewage it is necessary to apply #a4gi #h4c or #ad4i pounds of pure bleaching powder4 ,commercial bleaching powder is only about #fj per cent calcium hypochlorite4 ,it is therefore necessary to add #ad4i #j4fj or about #be pounds of commercial bleach4 ,since liquid chlorine is very nearly pure1 approximately #h pounds of it applied to #a1jjj1jjj gallons of sewage are equivalent to a dose of one part per million4 ,commercial bleaching powder is a dry white powder which absorbs moisture slowly1 and which loses its strength rapidly when exposed to the air4 ,it is packed in air-tight sheet iron containers1 which should be opened under water1 or emptied into water immediately on being opened4 ,the strength of the solution should be from to #a per cent4 ,the rate of the application of the solution to the sewage may be controlled by automatic feed devices1 or by hand-controlled devices4 ,commercial liquid chlorine is sold in heavy cast steel containers1 which hold #ajj to #adj pounds of liquid chlorine under a pressure of #ed pounds per square inch at zero degrees ,c4 or #aba pounds per square inch at #bj degrees4 ,the amount of chlorine used is dependent on the character of the sewage to be treated1 the stage of decomposition of the organic matter1 the desired degree of disinfection1 the period of contact1 and the temperature4 ,the amount of chlorine is expressed in parts per million of available chlorine1 regardless of the form in which the chlorine is applied4 ,in general about #ae to #bj parts per million of available chlorine with #cj minutes' contact at a temperature of about #ae ,c4 will effect an apparent removal of #ii per cent of the bacteria from the raw sewage4 ,the effect is only apparent because many of the bacteria encased in the solid matter of the sewage escape the effect of the chlorine1 or detection in the bacterial analysis4 ,stronger and older sewages1 higher temperatures1 and shorter periods of contact will demand more chlorine to produce the same results4 ,a septic effluent will require more chlorine than a raw sewage because of the greater oxygen demand by the septic sewage4 ,the results of experiments on disinfection made at different testing stations have shown such wide variations in the amount of chlorine necessary1 as to demonstrate the necessity for independent studies of any particular sewage which is to be chlorinated4 ,for instance1 at ,milwaukee approximately #ac p4p4m4 of available chlorine applied to an ,imhoff tank effluent effected a #ii per cent removal of bacteria1 whereas the same result was obtained at ,lawrence1 ,mass41 on crude sewage with only #f4f p4p4m4 and at ,marion1 ,ohio1 only #i per cent removal of bacteria was obtained by the addition of #d1hae p4p4m4 to crude sewage4 ,the ,ohio and ,massachusetts reports show irrational variations among themselves4 ,for instance1 #f4b p4p4m4 applied to a septic effluent effected #hh per cent removal whereas in another case #g4f p4p4m4 effected only #cf per cent removal4 ,at ,lawrence in one case it took #h4f p4p4m4 to remove #ii per cent from a sand filter effluent1 but only #f4c p4p4m4 to effect the same result in the effluent from a septic tank4 ,the most consistent results are those found at ,milwaukee which show a steadily increasing percentage removal with increasing amounts of chlorine4 ,some time after sewage has received its dose of chlorine the number of bacteria may be greater than in the raw sewage4 ,such bacteria are called aftergrowths4 ,certain forms of bacteria1 particularly the pathogenic or body temperature types1 are most susceptible to disinfecting agents4 ,these are killed off and leave the sewage in a condition more favorable to the growth of more resistant forms of bacteria4 ,as the latter are non-pathogenic and are generally arobic their presence is usually more beneficial than detrimental1 as they hasten the action of self-purification4 ,,references ,the following abbreviations will be used3 ,e4,c4 for ,engineering and ,contracting1 ,e4,n4 for ,engineering ,news1 ,e4,r4 for ,engineering ,record1 ,e4,n4,r4 for ,engineering ,news-,record1 ,m4,j4 for ,municipal ,journal1 p4 for page1 and ,v4 for volume4 ,no4 #a4 ,grease and ,fertilizer ,base for ,boston ,sewage1 by ,weston1 ,e4,n4 ,v4 #ge1 #aiaf1 p4 #iac and ,journal ,american ,public ,health ,association1 ,april1 #aiaf4 #b4 ,getting ,grease and ,fertilizer from ,city ,sewage1 by ,allen4 ,e4,n4 ,v4 #ge1 #aiaf1 p4 #ajje4 #c4 ,new ,haven ,tests ,five ,processes of ,sewage ,treatment4 ,e4,n4,r4 ,v4 #gi1 #aiag1 p4 #hbi4 #d4 ,recovery of ,grease and ,fertilizer from ,sewage ,comes to the ,front4 ,e4,n4,r4 ,v4 #hj1 #aiaf1 p4 #cai4 #e4 ,miles ,acid ,process may ,require ,aration of ,effluent1 by ,mohlman4 ,e4,n4,r4 ,v4 #ha1 #aiah1 p4 #bce4 #f4 ,promising ,results with ,miles ,acid ,process in ,new ,haven ,tests4 ,e4,n4,r4 ,v4 #ha1 #aiah1 p4 #ajcd4 #g4 ,baltimore ,experiments on ,grease from ,sewage4 ,e4,n4 ,v4 #ge1 #aiaf1 p4 #aaee4 #h4 ,report on ,industrial ,wastes from the ,stock ,yards and ,packingtown in ,chicago to the ,trustees of the ,sanitary ,district of ,chicago1 #aiad1 pp4 #ahg-aie4 #i4 ,the ,separation of ,grease from ,sewage1 by ,daniels and ,rosenfeld4 ,cornell ,civil ,engineer4 ,v4 #bd1 p4 #ac4 #aj4 ,the ,separation of ,grease from ,sewage ,sludge with ,special ,reference to ,plants and ,methods ,employed at ,bradford and ,oldham1 ,england1 by ,allen4 ,e4,c4 ,v4 #dj1 #aiac1 p4 #faa4 #aa4 ,acid ,treatment of ,sewage1 by ,dorr and ,weston4 ,journal ,boston ,society of ,civil ,engineers1 ,april1 #aiai4 ,e4,c4 ,v4 #ea1 #aiai1 p4 #eaj4 ,m4,j4 ,v4 #df1 #aiai1 p4 #cfe4 #ab4 ,the ,miles ,acid ,process for ,sewage ,disposal4 ,metallurgical and ,chemical ,engineering1 ,v4 #ah1 p4 #eia4 #ac4 ,miles ,acid ,treatment of ,sewage1 by ,winslow and ,mohlman4 ,journal ,american ,society ,municipal ,improvements1 ,oct41 #aiah4 ,m4,j4 ,v4 #de1 #aiah1 pp4 #bhj1 #big1 and #cba4 #ad4 ,new ,electrolytic ,sewage ,treatment4 ,m4,j4 ,v4 #cg1 #aiad1 p4 #eef4 #ae4 ,electrolytic ,sewage ,treatment4 ,m4,j4 ,v4 #dg1 #aiai1 p4 #aca4 #af4 ,electrolytic ,treatment of ,sewage at ,durant1 ,oklahoma1 by ,benham4 ,e4,n4 ,v4 #gf1 #aiaf1 p4 #edg4 ,municipal ,engineering1 ,v4 #di1 #aiaf1 p4 #ada4 #ag4 ,electrolytic ,treatment of ,sewage at ,elmhurst1 ,long ,island1 by ,travis4 ,report to the ,president of the ,borough of ,queens1 ,aug4 #ca1 #aiad4 ,e4,r4 ,v4 #gj1 #aiad1 pp4 #bib1 #cae1 and #dbi4 ,m4,j4 ,v4 #ci1 p4 #eea4 ,municipal ,engineering1 ,v4 #dg1 p4 #bha4 #ah4 ,tests of the ,electrolysis of ,sewage at ,toronto1 by ,nevitt4 ,e4,n4 ,v4 #ga1 #aiad1 p4 #ajgf4 #ai4 ,electrolytic ,treatment of ,sewage ,little ,better than ,lime ,alone1 by ,bartow4 ,e4,r4 ,v4 #gd1 #aiaf1 p4 #eif4 #bj4 ,electrolytic ,sewage ,treatment ,not ,yet an ,established ,process4 ,e4,n4,r4 ,v4 #hc1 #aiai1 p4 #eda4 #ba4 ,tests of ,electrolytic ,sewage ,treatment ,process at ,easton1 ,pa4 ,journal of the ,franklin ,institute1 ,aug41 #aiai4 ,e4,n4,r4 ,v4 #hc1 #aiai1 p4 #efi4 #bb4 ,the ,disinfection of ,sewage4 ,u4 ,s4 ,geological ,survey1 ,water ,supply ,paper1 ,no4 #bbi4 #bc4 ,sewage ,disinfection in ,actual ,practice1 by ,orchard4 ,e4,r4 ,v4 #gj1 #aiad1 p4 #afd4 #bd4 ,water and ,sewage ,purification in ,ohio4 ,report of the ,ohio ,state ,board of ,health1 #aijh1 pp4 #gch-gfb4 #be4 ,water ,purification1 by ,ellms4 ,published in #aiag by ,mc,graw-,hill ,book ,co4 #bf4 ,electrolytic ,sewage ,treatment1 ,a ,half ,century of ,invention and ,promotion4 ,e4,n4,r4 ,v4 #hf1 #aiba1 p4 #be4 ,,chapter ,,xx ,,sludge #bgh4 ,methods of ,disposal4--,sludge is the deposited suspended matter which accumulates as the result of the sedimentation of sewage4 ,the methods for the disposal of sludge as discussed herein will include the disposal of scum4 ,scum is a floating mass of sewage solids buoyed up in part by entrained gas or grease1 forming a greasy mat which remains on the surface of the sewage4#bja ,the sludges formed by different methods of sewage treatment are described in the chapter devoted to the particular method4 ,the disposal of sludge is a problem common to all methods of sewage treatment involving the use of sedimentation tanks4 ,sludge is disposed of by3 dilution1 burial1 lagooning1 burning1 filling land1 and as a fertilizer or fertilizer base4 ,certain methods of disposal1 such as burning or as a fertilizer1 demand that the sludge be dried preparatory to disposal4 ,sludge is dried on drying beds1 in a centrifuge1 in a press1 in a hot-air dryer1 or by acid precipitation4 #bgi4 ,lagooning4--,this is a method of sludge disposal in which fresh sludge is run on to previously prepared beds to a depth of #ab to #ah inches or more1 and allowed to stand without further attention4 ,the preparation of the lagoons requires leveling the ground1 building of embankments1 and1 if the ground is not porous1 the placing of underdrains laid in sand or gravel4 ,at ,reading1 ,pa41#bjb approximately one acre was required for #a1gjj cubic yards of wet sludge4 ,the results of lagooning at ,philadelphia are given in ,table #ajc4bjb ,,table #ajc ,,results ,,of ,,drying ,,sludge ,,in ,,lagoons ,,at ,,philadelphia 78,sewage ,sludge0 by ,allen7 ,treatment ,days ,depth1 ,per ,cent1,rainfall1 ,cubic ,inches ,moisture ,inches ,yards per ,acre ,screened #j #ab4bj #hb4h #j #afjj ,screened #bf #g4fg #eg4j #j #ajjj ,screened #di #c4ej #ea4f #j4dc #dgj ,screened #j #ac4ej #ij4a #j #ahjj ,screened #fb #g4jj #fa4j #c4ad #iej ,crude #j #ab4jj #hh4g #j #afjj ,crude #ei #d4gj #fb4h #b4ei #fdj ,during the period of standing in the lagoon the moisture drains out and evaporates and the organic matter putrefies1 giving off gases and foul odors4 ,in the course of three to six months1 biological action ceases and the sludge has become humified and reduced to about #ge per cent moisture4 ,in the utilization of this method of disposal the lagoons must be removed from settled districts and should occupy land of little value for other purposes4 ,the odors created at the lagoons may be intense and offensive4 ,the land so used is rendered unfit for other purposes for many years4 ,the digestion of sludge in special tanks is a form of lagooning in which an attempt is made to maintain septic action as a result of which a portion of the sludge is gasified or liquefied1 leaving less to be cared for by some of the other methods of treatment or disposal4 ,the results obtained by digestion tanks have not been entirely satisfactory4 ,a partial drying and consolidation of the sludge may be effected1 however1 by the process of decantation1 in which the supernatant liquid is run off1 followed by further sedimentation1 rendering the final product more compact4 #bhj4 ,dilution4--,in the disposal of sludge by dilution1 as in the disposal of sewage by dilution1 there must be sufficient oxygen available in the diluting water to prevent putrefaction1 and a swift current to prevent sedimentation4 ,such conditions exist in localities along the sea coast1 and in communities situated near rivers1 when the rivers are in flood4 ,in some seacoast towns1 for example at ,london and ,glasgow1 the sludge is taken out to sea in boats1 and dumped4 ,since it is not necessary to discharge sludge continuously1 it can be stored to advantage in the digestion chamber of a tank1 until the conditions in the body of diluting water are suitable to receive it4 ,the amount of diluting water to receive sewage sludge has not been sufficiently well determined to draw reliable general conclusions4 ,a dilution of #a1ejj to #b1jjj volumes may be considered sufficiently safe to avoid a nuisance provided there is a sufficient velocity to prevent sedimentation4 ,johnson's ,report on ,sewage ,purification at ,columbus1 ,ohio 7#aije71 states that a dilution of #a to #hjj is sufficient to avoid a nuisance4 ,the character of the sludge has a marked effect on the proper ratio of dilution1 the sludge from septic and sedimentation tanks requiring a greater dilution than that from ,imhoff tanks4 #bha4 ,burial4--,sludge can be disposed of by burial in trenches about #bd inches deep with at least #ab inches of earth cover1 without causing a nuisance4 ,the ground used for this purpose should be well drained4 ,this method of disposal is generally used as a makeshift and has not been practiced extensively because of the large amount of land required4 ,insufficient information is available to generalize on the amount of land required or the time before the land can be used for further sludge burial1 or for other purposes4 ,indications are that the sludge may remain moist and malodorous for years and that the land may be rendered permanently unfit for further sludge burial4 ,under some conditions the land may be used again for the same or other purposes4 ,for example1 ,kinnicutt1 ,winslow and ,pratt#bjc state that #ejj tons of wet sludge can be applied per acre and3 ,the same land1 it is claimed1 can be used again after a period of a year and a half to two years1 if in two months or so after covering the sludge with earth1 the ground is broken up1 planted1 and1 when the crop is removed1 again plowed and allowed to remain fallow for about a year4 #bhb4 ,drying4--,before sludge can be disposed of to fill land1 by burning1 or for use as a fertilizer filler it must be dried to a suitable degree of moisture4 ,the removal of moisture from the sludge decreases its volume and changes its characteristics so that sludge containing #ge per cent moisture has lost all the characteristics of a liquid4 ,it can be moved with a shovel or fork1 and can be transported in non-watertight containers4 ,a reduction in moisture from #ie to #ij per cent will cut the volume in half4 ,the change in volume on the removal of moisture can be represented as3 ,v#a ,v7#ajj ,p77#ajj ,p#a71 in which ,p the original percentage of moisture2 ,p#a the final percentage of moisture2 ,v the original volume2 ,v#a the final volume4 ,the drying of sludge on coarse sand filter beds is more particularly suited to sludge from ,imhoff tanks4 ,this sludge does not decompose during drying1 and is sufficiently light and porous in texture to permit of thorough draining4 ,the sludge from plain sedimentation or chemical precipitation tanks is high in moisture1 putrescible1 and when placed on a filter bed it settles into a heavy1 compact1 impervious mass which dries slowly4 ,in order to avoid this condition the sludge is run on to the beds as quickly as possible1 to a depth of not more than #f to #aj inches4 ,lime is sometimes added to the sludge at this time as it aids drying by assisting in the maintenance of the porosity of the sludge1 and it is advantageous in keeping down odors and insects4 ,sludge filter beds are made up of #ab to #bd inches of coarse sand1 well-screened cinders1 or other gritty material1 underlaid by #f inches of coarse gravel and #f or #h-;inch open-joint tile underdrains1 laid #d to #aj feet apart on centers1 dependent on the porosity of the subsoil4 ,the side walls of the filters are made of planks or of low earth embankments4 ,the sludge filters at ,hamilton1 ,ontario1 are shown in ,fig4 #agi4 ,illustration3 ,,fig4 #agi4--,sludge drying ,beds at ,hamilton1 ,ontario4 ,eng4 ,news1 ,vol4 #gc1 p4 #dbf4 ,the size of the bed is dependent mainly upon the characteristics of the sludge4 ,for ,imhoff tank sludge which comes from the tank with about #he per cent moisture1 the practice is to allow about #cejbjd square feet of filter surface per #a1jjj population contributing sludge4 ,for other types of sludge the area varies from #ijj to #i1jjj square foot per #a1jjj population contributing sludge1 and only experiments with the sludge in hand can determine the proper allowance4 ,imhoff recommends #a1jhj square feet per #a1jjj population for septic tank sludge1 and #f1dhj square feet for sludge from plain sedimentation tanks4#bje ,kinnicutt1 ,winslow1 and ,pratt in their book on ,sewage ,disposal state3 ,with an average depth of #aj inches per dose of sludge of #hg per cent water content1 one square foot of covered 7glass7 bed should dry to a spadable condition one cubic yard of sludge per year4 ,the sludge is run on the bed in small quantities at periods from two weeks to a month apart4 ,in favorable weather ,imhoff sludge will dry in two weeks or less to approximately #ej to #fj per cent moisture4 ,it is then suitable for use as a filling material on waste land1 for burning1 or for further drying by heat4 ,glass roofs1 similar to those used on green-houses1 have been used to speed the drying process by preventing the moistening of partly dried sludge during rainy weather4 ,in some instances sludge has dried to #aj per cent moisture on such beds4 ,imhoff sludge can be removed from the drying beds with a manure or hay fork4 ,it has an odor similar to well-fertilized garden soil4 ,it is stable1 dark brownish-gray in color1 is of light coarse material1 and is granular in texture4 ,sludge presses are suitable for removing moisture from the bulky wet sludge obtained from plain sedimentation1 chemical precipitation1 and the activated sludge process4 ,the details of a typical sludge press are shown in ,fig4 #ahj4 ,the press shown is made up of a number of corrugated metal plates about #cj inches in diameter with a hole in the center about #h inches in diameter4 ,the corrugations run vertically except for a distance about #c inches wide around the outer rim1 which is smooth4 ,to this smooth portion is fastened1 on each side of the plate1 an annular ring about an inch thick and #b to #c inches wide1 of the same outside diameter as the plate4 ,a circular piece of burlap1 canvas1 or other heavy cloth is fastened to this ring1 covering the plate completely4 ,a hole is cut in the center of the cloth slightly smaller in diameter than the center hole in the plate1 and the edges of the cloth on opposite sides of the plate are sewed together4 ,the plates are then pressed tightly together by means of the screw motion at the left end of the machine1 thus making a water-tight joint at the outer rim4 ,sludge is then forced under pressure into the space between the plates1 passing through the machine by means of the central hole4 ,the pressure on the sludge may be from #ej to #ajj pounds per square inch4 ,this pressure forces the water out of the sludge through the porous cloth from which it escapes to the bottom of the press along the corrugations of the separating plate4 ,after a period of #aj to #cj minutes the pressure is released1 the cells are opened1 and the moist sludge cake is removed4 ,the liquid pressed from the sludge is highly putrescible and should be returned to the influent of the treatment plant4 ,the pressing of wet greasy sludges is facilitated by the addition of from #h to #aj pounds of lime per cubic yard of sludge4 ,the cake thus formed is more cohesive and easy to handle4 ,the output of the press depends so much on the character of the sludge that a definite guarantee of capacity is seldom given by the manufacturer4 ,illustration3 ,,fig4 #ahj4--;,filter ,press4 ,the simplest form of centrifugal sludge dryer is a machine which consists of a perforated metal bowl lined with porous cloth in which the sludge is placed4 ,surrounding this bowl is a second water-tight metal bowl so arranged as to intercept the water thrown from the sides of the inner bowl as it revolves4 ,the peripheral velocity of the inner bowl is about #f1jjj feet per minute1 which makes the effective weight of each particle about #bej times its normal weight when at rest4 ,very few data are available on the operation of such machines1 and their use has not been extensive because of the difficulty of starting and stopping the machine at each filling1 and the difficulty of removing the partially dried sludge from the inner basket4 ,the ,besco-ter-,meer centrifuge1 manufactured by the ,barth ,engineering and ,sanitation ,co41 can be operated continuously and the difficulties of removing the dried sludge from the machine have been overcome4 ,according to the manufacturers the centrifuge has been operated very successfully in ,germany on plain septic tank sludge4 ,a removal of #gj per cent of suspended solids in the raw sludge and a production of #c1fjj pounds of sludge per hour1 containing #fj to #gj per cent of moisture1 can be obtained at less than #ijj r4p4m4 with a consumption of #ae horse-power4 ,extensive tests of the machine were made at ,milwaukee from ,october1 #aibj1 to ,september1 #aiba1 on activated sludge1 but results of these tests are not as yet available4 ,indications are that the centrifuge has acted as a classifier4 ,the coarser particles of sludge have been removed but the finer particles have been continuously returned with the liquid to the sedimentation tank1 ultimately filling this tank with fine particles of sludge4 ,an illustration of the unit tested at ,milwaukee is shown on this page4 ,illustration3 ,besco-ter-,meer ,sludge ,drying ,centrifuge at ,milwaukee1 ,wisconsin ,courtesy1 ,barth ,engineering and ,sanitation ,co4 ,experiments on the drying of sludge by acid flotation have not progressed sufficiently to allow the installation of a working unit4 ,the method1 which has been applied principally to activated sludge1 consists in adding a small amount of sulphuric acid to the sludge as it leaves the storage tank4 ,the sludge is coagulated by this action1 the coagulated material rising to the surface as a scum containing about #hf per cent moisture4 ,the consistency is such that it can be removed with a shovel4 ,the liquid can be withdrawn continuously from below the scum4 ,illustration3 ,,fig4 #aha4--;,direct-,indirect ,sludge ,dryer4 ,courtesy1 the ,buckeye ,dryer ,co4 ,the moisture content of sludge to be used in the manufacture of fertilizer must be reduced to #aj per cent or less4 ,none of the methods of drying described so far can be relied upon for such a product and it becomes necessary to use direct or indirect heat dryers4 ,there are various types of dryers on the market4 ,the details of a ,buckeye dryer are shown in ,fig4 #aha4 ,in the operation of this machine moist sludge is fed in at the left end at the point marked 8feed40 ,the hot gases pass from the fire box up and around the cylinder which revolves at about eight r4p4m4 ,the gases are drawn into the inner cylinder through the openings marked ,a which revolve with the two cylinders4 ,the gases escape from the inner cylinder through the openings to the right and flow towards the left in the outer cylinder4 ,they come in contact with the sludge at this point4 ,the gases then pass off through the fan at the left4 ,the sludge is lifted by the small longitudinal baffles fastened to the outer cylinder1 as the drying cylinders revolve4 ,the right end of the cylinder is placed lower than the left so that the drying sludge is lifted and dropped through the cylinder at the same time that it moves slowly toward the right hand end of the cylinder4 ,these dryers require about one pound of fuel for #aj pounds of water evaporated4 ,the odors from the dryer can be suppressed by passing the gases through a dust chamber and washer4 ,a summary of the results from methods of sludge drying at ,milwaukee#bjf follows3 ,excess sludge produced1 #ab1ajj gallons1 having #ig4e per cent moisture1 per million gallons of sewage treated4 ,sludge cake produced 7by presses71 #aj1jhc pounds having #hj4c per cent moisture1 per million gallons of sewage treated4 ,dried sludge 7from heat driers7 produced1 #b1eba pounds having #aj per cent moisture1 per million gallons of sewage treated4 ,press will produce #c pounds of cake per square foot of filter cloth in four and a half hours1 or five operations per twenty-four hours4 ,dryers will reduce #f1gjj pounds of sludge cake at #hj per cent moisture to #aj per cent moisture1 and will evaporate #h pounds of water per pound of combustible4 ,thickening devices known as ,dorr thickeners1 patented and manufactured by the ,dorr ,co4 and originally intended for metallurgical purposes1 have been adapted to the thickening of sewage sludge4 ,these thickeners are circular sedimentation tanks1 from #h to #ab feet deep1 more or less1 and are made in any diameter up to #bjj feet or more4 ,an arm1 pivoted in the center and extending to the circumference1 is provided at the bottom with a number of baffles or squeegees set at an angle with the arm4 ,the arm revolves at from one to fifteen revolutions per hour1 and the squeegees1 in contact with the bottom of the tank1 scrape the deposited sludge towards a central sump1 from which it is removed by a pump or by gravity1 without interrupting the operation of the thickener4 ,the sludge so thickened may be reduced to #ie or #if per cent moisture4 ,these devices are ordinarily used only in the activated sludge process in which they have been a pronounced success4 ,,chapter ,,xxi ,,automatic ,,dosing ,,devices #bhc4 ,types4--,automatic dosing devices are used to apply sewage to contact beds1 trickling filters1 and intermittent sand filters4 ,these devices can be separated into two classes2 those with moving parts and those without moving parts4 ,the latter are better known as air-locked dosing devices4 ,simple devices without moving parts are less liable to disorders and are nearer 8fool-proof0 than any device depending on moving parts for its operation4 ,no one type of moving part device has been used extensively in different sewage treatment plants4 ,designing engineers have exercised their ingenuity at different plants1 resulting in the production of different types4#bjg ,among the best known forms is the apparatus designed by ,j4 ,w4 ,alvord for the intermittent sand filters at ,lake ,forest1 ,illinois4#bjh ,in its operation4444 ,a float in the dosing chamber lifts an iron ball in one of a series of wooden columns1 and at a certain height the ball rolls through a trough from one column to the next1 in its passage striking a catch1 which opens an air valve attached to one of ten bell-siphons in the dosing chamber4 ,each of the siphons discharges on one of the ten sand beds1 which are thus dosed in rotation4 ,since air-locked dosing devices are in more general use their operation will be explained in greater detail4 #bhd4 ,operation4--,the simplest form of these devices is the automatic siphon used for flush-tanks1 the operation of which is described in ,art4 #fa4 ,in the operation of sand filters1 sprinkling filters1 or other forms of treatment where there are two or more units to be dosed it is desirable that the dosing of the beds be done alternately4 ,a simple arrangement for two siphons operating alternately is shown in ,fig4 #ahb4 ,they operate as follows3 with the dosing tank empty at the start water will stand at bb in siphon ,no4 #b and at aa in siphon ,no4 #a4 ,as the water enters through the inlet on the left the tank fills4 ,when the water rises sufficiently1 air is trapped in the bells1 and as the water continues to rise in the tank1 surfaces a and b are depressed an equal amount4 ,when b has been depressed to d1 a has been depressed to c4 ,air is released from siphon ,no4 #b through the short leg1 and siphon ,no4 #b goes into operation4 ,surface c rises in siphon ,no4 #a as the tank empties and when the action of ,siphon ,no4 #b is broken by the admission of air when the bottom of the bell is uncovered the water in siphon ,no4 #a has assumed the position of bb and that in ,no4 #b is at aa4 ,the conditions of the two siphons are now reversed from that at the beginning of the operation and as the tank refills siphon ,no4 #a will go into operation4 ,it is to be noted that these siphons are made to alternate by weakening the seal of the next one to discharge and by strengthening the seal of the one which has just discharged4 ,illustration3 ,,fig4 #ahb4--;,diagram ,showing the ,operation of ,two ,alternating ,siphons4 ,illustration3 ,,fig4 #ahc4--;,diagram ,showing the ,operation of ,three ,alternating ,siphons4 #bhe4 ,three ,alternating ,siphons4--,this principle can be extended to the operation of three alternating siphons as shown in ,fig4 ,no4 #ahc4 ,these operate as follows3 with the dosing tank empty at the start and water at aa in siphons #a and #b1 and at bb in siphon ,no4 #c1 the dosing tank will be allowed to fill4 ,as the water rises in the tank air is trapped in all the bells and surfaces a and b are depressed4 ,when surface b has been depressed to d1 a has been depressed to c4 ,air is released from siphon ,no4 #c and this siphon goes into action4 ,surface c rises in siphons #a and #b to the position b1 as the dosing tank is emptied4 ,at the same time a small amount of water is passed from siphon ,no4 #c to the short leg of siphon ,no4 #a1 through the small pipes shown1 thus filling this leg so that when siphon ,no4 #c ceases to operate the water in siphons #a and #c stands at aa and that in ,no4 #b stands at bb4 ,siphon ,no4 #b1 having the weaker seal1 will be the next to operate4 ,during its operation it will fill siphon ,no4 #c1 leaving ,no4 #a weak4 ,when ,no4 #a operates it will refill ,no4 #b1 leaving ,no4 #c weak1 thus completing a cycle for the three siphons4 ,this principle has not been applied to the operation of more than three alternating siphons and is seldom used on recent installations4 ,illustration3 ,,fig4 #ahd4--,miller ,plural ,alternating ,siphons4 ,courtesy1 ,pacific ,flush ,tank ,co4 #bhf4 ,four or ,more ,alternating ,siphons4--,an arrangement for the alternation of four or more siphons is illustrated in ,fig4 #ahd4 ,at the commencement of the cycle it will be assumed that all starting wells are filled with water except well ,no4 #a1 and that all main and all blow-off traps are filled with water4 ,the following description of the operation of the siphons is taken from the catalog of the ,pacific ,flush ,tank ,company3 ,the liquid in the tank gradually rises and finally overflows into the starting well ,no4 #a and the starting bell being filled with air1 pressure is developed which is transmitted1 as shown by the arrows1 to the blow-off trap connected with siphon ,no4 #b4 ,when the discharge line is reached1 sufficient head is obtained on the starting bell to force the seal in blow-off trap ,no4 #b1 thus releasing the air confined in siphon ,no4 #b and bringing it into full operation4 ,during the time that siphon ,no4 #b is operating1 siphonic action is developed in the draining siphon connected with starting well ,no4 #b and as soon as the level in the tank is below the top of the well it is drained down to a point below the bottom of starting well ,no4 #b4 ,it can now be seen that after the first discharge starting well ,no4 #b is empty1 whereas the other three are full4444 ,therefore when the tank is filled the second time1 pressure is developed in starting bell ,no4 #b1 which forces the seal of blow-off trap ,no4 #c1 thus starting siphon ,no4 #c4444 ,this alternation can be continued for any number of siphons4 ,other arrangements have been devised for the automatic control of alternating siphons1 but these principles of the air-locked devices are fundamental4 #bhg4 ,timed ,siphons4--,in the operation of a number of contact beds not only must the dosing of the tanks be alternated1 but some method is needed by which the beds shall be automatically emptied after the proper period of standing full4 ,to fulfill this need the principle of the timed siphon must be employed in conjunction with the alternating siphons4 ,fig4 #ahe illustrates the operation of the ,miller timed siphon4 ,its operation is as follows3 water is admitted to the contact bed and transmitted to the main siphon chamber through the 8opening into bed40 ,water flows from the main siphon chamber into the timing chamber at a rate determined by the timing valve4 ,the contact bed is held full during this period4 ,as the timing chamber fills with water air is caught in the starting bell and the pressure is increased until the seal in the main blow-off trap is blown and the main siphon is put into operation4 ,as the water level in the main siphon chamber descends1 water flows from the timing chamber into the main siphon through the draining siphon and the timing chamber is emptied1 ready to commence another cycle4 #bhh4 ,multiple ,alternating and ,timed ,siphons4#bji--,the alternating and timing of a number of beds is more complicated4 ,the arrangement necessary for this is shown in ,fig4 #ahf4 ,it will be assumed at the start that all beds are empty and that all feeds are air locked as shown in ,section ,,ab except that to bed ,no4 #d into which sewage is running4 ,as bed ,no4 #d fills1 sewage is transmitted through the opening in the wall into the timed siphon chamber ,no4 #d4 ,when the level of the water in the bed and therefore in this chamber has reached the top of the withdraw siphon leading to the compression dome chamber ,no4 #d1 this latter chamber is quickly filled4 ,the air pressure in starting bell ,no4 #d;a is transmitted to blow-off trap ,no4 #a;a4 ,the seal of this trap is blown1 releasing the air lock in feed ,no4 #a and the flow into bed ,no4 #a is commenced4 ,at the same time the air pressure in compression dome ,no4 #d is transmitted to feed ,no4 #d1 air locking this feed and stopping the flow into bed ,no4 #d4 ,the alternation of the feed into the different beds is continued in this manner4 ,illustration3 ,,fig4 #ahe4--,miller ,timed ,siphon4 ,courtesy1 ,pacific ,flush ,tank ,co4 ,bed ,no4 #d is now standing full and ,no4 #a is filling4 ,when compression dome chamber ,no4 #d was filled1 water started flowing through timing siphon valve ,no4 #d into timing chamber ,no4 #d at a rate determined by the amount of the opening of the timing valve4 ,as this chamber fills compression is transmitted to blow-off trap #d;b and when sufficiently great this trap is blown and timed siphon ,no4 #d is put into operation4 ,bed ,no4 #d is emptied by it1 and compression dome chamber ,no4 #d is emptied through the withdraw siphon at the same time4 ,this completes a cycle for the filling and emptying of one bed and the method of passing the dose on to another bed has been explained4 ,the principle can be extended to the operation of any number of beds4 ,illustration3 ,,fig4 #ahf4--,plural ,timed and ,alternating ,siphons for ,contact ,bed ,control4 ,courtesy1 ,pacific ,flush ,tank ,co4 ,,index ,a4 ,b4 ,c4 process of sewage treatment1 #d ,abandonment of contract1 #bbe ,access to work1 #bbh1 #bbi ,accident1 contractor's responsibility1 #bba1 #bbd ,acetylene1 explosive1 #cdg ,acid precipitation4 ,see ,miles ,acid ,process4 of sludge1 #ejc ,acids as disinfectants1 #dhi1 #dij ,activated sludge4 ,chapter ,,xviii1 #dfe-dgi advantages and disadvantages1 #dfi1 #dgj aration tank1 #dga1 #dgb air diffusion1 #dge1 #dgg air distribution1 #dgc-dgh air quantity1 #dge1 #dgf area of filtros plates1 #dgh colloid removal1 #ceh composition1 #dfe-dfi cost1 #dgh1 #dgi definition1 #dff dewatering1 #dfh1 #dfi1 #dig-eje fertilizing value1 #dfi1 #dgj historical1 #dgj1 #dga how obtained1 #dgh nitrogen content1 #dfh patent1 #dga process1 #dfe quantity1 #dfi rearation tank1 #dgc results1 #dfg1 #dfh1 #dgf sedimentation tank1 #dgb ,advertisement1 #bad ,aration1 effect on oxygen dissolved1 #cgc-cge of sewage1 #cga1 #cgf1 #dfe-dgi ,arobes1 #cfc ,arobic decomposition1 #cff1 #cfg ,aftergrowths1 #dib ,aggregates1 specifications1 #agb-agd ,air1 see also ventilation1 activated sludge1 compressed air1 etc4 ejectors1 #aej lock dosing apparatus4 ,chap4 ,,xxi1 #ejf-eab machinery for activated sludge1 #dgc1 #dgd ,alg1 #cfc ,alkalinity1 #ceh ,alleys1 sewers in1 #hj ,alum1 #djg1 #djh ,alvord tank1 #dbg1 #dbi ,ammonia1 #cff1 #cfg1 #cgd1 #cge1 #daj explosives1 #big ,analyses1 bacteriological1 #cfd chemical1 #ced1 #cee mechanical of sand1 #ahb physical1 #ceb-ced sewage1 #ceb-cfd ,anarobes1 #cfc1 #cfe-cfg ,anarobic1 action1 #daj bacteria1 #cfc conditions1 #cfg decomposition1 #cfe-cfg ,ann ,arbor1 ,michigan1 ,population1 #ad ,annual expense1 method of financing1 #aeg1 #aeh ,ansonia air ejector1 #aej1 #aea ,antibiosis1 definition1 #cfc ,appurtenances to sewers4 ,chap4 ,,vi1 #ii-aae ,arch1 analyses1 #bjd-bjh elastic method1 #bjf-bjh vouissoir analysis1 #bjd-bjf brick construction1 #cab1 #cac centers for brick sewers1 #cac concrete construction1 #cah-cba ,ardern and ,lockett1 development of activated sludge1 #dfg1 #dfh1 #dga ,area of cities1 #ca ,asphyxiation in sewer gas1 #ccf ,assessments1 special1 #ae1 #af ,augers1 earth1 #ba ,automatic1 regulators1 #aag-aba siphons1 flush-tanks1 #aaj double alternating1 #ejg multiple alternating1 #ejh-eab timed1 #eaj timed and multiple alternating1 #eaj-eab triple alternating1 #ejh ,bacillus1 definition and morphology1 #cfb1 #cfc ,backfilling1 #cbh-cca ,backfill1 puddling1 #ccj weight of1 #aii1 #bja ,backwater curve1 #gc ,bacteria1 definition and morphology1 #cfb1 #cfc good and bad1 #cfc1 #cfd nature of1 #cfb1 #cfc nitrifying1 #dca1 #dcb sanitary significance of1 #cfd in sewage1 #cfb1 #cfc total count1 #cfd ,bacterial analyses1 results in sewage1 #cfd ,baffles1 scum1 #djd1 #dac1 #dad1 #dba in sedimentation tanks1 #djd in septic tanks1 #dac1 #dad in ,imhoff tanks1 #dba ,balls1 for cleaning sewers1 #cch ,band screen1 #chd ,barring1 definition1 #bfc ,bars for screens1 #cij ,basins1 sedimentation1 baffling1 #djd bottoms1 #djd cleaning arrangements1 #djd depth1 #dja economical dimensions1 #dja-djc inlets and outlets1 #djd scum boards1 #djd types1 #cie ,basket handle sewer section1 #fg1 #fi ,bathing beaches1 pollution1 #cha ,bazin's formula1 #ed ,bearings1 for centrifugal pumps1 #aca1 #acg1 #ach thrust1 #ach ,bellmouth1 #aba1 #abb ,bends in pipe1 loss of head in1 #aaf ,berlin1 sewage farm1 #dfj1 #dfa sewers1 date of1 #c ,bids1 proposal1 #bag-bai ,bidder's duties1 #bae-bag ,bio-chemical oxygen demand1 #cei-cfa ,biolysis of sewage1 #cff1 #cfg ,black and ,phelps dilution formulas1 #cgg-cgi ,blasting and explosives1 #bid-cjd caps1 #big1 #bii1 #cjj detonators1 #bid1 #big-cjj firing1 #cjb-cjd fuses and detonators1 #big-cjj fuses1 delayed action1 #bia1 #cjj fuses1 electric1 #bii1 #cjj splicing1 #cjc gelatine1 #bif loading holes1 #cjc powder1 #bie precautions1 #cjj-cjb priming and loading1 #cjc rock1 #bfi size of charge1 #cjd1 #cje tunneling1 #bij1 #bia ,bleach1 characteristics of for disinfection1 #dia ,block sewer1 construction1 #caa-cad hollow tile as underdrains1 #abf ,blocks1 vitrified clay1 #ahi1 #aij ,boilers1 steam1 #adg-aej ,boilers1 efficiencies1 #adi horse-power1 #adi ,bond1 contractor's1 #bac1 #bad1 #bcb issues1 #ad ,bonds1 definition and types1 #ad-af ,boring underground1 #bj ,bottom1 activated sludge aration tank1 #dgb ,imhoff tanks1 #dbc sedimentation tanks1 #djd trickling filter1 #dea1 #deb ,box sheeting1 #bgb ,branch sewer1 defined1 #g ,breast boards1 #bhh ,brick1 arch construction1 #cab1 #cac and block sewer construction1 #caa-cae invert construction1 #caa1 #cab sewer construction1 #caa-cae arch centers1 #cac invert1 #caa-cab organization1 #cad1 #cae progress1 #cad row lock bond1 #cab specifications1 #ahh1 #ahi sewers1 life of1 #cea ,bricks for sewers1 #caf ,british ,royal ,commission on ,sewage ,disposal1 #d ,broad irrigation4 ,see under ,irrigation4 ,bucket excavators1 #bdf1 #bee1 #bef ,building material1 weight of1 #bja ,burkli-,ziegler formula1 #dg1 #dbe ,butyrine1 #cff ,cableway excavators1 #bdf1 #bej-beb ,cage screen1 #chd1 #che ,caisson excavation1 #bhe1 #bhf ,calcium carbide1 explosive1 #cdg ,calumet pumping station1 #abh1 #adb ,cameron septic patent1 #daa ,capacity of sewers1 diagrams1 #eg-fj ,capital1 private invested in sewers1 #ag ,capitalization1 method of financing1 #aeg-afj ,caps1 blasting4 ,see blasting4 ,carbohydrate1 #cff1 #cfg ,carbon1 analysis for1 #cef dioxide1 #cff1 #cfg ,carson ,trench machine1 #bej1 #bea ,cast-iron pipe1 #abb1 #afd1 #aij1 #aia joints1 #afd quality1 #aja1 #ajb1 #aij ,castings1 iron1 #aja1 #ajb ,catch-basins1 #ii1 #ajg-ajh1 #bag cleaning1 #cdc1 #cdd inspection1 #ccg ,catenary sewer section1 #fi ,cellars1 depth of1 #hh ,cellulose1 #cfg ,cement4 ,see also ,concrete1 pipe1 specifications1 manufacture and sizes1 #aga-agi vs4 concrete1 #afd ,centrifugal pumps4 ,see pumps1 centrifugal4 ,centrifuge for sludge drying1 #eja1 #ejb ,cesspool1 #daa1 #daf1 #dag ,champaign1 ,illinois1 septic tank1 #dae1 #daf ,changes in plan1 #bbb1 #bbc ,channeling1 definition1 #bfc ,character of surface1 #dd ,chemical analyses1 #ced-cfb ,chemical precipitation1 #cga1 #dje-dji chemicals used1 #dje-djg preparation of chemicals1 #djg1 #djh results1 #djh1 #dji at ,worcester1 #djh ,chezy formula1 #eb1 #ec ,chicago4 ,see also ,sanitary ,district of ,chicago4 drainage canal1 #cgd1 #cge dilution requirement for sewage1 #chj early sewers1 #c method of sewage disposal1 #cgd population and density1 #bi1 #cj trench excavation in1 #bdh ,chlorine4 ,see also ,disinfection4 disinfectant1 #dhi-dic in sewage1 #ceh1 #cgd1 #cge ,chlorine liquid1 application1 #dia1 #dib ,cholera1 transmittable disease1 #cfd ,chromatin1 #cfe ,chutes for concrete1 #ahg ,circular sewer section1 hydraulic elements1 #fe1 #ff1 #fi types1 #gj1 #ga ,city1 growth of area1 #ca growth of population1 #bd-bh legal powers1 #bai ,clay1 life of pipe1 #cdi-cea manufacture of pipe1 #afe-afg specifications for pipe1 #afh-agj unglazed for pipe1 #afe vitrified blocks1 #afg1 #ahi1 #aij vitrified pipe1 #afe-aga ,cleaning1 grit chambers1 #cih1 #djj sedimentation basins1 #djd sewers1 cost1 #cda in ,n4 ,y4 ,city1 #ccb methods1 #ccg-cdc tools1 #cch-cdj up after completion of work1 #bbh ,coccus1 #cfb ,coefficient of uniformity of sand1 #def ,coffin sewer regulator1 #aag1 #aah ,colloid1 nature of1 #ceh treatment for1 #ceh ,color of sewage1 #ceb1 #cec ,combined sewer system1 #gh1 #gi ,commercial districts1 characteristics of and sewage from1 #cb1 #cd1 #ce ,compensators for pumps1 #adb ,compressed air4 ,see also ventilation1 tunneling1 drilling1 etc4 activated sludge1 #dgc-dge for drilling1 #bfd-bfh in tunnels1 #bib-bid transporting concrete1 #cbj1 #cba ,concentration1 time of flood flow1 #da-dc1 #if1 #ig ,concrete1 aggregates1 #agb-agd mixing and placing1 #ahd-ahh pipe1 details1 #age-agi manufacture1 #aga-agi reinforcement1 #agg1 #agh1 #bji1 #baj pipe1 steam process1 #agf sizes1 #age pressure against forms1 #bcb1 #cbc ,concrete1 proportioning1 #agi-ahc qualities1 #agi1 #ahj reinforcement1 placing1 #agh1 #cbf1 #cbg reinforcing steel1 quality1 #aia sewer construction1 #cad-cbh arch1 #cah-cba form length1 #cai labor costs1 #cbg1 #cbh in open cut1 #cad-cbj in tunnel1 #cbj1 #cba invert1 #cae-cbj organization for1 #cbh working joints1 #cai sewer costs1 #cbg-cbi strength1 #aha waterproofing1 #ahd ,conduits1 special sections1 #fg1 #gj1 #ga ,connections to sewers1 ordinances1 #cdd1 #cde record of #ib1 #bch ,construction of sewers1 ,chap4 ,,xi1 #bcc-cca ,construction1 elements of1 #bcc organizations1 #cae1 #cbh ,contact bed1 #dcb-dcg1 #ejf advantages and disadvantages1 #dcb-dcd automatic control1 #dcg1 #ejf cleaning1 #dce clogging1 #dce construction1 #dcd-dcf control1 #dcg1 #ejf cycle1 #dcf1 #dcg depth1 #dcd description1 #dcb1 #dcc design1 #dcd-dcf dimensions1 #dcd1 #dce loss of capacity1 #dce material1 #dce1 #dcf multiple1 #dcc1 #dce operating conditions1 #dcb-dcg rate1 #dce results1 #dcc1 #dcd ripening1 #dcb ,continuous bucket excavators1 #bdf-bej ,contour interval on maps1 #gi1 #hj ,contracts1 ,chap4 ,x1 #baa-bcb abandonment of1 #bbe assignment1 #bbh completion of1 #bbb1 #bbh bond1 #bac1 #bbb content1 #bac1 #bcj1 #bca cost-plus1 #bab1 #bac disputes1 #bbj divisions of1 #bac drawings1 #bac engineer as an arbitrator1 #bbj the instrument1 #bcj1 #bca interpretation of1 #bbj1 #bcd1 #bce lump sum1 #bab nature of1 #baa1 #bab sample1 #bcj1 #bca time allowed1 #bbb types1 #bab1 #bac unit-price1 #bac ,contractor1 absence of1 #bbb bond1 #bcb claims against1 #bbh duties1 #bba liability1 #bbd relations with other contractors1 #bbh1 #bbi ,contractor's powder1 #bid ,control devices1 automatic1 for sewers1 #aag-aba for filters1 #ejj-eab inspection of1 #ccf1 #ccg ,copper sulphate1 disinfectant1 #dij ,copperas1 precipitant1 #djf-djh ,cordeau ,bickford1 #bih1 #cjc ,corrugated iron pipe1 #afe ,cost4 ,see under item wanted4 ,cost1 annual4 ,method of financing1 #aeg-afj capitalized4 ,method of financing1 #aeg-afj classification of1 #bce-bch comparisons of4 ,methods for making1 #aeg-afj collection of data1 #aj-ad1 #bce-bch estimate4 ,method of making1 #aj-ad overhead1 #bcg1 #bch ,couplings1 flexible for shafts1 #ach ,covers1 ,imhoff tanks1 #dbd septic tanks1 #dae trickling filters1 #dea ,crops on sewage farms1 #dfc1 #dfd ,cunette1 #fg1 #gj ,cut1 depth of excavation1 #hh1 #ib ,cycle1 contact bed1 #dcf life and death1 #cfg1 #dca nitrogen1 #cfg1 #cfh trickling filter1 #dda ,cylinders1 stresses in1 #aid1 #bjb-bjd ,cytoplasm1 #cfe ,damages1 liquidated1 #bbb material1 #bba1 #bbd ,darcy's formula1 #eb ,day labor1 #baa ,decomposition of sewage1 #cfe-cfg ,definitions4 ,see word defined4 ,deflagration1 definition1 #bid ,delays in contract work1 #bbh ,delayed action fuses1 #bia1 #cjj ,densities4 ,see population4 ,depreciation1 of sewers1 #cdh-cea rate of1 financial1 #aeh ,depth of sewers1 #hh ,design conditions1 #hh-ib economical1 mathematics of1 #dja-djc preparations for1 #ag-bc ,detention period1 grit chamber1 #cig ,imhoff tank1 #dai plain sedimentation1 #cib-cie1 #dja septic tank1 #dae ,detonation1 definition1 #bid ,detonator4 ,see blasting cap4 ,diameter of sewers1 #eg-fj1 #gb1 #hh-ib ,diaphragm pump1 #beg1 #beh ,diesel engine1 #aeb1 #aed ,digestion chamber1 ,imhoff tank1 #dbb1 #dbc ,digestion of sludge in separate tank1 #dbg-dcj1 #dig ,dilution1 amount needed1 #cgg-chj conditions for success1 #cgb1 #cgc ,dilution1 definition1 #cgb formulas for quantity1 #cgh-chj governmental control1 #chj1 #cha preliminary studies1 #cha1 #chb in salt water1 #cgf1 #cgg in streams1 #cgb-cgf of sewage1 #cgj and ,chap4 ,,xiv1 #cgb-chb ,diseases1 water-borne1 #cfd ,disinfection1 #dhi-dic action of1 #dhi-dia bleaching powder1 #dia chlorine1 liquid1 #dia amount of1 #dib disinfectants1 #dhi1 #dij purpose1 #dhi selective action of disinfectants1 #dib1 #dic ,disk screen1 #chd ,disposal of sewage1 ,see sewage treatment4 ,disputes1 engineer to settle1 #bbj ,dissolved oxygen4 ,see ,oxygen dissolved4 ,distribution of sewage1 contact beds1 #dcf irrigation1 #dfa1 #dfb nozzles1 #ddb-ddi sand filter1 #dej-deh traveling distributor1 #ddb trickling filters1 #dda-dea ,districts1 character of1 #bi1 #cj1 #cb-cg classification of1 #cd1 #ce ,domestic sewage1 defined1 #f1 #g1 #ceb ,dorr ,thickeners1 #dgb1 #ejd ,dortmund tank1 #djd ,dosing devices1 #ejf-eab alternating and timed siphons1 #ejj-eab ,alvord device at ,lake ,forest1 #ejf four or more alternating siphons1 #eji operation of automatic siphon1 #aaj three alternating siphons1 #ejh timed siphons1 #eaj two alternating siphons1 #ejg types1 #ejf ,dosing tank design1 for trickling filter1 #ddf-dej ,doten tank1 #dbi1 #dcj ,drag line excavators1 #bee1 #bef ,drainage areas1 #ha1 #hd1 #id ,drills1 electric1 #bfg jack hammer1 #bfd1 #bfe punch1 #bj size of cylinder for1 #bff tripod1 #bfd1 #bfe ,drilling1 methods1 #bj-bc1 #bfd-bgj depth1 diameter and spacing of holes1 #bfh-bgj power for1 #bfg1 #bfh rate of1 in rock1 #bfg steam and air1 #bfg1 #bfh ,drop manhole1 #ajj1 #aja ,drop-down curve1 #gc1 #gg ,drum screen1 #chd ,dry weather flow1 #bd1 #ch ,drying sludge4 ,see sludge drying4 ,dualin1 #bif ,duty of contractor4 ,see ,contractor1 duties ,duty of engineer4 ,see ,engineer1 duties4 ,duty of inspector4 ,see ,inspector1 duties4 ,duty of a pump1 defined1 #ace ,dynamite1 #bif-bih1 #cjj-cjb1 #cjd1 #cje cartridge1 #bfh1 #bif1 #cjb thawing1 #cja1 #cjb ,dysentery1 #cfe ,earth pressures1 theories1 #bgd1 #bge ,economical dimensions1 mathematics of1 #dja-djc ,effective size of sand1 defined1 #def ,efficiency of a pump1 defined1 #ace ,effluents1 character of activated sludge1 #dfg1 #dfh chemical precipitation1 #djh contact bed1 #dcd ,imhoff tank1 #dad1 #dbd1 #dbe1 #dcb lime and electricity1 #dhi ,miles acid process1 #dhd1 #dhe sand filter1 #dec ,effluents1 sedimentation tank1 #dja septic tank1 #dab-dad ,egg-shaped section1 #fg1 #fh1 #gj ,ejectors1 air1 #aej1 #aea ,elastic arch analysis1 #bjf-bjh ,electric motors1 #aej-aeb ,electrolytic treatment1 #dhg-dhi ,elevations1 method of recording1 #ib ,emergencies1 duties of engineer1 #bce ,emerson pump1 #bfa ,engines1 internal combustion1 #aeb-aed steam1 types1 #adb-add4 ,engineer1 absence of1 #bba defined1 #bbj disputes settled by1 #bbj1 #bcd duties of1 #i1 #aj1 #bbj1 #bcc1 #bcd1 #bch individuality and personality1 #i1 #bcd qualifications1 #i sanitary1 definition1 #b ,engineering ,news pile formula1 #abe1 #abf ,entering sewers1 precautions1 #cce1 #ccf ,enzymes1 #cfe ,equipment for construction1 #bcg ,equivalent sections1 defined1 #gb solution of problems in1 #fg-gb ,estimates1 cost and work done1 #aj-ad when made1 #bbf data for1 #bce ,excavation1 depth of open cut1 #bhd drainage1 #beb1 #bfb hand1 #bdb-bde1 #bdi economy1 #bde laborer's ability1 #bdc lay out of tasks1 #bdc ,excavation1 hand1 opening trench1 #bdc vs4 machine1 #bde1 #bdi tools1 #bdb machine1 #bdd-bdf economy1 #bde limitations1 #bdf vs4 hand1 #bde1 #bdi specifications1 #bdj1 #bda ,excavating machines1 bucket1 #bdf1 #bee cableway and trestle1 #bdf1 #bej-beb ,carson machine1 #bej1 #bea continuous belt1 #bdf bucket1 #bdf1 #bdg drag line1 #bee ,potter machine1 #bea steam shovel1 #beb-bed tower cableway1 #beb wheel excavators1 #bdf-bej ,excavation1 machine1 organization1 #bdi pumping and drainage1 #bef1 #beg quicksand1 #bef rock1 #bfc1 #bfd payment for1 #bcj specifications1 #bdj1 #bda trench bottom1 #bda1 #cjd1 #caa ,explosions in sewers1 #ajh1 #ccf1 #cdf-cdh causes of1 #cdf historical1 #cdf prevention1 #ajh1 #cdh ,explosives4 ,see also ,blasting4 ,explosives1 and blasting1 #bid-cjd ammonia compounds1 #big blasting gelatine1 #bif contractor's powder1 #bid deflagrating1 #bid detonating1 #bid detonators1 #bid1 #big-cjj 8,don'ts10 #cjj1 #cja dynamite1 #bif-bih1 #cjj-cjb1 #cjd1 #cje fuses and detonators1 #big-cjj gelatine dynamite1 #bif gunpowder1 #bie handling1 #cjj-cjb nitro-glycerine1 #bie nitro-substitution compounds1 #bie permissible1 #big quantity1 #cjd1 #cje requirements1 #bid strength of1 #big1 #bih ,t4,n4,t41 #bie types1 #bid-big ,exponential formulas for flow of water1 #ed1 #ee ,extra work1 compensation1 #bbg ,facultative bacteria1 #cfc ,fanning's run-off formula1 #di ,farms1 septic tanks for1 #daf1 #dag ,farming with sewage4 ,see irrigation4 ,fats in sewage1 #ceg-cei1 #cff1 #cfg from ,miles acid process1 #dhe-dhg ,feathers1 for splitting rock1 #bfd ,ferrous sulphate1 precipitant1 #djf-djh ,fertilizer from sludge1 #dgj1 #die1 #dig ,fertilizing value of1 activated sludge1 #dgj sewage1 #dei1 #dfj ,filter press for sludge1 #ejj1 #eja ,filters4 ,see under name of filter4 ,filtration1 of sewage1 #cgj1 #cga1 #dca-dei action in1 theory of1 #dca cost1 #deh1 #dei ,filtros plates1 #dgg1 #dgh ,finances1 mathematics of1 #aeg-afj ,financing1 methods of1 #ad-ag ,flamant's formula1 #ed1 #ef ,flies on trickling filters1 #dch ,flight sewer1 #aja1 #ajb ,flood1 crest velocities1 #db1 #dc flow computations1 #id-ih ,mc,math formula1 #id1 #if1 #ig ,rational method1 #ie-ih ,flow1 laws of1 #eb velocity of1 #eb1 #ij1 #ia ,fluctuations1 in rate of sewage flow1 #cc-ch in quality of sewage1 #cfh-cgj ,flush-tanks1 automatic1 #aji-aac capacity1 #aaa details1 #aaj1 #aab inspection of1 #ccf1 #ccg payment for1 #bag siphon sizes1 #aaa ,flushing1 #aji-aac1 #cda-cdc amount of water needed1 #aab methods1 #cda-cdc manhole1 #aji sewer1 defined1 #h ,foaming of ,imhoff tanks1 #dbe1 #dbf ,foot valves1 #ada ,force main1 defined1 #h ,forms1 design of1 #cbb1 #cbc length of1 #cai materials1 #cba1 #cbb oiling1 #agd1 #ahf1 #cbb specifications1 #cbb steel1 #cbe1 #cbf steel-lined1 #cbe support for1 #caf1 #cah time in place1 #cai wooden1 #cbc1 #cbd ,formulas1 hydraulic1 methods for solution1 #ee-fa for flow of water1 #eb-ee for rainfall4 ,see ,rainfall1 for run-off4 ,see ,run-off4 ,foundations1 #ii1 #abd-abf ,franchises for sewers1 #ag ,free ammonia1 #cff1 #cfg1 #cgd1 #cge1 #daj ,freezing1 catch-basins1 #ajh concrete1 #ahf1 #ahg dynamite1 #cja1 #cjb ,fresh sewage1 characteristics1 #ceb-ced ,friction losses4 ,see ,head losses4 flow in pipe1 #ea1 #eb ,fuel1 consumption by prime movers1 #aec costs1 #aec heat value1 #aej ,fungus growth in sewers1 #ccc ,fuses4 ,see blasting fuses4 ,ganguillet and ,kutter's formula1 #eb-fe ,gas1 chamber in ,imhoff tank4 ,see ,scum chamber4 engines1 #aeb-aed illuminating1 explosive1 #cdg sewer1 #cce1 #ccf ,gasoline1 explosive1 #ajh1 #aji1 #cce1 #cdf1 #cdg engines1 #aeb-aed and oil separator1 #aji odors1 significance1 #cce1 #cec ,gearing1 reduction for turbines1 #adj1 #adf ,gelatine dynamite1 #bif ,glycerol1 #cff ,gothic section1 #fg ,governmental control1 stream pollution1 #chj1 #cha ,grade1 of sewers4 ,see also ,slope4 how given1 #bha-bhd selection of1 #ij stakes1 #bba1 #bha-bhc ,gravel1 specifications1 #agb ,grease1 in sewers1 #ii1 #ajh1 #ccc1 #cde cutter1 #cdj ordinance concerning1 #cde traps1 #ii1 #ajh ,gregory's imperviousness formulas1 #dd1 #df ,grit1 clogs sewers1 #ccc chambers1 #abg1 #cig-dja description1 #cie1 #cih design1 #cig1 #cih dimensions1 #cig1 #cih existing1 #cih-djj outlet arrangements1 #djj results1 #cig retention period1 #cig sludge analyses1 #cig units1 number of1 #djj1 #dja velocity of flow in1 #cif-cih quantity and character of1 #cig ,grooves in concrete1 working joints1 #cai ,ground water in sewers1 #ch1 #ci1 #he1 #hg1 #bef1 #ceb ,gun cotton1 #bif ,gunpowder1 #bie ,hazen1 theory of sedimentation1 #cib-cie dilution formula1 #chj ,hazen and ,william's formula1 #ee1 #eg ,head loss1 in bends1 #aaf entrance1 #aae friction in straight pipe1 #ea1 #eb1 #aae ,hercules powder1 #bif ,hering1 ,rudolph1 dilution recommendations1 #chj ,hering1 ,rudolph1 introduction of ,imhoff tank and hydraulic formulas1 #dbe ,historical rsum of sewerage and sewage treatment1 #b-e ,hitch1 tunnel frame1 #bhf1 #bhg ,holes1 drill4 ,see ,drill holes4 ,holidays1 work on1 #bba ,hook for lifting pipe1 #cjd1 #cjf ,horse-power1 boiler1 #adi1 #aej of pumps1 #add-adf ,horseshoe sewer section1 #ga ,house1 connections1 record of1 #ib1 #bcd drains1 #g1 #hh1 #ij sewer1 defined1 #g ,hydraulic1 elements1 #fe1 #fi formulas1 #eb-ee jump1 #gc-gd principles1 #ea1 #eb1 #gb1 #gc value of settling particles1 #cic ,hydraulics of1 sewers1 ,chap4 ,,iv1 #ea-gg circular pipes partly full1 #fe1 #ff equivalent sections1 #gb non-uniform flow1 #gb-gg sections other than circular1 #fg-gb use of diagrams1 #fa-fe ,hydrocarbon1 #cfg ,hydrogen sulphide1 #cec1 #cff1 #daj ,hydrolytic tank1 #dbg1 #dbh 8,hypo0 as a disinfectant1 #dia ,hytor ,turbo blower1 #dgc1 #dgd ,illinois ,river1 self-purification1 #cgd-cgf ,imhoff tank1 and chlorination1 costs1 #dhg cover1 #dbd description1 #dag-dai design1 #dai-dbd digestion chamber1 #dbb inlet and outlet1 #dba operation1 #dbf-dbg patent1 #dah results1 #dad1 #dbd1 #dbe1 #dci1 #dfg sedimentation chamber1 #dai-dbb scum chamber1 #dbd slot1 #dbb sludge1 #dad1 #dfg sludge pipe1 #dbc1 #dbd status1 #dbe1 #dbf and trickling filter1 cost1 #dgi ,impeller1 for centrifugal pump1 #aca1 #acf ,imperviousness1 relative1 #dj1 #db1 #dd-df1 #ie-ig ,industrial1 districts1 #cb-cg wastes1 defined1 #g1 #ceb tannery1 #dia ,information and instructions for bidders1 #bac1 #bae-bag ,inlets1 street1 #ic1 #id1 #ii1 #ajd-ajg ,inspection1 contract stipulations1 #bba-bbd during construction1 #bcc1 #bcd for maintenance1 #ajd1 #ccc-ccg1 #cdh1 #cdi ,inspector1 absence of1 #bba1 #bbb duties1 #bcc-bcd qualifications1 #bcd ,institutional sewage treatment plants1 #daf1 #dag ,intercepting sewer1 defined1 #g ,intermittentsand filter4 ,see ,sand filter4 ,internal combustion engines1 #aeb-aed ,inverted siphon1 #aac-aaf ,iron1 ferrous sulphate1 precipitant1 #djf-djh cast4 ,see cast iron4 ,irrigation4 ,see also ,farming and ,sewage farming4 area required1 #dfc ,berlin sewage farm1 #dfj1 #dfa crops1 #dfc1 #dfd description1 #dei fertilizing value of sewage1 #dfj1 #dgj1 #die1 #dih vs4 farming1 #dei operation1 #dfa-dfc preliminary treatment1 #dfb1 #dfc preparation for1 #dfa-dfc process1 #dei1 #dfj sanitary aspects #dfc status1 #dfj1 #dfa theory1 #dcb in the ,united ,states1 #dfa ,jack hammer drill1 #bfd1 #bfe ,jetting method1 #ba-bc ,jet pump1 #bei1 #cda1 #cdc ,joints1 bituminous1 #cji-caa in cast-iron pipe1 #afd cement1 #cjg1 #cjh inspection of1 #bcd lead1 #afd mortar1 #cjg open1 #cjg poured1 #cji-caa cement1 #cji1 #caa riveted steel1 #aie1 #aif sulphur and sand1 #cji types1 for pipe1 #cjg working1 in concrete1 #cai ,junctions1 #ii ,kuichling1 run-off rules1 #df1 #dg1 #di storm intensity formulas1 #ej ,kutter's formula1 #eb-fe ,labor1 day vs4 contract1 #baa costs on concrete sewer1 #cbh1 #cbi ,labyrinth packing rings1 #acf1 #acg ,lagging1 tunnel frames1 #bhg for forms1 #cbb ,lagooning sludge1 #die-dig ,laitance1 #ahf1 #ahh ,lakes1 self-purification of1 #cgf ,lamp's formula1 #ed ,lampholes1 #ii1 #ajd ,lateral sewer1 defined1 #g ,lawrence ,experiment ,station1 #d ,leaping weir1 #aah-aba1 #ccg ,legal requirements1 construction1 #bbd dilution1 #chj1 #cha in design1 #i ,liernur system1 #e ,life1 organic in sewage1 #cfc1 #cfd of sewers1 #cdh-cea ,lime as a precipitant1 #dje-djh with electricity1 #dhh1 #dhi with iron1 #djf1 #djg ,line and grade1 #bha-bhd how given1 #bha-bhc ,liquefaction of sludge1 #daa-dac1 #dif1 #dig ,liquid chlorine4 ,see also ,chlorine1 #dia ,liquidated damages1 #bbb ,loads on1 pipe1 #aih-bjb ,marston's method1 #aih-bjb trench1 #aii-bjb ,lock bar pipe1 #aig ,lock-joint pipe1 #agg ,long loads1 #bja ,machine excavation4 ,see ,excavation4 ,macroscopic organisms1 #cfc1 #cfh ,main sewer1 defined1 #g ,maintenance of sewers1 ,chap4 ,,xii1 #ccb-cea catch-basin cleaning1 #cdc1 #cdd cleaning sewers1 #ccg-cdc complaints1 #ccc cost1 #cda entering sewers1 #cce1 #ccf flushing1 #aji-aac1 #cda-cdc hand cleaning1 #cda inspection1 #ccc-ccg organization1 #ccb protection of sewers1 #cdd1 #cde repairs1 #ccg tools1 #cch-cda troubles1 #ccc work involved1 #ccb ,man1 shoveling ability1 #bdc ,manholes1 #ha1 #ii-ajd bottom1 #ajj cover1 #ajb-ajc drop1 #aja flushing1 #aji1 #cdb location and numbering1 #ha payment methods1 #bag1 #bah steps1 #ajj1 #ajc1 #ajd ,manning's formula1 #ee ,map1 preliminary1 #ag1 #gi1 #hj1 #hb1 #hc ,marsh gas1 #cdg1 #cff1 #cfg1 #daj1 #dae ,marston's methods for external loads on buried pipe1 #aih-bjb ,materials1 for sewers1 ,chap4 ,,viii1 #afd-aic measurement of1 #bcf1 #bcg record of1 #bcg unit weights1 #bja1 #bjb ,mc,math's formula1 #dg1 #dh1 #id1 #ie ,meem's theory of earth pressure1 #bgd1 #bge ,mercaptan1 #cfg ,metabolism1 #cfe ,methane1 #cdg1 #cff1 #cfg1 #daj1 #dae ,methylene blue1 #cfj ,microscopic organisms1 #cfc1 #cfd1 #cfh ,miles acid process1 costs1 #dhg amount of acid1 #dhc analyses of sludge1 #dhe description1 #dhb results1 #dhc-dhg sludge1 #dhe ,mineral matter in sewage1 #ceg ,mirror1 inspecting device1 #ccd ,money retained by city1 #bbg ,mosquitoes in catch-basins1 #ajh ,motors1 electric1 #aej-aeb ,municipal1 bond1 #ad1 #ae corporations1 #ae n1 value of in ,kutter's formula1 #ec ,new ,york ,city1 density of population1 #bi1 #ca siphons under subway1 #aad grease and gasoline trap1 #ajh1 #aji aration of sewage1 #cgg1 #dgj cleaning sewers1 #ccb depreciation of sewers1 #cdh-cea ,needle beam1 #bhf1 #bhg ,night1 soil1 #e work1 #bba ,nitrates1 #cee1 #cef ,nitrites1 #cee1 #cef ,nitrifying organisms1 #dca1 #dcb ,nitrobacter1 #dca1 #dcb ,nitro explosives1 #bie1 #bif ,nitrogen1 cycle1 #cfg1 #cfh organic1 #cee1 #cef ,nitro-glycerine1 #bie ,nitrosomonas1 #dca1 #dcb ,nomograph1 #ee1 #ef ,non-uniform flow1 #gb-gg ,nozzles4 ,see also ,trickling filters4 coefficients of discharge1 #ddf types1 #dde ,numbering1 drainage areas1 #ha1 #id manholes1 #ha ,nye steam pump1 #bfj1 #bfc ,obstructions to construction1 #bce ,odor of sewage1 #cec ,oil in sewage1 #ajh1 #cdd-cdh ,oiling forms1 #agd1 #ahf1 #cbb ,olein1 #cff ,ordinances1 for protection of sewers1 #cdd1 #cde ,organisms in sewage1 #cfc1 #cfd1 #cfh ,organic matter1 composition1 #cff ,organizations for construction1 #cae1 #cag1 #cbh ,orders1 to whom given1 #bbb ,outfall sewer1 defined1 #h ,outlets1 #ii1 #abb-abd1 #cgc ,overflow weir1 #aah-aba inspection of1 #ccg ,overhead1 costs1 division of1 #aj1 #bcg1 #bch -track excavators1 #bdf1 #bej1 #bea ,oxidation in streams1 #cgc-cgf ,oxygen1 absorption of1 #cgd-cgg consumed1 #cee1 #cef demand1 #cei-cfa computation of1 #cfj bio-chemical1 #cei-cfa ,oxygen dissolved exhaustion of1 #cff in dilution1 #cha solubility1 #cfb supersaturation1 #cfa concentration for successful dilution1 #cgg-chj formulas for concentration1 #cgh-chj significance of in sewage1 #cei-cfb ,oysters1 contamination of1 #cgb1 #dhi ,packing rings1 labyrinth type1 #acf1 #acg ,palmatin1 #cff ,parasites1 #cfe ,paris sewage farm1 #dfj ,patents4 ,protection of ,city by contractor1 #bbd1 #bbe ,pathogenic bacteria1 #cfd ,pavement1 replacing1 #cbi ,payment1 final on contract1 #bbh ,payments1 methods of making1 #bag1 #bah ,periscope inspecting device1 #ccd1 #cce ,permissible explosives1 #big ,phenolphthalein indicator1 #djh ,photographic records1 #bch ,piles for foundations1 #abc-abf ,pills for cleaning sewers1 #cch ,pipe1 bedding1 #bcj1 #cjd1 #cbh cast-iron4 ,see under cast-iron pipe4 design of ring1 ,chap4 ,,ix1 #aid-baj external loads on1 #aih-bjb joints4 ,see ,joints4 sewer construction1 #cjd-caa laying1 line and grade1 #bhb-bhd organization1 #caa method of laying1 #cjd1 #cjf1 #cjg steel1 design1 #aie-aig stresses in1 external forces1 #aid1 #bjb-bjd stresses due to internal pressure1 #aid stresses in buried pipe1 #aih-bjd stresses in circular ring1 #bjb-bjd wood design1 #aig1 #aih ,plankton1 defined1 #cfc in sewage1 #cfh ,plans1 changes in contract1 #bbb1 #bbc ,plug and feathers for splitting rock1 #bfd ,pneumatic1 collection system1 #e concreting1 #cbj1 #cba ,poling boards1 in open cut1 #bga1 #bgb in tunnel1 #bhg ,pollution1 legal features1 #chj1 #cha ,population1 density1 #bh-ca predictions1 #bd-bg served by sewers in the ,u4 ,s41 #c sources of information1 #bg1 #bh and quantity of sewage1 #ca1 #cb ,potter trench machine1 #bea ,powder4 ,see ,blasting4 ,power pump1 #acb1 #acc ,precautions in entering sewers1 #cce1 #ccf ,precipitants1 chemical1 #dje-djg ,preliminary1 map1 #ag1 #gi1 #hj1 #hb1 #hc work1 #i1 #ag-bc ,present worth1 #aeh1 #afj ,pressing sludge1 #ejj1 #eja ,priming explosives1 #cjb-cjd ,private1 capital1 #ag sewers1 #ag ,privy1 #e ,profile1 for brick sewers1 #cab sewer1 #ib surface1 #hh ,progress1 rate of1 #bbb reports1 #bch ,promotion 7inception of sewers71 #i ,proportioning concrete4 ,see ,concrete proportioning4 ,proposal 7contract71 #bac1 #bag-bai ,protection of sewers 7ordinances71 #cdd1 #cde ,protein1 #cff ,puddling1 backfill1 #ccj ,pulsometer pump1 #bfj1 #bfa ,pumping1 in excavations1 #bef-bfc selection of machinery1 #aed-aef equipment1 cost comparison1 #afb station1 #abh1 #adb costs1 #aef-afc equipment1 #abg1 #abh ,pumps1 air ejector1 #aej1 #aea capacity1 #abi1 #afj-afc capacity of units1 #afj-afc centrifugal1 details1 #acj1 #aca1 #acf-ach automatic control1 #ada1 #adb characteristics1 #ach-adj efficiency1 #adj for excavation1 #bfb motors for driving1 #aej-aeb performance1 #ach-adj protection of1 by screens1 #chf selection of1 #aed-aef setting1 #adj-adb turbine1 #acj-acb1 #aed types1 #acj1 #aca ,pumps1 centrifugal1 volute1 #acj-acb1 #aed character of load1 #abi costs1 #aef1 #aeg description of types1 #acj-acd for construction work1 #bef-bfc diaphragm1 #beg1 #beh direct-acting1 #acc duty of1 #ace1 #acf efficiencies1 #ace1 #acf ejector1 #acd1 #aej1 #aea1 #bei1 #cda1 #cdc jet1 #bei need for1 #abg number of units1 #afj-afc packing of1 #acc1 #acd piston1 #acc speed1 #acc1 #acd plunger1 #acc power1 #acb1 #acc reciprocating1 #acj1 #acb-ace1 #aed-aef for excavation1 #bfb reliability1 #abg sizes1 #ace steam1 #acd1 #ace1 #adb-adf consumption1 #add1 #ade vacuum1 #bei1 #bfb improvised for trench work1 #beg turbine1 #acj-acb1 #aed volute1 #acj-acb1 #aed ,putrescibility1 #cei1 #cfj ,quantity1 of sewage1 #bd-ej1 #hd-hg variations1 #cc-ch storm water1 #dj-ej1 #id-ih ,quicksand1 definition1 #bef excavation in1 #bef safeguards1 #bce ,quiescent water1 self-purification1 #cgd ,racks4 ,see ,screens4 ,rainfall1 #ag1 #dj1 #da1 #ej1 #if1 #ig data1 #ag rate1 #if1 #ig ,rangers1 #bgj-bgd1 #bgf-bgi ,rankine's theory of earth pressure1 #bge ,rapid sand filtration of sewage1 #deh ,rational method of run-off determination1 #dj1 #ie-ih ,rearation tank in activated sludge1 #dgc ,receiving well1 capacity1 #abi1 #acj ,reciprocating pumps4 ,see ,pumps1 reciprocating4 ,records1 character of1 on construction1 #bch-bdj ,rectangular sewer section1 #fg-fi ,regulators1 #ii1 #aag-aba1 #ccg inspection of1 #ccg ,reinforced concrete sewer design1 #bji1 #baj ,reinforcing steel1 specifications1 #aia placing1 #cbf1 #cbg ,reinsch ,wurl screen1 #chd ,relative stability numbers1 #cei ,relief sewer1 defined1 #g ,repairs to sewers1 #ccg ,report1 engineer's preliminary1 #aj ,reservoir1 collecting capacity1 #abi1 #acj ,residences1 septic tanks for1 #daf1 #dag ,residential districts1 characteristics1 #cb-cg ,residue on evaporation1 #cef1 #ceg ,rideal's dilution formula1 #cgi ,ring1 design4 ,chap4 ,,ix1 #aid-baj stresses in circular1 #bjb-bjd ,river pollution1 legal features1 #chj1 #cha ,rivers1 self-purification of1 #cgc-cgf ,riveted joints1 properties1 #aif ,rock1 blasting1 #bfh1 #bij1 #bia definition1 #bfc drill1 data on1 #bff1 #bfg drilling4 ,see also ,drilling4 by hand1 #bfd by power1 #bfd-bfh rates1 #bfg excavation4 ,see also ,excavation4 payment for1 #bcj measurement of1 in place1 #bce tunnels1 #bij1 #bia ,rods1 sewer1 #cch ,roman ordinance relative to sewers1 #b ,roofs4 ,see ,covers4 ,root cutters1 #cdj ,roots1 #ccc1 #cdj ,row lock bond for bricks1 #cab ,running water1 self-purification1 #cgc-cgf ,run-off1 computations1 #ag1 #dj1 #df-ej1 #id-ih ,safeguards during construction1 #bba1 #bda ,salt water1 dilution in1 #cgf1 #cgg ,sand1 effective size1 #def uniformity coefficient1 #def filters1 #deb-dei action in1 #dca1 #dcb1 #deb-ded control1 #deh1 #ejf-eaj description1 #deb dimensions1 #def distribution systems1 #dcc1 #def-deh dosing1 #ded-def dosing devices1 #ejf-eaj materials1 #def operation1 #ded1 #dee preliminary treatment1 #dee rate1 #dee results1 #deb1 #dec size of sand for1 #def thickness1 #def in winter1 #dee ,sanitary ,district of ,chicago1 dilution factor1 #chj specifications1 for manhole covers1 #aja1 #ajb tunnel cover1 #bhd tunnel ventilation1 #bia ,sanitary engineering1 #a1 #b ,sanitary sewage1 defined1 #g1 #ceb ,saph and ,schoder's formula1 #ed ,saprophytes1 #cfe ,screed1 #caf ,screens1 #chc-cia chlorination and fine screens1 costs1 #dhg coarse1 #chf1 #cia data on fine1 #chh1 #chi design of1 #chi-cia fine1 #cha1 #chb1 #chg-chi fixed1 #che1 #cij medium1 #chf movable1 #che1 #chf1 #chi-cia moving1 #chd-chf openings1 #chf-chi protection to pumps1 #abg1 #ada purpose1 #chc results1 #chf-chi sewage treatment by1 #cga1 #cha size and performance1 #chf-chi sizes1 #chf-cia types1 #chd-chf ,screening1 vs4 sedimentation1 #chc purpose1 object1 #chc ,screenings1 character of1 #chf-chi ,scum1 boards for1 septic tanks1 #dac1 #dad ,imhoff tanks1 #dba chamber in an ,imhoff tank1 #dbd definition1 #die ,sediment1 velocity of transportation1 #cif1 #cig ,sedimentation1 #chc-dje definition1 #chc ,hazen's analysis1 #cib-cie hydraulic values1 #cic a method of treatment1 #cgj object1 #chc ,peoria ,lakes1 #cgf protection of siphons1 #aac1 #aad results from plain sedimentation1 #dja theory of1 #cia-cie transportation of debris1 #cif velocity of1 #cib1 #cic vs4 screening1 #chc velocities1 limiting1 #cif1 #cig ,sedimentation1 basins1 arrangement1 #cid baffling1 #djd cleaning1 #djd dimensions1 #dja-djc inlet and outlet1 #djd operation1 #daa types1 #cie chamber1 ,imhoff tank1 #dai-dbb ,self-purification of lakes1 #cgf ,self-purification of streams1 #cgc-cgf ,separate sewer systems1 #gh-hj ,septic action1 #cec1 #cfe-cfh1 #cga1 #daj1 #daa1 #dif1 #dig results1 #dab1 #dac vs4 sedimentation1 #daa ,septic tank1 #daa baffling1 #dac1 #dad capacities of small tanks1 #dag for country homes1 #daf1 #dag covers for1 #dae definition1 #daa design1 #dac-dag explosions in1 #dae results1 #dab1 #dac seeding1 #dac sludge storage1 #dad small1 #daf1 #dag units1 #dae ,septic sludge analysis1 #dad ,septicization4 ,chap4 ,,xvi1 #daj-dcj a method of treatment1 #cga the process1 #daj1 #daa results1 #dab1 #dac ,settling solids1 #ceg ,sewage and water supply1 #cb aration1 #cga1 #cgf1 #dfe-dgi alkalinity of1 #ceh analyses1 chemical1 #cee1 #cfi1 #dfg interpretation of1 #cef-cfb physical1 #ceb-ced average1 #ceb-cee bacteria1 #cfb-cfe biolysis of1 #cff1 #cfg changes in1 rate of discharge of1 #cc-ch characteristics1 #cfh-cgj characteristics of1 #ceb-ced chemical constituents1 #ced-cef classification of1 #f1 #g1 #ceb collection1 #e color1 #ceb1 #cec components and properties1 #ceb-cef decomposition of1 #cfe-cfg definition1 #f1 #g1 #ceb disposal4 ,see also ,sewage treatment4 methods1 #f1 #cgj1 #cga purposes1 #cgj1 #cga domestic1 #g1 #ceb farming4 ,see ,irrigation4 fertilizing value1 #dei1 #dfj flow fluctuations1 #cc-ch ratio of maximum to average1 #cf1 #cg1 #he fresh1 #ceb-ced gas1 #cce1 #ccf1 #cec industrial1 defined1 #g1 #ceb life in1 #cfc-cfe1 #cfh odor1 #cec physical1 analyses1 #ceb-ced characteristics1 #ceb-ced quality variations1 #cfh-cgj quantity4 ,chap4 ,,iii1 #bd-ej1 and #hd1 #hg and population1 #ca1 #cb of sanitary1 #bd-dj variations1 #cc-ch sanitary1 defined1 #g1 #ceb septic1 #cec1 #cfe-cfh1 #cga1 #daj1 #daa1 #dif1 #dig stability1 #cei1 #cfj stale1 #cec storm1 defined1 #g1 #ceb strong1 #cee temperature1 #cec turbidity1 #cec treatment processes1 #cgj1 #cga ,a4 ,b4 ,c41 #d activated sludge1 ,chap4 ,,xviii1 #dfe-dgi biological1 #cga chemical1 #cga contact bed1 #dcb-dcg1 #ejf costs1 #dei dilution4 ,chap4 ,,xiv1 #cgb-chb disinfection1 #dhi-dic electrolytic1 #dhg-dhi filtration1 #dca-dei increase of1 #c irrigation1 #dca1 #dei-dfd mechanical1 #dga ,miles acid process1 #dhb-dhg purpose of1 #f1 #cgj rsum1 #f1 #cgj1 #cga sand filter1 #deb-deh screening1 #chc-cia sedimentation1 #cia-dji1 #daa septicization4 ,chap4 ,,xvi1 #daj-dcj trickling filters1 #dcg-deb weak1 #cee and water supplies1 #ca1 #cb ,sewerage1 definition1 #g demand for1 #b design1 #gh-ih growth of1 #b-d historical1 #b-d ,sewers1 ancient1 #b1 #c capacity1 diagrams1 #ef-fj cost1 #aj-ad definitions of various types1 #g1 #h depth of1 #hh diameter1 #eh-fj1 #hh-ib flat grades1 #gc1 #aji flight1 #aja1 #ajb inspection of1 #ccc-ccg life of1 #cdh-cea location of1 #hj1 #ha1 #id materials4 ,chap4 ,,viii1 #afd-aic medieval1 #c pipe1 properties of concrete1 #age design4 ,chap4 ,,ix1 #aid-baj vitrified clay1 properties1 #afi-aga profile1 #hi1 #ib section of different types1 #fg-gb separate system1 #gh1 #gi1 #hb1 #hf1 #hg slope1 #hh-ib storm-water system1 #gh1 #gi1 #hc1 #ic1 #id stresses in1 #aid1 #aih-bjd ,shafts1 for tunnels1 #bhd-bhg ,sheeting1 #bgj-bhj alignment1 #bdj1 #bda backfilling1 #ccj box1 #bgb design1 #bge-bhj driving1 #bgc length1 #bgc lumber1 #bgg moving1 #bdh poling boards1 #bga1 #bgb1 #bhg pulling1 #bgd skeleton1 #bgj1 #bga stay bracing1 #bgj steel1 #beb1 #bhj1 #bha thickness1 #bgf-bgh types1 #bgj vertical1 #bgj1 #bgb-bgd ,wakefield piling1 #bgc ,shellfish contamination1 #cgb1 #dhi ,shields1 tunnel1 #bhh-bij ,short loads on trenches1 #bjb ,shovels1 for hand excavation1 #bdb steam4 ,see ,steam shovels4 ,shovel vane screen1 #chd ,shoveling by hand1 height raised1 #bdd performance by one man1 #bdc ,symbiosis1 definition1 #cfc example1 #dcb ,sinking fund1 #aeh ,siphons1 automatic4 ,chap4 ,,xxi1 #ejf-eab4 ,see also under ,dosing devices4 in flush-tanks1 #aji-aaj inspection1 #ccg operation1 #aji-aaj1 #ejf-eab for trickling filter1 #ddh-dea true and inverted1 #aac-aag ,skeleton sheeting1 #bgj1 #bga ,slope1 of sewers1 #hh-ib of tank bottoms1 ,imhoff1 #dai1 #dbc sedimentation tank1 #djd ,skewback1 #bjd ,sludge4 ,chap4 ,,xx1 #die-eje activated4 ,chap4 ,,xviii1 #dfe-dgi4 ,see also under ,activated sludge4 analyses1 #dad1 #dfg1 #dfh1 #dhe1 #dif characteristics1 #die definition1 #die digestion tanks1 #dbg-dcj1 #dig disposal methods1 #die drying1 #dig-eje acid flotation1 #ejc beds1 #dih1 #ejj centrifuge1 #eja-ejb heat1 #ejb1 #ejc press1 #ejj-eja thickeners1 #ejd1 #eje fertilizing value1 #dgj1 #die1 #dig ,sludge1 filters1 #dih-ejj lagooning1 #die1 #dif measurement1 #dbg press1 #ejj1 #eja sedimentation1 #dja septic analysis1 #dcd treatment methods1 #die ,soaps1 #ceg ,soil1 bearing value1 #abe stack1 definition1 #g ,solids in sewage1 #cef-cfh ,special assessment1 #ae1 #af ,specifications4 ,chap4 ,x1 #baa-bcb general1 #bai-bbi special1 #bcj technical1 #bbi1 #bcj ,spiling4 ,see ,piles4 ,spirillum1 #cfb ,spores1 #cfc ,springing line1 #bjd ,sprinkling filter4 ,see ,trickling filter ,square sewer section1 #fh1 #fi ,stability1 relative1 #cei-cfa ,stagnant water1 #cgd ,stakes1 contractor to provide1 #bba where driven1 #bha1 #bhb ,stationing1 #ib ,stay bracing1 #bgj ,steam boilers1 #adg-aej ,steam1 consumption by1 pumps1 #add1 #ade turbines1 #add1 #adg engines1 #add1 #ade pumping engines1 #adb-adf pumps4 ,see ,pumps1 steam4 shovels1 #bdf1 #beb-bed turbines1 #adf1 #adg ,stearin1 #cff ,steel1 forms4 ,see ,forms1 steel4 pipe1 #afd1 #aia1 #aib design1 #aie-aig specifications1 #aia reinforcement for concrete1 #aia1 #cbf-cbg sheet piling1 #beb1 #bhj1 #bha ,stench1 historic in ,london1 #d ,sterilization4 ,see ,disinfection4 ,storm1 sewage1 definition1 #g1 #ceb ,storm1 sewer system design1 #ic-ih water1 quantity1 #dj-ej ,storms1 extent and intensity1 #ej ,stream pollution1 regulation1 #chj1 #cha ,streams1 self-purification1 #cgc-cgf ,street1 inlet4 ,see ,inlets4 wash1 definition1 #ceb ,stresses1 in buried pipe1 #aih-bjd in circular ring1 #aid1 #bjb-bjd ,sub-main1 defined1 #g ,subsurface surveys1 #ah-bj ,suction for centrifugal pump1 #ada ,sulphur and sand joint compound1 #cji ,sunday work1 #bba ,surface1 elevation1 #ib of ground1 character1 #dd-df profile1 #hh water1 #g1 #ceb ,surveys1 underground1 #ah-bj ,suspended matter1 #ceg ,talbot's run-off formula1 #di ,tamping1 backfilling1 #cbh-cca ,tannery wastes1 disinfection1 #dia ,taxation1 general1 #af1 #ag ,taylor nozzles1 #ddd1 #dde ,temperature of sewage1 #cec ,templates1 brick sewers1 #cab ,thawing dynamite1 #cja1 #cjb ,tide gate1 #abb ,timbering tunnels1 #bhf-bhh ,timber1 strength of1 #bgg ,time of concentration1 #da-dc1 #ie-ig ,tools1 for cleaning sewers1 #ccg-cda excavating1 #bdb1 #bdf ,tower cableways1 #beb ,trade wastes4 ,see ,industrial wastes4 ,traps1 in catch-basins1 #ajg grease1 gasoline1 and oil1 #ajh1 #aji in street inlets1 #ajd1 #aje ,travis tank1 #dbg1 #dbh ,tree roots1 #ccc1 #cdj ,tremie1 #ahg1 #ahh ,trench1 backfilling1 #cbh-cca blasting in1 #bdd1 #bfi bottom1 shape of1 #bda1 #cjd1 #caa breaking surface1 #bdc1 #bdd drainage1 #bef-bfc excavating1 by hand1 #bdb-bde machine1 #bdd-bef guarding and lighting1 #bba layout of tasks1 #bdc length of open1 #bda1 #bdh line and grade1 #bha-bhd location1 #bdc1 #bha opening1 #bdc1 #bdd pumps1 #bef-bfc sheeting1 #bgj-bhj width1 #bdj1 #bda1 #bdf ,trestle excavators1 #bej1 #bea ,trickling filter1 #dcg-deb advantages1 #dch1 #dci covers for1 #dea depth1 #dda1 #ddb description1 #dcg1 #dch dimensions1 #ddb distribution of sewage1 #ddb-dea dosing siphon1 #ddf-dea dosing tank1 #ddf-dea head lost1 #dch insects1 #dch material1 #dda nozzles1 #ddb-dea layout1 #ddg-dea odors1 #dch1 #dci operation1 #dda rate1 #dda results1 #dci1 #ddj siphon size1 #ddi-dea underdrainage1 #dea1 #deb unloading1 #dca1 #dcg ,tripod drill1 #bfe ,triton1 #bie ,troubles with sewers1 causes1 #ccc ,trumpet arch1 #aba ,trunk sewer1 defined1 #g ,tunnels1 #bhc-bid backfilling1 #cca breast boards1 #bhh brick invert1 #cac compressed air in1 #bib-bid concrete construction1 #cbj1 #cba depth of cover1 #bhd line and grade in1 #bhc machines1 #bij rock1 #bij-bib shafts1 #bhd-bhf shield1 #bhh-bij timbering1 #bhd-bhh ventilation1 #bia1 #bib ,turbidity of sewage1 #cec ,turbine1 for cleaning sewers1 #cdj pumps1 #acj1 #acb steam1 #adf1 #adg ,typhoid fever1 #cfd ,u-shaped sewer section1 #fg1 #fi1 #ga ,underdrains for1 sewers1 #abf trickling filters1 #dea1 #deb ,underground surveys1 #ah-bj ,unexpected situations1 #bce ,uniformity coefficient of sand1 #def ,unloading of filters1 #dca1 #dcg ,urea1 #cfg ,valuation of sewers1 #ccb1 #cdh-cea ,velocities1 depositing1 #cie-cig distribution of1 #ea flow in sewers1 #ij over surface of ground1 #db limiting for sedimentation1 #cif1 #cig limiting in sewers1 #cif1 #cig principles of flow in sewers1 #ea transporting1 #cif ,ventilation1 air pressures1 #bia compressed air1 #bib-bid pipes1 #bia ,ventilation1 of sewers1 #ajb1 #ajc1 #cce tunnel1 #bia ,vertical sheeting1 #bgj-bgd ,vitrified clay4 ,see ,clay vitrified4 ,volatile matter in sewage1 #ceg ,volute pumps1 #acj1 #acb1 #aed ,vouissoir arch analysis1 #bjd ,wakefield piling1 #bgc ,wales1 #bhh ,waste pipe1 defined1 #g ,wastes4 ,see ,industrial wastes4 ,water consumption1 #ca-cc flow of1 #ea-gg rate of steam engines1 #add1 #ade supply and sewage flow1 #ca-cc ,watershed4 ,see ,drainage area4 ,weight1 of backfill1 #aii of building material1 #bja of moving loads1 #bjj1 #bjb ,well1 hole1 #aja points1 #bfb1 #bfc ,wheel excavator1 #bdf-bej ,wing screen1 #chd ,wood1 forms4 ,see ,forms4 pipe1 materials1 #afd1 #afe1 #aij1 #aib1 #aic design1 #aig1 #aih working strength of1 #bgg ,work1 extra1 #bbg preliminary to design1 #i ,sunday1 night1 and holiday1 #bba ,workmen1 competent1 #bbg dishonesty1 #bcc1 #bcd ----- ,footnote #a3 ,frontinus and the ,water ,supply of ,rome1 p4 #ha1 by ,clemens ,herschel4 ,footnote #b3 ,estimated by ,g4 ,w4 ,fuller1 ,trans4 ,am4 ,society of ,civil ,engineers1 ,vol4 #dd1 #aije1 p4 #adh4 ,the total population connected with sewerage systems was assumed to be the total population in the ,united ,states in cities over #djjj in population4 ,footnote #c3 ,estimated by ,metcalf and ,eddy1 ,american ,sewerage ,practice1 ,vol4 ,,iii1 p4 #bdj4 ,footnote #d3 ,computed from report of the ,united ,states ,census1 #aibj1 on the same basis as ,fuller's estimate for #aije4 ,footnote #e3 ,cosgrove1 ,history of ,sanitation4 ,footnote #f3 ,sedgwick3 ,sanitary ,science and ,public ,health4 ,footnote #g3 ,no detrimental effect on the public health was noted as a result of this condition however4 ,it has never been conclusively proven that such nuisances are detrimental to the public health4 ,footnote #h3 ,moore and ,silcock1 ,sanitary ,engineering1 p4 #fg1 #aiji4 ,footnote #i3 ,similar to the definition proposed by the ,am4 ,public ,health ,assn4 ,footnote #aj3 ,definition recommended by ,am4 ,public ,health ,assn4 ,footnote #aa3 ,ibid4 ,footnote #ab3 ,ibid4 ,footnote #ac3 ,eng4 ,news1 ,vol4 #gf1 #aiaf1 p4 #gha4 ,see also ,eng4 ,news-,record1 ,vol4 #he1 #aibj1 pp4 #bb1 #aage4 ,footnote #ad3 ,for a more extensive treatment of the subject see ,principles and ,methods of ,municipal ,administration by ,w4 ,b4 ,munro1 #aiaf4 ,footnote #ae3 ,eng4 ,record1 ,vol4 #gd1 #aiaf1 p4 #bfc4 ,footnote #af3 ,professional paper ,no4 #df1 ,united ,states ,geological ,survey1 #aijf1 p4 #ig4 ,footnote #ag3 ,united ,states ,geological ,survey1 ,water ,supply paper ,no4 #beg1 #aiaa4 ,footnote #ah3 ,from ,eng4 ,cont41 ,vol4 #da1 #aiad1 p4 #fih4 ,footnote #ai3 ,max4 represents only the average maximum1 not the greatest maximum4 ,footnote #bj3 ,eng4 ,news-,record1 ,vol4 #hj1 page #abcc1 #aiah4 ,footnote #ba3 ,infiltration of ,ground ,water into ,sewers4 ,transactions of the ,american ,society of ,civil ,engineers1 ,vol4 #gf1 #aiac1 p4 #aiji4 ,footnote #bb3 ,a comprehensive discussion of rainfall formulas will be found in ,vol4 #ed of the ,transactions ,am4 ,society of ,civil ,engineers1 #aije4 ,footnote #bc3 ,formula devised by ,h4 ,e4 ,babbitt from ,allen's #be-year curve4 ,footnote #bd3 ,see ,note under ,table #ad4 ,footnote #be3 ,sewerage by ,a4 ,p4 ,folwell4 ,footnote #bf3 ,from an article by ,e4 ,kuichling in ,transactions ,american ,society of ,civil ,engineers1 ,vol4 #fe1 #aiji1 p4 #cii4 ,footnote #bg3 ,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #eh1 #aijg1 p4 #dhc4 ,footnote #bh3 ,trans4 ,american ,society of ,civil ,engineers1 ,vol4 #eh1 #aijg1 p4 #dih4 ,footnote #bi3 ,ibid4 ,footnote #cj3 ,the principles governing the run-off from large areas are explained in ,elements of ,hydrology1 by ,a4 ,f4 ,meyer1 #aiag4 ,footnote #ca3 ,transactions of the ,american ,society of ,civil ,engineers1 ,vol4 #ea1 #aijc1 p4 #aa4 ,footnote #cb3 ,municipal and ,county ,engineering1 ,vol4 #eh4 #aibj1 p4 #afd4 ,footnote #cc3 ,industrial waste ,treated as ground water4 ,footnote #cd3 ,for diagrams for the ,solution of the ,rational ,method1 see ,eng4 ,news-,record1 ,vol4 #hc1 #aiai1 p4 #hfh and ,vol4 #he1 #aibj1 p4 #aea4 ,footnote #ce3 ,municipal and ,county ,engineering1 ,october1 #aiji4 ,footnote #cf3 8,cleaning and ,flushing ,sewers40 ,journal of the ,association of ,engineering ,societies1 ,vol4 #cc1 #aijd1 p4 #bab4 ,footnote #cg3 ,notes on the ,design and ,principles of ,sewage ,siphons1 ,eng4 ,news-,record1 ,vol4 #he1 #aibj1 p4 #ajda4 ,footnote #ch3 ,from ,a4 ,e4 ,phillips1 ,trans4 ,am4 ,society of ,municipal ,improvements1 #ahih1 p4 #gj4 ,footnote #ci3 ,trans4 ,am4 ,society of ,civil ,engineers1 ,vol4 #ae1 #ahhf4 ,footnote #dj3 ,true ,siphon at ,east ,providence1 ,eng4 ,news-,record1 ,vol4 #he1 #aibj1 p4 #hfb4 ,footnote #da3 8,the ,effect of ,mouthpieces on ,the ,flow of ,water ,through a ,submerged ,short ,pipe10 by ,f4 ,b4 ,seely4 ,bulletin ,no4 #if1 #aiag1 of the ,eng'g4 ,experiment ,station of the ,university of ,illinois4 ,footnote #db3 ,trans4 ,am4 ,society of ,civil ,engineers1 ,vol4 #di1 #aijb4 ,footnote #dc3 ,described by ,w4 ,l4 ,stevenson before the ,boston ,society of ,civil ,engineers in #aiaf4 ,footnote #dd3 ,multiple ,outlet for ,calumet ,intercepting ,sewer1 by ,s4 ,t4 ,smetters1 ,eng4 ,news-,record1 ,vol4 #hc1 #aiai1 p4 #gbh4 ,footnote #de3 8,direct ,acting ,steam ,pumps10 by ,f4 ,r4 ,nickel1 #aiae4 ,footnote #df3 ,from ,heat ,engines1 by ,allen and ,bursley4 ,footnote #dg3 8,the ,economy ,resulting from the ,use of ,variable ,speed ,induction ,motors for ,driving ,centrifugal ,pumps0 by ,m4 ,l4 ,enger and ,w4 ,j4 ,putnam4 ,journal ,am4 ,water ,works ,ass'n41 #aibj1 ,vol4 #g1 p4 #ecf4 ,footnote #dh3 ,c4 ,a4 ,hague in ,trans4 ,am4 ,society of ,civil ,engineers1 ,vol4 #gd1 #aiaa1 p4 #bj4 ,footnote #di3 ,includes screen chamber1 collecting reservoir1 and building4 ,footnote #ej3 ,computed on the assumption that the pumps may be operated at #ej per cent overload for short periods1 the rated capacity being equal to the loads given in ,table #cc4 ,footnote #ea3 ,for description of type see note under ,table #ce4 ,footnote #eb3 ,proceedings ,illinois ,society of ,engineers1 #aiaf1 page #ha4 ,footnote #ec3 ,municipal ,engineers' ,journal for ,april1 #aiah4 ,footnote #ed3 ,workability involves ease in placing and smoothness of working4 ,footnote #ee3 ,johnson's ,materials of ,construction1 #eth ,edition1 #aiah1 p4 #dcb4 ,footnote #ef3 ,trans4 ,am4 ,society of ,civil ,engineers1 ,vol4 #ei1 #aijg1 p4 #adf4 ,footnote #eg3 ,l4 ,n4 ,edwards1 ,trans4 ,am4 ,society ,testing ,materials1 #aiah1 and ,r4 ,b4 ,young1 ,eng4 ,news-,record1 ,vol4 #hb1 #aiai1 p4 #cc4 ,footnote #eh3 ,bulletin ,no4 #a1 ,structural ,materials ,research ,laboratory1 ,lewis ,institute1 ,chicago1 ,illinois4 ,footnote #ei3 ,proportioning ,concrete by ,voids in the ,mortar1 ,a4 ,n4 ,talbot1 read before ,am4 ,society ,testing ,materials1 ,june #bb1 #aiba4 ,abstract in ,eng4 ,news-,record1 ,vol4 #hg1 #aiba1 p4 #adg4 ,footnote #fj3 ,trans4 ,am4 ,society of ,civil ,engineers1 ,vol4 #ha1 #aiag1 p4 #aabb4 ,footnote #fa3 ,see also ,tentative ,specifications for ,concrete and ,reinforced ,concrete submitted by the ,joint ,committee to its ,constituent ,organizations1 ,june #d1 #aiba4 ,footnote #fb3 ,journal ,illinois ,society of ,engineers for #aiaf1 p4 #ge4 ,footnote #fc3 ,see ,a4 ,s4 ,t4 ,m4 ,standards for #aiah1 p4 #adh4 ,footnote #fd3 ,trans4 ,am4 ,society ,civil ,engrs41 ,vol4 #hb1 #aiah1 p4 #dei4 ,footnote #fe3 ,see ,trans4 ,am4 ,society ,civil ,eng41 ,vol4 #hb1 #aiah1 p4 #dhb4 ,footnote #ff3 ,see ,trans4 ,am4 ,society ,civil ,engr41 ,vol4 #da1 #ahii1 p4 #gf1 and ,vol4 #hb1 #aiah1 p4 #dcc1 ,eng4 ,news1 ,vol4 #gd1 #aiae1 p4 #djj1 and ,vol4 #ge1 #aiaf1 p4 #iaa4 ,footnote #fg3 ,trans4 ,am4 ,soc4 ,civil ,engrs41 ,vol4 #hb1 #aiah1 p4 #dcc4 ,footnote #fh3 ,bulletin ,no4 #ca of the ,engineering ,experiment ,station of the ,iowa ,state ,college of ,agriculture4 ,footnote #fi3 ,from bulletin ,no4 #ca1 ,engineering ,experiment ,station1 ,iowa ,state ,college of ,agriculture4 ,footnote #gj3 ,from ,bulletin ,no4 #ca1 ,engineering ,experiment ,station1 ,iowa ,state ,college of ,agriculture4 ,footnote #ga3 ,from ,bulletin ,no4 #ca1 ,engineering ,experiment ,station1 ,iowa ,state ,college of ,agriculture4 ,footnote #gb3 ,from ,vouissoir ,arches by ,cain4 ,footnote #gc3 ,baker's ,masonry1 #ajth ,edition1 p4 #fgf4 ,footnote #gd3 ,business ,law for ,engineers1 ,c4 ,frank ,allen1 ,mc,graw-,hill1 #aiag2 ,engineering ,contracts and ,specifications1 ,j4 ,b4 ,johnson1 ,mc,graw-,hill1 #aijd2 ,contracts in ,engineering1 ,j4 ,i4 ,tucker1 ,mc,graw-,hill1 #aiaj2 ,the ,law ,affecting ,engineers1 ,w4 ,v4 ,ball1 ,archibald ,constable1 #aiji2 ,law and ,business of ,engineering and ,contracting1 ,c4 ,e4 ,fowler1 ,mc,graw-,hill1 #aiji2 ,the ,economics of ,contracting1 ,d4 ,j4 ,hauer1 ,e4 ,h4 ,baumgartner1 #aiae2 ,the ,elements of ,specification ,writing1 ,r4 ,s4 ,kirby1 ,john ,wiley ,son1 #aiac2 ,contracts1 ,specifications and ,engineering ,relations1 ,d4 ,w4 ,mead1 ,mc,graw-,hill1 #aiaf2 ,engineering and ,architectural ,jurisprudence1 ,j4 ,c4 ,wait1 ,john ,wiley1 #aiab4 ,footnote #ge3 ,see article by ,e4 ,w4 ,bush in ,eng4 ,news-,record1 ,vol4 #he1 #aibj1 p4 #abb4 ,footnote #gf3 ,an unbalanced proposal is one in which the bids on some of the items are obviously low and on other items are obviously or suspiciously high4 ,the purpose of submitting unbalanced bids is to keep secret the true or supposed cost of the work to the contractor or to obtain more money by bidding high on those items which are believed to have been underestimated by the ,engineer4 ,a low bid is made on other items in order to keep down the total amount of the bid4 ,footnote #gg3 ,taken mainly from specifications of the ,sanitary ,district of ,chicago and the ,baltimore ,sewerage ,commission1 with miscellaneous selections from other sources4 ,footnote #gh3 ,restrictions are placed on work done outside of ordinary working hours in order that the ,contractor may not perform work in the absence of an engineer or inspector4 ,footnote #gi3 ,cost ,keeping and ,management1 by ,gillette and ,dana4 ,practical ,cost ,keeping for ,contractors1 by ,f4 ,r4 ,walker4 ,cost ,keeping in ,sewer ,work1 by ,k4 ,o4 ,guthrie in ,eng4 ,contracting1 ,vol4 #bh1 p4 #bch1 #aije4 ,sewer ,construction ,records at ,scarsdale1 ,eng4 ,news-,record1 ,vol4 #hc1 p4 #aaa1 #aiai4 ,footnote #hj3 ,see ,planning and ,progress on a ,big ,construction ,job1 by ,chas4 ,penrose1 ,eng4 ,news-,record1 ,vol4 #hd1 #aibj1 pp4 #eed and #fbg4 ,footnote #ha3 ,see also 8,ownership and ,operation of ,trench ,excavators by the ,water ,department of ,baltimore10 by ,v4 ,b4 ,seims1 presented before ,am4 ,water ,works ,association1 ,june #i1 #aiba4 ,footnote #hb3 ,eng4 and ,contracting1 ,vol4 #dh1 #aiag1 p4 #dib4 ,footnote #hc3 ,earth ,excavation by ,a4 ,b4 ,mc,daniel4 ,footnote #hd3 ,courtesy1 ,sanitary ,district of ,chicago4 ,footnote #he3 ,see article by ,j4 ,r4 ,gow1 ,journal ,new ,england ,waterworks ,ass'n1 ,sept41 #aibj1 also ,public ,works1 ,vol4 #ej1 p4 #ih4 ,footnote #hf3 ,diameter of diaphragm4 ,footnote #hg3 ,gallons per minute4 ,footnote #hh3 ,eng4 ,news1 ,vol4 #ge1 #aiaf p4 #ajej4 ,footnote #hi3 ,mun4 ,engineering1 ,vol4 #ec1 p4 #f4 ,footnote #ij3 ,for types of drill bits see article by ,t4 ,h4 ,proske1 ,mining and ,scientific ,press1 ,march #e1 #aiaj4 ,footnote #ia3 ,these intermediate holes are seldom more than #c feet apart4 ,footnote #ib3 ,earth ,pressures1 ,old ,theories and ,new ,test ,results1 ,eng4 ,news-,record1 ,vol4 #he1 #aibj1 p4 #fcb4 ,footnote #ic3 ,trans4 ,am4 ,society ,civil ,eng'rs1 ,vol4 #fj1 #aijh4 ,footnote #id3 ,adopted by the ,am4 ,ry4 and ,maintenance of ,way ,ass'n in #aijg4 ,footnote #ie3 ,tunneling ,machines ,successful on ,detroit ,sewers1 ,eng4 ,news-,record1 ,vol4 #hd1 #aibj1 p4 #cbi4 ,footnote #if3 ,rules on ,compressed-,air ,work of ,n4 ,y4 ,state ,industrial ,commission1 ,eng4 ,news-,record1 ,vol4 #he1 #aibj1 p4 #abbe4 ,footnote #ig3 ,taken mainly from the ,engineer ,field ,manual of the ,u4 ,s4 ,army2 ,safety ,factors in the ,use of ,explosives by ,w4 ,o4 ,snelling1 ,technical ,paper ,no4 #ah1 ,u4 ,s4 ,bureau of ,mines2 and an article in ,eng'g and ,contracting1 ,vol4 #eb1 #aiai1 p4 #ehe4 ,footnote #ih3 ,see paper by ,c4 ,t4 ,hall before ,am4 ,inst4 ,chemical ,engineers4 ,footnote #ii3 ,per cubic yard of material displaced4 ,footnote #ajj3 ,eng4 ,news1 ,vol4 #ge1 #aiaf1 p4 #eib4 ,footnote #aja3 ,pressure of ,concrete on ,forms ,measured in ,tests1 by ,e4 ,b4 ,smith1 before ,am4 ,concrete ,institute1 ,feb4 #ae1 #aibj4 ,abstracted in ,eng4 ,news-,record1 ,vol4 #hd1 #aibj1 p4 #ffe4 ,footnote #ajb3 ,see1 also1 ,concrete ,form ,design1 by ,e4 ,f4 ,rockwood1 ,eng4 and ,contracting1 ,vol4 #ee1 #aiba1 p4 #ebh4 ,footnote #ajc3 ,includes #f cents per foot for excavation4 ,labor for this was #eh per cent of the total labor cost4 ,footnote #ajd3 ,cement at #a4be per barrel4 ,footnote #aje3 ,mun4 ,journal1 ,vol4 #cf1 #aiad1 p4 #gcf4 ,footnote #ajf3 ,mun4 ,journal1 ,vol4 #ci1 #aiae1 p4 #iaa4 ,footnote #ajg3 ,formerly the ,municipal ,journal4 ,footnote #ajh3 ,see ,eng4 ,record1 ,vol4 #ge1 #aiag1 p4 #dfc4 ,footnote #aji3 ,eng4 ,record1 ,vol4 #gc1 #aiaf1 p4 #ada1 and ,eng4 ,news-,record1 ,vol4 #gi1 #aiag1 p4 #ajai4 ,footnote #aaj3 ,eng4 ,record1 ,vol4 #gb1 #aiae1 p4 #fij4 ,footnote #aaa3 ,eng4 ,record1 ,vol4 #ga1 #aiae1 p4 #bef4 ,footnote #aab3 ,eng4 and ,contr41 ,vol4 #da1 #aiad1 p4 #bej4 ,footnote #aac3 ,h4 ,j4 ,kellogg in ,journal ,connecticut ,society of ,civil ,engineers1 #aiad1 and ,technical ,paper #aag1 ,u4 ,s4 ,bureau of ,mines4 ,footnote #aad3 ,eng4 ,news1 ,vol4 #gj1 #aiac1 p4 #aaeg4 ,footnote #aae3 ,technical ,paper ,no4 #aag1 ,u4 ,s4 ,bureau of ,mines4 ,footnote #aaf3 ,eng4 ,news1 ,vol4 #ga1 #aiad1 p4 #hd4 ,footnote #aag3 ,eng4 ,news1 ,vol4 #ga1 #aiad1 p4 #hb4 ,footnote #aah3 ,similar to definition proposed by the ,am4 ,public ,health ,ass'n4 ,footnote #aai3 ,economic ,values in ,sewage and ,sewage ,sludge1 by ,raymond ,wells1 ,proceedings ,am4 ,society ,municipal ,improvements1 ,nov4 #ab1 #aiai4 ,eng4 ,news-,record1 ,vol4 #hc1 #aiai1 p4 #idh4 ,footnote #abj3 ,sample boiled for five minutes4 ,footnote #aba3 ,sample immersed in boiling water for #cj minutes4 ,footnote #abb3 ,four months4 ,footnote #abc3 ,one week in ,march1 #aiad4 ,footnote #abd3 ,r represents any chemical element such as ,k1 ,na1 etc4 ,footnote #abe3 ,standard ,methods of ,water ,analysis1 ,american ,public ,health ,association1 #aibj4 ,footnote #abf3 ,routine tests are ordinarily incubated for this period only1 and if not decolorized in this time are recorded as stable4 ,footnote #abg3 ,determination of the ,biochemical ,oxygen ,demand of ,sewage and ,industrial ,wastes1 by ,e4 ,j4 ,theriault1 ,report of the ,u4 ,s4 ,public ,health ,service1 ,vol4 #ce1 ,may #g1 #aibj1 ,no4 #ai1 p4 #ajhg4 ,footnote #abh3 ,standard ,methods of ,water ,analysis1 ,american ,public ,health ,association1 #aibj4 ,footnote #abi3 ,jordan1 ,general ,bacteriology1 #aiji1 p4 #ia4 ,footnote #acj3 ,ibid4 ,footnote #aca3 ,reprinted in ,vol4 ,,iii of ,contributions from the ,sanitary ,research ,laboratory of ,massachusetts ,institute of ,technology4 ,footnote #acb3 ,formerly ,chief ,engineer of the ,sanitary ,district of ,chicago4 ,footnote #acc3 ,from 8,sewage10 by ,samuel ,rideal1 #aijj1 p4 #af4 ,footnote #acd3 ,see ,am4 ,civil ,engineers' ,pocket ,book1 ,second ,edition1 p4 #ihb4 ,footnote #ace3 ,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #eh1 #aijg1 p4 #ihh4 ,footnote #acf3 ,not defined by the ,american ,public ,health ,association4 ,footnote #acg3 ,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #gh1 #aiae1 p4 #hib4 ,footnote #ach3 ,removal of ,suspended ,matter by ,sewage ,screens1 ,cornell ,civil ,engineer1 #aiad4 ,abstracted in ,engineering and ,contracting1 ,vol4 #da1 #aiad1 p4 #dea4 ,footnote #aci3 8,the ,clarification of ,sewage by ,fine ,screens10 ,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #gh1 #aiae1 p4 #ajjj4 ,footnote #adj3 ,langdon ,pearse1 ,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #gh1 #aiae1 p4 #ajjj4 ,footnote #ada3 ,meshes per inch4 ,footnote #adb3 ,see article by ,henry ,ryon in ,cornell ,civil ,engineer1 #aiaj4 ,footnote #adc3 ,the hydraulic coefficient is defined as the rate of settling in mm4 per second4 ,footnote #add3 ,definition suggested by the ,american ,public ,health ,association4 ,footnote #ade3 ,computed from formula by ,gilbert in 8,transportation of ,debris by ,running ,water10 ,u4 ,s4 ,geological ,survey1 ,professional ,paper ,no4 #hf1 #aiad4 ,diameter in mm4 7#a4bh 7velocity7#b4g77,sp4 gv4 #a74 ,footnote #adf3 ,computed from ,annual ,report of the ,superintendent of ,sewers1 ,nov4 #cj1 #aiai1 and #aibj4 ,footnote #adg3 ,these figures are for #aiai4 ,footnote #adh3 ,these figures are for #aije4 ,footnote #adi3 ,these figures are for #aijb4 ,footnote #aej3 ,report of the ,ohio ,state ,board of ,health1 #aijh1 page #dbe4 ,footnote #aea3 ,definition proposed by the ,am4 ,public ,health ,assn4 ,footnote #aeb3 ,see ,eng4 ,news4 ,vol4 #gc1 #aiae1 p4 #daj4 ,footnote #aec3 ,sewage ,treatment from ,single ,houses and ,small ,communities1 by ,l4 ,c4 ,frank4 ,u4 ,s4 ,public ,health ,service1 ,bulletin #aja1 #aibj4 ,footnote #aed3 ,eng4 ,news-,record1 ,vol4 #gh1 #aiag1 p4 #eff4 ,footnote #aee3 ,municipal ,engineering1 ,vol4 #ed1 p4 #adi4 ,footnote #aef3 ,eng4 ,record1 ,vol4 #fh1 #aiac1 p4 #deb4 ,footnote #aeg3 ,am4 ,sewerage ,practice1 ,vol4 ,,iii1 p4 #dcg4 ,footnote #aeh3 ,trans4 ,am4 ,society ,civil ,engineers1 ,vol4 #hc1 #aibj1 p4 #ccg4 ,footnote #aei3 ,eng4 ,news-,record1 ,vol4 #hc1 #aiai1 p4 #eaj4 ,footnote #afj3 ,see ,eng4 ,news1 ,vol4 #gj1 #aiac1 p4 #aaab2 ,eng4 ,record1 ,vol4 #fh1 #aiac1 p4 #ddj1 and ,eng4 ,news1 ,vol4 #ge1 #aiaf1 p4 #ajbh4 ,footnote #afa3 ,see ,eng4 ,record1 ,vol4 #fg1 #aiac1 p4 #bcb4 ,footnote #afb3 ,the use of half-spray nozzles is not always advocated as it is considered that their use does not markedly improve the distribution4 ,where half nozzles are used1 a margin of #ah inches to #b feet should be allowed between the edge of the filter and the nozzle1 to prevent the blowing of raw sewage from the filter4 ,footnote #afc3 ,from paper by ,e4 ,g4 ,bradbury in ,proceedings of the ,ohio ,eng4 ,society1 #aiaj1 p4 #gi4 ,footnote #afd3 ,the effective size of sand is the diameter in millimeters of the largest grain in that #aj per cent1 by weight1 of the material which contains the smallest grains4 ,footnote #afe3 ,the uniformity coefficient is the ratio of the diameter of the largest particle of the smallest #fj per cent1 by weight1 to the effective size4 ,footnote #aff3 ,interest at #f per cent4 ,footnote #afg3 ,worcester figures4 ,footnote #afh3 ,this method may show a profit from the sale of sludge4 ,footnote #afi3 ,sewage ,disposal1 #aiai1 p4 #bbc4 ,footnote #agj3 ,see ,eng4 ,news1 ,vol4 #i1 #ahhc1 p4 #bjc1 and ,vol4 #bi1 #ahic1 p4 #bg4 ,footnote #aga3 ,american ,sewerage ,practice1 ,vol4 ,,iii4 ,footnote #agb3 ,reference #aa1 at end of this chapter4 ,footnote #agc3 ,reference #ae4 ,footnote #agd3 ,reference #b4 ,footnote #age3 ,for mechanical methods of drying sludge1 see ,reference #bb1 p4 #aabg1 and ,no4 #cc1 p4 #hdc4 ,footnote #agf3 ,reference #aj4 ,footnote #agg3 ,reference #ac4 ,footnote #agh3 ,university of ,california1 ,bulletin #bea1 #aiae4 ,footnote #agi3 ,reference #be4 ,footnote #ahj3 ,see ,report by ,black ,phelps of ,metropolitan ,sewerage ,commission1 #aiaa1 reprinted as ,vol4 ,,vii of ,contributions from the ,sanitary ,research ,laboratory of the ,massachusetts ,institute of ,technology4 ,footnote #aha3 ,see ,reports1 ,mass4 ,state ,board of ,health4 ,footnote #ahb3 ,reference #dg4 ,footnote #ahc3 ,reference #aj4 ,footnote #ahd3 ,reference #aj4 ,footnote #ahe3 ,reference #aj4 ,footnote #ahf3 ,hatton1 reference #cc4 ,footnote #ahg3 ,reference #ah4 ,footnote #ahh3 ,reference #a1 at end of this chapter4 ,footnote #ahi3 ,reference #b4 ,footnote #aij3 ,reference #f4 ,footnote #aia3 ,reference #e4 ,footnote #aib3 ,reference #f4 ,footnote #aic3 ,reference #f4 ,footnote #aid3 ,reference #h4 ,footnote #aie3 ,reference #bj4 ,footnote #aif3 ,reference #ag4 ,footnote #aig3 ,reference #ai4 ,footnote #aih3 ,reference #ba4 ,footnote #aii3 ,reference #bd4 ,footnote #bjj3 ,inorganic ,chemistry1 by ,alexander ,smith4 ,footnote #bja3 ,american ,public ,health ,association definition4 ,footnote #bjb3 ,sewage ,sludge by ,allen4 ,footnote #bjc3 ,sewage ,disposal by ,kinnicutt1 ,winslow and ,pratt4 ,footnote #bjd3 ,sewage ,disposal by ,fuller4 ,footnote #bje3 ,sewage ,sludge by ,allen4 ,footnote #bjf3 ,from ,eng4 ,news-,record1 ,vol4 #hd1 #aibj1 p4 #iie4 ,footnote #bjg3 ,a ,simple ,mechanical ,control for ,dosing ,sewage ,beds1 by ,p4 ,thompson1 ,eng4 ,news-,record1 ,vol4 #hd1 #aibj1 p4 #ajah4 ,footnote #bjh3 ,sewage ,disposal by ,kinnicutt1 ,winslow and ,pratt4 ,footnote #bji3 ,design of ,siphon by ,g4 ,h4 ,bayles1 ,eng4 ,news-,record1 ,vol4 #hd1 #aibj1 p4 #igd4 ---------------------------------------- -------------------------------- ,,transcriber',s ,,notes #a4 ,silently corrected typographical errors and variations in spelling4 #b4 ,archaic1 non-standard1 and uncertain spellings retained as printed4 #c4 ,enclosed italics font in underscores4 #d4 ,enclosed bold font in equals4 #e4 ,superscripts are denoted by a caret before a single superscript character or a series of superscripted characters enclosed in curly braces1 e4g4 ,mr4 or ,mister4 #f4 ,subscripts are denoted by an underscore before a series of subscripted characters enclosed in curly braces1 e4g4 ,h#b,o4