THE LIBRARY OF THE UNIVERSITY OF CALIFORNIA LOS ANGELES GIFT OF John S.Prell m- ^Si €«ti: & SEWERAGE MAP — OF THE — VILLAGE OF WEST TROY NEW YORK. CADY STAjLEY. Engineer ■. d. PIERSON. ConstTQCtiag Engine 1555 T BXFLA.NA C0MMIS5I0NEB5. Peter A. Rogers. Pies. Terraace Cummings. Jajn.es C. Covert. 1 T. VanVranken. James H. Harmon. Alfred Mosber. William Andrews. Ificbolas T. Kane. THE SEPARATE SYSTEM OF SEWERAGE, ITS THEORY AND CONSTRUCTION, BY CADY STALEY, PRESIDENT OF CASE SCHOOL OF APPLIED SCIENCE, CLEVELAND, O. AND GEO. S. PIERSON, MEMBERS OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS. THIRD EDITION, REVISED AND ENLARGED, With a Chapter of Sewage Disposal. JOHfl S, PRELL Civil & Mechanical Engineer, SAN FS^^QlSefi, CAL. D. VAN NOSTRAND, CO., 23 Murray and 27 Warren Streets, 1899. Copyright, i886, by GEO. S. PIERSON. Copyright, 1891, by GEO. S. PIERSON. Copyright, 1899, by GEO. S. PIERSON. From the Press of Ihling Bros. & Everard, Kalamazoo, Mich. Eaginecriif Lifcraij PREFACE TO THE THIRD EDITION. The second edition of this book was exhausted about a year ag^o. The greater part of the book has been re-written. Statistical tables have been revised and new matter, includ- ing- many plates and diag^rams, has been added. Old matter that is now of doubtful value has been eliminated. PREFACE TO THE SECOND EDITION. The first edition of this book was exhausted some time since and numerous calls have been made for another edition. The book has been entirely re-written and much new matter has been added. An effort has been made to facilitate computations by Kutter's formula and tables of the value of ;/ have been added to assist in a proper determina- tion of its value for sewers. The question of Sewag^e Disposal has also received attention. 733285 PREFACE TO THE FIRST EDITION. The subject of the sewerag'e of towns is attracting" much more attention now than formerly. The reason for this is evident. While the country was new and the towns small and sparsely built, the disposal of the liquid wastes and other refuse was left to be provided for by each house- holder as he might deem best. Various plans were employed, most of which were objectionable, and, in many cases, no plan at all. But as the towns increase in size and are more compactly built the question of a proper system of Sewerage forces itself upon the attention of the people. Some general system must be adopted for the whole town and the question is, what system? The moderate cost of the "Separate System" makes it possible to carry out a system of sewerage in many cases where the expense of the "Combined System" would make the construction of sewers impossible. One hindrance to the rapid introduction of the Separate System has been the lack of available information concerning" it. Much has been written on the subject, but the neces- sary information is scattered in numerous pamphlets, reports and papers presented to scientific societies in the United States and in England. The object of this book is to explain what the Separate Vlll PREFACE TO THE FIRST EDITION. System is, what it is designed to do, and to g"ive practical directions for designing" and constructing sewers in accord- ance with that system. No single design, however complete in all its details, will be best adapted to every case. Each town will present some features peculiar to itself and the general plan must be modified to suit the conditions of each case. All that is here attempted is to give sufficient theory, data and results of experience to guide in properly designing and constructing sewers on the Separate System. CONTENTS. CHAPTER I. INTRODUCTION.^ — PAGK 17. Need of Sewerag^e. — Pollution of Streams. — Pollution of the Subsoil and Wells. — Typhoid Fever. — Analysis of Well Water. — Effect of Sewerag'e. — Systems in Use. CHAPTER n. WATER CARRIAGE SYSTEMS. — PAGE 39. The Combined System. — The Separate System. — Subsoil Drainag"e. CHAPTER m. THE SEPARATE SYSTEM. PAGE 46. Roof Water.- — Size and Material. — Flushing-. — Ventilation. — Special Features. — Adaptability of the Separate System. CHAPTER IV. PLANS. — PAGE 58. Sewag-e Disposal. — Storm Water. — The Preliminary Survey. — Capacity Required. — Chang-es of Temperature. — Use of Water Increasing*. CHAPTER V. QUANTITY OF SEWAGE. PAGE 66. The Quantity of Water Required. — Varying- Rates of Water Consumption. — Statistics of Water Consumption. — Sewer Gaug-ings. — Subsoil Water. CONTENTS. CHAPTER VI. LAWS OF FLOW IN SEWERS. — PAGE 94. Effect of Increasing- Size. — Effect of Hydraulic Mean Radius. ■ — Computation of Discharg-e and Velocity for any Diam- eter and any Depth of Flow. — Velocity Required to Prevent Deposit. — Effect of Decreasing- Quantity of Sewag-e. — Minimum Velocity. — Graphical Solution. — Comparison of Various Standard Formulae. — Loss of Head on Curves. — Empirical Formula. CHAPTER VII. MATERIAL AND ACCESSORIES. — PAGE 130. Sewer Pipes. — Hand-Holes. — Lamp-Holes. — Fresh Air In- lets. — Man-Holes. — Flush-Tanks. — Y Branches. CHAPTER VIII. SPECIFICATIONS AND CONTRACT. — PAGE 138. Letting- the Contract. — Form for Advertisement. — Instruct- ions to Contractors. — Form of Proposal. — Form for Specifications and Contract. — Form of Bond. CHAPTER IX. CONSTRUCTION. — PAGE 158. Importance of Record. — Alig-nment. — Reference Points. — Methods of Work. — Curves. — Transit Notes. ^ — Level Notes. — Profiles. — Working- Map. — Note Books. — Con- struction. — Pipe Laying-. — Depth. — Grade Line. — Brac- ing- and Sheet Piling-. — Inspection of Material. — Location of Y Branches. — Artificial Foundation. — Man-Holes. — Flush-Tanks. — Lamp-Holes. — Outlets. — House-Sewers. — Pumping- Stations. CONTENTS. XI CHAPTER X. FLUSHING AND VKNTILATING PAGE 200. In the Combined System. — In the Separate System. — Roof Water. — Traps on Main Drain. — Automatic Flush- Tanks. — Field-Waring- Flush-Tank. — Van Vranken's Flush-Tank. — The Miller Automatic Flush-Tank.— Rhoads-Williams Flush-Tank. — The Lig-htning- Auto- matic Flush-Tank. — Valve Tanks. — Requirements to be met. — Quantity of Water Required. — Rapidity of Discharg-e. — Experimental Data. — General Statements. CHAPTER XL HOUSE DRAINAGE AND PLUMBING. — PAGE 240. House Connections. — Municipal Control. — Form of Ordinance and Rules for Plumbing-. — Form of License. — Form of Bond. — Form of Application. — Form of Permit. — House Drains, th« Subsoil. — House Sewers. — Grease Traps. — Soil and Waste Pipes. — Traps and Ventilation. — General Features. CHAPTER XIL COST AND ASSESSMENTS. PAGE 268. Comparative Cost of the Separate and Combined Systems. — Cost of the Separate System. — Examples of Cost from Actual Work. — Data and Cost of Various Systems. — Examples of Cost Computed from Time Book.— Cost of Maintenance. — Sewer Assessments. — Assessments Dis- tributed over a Series of Years. — Installment Table. CHAPTER XIII. COMBINED SEWERS. — PAGE 292. Formula?.— Form of Sewers.— Materials.— Catch Basins. — Man-Holes. XII CONTENTS. CHAPTER XIV. SEWAGE DISPOSAL. — PAGE 296. Dilution. — Subsidence. — Filtration. — Chemical Processes. — Application to the Soil. CHAPTER XV. PURIFICATION OF SEWAGE BY APPLICATION TO THE SOIL. PAGE 299. General Considerations. — The Influence of the Bacteria of Nitrification.- — Nitrification. — Absorptive Power of the Soil. — The Function of Nitrates in Plant Life. — Experi- ments of the Massachusetts State Board of Health. — The Influence of Temperature. — Aeration of the Soil. — Effect of Different Soils. — Self Purification of the Soil. — Quantity and Concentration of Sewag"e. — Influence of Area. — Sewag^e Disposal at Pullman. LIST OF ILLUSTRATIONS. Page. Sewerag-e Map, West Troy, N. Y Shone Ejector 36 Diag-ram of Sewer Gaug-ing-s at St. Louis 87 Weir for Measuring Flow 90 Observation Opening, etc 97 Diagram Showing Comparative Velocity and Dis- charge in Circular Sewers of a Given Diameter and Grade for Various Depths of Flow 100 Graphical Sewer Calculations 108 Hand-Hole 133 Details of Fresh Air Inlet 135 Sketch of Construction — Photo. Engraving 167 Details of Sheet Piling 170 Cradle 172 Details of Man-Hole 173-4-5-9 Cast-iron Head and Dust Pan 181 Iron Cover, Man-Hole and Flush Tank 183 Outlet Chamber 185 Outlet Chamber with Relief Overflow 186 Submerged Iron Outlet, Dayton, Ohio 187-9 Photograph of Junction During Construction 191 Man-Hole— Brick Sewer 193 Pumping Plant 196 Branches, Curves and House Drains 197 Main Traps and Air Inlets 207 Main Traps and Air Inlets 211 Field-Waring Flush-Tank 216 Van Vranken Flush-Tank 218 Miller Flush-Tank 221-3 Rhoads-Williams Flush-Tank 226 The Lightning Automatic Flush-Tank 227 Flush- Wave 235-8 Interior Plumbing 255 Sewage Filter Beds at Pullman — Photo. Engraving.. 321 Broad Irrigation Area at Pullman — Photo. Engraving 323 LIST OF TABLES. Table No. Page. I. Urban Population of the United States 55 II. Cities Classified According- to Population. . . 56 III. Actual Consumption by Meter TO IV. Showing- Consumption of Water in Twelve American Cities in 1874 and 1884 72 V. Showing- Per Diem Per Capita Consumption of Water in One Hundred and Seventy-Six American Cities in 1884 73 VI. Illustrating- Monthly Variation in the Con- sumption of Water 74 VII. Illustrating- Extreme Daily Variations in Consumption of Water 75 VIII. Hourh' Variations in Water Consumption.. . 76 IX. Showing- Rates of Water Consumption for Different Periods of Twenty-Four Hours 77 X. Water Consumption at Louisville, Kv 79 XI. Sewer Gaug-ing-s at St. Louis 81 XII. Comparison of Sewer Gaug-ing-s 84 XIII. Gaug-ing-s of Water Street Main Sewer, Kal- amazoo, Mich 89 XIV. Illustrating- Effect of Increased Section, the VolumeofDischarg-e Remaining- the Same 95 XV. Showing- the Comparative Discharg-e and Velocity in Circular Sewers of a Given Diameter and Grade for A^arious Depths of Flow 99 XVI. Minimum Velocities and Grades in Circular Sewers 105 XVII. Showing- Maximum Rate of Sewag-e Flow. . . 109 XVIIL Values of //, Kutter's Formula 112 XVI LIST OF TABLES. XIX. Comparing- the Discharg-e in Various Cases as Given by Different Standard Formulae 125 XX. Showing- Increased Frictional Head Re- quired for Curves in Various Cases 128 XXL Tests of Sewer Pipe 131 XXII. Park Street Sewer 232 XXIII. Connecticut Avenue Sewer 233 XXIV. Chapin Street Sewer 234 XXV. Thirty-Second Street Sewer 234 XXVI. House Drains 254 XXVII. Bids on Sewer Construction, Schenectady, N. Y '.. 267 XXVIII. Bids on Sewer Construction, West Troy,N.Y. 269 XXIX. Bids on Sewer Construction, Dayton, Ohio. . 273 XXX. Cost of Thirty-Five Sewerage Systems 276 XXXI. Actual Cost of Labor and Material 278 XXXII. Actual Cost of Labor and Material 279 XXXIII. Actual Cost of Labor and Material 280 XXXIV. Actual Cost of Labor and Material 280 XXXV. Cost of Sewers in Chicago, 1890 281 XXXVI. Installment Table 289 The Separate System of Sewerage. CHAPTER I. INTRODUCTION. "Sanitar}^ Eng-ineerin^" has been defined as that branch of eng'ineerinw' which has for its object the improvement of the health of towns and districts, by bring-ing- to them a sup- ply of those thing's which promote health, and carrying- from them those thing-s which are injurious to it. The three principal requirements for the promotion of health are wholesome food, pure water, and pure air. An abundant and cheap supply of food is best secured by per- fecting- the means of transportation by land and water. Pure water may be supplied by suitable water works. The air is kept pure by removing- from the districts those thing-s which pollute it: that is, by removing- all g-arbag-e, and by carrying- out a proper system of drainag-e and sewerag-e. Although all of these works contribute to the health of a district, 3'et the subdivision of labor in these times has increased the number of specialties in the eng-ineering- pro- fession and has limited the field of the Sanitar}^ Eng-ineer. By common consent the eng-ineer who plans and executes works for improving the means for transportation is called a Civil Engineer; the eng-ineer of a system of water works is called a H)'draulic Eng-ineer; leaving- the Sanitarj^ Eng-ineer the task of removing- from any locality whatever may be det- rimental to health; thus assig-ning- to him the roll of scien- tific scaveng-er. 18 THE SEPARATE SYSTEM OF SEWERAGE. Man himself is the principal cause of the defilement of his surrounding's. His presence bring-s pollution to earth, air and water. Nature provides a remedy which is efficient only to a limited extent. Refuse from the animal king-dom is food for the veg-etable king-dom. But when human being-s cong-regfate in masses nature can no long^er meet the demands. In country districts, where the population is sparse, the disposal of excrementitious and refuse matter is easily man- ag-ed by each householder in his own way. And even if that way be unadvisable the only sufferers are himself and those of his own household, and no one else will care to interfere. The methods usually there adopted, however, become very objectionable wherever the people cong-reg"ate in larg-e num- bers. The conditions of living- become chang-ed. The sani- tary condition of the immediate surrounding's of each indi- vidual concerns not only himself, but the whole community in which he lives; and what was before a personal matter now becomes a question of public policy. In all densely populated areas, as in larg-e villag-es and cities, the disposal of the solid and liquid refuse becomes a serious problem. The Mosaic reg-ulations (Deut. xxiii, 12- 13) can not be enforced, and to store the filth of a city within the city is simply to invite disease and death. The use of the pits, dug- in the earth, as receptacles for refuse, is in every way objectionable. The soil becomes pol- luted with sewag-e, and the air is filled with the noxious g-ases arising- from the sewag-e soaked earth, and from the putrefy- ing- masses in vaults and cess-pools. The decomposition of so much refuse in such close proximity to the dwelling-s is detrimental to health in two ways. It uses up the oxyg-en from the air, and loads it with pestilential g-ases. If cess- pools are used at all, they should be water tig-ht. This necessitates the constantly recurring- trouble of carrying- CHAP. I. INTRODUCTION. 19 away the contents when they fill up, and only parti \' remov^es the difficulty. Need of Sewerage — An examination into the sanitary condition of a majority of our older cities and villag^es will show the g"reat need of some kind of sewerage. Many of them have never taken any measures to rid themselves of the necessary accumulations of filth, incident to a considerable population. For g^eneration after g^eneration the refuse which should have been removed far from the dwelling's, has been flung upon the surface of the g-round or into cess-pools, where the putrefying- mass poisons the air, and appeals in more ways than one for a remedy. "The offense, is rank." On one of the principal streets in one of our oldest cities it became necessar}- to remove several small houses to erect a larg-e building-. The interior of the block was thus exposed to view, and it simply made apparent the state of affairs in nearly every block in the city. Within the space of 150 feet long- by 50 feet wide, there were four wells and seven vaults and cess-pools. It needs no chemical analysis to determine the impurity of water obtained under such circumstances, nor a very vivid imag-ination to conceive the foulness of the atmosphere in that locality. The earth upon which many of our cities stand is liter- ally saturated with sewag-e. The vile odors which are exhaled from the polluted soil, and from the sinks of rotten- ness and putrefaction which it contains, contaminate the air in the streets, and are a constant reminder of the need of an efficient remedy. There they stand, j-eeking- in the accum- ulated filth of past g-enerations, never for a day free from malaria, and zymotic diseases; and yet the remedy is easih^ applied and the cost of it within the reach of the poorest hamlet. Pollution of Streams. — A small water course running- throug-h a city without sewers is sure to become a nuisance. Ever}' conceivable variety of filth and refuse will be thrown 20 THB SEPARATE SYSTEM OF SEWERAGE. into it, and it will soon be simply an open sewer. In dry weather, when the flow of water is at its minimum, the bed of the stream will become an elong"ated, open cess-pool of the worst variety. The channel is sometimes cleared by throw- ing" the accumulations of filth upon the banks: that is, the filth is spread over alarg-er surface instead of being- removed. Periodical cleanings of the bed and banks of the stream will only mitig-ate the nuisance temporarily. The cure must reach the cause of the evil if it is to be radical and entire. The sewage must be provided for in proper channels of its own, and only the storm water be allowed to run into the open water courses. The following extracts are taken from a report of the State Board of Health of New York. The name of the city referred to is omitted, but the name of any unsewered city or village might be filled into the blank spaces and the report would give the actual sanitary condition in a majority of cases: " Dr. Carroll's full report on the prevalence of filth and malarial diseases in , and the causes thereof, is well worthy a careful reading by every citizen of . " The record is both sad and alarming. Sad, because it shows that at least one-fifth of the deaths in your city during the past year were clearly preventable by ordinary municipal provision for cleanliness; alarming, because the already abnormal death rate from filth poisoning must, from the very nature of the cause, steadily increase. affords another of the many lamentable illus- trations of the apparently ineradicable popular delusions that natural water courses are the proper receptacles for sewage and house refuse of all kinds. * * It appears from the report that the number of fatal cases from diphthe- ria, typhoid fever, diarrhoea*and scarlet fever is, at least, three times as great as it should be under normal sanitary conditions. These diseases are known to be intensified, if not directly caused, by filth poisoning. The prevalence of malarial diseases is also reported. * * * There seems to be no doubt that there is a large amount of malarial trouble in . This disease is usually associated with surface or sub-soil saturation, occurring either immediately around dwellings or within such a distance that miasmatic emanations may be carried by the winds over an inhabited locality. There appear therefore, to be at least two prominent classes of more or less preventable diseases occurring in CHAP. I. INTRODUCTION. 21 , one of them dependent upon conditions of filth and the other upon undrained or saturated lands. The nature of these two classes leads to the conclusion, that filth is accumulating within the city of in such a way, and in such places, as to affect the public health, and that there are saturated tracts which produce malarial diseases. "The first and most important measure to stop the present death rate from filth diseases in is to provide proper means of carrying away the organic filth of the city. The use of open brook channels as sewers should be abso- lutely prohibited. They should be reserved for the drainage of surface water only. Such a prohibition can hardly be made effectual until some means are provided for carrying the sewage away from the city. For this purpose a system of sewers is strongly advised, and little relief can be expected from the present unwholesome condition of the city until sewers have been built. * *" Pollution of the Subsoil and of Wells. — The ordinary cess-pools are especially objectionable where wells are used as a source of water supply. A well is simply a hole dug- in the g-round, into which the water, which has sunk into the earth, may drain. The quality of the water will depend upon the condition of the soil through which it passes. In cities without sewerage, cess-pools by hundreds are formed in the earth, into which all manner of filth is thrown. Into this same soil wells are dug, and the drippings from the cess- pools are caught and drank, and the seeds of disease are sown broadcast in the community. One often hears it said that water which passes through the earth is filtered and purified. But it must not be forgotten that while the earth acts as a sieve, and removes the suspended impurities the oxydation and nitrifaction of organic matter depends upon circumstances which are not likely to be favorable very far beneath the surface of the ground. Whatever is in solution remains, to a larg-e extent, in the water. The Swiss village of Lausen, near Basle, is supplied with w'ater from a spring, situated at the foot of a mountainous ridge, called the Stockhalden. In this village, where there had not been a sing-le case of fever in many years, an epidemic of typhoid fever broke out, which struck down seventeen per cent, of the whole population. The cases of fever were 22 THE SEPARATE SYSTEM OF SEWERAGE. pretty evenly distributed among" the families in the village, with the exception of six. As the six families which escaped did not use water from the spring-, suspicions were aroused concerning- the water and investigations were made. It had previously been noticed that when the meadows in the Fur- lerthal — a little valley on the other side of the Stockhalden ridge — were irrig-ated, the volume of water in the spring was increased; and by the sinking of the soil in one of the meadows in the Furlerthal, a vein of water was discovered, which, it was supposed, led to the spring in Lausen. It was found, upon investigation, that a peasant living in the Fur- lerthal had returned home from a distant city, sick with fever, and that the brook in which his clothes had been washed and into which the slops from the house had been thrown, had been used to irrigate the meadows. This water thus spread out over the fields and then filtered through the ridge, a distance of a mile, still carried the germs of disease in it, and brought death to the unsuspecting inhabitants of Lausen. To prove, conclusively, that the spring was supplied from the Furlerthal, and to determine whether the water passed through an open vein or was filtered through porous material, the following experiments were made: Several hundred weight of salt was dissolved and poured into the hole in the Furlerthal, where the vein was discovered. In a few hours the water of the spring became very salt, and the connection between the water in the Furlerthal and the spring- at Lausen was established beyond a doubt. Thev now mixed two and a half tons of flour in water and poured it into the hole, but no trace of the flour could be found in the spring, proving that the water was so thoroughly filtered as to remove the minutest particles of the flour, and yet it still retained its infective properties. Clearness is no proof of purity in water. The water of the Saratoga Springs, although thoroughly impregnated with CHAP. I. INTRODUCTION. 23 various minerals, are as clear as ordinary spring water, and in a g-lass of water as clear as crystal there may be poison enoug-h to kill a whole family; not only by the comparatively slow and uncertain process of fever, but surely and immedi- ately. Deleterious g^ases may indeed add a sparkle to well water, and the peculiar flavor so hig-hly prized in some wells may be borrowed from a neig-hboring- cess-pool. Dr. Victor C. Vaug-hn, Professor of Physiolog-ical and Pathologfical chemistry in Michig-an University, states in a report to the State Board of Health, that a series of experi- ments which he has conducted confirms the g-erm theory in cases of typhoid fever. The fever was produced in a cat by inoculation and the cat showed all the symptomsof the disease. In connection with this Dr. Vaug^hn states: "Last August there was an epidemic of typhoid fever in the village of Iron Mountain, a place in Northern Michigan of about 4,000 inhabitants. Part of the town was supplied with water from a mountain spring, and part from pri- vate wells from six to twenty feet deep. It was noticed that all those who used the spring water escaped the disease, while those who depended upon the shal- low wells were stricken down. In all there were many hundred cases and about forty deaths. I secured some of the water from these shallow wells and with it experimented upon a number of cats, finally obtaining the result which I announced to the Board of Health." If, as Professor Vaug"hn states, these city wells contain fever germs enoug"h to kill a cat, with its traditional nine lives, what chance is there for an ordinary human being- with only one? The following- are the results of a very general examina- tion of the water in wells in one of the most beautiful and well kept smaller cities in the state of New York. The natural drainage facilities of the city are excellent. There are no sewers worthy the name, however. The results are particularly interesting, not only as showing the marked subsurface pollution within a compara- tively few years, but also as showing the increased mortality directlv resulting therefrom. 24 THE SEPARATE SYSTEM OF SEWERAGE. "I have made some chemical tests of water from nearly one hundred wells to determine, if possible, the extent of the pollution of the drinking water commonly used, and have made out a table which is given below, of the results of these tests. The amount of chlorine which a sample of water may contain and not be regarded as unsatisfactory is usually assumed as 3.5 grains per Impe- rial gallon. I have drawn a line at this point across the list of wells below, and another at 7.0 grains per gallon, which last may, at least, be called the danger line if not the death line. In the table with the analysis of the well water I have placed those of some other waters for comparison. No. 77 was urine diluted with 49 parts of pure water, Nos. 85 and 88 are from wells so situated as to drain large barn- yards. No. 93 is from the outlet of the sewer which last summer was turned across Main St. and carried down Mill St., joining the Bacon Street sewer. I have also marked those wells used by families where there have been cases of fever and (generally fatal) cases of diphtheria with an " F" and a " D " respect- ively. .Academy Filter .Thayer Spring .Rain . Hazelton Spring . Country Well .West Main .Country Well .Lincoln Avenue , East Main .Wolcott .West Main .Wolcott .Lincoln .South (i mile out) .East Main - .Well in Pasture , • East Main .Sewer, Lincoln .Spring in Pasture 25 50 55 70 80 80 95 05 40 50 60 65 75 75 00 05 15 15 35 E S ° -* 5 ° - Z c/3 U 20.... West Main 2.40 21. ...Summit 2.50 22.... Myrtle 2.50 23.... St. Marks 2.65 24 ...Church 2.65 25 . . . Wolcott 2 70 26.... Main 270 27. . . .Wolcott 2.95 28 ... . East Main 3 00 29. . . .West Main 3.20 30. . . .Wolcott 3.30 31 Maple ,. 3.40 32.... Myrtle 3.50 33.... Pond in Village 3.65 34.... Myrtle 3.65 Average of 9 Rochester ) „ Sewers (Dr. Lattimore) f •'■' 35... Myrtle 3.80 36 ... . East Main 4.00 CHAP. I. IXTRODUCTIOX. 25 z (jBUJa^ J3 O o 3 s o > h E c 1- u. (I. Uh ~ o o o C C G G o G G C 00 in lO m m o ■^ 00 N G m anuoiqo _ P) on 00 ft 00 M •^ '"' N M 0\ O CO VO m G o l-l PT) M ■<*- N f^ c o t^ m o vn t^ o\ in n a <- -^ o \a m in w t^ '1- m M ■S9?EJ}TN o Tj- in o o O c! n! m G 00 vO m 00 (I -r m m o o Z Z o o o GOO o o o naBojjjN o o o T in O O O in in in G G in MD 4) oiobSjo O O o o o o GOO GOO C o G O 1 ° m t-^ Binommv aaJ j; 00 o o o c t^ l^^ox *"* c^ o in N ssaupjBH in m jngnBuijaj t^ m u ssaapjBH -r m •jiaBJodui9x Tf 'S- o ;■ V-( v^ 1- u i-< v^ u w u « cd a a c ns n ni ct r CS •J0103 1> (U u i 0, 1- c < L, rt > T3 T re ^' > C J3 O a 0) a c o C o ^ CO C/) 7! o v •a[duiBs f5 f^ C/} . > dJ (U 0) Si J" > ^ Oi c a c s- >. > CO a ^ cfl > XI in H < ,i: a ° u. NAME OF PLACE. r8| a « 5 c = 8 (0 « M 0) (fi V .S'-S «£•? ac v^ 5f U 0) >^ 3 S = s t^t f%% a •0 « < < m OS « Cardiff 33-2 237 29.8 33 2 22 6 32 22 40 64 48 60 17 17 31 11 Croydod 18 6 Alacclesfield 23.7 26.2 20 Merthyr 18 Newport 31.8 27.5 21.6 32 20 36 75 32 49 Salisbury 21.9 30 THE SEPARATE SYSTEM OF SEWERAGE. "At Dantzic, the deaths from enteric fever per 100,000 living- were as follows: From 1865 to 1869, before any sanitary measures were taken, 108. From 1871 to 1875, after the introduction of water supply, 90. From 1876 to 1880, after the introduction of sewerage, 18." The death rate in London in the last half of the 17th cen- tury was eig"hty in ever}- thousand. Now it is about twenty- four in every thousand, althoug-h much more densely popu- lated. Irwin F. Smith, in a very comprehensive paper on the ^'Influence of sewerag^e and water supply on the death rate in cities" writes as follows: "Data drawn from sewered cities is now available for study and compari- son. To be of service such data must have been carefully gathered and must cover a considerable period, the population must be known to have been cor- rectly enumerated, and various other factors which enter into every considera- tion of the death rate of a place, such as race, age, condition in life, crowding, occupation, etc., must be given due weight. Taking all these factors into con- sideration, and casting up accounts, there remains a striking balance sheet in favor of the sewered cities In the consideration of this subject the general propositions which I wish to lay down, and which appear to me to be clearly deducible from the data at my disposal are as follows: "Typhoid fever and cholera decrease in proportion as a city is well sew- ered. This may be laid down as a fundamental proposition to which there are no exceptions. "The general death rate falls after the sewering of a city, and, other things being equal, never again reaches the maximum of its ante-sewered condition. "The cost of building and maintaining sanitary works is inconsiderable in comparison with the direct pecuniary loss by sickness and death, which their absence entails. "Drains imperfectly jointed and lacking the proper facilities for flushing or the necessary fall for the introduction of excreta and for proper clearing, are in no proper sense of the word sewers, and are not considered as such in this paper. If excreta be introduced into such drains it almost always proves a public nuisance, and the writer is far from denying that under some circum- CHAP. I. INTRODUCTION, 31 stances such drains, "sewers," so-called, may not become active promoters of infectious diseases. When I speak of the benefits arising from sewerage, I mean invariably, modern sewers, well built, well ventilated — the soil-pipes, traps, water-closets, etc., being constructed on approved plans and in the most workmanlike manner. My reason for selecting typhoid fever is that, although the nature of the typhoid poison is yet in dispute, we now understand very clearly the manner in which the disease is spread. Another reason is the gravity of the mortuary tax levied by typhoid fever. This will be at once apparent if we consider briefly the statistics of this disease." The following- graphical presentations of some of the sta- tistics collected b}' Mr. Smith are reproduced from his paper. DEATHS FROM TYPHOID FEVER TO EACH 10,000 INHABITANTS BEFORE, DURING AND SINCE THE INTRODUCTION OF SEWERAGE AND WATER SUPPLY. No. of Deaths Per 10,000 1861-59 .5^ B ES 1860-65 1866-73 1874-84 •i 1863-72 "i 1873-85 1863-75 1876-80 aa 1881-84 1851-66 1867-76 1877-84 CQ 1854-73 1873-77 1878-84 o3 a 6^ 1866-73 1874-79 1880-84 "3 1865-69 1870-74 CO 1875-84 1838-58 1 1859-65 1866-84 1850-70 ^ 1870-80 " 1881-84 03 fee 1850-71 1872-75 Ed 1876-83 s 1847-59 1860-69 !B= 1870-84 1846-49 J 1850-59 1860-69 1870-81 CO 1848-62 1867-79 1880-84 -cvim.hio©t-Qoo)2 = 2i22221:2®8N 13.3 2.4 9.3 7.4 1.5 9.2 7.6 2.9 13.0 3.1 10.0 10.3 I 9.3 9.0 9.0 6.6 17.4 (/I 00 rt to ^ m _>, t* , •"5. ^ C/5 Cu UJ 3 1 ■< ;_, H OJ 1 1 ^ rt u >> a '53 z a m Eh Q^ OJ w >, Z ■ZD < UJ "O ^T, S CO en Q o a a: i~ g Z . O 2i fe < CD bo - 1 o ^ rt ^ z CD (D ^ £ - q < y CO CO 2| . 1 i-t o a; 2 Qi O «4- C '" c « E a. a: C-l ■B S| —J O h O q: D Q 4J o -a 2i c n X U (U 1> U u f- Q. O r. -M ndantly supp ompletely se illy very defi < ^ ll°l ■ 1 o = i^ ^- II 1 < CO a ' a ^s '^ "^ S S3 ^ ll-l. O ■(-> ■a t ^ c ■ h^ 'S KH H^ J3 :::::":•::• ui ; : : ^ : : : ; : O : ; J ® c Q 0. 0. - D D C ■ w : : : H : : : : : D : : O lies of Gro ties of Gro to infectic LOCALl W YORK . . OOKLYN .. STON z z '■ < : a < > T. LOUIS.... HICAGO INCINNATI. EMPHIS (Te ARSEILLES, OULON APLES ALERMO AURIU T. PETERSU RUSSELS... RESLAU .... ONSTANTIN < Q '^ ■— c 1 W B! O O iJ W O U Q^ j3 XI o 1 z oa oa J o II z c/iuoSShZcuS^axu < ggggg g CO «o tc ?D »;5 *.■? tc CO o «o ift :r i.'S cD?o?o:o?ospw:ocoa3:o:;iC o X3 30 CO X' OO X) xxooooxxXaoacxxgx '"^ ^^ f— 1 a 1 II 34 THE SEPARATE SYSTEM OF SEWERAGE. Schenectady, N. Y., was sewered in 1884. The Health Of&cer, H. C. Van Zant, in his report for 1887 writes as fol- lows: "I remark this fact: in 1883, twenty-six deaths occurred from typhoid fever; 1885, eighteen deaths occurred from the same cause; 1887, five deaths are recorded as produced by typhoid fever. More deaths in 1883 than cases in 1887. The inference is easy." The desirability of the removal of filth from cities is no longer a matter of doubt. The beneficial effects of a proper system of sewerage is proven by abundant statistics. The results are shown in a decrease of disease, a lowering of the death rate, and in turning plague smitten cities into health- ful ones. The question no longer is, shall it be done? but, how shall it be done? Systems in Use. — The different systems for the removal of excrement and liquid refuse may be divided into three classes, viz.: by "Direct Removal," by the "Pneumatic Sys- tem," and by "Water Carriage." Under the head of "Direct Removal," the principal methods are the "Pail System" and the "Dry Earth Closet." In the Pail System the excreta is caught in a pail or tub and removed in carts at intervals, varying from one day to a week. This system is used in many large cities in Europe, and is advocated by eminent authorities. But the exchange and cleansing of the pails need to be enforced by such strict police regulations as would be difficult to carry out in the United States. There are several modifications of the Pail System. In one, the fluids' are allowed to filter through a sieve and run off into the sewers provided for the storm water, so that only the solid matter is carried away in the carts. In another, the tub is lined with some material, which acts as an absorbent and deodorizer, as in the Goux system. When the Dry Earth Closet is used, dry, powdered earth, or ashes, is added to the excreta in sufficient quanti- ties to absorb the moisture and deodorize the whole mass. So much care and attention is necessary to provide a proper CHAP. I. INTKODUCTION. 35 supply of dry earth, to apply it properly, and to attend to its removal, that it can only be used in exceptional cases, and cannot be relied upon for g^eneral use. To obviate the difficulty of the frequent exchang-es and constant supervision necessary to the successful operation of the Pail System, water-tig-ht cess-pools are sometimes used. They are made larg-e enoug-h to hold the sewag^e for a considerable time and when filled, the sewag"e is carried away. The nuisance of emptying- them is somewhat abated by the use of a larg-e air-tig-ht iron tank, mounted on wheels. The air is exhausted from the tank, and by making- a pipe connection between the interior of the tank and the sewag-e in the cess-pool, the contents of the cess-pool are forced by atmospheric pressure into the tank; or, the sewag-e may be pumped from the cess-pool into the tank. The three principal "Pneumatic Systems" are: the "Liernur, " "Berlier, " and "Shone." The Liernur and Berlier systems consist essentially of a network of air-tig-ht iron pipes, throug-h which the excremen- titious matter is drawn, by exhausting- the air from the pipes by means of larg-e air pumps. These systems are intended to dispose of only that part of the household wastes which is most valuable for manure. Separate conduits must be provided for the foul liquid wastes from dwelling-s, factories, etc. The necessary plant and appurtenances are very expensive, and even then these systems only partly answer the purpose of sewers. The prominent feature of the Shone S3'st€m is the use of compressed air for the purpose of raising- sewag-e from a low level to a hig-her one. It is especially valuable in towns where sufficient fall for sewers cannot be obtained. In this plan, the sewage is conducted throug-h pipes in the ordinary wa}" until it becomes necessary to carry it to a higher level. It then flows into a larg-e iron tank, called a "Pneumatic • Ejector." (See cut.) When the Ejector is full, compressed 36 THE SEPARATE SYSTEM OF SEWERAGE. air is automatically applied to force the sevvag-e into pipes at a hig'her level, when it is ag"ain allowed to flow onward towards the outfall under the influence of g-ravity, or directly through a discharge pipe to the point of outfall. Shone Ejectors ma}' also be utilized to deliver the sewag^e from an outlet below low water level. The air is com- pressed by steam or water power, at a central station and is led by pipes to the Ejectors, so that they can be placed in any convenient situation, and as frequently as the case may require. CHAP. I. INTWODUCTIOX. 37 In many instances the air compressing' machinery is located at a water pumping- station, and thus the wag-es of special attendants necessary to operate an ordinary sewag"e pumping" station obviated. The Shone Ejector takes the place of a pump for raising- sewag-e, and can be used with great advantag^e in situations where it would be difficult to bring- the sewag-e to one pump- ing- station. The Shone S3'stem is extensively used in Eng-land. In this country it is in operation in Chicago, Winona, Minn,, Worcester, Mass., Lynn, Mass., Fair Haven, Mass., Ithaca, N. Y., White Plains, N. Y., Charleston, S. C, Portsmouth, Va., Far Roc ka way, L. I., etc. All of the systems of direct removal require constant care and attention, and only partially accomplish the end in view. They are better than no system, but are not as effi- cient or as easily managed as the method of "water car- riage" or sewerage. Water is the great scavenger. It cleanses our houses, our clothes, our food, and ourselves; and having once been soiled it must be gotten rid of. In doing this, the water may be made the vehicle for carrying away excrementitious matter, which would, by putrefaction, vitiate the air and tend to produce disease. In the Pneumatic Systems costly machinery is neces- sary to provide for carrying away only a portion of the refuse which should be disposed of, and the expense of ope- rating is large and constant. The Water Carriage System is most favored by the leading English, German, French and American sanitarians. "As ordinarily managed, the earth closet and all other conservancy methods become a nuisance, only to be tolerated when sewerage proper cannot be secured." — h-win F. Smith. "I do not say that a well managed conservancy system is not better than a badly managed one, nor far better than no system at all, nor do I say that there are not places where the difficulty of carrying out a Water Carriage System is not so great as to be almost, if not quite, insurmountable; but I do say that in towns where a Water Carriage system is possible, there is no room for choice in the matter." — Corjield 38 THE SEPARATE SYSTEM OF SEWERAGE. In the Water Carriag^e System, all that is needed is a comparatively inexpensive conduit which provides for all of the sewag-e; and if properly constructed the cost of mainte- nance is trifling-. There are many cities which have provided themselves with an abundant supply of water, and yet have made no provisions for a system of sewers. Increasing- the water supply without providing- for its outflow after it has been fouled, only makes a bad matter worse. The number and size of the cess-pools must be increased. Instead of drain- ing- the soil, as common sense would dictate, additional water is poured into it by the millions of g-allons, and year by year the soil is more thoroug-hly soaked with sewage. The streams of filthy water which may be seen running- in the open drains, leading- from back yards into the streets, tell a story which all can read, and the effects of this state of affairs can be plainly seen if the Health Officer makes full reports. One of the twelve tasks imposed upon Hercules was to cleanse the stables of Aug-eas. In these stables vast herds of cattle had been kept for many years, and they had never been cleaned. He accomplished the task by turning- a stream of water throug-h them. This famous exploit — "cleansing- the Aug-ean stables" — is repeated over and over again wherever abundant water supply is supplemented b}^ thoroug-h sewerag-e. Had Hercules only planned to bring- the water into the stables and made no provision for its out- flow, the project would have been a miserable failure, and the sensible people of that day would have called Hercules a fool; and yet there are cities even in this enlig-htened ag-e, where such a plan has been pursued. "The yearly discharge from the sewers of Brooklyn equals in volume what would fill the entire streets and avenues of the city to a depth of twelve feet above the pavement or three feet over every parlor floor in the city. Such is the amount of work silently going on beneath our feet, of which we take no note save when it is interrupted "—Adams. CHAPTER II. WATER CARRIAGE SYSTEMS. A theoretically perfect sewer would be one in which all of the sewag"e would be carried rapidly to its outfall outside of the city, so that no time would be g^iven for decomposition. The conduit itself should be smooth, impervious to water, and should be water tig"ht throug^hout its entire length. It should be flushed at intervals, and so thoroug-hly that the development of any considerable amount of sewer gfas would be impossible. It should be so well ventilated that the small amount of sewer g-as which mig-ht unavoidably be g'enerated in the sewer would be so diluted with fresh air as to be rendered harmless. It should be provided with ample means for inspection and repair. It should be automatic in its action, so as to require the least possible amount of care and attention. One of the first questions which presents itself to the eng-ineer in planning- a system of sewers is, whether the sewers shall be made larg-e enoug-h to carry the storm water as well as the sewag-e, or the sewag-e only. When a system of sewers is desig^ned to carry both the storm water and the sewag"e, it is called the "Combined System." When the sys- tem is desig-ned to carry only the sewag^e proper, that is, the liquid refuse from dwelling's, factories, etc., it is called the "Separate System." The Combined System. ^ — The largfe sewers of the Com- bined System are usually built of brick. The brick beings porous, allows more or less of the sewag'e to escape into the 40 THE SEPARATE SYSTEM OF SEWERAGE. soil, even if every joint is water-tig^ht, which is never the case. The roug-h surface of the bricks soon become covered with a slime of organic matter, which is constantly decom- posing". In desig-ning- sewers on this system the size will be determined mainly by the amount of rainfall per hour during storms, and the surface to be drained. The volume of rain- fall to be provided for is so much more than the sewage, that the amount of sewage scarcely enters into the computation.* It is readily seen that ordinarily the sewage will be but a trickling- stream in a sewer large enough to carry the storm water. At the street corners are catch-basins into which the storm water passes on its wa}" to the sew^er. Here the sand and rubbish, carried along by the current from the street, is supposed to settle and remain in the basin, while the water passes through a trap into the sewer. In the rush of water during a storm, however, a considerable quantity of the material which is supposed to remain in the catch-basin is carried on into the sewer, and this, with other foreig-n substances, introduced into the sewer either by accident or malice, settles on the bottom. These obstructions form a series of small dams in the sewer, and in dry weather the sewage stands in a succession of pools along- the sewers, decomposing and sending volumes of sewer gas out of every crevice through which it can escape. The great size of the conduits of the Combined System, it is seen, is detrimental to their efficiency in removing- sew- ag-e rapidly and completely; and yet, for the purposes for which they are supposed to be designed, they are seldom large enough. Even where vast sums have been spent to construct the Combined System of sewers, it is seldom, if ever, that they will carry the water of great storms. In man}' cities — notably Chicago and London — where money has been poured out without stint, and millions of dollars have been expended for sewers of great size, the extraordi- *See chapter specially devoted to this subject. CHAP. II. WATKK CAWKIAGP: SYSTIOMS. 41 nary storms are not provided for, and the consequence is that the sewers overflow, and cellars and basements are flooded with sewag^e. Where the storm water is excluded from the sewers, or only a definite amount admitted for the purpose of flushing-, no such disaster can occur. The difficulties of properly flushing- and ventilating large sewers are almost insurmountable. Manv devices have been proposed for ventilation. Some have advocated hig-h chimneys with a fire in them to produce a draught. Oth- ers, a shaft with a screw or fan, for producing a current. None of these plans have proved efficient, and there seems to be no way of disposing of the g-as except to let it out into the street by openings from the sewer to the pavement. In any dry season, when there is the least amount of sewage and, therefore, the most sluggish flow and the greatest evolu- tion of gas, the water evaporates from the catch-basin trap and there is nothing to hinder the escape of gas into the streets. The catch-basin itself, unless kept clean, soon becomes a cess-pool, charged with filth from the streets and gutters, which soon decomposes. The flushing cannot be very thoroughly accomplished, owing to the rough interior surface of brick sewers, and to the large amount of water necessary in the large sewers. The most that can usually be done is to produce current enough to carry forward and out of the sewer the solid mat- ter and rubbish, which would obstruct the flow of the sew- age. Sometimes the sewage itself is stored up until a suffi- cient volume is collected to flush the sewer, when it is released. These points are so well brought out in the annual report of O. W. Wight, A. M., M. D., Health Officer, Detroit, Mich., to the Common Council, that we quote quite fullv from his report: "Ditches, gutters, tiles and porous brick conduits for removing surface and subsoil water are comparatively cheap. It adds immensely to the cost to trans- 42 THE SEPARATE SYSTEM OF SEWERAGE. form water drains into sewers, so as to make them at all fit to convey liquid wastes. The combined expense of a separate drainage system and an inde- pendent sewer system, is much less than the expense of a single system that cannot be so constructed as to perform well the double service of removing water from the soil and liquid from habitations. "In most places it is not difficult to find a proper out-fall for the water of a drainage system. As soon as sewage is mixed with the flow of drains the whole mass is contaminated, and the trouble and cost of securing a safe out-fall are, as a rule, greatly increased. The necessity of pumping vast quantities of rain water and subsoil water, mingled with the liquid refuse of houses and fac- tories in the same system in the new sewerage works of Berlin and Dantzic, increases the running expenses to an extent threatening failure. "The sewage proper of a city is nearly a constant quantity. It is approxi- mately measured by the amount of water daily used in houses and factories. Consequently, the engineer in constructing a system for the removal of sewage proper, can adapt it to a constant flow and make it self cleansing. On the con- trary, rain-fall is an immensely variable quantity. A drainage system for its removal must be of maximum size. When sewage, therefore, is turned into the drainage system, a slow flow will be inevitable much of the time, resulting in putrefaction and the generation of sewage gas, the presence of which, within the area of inhabited places, dangerously violates the mcst vital law of sanitation. "In the drainage system all conduits are purposely made to let water in. The object is to convey water away from the soil But a porous drain will strain sewage through into the earth, and gradually pollute it. Consequently, a conduit for the conveyance of sewage must be made tight. Hence the abso- lute incompatibility of the two ends sought in the same structure. A good sewer is a bad drain. A good drain is a dangerous sewer. Attempts are con- stantly renewed to attain the double quality of perviousness from without and imperviousness from within, with unceasing and inevitable failure. Sanita- rians who are quacks in engineering have tried it in vain; engineers who are quacks in sanitation have tried it equally in vain. Quacks in both engineering and sanitation, sometimes well represented in City Boards of Public Works, obstinately keep up their search for the unattainable, like the seekers for the philosopher's stone and the inventors of perpetual motion. "Water stored in cisterns is almost invariably poisoned by the way of overflow pipes which discharge into the sewer system of inhabited places and return the dangerous gas. And the drain pipes from cellars and basements generally furnish avenues through which this invisible foe of human life in cities finds easy ingress to habitations. A separate drainage system affords an easy means of guarding against peril from such a source Sanitary inspectors are often astounded by finding a tube from an ice box, in which choice and del- icate food, like meats and milk, is kept, running directly into a sewer pipe. CHAP. II. WATKK CAKKIAGK SYSTEMS. 43 The combined sanitary and engineering quack will tell you, with pitiful igno- rance, that the deadly sewer gas is kept out by means of a little water trap through which a baby could blow with a straw. A separate system, used exclusively for sewage, is the only certain safety against such danger. "With the clumsy, costly, perilous Combined System in general use for removing water and sewage together, the earth of towns gradually becomes infected with organic matter in a state of putrescence. Hence the water of springs and wells at length becomes polluted and unfit for use. With a sepa- rate, properly constructed and properly managed system of impervious pipes for the removal of all sewage, and with other sound sanitary regulations for the care and removal of solid organic refuse, there is no reason why the spring water and well water in towns should not remain clean and wholesome. Besides, when the earth of inhabited places is kept so clean as to preserve the purity of the water, no exhalations will arise from it deleterious to health and dangerous to life. "This is not the place to describe in detail the separate sewer systems for the removal of liquid organic wastes from inhabited places. The engineer must conform to the requirements of sanitary science. Any system will be faulty which allows sewage to putrefy at all, either in its source, on its journey from human abodes, or in its outfall. * * * * The great principle to be kept in view is the removal of sewage (not sewage diluted with vast quantities of surface and subsoil water) without pollution of the soil, without putrefac- tion, and consequently without generation of sewer gas on the journey. * * * The soil where man dwells is sacred, and it is sanitary sacrilege to pollute it. He who fouls the air that he breathes himself, or the water that he drinks, or the food that he eats, is a barbarian who might learn wisdom from the cat or decency from any swine not demoralized by contact with man. He who fouls the air that another must breathe, or the food that another must eat, or the water that another must drink is a criminal, to be classed with those who maim and kill. "There are more reasons for such care in the removal of organic wastes from inhabited places than appear on the surface. The chemistry and hygiene of putrefaction are complex, involving many practical considerations. Wher- ever there is a collection of putrefying organic matter, whether on the ground, in the ground, within a faulty sewer, or under a habitation, there is a tireless foe to health and life. Not only are putrescent collections of garbage, decay- ing vegetables, manure, offal and human excreta harmful in themselves, by reason of exhalations poisoning the air and leeching liquids polluting the earth; they are also depositories and multipliers of disease germs. Such collections may not produce infectious diseases dd novo, but they lessen the vitality of peo- ple living in the neighborhood, and thereby lessen the power of resisting epi- demics. It is a well known pathological fact that nature struggles to eliminate 44 THE SEPARATE SYSTEM OF SEWERAGE. disease by excretory processes. Accumulations of filth containing excreta may, therefore, harbor seeds of various communicable maladies. Sewer gas, while it may not beget scarlatina, diphtheria, smallpox and other contagious diseases, easily becomes the vehicle of conveying them, through obscure and intricate channels. * * * a foul sewer, swarming with scarlatina germs, may be more dangerous to a neighborhood than an infected school-house. * * * "It has been objected in relation to separate systems for drainage and the removal of sewage, that droppings of horses and other animals in the street, steeping in the rain-fall, will be a source of pollution to surface water, render- ingQit putrescible, and consequently, capable of generating sewer gas. The simple and effective remedy is cleaning the streets frequently and well. Most cities would thereby be greatly improved, both in appearance and salubrity. "It has also been objected, that, in quarters where the vitrified sewer pipe system for the removal of sewage does not extend, there the inhabitants must throw the liquid wastes of household life upon the gro.und. No such necessity exists. Even an isolated habitation in the country should have its sewer pipes, and entirely separate from the drainage system, to convey kitchen slops, wash- water and other dangerous liquids to a place of safety. The reason why typhoid fever, diphtheria, and some other filth diseases are so prevalent in country districts, is that privy vaults so frequently seep into wells, and animal excreta of pig pens and stables are left to poison the earth and the air. • The ground about kitchens, super-saturated with slops, very often becomes putres- cent in the summer warmth, breeding disease which superstitious ignorance attributes to Heaven. A householder may dispense with his parlor and its adornments, if necessary, but he cannot afford to invite upon himself and fam- ily disease and death by neglecting to provide the means of keeping the site of his habitation dry and clean. Laborare est orare — 'to labor is to pray'^said the wise old monk, and the most effective prayer for health is to supply every needed hygienic device for the sacred home of the family "It is further objected that most of the cities are sewered for the double purpose of removing storm water and sewage through the same conduits, and that we cannot afford to do the costly work over again. It is one of the fates of Progress that faulty methods must be followed by reconstruction. No works last forever, and when we build anew we can do it better. In the meantime the faulty sewers, with their dangerous debauchment into the nearest stream, lakes, or ocean harbor, can be washed out, disinfected, and used exclusively for water-drainage while a supplementary system, with safe out-fall, for the removal of sewage alone, is constructed with proper engineering skill under the direc- tion of sanitary science. The cost of such a supplementary system is not more than one-fourth of that of the prevailing system." CHAP. II. WATICK CAKKIAGK SYSTICMS. 45 Subsoil Drainage. — In some instances it will be neces- sary to lay special drains for the removal of ground water. It will be found, however, that often the strata are so broken up by dig-g-ing" the trench for the sewer and refilling" it, that the level of the g-round water will be materially lowered. This is especially the case when the soil is made up of alter- nating- strata of pervious and impervious material with an inclination unfavorable to the escape of the gfround water. Nothing- connected with desig-ning- and building- a sys- tem of sewers calls for more discretion on the part of the eng-ineer than proper provision for the g-round water. It has frequently happened that long- lines of sewer laid beneath the line of saturation have proved to be practically useless from lack of a proper conception of the influence of g-round water and lack of proper methods for its removal or exclu- sion from the sewers proper. The subject of subsoil drainage will be considered more at leng-th in a subsequent chapter. CHAPTER III. THE SEPARATE SYSTEM. The object of the Separate System of sewers is the com- plete removal of the sewag-e proper from towns, in such a manner as shall best subserve the convenience and health of the inhabitants. To accomplish this object in the most satisfactory man- ner, three thing^s are required, viz.: constant and rapid flow of the sewag-e, thoroug"h flushing", and adequate ventilation. Whatever tends to promote either of these three requirements is advantag^eous to the system and should be adopted. We will, therefore, consider what method of con- struction and combination of appliances will best attain the end in view. It is evident that to increase the size of the sewers, so as to make them larg-e enoug-h to carry the water of occasional storms, would be detrimental to the efficiency of the sewers, inasmuch as the ordinary flow would be impeded and retarded, and thoroug-h flushing- and ventilation made more difficult, if not impossible. In a majority of cases the storm water can, without causing trouble, run in the surface gutters and ditches until it reaches the natural water courses. Only in larg-e cities, where the water would need to run long- distances throug-h the streets, would any underg-round conduits for storm water be necessary. Where this is the case, either the sewer may be sufficiently enlarg-ed for that purpose, or a separate channel may be provided for the storm water. The necessary leng-th of these storm water sewers will, in any case, be but a small fraction of the whole system. CHAP. III. THIC SEPARATE SYSTEM. 47 Roof Water. — On the other hand, if the introduction of a certain amount of roof water into the sewers will insure their thorough flushing- whenever there is a sufficient shower, advantag-e should be taken of such ready means for accomplishing so desirable an end. The object being- not the disposal of the roof water but the flushing- of the sewers, no more roof water should be used than is sufficient for that purpose; and the eng-ineer must carefully determine at what points, and in what quan- tities, the roof water may be introduced. Size and Material. — The discussion in a subsequent chapter of the amount of sewag"e per capita which it is neces- sary to provide for, and the carrying- capacity of pipes, will show that the commonly received notions concerning- the required size of sewers are entirely erroneous. In a majority of cases the people's money is spent in building- larg-e sewers, when smaller ones would be more effi- cient and cost very much less. Having determined the amount of sewag-e to be provided for, and the size of conduit necessary, the next step is to determine the material for the conduit. Up to 18 inches in diameter the best material is g-lazed, vitrified, earthenware. It affords a smooth surface for the flow of the sewag-e, and is durable and cheap. Above 18 inches, sewers of brick, laid in hydraulic cement are preferable. Flushing. — While the problem of flushings the small sewers of the Separate System is a much less difficult one than that of flushing- the larg-e sewers of the Combined Sys- tem, still the matter is of the hig-hest importance and should receive the careful attention of the eng-ineer. Any of the methods made use of in the Combined System can be more easily employed in the Separate System, as a much smaller quantity of water is required. With the ordinary flow of sewag-e in the pipes a fung-ous g-rowth appears attached to the pipes beneath the flow line. This collects the sediment 48 THE se:parate system of sewerage. and slime from the sewag'e and retards the flow. Even in pipes, which are apparently in g^ood condition, a careful examination will disclose the fact that the surface of the pipe under the sewag^e is foul, and rapidly gfoing- from bad to worse. A rush of water will detach the fung-ous g-rowth, and with it all of the filth which it has collected, and will carry it on to the out-fall. Let any one examine a sewer which has not been flushed for several days. At first g"lance he will, perhaps, see noth- ing" amiss. All seems to be in g"ood order. But then dis- chargee a volume of water into the sewer, sufiicient to nearly fill it for several yards. The flakes of f ung"ous and the black shiny clots of putrefying- org-anic matter, which will be driven along" by the rush of water, will disclose how rapidly the sewers g"row foul with a quiet, even flow of sewag"e in them, and how essential the provision for frequent and thoroug"h flushing". If the rain could be relied upon to come at reg"ular inter- vals, the problem of flushing" would be readily solved. All that would be necessary, would be to provide for the dis- charg"e of the requisite amount of roof water into the sewers. But, unfortunately, there may be weeks without rain, and during" these seasons of drouth some means must be employed to supply the lack of rain water. This may be done in several ways. A flush tank mounted on wheels can be used, and this is available in towns without water works. In towns provided with water works the flushing" can be done directly from the water pipes, or by means of automatic flush tanks. Ventilation. — The ventilation of sewers has always been a difficult problem for the eng"ineer, and especially is this the case where the Combined System is used. In the Separate System, properly constructed, and where ample provision is made for flushing", the problem is much simplified. If only fresh, running" sewag"e is found in the sewers, and there is. CHAP. III. IHl'; SICPAKATIO SYSTICM. 49 no place where the sewag"e can stag"nate and decompose, there will be verj' little sewer g-as developed. If, in addition to this, the sewers are reg'ularl}'^ and thoroug-hly flushed, the air in the sewers will be so frequently chang-ed that there is less to be feared from them on account of sewer gas, even without an}^ special arrangement for ventilation, than from the Combined System with the most elaborate appliances for ventilation. Besides the ventilation secured on the street lines through the man-holes, lamp-holes and flush-tanks, a still more effective means of ventilation may be obtained by carrying- the pipes of the house drains, untrapped, up above the roofs of the houses. We quote the following from Dr. Alfred Carpenter in \\\Q. Journal of the Society of Arts: "If a sewer flushes clean, as it ought to do; if it does not become the habitat of sewerage confervoid growths upon its invert; that is, if it is regularly scoured above, as well as below the line at which the sewage ordinarily runs; if there is nothing to intercept the passage of sewage from its origin to its depart- ure at the outlet, then there will be no sewer gas, there will be no stink, there will be no danger to anybody. "The openings on the inverts of the arch of the street sewer will be inlets for fresh air, and the ventilators produced by the extension of the soil pipe of every water-closet above the level of the house top will be outlets for the air which has passed through the sewer. Thus a constant circulation will be pro- moted at all times by the ordinary laws which belong to gases, and which by their very nature prohibit stagnation in fluids of all kinds. Occasionally there may be down draughts, but they will be of no more moment than the down draughts through an ordinary chimney— indeed they will be as infrequent as a down draught into a furnace when the fire is low. Fresh sewage is not danger- ous to anybody, but if it is kept within the curtilage of the dwelling house by means of interceptors, or if it be allowed to stagnate in a badly constructed sewer until fermentative changes have arisen within its substance, it then pro- duces the chance of evil; but in the present day no authority ought to be allowed to keep sewage within its borders until such a change has taken place. It should be "moved on" out of range as rapidly as possible. The house is the unit of sanitary work, and it is wrong for selfishness to assert itself so as to determine that no man shall assist the local authority in its duty to provide for sewer ventilation. 50 THIC SICPAKAIK SYSTKM Ol" SKWIOKAGK. "I utterly object to the principle which is being tried to be established by various supposed authorities, viz.; that the duties of the individual are antago- nistic to the duties of the local authority in the matter of sewers. If each unit does his part, the duty of the local authority as to ventilation is simple. The latter has to convey away the sewage, and provide inlets for fresh air. The outlets must be at the highest points, and if they are so placed, there will not be a particle of danger from the production of sewer gas. An authority has an important duty to perform, viz.: to prevent the production of sewer air, as a major part of its work. The provision for its escape, if it does accidentally form, will be best met by details in the construction of the house drain. Con- centration should not take place, and without concentration sewer gas is per- fectly harmless. There will be no diffusion of eathetic germs, for they cannot live in fresh air long enough to spread infective disease, and if, perchance, a few should be discharged in the higher regions above the heads of a great or small community, they die in a very few seconds "The germs which produce enthetic disease cannot live in fresh air, an\ more than a fish can live in unaerated water. If discharged, they should be diffused above the heads of the people, and not at the street level. These are my reasons for advocating the extension of every soil pipe, so that each water closet has a ventilator in action, and by this means properly constructed sewers will admit fresh air at the street level; and under common conditions, foul air, if produced, will escape, where it will fail to set up even the smallest possible danger. I advocated this principle twenty years ago, and experience, since my first paper upon this subject, has imply proved that I am right." There are two methods of carrying- out the plan advo- cated by Dr. Carpenter. One is by carrying- the soil pipes up throug-h the house so that they may serve also as venti- lating^ pipes, and the other is b}' carrying- a separate venti- lating- pipe up on the outside of the house. Both of these plans will be considered in detail in a subsequent chapter. Special Features. — The Separate System of sewerag-e is not new and untried. It has been advocated by sanitary eng-ineers for nearly half a centur}', and the arg-uments for its adoption have been presented in many forms. It was lirst used in Eng-land. It is in successful operation in many towns in the United States, and is rapidly g-rowing- in popu- laritv as it is better known and understood. CHAP. III. rillO SKFAKA'IIC SYSTIOM. ,> 1 The separation of sewagfe proper (house sevvag-e) from the storm water falling- on pavements, roofs, areas and lawns has been much more complete in the United States than in Eng-land. The plans employed in the diiferent cities where it has been adopted are similar in g-eneral design, but differ in the details. The different conditions met with in the different localities would require a certain amount of variation, and each eng-ineer has followed his own methods for solving- the problems which presented themselves. The following- examples will show how the plans vary in different places: In the sewers of Memphis, Tenn., desig-ned by Geo. E. Waring-, Jr., all storm water was excluded, and a Field's flush tank was placed at the head of each branch sewer. The sewers are ventilated throug-h the uritrapped interior house drains and ventilating- pipes. Man-holes were g-ener- ally omitted. Drain tile was laid in the same trench with the sewers. In the sewers of Pullman, 111., desig-ned by Benezette Williams, C. E., the sewers are flushed by connections with the water mains, and the house drains are flushed b}^ auto- matic flushing basins. Man-holes were placed 160 feet apart on the mains and 200 feet apart on the laterals. In the sewers of Bing-hampton, N. Y., desig-ned bv Rudolph Hering-, roof water is used for flushing-, and in part of the system the sewers are made larg-e enoug-h to carry the storm water. The details of the plan adopted for the sewers of Sche- nectady, N. Y., and the methods employed in their construc- tion are similar to those described in the subsequent chap- ters. A Van Vranken flush tank is placed at each dead end. The sewers of West Troy, N. Y., are mainly the Sepa- rate System. Certain portions of the city, however, are relieved from storm water throug-h main sewers, which also serve as mains for the Separate System. Certain portions of 52 THE SEPAKATK SYS T KM OF SEWERAGE. the city where the volume of ground water was larg-e are also relieved by tile drains. These are ordinarily laid paral- lel with the sewers in the same trench and in most cases dis- charg"e into rnan-holes.* In the city of Dayton, Ohio, the sewers are mainly on the Separate System as shown by the map on a subsequent pag-e. The storm water is removed mainly throug-h surface g"ut- ters. In some cases, however, there are underg-round con- duits. The sewers of the Separate System in Dayton var}^ from forty-two inches in diameter to eig-ht inches in diameter. Man-holes are placed at all junctions and on long- blocks one is usually placed midway. All dead ends are provided with automatic flush tanks. A considerable portion of the city was formerly subject to overflow from which it is now protected by a levee. The entire system of sewers on the east side of the Miami river converge at a point near the levee at which there is a pump- ing- station of a capacity of about twenty million g-allons per day. The sewag-e is at present discharg-ed into the Aliami river. The pumping- station, however, commands consider- able area of low lying- land which, should future conditions dictate, can be utilized as a sewag-e farm. It is evident that the Separate System is especially appli- cable where, for any reason, sewag-e must be pumped; or where it is to be purified by any of the many processes for that purpose; or where the sewag-e is utilized on a sewag-e farm. In all of these cases the exclusion of the storm water from the sewag-e g-reatly reduces the attendant expense of the process. Among the many advantag-es in favor of the Separate System, the one which appeals most strong-ly to the averag-e citizen is that of reduced cost. This is the arg-ument which reaches the heart — t)r, what is quite as necessary, the pocket See map of West Troy. CHAP. III. THIO S1-:PAKAT1'; SVS'lIOM. 58 — of the tax-payer. One of the grave objections to the Com- bined System is its cost. The actual cost of such systems has been from S2.O0 to SIO.OO per foot. The cost of the Sep- arate System has varied from 75 cents to $2.00 per foot. It is" safe to say that under ordinary circumstances its cost will be from one-eig"hth to one-third of that of the Combined System. It may be asked why the Combined System is still adopted in so many cases, if the advantag"es of the Separate System are so apparent. The answer to that question is, that engineering- precedent carries g-reat weight with it among- eng"ineers, and a venerable error, even, is hard to put down. The Combined System is one of natural growth. In cities the natural water courses are covered over and con- verted into sewers, and branches are built leading into them. Then the branches are extended, until they form a complete system of sewers. You can see the beginning of this system in almost any town which has a small creek running through it. The creek will be parth' arched over, and branch drains will be constructed leading- into it, long- before the subject of sewers is brought up for consideration. When the matter does come up, the chances are that the system already beg-un is simply extended and completed, and another bad precedent is set, which makes the introduction of the better system more difficult. Although local conditions and considerations of economy may in some cases make it the part of wisdom to combine storm water and house wastes in the same conduits for removal, the attainment of perfect house drainag-e cannot be furthered by so doing-, and quite likely will be jeopardized. Nothing- interfering- with the utmost attainable perfection in the sanitary condition of the drains connected with the inte- rior of our dwellings should be allowed. If sub-surface con- duits for other purposes than house drainage, and not so 54 THIC SKPARATK SYSTKM OK SliWKHAGK. connected, are less perfect in their sanitary condition (and from the inconstant nature of their use they must be), it is a matter of less importance; since opening- into an unconfined and widely circulating- atmosphere, any noxious g-ases are in so much g-reater deg-ree diluted and rendered innocuous. The introduction of the Separate System marks an im- portant era in the development of sanitary drainage, recog^- nizing-, as no other system has, the prime importance of an early removal of household and industrial wastes, which are the main factors in soil pollution. That it will best meet the requirements of all larg-e and densely populated cities (econ- omy considered), is not probable. That, under competent advice, it can meet the requirements of house drainage more perfectly in any city than the Combined System, cannot be denied. It is peculiarly adapted to many of the numerous smaller cities, which have been practically debarred from sewerag-e by its cost, and to outlying- portions of larg-er ones. Its comparatively small cost permits an early and g-eneral extension, and the removal of domestic wastes before the soil has become saturated with them beyond a reasonable hope of iiuritication. The wid^ application which can be made of this system will be apparent upon an examination of the following- classi- fication of the cities and towns of the United States. The table classifies all the cities and towns of the United States of S,()()0 inhabitants and upward by the number of inhabi- tants as g-iven in the census of 18*.»0. The census returns also illustrate the increasing- tendency toward the ag-g-reg-a- tion of population in cities where sanitary works are imper- ative. "In the published records of former censuses urban population has been defined as that element living in cities, or other closely aggregated bodies of poptilation. containing 8,000 inhabitants or more. This definition of the urban element, although a somewhat arbitrary one, is used in the present discussion of the results of the Eleventh Census in order that they may be compared directly with those of earlier censuses. The limit of 8,000 inhabitants is, how- CHAP. III. 'PHio sioPAKA'iic systi:m. ever, a high one, inasmuch as most of the distinctive features of urban life are found in smaller bodies of population. Recognizing this fact, the discussion of the urban class was in 1880 extended in part to include all such bodies of pop- ulation down to a limit of 4,000, a precedent which will be followed in the more extended publications of the Eleventh Census "According to this definition the urban population of the country in 1890 was 18,235,670, the total population being 62,622,250. The urban population constituted in 1890, 29.12 per cent, of the total population. Corresponding fig- ures for the several censuses are given in the table opposite. "It will be seen that the proportion of urban population has increased gradually during the past century from 3.35 up to 29.12 per cent., or from one- thirtieth up to nearly one-third of the total population. The increase has been quite regular from the beginning up to 1880, while from 1880 to 1890 it has made a leap from 22.57 up to 29.12 per cent., thus illustrating in a forcible manner the accelerated tendency of our population toward urban life." TABLE I. I'RB.AN POPULATION" OF THE UNITED ST.^TES. CENSUS YEARS. 1790 1800. 1810. 1820. 1830 1840. 1850 i860. 1870. 1880. 1890. Population of the United States 3,929,214 5,308,483 7,239,881 9,633,822 12,866,020 17.069 453 23 191,876 31,443.321 38.558.371 50,155.783 62,622,250 Population of cities 131.472 210,873 356,920 475.135 864,509 1. 453.994 2,897,586 5,072,256 8,071,875 11,318,547 18,235,670 Inhabitants of cities in each 100 of the total population. 3 35 3 97 493 4 93 6.72 8.52 12 49 16.13 2093 22.57 29.12 56 'l'Hl<: SI2PAKATK SYSTIiM OF SEWKRAGE. "The following table shows the number of cities classified according to population at the date of each census. TABLE II. CITIES CLASSIFIED ACCORDING TO POPULATION. a > 3 a O d n H 12,000 to 20,000. 0" d I 40,000 to 75,000. d 80 o_ 'loo 250,000 to 500,000. d 1790 . 1800. . 6 I 3 I 6 I 3 I I81O 4 3 12 2 3 2 2 1820 13 26 4 7 1 1 2 2 1830. . 1840. . 1850. . 3 10 I I 2 * 44 85 17 36 I 3 3 I I 20 14 7 3 I r i860. . 141 62 34 23 12 2 5 I 2 1870. . 226 92 63 39 14 8 3 5 2 1880. . 286 1 10 76 55 21 9 7 4 3 I 1890. . 443 173 105 91 35 14 14 7 I 3 According' to the census of 1880 about seven-eig^hths of the cities of the United States C^OT) had less than 25,000 inhabitants. It is probable that most cities of less than 4,000 inhabitants, and many that have 8,000 inhabitants do not require an extensive system of sub-surface removal for storm water, and that in the fev^^ remaining- the sj^stem of conduits for sub-surface removal may be very limited. It is also probable that a ver}' small percentag'e of these cities of less than 8,000 inhabitants have a comprehensive plan of sewag^e for the removal of house wastes. The g^reat CHAP. III. THIO SICPAKATl-; SYSTIOM. .) ( majority of them are doubtless expending- what little capital they devote to this end, both public and private funds, in a wav that will not contribute, ultimately, toward a harmoni- ous system and consequently to a g^reat extent wastefully. In view of these facts and the statistics of the census bureau quoted, it becomes apparent that the Separate Sys- tem of se^verag■e must be widelv extended. CHAPTER IV. PLANS. In desig-ning a system of sewers for a town, there are several thing's to be taken into consideration before deciding- upon the plan to be adopted. The principal points to be considered are: the size of the town, its situation with refer- ence to the disposal of sewage, the compactness of its build- ings, its topography, its water supply-, the character of the soil, the sanitary habits of its citizens, and its financial con- dition. The amount of sewage in any town will depend upon the number of its inhabitants, their habits, and the abundance and convenience of the water supply. In a town without a public water supply, the amount of sewag"e per head will be much less than where water is abundant. With the intro- duction of water works comes the multiplication of water closets, and a rapid increase in the use of water for baths and various household purposes, and the amount of sewage will rapidly increase. The volume of sewage to be provided for, in any case, maA' safely be taken to be equal to the vol- ume of water used. Sewage Disposal. — The disposal of sewage is a problem of the highest importance. When sufficient fall can be obtained, the sewage is usually carried by gravity to the nearest stream, or large body of water. The effect of sew- age pollution on streams and lakes is a question which is rapidly growing in importance as our population grtnvs more dense, and more towns are sewered. In the older countries of Europe the pollution of water courses by sewag^e has forced itself upon the attention of CHAP. IV. PLANS. ,5i» g-overnment officials, and string-ent laws have been passed to protect the purity of streams. In this country the time is not far distant when the pollution of streams and lakes bv sewage will need to be forbidden by law, or in many localities pure drinking- water, in any considerable quantities, will not be obtainable. The State of Massachusetts, some years since, took steps in this direction throug-h "An act to protect the puritv of inland waters." Several other states have followed with like enactments. In many cases there is no available out-fall for the sew- ag-e, and the question of its disposal comes up at once with the inception of sewer projects. The methods for purifying- sewag-e by chemical pro- cesses are many and various. The object of these processes is to so purify the sewag-e that the water may be turned into the streams. The residuum is used as a fertilizer and for v^arious other purposes but is practically valueless in its crude state. Wherever the rig-ht kind of land is available, the sewag-e may be used for irrig-ating^ crops, and this has been successfully done in manv cases. Sometimes a town site is so flat that sufficient fall cannot be obtained to carry off the sewag-e. In this case the sewag-e may be pumped, or raised by Shone's System. Storm Water. — In towns where the houses are at con- siderable distances apart, and no very larj^e proportion of the surface is paved, the storm water will usually be easily dis- posed of without providing- any underg-round channels for it. But in larg-e cities compactly built, where the g-reater part of the surface is paved, and where the water would need to run in the streets for long- distances to reach an out-fall, provis- ion must be made for the storm water. This may be done by enlarg-ing^ part of the sewers so as to carry the surface water as well as the sewag-e, or by constructing- special con- 60 THK SEPARATE SYSTEM OF SlCWIiRAGP:. duits for the surface water. These special conduits may, in most cases, be very much shorter than the sewers, as the storm water can be delivered into any natural water course within the town, while the sewag"e must be carried entirely out of the town. In every town problems will arise peculiar to the circumstances in each case; and the details of the plan best adapted to any g^iven requirements must be worked out to suit the conditions of that special case. The Preliminary Survey. — Before any definite plans can be determined upon, a careful topog"raphical survey must be made. A study of a reliable map of a town, with the heights of the street corners and points at changes of slope noted on it — or, better still, with the contour lines drawn on it — will enable the engineer to determine approximately what g-rades are available for the sewers; the best lines for the mains; and will enable him to so desig^n the laterals as to lead the sewag^e by the most direct route to the out-fall. These approximate calculations can then be tested by final computations made from the diagram in Chapter VI. If there are any defects in the assumptions of inclination made, it will become apparent from the diag"ram when the sizes are determined, and proper corrections can then be made. It must not be forg-otten in determining- the g^rades to be adopted, that a continuous rise along- the crown of the sewer is required for the upward passage of air-currents, as well as a continuous descent along- the invert for the downward flow of sewag-e. To accomplish this, it is necessar\^ when the sewers flowing" into a man-hole are smaller than the outflow- ing- sewers to which they are tributary, to raise the crowns of the former slig-htly above that of the latter. This fre- quently occasions a considerable loss of grade. For exam- ple, if a man-hole having- an eig-hteen inch outlet has a twelve inch and a ten inch sewer tributar}', and to insure a free CHAP. IV. PLANS. 61 deliver}^ at all times we raise their crowns an inch above the crown of the outlet, tfie invert of the twelve inch pipe will be raised above the gfrade line seven inches and that of the ten inch pipe nine inches. This is illustrated in the drawing- of a man-hole, Plate V. Another reason for raising- the inverts of inflowing pipes at man-holes, is, that obstructions are more likely to occur at man-holes than when the sewer has its full circular section, and the increased descent thus secured tends to prevent deposits. A preliminary survey for sewers should include such measurements as will enable the engineer to make a map of the town and profiles of the streets. The lengths and direc- tions of the street lines should be carefullv measured, and levels should be taken at every one hundred feet and at every change of slope of the surface. A datum should be selected and its distance below some well known fixed point in the town be given. Bench marks for levels, and reference points for line should be established at everv street intersec- tion. The establishment of bench marks should be the first xstep in taking the levels, and it should be done independ- ently of the surface levels, as extreme accuracy in the final location of the g-rade line in construction is necessarv in order that portions of the S3^stem which may be constructed separately may be properh' joined. After the terrilor}' is covered with a proper S3'stem of bench marks, which have been carefully checked by cross lines and found to be cor- rect, the surface levels can be taken very rapidlv and with less care, as any error is not carried but is eliminated at the succeeding bench mark. The transit and level notes of the preliminarv survey should be carefully preserved, after they have served their purpose in the preliminary work, as they will serve as a check on the succeedinsf work. 62 TH1<: SEPAKATIC SYSTEM OF SP:WKRAGK. From these notes a map can be made and the contour lines drawn on it (as in the maps shown in front of book), or, the heig"ht of a suflicient number of stations marked on it. The surve}' should also include outlying- portions of the territory which may belong to the same natural drainage basin, and for the storm water of which it may be necessary to provide special conduits. Rough profiles of the streets can now be made, and the grade lines of the sewers laid down on the profiles. The method of determining the proper grades is fully described in the following pages, as also the method of determining the loss of elevation on curves and in the case of a smaller sewer being tributary- to a larger one. Having located the out-fall of the sewers and established its height, it will be best, in determining the grades, to work from the out-fall along the mains to the laterals, as this will show the height at which each junction must be, and what fall is available. Capacity Required. — In designing a system of sewerage, the final question to be decided, and the most important one, is the question of size. It is obvious that proportioning a plant to meet the demands of so inconstant and widely varying a use as the removal of storm water, presents especial difficulties, both as to economy and efficiency, and that, g'enerally speaking, the possibilities of economical construction and service are measured by the regularity of the work. The aggreg'ate yearly discharge of house drainag"e from areas fairly built up is in excess of the entire volume of storm water that ordinarily reaches the street catch-basins. Yet the capacity required for the ample service of house drainage is, approximately, but one-fortieth of that required for, or, more properly, of that usually given to, sewers for the removal of sewaofe in combination with storm water from \ CHAP. I\'. PLANS. 63 streets, g-ullies, roofs, paved areas, etc. In fact, thoug-h rep- resenting" ultimately the g"reater amount of work in the Com- bined System of sewers, it is considered unnecessary to make house drainag"e a factor in computations determining their sizes. (See Adams' "Sewers and Drains for Populous Districts," page 37.) It has, therefore, not been customary or necessary, in designing- sewers of the Combined System, to investigate carefully the statistics of water consumption, either as to its quantity or the varying rate of flow at which it finally reaches the sewers. In designing- a plant for the discharge of house sewage exclusively, a consideration of these ques- tions becomes of prime importance. Size is dependent not only on the qiaiiiti/y of sewage or of water consumed, which in ordinary cases is its measure, but upon the manner in which the water is used and the peculiar habits of the tributary population. A manufactur- ing district may consume and deliver to the sewers its entire quota, amounting to several hundred gallons per diem, per capita, within a few hours, while the sewag"e from a resi- dence district may be distributed over the twenty-four hours at a nearly uniform rate. The quantity of water actually used is but a small per- centage of that wasted, and while the use of water in dwell- ings is intermittent, having ordinarily three maxima, the waste of water is more nearly constant, being- caused b}" leaky and imperfect fixtures or taps purposely left open to secure fresh water or to prevent freezing. Besides the daily variations in sewage flow, there are wide variations on different days of the week, due to the varying daily habits of the people. The maximum weekly flow is ordinarily on Monday. Thus, representing the aver- age daily flow by 100, the maximum rate of flow during an average day may be 150, and Monday having in addition to these fluctuations those peculiar to itself, may have a maxi- 64 THE s1':pakati<; systi<:m oi~ sewkragk. mum rate of flow one-third g-reater, which would be repre- sented by 200; and since the sewers must be proportioned to discharg-e the maximum flow occurring- at any hour during- the week, in this case it should be made to carry twice the averag-e daily flow. Changes of Temperature. — There are also wide varia- tions in water consumption and consequently in sewag-e flow, due to climatic differences and variations in temperature, which are usually too little considered in proportioning- the size of sewers, and particularly of main sewers. In a majority of our cities, the maximum consumption of water occurs during- the winter months, and as it is due to water taps which are left open to prevent freezing-, a gfi'eater percentag-e of the total consumption than in ordinary cases reaches the sewers, and the maximum rate of water con- sumption becomes in still g-reater deg-ree the maximum rate of sewag-e flow. The secondary maximum of water con- sumption, occurring- in summer, is in greater deg-ree used for purposes which withdraw it from the sewers, as in street and lawn sprinkling, etc. It is during- this maximum rate of flow, occurring in the winter months, that sewers are more likely to be subcharg-ed than at any other time, and it should be carefully considered in proportioning- the sizes of pipes in the S3^stem. It is true that it is the result of a waste of water, which is perhaps extravag-ant, and which it mi^ht be better economy to check than to remove by sewerage. Use of Water Increasing. — It is also true that the per capita consumption and waste of water has been g-radually increasing- up to the present time, and is likely to reach still hig-her figures. This increased demand for water has been met by pumping- eng-ines of much higher duty, and by improvements in water works g-enerally, which enable them to furnish water to the consumer at lower and lower rates CHAP. IV. PLANS. 65 per g-allon, commensurate with the increased economy secured. This in turn encourag^es the use of water from the public mains for motive power, as the running- of eleva- tors, motors, etc., and for the thousand and one purposes of lig-ht manufacturing, requiring- the use of power, always ready, and costing- nothing- when not wanted. Rapid as has been the development of water supply- systems in the United States, their capacity has barely kept up with the demands of the people. It is likely, however, that recent developments in the electrical transmission of power and a g-rowing- tendency to conserve the water supply by more rig-id inspection and the g-eneral use of water meters, will tend to reduce the averag-e consumption of water in most cases. CHAPTER V. QUANTITY OF SEWAGE. Owing" to the scarcity and incompleteness of data at present accessible on the actual flow of sewers, and to their unreliability as well, and to the very complete records of water consumption, which are made possible by the use of pumping- machinery, automatically recording- its own per- formances, an investigation and classification of the statis- tics of water consumption will, undoubtedly, be of use in designing a sewerage system. Size is entirely a matter of calculation from data, mainly assumed, as: (1) The extent of the S3'stem. (2) The density of population, or the probable density of population in the near future. (3) The number of gallons of sewerage per diem per capita. (4) The varying rates of sewage discharge. (5) The inclination of the sewers. (6) The smoothness of the interior surfaces of the sewers. Of the above factors entering into calculations deter- mining size, those of extent and inclination only are capable of exact determination. And since, in designing a s^'stem of sewerage for American towns, the element of future growth must be considered, not only by increased density of popula- tion, but by the extension of the suburbs, thus extending the dead ends, and practically converting- what was formerly a lateral into a main, the factor of extent may be considered to have an element of uncertainty. CHAP. V. QUANTITY OK SEWA(il-;. f)7 Upon the accuracy of the assumption made by the eng^ineer, then, in regard to these variable factors entering- so largely into his calculations, will the efi&ciency of the sys- tem mainly depend. The following" statistics of water consumption are given with a view of showing what may be a proper value, for each of these variable factors in ordinary cases. They have been collected from various sources, and a summary is presented in condensed tabular form, convenient for reference. A few statistics of sewage discharge are also presented, but owing to the difficulties previously stated, they indicate the condi- tion of sewage flow for a very brief period only, and admit of but limited application. When examined in connection with the statistics of water consumption they are of increased interest. The consumption of water will be examined in the fol- lowing manner: (1) The quantity of water consumed. (2) Monthly variations. (3) Daily variations. (4) Hourly variations. (5) Variations due to extremes of temperature. (6) Special cases — as, cities using water larg-ely in manufacturing, brewing, etc. In the following tables the standard of comparison taken is the average per diem per capita consumption, which is, for purposes of comparison, assumed at 100, and from statis- tical data the per cent, comparison is made by computation, as this is most convenient for use. The average per diem per capita consumption is that most readily obtained, especially from pumping records of the smaller cities in which records are usually less per- fect, being computed from automatic counter readings. In many records of pumping works, where the supply is com- 68 THE SEPAKATK SVSTKM OF SKWERAGK. pared with the population, the results are misleading-. For instance: in the smaller cities of from 10,000 to 15,000 inhab- itants, while the per diem per capita consumption, based on the total population, is but little below the average, the actual per diem per capita consumption for each person using water from the city mains must be greatly above the average, as the proportionate number of consumers in such cities is frequently below one-half, and, consequently, the sewage flow in proportion to the actual tributary population is disproportionately large. This condition is, undoubtedly, owing to the usual laxity of cities of this class in controlling the use of water, and is corrected as the city increases in population and improves in its conduct of municipal affairs. The water statistics of larg-e cities are often misleading in the other direction, many supplying water from the city mains to their own entire population, and to outlying subur- ban districts as well, which, in many cases, is not stated in published reports. In many cases, also, the per capita' con- sumption in published returns is based upon estimates of population, which are merely guesses and may be wide of the mark. The sewerage of every city presents problems for solu- tion essentially peculiar to itself, and these must be carefully considered. The tables here given, while not strictly appli- cable to certain special cases, will, nevertheless, be a guide in determining their requirements. The Quantity of Water Required. — The following- is J. T. Fanning's estimate for American cities: * "In American cities having well arranged and maintained systems of water supply, and furnishing good, wholesome water for domestic use, and clean, soft water adapted to the use of the arts and for mechanical purposes, the aver- age consumption is found to be approximately as follows; (a) For ordinary domestic use, not including hose use: 20 gallons per capita per day. *From J. T. FanninK's Hydraulic Eiij^ineering, by permission CHAP. V, QUANTITY OK SKWAGIO. 6i» {&) For private stables, including carriage washing, when reckoned on the basis of inhabitants; 3 gallons per capita per day. (f) For commercial and manufacturing purposes; 5 to 15 gallons per cap- ita per day. ((/) For fountains, drinking and ornamental; 3 to 10 gallons per capita per day. [e) For fire purposes; i to 10 gallons per capita per day. (/) For private hose, sprinkling streets and yards; 10 gallons per capita per day during the four driest months of the year. (g) Waste, to prevent freezing of water in service pipes and house fix- tures in northern cities; 10 gallons per capita per day during the three coldest months of the year. {/i) Waste, by leakage of fixtures and pipes, and use for Hushing purposes; from 5 gallons per capita per day, upward. "The above estimates are on the basis of the total population of munici- palities. "The domestic use is greatest in the towns and cities, and in the portions of the towns and cities having the greatest wealth and refinement, where water is appreciated as a luxury as well as a necessity, and this is true of the yard sprinkling and ornamental fountain use, and the private stable use. * * * "The general introduction of public water works on the constant supply system, with liberal pressure in the mains and house services, throughout the American towns and cities has encouraged its liberal use in the households, so that it is believed that the /egitiinute and economical domestic use of water is of greater average in the American cities than in the cities of any other country. at the present time, avd its general use is steadily increasing." The proportion of the above per capita per day supply naturally reaching- the sewers ma}^ be summarized as fol- lows: (rt) Domestic use, ----- -20 g-allons. {b) .Stables, ------ 8 g-allons. (c) Manufacturing", - - - - 5 to 15 g-allons. {d) Fountains, - - - - - 8 to 10 g-allons. {g) Waste in winter, . - - - 10 g-allons. (h') Flushing-, ----- 5 to 15 g-allons. Total supply reaching- sewers, +6 to 78 g-allons. In the report of the Eng-ineer Department of Washing-- ton, D. C, for 18V>T, Captain Edward Burr makes the follow- 70 THK SKPARATK SYSTKM OF SKWKKAGK, ing" estimate, per capita, of the leg-itimate requirements of that city: For domestic purposes, - - - - 30 g^allons. For commercial and U. S. purposes, - 30 g-allons. For sprinkling- (maximum) - - - 15 g-allons. Total maximum leg-itimate use, Add for waste, not deliberate or wilful. 75 g-allons. 25 g-allons. Total, 100 g-allons. The actual consumption for 1897 was 164 gallons per capita for the entire population, including- suburban and rural population entirely without water facilities. As an example of the actual quantity of water needed for domestic purposes, the following- statistics of consumption, determined by meter measurements, are extracted from an article on "The Consumption and Waste of Water," by Dex- ter Brackett, M. Am. Soc. C. E., in the transactions of the American Society of Civil Eng-ineers, 1895: TABLE III. ACTUAL CONSUMPTION BY METER. No. Gallons CITY. of Class of Houses. per Houses. capita. Boston 31 Highest cost apartment houses 59 Boston 46 First class apartment houses 46 Boston 223 39 Moderate class apartment houses Poorest class apartment houses 3^ 16.6 Boston Newton 490 Houses supplied with modern plumbing 26.5 Fall River 28 The most expensive houses in the city 25-5 Fall River Total domestic consumption Total domestic consumption 12.3 16.8 Worcester . CHAP. V. yuAN'nrv of sewagk. 71 From these, and other statistics g-iven in his article, Mr. Brackett draws the following- conclusions: (1) The quantity needed for domestic use is not more than 3U gallons per inhabitant. (2) It is not probable that the actual requirement for mechanical and manufacturing uses at present exceeds 4-0 gal- lons per capita in any of our larg-e cities. (3) The quantity needed for public use is not more than .") gallons, making a total of 7.5 gallons as the maximum quantity needed for actual use, without any allowance for w'aste. It is estimated that in man}' places the needless and wil- ful waste of water is from 50 per cent, to 7.5 per cent, of the entire supply. The following table illustrates the increase in water con- sumption in several cities : 72 THI<: SKPAKATK SYSTICM OI' SKWKKAGK. TABLE IV. SHOWING CONSUMPTION OF WATER IN TWELVE AMERICAN CITIES. Based upon the Total Population, CITIES. Boston Brooklyn. . . . Buffalo Chicago Cincinnati . . Cleveland. . . Detroit Jersey City . . Louisville. . . Philadelphia Washington . Montreal. . . . Average Daily Supply Per Capita in Gallons. 1874* 60 58 60 84 45 45 87 86 24 58 66 18841 no 63 151 145 76 88 120 136 64 81 165 84 66 170 123 99 175 62 145 i897t 265 127 r28 130 215 164 *J. T. Fanning's Hydraulic Engineering;, tj. J. R. Croes' Statistical Tables. iS«5. tDepartnient Reports. The following" table compiled from the statistics of one hundred and seventy-six American cities, illustrates the con- sumption of water: CHAP. V. yuANTi'iv oi' si;\VA(;i:. TABLE V. SHOWING PER DIEM PER CAPITA CONSUMPTION OK WATER IN ONE H(JNDREl) AND SEVENTY-SIX AMERICAN CITIES IN 1884. Based upon the Total Population Census of 1880 * CITIES. NO. POPULATION. Average Consump- tion of water per diem per capita. 10,000 to 15.000 76 15,000 to 20,000 6g 20,000 to 25.000 71 25,000 to 50,000 50,000 to 75,000 75,000 to 100,000 100,000 to 250,000 250,000 to 500,000 500, 000 and over .86 .80 95 102 92 * Compiled from J. J. R. Croes' Statistiral Tables, 1885. The above tables, thougfh g-iving- the average dailv use, are not sufficient to predicate an assumption of sewag"e dis- charge upon, as they indicate simply averages obtained from widely varying rates of consumption. As previously stated, each day has a maximum rate of discharge, and there are also weekly and monthly maxima, varying- according to the habits of people, and to the conditions of temperature, etc., and the sewers (we are considering- the Separate System, which has no capacity of storage) must be proportioned to discharge their contents at the maximum rate at which they are received. 74 THK SKPARATE SYSTKM OF SF:WKRAGE. Varying Rates of ^A^ale^ Consumption. — There are two principal maxima of water consumption, one occurring" during^ the coldest weather, and one during- the warm and dr}- months of late summer. It is the former which particularly influence the sewag^e discharg^e, being" in most cases the max- imum rate of water suppl}" for the year, and nearly its entire volume reaching- the sewer, while the uses to which water is put during" the warm and dry weather maximum, diverts it larg-ely from the sewers. The following table indicates the monthly variations in water consumption during the year 18S4, in several Ameri- can cities, covering a considerable rang"e of latitude. The computations are made from statistics appearing in official reports of the water departments of the various cities, and are reduced to the per cent, basis in terms of the averag"e monthlv consumption. TABLE VI. ILLUSTRATING MONTHLY VARIATION IN CONSUMPTION OF WATER IN 1884. IN WHICH THE MEAN MONTHLY CONSUMPTION FOR EACH CITY IS REPRESENTED BY ICO CITIES. 3 C ct 105 138 90 88 103 III 116 u m D u XI lU bk 107 100 77 90 79 118 96 < 102 83 90 lOI 83 95 79 B S 3; E D. a; X 98 100 1 10 113 115 95 107 ..0 2 > u z Z Z 95 94 91 87 113 III no 92 106, 97 95 97 100 104 . Si E Chicago Columbus New Orleans. . Cincinnati . . . Wilmington , . . Buffalo Binghampton . 100 107 87 89 89 114 97 100 90 105 lOI 77 92 90 98 93 106 106 125 96 95 lOI I Of) 113 log 120 91 98 102 1 12 109 114 114 96 124 96J 95I 96- 86 90 99' From the above table we find the average maximum monthlv consumption forthe seven cities to be 119 H-7, or, practically, twenty per cent, in excess of the average monthly consumption. CHAP. V QUANTITY OI'^ SE\VA(;E. 75 The daily consumption has a weekly maximum independ- ent of atmospheric conditions, and which ordinarily occurs on Monday. The widest variations in daily consumption, however, are those due to extremes of temperature. The relative minimum, mean and maximum daily con- sumption, in a few cases, is illustrated in the following" table in terms of the mean daily consumption. The computations are based upon statistics contained in official reports. TABLE VII. ILLUSTRATING EXTREME DAILY VARIATIONS IN CONSUMPTION OF WATER IN 1884, IN WHICH MEAN DAILY CONSUMPTION IS REPRESENTED BY lOO. CITIES. Minimum Daily Con- sumption. Mean Daily Con- sumption. Maximum Daily Consumption Chicago Cincinnati Buffalo 82 60 68 100 100 100 100 120 152 140 176 DATE. Jan. 23 June 24 Feb. 5 Jan. 1 Columbus The averag^e maximum daily consumption in the cities, g-iven in table VII, is 147, or forty-seven per cent, in excess of the mean daily consumption of the year. The average maximum daily consumption, given above, indicates only averages for a period of twenty-four hours. It will be necessary to ascertain the rate of the heaviest hour's use. The following table indicates hourly consumption, com- puted from automatic counter readings of a direct service pumping engine, in Kalamazoo, Mich.: 7t) THl-: SliPAKATlO SYSTKM OF SKWKKAGE. TABLE VIII. HOURLY VARIATIONS IN WATER CONSUMPTION, MONDAY, MARCH Q, 1886. TIME. Ciallons per Hour. TIME. Gallons per Hour. I A. M. 52,528 I P. M. 58,520 2 49,964 2 ' ' 58,128 3 " 51.464 3 " 59.360 4 " 52,472 4 " 59,640 5 " 52,864 5 " 61,040 6 •■ 52,332 6 " 57,232 7 ■' 54,880 7 " 53.928 8 " 64 70S 8 " 56,560 9 " 62, 160 9 " 52,640 10 " 61,600 10 54,880 II 60,844 II 52,752 12 M. 61,964 12 " 48,328 PERCENTAGE RELATION. Average hourly rate loo Minimum " " 85.9 Maximum " " 115. i If this table be examined in connection with Table XII, showing' sewer g'aug'ing-s taken simultaneously with the counter reading", it will be particularly interesting". A g'raphical representation of the two on the same sheet shows almost precisely the same relative variation in each. During the week ending- Aug^ust 20th, 18H3, observations were made to determine the rates of consumption for differ- ent portions of the 24 hours, from the Mystic works, which supplied a population of 117,000, The results were as fol- lows: CHAP. V. OUANTI'lY OJ'' S)<:\VA(iK. TABLE IX. Gallons per Capita Percentage of per Day. Average. I A. M. to 4 A. M. 40 .s 55 4 " t0 7 " 58.6 80 7 " to lo " 103.8 140 lO " to I p. M. 930 126 I P M. to 4 " 93-2 126 4 " to 7 ■ ■ 79-5 108 7 " to lo " 61.9 84 lO " to 1 A. M. 52-9 72 Average 73 6 The following' illustrations and estimates of varying- con- sumption are taken from J. T. Fanning-'s Hydraulic Engi- neering: "The Brooklyn diagram shows that the average draught in the month of maximum consumption was in 1872, fifteen per cent, in excess of the average annual draught; in 1873, seventeen per cent, in excess; in 1874, thirteen per cent in excess. "A Boston Highlands direct pumping diagram, lying before the writer, shows that the average draught at 9 o'clock in the forenoon was thirty-seven per cent, in excess of the average hourly draught for three months. "The maximum hourly draught, indicated by the two diagrams taken together, is nearly seventy-five per cent, in excess of the average throughout the year. "In illustration we will assume a case of a suburban town, requiring, say, an average daily consumption for the year of 1,000,000 United States gallons of water, and compute the maximum rate of draught on the basis shown by the above named diagrams, thus: 78 THE SJiPAUATK SYSTICM OF SEWKKAGK. GALLONS. Average draught per year 1,000,000 I, 170,000 1,270,000 1,640,000 1,870,000 Add 17 per cent, for maximum monthly average draught, making Add to the last quantity 10 per cent, for the maximum weekly average draught, making Add to the last quantity 37 per cent, for the maximum hourly average draught, making Add to the last quantity 23 per cent, for the maximum hourly average draught on Mondays, making ' 'The maximum hourly draught is not infrequently one hundred per cent, in excess during several consecutive hours, independent of the occasional heavy draughts for fires." Fanning-'s estimate, as g^iven above, would require sew- ers capable of discharg-ing- twice the mean daily water con- sumption, upon the supposition that at the time of maximum consumption its entire volume reaches the sewers. And this being- ordinarily in the winter months, the supposition is a reasonable one. The following extracts from the report of the Louisville Water Works for 1890, shows the relation between "con- sumption of water per capita" and "consumption per each consumer" from 1861 to 1889. • It appears from the table that the consumption per con- sumer has been without any notable increase previous to 1880, since when there has been a considerable increase. During" this period the consumption per capita based on the total J>0'pulaiion has increased from 8.66 gallons to 67.32 gallons: CHAP. V. QUANTITY OF SKWAC.I-; 79 TABLE X. WATER CONSUMPTION AT LOUISVILLE. KY. V u-c •— i" ai 1) . V . 'X Oi -2 = a'c « atn a, « 1-. " i"^ s s "^ .— "7^ CO v° ■^z Z 6 a. .-"« -"a — Sfc- P ^!/i CL, j; a. xiC mO > 1 " -^ M 4) 0. 2.5 -3 ^ a, — a 1 - >- o.S 1 =< i= 1^ .= ■£ .§ ~ — M « z zS 1'* U Ul a " 1889 12,569 12,262 122,620 132,400 166,000 67.32 91.14 1888 11,698 11,398 113,980 131,700 165,000 62.23 77.96 1 '887 11,001 10,729 107,290 131.000 162,000 63.62 96.07 1886 10,243 9.990 99,900 130,500 160.000 64.95 104.02 1885 9,709 9.469 94,690 130,000 159.000 62.39 10477 1884 9,261 9.034 90,340 125,500 158,000 56.22 9833 1883 8,730 8,594 85,940 125,000 158,000 51-91 95-44 1882 8,293 8,201 82,010 124,500 157,000 47.11 go. 19 I88I 7.947 7.877 78,770 124,000 156,000 55 47 109.86 1880 7,506 7.462 74,620 123,000 i56,obo 42.09 88 01 1879 7-283 7.243 72.430 123,000 156,000 33 16 71.42 1878 7,012 6.978 69, 780 120.000 154,000 29 35 64-77 1877 6,820 6,797 67,970 117.000 154.000 28.62 64.65 1876 6.559 6.541 65.410 116,000 152,000 27.44 63-75 1875 6,234 6,228 62,280 114,000 152,000 23.76 57 98 1874 5.431 5.591 55.910 109,000 152,000 23.68 64.37 1873 4.742 4.932 49.320. 98,000 144,000 22.32 65.16 1872 4,268 4.452 44.520 84,000 136,000 21.69 66 25 I87I 3.911 4.131 41,310 76,000 129,000 20. 86 65-13 1 1870 3.436 3,668 36.680 70,000 122,000 23.09 79-53 1869 3.083 3.312 33,120 64,000 115,000 21-53 74.76 1868 2,695 3,089 30.000 62.000 109,000 18.86 66.30 1867 2,414 2.783 28,000 60,000 103,000 18.24 67.10 IS66 2,205 2.434 25,000 56,000 98 000 18.87 73.96 1865 1.766 2,019 20,190 51,000 92,000 18.55 85-35 1864 1.517 1.754 17.540 49.000 87,000 14.27 62.06 1863 1. 112 1,300 18,150 40.000 83.000 11-43 55-02 1862 794 925 13,000 34,000 78.000 12. 98 77.91 I86I 512 582 5,820 32.000 74,000 8.66 73 60 80 THK SP:PAKATK system Ol'^ SKWKKAGK. The amount of sewage to be provided for in the Sepa- rate System is an important question, and with published statistics showing- a variation more than ten fold between maximum and minimum in water consumption for different cities, the eng"ineer who essays to foretell what amount will reach the sewers, should carefully investig"ate the local con- ditions. ScAA^er Gaugings. — Exact measurements of the flow of house sewag-e for any considerable period are not accessible, if they have ever been made, and, consequently we cannot use them as a basis in determining the fluctuations in sewag"e flow, or the ratio of maximum to mean discharg-e. A limited number of g^aug^ings have, however, been made with the purpose of determining the maximum rate of flow per capita in certain cases, and an account of some of them appears in a report to the National Board of Health, by G. E. Waring, Jr. The most complete statistics recorded are those of gaugings made under the direction of Robert Moore, Esq., Civil Engineer, Commissioner of Sewers of St. Louis. The following is an abstract from the report: "The sewer drains an area containing 1,370 houses, occupied by a popula- tion of 8,200. The total number of water taps was 1,390. The diagrams show gaugings taken every hour from 6 p. m. Monday, March 15 to eleven a. m., March 16, and from 8 a. m., March 19. to 8 a m., March 23. These gaugings are averaged to make a typical day, in which, beginning at midnight with a flow of 75.32 cubic feet per minute the flow was reduced to 70.26 cubic feet per min- ute at 6 A. M., 130.26 cubic feet per minute at 11 a. m., 123.86 cubic feet per minute at 3 p. m., and steadily declined from this time until midnight, when the flow was 75.15 cubic feet per minute. The sewer is seven feet, three inches in diameter. It was obstructed by a dam, into which was built a twelve inch vitrified sewer pipe, which was continued for a length of twenty feet. The gaugings were taken simultaneously at three different points, the average of these being the assumed depth through the twenty feet of twelve inch pipe." The following is a condensed tabular statement- of the results obtained, as stated in the report: CHAP. V. QUANTITY OF SEWAGE. 81 TABLE XI. SEWER GAUGINGS MADE AT ST. LOUIS. DATA. DEDUCTIONS. D u a c a Velocity in Feet z u. per Second. fa2 ~Z ^S, ■Ss S OH •- tLl V CO .„ ■-fc. D M< Do Q Q Q W> .:£&- . a <:rTl ca o TO • — £.SS V a > J hJ < < J < March 15-16 15425 •5833 74.67 -3751 42.39 -4356 5.41 4-54 4.69 19 144.09 ■5341 77.64 -3985 114.30 .4689 5-65 4-43 5-27 " 20 132.34 ■5144 67.06 • 3751 102.18 -4519 5.41 4.16 4 94 " 21 133-79 •5177 68.58 .3568 96.49 .4298 5-86 4.27 493 " 22 123.57 .4961 69.54 -3802 101.78 -4452 5-54 4-23 5.02 23 118.79 •47OJ 73-95 -3725 79-74 ■3940 546 4-47 4.61 Typical I )ay, or a verage of Mar Dh 20, 2 I and 22 100.22 .4420 5-86 4.16 4-99 Number of houses connected with the sewer 1.37° Population 8,200 Number of water taps ii39i Cubic feet of sewage discharged per capita in twenty- four hours 17. 60 Upon the foreg^oing- statistics, the following- comment is made in the report: "A computation of the amount of flow as compared with the population makes it evident that the sewer must have received a very large amount of ground water, for the total flow (over 1,000,000 gallons per day) amounted to more than 130 gallons for each member of the population, which, in a district having only about one water tap to each house, would be an impossible amount. It is usual to estimate a maximum daily use for domestic purposes of about thirty-three gallons per head of population. Deciding the total flow by this amount, we might assume that the twelve inch pipe in this instance, carrying, at its maximum, less than seven inches in depth of water, was doing the amount of work that would be required for carrying the sewage only of a population of 30,000, -supposing the sewers to be absolutely tight, so that only household 82 THE SEPARATE SYSTEM OF SEWERAGE. wastes should enter them. This last example is, from its extent, and from the minuteness with which its details are worked out, the most important of the series. It seems to me to furnish a conclusive argument — an argument fully sustained by all of the other gaugings — in favor of the safety of depending upon very small conduits for the removal of the dry weather flow of sewage of cities and towns. It shows conclusively that the commission of the National Board of Health, which recommended the system carried out in Memphis— lateral sewers six inches in diameter, main outlet twenty inches in diameter — for a prospective population of 60,000, provided a wide margin for contingencies." Some of the conclusions drawn above are not justified by- recent experience, and do not seem to be supported by the statistics of water consumption or by other g-aug-ing-s on which they are predicated. The statistics of water consumption in St. Louis show an averag"e per diem consumption for each tap of 1,177 gal- lons for the entire city. Assuming the territory tributary to the sewer in which these gaugings were taken to repre- sent an average consumption for the city, the volume of sew- ag"e as found, 17.60 cubic feet, or 131.6 gallons per diem per capita, represents a trifle less than two-thirds the total aver- age water consumption for the territory tributary to the sewer. The diversion of more than one-third of the total water supply from the sewers, at the season at which these g'augings were made, would in many cases, cause a public nuisance. If the assumption of thirty-three gallons per diem per capita be properly founded on the observations made, it must be from some known local condition and not solely on the statistics as given, which are not widely at variance with similar observations made at points where it is known there can be no infiltration of sub-soil water. The results of other investigations published in the report are not reduced to gallons per diem per capita, but, for the purpose of more readily comparing" them with the g-augings made at St. Louis and elsewhere, the following" table has been compiled from computations based upon the CHAP. V. QUANTITY OF SKWAGE. S3 dimensions and measurements g-iven in the report. The results were obtained by g"raphical methods; but are intend- ed to be closely approximate. The g-augino-s were ordinarily taken by inserting- a pipe of smaller diameter in the sewers, through which the flow was directed and in which its depth was measured. The precise manner in which these smaller pipes were placed is not stated in every case, but, as the object of the gaugings was to "determine the actual pipe capacity required" in the several cases, it seems proper to assume that they were so placed as to secure results identical with those if the entire sewer had been of an equal diameter. This is assumed in the computations made. The gaugings of the College street sewer at Burlington, Vt., were taken at intervals of fifteen minutes from 7:30 a. m. to 10:30 A. M. The district which it drains contains eighty- five houses, of which fifty-four are connected with the sewer. The population tributary to the sewer embraces 325. There were two equal maxima in the flow, one occurring at 7:45 A. M., and the other at "J a. m. The mean rate of discharge in this case does not represent the mean daily rate, but the mean rate during the time the gaugings were taken — 7:45 A. M. to 9 A. M. 84 THE SEPARATE SYSTEM OF SEWERAGE. O o < o X g 3 ^ « fe <: o o S <; ;39j ui q^Sagq & ni 0) rt nil > 'n a < a rt a 3 si 2 o- - - ac c D (U OJ O IK S 6:^ b E CA) cn U K C/3 rt ■lUnLUIXBJ\[ N moo O O ^ O lO or^t^'rNa\ co r^ N M tH M t-l M Q ^ •aE9i^ M Tf M U-) N m ro M M M W M a. niniuiuij^ 00 o Tl- m On 0^ CJivO m ro < • D o 0, U9M9S O} XaBjnqux in t^ M t^ m M IBIOX 8,200 8,20O 8,200 in o O m O O O o o -f in M~ o X •mnuiixHj\[ o r- m o o o 3~, o H M N m m ■nB9i^ N N o T^ M -^ m o m >n m M h Z u Q •uinuiinii\[ O O Tf O m in 'j-oo •f -^ Tt- O in CO OOI J9d llEjJ ■ • ■ M in in lO O ■ ■ ■ M N N VO lO M . M ■s9qoni ai j949mBiQ PJNNOOO O O M M M MM N D C a; a a) tn J3 J3 ^ a a o ?^ 01 M-H ^ o "o) b o N -_^ >. H 3 o < CI 0) W n! rt § en CHAP. V. QUANTITY OF SEWAGE. 85 The following- is an account of the g"aug-ing-s taken in the Memphis main sewer by C, H. Latrobe, C. E,, and is quoted from his report to the Mayor and City Council of Baltimore: "By gaugings taken at the head of the twenty-inch main I found the hourly flow of sewage to be remarkably uniform. Thus, from six a. m. till one A. M. the following morning, a period of twenty hours, the flow oscillated in centre depth from twelve and one-half to fourteen and one-half inches, the minimum area of flow being 206.5 square inches; the maximum 245.73 square inches. From one a. m. till 5 a. m., a period of four hours, the centre depth of flow varied from eight and one-half inches to eleven and one-half inches, mini- mum area being 107.6 square inches; maximum area, 186.9 square inches. Taking the twenty-four hours, the minimum flow is 43.7 per cent, of the max- imum; taking the twenty-four hours of greatest flow, the minimum is 84 per cent, of the maximum and eight-ninths of the daily flow of sewage passed in twenty hours, one-ninth in four hours. This marked uniformity of flow during twenty hours of the day, and its oscillating character within such limits, must be somewhat influenced by the action of the flush-tanks, which probably dis- charge in small groups. * * * The accompanying system of tile drains has also thoroughly drained (as far as I know) the very tenacious sub-soil of the Cltv 4f "fr w w ^ "The errors or omissions in the Memphis system are: "First. Insufficient size in the mains to accommodate the excessive use or waste of water during severe winters, when people allow spigots to run all the time, to prevent freezing. During the winter just ended Major Humphries estimates that one hundred gallons per capita per day were often used, which caused the mains to run filU bore and occasioned a backing lip of the sewage in the lower parts of the city. This fault, of course, was not incident at all to the system, but was an oviersight in proportioning the mains, and would not be felt during an ordinary winter." Since in the case of Memphis special provision was made for the removal of the sub-soil water by separate channels, it is improbable that the flow of the sewers proper was aug:- mented by it. It must be borne in mind that these g^augfinofs were made before the completion of the system at Memphis, and repre- sent the discharg-e from but a limited portion of the territory upon which the per capita dischargfe is based, there being at that time but twenty miles of the system complete. It has since been extended to about fortv miles. On the other 86 THE SEPARATE SYSTEM OF SEWERAGE. hand, the introduction of the system into the houses was so g-eneral and prompt, that it is probable the territory sewered reached more nearly its maximum rate of discharg-e within the short time intervening- between its completion and the time at which the g-aug-ing-s were taken than would ordinarily be the case. The maximum rate of sewage discharg^e, then, as shown in Table XII (eig"hty g-allons per diem per capita), should properly be based on a much smaller population than 35,000. (The total population of the city, as g-iv^en in the census of 1880, is but 33,590.) No means of determining- the popula- tion occupying- the territory actually tributary to this twenty miles of sewers are at hand, but it has been estimated at 20,000. Upon this basis the maximum rate of discharg-e of eig-hty gallons, as shown in the table, becomes 140 g-allons. The population actually tributary to the Compton Avenue sewer at St. Louis is not stated. If, in the case, of theg-augings made in this sewer on Saturday, March 20, it be assumed that at the time of minimum flow, the entire volume discharg-ed was sub-soil water (which is certainly not a proper assumption, since at no time during- the twenty-four hours is the discharg-e of house sewage in a system of any extent wholly arrested), and its total amount at this assumed rate for the twenty-four hours be deducted from the dis- charg-e as shown by the g-aug-ing-s, the volume of discharg-e remaining- agg-reg-ates 1:3.4 g-allons per diem per capita. Again, if we assume the hourly variations of flow, as determined by the g-aug-ing-s taken at Memphis, to be a proper rang-e for St. Louis, or, in other words, assume that the ratio of minimum and maximum discharg-e of house sezv- apx only, in the two cities is the same, we can determine the amount of sub-soil water and eliminate it. A computation made on this assumption g-ives us in St. Louis, for the dis- charg-e of house sewag-e only, when based on the total popu- «5 05 CO 10 IN C CM U5 C c c» ■r^ "O "3 Oi «i 0; 00[ oc' 1^ l^ CO ! ' ' 1 ! „..i^. ^ ■^ 1 — 0' ^ •nr^ >i-IOI § >' i < / Q 'a h / Z''V 7i77.l \ / •osi- ^ ' . ^^ ~^ --^ ., \ 1 ~~~ ~~--— —i^ : !'°"l.\ r i ; J „" fi;:piL/ ' 7.P 0.1 — / 3 c u > <: B O a. & o O •ifi! 86l 1. 1^^ CD-li ^ OJ t 09-16 ' / i ^•-io 1 1 ^^ ". '"7 ^tE-?.e.-L 1 1 1 1 i i ! ''f*"'"^ \ 1 = 1 1 1 cs U 3 -Hi OS 0) i < 1 . \ )ft5oT ^^^HT _ 51 ) mz-V -J' — '''■a ^-A ' bo C 'Sj 3 M O CHAP. QUANTITY OF SKWAGE. 89 lation occupying- the territory, minimum, 65 g-allons; mean, 102 g-allons; maximum, IttH g-allons per diem per capita. The g-aug-ing-s made at the Compton Avenue sewer, St. Louis, cover the entire twenty-four hours. They are illus- trated g-raphically in the diag-rams on pag-e 87, taken from the report. Gaug-ing-s were made of the flow of the Water Street Main in Kalamazoo, Mich., on March 9, 1885, as follows: TABLE XIII. DISCHARGE OF WATER STREET MAIN SEWER, KALAMAZOO, MICHIGAN, MONDAY, MARCH 9, 1S85. Time. Q° 233 227 224 230 234 242 244 265 255 265 258 258 255 265 273 287 275 276 265 257 255 255 253 250 Minimum Maximum Average discharge per min- ute 254 Gallons. Maximum discharge per minute 287 Gallons. Minimum discharge per minute 224 Gallons. Percentage Relation of Maximum and Minimum Discharge to Mean Discharge. Minimum discharge 88 Mean discharge 100 Maximum discharge 113 90 THE SKPAKATE SYSTEM OF SEWERAGE. These g-aug^ing-s at Kalamazoo were made by weir meas- urement in the manner illustrated in Fig-. 1. The weir is made of galvanized sheet iron of the ordi- nary weig-ht, rolled up in the form of a funnel, and riveted or lapped and soldered, its smaller end being- slightly smaller ^ly Fig. 1. in diameter than the sewer in which it is to be inserted. The larger end is cut off at rig-ht angles to the side which is^ to lie in the bottom of the man-hole, and on this is fastened an end, having- cut in it the notch forming- the weir, as shown CHAP. V. QUANTITY OI'^ SKWAG]-:. 91 at h. The weir should stand sufficiently above the man-hole to counteract the effect of velocity of entry, and to g"ive a free run to the sewag"e. The depth of discharg^e over the weir is measured by a thin, g-raduated strip, on which travels a block having- a level attached for bring-ing the scale into a vertical position, and the point of contact with the surface of the water level with the index or point of reading at d. Still more accurate results might be had by taking the meas- urement from some fixed point above the weir, but in ordi- nary cases the method detailed above will be sufficiently accurate. The weir is easily transferred from one point to another, and is quickly set, requiring but a piece of cloth wrapped around the lower part, when it can be crowded into the lower branch of a man-hole, where its flexibility insures a perfect fit, and the pressure of water from above keeps it to its place. It is also very convenient in use, the observation being taken from above, where the peculiar light makes the least ripple of water against the point r, and the position of the level bubble plainly disting-uishable. The method of observing- the depth of flow in the sewer proper and computing from these data the discharge by for- mula or tables, though frequently used, is liable to error. The slightest obstruction below the point of observation increases the observed depth, and, consequently, g-ives results too hig-h, since the diminished velocity at the point of observation is not noted. A slight increase of flatness in the grade at the point at which the observ^ations are taken, below the grade at which the sewer may have been laid orig-inally, has the same efi^ect, as also the depression of a sing-le joint or section of pipe. Opposite conditions, by increasing- the velocity or by raising the measuring- scale, w^ll g-ive results too low. In the case of pipes of smaller diameter inserted in larger sewers, there are also difficulties in the way of secur- 92 THE SEPARATE SYSTEM OF SEWERAGE. ing- correct results. The following- g-aug-ing-s, made at Mil- waukee, will illustrate this point. They were made under the direction of G. E. Waring-, by A. H. Scott, C. E., for the National Board of Health, and a statement of them appears in the report of 1880. They were made in this way for a particular object: "Formulae in use among engineers would lead us to substantially the same result with actual gaugings, but their educational effect would be less marked, because calculations based upon scientific formulae are less readily compre- hended by the a\erage municipal ruler. * * * "The grade of the sewer at the point where the gaugings were taken is about I in 400. The greatest flow in the main sewer on 'washing day' — the greatest flow of the week — attained a depth of six inches, the diameter of the sewer being forty-two inches. The channel being reduced to a diameter of ten inches, the greatest depth of flow was 4.5 inches. Reduced to a diameter of eight inches, the depth remained the same — 4.5. Reduced to a diameter of six inches, it reached a depth of 55 inches. The influence on the velocity of the stream by increasing its hydraulic mean depth is illustrated by the following figures: "Forty-two inch sewer, six inches deep; cross section of stream 121 3 square inches. Ten inch sewer, 4.5 inches deep; cross section of stream 33.1 square inches. Eight inch sewer, 4.5 inches deep; cross section of stream 27 7 square inches. Six inch sewer, 5.5 inches deep; cross section of stream 27. 14 square inches." These lig-ures illustrate very forcibly the superior cleansing- effect of sewers discharg-ing- half full or more. They also illustrate the difficulty in securing- uniform results previously cited, as shown b}" the following- computa- tions. The volume discharg-ed in each case is stated as the same. The computed discharg-e is, approximately, as fol- lows, leaving- out of consideration the fortv-two inch sewer: CHAP. V. QUANTITY OF SEWAGE. 93 Diameter. Depth. Discharg-e in Cubic Ft. 10 inches. 8 inches. 6 inches. 4.5 inches. 4.5 inches. 5.5 inches. 30.45 23.06 17.48 The inaccuracies of this manner of measuring" flow become still more apparent as the depth of flow becomes less in proportion to the diameter of sewer. From the statistics of water consumption in the preced- ing- pages, we mav conclude that the discharge of house sezvage, at its maximum hourly flow during the year, is approximately twice the mean discharg-e. The records of sewage discharge show^ a variation dur- ing single days covered by the observations of thirty, forty, and in the case of the Compton Avenue sewer at St. Louis, on March 15 and 16, of nearly seventy per cent, above the mean daily rate. Observations covering- a long-er period and varying conditions of temperature would, undoubtedly, indi- cate a still greater maximum rate of discharge. Subsoil Water. — The probable amount of subsoil water sometimes requires consideration in proportioning- the sizes of sewers. This is a most difficult factor to determine. Although an effort should be made to lay the pipes with water tight joints, the trenching is sometim'es so difficult that it seems well nigh impossible to do so and instances are on record where the ground water found its way into the pipes throug-h imperfect joints to such a degree as to occupy nearly the capacity of the sewers before any sewag^e had been admitted to them. In some instances it is desirable to discharg-e subsoil drains, laid parallel with the sewers, into the sewers proper at a lower level and when this is done a judicious allowance for subsoil water is particularl}- important. 94 THK SEPARATK gYSTEM OF SEWERAGE, CHAPTER VI. LAWS OF FLOW IN SEWERS. A circular sewer reaches its g^reatest capacity of dis- charg"e when its depth of flow is about .933 of its diameter, being" at this point nearly eleven per cent, in excess of that attained when running- full. When the depth of flow is half the diameter, the velocity is equal to that when the sewer is running full and not under pressure. Circular sewers should be so proportioned as to size, throughout the system, that the depth of the ordinai'y daily flow will be sufficient to induce a fair velocity, and prevent deposits. The transporting power of circular sewers of small diameter is dependent on the depth of flow in a g^reat meas- ure, as well as on grade and velocity. A stream having- a depth of flow sufiicient to immerse solid matter held in sus- pension, to a certain extent lifts it and carries it forward. The entire surface is also exposed to the action of the cur- rent. A stream having an equal velocit}' but a less depth in proportion to the diameter of the solid matters to be trans- ported, evidently has less transporting power. As an illus- tration, a stream can be easily forded when its depth is below a man's waist, while the same stream in deeper water, even though the velocity be less, will carry a person down stream. Effect of Increasing Size.^ — An amount of sewag-e which can be properly transported by a circular sewer of a given CHAP. VI. LAWS OF FLOW IN SEWERS. 95 size, cannot be as efficiently transported by one of larger diameter, as the following- comparison will show: If we assume the contents of a sewer of six incbes in diameter, laid at a grade of .5 per hundred, and discharg-ing- half full, to be diverted to sewers of eig^ht, ten, twelve and fifteen inches in diameter respectively, and laid at the same g^rade, the follow- ing depth and velocities will be attained theoretically: TABLE XIV. ILLUSTRATING EFFECT OF INCREASED SECTION, THE VOLUME OF DISCHARGE REMAINING THE SAME. SEWER. Depth of Flow. Velocity in Feet per Minute. Discharge in Cubic Feet per Minute. 6 inch sewer. 8 " lO " 12 15 " 3.00 inches. 1.92 1.36 •• 1.03 •75 147 129 1X2 ICO 83 14.40 14 40 14.40 14.40 14.40 From tbe above comparison we see that, treated purely as a problem in hydraulics, both the velocity and depth, each of which is a factor in the transporting- power of the sewer, and, consequenth' in a deg-ree, a measure of its effectiveness, decrease as the size of pipe is increased. Like results have been shown practically in man}^ cases, by the substitution of lateral sewers of smaller diameter in place of those which have not had depth of flow sufficient to be self-cleansing-. It should be borne in mind, however, that while the above reasoning- is entirely pertinent as applied to the treat- ment of a liquid that sewers are liable to be the receptacles of a certain amount of solid and refuse matter which some- what modifies the above conclusions in some instances. The most perfect working- of the house sewers demands that they have a free out-fall into the lateral, as shown by the section in Plate I. A majority of the stoppag-es in house 96 THE SKPARATE SYSTEM OF SEWERAGE. sewers occur at their entrance into the laterals and mains, and if the flow in the laterals and mains be deep enoug^h to seal the outlet of the house sewers, the discharg-e of floating- paper, etc., is arrested, and the difficulty at this point very much ag-g-ravated. Good ventilation also demands a free passagfe of air currents throug^h every part of the mains, laterals and house drains. The connection of the house sewer with the street sewer is ordinarily and properly made with the common Y branch, elevated, as shown by section in Plate I. It is not made right and left hand, and when laid the sewer cannot be charg-ed more than half bore without setting- up into the house drain. The ordinary daily flow, then, for the reasons stated, and for other pertinent reasons that will appear later, should be accommodated below the horizontal diameter. An occasional extreme discharg-e of short duration, reaching- the full capacity of the sewer, will be beneficial rather than otherwise. PLATE I. \ I Jl :I ,iI,iI,i,I,iI,iI,,MjjaljIuj SELF READING ROD LOCATION OF Y'S ON LINE A B S;^3Ki''--^ ^■-i-;; fi "nflT'vV ^ t^' „.>v„ r'^'.' ■ ,-»s>. h'^ ■ , ll,\"^' V^r U ■'^^" ' '-. Ill '1 •fZ'. ; ^r=?'.;l I'^T xS; 1 ■ ".V ^s'-^ ips- 1 '^' ■ -.'■Vf;.! • ■■'#. •■•(^i: !"l ■:f(l1-- * '^'r ' ^ ■' -%: f^T*". ;J .--l- ri: ■V/-'.'. TEMPORARY OSSERVA riON' DEAD END OPENING LAWS OF I'^LOW IN SICWICKS. y!> Effect of Hydraulic Mean Radius.— The comparative velocity and discharg-e of circular sewers when running- at different depths, is well illustrated by the following- table: TABLE XV. SHOWING THE COMPARATIVE DISCHARGE AND VELOCITY IN CIRCULAR SEWERS OF A GIVEN DIAMETER AND GRADE FOR VARIOUS DEPTHS OF FLOW. [The depth of flow is expressed in terms of the diameter. The velocity and discharge are expressed in terms of the velocity and discharge when the sewer is running full, or when depth==i.] Depth of Flow. Velocity. Disc .harge. .067 .414 0119 .100 .498 0260 ■1465 602 0548 .200 .6942 0989 .250 .7698 1497 .300 .8210 2072 400 .9264 3457 .500 I.OOOO 5000 .600 10534 6598 700 1.0932 8174 .750 I 0984 8836 .800 I. 1028 9458 •«535 I.IOIO I 0009 .900 I 0918 I 0351 933 1.0794 I 0479 1. 000 I 0000 I 0000 If from the above table we construct the curves of velo- city and discharg-e by laying- off the depth of flow and the velocity and discharge as co-ordinates, the effect of the respective depths of flow upon velocity and discharg-e will be more apparent to the eye. Q c > 'So o O bo c '% o Xi tn > a CHAP. VI. LAWS OF FLOW IN SEWKKS. 101 Computation of Discharge and Velocity for any Diameter and any Depth of Flow. — The diagram affords a very con- venient and closely approximate method of computing- the discharg-e of any circular sewer discharg-ing- at anv depth. Nearly all hydraulic tables bearing- on this subject are computed to give the discharg-e of sewers running- full bore. A few give the discharg-e when flowing one-quarter, one- third, one-half, two-thirds or three-quarters full. This is about as wide a rang-e as can be covered without making- the tables too bulky for convenience. The discharg-e of a circular sewer of any size and g-rade, and flowing- at any depth, can be determined from the dia- gram, as follows: Divide the depth of flow by the diameter, and from the fractional depth on the vertical diameter thus indicated draw (by the eye) a horizontal line, intersecting- the curve of dis- charg-e, and from its point of intersection a vertical to the base. The percentag-e thus determined on the base, will be the relation of the discharg-e required to the discharg-e of the sewer when running- full, which can be taken from the table thus: Given, Diameter of sewer = 12 inches. Grade =1 in 200. Depth of flow =5 inches. Required the discharge. Solution: 5 — = .416. 12 Tracing a horizontal line from .416 on the vertical diam- eter to its intersection with. the curve of discharge, we read from the scale below .36. The discharge is thirt3'-six per cent, of that if the sewer were running full. From Baldwin Latham's Tables we see discharge when running- full = 167.2 102 THE SEPARATK SYSTEM OF SEWERAGE. cubic feet per minute. 167.2 X .36 = 60.192 cubic feet per minute, which is the required discharg-e. The velocity of any circular sewer, flowing- at any depth, can be ascertained from the diag^ram in the same way. The diag-ram has been carefully reduced to scale of one-half inch horizontal and one-fourth inch vertical, to facilitate calcula- tions of this kind, and the fractional divisions can be read by applying- an ordinary eng"ineer's scale. It is probable that neither the velocity nor discharg-e of sewers, whose depth of flow is but a small percentag-e of their diameters, attain in practice the value theory ascribes to them, since the solid matter held in suspension in all sew- ag-e becomes partiall}^ stranded, or is not lifted clear of the invert of the sewer, and th^ co-efficients of resistance appearing- in the formula, being- applicable to a liquid only, g-ive results too g-reat. Velocity Required to Prevent Deposit. — The velocity necessary to prevent deposit in sewers is variously esti- mated at from one to three feet per second by difi:erent authorities. Baldwin Latham states that he has found that, in order to prevent deposits in small, circular sewers, such as those of six-inch and nine-inch diameter, a velocity of not less than three feet per second should be produced. Sewers from twelve to twenty-four inches in diameter should have a velocity not less than 2J4 feet per second, and sewers of larg-er diameter should in no case have a less velocity than two feet per second. The minimum inclination securing- these velocities in the several cases, assuming; the sewers to run half full, or full, is: 6-inch pipe 1 in 142 = ,701 per 100 9-inch pipe 1 in 203 = .494 per 100 12-inch pipe 1 in 385 = . 260 per 100 24-inch pipe 1 in 775 = . 129 per 100 CHAP. VI. LAWS OI'^ FLOW IN SIC WICKS. 103 The minimum velocity recommended by several author- ities is as follows: Baldwin Latham . . .2 to 3 feet per second. Beardmore 2)4 to 3 feet per second. J. Phillips 2^^'2 to 3 feet per second. Rankin 1 to 4 feet per second. J. W. Adams 2^4 to 3 feet per second. Philbrick 2^2 to 3 feet per second. Gerhard 2 to 3 feet per second. While in extreme cases sewers may be laid at an inclina- tion inducing^ only a velocity of two feet per second, with reasonable expectation of their serving- a g^ood purpose, it cannot be denied that they are less satisfactory in their working's, and require more care in their maintenance, especially in the upper levels of the system, where the vol- ume of sewag^e is less constant. Effect of Decreasing Quantity of Sewage. — It must be borne in mind that the flow decreases in volume in arithmet- ical ratio as we ascend the sewer, becoming- zero at the sum- mit. In illustration: If we assume a six-inch sewer 4,000 feet long', with a g-rade of AH per 100, to have a tributar}' pop- ulation for each 100 feet of its leng-th of fifty persons, and each person to contribute fifty g'allons per day of sewag^e, to be discharg-ed in sixteen hours, with the sewer running- half full, the computed maximum velocity at its lowest level, becomes approximately, 144- feet per minute. The volume of sewag-e, however, at distances of 250, 500, 1,000, 2,000 and 3,000 feet from its summit, is but Vie, 's, X, /i and H of that at the point where it is running- half full, and, by computa- tion, supposing- the sewer laid at a uniform grade, the theo- retical velocities at these points become, approximately, as follows: 104 THE SEPARATE SYSTEM OF SEWERAGE. Distance . 250 ft. Velocity . 500 " .1000 " .2000 " .3000 " .4000 " 73.4 ft. per min. 89. 105.11 124.42 135.88 144. Or, assuming" the inclination to be increased as we approach the summit, so that the velocity shall be main- tained at the uniform rate of 144 feet per minute, the inclina- tion at the several points, theoretically, becomes about as follows: DISTANCE. INCLINATION. 250 feet 1 in 58.8= 1.700 per 100 500 " 1 " 85. = 1.176 " 100 1000 " 1 " 113.3= .870 " 100 2000 " . 1 " 158. = .632 " 100 3000 " 1 " 185. = .540 " 100 4000 " 1 " 208. = .480 " 100 These fig"ures very plainly illustrate what is so often observed in practice, and explain the frequency of stoppagfes in the hig"her levels of a system of sewers. They also illus- trate the g"reat benefit to be derived from the use of auto- matic flushing- tanks at dead ends, by which the sewer is intermittently filled to a fair working- capacity, and its stranded contents swept on to the mains before they have accumulated to a deg-ree interfering- with the working- of the sewer. Flushing- tanks at dead ends so surely counteract the defects above stated, that lateral sewers, to which they are applied may be desig-ned with uniform inclination throug-hout. The grade of streets frequently prevents the inclination of sewers being increased to the proper deg-ree toward the summits, and in this case flushing- is indispensible. CHAP. VI. LAWS OI' FLOW IN SEWP:RS. 105 Minimum Velocity. — Six-inch lateral sewers laid at a grade of A per 100 (1 in 250) are fairly satisfactor}' in their working's, when supplied with automatic flushing- tanks. The theoretical velocity in this case is VM feet per minute when running- half full. There is a marked difference observed, however, when the inclination is increased to .5 per 100, and the velocity to 147 feet per minute, especially during- that portion of the day when the sewer is discharg-ing- below its averag-e rate. Sewers of this diameter and g-rade are uniformly found in g-ood condition when properly con- structed and maintained; and, unless there is g-ood reason to the contrary, the inclination should be sufficient to secure this velocity. The velocity in sewers of larg-er diameter may be somewhat less, as being- ordinarily mains, their flow is more constant, and, having- a g-reater actual depth of flow, suspended matters are wholly immersed and lose weight in a greater degree, and, consequently, are transported at a lower velocit}'. Unless special means are taken to prevent deposit, the following may be taken as minimum velocities in circular pipe sewers: TABLE XVI. MINIMUM VELOCITIES AND GRADES IN CIRCULAR SEWERS Theoretical Inclination when depth of Velocity in Flow Equals One-Half the Diameter. Diameter of Sewer. Feet per Minute. FRACTIONAL. PER 100. 6 M7 I in 200 .5000 8 144 I " 280 3571 9 142.5 I " 320 3125 ID 141 I " 360 2777 12 138 I " 450 2222 15 134 I ' ' 600 1666 i8 129 I " 760 I315 20 126 I " 890 II23 2» 120 I " 1,160 0862 106 THE SEPARATE SYSTEM OF SEWERAGE. Main outlet sewers lying- beyond the point where houses are connected with the sewers, and which may safely work under lig^ht pressure at times, may have a lower inclination. Where it is impossible to secure the grades above given, special precaution should be taken to keep the sewers free. Low g-rades have been adopted in many cases as a choice of evils, and by special precautions have been made to serve a g-ood purpose. The following are examples: "At Wave Crest, Rockaway, L I., a four-inch sewer has been laid across a salt marsh for a distance of 2,800 feet. This small pipe is nearly level, the total fall being only three inches; yet, during the nine years in which it has been in use no stoppages have occurred, and no trouble of any sort has been met with. There are twenty-three houses on this line of pipe, most of which have their water-closets and one or two bath tubs. A flush tank at the end of the line of pipe is supplied by means of a windmill." — Andrezos in N. Y. State Board of Health. Undoubtedly, from the facts above given, the lower levels of this sewer work under a head, at least during por- tions of the time, and the velocity is induced, not by the fall divided bv the length ( aioo ), but by a certain head greater than .25 divided by the length. A main sewer in Kalamazoo, Mich., has a fall of but 1 in 1,200 for a distance of 7,-1:00 feet. The lower 5,000 feet of this sewer is twelve inches in diameter, and the upper 2,-1:00 feet is ten inches in diameter. The discharge is ordinarily at a rate of about 250 gallons per minute at its maximum, as taken by weir measurement. Theoretically, this should fill the twelve-inch pipe about half of its vertical diameter, and the ten-inch pipe about two-thirds of its verticjil diameter. Actually the sewer is often full nearly to its crown. This sewer has been in use sixteen years, and there has been no serious diificulty. There is a tendency toward deposits, however, but as the sewer has few connections on this portion of its length, any tendency of this kind resulting in decreased sectional area sets the sewage back until the CHAP. VI. LAWS Ol'^ I-'LOW IN SICWICRS. 107 I head thus g-ained induces a velocity which effectively removes all deposits. Neither of these cases then, can be considered as war- ranting- us in adopting- these grades for a sewer which is to be tapped throughout its length by house branches, and whose crown should have air space for ventilation. If we assume a minimum velocity of 180 feet per minute for house drains, the theoretical inclination under the above supposition (running half full) would be one in ninetv-two for a four-inch sewer. A sewer of this diameter and grade, running half full, would discharge 7.85 cubic feet per min- ute. If we assume it to be used by a family of six persons, using 75 g-allons per head per diem, the total per diem dis- charge becomes -t50 gallons. Assuming the maximum rate of discharg-e at 150 per cent, of the mean rate, the maximum discharge becomes .06*^-1: 'cubic feet per minute, or only eight-tenths of one per cent, of the volume necessary to secure the assumed velocity of 180 feet per minute at the g-rade of 1 in 9:2. The assumed velocity would only be reached in the case of a four-inch pipe, laid at a grade of 1 in 92, as assumed above, by increasing the number of users from 6 to 750. The actual maximum velocity obtained in the sewer when used by six persons, as above, is somewhat less than .3 its velocity when running half full, or 54 feet per minute. It is evident that in ordinary cases a g-rade of 1 in Iti' in house drains will not be sufficient to prevent the stranding of solid matters. Foui--inch house sewers should have a grade of 1 in 60, at least, and ordinarily of 1 in 48, and unless this can be obtained special precautions should be taken against stoppage. It is evident from an inspection of Table XIV that a sewer of six inches in diameter laid at the same grade, though having a greater velocity when working up to its capacity, would in this case, where the volume of flow is 108 the: separate .system of sewerage. limited, g"ive results inferior to a 4-inch sewer so far as the prompt removal of sewag^e is concerned. Graphical Solution. — A g'raphical indication of the rela- tions of the extent of the system, tributary population, dis- charg-e, inclination and velocity, thoug-h g-iving- but approxi- mate results, is much more convenient in use than the most extended tables. It makes the relation of the several factors more apparent to the eye, and assists in g^iving- the system a proper balance. It is sufficiently accurate for all ordinary computations. A diag"ram showing" at a glance the relation of these fac- tors, and by which may be solved graphically and in their proper order, the problems presented will be found on oppo- site page. The diagram is based upon the supposition that the depth of flow equals one-half the diameter at the time of aver- age maximum daily flow, which is assumed at 150 per, cent, of the mean daily flow for the twenty-four hours, or, a maxi- mum rate of discharg^e equal to the discharg^e of the sewag"e of twenty-four hours in sixteen hours. This relative maximum rate, though somewhat below that assumed by some authorities, will seldom be exceeded in American cities, where water is freely used, and where the waste, which is less intermittingly discharged than water legitimately used, is a large proportion of the sewag^e. The following table exhibits approximately the maxi- mum rate in several cases, expressed in terms of the time required for the discharge of twenty-four hours' sewage: Copyri Geo. S. P GRAPHICAL SEWER CALCULATIONS. BASED ON Baldwin Latham's Tables, KunER's Formula and Original Calculations. £-.1 s °- -: ^ — "T sjI — — — — 1 ? 1 1? Gallons per Uiem | Fall in 100 SUrk-i-tmLPiiHiit IMU.t j ucl, 100 Fl, of Sew |g S S g S per , ToUl Gallons per Olem Fall in 100 5S s g g s -. - .o , „ r^'^''S52"3"SS5SS -. ^ „ ,. .-, -T -T — 60,000 ~-x- 5 ^ u -1 . 500,000 ^^' ! ■' iOO 1,000 — — - ^; / :C — ^ ^ 100,000 ,v '^ - ^ 3 ~- .= ^^ =^ -^' — — — — F 1,000,000 -C 1,500 tfm ■^ ^ x; ?^ •^ 1,500 2.000 ^ y 7- 7 y 200,000 250,000 77 "? < == ■-4 =:- =fc = ;3^ '^^^ — ■= ^\ 2,000,000 \ps \7^ 7 \^ >^ J •> L_ _ ^ 1 - 2,500.000 ji_ \ ' <£- — — ~ 7 1 3,000 li / 300,000 Vv H/^ ^ / ^ ■--.- ' 3,000,000 \ ' ' ^ ■■ ^, /[// //■ 3,600 ^1 /t , 350,000 \ ^ \^ \ ^ 7,500,000 .ItIAj /\ \l / / / 8,000 / / 800,000 w ^ \ ^- ?7 ^ 8,000,000 \^ \r. h 17 / / / / 8,500 / 050,000 \\ \ \A' \ / 8,500,000 v» §\ ^ -r r '" / -H / / 9,000 , ' / ' 900,000 y \ r N ^ \ / 9,000,000 ^ Ti / // 9,500 // / 950,000 \ ' \ , 1 \ --N ^ / 9.500,000 \ 1 / / / / 10,000 / / / 1,000,000 A ^ \^ / \ ■^^ 10,000.000 1 \ 1 \ 10,500 1 / / / / 1 10,500 / / // 1.050,000 ' \ _ _\ _/ ■s. N />^ 10,500,p f 1 \ 11,000 1 /I // 1/ / 11,000 / / 1,100,000 rV r \ V 7 \ / - 11,000,000 I \ / 1 / / / I ^ / Y 11,500,000 I \, ll!,00t 1 fh" — ^ / // 12,000 / / / 1,200,000 \ \ -\ / Lin sin red ^.mp(l/ed fron \ 12,000,000 1 \ 1 J / / / / 1 \ \ |K,M ula HSU tllllf "— 013, ii"j 1 \ 13,00( 7 7 1/ / / / 13.00 7 TTlT 1,300,00 \ A " - 7 \ \ ~ ~ ~ 13,000,000 V ST - 13,S0( / / 1/ / 13,50 / , \ / 13,500,000 i U,0OI / 11 U,00 / / 1,400,00 \ 7 k \ / .„,„ h, 14,000,000 \ f U,50l l'''l 7 // IWOI / i \\\ 1,450,00 \ t L \ \ / »-"■ 14,500,000 i\ \ 1 Mm ./!/ Ji /v / 15,001 /i/l/ 1,500,0001 11 \ \ N 15,000,000 \ 1 _[ ") CHAP VI. LAWS OF I-'LOW IN SEWERS. 109 TABLE XVII. SHOWING MAXIMUM RATE OF SEWAGE FLOW. Gaugings Taken at St. Louis, Mo. Burlington, Vt. Memphis Kalamazoo, . . Time of Discharge of Twenty- Four Hours Sewage at Maximum Rate. 14-3 i8 6 17.6 16.4* 19.7 17.25 hours. *Eliminating bub-soil water upon the supposition made on page 86. Upon the assumption previous!}' made, that the maxi- mum rate of discharge for the year may reach twice the mean daily discharg^e, the maximum rate for the year will be one-third greater than that g^iven in the table. The following- is a comparison of the conditions of mini- mum, mean and maximum daily discharg^e, and of the maxi- mum discharg-e for the year represented by 60, 100, 150 and 200 per cent, respectively, as appears consistent from the investiirations made: Discharge. Depth of Flow in Terms of Diameter. Velocity in Terms of V. when Half Full. PER CENT. Minimum Daily, 6o Mean " loo Maximum " 150 Maximum Yearly 200 •^9 ■39 .50 .60 .82 .92 I.OO 1.05 The total theoretical capacity becomes 300 per cent., which is equal to a marg-in of fifty per cent, above the g-reat- est anticipated discharg-e. This would not be realized in practice, as the effect of numerous Y branches near the 110 THE SEPARATE SYSTEM OF SEWERAGE, crown of the sewer and the flow from tributary house drains, prevent the stream from reaching- its theoretical velocity. While the margin allowed by the above supposition for extraordinary conditions is but about fifty per cent, of the g"reatest anticipated flow, it will, except in extreme cases, be found ample. It should not be increased without reason, as this will impair the efficiency and cleanliness of the system during- the ordinary use. The diagram is based upon the tables of Baldwin Latham and the formula of Ganguillet and Kutter. The curves in black being computed from the formula of Weis- bach. >/2gh (Eq. 2) J^ in which // = head. /=]ength of pipe in feet. ^= diameter of pipe in feet. z/ = velocity in feet per second, when running full or half full. c= coefficient of friction in pipe. g = coefficient of resistance for entrance. .016921 c=. 011311 H e is assumed at an average of ..50.5. The coefficient of resistance for entrance ie) is not appli- cable to continuous, long pipes, fed at various points throughout their length. As it is usual, however, to place man-holes at intervals along- the sewer, the coefficient may properly be considered. The curves in red are computed from the formula of Ganguillet and Kutter. CHAP VI. LAWS OF FLOW IN SFWKRS. Ill r= '— ^ VRS^Cs/RS in which €' = mcan velocity in feet per second. 6=coefficient of mean velocity. 6'=sine of slope. 7?=hydraulic mean radius. ;; = the deg"ree of roug'hness of the sides of the con- duit, determined by experiment. In computing- the diagram the value of ;/ is taken as .018. It is probable that this value of n though somewhat above the values of ;/ as computed from gaugings of pipes under favorable conditions is a fair value for sewers having branches at intervals which considerably interfere with the continuity of the current. The formula of (Tanguillet and Kutter was elaborated from gaugings made in open channels. It is, however, undoubtedly applicable to a wider range of work than any of the older formulas and is fairly satisfac- tory when applied to sewers of small size. In order to properh* apply the formula it is necessary to know the value of ;/ where similar physical conditions prevail and in order to extend the usefulness of the formula as applied to sewers the following table is extracted from a larger table g^iven in the translation of the "Flow of Water in Rivers and other Channels — Ganguillet and Kutter," by Rudolph Hering and J. C. Trautwine, Jr. From the table values of >i for conditions similar to those for the work in hand can be determined. It is to be hoped that in the near future gaug^ings of pipe sewers will be extended so that results may be tabulated more closeh^ applicable to work of this class. The following extracts from the work of Ganguillet and Kutter are g^iven for the purpose of throwing more light upon the applicabilitv of the formula to sewers. TABLE SHOWING THE VALUES OF II AS PIPES. Earthenware Pipe. Flowing partly under a slight head Sheet Iron Rivited Pipe At North Bloomfield, funnel mouthpiece. . |H. Smith Jr., 1876 AUTHORITY. Bidder, 1853. New Cast Iron Pipe. New Cast Iron Pipe, Sudbury Conduit. Coated with Asphalt , Darcy, 185 1, Stearns, li Length in Feet. 2310 700 365 365 1747 OPEN Sudbury Conduit in Massachusetts. Plaster of pure cement over brick work . . . Fteley & Stearns 1880 Sudbury Conduit in Massachusetts. Hard brick, smooth surface, with mortar joints well made. Bottom slope, per thousand, about o. i6 490 600 XVIII. COMPUTED FROM ACTUAL GAUGINGS UNDER PRESSURE Diameter in Feet or Greatest Depth. Mean Hydraulic Radius in Feet A\ Hydraulic Gradient or Slope per Thousand 1000 5'. Mean Velocity in Feet per Second Coefficient in Formula 7'= tV ^^'^ C. Coefficient of Roughness «. 1-5 •375 2 50 3-581 117. .0111 .911 .228 8.50 4.712 107. 1 .0108 " ' ' 13-34 6.094 no. 6 .0106 " 16.95 6.927 III. 5 -OI05 ' ' ' ' 2559 8.659 113. 4 .0104 .9105 33-09 10.021 II5-5 .0102 .6168 •1542 •27 6 73 104.2 .0096 " * ' 3.68 2.487 104.4 .0100 ' ' ' ' 22.50 6.342 107.7 .0100 ' ' ' ' 109.80 14 183 log.o .0099 *' * ' 145 91 16.168 107 8 .0100 1.6404 .4101 45 1.472 108 4 .0116 ' ' ' ' 1.20 2.602 117. 3 OIII * ' 2.10 3-416 116. 4 .0112 ' * ' ' 2.60 3-674 112. 5 .0115 4.00 1.00 . -318 2.616 146.7 .0105 " ' ' .711 3-738 140. 1 .0109 " ' ' 1. 221 4 965 142.1 .0108 1.849 6.195 144. 1 .0107 CHANNELS. 3071 1.863 0. 1606 2.529 146.2 .0114 3-575 2.048 0. 1596 2.672 147 9 .0114 3768 2. Ill 0.1580 2.805 153.6 .0X11 .820 ■577 .1596 1. 149 119.7 .0110 1. 041 •751 ■ .1803 I 439 123.6 .0114 I 415 1. 016 .0140 -443 "7-3 .0108 Ill THK SEPARATl-: SYSTEM OF SKIWICR AGE. "We have not j^et found reason to modify our first formula. Still we must not neglect to say that it contains a variation of the coefficient (' which is open to some doubt, namely, a rapid decrease of C with decrease of slope in small channelswith very smooth sides. Since, however, we are not in possession of experimental data for such channels with very light slopes, we are unable to investigate as to whether our misgivings are well founded." "The coefficient n covers not only the mere roughness of the surface, but also the irregularities and imperfections of the bed of the channel or river; it includes, further the effect of loss of head or energy, in moving detritus or silt along the bed, in shifting the main channel or current from one side to the other of the bed, and in forming eddies or other lateral and irregular currents; in short, it embodies all conditions causing retardation of flow, the relative effect of which must be left to the judgment.'.; It should be borne in mind, that ;/ is to some extent dependent on the hydraulic mean radius. For the same con- ditions of perimeter it decreases as the hydraulic mean radius increases, "The coefficient of resistance or roughness can be found only by consulting cases where analagous physical conditions prevail, and for which its value has already been ascertained. In doing this we must consider the effect of. future contingencies upon the condition of the channel in question, such as the wash- ing in of detritus, etc." From an examination of diag"rams by Edmund B. Wes- ton, in Transactions of the American Society of Civil Eng^i- neers, January, 1890, comparing" the coefficients of friction in pipes as computed from a large number of actual gaugings of pipes having interior sides similar to new cast iron pipes, it appears that the values of ;/ in Kutter's formula for the pipes in question, lie mainly between the limits w = .010 and «=:.(>12 and in the majority of cases approximately w = .011. The value of C varies widely for different values of n as will be seen by an examination of Table XVIII. It may be remarked, however, that this is precisely the feature which makes the formula applicable to such a wide range of work and that the effort to embod}- in a formula a variable to which can be given a value according with the condition of the channel is a step decidedly in advance. CHAP. VI. LAWS OF ]''LOW IX SKWICKS. 115 Since in the g-eneral formula of Chezy v=CV^ (Eq. 1) in which t' = velocity, C=coefficient determined by experiment. area R=. ^ wetted perimeter head ,5"= = sine of slope. length area circle- we have R= when the pipe is running- full. circumference % area circle and /?= when pipe is running- half full. ^ circumference The velocity (z') is the same when the depth of flow is one-half the diameter as when the pipes are running- full. When the depth of flow is half the diameter the dis- charg-e in cubic feet per minute becomes -d' ] ^d' V=30z (Eq. 3) 4 ) 4 Assuming- the sewag-e of twent3^-four hours to be dis- charg-ed in sixteen hours, the daily capacity in g-allons of a sewer under the condition named, becomes yi-lv^mx - — y X 60 X 16 X 7.48 ( O in which 2:' = velocity in feet per second. ^= diameter in feet; or, >^-^— X 60 X-_lil_ -X 60X16X7.48 (Eq. 4) (60 4 ) in which T"= velocity in feet per minute. Z^ = diameter in inches. 116 THE skpakatp: system of sewerage. The expression reduces to the following' form: Daily capacity in g-allons = 19.5822 X V D"" (Eq. 5) If we represent the inclination and discharg-e g^raphi- cally, by the abscissa and ordinate respectively, of a co-ordi- nate system, the value of the ordinate corresponding- with any abscissa can be determined from the above formulae. If we make the diameter constant, and compute for varying" g-rades and velocities, the ordinates will determine a curve representing- pipe of the assumed diameter. If we make the velocity constant, and compute for varying- g-rades and diam- eters, the ordinates will determine a curve representing- the assumed velocity. In the equations of velocity and discharge, if we make D constant (the pipes running- half full) the hydraulic mean radius becomes constant, and the discharg-e varies as the square root of the sine of the ang-le of inclination, or as \ioo' S\ etc., and the equation may be reduced to the form: Discharg-e = Jc^;;5/^,;//X—, etc. ^ lOO The curves of diameter are, therefor*, parabolas and pass throug-h the zero of the co-ordinate system. When the depth of flow is equal to half the diameter, Yz (/>'X.7854 D R= = — >^(/>X 3.1416 1 •-C [p., •J? _ Discharge = 19. 5822 D' ^ J— s = 19.5822 C CHAP. VI. LAWS OF FLOW IX SKWICRS. 117 or, the discharg-e varies as the square root of the fifth power of the diameter. The use of the g"raphical diagram will best be illustrated by a few examples: (1) Required, the limiting- length of a sewer six inches in diameter, accommodating fifteen persons using- seventy gallons each for every oO-foot lot, the grade to be .5 per 100. Solution. Note the point at which the curve represent- ing diameter of sewer six inches is intersected by the per- pendicular line of fall in 100 = . 5. From this intersection trace a line to the left, preserving the same relative distance from the parallel lines on either side, until the vertical repre- senting seventy gallons per diem per capita is reached, then to the left and downward, preserving- the same relative dis; tance from the diverging lines on either side to the column of Tributary Population, then horizontally to the left, preserv- ing the relative distance, as before, to the vertical represent- ing- sixtv persons tributary to each 100 feet of sewer (fifteen persons for each lot fifty feet in width), then downward and to the left, preserving the same relative distance as before, to the intersection with the column of lineal feet when the distance required is read, being in this case about 2,500 feet. Incidentallv we determine that the total discharge is 105,000 gallons per day, and the total assumed population 1,500, by noting the point at which the line we traced crossed these columns in the table. (2) Required., the size of outfall necessary to discharge the sewage of 12,500 lineal feet of tributary lateral sewers, allowing ten persons for each twenty-five foot lot, and seventy-five gallons per diem per capita. Solution. Starting at the left hand column in the table at 12,500 lineal feet, follow the diagonal line upward and to the right to the vertical line of eighty persons, thence horizontally to the right across the column of Tributary Population (which is determined to be 10,000), thence diago- 118 THE SEPARATE SYSTEM OF SEWERAGE. nally upward and to the rig-ht to the vertical line of seventy- five g'allons (midway between seventy and eig"hty), thence horizonteilly to the rig-ht, when we note that the total daily discharge will be 750,000 gallons, and that it will require a sewer of the following dimensions: 20 inches in diameter ... .05 per 100 g"rade. 18 inches in diameter ... .11 per 100 grade. 15 inches in diameter ... .26 per 100 grade. 12 inches in diameter ... .75 per 100 grade. 10 inches in diameter . . ..1.S8 per 100 grade. But from the curves of velocity we note that the 20-inch sewer laid at a grade of .05 per 100 has a velocity less than 120 feet per minute, which is inadmissible, and the 18-inch sewer laid at a grade of .11 per 100 has a velocity of scarcely 120 feet per minute (118 by arithmetical computation), and the minimum velocity we have assumed in Table XVI is 129 feet per minute. The conditions will be met by either of- the other three sewers, and the velocity in each case will be approximately 170 feet, 240 feet and 390 feet per minute. (3) Required^ the size of outfall sewer to accommodate a population of 100,000, using seventy gallons per diem per capita. Solution. We observe that 15,000 is the greatest num- ber provided for in the column of Tributary Population. At the right, however, will be found a supplementary diagram, in which the gallons are ten times the corresponding- number of gallons in the main diagram. We can, therefore, use that part of the diagram to the left of the column marked "total gallons per diem" in connection with the supplementary table, by multiplying- "lineal feet of sewer" or "tributary population" by 10. Starting thus at 10,000 in the column of tributary population, trace the line upward and to the rig-ht, to its intersection with the vertical representing- ninety gal- lons, thence horizontally to the supplementary table, we read CHAP. VI. LAWS OF FLOW L\ SKWISKS. 110 9,000,000 g"allons daily, and continuing- the horLzontal line we cross the sewers of 54 inches in diameter at .06 per 100 g^rade. 48 inches in diameter at .11 per 100 grade. 40 inches in diameter at .26 per 100 grade. 36 inches in diameter at .44 per 100 grade. Either one of these sewers laid at the grade indicated will till the conditions. (4) Required^ the number of people using- sev^enty-five g-allons per diem each, that can be served by a 4-inch house drain, laid at a grade of 2 in 100. Sohitioii. Tracing a line from the point where the curve of 4-inch diameter is intersected by the vertical of grade per hundred = 2, to the left and horizontally to the vertical of seventy-five gallons, thence to the left and downward we read 1,000 people. Other uses of the diagram will readily suggest them- selves. Of the four quantities, Total gallons per day. Velocity, Fall in 100, Diameter, any two being given, the other two can be determined by inspection of the diagram. Let us take that portion of the Cit\' of Schenectady, N. Y., lying between the Erie Canal and the Mohawk River, and tributary to the Front street sub-main sewer, as an example illustrating- the use of the table in proportioning a complete system. The territory has at present a population of 5,000, dis- tributed with tolerable uniformity. The ag-g-reg-ate length of the sewer is 15,065 feet,- giving- thirty-three persons for each 100 feet of sewer. In this case it is not likely that the territory will ever reach a g-reater density of population. We will assume, however, that it may reach a density 120 THE SEPARATK SYSTEM OF SEWERAGE. expressed by fifty persons for each lOO feet of the sewer, and will assume a discharg^e of seventy-five g^allons per diem per capita. First, arrange the distance of the various branches so that the ag"g"reg"ate leng^th of sewer tributary to any point can readily be seen on inspection as follows: From corner Washington Ave. and Union St. to corner of State and Church Streets 860 Church — Union to State 400 1260 State — Church to Ferry 440 State — Canal to Ferry 530 • 2230 2230 Ferry — State to Liberty 245 Liberty — Erie Canal to Ferry 730 3205 Ferry — Liberty to Union 290 Washington Ave. and Union to Church 625 Church — Front to Union 450 1075 Union^Church to Ferry 425 1500 1500 4995 Ferry — Union to Front 725 Washington Ave. and Front to Ferry 1200 6920 Front — Ferry to College 935 College — Liberty to Union 350 Union — Ferry to College .... 830 College — Union to Green 665 1845 Green — Ferry to College .■ 825 Green— R, R, to College. i75 2845 College — Green to Front 560 3405 3405 1 1 260 CHAP. VI. LAWS OF FLOW IN SICWIOKS. 121 Bro!ii^^/if for-ward 1 1260 Front — College to John 420 John Street 74° 12420 Front —John to Jefferson 255 Jefferson 600 Madison 200 800 800 13475 Front — Jefferson to Monroe 250 13725 Monroe 5°° Front — Monroe to outlet main 840 15065 If we assume the smallest laterals to be six inches in diameter and the g-rade to be .5 per 100, we see from the diag-ram that their limiting- leng-th in this case is 2,800 feet. This size will, therefore, suffice until their agg"regate length exceeds 2,800 feet. Should the g-rade be increased, however, at this point the 6-inch sewer may be extended still farther. Inspecting- the fig-ures made above, we determine that the size must be increased after the junction of the Liberty street and Ferry street sewers. Assuming- the g-rade imme- diately below this point to be A per 100, we determine from the diag-ram that an 8-inch pipe will suffice up to an ag-gre- g-ate length of 5,000 feet. Inspecting- the summation above, we determine that this is reached after the Ferry street sewer receives the Union street sewer and its tributary branches. From this point then, the size must be increased. Assuming the grades from this point to be .28 per 100, we determine from the diagram the limiting- length of a 10-inch pipe to be 7,500 feet. From the summary of leng-th we see that this would require a still g-reater increase of size, the grade being- the same, 355 feet above the junction of the Col- lege street sewer. A man-hole at this point is not contem- 122 THE SEPARATE SYSTEM OF SEWERAGE. plated, and a chang"e in size between man-holes is not advisa- ble; we will, therefore, increase the g-rade, retaining- the same size. Recurring- to the diagram, we see that the required g-rade, the diameter being- ten inches and the ag^g-re- g-ate leng-th being- 7, 855 (or, in round numbers, 8,000) feet, is .32 per 100. The g-rade from a point 355 feet above College street, will, therefore, be increased to .32 per 100. Taking up, now, the branches tributary to the Colleg-e street sewer, and remembering- that our limiting distance for the smaller laterals is 2,S00 feet, we note that the size must be increased at the junction of the Green street sewer. It is evident that from this point to the Front street main an 8-inch pipe will be ample. Uniting- the College street sub-main with the Front street main, we have an aggreg-ate leng-th of 11,200 feet. Assuming the grade below to be .32 per 100, the diag-ram g-ives the limiting length for a 12-inch sewer as 12,700. This is reached when we add the Madison street sewer and tribu- taries. From this point the g-rade required to reach Monroe street (13,375 feet, ag-greg-ate distance), we find by the diag-ram to be .36 per 100, and to reach the main outlet (15,0(35 feet, ag-g-reg-ate distance), .14 per 100, the size of sewer being- maintained at twelve inches. Incidentally we note that the velocity at this point is two hundred feet per minute, and the daily discharg-e 565,000 gallons. If the formula of Kutter is preferred the procedure is precisely similar, using- the red lines instead of the black ones. The computations can be made with the same facility, commencing at the outlet and proceeding- toward the dead ends. A comparison of the results obtained from the dia- g-ram by different persons show them to ag-ree within about one per cent., an error of no consequence when the data can- not be stated with precision. CHAP. VI. LAWS OF FLOW IN Si: WICKS. 123 It is proper to state that Baldwin Latham, in calculating- the tables on which the diag^ram is based, has assumed a value for h equal to the velocity in feet per second in each case, to simplify the computations. The tables are, there- fore, stricth' correct only when the leng-th in feet equal the velocit}^ in feet per second; multiplied by the denominator of the fractional inclination. Thus: n 200 490 feet. n 100 355 feet. n 400 5)80 feet. n 200 710 feet. n 1000 2166 feet. n 5000 1575 feet. 6-inch pipe, g-rade 1 6-inch pipe, grade 1 12-inch pipe, g^rade 1 12-incb pipe, g-rade 1 24:-inch pipe, g-rade 1 21:-inch pipe, g-rade 1 Comparison of Various Standard Formulae. — Some authorities prefer to use other formuke than those of Weis- bach, on which the diag-ram is based. A comparison of the results obtained from various standard formulae is presented below. The following are some of the standard formulee used by the best authorities: _ n/2o7/ ^l+r+/: 1.S113 Baldwin Latham, J Weisbach, \ I w.m Kutter, . . r'= - ■ d .002807 S .002807 n y/RS = Cs/ RS in which t' = mean velocity in feet per second. C= coefficient of mean velocity. iS'=sine of slope. y?=hydraulic mean radius. ;/ = deg-reeof roug-hness, determined by experiment. Beardmore, .... z'=lOOs/ R^ Eytelwein, v — \Y?,Ax^ Rs 12-i THE SEPARATE SYSTEM OF SEWERAGE. Box Shone, ) '' 373. 98^ in which fl!'=diameter in inches. Zr=head in feet. Z=leng-th in yards. a = sectional area in square feet. . — N'.00371(^+1)Z in which ^= diameter in inches. //=head in feet. Z, = leng-th in feet. From these formula? the following- table has been com- puted: CHAP. VI. LAWS OF FLOW IN SKWFKS. 125 TABLE XIX. COMPARING THE DISCHARGE IN THE VARIOUS CASES AS GIVEN BY DIFFERENT STANDARD FORMULA. B - KUTTER. «= n .013 .015 6 •50 6 2.00 12 •25 12 1.50 18 .14 18 1.00 24 .10 24 .50 DISCHARGE IN CUBIC FEET. 28.81 60. 17 115 40 294 90 236.50 660.90 408.50 958.30 25.68 21. I 51 36 42.2 132.00 102.0 318 00 272.0 294.00 234 762.00 618.0 516.00 420.0 1, 170 00 9540 16.80 33 60 83 40 203.85 191 97 513 00 35800 801.00 29.4 58.8 118 288.4 243 649 421-5 942.6 27.69 55.38 no 90 270 go 229.00 612.00 398.00 888.00 27.0 54.2 108.4 223.0 30.9 61.8 128 315 264 718 472 ,056 PERCENTAGE RELATION. 6 ■50 6 2.00 2 •25 2 1.50 8 .14 8 1. 00 4 .10 4 .50 100 100 100 100 100 100 100 100 89 85 114 107 124 115 126 123 73 70 88 92 99 94 103 TOO 68 56 72 69 81 79 88 83 102 98 102 98 103 98 103 96 92 96 92 97 93 98 93 94 90 94 94 107 103 112 107 112 109 116 126 THE SEPARATE SYSTEM OT^ SEWERAGE. It will be observed that, with the exception of Kutter's formula, the results above g"iven, thoug-h not equal, run approximately parallel. Kutter's formula g^ives much smaller values for sewers of small diameter, and much larger values for sewers of larg-e diameter. When w = 15, the values g^iven by Kutter and Latham are approximately equal for a sewer five feet in diameter. This value of ;/, however, is not applicable to vitrified pipe sewers, well constructed, unless it be on verv sharp curves, where ordinarily the work is less perfect. Loss of Head on Curves. — An increase of inclination should be given around curves, both to overcome the increased friction due to ang-ular chang"e in direction, and also for the reason that, as ordinarily laid, there is a slig^ht opening" of the joints in the outward circumference and g-reater liability to stoppag^e from articles lodg-ing- crosswise. The allowance indicated by theory for the increase of friction on curves is not sufficient, for the reason that pipes are not usuall}^ laid so truly to line or g-rade as when laid in straig-ht lines, and, aside from the increased friction due to the angular chang-e in direction, we may properly increase the coefficient of resistance to flow in the pipe. The following- is Baldwin Latham's modification of Weis- bach's formula for loss of head due to ang^ular friction: /^ = head necessary to overcome ang^ular friction. z' = velocit3^ in feet per second. (/ = angle in deg^rees. r= radius of pipe. /."^radius of the bend. 2^=64.38. ^^coefficient. a V h — cV. — X — or, 90 2^ CHAP. VI. LAWS OF FLOW IN SICWIOKS. 127 ■X^?Xf 579.4 In which r=. 131X1.847 (Eq. 6) M /> .2 ■3 ■4 .5 1 .6 •7 .8 •9 I.O < = .i3i .138 .158 .206 .294 .440 .661 •977 1.408 1.978 Assuming- a 6-inch sewer laid with a curve of fifty feet radius, the ang^le of the curve being- sixty deg-rees, or its length 52.4 feet, and tlie velocity above the curve to be five feet per second, the increased head necessary to overcome friction due to angular change in direction is, according- to equation six, less than one-eighth of an inch. In no case which could possibly occur in curves of a proper radius will the formula give more than a small fraction of an inch as the value of //. This is too small to be considered in w'ork of this class. In proposing- a formula for the increased head or inclina- tion required for curves as ordinarily laid in sewer work, we may, therefore, disreg-ard the effect of ang-ular change in direction. If, however, we assume that the increased roug-hness of the pipe would increase the coefficient ;/, as g-iven in Kutter's formula, from ;/ = .011, its value as g-iven for plaster of cement with yz sand, to ;/ = .013 and ;/ = .015, its value as g-iven for brick work and terra cotta pipes wath imperfect joints and in bad order, we have from Kutter's formula, by computation, the following table: 128 THE SEPARATE SYSTEM OF SEWERAGE. TABLE XX. SHOWING INCREASED FRICTIONAL HEAD REQCIRED FOR CURVES IN VARIOUS CASES. r=2' 2 FEtT I'=5 FEET PER Diameter. Coefficient of Resist- ance. Velocity. age Rela- tion of C. * PER SECOND. SECOND. Grade per IOC. Loss of Grade per 100. Grade per 100. Loss of Grade per 100 6 inch ;/=.oii 87 35 VA^-^ 100.00 .65 .... 2.62 " " .==.013 69.777 A\S' 7986 1.02 ■37 4 10 1.48 " " ;;= 015 57.i5\/A\S- 66 00 1-53 .87 6.12 3^5o 12 inch //=.OII 105 74 V /\S 100 00 .22 .89 " //=.oi3 84.927^' 80.31 •34 .12 1.38 •49 " «=.oi5 70.8 V7^- 66 00 •49 .27 I 99 1. 10 i8 inch ;/=.oii 116. 2 V A^' 100.00 .12 •49 .. ,. //=.oi3 94 7 V^^ 81.45 .18 .06 •74 25 " ;/= 015 79.0 V^' 68.00 .26 ■14 1.06 ■57 *According to Kutter. In the columns of loss of grade per 100 feet can be found the increased fall necessary, under the supposition that, on ordinary curves, n is increased from .011 to .013, and on sharp curves from .011 to .01.5. It will be observed that when « = .013 the value of C is decreased to about eig^hty per cent, in all cases. Recurring- to the g-eneral formula of Chezy, which for the ordinary rang-e of diameter and velocity, becomes, approximate!}'. We mav write for ordinarv curves. z; = 80v/i?6" CHAP. VI. LAWS OF FLOW IN SEWERS. 129 in which S'= — = slope required. / From the preceding" equations we have S= (100)'/? S' = (80)*/? Or, since in each case the hydraulic mean radius when the sewer is half full= — 4 ^^' ^ — . 1600^/ 2500^ H—h' — // = = loss of head required (Eq. 7) In pipe sew^ers, however, the roug^hness is somewhat dependent on the ratio of the radius of the curve to diameter of the pipe. Empirical Formula. — The following" formula will g"ive g"Ood results in pipe sewers: z'V ( 10^ ) //= 1+ \ (Eq. 8) iOOOrt' { r ) in which z' = velocity in feet per second. /=leng-th of curve in feet. o pn m 00 m O o> d o -M^Mli oi-i in ro o in t^ J3 < ■SnizBio lO o rr' m o- rf rr in N (N r** m !-J t-~ w •ueds o CJ ^ c- O M rr c^ o o\ CT O c CT> 00 o PO •ni 9 jj z no -sqq N o- VO r^ PO o in in o o ^ o C »_( < J ■jooj jad •sqT UI }q3pA\ d IN O O r^ 1- "*■ ■^ -"l- Tl- rj- t: o o o r -^ '*- "*- -Jt H H EX, 1) c o td td tr. _C ] 4. o .c 4 C O H (d H 0^ o w i-T 3 o 15 C c C c c 1- < > C c K o: C O ^ o 6 c U <- m ^ .- tJ '^ 3 CQ >. 1 ^ c 1 a 'J- C c c 7 c > 0) N CO a E t: c a ;- C C "S o XI ii cfl U IS -a o 2 U <- 1 ■s < '3 c c ^ _c u ao < I- u c a C c : 'J C > c 1 1 lU tJ c 00 o t: 4. a 0. T C X. - - t/ "a >- a o s CM o c e s H ^ c a c ^ en 132 THE SEPARATE SYSTEM OF SEWERAGE. Tests of double strength sewer pipe, manufactured by Blackmer and Post were made b}' H. R. Gates, Superinten- dent of the Geo. J. Fritz Foundry and Machine Co., with the following- results: I Section 24-inch Double Strength Culvert Pipe, 2 inches thick, broke at 27,610 pounds. I Section 24-inch Double Strength Culvert Pipe, 2 inches thick, broke at 28,715 pounds. I Section 27-inch Double Strength Culvert Pipe. 2.% inches thick, broke at 33. 133 pounds. I Section 27-inch Double Strength Culvert Pipe, 254^ inches thick, broke at 32,763 pounds. I Section 30-inch Double Strength Culvert Pipe, 2% inches thick, broke at 27,987 pounds. I Section 30-inch Double Strength Culvert Pipe, 2)^ inches thick, broke at 24,297 pounds. I Section 27-inch Standard Culvert Pipe, 2]/% inches thick, broke at 23,986 pounds. I Section 27-inch Standard Culvert Pipe, 2]/% inches thick, broke at 22,530 pounds. I Section 30-inch Standard Culvert Pipe, 2% inches thick, broke at 27,875 pounds. Internal pressure was applied with the following results: 24-inch Culvert Pipe burst at 100 pounds pressure to the square inch, showing a horizontal crack on the side from end to end. 27-inch Culvert Pipe showed no weakness of the material or in the joint at 100 pounds pressure, but the bulkheads leaked so much that no more pressure could be applied. 30-inch Culvert Pipe showed no weakness of material or in the joint at 100 pounds pressure, but the bulkheads leaked so much that no more pressure could be applied. In making the tests as shown, blocks of wood were hollowed out to fit as nearly as practicable the shape of the pipe, each block coyering a little less than one-fourth the circumference of the pipe, the power being supplied by a hand-pump, the pressure being registered on the guage as applied. CHAP. YII. MATKKIAL AND ACCESSOKIIOS. 133 The capacity of vitrified salt-g-lazed sewer pipe to resist abrasion is very marked. Hand-Holes. — A "hand-hole" is a piece of pipe provided with a detachable section. See Fig-. 2. These hand-holes afford the means of removing- obstructions without breaking the pipe. They are usually laid at intervals of about one hundred feet. Their use may be dispensed wath and the sewer may be opened when necessary by removing the cap from a Y branch. Fig. 2. Lamp-Holes. — At intervals a T should be placed in the sewer and a stand-pipe carried to the surface, forming an opening where the action of the sewer may be observed. See Plate I. Part of them may stop just beneath the pavement and be covered with a lig-ht casting-, shown in Plate I, and at longer intervals part of them may be carried to the surface and protected with a cast iron cover. Fresh Air Inlets. — These will answer in place of man- holes in some cases when the distance between the junction of two or more sewers is considerable. They afford facili- ties for inspection, and have the advantage of preserving the flow of sewage in its proper sectional form and precluding- the possibility of deposit. They are, however, not as available as points from which cleaning tools can be inserted into the sewer. They should be covered with a perforated cast-iron cover, similar to that shown in Plate II, to assist in the venti- lation of the sewer. The}' can be very cheaply constructed. 134 THE sepakatp: system of sewerage. Man-Holes. — Where two or more sewers unite a man- hole should be placed. See Plates V, VI, VII, VIII. Thej should be built of selected, hard brick, laid in cement mor- tar, plastered outside, and surmounted by a heavy cast-iron cover. It is very difficult to make a proper connection between two pipe sewers of larg-e size by the use of the ordi- nary Y branch. The man-holes are also required for pur- poses of inspection, repair, removal of obstructions, and ventilation. The advisability of omitting- man-holes has been consid- erably discussed of late, but in cases where they have been omitted it has usually resulted in their being- built subse- quently. They add larg-ely to the cost in the Separate System and should not be used more frequently than is necessary. Flush-Tanks. — All dead ends should be supplied with automatic flushing tanks, the size of which should be propor- tioned to the size of the lateral. They should be built of selected, hard brick and cement mortar, and plastered inside and outside, and surmounted by a heavy iron cover. They are usually supplied with water from the street mains throug-h an ordinary service pipe of small size, and the admission of water is controlled by an ordinary lever handle stop-cock. They are built in various forms and will be more particularly described in the chapter on Flushing- and Ven- tilation. Y Branches. — The usual form of Y branch is shown in Plates I and X. It consists, essentially, of a cylinder of smaller diameter intersecting- the main pipe at an ang-le of about thirty deg-rees, measured on the side of the intersec- tion toward the socket end of the main pipe. The axis of the intersecting cylinders meet in a common point. The Y branch can, therefore, be turned to the right or left with equal facility. PLATE II. DETAILS — OF — FRESH AIR INLET. CHAP. VII. MATICKIAL AND ACCESSORIES 137 Another form of Y branch is shown in section in Plate I. It consists of an intersecting- frustum of a cone, the diam- eter of whose base is equal to the diameter of the main pipe and common with it. It is claimed for this branch that it induces a more perfect ventilation by entirely withdrawing- the air from the crown of the main sewer. It is open to the objection that it does not preserv^e the proper cross-sectional form of the stream but allows it to spread out laterally into the branch itself, thus breaking- up the continuity of the flow, decreasing- the velocity, and tend- ing- to the formation of eddies and deposits. The comparative effect of the two styles of Y branch upon-the cross section of the stream when the pipes are flow- ing- half full is shown in Plate I. CHAPTER VIII. SPECIFICATIONS AND CONTRACT. Letting the Contract. — Having- determined upon the plan for a system of sewers, the sizes of the pipes required for the different lines, and the details of the accessories, the next step is to arrange for constructing the sewers. The usual way is to advertise for bids for constructing" the work according" to the plans and specifications prepared by the Engineer. A description of the work and approxi- mate quantities — subject to change by the Eng'ineer — may be given either in the notice to conti'actors, or in an estimate filed with the detailed plans and profiles, which have been prepared to accompany the specifications. All drawings should be carefully made to scale, and full descriptions of them should be written out, so that every point may be made plain and nothing left to be inferred. As a guide in this work a few blank forms are presented, which can be modified to suit the requirements of particular cases. No general specifications can be properly applied in work where the conditions are unusual and these specifica- tions are to be used onl}' as a general guide upon which may be founded specifications adapted to local conditions and local laws. CHAP. VIII. SPECIFICATIONS AND CONTRACT. 139 [form for ADVERTISEMENT.] NOTICE TO CONTRACTORS. Sealed proposals will be received at the ofHce of the Sewer Commission in the City of until . . . . o'clock , on the day of , i . . . , for constructing sewers in Forms of proposals, copies of the specifications and instructions to con- tractors may be obtained of the Engineer; and the plans and profiles may be seen at his office. Each bid must be accompanied by a deposit of S as a guarantee of the good faith of the bidder. The Sewer Commission reserve the right to reject any or all bids. Address, Engineer. [instructions to CONTRACTORS.] TO CONTRACTORS. 1. All bids must be made upon the printed forms, to be obtained at the ofiice of the Engineer, and enclosed in a sealed envelope, directed to the Engineer of Sewers and endorsed upon the outside of the envelope. Proposal for constructing Sew- ers in the City of 2. Each bid must be accompanied by a deposit of Dollars, to be left in the hands of the City Clerk, subject to the conditions specified in the proposal hereto annexed, as a guarantee of the good faith of the bidder. 3. -Bids shall state the price per lineal foot of pipes of each size laid as herein specified, and for the various depths of trench named, also for all other items enumerated in the schedule opposite, which price shall be in full for all labor and materials required for the complete execution of the work. 4. All prices must be written in words, and also stated in figures. 140 THE SEPARATE SYSTEM OF SEWERAGE. 5. The place of residence of each bidder must be given after his signa- ture, which must be written in full. When firms bid, the individual names of the members shall be signed in full, and the firm name added. 6. The name of the contractor must be filled in the blanks left for that purpose. 7. The City of reserves the right to reject any or all bids. 8. Bidders are requested to be present at the openmg of the bids. g. The bond required of the successful bidder shall be in the sum of [form of proposal.] PROPOSAL. To the Sc'Toer Conuuissioii of the Lily of Gentlemen: The undersigned hereby propose to furnish all of the- mate- rials and do all of the work required to complete such amount of the above mentioned work as shall be awarded to the undersigned by the City of in a first class manner, and in accordance with the specifications hereto annexed, and the plans and drawings of the same on file in your Engineer's office, at the following prices, viz.: CHAP. VIII. SPECIFICATIONS AND CONTRACT. 141 ITEMS. Price per lineal foot for furnishing and laying i8-inch pipe, including Ys, branches, detachable covers, and cement joints Price per lineal foot for furnishing and laying 15-inch pipe, including Ys, branches, detachable covers, and cement joints ^^ Price per lineal foot for furnishing and laying 12-inch pipe, including Ys, branches, detachable covers, and cement joints Price per lineal foot for furnishing and laying lo-inch pipe, including Ys, branches, detachable covers, and cement joints Price per lineal foot for furnishing and laying 8-inch pipe, including Ys, branches, detachable covers, and cement joints Price per lineal foot for furnishing and laying 6-inch pipe, including \'s, branches, detachable covers, and cement joints Price per lineal foot for all excavation and back-filling under 6 feet deep Price per lineal foot for all excavation and back-filling 6 feet or over, and under 8 feet Price per lineal foot for all excavation and back-filling 8 feet or over, and under 10 feet Price per lineal foot for all excavation and back-filling 10 feet or over, and under i2 feet Price per lineal foot for all excavation and back-filling 12 feet or over, and under 14 feet Price per lineal foot for all excavation and back-filling 14 feet or over, and under 16 feet Price per lineal foot for all excavation and back-filling 16 feet or over, and under 18 feet Rock Trench per lineal foot, per foot in depth. Price per lineal foot for repaving Man-holes, complete, each Lamp-holes, " " Flush-Tanks. " " Price per ton for iron pipe, laid with lead joints, com plete 3-inch drain tile, laid, per foot.. 4-inch " 5-inch " " " Price in Figures. Price in Words. 142 THE SEPARATE SYSTEM OF SEWERAGE. 6-inch drain tile, laid per foot 42-inch brick sewer, laid, per foot.. 40-inch " " 36-inch " " " 30-inch " " " 24-inch " " " fc Embankment, price per cubic jard. And hereby agree to enter into a contract within five days from the date of your acceptance of this proposal, to finish and complete said work (by the day of, ), according to the form hereto attached, and the plans and specifications on file in the office of the Engineer, under which the bid was made, and will furnish such sureties for the faithful performance of such contract, the payment for materials contracted for, and for the payment of laborer's wages and liens which may arise there- from, as shall be approved by the Sewer Commission. In default of the performance of any of the conditions on part to be performed, the sum of Dollars, which have this day deposited with the Sewer Commission, shall, at the option of the said Sewer Commission, be absolutely forfeited to the City of but otherwise said sum of Dollars shall be returned to Dated at the day of I . . . . [Contractors Signature,] [P. O. Address,] No [State,] No City Clerk. chap. viii. spkcificatioxs and contract. 143 [fokm for specifications and contract,] ARTICLES OF AGREEMENT. Between the City of party of the first part, and Contractor, party of the second part, for building Sewers in ' This Agreement, made and entered into this day of in the year one thousand hundred , b\- and between the City of party of the first part, and Contractor. ., party of the second part. Witnesscth, Whereas, The City of in the State of : by virtue of the authority vested in the Sewer Commission by the Legislature of the State of and by the Charter and Ordinances of the City, agree to let unto the said Contractor . . the work of constructing certain Sewers, as per plans and profiles of the work on file in the office of the Engineer of Sewers. Now, Therefore, in consideration of the payments and covenants herein- after mentioned to be made and performed by said party of the first part, the said hereby covenants and agrees to do the work above mentioned in a substantial and workmanlike manner, in conformity with the plans, profiles and specifications of such work on file in the office of the Engineer, in strict obedience to the directions which may from time to time be given by the said Engineer or his duly authorized assistants, and in accordance with the following specifications. SPECIFICATIONS FOR SEWERS. In the City of BRICK SEWERS. I. The ground shall be excavated in open trenches to the necessary width and depth. The trenches shall be opened at least one foot wider on each side than the exterior diameter of the sewer intended to be laid. The bottom of the trenches shall be formed to the required grade and to the shape of the sewer, so that the whole surface of the under half of the sewer shall have an 144 THE SEPARATE SYSTEM OF SEWERAGE. even bearing throughout. In the trench thus formed shall be spread cement mortar, as the bricks are laid, not less than one inch thick; upon this shall be laid the inverted arch. The upper half of the sewer shall be covered with a coating of cement mortar not less than % inch thick. The work shall be backed in, carefully ramming and packing under and around the sewer with proper tools, by a trusty person approved by the Engineer. 2. In the construction of the work, none but the best quality of whole brick, burnt hard entirely through, shall be used. They shall be thoroughly wet immediately before being laid. Every brick is required to have full cement joints on the bed, sides and ends, unless otherwise ordered by the Engineer, which for each brick is to be formed at one operation, and in no case is to be made by working in the cement after the brick is laid; not more than two courses of bricks shall be laid without being lined. The bricks in each course shall be laid as stretchers and shall break joints with those of adjoining courses. The bricks shall be culled before being brought upon the ground, and all brick of an improper quality, and all bats, removed from the street. 3. The cement mortar shall be composed of the best quality of fresh ground cement, mixed in the proper proportion of one part of cement to two parts of clean sharp sand, free from loam and shall be used immediately after it has been mixed; any that has stiffened by commencing to set shall be rejected. All cement will be subject to inspection and test before it is used, the Engineer to decide upon the character and severity of the test, and if found of improper quality it must be immediately removed from the work. 4. Whenever it shall be deemed necessary by the Engineer, the sewer shall be built in a wooden invert constructed of ij^ inch pine plank, securely nailed to 2x3^ inch ribs placed not more than six feet apart and formed to cor- respond with the exterior of the sewer, which invert shall extend each side of the sewer at least one-third the height of the same. 5. The sewer shall conform in shape and size to the pattern furnished by the contractor, and made from drawings furnished by the engineer. 6. The whole of the joints of the inner face of the sewer, below the springing line of the arch, to be smoothly and properly struck. Those above the springing line, scraped even with the bricks, as soon as the centres are struck. The refuse mortar must be immediately removed from the sewer. 7. In keying the crown of the arch no headers are to be used. The inner and outer courses of stretchers are to be carried over and keyed separately, and each course in the crown of the arch is to be thoroughly grouted with grout composed of equal parts of clean, sharp sand, and best quality of fresh ground cement as directed by the Engineer. CHAP. VIII. SPIOCIFICATIONS AND CONTRACT. 145 8. All brick work must be racked back in courses, and when new work is to be joined to it, the surface of the bricks must be cleaned and moistened. The inner ring shall be laid of selected brick. No inside joint shall be greater than 3-16 inch. 9. The upper arch shall be laid upon centres, not less than 10 feet long for straight work. For curved brick sewers, the centres must correspond with the radius of the curve. The centres shall not be drawn until the back filling is above the top of the arch, without the permission of the Engineer. All centres and templets shall be scraped clean before use. The contractor will be held responsible for any distortion of the sewer by reason of the subsequent settlement of the trenches. 10. Man-holes shall be built into the sewer at such places as the Engineer may direct; the side walls to begin at the springing line of the upper arch of the sewer. Size, form, thickness of wall, cover and all details to conform to the Engineer's drawings accompanying the specifications. Wrought iron steps of 7-8 inch round iron shall be placed in the man-holes. Distance apart of steps, 18 inches; length of tread, 10 inches; projection from brick work, 4 inches. The iron to extend through the wall and clinch one inch on the out- side. 11. Branch sewer connections and house connections shall be built into the sewer at such points and in such manner as the Engineer may direct. Branches not to exceed on an average, one every 25 feet on each side. EARTHENWARE PIPE SEWERS. 12. The sewers shall be constructed of first quality vitrified, salt-glazed sewer pipe, sound and well burned thrcughout their thickness, impervious to moisture, of smooth and well glazed exterior and interior surfaces, free from cracks, flaws, blisters, fire-checks, end all other imperfections, circular in the bore, of true form in their lengths, whether straight or curved, internally of the exact specified diameter, r nd of uniform standard thickness. 13. All pipe shall be socket pipe, with true and circular sockets concen- tric with the bore of the pipe, and shall be furnished in pieces two feet long. For all junction pieces, a well fitted vitrified stopper shall be furnished, with- out charge. 14. A Y branch connection of inches, in diameter shall be provided every twenty-five feet en each side, when ordered by the Engineer. IRON PIPE. 15. Iron pipe shall be used where the sewer runs under or through water- ways — either natural or artificial — or under a railroad, or wherever it is deemed necessary by the Engineer. The joints shall be of lead properly caulked. The 146 THE SEPARATE SYSTE:M OF SEWERAGE. lengths of pipe, their diameter and thickness to be as directed by the Engineer. The weight of each pipe shall be plainly marked on it before leaving the factory. i6. The iron pipe shall be paid for by the ton, laid in place with joints complete. LOCATION. 17. The sewers shall be located on the lines shown on the plans of the work, and will be staked out by the Engineer. This line, whenever practica- ble, will be on the centre line of the street. The Commissioners, however, reserve the right to move the line of sewers to the right or left whenever obstructions are met which render a change of line desirable. 18. The contractor will be required to preserve all stakes and bench marks until permission is given by the Engineer to remove them. ig. The line for trenches will be indicated by stakes set at one side of the trench. A width of at least two feet, on the side of the trench where the stakes are, shall, as the work progresses be kept free from obstruction. EXCAVATION'. 20. All excavations shall be by open cut from the surface. No tunneling will be allowed, except written permission be previously obtained from the Engineer. 21. The contractor will be required to keep the sides of the excavation vertical, by bracing or otherwise; but no allowance will be made therefor unless the same is left in the trench by written order of the Engineer. 22. The excavation, at the bottom, is to be made and shaped as nearly as possible to fit the lower half of the pipe to be laid, with holes cut at the joints for the sockets to rest in, so that the pipe shall have a uniform bearing on the ground from end to end. 23. At the height of half of the diameter of the pipe from the bottom, that is, at the height of the greatest horizontal diameter of the pipe, all trenches are to be eighteen inches wider than the greatest diameter of the pipe to be laid therein. 24. The trench shall be dug to within six inches of grade by measurement from the witness stakes on the surface. The last six inches shall be taken out after the grade pegs have been set in the bottom of the trench by the contractor under the direction of the Engineer. 25. The excavations for all man-holes, flush tanks, and other accessories shall be sufficient to leave at least one foot in the clear between their outer surfaces and the embankment or timber which may be used to protect it. CHAP, \-iri. SPKCIl'ICATIOXS AND CONTKAC'l". 1-17 26. The approximate depth of the cutting will be given by the Engineer before the excavation is begun. Grade and line will be given by the Engineer every 25 feet at the bottom of the trench, on stakes to be furnished and set by the contractor; or on overhead pieces, from which the position of the invert may be determined by a line parallel therewith. 27. In no case, without previous written permission from the Engineer, shall more than 500 feet of trench be opened in advance of the completed sewer and on the completion of each 500 feet of sewer, the street surface must be restored in good condition and all surplus material and rubbish from that section be immediately removed. 28. The material excavated shall be laid compactly on the sides of the trench and kept trimmed up so as to be of as little inconvenience as possible to the traveling public and adjoining tenants. 29. The contractor shall not obstruct the gutter of any street, but shall use all proper measures to provide for the free passage of surface water along the gutters. 30. The contractor shall provide for all water courses and drains inter- rupted during the progress of the work, and replace them in as good condition as he found them. The use of any portion of the sewers shall not be con- structed as an acceptance of them by the Commissioners. 31. No additional compensation shall be allowed for excavating man- holes, or flush tanks over the price per lineal foot for trench. 32. The contractor shall keep the trenches free from water during the progress of the work, as no pipe of masonry shall be laid in the water. PROTECTION OF PROPERTY. 33. The contractor shall at his own expense, shore up, protect, and make good, as may be necessary, all buildings, walls, fences or other property injured, or liable to be injured during the progress of the work; and the con- tractor will be held responsible for all damage which may happen to neighbor- ing property from neglect of this precaution, or from any other cause connected with the prosecution of the work. PROTECTION OF WATER AND GAS PIPES, ETC. 34. The contractor shall do whatever may be necessary to keep in posi- tion and to protect from injury all water and gas pipes, lamp posts, service pipes, and all other fixtures which may be met with in carrying on the work. 35. In case any of the said gas or water pipes or other fixtures be dam- aged, they may be repaired by the parties having control of the same, and the expense of such repairs shall be deducted from the amounts which may become due the contractor. 148 THE SEPARATE SYSTEM OF SEWERAGE. PROTECTION AGAINST ACCIDENTS. 36. The contractor shall erect suitable barriers around all excavations, to prevent accidents to passengers on the streets, and shall place and maintain during the night sufficient red lights on or near the work. 37. The contractor shall have charge of, and be responsible for, the entire line of sewers for whose construction he has contracted, until their completion and acceptance. He shall also be liable for any defects which may appear in his work before the final payments specified herein. BACK-FILLING. 38. The earth filled around and on top of the sewers shall be free from stones, and tamped with the utmost care, so as to obtain the greatest compact- ness and solidity possible. In filling, the earth shall be kept at the same height on both sides of the sewer when required by the Engineer. The earth shall be rammed in layers of not more than one foot thick up to the surface of the street, and in no case shall the number of men filling be more than twice the number of men ramming. In lieu of ramming, the earth may be thoroughly puddled. 39. The contractor is required not to sell, remove or permit to be removed from the line of the work, before the trench shall have been refilled, any sand, gravel, or earth excavated therefrom which may be suitable and required for refilling. 40. The trench must in all cases be filled to the proper grade with suit- able material. Should there be a deficiency of proper material for refilling the trench the contractor will be required to furnish the same at his own cost. REPAYING AND RESTORING STREETS. 41. When the pavement has been removed, it must be replaced by the contractor and left in as good condition as it was before being removed. 42. As the trenches are filled in and the work completed, the contractor shall remove all surplus material, without additional compensation, to localities not interfering with the regulations of the city, and shall leave all roads and places free, clean and in good order. 43. All work of restoring the surface of the streets shall be done to the satisfaction of the superintendent of streets. 44. If at any time during a period of one year from the date of the final completion and acceptance of the sewer, the roadway on the line of the sewer shall require regrading, repaving or regraveling, by reason of the settlement of the trenches, the Commissioners shall notify the party of the second part to make the repairs so required; and if the party of the second part shall neglect for a period of ten days to make such repairs to the satisfaction of the Com- CHAP. VIII. spi:cii'iCA rioxs and contract. 141> missioners, then the Commissioners shall have the right to cause the repairs to be made, and to pay the expense thereof out of the sum retained for that purpose. EMBANKMENT. 45. Where embankment is necessary to support the foundations of the sewer, or to cover or protect it in any way, it shall be made of the width and slopes as shown on the plan. Th.e surface of the ground receiving the embank- ment shall be carefully cleared of all muck or unsuitable material, of whatever nature The embankment shall then be formed of good loam or gravel, free from all stones over four inches in diameter, and of those below that size in a pro- portion not exceeding one part of stone to three parts of earth in any place. If built to support the foundation of the sewer, the material is to be depos- ited in layers of not more than six inches in thickness, each layer to be sepa- rately compacted by heavy iron rollers, or, where these cannot be used, by heavy paver's rammers. No breaks, steps or irregularities in the distribution of material or formation of the layers will be allowed, and the whole embank- ment is to be carried up evenly so as to make a compact and solid foundation. PIPES — HOW L.AID. 46. All pipes over eight inches in diameter shall be laid with a straight edge. One end of the straight edge shall be placed on the nearest grade peg and the other on the flow line of the pipe already laid, and the pipe shall be so adjusted as to be in contact with the straight edge throughout its length. All pipes eight inches and less in diameter, except house branches, shall be laid in the following manner: A mason's line shall be tightly stretched parallel to the grade and slightly above the sockets of the pipes. This line shall be supported over the centre at distances not greater than twenty-five feet apart. The exact grade for each pipe shall be obtained by measuring down from this line to the invert of the sewer. 47. Especial care must be taken to lay the pipe to the exact grade and line. 48 All pipes, previous to being lowered into the trench, shall be fitted together and matched, so that when joined in the trench they may form a true and smooth line of pipes. No pipes shall be trimmed in any case. Pipes which do not fit truly shall be rejected. JOINTS. 49. A gasket of oakum or other material approved by the Engineer shall be pressed into the joint around the entire circumference of the pipe to pre- 150 THE SEPARATE SYSTEM OF SEWERAGE. vent the entrance of cement to the inside of the pipe. No joint shall be cemented until the gasket of the next joint in advance has been completed. 50. The cement shall be pressed into the space between the socket and spigot so as to entirely fill the space, and the bevel joint at the end of the socket shall be smoothly and evenly made. Special care must be taken to make perfect joints at the bottom of the pipe. 51. The excavation made for the socket of the pipe shall be filled with sand to support the cement firmly in position. When the joint is completed great care must be taken not to disturb the pipes. 52. The cement for filling the joints shall be pure fresh ground cement, of best quality, with only enough water added to give it the proper consistency, and shall be mixed only as needed for use. BRANCHES, "t's, " ETC. 53. The "Y" branches, "T's," lamp-holes, hand-holes, and man-holes shall be placed at points indicated by the Engineer. They shall not be covered until he has noted and recorded their exact position. The "Y" branches shall be elevated to correspond to the lateral sewers and house drains entering them. They shall be closed with an earthenware cap, and the space above the cap shall be filled with sand, covered with a thin coating of cement. SPECIAL PIECES. 54. Special pieces, such as Y branches, curves, T's, etc , shall be made according to drawings furnished by the Engineer. SEWERS TO BE KEPT CLEAN AND FREE FROM WATER. 55. All the pipes must be kept thoroughly clean, and no water will be allowed to flow through them, during the construction of the sewers. 56. When the trench is left for the night, or the pipe-laying is stopped by rain storms or any other cause, the ends of the pipes must be closed water-tight with bricks and cement 57. When running quicksand or other treacherous ground is encountered, the work shall be carried on day and night, should the Engineer so require. ARTIFICIAL FOUNDATION. 58. Whenever ordered by the Engineer, in writing, the contractor shall excavate to such depth below grade as the Engineer may direct, and the exca- vation shall be brought to grade with such material as shall be ordered by the Engineer; the extra work to be paid for upon the estimate of the Engineer. CHAP. VIII. SPIXIIICATIOXS AND CONTKACT. 151 59. If the contractor excavates below grade without orders, he will be required, at his own expense, to fill the excess of excavation with such material as the Engineer may direct. 60. Concrete foundations shall be placed under the flush-tanks and man- holes. ROCK CUT. 61. When blasting is resorted to for making the excavations, the trench shall be covered carefully on the top and sides with heavy timbers and plank, to prevent fragments of rock from being thrown out. In rock cut, the rock shall be taken out of the trench to a depth of four inches below the bell of the pipe when laid. The refilling from the bottom of the trench to one foot above the bell of pipe shall be of earth, free from stones, or such material as shall be approved by the Engineer. 62. All damages or injury to persons or property resulting from blasting operations, or from neglect in properly guarding the trenches, must be paid by the contractor; and no compensation to said contractor for losses thus incurred will be allowed. LAMP-HOLES. 63. Lamp-holes shall be constructed by placing an eight-inch "T" branch vertically in the sewer, and bringing it up to within one foot of the street sur- face by adding pipes of the same diameter. The top of the lamp-hole shall be protected by cover, as shown in the detail drawing. MAN-HOLES. 64. The man-holes shall be constructed of hard brick, laid in cement mortar, and plastered outside with cement mortar and washed inside with pure cement. The thickness of the wall shall be eight inches. The form shall be a truncated cone (see drawings). The bottom shall be formed of concrete, and the top' of the concrete shall be on a level with the bottom of the sewer pipe, and the top of the cover on a level with the street surface. Particular care must be taken in forming the bottom of man-holes to make the curves of tribu- tary sewers as easy as possible. The top shall be covered with a perforated cast iron cover, with dust pan underneath. (See drawings.) FLUSH TANKS. 65. Flush-tanks shall be constructed of hard-burned bricks, carefully laid in cement mortar, so as to be water tight. They shall be plastered outside and inside with cement mortar. (For form, size and details see drawings.) 66. The emptying device for the flush tanks shall be selected and pur- chased by the Commissioners and shall be properly set by the contractor. 152 thp: separate system of sewerage. 67. The water supply pipe, within the flush tank, and extending through the wall and one foot outside of the wall, together with a suitable brass stop- cock for regulating the water supply, shall be furnished by the contractor. BRICK MASONRY. 68. None but the best quality of whole, sound, well shaped brick, burned hard entirely through, shall be used. They are to be culled when delivered upon the ground, and all bats and imperfect bricks are to be immediately removed from the work. All bricks are to be thoroughly wet immediately before laying. Every brick is required to be laid in a full and close joint of cement mortar, on its beds, ends, and sides, at one operation. In no case is mortar to be slushed in afterwards. CEMENT MORT-AR. 6g. All cement mortar for man-holes, lamp-holes and concrete, shall be made of best quality of fresh ground cement and clean sharp sand, in the proportion of one measure of cement to two of sand. The sand and cement shall be thoroughly mixed dry, and such quantity of water added as to form a paste of the proper consistency. All mortar shall be fresh for the work in hand. No mortar that has begun to set shall be used. Every facility for inspecting and testing the cement shall be furnished by the contractor. CONCRETE. 70 The concrete used on the work shall be made of three parts of cement mortar (made as described) and two parts of clean gravel, or broken stone. It shall be quickly and thoroughly mixed, and iramjdiately deposited in place. MATERIALS. 71. All materials shall be furnished by the contractor, and shall be sub- ject to inspection and acceptance by the Engineer. LENGTH OF SEWER. 72. The length of the sewer will be measured on the centre line of the completed sewer. INTERPRETATION OF TERMS. 73. Wherever the word "Commissioners" is used in these specifications, it shall be held to mean the Board of Sewer Commissioners of the City of Wherever the word "Engineer" is used, it shall be held to mean the Engi- neer in charge of the sewers, or his authorized assistant. CHAP. VIII. SPKCIFICATIONS AND CONTKAC'J'. 1.53 Wherever the word "Contractor" is used, it shall be held to mean either any contractor or firm of contractors, or any member of a firm, contracting for work herein specified. GENERAL STIPULATIONS. 74. The contractor shall start the work at such points on the line of the sewer as the Engineer may from time to time direct, and shall progress from the outlet, or towards the outlet, at the option of the Engineer. 75. Xo pipes or ma.sonry shall be laid in freezing weather. 76. None of the work shall be sub-let without the permission of the Com- missioners. 77> The contractor shall also do such extra work in connection with his contract as the Engineer may in writing specially direct, and in a first-class manner, but no claim for extra work shall be allowed unless the same was done in pursuance of a written order, as aforesaid, to do the work as such and the claim presented at the first estimate after the work was done. Extra work shall be paid for on a basis of 15 per cent, in advance of the actual cost of labor and material as determined by the Engineer. 78. Although the Engineer may assent to special means for prosecuting work in difficult cases, this will not relieve the contractor of the responsibility as to the result. 79. The contractor upon being so directed by the Engineer, shall remove, or rebuild, or make good, at his own cost, any work which the latter shall decide to be deficiently executed. So. No work shall be covered until it has been examined by the Engineer or inspector. 81. The Contractor will be required to observe all City Ordinances in relation to obstructing streets, keeping open passage ways and protecting the same where exposed, and, generally, to obey all Ordinances, Rules and Regu- lations controlling or limiting those engaged on the work. 82. At the suspension of any work the trenches shall be filled and the street left clean and free for travel. 83. The contractor shall give notice in writing, at least twenty-four hours before breaking ground, to all persons (Superintendents, Inspectors or other- wise) in charge of property, streets, gas pipes, water pipes, railroads or other- wise, that may be effected by his operations. And it is further agreed that the said part of the second part shall not cause any hindrance to or inter- ference with any such company or companies in protecting their said work; but that the said part of the second part will suffer the said company or com- panies to take all such measures as they may deem necessary for the purpose aforesaid. 154 THE skparatp: system of sewerage:. 84. The Commissioners shall have a right to make alterations in the line, grade, plan, form or quantity of the work herein contemplated, either before or after the commencement of the work. If such alterations diminish the quantity of work to be done they shall not constitute a claim for damages, or for anticipated profits on the work dispensed with; if they increase the amount of work, such increase shall be paid for according to the quantity actually done, and the price or prices stipulated for such work in this contract. 85. If any person employed by the contractor on the work shall appear to the Engineer to be incompetent or disorderly, he shall, on the requisition of the Engineer, be immediately discharged, and such person shall not be again employed upon the work without the permission of the Engineer. 86. The work embraced in this contract shall be begun within days after the award of this contract, and carried on regularly and uninterruptedly thereafter, with such a force as to secure its full completion by ; but should the work be delayed or interrupted by the City, after the service of such notice, the contractor shall be entitled to an extension of time equal to the time of such interruption or delay, which shall be determined by the Engineer; the time of beginning, rate of progress, and time of completion being essential conditions of this contract; and if the contractor shall fail to complete the work by the time above specified, the sum of per day, for each and every day thereafter, until such completion, shall be deducted from the moneys payable under this contract. This sum shall be in addition to any penalties otherwise specified. 87. No charge shall be made by the contractor for hindrances or delay from any cause during the progress of any portion of the work embraced in this contract 88. No variation from the regular prices named in the proposal will be made or allowed, whether the material through which the trenches are e.xca- vated is hard or soft, or whether it is composed of rock, boulders, walls or com- mon earth. The Board of City Commissioners will not consider themselves bound to notify or inform contractors where material that is hard or e.xpensive to excavate occurs, or will be liable to be encountered. Furthermore no com- pensation for trenching done in excess of the orders of the Engineer will be allowed. 89. A watchman shall be employed on the work at night whenever in the opinion of the Engineer it shall be necessary. 90. House branches shall be laid to a point just within the curb lines where the Engineer shall direct. 91. Should any dispute arise between the Engineer and contractor as to the true meaning of the drawings or specifications in any point, or as to the CHAP. VIII. SPKCIFICATIONS AND CONTRACT. 155 manner of the execution of the work, or the quality of the work executed, the decision of the former shall be final and concjusive. 92. And the said contractor, hereby expressly binds himself to indemnify and save harmless the City of from all suits or actions of every name and description brought against the said City, for, or on account of any injuries or damages received or sustained by any party or parties by or from the said or his servants or agents, in the construction of said work, or by or in consequence of any negligence in guarding the same, or any improper materials used in its construction, or by or on account of any act or omission of the said or his agents. 93. Said part. . . .of the second part further agree, .that in case of failure to furnish materials or execute the work in accordance with the plans and specifi- cations to the satisfaction of the Engineer, or to proceed with the same as rapidly as the said Engineer shall direct, that it shall be lawful for the said Sewer Commission, after three days' written notice of their intention so to do, by serving the notice on the part. ... of the second part either personally or by leaving a copy at usual place of business or residence fand if said party of the second part consist of more than one person, then by such service upon either of them), and at the expiration of an additional ten days thereafter to cancel said contract, and relet the same, or proceed to complete the work by the purchase of material and the hiring of labor; and if the sum so paid for the completion of the said contract shall exceed the sum due the part. ... of the second part under this contract, then the said part of the second part and sureties shall become liable to the party of the first part for any sum by which the expense of so doing the work shall exceed the su"m due under this contract as liquidated damages, and not by way of penalty, and the said contract shall thereupon become void, as to the part.... of the second part, except as to any right of action which may have accrued to the party of the first part against the part of the second part and sureties for not properly proceeding with and completing the work. 94. In consideration of the completion by said party of the second part, of all the work embraced in this contract, in conformity with the specifications and stipulations herein contained, and in strict accordance with the instructions of the Engineer, the City of party of the first part, hereby agrees to pay to the said party of the second part, the prices named in the "Proposal" which is hereto annexed, and which is hereby made a part of this contract. 95. Payments for the work shall be made monthly upon the estimate of the Engineer. Ten per cent, of the amounts due will be retained as a guaran- 156 THE SEPARATE SYSTEM OP' SEWERAGIi. tee against poor workmanship and materials. One-half of this reserve will be paid as soon as the work is completed and accepted and the balance at the expiration of one year after the acceptance of the work. /;/ Witness Whereof, the City of has caused its name to be affixed by thereunto duly authorized, and the said party of the second part h hand, the day and year aforesaid. Attest : [form of bond.] BOND. KnP70 all Men by these Presents, That 7oe . are held and firmly bound unto the City of in the sum of Dollars, lawful money of the United States of America, to be paid to the said City of , or to its certain attorney or assigns, to which payment, well and truly to be made, we bind ourselves, our heirs, executors, and admin- istrators, and each and every of them, firmly by these presents. Signed and sealed with our seals, and dated at this day of i . . . . The Condition of this Obligation is such, That Whereas, the said ha. . . . entered into a contract with the city of bearing date the day of i which said contract is hereunto attached. CHAP. VIII. SPECIFICATIONS AND CONTKACT. N'ow, T/u-reforc, If the said shall well and truly keep and perform all the terms and conditions of said contract, on part to be kept and performed, and shall indemnify and save harmless the said City of as therein stipulated, then this obligation shall be of no effect, but otherwise it shall remain in full force and virtue. L. S. L. S. L. S. L. S. CHAPTER IX. CONSTRUCTION. Before staking- out the line it will be necessary to find out the location of whatever g^as, water, and sewer pipe may have been previously laid. This is not always easily accom- plished. Work of this kind is frequently done under the direction of the so-called "practical man," who scorns "theory and science," and whose sublime confidence in his own ability is only equaled by his capacity for eng^ineering- blunders, as exhibited in bad plans and worse construction. One of the most annoying" thing^s to be met with in locating" sewers is to find water and gfas pipes running- hap- hazard throug"h the streets, havings been put down without system or sense, and worse than all, to find that no map or record of their location has ever been made. Importance of Record. — The value of the work will larg^ely depend on the facility and accuracy with which the exact location, laterally and vertically, of every part of the system can be indicated; and hence in the construction notes such methods must be used as will be rapid, accurate in the g"reatest possible deg"ree, and least liable to mistakes in recording". The following" described methods have been found to g"ive g"ood results: Alignment. — First, let the centre line of the sewer be located carefully on the g"round with a transit, making" a study, as the line is extended, of the map of g"as, water and sewer pipes previously referred to. All measurements should be made with a steel tape, and all notes made to the centre line of the sewer as run. Since it would be impossible to preserve this line, however. CHAP IX. CONvSTKUCriOX. 159 during- the construction, no stakes need be left in it, but stakes sliould be set to the rig-ht or left a uniform distance of about one foot g-reater than half the width of the proposed trench. This will bring- them within the space on the bank- usually left clean for the workmen to pass and repass in handling material, etc. The position of stakes is shown in Plate I. The stakes should be set at uniform distances of about twenty-five feet apart. They should be about one inch square in section, square on top, and of such a leng-th that they can be driven flush with the surface of the street. Where extreme accuracy is required it will be well to indi- cate the precise point in the stake by a tack driven into its top; but ordinaril}^ with the size of stake indicated, this will be unnecessary. The offset line should uniformly be taken on the same side to avoid confusion, and the notes should indicate the side on which it is taken. Reference Points. — The line is best located by'observing- to the nearest tenth of a foot the station which is intersected by the prolong-ed lines of brick walls or other permanent Sta. 640.4 Sta. 600 Sta. 500 37 ft. Fig. 3. BRICK HOUSE. 160 THE SEPARATE SYSTEM OF SEWERAGE. lines which are clearly defined, and also the distance from the corner of the building-, the line of whose wall is pro- long-ed, to the centre line of the sewer at the station observed as above. (See Fig". 3; the prolong-ation of the brick wall intersecting- the true line at station (U0.4, and being- at this point 37 feet distant from the corner of the building.) This will be found a much more satisfactory location than the ordinary method of tie lines or focal co-ordinates, requiring- less description in the notes, and gMving a sharper determi- nation of the point. It may be supplemented at street inter- sections and chang-es in direction, however, by the latter method with advantag-e. Two rules should be kept in mind in this method of loca- tion, viz.: Never record a measurement to the offset line, as it is only for use temporarily. Never leave a permanent stake in the true line, as it may lead to confusion. There will be no difficulty in finding the offset stakes, even thoug-h they be driven flush with the surface of the ground, as, having a starting- point, nearly the precise loca- tion can be determined by measurement. When the streets are paved with stone pavement, a block can be removed and the stake driven, and then the stone replaced. At chang-es in direction, the angular deflection should be recorded, and also the location of the intersecting- tangents, with reference to prominent and permanent objects. Curves. — When the angular deflection is slight, no curve will be required in the orig-inal location on the g-round, but the notes should g-ive the offset to be made from the inter- section of tangents, and from short stations equally distant from it on either side. The exact location of the centre line can then be determined by. drawing- a tape on the tang-ents either way from the intersection of tang-ents, and measuring- the offset required from the proper points on the tape, with an offset rod. CHAP. IX. CONSTKUCTION. 161 When the anovular deflection is considerable the curve should be run by transit or chord deflections in stations of twenty-five feet. Intermediate points can be interpolated in construction by ordinates from the chord. The method above indicated, when faithfully pursued, will enable us to replace any point in the transit line with precision. Transit Notes. — The transit notes should indicate approximately the distance from the sewer line to the build- ing's on either side, where they stand back from the street line. This may be taken by a g-ood transit man with suffi- cient accurac}^ by the eye, aided b}^ an occasional measure- ment. The intersection of both lines of all crossing- streets should be noted by station on the transit line, and also the offset from the transit line to ang"les in the street line. All crossing's of streams should also be taken, and whatever notes are necessary to completely determine and indicate the physical characteristics of the territory. The location should proceed from the outlet upward toward the hig^her levels of the system, and the various trib- utary branches should be tied to one another and to the main lines as often as possible, as a check on the work and as a g-uide in platting- the finished map. Level Notes. — The transit party should be followed by the leveler and assistants. The surface elevation should be taken on the true line, which can readily be obtained from the stakes left by the transit party by an offset measured by the leveling- rod, or in ordinary cases can be determined with sufficient accuracy by the eye, after a little practice. The levels should be carefully checked at each bench-mark, as described on pag-e 61. In cases where there is a sharp transverse slope to the surface of the g-round, or when the 162 THE SEPARATK SYSTEM OF SEWERAGE. building-s on one side of the street are considerabl\" elevated or depressed below the street level, this should be carefully noted, and also the depth of basements, and any conditions, a knowledg^e of which will aid in g"iving a proper seweragfe S3' stem to each Ijuilding-. The level of all streams should be taken, and so far as it can be ascertained, the approximate level of the g"round water. This can be ascertained with tolerable precision by observing^ the condition of wells bordering- the street, when such can be found. The levels of water in these should be taken at intervals, and on both sides of the street, as the subterranean water surface may have a sharp decline in the direction of its natural drainag^e basin. In cases where it is probable that the construction work will shortlv follow the adoption of a plan and where the physical character of the territory is sharply defined, and the drainag-e lines are apparent on a superficial inspection, the preliminary and final survey ma}' be combined in one with economy. Profiles. — The transit and level notes being- complete, profiles of the several lines should be made to a larg-e scale, showing- the surface and grade lines, intersecting- streams, etc. It will save the eng-ineer much anno^-ance if the con- tractor be furnished a duplicate of the profile or a statement of the cuts at the several stations as he can then intellig-ently plan his work from the outset without further questions. The ordinary profile paper, known to the trade as Plate A, will be found suitable for this work, and a convenient scale will be one foot verticall}' for each one-fourth inch, and one hundred feet horizontally for each two and one-half inches, to which the Plate is adapted. Cuts can be taken from this scale with tolerable accuracy, and they will serve as a check on those found by computation. CHAP. IX. CONSTKUC'IION. 163 \Vorking Map. — The plan being- definitely decided upon, and the profiles made as described, a roug-h map should be made for use in construction, showing- position and size of sewers, location of man-holes, lamp-holes, flush tanks, and other accessories, and kept in the office for convenient refer- ence during- the prog-ress of the work. Note Books. — Each constr-ucting- engineer should be fur- nished with a field book, arrang-ed something- as follows: LEFT HAND PAGE. RIGHT HAND PAGE. Station. Surface. Grade. Cut. Construction Notes. The four columns at the left should be filled from the notes in the office, and the construction notes should be taken as the' work proceeds. Construction. — It is g-enerally best to commence the con- struction at the outlet and work toward the hig-her levels. When this is done, the spig-ot of each pipe is easil}^ inserted in the socket of that already laid. There is also no tendency of the pipes to crawl away from the work or to open at the joints before the cement may be entirely set. In some cases, however, where the grades are flat, and water is found in larg-e quantities in the trench, the pipes can be laid from above downward with advantag-e, as the water can thus be drawn away from the pipe into the lower levels of the trench and then pumped out without interfering- materially with the laying- of the pipe. The pipe should be laid in each case with sockets up or toward the summits, and 164 THE SEPARATE SYSTEM OF SEWERAGE. spig^ots down or toward the outlet; and when the work pro- ceeds from above there is more difficulty in makings proper joints and in inserting" the gasket. The pipe should be supported entirely on its cylindrical part, as shown in Plates I and X, a recess being- formed to receive the socket and the cement joint. Pipe Laying. — The organization of the gang for work may be as follows: The earth can be removed from the trenches to a depth of about the centre of the pipe by common laborers. The pipe laying" gang should be preceded by men trained to the purpose, whose business it is to shape the trench for the pipe. In laying the smaller sizes, the pipe layer will need no helper in the trench, but can receive the pipe from his helper on the bank, and place them unaided. In laying pipe of larger size, he should sit or stand astride of the pipes already laid, and his assistant should receive the pipes from above and assist in placing them. The joints should be cemented b}^ a person specially trained for the purpose. This can best be done by the hands encased in rubber mittens or gloves, and they should be wiped something" as a plumber wipes a joint. After the joints are cemented, the pipe should be care- fully bedded, and all Y branches carefulh^ packed and cov- ered by a trusty man in advance of the regular back-filling gang. When the depth of excavation is considerable, and the streets narrow, or the buildings close to the street line, Y branches should be more elevated than when opposite con- ditions are found. Various mechanical devices have been proposed for ensuring the concentricity of the pipes. It is doubtful if they are of any great benefit, however. Pipes which are not CHAP. IX. CONSTKUCTIOX. 165 truly formed should be rejected. Pipes which have too loosely fitting- spig-ots and sockets should also be rejected, as any imperfection in form is less apparent and the axes of the pipes when laid are less likely to coincide. Since the flow rarely rises above the horizontal diameter of the sewer, particular care should be taken to have its invert as perfect as possible. With g"ood management on the part of the contractor, sewers of vitrified pipe of small diameter, laid in trenches of the depth usually necessary, can be laid much more rapidly than sewers of larg-er diameter, the rate of progress being limited in either case by the work of one gang- of pipe layers or brick layers. Rapid and carefully systematized work by the engineer is therefore required, who should take personal charge, as the decisions constantly needed in its progress, the locating- and recording- of junctions and similar work cannot be left to an inspector. A sufiicient number of junc- tions should be inserted to meet all future demands. Con- nections by cutting into the pipes where no junctions are placed can be made with about the same facility as if the pipes were of plate glass, and if so made will ruin the sewers. A perfect record of everything- pertaining- to the work should be made for future reference. Depth. — The depth to which sewers should be laid in the street will be determined by local conditions. In the closely built business portions of towns, however, where the ground floor space is valuable, propert}' owners frequently desire to place water closets, urinals, laundries, etc., in the basement, and although this is not a desirable place for them it sometimes becomes necessary to adopt this course as the lesser of two evils. Pipes should never be laid under basement floors when it can be avoided, but should enter the basement just above 166 THE SKPAKATE SY.STEM .OF SEWERAGE. the floor and be supported by substantial iron brackets or hang-ers. In cases where it is necessary to locate plumbing" fix- tures in basements the following- will be a reasonable allow- ance for the depth of the sewer in the street: Depth of basement below street level g oo feet. Inclination of house sewer, 1-60 (50 feet) 83 Diameter of street sewer (8 inches) 67 It will often be impossible to secure the desired depth. The problem then becomes to secure the maximum depth consistent with requisite grade, etc. It is advisable in all cases to keep the sewers at least six or eig'ht feet below the street surface in northern towns, to avoid water and g"as service pipes and mains. There is little danger of sewers freezing, even thoug^h they be laid quite near the surface. Grade Line. — The pipe should be laid to line and grade indicated by stakes driven in the bottom of the trench, the top of the stakes being- to exact line and g-rade. These should be set in advance of the final shaping- of the trench, in the following- manner: The line is determined by laying- an offset rod across the trench at. the offset stakes, which were set in the final location, and setting- the stake in line by a plumb-bob. The stake should be driven to g-rade by a self- reading rod, read directly from the level whose elevation above the assumed datum should be carefully checked at each bench mark. No setting of g-rade peg-s by measure- ment of cuts from the surface should be allowed. A con- venient and cheap rod is shown in Plate I. Sixteen feet will be found a convenient lengfth. Bracing and Sheet Piling. — In many soils it will be necessary to protect the sides of the trench from caving" by timber and braces. A very g-ood method of doing- this is shown in detail in Plate IV. The iron screws will be found From Photograph of Sheet Pihng. CHAP. IX. COXSTKUCTIOX. HV.i a great saving- over the ordinary method of cutting timber shores, which, in many cases, can be used but once, and are liable at any time to become loosened. The iron screws can be used any number of times, will lit any width of trench within reasonal)le limits, can be' quickly placed and removed, without jarring' the trench, and can be tig'htenedat any time, without the trouble and risk of removing a short one and inserting a longer one in its place. One hundred screws of assorted lengths make a fair outfit for one gang of pipe lay- ers in ordinary- work. The method of bracing and sheet piling can be better understood from a study of the drawing than from a written description. It requires considerable experience to place it and remove it quickly and without damage to the material. By the use of this method of bracing and sheet piling, the driest sand and gravel can be excavated about as cheaply as soil sufficiently tenacious to support itself, in trenches exceeding seven or eight feet deep, thoug'h the sides of the latter need no protection. The drawing" shows two rows of piling; these can be increased to three or four, or still more, if necessary. Up to a depth of eight or nine feet one row of piling, in con- nection with the horizontal planking, will be sufficient. The following bill of material may be of service: SINGLE ROW OF SHEET PILING. This will be sufficient up to a depth of eight or nine feet. Each section of sixteen feet in length requires the fol- lowing material: LUMBER. 10 pieces 2x10, 16 feet long. 36 " ixlO, 7 " " i " 2x 8, 7 " " 550 feet B. M. 4: " 3x 6, 16 " 4 " 3x 6, 1 " 170 THE SEPARATE SYSTEM OF SEWERAGE. IKON SCREWS. 2 screws 36 inches long" (closed). 2 " 24 " " The above bill requires a trench four feet in width at the top, and g-ives a clear space at the horizontal diameter of the pipe of forty inches, and between the horizontal timbers a clear space of thirty-four inches. This will be sufficient for a pipe eig"hteen inches in interior diameter. For larger sizes the leng^th of the screws must be increased, and for smaller sizes the trench may be somewhat narrower. DOUBLE ROW OF SHEET PILING. This will be sufficient up to a depth of thirteen or four- teen feet. Each section of sixteen feet in length requires: LUMBER. 10 pieces 2x10, 16 feet long-. \ 72 " 1x10, 7 " " / 8 " 2x 8, 7 " " ; 829 feet B. M. 8 " 3x 6, 16 " " \ 6 " 3x 6, 1 " " / IKOX SCREWS. 2 screws 36 inches long- (closed). 1 " 30 1 " 24 " " 2 " 20 " " 2 " 14 " " The above bill is fig"ured for a trench four feet wide at the top, and g-ives a clear space at the horizontal diameter of the pipe of thirty inches, and a clear space between the lower horizontal timbers of twenty-four inches. This will be sufficient for pipes of twelve inches in diameter and less. For larg-er sizes the width of excavation should be increased. PLATE IV. CHAP. IX. CONSTRUCTION. 171 In heavy ground the leng-th of the horizontal timbers may be reduced to fourteen feet or twelve feet with advan- tag"e, or an extra set of uprigfhts may be used, dividing- the sixteen foot sections into thirds instead of into halves. Inspection of Material. — All sewer pipe should be inspected as fast as it is delivered at the work, and imperfect pipe should be plainly and indelibly marked and immediately removed. The eng^ineer should also carefully scrutinize all pipes as they are passed to the pipe layer, making sure that none which may have been broken since the formal inspec- tion are laid in the trench. The subsequent breaking- or g^iving- way of a sing-le section of pipe may cause a g-reat amount of damage. All other material should be inspected by the eng-ineer in a similar manner, and that which is unfit for use promptly removed. Location of Y Branches. — Property owners should be consulted as to the position in which they wish their Y branches placed, and it would be well to send them some- what in advance of the construction a printed notice. If no return is made by the property owner, the eng-ineer should locate the junction as appears most convenient for the prop- erty. The position of all Y branches should be located by station, specifying- whether they are north or south, east or west. Any other location is unnecessary and confusing-. The location is best made from the centre of the opening-, as shown in Plate I. This should be taken to the nearest tenth of a foot, and a plumb-bob should be used to transfer the point to the surface. Artificial Foundation. — When very treacherous soil is encountered it will be necessary to support the pipe on arti- ficial foundation. When soil of a less treacherous nature is encountered it may be sufficient to remove the soil somewhat below the grade line and replace with clean gravel. 172 THE SEPAKATl-: SYSTEM OF SEWEKAGE. Where artificial foundation is used as a support for pipe sewers the arrang^eraent should be such as will g^ive a uni- form and continuous support to the pipes throug^hout their leng-th. If they are not supported in this manner they will be likely to fail in trenches of any considerable depth. Sometimes blocks are used to support pipes in wet trenches, the pipes being- laid without bearing- upon the earth except as a bearing- is secured b}- filling and tamping- after the pipes are in position. Althoug-h it is possible to secure a proper foundation in this way in some cases, it is usuall}' a dangerous method since upon the settlement of the trenches the blocks are likeh^ to take more than their proper share of the bearing. The ideal condition is that in which the lower semi-cir- cumference of the sewer rests uniformly upon an unyielding- support. When this cannot be secured an effort should be made to support it in such a way that the settlement will be as little as possible and the support will offer a uniform resistance to the sewer at all points of its leng-th. Under some conditions a cradle such as is shown in Plate III may be used with advantag-e. In case the cradle is used as a support for pipe sewers a layer of sand or g-ravel should be interposed between the cradle and the pipe to dis- tribute the bearing-. PLATE III. ^) J CRADLE. PLATE V. '.320|SS^ M3M^£^i^^^^^M^7 SECTION ON A B DKTAI LS — OF — MAN HOLE. ..,--■ .--^:,;.....->^SS PLATE VI. p!p3C); DETAILS OF MAN-HOLE. PLATE VII. Vertical Lcngitudinal Section. Horizontal Section. DETAILS OF MAN-HOLE SHOWING DRAIN TILE CONNEC- TIONS. PLATE VIII. MAN-HOLE ON SEWER OF LARGE DIAMETER. CHAP. IX. CONSTRUCTION. 181 Particular care should be taken to secure a firm founda- tion for man-holes, flush tanks and lamp-holes, as their g-reater weig-ht may cause a settlement which will break the pipes. Man-Holes. — Man-holes should be built with an eig^ht- inch brick wall. The}- should be plastered outside and inside. The iron cover with which the}" are surmounted should weig-h from 300 to 500 pounds. The style shown in Plate IX has g-iven g-ood satisfaction when made to weig-h 350 pounds. It has the following- advantages: The least CAST-IRON HEAD AND DUST PAN. 182 THE SEPARATE SYSTEM OF SEWERAGE. possible surface is exposed to traffic. The impact of pass- ing- wheels comes well within the base. The interior down- ward projecting" rim prevents any loosened brick from fall- ing into the sewer. It is usual to hang a dust-pan below the perforations in the cover to catch the street detritus which may work through them. With good grades, however, there will be no danger of stoppage from this source when they are omitted. The method of forming the bottom of man-holes to pre- serve the proper cross-sectional form of the flow is shown in section. The method of connecting a sewer of small diam- eter with a larger one is also shown. Unless particular care is taken in forming these curves, solid matters will be stranded in the man-holes and become offensive. The best practice favors connecting pipe sewers at man-holes with no curves outside of the man-holes. Iron steps may be built in the wall, or a light portable ladder used in ascending and descending. The steps are most convenient, but are liable to collect street detritus fall- ing from above. Flush-Tanks. — Flush-tanks should be built with an eight-inch brick wall, and plastered inside and outside with cement mortar. The upper courses of both man-holes and flush-tanks are exposed to the action of alternating frost and moisture in an unusual degree, and to the constant impact of vehicles, and with the best of material a four-inch wall is not sufficiently durable. The interior of the flush-tank should be connected directl}' w4th the sewer, independently of its discharge, by a pipe of large diameter, as shown in the chapter on Flushing- and Ventilating. This will induce a current of air flowing along the crown of the sewer from the lower levels to pass into the tank and out throug^h the perforations in its cover. PLATE IX. IRON COVER, MAN HOLE ^'"-P) — AND — i 0r FLUSH TANK. .i; 1 V i'-y. < IW. • ^1 ^^M^feM^^ ''' ' ••-vi■^•■ CHAP. IX. CONSTRUCTION. 185 No other protection ag^ainst frost is needed. This is also a material aid in the ventilation of the sewers. All flush-tanks should be supplied with a dust-pan. The various types of flush-tanks will be more fullv dis- cussed in the chapter on Flushing- and Ventilation. Lamp-Holes. — Lamp-holes should have a concrete bed under them to prevent settlement. The}" should be carried up as the trench is filled, and care must be taken to keep the sections vertical. Care must be taken in locating- man-holes, flush-tanks and lamp-holes to avoid gutters, crossings and other objec- tionable locations. OUTLET CHAMBER. Outlets. — Outlets should be arranged to discharge the sewage in mid-current where possible. This is particularly 186 THE SEPAKATK SYSTEM OF SEWERAGE. essential in the case of broad and shallow streams with low banks and can usually be accomplished by a submerg-ed iron outlet. Such an outlet in process of construction is shown by the photo-eng-raving-s, Plates XI and XII. In this case the position of the outlet is ver^- fortunate, being- on a point of land between two confluent streams one of which can be seen at the right and the other at the left of the picture in Plate XII. PLATE XIV. OUTLET CHAMBER WITH RELEIF OVERFLOW^. PLATE XV. SECTION OF BRICK SEWER JUNCTION. PLATE XVI. MAN-HOLE— BRICK SEWER. CHAP. IX. CONSTKUCTION. 105 House Sewers. — Experience with sewers of the Sepa- rate System demonstrates that stoppag'es in the house sewers are much more frequent than in the hiterals; and the point in the house sewers which is particuhirly liable to obstruction is at the junction with the street sewer. Partic- ular care should, therefore, be taken in the construction at this point. The Y branch should be properly elevated so as to bring" the invert of the house sewer above the ordinary flow line of the street sewer, as shown in Plate XVII. The curve should have a sharp g-rade and particular care should be taken to have the spigots put squarely into the sockets and the gasket well placed. No cutting and trimming of the pipe should be allowed, as it is impossible to make smooth joints of terra cotta pipe in this way. Curved pipe always warps unevenly in the kiln, and from an ordinary stock there will be no difficulty in selecting a curve suitable for any reasonable case. Three or four of these, slightly varying- in radius should always be at hand. A very common defect is to allow the centre or belh' of the curve to drop down and open the joints before the}^ are hardened, or to do the refilling in such a manner that the subsequent settlement of the trench breaks the joints or pipe. This can be avoided by thoroughly ramming" the earth up to the horizontal diameter of the curve as it is laid and water-tamping or ramming in layers above this. House drains can be very accuratel}' laid in favorable g"round with an ordinary carpenter's level placed on each pipe as laid, one end of the level being supplied with a gradu- ated slide and set-screw, by which is set off the fall corres- ponding to one length of pipe. 196 THE SEPARATE SYSTEM OF SEWERAGE. Pumping Stations. — Sewag^e pumping- stations are often necessary to protect the sewers from back water during hig-h water or to deliver the sewag"e at some point for treat- ment or disposal not accessible by g"ravity flow. It may be necessary to operate them only at certain stag^es of water at the outlet and at infrequent intervals in some cases and in other instances they must be operated continuously. Usually the conditions are such that they are operated under a compai'atively light lift. The conditions under which the plant is to be operated should control its design. Obviously a larg-er outlay in first cost to secure a comparatively hig-h duty and economy in operation will be justified in the case of a plant continuously operated against a hig-h lift than if the plant is to be operated but a few days each year during- hig-h water. In the last case the cost of a days operation is comparatively imma- terial. It is necessary, however, that the plant be absolutely sure in its operation when pumping is necessary and it is desirable that the plant be constructed in duplicate so that an absolute failure in operation is improbable. For light lifls some of the various forms of centrifug-al puijips are well adapted. They cost comparatively less than others for the same capacity, are not likely to be obstructed by sewage and are simple and sure in operation. The most favorable results are secured by setting them immersed in the pumping- pit. The cut on the opposite pag-e shows a portion of a pumping plant thus equipped. The pumps are two 12-inch centrifug-al pumps immersed in the pumping- pit. They are operated from a counter shaft to which power is supplied b}- two eng-ines and the eng-ines are furnished steam from two boilers. The arrang-ement is such that an}' combination of power and pumps is possible. That is to say, — Either PLATE XVII. ELEVATION SECTION IRON PIPE through House Wall w^ ^MM^MMZ. HOUSE DRAIN SECTION BRANCHES, CURVES — AND — HOUSE DRAINS. CHAP. IX. COXSTKUC'riOX. 199 pump or both pumps may be run with either eng^ine or with both engines and either eng-ine or both eng"ines may be sup- plied with steam from one or both boilers. A similar combination has also been used by the author in which the eng-ines were directly connected without belt- ing" and with a considerable saving of floor space. 3oih of the above described pumping- plants were desig-ned for occa- sional pumping- only. Examples of more elaborate pumping- plants, desig-ned for continuous operation, are to be seen at Boston and at Pullman. CHAPTER X. FLUSHING AND VENTILATING. In the Combined System. — Any one seeing' the volume of warm vapor rising- from the man-holes of an ordinary combined sewer on a cold morning- will g-et some idea of the immense quantity of g"as which constantly rises from a sewer; and if he once g"ets a smell of the ascending- column he can form some slig-ht conception of its composition. An examination into the condition of the sewers will, in most cases, at once show the cause of this enormous evolu- tion of g-as. The sewers of the Combined System are desig-ned to carry not only the sewag-e of the town, but also the storm water from the roofs, yards and streets. Under these cir- cumstances the size of the sewer is determined solely by the amount of storm water to be provided for; the amount of sewag-e being- so small in comparison that it may be disre- g-arded. In fair weather, and especially in the long- continued dry weather in summer, the sewag-e forms only a very small stream in comparison with the capacity of the sewer. This comparatively small amount of sewag-e is spread out on the bottom of the larg-e sewer and the stream is shallow and slugg-ish. Since the capacity of a stream to carry solid matter depends upon its depth and velocity it is readily seen that the solid particles in the sewag-e soon g-et stranded and the sewer becomes foul even where street refuse is rig^idly excluded by the catch basin, which is not often the case. CHAP. X. FLUSHING AND VKNTILATIXG. 201 The storm water from the streets usually carries with it a larg-e amount of detritus, straw, leaves and sticks. As the flow in the sewer produced by the storm slackens this solid material is stranded, forming- small dams in the sewer. These hold the sewage in pools, where it decomposes and sends off immense volumes of sewer gas. Sewer gas contains sulphuretted hydrogen, carbu retted hydrogen, nitrogen, ammonium sulphide and foetid organic vapor. Besides these gases, and quite as much to be dreaded, are the disease producing- micro-organisms, commonly known by the name of bacteria, which abound in the warm, moist air of the sewers and are carried wherever the sewer g-as penetrates. Several diseases are known to be produced by bacteria, and it is highh' probable that the list will be increased as our, knowledge in this field is extended. In any place the struggle for life is between the bacteria and the human being. It is a survival of the fittest in any environment. Where sanitary matters are properly attended to and the environment is favorable for man it will be unfavor^able for the bacteria, so the man will live and the bacteria will die. But where sanitary laws are disregarded and the environment is unfavorable for man it will be fav^or- able for his enemy, and the bacteria will thrive and the man will die. The question arises — what remedy can be applied to improve the condition of the sewer, and to prevent or dimin- ish the dangers to health from this source? Two things are needed in order to accomplish this end: flushing and the ventilation of the sewer. Thorough Hush- ing will carry out the accumulations of solid matter and dis- pose of the pools of putrefying- sewage. Fresh sew^ag-e is not very offensive, and if it can be carried rapidh' to its out- fall before decomposition sets in it will cause verv little trouble either by becoming- obnoxious or dang-erous. It is 202 THE SEPARATK SYSTEM OF SEWERAGE. the standing- pools of decomposing- sewag^e which causes most of the trouble. Flushing- may be accomplished in several ways. One of the simplest of these is to dam up the sewag-e by g-ates in the sewers until the sewers are nearly or quite full and then suddenly release it, causing- a full strong- current in the sewers. Care must be taken not to hold the sewag-e until it backs up into the cellers and basements along- the line. To prevent the possibility of this, g-ates which only partly fill the sewers are used, so that when the sewag-e rises to a cer- tain heig-ht it flows over the g-ate. Automatic g-ates are also used which turn on a horizontal axis placed below the centre of the g-ate, the top turning- outward away from the confined sewag-e. When the sewer becomes nearly full, the pressure on the part of the valve above the axis being- g-reater than on the smaller section below the axis, the valve opens outwardly and releases the sewag-e. The principal objections to the use of g-ates in the sew- ers are that there is a tendency to deposit the solid particles on the bottom of the sewer where the sewag-e is impounded, and that the method cannot be applied to the upper ends of the sewers. At the upper ends other devices must be resorted to. One is to collect the sewag-e in tanks, which are discharg-ed automatically w^hen full. Another is to use automatic flush- ing- tanks tilled with water, either by collecting- rain water from the roofs, or from the public water works. When the water supply of a town is abundant the problem of flushing- sewers can usually be easily solved. In any Combined Sewer there will be a certain amount of org-anic matter smeared by the floods on its interior sur- face above the ordinary surface of the sewag-e, and the decomposition of this is constantly g-oing- on, developing- a considerable volume of g-as. Added to this is the g-as g-en- erated b}" the stag-nant sewag-e held in pools by the obstruc- CHAP. X. FLUSHING AND VICNTH^AIING. 203 tions in the sewers. If there are no opening's in the sewer the traps in the houses would be forced by the pressure of the g^ases produced. Opening's are absolutely necessary and wherever there is an opening the g"as will escape. To dis- pose of this g^as or to mix it with so larg-e a volume of air as to render it harmless is the problem which presents itself. The ventilation of a system of larg"e sewers is a difticult task, and up to date it has not been satisfactorily done. One of the best authorities after careful investigation gave it as his opinion that the only practicable plan was — to use his own words — "to just let the stink out in the middle of the street."' The use of high chimneys has been strong-ly recom- mended, and they have been experimented with to a consid- erable extent. It has been quite confidently stated that as some of the g'ases found in sewers are lighter than air there will always be an upward draught in the chimney without any artificial aid. Unfortunatelv this is not the case, and to insure a con- stant current of air from the sewer up the chimney some means must be employed to secure a draug^ht. This ma}' be accomplished either by a fire at the foot of the chimne}^ or a fan or screw in the chimney which is operated by a steam engfine or other power. When the fire is used the sewer g'as is usually passed throug^h the fire. In this thpre is an element of dang-er, as leaks from the g'as mains into the sewer are quite common and explosions from this cause have occurred. Owing- to the numerous openings into the sewers each chimney affects only a limited area, so that an extended system of sewers would need many chimneys. The cost of these chimneys and of running the fires in them pi'ohibits their use, except in special cases. This system can be made efficient if we disreg"ard expense, but eng-ineers soon find that the item of expense is one of the most important 204 THE SEPARATE SYSTEM OF SEWERAGE. considerations in any eng-ineering- project, especially if it relates to sanitary matters which are to be decided by the public. Another plan is to ventilate the sewers by running- an untrapped branch up throug^h each house, relj'ing- upon the heat in the house to create an up draug-ht in the pipe. This would be an efficient way of ventilating- sewers, but it g-reatlv increases the dang-er from them. A leak in the soil pipes, or the emptying* of a trap by evaporation or syphon- ag-e (and both of these conting-encies are much more common than is usually supposed) makes the house itself a ventilator for the sewer. The rain water conductors have sometimes been used as sewer ventilators, but this releases the sewer g-as in too close proximity to the windows of the upper story of the house and is a dang-erous practice. One of the best plans is to carry up an untrapped pipe on the outside of the house to a sufficient heig-ht above the roof. \i this plan could be g-enerally adopted on any line of sewers it would afford one of the best solutions to the ven- tilation problem. Various chemical processes for treating- sewer g-as in the sewers have been proposed, such as liberating- chlorine g-as, or sulphurous acid in the sewers. These methods have been tried on a small scale but the results have not thus far been encourag-ing-. A more successful plan has been to purify the sewer g-as as it comes from the sewers by passing- it throug-h loosely packed charcoal. This has been tried on a larg-e scale and has been fairly satisfactory althoug-h quite expensive. A patent was taken out in 1S5S for purifying- sewer air by passing- an electric current throug-h it. In the Separate System. — We have thus far been deal- ing- with the "Combined System" of sewers. Where the CHAP. X. FLUSHING AND VICNTH^ATING. 205 Separate System is employed the problems of flushing- and ventilation are materially simplified. As has been already stated the amount of sewag^e is so small in comparison with the storm water as to be neg-lectcd entireh' in computing- the sizes needed in a Combined Sys- tem. This being- the case it is readily seen that the neces- sary size of separate sewers is small in comparison with those of the Combined System, and hence much less water is needed for flushing". Ag-ain, since the flow of sewag-e is approximate!}' con- stant and not fluctuating- between the wide limits of the flow of storm water, the sizes of the pipes may be desig-ned so that the flow of the sewag-e will keep the mains in proper condition, while the upper ends can easily be flushed by means of automatic flushing tanks of small size, compared with those needed on the larg-e sewers of the Combined Sys- tem. A tank placed at each dead end and adjusted to dis- charge once every day will g-enerally keep the sewers well flushed. To thoroug-hly flush a sewer requires a volume of water sufficient to fill the sewer for a considerable distance. The best results would be obtained if the sewer could for a time be filled its entire leng-th, so as to flush all of the upper part of the pipe as well as the lower. This would not only cleanse the pipe, but materially aid in its ventilation by securing- an entire chang-e of air in the sewer. When flush tanks are used to flush the sewers, if the discharg-e from the tank is sufficiently rapid, the flushing- will be thoroug-h, for a g-reater or less distance, depending- upon the g-rade of the sewer. Gradually, however, the water will lose its velocity, and the flushing- effect will be less and less until it amounts to but verj^ little. 206 THE SEPARATE SYSTEM OF SEWERAGE. Roof Water. — The storm watei" from the roofs may be utilized for flushing- bj connecting- a limited number of rain water conductors with the sewers at the upper ends of the lateral branches. When roof water is used for flushing a difficulty arises in adjusting- the amount of water to be admitted. When the sewers are first completed, much more water will be needed to flush them than will be required after their use has become general, and the flow of sewage has more nearly reached its maximum. But having once permitted the roof water from any building to be turned into the sewers it is difficult to shut it out when the proper time comes. When the sewers are flushed by connecting the dead ends of the sewers with the water mains, the amount of water can readily be adjusted to suit the requirements in each case. The water from the mains may be admitted to the sewers by a direct pipe connection, provided with a suit- able valve, or it may be taken from a h^^drant and carried through a hose to a lamp hole at the dead end of the sewer, which in this case should be constructed as shown in Plate I. As the small sewers are of smooth earthenware pipes they are much easier kept clean than the rough interior sur- faces of the large brick sewers and flushing will be more effective. The ventilation of the separate sewers is a much sim- pler matter than in the case of the Combined System, When properh' designed and constructed there are no pools of decomposing sewage standing- along the lines, and as a consequence there is much less evolution of gas and hence much less need of special appliances for ventilation. The rush of water from the flush tanks changes the air in the upper ends of the sewers, and the fluctuations of flow in the mains is an important factor in changing the air in the sewers bv driving out the foul air as the sewag-e rises at the PLATE XVIII. U^ u CHAP. X. FLUSHING AND VKNTH-ATING. '20t> time of its maximum daily flow, and refilling- the pipes with pure air as the flow falls to its minimum. Any of the methods of ventilation which can be used on the Combined System are available for the Separate System, and as the amount of air to be moved is much less they will be more effective. The man-holes, flush-tanks and lamp-holes, when pro- vided with perforated covers, as shown in the plates, will assist in the ventilation for the street sewers of the Separate System. The house drains, however, need some special arrang-ement for that purpose. An opening- from the house drain to the air is necessary, not onl}' for ventilation but to prevent emptying- the traps by syphoning- when the sewer is flushed. The simplest method of accomplishing the ventilation of the house drains and at the same time of the sewers them- selves, is to extend the main drain upward and out through the roof, unbroken by a trap in any portion. In this case it serves the double purpose of soil and ventilating pipe, and the air which passes into the street sewers at man-holes sup- plies the draug-ht upward along the street sewers, and out through these and their upward extensions In this case the isolation of the interior of buildings from sewer air depends solely upon the trap under each fixture. Where street sewers are properly constructed on the Separate Sys- tem, and properly cared for, this method has proved entirely satisfactory. It certainly has g-reat advantag-es in simplicity and facility of arrang^ement. Where the sewers are built on the combined plan the method of isolation shown in Plates XVIII and XIX is to be preferred. This diverts the foul air currents from the interior pipe and provides a supply of fresh air for the upward current throug-h the soil and ventilating- pipe. If the street sewers are not properl}' ventilated at frequent intervals, either by the upward extension of exterior or 210 THE SEPARATE SYSTEM OE SEWERAGE. interior unobstructed pipes or otherwise, there may be reasons for believing- that an isolated one may draw from too wide a territory and prove offensive. In this case it is advisable to dispense with any vent pipe communicating- directly with the sewer. If we could be perfectly certain that all the drain, waste and soil pipes were perfectly gas tight throughout their whole length, and would remain so, and that no fixture traps w^ould ever be emptied by syphoning-, evaporation, capillary attraction, or any other of the many w^ays by which traps do g-et emptied, we might safely use untrappcd house drains. But taking the conditions as they are, it seems to be taking- too great a risk to ventilate the public and private sewers tlirongh the dwellings. S. Stevens Hellyer, the wx'U known sanitary engineer, writes as follows: "Where the drains (house drains) are carried direct into the sewer, without traps, the houses, through the sewer, are brought into direct communication with each other, /. e., the air in the drain of one house can pass into the drain of another house. Contagious diseases — typhoid or what not — may be infect- ing a house, and however isolated it may be from other houses above ground, it would not be so under ground with such a system. The untrapped drains branching into the sewer would form a subterraneous passage for the bad air or disease germs — coming from the stools of the infected patients — between house and house. But when each house drain is trapped off before entering the sewer, an all but impassable barrier would be placed between the drains, so that the houses would be as much isolated under as above ground." If every house could be thus provided with the means of ventilation the whole problem of the ventilation of sewers would be simplified, and the provision for ventilating the house drains would supply the needed ventilation of the sewers. Man-holes and flush-tanks are liable to be covered with snow or mud at times and their efficiency as ventilators interfered with. If all house connections are made in the way above described — that is, if there is a free communica- PLATE XIX. V/» MAIN VENTILATING PIPES AND TRAP. CHAP. X. FLUSHING AND VENTILATING. 213 tion between an uprig-ht ventilating- pipe on each premises and the sewer proper — we have substantially a horizontal pipe having at frequent intervals vertical pipes leading- from it. These vertical pipes are of varying- leng-ths and their upper ends are at different elevations, covering- a rang-e of several hundred feet, perhaps. These vertical pipes are also subjected to different conditions. For instance some of them are within building-s near artificial heat, some of them are at the south side of building-s where the sun will eft'ect them, some on the north side where the temperature is lower, some of them are short and some are long-. In short, the conditions are such that there cannot be an equi- librium of pressure throughout the system. Now, if the openings at the mouth of the sewer, at the man-holes and flush-tanks are relatively large enough, and the air space along the sewer toward the higher levels where the house connections are numerous, is relatively large enough, it ma}^ happen that there will be an upward current in all the house ventilating pipes, the air being supplied, of course, through the openings along the sewer proper. It is probable, how- ever, that this rarely occurs for the reason that the com- bined section of the ventilators is many times the section of the air passage in the sewer proper and consequently any difference in pressure that may be induced in the ventilating pipes by the causes above cited, is more easily restored by downward draughts in some of the ventilating pipes. It may thus happen that the short, cool ventilating pipes, par- ticularly at the lower levels have, some of the time at least, a downward draught and that the total volume of air which passes through the system at various points is greater than could be supplied through the outlet, man-holes, etc., at the velocity which would be likel}^ to be induced. 214 THK SKPARATE SYSTEM OF SEWERAGE. Automatic Flush Tanks.* — Flush-tanks are used either to collect the sewag^e and discharg-e it rapidly at intervals for the purpose of flushing- the sewers, or to collect and dis- charg-e clean water for the same purpose. They should be automatic in their action. This regular and automatic flushing is usually applied to Separate Systems, and the diminished size of the pipes renders it very effective. It sweeps down all deposits and stranded matter from the remotest portion of the system into the mains, and the ag-g-reg-ate of these discharges in the mains from tanks differently timed, continued with the flow of sewage proper, sweeps it on to the outlet. The more reg-ular flow in the Separate System and consequent immu- nity from variations in air space and pressure reduces the dang-er of forcing- traps. The smaller air space increases the efficiency of all opening-s in relieving- any pressure resulting- from such variations, and also increases their effi- ciency as ventilators. There are many forms of automatic flush-tanks, most of which may be classed under the four following- varieties: 1, Tilting- Tanks; 2, Syphon Tanks; 3, Valve Tanks; 4, Col- lapsing Tanks. Tilting- tanks are so desig-ned that as they lill the centre of g-ravity is chang-ed, until finally the equilibrium of the tank is destroyed and the tank tilts over and empties itself. The tank is so adjusted that when empty it returns to its proper position. A tilting- tank on a small scale is shown attached to the long- leg- of the syphon in Van Vranken's flush tank, Plate XXI. Syphon tanks are discharg-ed by means of a syphon. They differ in the devices for starting the syphon. In places where the sudden rush of a considerable quantity of *The following descriptions of flush tanks are taken mainly from the manufacturers catalogues. CHAP. X. r LUSHING AND VENTILATING. ^1,5 water can be secured, no device is necessary. Where house sewag"e is collected in tanks for flushing-, the rush of water caused by emptying- a bath tub, wash tub, etc., will be suffi- cient to start the syphon. But where the tank is filled by a stream of water small enoug-h to fill a tank holdings but a feu- hundred g-allons only once in twenty-four hours, some spec- ial arrang-ement will be necessary to start the syphon. This can be done by means of a small tilting- tank on the long leg of the syphon, as in Van Vranken's tank; by a sup- plementary tank and syphon, as in Field's; by a ball cock, increasing- the flow when the tank is nearly full, as in Vib- bard's; by haying- the long- arm of the syphon movable, as in Landon's; by a collapsing- disk or tube, as in Chaplin's; by an automatic valve on the long^ leg- of the syphon; by an aspirator; and in various other ways. Field- Waring Flush-Tank. — The syphon invented and patented by Kog-ers Field and improved by Col. Georg-e E. Waringf, Jr., consists (in the form shown) of an annular intaking- limb, and a discharging- limb at the top of which is an annular lip or mouth piece, the bottom of which is tapered to less diameter. The discharg-ing- limb terminates in a weir chamber which when full to its overflow point just seals the limb. Over the crest of the weir is a small syphon whose function is to draw the water from the weir chamber and thus unseal the syphon. At the lower end of the small syphon is a dam or obstruction to prevent its breaking. The main syphon is broug-ht into action (on the tank being- filled i by means of a small stream of water flowing over the annular mouth piece and falling- free of the sides of the dis- charging- limb. As soon as the lower end of the discharging- limb has been sealed by filling- the weir chamber the falling- stream of water g-athers u]) and carries out with it a portion of the contained air, thus producing- a slig-ht rarefaction. 216 THI-: SEPARATE SYSTEM OF SEWERAGE. PLATE XX. r^^ffW^f^^^^^ ii "^^ ■ '■^^g ' ^Ti^^'? ?^' riELD-WARING FLUSH-TANK. This rarefaction causes the water to rise in the intaking- limb hig"her than in the basin outside, and hence increases the stream of water flowing- over the mouth piece, which in turn increases the rarefaction, and the syphon is soon broug-ht into full pla}'. On the tank being- emptied to the bottom of the intaking- limb the flow is checked, and the small syphon over the crest of the weir draws the water from the weir chamber, air enters the discharg-ing- limb, and the syphon is vented ready for the tank to ag-ain fill. PLATE XXI. %" 4" *- ' VLSJJJfWW\ :#^^^^i^^P^ai^^igSg&y' VAN VRANKEN'S FLUSH TANK. CHAP, X. FLUSHING AND VKNTILATING. 219 Van Vranken's Flush Tank, — This tank consists of an ordinary syphon, to the ]ong-er or descending- limb of which is applied a small tilting- tank. The ari-angement of the parts is shown in Plate XXI, The tilting tank is hung directly below the descending limb of the syphon, at such a level as to leave its mouth sealed at all times. The tilting basin is contained in a small cast iron chamber, built into the bottom of the flush-tank chamber proper. The action of the tank is as follows: The water being admitted to the tank by an ordinary faucet, at whatever rate may be desired, gradually rises in the tank until it overflows from the ascending to the descending leg of the syphon and is collected in the tilting tank. As it accumulates in the tilting tank the center of gravity is thrown beyond the axis of support and the pan tilts, the water level in the basin being lowered about one inch. This produces a corresponding rarefaction in the syphon and brings it promptly into full action. When the tank ceases to discharge the tilting basin resumes its former position. The Miller Automatic Flush Tank.— This flush tank is shown in Plates XXII and XXIII, Previous syphons have been brought into action by the simple release or rare- faction of the air confined in the syphon, or by the sudden removal of such air by special subsidiary devices, which are entirely absent in the "Miller" syphon. It consists of two simple Castings, a U tube or trap and mouthpiece, cast in one piece, and a cast-iron bell which is placed over the longer leg of the syphon, and is held in place by brackets cast on the trap. The action of the syphon is as follows: As the water entering the tank rises above the lower edge of the bell, it incloses the air within, the lower portion of the trap being, of course, filled with water. As the water level of the tank rises, the confined air 220 THE SRPARATK SYSTEM OF SEWERAGE. gradually forces the water out of the long- leg- of the trap, until a point is reached when the air just endeavors to escape around the lower bend. Now, as the difference of water level in the two le^s equals the difference of the levels between the water in the tank and the water within the bell, it will be seen that the column of water in the short dis- charge leg- has practically the same depth as the head of water in the tank above the level at which it stands in the bell. The two columns of water, therefore, counterbalance each other at a certain fixed depth in the tank. As soon as this depth is increased by a further supply, however small, a portion of the confined air is forced around the lower bend, and by its upward rush carries with it some of the water in the short leg-, thus destroying- the equilibrium. But the secret of this invention is the free projection of the overflow edg-e, which allows of the instantaneous escape or falling- away of the heaved-up water. Thus, if the discharg-e mouth were formed as an ordinary bend, the s3'phon would not act (although the confined air rushes around the lower bend), for the simple reason that the heaved-up water has no means of instantaneous escape, and, therefore, the equilibrium is not sufficiently disturbed. It will thus be seen that the action of the syphon depends, not on the escape of air, but on the sudden reduction of a counterbalancing- column of water. Repeated trials have shown that a 6-inch syphon will discharg-e full bore a 500-g-allon tank, fed so slowly as only to be filled in fourteen days. There being- no internal obstruc- tion, the discharg-e is extremely rapid. Rhoads-Williams Flush-Tank.— The Rhoads-Williams syphon, as illustrated, consists of an annular intaking limb, and a discharg-ing- limb terminating- in a deep trap below the level of the sewer. Below the permanent water line in the discharging- limb, is connected one end of a small blow-off or relief-trap, having- a less depth of seal than the main trap. PLATE XXII THE MILLER AUTOMATIC FLUSH TANK. PLATE XXIII. THE MILLER AUTOMATIC PUSH TANK, Combined with Manhole. CHAP. X. FLUSHING AND VliNTH.ATING. 225 the other end of which joins the main trap on the opposite side, at its entrance to the sewer and above the water line of the trap. At the same point is connected an uprig-ht vent pipe which rises throug-h the tank to a point above the hig-h water line, and is turned down throug-h the top of, and into the intaking- limb of the syphon, terminating- at a g-iven point above its bottom. As the tank fills with water (the main and blow-off traps being- full) it rises in the intaking- limb even with the level of the water in the tank until reaching- the end of the vent pipe, a volume of air is confined in the two limbs of the syphon between the water in the intaking- limb and the water in the main trap. As the water rises higher in the tank the con- fined volume of air is compressed and the water is depressed in the main trap and in the blow-off trap. This process g-oes on until the water in the tank reaches its hig-hest level above the top of the intaking- limb at which time the water is depressed in the blow-off trap to the lowest point and the confined air breaks throug-h the seal, carrying the water with it out of the trap, thus releasing- the confined air and allowing- an inflow from the tank, putting- the syphon into operation. On the tank being- discharged to the bottom of the intak- ing limb, the flow is checked and the syphon is vented by the admission of air to it throug-h the vent pipe. The Lightning Automatic Flush-Tank. — The operation of this flush-tank is as follows: See Plate XXV. The water rises in the tank till it reaches the float "F" of the lever, it also rises under the air chamber, but owing- to compression of the contained air the water will rise only to within one inch below the top of the inner leg- at the time its outer level will have reached the center of the float in the tank. The rising- water acting on the float "F" then moves the lever "H" which holds down the hing-ed chamber "I." 226 THE SEPARATE SYSTEM OF SEWERAGE, PLATE XXIV. FTfSr^T3T^7?p^3" RHOADS-WILLIAMS FLUSH-TANK. The instant the lever moves and releases the chamber the latter springs open on its hing-es and the inner confined air bodily escapes. Gravity bring-s the chamber back to its orig-inal position immediately that the air has escaped, and full and complete syphonag-e takes place. Valve Tanks. — In the valve tanks the valve is usually operated by a float which releases the valve when the water has reached a certain level. PLATE XXV. THE LIGHTNING AUTOMATIC FLUSH-TANK CHAP. X. FLUSHING AND YPZNTILATINC. 229 Requirements to be Met. — The requisites for an auto- matic flush-tank are: 1, Certainty of action; 2, rapidity of discharg-e; 3, simplicity of construction; 4, ease of inspec- tion of all its parts; 5, durability; 6, economy of cost and maintenance. Strang-e as it may appear, there are flush-tank syphons, sold in considerable numbers, which cannot possibly be made to work under the usual conditions imposed b}' the requirements for flushing- sewers. Rapidity of discharg-e is next in importance to certainty of action. The sewer pipe should be filled for some distance in order to g-et the proper benefit from the flush. In simplicity of construction the syphon tanks are supe- rior to the valve tanks, and as durability is likely to depend upon simplicity of construction, the syphon tanks will, in g-eneral, be most durable. Complicated mechanism is undesirable for use in a flush-tank, which must work automaticall}', and often for a long- time without inspection. It is not at all uncommon to find that devices which look well on paper fail utterly when put to the test of actual service. Quantity of ^A^ater Required. — An erroneous idea pre- vails as to the quantity of water required for flushing- sewers bv the use of automatic flush tanks. A properly desig-ned system for a city of 10,000 inhabitants ordinarily requires from twenty to fifty flush-tanks, of a capacity of about 150 to 300 g-allons, discharg-ing- daily, or at most twice a day. The maximum amount of water required is about two per cent, of the water supply. This momentary discharg-e does not sensibly occupy the capacity of the main sewers further down the line, being-, as before stated, but a ver}' small per- centag-e of the ultimate discharg-e. An equally efficient flushing- by a constant stream, applied directly and without the intervention of a flush tank would require an amount of 230 THE SEPARATK SYSTEM OF SEWfc:RAGE. water materially encroaching- upon the capacity of the main sewers, and would be inadmissible under ordinary condi- tions of water supply, on the score of economy. Rapidity of Discharge. — Flush-tanks are ordinarily adjusted to discharg-e automatically once in each twenty-four hours. Their capacity of discharg-e should equal or exceed that of the pipe into which they empty. Experiments made by the writer with a flush-tank of 7,000 g-al Ions capacity, having- a ten-inch outlet, opening- into an eig-ht-inch sewer, demonstrated that with the minimum grades indicated in Table XV, there was no dang-er of g-org-- ing- the sew^er at a distance of one or two hundred feet from the flush-tank, althoug-h the hydraulic head was seven feet and the capacity of the tank was sufficient to fill the sewer for a distance of 2,682 feet. At a distance of 600 feet the flow, as observed in a man-hole, did not fill the sewer. In the case of flush tanks as ordinarily constructed the tank can hardly discharg-e too rapidly. The rate of discharg-e from the tank should at least equal the capacity of the sewer when the flow has acquired the velocity due to its inclination. A sewer six inches in diameter, laid at a g-rade of five-tenths per hundred, dis- charg-es, when full, at the rate of 215 g-allons per minute. The conditions above named would therefore require the tank to discharg-e at the rate of 100 g-allons in 28 seconds or less. Experimental Data.^Some valuable experiments were made upon the effect of flush tanks in the sewers in Wash- ing-ton, D. C, by Asa E. Phillips, Assistant Eng-ineer, Dis- trict of Columbia, and the results were presented by him in a paper read before the American Society Municipal Improvements, in October, 1898. CHAP. X. FLUSHING AND VICNTILATING. 231 The following- extracts are taken from his paper: "No formula has been proposed for the volume of water required for dif- ferent grades and sizes, and the only rule known to have been used appears to be of little value. This important detail is determined by individual judgment, generally unsupported by investigation or experience, so that the common practice has varied within a large range of values, while tanks of uniform size usually have been constructed regardless of differences in the size or gradient of the sewers to be flushed. The uncertainty as to the precise effect of the flush and the complex conditions as to contributing population, rate of water consumption, etc., have been justly considered a bar to any precision in this respect Recent discussion of the subject, however, has tended to establish certain limitations in the use of flushing devices which should lead to improve- ment in the general practice. "The work to be accomplished by the flush is the removal at regular and frequent intervals of solid matter flushed into the sewer from house laterals, and there stranded because of the shallow depth of flow and sluggish current and its carriage down the line to a point where the depth and velocity are sufiScient to insure removal to the ultimate point of discharge. The efficiency of the flushing device in performing this work is not well understood. But little is known of the effect under the varying conditions encountered, espe- cially for widely different grades and at considerable distance from the dead end. It is generally considered, however, that the effect diminishes very rapidly as the distance increases, and becomes almost imperceptible 600 or 700 feet from the tank, but, so far as can be ascertained, this has been observed only in cases of flush of small volume on flat grades, or where the depth of ordinary flow was considerable. Of the effect of discharge of 600 gallons or more, such as were used in the cases to follow, there appears to be no recorded observations, so that no comparison with those already published can be made. Several grade conditions have been selected for the purpose of illustrating the effect of the flush under such circumstances, and an attempt made to indicate by means of diagrams the different results obtained. For these no special accuracy is claimed, but in the few cases given the differences are sufficiently marked as to suggest certain conclusions therefrom. "The Park street line is the first of these. This sewer is 12 inches in diameter, about 1,870 feet in length, and has a uniform grade throughout of 9 inches per ico feet. Preliminary examination discovered slightly unfavorable conditions for experimental work, such as an uneven grade, rough joints, and poor alignment in places, all of which affected the observations and results to some extent. It may now be stated that, with the exception of the Chapin street line, the sewers cited are old and generally possess these irregularities, but, excepting slight silt accumulation at points distant from the basin, they were found to be very clean. The presence of even a small amount of silt in 232 THE SEPARATE SYSTEM OF SEWERAGE. the invert, particularly at man-holes, undoubtedly affected the flow and was the chief source of error in the observations "The tank on Park street was found to have an effective capacity of 84 cubic feet, or about 630 gallons, and discharged through an 8-inch syphon in the mean time of forty-two seconds. No attempt was made to determine the velocity at the point of discharge, but this data would indicate an approximate mean velocity of 6 feet per second. Observations of the flush were simulta- neously taken at all of the man-holes, and the depths of flow were recorded at intervals of fifteen seconds or less. These depths were referred to the time of syphon discharge, and the diagrams of the flush have been constructed from this datum. "The first diagram, (Fig. i, Plate XXVI), shows the form of the flush wave as taken at five consecutive man-holes within 1000 feet of the tank. The lower four man-holes were not platted because of the confusion of lines that would result, but the data are given in Table XXII. This diagram and tabulation show how well the depth of flow is maintained for very long distances. One thousand feet from the dead end the flush is very efficient, and at a distance of nearly 2,000 feet appears to be quite effective. This large radius of effect is doubtless due to the volume of water used, as published data for smaller dis- charges indicate that a tank of half this capacity would have a very greatly diminished influence. TABLE XXII.— F,irk Street Se'oer. CAPACITY OF TANK, 84 CUBIC FEET=630 GAL.; TIME OF DISCHARGE, 42 SEC. Manhole. Size (Diameter). Gradient. Distance from dead end. Depth of Flow. Duration of greatest effect. Normal. Flush. I 2 3 4 5 6 7 8 9 10 Inches. 12 12 12 12 12 12 12 12 12 12 Per cent . 75 75 75 75 75 75 75 75 75 75 FecH. 200 382 572 738 948 1,132 i>332 1,486 1,688 1,869 Inches. H % I Inches. 7% sYa 5 Min. Sec. I 00 I 15 1 45 2 00 2 15 1^4 4 y/z 3 '4 2 50 3 00 3 45 3 45 "The second diagram for this line, (Fig. 2, Plate XXVI), shows the com- puted velocity curve for the ordinary flow, the assumed velocity to prevent sed- imentation and the accelerated velocitv due to the flush. These curves are not CHAP. X. FLUSHING AND VENTILATING. 233 supposed to be precise, but they illustrate the purpose of the flushing device, and to some extent the degrees of effectiveness required. The curve of normal flow shows the very low velocity along the upper portion of the line, and its gradual increase approaching the required velocity at the lower end, while the flush curve shows a corresponding high velocity at the upper end and its rate of fall toward the 2J^-foot-per-second velocity, where in theory at least it would seem that the two curves meet at a common tangent point. In this sewer, it may be noted, the normal flow does not attain a rate of 2^ feet per second, and probably would not for a distance of 2,000 feet. It is also to be observed, however, that the flush would seem to maintain this velocity for a distance probably as great; so that, so far as these observations go, they indi- cate that for this very long line and flat grade the flush tank is efiBcient and of the proper size. "The second series, taken on one of the Connecticut avenue sewers, is chiefly interesting as showing the effect produced on a varying and decreasing gradient. TABLE XXni.—Connec/icitt .47'e?iue Sc-u-er. CAPACITY OF TANK, S2 CUBIC FEET=6l5 GAL.; TIME OF DISCHARGE, 45 SEC. Manhole. Size (Diameter). Grade. Distance from dead end. Depth of Flow. Duration of greatest effect. Normal. Flush. I 2 3 4 Inches. 12 12 12 12 Per cent. I I 0.4 I Feet 175 325 473 613 Inches. -A I Inches. 5'A 5% 5% 3% Min. Sec I 15 I 30 3 00 3 00 "The diagram, (Fig. 3, Plate XXVI), illustrates the diminished velocity and enlarged area of section of the flush wave, as recorded at man-hole No. 3, showing the marked effect of the diminished rate of grade in the portion of the sewer immediately above. Unfortunately this could not be further observed, owing to a change in gradient from this point. It probably indicates, however, that for a line of varying slope the minimum should be considered in fixing the capacity of the tank. "The third series was taken on the Chapin street sewer, which has the reversed conditions of a varying but rapidly increasing gradient. The observed effect of the flush is very clearly shown by the diagram, (Fig. 4, Plate XXVI). The rapid run-off and greatly reduced area of section toward the lower end of the sewer indicate the very high velocity which such steep slopes must produce. In this case the minimum grade being i per cent., and that for a length of only 234 THE SEPARATE SYSTEM OF SEWERAGP:. 190 feet, a flush tank of considerably less capacity would probably be suffi- ciently effective, if, indeed, for such grade conditions automatic flushing is at all necessary. TABLE XXIV. — «.///« S/reel Sewer. CAPACITY OF TANK 83 CUBIC FEET^620 GAL.; TIME OF DISCHARGE, 48 SEC. Manhole. Size (Diameter). Grade. Distance from dead end. Depth of Flow. Duration of greatest effect. Normal. Flush. I 2 3 4 Inches. 12 12 12 12 Per cent. I 2 5-6 9 Feel. 190 350 490 705 Inches. Inches. 3 M/n. Sec. I 00 I 00 I 00 I 00 "The fourth series, taken on one of the Thirty-second street sewers, shows the observed effects on a nearly uniform steep grade. The first diagram, (Fig. 5, Plate XXVI), for this line shows the form of the flush wave as observ.ed at each manhole. The quick run-off and nearly uniform area of section main- tained indicate the piston-like effect of the discharge. In fact, the flow was so rapid and so quickly past as to render the taking of the observations rather difficult and their relative accuracy to some degree uncertain. TABLE XXV.— Thir/r-Secom/ Street Sewer. CAPACITY OF TANK, 84 CUBIC FEET=63Q GAL.; TIME OF DISCHARGE, 48 SEC. "The curves here and there seem to suggest such unavoidable irregulari- ties, but the general effect is very clearly shown. The second diagram, (Fig. 6, Plate XXVI), indicates the appro.ximate velocity attained by the flush in •S3L|DU| Ul MOlJ p mdSG CHAP. X. FLUSHING AND VKNTILATING. 237 connection with the assumed 2^ feet per second constant, as well as the esti- mated velocity of ordinary flow. This shows in another form the marked effect of the discharge on a steep slope, and also how quickly on such grades the normal flow attains sufficient velocity to prevent deposit. From a study of these diagrams we may conclude that the flush increases rapidly in effective- ness as the grade increases, having a remarkable scouring power on grades of 4 per cent, or more, but at the same time the necessity of automatic flushing decreases correspondingly, there being apparently little need for such a device on slopes approaching 4 per cent." "As has been seen, no attempt is here made to indicate the results with a variable volume of discharge for the purpose of determining the comparative radius of effect under such circumstances. This and other interesting details are necessarily omitted, an effort having been made only to show the general influence of the slope on the flush, and, in a limited way, the range of efi'ect." Some valuable data on the effectiveness of flush-tanks has also been secured by Mr. H. N. Og"den from experi- ments at Ithica, N. Y., a record of which appears in the Transactions of the American Society of Civi'l Eng-ineers, December, 1898. Plate XXVII is reproduced from Mr. Fuertes discussion of the data in the Transactions and the following extract is also from his discussion: "On the diagram, Plate XXVII, is shown the form of the flushing wave dis- charged into the Green street sewer, drawn from the author's data. A profile of the wave is shown at the end of the ist, 2nd, 3rd, 4th, 6th, 8th and loth minutes. In this diagram the shapes of the waves are not claimed to be exact as to profile at all points. They are accurate at the points where they cross the man-holes, and the positions of the toes of the waves were interpolated; the remaining portions of the curves are sketched in. "The velocities corresponding to the greatest depths of flow were calcu- lated by the Kutter formula, (n==o.oi3). The velocities marked for the toe of the wave are the components, along the bottom of the sewer, of the velocities of the surface of the water at the given points when the wave reaches those points. "At the first man-hole the sewer was nearly full, and probably had been running under a head up to within about 60 feet of the man-hole. After pass- ing this point the foot of the descending body of water, under a free flow by gravity, rushed forward rapidly, the point being 135 ft., 265 ft., 391 ft., 513 ft., 630 ft., 743 ft., 852 ft., and 957 ft. distant from the man-hole in i, 2, 3, 4, 5, 6, 238 THE SEPARATE SYSTEM OF SEWERAGP:. 7 and 8 minutes, respectively. Traversing these distances in the times given corresponds to an average velocity between the respective points of 2.25 ft., 2.18 ft., 2 10 ft., 2.03 ft., 1.95 ft., i.8g ft., 1.81ft. and 1.75 ft. per second. These are the bottom velocities at the point of the wave, and are the actual maximum velocities at the respective points." ■«3«3S JO 3d01S UOi i33J JO 31VDSJ General Statements. — From the observed facts above quoted, and also from the theory of hydraulics, the following- general statements concerning- the efficiency of flushing may be made: CHAP. X. FLUSHING AND VENTILATING. 239 The efficiency of flush is proportional to (1) The velocity of flow; (2) The depth of flow; (3) The duration of flow. The velocity of flow is proportional to the rate of dis- charg-e and the inclination of the sewer. (We are now con- sidering- sewers of a g"iven diameter.) The inclination being- fixed and uniform the velocity is ordinarily less as the dis- tance from the flush tank increases. The depth of flow is proportional to the rate of dis- charg-e and (under the conditions usual in sewers) inversely proportional to the inclination of the sewer. The rate of discharg-e being- fixed and the inclination being- fixed and uniform it is usually less as the distance from the flush-tank increases. The duration of flow is proportional to the quantity and rate of discharge and inversely proportional to the inclina- tion of the sewer. Under the usual conditions of quantity, rate and inclination, the duration of flow is g-reatest at points farthest from the flush tank. This naturally follows from the fact that the wave crest becomes lower and the velocity less as the distance from the tank increases as illustrated in the diag-rams. The velocity and depth of flow are interdependent. Depth of flow is particularly advantag-eous as it induces velocity. Depth of flow is desirable, however, independent of its influence on velocity since it increases the cleansing- contact at the sides of the sewer, increases the section of stranded matters which are exposed to the current, and, by a g-reater degree of immersion makes their hold upon the invert of the sewer less stable. CHAPTER XI. HOUSE DRAINAGE AND PLUMBING. House Connections. — In order to protect the sewers from injury b}^ careless or incompetent workmen, or from stoppag-e by the introduction of improper substances into the sewers, proper rules and reg"ulations for house drains and connections are necessary. To permit each householder to connect with the sewers whatever he chooses, wherever he chooses and in whatever way he chooses, is to insure ruin to the whole system. The house drains should be connected only at the Y's, which have been placed in position when constructing- the sewers. All work should be done by competent workmen, who are under bonds to do the work properly and repair all dam- ag"e they may do, and under the direction of a trustworthy eng-ineer or inspector. Care must be taken to exclude everything* which will be liable to obstruct the sewers. The man who said that he thoug"ht "the sewers should carry potato peeling's and such thing-s" is not alone in his notions reg^arding^ the disposal of g"arbage. A larg^e majority of the domestics employed in families have unlimited faith in the capacity of waste pipes and sewers to carry empty cans, broken bottles, ashes, cin- ders, wash cloths, etc. This confidence in the carrying- power of a pipe is so firm that it will be found easier to ren- der the introduction of miscellaneous articles impossible than to demonstrate that the transportation qualities of a sewer are limited. It will be much better to prevent improper thing-s being- introduced into the sewers than to be oblig-ed to dig- up the pipes to remove obstructions. The sewers are intended to carry only fluid refuse from kitchens, CHAP. XI. HOUSK DRAINAGE AND PLUMBING. 241 laundries, water closets, bath-tubs, slop sinks, etc., and care must be taken to exclude all solids, cloths, mud and an}'- thing" which would be liable to obstruct the flow in the pipes. The house drains will be much more likely to g^et into bad condition than the public sewers, and hence the neces- sity for g"reat care in laying- the drain and in providing- for its ventilation and flushing-. Municipal Control. — It will be found best to pass a g-en- eral ordinance g-overning- the use of sewers by private indi- viduals. The following- forms thoug-h not universally applicable may be useful as g-uides in outlining work of this kind. ORDINANCE. An Ordinance Fixing and Regulating the Use of Sewers by Private Individuals in the City of Section i. The Sanitary Sewer system of the city of consists of Main and lateral conduits of salt-glazed, vitrified earthen-ware or brick, with necessary accessories. They are designed to carry off all liquid house wastes, and are known herein as sanitary sewers. The sewers in the streets passing in front of the various lots are called main or lateral sewers. The sewers leading from the main or lateral sewers to the property on either side are called house sewers. Porous drains laid for removing subsurface water are called subsoil drains. connections. Sec 2* All connections of house sewers, drains or plumbing work with the sewer system of the city of shall be made in accordance with these rules and regulations. licensed plumbers. Sec 3. No person, firm or corporation shall lay, alter or repair any house-drain, sewer or plumbing work or make any connections whatever with any sewer or drain belonging to the sanitary sewer system, or do any kind of work connected with the laying of house-drains or house-sewers or plumbing or making any repairs, additions to or alterations of any drain, sewer or plumb- 242 THK SliPAKATE SYSTEM OF SEWERAGE. ing connected, or designed to be connected with the sanitary sewer system, unless regularly licensed by the APPLICATION FOR LICENSE. Sec 4. Any person desiring to do business as a plumber, in connection with the sanitary sewer system, shall file in the ofifice of the a petition giving the name of the individual or firm and place of business, and asking to be licensed as a plumber. Said petition must be signed by two responsible citizens, of the city of vouching for the business capacity and reputation of the applicant — that he is a resident of a master of his trade, and willing to be governed in all respects by the rules and regulations which are or may be adopted by the Each applicant for a license shall e.vecute and deposit in the office of the with his appli- cation, a bond with two or more resident sureties, to be approved by said in the sum of conditioned that he will indemnify and save harmless the city of , ... from all accidents and damages caused by any negligence in protecting his work, or by any unfaithful, imperfect or inadequate work done by virtue of his license, and that he will also replace and restore sidewalk, pavement or street surface over any opening he may have made to as good state and condition as he found it, and keep and maintain the same in good order, to the satisfaction of the for the period of six months next thereafter, and that he will pay all fines imposed upon him for a violation of any of these rules or regulations. On receiving his license he shall have recorded in the office of the his actual place of business, the name under which the business is transacted, and shall immediately notify the of any change in either thereafter. No license will be granted for more than one year and all licenses will be granted to expire on the day of Removal of residence from the city shall act as a forfeiture of license. PERMITS. Sec. 5. Applications for permits to connect with the sewer system or do plumbing work to be connected therewith, must be made in writing by the owner of the property to be drained or his authorized agent. Such applica- tion shall give the precise location of the property, the name of the owner and the name of the person employed to do the work, and shall be made on blanks furnished for the purpose. No permit shall be deemed to authorize anything not stated in the application, and for any misrepresentation in such applica- tion the plumber shall be suspended; and if such misrepresentation appears to be wilful his license shall be revoked. Permits to make connection with the sewer system will be issued onh- when the plumbing in the house or building to be connected is in accordance CHAP. XI. nousi'; drainage and plumbing. 243 with the rules for plumbing hereinafter prescribed and has been inspected and approved by the Superintendent of Sewers, or in case of new buildings when a proper plan for the plumbing has been approved by the Superintendent. The Superintendent will designate the position of the "Y" branch in the street, as shown by the records in the office. All con- nections made with the sanitary sewers or drains and all plumbing connecting therewith shall be made under the direction of the Superintendent of Sewers PLAN OF PLUMBING. Sec. 6. Before a permit will be issued for doing plumbing work in a building, or before any additions are made, excepting necessary repairs, a plan and description of the work to be done signed by a licensed plumber on blanks furnished for the purpose shall be filed in the office of the sewer department, and no such work shall be commenced until such plan shall have been approved by the Superintendent. Every plan shall cotjtain a clear and full description of the plumbing, showing the position, size, kind and weight of all pipes, and the position and kind of traps, closets and other fixtures. All work done under such plans shall be subject to the inspection of the Superintendent, and no alteration shall be made in any plan or in the work without a special permit in writing from him. INSPECTION. Sec. 7. The Superintendent is to be given notice when any work is ready for inspection, and all work must be left uncovered and convenient for examination until inspected and approved. Such inspection shall be made within twenty-four hours after such notification. The Superintendent may apply the ether, peppermint, water or smoke test, and the plumber shall fur- nish all necessary tools, labor and assistants for such tests. The plumber shall remove or repair any defective material or labor when so ordered by the Superintendents STATEMENT OF WORK DONE. Sec 8. The plumber shall, on the completion of the work, file in the office of the Sewer Department, on blanks furnished for the purpose, a correct statement of the work done under the permit. CESS-POOLS — OVER-FLOWS. Sec. 9. No open gutter, cess-pool or privy vault shall be connected with any sewer or drain. Cellar and cistern over-flows may be connected with the sewer or drain only when they can be trapped in such a manner that the water seal cannot be destroyed. 244 THE SEPARATE SYSTEM OF SEWERAGE. INJURY TO SEWERS. Sec. io. No person, firm or corporation shall injure, break or remove any portion of any man-hole, lamp-hole, flush-tank, catch-basin or any part of the sewer system, or throw or deposit, or cause to be thrown or deposited in any sewer opening or receptacle connecting with the sewer system, any garb- age, offal, dead animals, vegetable parings, ashes, cinders, rags or any other matter or thing whatsoever, except faeces, urine, the necessary water-closet paper, liquid house or mill slops and roof water by special permit. WATER AND GAS PIPE. Sec. II. Any person, firm or corporation desiring to lay pipes for water, gas, steam, or any purpose, in any street or alley upon which sewers are laid, shall give at least twenty-four hours' notice to the Superintendent before open- ing the street, and the manner of excavating for laying and back-filling over such pipe shall be subject to the approval of the Superintendent. All such work shall be planned and executed so that no injury shall occur to any public sewer or drain or to any house sewer or drain connected therewith. OBSTRUCTIONS. Sec. 12. The Superintendent shall have the power to stop and prevent from discharging into the sewer system any private sewer or drain through which substances are discharged which are liable to injure the sewers or obstruct the flow of the sewage. Sec 13. Before any old private drain or sewer shall be connected with the sewer system, the owner of the private drain or sewer shall prove to the satisfaction of the Superintendent that it is clean and conforms in every respect with these rules and regulations. TRENCHING. Sec 14. The house sewer trench shall be dug so as to meet the public sewer at the position of the "Y" branch, as located by the Superintendent. The material thrown from the trench shall be placed so as not to obstruct and so as to cause the least inconvenience to the public. Proper barriers and lights must be maintained on the banks of the trench to guard the public against accidents during the progress of the work. In back-filling the earth shall be carefully rammed or flooded so as to keep the pipe in proper position and avoid settling, and no stone shall be used in filling until there has been a depth of two feet of fine earth or gravel placed over the pipe. MATERIAL FOR SEWERS AND DRAINS. Sec 15. The house sewer from a point three feet outside of the house to the street sewer, shall be of first quality, salt-glazed, vitrified earthenware pipe, CHAP. XI. HOUSK DKAIXAGK AND PLUMBING. 245 unless laid less than three feet deep, when it shall be of heavy cast or wrought iron. Its interior diameter shall be inches. Outside the curb line it shall be inches. Subsoil drains shall be of earthenware pipes. PIPE LAYING Sec. i6. The cover of the "Y" branch on the sewer shall be carefully removed, so as not to injure the socket. The first length of pipe attached to the "Y" branch shall be curved and set so as to give a good fall into the sewer. The pipe shall be laid on an even grade of not less than one-fourth of an inch to the foot, unless by special permission of the Superintendent, in which case provision must be made for regular and efficient flushing. Curved pipe shall be used for every deflection from a straight line of more than six inches in two feet. The joints of the earthenware pipe shall be made with the proper oakum or jute gasket, and pure cement of first quality; the joints of the iron pipe shall be of oakum and lead if cast-iron is used, or screwed joints with white lead if wrought iron is used. The ends of all private sewers not immediately connected with the plumb- ing fixtures shall be securely closed by water-tight imperishable material. If lead pipe, the end must be soldered; if wrought iron pipe, a plug must be screwed in the end; if cast-iron pipe, a cast-iron plug must be calked in with the lead. Cellars shall be drained, when possible, by means of suitable, properly laid earthenware tile pipes. They shall not communicate directly with any drain carrying foul sewage, or with a sewer or cess-pool. Where possible they shall connect with the sub-soil drains in the street. PLUMBING RULES. Sec. 17. All materials used must be of good quality and free from defects; the work must be executed in a thorough and workmanlike manner. From a point three feet outside the foundation wall of a building no material may be used within the building and connecting with the sewer, for soil, waste, or vent pipes, other than wrought or cast-iron pipes, with securely leaded joints, or lead pipes with soldered or wiped joints. Cement or putty joints, tin or sheet iron pipes, whether galvanized or not, shall not be used No soil or waste pipe shall have a fall of less than one inch in ten feet. 246 THE SEPARATE SYSTEM OF SEWERAGE. Sec. i8. All cast-iron pipes must be sound, free from holes or cracks, and of the grade known in commerce as extra heavy, coated with tar or asphaltum. The following weights per lineal foot will be accepted as standards: 2 inches 5j^ pounds per lineal foot. 3 inches gj^ pounds per lineal foot. 4 inches 13 pounds per lineal foot. 5 inches 17 pounds per lineal foot. 6 inches 20 pounds per lineal foot. All wrought iron pipe must be of standard weight. All fittings used in connection with such pipe shall correspond with it in weight and quality. Where lead pipe is used to connect fixtures with vertical soil or waste-pipes, or to connect traps with vertical vent pipes, it must not be lighter than "light pipe." The arrangement of soil and waste-pipes must be as direct as possible. The drain, soil and waste-pipes and traps should, if practicable, be exposed to view at all times, for ready inspection and for convenience of repairing. When necessarily placed within partitions or in recesses of walls, soil and waste pipes should be covered with wood-work so fastened with screws as to be readily removed. MAIN, SOIL AND WASTE PIPES. Sec ig. A main waste-pipe into which wash-basins, bath-tubs or kitchen sinks discharge must be at least two inches in diameter, with one and one-half inch branches. The main pipe from ihe sewer connection to the house tap must be at least four (4) inches in interior diameter at every point. No trap or any manner of obstruction to the free flow of air through the whole course of the main house- sewer or soil pipe will be allowed. This may be secured by an untrapped main house sewer and soil pipe, or if a trap is placed in the main soil-pipe, by a ventilating pipe leading to the roof from the lower side of the trap and a fresh air inlet connecting with the foot of the main soil-pipe just above the trap. Every vertical, soil and waste-pipe must be extended at least two feet above the highest part of the roof or coping. It must be of undiminished size, without return bend, with open or basket end. It must not open near a win- dow nor an air shaft which ventilates living rooms. Soil, waste and vent-pipes in an extension must be extended above the roof of the main building, when otherwise they would open within twenty feet of the windows of main house or the adjoining house. CHAP. XL HOUSE DKAINAGK AND PLUMBING. 1^41 JOINTS. Sec. 20. All joints in iron drain pipes, soil-pipes and waste-pipes, except where screw joints are used, must be so filled with oakum and lead and hand- caulked as to make them gas tight. All connections of lead pipes with iron pipes must be made with a brass or lead sleeve or ferrule of the same size as the lead pipe, put in the hub of the branch of the iron pipe and caulked with lead. The lead pipe must be attached to the ferrule by a wiped or over-cast joint. All connections of lead, waste and vent pipes shall be made by means of wiped joints. INSPECTION. Sec. 21. Before the fixtures are placed in connection with the plumbing of any house or building, and before the soil-pipe is connected with the sewer, the outlet of the soil-pipe and all openings into it below the top, shall be her- metically sealed; the pipe shall then be filled with water to its top, and every joint be carefully examined for leaks. Work already in place will be examined by the peppermint or other test. Defective pipes discovered must be removed and replaced by sound ones, and all defective joints made tight, and every part of the work be made to conform to these rules and regulations, and subject to the approval of the Inspector. In cases where plumbing work has been completed in a building before these rules and regulations came in force, if the plumbing has been done in accordance with these rules and regulations, permits will be granted for making connections with the sewer as in new work, but in case the plumbing is not in accordance with these rules and regulations, such alterations shall be made as the Superintendent shall direct, to make the plumbing safe to the persons residing in the house, and such as to be no source of injury or stoppage to the sewer. In all cases the soil pipe shall pass through and above the roof. Traps are to be ventilated, fixtures and pipes clean, and waste and soil-pipes to have sufficient fall. Sec. 22. Every water-closet, urinal, sink, wash-tray, bath-tub, and every tub or set of tubs must be separately and effectually trapped. Traps must be placed as near the fixtures as practicable. In no case shall water from bath tub or other fixture be connected with the water-closet trap. Sinks in all packing-houses, butcher shops, lard-rendering establishments, hotels, restaurants, boarding-houses and laundries shall be provided with a suitable grease trap. Wash-rooms for carriages must be provided with proper means for intercepting mud. 248 TH1<: SEPARATE SYSTEM OF SEWERAGE. VENT PIPES. Sec. 23. Traps must be protected from syphonage, or the waste pipe leading from them ventilated by a special air pipe, taken out of the crown of trap, in no case less than two inches in diameter for water-closet traps, and one inch and a quarter for other traps, except when more than fifteen feet in length, when it shall not be less than one and a half inches in diameter. The vertical vent-pipes for traps of water-closets in buildings more than four stories in height, must be at least three inches in diameter, with two-inch branches to each trap, and for traps of other fixtures not less than two inches in diameter, unless the trap is smaller, in which case the diameter of branch vent-pipe must be at least equal to the diameter of the trap. In all cases vent-pipes must be of cast or wrought iron and connected to traps with brass or lead ferrule. Vent-pipes must extend two feet above the highest part of the roof or coping. The extension to be not less than three inches in diameter to avoid obstruction from frost, or they may be branched into a soil-pipe above the inlet from the highest fixture. They may be combined by branching together those which serve several traps. These air pipes must always have a continu- ous slope to avoid collecting water by condensation. No trap vent-pipe shall be used as a waste or soil-pipe. No brick, sheet metal, earthenware or chimney flue shall be used as a sewer ventilator, nor to ventilate any trap, drain, soil or waste-pipe. SAFES — RAIN WATER. Sec. 24. Every lead safe under a wash-tray, urinal, refrigerator or water closet must be drained by a special pipe not directly connected with any waste pipe, soil-pipe or sewer. The drip pipe from refrigerators shall not be con- nected directly with the soil or waste-pipe or with the sewer. Rain water conductors shall not be connected with the sewers without a special permit. OVERFLOWS FROM FIXTURES. Sec. 25. Overflows from fixtures must, in each case, be connected on the inlet side of the trap. WATER-CLOSETS. * Sec. 26. Water-closets must be of an approved pattern (pan closets being absolutely prohibited), and should be supplied from a special tank placed over them, in which case the waste or overflow from the tank must discharge into the open air of the basin of the closet, and not into the soil-pipe directly. Direct service of a water-closet is prohibited. All interior water-closet compartments should be ventilated into air shafts where possible CHAP. XI. HOUSl': DKAIXAGE AND PI.UMHIXG. 249 STRAINERS. Sec. 27. Exit-pipes to all fixtures except water-closets shall be furnished with suitable permanently attached strainers. Sec. 28. No person shall place, or suffer to be placed, any bulky sub- stance in any sewer opening, or in the house connections, or private drains connecting with any public, main or lateral sewer, or any substance having a tendency to obstruct the free flowage of said sewers or to damage them in any way. Sec. 29. Any person violating any of the provisions of these rules and regulations shall be deemed guilty of a misdemeanor, and upon conviction thereof be fined in any sum not exceeding fifty dollars nor less than ten dollars, or imprisonment in the for a period not exceeding twenty days or by both such fine and imprisonment, at the discretion of the court. PLUMBER'S LICENSE. City of Sewer Dep.\rtment. No I .. hereby licensed to do plumbing and lay house sewers and drains in connection with the public sewers in this city in accordance with the provisions of an "Ordinance No fixing and regulating the use of sewers by private individuals in the city of Sewer . PLUMBERS BOND. Know all Men by these Presents, that we of the City of as principal, and and .as sureties, are held and firmly bound unto the City of in the penal sum of Dollars to be paid to the said, the City of . . . or to its certain attorney, successors or assigns. 250 THE SEPARATE SYSTEM OF SEWERAGE. For 7vhich Pavnu-nt well and truly to be made, we bind ourselves and our heirs, executors and administrators, jointly and severally, firmly by these presents. Scaled this day of in the year of our Lord one thousand Wh,-r,'as, The said party of the first part has made application to be licensed to engage in the business of plumbing in connection with the public sewers of said city, which license has been granted, conditioned upon the execution of this bond, as provided by Ordinance No of the Common Council of said city, passed Now, thei-efore the Condition of this Obligation is such. That if the said party of the first part shall well and faithfully, and in a workmanlike manner perform the work of connecting such sewers, and shall save and indemnify the party of the second part of and from all costs, damages and expenses arising from making such connections, or the negligence or carelessness of the party of the first part, his agents, servants or employees in making the same, then this obligation to be void, otherwise to remain in full force and virtue. Sealed and delivered in the presence of APPLICATION FOR PLUMBING. To the Department of Sercers , No I.... The undersigned applies for permission to connect premises No Street, with the public sewer in Street, and to do the necessary plumbing, and I hereby desire a permit to be issued to , a regularly authorized and licensed plumber. I hereby stipulate and agree that the work on said sewer shall be executed in strict conformity with the provisions of "An ordinance fixing and regulating the use of sewers by private individuals in the ....," and the plans and specifications approved by the Superintendent of Sewers in And the undersigned further agrees that all claims against the City of for damages occasioned in any manner by the putting in of said sewer shall be waived, and held null and void. Owner. CHAP. XI. HOUSI-: DKAINAGK AND PLUMBINCr, 2.1 1 PERMIT TO CONSTRUCT SEWER. No I.... Authority is hereby given to to execute the work for upon the terms and conditions specified in above application. No dwelling" of any pretentions is now considered com- plete or even looked upon with favor by a prospective tenant, unless it is fitted with "modern conveniences." These appliances are entirely proper and safe if the work is entrusted to proper hands. It is hard to conceive of a class of work, however, in which wrong- methods or poor work are more detrimental, or the resulting- influences more insidious. House Drainage. — House drainag-e in its broader sense means both the removal of the liquid waste and whatever it carries with it, and also the removal of the subsoil water and storm water. Indeed, what is often spoken of as house drainag-e is strictly house sewerag-e. House drainag"e is the removal of ground water. The Subsoil. — The principal distinction between a sewer and a drain is that the former, being- for the convey- ance of foul liquid, should be absolutely tig-ht, so that none of the contents may be lost by the way, and no vapors escape. A drain, on the contrary (as for instance a subsoil drain), must be laid with open joints, so that, the pressure being- from without, it will receive the g-round water all along- its course, and remove it. The functions of the two are dis- tinct. When both kinds of drainag-e are necessary, it is best to keep each system distinct. When a g-eneral system of sewerag"e is already constructed without reg-ard to subsoil drainag-e, the householder frequently has no option but to connect the drainag-e system with the sewer proper. A very g-ood method in such a case is to make the connection 252 THE SEPARATE SYSTEM OF SEWERAGE. throug"h the medium of a deep seal trap where the street sewer enters the house. This connection should be through an iron pipe, properly caulked into the trap, and provided with a brass-seated check valve which will prevent the sew- ag"e from fillings the subsoil drains, in case the street sewer becomes obstructed. The subsoil drains should be of small ag"ricultural tile laid well below the cellar bottom, and the joints properly protected. The sides and bottom of the cel- lar or basement should be thoroug^hly damp proof. We are aware that this point is g^enerally overlooked. We do not stop to consider that the earth below and about building-s is a great collector and retainer of filth, and that it is suffi- ciently porous to admit of the passage of air currents in con- siderable volume, especially under the influence of furnace draughts or other like causes. The action is not unlike what would occur if we suppose the house set on a sponge 50x100 feet, for instance, to which we constantly apply a stream of foul liquid, and then induce upward currents through the house by the action of heat. The cellar walls and floor can be very easily and cheaply made damp-proof and air-tight by a coating of some preparation of asphalt. House Sewers. — One of the most common blunders in house drainage is in making the house sewer too large. It is very rare that any house will require a house drain (i. e. the pipe which carries the sewage from the house to the public sewers) more than four or five inches in diameter, and yet it is not uncommon to find a private house provided with a drain large enough to carry the sewage of a town of five thousand inhabitants. This use of unnecessarily large pipe arises from two causes. The ignorance of the owner, who not knowing what is required, determines "to have it big enough, any way," and the cupidity of the plumber, who favors any plan which swells the amount of his bill. Any unnecessary addition to the size of a house drain not onl}- CHAP. XI. HOU.SI': DRAINAGE AND PLUMBING. 253 causes needless expense, but renders it more difficult to flush the drain and keep it clean. This point has been fully discussed in Chapter VI. The practice of placing^ the house sewer beneath the cellar floor is very objectionable for two reasons: It is out of sio^ht and cannot easily be inspected, and it is usually laid on too flat a gfrade, especially when it runs beneath the floor for a considerable distance. Where possible the pipe should be placed along- the cellar wall, or hung- from the floor beams, so that it can be readily inspected, and can be given a proper grade to secure a sufficiently rapid flow of the sewag-e. T branches with tight covers, placed along- the pipe will afford the means of inspecting the interior of the drain and remov- ing- obstructions. The house drain within the house should never be of earthenware. It should be of iron, and heavy enough to admit of having the lead joints caulked so as to be water and gas tight. If roof water is admitted directly to the sewers, the rain-water leader should connect with the main soil pipe directly above the main trap. No waste or soil pipe should be connected with the rain-water leader. In a great many cases it will be advisable not to discharge the roof water into the sewers, particularly in the case of isolated dwellings where a portion of it is retained by cisterns, and where lawns are of considerable extent. In the case of more com- pactly built city buildings it will often be best to allow the roof water to be discharged into the street gutters, espe- cially where these are properly arranged, and the descent is sufficient. The following table of the behavior of house drains when running three-fourths full was calculated by Robert Moore, C. E., of St. Louis, Mo.:— 254 THE SEPAKATE SYSTEM OF SEWERAGE. TABLE XXVI. TABLE OF DIAMETERS OF HOUSE DRAINS. With various grades, and for lots of different sizes, capable of discharging two inches of rain per hour, when running three-fourths full. Calculated by Robert Moore, C. E., St. Louis, Mo. FALL PER lOO. SIZE OF LOT IN FEET. 20x150 3>^ 25x150 3H 30x150 4 35x150 ^H 40x150 4>^ 45x150 1 4U 50x150 5 60x150 5^ 70x150 5^ 80x150 90x150 100x150 6 6/2 I.O 1.5 2.0 2.5 3.0 4.0 DIAMETERS IN INCHES. ■3/8 4 4X 4'A 5% 6 3 3% 3A 3% 3'A 4/8 4X A'A 4% 5X 5A 2% 3% 3H 3% 3% 4 4/8 4^8 4I4: 5 5^ 5% 3 3% 3/2 3H 3V& 4 4X ^A A% 5 5% 1% 2% 3 3% 3/2 3M 3% 4 4^ ^Vz 4^/4 5.0 2>^ 2^ 3 3% 3X 3^ 3% 3H 4/4 4U By an inspection of the Table, we see that a four-inch main house sewer is ample for any ordinar}^ condition of service, even if roof water be admitted, the discharg-e of house sewagfe proper being* only a very small percentage of the total volume. A smaller size than four inches is not to be recommended, however, for the reason that althoug-h it may be ample so far as estimated carrying" capacity is con- cerned, it is more liable to obstruction. Under some cir- cumstances it ma}^ be advisable to increase the size of the main drain to five or even six inches diameter, this limit should not be exceeded however. If one drain of this size is not ample it is better to increase the number. In order to provide for ventilating the house drain it should be carried full size up through the roof. This venti- PLATE XXVIII. INTERIOR PLUMBING. CHAP. XI. HOUSK DKAINAGI-: AND PLUMBING. 2.3 1 lation of house drains has been discussed in a previous chap- ter. Grease Traps. — The principal dang-er of stoppag^es in a house drain, properly laid, arises from the grease carried into it from the kitchen sink. This can be avoided by the use of a grease trap, placed under the sink. The objection to the use of a grease trap is that they need to be cleaned occasionally, and if not cleaned they get very foul. Soil and Waste Pipes. — Soil pipes, that is, pipes leading from water-closets, and waste pipes, that is, pipes leading from bath-tubs, wash stands, etc., may be either of iron or lead. Iron is the better material where it can be used, but lead is easier to fit and adjust where the connection between the fixture and the main drain is not direct. All iron pipes should be either enameled or coated inside and out with coal pitch varnish to give them a smooth surface and keep them from rusting. All junctions and changes in the direction of the pipe should be made by easy curves. A very common fault is to make the upward extension of the soil pipe after it passes the highest fixture, of galvanized sheet iron, or even of tin. This is highly objectionable. It should be of heavy iron pipe throughout, and should extend well above the roof. It is a good plan to increase it in size above the roof to six inches, so as to lessen the danger of its being obstructed by the accumulation of frost. Ventilating cowls are of doubtful utility. A plain wire basket to pre- vent the introduction of articles liable to obstruct the pipes is better. There is such a variety of branches, curves, off-sets, traps, etc., etc., now in the market, that there is no excuse for awkward and rough connections and interior projecting angles or pockets which will retain the solid portion of the sewage. The course of all pipes should be as direct as pos- 258 THE SEPARATE SYSTEM OF SEWERAGE. sible, and the fixtures should be grouped so as to be reached as nearly as possible by uprig-ht soil pipes and short horizon- tal soil or waste pipes. Horizontal pipes cannot be carried any g^reat distance along- floors or ceiling-s or between joists, and preserve a proper inclination, for reasons which are obvious. It is customary to make waste pipes, particularly short ones, of lead, for the reason that it is much more easily manipulated than iron. The proper method of connecting- the lead wastes to iron is by means of a thimble soldered to the lead pipe and caulked into a hub on the iron pipe. Traps and Ventilation. — Every fixture should be pro- vided with a trap, and since the object of the trap is to iso- late the fouled interior surface of the waste pipe from the air of the room it is evident that the trap should be as close to the fixture as possible. Notwithstanding- many efforts to introduce a trap whose seal cannot be broken by syphonag-e, and which will be self-cleansing, the plain-running- trap of uniform bore is still in g-eneral use. This trap is liable to have its seal broken by syphonag'e, and to prevent this it is necessary to resort to a back air pipe, which is connected with the crown of the trap on the downward side, and passes to the roof independently of the ventilating- pipe proper, or is connected with it above the hig-hest fixture. This back air pipe should be of ample capacity to preserve the equilibrium of air pressure. The system of back air vents is open to the following^ objections: It considerably complicates the system of pip- ing-, especially w'here fixtures are not closely g-rouped. There is a possibility of the pipes being- fouled at their junc- tion with the crown of the trap. It adds considerably to the expense. Back air vents tend to increase the interior circulation of air considerably. This is beneficial, so far as purity of the interior of the pipes is concerned, but it also increases the CHAP XI. HOUSH DKAINAGK AND PLUMBING. 259 evaporation from traps. This will do no harm if fixtures are in constant use. On the other hand, if special anti- syphoning- traps are used, and back vents are dispensed with, there will be little circulation of purifying outer air throug-h the waste pipes. General Features. — Corners and recesses within the pipes and plumbing- fixtures should be avoided. All interior surfaces should be thoroug-hly flushed at every rush of water throug-h the pipes, otherwise the animal matter left sticking- to the surface will decompose and send off foul g-ases. On this account the use of "pan closets," and many patterns of traps, should be discontinued. The plumbing- fixtures in a house should be as few as possible. Not only is every addi- tional fixture and pipe joint a possible source of dang-er, but the principal danger from sewer g-as arises from rarely used fixtures, from which the water in the traps has evaporated. The fixtures on the different floors should be arranged so as to have them as nearly in a vertical line as possible, in order to avoid running waste and soil pipes horizontally or with insufficient fall. The less wood-work around fixtures the better. Not only does the wood itself become foul, but the space within the casing is dark, damp and dirty — a favorable locality for mould and rot, and a breeding place for vermin. Unwholesome smells, which are attributed to some faulty construction or arrangement in the drainage pipes, often have their origin in these inclosed spaces. It is not uncommon in summer, when the air is loaded with moisture, to see water accumulate in bead-like drops on the surface of plumbing fixtures or pipes which are kept cool by a current of water from a tap, and bourse downward almost in streams. If the fixtures are not inclosed they can be readily wiped dry. If inclosed they receive no attention, 260 THE SEPARATE SYSTEM OF SEWERAGE. and the accumulation of dirt and moisture becomes very offensive. The better kinds of water closets are made so as to require no wood surrounding- them, except a cover. A very g-ood way to fit up wash stands is to support the slab upon brackets fastened to the wall, leaving" the under side entirely open, and the pipes, traps, etc., entirely exposed, or par- tially hid by a narrow slab placed edg-ewise under the shelf proper, and extending" downward about six inches. So far as possible it is preferable to have soil, waste and ventilating" pipes exposed, to having" them inclosed within partitions where they are inaccessible either for inspection or repair. This method of arrang"ement is not without its influence on the plumber. He is not less inclined to pour lead joints properly, or to thoroughly caulk them all around, or to make neat and perfect wiped joints, than when he knows that the carpenter or plasterer will cover his work within a few hours. The average house owner will look upon this arrangement as decidedly lacking" in finish and not in har- mony with interior decorations. Neither is a stove pipe, a furnace reg"ister, a steam radiator, or a g"as fixture. This is larg"ely a matter of education, and possibly we have been wrong"ly taug"ht. It is not customary, however, to place these fixtures in rooms where any exceptions can be taken to this method of arrang"ement. The common practice of placing water closets and other plumbing" fixtures in dark, ill-ventilated places, such as inside rooms, dark closets, under stairways, etc., is wrongs in every way. All plumbing" fixtures and pipes should as far as possible, be kept open to the air and lig"ht. The places which are naturally the most foul stand most in need of sun- lig"ht and pure air. Where it is possible to. avoid it, no plumbing fixtures should be placed in a bedroom. During" the night some CHAP. XI. Housio dkainagp: and plumbing. 261 decomposition will be gfoing- on abov^e the trap in any fixture, and some foul g"as will be g^iven off. This, with the chance of sewer g^as coming- in through some defective joint, pipe or trap makes the risk too g^reat to be taken if it can be avoided. They should be confined to the bath room, where special means of ventilation can be employed, and to the kitchen laundry and similar rooms. A multiplicity of fixtures should be discourag^ed. A fixture rarely used is a greater source of dang-er than one used frequently.. Particular care should be used in arranging- the ventila- tion of a building, so that the air currents tend to pass out- ward from the g-roup of rooms containing* plumbing- fixtures, fresh air being- admitted to other portions of the building-. The facility with which this can be accomplished, and also the proper g-rouping- of fixtures and simplicity of the system of pipes will depend larg-ely upon the architect. The ornamentation of porcelain ware and of surround- ing wood-work by raised or carved patterns is positively detrimental. A perfectly plain, smooth impervious surface is more conducive to cleanliness. Everything- connected with house drainag-e and plumb- ing- should be of the best material and most thoroug-h work- manship. The best plumbing is not too good. By best plumbing- is not meant the most showy, or necessarily the most expensive. Water closets and sinks are not the most appropriate places for g-ilt and tinsel. On the other hand, it is poor economy to risk health and life on cheap, bad work in the sanitary arrangements in our homes. When the soil, ventilating- and waste pipes are all in position, and before the fixtures are put in place, a test of the thoroug-hness of the work should be made. This can be done in a variety of ways. The following- will be a very g-ood test: Close up the main drain where the iron pipe termi- nates outside the house wall, also the exposed ends of all 262 THE SEPARATE SYSTEM OF SEWERAGE. pipes where fixtures are to be connected, and the fresh air inlet, if there is any. The ends of lead pipes should be left somewhat long-er than necessary, so that this can be conven- iently done by flattening- them and closing- with solder. When all openings in the entire system of soil, waste and ventilating pipes are tightly closed below, fill the entire system with water from above nearly to the top, and mark the heig-ht at which the water stands. If no leakage is apparent and the water stands at the same level for some hours, the joints may be considered good. The entire work should be carefully inspected while under pressure, and joints re-caulked where necessary. It is not proper to connect waste pipes from refrigera- tors or safes, or overflow pipes from water tanks or cisterns directly with the sewers or waste pipes. The discharg-e from these can be often collected at a common receptacle, however, which is isolated from the sewers by special means. CHAPTER XII. COST AND ASSESSMENTS. Comparative Cost of the Separate and Combined Sys- tems. — No grneral comparison of the economy of the Sepa- rate and Combined Systems of seweragfe can be made. It depends in all cases on the condition of each problem, and the relative economy in a particular case can be determined only by a competent eng"ineer, after thoroug-hly considering- the requirements to be met. As indicated in a previous chapter, there can be no ques- tion as to which system will secure the most perfect and sanitary house drainag^e, whatever the conditions may be. In the Separate System proper we are seeking" this with a sing-le aim, and may adopt anything" conducive to it and reject anything- detrimental to it. How far we may depart from this line from considerations of apparent economy is a serious question. It must not be forg-otten that we are establishing- a com- plete svstem of subterranean communication between the dwelling-s of all classes of society, interposing- but a small volume of water as a barrier to the circulation of air cur- rents, and when street water is admitted we are introducing- another element of dang-er. In many of the smaller cities of the United States (and they are comparatively numerous, as shown in Table II) there can be no question as to the superior advantag-es of the Separate System in economy, efficiency, and adaptability to all the requirements to be met. In cities of this class it is folly to construct a Combined System ill adapted to the work in hand. The question of relative cost, thoug-h favoring- the Separate Sys^tem, is, therefore, not a pertinent one. 264 THE SEPARATE SYSTEM OF SEWERAGfc:. A comparison as to cost can only be properly drawn in the case of cities where considerable areas are paved and the storm water from them cannot be carried to the nearest stream without accumulating- in the g^utters to a deg^ree interfering- with business or threatening damag"e to prop- erty. The admission of storm water to small streams travers- ing- a city is entirely proper and generally beneficial. Any filth broug-ht from foul pavements is thoroughly removed by the after-flow of the rain which bring-s it, and also the filth accumulated in the bed of the streams during- low stages of water, which is so potent a factor in pollution and the accu- mulation of which, despite the string-ent ordinances in force in cities of this class ag-ainst the pollution of streams, it seems well nig^h impossible to prevent. Even in the Combined System it is usual to provide over- flows for the escape of a portion of the storm water into the natural drainag-e channels. "No system of sewerage yet proposed in any city contemplates the removal of excessiTi- storm water by means of sewers alone — such storms, for instance, as discharge for short intervals two or three inches of rain in an hour These occur at long intervals and are of short duration and the damage is usually confined to limited areas, while the construction of sewers to meet the contin- gency would be attended with enormous expense over the whole city, both in construction and repair, and prove of doubtful efficiency when suddenly called upon, and extremely objectionable as conduits for the ordinary flow of sewage.' — Adams. In cities of this class, then, we may properly compare the cost of the Combined System uniting- the house and man- ufacturing- wastes with the storm water for removal in the same conduit on one hand, with the cost of the Separate Sys- tem proper, supplemented by conduits for the separate removal of surface water, where such are necessary, dis- charg-ing- into the nearest water-course. Sewers for house drainag-e are required in every street or alley. Conduits for the removal of storm water from streets are required, with CHAP. XII. COST AND ASSESSMENTS. 265 rare exceptions, only in alternate streets, extending- from the natural drainag^e channels toward the summits. It will thus be seen that even in very densely built por- tions of a city, if the sewag"e proper can be combined with the storm water without necessitating" an extension of the larg-e out-fall sewer, which otherwise would not be required, the sewers in alternate streets extending- parallel with storm water conduits, and in every street intersecting- them, may receive house drainag-e exclusively, to be linally discharg-ed into the common out-fall. In this case if the city be laid out in reg-ular squares, the Separate System will reach three-fourths of the dwelling's without requiring- a double system in any street. It often happens, however, that j^uch a combination can- not be made without requiring- the construction of a long- line of out-fall sewer of larg-e diameter, at a comparatively larg-e cost, which, if the storm water was not combined with the sewag-e, mig-ht be of comparativeh' small size and cost. In desig-ning- a system of sewerag-e, then, the vital ques- tion is not properly that of the comparative cost of the Sep- arate and Combined Systems, but a question of the proper means to be adopted for doing- the work required to be done. Cost of the Separate System. — The principal items in the cost of sewers are: the pipe, trenching, laying- pipe and refilling the trench, man-holes, flush-tanks, lamp-holes and eng-ineering- and superintendence. The pipe manufacturers issue price lists, and these with the discount (depending upon the season, amount required, etc.) can be obtained by applying- to the ag-ents or g-eneral offices. The only very uncertain item in the list is the second — trenching-, laving pipe and refilling-. This will depend upon the nature of the soil in which the sewer is laid. 266 THE SEPARATE SYSTEM OF^ SEWERAGE. Quicksand is the most difi&cult material to manag"e. It will cost from two to five times as much to put in a sewer in quicksand as it will in ordinary earth. Examples of Cost from Actual Work. — As a g"uide in estimating" the cost of sewers of the Separate System a few instances of the cost of actual work are here g"iven. In Table XXVII will be found a statement of bids received on sewer construction in Schenectady, N. Y. The soil in which these sewers were proposed to be laid was, for the most part, favorable. It was necessary, how- ever, to sheet pile the trenches nearly all the way. Very little hardpan was met in construction. About 1,500 feet of the Front Street main sewer was laid in quicksand, the water rising- to an average depth in the trenches of about two and one-half feet. The cut under the New York Cen- tral Railroad, on Front Street, was peculiarly difficult, the depth of trench at this point being- sixteen and one-half feet, the lower four feet of which was quicksand and Wciter. More or less quicksand and water were encountered on all the streets leading- from the lower levels of the town to the plateau on the east, and also in White, Romeyn, and Fonda Streets, South Avenue and Nott Terrace. On the eig-hteen- inch main in Fonda Street about two hundred feet of rock work was encountered, averag-ing- about two and one-half feet deep. It was removed by the contractor at a cost of about ninety cents per cubic yard and no extra allowance was made therefor. The conditions found in Schenectady do not seem to be widely at variance with those ordinarily met with. The contract was awarded to the bidder whose name appears twelfth in the schedule of bids, at the prices therein stated. Ninety-seven per cent, of the work was completed within six working- months. 30 »ft -* M »n O O O - O 1 O O fnao « ■- o o -joqcf pne sjoif-dmci isd aoiJd w o o o > ns.00n00 moo O < ■< 00 >n o - ao r^ -s-o i^ - in •joqEi puE ■jjUEj-qsng iad sauj •ioqei puE sjEuajEtn auipnioai 'aioq-nEtn jad aoud owoo'dSoSSoSoSoo r» N o o m u-i m o o >n o m d o 4- -9- t^l^ ■«-X 8n «^.o H- X 30 >nx fo o « c^»o r-% w r^ o o Orv»-'rxO'^**^ '^^ f^ o •adid qoui-s Huiaei puB Saiqsiujnj joj jooj [Eauii jad aou^j •jaaj 91 japun puB jaaj ti jaAO Suijm -SJDEq puE nojiBAEOxa JOJ jooj jad aoijj 1 N N M « — M ^ oomooor^ooooc ■jaaj ti japun poB laaj zi jaAO Suijig -^OEq pUE UOIJEAEOXa JOJ JOOJ jad aoijj ONO«m»nr«0-^0»nO»riON •^ I- mrsinoo r^r^mM -^-c^ moo •jaaj zi japun puE jaaj 01 JBAO 3u!i|iJ -JJOBq pUE UOlJEABDSa JOJ JOOJ jad aoUfj •jaaj 01 japnn pnB jaaj g jbao Suing -SJOEq pUB UOIJBABOXa JOJ JOOJ jad aouj m\o O CTiOnOvO O M*nO mmo ' 0\ c\ O m ro o »rjo ^ 0\ ^ cox w ' OOOTj-'^NOXWrnOO »nx N cr\ t^x m mio tn ■^ m invo (n f^ »-« 'i- ■jaaj 8 japun puB jaaj 9 jaAO 3u![ig -3(DBq pUE UOIJEAEOXa JOJ JOOJ jad aoiJd ■jaaj 9 japun Suing ->lOBq pUB UOIJEAEOXa JOJ JOOJ jad aoij(j o -j-t^l^^l'vN r^x ;£s 5-0 o - c 1/3 X -AO ait/iS-x.-J-.x. 268 THE SEPARATE SYSTEM OF SEWERAGE. The following- is a detailed estimate of the work as finally completed and represents the total cost of the work, exclusive of eng-ineering, expenses of sew^er commission, land damag-es, preparation of plans, records, etc.: Excavation $10,823 43 Pipe and laying 12,229 37 Accessories 5.739 87 Total, $28,792 67 A total cost, for construction proper, of $.55 per lineal foot. The work afforded the contractor a reasonable profit, but it is doubtful if at present prices it could be duplicated. At the time bids were submitted common laborers could be hired at from one dollar to one dollar and twenty-five cents per day. Prices of material were also depressed. The entire cost of the system, including man-holes, flush-tanks and all accessories, all expenses of engineering, and preparation of plans and records, expenses of sewer committee, and all costs, of whatever nature, chargeable to the sewers was $.72 per lineal foot. A tax of $2.50 per capita on the population accommo- dated by these sewers, or a tax of one-half of one per cent, on the assessed valuation of the city would have paid their cost. In Table XXVIII will be found a statement of bids received for the construction of a system of sewers in West Troy, N. Y. The contract was aw^arded to the bidder whose name appears first in the Table. ■siaEX-qsnij •3[Ofj-dniET •piB[ nox J3d adij nojj ■jjaoj JO} qidsp ui -jj joj ijieauiT jad gDuj 'SaiAcds^ •piBj niBJd aiij[ qouj-E ■piEi ad[d qoui-gi •piB] adid qoai-Si «ft in 00 00 m •^ t^ -r IT) M •piE| adfd qouj-zi <» o N •^ ■piB[ adij qoni-oi ^ O m o O o O •piBi adid qoai-g ■piBi adij qaui-g ■jaaj 91 oj ti ^niiitjj -5jOEg puE BauBAEoxg ■jaaj t-i OJ zi Bnifiij -JtOBg puE anijEAEoxg ■jaaj zi OJ 01 Sujuij -5]0Eg pUB SuiJEABOXg •jaaj 01 OJ 8 SunUH -jjOBg puB SuijEAEOxg -3(3Bg pOE auiJEAEOXg ■jaaj 9 japun SuiniJ- -s^oEg puB SuijBABOxg "So '-' r ? -^ a, n! O 2 "^ > S 25 O 270 THE SEPARATE SYSTEM OF SEWERAGE. The g-eneral statistics of the sewers are as follows: Total leng-th of sewers (18 8-10 miles) 96,319 feet Total cost (exclusive of g^eneral expenses).S95,241.78 Total cost per foot " " " 99 cents Deepest trench (rock ) 16 feet Number of flush-tanks 116 Larg-est size of pipe 18 inches Smallest size of pipe (with few exceptions). 8 " Number of canal crossing's 7 Number of outlets 7 Long-est continuous line of sewer. . .About 9,000 feet Number of flushing- inlets from canal 6 Datum level Low water in the Hudson River Leng-th of drain tile 18,926 feet The system is almost entirely the Separate System. The only exception being- a small territory tributary to the Sixth Street main from which surface water is admitted. As will be seen by the accompanying- map, the villag-e has a river front on the Hudson of about two miles. This affords an opportunity of employing- several outlets, and makes it possible to carry the sewag-e to its out-fall in the river by short, direct lines, except in special cases. By dividing the whole territory into several distinct systems, each with a separate outlet, larg-e mains were avoided and the cost of construction materially reduced. The villag-e extends back from the river a.bout half a mile, and as the g-eneral direction of the main was towards the river, no very long- lines were necessar}-. The surface of the ground falls towards the river with sufficient slope for sewer grades, so that fiat grades were rarely necessary. The Erie canal runs throug-h the villag-e from north to south, nearly parallel with the river, and about 800 feet from it. The surface of the water in the canal is on the averag-e about level with the natural surface of the g-round near the canal; in places rising above, and in places fallings below it. Besides the main line of the canal there are two branch canals, leading- to the river, and two larg-e basins. The CHAP. XII. COST AND ASSESSMENTS. 271 canal, branches and basins, greatly complicated the work of designing- the sewers, and increased the cost of construc- tion. The material to be excavated from the trenches con- sisted of gravel, sometimes containing large boulders, clay and rock, varying in quality from soft shale, which yielded readily to the pick, to hard arg-illaceous rock, seamed with quartz. The canal banks intercepted the natural flow of the g-round water towards the river and materially increased the trouble from this source. Since the water in the canal was about level with the natural surface of the ground near the canal, it is readily seen that the ground in the vicinity of the canal would be water-soaked, and that wet cellars and diffi- cult trenching- might be expected. In several places in the village the rock came to the surface in ridges, leaving- pockets of considerable extent without drainage. In these places wet cellars were common. So little attention had been g-iven to drainage that in some places stagnant pools of considerable extent remained all summer. The following is a statement in detail of the cost of the system: — Earth Excavation $ 16,008.23 Rock Excavation 26,891.79 Sewer pipe laid in the trench 2.5,716.74 Drain tile laid in the trench 2,41-6.34 Manholes 4,617.00 Flush-Tanks and connections and Flush- ing Inlets 11,699.60 Lamp-Holes 795.00 Iron pipe — laid 4,209.26 Outlets and miscellaneous 4,513.04 Expenses of Sewer Commission, engi- neering, land damages, superinten- dence 16,902.42 3113,799.42 Cost per foot of the entire system . . . .81.18 272 THE SKPAKATli SYSTEM OF SEWERAGE. The ag"gTeg"ate capacity of all the sub-systems enumer- ated is 3,940,000 gfallons of sewag^e proper per day. Equal to 75 g-allons per diem per capita for a population of 52,530, and at the same time a capacity to discharg-e about 2,000,000 g^al- lons of subsoil water per day. The total volume on this assumption will in no case fill the sewer more than 71-100 of its diameter at the time of averag"e maximum daily dis- charge. The following- is a schedule of bids received for con- structing- a system of sewers in Dayton, Ohio: o in 8 o o •spjEA 3!qn3 "? 'I t ■? 'aiPPnd 't'^lD « ■spjBA ojqno vg O ^ & o luaiusjuequig •snox ui aoud o o 8 N 8 8 'gdij uoji ^ Iri 00 r^. o 8 8 8 8 8 X •M"EJ.-qsnij ui „■ ui ui oi O o o 8 ■aiOH- m M en Q oo < O O er, J '^ Id a. o (n en 0, *? * a lO N O m N • • . o I^ O vC vo t* 5^ _: ifl BS H J! J3 s C 3 n Ou u 5 o 09 C Bh c XI 3 1 b a o K 03 274 THE SEPARATE SYSTEM OF SEWERAGE. This system is still in process of construction. The cost of construction proper, not including" the expenses of the commission for land damag^es, eng^ineering" and other g-eneral expenses of a like character for the heavier portion of the work including" main sewers that are intended to serve other districts is as follows: Brick sewer, 42 inches in diameter, 1304 feet. 40 " " " 30 36 " " " 3380 30 " " " 1809 Pipe sewer, 18 " " " 900 12 " " " 624 10 " " " 7853 8 " " " 30478 Man-Holes 135 Flush-Tanks 45 Lamp-Holes 166 42-inch iron outlet 100 feet. Cost of construction to date $57,040.88 Cost per foot including" man-holes, flush-tanks, etc $1.25 The work has been peculiarly difficult for the reason that nearly all of the brick sewer has been laid in g"round below the level of the river at times and it has been neces- sary to keep a steam pump in operation continuously day and nig-ht, and in some instances two of them. The remain- ing" portion of the work is much less difficult and the sewers of smaller diameter, being mainly laterals, so that the cost per foot of the entire system will be considerably reduced. A pumping" station has been constructed capable of handling" 20,000,000 g"allons of sewag"e per day at a cost of $6,562.26 for the building" and $5,810.00 for the machinery. This will add about $.19 per lineal foot to the cost of that CHAP. XII. COST AND ASSESSMENTS. 275 portion of the system which it is proposed to construct at present. The pumping- station will ultimately serve a much wider territory however. The following- Table gives in a condensed form valuable information as to the cost, etc., of thirty-five sewerage sys- tems. It was compiled from information gathered by the Public Improvement Commission of Troy, N. Y., and appears in a more extended form in the Engineering Record for October, 1891: TABLE DATA OF COST AND CONSTRUCTION City. Akron, O Alleghany, Pa. Altoona, Pa. . . Augusta Bloomington . . Boston Buffalo Burlington, Vt. Cambridge . . . . Camden, N. J . Chicago Cincinnati Cohoes Council Bluffs . Detroit Dubuque East Saginaw. . Elmira Erie Grand Rapids. Kansas City. . . Kingston Lancaster Lawrence Lincoln. . . . . . Little Rock Milwaukee . . . Newark . New Haven . . . Omaha Philadelphia. . Portland, Me. Providence. . . Rochester. . . Syracuse System. Combined j Combined j & separate Combined . . . Separate . Combined Separate . Combined Separate Combined 6 rarely. 0.25 to 0.6 0.25 0.2 . 15 0.25 16 5 • 0.2 . 25(?) 0.5 . \ Combined } I & separate f Combined Per Cent. Min. Grade Pipe Sewers. 5 8", 0.35 24", 0.07 0.24 . . . . 0.33 25(?) 0.15 0.4 O. I Sewage per Cap. Daily Gallons. 70 90 60 90 60 40 50 20 o. 17 0.22 0.42 0.25 0.5 0.25 0.25 0.25 150 80 Cost of Cleaning. $300 annually Nothing Nothing. $60 per mile. $110 per mile Nothing .... $200 per mile $13-56 " Nothing. .... $10 per mile. Nothing .... $155 per mile $19.98 pr mile Nothing $37.98 pr mile $64 50 " $1,000 ann'lly Nothing XXX. OF THIRTY-FIVE SEWERAGE SYSTEMS. Cost of Pipe Sewers. Cost of Brick Sewers. Average Depth of Sewers, feet. 8" 10" 12" 15" 18" 24" 30" 36" 48" 60" $o 30 $0 30 $1 50 I 50 I 75 $2 50 2 25 $2 50 4 00 3 00 I 13 $2 50 4 50 3 20 1 82 2 00 3 75 3 25 3 67 $g 00 5 50 6 70 2 85 5 00 4 50 4 00 $9 00 7 00 4 09 4 00 8 00 5 50 9 II to 12 10 to 12 5 to 20 10 10 gto2o 10 9 8 25 35 1 50 I 00 I 14 gs 38 Q 60 1 50 I 00 I 25 1 14 go gs 2 00 80 54 65 70 1 75 I 20 I 50 I 50 I 10 1 07 2 25 go 64 70 1 00 2 00 1 50 2 15 I 75 I 50 I 00 82 3 00 2 00 2 00 3 50 2 00 3 70 2 12 1 30 2 22 4 00 I 50 3 25 5 00 3 00 4 14 7 50 6 00 g 00 6 00 5 20 4 50 1 40 2 50 I 25 82 1 70 3 00 2 10 I 67 I 50 I 75 75 46 13 9 6 to 8 4-5 10 10 to 18 10 to 12 10 8 12 9 7 7^ to 8 8 to 12 10 io}i to I3>^ 10 loto 12 12/2 10 to 15 7>^ tog II 7 to 10 10 40 I 82 1 20 2 65 2 60 65 70 80 65 1 10 I 40 I 25 85 I 00 70 I 30 80 I 60 4 50 4 00 6 00 2 25 3 70 4 20 3 00 go I 85 3 05 gin. I 00 88 I 40 I 37 2 45 3 50 3 90 4 60 77 I 00 4 40 I 25 4 90 4 50 I 50 6 25 5 60 2 00 10 00 6 50 40 I 15 45 I 30 60 I 70 75 2 10 I 00 2 25 1 55 2 50 1 55 3 21 2 75 2 25 2 54 3 70 2 50 I 60 I 25 88 1 2g go 1 .361 1 48 I 00 70 I 3ql T fit; 3 10 3 20 4 28 3 80 2 25 3 03 4 33 2 50 3 65 3 46 5 83 3 90 2 25 3 97 5 05 5 00 3 25 4 75 5 63 7 50 4 00 '"7'76 6 41 7 00 6 55 16 47 g 80 5 00 8 36 7 80 55 80 I 12 I 68 1 10 2 25 2 39 I 82 I 25 I 00 1 36 2 05 1 40 2 25 1.865 2 00 I 50 I 25 70 2 00 64 80 t 1 .036 50 40 4 00 7 60 278 THE SEPARATE SYSTEM OF SEWERAGE. The Table also g-ives valuable information as to the practice, with reference to g-rades, cost of cleaning- and depth of sewers in the cities mentioned. Examples of Cost Computed from Time Book. — Tables XXXI, XXXII, XXXIII and XXXIV were compiled by Mr. W. E. Ely. They were computed from notes taken in actual work, and represent actual cost to the contractor. An allowance of fifteen to twenty-five per cent, above these prices would be proper in making- preliminarj' estimates of cost. The soil was loam, sand, and gravel, and the roadway compacted gravel. The trenches were sheet piled the entire leng-th. TABLE XXXI. ACTUAL COST OF LABOR AND MATERIAL. -a ^ - 5 - 0! ^ u .5 S V v XI cu u (X 3 u a, " 6C g.s u — 6 c ■6 a a. (*-( Oh H.C Oh i ft. 29.92 9.0 63 lO " 6}^ to 9 ft 19 36.82 1. 14 .60 4 II. 72 lO " 9 to 12 ft. 19 *57.68 1. 14 .60 4 15.5 87 lO 12 to 15 ft. 19 46.70 1. 14 .60 ' 12.6 84 *Considerable water was encountered at this depth, which accounts for the increased cost of excavation. CHAP. XII. COST AND assessmi<:nts. 279 Laborers' wag"es, $1.50 per day; superintendence, $10.00 per day. About one-sixth of the trenching- was in water whose averag"e static level was two feet above the g-rade line. The soil was of averag"e compactness. The trenches were sheet piled nearly the entire leng-th. TABLE XXXII ACTUAL COST OF LABOR AND MATERIAL. c cS i 3 o u 0. a, .S 1) S.s 1- — 6 B 4J 'o N 'o a Q Oh "o tn u "^ -^ .^^ nl en CO ^ u c E 4) u be D < h as. as. C/x. a.r. aj. as. C/j. 6 inch. Under 6>^ ft. 9 15 •54 • 47 3 1-5 29 6 " 6)4 to 9 ft. 9 21 •54 •47 3 4.0 38 6 " 9 to 12 ft. 9 28 •54 •47 3 7.0 48 6 " 12 to 15 ft. 9 *76 •54 •47 3 18.0 107 6 " 15 to 18 ft. 9 60 •54 •47 3 30.0 103 8 " 12 •77 .84 1-55 •58 60 3 4 5 lO ' ' 19 24 12 " .87 ♦Considerable water was encountered at this depth, which accounts for the increased cost of excavation. Laborers' wag-es, $1.50 per day; superintendence, $10.00 per day. Nearly all trenching- was dry. The soil was rather favorable than otherwise, but required sheet piling-. 280 THK SKPARATE SYSTEM OF SEWERAGE. TABLE XXXIII. ACTUAL COST OF LABOR AND MATERIA L. -a ^ _jj B ° o nl o u .5 aJ aj 0) ^ O- u 6 a- u a i.a D4 c IK a Pi ^ HE Cm «4-l O o 'o a E CO '1-1 ID J < N (U o v rt rt D C/5 Q u U U h-J Cfi H as. Oj. C/^. 0.r. Oj. a^. as. 8 inch. Under 6'-^ ft. 12 35 1. 1 .58 3 9-83 61 8 " 6)4 to 9 ft. 12 32 I . I .58 3 8.00 56 Laborers' wag-es, $1.50 per day; superintendence, $10.00 per day. Water was found about one-fourth of the distance, but did not seriously retard the work. The soil was of aver- ag"e compactness. TABLE XXXIV. ACTUAL COST OF LABOR AND MATERIAL. T! .^ • S ?Pv- .5 S ^ ' 10.9 2 65 45.839 70 7.762 3 8.4 3 50 27,167 00 5.942 zY^ ' 12.3 3 86 22,936 12 2,705 4 6.5 4 37 11,820 85 6,932 4^ ' 10.4 5 00 34,65o 00 10,767 5 9-5 4 41 + 58,277 47 2,623 s'A • 14-5 6 44 16,892 12 610 6 10. 5 71 3,483 10 1,650 7 ' 12.5 9 95 16,417 50 1.334 JVz ' lO.O 9 35 12,472 90 379,203 $682,075 06 282 THE SEPARATE SYSTEM OF SEWERAGE. Cost of 2,986 catch-basins built $119,440 00 Cost of 6,709 cubic yards of rock excavated. . 23,483 00 $142,923 00 Total for sewers and catch-basins $824,998 06 The cost of the entire Combined Sewerag"e system of the City of Chicag^o, up to and including- 1890, is shown by the same report to be about $2.65 per foot. The system consists of about 784.737 miles, of which 360.694 miles are constructed of brick and 424.043 miles of vitrified clay pipe. From the annual report of the city eng^ineer of Provi- dence, R. I., 1890, it appears that the averag-e contract cost of labor per foot on the different sizes of sewers built in Providence during- the last three years has been as follows: 8 inch pipe in basin connections $0 63 12 15 16 18 20 22 24 48 " sewer 1 20 1 34. sing-le course brick sewer 1 70 2 05 2 03 1 50 2 55 3 25 double 20x30 inch sing-le course brick sewer 2 15 22x33 " " " " " 2 60 24x36 " " " " " 2 30 26x39 " double " " " 2 60 28x42 " " " " " 3 00 36x54 " " " " " 2 65 38x57 " " " " " 3 67 40x60 " " " " " 5 47 Rock excavation per cubic yard 4 00 The averag-e cut for 12 and 15 inch pipe sewers was about 12 feet, for brick sewers 13 and 15 feet, with the CHAP. XII. COST AND ASSESSMENTS. :283 exception of the 40x60 inch sewers, when the averag^e cut was about 24 feet. The excavation was mostly in sand and gravel. Maintenance of Sewerage. — The cost of cleaning" and repairing sewers, the cost per mile, and number of miles; also the number of catch basins and man-hole chambers distributed in the three divisions of the City of Chicago, according- to the report of 1890, is as follows: Divisions. Miles of Sewers. Nainber of Number of Man- Catch-Basins. Hole Chaml)ers. West 319.074 South 312.246 North 153.417 Totals 784-737 10.968 10,041 5,480 26,489 11.337 12,258 6.395 29,990 The cost of repairing- sewers during- the year was Sl-t,- 648.97, being- an average of S18.67 per mile. The cost of cleaning- was $107,873.34, making- the aver- ag-e cost $137.46 per mile. The total cost of both repairs and cleaning- was S122,- 522.31, an averag-e cost of S156.13 per mile. Accounts, as found in the reports of Sewer Depart- ments, are rarely classified so that the cost for maintenance and repairs of the Separate System can be isolated. The cost of maintenance is very slig-ht, however, beings confined almost entirely to the cost of an inspector who has the care of the system and inspects it at frequent intervals. According- to the report of the Sewer Commissioners of Brockville, Ont., the yearly cost of a s^'stem of about nine miles, costing- about 8100,000.00 is S400.00, S200.00 of which is for repairs. 284 THE SEPARATE SYSTEM OF SEWERAGE. The cost of maintenance of forty-two miles of sewers on the Separate System, in Memphis, in 1S89, is g-iven as fol- lows in the Eng-ineer's report: MAINTENANCE. Repairing- flush-tanks $1,648 55 Repairing- man-holes 43 02 135 obstructions removed 718 01^ Repairing- streets 361 11 Repairing- damag-es 30 10 Repairing- sewers 127 81 Cleaning- sewers, main 89 46 Cleaning- sewers, laterals 93 20 Tools, etc 304 48 Office expenses 88 55 Superintendent 1,200 00 Miscellaneous 185 93 $4,890 22^ ' Some of the items, particularly $1,648 for repairing- flush tanks, seem to be larg-e for an averag-e year. Sewer Assessments. — The following- are some of the many plans adopted for assessing- the cost of sewers: 1. By a g-eneral sewer tax, paying- for the sewers as fast as they are built. 2. By issuing- bonds and providing- for their g-radual payment by a g-eneral tax. 3. By assessing- the property benefited. 4. By paying for the sewers by a g-eneral tax, and charg-ing- for permits to connect private sewers. 5. By assessing- the property adjoining- the sewers in proportion to the frontag^e of each lot. 6. By assessing- the adjoining- property in proportion to the area of each lot. CHAP. XII. COST AND ASSESSESSMETS. 285 7. By assessing- the adjoining property in proportion to the value of each lot. 8. By assessing- a certain part of the cost on the adjoin- ing property in proportion to the frontage (or area, or value) and raisings the remainder by a general tax. 1>. By assessing- a certain uniform amount per foot front on adjoining property and paying the remainder bv a g-eneral tax. The method of assessing- the cost of a sewer upon "the property benefited" g-ives rise to perplexing questions. The judg-ment of different individuals will differ widely as to the limits of the districts benefited, the proportion of benefit derived by each lot owner and the relative value of the lots. In assessing- the cost of sewers in any section on the abutting property a difficulty arises from the fact that some parts of an}' system will be much more expensiv^e than others, and the extra cost will not be justly charg-eable to the adjoining- property. In designing any system of sewers, the sewage of a whole town, and the convenience of all the citizens, will require the construction of mains costing- from two to four times as much as the laterals, and the conformation of the ground may necessitate much deeper cuts in some localities than in others. To compel the owners of the lots adjoining- the mains and deep cuts to pay all the cost of them, when the extra cost is incurred to benefit distant territory, is a manifest injustice. The burden of the expense may be more nearly equalized, either by paying for the whole sys- tem by a g-eneral tax or by assessing upon the lots a uniform amount per foot front (or in proportion to area, etc.), and paying for the remainder by a g-eneral tax. To charg-e for connecting- private sewers with the public sewers, more than a nominal fee to pa}^ for inspection, is not advisable. The policy should be to encourage the citizens to 286 THE SKPAKATE SYSTEM OF SEWERAGE. use the sewers and abandon the objectionable methods for the disposal of sewag"e which are employed where sewers are not used. The most advisable method of sewer assessment to adopt in an^^ place will depend upon the conditions. Among* the most important considerations are the following": Whether the whole system of sewers is to be built at once or by piecemeal, whether there is to be one outlet or several — that is, whether there are distinct sewer districts, the cost of the sewers and the financial ability of the citizens. It is evidently impossible by any of the above methods to distribute the cost of sewers with absolute justice. The method of general taxation discriminates ag^ainst outlying- propert}' adjoining which no sewers are built. It is applica- ble to districts the whole of which are tributary to one sys- tem where the system is all constructed at once so that all property is benefited. The method of assessing- in proportion to frontage dis- criminates against shallow lots and vacant property. The method of assessing according to area discriminates against deep lots and vacant areas. The method of assessing according to valuation, espe- cially where the tax is all spread in one payment, discrimi- nates against improved property as against vacant property which ma}^ possibly be improved the following year. According to information gathered by Cambridge, Mass., it appears that out of 66 cities 13 paid the cost of sewers by a general tax and 53 assessed benefits. Of the 53 assessing benefits, 14 assessed the whole cost, 15 assessed three-fourths of the cost, 10 assessed three- fourths of the cost according to foot frontage, 12 assessed one-half to three-fourths the cost and 2 assessed less than one-half the cost. The prevailing rule among those who clearly state their practice is to divide the cost according to frontage. CHAP, XII. COST AND ASSESSMENTS. 287 The City of Providence has g'iven considerable attention to this question and assesses according- to frontage for a cer- tain depth from the street, and for a certain depth farther assesses according- to area. This combination of the methods of area and frontag-e tends to correct and equalize the discriminations of either method used sing-ly. Whatever method of assessing- benefits be adopted there will be a proportion of property owners that will be dis- tressed if the whole of their assessments be levied for collec- tion in one payment as is almost universally the custom in the United States. In many cases it means to the owners of such property practically a forced sale of the property. This seems to be a proper field for the application of the principles of the Building- and Loan Association, or in other words a massing- of capital and an association of interests for the purpose of distributing- costs over a series of 3'ears and obtaining- money in comparatively larg-e amounts at corresponding-ly low rates. The application of this method to special assess- ments, whichever of the above mentioned methods of deter- mining- the proportion to be assessed be adopted, is not at all intricate as will be shown later. The municipality is not less interested in so distributing- the cost than is the individ- ual. Statistics show that a very small proportion of cities "pay as they g"o. " Almost without exception they borrow in large amounts on long time and usually at low rates. This is unavoidable in a wise policy of public improvements and sound finance. Otherwise public works would necessa- rily be constructed piecemeal at a greatly increased cost, and a great loss of efficiency, or on the other hand, if the proper amount of capital were massed at one time for the economical and efficient construction of a system of sewers, water works or other public works of corresponding- mag-ni- tude the variations in the percentage of taxes levied from 288 THK SEPARATK SYSTICM OF SEWERAGE. year to year would be appalling- and undoubtedly there would be an exodus of the population. Let us assume, for the purpose of illustrating", that it is proposed to construct a system of sewers for a certain dis- trict, which is entire within itself (whether converg^ing" to a sing-le outlet or not does not matter so long- as a like propor- tion of the cost may properly be distributed equally over the territory in question). Let us assume also that the cost of the system complete, including- g-eneral and extraordinary expenses is $1.00 per lineal foot and that private property is deemed to be benefited to the extent of $.40 per lineal foot on the frontag-e plan on each side of the street and that the balance of the cost, which will be somewhat in excess of $.20 per lineal foot, by reason of street intersections and the rebates which it will be necessary to allow in order to equal- ize the assessments on corner lots and triang-ular pieces, be borne by the city. We will assume also that this amount borne by the municipality is equal to one-third of the -total cost for the purpose of simplifying- the problem, and that it is desired to distribute the cost of the sewers over the term of 10 years, principal and interest to be met b}' 10 equal, annual payments. In the case of a property owner having- an ordinary lot of 50 feet frontag-e the total assessment will be $20.00. In Table XXXVI will be found the amount of equal annual payments, of principal and interest combined, necessary to cancel a loan of $100.00 at various rates, and maturing- in any number of years, from one to fifty. CHAP. XII. COST AND ASSESSMENTS. 289 TABLE XXXVI. INSTALLMENT TABLE. Showing the amount of equal annual payments (of principal and interest combined) necessary to cancel a loan of $ioo, at 3, 3^, 4, 4^, 5, 6 and 7 per cent., payable annually and maturing in any number of years from i to 50 si < a PER CENT. PER ANNUM. < K CQ Z X •03 .03>4 .04 .04.^ .05 .06 .07 I 103. oco 103.500 104.000 104.500 105.000 106.000 107.000 2 52.261 52.657 53-020 53.413 53.780 54-544 55 • 309 3 35-362 35-699 36.026 36.370 36.726 37.411 38.105 4 26.903 27.229 27-550 27-877 28.202 28.857 29.5-^3 5 21.832 22.147 22.464 22.778 23.096 23.741 24.389 6 18.460 18.771 19.077 19.386 19.702 20.337 20.980 7 16.049 16 353 16.662 16.969 17.282 17.914 18.555 8 14.244 14.548 14.852 15. 161 15.472 16. 103 16.747 9 12.843 13.145 13-450 13-757 14.069 14.702 15.348 10 11.723 12.024 12.330 12.637 12.950 13-5S6 14.238 II 10.808 11.109 II .416 11.725 12.039 12.679 13.336 12 10 046 10.348 10.656 10.966 11.283 11 .928 12.590 13 9 403 9.707 10.014 10.328 10.646 II .296 11.965 14 S 853 9-157 9.467 9 782 10. 103 10.759 11.434 15 8.377 8.683 8.994 9.311 9-634 10.296 10.979 16 7.961 8.268 8.582 8.902 9-227 9 895 10.586 17 7-596 7.904 8.220 8.542 8.870 9-544 10.242 18 7.271 7.580 7.899 8.224 8-555 9.236 9.941 19 6.981 7.294 7.614 7.941 8.275 8 962 9.675 20 6.722 7.036 7.358 7.688 8.024 8.718 9-439 21 6.487 6.804 7.128 7.460 7.800 8.500 9.229 22 6-275 6.593 6.920 7-255 7 597 8.305 9.041 23 6.081 6.402 6.731 7.068 7-414 8.128 8.871 24 5-905 6.227 6.559 6.899 7.247 7.968 8.719 25 5 743 6.058 6.401 6.744 7.095 7.823 8.581 26 5-594 5.921 6.257 6.602 6.956 7.690 8.456 27 5 456 5-785 6. 124 6.472 6.829 7-570 S.343 28 5.329 5.660 6.001 6.352 6.712 7-459 8.239 29 5.212 5.545 5.888 6.241 6.605 7.358 8.145 30 5. 102 5-437 5 783 6-139 6.505 7.265 S.059 (Table concluded on next Page.) 290 THE SEPARATE SYSTEM OF SEWEKAGIC. TABLE XXXVI CONTINUED. z w PER CENT. PER ANNUM. OS X < w u ^1 K O ' 5 •03 .03>^ .04 ■ 04 'A -05 .06 .07 31 5.000 5-337 5.686 6.044 6.413 7.179 7.980 32 4-905 5 244 5 595 5 956 6.328 7. 100 7 907 33 4.816 5 157 5 510 5 875 6.249 7.027 7 841 34 4-732 5 076 5 432 5 798 6.176 6.960 7 780 35 4.654 5 000 5 358 5 727 6. 107 6.897 7 723 36 4.580 4 928 5 289 5 661 6.043 6.839 7 672 37 4-511 4 861 5 224 5 598 5-984 6.786 7 624 38 4.446 4 798 5 163 5 540 5-928 6.736 7 579 39 4.384 4 739 5 106 5 486 5.876 6.689 7 539 40 4.326 4 683 5 052 5 434 5.828 6.646 7 501 41 4.271 4 630 5 002 5 386 5-782 6.606 7 466 42 4.219 4 580 4 954 5 341 5-739 6.568 7 434 43 4.170 4 533 4 909 5 298 5.699 6.533 7 404 44 4-123 4 488 4 »66 5 258 5.662 6.501 7 376 45 4.078 4 445 4 826 5 220 5.626 6.470 7 350 46 4-037 4 405 4 788 5 184 5-593 6.442 7 326 47 3 - 996 4 367 4 752 5 151 5-561 6-415 7 304 48 3-958 4 331 4 718 5 119 5-532 6. ^90 7 283 49 3.921 4 296 4 686 5 089 5-504 6.366 7 264 50 3 887 4 263 4 655 5 060 5.478 6.344 7 246 Assume that the municipality can obtain money at four per cent for the time stated. From the table we ascertain that a loan of $20.00, maturing- in ten years at 4 per cent, will be canceled by 10 equal annual payments of $2.46 each. If it be assumed that the cost of the entire improvement be $150,000.00 and the ag-g^re^ate amount assessed ag^ainst the property by special assessment by any of the methods described be $100,000.00 and the amount borne by the municipality at larg-e be $50,000.00 as previously stated, we find from the table that the amount to be borne by the city at larg-e will be paid by 10 equal annual payments of $6,- 165.00, which is the amount to be levied by g-eneral tax each CHAP. XII. COST AND ASSKSSMICNTS. 291 year, and the ag-greg-ate of the special assessments ag-ainst the property frontage will be $12,330 each year. A separate account should of course be kept of the fund and all that remains to be done is to add the several amounts charged against each property (corresponding to the $2.46 in the case cited) to the yearly assessment of the property and to add the municipality's proportion, (corresponding- to $6,- 165,00 in the case cited) to the amount to be levied in the g'en- eral tax roll each year for ten years, until the account is closed. The clerical work in this method is not more than when others are used. In some cases loans can be secured at a lower rate on bonds maturing after a stated number of years and bearing annual interest. Where it is desirable to secure funds in this manner the method above outlined can be used to pro- vide a sinking fund for the payment of these bonds at matu- rity. CHAPTER XIII. COMBINED SEWERS. Under some circumstances it may be necessary to con- struct combined sewers. When this is the case the size of the sewers is determined by the amount of storm water to be provided for. The volume of sewag"e proper is so small in comparison with the volume of the storm water during" the continuance of a storm that the sewage need not be taken into consideration. In determining- the size of "Combined Sewers" the fol- lowing points must be taken into consideration: 1. The area from which the storm water is to be g^athered. 2. The rate of rain-fall. 3. The relative proportion of the roofed and paved area to the whole area to be drained. 4. The nature of the soil in the unpaved part of the area. 5. The amount of g^round water. 6. The natural grade of the surface. 7. The available grade for the sewer. The rate of rainfall has been quite g"enerally determined in those sections which have been long- enough settled to feel the necessity for sewers. It is evident that the larg-er the proportion of the roof and paved area the larger will be the percentage of the rain- fall to be provided for by the sewers. The permeability of the soil in the unpaved areas will also materially effect the proportion of rainfall which reaches the sewers. The grade of the surface will determine the rapidity with which the storm water will flow to the sewer, and the CHAP. XIII. COMBINED SEWERS. 293 grade of the sewer will determine the velocity of the flow of the sewage, and hence the capacity of the sewer to dispose of the gathered storm water. It is very difficult to estimate the amount of ground water to be provided for. In some cases there ma}' be con- siderable water for a short time and but very little after- wards. Where the sewer intercepts a water bearing stratum the flow may be not only considerable but constant. Sewers are rarely built large enough to dispose of the most rapid falls of rain. A certain depth per hour is assumed as reaching the sewers and the sewers are designed to dispose of the amount of water falling on the sewered area at the assumed rate of rainfall over the whole surface. The depth of rainfall assumed as reaching the sewers varies under the different circumstances from half an inch to one inch per hour and even more in some cases. In exceptional cases rain has fallen at four or five times that rate. Several different formulas have been proposed for deter- mining the size of storm sewers. The following are some of these: Julius W. Adams' formulas.* - \ 1542. ^=>| 15427/ [IJ in which Z> = diameter of sewer in feet. ^=cubic feet per second to be provided for. X = length of sewer. j^=rise for length L. ^ 2 log. .1+ log. 7V^— 3.79 log. /? = ^ ^-^7^ [2] in which Z^ = diameter, in feet, of sewer. .4=acres to be drained. /V= length in feet in which the sewer falls one foot. *Sewers and drains for populous districts, pp. 47 — 68. 294 THE SEPARATE SYSTH:M OF SEWERAGE. These formulas are on the basis of one inch of rain per hour, one-half of which reaches the sewer within the hour. Thomas Hawksley's Formula, used in the main drain- ag"e of London: • r • .• • u N 3 1og-. .4+iV+6.8 ,.„ log-, diameter of mam (m mches)= — ■ [.ij ^ =acres drained. 7\^=leng'th in which the sewer falls one foot. This is on the basis of one inch of rain per hour. Knowing" the amount of storm water to be provided for, the size of the sewer may be determine'd by the formulas g"iven in a former chapter. The Burkli-Zieg"ler formula for the probable amount of storm water is: ^=1.25^r J^ W ^= cubic feet of water per acre reaching- the sewers in one second. c—a. coefficient depending upon the nature of the surface and varying- from 0.25 in rural districts to 0.60 for paved streets, averag-e 0.50. /-= cubic feet of water per second falling on an acre, ^'^the number of feet fall of the surface in 1000 feet. ^4=area drained in acres. Forms of Sewers. — For sewers flowing- half full, or more, the circular section is best. But when, as is usually the case with combined sewers, the ordinary flow of sewag-e fills but a very small part of the cross-section of the sewer, it is best to so form the cross-section as to concentrate the stream and g-ive it more depth. The form usually adopted is eg-g-shaped with the small end down. CHAP. XIII. COMBINED SEWEKS. 29.5 Materials. — Sewers may be built of brick, terra cotta, stone or concrete, or a combination of these materials. They are usually built of brick laid in hydraulic cement. The bricks should be burned hard and laid with full joints. Baldwin Latham g-ives the following- formula for deter- mining" the proper thickness of brick sew^ers: ——- = thickness of brick-work in feet. f/=depth of excavation in feet. r= external diameter of sewer in feet. Catch Basins. — The storm water from the street should be first received in a "catch basin," where the dirt and debris from the streets can settle and not be carried into the sewer. They are usually placed at the street corners, near the junction of the g"utters. Man-Holes. — These are similar to those on the separate sewers. Plates X and XVI. They start from the spring-- ing line of the upper arch of the sewer. It frequently happens that storm water conduits can be built separate from the sewers at a less cost than to build a combined sewer. The storm water conduit need not be as deep as a sewer.. It can be discharg-ed into the nearest natural water course, and this often very much shortens the necessary leng-th of the larg-e conduit. Where sewag"e must be pumped the separation of the storm water from the sewag-e is a necessity if economical workinof is desired. CHAPTER XIV. SEWAGE DISPOSAL. One of the most difficult problems presented for solu- tion to the Seinitary Eng-ineer to day, is that of sevvag^e dis- posal. How to effectually dispose of the solid and liquid wastes in any community so that they will be neither offen- sive or dang-erous to any one is a question of g-rowing- importance. The rapid increase in population of our cities and villag-es swells the flood of sewag^e which is poured into the streams, polluting- the natural sources of water supply, while the demand for pure water is of necessity rapidly increasing-. In the older countries of Europe the pollution of water courses by sewag-e has forced itself upon the attention of g-overnment officials, and string-ent laws have been passed to protect the purity of streams. In this country the time is not far distant when the pollution of streams and lakes by sewag-e will need to be forbidden by law, or in many local- ities pure drinking- water in any considerable quantities will not be obtainable. In many cases there is no available outfall for the sew- age and the question of its disposal comes up at once with the inception of sewer projects. Of the various methods of sewag-e disposal those which have been tested on any considerable scale may be classed as follows: 1. It may be emptied into a stream or large body of water. 2. It may first be clarified by straining-, by subsidence, by filtration, by chemical processes or by a combination of these and the effluent turned into a stream or bodv of water. CHAP. XIV. SICWAGIC DISPOSAL. 2!>7 ,3. It may be applied to the soil, as in intermittent downwai'd filtration, broad irrig-ation, or subsurface irrig-a- tion. Dilution. — When sewage is turned into a stream of con- siderable size the disappearance of the sewage is due to sev^- eral causes. The sewagejs diluted by the large amount of water into which it is discharged, some of the organic mat- ter becomes food for aquatic plant and animal life and some is destroyed by oxidation, and the remaining solid particles are deposited along the bed and banks of the stream. So long- as the amount of sewage is small in comparison with the volume of water this method may be admissible, but it is in use in scores of cases where it ought not to be. Rivers and lakes often become so polluted by sewag^e as to become a serious menace to the health of cities on their banks. The Chicago River and Lake Michigan at Chicago, and the Cuyahoga River and Lake Erie at Cleveland are examples of this. Subsidence. — When sewage is partly purified by subsi- dence the sewag-e is collected in tanks and allowed to stand until the solids are deposited and then the water is drawn off. Although somewhat less objectionable, the effluent water is charged with impurities and is still unfit to be turned into the natural water courses. Filtration. — Filtration is sometimes resorted to and the sewage is passed through filters of various sorts. This sep- arates more of the solids than can be obtained by subsi- dence, but the effluent is still unfit to be turned into the streams. Chemical Processes. — Chemical processes have been extensively used. In these some chemical solution is mixed with the impounded sewag-e, which precipitates not only the 298 THK SEPARATE SYSTEM OF SEWERAGE. solid matter but also a part of the substances held in solu- tion. There are scores of these patented processes — too many to even name within the limits of this chapter. The solid residuum or "sludg-e" is used as a fertilizer. The hope that the "sludg-e" would be of g-reat value as a fertilizer has not been realized and very little profit can usually be obtained from this source. The effluent water is far from pure and frequently decomposes after being- turned into a creek or river. This method mig-ht be used advantag-eously where the effluent passes into the sea or larg-e tidal rivers, where the water is not used for water supply. Application to the Soil. — Filtration through the soil, both upward and downward has been used. Intermittent downward filtration has worked quite successfully. By this method the sewage is turned on to g-round which has been thoroughly under drained. The sewage is filtered by passing- throug-h the soil and much of the organic matter is destroyed by oxidation and nitrification. Separate filtering- beds are prepared so that they may be used alternately. The effluent water is quite pure if the fil- ter beds are properly made and kept in g-ood condition. The amount of g-round necessary and the depth of the under drains depend upon the character of the soil. Where sufficient suitable land can be procured broad irrigation is the most satisfactory method of sewag-e dis- posal. The soil should be loose and thoroug-hly underdrained. Compact clay is not suitable for a sewag-e farm without special treatment for breaking- up and loosening- the subsoil. The amount of sewage per acre which can be disposed of varies with the nature of the soil, and its special prepara- tion for sewag-e disposal. In practice one acre of land has been used in broad irrigation for disposing- of the sewag-e of from 50 to 500 persons. CHAPTER XV. THE PURIFICATION OF SEWAGE BY APPLICA- TION TO THE SOIL. It is still an open question whether water which has been contaminated with sewagfe may be so thoroug^hlv puri- fied as to be entirely safe for culinary uses. So far as chemical purification is concerned there is no doubt it can be accomplished by filtration throug^h the soil under favorable conditions. Whether the effluent can be so purified by this means as to contain no trace of the bacteria which are supposed to incite various zymotic diseases, the water having- been previously contaminated with them, is still in dispute by eminent authorities who have labored in this field. It is well known that the purest of natural waters, as reg"ards organic matter, are those which have underg-one prolong-ed filtration throug-h the soil. Our knowl- edg-e of the causes which influence the purification of sewag^e when applied to land, either in broad irrig-ation, intermittent downward filtration or subsurface irrig-ation is rapidly extending-, however, and this is a field of such promise as to justify a reference more at leng-th to some of the later achievements and conclusions concerning- this method of purification. The impurities with which sewag-e is charged consist mainly of different org-anic compounds in various stag-es of decomposition. It is not practicable, or in fact desirable, to prevent the decomposition of these org-anic compounds. With the exception of the small portion which may be con- sumed as food by animal life, they must be resolved into their elementary substances before they canag-ain be utilized by plant life or otherwise rendered innocuous. It is, how- 300 THE SP:PAKATE SYSTIiM OF SEWERAGE. ever, practicable to so control the conditions of decomposi- tion that it shall become inoffensive and the resulting- com- pounds shall be fixed and rendered harmless by some sur- rounding- medium. The soil is a medium which not only renders these products innocuous but also favors a mechan- ical separation and aeration very conducive to the rapid dis- integ-ration and absorption of the putrescible matters con- tained in the sewag-e. In the report of the Select Committee on the Metropolis Sewag-e it is stated that, "No efficient artificial method has been discovered to purify, for drinking and culinary purposes, water which has once been infected by town sewage. By no known mechanical or chemical means can such water be more than par- tially cleansed; it is always liable to putrefy again. Processes of filtering and deodorization cannot, therefore, be relied upon to do more than mitigate the evil. Water which appears perfectly pure to the eye is sufficient, under certain conditions, to breed serious epidemics in the population which drinks it Soils, however, and the roots of growing plants have a great and rapid power of abstracting impurities from sewage water and rendering it again innocuous and free from contamination." The process of purification of sewag-e by filtration throug-h the soil is similar to that of burning- up or oxidizing- the org-anic matter leaving only a harmless mineral residue, which is soluble and passes off in the effluent, leaving- the filtering- medium, when properly manag-ed, undiminished in efficiency. The application of sewag-e intermittently serves to increase the amount of oxidation similarly to opening- the draft of a furnace. The chang-es produced by wet oxidation, however, are not the same as those produced by heat, there being- inter- mediate processes. In the former the nitrog-en of the organic matter first combines with the hydrog-en to produce aminonia which, upon uniting- with oxygen, produces nitric acid. This, in turn, combines with potash, soda, lime or some other base present in the sewage or in the soil to pro- duce a soluble nitrate. The extent to which this sequence CHAP. XV. THIO PUWII'ICATIOX OK SICWACrE. 301 of combinations has proceeded is a measure of the deg^ree of purification of the sewage. The larg-er the amount of nitrates in the effluent, therefore, and the smaller the amount of ammonia, the more completely has the org-anic matter of the sevvag"e been destroyed. Later investigations have shown that the earlier of these processes depend on the presence of living- organisms. The Influence of the Bacteria of Nitrification. — The fol- lowing interesting facts concerning nitrification or the con- version of ammonia and the nitrogen of organic matter into nitric acid in the soil, upon which process the purification of sewage largely depends, were given by Mr. R. Warrington, in a paper read before the Society of Arts in 1882.* "Diluted solutions of urine or of ammonium salts containing the essential constituents of plant food, undergo no nitrification, though freely exposed to the air, if only they have been previously boiled and the air supplied to them is filtered through cotton wool. If to such sterilized solutions a small particle of fresh soil is added no action at first appears but after awhile active nitrification sets in and the ammonium or urea is convened into a nitrate. For the pro- duction of nitric acid it is necessary that some base should be present with which the nitric acid may combine. The action proceeds best in the dark. When a solution has thus undergone nitrification a drop of it suffices to induce nitrification in another solution, which, unless thus seeded would have remained unchanged. Boiling the soil, or the solution that has nitrified, entirely destroys its power of causing nitrification. The presence of antiseptics also prevents nitrification. Lastly, nitrification is confined to the same range of temperature which limits other kinds of fermentation. The production of nitrates proceeds very slowly near the freezing point, but increases in rapidity as the tempera- ture rises, reaching its maximum of energy, according to Schlaesing and Miintz, at gg- Fahr. At higher temperatures the rate of nitrification rapidly dimin- ishes, it almost ceases, according to the same observers, at 122^ Fahr., and at 131- Fahr, no change occurs. It thus appears that nitrification can only be produced in the presence of some nitrified or nitrifying material, and the whole course of action is limited to the conditions suitable for the activity of a living ferment. The French chemists claim to have isolated the ferment by systematic cultivation. It belongs to the family of Baclciia. ''The Treatment and Utilization of Sewage — W. H. Coitield, 1S8-. 302 THE SEPARATE SYSTEM OF SEWliKAGE. The purifying action of the soil on sewage is probably due to three distinct actions: i. Simple filtration, or the separation of suspended matter. 2. The precipitation and retention by the soil of ammonia and various organic sub- stances previously in solution, 3. The oxidation of ammonia and organic matter by the agency of living organisms The last mode of action is undoubtedly the most important, as without oxidation the sewage matter must accumulate in the soil and the filter bed lose its efficacy. The filtering power of a soil will depend entirely on its mechan- ical condition. The precipitating power of soil, is on the other hand, a chem- ical function, in which the hydrated ferric oxide and alumina and the silicates of soils probably play an important part. The oxidizing power of a soil will depend partly on its mechanical, partly on its chemical and partly on its bio- logical condition. It was formerly supposed that the oxidizing power of a soil depended solely on its porosity, oxidation being assumed to occur by simple contact with air in the pores of the soil. We now know that a porous medium is by no means essential for nitrification; sewage may, indeed, be nitrified in a glass bottle, or when passing over polished pebbles. Though, however, porosity is by no means essential to the nitrifying power of a soil, it is undoubtedly a condition having a favorable influence on the rapidity of the process; a porous soil of open texture will present an immense surface* covered with oxidizing organisms and generally well supplied with air requisite for the discharge of their functions. It is doubtless owing to this fact that nitrification takes place with so much greater rapidity in a soil than in a liquid. The sewage will itself supply the substances required for the nourishment of the oxidizing organisms. * * * *Iii order to bring out the po.int here spoken of by Mr. Warrington a little more promi- nently the author made the following experiment, which may be of interest: Fifty cubic centimeters of ordinary screened mason's sand, of a fineness of 40 grains per lineal inch, were placed in a chemist's burette, having first been thoroughly freed from moisture by continued drying at a temperature of about 225°. Water was then introduced into the burette from below by aspiration, so as to facilitate the expulsion of contained air until the voids were entirely filled and the amount of water introduced carefully noted. The burette was then opened below and the excess of water over that naturally adhering to the particles of sand was allowed to drain otf. From the facts noted the following computa- tions were made: The total air space in the dry soil was 36 per cent, of the cubic contents. The water adhering to the particles of soil was 18 per cent, of the cubic contents. The total superficial area of the particles of soil for each cubic foot was 2,200 square feet. The water adhering to the particles of soil for each foot in depth was equivalent to a film of water i-iooo inches thick and 2,200 square feet in area. Since the purifying agencies within the soil and its con- tained air have been proved to be active to a depth of at least three feet we may assume that the surface of sewage which is exposed to the action of these purifying agencies is approximately 6,600 times greater when sewage is applied to the soil intermittently than when it is simply impounded over the sams area. CHAP. XV. THIC PUKII'^ICATIOX OF SICWAGIC. 303 * * The organisms which effect the oxidation of organic matter are abundantly present in surface soils but are probably absent, or nearly so, in subsoils. In surface soils they will probably be abundant in proportion to the richness of the soil in organic matter. Sewage also contains the organisms necessary for its own destruction, and under fav^orable conditions these may be so cultivated as to effect the purpose." Later investig-ations concerning- the function of living- organisms in the purification of sewage lead to the con- clusion that they increase in numbers wonderfully when sewage is applied to soil originally quite deficient in organic matter, the conditions thereby beings rendered favorable to their increase in proportion as their presence becomes need- ful to the purification of the organic substances supplied. This is shown in the experiments of the Massachusetts Board of Health, quotations from which are to be found farther on. It also appears from experiments carried on at the model farm at Rothamsted, under Messrs. Lawes & Gilbert, and elsewhere, that these organisms are decidedly more numerous and active near the surface of the g-round and their action under ordinar}' conditions is said to cease at a depth of about three feet and to be very uncertain below a depth of twelve or fifteen inches. In view of these conclusions it appears that so far as the action of these organisms is concerned it is unnecessary to fjrepare intermittent filtration beds as deep as was formerly thought advisable, and Dr. Frankland has stated* that whereas in the Rivers' Pollution Report he had recommended 6 feet depth of earth for intermittent filtration he now had reason to believe that two feet would be equall}' effective. These facts are also substantiated by the rapid purifi- cation which sewage undergoes when supplied to the soil immediately below the surface as in subsurface irrigation. A test made in one of the experimental filtration tanks of the Massachusetts State Board of Health, to determine *Van Nostrand's Engineering Magazine, November, 1886. 304 THE SEPARATE SYSTEM OF SEWERAGE. the distribution of bacteria at different depths gave the fol- lowing- results: NUMBER OF BACTERIA FOUND IN ONE GRAMME OF SAND AT VARIOUS DEPTHS. Distance from Surface. May 22, i88g. Distance from Surface. May 22, 1889. o to ]A inch 1,760,000 5 inches 63,400 Yz to K " 105 000 8 30,700 i'4:toi>^ '■ 207,200 12 " 34,100 2 inches 60,200 19 " 12,300 3 III, 300 60 4, 100 The most rapid decrease is in the upper few inches. Koch says that the micro org^anisms in the soils he has examined diminish rapidly with the depth and at the depth of a metre the soil is nearly free from bacteria. "It has been found that if one starts with an artificial filter bed of perfectly clean sand, containing no bacteria, and floods it with dirty water the water which comes through for the first few days, and for a much longer time if the weather be cold, will be but little, if at all, purified. Its coarser suspended particles may have been caught in the sand pores, and so it may be clearer, but its dissolved organic matter and its bacteria may not be at all diminished. Indeed, for some time, strange as it may appear, the numbers of the bacteria may have largely increased. In fact, it appears that the pores of such a fresh sand-filter with the organic matter suspended in the water, form a most excel- lent breeding place for bacteria. This seems discouraging, but let the experiment go on, and after a while if the dirty water has not been forced through the sand too fast, it will be found that the number of living germs which come out in thfe water at the bottom is growing steadily smaller and finally the water may be nearly or quite germ free. Now, if the chemist exposes some of the filtered water to his delicate tests he may find that the organic matter which was in solution in the water at the top has already diminished or entirely disappeared, being represented, perhaps, by nitrogen, which has formed harmless combinations with oxygen. It really seems as if the more of the living, growing bacteria you had in the upper layers ot your filter bed, the freer became the water below both in CHAP. XV. 'iHi<: PUKii'icA riox oi- siowAC.i:. 805 bacteria and organic matter. This is, in fact, the case. We do in this exper- iment what nature does on a larger scale — make the bacteria fight the organic matter and themselves But how is this effect produced? The bacteria are so small that hundreds of them could easily pass abreast through the smallest spaces between the sand particles. What holds them back? When the sand particles at the upper portion of these filter beds have been carefully examined it has bee*n found that they are, after a few days, com- pletely encased in a slimy gelatine-like envelope, formed of a material which many bacteria secrete around themselves as they grow This bacteria-formed slime more or less fills the pores of the filter bed, enclosing the bacteria them- selves and the sand particles, and catches and holds fast on its sticky surfaces not only suspended matter of various kinds but the new bacteria which come onto the filter and start to work their way down through its pores. Here, many of them, like good prisoners, set to work to make the best of the situa- tion, and if their nature permits, turn to and help to make more of this trap- slime to capture the next comers. Many of the enlarged germs, however, do not form this material and these may die in large numbers where they lie. On the other hand, this enforced detention is simply paradise for many of the germs. Here they are resting at ease in a slimy confinement, with boundless supplies of just the food they w-ant slowly trickling by them. The food is dead organic matter, which the average bacterium simply dotes on and reeks little whether it be in solid form or in solution, so there be enough of it. At it he goes then, and by some wholly inscrutable phase of the life power in his tiny body, asunder fall the atoms which have once been parts of animal or plant. That part which the tiny life spark needs to keep its glow agoing is appropriated. The rest he leaves, its atomic cravings unsatisfied, and only too ready to succumb to the wiles of the ever amorous oxygen, which must always be present in a perfectly acting filter bed. The slowness and the intermittent character of natural soil filtration is a very important matter in the accomplishment of perfect results, because in the times between rains the soil pores have a chance to become filled with stores of oxygen in the form of ground air. Behold now the secret of this marvelous alembic into which may go things most foul and harmful, but out of which comes the very type of cleanliness — clear spring water. It is largely the bacteria, living, growing, multiplying, following their life impulses silently and unseen, each after its kind, which, supported by the active agency of the oxygen, bring about this beneficient result." — Pnidden, in Drinking Water and Ice Supplies. 306 THE sii:parate system of sewerage. Nitrification. — "The conditions influencing nitrification have been for the most part already mentioned incidentally. We may, ho\^ver, advantageously recapitu- late them. "(a) The formation of nitrates appears to require, or to be facilitated by an elei'aled ieniperottire, and goes on most rapidly in hot weather and in hot climates. "(/'I According to Knop, ammonia that has been absorbed by a soil suf- fers no change so long as the soil is dry, but when the soil is moistened nitrifi- cation quickly ensues. Water thus appears to be indispensable in this process. "(<) \n alkali />ast' or carbonate a.^-peSirs to be essential for the nitric acid to combine with. It has been thought that the mere presence of potash, soda and lime favors nitrification, 'disposes,' as is said, nitrogen to unite with oxygen. Boussingault found, however, (Chii/iie Agricole, III, igS) that caustic lime developed ammonia from the organic matters of his garden soil without favoring nitrification as much as pure sand. The caustic lime by its chemical action, in fact, opposed nitrification, while pure sand, probably by dividing the particles of earth and thus perfecting their exposure to the air, facilitated this process."* Absorptive Power of the Soil. — The results of fifty-one experiments bv Dr. Lissauer to determine the absorptive power of soils point to the following- conclusions, among- others: "(/) The liquid entering the pores of the soil displaces the air or liquid previously present, forcing the former upwards into the atmosphere, and the latter downwards into the subsoil or effluent water. "{2) In order that the effluent water may not be directly polluted by the sewage liquid, the maximum supply of the latter must not be more than can be taken up b}^ the pores of the soil. "(j) Drv, loamy soil absorbs more than peaty soil and gives up less, whilst dry, sandy soil, on the contrary, absorbs less and gives up more. Con- sequently a loamy soil, though it absorbs a large quantity of liquid, can seldom be irrigated, whereas a sandy soil, though it absorbs but little may often be irrigated. "{4) The looser the soil the easier water courses are formed in it, and therefore the less can its maximum power of absorption be approached, other- wise the sewage liquid might penetrate the subsoil before the whole of the ground had been saturated. *Johnson — How Crops Feed. CHAP. XV. THIO Pl'KIFICATIOX Ol' SIOWAGK. 307 "(j) In order therefore that the effluent water may be protected from pollution it is especially necessary that the absorptive power of the soil should be known, but the determination is of no value unless it be made in a sample in which the natural position of the particles of earth has been undisturbed." The Function of Nitrates. — It should be stated in this connection that the nitrates, which are the product of the nitrification or oxidation of the or^^anic matter contained in sewag^e, supply nitrog-en in its most available form as plant food. "Experiments in artificial soil and in water culture show not only that nitrates supply nitrogen to plants, but demonstrate beyond doubt that Ihey alone are a sufficient source of this element, and that no other compound is so well adapted as nitric acid to furnish crops with nitrogen. "* In the absence of plant life, a portion of these nitrates being- verv soluble, passes away with the effluent in a harm- less form. The Committee of the British Association, on the Treat- ment and Utilization of Sewag-e, made an estimate of the amount of nitrog-en recovered in crops on Breton's farm, near Romford, with the following- results: "Of everv ico parts of nitrogen distributed over the farm during the twelve months, 10.67 parts, or about one-tenth, were found in the effluent water; 41.76 parts, or about four-tenths, were recovered in the crops, making together about half; and 47 57 parts were unaccounted for "f It was subsequently ascertained b}' analysis of the soil that the nitrogen in the soil had largely increased. Experiments of the Massachusetts State Board cf Health. — Bv far the most systematic experiiuents upon the filtration of sewage through the soil, which have come to the knowledge of the writer, are those being- conducted by the Mass. State Board of Health, at Lawrence, Mass. These experiments have been conducted so carefully and thor- oughly and over such a wide rang-e of conditions that they *Jobnson — How Crops Feed. p. 90. tCortield, on the Treatment and Utilization of Sewage, p. 419. 308 TH1<: SEPAKATK SYSTKM OF SKWKKAGE. are of particular interest. The results of the experiments are contained in the Report of the Board on Purification of Sewagfe and Water, 1890, from which the following- informa- tion is g-athered: "The filtering grounds comprise about two-thirds of an acre. Upon them are ten tanks, circular in plan, about 17 feet in diameter and allowing for material to be filled in 5 feet deep. From the lowest point in the bottom of each tank a 2-inch pipe conveys the drainage to a flume within a building, whence the effluent is taken for analysis and examination. The tanks were filled with different materials, as follows: No. i, very coarse, clean mortar sand; No. 2, very fine, nearly white sand; No. 3, peat; No. 4, river silt; No. 5, brown garden soil, well manured; No. 6, 7 and 8 were filled with 3 feet, 8 inches of coarse and fine sand, lo inches, of yellow, sandy loam and 6 inches of brown soil; No. 9, very compact, sandy, hardpan of clay, sand and gravel, covered with 9 inches of brown soil The sewage used in the experiments was taken from a main sewer draining a portion of the city. Apparatus was erected for measuring the sewage and the effluent, and biological and chemical analyses of both were made daily. The sewage was applied intermittently at intervals of one or more days." In the twentieth Report of the Board we find the follow- ing" statements reg-arding- the g-eneral results which have been obtained. •'Sewage can be much more efficiently filtered through open sand, than through sand covered with soil. Very fine material, like dust, in the upper layers of a filter, prevents free access of air, and when wet, may exclude air so completely as to render purification impossible. With soil or sand containing dust at the surface, periods of intermission in the application of sewage may be made so long that the surface, becoming dry, may allow air to enter, and a high degree of purification may result; but the quantity of sewage that can thus be purified is very much less than when the upper layers of the filter are composed of open sand, thrpugh which the sewage will rapidly disappear and will leave room for air to enter and come in contact with the thin laminas of liquid covering the particles of Fand. The experiments of last winter show that intermittent filtration can be carried on upon a bed of coarse sand through the coldest weather, when the beds are exposed to snow, but that the efficiency of the beds is much reduced by such exposure and the consequently low temperature of the sewage passing through the sand. Bv protecting the beds so that snow cannot fall upon them and reduce the temperature of the applied sewage to near the freezmg point, the experience of the present winter so far, indicates that very complete purifi- CHAP. XV. IIIIO PUWll-ICA'ilON Ol' SICWAGE, 809 cation may be continued through very cold weather by applying the sewage intermittently at the temperature at which it ordinarily comes from the sewer. The experiments of last winter show that, when the beds are exposed to the snow, intermittent filtration may be carried on through the moderate weather of winter, alternated .by continuous filtration during the colder period." "Four tanks, filled with clean coar.se mortar sand from the same pit, were subjected to different conditions. One of these was exposed to the cold and snow, and, although it received sewage daily and removed about two-thirds of the impurities of the sewage during the very cold months of January, February and March, when filtering at the rate of 30,000 gallons per acre per day, it is evident, from the results in the other three tanks, which were not expo.sed to frost, that the sewage entered and passed through but a fractional part of the area of this tank, and the result is as poor as if a much larger quantity had been applied to a like area not obstructed by frost. The three other tanks were supplied with sewage at the rate, respectively, of 30,000, 60,000 and 120,000 gallons per acre per day, and until nitrification commenced, in the latter part of March, periods of forty-one, thirty-one and twenty-seven days, respectively, the ammonias indicated that 97, 94 and 80 per cent, of the impurities of the sewage were removed. Nitrification began to increase in all of these tanks between March lU and 30, when the temperature of the effluent was at 39O or 40^. In the course of three weeks the nitrates had increased from 0,025 parts in 100,000 to o 250 parts, after which they increased much more rapidly, and nitrification was most complete from May 6 to 10, or six weeks after it began, the nitrates then amounting to from 2.5 to 3.0 parts per 100,000. During the increase in nitrification the ammonias also increased for a time, and became nearly one-third of those of the sewage; but generally before the nitrification reached its height the ammonias decreased rapidly, until they became one-half of i per cent, and li per cent, of those of the sewage. The rapidity of purification, as shown by the decrease in ammonias, was greatest in the tanks which had received the most sewage and had the greatest amount of nitrogenous matter stored in them — the effluent from the sand which had received the least sewage being more than a month later in reaching its condi- tion of greatest purification. The filter receiving sewage at the rate of 120,000 gallons per acre per day gave an effluent for three months after purification, resulting from nitrification, was established, in which the ammonias were less than lyi per cent, of those of the sewage. Upon increasing the amount filtered to 180,000 gallons per acre per day the ammonias increased, but for the next four months averaged less than 2 per cent of those of the sewage. One of the filters receiving sewage at the rate of 60, coo gallons per acre per day for seven months after purification was established, gave an effluent of nearly constant quality, having one-half of one per cent, of the ammonias of 310 THK SEPARATE SYSTEM OF SEWEKAGi:. the sewage, the free ammonia averaging 0.0012 parts and the albuminoid ammonia 0.0105 parts in 100 000 parts, showing less organic matter than many of the drinking waters of the State. The other filter of the same material, receiving 60,000 gallons of sewage per acre per day, gave an efHuent for three months after purification was estab- lished, having between i and 2 per cent of the ammonias of the sewage, but in the next two months these increased to 6 and then to 10 per cent. This increase was due in part to the imperfect distribution of the sewage over the whole surface, which being corrected, the percentage of the ammonias decreased and averaged for December 4)^2 per cent, of those of the sewage The tank of this material, which has filtered at the rate of 30,000 gallons per acre per day, was as stated, a month later than the others in reaching an established condition after nitrification became active. For the following six weeks the ammonias of the efHuent were but one per cent, of those of the sewage and the nitrates were a little more than one part per 100,000 ' In each of the experiments above recorded sewag^e was applied intermittently at intervals of one or more days, and disappeared from the surface in a few minutes or in a few hours. The results obtained by intermittent downward fil- ti'ation in the above experiments are very favorable and in striking- contrast to those obtained by continuous filtration as will be seen by the following" extract from the report. These experiments were made with a tank wliich received 30,000 gallons per acre per day in the experiments on intei*- mittent liltration and through the same material — coarse sand: "At the end of this time the outlet was closed and the tank filled with sew- age, and for the next four months the surface of the sand was kept covered with sewage, and the outlet was opened each day sufficiently to allow the reg- ular quantitv at the rate of 30,000 gallons per acre per day to flow out The filter was thus changed from the condition of intermittent filtration to that of continuous filtration. During the first month the nitrates were reduced from one part per 100,000 to less than o.oi part, at which they continued for the remaining three months. The ammonias rose in the first month from i per cent, to iK per cent, of those of the sewage. In the second month they became 31 per cent, and at the end of the fourth month were equal to those of the sewage. This shows distinctly the radical difference in result between intermittent and continuous filtration. In intermittent filtration the nitrification was active and, as shown by the ammonias, 99 per cent, of the organic impurities were CHAP. XV. THK PUHIl-ICA riON OF SICWAGIO. 311 removed, while in continuous filtration the nitrification ceased, and the same sand, filtering the same quantity of sewage, stored impurities for a time, but finally poured out an effluent quite as impure as the applied sewage " The biolog-ical analyses, an account of which appeal's below, are also of particular interest as furnishing- an index of the deg-ree to which it may be possible to free sewage from the contamination of disease g-erms by the methods adopted, and also as corroborating- the statement previously made that the bacteria of nitrification remain in the upper strata of the soil. •'From these open sands the number of bacteria in the effluent has, during the past six months, varied from 2 per cent, to a very small fraction of i per cent, of the number of bacteria in the sewage. A filter of very fine sand, after filtering an amount equivalent to 8,600,000 gallons of sewage upon an acre, filtered at the rate of 12, coo gallons per sere per day, giving an effluent in which the organic matter, shown by the loss on ignition, was but 3 per cent, of that of the sewage, and the nitrogenous matter. as shown by the ammonias, was but one-quarter of i per cent, of that of the sewage. The loss on ignition was 0.5000 parts in 100.000 The free ammonia 0.0002 parts in 100,000 The albuminoid ammonia was 0.0062 parts in 100,000 The nitrates were. o 7000 parts in 100 000 At the same time the bacteria of the sewage amounted to 591,000 in a cubic centimeter, while those of the same quantity of effluent amounted to 2, and these may have come from the air while collecting the sample. By both chemical and bacteriological analysis this effluent from sewage has less organic impurity than the water of Lake Winnipiseogee, and contains but little more nitrogenous organic matter than city water filtered through the same material a year ago. This sand stored much impurity in the winter. Nitrification began actively in June, and for three months appeared to be active in removing stored impurity, so that purification did not approach the completeness given above till September, since which time it has steadily grown more complete " "Garden soil makes a very poor filter. Upon applying sewage intermit- tently to a body of garden soil five feet deep, after the first month ths organic impurities increased continually for eight months, until the effluent became more impure than the applied sewage. There had then been applied 24,000 gallons, the equivalent of 4,800,000 gallons on an acre, and it was then being applied at the rate of 10,000 gallons per acre per day. The daily quantity passing through has since been reduced to 5,000 gallons per acre per day, and 312 THE SEPARATIC SYSTEM OF SEWERAGE. the quality of the effluent has somewhat improved, but still contains as much nitrogenous matter as crude sewage. "A very few vegetable organisms that can be identified by the microscope have been found to occasionally pass through the coarser filters, but in general none come through A few animal forms have been found in the effluent, but these may grow in the under drains and outlet pipe The question remains to be settled, whether any animal or vegetable microscopic organisms live to get through the filters of finer material at the rate which sewage has been filtering. Of the still more minute organisms, the bacteria, we found that soon after sewage was first applied to the tanks they came through in great numbers, but became reduced in number and during the later winter and spring months amounted to two per cent, and less of those of the applied sewage, but after nitrification commenced they decreased rapidly, and continued through the summer, in many cases less than one hundred, and in some less than ten, while the number in the same quantity of applied sewage was about a million." "The experiments made to the present time show that the number of bacteria in the sand decrease very rapidly from the surface downward. In the finer sands they nearly or quite disappear before the bottom is reached. * * * We have reason to hope that filters may be so made and managed that all disease germs may be, with certainty, removed." The Influence of Temperature. — Considerable discus- sion has arisen as'to the practicability of sewag^e disposal by application to the soil during- the winter months in northern latitudes. in the investig-ations of the Massachusetts State Board of Health previously quoted it was determined that: — "Durmg the cold months the nitrification was about nine-tenths as com- plete as the mean for the year and that the loss on ignition and the ammonias of the effluent were about one-fifth greater percentage of the amounts in the sewage producing the effluent than for the year. This is in all respects a very satisfactory result of continued purification by this filter (coarse sand) during the winter." The following' abstract from the report of the Commit- tee of the British Association is also of interest: "A comparison was made in January, 1871, during severe frost, of the results obtained in the purification of sewage at the three following farms. — Breton's farm, near Romford, Biddington farm, Croyden, and Norwood farm. It was found that in the latter two cases, where the sewage was passed over the land in the catch water system, it was not satisfactorily purified, the nitrogen escaping in the effluent water being only partially in the state of nitrates and CHAP. XV. I HI'; PrKIl'ICATION OK SICWAGIC. 313 nitrites; while at Breton's farm, where this sewage passes through the soil, the farm being in effect a large filter bed (i) oxidation goes on in winter as well as in summer, and almost all nitrogen lost is lost in an oxidized and inoffensive form; and (2) this loss is very slightly greater in winter with a very strong sewage than in summer with a weaker one."* "There is one point which I think deserves consideration in connection with the question of the winter disposal of sewage upon land, and this is the temperature of the sewage. * * * * While it is probable that the coldest sewage may be disposed of upon land in winter in this climate, such disposal may be rnore confidently advised where the sewage is warmer, and in seeking for precedents it is desirable to know the temperature of the sewage as well as the severity of the winters. "f Aeration of the Soil. — The effects of a lack of air in the interstices of the soil are apparent from the experiments on continuous filtration previously cited. At the time the experiments were in prog"ress the outlet pipe from the tank was trapped so that no air could enter the tank from below. There is reason to believe that the lack of nitrification in continuous filtration is due to the lack of oxygen. In order to substantiate this fact experiments on filtration were con- ducted at the experiment station at Lawrence, Mass., in a tank filled with coarse sand and arrang-ed so that the quan- tity of air admitted to the tank could be controlled by an aspirator. The conditions otherwise were the same as in intermittent filtration. Sewage was applied intermittently through a funnel and stop cock and distributed over the sur- face by a perforated plate. Nitrification ceased soon after the supply of air was stopped and the effluent was little better than the sewage. Subsequently the cock by which sewage was admitted to the tank was left open, thus ventil- ating the top of the tank. The condition of the effluent did not improve. Upon removing- the cover of the tank entirely the condition was but little improved by reason of the tank being clogged with org^anic matter which had not been oxi- *Treatinent and Utilization of Sewage — W. H. Corfield, p. 372. tF. P. Stearns in Transactions of the Am. Soc. C. E., January, 1888. 314 THE SlCPARATli SYSTP:M OF SliWliRAGI': dized diu"ing the time that the air was excluded. Upon removing- half an inch from the surface of the tank and applying- an aspirator below, drawing- a g-allon of air each four minutes, the effluent rapidly improved and in two weeks nitrification became complete. During- this time the air of the tank contained almost as much ox^^g-en as outside air. "This underground air is, however, almost as ceaselessly in motion as is that in which we move. Whenever the ground gets heated it streams out of the myriad pores of the surface into the sunshine. When the ground cools, back through the same pores rushes the aerial air. Every wind which sweeps the surface moves the air beneath in great volumes. With every rain it is driven deeper down. The movements of this buried atmosphere are slow, because it must find its way around the myriads of soil particles which block its course But it is of great extent and of great importance." — Priidden, in Drinking Water and Ice Supplies, iSgr . Effect of Different Soils. — In the experiments at Law- rence it was found that: — "With the gravels and sands, from the coarsest to the finest, nitrification takes place in all, when the quantity of sewage is adapted to their ability, and the surface is not allowed to become clogged by organic matter to the exclusion of air. With fine soils, containing in addition to their sand grains, two or three per cent, of alumina and oxide of iron and manganese, and six or seven per cent, of organic matter when only six inches in depth, resting upon fine, sandy material, they retain water so long that the quantity that can be applied is so small, and the interval in which this must settle and dry away to allow air to enter the filter is so long, that the amount of sewage that can be purified is very small. When the quantity applied is adapted to its ability such a filter may give an excellent effluent, quite free from bacteria." There is reason to believe that the effect of simple mechanical filtration throug-h the soil in the purification of sewag-e has been over-estimated. Where compact and retentive surface soils are found on a more open subsoil a much g-reater quantity of sewag-e can be satisfactorily purified by distributing- it beneath the sur- face throug-h tile drains with open joints as in subsurface irrig-ation. The application in this manner being- more CHAP. XV THK PURIFICATION OF SI'JWAGi:. 315 favorable to the admission of air throug-h the comparatively impervious surface, especially after continued use. In one of the experiments at Lawrence the capacity of the soil to purify sewaf^e was increased threefold in this manner. The averag-e results of purification, at Lawrence, bv various soils for periods of from three to eig^ht months, mostly in the second 3'ear of filtration, are g-iven in the fol- lowing- Table: CHAR.^CTER OF SOIL. a. (D « . ^ acres speciall}^ prepared for intermittent downward filtration, to which the sewag'e is applied during' a considerable portion of the win- ter, and whenever it cannot conveniently be applied to the surface under broad irrigation. These filter beds are underdrained by drains 12)^ feet apart which converg'e at a man-hole. The soil of the filter beds and of the entire farm is the rich alluvial prairie soil underlaid by a yellowish clay subsoil *I am indebted to Mr. Duane Doty, Editor of the Pullman Journal, Mr. Cox, Assistant Manager, Mr. C. W. Campbell, Superintendent of the sewage farm, and Mr. Chas. H O'Neil. Assistant Engineer of the sewage pumping station, for information and assistance. 320 THE SEPARATE SYSTPIM OF SEWERAGE. and poorly adapted for purifying- large quantities of sewagfe, especially when the temperature is low. Nevertheless the results obtained here are very flattering. I am informed that it is usual to apply the sewage of one day to about three of the beds, which are then allowed to rest for three days at least. About half of the filter beds are cropped each 3'ear with quickly maturing crops, such as plants to be transplanted. While the crops are growing no sewage is applied. Plate XXIX is reproduced from a pho- tograph of the filter beds taken at the time the examination was made, March 12th, 1891. The weather had been severe for about ten days previous and the temperature at 7 a. m. was 12° above zero. The beds are arranged, on ground slightly inclined, at different levels. Sewage is admitted to any of the high level beds at will through gate chambers, one of which is shown in the foreground. On the day previous the bed at the right was flooded with sewage to the depth of about 10 inches. This had nearly all disappeared beneath the surface, a thin sheet of ice one-fourth to one-half inch thick had formed on the impounded sewage, which, as the sewage sank beneath the surface was broken into small fragments. There is no accumulation of ice which inter- feres with the filtration of the sewage. The temperature of the sewage when applied to the beds, as taken in the carrier after being conve3'ed three miles underground at the season when the subsurface temperature as shown by observations is about at its lowest, was .51° F. The temperature of the effluent as taken in the man-hole to which the subsoil drains converge was 38° F. The latent heat given up by the sew- age during this fall in temperature quickly melts the ice that may have accumulated on the filter beds and the sewage sinks rapidly beneath the surface. Experiments previously detailed show that between these temperatures nitrification is comparatively active. PLATE XXIX. CHAP, XV. THK PUKIFICATIOX OF SICWAGK. 323 There was no offensive odor at the beds, with the excep- tion of that coming- from a deposit of sludg-e near the gate chamber, and this did not extend for an}- great distance. I am informed that it is usual to keep this sludge spaded beneath the surface. The surfaces of the beds are occa- sionall}- turned over with a plow to assist in keeping them from becoming sodden so as to exclude the air. A sample of the crude sewage was taken at the end of the carrier for analysis and also a sample of the purified effluent was taken from the man-hole to which the tile drains converge. The effluent was clear and sparkling and not unpleasant to the taste. The Table below contains the results of an analysis of the samples collected as above stated. ANALYSIS OF CRUDE AND PURIFIED SEWAGE FROM THE PULLMAN SEWAGE FARM. (PARTS PER 100,000.) Temperature Albuminoid Ammonia Free Ammonia Nitrogen as Nitrates Oxygen required to oxidize organic matter Chlorine Crude Sewage. Plrified Sewage. 51-F. .60 ■30 .41 6.40 4.20 38 -F. .040 •037 . 180 .760 2. 100 The degree to which the purification has proceeded (assuming- that there has been no concentration or dilution of sewage from evaporation, subsoil water or other causes) is indicated by the following Table: Albuminoid Ammonia. 93^ per cent. Free Ammonia 88 Nitrates 56 Oxidizable organic matter 88 Chlorine 50 Total Nitrogen in the EfiSuent 21% 324 THE SEPARATE SYSTEM OF SEWERAGE. Much more favorable results may be expected, of course, during- the warmer weather. The intention was to ascertain the conditions at about the most unfavorable sea- son. As previously stated the soil is not adapted to purify larg-e quantities of sewag^e having- too much finely divided org-anic matter in its upper layers which interferes with aeration and also too retentive a subsoil. Plate XXX is reproduced from a photog-raph of the area devoted to broad irrigation and crops. Sewag-e is applied to this area whenever the weather in spring and fall is favora- ble and it can be applied without interfering- with the crops. In g-eneral, however, no sewag-e is applied to g-rowing- crops. The sewage is distributed to this area throug-h a system of vitrified pipes having- hydrants at convenient intervals from which the sewag-e is allowed to flow over the surface of the ground. Sewage is also applied to meadow lands adjoining- this area in the spring. The principal crops raised upon the sewag-e farm are early potatoes, cabbag-es, beets, onions, celery, cauliflower, parsnips and squashes. Mr. Campbell, the superintendent, informs me that the g-ross receipts from the farm (l-iO acres) was about 31:^,000 last year. The experiments of the Massachusetts State Board of Health and the results obtained at Pullman under conditions more than usually unfavorable indicate that the disposal and purification of sewag-e on land in this climate is entirely practicable. The following- diagrams have been a convenience to the author in making- estimates and are added here with the hope that others may possibly find them so. They are compiled from computations but have been tested by actual account of materials used in construction and found to agree well with averag-e construction. The amounts of masonry and mortar g-iven include plas- tering for the exterior of the sewer. PLATE XXX. \:j' tn\m}memm t^^ mm^^^ eLtMftWTi ■ ■y-oT'-A'T « - . .. <3r«>vd -?''*'<<■>-', ^ -7-7 ydoc O J • Jrp"^TA'^ jTcrJ^i.^/t/'^BS/^ or^i^rc' 13 « > i-J Tl O 2. B 0) Ot> 11 to S. Reconnoissance Transit, one vernier to limb sJ^-inch needle, with vertical circle reading to 5 minutes, level on telescope, clamp and tangent to telescope axis, and tripod with extension legs. Our Latest Illustrated Catalogue and Price^List Mailed on Application, ;low. Fo __ x^v^iWoV^:** iiii?Mi'"^^^'' "f ^'-''VAl J3HAH,' Fitlj-. A 000 343 406 5