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 THE DISPOSAL OF THE 
 SEWAGE OF THE 
 SANITARY DISTRICT OF 
 CHICAGO. 
 
 ILLIHOlSSTi^T 
 
 
 
 
 
 
 1 — 
 
 
 
 
 ISWS Alvord, Burdick & Howson 
 
 B THE DISPOSAL OF THE 
 
 23 SEWAGE OF THE 
 
 Loan SANITARY DISTRICT OF 
 
 c. I CHICAGO. 
 
 05041003 
 
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/ 
 
STATE OF ILLINOIS 
 DEPARTMENT OF REGISTRATION AND EDUCATION 
 
 DIVISION OF THE 
 
 STATE WATER SURVEY 
 
 A. M. BUSWELL, Chief 
 
 BULLETIN NO. 23 
 
 THE DISPOSAL OF THE SEWAGE OF 
 THE SANITARY DISTRICT 
 OF CHICAGO 
 
 A Report to the District Engineer 
 U. S. Engineer Office, Chicago 
 
 BY 
 
 ALVORD, BURDICK & HOWSON, Engineers 
 
 [Printed by authority of the State of Illinois] 
 
 URBANA, ILLINOIS 
 
CONTENTS 
 
 Page 
 
 Organization , iv. 
 
 Letter of transmittal v. 
 
 Letter of authorization vi. 
 
 Part I. — Introduction, summary and conclusions 1 
 
 Part II. — Present disposal of sewage and deficiencies 12 
 
 Part III. — Population and growth 39 
 
 Part IV. — Amount and quality of sewage 48 
 
 Part V. — Standard of maximum pollution 64 
 
 Part VI. — Required degree of purification with various dilutions. 79 
 
 Part VII. — Protection of the water supply 85 
 
 Part VIII. — Savings effected by metering 101 
 
 Part IX. — Volume of sewage 114 
 
 Part X. - — Future intercepting sewer construction 119 
 
 Part XI. — Methods of sewage disposal and practicable efficiencies 128 
 
 Part XII. — Sewage disposal costs in other cities 145 
 
 Part XIII. — Required works for 10,000 cubic feet per second flow. 170 
 Part XIV. — Required works with 4,167 cubic feet per second flow. 174 
 
 Part XV. — Required works with miscellaneous flows 180 
 
 Part XVI. — Review of expenditures under various flows 185 
 
 PHILLIPS BROS.- PRINT. 
 SPRINGFIELD. ILLINOIS. 
 
 1 9 °2 7 
 (60418—1500) 
 
 iii. 
 
ORGANIZATION. 
 
 STATE OF ILLINOIS 
 Len Small, Governor 
 
 DEPARTMENT OF REGISTRATION AND EDUCATION 
 A. M. Shelton, Director 
 
 Board of Natural Resources and Conservation Advisers 
 
 A. M. Shelton, Chairman 
 
 William A. Noyes, Chemistry, Henry C. Cowles, Forestry. 
 
 Secretary. William Trelease, Biology. 
 
 John W. Alvord, Engineering. C. M. Thompson, Representing the 
 
 Edson S. Bastin, Geology. President of the University of Illi- 
 
 nois. 
 
 Water Survey 
 
 Division Committee 
 
 A. M. Shelton 
 
 C. M. Thompson 
 
 William A. Noyes 
 John W. Alvord 
 
 WATER SURVEY DIVISION 
 
 A. M. Buswt:ll, GTiief 
 
 iv. 
 
LETTER OF TRANSMITTAL. 
 
 State Water Survey Division 
 
 ARTHUR M. BUSWELL, CHIEF 
 
 Urbana, III. 
 
 February 18, 1927. 
 
 A. M. Shelton, Chairman, and Members of the Board of Natural 
 Resources and Conservation Advisors: 
 
 Gentlemen : Herewith I submit a report on the disposal of the 
 sewage of the Sanitary District of Chicago and recommend that it be 
 published as Bulletin No. 23 of the State Water Survey Division. 
 
 This report was prepared by Alvord, Burdick & Howson, consult- 
 ing engineers, of Chicago, by order of the Secretary of War pursuant 
 to a resolution of the Committee on Rivers and Harbors of the House 
 of Representatives, U. S., April 14th, 1924, and submitted to the Dis- 
 trict Engineer, U. S. Engineer Office, Chicago. 
 
 The printing of this report as a Water Survey Division Bulletin 
 has been authorized by the Secretary of War. The letter granting this 
 authorization is included herewith. 
 
 The material presented in this manuscript contains so much data 
 on the cause and remedy of the most serious stream pollution problem 
 in the State that it seems highly advisable to make it available to the 
 citizens of the State in published form. 
 
 Respectfully submitted, 
 
 A. M. Bus WELL, Chief. 
 
 V. 
 
LETTER OF AUTHORIZATION. 
 
 War Department 
 United States Engineer Office 
 537 South Dearborn Street 
 Chicago, Illinois 
 
 October 25, 1926. 
 
 Dr. A. M. Buszvelly Chief, State Water Survey Division, Board of 
 Natural Resources and Conservation, Urbana, Illinois, 
 
 Dear vSir : Your request for permission for the State Department 
 of Registration and Education to print the report of Alvord, Burdick & 
 Howson, Engineers, to the U. S. District Engineer on the Disposal of 
 the Sewage of the Sanitary District of Chicago, has been approved by 
 the Chief of Engineers, with the condition that Chapter XII be also 
 published, and that credijt and acknowledgment be made to the Chief of 
 Engineers and the War Department, for whom and under whom the 
 report was prepared. 
 
 Yours very truly, 
 
 Edward H. Schulz, 
 Colonel, Corps of Engineers, 
 District Engineer. 
 
 vi. 
 
PART I. 
 
 INTRODUCTION, SUMMARY, AND CONCLUSIONS. 
 
 District Engineer, 
 
 U. S. Engineer Office, 
 337 S. Dearborn St., 
 Chicago, 111. 
 Dear Sir: 
 
 Proceeding under our instructions of January 16, 1925, we have 
 studied the problem of sewage disposal for the City of Chicago and 
 vicinity, including more particularly that territory embraced within the 
 Sanitary District of Chicago. 
 
 Our study has been particularly directed to answers for the fol- 
 lowing questions : 
 
 (a) Determination of a pollution standard for the Chicago Drain- 
 age Canal for each of the following average diversions from Lake 
 Michigan ; —2,000, 4,167, 6,000, 7,500, 8,500 and 10,000 cubic feet per 
 second ; this standard to be the lowest that will prevent the occurrence 
 of nuisance in the Des Plaines and the Illinois River, and will permit 
 a thriving fish life therein. 
 
 These diversions include the sewage flow of the Sanitary District ; 
 and they therefore represent the dry weather flow of the Drainage 
 Canal at Lockport, approximately. 
 
 (b) Determination of the extent to which purification measures 
 must be taken by the Sanitary District of Chicago for each of the flows 
 specified above, in order that the pollution standard be maintained unim- 
 paired. 
 
 (c) Determination of the most feasible method of treating the 
 surplus pollution, and, for each flow specified, the cost of the necessary 
 works and the operating costs thereof. 
 
 (d) The determination of the time that reasonably would be re- 
 quired to build the necessary works and place them in operation for 
 each of the flows specified. 
 
 In the study of this matter the time at our disposal has not per- 
 mitted original investigations. It has been possible only to view the 
 present situation by inspection, and to study the large amount of data 
 that has been accumulated by the Sanitary District of Chicago and . 
 other agencies, bearing directly upon the answers to the above questions. 
 
2 
 
 We have further brought to bear upon the study of the problem the ex- 
 perience of other cities regarding sewage disposal, insofar as informa- 
 tion has been gained that would throw light upon the Chicago situation. 
 
 Upon the pages which follow we have stated the local problem in 
 some detail, and we have discussed the various phases of it insofar as 
 we believe is required for a general understanding of the problem, and 
 our answers to the questions previously stated. For the benefit of those 
 already somewhat familiar with this problem we will first briefly state 
 our summarized findings and conclusions. We will follow this statement 
 by a more detailed consideration of the problem, and a further state- 
 ment of the conditions and the reasons leading to the conclusions stated. 
 
 SUMMARIZED CONCLUSIONS. 
 
 1st. Present Disposal: 
 
 The diversion of the Chicago sewage from Lake Michigan, result- 
 ing from the Drainage Canal and other causes, has effected a remark- 
 able improvement in the death rate from water borne diseases. The 
 sewage nuisance in the streams of the Chicago district has been re- 
 duced^ to a large extent. 
 
 This result has been accomplished, however, by transferring the 
 bad conditions in Chicago to the Des Plaines and Illinois Rivers in 
 which a crying nuisance has been created for more than one hundred 
 miles ; and by diverting large amounts of water from the Great Lakes, 
 over strenuous objections from property owners claiming a right to the 
 water diverted. 
 
 It is generally conceded that the present conditions should not be 
 allowed to continue. The Sanitary District is already engaged upon 
 remedial measures through which a large part of the sewage will be 
 treated before discharge into the Drainage Canal. 
 
 2nd. Population and Growth: 
 
 In planning works for sewage disposal, it is necessary to consider 
 the future population of the locality. It is not financially practicable 
 to make expenditures now for a problematical future. It is necessary, 
 however, to determine the future populations approximately and to 
 adopt works capable of construction in units that may be increased in 
 capacity from time to time as occasion requires, without destroying 
 previous expenditures. Thus each dollar expended will provide a link 
 in a complete chain of sewage disposal works. 
 
 We have examined the forecast of population as estimated by the 
 Sanitary District of Chicago, and we believe it represents future proba- 
 bilities as accurately as required for the above purpose. This estimate 
 covering the population of the Sanitary District is as follows : 
 
3 
 
 1930 
 1940 
 1950 
 1960 
 1970 
 
 1920 census, 
 
 2,978,635 
 3,710,000 
 4,425,000 
 5,140,000 
 5,850,000 
 6,580,000 
 
 In addition to the population in the Sanitary District, there is now 
 (1925) a population of 180,000 in the northern Indiana cities bordering 
 the lake and draining through the Calumet River. Under ordinary low 
 flow conditions this drainage passes through the Sag Channel to the ■ 
 Main Drainage Channel and thus into the Illinois River. 
 
 The Sanitary District includes about eighty-five per cent of the 
 total population in the greater Chicago region which includes Cook, 
 Kane, DuPage, Lake and Will Counties in Illinois, and Lake County in 
 Indiana. The greater part of the outlying population has more or less 
 effect upon the pollution of the lake and the nearby streams. 
 
 3rd. Amount and Character of Sewage: 
 
 The present discharge of the sewers within the Sanitary District 
 is about 800 miUion gallons per day. This is equivalent to a river 100 
 feet wide and five feet deep flowing one and one-half miles per hour. 
 
 This sewage carries an organic load per capita greater than any 
 other large city for which accurate figures have been available to us. 
 This excessive load is partly due to a few great industries which pro- 
 duce an 'amount of pollution estimated by the Sanitary District to be the 
 equivalent of about 1,500,000 people (1920). 
 
 4th. Standard for Pollution: 
 
 In the consideration of sewage treatment works that wifl be re-- 
 quired under various drafts of dilution water from Lake Michigan, it 
 has been necessary to fix a standard of maximum pollution for the Chi- 
 cago Drainage Canal in order that reasonable sanitary conditions may 
 be maintained in the Des Plaines and Illinois Rivers. We suggest the 
 following as a reasonable standard : 
 
 The liquid discharged by the Drainage Canal, as evidenced by 
 the average of representative samples taken for any thirty consecu- 
 tive days shall, 
 
 (a) Be practically free from settleable solids deposited in 
 two hours, and, 
 
 (b) Shall contain dissolved oxygen equal to or exceeding the 
 biochemical oxygen demand of said liquid for five days when in- 
 cubated at 20 degrees C. 
 
4 
 
 (c) Shall contain not less than three parts per million of dis- 
 solved oxygen. 
 
 The treatment works hereinafter outlined in connection with 
 specified dilutions from the lake will meet this standard in our opinion. 
 
 5th. Protection of the Water Supply: 
 
 Even under the heavy diversions from Lake Michigan in recent 
 years and the generally favorable typhoid death rate, the quality of the 
 water supply for Chicago has been far from satisfactory. This is due 
 to the incidental pollution of the lake, periodic discharges from the 
 Chicago and Calumet Rivers and other causes. Occasionally sporadic 
 typhoid outbreaks have occurred attributable to the water. Safety is 
 only secured by heavy dosages of liquid chlorine which are extremely 
 objectionable to many people and which the Chicago authorities regard 
 as closely approaching the maximum dosage tolerable. 
 
 Compared to the usual standards applicable to clean water, the 
 water is dirty most of the time, and it is quite turbid more than ten 
 per cent of the time. Even when comparatively clear it often contains 
 miscroscopic animal organisms no doubt harmless, but very objection- 
 able to many people. 
 
 The filtration of drinking water has been extensively practiced for 
 more than twenty years. More than twenty million people are thus 
 supplied in the United States. Many filtration plants handle a water 
 polluted to a greater degree than Lake Michigan water would be under 
 any diversions for dilution purposes considered in this report. 
 
 Chicago can secure pure clean water at all times by the filtration of 
 its present supply. We regard this as the only means by which a satis- 
 factory supply of water may be obtained, regardless of any practicable 
 measures for sewage treatment or lake water diversions for dilution. 
 
 Filtration is considered as a pre-requisite to the adequate disposal 
 of sewage in all projects considered in this report. 
 
 6th. Metering of the Water Supply: 
 
 At the present time ninety per cent of all water services in Chicago 
 are served through so-called ''flat rates." The pumpage of water is 
 excessive, pressures are deficient, fire protection service is jeopardized 
 and the costs of water supply, intercepting sewers and sewage disposal 
 are greatly increased over what would be necessary if water waste were 
 restricted. 
 
 Universal metering of the water services is urgent. Metering 
 alone will 
 
 (a) Double the average pressure within the City of Chicago. 
 
5 
 
 (b) Furnish all adequate water service where but twenty-five 
 percent now enjoy it. 
 
 (c) Enable the present water works with but minor exten- 
 sions to serve the City for the next generation. 
 
 (d) Through the immense savings effected in deferred con- 
 struction costs enable the City to install filtration works. 
 
 If universal metering of the Chicago Water Works is accomplished 
 within the next ten years savings of from $200,000,000 to $225,000,000 
 will be effected prior to 1945. This amount is so great that in addition 
 to financing the installation of meters and filtration works for the 
 entire city, it would cover the cost of constructing the entire intercept- 
 ing sewer and sewage disposal works required in the Chicago Sanitary 
 District up to 1945 and leave a large surplus in addition. 
 
 The costs of sewage disposal are also influenced by the waste of 
 water. If universal metering of the water works services is not under- 
 taken, the estimated costs of the interceptors and sewage treatment 
 works outlined in this report must be increased by an amount of from 
 $42,000,000 to $53,000,000 depending upon the flow available for dilu- 
 tion and the types of plants required thereby. 
 
 7th. Volume of Sezvage: 
 
 The total quantity of sewage to be treated in the Chicago District 
 may be taken as approximately equal to the total water supply. This 
 assumes that infiltration into the sewers will be offset by that part of the 
 water supply used for sprinkling and other purposes which do not con- 
 tribute to the sewage flow. 
 
 At the present time, due to water waste, the pumpage of water in 
 the Chicago District is excessive. The dry weather flow of sewage is 
 correspondingly much larger than it would be if the waste of water were 
 curtailed. 
 
 The total volume of sewage under metered and unmetered condi- 
 tions has been estimated based upon the assumption that a ten year 
 period beginning in 1925 and terminating in 1935 will be required to 
 install meters on all water services in the City of Chicago, and that when 
 all services are metered the sewage per capita, including industrial and 
 all other uses, will be approximately 160 gallons per day. 
 
 Under these assumptions the following table shows the estimated 
 quantities for each five year period from 1925 to 1945. 
 
6 
 
 Million Gallons Sewage Daily. 
 
 Present Conditicns Universal 
 
 Year of Metering Metering 
 1925 877 
 
 1930 1,054 777 (50% metered) 
 
 1935 1,243 662 
 
 1940 1,437 711 
 
 1945 1,629 769 
 
 The installation of meters on all services will cause the sewage flow 
 of 1945 under complete metering to be less than at the present time, 
 when but ten percent of the services are metered. 
 
 8th. Intercepting Sezvers: 
 
 The Sanitary District has adopted tunnels for its intercepting 
 sewers. This appears to be a logical conclusion in view of congestion 
 on the ground surface. 
 
 Intercepting sewers have been built or are under construction for 
 all areas except the West Side and the Southwest Side. The intercept- 
 ing sewers to serve these two areas will in general extend along both 
 sides of the main channel and the north and south branches of the 
 Chicago River beginning with Fullerton Avenue on the North Side and 
 extending in a southwesterly direction to the site proposed for the West 
 and Southwest Side plants along the Drainage Canal near Summit. 
 
 It is beheved that with universal metering these intercepting sewers 
 should be designed of such capacity that they will carry a flow equiva- 
 lent to 375 gallons per capita per day. This is approximately two and 
 one-third times the average flow as it is estimated to be after the in- 
 stallation of meters. 
 
 It is believed that a 35-year period (i. e. to 1960) is that for which 
 the design of interceptors should be economically and practically made 
 for sewers constructed in tunnel, capable of duplication in the future 
 without excessive costs. 
 
 The 20 miles of intercepting sewers required for the West Side 
 system have been estimated to cost $7,890,000. 
 
 The 15 miles of sewers required for the Southwest Side plant have 
 been estimated to cost $4,495,700. 
 
 9th. Sezvage Disposal Costs in Other Cities: 
 
 Construction and operating costs of sewage pumping stations and 
 treatment works in other cities were compared with similar costs in- 
 curred by the Sanitary District of Chicago in certain works already 
 built. 
 
 In making this comparison consideration has been given to the 
 price basis when the work was done and the unit costs for labor and 
 materials in the cities compared. We deduce the following conclusions 
 from the comparison : 
 
7 
 
 (a) Recent intercepting sewer contract costs in Chicago have 
 been substantially double those secured in other cities under like con- 
 struction conditions. 
 
 (b) The Calumet Imhoff tank plant, constructed by the Sanitary 
 District of Chicago (after being credited with the reasonable cost of 
 an experimental sprinkHng filter and activated sludge plant), cost ap- 
 proximately three tim.es the average of tank plants of similar type in 
 other cities. 
 
 (c) The Des Plaines activated sludge plant of the Sanitary Dis- 
 trict of Chicago cost approximately three times the average cost of 
 similar plants in Milwaukee and Indianapolis. 
 
 (d) The cost of operating the Calumet Imhoff tank plant (after 
 being credited with the reasonable cost of operating a small sprinkHng 
 filter and a small activated sludge plant), is approximately four times 
 that of operating similar plants in other cities when compared on the 
 basis of cost per million gallons treated or ten times the average based 
 on cost per capita served. 
 
 (e) The cost of operating the Des Plaines activated sludge plant 
 of the Sanitary District of Chicago is from eight to ten times that 
 estimated to be necessary for the operation of the activated sludge plant 
 at Milwaukee. 
 
 (f) The cost of operating the 39th St., Lawrence Avenue and 
 Calumet pumping stations of the Sanitary . District of Chicago is approx- 
 imately three times as great per unit of work performed as that of other 
 stations of similar size and type in other cities. 
 
 10th. Basis of Cost EsPimates: 
 
 All estimates of cost of construction and operation used herein are 
 predicated upon labor and material prices prevailing in the Chicago 
 District in the early part of 1925. The estimates are further based upon 
 the average efficiency which it is practicable to secure in public enter- 
 prises of similar nature ; no better and no worse than conditions recently 
 prevailing in Detroit, Cleveland and Milwaukee. 
 
 11th. Types of Treatment Works: 
 
 At the present time the Des Plaines activated sludge plant and the 
 Calumet Imhofif tank plant are in operation. The Sanitary District is 
 also definitely committed to the construction of an activated sludge plant 
 at the North Side plant, the construction of which is about one-third 
 completed. 
 
 All of the estimates herein made for all amounts of flow considered 
 are based upon the Sanitary District's program of adding sprinkling 
 filters at the Calumet plant, and of building a sprinkling filter plant at 
 
8 
 
 the Corn Products Plant and an activated sludge plant at the Stock- 
 yards. The variations in degree of treatment required with the several 
 flows considered, are all secured herein by applying different treatment 
 processes to the West and Southwest Side plants. 
 
 All estimates of cost herein are in addition to contracts now let 
 and under construction on the North Side intercepting sewerg and that 
 part of the North Side disposal plant for which contracts have thus far 
 been let. 
 
 In our opinion the sites for proposed sewage disposal works are 
 well chosen. 
 
 12th. Additional Works Required zvith 10,000 Cubic Feet Per Second 
 Flozv: 
 
 A flow in the channel of 10,000 cubic feet per second will necessi- 
 tate in addition to the sewage disposal works now constructed or under 
 contract, preliminary or tank treatment of the sewage at the West Side 
 plant and complete tank and sprinkling filter treatment for the South- 
 west Side. 
 
 The cost of additional purification works including intercepting 
 sewers required with a total flow of 10,000 cubic feet per second is esti- 
 mated at $57,415,240 to 1935 and $64,692,700 to 1945. 
 
 The cost of operation of all pumping stations and sewage disposal 
 plants with a flow of 10,000 cubic feet per second is estimated at 
 $4,364,000 in 1935 and $5,004,800 in 1945. 
 
 13th. Required Works zvith 4,167 Cubic Feet Per Second Flozv: 
 
 With a smaller amount of diluting water, complete secondary 
 treatment of the sewages at both the West and Southwest Side plants 
 would be necessary. Tanks and sprinkling filter treatment would not 
 be suflicient by 1945. Activated sludge treatment is required to meet 
 the 1945 conditions with but 4,167 c. f. s. flow available. 
 
 The estimated cost of all interceptors and disposal plants required 
 with the flow of 4,167 cubic feet per second is $69,213,500 for 1935 con- 
 ditions, and $76,583,300 for 1945 conditions. 
 
 We estimate the cost of operating all sewage pumping stations and 
 sewage disposal plants necessary with the flow of 4,167 cubic feet per 
 second at $5,163,100 in 1935 and $5,817,600 in 1945. 
 
 14th. Required Works zvith 2,000 Cubic Feet Per Second Flozv: 
 
 With a flow as small as 2,000 cubic feet per second there is no prac- 
 ticable way of meeting the pollution standard herein suggested. 
 
 15th. Required Works zvith 7,500 Cubic Feet Per Second Flozv: 
 
 The 7,500 cubic feet per second flow requires that a complete 
 sprinkling filter plant be built at the West Side and tanks at the South- 
 
9 
 
 west Side. This will suffice up to as late as 1947 after which filters will 
 be required at the Southwest plant also. The estimated cost of con- 
 structing all plants under this flow is $61,477,920 in 1935, and $67,- 
 926,100 in 1945. 
 
 The annual cost of operating all pumping stations and disposal 
 plants is estimated at $4,530,400 in 1935 and $5,137,000 in 1945. 
 
 16th. Required Works with 8,500 Cubic Feet Per Second Flow: 
 
 The required works with 8,500 cubic feet per second flow would be 
 the same as those required for 10,000 cubic feet per second flow. The 
 construction and operating cost would be the same as those outlined un- 
 der the project in paragraph above. 
 
 17th. Review of Expenditures Under Various Diversions: 
 
 The expenditures for construction and operation of the treatment 
 works required for 1935 and 1945 conditions with flows varying from 
 2,000 to 10,000 cubic feet per second are shown in Table 1. 
 
 Increasing the flow from 4,167 to 10,000 cubic feet per second 
 saves but sixteen and one-half percent in the expenditures required for 
 sewage treatment, and but fourteen and one-half percent in the annual 
 operating costs. 
 
 18th. Suggestion for Stockyards Wastes: 
 
 The Sanitary District program contemplates a separate sprinkling 
 filter plant at Argo and a separate activated sludge plant for the Stock- 
 yards wastes. Other cities in which the packinghouse waste per capita 
 contributing sewage is as great as that at Chicago have found it practi- 
 cable to treat this waste, mixed with the domestic sewage, at either 
 sprinkling filter or activated sludge plants. At Chicago the Southwest 
 Side intercepter passes almost directly by the Stockyards, which sug- 
 gests the further practicability of combining this concentrated waste, 
 after the removal of the coarse solids, with the domestic sewage before 
 treatment. 
 
 If treatment of the Stockyards waste, mixed with the sewage of 
 the West and Southwest Side, is practicable on stone filters, there will 
 result a saving in construction cost of from $2,300,000 to $3,500,000. 
 There will also result a saving in annual cost of operation of $350,000 
 per year, even after crediting an income of $360,000 per year from the 
 sale of the sludge from the activated sludge plant. This annual saving 
 capitalized at four percent adds a further sum of $8,500,000, making the ^ 
 total capitalized saving between $10,800,000 and $12,000,000. 
 
 The rates of flow for dilution purposes, as stated in this report, are 
 the estimated rates required under warm weather conditions at which 
 
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 time the rate of diversion would necessarily be greatest. It is a fact 
 that considerably smaller rates of diversion will be required in the cooler 
 months of the year. Riparian owners on the Great Lakes and other 
 parties interested are chiefly concerned with the average yearly diver- 
 sion. It is believed to be proper therefore in the operation of the Drain- 
 age Canal to vary the draft of diversion water from month to month 
 dependent upon conditions. The ability to do this will provide a large 
 factor of safety for maintaining good conditions in the efiluent channels 
 and down-stream rivers. 
 
 We have made no allowance for the fact that more or less sewage 
 from the Indiana-Calumet region now containing 180,000 people, now 
 reaches the Sag Canal in a more or less unpurified state. This situation 
 must ultimately be solved by adequate purification works for this region, 
 and a specific allowance for dilution water if the sewage continues to 
 flow via the Illinois River. 
 
 The conclusions in this report are predicated on keeping the Drain- 
 age Canal reasonably clean of organic settlings by dredging. Very 
 little will be required in this regard after purification works are built, 
 and after the present deposits are removed. Several years may be re- 
 quired before existing sludge deposits in the Illinois River are com- 
 pletely eliminated. 
 
 We have given no consideration to the development of water 
 power. We have neither included the costs thereof, nor credited bene- 
 fits. Where power is required in the operations of pumping and sewage 
 disposal we have estimated the cost thereof on the basis of electric 
 power purchased from the Commonwealth Edison Company at their 
 published rates. 
 
 Upon the pages which follow we have discussed the matters above 
 treated in further detail. 
 
12 
 
 PART II. 
 
 PRESENT DISPOSAL OF SEWAGE AND DEFICIENCIES 
 
 Chicago, and the industrial region surrounding it, occupies the 
 Southwestern shore of Lake Michigan. The ground is comparatively 
 low. The greater part of it Hes less than 20 feet above Lake Michigan. 
 This entire region formerly drained naturally into the lake through the 
 Chicago and Calumet Rivers. That locality now constituting the west- 
 ern suburban area, however, is tributary to the Des Plaines River, which 
 parallels the lake shore about ten miles inland, the waters of which are 
 tributary to the Mississippi river system through the Illinois river. 
 
 More than three milHon people now occupy this territory. It is 
 conservatively estimated that the population will double within the next 
 thirty years. The present flow of sewage is about 800 million gallons 
 per day. This is equivalent to a river 100 feet wide and five feet deep 
 flowing one and one-half miles per hour. 
 
 The shore line of Lake Michigan from Gary on the south to Wau- 
 kegan upon the north is about seventy-five (75) miles in length. More 
 than half of it is densely populated. Much of it is occupied by industries. 
 The northern one-third of it is residential in character. 
 
 Development of Sewers. 
 
 Sewers were built as required, draining immediately to the nearest 
 water outlet. The earliest settlement of considerable size, was located 
 at the mouth of the Chicago river. In this locality all sewers drain 
 directly into the river or into its north or south branch. As the popula- 
 tion extended northward and southward, sewers were built discharging 
 directly into the Lake. When sewers became necessary in the region 
 adjoining the Calumet River, sewers were built discharging directly into 
 this stream. 
 
 The construction of sewers in Chicago was begun in 1856. At this 
 time the population was about 80,000. Thereafter the growth of the 
 city was very rapid. The mileage of sewers kept pace with the popula- 
 tion for in many localities the habitation was not practicable until sewers 
 had been built. 
 
 Early Disposal of Sewage. 
 
 Sewers discharging into the Chicago River and branches ultimately 
 reached the lake except for a small amount, which from the earliest use 
 
13 
 
 of sewers, reached the old IlHnois and Michigan canal by pumping, and 
 thus passed to the Des Plaines and Illinois Rivers. 
 
 Illinois and Michigan Canal. 
 
 The Illinois and Michigan canal was completed in 1848. It paral- 
 lels the Drainage Canal a few hundred feet to the south. Its water sup- 
 ply was obtained partly by gravity from the Calumet River and partly 
 by water pumped from the south branch of the Chicago River. From 
 time to time the pumping works were increased in capacity, which tem- 
 porarily tended to improve the foul conditions in the Chicago River, and 
 to divert some of the sewage from the lake. 
 
 Water Supply. 
 
 The water supply for the City of Chicago and for all its suburbs 
 bordering the lake is taken from Lake Michigan. Public Water Works 
 for Chicago began operation in 1856. Water was taken from the lake at 
 the foot of Chicago Avenue, about one mile north of the mouth of the 
 Chicago River. As the occupied area of the city grew it became neces- 
 sary to construct additional Water Works' intakes, and as the pollution 
 from the sewers was constantly increasing, the intake cribs were pro- 
 gressively located farther from the shore. 
 
 At the present time the city is supplied through six cribs varying 
 from two to four miles distant from the shore line. 
 
 In the years of rapid municipal growth up to 1890, the sanitary 
 conditions in the outlet streams, particularly the Chicago River and its 
 branches, became progressively worse. Comparatively great accumula- 
 tions of filth were washed into the lake, and occasionally reached the 
 Water Works' intakes. This resulted in the general prevalence of 
 typhoid fever, and occasional epidemics. 
 
 Drainage Canal. 
 
 We will not recite here all the steps that were taken to bring about 
 an improvement in the sanitary conditions. These matters, while of 
 general interest, are recited elsewhere, and bear only indirectly upon 
 this problem. The most important step taken toward improving condi- 
 tions was the passage of the State law creating the Sanitary District of 
 Chicago and empowering it to construct the Chicago Sanitary Ship 
 Canal, May 29th, 1889. 
 
 The Drainage Canal is twenty-eight miles long from the Chicago 
 River at Robey Street to the Controlling Works at Lockport. It creates 
 a reversal of the flow of the Chicago River, and in addition it draws in 
 certain quantities of water from Lake Michigan, depending upon its 
 controlled rate of flow. The flow is controlled at the foot of the Canal. 
 
14 
 
 This work was started in 1892 and completed January 2, 1900. The 
 flow capacity of the main channel is approximately 10,000 cubic feet per 
 second. 
 
 In 1907 the canal was extended beyond Lockport, a distance of 
 about four miles to concentrate an available fall of about thirty-four 
 feet, and utilize the same in the development of a water power in drop- 
 ping the canal flow down to the level of the Des Plaines River. Since 
 the completion of this power plant it has generally formed the means for 
 regulating the flow of the Drainage Canal, although the flow can also be 
 regulated at the Controlling Works, four miles upstream. 
 
 In connection with the utilization of the main drainage canal it was 
 necessary to improve the Chicago River in order to permit the desired 
 flow without interfering with navigation. The river was widened and 
 deepened at various places between the years 1897 and 1920. In 1910 
 the north shore channel was completed connecting the north branch of 
 the Chicago River with Lake Michigan at Wilmette. At this place a 
 pumping station was built operating at about three feet head. This 
 canal and pumping station serves the purpose of pumping fresh water 
 into the head of the north branch of the Chicago River, thus improving 
 the sanitary conditions therein, resulting from the large amount of sew- 
 age received. This channel is eight miles in length and has a capacity 
 of 1,000 cubic feet per second. 
 
 The Calumet Sag channel taps the little Calumet River at Blue 
 Island diverting the water thereof westerly and joining the main drain- 
 age canal at Sag. This canal was completed in 1922. It has a length of 
 sixteen miles and a capacity of 2,000 second feet. 
 
 Intercepting Sewers. 
 
 With the opening of the Drainage Canal January 2, 1900, all 
 sewage discharging into the Chicago River and branches was diverted 
 to the Illinois River. There remained, however, a considerable amount 
 of sewage which reached the lake, through the sewers discharging di- 
 rectly therein. To stop this pollution a system of intercepting sewers 
 along the lake shore was planned and built by the City of Chicago. 
 
 All sewage entering the lake, between the Chicago River on the 
 north and 87th St. on the south, is now intercepted by a main sewer on 
 ■ Stony Island Avenue running north from 83rd St. and thence following 
 Cornell Avenue and the shore of Lake Michigan to 39th St. At this 
 place the 39th St. pumping station lifts the sewage to the twenty feet 
 sewer running west on 39th St., entering the south branch of the Chi- 
 cago River. This station is also equipped with pumps to take dilution 
 water directly from the lake for the purpose of keeping the south fork 
 of the river clean. Plans are now under yvay to extend the 39th St. 
 
Figure 1.— Map of the Sanitary District at Chicago and irtelnltar. 
 
15 
 
 sewer so that it will enter the drainage canal at Western Avenue near 
 31st St. This will obviate the necessity for dilution water in the south 
 branch of the river. The southern part of the Stony Island Avenue 
 district is pumped into the Stony Island Avenue sewer by pumping 
 station constructed and operated by the City of Chicago at 73rd St. and 
 Stony Island Avenue. 
 
 The South Side intercepting sewer was completed in 1907. 
 
 The North Side sewers entering the lake were intercepted by the 
 construction of sewers paralleling the lake shore running north to Law- 
 rence Avenue, and from Howard Avenue running south to Lawrence 
 Avenue. At Lawrence and Racine Avenue a pumping station was con- 
 structed, discharging the sewage westward into the north branch of the 
 Chicago River. This station is also equipped with pumps to draw dilu- 
 tion water from Lake Michigan for the purpose of improving the char- 
 acter of the water in the north branch of the Chicago River. 
 
 A similar system of intercepting sewers north of Howard Avenue 
 lead to the Evanston pumping station at Orrington Avenue and Lake 
 Street, which intercepts the remainder of the lakeward flowing sewers 
 south of Wilmette and discharges the sewage into the north shore 
 channel. 
 
 All sewage originating in the Sanitary District north of Wilmette 
 is intercepted by a system of sewers terminating at the north shore 
 channel and Sheridan Road. The Wilmette pumping station, located 
 at this point, is equipped with pumps to draw dilution water from the 
 lake for the purpose of maintaining cleanly conditions in the north 
 shore channel and the north branch of the Chicago River. 
 
 The North Side intercepters, within the City of Chicago, became 
 effective in 1908. The intercepting sewer system north of Wilmette 
 became fully effective in 1916. The Evanston sewer and pumping 
 station was completed in 1921. 
 
 Calumet Region. 
 
 Sewage within the City of Chicago, south of 87th Street, has here- 
 tofore been discharged directly into the Calumet River, and considerable 
 of it still reaches the river. This will very shortly be corrected by the 
 completion of the Calumet intercepting sewer and the pumping station 
 at 95th Street and the Calumet pumping station at Indiana Avenue and 
 125th St. With the completion of these sewers all sewage south of 87th 
 St. will be pumped into the Calumet Sag Channel after treatment, and 
 delivered to the Chicago Drainage Canal at Sag. 
 
 The Sag Canal does not reverse the Calumet River system at all 
 times, the flood flow of this stream greatly exceeding the capacity of 
 
16 
 
 the Sag Canal. Periodic discharges from the Calumet River have been 
 a serious menace to the water supplies, particularly those near the 
 mouth of the Calumet. This menace will continue to a greater or less 
 extent. 
 
 
 TABLE 
 
 2. 
 
 
 
 FLOW IN MAIN 
 
 CHANNEL. 
 
 
 
 Authorized Flow 
 
 ♦Actual Flow 
 
 
 
 by State Law 
 
 V_/U.. H L. jJtJl Oct/. 
 
 Year 
 
 X^OpUldllOIl 
 
 r I. per oec. 
 
 as Corrected. 
 
 1900 
 
 1,640,000 
 
 5,467 
 
 2,990 
 
 1901 
 
 1,688,000 
 
 5,627 
 
 4,046 
 
 1902 
 
 1,736,000 
 
 5,787 
 
 4,302 
 
 1903 
 
 1,934',000 
 
 6,447 
 
 4,971 
 
 1904 
 
 1,985,000 
 
 6,617 
 
 4,793 
 
 1905 
 
 2,035,000 
 
 6,783 
 
 4,480 
 
 1906 
 
 2,090,000 
 
 6,967 
 
 4,473 
 
 1907 
 
 2,144',000 
 
 7,147 
 
 5,116 
 
 1908 
 
 2,195,000 
 
 7,317 
 
 6,443 
 
 1909 
 
 2^250^000 
 
 7^500 
 
 6,495 
 
 1910 
 
 2,308,000 
 
 7,693 
 
 6,833 
 
 1911 
 
 2,370,000 
 
 7,900 
 
 6,896 
 
 1912 
 
 2,432,000 
 
 8,107 
 
 6,938 
 
 1913 
 
 2,509,000 
 
 8,363 
 
 7,839 
 
 1914 
 
 2,589,000 
 
 8,630 
 
 7,815 
 
 lyio 
 
 2,652,000 
 
 8,840 
 
 1 790 
 
 I, too 
 
 1916 
 
 2,716,000 
 
 9,053 
 
 8,200 
 
 1917 
 
 2,782,000 
 
 9,273 
 
 8,726 
 
 1918 
 
 2,846,000 
 
 9,487 
 
 8,826 
 
 1919 
 
 2,916,000 
 
 9,720 
 
 8,595 
 
 1920 
 
 2,986,000 
 
 9,953 
 
 8,346 
 
 1921 
 
 3,063,000 
 
 10,210 
 
 8,355 
 
 1922 
 
 3,143,000 
 
 10,477 
 
 8,858 
 
 1923 
 
 3,214,000 
 
 10,713 
 
 8,348 
 
 1924 
 
 3,284,000 
 
 10,947 
 
 9,465 
 
 *These quantities have been computed from the latest available data. 
 Note — From Report of Engineering Board of Review, 
 
 Diluting Water. 
 
 It was the original idea in the construction of the Drainage Canal 
 that the sewage of the Sanitary District would be diluted by mixing 
 with a sufficient amount of fresh water from Lake Michigan to render 
 the mixture innocuous, and to assist in the natural purification of the 
 sewage in its transit through the Drainage Canal and the river system 
 
Id 
 
 Ql 
 
 ti 
 
 q 
 
 D 
 
 u 
 
 < 
 
 r 
 u 
 
100,000 
 901 000 
 tOlOOO 
 
 m 
 
 iii^^P8iiiy^^^iMllilyiyiiiyi^iiiiyililliliiyiliiiiiOilll»^ 
 
 4.000 
 
 \90l \ 190Z T 1903 T T t905 I 190* I l^T I t«>8 I >S09 | WIO T rail 
 
 it 
 
 L T »9»4 T 1915 I 1916 T r 1915 T 1919 I 1^20 j isjl T 
 
 1900 1901 
 
 t9ie 
 
 I9t3 
 
 Figure 2. — Hydrograph for Chicago Drainage Canal and Illinois River at Peoria, 1I00>19S4. 
 
 Flow of Illinois River as reported bv U. S. O. S. except year 1900, which is estimate by J. A. Harman. 
 
17 
 
 below same. 
 
 Table 2 shows the average flow at the outlet of the Drainage Canal 
 for each year since the canal was opened in 1900. This flow was limited 
 in the early years by the ability to get the water through the Chicago 
 River. Within the past ten years the flows have been more nearly up 
 to the pollution requirements of the population served, but they have 
 never been adequate to properly care for the sewage and trade wastes. 
 The table also shows the estimated amounts of flow required by the 
 State law creating the Sanitary District, under which a minimum dilu- 
 tion of three and one-third second feet per thousand people was re- 
 quired. 
 
 The above flows include the sewage, as well as the diversion, for 
 dilution purposes. Water for both purposes is taken from the lake. 
 The present Hquid volume of the Chicago sewage is approximately 1200 
 second feet or about twelve percent of a total diversion of 10,000 second 
 feet. 
 
 Additional Dilution. 
 
 Immediately after passing the controlling works at Lockport the 
 Drainage Canal water joins the natural flow of the Des Plaines River. 
 The flow of this stream during the late summer and fall is usually negli- 
 gible. Large flows of fresh water are, however, brought in during the 
 flood seasons. 
 
 Below Joliet the principal tributary is the Kankakee River, which 
 joins the Des Plaines forming the Illinois River. The next principal 
 tributary is the Fox. 
 
 The net effect of all these streams and other minor tributaries com- 
 ing in above Peoria is indicated on Figure 2, which shows graphically 
 the flow of the Illinois River at Peoria, and the flow of the Chicago 
 Drailiage Canal since the latter was opened in 1900, During the past ten 
 years the flow of the Drainage Canal at Lockport has generally ranged 
 between 8,000 and 9,000 second feet. During the two dryest months in 
 the year the additional flow coming in above Peoria has usually ranged 
 between ten and twenty per cent of the Drainage Canal flow. During the 
 remainder of the typical year this additional inflow has been consider- 
 ably more, possibly averaging as much as a fifty percent addition of 
 fresh Avater. During several months of nearly every year the additional 
 water coming in has been fully equal to the flow of the Drainage Canal. 
 In certain months of heavy flow it has been four to five times as great 
 as the Drainage Canal flow. During the year 1924, which was a year 
 of sustained natural flow in the Illinois river, the tributaries above 
 Peoria brought in a flow of fresh water fully equal to the Drainage 
 Canal flow throughout the year up to and including September. 
 
18 
 
 Sewage Treatment Works. 
 
 Realizing the inadequacy of dilution as a permanent solution for the 
 Chicago sewage problem, the Sanitary District some years ago began 
 experimentation and the preparation of plans for sewage disposal works 
 to supplement the dilution project. Up to the present time treatment 
 works have been built as follows : 
 
 Des Plaines River Treatment Plant. 
 
 The Des Plaines plant is located at Roosevelt Road and S. 1st 
 Avenue, Maywood. 
 
 At this place a system of intercepting sewers terminates, draining 
 an area of 18.5 square miles between North Avenue and 22d St., and 
 west of Harlem Avenue. The present population served is approxi- 
 mately 39,000. This plant serves the towns of Maywood, Melrose Park, 
 Forest Park, River Forest, the north part of Oak Park, and the U. S. 
 Government Speedway Hospital. 
 
 This plant began operation in August, 1922. It consists of a 
 pumping plant, an electric driven power plant and treatment works by 
 the activated sludge process, including a dewatering plant for sludge. 
 The capacity of the plant is four million gallons per day ; slightly less 
 than this amount of sewage is being treated at present. 
 
 This plant has been designed with the view to experimentation in 
 order more effectively to plan the larger plants subsequently to be 
 built. 
 
 Calumet Treatment Works. 
 
 The Calumet Treatment Works is located near E. 125th St. ad- 
 joining the west shore of Lake Calumet. It is intended to serve all the 
 territory south of 87th St. Sewage will be delivered by the Calumet 
 pumping station. Purified effluent will be discharged into the Calumet 
 Sag Channel. The area to be served is approximately 42.5 square miles. 
 It has a present population of 179,000 of which approximately 100,000 
 reaches the plant at present. 
 
 The plant consists of a system of Imhoff tanks having an estimated 
 daily capacity of 55 M. G. D. The plant was put in operation in Sep- 
 tember, 1922. A small activated sludge plant and a small trickling filter 
 are also in operation at this site for experimental purposes. 
 
 Other Works. 
 
 The Sanitary District includes forty-nine incorporated cities and 
 villages, many of which are so located as to make it economical to solve 
 their problems separately. 
 
19 
 
 Figure 3. — Map of the Sanitary District of Chicago showing sewage 
 treatment projects and intercepting sewers. 
 (Scale appox. 1 inch = 6 miles.) 
 
20 
 
 The District has built, and is operating a small settling tank and 
 trickling filter plant at Morton Grove, completed in 1914, serving J200 
 people. A small plant has also been completed at Glenn View. 
 
 Minor treatment projects are proposed for the towns of LaGrange, 
 Brookfield, LaGrange Park, North Brook, Oak Forest, Posen Robins, 
 Upper Des Plaines Towns, Harvey and Schiller Park. Other miscel- 
 laneous plants will ultimately be required for outlying towns. 
 
 North Side Plant. 
 
 Work is now well under way covering the North side sewage treat- 
 ment project located at Howard Avenue, immediately west of the North 
 Shore Channel. This plant will consist of a pumping station, an electric 
 driven power plant and an activated sludge plant. As now being built 
 it will have a capacity of 175 M. G. D., and it will be subject to indefinite 
 enlargement by the addition of units. Sludge will be pumped to lagoon- 
 ing beds southwest of the city. 
 
 The disposal tract covers 188 acres. The project serves all territory 
 in the Sanitary District lying north of Fullerton Avenue. Area sixty- 
 two square miles. Present population (1927) is approximately 737,000. 
 The plant is scheduled for completion in 1928. 
 
 West Side Sewage Treatment Project. 
 
 This treatment project is proposed to serve an area of 57.5 square 
 miles, embracing the heart of Chicago, and lying between Fullerton 
 Avenue on the north and 31st St. on the south, and extending from 
 Lake Michigan westward, including the loop district of the city. The 
 population at the present time is about 1,340,000. The plant will be 
 located adjoining the north bank of the drainage canal somewhere in the 
 vicinity of South Harlem Avenue. Plans for this plant have not been 
 made. It is tentatively proposed to use sedimentation tanks, supple- 
 mented by sprinkling filters when necessary. 
 
 Southzvest Side Treatment Works. 
 
 A similar plan is proposed for the Southwest side embracing all 
 remaining territory in the City of Chicago north of 87th St. and south 
 of 31st St., lying south of the drainage canal. This comprises an area 
 of 59 square miles. The population at present is about 910,000. Some 
 parts of the district are sparsely settled. 
 
 Industrial Wastes Treatment Projects. 
 
 A very important part of the organic load contained in the Chicago 
 sewage is contributed by certain industries, particularly the packing 
 industries located near the head of the Drainage Canal. Also the Corn 
 
21 
 
 Products Company located at Argo on the Drainage Canal and near 
 the western city limits. 
 
 The Packing Town wastes and the Corn Products wastes are de- 
 rived from comparatively small areas respectively. The wastes are 
 highly concentrated and require special treatment. Thoi:ough studies 
 have been made in cooperation with the industries. 
 
 Plans have been made to treat Packing Town wastes by the acti- 
 vated sludge process. 
 
 Further experimentation at the Corn Products plant is now under- 
 way. The experiments to date indicate that the wastes can best be 
 treated by sprinkling filters. 
 
 Effectiveness of Disposal Operations. 
 
 The diversion of the sewage from Lake Michigan has been fol- 
 lowed by a remarkable reduction in typhoid fever in the City of Chicago. 
 A number of other matters have contributed to this improvement, in- 
 cluding the chlorination of the water supply which was begun in 1912, 
 the pasteurization of milk begun in 1910, and also no doubt other im- 
 portant causes outside of the Chicago district, which have been instru- 
 mental in very greatly reducing the typhoid death rates throughout the 
 United States. Table 3 shows these facts in tabular form. 
 
 Condition of the Lake. 
 
 Lake Michigan is still badly polluted in the Indiana Calumet region, 
 from the Indiana cities and the periodic discharge of sewage from the 
 southern part of Chicago, a part of which still reaches the Lake. There 
 have also been periodic, but relatively infrequent sewage discharges 
 from the Chicago river due to flow reversals caused by floods. Minor 
 pollution still reaches the lake from the suburban towns north of the 
 Sanitary District. This pollution is comparatively small, and will prob- 
 ably become less with improved conditions in the North Shore Sanitary 
 District, embracing certain suburban towns north of the Cook County 
 line. 
 
 Particularly at times of great storms the sanitary condition of the 
 water at the Chicago intakes is very bad. This subject will be dis- 
 cussed hereinafter. 
 
 River Conditions. 
 
 During recent years the main channel of the Chicago River through 
 the heart of the city, while not seriously objectionable, nearly always 
 contains evidence of floating sewage. Conditions in the north branch 
 of the Chicago River generally range from bad to fair, depending upon 
 the extent of operation of the dilution pumps. The south branch of the 
 river to the head of the Drainage Canal increases in foulness as the 
 
22 
 
 additional sewers join the stream. The Drainage Canal throughout 
 its length, as would be expected, always bears evidence of the heavy 
 sewage load carried. Odors on the banks are usually noticeable, but 
 conditions only become very foul during the summer and early fall 
 months. 
 
 At Lockport dissolved oxygen is normally exhausted during the 
 warm weather season. A similar condition prevails generally through- 
 out the Illinois River to the head of Peoria lake about ninety-six miles 
 
 TABLE 3. 
 
 ANNUAL TYPHOID FEVER MORTALITIES IN CHICAGO PER 100,000 
 
 POPULATION. 
 
 From Report of Engineering Board of Review, and Supplemented. 
 
 Typhoid Percent 
 
 Fever of Total 
 
 Years Mortality Mortality Remarks 
 
 1867 73.3 3.45 
 
 1868 79.3 3.34 
 
 1869 65.3 2.82 
 
 1870 87.4 3.66 
 
 1871 61.0 2.92 
 
 1872 142.6 5.16 
 
 1873 71.6 2.85 
 
 1874 53.4 2.63 
 
 1875 51.7 2.62 
 
 1876 41.2 1.96 
 
 1877 37.0 1.98 
 
 1878 33.4 1.97 
 
 1879 42.3 2.41 
 
 1880 34.0 1.63 
 
 1881 105.2 4.03 
 
 1882 82.4 3.49 
 
 1883 62.2 3.12 
 
 1884 56.2 2.84 
 
 1885 74.6 3.98 
 
 1886 68.6 3.53 
 
 1887 50.3 2.48 
 
 1888 46.7 2.38 
 
 1889 48.4 2.67 
 
 1890 91.6 4.61 
 
 1891 173.8 7.20 
 
 1892 124.1 5.68 
 
 1893 53.5 2.47 
 
 1894 37.5 2.06 
 
 1895 37.9 2.14 
 
 1896 52.6 3.23 
 
 1897 29.3 2.00 
 
23 
 
 
 
 TABLE NO. 3— Continued. 
 
 
 J. J'^XXUiU 
 
 
 
 J? C V cx 
 
 KJL X. yj Lctl 
 
 Years 
 
 Mortality 
 
 Mortality Remarks 
 
 1898 
 
 40.8 
 
 2.79 
 
 1899 
 
 27.2 
 
 1.73 
 
 1900 
 
 19.8 
 
 1.35 Opening of Drainage Canal 
 
 1901 
 
 29.1 
 
 2.09 
 
 1902 
 
 44.5 
 
 3.03 
 
 1903 
 
 31.8 
 
 2.03 
 
 1904 
 
 19.6 
 
 1.42 
 
 1905 
 
 16.9 
 
 1.21 
 
 1906 
 
 18.5 
 
 1.27 Opening South Side Interceptors 
 
 1907 
 
 18.2 
 
 1.16 Completion South Side Interceptors 
 
 1908 
 
 15.8 
 
 1.09 Opening North Side Interceptors 
 
 1909 
 
 12.6 
 
 0.87 
 
 1910 
 
 13.7 
 
 0.90 Pasteurization of Milk 
 
 1911 
 
 10.7 
 
 0.74 Completion North Shore Interceptors 
 
 1912 
 
 7.6 
 
 0.51 Chlorination of Water Started 
 
 1913 
 
 10.6 
 
 0.71 
 
 1914 
 
 6.9 
 
 0.49 
 
 1915 
 
 5.3 
 
 0.37 
 
 1916 
 
 5.1 
 
 0.35 
 
 1917 
 
 1.6 
 
 0.11 Complete Chlorination of Water 
 
 1918 
 
 1.4 
 
 0.08 
 
 1919 
 
 1.2 
 
 0.09 Completion Evanston Interceptors 
 
 1920 
 
 1.1 
 
 0.09 
 
 1921 
 
 1.1 
 
 0.09 Completion Calumet Interceptors 
 
 1922 
 
 1.1 
 
 0.10 
 
 1923 
 
 1.9 
 
 0.16 
 
 1924 
 
 1.5 
 
 0.13 
 
24 
 
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Figure 4.— Watershed of tbe Illinois Rirer showing drainage of main stream and principal tributaries. 
 
25 
 
 below Lockport. Within this reach of the streams conditions vary, as 
 to the presence or absence of oxygen and the prevalence of putrefactive 
 odors. For ten years or more the natural life of the river, animal and 
 vegetable, has been destroyed. No life is present except sewage organ- 
 isms. The water is not suitable for bathing and is disagreeable for users 
 of pleasure craft. 
 
 During certain seasons objectionable conditions and the destruction 
 of the natural water life of the stream has occurred as far south as 
 Peoria. The wet season of 1924 has materially improved the conditions 
 in Peoria Lake. 
 
 Conditions in the Des Plaines and Illinois Rivers, below Lockport, 
 have been aggravated by large quantities of sewage sludge which passes 
 down the river during the colder months of the year, comparatively in 
 an undecomposed state, which tends to add materially to the demand on 
 the oxygen contained in the water during the summer months, when 
 decomposition reaches a maximum. This sewage sludge has accumu- 
 lated to great depths behind dams and in other places where the current 
 is slack during the twenty-five years that the Drainage Canal has been 
 operating. Conditions are becoming worse with the increasing organic 
 load discharged by the Chicago sewage and the Chicago industrial 
 wastes. 
 
 Incidentally the river receives additional pollution although com- 
 paratively of small amount from the cities between Joliet and Peoria. At 
 Peoria and Pekin important additional industrial wastes are added to 
 the river. Up to the present time this pollution has been small as com- 
 pared to the Chicago load. 
 
 It has been recognized, by all concerned, that the existing condi- 
 tions on the Illinois River should not be permanently tolerated. For 
 sometime it has been realized that unless corrective measures are ap- 
 plied promptly, these conditions will become materially worse with the 
 further growth of the Chicago region. 
 
 The Chicago sewage problem will not be solved until the water 
 supply of the Chicago district is adequately protected, and the streams 
 receiving sewage are restored to a condition of reasonable cleanliness. 
 
 Analytical Studies. 
 
 The most accurate picture of the sanitary conditions in the Des 
 Plaines and Illinois Rivers, below the outlet of the Chicago Drainage 
 Canal, is furnished by the comprehensive study of the U. S. Public 
 Health Service, covering fourteen months beginning July 1, 1921, 
 and ending August 31, 1922. A complete report of this investigation 
 has not yet been printed. There has been furnished to us, however, a 
 series of tabulations, summarizing the principal results. 
 
26 
 
 It was the purpose of this investigation to determine the extent of 
 pollution, the character of the water at various places within the streams 
 and the factors that particularly affect the decomposition of the organic 
 matters discharged therein. Twenty-seven sampling stations were es- 
 tablished between Lockport and the mouth of the Illinois River. Samples 
 were collected daily, or, at certain points tri-weekly, from mid-depth of 
 the stream. At the stations between Lockport and Shanahan, the latter 
 place just above the mouth of the Kankakee, samples were collected 
 from the center of the stream. At all stations below Shanahan samples 
 were taken at three points from the cross section. Samples were care- 
 fully taken, iced and promptly transported to the nearest laboratory. 
 Examination of samples was made in all cases in less than three hours. 
 The average time was much shorter. The report of the preliminary 
 examination states : "Due to fluctuations in the sewage strength from 
 night to day at the outlet of the Sanitary canal, and to the variation in 
 flow caused by opening and closing of the gates at the power plant above 
 Joliet, it is probable that the results of analyses recorded in the tables 
 which follow do not represent exactly the average condition throughout 
 the day of the water at the sampling point." 
 
 The tabular data, accompanying the preliminary report, is too bulky 
 to present in full. We summarize the principal features of it on Figures 
 5 to 8 inclusive. We show upon these diagrams the average dissolved 
 oxygen for each month during the investigation at each of the sampling 
 points. Also the five day bio-chemical oxygen demand for the same 
 places and times. These determinations represent the character of the 
 water from the pollution and nuisance standpoints. The bio-chemical 
 oxygen demand is representative of the amount of organic pollution 
 carried. The dissolved oxygen represents the possibility of local nuis- 
 ance and the practicability of existence of the natural water life of the 
 stream. Both determinations considered progressively down-stream 
 indicate the degree of improvement in the sanitary character of the 
 water flowing. 
 
 Winter Conditions. 
 
 We show separate diagrams intended to indicate typical conditions 
 in the four seasons of the year. In the winter time the dissolved oxygen - 
 is high in the water taken from the lake on account of its low tempera- 
 ture. It will be observed that at no point between Lockport and the 
 mouth of the Illinois does the dissolved oxygen fall below 7.5 p. p. m. ; 
 further there is very little reduction in the dissolved oxygen throughout 
 the travel of the water from. Lockport to the Mississippi. The net total 
 effect is an increase. 
 
27 
 
 The organic matter (as represented by 5 day b. o. d.) is very high 
 at Lockport, averaging generally from twenty to twenty-four p, p. m. 
 Near LaSalle it has been reduced about two-thirds in p. p. m. and about 
 one-third in the total load carried by the stream, allowing for the addi- 
 tional dilution water coming in from the tributary streams above 
 LaSalle. The improvement is probably due largely to sedimentation 
 supplemented by a small amount of oxidation. Between LaSalle and 
 
28 
 
 Peoria the improvement is much greater by reason of further sedimen- 
 tation in the wider and deeper river between LaSalle and Peoria. The 
 diagrams plainly show the additional pollution reaching the Illinois 
 River at Peoria and Pekin, and the improvement of the stream below 
 Havana. In the v/inter season there is apparently practically no im- 
 provement in the quality of the sewage and dilution water between Chi- 
 cago and Lockport. At this season of the year each sewer drops its 
 
 cr oo f- vx) 
 
29 
 
 load into a stream of ice cold lake water. Practically speaking, the 
 sewage travels in cold storage to Lockport and throughout its course to 
 the Mississippi River. Apparently the principal improvement in the 
 character of the stream is due to sedimentation. 
 
 Summer Conditions. 
 
 The summer conditions present a very different picture. At this 
 season of the year organic decomposition reaches its maximum, produc- 
 ing a heavy demand on the oxygen in the stream with a tendency to 
 produce putrefactive conditions with attendant odors and a reduction in 
 the oxygen to the point where the natural water life of the stream may 
 be suffocating. 
 
 At this season the mixture of sewage and lake water, as delivered 
 at Lockport, has an organic load slightly more than half that contained 
 in the winter season (5 day b. o. d.). This probably results from oxi- 
 dation and septic action in the Drainage Canal above Lockport, the 
 
30 
 
 result of the decomposition being carried away partly in gases and 
 partly in inert matter carried along with the water in suspension. At 
 this season oxygen is practically exhausted in the Drainage Canal be- 
 tween Chicago city limits and Lockport. It does not exceed 1 p. p. m. 
 at any place above Chillicothe, 110 miles below Lockport. Between 
 Chillicothe and Peoria the stream rapidly recovers its oxygen in its 
 traverse through Peoria Lake. This is due to the reduction in organic 
 
31 
 
 matter that has taken place up-stream, oxygen absorption from the 
 atmosphere on the large surface of Peoria lake, and the product of 
 oxygen-producing aquatic vegetation. Below Peoria and Pekin there is 
 a further draft upon the oxygen resulting from added pollution. It is 
 considerably reduced at the mouth of the Illinois. From Peoria to the 
 mouth, however, the Illinois River contains sufficient oxygen to permit 
 a thriving natural water life. The reduction in the organic matter (5 
 day b. o. d.) is somewhat greater than in the winter time, taking into 
 consideration the comparatively small amount of diluting water coming 
 in from the natural streams below Joliet. The organic load has been re- 
 duced nearly two-thirds from Lockport to Peoria. It suffers a large 
 increase at Peoria and Pekin and is again reduced in traveling to the 
 mouth of the stream. 
 
 As would be expected, from the absence of oxygen, between Lock- 
 port and Chillicothe the river is in a very foul condition. It is entirely 
 devoid of natural stream life. It is possible for sewage organisms only 
 to live in this water. Below Chillicothe the rapid increase in the dis- 
 solved oxygen creates a very different condition. Below Peoria in 
 1921-22 conditions probably permitted the presence of fishes of all kinds 
 naturally inhabiting the stream. 
 
 Spring and Fall Conditions. 
 
 The spring and fall conditions typify the transition from the winter 
 conditions to the summer conditions, and from the conditions of summer 
 to the conditions of winter. This is due to the gradually warming water 
 in spring as summer is approached, and the gradual chilling of the water 
 between September and November. This effect is plainly evident on 
 Figures 6 and 8. Each diagram carries a tabular statement of flow from 
 Joliet to Peoria. Attention is invited to the month of April, 1922, in 
 which the flow at Peoria was nearly five times the flow at Joliet. 
 
 The effect of this additional dilution water is evident in the reduced 
 organic content (5 day b. o. d.) at Peoria. Allowing for this dilution 
 the total organic load of the stream at Peoria is apparently reduced to 
 fifty percent as compared to the vicinity of Lockport, indicating that 
 the agencies of oxidation and possibly sedimentation persist in floods. 
 
 Past Conditions — Illinois and Des Plaines Rivers. 
 
 What has been said above typifies as accurately as possible condi- 
 tions which prevail at present. These conditions have been progres- 
 sively growing worse since the Drainage Canal began to operate in 1900. 
 
 The following is quoted from a recent statement of Dr. Stephen A. 
 Forbes, Chief, State Natural History Survey Division, Illinois Depart- 
 ment of Registration and Education : 
 
32 
 
 "A serious and practically continuous study of the system of the plant 
 and animal life of the Illinois River was begun by the State Natural History 
 Survey of Illinois in 1894 and has been continued with only one important 
 interruption to the present year. The actual periods of active field operations 
 on the river were as follows: 1894-1899 inclusive, 1901-1903, 1909-1912, 
 1913-1915, 1918, 1920, and 1922-1924. The interval of five years after 1903 was 
 given mainly to the preparation and publication of a final report on the 
 fishes of the State. 
 
 "We have had from the very beginning until now the continuous co- 
 operation of the Water Survey of the State, upon which we have depended 
 for chemical tests and analyses, and for bacterial data. 
 
 "Our reason for so prolonged attention to a single subject is found in the 
 progressive changes in the stream itself, its content, and its environment, 
 which have worked corresponding changes in the aspect and internal order 
 of its biology, requiring frequent repetition of our studies and a consequent 
 revision of our conclusions. The most important of these changes have been 
 the introduction of the European carp in 1885 and its enormous multiplication 
 until it has become more abundant than all the other fishes of the stream 
 taken together; a general diking and reclamation of the very extensive 
 bottomlands of the river and the draining of their numerous lakes; and a 
 rapidly increasing pollution of the stream by sewage wastes from towns on 
 its banks, and especially from the Sanitary District of Chicago. It is a very 
 difficult matter to disentangle these several causes of change in a way to 
 distinguish clearly their separate biological aspects. There was, for example, 
 a large and rapid increase in the fisheries yield of the river at about the 
 time of the opening of the sanitary canal in 1900, sometimes attributed to 
 the canal itself, but largely due to a rapid multiplication of the carp before 
 1900; and there has been of recent years a general falling off in the fisheries 
 yield coincident with increasing pollution of the stream, but this is in great 
 measure consequent upon a restriction of the overflow of levees and the 
 draining of the lakes. 
 
 "In this confusion of causes and effects, it is quite impossible to show 
 clearly and fully just how and to what extent the remarkable fisheries yield 
 of the river, amounting in 1908 in prices paid to fishermen, to a dollar for 
 every two feet of its length, has been affected by sewage pollution, but 
 I must do what I can to this end in the brief time alloted. 
 
 "The injurious biological effects of pollution of the Illinois River by raw 
 sewage from Chicago have, of course, varied widely according to a number 
 of local and temporary conditions. Being greatest at the upper end of the 
 river at mid-summer temperatures, and at low water, and increasing with 
 the population of the Sanitary District and with the activity of operations 
 at the Chicago Stock Yards, they have diminished downstream, with lower 
 temperatures of the advancing season, and with the rise of the river levels. 
 At their worst they have destroyed or driven from the upper Illinois all its 
 clean-water plants and animals, including, of course, its fishes, substituting 
 for them those normal to septic or pollutional conditions. In the mid- 
 summer of 1911 the upper ten miles of the river were practically a septic 
 tank, the gases of the bottom sludges being 79% methane; 19% carbon 
 dioxide; 1.02% nitrogen; 0.56% carbon monoxide; 0.03% oxygen. There 
 
33 
 
 were no fishes in that part of the stream, or for many miles below, and no 
 moUusks or crawfishes on the bottom, the only animals there being sludge 
 worms, certain midge larvae, and other foul water forms able to live without 
 oxygen on the crude sewage precipitates. From this extreme condition 
 there was a gradual shading off downstream until at a distance of sixty to 
 seventy miles from the point of entrance of Chicago sewage the plant and 
 animal life of the stream was virtually normal. Seven years later, however, 
 that is, in 1918, pollutional conditions had moved downward some 60 miles 
 farther, the river being at this time nearly deserted by fishes as far as the 
 Peoria lakes, 93 miles down the stream, characteristic sewage organisms 
 having extended their range in thrifty condition to 77 miles from its origin, 
 and the areas of offensive pollution, distinguished by a stinking sludge con- 
 taining an abundance of sewage worms and no clean water organisms, had 
 moved downstream from Ottawa to Lacon, a distance of 51 miles, 
 
 "An expansion of the river 17 miles long and up to a mile in width, 
 known as Peoria Lake, (although really a chain of three lakes connected by 
 so-called narrows) served as a partial barrier to a further extension of the 
 conditions of the upper river until the period of the world war when, coin- 
 cident with an enormous increase in the organic wastes of the Chicago 
 stockyards, these pollutional conditions were still further extended and 
 intensified, culminating in 1920 in a virtual extermination of the original life 
 of the river bottom as far down as Peoria Lake and in the lake itself and 
 in the substitution for it of plants and animals usually to be found only in 
 heavily polluted water. 
 
 "With the close of the war and a diminished outpouring of stockyards 
 sewage, there has been a noticeable improvement of conditions in Peoria 
 Lake, although in 1922 they were still far below their pre-war status; but in 
 this year 1924, which has been characterized by an extraordinary high water 
 level of unexampled long continuance, Chicago sewage has been so far 
 diluted that fishes have ascended the stream to LaSalle, 60 miles above 
 Peoria and only 50 miles from the river head, 
 
 "There seemed at one time to be good general ground for believing that 
 the addition of household sewage to a stream might increase its fisheries 
 yield, especially where, as in the Illinois River, this addition was made 
 far enough above the more productive fishing grounds to permit the oxida- 
 tion of nitrogenous materials and their conversion into forms available as 
 food for fishes young or old, but our more recent computations show that 
 there has always been an abundance of food in the Illinois River for a 
 much larger stock of fishes than it carried — that the food supply, in other 
 words, has not been the limiting factor in the river fishes, and that an in- 
 crease of it consequently could not be a benefit, 
 
 "The product of this present season's operations on the river has not 
 yet been sufficiently worked up to give us more than fragments of the biolo- 
 gical picture, but one feature may be of special interest to sanitary engineers. 
 We found in the summer of 1911 that heavy rains at a given point, followed 
 by a rise in the river, increased the organic contents of the water and 
 diminished the ratios of dissolved oxygen, the latter effect being continued 
 downstream as putrefaction increased, so that oxygen ratios were actually 
 diminished downwards instead of increasing as they usually do; and this 
 
34 
 
 effect of local contamination by washing rains was still more clearly shown 
 this summer by bacterial data contributed by the State Water Survey. 
 Taking, for example, two points below Peoria which were six miles apart 
 with a tributary stream between them; on July 31 the water at the upper- 
 most of these points averaged 8000 bacteria to the c. c. and that at the lower 
 point 32,000, while on August 8, soon after a very heavy rain, when the 
 upper count was 4,000 instead of the former 8,000, the lower count was 
 120,000 instead of the former 32,000, this jump in numbers being evidently 
 due to the muds swept in from the tributary after the storm. 
 
 "Time fails me to attempt to follow the effect of Chicago pollution 
 beyond the wide water of Peoria Lake, where the situation becomes com- 
 plicated, indeed, by a heavy addition of fresh sewage from Peoria itself and 
 from the city of Pekin, 9 miles below, and it is certain that in 1920 this lake 
 barrier was being forced and that the life of even the lowest of the chain 
 of three was far from normal — that the lakes were delivering to the river 
 beyond a considerable part of the load of trouble which they had received 
 from above." 
 
 It is impracticable definitely to show the progressive deterioration 
 in the quality of the water in the Illinois River throughout the entire 
 period during which the Drainage Canal has been contributing flow, 
 for the reason that during this period of twenty-five years the technique 
 of water analysis has changed so that results cannot be compared numer- 
 ically. No such comprehensive studies as that undertaken by the U. S. 
 Public Health Service have been made. More or less fragmentary 
 studies, however, indicate the increasing pollution with the growth of 
 the population and industries in Chicago. 
 
 We show on Figure 9 a series of dissolved oxygen readings made 
 by the State W ater Survey covering six round trips between July 22nd 
 and September 11th, 1911, a single trip between July 11th and July 13th, 
 1912, a single trip between August 28th and September 3rd, 1918, and 
 four round trips between July 15th and September 17th, 1920. This dia- 
 gram indicates that in 1911 the summer oxygen content was fairly satis- 
 factory up-stream as far as Marseilles. In 1918 and 1920 the conditions 
 were very similar to those typified by the Public Health studies as far 
 south as Chillicothe. 
 
 Ice Conditions. 
 
 Although the conditions on the Illinois River during the winter are 
 generally favorable as regards nuisance, and not particularly detrimental 
 to the natural life of the stream, yet occasionally protracted cold 
 weather and an unusually extensive covering of ice brings about unfa- 
 vorable conditions During the winter of 1924 and 1925 this unfavor- 
 able condition prevailed. 
 
 An investigation under the direction of Dr. Forbes brought out the 
 following facts. In Clear Lake, below Pekin, the dissolved oxygen con- 
 
35 
 
 tent of the water varied from 0.4 to 1.8 p. p. m. All kinds of fish were 
 found to be dead in set nets and also under the ice outside of the nets. 
 At Quiver Lake, just above Havana, where the water contained 2.5 
 p. p. m. a river seine hauled under the ice gave carp, buffalo and gars ; 
 
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 all stupid, pallid in color and of a disagreeable odor called "gassy" by 
 fishermen, characteristic of fish taken from polluted water. At Tread- 
 way Lake, near Meredosia, where the oxygen content was 5.4 to 5.8^ 
 practically the entire variety of river fish were being taken in hoop nets, 
 all in good condition. 
 
 Similar conditions were noted by the State Natural History Survey 
 in 1912. This condition unfavorable to fishes is brought about through 
 organic pollution in the water, coupled with the inability of the stream 
 to replenish its oxygen supply from the air. That these conditions are 
 due to sewage pollution is shown by recent observations of Dr. Forbes* 
 department, referring to Clear Lake, Quiver Lake, Coleman and Tread- 
 way Lakes. Also in Quiver Creek. Clear Lake is the farthest upstream 
 and contains only river water which begins to enter into it when the 
 river is three and one-half or four feet above low water mark at Peoria. 
 Conditions there were as previously described. Quiver Lake receives 
 water continually from the river, but also from Quiver Creek, an un- 
 polluted stream. Its condition is consequently not so deadly as that of 
 Clear Lake, although the mass of its water comes from the river. 
 
 Treadway and Coleman Lakes are 8 or 9 miles above Beardstown, 
 on the same side of the river and a little distance below the mouth of 
 the Sangamon, an unpolluted stream, from which they receive a large 
 part of their water. 
 
 Investigations in the above lakes show a gradation from practical 
 complete destruction of fish under the ice at Clear Lake, most open to 
 pollution, to normal conditions at Coleman and Treadway Lakes, also 
 frozen over but filled mainly with Sangamon River water. The Quiver 
 Creek, tributary of Quiver Lake, is reported to have shown 11.9 to 12.3 
 of oxygen, and to have yielded in hoop nets put down over night vigor- 
 ous and active European carp, native carp, or quill-back, buffalo, gars, 
 channel cat, bullheads, black bass, striped bass and sheepshead, a good 
 variety of ordinary fish in good condition. 
 
 Thus it will be noted that the fish which were in distress were oc- 
 cupying polluted waters, and were apparently not affected by the unpol- 
 luted streams, even although the same were ice bound. 
 
 In this connection it should be noted, however, that in natural lakes 
 and rivers, unpolluted by sewage, the exhaustion of oxygen and the dis- 
 tress of fishes may occur under the ice due to the decomposition of vege- 
 table organisms. The distress of fish in the ice bound condition of the 
 stream was observed upon the Illinois River prior to 1900. This situa- 
 tion may or may not have been brought about by sewage contamination. 
 While the stream did not receive a large pollution from Chicago it was 
 rather heavily polluted at Peoria, which may have contributed to the un- 
 

 
 
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37 
 
 favorable conditions noted. Relatively speaking the river as a whole 
 was an unpolluted stream at that time. 
 
 Future Effect of Water-Way Improvement. 
 
 When the Illinois water-way is built some changes will be brought 
 about in the river conditions, principally between Lockport and LaSalle. 
 In this reach of the Des Plaines and Illinois Rivers it is proposed to im- 
 prove the same on the basis of slack water navig'ation. To accompHsh 
 this purpose dams will be constructed at Brandon Road, Dresden Island, 
 Marseilles and Starved Rock. The pond created by each of these dams 
 will extend to the foot of the next dam up-stream. 
 
 At the present time the water occupies a period of about thirty- 
 seven hours in its passage from Brandon bridge to LaSalle. Except 
 for the pond created by the present Marseilles dam the current is rapid 
 and conditions are favorable for the absorption of atmospheric oxygen. 
 
 After the construction of the water-way based on present plans, 
 contemplating a flow of about 10,000 second feet, the time of travel be- 
 tween Joliet and LaSalle will be increased to about 66 hours. The 
 water surface area in this reach of the stream is about 10.5 square miles 
 at the present time. The dams will increase it to about thirteen square 
 miles. 
 
 Below LaSalle the flow of water is much less rapid. Six and one- 
 half days is at present required for it to flow from LaSalle to Peoria. 
 The total time of flow from Joliet to the mouth of the Illinois River is 
 about thirteen days at summer stages with present flows. 
 
 With the improved water-way assuming a flow of 10,000 second 
 feet conditions below LaSalle will not be greatly changed. Proposed 
 plans contemplate water surface elevations which differ not greatly from 
 those prevailing at present. With this flow, however, the existing dams 
 will probably be taken out. 
 
 Thus the net result of the construction of the water-way will be 
 practically to double the time of travel from Joliet to LaSalle, and to 
 increase the area of water surface about twenty-five percent. Below 
 LaSalle conditions will remain about as at present. 
 
 Conditions with Smaller Diversions. 
 
 If the diversion of water from Lake Michigan is very much below 
 10,000 second feet the plan for the Illinois water-way will probably 
 require the retention of the present dams below LaSalle. Above La- 
 Salle the dams contemplated under a 10,000 second foot flow would 
 probably be unchanged, and the existing areas would not be greatly al- 
 tered as compared to the larger flow. The time of travel, however. 
 
38 
 
 would be increased approximately in an average ratio to the quantity of 
 water flowing. 
 
 Rough approximations of the time of travel, assuming various 
 quantities flowing in the stream would be as follows : 
 
 TIME OF TRAVEL IN DAYS. 
 
 Joliet LaSalle 
 
 to to mouth of 
 
 LaSalle Illinois River 
 
 10,000 feet per second 2.7 14.5 
 
 8,500 " " " 3.2 17 
 
 7,500 " " " 3.6 19 
 
 4,167 " " " 6.4 35 
 
 2,000 " " " 13 73 
 
 It is believed that the net effect of the construction of the water- 
 way will be to introduce into the Illinois River a series of four ponds 
 above LaSalle, which may be expected to have a similar effect to that 
 now produced in Lake Peoria. It is believed that the net effect upon 
 the stream under present pollution and diversion conditions would be to 
 throw the "dead line" now existing near Peoria Lake much further up- 
 stream. 
 
39 
 
 PART III 
 
 POPULATION AND GROWTH. 
 
 Chicago has grown from a frontier trading post to the third city 
 of the world within a period of ninety years. It is the commercial and 
 transportation center of the largest and richest agricultural community 
 on this continent. Its position is such, as regards lines of communica- 
 tion, that it will continue to be the hub of interior America. Its future 
 development must inevitably follow the development of a vast interior 
 region, the limits of growth for which cannot be predicted. 
 
 In planning sewage disposal works for this great industrial center, 
 it obviously will be wise to plan for a larger future growth. It is not 
 financially practicable, however, nor is it wise to build very far in ad- 
 vance of immediate requirements. It is practicable, however, to plan 
 for future growth, and to build upon a unit system so that units may be 
 built a little in advance of need. If the plan is wisely made each unit 
 so built will be permanently useful. It will constitute a link in a future 
 chain of sev/age disposal works. Thus each dollar invested will be a 
 permanent investment. If the growth is more rapid than anticipated, 
 units can be added more rapidly, and assessed valuations will be avail- 
 able to meet the necessary charges. If growth is less rapid than is an- 
 ticipated, works constructed from year to year will be useful for a longer 
 time. 
 
 Population — Sanitary District: 
 
 The Sanitary District of Chicago includes fifty-two towns and 
 villages lying within Cook County, Illinois. The population by 1920 
 census was 2,978,635, of which 2,701,705 or ninety-one percent was resi- 
 dent within the corporate limits of the City of Chicago. Table 5 is a 
 statement of the population within the present boundaries of the Sani- 
 tary District in the census 1900 to 1920 inclusive. Within this period 
 the population of the district increased sixty-seven percent. The out- 
 lying towns and villages practically trebled in population during the two 
 decades. 
 
 Greater Chicago Region: 
 
 Since 1900 municipal growth has extended beyond the Illinois bor- 
 der line into Northern Indiana, in which a great industrial region is 
 developing, served by numerous main lines of railroad and new lake 
 
40 
 
 harbors, which have been built at Gary and East Chicago. Improved 
 labor conditions in the outlying localities, adjacent to Chicago, have 
 favored the location of certain industries, on the borders of the city 
 limits, and in certain cities outside of Cook County. The greater 
 Chicago region, as defined by U. S. census, includes Cook, Kane, Du- 
 Page, Lake and Will Counties in Illinois and Lake County in Indiana. 
 The total population of this region was 3,521,789 in 1920. It had in- 
 creased seventy-five percent in the two decades following 1900. Table 
 6 shows the population within this region for each county for the last 
 three census years. As will be noted the Sanitary District of Chicago 
 includes approximately eighty-five percent of the total population of the 
 greater Chicago region. 
 
 TABLE 5 
 
 POPULATION OF CITIES AND VILLAGES IN THE SANITARY DISTRICT 
 
 OF CHICAGO 
 
 Population 
 
 Name 
 
 1900 
 
 1910 
 
 1920 
 
 
 
 943 
 
 1,881 
 
 
 
 5,841 
 
 14,150 
 
 
 6.114 
 
 8,043 
 
 11,424 
 
 
 
 
 
 Brookfield (village) 
 
 1,111 
 
 2,186 
 
 3,589 
 
 Burnham (village) 
 
 
 328 
 
 795 
 
 
 
 
 1,237 
 2,701,705 
 
 Chicago (city) 
 
 , 1,698,575 
 
 2,185,283 
 
 Cicero (town) 
 
 16,310 
 
 14,557 
 
 44,995 
 
 DesPlaines (village) 
 
 1,666 
 
 2,348 
 
 3,451 
 
 Dolton (village) 
 
 1,229 
 
 1,869 
 
 2,076 
 
 Elm wood Park (village) 
 
 
 
 1,380 
 37,234 
 
 
 18,721 
 
 25,668 
 
 
 445 
 
 424 
 
 705 
 
 
 4,085 
 
 6,594 
 
 10,768 
 
 
 483 
 
 683 
 
 914 
 
 
 1,020 
 
 1,899 
 
 3,381 
 
 
 
 652 
 
 760 
 
 
 5,395 
 
 7,227 
 
 9,216 
 
 
 
 
 127 
 
 Hinsdale (village) (DuPage County) . . . 
 
 2,578 
 
 2,451 
 
 3,975 
 
 
 336 
 
 881 
 
 1,188 
 
 
 3,969 
 
 5,282 
 
 6,526 
 
 
 730 
 
 1,131 
 
 1,684 
 
 
 951 
 
 1,483 
 
 2,564 
 
 
 4,532 
 
 8,033 
 
 12,072 
 
 
 2,592 
 
 4,806 
 
 7,147 
 
 
 564 
 
 836 
 
 1,079 
 
 
 190 
 
 276 
 
 1,441 
 
 
 514 
 
 569 
 
 1,258 
 
41 
 
 
 eon 
 
 ceo 
 
 763 
 
 Northbrook (Schermerville) (village).... 
 
 
 
 CCA 
 
 554 
 
 
 
 
 
 
 3,447 
 
 5,251 
 
 6,897 
 
 Oak Park (village) 
 
 
 19,444 
 
 39,858 
 
 Park Ridge (city) 
 
 1,340 
 
 2,009 
 
 3,383 
 
 
 
 end 
 679 
 
 -1 rtoo 
 
 l,9od 
 
 
 
 AO 
 
 94 < 
 
 
 558 
 
 917 
 
 1,166 
 
 River Forest (village) 
 
 1,539 
 
 2,456 
 
 4,358 
 
 River Grove (village) 
 
 333 
 
 418 
 
 484 
 
 Riverside (inc. N. Riverside) (village) . . . 
 
 1,551 
 
 1,702 
 
 2,532 
 
 Riverview (village) 
 
 406 
 
 312 
 
 334 
 
 
 
 
 431 
 
 
 
 
 390 
 
 South Holland (portion village) 
 
 766 
 
 1,065 
 
 1,247 
 
 Stickney (village) 
 
 
 
 550 
 
 
 547 
 
 949 
 
 4,019 
 
 
 
 359 
 
 355 
 
 Western Springs (village) 
 
 662 
 
 905 
 
 1,258 
 
 West Hammond (Calumet City) (city) . . . 
 
 ^,9o5 
 
 4,948 
 
 7,492 
 
 
 2,300 
 
 4,943 
 
 7,814 
 
 Winnetka (village) 
 
 1,833 
 
 3,168 
 
 6,694 
 
 
 1,788,278 
 
 2,338,278 
 
 2,978,635 
 
 Total population, excluding Chicago. 
 
 89,703 
 
 152,995 
 
 276,930 
 
 TABLE 
 
 6 
 
 
 
 POPULATION OF THE CHICAGO 
 
 METROPOLITAN DISTRICT 
 
 
 1900 
 
 1910 
 
 1920 
 
 County 
 
 Census 
 
 Census 
 
 Census 
 
 
 1,838,735 
 
 2,405,233 
 
 3,053,017 
 
 
 78,792 
 
 91,862 
 
 99,499 
 
 
 28,196 
 
 33,432 
 
 42,120 
 
 
 34,504 
 
 55,058 
 
 74,285 
 
 Will 
 
 74,764 
 
 84,371 
 
 92,911 
 
 
 37,892 
 
 82,864 
 
 159,957 
 
 Total 
 
 2,092,883 
 
 2,752,820 
 
 3,521,789 
 
 Chicago Growth Compared to Other Cities: 
 
 We show on Figure 11 a diagrammatic representation of the 
 growth of Chicago with a comparison of the growth of London and 
 New York, the only cities which exceed it in population ; also several 
 other cities. It will be observed that the rate of growth of Chicago has 
 been exceeded only by that of New York, which has been largely in- 
 fluenced by annexations. Figure 12 is a similar diagram showing a 
 little more clearly the growth of the Chicago region, as compared to 
 
42 
 
 London and New York, the population of these two cities being platted 
 for the several decades immediately before and after the time when they 
 passed the three million mark, without regard to the year. 
 
 Within the past ten years there have been several comprehensive 
 studies of the future growth of Chicago and vicinity ; more particularly 
 the studies for the Chicago Traction Commission, the Commission on 
 Smoke Abatement and also several studies concerning the improvement 
 of the Chicago Water Works. The Chicago Telephone Company neces- 
 sarily keeps itself quite accurately informed as to the probable require- 
 ments for the extension of its service. It has recently made a study of 
 the growth of the Chicago region. 
 
 YtAR 
 
 Figure 11. — Population growth of Chicago and other large cities, with city- 
 engineer's forecast for the city of Chicago. 
 
43 
 
 All these investigations substantiate, with reasonable accuracy, 
 the figures which have been prepared by the Sanitary District of Chi- 
 cago, as representing the most probable future population of the Sani- 
 tary District so far as it can be determined in the light of past growth 
 and recent development in this region. 
 
 Forecast of the Sanitary District: 
 
 We show diagrammatically on Figure 12 the forecast of the Sani- 
 tary District for the population within the Sanitary District up to the 
 year 1970. In designing sewage purification works it will be important 
 
 iqoo iqio iq^o is^o iq4o iq^o isfco iq7o 
 
 (Do+cs refer +o loco! Popub-f ion onli^) 
 
 1. Chicago oni_y,Teacxioni Co. FoeECAST 
 
 2. II M A-.SN.OF COMfs^e.R.CE. Sn/\0<H. CoMM.'FoE.e.CAST 
 
 Figure 12. — Population growth and forecast for the Sanitary District of 
 Chicago and City of Chicago in comparison with growth of other 
 large cities. (Dates refer to local population only). 
 
 1. Chicago only, Traction Co. forecast. 
 
 2. Chicago only, Assn. of Commerce Smoke Comm. forecast. 
 *Note — Estimate of the Sanitary District of Chicago. 
 Greater London population 3,000,000 in 1857. 
 
 Greater New York population 3,000,000 in 1895. 
 
44 
 
 D iaqram Showinq 
 
 Population By Districts 
 Estimate op 5anitarv District 
 of chicago 
 
 To Accomporn^ R.cpor4- o-P 
 A\_VORD, &URD\CX;8cH0W50M 
 
 2.000,000 
 
 l,cioo,ooo 
 
 \.8oo,ooo 
 
 l.'/oopoo 
 
 1.600,000 
 
 t,5oo,ooo 
 
 1,4-00,000 
 
 !. 300.000 
 
 1.200,000 
 
 l,!00,000 
 
 1,000,000 
 cfoo.ooo 
 8do,ooo 
 700.000 
 €>oo,ooo 
 5oo,ooo 
 4oo,ooo 
 3oo,ooo 
 2oo,ooo 
 
 NAo iq5o 
 Vear 
 
 loo. 000 
 
 iq-io 
 
 Figure 13. — Population by districts. Estimate of Sanitary District 
 
 of Chicago. 
 
45 
 
 to determine present and prospective populations by locality, as a basis 
 for determining- the amount of sewage delivered to each plant. Table 
 7. shows the estimate of the Sanitary District for each future decade, 
 divided as between five localities in which purification works will prob- 
 ably be required. Figure 13 shows the same facts diagrammatically. 
 This diagram is chiefly useful in illustrating the comparative rates of 
 growth in the different parts of the district, and in preparing approxi- 
 mate estimates of population for the years intermediate between the 
 census years. 
 
 TABLE 7 
 
 PRESENT AND FUTURE POPULATION OF AREAS TRIBUTARY TO 
 TREATMENT PLANTS, AS ESTIMATED BY THE SANITARY 
 DISTRICT OF CHICAGO 
 
 Total 
 
 North West all 
 
 Year Side Side Calumet S. W. Side Misc. Plants 
 
 1920 590,000 1,300,000 160,000 850,000 100,000 3,000,000 
 
 1930 800,000 1,430,000 225,000 1,040,000 215,000 3,710,000 
 
 1935 915,000 1,490,000 255,000 1,135,000 275,000 . 4,070,000 
 
 1940 1,015,000 1,550,000 290,000 1,230,000 340,000 4,425,000 
 
 1950 1,230,000 1,680,000 350,000 1,415,000 465,000 5,140,000 
 
 1960 1,450,000 1,800,000 415,000 1,600,000 595,000 5,850,000 
 
 1970 1,670,000 1,920,000 480,000 1,780,000 730,000 6,580,000 
 
 Distribution of Population: 
 
 We present herewith Figures 14 and 15 which show a diagram- 
 matic representation of the distribution of the population of Chicago and 
 vicinity for the census year 1920, and the population distribution as it 
 will probably be in 1940. These diagrams were prepared by the Illi- 
 nois Bell Telephone Company ; each spot on the diagrams represents 
 100 families. These diagrams serve to indicate the most favorable loca- 
 tions for sewage purification works. As will be pointed out later the 
 Sanitary District has apparently selected the most favorable sites possi- 
 ble for purification works, in that localities have been chosen as remote 
 as possible from present and future habitation, with due regard to 
 proximity to the districts contributing sewage. 
 
Figure H.— Map of Chicago showing distribution of population in 1920. 
 
Figure 15. — Map of Chicago showing distribution of population in 1940. 
 
48 
 
 PART IV 
 
 AMOUNT AND QUALITY OF SEWAGE. 
 
 In a study of the sewage problem of any community, a knowledge 
 of the volume and quality of the sewage is of primary importance. 
 
 With respect to quality, sewages are often classified as domestic 
 and industrial, and the use of these terms is generally intended to convey 
 the idea that domestic sewage is that resulting from strictly domestic or 
 household operations, while industrial sewage is that resulting from 
 manufacturing or industrial operations. 
 
 A strictly domestic sewage consists of the water-borne wastes re- 
 sulting from household operations in the laundry, kitchen, bathroom, 
 and toilet and the qualitative character of such wastes is substantially the 
 same in any community where the habits of life of the people do not 
 differ materially. Sewage of a strictly domestic character is rarely 
 encountered in large cities, as most, if not all, of our large cities have 
 more or less varied industries, which produce waterborne wastes differ- 
 ing in quality from strictly domestic sewage. The character and extent 
 of industrial operations consequently are largely responsible for any 
 wide differences in quality which may be found in the sewages of 
 various cities. 
 
 Measurement of Load: 
 
 Various analytical determinations are made today to give expres- 
 sion to the quality or composition of sewage, such as total nitrogen, free 
 ammonia, suspended solids, settleable solids, oxygen absorbed from 
 permanganate, stability value, biochemical oxygen demand, etc., and in 
 the discussion of the quality of sewage, the only analytical value which 
 will be used for the present will be that secured by the biochemical oxy- 
 gen demand test. 
 
 The biochemical oxygen demand test consists of incubating a 
 known volume of sewage with known volumes of pure water containing 
 a known supply of oxygen in solution, and observing the rate at which 
 the oxygen is exhausted, also, the total amount of oxygen required to 
 effect a complete combustion of the putrescible matter in the sewage. 
 The incubation is carried out at a constant temperature, usually twenty 
 degrees C, and for a sufficient number of days to accomplish a practic- 
 ally complete destruction of the readily oxidizable material in the sew- 
 
49 
 
 age. This test attempts to show what happens in the way of oxygen 
 depletion in a stream of pure water when it is polkited with sewage. 
 
 It has long been known that streams are able to affect a destruction 
 of putrescible matter and after doing so to recover their original purity. 
 When sewage is discharged into a stream of water there begins a drama 
 with three actors, namely putrescible matter, bacteria and oxygen. 
 Bacteria and oxygen combine to destroy putrescible matter, and if the 
 bacteria have an ample supply of oxygen, putrescible matter is destroyed 
 in a quiet and orderly manner, but if the supply of oxygen is inadequate, 
 the drama may develop into a tragedy, and although the bacteria will 
 eventually triumph, the stream will suffer considerably from the exper- 
 ience. 
 
 The problem then is one of oxygen supply, if sewage destruction is 
 to be accomplished without offense, and there are a number of factors 
 which govern the supply of and demand for oxygen in a polluted stream 
 of water. One second foot of pure water at a temperature of 32° F. 
 is saturated when it carries 79 pounds of oxygen in solution in a twenty- 
 four hour period, whereas at a temperature of 86° F., it is saturated 
 when it carries 41 pounds of oxygen in solution. On the other hand, 
 the activity of the bacteria which destroy the putrescible matter, is al- 
 most nil at 32 degrees F., whereas at 86 degrees F., they are exceedingly 
 active. It is thus apparent that in cold weather there is a large oxygen 
 content in the water and a low rate of demand, whereas in warm 
 weather there is a low oxygen content in the water and a high rate of 
 demand. 
 
 R e aeration: 
 
 An additional factor in the recovery of a stream from pollution is 
 that of reaeration, which is more rapid in warm weather than in cold, 
 and also increases with the degree of depletion; i. e., if the water is 
 saturated, there will be no reaeration, if it has a zero saturation, the 
 reaeration will be at a maximum for any given condition, and the rate 
 of reaeration will decrease as the oxygen deficit decreases. Other fac- 
 tors affecting reaeration are turbulence and depth, the replenishment in- 
 creasing with the turbulence and decreasing with the depth. 
 
 Example of Oxygen Requirement: 
 
 As a concrete example of the relation of the oxygen demand of a 
 sewage and the oxygen supply of a stream, it will be assumed that one 
 second foot of sewage per day, or a total of 646,000 gallons has, by the 
 biochemical ox3^gen demand test, been shown to require 820 pounds of 
 oxygen to destroy its putrescible matter, and, that it is desired to mix 
 this second foot of sewage with enough second feet of saturated water 
 
so 
 
 at 86 degrees F. to supply all the oxygen required. The one second 
 foot of sewage per day require^ 820 pounds of oxygen and one second 
 foot of water per day at 86 degrees F. will supply 41 pounds of oxygen, 
 consequently twenty second feet of water will be required, neglecting, of 
 course, reaeration. 
 
 Reaeration is no doubt a big contributor to the total oxygen re- 
 quired to destroy putrescible matter in a stream, but, as it has a value 
 which is a resultant of depth of water, turbulence, temperature, and 
 degree of depletion, it is difficult to give it quantitative expression. The 
 efficacy of reaeration in preventing complete depletion of oxygen in a 
 stream is probably closely related to the excessive demand for oxygen 
 which occurs during the early stages of the incubation of the sewage 
 and stream water. 
 
 The results of many studies of the oxygen demand of mixtures of 
 pure water and sewage when incubated in closed containers, which pre- 
 vent reaeration, have indicated that on the basis of the total amount of 
 oxygen absorbed in twenty days at twenty degrees C, twenty-one per- 
 cent will be required the first day, sixteen percent the second day, thir- 
 teen percent the third day, eleven percent the fourt day and seven per- 
 cent the fifth day, making a total of sixty-eight percent for the first five 
 days. The second five days will require twenty-two percent of the total 
 and the next ten days, ten percent of the total of which, however, but 
 three percent is required in the last five days. 
 
 These rates are indicative of a general average result rather than 
 absolutely specific, and are given to show the need for a good supply of 
 oxygen during the first few days of contact between sewage and stream 
 water. In converting a given oxygen demand value secured by a given 
 period of incubation, to an oxygen demand value for a longer or shorter 
 period of incubation, the above rates of satisfaction have been used, as 
 the results of experimental studies in many places have shown them to 
 be reasonably reliable. 
 
 If the supply of oxygen, which the diluting water carries in solu- 
 tion, is insufficient to meet the needs of the wet combustion process 
 which takes place in a polluted stream, reaeration conditions may be 
 such that the oxygen supplied in that way will be used up as fast as it 
 is absorbed and distributed and the water of the stream will be left in a 
 condition of zero saturation. 
 
 With these considerations in mind, a study of daily oxygen require- 
 ments of the sewage of the Sanitary District of Chicago has been made, 
 and the results of this study are herewith presented. 
 
51 
 
 Load of Sanitary District: 
 
 There are two ways of expressing' the daily oxygen requirements, 
 namely, as a definite number of pounds of oxygen per person per day, 
 or, as a total number of pounds of, oxygen per day for the entire district. 
 
 The determination of the total daily oxygen load from a represen- 
 tative district divided by the population contributing to this load, will 
 give a per capita daily load which may be applied to the whole district. 
 In the event that there are large industrial loads that have a 
 marked effect on the total load, such industrial loads should be deter- 
 mined separately and added to the total load as estimated from the rep- 
 resentative district, in which event, the human population per capita 
 load will be increased, or, the industrial loads may be converted into an 
 industrial equivalent population load, in which case the human popula- 
 tion plus the industrial equivalent population times the human population 
 per capita load will give the total load. 
 
 A common way of expressing an industrial load is to convert it 
 into an equivalent human population, but in order to avoid confusion, 
 no use has been made of the industrial equivalent population. 
 
 The sewage of the entire Sanitary District of Chicago is discharged 
 by approximately 150 sewers, varying in diameter from two feet to 
 sixteen feet, into the north and south branches of the Chicago River, the 
 Des Plaines River, the Calumet River, and the Drainage Canal, making 
 it very difficult to get an accurate determination of the sewage flow of 
 the entire district. 
 
 Thirty-Ninth St. Studies 1914: 
 
 During the year 1914, hourly samples of sewage were taken at the 
 39th St. sewage pumping station, and dosed with nitrate solution of 
 known concentration, then allowed to incubate for ten days. At the end 
 of the ten-day period of incubation, the twenty-four hourly samples were 
 composited without correction for flow fluctuations and the residual 
 nitrite and nitrate determined on the composite sample. The oxygen 
 demand value secured in this way was taken as the mean value for the 
 day. The incubation was not carried out at a constant temperature, but 
 at whatever temperature happened to exist where the incubating samples 
 were stored. 
 
 The average oxygen demand as determined in this manner after a 
 ten-day incubation was found to be 121 parts per million, which means 
 that 121 pounds of oxygen would be required to destroy the putrescible 
 matter in one million pounds of sewage, or 1008 pounds of oxygen 
 would be required for one million gallons of sewage. The average rate 
 of pumpage was found to be 71 million gallons per day ( or *219 gals. 
 
 *Note — Total XDity pumpage year 1914, 2.54 g-als. per capita. 
 
52 
 
 per capita), and this was secured by taking the daily records of the 
 speed of the pumps and determining the discharge by using the manu- 
 facturer's speed, capacity, and head curves. There is some doubt as to 
 the accuracy of this method in determining the discharge of the pumps. 
 
 The population of the district contributing sewage to this station was 
 estimated at 324,000. On the basis of the above data the 
 daily per capita oxygen load was 1008 pounds times 71 M. G., 
 divided by v324,000 or 0.22 pounds of oxygen, on a ten-day oxygen de- 
 mand basis. 
 
 Thirty-Ninth St. Studies, 1920: 
 
 Between November 8th, 1920, and December 11th, 1920, a similar 
 investigation was made at the 39th St. sewage pumping station. The 
 oxygen demand was determined by the dilution method after a ten-day 
 incubation at a constant temperature of twenty degrees centigrade. 
 Samples were taken hourly, with four consecutive hourly samples com- 
 posited for a single oxygen demand test. Six composited samples per 
 day w^ere subjected to the oxygen demand test, and the mean of the six 
 values was taken as the daily mean value. No attempt was made to 
 weight samples to conform with hourly flow fluctuations. 
 
 The average oxygen demand after a ten-day incubation at 20 de- 
 grees C, was found to be 140 parts per million, which means that 1166 
 pounds of oxygen would be required to destroy the putrescible matter in 
 one million gallons of sewage. The average rate of pumpage was 
 found to be 86.17 million gallons per day ( or *207 gals, per capita), 
 the same being estimated as in the previous test. The population was 
 estimated to be 417600 and on the basis of the above data the daily per 
 capita ox3^gen load was 1166 pounds times 86.17 M. G. divided by 
 417600 or 0.24 pounds of oxygen on a ten-day oxygen demand basis. 
 
 Des Plaines Studies: 
 
 The operating results for the Des Plaines treatment works for the 
 year 1924 show an average daily sewage flow of four million gallons, 
 an average ten-day oxygen demand of 153 and a tributary population of 
 40000 and on the basis of the above data the daily per capita oxygen 
 load was 153 pounds times 8.33 times 4 M. G. divided by 40000 or 0.127 
 pounds of oxygen on a ten day oxygen demand basis. 
 
 Calumet Studies: : 
 
 The operating results for the Calumet treatment works for the year 
 1924, show an average daily sewage flow of thirty million gallons, an 
 average ten-day oxygen demand of eighty and a tributary population 
 
 *Note — Total city pumpage year 1920, 27G gals, per capita. 
 
53 
 
 of 107,000, and on the basis of this data, the daily per capita oxygen load 
 was 80 pounds times 8.33 times 30 M. G. divided by 107000 or 0.187 
 pounds of oxygen. 
 
 Comparison with Other Cities: 
 
 In Table 8, a comparison may be made between Chicago sewage and 
 that of other American and English cities. It is quite apparent from 
 the data contained in this table that Chicago sewage is considerably 
 stronger than the average strength of sewages listed in the table. 
 
 Industrial Load: 
 
 The Chicago industrial load is quite large in the aggregate, the 
 principal elements of which, in the order of their magnititde, are as 
 
 TABLE 8 
 
 TABLE SHOWING THE STRENGTH OF MUNICIPAL SEWAGES ON THE 
 BASIS OF THE OXYGEN REQUIREMENT IN POUNDS PER 
 CAPITA PER DAY 
 
 Gallons 
 
 
 sewage 
 
 5-Day 
 
 Pounds 
 
 
 per capita 
 
 oxygen 
 
 oxygen 
 
 
 per day by 
 
 demand 
 
 required 
 
 
 contributing 
 
 in 
 
 per capita 
 
 Ref. City 
 
 population 
 
 P. P. M. 
 
 per day 
 
 
 131 
 
 92 
 
 0.100 
 
 Baltimore, Md 
 
 106 
 
 120 
 
 0.106 
 
 Canton, Ohio 
 
 64 
 
 213 
 
 0.113 
 
 Columbus, Ohio 
 
 94 
 
 190 
 
 0.148 
 
 
 88 
 
 155 
 
 0.114 
 
 
 89 
 
 144 
 
 0.107 
 
 
 101 
 
 118 
 
 0.099 
 
 Rochester, N. Y 
 
 137 
 
 104 
 
 0.119 
 
 B Malton, Eng 
 
 40 
 
 467 
 
 0.155 
 
 C Huntingdon, Eng 
 
 27 
 
 475 
 
 0.107 
 
 D Brooklyn, N. Y 
 
 102 
 
 223 
 
 0.189 
 
 Min. value 
 
 
 
 0.099 
 
 Max. value 
 
 
 
 0.189 
 
 
 35 
 
 350 
 
 0.102 
 
 Strong Eng. Sewage 
 
 35 
 
 500 
 
 0.146 
 
 
 206 
 
 106 
 
 0.182 
 
 G Chicago 
 
 219 
 
 91 
 
 0.167 
 
 H Chicago 
 
 100 
 
 122 
 
 0.102 
 
 I Chicago 
 
 280 
 
 64 
 
 0.149 
 
 References: A. U. S. Public Health Service Bull., No. 132, p. 115. 
 
 B. Eighth Report Roy. Com. Sew. Disp. Vol. 2, Appendix, pages 27, 68, 81.. 
 
 C. Eighth Report Roy. Com. Sew. Disp. Vol. 2, Appendix, page 20. 
 
 D. Brooklyn, N. Y. Sewage Treatment Experiments by George T. Hammond, 
 
 Reprinted from 1919 Proc. Am. Soc. Mun. Improvements, p. 20 and 22 
 of Reprint. 
 
 E. Eighth Rept. Roy. Com. Sew. Disp. Vol. 1, page 9. 
 
 F. Operation data, 39th St. Sew. Pump. Sta. Year 1920. 
 
 G. Operation data, 39th St. Sew. Pump. Sta. Year 1914. 
 
 H. Operation data Des Plaines Sewage Treatment Works, Year 1924. 
 
 I. Operation data Calumet Sewage Treatment Works Year 1924. 
 
54 
 
 follows : Stockyards and Packingtown wastes, corn products wastes, 
 tannery wastes, wool pulling and washing wastes, and numerous other 
 smaller industrial wastes, many of which are common to all large cities. 
 The Stockyards and Packingtown wastes and the corn products wastes 
 have been and are now being extensively studied by the sanitary en- 
 gineering division of the Sanitary District and the conclusions which 
 they have arrived at may be summarized as follows : 
 
 The sewage flow from the packing industries is based on numer- 
 ous sewer gagings and the oxygen demand is an average value of numer- 
 ous determinations made between the years 1911 and 1918, all of which 
 data is reported in detail in the Reports on Industrial Wastes from the 
 Stockyards and Packingtown, Vol. 1 having been issued in October, 
 1914, and Vol. 2 in January, 1921. 
 
 The tannery and other miscellaneous wastes of the Sanitary Dis- 
 trict of Chicago have been estimated by officials of the Sanitary District 
 to have a daily oxygen requirement of 40,000 pounds. 
 
 The total industrial load of the district has been estimated by offi- 
 cials of the Sanitary District to have a daily oxygen requirement of 
 367,000 pounds. 
 
 Canal Studies: 
 
 An entirely separate study of the Chicago load has been made by 
 investigations conducted at several points along the canal between 
 Brandon Bridge below Joliet, and Summit. In these studies the load 
 was estimated by determining the oxygen lost from the mixture of lake 
 water and sewage to a given station or observation point, and adding 
 this load to the unsatisfied demand at the station. The sewage flow 
 was an assumed value, the dissolved oxygen content of the sewage was 
 assumed, the dissolved oxygen content of the diluting water was de- 
 termined by analysis, the total flow of the canal was taken from a rating 
 curve for a U. S. G. S. gaging station, and all other values were deter- 
 mined by analysis. The results of these studies as well as all other 
 studies of the Chicago load, which have been investigated, are recorded 
 
 Estimated average 
 daily sewage flow 
 in million gallons 
 for year 1925 
 
 Average 
 10-day oxy- 
 gen demand 
 
 value 
 900 
 600 
 
 Pounds 
 oxygen 
 required 
 per day 
 250,000 
 77,000 
 327,000 
 
 Stockyards Avastes . . . 
 Corn Products wastes 
 Total 
 
 33.5 
 15.5 
 49.0 
 
 in Table 10. 
 
55 
 
 An inspection of the data in Table 10 shows that the daily 
 oxygen load as estimated from the results of canal studies varies as 
 follows : 
 
 1. On basis of 5 day oxygen demand— 886000 to 1195000 pounds 
 
 2. On basis of 10 day oxygen demand— 1117000 to 1580000 pounds 
 
 3. On basis of 20 day oxygen demand — 1266000 to 1760000 pounds 
 
 TABLE 9. 
 
 SHOWING INDICATED TOTAL OXYGEN LOAD BASED ON 
 LOCKPORT DATA. 
 
 
 July 
 
 August 
 
 Febr'y 
 
 
 1922 
 
 1922 
 
 1922 
 
 Temp, lake water, degrees C* (temp.) 
 
 22.4 
 
 23.8 
 
 1.0 
 
 Oxygen in lake water, P. P.M.* (ave.) : . . . 
 
 8.45 
 
 7.88 
 
 12.37 
 
 Oxygen found at Lockport in P.P.M 
 
 0.01 
 
 0.01 
 
 9.11 
 
 
 8.44 
 
 7.87 
 
 3.26 
 
 Total flow in second feet 
 
 8696 
 
 8360 
 
 8330 
 
 Assumed sewage flow in sec. ft 
 
 1220 
 
 1220 
 
 1220 
 
 Dilution factor at Lockport 
 
 7.1 
 
 6.85 
 
 6.8 
 
 B.O.D. value reduction to Lockport (in 1220 
 
 
 
 
 sec. ft.) 
 
 60 
 
 54 
 
 22 
 
 B.O.D. value at Lockport — 5 day value 
 
 11.20 
 
 11.88 
 
 23.46 
 
 B.O.D. value at Lockport, corrected to 1220 
 
 
 
 
 sec. ft. — 5 day value 
 
 80 
 
 81 
 
 160 
 
 Total B.O.D. value at sewer outlets-5 day value 
 
 140 
 
 135 
 
 182 
 
 Total daily oxygen load in pounds 
 
 919,000 
 
 886,000 
 
 1,195,000 
 
 *Average9 found to prevail in these calendar months. 
 
 A further inspection of this table will show that the average daily 
 oxygen load of studies Nos. 7, 8, 9, and 10 (warm weather period) 
 based on the 20-day demand values, is 1,300,000 pounds and that the 
 average daily load of studies Nos. 5 and 6 (cold weather period) based 
 on the 20-day demand values, is 1,600,000 pounds. In view of the fact 
 that there was a marked oxygen depletion at the points of observation 
 during the warm weather tests, and probably a considerable amount of 
 replenished oxygen used in satisfying the demand up to the observation 
 station, and that this condition did not obtain to such a marked degree 
 in the cold weather tests, it seems probable that the total indicated load 
 of 1,600,000 pounds of oxygen is more nearly correct for the year 1922. 
 The average daily oxygen load based on the 10 day oxygen demand 
 values and the cold weather tests is 1,450,000 pounds and the average 
 daily oxygen load based on the 5-day oxygen demand values and the cold 
 
56 
 
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57 
 
 weather tests is 1,092,000 pounds. Taking human population for 1922 
 as 3,100,000, the oxygen load per capita per day was as follows : 
 
 Taking the human population for 1925 as 3,355,000, the total oxy- 
 gen load per day for the year 1925, would be as follows : 
 
 On basis of 20-day demand value .... 1,730,000 pounds 
 On basis of 10-day demand value. ... 1,570,000 pounds 
 On basis of 5-day demand value. ... 1,180,000 pounds 
 
 Resume of Studies: 
 
 In Table 11 are shown comparative data on the oxygen re- 
 quirements of the sewage of the Sanitary District of Chicago, as deter- 
 mined from three separate sources. 
 
 In the studies conducted by the U. S. PubHc Health Service during 
 the year 1922, samples were taken from the canal at Lockport between 
 6 a. m. and 8 a. m., and the oxygen demand determined after a 5-day 
 period of incubation at a constant temperature of twenty degrees C. 
 These studies were completed in August, 1922, and some doubt existed 
 as to the single samples being representative. The Sanitary District of 
 Chicago was asked to make a study which would show whether there 
 was a fluctuation in strength during a twenty-four hour period. 
 
 A study to determine this was made by the Sanitary District during 
 September, October, and November, 1922, samples being taken at the 
 same sampling point at Lockport as that from which the U. S. P. H. S. 
 samples were taken, and at 4 a. m., 8 a. m., noon, 4 p. m., 8 p. m., and 
 12 p. m. daily. The oxygen demand was determined on each sample 
 by a 5-day incubation at a constant temperature of 20 degrees C 
 
 A curve was plotted showing the daily fluctuations at four hour 
 intervals and another curve was plotted to show the fluctuations of the 
 flow during this period. From these two curves a correction factor of 
 1.27 was evolved to apply to the single daily sample taken from 6 a. m. 
 to 8 a. m. to make the oxygen demand representative. 
 
 An hourly fluctuation curve for oxygen demand resulting from the 
 temperatures obtaining in the canal water in September, October, and 
 November will probably be different from a similarly plotted curve for 
 warmer or colder weather ; consequently it is believed that this particu- 
 lar oxygen demand curve is not suitable or reliable for full year appli- 
 cation. The load value secured in this way is less convincing than it 
 would be had the results been based on weighted daily composites, and 
 it is impossible to say whether the indicated load is too high or too low. 
 
 On basis of 20-day demand value 
 On basis of 10-day demand value 
 On basis of 5-day demand value 
 
 0.516 
 0.468 
 0.352 
 
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59 
 
 The determination of the daily load from the results of the opera- 
 tion of the Calumet and Des Plaines sewage treatment works for the 
 year 1924, would be open to criticism because the use of a per capita 
 value secured from these results would result in adopting a load value 
 from about three percent of the population of the district and calling it 
 representative. 
 
 Best Criterion for Domestic Load: 
 
 The determination of the daily domestic load from the results of 
 the 1920 studies of the 39th Street sewer seems at this time to be the 
 most logical course to pursue for the following reasons : 
 
 1st. The district contributing to this sewer is considered to be 
 reasonably representative. 
 
 2nd. The study was made during a census year and for this reason 
 a reasonably accurate estimate of the contributing population could be 
 made. 
 
 3rd. The analytical data is complete and satisfactory for use in 
 determining the load. 
 
 4th. The pumpage record is not thought to be very accurate and 
 the average daily flow, if in error, is believed to be too high, and if this 
 is true the indicated load is too high and the error is on the side of 
 safety. 
 
 5th. The population contributing to this sewer is approximately 
 ten percent of the total population of 'the district. 
 
 From the data which has been reviewed, it is thought that the load 
 values as shown in Table 11 for the 39th Street sewer are the most 
 dependable. Furthermore, it is thought that a carefully planned study 
 of the canal at Lockport or at some other location or locations would 
 result in a more reliable determination of the daily load, and these 
 studies would also provide a check on the previous studies of the Stock- 
 yards and Corn Products wastes. 
 
 Summarized Conclusions on 1925 and Projected Daily Loads: 
 
 In estimating the total daily load of the entire Sanitary District for 
 the year 1925, and projecting these loads at five year intervals to 1945, 
 the following basic data have been accepted and used : 
 
 1. The 1920 results at the 39th St. sewer which show the daily 
 domestic load to be 0.24 pounds of oxygen per capita per day on a ten- 
 day oxygen demand basis. 
 
 2. The human population estimates of the Sanitary District for 
 five-year intervals from 1925 to 1945. 
 
 3. A value of 900 for ten-day oxygen demand for the packing 
 and stockyards industrial wastes, and the assumption that the strength 
 
60 
 
 of this waste will not change materially during the period of time 
 involved. 
 
 4. The estimate of the Sanitary District relative to the present 
 daily volume of the Packingtown and Stockyards wastes for the years 
 1925 and 1945, which volumes are respectively thirty-three and one-half 
 and 40 million gallons per day. 
 
 5. A value of 600 for the ten-day oxygen demand for the corn 
 products wastes and the assumption that the strength of this waste will 
 not change materially during the period of time involved. 
 
 6. The estimate of the Sanitary District relative to the present 
 daily volume of the corn products wastes for the years 1925 and 1945 
 which volumes are respectively 15 and 19 milHon gallons per day. 
 
 The oxygen demand values for the Packingtown and corn products 
 wastes are accepted after a study of the many analyses, which have been 
 made over a period of years. The actually determined value for the 
 
 Dav5 of Incubation at2o°c. 
 
 * G. L. Fugate, Eng. News-Record 94, No. 11. 
 t Data by Sanitary District of Chicago. 
 
 Figure 16— Biochemical oxygen demand based on various periods 
 
 of incubation. 
 
61 
 
 packing wastes is 900 parts per million for ten-days at 20 degrees C 
 The value of 680 for the five-day demand at 20 degrees C; is a calcula- 
 ted value which was furnished from the laboratory of the Sanitary 
 District. The twenty-day value was secured by dividing the ten-day 
 value by 0.90. 
 
 The basis for determining the load from the corn products plant 
 was a determined five-day oxygen demand value of 450 and a calculated 
 ten-day value of 600, both values being furnished from the laboratory 
 of the Sanitary District. The twenty-day value was secured by divid- 
 ing the ten-day value by 0.90. 
 
 The basis for determining the domestic load was the determined 
 ten-day oxygen demand value of 140 for the 39th St. sewer in 1920. 
 The five day and twenty-day values were calculated by using a rate of 
 satisfaction as follows: 
 
 5-day value 68% of 20-day value 
 10-day value 90% of 20-day value 
 20-day value 100% of 20-day value 
 
 A curve of oxygen demand for packing wastes of Chicago and 
 Houston, Texas, corn products wastes of Chicago, and 39th St. sewage 
 of Chicago accompanies this report. 
 
 Table 12 contains a summary of the estimated daily oxygen loads 
 of the domestic sewage, stockyards waste, and corn products waste, the 
 sum of which is taken as the total daily load of the entire district. 
 
 It will be noted in this table that the total daily load is shown on 
 the basis of 5, 10, and 20 day demand values, the 20-day value indicating 
 what might be termed a substantially complete oxygen requirement, 
 although it is not strictly an absolute value. 
 
 Although the total load as indicated by the 20-day value must be 
 disposed of finally, it is not required that this amount of oxygen must be 
 supplied as an initial content in lake water, as reaeration may be ex- 
 pected to contribute a substantial portion of the total oxygen required. 
 
 The rate of oxygen satisfaction occurring from the beginning to 
 the completion of a 20-day period of incubation in closed containers, 
 which has been referred to previously in this discussion, has been found 
 by a number of investigators to be reasonably reliable on a general 
 average basis. These rates of oxygen satisfaction grouped for five-day 
 intervals indicate the following period rates : 
 
 1st. 5 days — 68% of 20-day requirement 
 
 2nd. 5 days — 22% of 20-day requirement 
 
 3rd. 5 days — 7% of 20-day requirement 
 
 4th. 5 days — 3% of 20-day requirement 
 
62 
 
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63 
 
 The above rates indicate that the demand for oxygen during the 
 first quarter of the 20-day period is quite high and a substantial per- 
 centage of the total required for a reasonably complete destruction of 
 the polluting material. 
 
 The first 5-day period is also one in which poor reaeration condi- 
 tions would be most apt to cause serious conditions in a stream through 
 oxygen depletion resulting from a rapid rate of demand and a slow 
 rate of replenishment. 
 
 A study of the daily rates within the first 5 days shows that approx- 
 imately fifty-five per cent of the total 5-day requirement must be met 
 during the first two days. 
 
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 clean water incubated in open containers have shown invariably that 
 where a proper dilution was used and in which enough initial oxygen 
 was present to supply the needs for the first two days, an increase in 
 dissolved oxygen content began after the first two days of incubation. 
 
 Criterion for Load: 
 
 In view of such evidence as has been available and on the basis of 
 the observed behavior of mixtures of sewage and clean water which 
 have been shown to have reasonably definite general average rates of 
 demand for oxygen, it is considered that a supply of dilution water 
 having an initial oxygen content equal to the total 5-day oxygen demand 
 load of the Sanitary District will be sufficient and satisfactory. 
 
 For the above reasons, and for the reasons more fully stated in 
 Part V and Part VI, we conclude that the 5-day biochemical oxygen 
 demand of the sewage, and purification plant effluents, will furnish the 
 most useful criterion of organic load. 
 
64 
 
 PART V. 
 
 STANDARD OF MAXIMUM POLLUTION 
 
 It is desirable that a standard should be fixed to measure the eflPec- 
 tiveness of means to be taken to prevent excessive pollution of the 
 rivers below Joliet. This standard should be applicable whether the 
 protective measures consist of dilution from Lake Michigan, sewage 
 treatment works, or both. It will be most desirably and conveniently 
 applied at the foot of the Drainage Canal. A test must cover a period 
 sufficiently long to represent conditions which might create a nuisance, 
 to eliminate unavoidable errors in sampling, and to average up ordinary 
 variations that might be caused by excessive discharge frorri the storm 
 sewers. 
 
 It is regarded as essential that the standard should exclude settle- 
 able suspended matters of an organic character ; otherwise deposits in 
 the stream below Lockport, in the colder weather, will tend to rob the 
 stream of oxygen in summer, thus producing undesirable conditions, the 
 magnitude of which is not subject to prediction. 
 
 Subject to the above requirement, it is believed to be practicable to 
 prescribe an oxygen content and an organic load, which, aided by re- 
 aeration and added dilution from streams below Lockport, will permit of 
 satisfactory stream conditions at all places on the Illinois and Des 
 Plaines Rivers, including freedom from nuisance, conditions tolerable 
 for fishes in the Des Plaines and Upper Illinois, and such as to permit 
 a thriving fish fife in the lower Illinois. 
 
 Limitations of Standard: 
 
 In fixing a standard to be used as a governing basis for the pollu- 
 tion of the Illinois River, both now and hereafter, there are two con- 
 siderations that should be set forth clearly in the beginning : 
 
 1st. It is economically impractical to expect that the IlHnois River 
 should be returned to a condition such as exists in streams which receive 
 no pollution at all ; i. e., to a condition of pristine purity. 
 
 2nd. The existence of any appreciable amount of settleable pu- 
 trescible material in the drainage course is apt to upset all eflforts which 
 are aimed at the maintenance of proper stream conditions through 
 sewage treatment and regulated diversion. 
 
65 
 
 During the year 1922, the U. S. Public Health Service made a care- 
 ful and systematic study of the condition of the waters of the Illinois 
 River and its tributaries. 
 
 Condition of Illinois River: 
 
 The condition of the Illinois River was studied by taking daily 
 samples of the water at a number of stations between Lockport and 
 Kampsville and determining the dissolved oxygen and the five-day oxy- 
 gen demand at twenty degrees C, in addition to other determinations 
 the results of which will not be considered in this connection. The av- 
 erage monthly oxygen values for each sampling station are plotted on 
 Figures 5, 6, 7 and 8 to show winter, spring, summer and fall 
 conditions in the Illinois River. 
 
 An inspection of Figure 7 shows that during the winter months 
 of the year 1922, there was a marked preponderance of oxygen demand 
 over the dissolved oxygen supply at Lockport, and that a balance of 
 oxygen supply and demand was not reached for a distance of approxi- 
 mately 50 miles below Lockport. The dissolved oxygen content of the 
 water was, however, at no time or place below 7 parts per million, indi- 
 cating that a low rate of oxygen depletion was taking place and that 
 an absence of a smell nuisance existed. 
 
 An inspection of Figure 8 will show that during the spring- 
 months of the year, the same disparity between oxygen demand and 
 supply existed at Lockport, and that the balance was reached in April 
 29 miles below, in May 100 miles below, and in June 120 miles below 
 Lockport. The dissolved oxygen in April was not below three and 
 three-fourths parts per million, in May it reached a low value of one- 
 half of a part, and in June it was zero at Lockport. 
 
 Figure 5 shows the summer conditions in the river and the 
 oxygen values indicate that the Illinois River was practically dead for 
 a distance of 113 miles below Lockport, from which point its condition 
 began to improve until an oxygen balance existed at a distance of 125 
 miles below Lockport. 
 
 An inspection of Figure 6 shows conditions quite similar to 
 those which existed during the spring months with a progressive im- 
 provement from September to November. The oxygen balance was 
 established within the following distances below Lockport ; in Septem- 
 ber, 122 miles ; in October, 92 miles, and in November, 52 miles, the 
 improvement in the last month resulting both from an increase in dilu- 
 tion and a reduction in temperature. 
 
66 
 
 Condition of Tributaries to Illinois River: 
 
 The condition of the waters of the tributaries of the IlHnois is re- 
 flected by their dissolved oxygen content and the demand for oxygen 
 when incubated in closed containers for 5 days at 20 degrees C, and 
 these values are recorded in Table 13. 
 
 The values recorded in Table 13 are the mean values for the 
 months indicated, and are based on from ten to fifteen samples per 
 month for each stream so that the information thus secured gives a 
 very satisfactory index of the sanitary quality of the water. 
 
 It will be noted from these monthly averages that in only three 
 instances did the 5-day oxygen demand exceed the dissolved oxygen 
 content, and the average relation for all the streams was: dissolved 
 oxygen, 2.9, oxygen demand 1.0, indicating a very safe relation 
 between the oxygen supply and demand. 
 
 The best condition found among the several tributaries of the 
 Illinois was the average result for the Kankakee River, where the rela- 
 tion was 4.7 dissolved oxygen to 1.0 of oxygen demand. 
 
 A relationship for the Illinois River such as the average relation- 
 ship for its tributaries, we consider to be too severe and one which it 
 would be impractical to impose because the cost involved would prob- 
 ably be out of proportion to the advantages which would accrue there- 
 from. 
 
 Seasonable Dilutions: 
 
 It is a well known fact that a given dilution will be more potent 
 in preventing a nuisance in a polluted stream in cold weather than the 
 same dilution will be in warm weather, and this is due to the inhibiting 
 effect of low temperatures on bacterial activity, and this in turn reduces 
 quite materially the rate at which oxygen must be supplied. 
 
 The danger of oxygen depletion in a polluted stream where a given 
 dilution prevails, is very materially reduced with the coming of freezing 
 temperatures, consequently quite a material reduction in diversion water 
 can be made during periods of low temperatures. Sufficiently reliable 
 information is not available at this time upon which to base a schedule 
 of diversions which might be applied to take advantage of the changing 
 rates of oxygen satisfaction which accompany marked changes in 
 temperature. 
 
 An indication of the effect of temperature on the rate of oxygen 
 depletion is shown by the results of some laboratory studies conducted 
 at the sewage treatment works of Columbus, Ohio, some years ago, in 
 which mixtures of sewage and clean water were incubated in closed 
 containers for a period of twenty-four hours at various temperatures. 
 
67 
 
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 1= ^ 
 
68 
 
 The results of these studies showed the following rates of depletion, 
 takino- tlie rate at the hii^hcst temi)erature used (90 degrees F.) as 100 
 percent ; 90 degrees F. 100 percent ; 80 degrees F. 76 percent ; 70 de- 
 grees F. 55 percent ; 60 degrees F. 38 percent ; 50 degrees F. 22 percent ; 
 and 40 degrees F., 9 percent. 
 
 If the above rates of oxygen depletion are typical of what occurs 
 in the drainage course, it is evident that a very marked reduction in di- 
 version water could be made during freezing weather ; also a schedule 
 of seasonal diversions might be worked out which would materially re- 
 duce the total annual diversion required to meet the necessary sanitary 
 considerations. 
 
 Oxygen in Lake Walter: 
 
 In connection with the possibilities of regulated diversion to con- 
 form to temperature conditions and also to take advantage of the greater 
 amounts of dissolved oxygen which are present in cold water, the fol- 
 lowing table of typical average monthly temperatures and dissolved 
 oxygen content of lake water is of interest. The values given are mean 
 monthly averages based on daily analyses of lake water at the 39th St. 
 Pumping Station from September, 1921, through August, 1923. 
 
 Temp. Dissolved Oxygen Content 
 
 Month Degs. C. Parts per Million 
 
 January 2.5 13.48 
 
 February 2.5 13.17 
 
 March 3.7 12.98 
 
 April 8.6 11.72 
 
 May 12.4 10.59 
 
 June 17.4 9.28 
 
 July 20.2 8.10 
 
 August 21.5 7.80 
 
 September 19.2 9.08 
 
 October 14.2 9.55 
 
 November 8.6 10.97 
 
 December 4.3 12.31 
 
 Annual Mean 11.3 10.75 
 
 Stability Studies: 
 
 The results of many years of river inspection studies at Columbus, 
 Ohio, have shown certain relationships which exist between oxygen 
 demand, dissolved oxygen, and stability as determined by the methylene 
 blue test. Some of these relations are indicated in the following data: 
 
69 
 
 Range in oxy- 
 gen demand 
 values, 37 deg. 
 
 P 94. hrc 
 
 Ave. Oxy. de- 
 mand value 
 within the 
 
 Average dis- 
 solved oxy- 
 gen in water 
 
 in ciifn 
 
 Per cent dis- 
 solved oxy- 
 gen is of oxy- 
 gen demand 
 
 Stability 
 value of 
 water as 
 taken in situ 
 
 25-30 
 
 27.5 
 
 0.00 
 
 0.00 
 
 3 
 
 20-25 
 
 22.0 
 
 0.00 
 
 0.00 
 
 3 
 
 15-20 
 
 17.0 
 
 0.34 
 
 2.00 
 
 5 
 
 10-15 
 
 12.1 
 
 2.16 
 
 18.00 
 
 36 
 
 7-9 
 
 8.0 
 
 2.07 
 
 26.00 
 
 62 
 
 Below 7 
 
 4.4 
 
 3.92 
 
 89.00 
 
 84 
 
 A study of individual samples having oxygen demand values be- 
 tween 6 and 12 and showing complete stability by the methylene blue 
 test, has indicated that the dissolved oxygen does not have to equal the 
 oxygen demand value to insure complete stability, and a few instances 
 have been noted where the dissolved oxygen in the river water was only 
 forty percent of the oxygen demand yet the samples showed complete 
 stability, indicating that some other source of oxygen was available, 
 probably in the form of nitrites or nitrates. 
 
 Five-Day Value: 
 
 As the relationship between the rapidity of oxidation in sewage at 
 constant temperature is subject to prediction, approximately from day 
 to day, it would be possible to use any reasonable period of incubation 
 as a test citerion. The period of five days has been frequently used in 
 determining the quality of sewage and sewage polluted waters. It has 
 the advantage over other periods of incubation in that if a mixture of 
 sewage and water contains sufficient oxygen to meet the five day oxygen 
 demand of the organic matter content, then the liquid under ordinary 
 conditions in streams will not become entirely devoid of oxygen, and 
 thus no nuisance will be created. If a shorter period of incubation 
 should be used as a criterion, the oxygen content for equal freedom 
 from nuisance would necessarily exceed the biochemical oxygen de- 
 mand. If a period of incubation longer than five days should be taken, 
 an oxyben content less than the biochemical oxygen demand would be 
 justified. Therefore, the use of the period five days as an index is a con- 
 venient period for use. It has been used by the U. S. Public Health 
 Service in its stream studies in the United States, and it was 
 adopted by the Royal Commission on Sewage Disposal in its very com- 
 prehensive report upon "The Sewage Pollution of Streams" in England. 
 
 Laboratory Experiments : 
 
 Certain laboratory experiments at Columbus, Ohio, in connection 
 with the sewage disposal problem, bear upon this point. Table 14 
 shows certain data regarding the rapidity of oxygen depletion and the 
 recovery thereof with sewage in open containers. 
 
70 
 
 In the first two columns of this table it is apparent that all of the 
 oxygen absorbed from the air was used up at once and this continued 
 for six days in both the first and second tests. In the third test it was 
 five days before the original content of oxygen was restored, and in the 
 fourth test it was four days before this condition obtained. The last 
 three tests were made on diluted samples, and the results indicate that 
 the maximum depletion occurred during the first two days, and that 
 thereafter reaeration and demand were balanced. The last three tests 
 also show that the dissolved oxygen is drawn upon rather heavily before 
 reaeration becomes a marked factor, indicating that if a marked deple- 
 tion of dissolved oxygen is to be prevented the initial oxygen must be 
 considerably in excess of the two-day demand. 
 
 Reference in again made to the rates of satisfaction (page 50 of 
 this report) which is as follows : 
 
 In 1 day — 21% of total 20-day requirement 
 In 2 days — 37% of total 20-day requirement 
 In 3 days — 50% of total 20-day requirement 
 In 4 days — 61% of total 20-day requirement 
 In 5 days — 68% of total 20-day requirement 
 TABLE 14. 
 
 RESULTS OF OPEN INCUBATION TESTS OF RAW SEWAGE AND 
 TANK EFFLUENTS AT THE SEWAGE TREATMENT WORKS 
 AT COLUMBUS, OHIO. 
 
 Dissolved Oxygen Content in Parts per Million of 10 Gallon Mixtures After 
 Incubation in Open Containers at Room Temperature. 
 
 At Start . . 
 After 1 day 
 
 After 2 days. . . 
 After 3 days. . . 
 After 4 days. . . 
 After 5 days . . . 
 After 6 days . . . 
 After 7 days . . . 
 After 8 days. . . 
 After 9 days . . . 
 After 10 days . . 
 
 1.0 
 0.0 
 0.0 
 0.0 
 0.0 
 0.0 
 0.4 
 
 0.0 
 0.0 
 0.0 
 0.0 
 0.0 
 0.0 
 0.4 
 0.9 
 1.0 
 1.2 
 1.4 
 
 1.2 
 0.6 
 0.3 
 0.4 
 0.7 
 1.5 
 2.6 
 
 1.2 
 0.6 
 0.7 
 1.0 
 1.6 
 2.8 
 3.0 
 3.5 
 3.8 
 4.0 
 4.0 
 
 (1) 
 5.3 
 0.8 
 0.7 
 1.1 
 0.8 
 1.0 
 1.0 
 
 (2) 
 6.8 
 2.4 
 3.2 
 3.6 
 4.0 
 4.0 
 3.9 
 
 (3) 
 6.9 
 3.2 
 3.2 
 4.0 
 4.0 
 4.3 
 4.0 
 
 1. Raw sewage one volume, clean water 3 volumes. 
 
 2. Raw sewage one volume, clean water 7 volumes. 
 
 3. Raw sewage one volume, clean water 11 volumes. 
 
71 
 
 If the 5-day demand is taken as the total oxygen which must be 
 supplied by the dilution water, the relation is as follows : 
 
 Per cent of Per cent of 
 
 20 day demand 5 day demand 
 
 One day 21 30.9 
 
 Two days 37 54.4 
 
 Three days 50 73.5 
 
 Four days 61 89.7 
 
 Five days 68 ♦ 100.0 
 
 Reaeration Absent: 
 
 The standard hereinafter proposed in this report is that the resi- 
 dual dissolved oxygen and 5-day demand must be equivalent at Lock- 
 port, and the worst condition that might result is shown in the follow- 
 ing table, and is based on the entire absence of reaeration : 
 
 Dissolved Oxygen in P.P.IVI. 
 
 Initial Consumed Residual 
 
 Start 8.0 
 
 After 1 day 2.47 5.53 
 
 After 2 days 4.35 3.65 
 
 After 3 days. 5.88 2.12 
 
 After 4 days 6.18 1.82 
 
 After 5 days 8.00 0.00 
 
 In the above table it is assumed that the dissolved oxygen content 
 of the water is 8.0 parts per million, and complying with the standard 
 proposed in this report, the 5-day demand would be 8.0 parts per million. 
 
 Reaeration: 
 
 It is our belief that there will be enough reaeration to prevent a 
 serious depletion of oxygen in the Drainage Canal if the recommended 
 standard of pollution is adhered to. 
 
 When the mixed lake water and sewage reaches Lockport, in sum- 
 mer, the purifying action of the lake water is finished. The oxygen con- 
 tent of the liquid is practically zero. Nevertheless in its further flow to 
 Chillicothe, the total organic units, passing that point in a given time, are 
 greatly reduced through agencies other than Lake Michigan water. 
 This, notwithstanding the fact that the normal load in the summer 
 season is greatly augmented by river bottom deposits which have re- 
 mained in refrigeration during the colder months. 
 
72 
 
 An analysis of the studies of the U. S. P. H. Service for the 
 month of August, 1922, indicate that the purifying agencies acting be- 
 low Lockport and above Chillicothe, from sources other than Lake 
 Michigan, are more potent in total than the total diluting water from 
 Lake Michigan. These purifying agencies may include sedimentation, 
 putrefaction, and oxidation. In our opinion oxidation is the chief fac- 
 tor. This opinion is reinforced by the fact that between Chillicothe and 
 Peoria (in Peoria Lake) a distance of sixteen miles, the recovery of 
 oxygen units in the water is nearly as great as was obtained in total 
 diversion from Lake Michigan. 
 
 In addition to the natural agencies' there are artificial agencies that 
 may be called into action if needed to increase reaeration ; namely, the 
 fall at Lockport, and the available fall at the several state dams when 
 the Illinois waterway is built. Several studies of the river indicate a 
 marked recovery in oxygen at the Marseilles dam where much of the 
 water is wasted over the dam. At Lockport it nearly all passes through 
 the water wheels of the Sanitary District, with practically no oxygen 
 gain at present. 
 
 Thus in our opinion reaeration even of still water is a most impor- 
 tant agency of purification. 
 
 Dilution in Other Cities: 
 
 Attention is further invited to Table 15 which shows the dilu- 
 tion water available for several American cities which discharge un- 
 treated sewage into the streams along which they are located. The 
 data contained in this table simply shows what has been allowed to exist 
 as a permissible pollution and probably the conditions created therefrom 
 in the several streams have varied from satisfactory to doubtful. 
 
 The recommended standard contained in this report (eliminating 
 for the moment the matter of settleable solids) is that 5.9 cubic feet per 
 second per 1000 human population will be required to properly dispose 
 of the entire untreated sewage of the Sanitary District of Chicago dur- 
 ing the warm weather season of the year. 
 
 Dilution After Purification: 
 
 We show in Table 16 a Hst of cities in which more or less complete 
 purification has been adopted, together with the amount of diluting 
 water that is available in dry weather to mix with the purified effluent in 
 the stream below the purification works. The dilution is expressed in 
 cubic feet per second per thousand of population based on the 1920 
 census. 
 
 It will be observed that in several instances the stream goes dry. 
 
73 
 
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74 
 
 The numerical average dilution is .58 second feet per thousand 
 people. The weighted average is .42 second feet per thousand people. 
 Attention is called to the fact that as these cities grow the dilution ratio 
 must become less, for in all cases, so far as known, there is no practicable 
 means by which the dry weather flow of the stream will be increased. 
 
 As compared to the above figures the standard recommended in 
 this report and the recommended purification works contemplate dilu- 
 tions as follows : These dilutions are expressed in second feet of dilut- 
 ing water per thousand people as of the year 1935, when recommended 
 sewage works have been completed, and ten years thereafter. 
 
 With total diversion including In Year In Year 
 
 dilution water and sewage of 1935 1945 
 
 4,167 second feet 65 .5 
 
 6,000 second feet 1.1 .9 
 
 7,500 second feet. 1.5 1.2 
 
 8,500 second feet 1.7 1.4 
 
 10,000 second feet 2.1 1.7 
 
 These figures when compared with the data shown in Table 16 tend 
 to indicate that a liberal amount of dilution is provided by the recom- 
 mended standard for pollution and the recommended works for purifi- 
 cation. It would appear that if this dilution is not sufficient, then the 
 satisfactory disposal of sewage in many of our inland cities is impos- 
 sible. 
 
 Pollution and Fishes: 
 
 It is evidently desirable that our streams insofar as possible should 
 be sufficiently pure to permit the continuance of the natural water life 
 thereof, including the fishes. This matter is particularly important in 
 Illinois River which has been the best fish stream, in the Middle West. 
 For many years it has supported a commercial fishery with a catch 
 ranging from ten million to twenty-three million pounds per year. 
 About seventy-five percent "of the catch has been the so-called coarser 
 fishes such as Carp and Buffalo. The so-called game fishes have been 
 present in large numbers, and the Illinois River has been the playground 
 of the game fisherman, and is so at present in its lower reaches. Of 
 recent years the commercial catch has materially declined due in part 
 to causes other than sewage pollution. 
 
 Inorganic Wastes: 
 
 ^ In certain parts of the country inorganic wastes are produced by in- 
 dustries that have poisoned the fishes and entirely destroyed them 
 throughout long stretches of streams. Numerous industrial wastes are 
 poisonous to fishes when present in certain amounts. 
 
75 
 
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76 
 
 Upon the Illinois River, so far as we know, the inorganic pollution 
 has not reached amounts to be seriously detrimental to fishes. 
 
 Organic Pollution: 
 
 Certain of the coarser fishes may live and possibly thrive in waters 
 more or less heavily sewage polluted. There is, however, a limit to the 
 suspended organic matters present in waters in which fishes may main- 
 tain healthy conditions. All the fishes and the attendant train of water 
 life necessary for their existence are killed, if the air supply in the water 
 is reduced to zero for a sufficient period. This exhaustion of air may ^ 
 result from, the decomposition of organic matters. 
 
 With a reduction in the dissolved oxygen carried by a stream, the 
 more sensitive fishes, and ultimately all the fishes endeavor to get away. 
 If escape is impossible they die. Some of the so-called coarser fishes 
 may tolerate for a time, conditions in which oxygen is practically ex- 
 hausted from the water, due to their power to take, store, and use a cer- 
 tain amount of atmospheric oxygen. Other fishes do not have this 
 ability. 
 
 During the winter of 1924-5, ice conditions on the Illinois River re- 
 duced the dissolved oxygen to figures as low as from .4 to 1.8 parts per 
 million. Under conditions such as this all kinds of fish taken from nets 
 under the ice were found to be dead. At another place where the water 
 contained 2.5 parts per million of dissolved oxygen, only Carp, Buffalo, 
 and Gars were taken alive, all in a stupid condition. In another part of 
 the stream where the oxygen content was 5.4 to 5.8, all fish were found 
 in good condition under the ice. 
 
 It is believed that the above figures typify minimum conditions un- 
 der which the fishes may survive. They probably require more favor- 
 able conditions than this throughout most of the year, in order to pro- 
 pagate and thrive. 
 
 A study of the graphs and tables of pollution on the Des Plaines 
 and IlHnois Rivers herein-elsewhere shown, coupled with a knowledge 
 of the places where fishes may now be found, throw some light upon 
 limits of pollution. 
 
 Fishing conditions below Peoria in general are good. Above 
 Peoria fishes are practically extinct except as follows : In seasons of 
 low flow from the tributary streams, the dead line has moved down- 
 stream to Peoria and unfavorable conditions have been noted as far 
 south as Havana. In seasons of maximum flow from the tributaries, 
 the dead line moved upstream. It is understood that the 1925 season 
 finds fishes in Peoria Lake, from which they have been largely or en- 
 
77 
 
 tirely absent for several years. This is probably due to the heavy sum- 
 mer flows in 1924. 
 
 The study of the river seems to indicate that where the dissolved 
 oxygen exceeds the five-day demand of the organic matter in summer, 
 and considerably exceeds it throughout the remainder of the year that 
 fish may thrive providing that the minimum dissolved oxygen at any 
 time is three parts per million or more. 
 
 In the works which we have suggested for sewage treatment at 
 Chicago under various rates of dilution, and the standard herein-else- 
 where set down for the liquid discharged by the Drainage Canal at 
 Lockport, we believe that satisfactory fish conditions will be maintained 
 throughout the greater part of the Illinois River. We believe that con- 
 ditions will permit the coarser fishes to live at all places from Joliet to 
 the Mississippi. 
 
 Recommended Standard: 
 
 After reviewing all the data which has been available relative to 
 the past conditions which have prevailed in the Illinois River below 
 Lockport, in addition to the studies which have been made and which 
 indicate the sanitary quality of the waters of the streams which are trib- 
 utary to the Illinois ; and, with the purpose in view of seeking a reason- 
 able degree of cleanness in the Illinois River below the terminus of the 
 drainage canal ; and, in the belief that the maintenance of such condition 
 is not prohibitive in cost or unduly difficult of attainment ; the following 
 standards of maximum pollution are proposed : 
 
 The liquid discharged by the Drainage Canal, as evidenced by the 
 average of representative samples taken for any thirty consecutive days 
 shall: 
 
 (a) Be practically free from settleable solids deposited in two 
 hours and 
 
 (b) Shall contain dissolved oxygen equal to, or exceeding, the bio- 
 chemical oxygen demand of said Hquid for five days when incubated at 
 twenty degrees Centigrade. 
 
 (c) Shall contain not less than three parts per million of dissolved 
 oxygen. 
 
 In connection with the second standard relating to the oxygen bal- 
 ance, it is expected that there will be times when a condition of extreme 
 refrigeration will exist in the waters of the canal which may result in a 
 five-day oxygen demand value in excess of the dissolved oxygen content, 
 but it is considered that, with an absence of settleable, putrescible solids 
 in the water and the probability of the presence also of an ample supply 
 of dissolved oxygen, a violation of this standard under these conditions 
 
78 
 
 will not be detrimental to the maintenance of proper stream conditions 
 in the Illinois River below the terminus of the Drainage Canal. 
 
 It is also suggested in connection with the application of these 
 standards of permissible pollution that sewage treatment devices should 
 not be expected to register maximum efficiency at all times, and that 
 occasionally conditions will arise which will temporarily reduce their 
 efficiency until proper corrective measures can be applied. Fallibility 
 is characteristic of all things human, so that these standards are to be 
 considered, as a rule, with occasional justifiable and unavoidable ex- 
 ceptions. 
 
79 
 
 PART VI. 
 
 REQUIRED DEGREE OF PURIFICATION WITH 
 VARIOUS DILUTIONS. 
 
 Our instructions require that we should report upon the purifica- 
 tion works necessary under each of several diversions from Lake Michi- 
 gan ; namely 2,000, 4,167, 6,000, 7,500, 8,500, and 10,.000 cubic feet per 
 second. 
 
 We have been instructed to consider these quantities as stated to be 
 total diversions from the lake, including the water contained in the sew- 
 age plus the water used for diluting purposes. Thus practically speak- 
 ing, the total diversion is equivalent to the dry weather flow discharged 
 at the mouth of the Drainage Canal near Lockport. 
 
 Water for Dilution: 
 
 For the purpose of this study the amount of water available for 
 dilution in the critical period of the year, July and August, is considered 
 to be the total diversion less the liquid volume of sewage of the Sanitary 
 District. In this computation it will be assumed that the sewage liquid 
 is substantially the same as that which was analyzed in determining the 
 total organic load of the Sanitary District as summarized in Part IV of 
 this report. 
 
 In the estimates for purification works hereinafter made, the above 
 total diversions from the lake are considered as constant from year to 
 year. The organic load of the city as shown in Table 12 of Part IV 
 must grow from year to year. Experience indicates that during the hot 
 weather months the sewage has been delivered at the sewer outlets in a 
 condition practically devoid of oxygen. Within ordinary variations in 
 the supply of water per capita, this will probably continue to be the fact. 
 Therefore, with a constant total diversion from the lake and an increase 
 in organic load which is delivered at the sewer mouths devoid of oxy- 
 gen, the available diluting water will progressively decrease with the 
 growth of the city, and the effectiveness of works for purification must 
 progressively increase as time goes on. 
 
 Organic Load and Dilution: 
 
 The organic content of sewage for practical purposes must be deter- 
 mined at the point of deHvery of the sewers. At this point in warm 
 weather more or less oxidation has already taken place. The analysis 
 
80 
 
 represents the organic content of that particular sewage which has 
 passed through a certain history as regards amount of dilution and in 
 other respects. If the water supply per capita has been less, the analy- 
 sis would have shown a sewage somewhat stronger in organic load per 
 capita, for less oxidation would have taken place enroute to the sewer 
 outlet. If the water supply per capita had been greater, the analysis 
 would have shown less organic matter per capita, or more dissolved 
 oxygen in the sewage, possibly both. 
 
 It is believed that when considering such variations in the use of 
 water per capita as may occur in Chicago, it will be immaterial whether 
 the organic wastes of the city are diluted by water taken into the sewers 
 through the faucet or by water mixed with the sewage at the sewer out- 
 let. It is our opinion, therefore, that it will be logical and proper to 
 take the organic load of the District at the time when the analyses were 
 made ; to take the liquid volume of the sewage existing at the time when 
 the analyses were made ; to assume that all sewage is delivered to the 
 stream devoid of oxygen ; to assume that the liquid volume of the sew- 
 age will increase in proportion to the increase in the organic load, 
 namely, that the consumption of water per capita remains constant; 
 and that the available diluting water will be the total diversion less the 
 liquid sewage computed upon the basis as above. 
 
 The Sanitary District has made a careful estimate of the total liquid 
 load as of the year 1920 at 758 million gallons. This is equivalent to 
 253 gallons per capita. We have used the round number 250 gallons 
 ])er capita in computing Table 17, which shows the total net dilution 
 water available between 1925 and 1945 under the various specified total 
 diversions from 2,000 to 10,000 second feet. The table also shows the 
 available oxygen in the dilution water. These figures are used in Parts 
 XIII, XIV, and XV of this report. 
 
 Necessary Puri-fication Plant Efficimcies : 
 
 In selecting the type of treatment best adapted to supplement vari- 
 ous rates of dilution, it is useful to estimate the average rate of purifi- 
 cation that would be required to produce a satisfactory effluent. Upon 
 the following pages we describe the method of calculation, and tabulate 
 the principal results. 
 
 The degree of purification of the combined wastes of the Sanitary 
 District of Chicago which must be accomplished in order to make cer- 
 tain specified diversions effective in maintaining proper conditions in the 
 rivers which receive the discharge of the Drainage Canal, is determined 
 on the basis of the daily oxygen required by the entire liquid-borne 
 wastes of the District, and the supply of oxygen furnished daily by any 
 given diversion of lake water. 
 
81 
 
 TABLE 17. 
 
 ESTIMATED "NET DILUTION WATER" WITH VARIOUS "TOTAL 
 DIVERSIONS" AND OXYGEN AVAILABLE FOR DILUTION 
 IN JULY AND AUGUST. 
 
 Year 
 
 1925 
 
 1930 
 
 1935 
 
 1940 
 
 1945 
 
 Estimated volume of sewage deliv- 
 
 
 
 
 
 
 ered to stream devoid of oxygen — 
 
 
 
 
 
 
 
 1280 
 
 1410 
 
 1530 
 
 1650 
 
 1770 
 
 With 2000 sec. ft. Constant Diversion 
 
 
 
 
 
 
 Net water for dilution sec. ft 
 
 720 
 
 590 
 
 470 
 
 350 
 
 230 
 
 Available oxygen lbs. per day. . . . 
 
 31000 
 
 25400 
 
 20200 
 
 15000 
 
 9900 
 
 With 4167 sec. ft.Constant Diversion 
 
 
 
 
 
 
 
 2887 
 
 2757 
 
 2637 
 
 2517 
 
 2397 
 
 Available oxygen lbs. per day. . . . 
 
 124000 
 
 118400 
 
 113200 
 
 108000 
 
 103000 
 
 With 6000 sec. ft. Constant Diversion 
 
 
 
 
 
 
 Net water for dilution sec. ft 
 
 4720 
 
 4590 
 
 4470 
 
 4350 
 
 4230 
 
 Available oxygen lbs. per day. . . . 
 
 203000 
 
 197000 
 
 192000 
 
 187000 
 
 182000 
 
 With 7500 sec. ft. Constant Diversion 
 
 
 
 
 
 
 
 6220 
 
 6090 
 
 5970 
 
 5850 
 
 5730 
 
 Available oxygen lbs. per day. . . . 
 
 268000 
 
 262000 
 
 257000 
 
 252000 
 
 246000 
 
 With 8500 sec. ft. Constant Diversion 
 
 
 
 
 
 
 Net water for dilution sec. ft 
 
 7220 
 
 7090 
 
 6970 
 
 6850 
 
 6730 
 
 Available oxygen lbs. per day. . . . 
 
 310000 
 
 305000 
 
 300000 
 
 294500 
 
 289000 
 
 With 10000 sec. ft. Constant Diversion 
 
 
 
 
 
 
 Net water for dilution sec. ft 
 
 8720 
 
 8590 
 
 8470 
 
 8350 
 
 8230 
 
 Available oxygen lbs. per day. . . . 
 
 375000 
 
 370000 
 
 365000 
 
 360000 
 
 354000 
 
 The basic data for the first part of this computation is recorded in 
 Part IV, Table 12, in which is shown the total oxygen required per 
 day, separately and collectively, by the three polluting elements con- 
 tributing to the load. This same table also shows the total daily oxygen 
 loads of the entire district for the year 1925, and for five-year intervals 
 to 1945. 
 
 One second foot of lake water per day during the warm months of 
 the year (July and August) will supply forty-three pounds of oxygen, 
 and the second feet of lake water required per day during July and 
 August will be as shown in the first portion of Table 18. 
 
 Taking, for instance, the second feet per day required for the year 
 1925, Table 12 of Part IV shows the total daily oxygen requiremnt 
 on the five-day demand basis to be 856,000 pounds, consequently, 856- 
 000 pounds divided by forty-three pounds gives 19,900 as the second 
 feet required per day for untreated sewage. 
 
 Table 18 shows the daily oxygen loads for the polluting unit 
 of each polluting element ; also the second feet of water required per day 
 during July and August for each polluting unit. These months were 
 selected for use because they represent the critical period of the year 
 both as regards oxygen supply and demand. 
 
82 
 
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 111 
 
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 Day 
 Oxygen 
 
 
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 240 
 7500 
 5000 
 
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 Pounds 
 Per Pollul 
 
 CO 
 
 ft 
 
 182 
 5650 
 3750 
 
 
 
 Pounds Oxygen 
 Supplied During 
 July and August 
 Per Sec. Ft. Per 
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83 
 
 If it is desired to determine the pounds of oxygen available in one 
 second foot of lake water per day, the result is secured by multiplying 
 as follows : 
 
 Parts per million of dissolved oxygen in water X 0.646 M. G. in 
 one second foot per day X 8.33 pounds per gallon, or parts per million 
 of dissolved oxygen in water X 5.4. 
 
 The factor 5.4 is the product of 0.646 X 8.33 and is a constant. 
 
 Table 19 shows the second feet required per day during July 
 and August for five-year periods from 1925 to 1945, and for five, ten and 
 twenty-day oxygen demand values. The five-day demand is sixty-eight 
 percent of the twenty-day demand and the ten-day demand is ninety 
 percent of the twenty-day value. It is assumed in this computation 
 that the strength of the polluting unit of each polluting element will 
 remain the same during the period of time involved. 
 
 The second section of Table 19 shows the purification, expressed 
 in percent, required for gross diversions of 2,000, 4,167, 7,500, 8,500 
 and 10,000 second feet per day and for oxygen demand, values of five, 
 ten and twenty days. 
 
 The computation showing the percentage of purification required, 
 is simply one of subtraction and division, and may be illustrated by tak- 
 ing the first value in the table ; viz., 96.4 which is arrived at as follows: 
 19,900 second feet — (2,000 second feet —1,280 second feet) 
 divided by 19,900 or 96.4%. 
 
 The percentage values in this table are carried to the first place 
 beyond the decimal ; however, this is not intended to imply that this 
 degree of refinement should be followed in the use of these values as 
 they constitute simply a record of a mathematical computation. 
 
 With these data in hand and a knowledge of practicable plant effi- 
 ciencies, it is possible to select the types of treatment works that would 
 produce required results. 
 
 Seasonal Variations: 
 
 All the computations hereinabove made refer to the critical season 
 of the year, namely, the warm months of July and August. In the 
 winter time each unit of lake water will carry about double the amount 
 of oxygen available during the critical period. Furthermore, oxidation 
 takes place at a slower rate during the cooler months of the year, and 
 the sewage is thus afforded the opportunity to travel further down- 
 stream, to be subjected to additional aeration and to be mixed with ad- 
 ditional tributary waters. 
 
 For all these reasons, it is undoubtedly practicable to regulate the 
 diversion from the lake in accordance Vv^ith the needs of the situation 
 
84 
 
 existing from month to month. All the interests affected by diversion 
 of water from the lake are concerned only with an average diversion. 
 There appears to be no reason why it will not be entirely practicable to 
 materially increase the flows herein estimated for the warm months of 
 the year should occasion arise, and to save the water thus taken during 
 other months of the year, thus staying within a stipulated average 
 diversion. 
 
 Factor of Safety: 
 
 It must be admitted that it is not practicable to compute exactly the 
 amount of diluting water that necessarily must be added to the sewage 
 in order to obviate nuisance and to permit a thriving fish life. It is de- 
 sirable that there should be a factor of safety to provide against error. 
 In our opinion, it will be wise to adopt as the average diversion with 
 various degrees of purification the amounts herein set down as required 
 in the months of July and August, and to use the additional water avail- 
 able in the cooler months of the year as a factor of safety, thus permit- 
 ting some increase of the dilution in the hot months to cover, 
 
 (a) The possibility of less reaeration in the lower river than 
 herein contemplated. 
 
 (b) Washings from the sewers in storm that may be necessarily 
 by-passed from the sewage purification plants. 
 
 (c) The accidental depletion in the oxygen in the lower river 
 through the sudden death of green plant growths. 
 
 (d) Some degree of inferiority in the diluting water entering 
 through the Sag Canal and other minor drafts on the oxygen supply not 
 specifically considered herein. 
 
 Additional Oxygen: 
 
 No specific consideration has been given to additional oxygen that 
 may be furnished by the effluent from the sprinkling filter plants and the 
 activated sludge plants. This oxygen will be in addition to that ob- 
 tained from the lake and from the other sources mentioned. 
 
 At the present time practically no aeration is obtained at Lockport 
 in dropping the water from the Drainage Canal into the Des Plaines 
 River in passing through the water wheels. It would probably be pos- 
 sible to add from one to two parts per million to the sewage by an over- 
 fall especially designed for aeration. This possibility will occur at all 
 of the dams hereinafter constructed for navigation purposes on the 
 Illinois River except where the water may be used for power purposes. 
 
85 
 
 PART VII. 
 
 PROTECTION OF THE WATER SUPPLY 
 
 It must be a part of any scheme for sewage disposal that the water 
 supply should be protected against any possibility of sewage contamina- 
 tion. Unless this is accomplished sewage disposal fails in its principal 
 requirement. 
 
 This matter is particularly important to municipalities located on 
 the shores of the Great Lakes. In all of these cities the lakes constitute 
 the only practicable means for municipal water supply. In many in- 
 stances the lakes are the only practicable means for sewage discharge. 
 
 In the Chicago region the means has been provided through the 
 drainage canal, by which the great majority of all impurities are divert- 
 ed from Lake Michigan. As will be pointed out, certain sources of pol- 
 lution still remain, and will continue to exist, regardless of any improve- 
 ments in the Sanitary canal. These sources of pollution are sufficiently 
 great to seriously menace the water supply, unless adequate precautions 
 are taken to guard against them. 
 
 Lake Shore Line: 
 
 The south end of Lake Michigan is relatively shallow. On the Chi- 
 cago water front the distance outward for twenty-five feet depth varies 
 generally from half a mile to a mile. The four-mile crib at Chicago 
 stands in thirty-six feet of water. The depth of water is five to eight 
 feet less at the other intake cribs, located at lesser distances from shore. 
 Opposite the mouth of the Chicago River a depth of fifty feet is attained 
 only at seven miles from the shore. Opposite the mouth of the Calumet 
 River the same depth is only attained nine miles out. Opposite Gary 
 the lake is deeper ; fifty feet is attained at a distance of four miles from 
 shore. 
 
 At the shore line there is a fringe of sand generally varying from 
 ten feet more or less, at Chicago, to about fifty feet in the vicinity of 
 Gary. This sand is a superficial deposit upon a bed of blue clay. The 
 sand layer generally disappears within a mile or two from shore, and 
 the coating is scattering and thin at this distance out. 
 
 Intakes and Pollution Sources: 
 
 The accompanying map, Figure 1, shows the Lake Michigan shore 
 line, the location of the Water Works intakes, and the location of the 
 streams forming potential sources of pollution. 
 
The distance of the Chicago Water Works' cribs from the mouth 
 of the Chicago River, and Calum.et River respectively are as follows : 
 
 Miles from Chicago 
 River Mouth. 
 
 Miles from Calumet 
 River Mouth 
 
 Wilson Ave. Crib 
 
 Carter Harrison Crib 
 
 Chicago Ave. Crib 
 
 Four Mile Crib 
 
 Hyde Park & E. F. Dunn Cribs 
 
 5.2 
 
 2.3 
 
 1.3 
 
 3 
 
 8 
 
 16 
 12.7 
 12.2 
 9.3 
 3.7 
 
 About six miles southeast of the Calumet River mouth, the Indiana 
 Harbor canal is located, which taps the Grand Calumet River and dis- 
 charges more or less sewage into the lake. Between these two points 
 lie the Water Works' intakes of Whiting and Hammond, Indiana. The 
 East Chicago intake is close to the shore, and only a short distance from 
 the Indiana Harbor canal. The Gary intake is one and one-half miles 
 from shore, six miles east of the Indiana Harbor canal and twelve miles 
 from the Calumet River, measured in a direct line. 
 
 Sources of Pollution: . 
 
 From the mouth of the Calumet River, north to the Cook County 
 line, the sewers are now diverted from the lake. North of the Cook 
 County line the towns between Highland Park and Waukegan sewer 
 into the lake, except a small population in Highland Park which sewers 
 inland toward the Skokie Marsh. Most of this sewage reaches the 
 lake in a raw state at present. A portion of it is partially purified. 
 These cities are members of the North Shore Sanitary District, intended 
 to prevent excessive pollution of the lake. Conditions in this locality 
 will probably be somewhat improved hereafter. 
 
 Indiana Towns: 
 
 The Indiana towns from the State line eastward, including Gary, 
 now contain a population of 180,000. These towns are growing very 
 rapidly. They are the sites of some of the largest industries in the 
 Chicago region. Grand Calumet River is the main sewer of this region. 
 Considerable sewage from the shore population in Hammond and Whit- 
 ing, and from several industries, discharges directly to the lake. The 
 entire City of Gary, and the greater part of the sewage in East Chicago 
 and Hammond drains inland and only reaches the lake through the out- 
 lets of the Calumet. 
 
 Calumet River: 
 
 Attention is invited to the Grand Calumet and Little Calumet 
 Rivers, and their relation to Lake Calumet, the outlet of the two streams 
 into Lake Michigan, and the location of the Calumet Sag Channel. The 
 
87 
 
 Sag Channel is now designed for 2,000 second feet. At certain seasons 
 of the year this is sufficient to take the sewage of the Chicago Sanitary 
 District reaching it and the entire flows of the Grand and Little Calumet 
 Rivers. In seasons of flood the Sag Channel is very insufficient to take 
 the flow of these streams. 
 
 Figure 17 is a watershed map of the Grand Calumet and Little 
 Calumet Rivers. The total drainage area of these streams is 770 square 
 miles. 
 
 The maximum measured flood in this district occurred in February, 
 1887. It was measured at Riverdale on the Little Calumet River and 
 amounted to 13,300 second feet. The Sanitary District of Chicago has 
 estimated the maximum flood to be expected from the combined Grand 
 and Little Calumet Rivers at 16,000 second feet. The estimate of the 
 International Waterways Commission is substantially the same. 
 
 Continuous gaugings are not available showing the frequency and 
 duration of floods. In a report of Mr. Wisner, Chief Engineer, of the 
 Chicago Sanitary District, June 9, 1909, it is estimated that with 2,000 
 second feet flowing in the canal, there would be 22.4 days per year when 
 the flood flow from the Calumet Rivers would exceed the flow of the 
 Sag canal. The source of the information upon which this estimate is 
 based is not stated. Judging by the experience of the nearest adjoining 
 streams upon which flow records are available, it appears that the above 
 figure may be approximately true. Flow records on the Kalamazoo 
 River, draining somewhat similar territory in Michigan, applied to the 
 Calumet Rivers with drainage area correction, indicate a probabihty of 
 eighteen days per year when the flow of these screams might be expected 
 to exceed 2,000 second feet. A similar comparison based on daily gaug- 
 ings on the Des Plaines River, corrected for drainage area, indicate 
 about twenty-five days flow in excess of 2,000 second feet. 
 
 A large flood on these streams will undoubtedly wash great quanti- 
 ties of filth into Lake Michigan. The Calumet cities are beginning to 
 study the question of sewage purification. Conditions in the future will 
 no doubt be improved. No practicable means for sewage purification 
 will place these streams in condition where their waters may be period- 
 ically flushed into the water supply of the region even occasionally, with 
 safety to the water supplies. 
 
 Water Level Changes: 
 
 The lower Calumet River, between Calumet Lake and Lake Michi- 
 gan, is dredged 200 feet wide and twenty-one feet deep. It requires a 
 slope of only a small fraction of an inch from Lake Calumet to Lake 
 Michigan to discharge 1,000 second feet. A difference in level of slightly 
 over two inches will discharge 5,000 second feet. A recording guage at 
 
88 
 
89 
 
 the mouth of the Cahimet River shows that the surface of the lake is 
 constantly rising and falling, due principally to changes in direction and 
 velocity of the wind. Changes of six inches in less than an hour are 
 very common. It is an exceptional day in which the total variation is 
 less than six inches at different times during the day. Upon moderately 
 windy days the variation is frequently more than one foot. 
 
 Some years ago we conducted a systematic watch of the currents in 
 the lower Calumet River, estimating the current velocities by rod floats 
 This study confirmed what would be expected by the water level varia- 
 tions in Lake Michigan, and the comparatively large volume of stagnant 
 water in the Calumet Rivers and Lake Calumet. Whenever the lake 
 surface dropped a few inches a rapid current was set up toward Lake 
 Michigan, which continued until a change in the wind caused the lake 
 surface to rise, in which case if the rise was great enough the outflow 
 was stopped, the current reversed, and often a rapid current ran inland 
 for several hours, to return again with a subsequent fall in the lake level. 
 Thus on February 20, 1920, with a variation in lake level of about three 
 tenths of a foot and a brisk northwest wind gradually decreasing after 
 3 p. m., the flow of the river varied from 1,000 second feet from the lake 
 at 2 p. m. to 3,000 second feet toward the lake at 5 p. m. 
 
 On February 11th, with a brisk northeast wind, the flow from 1 - 
 to 5 p. m. varied from 1,000 to 1,500 second feet landward. For short 
 periods it became nearly stagnant. On February 12th with a mild 
 southwest wind the flow averaged about 2,000 second feet toward Lake 
 Michigan from 1 to 3 p. m., but stopped entirely as the wind died down 
 about 4 p. m. 
 
 Thus the Calumet Rivers and Lake are constantly ''breathing" in 
 and out, toward and from Lake Michigan, depending principally upon 
 the direction and velocity of the winds. In severe storms there are also 
 very important barometric changes causing lake level fluctuations of 
 several feet, bringing out heavy discharges for periods of many hours. 
 
 No doubt a similar condition exists where the Indiana Harbor 
 canal taps the Grand Calumet River. This is a wide and deep harbor ; 
 only a small difference in head, an inch or less, is required for the inter- 
 change of water between the river and Lake Michigan. The sewage of 
 Gary is supplemented by a large amount of condensing water from the 
 steel mills. A rapid flow is produced in the upper Grand Calumet. The 
 final disposition of this sewage laden water depends upon the stream 
 cross-sections, and the relative elevations of the moment as between the 
 Calumet Rivers and Lake Michigan. 
 
90 
 
 Chance Pollution from Chicago River: 
 
 Prior to the construction of the drainage canal, conditions at the 
 mouth of the Chicago River were somewhat similar to those previously 
 described as prevailing" in the Calumet region. The floods of the Chi- 
 cago River have not been accurately measured. It has been estimated 
 that the discharge capacity of the storm water sewers in Chicago makes 
 it possible to produce a flood of about 11,000 second feet. Possibly it 
 may be questioned whether this is so at the present time. If it is not 
 true today it probably will be true as the city becomes improved to a 
 greater extent than at present. With the drainage canal in operation at 
 the rates of flow, which have prevailed during the past ten years, there 
 is little danger of a material amount of flood water reaching Lake Michi- 
 gan. There have been a few occasions, however, for a short time when 
 a lakeward flow has been noticed following great rain storms. With 
 lesser flows in the drainage canal these occasions would become more 
 frequent and of longer duration. 
 
 At the present time lakeward flows of water would be very detri- 
 mental to the Chicago water supply. With the general adoption of 
 sewage purification works, and the consequent cleaning up of the Chi- 
 cago River, the dangers resulting from a lakeward flow of water would 
 be diminished but there would still be a potential danger to the water 
 supply. The purification of the sewage would not be a determining fac- 
 tor in the matter further than to diminish the quantity of filth that might 
 be washed into the lake by flow reversal. 
 
 Travel of Pollution in the Lake: _ 
 
 The question as to the travel of pollution in the waters of Lake 
 Michigan has been studied very thoroughly upon several occasions cov- 
 ering the Chicago water front, the water front opposite the Chicago 
 north shore suburban towns aixl further north along the lake at Racine 
 and Milwaukee. The results of these studies indicate similar conditions 
 wherever sewage contamination reaches the lake and variable winds and 
 waves are available for dispersion. The net results from these studies 
 are well summed up by Major W. V. Judson in his paper on currents 
 in Lake Michigan, (first report Lake Michigan Water Commission, 
 page 67). 
 
 "In my opinion the currents of Lake Michigan are so irregular in char- 
 acter that nothing would be gained worth the cost if attempt were made to 
 obtain classified further data of a general nature. If it is a question of pro- 
 tecting the water supply of any particular locality, in any event, special 
 study would have to be made inasmuch as the lake currents, available as they 
 are, are much influenced by local conditions. 
 
91 
 
 We do know, and perhaps it is enough for the purposes of this commis- 
 sion, that occasional currents of considerable velocity, say several miles per 
 hour, may be expected to arrive from almost any direction at any point 
 reasonably near either shore of the lake. It is, therefore, apparent that in a 
 general case if the waters of the lake are polluted by the discharge into it 
 of large quantities of sewage, then, practical localities in the lake, even 
 twenty or thirty miles distant from the point of entrance to the sewage, are 
 not safe places in which to derive water for domestic use." 
 
 Numerous special investigations of lake water condition, and the 
 practical experience in the operation of the water works intakes, all 
 indicate that in any particular place reasonably adjacent to the lake 
 shore the quality of the water varies between extremely wide limits, in- 
 cluding water almost sterile for considerable periods of time, the usual 
 prevalence of moderately heavy pollution, depending upon the locality, 
 with occasional gross pollutions, regardless of locality within practicable 
 reach of a water works inlet. 
 
 Turbidity: 
 
 In drawing a continuous supply for the wrater works, it is necessary 
 to locate the intake not closer than two or three thousand feet from the 
 shore, in order to prevent ingress of sand and stoppages from anchor 
 ice. A large supply must necessarily be taken further from the shore. 
 The Chicago intakes are located from two to four miles outward. 
 
 Upon the west shore of Lake Michigan there are long periods of 
 the summer season when the prevaihng winds are from the west and 
 southwest. At such times the surface water is blown out into the lake 
 and is replaced by a return current along the lake bottom. At such 
 times as this an exceptionally clear and pure water may be drawn from 
 an intake located at or below mid depth, in twenty-five to forty feet 
 depth. 
 
 Severe storms usually occur with an east or northeast wind, The 
 surface water is blown in toward the shore, breakers are formed in the 
 shallow water, the dirty sand and accumulated sludge adjoining the 
 shore are stirred up and the water is returned lakeward as an undertow. 
 The filth is, however, more or less intermixed, from bottom to top of 
 water, in depths under fifty feet. At such times as this no clean or pure 
 water can be obtained ; the degree of the turbidity and extent of pol- 
 lution depends principally upon the severity of the storm and somewhat 
 upon its direction. 
 
 Wind conditions varying between the two extremes, which have 
 been mentioned above, produce water conditions varying between the 
 extremes of quality previously mentioned. There are certain conditions 
 in storms when pollution may travel with great rapidity to a Water 
 
92 
 
 Works intake. The situation is much like the dissipation of smoke 
 from a tall chimney. In relatively calm weather it may disappear within 
 a short distance from the chimney. Under a current of wind it may 
 stream out in one direction, traveling for miles. Pollution in a lake may 
 travel in similar manner. 
 
 Present Condition of the Water Supply: 
 
 About two-thirds of the time the water drawn from the Chicago 
 cribs is clear. It is often quite pure for short periods. However, its 
 sanitary character cannot be depended upon from hour to hour. For a 
 considerable portion of time at all the intake cribs it is distinctly bad. 
 It can only be safely used after heavy doses of liquid chlorine. The re- 
 quired dosage has increased of recent years. Occasionally the Health 
 Department has advocated boiling. The water as delivered to con- 
 sumers is often decidely turbid for weeks at a time. 
 
 The net result from a sanitary standpoint from the water as chlor- 
 inated has been very good, although there have been times when it has 
 been suspected of producing typhoid fever in local instances, apparently 
 due to chance pollution. To a large number of people the taste imparted 
 to the water through the chlorine dosage is extremely objectionable. 
 The demand is becoming stronger from year to year for a water free 
 from the chlorine taste. 
 
 Records of Turbidity: 
 
 The two mile crib supplying the Chicago Avenue pumping station 
 and a part of the water of the 22nd St. Station furnishes about one-fifth 
 of the total water supply of the city, including the downtown district. 
 Table 20 shows the prevailing turbidity of the water drawn from this 
 crib during the past ten years. 
 
 In the consideration of turbidity, which represents the apparent 
 cleanliness of the water, it should be stated that a clean water, such as 
 produced by water filtration plants, has a turbidity of about five. A 
 turbidity of ten is noticeable by people accustomed to clear water. A 
 turbidity of fifteen would cause serious complaint where people are 
 accustomed to clear water. A turbidity of fifty represents a very dirty 
 water that would desirably be treated by sedimentation before applica- 
 tion to a mechanical filter. 
 
 The records for the two mile crib shows that the water has a tur- 
 bidity more than ten practically at all times. It has a turbidity above 
 fifty for periods totaling from two to seven weeks per year, excepting 
 one year. This crib being the nearest to shore generally has the highest 
 turbidity as compared to other Chicago cribs. 
 
93 
 
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96 
 
 Table 21 shows the maximum and average*turbidities at each of the 
 ChicagT cribs. The average turbidity was less than ten a little more 
 than haii the time during the year 1924, up to October. The average 
 turbidity at all the cribs ranged between twenty and thirty-five during 
 February, thirteen to twenty-five during March, and ten to fifteen dur- 
 ing April. The maximum turbidity was above ten at most of the cribs 
 during the months of February to October inclusive. It was above 
 fifty at all the cribs during February, from 30 to 55 during March, from 
 eighteen to fifty during April, and ten to forty in May. 
 
 Filtration: 
 
 All objection to the piesent water supply can be eliminated by 
 mechanical filtration, which it is practical to apply to the Chicago watc; 
 supply at a comparatively moderate expense. Filtration will give the 
 citizens of Chicago pure clean water all the time, eliminating all possi- 
 bility of danger from the chance pollutions of the lake. A number of 
 cities upon the Great Lakes have already installed filtration works, in- 
 cluding several of the srnaller cities in the Chicago region, also including 
 the cities of Detroit, Cleveland, Lorain, Erie and Niagara Falls. In 
 several cases highly polluted waters are rendered entirely satisfactory 
 for domestic consumption. 
 
 Polluted Waters Treated: 
 
 At several places, on the Great Lakes, lake water is safely filtered 
 after receiving the sewage of the city supplied through intakes removed 
 only a comparatively short distance from the sewage outlets. Cleveland 
 is an example of this type. At Cleveland the water is taken within 
 19,000 feet from sewer inlets receiving only partially purified sewage. 
 
 Upon the Ohio River, city after city, from Pittsburgh to Cairo, takes 
 its water supply from the river, returning the sewage again to the 
 stream, the water being again and again used by the cities downstream 
 after filtration. Table 22 shows a list of these cities with approximate 
 distances measured by river, from sewage outlet to water works intake. 
 
 Although it has been felt desirable, and is proper in all cases in the 
 water supply of cities, to select ^mre a source as possible even when 
 filtration is resorted to, it has been necessary in some cases to filter more 
 or less grossly polluted water. The results from the sanitary stand- 
 point can safely be said to have exceeded expectations wherever filtra- 
 tion has been resorted to. 
 
97 
 
 TABLE 22. 
 
 SUCCESSIVE POLLUTION AND USE FOR WATER SUPPLY OF THE 
 OHIO RIVER FROM PITTSBURGH TO CAIRO. 
 
 City Using Filtered River Water 
 Miles 
 
 Below Popu- 
 Pitts- lation 
 burgh City 1920 
 Pittsburgh 588.343 
 
 50 E. Liverpool 21,411 
 
 66 Toronto 4,684 
 
 80 Steubenville 28,508 
 
 105 Wheeling 56,208 
 
 110 Bellaire 15,061 
 
 190 Marietta 15,140 
 
 202 Parkersburg 20,050 
 
 322 Huntington 50,177 
 
 340 Ashland 14,729 
 
 344 Ironton 14,007 
 
 372 Portsmouth, 33,011 
 
 498 Cincinnati 401,247 
 
 499 Newport 29,317 
 
 520 Aurora 4,299 
 
 534 Louisville 234,891 
 
 539 New Albany 22,992 
 
 B04 Evansville 85,264 
 
 ^15 Henderson 12,169 
 
 ?37 Mt. Vernon 5,284 
 
 934 Paducah 24,735 
 
 979 Cairo 15,203 
 
 Nearest Principal Source of Pollution 
 Miles Popu- 
 Up- lation 
 stream City 1920 
 
 ! Beaver ) 
 Monaca [ ''''' 
 
 20 Wellsville 8,849 
 
 8 Toronto 4,864 
 
 25 Steubenville 28,508 
 
 5 Wheeling 56,208 
 
 73 Moundsville 10,669 
 
 12 Marietta 15,140 
 
 37 Gallipolis 6,070 
 
 4 Catlettsburg 4,183 
 
 4 Ashland 14,729 
 
 28 Ironton 14,007 
 
 126 Portsmouth 33,011 
 
 126 Portsmouth 33,011 
 
 22 Cincinnati 594,000* 
 
 136 Cincinnati 594,000* 
 
 5 Jeffersonville 10,098 
 
 35 Owensboro 17,424 
 
 11 Evansville 85,264 
 
 25 Henderson 12,169 
 
 105 Henderson 12,169 
 
 130 Evansville 85,264 
 
 45 Paducah 24,735 
 
 *Including adjoining river towns. 
 
 Niagara Falls: 
 
 A typical example as to whd.t filtration can accomplish with a 
 freshly polluted water is instanced by the experience at Niagara Falls, 
 New York. For many years prior to 1913 this city was one of the most 
 important typhoid centers in the U !:tcd States. The city water supply 
 is taken from Niagara River a few hours after the water receives the 
 sewage from more than 500,000 people at Buffalo, and from other 
 smaller cities downstream. The accompanying Table 23 shows the 
 typhoid history of Niagara Falls prior to and following the installation 
 of filter plants in the year 1913. Two plants were installed. The 
 municipal plant went into service in February and the New York Water 
 Company's plant went into service in June, 1913. For a period of eigh- 
 
98 
 
 teen months shortly following the installation of the filters no typhoid 
 deaths occurred in the city, although shortly prior thereto and for many 
 years previous the typhoid death rate had commonly exceeded 100 per 
 hundred thousand per annum. Within the past ten (10) years there 
 have been only a few cases reported, a careful tally of them has been 
 kept, and it is stated they have not been traced to water supply. 
 
 Cost of Filtration for Chicago: 
 
 It is believed that the most feasible plan for filtering the Chicago 
 water supply will consist of plants located on the lines of the intake 
 channels at or close to the Lake Shore line. The city could be served by 
 four (4) plants, namely at Wilson Avenue, Chicago Avenue, Roosevelt 
 Road and 67th St. It would be practicable to install bulkheads and 
 
 TABLE 23. 
 
 TYPHOID DEATH RATE AT CITY OF NIAGARA FALLS, N. Y. 
 
 Remarks 
 
 
 
 
 Typhoid 
 
 
 Typhoid 
 
 Estimated 
 
 Death Rate 
 
 Year 
 
 Deaths 
 
 Population 
 
 per 100,000 
 
 1899 
 
 24 
 
 17,261 
 
 139 
 
 1900 
 
 24 
 
 19,457* 
 
 123 
 
 1901 
 
 29 
 
 20,362 
 
 143 
 
 1902 
 
 22 
 
 21,267 
 
 103 
 
 1903 
 
 29 
 
 22,172 
 
 131 
 
 1904 
 
 34 
 
 25,037 
 
 135 
 
 1905 
 
 49 
 
 26,432 
 
 185 
 
 1906 
 
 43 
 
 27,827 
 
 154 
 
 1907 
 
 37 
 
 28,000 
 
 132 
 
 1908 
 
 28 
 
 29,000 
 
 97 
 
 1909 
 
 24 
 
 29,793 
 
 80 
 
 1910 
 
 32 
 
 30,445* 
 
 105 
 
 1911 
 
 55 
 
 32,800 
 
 168 
 
 1912 
 
 23 
 
 35,000 
 
 66 
 
 1913 
 
 10 
 
 37,000 
 
 27 B( 
 
 1914 
 
 3 
 
 39,000 
 
 7.7 
 
 1915 
 
 
 
 41,000 
 
 
 
 1916 
 
 5 
 
 43,000 
 
 11.6 
 
 1917 
 
 5 
 
 44,800 
 
 11.1 
 
 1918 
 
 2 
 
 46,600 
 
 4.3 
 
 1919 
 
 2 
 
 48,500 
 
 4.1 
 
 1920 
 
 5 
 
 50,760* 
 
 9.8 
 
 1921 
 
 5 
 
 52,600 
 
 9.5 
 
 1922 
 
 2 
 
 54,800 
 
 3.6 
 
 1923 
 
 1 
 
 57,000 
 
 1.8 
 
 1924 
 
 3 
 
 59,000 
 
 5.1 
 
 Began water filtration** 
 
 *U. S. Census. 
 
 **Municipal Water Filtration Plant put in operation in February. 
 **Westem New York Co. Filtration Plant put in operation in June. 
 
99 
 
 gates in the tunnels, pump the water to the surface, pass it through 
 sedimentation basins and filters, store it in clear water reservoirs of 
 moderate size, and return the water again to the tunnel system beyond 
 the shore gates where it could pass as at present to the pumping stations. 
 
 It is stated that the water in the tunnel system now receives some 
 pollution from unknown sources after entering the tunnels. The City 
 Engineer states that his investigations indicate that this pollution is 
 probably confined to pollution at certain shafts. It seems hardly possible 
 that pollution could enter the tunnels proper, after passing landward 
 from the shore line. It is feasible to stop the surface pollution at the 
 shafts, if it exists. It is further possible in the design of the filter 
 w^orks to eliminate any possibility of pollution by adopting an hydraulic 
 grade line in the tunnel system above the ground water plane. This 
 would be possible by extending the shafts at the pumping stations to a 
 higher elevation and pumping water to a corresponding height at the 
 shore line. This could be done without increased cost of pumping. It 
 is practicable to purchase low lift pumps in large units that will have 
 an efficiency substantially equal to the pumps used in delivering water to 
 the city, and there would be no net loss of head. 
 
 In several instances the filtration plants could be located in existing 
 city parks, or in connection with the lake shore park improvements now 
 under way. It is possible to design the plants so that they would add 
 materially to the beauty and interest of the parks. Where the lake 
 shore is not proposed to be used for park purposes, it is possible to con- 
 struct the plants upon made ground closely adjoining the shore line. 
 Much ground of this character has already been made adjacent to the 
 city, and is in process of making in connection with Chicago's lake front 
 improvements. 
 
 Tentative estimates made by City Engineer, John Ericson, on the 
 filtration of Chicago water are as follows : 
 
 Total annual 
 
 Q.^jg Annual expense in- 
 
 * ■ Investment Operating eluding 5% in- 
 perudy Expenses terest and 2% 
 
 depreciation 
 
 Wilson Ave. Plant 200 $ 4,000,000 $ 234,335 $ 514,335 
 
 Chicago Ave. Plant 500 10,000,000 676,705 1,376,705 
 
 Roosevelt Rd. Plant 155 3,100,000 188,120 405,120 
 
 eSth St. Plant 445 8,900,000 651,000 1,274,000 
 
 Totals 1,300 $26,000,000 $ 1,750,160 $ 3,570,160 
 
 The above estimate covers an installation that would be sufficient 
 to filter the present water supply. If the water supply of the city is 
 metered, the above plant would serve all requirements of the city until 
 
100 
 
 after the year 1960, making due allowance for the seasonal and hourly 
 variations in pumping. 
 
 The above total cost is approximately $8.65 per capita on the pres- 
 ent population of Chicago. The average annual cost, including opera- 
 ting and fixed charges, is approximately $1.20 per capita on the present 
 population, and would be materially less under the increased population 
 of Chicago during the next thirty years during which the investment 
 would be effective. 
 
 Conclusion Regarding Filtration: 
 
 Chicago is entitled to a clean water, safe from a Sanitary stand- 
 point 365 days per year. This standard is generally demanded through- 
 out the United States. It is only a question of time when it will be 
 demanded in Chicago. 
 
 In our opinion filtration will insure a pure clean water for Chicago 
 at all times, under any diversion through the drainage canal exceeding 
 2,000 second feet. It is our belief that no amount of diversion up to the 
 present capacity of the Chicago drainage canal will insure safe water 
 for Chicago without filtration. We believe this is true regardless of 
 any practicable measures that may be taken for sewage purification. 
 We believe it is the only adequate safeguard for the Chicago water 
 supply. 
 
101 
 
 PART VIII. 
 
 SAVINGS EFFECTED BY METERING. 
 
 The quantity of municipal sewage is largely dependent upon the 
 water supply. In Chicago where the population for which sewage treat- 
 ment is to be provided is large, the industrial load is great, and the 
 amount of water pumped is extravagant, the problem of keeping expen- 
 ditures for sewage treatment works reasonably low, is difficult. The 
 first two factors, i. e., population and industrial wastes, are fixed as of 
 any particular time ; the last factor, water pumpage, is capable of regu- 
 lation. The question of water waste restriction is acordingly a sewage 
 disposal problem as well as a water supply problem. With this in mind 
 a study of the effect of metering on the costs of sewers and sewage dis- 
 posal has been made herein and incidental thereto certain observations 
 as to the effect upon the water works and water service are included. 
 
 At the present time ninety percent of all of the consumers furnished 
 water by the Chicago Water Works are served through socalled ''flat 
 rates" under which there is no incentive to keep plumbing in repair, nor 
 to curtail other wastes. As a result the pumpage of water is excessive, 
 the water service is deficient as to quantity, qualify and pressures, and 
 the Water Department is confronted with the continual necessity of 
 making large expenditures in its hopeless effort to keep pace with the 
 open faucet. 
 
 In 1923, the last year for which published records are available, but 
 9.65 percent of all services were metered. The water passed through 
 these meters was 30.4 percent of the total pumpage. The revenue de- 
 rived from the sale of metered water was 57.96 percent of the total 
 revenue of the Water Works. 
 
 The metered water consumers paid an average of approximately 
 six and one-fourth cents per thousand gallons for the water consumed. 
 Approximately seventy percent of the gross pumpage which is unme- 
 tered yielded a revenue equivalent to approximately two cents per 1,000 
 gallons, or less than the actual cost of pumping. 
 
 Water waste is directly reflected in the costs of construction, and 
 the cost of operating the Water Works plant. In the past thirty years, 
 during which the population and the mileage of mains have increased 
 approximately 150 percent, the cost of im.provements to the Water 
 Works and the average daily pumpage have increased approximately 
 
102 
 
 400 percent, or at a rate two and a half times as fast as the population. 
 
 Pumpage and construction costs increase at approximately parallel 
 rates. 
 
 Water waste results in deficient water pressures throughout the 
 greater part of the city. At the present time approximately seventy-five 
 percent of the area of the city of Chicago suffers from inadequate pres- 
 sure during periods of peak consumption. 
 
 Water waste decreases the effectiveness of fire protection service. 
 
 Water waste is directly reflected in the dry weather sewage flow. 
 It therefore increases the costs of constructing intercepting sewers, sew- 
 age pumping stations and sewage disposal plants ; it is also directly re- 
 flected in the operating costs of sewage pumping stations and sewage 
 disposal plants. 
 
 Curtailment of Waste: 
 
 Ample precedent and experience are available from which it is 
 practicable to determine, within reasonable limits of accuracy, the possi- 
 bilities of waste restriction for Chicago, and its effect upon costs of 
 water service and sewage disposal. Table 24 presents the data 
 relative to results accomplished by metering in eleven American cities. 
 Figure 18 shows diasframmatically what has been accomplished by 
 meters in these and other cities. Numerous studies have been made of 
 the particular problem of restricting waste of water in this city. All in- 
 
 TABLE 24. 
 
 EFFECT OF METERING UPON THE CONSUMPTION OF WATER. 
 
 Use of Water in Gallons per Service 
 
 
 Before 
 
 After 
 
 
 Extensive 
 
 Extensive 
 
 City 
 
 Metering 
 
 Metering 
 
 
 1048 
 
 396 
 
 
 1108 
 
 734 
 
 Cleveland, 
 
 1258 
 
 688 
 
 Milwaukee, Wis 
 
 1314 
 
 656 
 
 Lowell, Mass 
 
 630 
 
 427 
 
 
 838 
 
 396 
 
 
 853 
 
 383 
 
 
 2240 
 
 1165 
 
 
 1560 
 
 508 
 
 
 1035 
 
 635 
 
 
 755 
 
 599 
 
 
 1149 
 
 599 
 
 
 6.7 
 
 95.0 
 
 Average reduction by increasing meters from 6.7% to 95.0% was 
 
 from 1149 to 599 gallons per service or 48%. 
 
103 
 
 vestigators have been in substantial accord as to the immense savings 
 in cost and benefits in service which would result therefrom. 
 
 Quite recently, at the mid-winter convocation of the Western 
 Society of Engineers, held in February, 1925, Mr. John Ericson, for 
 nearly thirty years city engineer of Chicago, presented a paper on 
 'THE WATER SUPPLY PROBLEM IN RELATION TO THE 
 FUTURE CHICAGO." In this paper Mr. Ericson effectively showed 
 
104 
 
 the need of metering and the results which might be accompHshed there- 
 
 Mr. Ericson estimated the pumpage requirements which the Chica- 
 go water supply would be called upon to meet if the present system of 
 metering were to continue, and also what these requirements would be 
 if all water consumers were to be metered within the next ten-year 
 period. - 
 
 The results of this analysis are shown in diagrammatic form on 
 Figure 19. It is estimated that the total pumpage in 1924, of approxi- 
 mately 800,000,000 gallons per day will increase to 2,200,000,000 gallons 
 per day by 1960, if the present system of metering is continued. If, 
 however, all water servtces are metered within the next ten years the 
 total pumpage of approximately 800,000,000 gallons per day at the pres- 
 ent can be reduced to approximately 520,000,000 gallons per day in 
 1935, increasing to 800,000,000 gallons per day by 1960. In other 
 words, the pumpage with universal metering, thirty-five years hence 
 will be less than the pumpage at the present time with but ten percent 
 of the services metered. We have carefully investigated this matter 
 and we believe that Mr. Ericson's estimates of reduced pumpage are 
 approximately correct. 
 
 This fact has an important bearing upon water works construction 
 costs. No additional crib intake or pumping station capacity and no 
 expenditures for feeder mains would be required for the next thirty-five 
 years if universal metering were to be adopted. 
 
 The savings to the Chicago Water Works, due to metering, have 
 been estimated at from $225,000,000 to $425,000,000 in the next twenty- 
 five to thirty-five years. Mr. Ericson, based upon a population of 
 5,000,000 people in 1960, figures that the saving in operation up to 
 that time will be $117,000,000, the saving in repairs and renewals 
 $43,000,000, and the saving in additions and extensions $143,000,000. 
 Total saving $303,000,000. This saving does not take into consideration 
 fixed charges on the savings in new construction, which if taken at a 
 rate of five percent and based upon the construction expenditures being 
 made at a uniform rate from the present time to 1960, would add an 
 additional $125,000,000, making the total saving to the Chicago Water 
 Works amount to $428,000,000 by 1960. 
 
 In a paper "What metering would do for the Chicago Water 
 Works" presented before the Western Society of Engineers by L. R. 
 Howson on February 1, 1923, it was estimated that the savings prior to 
 1950, due to universal metering would be $88,000,000 in construction 
 expenditures, $145,000,000 in operation, including saving in fixed 
 
105 
 
 
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 Year 
 
 Figure 19. 
 
 Effect of metering the Chicago water supply upon total daily 
 pumpage and per capita use. 
 
 From paper by John Ericson read before Western Society of Engineers. 
 
 charges, total saving $233,000,000, or approximately eight and one-half 
 million dollars per year. 
 
 Other estimates have been made, all of which show the enormous 
 savings which can be effected by metering. The exact amount is not of 
 so much importance when the lowest estimates that have been made by 
 competent engineers investigating this matter show a saving in the next 
 generation of over $200,000,000. 
 
 Effect of Metering on Intercepting Sewers and Sewage Disposal Costs: 
 
 The amount of water reaching the sewers is important in the de- 
 sign of intercepters and sewage disposal works. The costs of a large 
 part of this type of construction are directly proportional to the quan- 
 tity of sewage to be treated. 
 
106 
 
 Intercepting Sezvers: 
 
 The capacity of intercepters is directly affected by the amount of 
 the water supply, practically all of which reaches the sewers. If the 
 water pumpage is excessive and can be reduced to the extent of thirty- 
 five percent the intercepting sewer sizes can be reduced about twenty 
 percent and the cost a somewhat smaller percentage. In view of the 
 large mileage of intercepting sewers yet to be built the question of the 
 water supply and its eft'ect upon intercepter sizes is important. 
 
 At the present time the intercepting sewers for the Des Plaines and 
 Calumet plants have been completed. The intercepters leading to the 
 North Side plant are all under contract, and construction is well on to- 
 ward completion. The intercepting sewers leading to the West and 
 Southwest plants have not yet been started. Intercepting sewers for 
 the West Side plant, as tentatively designed by the Sanitary District, 
 include an approximate length of twenty miles of large size, the maxi- 
 mum being twenty-one and one-half feet in diameter. The tentative 
 design of the intercepting sewers for the Southwest plant includes some 
 fifteen miles of sewers, varying in size from five to eighteen feet. In 
 view of the status of the intercepting sewers for these two plants yet to 
 be built, it is pertinent to inquire into the affect of metering upon the de- 
 sign and costs of these sewers. 
 
 We have been furnished by the Sanitary District with the basis of 
 design for the West and Southwest sewers. They have furnished us 
 with the drainage areas tributary at points of interception, the popula- 
 tion estimated as being located on each drainage area in 1960, the in- 
 dustrial use as estimated by the Sanitary District in cooperation with 
 the City Water Department, and figures as to infiltration. The total 
 sewer capacity average over the entire district amounts to 600 gallons 
 per capita per day. 
 
 Based upon figures as furnished by the Sanitary District, the tenta- 
 tive design made by the District's engineers contemplates that the 
 sewers will flow three-fourths full under peak flow conditions. How- 
 ever, under the use of water estimated by Mr, Ericson and others under 
 present conditions of metering, the sewers would be flowing full in- 
 stead of three- fourths full if universal metering is not adopted. The 
 average use of water if unmetered will be 440 gallons per capita per day. 
 If thirty-five additional is added for the peak flow excess over average 
 the entire sewer capacity is required. 
 
 With the entire water supply metered the average use of water 
 would be but 160 gallons per capita per day or 280 gallons per capita 
 per day less than if the present system is continued. Deducting this 
 amount from the capacity allowed in the Sanitary District's estimates 
 
107 
 
 an equivalent capacity of 320 G. P. D. per capita would be indicated. 
 This is a lower figure than we would however care to adopt and we 
 have arbitrarily raised it to 375 gallons per capita per day. The effect 
 of metering upon sewer costs is therefore made on this basis. 
 
 The sizes of sewers required under both the metered and unmetered 
 bases have been determined for each reach of the intercepters serving 
 the West and Southwest areas in which construction for sewage dis- 
 posal has not already started. Comparable grades and velocities were 
 assumed. 
 
 The costs of the intercepters were estimated using the unit prices 
 developed as described in Part X. It was found that metering will 
 effect a saving of $3,105,500 in the cost of the intercepters to the West 
 Side plant, and $2,043,800 in the cost of the intercepters to the South- 
 west Side plant; a total of $5,149,300. This saving results from meter- 
 ing alone. It is a saving perfectly practicable of realization. Metering 
 must eventually come. 
 
 Had the actual costs of sewers built under contracts let by the 
 Chicago Sanitary District been used as a basis of the comparison the 
 indicated savings would have been much greater. 
 
 Metering cannot be retroactive in saving expenditures on sewers 
 already built ; it will , however, greatly extend the period of adequacy 
 of such sewers. 
 
 In view of the ultimate necessity for metering the Chicago Water 
 Supply, as agreed by all engineers who have given it thorough study, it 
 would seem a wise procedure to give due consideration to this question 
 in the design of sewers by the Sanitary District. Sewers built for the 
 present without meters will be adequate for 1960 with meters. 
 
 Effect of Metering on Sezvage Disposal Plant Costs: 
 
 The cost of certain parts of sewage disposal plants varies directly 
 with the quantity of sewage to be handled. These parts include pump- 
 ing stations, grit chambers, screens and aeration tanks ; other parts vary 
 directly with the solid or organic load of the sewage. These parts in- 
 clude sludge chambers of Imhoff tanks, sludge beds, and sludge pressing 
 and drying equipment, for activated sludge plants. 
 
 Other parts of the plants vary in a ratio which is neither directly in 
 proportion to organic load nor to the quantity coming to the plant. This 
 refers particularly to air compressor equipment and to sprinkling filters. 
 It has been found practicable to load sprinkling filters handling domestic 
 sewage with 2,000 to 4,000 people per acre foot depth of sprinkling 
 filters. It has also been found practicable to put sewage through these 
 filters at rates as high as 2,500,000 to 3,000,000 gallons per acre per day 
 without operating difficulties. 
 
108 
 
 The following table shows the operating rates on several plants 
 operating satisfactorily under reasonably heavy loadings. 
 
 
 Sprinkling 
 
 Filter Loads. 
 
 
 
 City 
 
 Pop. 
 
 Acre Fact of 
 
 Pop. per Sewage per 
 
 Served 
 
 Stone Filters 
 
 Acre foot capita (gal.) 
 
 Lincoln, Neb 
 
 . . 50,000 + 
 
 D X ^.o 
 
 -Id. 5 
 
 AAA 1 
 O,UU0 + 
 
 OA 
 
 80 
 
 Madison, Wis 
 
 . . 51,500 
 
 6X2.5: 
 
 =15 
 
 (a)3400 
 
 (a)102 
 
 Columbus, 
 
 . .270,000(1920) 
 
 51/3X10= 
 
 :53.3 
 
 5060 
 
 100 
 
 Atlanta, Ga, 
 
 
 
 
 
 
 Intrenchment 
 
 , 30,000 
 
 5%X2= 
 
 :11.5 
 
 2730 
 
 167 
 
 Lexington, Ky 
 
 . 28,000 
 
 6X2: 
 
 =12 
 
 2330 
 
 90 
 
 Baltimore, Md 
 
 , ,600,000(1924) 
 
 8y2X30= 
 
 =255 
 
 (a)2360 
 
 86 
 
 As operated for best 
 
 
 
 
 
 
 results 
 
 
 
 
 (a)3500 
 
 
 Average 
 
 
 
 
 3200 
 
 104 
 
 (a) Excliisive of packing house waste. 
 
 At Baltimore where there is a total of thirty acres of stone beds 
 the units are operated so as to maintain as nearly as possible from two 
 and one-half to three million gallons per acre per day rate (average is 
 from 2.79 to 2.91, C. E. Keefer, Engineering News Record, 2-7-24), 
 the equivalent under Balitmore conditions of approximately 3500 people 
 per acre foot of stone beds. 
 
 Included in this optimum loading of 3500 people per acre foot of 
 stone filters is a packing house waste, which, based upon weight of ani- 
 mals slaughtered per capita contributing sewage to the plant, is about 
 thirty-five percent as great as that of the Chicago stockyards wastes. 
 
 The Madison stone filters, aperating satisfactorily at a rate of 3400 
 people per acre foot have in addition a packing house waste practically 
 the same as the Chicago stockyards waste, compared on a slaughter 
 weight per capita basis. 
 
 A study of the effectiveness of sprinkling filters in reducing the 
 biochemical oxygen demand shows that the Baltimore and Columbus 
 filters reduce the demand sixty-seven and fifty-five percent respectively 
 as compared to thirty-one, thirty-one and forty-nine percent respectively 
 for the two Atlanta and Fitchburg plants with population loads per 
 acre foot, but about half of those at Baltimore and Columbus. 
 
 It is our opinion that good operation may be secured within the 
 upper limits of at least 3,000 people per acre foot, and three million 
 gallons per acre per day for six foot stone beds. 
 
 As with a per capita use of 160 gallons per day the population 
 served by a six and one-half foot filter operating at a three M. G. D. 
 per acre rate would be about 2850 per acre foot the rate of liquid dosage 
 
109 
 
 rather than the population load is considered the limiting factor in com- 
 paring the cost of sprinkling filters at Chicago under metered and un- 
 metered conditions. 
 
 In the estimated savings on the item of sprinkling filters, ef¥ected 
 by metering, we have therefore assumed that the more dilute sewage, 
 tinder unmetered conditions, would have a direct effect on area and cost 
 of beds. In other words, if the quantity of sewage is doubled due to 
 water waste the area and cost of stone beds would likewise be doubled 
 compared to areas and costs under fully metered conditions. 
 
 The effect of metering upon plants already built is to prolong their 
 period of usefulness and defer the time at which additions will be re- 
 quired. Each plant has been analyzed in its component parts, its capa- 
 cities studied with reference to future needs under metered and unmet- 
 ered water supply conditions, and the savings effected by universal 
 metering ascertained. 
 
 The following is a summarization of the savings which universal 
 metering will effect in the future construction costs of intercepters and 
 sewage disposal works. 
 
 Savings in intercepter costs are computed for 1960 quantities ; dis- 
 posal plants for 1945 conditions. 
 
 The total savings of approximately $50,000,000 do not include any 
 savings in the construction cost of sewage disposal works to the Chicago 
 Sanitary District after 1945. The savings cover the cost of construction 
 only, operating cost not having been taken into consideration in this 
 part of the study. 
 
 The small estimated saving with a flow of 4167 c. f. s. results from 
 the fact that a larger part of the cost of an activated sludge plant is in- 
 dependent of liquid volume than is the case with a sprinkling filter plant. 
 The sludge drying and pressing equipment varies only with the solid 
 content which is in turn independent of the dilution of the sewage. 
 
 The 4167 c. f. s. project is the only one contemplating activated 
 sludge treatment at the West and Southwest Side plants. 
 
 Savings in Operating Costs: 
 
 The restriction of water waste will also have a marked effect upon 
 operating costs of pumping stations and disposal works. Practically all 
 the costs of sewage treatment in plants such as herein considered vary 
 nearly in proportion to Hquid quantities, except costs incident to sludge 
 handling and sludge drying, which are practically independent of liquid 
 volume. In estimating the savings in operating cost due to metering, 
 the following bases have been assumed : 
 
 (a) The cost of power varies directly with the liquid volume. 
 
 (h) Pumping station labor costs vary at a rate of fifty percent as 
 
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 great as the variation in liquid volume, i. e. if the liquid volume is 
 doubled the station labor is increased fifty percent. 
 
 (c) Labor for sewage treatment plant operation varies as above 
 for station labor as the costs are approximately fifty percent determined 
 by liquid volume and fifty percent by total solids or sludge. 
 
 The estimated savings in disposal plant operating expenses result- 
 ing from metering of the water supply have been estimated as above 
 outlined for the year 1945. The savings vary from $3,000,000 to 
 $4,000,000 per year depending upon the treatment processes necessary 
 with the flows in the channel varying from 10,000 c. f. s. to 4167 c. f. s. 
 
 TABLE 26. 
 
 SAVINGS IN OPERATING COSTS (1945) 
 OF SEWAGE DISPOSAL WORKS (EXCLUSIVE OF FIXED CHARGES) — 
 EFFECTED BY METERING THE WATER SUPPLY. 
 
 Cubic Feet per Second Flow in Channel. 
 Plant 4167 6000 7500 8500 10000 
 
 Calumet $ 174,750 $ 174,750 $ 174,750 $ 174,750 $ 174,750 
 
 North Side 947,000 947,000 947,000 947,000 947,000 
 
 West Side 1,869,500 1,288,500 1,288,500 968,000 968,000 
 
 Southwest Side 1,289,500 850,800 636,800 850,800 850,800 
 
 Total Annual $4,230,750 $3,261,050 $3,047,050 $2,940,550 $2,940,550 
 
 Basis. 
 
 Sta. labor varies 50% with liquid volume — 50% not affected by volume. 
 Power varies directly with liquid volume. 
 
 Treatment plant operating cost varies 50% with liquid volume and 50% 
 with solids. 
 
 These savings in operating cost do not include savings in fixed 
 charges which at four percent for interest and two percent for deprecia- 
 tion reserve would amount to from $2,500,000 to $3,000,000 per year 
 in 1945. 
 
 The estimated saving in operating cost resulting from metering 
 for each flow is shown in the table included herewith. 
 
 Summarisation of Savings by Metering: 
 
 A study of the estimated savings to the Chicago Water Department 
 during the thirty-five year period to 1960 and other estimated savings 
 for other periods would lead us to believe that not less than $200,000,000 
 to $225,000,000 would represent a fair measure of the total savings 
 (including interest) to the Chicago Water Works prior to 1945 if 
 meters were adopted and universally installed within ten years. Add 
 
112 
 
 to this $200,000,000 saving in the water works, an additional saving of 
 $40,000,000 to $53,000,000 in sewers and sewage disposal and the 
 amount becomes $240,000,000 to $253,000,000 saved in twenty years, 
 an average of over $12,500,000 per year, through the introduction of 
 universal metering, and without crediting any savings after 1945. 
 
 An additional amount reaching $3,000,000 to $4,000,000 per year 
 in 1945 will be saved in operating costs of pumping stations and treat- 
 ment works. 
 
 Magnitude of Savings: 
 
 The estimated saving of approximately $250,000,000 in twenty 
 years is so great that it will in addition to installing meters at a cost 
 of approximately $10,000,000 build complete filtration works for the 
 Chicago water supply at an estimated cost of $26,000,000 (Mr. Ericson's 
 W. S. E. paper) finance complete sewage disposal for the entire city 
 and still leave over $100,000,000 net, which would be more than enough 
 to acquire the elevated lines and make a good start toward the subway 
 system. 
 
 Effect of Metering on Water Sermce: 
 
 In addition to the financial advantages, metering alone will double 
 the average pressure in the water m.ains of the city, and will enable the 
 water works to furnish all consumers adequate service, where but 
 twenty-five percent now have it. 
 
 Water metering will make filtration possible. Without it Chicago 
 must continue to drink unfiltered and at times turbid lake water, highly 
 chlorinated with resulting tastes and odors. 
 
 Eifect of Metering Upon Protection of Health: 
 
 Few sanitary engineers will dispute the assertion that $36,000,000 
 spent for meters and filtration plants will do more to protect the people 
 of Chicago from water-borne disease than will an equal or larger 
 amount spent for sewage disposal works. 
 
 It has been estimated that with a diversion of but 4167 c. f. s. there 
 would be from seven to eight reversals of flow with discharge of sewage 
 into the lake each year (see memorandum concerning drainage and 
 sewage conditions at Chicago, Sanitary District, December, 1923). It is 
 believed to be a safe assertion that seven or eight reversals with filtra- 
 tion would be much less hazardous than the one to four reversals now 
 occurring. 
 
 Filtration is the first line of defense against water borne disease. 
 Its results are positive, continuous and effectual. It has repeatedly 
 demonstrated its ability to safeguard the public health. 
 
113 
 
 Filtration is only practicable at Chicago if universal metering is 
 adopted. Its cost, together with large additional savings, can be re- 
 covered by metering. Metering is, therefore urgent to : 
 
 (a) Protect health against water borne disease. 
 
 (b) Enable the water plant to furnish adequate service and pres- 
 sure 
 
 (c) Prevent wasteful expenditures for the waterworks. 
 
 (d) Prevent wasteful expenditures for intercepting sewers and 
 se\vage disposal works. 
 
114 
 
 PART IX. 
 
 VOLUME OF SEWAGE. 
 
 The volume of sewage liquid to be treated is dependent upon : 
 1st. Tributary population. 
 2nd. The total water use, and 
 3rd. Infiltration. 
 
 So far as the sewage contributed by the domestic population of the 
 Chicago Sanitary District is concerned, practically the entire amount 
 will be collected in the five major sewage disposal plants; viz. The 
 Des Plaines, Calumet, North Side, West Side and Southwest side. The 
 distribution of the population for the present and for each five year 
 period up to 1945, is shown on Table 27. 
 
 It will be noted that the total population tributary to these five 
 major plants is somewhat less than the total population of the district 
 as estimated in Part III, and as shown in this table. It is estimated that 
 approximately 105,000 people residing in the district are not tributary 
 to any one of these five plants at the present time, and that it is probable, 
 due to the rapid expansion of the suburban area, that this number will 
 gradually increase and reach approximately 300,000 people by 1945. 
 The sewage originating from this population must either be treated by 
 outlying plants or by pumping to one of the major plants. 
 
 TABLE 27. 
 
 POPULATION TRIBUTARY TO EACH OF THE FIVE MAJOR SEWAGE 
 
 DISPOSAL PLANTS. 
 
 Popula- 
 tion, by 
 Sanitary 
 District 
 
 Disposal 
 
 Plant 1925 
 Des Plaines . . 50,000 
 
 Calumet 190,000 
 
 N. Side 690,000 
 
 I W. Side* . 
 I S. W. Side. 
 
 .1,370,000 
 .• 950,000 
 
 1930 
 60,000 
 225,000 
 800,000 
 1,430,000 
 1,040,000 
 
 1935 
 75,000 
 255,000 
 915,000 
 1,490,000 
 1,135,000 
 
 1940 
 90,000 
 
 290,000 
 1,015,000 
 1,550,000 
 1,230,000 
 
 1945 
 105,000 
 320,000 
 1,125,000 
 1,615,000 
 1,322,000 
 
 Total 5 Major Plants 3,250,000 3,555,000 3,870,000 4,175,000 4,487,000 
 
 Misc. Plants 105,000 155,000 200,000 250,000 298,000 
 
 Total Population of Dist. .3,355,000 3,710,000 4,070,000 4,425,000 4,785,000 
 
 *Excl. of 300,000 transient loop population. 
 
115 
 
 The table showing the distribution of the total population of the 
 district over the five plants leaves out of consideration the floating or 
 transient population, largely centered over the area tributary to the 
 West Side plant, which embraces the loop district. This floating popu- 
 lation is estimated at 300,000 people, both for the present and for 1945, 
 and in the quantities of sewage which are estimated as reaching the 
 West side plant, the resident population has arbitrarily been increased 
 300,000 people to care for the transient population. 
 
 This figure of 300,000 is considered as representative of the purely 
 transient population plus that part of the working or day population 
 which is employed in Chicago, largely in the area to be served by the 
 West side plant, and which lives outside of the area served by the Sani- 
 tary District. It necessarily is a more or less approximate figure, but 
 is probably as accurate as can be reasonably determined. Some allow- 
 ance obviously must be made in a city such as Chicago to care for this 
 sewage load contributed to the total by those not enumerated in the 
 Chicago census figures. 
 
 The quantity of sewage to be treated at each of the five major 
 plants has been estimated from a study of the population tributary to 
 each, and has been estimated upon two bases, viz. (a) under the 
 present system of metering, and (b) universal metering of the water 
 supply. 
 
 The greater part of the population residing within the Chicago 
 Sanitary District receives its water supply from the City of Chicago. 
 The total pumpage of the Chicago Water Works for the year 1923, 
 averaged 807,000,000 gallons daily, which the Chicago Water Depart- 
 ment estimates as having been supplied to 3,062,532 people, of which 
 approximately 150,000 were outside of the city of Chicago but within 
 the Chicago Sanitary District limits. 
 
 In addition to the pumpage by the Chicago Water Department, 
 some water reaches the sewers from private water supplies developed 
 by industries and from the supplies of suburban cities within the area 
 of the Sanitary District of Chicago. There are a few industries develop- 
 ing considerable supplies, notably those in the Stockyards and Corn 
 Products districts. 
 
 There is also a small population supplied from municipal supplies 
 within the Sanitary District other than the City of Chicago, the largest 
 of which is the Evanston supply. Others are those at LaGrange, River 
 Forest, Forest Park, Summit, etc. While we have no data as to the 
 total amount of water pumped by industries and municipalities other 
 than Chicago, within the Chicago Sanitary District, it is believed that in 
 total amount it does not exceed five percent of the water pumped by 
 
116 
 
 the City of Chicago. Most of the water pumped, in addition to that 
 pumped by the City of Chicago, is furnished under metered conditions, 
 with waste well restricted. 
 
 The total population of the cities and villages in the Sanitary Dis- 
 trict (excluding Chicago) has increased from 89,703 in 1900 to 276,930 
 in 1920. Based upon an average use of 100 gallons per day, the total 
 water used by these villages would be about 30,000,000 gallons per day 
 at the present time, or about four percent of the average daily pumpage 
 of Chicago. The industries probably use enough well water to raise 
 the total to approximately five percent of the Chicago pumpage. Table 
 5 shows the population of each of the cities and villages in the 
 Sanitary District. 
 
 Infiltration of ground water into the sewers is quite indeterminate 
 in amount. The Sanitary District of Chicago has substantially no 
 figures which would furnish reliable information to be used as a basis 
 for the amount of infiltration into the sewers of the various sections of 
 the city under varying soil conditions. No measurements are recorded 
 by the city. Such data as are available are fragmentary only. 
 
 The city of Chicago has designed its pumping stations on the basis 
 of 100 gallons per acre per day infiltration in clay soils and 1000 gallons 
 per acre per day in sandy soils. City sewer sizes are determined by 
 flood flows. The greater part of the city of Chicago has a dense clay 
 soil, through which infiltration into the sewers is low. A comparatively 
 small area is sandy. The Sanitary District of Chicago has made its 
 preliminary design of the West Side intercepters, using an infiltration 
 allowance of approximately 2000 gallons per acre per day. The average 
 flow, which is the governing consideration in sewage disposal plant de- 
 sign, is very much less than this amount. It is believed that, taken as an 
 average over the entire Sanitary District area, the infiltration of ground 
 water into the sewers is very small in amount. In th€ computations 
 hereinafter made in Part IX, the infiltration has been based upon 750 
 G. Po D. per acre which results in the infiltration about one-sixth of the 
 domestic flow or six percent of the total flow estimated for the West 
 Side intercepter. 
 
 A part of the water supply never reaches the sewers. It is used 
 for sprinkling and other uses which do not contribute to the sew- 
 age flow. The amount of water lost in this way is alos indeterminate. 
 
 Taken as a general average under the conditions prevailing here in 
 Chicago, it is probable that if the infiltration of ground water into the 
 sewers is considered equal to that part of the supply which does not 
 reach the sewers, the result will be not far from correct. This has been 
 
117 
 
 the basis upon which the size of the sewage disposal plants outlined in 
 this report has been predicted. 
 
 We have prepared a table based upon the estimated population and 
 the water use under universally metered and unmetered conditions, 
 showing the amount of sewage which it will be necessary to treat at 
 each of the five major plants for each five year interval from the present 
 to 1945. 
 
 The last line of this table shows the sewage flow per capita for the 
 entire Sanitary District. It will be noted that, under metering, the 
 total amount of sewage averages from 170 to 171 gallons per capita 
 per day as compared to the water consumption previously estimated 
 herein at 160 gallons per capita per day under completely metered con- 
 ditions. The discrepancy is due to the fact that in estimating the quan- 
 tity of sewage reaching the West Side plant, there has arbitrarily been 
 added the flow originating from the 300,000 floating population in that 
 area. 
 
 So far as the West Side plant alone is concerned, the basis is be- 
 lieved to be the correct procedure. It is also correct insofar as this 
 floating population represents the population originating outside the 
 boundaries of the Sanitary District of Chicago. Insofar as it includes 
 the population originating within the Sanitary District of Chicago, and 
 simply transferred during the working hours from the area tributary 
 to one of the other major sewage disposal plants to the West Side plant 
 area, it results in an over-estimate of the quantities taking the city as a 
 whole. 
 
 TABLE 28. 
 
 QUANTITIES OF SEWAGE TO BE TREATED UNDER UNIVERSAL 
 METERING AND PRESENT METERING OF WATER SUPPLY. 
 
 Plant 1925 1930 1935 1940 1945 
 
 Million Gallons Sewage Daily 
 
 
 (a) 
 
 (b) 
 
 (a) 
 
 (b) 
 
 (a) 
 
 (b) 
 
 (a) 
 
 (b) 
 
 (a) 
 
 
 Des Plaines . . 
 
 5 
 
 6 
 
 6 
 
 8 
 
 8 
 
 9 
 
 9 
 
 10 
 
 10 
 
 
 Calumet 
 
 53 
 
 50 
 
 67 
 
 41 
 
 83 
 
 46 
 
 102 
 
 51 
 
 118 
 
 
 North Side . . . 
 
 193 
 
 176 
 
 240 
 
 145 
 
 297 
 
 163 
 
 354 
 
 180 
 
 416 
 
 
 West Side 
 
 370 
 
 316 
 
 429 
 
 286 
 
 485 
 
 296 
 
 542 
 
 306 
 
 595 
 
 4- 114 
 
 S. W. Side.... 
 
 256 
 
 229 
 
 312 
 
 182 
 
 370 
 
 197 
 
 430 
 
 222 
 
 490 
 
 
 Totals 
 
 877 
 
 777 
 
 1054 
 
 662 
 
 1243 
 
 711 
 
 1437 
 
 769 
 
 1629 
 
 (1743) 
 
 Ave. G.P.D. per 
 
 
 
 
 
 
 
 
 
 
 
 cap 
 
 262 
 
 219 
 
 296 
 
 171 
 
 322 
 
 170 
 
 344 
 
 171 
 
 364 
 
 (390) 
 
 (a) Present system of metering. 
 
 (b) Universal metering. 
 
118 
 
 This allowance is, however, in the nature of a factor of safety in- 
 sofar as it is affected by the shifting of populations from one plant to 
 the other. If half the loop is assumed as originating within the Sanitary 
 District boundaries, this allowance for the West Side plant is equivalent 
 to including an allowance of approximately 150 gallons per acre per day 
 for infiltration. 
 
 Table 28 is a summarization of the quantities of sewage flow 
 to be expected at each of the five major plants under universal metering 
 and under present conditions of metering of the water supply from 1925 
 to 1945. 
 
119 
 
 PART X. 
 
 FUTURE INTERCEPTING SEWER CONSTRUCTION. 
 
 At the present time there are approximately 150 sewer outlets 
 emptying into the Chicago River and the Drainage Canal. The outlets 
 on the North Branch as far south as Fullerton Avenue are all to be in- 
 tercepted by the North side intercepting sewers for which contracts have 
 already been let. These intercepters serve the North Side treatment 
 works. The present outlets from Fullerton Ave. South and West 
 along the river and main Drainage Canal as far as the village of Sum- 
 mit, are yet to be intercepted and the dry weather flow carried to the 
 proposed West and Southwest Side disposal plants to be located in the 
 vicinity of Summit. 
 
 All but about thirty-five miles of the total length of intercepters 
 required have already been built. Of this thirty-five miles, twenty miles 
 will be required to collect the sewage and carry it to the West Side plant 
 and fifteen miles will be required for the Southwest Side plant. 
 
 Basis of Intercepter Design: 
 
 A glance at the map, Figure 3, shows the routes of the pro- 
 posed West and Southwest Side intercepting sewers. In general they 
 parallel the river and the Drainage Canal, extending along both sides 
 of these channels from Fullerton Ave. on the North Side, southerly to 
 the main channel where they are joined by intercepters laid from the 
 lake westerly, thence through the highly congested central district and 
 along the Drainage Canal to the vicinity of Summit. 
 
 In most of this length the congestion is such as to almost preclude 
 open cut methods of construction. The Sanitary District has accordingly 
 adopted tunnel methods of construction, for which the heavy clay soil 
 of this district is admirably adapted. The tunnels are in general at 
 shallow depths below the street surface. 
 
 Other cities such as Milwaukee, Detroit and Cleveland are using 
 tunnel rather than open cut methods quite largely. On paved streets in 
 Milwaukee it has been found economical to use tunnels in constructing 
 pipe sewers as small as ten inches or twelve inches in diameter. 
 
 With the conditions prevailing in Chicago, the adoption of tunnel- 
 ing rather than open cut methods will probably be economical, and will 
 greatly reduce inconvenience to the public. 
 
120 
 
 The Chicago Sanitary District has tentative designs for the West 
 and Southwest Side intercepting sewers, the results of which have been 
 furnished to us for our study. 
 
 An analysis of the design of the West Side intercepters serving 
 about 1,350,000 resident and 300,000 loop or transient population has 
 been made. In general the analysis shows that approximately 143 
 gallons per capita per day has been allowed for domestic water supply 
 (including the transient use as domestic) an average of approximately 
 2,050 gallons per acre per day (equivalent to 34 gallons per capita per 
 day 1960 population) has been allowed for infiltration and an additional 
 allowance for industrial water uses, amounting to approximately the 
 equivalent of 120 gallons per capita per day. All of these units are 
 based upon the sum of fixed and transient populations. The total water 
 reaching the sewers under average conditions is, therefore, 300 gallons 
 per capita per day under this design. This amount is increased by ap- 
 proximately fifty percent giving a peak rate flow of 450 gallons per 
 capita per day, which is then further increased by one-third in order to 
 provide for one- fourth of the sewer capacity always being available for 
 ventilation. The sewers as tentatively designed by the Sanitary Dis- 
 trict are, therefore, laid out on a basis equivalent to 600 gallons per 
 capita for the 1960 population. 
 
 It is believed that this total allowance, while it includes a larger 
 allowance for ground water than we would consider necessary for Chi- 
 cago conditions, is in the aggregate approximately correct as represen- 
 tative of the conditions of flow in the intercepting sewers if the Chicago 
 water supply is to remain unmetered. It has previously been shown that 
 if meters are not installed the per capita use in 1960 will approximate 
 440 gallons per capita per day. If this is increased by thirty-five per- 
 cent to care for peak flows (i. e. 150 gallons per capita per day which 
 is fifty percent of the 300 gallons per capita per day used by the Dis- 
 trict). The total of 600 G. P. D. per capita used by the Sanitary Dis- 
 trict would result. The Sanitary District design, therefore, would not 
 allow any excess capacity for ventilation in 1960, if meters are not 
 adopted. 
 
 It is, however, inconceivable that the Chicago water supply will 
 remain unmetered another thirty-five years. It is not believed to be 
 good economic engineering to design long lived structures, such as 
 intercepters for populations expected thirty-five years in the- future 
 and under the worst possible conditions of water waste. The necessity 
 for metering is so urgent and the benefits from it so great that it is in 
 our opinion decidely unwarranted to base intercepting sewer designs 
 upon a continuation of impossible water uses. Universal metering will 
 
121 
 
 effect a reduction in use per capita for the anticipated 1960 conditions of 
 approximately 280 gallons per capita per day which amount in our 
 opinion may be safely deducted in computing the required capacity of 
 the intercepting sewer system. In other words, an intercepting sewer 
 designed on the basis of 320 gallons per capita per day with universal 
 metering will be fully as adequate as the sewers designed without meter- 
 ing on a basis of 600 gallons per capita per day, the figure used by the 
 Chicago Sanitary District. 
 
 Basis of Design: 
 
 In Computing the capacity required for the West Side intercepters 
 we have adopted the following bases : 
 
 (a) Population tributary 1,370,389 (furnished from Sanitary Dis- 
 trict figures), floating or transient population in loop 300,000 people. 
 
 (b) Domestic water use 75 gallons per capita per day of resident 
 and floating population. 
 
 (c) Infiltration at the average rate of 750 gallons per acre per 
 
 day. 
 
 (d) Industrial use, as estimated by the Chicago Sanitary District, 
 with the exception of the loop population, the sewage of which we have 
 considered as domestic. 
 
 The total average sewage flow from this district for 1960 is thus 
 estimated as : 
 
 (a) Domestic flow 125 MGD. equivalent to 75 GPD. per capita 
 
 (b) Infiltration 21 MGD. equivalent to 12>^ GPD. per capita 
 
 (c) Industrial uses 204 MGD. equivalent to 122 GPD. per capita 
 
 Total 350 MGD. equivalent to 2091/2 GPD. per capita 
 
 Adding to this average flow approximately forty-five percent (90 
 G.P.D. per cap) for the excess peak rate and allowing sewer capacity 
 sufficient to provide one-third additional for ventilation, a total design 
 capacity of 375 gallons per capita per day is secured. 
 
 With the above as a basis, the intercepting sewers for the West 
 and Southwest treatment plants have been tentatively laid out. 
 
 The West Side intercepter includes approximately twenty-one miles 
 of sewers, varying in size from seven feet to seventeen feet. The 
 Southwest Side intercepter has a total length of approximately fifteen 
 miles, varying in size from four feet to fourteen feet three inches in 
 diameter. 
 
 The routes of the intercepters are as tentatively laid out by the 
 Sanitary District and are substantially as shown on Figure 3. The in- 
 
122 
 
 vert elevations at the disposal plants will be approximately thirty feet 
 below lake level. 
 
 Intercepting Sewer Costs: 
 
 In view of the large expenditures involved in the construction of 
 intercepting sewers yet to be built we have thought it advisable to ascer- 
 tain the facts relative to the costs of building intercepting sewers in 
 other large cities of the country. We have accordingly made investiga- 
 tions of the cost of sewer construction in Milwaukee, Detroit, Phila- 
 delphi, Cleveland and St. Louis. All of these places have been visited 
 and the facts relative to costs, labor conditions, difficulties encountered 
 in construction and other facts having a bearing upon and being neces- 
 sary to an adequate interpretation of costs were secured. 
 
 It was found that a large mileage of sewers up to fourteen feet in 
 diameter have been constructed within recent years under contracts 
 relative to which it was possible to secure complete information. An 
 analysis of all of the recent contract lettings in all of these cities was 
 made, and the data thus secured is shown in Figure 20. 
 
 Inasmuch as the construction of these sewers extended over the 
 past period of approximately five years in most cases, during which time 
 there have been rather violent fluctuations in labor and material costs, 
 the costs in each particular instance have been reduced to present day 
 equivalent costs in the cities in which these contracts were executed. 
 
 Further correction was then made in order to give adequate consid- 
 eration to the relation of costs in these other cities to costs in Chicago. 
 These adjustments were made on the basis of the labor scales prevailing 
 in other cities and in Chicago, and upon the proportions of labor and 
 materials entering into the several types of construction and sizes of 
 sewers. These adjusted costs are shown in Figure 21. 
 
 Variation in Conditions: 
 
 The soil conditions in the various cities and under the large num- 
 ber of contracts analyzed varied quite materially. We endeavored to 
 ascertain the facts in all cases in order that we might interpret the cost 
 data secured. 
 
 Of the several sewer contracts executed on the Cleveland inter- 
 cepting sewers, only three were constructed under conditions similar to 
 those prevailing in Chicago through the district yet to be served with 
 intercepters. Four of the sewers were constructed in whole or in part 
 in quicksand or in wet soil conditions which made the use of air neces- 
 sary. In our application to Chicago conditions these sewers were elim- 
 inated. 
 
123 
 
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 h 
 
 
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 a 
 
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 n inn pn m^Kowina 
 
 3oo 
 
 
 
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 ! - 
 
 CONSTRUCTIOM CO^TS OF 
 
 INTU^4NEL- ATT Ac-TUAU 
 
 Pr\ceis Pa\d 
 
 To Accomponq R.epor-4- o-P 
 
 AuVOR.D.6uT^DlC<.8cHoWSON 
 EnGinieerS Ch\ca<3^o 
 APR.ii_. \925 
 
 O Cl_eVEL_ANiO 
 
 Q MiuwAUK-EE- work done w'l+h ain 225 
 ^ De.T;soi-r 
 
 • Cmic^go Sahitart DiiTOicT- Ctc^rrf Con+rwc4s 
 
 No+e -.These resul+s include manholes i Mlsccl. 
 
 
 
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 A* ■ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 25 
 
 \5 
 
 20 
 
 Diameter \m feet 
 Figure 20. — Construction costs of sewers in tunnel, at actual prices paid. 
 
124 
 
 Diagram showing 
 
 Construction Costs or "DEVAjELR-b 
 iisTuhhELL- Adjusted to 
 Chicago 1925 Basis 
 
 275 
 
 To Accompanij Rcpor+ o-P 
 
 Alvord. Burdick ^ HOWSON 
 
 E.M<2>\»SEIE1RS Chicago 
 Apcil 1925 
 
 • Sanlt-artj Di5lVtc+ ConWac^'S N Side iNterce^-. r- 
 o E^.fimak5 bose^d on labor <J plant on vMwk done (or Sorify Di^f. [_ 
 
 * Mitwaukee-work done wi-fh air 
 
 250 
 
 225 
 
 A Octro i -I- 
 Q Cleveland 
 Nofc Thfcse. irKlutk Inanhole^. & Miace 
 
 5 10 
 
 Diameter in Teeit 
 
 Figure 21. — Construction costs of sewers in tunnel, adjusted to Chicago 
 
 1925 basis. 
 
125 
 
 At Detroit it was found that the conditions of excavation more 
 closely resembled those in Chicago than in any of the. other cities visited. 
 The Detroit conditions are, therefore, peculiarly comparable, so far as 
 costs are concerned. Detroit has also been very active in sewer con- 
 struction work. Over fifty contracts covering sewers from twelve inches 
 to fourteen feet in diameter have been executed in the past three years. 
 Tunnel work has been done on sizes twenty-four inches and larger. 
 
 Analysis of Detroit's bids shows good competition to have been 
 ■secured in which many of the best sewer contractors of the country 
 participated. The range of prices bid indicates that the work is being 
 done under conditions which secure good work at reasonable costs. 
 
 The Detroit contracts are platted on Figure 20 which indicates the 
 uniformity of prices secured on the Detroit contracts. 
 
 At Milwaukee considerable intercepting construction has been exe- 
 cuted in the past five or six years. Much of this work was in wet sand 
 and much of it necessitated the use of compressed air with attendant 
 higher costs. 
 
 The Milwaukee sew^er bids analyzed covered sizes from twelve 
 inches to nine feet. Good competition was secured on contracts and 
 considering the difficult conditions of excavation found on most of the 
 work the costs are reasonable and consistent. 
 
 In addition to making the comparative study of sewer costs in 
 other cities, we personally investigated the conditions under which the 
 North Side intercepters are now being built, and prepare 1 independent 
 estimates of the fair cost of doing work of that type. The estimates 
 made in this way independently check very well with the actual cost in 
 other cities adjusted for Chicago 1925 conditions. The results of the 
 investigations in other cities and our estimates of the reasonable cost of 
 intercepters are shown graphically on Figure 21. Upon this diagram 
 we have also shown by solid dots the cost of five North Side intercepter 
 contracts, let within the last year or two. It will be noted that these 
 contract costs by the Sanitary District are more than double the prices 
 at which other cities were able to let contracts with prices adjusted 
 to Chicago conditions. The Chicago prices are in many instances prac- 
 tically three times the costs at which the work was let in such cities as 
 Detroit and Milwaukee. Our estimates agree closely with the Sanitary 
 District's estimates for future large sewers. 
 
 The excavation conditions in most sections of Chicago are at least 
 as favorable as in any city studied. Our estimates assume conditions 
 for the central district and the West Side, about the same as conditions 
 -encountered in the North Side intercepters now under construction. 
 
126 
 
 Estimated Cost of West and Southzvest Intercepting Sewers: 
 
 Using as a basis the full curved line, showing the cost of sewers of 
 various sizes shown on Figure 21, the use of which assumes that it is 
 possible to build intercepters in Chicago under conditions of efficiency 
 and cost comparable to those obtained in other large American muni- 
 cipalities (adjusted for labor and material cost variations), we estimate 
 the cost of the West side intercepting sewers, including ten percent 
 for engineering and contingencies as $7,890,600. 
 
 Similarly we estimate the cost of the intercepting sewers for the 
 Southwest plant at $4,495,700. 
 
 Based upon the Chicago Sanitary District engineer's design as to 
 diameter, which is based upon continuation of the present metering 
 policy, and upon the unit prices herein developed, the cost would be 
 $10,996,100 for the West side sewers and $6,539,500 for the Southwest 
 Side intercepter. 
 
 Had the estimates been computed using the contract costs on inter- 
 cepting sewers recently let by the Sanitary District of Chicago, applied 
 to the same sewer quantities as in the first and second paragraphs of this 
 section, the totals would have been approximately $18,210,300 for the 
 West Side and $10,895,500 for the Southwest Side plants respectively, 
 both figures being more than double what are believed to be fair prices 
 for this work. 
 
 Period Covered by Design: 
 
 The intercepting sewers as laid out herein contemplate 1960 condi- 
 tions and as stated have a designed capacity equivalent to 375 gallons 
 per capita as of that date, or from 450 to 500 gallons per capita as ap- 
 plied to present population. 
 
 The period for which intercepters should be designed is dependent 
 upon a com.parison of the costs and practicability of providing capacity 
 at present for far distant needs and the same facts relative to providing 
 the additional capacity at such time in the future as the necessity occuri,. 
 With sewers built in open cut the cost of duplication usually becomes 
 excessive due to a more complete utilization of the streets by utilities and 
 the increasing difficulties due to community growth and congestion. 
 Such sewers are usually built for long periods in the future. 
 
 Where intercepters are built in tunnels, somewhat different condi- 
 tions prevail. Additional sewers can be built in tunnel at a later date 
 with little more difficulty and cost than experienced in the original con- 
 struction. With sewers in tunnel the period covered by the design ac- 
 cordingly depends quite largely upon a financial comparison of building 
 for ultimate needs or of building for a shorter period with additional 
 capacity added later as needed. 
 
127 
 
 We have made a financial comparison of the costs of intercepting 
 sewers for the West and Southwest Side plants on two bases, both of 
 which assume that by 1960 it will be necessary to double the capacity 
 now to be provided. In one case we have assumed that the sewer now 
 to be built will be constructed at its ultimate capacity, that is, twice what 
 would be required up to 1960. In the second case we have assumed 
 the sewer to be built now as required for 1960 conditions and that in 
 1960 a duplicate sewer will be built, the cost of which is reduced to 
 present worth and added to the present cost for comparison with the 
 first plan. 
 
 The cost comparison is as follows : 
 
 W. Side S. W. Side 
 
 (1) Cost of sewer whose capacity is two times that 
 
 reqd. for 1960 conditions $14,469,400 $ 7,746,200 
 
 (2) Cost of sewer for 1960 conditions 7,890,600 4,495,700 
 
 (3) Excess cost of (1) over (2) $ 6,578,800 $ 3,250,500 
 
 (4) Present worth of cost of duplicating present 
 
 sewer in 1960 @ 5% 1,430,000 815,000 
 
 (5) Saving by postponing construction to 1960 $ 5,148,800 $ 2,435,500 
 
 The sewer designed for double the 1960 requirements would be of 
 large diameter reaching twenty-four feet for the West Side plant. The 
 costs used in these estimates are secured from Figure 21 for all 
 sizes up to twenty feet. To secure a unit for sizes above twenty feet a 
 curve of cost per foot of diameter was platted and the unit prices taken 
 therefrom. 
 
 Obviously it will be better procedure to design conservatively both 
 with respect to period of time and quantities. Thirty-five years is be- 
 lieved ample provision for time. Quantities should consider metering 
 as being ultimately adopted. 
 
 We have given consideration to the general routing of sewers pro- 
 posed by the Sanitary District and are of the opinion that approximately 
 the routes selected will be desirably followed when the detailed surveys 
 and plans are made. 
 
 We have investigated the practicability of joining the West and 
 Southwest Side intercepters about two and one-half miles above the 
 tentative location of the Southwest Side plant but find that the saving 
 thus effected would probably be less than $100,000. Its practicabiHty 
 therefore is doubtful and can only be definitely ascertained by detailed 
 investigation when the plans are drawn with full information available. 
 
128 
 
 PART XI. 
 
 METHODS OF SEWAGE DISPOSAL AND PRACTICABLE 
 EFFICIENCIES. 
 
 Why Sezmge is Treated: 
 
 The water-borne wastes of a city are given the general designation 
 of sewage ; however, in recent years the tendency has been to restrict 
 the meaning of the word sewage to those wastes produced by house- 
 hold activities and to designate other water-borne impurities as indus- 
 trial wastes. In this discussion the word sewage will be used as inclu- 
 sive of both domestic and industrial water-borne wastes. 
 
 Sewage is composed of more than ninety-nine percent of water and 
 less than one percent of soluble, colloidal, and solid constituents. These 
 latter constitutents, in turn, are partly inert or stable and partly organic 
 or unstable. The unstable constituents of sewage are those which create 
 sight and smell nuisances in overtaxed watercourses, and these unstable 
 constituents may be rendered partially or wholly innocuous or inert by 
 subjecting them to proper processes of treatment. 
 
 The destruction of the unstable constituents of sewage is a bacterial 
 function which may be carried out in a watercourse or in treatment 
 works in which satisfactory conditions are provided for bacterial ac- 
 tivity. The processes by which unstable sewage constituents are des- 
 troyed in a stream are the same as those which result in their destruc- 
 tion in treatment works. 
 
 An important condition governing the bacterial destruction of sew- 
 age is that of oxygen supply, and in general, it may be said that in the 
 presence of an ample supply of oxygen the process of destruction will 
 proceed to completion in an inoffensive manner, and that in the absence 
 of an ample supply of oxygen, the process of destruction will result in 
 the production of offensive odors. In other words, aerobic conditions 
 favor inoffensive destruction, whereas anaerobic conditions favor 
 offensive destruction. 
 
 A somewhat analogous comparison is that of the operation of a 
 steam boiler plant. When the furnace is properly operated, no smoke 
 comes from the attack, but when the air supply is not properly adjusted, 
 large volumes of smoke or unburned carbon come from the stack. A 
 proper adjustment of the operation of the furnace eliminates the smoke 
 
129 
 
 nuisance, whereas an ample supply of oxygen will go far toward elimin- 
 ating the smell nuisance in the bacterial destruction of sewage. 
 
 Hozv Seivage is Treated: 
 
 The various agencies involved in the treatment of sewage may in a 
 general way be classified as physical, chemical, bacteriological, and bio- 
 logical, none of which alone would suffice. The physical agencies are 
 those of screening, sedimentation, aeration, diffusion, filtration, evapor- 
 ation, etc. The chemical agencies are those involved in coagulation, 
 sterilization, and in the mineralization of certain nitrified products. The 
 bacteriological agencies are those in which the various species of bac- 
 teria are the active agents in putrefaction, fermentation, nitrification, 
 and denitrification. The biological agencies are those in which low 
 forms of animal and vegetable life destroy certain constituents of the 
 sewage. 
 
 In the various methods of sewage treatment in use today practically 
 all of the above agencies are involved to a greater or less degree. Sew- 
 age treatment methods in use today may be classified, in a general way, 
 as follows : screening, sedimentation, sludge treatment, oxidation, fil- 
 tration and sterilization. 
 
 Sc?'eening: 
 
 As practiced in the United States today, the screening of sewage 
 may be classified on the basis of coarse and fine separation. Coarse 
 screens (two to four inch clear opening) have a negligible value as a 
 purifying process and serve simply to remove coarse, solids which might 
 obstruct passageways of pumps or be unsightly in treatment tanks or in 
 a stream. Screens of this character usually remain in a stationary 
 inclined position in the pathway of the incoming sewage and may be 
 cleaned in position, or lifted for cleaning. 
 
 Fine screens ordinarily have a clear opening of one-eighth of an 
 inch or less and usually rotate through the sewage stream. Most of them 
 are power-driven and are provided with self-cleaning mechanism. The 
 w^ork accomplished by the fine screen is intermediate between that ac- 
 complished by coarse screening and very rapid sedimentation. The fine 
 screen probably accomplishes less in proportion to its first cost and oper- 
 ating cost than do other methods of sewage treatment, except under 
 certain conditions where fine screens are particularly adaptable. 
 
 Sedimentation: 
 
 The treatment of sewage by sedimentation has for its object the re- 
 duction of the strength of the sewage by the removal of the settleable 
 solids. This is accomplished by passing the liquor through tanks at a 
 
130 
 
 very low velocity, which condition is conducive to a settling out of a 
 portion of the solid constituents. 
 
 There are two general types of sedimentation tanks in use today; 
 viz., those with one-story and those with two-stories. The one-story 
 tanks are further divided into three classes, viz., those with large capa- 
 city for the sludge deposits which are removed at infrequent intervals, 
 those with small capacity for the sludge deposits which are removed at 
 frequent intervals, and those which are provided with a rotating and 
 scraping mechanism for continuous sludge removal. 
 
 In the first type of one-story tank the incoming sewage is constantly 
 in contact with actively decomposing sludge for considerable periods of 
 time, and it becomes infected with the products resulting from the de- 
 composition of the sludge. In this type of tank the sedimentation and 
 sludge digestion functions are not separated. 
 
 In the second type of one-story tank, the injurious effect of the 
 non-separation of the two functions is greatly reduced by frequent re- 
 moval of the deposited sludge, while in the third type of one-story tank 
 the separation of these functions is practically complete due- to the con- 
 tinous removal of the deposited solids. 
 
 In the two-story type of tank the separation of the two functions is 
 accomplished by having a lower story for sludge reception and digestion 
 and an upper story for sedimentation. The upper and lower stories are 
 so constructed that by an arrangement of sloping bottoms, communi- 
 cating slots, baffles, and gas vents, the deposited solids enter the lower 
 compartment automatically and the digestion process may proceed with- 
 out interfering with the sedimentation process and without infecting the 
 incoming sewage. The two processes thus proceed harmoniously, but 
 sludge withdrawals must be made at proper intervals. In many of the 
 installations of this type, more or less serious trouble from foaming at 
 the gas vents has been experienced and corrective measures to date have 
 only been partially successful. 
 
 Sludge Treatment: 
 
 Solids removed from sewage by the sedimentation process are usu- 
 ally designated as sludge, which, in composition, consists of from ninety 
 to ninety-eight per cent water, and from two to ten percent of dry solids. 
 
 The treatment and final disposal of sludge is one of the most 
 troublesome problems of sewage disposal. As sludge increases in 
 moisture content, the volume produced per million gallons of sewage 
 treated increases very rapidly. If the volume of sludge produced per 
 million gallons of sewage be taken at 1.0 when the moisture content is 
 eighty-five percent, the approximate volumes for higher moisture con- 
 tent would be as follows: For ninety percent sludge 1.5, for ninety-five 
 
131 
 
 percent sludge, 3.0, and for ninety-eight percent sludge 7.5 ; consequent- 
 ly those processes of sewage treatment which produce sludge of high 
 moisture content, impose the hurden of a treatment of large bulk per 
 unit of dry solid content. 
 
 There are four general methods of sludge treatment in use today, 
 viz., 1st, lagooning on land, 2nd, pumping into scows and disposing of 
 it by discharging it into deep water at sea. 3rd, partially dewatering 
 it on specially constructed sand filters, after which it may be used to fill 
 waste places or spread on farm land and plowed in, 4th, partial or com- 
 plete dewatering by pressing, centrifuging, or drying, after which it 
 may be used as a fertilizer, or for filling in waste places. 
 
 The disposal of sludge at sea is obviously a method of limited avail- 
 ability. A high degree of dewatering of sewage sludge through the use 
 of presses, centrifuges, and driers, with the intention of producing a 
 marketable fertilizer, has as yet to be demonstrated as a feasible under- 
 taking. The city of Milwaukee, after a thorough and painstaking study 
 of sludge dewatering processes and the fertilizing value of sludge pro- 
 duced by the activated sludge method of sewage treatment, definitely 
 committed itself to the production of fertilizer sludge and now has a 
 very complete dewatering plant well under construction. 
 
 The treatment of sludge by m.ethods Nos. 1 and 3 has been prac- 
 tised most extensively in the United States with varying degrees of suc- 
 cess. The chief difficulty which has attended the use of these methods 
 of sludge treatment has arisen by reason of the fact that inadequate 
 disposal areas have been provided. 
 
 Oxidation: 
 
 There are four methods of sewage treatment which might be 
 termed '"'finishing processes," and which result in varying degrees of 
 stabilization of the soluble, colloidal and solid constituents of the sew- 
 age. In each of the four methods of treatment, the several constituents 
 of the sewage are changed from an unstable to a stable condition largely 
 by bacterial activities. 
 
 The four methods of securing a finishing treatment of sewage are 
 the sand filter, the contact bed, the trickling filter, and activated sludge. 
 These four methods of treatment vary widely in capacity per unit of 
 area, and taking the capacity of the sand filter per acre of area as 1.0, 
 the relative capacities of the other methods of treatment per acre of area 
 are approximately as follows : Contact beds, 7.0, trickling filters 20.0, 
 and activated sludge 150.0. 
 
 The sand filter when properly designed, constructed, and operated 
 produces an effluent which is clear and sparkling, practically free of sus- 
 pended matter, very low in bacterial content, highly nitrified, and with 
 
132 
 
 an oxygen demand which is so low as to obviate any dilution require- 
 ments in a stream. Treatment of the sewage of the Sanitary District of 
 Chicago by sand filters preceded by clarification in settling tanks would 
 require at the present time not less than 8,000 acres. 
 
 The contact bed is an oxidizing device and consists of a square or 
 rectangular tank filled with coarse broken stone or other suitable mater- 
 ial of varying depth and operated ordinarily on a fill-and-draw plan. 
 The effluent from the contact bed is ordinarily not clear or well nitrified, 
 has a comparatively high bacterial count, and an oxygen demand which 
 requires some dilution for stabihty. Not less than 1,200 acres would be 
 required to treat the sewage of the Sanitary District of Chicago fo-r the 
 year 1925, in addition to clarification in settling tanks. 
 
 The trickling filter is an oxidizing device similar to the contact bed 
 in' general construction but differing in the method of dosing. The trick- 
 ling filter is dosed by a system of distribution pipes operated under a 
 head and terminating with open spray nozzles properly located and 
 spaced to give uniform distribution over the entire surface. The sew- 
 age is sprayed into the air and falls on the broken stone or other filtering 
 medium through which it trickles to the underdrains which carry it 
 away. The cycle of operation consists of a short dosing period, followed 
 by a short resting period. Trickling filters which are properly designed, 
 constructed and operated will produce effluents having a substantial 
 total bacteria] count, a varying suspended matter content, a marked 
 reduction in oxygen demand, and often with a balanced oxygen relation 
 if the applied sewage is not particularly strong. Not less than 400 acres 
 of sprinkling filters would be required to treat the sewage of the Sani- 
 tary District of Chicago for the year 1925, in addition to a previous 
 clarification in settling tanks. 
 
 The activated sludge process is a comparatively recent modification 
 of older processes, and might be termed an accelerated bacterial treat- 
 ment in water. The only sizable plants of this character in operation in 
 the U. S. today are the two municipal plants at Houston, Texas. The 
 literature describing the results of the experimental studies which have 
 been made of this process is quite voluminous. Experimental plants of 
 this character, which have been operated on both large and small scales, 
 have given very promising results, and enough confidence in the pro- 
 cess has arisen to justify its adoption for several very large installations. 
 
 The principal operations in this method of treatment are coarse 
 screening, grit removal, fine screening, aeration in tanks, sedimentation, 
 sludge reaeration, return of a portion of the activated sludge to the 
 aeration tanks, and treatment and disposal of the excess sludge. 
 
133 
 
 The final effluents from this method of treatment as produced ex- 
 perimentally and by a small number of municipally operated plants have 
 resembled sand filter effluents with the exception that they have ordi- 
 narily not been so completely nitrified. The production of an effluent 
 which will not need dilution falls within the scope of the possibilities of 
 this method of treatment. The degree to which sewage may be rendered 
 stable by this method of treatment is capable of some adjustment. This 
 method of treatment is one in which careful and experienced supervision 
 is especially desirable. 
 
 Sterilisation: 
 
 It is possible to efifect a removal of from ninety to ninety-five per- 
 cent of the total number of bacteria in sewage by treatment with a steril- 
 izing agent. The efficacy of sterilization will be governed by the size of 
 dose, the comminution of the solids of the sewage, the distribution of 
 the sterilizing- agent, and the thoroughness and sufficiency of the con- 
 tact of the sterilizing agent with the sewage. 
 
 Experience with the sterilization of sewage to date seems to indi- 
 cate beyond doubt that it can be relied upon only to provide a lessening 
 of the burden of water purification where a contact exists. 
 
 Sterilization destroys bacteria but effects no marked reduction in 
 the organic load, consequently the steriHzation of sewage has no marked 
 effect on stream dilution requirements. 
 
 Prac tical E fficiencies : 
 
 Fine Screening — Table 29 is a partial list of fine screen in- 
 stallations in the U. S., and an inspection of this table will show that the 
 
 TABLE 29. 
 
 PARTIAL LIST OF FINE SCREENS. 
 
 New York City— Dyckman & 210th Sts 
 
 Long Beach, Cal. 
 Daytona, Fla. . . . 
 
 Plainfield, N. J 
 
 Rochester, N. Y., Irondequoit Works 
 
 Bridgeport, Conn. 
 
 No. 
 
 Dia. 
 14' 
 14' 
 10' 
 12' 
 12' 
 12' 
 22' 
 22' 
 14' 
 8' 
 
 Sep. 
 Ins. 
 
 3/64 
 4/64 
 4/64 
 24/64 
 8/64 
 4/64 
 1/64 
 2/64 
 2/64 
 5/64 
 
 Indianapolis, Ind. 
 Milwaukee, Wis. 
 
 12 
 8 
 1 
 
 6'd. 8'L. 
 8'd. 8'L. 
 14' 
 
 30 meshes 
 
 6/64 
 4/64 
 
 Chicago, Des Plaines River Plant 
 
134 
 
 clear openings in the screens vary from three-eighths of an inch to one- 
 sixty-fourth of an inch. 
 
 Table 30 shows the removal of total suspended solids by fine screens 
 operating on municipal sewage and on industrial waste. An inspec- 
 tion of this table will show that from eight to thirty-six parts per mil- 
 lion of suspended solids have been removed by fine screens from muni- 
 cipal sewage, and 103 parts per million from the strong packingtown 
 waste of Chicago. The sewage which is screened at the New York city 
 plant, located at Dyckman and 210th Streets, is a very fresh sewage 
 (less than thirty minutes old) from a residential area. 
 
 The removal of suspended solids by fine screening will be gov- 
 erned by the width of the slots, the rate at which the sewage is passed 
 through the screen, and the concentration and degree of comminution 
 of the soHds of the sewage. 
 
 The following results have been reported from the screen installa- 
 tion at the Irondequoit plant of the city of Rochester, New York : 
 Year 1918 — 6.31 cubic feet screenings per AI. G. 
 Year 1919 — 6.58 cubic feet screenings per M. G. 
 Year 1920 — 4.58 cubic feet screenings per M. G. 
 
 Sedimentation: 
 
 The improvement in the quality of sewage resulting from sedimen- 
 tation treatment will be governed by the concentration and comminu- 
 
 TABLE 30. 
 
 SHOWING REMOVAL OF TOTAL SUSPENDED SOLIDS BY 
 FINE SCREENS. 
 
 
 Width of 
 
 
 
 
 
 slots 
 
 Suspended 
 
 Solids 
 
 
 Source. 
 
 in 
 
 Removed 
 
 
 
 Inches 
 
 P.P.M 
 
 % 
 
 (A) 
 
 New York City— Dyckman & 210th Sts. 3/64 
 
 36 
 
 26.3 
 
 
 
 4/64 
 
 20 
 
 16.6 
 
 (B) 
 
 Long Beach, California 
 
 2/64 
 
 28 
 
 
 (C) 
 
 Milwaukee, Wisconsin 
 
 8/64 
 
 18 
 
 
 
 
 8/64 
 
 8 
 
 
 (D) 
 
 
 6/64 
 
 9 
 
 
 
 
 40 meshes 
 
 20 
 
 
 (E) 
 
 Packinghouse Industrial Waste Tests, 
 
 30 meshes 
 
 103 
 
 18.8 
 
 (A) Eng. News-Record, Vol. 84 p. 171, 1920 by C. E. Gregory. 
 
 (B) Eng. News-Record, Vol. 82, p. 1012, 1919. 
 (O) 6th Report Milwaukee Sew. Com., p. 41. 
 
 (D) 8th Report Milwaukee Sew. Com., p. 72, 73. 
 
 (E) Report on Industrial wastes from the Stockyards and Packingtown in Chicago, Vol. 2, 
 ■^921, p. 182. 
 
135 
 
 tion of the solids of the sewage treated, the detention period in the tanks, 
 and the degree to which stored sludge interferes with the settling pro- 
 cess. 
 
 Table 31 shows the improvement in sewage effecte 1 by prelim- 
 inary sedimentation as determined by long and short time tests on fif- 
 teen of the largest sewage treatment works in the United States. The 
 efficiency of these plants when based on the removal of total suspended 
 solids varies from twenty-two percent to eighty-six percent, with a 
 general average of fifty-five percent. The Proctor Creek plant at Atlan- 
 ta, Ga., shows a removal of eigthy-six percent, but this result is not 
 typical of plain sedimentation for such a large unit, and is accounted for 
 by the fact that certain industrial wastes in the sewage react in such a 
 way as to produce a chemical precipitation. The average result for six- 
 teen years at Columbus, O., is fifty-five percent, and the average result 
 at Baltimore, Md., for nine years is fifty-six percent. The average re- 
 sult for five years at Fitchburg, Mass , which is a smaller plant and 
 which treats a fresher sewage, is seventy-three percent. It would 
 therefore seem that a fifty-five percent removal of total suspended solids 
 is a very reasonable expectancy, and that a better removal may be se- 
 cured where conditions are more favorable. 
 
 A study of the settleable solids in daily composite samples of sew- 
 age collected during the past eight years at Columbus, Ohio, has shown 
 that an average of fifty-one percent of the total suspended solids is 
 settleable in a two-hour period in conical settling glasses. This result, 
 however, only applies to the Columbus sewage. 
 
 Table 31 also shows the improvement in sewage effected by 
 preliminary sedimentation on the basis of the oxygen demand. The de- 
 termination of oxygen demand is not a routine test at any of the sewage 
 plants listed in the table, consequently information of this character 
 must be based on short time studies. Oxygen demand results on eleven 
 separate plants show an average improvement of thirty-five percent, 
 with extremes of three percent and sixty-three percent. The longest 
 study along this line has been made at Columbus, Ohio, where oxygen 
 demand tests have been a daily routine for sixteen years and the sixteen- 
 year average improvement by sedimentation is twenty-nine percent. 
 The Columbus sewage is stale and all of it is pumped, both of which 
 conditions tend to reduce the efficiency of the sedimentation treatment. 
 
 It is considered that an improvement of thirty-five percent in oxy- 
 gen demand is a reasonable expectancy where the factors affecting sedi- 
 mentation are average. 
 
136 
 
 '0 "K ^1 SuiMo^^^i aS^Avag 
 
 3.97 
 4.44 
 21.2 
 
 3.35 
 
 '33.6 
 
 '55.6 
 
 2.62 
 5 . 00 
 
 • 
 
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 • * 
 
 Sut:)nqu;uoo 
 
 70, 000 
 
 OOK AAA 
 
 2^5, OUO 
 
 38, 000 
 
 240, 000 
 
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 28,000 
 20,000 
 30, 000 
 
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137 
 
 Sedimentation and Sand Filtration: 
 
 The treatment of sewage by sedimentation and sand filtration in the 
 United States today is, with one exception, limited to small municipaH- 
 ties and institutions. Numerous small plants of tliis character are in 
 service today but definite information relative to rates of treatment 
 and operating results is very scarce. 
 
 The largest sewage sand filter plant in the U. S. today is the muni- 
 cipal plant at Worcester, Mass., where, during the year 1923, 64.7 acres 
 of sand filters were operated at an average daily yield of 55,000 gallons. 
 A portion of the sewage of Worcester is treated by sand filtration by 
 reason of the fact that natural sand areas are available. 
 
 The average results secured at Worcester, during 1923, by the sand 
 filtration treatment were as follows : 
 
 Reduction in total albuminoid ammonia, 89%. 
 Reduction in total suspended solids, 100%. 
 Reduction in total oxygen consumed, 90%. 
 These average results represent a very high degree of treatment, 
 with probably a negative dilution requirement. 
 
 Sedimentation and Sprinkling Filters: 
 
 The sprinkling filter, almost without exception, is dosed with clari- 
 fied sewage and the effluent from the filter is often given a final clarifica- 
 tion before being discharged into a watercourse. The improvement 
 effected by tanks and sprinkling filters with and without final sedimen- 
 tation is shown in Table 32. 
 
 An inspection of this table will show that of the total amount of 
 suspended solids removed by tanks and sprinkling filters, eighty-five 
 percent is removed by the tanks and fifteen percent by the filters. In 
 the reduction of the oxygen demand by tanks and filters, the results 
 in Table 32 show that of the total reduction, forty-five percent comes 
 from the tank treatment and fifty-five percent from the sprinkling filter 
 treatment. If the two Atlanta and the Baltimore results are eliminated, 
 the ratio is for tanks forty percent and for sprinkling filters sixty per- 
 cent. 
 
 A further inspection of this table will show that the reduction in 
 oxygen demand in parts per million by tanks, with Baltimore results 
 excluded, will vary, on the basis of average results, from thirty to sixty 
 parts and that the reduction in oxygen demand by sprinkling filters, with 
 the Atlanta results excluded, will vary, on the basis of average results, 
 from seventy to ninety parts. The reduction by combined treatment 
 in tanks, sprinkling filters, and final settling basins, with the Atlanta 
 results excluded, will vary, on the basis of average results, from ninety 
 
138 
 
 to 135 parts. From a study of the best results obtainable, and as re- 
 corded in Table 32, a reasonable expectancy from tanks, sprinkling 
 filters and final settling basins is as follows : 
 
 Removal of total suspended solids, 75% average result. 
 Reduction in oxygen demand, 85% average result. 
 
 Reduction in oxygen demand in p.p.m., 130 average result. 
 Data relative to the reduction in the number of bacteria by this 
 method of treatment is limited to the total counts which have been made 
 at the Baltimore sewage works for a number of years. Average values 
 for a period of nine years from 1912 to 1920, inclusive, at the Baltimore 
 sewage works are as follows : 
 
 Reduction in the total count on plain agar, 67% 
 Reduction in acid forming bacteria, 90% 
 
 TABLE 32. 
 
 SHOWING IMPROVEMENTS EFFECTED BY TANKS AND SPRINKLING 
 FILTERS WITH AND WITHOUT FINAL SEDIMENTATION. 
 
 
 Location 
 
 By 
 Tanks 
 
 By 
 Sprinklers 
 
 By 
 Basins 
 
 
 
 Atlanta .... 
 
 ..(B) 
 
 37 
 
 23 
 
 
 
 60 
 
 Total Suspen 
 Solids Remo 
 in % of Tot 
 
 Columbus . . 
 Fitchburg . . 
 Lexington . 
 Baltimore . 
 
 ..(B) 
 ..(B) 
 ..(A) 
 ..(A) 
 ...(A) 
 
 70 
 55 
 79 
 60 
 56 
 
 13 
 10 
 
 4 
 16 
 
 6 
 
 
 3 
 5 
 16 
 
 83 
 65 
 86 
 71 
 78 
 
 
 
 . . (B) 
 
 63 
 
 31 
 
 
 
 94 
 
 Dem 
 ction 
 f Tot 
 
 Atlanta . . . . 
 Columbus . 
 
 ..(B) 
 ..(B) 
 
 62 
 25 
 
 31 
 
 . 55 
 
 
 
 93 
 80 
 
 Oxygen 
 Redu 
 in % 
 
 Fitchburg . . 
 
 ..(A) 
 
 38 
 
 49 
 
 
 
 87 
 
 Lexington . 
 Baltimore . . 
 
 ...(A) 
 ..(A) 
 
 40 
 3 
 
 67 
 
 49 
 
 10 
 
 89 
 80 
 
 a § 
 
 Atlanta . . . 
 
 ..(B) 
 
 32 
 
 16 
 
 
 
 48 
 
 a 1 S 
 
 
 ..(B) 
 
 39 
 
 19 
 
 
 
 58 
 
 .2 Q a 
 
 Baltimore . 
 
 ..(A) 
 
 4 
 
 76 
 
 
 11 
 
 91 
 
 
 Columbus . 
 
 ..(B) 
 
 39 
 
 87 
 
 
 
 126 
 
 o 
 
 Lexington . 
 Fitchburg . 
 
 ...(A) 
 . . . (A) 
 
 57 
 59 
 
 75 
 
 71 
 
 inc. 
 
 128 
 133 
 
 (A) Tanks, sprinkling filters and final settling basins. 
 
 (B) Tanks, and sprinkling filters. 
 
139 
 
 Sedimentation and Contact Beds: 
 
 Accurate operating results for tanks and contact beds are very 
 limited : however, in Table 33 are shown the analytical data secured 
 by the U. S. Public Health Service from a ten to twelve days' study of 
 the Alliance, Ohio and Canton, Ohio, sewage w^orks which employ this 
 method of treatment. The average results from these two plants show 
 that the improvement effected by this method of treatmeni" was as 
 follows : 
 
 Reduction in total suspended soHds, 85%. 
 
 Reduction in oxygen consumed, 71%. 
 
 Reduction in oxygen demand, 80%. 
 The contact beds of these two plants treat between 600,000 and 
 700,000 gallons per acre per day, which is about one-third of the volume 
 that can be treated satisfactorily by a sprinkling filter per acre per day. 
 
 Activated Sludge: 
 
 It is difficult to set a standard of practical efficiency for the acti- 
 vated sludge treatment of sewage without relying considerably on re- 
 sults secured by numerous experimental installations. Little doubt 
 exists today as to the soundness of the principles involved, but some 
 doubt does exist relative to the methods and appliances proposed for 
 carrying out these principles. Machinery plays a greater part in this 
 method of sewage treatment than in any other method in common use; 
 also a very extensive air distribution system must be used, which com- 
 prises valves, pipes of many sizes, and in all cases final air outlets which 
 are extremely small. The coefficient of dependability of some features 
 of this process may be said to be somewhat uncertain ; however, the 
 several features of this process have been very carefully investigated by 
 so many competent chemists and engineers and their conclusions have 
 been so well founded that its adoption as a practical method of sewage 
 treatment seems to be based on sound judgment. 
 
 In Table 33 will be found analytical data secured from a ten 
 to twelve-day study of the north side and south side plants at Houston, 
 Texas, analytical results secured from a two years' operation of the 
 same plants, analytical results of a ten to eleven-day study of the plants 
 at San Marcos, and Sherman, Texas ; also results of twenty-three 
 months of operation of the Des Plaines River plant of the Sanitary 
 District of Chicago. The Des Plaines plant has been operated on a com- 
 bined routine and experimental basis, consequently the results are prob- 
 ably not such as might be secured if it had been operated with a single 
 purpose in view. 
 
140 
 
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142 
 
 Omitting from consideration the results from the Des Plaines and 
 Sherman, Texas, plants, the results recorded in Table 33 indicate 
 an improvement from this method of treatment as follows : 
 Removal of suspended solids, 94%. 
 Reduction in oxygen consumed, 81%. 
 Reduction in oxygen demand, 92%. 
 The north side and south side plants at Houston, Texas, treat ap- 
 proximately six million and one and one-half million gallons per day, re- 
 spectively. The San Marcos, Texas, plant treats approximately 200,000 
 gallons of sewage per day. 
 
 The use of the activated sludge process for the treatment of pack- 
 ing and stockyards sewage has been tested experimentally by the Sani- 
 tary District of Chicago, and the improvement elfected, as based on 
 data recorded on pages 47 and 134 of the Report on Industrial Wastes 
 from the Stockyards and Packingtown in Chicago, Vol. 2, 1921, San. 
 Dist. of Chicago, is as follows : 
 
 Removal of total suspended solids, 91%. 
 Reduction of oxygen demand, 96%. 
 Reduction of organic nitrogen, 83%. 
 
 Warm Weather Efficiencies: 
 
 In view of the fact that during warm weather there is an accelera- 
 tion of bacterial activities both in polluted streams and in bacterial pro- 
 cesses of sewage treatment, it is evident that dilution requirements in a 
 stream during warm weather are at the maximum, and, for the same 
 reason, it would seem that the efficiency of sewage treatment would be 
 higher wherever bacterial processes are involved. 
 
 A study of the average monthly efficiencies at the Baltimore works 
 for a period of nine years, the sand filtration treatment at Worcester, 
 Mass., for 1923, and the Columbus works for the year 1913, indicate 
 that the average efficiency for June, July, August and September is 
 above the average efficiency for the year in the following amounts : 
 
 Baltimore, four percent ; Worcester, three percent ; Columbus, 
 three percent. 
 
 An average efficiency for the warm weather months of the year, of 
 three percent above the average annual efficiency is a reasonable assump- 
 tion for sand filter, contact bed, sprinkling filter and activated sludge 
 treatment. 
 
 Conclusion on Efficiency: 
 
 In consideration of treatment works for the largest sewage dis- 
 posal plant in the world, we believe we are warranted in expecting the 
 best of operating results. We conclude that it will be practicable to 
 
143 
 
 secure the following net efficiencies in the proposed Sanitary District 
 plants, in the warm or critical season of the year, expressed in percentage 
 of the biochemical oxygen demand removed from the sewage compared 
 to sew^age as delivered before treatment. 
 
 Tankage, 35%^. 
 
 Tanks and Sprinkling Filters, 88%. 
 
 Activated sludge on Domestic Sewage, 92%. 
 
 Activated sludge on Stock Yards waste, 95%. 
 
 Applicability of Other Means of Sewage Disposal: 
 
 The subject of sewage disposal for Chicago would not be complete 
 without consideration of certain means for sewage disposal that have 
 been extensively used abroad but which are not considered to be adapted 
 to the local situation at Chicago, particularly when taking into consider- 
 ation the expenditures that the Sanitary District has already made. We 
 believe it v^^ill be useful, briefly to outline these methods of disposal 
 and to show why it would not be practicable or economical to adopt 
 them. 
 
 Broad Irrigation: 
 
 The oldest method of sewage purification is the disposal of the sew- 
 age upon farm or garden land, commonly called Broad Irrigation. The 
 sewages of Berlin and Paris are thus treated, and the method has been 
 extensively used in Germany, France and England. 
 
 Inapplicable to Chicago Conditions: 
 
 If Broad Irrigation should be adopted for Chicago, about 60,000 
 acres or ninety-three square miles, would be required under the average 
 rate of application to land as practiced in England, where, in general, 
 available land contains more or less clay. 
 
 If sandy lands could be found, similar to that available for sewage 
 disposal at Berlin, about 25,000 acres or thirty-nine square miles, would 
 be required. It is believed that no such large areas are available, with- 
 out carrying the sewage a long distance from Chicago. 
 
 No surface soils' of a sandy nature are available nearer to Chicago 
 than the east line of Gary, which is approximately forty miles distant 
 from the Chicago loop district. A sufficient area could probably be 
 found east of Gary, but the land is very rough and large expenditures 
 in grading, or in pumping, would be required to make it useful. 
 
 A sewer about twenty-five feet in diameter would be required to 
 accommodate the present total sewage of the Sanitary District. This 
 sewer would cost about $1,500,000 per mile. Approximate estimates 
 indicate that the initial investment in an outlet sewer and pumping 
 
144 
 
 works alone would exceed the cost of the intercepting sewers and the 
 more modern methods of sewage disposal, for which we have previously 
 estimated the costs. In addition it would be necessary to purchase the 
 lands and put them into condition to receive sewage. 
 
 Site Below Jolict: 
 
 Before the drainage canal was built the suggestion was made to 
 carry the Chicago sewage through a tunnel and dispose of it by gravity 
 upon lands adjacent to the Des Plaines River below Joliet. This might 
 have been possible with the quantities of sewage produced by Chicago 
 thirty or forty years ago. At the present time it would not be possible 
 to. find an acreage sufficiently large to treat the sewage by Broad Irriga- 
 tion, delivering the sewage by gravity flow. Lands m.ight be found to 
 which the sewage could be pumped. 
 
 The land at this location is of a sandy and gravelly nature. It 
 would probably be well adapted to sewage farming. Rough estimates 
 indicate that the cost of development, including tunnel and pumping, 
 would not be less than the figures previously given covering sewage 
 farming on the lands east of Gary. Therefore the costs would materially 
 exceed the costs of work§, herein elsewhere estimated. 
 
 Broad Irrigation Not Practicable: 
 
 There are other and more important reasons why broad irrigation 
 would not be applicable. 
 
 (a) Sewage farming is viewed with disfavor by American health 
 authorities, as dangerous to public health. 
 
 (b) Climatic conditions arc much less favorable in this region 
 than in Western Europe by reason of the severe winters. 
 
 • (c) The American public is less tolerant of local nuisances than 
 the European public, and is less inclined to properly maintain its sewage 
 works. A sewage farm would be an intolerable nuisance unless well 
 operated. 
 
 Other Disposal Methods: 
 
 We have herein elsewhere mentioned contact beds and sand filters as 
 means for secondary purification, which have been more or less exten- 
 sively usd by small cities and large public institutions. Either of these 
 methods, by reason of the large areas required, would necessitate large 
 expenditures for intercepting sewers to carry the sewage to more or 
 less distant and remote locations. We believe that the relative areas 
 required, as stated elsewhere in this report, are sufficient to indicate 
 their higher cost as compared to the methods of sewage purification 
 upon which we have prepared detailed estimates. 
 
145 
 
 PART XII. 
 
 SEWAGE DISPOSAL COSTS IN OTHER CITIES. 
 
 Chicago, through the Sanitary District, is undertaking a great 
 sewage disposal program. To date, although the second Jargest city in 
 the United States, it has not constructed and operated disposal works 
 of magnitude commensurate with its wastes. 
 
 Certain other cities have had considerable experience in the con- 
 struction of sewage disposal works of the types generally considered as 
 applicable to Chicago conditions. The costs of these works, are capable 
 of analysis considered as units, so that knowing the number of units of 
 each plant item required, costs of similar plants in individual cities may 
 be compared. If in this comparison the varying costs of labor and 
 materials are brought to a common basis, the results are quite reliable 
 as an indication of fair costs under the conditions pertaining to that 
 basis. 
 
 In order that we might have first hand information as to the costs 
 of construction and operation of the larger sewage disposal plants of 
 the country, and have sufficient familiarity with the plants and their 
 operations to interpret the cost of construction and operations and trans- 
 late them to Chicago conditions, we visited the more important plants, 
 including Baltimore, Cleveland, Philadelphia, Albany, Indianapolis and 
 Milwaukee. At all of these plants we were courteously extended all of 
 the available information relative to cost of construction and operation. 
 This information has been supplemented by other cost data in our 
 possession. 
 
 We gave particular attention to the costs of construction and cost 
 of operating: 
 
 (a) Tankage plants. 
 
 (b) Tankage and trickling filters. 
 
 (c) Activated sludge plants. 
 
 (d) Pumping Stations. 
 
 which types of construction must necessarily be included in any compre- 
 hensive study of the Chicago situation. We also investigated sewer 
 construction and costs in a great many cities. 
 
 Adjustment of Costs to Chicago 1925 Basis: 
 
 In each of the several cities visited to secure costs of sewer and 
 sewage disposal plant construction the costs of labor were found to vary. 
 
146 
 
 It was also found that the construction studied in the several cities had 
 been executed at different time periods and accordingly under varying 
 price level conditions. 
 
 In adapting these data for use in studying reasonable Chicago con- 
 struction costs, it was accordingly necessary to make two adjustments, 
 viz : 
 
 (a) For location. 
 
 (b) For time. 
 
 The first adjustment was made by studying the labor costs for the 
 various types of labor involved in each construction project and ascer- 
 taining the weighted average relation of those costs in the city being 
 studied to those prevailing in Chicago. This resulted in securing a fac- 
 tor wliich applied to the costs in the city studied, would reasonably indi- 
 cate the costs in Chicago as of the same period. In cities for which 
 there were no printed data available as to labor costs inquiry was either 
 made by letter or the costs prevailing in the nearest city for which the 
 data available were used. Table 34 shows the rates for skilled 
 construction, skilled operating and common labor in a number of cities 
 expressed in percentage of Chicago rates for the same classes of labor. 
 The comparison is as of 1925. 
 
 The adjustment for time was made by using the United States 
 Department of Labor data relative to fluctuations in prices for building 
 materials, and the prices paid by the City of Chicago for skilled con- 
 struction labor, common labor, skilled operating labor and engineering 
 or supervisory services. 
 
 Figure 22 shows diagrammatically the cost index of building 
 materials from 1913 to 1925, based on United States Department of 
 Labor data. 
 
 Figure 23 shows the variations in the rates paid by the City of 
 Chicago for various classes of labor entering into the construction and 
 operation of sewers and sewage disposal works. 
 
 In the application of these data to the various types of construction 
 it was necessary to estimate approximately the percentages of materials 
 and labor and the relative proportions of each class of labor required. 
 
 All time corrections were computed as of the date of letting con- 
 tracts. In some cases where several contracts were involved the result- 
 ing time factor w'as a weighted composite of the individual contracts. 
 In case of defaulting of the original contractor and the reletting of the 
 work the latter date and contract cost were used for the date and pay- 
 ments under the original contract. 
 
147 
 
 Co=»T \noex op Bu\ud\ng MATC^IAU^) 
 U. e>. Oh.p>-t of Labor. 
 loiN-bm too % 
 
 Figure 22. — Cost index of building materials. 
 
 
 
 
 
 
 
 
 
 
 
 WS.-r*.-r>o»4 OT=^«.Jfc.-r 
 
 /5\ Sk.\\_\_«.o \_A.e>oH. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 3 
 
 
 
 
 
 
 
 
 
 
 =^ 
 
 
 
 1 
 
 
 
 
 
 
 
 
 
 
 \ 
 
 
 
 
 ^ — 
 
 
 
 
 
 
 
 
 
 
 
 
 r — P 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 6, 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 
 r- 
 
 i 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 A 
 
 < — / 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 — / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 !qi4. T^Ts ioTTiqii i^iq ii-zo iqii nrz ii-za 1925 
 
 Figure 23. — Variations in skilled and unskilled labor rates in Chicago, based 
 on City of Chicago records, 1913 being 100%. 
 
148 
 
 TABLE 34. 
 
 TABLE SHOWING % RATIO OF SALARIES PAID TO SKILLED AND 
 UNSKILLED LABOR IN VARIOUS CITIES, BASED ON 
 CHICAGO PRICES IN 1925 BEING 100%. 
 
 Common Skilled Labor 
 
 City Labor Construction Operation 
 
 Albany, N. Y 
 
 Atlanta, Ga 
 
 Baltimore, Md 
 
 Boston, Mass 
 
 Columbus, Ohio . 
 Fitchburg, Mass. 
 Houston, Texas . 
 Indianapolis, Ind. 
 Lincoln, Neb. . . . 
 Milwaukee, Wis. 
 Marion, Ohio . . . . 
 New Orleans, La. 
 
 Rochester, N. Y. 
 Syracuse, N. Y. . 
 Urbana, 111 
 
 Detroit, 
 
 85.0 
 
 92.5 
 
 87.0 
 
 36.4 
 
 78.8 
 
 61.8 
 
 48.5 
 
 96.0 
 
 68.0 
 
 78.8 
 
 84.5 
 
 85.1 
 
 100.0 
 
 100.0 
 
 100.0 
 
 106.0 
 
 99.5 
 
 103.8 
 
 48.5 
 
 88.4 
 
 83.3 
 
 60.6 
 
 84.1 
 
 81.6 
 
 48.5 
 
 96.6 
 
 81.0 
 
 54.5 
 
 95.9 
 
 95.5 
 
 40.0 
 
 
 to.o 
 
 < Z.b 
 
 ol.v 
 
 <y.o 
 
 O'l.O 
 
 '7Q a 
 
 
 60.6 
 
 81.1 
 
 8^.0 
 
 60.6 
 
 92.5 
 
 88.0 
 
 60.6 
 
 86.4 
 
 75.7 
 
 84.9 
 
 91.5 
 
 86.9 
 
 84.9 
 
 84.7 
 
 80.5 
 
 66.6 
 
 92.1 
 
 84.0 
 
 48.5 
 
 73.8 
 
 73.8 
 
 66.6 
 
 87.8 
 
 70.0 
 
 66.6 
 
 87.8 
 
 70.0 
 
 72.8 
 
 93.5 
 
 95.0 
 
 106.0 
 
 116.0 
 
 102.7 
 
 64.6 
 
 87.0 
 
 76.8 
 
 Tankage Plants: 
 
 The largest tankage plants of the country, which at the present 
 time are operating without secondary treatment, are those of Cleveland 
 (Westerly Plant), Rochester, (Irondequoit Plant), Philadelphia and 
 Albany. In each of these plants we ascertained the facts relative to 
 first costs, date of construction, and the costs of operation. 
 
 The data relative to construction costs are shown on Table 35. 
 Inasmuch as these costs were incurred during a period of rapid and 
 great fluctuations in prices, all of these costs have been reduced to the 
 basis of 1925 conditions, and then further adjusted for the difference in 
 conditions prevailing in -each of these towns as compared to Chicago. 
 
 ~ The costs reduced to the 1925 Chicago basis average $5.00 per 
 capita and $30,750 per million gallons daily capacity. 
 
 At the bottom of this table are shown similar figures for the Calu- 
 met plant of the Sanitary District of Chicago. The per capita cost of 
 
149 
 
 the Calumet plant is $26.40 and the cost per M.G.D. capacity is $86,000. 
 The tabulation of bids on the Calumet plant shows that the concrete for 
 the tanks, 28,000 cubic yards, was let at a price of $64.00 per cubic yard 
 exclusive of reinforcing steel. The steel, 3,000,000 pounds, was let at a 
 unit price of twenty-three cents per pound. The concrete complete, 
 therefore, was let at a unit price exceeding $85.00 per cubic yard. The. 
 work included thirty tanks permitting multiple use of forms and plant. 
 
 In making the comparison of construction costs for utilization in 
 preparing estimates for Chicago plants yet to be built, all figures w^ere 
 reduced insofar as possible to a unit volume or capacity basis. On tank- 
 age plants for example the comparison is based upon the displacement 
 
 TABLE 35. 
 
 CONSTRUCTION COSTS OF TANKAGE PLANTS (2 Story Type) 
 INCLUDING SCREENING, GRIT CHAMBERS AND SLUDGE DISPOSAL. 
 
 • 
 
 Ition 
 Led for 
 
 Year Built 
 
 ity de- 
 L for MGD 
 
 ruction 
 
 rsion 
 
 Construction Costs 
 
 a'm 
 
 O <D 
 
 Quant 
 signed 
 
 Actual 
 
 L/Onsil 
 
 Cost 
 
 Conve 
 Facto: 
 
 Based on Chicago 
 Prices of Material 
 and Labor, 1925. 
 
 
 
 
 
 
 Per 
 
 Per 
 
 
 
 
 Total 
 
 
 Total Capita 
 
 M.G.D. 
 
 ♦♦Cleveland 288,000 
 
 1916-23 
 
 36 
 
 $ 944,130 
 
 1.06 
 
 $1,000,000 ?3.47 
 
 $27,800 
 
 (Westerly) 
 
 
 
 
 
 
 
 Rochester, N. Y.. 200,000 
 
 1916 
 
 34 
 
 500,250 
 
 1.87 
 
 935,000 4.67 
 
 27,500 
 
 (Irondequoit) 
 
 
 
 
 
 
 
 (a) Philadelphia. 300,000 
 
 1917-23 
 
 60 
 
 1,698,770 
 
 1.23 
 
 2,085,000 6.95 
 
 34,800 
 
 Albany 156,000 
 
 1915 
 
 30 
 
 443,080 
 
 2.03 
 
 901,000 5.77 
 
 30,000 
 
 
 
 
 
 
 5.22 
 
 30,025 
 
 Weighted average 
 
 
 
 
 
 5.00 
 
 30,750 
 
 Chicago, Calumet 
 
 
 
 
 
 
 
 Plant 179,000 
 
 1920-23 55.0 
 
 *$5,207,569 
 
 .91 
 
 *$4,747,000 $26.40 
 
 $86,000 
 
 *Corrected for 1 M. G. D. activated sludge and 4.44 acre ft. of filters and for land. 
 **No sludge drying beds — Cost adjusted on basis of 1919. 
 
 (a One-third built under original contract — two thirds under new contract let in July, 1920. 
 No Intercepters or Pumping Stations included. 
 
 volume of both the flow and digestion chambers in order to eliminate 
 the variations in detention periods, sludge storage per capita, strength 
 and amount of sev^age and the momentary under or overbuilt condition 
 of the plant. The average and weighted average of the costs for each 
 part of the plants, such as screens, grit chambers, tanks, sludge beds, 
 etc., were secured for use in estimating reasonable construction costs 
 for Chicago conditions. The detailed data are shown in Table 38. 
 
150 
 
 Weighted averages were computed in order that the relative effect of 
 size of units upon cost might be taken into consideration. 
 
 Table 36 shows the operating costs of these Imhoff tank plants. It 
 shows also the cost of operating the separate digestion tanks at Balti- 
 more in which the operating costs are excellently sub-divided so that the 
 ,tank and sludge operations are available. We have also shown the 
 facts relative to the Calumet plant of the Chicago Sanitary District on 
 this table. 
 
 TABLE 36. 
 
 OPERATING COSTS OF TANKAGE PLANTS. 
 
 
 
 Liting 
 ion 
 
 
 bo 
 d 
 
 o. 
 
 Operating Costs re- 
 
 
 ar Co 
 iered 
 
 ntribi 
 pulat 
 
 eated 
 
 nual 
 
 erati] 
 sts 
 
 avers 
 ctor 
 
 duced to 
 asis — ; 
 
 Chicago 1925 
 Labor Only 
 
 
 
 o o 
 
 
 c a o 
 
 O 03 
 
 Changed 
 
 
 
 
 
 
 
 
 
 per 
 
 per 
 
 City 
 
 
 
 
 Total 
 
 
 Total" 
 
 Capita 
 
 M.G. 
 
 ♦Cleveland 
 
 1924 
 
 87,000 
 
 4,800 
 
 $ 33,847 
 
 0.975 
 
 $ 32,929 
 
 $ .378 
 
 $6.85 
 
 Rochester .... 
 
 1919 
 
 240,000 
 
 12,050 
 
 30,809 
 
 1.48 
 
 45,625 
 
 .190 
 
 3.78 
 
 '♦Philadelphia .. 
 
 1924 
 
 117,000 
 
 8,100 
 
 28,420 
 
 1.31 
 
 37,280 
 
 .319 
 
 4.61 
 
 Albany 
 
 1920 
 
 104,358 
 
 5,220 
 
 21,127 
 
 1.29 
 
 27,202 
 
 .261 
 
 5.21 
 
 Baltimore .... 
 
 1923 
 
 690,000 
 
 20,100 
 
 75,842 
 
 1.07 
 
 81,352 
 
 .135 
 
 4.04 
 
 Average 
 
 
 
 
 
 
 
 .256 
 
 4.90 
 
 Weighted Ave. . 
 
 
 
 
 
 
 
 .192 
 
 4.47 
 
 Calumet, Chicago 
 
 
 
 
 
 
 
 
 Sanitary Dist. 
 
 1924 
 
 90,000 
 
 10,600t 
 
 $199,567t 
 
 
 $199,567t 
 
 $2.22 
 
 $18.82 
 
 *No sludge drying beds — sludge pumped to Lake Erie. 
 **No sludge drawn to beds in 1924. 
 
 tDeducted 1180 M. G. estimated sljidge operation @ $21.95 = $25,800. 
 
 At the Westerly Cleveland plant the sludge instead of being dried 
 on beds is discharged into the outlet sewer. The total operating ex- 
 penses of this plant were credited with the cost of chlorination which is 
 practiced during the summer season. 
 
 At Philadelphia the plant is provided with sand sludge drying beds 
 but no sludge was removed during 1924. 
 
 Baltimore, a separate sludge digestion type of plant, has the lowest 
 per capita expenditure for tank and sludge bed treatment of any of the 
 large plants studied. 
 
 It will be noticed that the weighted average cost of operating Im- 
 hoff tank plants adjusted to Chicago 1925 conditions was 19.2 cents per 
 capita and $4.47 per million gallons treated. The Calumet plant in 
 Chicago, built in 1920, with costs adjusted for a small experimental 
 plant and reduced to 1925 conditions on the same basis as the other 
 
151 
 
 plants was $2.22 per capita and $18.82 per million gallons. The per 
 capita cost was ten times the average of the other plants, and the cost 
 per M. G., due to the higher per capita use, was still over four times the 
 average and nearly three times the highest of the other plants. 
 
 Comparative cost of construction of these plants is shown dia- 
 grammatically on Figure 24. 
 
 The operating costs of Tankage plants in cities other than Chicago 
 vary from 13.5 cents to nearly 38 cents per capita, adjusted to the 
 
 HecivL3 linee indicafe 1000 DoUart> per M.G.D 
 LiQh'i ■• - Dollars perCapifa 
 
 UnisHoded cir-<r o s. or-e cor-r-eci+(or-\'3 
 ■^or- Coicaqo cood i-Viori<s 
 'oHode or-eQ<5 ore oc+uol Cos-V 
 
 Plants 
 
 Figure 24. — Cost of constructing Imhoff tank disposal plants, based on 
 1925 Chicago conditions. 
 
152 
 
 Chicago 1925 basis and from $3.78 to $6.85 per million gallons treated 
 referred to the Chicago 1925 price basis. These facts relative to operat- 
 ing costs, together with the operating cost of the Calumet plant of the 
 Chicago vSanitary District are shown diagrammatically on Figure 25. 
 
 Opcra+ion Maw^dnanca. - Dollars per Million Gallons. 
 
 O cn 5 ui o 
 
 ROCHESTCR 
 
 Balximorc. 
 
 Philaoc.i_p>mia 
 
 No sludqe rzrr\o^e.c 
 
 ho eludgc beds 
 
 Crediteci With 
 Sluolg«Plan+ 
 
 rr-ioU Ac+ivated 
 Operation 
 
 o - M o» 
 
 Opero+ion Sk W\Q\r\\Q,rtariCC- Dollars per Cap! fa 
 
 Figure 25. — Cost of operating tank disposal plants, based on 1925 
 Chicago conditions. 
 
 Heavy lines indicate $ per million gallons. 
 Light lines indicate $ per capita. 
 
 Imhoif Tank^ Sprinkling Filter Plants: 
 
 In a manner similar to that just outlined we investigates! the costs 
 of construction and operation of eight (8) Imhoff tank sprinkling 
 filter plants, all cost being reduced to the 1925 Chicago basis. 
 
 Insofar as possible the costs of construction of these plants were 
 likewise subdivided into the various units of the plants, such as screens, 
 grit chambers, settling tanks, digestion tanks or digestion compartments 
 sprinkling filters, secondary tanks, sludge beds, etc. These costs were 
 
153 
 
 further reduced to the cost per unit of capacity, either per capita, per 
 million gallons or unit of organic load, so that insofar as possible the 
 unit prices thus secured might be available for use in estimates for 
 Chicago costs. 
 
 The comparison of the unit construction costs of these plants is 
 shown on Table 35 hereinbefore referred to under Imhoff Tanks. 
 
 On Table 37 we have shown the summarized costs of the sprinkling 
 filter plants taken as a whole, without respect to the variations in design 
 periods, rates, etc. These costs while more general than those secured 
 from the analysis of the several parts of each plant nevertheless are of 
 interest in showing the average costs of complete plants under widely 
 varying designs. An estimate for any particular set of design conditions 
 can be prepared by applying the unit costs set forth in Table 38 to the 
 corresponding units determined upon. 
 
 A study of the operating costs of the tank-sprinkhng filter plants 
 was also made, the results of which are shown on Table 39. This table 
 shows contributing population,, million gallons treated during the year, 
 the actual operating costs furnished us, these costs reduced to Chicago 
 1925 conditions and expressed in total, per capita, and per million 
 gallons. 
 
 All of these plants are complete and the costs of operation include 
 all such items as labor on coarse screens and grit chambers, labor and 
 power on fine screens at Baltimore (the only plant in this number hav- 
 ing fine screens) sludge handling, sludge drying, cleaning of sprinkler 
 nozzles, operation of laboratory, superintendence, maintenance and re- 
 pairs. 
 
 The detailed costs under each of these subheads are not available 
 for the several plants in comparable form and are accordingly omitted 
 herein. 
 
 It will be noted that the weighted average cost of operating tank 
 sprinkling filter plants was 26.1c per capita or $8.82 per million gallons 
 treated, based on Chicago 1925 conditions. 
 
 Activated Sludge Plants: 
 
 Three large activated sludge plants are now in construction, namely 
 Milwaukee, Indianapolis and the North Side plant in Chicago. The Mil- 
 waukee plant is practically completed, and it is expected will go into 
 operation this year. All construction has either been completed or is 
 under contract so that the entire cost of the work is now ascertained 
 within reasonable limits. 
 
 Mr. T. Chalkeley Hatton, Chief Engineer of the Milwaukee Sewer- 
 age Commission, has very kindly furnished us with a most excellent de- 
 
154 
 
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158 
 
 tailed analysis of the costs of this plant, which is reproduced in summar- 
 ized form on Table 40. In this table we have adjusted the Milwaukee 
 costs for Chicago conditions and expressed the results in cost per mil- 
 lion gallons and per capita for each of the several parts of the plant. 
 
 Mr. Hatton has also made a detailed study of the estimated costs of 
 operating this plant based upon observations and data collected during 
 the extended experimental work at Milwaukee. These estimates of 
 operating cost are contained in the Eighth Annual Report of the Sewage 
 Commission of the City of Milwaukee. We are advised by Mr. Hatton 
 that although these estimates were made about three years ago, they are 
 believed to represent conditions at the present time except for fixed 
 charges. 
 
 We have also been furnished through the courtesy of Mr. Charles 
 H. Hurd, Consulting Engineer of the Indianapolis Commission, an 
 analysis of the construction cost of that plant, which is reproduced in 
 abstracted form on Table 41. 
 
 In addition to these two large activated sludge plants, both of 
 which are substantially ready to start operation, there have been two 
 activated sludge plants in Houston, Texas, which have been in operation 
 for over five years. These plants have capacities of ten and five million 
 gallons per day respectively. Neither of the Houston plants provide for 
 dewatering of the sludge although considerable experimental work on 
 sludge dewatering has been carried on from time to time. 
 
 The two Houston plants are the only activated sludge plants in this 
 country except the Des Plaines plant of the Chicago Sanitary District, 
 which have had real operating- experience, although the Milwaukee ex- 
 periments were conducted on a sufficiently large scale to make them 
 quite indicative of operating difiiculties and costs. 
 
 The data relative to the cost of construction of the Milwaukee, 
 Indianapolis and two Houston plants and of the Des Plaines River 
 plant of the Sanitary District of Chicago, which is substantially the 
 same size as the small Houston plant built in 1920, is shown in Table 42. 
 
 It will be noticed that the weighted average cost of construction of 
 the Milwaukee and Indianapolis plants under 1925 Chicago conditions 
 is $10.45 per capita or $74,300 per million gallons daily capacity. The 
 Des Plaines plant has a per capita cost of $30.65 and a cost per million 
 gallons per day of $306,500. 
 
 These facts relative to construction costs of all plants are shown 
 diagrammatically on Figure 26. 
 
 The cost of operating the Houston plants and the estimated cost of 
 operating the Milwaukee plant, as worked out in detail by Mr. Hatton, 
 and the actual cost of operating the Des Plaines plant of the Chicago 
 
159 
 
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161 
 
 Sanitary District for the year 1924, are shown in tabular form on 
 Table 43 and diagrammatically on Figure 27. 
 
 The Des Plaines plant of the Sanitary District of Chicago has an 
 operating cost approximately eight times the estimated cost of operating 
 the Milwaukee plant expressed on the per capita basis, and ten times 
 these figures when expressed in terms of million gallons treated. 
 
 The Des Plaines operating costs include some items properly 
 chargeable to experimental work. 
 
 jnOlAhAP< )H3 
 
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 Figure 26. — Cost of construction of activated sludge plants, based on 1925 
 
 Chicago conditions. 
 
 Shaded areas are actual costs. 
 
 Unshaded areas are corrections for Chicago conditions. 
 
162 
 
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 Figure 27. — Cost of operating activated sludge plants, based on 
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 Pumping Station Costs: 
 
 As due to the level character of the topography in the Chicago 
 district, practically all of the sewage in Chicago requires pumping be- 
 fore treatment, the costs involved in the construction and operation of 
 sewage pumping stations becomes a large item. 
 
 In addition to ascertaining the facts relative to costs of pumping 
 stations and pumping station operations at Chicago we collected data 
 relative to cost of construction and operation of sewage pumping sta- 
 
164 
 
 tions in other cities. There are many such stations scattered through- 
 out the country, but unfortunately for our purposes most of these sta- 
 tions are smaller in size than those required in Chicago, and most of the 
 larger ones were built so long ago as to make the costs of construction 
 subject to less accurate _ adjustment to the 1925 Chicago basis than 
 would be the case if they had. been built more recently. 
 
 We were, however, able to secure sufficient operating data relative 
 to large sewage pumping stations in four cities to furnish a very good 
 idea as to the fair and reasonable cost of operating them. On Table 
 44 we show the cost of operating a large number of sewage pumping 
 stations including the stations at Baltimore, New Orleans, four stations 
 in Boston and the Albany sewage pumping station, together with several 
 stations operated by the City of Chicago and the Chicago Sanitary 
 District. 
 
 Abstracting from the larger tabulation only those stations which 
 have an annual output of about 200,000 million foot gallons per year 
 above which there is little reduction in the unit cost of pumping station 
 operation, we have the following data: 
 
 
 Million 
 
 Annual Cost 
 
 
 Foot 
 
 per Million Foot 
 
 City 
 
 Gallons 
 
 Gallons — Chicago 
 
 
 Output 
 
 1925 Basis 
 
 
 591,000 
 
 19.5^* 
 
 New Orleans (8 Stations),. 
 
 485,000 
 
 14.1 
 
 Boston (4 Stations) 
 
 , , 1,297,000 
 
 18.0 
 
 Albany 
 
 198,500 
 
 17.4 
 
 
 160,800 
 
 20.0 
 
 Milwaukee (Kinnickinnick) 
 
 183,000 
 
 19.6 
 
 
 
 ISM 
 
 Chicago— 
 
 -Sanitary District. 
 
 
 39th St. (1920) 
 
 432,900 
 
 59.5^ 
 
 Lawrence Ave. (1919) 
 
 131,800 
 
 65.3 
 
 Calumet (1924) 274,000 49.1 
 
 Average 58.0^^ 
 
 The Chicago Sanitary District pumping station operating costs, 
 excluding power charge, average approximately three times those of 
 similar stations elsewhere including the cost of power. 
 
 The operating costs are compared on a basis of costs per million 
 foot gallons as actually reported and as adjusted for the 1925 Chicago 
 conditions. 
 
165 
 
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 The figures on this table are shown in diagrammatic form on 
 Figure 28 and 29. 
 
 Basis of Cost Estimates in this Report: 
 
 The foregoing studies and cost analyses were used as a basis for 
 estimating the reasonable costs of sewers and sewage disposal works 
 required for each of the several flows considered as possibly available 
 for the sewage plant effluents of the Chicago Sanitary District. 
 
 This adjusted comparative method of ascertaining fair costs of con- 
 struction and operation of public works is believed to furnish an excel- 
 lent criterion as to the costs which should practicably be secured. Its ad- 
 vantages include the following: 
 
 Mew Orlcans 
 
 Ai_e>Aisiv 
 
 bOSTON 
 
 A StoiionS) 
 BALTTVtORE 
 
 CALJJ vlET-CfjllCAGO 5Ar|)ITAR>' DISTRICT 
 
 CK-ediied With 
 
 32> Th. St-Ci- ICA60 SanItary DistRicr 
 
 Lawc'ENCE /we- Chicago Sanitary Dist 
 
 PoweR. Crene rated 
 
 RICT 
 
 Cent% Per Mill-\on Foot Gai_L-Ons 
 
 Figure 28. — Operating costs of large sewage pumping stations (over 200,000 
 million foot galons per year). 
 
 Shaded areas are actual costs. 
 
 Unshaded areas are corrections for Chicago conditions. 
 
168 
 
169 
 
 (a) Being based upon analyses of costs of like work in other 
 municipalities, it automatically allows for the average percentage of in- 
 efficiency found in public enterprises. 
 
 (b) The study embracing a large number of cities, in this case 
 including a study of costs at Baltimore, Albany, Rochester, Philadelphia, 
 Cleveland, Milwaukee, Indianapolis, Houston and many other important 
 cities, gives a representative average basis of municipal costs. 
 
 (c) The application of these unit costs in this study presupposes 
 that the Sanitary District of Chicago will execute its construction pro- 
 gram and its operations with efficiency and freedom from political inter- 
 ference equal to (neither better nor worse) than those found practicable 
 in other public bodies executing similar work. 
 
 (d) This method is particularly applicable to large operating 
 units in which the several operations are of sufficient magnitude to es- 
 tablish complete organizations such as is the case at all Chicago plants. 
 
 This method and the data contained in Chapter X relative to sewer 
 costs and in this Chapter XII relative to sewage disposal plant costs 
 have been used as the basis of estimates of costs of plants and opera- 
 tion for several flows studied, all as outlined in Chapters XIII, XIV, 
 and XV. 
 
170 
 
 PART XIII. 
 
 REQUIRED WORKS FOR 10,000 CUBIC FEET 
 PER SECOND FLOW. 
 
 Basis of Cost Estimates For All Projects: 
 
 With a total flow in the drainage channel at Lockport of 10,000 
 cubic feet per second, there will be available during the warm months 
 of July and August approximately 365,000 pounds of oxygen per day 
 in 1935 and 354,000 pounds per day in 1945. (See Table 17.) Of 
 this total amount a relatively small part will be required to provide for 
 the effluents from the sewage disposal plants which are now under con- 
 struction or which are included in the tentative plans of the District 
 to be constructed in the very near future, all of which it is assumed will 
 soon provide complete secondary treatment. 
 
 The oxygen requirements for the effluents of these plants are esti- 
 mated as shown in Table 45. 
 
 The amount of oxygen left for disposing of the effluents from the 
 West and Southwest plants will be approximately 330,585 pounds in 
 1935 and approximately 314,210 pounds in 1945. We have endeavored 
 to ascertain the extent of treatment for the West and Southwest Side 
 sewage, which will utilize this available oxygen to the fullest extent and 
 with the most efficiency. 
 
 If deposits are to be prevented in the Illinois River at least tankage 
 must be installed at both the West and Southwest plants. The installa- 
 tion of tanks alone will reduce the B. O. D. of the sewage reaching the 
 two plants from 532,500 pounds to 346,000 pounds per day. As this 
 amount exceeds the 330,585 pounds available in the total flow in the 
 channel of 10,000 C. F. S. some secondary treatment will be required 
 even in 1935. 
 
 The addition of sprinkling filters to the Southwest plant will reduce 
 the B. O. D. of the two plant effl.uents to 242,800 pounds per day for 
 1935 and 254,900 pounds per day for 1945 conditions. This treatment 
 will so reduce the B. O. D. that the total flow in the channel of 10,000 
 C. F. S. would supply an adequate amount of oxygen up to as late as 
 about 1960. 
 
 Briefly summarized a total flow of 10,000 C. F. S. will provide 
 adequately for the dilution of treated sewage from the Sanitary District 
 to 1960 providing: 
 
171 
 
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172 
 
 (a) Activated sludge plants are in operation for the North Side, 
 Des Plaines and Stockyards. 
 
 (b) Tanks and Sprinkhng filters are in operation for the Argo, 
 Calumet and Southwest Side. 
 
 (c) Tanks are in operation at the West Side. 
 
 Estimated Cost of Works Required for 10,000 Cubic Feet Per Second 
 Flow: 
 
 We have estimated the cost of the works required to handle the 
 sewage of the Sanitary District of Chicago, based upon a total flow of 
 10,000 cubic feet per second in the Drainage Canal. This estimate is 
 as follows : 
 
 Construction Costs 
 
 
 1935 
 
 1945 
 
 
 Conditions 
 
 Conditions 
 
 Des Plaines Activated Sludge 
 
 $ 264,700 
 
 $ 439,300 
 
 Calumet — Sprinkling Filters 
 
 1,564,420 
 
 2,021,700 
 
 North Side — Activated Sludge 
 
 5,600,800 
 
 5,947,300 
 
 Argo — Sprinkling Filters 
 
 2,544,200 
 
 2,808,800 
 
 
 7,804,800 
 
 8,601,600 
 
 West Side — Intercepters 
 
 7,890,600 
 
 7,890,600 
 
 West Side— Tanks 
 
 10,120,440 
 
 10,699,700 
 
 S. W. — Intercepters 
 
 4,495,700 
 
 4,405,700 
 
 S. W. Side— Sprinkling Filters 
 
 13,793,500 
 
 16,362,000 
 
 Miscellaneous Plants 
 
 3,336,000 
 
 5,336,000 
 
 Total Estimated Costs 
 
 $57,415,240 
 
 $64,692,700 
 
 It will be noted that an expenditure of approximately $57,000,000 
 is required for the 1935 sewage load even with 10,000 C. F. S. flow. If 
 the industries were to pay one-half the cost of the Corn Products and 
 Stockyards plants this total would be credited with approximately 
 $5,000,000. 
 
 An additional expenditure of approximately $7,000,000 will be re- 
 quired to provide the additional capacity for 1945 conditions. Even a 
 10,000 cubic feet per second flow requires, as promptly as possible, com- 
 plete treatment ; that is, either tanks and sprinkling filters or activated 
 sludge for all of the sewage of the Sanitary District of Chicago, with 
 the exception of that of the West Side district which may have tankage 
 only for the present. 
 
 Operating Expenses: 
 
 The cost of operating the pumping and treatment plants outlined 
 under the 10,000 c. f. s. project is estimated as follows: 
 
173 
 
 Operating Expenses 
 1935 1945 
 
 Des Plaines — Activated Sludge 
 North Side — Activated Sludge. 
 
 78,500 $ 102,240 
 
 882,500 1,042,500 
 
 552,600 611,800 
 
 197,800 244,900 
 
 77,200 86,160 
 
 1,043,300 1,273,200 
 
 1,182,500 1,264,000 
 
 350,000 380,000 
 
 <a) Stock Yards — Activated Sludge 
 Calumet — Sprinkling Filters . . . 
 
 <a) Corn Products — Sprinkling Filters . . . 
 South West Side— Sprinkling Filters 
 
 West Side Tanks 
 
 Miscellaneous Plants 
 
 Total Treatment Oper. Costs 
 
 (b) General Office Expense 
 
 <b) Bridge and Channel Expense . . . 
 
 $ 4,364,400 
 360,000 
 253,000 
 
 $ 5,004,800 
 440,000 
 264,000 
 
 Total Cost of Operating Sanitary District $ 4,977,400 $ 5,708,800 
 
 (Exc'l fixed charges) 
 
 ♦Credited with sale of sludge @ $10. /ton. 
 
 (a) No credit given for possibility of industries assuming part of this cost. 
 
 (b) Estimated from past study of records of Sanitary District. 
 
 We have made no detailed analysis of the necessity for the amounts 
 shown as ''General Office Expense" and "Bridge and Channel Ex- 
 pense". The amounts included in the estimated operating expenses of 
 the Sanitary District for each project are the same in each case" and are 
 based wholly upon a study of expenditures actually charged to these 
 items in the past by the District. 
 
174 
 
 PART XIV. 
 
 REQUIRED WORKS WITH 4167 CUBIC FEET 
 PER SECOND FLOW. 
 
 With 4167 cubic feet per second total flow in the Drainage Canal 
 there would be available during the summer months of July and August 
 approximately 113,200 pounds per day of oxygen in 1935 and 103,000 
 pounds per day in 1945. Of this total it has been shown in Part XIII 
 that approximately 33,415 pounds in 1935 and 39,790 pounds in 1945 
 would be required to care for the effluent of the Des Plaines, Calumet, 
 North Side, Argo and Stockyards plants. There would therefore be 
 available from the flow of 4167 c. f. s. approximately 79,785 pounds of 
 oxygen per day in 1935 and 63,210 pounds in 1945 to care for the 
 effluents from the West and Southwest Side treatment plants. 
 
 The total oxygen requirement of the sewage reaching these plants 
 in 1935 and 1945 is estimated as follows: 
 
 1935 1945 
 
 West Side Plant 326,000 # 349,000 # 
 
 Southwest Side Plant 206,500 241,000 
 
 Totals 532,500 590,000 
 
 These totals are seven to nine times the oxygen available from the 
 4167 c. f. s. flow after the other plant effluent requirements have been 
 satisfied. 
 
 The type of treatment adopted therefore must be such that it will 
 reduce the bio-chemical oxygen demand in 1935 by approximately 
 eighty-five percent and in 1945 by approximately eighty-nine and one- 
 half percent. Th two most practicable methods of accompHshing this 
 reduction are by tank-sprinkling filter plants and by activated sludge 
 treatment. 
 
 We have made a comparison of the costs of construction and the 
 costs of operation of these two methods of sewage disposal as applied to 
 the West Side and Southwest Side conditions for 1935 and 1945 respec- 
 tively. We have also estimated the annual costs, which are made up of 
 interest which we have taken at four percent, depreciation which we 
 have taken at two percent on sprinkling filter plants and four percent 
 on activated sludge, and operating costs. The higher depreciation al- 
 lowance for activated sludge plants is adopted because of the process 
 
175 
 
 requiring more mechanical equipment of relatively short life and which 
 due to the present experimental nature of the process suffers higher ob- 
 solescence than sprinkling filters which have been in use a generation 
 or more. 
 
 In both the cost of construction and the cost of operating activated 
 sludge plants we have based our estimates upon two sets of conditions : 
 
 First. Complete plants, including equipment for sludge pressing, 
 drying and storage and including in the operating expenses a credit for 
 the sale of sludge and 
 
 Second. Based upon no drying or storage of sludge but instead 
 upon pumping the sludge to abandoned quarries and vacant land along 
 the drainage canal. 
 
 Table 46 shows the comparative first and annual costs of construc- 
 tion under each of these three alternatives. It will be noticed that so 
 far as first cost is concerned approximately $10,000,000 is saved in in- 
 vestment in the construction of an activated sludge plant with no sludge 
 pressing or drying equipment as compared to either of the other plants. 
 The annual cost of operation of a disposal plant of this type, however, 
 is approximately $300,000 greater than that of the tanks and sprinkling 
 filters in 1935 and approximately $500,000 per year greater in 1945. 
 
 The cost of activated sludge treatment, including complete sludge 
 drying, and crediting the operating cost with a revenue from sludge 
 sales equivalent to $10.00 per ton of sludge, is about fifteen percent to 
 twenty percent higher than that of either the sprinkling filter or the 
 activated sludge plan with lagooning of sludge. 
 
 The sludge produced by the activated sludge method is about 
 ninety-eight to ninety-nine percent moisture as compared to eighty-five 
 to ninety percent moisture for Imhoff tank sludge. In volume, there- 
 fore, it is from seven to ten times as great as tank sludge from sewage 
 of the same solid content. The sludge disposal problem with the acti- 
 vated sludge process is a difficult one. Sludge drying is possible but 
 the practicability of drying it at a cost less than the am.ount which can 
 be realized from its sale as fertilizer has not as yet been fully demon- 
 strated. It is possible to lagoon this sludge and for this purpose the 
 Sanitary District of Chicago has available a large amount of land and 
 abandoned quarry capacity. 
 
 In order to secure some idea as to the practicability of lagooning or 
 disposing of large quantities of wet sludge in the abandoned quarries, 
 we have given this phase of the matter some little attention. We have 
 been furnished by the Sanitary District with a study which has been 
 made by the district of the abandoned quarries along the main drainage 
 channel. Ten abandoned quarries with a total storage capacity of nearly 
 
176 
 
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177 
 
 5,000,000 cubic yards were located between Summit and Lockport. 
 Nearly half of the total capacity is located immediately adjacent to 
 Summit. 
 
 If is the Sanitary District's plan to utilize these quarries for dis- 
 posal of the sludge from the North side activated sludge plant, which is 
 now under construction, and from which the sludge will be conducted 
 to the quarries through a cast iron force main. 
 
 The sludge as pumped will contain approximately two percent of 
 sludge materials and ninety-eight percent of moisture. It will amount 
 to approximately 1,100,000 gallons per day at the present time, increas- 
 ing to approximately 1,790,000 gallons per day by 1945. After this ex- 
 tremely wet sludge is pumped into the quarries which have depths as 
 great as approximately 100 feet, and as the quarries fill, the sludge will 
 be to a certain extent dewatered due to the hydraulic pressure exerted. 
 
 If there was no dewatering effect the total capacity of all the quar- 
 ries would be sufficient for the sludge from the North Side plant alone 
 for only about two years and four months. If the sludge dewaters itself 
 to ninety percent moisture as an average, these quarries would be suffi- 
 cient for the North Side sludge for a period of twelve years. If the 
 sludge should be dewatered due to its depth and pressure to eighty per- 
 cent moisture these quarries would be sufficient for the North Side plant 
 sludge for about twenty-four years. 
 
 In addition to the abandoned quarries, the Sanitary District owns a 
 strip of land in many places nearly a mile in width and extending over 
 most of the reach from Summit to Lockport, a distance of some fifteen 
 miles. The total area between summit and Lockport is approximately 
 3,200 acres. Most of this land is of little value from the agricultural 
 standpoint and is lying idle at the present time. 
 
 If the West and Southwest plants were also to be provided with 
 activated sludge type treatm.ent, and the sludge lagooned in the quarries 
 and on this vacant ground, the amount of sludge to be handled would be 
 greatly increased and its disposal would become a much more difficult 
 problem. The quantity of wet sludge to be taken care of from the North 
 Side, the West and Southwest Side plants combined would be over 
 four times that to be handled from the North Side alone. All the quar- 
 ries covered by the Sanitary District survey would be filled in less than 
 seven months by the sludge pumped from these three plants if it is 
 assumed that there would be no reduction in the moisture content below 
 the ninety-eight percent at which it reached the quarries. 
 
 If the moisture content were reduced to ninety percent all of the 
 quarries would last for only two years and ten months, and if the sludge 
 moisture were reduced to eighty percent all of these quarries would last 
 only five years and seven months. 
 
178 
 
 The question of disposing of this vast amount of wet sludge is 
 therefore a real problem. It is so great in quantity that an area of 
 approximately nine square miles, that is one mile in width and nine 
 miles in length extending along the drainage canal, would be covered 
 with wet sludge to a depth of one foot each year. The land owned by 
 the Sanitary District would have to take a dosage of nearly twenty 
 inches per year. There would of course be some very material shrink- 
 age in the drying out of this sludge. However, there is no data available 
 from which it is possible to determine with any degree of certainty what 
 the conditions of sludge drying under these conditions of lagooning 
 would be. 
 
 It might be found that by skillful utilization of the land and quar- 
 ries for lagooning, the sludge from all three plants could be disposed of 
 without the installation of sludge pressing and drying equipment for a 
 considerable period. The uncertainties are, however, very great. 
 
 In view of the fact that the activated sludge treatment will reduce 
 the oxygen demand of the effluent below that of sprinkling filter plants 
 (ninety-two percent compared to eighty-eight percent B. O. D. re- 
 duction) and thus extend the period for which expenditures now to be 
 made at the West and Southwest plants will be adequate and in view 
 of the further fact that the costs of constructing the two types of plants 
 are substantially the same including complete sludge handling equipmnt 
 in the activated sludge treatment, it is believed that the procedure for 
 handling the sewage of the West and Southwest Side districts with a 
 total flow restricted to 4167 C. F. S. is through activated sludge which 
 will adequately treat the sewage with a flow in the channel of 4167 
 C. F. S. as late as 1952. 
 
 While it might be practicable to lagoon the sludge at least for a 
 time it is believed that complete sludge handling equipment should be 
 provided for in this project and this has accordingly been done. 
 
 We have estimated the cost of the disposal works required for a 
 4167 cubic feet per second flow as follows : 
 
 Estimated Cost of Works Required for 4167 C.F.S. Diversion. 
 
 Des Plaines Activated Sludge Plant 
 Calumet — Sprinkling Filters 
 
 1935 
 $ 264,700 
 
 439,300 
 2,021,700 
 5,947,300 
 2,808,800 
 8,601,600 
 
 22,544,600 
 7,890,600 
 
 16,496,700 
 
 1045 
 
 (a) S. W. Side — Activated Sludge 
 
 (a) West Side — Activated Sludge 
 
 North Side — Activated Sludge Plant 
 *Corn Products — Sprinkling Filters. 
 * Stockyards — Activated Sludge Plant 
 
 West Side — Intercepters 
 
 1,564,420 
 5,600,800 
 2,544,200 
 7,804,800 
 
 21,287,900 
 7,890,600 
 
 14,424,400 
 
179 
 
 S. W. Side— Intercepters 4,495,700 4,495,700 
 
 Miscellaneous Plants 3,336,000 5,336,000 
 
 Total Estimated Costs $69,213,520 $76,583,300 
 
 • San. Dist. has started suit to require industries to bear part of this cost, 
 (a) Sludge drying included. 
 
 It will be noted that a total expenditure of over $69,000,000 will be 
 required by 1935 for intercepting sewers and sewage disposal for the 
 complete treatment of the sewage of the West and Southwest side 
 plants to the degree which will enable the effluent from these plants to- 
 gether with the effluent of the other plants within the Sanitary District of 
 Chicago to be adequately provided with the necessary oxygen by a flow 
 of 4167 cubic feet per second in the Drainage Canal. By 1945 an addi- 
 tional $7,000,000 of investment will be required to take care of the 
 increased demand due to population and industrial growth. By 1952 
 with a flow of 4,167 C. F. S. additional refinement to still further reduce 
 the B. O. D. will probably become necessary. 
 
 Both of the above figures include the entire cost of disposal w^orks 
 for the stockyards and Corn Products wastes. If half of the cost of 
 these works is properly chargeable to the industries creating these 
 wastes, approximately $5,000,000 should be deducted from the figures 
 for both the 1935 and 1945 debts. 
 
 The cost of operating the puniping and treatment plants outlined 
 under the 4,167 C. F. S. project is estimated as follows: 
 
 1935 1945 
 
 Des Plaines Activated Sludge $ 78,500 $ 102,240 
 
 Calumet— Sprinkling Filters 197,800 244,900 
 
 North Side— Activated Sludge 882,500 1,042,500 
 
 (a) Corn Products— Sprinkling Filters , 77,200 86,160 
 
 (a) Stockyards— Activated Sludge 552,600 611,800 
 
 ♦West Side Activated Sludge 1,776,500 1,941,000 
 
 *S. W. Side Activated Sludge 1,248,000 1,409,000 
 
 Miscellaneous Plants 350,000 380,000 
 
 Totals $ 5,163,100 $ 5,817,600 
 
 General Office Expense 360,000 440,000 
 
 Bridge and Channel Expenses 253,000 264,000 
 
 Total Fair Cost of Operating District 5,776,100 6,521,600 
 
 ♦Credited with the sale of sludge @ $10/ton. 
 
 (a) No credit given for industries possibly assuming part of this cost. 
 
180 
 
 PART XV. 
 
 REQUIRED WORKS WITH MISCELLANEOUS FLOWS. 
 
 In addition to the channel flows of 10,000 c. f. s. and 4,167 c. f. s. 
 
 discussed in detail in Parts XITI and XIV, respectively, we have made 
 studies of the requirements and the costs of sewage disposal with flows 
 of 2,000, 6,000, 7,500, and 8,500 c. f. s. 
 
 Required Works with 2,000 C. F. S. Flow: 
 
 With 2,000 c. f. s. flow there would be available during the months 
 of July and August approximately 20,200 pounds of oxygen per day in 
 1935, and 10,000 pounds per day in 1945. As hereinbefore shown, the 
 oxygen requirements for the effluent of the Des Plaines, Calumet, 
 North Side, Corn Products and Stockyards plants are 33,415 pounds of 
 oxygen in 1935 and 39,790 in 1945. 
 
 Inasmuch as the effluents from the above plants require more oxy- 
 gent even at the present time than is available in the 2,000 c. f. s. total 
 flow in the channel, it is obvious that there is no practicable means of 
 meeting the requirements of the pollution standard hereinbefore out- 
 lined with so small a flow in the channel. 
 
 Many cities are so located that standards less adequate are neces- 
 sarily adopted ; however, a pollution standard which provides for a 
 thriving fish life in Illinois River cannot practicably be complied with 
 when the total flow in the Drainage Canal is as low as 2,000 c. f. s. 
 
 Required Works with 6,000 C. F. S. Flow: 
 
 With a total flow of 6,000 c. f. s. in the Drainage Canal, the avail- 
 able oxygen during July and August would be approximately 192,000 
 pounds per day in 1935 and 182,000 pounds in 1945. Of this amount 
 33,415 pounds in 1935 and 39,790 pounds in 1945 wiU be required for 
 the effluents of the Des Plaines, Calumet, North Side, Corn Products 
 and Stockyards plants, leaving 158,585 pounds in 1935 and 142,210 
 pounds in 1945 for the West and Southwest plant effluents. The fol- 
 lowing table shows the requirements of these two plant sewages with 
 varying types of treatment : 
 
181 
 
 Type of Treatment B.O.D. of Effluents from 
 
 West Southwest Both Plants 
 
 Side Side 1935 1945 
 
 Raw Sewage Kaw Sewage 532,500 lbs. 589,000 lbs. 
 
 Tanks Tanks 346,000 lbs. 383,000 lbs. 
 
 Tanks Sprinkling Filters 236,800 lbs. 254,900 lbs. 
 
 Sprinkling Filters. . .Sprinkling Filters 63,900 lbs. 70,600 lbs. 
 
 Sprinkling Filters. . .Tanks 173,100 lbs. 198,700 lbs. 
 
 Activated Sludge. .. .Activated Sludge 42,600 lbs. 47,100 lbs. 
 
 Sand Filters Sand Filters lbs. lbs. 
 
 From the above table it is apparent that nothing less than sprink- 
 ling filters for both plants will accompHsh the results. The flow of 
 6,000 c. f. s. accordingly requires the construction of tanks and sprink- 
 ling filters at both the West and Southwest plants. 
 
 We have estimated the cost of the disposal works required for a 
 6,000 cubic feet per second flow as follows : 
 
 Estimated Cost of Works Required for 6,000 C.F.S. Flow. 
 
 
 1935 
 
 1945 
 
 Des Plaines Activated Sludge Plant 
 
 $ 264,700 
 
 $ 439,300 
 
 
 1,564,420 
 
 2,021,700 
 
 North Side — Activated Sludge Plant 
 
 5,6-00,800 
 
 5,947,300 
 
 
 2,544,200 
 
 2,808,800 
 
 
 7,804,800 
 
 8,601,600 
 
 
 21,431,700 
 
 22,837,100 
 
 West Side — Intercepters 
 
 7,890,600 
 
 7,890,600 
 
 S. W. Side— Sprinkling Filters 
 
 13,793,500 
 
 16,362,000 
 
 
 4,495,700 
 
 4,495,700 
 
 Miscellaneous Plants 
 
 3,338,000 
 
 5,336,000 
 
 Total Estimated Costs $ 68,726,620 $ 76,740,100 
 
 *San. Dist. has started suit to require industries to bear part of this cost. 
 
 Both of the above figures include the entire cost of disposal works 
 for the stockyards and Corn Products wastes. If half of the cost of 
 these works is properly chargeable to the industries creating these 
 wastes, approximately $5,000,000 should be deducted from the figures 
 for both 1935 and 1945. 
 
 The cost of operating the pumping and treatment plants outlined 
 under the 6,000 c. f . s. project is estimated as follows : 
 
 Plant 
 
 1935 
 
 1945 
 
 
 $ 78,500 
 
 $ 102,240 
 
 Calumet — Sprinkling Filters 
 
 197,800 
 
 244,900 
 
 
 882,500 
 
 1,042,500 
 
 (a) Corn Products — Sprinkling Filters 
 
 77,200 
 
 86,160 
 
 * (a) Stockyards — Activated Sludge 
 
 552,600 
 
 611,800 
 
182 
 
 West Side— Sprinkling Filters. 1,637,500 1,749,200 
 
 S. W. Side— Sprinkling Filters 1,043,300 1,273,200 
 
 Miscellaneous Plants 350,000 380,000 
 
 Totals $ 4,819,400 $ 5,490,000 
 
 General Office Expense $ 360,000 $ 440,000 
 
 Bridge and Channel Expense 253,000 264,000 
 
 Total Fair Cost of Operating District $ 5,432,400 $ 6,194,000 
 
 *Credited with the sale of sludge @ $10/ton. 
 
 (a) No credit given for industries possibly assuming part of this cost. 
 
 Required Works With 7,500 Cubic Feet Per Second: 
 
 With a flow in the channel of 7,500 c. f. s. there will be available 
 257,000 pounds of oxygen per day during the months of July and 
 August in 1935 and 246,000 pounds in 1945. It would be possible to 
 keep the total oxygen demand of the sewage and industrial wastes of 
 the entire district below this amount of available oxygen by having con- 
 structed activated sludge plants at Des Plaines, the North Side and 
 Stockyards, and sprinkling filter plants at Calumet, the Corn Products 
 Plant and at the West Side Plant, with tanks at the Southwest Side 
 Plant. Soon after 1945 a part of the sprinkling filters for the South- 
 west plant would have to be constructed, as by that time the oxygen 
 demand of the effluents would exceed the available oxygen. 
 
 It has, therefore, been assumed that for 7,500 c. f. s. flow the West 
 plant would be a complete sprinkling filter plant constructed at once, 
 and that the Southwest plant would have tanks only. Under this pro- 
 gram the oxygen provided by the 7,500 c. f. s. flow would be suflicrent 
 to care for the effluent from all plants as late as 1947. 
 
 The estimated cost of construction under this program is as 
 follows : 
 
 
 1935 
 
 1945 
 
 Des Plaines Activated Sludge 
 
 % 264,700 
 
 $ 439,300 
 
 Calumet Sprinkling Filters 
 
 1,564,420 
 
 2,021,700 
 
 North Side Activated Sludge 
 
 5,600,800 
 
 5,947,300 
 
 Corn Products Sprinkling Filters 
 
 2,544,200 
 
 2,808,800 
 
 
 7,804,800 
 
 8,601,600 
 
 
 21,431,700 
 
 22,837,100 
 
 West Side Intercepter 
 
 7,890,600 
 
 7,890,600 
 
 
 6,545,000 
 
 7,548,000 
 
 
 4,495,700 
 
 4,495,700 
 
 
 3,336,000 
 
 5,336,000 
 
 Total 
 
 $61,477,920 
 
 $67,926,100 
 
183 
 
 The cost of operating the pumping and treatment plants outlined 
 under the 7,500 c. f. s. project is estimated as follows: 
 
 
 1 Q*? 
 
 
 
 $ 78,500 
 
 $ 102,240 
 
 Calumet Sprinkling Filters 
 
 197,800 
 
 244,000 
 
 
 882,500 
 
 1,042,500 
 
 
 77,200 
 
 86,160 
 
 
 552,600 
 
 611,800 
 
 West Side Sprinkling Filters 
 
 1,637,500 
 
 1,749,200 
 
 Southwest Side Settling Tanks only 
 
 754,300 
 
 920,200 
 
 
 350,000 
 
 380,000 
 
 Total 
 
 $ 4,530,400 
 
 $ 5,137,000 
 
 General Office Expenses 
 
 360,000 
 
 440,000 
 
 Bridge and Channel Expenses 
 
 253,000 
 
 264,000 
 
 Total Fair Cost of Operating Sanitary District. .$ 5,143,400 $ 5,841,000 
 
 * Credited with the sale of sludge @ $10.00 per ton. 
 (a) No credit given for industries assuming part of this cost. 
 
 Required Works with 8,500 Cubic Feet Per Seeond Flozc: 
 
 With 8,500 cubic feet per second flow, the oxygen available would 
 amount to approximately 300,000 pounds per day in 1935, and 289,000 
 pounds in 1945. A study of the utilization of this amount of oxygen 
 shows that it would require no more construction up to as late as 1945, 
 than would be required for 10,000 cubic feet per second, or, in other 
 words, that the difiference in the oxygen supply between 8,500 and 
 10,000 second feet flow is insufficient to permit of the adoption of a 
 less efficient type of treatment at any one of the plants yet to be con- 
 structed. 
 
 The dilution afforded by 8,500 c. f. s. is obviously less than that 
 afforded by 10,000 c. f. s. but the dift'erence is not sufficient to permit 
 the adoption of a less degree of purification at either the West or South- 
 west plant considered as a whole. The providing of secondary treat- 
 ment for a part only of either plant is considered an unwarranted refine- 
 ment in this comparison, it being considered preferable to express the 
 advantage of 10,000 c. f. s. over 8,500 by stating that the expenditures 
 with 10,000 c. f. s, will be adequate until 1960 while further expendi- 
 tures will be required by 1945 if the flow is 8,500 c. f. s. 
 
 . The works required, therefore, for 8,500 cubic feet per second 
 diversion are considered the same as those required for the 10,000 cubic 
 feet per second diversion, which was outlined quite fully in Part XIIL 
 The construction costs and the annual cost of operation are the same as 
 therein set forth. 
 
184 
 
 An expenditure of $57,415,240 would be required for construction 
 up to 1935. The annual cost of operating the District in 1935 (exclu- 
 sive of fixed charges) is estimated as $4,977,400. 
 
 By 1945 the total construction expenditure will have reached 
 $64,692,700 and the cost of operating the District increased to $5,708,- 
 800 (exclusive of fixed charges). 
 
185 
 
 PART XVI. 
 
 REVIEW OF EXPENDITURES UNDER VARIOUS FLOWS 
 
 In Parts XITI, XIV and XV the utilization of the oxygen provided 
 by flows of 2,000, 4,167, 6,000, 7,500, 8,500, and 10,000 cubic feet per 
 second has been discussed and estimates of the cost of constructing and 
 operating the various disposal works best adapted to the utilization of 
 this oxygen has been outlined. The figures of construction and annual 
 cost of operation for 1935 and 1945 which cover conditions for each of 
 these flows, have been summarized as shown in Table 1. 
 
 A study of this table shows that so far as 1935 is concerned an 
 expenditure of $57,415,240 will be required, even with 10,000 cubic 
 feet per second, and that this expenditure would only be increased 
 $11,000,000 or approximately twenty percent in order to meet the more 
 exacting requirements of a flow as low as 4,167 cubic feet per second. 
 
 The cost of operation in 1935 (exclusive of fixed charges) of the 
 works required with 10,000 cubic feet per second flow would be $4,364,- 
 000 per year, and $5,163,100 or about eighteen percent higher, with the 
 flow of but 4,167 cubic feet per second. 
 
 In other words, the difference between the completeness of the 
 treatment processes required under the 10,000 and 4,167 cubic feet per 
 second projects under the 1935 conditions represents a difference in 
 expenditures for plant construction of approximately $11,000,000 
 (20%) and a difference in operating costs of approximately $800,000 
 (18%) per year. 
 
 As applied to the 1945 conditions, the 10,000 cubic feet per second 
 project will require a total expenditure of approximately $64,692,700 
 as compared to approximately $76,583,300 if the flow were but 4,167 
 cubic feet per second, the latter construction cost being nineteen per- 
 cent higher than the former. The cost of operation for 1945 conditions 
 will be approximately $5,004,800 with 10,000 cubic feet per second and 
 approximately $5,817,600 with 4,167 cubic feet per second flow, the lat- 
 ter being sixteen percent higher than the former. 
 
 The construction outlined under the 10,000 cubic feet per second 
 flow will, however, be adequate to meet the conditions to approximately 
 1960, while the construction outlined under the 4,167 cubic feet per sec- 
 ond diversion will become inadequate about 1950. Additional expendi- 
 
186 
 
 tures will be required at an earlier date under the 4,167 cubic feet per 
 second plan than under the one outlined for 10,000 c. f. s. 
 
 We have prepared a diagram showing the adequacy of the various 
 flows with varying degrees of sewage treatment. This diagram shows 
 the length of time for which various projects will be adequate and when 
 additional treatment or greater quantities of dilution water are neces- 
 sary. 
 
 4oo,ooo 
 
 n3o 
 
 jc|4o ic|43 
 
 Figure 30. — Adequacy of various dilutions with various degrees of sewage ^ 
 disposal, based on (1) activiated sludge at Northside & Stock 
 Yards, and (2) tanks and filters at Argo and Calumet. 
 
 Reduction in B. 0. D. 
 
 Basis: Imhoff tanks 35% 
 
 Imhoff tanks and sprinkling filters 88% 
 
 Activated sludge, domestic sewage 92% 
 
 Stock yards and corn products 95% 
 
 All of these costs include the full cost of the Stockyards and Argo 
 plants, for the collection of a part of which the Sanitary District of 
 
187 
 
 Chicago has instituted suits against the Packers and the Corn Products 
 Company, respectively. 
 
 These estimated costs are also based upon the construction of a sep- 
 arate plant to handle the Stockyards wastes. It would seem that there 
 might be very substantial savings effected by the combining of this 
 waste with the domestic sewage of the West and Southwest Side plants, 
 which would result in diluting this strong waste approximately fifteen 
 parts of domestic sewage to each part of Stockyards waste, and enable 
 it to be readily handled by the secondary treatment to be added at the 
 South and Southwest Side sites. This possibility is so important and 
 involves such large expenditures that we have given it somewhat de- 
 tailed consideration. 
 
 Separate Activated Sludge Plant for Treatment of Stockyards Wastes 
 z's. Sprinkling Filter Treatment of Combination of Stocky a/rds with 
 West and Southwest Plant Sewages: 
 
 The possibility of combining the industrial waste from the stock- 
 yards with the immense amount of sewage to be treated at the West and 
 Southwest Side plants, which will be so located as to be substantially 
 one plant, is suggested by the fact that the Southwest Side intercepting 
 sewer runs practically by the site of the proposed Stockyards disposal 
 plant. The combining of all of these sewages and thus obviating the 
 costly construction and operation of an activated sludge plant is further 
 suggested by the necessity of building either the West or Southwest 
 Side plant complete at an early date, under any flows in the channel 
 herein considered ; and both plants for any flow under 7,500 c. f. s. 
 whereas it has apparently been the thought of the Sanitary District that 
 the construction of these plants to give any greater degree of purifica- 
 tion than tankage was a matter of the far distant future. 
 
 The Stockyards wastes, while very strong and having a high oxy- 
 gen demand, are small in volume, amounting at the present time to only 
 32,000,000 gallons per day, increasing to 40,000,000 gallons per day 
 average in 1940. The necessary sewer capacity to transport this small 
 additional flow from the Stockyards to the West and Southwest Side 
 plants is not a material item. 
 
 We have estimated the effect of adding this amount of flow to the 
 Southwest Side intercepter, and find that it will increase the cost of this 
 sewer only $472,000. 
 
 Eifect of Stockyards Wastes upon Sewage at West and Southwest Side 
 Plants: 
 
 The total quantity of sewage to be handled by the West and South- 
 west Side plants under complete metering amounts to 468,000,000 
 
188 
 
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 gallons per day in 1935 and 528,000,000 gallons per day in 1945, as com- 
 pared to the volume of the Stockyards wastes of 32,000,000 and 40,- 
 000,000 gallons per day respectively, at these two periods. The Stock- 
 yards waste, however, has a very high oxygen demand, and we have 
 made some study of the practicability of handling the combined domes- 
 tic sewage and stockyards wastes of these amounts with sprinkling 
 filter treatment. 
 
 Table 47 shows the facts relative to the sewage flow and 
 the strength of the sewage to be handled by the West and 
 Southwest Side plants with and without the addition of the Stockyards 
 wastes. It will be noted that even with the Stockyards waste added to 
 the domestic sewages of the West and Southwest Side district, the com- 
 bined oxygen demand in 1946 will be but 170, as compared to an aver- 
 age for Columbus of 190 parts per million. 
 
 We have further made investigations as to the relative amount of 
 packinghouse wastes in Chicago, as compared to other cities, the results 
 of which are summarized in Table 48. 
 
 It will be noticed that the total pounds of live stock slaughtered in 
 Chicago per person tributary to the West and Southwest Side plants is 
 somewhat less than that in Indianapolis, and only slightly above that at 
 
 TABLE 48. 
 
 IMPORTANCE OF PACKING HOUSE WASTES IN VARIOUS CITIES. 
 
 
 
 Total Pounds 
 
 Pounds 
 
 
 
 of Animals 
 
 Slaughtered 
 
 City. 
 
 Year. 
 
 Slaughtered 
 
 Per Capita. 
 
 
 1922 
 
 3,896,017,318 
 
 1442 d 
 
 
 1923 
 
 4,326,242,144 
 
 1601 d 
 
 
 1924 
 
 4,186,373,884 
 
 1549 d 
 
 (b) Milwaukee 
 
 1922 
 
 440,000,000* 
 
 963 
 
 
 1923 
 
 497,000,000* 
 
 1069 
 
 
 1924 
 
 461,200,000 
 
 1008 
 
 
 1922 
 
 353,000,000 
 
 482 
 
 
 1923 
 
 395,000,000 
 
 538 
 
 
 1924 
 
 397,000,000 
 
 542 
 
 
 1924 
 
 71,000,000 
 
 1385 
 
 (c) IndlanapoHs 
 
 1922 
 
 517,000,000 
 
 1645 
 
 
 1923 
 
 555,000,000 
 
 1768 
 
 
 1924 
 
 526,000,000 
 
 1673 
 
 
 . , 1922 
 
 38,000,000 
 
 493 
 
 
 1923 
 
 38,800,000 
 
 510 
 
 
 1924 
 
 43,100,000 
 
 566 
 
 (a) Head and weights of each class available. 
 
 (b) Head and part of weights available. 
 
 (c) Head available, weights estimated from data available for all markets or adjacent 
 markets. 
 
 (d) Based on population tributary to West and S. W. side plants, including 300,000 tran- 
 sient population. 
 
 * Estimated on basis of 1924. 
 
190 
 
 Madison, Wis. At the latter place it is being handled mixed with 
 domestic sewage at a plant which has a loading of 3,400 people per 
 acre foot of stone beds and the stone beds are being dosed at a rate of 
 approximately two and one-half million gallons per acre per day, and 
 producing an excellent effluent. 
 
 At Indianapolis where the pounds kill per capita is greater than at 
 Chicago, the packing wastes are to be mixed with the domestic sewage 
 and the mixture treated at the sewage disposal plant by the activated 
 sludge method and the use of but one cubic foot of air per gallon of 
 sewage. 
 
 At Milwaukee a packing house waste two-thirds as great propor- 
 tionately as that at Chicago is to be treated with other trade wastes 
 mixed with the domestic sewage, all at one disposal plant. 
 
 The Baltimore sprinkling filter plant handling a concentrated do- 
 mestic sewage with a packing house waste one-third as great propor- 
 tionately as that at Chicago has been operating satisfactorily for years 
 at a dosage rate of 3,500 people per acre. 
 
 It is believed that it should be possible to dose the filters of the 
 South and Southwest Side plants with domestic sewage computed at a 
 rate of 160 gallons per capita per day to which has been added about 
 eight percent by volume of packing house wastes, and maintain a rate 
 
 SAVINGS EFFECTED BY COMBINING STOCKYARDS WITH WEST AND 
 
 SOUTHWEST PLANTS (1935 CONDITIONS). 
 
 Stockyards Additional Cost 
 Alone at West & S. W. 
 Activated Plants due to 
 Sludge Stockyards 
 
 TABLE 49. 
 
 First Cost: 
 
 (1) Intercepters . . 
 
 (2) Disposal Plant 
 
 $ 7,804,000 
 
 Tanks & Filters 
 $ 472,000 
 4,028,000 
 
 Total 
 
 Annual Cost: 
 
 Interest @ 4% 
 Depreciation . . 
 Operation 
 
 $ 7,804,000 
 
 $ 5,500,000 
 
 . ..$ 312,192 $ 220,000 
 @ 4% 312,192 @ 2% 110,000 
 552,600* 206,000 
 
 Total Annual Costs $ 1,176,984 I 
 
 Savings : 
 
 (1) In first cost ' 
 
 (3) In Annual Cost 
 
 (3) In Operation 
 
 (4) In operation capitalized @ 4% plus saving in First 
 
 $ 436,000 
 
 $ 2,304,000 
 740,984 
 346,600 
 
 Cost 
 
 10,969,800 
 
 ♦Includes credit for sale of 36,000 tons of sludge at $10.00 per ton. 
 
191 
 
 of 3,000,000 gallons per acre per day by increasing the depth of the 
 stone filters to eight feet. 
 
 With this as a basis we have made a study of the savings which 
 might be effected by combining the Stockyards wastes with the West 
 and Southwest Side plants, the results of which are shown in Table 49. 
 
 It will be noted that the saving in first cost is $2,304,000, based on 
 1935 conditions. It will somewhat exceed this amount based upon 1945 
 conditions. This is also based upon the use of eight foot instead of six 
 and one-half foot stone beds. If it were found practicable to use the 
 six and one-half foot depth, as is quite possible, the saving would be 
 further increased by $1,200,000. 
 
 Due to the elim.ination of the costly operation of the activated 
 sludge plant at the Stockyards (which is estimated to be $91,600 per 
 year in 1935, exclusive of the credit from the sale of sludge) and the 
 substitution therefore of the less costly treatment by stone filters, there 
 will be a saving in operating cost of $346,600 per year. This saving, 
 capitaHzed at four percent and added to the saving in first cost, shows 
 a total saving of $10,969,800 with eight foot filters and $12,169,800 
 with six and one-half foot filters, which might be effected by combining 
 the Stockyards sewage Avith that of the West and Southwest plants, and 
 treating it by tanks followed by sprinkHng filters rather than by the 
 activated sludge method. 
 
 It must be pointed out that if this procedure were to be adopted all 
 of the grease and coarse soHds possible should be recovered before 
 turning the wastes into the intercepting sewer. It might be accom- 
 plished by screening or short tankage with Dorr Clarifiers which for this 
 investigation it has been assumed would be built and operated by the 
 industries. 
 
 This procedure offers possibility of savings which are so large and 
 so important to the Sanitary District, as well as to the Stockyards inter- 
 ests, that they are certainly worthy of more investigation than we have 
 been able to give to the subject. 
 
 Even if the Stockyards were to pay half the cost of the treatment 
 plant, their share of that cost being understood to be approximately 
 $4,000,000, that contribution would little more than offset the saving in 
 construction cost that could be effected, if the procedure outlined herein 
 is practicable. In addition, the saving in operating expense would be 
 $346,600 per year which is four percent interest on over $8,500,000 so 
 that considered broadly, and on the investment basis, the Sanitary Dis- 
 trict would be giving up $11,000,000 to $12,000,000 as compared to re- 
 ceiving fifty percent share of a separate plant built to handle the pack- 
 inghouse wastes. 
 
192 
 
 This procedure is suggestive of the possibility of important sav- 
 ings, and by a method which, in our opinion, offers considerable assur- 
 ance of being practicable, particularly as this investigation shoves the 
 necessity for building the West and Southwest side plants at an early 
 date. 
 
 Period Required for Construction: 
 
 Our instructions include the determination of the time that reason- 
 ably would be required to build the necessary works and place them in 
 operation. We are instructed to disregard the ability to raise funds, 
 namely, to assume that funds would be available as needed. We inter- 
 pret this instruction to require the development of a program which 
 shall be as rapid as possible and yet not so rapid as to be wasteful. The 
 effect of varying the amount of diluting water upon the magnitude of 
 the construction undertaking is not sufficient in amount to have any 
 material effect upon the length of the construction period required. We 
 have therefore limited this consideration of time required for construc- 
 tion to one flow, viz, 6,000 c. f. s. 
 
 The following is a summarization of the expenditures required for 
 the 6,000 cubic feet per second flow. 
 
 Construction Estimated Cost 
 
 Item. to 1935- 
 
 Des Plaines Plant .$ 264,700 
 
 Calumet Plant 1,564,420 
 
 North Side Plant 5,600,800 
 
 Argo Plant 2,544,200 
 
 Stockyards Plant 7,804,800 
 
 West Side Plant 21,431,700 
 
 Southwest Side Plant 13,793,500 
 
 Miscellaneous Plant 3,338,620 
 
 West Side Intercepter 7,890,600 
 
 Southwest Side Intercepter 4,495,700 
 
 $68,729,040 
 
 The total expenditure of nearly $69,000,000 required for 1935 is, 
 as above shown, to be divided $12,386,300 for intercepting sewers and 
 $56,342,740 for seven major and several smaller disposal plants. 
 
 The intercepting sewers cover a length of approximately thirty-five 
 miles. In constructing the North Side intercepting sewers the Nash 
 contract covering four miles, and an aggregate expenditure of $1,998,000 
 was executed in one year. Five contracts aggregating ten miles and an 
 expenditure of $5,488,000 were completed in two years. 
 
193 
 
 We have assembled the data relative to construction progress on 
 Sanitary District contracts and also on other public or semi-public con- 
 struction of large magnitude, as shown in summarized form on Table 50. 
 
 It will be noticed from this table that construction progress of a type 
 comparable to sewage disposal plants has been rapid in many cases. 
 The construction of the Chicago Produce Market at a cost of $17- 
 000,000 in approximately six months' time, is a most striking illustra- 
 tion of what can be accomplished in the way of rapid construction of a 
 type consisting largely of duplicate units, such as is also the case with 
 sewage disposal plants. 
 
 Based upon the progress on prior Sanitary District contracts and 
 elsewhere there should be no difficulty in building the twenty miles of 
 West Side intercepters and the fifteen miles of Southwest Side inter- 
 cepters so as to be finished by the end of 1930. This would require less 
 than double the progress secured on the North Side intercepters. 
 
 The expenditures for the Des Plaines, Calumet and North side 
 plant enlargements can all be finished in the next two or three years. 
 So far as disposal plants are concerned, the real question as to time 
 therefore hinges upon the Argo, Stockyards, West and Southwest side 
 plants. 
 
 The Sanitary District in arranging its program of design and con- 
 struction has estimated that the West side plant, including tanks and 
 sludge handling facilities, can be completed by December, 1929. We 
 see no reason why, if plants are started promptly, the construction of the 
 stone sprinkling filters for the secondary treatment cannot be completed 
 within a year thereafter, viz. December, 1930, and possibly simultan- 
 eously with the tanks. 
 
 The Southwest side involves construction similar to that at the 
 West side, but only approximately two-thirds as great in amount. It 
 should, therefore, be practicable to design and build the southwest side 
 plant so that it will be finished without difficulty by the end of 1930. 
 
 The Argo and Corn Products plants are comparatively small, al- 
 though they involve a more thorough study of experimental work and 
 a more complicated design than is required for the West and South- 
 west side plants. It is believed, however, that they can be designed and 
 built so as to be ready for operation by 1930. 
 
 Summarisation of the Construction Period Reasonably Required: 
 
 It would be our opinion that five years' time, under average con- 
 struction conditions, would be a reasonable minimum estimate of the 
 time required to design and build the intercepters and sewage treatment 
 plants at the costs herein outhned. Even with .the most unfavorable 
 
194 
 
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195 
 
 construction conditions, the contingency of labor troubles, and similar 
 delays, we can see no reason why the period should exceed eight to ten 
 years. 
 
 All of the above is predicated upon the ability of the Sanitary Dis- 
 trict to finance the program within the construction period. 
 
 A ckn owledgm ent: 
 
 In the preparation of this report the Sanitary District of Chicago 
 has furnished to us numerous data and studies bearing upon the prob- 
 lems here considered. There has also been placed at our disposal the 
 valuable studies. of the U. S. Public Health Service relating to the 
 Des Plaines and Illinois Rivers, which we have freely used. The 
 Illinois State Water Survey has furnished many valuable data relating 
 to the past conditions in the downstream rivers, and we are particularly 
 indebted to the Illinois State Natural History Survey for information 
 on the same streams, particularly relating to the welfare of fishwife. 
 
 In connection with our work we have been assisted by Mr. Clarence 
 B. Hoover, Superintendent, Division of Water and Sewage Disposal, 
 Columbus, Ohio, a practical sewage plant operator for the past sixteen 
 years. We have also been assisted by Mr. T. McLean Jasper, Research 
 Laboratory, University of Illinois. 
 
 Respectfully submitted, 
 ALVORD, BURDICK & HOWSON, 
 (Signed) Chas. B, Buedick, 
 
 (Signed) L. R. Howson, 
 
 Chicago, Illinois, 
 April 16, 1925. 
 
PUBLICATIONS OF THE STATE WATER SURVEY. 
 
 No. 1-9. Out of print. 
 
 No. 10. Chemical and biological survey of the waters of Illinois 
 Report for 1912. 198 pp., 19 cuts. 
 
 No. 11. Chemical and biological survey of the waters of Illinois. 
 Report for 1913. 473 pp., 106 cuts. 
 
 No. 12. Chemical and biological survey of the waters of Illinois. 
 Report for 1914. 261 pp., 32 cuts. 
 
 No. 13. Chemical and biological survey of the waters of Illinois. 
 Report for 1915. 381 pp., 36 cuts. 
 
 No. 14. Chemical and biological survey of the waters of Illinois. 
 Report for 1916. 192 pp., 40 cuts. 
 
 No. 15. Chemical and biological survey of the waters of Illinois. 
 Report for 1917. 136 pp., 8 cuts. 
 
 No. 16. Chemical and biological survey of the waters of Illinois. 
 Report for 1918 and 1919. 280 pp., 36 cuts. 
 
 No. 17. Index to Bulletins 1-16. 1921. 17 pp. 
 
 No. 18. Activated sludge studies, 1920-1922. 150 pp., 31 cuts. 
 
 No. 19. Solubility and rate of solution of gases. Bibliography. 
 1924. 49 pp. 
 
 No. 20. Comparison of chemical and bacteriological examina- 
 tions made on the Illinois River during a season of 
 low water and a season of high water — 1923-1924, 
 33 pp., 4 cuts. 
 
 • 
 
 A preliminary notice of a survey of the sources of pol- 
 lution of the streams of Illinois. 1924. 26 pp., 4 cuts. 
 
 No. 21. Public ground-water supplies , in Illinois. 1925. 710 pp., 
 11 cuts. (Price $1.00.) 
 
 No. 22. Investigations of chemical reactions involved in water 
 purification, 1920-1925. 133 pp., 17 cuts. (Price 75c.) 
 
 For copies of these l)ulletins or for other information address - 
 Chief, State Water Survey, Urbana, Illinois.