REPORT ON THE a kee COLLECTION AND TREATMENT OF THE G Z 3 ZY SEWAGE % (* L,, AS aS 3 | AAG OF THE Qe & Mi CITY OF NEW HAVEN, CONN. “Cr, DECEMBER 1, 1926 FULLER & McCLINTOCK 170 BROADWAY NEW YORK REPORT ON THE COLLECTION AND TREATMENT OF THE SEWAGE OF THE CITY OF NEW HAVEN, CONN. DECEMBER 1, 1926 FULLER & McCLINTOCK 170 BROADWAY NEW YORK ko ka. DECEMBER I, 1920. Honorable John B. Tower, Mayor, City of New Haven, Conn. DEAR Sir: As authorized on March 5, 1926, we have made a study of sewerage and sewage disposal conditions in the City of New Haven and adjacent territory. We report herewith our findings and recommendations, to which is attached a summary of supporting data. GENERAL CONDITIONS. 1.—The City of New Haven has a population of over 180,000 with a water supply pains about 24 million gallons daily. 2.—The sewerage system comprises approximately 155 miles of sewers, and with the exception of three wards on the eastern shore of the harbor, very few streets are without sewerage facilities. It is on the combined plan, transporting sanitary sewage and storm water in the same pipe lines, excepting in the Westville district, which is provided with some 10 miles of separate sanitary sewers, and 5 miles of storm water conduits. Sanitary sewers serving a population of approximately 4,500 in the town of Hamden, north of the City, empty into the City sewers, under agreement between the two municipalities. 3.—Sewage and industrial wastes are discharged un- treated into the inner harbor and the West, Mill and Quinnipiac Rivers, about 90 per cent. being carried by the five main outfall sewers, and the remainder by numerous private sewers and drains from industries and residences. The location of the main outlets is shown on Plate I. 36579 ) Ze : fo} eal MAIN OUTFALLS AND STORM WATER OVERFLOWS 3 4.—There are eighteen storm overflows on the main sewers which discharge a portion of the excess flow of sewage and rain water into the harbor and rivers during storms. Some of these overflows are at such elevations as to operate during light storms, discharging sewage into the rivers, when there is but little clean water available for dilution. CONDITION OF HARBOR AND TRIBUTARY STREAMS. 5.—Insanitary conditions have long existed to a serious degree in the harbor and Mill River, and to a lesser extent in West and Quinnipiac Rivers, due to discharge of un- treated sewage and industrial wastes. Manifestations of these insanitary conditions include the following:— (a) Bathing Beach Pollution. The waters of the entire harbor are polluted, constituting a menace to public health of greater proportions than generally realized. Should numerous cases of typhoid fever, or other water-borne disease, appear in New Haven, re- gardless of the source of infection, the present method of sewage disposal would make the existing pollution of bathing beaches a very serious matter. This danger has been emphasized by the City Board of Health during the past years. (b) Relation to Shellfish. The State of Connecticut prohibits the direct marketing of oysters from all of the harbor above a line between Oyster River Point and Old Light, because of widespread danger of disease which would result through shipment of the oysters. Owing to the continued presence of sewage bacteria in large numbers in the outer harbor, it has been recently proposed to move this line outward so as to extend from Oyster River Point to Morgans Point. (c) Sludge Deposits. The discharge of thousands of tons of settleable sewage solids each year has formed accumulations of putrescible matter on the bed of the harbor and its branches, ranging in depth from a few 4 inches to over ten feet. The decomposition of these solids during warm weather exhausts the oxygen naturally contained in the harbor water, interferes with fish life, and causes objectionable odors discernible at considerable distances from the water front. (d) Sewage Mud Flats. In the relatively shallow inner harbor and the lower stretches of the rivers, where large areas of foul deposits are exposed at low tide, conditions are particularly disgusting to sight and smell, and constitute an additional menace to public health, in that flies may carry infection to nearby markets and homes. (e) Appearance of Harbor. Oil sleek on the harbor and rivers, increase of floating solids, and discoloration due to dye works wastes, show the absence of a suitable standard in this branch of municipal cleanliness. The above conditions generally are prejudicial to con- tinued development of the City, in that they needlessly hazard property values along the water fronts. CONCLUSIONS AS TO NEEDED TREATMENT AND DISPOSAL OF SEWAGE. 6.—Outfall Into Long Island Sound Too Expensive. The disposal of the sewage through long outfalls into the deep waters of Long Island Sound would involve greater construction costs than for other methods of disposal, and require expensive pumping facilities. Furthermore such disposal could not be considered as complying with the general program for protection and improvement of coastal waters instituted by the State Department of Health, the State Water Commission, and the State Shellfish Com- mission. 7.—Treaiment Necessary. Sewage treatment should eliminate visible evidence of sewage from the waters of the harbor and rivers; should prevent formation of extensive We ae \. 4 dds : é DNS Sa neste ty Sec VS? 6 arr es ee ek eee I ot ee Be ‘a A. ee oy tes hal es ’ ee ena ean APO tN 9 CO LAF ag MD ANSE PNT GRADING ee Caine zy is . ie ; a i = ~ “4 District Br; el Os . Gi a ator Pj eee Present City. Limits -—— Town Limits > 2 fj --——furfure Jewerage District Limits . - © z ij---—-- Storm Water Relief Sewers eZ intercepting Sewers \\ a Boulevard Sedimentation Tanks Meadow Sit a ” BOST OF if if Eastern Shore if u James St Grit Chamber Forbes Ave. Pumping Station District Pumping Stations Jludge Digestion Site (A/ternate Project. ©@@Q@@@QHOWO NEW . HAVEN Scace in Feet SR ER SN ee NT TN NS eT te) 2000 4000 6000 6000 Morgan Pt. ° at ‘ : es King - rp LINg mes of Te tion. .of oysfer— Li Gipeeiblt as ail LOCATION OF possib! ! Oyster River Pt. RELIEF SEWERS & TREATMENT PLANTS =} es _ ; > 3 ~ _ oe sludge banks; and should reduce bacterial content so as not to dangerously pollute bathing beaches or shellfish layings at the mouth of the harbor. The complete purifica- tion of sewage will not be necessary to subserve the general interests of the public health for some years to come. 8.—Screens Inadequate. Sewage treatment by fine screens alone is not adequate for local conditions. The removal of from five to fifteen per cent. of sewage filth would not prevent the formation of sludge deposits on the harbor bottom, as the population increases through a term of years, nor would such degree of clarification be commensurate with the cost. 9.—Sedimentation Needed. Adequate removal of settle- able solids can be effected in suitably designed plain sedi- mentation tanks which will remove from fifty to seventy per cent. of the organic solids and bacteria from the sewage, or ninety per cent. or more of the readily settleable solids. This removal is equivalent to from four to ten times that which would be effected by fine screens. Chambers should be provided for removal of grit carried by the sewage, and for skimming grease floating on the surface. Sludge should be collected in suitable sumps by mechanical scrapers, or other devices, before decomposition begins. 10.—Location of Suitable Treatment Works. There should be four sedimentation plants, three being located adjacent to the present Boulevard, Meadow and East Street outfalls, and the fourth on meadow land near the northern end of Nathan Hale Park on the eastern shore. This latter plant would receive sewage from James and Poplar Street outfalls, and from sewers to be installed in the eastern shore districts, and is the only one where pumping of the sewage would be required. The general locations of the sedimentation plants and intercepting sewers are shown on: Plate IT. 6 11.—-Chlorination. To protect bathing beaches against pollution by the sewage, the tank effluent should be treated with chlorine gas as a germicide. The application of about 45 pounds of chlorine gas to each million gallons of sewage passing through the tanks is ordinarily sufficient. The duration of the chlorination period will depend to a large extent upon the future location, use and condition of bathing beaches, but will probably be from three to four months each year. 12.—Capacity of Sewage Treatment Works. Construc- tion of sewage treatment works should be undertaken promptly under a progressive program whereby the first installations will provide capacity for treatment of sewage flow as expected in about the year 1940 (estimated popula- tion 240,500), with arrangements for convenient extension as required to about the year 1970. In 1940 an average dry weather flow of approximately 33.6 million gallons a day can be expected, and in 1970 a corresponding flow of ap- proximately 55.75 million gallons daily. In addition to sanitary sewage and industrial wastes, the first flush of storm water from the streets should be delivered to the treatment works by suitable regulators. 13.—Sludge Disposal. Consideration has been given to two methods of disposal of the sewage solids removed daily as sludge from the bottom of the sedimentation tanks. One method would be to pump the sludge through cast iron pipe lines to separate sludge digestion tanks which would be located in East Haven in the farming district in the general vicinity of the State Rifle Range. Here the sludge would be mixed and limed in masonry tanks equipped with collectors so that the gases would not escape into the atmosphere, but could be burned or utilized as desired. The thoroughly digested and inodorous sludge would be de- watered on underdrained sand beds. The dry solids could then be used for filling, or as a fertilizer, and the liquid returned to the sedimentation tanks through the connecting 7 pipe lines. Such a method is in successful use in numerous places in England and Germany, and is coming into vogue in this country. As an alternate arrangement we have considered the collecticn of sludge in holding or decantation compart- ments adjacent to the several sedimentation plants, from which it would be discharged into tank steamers resembling “oil tankers’, and disposed of in the open ocean. This is the method practiced by every sizable seacoast city in Great Britain, and by the Passaic Valley Sewerage District in New Jersey. Of these two methods, it is our opinion that disposal at sea is the cheaper and simpler under local conditions, and it is accordingly embodied in our recommended project. SEWER SYSTEM DEFICIENCIES. 14.—Replacement Sewers. Some of the older sewers, constructed for the most part prior to adoption of the Chesbrough plan in 1872, are commencing to disintegrate, or are so worn by continued scour of mineral matters that replacement is necessary. The length of these sewers is approximately 2.5 miles, and replacement costs are estimated at $175,000. Sewer construction and maintenance in gen- eral, has been excellent throughout the City. 15.—Rehef Sewers. Overloading or surcharging of sewers, with backflooding of cellars, occurs in several sec- tions of the City during intense storms. This condition is quite generally encountered in the larger cities having combined sewers constructed many years ago, and is largely due to the greater prevalence of impervious street pavements and sidewalks, paving of yards, closer spacing of buildings, and similar conditions associated with development of the City, and which cause more rapid concentration of storm water in the sewers. It is also partially due to extension of sewers into territory not contemplated in the original design. Backflooding of cellars is experienced at frequent inter- 8 vals in portions of Church Street from George to Elm; in Orange and State Streets from George to Bradley; Temple from Crown to Trumbull; Lincoln from Trumbull to north of Bradley; Chapel from College to Olive; Court from Church to Olive; Elm from College to Orange; Oak from Broad to Congress; Congress from Lafayette to Meadow; Meadow from Congress to Whiting; Orange from Lawrence to Willow; Livingston from Edwards to Canner; Winchester from Sachen to Ivy; Canal from Bristol to Munson, and in Division and Starr from Win- chester to west of Newhall. | Relief sewers for these districts can be installed as shown on Plate IH, and will total 12.3 miles in length, involving expenditures of $675,000. at the present time, and an additional estimated sum of $1,500,000., distributed over the next 15 to 20 years. SEWER EXTENSIONS. 16.—Future Districts. To maintain the rivers reason- ably free from sewage pollution, and to protect the sources of public water supply, it is desirable to extend the City sewer system to the north and east into Woodbridge, North Haven, East Haven, and additional districts of Hamden, to the approximate limits shown on Plate II, under agree- ment with the respective municipalities providing for re- imbursement for additional construction costs and operating charges required for transportation and treatment of the sewage from such portions of these communities as will flow through the City territory. 17. Iype of Sewers. The existing system of combined sewers should be maintained in service, and the separate system of sewerage, which has been installed in the Wood- bridge district and the town of Hamden, should be adopted for the eastern shore wards, and also for the suburban districts which will ultimately form portions of the gen- eral sewerage system. 9 ESTIMATED Cost OF IMMEDIATE CONSTRUCTION PROGRAM. Estimated construction costs for the various works, ex- cluding land acquisition, are given in the following table: PRU RIOeIC ROG W CLSat a line sihaGetirok nee le ase as $175,000. POCO WELS TE te eerie ieee ais 675,000. Saerrrryy ALCL MINeOUlAtO Cag chien te ers ein as", 65,000. © Eastern Shore District: Porerceptine dnGsLrunk OeWeLst.. west. s,0 385,000. Vee” AON sm ee ee arias aut a eae ets 175,000. Sewage Treatment Works: Boulevard Sedimentation Plant capacity 8.5 HAT a aM WELT S.A A a ean rae lS Oe atoll 375,000. Meadow Street Sedimentation Plant capacity Bruni L Aa ioeaC ally eyese he ee te ela crn at viata: 275,000. East Street Sedimentation Plant capacity Bevel OA ae Voc tte es Ae ield ewig we ee epee 475,000. Eastern Shore Sedimentation Plant capacity Eerste oie CLA Vette ce en eee ne testa ss 300,000. TES POAT Mer Ff alirin Poise lepal. ahd ye efoheis. ein ohh 100,000. $3,000,000. Very truly yours, FULLER & McCLINTOCK, By GeorcE W. FULLER. 10 SUPPORTING DATA DESCRIPTIVE OF PRESENT CONDITIONS AT NEW HAVEN AND PROGRAM FOR IMPROVEMENTS. PAGE 1.—Conditions in New Haven Harbor and Tribu- tary (Streaiis 25. aate ss We ee 12-15 2,—-Sewage Treatment. “Propramt (2-03 9.0 o. amet 15-20 Available’ Sites i771 50 os cent see 15 Development of Sedimentation Process.... 15 Plain Sedinientation Tanks /..\,; 7). seen 16 Grif Chambers v5 Wins 8 eee ee ee Ly Disposal of Sludge at Sea ney. sa eee ce 17 separate SludpeDicestion: jaa 19-7) ee ee 18 Improvements in Sludge Digestion ....... 18 sludge:Dewatering 4:72, pean ae eee 19 Miles -AcidProcess) 00). :\k ales. 3a aes 19 Conclitsions) <>.) 4 sae to heen a 20 3.—Treatment Works Recommended ............ 20-24 Capacities i. o5i.4'5 ak ear eearegteg Chars alee eee 20 Filevations oi. 2 eas ae ie hate ane eee 21 Regulators ort ee ey sere ce ae 21 Screens and Grit’ Ghambers 449) ho, 21 Sedimentation Vanke ts .002n ei. a aes 22 sludge Disposal: ate Seager to cee ee eee 22 Separate Sludge Digestion nye ees ae plidgvestorce: Mains (i cs ees 23 Sludge Digestion Tanks corn vee ee 23 pludge Beds). a ee en ee 24 4,— Storm: Water ‘Reliel Sewers 2.02 ie nee ae 24-28 Storm: Water: QOverflows it.) 00) 3. cls eee 26 Location of Relief Sewers) 4.0: 2 cee 26 Immediate Construction) 2... 2.2.57 Prk 26 Meadow, Street, District 77.) (uacnmees 26 East! Street District) uae eee 26 zi] TaemmOmearerooraails we merit. a7 Boulevards Wietkiete ws ok eats 27 Meadow Street»loistrict? 3. aya. 8 27 Paet ULeCOta IS LEICt oni MOG, o Ruts Sule oy 27 Pott mea Vets ast LIIStrictn ast. ie steele cs 28 ereatmetiinG ty OLOrRRe VW ALC ie kcwwin see 2 28 5.—Extent of Adoption of Separate System of PIGWOT CS Merit EIULiILE penarae tai tus any in ye et 28-31 Extent of Future Sewerage District outside Clb ates toner uranic em ianie Aare te ge AI 30 Eastern Shore Pumping Stations ........ 31 Sie TIGLCASCO IP ODUIALION ete cial oc lubaiis eben eda) > 31-34 Commercial and Industrial Areas ois. 5 0 « 32 eee W OCT IOW ETS ls co.cc Ub MM eet catia v at da Waal’ g large « 34-37 Industrial and Commercial Sewage Flow.. 35 HI OMESLICI SEWAGE EMO, Soh occ Corl glee’ sia 36 8.—Composition of Sewage and Industrial Wastes. 37-38 EX GRNOWICCOIIET tS chit. cI G0UNs inl cg ot ote 8 ein) ese fu 39 4 I.—CONDITIONS IN NEw HAVEN HARBOR AND TRIBUTARY STREAMS. Deposits réaching’ a maximum depth of more than 10 feet were found in the inner harbor west and south of Long Wharf’ in ‘the vicinity of the Meadow Street and Boulevard outfalls. In the eastern portion of the harbor, deposits at places reach a depth of from two to three feet: In Mill River’ above Chapel Street depths of over three feet were recorded. The eastern shore is practically free from deposits. Sep! ie The putrefaction of the thousands of tons of sludge deposits which have accumulated on the harbor floor in- creases the total oxygen demand much above that of the fresh incoming sewage, and, by exhaustion of the oxygen from immediately overlying water, cause local nuisances. Over four billion gallons of water enter New Haven harbor from Long Island Sound twice a day on normal flood tides. The discharge of raw sewage and industrial wastes approximates 25 million gallons a day. If this sewage could be thoroughly mixed with such a volume of new unpolluted sea water, and entirely removed from the harbor on each tide, it would be more than sufficient to dilute and assimilate the sewage without nuisance or menace to health. That this does not occur is proven by foul accumulations of sewage solids exposed at low tide throughout the inner harbor. As a matter of fact, the sewage does not pass entirely out of the harbor into Long Island Sound on a single ebb tide, as has been demonstrated by the movement of tidal floats, but to a material extent is pushed back into the upper harbor by the next flood tide, so that sewage solids, carried in suspension, are moved back and forth, and a considerable portion are finally stranded on the harbor floor with slackening of the current. This is particularly the case in the western part of the inner harbor, where the Shag Bank interferes with the free movement of the tides, and in the slips and undredged 13 portions of the rivers where currents are seldom sufficient to produce scouring velocities. Another item for special consideration is that compara- tively little fresh water enters the harbor to reinforce the scouring action of the ebb, and displace sewage laden water left in the harbor at low tide. The total watershed area of the three rivers entering the harbor is only 202 square miles, and of this some 53 miles are above impounding water reservoirs which retain most of the flow for months at a time during drought periods. Taking account of the watershed areas below the reservoirs, and using a yield of 0.4 cubic feet per square mile, which is conservative for dry weather periods, the runoff available for sewage dilu- tion would be equivalent to an average of about one and one-half times the sewage flow. It is, therefore, a factor of little moment. The phenomenon of surging back and forth of the tides is not peculiar to New Haven. In New York harbor, where displacement action is particularly favorable, due to the large flow of the Hudson River and cross currents of sea water entering through the Lower Bay and Long Island Sound, it is estimated that about 80 per cent. of the water entering on each flood has been in the harbor before and consequently carries some burden of sewage. In Philadelphia harbor it has been estimated that a par- ticle of sewage solids moves back and forth a total distance of 540 miles in progressing forward 17 miles in the Dela- ware from Philadelphia to Chester, and if not stranded would consume about 16 days in transit. The extent of organic pollution of the harbor water can be gauged by a deficiency of dissolved oxygen below the condition of practically complete saturation, which obtains in the open waters of the Sound. To determine the concentration of organic matter from sewage and industrial wastes, as reflected by oxygen depletion, fifty- two separate samples for analysis were taken on August 27 and September 10, during varying stages of tide, at thirty stations in the outer and inner harbor. The results are summarized in the following table:— 14 Number Sampling Per cent. Saturation Stations Avg. Max. Main. Bradley Pt. to Lighthouse Pt. 4 88 100 65 Nioriis: Cove <2. cere 2 63 64 62 paldlyat te tocy Ort tialeiencgs 3 59 64 51 Oyster Pt to (Cranes Barae ee 54. 66 34 Parent arbOte oe oes ae 6 46 64 34 (UIA PiaC IN IVels eee ee 4. A4. 57 39 Mill Rivert ccevasie eae eyeee 7 15 35 O As a further direct measure of harbor pollution, ninety- eight samples for bacteriological examination were taken on the flood and on the ebb tide September 8 and 9, from twenty-five different stations. One sample was taken near the bottom and another from just below the surface at each station. Samples were examined to determine the relative presence of B. Coli, which is a group indicative of sewage pollution. The numbers of B. Coli, as summarized in the following table, were obtained by averaging the results of individual tests made with varying dilutions of sterile water. Number O B. Col per too C. C. Location of Stations Samples Flood Tide Ebb Tide Savin Rock to Lighthouse Point 52 495 320 Sandy Point to Fort Hale...... 22 820 700 Oyster Pointto; Crates Barta. ae 24 925 1000 Samples taken during flood tide in the outer harbor show a greater B. Coli density than those taken on the ebb, illustrating the accumulative effect of pushing back into the harbor the sewage laden water brought down during the latter portion of the previous ebb. The greater density in samples from the inner harbor, taken during the ebb tide, are indicative of the effect of holding back sewage in the land-locked upper harbor during the quiescent period of high tide. It is worthy of comment that the U. S. Public Health Service standard for drinking water used on carriers in ee) interstate traffic is a content of 1 B. Coli per roo c. ¢.,, and that the standards proposed by the Association of State Sanitary Engineers for quality of water in swim- ming pools would limit the presence of B. Coli to less than 4 per 100 c. ¢. 2.—SEWAGE TREATMENT PROGRAM. Available Sites. With the exception of the park prop- erty on the eastern shore, there are no large undeveloped tracts of land bordering on the harbor. Available sites elsewhere are restricted to the shoals near sewer outfalls outside the high water line. If all sewage were to be con- centrated at one point for treatment, expensive underwater collecting conduits would be required, and all the sewage would need to be pumped, as head consumed in the collect- ing lines would make sewage level in the treatment plant too low to permit gravity operation. These conditions are met by providing four treatment plants of which three, namely the Boulevard, Meadow and East Street plants, will be located adjacent to the existing outfall sewers and operate entirely by gravity, and the fourth or eastern shore plant will be constructed in or near the upper end of Nathan Hale Park, receiving sewage from the James Street, the Poplar Street, and the eastern shore districts, and will be the only one where sewage pumping will be required. Foundation conditions are such that plants must be of a compact type and supported on piles, which means that excavations must not be needlessly deep. Location near high value commercial and industrial dis- tricts and in the vicinity of residential and park areas re- quires that there be reasonable assurance of freedom from offensive odors in the immediate vicinity of the plants. Development of Sedimentation Process. A brief recital of the development of the sedimentation process will ex- plain the applicability of the particular type of treatment tank which is recommended. 16 About a generation ago treatment of sewage with chemicals to precipitate the solids was practiced at several places in Europe and in this country, but the expense of chemicals and cost of handling excessive quantities of sludge, which were produced, caused general abandon- ment of the process. Septic tanks which provided for re- moval of the solids by sedimentation in single story tanks came into vogue about 1895, and were adopted generally in Europe and this country for about 15 years. While these tanks brought about a reduction of from 45 to 60 per cent. of the organic solids, the results were not entirely satisfactory, particularly because of odors and sudden lapses in efficiency when masses of solids digesting in the lower part of the tanks were lifted into the flowing sewage by gases of putrefaction and carried out with the effluent. These difficulties are partially overcome by two-story tanks, frequently called Imhoff or Emscher tanks, in which are diaphragms having a slot through which the sludge passes into a lower compartment as it settles from the sew- age. These tanks, since their rise to popularity in about 1910, have been of much value, but along the populated water fronts of the large cities they are often at a disad- vantage, because of expense of construction, due to the depth of the tanks and the lack of adequate areas for drying sludge. Plain Sedimentation Tanks. During the past ten years both in Europe and in this country, plain sedimentation tanks have come to the front. In these tanks the sludge de- posited from the slowly moving sewage is promptly re- moved before onset of putrefaction with dispersion of offensive gases throughout the neighborhood, and occasional breaks in efficiency of sedimentation. Sludge removal is accomplished by mechanical concentrating devices of which there are several successful types available. A further advantage of these tanks is adaptability to arrangements for use of air, either as in the activated sludge process, or as in contact aerators, if in later years 17 it should be desired to carry purification one step further and treat non-settling organic impurities. Grit Chambers. The grit contained in storm water flows should be removed from the sewage before it enters the sedimentation tanks. Otherwise, this relatively clean sand and silt becomes a part of the sludge and adds to the difficulty and expense of sludge handling. Oil and grease should also be skimmed from the surface of the sewage either in the grit chambers, or the sedimentation tanks, or both. Disposal of Sludge at Sea. At many of the large European coast cities, such as London, Manchester, Dublin, Glasgow, and Southampton, sludge from the sedimentation tanks is taken to sea in self-propelled tank boats and dumped. In this country a similar procedure is in force at the Passaic Valley Joint Trunk Sewer disposal works, whereby under contract sludge is carried in self-propelled tankers and dis- charged at a point some seven miles southeast of Scotland Light, a distance of ten to twelve miles from the New Jersey bathing beaches. The method has been used in London for more than twenty years, a fleet of six steamers carrying the sludge to Barrow Deep, off the mouth of the Thames River, a dis- tance of about fifty miles from the sedimentation works at Barking and Crossness. The boats steam slowly when ar- riving at the disposal area, and cover a distance of approxi- mately ten miles while the sludge is being discharged from the tanks. Careful investigations have indicated absence of undue pollution of the sea water, and the results secured have been described by Sir Alexander Houston as “satis- factory.” We estimate that at New Haven the quantity of sludge, after removal of a large proportion of the supernatant liquor by sedimentation and decantation, would amount to about 71% cubic yards to the million gallons of sewage, or from 200 to 250 cubic yards a day during the first few 18 years. If a second-hand, self-propelled oil tanker, having a capacity of from 750 to 1000 cubic yards, were purchased, only about two trips a week would be required for several years. To avoid possible pollution of shellfish areas and bath- ing beaches, it would be advisable to dispose of sludge in the open sea east of Long Island, at a distance of from 60 to 65 miles from the sedimentation plants in the upper end of the harbor, Separate Sludge Digestion. For purposes of record, a statement is given regarding the alternate process of separate sludge digestion, although it is not the project recommended in this report. If this process were to be adopted, the sludge removed at the plain sedimentation tanks would be pumped to a battery of tanks east of the City, where by suitable mixing and other control operations, the process of digestion would be completed without com- plications due to odors. The principles governing the successful use of these tanks have been developed in England during the past 14 years, and at over-a score of comparatively recent installations in Germany and in this country. Of particular advantage is the fact that sludge removed from tanks in built-up districts can be pumped to separate digestion tanks, located in suitably isolated areas, where sludge drying beds may be provided. With adequate design of digestion tanks and proper operation, the sludge can be so prepared that the drying can be effected without offensive odors. Improvements in Sludge Digestion. The collection of all gases of putrefaction for burning on the grounds, use for power about the plant, or for sale, is now on a practical footing. In fact at Birmingham, England, it has been used for four years for operating a combustion engine, and in Germany it is sold to the local gas works in a dozen or more instances. The main point for emphasis is that by £9 collection and burning, the gas is not disseminated through the air to cause complaint; the utilitarian phase is of secondary importance. By placing gas collectors below the surface of the liquid, scum is kept away from the air and digests as thoroughly as solids settling to the bottom of the tanks, thus removing another troublesome factor of earlier tanks. Control of the ripening stage of sludge, made possible through recent research, has removed complications due to acid formation which in the past were the cause of occa- sional irregularities, and oftentimes necessitated discharge of odorous sludge. Sludge Dewatering. Power presses of various types, filters and heat dryers have been brought to a moderately satisfactory standard for dewatering activated and chemical precipitation sludges. With the possible exception of a complicated and cumbersome centrifugal dryer which was installed at a few locations, the accepted method for de- watering sludge from sedimentation tanks is through the use of underdrained sand or cinder beds. There are scores of such installations in service, for the most part uncovered, but in a few recent installations provided with glass roofs of the greenhouse type. Sludge is reduced to a condition readily removable from the beds with a spade, and can be used as fill about the plant. It has a slight fertilizer value. The sludge bed area required ranges from 0.6 to 1.0 square feet per capita for northern latitudes for open beds, and perhaps % to % as much for covered. The effluent from the beds is putrescible, but can be readily purified in small filters, or returned to the tanks for further treatment. Miles Acid Process. The investigations at New Haven during 1917-18 which led to recommendation for adoption of a modified chemical treatment process, known as the “Miles Acid Process,” for the East Street sewage, with possibility of additional installations at the other outfalls, 20 were made at a time when conditions were abnormal due to activity of ammunition plants discharging great volumes of industrial wastes into the sewers. This process then seemed of particular merit, because through it alone was it deemed possible to satisfactorily treat sewage having a high acid content and carrying a considerable proportion of wastes which would interfere with biological action in the ordinary treatment process. At that time also market conditions were favorable for disposal of grease and fertilizing materials which would be produced in varying amounts as by-products. With the termination of the war, the quantity of indus- trial wastes having an inhibiting effect on biological pro- cesses was considerably reduced, and methods for treatment of such wastes, before discharge into the sewer system have since been developed to such an extent in this country and abroad that their presence is no longer a controlling factor. Furthermore, in recent years the markets for by- products which would be produced by this process have not been such as to indicate any financial savings through its adoption. The process has not made progress to the extent of adoption for large size installations. Conclusions. From the standpoint of elimination of sludge deposits from the harbor bottom and required reduc- tion of bacteria, sedimentation is the only process which will assure satisfactory results and benefits commensurate with the cost. 3.—TREATMENT WorxKs RECOMMENDED. The principal features of the treatment process recom- mended, namely plain sedimentation, and chlorination during the bathing season with disposal at sea, together with the alternate method of digestion and drying the sludge at a location outside the City limits, are briefly discussed in the following paragraphs:— Capacities. In general the first construction of treatment plant units should be adequate for the sewage flow to be 2I expected during a period of 10 to 15 years, or roughly until about the year 1940, assuming early inception of the construction program. In addition to dry weather flow, it is proposed to divert to the sedimentation units the first flush of storm water from the streets in suitable volumes. Needed capacities of the various treatment works ex- pressed in million gallons daily, under 1940 conditions, are estimated as follows:— Eastern Rates of Flow Boulevard Meadow East Shore _ Average Daily .. 85 5.2 ‘i 8.6 Business Hours .. 12.0 8.3 17.0 11.8 Elevations. Gravity flow can be obtained for all plants, excepting that for the East Shore. Surface level in the sedimentation tanks would be approximately that of sewage flowing in the sewers during low tide, the tank walls, how- ever, extending to elevations above maximum recorded tide. During high tide, level in the tanks would rise, but as the design would be such as to produce a continuous outward flow, there would be no material interference with effective sedimentation. Outlet conduits would be equipped with suitable tide gates to prevent entry of harbor water during high tide. Regulators. Suitable regulators should be located in the various outfall sewers to prevent backflooding of the sedi- mentation tanks during high tides, and to divert the dry weather sewage flow and the first flush of storm water. Screens and Grit Chambers. Coarse screens of the bar type would be provided for removal of large suspended solids and floating materials generally of inorganic origin. Screenings would be of small volume and should be in- cinerated or buried. Following the screens, sewage would pass through grit chambers where the flow would be reduced to a velocity of approximately one foot a second, and mineral matters 23 scoured from the streets would be deposited, thus preventing complications in the sedimentation and digestion tanks due to their presence. The deposited materials are mostly relatively clean sand. Suitable equipment should be pro- vided for mechanical cleaning of the grit chambers. Here also would be located appropriate skimming devices for removing oil from the surface of the sewage. Sedimentation Tanks. The sedimentation tanks would be designed to provide a sedimentation period of from one hour and three-quarters to two hours for the average flow of sewage, when population has reached the ultimate density. During business hours, when sewage flow would be at a maximum, the detention period would be reduced to about one hour and a quarter, depending upon the stage of the tide, and at times of storm when the first flush of gutter water reached the plants, it would be further reduced to approximately one hour. The average velocities of flows through the tanks under the above conditions would range from about % to % inches a second, or an average of about 75 feet per hour. The tanks would be equipped with mechanically operated scrapers and pumps for removal of sedimented solids, as well as with suitable apparatus for chlorination of the effluent. Preferably they should be so designed as to per- mit addition of apparatus for use of air at a later date. should further purification of the sewage be deemed advisable. Sludge Disposal at Sea. As previously stated, we pro- pose to use a second-hand oil tanker of from 750 to 1000 cubic yards capacity, propelled by steam or Deisel engine, depending on what type of boat can be most advan- tageously purchased. A new boat is not required for this service where it will not meet particularly difficult con- ditions of wind and weather. The capacity of the boat and the sludge decantation tanks would be sufficient for a five day collection period, so that it would not be neces- TD gm 23 sary to make trips on very foggy days, or under extreme weather conditions. Short dredged channels would be required to the sedimentation tanks, and piers suitable for use of the sludge boat. At times when the boat would be laid up for repairs or overhauling, which periods should be short and infrequent, bottom dumping scows and tug boats could be used. These are readily procurable at all points along the coast. Separate Sludge Digestion. The following paragraphs are descriptive of sludge force-mains, sludge digestion tanks, and sludge beds, which would be required under the alternate process of separate sludge digestion. The descriptions are here given principally for record purposes. The necessary construction cost of the units suitable for 1940 conditions is estimated at $755,000. Sludge Force-Mains. Pumps would be installed at each sedimentation plant for delivering sludge through branch lines to a main pipe line laid in duplicate, some 8 inches in diameter, extending to the sludge digestion tanks. Sludge would be withdrawn from the different tanks for periods of two or three hours each day on a pre-deter- mined schedule, so that friction complications, due to simultaneous operation of the pumps at different plants would be avoided. One of the force mains would ordi- narily be used for returning to the sedimentation tanks the effluent from the sludge beds and excess water from the digestion tanks, but would be available as a sludge force main in event of serious leaks developing, or other emergency conditions. Sludge lines would be provided with hatchways at intervals of one-half mile or less to facilitate cleaning or repair operations. Sludge Digestion Tanks. These tanks would be ar- ranged in batteries, and equipped with covered channnels or partitions somewhat on the principle of small Imhoff tanks to assist in separation of excess water from the sludge 24 as added to the various units. Piping arrangements should be such as to facilitate transfer of sludge from one tank to another, for mixing partially digested with fresh in- coming sludge, and for liming, as desired for control of ripening operations. Excess water would be returned through the force mains to the sedimentation tanks. Suitable devices should be provided for preventing rise of scum to the surface of the liquid, and for collection of the gas for burning, or use for power or lighting purposes at the plant. The tanks would be entirely surrounded and covered with earth embankment to conserve the heat of incoming sludge, so far as possible, to facilitate digestion during winter temperature. The first installation should provide a total sludge capacity of approximately one-half million cubic feet, or two cubic feet per capita for the estimated 1940 contributary population. Sludge Beds. Sludge beds would be divided into several units, and have a total area of approximately 4.5 acres, or eight-tenths square foot per capita of contributing population. Beds would be of underdrained sand or cinders, would be uncovered, and provided with simple mechanical equipment for removal of dried sludge. The effluent from the beds would be returned to the plain sedi- mentation tanks, together with the excess water removed in the sludge digestion tanks. Dried sludge would be dis- posed of in fills around the plant, or might possibly be taken by farmers, in the vicinity, for fertilizer. 4.—STORM WATER RELIEF SEWERS. In general the main sewers and principal branches following the Chesbrough plan, inaugurated in 1872, were designed to care for a rainfall of one inch an hour, with some allowance for variation in the slope of the ground and the completeness of development which would affect the rate of flow of storm water to street inlets, and also the proportion which would be absorbed by the ground. 25 In providing for relief sewers to take care of storm flows in locations where existing sewers were found in- adequate, the so-called “rational’’ method of analysis was used to determine the total volume of storm water which might be expected in any particular location, and from this figure was deducted the capacity of existing sewers, the remainder being the measure of relief required. Records of the local office of the U. S. Weather Bureau for the past twenty-five years were tabulated to show the intensity and duration of storms which might be expected at average frequencies of 1, 5 and 10 years, and appear in the following table:— Precipitation in Inches an Hour Duration Once in Once in in Minutes Annual 5 Years 10 Years 118 Galatry td A ak ei 270) 3.95 4.30 GAUDI, 20 Ue ance 1.75 2.68 2.98 SY Oh: Kapaa ts ie Sl a ae 1.40 2A 260 ER Mere tial onc 1A) Gey 1.80 2.08 ice) stared ants ae 0.95 1.60 1.80 8 BA el Mace a ARE a O Kr 6 Ten 1.35 1220} yO I Nene a fe eR 0.55 0.95 I.05 Our staff found that typical blocks show relative pro- portion of impervious areas, ranging from 30 per cent. to 45 per cent. for residential, and from 50 per cent. to 90 per cent. for closely built up commercial and industrial districts. Runoffs for the particular districts were selected from these ranges to conform to development which might be reasonably expected to occur within the next 40 to 50 years. In general, relief sewers are provided to care for the runoff of storms having an average frequency of once in 5 years. In the Meadow Street district, where property values are relatively high, and where automatic valves have been installed with fair success in most of the deeper cellars, relief sewers are provided on the basis of the storm which might be expected once in 10 years, and permitting 26 both existing and relief sewers to operate under a pressure equivalent to a 50 per cent. surcharge during such a storm when the district shall have attained the density of develop- ment expected in 1970. Storm Water Overflows. In several instances the sills of storm water overflows are at such slight elevations above the invert of the main sewer that the overflow operates, discharging mingled sewage and storm water into the rivers during storms of slight intensity when there is but little dilution. The sills of some overflows are below the elevations of high tides, so that inflow of salt water from the rivers would interfere mechanically with the normal operating program of the sedimentation basins. The sills should be adjusted to prevent operation of the overflows until the main sewer is carrying a volume equivalent to the estimated 1970 sewage flow, and storm water equal to the runoff from a storm having an intensity of about 0.04 inch an hour. Under such conditions the dilution would be sufficient to avoid undue sludge deposits in the vicinity of the overflows. Suitable automatic gates should be placed at overflows having sills below elevation of high tides. Location of Relief Sewers. Routes for necessary relief sewers classified by the various sewerage districts, and for immediate and future construction would be as follows: IMMEDIATE CONSTRUCTION. Meadow Street: District: A main outlet in State Street extending from the harbor to Crown Street, and in Crown to Orange Street, with branch in Crown to Temple Street, and in Orange to Elm Street, thence extending in Elm Street to York Street. East Street District: A main outlet in State Street extending from Mill River to Edwards Street, and in Edwards Street to Orange 27 Street, thence in Orange to Pearl Street, and in Pearl to Lincoln Street, and in Lincoln Street to junction with the present 60 inch sewer at Trumbull Street. Branches would extend in Foster and Orange Streets from Lawrence to Edwards Street, in Edwards from Whitney to Orange, and in Whitney from Edwards to Lawrence. IO TO 20 YEAR PROGRAM. Boulevard District: Derby Avenue from George St. to Mead Street. Dixwell Ave. from Dorman St. to W. Division St., and W. Division St. from Dixwell Ave. to Shelton Avenue. From Boulevard and Elm St., through Boulevard, Sherman, Elm, Norton and Edgewood Sts. to West River. From Shelton and Argyle Streets, through Shelton, Munson and Crescent Streets, to Beaver Pond outlet. Meadow Street District: From Elm and University Place through Elm, Dwight, Edgewood, Howe, and Crown to Crown and Temple, with branches in Chapel, Park and York Streets. From Oak and Davenport through Oak, Congress, Commerce, Whiting and Meadow Streets to the harbor, with branches up Water to Silver, up Union to Port- sea, and up Columbus to Lafayette, and a sewer in Silver St. from Liberty to Hill Street. East Street District: In Water St. from Olive to Chestnut St., and from Franklin to Chestnut St., and in Chestnut St. from Water St. to the harbor. In Division St. from Winchester to Shelton Ave., and in Shelton from Ivy to Argyle. 28 In Orange St. from Canner to Mill River. In East Rock Road from Everit to Mill River. Fair Haven District: In Blatchley from Grand to the harbor, with branches up Exchange to Poplar, up Grand to Fillmore, up Saltonstall to Poplar, and up Fillmore from Grand to Pine. In State St. from Grace to James Street. In Exchange St. from James St. to Mill River. In James St. from Clay to Grand Street. Treatment of Storm Water. Even though the first flush of storm water is diverted to sewage treatment works, the flow passing through the overflows into the streams carries some organic solids, and if the receiving body of water 1s small there is possibility of some objectionable deposits occurring in the vicinity of the overflows through a term of years. Under local conditions two such instances may develop, the first at the new relief overflow recommended at State and Edward Streets in the East Street District, where the flow in Mill River is slight, due to storage of water in Lake Whitney; and the second at the Crescent Street overflow into West River in Beaver Pond Park. At these locations it will be advisable in coming years to install large grit chambers or detritus tanks to reduce the velocity of flow during storms sufficient to cause sedi- mentation of solids which would be liable to form objection- able deposits. 5.—EXTENT OF ADOPTION OF SEPARATE SYSTEM OF SEWER- AGE IN FUTURE. In general, districts which are now sewered on the com- bined system must so continue in the future for economic reasons. To install storm water conduits throughout such districts to collect water now reaching street inlets, and a 29 sufficient portion of roof water, to adequately relieve exist- ing sewers from overloading, would require so many miles of sewers and such expense for changing connections from individual houses, that the total would be greater than the sum required for reasonable relief of the combined system. The present policy of constructing separate sanitary sewers in Westville and Hamden should be continued, and should be adopted for the Fair Haven East wards, as well as the portions of East Haven, North Haven and Wood- bridge, which will ultimately be included in the sewerage district. ) By adoption of the separate system in these outlying dis- tricts, present expenditures will be held at a minimum because of the relatively small size of sewage sewers as compared with combined sewers. In construction of sanitary sewers particular care 1s necessary to secure tight joints so as to keep infiltration of ground water at a minimum, otherwise an unjustifiable burden will be placed on the treatment plants. Storm-water drains of moderate length and size, dis- charging into nearby watercourses, could be provided at reasonable cost, as required to meet the demands of par- ticular sections, but general construction of storm water conduits could be postponed for many years.’ The sums represented by the savings in interest charges on sanitary sewers and such storm sewers as it would be necessary to construct at present, as contrasted with general installation of combined sewers throughout these outlying districts, would be considerable. Small sanitary sewers should be installed along Mill River Street north and south from Grand Avenue, to collect sewage now entering Mill River through private sewers. A small automatic pumping station would raise this sewage to the elevation of the East Street sewer, and a similar pumping station would intercept sewage reaching the Grand Street overflow on the east side of the river. Industries along Mill River and the harbor now discharg- ing directly through private sewers should be required to 30 connect to the public sewers, installing small pumping sta- tions on their own property, if necessary, to raise sewage to level of the public sewers. In many instances industries, by rearrangement of sewers, can continue to discharge cool- ing water directly into the harbor or rivers through private sewers, together with a large portion of the industrial waste flow, which is practically free from polluting matters, leav- ing only a relatively small volume of rather concentrated wastes to be discharged into the municipal sewers. Extent of Future Sewerage District Outside City. In determining territory outside the present City limits, which should be included in a general sewerage project, considera- tion has been given not alone to natural drainage and to the economic features which would influence future develop- ment, such as railroad and trolley lines, through highways and present use of the land, but also as to whether sewage from these outlying districts could better be treated in separate plants. The boundaries of this territory, as determined by these studies, are shown on Plate II. The portion of East Haven situated west of a line repre- sented by Morris, Kenneth, Prospect and Hemingway Streets, and south of the railroad and territory north of the railroad west of Laurel and Bradley Streets would be tributary to the Fair Haven East sewers. The districts of Hamden and North Haven bounded by the railroad and the Quinnipiac on the east, and West Rock Ridge on the west, and extending northward to a line roughly represented by Circular Avenue and Benham Street in the northwestern portion; Dickerman and Ives Streets in the north central section, and Broadway and Ridge Road in the northeastern portion, would become tributary to the James Street, East Street and Boulevard sewer systems. The district of Woodbridge northwest of the City on the watershed of West River, and extending as far north as Lake Dawson, would become tributary to the Boulevard 31 system through connections to sewers on Whalley Avenue, Chapel and Derby Streets. Sewage from West Haven is now treated at plants located along the water front. There is no present need to abandon these plants and deliver sewage to the New Haven treatment works. Eastern Shore Pumping Stations. Owing to the topog- raphy in the districts east of the harbor and the Quinnipiac, it will be necessary to pump sewage from three small districts. The pumping stations as indicated on Plate II, will be located as follows:— Along Morris Creek at intersection of Thompson Avenue, to handle sewage from the Lighthouse Point section. Near Pope Street and Woodward Avenue, to handle sewage from low-lying streets in that vicinity. Near intersection of Essex Street and Quinnipiac Avenue, to receive sewage from low-lying streets in the upper portion of the district and deliver the same into the receiving well of the Forbes Avenue pumping station for delivery to the treatment plant, together with the flow from the James and Poplar Street outfalls. 6.—INCREASE OF POPULATION. In estimating future population, consideration has been given to the rate of increase of the various wards of the City in the past, and to the probable changes in character of development in the various districts which will in- fluence the density of population in City and suburban districts which must be considered as integral parts of the municipal sewerage problem. Comparisons have also been made with the rate of in- crease of New Haven County, the State, the larger cities of New England, and with a group of similar cities through- out the country after attaining the present population of New Haven. Estimates of population increase prepared by the Southern New England Telephone Company and other public utilities have likewise been studied. 32 _ Based on these various studies, the following estimate of the population of the City and portions of the suburbs resident in the sewerage districts has been prepared:— Location 1930 1940 1950 1960 I970 New Haven.. 192,500 222,000 249,500 277,000 304,000 Hamden.... 8,500 ~18,000) 25,500 34,000 ° 43,006 North Haven. ee 500°. 1,000. 1,500. 227068 Rast shlaven so. ark ~ asa 20,5002. 7,500. oer Woodbridge . pe Te ey 500°) 715000 1j00e SOTA lien eae 201,000 240,500 283,000 321,000 358,000 Population of the City arranged according to the main sewerage districts, as recorded by the 1920 census, and as acaan for 1970, with corresponding teas: per acre, appears in the following.table:— nh 1920 I970 Persons Persons per Acre e Population per Acre Population Gross Net* boulevard wees 56,037... 11.8. 5 328,700. (20; See NMeadow!.«0- etn 2O 110. ef0e3 33,700) 50.0; eee Pasty. 7) cae A AO Mee OeL. 86,500 48.3. 51.0 Jamnes?.”, {eee AAO elo 17,700) 20.4 gee Poplarss it Wee 570 mae eae, 15,200, 32.870 ieee Fair Haven Face 7,000 ort 22,200 6.7 7.4 Entire City %'.162;537 “¥ 14-2) 204,000" (260 Gren 30.8 * Net area = land area minus area of parks and City squares. Commercial and Industrial Areas. In making studies of the probable location and extent of commercial and in: dustrial area, the availability of rail and water transporta- tion facilities, proximity of residences of industrial workers, and of a source of water supply for industrial purposes, as well as arrangement of through highways and street car lines, were given consideration. The probable extent of these areas, as determined by such studies and consultation with representatives of the City Planning Commission, ‘is shown on Plate III. PRESENT & ASSUMED FUTURE COMMERCIAL & INDUSTRIAL DISTRICTS LEGEND E3926 Commercial Areas ERB Additions by/970 to 1/926 Commercial Areas F289 /926 Industrial Areas ESAdditions by 1970 ta 1926 Industrial Areas 34 The totals for the various sewer districts of the City appear in the following table:— Commercial Industrial Areas in Acres District Present 1970 Present 1970 HOU var e eC een 76 291 83 166 ECAC OS: a wine rene ei nomen tale 289 409 14 14 Bast sown. cee eee ae T22 247 265 438 TAMmeS cri tasty ie oe Sey ¥f SI ae inZ ODL AT A iis need tae cee tre 33 85 39 Za Pairilayen; act a0. nas ee, 3 102 120 621 Ota ease hin mae rae eters \arrals 592 1467 7.—SEWAGE FLow. In addition to the flow from public sewers, it is estimated that 250,000 gallons of sewage a day enter the Quinnipiac River; that 1,650,000 gallons enter Mill River, and 940,000 gallons enter the harbor through private sewers from resi- dences and industries. This additional contribution of 2,840,000 gallons is derived in part from private wells, and in part from the public water supply. Weirs were installed in the main sewer outlets, and sewage flow measured for a period of about eight weeks from May 23 to July 17. Automatic recording gauges were used at the Boulevard, Meadow and East Street outlets, and hand gauges at the remaining three. Readings during rains or when high tides interfered with free discharge at the outlets were disregarded. The rates of flow for the various sewers, expressed in million gallons per 24 hours, and exclusive of the 2.84 m. g. d. noted above, appear in the following table:— Average Average Average Week-Day Night Flow Daily 9.30 A.M. 2A.M.to Sewer Flow to 5.30 P.M. 5A. M. BOwlevardy ae. 5.59 7.79 2.89 WLEACOW “eh tuarea ec 7 a7 3.45 1.48 SEALE IS We Arrant ch 1.90 0.60 PCS tet. ie teen oa 9.31 14.02 4.05 POUeSa, eee eto) 1.34 0.36 Poplarg eae wecacO Be 0.72 0.15 A Oba ia ea 29.22 9.53 35 Some 48 per cent. of the entire sewage flow occurs during the eight maximum hours of the day, and during these hours the rate is 44 per cent. greater than the average for the entire day. The total average sewage flow was estimated as 24.8 million gallons daily in 1916, and as 29.5 million gallons daily in 1917, which figures are respectively 22 per cent. and 45 per cent. higher than found in 1926. Present water consumption figures likewise show a falling off, the total for the entire New Haven district in 1925 being approximately the same as in the year 1915, and considerably less than for any subsequent year. ‘The reduction in sewage flow is partly due to shutting down of war-time operations in the industries, and partly to the more extensive use of water meters throughout the City. Industrial and Commercial Sewage Flow. Water con- sumption records of the larger industrial concerns through- out the city were investigated, and the quantity of water pumped from various private supplies was added to the water purchased from the public supply. Deductions were then made to represent the quantity which would not enter the sewer system, and a factor applied to give the rate of discharge during normal operating hours of the plant. This figure was applied to the total area of the plant and indicates a rate of 17,000 gallons per acre daily, as the average contribution from industrial areas. For future areas which will not attain full development for many years, an allowance of 12,000 gallons an acre is considered as sufficient. In the case of certain industries where unusual quantities of water are used, specific rates should be applied rather than the average. A similar procedure for the larger commercial establish- ments in the central business district indicates an average of 15,000 gallons an acre discharged into the sewers at a rate of 30,000 gallons an acre when the district shall attain its full development. For small stores in outlying districts, a rate of 5,000 gallons an acre a day should be made in addition to the domestic sewage for the district. 30 Domestic Sewage Flow. Analysis of water meter records indicates a consumption for domestic and commercial pur- poses equivalent to 58 gallons per capita daily for the entire population supplied with water. A census of several hun- dred homes in different portions of the City covering the highest, middle, and poorer types, gave an average water consumption of 70 gallons per capita daily for the highest class of homes, and for the middle and poorer classes taken together, an average of 42 gallons per capita. Measurements of sewage flow from purely residential districts containing the highest class of homes, indicated a flow of 67 gallons per capita daily, after making suitable reductions for ground water entering the sewers. Considering the relative proportion of the various classes of homes, 44 gallons per capita daily was selected as a reasonable figure to represent the average daily discharge from the entire district. As most cities show a tendency to increasing use of water for domestic purposes, because of better sanitary standards and general adoption of modern plumbing, domestic sewage flow is considered as increasing to an average of 50 gallons per capita daily by 1940, or some I5 per cent. greater than at the present time. In order to allow for daily and monthly variation, a sewage flow of 65 gallons per capita, or approximately 130 per cent. of the 1940 average was selected to represent 1970 conditions. Rainfall during the period of sewer gaugings was below the average for the year, and accordingly the minimum recorded flows cannot be considered as representing ground water infiltration during wet seasons. These flows in gallons per 24 hours per acre of drainage area, as recorded for the various districts, appear in the following table:— District Rate per Acre Boulevard uaa ce eee ee SAG He 442 Meadow and ‘State: cn te) aoe ree 307 JAMNOS ig Aiton bocce ats oo iets cee ee ete 193 37 An allowance of 500 gallons an acre for the entire district is believed to be sufficient for ground water in- filtration under average conditions. 8.—COMPOSITION OF SEWAGE AND INDUSTRIAL WASTES. In view of the extensive analytical work during the in- vestigation in 1918, it was only necessary at this time to make analyses to check the general characteristics of the sewage flow to make certain that no unexpected changes had occurred. As noted in the previous investigation, New Haven sewage is somewhat weaker than found in many of the larger cities having combined systems of sewers. This is due in part to the preponderance of metal working indus- tries in which the volume of industrial waste, although comparatively large, contains but little organic matter, and in part to the fact that certain industries having wastes relatively high in organic content have private sewers lead- ing directly to the rivers or the harbor. There is also considerable depositing of solids in the sewers, as evidenced by records of the Superintendent of Sewers. A material percentage of these solids is undoubt- edly flushed through the sewers during the first periods of heavy precipitation, and would reach the treatment works. Allowance for these conditions must be made in consider- ing the results of analysis of samples taken during short periods or at irregular intervals. The total solids ranged from an average of 1027 parts per million in the East Street sewer to 2710 p. p. m. in the Poplar Street sewer. Suspended solids ranged from 100 p. p. m. in the East Street sewer to 183 p. p. m. in the James Street sewer. The analytical work was carried on during the latter part of August when the rate of ground water flow was above the average for the entire summer, due to the unusual prevalence of rains during the month. It also was just fol- lowing a period when the sewers had received a thorough flushing by intense storms.” As is the case in other large municipalities, the sewage contains a considerable proportion of fats and mineral 38 oils, the content of ether soluble matter ranging from 24 to 54 p. p. m. As a measure of the putrescible character of the sewage, biochemical oxygen demand tests were made during the daylight hours and gave an oxygen demand equivalent to .22 pounds per capita daily. These figures correspond closely with results obtained in other cities for the average discharge from combined sewers. Owing to the use of harbor water for cooling purposes at one of the industries, chloride content of the East Street sewage was greatly above that for the other sewers, ranging as high as 3540 p. p.m. When this cooling water does not reach the East Street sewer, chlorides drop to about 68 parts per million. Should the mineral solids, due to this waste, prove at all troublesome in sewage treatment, their elimination could be easily effected by return of the cooling water to the harbor instead of its discharge into the sewer. As in previous investigations, copper was found in the East Street sewage due to wastes from a few industrial establishments, where brass and copper are cleaned by acid. The germicidal effect of this acid waste was plainly notice- able in the bacteriological analyses, the total number of bacteria living at temperatures of the human body being only 2,000 per c. c. in a sample taken from the sewer below one of the industrial plants, in contrast to a content of 400,000 per c. c. in a sample from the same sewer above the industry. Laboratory experiments on samples of wastes from these different industries indicated that they can be treated at a reasonable cost before discharge into the sewer system, and the copper content reduced to a degree such that it will not be detrimental to the ordinary methods of sewage treatment. As a matter of fact such treatment is being successfully carried on at industries in England and in Germany, and at other points in this country. Analyses were made of the wastes from numerous other industries in the City, but in no case would the results in- dicate a discharge into the sewers, or directly into the stream, of wastes which would interfere with, or materially burden, sewage treatment processes. oo ACKNOWLEDGMENTS. During the progress of our investigations we have been aided by previous studies of the New Haven sewerage problem, and particularly by the investigation of a Citizens’ Committee in 1917-18, under the Chairmanship of Pro- fessor C. E.-A. Winslow, and the report on possibilities of treatment of the sewage prepared by City Engineer Nettle- ton in September, 1925. We wish to express appreciation of the courtesies ex- tended by Mr. E. S. Nettleton, City Engineer; Mr, H. J. Kellogg, Engineer in Charge of the Sewer Division; Mr. C. W. Merrells, and other Assistant Engineers of the Bureau of Engineering; Mr. W. C. Kinney, Superintend- ent or sewers, Dr. J; L. Rice, City Health Officer, and the various inspectors of the Health Department. The field investigations in New Haven were in immediate charge of C. A. Emerson, and the principal members of our resident staff were G. S. Long, L. L. Campbell, and J. S. Parker, Jr. Analytical work was performed by A. F. Dolloff, L. E. Steiner and G. L. Frear. 40 SUPPLEMENTARY: | DATA! FILED “WITH Gli No. . Map Showing Boundaries of Sewerage Districts. . Tabulation of Measurements of Sewage Flow. . Estimated Population Densities for Various Sewerage ENGINEER. DESCRIPTION. Districts. . Estimated Domestic, Commercial & Industrial Sewage Flow. . New Haven District Water Consumption Records. . List of Replacement Sewers. . Details of Routes and Sizes of Storm Water Relief Sewers. . Notes on Removal of Accumulations from Sewers. . Notes on Sludge Soundings in Harbor. . Curves Showing Intensity of Storms to be expected at Intervals of 1, 5 and I0 years. . Details of Analysis of Sewage. . Details of Analysis of Industrial Waste. . Details of Dissolved Oxygen Tests in Harbor. . Details of Bacteriological Examination of Harbor Water. . Plant Cost of Sludge Digestion and Dumping at Sea. . Cost-of Pumping Stations and Intercepting Sewers. A Tea m) wie % ;