REPORT ON THE DISPOSAL OF THE SEWAGE OF THE CITY OF ROCHESTER, N. Y. BY E. KUICHLING, C. E. CONSULTING ENGINEER PRESENTED TO THE MAYOR FEBRUARY, 1907 Concurred in by GEORGE H. BENZENBERG AND RUDOLPH HERING CONSULTING ENGINEERS The M0RRI80N PRESS • X"2. & \ MX\ A'a'aVu 2, t„ *.?.■>> \ e & r V l > 52 Broadway, N. Y., Feb. 1, 1907. Hon. James G. Cutler, Mayor, City of Rochester, New York. Dear Sir:—In accordance with your request to revise the recommenda¬ tions made by me in 1889 for the disposal of the sewage of the East Side of the City of Rochester, and-to extend my review so as to embrace the sewage of the entire city, I submit herewith for your consideration the results of my further studies of the subject. In this report I have endeavored to present a statement of the essential factors involved in the problem, along with an impartial discussion of each of the various modes of solution that seemed feasible. Much collateral study and numerous computations were thereby entailed, and by embodying the results of this work, the report has greatly exceeded its anticipated length. After the first draft of my report had been prepared, it was submitted at your request to two of our foremost American municipal and sanitary engineers, Messrs. George H. Benzenberg and Rudolph Hering, as well as to City Engineer Edwin A. Fisher, for criticism. It was then rewritten and now includes the modifications deemed advisable after a number of long conferences with the gentlemen mentioned. Yours respectfully, E. KUICHLING. Digitized by the Internet Archive in 2019 with funding from University of Illinois Urbana-Champaign Alternates https://archive.org/details/reportondisposalOOkuic REPORT ON THE DISPOSAL OF THE SEWAGE OF THE CITY OF ROCHESTER, N. Y., BY E. KUICHLING, C. E„ FEBRUARY \ f 1907. POPULATION AND AREA OF CITY. According to the various official enumerations, the population of the city was 81,722 in 1875; 89,366 in 1880; 133,896 in 1890; 144,834 in 1892; 162,608 in 1900, and 180,525 in 1905, not including the recently annexed village of Brighton. These figures indicate that during the past 30 years there was an increase of 98,803 in the population, and that this has taken place at a nearly uniform annual rate. It is also well recognized by statisticians that the annual growth of communities of this magnitude rarely ever reduces, but almost invariably becomes larger; hence it may be safely assumed that the future growth of Rochester will gradually increase so as to give the present municipal area, exclusive of Brighton, a population of 184,000 in 1906 and 260,000 in 1925. The total area of the city is now 12,627 acres, of which 1,313 acres are occupied by parks, cemeteries, river, canal, etc., and 794 acres are the former village of Brighton. The natural drainage of Brighton is towards Ironde- quoit Bay, and the sewage from most of the recently annexed territory can¬ not flow into the Genesee River,, or into any of the existing outlet sewers of the city, unless it is forced therein by pumps. As the City Engineer is planning for the disposal of the Brighton sewage independently, it will accordingly be omitted from further consideration here, and hence the present habitable municipal area that will be taken into account is approx¬ imately 10,565 acres. There is, however, a large extent of territory in the townships of Gates and Greece, adjacent to the western boundary of the city, which is particularly well adapted for urban development, owing to its excellent railroad, canal and sewerage facilities. Of this an area of 5,513 acres in the township of Gates has contributed to the cost of the West Side Trunk Sewer, and at least 300 acres in the township of Greece can make use of the new outlet sewer for the northern district of Lake Avenue. With reference to the question of future population and sewage disposal, this territory should obviously be regarded as likely to be annexed to the city within the next 25 years, and hence the future habitable municipal area, exclusive of Brighton, tributary to the existing sewerage system will be at least 16,000 acres. As to the future population of the said territory adjoining the present western boundary of the city, it will certainly be conservative to assume that it will become about 15,000 within 20 years, and it may therefore be expected that about the year 1925 the total population tributary to the existing outlet sewers will be approximately 275,000. 5 OUTLET SEWERS, WITH TRIBUTARY AREAS AND POPULATION. Of the aforesaid habitable area of 10,565 acres now within the city limits, about 60 per cent lies on the east side of the Genesee River, and 40 per cent on the west side. The population is divided in nearly the same propor¬ tions, 61.6 per cent, being on the east side and 38.4 per cent, on the west side. The sewage from the entire population is at present discharged into the river through eight main outlet sewers, of which three are on the east side and five on the west side. The areas and populations in 1905 and 1925 served by these main outlet sewers are estimated approximately as follows: I. EAST SIDE. Approx. area, Estimated population, Acres 1905 1925 East Main Street & Central Avenue, Lowell Street, Evergreen Street and 295 13,000 15,500 Avenue B, 543 14,800 20,500 East Side Trunk Sewer, (inside city) 4,850 83,200 112,500 Total sewered, (inside city), Area outside of city boundaries sew- 5,688 111,000 148,500 ered by East Side Trunk Sewer, Various areas within city boundaries 231 200 200 not sewered, but draining into river, * canal and feeder, Areas in N. E. corner of city not sew- 684 100 250 ered, but draining into Irondequoit Bay, 63 10 50 Totals, 6,666 111,310 149,300 II. WEST SIDE. 4. Front and Allen Streets, 5. Genesee Valley Canal and 6. Spencer, Lyell Avenue Street, Total sewered (inside city), 7b. West Side Trunk Sewer, ( city), 8b. Lake Avenue, 187 4,650 9,500 , 1,574 22,050 40,500 L 783 24,500 35,500 1,047 14,500 22,500 596 3,700 6,000 4,187 69,400 111,000 5,513 600 12,500 300 100 2,500 10,000 70,100 126,000 Totals, 6 In general terms, the average level of the inhabited portion of the city may be regarded as being the same as the surface of the Erie Canal. The natural drainage of the entire West Side and a relatively small portion of the East Side is into the Genesee River, but by the construction of the East Side Trunk Sewer nearly all of the remainder of the East Side has been made tributary to the river. In the southern half of the city, the ordinary surface of the river is only from 8 to 20 feet below the surface of the adja¬ cent lands, but in the northern half the river flows through a deep gorge with precipitous sides. The upper falls, approximately 100 feet in height, are almost at the middle point of the city; the middle falls nearly 30 feet in height, are located about 1.25 miles northerly; and 0.25 mile beyond the latter, the lower falls have a drop of nearly 100 feet. The total descent of the river in a distance of 4.3 miles between the southern and northern boundaries of the city is about 264 feet, and in the remainder of its course to Lake Ontario, a distance of six miles, the fall is very slight. Two of the outlet sewers mentioned discharge into the river immediately below the upper falls, and the remaining six discharge at different distances northerly. In all cases the sewer terminates either in a deep vertical shaft and short tunnel, or in a steel pipe laid on the steep side of the gorge. The location and elevation of the bottom of each of the said eight sewers, at or near the top of the vertical shaft or pipe, are given as follows, the datum for the elevations being about 15 feet above the surface of Lake Ontario: Elev. of invert. Location. 1. East Main Street and Central Ave., -T 221.26 East Side, at inter¬ section of Central Avenue and North Water Street, near upper falls. 2. Avenue B outlet sewer, +192.09 East Side, at inter¬ section of Avenue B; and St. Paul Street,. 7,000 ft. N. of upper falls. 3. East Side Trunk Sewer, + 151.34 East Side, at inter¬ section of Norton Street and St. Paul Street, 9,450 ft. N„ of upper falls. 3a. East Side Trunk Sewer, 4-162.76 East Side, at inter¬ section of Norton and Hollenbeck Sts., 9,450 ft. N. of upper falls, and 2,100 ft. E. of river. 4. Front and Allen streets, + 190.08 West Side, near foot of Commercial St., at upper falls. 7 4a. Front and Allen streets, + 214.89 5. Genesee Valley Canal and Platt Street, +199.32 6. Spencer, Lyell Avenue and Saxton Street,+ 202.30 7. West Side Trunk Sewer, +156.31 8. Lake Avenue (Northern district) +128.25 West Side, near in¬ tersection of Front Street and Central Avenue. West Side, at inter- tersection of Fac¬ tory and Mill Sts., 1,200 ft. N. of upper falls. West Side, at foot of Spencer St., 3,450 ft., N. of upper falls. West Side, near in¬ tersection of Lex¬ ington Avenue and Hastings Street at lower falls, and 7,860 ft. N. of upper falls. West Side, at foot of Lapham Street, 5,700 ft. N. of lower falls, 12,300 ft. N. of upper falls. It may also be remarked that when the East Side Trunk Sewer was designed by the writer in 1889, the probability of a strong pollution of the lower river was foreseen, and hence the elevation of the invert of this sewer at the intersection of Norton and Hollenbeck streets was made such that the dry-weather flow might readily be diverted therefrom by gravity to a sewage purification works located at a suitable place on the East Side beyond the city line. This elevation was also chosen with the view of intercepting, whenever it might become necessary, the dry-weather flow of most of the other outlet sewers mentioned above, and conducting the liquid by a pipe and conduit to the same purification works. The latter were planned to be on the east side of the river, because no suitable and economical site could be found therefor on the west side. No effort, however, was made to secure the necessary land, as it was hoped by the municipal authorities that the dry-season flow of the river would soon be largely increased for the development of water power by the construction of a great reservoir in the vicinity of Mt. Morris or Portage for impounding the flood waters of the upper river. For a time it appeared probable that this project would be carried out, in which event the sewage purification would become unnecessary for many years; but the expense involved in the undertaking was found to be so large that its execution has been postponed until new demands for power warrant the outlay. Meanwhile the city has grown rapidly, and the pollution of the river has increased to such extent as to compel attention to the subject of the most expedient manner of disposing of the sewage. 8 DRY-SEASON FLOW OF RIVER. From the records of the daily stage of the river at the Court Street dam, which have been kept by the City Engineer since 1893, it is found that on the average there is little flow over said dam for about five months in the year; and from a series of incomplete gaugings of the two upper races by the U. S. Geological Survey in 1903, it would seem that during this period the discharge of the river may range from 1200 to 400 cu. ft. per second. In fact, however, nothing definite is known of the normal low-water flow, owing to the variable rates of draft by the users of the water power, but it might be inferred from these data that in ordinary years the discharge does not fall much below 400 cu. ft. per second. These records indicate that low water may occur during the months of February, June, July, August, September, October, November and December, but rarely during all these months in the same year; also that the lowest average monthly flow during August, September and October is 540 cu. ft. per second; that the average for these three consecutive months is about 560 cu. ft. per second; and finally, that the least daily flow was about 510 cu. ft. per second. It should, however, be noted that the observations of the stage of the water are usually made in the morning when the pool above the Court Street dam is replenished by the flow during the night, and that in the dry season considerably lower stages occur soon afterward and prevail until evening. In view of these facts, the aforesaid average monthly discharges of the river must be reduced materially in order to obtain the true dry- season flow. From numerous gaugings made by the undersigned and others in former years, it may safely be assumeds that for several weeks during severe droughts the average flow will not exceed 200 cu. ft. per second, or 129,000,000 gallons per day, and that in the dry season of ordinary years the least average monthly flow will be about 300 cu. ft. per second, or 194,000,000 gallons per day. DISPOSAL OF SEWAGE BY DILUTION IN RIVER. Having thus established the approximate dry-season flow of the river, the question next arises as to the quantity of crude sewage which can be discharged into the stream without causing serious offense by disagreeable emanations from the channel. No argument is necessary to prove that trouble of this kind is likely to occur only during the warm season, and that the processes of putrefaction are almost wholly arrested in cold weather. The consideration of the matter is therefore practically limited to the period from June to November. In forming a judgment as to the discharge of crude sewage into the river, the following facts must be kept clearly in mind. Prior to the com¬ pletion of the East Side Trunk Sewer in 1893, the sewage from about one- half the population on the East Side found its way into Irondequoit Bay, while that from the remainder of the city was discharged into the river. No appreciable pollution of the stream resulted, especially in the section from the lower falls to the lake, notwithstanding the evidence of some 9 septic action in the channel in severe summer droughts, and fish continued to abound except when destroyed by various trade wastes, such as the refuse from gas works and paper mills. In 1890 the population of the city was nearly 134,000, and the crude sewage of about 94,000 persons, along with nearly all the trade wastes, emptied into the river. The average consump¬ tion of water was then about 63 gallons per head daily, thus making a dis¬ charge of about 6,000,000 gallons per day of crude sewage into the river whose low-water flow did not exceed 140,000,000 gallons per day. This con¬ dition accordingly represents a 23-fold dilution of the sewage, or a minimum river flow of 138 cu. ft. per minute for every 1,000 persons contributing sewage. It should be noted, however, that in 1890 the water supply of the city became very limited, and that preparations were being made for securing an additional supply. The consumption of water was therefore unusually small, thus making a large ratio of sewage dilution. After the new water works were completed, the consumption quickly increased to 77 gallons per capita daily in 1895, since which time it has steadily advanced to about 87 gallons in 1904. From 1890 to 1900, and especially since the completion of the East Side Trunk Sewer in 1893, the writer made many close obser¬ vations of the condition of the lower river during the low-water season of each year; and aside from an offensive appearance of the water and some unpleasant odors in the vicinity of the mouth of that sewer, due to the lack of properly mixing the sewage with the water of the stream, he never detected any disagreeable emanations from the river between Brewer's dock and the lake, nor was he able to find any unprejudiced person who had noticed such. In the autumn of 1904 the writer again investigated the condition of the lower river in company with City Engineer Fisher, and found that while the appearance of the east side of the channel from Norton street to Brewer’s dock had become somewhat more offensive than formerly, yet no disagree¬ able odors arose from the water below the dock. Numerous inquiries were also made at that time and since of many citizens who had traversed the lower river more or less frequently in boats during the summer, and the testimony thus obtained was unanimous a's to the absence of unpleasant emanations from the water in the distance of 5.6 miles between the dock and the lake. . Complaints, however, had been made at various times since 1894 of the occasional existence of disagreeable odors in the vicinity of the intersection of St. Paul a.nd Norton streets, on ground whose elevation is from 170 to 190 ft. above the lower river, but the investigations invariably showed that these odors came from the manholes and gutter inlets of the sewers on the high ground mentioned, and at times also from the mouth of the trunk sewer at the river’s edge. The essential cause of the offense was therefore “sewer gas” or foul air issuing from the sewers, instead of emanations arising from the river after receiving the sewage. This is an important distinction in considering the question of sewage disposal by dilution with river water. It is unfortunate that accurate data concerning the low-water flow of the river for a long term of years are not available, especially since the completion of the East and West Side Trunk sewers; but in order to 10 present some correct figures for consideration, it may be stated that the average daily discharges of the river, computed from observations made under the writer’s direction three times each day during the months of July, August and September, 1888, ranged from 7,228 to 9,625 cu. ft. per minute, the mean being 8,692 cu. ft. per minute, or 93,630,000 gallons per day. In that year the average daily consumption of water in the city was 7,745,000 gallons, and the estimated population was 125,000, of which approximately 87,500 or 70 per cent, discharged their sewage and trade wastes into the river. This indicates that the sewage was then diluted about 17-fold by the river, or that an average flow of 99 cu. ft. per minute during the dry season for every 1,000 persons was able to dilute inoffensively the sewage of the tributary population. With the said minimum flow of 7,228 cu. ft. per minute, the sewage was diluted only about 14-fold, or an average flow of 83 cu. ft. per minute adequately diluted the sewage of 1,000 persons. Similar observations of the discharge of the river were made by City Engineer Fisher in the summer and autumn of 1896, when the population was about 153,600, and the average daily consumption of water in the city 11,951,000 gallons. In that year the East Side Trunk Sewer was in full ■Operation, so that the sewage and trade wastes from practically the entire city were emptied into the river. The writer is informed by Mr. Fisher that for considerable portions of the time in the dry season of 1896 the flow of the river did not exceed 12,000 cu. ft. per minute, or 129,264,000 gallons per day; hence the sewage was then diluted only about 11-fold by the river, or a flow of 78 cu. ft. per minute for every 1,000 persons was sufficient to produce an inoffensive dilution of the sewage. In 1904 and 1905 the flow of the river was observed by the U. S. Geological Survey at Elmwood Avenue, which is the southern boundary of the city. The gaugings at low water have not yet been sufficiently numerous at this point to establish the minimum flow with certainty, but it is probable that the same did not exceed 21,000 cu. ft. per minute, or 226,212,000 gallons per day, in these two years. In 1905 the population, exclusive of Brighton, was 180,525, and the average daily water consumption was 15,563,000 gallons; therefore the sewage in the dry season was probably diluted not more than 14.5-fold, or a flow of 116 cu. ft. per minute for every 1,000 persons sufficed to make an inoffensive dilution of the sewage and trade wastes. These results agree with the extensive observations that were formerly made by the State Board of Health of Illinois with a portion of the sewage of Chicago in the Illinois and Michigan Canal and the Des Plaines River, and also more recently with the bulk of the sewage of that City in the large Drainage Canal. Other authorities, both in this country and abroad, have found that dilutions of 14 to 20-fold were entirely satisfactory. In a paper read before the American Public Health Association in 1887, Mr. Rudolph Hering, C. E., one of the foremost sanitary engineers, arrived at the conclusion that rivers which were not used as sources of domestic water supply might receive the sewage from 1,000 persons for at least every 150 to 200 cu. ft. of minimum flow per minute, (or 2.5 to 3.3 cu. ft. per second), supposing that natural subsidence of the heavier matter takes place immediately below the point of discharge. To convert these figures into terms of dilution, it may be assumed that in American cities sewage 11 is produced (measured by the water supply) at the rate of 100 gallons per head per day, which corresponds to 9.35 cu. ft. per minute per 1,000 popula¬ tion ; hence on this basis the rate named by Mr. Hering corresponds to a minimum dilution of from 15 to 21-fold. It may also be remarked that the portion of the river below the lower falls is particularly well adapted to receiving sewage, owing to the extreme aeration of the water by the falls above, the depth and uniformity of its channel, its sluggish current in time of drought, and its strong floods every spring. By reason of these peculiarities, a thorough sedimentation of the sewage takes place in a long stretch of the deep channel during the dry season, and the accumulated deposit is scoured away into Lake Ontario by the next high freshet. In warm weather the sediment undergoes septic action to some extent, which is demonstrated by a copious evolution of bubbles of inodorous marsh gas, but the development of sulphurated hydrogen and other offensive gases has not yet occurred in appreciable quantity, except when the mud in the shallow parts of the channel is disturbed by steam¬ boats. Fortunately, however, there is little navigation in this section of the river, so that annoyances from boat traffic can be left out of consideration. From the foregoing statements and experiences concerning the disposal of sewage by dilution, it is probable that the volume of sewage produced by the city has now reached such a magnitude, that the ability of the river to absorb it without serious offense during the season of low water will soon reach its limit; and if the practice is to be continued, it follows that either the low-water flow of the stream must be increased in some manner, or the quantity of crude sewage discharged into the stream must be reduced during the summer and autumn months in proportion as the population of the city increases. In other words, the river in its natural state can deal safely by dilution with only a definite quantity of raw sewage during the warm season, and this limit has apparently been reached. INCREASING THE LOW-WATER FLOW OF THE RIVER BY STORAGE. The flow of the river during the low-water season can be increased either by the provision of adequate storage for use during four or five months each year, or by diverting into its channel water from another source. The first alternative has been under active consideration during the past 16 years, both by the State for canal purposes, and by private enter¬ prise for the improvement of the water power, but the great cost of the undertaking has hitherto prevented its execution. To indicate the magni¬ tude of the storage that would be required for the proper dilution of the city’s sewage during a period of unusual drought, it may be assumed that the average natural flow of the river will not exceed 300 cu. ft. per second during six consecutive months. This quantity is computed from the gaug- ings of the river in 1895 near Mt. Morris, N. Y., where the drainage area is 1,070 sq. miles, on the basis that the 1430 sq. miles of additional territory between Mt. Morris and Rochester contributed at the same rate per square mile as the upper part of the watershed. 12 It may also be assumed that in constructing the storage reservoir pro¬ vision should be made for a population of 300,000 in the city, with a sewage discharge of 30,000,000 gallons per day, or 46.42 cu. ft. per second; and in order to be conservative, the dilution may be taken at 20-fold, thus requiring a flow of 928 cu. ft. per second. It therefore follows that in a year like 1895, there will be a deficiency of 628 cu. ft. per second in the natural flow of the river for a period of 180 days, which corresponds to a storage volume of nearly 10,000,000,000 cu. ft., unless a portion of the defi¬ ciency is supplied from the Erie or Barge Canal. As an indication of the cost of such a reservoir, it may be stated that in 1894, the State Engineer estimated an outlay of about $2,500,000 for providing 7,300,000,000 cu. ft. of storage in the river gorge near Mt. Morris, and in 1896 he submitted an estimate of $2,600,000 for a reservoir holding 15,000,000,000 cu. ft. at Portage. It might be urged that the construction of such a reservoir would be a great benefit to all the owners of water power on the river, and that they should bear the greater part of the expense. This is perfectly true, but there is no way to compel such owners to unite in the undertaking, either by .themselves or in conjunction with the City or the State. An organiza¬ tion for the purpose was made in 1898, but it failed to secure the necessary backing, or even to test the constitutionality of the rights given to the com¬ pany by the Legislature. Moreover, an enterprise of this magnitude usually requires several years to harmonize by legislation and tedious legal processes the varied interests that are involved, and several years more will be needed for construction; hence it may be concluded that notwithstanding the attractiveness of the proposition, the sewage pollution of the lower part of the river will exceed endurable bounds before the project can be executed, and that relief in the meantime must be provided by other means. But even if the river might continue to receive the crude sewage of the city until the completion of such a storage reservoir, the equalized flow of the stream in years of low rainfall would suffice to dilute inoffen¬ sively the sewage from only a limited future population. On the basis of 200 cu. ft. of river water per minute for every 1,000 persons contributing sewage, a constant flow of 1,000 cu. ft. per second through the city would suffice for a population of not more than 300,000, and after this limit is reached it will become necessary either to increase the storage, or to devise means for preventing a larger discharge of crude sewage into the stream; hence conditions would arise which are like those now confronting the city. It may also be added that the aforesaid ratio of 20 to 1 for diluting sewage is regarded by Mr. Hering as applicable only when the most troublesome trade wastes are excluded from the sewers, and that if no restriction in this respect is enforced, a much larger ratio must be taken to secure satisfactory results. Relief can also be obtained after the Barge Canal is in operation, by the constant discharge of a large volume of water therefrom into the river. The only question in this case is about the quantity and permanency of the sup¬ ply that may thus become available. Under ordinary conditions a surplus of about 300 cu. ft. per second might be counted on from this source, but circumstances may arise whereby the quantity delivered would become much less, and in the event of a break in the banks between Rochester and Buffalo, the supply would cease entirely for a time. It is therefore unwise to con- 13 sider that so large an additional flow as 600 cu. ft. per second can be obtained permanently from the Barge Canal, unless the present plans for its construc¬ tion are modified. Furthermore, the Canal is yet far from completion, whereas the necessity for a substantial betterment of the condition of the lower river is close at hand. Another suggested method of improvement would be a frequent flushing, of the lower river by releasing a large volume of water that might be impounded periodically in the upper river at some favorable locality above the city; but as such storage in the dry season involves a corresponding large reduction of the natural flow between the intervals of flushing, an inter¬ ference with the rights of the owners of the water power would at once ensue. To give an idea of the quantity of water that would be necessary for this purpose, it may be added that the capacity of the river channel from Norton Street to the Lake at low water is about 130,000,000 cu. ft., which is 7.5 times the daily flow at the minimum rate of 200 cu. ft. per second, and 5.0 times the daily flow at 300 cu. ft. per second. In order to secure enough water to renew the contents of the 5.92 miles of channel between the points mentioned, it would accordingly be necessary to wait for a considerable rise of the river by rains, and as several weeks might elapse in a period of drought before such a rise would occur, it follows that this plan of flushing is impracticable. The only way of accomplishing the purpose without seriously trespassing on the rights of the owners of water power, is to store a sufficient quantity of flood water for use during the season of low water. It is reasonable to assume that s/ich a flushing would be necessary at least ten times in the course of five jr six months of warm weather, and hence a storage of about 1,300,000,000 cu. ft. would have to be provided. A practical reservoir site of this large capacity, however, cannot be found on the river below Mt. Morris, nor is there between Rochester and Mt. Morris an economical site for a reservoir of even one-fifth of this volume. Without extensive preliminary surveys and computations, an accurate estimate of the cost of such a reservoir in the vicinity of Mt. Morris cannot be made, but by comparison with the cost of similar undertakings elsewhere, it is probable that the expense will not be much less than $900,000. In view of its large cost and the uncertainty of its effect in remedying the pollution of the lower river, this plan cannot be recommended. INCREASING THE LOW-WATER FLOW OF THE RIVER BY PUMPING FROM LAKE OR BAY. A remaining method is to flush the lower river by pumping the necessary supply of water for adequately diluting the crude sewage of the city from the Lake or Irondequoit Bay. As the shortest distance from the foot of Nor¬ ton Street to the shore of the lake is about the same as to the bay, namely 4.66 miles in a direct line, and as the conduit would have to be in tunnel' through rock for practically the entire distance, there is little choice between these two sources. It is also apparent that such constructions should not be frequently duplicated, and that it will be expedient to provide in the outset 14 sufficient tunnel capacity to meet the requirement at the end of at least 20 years, or when the population has become at least 275,000. Additional pump¬ ing machinery on the other hand, may be installed at intervals of about five years. On the assumption that the population in 1925 will be 275,000, and that each person will then produce 100 gallons of sewage per day, the dry-weather flow of the sewers will be at the average rate of 42.5 cu. ft. per second; and if we assume that a 20-fold dilution thereof will be needed in order to keep the lower river in tolerable condition, the flow of the stream must be at least 850 cu. ft. per second. It will also be assumed that the average natural dry- season flow, along with the surplus water of the canal, is 350 cu. ft. per second during a period of 120 consecutive days, thus making it necessary to supply an average of 500 cu. ft. per second by pumping from the lake or bay through a conduit 4.66 miles long. On investigating this proposition, it will be found that the most economi¬ cal conditions will be obtained with a smoothly-lined circular conduit or tunnel 12.0 ft. in diameter, and steam pumping machinery operating centrif¬ ugal pumps of high efficiency. The quantity of water to be pumped obvi¬ ously varies with the stage of the river, and will probably range from 100 to 600 cu. ft. per second, while the fixed grade of the tunnel is adapted to the average discharge. When the river is at its lowest stage, the largest quantity of water must be pumped, whereby about 1900 IHP will be required eventually. Under these conditions, including tunneling in rock, the costs will be approximately as follows: For 24,600 lin. ft. of tunnel, including 7 shafts, $1,156,200; for steam engines, boilers, centrifugal pumps and accessories, adapted to develop 1900 IHP, $117,800; for buildings and foundations of pumping station $30,000; for lands and rights of way $18,800; for con¬ tingent expenses about 10 per cent, of the foregoing, or $132,200; total $1,455,000. In computing the annual operating expenses of such a plant, in which work is done for only four or five months in the year on the average, it must be remembered that at least three skilled employees must be retained permanently, and that under the 8-hour law three crews of men will be employed during 5 months of each year on the average, as a fixed time for beginning and ending the work cannot be set. Basing the pumpage on the use of only 724 IHP. on the average for 120 days, with coal at $3.00 per ton and a consumption of 3 lbs. per horse power per hour, the cost of the- necessary fuel will be $9,450; salaries of 3 permanent skilled employees,. $3,000; wages of temporary employees for 5 months, $6,000; station supplies,, maintenance of machinery, etc., and incidentals, $2,150; total, $20,600 per year. This annual expense does not include interest, depreciation and sink¬ ing fund charges, and relates to the time when the population is 275,000. It will be noticed that a 20-fold dilution of the crude sewage was assumed in making the preceding estimate; but in view of the actual condi¬ tion of the lower river in dry seasons, it may be urged that a lesser dilution would produce entirely satisfactory results. For the purpose of making com¬ parisons of cost, a second computation was accordingly made on the assump¬ tion that a 14-fold dilution would be sufficient, and that an average pumpage of only 200 cu. ft. per second, with a maximum of 400, would be required during the low-water season of 120 consecutive days. The results showed 15 that the diameter of the flushing tunnel should be 10.0 ft., and that the steam engines should have a maximum capacity of 920 IHP., the average use being 460 IHP. during the season. The total cost in this case was estimated at $1,214,000, and the yearly operating expense at $16,000 when the population reaches the magnitude named above. The foregoing plan has some attractive features, but is open to the objec¬ tion that it makes no provision whatever for improving the condition of the 8,500 ft. of river channel from the upper to the lower falls, or in fact to the mouth of the East Side Trunk Sewer, 3,100 ft. below the lower falls. To deliver the flushing water at any higher elevation than the surface of the lower river is manifestly too expensive for serious consideration, and if the tunnel were carried to the foot of the lower falls where it would serve for diluting the sewage of the West Side Trunk Sewer, the length and cost of the work would be largely increased. The plan therefore entails the eventual interception of the dry-weather flow of the outlet sewers which now dis¬ charge above the lower falls, in the manner that will be outlined hereafter, and the delivery of this flow either directly into the flushing tunnel, or into the river near the mouth of said tunnel. QUANTITY OF SEWAGE PRODUCED. In a city provided with an extensive system of water works and sewers, it is customary to assume that in dry weather the sewage is produced at prac¬ tically the same rate as the water is consumed from the various sources of supply. The total daily quantity discharged may, however, vary considerably from the daily water supply in consequence of the lack of perfect water-tight¬ ness of the sewers, whereby either a considerable loss of liquid may occur by leakage into a porous and absorptive subsoil, or an appreciable gain may ensue by the infiltration of ground-water. In the case of Rochester, no systematic gaugings of the discharge of the various outlet sewers have been made; but as most of them are excavated in the underlying rock, and as they also intercept whatever seepage occurs from the Erie Canal which passes diagon¬ ally through the city, it will be safe to consider that the dry-weather flow of sewage is somewhat greater than the water supply. During the eight years from January 1, 1895, to January 1, 1903, the average consumption of water from the public supply gradually increased from 77 to 94 gallons per capita daily, and in the next two years it was reduced to 87. For the entire 10-year period the average was 84 gallons per capita daily, and in 1904 the mean daily consumption was 15,238,000 gallons. It is, however, highly probable that the per capita consumption of water will gradually increase in the future as in the past, although it may be checked temporarily by the application of meters, or by various other causes; and hence it will be assumed that in the course of the next twenty years this consumption will advance so that the dry-weather flow of sewage and infiltering ground-water will be about 100 gallons per head daily. This quan¬ tity was adopted in the preceding estimates, and will be retained for com¬ puting the sizes of the various pipes and conduits involved in other plans. 16 MECHANICAL AND CHEMICAL CLARIFICATION OF SEWAGE. If the crude sewage of a city cannot be discharged continuously and inoffensively into a large river, a considerable improvement in the appear¬ ance of the stream during the low-water season can be secured by removing from the sewage more or less of the solid organic matter which it carries in suspension. Such removal may be accomplished either by mechanical or chemical means, and the resulting clarified liquid can then be discharged inoffensively into a correspondingly smaller flowing stream than is required for the satisfactory dilution of crude sewage. This is equivalent to stating that each unit of volume of relatively clean river water can receive a certain maximum quantity of organic matter from sewage without becoming offensive to sight and smell, and it becomes important to ascertain this limiting quantity in the case under consideration. It was shown in the foregoing that, aside from the unsightly conditions at the mouth of the East Side Trunk Sewer, the water of the lower river has not become noticeably malodorous when mixed with crude sewage in the proportion of 14 to 1 by measure or volume, and that in 1904 and 1905 the sewage was discharged into the river at the average rate of 86 gallons per head of population per day. Unfortunately no chemical analyses of the sewage of Rochester are available; but as there is no reason for considering that it differs materially in composition from the sewage of other large cities, it can be assumed that on the average the total quantity of dry volatile matter, or “loss on ignition,” in the liquid amounts to about 100 grams or 3.53 ounces per capita daily, of which 55 grams or 1.94 ounces are dissolved and 45 grams or 1.59 ounces are suspended in the water. This dry volatile matter is regarded as being approximately the quantity of organic matter of every description contained in the sewage, but it must also be remembered that some of it consists of soot, coal, coke, wood and other organic sub¬ stances which are not offensive or putrescible. As to human excreta, the usual average figures for a mixed population of adults and children of both sexes are 0.63 ounce of dry fecal matter mostly in suspension, and 1.52 ounces of evaporated urine in solution, per capita daily. Of these quantities about 4 and 2 per cent respectively are mineral matters, thus leaving 2.09 ounces of organic matter, of which 1.61 ounces or 77 per cent, is dissolved; and on comparing these figures with those previously given for the total dry organic matter, it will be seen that at legist 1.11 ounces of dry suspended and 0.33 ounce of dry soluble organic matter per capita daily are derived from other sources than human excreta. With • 14-fold dilution and 86 gallons of crude sewage per head, the river water thus contains in the dry season about 3.53 ounces of dry organic matter in every 1,290 gallons flowing to the lake; or expressed otherwise, a population of 178,000 in 1904 discharged daily 19.63 tons of dry organic matter into the river whose dry-season flow including the sewage was probably not more than 355 cu. ft. per second, and of this matter 10.79 tons were dissolved, and 8.84 tons were suspended in the water. As it is probable that the lower river cannot be polluted to a much greater degree without giving rise to disagreeable emanations, these figures may accordingly be adopted as limits beyond which it will be unsafe to go. 17 Concerning the relative offensiveness of the putrescible organic matters which are carried in solution and suspension in the sewage, little seems to be known at the present time, except that the suspended matter is generally regarded as being much more objectionable than the dissolved matter. The latter is absorbed by algae and is also rapidly oxidized or changed in char¬ acter by numerous aerobic organisms in open streams, whereas the solid matter is attacked slowly and by sinking to the bottom of the channel, it is cut off from exposure to the air and left to undergo putrefactive decomposi¬ tion. In this process a certain amount of the settled matter is liquefied and marsh gas is evolved, whereby a considerable degree of purification is effected in water of moderate depth. In view of the general opinion that the suspended organic matter is much more offensive in a stream than that which is in solution, and in the absence of any definite observations in this respect other than practical experience with the effluents of precipitation works and a number of experiments made by the writer some years ago, it may be assumed that the sewage water can be divided into two equal parts of 43 gallons per capita each, and that a 10-fold dilution of the part containing the dry soluble organic matter will suffice to prevent disagreeable emanations from the water, while a 20-fold dilution is necessary in the case of the part containing the dry suspended organic matter. With these dilutions the resultant flow of the river would be 10 x 43 equals 430 gallons for 1.94 ounces of dissolved dry organic matter, and 20 x 43 equals 860 gallons for 1.59 ounces of suspended dry organic matter, or a total of 1,290 gallons for the aforesaid total of 3.53 ounces per capita daily, corresponding to the addition of 14 parts of relatively clean water to one part of crude sewage. The liberality of the preceding estimate for the inoffensive dilution of the dissolved and suspended organic components of sewage will be appreciated by a few comparisons. In many of the English and European cities the sewage is much stronger, or smaller in volume per capita, than in American cities, and is purified by chemical treatment, by which about two-thirds of the suspended matter and more than one-half of the organic matter therein are removed. The effluents in these places discharge into small streams whose dry-weather flow is often only a few times greater than the volume of partially clarified sewage, and no offensive condition of the stream ensues. The same observation has also been made with the effluent of the sewage works of Worcester, Mass., as the writer was recently informed by Dr. Id. P. Eddy, who has had charge of these works for the past ten years, that when the flow of the Blackstone River was from 8 to 10 times larger than the discharge from the precipitation tanks, the stream remained in excellent condition. It must also be remembered that a 20-fold dilution for very strong crude sewage has been found adequate in many cases, and it cannot be presumed that as much diluting water is needed for a part of the organic matter as for the whole. On the basis mentioned above, the removal of the whole of the suspended organic matter from the sewage would leave the same quantity of river water capable of diluting inoffensively the dissolved organic matter from 3.22 times as many people as before; and if two-thirds of the suspended organic matter were removed, the same quantity of river water would render inoffensive the rest of the matter in the sewage of 1.87 times the number of persons. 18 Similarly, if one-half of the suspended organic matter were removed, the sewage of about 1.54 times as many people would be adequately diluted; if one-third were removed, the resultant dilution would suffice for 1.31 times as many people; and if one-fourth were removed, the dilution would suffice for 1.22 times as many people as before. It is thus seep that with a steadily increasing population the sewage pollution of the lower river can be maintained at a certain constant degree, defined by the absence of offensive emanations from the water, if a gradually increasing proportion of the suspended organic matter in the sewage is removed from either a part or the whole of the liquid before allowing it to discharge into the river, and also if a thorough mixture of the sewage with the river water is secured. The recognition of this fundamental principle is a matter of great importance, so far as the cost of permanently improving the present condition of the river is concerned. The removal of suspended matter from sewage by mechanical means is accomplished by screening and plain sedimentation in basins of suitable form and mineral substance is washed into the sewers from the streets and roofs, and magnitude. This master varies considerably in amount both in different hours of the day and on different days of the week, and also with the state of the weather. In the early part of a rainstorm, a large quantity of earthy and the increased flow also scours out deposits which may have accumulated in the sewers themselves; but after a short time the water rapidly becomes clearer. Provision is therefore made in all sewage purification works to receive from 2 to 4 times the dry-weather flow, the remainder of the liquid being allowed to escape at storm-water outlets. On arriving at the works, the sewage should flow through a grating or rack on which the coarse floating matter is retained, and then through a relatively wide and deep chamber in which the heavier mineral matter is deposited. It passes next through one or more screens with small meshes to extract all but the finely comminuted suspended matter, and then flows into a series of large tanks in which most of the remaining suspended matter set¬ tles slowly. In these tanks its motion is generally very slow, the mean velocity usually being from 8 to 12 inches per minute, and the length of the tank being such as to make the time of passage from 2 to 3 hours. The sewage then flows continuously in a thin sheet over the end wall of the tank into an outlet channel which conveys it to the river or other outfall. Much attention has recently been given to the details of clarification pro¬ duced by sedimentation or precipitation and the results thereby accomplished. At Columbus, O., experimental tanks 40 ft. long, 8 ft. wide and 8 ft. deep were used in 1905, and about two-thirds of the total suspended matter, including more than one-half of the organic matter therein, was removed by plain ■subsidence; while by precipitation with aluminum sulphate about three- fourths of the total suspended matter, including 80 per cent, of the organic matter therein, was removed. At Worcester, Mass., where in 1905 an average daily flow of 10,110,000 gallons of sewage was precipitated with lime in a series of large masonry tanks having an aggregate capacity of 5,500,000 gal¬ lons, 85.8 per cent, of the total suspended matter and 51.5 per cent, of the total organic matter were removed; and similarly, at Providence, R. I., where in 1904 an average daily flow of 20,000,000 gallons of sewage was precipitated with lime and copperas in like manner, 82.7 per cent, of the total suspended 19 matter and 49.4 per cent, of the total organic matter were removed. These two works are the largest of their kind in this country. In Great Britain there are many sewage works of greater magnitude than these at Worcester and Providence, and which accomplish the same results. Plain sedimentation without the use of chemicals, however, is little practised, owing to the relative smallness of the streams and the constant necessity of removing the greatest practicable quantity of organic matter from the sewage. Although several biological processes of treatment have organic matter has been considerably overrated. It is therefore very probable been extensively exploited there during the past twelve years, it has now come to be recognized that the settling of the suspended matter by gravity in suitable economical point of view the efficiency of bacterial action upon the solid tanks is the essential preparatory feature, and that from a practical and that the removal of the suspended matter in sewage by improved mechanical' and sedimentation processes will become an important factor in future methods of purification. In Germany this subject has recently been studied very closely, and elaborate experiments with settling tanks of full size have been made at Cologne, Hanover, Frankfort and other cities, in addition to the highly scientific work which has been done during the past ten years in laboratories with small tanks like those used at Columbus. The object of these investiga¬ tions was to determine by practical demonstrations whether the use of chemicals for precipitating the suspended solids could not safely be omitted, thereby saving a large percentage of the cost of treating the sewage before- discharging it into the rivers; and the results proved to be so satisfactory that wherever the stream was of sufficient magnitude to insure adequate dilution, the governmental conditions respecting the use of chemicals were withdrawn, and permission was given to clarify the sewage by screening and plain sedimentation. It is, however, proper to state that while no limit was named in these cases, the minimum flow of the stream always afforded a dilution of more than 20 times the volume of sewage effluent. At Cologne, the large experimental tank was 148 feet long, 26 feet wide and had an average depth of 6.5 feet. The population connected with the sewerage system in 1901 was 348,000, and the average quantity of sewage per capita daily was 160 liters or 42.25 gallons, containing 48.5 grams or 3.14 ounces of dried suspended matter, and 142.7 grams or 9.25 ounces of dried dissolved matter. The total amount of dry solid matter in the sewage was thus 191.2 grams or 12.39 ounces per capita daily, of which 71.1 grams or 4.61 ounces were organic or volatile at low red heat; and of this latter 2.23' ounces were suspended and 2.38 ounces dissolved. The sewage thus con¬ tained 31 per cent, more organic matter per capita daily than the quantity (3.53 ounces) assumed for Rochester, which is probably excessive for Ameri¬ can cities. The experiments were made with mean velocities of flow through the tank of 9.45, 47.3 and 94.5 inches per minute; and it was found from hundreds of accurate analyses that with a velocity of 9.45 inches per minute, 70.9 per cent, of the suspended and 9.1 per cent, of the dissolved organic matter were removed, while with a velocity of 47.3 inches per minute the removal was respectively 68.6 and 3.6 per cent., and with 94.5 inches it was respectively 59.3 and 2.7 per cent, on the average. Percentages of removal of mineral matter are here omitted as being of no significance in the present case. 20 At Cassel, with tanks similar to that at Cologne, and with velocities varying from 5 to 24 inches per minute, 77.5 per cent, of the organic matter in the sewage is removed by plain sedimentation. At Frankfort, under like conditions, from 70 to 90 per cent, of the suspended matter is removed, and it has been found by long trials that little improvement in the efficiency of the tanks was gained by the moderate use of chemicals; hence the work is now done exclusively by screening and plain sedimentation. Numerous other instances of sewage clarification by this simple process might be cited, but it is believed that the foregoing will suffice to show its applicability in many ■cases where a high degree of purity for the effluent is unnecessary. It must be remembered, however, that the choice between plain sediment¬ ation and chemical precipitation will be governed in a large degree by the character of the sewage, the trade wastes it contains and its odor. If the latter is very offensive, and cannot be abated by maintaining the system of sewers in a comparatively clean condition by proper flushing, it may be ex¬ pedient to effect at least a partial deodorization by adding some suitable chemi¬ cal substance, such as sulphate of iron, sulphate of alumina, or chloride of lime, to the liquid before its entrance into the settling tanks. In many cases the trouble is caused by the decomposition of organic sediment in sewers having flat grades, as it is found that the odor disappears after the flushing produced by a heavy rainfall, while in others it is due to certain trade refuse. The most common precipitating reagent is freshly-slaked quicklime on account ■of its cheapness, but it is often supplemented with a small addition of copperas or crude alum. Lime is used at the rate of 400 to 1,200 lbs. per million gal¬ lons, copperas at from 120 to 600 lbs. and crude alum or compound of iron and aluminum sulphate at from 180 to 1,000 lbs. The quantity used varies with the character of the sewage and trade wastes, and the rate of admixture is generally varied at different hours of each day. At wholesale the present prices per ton of these substances are as follows:— Lime of best quality, $5.85; copperas, $10.00; crude sulphate of alumina, $25.00. To indicate the cost of operating such chemical precipit¬ ation works on a large scale, it may be noted that at Worcester, Mass., where lime alone is used, the cost of treatment in 1905 was $5.56 per million gallons, in which quantity an average of 999 lbs. of lime was placed; and that at Providence, R. I., where 683 lbs. of lime and 58 lbs. of copperas per million gallons were used in 1904, the cost was $3.42. These figures are for the precipitation expenses alone, and in addition thereto the costs of disposing ■of the sludge were respectively $6.33 and $2.57 per millon gallons of sewage; they are here given separately, as a different and much cheaper method of g-etting rid of the sludge is available at Rochester. The quantity of wet sludge, containing about 90 per cent water, deposited in the tanks per million gallons of sewage was 4,190 gallons (18.54 tons) at Worcester, and 4,003 gallons (17.71 tons) at Providence. INTERCEPTION OE THE PRINCIPAL OUTLET SEWERS. In order to compare the cost of flushing the lower river, as previously described, with the costs of plain sedimentation and chemical treatment of the sewage of the entire city, it is necessary to outline a method by which the latter process can be accomplished at a single station, as in the' case of Worcester and Providence. A study of the sewerage system shows that about three times the estimated future volume of the dry-weather flow of the principal outlet sewers on the east and west sides of the river can be collected at a point about 800 ft. north of the intersection of Norton Street and Hollen¬ beck Street in the following manner:— By a tunnel 700 ft. long and containing an 18-inch pipe to carry the sewage, from the intersection of Central Avenue and North Water Street to- the tunnel of the Front Street outlet sewer near the intersection of Central Avenue and Front Street; thence by a 20-inch pipe to carry the combined flow of the first-named and the Front Street sewer through the latter tunnel and its shaft to the flats on the west side of the river below the upper falls, a distance of 800 ft.; thence likewise by 20-inch pipe, 900 ft. through these flats to the intersection of Factory and Falls streets, where the 20-inch pipe would, be joined by a lateral 30-inch pipe 450 ft. long, placed in a new shaft and tunnel for diverting the sewage of the Genesee Valley Canal and Platt Street outlet sewers at the intersection of Factory and Mill streets; thence by a 36-inch pipe to carry the combined dry-weather flow of the aforesaid three outlet sewers, northerly through Falls Street and along the western edge of the river to the foot of Spencer Street, a distance of 2,400 ft.; here the 36-inch pipe would be joined by a lateral 16-inch pipe 250 ft. long, placed in the existing shaft and tunnel for the Spencer Street outlet sewer; thence by a 42-inch pipe to carry the combined flow of the said four outlet sewers, northerly to the foot of Avenue B on the east side of the river, a distance of 4,400 ft., of which 700 ft. is in tunnel through the cliff from Spencer to the R. W. & O. R. R. bridge, 1,700 ft. in passing through the flats on the west side and the remaining 2,000 ft. in crossing the river and passing through the flats and up Brewer Street. The above described routes, sizes and distances must be considered only as approximations until accurate surveys and gaugings of the sewers are made. At the intersection of Avenue B and Brewer Street the surface is at elevation +203.5, and the top of the 42-inch pipe should be about at elevation+ 174.0, in order to obtain the necessary fall for the pipe and also allow ample fall for a conduit 5,800 ft. long from that point to the conduit in Hollenbeck Street for diverting the dry-weather flow from the East Side Trunk Sewer to the sewage purification works, the elevation of the top of the latter conduit being about + 161.0 at the place of junction, 800 ft. north of Norton Street. To avoid passing through private property a route for this conduit would be through Avenue B to St. Paul Street, thence through the latter to Strong Street, and thence to the intersection of Strong and Hollenbeck streets. Owing to the great depth of the conduit below the surface in the first half of this route, it will be expedient to construct this part of the work in tunnel, but in the remainder of the distance it can readily be done in open excavation. At the intersection of Avenue B and Brewer Street, the conduit would be 5.0 ft. in diameter and receive directly the discharge of the said 42-inch pipe and the dry-weather flow of the Avenue B outlet sewer; but as its elevation is here 18 ft. above that of the invert of the West Side Trunk Sewer at the top of the Hastings Street shaft, the normal flow of this sewer can be diverted into it only by pumping through a 30-inch pipe about 1,200 ft. long. 22 It is thus shown how the sewage from seven of the eight principal outlet sewers of the entire city can be permanently diverted from the river and delivered at a purification plant located on the east side at some suitable point north of the city line. The normal flow of the eighth outlet sewer (for the Lake Avenue district north of Lake View Park) might also be diverted in like manner by pumping, but as the quantity of sewage is relatively small, while the cost of diversion will be unduly large, it may be permitted to dis¬ charge directly into the river for many years, if the flow of all the other sewers is intercepted and purified as outlined above. It should be further noted that the sizes and grades of the said system of pipes and conduits are adapted to carry about three times the estimated dry-weather flow of these outlet sewers in the year 1925, thus providing also for the removal and treat¬ ment of the storm water from light rainfalls, or the first flushing of the sew¬ ers by heavier showers. The estimated cost of this work from the intersection of Central Avenue and North Water Street to the intersection of Strong and Hollenbeck streets, including 800 ft. of conduit 4.0 ft. in diameter from the East Side Trunk Sewer, is as follows:— 1. 700 lin. ft. tunnel and 18-inch pipe under river and races from North Water Street to Front Street outlet sewer tunnel.$ 20,000 2. Trimming 800 lin. ft. rock walls of Front Street outlet sewer tunnel and shaft, to receive 20-inch pipe, and laying said pipe therein, also for laying 900 lin. ft. additional of such pipe in flats on west side of river to south end of Falls Street. 11,500 3. 350 lin. ft. shaft and tunnel and 100 ft. open trench from intersec¬ tion of Mill and Factory streets to flats near south end of Falls Street, also laying 450 lin. ft. of 30-inch pipe in said shaft, tunnel and trench to junction with aforesaid 20-inch pipe. 13,700 4. 2,400 lin. ft. trenching and laying 36-inch pipe through Falls Street , and lands at west edge of river to foot of Spencer Street including 200 ft. of tunnel. 26,700 5. Trimming 250 lin. ft. rock walls of Spencer Street outlet sewer tunnel and shaft, to receive 16-inch pipe, and laying said pipe therein, to junction with 36-inch pipe. 3,000 6. 700 lin. ft. tunnel, 400 lin. ft. river crossing and 3,300 lin. ft. trenching in flats on west and east sides of river and in Brewer Street, from Spencer Street to Avenue B, and laying 4,400 lin. ft. of 42-inch pipe. 74,500 7. 1,200 lin. ft. trenching and laying 30-inch pipe in Hastings Street, across river and up east high bank of river from shaft of West Side Trunk Sewer to foot of Avenue B on east side. 16,500 8. Pumping station and steam machinery in duplicate, for forcing dry-weather flow and some storm water from West Side Trunk Sewer through said 30-inch pipe into head of masonry conduit at foot of Brewer Street. 25,'000 23 9. Masonry conduit 5.0 ft. diameter, constructed for 2,850 ft. in tunnel and for 2,950 ft. in open trench, through Avenue B, St. Paul Street and Strong Street to Hollenbeck Street. 108,500 10. 800 lin. ft. masonry conduit 4.0 ft. diameter in Hollenbeck Street from Norton Street to Strong Street, to intercept dry-weather flow and some storm water from East Side Trunk Sewer.... 13,600 Total, exclusive of contingencies.$313,000 By this plan of interception the discharge from all of the said outlet sewers, except the West Side Trunk Sewer, would be carried away by gravity, while that from the latter must be pumped continuously during the low-water season against a head of at least 21.0 ft. On referring to the table giving the areas and prospective populations of the several outlet sewer districts, it will be found that the West Side Trunk Sewer serves an area of 6,560 acres or 10.25 square miles, of which 1,047 acres are within the present city limits, and that the estimated future population thereof is 35,000. At the rate of 100 gallons per capita daily, the dry-weather flow of sewage from this district will eventually become 5.43 cu. ft. per second, and by adding twice as much storm-water the maximum pumpage would be about 16.5 cu. ft. per second. With centrifugal pumps having an efficiency of 65 per cent., the power needed for pumping thus ranges from 22 to 70 IHP., and as the district is so large, it can safely be assumed that an average of at least 50 HP. will be required constantly during the season. Owing to the irregular character of the pumping service, it is probable that the work can be done more economically by steam than by electric power, if the latter is purchased of a private corporation; and if it be assumed that the pumping will embrace an average of 120 days per year, during which coal is consumed at the rate of 5 lbs. per horse-power per hour, that the coal will cost $3.25 per ton, and that three crews of two men each must be employed daily for 5 months per year, the annual operating expenses and maintenance of the pumping station, exclusive of interest and other fixed charges, will be about $4,000, of which $1,200 is for coal. It will be shown subsequently how this power can be developed at very small cost by the clarified sewage effluent of the purification works, and be transmitted electrically to the pumping station. COSTS OF MECHANICAL AND CHEMICAL CLARIFICATION OF THE SEWAGE OF ROCHESTER. I From the intersection of Strong and Hollenbeck streets, the intercepted sewage, along with the limited quantity of storm-water mentioned, would be conveyed to some suitable site about 5,500 ft. (more or less) north for treatment. The masonry conduit for this purpose would be 6.0 ft. in diameter, and for the length named its cost would be $86,000. To avoid litigation arising from existing prejudices against the establishment of sewage purifi¬ cation works in any locality, and to minimize the notice of any possible devel- 24 opment of disagreeable odors therefrom, it will be expedient to purchase in the outset an approximately square tract of land containing at least 150 acres, and to locate the tanks in the middle thereof. The probable cost of this quantity of land is not known at present; but as not more than 10 acres will be required for the sedimentation tanks and accessory works, the remainder -of the area can doubtless be rented advantageously for agricultural purposes, especially if coupled with the promise of supplying freely all the sewage that may be needed thereon for fertilization and irrigation. It is therefore reason¬ able to expect a constant yearly revenue from this source which will be ■equivalent to reducing the purchase price considerably. In the aforesaid plan for flushing the lower river, a population of 275,000 was assumed with a sewage discharge of 42.5 cu. ft. per second. The same discharge will be taken for estimating the costs of sedimentation and chemi¬ cal treatment, with 25 per cent, additional quantity for storm water, as the latter appears only at intervals aggregating not more than 360 hours during 120 days of summer and autumn. Tank capacity need be provided only for the dry-weather flow on the basis of 21,000 cu. ft. per tank of 150 ft. length, 20 ft. average width, and 7 ft. average depth, with 2.4 hours’ time of passage, as only one hour will suffice when the sewage is mixed with storm water. This requires about 18 tanks, but as some reserve capacity is needed for use while two or more tanks are being cleaned, 22 such open basins will be assumed. The average cost of such a tank with its accessory channels and appliances for receiving and * removing the sewage, sludge and clarified effluent is approximately $5,200; hence for 22 tanks about $114,400 would be required. Before entering the tanks the crude sewage would pass through a ■detritus chamber and two sets of screens for extracting the coarser sus¬ pended matter, as already described. This apparatus will cost about $6,000. Provision must also be made for the convenient removal of the sludge or sediment from each tank by means of a suitable conduit and pump, and its temporary storage in a large covered basin. The cost of the latter, along with the pump well and sludge conduit connecting the two series of tanks will be $7,500, and the cost of a combined sludge pumping station and laboratory, with its proper equipment will be $10,000. The group of sedimentation tanks can be located at a point about 2,500 ft. easterly of the top of the high bank of the lower river, and the effluent would be carried to the edge of the declivity in a masonry conduit 6.5 ft. in diameter costing $25,000, and thence down the high bank into the river in a suitable pipe. As the site of the works is upward of 140 ft. above the river, the effluent from the tanks will at once become available for the development of a large amount of water power at the edge of the stream. A small part of this power can easily be transmitted electrically to the sludge pumping station for use in forcing the wet sludge through a 6-inch pipe costing $2,700 into suitably covered tank-barges at the power station on the edge of the river. The remainder of the power so generated can likewise be transmitted elec¬ trically two miles southerly to the previously mentioned pumping station near the mouth of the West Side Trunk Sewer, where it would take the place of steam power. The costs of the constructions involved in this use of the effluent and production of electrical power for said pumping purposes are as follows : For two 36-inch steel outlet pipes down the high bank of the river, $5,300; for barge dock and power station at edge of river, and its 25 equipment with the necessary hydraulic and electrical apparatus in duplicate- for producing 100 HP., $17,700; for three covered tank-barges for carrying and dumping the wet sludge far out in the lake, $16,500; for 2.5 miles of electrical transmission line, $3,500. The sum of the foregoing items of cost for conduits, pipes, sedimenta¬ tion and sludge tanks, pumping stations, power-generating apparatus and sludge barges, from the intersection of Hollenbeck and Strong streets to the barge dock at the edge of the river, is $294,600. To this should be added’ $29,400 for general contingent expenses of construction, such as engineering, inspection, legal services and unforeseen expenses, thus making the cost $324,- 000, exclusive of the purchase price of the 150 acres of land deemed necessary for the site of the tanks and for avoiding complaints from the owners of the adjacent properties. Should it be found that said land can be acquired for $76,000, then the estimate for the total cost of the plant described would be- $400,000. With respect to the annual operating expenses of the purification works, it will be assumed that the cost of chemical treatment alone per million gal¬ lons of sewage is $4.49, which is the average of the costs at Worcester and Providence; also that including the storm water, an average of 34,000,000' gallons per day will eventually be so treated for 120 days. For this part of the work the ultimate seasonal expense will thus be $18,300, to which must be added the salaries of several skilled attendants for the remainder of the year, along with the costs of maintaining the electrical power for pumping the sludge and of getting rid of the same. Including the pumping station of the West Side Trunk Sewer, it is estimated that the salaries of eight such permanent skilled attendants for eight months will amount to $5,200, and that on the basis of 8 hours’ work per day the wages for four months of the permanent and temporary attendants for producing the power and pumping sewage and sludge will be $5,900. The total of these three items is $29,400. When the population becomes 275,000 and the average daily flow of sewage to be treated is 34,000,000 gallons, as aforesaid, wet sludge will be produced in the precipitation tanks at the average rate of 4,100 gallons per million gallons of sewage, thus making the daily yield 139,400 gallons or 603' tons. It is proposed to pump this fresh sludge into covered tank-barges, at the said electrical power station at the edge of the river, and then to tow them 8 or 10 miles out in the lake, where the contents would be quickly dis¬ charged by merely opening a few large valves in the bottom of each vessel. Such discharge would always be made at a point sufficiently far from shore- to prevent any of the matter from being carried back by wind or waves. In this manner the ultimate daily product of wet sludge can easily be removed within a period of 8 or 10 hours at a cost of not more than $28.00* per day, embracing rental of tug-boat and wages of barge crew; hence for the stated season of 120 days, the cost of getting rid of the sludge will be- about $3,400. The total yearly expense of operating the said chemical purification plant will thus be $32,800 when the population and quantity of sewage treated' reaches the limits named, but previous to that time it will be proportionally less. It may also be stated that the average of the costs at Worcester and’ Providence for precipitation alone is $2.68 for chemicals and $1.81 for labor per million gallons of sewage treated at the works, not counting what is; 26 required for disposing of the sludge. On the basis of 34,000,000 gallons- daily, the expense for lime and copperas used during the estimated season of 120 days would thus be about $10,900; and hence if it should be found by actual experience that an adequate clarification of the Rochester sewage can be secured by plain sedimentation without the use of chemicals, the total yearly cost of thus treating 34 million gallons per day for 120 days will be- only $21,900, instead of $32,800. COMMENTS ON MECHANICAL AND CHEMICAL CLARIFI¬ CATION PROCESS. It was shown in a previous paragraph that by removing two-thirds of the- suspended organic matter in the sewage, or the greater part of that which- tends to cause the river to become offensive, the partially clarified effluent from 1.87 times as many persons should be inoffensively diluted by the same quantity of relatively clean river water as was needed for adequately diluting the crude sewage of the original population. It was also seen that the minimum flow of the Genesee River was capable of producing an inoffensive dilution of the sewage of about 180,000 people; hence it follows that even if the minimum flow of the stream is not increased, it should be able to dilute inoffensively the effluent from a proper chemical treatment of the sewage of about 336,000 people. It may, however, be urged that the usual chemical treatment of sewage does not always accomplish the removal of two-thirds of the suspended organic matter, and that in many cases not more than one-half of this matter is so removed. Granting that such is the fact, it follows that even if only one-half of the suspended organic matter is removed by such a process, the minimum flow of the river should still be able to dilute inoffensively, the par¬ tially clarified sewage from 1.54 times as many people as in the year 1905, or from a population of about 275,000, which has been set as a limit for present consideration. It was also shown that equally good results had been accomplished by plain sedimentation of the sewage in the precipitation tanks without the addition of chemicals. In view of these conditions and the successful results attained at Wor¬ cester and Providence, as well as in many foreign cities, the relatively inex¬ pensive method of sewage treatment outlined above is worthy of the most careful consideration. It should also be borne in mind that the process ol clarification is the first step that must be taken in any known mode of purifying sewage other than by natural agencies in a large body of water. The objections are that such a plant is always an undesirable feature in the suburbs of a large city, and that great care must constantly be exercised to- keep it from becoming offensive; also that the addition of future trade wastes may make the process much more expensive. The principal difficulty associated with sedimentation and precipitation processes has hitherto been the economical disposal of the wet sludge. In most cases where the purification of sewage has been found necessary, great bodie$ of water like Lake Ontario or the ocean have not been available, and hence ingenuity has been taxed to the utmost to devise means for getting rid 27 -of the sludge inoffensively and inexpensively. After unsatisfactory experi¬ ences with various other methods, the plan of removing most of the water from the sludge by means of a filter-press was developed, and it is now generally adopted in localities where disposal at sea is not feasible. In this process the liquid is usually mixed with a certain quantity of lime and is then forced by pumps and high air-pressure through sheets of canvas placed between large,cast-iron plates which are arranged in a suitable frame. Most of the water is thus blown out while the solid matter is retained between the plates in the form of a moist cake, which can readily be transported by wagon and dumped in some place where its subsequent decay will not cause offense. At Worcester and Providence the sludge is treated in this manner, and the resulting product is dumped on low lands in the vicinity of the purifica¬ tion works. As mentioned above, the costs of dealing with the sludge at these two places are respectively $6.33 and $2.57 per million gallons of sewage; hence it will be seen that the plan outlined above for getting rid of the sludge from the proposed sedimentation tanks is vastly more economical. If the farming land in the region is deficient in lime, the cakes of pressed sludge may be used advantageously as a top-dressing, and it may be expected that in this way a considerable quantity of the material will be carted away by farmers; but as the demand for it is necessarily limited, both as to time and distance, an extensive permanent dumping ground must usually be acquired in the neighborhood of all large works. Low or marshy land is generally selected for this purpose, the cakes being conveyed thereto in tramway cars from the pressing house; and if the daily product is large, the transportation is done by trolley or by a small steam locomotive. It will thus be recognized that the disposal of the sludge from large precipitation plants is a serious and expensive matter when other simpler means, such as those proposed and described above, are not applicable. As to the propriety of dumping the fresh, wet sludge into the lake far from shore, it may be remarked that little can justly be said in opposition on account of its great depth and magnitude. There is no scruple about dis¬ charging therein the crude sewage from Buffalo, Toronto and many other smaller communities situated on its shores and tributaries. There is also no essential difference in composition between the sludge and the sewage, except in respect to dilution, and this is very quickly changed after the tank-barge is emptied. This method of disposal has been practiced by London since 1888 and by Manchester since 1897, and the following description of the results near the mouth of the Thames, given on page 214 of Dibdin’s treatise on the “Purification of Sewage and Water,” London, 1903, may be of interest: “The discharge takes place on the Barrow Deep, commencing at a point 10 miles east of the Nore, and proceeding thence from 5 to 10 miles down that channel. * * * As the sludge is discharged from the bottom of the vessel, ■some 10 ft. under water, and is thus agitated by the action of the twin screws (of the tank steamer carrying 1,000 tons), the diffusion of the sludge in the water in the wake of the vessel is very complete, so much so that when there is but a slight ripple, the visible effect of the sludge is lost after a few minutes. The sand and earthy matters soon separate by subsidence, and the animal and vegetable debris is rapidly consumed by the organic life in the sea water. This is evidenced by the fact that, although over 20,000,000 tons 28 of sludge have now (1894) been deposited in this part of the estuary, the most careful microscopical examination and chemical analysis fail to detect more than the merest trace of the mineral portion of the sludge, either ins dredgings from the bottom of the channels or on the surface of the sand¬ banks, which are now as clean as in 1888.” • On comparing the costs of sewer interception and chemical treatment with the corresponding ones for flushing the river, and remembering that plain sedimentation will probably be sufficient for a long time, it will be seen- that the flushing projects are much more expensive under the same conditions. Furthermore, these projects are comparatively inelastic from a financial point of view, as a very large outlay is involved in the outset for a great reservoir or a long tunnel in anticipation of the future growth of population; whereas; in the case of the proposed purification works, the payment of a considerable portion of the ultimate cost and yearly expense can be deferred until made necessary by circumstances. It may also happen that certain trade wastes will hereafter be produced in the city, which will require a much larger dilution for the crude sewage than was estimated above, but which may be favorable for sedimentation or chemical precipitation; and if this should! ever occur, the flushing apparatus would be at a serious disadvantage. AVAILABILITY OF CLARIFIED SEWAGE FOR PRODUC¬ TION OF POWER AND IRRIGATION. ✓ There are, however, other good reasons for adopting the plan of clari¬ fying the sewage which has been outlined above. At one of the sites still available for the works, and which was pointed out to the City Engineer,, the fall to the river is at least 140 feet. The estimated future dry-weather flow of sewage from the seven principal outlet sewers to be intercepted as previously described is 26,600,000 gallons per day; and as the, rate at which sewage is produced is usually about twice as great during the day-time as at night, this daily quantity will accordingly be equivalent to a flow of approxi¬ mately 60 cu. ft. per second for 8 hours and 30 cu. ft. per second for 16 hours of the day. With an effective head of 140 ft., these volumes of clarified sewage will yield respectively 700 and 350 HP. on turbine shafts of a power station at the edge of the river, about one-half mile distant from the precipita¬ tion tanks. As already indicated, this power can be transformed into electrical energy and transmitted economically to any desired locality a few miles distant with a loss of not more than 20 per cent., so that the future available power in dry weather at such point will be at least 560 H.. P. during the day and 280 H. P. during the night. These quantities may safely be regarded as minima, since the sewers will doubtless receive an appreciable volume of ground water by infiltration. Of the power so produced, about 70 H. P. will be required for the aforesaid pumping station of the West Side Trunk Sewer, and about 15 H. P. will be needed for pumping sludge and electric lighting at the purification works, so that at least 475 H. P. during the day-time and 195 H. P. at night will ultimately become available for other purposes. It must also be remembered that with duplicate machinery this surplus power 29 •will be constant and reliable every day in the year, and is therefore of the highest market value. It can be impaired only by the failure of the city’s water supply, which is a contingency too remote for serious consideration. For the development of 700 H. P. at the said power station throughout the year, it will only be necessary to enlarge the building and power apparatus previously described, and to make permanent the employment of several of the otherwise temporary attendants at the purification works and West Side Trunk Sewer pumping station. During an average of eight months in the year the crude sewage would thus be merely screened at an additional yearly cost of $3,600, and the constant employment of the various attendants at the three power stations for the same period would involve an additional expense of $10,000. The cost of the additional power plant in duplicate will not exceed $50,000, and if an allowance of 9 per cent, thereon be made for interest, maintenance and sinking fund, the total additional yearly cost of producing the said quantities of surplus permanent power will be $18,100. Reckoning that the surplus of 475 H. P. in the day-time continues for only 8 hours, while that of 195 H. P. at night continues for 16 hours, each day in the year, the total yearly output of surplus power will be about 1,894,000 kilo-watt hours of electrical energy. This should have a wholesale market value to the city’s lighting and traction interests of at least 1.25c. per kilo¬ watt hour, and thus produce a revenue of $23,675, or a net annual profit of $5,575, which could be applied to reducing the cost of operating the sewage purification works during four months of the year. It may be added that this estimate has been made on a very conservative basis, and that if such a market for all the surplus power produced by the sewage can be found, both the quantity and the net profit will be considerably increased by making use of the intercepted storm water which is carried to the purification works. Another use that might be made of the clarified sewage is for cheaply irrigating an area of from 10,000 to 15,000 acres of sandy farming land in the township of Irondequoit. By this means the productiveness of the land will be greatly increased, and it may safely be presumed that after a demonstra¬ tion has been given on the land at the precipitation tanks, the surrounding farm-owners will unite in providing a distributing system at their own expense. Probably preference will be given to the clarified liquid, so that no saving in tank capacity or sludge disposal will occur from such use; but the lower river will then be relieved of the duty of diluting the quantity of •clarified sewage so diverted. The manner in which this can be accomplished is as follows:— With a Read of 140 ft., one-third of the effluent from the tanks will produce suffic¬ ient power to pump the remaining two-thirds of either the screened or clari¬ fied sewage to an elevation in a stand-pipe high enough to allow it to be distributed by gravity through a system of pipes and open ditches in the territory mentioned. The cost of the necessary additional power plant, centrif¬ ugal pumps and stand-pipe would not exceed $25,000, and there would be no increase in the annual operating expenses, as the irrigation service would be performed and required only during the four months of the dry season of each year. It is, however, not expedient for the city to construct and operate the distributing system, and therefore this part of the work would have to be done by an organization of the land-owners, under positive agreement to take a definite quantity of liquid each week during the season. 30 Of the comparative merits of these two plans for utilizing the sewage, little further need be said. Both involve co-operation with private interests, and unless the strongest assurance is given that the agreements will be faith¬ fully observed for a long term of years, the initial outlay on the part of the city for the necessary additional plant cannot be justified. DISCHARGE OF THE CRUDE SEWAGE DIRECTLY INTO LAKE ONTARIO. The conditions under which the crude sewage of the city can be discharg¬ ed directly into Lake Ontario will next .be considered. On the west side of the river, the shortest distance to the lake, from a point in Lake Avenue ■opposite Norton Street, is about 5.22 miles, while on the east side it is 4.43 miles in a direct line from the intersection of Norton and Hollenbeck streets. On referring to the map of the lake, it will be seen that from Manitou Point to Irondequoit Bay the shore has a southeasterly direction, and then turns abruptly to the northeast for a distance of 8 miles to a point near the east line of Monroe County, thus forming an extensive indentation. The distance in a straight line between the two points named is 19 miles, and from this line to the bar between the lake and the bay the distance is 5 miles, while at the mouth of the river it is 4 miles. Near the shore the water is quite ■shallow, but it gradually becomes deeper until a depth of 35 feet is reached at a distance of 5,000 ft., and beyond that distance the depth increases to a maximum about 700 feet. The width of the lake in this locality is about 46 miles, and the prevalent winds are from the northwest. At the mouth of the river the water is generally shallower than else¬ where, and a channel for navigation is maintained by two parallel jetties about 2,600 feet long. For a distance of two miles on each side of the river, the shore of the lake is thickly lined with cottages and summer resorts, and similar settlements are in process of development at various other places between Manitou and Nine-Mile points. It is therefore very apparent that the delivery of large quantities of crude sewage at or near the shore would not be tolerated, and that if it were done at all, the foul liquid would have to be conveyed in a pipe not less than 5,000 ft. long into water at least 35 ft. in depth. It is also highly probable that unless the pipe were made much longer than 5,000 ft., this mode of disposing of the sewage would soon give rise to serious complaints, with the result that some process of purification would have to be established under far less favorable conditions for economy of operation than those existing near the northern boundary of the city. Owing to these circumstances, as well as to the long distance from Norton Street to the lake, the exclusion of practically all the sewage from the river would make it expedient to collect the dry-weather flow from various outlet sewers, as previously indicated, into a single conduit on the east side of the river; and as such an undertaking would be expected to remain adequate for at least 20 years, at the end of which time the population will probably be not less than 275,000, it would be prudent to make the discharging capacity of such conduit about 150 cu. ft. per second. This quantity represents the estimated volume of sewage at the rate of 100 gallons per head daily, with the addition of an average of 2.5 times as much storm-water. 31 In my former report several routes for such an outlet sewer were con¬ sidered. The most expedient one is from the intersection of Strong and Hollenbeck streets to a point on the shore about 1.5 miles east of Summer¬ ville. It has a length of about 23,000 ft., or 4.36 miles, and the grades of the conduit vary from 1 in 300 to 1 in 1,000 for the greater part of the way. With a discharge of 150 cu. ft. per second, the diameter would thus range from 5.5 to 7.0 ft.; and with present prices of labor and materials, the average cost would be about $14.00 per lineal foot, including a moderate allowance for right of way and land damages where the location is in fields. At this price the cost of the masonry conduit would be $322,000, to which $3,000 should be added for manholes. Near the shore the land is approximately 50 ft. above the ordinary surface of the water, and most of this height must be utilized to overcome the fric¬ tional resistances in the terminal outlet conduit to a point as far out in the lake as practicable. To avoid suits for damages caused by pollution, this point should be located at least 7,000 ft. from shore, where the depth of the water is about 45 ft., in order that thorough sedimentation of the sus¬ pended matter and diffusion of the dissolved matter may take place. Deep borings for wells in this locality indicate that the subsoil consists of fine silt interspersed with veins or strata of quicksand, and consequently tunneling operations under the bed of the lake will be extremely expensive and hazardous. It therefore follows that the sewage should preferably be conveyed from the shore in a submerged pipe, laid in a dredged trench so as not to cause interference with navigation and be protected from injury and displacement by wave action, dragging anchors and wrecks. The surface of the lake, moreover, is subject to annual and seasonal fluctu¬ ations of elevation, due to excess or deficiency of rainfall, and also to the action of strong winds. Since 1860, the extreme seasonal variation has been 5.5 ft. from the maximum in the summer of 1870 to the minimum in the winter of 1895-96, and a temporary rise of two feet or more may be caused' by northerly gales. In 1904 there was a seasonal rise of 3 ft. from January to July, which is the largest that has been observed since 1892. In computing the size of the outlet pipe, allowance must therefore be made for a high elevation of the surface of the lake, as well as for a length of about 600 feet from the shore inland; and it will accordingly be assumed that the pipe is- 7,600 feet long, with an effective head of 40 feet, and a discharging capacity of 150 cu. ft. per second. For a riveted steel pipe these conditions require a diameter of 5.0 feet. Of the total length, about 6,600 feet would be provided with either flexible or flanged joints at intervals of 110 ft., and be laid in the dredged trench either from scows or with the aid of divers. At its end the pipe would be enclosed in a submerged crib and equipped with three 34" outlets, to distribute the sewage in different directions. The remaining 1,000 ft. of the pipe at the shore would be laid in the usual manner in an open trench, of which three or four hundred feet would be protected by a suitable coffer-dam. The estimated cost of this outlet pipe with its accessories is $195,000, and if that of the 23,000 feet of masonry conduit from Strong Street to the lake shore is added, along with 10 per cent for contingencies, the sum will be $572,000. This estimate contains no provision for a considerable area of land near the shore of the lake for settling tanks or other partial purification 32 "works that may become necessary in the future, and it. will therefore be prudent to anticipate that such works will ultimately be required. For this purpose at least 100 acres should be acquired in order to avoid complaints from offensive odors; and as the land can doubtless be obtained now on more favorable terms than hereafter, its cost should properly be included in the estimate. The undersigned has no definite knowledge of the market value of the land in question, but will assume that such a tract can be pur¬ chased for about $38,000. It will also be assumed that an expensive purifi¬ cation of the sewage at the lake shore will not become necessary within the next 30 years, so that the total cost of this method of disposal may be taken at $610,000, exclusive of the system of intercepting pipes and conduits from the upper falls to the intersection of Strong and Hollenbeck streets. In view of the existing cottages and summer resorts on the shore of the lake, it will be reasonable to consider that the crude sewage must at least be freed from the coarse matter carried in suspension before it can be dis¬ charged at a distance of even 7,000 feet from shore. This extraction of coarse solids must be carried on continuously throughout the year in order to pre¬ vent the beach from becoming offensive, and hence the plan entails a constant operating expense for attendance at the screens and disposing of the matter "by burial or burning. As the work must be done at all hours of the day, three crews of attendants will be required, and a very moderate estimate •of the annual cost for labor and maintenance of the screening plant is $8,000. By this plan, however, no power can be developed with the sewage, and it will become necessary to operate the pumping station of the West Side Trunk Sewer by steam, or its equivalent. If the station is equipped with steam engines and boilers, the operating expenses for four months per year will be $4,000, as previously stated. This annual sum must obviously be taken into account in comparing the costs of discharging the sewage into the lake with those of chemical or sedimentation treatment and the devel¬ opment of electrical power, as in the operating expenses for the latter the cost of all necessary attendance for the said pumping station was included. The yearly charge for the operation of the lake plan, including said station, will thus be at least $12,000. The arguments in favor of this plan of sewage disposal are as follows :— In passing through the long submerged outlet pipe, the sewage will acquire nearly the same temperature as the water of the lake at the depth of 45 ft. According to the observations made by Mr. George H. Benzenberg, C. E., in connection with the submerged 60-inch intake pipes from Lake Michigan for the water supply of Milwaukee, the temperature of the lake water at the depth of 60 ft. ranges throughout the year from 37° to 42° F., thus varying but little from that (39.2° F.) at. which fresh water attains its maximum density. In Lake Erie, near Cleveland, Mr. George G. Whipple, C. E., found that during the spring of 1904 the temperature of the water was substantially the same at all depths, being about 36° F., while during the summer of that year it rose to 70° F. at a depth of 45 ft. and remained practically uniform, but that between 45 ft. and 55 ft. it fell rapidly and was 50° F. at a depth of 60 ft. Definite observations of the temperature at dif¬ ferent depths in Lake Ontario at Charlotte are not available, but it is well known to divers that in summer the water at a depth of 40 ft. is much colder than 70° F., and is probably not more than 55° F. 33 At this depth and summer temperature, there will be no tendency for the screened sewage to rise to the surface of the lake, and a rapid sedimenta¬ tion of the suspended matter will take place. Putrefactive processes will' also be greatly retarded and the dissolved organic matter will be thoroughly diffused in a vast volume of water by the action of the winds and currents. No disturbance of the accumulating sediment will usually occur by wave action until it rises to within 30 ft. of the surface, when the upper layer of the mass will be carried away to settle in another place where the water is deeper. In the course of time portions of the organic matter in the deposit will disappear entirely by natural microbic agencies, and if the- coarse mineral matter is abstracted from the sewage by means of a relatively small detritus tank before it enters the outlet pipe, the tendency to form a sand bank at the point of discharge will be minimized. The worst that can happen in this respect will be the necessity for some dredging in the locality at intervals of a few years. A serious pollution of the lake water is not to be feared, as it has not occurred in the past from the sewage of all the cities on the great lakes. The Niagara River delivers into the western end of the lake more than 220,000 cu. ft. of highly oxygenated water every second, and the St. Lawrence River carries this away at the eastern end, so that a slow but steady current to the east is constantly in operation. It has also been found by long experi¬ ence with the water supplies of the cities on the Great Lakes that when the intake is located tw r o or three miles above the mouth of a sewage-polluted’ river, no contamination of the water ensues. This matter accordingly becomes of significance only if the city should grow to such magnitude as tO' render it necessary to resort to the lake for a future additional water supply; and in this event the intake would doubtless be located west of Manitou Point, which is about 9 miles west or above the mouth of the said outlet pipe. Another strong reason for adopting the plan in preference to chemical treatment of the sewage near the northern boundary of the city, is its simplicity of operation and the relatively small annual operating expenses' which it entails. The number of permanent and temporary employees is small, and the work is not associated with dangers of any kind. Futhermore,. the topography of the region along the shore from Windsor Beach to- Irondequoit Bay, and extending for nearly two miles inland, is so broken by numerous deep gullies that it is not adapted for even village development; and hence it cannot be alleged that an impairment of the prospective value of the land for residence purposes will result, even if future conditions should compel the city to subject the sewage to a sedimentation process before dis¬ charging it into the lake. The project is therefore free in large measure from the objection to the establishment of a purification plant near the present city limits. On the other hand it may be argued that in consequence of future legislation or litigation, the sewage will eventually have to undergo- further treatment before flowing into the outlet pipe. In that case, the same system of sedimentation tanks already described must be provided and oper¬ ated as a preliminary to some still more efficient method of purification; and as the land near the shore of the lake is not adapted to sewage irrigation or filtration, the site should be so chosen and the works so planned as to afford ample space for the various artificial filter beds and the disposal of the- 34 sludge. It must also be remembered that in this location there is no available fall for generating water-power with the sewage, and that any power that may be needed for pumping and lighting must be derived from steam. These considerations, coupled with the manifest necessity of constantly operating the plant, will make it clear that the annual expenses of treating the sewage will be considerably greater than at the location previously indicated. In the latter case the lower river with its large channel, its length of six miles and its usually sluggish current, acts as a vast settling tank in which the dissolved and finely-divided organic matter, along with the sewage bac¬ teria, are constantly attacked by another class of bacteria and organisms, and are soon changed into harmless chemical compounds. If the pollution is restricted to proper limits, these natural agencies are fully as efficient and reliable as any artificial device for refining the effluent of a sedimentation or precipitation process, so that the river becomes a highly important and valuable adjunct to such methods of sewage purification. It practically takes the place of a large number of sprinkling filters or contact beds with their costly accessories, so far as the quality of the water at Charlotte is con¬ cerned. It must also be remembered that it is utterly impracticable to render the water potable within the city limits, as the river must always continue to receive the storm drainage of the city, along with that of the remainder of its large watershed; and if it is relieved during the season of low-water of the greater part of the offensive suspended matter in the sewage, as above out¬ lined, it will certainly be able to deal at such time with the remainder. As the flow increases, a larger amount of pollution will be permissible, until the river finally reaches a stage at which experience has demonstrated that the whole of the sewage can safely be admitted without treatment. With a precipitation plant located near the present northern boundary of the city,, the aim should be to maintain the quality of the water at the mouth of the river at a nearly uniform standard of relative purity throughout the year, by taking advantage of the varying rates of flow and the natural processes of purification just indicated, at the same time keeping the portion of the stream above its mouth in such condition that it will not be offensive to sight and smell. OTHER METHODS OF SEWAGE TREATMENT. In my former report, and also in the foregoing, reference was made to> other methods of purifying sewage, and a brief consideration of such will now be offered. Concerning irrigation and intermittent filtration of sewage through natural porous soil, combined with profitable agriculture, it can be said that on a large scale this method involves entirely too much area and skilled labor for its successful practice by American municipal administra¬ tions, and that satisfactory results can be expected only when the work of distributing the sewage is performed by an association of private land- owners. In any event, conditions of weather and crops may often occur, especially in the cold season, when an independent outlet for the sewage becomes necessary; and if the city incurs the expense for the latter, it will 35 generally be found that the same can be made available during the entire time with less additional cost than by acquiring and cultivating the requisite area of farming land. This remark also applies to the case of intermittent filtration through natural soil without cultivation. The biological or bio-chemical methods of purifying sewage that have been developed within the past ten years involve four distinct procedures. The first is the removal of the coarse organic and mineral solids ; the second is the removal of most of the fine matter in suspension, or the clarification of the liquid; the third is the oxidation of the dissolved organic matter to such extent as to render the liquid non-putrescible for a few days in summer; and the fourth is the disposal of the coarse solids and fine sludge. By the septic tank, a relatively small part of the suspended organic matter becomes liquefied, and another small part is converted into gas which escapes into the atmosphere. In most cases, however, a very considerable portion of the suspended organic matter remains in the tank in the form of scum and sludge which must be removed from time to time. The liquid effluent is usually turbid and offensive in odor, and when it is sprayed or poured in thin films over a mass of very porous material like screened gravel or broken stone for the purpose of oxidation, the odor is liberated much more exten¬ sively than from open settling tanks containing the original crude sewage. In this way a nuisance is caused from large works which depends greatly on the weather, the character of the sewage, its degree of septicity, and the efficiency of the preparatory process of clarification. In the septic method of treatment, the sewage remains in the tank from £ to 16 hours, and hence a much larger storage capacity is required than for plain sedimentation. The cost of the plant is thereby greatly increased. Recent experiments, however, have shown that satisfactory results can often be attained by oxidizing in the manner indicated above the effluent from sedi¬ mentation tanks after only two or three hours, but this seems to depend on the composition of the sewage and the degree of cleanliness maintained in the entire system of sewers. If the pipes and conduits are not kept free from •deposits, septic action takes place therein, and the difficulties of treatment are at once augmented. Certain trade wastes, such as those from breweries and distilleries, also tend to increase the odors, while others which decompose slowly intensify the troubles of sedimentation and sludge disposal. The sew¬ age of each city thus has a specific character which varies with the nature and magnitude of the industries pursued, and hence a method of treatment that is successful at one time may require extensive modification at another. The process of oxidizing the effluent from a sedimentation or septic tank is usually done by exposing it to the action of the air and certain micro¬ organisms contained in so-called “contact beds” or “sprinkling filters,” which are essentially large masses of very porous inorganic material like coke, furnace slag, pebbles and broken stone. Experiments at Columbus, O., have shown that beds of this kind 5 ft. in depth can effect the oxidation of only a limited quantity of dissolved organic matter, and that the liquid should not be applied at greater rates than 700,000 gallons per acre daily to contact beds, and 2,000,000 gallons per acre daily to sprinkling filters. In both cases the beds must obviously be thoroughly underdrained. If contact beds are used, they can be filled without much fall or loss of head directly from the sedi¬ mentation tanks; but in the case of sprinkling filters, the top of the beds must 36 be from 4 to 8 feet lower than the surface of the liquid in the effluent channel from the tanks in order to form a proper spray. This latter condition thus involves a location on sloping ground, or else the cost of deep excavation for constructing and underdraining the filters, or the cost of pumping the liquid after leaving the sedimentation tanks. ^ It should also be noted that the effluents from contact beds and sprinkling filters are usually somewhat turbid, and that if a clear water is desired, they must be further purified by filtration through natural or artificial beds of sand or fine gravel, or by settling for several hours in another set of tanks. This finishing process involves an additional fall or loss of head, as well as a large additional cost for filters or tanks. If sand filters are used, the rate of application will probably not exceed 1,000,000 gallons of the effluent from the final settling tanks per acre daily on the average, as the material is apt to- become clogged. For the treatment of the sewage of Columbus, O., the recommendations made in November, 1905, were as follows: “1. Preliminary clarification of the sewage in basins holding on an average about an 8-hour flow, and operated on the basis of the septic treatment. 2. Purification of the septic effluent to a non-putrescible state by sprinkling filters at an average net rate of 2,000,- 000 gallons per acre daily. 3. Final clarification of the effluent of the sprink¬ ling filters in basins holding an average flow of about two hours. This process produces a non-putrescible effluent of satisfactory appearance, and from which about 90 per cent, of the bacteria in the raw sewage are removed.” Similar recommendations were made in May, 1906, for the treatment of the sewage of Baltimore, Md., with the addition that the effluent from the last set of settling basins should be still further purified by intermittent filtra¬ tion through artificial sand filters, “by which substantially all the remaining bacteria and fine suspended matter are removed, so that the final effluent is; clear and has obtained the highest practicable degree of purity.” As to the costs of these methods of treatment, it is obvious that they will be much greater than those of the simpler method which is, in my opinion, ample and entirely satisfactory for Rochester. For the proposed Baltimore- plant to purify 75,000,000 gallons of sewage per day, the estimated cost was $3,283,250, exclusive of the cost of the necessary land, and the annual operat¬ ing expenses were $115,500, exclusive of interest and other fixed charges. At the same rate per million gallons, the cost of a similar plant for purifying 27,000,000 gallons of sewage at Rochester would be about $1,204,000, exclusive- of the necessary land and the system of conduits for intercepting and con¬ veying the sewage to the works; and if the plant were adapted to purify an’ average of 34,000,000 gallons of sewage and intercepted storm water per day from the assumed future population of 275,000, the costs would be still greater. In view of the great expense of these refined modern methods of purify¬ ing sewage, and the availability at Rochester of much cheaper ones that will doubtless prove to be entirely satisfactory for many years, the writer has deemed it unnecessary to submit here other details relating to the construc¬ tion, operation and costs of contact beds and sprinkling filters. To those- familiar with the capacity of the river and lake to absorb sewage inoffensively,, the necessity for resorting to an extreme purification does not appear; and 37 it has also been assumed that any acceptable plan for dealing with the sewage of the City should involve no expenses that can reasonably be avoided. COMPARISON OF COSTS OF SEWAGE DISPOSAL. w c It has been attempted in the foregoing to describe briefly the various plans that seemed practicable to the writer for improving the sewage-polluted con¬ dition of the Genesee River from the upper falls to Lake Ontario, together with the probable costs of construction and operation, based on an assumed population of 275,000 in the year 1925 ; and it now becomes of interest to make a short summary of such methods and costs. These plans fall into two general classes, one involving an adequate increase of the minimum flow of the river above the City, so as to allow the existing principal outlet sewers to continue to discharge their contents directly into the stream as at present, and the other involving an interception and removal of the dry-weather flow of said sewers to other localities. The first class embraces two plans, while the second embraces four. 1. Constant Dilution by Means of Storage Reservoir. Cost of storage reservoir at Portage or Mt. Morris, as per estimates of State Engineer in 1894 and 1896, from $2,500,000 to $2,600,000. These esti¬ mates should be increased considerably to meet the greater present values of lands, materials and labor. This plan cannot be carried out independently by the city, and it has also a limited applicability as the minimum flow of the river will then not become more than 1,000 cu. ft. per second. Even if satisfactory agreements could be reached between the city, the owners of the water-power, and the State in behalf of the canal interests, the time needed for the execution of the work is much longer than seems to be tolerable. The plan is accordingly rejected. .2. Periodical Flushing by Smaller Storage Reservoir. Cost of storage reservoir of relatively small capacity near Mt. Morris .at least $900,000. This plan also involves agreements with owners of water¬ power and the State, and cannot be recommended on account of the improb¬ ability of attaining satisfactory results. .3. Constant Flushing of the Lower River by Pumping from Lake or Bay. Cost of 12 ft. tunnel 4.66 miles long and pumping plant to secure a 20-fold dilution of the sewage from a future population of 275,000, $1,455,000; annual •operating expenses for 120 days per year $20,600. With a 14-fold dilution of the sewage, the cost of 10 ft. tunnel and smaller pumping plant would be $1,214,000, and the annual operating expenses for 120 days per year $16,000. In both of these cases, the cost of intercepting the dry-weather flow of sewage from the several outlet sewers which discharge into the river above the lower falls, has not been included. This interception may become a very important feature hereafter, and if it is not done, the condition of the .8,500 ft. of river channel between the upper and lower falls may become 38 intolerable. The least expensive plan of such interception would be by means of the system of pipes previously described, but terminating at the shaft of the West Side Trunk Sewer, and costing approximately $210,000. This sum should accordingly be added to the above estimates, thus making the same respectively $1,665,000 and $1,424,000. 4. Clarification of Sewage by Sedimentation at Works Located 1.25 Miles North of Norton Street. This plan involves the interception of the dry-weather flow of sewage from all the principal outlet sewers, except the one for the northern district •of Lake Avenue. Cost of system of intercepting pipes and conduits from upper falls to intersection of Strong and Hollenbeck streets, including West Side Trunk Sewer pumping station and 10 per cent, for contingencies, $344,- ■300; cost of conduit from Strong Street to sedimentation plant, and also latter complete, adapted to treatment of 34,000,000 gallons of sewage per day, including electrical power development for 100 H. P. and transmission line to West Side Trunk Sewer pumping station, $324,000; assumed cost of 150 acres of land for plant and other easements, $101,700; total cost $770,000. Operating expenses during 120 days per year, for sedimentation of an aver¬ age flow of 34,000,000 gallons of sewage and storm water per day, disposal of sludge and operation of West Side Trunk Sewer pumping station by ■electrical power, $21,900; but as the time named may be exceeded somewhat, it will be safer to assume that the yearly operating expenses will ultimately be $25,000. With respect to this plan, it may be urged that the establishment of a sewage purification works so near to the present northern boundary of the •city will tend to stop the growth of the city in this direction; also that the partial purification contemplated will eventually become inadequate unless the dry-season flow of the river is largely increased either by water-storage ■operations, or by surplus water from the Barge Canal. It may likewise be •expected that if such storage operations are carried out in the future, and the sewage is only partly purified, the city will be required to pay a portion of the expense of increasing the minimum flow of the river. In this event the •estimated cost of the plan named would not represent the ultimate cost. 5. Clarification of Sewage by Chemical Precipitation at Works Located 1.25 Miles North of Norton Street. This plan is the same as the preceding one in all respects, except that the •ultimate annual operating expenses are $36,000. Concerning this project, it may be said that a considerably higher degree of purification will be effected than by plain sedimentation, and hence that a correspondingly smaller charge should be made against the city for the benefit accruing to it in consequence •of increasing the dry-season flow of the river. While the equities in the case might readily be determined, it is nevertheless uncertain how the interests •of the city would be affected by legislation. The plan is therefore invested with some risk that the estimated cost will ultimately be exceeded, but such risk is manifestly smaller than in the preceding case. Both of these plans, however, possess the great merit of being elastic 39 from a financial standpoint, or capable of development from time to time as circumstances may require. This is an important consideration that should not be overlooked. 6. Screening and Discharging Sewage into Lake Ontario, East of Windsor Beach. This plan also involves the interception of the dry-weather flow of sewage from all of the principal outlet sewers, except the one for the northern district of Lake Avenue. As no power can here be generated from the sewage, the discharge of the West Side Trunk Sewer must be pumped by steam power for 120 days per year at a cost of $4,000. The screening must be done throughout the year at a cost of $8,000. Cost of system of intercepting pipes and conduits from upper falls to intersection of Strong and Hollenbeck streets, including West Side Trunk Sewer pumping station and 10 per cent, for contingencies, $344,300; cost of masonry conduit from Strong Street to shore of lake and subrnerged outlet pipe, $572,000; assumed cost of about 100' acres of land surrounding screening and detritus tank, $38,000; total cost $954,300. Annual operating expenses as above, $12,000. In this project, the great advantage is secured of excluding the normal flow of sewage from the river throughout the entire year, thereby rendering the lower portion of the stream unquestionably salubrious and attractive for pleasure navigation. The sewage will be permanently out of sight, and judging from the experience gained in other large cities on the Great Lakes, no serious contamination of the lake water or pollution of the beaches will ensue. It is also very probable that a considerable reduction of cost can be secured by the use of a wooden stave pipe for the long submerged outlet in: place of the riveted steel pipe. CHOICE OF PLAN. In view of the fact that any water storage scheme on the Genesee River and its tributaries cannot be carried out by the city independently, and also- owing to the long time needed therefor, the first and second plans described above cannot be considered, and the choice is therefore restricted to the remaining four. To facilitate comparison, the annual operating expenses may be capitalized at 5 per cent., and the corresponding principals added to the estimated costs of construction and land in each case, whereby the following, results will be obtained. It should also be noted that these results apply to the conditions presumed to exist about 20 years hence when the population reaches 275,000, and embrace the costs of the system of intercepting pipes and conduits. For 20-fold dilution of sewage by pumping. $2,077,000* For 14-fold dilution of sewage by pumping. $1,744,000 For clarification of sewage by sedimentation. $1,270,000 For clarification of sewage by precipitation. $1,490,000 For discharge of sewage into Lake Ontario. $1,194,300) 40 It is understood that in each instance the annual operating expenses mentioned do not include the usual fixed charges consisting of interest on capital expended for construction and land, depreciation of plant, taxes, insurance and sinking fund. From this comparison it is seen that the plan of discharging the sewage into Lake Ontario is the least costly, and probably also the most satisfactory one, in view of the existing prejudices against sewage purification works and the utilization of either screened or clarified sewage for agriculture. If these prejudices could be overcome and the citizens would be content with an inoffensive contamination of the water of the lower river, the plan of par¬ tially purifying the sewage during the dry-season at a point about 1.25 miles north of Norton Street would become more expedient for adoption, as the accumulation of savings in annual operating expenses and fixed charges on the much smaller costs of construction during 20 years or more would over¬ balance the apparent difference shown above. In further support of the latter process, it may be remarked that advances in the art of treating sewage will doubtless be made in the next 20 years, whereby the great expense of sprinkling filters or contact beds, and the subsequent clarification of the effluent, will be avoided when a large river is available as an outfall. It may also be expected that the dry-season flow of the river will be increased by a considerable quantity of surplus water from the Barge Canal, which will assist very materially in the required dilution of the effluent from the sedimentation tanks; and if the project of storing water at Portage or Mt. Morris is meanwhile carried out, there will be no necessity for any treatment of the sewage until the population greatly ■exceeds the limit mentioned. Should any of these expectations be realized, it will follow that the plan of treating the sewage in the manner indicated near the present northern boundary of the city will involve the least aggregate outlay, and will also have the highest salvage value in case of voluntary abandonment or enforced modification. Thus if it should ever become necessary to subject the crude sewage at the lake shore to any better treatment than screening, such work can manifestly be done far more economically at the site first named. It may also be added that for the performance of such work, the said site is much better adapted in all respects than any other site in the entire region. In the plan for carrying the sewage to Lake Ontario, it was deemed proper to provide for intercepting the dry-weather flow and a part of the storm water of all the principal outlet sewers on both sides of the river, except the ■one for the northern district of Lake Avenue. Any permanent modification of this plan by permitting some of these outlet sewers to continue to dis¬ charge into the river, and thereby reduce the size of the conduit to the lake shore, is not advisable, as the difference in cost is not large enough to out¬ weigh the disadvantage of maintaining a continuous pollution of the stream, ■especially between the upper and lower falls. The same remark is still more applicable to the rival plan of partially purifying the sewage at the aforesaid site. This statement, however, should not be construed to mean that it is imperative to perform the whole of the work of interception at once, or even in a single year, but rather that it be planned with the view of embracing the .sewage of practically the entire future city, and proceed from time to time 41 as circumstances may require. It will naturally begin with the diversion of the normal flow of the East Side Trunk Sewer, and be followed by the con¬ duit and tunnel to the foot of Avenue B. Next in order will be the inter¬ ception of the West Side Trunk Sewer, if the anticipated industrial devel¬ opment of the western part of the city and the adjacent part of the Town of Gates takes place; otherwise the next step will be the interception of the Platt Street and Spencer Street outlet sewers. The last step is the intercep¬ tion of the Central Avenue and Front Street outlet sewers, and perhaps, also the Lake Avenue outlet. CONCLUSION AND RECOMMENDATIONS. After careful consideration of the several plans that have been described' and discussed in the foregoing, the undersigned has reached the conclusion that preference should be given to the project for discharging the crude sew¬ age of the city into Lake Ontario. Although somewhat more expensive in first cost than the plan involving sedimentation and chemical treatment, it has the great advantage of simplicity of management and independence of the exercise of constant skillful supervision. The latter is not always available,, and its absence for any reason may lead to unpleasant results, both with respect to the condition of the river and to the development of disagreeable odors by the works. Under such conditions the difference in cost may quickly disappear by expenditures for damages and futile experiments. With reference to freedom from the production of offensive conditions at the lake, little further can be said than was set forth above. In the vicinity of the mouth of the river, the water will always be more or less contaminated from the surface drainage of the entire watershed, and it is difficult to see how this will be aggravated materially by the discharge of the screened sewage into deep water so far from shore. It should also be remembered that the outlet pipe can readily be extended to a much greater distance than 7,000 ft. without involving a proportionally greater cost, as a large percentage of the estimated expense for this pipe is for accessory appliances and constructions that will not be needed in making a future extension. Furthermore, the exact location of the mouth of the outlet pipe has not yet been definitely fixed, as the most recent available hydrographic chart of the U. S. Lake Survey showing soundings along this portion of the shore was made several years ago, and it is possible that new surveys will show that a depth of 45 ft. occurs somewhat farther out. It may also be added that the estimates have been made on a sufficiently liberal basis to admit of extending the pipe 1,000 ft., provided that due economy is exercised in the prosecution of the work. As the sewers will continue to discharge storm water in the future, as in the past, it need scarcely be said that proper attention should constantly be given to keep the outlets and the adjacent river channel in good order. This has not been done at the mouth of the East Side Trunk Sewer, in consequence of which the small channel into which it discharges has become very foul. If the channel were dredged out so as to carry at least one-half 42 of the ordinary flow of the river, the unsightly conditions at this place would soon disappear. Attention may also be called to the necessity for a systematic cleaning of the sewers, as neglect in this respect gives rise to offensive emanations at all openings. In cities where the sewers are kept clean by proper flushing, there is little complaint about disagreeable odors from manholes and catch-basins. At the places where sewers pass under the Erie Canal, such flushing can easily be done with canal water at regular intervals by means of siphons, and as the quantity of water needed for the purpose is comparatively small, the consent of the canal authorities for such occasional use should readily be obtained. In concluding this report, the writer takes pleasure in acknowledging his indebtedness to City Engineer Edwin A. Fisher for many courtesies and valuable suggestions, as well as for the preparation of numerous necessary maps and data which have greatly facilitated the study of the problem. Respectfully submitted, E. KUICHLING, Consulting Engineer. Cincinnati, Ohio, Feb. 6, 1907. Hon. James G. Cutler, Mayor, City of Rochester, N. Y. Dear Sir:—The undersigned, having at your request carefully considered with Mr. Emil Kuichling the subject of his report on the disposal of the sewage of the City of Rochester, after a study of the data and information collected by him which have any bearing thereupon and after several long conferences with him and Mr. E. A. Fisher, your City Engineer, in both New York and Rochester and after a personal inspection of the river, the lake and the territory north of the City, and having in mind your instructions to recommend to you the best method, all things considered, for disposing of the sewage of the City of Rochester, we desire herewith to state that we fully concur in the conclusion and recommendations expressed in the foregoing report, as submitted by Mr. Emil Kuichling, being of the firm belief that the permanent exclusion from the river of all sewage proper and the discharge of the same at a long distance from the shore and at a considerable depth into cold water, after all floating material has been previously removed, will, all things considered, secure to your people the most satisfactory solution of the problem. Respectfully submitted, G. H. BENZENBERG, RUDOLPH HERING, Consulting Engineers. 43 CONTENTS Page. Letter of transmittal .3 Population and area of city . 5 Outlet sewers, with tributary areas and population .6 Elevations of sewer inverts at outlets .7 Dry-season flow of Genesee River .9 Disposal of sewage by dilution in river .9 Increasing low-water flow of river by storage .•.12 Increasing low-water flow of river by pumping from lake or bay.14 Quantity of sewage produced in city ..16 Mechanical and chemical clarification of sewage .17 Interception of principal outlet sewers.21 Costs of mechanical and chemical clarification of the sewage of Rochester. .24 Comments on mechanical and chemical clarification process.27 Availability of clarified sewage for power and irrigation.....29 Discharge of crude sewage into Lake Ontario.31 Other methods of sewage treatment ..35 Comparison of costs of various plans of sewage disposal.38 Choice of plan of sewage disposal for city.40 Conclusion and recommendations .42 Concurrence of Consulting Engineers .43 UNIVERSITY OF ILUNOIS-URBANA N30112104323578A