The personnel of the organization conducting the studies with their terms of service was as follows: H. C. McRae, district engineer, February 15, 1915-April 1, 1916. Irving P. Kane, assistant district engineer, March 1, 1915December 1, 1915. Russell E. Takken, draftsman, March 19-December 1, 1915. L. G. Lenhardt, draftsman, March 5-December 1, 1915. The district engineer was responsible for the general conduct of the work and for the treatment plant studies, the assistant district engineer for the interceptor studies and the draftsmen for the compilation of data, detailed computations, and the preparation of the plates. The faithful and energetic services of the members of the office force have contributed largely to the outcome of this investigation, and are hereby acknowledged. It is a pleasure to record here appreciation of the courtesy of Dr. John W. S. McCullough and Mr. Frederick A. Dallyn, B. A. Sc., respectively, chief health officer of Ontario and provincial sanitary engineer of Ontario, in rendering assistance in the studies for the cities in Ontario. The Detroit studies were made in close cooperation with Mr. Clarence W. Hubbell, consulting engineer. and his office force, to whom had been referred, on the part of the city of Detroit, certain questions pertaining to the sewerage and sewage disposal problems of that city. DETROIT, MICH. METROPOLITAN DISTRICT. The city of Detroit lies in such a position that it completely separates from the Detroit River the important villages of Highland Park and Hamtramck, as well as other minor but growing communities, which, because of their topographical position, should logically, and actually do, discharge their sewage through Detroit's sewers. One of these villages is now seeking further relief through the medium of litigation. Sewerage needs will soon be pressing also in the part of the Grosse Point section east of that portion which now drains through the Jefferson Avenue sewer to the Fairview pumping station in Detroit. The villages in this section must drain either through Detroit or directly into Lake St. Clair, or indirectly into Lake St. Clair through small, sluggish water courses; and neither of the last two alternatives are satisfactory, nor will they likely be in the future. Furthermore, so long as the various communities referred to continue to act independently in solving their sewerage problems, it seems certain that there will be friction between them and economic waste, due to duplication of effort and the lack of coordination in planning for future needs. In consequence of the conditions cited, and of the fact that this section is developing and increasing in population very rapidly, it would be illogical to confine a study of the future sewerage problems of this district to the area now included within the corporate limits of Detroit, and such a course would surely be fruitless of concrete results. The establishment of a logical drainage district, termed here for convenience the "Detroit metropolitan drainage district," would be advantageous in (1) Preventing disputes between the various interested communities. (2) Effecting economies and producing more satisfactory conditions generally by means of comprehensive planning. Such a proposed metropolitan district has therefore been selected as a basis for these studies and has been delimited on plate 2 more or less arbitrarily, but with the following points in mind: 1. The inclusion of all territory that is at all likely to become a part of or drain through the corporate city within the next 50 or 60 years. 2. The limitations of position which might tend to prevent existing corporations from being included in such a district. 3. The exclusion of territory beyond the limits of Wayne County. This area, consisting of about 74,580 acres, includes the villages of Highland Park, Hamtramck, and the Grosse Point section. The natural drainage is for the most part through the Detroit River and its tributaries, River Rouge and Conners Creek. A small section in the northeast corner drains through the Milk River to Lake St. Clair, and a narrow strip near the Wayne County line drains to lakes in Macomb County and finally through the Huron River to Lake Erie, just below the mouth of the Detroit River. The topography provides easy slopes, there being, in fact, one section where the average slope for a distance of 4 miles is only 2.2 feet per mile. Approximately one-half of the area is less than 45 feet above mean river level, and about one-seventh is less than 65 feet above the same point. EXISTING SEWERAGE SYSTEM. The sewerage system of Detroit is a combined system which provides outlets for similar systems in the suburban villages of Highland Park, Hamtramck, part of the Grosse Point section, and other outlying sections. All sewers larger than terra-cotta pipe sizes are built of a local brick which is quite porous and not very well formed, but which is reputed to possess good wearing qualities. The quality of workmanship is only fair. Main sewers are for the most part built in the parallel streets which run perpendicular to the general course of the Detroit River, into which they all discharge, directly or through the River Rouge. Their discharge is, with one exception, by gravity, and is in many cases through multiple barrel outlets and at a variety of elevations. In no case, however, is the outlet submerged at ordinary river stages. The plan and profile records of sewers constructed in recent years are complete and may be considered accurate, but the 1ecords of some of the older sewers are reported to be of doubtful accuracy. The storm-water inlets are of the catch-basin type so that a large portion of grit from the streets is prevented from entering the sewers. There is very little territory in the district that can not, from physical reasons alone, have its storm water discharged by gravity. In view of this fact there is onc novel but important exception to the general plan that has been followed in laying out the main sewers. Reference is made here to the Jefferson Avenue sewer, 9 feet in diameter, the discharge of which is pumped at the Fairview pumping station. This station is a large one, located about 2,000 feet downstream from the water-supply intake crib and is designed to pump all the drainage, both sanitary and storm water, from the locality served by the Jefferson Avenue sewer. This district includes a small section of the eastern portion of the city and a part of the Grosse Point section east of the present city limits. The purpose of this arrangement was the protection of the water supply from polluting drainage which might otherwise have been discharged in the vicinity of the water in take, either directly into the Detroit River or indirectly through Conners Creek. PROPOSED MODIFICATIONS. Because of the protective influence of natural currents, it is a mooted question whether the discharge from Conners Creek ever becomes so intermingled with the waters of the Detroit River as to contaminate the present source of water supply. Nevertheless there appears to have been sufficient reason for the establishment of the Fairview pumping station, at least so far as the diversion of the sanitary sewage is concerned. Whether a necessity has existed in the past for pumping the storm water is perhaps an open question, but there is no doubt that the extension of the present protecting measures of pumping both sanitary and storm-water drainage so as to include all of the rapidly growing Grosse Point villages would be prohibitively expensive. It would be better to move the existing water intake to a more distant location in Lake St. Clair. It has therefore been assumed in these studies that the Jefferson Avenue sewer can in the future be used solely for conveying sanitary sewage from the section now served by it, as well as the remainder of the Grosse Point section, and that the storm water from this section will be discharged through other drains into Lake St. Clair, Conners Creek, and the Detroit River. This can be accomplished for the most part by gravity, though there is a small section which will require low-lift pumping. It will also be highly advantageous if, in future developments the storm-water needs of the territory not now provided for be taken care of by large drains constructed for this purpose, preferably in the Conners Creek and Rouge River valleys, and if this ter ritory be provided with collecting systems designed to carry only sanitary sewage. There appear to be attractive possibilities in a project for covering over, and straightening the course of, the lower reaches of Conners Creek. This would provide an outlet following natural drainage lines for the storm drainage from an extensive area, and would permit the utilization of considerable land now unserviceable. This land might be used for park purposes, or the returns from the enhancement of its value as a result of the improvement might be used to cover a part of the expense. Such an improvement would also provide an outlet for the effluent of a treatment plant on Conners Creek at practically no additional expense. POPULATION. The recent rate of growth of the Detroit district has been so exceedingly rapid that it is difficult to make a forecast which can be relied upon with any degree of certainty, for it is hardly possible for such rapid growth to be continued for very long. This community has enjoyed an unusual development in company with the rapid increase of the motor car industry, and, while this industry will no doubt contribute largely in the future toward a healthy growth, it does not seem likely that it will itself grow, in the future, at as high a percentage rate as it has in the past. On the other hand, there are numerous other industries which will contribute substantially to the further development of the district, such as the manufacture of drugs, stoves, and salt products. These are now large, and the last certainly will increase rather than diminish, for the reason that it is founded on a great natural resource of the district. Furthermore, there are apparent advantages of location in the existing and proposed railroad traffic connections with the East and West, the water connection with northern iron ore fields, and proximity to Canadian territory on the natural traffic line from the West to eastern Canada. These factors all point to the conclusion that the past growth and development has rested on solid foundations, and the prediction that future development will be substantial. The population records that are available are complete. They consist of annual censuses of the water board which check with the United States Census figures every 10 years, so that they may be considered sufficiently accurate for all practical purposes, and from them the plot of plate 3 has been prepared, the solid portion representing the growth in population from 1860 to 1915 and the dotted portion the forecast of future growth. This plot is of value in that it assists in the forming of a proper conception of the magnitude of projects now under consideration, but for the purpose of sewer design it was necessary to determine upon a probable distribution of population, or, in other words, a probable density of population for the different parts of the district. It is well known that the density of population varies greatly over the area of a large city, being affected by various factors, such as the localization of industrial activities and commercial centers and the characteristics of the dwellers in the various sections. It may be said in general that the residential sections have been developed in a manner typical of many western cities, in that a large percentage of the dwelling houses are detached houses surrounded by ample lawns and numerous shade trees. In the study of population density a large number of house counts were made on known areas in sections that seemed to be representative of various types of development. It was found also that the report of Barclay Parsons & Klapp on the rerouting of street cars contained a very careful study of population distribution, and this was freely consulted. After careful consider 30568-18-3 Section bounded by the Detroit River, Seminole Avenue, the northern city boundary line, and St. Jean avenue___ 50 Section bounded by the Detroit River, Eighteenth Street, the northern city boundary line, Livernois Avenue, and Artillery Avenue___ Section bounded by Grand Boulevard, the northern city boundary line, Livernois Avenue extended, Joy Road, and Jos. Campau Avenue_‒‒‒‒. Section bounded by the Detroit River, Artillery Avenue, Section bounded by the Detroit River, St. Jean Avenue, AREAS. 50 50 50 40 40 30 30 The total area of the district outlined on Plate 2, as stated previously, is approximately 74,580 acres. In Detroit, as in all large cities, certain sections are given over almost entirely to industrial uses, and other sections are similarly given over to commercial uses. Taking the present city of Detroit as sufficiently representative of the proposed district, an industrial map was studied and computations were made to determine upon a reasonable percentage of the total area to allow for industrial development. It appeared that about 20 per cent of the area should be allowed for this purpose. This is in fair accord with conditions in other cities, and was therefore adopted. Furthermore, certain areas were definitely delimited on working maps in that portion of the district which has already developed sufficiently to render such a procedure reason able. There was little guiding evidence available for the delimitation of a commercial area, but for the purpose of definiteness an area of 500 acres centering around the present commercial section of the city was adopted. WATER CONSUMPTION. All the water used by Detroit and the suburbs supplied by the city is pumped from the Detroit River. The pumping station is located on East Jefferson Avenue near Pennsylvania Avenue, and draws water through a tunnel from a crib which is located just off the head of Belle Isle. The sixty-second annual report of the board of water commissioners for the |