[12] Upon recommendation by the Bureau of Surveys and to conform to the requirements of the above Act, City Councils, by Ordinance approved July 20, 1907, authorized the Department of Public Works to make investigations and required it to report on the problem. (See Appendix A for Ordinance)

In January, 1908, Mr. George R. Stearns, Director, Department of Public Works, and Mr. George S. Webster, Chief Engineer, Bureau of Surveys, were commissioned by the Mayor to visit England and the Continent of Europe to study the methods of sewage disposal then in use. Their report to the Mayor was made under date of February 29, 1908. In the summer of 1913, Mr. George E. Datesman, Principal Assistant Engineer, Bureau of Surveys, visited the principal sewage disposal works of Europe, and his report is given in Appendix E. During the investigations, visits were made by officials of the Bureau of Surveys to the sewage disposal works in course of construction or in operation in a number of cities in the eastern part of the United States.

The investigation and preparation of plans have been carried on by the Sewage Disposal Division of the Bureau of Surveys, under the direction of Mr. George S. Webster, Chief Engineer; Mr. George E. Datesman, Principal Assistant Engineer, and Mr. W. L. Stevenson, Assistant Engineer. Dr. Rudolph Hering, Consulting Engineer, was engaged from time to time for advice.

PRESENT CONDITIONS

Population
(For details of population studies, see Appendix B)

The U. S. Census of 1900 showed that the population of Philadelphia was 1,549,008. The Bureau of the Census estimated [13] that on July 1, 1914, there were 1,657,810 persons in Philadelphia and estimates of the Bureau of Surveys indicate that by 1950 the population will be 3,095,000.

The Water Supply

The water supply of Philadelphia is obtained from the Schuylkill River above Fairmount Dam, and from the Delaware River near the northern (or upstream) limits of the city. All the water is purified by preliminary and slow sand filters and, in addition, each plant is equipped with a liquid chlorine outfit for use in emergencies. The water taken from the Schuylkill is purified at the Roxborough, Queen Lane and Belmont filters, and that taken from the Delaware, which provides three-fifths of the city's water supply, is purified at the Torresdale filters. The good design and efficient operation of these plants provide the city with a superior quality of water which has been a large factor in reducing the typhoid death rate from an average of 60 per 100,000 for 1902 to 1906, to 7.5 in 1914, when all the water was purified. One hundred and five billion gallons of filtered water were delivered to the citizens of Philadelphia during the year 1913, representing two hundred eighty-eight million gallons a day and one hundred seventy-eight gallons per capita per diem.

The Sewer System

The present sewer system is the result of many years' growth. The earliest sewers were merely drains designed to carry off rain water and to lower the level of the ground water. When water closets were introduced, the house fixtures were connected to these drains and the wastes of domestic life thus conveyed to the nearest water courses. As the population of the City increased and the built-up [14] territory extended, it became necessary to build sewers for sanitary purposes, and to collect liquid trade wastes. These sewers became tributaries to the early main drains. The greater part of the present sewer system of Philadelphia is designed for this dual function of carrying both rain water and sewage in the same conduit, which is known as the combined sewer system.

The first kind of work undertaken by the city to prevent the discharge of sewage into the water courses was in 1883, when the construction of an intercepting sewer was begun along the east bank of the Schuylkill River from tide water below Fairmount dam and continued to near the northern boundary of the city, with a main branch extending north along the Wissahickon Creek, having spurs up Monoshone and Cresheim Creek valleys, thus keeping out of the water supply taken from the Schuylkill River all the sewage collected by an extensive system of separate sewers from Manayunk, Roxborough, Falls of Schuylkill and portions of Germantown and Chestnut Hill lying on the Wissahickon and Schuylkill watersheds within the city limits. The rain water from this territory is collected in storm water conduits which discharge directly into the stream.

The second kind of work for the protection of a water-course was a collecting sewer built along the east bank of Cobbs Creek from tide water northwardly nearly to County Line. This collector passes under each combined sewer outlet and suitable connections between them permit the dry weather flow of sewage and the first flush of rain water to enter the collector, while the excess storm water flows into the creek. In the illustration of the outlet of the Thomas Run sewer during construction, there is shown the cut stone slot in the bottom of the sewer through which the dry weather flow of sewage and first flush of rainfall enter the cast iron pipe, and are conveyed to the collector. [15] The photograph of the outlet of the Thomas Run sewer as completed, shows the sewage excluded from the creek. It will be noticed that the bottom of the sewer is entirely dry but during heavy storms the rain water is discharged through this outlet into the creek.

The present sewer system of the city may be divided into three classes:

1. Combined sewer systems carrying sewage and rain water and discharging both into the water courses.

2. Separate sewer systems in which the rain water conduits discharge into the water courses and the sewage sewers discharge into an intercepting sewer parallel to the water courses.

3. Combined sewer systems having transverse collectors for the dry weather flow of sewage and first flush of rain water, while the excess storm water flows on to the water course.

[16] In any new project the present sewer system must be considered as a valuable permanent asset; therefore, the proposed collecting sewers should be adapted to the existing system. For further details of the sewer system see Appendix B.

The Water Courses

Sanitary surveys of the creeks and rivers at Philadelphia have been made to determine the effect upon them of the discharge of crude sewage from the present sewer outlets.

Poquessing Creek: This creek forms the northern boundary of Philadelphia and on its watershed is principally farm land. The waters of this creek are not noticeably polluted. There are no sewers now built on the area, nor is the territory sufficiently developed to require the design of a sewer system. The city owns a large tract of land on this watershed, upon which municipal institutions are being built, and for which a local sewer system and treatment works are being provided.

Pennypack Creek: The condition of this creek above the dam at Frankford Avenue is generally similar to Poquessing Creek. Below the dam there was formerly discharged the crude sewage from Holmesburg, the County Prison and the House of Correction. This caused a serious pollution, and as the creek enters the Delaware River within 2,000 feet of the intake of the Torresdale filters, it was of vital importance to remove this local pollution of the source of the water supply. Collecting sewers were built along the bank of the creek to gather the sewage and first flush of rain water from [17] existing sewer outlets, and from the institutions and convey it to a pumping station, where it is screened, passed through a grit chamber and forced to treatment works, consisting of two sedimentation tanks of the Ernscher type for the removal of the suspended matter in the sewage, one acre of percolating filters for the removal of the putrescibility of the sewage, a disinfection house where a solution of hypochlorite of calcium is added to destroy the disease germs, and a final settling basin to remove the settleable material which may pass through the prior processes. The collection of the sewage and the operation of this plant have resulted in restoring Pennypack Creek to a clean condition, and the effluent of the plant, when discharged, is practically free from suspended matter, will not putrefy and contains no disease germs.

Frankford Creek: The upper reaches of this creek are similar to Poquessing Creek and present a clean appearance. Where, however, the Wingohocking Creek joins it, carrying the sewage of 85,000 people, collected by the Wingohocking sewer system from Germantown, the waters of the creek are inadequate in volume to properly dilute the sewage and the creek becomes seriously polluted. In this condition the creek flows on toward the Delaware River and sewage and trade wastes are continually being added to the already overtaxed water. A dam on the creek causes low velocities of flow, so that heavy deposits of sewage sludge exist on the bed of the creek which, by the putrefaction and decomposition of the sewage matters, add to the polluted appearance of the water. The lower, or tidal part of the creek, is benefited by the refreshing action of the tidal flow, whereby the water of the Delaware River is carried up-stream and helps to dilute the sewage.

[18]
Cobbs Creek: A collector has been constructed along the east bank of the creek, through which the sewage of more than half the drainage area tributary to the creek within Philadelphia is carried to the tidal part of the creek. Its present polluted condition is, therefore, largely due to the sewage discharged from the adjoining county.

Schuylkill River: The portion of the river above Fairmount Dam is protected from sewage pollution from Philadelphia by the intercepting sewer described above. Below the dam, however, the sewage of about 500,000 people is discharged into the river; the volume of diluting water is inadequate to inoffensively dispose of the sewage and the velocities of flow are insufficient to maintain the sewage matters in suspension. As a result the Schuylkill River between Fairmount Dam and its mouth is grossly polluted; sewage matters float upon the surface of the river; the water is turbid and frequently highly discolored, the putrefaction of the sewage matters deposited on the bed of the river causes an almost constant ebullition of gas which, at times, is offensive; at low tide the sloping banks of the lower part of the river are exposed and show the putrefying black mud of sewage origin. These conditions prevent the attractive development of the banks of the river either for pleasure or business purposes and, as a consequence, there have grown up adjacent to them a number of oil refineries and garbage reduction works.

In order to observe the effect upon this river of the present discharge of sewage directly from the sewers and indirectly from the creeks and lower Schuylkill, the condition of the water and of the bottom of the river has been very carefully examined and studied; as a knowledge of the present conditions will afford information as to the degree of treatment required for the sewage of the city when it is collected at suitable points for disposal. Under normal conditions of the Delaware River its water at the northern (or upstream) limits of the city is free from noticeable sewage pollution and presents an attractive appearance. The water at this point contains even in summer sufficient dissolved oxygen to justify its use for the purpose of diluting and oxidizing the effluent from the proposed sewage treatment works. But the sewage discharged into the river from towns above Philadelphia and that carried up by the flood tide from the city is evident from the almost constant presence in the water of the bacillus coli, as shown in the following table taken from the Report of the Bureau of Water for 1913. [See left]

[21] As the river flows past the city it receives the crude sewage of Philadelphia and neighboring communities discharged by the sewers at the banks or into the docks. When the sewers discharge at the shore of the river the sewage does not at once diffuse with the main body of the river, but flows for some distance parallel to the bank. In cases where sewers discharge into docks, sludge deposits are formed on account of the absence of currents to maintain the sewage matters in suspension. The decomposition of these sludge deposits causes gross nuisance to both sight and smell in the vicinity of the piers.

In the accompanying illustration is shown one of the outlets at Laurel Street of the Cohocksink sewer system. It is estimated that sewage from a population of 260,000 people, amounting to 60,000,000 gallons a day, is discharged from this 18 feet 6-inch diameter sewer into the confined dock.

The Delaware River also receives the polluted waters of Frankford Creek and the lower Schuylkill River, which carry respectively the sewage of 140,000 and 500,000 people, and are so polluted that frequently no dissolved oxygen is present in their waters. The shipping in the harbor also contributes sewage and considerable debris. Fortunately, the tidal velocities in the Delaware River are sufficient to maintain the solid sewage matters in suspension, and they are progressively carried forward by the tidal movement toward the ocean. The surveys of the bottom of the river at Philadelphia show it to be clean and free from any deposits of sewage origin (except in the docks). This is of the greatest importance in the utilization of the assimilating and oxidizing capacity of the river, for where sludge deposits exist upon the bed of a stream the [22] products of decomposition, mingling with the water, are a serious tax upon its oxidizing power and, consequently, proportionately reduce the amount of sewage which the river can inoffensively assimilate.

As a result of the discharge of crude sewage from this and other communities into the Delaware River, its water in front of and below the city has a decidedly turbid appearance, debris and floating sewage matters are seen upon the surface, and during the summer the oxygen dissolved in the water is nearly exhausted, but no nuisance to smell has been noticeable at such times, except in the docks where sewage deposits exist. A material decrease in the amount of dissolved oxygen in the water has been noted between the observations made in 1912 and in 1914, as shown in the accompanying diagram.

The reason for this is that while the volume of flow and oxidizing power of the river remain practically the same, the quantity of sewage is steadily increasing each year, due to growth in population, development of industry and consequent extension of the sewer system. It must, therefore, be emphasized that any delay in constructing the works for the interception and treatment of the sewage of Philadelphia and neighboring communities will result in overtaxing the diluting and oxidizing capacity of the river, which will cause the creation of a nuisance in the river channel, and of greater importance is the danger of jeopardizing the public health by overtaxing the Torresdale filters. In Appendix D further details of the sanitary surveys are given.

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