City of Newton, Mass. Annual report of the city engineer for the year 1892. Albert F. Noyes, city engineer. In accordance with a vote of the water board under date of August 26, 1892, preparations were made for the constructing of the wooden filtering conduit in that portion of the filtering basin upon which the work was left incomplete in the spring of 1891, and for filling in over it. The filtering conduit may be briefly described as consisting of a wooden flume four feet square inside of the frames, placed between six and ten feet below the normal level of the water in the rim. Frames of spruce plank four inches thick by six inches deep for uprights, and four inches thick by eight inches deep for caps and sills, were placed three feet apart on centres, and covered with hemlock planks four inches thick laid close, but with space enough between each to allow for the infiltration of water. Tube wells two and one-half inches in diameter were driven to the water bearing strata at varying depths below the level of the conduit. As the water is lowered by the draught of the pumps, the water flows from the tube wells on the same principle as in the artesian wells. . . .
In order to satisfy themselves of the efficiency of pumping engines and boilers, the contractors for the construction of the pumping machinery, the Geo. F. Blake Manufacturing Company of Boston, had a preliminary test conducted by Professor Cecil H. Peabody of the Massachusetts Institute of Technology, which showed that the engines exceeded contract requirements by 8.87 per cent. The official test was conducted by Frank W. Dean, mechanical engineer of Boston, on September 30 and October I, 1892, which showed that the pumps exceeded the contract requirements by g.12 per cent, and the boilers by 10.98 per cent. , , ,
Sewers.—Descriptions of system as constructed. The water over a large portion of the city Is retained in the ground so near the surface as to cause inconvenience, and under many houses unhealthy and damp from the presence of water in cellars and basements. Under these conditions of water level it was apparent it would be difficult, if not impossible, without some provision for the removal of ground water, to construct a system of sewers which would be free from the infiltration of an amount of ground water equal to a considerable percentage of their capacity. The gradual extension of the collecting system of sewer* constructed without said provision would discharge into the metropolitan sewer a volume of water in addition to the sewage far in excess of the proportion allotted to the city’s use. . . .
In order to get the full benefit of the sewer system it was imperative that the level of the ground water should be lowered. It was felt that extra cost of construction of surface sewers at a level low enough to take the ground water from the cellars or basements of the houses, and to prevent any pressure on, or infiltration into the house sewers, and of a sufficient size to take the storm water without damage from overflow into houses which may be connected with them would be in excess of the benefit derived thereby. The plan for removing the ground water which was submitted, and upon which the system has been constructed, provided for the constructing of a sub-drain immediately below or a little to one side of the house sewer. . . .
Wherever found desirable a sub-drain is laid to the foundation wall of any building to intercept ground water, which otherwise would find its way to the basement of a building. As far as possible the sub-drains are designed and constructed so as to discharge from the whole system into the largest stream. . . .
The main drainage districts were divided and sub-divided into smaller districts, the sewers constructed in each were designed to connect with their main intercepting sewer by a route which would give the most economical results in cost of construction and maintenance. . . .
A study of the topography of the city shows that practicable routes can be obtained by which sewage can be conveyed by gravity to the metropolitan intercepting sewer for nearly the whole area, with the exception of a portion of land . . .
which can be more economically drained into tkwers laid through the city of Boston. A small section . , . can be best drained through Brookline or West Roxbury. There are also a few sections of small area where the removal of sewage by gravity would involve the lowering of a long and expensive main line, which would be below the permanent level of the ground water, and it will be more economical to install and maintain an electric or small water motor which can be so constructed that by a loss of city pressure the water used can pump the sewage into the sewer. , . .
Size of sewers are determined by estimating the maximum number of population to be provided for within the limit of time for which the sewers are designsd, the amount of sewage or waste to be allowed for each person per day the portion of the day during which the greatest proportion of the sewage is discharged, and the proportion of the sewer it is desirable to fill. At the present time the average number of people in the sewer district is a fraction less than three persons per acre. The maximum number of persons living at the present time on any single acre t estimate to be about thirty, while the average for any considerable area, to be from ten to fifteen per acre, having the example of the growth of other places to form a basis for estimate … a maximum population of sixty person per acre, and for the balance of the sewer area a maximum of forty persons per acre.
From gaugings made in other cities of the volume of sewage flowing in a sewer at different portions of the day, it has been found that about half of the daily discharge is made in six hours. The record of the amount of water used per person which approximates closely to the amount of sewage to be provided for, has been found to be about fifty gallons or about seven cubic feet per day.
ft has been found that in order to provide for any unusual conditions of discharge the sewer should be designed of a size to take the maximum flow when one-half full. From the above rule would be deduced—estimate of sufficient size to carry one-half of seven cubic feet of sewage for each person in six hours with sewer flowing one-half full. . . .
The minimum size sewer is recommended to be six inches, to be used when the grade is four feet or over per hundred feet.
Depth of sewers to be eight and one-half feet from the surface of the street to crown of sewer.
The following rate of slopes or grades for the constructing of sewers has been adopted as a minimum, and the rule has only been departed from in exceptional cases :
Four inch, 5-inch and 6-inch pipe a grade not less than a feet per too feet.
34 x 36-inch egg shaped brick sewer with ta-inch invert a grade of o.t6 feet per too feet.
Illustrations.—Flates No. 1 and a, Newton sewerage system, standard section.
Plates No. 3, 4. 5 and 6, details of manholes.
Tables.—Water analysis of under drains ; canvass of bids for sewer construction, showing lengths and cost of sewers built.
Topographical map showing improvement of the valley of Cheese Cake brook and profile of same.
Appendix A. pump test; appendix If. ordinances relating to city engineers’ department; appendix C, rules and regulations of the Newton Water Department, relating to the city engineer; appendix D. ordinance relating to drains and sewers.