THE JEROME PARK RESERVOIR
The daily capacity of the old Croton aqueduct is 75,000,000 gallons; that of the new aqueduct is 300,000,000. While the former was built almost entirely upon the side hill and above ground, the latter is nearly entirely tunnel and carried, as far as practicable, in a straight line from the Croton reservoir to the Harlem river, both discharging into a terminal gatehouse at 135th street and Amsterdam avenue, whence the water is led by twelve forty-eight-inch pipes into the city mains and the Central Park reservoirs. The capacity of the latter is nominally 1,000,000,000 gallons— sufficient to supply the city for five days. Since, however, the high-water level of these reservoirs is only 115 feet above sea-level, before their supply can be entirely run out, the pressure fails to such an extent that what water remains cannot reach the higher floors of buildings in the city— making the supply in them practically sufficient for three or at most four days. To provide against any possible failure, therefore, in reservoir or aqueduct, the Croton aqueduct commissioners some ten or twelve years ago determined to provide additional storage facilities at the city end by building the Jerome Park avenue reservoir with a capacity of 3,000.000.000 gallons—about fourteen days’ supply. The westerly basin will he completed this year, the work on the reservoir having been begun in 1896. The site is on the high ridge of land running north and south between the New York and Putnam and the Harlem railways, where a natural depression is formed on the summit of the ridge. It is surrounded by rising ground for half ittotal distance (the area is 239 acres; the depth, twenty-six and one-half feet). A solid masonry retaining-wall and embankment shut in the remaining half. The face of this wall is almost perpendicular, rendering an increase of ten acres in the area of the bottom—namely that contained betwen the toe of what was at first intended to he an earthen slope and the line of the inside foot of the perpendicular wall. No part of the natural surface being less than sixteen feet above the proposed liottom (twenty-nine feet below the crest of the retaining wall and thirty-two and oneItalf below the top of the finished embankment), the excavation required was 7,200,000 yards, some r 1.000.000 cubic yards having been blasted out, The old aqueduct passes through the site at ground level; the new, about 100 feet under the surface. Owing to the bottom of the reservoir lying below the foundation of the old aqueduct, the latter was taken down and rebuilt. About a mile to the north, where the new aqueduct is at the ground level, it has been depressed and carried in a tunnel to the deep level above mentioned, at which it is carried under the Harlem river. Somewhere about the centre of the reservoir a vertical shaft (No. 21) rises from this aqueduct to the bottom of the reservoir, and at the point where the change of grade in the new aqueduct already mentioned occurs are being built a deflecting gate-chamber and a surface branch aqueduct, the latter running parallel with the old aqueduct till the northern end of the aqueduct is reached, when the two aqueducts are continued in gateway No. 7, whence the flow can be discharged into either the east or the west basin or continued south through the masonry division wall. The latter, which is built upon the solid rock, runs north and south through the reservoir. The two basins thus formed are approximately equal and entirely separate, the top of the structure being at elevation 136.5 and level with the top of the embankment—five feet above the maximum high-water level in the reservoir. At the centre of its length, and opposite the vertical shaft mentioned above as leading down to the new aqueduct is a large main central gatehouse No. 5 (illustrated herewith through the courtesy of the management of the Scientific American). From it a short conduit connects through the shaft with the new aqueduct below ground. South of it two eleven-foot conduits are continued at bottom elevation—107 for distribution purposes, and above these the old aqueduct is continued at its former elevation. Fifteen hundred feet south of the gatehouse these conduits lead into the two basins, and thus six separate distribution systems are secured. Water can also be discharged into, or taken away from the old aqueduct at the gatehouse No. 6, and the reservoir may be filled or the water distributed directly from either aqueduct or from the subterranean aqueduct through shaft twenty-one, all the operations being controled at the main gatehouses Nos. 5, 6. 7. From the first-named radiate six lines of forty-eight-inch pipes—two at Van Cortlandt avenue gatehouse to the northwest: two at Sedgewick avenue gatehouse to the west; and two at Jerome avenue gatehouse to the southeast, one leading to a high-service pumping station. Two forty-eight-inch pipes will also lead south to Manhattan from the gatehouse at Kingsbridge road. By the main gatehouse connections supply for these pipes may be from either basin or aqueduct. The forty-eight-inch pipes, aided by the new pumping stations, will supply the Bronx district north of the Harlem river, and a double line of forty-eight-inch pipes will also be carried south across the Harlem river to connect directly with the Manhattan mains, so as to afford an independent supply in case of accident to either of the aqueducts where they cross the Harlem river. If, also, the reservoir should require cleaning, four lines of forty-eight-inch pipes will be taken off east arud west from the north end of gatehouse No. 7, connecting with the city system. The westerly half will be finished this year. The work of concreting its bottom was begun in 1904, during which year 30.25 acres of concrete were laid. At the end of March, 1905, the work was resumed, and with sixteen mixers (at present at work) in operation, it is hoped to exceed the estimated output of concrete by twenty per cent., and carry the daily total up to 3,000 square yards—seven-tenths of an acre. A concrete flooring of six inches thick has to cover 101.25 acres—that is, a total of 1.750.000 cubic feet of concrete must be mixed, carried to its proper site, and carefully tamped and surfaced. The eastern basin will not be finished for at least another year.