THE CATSKILL WATERSHED
When the whole of the Catskill water supply for New York city has been developed, the water will be taken from four different sources—the Esopus creek, with a watershed of 255 sq. m., whose water will be impounded by the Ashokan dam. with a maximum height of 220 ft. and a length of 5,650 ft., now being built at Olive bridge in Ulster county. The water area of the reservior thus created will be 2)4 miles wide; its capacity, 170,000,000,000 gal., furnishes a daily supply of 250,000.000. The Rondout, the Schoharie and the Catskill rivers will ultimately be drawn upon. The Esopus creek water is now being dealt with. The Ashokan dam (sections of which are illustrated herewith), as has before been told in these columns, will be part masonry and part earth. The width of its base at the centre will be nearly 200 ft. The earth and core-wall portions will extend from the masonry middle section to a junction with the valley on one side and some high ground on the other, and, in addition to the dam, will be a series of dykes, which will be built across depressions in the country to hold the water at the desired level. Beyond the dykes will he a large waste-weir, which, together . with the dykes, will have a total length of 3.8 miles. The preliminary work in the way of excavations for the dam is shown in the accompanying illustration, from which it will be seen that the water of the Esopus creek is bypassed during construction by two 8-ft. steel pipes, big enough to accommodate the creek at its ordinary level, and. as the excavation is carried farther down, the water will he diverted through a channel running along the side of the valley. While the masonry work of the dam is being erected a tunnel, which will be left open till the work is completed, will carry the water away. From the dam the water will flow by gravity through a steel-and-concrete aqueduct (illustrated herewith), 17 ft. in the clear in height and 17)4 ft. wide, built partly in tunnel and partly in the cutand-cover method to the west bank of the Hudson river, at a point between Cornwall and West Point. As for the support of this conduit, no proper wall foundation can be found in the Hudson river, it is almost certain thatit will have to rest on a huge viaduct built across the river to the east bank of the river and continued till it reaches the new Croton reservoir, where connections will be made to draw the water directly from the Ashokan dam into the Croton reservoir until such time as the aqueduct from Ashokan to New York city shall have been completed. From the Croton reservoir the aqueduct will be carried on to the enlarged Kensico reservoir (which will then include Rye pond). This will form an auxiliary storage-reservoir 355 ft. above mean tide and will have a capacity of 25,000,000,000 gal.—sufficient to supply the city for fifty days with 500,000,000 gal. per day. About four miles south of Kensico. at Scarsdale, will be built a large filtration plant, and at Hillview, 6 miles farther south, will be another storage reservoir.
A tunnel of 200,000,000-gal. capacity below the East river, Brooklyn and Richmond (Staten Island) boroughs will be supplied with 100,000,000 gal. daily, the aqueduct terminating in a large reservoir to be built in Forest Park. From the point on Long Island, where this tunnel touches, a line of 20,000,000-gal. capacity will be built through Brooklyn and between the Narrows to Staten Island.