Home >> Encyclopedia Americana, Volume 8 >> Cromer to Curves Of Double Curvature >> Croton Aqueduct

Croton Aqueduct

dam, feet, gallons, rock, miles, capacity and water

CROTON AQUEDUCT and CROTON DAM, an aqueduct and dam for many years the only means of water supply for the city of New York. The waters of Croton Lake, an artificial body of water formed by damming the Croton River, were first conveyed to the city in 1842, by what is known as the old aqueduct, and a new aqueduct was opened in 1890. The old aqueduct was of masonry lined with brick, and had a cross-section area of 53.34 square feet, and a nominal capacity of 72,000,000 gallons per day. On occasions it has actually delivered 95,000,000 gallons in 24 hours. (See AQUEDUCTS). The new aqueduct has a cross-section area of 155.57 square feet, and a flow capacity of 300,000,000 gallons per day. It passes in its lower course under the northern part of Manhattan Island rising at 135th street, where a gatehouse is con structed from which the water is distributed through 12 lines of 48-inch iron pipe, four of which enter the reservoir in Central Park. Throughout its entire length this great tunnel was blasted out of solid rock, with the exception of three or four spots where "blow-ofte were constructed with the object of rapidly emptying the aqueduct—which here meets the surface— for the purpose of examination, repair or cleans ing. The tunnel is lined throughout with brick, and in one or two places where the rock has been found imperfect and a leakage is possible an iron lining has been added.

As early as 1881 the question arose of pro viding a large water-supply for the future needs of the city, and a new dam across the Croton River was ultimately decided on, the contract for the structure being awarded 26 Aug. 1892, the work to be completed 1 July 1899. It was not finished, however, until 1906. In 1901 the dam was about half completed and a modifica tion of the design at that time involved doing away with the proposed earthen section of the dam and building the whole of masonry, except a low embankment at the south end. The dam crosses the valley about three and a fourth miles above the mouth of the Croton. The first step in its construction was the cutting through solid rock of a canal 1,100 feet long and 125 feet wide to turn aside the river. The foundation pit for the dam was finished in September 1897.

The excavation reached about 75 feet below the country level at the centre of the valley to bed rock, and involved the removal of 1,821,400 cubic yards of earth and 400,250 cubic yards of rock. The dam is 1,168 feet long and 294 feet high, from its foundation, and 210 feet above the former level of the river, the width at the base being 206 feet, from which the structure tapers to 22 feet at the top. At the north end of the dam is a spillway or overflow, 1,000 feet long, built in continuity with the dam and nearly at right angles to it, reaching up the val ley. The waste from this spillway is discharged into a channel 50 feet wide at its upper end and 125 feet at the lower end, cut into the solid rock. At the southern end the masonry of the old aqueduct runs through the dam. This great mass of masonry forms the largest and most expensive dam ever constructed on this continent and its height is second only to that of the Shoshone irrigation dam (324 feet), which, however, contains less than half the mass of the Croton dam. The steam and machinery equipment equaled that of an ordinary railroad, for besides the many hoists and derricks, there were used several miles of tracks and 11 loco motives of the dinky type and 282 cars in haul ing earth and stone, besides 39 steam boilers and 51 hoisting engines. The new dam increased the storage capacity of the city water supply by 30,000,000,000 gallons. The old Croton dam im pounded 2,000,000,000 gallons in a lake 51/2 miles long and covering 500 acres. This old dam now lies 30 feet below the level of the new lake. The new dam forms a lake 193i miles long covering 3,425 acres. The watershed of the Croton River Valley has an area of about 340 square miles. In this area there are a dozen or more reserve dams auxiliary to the Croton dam, and these impound a total of 67,952,000,000 gallons, making the capacity of the Croton sys tem close to 100,000,000,000 gallons. The in take from the large new reservoir is from the upper gatehouse where there are 22 gates each supplied with charcoal-filters through which the water mustpass before it is turned into the aqueducts. These intakes have a capacity of 400,000,000 gallons a day.