Engineering Wonders of the World
Volume III

THE WATER SUPPLY OF NEW YORK CITY. 107 temperature of a large mass of masonry, such as a great dam, will rise as high as 120°, and then gradually fall to, say, 50°, these changes being, of course, accompanied with corre- sponding expansion or contraction of the structure. If the latter is built absolutely monolithic, as is usually the case, the ex- pansion will produce cracks at one or more a channel will be constructed for the same purpose along the side of the valley. Ulti- mately the water will be allowed to flow through a tunnel formed in the masonry of the dam, which will be closed when the dam is com- pleted. The future reservoir basin is at present crossed by a railway, for which a new location MAP OF WATERSHED AREA WHICH WILL ULTIMATELY 0 * SUPPLY THE CATSKILL AQUEDUCT. The course of the Aqueduct is shown by a heavy black line. This Aqueduct will be able to pass 500,000,000 gallons a day, and if the need arises it will be duplicated. Its projected length, measured from the Ashokan Reservoir to the storage \ reservoir in Staten Island, is 126 miles. points, and these will not necessarily follow the joints in the masonry, but may result in the great stones being torn asunder during the shrinkage. By the provision, however, of vertical joints at intervals of every 84 feet of the length of the Ashokan Dam, the masonry will be divided into sections, and the total movement due to changes of temperature so distributed among a large number of joints as to become inappreciable at each. At the same time, it should be noted, the strength of the masonry to withstand the horizontal thrust of the water will be in no way impaired. It being necessary to excavate at the site of the dam down to solid rock, provision has had to be made for passing away the waters of Esopus Creek. For the present, as shown in the illustration on page 105, this is being done by means of two 8 feet steel pipes. Later on, however, when the excavation is carried lower, will have to be provided. Seven small villages also exist in the territory to be submerged. In all, to secure absolute control over the shores of the reservoir, 23 square miles of land will have to be acquired. There will also require to be built about 40 miles of new highway. For the accommodation of their employees, the contractors have built in the neighbourhood of the works about one hundred and sixty buildings, including a school, hospital, and engineers’, doctors’, and teachers’ dwell- ings. Very elaborate provisions are included in the contract in respect of sanitation, in- spection, and the like. To deliver to the city the daily supply of 250,000,000 gallons, which the first development of the Cats- The Catskill kill watershed is expected to yield, the construction of a great aqueduct —far surpassing any work of like character—