Page:Collier's New Encyclopedia v. 03.djvu/295

LEFT DAM 251 DAM which is located 85 feet above the base, the dam is 390 feet thick, and it is 100 feet thick at its top. The dam is built with very flat slopes to provide unusual stability. The dam has a spillway chan- nel 819 feet wide. Over 20,000,000 cubic yards of material were used in its con- struction. The San Leandro Dam of the San Francisco waterworks is an earth dam with no core-wall, and is 158 feet high. The Goose Creek Dam of the Oakley Irrigation project is an earth dam built in layers, and completed in 1913. It is 145 feet high, 1,025 feet long and 750 feet wide at the base. The Shoshone Dam is a masonry dam built by the United States Reclamation Service in Wyoming near Cody. It is 324 feet high, curved upstream, 10 feet thick at the crest, and 108 feet thick at its base, which thickness is continued up to the level of the river bed. The Roosevelt Dam was also constructed by the United States Reclamation Service. It is located in Arizona, has a maximum height of 284 feet, a storage capacity of 420,000,000,000, and was completed in 1911. The Arrowrock, near Boise, Idaho, construction of which was started in 1914 by the same Government agency, is 354 feet high, and 1,060 feet long. It NEW CROTON DAM, NEW YORK The highest earth dam ever attempted is the Calaveras Dam of the Spring Valley Water Company of San Fran- cisco. This dam is 240 feet high, the crest length is 1,300 feet, the base is 1,300 feet wide, the upstream slope is 3 to 1, and the down stream slope is 2% to 1. It is a hydraulic fill dam. The new Croton Dam of the New York City Water Supply System was completed in 1907, and provides a stor- age capacity of 32,000,000,000 gallons of water. It is a masonry dam with a crest length of 2,168 feet, and a height of almost 300 feet. There is a roadway on the top of the dam. The spillway is 1,000 feet long, and varies in width from 50 to 125 feet. is curved upstream, with a gravity sec- tion, and is built of concrete. The Keokuk Dam, which crosses the Mississippi river at Keokuk, la., is a 'ong, low concrete dam. Besides the spillway section, 4,278 feet long, there is an abutment 290 feet long, a combina- tion, another 1,700 feet long, in the form of a power house, and a lock section of about 600 feet. The Elephant Butte Dam, located near Engle, N. M., was dedicated on Oct. 19, 1916. It is a Reclamation Serv- ice dam of rubble concrete, with a gravity section. It is 1,200 feet long and 304.5 feet high from base to top. The hydro-electric development dam of the Yadkin river, N. C, contains a dam