The following descriptions give the principal dimensions of the profiles of a few of the highest gravity masonry dams in the world at the present time (1909).
New Croton Dam. This dam was built, in 1892-1907, about 30 miles north of New York City, to store water for that munici pality. Fig. 102 shows the profile of the maximum section and also some of the data concerning its stability. The height from the lowest point of the dation to the top of the parapet is 297 ft., and the depth of the water impounded is 150 ft. The profile is substantially that designed for a dam proposed in 1888 for a site about 1 mile further stream, known as the Quaker Bridge Dam, which was not built. Fig. 102 shows that the line of sistance (the line joining the centers of pressure of the several joints) always lies within the middle third of the length of any imaginary horizontal joint. The nominal factor of safety for sliding and the true factor of safety for overturning when the servoir is full are given for a few points; and also the maximum unit pressure at the toe when the reservoir is full and at the heel when the reservoir is empty are shown. The maximum coefficient of friction required to prevent sliding is 0.597 at a section 121 ft. above the base of the dam.
The main dam is straight in plan and about 600 ft. long. For a detailed description, see Reports of the New Croton Aqueduct from 1895-1907, pages 90-102; or Wegmann's Design and Construction of Dams, pages 162-84.
U. S. Reclamation Service Danis. The United States Government, through its Reclamation Service, a branch of the U. S.
Geological Survey, now (1909) has in progress three notable masonry dams,—the Roosevelt, the Shoshone, and the Pathfinder.
The Roosevelt Dam is situated in the canyon of Salt River, just below the mouth of Tonto Creek, about 70 miles above Phoenix, Arizona, and is to store water for irrigation. Fig. 103 shows the profile of the maximum vertical cross section. Notice that Fig. 103 is similar to, but less heavy than, Fig. 102. The height of the spillway above mean low water is 220 ft., the
height of the roadway above the general foundation level is 260 ft.; and the top of the parapet is 284 ft. above the lowest point of the founda tion. The length of the crest is 780 ft. In plan the dam is curved to a radius of 400 ft. The roadway is 16 ft. in the clear.
The Shoshone Dam is an irrigation dam situated on the Shoshone River in Wyoming. It has a maximum height of 305 ft. above the foundation, and a flow line 295 ft. above the foundation; and it im pounds water 235 ft. deep. The dam has a top width of 10 ft., and both sides of the profile are straight lines, the up-stream face having a batter of 0.15 to 1 and the down-stream 0.25 to 1. The dam will be about 168 ft. long on top, and is curved in plan to a radius of 150 ft.
The Pathfinder Dam is situated on the North Platte River in Wyoming, 4 miles below the mouth of the Sweetwater, and is to Impound water for irrigation. The maximum height above the foundation is 210 ft., the flow line is 200 ft. above the foundation, and the maximum depth of water is 195 ft. The length on top is 160 ft., and the center line of the crest is curved to a radius of 150 ft.
The depth of water stored is 95 ft. The profile has the same general character as that of the New Croton Dam. The extreme width on top is 25 ft. 9 in.
The Cheesman Dam impounds water for the city of Denver, Colorado, and was built in 1900-04. It has a flow line 227 ft. above the foun dation and a total height of 231 ft. The dam is 675 ft. long on top, is curved in plan, and has a profile of the type of the New Croton Dam.
The Olive Bridge Dam, which forms the Ashokan Reservoir of the Catskill Water Supply of New York City, is to be 220 ft. above the foundation, and will impound water 130 ft. deep. The profile is of the same general form as that of the New Croton Dam.