New Exchequer Dam
| New Exchequer Dam | |
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New Exchequer Dam and Lake McClure viewed from the air
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| Country | United States |
| Location | Mariposa County, California |
| Coordinates | 37°35′10″N 120°16′10″W / 37.58611°N 120.26944°WCoordinates: 37°35′10″N 120°16′10″W / 37.58611°N 120.26944°W |
| Construction began | 1964 |
| Opening date | 1967 |
| Owner(s) | Merced Irrigation District |
| Dam and spillways | |
| Type of dam | Concrete–faced rockfill |
| Impounds | Merced River |
| Height | 490 ft (150 m) |
| Length | 1,220 ft (370 m) |
| Elevation at crest | 879 ft (268 m) |
| Spillways | Gated ogee crest |
| Reservoir | |
| Creates | Lake McClure |
| Total capacity | 1,024,600 acre feet (1.2638 km3) |
| Catchment area | 1,040.1 sq mi (2,694 km2) |
| Surface area | 7,147 acres (2,892 ha) |
| Maximum length | 29 mi (47 km) |
| Normal elevation | 867 ft (264 m) |
| Power station | |
| Hydraulic head | 437 ft (133 m) |
| Installed capacity | 94.5 MW |
| Annual generation | 316,000,000 KWh |
New Exchequer Dam is a concrete–faced, rock-fill dam on the Merced River in central California in the United States. It forms Lake McClure, which impounds the river for irrigation and hydroelectric power production and has a capacity of more than 1,000,000 acre feet (1.2 km3). The Merced Irrigation District (MID) operates the dam and was also responsible for its construction.
Built between 1964 and 1967, the dam replaced the old arch type Exchequer Dam and stands 490 feet (150 m) high. At the time of completion, it was the largest dam of its kind in the world. The dam is named for the town of Exchequer which now lies under the reservoir, while the reservoir is named for Wilbur F. McClure, the State Engineer of California during construction.
In 1926, after five years of planning and construction, MID completed the Exchequer or "Great Exchequer" Dam across the Merced River six miles (9.7 km) above the town of Merced Falls. The dam was a concrete gravity–arch structure 326 feet (99 m) high, holding a 14-mile (23 km) lake with a capacity of 281,000 acre feet (347,000,000 m3) of water. Although the dam was to serve primarily for irrigation, power production began ceremoniously on June 23, 1926 with a press of a telegraph key by President Calvin Coolidge, starting the turbines at a 31 megawatt hydroelectric plant.
By the 1950s, it became apparent that the limited storage capacity at Exchequer was no longer enough to serve the needs of farmers in the Merced River valley. A high dam was proposed to be built just downstream, creating a reservoir nearly four times the size of Exchequer.
Construction of New Exchequer Dam began on July 8, 1964, directly downstream from the old concrete arch dam. Tudor Engineering Company of San Francisco was responsible for the design of the new dam. The dam wall was constructed in vertical zones, which consisted of compacted, alternating layers of coarse and fine material ranging in thickness from 1.6 to 66 feet (0.49 to 20.12 m). The old Exchequer Dam was incorporated as an upstream toe to help support the rock-fill embankment, which was then armored with a layer of reinforced concrete. The dam was topped out in early 1967 and the power plant went into commercial operation by July.
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