Lower Granite Lock and Dam
| Lower Granite Dam | |
|---|---|
View from the northwest
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| Country | United States |
| Location |
Garfield / Whitman counties, Washington |
| Coordinates | 46°39′38″N 117°25′41″W / 46.66056°N 117.42806°WCoordinates: 46°39′38″N 117°25′41″W / 46.66056°N 117.42806°W |
| Construction began | July 1965 |
| Opening date | June 1975 |
| Construction cost | $624,098,663 |
| Operator(s) | U.S. Army Corps of Engineers |
| Dam and spillways | |
| Type of dam | Gravity dam |
| Impounds | Snake River |
| Height | 100 ft (30 m) |
| Length | 3,200 ft (980 m) |
| Spillway type | Service, gate-controlled |
| Spillway capacity | 850,000 cu ft/s (24,000 m3/s) |
| Reservoir | |
| Creates | Lower Granite Lake |
| Total capacity | 440,200 acre·ft (0.543 km3) |
| Surface area | 8,900 acres (36.0 km2) |
| Normal elevation | 741 ft (226 m) |
| Power station | |
| Type | Run-of-the-river |
| Turbines | 6 × 135-155 MW units |
| Installed capacity | 810 MW |
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Lower Granite Lock and Dam is a concrete gravity run-of-the-river dam in the northwest United States. On the lower Snake River, it bridges Whitman and Garfield counties in southeastern Washington. The dam is located 22 miles (35 km) south of the town of Colfax, and 35 miles (56 km) north of Pomeroy.
Lower Granite Dam is part of the Columbia River Basin system of dams. It was built and is operated by the United States Army Corps of Engineers. Power generated is distributed by the Bonneville Power Administration.
Lower Granite Lake, which extends 39 miles (63 km) east to Lewiston, Idaho, is formed behind the dam, and allowed the city to become a port.Lake Bryan, formed from Little Goose Dam, runs 37 miles (60 km) downstream from the base of the dam.
Construction began in July 1965, but was halted less than two years later due to lack of funding. Work restarted in 1970, concrete was first poured in 1971, and the main structure and three generators were completed in 1975. An additional three generators were finished in May 1978, bringing the generating capacity to 810 megawatts, with an overload capacity of 932 MW. The spillway has eight gates and is 512 feet (156 m) long. An 86-by-674-foot (26 m × 205 m) navigation lock was also included in construction.
Lower Granite Dam is the most upstream dam in the Snake River system that has a fish ladder to allow adult salmon and steelhead to migrate upstream. The Columbia River treaty tribes along with some environmental groups have recommended that this dam along with the other three lower Snake River dams be decommissioned and/or removed because of their impact on threatened and endangered chinook (threatened) and sockeye salmon (endangered) and steelhead (threatened) populations., A significant increase in the Sockeye Salmon return to the Columbia River in 2008 proved a pleasant surprise and raised hopes for increased salmon runs across the Lower Granite. Wildlife officials were not certain of the reason for the increased salmon return (Idaho Statesman, June 28, 2008) The Army Corps of Engineers has installed new devices such as removable spillway weirs in an attempt to make the dam less harmful to juvenile salmon.
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Wikipedia