Lower Granite Dam

Lower Granite Dam
270px View from the northwest
Country	United States
Location	Garfield / Whitman counties, Washington
Coordinates
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

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

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-74-foot (26 m × 23 m) navigation lock was also included in construction.

Fishery

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.

There is also a juvenile bypass/collection facility that collects juvenile migrating salmon and steelhead so they can be transported downstream by barge.

Navigation lock

• Single-lift
• Width: 86 feet (26 m)
• Length: 674 feet (205 m)

Lower Granite Dam with the lock in the center, the power generation on the south side of the river, and spillway in the middle of the dam, between the powerhouse and the lock.

Asotin Dam

Authorized by Congress in 1962, a fifth dam on the lower Snake River was proposed several miles upstream of Lewiston. Concerns over its environmental and recreational impact stalled the Asotin Dam project, and it was ultimately canceled in 1980. The Asotin County public utilities district attempted to revive the project in 1988, but it was quickly blocked by Congress, and a law banning future dams was signed into law by President Reagan on November 17.

Other proposed dams further upstream were not built either: the High Mountain Sheep Dam above the confluence with the Salmon River, and the Nez Perce Dam, just below it.

Road closed

Following the September 11 attacks in 2001, the road across the Lower Granite Dam was closed for over six years; it reopened for weekend traffic in May 2008. The sand dune area downstream on the south shore (), accessed over the dam, was popular with local college students from Washington State University and the University of Idaho.

See also

• List of dams in the Columbia River watershed
• Ice Harbor Dam
• Little Goose Dam
• Lower Monumental Dam

External links

• U.S. Army Corps Engineers: Lower Granite Dam
  • Lower Granite Recreation
• Columbia River Inter-Tribal Fish Commission
• Fish Passage Center Dam Counts
• History Link: Lower Granite Dam
• Boyer Park and Marina