Lower Granite Lock and Dam

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Lower Granite Dam and the Snake River from the northwest, looking southeast, upstream.
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Lower Granite Dam and the Snake River from the northwest, looking southeast, upstream.

Lower Granite Lock and Dam is a hydroelectric, concrete, gravity dam on the Snake River, and bridges Whitman County and Garfield County, in the state of Washington. The dam is located 22 miles (35 km) south of the town of Colfax, and 35 miles (56 km) north of Pomeroy.

Construction began in July 1965. The main structure and three generators were completed in 1972, with an additional three generators finished in 1979. Generating capacity is 810 megawatts, with an overload capacity of 932 MW. The spillway has eight gates and is 512 feet (156 m) long.

Lower Granite Dam is part of the Columbia River Basin system of dams.

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.
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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.

Lower Granite Lake, which extends 39-miles east to Lewiston, Idaho, is formed behind the dam. Lake Bryan, formed from Little Goose Dam, runs 37 miles (60 km) downstream from the base of the dam.

Stats:

  • Location: 46.6604369 -117.4279602
    (46°39′37″N, 117°25′40″W)
  • Altitude: 741 feet (226 m) above sea level
  • Height: 100 feet (30 m)
  • Length: 3,200 feet (975 m)
  • Navigation lock:
    • Single-lift
    • 86 feet (26 m) wide
    • 674 feet (205 m) long
  • Powerhouse
    • Six 135,000-megawatt units [1]
Columbia River Basin
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Columbia River Basin

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