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Lower Monumental Lock and Dam
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Lower Monumental Lock and Dam is a run-of-the-river hydroelectric dam on the Snake River, and bridges Franklin County and Walla Walla County, in the state of Washington. The dam is located six miles (10 km) south of the town of Kahlotus, and 43 miles (69 km) north of the town of Walla Walla.
Construction of Lower Monumental Lock and Dam began in June 1961. The main structure and three generators were completed in 1969, with an additional three generators finished in 1981. Generating capacity is 810 megawatts, with an overload capacity of 932 MW. The spillway has eight gates and is 572 feet (176 m) long.
Lower Monumental Dam is part of the Columbia River Basin system of dams.
Lake Herbert G. West, which extends 28 miles (45 km) east to the base of Little Goose Dam, is formed behind the dam. Lake Sacajawea, formed from Ice Harbor Dam, runs 35 miles (56 km) southwest, downstream from the base of the dam.
| Lower Monumental Dam | |
|---|---|
| Locale | Franklin / Walla Walla counties, Washington, USA |
| Construction began | June 1961 |
| Opening date | 1969 |
| Dam and spillways | |
| Type of dam | Concrete gravity, run-of-the-river |
| Height | 100 feet (30 m) |
| Length | 3,791 feet (1,155 m) |
| Impounds | Snake River |
| Type of spillway | Service, gate-controlled |
| Reservoir | |
| Creates | Lake Herbert G. West |
| Capacity | 32,266,666 cubic yards (24,669,636 m3) |
| Surface area | 6,590 acres (26.7 km2) |
| Power station | |
| Type | Yes |
| Turbines | 6 x 135-153 MW |
| Installed capacity | 810 MW |
| Maximum capacity | 932 MW |
