Hydroelectric Information for Columbia and Snake River Projects

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Lower Monumental Dam - General Information

Image Source: USACE Digital Visual Library

Dam: Lower Monumental Dam. Snake River. River Mile 41.6

Constructed ¹: 1969 (units 1-3); additional units 4-6 completed in 1981

Owner: U.S. Army Corps of Engineers, Walla Walla District

Normal Operating Pool ²: 537.0-540.0 feet

Maximum Pool ²: 548.3 feet

Powerhouse Capacity:

Nameplate capacity: 6 @ 135 MW, 810 MW total

Overload capacity: 6 @ 155 MW, 930 MW total

Hydraulic capacity: 130 kcfs

Spillway ¹: 572 feet, 8 gates

• Visitor Information: see Lower Monumental Dam Recreation Area page, USACE Walla Walla District
• USACE Walla Walla District for information, history and color photo.
• USACE Walla Walla District for Pertinent Data (including stats on cost, reservoir, spillway, and powerplant).
• USACE Hydroelectric Design Center for detailed hydroplant (pdf) information.