Briefing on Lower Monumental

Lower Monumental Lock and Dam, a 810 MW hydroelectric plant, has been a long-standing contributor to the grid since 1969, though recent generation has seen a significant decline of 30%.

Overview

• Lower Monumental Lock and Dam is a 810 MW Conventional Hydroelectric plant located on the lower Snake River in southeast Washington, bridging Franklin and Walla Walla counties.

• It has been Operating since 1969 with 6 generators.

• The plant is owned and operated by the USACE Northwestern Division.

• It is part of the WECC NERC region and its balancing authority is Bonneville Power Administration.

Operational Performance

• The plant has an annual generation of 1477 GWh with a capacity factor of 20.8%.

• Recent monthly generation includes 86 GWh in October 2025, 94 GWh in November 2025, and 196 GWh in December 2025.

• Generation has shown a down 30% trend over the past 6 months compared to the prior 6 months.

Financial and Related Information

• The plant's Capital Expenditure (CapEx) is $2294/kW.

• Recent news indicates involvement of Eolink (SingularityHub, 2022-12-12) and the DOE (Tri-City Herald, 2025-05-13) with the plant.

• The latest activity was a technology_launch (SingularityHub, 2022-12-12) and the latest ruling was a notice (Capital Press, 2024-04-08).