Lower Monumental — Plant Summary
- EIA Plant ID
- 3927
- Capacity
- 810 MW
- Primary Fuel
- Hydro
- Technology
- Conventional Hydroelectric
- Status
- Operating
- Location
- Walla Walla, WA
- Operating Since
- 1969
- Generators
- 6
- Operator
- USACE Northwestern Division
- Parent Company
- —
- Annual Generation
- 1,476,976 MWh
- Capacity Factor
- 20.8%
- Balancing Authority
- Bonneville Power Administration
- ISO/RTO
- —
- NERC Region
- WECC
Lower Monumental
OperatingHydro
Ranked #9 of 75 Hydro plants in WA#30 of 1454 nationally
810 MW Hydro operating in Walla Walla, WA — Bonneville Power Administration
EIAGEMWD
810 MW
Nameplate Capacity
6
Generators
units
Conventional Hydroelectric
Technology
1969
Operating Since
Location
Coordinates
46.5635, -118.5397
County
Walla Walla, WA
Ownership & Operator
Owner data does not fully agree across sources.
EIA typically reports the operating utility, while GEM resolves to the financial owner or parent corporation. Both can be correct.
| Field | EIA | GEM | Wikidata |
|---|---|---|---|
| Operator | USACE Northwestern Division | US Army Corps of Engineers - Walla Walla District | United States Army Corps of Engineers |
| Owner(s) | USACE Northwestern Division | US Army Corps of Engineers - Walla Walla District [100%] | — |
| Status | Operating | operating | — |
Ownership Chain
GEM identifies the owner as US Army Corps of Engineers - Walla Walla District [100%]
This entity is not yet in the GEM ownership database — chain unavailable.
About
Lower Monumental Lock and Dam is a hydroelectric, concrete, run-of-the-river dam in the northwest United States. Located on the lower Snake River in southeast Washington, it bridges Franklin and Walla Walla counties; it is six miles (10 km) south of Kahlotus and 43 miles (70 km) north of Walla Walla.
Read more on WikipediaLower Monumental is a hydroelectric power plant located in Walla Walla County, Washington. The plant, which began operating in 1969, has a total capacity of 810 MW distributed across six generators. It is owned and operated by the USACE Northwestern Division. The plant uses water as its primary fuel source and employs conventional hydroelectric technology. Lower Monumental ranks as the 10th largest power plant in Washington state out of 23, and 31st nationally out of 194 plants.
In the most recent year with available data, Lower Monumental generated 1,476,976 MWh of electricity, resulting in a capacity factor of 20.8%. The plant operates within the Bonneville Power Administration balancing authority and the Western Electricity Coordinating Council (WECC) NERC region. Recent news coverage of the plant includes 10 articles, with a focus on regulatory matters.
Generated from EIA, GEM, and public data sources
Engineering & Generators
Grid Context
NERC Region
WECC
Balancing Authority
Bonneville Power Administration
Grid Voltage
500 kV
Regulatory Status
RE
Entity Type
Federal
Sector
Electric Utility
Generation
195.9K MWh
Latest Month
1.5M MWh
Annual Generation
20.8%
Capacity Factor
Jan 2023 – Dec 2025
Financial Data
No financial data available for this plant.
Pricing & Market Data
This plant is outside organized wholesale electricity markets (ISOs/RTOs). Nodal pricing data is not available.
News & Articles (9)Beta
Last updated 2026-03-26
View all 9 articles