Mayfield
Mayfield is a 162 MW hydroelectric power plant in Lewis County, Washington, operated by City of Tacoma - (WA). EIA-860M lists 4 generating units here. Its units entered service between 1963 and 1983.
As of 2026-07 (inventory dated 2026-07-31) · EIA-860M Preliminary Monthly Electric Generator Inventory · eia.gov/…/july_generator2026.xlsx · eia.gov/…/eia860m
- Nameplate capacity
- 162 MW
- 164 MW net summer
- Generating units
- 4
- In service
- 1963–1983
- EIA plant ID
- 3917
Where it is
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- County
- Lewis County, Washington
- Coordinates
- 46.5035, -122.5885
- Balancing authority
- TPWR
- Sector
- Electric Utility
Units, technology and status
- Operator of record
- City of Tacoma - (WA)
- Primary energy source
- Hydro
- Technologies
- Conventional Hydroelectric
- Status
- Operating
Mayfield: FAQ
- Where is Mayfield?
- In Lewis County, Washington (WA). The map on this page is placed at the coordinates EIA files for the plant, which locate the site rather than any individual unit.
- How big is Mayfield?
- 162 MW of nameplate capacity across 4 units, as of the EIA-860M release for 2026-07.
- Who owns Mayfield?
- EIA-860M names City of Tacoma - (WA) as the reporting entity. That is the operator of record on the survey, which is not always the ultimate owner.
- Is this the same as Mayfield LLC?
- Probably, but EIA-860M does not say. The survey records a plant name and a reporting entity — City of Tacoma - (WA) here — not the project company that holds the asset. Project companies are commonly registered as an LLC carrying the plant's name, so a search for "Mayfield LLC" usually means this site. This page shows only what EIA files, and does not assert a corporate structure it cannot see.
- Is Mayfield still running?
- EIA-860M files it as "Operating" for 2026-07. Statuses change monthly, and this page follows the monthly release.