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300 MW Hydro operating in Lewis, WA — City of Tacoma, Department of Public Utilities, Light Division
300 MW
Nameplate Capacity
2
Generators
units
Conventional Hydroelectric
Technology
1968
Operating Since
Coordinates
46.5347, -122.4247
County
Lewis, WA
Nearby Plants
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 | City of Tacoma - (WA) | Tacoma Power | — |
| Owner(s) | City of Tacoma - (WA) | Tacoma Power | — |
| Status | Operating | operating | — |
GEM identifies the owner as Tacoma Power
This entity is not yet in the GEM ownership database — chain unavailable.
Mossyrock Dam is a concrete double-arch-gravity dam on the Cowlitz River near Mossyrock in Lewis County, Washington, United States. The reservoir created by the dam is called Riffe Lake. The primary purpose of the dam is hydroelectric production while flood control is a secondary function. The dam is the tallest in Washington state and its hydroelectric power station supplies 40% of Tacoma Power's electricity.
Read more on WikipediaMossyrock is a 300 MW hydroelectric power plant located in Lewis County, Washington. The plant began operating in 1968 and is owned and operated by the City of Tacoma - (WA). It utilizes conventional hydroelectric technology with water as its primary fuel source. The facility consists of 2 generators. Mossyrock is the 14th largest power plant in Washington out of 23, and ranks 71st nationally out of 194 plants.
In the most recent year of data, Mossyrock generated 902,717 MWh of electricity, achieving a capacity factor of 34.3%. The plant operates within the Western Electricity Coordinating Council (WECC) NERC region, and its balancing authority is the City of Tacoma, Department of Public Utilities, Light Division.
Generated from EIA, GEM, and public data sources
Grid Region
Pacific Northwest
Market
WEIM Participant
NERC Region
WECC — Western Electricity Coordinating Council
Balancing Authority
185.2K MWh
Latest Month
902.7K MWh
Annual Generation
34.3%
Capacity Factor
2013
$2,294/kW
Est. Construction Cost
Total estimated cost: $688.3M
This plant's balancing authority participates in CAISO's Western Energy Imbalance Market (WEIM). Direct nodal pricing data is not yet available.
Last updated 2026-03-26
View all articlesNo ask pi reports yet for this entity.
ask pi about MossyrockCity of Tacoma, Department of Public Utilities, Light Division (TPWR)
Grid Voltage
240.0 kV
Regulatory Status
RE — Regulated
Entity Type
Municipal
Sector
Electric Utility