Bureau of Reclamation - Merced County - CAISO
The William R. Gianelli Powerplant is a 424 MW, eight-unit pumped-storage plant that moves water between O'Neill Forebay and San Luis Reservoir. Owned by the Bureau of Reclamation and operated by California's Department of Water Resources, it is both a grid-scale storage asset and a working part of the joint state-federal water system serving the State Water Project and Central Valley Project.
Answers use this researched asset profile with live CAISO data. Ask about ownership, equipment, project history, or current grid context.
Live CAISO public data · answers can be wrong, verify against source data or the ISO.
Canonical EIA plant baseline.
plant-448
Similar plants ranked by technology, capacity, and distance.
Source-backed project transactions, agreements, land records, permits, and environmental disclosures. Portfolio and adjacent-project facts remain explicitly scoped.
Parties, market resources, and identifiers tied to this asset, with owner, operator, developer, EPC, compliance provider, and interconnecting entity roles kept separate.
Project milestones and public references behind the asset profile.
The Bureau of Reclamation and California agreed to coordinated operation and construction of joint-use facilities with a 55/45 state-federal cost split.
Public Law 86-488 (San Luis Authorizing Act), signed by President Dwight Eisenhower, authorized the San Luis Unit and the Secretary of Interior to negotiate and enter into the joint-use agreement with California.
California voters approved a $1.75 billion general-obligation bond issue to finance State Water Project dams, pumping plants, and aqueducts, including the Gianelli plant.
The United States and California Department of Water Resources executed the Joint Use Agreement, providing for shared construction costs, state conveyance of required land title to the United States, and state operation of the joint-use facilities after completion.
Construction of the Gianelli Pumping-Generating Plant began as part of the San Luis Unit.
Morrison-Knudsen, Utah Construction Co., and Brown and Root won the pumping-generating plant construction contract with a combined bid of $38.3 million.
The plant was completed with eight pump-turbines and approximately 424 MW of generating capacity. Reclamation's project history states it was then California's largest hydroelectric plant.
The Bureau of Reclamation facility record lists initial operation in fiscal year 1968.
State Water Project water first reached O'Neill Forebay, marking integration of the Gianelli plant into the joint-use system serving both the CVP and SWP.
The San Luis Dam was dedicated by Secretary of the Interior Stewart L. Udall, who highlighted the unprecedented federal-state partnership.
San Luis Reservoir was completely filled, signaling completion of the joint-use system and full operational readiness of the Gianelli plant.
The San Luis Pumping-Generating Plant was officially designated the William R. Gianelli Pumping-Generating Plant, honoring William R. Gianelli, who served as director of the California Department of Water Resources during critical construction years (1967–1973).
Answered from the published record above. Questions whose inputs this profile does not carry are omitted rather than estimated.
San Luis (William R. Gianelli) Powerplant has a reported capacity of 424 MW. Source: EIA Form 860M.
San Luis (William R. Gianelli) Powerplant is a Hydroelectric Pumped Storage facility in Merced County, CA, participating in the CAISO market.
San Luis (William R. Gianelli) Powerplant is in Merced County, CA, inside the CAISO balancing area.
San Luis (William R. Gianelli) Powerplant is operated by California Dept. of Water Resources according to the EIA generator inventory. Reporting membership does not by itself establish ultimate ownership.
Plants within 25 km, nearest first, regardless of technology. Proximity is straight-line distance between mapped plant coordinates; it does not by itself establish a shared point of interconnection.