B.F. Sisk Dam Safety of Dams Modification Project
B.F. Sisk Dam and San Luis Reservoir, located on the west side of California’s Central Valley near Los Banos, are an integral part of the federal Central Valley Project (CVP) and State Water Project (SWP). The dam, built between 1963 and 1967, is a 382-foot-high earthfill embankment over 3.5-miles long that impounds San Luis Reservoir, the largest offstream reservoir in the nation. The reservoir has a total capacity of more than 2 million acre-feet, which provides water for farms, communities, and wildlife refuges south of the Sacramento-San Joaquin Delta. B.F. Sisk, previously called San Luis Dam, is owned by the Bureau of Reclamation and operated by the California Department of Water Resources.
B.F. Sisk Dam and San Luis Reservoir are located in an area of high potential for earthquakes from identified active faults, primarily the Ortigalita Fault, which crosses the reservoir. Past investigations indicated that sections of the dam are founded on liquefiable and soft soils. During a seismic event, sections of the dam could slump below the water or allow cracking to develop through the embankment, which could lead to dam failure.
1978 Safety of Dams Act
The Safety of Dams Act was passed in 1978 to authorize the Secretary of the Interior to construct, restore, operate, and maintain new or modified features at existing federal Reclamation dams for safety purposes. The program focuses on evaluating and implementing actions to resolve safety concerns at Reclamation dams.
As part of the Safety of Dams Program, Reclamation delivered the B.F. Sisk Dam Safety of Dams Modification Report to Congress in August 2020. The $1.1 billion effort is Reclamation’s largest project under the 1978 Act, and when complete will modernize the structure to reduce risks due to seismic events.
On March 22, 2022, the Department of the Interior announced a $100 million investment for the dam safety project as part of the Bipartisan Infrastructure Law. Reclamation celebrated the announcement in conjunction with Reclamation’s 120th anniversary at the same location that President Kennedy dedicated the dam in 1962.
The dam safety project is adding stability berms and other dam safety features to the existing 3.5-mile-long earthen dam. Increasing the dam crest by 10-feet will reduce downstream public safety concerns by reducing the likelihood of overtopping if slumping were to occur during a large earthquake.
The project is divided into three phases and contracts. Phase 1 began in the summer of 2022 and the last phase is expected to be completed by 2032.
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For additional information, please contact CGB Region Safety of Dams or call 916-978-5328.