A $1 billion effort to expand the B.F. Sisk Dam in California’s Central Valley was approved in October by the U.S. Dept. of the Interior and San Luis & Delta-Mendota Water Authority. When completed, the project will raise the dam height by 10 ft creating an additional 130,000 acre-ft of storage space in San Luis Reservoir, the nation’s largest offstream reservoir.

The B.F. Sisk Dam Raise and Reservoir Expansion Project will create additional water supply for two million people, over one million acres of farmland and 135,000 acres of Pacific Flyway wetlands and critical wildlife habitat, say officials. 

“San Luis Reservoir has served as the hub of California’s water system south of the Sacramento San Joaquin Bay-Delta since its completion in 1967,” said San Luis & Delta-Mendota Water Authority Board Chair Cannon Michael in a news release. “The ability to capture more water in the years it is available, particularly given California’s changing climate, is a critical component of a more secure future for the communities, farms and wildlife dependent on the Central Valley Project for their water supply.”

The signing of the Record of Decision and Notice of Determination is the first approval of a major water storage project in California since 2011. A total of $95 million in federal contributions has been made available to date for the project including received $25 million under the 2021 Infrastructure Investment and Jobs Act (IIJA) in October 2022 and $10 million in July 2023. An additional $60 million was authorized for project construction from the Water Infrastructure Improvements for the Nation Act. 

The project is currently in design, which is projected to complete in early 2025, with construction awards in early 2026. The design team includes Bureau of Reclamation, San Luis & Delta-Mendota Water Authority, and CDM Smith. The Hallmark Group is providing project management and support to our non-federal partner, San Luis & Delta-Mendota Water Authority.  

Located in California’s Central Valley, The B.F. Sisk Dam and San Luis Reservoir are important parts of the federal Central Valley Project (CVP) and State Water Project (SWP). The dam, built between 1963 and 1967, is a 382-ft-high earthfill embankment over 3.5-miles long that impounds San Luis Reservoir. The reservoir has a total capacity of more than 2 million acre-ft, which provides water for farms, communities, and wildlife refuges south of the Sacramento-San Joaquin Delta. 

Miners inside one of the fuel tanks

Cutaway graphic of the B.F. Sisk Dam upgrade and expansion.
Photo courtesy of Bureau of Reclamation

Besides the Dam Raise and Reservoir Expansion Project, a major safety project is currently underway at B.F. Sisk Dam. Costing about $1.1 billion, the B.F. Sisk Dam Safety of Dams Modification Project is increasing the dam crest by 10 ft to improve seismic safety. The job is adding stability berms and other dam safety features to the existing 3.5-mile-long earthen dam. Increasing the dam crest will reduce downstream public safety concerns by reducing the likelihood of overtopping if slumping were to occur during a large earthquake. The project, expected to complete by 2032, is the Bureau of Reclamation’s largest project under the 1978 Safety of Dams Act.