The Bureau of Reclamation has awarded a $255 million construction contract to NW Construction for Phase 2 of the B.F. Sisk Dam Safety of Dams Modification Project in Los Banos, California. The project is part of Reclamation’s ongoing effort to strengthen dam safety and maintain water supply reliability in the Central Valley.
B.F. Sisk Dam, built in 1967, impounds the San Luis Reservoir—the largest offstream reservoir in the United States. Located in a seismic zone near the Ortigalita Fault, the dam plays a key role in storing and delivering water for agriculture, municipalities, and wildlife habitats as part of the Central Valley Project and the State Water Project.
Phase 2 will involve building a large stability berm along the dam’s central section. Crews will place approximately 15 million cubic yards of engineered earthen material to enhance the dam’s structural resilience against seismic events. The final phase will raise the dam crest by 10 feet to reduce overtopping risks in the event of slumping.
This work follows the completion of Phase 1, which began in 2021 and involved foundation preparation and initial berm construction. Reclamation is managing the project under the authority of the Safety of Dams Act of 1978.