May 29, 2025 – LOS BANOS, Calif. – The Bureau of Reclamation has awarded a $255 million construction contract to NW Construction to begin Phase 2 of the B.F. Sisk Safety of Dams Modification Project, a critical infrastructure initiative in Merced County aimed at protecting California's water supply and improving public safety.

The B.F. Sisk Dam, originally completed in 1967, forms the San Luis Reservoir, the largest offstream reservoir in the United States. This facility is a vital component of the Central Valley Project and the State Water Project, supplying irrigation water to prime farmland, drinking water to California communities, and habitat support for regional wildlife refuges.

The dam stands 382 feet tall and stretches 3.5 miles across. It is located in a seismically active zone near the Ortigalita Fault, a geological feature that presents significant risk in the event of an earthquake. The safety upgrade is the largest project ever undertaken under the authority of the 1978 Safety of Dams Act.

“Reclamation is committed to ensuring the safety and integrity of our water infrastructure,” said Reclamation Acting Regional Director Adam Nickels. “This project represents a major investment in the future of California’s water supply and the communities and ecosystems that depend on it.”

The multi-phase safety project is designed to reduce seismic risk and prevent potential dam failure caused by slumping or overtopping during a major earthquake. Phase 1, completed in 2024, involved the construction of preliminary stability berms and foundational enhancements along portions of the dam.

Phase 2, now underway, will focus on building a large central stability berm and placing approximately 15 million cubic yards of engineered earthen material. These measures are intended to reinforce the dam’s structural integrity and mitigate seismic vulnerability. The final phase of the project will include raising the dam crest by 10 feet to further enhance flood resilience and operational safety.

The combination of berms, shear keys, and elevation increases is expected to significantly reduce the likelihood of overtopping and potential dam failure in the event of slumping during seismic activity. These modifications also align with Reclamation's broader mission to modernize infrastructure and adapt to increasing water demands and environmental pressures in California.

The project has received wide support from regional water agencies, agricultural stakeholders, and environmental groups due to its long-term benefits to water storage reliability and public protection.

More information about the B.F. Sisk Safety of Dams Modification Project can be found at:
www.usbr.gov/mp/sod/projects/sisk/index.html

Originally reported by Goldrushcam.