Following recent safety evaluations, the US Bureau of Reclamation (USBR) and California Department of Water Resources (DWR) have announced that they are planning corrective actions to strengthen B.F. Sisk dam to reduce the risk of earthquake damage.
The dam, also known as San Luis dam, is located between Los Banos and Gilroy, California, along Pacheco Pass. It creates San Luis reservoir, which serves as an off-stream reservoir for the Federal Central Valley Project and the California State Water Project.
The dam is in a seismically active area and very close to the Ortigalita Fault that crosses the reservoir. Studies and analyses indicate that a major earthquake could result in substantial consequences, although the possibility of dam failure is remote.
USBR regularly reviews its dams to ensure they do not present unreasonable risks to the public, property, and the environment. A Corrective Action Study has been initiated at the dam to identify and develop alternatives to reduce risks. USBR and DWR will jointly participate in the process to select and implement a risk reduction action plan.
The earth-filled gravity embankment dam is 93m tall and was completed in 1967. San Luis reservoir is the largest off-stream reservoir in the US, with a capacity of 2.5Bm3. The dam is owned by USBR and operated by DWR.