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B.F. Sisk Dam is a 300-foot-high zoned compacted earthfill embankment located on the west side of California's Central Valley approximately 12 miles west of Los Banos, California.  The dam is over 3 ½ miles long and impounds San Luis Reservoir which has a total capacity of over 2 million acre-feet. 

The dam was built between 1963 and 1967 to provide supplemental irrigation water storage for the Federal Central Valley Project and municipal and industrial water for the California State Water Project.  Water is lifted into the reservoir for storage by the Gianelli Pumping – Generating Plant from the California Aqueduct and from the Delta-Mendota Canal via O’Neill Forebay. 

B.F. Sisk Dam (also known as San Luis Dam) is owned by the Bureau of Reclamation and operated by the California Department of Water Resources.  Reservoir storage space is allotted 55 percent State and 45 percent Federal.

Phase: Corrective Action Study

Background:  A series of studies and analyses culminating in the seismic risk analysis that was completed in 2006 determined that there is justification to take action to reduce risk to the downstream public.  This decision was a result of the following developments:

• Increases in the estimates of both the severity of ground shaking due to nearby earthquake faults, primarily the Ortigalita fault, which crosses San Luis Reservoir and the probability of a large event on the Ortigalita fault.
• New understanding of the properties of the dam’s foundation materials and their ability to resist deformation when subjected to severe shaking.
• Advances in computer-based analysis methods, which allow better assessment of the behavior of the dam under seismic loading.

Status: Corrective action alternatives are expected to be identified during early 2008.  The best alternatives will be selected for further development including feasibility level designs and risk reduction estimates.