A 2012 independent engineering study identified Calero Dam as a seismic risk due to the presence of alluvium – gravel and sand from the underlying creek bed – under the downstream dam embankment. That material could liquefy during a major earthquake on a nearby fault and cause the dam to deform significantly, risking an uncontrolled release of reservoir water. In response, the state Division of Safety and Dams (DSOD) imposed storage restrictions for the reservoir of 19-feet below the spillway crest, keeping water levels lower than normal to prevent topping in the event of a major earthquake until the water district assesses and conducts corrective action to restore the dam’s full integrity.
The Santa Clara Valley Water District is moving forward on the project design for the Calero Dam Seismic Retrofit Project. This summer, the water district will hold a scoping meeting for the project, collecting public input that will help form the final Environmental Impact Report (EIR). This report identifies likely effects of the project on the surrounding area and proposes measures to offset them.
The Calero Dam Seismic Retrofit Project will:
- Stabilize dam embankments
- Replace and modernize the outlet works
- Replace and modernize the spillway to increase freeboard
- Breach Fellow’s Dike, an older and smaller dam located on the southern-most section of the reservoir that is severely deteriorated.
The Santa Clara Valley Water District built the Calero Dam during the Great Depression, completing it in 1935 after acquiring land as the Santa Clara Valley Water Conservation District. The dam and reservoir is one of the six original reservoirs approved for construction by voters in May 1934.
The reservoir has a surface area of 349 acres and is a popular venue for boating, water skiing and jet skiing. The dam is critical to the district's water storage and management, capturing runoff from the nearby foothills and transfers Almaden Reservoir.