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.
Project update
The Santa Clara Valley Water District is moving forward on the project design for the Calero Dam Seismic Retrofit Project.
On Wednesday, July 18, the water district held a scoping meeting to gather input that needs consideration in the draft Environmental Impact Report (EIR) before doing the project takes place. An EIR takes a close look at a project’s potential impacts on such areas as traffic, wildlife and recreation. The draft EIR, which satisfies requirements within the California Environmental Quality Act (CEQA), is expected to be completed in summer 2019.
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.