Anderson Reservoir was at about 54 percent capacity this week, but it still welcomed recreational boaters for a new season, which began April 15.
“Enjoy it while you can,” could have been the message to the boaters this spring, with a five-year complete closure and $550 million dam reconstruction still set to begin in 2022.
Fishing is allowed in the reservoir, but signs posted at the reservoir warn against eating any of the fish because of possible mercury contamination.
For boaters—as well as the cyclists and hikers who regularly visit the scenic reservoir—who wonder about drilling equipment and trucks at the dam’s north end: The Santa Clara Valley Water District, which owns and manages the reservoir, last month began a geotechnical investigation as the first step in the dam’s redesign and reconstruction. The study will continue through the summer.
The district also has hired archeologists to conduct a “cultural resource” study to determine the presence of any historic or culturally significant items in the dam reconstruction project boundary. The district said the geotechnical investigation will test the soil and rock strength of the nearly 70-year-old earthen dam to provide a comprehensive look at its foundations.
The dam reconstruction plan was first announced by the water district in 2013, about four years after authorities learned the current structure could collapse in a major earthquake, causing catastrophic flooding of the entire Santa Clara Valley. New seismic data in late 2016 prompted the district to revise its plans, shifting from a “seismic retrofit” to a complete reconstruction. When the project is completed in 2027, the reservoir will return to its original storage capacity behind a structure that is more resistant to earthquake damage or collapse. The reservoir will be drained and closed to the public during the five years of reconstruction.
Anderson Dam creates the county’s largest surface water reservoir, which stores local rainfall runoff and imported water from the Central Valley. The reservoir is an important water source for treatment plants and the recharge of the groundwater basin.
During some of the heavy rains this past winter, the water district made controlled releases from Anderson Reservoir to reduce the chance of the reservoir reaching its restricted storage limit of 58 percent.
The reservoir’s outlet pipe runs through the bottom of the dam and releases water to Coyote Creek, which borders several new housing developments at Morgan Hill’s northeastern edge.
Valley Water, the new name for the Santa Clara Valley Water District, manages an integrated water resources system that includes the supply of drinking water, flood protection and stewardship of streams in Santa Clara County.