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The South Bay’s largest reservoir will be unusable for the next 10 years

The South Bay’s largest reservoir will be unusable for the next 10 years
Photo Credit: SCVWD
By Wesley Severson - Published on July 08, 2021.

Anderson Dam and Reservoir are about to undergo a massive reconstruction project that will take a decade to complete. That means the Valley Water District will have to drain Santa Clara County’s largest reservoir and look to new sources for water storage just as the state sinks back into serious drought conditions. 

The reservoir has been at a low capacity for years because the dam that holds back almost 90,000 acre-feet of water has shown signs that it could collapse if a large earthquake hits the area. Right now, Anderson Reservoir is at 3% of capacity and according to Silicon Valley Business Journal, it fully closed last October when it was at 58% capacity.

Silicon Valley Congresswoman Zoe Lofgren attended a groundbreaking ceremony for the project where she said the result of an earthquake would be catastrophic if the reservoir was full of water. "There’d be a wall of water into Morgan Hill in under 14 minutes, but it would also flood all the way up to Palo Alto and all the way into Monterey Bay,” Lofgren said.

Phase one of the project is expected to be completed in 2024 and will consist of building a 1,700-foot tunnel that funnels water from the reservoir while crews can completely rebuild the dam itself. It will then take seven more years for the construction of the dam to be completed.

Valley Water District Director John Verela told KTVU, "We understand this will be a long endeavor and will do our best to minimize any impacts to the neighborhoods as we move forward." The price of the entire project is $576 million dollars but that could fluctuate. 

Now that construction is underway, the Santa Clara Valley Water District is trying to figure out how to deal with the drought gripping the South Bay. Losing Anderson Reservoir equates to a lot less water storage area for the region. “We purchased water for this year and then a few years from now. That’s what we tried to do. [At the] same time, we’ve been looking at storage outside the county," Valley Water District board chair Tony Estremera told NBC Bay Area.

Santa Clara County is already asking residents to cut back on water use because of the drought emergency, but the Valley Water District argues the Anderson Dam project is absolutely critical when it comes to dealing with even bigger droughts in the future.