MORGAN HILL (KCBS) — The idea of completely draining one of the Bay Area’s largest reservoirs of drinking water might be shocking to drought-conscious Californians. But that’s exactly what will happen next year when a seismic retrofit will begin at Anderson Dam and Reservoir near Morgan Hill.

The Santa Clara Valley Water District plans to drain the reservoir in the fall of 2015.

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Katherine Oven, an engineer with the district, said they can’t put off seismic safety work any longer and that studies have shown a 6.6-magnitude earthquake could destroy the 60-year-old dam. “We want to proceed with the retrofit of that dam so that the communities below it are safe,” she told KCBS.

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“The entire dam will just erode in matter of hours, and anything inside the dam will be released down into the Valley so it would be a catastrophic event,” Oven added.

But during a drought, the water district has a tough choice: delay the draining and risk catastrophic flooding, or go forward and loose out on capturing billions of gallons of water. Water District board member Richard Santos said they must err on the side of public safety.

“We’re a public service and we want to make sure our constituents have water not at the expense of somebody getting hurt—there is no way in the world,” Santos said.

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Santos said there may be a way to tweak the timing of the draining to still capture some rain water and that they hope to save as much of Anderson’s water as they can by pumping it into nearby treatment plants.