Politics & Government

Local Dams Vulnerable to Earthquakes

Santa Clara Valley Water District increases storage restrictions as safety measure.

Calero and Guadalupe dams are in deep doodoo should the earth underneath them start shaking and rolling, officials said this week.

A Santa Clara Valley Water District study has found that both dams are subject to significant damage if a major earthquake were to occur.

Guadalupe Reservoir is located southeast of Los Gatos, on the western edge of Almaden Quicksilver County Park and Calero Reservoir is located in the hills south of Almaden Valley, on McKean Road.

Find out what's happening in Los Gatoswith free, real-time updates from Patch.

The dams have been subject to storage restrictions based on earlier similar findings, according to district spokesman Marty Grimes.

As a result of the new findings, the district has voluntarily decreased the amount of water the dams can hold to 25 feet below their crest. The new operating restrictions are now subject to approval by the state Division of Safety of Dams (DSOD), Grimes explained.

Find out what's happening in Los Gatoswith free, real-time updates from Patch.

Calero has been under a storage restriction of 20 feet below the dam’s crest since January of 2011, when preliminary data indicated the presence of alluvium—gravel and sand from the underlying creek bed—under the downstream dam embankment. The condition could make the dam vulnerable to damage during a major earthquake, Grimes added.

The additional 5-foot restriction would reduce the available storage capacity by 1,136 acre-feet, he said.

Guadalupe has been under a storage restriction of 14 feet below the dam’s crest since October of 2006. The additional 11-foot restriction would reduce the available storage capacity by 1,003 acre-feet.

The district expects to initiate a capital project to study possible remedial options for the dams, but it's not known how much it will cost.

The district is the largest water services provider in Santa Clara County providing flood protection services to about 1.8 million residents.


Get more local news delivered straight to your inbox. Sign up for free Patch newsletters and alerts.

We’ve removed the ability to reply as we work to make improvements. Learn more here