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Fixing Anderson Dam is a priority for Valley Water

Valley Water, Santa Clara County, Morgan Hill, CA

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Anderson Reservoir on the Calaveras fault line.  Photo Credit

Seismic Concerns and Aging Dam at Anderson Reservoir

Anderson Reservoir is currently limited to about 58% of its capacity due to seismic concerns costing Santa Clara County valuable drinking water resources. This project covers earthquake retrofitting of Anderson Dam to improve reliability and safety, and returns the reservoir to its original storage capacity.

Anderson Dam creates the county’s largest surface water reservoir—Anderson Reservoir— which stores local rainfall runoff and imported water from the Central Valley Project. The reservoir is an important water source for treatment plants and the recharge of the groundwater basin. Besides restoring drinking water supplies, the upgrade also supports compliance with environmental regulations. Valley Water’s regular reservoir releases ensure that downstream habitat has healthy flows and temperatures to sustain wildlife.

A breach of Anderson Dam at full capacity could have catastrophic consequences, including inundation of surrounding land more than 30 miles northwest to San Francisco Bay, and more than 40 miles southeast to Monterey Bay.

In December 2016, the Board was informed by Valley Water staff that findings from the geotechnical and geologic investigations performed during the project’s design phase led to the conclusion that a more extensive dam retrofit than had originally been envisioned would have to be performed. Further, the Board was informed that the more extensive retrofit work would double the previous project’s estimated cost. Valley Water staff presented the Board with a water supply cost-benefit analysis that showed the benefits of the more extensive retrofit project significantly outweighed the cost of not proceeding with the retrofit, which would require Valley Water to purchase additional imported water every year to make up for the loss of long-term storage at Anderson Reservoir. Based upon this information and analysis, the Board directed Valley Water to continue work on this critical infrastructure project.

Eyasco's Earth QuB Application at Anderson Dam

Eyasco Inc. working closely with the Santa Clara Valley Water District has designed a system to monitor dam behavior, specifically related to material (soil) behavior. The installed stations known as Earth QuBs include piezometers, inclinometers, extensometers, strain gauges and meteorological sensors to detect water levels, settlement, displacement, consolitation, etc. The intended purpose is to predict changes in the dam integrity that may possibly lead to a structural failure. The data gathered and provided was key in determining that the dam does in fact, need a retrofit upgrade.

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The Earth QuB configuration on Anderson Dam, located in Morgan Hill, California

Located on both sides of the dam, an array of Eyasco Earth QuBs gather and transmit data to Eyasco's web based servers. The data is converted to readable analytic information that is easily organized and viewed on a web browser. When a seismic event occurs, the Earth QuB are positioned to detect movement and changes in the dam's material and structure.

Read more about Eyasco's Earth QuB

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