Priority C: Protect Our Water Supply from Earthquakes and Natural Disasters


Wildfires, earthquakes and other natural disasters can strike without warning. Having a water supply that persists through an emergency means a faster recovery for everyone. To ensure that our water supply remains safe and reliable during and after an emergency, Valley Water is working to protect our water supply infrastructure from the effects of natural disasters. This priority contains the Anderson Dam Seismic Retrofit Project.



Anderson Dam Seismic Retrofit Project

Anderson Dam creates the county’s largest surface water reservoir—Anderson Reservoir— that stores local rainfall runoff and imported water from the Central Valley Project. With a capacity of nearly 90,000 acre-feet (enough water to supply almost a million people for a year), the reservoir is a critical part of the region’s water supply system. The reservoir provides water to drinking water treatment plants and for groundwater recharge.

Anderson Dam, situated in Morgan Hill, was built in 1950 to the seismic and dam safety standards of the day. The Coyote Creek Fault is located directly under the dam and the Calaveras Fault is located nearby. Studies have shown a large earthquake on one of these faults could result in significant damage to the dam, causing an uncontrolled release of water that could inundate cities and rural areas from San Francisco Bay south to Monterey Bay, including much of Silicon Valley. Additionally, a large earthquake could damage the outlet pipe used for safe drainage of the reservoir.

The Anderson Dam Seismic Retrofit Project will rebuild the dam in compliance with today’s seismic and safety standards and regulations. The project will also increase the dam’s spillway and outlet capacities to allow a rapid, controlled drawdown in emergency and to enhance incidental flood protection.

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