Anderson Reservoir is currently being limited to 58 percent 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. This voluntary restriction exceeds the restriction approved by the regulatory agencies (California Division of Safety of Dams and the Federal Energy Regulatory Commission) and was instituted by the water district in response to additional findings during the project’s design phase. The water district and regulatory agencies believe that this restriction will prevent the uncontrolled release of water in case the dam is structurally damaged after a major earthquake.
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 seismic retrofit will also support compliance with environmental regulations. The water district’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 and other significant impacts to surrounding land more than 30 miles northwest to San Francisco Bay, and more than 40 miles southeast to Monterey Bay.
- Brings the dam into compliance with today’s seismic standards
- Increases reliability and safety of our area’s largest reservoir by protecting it from earthquakes
- Eliminates operational restrictions issued by the state Division of Safety of Dams which would restore Anderson Reservoir to its full capacity of approximately 30 billion gallons, regaining 42 percent or 12.6 billion gallons of water storage for our current and future supply
- Ensures compliance with environmental laws requiring reservoir releases that maintain appropriate flows and temperatures to support downstream wildlife habitat
- Minimizes the risk of uncontrollable releases from the reservoir which could cause downstream flooding, despite the fact it is not constructed as a flood control project
(As of February 2017)
- Phase 2 geotechnical investigations for the design phase completed.
- Modified project defined to address all existing deficiencies
- Design phase of modified project ongoing; expected to be completed Winter 2018/2019
The Draft EIR document is slated to be released for public review in Spring 2018
Start of construction planned for Spring 2020
Key Performance Indicator
- Provide portion of funds, up to $66.1 million, to help restore full operating reservoir capacity of 90,373 acre-feet
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