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C1: Anderson Dam Seismic Retrofit

Anderson Reservoir is currently being limited to about 52% 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 seismic retrofit will also support compliance with environmental regulations. The 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.

In December 2016, the Board was informed by the District that findings from the geotechnical  and geologic investigations performed during the project's design phase let 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 estimate cost. The District presented the Board with a water supply cost-benefit analysis that showed the benefits of the more extensive retrofit, which would require the District to purchase additional imported water every year to make up for the loss of long-term storage at Anderson Reservoir. Base upon this information and analysis, the Board directed the District to continue work on this critical infrastructure project. 



Benefits

  • 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 (DSOD) which would restore Anderson Reservoir to its full capacity of approximately 90,373 acre-feet, regaining 48% or about 43,500 acre-feet of water storage for our current and future water 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

Project Status

(As of June 2017)

  • In May 2015, the Board approved, as part of its annual groundwater production charge setting, that $14 million of Safe, Clean Water funding be transferred to the Water Utility Enterprise Fund as reimbursement for the Anderson Dam project in FY16 instead of the Safe, Clean Water-scheduled $15 million transfer in FY18. The purpose of this earlier transfer was to offset the groundwater production charge increase for FY16.  
  • The next fund transfer is scheduled for FY28. 
Visit the Anderson Dam and Reservoir webpage for detailed project information. 

  1.  

Key Performance Indicator

  1. Provide portion of funds, up to $45 million, to help restore full operating reservoir capacity of 90,373 acre-feet.

  

 

 For more information:

 

 

Priority C-200

Project Information

StatusAdjusted
Project StartFY 2014
Project FinishFY 2020
Safe Clean Water
Program funding

$66.1 M**

(2015 Dollars)

**More financial information: 5-Year Implementation Plan, pages: 19-27
LocationCountywide


For more information: