Santa Clara Valley Water District

Anderson Dam Seismic Stability Study is now complete (Updated 7-5-11)

The Santa Clara Valley Water District completed a seismic stability evaluation of Anderson Dam. The evaluation found that the dam is subject to significant damage if a large earthquake were to occur close to the dam.

A storage restriction of 25.5 feet below the spillway has been put in place to protect public safety. The dam’s two regulatory agencies, the California Division of Safety of Dams and the Federal Energy Regulatory Commission approved the restriction. The restriction will allow the dam to fill to 68 percent of its full storage capacity. Staff believes that this will prevent the uncontrolled release of water after a major earthquake.

The water district initiated a capital project to complete the planning, design and construction of a seismic retrofit by the end of 2018. The operating restriction will remain in place until the project is completed.

Links to seismic stability study evaluation of Anderson Dam

• Introduction and overview to the evaluation documents - Read me first
  
  
• Anderson Dam Seismic Stability Study Report - Executive Summary
  
  
• Seismic Stability Evaluation of Anderson Dam Report (SSE-1A)      
  SSE-1A Appendices
  
  
• Technical Memorandum (TM-2A), Field Investigation Plan      
  Additional Field Investigation Plan
  
  
• Technical Memorandum (TM-3A), Design Ground Motions
  
  
• Technical Memorandum (TM-4), Preliminary Seismic Stability Evaluation
  
  
• Technical Memorandum (TM-6), Phase 1 Fault Rupture Evaluation
  
  
• Technical Memorandum (TM-7), Recommended Reservoir Restrictions
  
  
• Technical Memorandum (TM-8A), Conceptual Remedial Design Alternatives for Dam Embankment
  
  
• Technical Memorandum (TM-8B), Conceptual Remedial Design Alternatives for Outlet Works
  
  
• Technical Memorandum (TM-10), Phase 2 Fault Rupture Evaluation
  
  
• Technical Memorandum (TM-10A), Phase 2 Fault Rupture Evaluation, Addendum 1

Other information:

• News release: July 6, 2011 - Final Anderson Dam seismic study concludes that storage restrictions can be loosened but dam must be retrofitted
• Anderson Dam Seismic Study and Retrofit Project (June 2011) [PDF]
• Reservoir Operating Restrictions  (June 2011) [PDF]
• Seismic Stability Evaluation FAQ [PDF]
• Dam Safety Program [PDF]
• Dams and Reservoirs [PDF]

Anderson Dam Seismic Stability Evaluation Preliminary Findings Presentation
October 26, 2010 Board Meeting 

Public meetings:
Anderson Reservoir and Dam Good Neighbor Meeting (PDF)
Wednesday, Feb. 9, 2011 (6:30 - 8:30 p.m.)
Jackson Elementary School, Library
2700 Fountain Oaks Drive, Morgan Hill, 95037
Powerpoint presentation (PDF) 

The Santa Clara Valley Water District and water district board chairman Don Gage hosted an information meeting for residents living near Anderson Reservoir and Dam. The water district has numerous facilities in this community including Anderson Reservoir and Dam, a pumping plant, percolation ponds, pipelines, canals and creeks.

Water district staff from various departments responded to questions raised and heard your concerns on the following topics:

• Anderson Dam operations
• Pump station and pipeline operations
• Anderson as a drinking water source
• Dam seismic safety

Questions raised and responses to them (PDF)

Aerial view of Anderson Dam

Anderson Dam and Reservoir was named for Leroy Anderson, the key founder and first president of the Santa Clara Valley Water Conservation District. It was built in 1950, on a 500-acre dairy and cattle ranch along Coyote Creek purchased from the estate of John Cochran and his wife, Aphelia Farmington. The 7.8-miles-long Anderson Reservoir is the largest man-made lake in Santa Clara County. The reservoir can store 90,373 acre-feet of water. Its surface area is 1,271 acres.*

*Reservoir storage values have been updated to reflect recent survey results.