Morgan Hill Today 2013 06 Summer | Page 42

Today and Tomorrow

Anderson Dam is a recreational center for boating , water skiing and fishing . These recreational activities can make the Dam a busy location during the summer months . There is a 35 MPH speed limit on the lake as well as protected slow zones on each side to afford anglers the best opportunity to catch small bass , crappie , catfish and carp . Anglers not having a boat available to them can find good fishing near the bridge and the edges of the rock wall .

In 2011 , a seismic study of Anderson Dam showed that a 7.25 magnitude earthquake on the Calaveras Fault would cause the dam to weaken due to liquefaction . The result could then be the uncontrolled release of reservoir water . The 1984 Morgan Hill Earthquake and the 1989 Loma Pieta Earthquake showed evidence of movement at the top of the dam .
As a result of the 2011 study , showing the possible loss of up to 25 feet of the vertical face and an additional 15 feet of cracking of the dam , it was recommended that the water level be restricted to 40-45 feet below the dam crest . This was to provide an adequate level of safety to the public downstream and would prevent an uncontrolled release of water . This restriction , as well as several others , are in place and will remain until the improvements are made to Anderson Dam .
This brings us to the present day and the Anderson Dam Seismic Retrofit Project . The proposed changes to the dam are based on the earthquake issues and changes to the regulatory requirements from the Division of Safety of Dams and Federal Energy Regulatory Commission . The Retrofit Project will result in changes to the spillway , the outlet pipe , the crest of the dam , and the embankment on both sides of the dam . The project began with planning and study in 2011 and is scheduled for completion in 2019 .
The Santa Clara Valley Water District is currently reviewing six different options to address the deficiencies of the current dam . After an option is selected , residents of Morgan Hill and users of Anderson will see four major changes :
1 . The dam will be closed to boating and fishing ; the water will be drawn down to allow for construction work and shoring up the embankments . 2 . The boat ramp and surrounding trails will be closed . 3 . Cochrane Road will be closed except to local traffic . 4 . The lake park and picnic area will be closed .
Timelines on these changes and closures are yet to be determined . Residents near the dam are likely to experience
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“ Anderson Dam , Lake and Park are wonderful community assets — providing water for ground water recharge , supply to our water treatment facilities , and floodwater protection . They also provide boating , jet-skiing and fishing and camping opportunities for all of us to enjoy .
As much as we want to keep the lake full , we must proceed with the seismic retrofit of the dam , to insure the safety of the thousands of downstream residents and the viability of the dam for its intended purpose . The Santa Clara Valley Water District will keep the community informed as planning , engineering and construction progresses . It is anticipated that the seismic , retrofit , construction work will begin in 2016 .”
Dennis Kennedy , Director District 1 , Santa Clara Valley Water District
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