BOARD AGENDA MEMORANDUM
SUBJECT:
Title
Update for the Anderson Dam Seismic Retrofit Project - Project No. 91864005 (Morgan Hill) (District 1).
End
RECOMMENDATION:
Recommendation
Receive an update on the environmental and permitting strategy for the Anderson Dam Seismic Retrofit Project.
Body
SUMMARY:
The purpose of this agenda item is to present a more detailed update on the Anderson Dam Seismic Retrofit Project (Project) environmental documentation and permitting strategy and Project schedule.
Project Background
In 2011, the District completed a seismic study of Anderson Dam, which indicated that material at the base and foundation of the dam embankment could weaken due to liquefaction in a 7.25 magnitude earthquake [the maximum credible earthquake (MCE)] on the Calaveras Fault, located approximately 1.2 miles from the dam. Such an event could significantly deform the dam embankment, risking an uncontrolled release from Anderson Reservoir. The 2011 study also indicated that an MCE could trigger fault offset on the conditionally-active Coyote Creek-Range Front fault zone located in the vicinity of the dam, which would damage the existing outlet pipe, precluding safe drainage of the reservoir.
The District initiated the Anderson Dam Seismic Retrofit Project in 2012 to address the seismic deficiencies at the dam and to meet the design requirements of the Federal Energy Regulatory Commission (FERC) and the California Department of Water Resources, Division of Safety of Dams (DSOD).
The Project's Planning Phase was initiated in 2012 and completed in July 2013. The Design Phase was initiated in August 2013. As project design work proceeded, an administrative draft of an Environmental Impact Report (EIR) was prepared in 2014, as required by the California Environmental Quality Act (CEQA) for the Project.
Between 2014 and 2016, detailed geotechnical and geologic investigations were performed on and around the dam embankments to further inform the ...
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