Study: San Luis Reservoir Expansion Would Cost $360 Million

A U.S. Bureau of Reclamation report released earlier this month looks at how San Luis Reservoir could be enlarged while also improving the resiliency of B.F. Sisk Dam in the event of an earthquake.

Reclamation’s Draft Appraisal Report considers a scenario where a multi-faceted $360 million project would raise the dam by 20 feet in order to add 130,000 acre-feet to the reservoir’s current capacity of 2.04 million acre-feet. The construction would modify and retrofit the dam embankment and dikes, spillway, intake towers and access bridge.

For more than a decade officials have been exploring the idea that more capacity at the jointly-operated reservoir near Los Banos would help eliminate harmful algal blooms that sometimes occur when water levels are low, and also help California prepare for climate change that necessitates more surface storage. The project also could improve water reliability for farms, cities and other south-of-Delta contractors that receive water from the Central Valley Project (CVP) via the reservoir.

“An expansion of the dam and reservoir would address at least four factors affecting the reliability of CVP deliveries associated with San Luis Reservoir. These factors include water quality in the reservoir, seismic risk to the dam, Delta conditions and regulations affecting the timing and volume of water available to store in the reservoir, and timing and volume of demand for water stored in the reservoir,” Reclamation Mid-Pacific Regional Director David Murillo wrote in a letter about the San Luis expansion study.

Pumping restrictions in the Delta — put in place to protect smelt and other threatened fish — continue to limit how much water is pumped into San Luis and when those deliveries occur. Due to record-dry conditions during 2013 and the pumping restrictions, San Luis has been unusually low this year, just 26% full on Dec. 11, which is only 41% of average for the date.

A 2006 report from the Bureau concluded that B.F. Sisk Dam, completed in 1967, potentially could fail if seismic activity occurs due to its proximity to several faults. A follow-up study identified raising the dam as one potential fix.

Reclamation would like to work with its partners — the California Department of Water Resources, the Santa Clara Valley Water District and the San Luis & Delta-Mendota Water Authority — to further investigate how San Luis can be enlarged.

The Bureau is taking public comment on the Draft Appraisal Report until Jan. 17, 2014. Send your responses to William Aley, 2800 Cottage Way, Sacramento, CA 95825, or email waley@usbr.gov, or fax (916) 978-5094.

Access the report at the Reclamation here.