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HomeMy WebLinkAbout05-07-2013 c10 conclusion of salinas resevoir expansion studycouncrL âqenòâ pepoRt vleetinB Date o5-o7t017 tem Nuhber c10 FROM: Prepared By: SUBJECT: CITY OF SAN LUIS OBISPO Carrie Mattingly, Utilities Director 'Wade Horton,'Water Division Manager CONCLUSION OF SALINAS RESERVOIR EXPANSION STUDY RECOMMENDATION Conclude the Salinas Reservoir Expansion Study BACKGROUNI) The federal government constructed Salinas Dam in 1941 as a Military Works project to supply water to Camp San Luis Obispo and the City of San Luis Obispo (City). The federal government owns Salinas Dam and the United States Army Corps of Engineers (Army Corps) exercises oversight responsibilities for it. The City and Army Corps are co-permittees of State Water Resources Control Board Permit 5882, which allows for the appropriation, storage, and beneficial use of water from the Salinas River, including storage in the Salinas Reservoir. The City also holds a license from the Army Corps which allows connection to the Army Corps' pipeline to supply water to the City from Salinas Reservoir. ln accordance with a separate lease with the Army Corps, the San Luis Obispo County Flood Control &'Water Conservation District (District) operates the dam and has a separate lease from the Army Corps to use the areas surrounding the dam for recreational purposes. DISCUSSION Beginning in the 1980s, the City pursued options to increase available water supplies to meet community water needs. The Salinas Reservoir Expansion Project was one of two water supply projects under consideration (the Nacimiento Pipeline Project was on aparallel track). As proposed, the Salinas Reservoir Expansion Project involved the installation of spillway gates on the dam in order to increase reservoir storage capacity. As a condition of installing spillway gates, it was understood that dam ownership would be transferred from the federal government to a local agency, thereby transferring dam oversight from federal to state jurisdiction. The California Department of 'Water Resources, Division of Safety of Dams (DSOD) has regulatory oversight of non-federal dams in California. During the course of evaluating the feasibility of installing the spillway gates, and in response to the potential transfer of the dam from federal to state jurisdiction, the City hired Woodward-Clyde Consultants to conduct an inundation study for the existing (without spillway gates) and proposed (with spillway gates) dam configuration. This analysis was completed in May 1993. The City also c10-1 Gouncil Agenda Report - Conclusion of Salinas Reservoir Expansion Study Page 2 commissioned URS in 1999 to perform a seismic analysis of the dam structure. On June 28, 2000, URS issued the Salinas Reservoir Expansion Project - Dam Sa.fety Evaluation Volume I - Report which concluded: The dam with the existing maximum reservoir level satisfies modern seismic performance evaluation criteria such as those currently used by DSOD (pg ES-5). In June 2004 the City executed the Nacimiento 'Water Supply Agreement through which the City would receive up to 3,380 acre feet of water per year from the Nacimiento Water Supply Project. Although this project would serve the water supply needs of the community, coordination with DSOD and the Army Corps related to Salinas Dam continued, including discussions on the potential for transfer of ownership of the dam to a local agency. In early 2005, a meeting with DSOD, City, and Army Corps staff was held to further discuss the impacts of ownership transfer from the federal government to a local agency. It was concluded that considering new analytical criteria published in2003, an analysis beyond that which was performed in 2000 was required to determine if Salinas Dam would meet DSOD standards were it to be transferred to state jurisdiction. The City contracted with URS in 2006 to perform a "non-linear" seismic analysis of Salinas Dam, which was a more complex methodology for dam evaluation. As stated in the January 17,2006 Council Agenda Report: The potential transfer of ownership of the dam is the primary reason for pursuing the additional seismic analysis recommended in this report. The transfer of ownership of the damfrom thefederal government to a local agency will require that the dam meet the design standard of the DSOD. The URS contract was amendedin200l to complete additional analysis with some modifications to the seismic computer model based on DSOD recommendations. Study Findings Due to a number of factors, including a highly complex analysis and extensive coordination and review time required among the City, DSOD, and Army Corps, the final seismic report was completed in October 2012. The URS report concluded, based on analysis completed to date, Salinas Dam is unlikely to meet the more stringent DSOD seismic requirements if the dam were to transfer from federal to state jurisdiction. The conclusion of the October 2012 rcport does not equate to a current dam safety evaluation, nor does it suggest a situation of imminent dam failure. On November 26,2012, City staff discussed the October 2012 report conclusions with the Army Corps Los Angeles District Office. The City confirmed it does not wish to pursue installing the spillway gates or ownership transfer. The Army Corps reaffirmed that Salinas Dam is a federal asset under federal jurisdiction. As the federal ageîcy that retains ownership of the dam, the Army Corps is responsible for dam safety. In 2009, as a result of the Army Corps' screening for Portfolio Risk Analysis, the Army Corps assigned a Dam Safety Action Classification (DSAC) IV to Salinas Dam. Although dams with a DSAC [V classification have some deficiencies that should be resolved, DSAC IV dams are considered to be low risk. This DSAC fV classification is the highest (best) for the 18 Federal dams in the Army Corps'Los Angeles District inventory. c10-2 Gouncil Agenda Report - Conclusion of Salinas Reservoir Expansion Study Page 3 The Seismic Analysis of Salinas Dom, San Luis Obispo, CA, dated October 2012 contains information on a federal facility that may expose vulnerabilities, and the Army Corps has directed that it be treated as For Official Use Only (FOUO), which precludes its release in an uncontrolled manner. Thus, only the conclusion of the report, rather than publication of the detail is included in this report. The Salinas Reservoir Expansion Study is now concluded. The City will continue to coordinate with the District regarding Salinas Reservoir as a City water supply and its impact related to county-wide water resource management. FISCAL IMPACT There is no fiscal impact associated with staff recommendahons c10-3 Page intentiona I ly left blank. c10-4