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Attachment 1 <br /> Salinas Reservoir Expansion Project <br /> Dam Safety Evaluation <br /> Executive Summary <br /> INTRODUCTION <br /> Salinas Dam is a 135-foot high concrete arch-shaped dam, located in San Luis Obispo <br /> County on the Salinas River, about 9 miles southeast of the town of Santa Margarita, <br /> California. The reservoir at the dam is referred to as Santa Margarita Lake. The dam is <br /> owned by the US Army Corps of Engineers, and was constructed by the Corps between <br /> late 1941 through early.1942. The original purpose of the dam was to provide wartime <br /> water supply to Camp San Luis Obispo. The dam was constructed in accordance with the <br /> engineering standards of practice at the time,and visually appears to be in good shape. <br /> The County of San Luis Obispo currently operates the reservoir for the Corps of <br /> Engineers,to provide municipal water supply to the City of San Luis Obispo (City) and <br /> for recreation. The reservoir provides approximately 70 percent of the water supply to <br /> the City, and along with the Whale Rock Reservoir, is one of two surface water reservoirs <br /> providing water for the City's use. <br /> REASONS FOR STUDY <br /> The City is considering expanding the capacity of Santa Margarita Reservoir to meet the <br /> growth proposed in the City's General Plan. The current capacity of the reservoir of <br /> 23,840 acre-feet(af) would be increased by 17,950 of following completion of the <br /> expansion project. The"safe yield"(the amount of water which would be available for <br /> use each year through a critical drought period) would increase by approximately 1650 <br /> acre-feet per year. A separate Environmental Impact Report has been prepared <br /> describing the project, impacts from the project, and proposed mitigation measures. <br /> The layout of the dam includes a concrete-lined spillway channel on the north (right) side <br /> of the dam to convey flood flows past the dam. The crest elevation of the spillway (the <br /> spillway's highest location) is approximately 20 feet below the top of the dam. <br /> Therefore,to store additional water, spillway gates or other barriers would be installed at <br /> the spillway crest location. With the gates in place the reservoir level would be <br /> approximately 19 feet higher than currently exists when the reservoir is full. The dam <br /> would not be increased in height. <br /> As part of the proposed reservoir expansion, dam ownership would be transferred from <br /> the Corps of Engineers to local control and the safety of the dam would therefore come <br /> under state jurisdiction. The California, Department of Water Resources, Division of <br /> Safety of Dams(DSOD) is responsible for dam safety for all jurisdictional non-federal <br /> dams in California. The DSOD takes a careful and stringent review of dam safety, <br /> because the consequences of the failure of a dam can be considerable. They have <br /> developed general guidelines for use in assessing dam safety during an earthquake or <br /> flood. <br /> 1-5 <br />