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Crystal Springs Dam is a gravity dam constructed across the San Mateo Creek, impounding water to form the Lower Crystal Springs Reservoir in San Mateo County, California. It was among the first concrete gravity dams built in the western United States.〔Advanced Dam Engineering for Design, Construction, and Rehabilitation, by Robert B. Jansen, page 117〕 The structure was completed in 1888, and has survived both the 1906 San Francisco earthquake and the 1989 Loma Prieta earthquake — despite its location directly on the San Andreas Fault. The designer was Hermann Schussler, Chief Engineer of the Spring Valley Water Company. The dam was constructed by using large blocks poured separately, and allowed to set before adjoining blocks were poured. The unique feature of this dam is the fact that none of the horizontal or vertical joints match up. Schussler was also very demanding that the concrete be batched in the exact proportions of his mix design. Although this dam was erected about 100 yards east of the San Andreas fault line and was subject to severe shaking it survived relatively undamaged.〔Advanced Dam Engineering for Design, Construction, and Rehabilitation, by Robert B. Jansen, page 117〕 The dam has a road running over it and forms the trailhead of the popular Sawyer Camp Trail. The roadway on top of the dam is closed. The San Francisco Public Utilities Commission began the process of renovating the dam in 2003. A major step in the renovation process, doubling the width of the main spillway and raising the dam to increase the water storage capacity, was completed in 2012. The renovations, which are intended to improve the reliability of the system in the event of an earthquake, are on schedule to be completed in 2016. File:Crystal Springs Dam Leeside.jpg|Lower Crystal Springs Dam File:Crystal Springs Reservoir.jpg|Lower Crystal Springs Reservoir ==See also== * List of dams and reservoirs in California 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Crystal Springs Dam」の詳細全文を読む スポンサード リンク
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