Upgrading the Seismic Resistance of Stevens Creek Dam

Stevens Creek Darn is a rolled earthfill structure with a height of about 120 feet. A seismic safety evaluation in 1978 concluded that the darn would probably be severely damaged if subjected to a maximum credible earthquake originating on the nearby San Andreas fault. Normal reservoir operation was immediately restricted, pending decisions as to the fate of the project. Conceptual design studies were completed in 1982 to identify the most promising alternative remedial concepts. The most promising concepts were chosen and final design of modifications to the dam and its appurtenant hydraulic structures were completed in 1984. Modification of the darn was completed in 1986, involving the placement of massive buttresses on both the upstream and downstream slopes and installation of internal drains to control the phreatic line. This required extension of the existing outlet conduit and construction of new inlet and outlet control structures