Seismic Safety Modification of an Old Earthfill Dam

by James E. Cavallin, Woodward-Clyde Consultants, San Diego, United States,

Document Type: Proceeding Paper

Part of: Geotechnical Practice in Dam Rehabilitation


Chollas Dam was built as a water supply reservoir for the City of San Diego. The reservoir is no longer a part of the municipal water system but has been operated since 1966 as a recreational lake. The city has grown around the lake, substantial residential development occurred downstream, and more was proposed. This paper describes studies made to evaluate stability and modify the dam. Initial phases of work indicated the possibility that a magnitude 6.5 earthquake on the La Nacion fault located approximately 1.22 kilometers from the dam could cause large displacements. Modification consisted of removing liquefiable foundation material, adding a chimney drain and downstream buttress as well as lowering the spillway crest.

Subject Headings: Seismic tests | Seismic effects | Dam safety | Earth fills | Earthfill dams | Reservoirs | Urban areas | Municipal water | California | United States

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