San Clemente Dam Seismic Safety Project EIR/EIS

Location: Monterey County, CA

Summary: Cardno ENTRIX prepared a Joint EIS/EIR for the San Clemente Dam Seismic Safety Project, owned and operated by the Coastal Division of California-American Water (CAW). The lead agencies are the U.S. Army Corps of Engineers (USACE) under NEPA and the California Department of Water Resources (DWR) under CEQA.

Cardno ENTRIX engineers and biologists evaluated several options to bring the San Clemente Dam up to seismic standards required by the California Division of Safety of Dams. Our staff assessed the potential impacts of the San Clemente Dam Seismic Safety Project to resources of the Carmel River area near Carmel Valley. Concerns expressed by the National Marine Fisheries Service (NMFS) resulted in an extensive modeling effort focused on addressing disposal of over 2,000-acre feet of sediment in the reservoir behind the dam during a notching or removal alternatives. Cardno ENTRIX evaluated different scenarios for a managed sediment release from behind the dam and examined sedimentation effects to 18.5 miles of downstream river channel.

The analysis was used to assess potential benefits and impacts of dam removal, dam strengthening or dam notching. In addition, one dam removal alternative evaluated the impacts of re-routing the Carmel River to avoid impacts associated with sediment removal from the area. The EIR/EIS impact analysis evaluated construction activities for the multi-year construction period and disturbance-related water quality and fish passage issues in addition to long-term operations. Extensive consultation with the National Marine Fisheries Service, U.S. Fish and Wildlife Service, and the California Department of Fish and Game, as part of the biological assessment process, was used to integrate management concerns for steelhead, which are listed as a threatened species in this region of the California coast, and the California red-legged frog listed as Threatened under the federal Endangered Species Act (ESA).