This EIS/Environmental Impact Report was prepared by the Department of the Interior (Bureau of Reclamation, Mid-Pacific Region) and the Contra Costa Water District to evaluate the environmental impacts of a proposal to enlarge the existing Los Vaqueros Reservoir in Contra Costa County, California. DOE’s Western Area Power Administration (Western) was a cooperating agency because it has jurisdiction over transmission facilities that were expected to be relocated under the proposed action. Based on project changes, however, Western has no action and therefore will not adopt the EIS or issue a ROD.