The action assessed is the guaranty of a loan by DOE to finance geothermal exploration, development, and testing by Mapco Geothermal, Inc. and Republic Geothermal, Inc. in the Westmorland area of Imperial County, California. Initial drilling and flow testing of up to three production wells will occur in the exploratory phase. Exploration is proposed for either or both of two portions of the leasehold area. If exploration confirms the presence of a viable resource in the Sweetwater area, the preferred site based on limited temperature data, then up to 19 new production wells and three new injection wells may be drilled and tested there in preparation for the construction of a 55-MW double-flash electric power plant. If, however, the Sweetwater resource proves infeasible, further exploration and possible full-field development may occur instead at the Dearborn-Kalin-Landers area. At this site, up to 19 new production wells and three new injection wells may be drilled and tested, with six existing wells also used for injection. This environmental assessment chiefly addresses effects of the drilling and testing program. In summary, this paper discusses the proposed action, describes the existing environment and discusses the potential environmental impacts. 75 refs. (LSP).