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California l*ional Water Quality Cor A Board <br /> Central Valley Region <br /> Karl E. Longley, ScD, P.E., Chair � <br /> Linda S.Adams Arnold <br /> Secretary for 1685E Street, Fresno,California 06 Schwarzenegger <br /> Environmental (559)445-5116 • Fax(559)445-5915910 Governor <br /> Protection http://www.waterboards.ca.gov/centralvalley <br /> 18 November 2009 Lf�l �CF1 ,J W 1ED <br /> NOV 1 9 X009 <br /> ENVIRONMENT HEA1 H <br /> M. Scott Mansholt {'ERNlITI5ERt,1lCES <br /> Chevron Environmental Management Company <br /> 6111 Bollinger Canyon Road <br /> Rm 3432 <br /> San Ramon, CA 94583 <br /> REVIEW - NO FURTHER ACTION REQUIRED REQUEST, VERNALIS OFFSITE, <br /> VERNALIS, SAN JOAQUIN AND STANISLAUS COUNTIES <br /> On behalf of Chevron Environmental Management Company (Chevron), Science Applications <br /> International Corporation (SAIC) submitted the 14 August 2009 report No Further Action <br /> Request (NFAR), Vernalis Offsite, Vernalis (Site). The Site is east of the former Vernalis <br /> Pump Station project. These two Vernalis projects are being investigated separately by <br /> Chevron with oversight provided by Central Valley Regional Water Quality Control Board <br /> (Central Valley Water Board) staff. Land use in the area includes orchards and alfalfa fields <br /> within a rural and light-industrial area of southern San Joaquin and northwest Stanislaus <br /> Counties. California State Highway 33 and the Union Pacific Railroad (UPRR) are adjacent to <br /> the west side of the Site. <br /> During initial characterization of the former Vernalis Pump Station, it was determined that <br /> crude oil affected groundwater had migrated offsite. Consequently, the Site was designated <br /> as a separate project. Central Valley Water Board staff has reviewed the NFAR and related <br /> Site soil and groundwater investigation reports. <br /> Two monitoring wells were installed and 12 borings drilled on the Site between 2005 and 2008 <br /> as part of the downgradient groundwater evaluation. Depth to groundwater is approximately <br /> 32 to 40 feet below ground surface (bgs) and the gradient is easterly. The vertical extent of <br /> affected groundwater was determined during earlier investigations. <br /> Visually affected soil was not observed in borings drilled to depths of 40 to 44 feet bgs. With <br /> one exception, total petroleum hydrocarbon as crude oil (TPHc) was non-detect (ND) for <br /> petroleum hydrocarbon compounds. TPHc at a concentration of 380 milligrams per kilogram <br /> (mg/kg) was reported in a soil sample collected at a depth of one foot bgs in a boring at a <br /> location more than 200 feet east of the former pipelines. The result exceeded the <br /> environmental screening level (370 mg/kg) for direct human exposure contact. According to <br /> SAIC's report, it is likely the TPHc detected was from a source other than the historical <br /> pipelines. <br /> California Environmental Protection Agency <br /> ZYecycled Paper <br />