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California ivegional Water Quality Cont,,.sl Board <br /> Central Valley Region <br /> ion ^0 <br /> k . <br /> Karl E. Longley,ScD,P.E.,Chair <br /> Linda S.AdamsArnold <br /> Secretaryjor 11020 Sun Center Drive#200,Rancho Cordova,California 95670-6114 Schwarzenegger <br /> Environmental Phone(916)464-3291 •FAX(916)464-4645 Governor <br /> Protection http://www.waterboards.ca.gov/centralvalley <br /> 16 December 2009 <br /> Fo) EVED <br /> DEC 1 8 2009 <br /> Ms. Anne Conner ENVIRONMENT HEALTH <br /> Pacific Gas and Electric Company pER�fI1TJSERVICE� <br /> 375 N. Wiget Lane <br /> Walnut Creek, CA 94598 <br /> SITE UPDATE LETTER AND HISTORICAL SOIL CONCENTRATIONS, PG&E FRENCH <br /> CAMP-GENERAL CONSTRUCTION YARD, FRENCH CAMP, SAN-JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff reviewed the following documents: <br /> • 19 October 2009 Site Update Letter(Letter) <br /> • 23 November 2009 Historical Soil Data Email (Email) <br /> Stantec Consulting Corporation (Stantec) submitted these reports on behalf of Pacific Gas & <br /> Electric Company (PG&E) for the general construction yard at 401 East French Camp Road in <br /> French Camp (Site). <br /> PG&E has used the Site since the late 1950s as a general construction yard and purchased <br /> the property in 1991. In June 2005, PG&E performed a Phase I environmental site <br /> assessment, which found that in 1995, PG&E removed one concrete ConVault-style <br /> aboveground tank (AGT). The ConVault tank had replaced older steel AGTs and consisted of <br /> separate vessels for storing diesel and gasoline. The French Camp Fire Department oversaw <br /> the 1995 removal of the ConVault AGT. It is unknown when the steel AGTs were removed. <br /> The Letter summarizes the June and September 2009 investigation activities conducted at the <br /> Site to June 2009, PG&E properly abandoned the three Site monitoring wells and the onsite <br /> domestic well, and drilled six soil borings to 20 feet below ground surface (bgs). PG&E <br /> collected soil samples from the soil borings to define the lateral extent of the soil <br /> contamination. Total petroleum hydrocarbons as diesel (TPHd) concentrations in soil samples <br /> collected below 11 feet bgs in two borings exceeded the California Regional Water Quality <br /> Control Board — San Francisco Bay Region Environmental Screening Levels (ESLs) gross <br /> contamination level. <br /> In August and September 2009, PG&E collected additional data to support a risk assessment <br /> and development of cleanup goals. PG&E drilled six soil borings adjacent to the June 2009 <br /> locations and analyzed soil samples for volatile organic compounds, semi-volatile organic <br /> compounds, and carbon chain fractionation of fuel hydrocarbons. PG&E converted three of <br /> the soil borings to semi-permanent soil gas sampling probes. PG&E collected soil gas <br /> samples at five and 12 feet bgs. Several soil vapor probes exceed the ESLs for naphthalene. <br /> California Environmental Protection Agency <br /> rr1 Recycled Paper <br />