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California Regional Water Quality Control Board <br /> Central Valley Region 0 <br /> v Katherine Hart, Chair <br /> Edmund G.Brown,Jr. <br /> Matthew Rodriguez 11020 Sun Center Drive#200,Rancho Cordova, California 95670-6114 Governor <br /> Secretary-forPhone(916)464-3291 •FAX(916)4644645 <br /> �onmenral Protection http:llwww.waterboards.ca.gov/centralvalley <br /> 19 December 2011 <br /> Mr. Dan Schreiner <br /> Stantec <br /> 3017 Kilgore Road, Suite 100 <br /> Rancho Cordova, CA 95670 <br /> COMMENTS ON THE WATERFRONT TOWERS AND L&M OPERABLE UNIT SITE <br /> INVESTIGATION, SAN JOAQUIN COUNTY <br /> California Regional Water Quality Control Board, Central Valley Region (Central Valley Water <br /> Board) staff has reviewed your submittal titled Report of Findings for the Waterfront Towers <br /> Separate Phase Hydrocarbon Investigation and Unocal Extraction Well Pilot Study (Report) <br /> prepared by Stantec on behalf of Chevron Environmental Management Company and Conoco <br /> Phillips (L&M Group) dated 4 March 2011. Central Valley Water Board staff and the L&M <br /> Group met in August 2011 to discuss the Report and future activities at the site. The Report <br /> • discusses the results of a qualitative investigation of separate phase hydrocarbons that was <br /> conducted to provide additional characterization of petroleum impacts in the Waterfront <br /> Towers (WOTOA) parking lot. The Report also includes the results from an aquifer test <br /> conducted at the Unocal site using the existing dual phase extraction (DPE) system located on <br /> the L&M Group site. This letter includes comments on the Report and also addresses the <br /> L&M Group's request to revise the current Monitoring and Reporting Program (MRP) and to <br /> perform a rebound study on a portion of their DPE system. <br /> Qualitative Investigation of Separate Phase Hydrocarbons <br /> In August 2010, the L&M Group performed a qualitative site investigation of separate phase <br /> hydrocarbons in the WOTOA parking lot using Ultra-Violet Optical Scanning Tool (UVOST) <br /> technology. The investigation was performed as a means to collect additional data to further <br /> characterize the petroleum impacts in soil and groundwater at the site. The investigation <br /> consisted of nine continuously cored boreholes using UVOST, which analyzes lithology and <br /> relative petroleum hydrocarbon impacts. The results of the investigation indicate significant <br /> petroleum hydrocarbon impacts in soil at approximately 45 feet bgs. These findings are <br /> consistent with our current understanding of the site. We concur with the L&M Group's <br /> opinion that the data collected is sufficient to determine the next step in the on-going <br /> remediation of the site's soils and groundwater. <br /> • DEC L_J: <br /> t <br /> California Environmental Protection Agency - <br /> cYecycled Paper <br />