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q,o <br /> , 9,,��' <br /> Stantec consulting corporation U-u <br /> Kil <br /> f FaxRoad Suie 100 <br /> Ran9,6)881-0400rdova CA gt�7 RECEIVED <br /> 91 <br /> Stantec <br /> ENVIRONMENTAL HEALTH <br /> September 20, 2011 PERMIT/SERVICES <br /> Mr. Mike Infurna <br /> San Joaquin County Environmental Health Department <br /> 600 East Main Street <br /> Stockton, California 95202 <br /> RE: Work Plan, MWAS Rehabilitation, and Bulk Extraction <br /> Former ARCO Service Station No. 443 <br /> 2478 E. Oak Street <br /> Stockton, California 95205 <br /> File No.: 211601012.400.480 <br /> Dear Mr. Infurna: <br /> This work plan has been prepared by Stantec Consulting Corporation (Stantec) on behalf of <br /> Atlantic Richfield Company (ARC), a BP Affiliated Company, in response to the letter from the <br /> San Joaquin County Environmental Health Department (SJCEHD) dated June 8, 2011 <br /> (Attachment A). Stantec sent a 30-day extension request to SJCEHD via email on August 4, <br /> 2011. This document presents a clarification regarding conclusions presented in the Quarterly <br /> Status Summary Report — First Quarter 2011 (1Q QMR) submitted by Stantec, a plan for the <br /> rehabilitation of monitoring well MW-1S, and a plan for interim remedial action through vacuum <br /> removal of product in MW-1S at Former ARCO Service Station No. 443 (site). <br /> Clarification of Conclusions in QMR and Status of Delineation <br /> In the 1Q QMR submitted by Stantec a statement was made indicating "Petroleum hydrocarbon <br /> impact beneath the site has not been adequately delineated by the existing well network and <br /> previous site assessment activities." Based on the most recent data collected during the <br /> second quarter groundwater sampling event, submitted in the Semiannual Groundwater <br /> Monitoring Report— Second Quarter 2011 (2Q SMR) dated 8/15/2011, the groundwater plume <br /> is delineated to the north by non-detect concentrations in MW-6, to the northwest by non-detect <br /> concentrations in MW-5, and the east by non-detect concentrations in MW-7. To the south of <br /> the site the groundwater plume is delineated by monitoring wells associated with the Shell <br /> Station located at 2494 Fremont Street (Shell Site). <br /> Based on a review of available information on Geotracker for the Shell Site and a verbal <br /> conversation with their consultant Conestoga-Rovers & Associates, assessment activities <br /> proposed in Shell's Subsurface Investigation Work Plan (Work Plan) dated May 21, 2009 were <br /> recently completed and data generated during the investigation will be available shortly. Among <br /> the locations proposed in the Shell Work Plan are several borings located along Fremont Street <br /> that will provide additional characterization information between the two sites. <br /> Once the newly generated assessment data is made available to Stantec we will review the <br /> need to perform additional assessment. <br /> 443 WorkPlan MW1S Bulk Extraction 2011.doc <br />