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zCORNERSTONE <br /> Environmental Group, LLC <br /> 7600 Dublin Boulevard, Suite 200•Dublin,CA 94568• (877)633-5520•Fax: (925)560-9879 <br /> November 1, 2010 <br /> Mr. Robert McClellon <br /> County of San Joaquin <br /> Environmental Health Department <br /> 600 East Main Street <br /> Stockton, CA 95202 <br /> (559) 230-6000 <br /> Re: Forward Landfill <br /> Proposed Soil Vapor Extraction (SVE) Wells Proximity to Existing Landfill Gas <br /> Monitoring Probes <br /> Dear Mr. McClellon: <br /> Cornerstone Environmental Group, LLC (Cornerstone), on behalf of Forward Landfill, Inc., <br /> owner and operator of the Forward Landfill (Forward), is submitting this "Evaluation" of the <br /> proposed soil vapor extraction (SVE) wells in accordance with SCS Engineers' (SCS) <br /> October 15, 2010 response to your comments dated October 13, 2010 regarding the Work <br /> Plan for Landfill Gas System Upgrades and Perimeter Probe Construction at Forward <br /> Landfill (SCS, October 1, 2010). Specifically, this is the "Evaluation" as referenced in <br /> SOS's response to Item Number (No.) 4 of your October 13, 2010 comments. The <br /> Environmental Health Department (EHD) Comment Item No. 4 and SCS' October 15th <br /> response are both shown below. <br /> October 13, 2010 Environmental Health Department (EHD) Comment No. 4 — The SVE <br /> wells need to be located outside the sphere of influence of the perimeter monitoring points <br /> (GP12, GP11, GP10). A minimum distance of 300 feet shall be maintained. The SVE wells <br /> should be clustered and positioned to collect the landfill gas without drawing the landfill gas <br /> into the perimeter monitoring probes. The prior installation of SVE wells along the western <br /> property boundary of the "Old Forward"site was not effective in controlling the landfill gas <br /> at the boundary. The methane concentrations in the compliance monitoring probes <br /> increased greatly shortly after bringing those wells online. <br />