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Ilia January 29, 2016 RECEIV 6.N Mr. Robert McClellon FEB 01 201 Supervisor R.E.H.S. ENVIRONMENTAL HEALTH San Joaquin County Environmental Health Department PERMIT/SERVICES 1868 East Hazelton Avenue Stockton,California 95205-6232 Subject: Annual Monitoring Report World Enterprises Site Stockton, California Dear Mr. McClellon: URS Corporation Americas(URS), now an AECOM Company, has prepared this letter report on behalf of RS Legacy Corporation, formerly known as RadioShack Corporation. This report provides a description of the monitoring activities completed at the World Enterprises site in Stockton, California (Figure 1), during the fourth quarter of 2015 (4Q15), and summarizes the results of these monitoring activities. This report is organized in the following four sections: Background,Field Activities, Results, and Conclusions and Recommendations. BACKGROUND The World Enterprises site is in Stockton, California. From 1970 to 1978,this site operated as a debris disposal site; debris came from demolished buildings, and included wood,rubble,concrete,and other fill materials.The site operated under San Joaquin Local Health District Use Permits to World Enterprises. On July 17,2003, during an annual site inspection,the San Joaquin County Environmental Health Department(SJCEHD)staff measured methane gas concentrations up to 30,000 parts per million by volume(ppmv, or 3 percent [%] by volume)along the property boundary. As a result of this inspection, SJCEHD required Tandy Corporation(the site owner,currently known as RS Legacy Corporation)to assess whether the methane concentration along the property boundary was greater than 5%by volume, and if found to be greater than 5%by volume, implement measures for controlling methane from leaving the site. RS Legacy Corporation contracted with URS to assess the extent of methane at the World Enterprises site. URS installed 10 gas migration monitoring probes and two vapor extraction wells at the World Enterprises site(Figure 1). URS field investigations determined that methane concentrations along a portion of the property boundary were found to be above 5%by volume. In September 2006, a passive soil vapor extraction trench was installed to control methane from migrating off the site. In December 2005,a vapor extraction pilot test was conducted to evaluate the feasibility of installing a permanent landfill gas extraction system. During this test,vapor samples were collected from the two extraction wells and analyzed for volatile organic compounds(VOCs). Analytical results of these samples confirmed the presence of VOCs where the total VOC concentration in each of the vapor extraction wells was below 5 ppmv. Based on these results, VOC constituents could be present in groundwater.To assess the presence or absence of VOC constituents in groundwater,three groundwater URS Corporation Crown Corporate Center 2870 Gateway Oaks Drive,Suite 150 Sacramento,CA 95833 Tel: 916.679.2000 Fax:916.679.2900