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a URS January 31, 2008 Mr. Robert McClellon Supervisor R.E.H.S. San Joaquin County Environmental Health Department 304 East Weber Avenue,Third Floor Stockton,California 95202-2708 NVIHO NIVIENT HEALTH r,��,�1TiSERVICE� Subject: Quarterly Monitoring Report World Enterprises Site Stockton,California Dear Mr. McClellon: URS Corporation(URS)has prepared this letter report on behalf of RadioShack. It describes the monitoring activities completed at the World Enterprises site in Stockton,California(Figure 1), during the fourth quarter of 2007 and summarizes the results of these monitoring activities. This report is organized in the following sections: Background,Field Activities,Results,and Conclusions and Recommendations. BACKGROUND The World Enterprises site is located in Stockton,California. This site was operated as a debris disposal site(debris from demolished buildings, including wood,rubble,concrete,and other fill materials)under San Joaquin Local Health District Use Permits to World Enterprises from 1970 to 1978. 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)(3%by volume)along the property boundary. As a result of this inspection, SJCEHD required Tandy Corporation(site owner,currently known as RadioShack)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,to implement measures for controlling methane from leaving the site. RadioShack contracted with URS to assess extent of methane at the World Enterprises site. Since 2004, URS has installed 10 gas-migration monitoring probes,two vapor extraction wells,and three groundwater monitoring wells at the World Enterprises site(Figure 1). As a result of the field investigations,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 leaving 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 URS Group, Inc. Crown Corporate Center 2870 Gateway Oaks Drive,Suite 150 Sacramento,CA 95833 Tel:916.679.2000 Fax: 916.679.2900 K:\Wprocess\25532\WorldEnterprise\Quarterly Rpt\2007\4Q07\CovLtrRpt.doc