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4 <br /> URS <br /> January 31, 2012 RECEIVED <br /> Mr. Robert McClellon JAN 3 12012 <br /> Supervisor R.E.H.S. <br /> San Joaquin County Environmental Health Department ENVIRONMENTAL HEALTH <br /> 304 East Weber Avenue, Third Floor PERMIT/SERVICES <br /> Stockton, California 95202-2708 <br /> Subject: Well Decommissioning and Annual Monitoring Report <br /> World Enterprises Site <br /> Stockton, California <br /> Dear Mr. McClellon: <br /> URS Corporation Americas(URS)has prepared this letter report on behalf of RadioShack. This report <br /> provides a description of the monitoring activities completed at the World Enterprises site in Stockton, <br /> California(Figure 1), during the fourth quarter of 2011 (4Q11)and summarizes the results of these <br /> monitoring activities. Additionally,this report summarizes the decommissioning activities for on-site <br /> groundwater monitoring wells(MW-1 through MW-3). This report is organized in the following four <br /> sections: Background,Field Activities,Results, and Conclusions and Recommendations. <br /> BACKGROUND <br /> The World Enterprises site is located in Stockton, California. From 1970 to 1978,this site operated as a <br /> debris disposal site(debris from demolished buildings, including wood,rubble,concrete, and other fill <br /> materials)under San Joaquin Local Health District Use Permits to World Enterprises. On July 17, 2003, <br /> during an annual site inspection,the San Joaquin County Environmental Health Department(SJCEHD) <br /> staff measured methane gas concentrations up to 30,000 parts per million by volume(ppmV)(3 percent <br /> [%] by volume)along the property boundary. As a result of this inspection, SJCEHD required Tandy <br /> Corporation(site owner, currently known as RadioShack)to assess whether the methane concentration <br /> along the property boundary was greater than 5%by volume, and if found to be greater than 5%by <br /> volume, implement measures for controlling methane from leaving the site. RadioShack contracted with <br /> URS to assess the extent of methane at the World Enterprises site. Since 2004,URS has installed 10 gas <br /> migration monitoring probes,2 vapor extraction wells,and 3 groundwater monitoring wells at the World <br /> Enterprises site(Figure 1). <br /> As a result of the field investigations,methane concentrations along a portion of the property boundary <br /> were found to be above 5%by volume. In September 2006, a passive soil vapor extraction trench was <br /> installed to control methane from leaving the site. <br /> In December 2005, a vapor extraction pilot test was conducted to evaluate the feasibility of installing a <br /> permanent landfill gas extraction system. During this test,vapor samples were collected from the two <br /> extraction wells and analyzed for volatile organic compounds(VOCs). Analytical results of these <br /> samples confirmed the presence of VOCs where the total VOC concentration in each of the vapor <br /> extraction wells was below 5 ppmV. Based on these results,VOC constituents could be present in <br /> URS Corporation <br /> Crown Corporate Center <br /> 2870 Gateway Oaks Drive,Suite 150 <br /> Sacramento,CA 95833 <br /> Tel:916.679.2000 <br /> Fax:916.679.2900 H:\Wprocess\25532\WorldEnterprise\Radio Shack0ecomm_Annual Rpffext.doc <br /> a <br />