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July 9, 2008 <br />Mr. Robert McClellon <br />Supervisor R.E.H.S. <br />San Joaquin County Environmental Health Department <br />304 East Weber Avenue, Third Floor <br />Stockton, California 95202-2708 <br />Subject: Quarterly Monitoring Report <br />World Enterprises Site <br />Stockton, California <br />Dear Mr. McClellon: <br />N �� Ell!' <br />i«l_ 1 (' 2008 <br />URS Corporation (URS) has prepared this letter report on behalf of RadioShack. It describes the <br />monitoring activities completed at the World Enterprises site in Stockton, California (Figure 1), during <br />the second quarter of 2008 and summarizes the results of these monitoring activities. This report is <br />organized in the following sections: Background, Field Activities, Results, and Conclusions and <br />Recommendations. <br />BACKGROUND <br />The World Enterprises site is located in Stockton, California. This site was operated as a debris disposal <br />site (debris from demolished buildings, including wood, rubble, concrete, and other fill materials) under <br />San Joaquin Local Health District Use Permits to World Enterprises from 1970 to 1978. On July 17, <br />2003, during an annual site inspection, the San Joaquin County Environmental Health Department <br />(SJCEHD) staff measured methane gas concentrations up to 30,000 parts per million by volume (ppmV) <br />(3 percent by volume) along the property boundary. As a result of this inspection, SJCEHD required <br />Tandy Corporation (site owner, currently known as RadioShack) to assess whether the methane <br />concentration along the property boundary was greater than 5 percent by volume, and if found to be <br />greater than 5 percent by volume, to implement measures for controlling methane from leaving the site. <br />RadioShack contracted with URS to assess extent of methane at the World Enterprises site. Since 2004, <br />URS has installed 10 gas -migration monitoring probes, two vapor extraction wells, and three <br />groundwater monitoring wells at the World 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 percent by volume. In September 2006, a passive soil vapor extraction trench <br />was 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 less than 5 ppmV. Based on these results, VOC constituents could be present in <br />groundwater. To assess the presence or absence of VOC constituents in the groundwater, three <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 K:\Wprocess\25532\WorldEnterprise\Quarterly Rpt\2008\2Q08\070908.doc <br />