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URS r 0 <br />July 22, 2009 <br />Mr. Robert McClellon <br />Supervisor R.E.H.S. <br />San Joaquin County Environmental Health Department �� (' fi / DID <br />304 East Weber Avenue, Third Floor ,� � I� <br />Stockton, California 95202-2708 2009 <br />Subject: Quarterly Monitoring Report tt;il.' `'-i`i ?FfV i HEALTH <br />World Enterprises Site �'5+�� i /SERVICES <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 second quarter of 2009 and summarizes the results of these monitoring <br />activities. This report is organized in the following sections: Background, Field Activities, Results, and <br />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 percent by volume, and if found to be greater than <br />5 percent by volume, to implement measures for controlling methane from leaving the site. RadioShack <br />contracted with URS to assess the extent of methane at the World Enterprises site. Since 2004, URS has <br />installed 10 gas -migration monitoring probes, two vapor extraction wells, and three groundwater <br />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 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 <br />K:\Wprocess\25532\WorldEnterprise\Radio Shack\072209.doc <br />