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URS <br />October 31, 2006 <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 />IRECENED <br />NOV - 9 2006 <br />ENVIRONMENT HEALTH <br />PERMIT/SERVICES <br />Subject: Passive Soil Vapor Extraction Trench Installation Report and <br />Quarterly Monitoring Report <br />World Enterprises Site <br />Stockton, California <br />Dear Mr. McClellon: <br />URS has prepared this letter report on behalf of RadioShack to describe the field activities to install the <br />passive soil vapor extraction trench and the results of these field activities, which were completed at the <br />World Enterprises site in Stockton, California, in September 2006 (Figure 1). In addition, this letter <br />report describes the monitoring activities completed at this site on September 29, 2006 for the third <br />quarter of 2006, and summarizes the results of these monitoring activities. <br />This report has been organized into the following sections: Background, Field Activities, Results, and <br />Conclusions and 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. During an <br />annual inspection of the site on July 17, 2003, the San Joaquin County Environmental Health <br />Department (SJCEHD) staff measured methane gas concentration up to 30,000 parts per million volume <br />(ppmv) (3% by volume) along the property boundary. As a result of this inspection, SJCEHD required <br />Tandy Corporation (site owner and currently known as RadioShack) to assess whether the methane <br />concentration along the property boundary was greater than 5%, and if the methane concentration along <br />the property boundary was found to be greater than 5%, to implement measures for controlling methane <br />from leaving the site. Since 2004, URS has installed 10 gas -migration monitoring probes, two vapor <br />extraction wells, and three groundwater monitoring wells at the World Enterprises site (Figure 1) during <br />our field investigation activities. <br />As a result of the field investigations, methane concentrations along the property boundary were found to <br />be above 5 percent. To evaluate the feasibility of installing a permanent landfill gas extraction system, a <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 />