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URS <br /> January 31, 2007 <br /> Mr.Robert McClellon <br /> Supervisor R.E.H.S. UIZ�'EYE , <br /> San Joaquin County Environmental Health Department <br /> 304 East Weber Avenue,Third Floor <br /> Stockton,California 95202-2708 FEB 0 2 2007 <br /> Subject: Quarterly Monitoring Report and Tank Removal Report ENVIRONMENT HEALTH <br /> World Enterprises Site PERMIT/SERVICES <br /> Stockton, California <br /> Dear Mr.McClellon: <br /> URS has prepared this letter report on behalf of RadioShack to describe the monitoring activities <br /> completed at the World Enterprises site in Stockton, California (Figure 1) during the fourth quarter of <br /> 2006, and the results of these monitoring activities. In addition, this report describes the tank removal <br /> activities completed on November 30,2006. <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 Depart- <br /> ment (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, 2 vapor <br /> extraction wells, and 3 groundwater monitoring wells at the World Enterprises site(Figure 1) during our <br /> field investigation activities. <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. To evaluate the feasibility of installing a permanent landfill gas <br /> extraction system, a vapor extraction pilot test was conducted in December 2005. During this test, vapor <br /> samples were collected from the two extraction wells and analyzed for volatile organic compounds <br /> (VOCs). The VOC analytical results showed that VOCs were present. The total VOC concentration in <br /> each vapor extraction well was less than 5 ppmv. Based on these results, there was a potential for VOC <br /> constituents to be present in groundwater. To assess the presence or absence of VOC constituents in the <br /> groundwater,three groundwater monitoring wells were installed at the site on June 12, 2006, <br /> URS Group, Inc. <br /> Crown Corporate Center <br /> 2870 Gateway Oaks Drive, Suite 150 <br /> Sacramento,CA 95833-3200 <br /> Tel:916.679.2000 <br /> Fax: 916.679.2833 K:\Wprocess\25532\WorldEnterprise\Quarterly Rpt\4Q06\CovLtrRpt.doc <br />