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October 31, 2007 mc) E C. XED Mr. Robert McClellon NOV t 2 2007 Supervisor R.E.H.S. San Joaquin County Environmental Health Department ENVIRONMENT HEALTH 304 East Weber Avenue,Third Floor PERMIT/SERVICES Stockton, California 95202-2708 SUBJECT: Quarterly Monitoring Report and Excess Passive Soil Vapor Extraction Material Removal Report World Enterprises Site Stockton, California Dear Mr. McClellon: URS Corporation(URS)has prepared this letter report on behalf of RadioShack. It describes the monitoring activities completed at the World Enterprises site in Stockton, California(Figure 1), during the third quarter of 2007 and summarizes the results of these monitoring activities. In addition,this report summarizes the field activities to remove the excess passive soil vapor extraction material completed during the week ending September 28, 2007.This report is organized in the following sections: Background,Field Activities,Results, and Conclusions and Recommendations. BACKGROUND The World Enterprises site is located in Stockton, California.This site was operated as a debris disposal site(debris from demolished buildings, including wood,rubble,concrete,and other fill materials)under San Joaquin Local Health District Use Permits to World Enterprises from 1970 to 1978. On July 17, 2003, during an annual site inspection,the San Joaquin County Environmental Health Department (SJCEHD)staff measured methane gas concentrations up to 30,000 parts per million by volume(ppmv) (3 percent by volume)along the property boundary. As a result of this inspection, SJCEHD required Tandy Corporation(site owner,currently known as RadioShack)to assess whether the methane concentration along the property boundary was greater than 5 percent by volume, and if found to be greater than 5 percent by volume,to implement measures for controlling methane from leaving the site. Since 2004,URS has installed 10 gas-migration monitoring probes,two vapor extraction wells, and three groundwater monitoring wells at the World Enterprises site(Figure 1). As a result of the field investigations,methane concentrations along a portion of the property boundary were found to be above 5 percent by volume. In September 2006, a passive soil vapor extraction trench was installed to control methane from leaving the site. As a result of the passive soil vapor extraction trench installation activities,excess excavated material was stockpiled at the site.During the excavation activities,the excess excavated material was separated by material type(concrete debris,wood debris, soil with construction debris [large and small], and tank soil). A small tank was uncovered during the excavation activities. The tank and the soil beneath the tank were placed in a separate stockpile.The small tank was removed from the site on November 30,2006. In addition,numerous tires of various sizes were uncovered. URS Corporation Crown Corporate Center 2870 Gateway Oaks Drive,Suite 150 Sacramento,CA 95833 Tel: 916.679.2000 Fax: 916.679.2900 K:\Wprocess\25532\WorldEnterprise\Quarterly Rpt\2007\3Q07\103107.doc