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URS July 7, 2006 RIC, Mr. Robert McClellon Supervisor R.E.H.S. 'l 11L. I F1 '00 San Joaquin County Environmental Health Department !i ENVIp, IV 304 East Weber Avenue,Third Floor PERP 1 i a.vl c_t 1 HEALTH Stockton, California 95202-2708 SIT,SERVICES Subject: Work Plan to Install Passive Soil Vapor Extraction Trench World Enterprises Site Stockton,California Dear Mr. McClellon, On behalf of RadioShack Corporation,URS has prepared this work plan to install a passive soil vapor extraction trench at the World Enterprises site in Stockton,California.We plan to install this trench following your approval of this work plan and concurrence from the San Joaquin Valley Air Pollution Control District(SJVAPCD). Background The World Enterprises site is located in Stockton,California.This site was operated as a debris disposal site(debris from demolished buildings to include wood,rubble,concrete,and other fill materials)under permit to World Enterprises from 1970 to 1978. During an annual inspection of the site on July 17,2003, the San Joaquin County Environmental Health Department(SJCEHD) staff measured methane gas concentration up to 30,000 parts per million volume(ppmV)(3 percent by volume) along the property boundary. As a result of this inspection, SJCEHD required Tandy Corporation(currently known as RadioShack)to assess whether the methane concentration along the property boundary was greater than 5 percent,and if the methane concentration along the property boundary was found to be greater than 5 percent,to implement measures for controlling methane from leaving the site. URS has installed 10 gas- migration monitoring probes and two vapor extraction wells at the World Enterprises site(Figure 1) during our field investigation activities. Based on the field investigation results,the limit of the methane plume along the northern boundary of the site appears to have been delineated. Methane concentrations within the probes located along the property boundary has been measured up to 22.7 percent during the quarterly monitoring events. To control methane from leaving the site, we propose to install a passive soil vapor extraction trench. On May 22, 2006,the URS staff met with Mr.Fred Cruz of the SJVAPCD to obtain his opinion of whether a permit was required from SJVAPCD to install and operate a passive soil vapor extraction URS Corporation Crown Corporate Center 2870 Gateway Oaks Drive,Suite 150 Sacramento,CA 95833 Tel:916.679.2000 Fax:916.679.2900