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URS <br /> May 15,2007 <br /> Mr. Ross Atkinson t.r 53_ <br /> Associate Engineering Geologist .' <br /> California Regional Water Quality Control Board <br /> Central Valley Region ` <br /> 11020 Sun Center Drive 4200 <br /> Rancho Cordova, California 95670 <br /> Subject: Request for Time Extension <br /> World Enterprises Site <br /> Stockton, California <br /> Dear Mr.Atkinson: <br /> URS has prepared this letter on behalf of RadioShack for the World Enterprises site in Stockton, <br /> California(Figure 1) in response to your letter dated February 20, 2007. In your letter,you requested <br /> the following: <br /> • A work plan with a time schedule be submitted to investigate the horizontal and vertical extent <br /> of groundwater impacts; <br /> • A plan with time schedule be submitted to monitor groundwater and surface water quality for <br /> general minerals and metals on a quarterly basis; and <br /> • A site groundwater investigation report be submitted. <br /> This letter has been organized into the following sections: Background,Responses to RWQCB <br /> Requirements, and Schedule. <br /> BACKGROUND <br /> The World Enterprises site is located in Stockton,California. This site was operated as a debris <br /> 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 from 1970 to <br /> 1978. During an annual inspection of the site on July 17, 2003,the San Joaquin County <br /> Environmental Health Department(SJCEHD)staff measured methane gas concentrations up to <br /> 30,000 parts per million by volume(ppmV) (3%by volume) along the property boundary.As a <br /> result of this inspection, SJCEHD required Tandy Corporation(site owner and currently known as <br /> RadioShack)to assess whether the methane concentration along the property boundary exceeded 5% <br /> by volume, and if the methane concentration along the property boundary was found to be greater <br /> than 5%,to implement measures for controlling methane from leaving the site. Since 2004,URS has <br /> installed 10 gas-migration monitoring probes,2 vapor extraction wells,and 3 groundwater <br /> monitoring wells at the World Enterprises site(Figure 1) during our field investigation activities.As <br /> a result of the field investigations,methane concentrations along a portion of the property boundary <br /> were found to be above 5 percent. <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 K:\Wprocess\25532\WorldEnterprise\Misc.Correspondence\051507.doc <br />