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f I{ rF COR <br /> ' Inti national Incorporated <br /> June 27, 2002 02 411 10 30 <br /> Project 77TO 64409 00 0007 <br /> Mr Michael Infurna <br /> San Joaquin County Public Health Services <br /> Environmental Health Division <br /> 304 East Webber Avenue,Third Floor �4/ <br /> Stockton, CA 95202 <br /> Re- Work Plan for Additional Off-Site Assessment <br /> Tosco Service Station No 4409 <br /> 1502 El Dorado Street <br /> Stockton, California <br /> Dear Mr Infurna <br /> This letter, prepared by SECOR International Incorporated (SECOR) on behalf of Tosco <br /> Corporation (Tosco), a subsidiary of Phillips Petroleum Company, provides a work plan <br /> for off-site groundwater investigation in the vicinity of the subject site (Figures 1 and <br /> 2) The purpose of the above work is to delineate the off-site extent of petroleum <br /> hydrocarbons in groundwater This work plan includes a brief discussion of site <br /> background, scope of work, and schedule <br /> SITE DESCRIPTION AND BACKGROUND <br /> The site is located on the northeast corner of Harding Way and El Dorado Street in <br /> Stockton, California(Figures 1 and 2) The site is a former Unocal service station that <br /> sold gasoline and diesel fuel <br /> On April 7, 1999, three 10,000-gallon capacity underground storage tanks (USTs), <br /> which contained gasoline and diesel fuel, were removed from the site Excavation <br /> dimensions were approximately 35 feet by 40 feet by 15 feet deep Initial remedial <br /> activities included source removal of obviously impacted soil to a depth of <br /> approximately 18 feet below ground surface (bgs) beneath the center of the western fuel <br /> tank Additional remedial activities included source removal of obviously impacted soil <br /> in the area beneath the former dispenser and product lines A concrete pad restricted the <br /> lateral extent of excavation During excavation of impacted soil, unidentified fiberglass <br /> piping was found Additional excavation and sampling was completed on April 8, 1999 <br /> to remove the unidentified piping Samples were collected from the bottom and <br /> sidewalls of the excavated area Following removal of the former station canopy, <br /> canopy footings and kiosk, additional over-excavation was completed in the dispenser <br /> area Over-excavation was terminated when obviously impacted soil was removed, the <br /> structural integrity of the sidewalk was endangered, or groundwater was encountered <br /> A total of approximately 1,707 tons of soil was transported off-site for disposal at the <br /> Forward Landfill in Manteca, California (IT Group [IT], July 29, 1999) <br /> 3017 Kilgore Road, Suite 100, Rancho Cordova, Cif 95670 916 861 0400 916 861 0430 Fax www secor com <br />