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/ r <br /> 1 <br /> O <br /> o <br /> September 25, 1997 <br /> Mr. Harlin Knoll <br /> San Joaquin County Public Health Services <br /> P O Box 388 <br /> Stockton, California 95201-0388 <br /> RE: Shell Service Station <br /> 4445 Pershing Avenue <br /> Stockton, California <br /> WIC #204-7524-2408 <br /> Dear Mr Knoll <br /> This work plan has been prepared by Envtros, Inc (Enviros) on behalf of Shell Oil <br /> Products Company to further investigate the area of the eastern fuel dispenser as requested <br /> by San Joaquin County Public Health Services (SJCPHS) in a letter dated May 25, 1997 <br /> The scope of work presented in this document will comply with SJCPHS and Regional <br /> Water Quality Control Board (RWQCB) guidelines <br /> Site Description and Background <br /> . The subject property is located on the southwest corner of the intersection of Pershing <br /> Avenue and Rose Marie Lane in Stockton, California The site is an operating Shell service <br /> station with three 12,000-gallon double walled fiberglass underground gasoline storage <br /> tanks (USTs), one underground waste oil tank, two dispenser islands, and a station <br /> building (Plate 2) <br /> In October 1989, twelve soil borings were drilled to assess soil conditions in the vicinity of <br /> the gasoline USTs and in the vicinity of the future USTs Soil samples collected at depths <br /> of 15 to 20 feet below grade (fbg) were submitted for chemical analysis TPHg and BTEX <br /> were not detected in these soil samples with the exception of 0 07 ppm of benzene detected <br /> in Boring B-4 at a depth of 20 fbg <br /> In June 1990, one 10,000-gallon, one 7,500-gallon and two 5,000-gallon USTs were <br /> removed Soil samples were collected during the UST and product line removal TPH-g <br /> was detected at a maximum concentration of 4,300 ppm in sample T2-S which was <br /> collected from the UST excavation TPH-g concentrations were below 100 ppm in all <br /> other samples collected from the UST excavation and product line trenches <br /> In July 1990, three ground water monitoring wells and two vapor extraction wells were <br /> installed In December 1991, one monitoring well (MW-4) was installed down gradient of <br /> the former USTs Between December 1991 and February 1992, soil vapor extraction was <br /> conducted to remediate impacted soil in the area of the former USTs <br /> TPH-g and benzene have not been detected in ground water samples collected from <br /> monitoring well MW-4 since February 1995 Well MW-4 is located down gradient and <br /> adjacent to the former gasoline USTs <br /> Envlros Inc 270 Perkins Street Sonoma California Tel 707/935 4850 <br /> P 0 Box 259 95476 0259 Fax 7071935 6549 <br />