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Additional Site Assessment and Soil Vapor Extraction Test,Second Quarter 2002 Groundwater Monitoring Data 1 <br /> 7-Eleven Inc,Store 21756, 853 E Yosemite Avenue Manteca California August 5, 2002 <br /> ' 10 INTRODUCTION <br /> This report is submitted by Shaw Environmental & Infrastructure, Inc (formerly IT Corporation) to <br /> 1 summarize the results of site assessment and soil vapor extraction (SVE)testing conducted at 7-Eleven <br /> Store No 21756, located at 853 East Yosemite Avenue, Manteca, California (Figure 1) The scope of <br /> work Included Installation of one Geoprobe boring, one groundwater monitoring well, one double-nested <br /> ' sparge/vent well, and collection of soil and groundwater samples (Figure 2) <br /> ' The work scope was designed to meet general criteria for site assessment in accordance with San <br /> Joaquin County Public Health Services/Environmental Health Department(SJCPHS) standards <br /> Additional soil and groundwater hydrocarbon delineation was requested by the SJCPHS in their <br /> IAugust 10, 2001 letter(received by IT Corporation September 25, 2001) <br /> The work described in this report was completed at the site from April 1 through 3, 2002 (drilling) and <br /> ' April 24, 2002 (SVE testing), in accordance with IT Corporation's Work Plan for Additional Site <br /> Assessment and Feasibility Testing(October 17, 2001), which was approved by the SJCPHS prior to <br /> ' fieldwork initiation Quarterly groundwater monitoring and sampling were performed on April 8, 2002 <br /> 20 BACKGROUND <br /> On December 9, 1998, three 10,000-gallon steel single-wall underground storage tanks (USTs)were <br /> removed from the site (IT Corporation, January 1999) Six soil samples were obtained from the base of <br /> ' the UST pit, and two soil samples were obtained from beneath the pump islands and associated fuel <br /> dispensing piping Tank pit soil samples were collected from about 14 feet below grade (bg), pump-island- <br /> area samples were obtained from depths of about 4 feet bg <br /> ' All soil samples were analyzed for benzene, toluene, ethyl-benzene, xylenes (BTEX , total petroleum <br /> ' hydrocarbons as gasoline (TPH-G), and total petroleum hydrocarbons as diesel (TPH-D) by EPA Methods <br /> 8015/8020 Methyl-tert-butyl ether (MTBE) and other oxygenates were analyzed for using EPA Method <br /> 8260 <br /> None of the soil samples contained detectable levels of BTEX, TPH-G, or TPH-D, soil MTBE levels <br /> ranged up to 0 18 milligrams per kilogram (mg/kg), in the northwest corner of the UST pit at a depth of <br /> 1 about 14 feet bg <br /> ' Initial site assessment was conducted in June 1999 (IT Corporation, 1999)and consisted of the <br /> Installation of five push-probe borings to total depths of up to 25 feet bg Soil samples collected during <br /> drilling contained up to 0 167 mglkg MTBE, and no detectable benzene or TPH-G Grab groundwater <br /> ' samples collected at the base of the borings contained up to 607 micrograms per liter(ug/L) benzene, <br /> 32,200 ug/L TPH-G, and 46,300 ug/L MTBE(the highest concentrations were observed in boring GP-3, <br /> located near the western end of the former dispenser island location) <br /> 21756SAR doc <br />