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1 <br /> REPORT ON ADDITIONAL_SITE ASSESSMENT AND RECOMMENDATIONS 1 <br /> 7-Eleven Store No 14117,2725 Country Club Blvd Stockton CA December 12,2001 <br /> ' 1 0 INTRODUCTION <br /> ' This report is submitted b IT Corporation, Inc IT Corporation)to summarize the results of <br /> P Y P ( P ) <br /> ' additional site assessment conducted at 7-Eleven Store No 14117, 2725 Country Club Boulevard, <br /> Stockton, California (Figures 1 and 2) The scope of work Included Installation of three additional <br /> ' groundwater monitoring wells, collection of soil samples, and collection of groundwater samples <br /> from existing and newly-Installed wells as part of fourth quarter 2001 quarterly monitoring <br /> 1 The work was designed to fulfill the requirements of the San Joaquin County Department of Public <br /> Health Services (SJCPHS)for additional site assessment as expressed in their May 14, 2001 letter <br /> The workplan for additional assessment was prepared by IT Corporation and was submitted to the <br /> ' SJCPHS on July 9, 2001 <br /> 20 BACKGROUND <br /> ' The underground storage tanks at the site were replaced in July, 1998 (Fluor Daniel GTI, 1998) <br /> Soil samples collected from beneath the tanks at depths of up to 14 5 feet below grade contained <br /> up to 63 milligrams per kilogram (mg/kg) benzene, 7,200 mg/kg total petroleum hydrocarbons as <br /> ' gasoline (TPH-G), and up to 40 mg/kg methyl tertiary butyl ether(MTBE) The new tanks were <br /> installed in a tank pit located to the east and slightly north of the ongmal tank location (Figure 2) <br /> ' Grab groundwater samples collected from groundwater ponded in the base of the tank pit contained <br /> up to 5,000 micrograms per liter(ug/L) benzene, 140,000 ug/L TPH-G, 68,000 ug/L MTBE, and <br /> ' 23,000 ug/L tert-amyl methyl ether(TAME) <br /> ' During installation of the new tank pit, a grab groundwater sample was collected, analyzed, and <br /> found to contain 300 ug/L benzene, 3,100 ug/LTPH-G, and 27 ug/L MTBE Conductor casing was <br /> ' Installed In three locations between the two new 10,000-gallon underground storage tanks, for <br /> future use as groundwater monitoring well installation guides The casing is 10-Inch diameter <br /> unperforated PVC extending to 12 feet below grade <br /> 1 <br />