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' Shaw Environmental & Infrastructure, Inc <br /> 4005 Port Chicago Highway <br /> Concord CA 94520-1120 <br /> 925 288 9898 <br /> Fax 925 288 0888 <br /> IShaW The Shaw Group Inc' <br /> ' July 25, 2002 <br /> ' Mr Bob DeNinno <br /> 7-Eleven, Inc <br /> 10220 S W Greenburg Road, Suite 470 <br /> Portland, OR 97223 <br /> Subject Second Quarter 2002 Monitoring and Sampling Report <br /> 7-Eleven Store No 14117 <br /> 2725 Country Club Boulevard <br /> Stockton, California <br /> ' IT Project No 779966 <br /> Dear Mr DeNinno <br /> This Second Quarter 2002 Monitoring and Sampling Report presents the results of activities performed by <br /> Shaw Environmental & Infrastructure (formerly IT Corporation) at the subject site (Attachment 1, Figure 1) <br /> on April 12, 2002 <br /> A summary of activities conducted during this reporting period is provided below <br /> ' c Depth to water (DTW) was gauged in seven site-related groundwater monitoring wells (MW-1 <br /> through MW-7) <br /> ' a Groundwater samples were collected from seven groundwater monitoring wells and submitted <br /> to a California-certified laboratory for analysis for benzene, toluene, ethylbenzene and xylenes <br /> (BTEX), total petroleum hydrocarbons-as-gasoline (TPH-G), and oxygenates methyl-tert-butyl- <br /> ' ether(MTBE), tert-butanol (TBA), dusopropyl ether(DIPS), ethyl-tert-butyl ether(ETBE), and <br /> tert-amylmethyl ether (TAME) <br /> ' Background <br /> Underground storage tanks (USTs) at the site were replaced in July 1998 The new tanks were installed <br /> ' <br /> In a tank pit located to the east and slightly north of the original tank location Subsequent subsurface <br /> Investigations in 1998 and 1999 indicated that the highest MTBE concentrations were in well MW-2, <br /> installed in the new tank pit area Selected halocarbons (analyzed at the request of San Joaquin County <br /> ' Public Health Services [SJCPHS]) also indicated possible dry cleaner plume contributions Three <br /> additional groundwater monitoring wells (MW-5, MW-6, and MW-7)were installed in October 2001, to <br /> further investigate subsurface sod and groundwater conditions at the site The October 2001 data were <br /> used to delineate existing hydrocarbon plume distribution to the west, northwest, and south of existing and <br /> • former tank areas East(crossgradient) of the site is an Exxon service station, plume commingling may <br /> ' be possible <br /> ' 14117Q22 doc <br />