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i First Quarter 2001 Monitoring and Sampltng Report 2 7-Eleven, Inc,Store#14117,2725 Country Club Boulevards Stockton, CA March 30,2001 Monitoring Well Sampling and Analytical Results ' Before sampling, at least four well-casing volumes of water was removed from each well The groundwater samples were collected using disposable bailers Groundwater samples were placed in 40- milliliter glass vials,which were acidified with hydrochloric acid to preserve the samples The samples were ' then sealed using Teflon septum caps, labeled with the job Identification number,the sample number, date, time, and type of laboratory analysis required The samples were stored on ice and transported with a chain-of-custody record to a state-certified laboratory for analysis The groundwater samples were analyzed for BTEX, MTBE and TPH-G using Environmental Protection Agency(EPA) methods 8021 B/modified 8015, and for oxygenates MTBE,TBA, DIPS, ETRE, and TAME using EPA method 8260B ' The analytical results for groundwater samples are summarized In Table 1 Dissolved benzene, MTBE and TPH-G concentrations ranged up to 940 micrograms per liter(pg/L), 11,000 pg/L and 24,000 pg/L, respectively Highest MTBE levels were reported in well MW-2 located in the underground storage tank pit (UST) area,whereas highest benzene concentrations were detected in well MW-3 located downgradient from the pump Island The laboratory analytical reports for the groundwater samples are included in Attachment 4 Dissolved oxygen data taken from the monitoring wells indicate generally anaerobic conditions,with dissolved oxygen levels of less than 1 milligrams per liter (mg/L) (Table 1) There are no known public water supply wells located within one mile downgradient or crossgradient from the site ' Purge Water Transportation and Disposal All purge water generated dunng this quarterly monitoring and sampling event was stored in 55-gallon ' Department of Transportation (DOT)-approved drums pending characterization and proper disposal Waste disposal documentation will be forwarded once received 1 1 14117Q11 RPT