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1 First Quarter 2000 Monitoring and Sampling Report 2 7-Eleven Inc Store#14117 2725 Country Club Boulevard Stockton,CA June 9 2000 Monitoring Well Sampling and Analytical Results ' On May 16, 2000, groundwater samples were collected from groundwater monitoring wells MW-1, MW- 2, MW-3, and MW-4 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 Blmodified 8015, and for oxygenates MTBE, TBA, DIPE, ETRE, and TAME using EPA ' method 82606 - The analytical results for groundwater samples are summarized In Table 1 Dissolved benzene, MTBE and TPH-G concentrations ranged up to 1,400 micrograms per liter (pg/L), 3,000 pg/L and 17,000 pg/L, respectively Highest MTBE levels were reported In well MW-2 located in the underground storage tank ' pit (UST) area, whereas highest benzene and TPH-G concentrations were detected in well MW-3 located crossgradient from the pump island and former USTs) The laboratory analytical reports for the groundwater samples are included In Attachment 4 Dissolved oxygen data taken from the monitoring wells on May 16, 2000 indicate generally anaerobic conditions Dissolved oxygen levels ranged from 0 4 milligrams per liter(mg/L)to 1 0 mg/L (Table 1) Well Search ' IT Corporation performed a well search using multiple sources of information to assemble a database for public water supply wells located within one mile of the site The database includes (where available)well ownership, depth of sanitary seal, well type, length of screen, location, operating pumping rate, status, and ' any available testing information The database for this site (Attachment 5) Indicates that there are no public water supply wells located within one mile downgradient or crossgradient from the site ' purge Water Transportation and Disposal All purge water generated during 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 14117020 RPT