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Third Quarter 2000 Monitoring and Sampling Report 2 • 7-Eleven, Inc Store#20632 4627 DaVinci Drive,Stockton CA September 14 2000 Monitoring Well Sampling and Analytical Results On August 8, 2000, groundwater samples were collected from four wells (MW-1, MW-2, MW-3 and MW-5), well MW-4 was abandoned during UST upgrades in 1998 Before sampling, at least 4 well casing volumes of groundwater was removed from each monitoring well The groundwater samples were collected using disposable bailers Groundwater samples were placed In analysis-specific 1° containers with analysis-specific preservative The samples were then sealed using Teflon septum caps, labeled with the lob Identification number, the sample number, date, time, and type of laboratory analysis required The samples were stored on Ice and transported under a chain-of-custody record to a state-certified laboratory Groundwater samples were analyzed for BTEX and TPH-G using Environmental Protection Agency(EPA) methods 8021 B/modified 8015, and for oxygenates MTBE, TBA, DIPE, ETRE, and TAME using EPA method 82606 Laboratory analytical results for groundwater samples collected on August 8, 2000 are presented in Table 1 The laboratory analytical reports for the groundwater samples are Included In Attachment 4 Historical data are Included in Table 2 Dissolved benzene was detected at or near detection limits In wells MW-1 and MW-5 The highest dissolved TPH-G concentration was detected In MW-3 at 4,100 micrograms per liter(NgIL) and dissolved MTBE concentrations were highest In well MW-2 at 3,300 NgIL Dissolved MTBE concentrations versus water table elevations for wells MW-1 and MW-2 are plotted on Figures 3 and 4 Observed concentrations and hydrocarbon distribution are generally lower than previous quarters Dissolved oxygen levels are reduced to 0 3 -0 6 milligram per liter(mglL) due to intrinsic biodegradation Sensitive Receptors As mentioned In the previous quarterly report, 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 for this site Indicates that there are no active municipal wells located within a mile Idowngradient from the site Purge Water Transportation and Disposal I All purge water generated during this quarterly monitoring and sampling event was stored in 55-gallon P 9e 9 9 q Y 9 P g 9 Department of Transportation (DOT)-approved drums pending characterization and proper disposal Waste disposal documentation will be forwarded once received I20632Q30 RPT IT CORPORATION • l