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First Quarter 2002 Monitoring and Sampling Report 3 7-Eleven, Inc Store No 20632,4627 DaVinci Drive,Stockton, CA April 1, 2002 Monitoring Well Sampling and Analytical Results ' Quarterly groundwater samples were collected after purging at least 4 well-casing volumes of groundwater from each monitoring well, unless the well was purged dry Prior to purging, dissolved oxygen (DO) levels ' were recorded in each well The groundwater samples were collected using disposable bailers Groundwater samples were placed in analysis-specific 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 with a chain-of-custody record to a state-certified laboratory for analysis Groundwater ' samples were analyzed for BTEX and TPH-G using Environmental Protection Agency (EPA) methods 8021B/modified 8015, and for the oxygenates MTBE, TBA, DIPS, ETBE, and TAME using EPA method 8260B ' Quarterly analytical results are presented in Table 1 Dissolved benzene was not detected above reporting limits m wells MW-1, MW-2, MW-3, or MW-5 Dissolved MTBE was detected in wells MW-1 (180 ug/L), ' MW-2 (8,950 ug/L) and MW-5 (52 uglL), MTBE was not detected in well MW-3 Selected dissolved constituents are plotted on Figure 2 The laboratory analytical reports are included in Attachment 4 ' Dissolved oxygen (DO) levels ranged from 0 7 milligrams per liter(mg/L) in well MW-3 to 1 0 mg/L in well MW-2, indicating anaerobic conditions (less than 1 0 mg/L) Purgewater Transportation and Disposal All purgewater generated during this quarterly monitoring and sampling event was stored onsite in 55-gallon Department of Transportation (DOT)-approved drums, pending characterization and proper ' disposal at a licensed recycling facility Waste disposal documentation will be forwarded if requested Conclusion and Recommendations Quarterly data obtained during this sampling event suggest a reduction in the geographic distribution of analytes detected above the reporting limits Plume delineation will be reviewed in the context of additional ' site assessment Feasibility testing results (sod vapor extraction and air-sparging) will be evaluated within the context of plume delineation and remedial goals for the site based on basin water quality objectives 1 1 1 ' 20632Q21 OMR DOC