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Third Quarter 2002 Monitoring and Sampling Report 4 7-Eleven,Inc,Store#21756,853 E Yosemite Avenue, Manteca, CA October 21,2002 Dissolved benzene and TPH-G were not detected in any of the wells Dissolved MTBE concentrations were detected In well MW-2 (5 1 pgIL) and MW-1 (3,700 pg/L) Very low level detections of xylenes were reported In wells MW-3 (0 61 ug/L) and MW-4 (0 78 ug/L) No other analytes were reported above detection limits in any of the wells sampled Quarterly and historic analytical results for the groundwater samples are summarized In Tables 1 and 1A, respectively (Attachment 2) The laboratory analytical reports for the groundwater samples are included in Attachment 4 Dissolved oxygen readings ranged from 1 0 milligrams per liter (mg/L) In well MW-1 to 1 6 mg/L In well MW-4, indicating generally anaerobic conditions jPurge Water Transportation and Disposal 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 by a licensed waste hauling company Waste disposal documentation will be forwarded If requested Conclusion and Recommendations Groundwater concentrations reported for third quarter 2002 indicate continued dissolved MTBE plume delineation, and stability of plume conditions with highest MTBE concentrations In well MW-1, downgradlent of boring location GP-3, which area had the highest reported dissolved MTBE concentrations as of June 1999 Non-detectable levels of MTBE in furthest downgradlent well MW-4 verify continued downgradlent delineation of the MTBE plume SVE testing data indicate that SVE potential in the former tank pit area may be limited To augment previous data, additional evaluation of SVE as a remediation alternative will be conducted In the areas of MW-1 and SPV-2 during the fourth quarter 2002 I 1 I i i I