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Third Quarter 2002 Monitonng, Sampling, and Intenm Remediation Report 3 7-Eleven Inc Store No 20632 4627 DaVinci Drive,Stockton, CA October 28, 2002 Monitoring Well Sampling and Analytical Results Quarterly groundwater samples were collected after purging at least four 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 Groundwater samples were collected using disposable bailers Samples were placed in analysis-specific containers with analysis-specific preservative The samples were then sealed using Teflon septum caps, labeled with the fob 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 8021 B/modified 8015, and for oxygenates MTBE, TBA, DIPS, ETBE, and TAME using EPA method 826aB Dissolved benzene was detected in MW-4R at 340 micrograms per liter(ug/L), MW-3 at 0 84 pg/L, and MW-5 at 0 86 pg/L Dissolved MTBE was detected In all wells at concentrations ranging from 1 3 pg/L in well MW-6 to 30,000 dig/L in well MW-7 Quarterly and historical analytical results for groundwater samples are summarized in Tables 1 and 1A, respectively (Attachment 2) Laboratory analytical reports are included in Attachment 4 Dissolved oxygen (DO) levels ranged from 0 9 milligrams per liter(mg1L) in well MW-3 to 1 5 mg/L in the MW-4R, indicating anaerobic (less than 2 0 mg/L) conditions Well MW-7 contained 30,000 pg/L MTBE Additional lateral plume delineation is planned for early 2003 Access to the property (2628 W March Lane, parcel number 110-020-08, Attachment 1, Figure 3) to the west of 7-Eleven #20632 has been granted by Jean Good Lietzau, property owner A workplan to install one additional groundwater monitoring well on said property and downgradient of the impacted MW-7 will be submitted 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 tConclusion and Recommendations Additional delineation is recommended to proceed pending workplan and permit approval during early 2003, followed by submittal of recommendations for remedial action 20632Q23 QMR DOC