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r, Second Quarter 2001 Monitoring and Sampling Report and Request for No Further Action Ju 9 7-Eleven lnc Store#17647, 1048 West Yosemite Avenue Manteca CA / Groundwater monitoring results for the quarter are presented in Table 1 (Attachment 2) potenti indicates ria`i >i'S ' surface map was prepared using the quarterly groundwater elevation data (Figure 2), h of the date of the sampling event,groundwater flow was toward the northwest at a gradient of approximately ' 0 0018 ftlft Field data sheets are included in Attachment 3 LMonitoring Well Sampling and Analytical Results Groundwater samples were collected from the three monitoring wells Dissolved oxygen(DO) concentrations were measured in the three wells prior to sampling The groundwater samples were collected using disposable bailers Groundwater samples were placed in analysis-specific beled with theontaers n b identification analysis-specific preservative The samples were then sealed using Teflon septum caps, ' number,the sample number, date,time, and type of laboratory analysis required The samples were stored ord to a state-certified labortory Groundwater on ace and transported with' achain-of-custadyreine hods 8021/modified 8015aand for the oxygenates pies were analyzed for BTEX and TPH-G using EPA MTBE,TBA, DIPS, ETBE, and TAME using EPA method 8260 Dissolved oxygen data indicate relatively uniform,generally anaerobic conditions Dissolved oxygen levels ' ranged between about 1 0 and 1 1 milligrams per later(rng/L) Laboratory analytical results for quarterly groundwater samples are summarized in Table 1 Dissolved BTEX and T PH-G concentrations were not detected above reporting limits in any of the wells sampled Dissolved MTBE concentrations were only detected in downgradient well MW-3 at 23 pg/L The other oxygenates were ' not reported above detection limits in any of the wells as has been the case for a total of five quarterly sampling events All gasoline constituents analyzed remained below detection limits in groundwater samples radient ell from the two upgradierit wells(MW-1 and MW-2) MBE plume appears restricted MTBE concentrations in to a Iwmited area between ' declined since the first quarter 2000 The dissolved between the former underground storage tanks and MW-3 Low and non-detectable dissolved gasoline- constituent concentrations with declining dissolved oxygen levels(MW-3) indicate that natural ' attenuabonlbiodegradation is occurring The laboratory analytical reports for the groundwater samples are included in Attachment 4 ' Well Search his site ndicates the nearest wells are proximately As mentioned previously, a well search' data�eas{h�o�tae two idowngradsent wells located approximatelyp4,956 993 feet to the north {crossgradient) of the site, feet southwest of the site ' Purge Water Transportation and Disposal sam ling event was stored In ' All purge water generated during this quarterly monitoring icharacterization lzafion and proper disposal ln Department of Transportation (DOT)-approved pending 1 1 z175ey4 gas