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F <br /> First Quarter 2001 Monitoringand Sampling <br /> rt <br /> 7-Eleven Inc. Store#21756853 E.Yosemite Av nue Manteca CA <br /> . 2 <br /> March 30 2001 <br /> Monitoring Well Sampling and Analytical Results <br /> The groundwater samples were collected using disposable bailers. Groundwater samples were <br /> analysis-specific p placed in <br /> ys pecific containers with analysis-specific preservative. The samples were then sealed using Teflon <br /> septum caps, labeled with the job identification number,the sample number,date,time, and type of <br /> laboratory analysis required. The samples were stored on ice and transported with a chain-of-custody <br /> record to a state-certified laboratory. Groundwater samples were analyzed for BTEX, MTBE,and TPH-G <br /> 4 . using EPA methods 8021/modified 8015 and for the oxygenates: MTBE TBA DIP <br /> using EPA method 8260. E, ETBE, and TAME <br /> f <br /> Dissolved oxygen (DO) concentrations were measured in the three wells prior to sampling. Dissolved <br /> oxygen readings ranged from 0.79 mg/L to 1.6 mg/L(Table 1). <br /> i ' 6 <br /> Quarterly analytical results are summarized in Table 1 and historical results are summarized in Table 2. <br /> F, Dissolved benzene concentrations ranged between non-detectable (well MW-3) and 4,700 micrograms per <br /> liter(ug/L) (well MW-2). Dissolved TPH-G levels ranged between non-detectable (well MW-3)and 64,000 <br /> ug/L(well MW-2). Dissolved MTBE concentrations ranged between 21 ug/L(well MW-3) and 3,400 ug/L <br /> (well MW-1). The other oxygenates were not reported above detection limits in any of the wells sampled. <br /> The laboratory analytical reports for the groundwater samples are included in Attachment 4. <br /> FWell Search <br /> As mentioned in previous quarterly reports, a well search database for public water supply wells located <br /> within one mile of the site indicates that the nearest well is an active municipal well located 1,987 feet <br /> downgradient of the site; it is 155 feet deep,with top of screen at approximately 65 feet below grade. <br /> Purge Water Transportation and Disposal <br /> Y <br /> Purge water generated during this quarterly monitoring and sampling event was stored in 55-gallon <br /> • <br /> Department of Transportation (DOT) -approved drums pending characterization and proper disposal by a <br /> licensed waste hauling company. <br /> F ; <br /> r~ <br /> U <br /> j <br />