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Fourth Quarter 2002 Monitoring and Sampling Report 4 7-Eleven Inc,Store#21756 853 E Yosemite Avenue,Manteca,CA December 10,2002 ' Monitoring Well Sampling and Analytical Results I Dissolved oxygen (DO)concentrations were measured in the wells prior to sampling 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 job 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 Groundwater samples were analyzed for BTEX, MTBE, and TPH-G using EPA methods 8021/modified 8015 and for oxygenates MTBE, TBA, RIPE, ETBE, and TAME using EPA method 8260 ' Dissolved benzene and TPH-G were not detected in any of the wells Dissolved MTBE concentrations were detected in well MW-1 at 2,900 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 t DO readings ranged from 1 0 milligrams per liter m IL in well MW-3 to 1 3 m IL in well MW-2, indicating g g 9 P ( g ) 9 g , generally anaerobic conditions Purge Water Transportation and Disposal tPurge 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 Soil Vapor Extraction Testing SVE testing was conducted on October 17, 2002, by applying a vacuum to wells SPV-2 and MW-1 for three and four hours, respectively During the test, wells not undergoing extraction were fitted with Magnehelic gauges to measure pressure changes during the test ' During the test, extracted air was channeled to a 250-cubic-foot-per-minute (cfm) thermal oxidizer after passing through a moisture knockout device and an air filter Soil vapors were then treated by passing them through the oxidizer prior to discharge to the atmosphere Extracted vapor concentrations were ' measured using aflame ionization detector(FID) Pressure readings and FID readings were recorded at periodic intervals throughout the test 1