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i <br /> } <br /> Mr Nuel Henderson <br /> • Page 3 of 4 <br /> Analytical results for gasoline oxygenates, EDB and 1,2-DCA are summarized in Table 3 <br /> Attachment B contains laboratory reports and chain of custody documentation <br /> Vapor Extraction Wells <br /> jRelative to the previous sampling event the TPHg and benzene concentrations reported in vapor <br /> well VW1 decreased approximately 50% In vapor well VW6, however, TPHg increased <br /> approximately 3x and benzene increased approximately 6x No gasoline oxygenate additives, <br /> EDB, 1,2-DCA were detected in wells VW1 and VW6 TPHg and BTEX concentrations are <br /> summarized in Table 2 1,2-DCA, EDB and gasoline oxygenate additive concentrations are <br /> summarized in Table 3 Attachment B contains laboratory reports and chain of custody <br /> documentation <br /> GROUNDWATER SAMPLING SUMMARY AND DISCUSSION <br /> • Water levels fell during this quarter Groundwater elevation data continue to show an easterly <br /> groundwater flow direction <br /> • Despite variability from sampling event to sampling event, the extent of groundwater <br /> . contamination associated with the onsite release is stable, and concentrations are stable to <br /> decreasing <br /> • High levels of MTBE persist in the wells located along the southern portion of the property <br /> The contamination plume originating at the Top Filling Station is continuing to spread The <br /> increasing concentrations in wells MW3, MW4, MW7, MW11, MW 12, and most notably <br /> MW 14 attest to plume mobility <br /> VAPOR EXTRACTION SYSTEM ACTIVITIES <br /> Vapor Extraction System Operation <br /> The soil vapor extraction system was not operated during the third quarter of 2002 Recent <br /> evaluation of the remedial system has determined that it is not econonucally feasible to remove the <br /> small hydrocarbon mass remaining in the vadose soil <br /> RECOMMENDATIONS <br /> Groundwater Monitoring and Sampling <br /> i <br /> • Transfer ownership and responsibility for wells MW3, MW4, MW7, MW 11 and MW 14 to Top <br /> Filling Historical groundwater monitoring data coupled with the ever-increasing levels of MTBE <br /> I <br /> IIGZa_FSIbt S011Dala1GROUNBZEIROF-K\QN[R\200213gm200Z dac <br />