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Mr Nuel Henderson <br /> Page 3 of 4 <br /> Vapor Extraction Wells <br /> Petroleum hydrocarbon concentrations in the sampled vapor wells were within historical ranges 1,2- <br /> DCA was detected in well VW4 at a concentration of 48 ppb but was not detected in wells MW3 and <br /> VW6 Gasoline oxygenate additives, and EDB were not detected in wells VW3, VW4 and VW6 <br /> TPHg and BTEX concentrations are summarized in Table 2 1,2-DCA, EDB and gasoline oxygenate <br /> additive concentrations are summarized in Table 3 Attachment B contains laboratory reports and <br /> chain of custody 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 /> • Petroleum hydrocarbon concentrations in the wells affected by the onsite release were within <br /> historical ranges Despite the variability from sampling event to sampling event, the extent of <br /> groundwater contamination associated with the onsite release is stable, and concentrations are <br /> stable to decreasing <br /> • High levels of MTBE persist in wells NIW3, MW4, MWl l and MW 14, which are located along <br /> the southern portion of the property The contamination plume originating at Top Filling Station is <br /> continuing to spread The ever-increasing concentrations in these wells (most notably MWl4) <br /> attests to plume mobility <br /> VAPOR EXTRACTION SYSTEM ACTIVITIES <br /> Vapor Extraction System Operation <br /> The soil vapor extraction system was not operated during the fourth quarter of 2002 Recent <br /> evaluation of the remedial system has determined that it is not economically feasible to remove the <br /> small hydrocarbon mass remaining in the vadose soil <br /> RECOMMENDATIONS <br /> Groundwater Monitoring and Sampling <br /> Transfer ownership and responsibility for wells MW3, MW4, MW7, MW11 and MW14 to Top <br /> Filling Historical groundwater monitoring data coupled with the ever-increasing levels of MTBE <br /> indicate that these wells have been impacted by the contaminant plume originating from the Top Filling <br /> site <br /> 11G7-A FSISYSOIIData1GROUt DZEIROEK�QMS212002Agm2002 doc <br />