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r <br /> Mr Nuel Henderson <br /> Page 3 of 4 <br /> and 320 ppb, respectively Elevated levels of MTBE were also found in cross-gradient wells <br /> MW 16A (1,400 ppb) and MW16B (120 ppb) These wells are clearly affected by offsite <br /> releases <br /> EDB was not detected in any of the momtormg wells sampled 1,2-DCA was detected in wells <br /> MW2, MW9, MW12, MW13B, MW15A and MW15B Detected concentrations of 1,2-DCA <br /> ranged from 2 6 ppb (MW15A) to 230 ppb (MW13B) Analytical results for gasoline <br /> oxygenates, EDB and 1,2-DCA are summarized in Table 3 Attachment B contains laboratory <br /> reports and chain of custody documentation <br /> Vapor Extraction Wells <br /> Petroleum hydrocarbon concentrations in the sampled vapor wells were within historical <br /> ranges Gasoline oxygenate additives were not detected in VW1 and VW3 EDB and 1,2- <br /> DCA were not detected in well VW3 EDB and 1,2-DCA were reported in well VWl at <br /> concentrations of 720 ppb and 360 ppb, respectively TPHg and BTEX concentrations are <br /> summarized in Table 2 1,2-DCA, EDB and gasoline oxygenate additive concentrations are <br /> summarized to 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 <br /> easterly groundwater flow direction Well cluster MW15A/BIC continues to exhibit an <br /> upward vertical gradient component, while at the MW16A/B well cluster the vertical <br /> gradient component continues to be downward <br /> • Petroleum hydrocarbon concentrations in the wells affected by the onsite release were <br /> within historical ranges The extent of groundwater contamination associated with the <br /> onsite release is stable, and the concentrations are stable to decreasing <br /> • The plume of contamination originating from offsite source(s) is continuing to spread <br /> High levels of MTBE persist in wells along the southern portion of the property <br /> Moreover, the concentrations of MTBE to downgradient well MW15B are increasing <br /> VAPOR EXTRACTION SYSTEM ACTIVITIES <br /> Vapor Extraction System Operation <br /> The soil vapor extraction system was not operated during the third quarter of 2003 <br /> N\GZA FSIVOL 11DATAIGROUNDZEIROEKIQMR120Q313gm2043 doc <br />