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i <br /> ' Mr Nuel Henderson <br /> Page 3 of 5 <br /> respectively Elevated levels of MTBE were also found in cross-gradient wells MW 16A <br /> (3,300 ppb) and MW16B (140 ppb) These wells are clearly affected by offsite releases <br /> EDB was not detected in any of the monitoring wells sampled 1,2-DCA was detected in wells <br /> MW10, MW11, MW15A and MW15B Detected concentrations of 1,2-DCA ranged from <br /> ' 4 3 ppb (MW 15A) to 10 ppb (MW 10) Analytical results for gasoline oxygenates, EDB and <br /> 1,2-DCA are summarized in Table 3 Attachment B contains laboratory reports and chain of <br /> 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 VW4 and VW6 EDB was detected <br /> ' in well VW4 at a concentration of 30 ppb 1,2-DCA was reported in well VW6 at a <br /> concentration of 570 ppb This is the first time detectable levels of 1,2-DCA have been <br /> reported in VW6 TPHg and BTEX concentrations are summarized in Table 2 1,2-DCA, <br /> ' EDB and gasoline oxygenate additive concentrations are summarized in Table 3 Attachment <br /> B contains laboratory reports and chain of custody 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 MW 15AIB/C continues to exhibit an <br /> upward vertical gradient component, while at the MW 16A/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 in downgradients wells MW 11 and MW 15B are <br /> continuing to increase <br /> ' VAPOR EXTRACTION SYSTEM ACTIVITIES <br /> ' Vapor Extraction System Operation <br /> As requested by EHD, the soil vapor extraction was operated briefly during the fourth quarter <br /> ' of 2003 to evaluate current hydrocarbon removal capabilities <br /> • <br /> G 1GROUNDZEIROEKIQMR1200314gm2UO3 doc <br />