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it <br /> Mr. Nuel Henderson <br /> Page 3 of 5 <br /> ' reports and chain of custody documentation. Attachment C containsra hs of contaminant <br /> g P <br /> concentrations over time. <br /> MTBE was not detected in wells MW 1 <br /> 8, MW 3B and MW15C. MTBE was detected in wells <br /> ' MW 1 (5.7 ppb), MW 11 (59 ppb), MW12 (280 ppb), MW 15A (2.5 ppb), and MW 15B (380 <br /> ppb). These wells are affected by MTBE releases originating at 101 S. Wilson Way and/or <br /> 130 S. Wilson Way. <br /> ' EDB was not detected in any of the wells sampled. 1,2-DCA was detected in each of the <br /> sampled wells. Concentrations of 1,2-DCA ranged from 3.3 ppb in MW8 to 1,300 ppb in <br /> MW13B. Analytical results for gasoline oxygenates, EDB and 1,2-DCA are summarized in <br /> Table 3. Attachment B contains laboratory reports and chain of custody documentation. <br /> Vapor Extraction Wells <br /> TPHg and BTEX concentrations in the water sample collected from VW1 were within <br /> historical ranges. MTBE was not detected in well VWL The water sample collected from <br /> vapor well VW1 contained 1,2-DCA at a concentration of 830 ppb. TPHg and BTEX <br /> concentrations are summarized in Table 2. 1,2-DCA, EDB and gasoline oxygenate additive <br /> I ' concentrations are summarized in Table 3. Attachment B contains laboratory reports and <br /> chain of custody documentation. <br /> GROUNDWATER SAMPLING SUMMARY AND DISCUSSION <br /> o Water levels rose during this quarter. Groundwater elevation data continue to show a <br /> predominantly easterly-northeasterly groundwater flow direction. An upward vertical <br /> ' gradient component was observed across the site. <br /> 0 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 contaminant concentrations are stable to decreasing. <br /> I ' o 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. MTBE <br /> has also affected downgradient wells MW11, MW12, and MW15B. Concentrations of <br /> ' MTBE detected in MW12 during this event are the highest ever recorded in that well. <br /> ' G:IGROUNDZE\ROEIC1QMR12005'Ogm2O05.doc <br />