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Mr. Nuel Henderson <br /> Page 3 of 4 <br /> . EDB was not detected in any of the wells sampled. 1,2-DCA was detected in wells MW8, MW 11, <br /> MW 12, MW 15A, MW 15B and MW 15C. Detected concentrations of 1,2-DCA ranged from 1.0 <br /> ppb in MW8 to 18 ppb in MW 12. Analytical results for gasoline oxygenates, EDB and 1,2-DCA <br /> are summarized in Table 3. Attachment B contains laboratory reports and chain of custody <br /> documentation. <br /> Vapor Extraction Wells <br /> Vapor extraction wells VW1 through VW6 were not sampled during the quarter. <br /> GROUNDWATER SAMPLING SUMMARY AND DISCUSSION <br /> • Water levels rose during this quarter. Groundwater elevation data continue to show a <br /> predominantly easterly-northeasterly groundwater flow direction. An upward vertical gradient <br /> component was observed across the site. <br /> + Petroleum hydrocarbon concentrations in the wells affected by the onsite release were within <br /> historical ranges. The extent of groundwater contamination associated with the onsite release is <br /> stable and contaminant concentrations are stable to decreasing. <br /> • The plume of contamination originating from offsite source(s) is continuing to spread. High <br /> levels of MTBE persist in wells along the southern portion of the property. MTBE has also <br /> affected downgradient wells MW11 and MW15B where the concentrations detected during this <br /> event are the highest ever recorded in those wells. <br /> VAPOR EXTRACTION SYSTEM ACTIVITIES <br /> Vapor Extraction System Operation <br /> The vapor extraction system was not in operation during this quarter. Additional repairs are <br /> necessary before the system can be placed back in operation. <br /> RECOMMENDATIONS <br /> Groundwater Monitoring and Sampling <br /> Reduce the sampling frequency for wells that are monitoring the plume of contamination <br /> originating from the onsite release to an annual schedule. Given the massive quantity of historical <br /> groundwater data at this site, continued quarterly sampling is not warranted. We also recommend <br /> that sampling responsibility for the wells that are affected by the offsite release(s) be transferred to <br /> the appropriate responsible parties. <br /> G:\GROUNDZE\ROEK\QMR\2005\2qm2OO5.doc <br />