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Mr. Nuel Henderson <br /> Page 3 of 4 <br /> . EDB was not detected in any of the monitoring wells sampled. 1,2-DCA was detected in wells <br /> MW2, MW 12, MW 15A and MW 15B. Detected concentrations of 1,2-DCA ranged from 4.8 <br /> ppb (MW15B) to 17 ppb (MW2). Analytical results for gasoline oxygenates, EDB and 1,2- <br /> DCA are summarized in Table 3. Attachment B contains laboratory reports and chain of <br /> custody documentation. <br /> Vapor Extraction Wells <br /> TPHg and BTEX concentrations in water samples collected from VWl and VW3 were within <br /> historical ranges. Gasoline oxygenate additives were not detected in either well. The water <br /> sample collected from vapor well VW1 contained both 1,2-DCA and EDB. These additives <br /> were not detected in the sample from vapor well VW3. TPHg and BTEX concentrations are <br /> summarized in Table 2. 1,2-DCA, EDB and gasoline oxygenate additive concentrations are <br /> summarized in Table 3. Attachment B contains laboratory reports and chain of custody <br /> documentation. <br /> GROUNDWATER SAMPLING SUMMARY AND DISCUSSION <br /> • Water levels rose during this quarter. Groundwater elevation data continue to show an <br /> easterly groundwater flow direction. Well cluster MW15A/B/C continues to exhibit an <br /> • upward vertical gradient component, while at the MW 16AIB 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 /> VAPOR EXTRACTION SYSTEM ACTIVITIES <br /> Vapor Extraction System Operation <br /> The soil vapor extraction was operated briefly during the first quarter of 2004. On February 18, <br /> the VES was restarted. The system operated intermittently for 65 hours between February 18 <br /> and February 25, when strong winds blew a canvas and steel-frame canopy from an adjacent <br /> food vendor into the system exhaust stack, toppling the stack. The system is currently down <br /> pending repair of the exhaust stack. Field notes are included in Attachment C. <br /> 11GZA_FS1V OL_11DATAIGROUNDZEaOEKIQMR1200411 gm2DO4.doc <br />