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1,. �., Despite the five original monitoring wells being screened below the groundwater table, the static groundwater table elevations in these wells are consistent with the static groundwater table elevations calculated in the shallower wells (e.g., MW-6, MW-7, MW-8A). This suggests that a significant vertical groundwater gradient does not exist beneath the site. The groundwater flow direction and gradient are relatively similar, if calculated using the . shallow wells or the deep wells (Figures 6 and 7). In general, the direction of groundwater flow is toward the north-northeast at a gradient of between approximately 0.002 and 0.004 foot per foot. t..• 3.2.3 Plume of Impacted Groundwater Prior to the completion of soil vapor extraction and air sparging in June 2000, the plume of impacted groundwater was concentrated near the former UST source area, and consisted of we dissolved concentrations of TPH-as-gasoline, BTEX compounds and MTBE. After June 2000, the concentrations of TPH-as-gasoline and BTEX compounds in groundwater declined to below reporting limits. In general, MTBE concentrations in groundwater initially increased �.. after June 2000, and then gradually declined. Charts of MTBE in groundwater versus time for NO. MW-5, MW-7 and VW-21D are included in Appendix D. �w During the fourth quarter of 2005, only MTBE and 1,2-DCA were detected in groundwater. %r The highest concentrations (52.1 µg11 of MTBE and 12.2 gg/1 of 1,2-DCA) were detected in %W MW-5, approximately 100 feet northeast (downgradient) of the former UST source area. The plume of impacted groundwater,appears to be defined and adequately characterized. Except for one anomalous detection of 0.66 µg/I of MTBE in groundwater at MW-8A, on June 2, 2004, no gasoline compounds have been detected in the downgradient monitoring well cluster (MW-8A and MW-8B) in 16 quarterly sampling events. Groundwater collected from Irrigation Well #2 has been free of gasoline compounds for 23 consecutive quarters. Concentrations are declining and the plume of impacted groundwater appears to be stable. By projecting a linear concentration trend derived from the last nine quarters of groundwater analytical results from MW-5, the concentration of MTBE in groundwater should continue to decline to below reporting limits by approximately the fourth quarter of 2008. The chart �., showing the projected concentration trend for MW-5 is also included in Appendix D. 15 t�