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1 ' 12 December 2006 . AGE-NC Project No 01-0827 ' Page 10 of 14 ' 6 2 GROUND WATER MONITORING RESULTS Between December 1998 and July 2006, 45 ground water monitoring events were performed on the ' monitoring wells,to measure dissolved petroleum hydrocarbon concentrations in ground water and to characterize ground water flow direction and gradient on the site ' Since initiation of groundwater monitoring in December 1998,groundwater elevatio have ranged at the site from approximately 9 to 34 feet below mean sea level as depicted in TableThe ground water flow direction at the site had been dominantly east to northeast, at the former UST area ' Laboratory analysis of shallow ground water monitoring well samples(between 25 and 30 feet bsg) historically detected TPH-g and BTEX compounds in water samples collected from wells MW-1, ' VW-1 and VW-2, the highest dissolved concentrations were detected in wells MW-1 and VW2 during their first sampling events on 22 December 1988 and 26 November 1997, respectively The highest concentrations of TPH-g was 34,000 micrograms per liter(µg/1)from well VW-2d,followed ' closely in magnitude by 33,700 µg11 in well MW-1 and 32,000 µg/1 or 29,000 µg11 in vapor well VW-5s and VW-1, respectively TPH-g and BTEX compound concentrations generally declined at well MW-1 and the former UST area during the declining ground water table elevation of the early '. 1990's The TPH-g detections then rebounded to a high concentration in October 1996 during which time water rose to 30 feet bsg or within the mayor coarse sand and gravel layers at the site, and/or ' the water table was five feet above the top of the MW-1 well screen BTEX compounds have been detected as great as 6,100 µg/1 benzene, 4,900 µg/l toluene, 2,300 µg/1 ethyl-benzene and 6,100 xylene (VW2d) Analytical results of ground water samples are summarized in Table 5 IHowever,all these concentrations decreased after the initial sampling TPH-g and BTEX,along with fuel additive concentrations decreased in vapor wells and the monitoring wells,during SVE and IAS I remediation near the former UST area Monitoring well MW-1,vapor wells VW-1 and VW5d have declined to non-detect levels, since July of 2003 The concentration trends of TPH-g and BTEX detections in the samples from well VW-2d, at the former UST area, are depicted in Appendix F Laboratory analysis of samples from well MW-6, representing the deeper ground water, have detected TPH-g as high as 1,000 µg/1 in the July 2003 sample Concentrations of TPH-g in well I MW-6 have steadily declined to a non-detect level during six sampling events, over 18 months Additionally, BTEX compounds had been observed in the samples from well MW-6 at concentrations up to 62 µg11 of benzene, 7 4 µg/l of toluene, 31 pg/I of ethyl-benzene and 19 µg/1 I of xylene The BTEX concentrations have also declined to non-detect levels or at levels below concern or maximum contaminant limits, since July 2003 The ground water samples collected from well MW-6 was non-detect for hydrocarbons for three straight events (Dec 2004 - March 2006) I Laboratory analysis has also detected the fuel additives methyl tert butyl. � Y tY ether (MTBE), ), IAdvanced GeoEnvironmental,Inc