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I20 December 2005 . AGE-NC Project No 95-0184 ' Page 4 of 5 ' 4.0. SUMMARY AND CONCLUSIONS Based upon data collected from the site, AGE concludes the following ' • Ground water elevations at the site averaged approximately 22 90 feet below MSL All ground water wells except VW-3,VW-4,and VW-5B were"drowned",with water levels as ' high as 19 feet above the screened intervals of the drowned wells (MW-1) • The ground water was inferred to flow generally northeast across much of the site at a gradient of approximately 0 004 ft/ft This ground water flow direction is consistent with the ' last 27 of 28 monitoring events (Table 4) • Detectable concentrations of TPH-g were found in all of the ground water wells sampled Concentrations generally remained stable or decreased slightly in all wells as compared to the previous quarter One or more BTEX compounds were found in all ground water samples collected Concentrations of BTEX compounds were detected above the solubility limits for water, therefore free-phase product may be present in coarse grained soils at the site or adsorbed hydrocarbons are being readily liberated during the ground water purging procedures • • MTBE was detected in samples from wells MW-4, VW-2B, VW-3 and VW-4 at concentrations ranging from 64 µg/l (VW-3) to 480 µg11(VW-4) 1,2-DCA was detected in ' MW-1, MW-2, MW-4, VW-2B, VW-3, VW-4, VW-5B, and VW-5C at concentrations ranging from 4 9 µg/l (MW-1) to 380 µg/l (VW-4), EDB was detected in VW-2B at a concentration of 86 µg/l The concentrations of MTBE, 1,2-DCA, and EDB in the ground ' water samples exceed their respective MCLS for drinking water A map of dissolved TPH-g, benzene, MTBE and 1,2-DCA concentrations are shown on Figures 4 through 7 r� ' Naphthalene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, and n-propylbenzene were detected in ground water samples at concentrations above the DHS-recommended drinking water Action Levels VOC concentrations have decreased in wells VW-4 and VW-5B and remained relatively stable in the remaining wells • The vertical and lateral extent of impacted soil and ground water has not yet been defined The concentration of dissolved constituents collected in samples from deeper monitoring wells have been documented to be lower than the shallow, vapor well samples Therefore, the maximum concentration of the release appears to reside in the upper 50 feet of the ' subsurface ' Advanced GcoEnvironmental,Inc 1