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f �' c ..-. Y .. Fs W -1 £ - -' . n xw - z.. - -` + i .. ..0 ti u i �A..✓` 1 f A 23 December 2005 (� AGE-NC Project No 00-0769 Page 7 of 8 I4.0. SUMMARY AND CONCLUSIONS Based on data collected during the September 2005 groundwater monitoring event,AGE concludes I , r Ground water elevation at the site ranged from 13 16 feet to 17 05 feet below MSL during the'September 2005 monitoring event ' 0 Ground water in HU-1 flows to the east and southwest at gradients between 0 002 ft/ft and 0 004 ft/ft, away from a north-south trending ridge in the potentiometric surface (Figure 3) Ground water in HU-2 generally flows to the southwest and east, away from a north-south ' trending ridge in the potentiometric surface, hydraulic gradients range from 0 002 to 0 008 ft/ft(Figure 4) Ground water in HU-3 flows generally towards the southwest and southeast at hydraulic gradients between 0 002 ft/ft and 0 004 ft/ft (Figure 5) Ground water in HU-4 ' generally flows to the northwest and northeast;away from a northwest-plunging ridge in the potentiometric surface, at a hydraulic gradient of 0 009 ft/ft (Figure 6) I0 The most highly impacted ground water appears to be located near the former USTs Laterally, analytes of concern were detected at or above laboratory reporting limits in all wells except multi-level wells MW-8 and MW-9 Vertically,hydrocarbon-impacted ground water was detected in all wells except single-level well MW-2A and multi-level wells MW-8 f and MW-9, although contaminant levels generally decline with depth,mayor increases have been detected in well MW-4D (HU-4 - 160 feet to 175 feet bsg) since September 2004 G The lateral and vertical extents of petroleum hydrocarbon-impacted ground water have not been defined The vertical extent of the fuel additive 1,2-DCA is not defined, although the ' - lateral extent of 1,2-DCA appears to be fairly well-defined except to the southeast ' • BTEX compounds and 1,2-DCA are present in on-site monitoring wells at concentrations that,exceed the DHS's Maximum Contaminant Levels (MCLs) for these contaminants in drinking water r h ^ 5.0. RECOMMENDATIONS ' Based on this and previous site investigations, AGE recommends 1 • Continued quarterly monitoring of the well network The fourth quarterly monitoring event is scheduled for 21 December 2005 y Conduct additional assessment to define the eastern extent of petroleum hydrocarbon- impacted ground water ' y Advanced GeoEnvironmental,Inc t