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r_ r - , ' 23 June 2003 AGE-NC Project No 00-0769 Page 8of13 r 0209-021-16,0209-021-21,0209-021-23,0209-02t-27,0209-021-28 and 0209-021--29)is included ' in Appendix G ' 4 4 GROUND WATER ELEVATION AND GRADIENT The depths to groundwater were measured at between 20 75 feet(MW-8A)and 30 18 feet(MW-5E) ' below the tops of the well casings on 21 November 2002, the pre-purge depth measurement at MW 6A was not used this quarter because the anomalously high measurement(15 93 feet)and large ' difference between the pre-purge and post-purge depth values suggest that the pre-purge depth measurement at MW-6A was erroneous Ground water elevations were calculated to be between 11 38 feet (MW-8A) and 19 23 feet 1 (MW-7D) below mean sea level (MSL) The 21 November 2002 ground water elevation data collected from the site and the adjacent Arc Pump and Weld site were plotted for the informal HU-1 ' through HU-4 hydrogeologic flow units as defined in Section 4 2 are depicted in Figures 7 through 10 4 4 1 HU 1 Ground water elevation data collected in HU-1 Upper Zone(25 to 51 feet bsg)indicated that ground water flow direction was generally east-southeast to southeast in the area of former UST-3, but apparently veering towards the south to southwest near the former UST Nos 1 and 2(Figure 7) The ground water gradients ranged from approximately 0 02 ft/ft near the former UST Nos 1 and 2 to 0 05 ft/ft near the former UST No 3 1 4 4 2 HU2 ' Based on ground water elevation data collected in HU-2 (112 to 125 feet bsg)the net ground water flow flow direction was inferred to be towards the north-northeast (Figure 8) under a gradient of ' approximately 0 03 ft/ft ' 443 HU3 Based on ground water elevation data collected in HU-3(140 to 160 feet bsg)the ground water flow ' direction was inferred to be towards the north under a gradient of approximately 0 03 ft/ft(Figure 9) ' Advanced Geo Environmental,Inc