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. 29 July 2005 AGE-NC Project No 96-0232 Page 4 of 9 2 4 1 Ground Water Elevation and Gradient The depths to ground water were measured at between 8 92 feet(MW-18)and 13 31 feet(MW-9C) below the tops of the well casings on 27 June 2005, ground water elevations were calculated to be between 0 51 feet (MW-14) and 1 84 feet (MW-13B-C) above mean sea level (MSL) Ground water elevation data collected from Flag City Chevron wells MW-9 (A-C),MW-11 (A-D), MW-13 (A-D), MW-16, MW-17, MW-18 and Three B's Truck Plaza wells MW-6, MW-9 (A-E) and MW-10(A-F)on 27 June 2005 is depicted on cross section C-C'(Figure 3),by determining the difference between ground water elevations(dh)and dividing by the difference of the screen interval midpoints (dl), the vertical gradient between adjacent screen intervals was calculated Generally, slightly upward vertical gradients were observed between the First Zone and Second Zone, nearly neutral vertical gradients were observed between Rocky's Upper Zone and Secondary Aquifer Zone, and pronounced downward vertical gradients were observed between Secondary Aquifer Zone and Primary Aquifer Zone (Figure 3) The 27 June 2005 ground water elevation data collected from the Flag City Chevron site and the adjacent Three B's Truck Plaza site were plotted for the informal First Zone, Second Zone, Secondary Aquifer Zone and Primary Aquifer Zone hydrogeologic units as defined in AGE's Final Remediation Plan, and are depicted in Figures 4, 5, 6 and 7, respectively 2 4 1 1 First Zone Aquifer Ground water elevation data collected in the First Zone Aquifer(15 to 35 feet bsg) at the Flag City Chevron inferred a net ground water flow towards the east at a hydraulic gradient of 0 001 ft/ft or less The ground water gradient along the western edge of the Three B's Truck Plaza inferred a net ground water flow direction towards the east-northeast at a hydraulic gradient of approximately 0 001 ft/ft, the gradient apparently decreases to essentially flat at the western portion of the Three B's site (Figure 4) 2 4 12 Second Zone Aquifer Ground water elevation data collected in the Second Zone Aquifer(40 to 60 feet bsg) inferred a net ground water flow direction at the Flag City Chevron towards the southeast at a hydraulic gradient of 0 001 ft/ft or less The ground water gradient at the Three B's Truck Plaza inferred a net ground water flow direction towards the east-northeast at a hydraulic gradient of 0 001 ft/ft or less (Figure 5) Advanced GeoEnvironmental,Inc