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I11 August 2003 • AGE-NC Project No 96-0232 Page 9 of 15 3 4 1 Ground Water Elevation and Gradient The depths to groundwaterwere measured at between 12 59 feet(MW-17)and 16 36 feet(MW-9A) below the tops of the well casings on 24 June 2003, ground water elevations were calculated to be between 4 33 feet (MW-10C, MW-13D) and 5 27 feet (MW-18) below mean sea level (MSL) Ground water elevation at the site generally decreased an average 2 11 feet between the March and IJune 2003 ground water monitoring events 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 24 June 2003 was 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, nearly flat, very slight upward vertical gradients were observed between the First Zone, Second Zone, Rocky's Upper Zone, Secondary Zone and Primary Zone screen intervals of all the above wells, however, significant downward vertical gradients were measured between Rocky's Upper Zone and Secondary Aquifer Zone in the area of wells MW-9 and DW-1 and between Second Zone and Rocky's Upper Zane in the area of wells MW-16, MW-17 and MW-18 (Figure 3) • The 24 June 2003 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 hydrogeologrc flow units as defined in AGE's Final Remediation Plan, and are depicted in Figures 4, 5, 6 and 7,respectively 3 4 1 1 First Zone Aquifer rGround water elevation data collected in the First Zone Aquifer(10 to 35 feet bsg) at the Flag City Chevron and Three B's Truck Plaza sites was inferred to have a radially inward flow direction ' towards a ground water depression in the area ofFlag City Chevron wells MW-1,MW-2 and MW-5 (Figure 4) The ground water gradients were approximately 0 002 ft/ft or less near the Flag City Chevron, and approximately 0 001 ft/ft or less near the Three B's Truck Plaza 3 4 12 Second Zone Aqui ' Ground water elevation data collected in the Second Zone Aquifer (40 to 60 feet bsg) inferred a radially-inward ground water flow, towards a ground water depression in the area of Flag City ' Chevron wells MW-6B and MW-9A, ground water gradients are approximately 0 002 ft/ft or less (Figure 5) At the Three B's Truck Plaza west of Flag City Chevron, ground water flow is generally northerly to northeasterly at low gradients of Q 001 ft/ft and less ' Advanced GeoEnvaronmental,Inc