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• 30 January 2004 AGE-NC Project No 01-0865 Page 3 of 7 3 1 GROUND WATER GRADIENT AND FLOW DIRECTION The elevation of ground water in each well was calculated by subtracting the depth to ground water from the surveyed well casing elevation(Table 1) The depth to ground water ranged from 0 50 feet (MW-7) to 22 85 feet (MW-11)below the tops of the well casings Ground water elevations at the site ranged from 3 17 feet above mean sea level(MSL)in well MW-12 to 16 45 feet below MSL in well EW-1, relative to the September 2003 monitoring event, ground water elevation increased in all first water and deep-screened wells,the average ground water elevation at the site was 13 32 feet below MSL, which represents an overall elevation increase of approximately 1 54 feet between the September 2003 and December 2003 sampling events The ground water flow direction of first ground water on 31 December 2003 was inferred to be towards the southeast under an average ground water gradient of approximately 0 25 foot/foot in the central portion of the levee (former USTs location), rotating to a more easterly flow with a lower gradient of 0 085 foot/foot toward the northern part of the site (Figure 3) At the eastern portion of the site, the flow direction rotates to a more southerly direction and the gradient decreases to approximately 0 027 foot/foot The dominate gradient direction remains southeast,while the central component of the gradient at the levee is very steep, dropping one foot of elevation for every four lateral feet The ground water flow inferred from deep-screened (50 feet to 60 feet bsg) wells MW-6 through MW-8 and MW-1 I atop the levee (70 feet to 80 feet bsg) was east, but under a much shallower average gradient of 0 005 foot/foot(Figure 4) The gradient remained very similar to the September 2003 gradient, though the direction did shift slightly north The ground water at the site is very dynamic and can be influenced greatly by seasonal variations, tidal effect and human influences (e g island draining pumps) 3 2 ANALYTICAL RESULTS OF GROUND WATER SAMPLES TPH-g was detected in the water samples collected from wells MW-2 through MW-6 and EW-1 at concentrations ranging from of 820 micrograms per liter(µg/1)(MW-4)to 76,000 µg/l(MW-2) An iso-concentration map illustrating the approximate distnbution of dissolved TPH-g is depicted on Figure 5 One or more BTEX compounds were detected in the samples collected from wells MW-2 through MW-6 at the following maximum concentrations 55 µg/1 benzene (MW-2), 120 µg/1 toluene (MW-2), 12 µg/l ethylbenzene (MW-4) and 91 µg/1 xylenes (MW-4) An iso-concentration map showing the approximate distribution of dissolved benzene is provided in Figure 7 Advanced GeoEnvironmental,Inc