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I ' 12 May 2005 • AGE-NC Project No 96-0229 ' Page 3 of 6 I Ethylene dibromide (EDB), 1,2-dichloroethane (1,2-DCA), tert-butyl alcohol (TBA), di- Isopropyl ether(DIPE), ethyl tert-butyl ether(ETBE),tert-amyl methyl ether(TAME), and methyl tert-buyl ether(MTBE) by EPA Method 8260B 3.4. FINDINGS Ground water monitoring field data was utilized to determine ground water flow direction and ' gradient, petroleum hydrocarbon-impact to ground water was quantified by laboratory analysis of samples ' 3 1 GROUND WATER ELEVATION AND GRADIENT I The depth to ground water measurements on 07 December 2004 ranged between 33 25 feet(MW-3) and 36 25 feet (MW-12) below the tops of the well casings Generally, the average ground water depth at the site was equal to 35 22 feet, ground water levels generally increased an average of I . 0 31 feet between the September 2004 and the December 2004 ground water monitoring events Ground water elevations were calculated by subtracting the measured depth to ground water from ' the surveyed casing elevations The ground water elevations averaged 22 18 feet below mean sea level (MSL) at the site, with a range of between 19 72 feet(MW-3)and 23 29 feet(MW-12)below MSL ' Ground water elevation data collected from wells MW-1, MW-2, MW-3, MW-13 (A-D), MW-14 (A-D), and MW-16 (A-E) on 07 December 2004 is depicted on cross section B-B' (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 vertical gradients and slightly downward vertical gradients were observed between the Second Water Zone, Second Confining Unit and Third Water Zone screen Intervals of all the above wells (Figure 3), however, moderate downward vertical gradients were generally observed in the First Confining Unit Ground water elevations were plotted on scaled site plans for the informal First Water Zone ' (between 15 and 45 feet, Figure 4) and Second Water Zone (between 70 and 95 feet, Figure 5) 3 1 1 First Water Zone Ground water elevation data collected in the First Water Zone(15 to 45 feet bsg)at the site inferred Advanced GeoEnvuronmental,Inc