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25 January 2005 <br /> AGE-NC Project No 97-0301 <br /> ' Page 3 of 6 <br /> • Benzene, toluene, ethylbenzene, and xylenes(BTEX),methyl tertiary-butyl ether(MTBE), <br /> ' 1,2-Dlchloroethane(1,2-DCA),ethylene dlbromlde(EBD),di-Isopropyl ether(DIPE),ethyl <br /> tert-butyl ether(ETBE),tort-amyl methyl ether(TAME),and tertiary butanoI(TBA)by EPA <br /> ' Method 8260B <br /> 3.0 FINDINGS <br /> Ground water elevation, flow direction, and gradient were determined from field data collected <br /> ' on 30 September 2004 The contaminant impact to groundwater was quantified by the groundwater <br /> samples collected on 01 October 2004 <br /> 3 1 GROUND WATER ELEVATION AND GRADIENT <br /> ' The depth to ground water measurements at wells MW-1 through MW-12 vaned between 35 70 feet <br /> (MW-9B)and 37 50 feet(MW-8C)below the tops of the well casings,ground water elevations were <br /> ' calculated to be between 23 31 feet(MW-10A&B)and 24 91 feet(MW-12D)below mean sea level <br /> (MSL) The average ground water elevation at the site on 30 September 2004 was 24 06 feet below <br /> MSL Generally,ground water elevation at the site decreased an average 2 68 feet between the June <br /> ' 2004 and the September 2004 ground water monitoring events <br /> Ground water elevation data collected on 30 September 2004 from wells MW-8 (A-C),MW-9 (A- <br /> D), and MW-12 (A-D)Is depicted on cross section D-D'(Flgurc 3) By determining the difference <br /> between ground water elevations(dh)and dividing by the difference of the screen Interval midpoints <br /> (dl), the vertical gradient between adjacent screen Intervals was calculated Generally, moderately <br /> ' steep to steep downward vertical gradients were observed between the Second, Third, and Fourth <br /> Water Zones,while near neutral vertical gradients were observed between the First Water Zone and <br /> the Second Water Zone In the southern portion of the site (Figure 3) <br /> ground water elevations at wells MW-1 through MW-12 were calculated b subtracting the <br /> i The grou g Y g <br /> measured depth to ground water from the surveyed casing elevation The September 2004 ground <br /> ' water elevation data collected from wells MW-1 through MW-7 were plotted for the First Water <br /> Zone(Figure 4)as defined In AGE's CPT Site investigation- Third Quarter 2001 (dated 25 October <br /> ' 2001) Generally, the net ground water flow direction was toward the east to northeast at an <br /> approximate hydraulic gradient of 0 002 foot/foot(ft/ft) <br /> 1 <br /> Advanced GeoEnvlronmental,Inc <br />