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' 12 March 1999 AGE-NC Project No 95-0121 - Page 5 of 7 (TPH-g and TPH-d, respectively), 1 • EPA Method 8020 for volatile aromatics (benzene, toluene, ethyl benzene and,xylene BTEX) with methyl-tertiary butyl ether(MTBE), and ' k ' • EPA Method 8260 for tertiary butanol (TBA), di-isopropyl ether (DIPE), ethyl tent butyl ether(ETBE), tert amyl methyl ether (TAME) and MTBE t3.0. FINDINGS ,Froin ground water monitonng field data, AGE was able to determine groundwater now direction ' and gradient Laboratory analysis of nine ground water samples detected TPH-g and BTEX in five of the nine samples, MTBE was confirmed in three ground water samples ' 3 1 RELATIVE GROUND WATER ELEVATION AND GRADIENT w During the December 1998 monitoring event, depths to ground water from wells MW-1 through MW-9 were measured between 14 75 and' 16 22 feet below the top of well casings, relative ground ' water elevations were calculated between 83 85 feet and 84 39 feet Ground water elevation at the site decreased an average 0 60 feet between the August 1998 and the December 1998 ground water monitoring events, decreasing ground water elevations have been observed at the site since May 1998 The ground water elevation data for MW-I through MW-9 during the December 1998 ground ' water monitoring event is depicted in Figure 3 Ground water monitoring data collected in December 1998 in the area of wells MW-1,MW-2, MW- _ ' 3, MW-6, MW-7 and MW-9 indicated that the ground water flow direction was generally toward the r northeast at a gradient of 0 003 ft/ft, or approximately 16 feet per mile (Figure 6), data collected in ' the area of wells MW4, MW-5 and MW-8 indicated that ground water flow dii ection was generally' toward the northwest at a gradient of 0 002 ft/ft, or approximately 11 feet per mile Ground water was approximately 14 to 17 feet above the screened intervals in monitoring rvells MW-1, MW-2, ' MW-3 and MW-5, ground water was approximately 7 to 10 feet above the screen intervals at MW-4, MW-6, MW-7, MW-8 and MW-9 Therefore, the wells are "drowned", and may not yield samples fully representative of ground water conditions near the top of the saturated zone, where fuel ' hydrocarbons would be expected to have the greatest impact r Advanced GeoEnviron mental,Inc 1 j