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r 22 July 2002 AGE-NC Project No 96-0235 = ' Page 3 of 5 ' 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 casing elevations (Table 1) Depths to ground water ranged from 16 35 feet to 19 OS feet below the tops of the well casings, ground water was within the screened intervals of the shallow-screened wells,but was approximately 12 feet above the screened interval of interrn diate- ' screened wells MW-3 and EW-2 and between 20 95 and 23 36 feet above the screened intervals of the deep-screened wells ' Ground water elevations at the site ranged,from 10 22 feet (MW-7) to 12 60 feet (MW-2) below mean sea level The average ground water elevation in the wells decreased by approximately 0 2 feet ' Figure 3 illustrates the ground water potentiometnc surface based on the shallow-and deep-screened data sets Near the former UST cluster, the shallow- and deep-screened data delineated a dominant ground water flow direction toward the east, ranging from northeast to southeast Near the former ' UST No 3 excavation ground water flow direction at the shallow-screened level was inferred to be radially outward between west and northeast,ground water flow direction at the deep-screened level was inferred to be radially between south and southwest The inferred ground water gradient in the ' shallow zone was 0 002 ft/ft near the former UST cluster and 0 014 ft/ft near the former UST No 3 location, the inferred ground water gradient in the deep zone was 0 002 ft/fl near the former UST ' cluster and 0 012 ft/ft near the former UST No 3 32 ANALYTICAL RESULTS OF WATER SAMPLES TPH-g was detected in the samples collected from MW-1, MW'2, MW-10, EW-1 and EW-2 at ' concentrations as high as 31,000 micrograms per liter (µg/1) in the sample collected from EW-1 TPH-d was detected in samples collected from MW-1, MW-2, MW-9, MW-10, MW-11B, EW-1 and EW-2 at concentrations'as high as 13,000 µg/l (MW-10) ' BTEX compounds were detected in samples MW-1,MW-2,MW-10,EW-1 and EW-2 at maximum - concentrations of-1;200Jµg/1-benzene, 3;900'µg/1 toluene;-1;800-µg/1-ethylbenzene and 7,200-µg/1 ' xylenes, in the sample from EW-1 MTBE was detected by EPA Method 8260B,in the water samples collected from MW-9, MW-10, MW-11B, MW-12B, MW-13A, MW-13B and EW-1 at concentrations ranging from 21 µg/1 (MW-13A)to 420µg/1(EW-1) TBA was detected in the water samples collected from MW-6B and ' MW-11B at a concentrations of 19 µg/1 and 8 3 µg/1, respectively Water samples analyzed from MW-2, MW-5, MW-6A, MW-6B, MW-7, MW-1113, MW-1213, MW-1313, EW-1 and EW-2 • contained detectable concentrations of 1,2-DCA ranging from 096 µg/1 (MW-7) to 20 µg/1 ' Advanced GeoEnviron mental,Inc I