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22 November 1996 AGE-NC Project No. 95-0185 Page 2 of 4 1 samples were placed in a chilled container and transported under chain-of-custody to MAI. Each sample was analyzed for total petroleum hydrocarbons quantified as diesel (TPH-d),three of the four samples were analyzed for total petroleum hydrocarbons quantified as gasoline (TPH-g) and each ' sample was analyzed for volatile aromatic compounds (benzene, toluene, ethylbenzene and total xylene: BTE&X), with methyl-tert-butyl ether (MTBE) in accordance with EPA methods 5030/8015m, 5030/8015m, 602 and 602, respectively. j1 3.0. FINDINGS ' 3.1. GROUND WATER GRADIENT AND FLOW DIRECTION The relative elevation of ground water in each well was calculated by subtracting the ground water depth from the surveyed casing elevation (Table 1). Monitoring well casing elevations were surveyed relative to a MW-4,which was assigned an arbitrary elevation of 60 feet above sea level. Depth to ground water at the site ranged from 21.28 to 21.96 feet below surface grade (bsg). The relative ground water elevations at the site are contoured on Figure 3 - Relative Ground Water Elevation. Ground water at the site has a very low gradient. At such a low gradient, normal measurement error can greatly influence the inferred ground water flow direction determination. The ground water profile is slightly depressed in the vicinity of the former UST area due to the presence ; of the free product below the former USTs. The ground water flow direction is generally toward the northwest, at a hydraulic gradient of 0.0002 ft/ft. ' The regional ground water flow direction is generally southwest and the observed gradient is a g Y variation from the regional trend. This variation may be due in part to seasonal changes in the local ' ground water flow patterns and to the low gradient. ' 3.2. LABORATORY RESULTS OF GROUND WATER SAMPLES TPH-d was detected in ground water samples collected on 24 September 1996, from monitoring wells MW-1, MW-3 and MW-4 at concentrations of 15,000 parts per billion (ppb, reported as micrograms per liter) , 400 ppb and 140,000 ppb, respectively. TPH-g was detected in ground water samples from MW-I at a concentration of 730 ppb. BTE&X compounds were detected in samples collected from MW-1 and MW-4 at concentrations as high as 50 ppb (xylenes, MW- 1). Benzene was detected in the water sample from MW-4,near the former UST area, at 10 ppb. MTBE was not detected in any of the water samples collected during this quarter. Analytical results of monitoring well ground water samples are summarized in Table 2 - Analytical Results of Ground Water Samples. The laboratory report (MAI Laboratory I.D. Nos. 69445 to 69448), and chain-of-custody