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19 February 1997 AGE-NC Project No. 95-0185 ' Page 2 of 4 placed in a chilled container and transported under chain-of-custody to McCampbell Analytical Inc. ' (MAI) in Pacheco, California. Each sample was analyzed for total petroleum hydrocarbons quantified as gasoline and diesel (TPH-g and TPH-d), and for volatile aromatic compounds (benzene, toluene, ethylbenzene and total xylene: BTE&X) in accordance with EPA methods 5030/8015m and 602, respectively. i' 3.0. FINDINGS ' 3.1. GROUNDWATER 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 21.14 to 21.82 feet below surface grade (bsg). Ground water at the site has a very low gradient. At such a low gradient, normal measurement error M can equal or even surpass the differences between wells, and can greatly influence the inferred ground water flow direction determination. The ground water flow direction is generally toward the east, at a hydraulic gradient of 0.0002 ft/ft. The relative ground water elevations at the site are ' contoured on Figure 3 - Relative Ground Water- Elevation. Traces of free product were noted following purging of MW-1, which may effect the ground water elevation very slightly near the former USTs location. ' The regional ground water flow direction is generally southwest and the maPPed flow direction on the site is a 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 very low gradient. ' 3.2. LABORATORYRESULTS OF GROUND WATER SAMPLES TPH-d was detected in ground water samples collected on 05 December 1996, from monitoring ' wells MW-1, MW-3 and MW-4 at concentrations of 26,000 parts per billion (ppb, reported as micrograms per liter: ,ug/l: ppb), 180 ppb and 44,000 ppb, respectively. TPH-g was detected in ' ground water samples from MWA and MW-4 at concentrations of 400 ppb ,and 300 ppb, respectively: BTE&X compounds were detected in sainples collected from MW-1' and MW-4 at concentrations as high as 20 ppb (xylenes, MW- 1). Benzene was detected in the water sample from MW-4, near the former UST area, at 3.8 ppb. Traces of free product were noted during purging of MW-1. The laboratory report noted an immiscible sheen in the samples collected from MWA and MW-4. Analytical results of monitoring well ground water samples are summarized in Table 2 -