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IAppendix A AGE NC Project No 99-0570 Page 4 of 5 I Vadose Zone -This zone extends from surface grade to approximately 15 feet bsg,the depth to the water table The vadose zone is predominantly fine-grained material from surface grade to 15 feet bsg wI a coarse-grained sand t occurring between 20 feet and 25 feet bsg at CPT-2 The zone (FMa-ractenzed by low gore-pressures Hydrogeologic Unit 1 (HU 1) - At the top of the current saturated zone, HU 1 extends from 15 feet to approximately 60 feet bsg and is comprised of laterally continuous, alternating layers of poorly graded sand with silt and silty sand This unit has flow unit characteristics Hydrogeologic Unit 2 (HU2) - HU2 extends from 60 feet to approximately 90 feet bsg and Is comprised predominantly of stiff, fine-grained soil, with silty clay and a thin bed of poorly graded sand at 80 feet bsg Hydrogeologic Unit 3 (HU3) -HU3 extends from 90 feet bsg to total depth, this zone is composed I of interbedded stiff,fine-grained soil,silty poorly graded sand,silty clay,and silty sands from 90 feet bsg to approximately 110 feet bsg This unit has flow unit characteristics Hydrogeologic units were depicted in cross-sectional view 13-13' in the AGE-prepared Cone Penetrometer Testing Report- 4pn'1 zed `SPO.; Analytical data from a total of eight grab ground water samples from HU1, HU2, and 14U3 are as follows TPH-g and TPH-d were detected in grab water samples collected from CPT2-89 at concentrations of 120 µg/1 and 95µg/1,respectively These detections are likely due to silt within the water sample causing a false detection of TPH-d, TPH-g and TPH-d were detected in grab water samples collected from CPT2-110 at concentrations of 380 µg/l and 3804g/l, respectively These detections are likely due to a detection of general biological impact to the site,such as natural ethene from a septic system or silt within the water sample causing a false detection of TPH-d The BTEX compounds toluene and ethylbenzene were detected in ground water samples collected from CPT2-110 at concentrations of 13 µg/1 and 1 0 µg/1, respectively However, gas chromatography mass spectrophotometer analysis did not identify either of these compounds ISITE CONCEPTUAL MODEL The general release of hydrocarbons and fuel additives emanated from the eastern edge of the northern dispenser island,and the product piping j oining the two island northern most islands Once released into the subsurface,the shallow soil near the dispensers and a coarse grained,poorly to well sorted sand was impacted Once dissolved in the groundwater,the hydrocarbons only appear to have Advanced GeoEnvaronmeatal,Inc I