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Parsons Engineering Science, Inc ' i Aromatic Hydrocarbons BTEX compounds were not detected in any of the groundwater samples (Figure 4 and Table 3) ' ASSESSMENT OF CONTAMINATION Introduction This section provides an assessment of the type, magnitude and extent of soil and groundwater contamination associated with the former UFST and associated piping Both historical data and data recently collected are used in this assessment Geolo ical and H dro eolo :cal Assessment A cross-section location map is presented as Figure 5 Strati&we—recompll o s are presented as Figures b and 7 The continuity between data pon the laterally discontinuous nature of the sediments These cross-sectsd using borehole data from several sources, including ES (1991, 1993ecently performed and described in this report Examination of the geologic cross-sections (Figures 6 and 7) indicate that the subsurface environment is heterogeneous and anisotropic The predominant materials encountered were silts and clays with minor lenses/layers of silty/clayey sands Between 1 and 15 feet bgs a ' deposit of fill material, consisting of brown sand, was encountered The thickest sequences of fill material were encountered in the vicinity of the former UFST excavation pit Below this fill layer is the sequence of silts and clays with interbedded sands (ranging from I to 10 feet in thickness) This sequence extends at least to a depth of 52 feet bgs Onsite water level measurements indicate that the depth to groundwater has ranged from approximately 28 to 45 feet bas (Appendix G) Previous water level measurements in wells MW-1, 2, and 3 have indicated that the horizontal groundwater flow direction onsite is south- southwest The September 1996 measurements, which include a measurement from monitoring well MW-4, indicate that the horizontal flow direction is west-southwest Soil Contamination Assessment The type of contaminants detected in soil samples include TPH-D and BTEX TPH-G was not detected in the six subsurface soil samples that were analyzed for TPH-G A total of 90 subsurface soil samples have been collected on and near the site since September 1991 (Appendix H) TPH-D was not detected in 48 of these samples Concentrations in the other samples ranged from 1 0 mg/kg (Samples SBI-15, SBI-35, and SB3-10) to 15,000 mg/kg (Sample SB7-15) in the remaining 42, however, only five samples PARESSYROE VOL]R 1WP1727607 80969127607803 WW6 8