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and 130 feet bsg and between 140 and approximately 160 feet bsg The sands appeared to be continuous throughout the site,with the exception of the uppermost sand layer,which may be limited laterally to the northernmost portion of the site Measured hydraulic conductivities in the sand- bearing intervals, based on CPT dissipation tests, were typical for sand mixtures HYDROGEOLOGICAL MODEL Based on the CPT results, AGE has developed a preliminary subsurface model of the site sediment stratigraphy comprised of nine informal zones,a vadose(unsaturated) zone and approximately nine hydrogeologic units Hydrogeologic or hydrostratigraphic units (HUs) are defined as a body of sediment that has hydrogeologic characteristics that make it distinct from surrounding bodies of sediment or a part of a body of rock that forms a distinct hydrologic unit with respect to the flow of ground water A `flow unit' may be defined as a hydrogeologic unit and is characterized by significantly greater hydraulic conductivity values than overlying and underlying units, a flow unit is capable of serving as a preferred migration route, and could potentially allow migration of large contaminant masses over great distances The model presented is interpretational and will be modified as more data is collected The nine vertical zones identified are as follows (depths are approximate and can vary by several feet across the site) Vadose Zone - Extending from surface grade to approximately 35 feet bsg, the depth to the water table The vadose zone is predominantly fine grained material from surface grade to 25 feet bsg,with a sand unit occurring between 25 feet bsg at CPTI on-site Pore pressures in this unsaturated zone is characteristically low or at zero Hydiologic Units 1a 2, 4, 6 and 8 (HrJla, HU2, ITU4, HU6 and HU8) are sand-bearing units characterized by low CPT pore pressures (Appendix B) HU 1 a,HU2 and HU9 are dominantly sand unAs, HU4 and HU6 are composed of inter-bedded layers of sand and sandy silt Hydraulic conductivities,based on CPT soil behavior types(SBT) should range between 1 X10 6 to 1 meters per second(m/s) for sandy silt to gravelly sand, measured hydraulic conductivities,based on CPT pore pressure dissipation tests, weie between I X 10 to 1 x 10-8 m/s Hydrologic Units 1, 3, 5, 7 and 9 (HUI, HU3, HU5, HU7 and HU9) are fine-grained intervals composed of clay, silty clay, clayey silt, silt, and stiff, fine grained soil These intervals are characterized by low to moderately low pore pressure in the clay and silt, generally moderate pressures for the clayey silt to silty clay, and variable pore pressure, from moderately low to high, in the stiff, fine-grained soil Hydraulic conductivities based on SBT should range between 1 x 10-1° to 1 X 10-7 rn/9 for clay to silt, and between 1 x 10 9 to 1 X 10 7 M/s for stiff, fine-grained soil ANALYTICAL RESULTS A total of seventeen `grab' ground water samples and two soil samples were collected from on- and off-site and submitted for laboratory analysis The concentrations of TPH-g, TPH-d and benzene were non-detect in the soil sample collected from CPT1 at 55 feet bsg, however, ethylbenzene and xylene and were detected at maximum concentrations of 0 025 mg/kg Advanced GeoEnvironmental