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C) Site Background Information: Vanco Truck&Auto Plaza Page 4 of 6 The model presented is interpretational and will be modified as more data is collected. The eight vertical zones are identified as follows(depths are apprc ximate and can vary by several feet across the site): Vadose/First Water Zone-This zone extends fromsurface grade to approximately 20 feet bsg.Static water is at 20 feet bsg in the monitoring wells, howe er, the first saturated soil samples were collected at 30 feet bsg.This indicates that the water table is confined by the overlying fine-grained materials.This zone is characterized by moderate pore pressures. Hydrogeologic Unit 1 (HU1) - Extending from 20 f t to approximately 30 feet bsg, HU1 is comprised predominantly of sandy silt,clayey silt,and silt.Dominant hydraulic conductivities,based on CPT soil behavior types(SBTs),range between 1 x I O and 1 x 1 V centimeters per second(cm/s) for silty to clayey type soils. This interval is characterized by generally moderate pore pressures. Hydrogeologic Unit 2(HU2)-At the top of the current saturated zone, HU2 extends from 30 feet to approximately 38 feet bsg and is composed of ilty sand to sand type soils. Hydraulic conductivities for HU2 typically vary between 1 x 10' and I x 10' cm/s. HU2 is characterized by generally lower pore pressures and is classified as a flow unit. Hydrogeologic Unit 3 (HU3) - HU3 extends from 38 feet to approximately 45 feet bsg and is composed primarily of stiff, fine-grained soils, clay y silts, silts, and silty clays. Hydraulic conductivities for these soil types generally range between I x 10-4 and 1 x 10-1 cm/s for clays, silts, and stiff, fine-grained soils. HU3 is characterized by varying pore pressures ranging between moderate and high and is identified as a confuting layer Hydrogeologic Unit 4(HU4) - HU4 extends from 45 feet bsg to approximately 50 feet bsg and is composed of silty sand to sand type soils.Hydraulic Gond ctivities for HU4 generally range between 1 x 10-2 and 1 x I V cm/s.HU4 is characterized by generally lower pore pressures and is classified as a flow unit. HydrogeoIogic Unit 5 (HU5) - Extending from 50 feet to approximately 70 feet bsg, HU5 is composed predominantly of stiff,fine-grained clayey silts,silty clays,and clay.A thin silty sand to sand type soil is encountered at approximately 58 to 2 feet bsg and has characteristically low hydraulic conductivity.Hydraulic conductivity generally ranges between 1 x 10'5 and 1 x 10-`S cm/s for clays,silts,and stiff,fine-grained soils.HU5 is characterized by varying pore pressures varying from moderate to very high, and is identified as a confining layer. Hydrogeologic Unit 6(HU6)-HU6 extends from 70 feet to 82 feet bsg and is composed of silty sand to sand type soils.Hydraulic conductivities for HU6 get erally range between 1 x 10'and 5.0 cm/s. HU6 is characterized by very low pore pressures, and is classified as a flow unit. Advanced GeoEnvironmental,Inc.