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' 02 September 2003 AGE-NC Project No. 98-046$ ' Page 9 of 11 ' Vadose Zone - Extending from surface grade to approximately 10 feet bsg, the depth to the water table.The vadose zone is predominantly fine grained material from surface grade to 10 feet bsg,with a sand unit occurring at 10 feet bsg. The zone is characterized by relatively low pore pressures. Hydrological Unit 1 (HU 1),above the current saturated zone,extends from 10 feet to approximately 15 feet bsg and is comprised predominantly of silt and with clay at the lower boundary. This interval ' is characterized by generally low pore pressures above 50 feet and medium pressure below 50 feet bsg. ' Hydrological Unit 2 (HU2) extends from 15 feet to approximately 30 feet bsg and is composed dominantly of stiff, fine-grained soil, as defined by the CPT calculation with clayey silt, silt to clay at the northern edge of the site and is in contact with unit HU3 below. HU2 is characterized by ' varying pore pressures ranging between moderate and high, particularly higher in,sand. Hydrological Unit 3 (HU3)extends from 30 feet bsg to 55 feet bsg.HU3 is composed of silt and two ' laterally seperated and discontinuous sand units. HU3 is characterized by generally low pore pressures, and may be classified as a flow unit. Hydrological.Unit 4 (HU4) extends from 55 feet to approximately 65 feet bsg and is composed of silty sand, sand, to a gravelly sand. HU7 is characterized by generally low pore pressures;and may ' be classified as a significant flow unit. i Hydrological Unit 5 (HU5) extends from 65 feet to 75 feet bsg total depth; HU5 is composed of a ' continuous silt and clay unit in contact with lower unit HU6_ HU5 is characterized by generally low -pore pressures. ' Hydrological Unit 6 (HU6) extends from 75 feet to approximately 90 feet bsg and is composed of silty sand, sand, to a gravelly sand. HU7 is characterized by generally low pore pressures, and may be classified as a significant flow unit. Hydrological Unit 7 (HU7) extends from .90 feet bsg to 105 or 125 feet bsg at CPT1. HU7 is composed of silt and few discontinuous clay lenses. HU7 is characterized by generally low pore ' pressures. Hydrological units are depicted in cross sectional view A-A' (Figures 3). 5.3. LABORATORY RESULTS OF GRAB GROUND WATER SAMPLES • The five grab ground water samples were'collected from CPT1 and CPT2 were submitted for laboratory analysis for the constituents listed in Section 2.2. TPH-g, BTEX and fuel additives were Advanced GcoEnvironmental,Inc.