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I ' 21 June 2002 AGE-NC Project No 99-0624 ' Page 4of6 Vadose Zone-Extending from surface grade to 55 feet bsg(estimated depth to the water table) The ' uppermost 7 feet is silt, underlain by predominantly coarse-grained sediment (sand, cemented sand and gravel)from 7 feet to 20 feet bsg Below 20 feet bsg are alternating layers of generally thick, stiff ' fine-grained sediments(up to 10 feet thick)and thin(less than 4 feet thick)sand,cemented sand,silt and clay The pore pressure in this zone is uniformly low except for thin,high pore pressure Intervals encountered at cemented sand or at a few clayey silt or stiff fine-grained layers ' Hydrologic Unit 1 (HU1), at the top of the current saturated zone, extends from approximately 55 feet to 63 feet bsg and is comprised primarily of stiff fine-grained sediments(up to 5 feet thick) and ' thin (less than 4 feet thick) sand, cemented sand, silt and clay The pore pressure is low except for low to moderate pressures encountered at cemented sand or stiff fine-grained layers ' Hydrologic Unit 2 (HU2) extends from approximately 63 feet to 68 feet bsg and is predominantly stiff, fine-grained sediment This unit exhibits gradually increasing pore pressure with increasing depth Local zones of low pore pressure appeared to be due to the presence of interbedded sand and ' silt Hydrologic Units 3, 5 and 7 (HU3, HUS, HU7) extend from approximately 68 feet to 75 feet bsg, ' 78 feet to 90 feet bsg,and below 95 feet bsg,respectively,are predominantly composed of sand, silt, clay,and stiff fine-grained sediments These zones are characterized by generally low pore pressure, except for high-pressure peaks associated with cemented sands or less permeable stiff fine-grained ' sediments ' Hydrologic Units 4, and 6(HU4,HU6)extend from approximately 75 feet to 78 feet bsg and 90 feet to approximately 95 feet bsg, and consist primarily of stiff fine-grained sediment, thin layers of clayey silt, silt, and cemented sand are intercalated with the stiff fine-gained layers in HU4 These ' zones are characterized by moderately high to high pore pressures ' 3 3 LABORATORY RESULTS OF GRAB GROUND WATER SAMPLES A total of twelve grab ground water samples were collected from CPT-1 through CPT-4 and ' submitted for laboratory analysis for the constituents listed in Section 2 2 The laboratory analysis did not detect TPH-g in any of the samples (Table 1), of the BTEX compounds, only benzene was detected in sample CPT-3-68 at a concentration of 1 3 micrograms per liter (jig/1) ' MTBE was detected from CPT-1 at depths of 60 feet and 76 feet bsg at concentrations of 88 µg/l and 16 gg/l,respectively, from CPT-2 at depths of 76 feet, 80 feet and 100 feet at concentrations as high 1 ' Advanced GeoEnvironmental,Inc I