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F _ I14 ,September 2004 . AGE-NC Project No 96-0235 ' Page 5 of 8, _ u Hydrogeologic Unit 2(HU2) extends from a minimum depth of 31 feet bsg to a maximum depth of ' 72 feet bsg and is composed dominantly of stiff, fine-grained soils including silt' and clay, interbedded with laterally discontinuous fine sand intervals HU2 is characterized by generally- moderate � _ f ' moderate to high pore pressures Hydrogeologic Unit 3 (HU3) extends from a minimum depth of 62 feet bsg to a maximum depth of ' ' 90 feet bsg, HU3 is composed primarily of laterally continuous silty sand, sand and gravelly sand interbedded with stiff, fine-grained soil, clayey silt, silt and clay HU3 is characterized by generally low pore pressures, and may be classified as a flow unit F ' Hydrogeologic Unit 4(HU4)extends from a minimum depth of 83 feet bsg to a maximum depth of 170 feet bsg, HU4 is composed primarily of fine-grained soils ,including clayey silt' and silt interbedded with laterally discontinuous silty sand,sand and gravelly sand Minor sandy silt and clay intervals were observed at various depths HU4 is characterized by generally moderate to high pore , ' pressures, Hydrogeologic Unit 5 (HU5) extends from a minimum depth of 166 feet bsg to approximately 191 feet bsg, HU5 is composed primarily of coarse-grained soils including sand and gravelly sand interbedded with minor silt and clayey silt and silt HU5 is characterized by generally low pore pressures, and may be classified as a flow unit HU5 was observed in borings CPT-03 and CPT-04 1 and appears to be laterally continuous beneath the site Hydrogeologic Unit 6 (HU6) was encountered inr CPT-03 from approximately 191 feet bsg to approximately 210 feet bsg The lateral extent of HU6 is not well defined at the site, CPT-01, CPT-02,and CPT-04 were terminated prior to encountering HU6 HU6 is composed primarily of fine-grained soils including clayey silt and silt HU6 is characterized by generally moderate�to high ' pore pressures The model presented is interpretational and will be modified as more data is collected Depths are ' approximate and can vary by`several feet across the site Hydrogeologic units are depicted in cross , sectional views A-A' through D-D' (Figures 5 through 12) 3 3 ANALYTICAL RESULTS OF GROUND WATER SAMPLES Various concentrations of target analytes were detected in each grab ground water sample collected from each sampling interval in soil borings advanced near the former UST No 3 location(CPT-01 through CPT-03,Figures 2 and 3) Analytes of concern were not detected above laboratory reporting limits in grab ground water samples collected from soil borings advanced near the former UST cluster area (CPT-04 and CHB-01, Figures 2 and 4) Advanced GeoEnvironmental,Inc