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15 March 2002 <br /> AGE-NC Project No 97-0249 <br />' Page 4 of 10 <br /> • Hydrologic Unit 5 (HUS) - Located between 110 and 135 feet bsg Generally characterized <br /> by low pore pressures between 110 feet and 125 feet bsg and comprised primarily by semi- <br /> permeable, stiff fine grained, silt,silty sand and localized gravelly sand The interval between <br /> 125 feet and 135 feet bsg is generally characterized by variable medium to high pore <br /> pressures and comprised primarily by less permeable, stiff fine grained silt and clay <br /> • Hydrologic Unit 6 (HU6) - Located between 135 feet and 150 feet bsg and generally <br /> characterized by low pore pressures and comprised primarily by permeable silty sand, <br /> gravelly sand and fine to medium sand <br /> 24 PORE PRESSURE DISSIPATION TESTING <br /> Pore pressure dissipation tests were conducted at various hydrologic intervals to measure hydrostatic <br /> water pressures and approximate depth to ground water The approximate depth to ground water was <br /> calculated using the equation (Appendix B) Dw= Drone - Hwater <br /> where D,,,=Depth to Ground Water(ft) <br /> Done =Depth of CPT Tip <br /> Hwafer= Hydrostatic Water Head (1 psi = 2 31 ft) <br /> Pore pressure dissipation testing was conducted in the following informal hydrologic units <br /> • HU2 (42 feet bsg) - Pore pressure appeared to stabilize at approximately 9 5 psi after 205 <br /> seconds at P-14, depth to ground water was calculated at 20 01 feet bsg <br /> • HU2 (42 3 feet bsg) -Pore pressure appeared to stabilize at approximately 12 9 psi after 265 <br />' seconds at P-18, depth to ground water was calculated at 12 5 feet bsg <br /> • HU3 (64 5 feet bsg) - Pore pressure did not appear to stabilize at P-13 after 290 seconds, <br /> however the greatest pore pressure was recorded at approximately 17 psi, depth to ground <br /> water was calculated at 25 23 feet <br /> I • HU4 (95 feet bsg) - Pore pressure appeared to stabilize at approximately 32 psi after 190 <br /> seconds at P-13, depth to ground water was calculated at 2108 feet bsg <br /> • HU4 (97 1 feet bsg) - Pore pressure appeared to stabilize at approximately 30 psi after 35 <br /> seconds at P-14, depth to ground water was calculated at 27 8 feet <br /> Advanced GeoEnviran mental,Inc <br />