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1 ' 24 October 2005 i AGE-NC Project No 95-0167 ' Page 9 of 10 4.0. SUMMARY AND CONCLUSIONS ' In general,brown d to dam silt clay,clayey silt,and clay was encountered from surface • g �dry p Y grade to approximately 15 feet bsg From 15 feet to approximately 33 feet bsg, sandy ' material was encountered, grain size increased with depth, and sub-rounded pebbles were present with diameters as large as %z inch From 33 feet to 41 feet bsg, clay, silty clay, and clayey silt were primarily encountered Alternating layers of silty and sandy material were ' Identified from approximately 41 feet bsg to the total depth of boring CPT-1 Based on the CPT results and comparison with soil descriptions from borings previously advanced on the ' site, AGE has developed a preliminary subsurface model of the site soil stratigraphy comprised of six Informal zones - a vadose (unsaturated) zone and five hydrologic units • On 24 September 2004, depths to ground water ranged ftom 16 13 feet to 16 94 feet below ' the tops of the well casings Ground water elevations at the site averaged approximately 5 15 feet below MSL, indicating an average elevation Increase of 1 55 feet since the last ' monitoring event In June 2004 • The shape of the water table at the time of the September 2004 monitoring event was in the form of a mound centered over monitoring well MW-2, with a trough Immediately to the ' west Ground water at the site was determined to be flowing radially outward from the mound under an average hydraulic gradient of approximately 0 012 ft/ft ' A total of seven soil samples were collected from pilot borings MW-7 and MW-8 and analyzed for the constituents listed in section 2 1 1 ,no petroleum hydrocarbon constituents were detected at or above laboratory reporting limits in the soil samples analyzed ' During the September 2004 ground water monitoring event,TPH-g was detected in ground water samples collected from monitoring wells MW-1 and MW-7 at concentrations of 23,000µg11 and 700 µg/l,respectively BTEX compounds were detected In the ground water ' samples collected from monitoring wells MW-1 and MW-7 at maximum concentrations in well MW-1 of 4,600 µg/l benzene, 4,800 µg11 toluene, 1,300 µg/l ethylbenzene, and 6,900 µg11 total xylenes MTBE was detected In sample MW-1 at a concentration of 37µg/l ' A total of three grab ground water samples were collected from soil boring CPT-1 (one sample each from HU1, HU3, and HU5) and submitted for laboratory analysis for the ' constituents listed in Section 2 1 1 No petroleum hydrocarbons were detected at or above laboratory reporting limits ' No petroleum hydrocarbon contamination was detected in any of the CPT grab ground water samples,though contamination was detected In ground water samples from monitoring well MW-1, approximately 18 feet southwest of CPT-1 This Indicates that ground water ' contamination is confined to soil in the upper section of HU1 • The lateral extent of petroleum hydrocarbon contamination Is defined to the west by well ' Advanced GeoEnvironmental,Inc