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04 October 2005 <br /> AGE-NC Project No 98-0432 <br /> Page 4 of 6 <br /> performance of a ground water pumping test Soil boring EW-1 was advanced vertically to a depth <br /> of 3 0 feet bsg Boring EW-1 was single-completed as a 6-inch diameter ground water extraction well <br /> with screen Intervals between 15 feet and 30 feet bsg Soil and ground water samples were not <br /> collected during this Investigation <br /> On 01 November 2002, ground water monitoring wells MW-7 and MW-8, screened from 10 feet to <br /> 30 feet bsg, were Installed off-site to further assess the lateral extent of MTBE-impacted ground <br /> water Soil samples were not collected during the well Installations <br /> 3.0. SOIL PROFILE <br /> Based on soil data collected from soil borings B1 through B9,MW-1 through MW-4, and the UST <br /> excavations, the subsurface soil consists of silty sand from surface grade to approximately 30 feet <br /> bsg to the west and east of the former diesel UST, while silty sand and Inter-bedded silty clay were <br /> encountered south and north of the former diesel UST from approximately 15 feet to 30 feet bsg A <br /> clay to clayey silt layer was encountered at the base of the former diesel UST area at depths of 20 feet <br /> to 25 feet bsg A sand layer was encountered south of the UST at a depth of 20 feet bsg and under <br /> the UST at a depth of 25 feet bsg <br /> 4.0. PETROLEUM HYDROCARBON DISTRIBUTION IN SOIL <br /> The majority of petroleum hydrocarbon-impacted soil appeared to be limited to the area near the <br /> former UST, designated T1 (Figure 2) The highest petroleum hydrocarbon concentrations in soil, <br /> namely TPH-d,were detected in sam les T1NW and TISE, collected in September 1998 (Table 2) <br /> Au la m°�dyc�.dt e Z.58 "`�11�- <br /> Based on lot'concentrations of TPH-d in soil samps collected during the UST removal and <br /> over-excavation and the concentrations of MTBE detected in soil samples collected from the water <br /> bearing zone, AGE believes soil contamination is minimal due to the affinity of MTBE to dissolve <br /> and migrate in ground water and due to the lack of adsorbed contamination above the current and <br /> past water table depths <br /> 5.0. PETROLEUM HYDROCARBON IMPACT TO GROUNDWATER <br /> Historu,ally,petroleum hydruc irbon-Imp wtud ground watut has been duteued wnblstently only in <br /> monitoring wells MW-1 and MW-2 Wells MW-3 through MW-5 ancV%-8 have had only <br /> occasional detections of petroleum hydrocarbons through April 2005,petroleum hydrocarbons have mT6 <br /> not been detected in well MW-6 Monitoring well MW-7 has remained uncontaminated, with the V <br /> exception of a detection of MTBE during the initial ground water sampling in December 2002 after qq <br /> Advanced GeoEnvironmental,Inc �,p <br /> 10 <br />