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' 10 February 2006 AGE-NC Project No 02-0977 Page 10 of 12 bsg and B5 at 55 feet bsg (Figure 11) • Based on the guide How to Evaluate Alternative Cleanup Technologies For UST Sites (October 1994) published by the United States Environmental Protection Agency (EPA) ' Office of USTs,intrinsic permeability values between the magnitude of 10 z cm2 and 10-1 cm2 are generally adequate for soil vapor extraction (SVE) technology (Exhibit IT& Intrinsic Permeability And SVE Effectiveness) with respect to gasoline-impacted sites Based on information gained through laboratory analysis,the average vadose zone permeability at the site was between 2 x 10-4 cm/s (B7 at 35 feet bsg) and 2 x 10' cm/s (B6 at 40 feet bsg) The laboratory analysis indicated permeability conditions at the site should be effective for SVE technology ' The implications from the findings of the December 2005 ground water monitoring event are • Ground water flow direction at the site was inferred to be towards the south-southeast at an approximate gradient of 0 002 ft/ft This appears to be the prevailing flow direction for the area(Figure 9) • • The depth to ground water at the site was between 53 81 feet and 54 94 feet TOC, the calculated ground water elevations was ranged between 15 51 feet and 15 76 feet below MSL • Due to the low hydraulic gradient at the site, slight variations in ground water measurements or changes of recharge/discharge of the local ground water could modify the inferred ground water flow direction • The ground water elevation at the site was within the screened intervals of wells MW-1 through MW-6 and MW-8,which should yield samples fully representative of shallow ground water conditions,however,the ground water elevation determined from MW-7 (screened 80 Ito 90 feet bsg) was approximately 26 feet submerged, and more representative of deeper' ground water conditions • The fuel additive MTBE was detected in samples from wells MW-2, MW-3and MW-5 at a maximum concentration of 80,000 µg/l (MW-2) The general trend of increasing dissolved MTBE concentrations at well MW-2 indicates a migration from the soil into the shallow ' ground water table near well MW-2 • Between July and December 2005,MTBE concentrations decreased from 950 µg/l to 63 µg/1 at MW-1,conversely,MTBE concentrations increased from 42µg/1 to 220µg/1 at MW-5 The above referenced increases and decreases implies a south-southeast shift in the dissolved MTBE plume • The fuel additive TAME was detected in samples from wells MW-2 and MW-3 at a maximum concentration of 18 µg11 (MW-2) Advanced GeoEnvironmental,inc I