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17 July 2002 AGE-NC Project No. 97-0327 Page 9 of 10 ' TPH-d, TPH-g and low BTEX concentrations were detected in the 40 foot soil sample collected from boring P-10, detected in the 45 foot soil sample collected from boring P-11 and detected in the 45 foot and 55 foot soil samples collected at P-12. Petroleum hydrocarbons appear to have migrated laterally between 40 and 55 feet bsg. r • MTBE was detected in the 45-foot sample collected from boring P-11. ' Generally, the TPH-g/TPH-d/BTEX soil plume beneath the former UST area appears to extend vertically at least 55 feet bsg, at least 60 feet toward the southeast, at least 30 feet toward the northwest, at least 40 feet toward the southwest and at least 60 feet bsg toward ' the northeast. The approximate models are shown in cross sectional views A-A'and B-B'in Figures 6 and 7, respectively. ' The results of the microbial enumeration and physicochemical analysis indicated that hydrocarbon-degrading microorganisms were detected as high as 1.2 x 105 CFU per gram, or approximately 12 percent the total sample population. The laboratory indicated that the physicochemical conditions at the site were well within the range necessary to support microbial growth and bioremedial activity. • Based on the guide Haw 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 10-2 and 10' 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 permeability (hydraulic conductivity) at the site was between 3 x 10-5 cm/sec(P-11 at 35 feet bsg)and 6 x 10.6 cm/sec . (P-11 at 55 feet bsg); hydraulic conductivity is converted to intrinsic permeability utilizing the conversion factor of 1.02 x 10'5 cm/sec which yields intrinsic permeability values between 3.6 x 10`cm2 and 6.12 x 10-" cm2. The laboratory analysis indicated permeability conditions at the site should be marginal to ineffective for SVE and TAS technology. ' The implications from the March 2002 ground water monitoring event are as follows: • Ground water elevation increased approximately 2.25 feet between December 2001 and ' March 2002. • Ground water flow direction at the site was inferred to be toward the southwest at a gradient of 0.001 ft/ft or less. Due to the low gradient at the site, slight variations in ground water measurements'or changes of recharge/discharge of the local ground water'could greatly - modify ground water flow direction. i ' Advanced GeoEnvironmental,Inc. 1