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Mr Lawrence H Beasley Project 22611-100 001 • July 18, 1997 Page 7 The total pounds of hydrocarbons currently remaining in soil from 17 to 41 feet bgs Hydrocarbons remaining=20 mg/kg x 1 x 10"6 kg/mg x 87 6 lbs/W x 132,93 5 ft' =223 lbs of hydrocarbon remaining from 17 to 41 feet bgs The total pounds of hydrocarbons currently remaining in soil from 42 to 51 feet bgs Hydrocarbons remaining= 595 mg/kg x 1 x 10"6 kg/mg x 85 7 lbs1W x 112158 ft' = 5,719 lbs of hydrocarbon remaining from 42 to 51 feet bgs The total mass of TPHG currently in soil is approximately 5,942 lbs (approximately 967 gallons) Groundwater Analytical results of groundwater samples collected during the nine sampling events over the past 2 years indicate that TPHG and BTEX were not present in samples collected from monitoring wells MW-2, MW-4, MW-6, and MW-7 Dissolved hydrocarbons have generally been detected in monitoring wells MW-3 and MW-5, and vapor extraction well VEW-1 TPHG and benzene concentrations in the wells have generally ranged from below laboratory detection limits to 12,000 parts per billion (ppb) and below laboratory detection limits to 210 ppb, respectively Based on the groundwater sampling event performed during March 1997, TPHG was detected in well VEW-1 and MW-5 at concentrations of 11,000 ppb and 72 ppb, respectively, but was below laboratory detection limits in well MW-4 Benzene was detected in well VEW-1 and MW-4 at a concentrations of 180 ppb and 0 83 ppb, respectively, but was below laboratory detection limits in well MW-5 However, based on the location of well MW-4 (crossgradient approximately 315 feet from the former UST) and historical analytical data, it is EMCON's opinion that the analytical results for well MW-4 during the March 1997 sampling event are suspect and may be due to laboratory error Because VEW-1 is used as an extraction well, dissolved hydrocarbon concentrations observed in the groundwater sample collected from well VEW-1, may not represent actual groundwater condition beneath the former UST It is EMCON's opinion that the groundwater samples may have been compromised due to the condensation of hydrocarbons along the casing during SVE Results of analyses are presented in Appendix A In general, in those wells in which dissolved hydrocarbons have been detected, concentrations have declined since groundwater monitoring was initiated in December SACIK\2611CLOS URE-95klms 1