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.. . ... .. .. . . .. . ... 06 February 2001 AGE-NC Project No. 95-0118 Page 2 of 7 On 30 and 31 July 1998, six remediation wells were installed on the site. Two soil vapor extraction wells and four in-situ air sparging wells were established.in preparation for corrective action. During July through September 1999, the remediation piping network and remediation equipment were installed and start-up procedures were conducted. • On 23 August 1999, initiation of an IAS ground water remediation program, in combination with SVE remediation began. An internal combustion-catalytic converted (IC) soil-vapor extraction SVE unit,with a capacity of removing 100 cubic feet per minute (cfm), operated at the site until 14 September 2000. The IC unit was replaced with an active vacuum blower, discharging the hydrocarbon emissions without treatment at approximately 20 cftn. The soil- vapor concentration of hydrocarbon had declined to concentrations that would not require a destruction process for the recovered vapor stream according to the permit to operate the SVE. • During the 18 months of soil vapor extraction, an estimated 134 gallons of petroleum as gasoline have been extracted. - On 13 October 2000, two soil probe borings were advanced at the site to a depth of 35 feet bsg. The probe borings were advanced in the areas of the former fuel dispenser island(B 1) and the former UST excavation (VW-1). Probe boring locations are shown on Figure 2. -� Probe borings CB 1 and CB2 were advanced at the locations of soil boring B 1 near the former ' dispenser island and near the area of vapor extraction well VW-1,respectively, to allow for hydrocarbon concentration comparisons. Soil samples were collected from the soil borings for analysis to confirm hydrocarbon mass removal. The soil samples had detectable concentrations of TPH-g and various BTEX compounds. TPH-g was detected at concentrations as high as 93 milligram per kilogram (mg/kg). Benzene was not detected in the soil samples collected and analyzed. Other BTEX compounds were detected at concentrations as high as 0.52 mg/kg of xylene. Analytical i results of all soil samples are presented in Table 1. - 1 The confirmation soil samples had reduced concentrations of TPH-g and overall BTEX compounds. Benzene was not detected in the samples collected near former sampling points of benzene detection. The reduction of benzene concentrations at depths of 15 feet to 35 feet is nearly 100%. The estimated reduction of TPH-g mass at a depth of 15 feet to 35 feet bsg is approximately 95 %to 100% (Appendix A). The mass of remaining TPH-g is estimate_ d at 5.1 kg as demonstratedin the mass removal comparison (Appendix B). Advanced GeoEnvironmentel,Inc. J:!