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Prior to operation of the SVE system, the highest concentration of petroleum hydrocarbons in soil samples was detected in a sample collected in the directional soil boring SBI at 35 1 feet bgs beneath former UST B, which contained 63 mg/kg benzene and 16,000 mg/kg TPH-g Four of the six tank removal confirmation soil samples collected at 16 feet bgs contained TPH-g at concentrations ranging from 3,400 to 5,300 mg/kg, and benzene at concentrations ranging from 0 027 to 11 mg/kg TPH-g and benzene were not detected in any of the soil samples collected during the installation of monitoring wells MWI-MW7 A comparison of concentrations of benzene and TPH-g in samples collected in approximately the same location before and after operation of the SVE system is presented in Table 5 These analytical results are also presented on hydrogeologic cross-sections in Figures 4a, 4b, and 5 to demonstrate the close proximity of sample locations As presented in Table 5, concentrations were significantly decreased by remediation in each instance with the exception of the comparison of TPH-g concentrations in sample SB1-40 5 (16,000 mg/kg TPH-g, 63 mg/kg benzene) collected daring the directional drilling of SBI at 35 1 feet bgs, and confirmation soil sample SB5-36 (14,300 mg/kg TPH-g, 3 81 mg/kg benzene) ' Confirmation soil sample SB5-36 was saturated prior to collection, as the average depth to groundwater across the site on 30 July 1999 was 26 feet As presented in Figure 4a, the numerous soil samples collected for analysis from the confirmation sod bonngs, as well as ' samples collected before remedial efforts, allows this detection of 14,300 mg/kg TPH-g in sample SB5-36 to be defined as limited in extent Soil samples collected from above and below sample SB5-36 (SB5-31 and SB-48) as well as to the east (SB4-31) and west (SB6-26 and SB6-36) of SB5-36, did not contain detectable concentrations of TPH-g, benzene, or MTBE, with the exception of 0 501 mg/kg TPH-g detected in sample SB6-36 Additionally, the lateral extent of hydrocarbons detected in sample SB1-40 5 (35 1 feet bgs) is shown to have been limited prior to remedial efforts by samples SB1-36 (31 2 feet bgs), which contained 0 800 mg/kg TPH-g and 0 110 mg/kg benzene, and sample SB 1-46 ' (39 8 feet bgs), which did not contain detectable concentrations of TPH-g or benzene 4.2 SITE CHARACTERIZATION COMPLETION The hydrogeologic characterization of the site and lateral extent of the residual hydrocarbons is complete for both the soil and water medium This assessment includes both onsite and offsite ' data 4,2,1 Soil Characterization ' Prior to operation of the SVE system, the lateral extent of petroleum hydrocarbons in soil was defined by soil samples collected during installation of onsite wells MW1 to MW5 The soil samples from these borings did not contain detectable concentrations of benzene or TPH-g The SVE system successfully removed a significant amount of the volatile portion of the petroleum hydrocarbons in the soil in the immediate area of the former USTs This is demonstrated by the analytical results from the five confirnnation borings TPH-g and BTEX were detected in only three samples (SB5-36, SB7-16, and SB6-36) Oxygenates, EDB, and 1,2-DCA were not h VPwije,(31701371Ma tci\WWClosuicl 10010137mert doc 10