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27 December 1996 AGE-NC Project No 95-0143 ' Page 3 of 19 3.0. ASSESSMENT OF HYDROCARBON-IMPACTED SOIL AND GROUND WATER Between 1990 and 1994 four ground water monitoring wells(MW-3,MW-6,MW-7 and MW-9) and ' three soil borings (SB3, S134 and SB5) were drilled and installed on the site to delineate the extent of hydrocarbon-impacted soil and ground water in the vicinity of the former LIST Hydrocarbon- impacted soil and ground water were encountered in each boring Details were presented in a March ' 1991 Progress Report and August 1994 Summary Report/Additional Site Investigation prepared by Resna Industries ' On 17 and 18 Tuly 1995, sixteen soil probe borings were advanced on and around the site Soil samples were collected from five probe bonngs and water samples were collected from eleven probe borings, delineating the extent of the impacted soil and ground water Details and results of the soil ' probing investigation were summarized in the Quarterly Report -June 1995 prepared by AGE From September to November 1995, five additional monitoring wells (MW-10, MW-14, MW-15, ' MW-16 and MW-17)were installed on and near the site Petroleum hydrocarbons "ere not detected in any of the soil samples analyzed Procedures and findings were summarized in the Quaff tet ly Report- December 1995 prepared by AGE Cross sections C-C' and D-D' (Figures 3 and 4) illustrate the encountered soil profile and the ' estimated extent of impacted soil at the site Approximately 1,100 cubic yard of impacted soil ale estimated to be present in the vadose zone, centered near MW-3 Impacted soil is also present below the current ground water table, most likely due to historic fluctuations of ground water elevations ' at the site, especially in the area of MW-3 Analytical results of soil samples are summarized on Table 1 Currently, ground water samples have been collected from the monitoring wells on sixteen occasions Petroleum hydrocarbons were not detected in samples collected from monitoring wells MW-14,MW-15 or MW-17 Only trace concentrations of toluene and xylenes were detected in MW- 10 during one sampling event During the last four sampling events, however, no hydrocarbon compounds were detected in samples from this well Xylenes were detected in a sample from MW- 16 at a trace concentration of 1 1 ppb during the November 1996 monitoring event Petroleum hydrocarbons had not been detected in samples from MW-16 during any of the previous four sampling events IPetroleum hydrocarbons have been detected in ground water samples collected from the MW-3, MW-6, MW-7 and MW-9 during each monitoring event Free product was present in monitoring I well MW-3 through May 1996 In 1994, a compressor-driven skimmer was installed to remove floating product from MW-3 Free product was not detected in MW-3 during the August or . November 1996 sampling events Therefore, the skimmer has not been in operation during the past I