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r 7 F 27 May 2004 AGE-NC Project No 96-0254 Page 5 of 6 Figure 4 AGE's calculations estimated that approximately 992 lbs or 159 gal of gasoline were Iremoved from the site during the soil over-excavation procedures The removal volume and mass calculations ar`e presented in Appendix D r 3 2 2 Mass of Petroleum Hydrocarbons Remaining r , The mass of petroleum hydrocarbons removed in soil was determined on the basis of the averaged concentrations of TPH-g in the soil samples collected from the walls and floor of the excavation area during excavation and previous site assessment activities AGE's calculations estimated that approximately 5 2 lbs or 0 8 gal of gasoline remain in soil at the site A cross-section of impacted soil is depicted in Figure 4 The residual volume arfd mass calculations are presented in Appendix D 4.0. SUMMARY AND CONCLUSIONS ' Based on the data collected from the site, AGE finds i l MTBE was detected two of the samples collected from the sidewalls of the excavation at ie relatively low concentrations(0 010 mg/kg and 0 050 mg/kg) Other target analytes were not detected above laboratory reporting limits in the same samples Additionally, analytes of ' concern were not detected above laboratory reporting limits in the remaining sidewall and floor sample Tables 1 and 2 contain a summary of excavation analytical results Historical analytical results of soil samples are presented in Table 3 ' The low to non-detect concentrations of petroleum hydrocarbons in the soil samples ^ collected from the sidewalls and floor of the excavation suggest that the mayor portion of the most significantly impacted soil was removed during over-excavation • The lateral extent of hydrocarbon-impacted soil near the former Cluster UST area is defined_ to the north and west by soil samples EX1-N and EX1-W, respectively In addition, the ' vertical extent of impacted soil is defined by soil sample B9-65 collected from soil bonng B-9 and by excavation floor sample FLR-01 Minor concentrations of MTBE were detected in soil samples collected from the south and east excavation sidewalls, thereby virtually- defining irtuallydefining the lateral extent of impacted soil to the south andieast • Based on the analytical results of soil stockpile samples collected during the over-excavation, x ' with prior extraction well soil samples, AGE calculates that approximately 992 lbs or 159, gal of gasoline were removed during over-excavation in December 2003 Advanced GeoEnvironmental,Inc i i