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I ' 09 January 2004 . AGE-NC Project No 96-0254 ' Page 5 of 6 ' 3 2 2 Mass of Petroleum Hydrocarbons Remaining The mass of petroleum hydrocarbons 40 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 397 lbs or 25 6 gal of gasoline remain in soil at the site The mass and volume ' calculations are presented in Appendix E ' 4.0. SUMMARY AND CONCLUSIONS Based on the data collected from the site, AGE finds ' TPH-g was detected in 28 of the 33 soil samples at concentrations ranging from 1 4 milligrams per kilogram (mg/kg) in soil sample EXE-21 to 2,200 mg/kg (EXE-20) ' TPH-d was detected in 14 of the 33 soil samples at concentrations ranging from 98 mg/kg (EXE15) to 1,300 mg/kg(FLR-02) BTEX constituents were detected in 26 soil samples at concentrations as high as 25 mg/kg benzene (EXE-18), 72 mg/kg toluene (EXE-17), 62 mg/kg (EXE-17) and 260 mg/kg xylenes (EXE-17) Fuel additives and lead were not detected above laboratory reporting limits in any of the samples analyzed Tables 1 and 2 contain a summary of excavation analytical results Historical analytical results of soil Isamples are presented in Table 3 • Relatively low concentration of petroleum hydrocarbons were detected in the majority of soil samples collected from the sidewalls and floor of the excavation However, significant concentrations of petroleum hydrocarbons were detected in soil samples collected near the former UST and dispenser areas On-site structures prevented excavation of impacted soil I south and west of the former UST and dispenser areas, respectively Based on soil samples collected from PB4, AGE does not believe that the higher concentrations detected in soil samples collected from near the former UST area represent a significant volume of impacted soil The Inferred extent of remaining hydrocarbon-impacted soil is illustrated in Figures 4 through 8 • The low concentrations of petroleum hydrocarbons in the majority of soil samples collected from the walls and floor of the excavation suggests 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 gasoline UST area is defined to the north by soil boring PB-5,to the west by soil boring PB3 and to the east by soil boring PB2 Minor concentrations of BTEX constituents were detected in soil samples collected from B6 and PB4, thereby virtually defining the lateral extent of Impacted soil to the northwest and south, respectively Furthermore, soil samples collected from borings B2 (16 feet bsg) and PB1 (24 feet and 28 feet bsg), located adjacent to the former gasoline UST Advanced GeoEnvironmental,Inc I