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09 January 2004 <br /> • AGE-NC Protect No 96-0254 <br /> Page 5 of 6 <br /> 322 Mass of petroleum Hydrocarbons Remaining <br /> IraM °�"` soil was determined on the basis of the averaged <br /> The mass of petroleum hydrocarbons r <br /> 1 concentrations ofTPH-g <br /> In sot,samples collected from the walls and floor of the excavation area <br /> during excavation tf and previous site assessment activities AGE's calculations estimated that <br /> I- approximately 397 lbs or 25 6 al of gasoline remain to soil at the site The mass and volume <br /> calculations are presented TnAppen ix Show b� S <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> Based on the data collected from the site, AGE finds <br /> • TPH-g was detected in 28 of the 33 soil samples at concentrations ranging from <br /> 1 4 milligrams per kilogram'(mg/kg) in soil sample EXE-21 to 2,200 mg/kg (EXE-20) <br /> TPH-d was detected in 14 of the 33 soil samples at concentrations ranging from 98 mg/kg <br /> (EXE 15)to 1,300 mg/kg(FLR-02) BTEX constituents were detected in 26 soil samples at <br /> concentrations as high as 25 mg/kg benzene (EXE-18), 72 mg/kg toluene (EXE-17), <br /> . 62 mg/kg (EXE-17) and 260 mg/kg xylenes (EXE-17) Fuel additives and lead were not <br /> detected above laboratory reporting limits In any of the samples analyzed Tables 1 and 2 <br /> contain a summary of excavation analytical results Historical analytical results of soil <br /> samples are presented in Table 3 <br /> • Relatively low concentration of petroleum hydrocarbons were detected in the majontyof soil <br /> ,samples collected from the sidewalls and floor of the excavation However, significant <br /> concentrations of petroleum hydrocarbons were detected in soil samples collected near the <br /> former UST and dispenser areas On-site structures prevented excavation of impacted soil <br /> south and west of the former UST and dispenser areas, respectively Based on soil samples <br /> collected from PB4, AGE does not believe that the higher concentrations detected in soil <br /> samples collected from near the former UST area represent a significant volume of impacted <br /> soil The inferred extent of remaining hydrocarbon-impacted soil is illustrated in Figures 4 <br /> through 8 <br /> • The low concentrations of petroleum hydrocarbons in the majority of soil samples collected <br /> from the walls and floor of the excavation suggests that the major portion of the most <br /> significantly impacted soil was removed during over-excavation <br /> • The lateral extent ofhydrocarbon-impacted soil near the former gasoline UST area is defined <br /> to the north by soil boring PB-5,to the west by soil boring P133 and to the east by soil boring <br /> PB2 Minor concentrations of BTEX constituents were detected in soil samples collected <br /> from 136 and P134, thereby virtually defining the lateral extent of impacted soil to the <br /> . northwest and south, respectively Furthermore, soil samples collected from borings B2 <br /> (16 feet bsg) and PB1 (24 feetand 28 feet bsg),located adjacent to the former gasoline UST <br /> Advanced GeoEnv,ronmental,Inc <br />