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09 August 1999 <br /> AGE-NC Project No. 98-0466 <br /> Page 9 of 10 <br /> Damp,to moist silt and clayey silt was encountered at 45 feet and 50 feet bsg in P4.None of the soil <br /> samples released detectable concentrations of volatile organic compounds that could be detected with <br /> the OVM. Hydrocarbon,odor was not noted for any of the soil samples. None of the soil samples <br /> r appeared to be stained... <br /> None of the analytes of interest(TPH-d, BTEX or MTBE)were present at detectable concentrations <br /> in any of the six analyzed soil samples (PI-DI 0,P2-1325, P2-D35, P3-D45, P3-50, and.SP1). <br /> Neither BTEX compounds nor MTBE were detected in ground water samples,P2-6/22/99 or P3- <br /> 6122199. TPH-d was detected at 110 micrograms per li er (µg11) in grab ground water sample P4- <br /> 6/24/99. Analytical results for the,'current investigation are tabulated in Tables 4 and'5. <br /> 5.0. .DISCUSSION <br /> i" The results demonstrate that the release of diesel fuel de cted in the former UST pit during the tank <br /> t removal either was of very small volume or did not originate from the UST itself. No indication of <br /> diesel fuel-impacted soil underlying-the former UST was encountered during this investigation. The <br /> area under the former UST where 63 mg/kg TPH-d was ncountered in soil was not excavated, but." <br /> the extent of the TPH-d-impacted soil under the former UST is quite limited, as shown.by the Iack <br /> of detectable TPH-d concentrationin soil samples PI-13.20, P2-D25 and P2-D35, all underlying the <br /> former UST site. <br /> Assuming that the-area of impacted soil at the south end f the former UST hada radius of 5 feet and <br /> the impacted soil,extended 10 feet below the impacted soil sample, the'volume of impacted soil <br /> would be approximately 29 cubic yards. if the whole volume was evenly impacted by the 63 mg/kg <br /> TPH-d detected, then the calculated mass of diesel el in the soil would be 4.93 lbs and the <br /> impacting diesel, fuel would have a volume of 0.7 gallons, as calculated for the removed soil in <br /> Section 2.3. above.-AGE believes this to be an oversimplification and probably an overestimation <br /> r of TPH-d left in place in the former UST.No.I pit: <br /> The significant diesel fuel `release from the dispens r and/or product piping was apparently <br /> effectively removed during the excavation-remedial action. No indication of diesel fuel-impacted <br /> soil was encountered in the backfilled soil or in the nativ ,soil underlying the backfilled excavation. <br />. The only possible,indication of the diesel release enc untered was the-minimal 110 µg11 TPH=d - <br /> detected in the .grab ground water sample collected beneaff the backfilled excavation. The <br /> concentration is low and of little potential environmental concern. The detected TPH-d may be the <br /> result of ground water in contact with a small pod of impacted soil Ieft in place during excavation <br /> of impacted soil or may have originated-from the up-grad ient former UST site located within a few <br /> hundred of feet ofthe former UST No. 1. <br /> Advanced GeoEnvironmental,Inc. <br /> f <br />