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20 April 1995 <br /> AGE-NC-95-0109 <br /> Page 7 of 8 <br /> oxygen imply continued biological activity in the ground water <br /> 5 2 HYDROCARBON-IMPACTED SOIL <br /> Concentrations of petroleum hydrocarbons in the soil continue to show a dramatic decrease <br /> Near the southern end of the impacted soil pIume, borings P-6 and P-8 indicate that <br /> petroleum hydrocarbon concentrations in the soil are well below 100 ppm, indicating a <br /> decrease of as much as 98%, it should be noted that benzene was not detected in soil <br /> samples from either boring <br /> Near the north end of the site, petioleuni hydrocarbon concentrations in P-7 and P-9 have <br /> decreased to 410 ppm or less As indicated in the previous monitoring report, which was <br /> prepared by GeoAudrt, overall petroleum hydrocarbon concentrations at the site have <br /> decreased as much as 90% <br /> The most recent soil samples continue to indicate that petioleuni hydrocarbon impacted soil <br /> remanns only in a narrow zone 10 to 15 feet thick near the south end of the site However, <br /> the zone widens to approvniately 30 feet near the north end of the piopeit}, <br /> Compaiison of the microbiological and soil vapor data collected at the site and the analysis <br /> of soil samples from borings P-5 through P-9 continues to indicate that the addition of <br /> hydrocarbon-degrading bacteria has had a positive influence on the reduction of <br /> hydr ocar bon concentrations in the soil <br /> 5 3 RECOMMENDATIONS <br /> Both soil and groundwater data collected during the fust quarter of 1995 continue to <br /> indicate that hydrocarbon concentrations at the site are decreasing Soil vapor and <br /> groundwater monitoring will continue accoidrng to the RMRP Additional soil samples will <br /> be collected in June 1995 Furthermore, we recommend analysis of the hydrocarbon <br /> impacted soil at the site using a computer modeling program for nsk assessment, such as <br /> the American Petroleum Institute's SESOIL to evaluat the feasibility of facilitating site <br /> closure <br /> 6 0. LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily <br /> exercised by environmental consultants practicing rn this or similar localities The findings <br />