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19 July 1996 <br /> AGE-NC-95-0109 <br />' Page 5 of 6 <br />' 4.0. CONCLUSIONS AND RECOMMENDATIONS <br /> 4.1. HYDROCARBON-IMPACTED SOIL <br />' Soil samples were not collected during the second quarter of 1996. <br /> Soil samples collected between September 1994 and March 1996 have indicated an overall decrease <br /> of hydrocarbons at the site; locally, concentrations have decreased up to 90 percent. Therefore, we <br /> recommend preparation of a mass balance calculation and fate and transport model of remaining <br />' petroleum hydrocarbons in soil at the site. <br /> However, if continued active remediation is required at the site, the addition of nutrients to the <br />' subsurface soil should be considered. Recommended nutrient additions were detailed in the Work <br /> Plan for Modifications to Bioremediation of Soil and Ground Water- dated 13 December 1995. <br /> 4.2. HYDROCARBON-IMPACTED GROUND WATER <br /> Ground water elevation has dropped slightly between March and June 1996 {see Table 5}. The <br /> ground water flow direction continues to be toward the south-southwest. Analytical results from <br />' MW-6, MW-10, MW-12 and MW-13 continue to indicate that the hydrocarbon plume has not <br /> migrated beyond the known plume boundaries. TPH-g was detected in MW-7 and MW-11 at <br /> concentrations slightly above the detection limit, indicating that these wells are near the current edge <br />' of the hydrocarbon plume. <br /> Hydrocarbon concentrations increased in several wells during the second quarter of 1996: higher <br />' hydrocarbon concentrations observed in samples collected from MW-8, MW-9 and MW-14 during <br /> the current quarter. The contaminant plume appears to have split into two "hot spots" centered near <br />' MW-14 and MW-9. The greatest reduction in hydrocarbon concentrations has occurred at EW-1, <br /> near the center of the original plume. <br />' Results of microbiological and physicochemical analysis performed by an independent consultant <br /> indicate a slight decrease in biodegradational activity toward the end of the second quarter of 1996. <br /> Nutrient concentrations have decreased since March 1996 and are still below optimum for favorable <br /> I microbial activity. If the trend observed during the June 1996 monitoring event continue, nutrient <br /> supplementation may be required as detailed in the Work Plan for Modifications to Bioremediation <br /> of Soil and Ground Water dated 13 December 1995. <br />