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26 December 1995 <br /> AGE-NC Project No. 95-0118 <br /> Page 5 of 6 <br /> 5A. CONCLUSIONS & RECOMMENDATIONS <br /> 5.1. HYDROCARBON-ROPACTED SOIL <br /> Hydrocarbon-impacted soil remains in the area of the former UST excavation. Feasibility testing <br /> =' should be performed to determine the most cost-effective method of soil remediation. <br /> We recommend the installation of two soil vapor extraction(SVE) wells. The first extraction well <br /> should be installed within the former UST excavation. A second extraction well should be installed <br /> ' approximately 20 feet east, adjacent to the maintenance building. Proposed SVE well locations are <br /> illustrated on Figure 4. Each well should be screened throughout the entire depth of soil <br /> contamination. Upon completion of well installation, an 8-hour(minimum) SVE pilot test should be <br /> performed at the site. Data obtained from the pilot test should be used to prepare a Corrective Action <br /> Plan(CAP) for the site. <br /> Soil samples collected during the installation of the proposed SVE wells should be submitted to a <br /> microbiological laboratory for analysis of physicochemical properties and microbial enumeration. <br /> crobiological data obtained from the analysis should be used to determine the feasibility of in-situ <br /> bioremediation and/or bioventing at the site. These results should also be included in the CAP. <br /> 5.2. HYDROCARBON-]MPACTED GROUND WATER <br /> Groundwater flow direction continues to shift at the site.During the September 1995 sampling event, <br /> the flow direction was divergent from MW=3. Monitoring wells MW-3 and MW-6 are down gradient <br /> of the former UST excavation. However, petroleum hydrocarbons were not detected in MW-6. <br /> It appears that the lateral extent of hydrocarbon-impacted ground water at the site has been <br /> delineated. Figure 4 illustrates the estimated area of the dissolved hydrocarbon plume. Since the <br /> primary contaminants in ground water at the site is gasoline, it is likely that in-situ air sparging will <br /> be the most effective remediation alternative. After completion of soil feasibility studies, groundwater <br /> `J remediation alternatives should be discussed in the CAP. <br /> 6.0. LIMITATIONS <br /> Our professional services were performed using that degree of care and skill ordinarily exercised by <br /> environmental consultants practicing in this or similar localities. The findings were based upon <br /> analytical results provided by an independent laboratory. Evaluations of the geologiclhydrogeologic <br /> conditions at the site for the purpose of this investigation are made from a limited number of available <br /> -i <br />