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1 <br /> 20 January 2005 <br /> AGE-NC Project No 97-0343 <br /> Page 14 of 21 <br /> Fate and transport modeling may indicate that hydrocarbons in soil do not pose a threat to ground <br /> water Where ground water has been impacted or has a high potential to become Impacted,modeling <br /> may be used to evaluate the potential for the hydrocarbons to Impact nearby ground water receptors <br /> I <br /> 9 3 3 Feasibility <br /> Although locally high concentrations of petroleum hydrocarbon-Impacted soil occur at the site,the <br /> major portion of Impacted soil contains only minor concentrations Additionally, about half of the <br /> soil contamination is composed of relatively Immobile long-chain hydrocarbons Considering the <br /> current depth to ground water and that a source for further contamination does not exist at the site, <br /> it is unlikely that significant additional ground water contamination will occur <br /> 1 <br /> 9 3 4 Estimated Costs <br /> Additional assessments including additional laboratoryanalysis of soil samples and/or confirmation <br /> soil sampling would be required to monitor and verify the effectiveness of passive remediation A <br /> long-term monitoring program,perhaps greater than 10 years,would be Initiated Generally,the costs <br /> would Include quarterly ground water monitoring and sampling, semiannual soil borings to monitor <br />' the progress of passive remediation and report preparation Therefore, annual cost for passive <br /> remediation should be on the order of $10,000 to $22,000 Based on a duration of 10 years of <br /> monitoring, the total cost for passive remediation is estimated to be approximately $100,000 to <br />' $220,000 <br />' 10.0. GROUND WATER REMEDIATION ALTERNATIVES <br /> Three methods believed to be most amenable to remediation of hydrocarbon-Impacted ground water <br />' on the site have been evaluated The methods Include in-situ air sparging, ground water extraction <br /> (pump and treat) and natural attenuation <br />' 10 1 IN-SITU AIR SPARGING <br /> In-situ air sparging (IAS) utilizes air Injection to volatilize dissolved hydrocarbons and strip <br /> hydrocarbon vapor Into the vadose zone, where It can be withdrawn by a vapor extraction system <br /> Air sparging is commonly conducted concurrently with soil vapor extraction <br /> Advanced GeoEnvironmental,Inc <br />