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31 January 2013 <br />AGE-NC Project No. 02-0926 <br />Page 16 of 21 <br />expected to occur at the site. <br />Use of this technology would require the installation of additional air injection points <br />screened approximately five feet below the water. Based on pilot testing (Section 8.0) deep <br />injection points like MW-6 are capable of communicating with the upper aquifer. Additional <br />air injection wells should however be installed at least five feet below the current and <br />historic groundwater levels at the site. Further the air injection system would be <br />accompanied by the onsite vapor extraction system to contain vapor stripped from the <br />ground water. The installation of at least one additional extraction well would be required <br />to effectively mitigate the remaining impact at the site. <br />9.3.3. Monitoring Activities <br />One of the potential problems associated with air sparging is lateral spreading of the <br />contaminant plume. This can be caused by either mounding of ground water above <br />injection points or lateral air flow away from sparging wells. Based on pilot activities <br />performed at the site and monitoring events performed following sparging activities <br />mounding and plume migration did not appear to occur. During sparging depth to water <br />measurements and organic vapor readings should be collected on a periodic basis. <br />9.3.4. Feasibility <br />To date, two IAS pilot studies have been performed at the site as mentioned in Section 8.0. <br />Based on the results from the performed pilot studies IAS air sparging of the remaining <br />drowned adsorbed and dissolved hydrocarbons is the most feasible remedial option for the <br />site. Currently, the site is equipped with a deep groundwater monitoring well (MW-6), and <br />vapor recovery wells (VW-1 and MW-5), which could be utilized to perform the suggested <br />remedial technology. Further, the site is currently equipped with a dedicated air <br />compressor, installed utility infrastructure and a vapor recovery system, which could also <br />be used immediately for remedial implementation. At least two additional air sparging wells <br />should be installed near the location of boring B5 and adjacent (to the west) of monitoring <br />well MW-5 to expedite remedial efforts. An additional vapor recovery well is suggested for <br />installation near the MW-5 location. <br />9.3.5. Duration <br />Air sparging in high permeable aquifers generally results in a moderate reduction of volatile <br />hydrocarbon concentrations in the saturated zone. Remediation times are generally <br />expected to be between 12 to 24 months based on current site conditions. <br />Advanced GeoEnvironmental, Inc.