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1 <br /> 01 June 1999 <br /> AGE-NC Project No 95-0137 <br /> Page 17 of 26 <br /> with low permeability are Interbedded with coarse-grained strata in the saturated zone Air flow is <br /> retarded within fine-grained strata and may spread laterally, hydrocarbon recovery could be poor <br /> ' Use of this technology would require the installation of air Injection points, screened at depths of <br /> approximately 25 to 30 feet bsg The IAS system must be combined with vapor extraction to capture <br /> vapor stripped from the ground water The Installation of extraction wells would also be required <br /> 1 <br /> 6 13 Monitoring Activities <br /> ' One of the potential problems associated with airsparging is lateralspreading of the contaminant <br /> plume This can be caused by either mounding of ground water above injection points or lateral air <br /> ' flow away from sparging wells To detect this problem, ground water elevations in monitoring wells <br /> and extraction wells (if appropriate) should be monitored on a monthly basis, at the minimum, to <br /> ' detect mounding and the presence of organic vapor <br /> 614 Feasibility <br /> Remediation of small dissolved ground water plumes requires the installation of a few injection and <br /> extraction wells An extensive piping network for injection and extraction must also be installed Air <br /> injection and extracon rates must be balanced to prevent the forced migration of contaminants <br /> However, air spargir g has proven itself as a very effective method for remediation of soil in the <br /> ' smear zone As in vapor extraction, air sparging has a low to moderate effectiveness for the <br /> remediation of longer-chain hydrocarbons <br /> ' 6 1 5 Field Pilot Test <br /> ' An in-situ air sparging pilot test was performed at the site from 17 to 20 November 1998 This pilot <br /> test was conducted to provide data on the feasibility of air sparging as a remediation method at the <br /> ' site <br /> Procedures One sparging well was supplied with approximately 15 pounds per square inch (psi) of <br /> ' air during the test to overcome the water column in the sparging well Induced pressure, organic soil <br /> vapor concentrations, ground water depth and dissolved oxygen concentrations were measured at <br /> surrounding monitoring wells PVC piping was installed from a temporary air compressor to <br /> ' sparging well VW-1 Ambient air was cyclically injected for two-hour periods interrupted by one- <br /> hour non-injection intervals <br /> Advanced GcoEnN ironmental,Inc <br /> 1 <br />