Laserfiche WebLink
1 <br />' 10 June 1999 <br /> AGE-NC Project No 97-0290 <br /> Page 18 of 26 <br /> 8 12 Basic System Design <br />' Injection wells are screened within the saturated zone and normally have limited screened intervals <br /> typically five feet Since most of the air escapes from the upper part of the screened interval, where <br />' head pressure is the least, little is gained by increasing the length of the screened interval <br />' The radius of influence of a sparging well is dependent on site lithology and the depth of the <br /> sparging well Sandy soil types tend to produce a larger radius of influence, clayey soil types tend <br /> to produce a more limited radius of influence However, well-sorted sandy soils may produce a very <br />' smalI radius of influence, since the injected air can rise vertically with little interference to cause <br /> lateral spreading <br />' Unless injection wells are properly located, channeling of air flow streams may occur and <br /> contamination pockets may be bypassed This problem is more common where fine-grained strata <br /> having low permeability are interbedded with coarse-grained strata in the saturated zone Air flow <br />' is retarded within fine-grained strata, and hydrocarbon recovery is poor <br /> Use of this technology would require the installation of air injection points with screened intervals <br />' below the water The IAS system must be combined with vapor extraction to contain and capture <br /> vapor stnpped from the ground water The installation of additional extraction wells would also be <br /> required <br /> 8 13 Monitoring Activities <br /> One of the potential problems associated with air sparging is lateral spreading 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 /> 814 Feasibility <br /> In-situ air sparging of dissolved hydrocarbons in ground water has moderate feasibility at the site <br /> Remediation of ground water at the site would require additional injection and extraction points An <br /> intensive piping network for injection and extraction must also be installed Air injection and <br /> extraction rates must be balanced to prevent the forced migration of contaminants <br /> Based on data collected during an IAS feasibility pilot test performed at the site, a limited radius of <br /> Advanced GeoEnvironmcntal,Inc <br /> I <br />