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18 February 1997 <br /> • AGE-NC Project No 95-0104 <br /> Page 15 ofT) <br /> 7 1 3 MONITORING ACTIVITIES <br /> One of the potential problems associated with air sparging is lateral spreading of the contaminant <br /> I 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 /> Idetect mounding and the presence of organic vapor <br />' 714 FEASIBILITY <br />' Remediation of ground water at the site would require only a moderate number of injection and <br /> extraction points An intensive piping network for injection and extraction must also be installed Air <br /> injection and extraction rates must be balanced to prevent the forced migration of contaminants <br /> I However, air sparging has proven itself as a very effective method for remediation of soil in the smear <br /> zone impacted by volatile petroleum hydrocarbons <br /> • A concern with air sparging is precipitation of iron, which can cause clogging of sparging points <br /> Prior to initiation of an IAS system, ground water samples would have to be collected and analyzed <br /> for iron to determine existing conditions <br /> No site specific IAS feasibility tests were performed at the site However, the IAS method has been <br /> proven to be effective in many different soil types and at sites in California with varied ground water <br /> depths <br /> 715 DURATION <br /> Air sparging in highly permeable aquifers generally results in rapid reduction of volatile hydrocarbon <br /> concentrations in the saturated zone Remediation times are generally comparable with soil vapor <br /> extraction times At the site, we estimate a remediation period of 12 to 24 months for shorter-chain <br /> Ihydrocarbons <br /> I7 1 6 COST <br /> Installation of an in-situ air sparging system will require the installation of numerous sparging and <br /> Iextraction wells, piping system and equipment Setup costs would likely range from $30,000 to <br /> • $40,000 Sparging equipment maintenance and monitoring would range from $5,000 to $10,000 <br /> annually Based upon a treatment period of 24 months, the total costs would be in the range of <br /> $40,000 to $ 0,000 <br /> 6oid�a <br /> I <br />