ARCHIVED REPORTS XR0004798 - Laserfiche WebLink

Home Browse Search

I ' , , I 28 February 1997 AGE-NC Project No 95-0144 ' Page 14 of 20 infection and extraction rates must be balanced to prevent the forced migration of contaminants ' However, air sparging has proven itself as a very effective method for remediation of soil in the smear zone As,in vapor extraction, air sparging is not effective for the remediation of longer-chain ' hydrocarbons An in-situ air sparging pilot test was performed at the site from 02 to 07 February 1996 Two , sparging wells were supplied with approximately 15 psi of air during the test Induced pressure, organic vapor concentrations, ground water depth and dissolved oxygen concentrations were Ilk measured at surrounding monitoring wells Ground water samples were collected from monitoring , ' wells before and after the sparging test Detailed procedures and results of the test were included in N the Corrective Action Plan -Febi uary 1996 prepared by AGE ' ,Increased concentrations of organic vapor were observed at surrounding m6nitoring wells Induced pressure showed an initial,increase during the pilot test, but diminished over the time of the test ' 'Initially, dissolved oxygen increased at the site, but also decreased over the duration of the spaiging test These two anomalies may have been caused by channeling of the air flow from the sparging points A lower injectibn pressure, approximately 10 psi, combined with surging the infected air M should be used to minimize the effects of air channeling and promote maximum interaction of the infected air with ground water A closer injection well spacing would be required with a lower infection rate Only slight ground water mounding was observed during the sparging.test Data from the air sparging pilot test are included on Table 4 Another concern with air sparging is precipitation of iron, which can cause clogging of sparging ' points, Laboratory analysis of water samples indicated low concentrations of iron in water at the site, indicating minimal concern for iron precipitation ', 615 DURATION Air sparging in highly permeable aquifers generally results in rapid reduction of hydrocarbon a concentrations in the saturated zone Remediation times are generally comparable with soil vapor extraction times At the subject site,we estimate a remediation period of I2 to 24 months for shorter- chain hydrocarbons Longer-chain {diesel} hydrocarboris were detected water samples collected at the site, and would require longer remediation periods If ground water remains at its current ' elevation,impacted silt within,the upper saturated zone may slow overall site remediation and hinder extraction of volatilized hydrocarbons 1