ARCHIVED REPORTS XR0004801 - Laserfiche WebLink

Home Browse Search

r 04 March 1996 AGE-NC Project No 95-0144 Page 14 of 18 ' installation of additional injection points, screened at a depth of approximately 35 feet bsg IAS must be combined with vapor extraction to contain vapors stripped from'the ground water The installation of extraction wells would also be required , E 7 1 3 MONITORING ACTIVITIES v One potential problem associated wi6air sparging is inad%extent lateral spreading of the' hydrocarbon plume This is due either to mounding of ground water above injection points or lateral air flow away froin sparging wells To detect thus problem, ground water,depths in monitoring wells and extraction wells (if appropriate) should be monitored on a monthly basis (nuninium) to detect mounding and the ' (presence of organic vapors ' 714 FEASIBILITY _ 3^ Air injection and extraction rates must be balanced to prey ent the forced migration of contaminants An intensive piping network for injection and extraction must be installed for this method to be etlective As in vapor extraction, air sparging is not effective in the remediation of Ionger-chain hydrocarbons, which are practically not strippable from v ater Data from the aur sparging pilot test r indicated the movement of hydrocarbons to extraction points A lower injection pressui e, approximately 10 psi, and surging of injected air should be used at the site to minimize aur channeling and promote maximum interaction of injected air with ground water A closer injection well spacing would be required with a lower injection rate Very low concentrations of dissolved iron were detected in water samples at the site Therefore, clogging of sparging points and foriniation pore space ' shoufd not occur due to iron precipitation h ' 715 DURATION Air sparging in highly permeable aquifers generally, results in rapid reduction of hydrocarbon concentrations in the satur=ated zone Remediation times are generally comparable with soil vapor extraction times At the subject site, we estimate a remediation pei i-od of 12 to 24 months for shorter- chain hydrocarbons 'Longer-chain(diesel) hydrocarbons were detected water samples collected fi om 1 monitoring wells MW-1 and MW-12 during the October 1995 sampling However, the presence of. diesel was not confit coed during the February 1996 monitoring event