ARCHIVED REPORTS_XR0005705 - Laserfiche WebLink

Home Browse Search

1 Operation of the system is ongoing,performance mfonnation is not available at this time Remediation goals include<0 001 mg/L (phenol), 0 003 mg/L(1,2-dichloroethane), <0 005 mg/L (methylene chloride, toluene,ethyl benzene,and xylene), and 0 005 mg/L (tnchloroethylene and benzene) 4.4.1.4 Underground Storage Tank Release from a Gasoline Station in Indiana Two-phase vacuum extraction, a form of well-screen entramment extraction,was implemented to remediate ' contamination resulting from UST leakage at a gasoline station(Lindhult and others 1995) A soil VOC plume was detected during an environmental audit at a nearby shopping mall Subsequent investigations ' revealed that two groundwater plumes were associated with the soil contamination and that one of the plumes had migrated off site from the gasoline station The extraction system included a vapor/liquid separator, a vacuum blower, and vapor and water treatment Five extraction wells were initially installed at depths of approximately 25 feet, and two wells were ' installed subsequently to address additional areas of contamination The extraction wells were screened in the vadose and saturated zones Vacuum of approximately 23 inches of mercury was applied directly to the wells for removal of vapor and groundwater-- Site roundwater__Site soils consisted of fairly uniform clays Results of a soil gas survey indicated that a significant portion 1 of site soils contained VOCs at concentrations exceeding 1,000 mg/kg, and two areas contained ' concentrations exceeding 10,000 mg/kg Two groundwater BTEX plumes were associated with the soil contamination one with maximum BTEX concentrations exceeding 1,000,ug/L and one with maximum ' BTEX concentrations exceeding 16,000 Mg/L A thin layer of free product was found in one monitoring well ' After several weeks of operation,the thin layer of free product in the monitoring well disappeared During the initial 142 days of operation,BTEX removal efficiencies in the recovery wells ranged from 93 to greater than 99 percent After 407 days of operation,total BTEX concentrations in all recovery wells decreased by greater than 97 percent,except for one,which was at 88 percent Periodic increases in concentrations in the monitonng well were attributed to potential capture of pockets of groundwater that had migrated past the recovery wells At the time of reporting,the system had reduced BTEX ' concentrations to below the alternate cleanup criteria of 250 Mg/L benzene and 1,000 ug/L total BTEX for 4-17