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• ! CASE STUDY: Ozone Injection for Soil and Groundwater Remediation Site Name: Machine Parts Manufacturer, Warwick, Rhode Island Contaminants of Trichloroethene (TCE), Tetrachloroethene (PCE), and Dichloroethene Concern: (DCE) Site Geology: The site is comprised of fill from 0 to 12 feet below ground surface (bgs) The fill is mostly fine to medium sand with cobbles and organic silt. Fine to medium sand is encountered from 12 to 28 feet bgs. Groundwater is present at an average depth of 18 feet bgs. History of Release: The site has been an industrial facility since 1922. Throughout the history of the facility, chlorinated solvents were used as part of the manufacturing processes A release of chlorinated solvents was discovered as part of a dry well closure A subsequent subsurface investigation revealed the VOCs TCE, PCE, and DCE were present in soul and groundwater at concentrations exceeding the Rhode Island Department of Environmental Management(RIDEM)cleanup criteria. A significant portion of the contaminated soul and groundwater was present beneath the eastern portion of the budding. Remedial Activities: As part of the approved remediation plan, ozone was infected into the contaminated soil and was sparged through the impacted groundwater iA series of five ozone infection wells and six ozone sparge wells were ms#a?led to dehve the oxtdizpr thr-:# tlne contani.nated zee T13e screen intervals of the ozone injection wells were placed in the source zone The six ozone sparge wells were screened 10 feet below the water table throughout the impacted groundwater plume. A one pound per day ozone generator was used to inject ozone at a rate of 1 standard cubic foot per minute (scfin) into the sparge wells. A PLC- based control system automatically opened and closed solenoid valves to switch the injection of ozone through a series of pre-programmed well configurations Ambient air concentrations were continuously monitored to ensure that workers who were present in the plant were not exposed to ozone at concentrations above health based action levels. Results: Within three months of operation the concentration of chlorinated VOCs in soil was reduced from 280 milligrams per kilogram (mg/kg)to less than 6 mg/kg Similarly, concentrations of VOCs in groundwater were reduced from an-average of 254 mncrogrWas per Inter(u&4) to less dwn 10 ug/l. It is anticipated that within the next six months soil and groundwater will meet the RIDEM cleanup enteria and system operation will be terminated.No ambient air quality standards for ozone were exceeded during the ozone injection