Combined Use of ISCO for Source Treatment and Reductive PRB for Plume Control and Treatment

摘要

Groundwater at an industrial site in Texas is impacted with chlorinated volatile organic carbons, primarily tetrachloroethene and trichloroethene, from historical waste disposal. Site topography slopes steeply towards a small channel where the groundwater discharges. Depth to groundwater ranges from approximately 20 feet below ground surface (bgs) at the source area to 1 feet bgs adjacent to the channel. The soil consists of silty clays. Remedial objectives are to achieve the Texas Risk Reduction Program Tier 1 residential protective concentration levels (PCLs). Prior to in situ applications, source area soil was excavated from the vadose zone. Remediation of site groundwater has entailed a combined approach employing chemical oxidation at the source area and a reductive permeable reactive barrier (PRB) for passive plume control and treatment along the channel. Reductive technologies were preferred adjacent to the channel in order to protect the water body and aquatic life. These combined measures have resulted in >96% reduction in total chlorinated ethenes in groundwater at the source area and >98% removal of total chlorinated ethenes directly downgradient from the reductive treatment zone. Residential PCLs have been met on the Site, with only minor exceedances (<0.010 mg/L total COCs) off site and upgradient of the PRBs.