Dr. Mitchell Olson holds a BS degree in chemical engineering from the University of Minnesota Duluth and MS and PhD degrees in environmental engineering from Colorado State University (CSU). He worked at CSU in Dr. Tom Sale’s research group as a Research Associate/Scientist from 2005 to 2015. His research at CSU focused on transport and degradation processes for organic contaminants, including hydrocarbons, chlorinated solvents, and persistent organic contaminants (e.g., PCBs). A primary research focus area involved remediation of chlorinated solvent source zones via soil mixing with zero valent iron and bentonite. In 2015 he began working with Trihydro as an Environmental Engineer. Within Trihydro, Dr. Olson is providing technical input on a variety of projects involving hydrocarbons, chlorinated solvents, and perfluoroalkyl substances (PFAS). He has recently participated in a National Groundwater Association PFAS document and is currently involved in the ITRC PFAS team. Dr. Olson currently holds an Affiliate Faculty position in the Department of Civil and Environmental Engineering at CSU and is a registered Professional Engineer in Colorado and Nebraska.
In Situ Reduction with ZVI: Performance Assessment with High Resolution Data
Soil mixing has become an established technology for source-zone remediation, due to its ability to overcome contaminant/reagent contact limitations. Soil mixing for delivery of zero valent iron (ZVI) and bentonite, a technology is referred to as ‘ZVI-Clay,’ can be particularly effective for treatment of chlorinated solvent source zones. This presentation focuses on an ESTCP-funded project in which a novel site characterization technology, cryogenic core collection (C3), was used to conduct post-remediation performance assessment at a former TCE source zone, four years after ZVI-Clay remediation was complete. The C3 technology uses liquid nitrogen to freeze soil cores in situ, preserving subsurface conditions including volatile organics and gaseous degradation products (e.g., ethene and acetylene) that can be useful for evaluating in situ reductive processes at chlorinated solvent sites. Prior to C3 evaluation at the project site, groundwater concentrations from within the treated former source zone suggested concentrations had declined by greater than four orders of magnitude. The C3 data confirmed that only small quantities of chlorinated solvent mass remained within the treated former source area, thus concentration rebound is highly unlikely. Downgradient of the treated zone, the C3 data indicate that contaminant mass is stored in low-permeability zones, which are likely to provide an ongoing source of contaminant mass to the groundwater plume. The concentration profiles for ethene and ethane suggest biological chlorinated solvent degradation is likely occurring within low-permeability zones and measured acetylene concentrations suggests that abiotic degradation processes are occurring on the perimeter of the ZVI-treated former source zone.