Dr. Mitch Olson has been an Environmental Engineer with Trihydro since April 2015. Prior to this, he worked as a Research Associate/Research Scientist at Colorado State University for 10 years. Mitch has a BS degree in chemical engineering from Minnesota Duluth and MS and PhD degrees from Colorado State University in environmental engineering.
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Cryogenic Soil Core Collection: A Novel and Powerful Method for Post-Remediation Performance Assessment
This presentation advances a practical approach for Cryogenic Core Collection (CCC) as a method to efficiently generate high-resolution subsurface data. CCC techniques were developed to improve core recovery and preserve properties, such as volatile organic compound (VOC) concentrations and redox-sensitive parameters. To accomplish this, CCC involves freezing soil cores in situ, using liquid N2, and then transporting the cores (while frozen) to a laboratory for analysis. Development of the CCC approach has been led by Oregon Health & Science University, Colorado State University, and Drilling Engineers Inc. under SERDP-funded research (ER-1559 and ER-1740). This presentation presents methods and results of a current ESTCP-funded project (ER-201587-PR) conducted in the summer of 2016. CCC was employed to conduct post-remediation assessment at a former chlorinated-solvent source zone that was remediated in 2012 via soil mixing with zero valent iron (ZVI) and clay.
For this project, CCC is used to collect samples from within and downgradient of the remediated source zone. Samples are shipped to a laboratory at Colorado State University for processing. The processing consists of cutting cores (while still frozen) into subsamples for a suite of analysis, using “assembly line” methods for high-throughput characterization. The chemical analyses include methanol extraction for total VOC concentrations, aqueous extraction for pore-water concentrations (e.g., methane, ethene, ethane, and acetylene), dissolved inorganic analytes, and oxidation/reduction potential. Biological analyses include DNA extraction for qPCR and 16S-RNA microbial community characterization. Sub-sections are also analyzed for physical properties including porosity, organic carbon content, and hydraulic conductivity (K).
The cryogenic core collection is scheduled to be completed in the summer of 2016. Methods, results, and lessons learned from the ESTCP-funded field effort will be presented.