“New Application of a Geotechnical Technology to Remediate Low-Permeability Contaminated Media” by Dr. Steve Richardson (ESTCP Project ER-201627)

A critical challenge preventing many chlorinated solvent sites from reaching cleanup goals is the persistent release of residual contaminants from low permeability (low-k) media. To address this challenge, this ESTCP project aimed to demonstrate an innovative application of a geotechnical technology, the “Grout Bomber,” to improve the delivery of remedial amendments at matrix-diffusion sites. The “Grout Bomber” is a soil stabilization technology that uses an excavator equipped with specialized equipment (a “stitcher” mast) to quickly emplace cement grout into subsurface voids. Its speed and efficiency are advantageous to the field of environmental remediation, particularly remedial amendment applications. Specific project objectives included demonstrating that (1) conventional “Grout Bomber” equipment can be repurposed to efficiently install hundreds of closely-spaced vertical reaction columns containing zero-valent iron and vegetable oil; (2) the amendments stimulate abiotic/biotic degradation processes and generate concentration gradients that drive contaminant diffusion from low-k zones towards the reaction columns; and (3) by having closely-spaced (every 2 to 3 feet) vertical reaction columns, chlorinated solvent concentrations in low-k zones can be reduced, thus shortening the “long tail” of contaminant flux from matrix diffusion. This presentation discussed the operational and performance results for this diffusion-based technology at Site 17, Naval Support Facility Indian Head, Maryland.

“The Horizontal Reactive Media Treatment Well (HRX Well®) – A New Technology for In-Situ Remediation” by Dr. Craig Divine (ESTCP Project ER-201631)

For many Department of Defense (DoD) sites, remedial objectives and technologies focusing primarily on long-term mass discharge reduction will be increasingly favored. This project demonstrated a new in-situ remediation concept termed a Horizontal Reactive Media Treatment Well (HRX Well®) that is particularly well-suited for sites where long-term mass discharge control is a primary performance objective. The HRX Well® utilizes horizontal wells oriented parallel to groundwater flow filled with a treatment media. The design leverages natural “flow-focusing” behavior induced by the engineered hydraulic conductivity contrast to passively capture and treat proportionally large volumes of groundwater within the well in situ. Clean groundwater then exits the horizontal well along its down-gradient sections. Many different types of treatment media are already available, including zero valent iron, activated carbon, biodegradable particulate organic matter such as mulch, ion exchange resins, zeolite, apatite and chitin. Therefore, this concept could be used to address a wide range of contaminants. The approach requires no above-ground treatment, minimal footprint and limited ongoing maintenance. This presentation discussed in detail the results of the modeling, tank tests and field implementation at Vandenberg Air Force Base, California.

Dr. Steve Richardson is a principal engineer with GSI Environmental in Austin, Texas. He specializes in the application of innovative strategies to treat conventional and emerging contaminants in soil, groundwater and surface water at a wide range of contaminated sites. He has served as a principal investigator on several DoD-sponsored research projects on cometabolic biodegradation of 1,4-dioxane, innovative approaches for treatment of chlorinated solvents in low permeability zones, anaerobic bioremediation of dense non-aqueous phase liquids, and treatment of per- and polyfluoroalkyl substances. Stephen has authored more than 15 peer-reviewed journal articles on in situ bioremediation, chemical oxidation, cosolvent flushing, decentralized water treatment, contaminant bioavailability, and water chemistry in areas of oil and gas development. He received a bachelor’s degree from the University of Waterloo, a master’s degree from Louisiana State University, and a doctoral degree in environmental engineering from the University of North Carolina at Chapel Hill.

Dr. Craig Divine is a technical expert and Vice President at Arcadis in Irvine, California. He has more than 20 years of experience remediating large groundwater plumes utilizing a wide range of technologies. He has developed and field-tested passive diffusion samplers for dissolved gas tracers, point velocity probes, partitioning interwell tracer tests, light non-aqueous phase liquid tracer testing, nuclear magnetic resonance imaging, and low-temperature heating to enhance degradation rates for chlorinated solvents. He is currently collaborating on a project using IBM’s Watson platform to build a machine learning-powered expert system to support remediation decision-making. He currently serves as a principal investigator on projects to develop and demonstrate the Min-Trap™ and the HRX Well® technologies. He earned a bachelor's degree in biology from Wheaton College in Illinois, a master's degree in watershed science from Colorado State University in Fort Collins, and a doctoral degree in geochemistry/hydrogeology from the Colorado School of Mines.