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RemTEC Summit

Lloyd Steward
Dr. Mark Widdowson

Professor and Department Head of Civil and Environmental Engineering
Virginia Tech

Dr. Widdowson is the co-author and principal investigator of the solute transport code SEAM3D (Sequential Electron Acceptor Model, 3D Transport) and the decision-support tool NAS (Natural Attenuation Software). His research expertise includes mathematical modeling and experimental studies on the fate and transport of contaminants in soil, sediments and groundwater, including chlorinated solvents (PCE, TCE, vinyl chloride); chlorinated compounds (PCBs); petroleum hydrocarbons (benzene, BTEX, MTBE), coal tar and creosote (PAH compounds); inorganics (nitrate, nitrite); metals (arsenic).


ESTCP Workshop

Workshop 1 - Volume-Averaged Modeling of Complex NAPL Dissolution and Remediation

Current approaches to predict NAPL dissolution and cleanup include: (1) screening models that lack a physical basis, and (2) coupled numerical transport and reaction models, which are complex, costly, and often unworkable. This workshop presents a practical, physically-based alternative – a volume-averaged model using dimensional scales of NAPL sources and remedial action implementation. The approach models cleanup of NAPL source zones based on the characteristic dimensions and saturations of NAPL accumulations combined with first order models of dissolution and the processes governing remedial measures. For example, first order equations describing injection of an aqueous amendment, mixing, and reaction rates constrained by NAPL dissolution can be readily solved. Case studies demonstrate results comparable to much more intensive numerical modeling. Given a modest amount of site characterization data, the approach provides quantitative assessment of changes in NAPL source concentration and flux over time, thus supporting scientifically defensible NAPL source remediation.