Dr. Lloyd Steward
Praxis Environmental Technologies, Inc.
Dr. Stewart has over 30 years of experience in all aspects of environmental remediation research and development, including technology development; technology testing and evaluation; and remedial design. His hands-on experience includes laboratory testing, pilot-scale investigations, and full-scale implementations, supported by applied mathematical modeling. He has served as principal investigator on numerous innovative remediation and site characterization demonstrations for EPA, DoD, and SERDP and ESTCP. He has published papers and guidance on soil vapor extraction (SVE), vadose zone characterization, vapor intrusion, NAPL mass transfer, steam injection and UXO energetics release.
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.