Associate Professor and Director, Center for Contaminant Hydrology, Civil and Environmental Engineering
Colorado State University
Dr. Tom Sale is an Associate Professor in Civil Engineering at Colorado State University and an independent consulting hydrogeologist. Research and consulting activities are focused on anthropogenic releases of contaminants to subsurface environments and their subsequent transport, fate, and management. Specific areas of interest are pragmatic expectations for Nonaqueous Phase Liquid (NAPL) remedies and passive strategies for management of NAPL releases.
Dr. Sale received his Ph.D. from Colorado State University, M.S. Degree from the University of Arizona, and B.A. degrees from Miami of Ohio. The focus of his dissertation research was the affect of fractional NAPL removal on downgradient water quality and source longevity. Dr. Sale has been actively involved in the characterization and remediation of subsurface releases of Nonaqueous Phase Liquids (NAPLs) since 1981.
SESSION KEYNOTE PRESENTER - NAPL Characterization and Depletion: My Old Friend
Emerging Concepts for Resolving LNAPL Longevity
Absent active releases, shallow LNAPL bodies evolve through early, middle, and late stages, ending in complete depletion of LNAPL. Evolution of LNAPL bodies through time, due to evaporation and dissolution, is demonstrated through sand tank studies over a time frame of days using a highly volatile/soluble single component LNAPL (MTBE). Experimental variables for the MTBE studies include water-level fluctuation and early-stage hydraulic LNAPL recovery. While the areal extents of the LNAPL bodies are present as a continuous phase, natural losses due to dissolution and volatilization follow a zero-order rate model. Complementary laboratory studies indicate that LNAPL depletion by sulfate reduction and methanogenesis, primary factors leading to the depletion of LNAPL under field conditions, also follow a zero-order rate model, and that their rates are similar. Lastly, collection and analysis of core from a late-stage LNAPL release, over five years, suggest zero-order loss rates of LNAPL. Summing the effects of zero-order natural source zone depletion and first-order LNAPL depletion via hydraulic recovery provides a means for estimating the longevity of known amounts of LNAPL. Modeling and field studies suggest nearly-complete depletion of LNAPL can be achieved in 40 years at two study sites, given no active releases. Collectively, predictions of LNAPL longevity provide a basis for resolving the merits of natural source zone depletion remedies.