Wednesday, April 2, 2008 : 9:40 a.m.
Modeling Natural Attenuation of Chlorinated Ethylenes and Ethanes
Ground water flow and reactive transport modeling is utilized to define target cleanup goals at a mixed DNAPL site beneath an inactive, Army installation in Connecticut. The 3D hydrogeologic conceptual model is defined for the glacial and reworked glacial strata using the DoD Groundwater Modeling System (GMS). Regional ground water flow is modeled with FEMWATER using surface water features and groundwater divides as natual boundaries. The calibrated FEMWATER model is used to define flow boundary conditions for an inset domain, centered on the solvent plumes, in which more detailed flow and transport sceanrios are considered using MODFLOW, RT3D, and GMS. A new RT3D module is developed for the linked degradation pathways of PCE, TCE, and TCA solvents. The model includes first-order reaction kinetics, linear adsorption, and a simple inhibition model to describe reduced microbial activity at elevated solvent concentrations proximal to DNAPL source areas, which are treated as constant-concentration cells.
Christian J. McGrath, PG, U.S. Army Engineer Research & Development Center Mr. McGrath is a Research Physical Scientist with the U.S. Army Engineer R&D Center, Environmental Laboratory in Vicksburg, MS. He conducts applied and basic research consistent with Army/Corps priorities related to groundwater cleanup and biogeochemical reactive transport modeling. Mr. McGrath holds a B.S. and M.S. in Geology (U. Georgia and U. Nebraska, respectively), is a registered PG in Tennessee, and continues his graduate education in materials science.