P Area Reactor - Savannah River Site, SC

     Our basic hypothesis is significant improvement in the prediction of contaminant migration can be achieved through finer scale understanding of hydrogeologic heterogeneity, which dominates advective transport, and incorporation of this understanding in groundwater flow and solute transport modeling. Our working hypothesis is fine spatial scale (1 m resolution or less) characterization of hydraulic conductivity and porosity can be achieved through an integration of hydrogeophysical measurements and analyses with understanding of the subsurface depositional environment and the hydrogeologic facies configuration. Further, improvement in prediction of subsurface contaminant migration can be achieved by incorporating the finer scale hydrogeologic heterogeneity in a dual-domain transport model.
 

     A major component of this effort is the integration of hydrogeophysical-based borehole and surface data with hydrogeologic information (e.g., facies modeling) to extend the finer scale parameterization to field scale for flow and transport modeling purposes. A second component of the research is to incorporate the parameter upscaling in a dual-domain solute transport modeling process. Even with improved parameterization, small to intermediate scale heterogeneity is present and significantly influences contaminant migration. Although computing capabilities continue to advance, explicit representation of these smaller scale features through very high resolution simulation is not likely to support the vast majority of the U.S. Department of Energy’s (DOE) environmental clean-up efforts over the next decade. Therefore, the impact of sub-grid scale heterogeneity on plume dispersion must be cost-effectively addressed as part of an overall, multi-scale, treatment of subsurface variability. We propose using a dual-domain solute transport formulation to handle sub-grid scale heterogeneity identified through finer scale site characterization. The results of our research will complement efforts by others addressing issues surrounding coupled reactive transport so that, in the end, overall improvement in DOE subsurface transport modeling will be maximized.

     We propose to test our hypotheses through a series of hydrogeophysical experiments (i.e., seismic, radar, tomography) conducted at the P-Area Reactor at the Savannah River Site (SRS) in South Carolina. Several plumes have been identified here and the plume of interest is a trichloroethylene (TCE) plume that emanates from the northwest section of the reactor facility and discharges to nearby Steel Creek.  Our goal is to develop a new approach for upscaling in heterogeneous environments, via hydrogeophysical characterization and interpretation coupled to geologic modeling, and prove the efficacy of this approach through dual-domain solute transport modeling. We will use our experience at the P-Area Reactor site to also critically evaluate the effectiveness and suitability of our methodology for application at other DOE sites paying particular attention to the advantages and limitations, including costs, of our approach applied to different geologic/hydrogeologic environments.

     This research is supported by the Office of Science (BER). U.S. Department of Energy, Grant No. DE-FG02-06ER64201.