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Hydrogeophysical Characterization

Dual Domain
 Modeling

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 Research Approach
 

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.
Our research approach is two-fold: 1) spatially-dense integrated hydrogeophysical characterization using multiple complementary lines of evidence including surface and borehole ground penetrating radar (GPR) and seismic data, cone penetration testing (CPT), borehole logging, sediment/facies descriptions from core, and borehole flowmeter and slug testing; and 2) high-resolution groundwater flow and dual-domain transport modeling based on 3D hydrogeophysical mapping developed from the above and a priori optimal parameter specification. Motivation: Conventional characterization approaches (e.g. wellbore, direct push) produce only point or vertical line measurements of very localized conditions. Thus comprehensive field site characterization is cost prohibitive, and models are severely constrained from lack of data.	Field study site adjacent to P-Area Reactor Facility. Preliminary  characterization revealed a TCE plum emanating from the northwest section of the reactor facility.
Just as medical imaging technology has reduced the need for invasive exploratory surgery, geophysical methods hold promise for rapid, non-destructive, relatively inexpensive and vastly improved characterization and monitoring of the shallow subsurface. While promising, additional research is needed to further develop these methods for a variety of geological settings.      We anticipate that integrated geophysical and hydrogeological testing can provide dense, three-dimensional, data sets for explicit incorporation into a field-scale flow model hydraulic conductivity field of comparable resolution. The primary improvement anticipated is more accurate simulation of bulk plume movement, and to some extent dispersion. However, even with improved characterization of this nature, small- to intermediate-scale heterogeneity is present and significantly influences contaminant migration. 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 a dual-domain formulation to efficiently handle sub-grid scale heterogeneity.