The Department of Energy is currently undertaking a massive environmental cleanup program to deal with the legacy of the manufacture and testing of nuclear weapons. The geologic subsurface plays a unique role in this cleanup effort. It is the location of numerous contaminated sites requiring treatment and at the same time that figures prominently in the Department of Energy's long term waste disposition plans. This is typified by engineered disposal sites such as the Waste Isolation Pilot Plant and the Yucca Mountain Repository. Common across both of these areas is the complexity of the subsurface environment in terms of scale, time, and interactions of biological, chemical, and physical processes and our limited ability to truly understand how all of these factors impact treatment and storage decisions.
The Idaho National Engineering and Environmental Laboratory has initiated a Subsurface Science Program to help address the issues described above. The initiative has as its challenge to "Understand and predict processes in the subsurface as scale and complexity are increased". The subsurface is complex. There are multiple scales of heterogeneity; physical, biological, and chemical processes interact; processes are nonlinear, stochastic, hysteretic, and scale dependent; and subsurface systems span temporal and spatial scales. We lack an understanding of whole subsurface system behavior and the relationships between laboratory measurement and field observations. To help address the challenge the INEEL Subsurface Science Program will address the area of Subsurface Physical Transport and the area of Biogeochemical Processes and Interactions. In these areas the INEEL will develop alternative research approaches that seek to 1) obtain observations at relevant spatial frequency and time duration, 2) emphasize interactions among components, behaviors, and properties, 3) integrate system components to whole system behavior, and 4) emphasize importance of temporal and physical scale.
Subsurface processes must be understood at the field scale to solve DOE's environmental subsurface contamination problems. Past efforts to understand these processes have included field-scale experiments that disturb the in situ phenomena or processes one is trying to understand. In addition, field experiments are not reproducible because variables change and cannot be easily controlled in a field setting. However, field observations can be used to develop meso-scale laboratory testable hypotheses, experiments conducted at a scale at which processes couple correctly. This will be the approach taken in the INEEL Subsurface Science Program. Once these hypotheses are understood from meso-scale experiments, field scale experiments will then be used to confirm or reject the hypotheses.
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