1a.Objectives (from AD-416)
The objective of this research effort is to develop a strategy for incorporating model abstraction techniques into ground-water monitoring and performance assessment programs. The enhanced abstraction strategies and models shall be tested using site-specific databases for specified contaminant sources introduced and monitored in shallow subsurface environments.
1b.Approach (from AD-416)
Analyze the OPE3 tracer experiment using highly-realistic model(s) and subsets of those model(s) with varying degrees of abstraction to simulate a range of model outcomes for comparison to the detailed monitoring datasets; conduct sensitivity analyses on various parameters which were monitored to determine the impact each has on the overall model; use the spatio-temporal geo-statistics and genetic algorithms to optimize the locations and types of sensors as required by different conceptual models; use the models abstraction to develop a screening approach for determining the appropriate model abstraction techniques for modeling a specific site.
The research consisted of data analysis and modeling according to the Task 3 “Develop and Implement a Systematic Approach to Simplifying the Model of the OPE3 Watershed” of the research plan. The first step of simplification was based on the sensitivity to soil material parameters. This step was performed with parallel computations on the multiprocessor Windows machine with the latest versions of HYDRUS and TOUGH software. Simulations were done with about 50,000 computational cells. It was found that the lateral chemical movement is mostly sensitive to properties of materials in the water-saturated zone. This provided essential information for simplification of the model; only vertical chemical transport needed to be considered in water-unsaturated zone. Other simplifications, or model abstractions, are now being developed including corrections for laboratory-determined parameters to be used in the field. Model abstraction is the methodology for reducing the complexity of a simulation model while maintaining the validity of the simulation results with respect to the question that the simulation is being used to address. Model abstraction can help NRC determine whether a simple model can be used that is easy to understand and easily communicated to regulators, stakeholders, and the general public, while at the same time adequately representing their site. The balance between model complexity and model accuracy is extremely important in development of viable models of pathogen fate and transport. The progress of the work has been monitored by monthly teleconferences, three meetings with the NRC technical advisory group, and weekly group meetings. Additionally the field training for NRC technical advisory staff was carried out as scheduled in the research plan.