2012 Annual Report 1a.Objectives (from AD-416): To apply the model abstraction techniques to improve the contaminant transport monitoring strategies. The Cooperator has expertise we do not have in a model abstraction approach that can be used to improve the efficiency of modeling of water flow and chemical transport in the unsaturated zone. 1b.Approach (from AD-416): ARS will provide data and their analysis on experiments on flow and contaminant transport at the OPE3 site and the basic conceptualizations of events, and processes that can be encountered in the NRC practice and have been realized at the OPE3 site. The cooperator, in cooperation with USDA-ARS and NRC staff, will create and evaluate the simplifications with various monitoring data collected from the OPE3 site to develop the abstraction screening approach and the guidance document to be used by NRC experts. 3.Progress Report: The cooperator has evaluated data (provided by ARS) on contaminant transport at a field site with the goal of developing an abstraction screening approach for simplifying modeling systems. Specifically, the cooperator developed approaches to reduce complexity of modeling systems with respect to key processes and parameters of the system; conducted a series of computer experiments using various monitoring data; and validated applicability of the model simplification approaches on data from the ARS-Beltsville site. The approach developed by the cooperator included model simplification based on sensitivity analysis with respect to the performance assessment indicators such as subsurface textural units, boundary condition definitions, temporal details, geometry of the simulation domain, and modeling scenarios. The cooperator also used abstractions based on applying pedotransfer functions to flow and transport parameter estimation, abstraction of scale change, and dimension reduction. Overall, an exhaustive and highly technical model abstraction analysis has been performed as mutually agreed. This information will be incorporated into a guidance document to be used by U. S. Nuclear Regulatory Commission experts.