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United States Department of Agriculture

Agricultural Research Service

Title: A Decision Tool for Selecting Trench Cap Designs

Authors
item Paige, Virginia
item Stone, Jeffry
item Hakonson, T. - COLO. STATE UNIV.
item Lane, Leonard

Submitted to: Department Of Energy: Low Level Radioactive Waste Management Conference
Publication Type: Proceedings
Publication Acceptance Date: December 12, 1995
Publication Date: N/A

Interpretive Summary: A decision tool to aid risk managers in selecting the appropriate trench cap for low-level radioactive waste sites is presented. The decision theory and the components of the decision tool, the Prototype Decision Support System (PDSS), are described. The PDSS is demonstrated using four trench cap designs from the Hill Air Force Base cover demonstration study. Both field data and simulation models are used to evaluate the trench cap design alternatives. For this study, version 3 of the HELP (Hydrologic Evaluation of Landfill Performance) model was used to simulate two of the design alternatives. The trench caps were evaluated using a set of decision criteria based on federal regulation. The criteria included: the ability of the cover to control water movement into the landfill, to minimize erosion of the cap, and cost. The risk manager is able to change the importance order of the decision criteria and evaluate the results from the PDSS. The demonstration of the PDSS illustrated the ability of the PDSS to evaluate alternative trench cap designs using multi-objective decision theory and determine the "best" trench cap design based on an ordering of the decision criteria.

Technical Abstract: A computer based prototype decision support system (PDSS) is being developed to assist the risk manager in selecting an appropriate trench cap design for waste disposal sites. The selection of the "best" design among feasible alternatives requires consideration of multiple and often conflicting objectives. The methodology used in the selection process consists of: selecting and parameterizing decision variables using data, simulation models, or expert opinion; selecting feasible trench cap design alternatives; ordering the decision variables and ranking the design alternatives. The decision model is based on multi-objective decision theory and uses a unique approach to order the decision variables and rank the design alternatives. Trench cap designs are evaluated based on federal regulations, hydrologic performance, cover stability and cost. Four alternative landfill cover designs, which were monitored for a four year period at Hill Air Force Base in Utah, are used to demonstrate the application of the PDSS and evaluate the results of decision model. The results of the PDSS, using both data and simulations, illustrate the relative advantages of each of the cap designs and which cap is the "best" alternative for a given set of criteria and a particular importance order of those decision criteria.

Last Modified: 7/25/2014
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