Influence of Coupling Erosion and Hydrology on the Long-Term Performance of Engineered Surface Barriers (NUREG/CR-7200)

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Publication Information

Manuscript Completed: May 2016
Date Published: May 2016

Prepared by:
Crystal L. Smith and Craig H. Benson
Geological Engineering
University of Wisconsin-Madison
1415 Engineering Drive
Madison, WI 53706

Jacob Philip, NRC Project Manager

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington DC 20555-0001

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Abstract

Design strategies were evaluated that couple erosion and hydrology for barriers over low level radioactive waste (LLW) disposal facilities by conducting long-term (1000 yr) parametric simulations with a landform evolution and hydrologic models. Topography of the Grand Junction Uranium Mill Tailings Disposal Site in Grand Junction, CO was used to define a realistic geometry. The most significant differences in maximum erosion depths were attributed to climate and vegetation. Approximately 4 m greater maximum erosion depth was estimated in semi-arid climates compared to humid climate for simulations with a rip-rap or gravel admixture surface. Vegetation decreased erosion in the semi-arid climate by 1.5 m, and by 4 m in the humid climate. Vegetation also increased the amount of evapotranspiration that occurred, decreasing percolation into the waste. Short slopes, slopes with a low grade, and slopes with small grade differences at the nickpoint decreased erosion. The humid climate had the least erosion when terraced slopes were utilized. Due to higher erosion rates in the semi-arid climate, natural and concave slopes that promote deposition produced the least erosion. Overall, a rip-rap surface layer prevented erosion most effectively for any type of topography, climate, or cover type. However, covers with a riprap surface had higher percolation rates. In contrast, a gravel admixture surface had slightly greater erosion, but was more effective in limited percolation.