Soil-Water Impacts from Using Vegetation and Rock Covers for Surface Stabilization of Uranium-Mill Tailings

摘要

This paper presents the results from an analysis of vegetated and rock covers and their effect on the moisture content in a covered uranium mill tailings system. Based on a one-dimensional analysis of moisture movement, the results indicate that care must be taken when selecting a surface stabilization system for a tailings pile. The moisture-content response of the tailings pile and cover system can be radically altered by different surface treatments. The two cases considered in this study indicate that (under climatic conditions occurring at Grand Junction, Colorado) the evapotranspiration from a vegetated cover can result in a relatively stable moisture content. A rock cover, however, may increase the moisture content of the tailings pile by significantly reducing evaporation. In fact, moisture storage may increase to the point that drainage occurs. If drainage does occur, the potential for groundwater pollution is increased. These results suggest that vegetation, thinner rock covers, engineered drainage systems, and/or liner systems may be needed to reduce drainage and potential leaching of contaminants. Additional work is needed to improve the description of the surface boundary condition and provide a more accurate moisture sink term. This work should focus on better descriptions of plant growth and moisture extraction behavior as a function of climatological and soil conditions. Additional work is required to more accurately describe the diffusion of water vapor through rock covers, and to quantify the effects of wind.