Hydrological properties of a double-layer soil cover system for uranium mining dumps in Eastern Germany

Abstract

As an adequate rehabilitation strategy for less heavy metal contaminated and non acid-generating waste rock dumps of uranium mining in Eastern Germany a soil cover system with 0.8 m compacted loam sublayer and 0.2 m toplayer of compost and mineral soil (vol. 50%/vol. 50%) was suggested. However, at slope inclinations upto 1: 2.5 it was unclear whether this cover system would remain stable in case of high precipitation (100-year event) and to which degree water infiltration into the pile could be reduced. Within a six-year lysimeter study it was shown that after establishing permanent grassland surface, run-off and lateral water fluxes did not exceed 5% of annual precipitation, even at high rainfall. Moreover, depending on the exposure, water infiltration into the waste rock dump was reduced to 22% of annual precipitation (SE slope) and 32% (NE slope) with a linear correlation between annual rainfall and water fluxes. The hydrology of the double-layer covering was governed by the transpiration of the vegetation. Therefore, the cover system is quite advantageous under low precipitation conditions with predominating rainfall in the growing season and high potential evapotranspiration.