Wind erosion design considerations for closure of tailings storage facilities in South Africa: A case study

Abstract

Environmental pressure is ever mounting on mining companies to prove that mine residue facilities will be stable landforms after closure. Designing tailings storage facilities (TSFs) for reduced dust emissions is also not readily considered as part of the tailings engineering process, and most TSFs are still uncovered in South Africa. This paper advocates proactively engineered, wind resistant tailings landscapes by incorporating principles of aerodynamic design into final closure design content. This is imperative in the wake of much dryer, windier, and warmer climate predicted for sub-Saharan Africa. This paper considers tailings specific wind erosion scenarios modelled from field data for a large TSF in South Africa. The revised wind erosion equation is applied to determine comparative wind erosion scenarios for geometric variation that informs the landscape engineering process. The methodology considers local climate, surrounding regional relief (wind direction and energy scenarios), TSF construction methodology (particulate grading and segregation), geometrical design (wind speed amplification), and material physical and chemical characteristics (particle size, moisture regimes, and dispersion properties). The modelled output demonstrates that wind erosion exponentially increases on unprotected slopes with an increase in slope angle comparing 14, 18, and 26° slope angles, implying that uncovered tailings landscapes should be designed much flatter to withstand wind erosivity over time. Mitigation scenarios are incorporated into the model to evaluate effectiveness of surface protection considering the scale of high dust risk areas and the degree of effectiveness that can be expected. The outcomes of this study suggest that unless the substantial effects of wind are not considered during the geometrical design and final closure landscape planning stages, uncovered tailings landscapes will remain serious sources of dust pollution. A case is made that wind erosion should be incorporated as a matter of principle closure design of TSFs.