An Integrated Qualitative and Quantitative Approach for Ranking the Risks of Abandoned Mine Sites for Rehabilitation

Rehabilitation of mine features associated with abandoned mines is a global challenge in many countries, including South Africa, which has had a mature mining industry since the 1860s. Most existing rehabilitation approaches do not adequately address the physical, chemical, and environmental hazards associated with abandoned mines. In this study, the abandoned mine features at the Louis Moore and Klein Letaba abandoned gold mine sites were identified, assessed, scored, and ranked based on their existing and potential negative impacts on the environment and human health. Soil around the studied abandoned mine features was collected at a depth of 10-30 cm to assess contamination levels. The tailings at the abandoned mines show the decreasing order of A s˃ Co ˃ Ni ˃ Cu ˃ Zn ˃ Pb ˃ Cd. The maximum concentrations of Cu (81mg/kg), Zn (465 mg/kg), As (694 mg/kg), Ni (1213 mg/kg), and Pb (109 mg/kg) exceed the maximum permissible limits in natural soils, indicating that the tailings material was contaminated by these metals. The total physical hazard scores computed for abandoned mine features at Louis Moore and Klein Letaba are 40.96 and 16.04, respectively. Mine features for rehabilitation are prioritized as mine shafts, mine tailings, rock dumps, water reservoirs, silos, ball mills, and old buildings. The highest potential environmental hazard and risk, with a score of 9, is assigned because flooding has high potential to pollute water systems. The flooding of abandoned mine shafts, ore spillages, and toxic metals of abandoned mine dumps contaminate nearby water systems and soil.