Development of an integrated approach for prioritization of mine features of selected abandoned mines for rehabilitation in the Giyani Greenstone Belt

Abstract

Mining has a potential to provide sustainable economic and social benefits to communities and the regions in which mining companies operate. However, many mines have been abandoned and/or improperly closed which has lasting impacts on public health and safety and the environment. South Africa has more than 5906 abandoned mine sites that were left unrehabilitated. Although the problems of abandoned mine sites are well documented, little has been done to rehabilitate the mine sites. This may be attributed to costs associated with rehabilitation and standard criteria to aid the rehabilitation process. Most of the existing rehabilitation approaches do not adequately address the physical, chemical, and environmental hazards associated with abandoned mines. The purpose of this study was therefore to develop an integrated approach that will not only assess impacts of abandoned mines but also prioritize abandoned mine features for rehabilitation based on their associated physical, chemical, and environmental hazards. In developing an integrated rehabilitation approach, two abandoned mines were selected, and all the mine features were studied by identifying, locating, mapping, and documenting them. The hazards linked to the mine features were classified as physical, chemical, and environmental hazards. A scoring and ranking approach was developed to quantify physical, chemical and environmental hazards of each abandoned mine feature. Sources of contamination, pathways and impacts of abandoned mine features were scored and ranked for physical and environmental hazards. Abandoned mine features with greater physical, environmental, and chemical scores were then prioritized for rehabilitation. In quantifying and ranking chemical hazards posed by the abandoned mine features, parameters such as Pollution Load Index, Geo-accumulation index, Contamination Factor and Potential Ecological Risk Index were used. The physical, chemical, and environmental scores were combined to determine the total hazard score for the abandoned mine sites. The hazard scores were then integrated to determine the overall hazard score per mine site. The results of the study showed that physical, environmental, and chemical hazard scores for Klein Letaba were 2.5, 1.5 and 2.2 times respectively higher than those of Louise Moore. The total hazard score for Louis Moore and Klein Letaba was 47.44 and 89.46 respectively. The results also revealed that the overall hazard score at Klein Letaba was higher than that of Louis Moore and this suggests that the associated risks at Klein Letaba are higher. Based on these findings, abandoned mine features at Klein Letaba must be prioritized for rehabilitation over features at Louis Moore. The new and integrated approach provides a framework to identify, characterize, quantify, and prioritize high risk abandoned mine features for rehabilitation. The drawbacks of the existing rehabilitation prioritization methods have been identified and examined and the new integrated approach of prioritization of mine site rehabilitation addresses these concerns. As such, this new integrated approach provides a holistic, transparent, unique, cost-saving and practicable technique of prioritizing and addressing undesirable impacts of abandoned mine sites. It is recommended that best practicable strategies be developed to mitigate the adverse impacts of the abandoned features and their detailed cost analysis conducted. Additionally, the involvement of local authorities and all other stakeholders will be crucial in increasing awareness of the seriousness of the environmental and safety concerns of the abandoned mine features at the mine sites.