Evaluation of strategies for rehabilitation of selected abandoned/historic mine sites in the Giyani Greenstone Belt, Limpopo Province of South Africa

Abstract

Mining has historically been the mainstay of the South African economy and has both shaped its social and environmental fabric. However, it has left the country with a negative legacy of abandoned mines that present environmental problems, and public health and safety concerns. The common physical and environmental problems of most of these abandoned mines are associated with open shafts, unstable slopes of waste dumps and pits, and dilapidated mine infrastructure. Even though the problems of these abandoned mines are known, little has been done to rehabilitate these mines. Some attempts have been made to rehabilitate mine openings but efforts to rehabilitate features such as mine waste dumps and dilapidated infrastructure has been woefully inadequate. The reasons for ineffective rehabilitation measures may include inappropriate measures that are used in rehabilitation of the abandoned mines, lack of financial resources to carry out the rehabilitation and the need to prioritize abandoned mine features and mine sites for rehabilitation in view of the fact that there are many of these abandoned mines that require urgent attention and resources to rehabilitate them are limited. It is therefore important that practicable rehabilitation strategies are developed and used to rehabilitate mine features and sites to provide long-lasting solutions to the physical, environmental, and social problems. This study focused on the evaluation of strategies for rehabilitation of selected abandoned mine sites in the Giyani Greenstone Belt. The approach used in this study involved conducting a detailed field inventory and characterization to establish the nature and seriousness of the physical and environmental conditions of the selected abandoned/historic mining sites in Giyani Greenstone Belt. Field inventory and characterization involved traversing around the mine-site to locate and describe abandoned mine features. The Global Positioning System (GPS) was used in capturing the absolute location of the identified major abandoned mine features such as open mine shafts, tailings dump, and dilapidated infrastructure. Each of the identified mine features was critically analyzed by scoring and ranking the associated hazards. The scoring focused on the source of the hazard, exposure pathways, and possible damage that might be caused by the hazard. Analytical Hierarchy Process (AHP) and Pugh Matrix were used to devise a multi-criteria framework for evaluating mine site rehabilitation strategies. AHP method was utilized to evaluate the significance of the deciding factors and the Pugh Matrix to relatively compare the strategies for the selection of the appropriate rehabilitation options. The results of the study showed that the best approach to effectively address the physical and environmental hazards at Louis Moore and Klein Letaba abandoned mines of the Giyani Greenstone Belt was to give priority to extremely hazardous open mine shafts and tailings dumps. Mine shafts present a high risk of falling and drowning in water in the mine workings. Such risks are likely to lead to death with no hope of recovery of the body. The next mine features to be rehabilitated are the tailings dumps since they have relatively less physical hazards but extremely high environmental hazards. Abandoned mine infrastructure was found to be less hazardous and should, therefore, receive the least attention. The preferred rehabilitation strategies for abandoned mines features were evaluated after a comprehensive characterization of the site, this was done to ensure that the selected strategy addresses both physical and environmental problems identified on the site. Based on the results of evaluation, backfilling was selected to be the most suitable rehabilitation strategy for mine shafts as it has a very high potential to eliminate the risks of people falling into the mine shaft and the chances of water contamination by abandoned mine shafts. The most ideal rehabilitation option for tailings dumps was revegetation, since it ensures the safety of the site after implementation and minimizes the future environmental impacts such as the discharge of contaminants to the nearby environment. The most preferred rehabilitation strategy for dilapidated abandoned infrastructure in the study area was the demolition of the infrastructure, this strategy will improve the safety status of the mine sites and make the land they occupy available for other traditional post-mining land uses. It was concluded that the approach of prioritizing the extremely and moderately hazardous abandoned mine features is appropriate for use in developing countries where there are numerous abandoned mines and limited resources to rehabilitate them. This will go a long way in ensuring that characterization and rehabilitation of the abandoned mine features are effectively carried out within the constraints of resources.