Review of mine waste capping methodologies for use in semi-arid regions of Queensland, Australia

Authors: Williams, DJ Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2215_73

Cite As:
Williams, DJ 2022, 'Review of mine waste capping methodologies for use in semi-arid regions of Queensland, Australia', in AB Fourie, M Tibbett & G Boggs (eds), Mine Closure 2022: Proceedings of the 15th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 999-1012, https://doi.org/10.36487/ACG_repo/2215_73



Abstract:
The paper reviews conventional surface mine waste management practices and the development of capping methodologies over potentially contaminating mine wastes using soil covers. The paper then focuses on the store and release cover system appropriate for the tops of potentially contaminating mine waste storages in the semi-arid regions of Queensland, Australia. The treatment and drainage of the slopes of such mine waste storages are also described. In Queensland, the Queensland Estimated Rehabilitation Cost User Guide (ERC User Guide) recommends soil cover layers and their thicknesses for the risk category assigned to stored mine wastes. The paper outlines the recommendations of the ERC User Guide and offers commentaries on their application in semi-arid regions of Queensland. It is noted that the ERC User Guide does not specify cover designs for different climatic settings, nor the materials or placement to be applied to the layers defined, which are key to the success of a cover system. Rather, the focus is on assigning a risk category to the stored mine wastes, covering both chemical and physical risks, and specifying the type and thickness of cover layers for that risk category. Attention should focus on the design, materials selection, and construction of mine waste covers to ensure that they are appropriate for the mine wastes stored and the climatic setting of the site. Further, the ERC User Guide does not specify the slope angle and treatment for waste rock dumps (WRDs), heap leach pads and tailings storage facilities, but presumes ‘reprofiling’, which forms the basis for estimating slope rehabilitation costs. Leaving angle of repose non-acid forming WRD slopes is not considered in the ERC User Guide, despite it being successfully applied at a number of mine sites in Queensland. The ERC User Guide states that “drainage is typically required on the finished cap to ensure that surface water drains off the cap”, despite this concentrating rainfall runoff.

Keywords: cover system, estimated rehabilitation cost, mine waste storages, rehabilitation, slope treatment

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