Progressive Mine Reclamation… Can We Enhance it to Include Mine Rock Facility Design?

摘要

Progressive mine reclamation is defined differently across the mining industry, yet the consensus is that it represents “best available technology” for reducing environmental risks at closure and optimizing closure costs. In terms of mine rock storage facilities (MRSFs) which contain potentially acid generating (PAG) material, current industry practices and the majority of guidance documents focus on phased cover system construction and revegetation. The idea is that through reduction of oxygen ingress and surface water infiltration following progressive construction of the MRSFs cover system, and revegetating, management of metal leaching and acid rock drainage (ML-ARD) can be “optimized”. While the above is certainly true, this paper will address whether an enhanced methodology can be applied for progressively reclaiming a MRSFs, which will provide substantially more reduction in financial security requirements, and the timeframes for which financial security is required, as compared to the “typical” progressive reclamation approach for a MRSFs. An important additional benefit is that the enhanced progressive reclamation methodology can reduce reliance on cover system performance and longevity. This improved MRSFs progressive reclamation methodology focuses on changing the typical physical environment in which sulfide materials are placed into during MRSFs construction. Rather than PAG placed into the MRSFs such that oxygen supply following mine rock placement is unchecked, the MRSFs is designed using mine rock placement strategies that focus on managing gas transport as the MRSFs is being constructed and post closure. This limits sulfide oxidation and generation of stored acidity, increases longevity of any available alkalinity, and thus moves us closer to the essence of progressive reclamation than the typical approach. A case study is provided to illustrate the MRSF design methodology. The case study illustrates that MRSFs design, allows management of ML-ARD risk to be evaluated during MRSF, rather than waiting until later, as is typically done.