Herrell, M & Farmer, D 2026, 'Development of a progressive closure strategy for management of potentially 
acid-generating materials at a coal mine in British Columbia, Canada', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-10, https://doi.org/10.36487/ACG_repo/2615_130
(https://papers.acg.uwa.edu.au/p/2615_130_Herrell/)
Abstract: Mining has to the potential to expose rock containing acid-producing sulphide minerals, that in their natural state, are benign. When exposed to atmospheric oxygen, these minerals oxidise and produce acidity. If the mine rock does not contain sufficient neutralisation potential to offset acid production, acid rock drainage (ARD) will occur. As the pH of the drainage is depressed, oxidation rates increase, and the solubility of several mineral phases concurrently increases, leading to drainage quality characterised by elevated ion concentrations. 
Once initiated, ARD is difficult to reverse. Robust geochemical characterisation studies are therefore required at the inception of new mining projects to inform mine material management and develop proactive closure strategies to minimise ARD and potentially reduce closures costs. 
Geochemical characterisation of materials at the Tenas Steelmaking Coal Project (Tenas Project), located 7 km south of the village of Telkwa, British Columbia, Canada, indicates that ARD management will be required. To mitigate ARD, Telkwa Mining Limited (TML) has developed a progressive reclamation strategy that includes mine scheduling to facilitate construction of management ponds external to the open pit and within mined-out areas of the open pit. The management ponds will be used as reservoirs to submerge potentially acid-generating (PAG) rock progressively during operations to preclude oxidation of sulphide minerals. The proactive management of PAG rock during operations is designed to reduce the long-term closure liability associated with a project. This paper presents a practical case study of the use of a geochemical characterisation study as a direct input to the mine design and long-term closure strategy at the planning stage of a project.