Worthington, T, Green, R, Latham, CL & Yaqub, B 2019, 'Rehabilitation of the North End Box Cut dump at Tom Price mine operation: a legacy management case study', in AB Fourie & M Tibbett (eds), Proceedings of the 13th International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 1233-1240.
The North End Box Cut (NEBC) waste dump at Rio Tinto’s Tom Price iron ore operation is an historic waste dump that contains an estimated 2.6 Mtof potentially acid forming (PAF) shale material. The dump is 75 ha in size and is positioned on the edge of the site’s current operational footprint.
Construction of the NEBC waste dump began in the 1990s, and the PAF material was encapsulated within the dump. However, the dump does not meet Rio Tinto’s current standards for PAF material management or landform design, which were first developed in 1999 but have been updated since to reflect changes in industry knowledge on PAF material and its management. In particular, there is limited information on the position of the PAF cells within the NEBC waste dump, and the risk of surface exposure of PAF material during rehabilitation earthworks is considered high.
The dump is scheduled for rehabilitation commencing in 2019 and presents significant challenges regarding the application of current best practice standards to a legacy waste dump. The current approach for rehabilitating the NEBC waste dump involves significant reshaping works to achieve a stable landform design, followed by encapsulation of PAF material under all batters and berm surfaces with inert waste to minimise the risk of water and oxygen ingress into the dump. This approach necessitates the movement of millions of cubic metres of inert mineral waste to achieve the final design and to manage the potential for acid and/or neutral mine drainage. To achieve the rehabilitation design, the rehabilitation requirements have been integrated into the site mine plan, allowing the project to capitalise on scheduled ex-pit waste movements. This paper reviews the challenges that have arisen throughout the project and highlights the opportunities that can present when rehabilitation activities are integrated into the mine plan.
Keywords: legacy, rehabilitation, potentially acid forming, black shale, waste dump
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