Rock Dump Design to Limit Potential Acid Drainage

Authors: Williams, DJ; Scott, P; Johnston, D; Lee, G Download Paper

DOI https://doi.org/10.36487/ACG_repo/802_18

Cite As:
Williams, DJ, Scott, P, Johnston, D & Lee, G 2008, 'Rock Dump Design to Limit Potential Acid Drainage', in AB Fourie (ed.), Rock Dumps 2008: Proceedings of the First International Seminar on the Management of Rock Dumps, Stockpiles and Heap Leach Pads, Australian Centre for Geomechanics, Perth, pp. 207-217, https://doi.org/10.36487/ACG_repo/802_18



Abstract:
The design of rock dumps comprising reactive rock should aim to limit the potential for the release of acid drainage to the environment. This requires the recognition of a number of contributing factors. Clean runoff should be kept separate from mine water, by diverting runoff upslope of the dump and lining surface drainage channels to be buried by the dump with benign rock. There is a need to selectively place benign and reactive rock to encapsulate the reactive rock. The rock dump hydrology needs to be understood, in particular the wetting-up of the dump by rainfall infiltration, in the context of the climatic setting, the surface hydrology, and the groundwater regime. Finally, a low percolation cover is required over the top of the dump, and side slopes should not be underlain by reactive rock and should be designed to minimise erosion. The paper describes the application of these principles to the design of a new rock dump being constructed at an existing open pit mine that has experienced acid drainage from a past rock dump. The design of the new rock dump to limit the potential for acid drainage required a change in the mind set for rock dump construction, and imposed a number of constraints on site preparation, construction of the rock dump, and the sequencing of rock dumping, which had to be overcome.

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