An Investigation into the Depth and Rate of Weathering on Witwatersrand Gold Tailings Dam Surfaces as Key Information for Long-Term Acid Rock Drainage Risk Assessments

Authors: Bezuidenhout, N; Rousseau, PDS

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DOI https://doi.org/10.36487/ACG_repo/852_46

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Bezuidenhout, N & Rousseau, PDS 2008, 'An Investigation into the Depth and Rate of Weathering on Witwatersrand Gold Tailings Dam Surfaces as Key Information for Long-Term Acid Rock Drainage Risk Assessments', in AB Fourie, M Tibbett, I Weiersbye & P Dye (eds), Mine Closure 2008: Proceedings of the Third International Seminar on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 511-520, https://doi.org/10.36487/ACG_repo/852_46

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Abstract:
The generation of acid rock drainage (ARD) from tailings dams of the Witwatersrand gold fields in South Africa is arguably one of the main strategic environmental issues facing the gold mining industry and the South African Government. Fine-grained, sulphidic, tailings impoundments generate ARD through the diffusive ingress of oxygen into unsaturated pore spaces. Research was conducted on behalf of the Water Research Commission of South Africa to determine what the likely rate and depth of oxidation is within typical tailings impoundments of the Witwatersrand gold fields. It was found – through a combination of literature, field work and first order modeling – that the bulk of a typical Witwatersrand tailings facility will only acidify after hundreds to thousands of years. However, acidic drainage may well occur from the wall and toe paddock sections during the operational phase or within a couple of years after decommissioning and closure, and can therefore be effectively mitigated during the operational phase.

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