A water-covered waste dump in an arid climate? A remediation concept for Brukunga Mine

Authors: Brett, D; O'Kane, M; Scott, P; Taylor, JR; McLeary, M; Williams, DJ Download Paper

DOI https://doi.org/10.36487/ACG_rep/1152_65_Brett

Cite As:
Brett, D, O'Kane, M, Scott, P, Taylor, JR, McLeary, M & Williams, DJ 2011, 'A water-covered waste dump in an arid climate? A remediation concept for Brukunga Mine', in AB Fourie, M Tibbett & A Beersing (eds), Mine Closure 2011: Proceedings of the Sixth International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 623-632, https://doi.org/10.36487/ACG_rep/1152_65_Brett



Abstract:
The Brukunga Mine in the Adelaide Hills, 40 km east of the city, was a source of pyrite for fertiliser manufacture during the mid twentieth century. The legacy is an ongoing source of acid and metalliferous drainage (AMD) requiring continuous collection, treatment with lime and disposal of sludge. The sources of AMD include a tailings storage facility, waste rock dumps and the exposed mine highwall. The site is currently being managed by Primary Industry and Resources, South Australia (PIRSA), which initiated a study to review options for remediation of the site using a Technical Advisory Group (TAG) of specialist consultants. The overall process is described in a companion paper (Scott et al., 2011) at this conference and in more detail by McCleary (McCleary, 2009). The TAG’s recommended solution comprised remixing the wastes and constructing a new disposal structure allowing continual saturation of the codisposed material. Studies, including field trials of mixed tailings and waste rock to determine geotechnical properties, demonstrated that this can be achieved despite the relatively dry climate of the site. The paper describes the development of the saturated dump concept, including discussion of geotechnical investigations, hydrogeological studies, water balance and both 2-D and 3-D hydrologic modelling. The water balance is achieved by minimising open water exposure while a permeable layer incorporated within the waste cover allows capture and distribution of recharge water from local streams. Saturation is maintained due to the relatively low permeability of the mixed waste material and the low water losses, even during prolonged dry periods. The critical aspect of the study was confirmation that there was a low risk of saturation levels within the co-disposed waste dropping sufficiently to allow oxidation to take place.

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