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
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.
Earth Systems (2008) Waste rock test work at the Brukunga Mine Site, South Australia, Summary of November 2008 to August 2009. Report prepared for Primary Industries and Resources South Australia (PIRSA).
GHD (2009a) Site Water Balance Model, 30 September 2009. Report prepared for Primary Industries and Resources South Australia (PIRSA).
GHD (2009b) Predicted Post-Remediation Water Balance Model, September 2009. Report prepared for Primary Industries and Resources South Australia (PIRSA).
Golder Associates (2009) Report prepared for Primary Industries and Resources South Australia (PIRSA), Three-Dimensional Regional Groundwater Flow Modelling (FEFLOW) – Brukunga Mine Rehabilitation Program, October 2009.
McCleary, M.B. (2009) Striving for “walk away” – focussing an expert group on the “holy grail” of mine closure, Proceedings of the Fourth International Conference on Mine Closure 2009, A. Fourie and M. Tibbett (eds), 9–11 September 2011, Australian Centre of Geomechanics, Perth, Western Australia, pp. 359–373.
Newmans (2009) Report on Seepage Analysis, Newmans Geotechnique, Report prepared for Primary Industries and Resources South Australia (PIRSA).
Scott, P.A., Taylor, J., Grindley, P., McLeary, M., Brett, D., Williams, D. and O’Kane, M. (2011) Case Study for Avoiding Treatment in Perpetuity – The Brukunga Pyrite Mine Example, Mine Closure 2011, Calgary, in press.
SKM (2009) Geotechnical, Geochemical and Hydrogeological Drilling Investigations (BR01-02), PHASE 1–5, DRAFT, 20 August 2009.
TAG (2008) Technical Advisory Group. Final Report on the Development and Assessment of Remediation Options for the Brukunga Remediation Project, Prepared for the Department of Primary Industries and Resources South Australia (PIRSA) by Technical Advisory Group (TAG), 31 October 2008, unpublished.
TAG (2009) Technical Advisory Group. Phase 2 Report – Validating the technical feasibility of a saturated waste remediation option for the Brukunga Remediation Project, Prepared for the Department of Primary Industries and Resources South Australia (PIRSA) by Technical Advisory Group (TAG), October 2009, unpublished.
Williams, D.J. (2009) Report on Co-Disposal Trials. Prepared for the Department of Primary Industries and Resources South Australia (PIRSA), 11 September 2009.