Improving performance of soil covers over waste rock dump tops in dry climates
|
Authors: Williams, DJ |
DOI https://doi.org/10.36487/ACG_rep/1352_22_Williams
Cite As:
Williams, DJ 2013, 'Improving performance of soil covers over waste rock dump tops in dry climates', in M Tibbett, AB Fourie & C Digby (eds), Mine Closure 2013: Proceedings of the Eighth International Seminar on Mine Closure, Australian Centre for Geomechanics, Cornwall, pp. 265-278, https://doi.org/10.36487/ACG_rep/1352_22_Williams
Abstract:
Soil covers over mine waste rock dump tops in dry climates are intended to limit the ingress of oxygen and/or to limit the net percolation of rainfall infiltration into the underling potentially reactive waste rock excavated, in particular, on open pit mining. The climate in which the mine is located plays a key role. The aim of limiting the ingress of oxygen into the dump is to minimise the oxidation of any sulphidic waste rock, which is often found on mining an ore body beneath the groundwater table. The aim of limiting the net percolation of rainfall infiltration into an oxidising waste rock dump is to limit the transport of the oxidation products to the environment. In the absence of a water cover, limiting the ingress of oxygen into a dump is best achieved by using a near-saturated soil cover, while limiting net percolation is potentially achieved by applying a rainfall-shedding soil cover, or by applying a store-and-release soil cover. In practice, there are many impediments to achieving good performance from a soil cover over a waste rock dump. It takes a number of years to construct a waste rock dump as open pit mining proceeds. The waste rock will emerge from the pit in a relatively dry state, and it will readily become, and will remain during construction of the dump, well oxygenated. Hence, there is ample opportunity for sulphidic waste rock in the dump to oxidise during the construction of the dump, so that limiting further oxygen ingress may be of limited value. During construction, a dump is also open to rainfall infiltration, allowing the wetting-up of the dump and the ultimate transport of any oxidation products that form. When the dump is eventually covered, the best that can be achieved is limiting further oxygen ingress and/or limiting the transport of oxidation products. However, this assumes that an effective cover can be constructed. This is made difficult by the ongoing settlement of the dump, by the potential absence of suitable cover materials, by the use of large-scale mine site equipment to construct the cover, by insufficient attention paid to cover design, construction and maintenance, and by climatic variability. The relatively poor performance of dry-climate soil covers over waste rock dumps is compared with the performance of dry-climate soil covers over landfills, which typically display good performance.
References:
Ayres, B.K., O’Kane, M.O., Christensen, D. and Lanteigne, L. (2002) Construction and instrumentation of waste rock test covers at Whistle Mine, Ontario, Canada, in Proceedings Tailings and Mine Waste Vol. 02, 27–30 January, Fort Collins, Colorado, pp. 163–171.
Benson, C., Albright, W., Roesler, A. and Abichou, T. (2002) Evaluation of final cover performance: field data from the alternative cover assessment program (ACAP), in Proceedings Waste Management Vol. 02, 24–28 February 2002, Tucson, pp. 1–18.
DITR (Department of Industry Tourism and Resources) (2006) Mine Rehabilitation Leading Practice Handbook, Australian Government.
DITR (Department of Industry Tourism and Resources) (2007) Managing Acid and Metalliferous Drainage Leading Practice Handbook, Australian Government.
DITR (Department of Industry Tourism and Resources) (2009) Mine Closure and Completion Leading Practice Handbook, Australian Government.
EGi (Environmental Geochemistry International) (1997) Waste Rock Characterisation for Century Mine.
Fredlund, M.D., Fredlund, D.G. and Wilson, G.W. (1997) Prediction of the soil water characteristic curve from grain size distribution and volume mass properties, in Proceedings Third Brazilian Symposium on Unsaturated Soils, 22–25 April, Rio de Janeiro, Brazil, 12 p.
Fredlund, D.G., Xing, A. and Huang, S. (1994) Predicting the permeability function for unsaturated soils using the soil water characteristic curve, Canadian Geotechnical Journal, Vol. 31, pp. 533–546.
INAP (International Network for Acid Prevention) (2003) Evaluation of the Long-term Performance of Dry Cover Systems, Final Report, O’Kane Consultants Inc. (ed.), Report No. 684–02.
MEND (Mine Environment Neutral Drainage Program) (2001) Prevention and Control, Vol. 4, Manual 5.4.2d., G.A. Tremblay and C.M. Hogan (eds), CANMET.
O’Kane, M.O. and Wels, C. (2003) Mine waste cover system design – linking predicted performance to groundwater and surface water impacts, in Proceedings Sixth International Conference on Acid Rock Drainage, 12–18 July, Cairns, Australia, pp. 341–349.
Ricard, J.F., Aubertin, M., Firlotte, F.W., Knapp, R. and McMullen, J. (1997) Design and construction of a dry cover made of tailings for the closure of Les Terrains Aurifères site, Malartic, Québec, Canada, in Proceedings Fourth International Conference on Acid Rock Drainage, 31 May–6 June, Vancouver, Canada, Vol. 4, pp. 1515–1530.
Rykaart, E.M., Hockley, D., Noël, M. and Paul, M. (2006) Findings of international review of soil cover design and construction practices for mine waste closure, in Proceedings Seventh International Conference on Acid Rock Drainage, 26–30 March, St. Louis, Mo., pp. 1804–1822.
USEPA (2011) Fact Sheet on Evapotranspiration Cover Systems for Waste Containment, EPA 542-F-11-2011, and .
Wickland, B.E., Wilson, G.W., Wijewickreme, D. and Klein, B. (2006) Design and evaluation of mixtures of mine waste rock and tailings, Canadian Geotechnical Journal, Vol. 43, pp. 928–945.
Williams, D.J., Wilson, G.W. and Currey, N.A. (1997) A cover system for a potentially acid forming waste rock dump in a dry climate, in Proceedings Fourth International Conference on Tailings and Mine Waste, 13–17 January, Fort Collins, Colo., pp. 231–235.
Williams, D.J., Currey, N.A. and Ritchie, P.J. (2003) Kidston waste rock dump design and ‘store and release’ cover system seven years on, in Proceedings Sixth International Conference on Acid Rock Drainage, 14–17 July, Cairns, Australia, pp. 419–426.
Williams, D.J., Stolberg, D.J. and Currey, N.A. (2006) Long-term performance of Kidston’s ‘store/release’ cover system over potentially acid forming waste rock dumps, in Proceedings Seventh International Conference on Acid Rock Drainage, 26–30 March, St Louis, Mo., pp. 2385–2396.
Wilson, G.W., Williams, D.J. and Rykaart, E.M. (2003) The integrity of cover systems – an update, in Proceedings Sixth International Conference on Acid Rock Drainage, 14–17 July, Cairns, Australia, pp. 445–452.
Yanful, E.K. and Lin, M. (1998) An integrated approach to designing soil covers for reactive mine waste, in Proceedings Fifty-First Canadian Geotechnical Conference, 4–7 October, Edmonton, Canada, Vol. I, pp. 141–148.
Zhan, G., Schafer, W., Milczarek, M., Myers, K., Giraudo, J. and Espell, R. (2006) The evolution of evapotranspiration cover system at Barrick Goldstrike Mines, in Proceedings Seventh International Conference on Acid Rock Drainage, 26–30 March, St Louis, Mo., pp. 2585–2603.
© Copyright 2024, Australian Centre for Geomechanics (ACG), The University of Western Australia. All rights reserved.
View copyright/legal information
Please direct any queries or error reports to repository-acg@uwa.edu.au
View copyright/legal information
Please direct any queries or error reports to repository-acg@uwa.edu.au