Song, Q, O'Kane, M, Dhadli, N & Matthews, J 2011, 'Deposition thickness and evaporative drying for oil sands tailings in northern Alberta', in AB Fourie, M Tibbett & A Beersing (eds), Proceedings of the Sixth International Conference on Mine Closure
, Australian Centre for Geomechanics, Perth, pp. 373-382.
Directive 074 issued by Alberta Energy Resources Conservation Board (ERCB) requires that fine tailings materials deposited each year must achieve a minimum undrained shear strength of 5 kPa within one year following deposition. Challenged with this requirement, oil sands owners and operators in Alberta, Canada, are evaluating several opportunities for tailings dewatering. One opportunity is taking advantage of the evaporation potential, following deposition, to assist with dewatering tailings. Three types of tailings, namely, non-segregated tailings (NST), mature fine tailings (MFT), and treated thickened tailings (TT) were generally produced by Shell Canada Limited’s Albian Sands Energy operation with different treatment technologies. These three types of tailings have various consolidation behaviours and initial solids contents, which imply that the tailings deposition thickness will be different from each other in order to achieve the ERCB-D 074 requirements while utilising evaporative drying to dewater the fluid tailings. The average annual precipitation and potential evaporation are approximately 470 and 640 mm, respectively in the northern Alberta area. A simplified methodology based on tailings consolidation properties, meteorological data, and initial state of tailings deposits is presented in this paper to determine appropriate fine tailings deposition thicknesses, in the context of the exceedance probability of achieving the desired solids content (and hence undrained shear strength), for different times of the year. The maximum yearly deposition thickness with 80% probability of exceedance is approximately 200 cm for NST with enhanced initial deposition solids content, approximately 160 cm for enhanced TT, and approximately 144 cm for enhanced MFT. The methodology presented in this paper can be used to develop understanding for potential tailings deposition thickness that will have a high probability of achieving the target solids contents and shear strengths due to evaporative drying. Site-specific conditions can then be used to optimise fine tailings management.
Allen, R.G., Pereira, L.S., Raes, D. and Smith, M. (1998) Crop evapotranspiration—Guidelines for computing crop water requirements—FAO Irrigation and drainage paper 56. Food and Agriculture Organization of the United Nations, Rome, Italy, viewed 11 April 2011,
Boswell, J.E.S. (2009) Strategies for dealing with fine fluid tailings and suspended fines: some international perspectives, Proceedings of the Thirteenth International Conference on Tailings and Mine Waste ’09, D.Sego, M. Alostaz and N. Beier (eds), 1–4 November, Banff, Canada, pp. 171–184.
Boswell, J.E.S. and Sobkowicz, J.C. (2010) Environmental assistance for tailings disposal, Proceedings of the 63rd Canadian Geotechnical Conference and 6th Canadian Permafrost Conference, 12–16 September, Calgary, Canada, pp. 665–669.
Chen, X.Y. (1992) Evaporation from a salt-encrusted sediment surface: field and laboratory studies, Australian Journal of Soil Research, CSIRO Publishing, Vol. 30, pp. 429–442.
Energy Resources Conservation Board (ERCB) (2009) Tailings performance criteria and requirements for oil sands mining schemes. Directive 074, ERCB, Edmonton, Canada, 14 p.
Fahey, M. and Fujiyasu, Y. (1994) The influence of evaporation on the consolidation behaviour of gold tailings, Proceedings of the 1st International Conference on Environmental Geotechnics, Edmonton, Canada,
Hyndman, A. and Sobkowicz, J. (2010) Oil sands tailings: reclamation goals & the state of technology, Proceedings of the 63rd Canadian Geotechnical Conference and 6th Canadian Permafrost Conference, 12–16 September, Calgary, Canada, pp. 642–655.
Malek, E., Bingham, G.E. and McCurdy, G.D. (1990) Evapotranspiration from the margin and moist playa of a closed desert valley, Journal of Hydrology, Elsevier B.V., Vol. 120, pp. 15–34.
Penman, H.L. (1948) Natural evapotranspiration from open water, bare soil and grass, Proceedings of the Royal Society of London, Series A, Mathematical and Physical Sciences, The Royal Society, Vol. 193, pp. 120–146.
Seneviratne, N.H., Fahey, M., Newson, T.A. and Fujiyasu, Y. (1996) Numerical modelling of consolidation and evaporation of slurried mine tailings, International Journal for Numerical and Analytical Methods in Geomechanics, John Wiley & Sons, Ltd., Vol. 20, pp. 647–671.
Simms, P., Dunmola, A. and Fisseha, B. (2009) Generic predictions of drying time in surface deposited thickened tailings in a “wet” climate, Proceedings of the Thirteenth International Conference on Tailings and Mine Waste ’09, D. Sego, M. Alostaz and N. Beier (eds), 1–4 November, Banff, Canada, pp. 749–757.