Stress testing geomorphic and traditional tailings dam designs for closure using a landscape evolution model

Authors: Slingerland, N; Beier, NA; Wilson, GW Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_rep/1915_120_Slingerland

Cite As:
Slingerland, N, Beier, NA & Wilson, GW 2019, 'Stress testing geomorphic and traditional tailings dam designs for closure using a landscape evolution model', in AB Fourie & M Tibbett (eds), Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1533-1544, https://doi.org/10.36487/ACG_rep/1915_120_Slingerland



Abstract:
The design of tailings dams with respect to closure has evolved over the last 50 years; however, their long-term erosion continues to be a challenge. Erosion is a well-known and established failure mode with several high-profile incidents at hydro-electric dams in recent history, such as the Oroville, California (2017) and Archusa Creek, Michigan (1998) dams. The goal of tailings dam closure and reclamation is often to create a ‘walk-away’ state: an impediment to achieving this is long-term erosion. Various design strategies have been employed as alternatives to uniform downstream dam slopes that are erosion-prone due to the long and steep flow paths generated. This study used the CAESAR-Lisflood landscape evolution model to stress test five different dam designs using Alberta oil sands climate and material inputs. The fictional dam designs included a traditional uniform slope, a platform-bank slope, a catena or ‘s-curve’ slope, an alternating uniform-to-catena slope, and an alternating uniform-to-catena slope with armouring along the central channel. Stress testing allowed for efficient comparative assessment of the long-term geomorphic stability of the designs, and a method of quantifying dam performance for cost-benefit analysis. Results indicated that more natural slopes performed better than those uncommon in nature, and that mobile channel base sediment was more beneficial than a rigid (armoured) base. This has implications for long-term cost-benefit analyses for tailings dam construction and maintenance.

Keywords: dam design, erosion, geomorphology, landscape evolution model, mine closure, sustainability