Assessing mine closure and cover system design strategies with consideration for climate change risks at Aitik mine

Authors: McKeown, M; Christensen, D; Cunningham, H; Mueller, S Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2515_93

Cite As:
McKeown, M, Christensen, D, Cunningham, H & Mueller, S 2025, 'Assessing mine closure and cover system design strategies with consideration for climate change risks at Aitik mine', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-11, https://doi.org/10.36487/ACG_repo/2515_93



Abstract:
When planning for closure, mining operations need to consider that closure timeframes can be more than 100 years. Cover systems designed to support land transition plans are subject to changes in climate far into the future. Effective and safe management of climate risk requires a deliberate approach to understanding, assessing, and responding to the potential impacts of climate change at a site-specific level. It is critical that climate change risk be incorporated into closure plans and cover systems designs to enable resiliency and capacity for adaptation over the long-term. Boliden is updating its closure plan for the Aitik mine site in northern Sweden. A major component of the workflow incorporates a risk-based approach into closure planning; specifically, applying the failure modes and effects analysis (FMEA) approach to inform design.  One feature being evaluated is the engineered cover system for the potentially acid forming waste rock storage facility (WRSF), also referred to a mine rock stockpile. Okane completed one-dimensional soil–plant–atmosphere numerical modelling to evaluate design alternatives for the WRSF with inputs from synthetic climate data sets developed by The Swedish Meteorological and Hydrologic Institute. The primary objectives of the closure cover system are to manage oxygen ingress to the underlying waste materials, manage net percolation of meteoric waters, and to provide a medium for development of a vegetative cover consistent with returning land use objectives. An important failure mode identified as part of the FMEA process was that future climate extremes may not be represented by the climate datasets used in the model simulation. Okane completed cover system sensitivity analyses by modelling the driest and warmest of the available climate datasets to maximise the range of climate conditions examined. Outcomes of this assessment have highlighted the importance of considering climate change in cover system design, even while an existing compacted till design is performing well in monitored field trials under current conditions.

Keywords: climate change, cover system design, cold regions, risk assessment

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