The exploration phase consists of prospecting for promising mineral deposits and a feasibility assessment of their viability from both technical and financial perspectives. Because this first phase is relatively short compared to the other phases of a mine’s life cycle, it is less affected by the impacts of climate change.
On the other hand, access to prospecting areas may prove to be more difficult and exploration activities may have to be suspended should an extreme climate event (temperature, precipitation, etc.) occur. Additionally, in northern Quebec, operating equipment on frozen water bodies is increasingly risky on account of the region’s shorter, milder winters, which may have an impact on operational activities.
The operations phase is more vulnerable to the impacts of climate change, notably because it is longer in duration. During operations, water management may prove to be a significant issue due to expected changes in precipitation patterns.
Indeed, mine operators must also manage the tailings produced during this phase. These tailings are stored in containment structures, which are sometimes open. Overflows can occur at these structures if they are not designed to account for extreme precipitation events, which are expected to increase in both intensity and frequency over the coming decades. Additionally, longer and more frequent droughts may trigger decreased water availability needed for operations.
On the other hand, mining and access infrastructure (e.g. roads, airports) may be damaged by extreme climate events as well as thawing permafrost, which is greatly accelerated by climate change. Transporting minerals therefore becomes more challenging, which has an economic impact on the entire distribution cycle.
Ouvrage de confinement pour résidus du site minier de Barvue (crédit photo : MERN)
Definition | Containment Structures
Containment structures are various types of constructions (pools, dams, dikes, etc.) designed to store tailings or contaminated water produced in the course of mining operations. These toxic substances can contaminate the environment and must therefore be safely and effectively stored over the long term. Seepage into the surrounding ecosystems can affect local flora and fauna, not to mention natural resources such as drinking water. Communities in proximity to mines may therefore find themselves with low-quality drinking water, as well as contaminants that have bioaccumulated in the species that they consume (fish, game, plants, etc.).
Of a mine’s three phases, the restoration phase is the longest, sometimes lasting up to a century. This phase aims to contain dangerous tailings and restore the surrounding environment to its original state. Given the long duration of this phase, the design should take into consideration anticipated changes in the climate , as the facilities will be exposed to more significant changes than they were in the past. Changes in temperature normals and precipitation patterns can therefore compromise the efficacy of mine restoration methods. For example, oxygen barriers that aim to isolate mine tailings and prevent them from oxidizing are generally in the form of water.
Integration of climate change into the design and rehabilitation of tailings storage facilities
This study responds to a need expressed by mining companies and the provincial government to review mining waste management measures by considering climate change and its impacts on the industry in order to ensure the long-term sustainability and safety of tailings structures.
The uptick in extreme precipitation events as well as the aggravation of dry periods can threaten their stability and efficacy (overflow, erosion, increased pore pressure, decreased aqueous layer, etc.).
All restoration methods will be influenced by climate change but at different degrees and according to different characteristics, several of which are site-specific. Thus, the same technology used at two different sites exposed to similar climate conditions will not necessarily exhibit the same vulnerability.
Some containment structures may also be affected by more abundant vegetation brought about by higher temperatures. Additionally, for mines lying at more northerly latitudes of the province, thawing permafrost may compromise the efficacy of the different methods used to contain tailings, which must remain intact for the entire restoration phase. Due to climate change, the risks of seepage and environmental contamination must therefore be considered in this phase.