Historically mine waste has been deposited in above-ground mine waste management impoundments which are conventionally reclaimed, using a combination of soil and vegetation covers. This technology works well for non-reactive wastes; however, it is less effective with wastes that contain sulphide minerals, which when exposed to atmospheric air and water, result in acid mine/rock drainage and metal leaching with the potential for serious consequences for the environment if not properly treated.
Significant progress in mine waste management strategies has been made in the last 25 years. The development of water covers has minimized the potential for sulphide minerals to react with oxygen in the submerged waste, thereby preventing or significantly reducing the potential for acid mine/rock drainage and metal leaching. Water covers minimize or eliminate long-term effluent treatment and management requirements, limit environmental impacts and facilitate site closure in a shorter time frame of 10 to 20 years rather than 100 or more years for dry covers.
Older mine tailings sites with perpetual effluent treatment requirements are typically reclaimed by lime/limestone and fertilizer amendments to establish self-sustaining vegetation covers. Organic amendments are also used to accelerate the establishment of crops or trees on tailings. With changes in the legislation in some jurisdictions to eliminate organic materials from landfills, there is an increasing pressure to divert this organic material onto carbon and nutrient-depleted lands for reclamation. Many mines are already using biosolids on tailings for revegetation. There are questions, however, related to how this strategy may affect water quality and tailings stability in the long-term. By providing a supply of carbon, nitrogen and phosphorus to the system, the cover material may inadvertently promote the growth of bacteria capable of exerting significant deleterious effects on the local geochemical environment.
CanmetMINING, working in partnership with the mining industry, academia and others is undertaking research to address issues such as:
- enhancing the current water-cover technology and adaptation of the technology for the northern climatic conditions;
- minimizing future legacy and ongoing liability by obtaining facility closure, and by clarifying the effects of current reclamation practices on effluent water quality and tailings stability at older mine sites; and
- minimizing mining footprint and prevent metal mobilization from mine waste management facilities by developing optimized reclamation strategies.
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