About mine site reclamation

The government oversees the reclamation of active mine sites and takes over the reclamation of abandoned mine sites under government responsibility.

The government analyzes and approves plans to rehabilitate and reclaim active mine sites. It also their application and verifies that the condition of the mine sites is satisfactory monitors after reclamation work.

When a mine site has been abandoned, and there is no one responsible for it, the government assumes the liability for its reclamation.

Leading-edge expertise

Québec has recognized expertise in mine reclamation, which includes the development of reclamation solutions. Scientific knowledge is required to select the reclamation techniques to be used, and that knowledge evolves rapidly. The techniques must be sustainable. In addition, their potential to achieve reclamation objectives and long-term effectiveness must be demonstrated.

For their part, mining companies must file a closure plan related to their mining activities as well as a financial guarantee equal to the cost of that reclamation work. They must therefore think about the reclamation steps as soon as they start their operation.

A mine can be underground, accessible through a mine shaft, or an open pit. Access to the ore (mineral of interest) requires extraction of waste rock, i.e., rock that has no economic value. Tailings are also generated as a result of plant processing.

On the surface, mine waste rock is typically stored in piles. As for mine tailings, they are stored in ponds. Waste rock piles and tailings ponds are storage areas.

Other infrastructure, such as many buildings (plants, administrative facilities, garages, etc.), water basins, surface openings, roads and ditches are also part of the mine site.

All these elements need to be reclaimed at the end of the mine's life.

Mine drainage prevention

One of the most significant environmental problems associated with mining is the presence of mine drainage resulting from the exposure of waste rock and tailings to climatic conditions.

Acid mine drainage occurs naturally when rock containing sulphides (e.g., pyrite) is in contact with water and air. This reaction releases sulphuric acid and heavy metals, which then contaminate soils and watercourses.

For contaminated neutral drainage, the water is not acidic but is still charged with metals and other dissolved contaminants. These phenomena are accentuated when the rock is crushed, as after ore processing.

Therefore, it is essential to design and reclaim storage areas to prevent mine drainage generation.

Main reclamation methods

The main reclamation methods to prevent mine drainage are aimed at limiting the presence of oxygen, water or sulphides, thereby reducing the production of contaminants in the environment.

To do so, covers are installed over mine tailings and waste rock. To limit water infiltration, covers may consist of one or more layers of materials with specific properties and varying thickness, depending on site conditions and reclamation objectives. These materials may be natural, but it is also possible to use synthetic materials such as a geomembrane or bentonitic geocomposite.

To limit oxygen supply, the installation of a cover with low oxygen permeability is ideal. Water, heavily water-saturated soils and synthetic materials can act as a barrier to oxygen. These oxygen barrier techniques include water covers, single-layer covers with a elevated water table and covers with capillary barrier effects.

Additional water treatment may be required at the mine site to adjust pH and alkalinity or to encourage precipitation of metals and sulphates.

Ensure the physical stability of the storage areas

Storage areas and reclamation methods shall be designed to reduce the risks associated with site integrity and possible structural failure.

Closure to a satisfactory condition

The goal of mine site reclamation is to bring a site to a state deemed satisfactory by the government. The condition of a site is considered satisfactory when it:

• integrates with their environment;
• is safe for the environment and the public;
• requires minimal maintenance and intervention.

To achieve this result, it is necessary to:

• secure excavated areas, including the open pit;
• ensure the physical and chemical stability of waste rock piles and tailings ponds;
• remove all buildings or infrastructures;
• revegetate the site so it can return close to its original natural state.

The solutions put in place must be recognized as effective and require minimal follow-up and maintenance.