Mines

List of Abandoned Mining Sites

The following paragraphs provide details of the main steps in the management of abandoned mining sites taken over by the Ministère de l’Énergie et des Ressources naturelles (MERN).

Definitions

Acid mine drainage

Outflow of acidic water containing dissolved metals produced by oxidation of sulphide minerals contained in waste rock, ore and mine tailings following exposure to air and water.

Contaminated neutral drainage

Outflow of water containing dissolved metals in concentrations over and above environmental standards, when the pH is close to neutrality.

Main steps

1. Inspection

Abandoned mining sites are visited regularly, for visual assessment and identification of obvious risks, so that remedial action can be taken and developments monitored as needed. Frequency of visits depends on the condition of the site and the problems identified.

2. Site characterization

Characterization is a process that determines the presence of contamination at a site to identify the ensuing risks and impacts. It includes actions ranging from sampling, surveys, drilling and installation of observation wells. Environmental characterization is used to identify real and anticipated environmental impacts at a given the site.

3. Conceptual engineering

Conceptual engineering consists in selecting a reclamation scenario for a mining site. The elements used to assess the proposed reclamation options are presented, along with the scenario selection process (design criteria, assumptions, risk analysis, etc.). Where necessary, different reclamation techniques are combined to address the specific features of the site and identify a suitable reclamation scenario.

4. Validation and optimization of the reclamation scenario

The chosen reclamation scenario must use the best available reclamation techniques and be technically and economically feasible. Once chosen, it must be validated. Modelling and laboratory or field testing may be required to confirm certain design elements. The scenario is then adjusted and optimized, based on the test results.

5. Detailed engineering (plans and specifications)

Detailed engineering, which includes the production of plans and specifications for the reclamation scenario, is the final stage before reclamation work actually takes place. It is carried out after validation, optimization and adjustment of the scenario, and provides the technical details required to carry out the work.

6. Reclamation work

At this stage, the work shown in the plans and specifications is performed by a contractor chosen by means of a public call for bids.

7. Monitoring and maintenance

The MERN is responsible for post-completion monitoring of reclamation work. Surveillance and maintenance may be required to ensure the integrity of the site, and environmental monitoring is also carried out.