Mining Sites Reclamation: Case Studies and Environmental Challenges

The Mining Site Restoration Directorate (DRSM), in collaboration with UQAT, will present the restoration of the former East Sullivan mine site, located in Abitibi-Témiscamingue.

Operated between 1949 and 1966 for the extraction of gold, copper, and zinc, this mine left a heavy environmental legacy: 15 Mt of mine tailings generating acid mine drainage (AMD) and 0.2 Mt of waste rock spread over an area of 228 ha.

The site was restored between 1984 and 1992 by the MRNF. An organic cover composed of residual wood was applied to the oxidized tailings, to prevent the generation of AMD, and wetlands were constructed for the passive polishing of AMD-contaminated pore water. To improve AMD treatment efficiency, between 1997 and 2005, the supernatant from the constructed wetlands was also collected and pumped through the organic cover. As a result, water quality improved, and the site represents a true restoration success.

The presentation will cover the history of the site, the various stages of its restoration, and the associated monitoring and maintenance challenges to maintain the environmental success associated with the restoration of the East-Sullivan site.

The Bouchard-Hébert mine is a closed zinc operation located approximately 30 km northeast of the city of Rouyn-Noranda in the Abitibi region of Québec, Canada. The mine operated from 1987 to 2002 and was closed in 2005. In 2021 approximately 50,000 m³ of potentially acid generating (PAG) waste rock was relocated to the permanently flooded portion of the nearby open pit. This was done to both improve site aesthetics and reduce contaminant loads to groundwater downgradient and the site’s water treatment system. The waste rock is partially oxidised and has generated substantial acidity and metal-laden seepage due to acid rock drainage/metal leaching (ARD/ML) since it was deposited. An additional 18,700 m³ of waste rock was relocated to the pit in 2023 as part of ongoing reclamation activities.

Submerging PAG waste rock under water will eliminate future ARD/ML generation by these materials by preventing sulphide oxidation. This is best management practice for reactive, sulphide-bearing materials according to local and international guidelines. PAG waste rock relocated to the pit was amended with a neutralant (crushed limestone) to neutralise its existing acidity (titratable acidity plus jarosite acidity) content and thereby prevent the release of acidity and metals to groundwater once the waste rock is submerged. This talk describes how dosing rates were estimated and the process of mixing waste rock and limestone during relocation to the pit. The findings from recent sampling of the waste rock relocated in 2021 confirm that the jarosite in waste rock has decomposed.

The Solbec mine site, located in Stratford in the Estrie region, is a former copper, zinc, and lead mine that was operated during the 1960s. The concentrator ceased operations in 1977. The site was rehabilitated in the 1990s, and the flooded tailings facility has since become an artificial lake, now bordered by numerous residential properties.

The Yvan Vézina mine site, located in Destor in the Abitibi region, is a former gold mine that was active during the 1980s. The concentrator shut down in 1997. Site rehabilitation was carried out in the early 2000s. The tailings facility was drained, then covered with either non-reactive tailings or low-permeability soils depending on the area, and was subsequently revegetated.

The passage of time provides valuable insights that help inform the future management of mine sites.

Gaspé Copper Mines began production in 1951 and processed more than 150 million tonnes of ore in an on-site concentrator. A smelter was also in operation during those years, treating not only the mine’s concentrate but also concentrate from other mines, which was shipped by boat to Gaspé and then transported by truck to the smelter. The mine ceased operations in 1999, followed by the smelter in 2002. A major restoration project for the site, the town of Murdochville, and the Sandy Beach port in Gaspé was launched and continued for several years. In 2023, Osisko Metals acquired the property from Glencore. The site is now in a post-restoration phase and requires ongoing monitoring to ensure proper maintenance. At the same time, Osisko Metals is carrying out exploration and definition drilling activities. Restarting operations to develop the post-restored site poses logistical and permitting challenges, and concrete examples will be presented.