Mining remediation in the Sudbury region of Ontario

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The Sudbury region of Ontario is rich in metallic ores. Underground mining operations at the 15 active mines of Inco Ltd. and Falconbridge Ltd. in Sudbury currently produce 51,000 tons of ore per day [note: these figures are from the late 1990s], and five other mines within 500 km of Sudbury produce another 50,000 tons per day. By-products of nickel-copper production include cobalt, platinum group metals, gold, silver, selenium, tellurium, sulfuric acid, liquid sulfur dioxide, and slag for road construction.

In the mid-1800s, during the building of the Canadian Pacific Railroad, a blacksmith working on the CPR discovered the first nickel-copper orebody known in the Sudbury area. The discovery fueled the growth and development of Sudbury, and the Canadian Copper Company mines started production in 1886. Although the ore was rich in nickel, that metal was considered of little value. Demand for nickel was less than 1,000 tons per year worldwide in 1887, and it only became a marketable commodity early in the 20th century.

As mining, stripping, sintering, and smelting operations increased with world demand for metals, Sudbury’s landscape began to look like a barren moonscape. The mining and processing of sulfide minerals released sulfur that contaminated and acidified soils. In the past 25 years, however,  residents have restored and transformed the landscape. Today, Sudbury boasts the largest, most successful environmental restoration program in the world.

Sunset skyline of Sudbury, Ontario, Canada, with the Inco Superstack seen across Ramsey Lake. Licensed under Creative Commons, CC-BY-SA-3.0, Image Credit: Wikimedia Commons User P199

Sunset skyline of Sudbury, Ontario, Canada, with the Inco Superstack seen across Ramsey Lake. Licensed under Creative Commons, CC-BY-SA-3.0, Image Credit: Wikimedia Commons User P199

When restoration efforts began in 1969, germinating seeds died on contact with contaminated soils, and thousands of tree seedlings planted in the first two years died within a year of planting. Residents decided to try a different approach. They applied lime to the soils to neutralize the acidity and planted grasses and clovers instead of trees. By 1974, a 3-hectare (7.4 acre) patch had a sparse grass cover. Nature took over then, and wildflowers, shrubs, and birches and poplars began to grow.

While citizens and students worked to restore the environment, the mining companies worked to reduce pollution and control wastewater quality. In 1972, Inco completed construction of a giant smokestack that reduced sulfur dioxide emissions. Inco completed a sulfur abatement program in 1994 that further reduced emissions to 10 percent, and planted the millionth tree seedling of its own land reclamation program.

Falconbridge has planted 600,000 trees on its properties in the Sudbury area since 1955. The company opened a new smelter and acid plant in 1978 that reduced sulfur emissions. The smelter was renovated in 1994 to reduce emissions further. Falconbridge recycles nearly half of the water it uses and treats wastewater to control acidity, heavy-metal content, and suspended solids. The treated water flows into a 299-hectare (494-acre) peat bog that in 15 years was rejuvenated from an acidic wasteland to a productive wetland and transformed from a hostile environment into a wildlife sanctuary.

More than 3,000 hectares (7,410 acres) of land have been restored [as of the late 1990s]. An additional 2 million trees were planted through a joint program run by the Regional Municipality of Sudbury and financed by job-creation funding from the government and industry. In recognition of its environmental transformation, Sudbury received the United Nations Local Government Honors Award at the 1992 Earth Summit in Rio de Janeiro. 

Additional Information

Case study from: Hudson, T.L, Fox, F.D., and Plumlee, G.S. 1999. Metal Mining and the Environment, p. 54. Published by the American Geosciences Institute Environmental Awareness Series. Click here to download the full handbook.