History
The Superstack was built by Inco Limited (and later purchased by Vale) at an estimated cost of 25 million dollars.[11] Construction was delayed by a 13-week labour dispute.[12] Construction on the structure was underway during the Sudbury tornado of August 20, 1970; the structure swayed heavily in the wind but remained standing and suffered only minor damage.[13][14][15] Six workers were on top of the construction platform when the storm hit, all of whom survived.[13][15] The same day was the final day of construction on the stack, with the construction fully completed by the evening of August 21, 1970.[16]
The stack entered full operation in 1972.[17] From the date of its completion until the Ekibastuz GRES-2 chimney was constructed in 1987 in Kazakhstan, it was the world's tallest smokestack.[18] Until the CN Tower's completion in 1975, it was the tallest freestanding structure in Canada for just under 3 years.[19][20]
Prior to the construction of the Superstack, the waste gases had contributed to severe local ecological damage. The Copper Cliff smelter was already home to some of the world's tallest stacks, including two 500 ft chimneys constructed in 1928-29 and 1936.[21][22] However, they proved to be insufficient and were compounded by open coke beds in the early-to-mid-20th century and by logging for fuel, which inevitably caused a near-total loss of native vegetation and soil erosion.[23][24] Of particular interest to geologists are the now-exposed rocky outcrops, which have been permanently stained charcoal black by pollution and acid rain in a layer which penetrates into the once pink-grey granite.[25]
The Superstack was built to disperse sulphur gases and other byproducts of the smelting process away from the city of Sudbury. It did so by placing the gases high in the air, where they normally blew right past the city on the prevailing winds.[26] As a result, the gases could be detected in the atmosphere around Greater Sudbury in a 240 km radius of the Inco plant.[27] The addition of the Superstack and dispersal of sulphur dioxide helped reduce acidity of lakes, however many lakes in the surrounding areas are still highly acidic.[28] Research has shown that the long term decrease in toxic emission will result in rehabiliation for water bodies such as the lakes near Copper Cliff.[29] During the 1970s and 80s, the sulphur dioxide plume formed a permanent, opaque, cloud-like formation running across the entire horizon as seen from a distance. Periodic inversions would cause the plume to fall into the city. [28]
Construction of the Superstack was followed by an environmental reclamation project, which included rehabilitation of existing landscapes and selected water bodies such as Lake Ramsey. An ambitious regreening plan saw over three million new trees planted within the Greater Sudbury area. The application of limestone to soil and lakes was also done to increase pH levels.[30] In 1992, Inco and the city were given an award by the United Nations in honour of their environmental rehabilitation programmes.[31][32]
On November 3, 2014, Vale announced that it may decide to stop using the stack after a $1 billion project to reduce emissions by 85% negated the need for the stack. If no other use for it was found, Vale was to decommission the Superstack, demolish it, and replace it with a much smaller chimney.[33] In 2017, Vale announced plans to decommission the Superstack upon the construction of two smaller, more energy efficient stacks.[34][35] On July 28, 2020, Vale updated that news and stated that the Superstack at its Copper Cliff Complex had been taken out of service. It would remain on "hot standby" for about two months while the replacement flue connections were tested, but it would then be demolished over the years.[36]
