Sudbury’s 318-metre Superstack to be demolished starting next year

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The second-tallest freestanding structure in Canada has been slated for demolition. But unlike the CN Tower or one of Toronto’s many skyscrapers, this behemoth is located in Sudbury. It’s a smokestack.

The Superstack, as it’s known, is owned by Brazil-based Vale and is part of the mining company’s Copper Cliff processing facility. At 381 metres tall it is in Canada second only to the 533-metre CN Tower in height, and would loom over even The One, a 306-metre building under construction at Toronto’s Yonge/Bloor intersection, and destined to be Canada’s tallest building when completed.

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The Superstack is the tallest chimney in the Western hemisphere, the second-tallest freestanding chimney in the world (after one in Kazakhstan) and the 51st tallest freestanding structure on Earth, with most of the others being skyscrapers rather than chimneys or towers. (Also, a freestanding structure is one that supports and steadies its own weight, as opposed to being anchored by guy wires.)

It’s also no longer in use. Built in 1970 and fully operational two years later, the smokestack was taken out of service in 2020 after the company cut sulphur dioxide emissions at the Copper Cliff Complex by 100,000 tonnes per year, in line with provincial limits. Now it’s coming down.

The Superstack is 35 metres wide at its base, with one-metre-thick concrete walls, tapering to just under 17 metres at the top, where its walls are about 25 centimetres thick. It got a true test of its strength in 1970 when, a day before it was completed, a tornado struck the city. Though the smokestack swayed, damage was minimal, and six workers who were on the structure at the time were unharmed.

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In a press release this week, Vale said: “Since 2020 the Superstack has been inactive but work on preparing it for dismantling has not stopped.” It added: “Time was spent slowly cleaning the stack’s interior, removing the steel liner and sealing or removing accessory structures in preparation for a future dismantling.”

With just the concrete shell remaining, the plan is to dismantle the structure over a five-year period beginning in 2025. In the meantime, Vale’s much smaller Copperstack smokestack (just 137 metres tall), which is situated on the same site and has also been decommissioned, will be demolished.

Vale has released a video showing how the Copperstack will be taken down from the top, with debris basically being thrown down the chimney, and periodically removed from a hole cut in the base. That’s expected to take less than two years.

The Superstack dismantling will take some 40,000 person-hours of labour, with as many as 35 workers on site during the operation.

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Although some would consider it an eyesore, the Superstack has been a part of the Sudbury skyline for more than 50 years, and the company is reaching out to the public for ideas on how to commemorate its passing. Options include a digital archive and charity coffee table book; a mural to be located within the City of Greater Sudbury; or a monument to the Superstack, presumably at a greatly reduced scale. Anyone can vote on the proposals until Sept. 27.

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