Cementation Canada Ltd. of North Bay, Ont. bills itself as “one of the premier shaft sinking companies in the world,” and it has the track record to back up that claim.
With some 20 projects on the go in Canada, the U.S. and elsewhere around the world, Cementation is also on record for having sunk the deepest shaft in Canada at the Kidd Creek Mine in Timmins, the deepest single lift shaft in the U.S. at the Resolution Copper Project in Superior, Arizona, and the deepest single lift shaft in the world at the South Deep Gold Mine in South Africa.
But by the end of March, Cementation crews will start a completely different sort of project at the Sifto Canada salt mine in Goderich, Ont., on the shore of Lake Huron. They will begin refurbishing the liners inside two of the mine’s three shafts, which will take almost four years, and rank among the most challenging work the company has taken on in recent years.
“Technically, this is a very different project,” says President and Chief Executive Officer Roy Slack. “It’s not like designing a shaft or shaft liner from scratch. We have to adapt to what’s there.”
In both cases, what’s there is a concrete liner that has deteriorated and sprung leaks. In some places water is seeping in. Elsewhere, it is surging through the concrete as though driven from a garden hose.
The problem is partly a function of age. Shaft one, which is now out of commission, was sunk in the late 1950s, while shaft two, currently used to move miners and materials, was built in the early 1960s.
The construction standards of the day have also played a role, says Mike Marksberry, Director of Mine Engineering with Compass Minerals Inc., the Kansas-based company which owns Sifto Canada.
“They used thicker concrete where water was an issue and thinner concrete where it wasn’t,” says Marksberry. “But over the years with ground movement from mining and everything, water has migrated everywhere.”
A third shaft, sunk in the late 1970s, remains in good shape and is not in need of repairs. It is equipped with a cage to transport miners and materials as well as skips to haul salt to the surface and will remain in operation while the other two are refurbished.
All three shafts were sunk to a depth of 543m to tap a vast, nearly pure salt deposit which is some 25m thick and extends for hundreds of square miles beneath Lake Huron.
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