Canadian Consulting Engineer

On Thin Ice in Ottawa

Every winter for almost 40 years, about a million red-nosed and toque-topped skaters glide along the Rideau Canal Skateway, Canada's largest outdoor ice rink. Few probably give thought as to how thick...

January 1, 2009   By Nerys Parry

Every winter for almost 40 years, about a million red-nosed and toque-topped skaters glide along the Rideau Canal Skateway, Canada’s largest outdoor ice rink. Few probably give thought as to how thick — or thin — the ice is that they’re skating on. Or that it might soon be growing thinner.

The agency in charge of operating the Skateway, the National Capital Commission (NCC), has always relied on National Research Council advice and basic rules of thumb, like a minimum 30 centimetres equivalent depth of ‘clear’ ice, to determine ice safety.

Ice comprises layers, with different strengths. The NCC’s traditional method for assessing ice strength was to assume ‘clear’ ice had full-strength, and ‘white’ ice (formed from frozen snow, refrozen slush, or during flooding) had half that strength. The effective ice thickness was adjusted accordingly, with every two centimetres of white ice being equal to every centimetre of clear ice.

NCC’s consultants, BMT Fleet Technology, conducted a study and concluded that flooded ice, under certain conditions, may be as strong as clear ice — and maybe even stronger. This winter, BMT will be conducting tests, and at the National Research Council laboratories, researchers will quantify the strength differences between the various types of ice to modify the ice load formula accordingly.

Razek Abdelnour of BMT Fleet Technology says that the results may allow the canal to be opened earlier, and kept open later, especially during relatively warmer years.

That’s good news for skaters and for Ottawa, which expects to earn $73 million during the three weekends of Winterlude alone.


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