Simon Racicot, director of production and maintenance with Hydro-Quebec, told reporters on Thursday evening (April 25th) the dam at Chute Bell was built to withstand what he called a millennial flood. “That means a flood that happens every 1,000 years,” he said. Hydro workers discovered earlier in the day the millennial level of water had been reached. “We are confident that the structure is solid,” Racicot said. “But the protocols force us to warn people of the danger.
The largely rural section of river affected is in Quebec’s Lower Laurentians region, about 140 kilometres west of Montreal, stretching about 18 kilometres south to the Ottawa River. Quebec provincial police tweeted they were helping about 250 people get clear of the affected area as a preventive measure. Several dozen officers were taking part in the operation with the aid of all-terrain vehicles and helicopters. About a dozen people living in areas not easily reached by land were airlifted out. Tom Arnold, mayor of Grenville-sur-la-Rouge, said it could be weeks before evacuees can return home, even if the dam holds.
Hydro-Quebec said through social media that if the dam breaks, the water flow would have minimal impact on locations downstream once it joined with the Ottawa River. According to the utility’s web site, the concrete dam, built in 1942, is 19 metres high and almost 60 metres long. It has the capacity to hold back 4 million cubic metres of water.
Regular updates are being provided on the Hydro-Quebec Twitter page: https://twitter.com/hydroquebec/status/