06/28/2013 06:44 EDT | Updated 08/28/2013 05:12 EDT

Calgary Train Derailment: Tanker Cars Drained, Cleared From Broken Bonnybrook Bridge

CALGARY - Six tanker cars that teetered on a partially collapsed railway bridge over Calgary's swollen Bow River were successfully removed early Friday.

Five of the derailed cars from a Canadian Pacific Railway freight train (TSX:CP) were originally carrying a product used to dilute raw oilsands bitumen, but workers earlier removed it to new cars on an adjacent stable bridge.

The partially collapsed structure gave way after most of the train had crossed. The rail cars were stabilized and locomotives positioned on each end of the damaged bridge pulled them safely to each side.

"They lifted it up and then they pulled in both directions and broke the coupler in the middle, so three of the damaged cars went one way and three went the other," said Calgary's acting fire Chief Ken Uzeloc.

"This came off without incident," he said.

"There was no product released at all into the Bow River and no injuries related to this and, again, in less than 24 hours those cars were removed. Now CP will start working on the bridge repair replacement based on their engineers."

Hunter Harrison, CEO of Canadian Pacific Railway, called the broken bridge an "extraordinary" event. He said piers at the bottom of the river failed when raging river water scoured away gravel. Harrison said divers couldn't get into the water to inspect underneath because it was too dangerous.

The Transportation Safety Board said it will investigate the incident, something that could take as long as a year.

Spokesman George Fowler confirmed that it appears "scouring" caused the collapse.

"Bridges fail," he told a news conference Friday near the bridge. "The primary cause of fail is what you see behind me — scour, undermining of the foundation. It is a very rare event that the superstructure, that the steel itself will fail."

He said what happened is clear, but figuring out why it happened will take longer.

On Friday, Deepak Obhrai, MP for Calgary East, said the incident and CP's explanation for it was unacceptable.

Obhrai, who represents the area where the bridge is located, questioned why CP allowed rail traffic to resume if the entire bridge hadn't been checked.

"You don’t need a rocket scientist to figure out that with massive flooding the base of the piers could be weakened, and if they could not inspect the base, as CP has said, then traffic should have been stopped until inspection of the piers was possible," he said.

Harrison said the company had no idea how long record water levels would remain and CP didn't want to "jeopardize commerce."

"Corporate profit cannot trump people's well-being," Obhrai suggested.

Uzeloc said there were concerns that things could have ended much worse.

"You had five railcars full of flammable liquid that if they had ruptured or opened up could have leaked into the river," he said.

"You also had railcars, if they had gone into the river, would have floated down a significant portion of the river, then could have run into other bridge abutments or caused damage further down."

The worst flooding in Alberta history caused extensive damage in Calgary and forced 100,000 people from their homes.

Other parts of southern Alberta, particularly the town of High River, south of Calgary, were also devastated by flooding.

Calgary Mayor Naheed Nenshi was initially critical of CP. Hours after the derailment, he questioned when and how many times CP had inspected the bridge. Later in the day he said that he and Harrison had spoken and the company apologized for what had happened.

Uzeloc said the bridge collapse initially sounded like some sort of emergency preparedness exercise.

"I think we're due for a couple of nice, calm days."

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