Provincial engineers are warning that the suspension lines of Quebec City's Pierre-Laporte Bridge are weak enough that some could give way at any time, according to information and reports obtained by Radio-Canada.
At the request of Quebec's Transport Ministry, five cables that had been removed from the bridge were tested by a laboratory at the engineering school Polytechnique Montreal, to assess their strength.
The tests found the cables' resistance was the weakest they've ever been since tests began nearly seven years ago. Two of the five cables were urgently replaced last fall, with one cable only reporting 43 per cent of its original strength, the worst result in the bridge's history.
According to the report, while the 160 suspension lines of the bridge are checked during general inspections, it's impossible to know their real condition and remaining strength until they are removed and tested. However, visual inspections also report the cables are increasingly rusty.
The authors of the report, who are both engineers with the Transport Ministry, recommended the replacement of all the cables, "the sooner the better," noting that some replacements need to be done in the short-term to avoid emergency replacements down the line.
The report also warns of the potential for a "cascading failure," as when one cable breaks, the nearby cables would need to pick up the slack. But the neighbouring cables may not be able to handle the added weight, creating a domino effect, the report says.
"It is absolutely necessary to avoid the breaking of one or more lines with the unlikely but potential end result of a catastrophic break … that could ultimately cause the collapse of the structure," the report says.
"How quickly the damage will progress is almost impossible to estimate. Management of the risk of line breakage is not acceptable over a long period."
Team responsible for bridge hadn't seen report
Christian Mercier, the major structures coordinator at the Chaudière-Appalaches territorial branch for the Transport Ministry said he had not received the report signed by two of the ministry's engineers.
Mercier, who leads the team that manages and plans work and inspections along the Pierre-Laporte Bridge, said he knew a report was coming, but he didn't know the urgency of the contents.
"We follow the recommendations we receive. We did not have any recommendation that the lines should be replaced in the very short term," he told Radio-Canada.
Mercier said he didn't know why the document, which senior officials with the ministry have reportedly had for almost two months, was not sent to him.
He said his team relies on the expertise of an American firm, which is carrying out additional tests on the cables. The results of the Polytechnique tests had been sent to the firm, and Mercier said he expects to receive their recommendations shortly.
Few cables have ever been replaced
There were no previous plans to replace the bridge's 160 cables in the short-term. According to documents seen by Radio-Canada, the government had planned to replace them over a period of five to 15 years.
Only 15 cables have ever been replaced on the bridge since it opened. The other 145 are originals from the bridge's construction in 1970.
François Bonnardel, Quebec's transportation minister, said in a statement that he only found out about this report on Tuesday, and that it was unacceptable that it wasn't shown to him when the ministry first received it.
Earlier this year, the union representing government engineers expressed concern about the bridge, saying it required immediate work to ensure people's safety. At the time, Bonnardel called their comments irresponsible.
The union is now asking the minister to apologise for his comments.