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Bridge lanes closed after girder crack found

Aug 30, 2011 | 9:17 AM

The city has closed southbound lanes on the Diefenbaker Bridge as a precautionary measure after a crack was found in one of the bridge’s support girders.

On Sunday, a local resident spotted the large crack, which the city calls a fatigue failure, while canoeing on the river.

After preliminary inspections, the city moved to close the southbound lanes in order to reduce the load on the girder.

“What it looks like is that we have a crack that completely goes through the girder and at the bottom it’s about an inch in width,” said city manager Robert Cotterill.

“As soon as we saw the failure mechanism we knew that we had to take out the load off it until you know what it will take to put it back into condition and since we are not able to calculate at this time what the effect is we have to assume the worst.”

Bridge still safe

At a press conference on Tuesday, Mayor Jim Scarrow said that despite the closure, the overall support structure of the bridge was safe.

“At this point, it could be considered serious, but not dangerous,” he said.

“But it was prudent for the city to have acted as quickly as they did in shutting down the southbound lanes.”

Cotterill agreed with the mayor's statement and provided some technical information about the bridge's structure.

“What we appear to have is a fatigue failure that wasn’t there when inspected,” he said. “Is it safe? Right now, we believe it is.”

“There are two sides to bridge and each one acts independently so what we’ve done is we’ve moved the loads from the southbound lanes to the northbound lanes.”

Cause undetermined

Cotterill said there wasn’t any way of knowing what the cause of the crack was.

“(To determine) causes is really difficult,” he said.

“The kind of failure indicates a fatigue but we’ll wait until the final report comes in before we know exactly why.”

Cotterill said it was a surprise because the city had recently contracted a biannual bridge inspection that determined that the bridge was safe to operate at its current load.

Lanes to be closed indefinitely

Cotterill explained that the next step would be to conduct detailed studies and find out what the best course of action would be to bring the bridge back into full operation. He said the inspection would look at the extent of the failure and if there are others on the bridge.

However, he said they would be limited in their response time due to the availability of steel and bridge experts.

Cotterill said the city would be working with the province to put in place a load restriction to reduce strain on the bridge in the meantime.

Load restriction in place

At about 4 p.m. the city put in place a load restriction on the bridge. Vehicles with loads over 33,000 pounds are prohibited from crossing the bridge. Alternative routes are available through the city's public works department.

The load restriction will remain in place at least until a bridge inspection can be conducted on Aug. 31.

adesouza@panow.com