Sinking bridge a repair headache

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This article was published 25/08/2009 (6101 days ago), so information in it may no longer be current.

DYNAMITE or robots?

Or both, perhaps?

Those are just two ideas percolating in the minds of engineers and construction experts as they ponder what should be done with the sag­ging St. Adolphe bridge.

Driving their thinking is that fixing the bridge should not put anyone at risk, Ron Weatherburn, head of construction and maintenance for the province, said Monday.

But nothing can be done immediately until the bridge stops shifting, he added.

"The bridge continues to move," he said.

The province first closed the bridge that spans the Red River at Provincial Road 210 last Thurs­day when workers discovered the second pier from the west had sunk several inches. That pier continued to sink over the next 24 hours, forcing the province to barricade the bridge for the fore­seeable future. It’s now dropped more than three metres and caused the bridge deck to buckle.

Weatherburn said the shifting slowed down over the weekend and now officials are putting together a plan to fix it.

That means the pier and a portion of the span must be demolished and replaced.

"We are evaluating alternatives for controlled demolition of the affected spans, which could possibly include controlled explosive or non-ex­plosive demolition," he said.

The province is also looking at using powerful robotic saws that could be used to slowly disman­tle pieces of the bridge and eliminate any danger before workers move in to demolish and remove the rest.

Weatherburn said it’s hoped that most of the bridge can be salvaged, as it has not moved and appears undamaged.

Officials believe the pier started moving short­ly after the spring flood, when waters receded on the Red River. No other bridge on the Red, including in Winnipeg, has seen a similar type of movement.

"The bridge is in good condition," Weather­burn said. "It’s a slope stability issue."

Such stability problems are impossible to pre­dict, as the cause of movement is underground.

City bridge design and projects engineer Bill Ebenspanger said the difference between bridg­es in Winnipeg and the St. Adolphe bridge is the Red River Floodway. The floodway controls the level of the Red in the city in a flood situation. The St. Adolphe bridge is south of the floodway gates and as a result is prone to higher water along the Red’s banks.

Many residents in and near St. Adolphe can hardly wait to see the bridge fixed.

"If they’re going to do something, do it right," Elaine Trudel said.

Trudel said the bridge has seen steadily in­creasing traffic, including large trucks, because it connects highways 75 and 59. Truck traffic increased when the province closed parts of the South Perimeter Bridge in 2008 for repairs.

More concerning is next spring, she added. Should there be another large flood, the bridge is the main route out for many residents, she said. Without it, they might have to be evacuated.

Weatherburn said work to fix the bridge could begin this fall, but that there’s also a chance the span could collapse into the river.

"There are a lot of unknowns right now," he said.

bruce.owen@freepress.mb.ca