Engineer questions repair strategy for Quinpool Road bridge
'It seems like they're kind of taking a brute-force method,' says structural engineer Sheldon Hart
Repair work that's expected to take at least four months to fix a bridge on Quinpool Road in Halifax could have been less disruptive had CN Rail chosen a different approach, says a local structural engineer.
On April 1, CN will begin repair work to the roughly 100-year-old bridge structure found on the stretch of road between Armview Avenue and MacDonald Street. It is expected to cause significant traffic disruption for much of the summer.
The repair work will include removing concrete spandrel walls, constructing a new concrete arch, reconstructing the spandrel walls, waterproofing the arch and making concrete repairs to the wingwalls and abutment face, CN spokesperson Alexandre Boulé said in an email.
Engineer Sheldon Hart said there are other options that would be preferable.
"It seems like they're kind of taking a brute-force method," he said. "They are basically blasting off all the old concrete and pouring new concrete over top."
Hart said there are a few problems with this approach, including that it's noisy, dirty and unpredictable.
"You don't really know what you're getting into," he said. "You kind of lose control of the project. What happens if they blast that off and they realize some of the rebar is corroded away?"
Because CN owns the bridge, it is responsible for the rehabilitation. The municipality is responsible for installing railings and paving the bridge once CN's work is complete.
Hart, with experience erecting and fabricating steel bridges and general knowledge about bridge construction, said one option CN could have used is a prefabricated structure to replace, rather than repair, the bridge.
With this method, after demolishing the existing structure, a prefabricated structure could then be put in place. Hart estimates this approach could take a month to complete.
He said the expertise exists locally to do the work and points to the repair work done as part of the Macdonald Bridge's Big Lift project.
With that project, crews spliced the suspended structure into about 20-metre-long sections weighing up to 150 tonnes that were lowered onto trucks or barges in the harbour. New deck segments were then put in to fill the gaps in time for daily rush-hour traffic.
"Why is it on a 65-foot span they're taking almost an archaic approach in closing it down for four months?" said Hart.
He said some of the advantages of using a prefabricated structure are that the costs are more predictable and less money is spent on traffic control.
CN didn't respond to CBC's questions about what bridge repair or replacement options were considered, and why the chosen approach was selected.
The project has commuters, including Hart, worried about traffic delays because of the detour plan.
He and his wife live in Herring Cove. While he travels to work in Dartmouth via Chebucto Road, she takes Quinpool Road to get to her job at Dalhousie University.
He's worried the traffic delays will mean they get to spend less time with their two young children and they'll also have to shell out more money for gas.
As a result of the work, non-local vehicular traffic will be detoured onto Chebucto Road. The detour will extend to Connaught Avenue and then south back on to Quinpool Road. Local vehicle traffic will be able to use Armview Avenue.
City spokesperson Brynn Langille said there's a reason why Chebucto Road was chosen as the detour route.
"When mapping out a detour that involves an arterial road, we have to do our best to direct the traffic onto roads of similar classification, so Chebucto Road and Connaught Avenue are also arterial roads," she said.
Will there be more buses in service?
Langille said residents should consider using alternative forms of transportation, such as carpooling, transit or active transportation.
She said the number of buses serving the area won't change during construction.
"We simply wouldn't have the capacity to react to construction projects in that way," she said.
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