MacKay Bridge's lifespan is almost up, but what happens next isn't clear

Yahoo

2 days ago

The A. Murray MacKay Bridge that spans Halifax harbour is wearing out, leaving some big decisions ahead over the next few years.
The commission that runs the bridge that opened in 1970 says gridlock-inducing closures for repair work will become more common the longer it's in use, but it's still not clear whether the bridge will be replaced or refurbished.
"We're predicting maintenance to substantially increase over the next couple of years, just cause it was designed as a 50-year bridge and now we're in year 55," said Tony Wright, the chief executive officer of Halifax Harbour Bridges.
"It's nearing the end of its service life. And so by 2035, 2040, we anticipate the level of maintenance required to keep it operational, we'll be getting little value for money at that point. So we're really looking at the long term."
Wright said work will be done at night or by closing one lane at a time whenever that's possible, but some full shutdowns are inevitable.
There is a weekend closure for maintenance starting July 25, one of four expected this year.
Unclear if toll removal impacting traffic
Upwards of 115,000 vehicles typically cross the two suspension bridges connecting Halifax and Dartmouth every day — with more than half of them using the MacKay, which shoulders the heavier commercial traffic.
When the premier announced earlier this year that the bridge tolls would be removed, some experts cautioned that the move would drive up traffic.
Wright said it's not yet clear whether that has happened since the tolls came off March 17 because they're still validating data gathered by new cameras. Halifax Harbour Bridges used to monitor traffic through the tolling system.
More important than the number of vehicles though, Wright said, is installing a system to measure the amount of weight crossing the bridges because the load "impacts features like the integrity of the deck system."
"We're really interested in understanding any changes in commercial traffic growth. We know the city has adopted electric buses. Those vehicles weigh almost twice as much as traditional buses … and vehicles are getting heavier," he said.
This means any increase in commercial traffic will increase the wear and tear on the bridge and speed up the need for maintenance.
Kathryn Morse, the councillor for Halifax-Bedford Basin West who sits on the bridge's board of commissioners, said she is concerned about that happening and is looking forward to seeing data when it's available.
"The bridges are the most critical piece of transportation infrastructure in the city, they are really key to getting a handle on all our traffic issues," she said, adding that it's also important to know the long-term plans for the aging structure.
"One recent example, it's difficult to plan the Windsor Street exchange without knowing the implications of what's happening with the bridge," Morse said.
New bridge versus retrofit
A 2018 feasibility study by the engineering consulting firm COWI North America looked at nine different scenarios for extending the bridge's use or building a new structure. It recommended constructing a new, slightly longer bridge north of the existing bridge, with six lanes of traffic and two active transportation lanes.
But Wright says that report was "very high level." Aecon Group, a construction and engineering company, was hired subsequently to study what exactly refurbishing the bridge would involve.
"What we're talking about here now is doing … some preliminary engineering. How would you do a rehab of the deck? How would you do the Big Lift? What are your options?" he said.
"That's a much more in-depth analysis. And I think we need to do that … because we're dealing with such a significant cost here."
Though the study isn't done, Wright said it's clear upgrading the structure would be complex — the approach spans need work and the deck's thickness is well below the current Canadian standard.
"You would have to fortify, strengthen the main towers, you'd have to make sure the foundations can withstand that additional loading. You'd have to install a new main cable or supplementary main cable. and then you're ready to do your big lift, none of which had to happen on the Macdonald."
A retrofit could cost between $600 and $700 million, while a new bridge could be double that, he said, but called any estimates "a little premature."
"Eight lanes, six lanes, four lanes, what does it need to carry really drives the cost. We don't have that information yet. So, I think estimating new bridge costs today is a little premature.… This is why we need to get on with this business case."
Those aren't the only two options considered, either. Wright said a firm specializing in tunnels found one under the harbour would have to start at Highway 111 near Burnside and go all the way to the Windsor Street exchange — meaning it would be three times as long as the MacKay Bridge, and tunnels are typically five times as expensive to build.
Ultimately, it'll be up to the province to consider the costs, the impact on traffic disruption and the lifespan of the new project when choosing the best route, he said.
Any option will take time.
Planning and procurement can take three to five years and construction work could take another six to 10 years, impacted by the availability of specialized labour, Wright said, which puts the timeline at the end of the MacKay's service life.
"I don't want it to go too much beyond that because then you're really essentially forced into a rehab situation that you're not planning for and that's what we're trying to avoid," he said.
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