The Big Paint: Macdonald Bridge to undergo $75M recoating project

Halifax's Macdonald Bridge is gearing up for a $75-million makeover that will strip away decades of old paint to start fresh.

Since the bridge opened in 1955, Halifax Harbour Bridges said crews have mostly been doing spot touch-ups and small repairs on the structure. The new project will be the first time workers sandblast to the bare steel over the entire bridge and apply three new coats of paint.

The goal is to extend the bridge's life by 75 years, said chief engineer Ahsan Chowdhury.

The thick layer of paint that has built up on the bridge over the years has actually stopped properly protecting the steel, he said. Water can now seep underneath it to erode the beams, even if the damage isn't actually visible from the outside.

Removing the paint, repairing the steel and applying three coats of new paint will save a "significant" amount of money in the long run and avoid major issues, Chowdhury said.

"We have to maintain it to be safe," he said. "We don't want to wait until it fails."

Ahsan Chowdhury is chief engineer with Halifax Harbour Bridges. (CBC)

Halifax Harbour Bridges undertook a pilot project on the Halifax approach span back in 2017 to figure out how to best tackle the job.

The fresh coat of slightly lighter-green paint that can be seen by looking up at the bridge from Barrington Street is an example of how the rest of the Macdonald look after the recoating project. They also stripped and painted smaller sections on the Halifax and Dartmouth ends of the bridge over the past few years.

Chowdhury said he and some of his colleagues also visited similar bridges in the U.S. and Canada to look at how they handled recoating.

Canadian engineering firm Stantec is designing the $75-million dollar project, which is expected to go out for tender this spring, with work likely to begin in the fall. About half the price tag is for steel replacement, and half for paint.

A patchwork of paint layers and spots of damage on steel beams underneath the bridge. (Craig Paisley/CBC)

The remaining work includes the two bridge towers and parts of the Halifax and Dartmouth approaches and spans. The new decking on the suspended span that was put in during the Big Lift has new steel and paint, so won't need any work.

Peter Flower, project manager at Stantec, said their team has created a computer model of the Macdonald to analyze where problems might be located, and which pieces may need to be replaced.

"There's a lot of work and prep work that goes into the project, so you know, it might be 2025 before any paint is applied," he said.

A section of the Macdonald Bridge before sandblasting (top) and after (bottom), showing the bare steel. (Halifax Harbour Bridges)

The winning contractor will have to follow strict environmental regulations around capturing the old paint as it's being sandblasted, Flower said, and disposing of it properly.

The hope is to attract one of the American companies that specializes in recoating bridges, he said, as they could deliver the work "quite easily and cost effectively."

Full bridge closures aren't expected. Instead crews will close one lane, at most, outside busy times to put up scaffolding on the towers, Chowdhury said.

The project is expected to be completed by 2027.

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