Toronto has found a way to shave years off the reconstruction of the Gardiner Expressway and save its users $3 billion worth of wasted time, by using prefabricated sections of road.

“The savings are so massively significant that this really is a solution that should sail past council,” said Councillor Denzil Minnan-Wong, who asked staff to look for ways to shorten the timeline needed to replace the expressway’s deck, the steel-reinforced concrete layer below the asphalt. The staff report goes to public works for approval on Tuesday.

“We save eight years of massive congestion and gridlock,” he said.

The time savings will be made on the elevated section of the expressway from Dufferin St. east to the Don Roadway, where the new system, which has been used before in bridges, will be employed on the Gardiner for the first time.

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“Technology is ever-evolving and this is a relatively new approach,” said Michael D’Andrea, the city’s executive director for engineering and construction services.

Entire cross-sections of the expressway, including asphalt, concrete decking and steel girders, will be cut out and replaced with the prefabricated pieces.

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“Instead of placing rebar and pouring concrete, we’re going to prefabricate pieces at another site and come in and drop in sections of the deck,” said Minnan-Wong. The work is expected to take 12 years instead of 20.

The method will replace conventional repairs, which involve stripping away the asphalt road surface and sawing and chipping away at the deck below to free the concrete from the metal studs that anchor it to the steel girders below. Afterwards, steel rebar is installed and new concrete is poured.

“It’s a very time-consuming process,” D’Andrea said.

The prefabricated pieces will add about $115 million to reconstruction costs, but users of the Gardiner will save $3 billion, he said. Staff arrived at that figure by calculating lost work productivity (time) based on a “conservative” 30-minute traffic delay for both methods — $7.4 billion compared with $4.5 billion using the accelerated system.

The conventional method of deck replacement will still be used on the at-grade section of the expressway from Dufferin Ave. west to Highway 427. Council has yet to decide whether to remove the elevated portion of the Gardiner east of Jarvis St., following a recommendation made by city staff and Waterfront Toronto after a recent environmental assessment.

The city would need to approve an additional $400 million more over the next 10 years for the new method, but only because the timeline to replace the deck has been moved up and the money is needed to do the work more quickly.

D’Andrea says the prefabricated pieces will last longer.

“It would be a much higher quality product than what we would be able to do as a cast-in-place concrete. You can imagine, in the middle of the summer, in the blazing sun and heat, there are some challenges with the concrete drying too quickly,” he said.

“In a controlled environment — moisture- and temperature-controlled — it would be a much higher quality product and would last longer.”

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