The Ford government’s work to study a tunnel under Highway 401 ground to a halt almost four years ago, Global News can reveal, partly because the province’s internal analysis concluded a “potential for roadway collapse.”

An internal assessment of the plan, completed in 2021 but never revealed to the public, also determined that burrowing a tunnel under an active highway would face a slew of technical and financial problems and could pose “risks to public safety.”

The latest revelations, informed by internal documents obtained using freedom of information laws, come as the government ponders exempting its Highway 401 tunnel plan from municipal and provincial laws under the controversial law that allows Ford’s cabinet to create “special economic zones.”

The project remains at least two years away from any construction work and has been considered by the Ministry of Transportation — in some form — since 2019.

“Our government is exploring every option to tackle gridlock and ensure that critical infrastructure can keep up with the unprecedented pace of growth of nearly two million people since 2021,” a spokesperson for the government said.

“Our modelling confirms that all 400-series highways, including Highway 401, will be at or above capacity within the next decade.”

When Premier Doug Ford announced his plan to build a 50-kilometre tunnel under Highway 401 in September 2024, the initial studies and expert feedback were left unmentioned.

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Instead, Ford claimed his opponents would say the project was impossible.

“Every proposal to get people out of gridlock and get our province moving, they say no,” Ford said on Sept. 25, 2024, referring to the Ontario Liberals and NDP.

Behind the scenes, however, the list of people pushing back against the premier’s plan grew to include civil servants with the Ministry of Transportation and external experts, all of whom relied on the earlier feasibility study.

Internal emails, meeting notes and briefing decks obtained by Global News show the idea was first floated as early as 2019. Then, sometime in 2021, it was decided that the dream of tunnelling under Ontario’s busiest highway was unlikely to work.

A briefing deck summarizing a 2021 analysis said the work had uncovered “several financial and construction challenges and risks to the project.”

Those included, “Risks to public safety from impacts of the tunnel to Highway 401 such as potential for roadway collapse, as well as availability of labour, market capacity/interest, and securing financing).”

The full detailed report was not included in the documents released to Global News as part of the freedom of information request.

Ontario NDP Leader Marit Stiles said the warnings meant continuing to study the potential tunnel was a waste of time and money.

“This project is going to take two years to study to tell us what we now know, (what) government already knows, which is it’s not a viable option,” she said.

“It will collapse. So I think this is a ridiculous plan and it’s all about Doug Ford’s ego, again.”

The communications seen by Global News indicate concerns about the viability of tunnelling under Highway 401 were raised last year, too.

Recent struggles constructing the Scarborough Subway Extension, which will cross under Highway 401, remain fresh in the minds of some civil servants, who raised it as evidence that a tunnelled highway would be tough.

One note from a civil servant, written in the summer of 2024, pointed to difficulties Strabag — the company building the Scarborough Subway Extension — had with its project.

“Risk of extensive settlement along the 401 and related impacts to traffic should tunnelling occur for this proposal, based on MTO’s experience with Strabag and the soil conditions present while tunnelling under and near the 401 over the past few months,” the note said.

The Scarborough Subway Extension involves building a tunnel to cross Highway 401, rather than running underneath it. Even boring along that short section proved complicated.

“We’ve encountered soil conditions different than expected that have hampered the progress of the tunnel-boring machine,” former Metrolinx CEO Phil Verster explained in November.

One infrastructure expert told Global News the problems didn’t mean building a Highway 401 tunnel was impossible, just enormously expensive.

“The challenge is that when you look at it in any level of detail, you see that technically it could be feasible, but it will be hugely expensive,” Matti Siemiatycki, director of the infrastructure institute at the University of Toronto, told Global News.

“And over the long-term, it won’t solve the problem.”

While the final route of the current tunnel proposal has yet to be finalized, the premier has mused about an expressway for traffic and transit that stretches from Brampton to Scarborough.

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