Fresh questions are being raised about the viability of Ontario Premier Doug Ford’s plan to tunnel beneath Highway 401, after new internal documents reveal the extensive difficulties a major provincial transit project has experienced trying to go under the artery.
Since early 2023, a tunnel boring machine has been slowly making its way south from Sheppard Avenue and McCowan Road, digging out a route for the three-stop Scarborough Subway Extension.
During the summer of 2024, the machine reached Highway 401, forging a path under the road and onto the other side.
Internal documents obtained by the Ontario NDP, however, suggest the work was far from smooth.
Redacted reports and presentations from provincial transit agency Metrolinx reveal how problematic the tunnelling was.
The documents, seen by Global News, show:
- The Ministry of Transportation had to put partial road lane closures in place for three weeks
- Tunnelling was more complicated than the contractor performing it had expected
- The boring machine required an eight-month break for repairs once it had burrowed under the 401
NDP Leader Marit Stiles said the issues with tunnelling under a cross-section of Highway 401 serve as evidence that the premier’s plan to build a 50-kilometre expressway beneath it is impossible.
“I think it causes us to question the premier’s obsession around this vanity project that he has to build a tunnel under the 401,” she said.
Issues with tunnelling under highway
The internal documents reveal the tunnel boring machine for the Scarborough Subway, which was launched at the north end of the route, experienced “issues” almost immediately after it launched.
Throughout 2023 and 2024, the boring machine experienced “subsidence” (sinking) issues.
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By June 2024, as the machine made its way southbound under the 401, documents show partial lane closures were put in place for roughly three weeks to accommodate the work.
A spokesperson for Metrolinx confirmed to Global News the boring machine had initially struggled in its work, forcing a decision to shut parts of the artery to traffic.
“Scarborough Subway Extension tunneling experienced unforeseen challenges during its initial phases,” they wrote in a statement.
“The ground conditions combined with the wear and tear on the machine, heightened the risk of soil shifting and out of an abundance of caution, lanes were closed on Highway 401 in June and July 2024, which was shared with the public through 511 notices.”
Once the tunnel boring machine made it to the other side of the highway, it had to stop for repairs, the documents show.
Metrolinx recorded “concern over elevated cutterhead torque and thrust forces experienced during the last 3-4 advances” of the machine. The contractor concluded “a series of repairs and improvements are required to the TBM and that such repairs must be performed in atmospheric conditions.”
In order to do that, they built a “safe haven” to access the machine, creating a delay of eight months.
Stiles said the issues the machine had encountered tunnelling just a short section of Highway 401 raised questions about the viability of Premier Ford’s vision of tunnelling the length of the route.
“This is our money, it is the people’s money that’s building these projects and people have a right to know when things are going wrong or going sideways and what’s causing delays. And over and over again, we see these big projects delayed,” she said.
“We know, and everybody knows, that the premier is really obsessed with this idea he had of building a tunnel under the 401 and (he) doesn’t seem to be listening to sense about it.”
Internally, the Ministry of Transportation has drawn a line between the Scarborough Subway issues and Ford’s Highway 401 tunnel.
“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,” a note obtained by Global News earlier this year said, seemingly referring to the same incident described in the Metrolinx documents.
A spokesperson for the Ministry of Transportation, which is leading work on the idea of a Highway 401 tunnel, said it remained an important project.
“We are delivering the critical infrastructure our province needs, including the 401 tunnel which is currently undergoing a feasibility study,” a spokesperson wrote.
© 2025 Global News, a division of Corus Entertainment Inc.
