Technically, a tunnel could be built to replace the crumbling Gardiner Expressway, experts say.

“It is something that can be done from an engineering perspective,” says Sandro Perruzza, chief executive of the Ontario Society of Professional Engineers. “But, that close to the lake, you need to go deep into the bedrock, and of course that’s very costly and the city has no money.”

Though many thought the issue long buried — repeatedly batted away by mayors and councils of the past over costs — it was raised again last week by rookie Councillor Jim Karygiannis (open Jim Karygiannis's policard), who demanded a thorough study on the feasibility of a tunnel.

His argument became the linchpin in a contentious debate that had both sides, for and against tearing down the eastern Gardiner, lobbying in what became a close vote for John Tory (open John Tory's policard)’s so-called “hybrid” option that would leave most of the elevated expressway intact.

In the end, council voted 28-17 in favour of a tunnel study that’s expected to come back this September.

The perennial proposals to bury the Gardiner have led to many reports and renderings. But the pipe dream has always been shelved when the question of who will pay goes unanswered.

Last November, just after his election the mayor — who ultimately moved the motion to request additional study — asked about the possibility of tunneling.

Staff told him then that a one-kilometre tunnel had been considered in 2013 but was ultimately ruled out. The major knock was the estimated $2.5 billion cost — nearly the equivalent of the entire 10-year state-of-good-repair backlog for Toronto Community Housing.

That was on top of “significant” costs to maintain it and the paucity of north-south connections it would allow, when few drivers use the Gardiner to go all the way through downtown.

But some maintain a tunnel is still the best option.

Michael Meschino, a principal with engineering firm Entuitive, which has looked at the future of the Gardiner, agrees cost is the biggest obstacle but puts the number at closer to $1.6 billion for capital and maintenance for the eastern section.

“My viewpoint is that it gives us the chance to do something transformational with the city,” Meschino said. “The tunnel option, although it’s the most expensive, it gives you the best chance to build something in this city that is quite beautiful, and that’s what's missing from the other options.”

Gordon Gill, whose architecture firm submitted designs that included a tunnel in the most recent Gardiner study, said it’s important to consider the value of unlocking those waterfront lands — with the potential to pay for the tunnel many times over.

Developer Bill Teron was saying the same thing back in the late 1980s, when he proposed burying the whole thing without charging taxpayers — in exchange for the use of developable land topside.

Some plans over the past three decades have called for a shallow tunnel — 12 lanes, eight lanes, four lanes. Other designs had it dug just offshore, under Lake Ontario. They talked of parks and other waterfront amenities. They cited figures of $1 billion and higher.

Developers and architects who have come forward on the Gardiner plans have all had one thing in common: They’ve insisted something bold was required.

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But for the cost, none have ever seen their dreams go underground.

Now it’s up to Tory and this council whether to dig the tunnel idea up again, or bury it for good.

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