With Toronto facing an estimated $106-million cleanup bill after last month's devastating ice storm, some on council are asking why hydro lines can't be buried underground where they are safe from ice-laden limbs knocking out power.

Coun. Denzil Minnan-Wong put forward a motion Thursday asking senior city staff — in consultation with Toronto Hydro and provincial bodies — to look at the cost putting wires underground.

Arriving three days before Christmas, the ice storm knocked out power to 300,000 Toronto Hydro customers. Many were without power in freezing temperatures for more than a week while hydro crews worked around the clock to restore power.

And while Minnan-Wong was circulating his motion at city hall on Thursday, Toronto Hydro CEO Anthony Haines was addressing the question at a media briefing held to discuss technical issues arising from the storm.

Haines said it would cost an estimated $15 billion to move Toronto's 15,000 kilometres of power lines underground. Burying lines in residential areas alone would cost $5 billion, he said.

"It's a substantial financial cost," said Haines, estimating that such an undertaking would mean a 300 per cent rate increase.

At Thursday's technical briefing Toronto Hydro had on display some of the old materials they were tasked with repairing during last month's ice storm. This is an old service wire with cloth insulation that had flaked away, exposing bare wire. (Andrew Lupton/CBC)

Haines and other Toronto Hydro officials also said moving lines underground may solve the tree problem, but would create new challenges for hydro crews. Underground lines are harder to access and repair during an outage. Also, lines in the ground can come into contact with water, which caused problems during last July's rainstorm.

"[Burying lines] is not a perfect solution," said Haines. "During the floods, people were saying 'why are the lines underground?'"

Resistance from residents

Toronto Hydro construction supervisor Rob Milner, who worked with crews to restore power during the storm, also said moving lines underground isn't a cure-all.

He spoke of headaches Toronto Hydro faced during a project five years ago in the Forest Hill neighbourhood.

The project was a "backyard conversion," and involved pulling a run of power lines out of backyards, where they are difficult to access, and moving them underground.

Bringing underground lines into a house means digging an access pit below the hydro meter. Milner said Toronto Hydro faced resistance, and some lawsuits, from residents who didn't care to see their gardens dug up.

Underground access also isn't easy in densely populated neighbourhoods where the power lines compete for space with existing gas, water, sewer and fibre optic lines.

Also, underground lines require large switch boxes, about one on every block. They take up a footprint of more than two square metres and stand almost two metres high. In a new subdivision they can be located in ways that are unobtrusive, but that's difficult to do in Toronto's older, densely populated neighbourhoods.

This is a porcelain insulator, known as a house knob, damaged in last month's ice storm. (Andrew Lupton/CBC)

"The question becomes where do you locate that?" said Milner. "Because no one wants one of those in front of their house. You run into resistance."

Many new subdivisions are served by underground power lines. Milner's home in Milton, Ont., has them but he was still without power for four hours during the storm.

That pales in comparison to thousands who were without power for days but Milner said it's proof subdivisions with underground lines aren't immune to outages.

Still, many are wondering if moving wires underground is worth the staggering cost.

Coun. Joe Mihevc, in a recent opinion piece in the Toronto Star, suggested that moving the wires underground may be worth the staggering cost, especially if it's spread over the long term.

"It is now clear that the cost of these kinds of storms needs to be a part of the calculation," he wrote.