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A TTC bus cross the corner of Warden and Sheppard Ave East in Scarborough, Dec. 11, 2010.J.P. Moczulski for The Globe and Mail

Long before Mayor Rob Ford killed Transit City, the Eglinton Crosstown LRT was an enormously complicated engineering project, but the plan to bury the 25-km line is creating new engineering and soil disposal headaches that could drive up both cost and complexity.

The estimated cost already jumped from $4.6-billion to $8.2-billion, after Queen's Park agreed to take the line underground.

The design riddles associated with tunneling under the Don River and Black Creek could provide Mr. Ford's critics with an opening to block the revised plan in council next year. And there could be a domino effect on Mr. Ford's Sheppard subway plan. Under his deal with the province, if the Crosstown line comes in under budget, unspent funds will go toward the subway.

The Don Valley

Under the Transit City strategy, the LRT was to emerge from a tunnel east of Laird and continue eastward on a right-of-way in the middle of Eglinton. But because of Mr. Ford's changes, Metrolinx officials have spent months grappling with the question of how to get the Crosstown line across the Don Valley.

A tunnel may prove to be too deep and too steep for light rail vehicles, so Bruce McCuaig, president and CEO of Metrolinx, said the agency is looking at building a grade-separated bridge for the LRT as it crosses the ravines. Public consultations on an environmental assessment examining a bridge and other tunnel configurations will begin in early 2012.

Yet some councillors are already questioning both alternatives.

Deputy Speaker John Parker, whose ward includes that stretch of Eglinton, said there's "a strong argument" for running the LRT on a right-of-way on Eglinton as it traverses the Don Valley. Transit City supporter Gord Perks (Parkdale-High Park) took a stronger line: "Why don't they just go back to the original idea? They can't get it under the Don."

Mr. McCuaig couldn't say whether the public will be asked to comment on a surface option during next year's EA and added that he's not sure whether council will even be asked to make the ultimate decision.

Mr. Perks, however, predicted that Metrolinx's EA, which he said is subject to council approval, could become a lightning rod for critics of Mr. Ford's plan. "This could be the issue that forces Transit City in front of this council for the first time."

Soil disposal

The tunnels and the stations for the Eglinton line will yield enough soil to fill the Rogers Centre – between 1 million and 2 million cubic metres. For the last project of this scale – the Bloor-Danforth subway line – the Toronto Transit Commission dumped excess fill into the Garrison Creek ravines.

The rules have changed dramatically since the 1960s. As recently as last summer, new provincial regulations imposed tougher remediation standards on excavated soil, while revised "best management practice" guidelines for the disposal of excavated fill are expected next year.

Officials with Metrolinx and the TTC insist the new standards won't affect the Eglinton line. "It shouldn't have an impact at all," said project manager Sameh Ghaly, noting that the excavated soil from the tunnels will be dug from a depth of about seven metres to 10 metres.

"My understanding is that the soil will be in pristine shape," added Mr. McCuaig.

Construction industry sources disagree. The new standards are "going to make it more difficult to dispose of excess construction soils," said Andy Manahan, executive director of the Residential and Civil Construction Alliance of Ontario. "I would think these regulations will impact the cost of Metrolinx projects."

Environmental lawyer Janet Bobechko, a partner with Blaney McMurtry, added that surface contamination from gas stations and dry cleaners has been known to leach down to the tunnel depths.

TTC has been doing geotechnical assessments for the past year, and soil testing on the eastern stretch began in late October.

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