Renovations to Toronto's Union Station will not be completed until 2017 at the earliest – two years behind schedule and $160-million over the original budget.

The city's government management committee met Monday to approve an additional $4-million for the project, bringing the total cost of the renovations to $800-million – up from its original $640-million price-tag. And the project, originally expected to reach "substantial completion" in 2015, now won't be ready until 2017.

The committee also voted to push back spending an additional $55-million to expand the underground PATH further northwest to Wellington Street.

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A report from city staff this month blamed "multiple unforeseen site conditions," including "subterranean structural features, heritage elements, electrical services that were not included on any drawings, etc." The building's status as a national historic site added to the complexity of the project, it says.

The report also says that when the project's original budget of $640-million was approved in 2009, detailed drawings and technical information were not yet available.

Since their start, renovations to Canada's busiest transit hub have been plagued by delays and budget overruns. The project was approved by the City of Toronto in 2009, with funding from all three levels of government.

And while the staff report says that the project was never meant to be completed in time for the Pan Am Games, the team overseeing the renovations has "successfully mitigated any significant impacts of the project" on the July event.

The project includes the expansion of the GO concourses, creation of a new PATH system, an increased number of station entrances and the restoration of the VIA Rail concourse.