Building a 21-acre urban park above a downtown rail corridor will cost about $600 million more than initially estimated.

A feasibility study that was requested by city council last October and released on Tuesday has pegged the preliminary cost of building Rail Deck Park at about $1.665 billion, or about $83 million per acre.

The estimate, which the study says is still preliminary, represents a substantial increase from the $1.05 billion price tag initially put forward by city staff when the proposal first surfaced.

Staff, however, are pushing for Rail Deck Park to be constructed in four phases.

The first phase, identified in the report as the “priority phase,” would span from Spadina Avenue to the bright yellow Puente de Luez pedestrian bridge at the foot of Portland Street, covering about 9.4 acres.

That section would cost about $872 million.

The completion of the remaining sections would mean that the park would eventually span from Bathurst Street to Blue Jays Way with 20 of the parks 21 acres located on a deck that would be built above the rail corridor.

“The phase one area will create a large, contiguous park space to provide for a range of recreation and culture uses,” the feasibility study states. “The phase one area would be roughly twice the size of the new Grange Park.”

It remains unclear how the city will pay for Rail Deck Park, however in the feasibility study staff suggest that development charges, commercial contributions and federal and provincial funding will all be relied on to help foot the bill.

The study also says that council could consider implementing a Special Area Levy, wherein residents in a given area face an additional charge on their property taxes.

Staff do caution that in order to implement such a levy there would have to be “strong

factual evidence of the park providing a special and unique benefit to a particular part of the city.”

In outlining the merits of the project, staff say that acquiring land suitable for parks in the westen part of Toronto can carry a price tag of between $95 to $115 million.

They say that Rail Deck Park presents a “unique opportunity to provide necessary parkland to address not only the current deficiency” of parkland in the downtown core but also “forecasted growth-related needs.”

The feasibility study, which carried a cost of $2.423 million, will be considered by Mayor Tory’s executive committee next week.

Staff are asking council to authorize them to undertake a “due diligence and concept development work plan” that would address “various outstanding technical, financial and real estate matters” with Rail Deck Park, including the acquisition of air rights to actually build the park above the rail corridor.

Toronto East York Community Council has already approved zoning changes that designate the area above the rail tracks for parks and open spaces.