A 21-acre urban park could one day be built atop the rail tracks spanning from Bathurst Street to Blue Jays way.

Mayor John Tory announced his intentions to build the park on Wednesday, noting that it has the potential to be a “signature project” for the city.

“I believe that creating a new downtown park is the best thing we can do for future generations,” Tory said. “This new park has the potential to be bold, innovative, sustainable and surprising.”

The air-rights to the tracks are currently owned by the Canadian National Railway Company and the city will have to purchase those rights or be granted permission by CN in order to add a deck to the track and develop the space above it.

In a news release, the city points out that decking the track is “feasible” with the developers of an office tower on Bay Street already proposing to deck a small section of track in order to create open space near their building.

The cost of building the park, tentatively dubbed Rail Deck Park, could be considerable, though, with Tory estimating that it would be in the “tens of millions of dollars per acre.”

As a point of comparison, the2.3-kilometre Highline park in New York cost $150 million U.S. to build. That park, however, was built on an abandoned train track that was no longer being used and not a busy active track. It was also largely funded through private donations.

“We are talking here about a very major project. There is no mistake about that but I think it is an opportunity just waiting to happen” Tory told reporters on Wednesday. “This space is in some ways an eyesore and it is certainly underutilized.”

Park would address lack of green space in core

The idea of building a park atop the rail tracks in the city’s downtown core arose from the TOcore project, which is studying ways to provide adequate infrastructure amid booming development in downtown Toronto.

Speaking with reporters at the proposed western terminus of the project, Tory said the city’s downtown is the most “park deficient” part of Toronto with 75 per cent of green space measuring no more than one hectare.

Rail Deck Park, Tory said, is a way to finally provide the core with the green space it desperately needs. According to the city, the population in the neighbourhoods immediately adjacent to the proposed park – CityPlace and King and Spadina – the population has grown from 1,000 in 1996 to just under 40,000 today.

“We cannot go on allowing this development to continue and not have adequate parkland,” Tory said.

Tory said the first step in developing the park will be to request a staff report by September 22, which will outline the parameters of the project as well as the potential cost.

From there, Tory said that negotiations can begin with CN on securing air rights so the rail tracks can be protected for future development.

There is no timeline for the development of the park, however Tory said it would take "four or five years" at a minimum.

“This idea won’t happen overnight,” Coun. Joe Cressy told reporters. “It will take years but it is bold, it is ambitious and it is exactly the type of big thinking that Toronto needs.”