City of Toronto officials estimate that it would cost at least $1.05 billion to fully build the 21-acre urban park above the rail corridor downtown that was introduced by Mayor John Tory last month.

In a report provided to council Thursday, staff estimates that covering the area between Bathurst Street and Spadina Avenue would cost $34 million per acre, or a total of $581.4 million.

To cover the remaining 4.2 acres of the rail corridor between Spadina Avenue and Blue Jays Way, it would cost $29 million per acre, or $121.8 million.

In addition, staff says that building safety and ventilation systems underneath the rail deck would cost $2 million per acre, and landscaping the area above would cost $3 million per acre.

Add in another 30 per cent of the project’s construction cost to pay for design, engineering and contract management costs, and the total cost of covering the rail corridor with parkland is $1.05 billion.

Staff also developed several scaled back options for the park, ranging in cost from $4 million to $36 million per acre, but covering a far smaller footprint of not more than 8.6 acres.

But the report does not address how costly it could be for the city to acquire the “air rights” to the space, which are currently split between CN Rail, Toronto Terminals Railway, Metrolinx and the city itself.

Staff says figuring out how to acquire all the necessary rights to the area will require extensive research

Speaking to reporters on Aug. 3, Mayor Tory said the city is prepared to negotiate with CN to acquire the rights.

The report suggests the city could use development charges, solicit private donations, funding from higher levels of government and other means to pay for the park.

Tory said last month that developing the park is “four or five years away” at a minimum.

City officials say building a park over the rail corridor “is the last opportunity to secure space for a major park to serve the downtown area.”

They say the core of the city “has been identified among the areas with the lowest levels of park provision in the city” and “expected growth will compound this issue over the coming decades.”

By 2041, staff writes that the downtown core could be home to 475,000 residents, up from 200,000 in 2011. The immediate area around the proposed park site now houses almost 40,000 people, up from 1,000 in 1996.

The staff report calls on council to spend $2.5 million over the next two years to study feasibility of the project, securing air rights, engaging the public on the project and developing funding options.