The $3 billion Scarborough subway appears to be moving ahead even though the city and Metrolinx have yet to sign an agreement for financing the project and a $1.48-billion contribution from the province.

The TTC board is expected to approve a $30-million, five-year contract for the design of a 7.5-km subway tunnel when it meets Tuesday.

“We have to get a contractor aboard to start thinking about that work, because it's very complicated work and it can have an impact on schedule. If you don't start getting some of that work done immediately you can fall behind very, very quickly on these projects, so we don't want to do that,” said TTC spokesman Brad Ross.

Hatch Mott MacDonald Ltd. won the contract over two other qualified companies, AECOM Canada Ltd. and MMM Group-Jacobs Associates Joint Venture.

The city has already begun work on the environmental assessment, which will ultimately determine a route for the subway, and public consultation portions of the Scarborough project.

The three-stop subway was approved in October 2013 when city council overturned its previous support for a seven-stop LRT to replace the aging Scarborough RT. Mayor John Tory supported the subway option during his campaign.

But the project is expected to cost about twice as much as the province has agreed to pay toward the SRT replacement. An additional $660 million is expected to come from Ottawa and the city's contribution is estimated to be a further $910 million. That includes $745 million in property taxes and $165 million from development charges.

The master agreement among the city, TTC and Metrolinx has not yet been changed to reflect the fact a subway is to be built, rather than the less costly LRT that would have been fully funded by the province.