Design on a connection between the Red and Blue lines is almost ready for public debate, though the largest hurdle of actually funding the construction of the new track remains.

State transit officials published further details of the proposed blueprints on August 9, looking forward toward environmental review. The current design sits at roughly a third complete, with $40 million allocated by the state legislature to conduct outreach and finish the blueprints.

Planners have been flirting with the idea of a Red/Blue connector since 2010 under the administration of Deval Patrick. After some preliminary design work and certifications, however, it was abandoned for the better part of a decade before being resuscitated in 2018.

The initial plans recommended a variety of tunneling methods, but planners now say using “cut and cover” for the entire length would be cheapest, fastest and most flexible. Details on how and for what duration construction would affect Cambridge Street are scarce at this point.

The project would decommission Bowdoin station entirely, extending the Blue line half a mile down Cambridge Street to link up with the Red line at Massachusetts General Hospital. The defunct station would still be used by transit personnel for maintenance, a ventilation plant and an emergency exit. Designers have also committed to drawing up plans to use the tracks for storage, though whether it will be worth actually implementing hasn’t yet been decided.

The project’s next steps are finishing design and getting recertified by state and national environmental review processes, since the original 2010 certifications are no longer valid.

For the public the project’s next big step is engagement and outreach from state planners on a variety of issues, with special focus on environmental justice and affordable housing in the area. That’s expected to take place in the coming months according to State Representative Jay Livingstone.

“I’m looking forward to seeing what issues arise during outreach, especially as the state starts to outline the impact on the surrounding community and how they’re going to mitigate those disruptions,” he said.

Then comes the last and perhaps largest hurdle, getting funding from the state legislature for the massive undertaking.

The scope and difficulty of that are going to depend on the final design, and while there’s no estimated timeline Livingstone is optimistic about the level of support he sees.

“Funding is the biggest obstacle, it’s probably going to be a billion-dollar project,” he said. “I’m more hopeful than I’ve ever been. We have an administration focused on completing this task. It’s great that they’re working toward a final design. The MBTA has never been more motivated to complete this work.”