Charles/MGH Station in Boston. (Photo: Massachusetts Office Of Travel & Tourism via Flickr)

After five decades of discussion, the MBTA has unveiled concrete plans for a connector between the blue subway line and red, which has six stations serving Cambridge and Somerville.

In public hearings Oct. 16 and 19, the transit agency outlined plans for extending blue line tracks to the station at Charles/MGH in Boston – one stop from Cambridge. As discussed in a presentation, the connector is intended to reduce travel time and the number of transfers, as well as increase accessibility for riders.

The estimated cost of the project is $850 million. Completion is expected in 2031, though deadlines and speed have not traditionally been hallmarks of the Massachusetts Bay Transit Authority.

The connector has been on the MBTA’s radar since 1972, when the concept was outlined as part of a moratorium on expressways within Route 128. The idea has come up time and time again, with a 1986 Connector study, 1990 Third Harbor Tunnel Commitment and 2010 Draft Environmental Impact report and revisions.

The connector is outlined in an MBTA 5-year Capital Investment Plan approved by its board of directors July 27, starting with $15 million dedicated to design and engineering work associated with the connector. (A cost update is expected at the 15 percent design stage.) Instrumental in the securing of these funds was transportation advocate group Transit Matters, which has drawn attention to the connector’s necessity through a series of initiatives including events, campaigns and published think pieces.

“In the Boston subway system, there are only two lines that have never been completed in terms of connecting. And that’s the red and the blue,” said Jim Aloisi, former Massachusetts transportation secretary and current board member of Transit Matters. “You’ve got the single mother with a sick child from East Boston who has to walk three blocks from Bowdoin, the phlebotomist who has to get to Mass General who lives in Chelsea … the connector makes sense to address a lot of these access and equity issues.”

Transit Matters additionally cites access to jobs – including from Logan Airport, which has a blue line stop – and environmental considerations for the connector. “It serves the Kendall Central-Harvard Square route by giving people a valid, viable option to the airport that I believe will get them out of cars,” Aloisi said. “If you’re anywhere along the northern red line quarter, this magnificent academic environment of Kendall Square – where there is Google now, and Microsoft – there is no feasible way to really take transit. They end up taking a personal vehicle, congesting the streets, polluting and going against every sustainability climate goal we have.”

Promised from Big Dig

The T is running with systemwide speed restrictions and is overwhelmed by the demands of deferred maintenance. During the October hearings, an attendee questioned whether focus on the connector would take away from the MBTA’s other initiatives and operational concerns.

“That’s the stupidest way to think about it. You should be able to chew gum and walk at the same time,” Aloisi said. “You should fix the system, but that doesn’t mean [the MBTA] can’t take actions to modernize, improve and connect lines that should have been connected years ago.”

The red-blue connector was promised – along with the long overdue but recently completed green line extension through Cambridge into Somerville and ending at Tufts University in Medford – as environmental mitigation to the Big Dig, a 2000s mega project to put Interstate 93 through Boston into the Thomas P. O’Neill Jr. Tunnel. Despite that, the connector was dropped in 2013 under former governor Deval Patrick. In 2017, during Boston’s pitch to bring a second Amazon headquarters to Suffolk Downs, the connector was dangled briefly as a possible selling point.

Aloisi attributed the MBTA’s newfound interest in the connector to turnover in state and city politics. “Now we have a governor, we have a mayor, who rather than just pay lip service to the project, is actually very strongly supportive,” he said.

No more Bowdoin station

According to the design report, the connector will bridge the red and blue lines with a 2,500-foot two-track tunnel under Cambridge Street that will involve the permanent decommissioning of the Bowdoin blue line station. Bowdoin has the third-lowest ridership on the heavy rail system and is the only station on the line not accessible to people with disabilities. The current proposal, based upon a 2018 study refining the 2010 report, suggests a cut-and-cover tunneling method to reduce cost and construction duration.

On the top of the list for the project’s next steps is identifying funding. The connector has $30 million in programmed funding to complete 30 percent of design, environmental review and design-build bid documents.

After the MBTA submitted a Notice of Project Change to the Massachusetts Environmental Policy Act Office on Oct. 2, updating the 2010 environmental Impact report, public comments on the proposal were open until Oct. 31. A MEPA certificate of review was expected Monday.