Rafael Mares, with the Conservation Law Foundation, the group that negotiated the original commitment to build the project, says any alternatives would have to be built in the same service area — something he doesn't see as feasible.

And since the state is required to complete the project as part of a lawsuit settlement to mitigate the environmental impacts of the Big Dig, canceling it could leave the state open to litigation. However, an attorney for the T said Wednesday the state has legal alternatives -- such as replacing the Green Line extension with a project that "provides at least 110 percent of the air quality benefits of the original project."

The state would lose an estimated $742.3 million in "sunk costs" if it decided to nix the project -- though Pollack pointed out that figure includes the purchase of 24 new Green Line cars that would still benefit the system. The state would also lose $1 billion in federal transit funding tied to the extension.

Pollack made the comments during a packed public meeting of the MBTA's fiscal control board and the board of the Department of Transportation. Both boards have been considering how to move forward with the Green Line extension since it was revealed in August that the project could cost about $3 billion to complete in its current form — $1 billion more than previously expected.

"We believe that we need to consider not just potentially saying no to this project, but also saying yes to focusing on and investing in the core system with resources that would otherwise be used for this," she said.

As state transportation officials look for ways to cut the cost of building the Green Line extension to Somerville and Medford, Transportation Secretary Stephanie Pollack said Wednesday that canceling the project is still on the table.

"The idea that you would be able to do another project from scratch, that has as many benefits as the Green Line extension, seems like a pipe dream to me."

"The idea that you would be able to do another project from scratch, that has as many benefits as the Green Line extension, seems like a pipe dream to me," Mares told reporters after the meeting. "If that's the road that they're going down we will obviously have to consider our options [such as litigation]."

While canceling the project is still a possibility, state officials are also considering other options. It appears clear that the boards aren't interested in moving forward with the project as is. But some members seemed open to exploring ideas for redesigning and rebidding the project in order to cut costs. Those options were presented to the board on Wednesday by consultants tasked with charting a potential path forward.

On the design front, John Karn, with the consultant group ARUP, said design changes could prevent the need to relocate both of the commuter rail tracks that the new Green Line tracks would run alongside. He also suggested scaling back station designs, downsizing a planned vehicle maintenance facility and finding ways to speed up the project timeline.

Likely to be the most controversial suggestion, Karn said the T could also cut costs by finding alternatives to the proposed station in Union Square.

As currently designed, the Green Line extension project would have two branches out of Lechmere. One branch would have just one stop, in Union Square in Somerville. The other branch, heading toward Medford, would have five stops — including one on Washington Street in Somerville, which Karn pointed out is a half mile away from the proposed Union Square stop on the other branch.

A map of the proposed Green Line extension to Somerville and Medford. (Source: MBTA)

Karn suggested the T could instead add a stop on the commuter rail line that already runs through Union Square to North Station but doesn't stop — eliminating the need to relocate the current commuter rail tracks. Karn also said a shuttle bus could be considered to link Union Square to Lechmere.

Mares said he was pleased with some of the proposed cost-saving design changes but doesn't think the T should consider any changes that would take proposed services away from riders — such as eliminating the Union Square stop.

Mares also said the T needs to release solid figures for how much money each of the proposed design changes could save — something Pollack said the T couldn't do yet, because it doesn't have a reliable budget for the project.

Another consultant addressed both boards Wednesday about how to move forward with rebidding the project. Geoffrey Yarema, of Nossaman LLP, suggested the T drop its current procurement process — which the T's failure to implement properly was blamed for helping drive up the cost of the project. Yarema instead suggested the T put the remainder of the project out to bid as a single contract using a method known as "design-build."

Yarema said a test of the market showed there was significant interest from contractors to bid for the project under these new conditions. Yarema also said the T could use the new method to maximize cost certainty, but he emphasized that the T would have to manage a new contract better than it did previously.

Before stepping into a closed executive session following Wednesday's public meeting, Pollack told reporters it will likely be "months, not weeks" before a decision is made on the future of the project.

"I think we have a lot of work to do to get the project to a place where we have the confidence of the administration, of the Legislature, and of these two boards in order to move forward," she said.