The long-awaited Green Line Extension is on track to move ahead, with the final design of the $1.1 billion public transit project due to be completed in March. The first phase of construction, including the widening of railroad bridges in Medford and Somerville, will start by the end of this year, MBTA project officials said.
“Our goal is get into construction this calendar year,’’ said Michael J. McBride, the Green Line Extension program manager at HDR/Gilbane, the contractor chosen by the MBTA to manage construction.
Plans for the $20 million first phase were outlined last week at a community meeting at Somerville High School, the first of several the MBTA plans to hold to keep area residents informed.
The extension gets underway as the MBTA proposes fare hikes and service cuts to close a $161 million deficit for the fiscal year that starts July 1. The authority is holding meetings across the region to gather public comment on its cost-saving proposals, which include eliminating some bus service in Medford and Somerville.
An MBTA spokesman said the Green Line Extension won’t add to the T’s debt load. “It’s . . . important to note that the project will be funded by the Commonwealth and federal grants, not the MBTA,’’ Joe Pesaturo wrote in an e-mail to the Globe.
The extension is one of several projects the state is required to build to comply with federal air quality measures as a result of the Big Dig construction project. “Aside from the economic and mobility benefits the project would bring to the area it would serve, construction of the Green Line Extension is required by law,’’ Pesaturo said.
At least one resident is concerned funding could be a factor down the road. “The state and the T have so many financial problems, who knows?’’ said Jim McGuinness, a Union Square resident who attended the meeting. “The pace of this has been so slow, mostly due to a lack of finance. The state has to allocate this money.’’
But at the meeting, McBride assured those in attendance the cost of the first phase is covered. “It’s fully funded by the state,’’ he said.
The reassurance pleased some local residents at the meeting. “This is a small step, but a big deal,’’ McGuinness said.
The project will extend the Green Line from Lechmere station in Cambridge to Union Square in Somerville and College Avenue in Medford. It will be built in four phases.
The first phase is scheduled to take about 18 months, and largely involves rebuilding commuter rail bridges on Medford Street in Somerville and Harvard Street in Medford. An MBTA tire repair facility at 21 Water St. in Cambridge also will be demolished, and the area could be used as a staging area during construction, officials said.
The MBTA plans to hold other public forums, including neighborhood meetings, as work progresses, officials said.
“There will be a wide discussion,’’ said Karen E. Arpino-Shaffer, deputy program manager at HDR/Gilbane. “We know there is a tremendous amount of interest in this project.’’
In all, the Green Line Extension will result in seven new T stations, including a new station at Lechmere. Railroad tracks and utility lines must be relocated. Retaining walls and noise barriers to shield neighborhoods along the route will be erected.
Still, it will be years before the Green Line rolls into communities. At the earliest, passenger service would begin in the fall of 2018, and no later than the summer of 2020, according to the MBTA.
“This project is really like two projects in one,’’ Mary Ainsley, director of design and construction at the MBTA, said in an interview after the meeting. “It requires moving the existing commuter rail tracks and laying new tracks for the Green Line . . . It’s a major undertaking.’’
Ken Kraus, a Medford resident, said the Green Line ultimately will improve transit options in West Medford, which now is served only by commuter rail. “It will improve access, and it should take a lot of cars off the road,’’ he said.
Wig Zamore, a founding member of the nonprofit Somerville Transportation Equity Partnership, said the timeline for the first phase is encouraging. “It’s taken a very long time to get just to this point,’’ he said.
“Somerville is a small, dense city. . . . For us to see a shift to clean transit, so that people don’t have to rely on cars, is going to make this a more liveable community.’’
Project managers still are meeting with local officials in Cambridge, Medford, and Somerville to address the impact of the project on each community.
In Medford, the MBTA already has agreed to address flooding problems near the Harvard Street rail bridge. The new bridge will be raised by a foot. The grade of the road also will be raised by a foot and a new 30-inch diameter pipe will be installed.
“We hope this will help,’’ McBride said. “At least it should mitigate the depth of the flooding problem there.’’Kathy McCabe can be reached at email@example.com. Follow her on Twitter @GlobeKMcCabe.