The Massachusetts's Bay Transportation Authority's long-delayed Green Line Extension project finally received a big chunk of green from the federal government.

The U.S. Dept. of Transportation on Dec. 21 granted the MBTA a $100-million installment of a $1-billion grant for the 4.7-mile light-rail line, from Cambridge to Medford. The grant was first approved in 2015, when the project was predicted to cost $2 billion. But the project's federal funding fell into limbo after the budget ballooned to $3 billion. The MBTA fired its contractors, scaled down the project's design to bring the budget down to $2.3 billion and eventually got re-approval for the $1 billion in federal funding.   

The state received a $1.7-million federal payment for the project in July. In November, a Fluor and Middlesex Corp.-led joint venture, GLX Constructors, won the bid to build the rail line. 

Besides successfully completing a series of federal design reviews, the creation in 2015 of the state's Fiscal and Management Control Board was also a "critical factor" in deciding to proceed with the grant, stated a press release announcing the award.   

"Gov. Charlie Baker's commitment to responsibly manage taxpayer dollars in the building of this project was persuasive," U.S. Secretary of Transportation Elaine L. Chao said in a statement. "The region can now look forward to an enhanced transportation network as the Green Line is extended to serve tens of thousands of area residents daily."

In a statement, Baker said, "The Green Line Extension project will provide important public transit service that will have a transformational impact for this region of the Commonwealth to accommodate riders and spur economic growth."