New Green Line stations are expected to be completed by 2017, Boston.com reports.

A MassDOT panel unanimously approved a $393 million contract earlier this week for construction of three new stations, including a new Lechmere terminal across the street from its current location. The two other stations will be built in Somerville’s Brickbottom  and Union Square neighborhoods.

Financially, this was the Green Line Extension project’s biggest commitment, Boston.com reports.

Mary Ainsley, MBTA Design and Construction Department Director, told a MassDOT panel that the Union Square and Brickbottom projects should be completed by 2017, according to Boston.com. Construction is expected to start next spring.

In addition to the new stations, the expansion is set to bring the trolley line to Medford, with stops at Gilman Square, Lowell Street, Ball Square and College Avenue.

White Skanska Kiewit will help construct and design the the multiphase extension plan. Phase one consist of repairs — already in progress — to two bridges in Cambridge.

The Green Line Extension was originally required to be completed by Dec. 31 2014, but that deadline was never expected to be met, according to the Boston.com report.

The MBTA’s website says that the “GLX” will eventually bring a total of seven new stations to right-of-way Lowell and Fitchburg lines. A “mainline” would operate between new Lechmere Station in Cambridge and Medford while another branch will provide services along the Fitchburg Line to Union Square.

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