SOMERVILLE (AP) — A major Massachusetts transportation project is under way.

Republican Gov. Charlie Baker joined U.S. Transportation Secretary Elaine Chao and Somerville Mayor Joseph Curtatone, a Democrat, for a groundbreaking ceremony Monday for the $2.3 billion Green Line extension project.

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Gov. Charlie Baker and transportation officials at Green Line Extension groundbreaking (WBZ-TV)

It’s designed to extend the public transit line about 4.7 miles through east Cambridge into Somerville and Medford.

Chao used the event to announce the release of a $225 million federal grant agreement for the Massachusetts Bay Transportation Authority to extend the Green Line.

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The project includes seven new light rail stations, the replacement or rehabilitation of eight bridges, and a new pedestrian/bike path.

Green Line extension map. (WBZ-TV)

The extension is expected to generate about 40,000 new transit trips a day, improving access to jobs and opportunities in Boston and the communities of Somerville and Medford.

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