The MBTA will shut down service a few hours earlier than usual on the Green Line Extension on more than a dozen nights starting later this month while crews fix tracks that were improperly installed, officials announced Thursday.

Nearly a month after MBTA General Manager Phil Eng revealed that rails are too close together on more than two-thirds of the expansion, he laid out details for how workers will address the problems.

Trains will stop running on both the Union Square and Medford branches around 8:45 p.m. each night between Monday, Nov. 27 and Sunday, Dec. 10. During that time, shuttle buses will replace trains between North Station and Medford/Tufts, while riders hoping to get to Union Square will instead need to take other bus routes or the Orange Line, which travels to Sullivan Square.

Normal Green Line Extension service will resume at the start of each day, except for Dec. 4 and Dec. 5, when buses will replace trains between Lechmere and North Station all day.

“The intent is to tackle all of the tight gauge from end to end, Medford/Tufts and Union Square, and eliminate that issue once and for all,” Eng said at an MBTA board meeting on Thursday.

Eng said the T also plans to repair tracks on the Lechmere Viaduct during the upcoming nighttime work, which will allow the agency to lift a pair of slow zones.

The start of the GLX repairs will overlap with planned 24-hour closures of the Green Line between North Station and Babcock Street, Heath Street and Kenmore Stations, part of a sweeping maintenance campaign Eng rolled out last week.

MBTA officials suddenly slowed travel on large stretches of the nearly brand-new Green Line Extension to a crawl this fall after discovering that tracks were too close together.

Repairs allowed the T to resume full-speed travel, but Eng, who started on the job in April, said last month that 50 percent of the Union Square branch and 80 percent of the Medford/Tufts branch is still narrower than the construction standard and will need to be fixed.

Other officials at the MBTA were or could have been aware of the problem as early as 2021, before either branch opened to the public, Eng said. MBTA officials said last month that two senior employees on the Green Line Extension project left after the previous missed warnings became clear.

It was not immediately clear Thursday how much the upcoming work would cost or who would cover the bill. Healey administration officials have said they want Green Line Extension Constructors, a joint venture of contractors that built the expansion including Fluor Enterprises Inc., The Middlesex Corp., Herzog Contracting Corp. and Balfour Beatty Infrastructure Inc., to pay for the repairs.

(Copyright (c) 2023 State House News Service.

Join our Newsletter for the latest news right to your inbox