A Green Line train proceeds onto a stretch of brand-new tracks between Science Park and a freshly constructed Lechmere Station during a test run on Feb. 3, 2022. Photo by Chris Lisinski | State House News Service

Contractors responsible for fixing narrow rails on the MBTA’s newest stretch of tracks requested a second extension for their project that could push its endpoint into the new year, the agency’s top boss said Wednesday.

MBTA General Manager Phil Eng said his team has not yet approved the latest proposal for more work to widen rails across the 4.4-mile Green Line Extension, more than two-thirds of which are too close together.

Green Line Extension Constructors, the consortium of contractors that built the tracks and is now tasked with resolving the problems, was unable to complete repairs on the initial timeline that involved 14 nights of work.

Eng said once GLXC requested its first extension, T officials told contractors to come up with “a new staffing plan” including “the level of supervision that will be there.” Firms increased the number of employees on site from 14 to about 30, he said, adding that “the production levels have improved.”

MBTA officials announced Friday they gave the firms at least another week of evening and nighttime access to continue the work.

“We do have another request from them for additional nights in January, which we have not approved at this point. Part of the reason for that is that we are reviewing the work that we need to accomplish as well as the amount of support that they need,” Eng said Wednesday. “We are still committed to getting this work done. They’re committed to delivering it, and we’ve made it clear to them this is their responsibility and not something the MBTA is going to be responsible for.

They need to own this and they need to accomplish it.”

Eng has previously said he intends for GLXC – a joint venture that includes Fluor Enterprises Inc., The Middlesex Corp., Herzog Contracting Corp. and Balfour Beatty Infrastructure Inc. – to cover the costs of repairs, not the MBTA itself or taxpayers.

T officials under the Baker administration knew as early as 2021 that some tracks for the Green Line Extension were too tight, but they did not prevent the problem from becoming widespread and it exploded into public view this year with disruptions to travel speeds.