The opening of the first Green Line Extension branch has been delayed — again

MBTA officials had initially envisioned beginning passenger service on the Green Line Extension’s shorter branch to Union Square this month. Then, in June, they announced the branch’s opening would be delayed until December.

Now, that ribbon cutting is going to have to wait another three months — and the planned May 2022 opening date of the longer Medford branch may be pushed back as well.

Primarily citing unexpected issues with a power substation built for the project, MBTA General Manager Steve Poftak announced Thursday afternoon that the opening of the Union Square branch would be postponed until March.

“That’s unfortunate,” Poftak tolder reporters during a conference call. “We really were looking forward to delivering this project in December. But we’ve faced a variety of challenges that have forced us to push the schedule out.”

Officials had cited supply chain issues exacerbated by the COVID-19 pandemic for the first delay announced in June.

Poftak said the new delay was primarily due to productivity challenges setting up an electric substation — located near an elevated viaduct near the Cambridge-Somerville border where the two GLX branches diverge — that will provide power to the Green Line trolleys on the one-stop Union Square branch.

According to Poftak, crews were constrained by the size of the station, making the process “more challenging than the original schedule had envisioned.”

“There’s only so many people who can fit inside that space and do productive, technically demanding work,” Poftak said. “And I think that proved to be one of the challenges.”

Poftak noted that there are two similarly sized power stations along the longer, five-stop branch through Somerville to Medford, and said that crews are hoping to apply the newly learned lessons to their work on the so-called “Branch 2.”

However, he suggested that the Medford branch’s opening — already delayed from this December until May 2022 — would likely be delayed as well.

“It is one of the challenges we are facing, and it is one of the areas that we are concentrating on as one of the critical path items,” Poftak said. “If we’re not more productive and more efficient in building out these next two traction power substations, it is going to impact the schedule.”

Poftak noted that the MBTA has been in close conversations with GLX Constructors — the group of companies contracted to build the $2.3 billion project — about the impacts on the Medford branch and would make an announcement when they had more confidence in the schedule.

“I have not abandoned all hope on that,” he said.

While he acknowledged the news was “disappointing,” Poftak expressed confidence that Thursday would be the last time he would have to make such an announcement, at least when it came to the Union Square branch.

“I have a real high level of confidence that this will be the last delay, sort of leaving open that we are still working on Branch 2,” Poftak told reporters.

“It was my hope that the announcement in June was our final announcement related to schedule,” he said. “Obviously, that’s not the case. We have spent an awful lot of time — both internally at the T and with GLXC — to make sure that we can hit this March date.”