THE MBTA IS BUILDING OUT its project staff for the Green Line Extension into Somerville and Medford and keeping on board two consulting firms that have helped steer the project to its current slimmed-down form.

The Fiscal and Management Control Board on Monday agreed to pay Weston & Sampson as much as $16 million and Arup as much as $24 million to provide support services for the Green Line Extension. Both consulting firms played key roles in scaling back the cost of the project when the price tag ballooned from $2 billion to more than $3 billion. With the project’s redesign, the current price estimate is $2.3 billion.

John Dalton, the T’s point person on the Green Line Extension, also said he has hired four other employees to help him oversee the project, leaving only two vacancies on his seven-person team. Asked for the names of the new employees, T officials declined to release them, saying the workers had been selected but not officially hired yet.

The T is meeting Wednesday and Thursday with federal regulators to complete a risk assessment of the project that will go a long way toward determining whether the Federal Transit Authority feels confident enough to release the $1 billion it has set aside for the Green Line Extension. One of the chief concerns of federal regulators has been whether the T has sufficient management expertise to oversee the project and keep costs under control.

Dalton said he plans to formally issue a request for proposals from construction teams in May and ask that the final proposals be submitted by the end of September. He said the request for proposals will encourage builders to consider innovative ways to reduce costs further or include aspects of the project that were whittled away when the project was redesigned. Several advocates are pushing for a community path along the length of the transit project, but T officials are not committing to that.

Still, Dalton sounded confident the Green Line Extension is about to move forward. “There’s real momentum on the GLX now,” he said.

Bruce Mohl oversees the production of content and edits reports, along with carrying out his own reporting with a particular focus on transportation, energy, and climate issues. He previously worked...