All aboard? Amtrak joins push to relocate USPS and expand South Station.

Momentum is building (again) to move the US Postal Service and make way to expand South Station

The US Postal Service sorting facility alongside South Station.David L. Ryan/Globe Staff

Maybe there’s finally light at the end of the tunnel in the state’s quest to expand jam-packed South Station.

The reason for newfound optimism? Amtrak is now a full partner in the hunt for a deal that would persuade the US Postal Service to leave its spot next door to Boston’s busiest station, so it can get even busier. Governor Maura Healey’s administration hopes to pull off what previous administrations could not by securing this valuable site overlooking Fort Point Channel to add more tracks. Without it, there’s no space to grow. Having Amtrak fully on board should help, considering the national railroad operator’s own ambitions for increasing service in the Northeast.

Top officials at Amtrak, the Massachusetts Department of Transportation, and the MBTA just wrote to the USPS to reopen negotiations for the 14-acre property. The $2 billion-plus South Station expansion, which would add up to 10 tracks to the existing 13, had been sidelined in part because the postal service showed no sign of budging.

The station is essentially at capacity now, putting the brakes on any plans to add more trains.

East-West Rail? MassDOT just landed $108 million in federal infrastructure funds to improve tracks between Springfield and Worcester, paving the way for Amtrak to add two cross-state trains to its lone daily sojourn. But without more room in Boston, that only goes so far. South Coast Rail? Extending existing trains further south to Fall River and New Bedford will be fine when that service launches next year, but increasing the frequency on those trips could be tough.

And the Fairmount Line? Dreams of converting this relatively short route through Roxbury, Dorchester, and Mattapan into electrified rapid transit with increased frequency would also hinge on a station expansion.

No wonder Healey made the postal service a priority during her first year as governor. In March, MassDOT asked USPS to restart negotiations. MassDOT and Amtrak wouldn’t have sent the latest letter, a more formal entreaty, if the postal service had closed the door. In fact, the letter indicates the USPS has signaled that it’s prepared to enter negotiations to sell the site. This could be getting serious.

Bill Hughes, a US Postal Service driver, loaded trucks with mail at the Fort Point United States Postal Service processing facility in 2021.Erin Clark/Globe Staff

MassDOT declined to share the letter with the Globe. Instead, the agency issued a brief statement saying it is pursuing talks with the postal service alongside the MBTA and Amtrak about the possible acquisition of the sprawling property at 25 Dorchester Ave., a hub for mail sorting and delivery as well as USPS administrative staff.

A spokesperson for Amtrak responded with the same statement when asked about the negotiations. Well, at least we know they’re on the same page, right?

Yes, Amtrak’s presence is important. But also noteworthy in this round of negotiation is who is absent: the Massachusetts Port Authority.

That’s a big change. For most of the past two decades, Massport had been integral to these discussions, because of its vast real estate holdings. State transportation officials had long wanted to offer USPS a new home, to sweeten the deal, and saw Massport-owned land about a mile away by the Reserved Channel in South Boston as an ideal spot. Bring the USPS closer to Logan Airport, the thinking went, and keep blue-collar jobs in the city. Massport would have traded that land for USPS parking lots in Fort Point, a land swap that complicated matters.

Now, Massport is no longer involved. Representative Bill Straus, co-chairperson of the state Legislature’s transportation committee, sees this as a positive step. It simplifies negotiations immensely. Instead of three-dimensional chess requiring three major transactions in a booming part of the city, the talks would now be focused on one thing: control of the USPS site.

Ten years after he tried to pull this off, former state transportation secretary Rich Davey still refers to the USPS site as “one of those big fish that got away.” Now president of New York City Transit, Davey praised the Healey administration for pursuing a prize that eluded her predecessors, including his former boss, then-governor Deval Patrick.

The property, in Davey’s view, remains much better suited for an expanded South Station with a private-sector air rights development on top than for mail processing. Davey said he kept Amtrak in the loop while representing Patrick, and he’s encouraged that Amtrak has a more active role now. Obtaining the property was a no-brainer back then, Davey said, and it makes even more sense today.

Postal trucks left the USPS sorting facility along Fort Point Channel downtown.Jonathan Wiggs/Globe Staff

Kate Dineen, head of business group A Better City, also praised Amtrak’s stepped-up participation. Amtrak offers important clout in Washington, she noted, something that may prove crucial to a deal. This, she said, seems like a natural next step after MassDOT and Amtrak landed that grant to improve the tracks in Central Massachusetts.

Not everyone will be on board, though.

Some fans of a North-South Rail Link worry that the billions to expand South Station would be better spent on their preferred alternative: a tunnel that finally connects South Station and North Station, allowing trains to roll right through and minimizing the need for extra platforms. Among those South Station expansion skeptics is US Representative Seth Moulton, a longtime N-S Rail Link proponent. Through a spokesperson, Moulton said he supports efforts to secure such a valuable property. But he argues it should be used for more than a “train parking lot” and instead be the foundation for “an inclusive, dynamic neighborhood.”

All eyes will be on Moulton’s colleague, US Representative Stephen Lynch, the Massachusetts delegation’s point person on postal issues. As a lawmaker from South Boston, Lynch has long supported the land swap that would keep these jobs nearby. It’s not clear whether he would embrace a plan to buy out the USPS, which employed up to 2,000 people there in the spring, without a plan to keep those jobs in the city. (Lynch could not be reached for comment.)

Then there’s the price tag. These 14 acres are worth tens, if not hundreds, of millions of dollars. Healey and her team are fully aware of the once-in-a-generation availability of federal infrastructure funds. They want to strike before these pots get emptied out.

In some ways, elements of a South Station expansion are coming together. The MBTA acquired nearby Widett Circle for train layover, and improvements are underway to signals and switches between Back Bay and South Station.

But a big piece remains missing. And it remains to be seen whether the Healey administration, working with Amtrak, can secure it before the gravy train from Washington leaves the station.