Ronkonkoma's new downtown is about to get bigger. TRITEC Real Estate, Northwell Health and a lineup of county and town officials gather Tuesday morning at the Carroll Avenue end of Station Yards to break ground on the project's next phase: three new five-story buildings holding 285 apartments and a 30,000-square-foot Northwell medical hub, a $175 million addition to the neighborhood rising across from the Ronkonkoma train station.

The ceremony, set for 10 a.m., marks the fourth phase of a development that has been remaking the blocks around Long Island's busiest LIRR hub since the first shovels went in. At a planned $1.3 billion overall, Station Yards is the largest transit-oriented development on Long Island, one of the biggest bets anywhere in the state on the idea that Long Islanders will trade a yard for a walk to the train, and it sits beside one of the Island's busiest train stations.

What Phase 2C actually builds

The new phase, which TRITEC calls Phase 2C, covers a 6.72-acre site bordered by Union Avenue and Carroll Avenue. Demolition to clear the land began over the summer, and construction on the three buildings is expected to run about 18 months, which puts the first move-ins and the first medical appointments somewhere in 2028.

The 285 apartments will spread across all three buildings, designed by Marc Spector of the Woodbury-based Spector Companies. They join a rental neighborhood that has been filling steadily since the first phase opened, with ground-floor storefronts that already include a French bakery and a growing roster of shops and services.

The anchor tenant is the bigger story. Northwell Health has taken 30,000 square feet on the ground floor of one of the new buildings for a multi-specialty practice, the largest commercial lease Station Yards has signed to date. For the health system, it is a flag planted directly on top of a commuter hub where thousands of people pass through every weekday. For residents of the new buildings and the older ones around them, it means a doctor's office a short walk from home instead of another errand by car.

A downtown that did not exist five years ago

Anyone who parked in the old Ronkonkoma station lots remembers what this land used to look like: acres of cracked asphalt and chain-link beside the tracks. The transformation since then has been steady. The first phase, a 489-unit complex called Alston, was finished in 2020 and filled almost immediately. The Core followed at 3 Hawkins Avenue, stacking 388 more apartments above 70,000 square feet of retail, and its second building celebrated completion this past June. At street level, The French Workshop bakery is open and baking, Bloom has brought a florist, salon and spa to the neighborhood, and Island Greens is bringing its indoor golf lounge out from Franklin Square so commuters can swing a club before the 7:14.

Each new phase has added not just apartments but reasons for people who do not live there to show up, and Tuesday's groundbreaking leans into that. A medical anchor generates daytime foot traffic in a way that apartments alone cannot, and the restaurants and retailers already open at Station Yards are counting on those patients, employees and visitors to fill lunchtime seats that commuter neighborhoods traditionally leave empty.

Who is showing up for the shovels

The guest list for Tuesday's ceremony says something about how much institutional weight is behind the project. Suffolk County Executive Ed Romaine is expected, along with Sarah Lansdale, the county's planning and economic development commissioner, and Lisa Mulligan, who runs the Town of Brookhaven's Industrial Development Agency. Northwell is sending Stephen Bello, the executive vice president who runs the health system's eastern market, and TRITEC's co-presidents Kelley Heck and Jimmy Coughlan will be there for the company that has steered the project from the start.

TRITEC has said the Northwell lease strengthens the vision of Station Yards as a true mixed-use destination, bringing new jobs, daytime activity and everyday health care to a neighborhood built around the train. The company expects the steady flow of employees, patients and visitors to feed the retailers and restaurants that give a downtown its pulse.

What it means if you live here

For renters, 285 new units is the largest single addition of apartments Station Yards has announced since its early phases, in a region where new rental housing is scarce enough that every building fills. For commuters, it is another stretch of the walk from the platform that looks like a neighborhood instead of a parking field. And for anyone in the Ronkonkoma, Lake Ronkonkoma or Holbrook orbit, the Northwell hub will eventually mean specialist appointments a few steps from the train rather than a schlep west on the LIE.

There is also a quieter milestone in Tuesday's ceremony. Big Long Island projects are routinely announced, rendered and then stalled for years. Station Yards keeps doing the unglamorous thing instead: finishing a phase, then starting the next one. The cranes that go up over Union Avenue this fall will be visible from the platform, which means tens of thousands of commuters get to watch the next piece of their station neighborhood arrive one floor at a time.