Union Square

Updated September 21, 2026

What's happening

Twelve years after US2's 2014 kickoff, Union Square is one-quarter built and the commercial half is stalled. The D2 block — the old scrapyard, now the 450-unit Prospect Union Square with its 25-story tower — represents 25.3% of the master plan and is in leasing and occupancy. The 196,500 sq ft lab and office building next door at 10 Prospect Street, finished in 2024, still has no announced tenant. The next piece, a nine-story, 280,000 sq ft R&D building at 50 Webster Avenue worth another 11.7% of the plan, is fully permitted and shovel-ready and is waiting for the commercial leasing market to come back (Somerville Times, March 11).

The other Union Square story of 2026 was the Hamilton Company's attempt to rezone the block it had quietly assembled — from Dunkin' Donuts up to Midnite Convenience — out of commercial zoning and into housing. That petition drew heavy opposition at an April 16 hearing and was withdrawn in June. Hamilton restarted from the community end, hosting a "Community Meeting for One Union Square" on September 9 at Urban Axes, 2 Union Square, to "share your ideas for creating new housing and green space" (Somerville Chamber of Commerce newsletters, August 14, 20, 26 and September 9); what was said there, and whether a new rezoning petition follows, is not in our sources yet. The neighborhood council that would negotiate any benefits is itself in flux: its co-chair Emily Doran, part of the Somernova benefits team, has expressed interest in running for the Ward 2 seat JT Scott is vacating (Cambridge Somerville Independent, Sept 12; Three Council seats turn over).

The MBTA may also make the square a transit hub of a different kind. Package C of the agency's proposed Bus Network Redesign amendments would reroute Route 96 to end at Union Square instead of Harvard and make it a "frequent" route, every 15 minutes or better, because the agency wants a frequent route through "a neighborhood that currently lacks frequent service"; nothing changes before 2028 at the earliest (Streetsblog, Sept 4). See Mobility projects.

The story

What US2 has and hasn't delivered

US2 (Union Square Station Associates) was selected as master developer by the Somerville Redevelopment Authority in 2014, over a Citizens' Advisory Committee that had recommended a different firm. Its president, Greg Karczewski, gave the SRA a progress report on March 4, 2026. The completed first phase includes the Green Line station (opened 2022), Somerville Avenue and Eversource infrastructure, the city's first community benefits agreement, the D2 conversion, a one-time $36 million fiscal benefit and roughly $4 million a year in new taxes. The full build is envisioned as about 17 buildings, 11 public open spaces and 3.6 acres of civic space and public realm, roughly 60% commercial and 40% residential by zoning.

That 60/40 split is the problem. Karczewski described a concerted push to fill 10 Prospect Street — nearly 30 events hosted to court life sciences, AI, robotics and climate tech, spec suites on floors five and six ranging from 10,500 to 31,500 sq ft — and called the building "a catalyst for the commercial development and urban revitalization of the neighborhood." A year and a half after completion it is still empty, which Bisnow reported in October 2025 alongside the same story at Boynton Gateway and 808 Windsor. Roughly 55% of lab space in the Watertown–Somerville–Allston–Brighton–Fenway ring was available; more than two-thirds of the region's leasing was going to Cambridge. See The lab glut and the tax base for what that does to the city's budget.

Economic Development Director Rachel Nadkarni told the Finance Committee on June 17 that movement is expected on Union Square's D-4.3 parcel in FY27 (June 17 Finance).

The Hamilton rezoning fight

On February 12 the Council referred to Land Use a request from Union 2 Associates LLC to rezone 2 and 9 Union Square and 286, 290 and 298 Somerville Avenue from Commercial Core 5 — which allows no residential — to Mid-Rise 6 (Feb 12 Council). At the joint Land Use and Planning Board hearing on April 16, architect Tim Talen and principal Jameson Brown pitched 150 to 200 housing units with 30 to 40 affordable (20% on site), civic open space at the Prospect Street corner, a possible ground-floor branch library, streetscape work including a two-way bike lane on Prospect Street, and a commitment that at least half the units be two- and three-bedrooms (April 16 Land Use).

Testimony ran heavily against, on three tracks:

Tax base. Bill Shelton, Megan Minger, Tori Antonino and Mike Grunko argued Somerville's 18.8% commercial tax base is already dangerously low and that converting prime commercial land to housing makes the city's fiscal position worse. Shelton cited city-funded studies showing commercial space generates far more net revenue per square foot than residential.
Spot zoning. Meredith Porter and Brian Hochleitner, counsel for US2, called it spot zoning inconsistent with the 2016 Union Square Neighborhood Plan and the master developer agreements. Hochleitner said it would violate the Master Land Disposition Agreement between US2 and the SRA, and that eminent domain provisions in those agreements could make Hamilton's plan impractical.
Affordability. Several speakers said 20% is not enough and that the city needs affordable housing, not more market-rate units.

Two speakers supported the change, arguing the Commercial Core category should be phased out citywide.

Shelton's April 15 op-ed in the Somerville Times, "The wrong use in the wrong place," is the fullest statement of the anti-conversion case. It recounts Hamilton's Boston record — identified as a slumlord by Allston-Brighton tenant organizers and Jamaica Plain's City Life/Vida Urbana, and often at or near the top of Boston Inspectional Services complaints — and then the planning history: SomerVision 2030's goals of 30,000 jobs, 125 acres of open space and 6,000 housing units; the 2016 neighborhood plan that delivered 3,130 units and "meager open space" but did zone the Hamilton block commercial; and the 2017 Mandatory Mixed Use Ratio requiring at least 68% commercial square footage in Union Square, Assembly Square, Boynton Yards, Brickbottom and Inner Belt, which Shelton says planning staff never implemented and which was dropped from the 2019 zoning overhaul. (Shelton's piece describes the request as Mid-Rise 5; the filing was Mid-Rise 6.) The comment thread under it is the argument in miniature — one reader calling the commercial case "stuck in a bygone playbook" given empty labs, another replying that "commercial demand is cyclical."

The petition was withdrawn at the applicant's request on June 18, with no discussion (June 18 Land Use). Ward 3 Councilor Ben Ewen-Campen noted it a week later, describing the block as running "from Dunkin' Donuts all the way over to where Baek Gyeong, Korean restaurant is" (June 25 Council). Nothing in our sources shows a refiled petition — the September 9 meeting is Hamilton starting the conversation over, on housing and green space, before it files anything.

The other zoning news

The Planning Board adopted the Arts and Innovation District Urban Design Framework on August 6. It began in December 2024 as a response to Rafi Properties' SomerNova rezoning proposal and was worked out with neighbors, the Union Square Neighborhood Council, Rafi and planning staff; the city calls it the final component of the Five Point Plan and the design standard for growth along Central Somerville Avenue (Planning Division newsletter, August 28; Planning Board agenda, August 6). The same agenda carried a design recommendation for 32 Webster. At 24 Webster Avenue, a foundation-only permit for a 42-unit building was issued on March 9 (city permit data, Citizenserve export, 2026-09-01).

Transit work in the square — the red bus lanes on Prospect Street tied to the MBTA bus network redesign, and the Eastern Washington Street transit priority project that drew a $284,700 Gaming Commission grant referred to Finance on August 27 (item 26-1241) — is tracked on Mobility projects.

What's next

After September 9 — whether Hamilton files a new rezoning petition for 2 and 9 Union Square, and in what district, after its "One Union Square" community meeting (outcome not in our sources yet).
End of 2026 — the MBTA hopes for clarity on its bus-redesign amendments, including the Route 96 reroute to Union Square; implementation not before 2028.
FY27 — US2 expects movement on the D-4.3 parcel.
50 Webster Avenue — permitted and shovel-ready; the trigger is commercial leasing conditions, not city approvals.
10 Prospect Street — a lease here would be the clearest sign the Union Square commercial program is alive.