Developers and MBTA clarify bridge and emergency access for 10 Plain Street; board seeks time triggers and monitoring

The Planning Board continued its public hearing on the 10 Plain Street project (planning file 25 0 6) and heard detailed updates from the applicant, Trammell Crow Residential (TCR), planning staff and peer consultants.

Mark Baranski of Trammell Crow said SLR’s updated base flood elevation work concluded the project would not create adverse impacts on bordering land subject to flooding; the applicant used conservative assumptions, adding two feet to targeted floodplain elevations to create a resiliency buffer. "SLR has confirmed that the project is not going to be creating any adverse impacts on the bordering land subject to flooding," Baranski said.

Baranski and staff described coordination with the MBTA on Hancock Crossing: the MBTA will permit a gated crossing for emergency vehicles only, and it will permit temporary construction access for bridge building, but it will not allow pedestrian or resident vehicle access. Planning staff told the board the MBTA indicated it did not want occupancy permits granted for Buildings 4A and 4B prior to completion of the bridge across the river; staff said the applicant accepted that condition as part of the project discussions.

The applicant presented a construction sequencing schedule showing Phase 1 (Buildings 1A/1B, 2 and 3 and early work on 4A/4B) delivered in staged lags and the bridge constructed early in the process so it is complete before west‑side occupancy. Baranski said Phase 2 construction will begin while Phase 1 is still being completed and that construction access will be routed in a way that segregates heavy construction traffic from early resident occupancy.

Traffic consultant Robert Michaud (MDM) said the analysis predicts the most critical movement at the Plain Street driveway is about just over one left turn per minute — roughly 75 vehicles per hour — and that monitoring and conservative assumptions indicate the driveway will operate under manageable delays. "Even at full occupancy of Phase 1 ... we're looking at volume at the Plain Street driveway for left turns ... about just over 1 per minute. That's 75 vehicles an hour," Michaud said. The consultant said data and peer review provide confidence that signal retiming or other operational fixes would address localized queueing if monitoring showed problems; police details would be a last resort.

Board members repeatedly pressed the applicant for contingency language in the draft conditions if Phase 2 were delayed or did not proceed (for example, requiring a second entrance or a time trigger to require additional access). TCR said it has contractual rights that would allow grading and making a transition area available for residential vehicles if necessary and said it would consider a time‑based condition; staff said the board could explore a requirement tied to closing or a set interval.

Members discussed community amenities: the applicant presented a sidewalk inventory and proposed sidewalk extensions, 15 daytime public parking spaces near a proposed playground, restroom access provisions and possible historical markers. The board asked the applicant and its landscape architect to revisit playground programming and consider a design that balances visibility, safety and passive uses.

During public comment, Robert Tomer, a nearby resident, urged caution about the riverwalk and boardwalk access, saying the existing boardwalk currently terminates in an area he described as unsafe and noted evidence of homeless encampments. "I wouldn't let anybody go down there," Tomer said, urging the town to hold off on recommending public use until the area is safe and integrated into the project.

Staff and applicant said they will continue drafting findings and conditions and will hold a special meeting to continue the hearing. The board set a special meeting for March 3 at 7:30 p.m. (to be held in Johnson Chambers) to continue review of findings and conditions.