Boston has not seen development over the Massachusetts Turnpike since the 1980’s. Financing and engineering challenges have plagued numerous proposals, but plans for Parcel 12 Air Rights are finally under way. Developer Samuels & Associates is constructing a mixed use project on an approximately 1.81 acre site where the Massachusetts Turnpike (I-90) intersects Boylston Street and Massachusetts Avenue.
The veteran Boston developer secured the air rights for the project from the Massachusetts Department of Transportation in 2013 and after obtaining financing, the project is moving toward a 2023 completion date. The new construction includes an office component, a hotel component, a 2-level, below grade parking facility with 150 spaces, as well as retail/restaurant component that wraps around a new, urban landscaped plaza.
The $700 million complex features two high-rises on either side of a one-acre deck over I-90 in a long-neglected corner of Boston’s Back Bay. Building over eight lanes of highway and MBTA Commuter Rail tracks requires extensive coordination. The creative design puts less weight on the air-rights deck which helped to keep costs down. The layout allows the foundation for the two high-rises to anchor in bedrock next to the deck.
The complex coordination is being orchestrated by General Contractor Suffolk Construction, and can be seen as work crews and equipment tackle the tight urban site. Along with spanning over the highway, the developer was also required to complete significant additional infrastructure work around the site. That work includes wider sidewalks, new bike lanes, an entrance to the MBTA Green Line stop, a renovated pedestrian tunnel to the Convention Center, and a half-acre plaza that is accessible to the public.
Another aspect that needed to be completed before work could begin on the vertical construction was the relocation of the turnpike’s westbound onramp from Mass. Ave. to Newbury Street. Moving the I-90 ramp to the west completed the pedestrian and retail loop between Newbury and Boylston Streets.
Given the logistics and no storage or lay down area, pre-fabricated materials were necessary. Precast concrete slabs comprise the podium deck which were fabricated off site, trucked to the job and then assembled. JP Carrara & Sons, Inc. designed and manufactured structural precast components including Prestressed Solid Deck Beams, L-Beams, Solid Slabs and Balcony Slabs on a design-assist basis.
Precast Solid Deck Beams spanned 40-feet and were 15-inches thick. Some 200 solid slabs were 8-inches thick and spanned up to 27-feet. To meet the increased fire resistance requirements of tunnel construction, Carrara applied fireproofing at the precast plant prior to shipping the precast pieces to the jobsite. They utilized a stainless steel metal lath system as a platform to embed and attach the sprayed- on fireproofing material to the structural members of the deck.
The construction of the deck required partial lane closures along the turnpike. Installation of the more than 250 precast components began in November of 2021 and wrapped up in April of 2022. In total the precast podium deck above I-90 extended 272-feet long by 100-feet wide and the MBTA podium deck dimensions were 272-feet long by 40-feet wide.
The proposed mixed use project is an opportunity to reunite Boston neighborhoods that were disrupted by the Turnpike extension decades ago. The two towers that flank the new public plaza will provide the missing link for visitors and residents of the Back Bay.
Precast concrete slabs created a platform over the railroad and highway so that vertical construction of the buildings can begin. After a decade of planning and preparation for this air rights project, completion is scheduled for 2023.