ENR 2024 New England Best Projects
Best Project, Landscape/Urban Development: Boston City Hall Plaza
Photo courtesy Shawmut Design and Construction
Boston City Hall Plaza
Boston
BEST PROJECT
Submitted by: Shawmut Design and Construction
Owner: City of Boston
Lead Design Firm/Civil Engineer: Sasaki
General Contractor: Shawmut Design and Construction
MEP Engineer: Arup
Structural Engineers: Weston & Sampson; SGH
Owner’s Representative: Skanska USA
Spanning seven acres, the comprehensive $70-million renovation has revitalized an iconic public space into a vibrant, accessible, and sustainable urban plaza. The transformed space offers a variety of seating options, a public art space, speaker’s podium, interactive water features, playground and other interactive elements that encourage social interaction and community engagement.
To reconcile a step-filled 26-ft vertical elevation change across the plaza, the project team collaborated closely with Boston’s Disabilities Commission to create Hanover Promenade, a gently sloping central pathway that ensures universal access to all program areas.
Photo courtesy Shawmut Design and Construction
Sustainability is at the heart of this renovation. Where original impermeable surfaces contributed to neighborhood stormwater runoff issues, the combination of planting beds, permeable pavement, rain gardens and other green infrastructure filters 60% of the plaza’s rainwater and restores the groundwater conditions.
Most of the rainwater from other parts of the plaza is collected in a 10,000-gallon tank for reuse as irrigation. Solar panels installed on site support the plaza’s energy needs, reflecting Boston’s commitment to renewable energy.
Photo courtesy Shawmut Design and Construction
More than 250 trees, 3,000 shrubs and 10,000 new perennials and grasses shade more than half of the new plaza. Along with creating a diverse plant-rich environment that supports local ecology, the extensive vegetation minimizes heat-island effect and sequestered more than 55,000 tons of carbon emissions.
A key challenge for the project team was the presence of three subway tunnels and associated vent structures beneath the plaza. Constructed in 1898, the tunnels had not been load-rated. To mitigate the risk of differential settlement under new loads, detailed inspections and structural evaluations were conducted to identify and repair compromised columns.
Photo courtesy Shawmut Design and Construction
The team also over-excavated soils above the tunnels and installed lightweight fill materials such as geofoam and foam glass aggregate. This innovative approach ensures long-term stability of both the plaza and underlying infrastructure, and reduced project duration by more than six months.
The renovated plaza now serves as a dynamic civic space, hosting a wide range of public events from farmers markets to concerts and cultural festivals—setting a new standard for sustainable, inclusive and resilient public design.
