Multidisciplinary Engineering Services at Boston City Hall Plaza

Weston & Sampson provided environmental and geotechnical investigations and geotechnical and structural engineering for the 7-acre $80M City Hall Plaza Renovation as part of the Sasaki Associates team working for the City of Boston Public Facilities Department.

Proposed loads from the plaza on three MBTA tunnels (constructed in 1898) and potential associated differential settlement required creative solutions. Our team identified compromised columns, designed repairs, and conducted inspection during construction. Soils above the tunnel were over-excavated and replaced with lightweight fill, including geofoam and foam glass aggregate. Our design included tying the new plaza support structure into the tunnel walls. This approach required additional up-front work but ultimately saved $6M in construction and more than six months. We also designed large spans around vent structures and provided geotechnical engineering for a new public building with one below-grade level on three sides, among other elements.