The $95 million Boston City Hall and Plaza Renovation aimed to re-develop the 7-acre plaza to create a more accessible, sustainable and comfortable place for Boston residents and visitors alike. The renovation included 12,000 square-feet of playscapes for children and families, an 11,000 square-feet of terraces for pop-ups and interactive public art as well as a new Civic Pavilion Building on Congress Street and three smaller event and gathering places.
Several challenges were faced a this project due to the site constraints of the Plaza itself. Several MBTA subway tunnels stretched across the site below grade required spanning at several locations with bridges with foundations supported by new drilled micropiles. Additionally, crane locations were an issue on the site, as the MBTA subway tunnels were not able to support crane surcharge loadings; therefore, an earth support system was required at the North side of the site. The earth support system was directly adjacent to the new Civic Pavilion Building location and the John F. Kennedy Federal Building to support a location where a crane could be located while excavations took place for the Civic Pavilion Building and adjacent MBTA tunnel. Additionally, the Civic Pavilion Building was designed such that no lateral earth or surcharge pressures could be placed against the West wall, and therefore the SOE was designed as a permanent structure at this location. The Civic Pavilion Building also was founded on new drilled micropiles.
Atlas Drilling LLC (Atlas) was subcontracted by the General Contractor, Shawmut Design and Construction, to install drilled micropile foundations and temporary earth support systems. Atlas engaged GTR to provide geotechnical and structural design services including temporary and permanent earth support design, drilled micropile design for the bridges (AASHTO and Massachusetts State Building Code designs) and static load testing. Additionally, GTR performed on-site quality control inspection services for the construction of the earth support system.
