Phoenix Project #2021
The town of Dedham began construction of a combined public safety building in December 2020 on the site of the former Town Hall at 26 Bryant Street. The new building would house the staff and equipment of Fire, Police, and Dispatch departments.
Phoenix was hired by The Welch Corp to design and install a temporary soil nail system to support the excavation for the foundation and underground parking. Soil conditions may have allowed for the use of a traditional driven sheetpile system, but overhead power lines running along the perimeter of the property forced alternative soil retention systems to be considered instead.
Temporary soil nailing is typically progressed in vertical excavation depths of approximately five (5) feet at a time. As the excavation is performed, a temporary shotcrete facing is constructed against the excavated face, supported structurally with a layer of welded wire reinforcement. Soil nails are then drilled through the shotcrete facing (or prior to the placement of the shotcrete facing in some cases), leaving a fully grouted and reinforced borehole at each nail location. Proof testing of a number of soil nails at each vertical level is standard practice, providing added assurance that production work is being performed in accordance with the design and specifications.
All told, Phoenix installed over 350 soil nails and placed nearly 9,000 square feet of shotcrete to support cut heights of up to 15 feet. Notably, the entirety of this project was performed during the months of January and February, contradicting the common misconception that shotcrete work cannot be performed during the winter.