PROJECT OVERVIEW
Phoenix Project #2106
Phoenix was contracted to install 45 drilled shaft foundations for the expansion of a “live” electrical substation in Cambridge, MA. All equipment was required to be grounded for safety reasons, and special fire-resistant (“FR”) clothing would need to be worn by the crew at all times. Several of the drilled shafts were so close to existing structures that special power outages had to be coordinated with Eversource’s regional operations before that work could be performed safely.
During the preconstruction phase, Phoenix reviewed the design parameters and assisted in re-engineering some of the drilled shafts to utilize shortened depths to save the project both costs and duration. In the end, our scope included the installation of 36 shafts (36” diameter) to support new transformer pads, with an additional 9 shafts (42” diameter) serving as mono-pole foundations for new lightning masts. Each foundation ranged from 17 to 30 feet in overall depth, and included up to a 24” finished concrete reveal above the existing ground surface. All shafts required the installation of both reinforcing cages as well as anchor bolt templates, which had critical tolerances of no more than 0.25 inch in any direction.
One additional challenge faced on this project was unforeseen subsurface obstructions. Drilling difficulties aside, the presence of a subsurface grounding grid required that special care be taken throughout the process of obstruction penetration and/or removal. Another challenge faced was when the robotic survey instrumentation being used by others experienced interference with the live power running through the substation. Ultimately, each obstacle was met and overcome by timely communication and collaboration between Phoenix, G. Greene, and Eversource.
