Phoenix Project #1908
Renovations to the side entrance and interior of St. Cecelia’s Parish in Boston required the installation of 14 drilled micropiles (“DMPs”), with piles located both inside and outside the historic structure. The piles had a capacity of 30 tons, incorporating permanent drill casing through the fill soils and an uncased bond length within the underlying sand layer. Despite the piles only being 30 to 35 feet deep, this project was not without its challenges.
The outside piles were located within a very tight site that was boxed in on all sides and depressed 4 feet below street grade. These site constraints made maneuvering the drill rig into position and navigating around newly-installed piles a constant challenge. Additionally, the site was riddled with shallow obstructions. A few locations were pre-excavated where practical; the remaining obstructions were eventually drilled through during the micropile installation.
As is the case with a majority of project sites, spoils management was critical. Having such a small footprint, this site had the potential to flood quickly once drilling began. In order to maintain control of spoils, an open top water tank was brought on-site. As drilling proceeded, liquid spoils were pumped away from the drill location and into the tank, allowing Phoenix to then recirculate water out of the tank and back to the drill rig. This process significantly reduced the amount of fresh water that had to be introduced to the site.
After completing the 10 exterior piles, Phoenix still need to install the 4 interior piles. This required walking the drill rig through a narrow opening in the side of the building, down a steep ramp, and into a tight room within the basement that would eventually house the elevator shaft. This was accomplished with a nimble track-mounted drill rig manufactured by Davey Kent, the first rig that Phoenix procured for its drilling fleet.
The Davey Kent DK-525 specializes in limited access projects, yet is versatile and powerful enough to tackle many outdoor drilling applications as well. With a detachable power pack that can be left up to 90ft away from the rig itself, this machine is ideal for tight access and low headroom drilling. Additionally, having the power pack remain outside while drilling inside helps to mitigate noise and exhaust issues that would otherwise result from running a diesel drill rig inside a building.