PROJECT OVERVIEW
Phoenix Project #2424
This project involved constructing a geothermal borefield of 22 vertical boreholes to serve the first new building at the Mary Ellen McCormack campus in South Boston, Massachusetts. The building site occupied a small parcel of land, requiring Phoenix to carefully plan and execute its work with a strong focus on safety, efficiency, and quality. Effective coordination of drilling operations within a multi-trade environment allowed the team to successfully complete the project despite the constrained footprint and limited access.
During construction, sacrificial steel drill casing was advanced through the overburden and seated into bedrock at depths typically exceeding 200 feet below ground surface. Drilling then continued through uncased bedrock to a final design depth of 815 feet. Once this depth was reached, each borehole was filled with water and flushed clean to ensure proper installation of the geothermal HDPE loop piping and tremie pipe. After removing the drilling tools, Phoenix installed 1.50-inch double (or “quad”) HDPE closed U-bend heat exchanger loops along with the tremie pipe. Both were installed simultaneously to allow placement of a specially formulated, saline-resistant, thermally conductive (TC) grout from the bottom up. The tremie pipe was gradually extracted during grouting in accordance with QA/QC protocols, ensuring a continuous and uniform grout column throughout the borehole.
After completing the boreholes, Phoenix conducted flow and pressure testing on all loop piping, achieving favorable results. Working in close coordination with mechanical, plumbing, electrical, and excavation trades, Phoenix’s skilled union workforce self- performed the installation of all lateral HDPE circuit piping to the mechanical room. The entire borefield piping system was successfully tested and approved by both the project designer and owner.
