Geothermal Boreholes & Borefields
Geothermal (GT) borefields provide a sustainable energy source for heating, ventilation, and air conditioning (HVAC) systems in buildings, structures, and communities. They are also among the most efficient Earth-powered systems for heating and cooling.
Heat transfer fluids, typically water and antifreeze mixtures, circulate within a Closed- Loop Ground Source Heat Exchanger (GSHX). These fluids obtain thermal energy from the boreholes’ conductive grout and the surrounding soil or rock. Geothermal boreholes are usually 5 to 8 inches in diameter and typically range from 500 to 1,000 feet in depth. A borefield may consist of dozens to several hundred boreholes, depending on the system design.
Similar to drilling for micropiles or conventional water wells, geothermal boreholes are advanced through overburden soils to suitable bedrock. This process uses either permanent or temporary drill casing with air or wet-rotary flushing, or open-hole wet rotary methods. Once bedrock is reached, the boreholes are extended to the required design depth using pneumatic or wet-rotary techniques. After reaching the target depth, the boreholes are cleared of spoils, sediment, and rock fragments before installing the geothermal HDPE loop piping and tremie pipe.
Phoenix Foundation Company uses duplex-style drilling, similar to methods used for micropiles, to improve productivity during borehole advancement. This approach is effective for both vertical and inclined geothermal boreholes. Phoenix employs a highly- skilled and trained union workforce, and utilizes federally qualified apprenticeship programs to deliver consistent, high-quality service across all geotechnical and geostructural projects.
We also offer options for connecting geothermal boreholes and borefields to the buildings and systems they serve. These connections are made through lateral circuit piping, header pipes, manifolds, and geothermal vaults. Each individual loop or circuit is flushed and purged, then tested for flow and hydrostatic pressure during construction to ensure system integrity.
Phoenix has State Certified Well/Borehole Drillers, National Groundwater Association (NGWA) Accredited Drillers, International Ground Source Heat Pump Association (IGSHPA) Accredited Installers, and McElroy Certified fusing Installers on staff for every project.
