The National Ground Water Assn. (NGWA) unveiled its revised “Guidelines for the Construction of Vertical Boreholes for Closed Loop Heat Pump Systems” at its 2009 Ground Water Expo and Annual Meeting.
The guidelines come at a time when the demand for geothermal heat pump systems is rising, said NGWA, due in part to increasing energy costs and the availability of federal tax credits.
Revision of the original guidelines, developed in 1997, was in response to a demand for updated information from a variety of geothermal stakeholders.
“This guideline is written for many materially affected individuals within the groundwater industry including but not limited to geothermal borehole contractors, geothermal borehole design consultants, government officials, educators, students and consumers,” the guideline introduction said. “Our effort was intended to create an exposure to the current issues related to construction of vertical boreholes for closed loop heat pump systems and to offer insights as to the practical resolution of these issues. However, of paramount concern at all times was that we develop guidelines consistent with the protection of human health and the environment.”
The guidelines are not intended to be used for the designing of loop fields. Rather, the intent is to familiarize the drilling contractor with loop field design parameters.
The technical guidelines cover loop field design, test holes and samples; borehole construction; piping; borehole grouting; loop field identification; and permanent loop piping decommissioning. It also includes appendices on heat transfer fluids, tables of related interest, a glossary of technical terms and organizations with related interest.
Arthur E. Becker, CWD/PI, a member of the work group that revised the guidelines, said that there were 63 revised drafts developed before a final version was approved.