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As institutions look to decarbonize their campuses with ground source heat pumps and geothermal, it is important to understand what factors could contribute to elevated drilling and system installation costs. Here are 5 things to consider for reducing or controlling costs as national demand increases for these systems.
1. Evaluate rock profile depths to understand cost magnitudes and save on schedule.
- Utilize a geotechnical engineer to drill bore samples to understand depths of bedrock.
- Evaluate if any subsurface rock is rippable or will require hammering or blasting to install lateral piping.
2. Evaluate site slope and water-table.
- Sites with elevated degrees of slope could require excessive excavation and shoring to make the site grade suitable for drilling.
- A high water-table can be a challenge to manage depending on the type of drill rig. Added equipment will be needed to manage and discard water if present.
- DEP and other environmental agencies will require monitoring and lengthy approvals if discharging ground water to the local storm sewer. They may also require third-party inspections by an IGSHPA accredited engineer.
3. Evaluate bore depth.
- Deeper bores limit the number of drillers available to reach further depths, making competitive bidding less effective (>600 feet).
- Shallower bores are more cost effective and there are more drillers available to complete drilling (<600 feet). This is not always the best option if available sites are limited in size, and the total campus build-out requires deeper bores to meet the plans ground storage capacity.
4. Evaluate the need for monitoring wells.
- Monitoring wells provides an accessible means to view the thermal conductivity of the geoexchange field at any time. While this is great data to have, it does come with added cost for the fiber cabling, conduit, software, hardware, and the additional bore(s) installation itself. It may also be required by governing regulatory agencies.
5. Evaluate the geo-pipe route back to the central plant.
- Surveying the geo-pipe route in advance of starting your project is important to understand what utilities your distribution pipe needs to avoid or cross. Digging test pits and conducting ground penetrating radar (GPR) scans will help to understand how deep your pipe will need to be installed to avoid utility conflicts. Conducting this evaluation may prove the need for alternative paths to reach the plant or help avoid extra excavation costs and contractor change orders.
- Collaborating with your engineer or planning consultant, you should assess your designed geo pipe size to consider whether it accounts for additional bore fields in your planned conversion program (if applicable). This will avoid replacing it later with a larger diameter pipe or adding additional piping in the future to serve other bore fields in the area.
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