Find out if your area is on an aquifer that flows or sits still. I've had exposure to a commercial building with geothermal heating/cooling. However, there is no circulation of the groundwater in that area, which means that after 15 years operation, the ground heat sink has warmed (cooling dominated climate), with a resultant drop in efficiency and capacity. That building has now installed additional condensers (cooling towers) to dissipate the surplus heat.
Its something we never though of when the system went in, and only became apparent long after the defect liability period (warranty) expired.