Q: Is a full geological survey required with every ground source heat pump installation?
A: Yes and no. Yes, if you want to use boreholes. The ‘desktop’ surveys provided by the British Geological Survey are excellent at an early stage of the planning when you are trying to determine whether a GSHP might be possible for your project. However, before you start drilling you should have a full on-site survey carried out by a geological specialist. Installers have encountered problems with undetected mineshafts and subterranean pools, which would not necessarily be picked up by a general survey. Ideally, boreholes should be drilled to around 100 metres and the rock formations and soil densities can change dramatically in that distance.
However, a full survey is not required if you go with horizontal ground loops that are buried, ideally, at a depth of 1.2 metres and the desktop survey should be able to give you the necessary information about soil characteristics so that you can gauge how good a performance you will get from the ground loops. You will, of course, need a fairly large garden area to get the required temperature to extract. Alternatively, you can go with an open loop system if there is a handy, large standing body of water nearby or buried close to the site.
Please also allow for access to the site for drilling rigs in your planning if you opt for boreholes.