The operator of a facility – in this case, you as an individual – is liable for the construction and operation of the facility in compliance with the applicable provisions and for all damages that may result therefrom. You should therefore check carefully that the drilling documents are complete. These should include:
the completed pressure test form as proof of the tightness of the geothermal probe once the probe has been placed (ask the drilling company if this report complies with VDI Guideline 4640);
the complete drilling report.