This Code of Practice W 122 incorporates operational issues insofar as they have an immediate effect on the requirements placed on the planning and construction of closing-off structures. It applies to closing-off structures of wells used for ground water production and reinjection for the purpose of drinking water and service water abstraction. It can analogously also be applied to the thermal utilisation of groundwater wells. Design and construction of well borehole, well casing and well equipment are not subject of this code of practice. The design examples in the informative annex provide suggestions for planning and construction.