Key legal question
Whether the municipality could introduce a drainage fee in addition to sewage treatment charges based on water consumption.
Extracted holding
Yes. The municipality remained free, within the cantonal legal framework, to choose a different but causally justified basis for the recurring usage fee.
Extracted reasoning
The cantonal provisions require fees to be oriented to use only in principle; they do not exhaustively regulate the calculation basis. A surface-based charge is permissible when it better reflects the cause of runoff and remains within the legal framework.