Waters Protection Ordinance
(WPO)

¹ Drain­age wa­ter from un­der­ground build­ings must be con­tained and chan­nelled off in such a way that it can­not be pol­luted by such con­struc­tion op­er­a­tions, in par­tic­u­lar by ex­cep­tion­al events. This does not ap­ply to small amounts of drain­age wa­ter if re­ten­tion meas­ures pre­vent the pol­lu­tion of the re­ceiv­ing wa­ters.

² For the dis­charge of drain­age wa­ter from un­der­ground build­ings in­to wa­ter­courses, the fol­low­ing ap­plies:

a.

the spill­way con­struc­tion must be such as to en­sure ho­mo­gen­eous and rap­id mix­ing of the wa­ter;

b.

the tem­per­at­ure of the re­ceiv­ing wa­ters must not be raised over its near as pos­sible nat­ur­al state by more than 3 °C; if the stretch be­longs to a trout zone, the tem­per­at­ure must not be raised by more than 1.5 °C;

c.

the dis­charge must not res­ult in the wa­ter tem­per­at­ure ex­ceed­ing 25 °C.

³ De­pend­ing on loc­al cir­cum­stances the au­thor­it­ies shall spe­cify:

a.

re­quire­ments for dis­charge in­to lakes and in­filt­ra­tion;

b.

ad­di­tion­al re­quire­ments for dis­charge in­to wa­ter­courses if ne­ces­sary.