Waters Protection Ordinance
(WPO)

¹ Be­fore an au­thor­ity au­thor­ises the flush­ing out or empty­ing of an im­pound­ment, it shall en­sure that sed­i­ments are re­moved oth­er than by wash­ing away if this is en­vir­on­ment­ally com­pat­ible and eco­nom­ic­ally ac­cept­able.

² When wash­ing away sed­i­ments the au­thor­it­ies shall en­sure that com­munit­ies of plants, an­im­als and mi­cro-or­gan­isms are harmed as little as pos­sible, in par­tic­u­lar by lay­ing down:

a.

time and type of flush­ing out or empty­ing;

b.

the max­im­um con­cen­tra­tion of sus­pen­ded mat­ter in the wa­ter which must be re­spec­ted dur­ing the flush­ing out or empty­ing;

c.

to what ex­tent wash­ing away must be car­ried out so that dur­ing the flush­ing out or empty­ing, fine mat­ter de­pos­ited in wa­ter­courses is re­moved.

³ Para­graphs 1 and 2 do not ap­ply to the ab­rupt lower­ing of the wa­ter level fol­low­ing an ex­cep­tion­al event (Art. 40 para. 3 WPA).