National road B229 was built in 2010. This road handles heavy traffic and its runoff water therefore has to be treated. The crossing between the B229 and Rönkhauser street corresponds to a catchment area of about 1000 m². The receiving environment for the treated water is a small stream : the Röhr. The choice for STOPPOL ® was made according to the surface to be treated , and its location next to the road.