Highway runoff treatment by nature based systems - Along the 18 km of the new highway A34, 56 nature-based systems designed by IRIDRA are in operation for the treatment and management of the rainwater. Each unit is including a HF CW that is treating the first flush, a pond which receives the effluents from the 1st stage + the 2nd flush and finally an extended retention basin for infiltration in the karst soil.