A chemical plant manufacturing basic organic chemicals was partly flooded when the reactors were being washed. The washing water (acrylic emulsions) got mixed with the flood water due to the backflow of the water in the pipeline and in the mouth of the drain located in the traffic lane. The abrupt rise in the level of the La BRENNE river submerged the efflumeter containing effluents from the sewage treatment plant. Red coloured water flowed out of this efflumeter and spread onto the ground near the plant. Each time the La BRENNE river flooded, a low point at the main fire door caused the site to regularly flood. The inspection authorities for classified facilities observed the facts and ordered a hydraulic study taking into account data on the river and a study on the measures to be implemented to prevent the flooding of the site (removal of the low point, protective dam, transfer of sensitive stock to flood risk-free zones, etc.) and carry out identified operations. The prefectoral decree dated 16/02/04 has ordered the protection of the site against floods.