Around 4.10 am, an automatic extinguishing system on hydrocarbon tanks is triggered without any fire starting. Foam, 200 l, is spread over the tanks, as well as 230 m³ of water. The storm basin, equipped with a separator closed by a valve, collects part of the water/foam mixture. For an undetermined reason, another part of this mixture is discharged into the BOURBINCE. This foam is an easily biodegradable product that does not bioaccumulate. Employees give the alarm around 11 am. The fire brigade destroys the foam with fire hoses. Downstream municipalities are warned so that the pumping of water for drinking purposes is temporarily stopped. No aquatic mortality is observed.

The automatic extinguishing system was triggered due to a change in internal pressure. These pressure changes were caused by leaks in the pipes of the old installation, which was about ten years old, to which the new installation was added. The small compressor used to fill the pressure gaps was faulty. The foam spilled into the river because a branch of the old pipeline network had remained in place and passed through a manhole also used by the new network. The branch of the old network was located above the new network but the voluminous foam filled the entire manhole.