Employees in a cement works noticed pollution of the AZERGUES river by hydrocarbons at around 7.20 am. They alerted the neighbouring textile finishing company that only contacted the fire brigade at around 10.20 am. The inspection authorities for classified facilities was informed and went on site at around 12.45 pm. The company, which operates a heavy fuel oil and domestic fuel oil depot, obtains its water from 2 basins, which are fed by the AZERGUES river. The overflow flows into an underground pipe below the plant then into a ditch joining the river. The pollution (highly viscous heavy fuel oil and oils?) was located where the water is discharged into the ditch, which was also collecting drainage from a fuel oil pipe gutter. The operator set up an initial barrier using bales of straw; a second was established by firefighters 20 m farther before the ditch joins the river. These provisions were too late and the pollution spread over 10 km or so, in the form of sheen and clumps. Between 100 and 400 l of hydrocarbons were discharged.

An oil separator that had not been serviced, and which was not on the company’s pipe drawings, was suspected of causing the pollution. But why it had produced the sudden spillage of hydrocarbons into the ditch could not be explained. The cause of the discharge was finally located on a fuel oil pipe gutter where a leak that the operator was aware of but had not repaired, had caused the accumulation of hydrocarbons then their spillage. The inspection authorities for classified facilities drew up reports establishing the facts.

An external company cleaned the plant’s gutters and the ditch up to the AZERGUES river. A section of the gutters was concreted to prevent any leaks to the outside and to allow subsequent treatment of affected areas. The operator temporarily diverted the rainwater that was likely to flow into the polluted areas towards the site’s treatment installation. A 2nd barrier was established upstream of the AZERGUES river to complement that of the firefighters. A pollution control company had to collect the stagnant hydrocarbons and clean the banks of the river. These various interventions, in accordance with the objectives laid down in the emergency response measures order, signed on the same day, had to prevent any new environmental contamination, even in the event of subsequent rainfall. The operator had to supply a report on the accident in particular stating its causes, its impacts and the measures taken to prevent it from happening again.