At around 6.30 a.m., when starting a transfer operation, an iron silo 15m high containing 150t of hot ashes and resting on a stand 10m high collapsed in a non-hazardous waste incineration plant. The transfer operation was stopped. The silo was bent at its cylindrical base and the risk of collapse could not be ruled out. The inclined silo rested on an adjacent building housing a 10t silo of activated carbon. Steam pipes were located nearby. The firefighters set up a 60m safety perimeter around the silo and a water curtain around the activated carbon silo to prevent the risk of explosion through a domino effect. The outage of the treatment residue evacuation circuit forced the facility to stop supplying the furnaces with household refuse at the start of the afternoon. Steam production was maintained by the gas burners. A laser telemeter was set up under the responsibility of the industrial firm to perform monitoring of the zone. Three anchoring points were created, to prevent collapse due to silo rotation. A crane was used to hold the equipment in position. Water cannons were installed to spray the silo in the event of dispersion of the product. Private companies secured the facilities the next day. Four days after the start of the incident, silo emptying started in the lower section and then in the upper section and continued for several days. The ashes were stored in big bags. The incident disrupted the supply of one of the district heating systems. The standby system took over, but 3 buildings were deprived of heating for one day. The direct damage of the incident was estimated at more than €1 million and the indirect damage (operating losses, management of the ashes, etc.) at more than €1.5 million.

The collapse was due to corrosion of the silo’s steel. An expert appraisal showed that this steel had no corrosion protection (such as a coat of paint) and that the damage was more pronounced on the ashes side. The chlorine present in the ashes was apparently, in the presence of moisture, the aggressive agent causing corrosion of the silo.