Rain

Precipitation of about 300 mm from 31 October to 2 November with a 3-hour extremely heavy downpour.

The safety studies completed in July 2003 had indicated the risk of rain water stagnation at the site. After the flooding in 2003, the operator improved the site’s water drainage system but no initiative had been taken on public infrastructures. Also, the risk of floods had not been considered in the internal emergency plan. Following this event, floods were included as a threat in the internal emergency plan.

Once the alert was given, the operator deployed significant resources to raise to higher elevations or evacuate the equipment and products, to stop manufacturing processes together with a safety fold back of equipment, and to plan power cuts before the water could flood sensitive equipment.

Only 5 out of the 12 inverters could be shut down before the water started rising. The remaining 7 had to be replaced, which had, however, no negative impact when the accident occurred.

After the triggering of the internal emergency plan, power was cut to avoid damage to sensitive equipment due to water intrusion. The power cut rendered, however, leak detectors, and in particular gas indicators, inoperable. Consequently, staff patrolled the site and carried out manual measurements.

On 3 November, a truck, a power lift, and two high-speed pumps were used to move objects and to rapidly drain the residual water (drainage terminated at around 1:00 pm).

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The number of staff present on site varied depending on the time of day and the accident progression. The flood did not result in any casualties.

No pollution was observed, except for the release of 200 g of chemical powder and a spill of 2 to 5 litres of a hydrocarbon compound in a laboratory.

The economic damages were estimated as 10 million EUR at the beginning of 2009.

The flooding resulted in significant water damage to administrative documents, some equipment, and in certain premises (perimetrical system for the detection of intrusions, changing rooms, laboratory partitions, low-lying equipment, etc.). The products stored in refrigerated containers, were not impacted, in spite of the power cut.

The operating losses were limited despite the shut-down of the plant for several days.

Production facilities, air cooling towers as well as electrical equipment and rotating machines were monitored during start up.

During the fold back of facilities, checks were made to ensure the phase of fold back was in line with the predicted status. The air cooling towers were re-commissioned after the chlorine treatments. Samples were taken to screen for legionella. The thermal oxidiser for volatile organic compounds was monitored upon recommissioning and the affected insulators were checked using infrared camera. For several months, electrical equipment and rotating machines (that were in contact with water) were monitored by specialized staff.

When storing sensitive products (e.g. chemicals that violently react with water) and/or equipment, they should be located above the maximum predicted water level.

In case of floods, power to electrical equipment should be cut to avoid damage due to water intrusion.

Electrical equipment can be re-commissioned only once it has dried. Insulators, electrical equipment, and rotating machines have to be examined and monitored after the incident. Air cooling towers require special procedures before restarting.

Quick operator action in case of an alert can limit damage to a plant significantly.

There should be awareness that even areas that are not identified as flood-prone can be inundated in case of heavy rain. Also, awareness of historical flood events in and around the site should be maintained.

The risk of flooding should be evaluated periodically by taking into account the entire catchment area and potential modifications (sealing of the surface, changes to the water flow, etc.).

For safe shutdown it is essential that the safety fold back stages are known. This is of particular importance in case of flood events, when monitoring and control systems might be lost due to power cuts and IT problems.

After a flood, an analysis of the risk of (differential) subsidence should be carried out.

Early flood warning is crucial for preparedness.

The onsite availability of response equipment, e.g. power lift trucks with exhaust pipes and air vents at higher levels, as well as high-capacity pumps, facilitates the quick draining of the flood waters and helps to mitigate the consequences of the flood.