At around 9:50 a.m., a loading technician at a soap and detergent factory saw a cystern overflowing just 10 minutes after alkyl benzalkonium from a storage tank had started to be filled into the cystern. He activated the emergency stop and reversed the rotation of the loading pump to draw liquid back into the storage tank. The floor was covered with 1800 kg of liquid. The floor and cystern were cleaned by spreading absorbent and then shovelling it up. The liquid was pumped to the stormwater pond.

The overflow was caused by an error made by the carrier’s driver whilst venting the cystern. Instead of opening the manhole, as specified in the instructions posted at the station, he used the drop tube to vent the cystern but incorrectly identified the hole corresponding to the drop tube. The driver then told the loading technician that he had opened the manhole, unaware that he had made a mistake. The loading operator then began the filling operation without checking first.

This type of cystern with drop tube had already been involved in a similar incident a few weeks earlier. After this new incident, the operator removed the drop tubes (which were not used) from the cysterns. The various loading methods (top, bottom) are specified in the loading protocols shared between the operator and his carriers.