Pollution
Humain
Environnement
Economique

At 2:40 p.m., a storage tank containing alcohol overflowed into its retention system during an unloading operation at a plant that stores and treats various alcohols. The loading technicians closed the tank’s bottom valve and halted unloading. The alcohol that spilt into the retention system was diluted using the fire suppression system. The lower explosive limit (LEL) was measured but did not exceed 5%. The technicians pumped the contents of the retention system into another containment.

A total of 10 m³ of alcohol flowed into the storage tank farm’s retention. The economic losses amounted to €9,000.

The incident was caused by an issue in the monitoring of the tank’s level. The tank was not fitted with a radar level gauge, as levels are tracked via the stock accounting data. The loading technicians measured the level once a day and entered this data in a table. The table was progressively aggregated by the theoretical contents of unloaded bulk tanks. When the incident occurred, the day’s bulk tanks had not yet been entered. In addition, a high level had been entered in the table the day before. The overflow was caused by unloading operations carried out until 2:30 p.m.

In addition, the shipping manager, who is in charge of identifying which tanks are to be filled, was absent that day. The person replacing him had received the appropriate training but, according to the operator, had not acquired all the necessary knowledge, particularly regarding the risks of overfilling during unloading of bulk tanks into storage tanks. The procedure associated with loading/unloading operations did not describe how to identify the destination of the contents of the bulk tanks. In addition, training to properly understand the instructions was incomplete.

The operator supplemented and improved the storage tank monitoring file with a colour code indicating the storage tank levels not to be exceeded. He also planned to:

  • fit high and very high radar level gauges on the storage tanks,
  • revise the bulk tank loading and unloading procedure,
  • identify staff training needs.