At 6 a.m., a technician was in the process of restarting the esterification unit in the control room following a ten-day shutdown period to replace the hydrochloric acid tank. He noted that the level of the tank, which had been filled with 17 m³ of acid just 3 days earlier, had dropped from 29% to 5% at 8:25 a.m. At 8:45 a.m., during his rounds, he was able to confirm that 15 m³ of 33% hydrochloric acid had flowed into the retention tank. A safety perimeter was established, and the facility operator called a service provider to pump the oil that had spilt.

At 2:30 p.m., while a pumping vehicle was in place, the operator noticed that the retention tank had suffered a loss of containment. The acid, which was flowing through the lower part of the wall through two unrepaired openings at the location of a former safety shower and from the corner of the retaining gutter, was spreading over the site’s service road and reaching the internal rainwater network.

The site operator shut off the storm water lift pumps, closed the valve on the containment basin, prepared absorbent products and deployed dams to contain the leak on the roadway. He also alerted the emergency services which used water hoses to dilute the spilt acid. The entire rainwater network was directed to the containment basin.

The pumping operation was able to recover 5 m³ of product. Cubitainers containing 15% sodium hydroxide were set up to neutralise the acid recovered at the dams. Measurements of the acid gas content were performed at various points in the area, and the pH of the effluents collected in the rainwater network was monitored. The effluents collected in the basin and in objects in contact with the acid were collected for processing at specialised sites.

The purge valves and the valves at the base of the tank had remained open, allowing the acid to flow into the retention basin.

The operator has repaired the concrete on the retention basin and the waterproofing with an acid-resistant material. An alarm device for detecting the presence of acid was also installed. The installations’ start-up and shut-down procedures for all the workshops were also reinforced with a greater number of rounds being performed. The personnel also received awareness training regarding the installations’ start-up and shut-down phases.