A coupling on the transfer pump between a 40 m³ tank of molasses and the manufacturing process of an animal feed processing plant began leaking shortly after 8:00 a.m. Then, at 8:11 a.m., a manufacturing fault appeared on the control computer. At 8:21 a.m., employees saw that the coupling on a transfer pump had burst. They turned off the pump. A dark brown, slightly viscous nitrogen-rich concentrate obtained from fermentation of beet molasses and other organic substances spilled into the storage tank’s bund. At 9:12 a.m., the coupling was repaired and the process was restarted. At 12:30 p.m., a technician noticed a drop in the bund’s level (likely due to cracks in the bund). Plugs were placed on the stormwater network’s two main access covers after the concentrate was found in one of them. The bund was pumped out in the late afternoon.

The area downstream of the stormwater outlet was monitored, but no suspicious discharges were found. An estimated 3.2 m³ spilt into the bund and 50 l seeped through the bund’s cracks. The tank contained less than 10 m³.

Corrosion is what caused the coupling to burst. The operator replaced the failed coupling by a stainless steel coupling and asked for quotes to seal the bund with resin.

Two months later, the inspection authorities for classified facilities observed that:

• two months after the incident, the bund had not been repaired or sealed;
• the operator made no proposals in its incident report to prevent the incident recurring;
• deficiencies in the monitoring and maintenance of the facilities remained: no written procedure for visually inspecting the condition of the plant’s bunds, presence of a hole in the bund’s concrete slab, the pipes connected to the plant’s liquefied flammable gas storage tank were corroded.

The operator subsequently emailed the corrective action plan being implemented by it:

• the hole in the bund was filled with polyurethane foam;
• the quarter-turn valves of each tank are closed at the end of each production run;
• production staff carry out surveillance patrols more frequently;
• an inflatable plug is fitted in the stormwater access cover;
• confirmation that a mason repaired the cracked bund;
• the bund was filled with water to check its integrity.