An alarm sounded in the guard station of a condiment factory at around 6:30 a.m., indicating that the high level had been reached in the retention basin of the vegetable oil pumping station. A production technician went to the site and found just a small amount of oil in the retention basin but no sign of leakage. At 1 p.m., a maintenance technician passing through the guard station noticed that the alarm was once again active. He went to check out the site, noticed oil trickling out of the retention basin, and then closed the stormwater valve. In the afternoon, a specialised company was called in, to pump out the retention basin, clean the yard and skim off the rainwater manholes. The discharge valve was reopened at that time.
The following day, at 7:30 a.m., traces of oil were found during the inspection in the discharge ditch. A clean-up operation was performed again. At 1 p.m., a stream of oil was discovered trickling in the ditch, making its way to the Norges River. Firefighters deployed a floating boom to limit pollution, and the Inspection authorities for classified facilities were notified. It was estimated that 200 l of oil was involved.
The oil leak was caused by the failure of the valve seal on an oil pump conveying oil to the production area. The oil leaked onto siding that was too short and did not extend into the retention basin. From there, it flowed to the ground and into the stormwater system. As the leak was significant only when oil was being pumped to the process, the spill was not detected in time and the stormwater basin discharge valve, which should only be closed if there is a risk of spillage into the rainwater system, was re-opened. The oil therefore reached the ditch.
The facility operator replaced the faulty O-ring and installed 6 tightening screws instead of just 3. The oil pumps were slaved to the retention basin’s alarm level. The cladding was also extended to reach the retention basin. The production and maintenance technicians were trained in alarm operation, retention basin management and were given instructions in the event of product spillage or leakage.
