During the transfer of a tank within a condiments and seasonings plant, 600 litres of cooking oil overflowed downstream of the facility into the stormwater drainage ditch that emptied into the Norges River. The emergency response unit set up a dam at the confluence of the ditch and the river.

The classified facilities inspectorate visited the site the very same day ; a previous inspection (on 12th January, 2010) had already identified the poor state of maintenance on the stormwater collection network, along with traces of pollution tied to the presence of organic matter in the network among which several sources of this pollution could be exposed. An unscheduled sampling of stormwater the following day at 3 points downstream of the network revealed noncompliance with a number of concentration thresholds (suspended solids, chemical oxygen demand) established in the prefectural order first authorising facility operations. According to the operator, overflow of the tank containing mustardy water at the beginning of the month would at least partially explain this pollution.

The oil spill would have resulted from a combination of 3 deficiencies: anomaly on the pressure sensor serving to track the volume of oil contained in the tank; a defective detector of the high oil level; and ineffective retention basin drainage due to the valve stuck open.

Once initiated, the transfer step continued without any monitoring intervention. The classified facilities inspectorate noted that the poorly-positioned tank vent had led to a spattering of oil outside the retention basin; this oil then overflowed into a manhole directly connected to the collector without being stopped by the facility’s sedimentation basins / oil separators.

A proposed injunction was submitted to the Prefect’s Office calling for compliance with the prescriptions set forth in this order relative to the prevention of accidental pollution of water and liquid product storage. A series of emergency measures were also imposed upon the operator; these included: building a dam between the ditch and the Norges River; installing liquid product storage units (especially bag-in-boxes) on the retention basins; cleaning the ditch and stormwater collection network; controlling the good working order of outside tank safety systems; and adopting the appropriate organisational measures to prevent this type of accident in the future.