Epichlorohydrin is toxic, flammable and highly reactive. This substance is used to make a reagent for modifying potato starch. It is stored in 2 tanks of 80 and 45 m³, under an inert atmosphere. It is transferred under nitrogen pressure to the receiving tank, whose valve is open to a gas washing tower. The storage and transfer area, which has no electrical equipment, is equipped with sprinkler ramps to reduce the vapours in the event of accidental transfer in the open air, the start of a fire or cooling of the storage units if necessary (rise in temperature).
At around 10:50 a.m., epichlorohydrin accidentally spilt out while a tanker was being unloaded at a starch manufacturing plant. Sensors located above the lorry’s tanker detected the spill and caused the unloading valve and the nitrogen supply valve (used to pressurise the tank for the transfer operation) to close immediately. The unloading station’s deluge system came on. Because the residual pressure in the tank , the leak continued and was only stopped 40 minutes later by an employee.
The 200 m³ of spray water was channelled to a 1,500 m³ settling tank, which contained 1,000 m³ of water containing 800 ppm of epichlorohydrin (1,000–1,200 kg of epichlorohydrin). The operator used 4.5 m³ of sodium hydroxide to degrade the epichlorohydrin to glycerine so that it could be treated at the wastewater treatment plant. The concentration progressively dropped. At 6:00 a.m. on 16 March it was measured at 290 ppm. A 50 m cordon was set up after a person reported a slight odour coming from the settling tank. A sensor to measure the epichlorohydrin concentration was installed at the edge of the settling tank. The concentration dropped to 40 ppm on 19 March. The settling tank continued filling up following the spraying of the epichlorohydrin area. The overflow was fed to the plant’s second settling tank, which has a capacity of 3,000 m³. On 22 March, the concentration in the first tank was 8 ppm and 30 ppm in the second tank (no stirring or sodium hydroxide treatment). The cordon around the first tank was removed on 23 March.
A faulty seal on the road tanker is what caused the epichlorohydrin spill. The damage was estimated at more than €50,000.
A specialist contractor disposed of and treated the polluted water at an estimated cost of €750,000 for 3,000 m³. On 3 April, the situation was reviewed with the inspection authorities for classified facilities. The pH in the first tank remained high despite epichlorohydrin no longer being contained in it since 23 March. However, on 28 March an external laboratory measured a concentration of 24 ppm of glycidol (a reaction by-product) and traces of epichlorohydrin. The settling tank remained confined. The operator developed an action strategy. The second tank, which was used to collect rainwater, did not contain either substance and was nearly full. The operator sent its contents to the wastewater treatment plant. The various tanks and the wastewater treatment plant’s discharge point were tested.
The operator provided the inspection authorities with:
- the emptying protocol for the second tank;
- daily monitoring of the volumes sent for treatment and then discharged to the River Somme, along with the test results;
- the updated action plan;
- the preventive measures implemented with the epichlorohydrin supplier.
The operator must also inform the inspection authorities of the fate of the polluted water still confined in the first tank and update his safety report to include feedback from this accident (particularly the management of polluted water).
