At 9:30 a.m., the fourth wagon in a six-wagon train derailed as it passed over a point at a company that manufactures nitrogenous substances and fertilisers. The wagon, which was loaded with 50 t of ammonia, remained upright and landed on the ballast. No leaks were found. The operator requested that the railway services conduct an inspection so that the wagon could be put back on the tracks. An emergency response unit was set up and a conference call involving the operator, firefighters, the inspection authorities for classified facilities and the prefecture was held.

The railway services commenced lifting operations at around 7:00 p.m. Preventive water sprays and a mobile detection system were set up around the wagons. The fourth wagon was lifted back onto the track using a system of trolleys and metal sleepers secured in place against the rails with chocks. The transfer to the unloading stations ended at around 1:00 a.m. the next morning.

Wagon loading operations were halted for one day. The damaged tracks (rails and ties) were repaired as well.

The operator suspected a defect that caused the point to change position (there was no position lock). After the tracks were repaired, the operator decided to install securing bolts on the points and drew up a preventive track maintenance programme. The marshy terrain weakens the soil’s strength and can exacerbate the problem.

Another derailment occurred at the plant seven months later, this time at a point whilst a train of empty wagons was passing. Despite the securing bolt, the point moved in the opposite direction as the wagons passed. There was no bolt installation procedure. This one was poorly positioned in that it was not flat and its shoe was open. On the recommendation of a railway expert, the operator checked the coupling tension between the wagons. They were tightened by two threads, just as in the previous derailment. When the train arrived at the operator’s industrial spur, the tension applied by the carrier was not checked and/or adjusted by the operator even though some track curve radii are small (less than 150 m). When the train travelled along curves with a radius of less than 150 m, the buffer plungers were in contact and the coupling had no elasticity. The joints of wagons thus coupled were stiff on the inner side of curves, exerting considerable stress on the track and points and crossings (rail uncoupling, detachment of point blades on loop points, damage to fasteners and point stops). These deficiencies were all potential sources of derailment. Whenever a train arrives, the operator now adjusts the coupling tension of the wagons to five threads. This tightness is maintained until the train leaves the industrial spur.