At a hydrocarbon depot located in an urbanized zone, welding work was underway on the “emergency access track”. At 11:15 am, a leak of premium-grade gasoline occurred, succeeded by a sudden flash. Site technicians attempted to extinguish the ensuing pool fire. The operator activated the internal emergency plan, issued the order to close all motorised valves (execution time: 45-60 sec) and called for assistance from petroleum industry partners. The neighborhood was evacuated and rail traffic disrupted.

Fire-fighters deployed major resources to tackle such an intense fire. Unburned gasoline flowed towards the railroad and this caused the blaze to spread. At 12:30 pm, despite repeated operator denials, fire-fighters detected a source of leakage that several valve inspections could not locate. At 2 pm, emergency responders were unsuccessful in suffocating the fire with sand. Then at 3:55 pm, the foot valve on gasoline tank no. 1 was found open and ultimately closed, at which point the fire receded. According to the site director, this pipe should have been submerged in water during the onsite works and therefore was omitted from the valve closure checklist and control diagram. A less intense fire persisted in tank no. 2. At 7:12 pm, the fire was extinguished; the site remained under surveillance until 16th June, 5:45 pm.

Intervention efforts were substantial (472 fire-fighters, 20 nozzles, 10 km of pipes, 3,000 m³ of water, 42 m³ of emulsifier) and the toll quite heavy (15 fire-fighters injured, 4 of whom seriously upon re-ignition of the pool of gasoline and explosion of 2 acetylene bottles, 1 slight injury among the local population, 670 m³ of hydrocarbons burned, €2.7 million in property damage). The 1,800 m³ of fire extinction water remained confined onsite while awaiting evacuation and treatment.

The initially open valve (suspected human error) stayed that way despite application of the site’s safety measures. This valve fed an underground pipe equipped with maintenance drains closed by plugs. One such drain had been insufficiently tightened (just 1 of 4 bolts fastened) and pivoted under the pressure of gasoline contained in tank no. 1, resulting in gasoline escaping at a 150 m³/h flow rate. A spark produced by the ongoing welding work then ignited the vapours.

First responders encountered myriad difficulties : an ignited “emergency track”, fire water pipes bursting under the wheels of vehicles evacuating the zone, lack of information on the fire source, a pipe network diagram not updated following emergency shutdown, etc.

Several organisational deficiencies prevented more rapid fire containment: judgment error on the valve considered close, inadequate attention paid to critical safety parameters and equipment (valve inlets, control diagram).

The accident analysis led to implementing the following measures: manual valve and retention for drain taps, a 15-min backup control diagram, backup of motorised valves by automated flap gates, aboveground maintenance drains, facilitated site access…

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