The Accident Investigation Board (AIBN) in Norway reports that the trailer broke loose from the tank truck and drove into the tunnel wall, and the front tank chamber got perforated. This caused petrol to leak out and run nearly 500 meters down towards the lowest point of the tunnel. The petrol ignited probably by heat/ignitions from the engine in a recreational vehicle that stopped close to the trailer. The fire in the petrol that had spread on the road surface and the tunnel drainage system escalated rapidly. There was an intence fire which melted holes in all fuelchambers and the tanktrailer incinerated completely.
The AIBN recommends (short version):
- revise its requirements for tunnel drainage systems, so that they are designed to handle large spills of dangerous liquids carried by vehicles.
- when conducting risk analyses, describe and follow up measures related to the described scenarios/incidents.
- introduce restrictions on the transportation of dangerous goods through tunnels, based on a risk assessment of each individual tunnel.
- review and strengthen its follow-up of safety in the tunnel and other similar tunnels on the county roads.
Similar potential for damage as in the previous fires in Norway was also present at the fire in the Skatestraum tunnel, and the fire reminded the public of another danger potential - the danger of dangerous gods in tunnels.
De different design features are important, especially in subsea tunnels. The investigation revealed weaknesses in the tunnel design and the ability to resist the spread of fire. The steep gradient in the tunnel helped the fire spread over a wide road surface area and the tunnel’s drain system was not designed to handle the amount of petrol that leaked out. This is one of many learning points from the fire in the Skatestraum tunnel. In upgrades of corresponding tunnels, a much larger capacity is added in the drainage solutions as a result from this incident.