Found forgotten explosives in the Oslofjord tunnel

The Oslofjord tunnel is one of Norway’s steepest tunnels. The 7.3 kilometer long stretch connects Frogn in the east with Asker in the west, and is 134 meters below sea level at the very deepest.

The tunnel has also been exposed to a number of accidents and fires. A survey conducted by the Norwegian Public Roads Administration in 2018 showed that several of the fires occurred due to heat in the engines of lorries on the steep stretches.

What no one knew is that there has always been explosives in the walls of the tunnel.

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Have been lying there for 21 years

When the Finnish consulting company Pöyry carried out an inspection of the Oslo Fjord Tunnel in 2015, they made a surprising discovery. They found 20 drilling rigs with explosives inside the tunnel walls.

A new inspection last year revealed another 13 charges of explosives.

The explosive was forgotten when the tunnel was built in the year 2000. But despite the Norwegian Public Roads Administration finding out about the discovery, the explosive was never removed.

Cato Løkken is department director in the Norwegian Public Roads Administration with responsibility for operation and maintenance of the Oslofjord tunnel. He admits that the explosive should have been removed when it was discovered in 2015.

– It is a routine failure that means that the explosive was not removed. We do not know exactly why it never happened, it is something we have to go through.

– Has this been dangerous, considering that the Oslofjord tunnel is particularly exposed to fires?

– Our blasting experts have always believed that the explosive did not pose any risk because it was behind the concrete walls in the tunnel. But the Directorate for Civil Protection and Emergency Planning has ordered us to remove it, which is why we are doing it now, he says.

– Very stable

This week, the tunnel has been closed at night while blasting experts from the Norwegian Public Roads Administration and Veidekke have removed the explosive. TV 2 was present when the experts entered the cramped rooms at the back of the tunnel walls.

– The 33 charges consist of boreholes in the rock. The holes are then filled with fuses and slurry, explains Oddvar Pedersen, blasting expert at the Norwegian Public Roads Administration.

Slurry is a so-called liquid emulsion explosive that is used to blow up rocks.

– We simply remove it by flushing water into the boreholes, Pedersen says.

– Is it dangerous?

– No, this is very stable. Much of it has crystallized and has in any case lost effect over time. We have good progress and will be finished during the week, he continues.

Must check all Norwegian tunnels

Cato Løkken in the Norwegian Public Roads Administration has no explanation for why it has taken six years to remove the explosive.

But as a consequence of the discovery in the Oslofjord tunnel, he says that they will now examine all tunnels in Norway for explosives.