The daily Aftenposten has an interesting article over the Follobanen (Follo Line).

The newspaper writes that when Bane NOR (The Norwegian railway infrastructure company) awarded the work to contractors, Bane NOR wanted a water-tight tunnel with the contract clearly stating that "No drip or visible water is allowed whatsoever,".

As we know, this was not the case and the 18,5km long Blixt Tunnel (which makes most of the Follobanen) was a water-drippling tunnel. An earlier article on Aftenposten reported that, as early as in August 2022, an inspection discovered 525 (five hundred twenty five) 'unacceptable' leakage points. This is a serious problem with electrical systems. The water leaking normally can easily be collected by the water collection system. But this is not a normal rainwater. When water is passing through the tunnel structure, it gets contaminated. Later, when the contaminated water dries our on the tunnel service, the remaining salt conducts the electricity causing short circuits. This can in turn start fires. This was the reason why the Follobanen had been abruptly closed shortly after it was opened with a ceremony. You can read the whole story at The shutdown of the Follo Line: Minister receives external report: Inadequate tunnel sealing, backfill which causes short circuits. Comes new rules & a new CEO for Bane NOR.

Now Aftenposten writes that Bane NOR's choice of aluminum cabling instead op copper cabling for the tunnel's electrical systems has made the corrosion worse. Bane NOR has been warned a year ago about the choice of aluminum which is much more susceptible to corrosion when in contact with water.

As it looks now, Bane NOR had so much faith in the contractors that they thought they would get a water-tight tunnel and aluminum cabling would not be a problem. Now they have to replace them all with copper wiring in the water-drippling tunnel... In the process, probably only one of the tubes will be available drastically limiting the traffic in 2024.

https://www.aftenposten.no/norge/i/y6qb3x/bane-nor-valgte-aluminiumskabler-til-tross-for-advarsler-naa-stenges-deler-av-follobanen-neste-aar