Norway is building the longest underwater tunnel in the world

Construction is underway in Norway on a 27-kilometer tunnel that will connect the coastal cities of Stavanger and Haugesund, becoming part of the European route E39. Rogfast, as the project is called, will break world records for both length and depth of underwater roads, and its development is designed to respect the environment and climate.

At least three world records

The planned Rogfast tunnel route leads from Randaberg, located on the outskirts of the port city of Stavanger, to Bokn near Haugesund. The four-lane underwater road will also offer an exit to Kvitsøy, Norway’s smallest municipality, situated on a charming but hard-to-reach island. This means the tunnel will include the world’s deepest roundabout, located about 250 m below sea level.

At its deepest point Rogfast will run at a depth of 392 m, setting a new world record. With a length of around 27 km, it will also surpass the current record holder for length, another Norwegian tunnel – Lærdal (24.5 km). The entire project has been divided into four sections, and the deepest one, submerged over 9 km, is being built by the Scandinavian company Skanska.

Rogfast construction faces challenges

The first works, including a ceremonial blasting of rock at one of the tunnel entrances, took place back in 2018. However, the project was halted due to cost overruns in the updated budget and issues in the tendering procedure. After a three-year break and a rise in the total cost to 25 billion Norwegian kroner (over 2 billion euros), construction resumed.

Work is currently being carried out simultaneously from both ends, and engineers expect that the deviation in the axis at the meeting point will not exceed 5 cm. Such precision is possible thanks to state-of-the-art laser technologies and a digital model of the tunnel. Technical difficulties are plentiful – at a depth of 300 m seawater is already seeping into the tunnel. Effective ventilation and ensuring traveler safety in case of an accident also remain major challenges.

The Norwegian government is financing only part of the project (9.9 billion kroner). The rest of the capital comes from a loan that will be repaid using tolls charged to future tunnel users. Completion of the project is planned for 2033.

The underwater tunnel will shorten travel time

The tunnel route runs beneath the Boknafjord and Kvitsøyfjord, providing the shortest possible connection between Stavanger and Bergen, the fourth-largest and second-largest cities in Norway, respectively. For drivers, this will mean cutting travel time by 40 minutes.

In a broader context, Rogfast is part of the modernization of the 1100 km E39 highway from Trondheim to Kristiansand. Currently, the journey requires 21 hours and seven ferry crossings. By 2050, a network of bridges and tunnels is expected to eliminate ferry connections entirely and reduce travel time by half.
Minimizing ferry traffic along the Norwegian fjords will benefit marine ecosystems. In addition, investors place strong emphasis on reducing the project’s climate impact. During construction, priority is given to reducing energy consumption and sourcing the necessary energy from renewable sources, particularly wind, solar, geothermal and wave energy.

The project lays the foundation for more sustainable and integrated regional development along Norway’s rugged western coast, Anne Brit Moen, project manager at Skanska, told CNN.

It is worth noting that traveling through such a long underwater tunnel will not be as unpleasant as one might expect. To ease anxiety and enhance the aesthetic experience, designers have planned dynamic lighting and an art installation.

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main graphics: Norconsult