A tunnel 26.7 kilometers long, carved nearly 400 meters below sea level, connecting Stavanger and Bergen while eliminating two ferry crossings. This is not science fiction, but the Rogfast project, the world's longest and deepest subsea road tunnel, currently under construction in the Norwegian fjords. I visited the site to understand how such an ambitious feat is achieved, amid blasts, water, and typical Norwegian determination.
Working 300 meters below sea level
Descending 300 meters beneath the North Sea is surreal. The rock is damp, the air dusty, and the noise of drilling rigs deafening. I wear a special hard hat and foggy safety goggles. The water pressure above me exceeds 500 pounds per square inch, comparable to a baby rhino on a postage stamp. Only exceptional engineering keeps me from being crushed. "Don't worry, if you don't make it, we'll send your stuff to your office," jokes geologist Anne-Merete Gilje. Norwegian humor is essential for such conditions.
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The Norwegian drill-and-blast method
Norway uses the drill-and-blast method, advancing 5-6 meters per charge. Unlike tunnel boring machines, this technique offers flexibility in complex geology. The project has two fronts: Skanska from the north, and Implenia with Stangeland from the south, guided by daily laser scans. The two ends will meet in 2029 with only a few centimeters deviation. "Every blast creates a new world," says Niclas Brusehed, tunnel foreman. Workers endure 12-hour shifts for 12 days straight, then 16 days off. "You have to be a little crazy to work underground all the time," Brusehed laughs.
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The endless battle against water
Water is the primary enemy. Before each blast, probe holes are drilled to check infiltration. If flow exceeds 4 liters per hole per minute, grouting seals the cracks. "Stopping water behind you is much harder," explains Ole Magne Rønning, project leader. Grouting specialist Tarald Johan Nomeland says, "There's not just one solution; there may be many." Seeping water will be collected and pumped out. Progress speed depends on grouting volume: sometimes 30 meters per week, sometimes as few as 10.
An unprecedented engineering feat
Rogfast includes two undersea roundabouts 220 meters below sea level, and a section where only 50 meters of rock separates drivers from the ocean floor. Completion is scheduled for 2033, cutting the Stavanger-Bergen journey by 40 minutes from 5 hours with two ferries. Norway has built over a thousand kilometers of tunnels, but Rogfast surpasses them all. Norwegian expertise attracts interest from Japan, Spain, Morocco, and US states that visited the site in May. Just as in modern software development, where performance is critical, every detail here is optimized for extreme conditions. To learn about scaling code, read our article on Modern Java and Spring Boot 3. For more on Rogfast, see the Wikipedia page.
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Source: https://www.technologyreview.com/2026/06/22/1138821/inside-worlds-deepest-longest-subsea-road-tunnel
