Rogfast: Norway’s 26.7-km subsea road tunnel, 390 m deep

Rogfast is a 26.7-kilometer subsea road tunnel reaching 390 meters below the North Sea, currently under construction and scheduled to open in 2033. When finished it will funnel four lanes of traffic beneath the Boknafjord and Kvitsøyfjord, eliminate two ferry routes, and shave 40 minutes off the five-hour trip between Stavanger and Bergen.

How is Rogfast being built?

Rogfast is being excavated with the drill-and-blast method, advancing inward from both ends, with daily laser scans to maintain alignment; each blast adds about five to six meters and the two ends should meet sometime in 2029 with only a few centimeters of deviation. Skanska leads from the north (Vestre Bokn) and Implenia with Stangeland from the south (Randaberg). The teams probe ahead with narrow drill holes 25 to 30 meters deep, use seismic surveys and seabed core samples taken before construction, and constantly re-evaluate the rock so the tunnel stays on course.

After blasting, crews install structural supports tailored to the rock class and spray shotcrete, then fit a plastic membrane and concrete panels. Workers operate 12-hour shifts, typically on a 12 days on, 16 days off rotation. Daily logistics include giant ventilation tubes during construction and eventual permanent ventilation through two nine-meter-wide shafts bored down from Kvitsøy roughly halfway along the route.

What engineering challenges does Rogfast face?

The project must manage extreme water pressure, mixed geology, ventilation for road traffic, and complex logistics: the sea above pushes down with a force of more than 500 pounds per square inch, and at the deepest point only 50 meters of rock separate the tunnel from the North Sea. Engineers expect constant leakage, so they drill probe holes for leaks and, if a hole exceeds around four liters per hole per minute, they move to grouting — pumping cement-like slurry into fan-out holes above and around the face to seal water pathways.

The seabed geology is heterogeneous thanks to glacial carving: some sections are phyllite (compact, quartz-rich, and needing more explosives) while others are granite and gneiss with fractures that let seawater trickle through. Rock is graded on a 1-to-5 scale; reaching class 5 means conditions are almost soil-like and require different support. Ventilation adds another layer of complexity: during construction fresh air comes through large plastic tubes, but permanent ventilation will rely on the two nine-meter shafts and giant systems to move fumes in a four-lane road tunnel. The build also includes two undersea roundabouts located 220 meters below sea level, unusual components for any tunnel project.

Why it matters

Rogfast scales Norway’s long history of tunnel engineering into a project that dwarfs previous builds: Norway already has the 14.4-kilometer Ryfylke subsea tunnel, but Rogfast will nearly double that length and reach far greater depths. The techniques on display — drill-and-blast advancement, frequent laser re-surveying, intensive grouting, and bespoke support systems for variable rock classes — offer an operational template that has drawn attention from Japan, Spain, Morocco and several U.S. state delegations. If the project meets its targets, it will reinforce a practical playbook for very-long subsea road links that other countries can study.

What to watch

The next concrete milestones are the planned meeting of the two tunnel ends in 2029 and the overall completion scheduled for 2033. Track how grouting impacts face advance rates — Skanska’s face can move 30 meters some weeks and as few as 10 meters in others — and whether the final alignment comes within the few-centimeter tolerance the teams aim for. Also watch progress on the two nine-meter ventilation shafts on Kvitsøy and the management of silica exposure in quartz-rich phyllite sections.

One on-site voice captured the scale of the effort: "It's the longest continuous blast on the sea," says John Olaf Østerhus, assistant project manager at Implenia, underscoring the unprecedented nature of the excavation.