Norway constructs the world's longest and deepest underwater road tunnel

Norway is currently constructing the longest and deepest undersea road tunnel on Earth, aiming to reduce travel times between major cities and form a key part of a ferry-free coastal highway along the countrys western shoreline. The tunnel, named Rogfast derived from "Rogaland fastforbindelse," referencing the region and meaning fixed link in Norwegian will span 27 kilometers (17 miles) and reach a maximum depth of 392 meters (1,286 feet) below sea level.

Construction began in January 2018 but was paused in late 2019 due to projected cost overruns, leading to contract cancellations and project restructuring. Work resumed in late 2021, with completion anticipated in 2033 at an estimated cost of 25 billion Norwegian kroner (approximately $2.4 billion).

Rogfast will greatly enhance connectivity along the western coast, providing a faster, more dependable route between Stavanger and Haugesund, stated Anne Brit Moen, project manager at Skanska, the company handling the tunnels northern section, which is 9 kilometers (5.5 miles) long and the deepest part of the tunnel.

By replacing ferry services, Rogfast is expected to cut travel time between Bergen and Stavanger Norways second and fourth largest cities by around 40 minutes, making daily commuting more convenient. The tunnel will consist of two separate tubes, each containing two lanes of road traffic. Notably, halfway along its route, it will feature a double roundabout 260 meters deep, connecting to a tunnel leading to the island of Kvitsy, Norways smallest municipality.

Constructing such a long undersea tunnel presents substantial engineering challenges. To expedite the process, Rogfast is being excavated simultaneously from both ends, targeting a mid-point connection with a tolerance of just 5 centimeters (1.97 inches). Precision is achieved using advanced laser equipment, including spinning mirrored scanners that generate a digital twin of the tunnel by collecting two million data points per second, which is then cross-checked against design plans.

Its far from the romantic image of a surveyor peering through an eyepiece, remarked Burkhard Boeckem, CTO at Hexagon, the company providing the tunnels measurement solutions. Maintaining such a narrow margin of error helps minimize material waste, reduce costs, and lower emissions.

Rogfast is part of the modernization of Norways E39 coastal highway, which stretches 1,100 kilometers (684 miles) from Trondheim in the north to Kristiansand in the south. Currently, seven ferry crossings extend the journey to 21 hours. The long-term goal is to eliminate ferries through bridges and tunnels, cutting travel times by half, with full completion expected by 2050.

One of the biggest hurdles has been developing effective grouting techniques to seal the rock, Moen explained. At 300 meters (984 feet) below sea level, weve experienced significant saltwater leaks. As we reach 392 meters (1,286 feet), ensuring safe and efficient conditions for workers is a top priority. Geological data is continually analyzed to guide construction methods.

Safety and ventilation are critical for motorists. Rogfast will employ a longitudinal ventilation system using jet fans, complemented by shafts extending to Kvitsy to maintain air quality throughout the tunnel. Real-time monitoring, including cameras, radar, and incident alerts, will ensure rapid response to breakdowns or congestion.

While ferry jobs may be affected, the tunnel is expected to improve access to employment, education, and public services, benefiting local communities and the regional economy, particularly the seafood industry. The construction phase also provides substantial employment opportunities.

The tunnels design features dual tubes with a central emergency passage, cross connections, pedestrian escape routes, and comprehensive safety installations to facilitate traffic flow and emergency access.

Currently, the Seikan Tunnel in Japan holds the record for the longest tunnel with an undersea section at 53.85 kilometers (33.5 miles), while the Channel Tunnel connecting England and France measures 50.46 kilometers (31.35 miles). Rogfast will surpass these in depth, reaching 392 meters (1,286 feet) below sea level, compared to Seikans 240 meters and the Channel Tunnels 115 meters.

Author: Sophia Brooks