Illustration of the proposed Fehmarnbelt tunnel entrance on the Denmark side.
A once-in-a-generation construction project is set to transform travel between central Europe and Scandinavia. When completed in 2029, the $8 billion Fehmarnbelt tunnel will be both the longest combined road and rail tunnel and the longest immersed tunnel anywhere in the world.
Officially known as the Fehmarnbelt Fixed Link, the 11-mile-long tunnel linking Germany and Denmark will sit in a trench at the bottom of the Baltic Sea at a depth of up to 130 feet.
It’s a key component in the development of the Scan-Med corridor, a transportation network that spans more than 3,000 miles from Malta in the south to Finland in the north. Along the way, it tunnels through Alpine mountains and crosses oceans. But approaching Scandinavia, a stretch of water known as the Fehmarn strait causes a 300-mile detour for both road and rail traffic on the north-south route.
The planned rail link will reduce travel time from Hamburg to Copenhagen from five hours to less than three hours, while the road link will replace a heavily-trafficked ferry service and reduce travel time by about one hour.
How to build an immersed tunnel
The megaproject is already well underway. From an engineering perspective, the project is truly fascinating.
The immersed tunnel will be built in segments on land and connected at sea (visualization).
The tunnel will consist of 89 standard concrete elements, each 712 feet long. Each element will contain two tubes for the highway, two for the railroad and one for service access. When complete, each element will be fitted into place in a trench 39 feet deep.
Dredging that trench is expected to produce 671 million cubic feet of soil, sand and rock, which will be turned into new land and beaches near the construction sites.
Preparatory work on the necessary harbor and tunnel factory began in 2020 to allow the actual construction work to begin on January 1, 2021. By mid-2022, dredging work was already 50% complete.
Those interested in the engineering can actually visit the site in Rødbyhavn on the Danish side of the tunnel to learn more. Tours of the exhibition center are available while a viewing platform with binoculars gives visitors the chance to explore the construction site with their own eyes.
The project has a controversial side
Not everyone is a supporter of the Fehmarnbelt tunnel. As with all megaprojects, the eye-watering cost of construction has raised many questions over its value, while environmental campaigners are concerned about the impact the dredging work will have on the local marine ecosystem.
The construction site at Rødbyhavn, Denmark, pictured in December 2022.
Almost all of the estimated $8 billion price tag is being funded by Denmark, to be repaid by hefty toll fees after opening. Many are questioning the value of such an investment but supporters of the project point to the iconic Øresund bridge that links Denmark and Sweden. It is widely deemed to have been a long-term success despite some fierce criticism of its cost during construction in the 1990s.
Now that the construction of the Fehmarnbelt tunnel is underway, environmental campaigners have switched their approach from trying to get the project canceled to monitoring its impact. The marine life in this area of the Baltic Sea thrives in clear water conditions, something the dredging of the sea bed to create the trench for the tunnel will disturb.
In an interview with B1M, local campaigner Hendrick Kerlen said “the ecology of the Fehmarn belt is very diverse. The clouding of the Fehmarn belt will reduce the growth of macrophytes and plankton and will of course have repercussions for all living fauna and marine flora.”
Femern A/S, the company responsible for the construction project, said that sedimentation is one of the most closely monitored environmental impacts on the project. Patrol boats and monitoring stations collect data on water clouding, which is published on the Femern website.
