Illustration of the proposed Fehmarnbelt tunnel entrance on the Danish side.
A once-in-a-generation construction project will 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 submerged tunnel in the world.
Officially known as the Fehmarnbelt Fixed Link, the 11-mile long tunnel connecting Germany and Denmark will be located in a trench at the bottom of the Baltic Sea at a depth of up to 130 feet.
It is a key component in the development of the Scan-Med Corridor, a transport network that spans more than 3,000 miles from Malta in the south to Finland in the north. On its 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 diversion for both road and rail traffic on the north-south route.
The planned rail link will cut travel time from Hamburg to Copenhagen from five hours to less than three hours, while the road link will replace the heavily trafficked ferry service and cut travel times by around one hour.
How to build a submerged tunnel
The mega project is already underway. From an engineering point of view, the project is truly fascinating.
The submersible 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 pipes for highway, two for rail and one for service access. When completed, each element will be installed in place in a 39-foot-deep trench.
Dredging of this excavation is expected to produce 671 million cubic feet of soil, sand and rock that will be converted into new land and beaches near the construction sites.
Preparatory work on the required port and tunnel factory began in 2020, so that actual construction work could begin on 1 January 2021. By mid-2022, the 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 allows visitors to explore the construction site with their own eyes.
The project also has a controversial side
Not everyone is a fan of the Fehmarnbelt tunnel. As with all megaprojects, the impressive cost of construction has raised many questions about its value, while environmental activists are concerned about the impact the dredging work will have on the local marine ecosystem.
The construction site in Rødbyhavn, Denmark, taken in December 2022.
Almost the entire cost, estimated at $8 billion, is being financed by Denmark and will be paid for by hefty tolls once it opens. Many question the value of such an investment, but supporters of the project point to the iconic Øresund Bridge, which connects Denmark and Sweden. It is widely believed to have been a long-term success despite some fierce criticism of its costs during construction in the 1990s.
Now that construction on the Fehmarnbelt tunnel is underway, environmental activists have shifted their approach from trying to get the project canceled to monitoring its impact. Marine life in this area of the Baltic Sea thrives in clear water conditions, something that dredging the seabed to create the tunnel trench will disrupt.
In an interview with B1M, local activist Hendrik Kerlen said that “the ecology of the Fehmarn belt is very diverse. The fogging of the Fehmarn belt will reduce the growth of macrophytes and plankton and will of course have consequences for all living fauna and marine flora.
Femern A/S, the company responsible for the construction project, said sedimentation was one of the most closely watched environmental impacts on the project. Patrol boats and observation stations collect data on water turbidity, which is published on the Femern website.