Fehmarnbelt Tunnel Construction Underway

Anyone who has driven from the Netherlands to Scandinavia will recognize the dilemma: either you take the ferry from Germany (Puttgarden on the island of Fehmarn) across the Fehmarnbelt to Denmark (Rødby on the island of Lolland), which will take you across in less than an hour, or you detour 160 km through Jutland and over the Great Belt Bridge. After 2029, this choice might become a lot easier, as the world's longest immersed tunnel will open between Fehmarn and Lolland: the Fehmarnbelt Tunnel. Through this 18-kilometer-long tunnel, you can drive to the other side in just ten minutes, saving about an hour of travel time. Rail transport benefits even more, as the duration of a train journey between Copenhagen and Hamburg will almost halve from 4.5 hours to 2.5 hours. But before that happens, there is still a lot of (civil) work to be done on Northern Europe's largest infrastructure project, with a budget of around €7 billion; and a significant role is played by Dutch engineers and contractors.

Initiation phase
As early as 1991, Denmark and Sweden expressed their intention to realize a fixed link across the Fehmarnbelt. An agreement between Denmark and Germany followed in 2008. The subsequent design competition in 2011 concluded that an immersed tunnel is the best solution for the intended location. The presence of particularly large boulders in the seabed meant that a bored tunnel was not the preferred option. The main objections to a bridge connection were the presence of important bird migration routes and the lower availability of a bridge compared to a tunnel. After a long permit process, the German supreme court gave the final green light in the autumn of 2018, and realization started in 2019.

Organization
The project owner and future operator of the tunnel is Femern A/S, a state-owned company which falls under the Danish Ministry of Infrastructure. Femern A/S contracted the joint venture RAT as a consultant, which consists of engineering consultants Rambøll, ARUP and the Dutch Tunnel Engineering Consultants (TEC). The latter, a global leader in the design and maintenance of immersed tunnels, is a permanent partnership between Haskoning and Witteveen+Bos.

The tunnel
The Fehmarnbelt tunnel consists of two railway bores each with one track, and two road bores, each with two lanes, and an emergency lane. Between the road bores is a central gallery for cables and emergency exits among other things. The 18-kilometer- long immersed tunnel will be constructed from 89 concrete tunnel elements, including 79 standard tunnel elements and 10 special elements. The standard elements have a length of 217 meters, a height of 8.9 meters and a width of 43 meters, including the lifting corbels which connect to the lifting hooks of the immersion pontoon. Each element weighs 73,000 tonnes. The special elements, which are placed in between every eight standard elements, have a different design with a length of ‘only’ 38 meters. The special elements are about three meters higher, providing space for an extra level to accommodate technical installations and a pump sump (see Figure 1). To access this lower level without causing any disruption to traffic, the western road bore is provided with a parking bay. This makes the special elements seven meters wider than the standard elements.