By November 2010, Femern A/S had gathered sufficient information to allow it to recommend a preferred technical solution that would be presented to the Danish and German authorities. Both alternatives had proved to be feasible in construction terms and were possibly approvable on environmental grounds. The company concluded, however, that the immersed tunnel would be the best overall solution.
This assessment was based on a number of factors, including technical, safety, risk, financial and environmental aspects:
- The technical challenge of building a bridge with two world record spans of 724 metres for shipping traffic would be greater than the challenges associated with the construction of an immersed tunnel.
- Unlike a bridge, the tunnel would not affect navigational safety for marine traffic on the Fehmarnbelt during the operation phase. The risk of a collision between a vessel and the bridge can be minimized, but not eliminated. Traffic in a tunnel would also not be exposed to adverse weather conditions.
- Originally, the immersed tunnel was expected to be more expensive than the cable-stayed bridge. However, in-depth planning revealed that both solutions would cost a similar amount.
- The cable-stayed bridge would have a lesser butpermanent impact on the marine environment since its pillars could affect the water exchange in the Fehmarnbelt. Unlike a tunnel, a bridge would also be at risk of impairing bird migration in the region.
On 1 February 2011, the Danish Minister of Transport and the parties in the Danish parliament behind the project agreed to Femern A/S’ recommendation of an immersed tunnel.
In 2012, Femern A/S concluded all the project investigations which would be the basis for the documentation to besubmitted to the Danish and German authorities in 2013 in order to get the project approved. In this context, all four technical solutions were further examined to provide a level of detail that justified the selection of the immersed tunnel.