The timing for the submersion of the first tunnel element is set for mid-May. This is according to an internal schedule that Sund & Bælt has sent to the German authorities in Schleswig-Holstein, and which FemernBusiness has obtained access to.
In January, Sund & Bælt announced that the submersion would occur during the spring of 2026. However, in a schedule sent to the German authorities a few weeks later, with status as of 2 February, the first submersion is scheduled for mid-May.
This places the start time in the latter part of the spring that Sund & Bælt themselves have indicated.
This follows a period where the schedule has been postponed several times.
The submersion of the first tunnel element is more than two years delayed and is crucial for the entire construction of the 18-kilometre-long immersed tunnel between Rødbyhavn and Puttgarden. The original plans showed that the work should have begun at the start of January 2024. Since then, the timing was set for 2025.
As recently as 4 December 2025, the expectation was that the first tunnel element would be submerged in February 2026.
Lacks approval
That plan fell through shortly after because the submersion vessel Ivy had its temporary sailing certificate revoked and was detained by the authorities. Thus, the basis for starting the work as planned disappeared.
Progress depends on a number of conditions that are not yet in place. One of the most crucial is Ivy. The vessel is specifically built for the Femern project and is intended to transport and stabilise the enormous tunnel elements as they are lowered and placed with high precision on the seabed. Without an approved vessel, the work cannot be carried out.
The vessel is still under testing and still lacks final approval. However, Ivy has been thoroughly tested in the working harbour in Rødbyhavn, and final approval should be imminent.
The controversy over the tunnel trench
At the same time, there is still uncertainty about the tunnel trench in which the elements are to be placed.
The trench is excavated along the future tunnel route and serves as the foundation for the entire construction. Before work can begin, it must meet a number of requirements, including depth and smoothness.
Internal assessments have shown that the trench cannot be approved in its current form and requires further adjustments. The work on the trench has also been the subject of disagreement between the client and the contractor, who have had different assessments of the quality and data basis. The current status is that work is underway to get the first 650 metres ready.
Strict environmental requirements
In addition to the technical aspects, the work is also subject to a number of environmental requirements from the German side.
Fehmarn Belt is a protected marine area, and limits have been set on how much noise the work may create underwater.
From 1 June to 30 September, the most restrictive conditions apply. During this period, only a very small part of the area may be affected by loud noise, and this can significantly limit the work. At the same time, there is a year-round limit on how much of the belt may be affected.
According to the original schedules, the submersion of the 89 tunnel elements takes at least three years. This is followed by an additional two years of installation and testing before the tunnel can open.
The work thus takes place within a narrow window. The noise limits mean that even minor exceedances can lead to stoppages, and the weather in the Fehmarn Belt can also prevent submersion operations from being carried out as planned.
