The first tunnel element now rests on the seabed off Rødbyhavn. It is a historic milestone in Denmark’s largest construction project, and a moment long awaited by the client, the contractors and politicians alike. The immersion was completed without technical problems, meaning the Femern project has passed its first practical test in the phase long described as the most complex and risky part of the build.
But a single successful immersion does not resolve the problems that have accumulated around the project. The Fehmarn Belt fixed link is more than two years behind schedule. The tunnel trench remains at the centre of a major dispute between the client and the main contractor, and relations between the parties are marked by open mistrust. Added to that are a DKK 14.5bn claim, an international arbitration case and German environmental requirements that could have a significant bearing on the pace of work in the coming years.
Thursday’s milestone is therefore both a breakthrough and the start of a new test. The issue is no longer whether the first element can be lowered. That has now been demonstrated. The question is whether the project can repeat the operation again and again, at a pace that brings the timetable back within reach.
Attention now shifts from the first spectacular operation to the more awkward questions of progress, responsibility and money. How quickly can the elements be immersed? How much of the tunnel trench needs to be repaired? Who will pay for the delays? And when can motorists realistically drive under the Fehmarn Belt?
There is no shortage of issues to untangle. Here is an attempt to answer some of the questions still hanging over the project after the first successful immersion.
Why is the immersion of the tunnel elements such a decisive turning point?
Because this is where the project has to prove that it works in practice.
For a sense of how significant that point is, look no further than the clash between Sébastien Bliaut, the now former chairman of the main contractor Femern Link Contractors, and Jacob Heinsen, the permanent secretary at Denmark’s Ministry of Transport.
Heinsen pointed to problems with the specialist vessel Ivy and the immersion work, and said the scale of the delays had raised concerns over whether FLC was capable of completing the project at all. The ministry’s demand was that this had to be proved in practice: not through theoretical calculations, but by actually lowering and correctly placing a tunnel element in the trench.
That has now happened.
Why is the immersion work so time-consuming?
A large part of the Fehmarn Belt is classified as a Natura 2000 area. That brings strict rules for the work.
In practice, those rules can act as a stop button. If noise measurements or model calculations show that thresholds have been exceeded, work must be halted immediately. The same applies if marine mammals are observed close to the work area. This is particularly important in the summer months, when the weather would otherwise normally offer the best and calmest working conditions.
The Fehmarn project itself describes immersion as the most complex and weather-sensitive part of the entire construction process. The operation requires several consecutive days of calm conditions so that towing, precise positioning, lowering and connection can take place without interruption. Strong winds, currents and rough seas can stop work in the middle of an operation.
The crucial question is how quickly the remaining elements can be lowered. The official schedules allocate three years.
Why has the tunnel trench become such a toxic issue?
The trench is the 18-kilometre track on the seabed in which the tunnel will sit. Before the 89 tunnel elements can be lowered, the trench must be excavated, inspected and approved.
That work was carried out by the Dutch consortium Femern Belt Contractors. But it has not been done properly, and the other consortium, Femern Link Contractors, has therefore refused to take over the trench.
The difficulty is that the client has approved the work. FLC has measurements showing large holes and a trench that is far from ready. The client has played down the problems and described the issue as one of excavation going 30cm too deep.
Kim Haugbølle, a senior researcher at Aalborg University, has previously pointed out that the contractor cannot proceed if the trench has not been approved. That makes it the client’s problem.
“The contractor cannot place elements in a trench that does not meet the requirements,” he said.
On January 21, it was announced that a solution had been found for the first 650 metres of the trench, which is now being corrected. Sund & Bælt is paying for the remedial work.
There is still disagreement over the quality of the rest of the trench. That means Sund & Bælt is currently negotiating with the main contractor, Femern Link Contractors, over what happens once the first three elements have been placed on the initial 650 metres.
That is not an ideal position.
Why has the relationship between the parties deteriorated so badly?
On a project of this scale, almost everything is written down and agreed in advance. The contracts try to anticipate every conceivable problem. One of the mechanisms is a Dispute Review Board, intended to handle disagreements and prevent every dispute from ending up in international arbitration.
Covid disrupted many construction projects. Femern was no exception. The disagreement over costs was submitted to the dispute board. Femern Link Contractors’ claim was €77mn, equivalent to DKK 570mn.
In the spring of 2024, the board gave FLC partial approval of its main claim and awarded the consortium €56mn, equivalent to DKK 417mn. Rather than accept the ruling, the client, Femern A/S under Sund & Bælt, chose to take the case further and refer it to international arbitration.
That case has not yet been concluded. It is costing millions in legal fees and remains a long way from a decision. Sources close to the project say this was the point at which the relationship came under serious strain.
Will it be expensive?
If the first three tunnel elements are lowered before the summer holidays, the expectation is that an updated timetable will be published. There will also be strong pressure to provide an updated cost estimate.
That part is more uncertain. It has already been acknowledged that the budget of about DKK 67bn will not hold.
When will motorists be able to drive to Germany under the Fehmarn Belt?
This is where the arithmetic becomes serious.
The starting point is relatively fixed. The main timetable allows 36 months for lowering the tunnel elements, followed by roughly two years for installations and testing. That points to an opening about five and a half years after the first immersion. With the first element lowered in May 2026, that calculation points to autumn 2031.
But there are strong indications that the immersion phase cannot be completed within 36 months. This is where the strict environmental requirements imposed by the German authorities come into play.
Femern Link Contractors has put both a time and a price on that problem: 20 months and a claim of DKK 14.5bn. In other words, 20 additional months to lower the tunnel elements because of restrictions on offshore work.
On the big calculator, 20 months added to autumn 2031 takes the opening to spring 2033. That is the current worst-case scenario.
But there are also factors that could pull the timetable in the other direction. In a megaproject like this, there are many levers to pull once the elements begin to be placed on the seabed of the Fehmarn Belt. The period for installations and testing could probably be shortened, perhaps saving half a year.
The rail contract has now been postponed, meaning that once the elements are in place, only the road section needs to be completed first. That makes the timetable more robust and reduces the delay to the road opening.
This is the “road first, rail later” scenario. It could allow King Frederik to cut the ribbon on a fixed link in 2032, with the trains following later.
