When the tunnel trench was declared finished in the summer of 2024, it was celebrated and hailed as the largest excavation in Danish history. The Dutch consortium FBC, led by Boskalis and Van Oord, had removed 15 million cubic metres of soil and rock from the bottom of the Fehmarn Belt in three years - equivalent to six Khufu pyramids. The work was carried out with a fleet of nearly 70 specialised vessels and was presented as an unparalleled engineering achievement.
At Femern A/S, the completion was marked as a milestone. The consortium could report on difficult soil types, heavy granite blocks, and a technically complicated process that had been resolved on time and to the client's satisfaction. The excavation was seen as the foundation of the entire tunnel - both literally and figuratively.
But a year later, the picture has changed. The trench, which was celebrated as a success in 2024, is now described in the July 2025 status report as unusable in its current form. The main contractor, Femern Link Contractors (FLC), assesses that the trench does not meet the requirements and therefore cannot be approved for use. However, Femern A/S has approved it and paid for the work by the Dutch contractor and is therefore left holding the bag.
The status report points to a number of problems with the tunnel trench. Here are the most important:
Data and measurements cannot be used
The status report concludes that the data about the trench, previously provided by Femern A/S, cannot be used. They are marked by errors and discrepancies, and the contractor considers them unusable. This means that, according to Femern Link Contractors, the client's official material can no longer form the basis for the work.
The first 650 metres rejected
After Femern A/S had approved FBC's excavation, the main contractor FLC itself examined the first 650 metres of the trench, in the section called LA01 A1. The investigations include new measurements and analyses of the base's structure. The result shows that the trench does not meet the established requirements. The foundation proved to be less stable than expected and does not show the same as data from Femern A/S. This means that FLC cannot use the client's material as a basis but must base the work on its own measurements and corrective actions.
The layer of chippings and type of gravel
The ship Vox Amalia was used to create the tunnel trench.Femern A/S
According to the original design, the trench was to be prepared with a single layer of chippings at the bottom. This would be sufficient to ensure the stability under the tunnel elements. FLC now assesses that this is not adequate. In the status report, a possible correction is described: first a layer of chippings, as planned, and then an additional finer layer of gravel, compacted in thin layers with special equipment. In this way, stability is achieved through an extra build-up that was not part of the original design.
Requirements for Rectification Works
FLC points out that extensive rectification work must first be carried out before the trench can be approved. This includes vibration compaction, where the gravel is shaken and compressed, as well as experiments with different types of gravel laid in thin layers of 100-125 millimetres. These experiments are conducted both on land and at sea. Only when the method is tested and verified can the rectifications be rolled out on a full scale in the trench itself.
Risk of Redesigning the Foundation
Even if the rectifications succeed, it is not certain that it will be enough. The report states that the first submersion depends on a possible redesign of the foundation in the trench. This could mean new engineering calculations and adjustments to the construction under the elements, which would further delay the schedule.
Consequences for Schedule and Production
Because the trench cannot be approved, FLC has no reliable schedule for the upcoming submersions, the report states. Meanwhile, the production of tunnel elements continues in Rødbyhavn, where storage space is limited. The status report already warns that the accumulation of elements causes standstill periods on the production lines, especially for the 10 special elements. If the trench cannot be used soon, the project risks a domino effect with production stops, delays in submersion, and massive postponements.
