Construction on what will be the world’s longest sunken tube road/rail tunnel is set to begin following a Danish government approval.

Site work on the roughly 18-km, Denmark-Germany Femern crossing will start in January, after being delayed several months by the coronavirus and legal questions over financing of the $7.5-billion project.

With all Danish approvals now in place for the 8.5-year project, Femern Link Contractors (FLC), led by VINCI Construction Grands Projets, will start developing a facility to produce elements of the concrete sunken tube tunnel at Rødbyhavn, along with a tunnel ramp and other onshore facilities.

The link will require 79 precast concrete elements, each 217 m long and weighing about 73,000 tonnes. Their casting is due to start early 2023 followed by full production that summer. FLC is then expected to start sinking the elements into a sea bed trench between Denmark’s Lolland island and Fehmarn, Germany, in early 2024.

FLC’s won the $3.7-billion tunnel contract in 2016 before Denmark’s state-owned project company Femern A/S had secured all necessary Danish and German approvals. The FLC joint venture also includes units of Royal BAM Group, Solétanche-Bachy International, CFE, Dredging International and Max Bögl Stiftung & Co. The design firm for the project is COWI A/S.

At the same time, Femern A/S awarded roughly $325 million of dredging and reclamation work to the Fehmarn Belt Contractors team of Boskalis International B.V., HOCHTIEF Solutions A.G., Ed. Züblin A.G. and Van Oord Dredging and Marine Contractors B.V., with SWECO Denmark A/S, acting as the lead design firm.

Lacking all the necessary approvals, the contracts included break clauses allowing a review in 2019. Denmark quickly provided its approvals but the process was slower in Germany, where environmental objectors fought the project.

The Ministry of Transport of Germany’s Schleswig-Holstein state gave the go ahead in December 2018. But its decision was challenged in the Federal Administrative Court. Final hearings at that court are set for this autumn, according Femern A/S.

While Femern A/S authorized the dredging work in March 2019 the main tunnel contract was delayed partly by questions over how Denmark is financing the project.

For historical reasons, Denmark is controlling the project and financing all the work up to the German border with government guaranteed loans. Because the toll project will have a commercial use, it must comply with European Union rules on state aid.

The European Commission approved the funding model in July 2015 but objections from shipping companies made to the EU General Court partially overturned that decision in December 2018. Following an investigation, the European Commission this March again approved the financing.