Oosterweel Link: Third Scheldt Tunnel element successfully immersed in Antwerp, Belgium

As with the previous immersions, the operation required meticulous planning and execution. The COTU joint venture positioned the prefabricated concrete element on the riverbed within a 35-millimetre margin, using ballast tanks, immersion catamarans, and anchor cables fixed to both banks.

The operation took place during a narrow tidal window known as ‘slack tide’, when water movement is minimal, allowing for the safest and most stable conditions for immersion. The element was gently lowered into place and aligned with previously installed elements, forming part of the tunnel that will eventually connect Antwerp’s Left and Right Banks.

The total immersion operation, including the transport from the Doel Dock where the elements are stored and finishing works underwater, takes about 130 hours. The immersion itself takes about 24 to 30 hours.

In total, three out of eight elements have now been immersed. By the end of 2025, all elements will be in place, after which finishing works will take place. The tunnel is expected to open to cyclists in 2028, with motorised traffic following in 2030.

This third immersion attracted international attention. A delegation from São Paulo (Brazil), including representatives from the Department of Highways (DER) and the state transport regulator ARTESP, attended the operation to learn from Belgian expertise in immersed tunnel construction. São Paulo is preparing for its first undersea tunnel project, a 870-metre-long tunnel under the ocean, connecting the cities of Santos and Guarujá. Similar to the Scheldt Tunnel, this initiative will employ prefabricated concrete segments installed at a depth of 20 metres.

Raquel França Carneiro, director at ARTESP, was present on site and expressed keen interest in the technical approach and collaborative model used in Antwerp. The visit underscores the global relevance of the engineering solutions developed by BESIX and its joint venture partners.

The Scheldt Tunnel is a vital component of the Oosterweel Link. Once completed, it will provide a new crossing under the Scheldt for motorized traffic, cyclists and emergency services. The tunnel includes two traffic tubes, an emergency tube and a six-metre-wide cycle tube.

Beyond its technical complexity, the project is a symbol of connection: between communities, between engineering disciplines, and now, between continents. BESIX is proud to contribute its expertise to this landmark infrastructure and to share knowledge with international partners shaping the future of mobility.

TM COTU stands for "Tijdelijke Maatschap Combinatie Oosterweeltunnel" and brings together the Belgian construction groups BESIX, Stadsbader Contractors, DEME, and Jan De Nul.

The planning of the immersions is subject to change and depends on several factors, including weather, wind, wave conditions, currents, and tides. You can follow all important operations via the live blog www.kanjersopkomst.be.