We are proud to announce that on Friday 4 July 2025 JV COTU officially began the sinking operation of the first tunnel element of the Scheldt Tunnel in Antwerp, Belgium. This large-scale, technically advanced operation marks a historic milestone in the realisation of the Oosterweel Link, the project that will finally complete the Antwerp Ring.
Technical masterpiece in progress
In recent weeks, the first four of a total of eight tunnel elements were successfully transported to Antwerp, where they are temporarily housed in the Doeldok. With maximum storage capacity of this dock reached, the carefully coordinated process of sinking the elements begins: each segment is placed step by step on the bottom of the Scheldt. "This is what it's all been about," says Gert Osselaer, Director of Operations at Lantis. "It's the absolute pinnacle of the operation. Everything we've built, designed, and tested in recent years is now coming together." The remaining four tunnel elements will be transported to the Doeldok later this summer. By the end of the year, all elements should be in place at the bottom of the Scheldt.
Precision in sync with the moon
Submerging a tunnel element in a tidal river like the Scheldt is a challenging task, planned down to the smallest detail. This work takes place around neap tide, the optimal moment when both current and water level are at their lowest. This ensures a stable and safe operation, which takes approximately two days each time. Neap tides occur about twice a month, around the first and last quarter of the moon.
A technical feat
Each concrete tunnel segment measures 160 metres long, 42 metres wide, and 10 metres high, with a weight of approximately 60,000 tonnes. The element is first transported from the Doeldok to the sinking location. There, it must be positioned transversely across the Scheldt. “Six winch wires, attached to anchor poles on both banks, take over one by one from the tugboats and carefully position the tunnel section with the help of the ebb current, which assists the turning movement,” explains Jan Bauwens of BESIX and project director at JV COTU.
Subsequently, the ballast tanks in the tunnel section are filled with water so that the element is just heavy enough to sink. Sinking catamarans help to keep the element stable and ensure it descends at the correct speed. “Every step is literally a matter of millimetres: once on the Scheldt bed, the tunnel element must not deviate more than 35 millimetres from the pre-calculated position,” says Bauwens. The entire operation is monitored from a specially equipped control room on the left bank. The sinking is done very slowly to minimise errors as much as possible.
On the Scheldt bed, two concrete slabs of 120 tonnes each serve as supports. Once the tunnel element lands on them, a hydraulic pump presses it firmly against the adjoining tunnel mouth on the left bank. The elements are made watertight with a rubber joint profile, and the space between the underside of the element and the concrete support slabs is filled with a sand mixture. After all this, the element is finally in place!
The animation below provides a visual representation of the transport and sinking of the massive tunnel elements:
The sinking operation will take two days. You can follow it live in Antwerp from the embankment along the Scheldelaan on Right Bank, near the radar tower, or you can follow digitally via the live blog www.kanjersopkomst.be.
The Scheldt Tunnel: a new future for Antwerp
The Scheldt Tunnel is the final piece of the Oosterweel link, featuring two tubes for car traffic, a special emergency tube, and a six-metre-wide cycle tube. This tunnel will not only provide Antwerp with an additional underpass beneath the Scheldt for road traffic, but from 2028, it will also establish a safe, direct cycle connection between the Left and Right Banks. Car traffic will follow in 2030, with the entire Oosterweel link opening in 2033.
World-class Belgian teamwork
JV COTU is a collaboration of the Belgian construction groups BESIX, Stadsbader Contractors, DEME, and Jan De Nul. Together, they are realising one of the most ambitious infrastructure projects in Belgian history.
Would you like to know more about how BESIX is involved in these works? Make sure to watch this video:
