Two weeks ago, the immersion operation of the fourth tunnel element of the Scheldetunnel — weighing approximately 60,000 tonnes — was temporarily halted. During positioning, an unexpected sand accumulation was discovered, preventing the element from being installed in the correct location. Although it was successfully connected to the third tunnel element, it was placed on temporary supports on the Scheldt riverbed while a corrective measure was prepared.

Last week, the project team carried out a unique and technically challenging recovery operation to safely disconnect, lift, and return the fourth tunnel element to the mooring location in the Doeldok.

A Unique Maritime Operation

Recovering a tunnel element of this magnitude is an unprecedented and high-risk operation requiring exceptional precision and teamwork.
After the joint between the third and fourth elements was filled with water, TE4 was carefully disconnected. The element was then gradually and safely lifted from its temporary supports using the immersion pontoons, while the winch pontoons kept it horizontally aligned.

Once the tunnel element was securely positioned between the pontoons at water level, the remaining ballast water was pumped out of its tanks. At the optimal tide moment, the element was transported back to the Doeldok.

Next Steps

The fourth tunnel element will remain in the Doeldok in the coming weeks until the next suitable slack-tide window. After that, a renewed immersion operation will take place to install the element in its final position.

This operation showcases remarkable craftsmanship, teamwork, and maritime engineering within a highly challenging infrastructure project.

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