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Excavation of the construction pits for the SuedLink Elbe crossing ElbX has begun

After the diaphragm walls for the launch pit on the Schleswig-Holstein side of the Elbe near Wewelsfleth were completed on schedule in the ElbX project, the first stiffener layer of steel girders was installed in April 2024. The wet excavation of around 25,000 m³ of marsh soil has begun and the project is right on schedule. A visitor centre has been opened by the project developer TenneT so that the public can take a look at the construction work.

ϲ has overall responsibility for the ElbX project on behalf of the transmission system operator TenneT TSO. 

 

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ϲ has overall responsibility for the ElbX project on behalf of the transmission system operator TenneT TSO. With a length of around 5.2 kilometres and an internal diameter of 4 metres, a tunnel is being built using the segmental lining method to route the underground cable of the SuedLink wind power line between Wewelsfleth in Schleswig-Holstein and Wischhafen in Lower Saxony under the Elbe. As a connecting structure between the SuedLink line and the tunnel, an approximately 84 metre long, 17 metre wide, 24 metre deep and 8 metre high, flood-proof shaft building will be constructed on each side of the Elbe from the main dyke. The cables will be connected in a dust-protected manner in the associated underground sleeve structure.

High environmental protection requirements for special civil engineering

The combined starting excavation pit for tunnelling and underground buildings is around 1500 m² in size, the target excavation pit on the Lower Saxony side around 1350 m². The depth of each is approx. 25 metres. Due to the high groundwater level, the construction pits must be watertight with diaphragm walls up to 54 metres deep. "Due to high environmental regulations in the area of the dyke crowns, we were unable to lay a pressure pipe to keep the water level in the construction pits constant. We therefore have to closely monitor whether there is a risk of a subsoil breach. Occasional contamination from construction equipment must also be removed," explains ϲ project manager Ronny Iffländer.

The construction site team is supported by specialised divers during the wet excavation as well as the construction of the underwater concrete base, which is intended to seal the construction pit from the groundwater. They monitor the progress of the work, remove slurry residue and sludge and prepare the subsoil of the construction pit for the production of the underwater concrete base.

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