Düsseldorf/Wewelsfleth, 14 Sep 2023 - On 11 September 2023, the official start of construction took place with the symbolic ground-breaking ceremony for the Elbe crossing (ElbX) in the major SuedLink project. On behalf of the leading European transmission grid operator TenneT TSO GmbH, PORR is realising the tunnelling of the Elbe with its tunnelling, special civil engineering and structural engineering divisions. The tunnel construction represents one of the most challenging project sections for the construction of the SuedLink power line, which is to transport wind power from the north to the south.
With a ceremonial event in Wewelsfleth (Schleswig-Holstein), where the access structure to the tunnel is being built, Federal Minister for Economic Affairs and Climate Protection Robert Habeck, TenneT COO Tim Meyerjürgens, Lower Saxony's Energy Minister Christian Meyer, Schleswig-Holstein's State Secretary for Energy Joschka Knuth, Head of the Grid Expansion Department at the Federal Grid Agency Matthias Otte as well as PORR CEO Karl-Heinz Strauss in the presence of over 150 guests and numerous media representatives.
Hand in hand: tunnelling, special civil engineering, structural engineering and cable construction
A 5.2 km long tunnel with an inner diameter of 4 m is being built from Wewelsfleth to the target shaft in Lower Saxony near Wischhafen. As the start and target shafts are located in groundwater, the construction pits for the shafts have to be made watertight and stable before excavation. Afterwards, the construction pits, which are around 25 m deep, are excavated under water. This is followed by buoyancy control and the casting of the underwater concrete base. To construct the shaft building, the construction pits are first drained and secured with steel girders. These will be dismantled as construction progresses. Then the preparations for the tunnel drive and the assembly of the tunnel boring machine, which is specially manufactured for the subway, begin. It is designed for the changeable ground conditions under the Elbe. The tubbing construction method is being used for the tunnelling. Around 20 m below the Elbe, the tunnel boring machine will work its way through the soil. Six 525 kV direct current cables will be pulled into the finished tunnel and connected to the SuedLink underground cables on both sides of the Elbe. Rails in the tunnel allow tunnel vehicles to drive through it, so that the tunnel can be accessed quickly and safely for maintenance and repair work even after completion of the construction phase.
The preparatory measures for construction at the shaft site in Schleswig-Holstein were already completed in June. The measures included, among other things, the construction of the surface pavement. PORR's special civil engineering division is now ready to start the pile foundations and subsequent diaphragm wall work for the construction pit of the access structure. The power line is scheduled to go into operation in 2028. In order to achieve this goal safely, tunnelling (ARGE PORR-Wayss & Freytag), special civil engineering, structural engineering and cable construction are working hand in hand in the ElbX project. "The close interaction between the teams on the construction site with the client and all those involved in the provision of services is decisive for the timely implementation. Doing things together' is the basis for successful and on-time realisation," emphasises Karl-Heinz Strauss, CEO of PORR AG.
Start of construction is a decisive milestone for the energy transition
With a length of around 700 kilometres and a transmission capacity of four gigawatts, SuedLink is a key infrastructure project for the energy transition in Germany. "With SuedLink, the south of Germany will be able to benefit from the large amounts of wind power from the north in the future. This will strengthen the security of supply in Germany and also that of our neighbouring countries," said Federal Minister of Economics Robert Habeck at the official start of construction.
