On 11 September 2023, the official start of construction for the Elbe crossing (ElbX) in the major SuedLink project took place. PORR GmbH is carrying out the tunnelling under the Elbe on behalf of the transmission grid operator TenneT TSO GmbH. For the construction of the SuedLink power line, the tunnel represents one of the most challenging project sections for transporting electricity generated by wind power from the north to the south.
The access structure to the tunnel is being built in Wewelsfleth in Schleswig-Holstein. There, 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 Bundesnetzagentur Matthias Otte and PORR CEO Karl-Heinz Strauss ceremoniously opened construction with a groundbreaking in the circle of 150 guests.
Tunnelling, foundation engineering, civil engineering and cable construction
A 5.2 km long tunnel with an internal diameter of 4 m is being built between Wewelsfleth and the target shaft near Wischhafen in Lower Saxony. The excavation pits for the shafts have to be made watertight and stable before excavation, as the start and target shafts are located in groundwater.
Subsequently, the construction pits, which are around 25 m deep, are excavated under water, followed by buoyancy control and the casting of the underwater concrete base. To construct the shaft building, the excavation pit is first drained and secured with steel girders, which are later removed. Afterwards, preparations for the tunnel drive and the assembly of the tunnel boring machine, which was specially manufactured for the subway, will begin. The machine will work its way through the soil about 20 m below the Elbe. 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. Tunnel vehicles will be able to drive inside the structure by means of rails. In this way, the tunnel can be accessed safely and quickly for maintenance and repair work even after the construction phase has been completed.
Central infrastructure project
In June, the measures to prepare for construction - such as the surface stabilisation - were already completed at the shaft location in Schleswig-Holstein. The ElbX tunnel construction project (ARGE PORR-Wayss & Freytag) is working hand in hand with specialist foundation engineering, civil engineering and cable construction to ensure that the project is completed on time.
With a total length of around 700 km and 4 GW transmission capacity, 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.