During the past summer, we simultaneously installed three subsea power cables and a fibre-optic cable in the German Wadden Sea. The six-kilometre route runs from the island of Baltrum to the mainland. Completing this Wadden Sea section is the first milestone of the export cable projects we are delivering under TenneT’s 2GW Programme. In total, we are carrying out four similar subsea cable projects that will bring renewable energy to more than eight million German households.
Working in an ecologically sensitive intertidal area
Over three months, we laid and protected the four cables and carried out cable pull-ins through pre-installed pipes beneath Baltrum Island and beneath the mainland’s coastal defences. Working in the Wadden Sea, a protected area shaped by the tides, presented unique challenges. Large parts of the seabed are exposed at low tide, while the water remains extremely shallow even at high tide. During the works, we overcame significant technical and logistical constraints while keeping our impact on this sensitive ecosystem to a minimum.
Specialised equipment with minimal environmental impact
As the shallow, tidal conditions rule out conventional cable installation vessels, we deployed purpose-designed equipment for our works.
First, our cable-laying barge Waadrinner installed the cables on the seabed. The barge consists of three interconnected pontoons, each with its own cable carousel, equipped with a highly accurate positioning system. This setup allowed us to install the three power cables and fibre optic cable simultaneously. This innovative equipment, with optimised weight and draught, facilitated operations and minimised our impact on the environment.
We then used our Sunfish trencher to bury and protect the cables beneath the seabed. We specifically designed the machine to handle all three power cables and the fibre-optic cable simultaneously. Despite its dimensions and weight, Sunfish exerts less pressure on the seabed than an adult standing.
Smooth execution through thorough preparation
In this intertidal area, water levels, soil conditions and access to the worksite continuously change. Meticulous planning and close coordination of operations, personnel and equipment were essential, with safety remaining a priority throughout.
“Our team spent three years preparing for this project. Thorough preparation, the right equipment and team work with TenneT, allowed us to carry out the works as planned and complete them in just three months. We will take the knowledge and experience to our next projects for TenneT in the Wadden Sea, allowing us to work even more efficiently on the projects ahead.”
Arjen Van den Bos
Project Manager
Part of TenneT’s 2GW Programme
These works are part of four similar subsea cable projects that we are delivering for transmission system operator TenneT’s 2GW Programme, together with LS Cable & System and Denys. Across the programme, we will transport, install and protect 4,000 kilometres of cable, helping to bring renewable energy ashore for eight million German households.
By taking this long-term portfolio approach, we can use the same design, specialised equipment and core team across multiple projects. This not only creates efficiencies but also allows us to apply the lessons from each project to the next. Accordingly, Waadrinner and Sunfish will return for future projects in the Wadden Sea. From 2027, our newest cable-laying vessels, Fleeming Jenkin and William Thomson, will then install the longer offshore sections in the deeper waters of the North Sea.
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12 November 2026
