A range of Boskalis business units have been involved in various activities in the Borssele project, including dike upgrades, trenching, and laying, landing and installing the two 60-kilometer-long export cables that connect the future offshore wind farms to the Dutch power grid. In this article we put the spotlight on some areas of the project.
“We have buried all the cables in recent months,” says Project Manager Simon Overgaauw. “In the offshore section, the Trenchformer burying tool has finished its work from the Ndurance cable-laying vessel. On the nearshore section, the Giant 7 has performed excellently as a cablelaying vessel working with the new BSS3 burying tool that we developed in-house specifically for this project. The BSS3 buried the cables at depths ranging from 3 to 8 meters. That is unique: no other company has the capacity to install cables of this type at these depths. We also completed the two landfalls in the nearshore section: the first on 12 April 2019 and the second on 11 May 2019. The cables were pulled more than a kilometer and a half over the mud flat to the station in Borssele. After the completion of the landfalls, the Giant 7 crossed the waterway twice to lay the cables here at a wide range of depths. To allow this work to be done, the shipping route to and from the port of Antwerp was completely closed on 14 April 2019 and 13 May 2019. In both cases, we had to complete the work in just ten hours. So there was a lot at stake but we managed to stick to the time limit on both occasions.”
No other company has the capacity to install cables of this type at these depths
Project Director Hans Veth: “After laying the last cable, we converted the Giant 7 in the port of Flushing to make the offshore joints (aka the cable connections). The total distance covered by the cables is more than the cable length that we could carry on the ship at once. As a result, there are separate cable sections on the seabed at four locations that we still have to connect to each other,” says Hans. “That process began in mid-June 2019. Each connection takes about ten days to make so we expect to complete the work here by the end of July 2019. On top of that, we are now working with excavators to cover the cables with rock at the landfalls. We also mobilized our fallpipe vessel Rockpiper to protect the cables with rock in the fairway at depths of thirty to sixty meters. That involved bringing in a total of 70,000 tons of rock from Norway.” Preparations for the Borssele Beta project are now also in full swing. This work includes the installation of two 65-kilometer-long export cables and a 7-kilometer-long interlink cable between the Alpha and Beta platforms. “The first three cables have already arrived in the Netherlands and the first dredging work will start in late July 2019,” says Hans.