• 580 capacity in MW
  • 500000 families supplied with green electricity
  • 148 km of cable

Jan De Nul pulled out all the stops for the cable installation project at the Race Bank Wind Farm. The job description read as follows: realising a cable connection between the wind farm and the mainland on the English East Coast. A distance of 71 km had to be bridged by two export cables. It was a huge technical and environmental challenge. Ørsted, along with most clients, required not only quality and reliability but also timely project delivery, all of these criteria were crucial. For the licensing authorities, negative experiences from the past were sufficient reason to impose very strict conditions, particularly for the works in the salt marshes and mud flats of The Wash nature reserve. The cable-laying vessel Isaac Newton was the perfect vessel for the works in the deeper sections. However, for the works within the final 8 km of the cable trajectory – a tidal area – suitable environmentally friendly equipment simply did not exist on the market. Undeterred, the various engineering teams of Jan De Nul set to work to solve these unique problems. In so doing, by designing and creating the sister installation and burial tracked vehicles, Sunfish and Moonfish, they have set the standard for working in such vulnerable areas. 


Project Manager Patrik Lowie remembers the extent of the challenge. The conditions imposed by the local authorities were absolutely unique, that together with the local circumstances made matters hugely complex. “In the area from the coast up to about 5 km out to sea, the tidal water level varies between 0 and 7 metre, depending on the lunar cycle. So, laying cables here wasn’t an easy job to begin with. But the environmental authority also asked to bury the cables: one and a half metres deep in the swampy coastal area, which dries up about once to twice a month, and up to 5 metres deep in the subsequent tidal area.”

“In addition, the sensitive vegetation in the swampy salt marshes had to be protected against damage. The number of times that we went in here had to be limited to an absolute minimum – preferably only once. It will be clear that using traditional excavators, even when fitted with low ground pressure tracks, for digging a trench and backfilling it was totally out of the question. The ground pressure had to be limited to about 15 kPa, bearing in mind that the pressure exercised on the ground by an average human being is about 30 kPa. Nevertheless, our machine had to create sufficient traction to move on in the wet, growth-covered underground. In the tidal area, the so-called mud flats, the main problem was that the equipment used would have to operate alternatingly in dry conditions and under water. Thus, what we needed was an amphibious vehicle “suited for use in salt water”, which according to experts is more than a petty detail.

"At Jan De Nul we have a justified belief in our own capabilities"

“The engineers started looking for existing machines that could meet all requirements but – as could be expected – to no avail. So we did what we at Jan De Nul do best,” says Patrik Lowie. “We decided to create our own solutions. If there is one thing we all have plenty of here, it’s a justified belief in our own capabilities. Jan De Nul’s engineering departments designed two completely new tools, the Sunfish for the marshland and the Moonfish for the amphibious section in the tidal area of The Wash. “Our engineers created two machines that did not yet exist before we designed them. Along with the DN120, a converted pontoon, and the Isaac Newton, the Sun- and Moonfish made the perfect combination. Together, these tools and vessels would bring the whole project towards a successful conclusion. We succeeded during the competitive tender process of Ørsted, the very experienced client, by showing that we were the right firm to overcome the challenge. The fact that we were able to develop the necessary machines, designed and built in-house in our own workshops, within such a short time frame, was able to support their decision process. 

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