200 ‘Reef balls’ installed in lake IJsselmeer

200 'Reef balls' installed in lake IJsselmeer

In the northwest corner of Flevoland, in the municipalities of Dronten and Lelystad, a new wind farm is being developed by Vattenfall and SwifterwinT under the name: ‘Windplanblauw’.

The wind park will soon consist of 37 wind turbines on land and 24 wind turbines in the lake IJsselmeer. Windplanblauw is taking the flora and fauna in the area into account during and after construction.

That is why 200 ‘reef balls’ were recently installed in lake IJsselmeer. These concrete balls have openings in the wall and a floor plate. The purpose is that fish can safely shelter in these balls in effect, so they are Fish Hotels.

Doggerland Offshore performed this work as a subcontractor to Ballast Nedam.
It involved:

  • writing the necessary method statements and risk analyses,
  • transporting the ‘reef balls’ from the factory to the project site,
  • placing the ‘reef balls’ and
  • creating a delivery file.

The reef balls were transported from the factory by truck to an unloading quay on the Ketelmeer.
After all the balls were stored, a crane ship was mobilised which could load about 75 balls at a time.
The balls were accurately placed at predetermined GPS positions in clusters along the foot of the IJsselmeer dyke.
A clever lifting hook enabled safe lifting without the risk of the hook opening unexpectedly and yet the hook could be opened underwater without divers or extra opening wires.

Martijn Jongmans
Martijn JongmansProject engineer Ballast Nedam
Read More
"The work plan was very complete and professionally set up. This was the first work plan in this project on which no comments were made by either the end client or the Marine Warranty Surveyor. The final report was perfect.

I found the cooperation with Doggerland Offshore and Ewoud very good. He is -rightly- contractually sharp but very friendly and pleasant to deal with and has enormous practical experience. The agreements were met punctually. For us, Doggerland Offshore is now on the list of reliable subcontractors and I would definitely also recommend my colleagues to work with Doggerland Offshore in the future."