Based on the extensive seabed surveys carried out in 2010, 42 turbine positions at Anholt offshore wind farm site have been identified as being at risk of extreme scour formation around the turbine foundation and it has therefore been decided to place a pile of rocks at the positions before the monopole is driven into the seabed.
The rocks are placed by special-purpose vessels that lay the rocks in one layer with a thickness of approx one metre and a diameter of 20-23 metres around the turbine position. Of the 42 positions, rock piles have now been installed at 28 positions.
Good weather has made it possible for the stone fishers to continue moving rocks from positions that collide with the installation activities. Approx 80% of the 5,000 rocks have now been moved and used to build a number of artificial reefs inside the wind farm area.
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Offshore WIND staff, February 07, 2012; Image: dongenergy