Scour protection completed at Amrumbank

Using up to four of the company’s vessels, Peter Madsen crews have placed some 45,000 1.5 tonne bags across the 80 turbine positions in advance of the construction of the wind farm. The intention is to use this innovative and environmentally stable technique to prevent scour forming around the turbines after they are installed. By placing the scour prevention before the piles are driven, the mobile, sandy seabed can be stabilised and the foundations protected.

After a nine month assembly period, during which over 60,000 tonnes of dredged sand was turned into 45,000 filled sand bags, Peter Madsen loaded a supply barge and sailed to the Amrumbank site, some 20 nautical miles off the west coast of Germany. From here four Peter Madsen vessels placed two layers of sand bags in a 25m diameter circular array at each of the 80 planned turbine locations.

Placing the bags could only be carried out in fair weather. Despite numerous periods of unsuitable weather, the final bags were placed in September after just six months of site operations.

As well as being a physical challenge, the project was a considerable logistic and quality operation. From the individually weight batched bags, the accurate offshore positioning, the 45,000 separate bag locations, and the many multi-beam surveys, the engineering, surveying and IT staff at Peter Madsen had to handle vast amounts of computer data and achieve the quality controls required by the client, E.ON. This was carried out in the companies head office in Aarhus, Denmark and at

Amrumbank onboard Peter Madsen’s survey vessel. Despite of the challenges a new technique, the relatively long distance from port, the variable weather and the sheer volume of materials and data to be managed, the work was completed within schedule, budget and without any personal injury accidents.