The Borkum Riffgrund 1 offshore windfarm (BKR1) is located at 38 km north of the westernmost Frisian Wadden island of Borkum, in the German Exclusive Economic Zone. The 35 km² wind farm is owned and operated by DONG Energy, and consists of 77 Monopile and Transition Piece foundations, and one tripod Suction Bucket Jacket (SBJ).
With a capacity of 3,2 MW, the 78 wind turbine generators are installed on top of foundations that are piled 16 to 30 m into the seabed in water depths of 23 to 29 m. Challenges included wind, waves, and currents, as well as technical matters. The sheer size, the weight, and the volume of monopiles and transition pieces required very specific experience – particularly with regard to operations in rough offshore conditions in the German Bight. The monopile weight varies in-between 495 tonnes and 684 tonnes and measures a diameter of 5,9 m and a length of up to 66 m. Transition Pieces weight measures around 330 tonnes.
DONG Energy awarded the contract to geotechnical and foundation specialist GeoSea for the logistics works, consisting of the transport of monopiles and transition pieces from the fabrication yard at Aalborg to the marshalling harbor of Eemshaven where the plant was temporarily stored. The foundation installation works were executed in four phases, in record time and completed ahead of schedule.
The client provided the installation vessel Pacific Orca. During the Monopile and Transition Piece installation, GeoSea used a Noise Mitigation System (NMS) in order to comply with the German noise regulation. Following the installation of the 77 Monopiles and Transition Pieces, GeoSea executed the floating load out at Aalborg, the transport and the successful installation of the 57 m high Suction Bucket Jacket (SBJ), a new 850 tonnes type of foundation that is being used for the first time in offshore wind on Borkum Riffgrund 1.
Tideway, a sister company of GeoSea, carried out several campaigns of filter and armour stone scour protection at BKR1. All works were executed in time and on budget.