Cathie Associates have performed a study which enabled the reduction of noise in the water column created by monopile driving at the Arkona offshore wind farm site in Germany, the company informed after all the 60 foundations were installed .
The offshore geoscience and geotechnical engineering consultancy carried out the study for E.ON during the planning of the monopile installation operations. It enabled the development of a hammer energy profile which allowed monopiles to be driven at reduced energy levels while still achieving required target penetration depth within the driving pile time restrictions applicable in Germany. This contributed to the reduction of the noise in the water column produced by the pile driving process, versus a more standard hammer energy profile.
Rui Silvano , a senior engineer at Cathie Associates, said: “Although reducing the energy will no doubt help reducing the resultant noise in the water column, the challenge was in achieving a fine balance: We had to ensure the recommended energy profile was optimised to drive the monopiles to the required depth within the 180 minute time restriction required by the BSH in Germany while verifying that the monopile fatigue during driving remained low despite the increased number of hammer blows associated with a reduced hammer energy.”
Each of the 81-metre monopiles, manufactured by the Rostock-based EEW SPC, was launched and floated to the construction site, where Van Oord’s heavy-load crane ship Svanen then hammered it 40 metres deep into the seabed. The first monopile was floated over and installed in August 2017.
The first of the 60 transition pieces, which were installed by Jumbo’s heavy lift crane vessel Fairplayer, was installed in November 2017.
The Arkona offshore wind farm, located 35 kilometres northeast of the island of Rügen, will comprise 60 Siemens 6MW turbines and is scheduled for commissioning in 2019.