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France: Bauer Spezialtiefbau executes offshore wind farm foundation works under the most challenging conditions – around two thirds of the offshore pin piles completed

190 subsea drilled and grouted pin piles for 62 wind turbine generator locations and one offshore substation around 16 km off the coast of northern France, subsoils with strengths in excess of 150 MPa, utilizing brand-new technology which is fully remote controlled from a command center on the offshore construction vessel – these are the challenging and far from standard conditions under which the foundation work for the new Saint-Brieuc offshore wind farm is currently proceeding. The wind farm is scheduled to go into operation during the course of this year.

Underwater drilling work, for which BAUER Spezialtiefbau GmbH has been commissioned, has been underway since 2021. “The subsoil has turned out to be unexpectedly hard and extremely abrasive,” explains Bauer Project Manager Niklas Haag. “After initial difficulties, we made very good progress with the work in 2022. Despite the most difficult drilling conditions, we have successfully drilled and grouted two thirds of the upcoming boreholes in a short time. The wind farm owner has also given us feedback that he is very satisfied with the progress of the project.”

Specifically, Bauer is responsible for carrying out subsea drilling and grouting of pin piles as part of the jacket foundation work. Three specially designed BAUER Dive Drills are being used, which are working in water depths of up to 40 m and simultaneously drill holes up to 47 m deep and 3 m in diameter. The three-legged jackets for each of the 62 wind turbines as well as an offshore substation are secured to the seabed via the drilled and grouted pin piles. “In these conditions, with not only the extremely hard rock that has to be drilled through, but also granular and cohesive soil strata layers, the drilled holes are fully protected at all times over the entire length by recoverable casing. This is a real first in the history of offshore foundations,” says Barry Eagles, Managing Director at BAUER Offshore Technologies GmbH.

The second phase of drilling operations was completed in November 2022. After a winter break, the final phase will then start in the first quarter of this year, during which the remaining drilled and grouted pin piles will be installed. “We are very confident that we will complete the work by the summer,” explains Harald Heinzelmann, Managing Director at BAUER Spezialtiefbau GmbH. He is proud of the performance achieved by the team together with the equipment developed by Bauer. “We have demonstrated that we are in all aspects technically capable of realizing such a challenging project. We see further potential for our technology, especially for difficult foundations in challenging soils in deeper water and including mooring piles for floating offshore wind farms.”

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