An evaluation of the noise mitigation achieved by using double big bubble curtains in offshore pile driving in the southern North Sea
Norro, A. (2020). An evaluation of the noise mitigation achieved by using double big bubble curtains in offshore pile driving in the southern North Sea, in: Degraer, S. et al. Environmental impacts of offshore wind farms in the Belgian part of the North Sea: Empirical evidence inspiring priority monitoring, research and management. Memoirs on the Marine Environment, : pp. 19-27 In: Degraer, S. et al. (2020). Environmental impacts of offshore wind farms in the Belgian part of the North Sea: Empirical evidence inspiring priority monitoring, research and management. Memoirs on the Marine Environment. Royal Belgian Institute of Natural Sciences, OD Natural Environment, Marine Ecology and Management: Brussels. ISBN 978-9-0732-4252-4. 131 pp., more In: Memoirs on the Marine Environment. Royal Belgian Institute of Natural Sciences, OD Natural Environment: Brussels, more |  |
| Abstract | In Belgian waters, in 2019, two wind farm construction projects were ongoing, the Northwester 2 (NW2) and the Seamade (SEA) projects. For both projects, turbine foundations were installed using hydraulic pile driving technique with a double big bubble curtain (DBBC) deployed to minimise the underwater sound levels emitted. For the installation of steel monopiles of 7.4 and 8 m diameter, large hydraulic hammers were used of 3000 and 4000 kJ respectively. These projects were the first to use the DBBC mitigation system in Belgian waters. In this study, the underwater sound generated during 14 full-pile driving events, seven per project, was analysed in situ. Measured zero to peak sound levels (Lz-p) showed values ranging from 183 to 193 dB re 1 μPa when normalised to a distance of 750 m from the source. This represented an estimated sound reduction of 20 dB re 1 μPa for NW2 and 12 to 20 dB re 1 μPa for Seastar. This made NW2 the first offshore wind farm whose pile driving was in compliance with the current Belgian Marine Strategy Framework Directive (MSFD) threshold for impulsive underwater sound. |
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