SMRU Consulting are delighted to announce the release of our latest Scottish Natural Heritage (SNH) commissioned report – a review of noise abatement systems (NAS) for offshore wind farm (OWF) construction noise, and the potential for their application in Scottish waters.

The Scottish Government supports plans to develop a large number of OWFs in Scottish territorial waters and the exclusive economic zone. The installation of foundations for offshore wind turbines often involves pile driving operations which introduce significant noise into the marine environment and has the potential to impact marine mammals and fish.

In German waters, NAS are regularly used to reduce piling noise during OWF construction. These systems may be considered if there is a need to reduce noise in Scottish waters, especially given the current trend of increasing pile sizes and hammer energies (pile diameters increased from around 2 m in 2012 to up to 8 m in 2018), which inevitably lead to higher noise levels during piling. However, the environmental conditions in Scottish waters, which differ from those in German waters, may limit the use of NAS.

The primary objective of this study was to undertake a review of available NAS in relation to their applicability for use at pile-driving operations for OWF construction in Scottish waters. Of particular interest was the reduction in noise levels that can be achieved and the resulting benefit to marine fauna, as well as the practicality of use, cost, and impact/influence on the construction schedules of projects.

The study was based on a review of published peer-reviewed and relevant ‘grey’ literature, combined with a questionnaire-based survey followed up by interviews with NAS suppliers and end-users. The NAS considered were bubble curtains, casings, resonators and alternative hammers. The environmental conditions at future Scottish OWF sites were characterised to determine the conditions within which the NAS would need to operate. It was a pleasure to work with the offshore wind industry, NAS users and NAS developers, and we are grateful for all the contributions we received to inform this review.

Based on the information gathered in this review, some of the NAS may be potentially suitable for use in future Scottish OWF sites and could reduce sound exposure levels by 10 to 18 dB using a single system and up to 28 dB using a combination of systems. However, operational experience of OWF construction in depths deeper than 50 m is lacking. The report provides:

  • A description of the status of currently commercially available and frequently used NAS and those under development,
  • A summary of the experience of NAS users and NAS providers with regard to the logistical requirements and limitations for the deployment and operation of these NAS,
  • A review of the environmental limitations that may influence the deployment and operation of NAS,
  • A review of the direct cost implications associated with the use of NAS,
  • A review of the noise reduction efficacy of NAS, specifically with reference to the marine species inhabiting Scottish waters.

Data gaps are highlighted which will help to identify future work required for a better understanding of the applicability of the NAS in Scottish waters.

Caroline Carter from SNH said the report was:

an excellent review containing lots of useful information. This will be very helpful in understanding the potential of applying NAS at Scottish wind farm sites

 

Please find the full report for download here. Any feedback on the report is welcomed – please feel free to contact the lead author Ursula Verfuss.

Also, if you are attending the 2019 Aquatic Noise Conference, Rachael Sinclair will be presenting this work at the poster session on Thursday 11th July – please pop along at poster #129 to find out more!