What is the impact of underwater noise on marine mammals?

The effects are investigated in the Nature Assessment.

Construction phase

The driving of the anchoring piles to install the production platform is the main source of underwater noise. This takes approximately two days.

The driving of the anchor piles requires mitigating measures. To mitigate the effects of underwater noise on marine animals, a bubble screen is installed around the platform during the pile driving. This will lead to a considerable reduction of the underwater noise by 7 to 11 decibels. The noise pollution therefore remains within the Dutch and German standards. ONE-Dyas will keep the option open to apply other noise-reduction techniques, as long as these can reduce the noise by a sufficient number of decibels.

Drilling phase

The most significant noise emissions in the drilling phase are caused by the driving of the conductors (maximum of twelve). The driving of each conductor takes approximately twelve hours. After the drilling is completed, a VSP survey is carried out. VSP stands for Vertical Seismic Profiling. This involves a detailed mapping of the earth layers that have been drilled through. The sound waves of the VSP survey (up to five) also create underwater noise. Each survey takes approximately one day. Temporary disturbance of marine mammals by underwater noise is avoided as much as possible by starting the VSP surveys with a low source power to give them enough time to leave the area (a soft start).

The driving of the conductors and the performance of a VSP survey comply with the legal standards.