L. A. Kyhn & J. Tougaard. 2021. Kattegatt Syd Offshore Wind Farm. Assessment of impact from pre-project surveys. Aarhus University, DCE – Danish Centre for Environment and Energy, 52 pp. Scientific Report No. 423. http://dce2.au.dk/pub/SR423.pdf
Impacts of use of three specific instruments for pre-investigations at the potential offshore windfarm site Kattegatt Syd was assessed with regard to harbour porpoises and seals. The assessed instruments were a sparker, a sub bottom profiler of specified source level, frequency and duty cycle and a small seismic air gun. Impact ranges were modelled by Rambøll (Rambøll, 2021).
Impact magnitude and significance was assessed for two types of impact: noise-inflicted permanent hearing loss (PTS) and behavioural disturbance.
The assessment showed that the risk of inflicting hearing loss by the survey equipment is negligible, provided the equipment is turned on with a suitably designed soft start sequence. The survey equipment is assessed to be able to disturb porpoise behaviour at maximum distances up to estimated 3-4 km (mean and max values) from the survey ship (using a sparker as source), and the consequences of this behavioural disturbance on the population of seals and porpoises in southern Kattegat is assessed as minor.
The disturbance of Natura 2000 sites from the mini-airgun, sub-bottom profiler, and sparker was assessed as acceptable following JNCC guidelines, and impact inside Natura 2000 sites can be avoided, if the vessel keeps a distance of 1 km or 3 km to the border of the windfarm site with the Sub Bottom Profiler and Sparker, respectively, based on maximum values. The range between the Natura 2000 sites and the potential windfarm area is 1 km.