Pelagic fish may exhibit a general behavioural response at a range of about 16km to 48km around the foundation. Fish near the seabed may show an equivalent response at smaller ranges of up to about 11km to 34km. The extent of the range depends on the location of the foundation within the site, the surrounding bathymetry, the type of fish, its sex, age and condition, as well as other stressors to which the fish is or has been exposed. The response of the fish may also depend on the reasons and drivers for the fish being in the area (e.g., feeding and spawning). It should be noted that the longer avoidance distances only occur along a limited number of transects from the source.
34. 35.
The impact range estimates outlined above represent the 3,500kJ hammer blow energy.
There is considerable variability in the extent of impact ranges across the East Anglia THREE site due to variable bathymetry, with the greatest ranges observed to the west (south-west to north-west) of the proposed East Anglia THREE project.
36.
For concurrent piling using two piling vessels the instantaneous SPL is highly unlikely to add up in such a way as to increase the peak noise level. The size of the impacted area would be dependent on the separation between the vessels.
37.
Possible noise from the operation of the windfarm has also been considered based on previously published measurement data which suggests that broadband noise levels within the boundary of the windfarm are not likely to be significantly above ambient noise, although the operation of the wind turbines may increase the ambient noise slightly during periods of light winds, calm seas and low shipping traffic, assuming that the wind is sufficient to turn the wind turbines. There is not expected to be any significant behavioural disturbance associated with the operation of the wind turbines although the potential increase in ambient noise within the boundary of the site may influence behavioural patterns of those species present which are sensitive to increasing levels of ambient noise.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 9 Underwater Noise Page 11
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