levels could be sufficient to cause local disturbance of sensitive marine fauna in the immediate vicinity of the vessel, depending on ambient noise levels.
136. Considering previously reported data on the operational turbine noise of a windfarm and the likely noise from any associated service vessels, any increase in the ambient noise levels at the windfarm site might be expected to be small relative to the noise associated with near-by shipping lanes.
137. Given the low noise levels associated with turbine noise the risk of behavioural disturbance for most marine mammals and fish would likely be limited to the area immediately surrounding the turbine, which represents a small proportion of the area of East Anglia THREE. It should be noted that a major contribution to the ambient noise would result from sea-state, which would be expected to increase as the turbine rotational speed increases with wind speed. Increased ambient noise may exceed the turbine noise, as has been observed by Tougaard and Henriksen (2009) and result in no response to the turbine noise. Modelling of the noise radiated by operational turbines by Marmo et al. (2013) shows potential for variation between foundation types but reports underwater noise levels which are broadly consistent with previously measured data.
9.6.3 Decommissioning 138. Temporarily elevated underwater noise levels might be expected during the decommissioning phase due to increased vessel movements and removal of the turbine foundations. The resulting noise levels will depend on the method used for removal of the foundation. For abrasive cutting, often anticipated for wind turbine removal, the noise level would not be expected to be significantly higher than general surface vessel noise. Studies of underwater construction noise (decommissioning) report source level which are similar to those reported for medium sized surface vessels and ferries (Malme et al. 1989; Richardson et al. 1995). The noise resulting from wind turbine decommissioning employing abrasive cutting is unlikely to result in injury, or significant disturbance of local marine receptor populations, although some temporary disturbance might be experienced in the vicinity of the decommissioning activity.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Appendix 9.1 Underwater Noise Modelling 63
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