dealing with uncertainty has led to a very precautionary assessment of the cumulative impacts, especially for pile driving (ETG meeting 3, Appendix 12.1).
497. The level of uncertainty in completing a CIA further supports the need for strategic assessment rather than developer led assessment. Ongoing work streams, such as DEPONS projects and the interim PCoD will also allow consideration of the biological fitness consequences of disturbance from underwater noise, and the conclusions of a quantitative impact assessment to be put into a population level context.
12.7.1 Impact 1: Underwater noise 498. The cumulative assessment of underwater noise considers the impacts from noise during all phases of East Anglia THREE, as well as potential impacts from those projects screened in to the CIA. All types of plans or projects outlined in Table 12.11 have the potential to create underwater noise from construction activities and/or operational activities (including vessel noise) and in some cases decommissioning noise.
499. The sources of underwater noise during each phase of a plan or project are summarised in Table 12.18. Pile driving could occur during port or harbour works, oil and gas platform installation as well as offshore windfarm installation. As discussed previously this type of noise can cause auditory injury to marine mammals if sufficient mitigation measures are not in place (JNCC 2010b). Auditory injury could also occur from underwater explosives (used occasionally during the removal of underwater structures), and seismic surveys. Guidelines also exist to mitigate the potential for injury to EPS from these activities (see JNCC 2010c and JNCC 2010d).
500. Other activities such as dredging, drilling, rock dumping/disposal, vessel activity, and operational windfarms, oil and gas installations or wave and tidal sites will emit broadband noise in lower frequencies. Therefore, auditory injury from these activities is very unlikely, with the main likely response to these noise stimuli being behavioural changes.
501. For many of the plans or projects screened into the CIA (Appendix 12.5) the potential impacts have not been quantified, and there is also a large amount of uncertainty around decommissioning impacts. It is therefore not possible to make a quantified CIA for all of the plans and projects screened in.
502. The greatest noise source is likely to result from pile driving during the construction of offshore windfarms. During the completion of environmental impact assessments many of the plans and projects screened in to the CIA have made some quantification of impact for the key receptors. Where such information has been
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 105
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