the scoured sea bed sediments would be lower than those previously assessed during the construction phase for sea bed preparation activities.


352. The precise need (or otherwise) for scour protection would be defined during the detailed engineering stages. If scour protection is used at all gravity base structures, the area of sea bed affected by the direct foundation footprint and scour protection footprint combined for 108 foundations increases to a maximum of 2,708,660m2. This represents 0.89% of the total sea bed area within the East Anglia THREE site.


7.6.2.5.1 Assessment of effect magnitude and/or impact significance 353. Taking the aforementioned considerations into account, the worst case changes to the sea bed morphology due to the presence of foundation structures are likely to have the following magnitudes of effect (Table 7.32):


Table 7.32Magnitude of effects on sea bed morphology due to the presence of foundations under worst case scenario


Location


Near-field* Far-field


Scale High Negligible Duration High Negligible Frequency High Negligible


Reversibility Magnitude of Effect


Negligible Negligible


High Negligible


* The near-field effects are confined to a small area (likely to be of the order of several hundred metres up to a kilometre fromthe foundation (in the absence of scour protection) or within the


footprint of scour protection, should it be provided), andwould not cover the whole East Anglia THREE site.


354. The effects on sea bed morphology arising from the presence of foundation structures would not extend more than a few hundred metres away from each wind turbine location before any scoured sediment settles on the bed (should no scour protection be provided), or would be confined to within the direct footprint of the scour protection material (should this be provided). In the case of no scour protection being provided, the scour hole would respond dynamically to the prevailing tidal current and wave conditions, but the dynamic responses would be lower than magnitudes of natural change in sea bed levels. Therefore, there is no impact associated with the proposed project on the identified marine geology, oceanography and physical processes receptor groups since these are located remotely from this zone of potential effect.


355. The significance of these effects on other receptors is addressed within relevant chapters of the PEIR.


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 70


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