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243. Although the modelling used a smaller volume of material (982m3 associated with jackets) than the worst case for the proposed East Anglia THREE windfarm (4,524m3 associated with monopiles) it does support the principles of the expert-based assessment that the envisaged scale of bed level change would be small.


244. The bed level changes that are anticipated above would move across the site with progression of the construction sequence as the point of sediment release (and hence geographic location of the zone of effect) changes with the installation of foundations at different wind turbine locations.


7.6.1.2.3 Assessment of effect magnitude and/or impact significance 245. Given that the expert-based assessments of the bed level changes associated with foundation installation for the proposed East Anglia THREE project are consistent with the findings of the earlier modelling studies for the proposed East Anglia ONE project, there is high confidence in the assessment of effects, including their scaling up from modelling results of a sub-set of wind turbines to the whole project area.


246. The worst case changes in bed levels due to foundation installation are likely to have the following magnitudes of effect (Table 7.18):


Table 7.18Magnitude of effects on bed level changes due to foundation installation under worst case scenario


Location


Near-field* Far-field


Scale


Medium Negligible


Duration


Negligible Negligible


Frequency


Negligible Negligible


Reversibility Magnitude of Effect


Negligible Negligible


Low Negligible


* The near-field effects are confined to a small area of sea bed (likely to be of the order of several hundred metres up to a kilometre from each foundation location), andwould not cover the whole East Anglia THREE site.


247. These effects on sea bed level have the potential to impact directly upon the identified receptors groups for marine geology, oceanography and physical processes. However, as there is a large separation distance (well beyond one tidal ellipse) there is no evidence to support the existence of a pathway between the source and receptor.


248. The overall impact of foundation installation activities for the proposed project under a worst case scenario on bed level changes for identified morphological receptor groups is considered to be no impact.


249. The worst case assumes that piled foundations would be drilled to their full depth and that sea bed preparation activities would be at the maximum values for the


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 50


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