Table 7.28 Likely envelope of turbines and gravity base structures for worst case scenario Lower limit
Water depth (m)
<35m
35-45m >45m
Total
Site area (%)
15.6 79.8 4.6
100.0
7MW wind turbines
27
137 8
172 Basal
diameter (m) 20
25 40
-
12MW wind turbines
16 80 4
100
Upper limit Basal
diameter (m) 50
55 60
-
326. The modelling for the proposed East Anglia ONE project is considerablymore conservative in terms of the number of foundations being considered for the proposed East Anglia THREE project. The wave climate at the East Anglia THREE site is characterised by a far greater proportion of waves approaching from the southwest, due to the prevailing wind climate and greater distance from shore, than compared to East Anglia ONE. Therefore there is less likelihood of any change affecting an identified receptor group.
327. Expert-based assessment suggests, therefore, that both the magnitude and spatial extent of effects on the wave climate at the East Anglia THREE site would be less than those previously assessed for the proposed East Anglia ONE project.
7.6.2.2.1 Assessment of effect magnitude and/or impact significance 328. Taking the aforementioned considerations into account, the worst case changes in terms of the wave regime due to the presence of foundations are likely to have the following magnitudes of effect (Table 7.29):
Table 7.29Magnitude of effect on the wave regime due to the presence of foundations under worst case scenario
Location
Near-field Far-field
Scale Low Negligible Duration
High High
Frequency
Medium Medium
Reversibility Magnitude of Effect
Negligible Negligible
Low Negligible
329. These effects on the wave regime have been translated into a ‘zone of potential influence’ based on an understanding of the wave roses, previous numerical modelling of effects, and using expert-based assessment.
330. Figure 7.7 shows the wave rose from within the East Anglia THREE site. Waves are predominantly aligned north-northwest to south-southwest and this would be the axis of greatest potential influence.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 65
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