391. As the leg is retracted, some of the material would return to the hole via mass slumping under gravity until a stable slope angle is achieved. Over the longer term, the pit would become shallower and less distinct due to infilling with mobile sediments.
392. For purposes of a worst case, it has been assumed that the total area of sea bed that may be affected by these activities is 0.88km2 per year (based on up to 730 visits by jack-up vessels with a footprint of 1200m2). It is possible that different areas would be affected in each year of the operational phase.
7.6.2.9.1 Assessment of effect magnitude and/or impact significance 393. The worst case changes in terms of indentations on the sea bed due to maintenance vessels are likely to have the following magnitudes of effect (Table 7.36):
Table 7.36Magnitude of effect on sea bed due to installation vessels under worst case scenario Location
Scale
Near-field (immediate
vicinity of leg)
Near-field (beyond
immediate
vicinity of leg) Far-field
No change No change - - - - - - No change No change
394. There is no impact under a worst case scenario on the identified morphological receptor groups since they are remote from the immediate vicinity of each leg.
395. The significance of these effects on other receptors is addressed within relevant chapters of the PEIR.
7.6.3 Potential Impacts during Decommissioning 396. On expiry of the lease, there is a statutory requirement for EATL to decommission the East Anglia THREE project. The scope of the decommissioning works would most likely involve removal of the accessible installed components. Offshore, this is likely to include all of the wind turbine components, part of the foundations (those above sea bed level) and the sections of the inter-array cables close to the offshore structures.
397. With regards to offshore cables, general UK practice would be followed, i.e. buried cables would simply be cut at the ends and left in situ, with the exception of the
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 76
High Duration Negligible Frequency Negligible Medium
Reversibility Magnitude of Effect
Medium
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