382. In areas offshore of the cable crossings there would be direct impacts ofminor significance on the ‘Suffolk Natura 2000’ site.


383. In areas inshore of the cable crossings there would be direct impacts ofminor significance on the ‘Suffolk Natura 2000’ site and these, in turn, would cause indirect impacts ofminor significance on the East Anglia coast due to interruptions to sediment transport processes.


384. There would be no impact on the other identified marine geology, oceanography and physical processes receptor groups since these are located remotely from the locations of potential effect.


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


7.6.2.8 Impact 8: Morphological effects due to cable protection measures at the offshore cable landfall


386. As the offshore export cable would remain buried at the landfall throughout the operational life of 25 years, no cable protection would be required and as such no morphological effects would take place.


387. Analysis of past coastal change and future coastal projections would inform detailed engineering decisions about cable burial depths.


7.6.2.8.1 Assessment of effect magnitude and/or impact significance 388. Taking the above considerations into account, the worst case effects on the coastline morphology at the cable landfall during the operational phase of the proposed East Anglia THREE project are no impact.


7.6.2.9 Impact 9: Indentations on the sea bed due to maintenance vessels 389. There is potential for certain vessels used during the maintenance of the windfarm and offshore cable infrastructure to directly impact the sea bed during the operation phase. This applies for those vessels that utilise jack-up legs or a number of anchors to hold station and to provide stability for a working platform. Where legs or anchors (and associated chains) have been inserted into the sea bed and then removed, there is potential for an indentation proportional to the dimensions of the object to remain. The worst case is considered to correspond to the use of jack-up vessels since the depressions would be greater than the anchor scars.


390. As the leg is inserted, the sea bed sediments would primarily be compressed vertically downwards and displaced laterally. This may cause the sea bed around the inserted leg to be raised in a series of concentric pressure ridges.


Preliminary Environmental Information May 2014


East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 75


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