71.
For the purposes of a worst case, it has been assumed that up to 10% of the export cables within the offshore cable corridor would be unburied and require protection in locations that are to the east of the cable crossings and that up to 2.5% of the export cables would require protection in locations to the west of the cable crossings. The height of cable protection measures from the sea bed would range from 1mwhere burial of the cable is not possible due to ground conditions to up to 4mwhere East Anglia THREE offshore export cables cross other infrastructure (such as cables and pipelines).
72. Detailed pre-construction design work would be required to refine these figures and to determine locations at which burial would not be possible. The worst case values used in the assessment are intended to allow for flexibility within the DCO and are based on recent practical experience of cable installation which demonstrates that achieving 100% burial is not always possible.
73. During the construction phase, inter-array and export cable would be installed using a best practice approach with the objective of minimising, as far as practicable, possible effects on key receptors (e.g. marine water and sediment quality, fish and shellfish ecology, commercial fisheries, benthic ecology, etc.). A detailed cable laying plan would be developed which incorporates a cable burial risk assessment to ascertain burial depths and cable laying techniques in accordance with the draft DCO and with the objective of achieving optimum cable burial and thereby minimising the lengths of remaining unburied cable that would require protection.
74.
It is agreed that EATL would adopt a hierarchical approach to cable protection options in the event that full burial of the entire lengths of inter-array and export cable cannot be achieved. Under this approach, protection options would be assessed using a number of criteria, including the aim of selecting protection methods which would cause least disturbance to sensitive receptors.
7.3.2.8 Cable Landfall 75.
The offshore export cable would make landfall at Bawdsey in Suffolk, within an offshore cable corridor that is common to the proposed East Anglia ONE project. Suitable allowance would be made in the design to accommodate the predicted future rates of cliff recession and foreshore lowering throughout the operational phase. Specific assessment of the baseline coastal characteristics and the predicted future coastal change at the landfall has been made (ABPmer 2012c; 2013) and is summarised in Appendix 7.4.
76.
At the landfall, the offshore export cables would be installed to depths of 3 to 10m below the sea bed and under the existing coastal defences. It is anticipated that the
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 16
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