83.
For the foundation types that would experience the potential for greatest scour, namely gravity base structures, scour protection material is likely to be installed during the construction process in order to mitigate the effects of scour on the suspended sediment and bed level changes in the vicinity of each wind turbine location.
84.
For other foundation types, where the scour potential involves lower quantities of sediment release due to scour processes, the design would, where feasible to do so, allow for local scour around the piles to minimise the footprint of ‘foreign’(scour protection) material that is introduced on the sea bed.
85.
For piled foundation types, such as monopiles and jackets with pin piles, pile-driving would be used in preference to drilling where it is practicable to do so, i.e. where ground conditions allow. This would ensure that only the minimum quantity of sub- surface sediment is released into the water column from the installation process.
86. Micro-siting would be used to minimise the requirements for sea bed preparation prior to foundation installation. Gravity base structures would not be used in areas characterised by sandbanks or sand waves with heights greater than 5m in further pursuance of this aim.
87.
Inter-array, HVAC and HVDC export cables would be buried where possible, to the maximum feasible depth. This would reduce the risk of exposure of buried cable due to bed level changes, reducing the need for subsequent re-burial which would cause further disturbance to the sea bed. In addition, ensuring cable burial in areas where it is practicable to do so would minimise the requirement for cable protection measures. These measures would only be applied in areas where burial is not possible, e.g. where the proposed East Anglia THREE project cables are required to cross existing cables or in areas of hard ground, in order to mitigate the potential to affect sediment transport processes.
7.4 Assessment Methodology
7.4.1 Legislation, Policy and Guidance 88.
The National Policy Statements (NPS) of direct relevance to this chapter are:
Overarching NPS for Energy (EN-1) (July 2011); and NPS for Renewable Energy Infrastructure (EN-3) (July 2011).
89.
With regard to the physical environment, EN-3 states that geotechnical investigations should form part of the assessment as this will enable design of
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 18
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95