horizontal directional drilling (HDD) technique, or similar, would be used and open trenching would only be used where there are no coastal defences and when it can be demonstrated that the impact is less than using HDD. There are two variants of the HDD method, a ‘long’ or ‘short’ HDD.
77. 78. 79.
The ‘long’ method would use HDD techniques to install the cable below the sea bed up to 1,100m from the base of the cliff.
The ‘short’ method would have a shorter offshore set-back distance, and offshore a trench would be excavated towards deeper water.
The ‘short’ HDD method is considered the worst case since it causes greatest physical disturbance to the sea bed and could result in greatest suspension of sediment off the sea bed and into the water column.
80.
In addition it should be noted that there would be up to two cables to interconnect the proposed East Anglia THREE and East Anglia ONE projects. The cables would be subject to detailed design and future technology developments. Each would be up to 90km in length. The locations where these interconnections join the East Anglia ONE electrical infrastructure would be identified following detailed electrical design and would be dependent upon the location of the East Anglia ONE converter stations. These cables have not been assessed as part of the worst case and once interconnection cable routeing has been determined they will be added into the assessment.
7.3.3 Embedded Mitigation Specific to Marine Geology, Oceanography and Physical Processes
81.
The proposed East Anglia THREE project would have a total capacity of 1,200MW, with between 100 (12MW) and 172 (7MW) wind turbines being present. In order to mitigate the effects of on the marine geology, oceanography and physical processes, a minimum separation of 675m has been defined between adjacent wind turbines within each row and a minimum spacing of 900m has been defined between rows in order that the potential for interaction of effect between adjacent wind turbines is minimised.
82.
The selection of appropriate foundation designs and sizes at each wind turbine location would be made following interpretation of geophysical and geotechnical data from within the proposed windfarm site. This would ensure that the worst case foundation types and sizes are not applied universally across the whole site, but are tailored to those areas where the physical conditions dictate their need.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Chapter 7 Marine Geology, Oceanography and Physical Processes Page 17
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