Impact
Impact 3: Smothering through increased suspended sediment
Key design parameters forming the worst case scenario
predict at this stage of the project what the likely area of disturbance may be for these activities.
The maximum amount of sediment that would be placed into suspension due to changes in tidal regime around infrastructure with no scour protection has been calculated based on scour produced by 60m diameter gravity base foundations which has been calculated as 4,580m3 per foundation (see Chapter 7 Marine Geology, Oceanography and physical processes Table 7.6). Therefore for 108 foundations (see Rationale column) the maximum expected amount scour released into the water column is 494,640m3.
The above are based on a 1 in 50 year return period.
The need for scour protection would not be determined until the wind turbine location and associated foundation types are known. Therefore, the worst case scenario involves the use of no scour protection which would result in sediment being bought into the water column.
Of all the foundation options under consideration, 60m diameter gravity base foundations would cause the greatest amount of scour. Only the largest wind turbines (12MW) would be installed on 60m diameter gravity base foundations and the scenario that leads to the greatest amount of scour would be 100 wind turbine foundations (Chapter 7 Marine Geology, Oceanography and physical processes). It has been assumed that the worst case for up to: five foundations for converter and collector stations, two meteorological masts and one accommodation platform would result in a similar amount of scour to that of the wind turbines.
As scour would take place immediately following installation, the release of scour from each piece of infrastructure would be sequential rather than concurrent.
Impact 4: Re-mobilisation of contaminated sediments
Impact 5: Colonisation of introduced substrate
As Above
The introduction of new hard structures with a maximum surface area provided by the following project infrastructure:
1. Gravity base foundations for wind turbines
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
The worst case would involve the maximum amount of suspended sediment released into the water column. This is calculated in the row above.
It is not possible to accurately calculate the surface area that would be available for colonisation. It would however be greater than the figure presented for “footprint” in operation
Chapter 10 Benthic Ecology Page 13
Rationale
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 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104