9.7 Summary
140. This report describes the underwater noise modelling undertaken to assess the likely underwater noise levels generated by the installation of wind turbine foundations at East Anglia THREE in support of the Environmental Impact Assessment. Marine impact piling is considered to be the most prevalent source of high amplitude underwater noise during the development of an offshore windfarm that has the potential for a significant impact on marine fauna.
141. Multiple foundation locations were modelled representing a range of water depths and bathymetry profiles across the sites. The modelled sources were based on the use of various hammer blow energies that may be used during construction at East Anglia THREE, ranging from 1,400kJ to 3,500kJ, with 3,500kJ being the maximum hammer energy being considered. The propagation model used was based on an energy flux approach and provided SEL and peak pressure received level output as a function of range away from each modelled location whilst accounting for seabed properties and varying bathymetry. The modelling indicates that there is considerable variation in noise propagation across East Anglia THREE and the surrounding areas due to bathymetry.
142. The injury and behaviour criteria outlined in the report have been applied to the outputs of the underwater noise modelling to predict the potential impact ranges during pile driving. From this it has been estimated that for East Anglia THREE and for a maximum hammer blow energy of 3,500kJ;
• Mortality of marine mammals or fish would be unlikely to occur except in very close proximity to the pile or in the case of prolonged noise exposure close to the pile. The former case would likely be mitigated by the use of a soft-start combined with the use of a mitigation zone following JNCC guidance (JNCC 2010), whilst the latter case would likely be mitigated by the animal fleeing the noise at close range.
• At the onset of piling, the potential for instantaneous auditory injury (PTS onset) of marine mammals may be expected to be mitigated by the 500m mitigation zone employed during the pre-piling watch provided the hammer energy during the minimum soft-start period does not exceed 2,300kJ and assuming the animal swims away from the sound source at the onset of piling (as per JNCC guidance (JNCC 2010)). The onset of auditory injury could also be considered unlikely for pile driving at East Anglia THREE using the higher hammer blow energies following the soft-start, as the animal would be expected to be beyond the predicted impact ranges from the pile, provided it
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm Appendix 9.1 Underwater Noise Modelling 64
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 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150