328. Noise levels reported by Malme et al. (1989) and Richardson et al. (1995) for large surface vessels indicate that physiological damage to marine mammals is unlikely. However, the levels could be sufficient to cause local disturbance of sensitive marine fauna in the immediate vicinity of the vessel, depending on ambient noise levels.
12.6.1.2.2Magnitude
329. The construction phase of the project will last up to two years, but additional vessel movements during construction phase are likely to be short-term and localised in comparison to existing shipping noise.
330. The densities of harbour porpoise in the East Anglia THREE site are relatively low compared to other parts of their range and the disturbance effects around vessels will only occur over relatively short ranges.
331. Despite the low density of both species of seal in the East Anglia THREE site, increased vessel activity may occur closer to haul out sites, but this will be largely dependent on the choice of port.
332. Based on the definitions in Table 12.8 the magnitude of effect at the population level of harbour porpoise is predicted to be negligible, with less than 1% of the reference population being temporality impacted.
333. In the case of harbour seal (at the UK level) the magnitude of effect is still considered to be negligible (less than 1% of the South-east England MU, or 36 seals) due to the very low at sea densities in this region.
12.6.1.2.3Impact significance
334. The significance of the impact on harbour porpoise, harbour seal and grey seal is negligible.
335. The confidence in the data used in this assessment is medium to high.
336. No further mitigation measures are considered for this impact beyond those embedded measures presented in section 12.3.2.
12.6.1.3 Underwater noise: seabed preparations, rock dumping and cable installation 337. These impacts are assessed as the worst case construction methods for installation of the cables and any other noise not associated with the vessel traffic or worst case foundation installation scenario of pile driving. The worst case (Table 12.2) considers ploughing / jetting / pre-trenching or cutting for installation of cables, and rock dumping for protection of the cables, for a total period of up to 104 weeks. There will be 550km of inter-array cables, 210km or inter-connecting cables, and 620km of export cables.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 84
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