Table 12.14 Summary of PTS onset distances (around mid-water column) estimated for pile driving during construction at East Anglia THREE for different hammer energies. Species or species group
Impact criteria SEL (dB re 1 μPa2·s)
Harbour porpoise
Pinnipeds (in water)
Low-frequency cetaceans
Mid-frequency cetaceans
179 186
198 198
Maximum hammer energy kJ 1,400
2,000
<500m <500m
<500m <500m
<500m <500m
<500m <500m
3,500 <1km
<500m <500m <500m
270. As a result of the establishment of mitigation zones through the MMMP, there should be no marine mammals exposed to noise levels that could lead to the instantaneous onset of PTS. Therefore, the magnitude of effect is no change.
271. The potential for prolonged exposure to noise levels in a SEL dose will be considered in the final noise assessment when details of the piling profile are available. In the interim an example of the SEL dose modelling has been provided using a generic piling sequence (Plate 9.4 in Appendix 9.1).
272. The assessment calculates the received noise dose that an individual animal could be exposed to during a piling sequence. It is assumed that individuals flee the noise source at the initiation of the soft start.
273. The assessment suggests starting ranges, which indicate the distance that an individual needs to be from the noise source at the onset of the piling sequence to prevent a cumulative noise exposure which could lead to PTS. However, this type of assessment is based on a number of assumptions, and does not take account of different exposure levels an animal will receive at different depths in the water column, or periods where exposure will be reduced in seals when their heads are out of the water. Therefore, this type of assessment is completed for information, and is not used to quantify potential impacts in any receptor.
274. The example assessment suggests that during a normal piling sequence high frequency and mid frequency cetaceans will not be exposed to noise levels that could cause PTS, as at a start range of less than 500m the cumulative SEL dose does not reach the PTS thresholds. In the case of low frequency cetaceans, the starting range is greater than 500m, but less than 1km. In these species, which may be occasional visitors to the East Anglia THREE Zone, the potential for a cumulative dose SEL should be mitigated by the establishment of a mitigation zone by the MMMP out
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 73
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