provided by the individual developers, it is possible to provide a more quantified assessment of the potential impacts.
12.7.1.1 Harbour seal 503. The potential effects from underwater noise on harbour seal from East Anglia THREE include behavioural avoidance and the potential for PTS from a prolonged noise exposure in an SEL dose. However, due to the large amount of uncertainty around the calculation of the cumulative SEL dose, and quantifying the potential impact this is only considered in a qualitative way in the CIA.
12.7.1.1.1 Sensitivity
504. As previously discussed harbour seal are assessed as having low sensitivity to behavioural disturbance from underwater noise, and low sensitivity to PTS.
12.7.1.1.2Magnitude
505. The CIA for harbour seal includes all phases of East Anglia THREE, as well as construction noise from 30 offshore wind farms, operational noise from 31 offshore wind farms and decommissioning noise from 42 offshore windfarms, construction and operational noise from one port development, and 84 oil and gas Licence areas (assessed for exploration/commission and/or production activities, Table 12.19). Some of these plans and projects occur in areas of higher harbour seal density that the East Anglia THREE site.
506. A quantified assessment of the magnitude of this temporary effect is only be made for pile driving during the construction of offshore wind farms where sufficient data have been provided within full or draft Environmental Statements (Table 12.20). All other plans or projects are in cooperated into the assessment in a qualitative manner.
507. The total number of harbour seal that could be displaced as a result of pile driving at those projects where the impacts are quantified is 371 seals (1.2% of the reference population or 10.4% of the UK south east England MU). When considering the projects where the magnitude of effect is not quantified (including projects other than offshore wind farms) there is the potential for more harbour seal to be disturbed.
508. Based on the available evidence, the magnitude of the effect is assessed as low for the reference population (between 304 and 1,518 harbour seal being affected within a year) and high for the UK south east England MU (greater than 357 harbour seal being affected).
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 12 Marine Mammal Ecology Page 106
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