10.6.2.4 Impact 4: Re-mobilisation of contaminated sediments 253. Given the absence of contaminants present in the sediments of the East Anglia THREE site and the offshore cable corridor, changes in water and sediment quality due to re-suspension of contaminants during operation have been assessed as negligible (Chapter 8 Marine Water and Sediment Quality). As a result, the impact on benthos is expected to be no impact.
254. Also assessed within Chapter 8 Marine Water and Sediment Quality is the potential for accidental releases or spills during maintenance activities. EATL is committed to ensuring that all vessels would adhere to the requirements of the MARPOL Convention Regulations with appropriate preventative and control measures. This would ensure that the chances of such an impact occurring is small. Therefore, it is considered likely that there would be no impact to the benthic environment due to accidental releases or spills.
10.6.2.5 Impact 5: Colonisation of Introduced Substrate 255. When assessing the colonisation of introduced substrate it is important to note that any introduced substrate is considered to be a change from the existing environment presented in section 10.5 and is therefore cannot be considered to be beneficial in ecological terms.
256. All project infrastructure that has a sub sea-surface element would represent a potential substrate for colonisation by marine fauna and flora, including species that may not currently be found within the existing environment. Therefore, the assessment of this impact does not make a distinction between sources of impact in the two different study areas as is the case with other impacts.
257. The addition of hard substrate is of particular importance given the otherwise sedimentary environments found within the East Anglia Zone where substrates for colonisation by encrusting epifauna are very limited.
258. Hard substrates introduced by the project would include foundations for wind turbines, collector stations, convertor stations, accommodation platform, meteorological masts and cable protection. It is difficult to calculate the exact area of introduced substrate due to its 3- dimensional nature, but under the worst case scenario, which assumes the maximum amount of introduced substrate, the area would be in excess of the 3.28km2 footprint of the proposed East Anglia THREE project.
259. Studies of operational windfarms in the North Sea have found that widespread colonisation of sub-sea surfaces occurs. Lindeboom et al. (2011) demonstrated that at the Egmond aan Zee Offshore Windfarm in Dutch waters, new hard substrate led
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
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