294. It is likely that the locations at which cable burial would not be possible and cable protection would be required would coincide for all three projects creating a concentration of cable protection in one area.
295. Furthermore, the 12 cables would cross three export cables from Greater Gabbard Offshore Windfarm and up to three cables fromGalloper OffshoreWindfarm. This would result in up to 72 cables crossings which may all be located in an area of approximately 13.76km² Figure 10.13.
296. Depending on the nature of how these cables would be crossed and what materials would be used, the magnitude of this cumulative impact could be medium with so many crossings in a concentrated area although not significant in the wider context. As discussed previously the sensitivity of the habitats and species present within the offshore cable corridor is considered to be low and species and habitats would be expected to recover rapidly after disturbance even if construction periods of windfarms were to overlap. Therefore the impact is ofminor adverse significance is predicted.
10.7.2.2 Impact 2: increased suspended sediment leading to smothering 297. The marine aggregate extraction licence Area 430 is located approximately 925m north of the northern boundary of the offshore cable corridor3. Sediment plumes from dredging vessels can extend on the tide for up to 2.5km from the vessel. If aggregate dredging takes place in Area 430 at the same time as the offshore cable corridor installation work, there would be potential for cumulative impacts from elevated turbidity and smothering on the benthos within the footprint of the two sediment plumes. However, as a result of the limited duration and low probability of this scenario occurring, combined with the low sensitivity of the habitats present to increased suspended sediment concentrations and smothering (as previously discussed, Construction Impact 3 and Operation Impact 3) the cumulative impacts are considered to be at worst minor adverse significance.
10.7.2.3 Impact 3: Colonisation of Introduced Substrate 298. As previously discussed in section 10.7.2.1 there could be up to 72 cable crossings between the East Anglia cables from projects ONE, THREE and FOUR and the Greater Gabbard Offshore Wind Farm and Galloper Wind Farm export cables. These cable crossings would require cable protection at each crossing point. The nature of the cable protection is likely to be concrete mattresses no more than 1m high. These would represent the introduction of a hard substrate in an otherwise sediment habitat and would therefore be colonised by marine flora and fauna.
3 Note that Licence Application and Prospecting Area 496 is also located approximately 2.5km to the north of the offshore cable corridor however this area is no longer being taken forward for extraction.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 1 Introduction Page 84
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