generation (Gill et al. 2009). Monitoring at Kentish Flats found an increase in thornback rays, smoothhounds and other elasmobranchs during post-construction surveys in comparison to surveys before construction. There appeared, however, not to be any discernible difference between the data for the windfarm and reference areas, including population structure changes, and it was concluded that the population increase observed was unlikely to be related to the operation of the windfarm (Cefas 2009).
86.
There is potential for avoidance / repulsion of benthic elasmobranchs by the strongest iE fields in close proximity to the cables. Although a potential impact cannot be ruled out, there is insufficient information to determine conclusively whether there would be any effect, let alone an ecologically significant one. There is also potential for confusion of iE fields with bioelectric fields by elasmobranchs within close proximity of cables but the likelihood or significance of this is unknown.
9.12 Summary - EMF 87.
There are a number of cabling designs being considered for the East Anglia THREE project, which include alternating current (AC) and direct current (DC) cables of different voltage ratings. AC cables are most likely to consist of three-core technology, although there is a small possibility that single-core cables might be used (deployed in trefoil but possibly separately). DC cables would be bipole systems, whereby current is transmitted along two separate cables in opposite directions with bundling of the two cables the most likely deployment method although there is a small possibility that they may be separated.
88.
B fields from AC cables likely to be used within the East Anglia THREE project are predicted to be of lower intensity than the earth’s magnetic field. iE fields associated with 132kV and 220kV cables are predicted to be above background fields but are expected to fall to background levels within 0.5-1m (132kV) and 5-10m (220kV) from each cable (assuming burial to 1m).
89.
For the likely worst case 320kV cables buried to 0.5m, both B and iE fields would fall to below background levels within a distance of 0.5m if cables are bundled and 4.5m if cables are laid separately. For 500kV cables buried to 0.5m, fields would fall to background within a distance of 2.5m if cables are bundled and 9.5m if cables are laid separately.
90.
The ecological significance of the predicted EMFs has been assessed using available literature. No effects are expected on marine mammals and impacts of EMF to marine mammals have not been taken forward to the marine mammal assessment
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 9 Underwater Noise Page 21
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