Impact
Key design parameters forming the worst case scenario
2. Gravity base foundations for offshore platforms and meteorological masts,
3. Inter-array cable protection and crossings, 4. cable protection of HVAC export cables between collector and converter stations
5. Cable protection of HVDC export cable
Impact 6: Potential impacts on sites of marine conservation interest
A small area of the offshore cable corridor overlaps with the Outer Thames SPA (approximately 120km2). The worst case scenario would be that the maximum amount of cable protection would be located within this overlapping section. EATL have committed to ensuring that a maximum of 2.5% of the export cables length to the west of the crossing point with the Greater Gabbard Offshore Wind farmexport cables is covered with cable protection. The overlap between the cable corridor and the SPA is to the west of this crossing point. Therefore, cable protection covering an area of up to 0.02km2 could be placed within the SPA, this represents 0.014% of the area of overlap with the SPA and 0.0004% of the total SPA area.
Impact 7: Electromagnetic Fields (EMF)
The greatest impact from EMF would occur if cables are buried to the shallowest depth of 0.5m, and the maximum amount of cable of themaximum cable rating is utilised, based on:
1. Maximum length of inter-array (up to 75kV of alternating current) and HVAC export cables between collector and converter stations (up to 275kV) would be 745km.
2. Maximum length of HVDC export cable (up to 600kV) would be 620km. The total length of cable laid would be up to 1,365km
The described scenario would lead to cable protection installed within the SPA. This could affect physical processes and alter the benthic ecology within that area causing a change to the prey species of the red-throated diver (the primary designated species of the SPA).
Rationale
Impact 1 (above) as the former is a 3-D metric, whilst the latter is 2-D.
The scenario described would pertain to the largest possible area that could be impacted by EMF.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 10 Benthic Ecology Page 14
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