Impact Decommissioning
Impact 1: Temporary Physical disturbance
The maximum area of disturbance during decommissioning is based on:
1. Removal of 60mgravity base foundations and scour protection calculated as 25,500m2 per foundation (see construction impact 1). Therefore for 106 foundations the maximum area of disturbance would be 2.68km2.
2. Removal of up to two meteorological masts and scour protection, each with a footprint of 2,830m2 and a combined area of 0.01km2.
3. The footprint of the jack-up barge removing 180 foundations (based on a jack up barge footprint of 1,200m2and three movements per foundation) the maximum disturbance would be 0.65km2.
4. Removal of inter-array cable crossing protection 0.0007km2. 5. Removal of cable protection for inter-array, and HVAC export cables between collector and converter station would disturb an area of 0.45km2.
Total decommissioning footprint within the East Anglia THREE site during decommissioning would be approximately 3.80km2 (1.25% of the East Anglia THREE site).
6. Removal of cable protection from the up to 10% of the 508km HVDC export cable: 0.3km2
7. Removal cable protection of up to 2.5% of the up to 112km HVDC 2.5%: 0.02km2.
8. Removal of export cables within the intertidal.
Total decommissioning footprint within the offshore cable corridor would be approximately 0.32km2. (0.03% of the offshore cable corridor)
The overall total footprint is 4.25km2
See construction impact 1 for rationale on the number and size of foundations.
All buried cables would simply be cut at the ends and left in- situ. The removal of cable protection would be agreed with the relevant authority at the time however worst case for disturbance would be its removal. See operation impact 1 for rationale with regard to cable protection calculations.
Key design parameters forming the worst case scenario
Rationale
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 10 Benthic Ecology Page 15
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