Since control measures would be in place, the risk of a spill and associated adverse impact is considered to be of low likelihood and of a negligible significance.
8.6.3 Potential Impacts during Decommissioning
8.6.3.1 Impact 1: Deterioration in water quality due to re-suspension of sediments associated with the removal of foundations.
104. At decommissioning, the foundation structures would be removed (to just below the sea bed) which is likely to result in disturbance to sediments. It is anticipated that both inter-array and export cables would be left in situ. Potential impacts are therefore anticipated to be similar in nature to those outlined for foundation installation during the construction phase, although much reduced in magnitude (unless sediment quality has deteriorated significantly during the lifespan of the proposed East Anglia THREE project due to outside influences (i.e. a general reduction in water quality and presence of contaminants)). It is therefore considered that any impacts would be negligible.
8.6.3.2 Impact 2: Deterioration in water quality due to re-suspension of sediments associated with cable
105. Any fluids or contaminants contained within the structures on decommissioning have the potential to leak into the marine environment. A decommissioning plan will be required by the Secretary of State under the Energy Act 2004. The plan will reduce the likelihood of these releases through the visual monitoring of the structures during their removal. Operating procedures contained within the decommissioning plan would be developed in order to address this potential risk.
106. As the magnitude of the effect is difficult to assess, the assessment in this instance is considered in terms of the risk of a spill or other accidental pollution event occurring. Since control measures would be in place, the risk of a spill and associated adverse impact is considered to be of low likelihood and of a negligible significance.
8.7 Cumulative Impacts 107. Potential impacts to the water and sediment quality are:
Change in water quality due to re-suspension of sediments; Deterioration in water quality due to re-suspension of contaminants; and
Deterioration in sediment and water quality in relation to accidental spillages and discharges of grey water and chemicals.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 8 Marine Water and Sediment Quality Page 32
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