that are located directly within the East Anglia THREE site, these sediments are likely to be finer and therefore could potentially be dispersed further. However, the amounts released are likely to be less than those released during sea bed preparation for gravity base structure foundations. As a result, the concentrations found within any plume formed are likely to be lower. Again, this was confirmed in the modelling undertaken to inform the impact on suspended solid concentrations during the construction of the proposed East Anglia ONE project which predicts that away from the immediate release locations, elevations in suspended sediment concentration above background levels were low (<10mg/l) and within the range of natural variability.
83.
Overall, the marine area in which the proposed East Anglia THREE project is located is considered to be of low sensitivity. The magnitude of effect is considered to be low during the installation of foundations; although larger amounts of sediment are likely to be released, the associated plume would be within natural variations of suspended solid concentrations. Conditions would, however, return to baseline following cessation of activities and so any impact from both activities would only be present during the installation process. The magnitude of effect is considered to be negligible during installation of the inter-array cables due to the shorter duration of cable installation activities (as compared to foundation installation) and smaller footprint as well as the rapid settling of disturbed sediment. Therefore, based on the above, the overall impact is predicted to be negligible.
8.6.1.2 Impact 2: Change inWater Quality due to Re-suspension of Sediments during Offshore Export Cable Installation
84. Modelling undertaken to inform the proposed East Anglia ONE project EIA predicted that peak suspended sediment concentrations are likely to occur in the shallower water depths nearer to shore and approach 400mg/l at their peak. However, these plumes would be localised to within <1km of the installation location and would persist for no longer than a few hours. It is also predicted that 180 hours following cessation of installation activities, any plume would have been fully dispersed and conditions would return to baseline.
85.
There are no sensitive areas such as designated bathing waters located in the inshore areas; those closest are located 6km and 9km away (i.e. they are outwith any potential plume), therefore, the sensitivity is low. Given the localised and short term nature of the impact, the potential effects would be of negligible magnitude and as a result a negligible impact is predicted.
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 8 Marine Water and Sediment Quality Page 28
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