7.13. Proposed Monitoring

  1. No physical processes monitoring to test the predictions made within the assessment of LSE1 on physical processes is considered necessary.
  2. No monitoring as a result of the CEA is proposed.
  3. During the operation and maintenance phase of the Array, monitoring will be undertaken for engineering/asset security purposes.

7.14. Transboundary Effects

  1. A screening of transboundary impacts has been carried out and has identified that there were no likely significant transboundary effects with regard to physical processes from the Array upon the interests of European Economic Area (EEA) states.

7.15. Inter-Related Effects (and Ecosystem Assessment)

  1. A description of the likely inter-related effects arising from the Array on physical processes is provided in volume 2, appendix 19 of the Array EIA Report.
  2. For physical processes, the following potential impacts have been considered within the inter-related assessment:
  • increase in SSCs and associated deposition and sediment transport due to operation and maintenance activities;
  • impacts to the wind field due to the presence of infrastructure; and
  • impacts to seasonal stratification due to the presence of infrastructure.
  1. Table 7.15   Open ▸ lists the inter-related effects (project lifetime effects) that are predicted to arise during the construction, operation and maintenance phase, and decommissioning of the Array and also the inter-related effects (receptor-led effects) that are predicted to arise for physical processes receptors.
  2. Physical processes receptors have the potential to have secondary effects on other receptors and these effects are fully considered in the topic specific chapters. These receptors and effects are:
  • benthic subtidal ecology

–           increased SSCs; and

–           increased sediment deposition; and

–           changes to seasonal stratification.

  • marine mammals

–           increased SSCs;

–           sediment deposition; and

–           changes to seasonal stratification.

  • infrastructure and other users

–           increased SSCs.

 

Table 7.15:
Summary of Likely Significant Inter-Related Effects for Physical Processes from Individual Effects Occurring Across the Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

Table 7.15: Summary of Likely Significant Inter-Related Effects for Physical Processes from Individual Effects Occurring Across the Construction, Operation and Maintenance and Decommissioning Phases of the Array (Array Lifetime Effects) and from Multiple Effects Interacting Across all Phases (Receptor-led Effects)

 

7.16. Summary of Impacts, Mitigation, LSE1 and Monitoring

  1. Information on physical processes within the physical processes study area was collected through a detailed desktop review of existing studies and datasets, in addition to site-specific surveys. This information is summarised in Table 7.5   Open ▸ and Table 7.6   Open ▸ .
  2. Table 7.16   Open ▸ presents a summary of the potential impacts, designed in measures and the conclusion of LSE1 in EIA terms in respect to physical processes. The impacts assessed include:
  • increase in SSCs and associated deposition and sediment transport due to operation and maintenance activities;
  • impacts to the wind field due to the presence of infrastructure; and
  • impacts to seasonal stratification due to the presence of infrastructure.
  1. Each of these impacts are relevant to the operation and maintenance phase of the Array, with all construction and decommissioning impacts screened out, as discussed under section 7.8.2.
  2. Increased SSCs associated with mooring lines making contact with and moving on the seabed may impact on physical features within the Array but will not extend to any designated areas. The estimated potential increases in SSCs are low in magnitude and likely to be significantly less than the baseline winter storm scenario. The sensitivity of the seabed morphology receptor is considered to be low, with no significant effects predicted.
  3. There is potential for the presence of infrastructure within the Array to alter the wind field, potentially impacting on mixing and stratification. However, it was estimated that the maximum percentage reduction to mean wind speeds in the wake of each individual wind turbine was seen to be circa 10% at 10 m above MSL and the magnitude of this impact considered as medium. The effect on wind speeds will be reduced at the water surface, with previous North Sea studies having shown wind speed reductions at the surface due to these wakes in the order of 0.1 to 0.5 m/s. Furthermore, the baseline evidence has shown that the impact of wind on seasonal stratification through the water column at the Array are limited. No significant effects are predicted.
  4. The impact on waves and tides due to the presence of infrastructure within the water column may also alter seasonal stratification. However, there is much evidence from other offshore wind farm studies that predict no significant effects, even though they are situated in shallower water and using fixed foundations. The presence of the floating foundations within the water column was shown to be only a small proportion of the Array as a whole, with any impacts to waves and tides and hence seasonal stratification are predicted to be medium in magnitude. If any impact exists, it is likely that a reduction to stratification may occur due to the presence of the foundations within the upper water column. This would likely be countered by any potential increase to stratification caused by a decrease in wind speeds, as the two impacts would likely have the opposite effects. No significant effects are predicted.
  5. Overall, it is concluded that there will be no LSE1 arising from the Array during the construction, operation and maintenance or decommissioning phases.
  6. The impacts listed in paragraph 180 have been assessed cumulatively and Table 7.17   Open ▸ presents a summary of the potential impacts, designed in measures and the conclusion of LSE1 on physical processes in EIA terms.
  7. Four projects were identified for the CEA, which have the potential to coincide spatially and temporarily with the operation and maintenance phase of the Array. However, as discussed under section 7.12.3, it is unlikely that cable reburial and repair activities or decommissioning activities will occur simultaneously to the MDS for SSCs for the Array, and even if this did occur, these activities would be of limited spatial extent and frequency. The low sediment transport rates in the physical processes study area should restrict the potential impact on sediment transport due to fixed foundations from other projects. No significant cumulative effects are predicted.
  8. The cumulative effects on wind wakes as a result of the Array and neighbouring offshore wind farms were assessed, showing no likely significant cumulative effects due to the limited reduction in wind speeds at any significant distance to the lee of the wind turbines.
  9. There is some potential for the effects of underwater infrastructure from other projects to affect the seasonal stratification within the physical processes study area, however, this long term impact was assessed to be medium in magnitude due to the weak stratification in the area and the distance from the other projects. No significant cumulative effects are predicted.
  10. Overall, it is concluded that there will be no likely significant cumulative effects from the Array alongside other projects/plans.
  11. No likely significant transboundary effects have been identified in regard to effects of the Array.

 

Table 7.16:
Summary of Likely Significant Environmental Effects, Secondary Mitigation and Monitoring

Table 7.16: Summary of Likely Significant Environmental Effects, Secondary Mitigation and Monitoring

 

Table 7.17:
Summary of Likely Significant Cumulative Environment Effects, Mitigation and Monitoring

Table 7.17: Summary of Likely Significant Cumulative Environment Effects, Mitigation and Monitoring