Significance of the Effect
  1. During the installation of the wind turbines in the Firth of Forth Banks Complex ncMPA, the peak sediment plumes are <5 mg/l and do not persist or result in discernible sedimentation. However, these sediment concentrations do not extend as far south as Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI and St Abb's Head to Fast Castle SSSI.
  2. Sediment plumes associated with the inter-array and interconnector cable installation creates plumes on average <100 mg/l, highest during the release (of material) phase however these plume concentrations do not persist in the Firth of Forth Banks Complex ncMPA and do not reach Montrose Bank to the north. Sedimentation is typically <5 mm beyond the immediate vicinity of the installation and less than one tenth of this value in the wider domain and would therefore not affect composite banks beyond the development area (i.e. limited to Berwick and Marr Banks). These plumes do not extend to any of the other designated sites with sediment concentrations settling to background levels within the Proposed Development.
  3. In terms of the Firth of Forth Banks Complex ncMPA, the structure of the offshore subtidal sands and gravels would remain unchanged as the deposition is of native material and the supporting hydrodynamic processes are not altered by the minimal level of bathymetric change as a result of the construction phase sediment releases. Similarly, shelfs, banks and mound features would remain stable and supporting hydrodynamics processes for ocean quahog colonisation remain unaffected.
  4. Offshore export cable trenching routes do not pass through either of the designated sites Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, Barns Ness SSSI or St Abb's Head to Fast Castle SSSI. Although plumes resulting from the offshore export cable trenching may reach the outer extent of the Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI. This increase sediment entering the sediment cell causes sediment thickness of <3 mm at the coast off Torness Point adjacent to the offshore export cable trenching operations however this material is native to the sediment cell and will therefore not affect geodiversity.
  5. The Skateraw landfall for the offshore export cables borders the Barns Ness Coast SSSI. Within the intertidal zone the offshore export cables will be installed using trenchless technology. Therefore, similar to the other designated sites the increased sedimentation from the offshore export cables installation causes little or no sedimentation in the intertidal zone which would be insufficient to affect beach morphology.
  6. Within the Firth of Forth Banks Complex ncMPA the magnitude of the impact on receptors is deemed to be low, and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms. For intertidal and coastal areas such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI, the magnitude of impacts is negligible giving rise to effects of negligible adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. In general, no physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms. The Project design has determined that the method to be employed at landfall is trenchless technologies.

Operation and Maintenance Phase

Magnitude of Impact
  1. Operation and maintenance activities within the Proposed Development array area and Proposed Development export cable corridor may lead to increases in SSC and associated sediment deposition.
  2. The maximum design scenario is for up to ten inter-array cable repair and reburial events, including four offshore export cables repair and reburial events over the 35 year lifetime of the project ( Table 7.9   Open ▸ ). Using similar methods as those for cable installation activities (i.e. trenching/jetting, with trench width up to 2 m and trench depth up to 3 m).
  3. In each case the length of the repair or reburial activity may be up to 3 km; therefore, the magnitude of the impacts would be a fraction of those quantified for the construction phase. In the case of the offshore export cables the total length of works would be c. 1 km of the length assessed for the construction phase with events being undertaken over the course of the 35 year project lifetime. The sediment plumes and sedimentation footprints would be dependent on which section of the cable is being repaired however the entire length has been quantified under the construction phase scenario discussed above.
  4. The impact is predicted to be of local spatial extent, short term duration, intermittent and of high reversibility. It is predicted that the impact will affect the Firth of Forth Banks Complex ncMPA directly and other receptors indirectly to a much lesser degree than the construction phase. The magnitude is therefore, considered to be negligible.
Sensitivity of the Receptor
  1. The sensitivity of receptors to changes in suspended sediments concentration and sedimentation remains low, the same as for all construction phases. The significance of the effects will however be reduced as the works are limited to intermittent, discrete repair activities.
Significance of the Effect
  1. Within the Firth of Forth Banks Complex ncMPA the magnitude of the impact on receptors is deemed to be low, and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms. For intertidal and coastal areas such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI, the magnitude of impacts is negligible giving rise to effects of negligible adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms.
  2. Decommissioning phase as per the maximum design scenario ( Table 7.9   Open ▸ ), during the decommissioning phase it is anticipated that all structures above the seabed level will be completely removed wherever possible. The intention is to cut off piled structures at an agreed depth below the seabed. It is proposed to remove all export, inter-array and inter-connector cables and scour protection where possible and appropriate to do so.
Magnitude of Impact
  1. During decommissioning cables would be removed by similar processes as undertaken during installation therefore increases in SSC would be of a similar form and magnitude. Following decommissioning, changes in suspended sediments concentration and sedimentation would return to baseline levels as it is anticipated that all structures above the seabed level will be completely removed and no further activities resulting in seabed disturbance would be undertaken.
  2. The impact of increased suspended sediment levels and associated sedimentation during removal of infrastructure is predicted to be of local spatial extent, short term duration and intermittent and of high reversibility. It would not be of sufficient magnitude to alter the hydrodynamic regime or offshore bank or beach morphology. It is predicted that the impact will affect the Firth of Forth Banks Complex ncMPA directly whilst affecting the remaining receptors indirectly. The magnitude is therefore, considered to be low for the receptors within the ncMPA and negligible for other receptor groups.
Sensitivity of the Receptor
  1. As with the construction phase, in response to sedimentation which has been identified as localised and composed of native material therefore the structure and function of the designated features is of low vulnerability and recoverable. The sensitivity of the ncMPA (direct) to changes as a result of decommissioning activity, removal of export, inter-array and inter-connector cables and scour protection where possible is therefore considered to be low. It is expected that the sensitivity of the other receptors (indirect) to decommissioning activity, removal of export, inter-array and inter-connector cables and scour protection where possible is therefore considered to be negligible.
Significance of the Effect
  1. Within the Firth of Forth Banks Complex ncMPA the magnitude of the impact on receptors is deemed to be low, and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms. For intertidal and coastal areas such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI, the magnitude of impacts is negligible giving rise to effects of negligible adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms.

Presence of Infrastructure may Lead to Changes to Tidal Currents, Wave Climate, Littoral Currents and Sediment Transport

  1. The presence of infrastructure may lead to changes to tidal currents, wave climate, littoral currents, and sediment transport principally during the operation and maintenance phase of the Proposed Development and following decommissioning associated with residual infrastructure. Infrastructure will undergo detailed design in line with best practice. Should cable protection be required in the nearshore region circa 500 m offshore of LAT, with minimum water depths of 6 m, suitable protection measures would be employed, such as concrete mattresses. These would be of limited height circa 30-60 cm to have negligible impact on tidal flow and profiled to allow any existing baseline sediment transport pathways to be maintained.
  2. Modelling was undertaken using the maximum design scenario as outlined in Table 7.9   Open ▸ including the presence of scour protection as outlined in the project description (volume 1, chapter 3 of the Offshore EIA Report). The detail of the numerical modelling underpinning the assessment is provided in volume 3, appendix 7.1. The magnitude of the impact is detailed in this section along with the assessment of the effect of changes to physical processes on relevant receptors.

Construction Phase

  1. An assessment has been carried out with and without the presence of infrastructure. With changes to tidal currents, wave climate, littoral currents, and sediment transport and associated potential impacts ranging from the baseline environment (no presence of infrastructure) to the operation and maintenance phase (maximum design scenario) as assessed in the following section. Based on this, it can be inferred that during the construction phase there will be gradual changes to tidal currents, wave climate, littoral currents and sediment transport as infrastructure is introduced into the environment. The significance of effect taken at the end of construction (the same as the operation and maintenance phase described below) will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms. For intertidal and coastal areas such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI, the magnitude of impacts is negligible giving rise to effects of negligible adverse significance, which is not significant in EIA terms.

Operation and Maintenance Phase

Magnitude of Impact
  1. The presence of infrastructure within the Proposed Development may lead to changes in tidal currents, wave climate, littoral currents, and sediment transport during the operation and maintenance phase of the Proposed Development. The maximum design scenario in terms of hydrographic impacts is for up to 179 wind turbines with four legs at 5 m diameter spaced 60 m apart at seabed with scour protection at each 20 m caisson leg foundation of 2 m in height and 80 m diameter covering a total footprint of 12,240 m2 per unit.
  2. Additionally, the maximum design scenario includes eight HVAC offshore station platforms (OSPs)/Offshore convertor station platforms each with six jacket legs comprising suction caissons of 15 m in diameter with associated scour protection of 60 m diameter and a height of 2 m giving rise to 6,206 m2 footprint per unit. The six legs of 4 m diameter spaced 40 m apart at the seabed were also included within the water column to model associated influence on wave climate and tidal currents. Similarly, two HVDC offshore converter station platforms each with eight jacket legs comprising suction caissons of 15 m in diameter with associated scour protection of 60 m diameter and a height of 2 m giving rise to 12,559 m2 footprint per unit. The eight legs of 5 m diameter spaced 80 m apart at the seabed were also included. The modelling was undertaken with 15% of the cable length having 3m height protection, this protection was placed along sections of the cable where the bed is rock outcrops and trenching would not be possible.
  3. The results of the modelling indicated that peak tidal flows are redirected in the immediate proximity of structures by a maximum variation of 1 cm/s which constitutes as less than 2% of the peak flow and reduces significantly with distance from the structures. These changes are also limited to the immediate Proposed Development array area which may have a direct impact on the hydrodynamic regime and persist for the entire lifecycle of the Proposed Development. However, they would be imperceptible beyond the immediate vicinity of the offshore wind farm area and would be reversible on decommissioning. The limited nature of these changes would not influence the hydrodynamic regime which underpins offshore bank morphology and is the supporting process for aspects of the Firth of Forth Banks Complex ncMPA, in particular Berwick and Marr Banks, including shelfs, banks and mounds and the environment for ocean quahog aggregations.
  4. Examination of a one in one year storm from the northernly sector (of greatest influence of approaching storms) shows the deflection of waves by the structures result in a reduction in the lee and increases where the waves had been deflected either side of each structure. Changes in the wave height were in the order of 2 cm equating to <1% of the baseline significant wave height. For a 1 in 20 year storm event, the pattern is similar however the change in wave height at the structures is 2 cm to 4 cm and due to the larger baseline associated with the return period the overall impact on the wave climate is less obvious.
  5. Sediment transport is driven by a combination of tidal currents and wave conditions, the magnitude of these has been individually quantified as described above. For a one in one year storm from 000° during the flood tide the wave climate is in concert with tidal flow reducing the tidal flow on the lee side of the structure further. However, during the ebb flow, the wave climate and tidal flow are in opposition reducing the magnitude of the littoral current. With the presence of infrastructure, wave climate causes a small reduction in the magnitude of flow whilst there is little difference between the magnitude of littoral current flow and the tidal flows. Changes in magnitude compared to baseline current flow are ±5% which would not be sufficient to disrupt beach and offshore bank morphological processes or destabilise coastal features.
  6. Residual currents are effectively the driver of sediment transport and therefore any changes to residual currents would have a direct impact on sediment transport which would persist for the lifecycle of the Proposed Development. However, if the presence of the foundation structures does not have a significant influence on either tide or wave conditions (see assessment of effects presented above for changes in tidal currents and changes to wave climate and littoral current) they cannot therefore have a significant effect on the sediment transport regime. For completeness, the residual current and sediment transport was simulated with the foundations in place. The maximum change in residual current and sediment transport is circa ±15% within close proximity to the structure (i.e. as a result of the scour protection). Changes in the residual current and sediment transport reduce with increasing distance from the wind turbines towards baseline levels.
  7. The hydrodynamic regime is highly variable through tidal cycles and due to meteorological conditions, with the scale of the impact being well within the natural variation. The changes to tidal currents, wave climate, littoral currents, and sediment transport are insignificant in terms of the hydrodynamic regime and would not alter beach and offshore bank morphological processes. Effects on tidal current and wave climate would be reversible on decommissioning (i.e. following removal of the wind turbines).
  8. The impact is predicted to be of local spatial extent, long term duration, continuous and of high reversibility. It is predicted that the impact will affect the Firth of Forth Banks Complex ncMPA both directly and indirectly whilst other receptors are affected indirectly. The magnitude is therefore, considered to be low within the ncMPA and negligible at coastal and intertidal receptors.
Sensitivity of the Receptor
  1. The Firth of Forth Banks Complex ncMPA is a composite site which include the following designated features; offshore subtidal sands and gravels, shelf banks and moulds and provide habitat to aggregations of ocean quahog. The hydrodynamic regime forms the supporting process for these marine features. Due to the localised and limited changes in tides, waves, littoral currents, and sediment transport, the Firth of Forth Banks Complex ncMPA is deemed to be of low vulnerability and recoverable as the area is extensive. The sensitivity of this is therefore considered to be low.
  2. The Berwickshire and North Northumberland Coast SAC mostly lies below the HWM with designated features such as reefs, submerged/partially submerged sea caves, intertidal mudflats/sandflats and shallow inlets and bays. Similarly, Berwickshire Coast SSSI is intertidal with features including sea caves and the rocky shore. These areas are vast and would recover from the low magnitude of impact from hydrodynamic changes which do not reach the intertidal zone. This receptor is therefore deemed to be of low vulnerability to changes in tides, waves, littoral currents, and sediment transport and is therefore considered to be negligible.
  3. St Abb's Head to Fast Castle SSSI is characterised for its geomorphological coastal interests in particular the spectacular assemblage of rock coast landforms including clefts, gullies, geos, caves, stacks, reefs and skerries. No erosion of rock formations is expected due to the negligible changes in hydrodynamics away from the Proposed Development. The sensitivity of the receptor to changes in tides, waves, littoral currents, and sediment transport is therefore considered to be negligible.
  4. Pease Bay SSSI is designated on sea cliffs which provide exposures of a continuous succession of Upper Devonian and Lower Carboniferous strata which is of national and international importance. No undercutting of cliffs or erosion is expected due to the negligible changes in hydrodynamics away from the Proposed Development. The sensitivity of the receptor to changes in tides, waves, littoral currents, and sediment transport is therefore considered to be negligible.
  5. The Firth of Forth SSSI is comprised of features such as mudflat, sand dune, saltmarsh, and sea cliffs. Changes in the hydrodynamics are indiscernible at this distance from the Proposed Development. This receptor is therefore deemed to be of low vulnerability to changes in tides, waves, littoral currents, and sediment transport and is therefore considered to be negligible.
  6. Barns Ness Coast SSSI contains a variety of coastal features such as saltmarsh, sand dunes and shingle. Due to the negligible changes in hydrodynamics away from the Proposed Development in the intertidal zone, the sensitivity of the receptor to changes in tides, waves, littoral currents, and sediment transport is therefore considered to be negligible.
  7. Bathing water quality is measured in terms of biological levels and due to the distance from the Proposed Development site, it is expected that the sensitivity of the receptor to changes in tides, waves, littoral currents, and sediment transport is therefore considered to be negligible.
Significance of the Effect
  1. Changes to tides, waves, littoral currents and sediment transport due to the presence of the infrastructure do not extend to Firth of Forth SSSI, Barns Ness Coast SSSI, Pease Bay SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire SSSI or St Abb's Head to Fast Castle SSSI but do extend to the Firth of Forth Banks Complex ncMPA.
  2. Post construction tidal velocity is limited to the vicinity of the wind turbines and changes in magnitude are maximum of 1 cm/s and in the lee of the structure the peak flow is reduced by 2% which decreases further moving away from the structure.
  3. Similarly, the wave climate reduces in the lee of the structure by less than 1% of baseline significant wave heights increasing either side of the wind turbine. Changes are concentrated on the specific location of the wind turbine and do not extent beyond the Proposed Development area. Diminutive changes are observed with the littoral current flow due to the installation of the wind farm. Offshore bank and beach morphology would not be influenced by changes of this magnitude.
  4. In terms of the Firth of Forth Banks Complex ncMPA, the limited and localised changes to hydrography seen in relation to the Berwick and Marr Banks, would not result in changes to the hydrodynamic regime or sediment composition. The structure of the offshore subtidal sands and gravels would remain unchanged. Similarly, shelfs, banks and mound features would remain stable and supporting hydrodynamics processes for ocean quahog colonisation remain unaffected.
  5. Overall, the magnitude of the impact on the Firth of Forth Banks Complex ncMPA is deemed to be low and overall the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms. For intertidal and coastal areas such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI, the magnitude of impacts is negligible giving rise to effects of negligible adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact
  1. Following decommissioning, changes to physical processes would be of far less magnitude than the operation and maintenance phase, as no structures would remain in the water column to influence wave climate and tidal currents. Additionally, only those scour and cable protection structures not possible or practical to be removed would continue to influence sediment transport pathways. The magnitude is therefore, considered to be negligible.
Sensitivity of the Receptor
  1. As with the operation and maintenance phase, in response to localised changes in tides, waves, littoral currents, and sediment transport, the Firth of Forth Banks Complex ncMPA is deemed to be of low vulnerability and recoverable as the area is extensive. The sensitivity of this is therefore considered to be low. Overall, the magnitude of the impact is deemed to be negligible and the sensitivity of the Firth of Forth Banks Complex ncMPA is considered to be low.
Significance of the Effect
  1. Within the Firth of Forth Banks Complex ncMPA the magnitude of the impact on receptors is deemed to be low, and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms. For intertidal and coastal areas such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI, the magnitude of impacts is negligible giving rise to effects of negligible adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms.

Proposed Monitoring

  1. The project description (volume 1, chapter 3) includes routine inspection and geophysical surveys of wind turbine and OSP/Offshore convertor station platform foundations. Also export, offshore and inter-array cable burial and protection will be inspected and surveyed as part of the maintenance programme. Proposed monitoring relevant to physical processes also involves the recovery of sand waves to contribute to the body of knowledge on the influence of offshore energy development (see Table 7.15   Open ▸ ).

 

Table 7.15:
Proposed Monitoring and the Method of Implementation

Table 7.15: Proposed Monitoring and the Method of Implementation

 

7.12. Cumulative Effects Assessment

7.12.1.              Methodology

  1. The CEA assesses the impact associated with the Proposed Development together with other relevant plans, projects and activities. Cumulative effects are therefore the combined effect of the Proposed Development in combination with the effects from a number of different projects, on the same receptor or resource. Refer to volume 1, chapter 6 for detail on CEA methodology.
  2. The projects and plans selected as relevant to the CEA presented within this chapter are based upon the results of a screening exercise (see volume 3, appendix 6.4 of the Offshore EIA Report). Volume 3, appendix 6.4 further provides information regarding how information pertaining to other plans and projects is gained and applied to the assessment. Each project or plan has been considered on a case by case basis for screening in or out of this chapter's assessment based upon data confidence, effect-receptor pathways and the spatial/temporal scales involved.
  3. In undertaking the CEA for the Proposed Development, it is important to bear in mind that other projects and plans under consideration will have differing potential for proceeding to an operational stage and hence a differing potential to ultimately contribute to a cumulative impact alongside the Proposed Development. Therefore, a tiered approach has been adopted. This provides a framework for placing relative weight upon the potential for each project/plan to be included in the CEA to ultimately be realised, based upon the project/plan’s current stage of maturity and certainty in the projects’ parameters. The tiered approach which will be utilised within the Proposed Development CEA employs the following tiers:
  • tier 1 assessment – Proposed Development (Berwick Bank Wind Farm offshore) with Berwick Bank Wind Farm onshore;
  • tier 2 assessment – All plans/projects assessed under Tier 1, plus projects which became operational since baseline characterisation, those under construction and those with consent and submitted but not yet determined;
  • tier 3 assessment – All plans/projects assessed under Tier 2, plus those projects with a Scoping Report; and
  • tier 4 assessment – All plans/projects assessed under Tier 3, which are reasonably foreseeable, plus those projects likely to come forward where an Agreement for Lease (AfL) has been granted.
    1. The specific projects scoped into the CEA for physical processes, are outlined in Table 7.16   Open ▸ and presented in Figure 7.5   Open ▸
    2. Figure 7.5   Open ▸ . The projects scoped in, fall within the physical processes CEA study area ( Figure 7.5   Open ▸ ) which is defined by two tidal excursions (a 20 km buffer around the Project Development array area and export cable corridor) in order to assess the interaction of sediment plumes from the Proposed Development and surrounding projects.
    3. The range of potential cumulative impacts that are identified and included in Table 7.17   Open ▸ , is a subset of those considered for the Proposed Development alone. This is because some of the potential impacts identified and assessed for the Proposed Development alone, are localised and temporary in nature. It is considered therefore, that these potential impacts have limited or no potential to interact with similar changes associated with other plans or projects. These have therefore been scoped out of the cumulative effects assessment.
    4. Similarly, some of the potential impacts considered within the Proposed Development alone assessment are specific to a particular phase of development (e.g. construction, operation and maintenance or decommissioning). Where the potential for cumulative effects with other plans or projects only have potential to occur where there is spatial or temporal overlap with the Proposed Development during certain phases of development, impacts associated with a certain phase may be omitted from further consideration where no plans or projects have been identified that have the potential for cumulative effects during this period.
    5. The physical processes CEA study area for the Proposed Development extends to MHWS whilst the Onshore EIA extend to MLWS however, due to the proposed use of trenchless technology at landfall, there are no cumulative impacts anticipated relating to the intertidal zone. In each of the projects relating to offshore cables, changes to metocean, bathymetry and sediment transport were scoped out of their respective EIA. Therefore, these aspects are not included in the cumulative assessment of changes to tidal currents, wave climate, littoral currents and sediment transport due to the presence of infrastructure. However, construction phase increases in SSCs due to cable installation are included.
    6. Intermittent operations, such as the use of offshore disposal sites, have been included in the cumulative assessment. These activities, although potentially in their operation and maintenance phase, are not included within the background assessment as they are not continual and therefore do not contribute to background conditions in a consistent manner.
Table 7.16:
List of Other Developments Considered within the CEA for Physical Processes

Table 7.16: List of Other Developments Considered within the CEA for Physical Processes

Figure 7.5:
Other Developments Screened into the Cumulative Effects Assessment for Physical Processes

Figure 7.5: Other Developments Screened into the Cumulative Effects Assessment for Physical Processes

7.12.2.              Maximum Design Scenario

  1. The maximum design scenarios identified in Table 7.17   Open ▸ have been selected as those having the potential to result in the greatest effect on an identified receptor or receptor group. The cumulative effects presented and assessed in this section have been selected from the details provided in volume 1, chapter 3 of the Offshore EIA Report as well as the information available on other projects and plans (see volume 3, appendix 6.4), to inform a ‘maximum design scenario’. Effects of greater adverse significance are not predicted to arise should any other development scenario, based on details within the PDE (e.g. different wind turbine layout), to that assessed here, be taken forward in the final design scheme.

 

Table 7.17:
Maximum Design Scenario Considered for Each Impact as part of the Assessment of Likely Significant Cumulative Effects on Physical Processes

Table 7.17: Maximum Design Scenario Considered for Each Impact as part of the Assessment of Likely Significant Cumulative Effects on Physical Processes

 

7.12.3.              Cumulative Effects Assessment

  1. An assessment of the likely significance of the cumulative effects of the Proposed Development upon physical processes receptors arising from each identified impact is given in the following sections.

Increased Suspended Sediment Concentrations and Associated Deposition on Physical Features as a Result of Seabed Preparation, Foundation Insatllation and Cable Installation

  1. Increased SSCs and associated deposition on physical features may arise due to the seabed preparation, installation of the wind turbines and OSP/Offshore convertor station platform foundations, the installation and/or maintenance of inter-array cables and offshore export cables. Should the other projects cited take place concurrently with the Proposed Development construction or maintenance, there is potential for cumulative increased turbidity levels.

Tier 2

Construction phase

Magnitude of impact

  1. The magnitude of the increase in SSCs and associated deposition arising from the installation of wind turbines and OSP/Offshore convertor station platform foundations, inter-array cables and offshore export cables during the construction phase, has been assessed as negligible to low for the Proposed Development alone, as described in section 7.11 with the greatest impacts due to installation of inter-array cabling within the Firth of Forth Banks Complex ncMPA.
  2. The construction phase of the Proposed Development coincides with the construction phase for the Seagreen 1A Offshore Wind Farm. It is noted that these are due for completion in the third quarter of 2025 with the installation of wind turbines being undertaken in the final months. Therefore, the installation of cables and foundations for this project will not coincide with the Proposed Development construction phase. The Inch Cape Offshore Wind Farm will be in the final year of construction, being programmed to overlap for a period with the installation of the offshore export cables. The offshore export cable corridor for Inch Cape is located to the east of the Proposed Development, beyond the Forth Banks Complex ncMPA and should trenching activities be undertaken simultaneously the sediment plumes would not interact with those from the Proposed Development.
  3. During the Proposed Development’s construction phase, the Neart na Gaoithe Offshore Wind Farm and the Seagreen 1A Export Cable Corridor will be in operational phase and maintenance activities may result in increased SSCs, however these activities would be of limited spatial extent and frequency and unlikely to interact with sediment plumes from the Proposed Development.
  4. The CEA considers sea disposal of dredged material at the Eyemouth disposal site, located 31 km and 16.5 km from the Proposed Development array area and export cable corridor respectively. If offshore cable installation and dredge material disposal coincided both resultant plumes would be advected on the tidal currents, they would travel in parallel, and not towards one another, and are unlikely to interact in the event that offshore cable installation coincides with the use of the licensed sea disposal site.
  5. The Eastern Link 1 Cable has Scottish landfall near Thorntonloch Beach, East Lothian. The landfall installation is proposed to be trenchless techniques (e.g. HDD) and although it is not yet confirmed which subsea trenching techniques will be used to install the cables, it is anticipated that mechanical ploughing or cutting and/or water jetting or Mass Flow Excavation (MFE) techniques will be used at different points along the route, in response to the seabed sediment conditions. Installation of the cables into soft sediments will seek to achieve a target burial depth of at least 1.5 m to 2 m and below the depth of mobile sediments depending on the nature of the seabed and potential hazards. The scheme is located 1.8 km from the Firth of Forth Banks Complex ncMPA therefore may be impacted indirectly however, significant impacts of sediment plumes arising from cable laying activities are not anticipated. These installation parameters are similar to those for the Proposed Development export cable corridor installation and therefore the magnitude of the impact on the MPA receptors is anticipated to be low whilst at the coastal receptors this would be negligible.
  6. The Eastern Link 2 Cable runs to the east of the Proposed Development, skirting the Firth of Forth Banks Complex ncMPA. For the extent of the overlap with the Proposed Development CEA study area this is an offshore marine cable. The preferred subsea cable protection method is burial through trenching. It is not yet confirmed what subsea trenching equipment will be used to install the cables; however, it is anticipated similar methods to those proposed for Eastern Link 1 may be required, but this is dependent on the seabed conditions present within the Proposed Development export cable corridor: It is anticipated that the magnitude of the impact on the ncMPA would be low whilst at the coastal receptors not be affected.
  7. The cumulative impact is predicted to be of local spatial extent, short term duration, intermittent and of high reversibility. The additional impact of the cumulative projects is negligible therefore the predicted impacts on the Firth of Forth Banks Complex ncMPA remains low, and negligible for the remaining coastal and intertidal receptors.

Sensitivity of the receptor

  1. As with the Proposed Development, the sensitivity of the Firth of Forth Banks Complex ncMPA, comprising offshore subtidal sands and gravels, shelf banks and mounds and habitat to aggregations of ocean quahog is of low sensitivity to low magnitude intermittent changes in SSCs and sedimentations. The coastal receptors such as maritime cliffs and saltmarshes associated with the Firth of Forth SSSI and Barns Ness Coast SSSI are of negligible sensitivity and the magnitude is negligible.

Significance of the effect

  1. The cumulative effect will therefore be of negligible to minor adverse significance for the Firth of Forth Banks Complex ncMPA receptors and of negligible adverse significance for the coastal receptors (Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI) which is not significant in EIA terms.

Further mitigation and residual effect

  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms.
Operation and maintenance phase

Magnitude of impact

  1. The magnitude of the increase in SSCs and associated deposition arising from the installation of wind turbines and OSP/Offshore convertor station platform foundations, inter-array cables and offshore export cables during the operation and maintenance phase, has been assessed as negligible to low for the Proposed Development alone, as described in section 7.11. With impacts relating to maintenance work within the Firth of Forth Banks Complex ncMPA.
  2. The projects cited within the construction phase cumulative assessment will all be within the operation and maintenance phases therefore, as previously, maintenance activities may result in increased SSCs, however these activities would be of limited spatial extent and frequency. The cumulative impacts would therefore be of a lesser magnitude (i.e. also negligible).
  3. Potential cumulative impacts may relate to maintenance and reburial of the offshore export cables coinciding with the use of the Eyemouth disposal site. Maintenance activities are both intermittent and of smaller scale than the construction phase and therefore any potential cumulative impacts are less likely to occur and be of a smaller scale.
  4. The cumulative impact is predicted to be of local spatial extent, short term duration, intermittent and of high reversibility. The additional impact of the cumulative projects is negligible therefore the predicted impacts on the Firth of Forth Banks Complex ncMPA remains low, and negligible for the remaining coastal and intertidal receptors.

Sensitivity of the receptor

  1. As with the Proposed Development, the sensitivity of the Firth of Forth Banks Complex ncMPA, comprising offshore subtidal sands and gravels, shelf banks and mounds and habitat to aggregations of ocean quahog is of low sensitivity to low magnitude intermittent changes in suspended sediment concentration and sedimentations. The coastal receptors such as maritime cliffs and saltmarshes associated with the Firth of Forth SSSI and Barns Ness Coast SSSI are of negligible sensitivity and the magnitude is negligible.

Significance of the effect

  1. The cumulative effect will therefore be of negligible to minor adverse significance for the Firth of Forth Banks Complex ncMPA receptors and of negligible adverse significance for the coastal receptors (Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI) which is not significant in EIA terms.

Further mitigation and residual effect

  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms
Decommissioning phase
  1. As per the maximum design scenario ( Table 7.9   Open ▸ ), during the decommissioning phase it is anticipated that all structures above the seabed level will be completely removed, depending on seabed mobility. The intention is to cut off piled structures at an agreed depth below the seabed. It is proposed to remove all export, inter-array and inter-connector cables and scour protection where possible and appropriate to do so.

Magnitude of impact

  1. Following decommissioning, changes in suspended sediments concentration and sedimentation would be of lesser magnitude than the operation and maintenance phase, it is anticipated that all structures above the seabed level will be completely removed, depending on seabed mobility.
  2. During the decommissioning of the Proposed Development there is potential for a cumulative impact from the decommissioning of other offshore wind farms on similar project timelines (Neart na Gaoithe, Seagreen 1, Inch Cape and Seagreen 1A). However, any potential increase in SSC would be advected on tidal currents running in parrallel and not overlap with each other this impact would be localised and of a lesser magnitude than the construction phase.
  3. The impact of increased suspended sediment levels and associated sedimentation is predicted to be of local spatial extent, short term duration and intermittent and of high reversibility. It would not be of sufficient magnitude to alter the hydrodynamic regime or offshore bank or beach morphology. It is predicted that the impact will affect the Firth of Forth Banks Complex ncMPA directly whilst affecting the remaining receptors indirectly. The magnitude is therefore, considered to be low for the receptors within the ncMPA and negligible for other receptor groups.

Sensitivity of the receptor

  1. As with the construction phase, in response to sedimentation which has been identified as localised and composed of native material therefore the structure and function of the designated features is of low vulnerability and recoverable. The sensitivity of the ncMPA (direct) to changes as a result of decommissioning activity, removal of export, inter-array and inter-connector cables and scour protection where possible is therefore considered to be low. It is expected that the sensitivity of the other receptors (indirect) to decommissioning activity, removal of export, inter-array and inter-connector cables and scour protection where possible is therefore considered to be negligible.

Significance of the effect

  1. The effect will, therefore, be of negligible to minor significance, which is not significant in EIA terms for the Firth of Forth Banks Complex ncMPA. For coastal and intertidal receptors such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI the effects will be of negligible significance, which is not significant in EIA terms.

Further mitigation and residual effect

  1. No physical processes mitigation is considered necessary because the predicted impact in the absence of mitigation is not significant in EIA terms. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms.

Tier 3

Construction phase

Magnitude of impact

  1. During the construction phase of the Proposed Development there is the potential for cumulative impacts with three Tier 3 cable installations. The Cambois connection is a 170 km cable route extending southwards from the Proposed Development array area at Berwick Bank, it will therefore directly impact the Firth of Forth Banks Complex ncMPA complex. Scoping indicates the project will consist of four cables installed in 2 m wide trenches up to 3 m in depth. Installation techniques may include the use of a jet trencher, deep jet trencher, mechanical trencher, cable plough (displacement and non-displacement) and mass flow excavator (MFE), as ground conditions dictate. Site preparation will be required, such as boulder clearance, sandwave clearance, grapnel run will be needed in advance of cable installation as part of the 24 month construction programme. These installation parameters are similar to those of the Proposed Development and therefore the magnitude of the impact on the ncMPA receptors is anticipated to be low whilst at the coastal receptors this would be negligible.

Sensitivity of the receptor

  1. The sensitivity of the Firth of Forth Banks Complex ncMPA, comprising offshore subtidal sands and gravels, shelf banks and mounds and habitat to aggregations of ocean quahog is of low sensitivity to low magnitude intermittent changes in SSCs and sedimentations. The coastal receptors such as maritime cliffs and saltmarshes associated with the Firth of Forth SSSI and Barns Ness Coast SSSI are of negligible sensitivity and the magnitude is negligible.

Significance of the effect

  1. The cumulative effect will therefore be of negligible to minor adverse significance for the Firth of Forth Banks Complex ncMPA receptors and of negligible adverse significance for the coastal receptors (Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI) which is not significant in EIA terms.

Further mitigation and residual effect

  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms
Operation and maintenance phase

Magnitude of impact

  1. During the operation and maintenance phase of the Proposed Development there is the potential for cumulative impacts with three Tier 3 cable installations. The CEA for the Cambois connection is based on information presented in the Scoping Report submitted in October 2022 (SSER, 2022e). The Cambois connection is a 170 km cable route extending southwards from the Proposed Development array area, it will therefore directly impact the Firth of Forth Banks Complex ncMPA. Scoping indicates the project will consist of four cables installed in 2 m wide trenches up to 3 m in depth. Installation techniques may include jet trenching or MFE techniques as ground conditions dictate. Site preparation will be required, such as boulder and sand wave clearance as part of the 24 month construction programme. These installation parameters are similar to those of the Proposed Development and therefore the magnitude of the impact on the ncMPA receptors is anticipated to be low whilst at the coastal receptors this would be negligible.
  2. The Cambois connection, Eastern Link 1 and Eastern Link 2 Cables will all be operational when the Proposed Development reaches the operation and maintenance phase. Therefore, as previously, maintenance activities may result in increased SSCs, however these activities would be of limited spatial extent and frequency. The cumulative impacts would therefore be of a lesser magnitude.
  3. The cumulative impact is predicted to be of local spatial extent, short term duration, intermittent and of high reversibility. The additional impact of the cumulative projects is low to negligible therefore the predicted impacts on the Firth of Forth Banks Complex ncMPA remains low, and negligible for the remaining receptors.

Sensitivity of the receptor

  1. The sensitivity of the Firth of Forth Banks Complex ncMPA, comprising offshore subtidal sands and gravels, shelf banks and mounds and habitat to aggregations of ocean quahog is of low sensitivity to low magnitude intermittent changes in suspended sediment concentration and sedimentations. The coastal receptors such as maritime cliffs and saltmarshes associated with the Firth of Forth SSSI and Barns Ness Coast SSSI are of negligible sensitivity and the magnitude is negligible.

Significance of the effect

  1. The cumulative effect will therefore be of negligible to minor adverse significance for the Firth of Forth Banks Complex ncMPA receptors and of negligible adverse significance for the coastal receptors (Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI) which is not significant in EIA terms.

Further mitigation and residual effect

  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms.
Decommissioning phase
  1. As per the maximum design scenario ( Table 7.9   Open ▸ ), during the decommissioning phase it is anticipated that all structures above the seabed level will be completely removed. The intention is to cut off piled structures at an agreed depth below the seabed, and suction caisson structures will be fully removed. It is proposed to remove all export, inter-array and inter-connector cables and scour protection where possible and appropriate to do so.

Magnitude of impact

  1. During decommissioning cables would be removed by similar processes as undertaken during installation therefore increases in SSC would be of a similar form and magnitude. Following decommissioning, changes in suspended sediments concentration and sedimentation would return to baseline levels as it is anticipated that all structures above the seabed level will be completely removed and no further operation to disturb the seabed would be required.
  2. The impact of increased suspended sediment levels and associated sedimentation is predicted to be of local spatial extent, short term duration and intermittent and of high reversibility. It would not be of sufficient magnitude to alter the hydrodynamic regime or offshore bank or beach morphology. It is predicted that the impact will affect the Firth of Forth Banks Complex ncMPA directly whilst affecting the remaining receptors indirectly. The magnitude is therefore, considered to be low for the receptors within the ncMPA and negligible for other receptor groups.

Sensitivity of the receptor

  1. As with the construction phase, in response to sedimentation which has been identified as localised and composed of native material therefore the structure and function of the designated features is of low vulnerability and recoverable. The sensitivity of the ncMPA (direct) to changes as a result of decommissioning activity, removal of export, inter-array and inter-connector cables and scour protection where possible is therefore considered to be low. It is expected that the sensitivity of the other receptors (indirect) to decommissioning activity, removal of export, inter-array and inter-connector cables and scour protection where possible is therefore considered to be negligible.

Significance of the effect

  1. For the Firth of Forth Banks Complex ncMPA, the effect will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms. For coastal and intertidal receptors such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI the effects will be of negligible adverse significance, which is not significant in EIA terms.

Further mitigation and residual effect

  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms.

Presence of Infrastructure may Lead to Changes to Tidal Currents, Wave Climate, Littoral Currents and Sediment Transport

Tier 2

Construction phase
  1. Assessment of the Proposed Development was carried out with and without the presence of infrastructure. It can be inferred that during the construction phase there will be gradual changes to tidal currents, wave climate, littoral currents and sediment transport as infrastructure is built. With changes occurring from the baseline environment (no presence of infrastructure) to the operation and maintenance phase (maximum design scenario). This would also be the case for the Offshore Wind Farm developments under construction during this period (i.e. Inch Cape, Seagreen 1 and Seagreen 1A). Although, as previously noted, construction of subsea elements such as foundations and cable installation will be largely completed prior to commencing the construction phase of the Proposed Development. The significance of effect taken at the end of construction (the same as the operation and maintenance phase) will, therefore, be of negligible to minor adverse significance, which is not significant in EIA terms. For intertidal and coastal areas such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI, the magnitude of impacts is negligible giving rise to effects of negligible adverse significance, which is not significant in EIA terms.
Operation and maintenance phase

Magnitude of impact

  1. The magnitude of increased infrastructure leading to changes in the hydrodynamic environment and sediment transport during the operation and maintenance phase has been assessed as negligible to minor for the Proposed Development alone for the receptors within the Forth Banks Complex ncMPA and negligible for the intertidal and coastal receptors (section 7.11). The construction of Seagreen 1, Inch Cape and Neart na Gaoithe Offshore Wind Farms are due to be completed prior to the operation and maintenance phase of the Proposed Development.
  2. The Neart na Gaoithe Offshore Wind Farm EIA Report (Mainstream Renewable Power Ltd, 2012) included a comprehensive numerical modelling study which incorporated modelling of the cumulative impacts of the offshore wind farms within the physical processes CEA study area for the Proposed Development (Intertek METOC, 2011).
  3. The modelling and assessment for Neart na Gaoithe included Neart na Gaoithe, Inch Cape, Seagreen in addition to the Proposed Development (which is referred to in the documentation as Seagreen Phase 2 and Phase 3). Within said modelling, the Proposed Development was modelled with 725 wind turbines each with an 8 m tower diameter relating to 6 MW wind turbines. The Proposed Development however incorporates a maximum of 307 14 MW wind turbine which is significantly less than the scenario modelled and therefore the impacts would, in reality, be less than those reported. The impact of multiple developments on tidal currents was predicted by the study to be low and localised to the near field of each development.
  4. The Neart na Gaoithe study also showed that with all offshore wind farms in situ, the cumulative effect on the wave climate is low (< 3% average significant wave height) but the effect on wave climate has a larger extent than a single offshore wind farm. The cumulative effect from the combined wind farm developments on sediment transport processes is low, resulting in a 1% to 3% exceedance in the typical critical bed shear stress. Changes are within the immediate vicinity of each of the developments and it is not expected that there would be changes to the far field sediment regimes.
  5. The cumulative impact is predicted to be of local spatial extent, long term duration, continuous and high reversibility. It is predicted that the impact will affect the Firth of Forth Banks Complex ncMPA directly with a low magnitude and other intertidal and coastal receptors such as Firth of Forth SSSI, Berwickshire and North Northumberland Coast SAC, Berwickshire Coast SSSI, Pease Bay SSSI, St Abb's Head to Fast Castle SSSI and Barns Ness SSSI indirectly with a negligible magnitude.

Sensitivity of the receptor

  1. The cumulative effects of the presence of infrastructure from multiple offshore wind farm developments in situ, operating and maintained concurrently does not further impact the Firth of Forth Banks Complex ncMPA or other receptors, more than a single development due to the impacts of infrastructure typically reserved to the vicinity of the developments.

Significance of the effect

  1. The cumulative effect will therefore be of negligible to minor adverse significance for the Firth of Forth Banks Complex ncMPA receptors, such as shelf, banks and mounds, and of negligible adverse significance for the coastal receptors, such as maritime cliffs and saltmarshes, which is not significant in EIA terms.

Further mitigation and residual effect

  1. No physical processes mitigation is considered necessary because the likely effect in the absence of further mitigation (beyond the designed in measures outlined in section Table 7.14   Open ▸ ) is not significant in EIA terms