Tier 1

                        Construction and operation and maintenance phases
Magnitude of impact
  1. There were two Tier 1 projects identified with potential for cumulative effects associated with this impact:
  • all phases of the Proposed offshore export cable corridor(s); and
  • the operation and maintenance and decommissioning phases of the Eastern Green Link 2 ( Table 8.23   Open ▸ ).
  1. At the time of writing this Array EIA Report, there was no Offshore EIA Report available for the Proposed offshore export cable corridor(s). However, given that these two Tier 1 projects are both HVDC subsea power cables, there will be less infrastructure installed to constitute long term habitat loss than for the Array. It is likely that long term habitat loss will occur at the Tier 1 projects as a result of cable and/or pipeline protection and crossing protection.
  2. For the Array, up to 19.27 km2 of long term habitat loss and disturbance may occur due to the installation of infrastructure, and an additional 778,464 m2 due to long term seabed disturbance from mooring lines and dynamic cabling ( Table 8.12   Open ▸ ). Within the Environmental Appraisal Report for the Eastern Green Link 2, a total footprint of up to 2.20 km2 long term habitat loss and disturbance was predicted to occur ( Table 8.25   Open ▸ ) (National Grid Electricity Transmission and Scottish Hydro Electric Transmission plc, 2022). This was comprised of up to 2 km2 of rock berm and up to 0.2 km2 of pipeline and cable crossing protection (National Grid Electricity Transmission and Scottish Hydro Electric Transmission plc, 2022). This is considerably lower than the total 20.08 km2 of long term habitat loss included in the MDS for the Array ( Table 8.25   Open ▸ ).

 

Table 8.25:
Cumulative Footprint of Long Term Habitat Loss and Disturbance (km2) for the Tier 1 Projects

Table 8.25: Cumulative Footprint of Long Term Habitat Loss and Disturbance (km2) for the Tier 1 Projects

 

  1. As outlined in paragraph 93 for the Array alone, this impact presents some measurable but minor long term loss of and alteration to the affected areas of seabed within the entire Array benthic subtidal ecology study area and but less so within the regional benthic subtidal ecology study area. The cumulative magnitude of impact of the Array with the Tier 1 projects is therefore not expected to represent a material additional impact to that defined for the assessment of the Array alone (section 8.11).
  2. The cumulative impact is predicted to be of local spatial extent, long term duration, continuous and of low reversibility within the construction and operation and maintenance phase. It is predicted that the impact will affect the receptors directly. The magnitude is therefore, considered to be low.
Sensitivity of the receptor
  1. The sensitivities of the benthic subtidal ecology IEFs are as previously described above for the assessment of the Array alone (see Table 8.19   Open ▸ and paragraphs 94 to 97).
  2. Overall, the dead man’s fingers IEF and sea tamarisk IEF are deemed to be of low vulnerability, medium recoverability, and regional value. The sensitivities of the receptors are, therefore, considered to be low.
  3. Overall, all other IEFs are deemed to be of high vulnerability, low recoverability, and regional to national value. The sensitivities of the receptors are, therefore, considered to be high.
Significance of effect
  1. Overall, for the dead man’s fingers IEF and sea tamarisk IEF, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be low. Based on Table 8.16   Open ▸ , the cumulative effect will, therefore, be of negligible to minor adverse significance. Based on expert judgement and adopting a precautionary approach, the cumulative effect has been concluded to be of minor adverse significance, which is not significant in EIA terms.
  2. For all other IEFs, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be high. As per Table 8.16   Open ▸ , the effect will, therefore, be of minor to moderate adverse significance. Given the low footprint of long term habitat loss and disturbance with respect to both the Tier 1 projects and the North Sea as a whole, and the widespread availability of alternative suitable habitat, the cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No benthic subtidal ecology mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 8.10) is not significant in EIA terms.

                        Tier 2

                        Construction and operation and maintenance phase
Magnitude of impact
  1. In addition to the Tier 1 projects, there was one Tier 2 project identified with potential for cumulative effects associated with this impact: Morven Offshore Wind Farm ( Table 8.23   Open ▸ ). As with the Array, infrastructure associated with long term habitat loss and disturbance includes foundations, scour protection, cable protection, and cable crossing protection, although further detail was not provided in the Scoping Report for Morven Offshore Wind Farm (Morven Offshore Wind Limited, 2023).
  2. For the Array, up to 19.27 km2 of long term habitat loss and disturbance may occur due to the installation of infrastructure, and an additional 778,464 m2 due to long term seabed disturbance from mooring lines and dynamic cabling ( Table 8.12   Open ▸ ). Given that Morven will be a fixed foundation Wind Farm and the Array is floating, it is not possible to determine which one will have a greater footprint of long term habitat loss and disturbance given the difference in wind turbine numbers between them. In the absence of a MDS for Morven Offshore Wind Farm, even if it is assumed that it will have a larger potential for long term habitat loss and disturbance, the cumulative magnitude of impact is still not expected to represent a material additional impact to that defined for the assessment of the Array alone (section 8.11). This is due to the low footprint of impact (2.25% of the Array benthic subtidal ecology study area) associated with this impact, in context of available habitat in the regional benthic subtidal ecology study area. Further, there will be no spatial overlap between long term habitat loss associated with the Array and Morven Offshore Wind Farm, thereby reducing the likelihood of a cumulative impact.
  3. The cumulative impact is predicted to be of local spatial extent, long term duration, continuous and of low reversibility within the construction and operation and maintenance phase. It is predicted that the impact will affect the receptors directly. The magnitude is therefore, considered to be low.
Sensitivity of the receptor
  1. The sensitivities of the benthic subtidal ecology IEFs are as previously described above for the assessment of the Array alone (see Table 8.19   Open ▸ and paragraphs 94 to 97).
  2. Overall, the dead man’s fingers IEF and sea tamarisk IEF are deemed to be of low vulnerability, medium recoverability, and regional value. The sensitivities of the receptors are, therefore, considered to be low.
  3. Overall, all other IEFs are deemed to be of high vulnerability, low recoverability, and regional to national value. The sensitivities of the receptors are, therefore, considered to be high.
Significance of effect
  1. Overall, for the dead man’s fingers IEF and sea tamarisk IEF, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be low. Based on Table 8.16   Open ▸ , the cumulative effect will, therefore, be of negligible to minor adverse significance. Based on expert judgement and adopting a precautionary approach, the cumulative effect has been concluded to be of minor adverse significance, which is not significant in EIA terms.
  2. For all other IEFs, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be high. For all other IEFs, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be high. As per Table 8.16   Open ▸ , the effect will, therefore, be of minor to moderate adverse significance. Given the low footprint of long term habitat loss and disturbance with respect to both the Tier 2 projects and the North Sea as a whole, and the widespread availability of alternative suitable habitat, the cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No benthic subtidal ecology mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 8.10) is not significant in EIA terms.

                        Tier 3

                        Construction and operation and maintenance phase
Magnitude of impact
  1. In addition to the Tier 1 and Tier 2 projects, there were six Tier 3 projects identified with potential for cumulative effects associated with this impact:
  • Morven Offshore Export Cable Corridor(s);
  • Bellrock Offshore Wind Farm;
  • Bowdun Offshore Wind Farm;
  • Campion Offshore Wind Farm;
  • Eastern Green Link 3; and
  • Eastern Green Link 4 ( Table 8.23   Open ▸ ).
  1. As these are Tier 3 projects, there are no Scoping Reports or EIA documents available in the public domain. Therefore, there is no information available on the impact that these Tier 3 projects will have on benthic subtidal ecology. The infrastructure associated with Bellrock, Bowdun, and Campion Offshore Wind Farms is likely to be similar to that of the Array, and those associated with Morven Offshore Export Cable Corridor(s) and Eastern Green Link 3 and 4 are likely to be similar to those discussed above for the Eastern Green Link 2 in the Tier 1 assessment (paragraphs 282 to 286).
  2. For the Array, up to 19.27 km2 of long term habitat loss and disturbance may occur due to the installation of infrastructure, and an additional 778,464 m2 due to long term seabed disturbance from mooring lines and dynamic cabling ( Table 8.12   Open ▸ ). The three Tier 3 offshore wind farms are either fully floating or containing some floating wind turbines, similar to the Array, which is a fully floating project. Therefore, given the higher number of wind turbines and energy generation capacity of the Array in comparison to the Tier 3 offshore wind farms ( Table 8.22   Open ▸ ), it is likely that the maximum footprint of long term habitat loss and disturbance of the Array will be larger than those of the Tier 3 projects.
  3. The cumulative spatial extent of this impact in the construction and operation and maintenance phase is likely to be small in relation to the whole Array benthic subtidal ecology study area. The cumulative magnitude of impact of the Tier 3 assessment is not expected to represent a material additional impact to that defined for the assessment of the Array alone (section 8.11).
  4. The cumulative impact is predicted to be of local spatial extent, long term duration, intermittent and low reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore, considered to be low.
Sensitivity of the receptor
  1. The sensitivities of the benthic subtidal ecology IEFs are as previously described above for the assessment of the Array alone (see Table 8.19   Open ▸ and paragraphs 94 to 97).
  2. Overall, the dead man’s fingers IEF and sea tamarisk IEF are deemed to be of low vulnerability, medium recoverability, and regional value. The sensitivities of the receptors are, therefore, considered to be low.
  3. Overall, all other IEFs are deemed to be of high vulnerability, low recoverability, and regional to national value. The sensitivities of the receptors are, therefore, considered to be high.
Significance of effect
  1. Overall, for the dead man’s fingers IEF and sea tamarisk IEF, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be low. Based on Table 8.16   Open ▸ , the cumulative effect will, therefore, be of negligible to minor adverse significance. Based on expert judgement and adopting a precautionary approach, the cumulative effect has been concluded to be of minor adverse significance, which is not significant in EIA terms.
  2. For all other IEFs, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be high. As per Table 8.16   Open ▸ , the effect will, therefore, be of minor to moderate adverse significance. Given the low footprint of long term habitat loss and disturbance with respect to both the Tier 3 projects and the North Sea as a whole, and the widespread availability of alternative suitable habitat, the cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No benthic subtidal ecology mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 8.10) is not significant in EIA terms.

Effects to benthic subtidal ecology due to EMF from subsea electrical cabling

  1. Within the operation and maintenance phase, there is potential for EMFs to be produced by the subsea electrical cabling associated with the Array and the other plans and projects. For the purposes of this EIA Report, this effect has been assessed using the tiered approach outlined in section 8.12.1. The plans and projects screened into the CEA for this impact and their respective Tiers are outlined in Table 8.23   Open ▸ .

                        Tier 1

                        Operation and maintenance phase
Magnitude of impact
  1. There were two Tier 1 projects identified with potential for cumulative effects associated with this impact:
  • the operation and maintenance phases of the Proposed offshore export cable corridor(s); and
  • the operation and maintenance phases of the Eastern Green Link 2 ( Table 8.23   Open ▸ ).
  1. At the time of writing this EIA Report, there was no Offshore EIA Report available for the Proposed offshore export cable corridor(s). However, given that these two Tier 1 projects are both HVDC subsea power cables, they will not include dynamic cabling, and will likely be entirely buried and protected where burial is not practicable. It can be assumed that for the Proposed offshore export cable corridor(s), as per the Array, cables will be buried to a depth of at least 0.4 m and cable protection will be used where not possible, and length will be approximately 400 km. As detailed in the assessment for the Array alone (section 8.11), cable burial and cable protection are common industry practice measures, which can reduce EMF levels in the benthic environment (Chapman et al., 2023, CSA Ocean Sciences Inc and Exponent, 2019, Gill et al., 2005, Gill et al., 2009, Hervé, 2021). For example, the Environmental Appraisal Report for the Eastern Green Link 2 presented modelling that a burial depth of 1 m reduced EMFs to background levels by 20 m distance from the cable, both vertically and horizontally (National Grid Electricity Transmission and Scottish Hydro Electric Transmission plc, 2022)
  2. The MDS for the Array accounts for up to 1,261 km of 66 kV inter-array cables, with up to 116 km within the water column (i.e. ‘dynamic cables’) and the rest buried at a minimum target depth of 0.4 m ( Table 8.12   Open ▸ ). There will also be up to 236 km of interconnector cables buried to a minimum target depth of 0.4 m ( Table 8.12   Open ▸ ). It has been estimated in the MDS that up to 20% of these buried cables will require cable protection, with up to 24 cable crossings also requiring protection.
  3. As presented in paragraph 142, EMF levels in the vicinity of subsea cables are influenced by a variety of design and installation factors, including distance between cables, cable sheathing, number of conductors, and internal cable configuration. Further, the intensity of EMF from subsea cables decreases at approximately the inverse square/power of the distance away from the cable (Hutchison et al., 2021). This attenuation is the same for buried, unburied, and dynamic cables (Hutchison et al., 2021). Therefore, the cumulative magnitude of impact with the Tier 1 projects is likely to be highly localised to within metres to tens of metres from cables.
  4. The cumulative impact is predicted to be of local spatial extent (given impacts are likely to be highly localised to cables), long term duration, continuous, and of high reversibility (as cables will be removed after the operation and maintenance phase). It is predicted that the impact will affect the receptors directly. This impact presents some measurable, long term minor alteration to the affected areas of seabed. The magnitude is therefore considered to be low.
Sensitivity of the receptor
  1. The sensitivities of the benthic subtidal ecology IEFs are as previously described above for the assessment of the Array alone (see paragraphs 145 to 150).
  2. Overall, on a precautionary basis in the absence of more information, all IEFs are deemed to be of medium vulnerability, medium recoverability, and regional to national value. The sensitivities of the receptors are, therefore, considered to be medium.
Significance of effect
  1. For all IEFs, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be medium. The cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No benthic subtidal ecology mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 8.10) is not significant in EIA terms.

                        Tier 2

                        Operation and maintenance phase
Magnitude of impact
  1. In addition to the Tier 1 projects, there was one Tier 2 project identified with potential for cumulative effects associated with this impact: Morven Offshore Wind Farm ( Table 8.23   Open ▸ ). The MDS for the Array accounts for up to 1,261 km of 66 kV inter-array cables, with up to 116 km within the water column (i.e. ‘dynamic cables’) and the rest buried at a minimum target  burial depth of 0.4 m ( Table 8.12   Open ▸ ). There will also be up to 236 km of interconnector cables buried to a minimum target burial depth of 0.4 m ( Table 8.12   Open ▸ ). Final target burial depths will be subject to a CBRA. It has been estimated in the MDS that up to 20% of these buried cables will require cable protection, with up to 24 cable crossings also requiring protection. As only a Scoping Report is available for the Morven Offshore Wind Farm, cable lengths, dimensions, and voltages are not currently available. However, given the scale of the project, it is likely that they will be of a similar extent to those of the Array, albeit with less dynamic cabling given that the Morven Offshore Wind Farm is not a floating project.
  2. As presented in paragraph 142 and within the Tier 1 assessment, EMF levels in the vicinity of subsea cables are influenced by a variety of design and installation factors, including distance between cables, cable sheathing, number of conductors, and internal cable configuration. As detailed in the assessment for the Array alone (section 8.11), cable burial and cable protection are common industry practice measures, which can reduce EMF levels in the benthic environment (Chapman et al., 2023, CSA Ocean Sciences Inc and Exponent, 2019, Gill et al., 2005, Gill et al., 2009, Hervé, 2021). Further, this was demonstrated in the Environmental Appraisal Report for the Eastern Green Link 2 in the Tier 1 assessment (paragraph 315), which found that burial at 1 m reduced EMFs to background levels by 20 m both vertically and horizontally (National Grid Electricity Transmission and Scottish Hydro Electric Transmission plc, 2022). Further, the intensity of EMF from subsea cables decreases at approximately the inverse square/power of the distance away from the cable (Hutchison et al., 2021). This attenuation is the same for buried, unburied, and dynamic cables (Hutchison et al., 2021). Therefore, the cumulative magnitude of impact with the Tier 2 projects is likely to be highly localised to within metres to tens of metres from cables.
  3. The cumulative impact is predicted to be of local spatial extent (given impacts are likely to be highly localised to cables), long term duration, continuous, and of high reversibility (as cables will be removed after the operation and maintenance phase). It is predicted that the impact will affect the receptors directly. This impact presents some measurable, long term minor alteration to the affected areas of seabed. The magnitude is therefore considered to be low.
Sensitivity of the receptor
  1. The sensitivities of the benthic subtidal ecology IEFs are as previously described above for the assessment of the Array alone (see paragraphs 145 to 150).
  2. Overall, on a precautionary basis in the absence of more information, all IEFs are deemed to be of medium vulnerability, medium recoverability, and regional to national value. The sensitivities of the receptors are, therefore, considered to be medium.
Significance of effect
  1. For all IEFs, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be medium. The cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No benthic subtidal ecology mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 8.10) is not significant in EIA terms.

                        Tier 3

                        Operation and maintenance phase
Magnitude of impact
  1. In addition to the Tier 1 and Tier 2 projects, there were six Tier 3 projects identified with potential for cumulative effects associated with this impact:
  • Morven Offshore Export Cable Corridor(s);
  • Bellrock Offshore Wind Farm;
  • Bowdun Offshore Wind Farm;
  • Campion Offshore Wind Farm;
  • Eastern Green Link 3; and
  • Eastern Green Link 4 ( Table 8.23   Open ▸ ).
  1. The MDS for the Array accounts for up to 1,261 km of 66 kV inter-array cables, with up to 116 km within the water column (dynamic cables) and the rest buried at a minimum target depth of 0.4 m ( Table 8.12   Open ▸ ). There will also be up to 236 km of interconnector cables buried to a minimum target depth of 0.4 m ( Table 8.12   Open ▸ ). It has been estimated in the MDS that up to 20% of these buried cables will require cable protection, with up to 24 cable crossings also requiring protection. As there is no project specific information regarding cable lengths, dimension, and voltages currently available for the Tier 3 projects. However, given the scale of the projects, it is likely that the Bellrock, Bowdun, and Campion Offshore Wind Farms will be of a similar extent to those of the Array and Morven Offshore Wind Farm. Similarly, the Morven Offshore Export Cable Corridor(s) and Eastern Green Link 3 and 4 are likely to be similar to as described in paragraph 315 for the Eastern Green Link 2.
  2. As presented in paragraph 142 and within the Tier 1 assessment, EMF levels in the vicinity of subsea cables are influenced by a variety of design and installation factors, including distance between cables, cable sheathing, number of conductors, and internal cable configuration. As detailed in the assessment for the Array alone (section 8.11), cable burial and cable protection are common industry practice measures, which can reduce EMF levels in the benthic environment (Chapman et al., 2023, CSA Ocean Sciences Inc and Exponent, 2019, Gill et al., 2005, Gill et al., 2009, Hervé, 2021). Further, this was demonstrated in the Environmental Appraisal Report for the Eastern Green Link 2 in the Tier 1 assessment (paragraph 315), which found that burial at 1 m reduced EMFs to background levels by 20 m both vertically and horizontally (National Grid Electricity Transmission and Scottish Hydro Electric Transmission plc, 2022). Further, the intensity of EMF from subsea cables decreases at approximately the inverse square/power of the distance away from the cable (Hutchison et al., 2021). This attenuation is the same for buried, unburied, and dynamic cables (Hutchison et al., 2021). Therefore, the cumulative magnitude of impact with the Tier 3 projects is likely to be highly localised to within metres to tens of metres from cables.
  3. The cumulative impact is predicted to be of local spatial extent (given impacts are likely to be highly localised to cables), long term duration, continuous, and of high reversibility (as cables will be removed after the operation and maintenance phase). It is predicted that the impact will affect the receptors directly. This impact presents some measurable, long term minor alteration to the affected areas of seabed. The magnitude is therefore considered to be low.
Sensitivity of the receptor
  1. The sensitivities of the benthic subtidal ecology IEFs are as previously described above for the assessment of the Array alone (see paragraphs 145 to 150).
  2. Overall, on a precautionary basis in the absence of more information, all IEFs are deemed to be of medium vulnerability, medium recoverability, and regional to national value. The sensitivities of the receptors are, therefore, considered to be medium.
Significance of effect
  1. For all IEFs, the cumulative magnitude of the impact is deemed to be low, and the sensitivities of the receptors are considered to be medium. The cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No benthic subtidal ecology mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 8.10) is not significant in EIA terms.

Colonisation of Hard Substrates

  1. The introduction of the hard substrates at the Array and the other projects may potentially affect the established benthic community by providing new habitat and ecosystem function. Hard substrates include foundations, scour protection, cable protection, cable crossing protection, and junction boxes. These artificial hard structures are expected to be colonised by a range of organisms, which could lead to local biodiversity increases. For the purposes of this EIA Report, this effect has been assessed using the tiered approach outlined in section 8.12.1. The plans and projects screened into the CEA for this impact and their respective Tiers are outlined in Table 8.23   Open ▸ .

                        Tier 1

                        Operation and maintenance phase
Magnitude of impact
  1. There were two Tier 1 projects identified with potential for cumulative effects associated with this impact:
  • the operation and maintenance phases of the Proposed offshore export cable corridor(s); and
  • the operation and maintenance phases of the Eastern Green Link 2 ( Table 8.23   Open ▸ ).
  1. At the time of writing this EIA Report, there was no Offshore EIA Report available for the Proposed offshore export cable corridor(s). However, given that these two projects are both HVDC subsea power cables, the area of hard structures installed will be of a significantly lesser extent to that represented by the MDS for the Array alone, which is up to 19.27 km2 on the seabed and an unquantified area within the water column ( Table 8.26   Open ▸ ). The cumulative magnitude of impact of the Array with the Tier 1 projects is therefore not expected to represent a material additional impact to that defined for the assessment of the Array alone (section 8.11).
  2. Within the Environmental Appraisal Report for the Eastern Green Link 2, a total footprint of up to 2.20 km2 of artificial hard substrates was predicted to be installed (see Table 8.26   Open ▸ ), comprised of up to 2 km2 of rock berm and up to 0.2 km2 of pipeline and cable crossing protection (National Grid Electricity Transmission and Scottish Hydro Electric Transmission plc, 2022). For the Proposed offshore export cable corridor(s), the area of installed hard substrate is expected to be similar to that of the Eastern Green Link 2, given the similarity in nature of the two Tier 1 projects. The cumulative spatial extent of this impact in the operation and maintenance phase therefore likely to be small in relation to the whole Array benthic subtidal ecology study area.

 

Table 8.26:
Cumulative Footprint of Hard Substrates Installed (km2) for the Tier 1 Projects

Table 8.26: Cumulative Footprint of Hard Substrates Installed (km2) for the Tier 1 Projects

 

  1. Further, as per paragraph 156, it expected that these artificial hard substrates will be colonised by epifaunal species local to the Array benthic subtidal ecology study area. However, this impact will represent a shift in the baseline seabed conditions from soft to hard substrate in the areas where the infrastructure is installed. This could result in beneficial effects, such as increased biodiversity and potential reef effects (Bender et al., 2020, De Mesel et al., 2015, Karlsson et al., 2022, Lindeboom et al., 2011, Mavraki et al., 2020).
  2. Although this impact is expected to be beneficial in terms of increasing biodiversity and enhancing reef effects, the installation of hard structures will result in habitat loss for the Offshore subtidal sands and gravels IEF and the Subtidal sands and gravels IEF. However, given the wide availability of both habitats over the Array benthic subtidal ecology study area and regional benthic subtidal ecology study area, and the localised nature of this impact, this impact is only expected to result in minor loss or alteration to the soft bottom sediments of these IEFs as a whole. The cumulative magnitude of impact of the Array with the Tier 1 projects is not expected to represent a material additional impact to that defined for the assessment of the Array alone (section 8.11).
  3. Overall, for all IEFs, the cumulative impact is predicted to be of local spatial extent, long term duration, continuous, and low reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore, considered to be low.
Sensitivity of the receptor
  1. The sensitivities of the benthic subtidal ecology IEFs are as previously described above for the assessment of the Array alone (see Table 8.19   Open ▸ and paragraphs 159 to 165).
  2. Overall, the dead man’s fingers IEF and sea tamarisk IEF are deemed to be of low vulnerability, medium recoverability, and regional value. The sensitivities of the receptors are, therefore, considered to be low.
  3. Overall, all other IEFs are deemed to be of high vulnerability, low recoverability, and national and regional value. The sensitivities of the receptors are, therefore, considered to be high.
Significance of effect
  1. Overall, for the dead man’s fingers IEF and sea tamarisk IEF, the cumulative magnitude of impact is deemed to be low, and the sensitivities of the receptors are considered to be low. Based on Table 8.16   Open ▸ , the cumulative effect will, therefore, be of negligible to minor beneficial significance. Based on expert judgement and adopting a precautionary approach, the cumulative effect has been concluded to be of minor beneficial significance, which is not significant in EIA terms.
  2. For all other IEFs, the cumulative magnitude of impact is deemed to be low, and the sensitivities of the receptors are considered to be high. As per Table 8.16   Open ▸ , the effect will, therefore, be of minor to moderate significance. The potential for increased biodiversity as a result of this impact could be considered to be beneficial, however introduction of hard substrates would represent some small-scale habitat loss for these IEFs. Given the low footprint of long term habitat loss with respect to the Tier 1 projects and the North Sea as a whole, and the widespread availability of alternative suitable habitat, the cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No benthic subtidal ecology mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 8.10) is not significant in EIA terms.

                        Tier 2

                        Operation and maintenance phase
Magnitude of impact
  1. In addition to the Tier 1 projects, there was one Tier 2 project identified with potential for cumulative effects associated with this impact: Morven Offshore Wind Farm ( Table 8.23   Open ▸ ). As with the Array, hard substrates installed at the Morven Offshore Wind Farm include foundations, scour protection, and cable protection (Morven Offshore Wind Limited, 2023).
  2. For the Array, hard structures will be installed on the seabed and in the water column ( Table 8.12   Open ▸ ). Given that Morven will be a fixed foundation wind farm and the Array is floating, it is not possible to determine which one will have a greater footprint of hard substrate, given the difference in wind turbine numbers between them. In the absence of a MDS for Morven Offshore Wind Farm, even if it is assumed that it will have a larger footprint, the cumulative magnitude of impact is still not expected to represent a material additional impact to that defined for the assessment of the Array alone (section 8.11). This is due to the low footprint of impact (2.25% of the Array benthic subtidal ecology study area) associated with this impact, in context of available habitat in the regional benthic subtidal ecology study area. Further, there will be no spatial overlap between installed hard structures associated with the Array and Morven Offshore Wind Farm, thereby reducing the likelihood of a cumulative impact.
  3. As per paragraphs 342 to 344 for the Tier 1 assessment, it is expected that the hard substrates will be colonised by local epifauna, but will still represent a shift in the baseline conditions from soft sediments to hard substrate. However, this is expected to have beneficial effects, such as increased biodiversity and reef effects (Bender et al., 2020, De Mesel et al., 2015, Karlsson et al., 2022, Lindeboom et al., 2011, Mavraki et al., 2020). Although a shift from soft sediments to hard structures will constitute habitat loss for the Offshore subtidal sands and gravels IEF and the Subtidal sands and gravels IEF, the localised nature of the footprints is likely to only result in a minor loss to the soft bottom substrates in the Array benthic subtidal ecology study area and less so within the regional benthic subtidal ecology study area.
  4. Overall, for all IEFs, the cumulative impact is predicted to be of local spatial extent, long term duration, continuous, and low reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore, considered to be low.
Sensitivity of the receptor
  1. The sensitivities of the benthic subtidal ecology IEFs are as previously described above for the assessment of the Array alone (see Table 8.19   Open ▸ and paragraphs 159 to 165).
  2. Overall, the dead man’s fingers IEF and sea tamarisk IEF are deemed to be of low vulnerability, medium recoverability, and regional value. The sensitivities of the receptors are, therefore, considered to be low.
  3. Overall, all other IEFs are deemed to be of high vulnerability, low recoverability, and national and regional value. The sensitivities of the receptors are, therefore, considered to be high.
Significance of effect
  1. Overall, for the dead man’s fingers IEF and sea tamarisk IEF, the cumulative magnitude of impact is deemed to be low, and the sensitivities of the receptors are considered to be low. Based on Table 8.16   Open ▸ , the cumulative effect will, therefore, be of negligible to minor beneficial significance. Based on expert judgement and adopting a precautionary approach, the cumulative effect has been concluded to be of minor beneficial significance, which is not significant in EIA terms.
  2. For all other IEFs, the cumulative magnitude of impact is deemed to be low, and the sensitivities of the receptors are considered to be high. As per Table 8.16   Open ▸ , the effect will, therefore, be of minor to moderate significance. The potential for increased biodiversity as a result of this impact could be considered to be beneficial, however introduction of hard substrates would represent some small-scale habitat loss for these IEFs. Given the low footprint of long term habitat loss with respect to the Tier 2 projects and the North Sea as a whole, and the widespread availability of alternative suitable habitat, the cumulative effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
  1. No benthic subtidal ecology mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 8.10) is not significant in EIA terms.

                        Tier 3

                        Operation and maintenance phase
Magnitude of impact
  1. In addition to the Tier 1 and Tier 2 projects, there were six Tier 3 projects identified with potential for cumulative effects associated with this impact:
  • Morven Offshore Export Cable Corridor(s);
  • Bellrock Offshore Wind Farm;
  • Bowdun Offshore Wind Farm;
  • Campion Offshore Wind Farm;
  • Eastern Green Link 3; and
  • Eastern Green Link 4 ( Table 8.23   Open ▸ ).
  1. As these are Tier 3 projects, there are no Scoping Reports or EIA documents available in the public domain. Therefore, there is no information available on the impact that these Tier 3 projects will have on benthic subtidal ecology. The extent of hard substrates associated with Bellrock, Bowdun, and Campion Offshore Wind Farms is likely to be similar to that of the Array, and those associated with Morven Offshore Export Cable Corridor(s) and Eastern Green Link 3 and 4 likely to be similar to those discussed above for the Eastern Green Link 2 in the Tier 1 assessment (paragraphs 339 to 344).
  2. For the Array, hard structures will be installed on the seabed and in the water column ( Table 8.12   Open ▸ ). The three Tier 3 offshore wind farms are either fully floating or containing some floating wind turbines, similar to the Array which is a fully floating project. Therefore, given the higher number of wind turbines and energy generation capacity of the Array in comparison to the Tier 3 offshore wind farms ( Table 8.22   Open ▸ ), it is likely that the maximum footprint of hard structures installed for the Array will be larger than those of the Tier 3 projects. The cumulative magnitude of impact of the Tier 3 projects is not expected to represent a material additional impact to that defined for the assessment of the Array alone (section 8.11).
  3. As per paragraphs 342 to 344 for the Tier 1 assessment, it is expected that the hard substrates will be colonised by local epifauna, but will still represent a shift in the baseline conditions from soft sediments to hard substrate. However, this is expected to have beneficial effects, such as increased biodiversity and reef effects (Bender et al., 2020, De Mesel et al., 2015, Karlsson et al., 2022, Lindeboom et al., 2011, Mavraki et al., 2020). Although a shift from soft sediments to hard structures will constitute habitat loss for the Offshore subtidal sands and gravels IEF and the Subtidal sands and gravels IEF, the localised nature of the footprints is likely to only result in a minor loss to the soft bottom substrates in the Array benthic subtidal ecology study area and less so within the regional benthic subtidal ecology study area.  
  4. Overall, for all IEFs, the cumulative impact is predicted to be of local spatial extent, long term duration, continuous, and low reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore, considered to be low.