Tier 2
Site preparation and construction phase
Magnitude of impact
450. In addition to the Tier 1 projects, three Tier 2 projects were identified with potential for cumulative effects associated with this impact:
- Morven Offshore Wind Farm (site preparation and construction phases);
- Cenos Offshore Wind Farm (construction); and
- Salamander Offshore Wind Farm (construction) ( Table 9.30 Open ▸ ).
451. The MDS for the Array’s construction is given in Table 9.13 Open ▸ and summarised in paragraph 438, which considers the greatest effect from underwater noise on fish and shellfish IEFs, based on the greatest hammer energy.
452. Currently, there is no EIA Report available for the Morven Offshore Wind Farm, although piling activities during the construction phase are expected to be similar in nature to that of the Array. Although information on hammer energies and piling durations are not available for the Morven Offshore Wind Farm, the impact is likely to be of medium term duration, with noise generation being intermittent during the construction phase.
453. No EIA Report is available for the Cenos Offshore Wind Farm, although the Scoping Report indicates that the development will encompass 70 to 100 floating offshore wind turbine foundations each fitted with up to six mooring points (Flotation Energy, 2023). A range of anchoring options are under consideration for the floating foundations, including piled anchors. A single offshore fixed foundation platform comprising up to 12 pin piles, each of 3 m diameter is also proposed to form an Electrical Hub. UXO clearance may also be required should any potential UXO be identified during pre-construction geophysical surveys. Seabed preparation and construction is expected to be undertaken over a period of four years. No specific details are available regarding maximum piling durations, or the quantity of UXO clearance considered for assessment. Based upon the scale of the Cenos Offshore Wind Farm, which is smaller than the Array, these project aspects are therefore expected to be of smaller magnitude than the Array. The impact is considered to be of medium term duration, with noise generation being intermittent during the construction phase, and reversible upon completion of construction.
454. No EIA Report is available for the Salamander Offshore Wind Farm, however the Scoping Report states that the project will comprise up to seven floating offshore wind turbine foundations with several floating foundation design options under consideration (Simply Blue Energy (Scotland) Ltd., 2023). A number of anchoring mechanisms are also under consideration (including piled anchors), with between three and nine mooring lines affixed to each floating structure. UXO clearance may also be required should any potential UXO be identified during pre-construction geophysical surveys, but this will be subject to a separate Marine Licence Application. No specific details are available regarding maximum piling durations, or the quantity of UXO clearance considered for assessment, however offshore construction is expected to be undertaken over two six month phases within a two year construction programme. The Salamander Offshore Wind Farm is of a considerably smaller scale than the Array and other Tier 1 and 2 projects considered with regards to effects from underwater noise. The impact is considered to be of medium term duration, with noise generation being intermittent during the construction phase, and reversible upon completion of construction.
455. The cumulative impact of underwater noise on fish and shellfish ecology receptors during the construction phase is predicted to be of regional spatial extent, medium term duration, intermittent and of high reversibility. It is predicted that the impact may affect the receptor directly. The magnitude is therefore considered to be low.
Sensitivity of receptor
456. The sensitivities of the fish and shellfish IEFs are as previously described above for the assessment of the Array alone (paragraphs 168 et seq.).
Significance of effect
457. For most marine fish, diadromous fish, and shellfish, the cumulative magnitude of the impact is deemed to be low, and the sensitivity of most marine fish IEFs is considered low. The effect will, therefore, be of minor significance, which is not significant in EIA terms.
458. For herring, the cumulative magnitude of the impact is deemed to be low, and the sensitivity of herring is considered to be medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
459. No secondary mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.
Tier 3
Site preparation and construction phase
Magnitude of impact
460. In addition to the Tier 1 and Tier 2 projects, seven Tier 3 projects were 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;
- unknown phases of Cedar;
- unknown phases of Flora; and
- unknown phases of Aspen ( Table 9.30 Open ▸ ).
461. As these are Tier 3 projects, there are no Scoping Reports in the public domain. Therefore, there is no information available on the impact that these Tier 3 projects will have on fish and shellfish ecology, though piling activities during the construction phase are expected to be similar in nature as that of the Array. Although information on hammer energies, piling durations, and UXO clearance requirements are not available for the Tier 3 projects, the impact is likely to be of medium term duration, with noise being intermittent during the construction phase.
462. The maximum duration of the offshore construction phase for the Array is up to eight years (2031 to 2038). There is currently no information available for the Cedar, Flora and Aspen projects; therefore, a precautionary assumption has been made that these may have overlapping piling phases with the Array ( Table 9.30 Open ▸ ). Therefore, there may be minimal overlap between the site preparation and construction activities of the Array and that of the Tier 3 projects.
463. The cumulative impact of underwater noise on fish and shellfish ecology receptors during the construction phase is predicted to be of regional spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact may affect the receptor directly. The magnitude is therefore considered to be low.
Sensitivity of receptor
464. The sensitivities of the fish and shellfish IEFs are as previously described above for the assessment of the Array alone (paragraphs 168 et seq.).
Significance of effect
465. For most marine fish, diadromous fish, and shellfish, the cumulative magnitude of the impact is deemed to be low, and the sensitivity of most marine fish IEFs is considered low. The effect will, therefore, be of minor significance, which is not significant in EIA terms.
466. For herring, the cumulative magnitude of the impact is deemed to be low, and the sensitivity of herring is considered to be medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
Further mitigation and residual effect
467. No secondary mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.
Effects to fish and shellfish Ecology receptors due to EMF from subsea electrical cabling
468. Within the operation and maintenance phases, 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 Array EIA Report, this impact has been assessed using the tiered approach outlined in section 9.12.1. The plans and projects screened into the CEA for this impact and their respective tiers are outlined in Table 9.31 Open ▸ .
Tier 1
Operation and maintenance phase
Magnitude of impact
- Proposed offshore export cable corridor(s); and
- Eastern Green Link 2 ( Table 9.31 Open ▸ ).
471. The MDS for the Array accounts for up to 1,261 km of 66 kV inter-array cables, with up to 116 km as ‘dynamic cables’ in the water column, and the rest buried at a depth of at least 0.4 m ( Table 9.13 Open ▸ ). There will also be up to 236 km of interconnector cables buried to a minimum depth of 0.4 m and maximum depth of 3 m ( Table 9.13 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. The Eastern Green Link 2 project has two 436 km HDVC cables, totalling 872 km of subsea cabling which may emit EMFs (National Grid Electricity Transmission and Scottish National Power Transmission, 2022), which extends outside the fish and shellfish ecology study area.
472. The 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.
473. The cumulative impact is predicted to be of local spatial extent, 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 receptor directly. This impact may therefore represent some measurable, long term minor alteration to fish and shellfish behaviour in the vicinity of cables buried beneath the seabed or in the water column. The magnitude is therefore considered to be low.
Sensitivity of receptor
474. The sensitivities of the fish and shellfish IEFs are as previously described above for the assessment of the Array alone (paragraphs 278 et seq.).
Significance of effect
475. For most fish and shellfish IEF species, the cumulative magnitude of the impact 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.
476. For European lobster, Nephrops, edible crab and elasmobranchs, the cumulative magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
477. For diadromous fish, the cumulative magnitude of the impact 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 significance, which is not significant in EIA terms.
Further mitigation and residual effect
478. No secondary mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.
Tier 2
Operation and maintenance phase
Magnitude of impact
479. In addition to the Tier 1 projects, there was one Tier 2 project identified with potential for cumulative effects associated with this impact: the operation and maintenance phase of the Morven Offshore Wind Farm ( Table 9.30 Open ▸ ). The MDS for the Array is summarised in paragraph 471. 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.
480. As presented in paragraph 120 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. 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.
481. The cumulative impact is predicted to be of local spatial extent, long term duration, continuous, and of high reversibility (EMF emissions will only occur when cables are operational during the operation and maintenance phase). It is predicted that the impact will affect the receptor directly. This impact may therefore represent some measurable, long term minor alteration to fish and shellfish behaviour in the vicinity of cables buried beneath the seabed or in the water column. The magnitude is therefore considered to be low.
Sensitivity of receptor
482. The sensitivities of the fish and shellfish IEFs are as previously described above for the assessment of the Array alone (paragraphs 278 et seq.).
Significance of effect
483. For most fish and shellfish IEF species, the cumulative magnitude of the impact 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.
484. For European lobster, Nephrops, edible crab and elasmobranchs, the cumulative magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
485. For diadromous fish, the cumulative magnitude of the impact 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 significance, which is not significant in EIA terms.
Further mitigation and residual effect
486. No secondary mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.
Tier 3
Operation and maintenance phase
Magnitude of impact
487. 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 9.30 Open ▸ ).
488. The MDS for the Array accounts for up to 1,261 km of 66 kV inter-array cables, with up to 116 km as ‘dynamic cables’ in the water column, and the rest buried to a minimum target depth of 0.4 m (subject to CBRA) ( Table 9.13 Open ▸ ). There will also be up to 236 km of interconnector cables buried to a minimum target depth of 0.4 m (subject to CBRA) ( Table 9.13 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 published EIA, 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 EMF related impacts associated with the Bellrock, Bowdun, and Campion Offshore Wind Farms will be of a similar in nature and extent to those of the Array and Morven Offshore Wind Farm.
489. Impacts associated with the Morven Offshore Export Cable Corridor(s) and Eastern Green Link 3 and 4 are likely to be similar to those assessed in Tier 1 for the Proposed offshore export cable corridor(s) and Eastern Green Link 2 (see paragraphs 469 et seq.).
490. As presented 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. 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.
491. The cumulative impact is predicted to be of local spatial extent, 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 receptor directly. This impact may therefore represent some measurable, long term minor alteration to fish and shellfish behaviour in the vicinity of cables buried beneath the seabed or in the water column. The magnitude is therefore considered to be low.
Sensitivity of receptor
492. The sensitivities of the fish and shellfish IEFs are as previously described above for the assessment of the Array alone (paragraphs 278 et seq.).
Significance of effect
493. For most fish and shellfish IEF species, the cumulative magnitude of the impact 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.
494. For European lobster, Nephrops, edible crab and elasmobranchs, the cumulative magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be low. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
495. For diadromous fish, the cumulative magnitude of the impact 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 significance, which is not significant in EIA terms.
Further mitigation and residual effect
496. No secondary mitigation is considered necessary because the likely cumulative effect in the absence of further mitigation (beyond the designed in measures outlined in section 9.10) is not significant in EIA terms.