12.5 Information to Inform Assessment of Adverse Effects on Integrity
12.5.1 Tweed Estuary SAC
European site information
351 The Tweed Estuary SAC is located 46.5 km from the Proposed Development array area and 29 km from the Proposed Development export cable corridor. The site, located in Northumberland, encompasses the Tweed Estuary, a long and narrow estuary discharging into the North Sea. The site is designated for Annex I habitats and Annex II species, including diadromous fish species river lamprey and sea lamprey. The condition of the SAC’s features had not been assessed at the time of writing.
352 Further information on this European site is presented in appendix A.
Conservation objectives
353 The conservation objectives for the Tweed Estuary SAC have been developed by Natural England and apply to the site and the individual species and/or assemblage of species for which the site has been classified. These high-level objectives are to ensure that, subject to natural change, the integrity of the site is maintained or restored as appropriate, and that the site contributes to achieving the favourable conservation status of its qualifying features, by maintaining or restoring:
- The extent and distribution of qualifying natural habitats and habitats of the qualifying species;
- The structure and function (including typical species) of qualifying natural habitats;
- The structure and function of the habitats of the qualifying species;
- The supporting processes on which qualifying natural habitats and the habitats of qualifying species rely;
- The populations of each of the qualifying species; and
- The distribution of qualifying species within the site.
354 A condition assessment has not yet been undertaken for this site.
355 Supplementary advice on conservation objectives, last updated on the 13 March 2020, provides the site-specific attributes and targets specific to the sea lamprey and river lamprey features of the site. These supplementary attributes and targets are considered in the assessments below and are provided for reference in appendix A.
Features and effects for assessment
357 Table 12.16 Open ▸ summarises the LSEs that were identified for the Annex II diadromous fish species features of the Tweed Estuary SAC and the features and effects which have been considered in the assessment of Adverse Effects on Integrity for this site.
Table 12.16: Summary of Features and Effects Considered in the Assessment of Adverse Effects on Integrity for the Tweed Estuary SAC
Construction and decommissioning
Injury and/or disturbance from underwater noise and vibration
Sea lamprey
358 As discussed in section 12.3.1, pile driving during the installation of foundations for wind turbines and OSP/Offshore convertor station platforms within the Proposed Development array area and UXO clearance pre-construction, have the potential to lead to injury and/or disturbance to sea lamprey due to underwater noise impacts. Sea lamprey, which are considered to be a Group 1 fish in terms of hearing sensitivity, has relatively low sensitivity to underwater noise.
359 The results of project specific modelling, as discussed in paragraphs 283 to 287, indicate that injury and/or mortality to sea lamprey can be expected only for individuals within approximately 138 m of the piling. A temporary hearing impairment (i.e. TTS), from which animals will recover, was predicted to occur out to a maximum range of 4.161 km for Group 1 species from piling operations. For concurrent piling, whilst mortality and recoverable injury ranges were unchanged (i.e. 138 m for Group 1 species) TTS ranges for Group 1 fish (sea lamprey) may increase up to 7.1 km from the piling location for the maximum energy scenario ( Table 12.7 Open ▸ ).
360 However, as discussed in paragraph 286, the risk of fish injury will be considerably lower due to hammer energies being considerably lower than the absolute maximum modelled. Additionally, the expected fleeing behaviour of fish from the area affected when exposed to high levels of noise and the soft start procedure, which will be employed for all piling, mean that fish will have sufficient time to vacate the areas where injury may occur prior to noise levels reaching that level.
361 As discussed in paragraph 268, pre-construction UXO clearance may also lead to injury and/or disturbance to sea lamprey. Detonation of UXO would represent a short term (i.e. seconds) increase in underwater noise which will be elevated to levels which may result in injury or behavioural effects on fish species. The results of project specific modelling, discussed in paragraphs 288 to 289, indicate that mortality/mortal injury for all fish would occur within a range of 30-45 m from the source following low order detonation (the dominant method of UXO detonation). Higher order detonations may also occur if low order is not successful or unintentionally as part of the low order process. In this case mortality would occur within 410-680 m of the noise source.
362 However, due to the nature of diadromous fish species such as sea lamprey being highly mobile and tending to only utilise the environment within the Proposed Development fish and shellfish ecology study area to pass through during migration, significant mortality of sea lamprey is not expected. Sea lamprey spend most of their adult life at sea and it has been suggested that they are widely dispersed at sea, possibly feeding in deeper offshore waters (OSPAR Commission, 2009). They are rarely captured in coastal and estuarine waters, suggesting that they are solitary hunters and widely dispersed at sea as opposed to remaining in coastal waters (Marine Scotland Directorate, 2019).
363 In contrast, behavioural effects (including startle response, disruption of feeding or avoidance of an area) in response to piling are expected over much larger ranges of 10 km to 20 km, as discussed in paragraphs 295 to 296. Due to the distance between the Proposed Development array area and the coast, these behavioural impacts are unlikely to cause barrier effects between the Proposed Development fish and shellfish ecology study area and the migration routes of sea lamprey along the east coast of Scotland, due to the relatively small area around piling events where noise levels are high enough to cause behavioural responses (as shown in Figure 12.1 Open ▸ and Figure 12.2 Open ▸ ).
364 Given the above, the population of sea lamprey will be maintained as a viable component of the site and the extent and distribution of sea lamprey will not be reduced. The Proposed Development does not overlap with the Tweed Estuary SAC so the extent and distribution and the structure and function of sea lamprey habitat will be unaffected. Therefore, there will be no significant adverse effects on the qualifying Annex II diadromous fish feature, sea lamprey of the Tweed Estuary SAC as a result of underwater noise impacts during the construction and decommissioning phases.
River lamprey
365 River lamprey is, like sea lamprey, classified as a Group 1 fish for the purposes of hearing sensitivity and as such the assessment for sea lamprey presented above in paragraphs 358 to 363 also applies to river lamprey. In addition, due to river lamprey’s preference for estuarine waters, it is unlikely that river lamprey will interact with the Proposed Development.
366 The population of river lamprey will be maintained as a viable component of the site and the extent and distribution of river lamprey will not be reduced. The Proposed Development does not overlap with the Tweed Estuary SAC therefore the extent and distribution of river lamprey habitat will be unaffected. There will, therefore, be no significant adverse effects on the qualifying Annex II diadromous fish feature, river lamprey of the Tweed Estuary SAC, as a result of underwater noise impacts during the construction and decommissioning phases.
Conclusion
367 The assessment has concluded that there is no direct spatial overlap between the Proposed Development and the Tweed Estuary SAC, so the extent and distribution and structure and function of supporting habitats of the qualifying species will not be reduced. Similarly, the supporting processes on which the habitats of the qualifying species rely will be unaffected. Given the relatively low sensitivity of the qualifying species to underwater noise impacts, the low probability of individuals being present within the ZoI of underwater noise impacts at the time of piling and UXO activities, the use of soft start procedures allowing individuals to flee areas where they may be exposed to noise levels that would lead to injury, and the absence of any barrier effects to migration of adult or juvenile diadromous species, the populations and the distribution of the qualifying species will be maintained.
368 Therefore, it can be concluded that there is no risk of an adverse effect on the integrity of the Tweed Estuary SAC as a result of underwater noise impacts with respect to construction and decommissioning of the Proposed Development acting alone.
Increased suspended sediment concentrations and associated sediment deposition
Sea lamprey
369 As detailed in section 12.3.2, increases in SSC and associated sediment deposition during construction and decommissioning have the potential to cause behavioural responses (avoidance) in migratory fish. This in turn has the potential to result in barriers to migration.
370 The results of project specific modelling summarised in section 12.3.2, indicate that increases in SSC are predicted to be temporary, short-lived and at levels well below those naturally experienced in estuarine environments. Sea lamprey are expected to have some tolerance to naturally high SSC, given their migration routes typically pass through estuarine habitats which have background SSC which are considerably higher than those expected in the offshore areas of the Proposed Development northern North Sea fish and shellfish ecology study area. As such, no barriers to the migratory patterns of sea lamprey are expected.
River lamprey
372 River lamprey will have a similar sensitivity to SSC as sea lamprey therefore the assessment for sea lamprey, presented in paragraphs 369 to 370, is applicable to river lamprey.
373 In addition, due to river lamprey’s preference for estuarine waters, it is unlikely that river lamprey will interact with SSC and sediment deposition arising from the construction and decommissioning of the Proposed Development.
374 Given the above, the population of river lamprey will be maintained as a viable component of the site and the extent and distribution of river lamprey will not be reduced. The Proposed Development does not overlap with the Tweed Estuary SAC so the extent and distribution and the structure and function of river lamprey habitat will be unaffected. Therefore, there will be no significant adverse effects on the qualifying Annex II diadromous fish feature, river lamprey, of the Tweed Estuary SAC, as a result of increased SSC and sediment deposition impacts during the construction and decommissioning phases.
Conclusion
375 The assessment has concluded that there is no direct spatial overlap between the Proposed Development and the Tweed Estuary SAC, and so the extent and distribution and structure and function of the supporting habitats of the qualifying species will not be reduced. Similarly, the supporting processes on which the habitats of the qualifying species rely will be unaffected. Given that any increases in SSC are predicted to be temporary, short lived and lower than estuarine levels, there will be no barriers to the migration of the qualifying species. As such, the population and the distribution of the qualifying species will be maintained.
376 Therefore, it can be concluded that there is no risk of an adverse effect on the integrity of the Tweed Estuary SAC as a result of increased SSC and sediment deposition impacts with respect to construction and decommissioning of the Proposed Development acting alone.
Operation and maintenance
EMF from subsea electrical cabling
Sea lamprey
377 As discussed in section 12.4.1, the emission of localised EMFs from the operation of inter-array, interconnector and offshore export cables could potentially interfere with the navigation of diadromous fish species such as sea lamprey. However, the limited available evidence suggests that disturbance to sea lamprey from EMF occurs at intensities considerably higher than those expected from AC subsea cables (see Table 12.14 Open ▸ ). Due to sea lamprey’s parasitic nature at sea, attaching to the body of larger, highly mobile species, well above the seafloor also means that they can be expected to rarely be exposed to the EMF at the lowest levels from AC undersea power cables buried in the seafloor. Therefore, any impacts would be localised and transient.
378 Given the above, the population of sea lamprey will be maintained as a viable component of the site and the extent and distribution of sea lamprey will not be reduced., The Proposed Development does not overlap with the Tweed Estuary SAC so the extent and distribution and the structure and function of sea lamprey habitat will be unaffected. Therefore, there will be no significant adverse effects on the qualifying Annex II diadromous fish feature, sea lamprey of the Tweed Estuary SAC as a result of EMF from subsea electrical cabling impacts during the operation and maintenance phase.
River lamprey
379 River lamprey will have a similar sensitivity to EMF as sea lamprey therefore the assessment presented in paragraphs 377 to 378 for sea lamprey is also applicable to river lamprey. In addition, due to river lamprey’s preference for estuarine waters, it is unlikely that river lamprey will interact with cables associated with the Proposed Development.
Conclusion
381 The assessment has concluded that there is no direct spatial overlap between the Proposed Development and the Tweed Estuary SAC, and so the extent and distribution and structure and function of the supporting habitats of the qualifying species will not be reduced. Similarly, the supporting processes on which the habitats of the qualifying species rely will be unaffected. Given any impacts from EMF will be localised and transient and predicted low sensitivity of the qualifying species to this impact, the population and distribution of the qualifying species will be maintained.
382 Therefore, it can be concluded that there is no risk of an Adverse Effect on Integrity on the Tweed Estuary SAC as a result of EMF impacts with respect to operation and maintenance of the Proposed Development acting alone.
Colonisation of foundations, scour protection and cable protection
Sea lamprey
383 As discussed in section 12.4.2, colonisation of foundations, scour protection and cable protection, has the potential to result in increased predation on diadromous fish species by marine mammal species within offshore wind farms. It is not certain exactly to what extent seals utilise offshore wind developments (as discussed in paragraph 346) and therefore effects may be site specific. Assuming that seals do utilise offshore wind developments as foraging areas, sea lamprey may be impacted by the increased predation in an area where predation was lower prior to development.
385 The population of sea lamprey will be maintained as a viable component of the site and the extent and distribution of sea lamprey will not be reduced. The Proposed Development does not overlap with the Tweed Estuary SAC so the extent and distribution and the structure and function of sea lamprey habitat will be unaffected. Therefore, there will be no significant adverse effects on the qualifying Annex II diadromous fish feature, sea lamprey of the Tweed Estuary SAC as a result of colonisation of foundations, scour protection and cable protection impacts during the operation and maintenance phase.
River lamprey
386 River lamprey will have a similar sensitivity to colonisation of foundations, scour protection and cable protection impacts as sea lamprey therefore the assessment presented in paragraphs 383 to 384 for sea lamprey will also apply to river lamprey. In addition, due to river lamprey’s preference for estuarine waters, it is unlikely that river lamprey will interact with structures associated with the Proposed Development.
387 The population of river lamprey will be maintained as a viable component of the site and the extent and distribution of river lamprey will not be reduced. The Proposed Development does not overlap with the Tweed Estuary SAC so the extent and distribution and the structure and function of river lamprey habitat will be unaffected. Therefore, there will be no significant adverse effects on the qualifying Annex II diadromous fish feature, river lamprey of the Tweed Estuary SAC are not predicted to occur as a result of colonisation of foundations, scour protection and cable protection impacts during the operation and maintenance phase.
Conclusion
388 The assessment has concluded that there is no direct spatial overlap between the Proposed Development and the Tweed Estuary SAC, and so the extent and distribution and structure and function of the supporting habitats of the qualifying species will not be reduced. Similarly, the supporting processes on which the habitats of the qualifying species rely will be unaffected. Given the limited interaction between the qualifying species and the Proposed Development significant predation in relation the colonisation of foundations, scour protection and cable protection impact are not expected therefore the population and distribution of the qualifying species will be maintained.
389 Therefore, it can be concluded that there is no risk of an Adverse Effect on Integrity on the Tweed Estuary SAC as a result of colonisation of foundation, scour protection and cable protection impact with respect to the operation and maintenance of the Proposed Development acting alone.
Effects in-combination
390 An assessment of in-combination effects upon the qualifying Annex II diadromous fish species of the Tweed Estuary SAC arising from each identified impact is provided below.
Assessment of In-combination Effects During Construction
Injury and/or disturbance from underwater noise and vibration
391 There is potential for in-combination effects from injury and/or disturbance from underwater noise and vibration to Annex II diadromous fish during the construction phase of the Proposed Development with activities associated with the following projects:
- Tier 2:
– Inch Cape Offshore Wind Farm (construction phase); and
– Seagreen 1A Project (construction phase).
- Tier 3:
– There is no information provided regarding UXO clearance for the Cambois connection therefore no meaningful assessment can be made at this time.
Tier 2
392 The Tier 2 projects included in the in-combination assessment (i.e. Inch Cape and Seagreen 1A Project) include similar construction activities as those described for the Proposed Development alone including piling of wind turbine and OSP/Offshore convertor station platform foundations. All other noise sources including cable installation and foundation drilling will result in much lower noise levels than piling and will not represent a risk to injury or cause significant disturbance to diadromous fish, such that they would result in in-combination effects with or from other projects. As such, the scope of this assessment focusses on piling noise, which represents the greatest risk to diadromous fish receptors.
393 The construction phases of Inch Cape Offshore Wind Farm and Seagreen 1A Project overlap the construction phase of the Proposed Development with construction for Inch Cape Offshore Wind Farm predicted to end in 2025 and Seagreen 1A Project predicted to end in 2025. During the time when construction phases overlap, there is the potential for in-combination effects.
394 Neither Inch Cape Offshore Wind Farm nor Seagreen Alpha/Bravo Offshore Wind Farm EIA Reports predicted significant effects on fish and shellfish receptors. Any effects were predicted to be temporary and reversible following cessation of piling activities. Additionally, the injury ranges reported are likely to be conservative as soft start measures will be implemented as part of the Inch Cape Offshore Wind Farm and Seagreen 1A Project construction programmes, which will reduce the risk of injury considerably. Due to the limited range over which injury effects may occur due to piling activities (i.e. tens to hundreds of metres), mitigation to minimise the potential for injury and the minor overlap in construction phases of the Proposed Development and Inch Cape Offshore Wind Farm and Seagreen 1A Project, in-combination effects are not predicted to result in effects of greater significance than as assessed for the Proposed Development alone.
395 The in-combination effect is predicted to be of regional spatial extent, short term duration and intermittent and of high reversibility and diadromous fish species are assessed as having low sensitivity to the effect.
396 Significant adverse effects on the qualifying Annex II diadromous fish species, sea lamprey and river lamprey, of the Tweed Estuary SAC are not predicted to occur as a result of injury and/or disturbance from underwater noise and vibration during the construction phase of the Proposed Development in-combination with other projects.
397 Therefore, it can be concluded that there is no risk of an Adverse Effect on Integrity on the Tweed Estuary SAC as a result of injury and/or disturbance from underwater noise and vibration with respect to the Proposed Development acting in-combination with Tier 2 projects.
Increased Suspended Sediment Concentrations and Associated Sediment Deposition
398 There is potential for in-combination effects from increased SSC and associated sediment deposition impacts to Annex II diadromous fish during the construction phase of the Proposed Development with activities associated with the following projects:
- Tier 2:
– Inch Cape Offshore Wind Farm (construction phase);
– Seagreen 1A Project (construction phase);
– Seagreen 1 (operation and maintenance phase);
– Seagreen 1A Export Cable (operation and maintenance phase);
– Neart na Gaoithe Offshore Wind Farm (operation and maintenance phase);
– Eastern Link 1 (construction phase);
– Eastern Link 2 (construction phase); and
– Eyemouth disposal site.
- Tier 3:
– Cambois connection (construction and operation and maintenance phases).
Tier 2
399 The Inch Cape Offshore Wind Farm will be in the final year of construction, with the installation of the offshore export cable being programmed for the period of overlap with the Proposed Development. The cable route is located to the east of the Proposed Development and should trenching activities be undertaken simultaneously the sediment plumes would not interact with those from the Proposed Development.
400 The construction phase of the Proposed Development coincides with the construction phase for the Seagreen 1A Project. Construction of its 36 wind turbines will be completed by the end of 2025, which will lead to a potential overlap with the construction phase of the Proposed Development.
401 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.
402 The Eastern Link 1 Cable has a Scottish landfall near Thorntonloch Beach, East Lothian. The landfall installation is proposed to be by Horizontal Directional Drilling (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 excavator 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. These activities would be of limited spatial extent and frequency and unlikely to interact with sediment plumes from the Proposed Development.
403 The Eastern Link 2 Cable runs to the east of the Proposed Development. 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 cable corridor. These activities would be of limited spatial extent and frequency and unlikely to interact with sediment plumes from the Proposed Development.
404 The in-combination effects assessment 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 Proposed Development export cable corridor respectively. If offshore cable installation and dredge material disposal coincided, both resultant plumes would be advected on the tidal currents. The plumes would travel in parallel, and not towards one another, and are unlikely to interact in the event that offshore cables installation coincides with the use of the licensed sea disposal site (see volume 3, appendix 7.1 of the Offshore EIA Report).
405 The in-combination effect is predicted to be of local spatial extent, short term duration and intermittent and of high reversibility and diadromous fish species are assessed as having low sensitivity to the effect.
406 Therefore, it can be concluded that there is no risk of an Adverse Effect on Integrity on the Tweed Estuary SAC as a result of increased SSC and associated sediment deposition impacts with respect to the Proposed Development acting in-combination with Tier 2 projects.
Tier 3
407 During the construction phase of the Proposed Development there is the potential for in-combination effects with one Tier 3 cable installation. The Cambois connection is a 170 km cable route extending southwards from the Proposed Development array area. 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 cable ploughing, as ground conditions dictate. Site preparation will be required, such as boulder and sand wave clearance as part of the 36-month construction programme.
408 The in-combination effect is predicted to be of local spatial extent, short term duration, intermittent and of high reversibility and diadromous fish species are assessed as having low sensitivity to the effect. As such, there will be no effect on the ability of diadromous fish to migrate to and from the relevant SACs considered within this RIAA.
409 Significant adverse effects on the qualifying Annex II diadromous fish species, sea lamprey and river lamprey, of the Tweed Estuary SAC are not predicted to occur as a result of increased SSC and associated sediment deposition during the construction phase of the Proposed Development in-combination with other projects.
410 Therefore, it can be concluded that there is no risk of an Adverse Effect on Integrity on the Tweed Estuary SAC as a result of increased SSC and associated sediment deposition impacts with respect to the Proposed Development acting in-combination with Tier 3 projects.
Assessment of in-combination effects during the operation and maintenance phase
EMF from subsea electrical cabling
411 There is potential for in-combination effects from EMFs from subsea electrical cabling impacts to Annex II diadromous fish during the operation and maintenance phase of the Proposed Development with activities associated with the following projects:
- Tier 2:
– Inch Cape Offshore Wind Farm;
– Neart na Gaoithe Offshore Wind Farm;
– Seagreen 1;
– Seagreen 1A Project;
– Seagreen 1A Export Cable Corridor;
– Eastern Link 1;
– Eastern Link 2.
- Tier 3:
– Cambois connection
Tier 2
412 Inch Cape Offshore Wind Farm has the potential to produce EMF from 553 km of inter-array cables suitably buried and protected where burial is not possible. Additionally, the offshore export cables are approximately 83 km for each six cables, therefore the offshore export cables total length is 498 km. This project will use a combination of HVAC and HVDC, however the design was not finalised in the environmental statement.
413 Neart na Gaoithe Offshore Wind Farm has the potential to produce EMF from 66 km of offshore export cables as well as 140 km of inter-array cables. This project will use a combination of HVAC and HVDC, however the design was not finalised in the environmental statement.
414 Seagreen 1 and Seagreen 1A Project have the potential to produce EMF from 710 km of inter-array cables and 530 km of offshore export cables resulting in 1,240 km of subsea cabling. These projects will use a combination of HVAC and HVDC however the design was not finalised in the environmental statement. The Seagreen 1A Export Cable environmental statement does not provide details of the cable specifications used, but provides an approximate cable length of 110 km, which will have the potential to cause EMF effects. Eastern Link 1 and Eastern Link 2 cables also have the potential to cause EMF effects.
415 The potential for in-combination effects of EMF on diadromous fish species during the Proposed Development operation and maintenance phase results from up to 6,112 km of subsea cabling, including the cables associated with the Proposed Development.
416 Whilst any in-combination effects are predicted to be of long-term duration, continuous and not reversible during the operation of the relevant projects, they are also predicted to be of local spatial extent. Diadromous fish species have been assessed as having low sensitivity to EMF from electrical subsea cabling. This can be concluded as EMF effects are confined to the close vicinity of cables. Diadromous fish species are pelagic, swimming in the water column and therefore less likely to interact with emitted EMF from subsea cables. While the sediments in which cables are buried will not reduce the strength of EMF, the burial of cables does increase the distance between cables and diadromous fish, with greater attenuation of EMFs with greater distance from the cable, thereby reducing the effect of EMFs on diadromous fish.
Tier 3
418 The Tier 3 project which has the potential to result in in-combination EMF effects from subsea electrical cabling within the Proposed Development fish and shellfish ecology study area is the Cambois connection. There is, however, currently no information on the impact that this project will have on diadromous fish, however effects of EMF from the Cambois connection are likely to be similar in magnitude and extent as that discussed for the Proposed Development and the other projects considered in the in combination assessment as set out above.
419 The in-combination effect is predicted to be low and the sensitivity of diadromous fish species is predicted to be low with high recoverability.
420 Significant adverse effects on the qualifying Annex II diadromous fish species, sea lamprey and river lamprey, of the Tweed Estuary SAC are not predicted to occur as a result of EMF from subsea electrical cabling during the operation of the Proposed Development in-combination with other projects.
421 Therefore, it can be concluded that there is no risk of an Adverse Effect on Integrity on the Tweed Estuary SAC as a result of EMF impacts with respect to the Proposed Development acting in-combination with Tier 3 projects.
Colonisation of foundations, scour protection and cable protection
422 The introduction of hard substrate into areas of predominantly soft sediments has the potential to alter community composition and biodiversity. This impact is only relevant to the operation and maintenance phase as it takes time for colonisation to establish post construction. The presence of the following projects has the potential to lead to in-combination effects arising from the colonisation of hard structures:
- Tier 2:
– Inch Cape Offshore Wind Farm;
– Neart na Gaoithe Offshore Wind Farm;
– Seagreen 1;
– Seagreen 1A Project;
– Seagreen 1A Export Cable Corridor;
– Eastern Link 1; and
– Eastern Link 2.
- Tier 3:
– Cambois connection
–
Tier 2
423 There are no values for long term habitat loss provided in the EIA Report for Seagreen 1A Export Cable Corridor however 20% of the 110 km may require cable protection up to 6 m wide (Seagreen Wind Energy Ltd., 2021).
424 Inch Cape Offshore Wind Farm will contribute to in-combination effects from the colonisation of hard structures through the presence of wind turbines, substations, and meteorological masts, as well as cable protection for the inter-array and offshore export cables. In the Inch Cape EIA Report it is stated that the amount of new hard substrate resulting from Inch Cape Offshore Wind Farm is equivalent to the amount of long-term habitat loss (Inch Cape Offshore Limited, 2018) equates to 2,470,000 m2 of new hard structures (Inch Cape Offshore Limited, 2018).
425 At the Neart na Gaoithe Offshore Wind Farm, colonisation of hard substrate is predicted to result from the presence of gravity base foundations for the wind turbine foundations, substation foundations, scour protection and cable protection. The amount of new hard substrate available is equivalent to the amount of long-term habitat loss which equates to 460,000 m2 of new hard structures (Mainstream Renewable Power, 2019).
426 Seagreen 1 and Seagreen 1A Project maximum design scenario for the colonisation of hard structures, as stated in the environmental statements (Seagreen Wind Energy, 2012), show that the area available for colonisation is expected to be approximately the same area as is considered for as for long-term habitat loss, which equates to 2,184,100 m2 of new hard structure (Seagreen Wind Energy, 2012).
427 The hard substrate installed for Eastern Link 1 includes rock berm with a maximum width of 7 m, no further values regarding hard substrate have been provided (National Grid Electricity Transmission and Scottish Power Transmission, 2022). The hard substrate installed for Eastern Link 2 includes rock berms up to 138 km, six pipeline crossings, 18 cable crossings and rock protection at the landfall. The amount of new hard substrate available equates to 2,200,200 m2 (National Grid Electricity Transmission and Scottish Hydro Electric Transmission plc, 2022).
428 The presence of the Tier 2 projects has the potential to lead to cumulative impacts arising from the colonisation of up to 17,513,271 m2 of hard structures.
429 The assessment of effects on diadromous fish from the Proposed Development alone concluded that Annex II diadromous fish species have low vulnerability, high recoverability, and therefore low sensitivity to colonisation of foundations, scour protection and cable protection. This is because, diadromous fish are only likely to interact with the Proposed Development when passing through the area during migrations to and from rivers located on the east coast of Scotland. In most cases, it is expected that diadromous fish are unlikely to utilise the increase in hard substrate from the Proposed Development for feeding or shelter opportunities. Whilst there is potential for increased predation of diadromous fish by marine mammal species attracted to offshore wind farm structures, again impacts on diadromous fish are not anticipated to be significant given diadromous fish spend little time in coastal waters and are unlikely to spend time foraging around wind turbines foundations and therefore are at low risk from increased predation.
430 Whilst the in-combination effect is predicted to be of long-term duration and continuous, it is predicted to be of local spatial extent, of high reversibility and diadromous fish species are assessed as having low sensitivity to the effect.
431 Significant adverse effects on the qualifying Annex II diadromous fish species, sea lamprey and river lamprey, of the Tweed Estuary SAC are not predicted to occur as a result of colonisation of foundations, scour protection and cable protection during the operation of the Proposed Development in-combination with other projects.
432 Therefore, it can be concluded that there is no risk of an Adverse Effect on Integrity on the Tweed Estuary SAC as a result of colonisation of foundations, scour protection and cable protection impacts with respect to the Proposed Development acting in-combination with Tier 2 projects.
Tier 3
433 The Tier 3 project which has the potential to result in in-combination effects associated with the colonisation of structures is the Cambois connection. The Cambois connection has the potential to create 306,000 m2 of new hard habitat associated with rock/mattress cable protection which represents protection covering 15% the total length the four offshore export cables, therefore it is likely that only a proportion of the cable protection will occupy the fish and shellfish ecology CEA study area, or potentially none of it. The cable protection represents a change in seabed type, however as the cable protection does not extend into the water column the opportunity for colonisation by some species is reduced. The presence of the Tier 2 and 3 projects has the potential to lead to cumulative impacts arising from the colonisation of up to 17,543,971 m2 of hard structures.
434 Whilst the in-combination effect is predicted to be of long-term duration and continuous, it is predicted to be of local spatial extent, of high reversibility and diadromous fish species are assessed as having low sensitivity to the effect.
435 Significant adverse effects on the qualifying Annex II diadromous fish species, sea lamprey and river lamprey, of the Tweed Estuary SAC are not predicted to occur as a result of colonisation of foundations, scour protection and cable protection during the operation of the Proposed Development in-combination with other projects.
436 Therefore, it can be concluded that there is no risk of an Adverse Effect on Integrity on the Tweed Estuary SAC as a result of colonisation of foundations, scour protection and cable protection impacts with respect to the Proposed Development acting in-combination with Tier 3 projects.