Sensitivity of the Receptor

Subtidal Habitat IEFs

  1. The sensitivity of the IEFs to physical change (to another substratum) is as described previously for the long term subtidal habitat loss assessment and above in Table 8.25   Open ▸ .
  2. Within the benthic subtidal and intertidal ecology study area sediments are dominated by gravelly sand, slightly gravelly sand, and a higher proportion of muddy sand in the offshore Proposed Development export cable corridor. Furthermore, Annex I reefs have also been identified in the Proposed Development benthic subtidal and intertidal ecology study area including cobble/stony reef and rocky reef in the nearshore area, and Sabellaria reef. As such, the introduction of hard substrates due to installation of foundation structures, associated scour protection, and any cable protection, will represent a shift in community type and will have a direct effect on benthic ecology IEFs through the colonisation of these hard substrates.
  3. The colonisation of hard structures will affect subtidal IEFs only (subtidal sand and muddy sand sediments IEF, subtidal coarse and mixed sediments IEF, moderate energy subtidal rock IEF, seapens and burrowing megafauna IEF, cobble/stony and rocky reef outside of an SAC IEF, and Sabellaria reef outside of an SAC IEF). Cables will be installed at the landfall via trenchless techniques which means there will be no impact to, or introduction of hard structures, into any intertidal IEFs and they have not been considered further in this assessment. As outlined in Table 8.16   Open ▸ , a pre-construction Annex I reef survey will be undertaken to determine the location, extent and composition of any biogenic/geogenic reefs within the Proposed Development. Should such reef features be identified during pre-construction surveys, appropriate measures will be discussed with statutory consultees to avoid direct impacts to these features, where reasonably practicable, and on the basis of the extent of these features at the time of operation and maintenance, and on the basis of the extent of these features at the time of construction. This means that impacts to the Sabellaria reef outside of an SAC IEF will also be avoided.
  4. Colonisation of the wind turbine foundations, associated scour protection and cable protection may have indirect adverse effects on the baseline communities and habitats due to increased predation on and competition with the existing soft sediment species. These effects are difficult to predict, especially as monitoring to date has focused on the colonisation and aggregation of species close to the foundations rather than broad scale studies.
  5. Some studies have also shown that the installation and operation of offshore wind farms have no significant impact on the soft sediment environments. De Backer et al. (2020) found that eight to nine years after the installation of C-power and Belwind offshore wind farms (offshore Belgium) the soft sediment epibenthos underwent no drastic changes; and the species originally inhabiting the sandy bottom were still present and remained dominant in both wind farms. Additionally, a review of monitoring from Block Island wind farm in the United States showed no strong gradients of change in sediment grain size, enrichment, or benthic macrofauna within 30 m to 90 m distance bands of the wind turbines (Hutchison et al., 2020).
  6. Where scour and cable protection are deployed, use of smaller rock sizes, where reasonably practicable at the time of operation and maintenance, may facilitate the colonisation of rock protection by epifaunal species typical of coarse sediment which are found within the Proposed Development export cable corridor. Previous studies have shown that for artificial hard substrate to be colonised by a benthic community similar to that of the baseline, its structure should resemble that of the baseline habitat as far as far as reasonably practicable (Coolen, 2017). The addition of smaller grained material to scour/cable protection may therefore be of some benefit to the native epifaunal communities (Van Duren et al., 2017; Lengkeek et al., 2017).
  7. Coolen et al. (2020) examined the differences in communities and species richness between a natural reef and a wind farm. They found some overlap in the species found on each substrate but also a number of substrate specific species which are the result in differences in material and the depth of the structures. The impact of colonisation of wind farm structures will likely impact a small area (i.e. close to the wind turbines), and none of the reviewed studies reported impacts at entire offshore wind farm scale (Bergström et al., 2014). Therefore, it is unlikely that any of the reefs within the Proposed Development array area will be adversely impacted by habitat creation and they may even offer some benefit by providing habitat for some rocky reef species. The potential benefits of offshore wind farms for epifaunal organisms has been recognised in recent research by Hofstede et al. (2022). This research concluded that scour protection in particular can provide refuge and complex habitats for many North Sea benthic species. Species abundance was found to be higher on scour protection compared to the surrounding seabed. This suggests that these structures can provide habitat for rock-dwelling species where it has been removed or degraded by bottom-trawling over the last century.
  8. The most recent monitoring data to come from an operational wind farm has come from Beatrice Offshore Wind farm Post-Construction Monitoring (APEM, 2021). This monitoring was undertaken in October 2020 and used DDV, remotely operated vehicles and grab samples to gather qualitative data on the biofouling community composition on wind turbines (four wind turbines with jacketed foundations in four different locations within the wind farm, assessed to a depth of 45 m) and the surrounding seabed. The results found extensive biofouling on all the wind turbines with signs of zonation and successional development. The zonation was dependent on depth and the dominance of a few key species. Across all wind turbines Metridium senile plumose anemones and Spirobranchus triqueter keel worms were the most abundant species, with the highest biomass found at mid depths of 40 m with lower biomass above and below. The splash zone and top 5 m of the foundations was dominated by algal turf and kelp, this gave way to cnidarian dominated community at around 5 m to 10 m and this transitioned to a keel worm dominated zone between 25 m and 40 m depth. At the base in the immediate vicinity of the wind turbines the Pagurus bernhardus hermit crabs, flatfish and Echinus esculentus common sea urchin were found with decreasing abundance further from the foundation indicating a source of food although no biological matter could be seen. Gadoid fish could also be seen but not identified to species level. The zonation pattern is likely to remain constant except for small scale changes. The zonation pattern may change if the communities are disturbed by the introduction of a new species such as the Mytilus edulis blue mussel which is notably absent, although it is commonly found in other wind farms.
  9. All of the relevant benthic ecology subtidal IEFs are deemed to be of high vulnerability, low recoverability, and regional to national value. The sensitivity of the IEFs is therefore, considered to be high.
  10. Although there is an impact on PMF(s) this will not create significant impact on the national status of these features. Colonisation is likely to only occur on new infrastructure and not extend far beyond the infrastructure because the communities colonising the hard structures are unlikely to be suited to the sedimentary habitats which the Proposed Development is largely composed of. In regard to rocky and cobble/stony reefs the species which colonise the hard substrate are likely to be similar to the baseline communities therefore potentially extending the available space for communities from these IEFs. Ultimately the colonisation of new structures is unlikely to present a change in the seabed habitats and therefore the national status of the relevant PMF(s) will be preserved.

Firth of Forth Banks Complex MPA

  1. The sensitivity of the IEFs within the FFBC MPA to physical change (to another substratum) is as described previously for the long term subtidal habitat loss assessment and in Table 8.26   Open ▸ .
  2. The discussion regarding the potential adverse and beneficial impact of the introduction of hard substrate into soft sediment environments is also relevant to the IEFs found within the FFBC MPA. See paragraphs 329 to 336 for further detail on this impact.
  3. The subtidal sands and gravels IEF and the shelf banks and mounds IEF are deemed to be of high vulnerability, low recoverability, and national value. The sensitivity of the IEFs is therefore, considered to be high.
  4. The ocean quahog IEF is deemed to be of high vulnerability, low recoverability, and national value. The sensitivity of the IEF is therefore, considered to be high.
Significance of the Effect

Subtidal Habitat IEFs

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptors (subtidal sand and muddy sand sediments IEF, subtidal coarse and mixed sediments IEF, moderate energy subtidal rock IEF, cobble/stony reef outside of an SAC IEF, rocky reef outside an SAC IEF and Sabellaria reef outside of an SAC IEF) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms. This is concluded because of the high likelihood that benthic species and communities will colonise the infrastructure in areas where soft substrates have been lost. The impact is of a limited spatial extent which will not increase over the lifetime of the project,

Firth of Forth Banks Complex MPA

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptors (subtidal sands and gravels IEF, shelf banks and mounds IEF, and ocean quahog IEF) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of the limited spatial extent of the impact and that fact that it will not increase over the lifetime of the project.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of colonisation of hard structures because the likely effects in the absence of further mitigation (beyond the designed in measures outlined in section 8.10), are not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

Subtidal Habitat IEFs

  1. During the decommissioning phase, some infrastructure is assumed to be left in situ with the impact of colonisation of infrastructure continuing in perpetuity following decommissioning. The maximum design scenario assumes that the wind turbine/OSP-Offshore convertor station platform foundation will be removed and that scour protection and cable protection may be left in situ. As detailed in Table 8.10   Open ▸ , the maximum design scenario assumes that up to 7,493,186 m2 of habitat associated with hard substrate may persist following decommissioning in association with scour protection and cable protection for cables and cable crossings. This equates to a small proportion (0.52%) of the Proposed Development benthic subtidal and intertidal ecology study area.
  2. The impact is predicted to be of local spatial extent, permanent duration continuous and irreversible. It is predicted that the impact will affect the receptors indirectly. The magnitude is therefore considered to be low.

Firth of Forth Banks Complex MPA

  1. The FFBC MPA overlaps with the site boundary for the Proposed Development and therefore some habitat creation and colonisation of hard structures may persist within the FFBC MPA following the decommissioning phase and beyond. The overall figures for the spatial overlap are outlined in paragraph 85 together with the assumptions for the overlap of infrastructure/activities with the FFBC MPA. Based on this percentage of overlap and the maximum design scenario for the operation and maintenance phases, for the purposes of this assessment it is assumed that up to 1,867,831 m2 of new habitat for colonisation will persist post-decommissioning within the FFBC MPA, which equates to 0.09% of the FFBC MPA. For the purposes of this assessment, it is assumed that up to 1,292,334 m2 may occur within Berwick Bank part of the MPA (0.24% of the area of Berwick Bank) and up to 575,497 m2 may occur within Scalp and Wee Bankie (0.07% of the area of Scalp and Wee Bankie).
  2. The impact is predicted to be of local spatial extent, long term duration (35 year operation and maintenance phase), continuous and irreversible during the lifetime of the Proposed Development. It is predicted that the impact will affect the receptors indirectly. The magnitude is therefore considered to be low.
Sensitivity of the Receptor

Subtidal Habitat IEFs

  1. The sensitivity of all benthic subtidal IEFs, is as described for the operation and maintenance phase assessment (paragraph 328 et seq.) and are concluded to be high.

Firth of Forth Banks Complex MPA

  1. The sensitivity of all benthic subtidal IEFs, is as described for the operation and maintenance phase assessment (paragraph 338 et seq.) and are concluded to be high.
Significance of the Effect

Subtidal Habitat IEFs

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptors (subtidal sand and muddy sand sediments IEF, subtidal coarse and mixed sediments IEF, moderate energy subtidal rock IEF, cobble/stony reef outside of an SAC IEF, rocky reef outside an SAC IEF and Sabellaria reef outside of an SAC IEF) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of the infrastructure will be utilised by the communities of some IEFs and has a limited extent overall.

Firth of Forth Banks Complex MPA

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptors (subtidal sands and gravels, shelf banks and mounds and ocean quahog) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of the limited spatial extent in relation to the MPA and the impact area will not increase post decommissioning.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of colonisation of hard structures because the likely effects in the absence of further mitigation (beyond the designed in measures outlined in section 8.10), are not significant in EIA terms.

Increased Risk of Introduction and Spread of Invasive and Non-Native Species

  1. The risk of introduction and spread of INNS during the construction, operation and maintenance and decommissioning phases has been considered in this assessment.
  2. The benchmark for the relevant MarESA pressure which has been used to inform this assessment of effect is described here.
  • Introduction or spread of INNS: the benchmark for which is the introduction of one or more INNS.
    1. The benchmark for the relevant FeAST pressure which has been used to inform this assessment of effect is described below.
  • Introduction or spread of non-native species and translocations (competition): the benchmark for which is a significant pathway exists for introduction of one or more INNS.
    1. This pressure is relevant to the introduction of new substrates into an established community.
    2. As discussed in paragraph 40, this assessment has been undertaken on the broad IEFs and separately on the IEFs that comprise features of the FFBC MPA.

Construction Phase

Magnitude of Impact

Subtidal Habitat IEFs

  1. The installation of hard substrates and the presence of construction vessels may lead to an increased risk of introduction and spread of INNS. The maximum design scenario is represented by up to 11,484 vessel round trips during the construction phase, including those required during site preparation activities, which will occur over a maximum duration of up to 96 months ( Table 8.10   Open ▸ ).
  2. There are a number of existing vessel movements occurring within the benthic subtidal and intertidal ecology study area, including cargo vessels, tankers, fishing vessels, recreational vessels, and service vessels (volume 3, appendix 13.1). The baseline identified in this appendix identified 14 unique vessel movements per day over the summer survey period and 16 per day in the winter period in the Proposed Development array area, cargo vessels, tankers and commercial fishing vessels were the most common vessel type. There were 24 unique vessel movements per day over the survey period in the Proposed Development export cable corridor Shipping and Navigation study area for the summer period and 18 per day in the winter period. Therefore, the additional vessels associated with the Proposed Development are unlikely to significantly add to the risk of introduction and spread of INNS.
  3. As presented in Table 8.10   Open ▸ , the risk of introduction and spread of INNS will be increased through the construction period due to the creation of 10,198,971 m2 of hard substrate from the installation of jacket foundations, associated scour protection and any cable protection. There are already natural hard substrates within the vicinity of the Proposed Development array area and offshore Proposed Development export cable corridor (e.g. moderate energy subtidal rock, cobble/stony reefs, and rocky reefs in the nearshore section of the Proposed Development export cable corridor). Furthermore, there are pre-existing wind turbine foundations associated with Seagreen 1, Seagreen 1A Project as well as the Neart na Gaoithe offshore wind farm which are currently under construction and Inch Cape offshore wind farm, which is consented.
  4. There are multiple marine INNS that are now widespread and well established in Scotland. Some of which have been reported in the Firth of Forth as well as the surrounding area (based on NBN Atlas data) and therefore have the potential to colonise the Potential Development infrastructure and surrounding area. These include Japanese skeleton shrimp Caprella mutica (MSS, 2020), carpet sea-squirt Didemnum vexillum, green sea fingers Codium fragile subsp. fragile, wakame Undaria pinnatifida and wire weed Sargassum muticum (NatureScot, 2021).
  5. There are several other marine INNS which are of only patchy distribution or are currently only known from the rest of the UK. These include American lobster Homarus americanus, Pacific oyster Crassostrea gigas, Chinese mitten crab Eriocheir sinensis, and slipper limpet Crepidula fornicata (NatureScot, 2021).
  6. The vessels used for construction will largely be local therefore the introduction of species form outside the region is unlikely, some of the species already in the region however are known to spread as fouling on ships hulls which could introduce then to the Proposed Development array area and Proposed Development export cable corridor, including wakame, green sea fingers and carpet sea-squirt (Beveridge et al., 2011; Invasive Species Compendium, 2019).
  7. As set out in Table 8.16   Open ▸ , an INNSMP and EMP (see volume 4, appendix 22), which will include measures such as ensuring any new infrastructure coming from another marine environment are cleaned and checked prior to installation and that vessels comply with the IMO ballast water management guidelines will be developed and adhered to for the Proposed Development. This will ensure that the risk of potential introduction and spread of INNS will be minimised.
  8. The latest post-construction monitoring data from the Beatrice Offshore Wind farm (APEM, 2021) found no evidence for the presence of INNS on wind turbine foundations, which is evidence to suggest that the introduction of structure such as offshore wind turbine foundation into the benthic environment doesn’t necessarily lead to the spread of INNS in Scottish waters.
  9. The 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 receptor directly. The magnitude is therefore considered to be low.

Firth of Forth Banks Complex MPA

  1. The FFBC MPA overlaps with the site boundary for the Proposed Development and therefore there is the potential for the introduction of infrastructure within the MPA to result in the introduction and spread of INNS. The overall figures for the spatial overlap are outlined in paragraph 85 together with the assumptions for the overlap of infrastructure/activities with the FFBC MPA. Based on this percentage of overlap and the maximum design scenario for the construction phase, for the purposes of this assessment it is assumed that up to 2,715,565 m2 of hard substrate will be installed within the FFBC MPA which could aid the spread of INNS, which equates to 0.13% of the FFBC MPA. For the purposes of this assessment it is assumed that of the total, up to 1,878,873 m2 may occur within Berwick Bank (0.35% of the area of Berwick Bank) and up to 836,692 m2 may occur within Scalp and Wee Bankie (0.10% of the area of Scalp and Wee Bankie). This however will start off as much less and increase throughout construction. Vessel movements will also occur throughout the MPA during construction, the amount of activity specifically in the MPA area is unknown.
  2. As set out in Table 8.16   Open ▸ , an INNSMP and EMP (see volume 4, appendix 22), which will include measures such as ensuring any new infrastructure coming from another marine environment are cleaned and checked prior to installation and that vessels comply with the IMO ballast water management guidelines will be developed and adhered to for the Proposed Development. This will ensure that the risk of potential introduction and spread of INNS will be minimised.
  3. The 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 receptor directly. The magnitude is therefore considered to be low.

Berwickshire and North Northumberland Coast SAC

  1. The Berwickshire and North Northumberland Coast SAC is located 4.12 km from the Proposed Development export cable corridor, and 30 km from the Proposed Development array area. On the basis that there is no spatial overlap between the Proposed Development and the SAC there will be no habitat creation within the SAC therefore there is minimal potential for the introduction and spread of INNS within the SAC. No further assessment is therefore required for this impact.
Sensitivity of the Receptor

Subtidal Habitat IEFs

  1. The sensitivities of the benthic subtidal IEFs to this impact are presented in Table 8.26   Open ▸ and based on the information available to inform the MarESA and FeAST, there is a range in sensitivity of the IEFs present to the increased risk of introduction and spread of INNS.
  2. The FeAST assessed the sensitivity of continental shelf muds, sand, and coarse sediments to be medium for INNS, although no supporting evidence is provided. The FeAST also assesses the sensitivity of continental shelf mixed sediments to be high for INNS. Based on the assessment of sensitivity made by the MarESA the subtidal sand and muddy sand sediment, and subtidal coarse and mixed sediments IEFs have a high sensitivity to INNS, noting that there is no evidence for this pressure for three of the 11 characterising biotopes ( Table 8.26   Open ▸ ). The sediments characterising all of the aforementioned IEFs are likely to be too mobile for most INNS (Tillin, 2016), based on evidence from SS.SSa.CFiSa.EpusOborApri, SS.SMx.OMx.PoVen, and IR.MIR.KR.Ldig.Bo. The INNS of concern for the aforementioned IEFs are the slipper limpet and the carpet sea-squirt. Carpet sea-squirt however are unlikely to be compatible with areas of mobile sand (Valentine et al., 2007), reducing the risk of invasion to the subtidal sand and muddy sand sediment and subtidal sands and gravel IEFs. Slipper limpets may colonise all of the aforementioned IEFs by settling on stones or bivalve shells resulting in eventual habitat change as they smother the seabed and make it unsuitable for the settlement of characteristic species larva.
  3. The moderate energy subtidal rock IEF also has a high sensitivity to introduction or spread of INNS. These biotopes are at risk from habitat alteration as well as the native flora and fauna being out competed by invasive species, disturbances in these biotopes can leave space for invasion. The INNS of concern in these habitats are wakame and wire weed. Wire weed has been shown to competitively replace Laminaria species in Denmark (Staehr et al., 2000) and where present an abundance of wakame has corresponded to a decline in Laminaria sp. (Hieser et al., 2014).
  4. Sabellaria reef outside of an SAC IEF has not been found to be impacted by INNS. C. fornicata has been recorded in association with Sabellaria reefs (Pearce, 2007), however the relationship between them has not been investigated. Likely significant effects on Sabellaria reefs could occur through changes to substratum suitability or other interactions. Sabellaria reefs support a variety of attached epifauna including species of bryozoans, hydroids and sponges. As Sabellaria reefs are known to support encrusting organisms without apparent adverse effect the impact of INNS is likely to be low.
  5. There is very little evidence for the Annex I reef IEFs to support an assessment of their level of sensitivity towards the introduction or spread of INNS. Cobble/stony reef outside of an SAC and rocky reef outside an SAC however have been found to have high sensitivity to D. vexillum which can form extensive mats, binding over boulders and cobbles smothering the resident biological community (Griffith et al., 2009). As a result, we can assume both of these IEFs have a high sensitivity to the introduction and spread of INNS should a species which is compatible to the habitat be introduced.
  6. The seapens and burrowing megafauna also has very little evidence to support an assessment of their sensitivity. They have been shown to not be sensitive to the invasive polychaete Sternapsis scutata in a laboratory experiment (Shelley et al., 2008). They may be vulnerable to voracious omnivorous predators feeding on the seabed such as Paralithodes camtschaticus, however this has yet to be proven (GBNNSIP, 2011).
  7. The subtidal sand and muddy sand sediments IEF, and the subtidal coarse and mixed sediments IEF are deemed to be of high vulnerability, low recoverability, and regional value. The sensitivity of all the IEFs is therefore, considered to be high.
  8. The moderate energy subtidal rock IEF is deemed to be of high vulnerability, low recoverability, and national value. The sensitivity of all the IEFs is therefore, considered to be high.
  9. The Sabellaria reef outside of an SAC IEF is deemed to be of low vulnerability, high recoverability, and national value. The sensitivity of the IEF is therefore, considered to be low.
  10. The seapens and burrowing megafauna IEF, cobble/stony reef outside of an SAC IEF, and rocky reef outside an SAC IEFs do not have enough evidence in the MarESA or FeAST Tool to determine their sensitivity to INNS. A precautionary approach therefore assumes that they are deemed to be of high vulnerability, low recoverability, and national value. The sensitivity of the IEFs is therefore, considered to be high.
  11. Although there is an impact on PMF(s) this will not create significant impact on the national status of these features. This can be justified as the potential area of impact based on the designed in measures to reduce the potential introduction of INNS coupled with the very small number of relevant INNS in the region, as well as the suitability of these habitats to the INNS in the area means the impact is unlikely to change the national status of these PMF(s).

Table 8.27:
Sensitivity of the Benthic Subtidal IEFs to Introduction or Spread of INNS

Table 8.27: Sensitivity of the Benthic Subtidal IEFs to Introduction or Spread of INNS

 

Firth of Forth Banks Complex MPA

  1. The FeAST assesses continental shelf sand and coarse sediments to be of a medium sensitivity to INNS however no evidence to support this assessment is provided ( Table 8.27   Open ▸ ). The sensitive biotopes within the subtidal sands and gravels IEF based on the MarESA indicates a high sensitivity to INNS. The sediments characterising this IEF are likely to be too mobile for most INNS (Tillin, 2016), based on evidence from SS.SSa.CFiSa.EpusOborApri and SS.SSa.CFiSa.ApriBatPo. Additionally, as mentioned in paragraph 373, carpet sea-squirt and slipper limpets are the organisms most likely to invade, however carpet sea-squirts are unlikely to be compatible with sand-based habitats.
  2. The shelf banks and mounds IEF has the same sensitivity as the subtidal sands and gravel IEF as it contains the same biotopes.
  3. The subtidal sands and gravels IEF and the shelf banks and mounds IEF are deemed to be of high vulnerability, low recoverability, and national value. The sensitivity of the IEFs is therefore, considered to be high.
  4. Ocean quahog were not assessed by either the MarESA or the FeAST so their sensitivity to INNS is unknown. They are however slow to reach sexual maturity, taking between 5 and 11 years depending on growth rate (Thorarinsdóttir, 1999), which could lead to a high sensitivity to INNS which are often characterised by their ability to spread quickly, ocean quahog may struggle to compete as a result. A precautionary approach therefore assumes that they are deemed to be of high vulnerability, low recoverability, and national value. The sensitivity of the IEF is therefore, considered to be high.
Significance of the Effect

Subtidal Habitat IEFs

  1. Overall, the magnitude of the impact is deemed to be low, and the sensitivity of the subtidal habitat receptors (subtidal sand and muddy sand sediments, subtidal coarse and mixed sediments, moderate energy subtidal rock, seapens and burrowing megafauna, cobble/stony reef outside of an SAC, and rocky reef outside an SAC) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of limited ability of most invasive species to colonise the majority of these IEFs and where invasive species may be introduced measures will be put in place to reduce the overall risk.
  2. The Sabellaria reef outside of an SAC IEF, the magnitude of the impact is deemed to be low, and the sensitivity of the receptors is considered to be low. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of the ability of this IEF to continue to thrive alongside other encrusting species.

Firth of Forth Banks Complex MPA

  1. Overall, the magnitude of the impact is deemed to be low, and the sensitivity of all receptors (subtidal sands and gravels, shelf banks and mounds, and ocean quahog) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms because of limited ability of most invasive species to colonise the majority of these IEFs and where invasive species may be introduced measures will be put in place to reduce the overall.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of the increased risk of introduction and spread of INNS during the construction phase because the likely effects in the absence of further mitigation (beyond the designed in measures outlined in section 8.10),are not significant in EIA terms.

 

Table 8.28:
Sensitivity of the Benthic Subtidal IEFs found within the FFBC MPA to INNS

Table 8.28:  Sensitivity of the Benthic Subtidal IEFs found within the FFBC MPA to INNS

Operation and Maintenance Phase

Magnitude of Impact

Subtidal Habitat IEFs

  1. The installation of hard substrates and the presence of operation and maintenance vessels may lead to an increased risk of introduction and spread of INNS. The maximum design scenario is represented by up to 2,324 vessels round trips per year during the operation and maintenance phase ( Table 8.10   Open ▸ ) which is a reduction from the construction phase. Furthermore, the long-term creation of 10,198,971 m2 hard substrate, in the form of jacket foundations, associated scour protection and cable protection/crossings, has the potential to contribute to the introduction and spread of INNS. As outlined in paragraph 315 the estimate for habitat creation is considered to be conservative as the lattice nature of jacket foundations will result in a smaller area of habitat created than has been assumed for a foundation with solid sides.
  2. The removal of encrusted growth may also occur during the operation and maintenance phase, however, no quantitative assessment can be made as the volume of encrusting is not known. Removal of marine growth has the potential to release invasive species if the materials and equipment used in the process have not been properly cleaned after use at a previous location that may have had invasive species present. To control this however an invasive species management plan has been introduced to reduce the transmission of species through actions involved in the various phases of the Proposed Development ( Table 8.16   Open ▸ ).
  3. Details of INNS of concern in this region of Scotland are as outlined previously in paragraphs 362 and 363.
  4. As set out in Table 8.16   Open ▸ , an INNSMP and EMP (see volume 4, appendix 22), which will include measures such as ensuring any new infrastructure coming from another marine environment are cleaned and checked prior to installation and that vessels comply with the IMO ballast water management guidelines will be developed and adhered to for the Proposed Development. This will ensure that the risk of potential introduction and spread of INNS will be minimised.
  5. The 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 receptor directly. The magnitude is therefore considered to be low.

Firth of Forth Banks Complex MPA

  1. During the operation and maintenance phase of the Proposed Development the amount of contributing infrastructure will be the same as the final construction figure detailed in paragraph 368. Vessel movement will still occur for maintenance of infrastructure however it will be greatly reduced from the construction phase, the specific figure from vessel movement within the FFBC MPA is unknown.
  2. The 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 receptor directly. The magnitude is therefore considered to be low.
Sensitivity of the Receptor

Subtidal Habitat IEFs

  1. The sensitivity of the IEFs is as described previously for the construction phase assessment and in Table 8.27   Open ▸ .

Firth of Forth Banks Complex MPA

  1. The sensitivity of the IEFs is as described previously for the construction phase assessment and in Table 8.28   Open ▸ .
Significance of the Effect

Subtidal Habitat IEFs

  1. Overall, the magnitude of the impact is deemed to be low, and the sensitivity of the receptors (subtidal sand and muddy sand sediments, subtidal coarse and mixed sediments, moderate energy subtidal rock, seapens and burrowing megafauna, cobble/stony reef outside of an SAC, and rocky reef outside an SAC) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of limited ability of most invasive species to colonise the majority of these IEFs, the intermittent nature of the impact over a long period of time and where invasive species may be introduced measures will be put in place to reduce the overall risk.
  2. The Sabellaria reef outside of an SAC IEF is deemed of low magnitude and the sensitivity of the receptors is considered to be low. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of the measures that will be put in place to reduce the overall risk, the intermittent nature of the impact over a long period of time and this IEFs ability to thrive alongside other encrusting species.

Firth of Forth Banks Complex MPA

  1. Overall, the magnitude of the impact is deemed to be low, and the sensitivity of the receptors (subtidal sands and gravels, shelf banks and mounds, and ocean quahog) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of the limited ability of most invasive species to colonise the majority of these IEFs, the intermittent nature of the impact over a long period of time and where invasive species may be introduced measures will be put in place to reduce the overall risk.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of increased risk of introduction and spread of INNS during the operation and maintenance phase because the predicted effects in the absence of further mitigation (beyond the designed in measures outlined in section 8.10), are not significant in EIA terms.

Decommissioning Phase

Magnitude of Impact

Subtidal Habitat IEFs

  1. The presence of decommissioning vessels may lead to an increased risk of introduction and spread of INNS. The maximum design scenario for the decommissioning phase contains the same number of vessel movements as the construction phase (11,484) ( Table 8.10   Open ▸ ). Permanent habitat creation (i.e. persisting post-decommissioning) of up to 7,493,186 m2 due to the presence of scour and cable protection, including cable protection for cable crossing, being potentially left in situ (0.52% of the Proposed Development benthic subtidal and intertidal ecology study area).
  2. As set out in Table 8.16   Open ▸ , an INNSMP and EMP (see volume 4, appendix 22), which will include measures such as ensuring any new infrastructure coming from another marine environment are cleaned and checked prior to installation and that vessels comply with the IMO ballast water management guidelines will be developed and adhered to for the Proposed Development. This will ensure that the risk of potential introduction and spread of INNS will be minimised.
  3. The 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 receptor directly. The magnitude is therefore considered to be low.

Firth of Forth Banks Complex MPA

  1. The FFBC MPA overlaps with the site boundary for the Proposed Development and therefore there is the potential for the introduction of infrastructure within the MPA to result in the introduction and spread of INNS. The overall figures for the spatial overlap are outlined in paragraph 85 together with the assumptions for the overlap of infrastructure/activities with the FFBC MPA. Based on this percentage of overlap and the maximum design scenario for the construction phase, for the purposes of this assessment it is assumed that up to 1,867,831 m2 of hard substrate will be installed within the FFBC MPA which could aid the spread of INNS, which equates to 0.09% of the FFBC MPA. For the purposes of this assessment it is assumed that of the total, up to 1,292,334 m2 may occur within Berwick Bank (0.35% of the area of Berwick Bank) and up to 575,497 m2 may occur within Scalp and Wee Bankie (0.10% of the area of Scalp and Wee Bankie).
  2. As set out in Table 8.16   Open ▸ , an INNSMP and EMP (see volume 4, appendix 22), which will include measures such as ensuring any new infrastructure coming from another marine environment are cleaned and checked prior to installation and that vessels comply with the IMO ballast water management guidelines will be developed and adhered to for the Proposed Development. This will ensure that the risk of potential introduction and spread of INNS will be minimised.
  3. The 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 receptor directly. The magnitude is therefore considered to be low.
Sensitivity of the Receptor

Subtidal Habitat IEFs

  1. The sensitivity of the IEFs is as described previously for the construction phase assessment and in Table 8.27   Open ▸ .

Firth of Forth Banks Complex MPA

  1. The sensitivity of the IEFs is as described previously for the construction phase assessment and in Table 8.28   Open ▸ .
  2. Significance of the effect

Subtidal Habitat IEFs

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of all receptors (subtidal sand and muddy sand sediments, subtidal coarse and mixed sediments, moderate energy subtidal rock, seapens and burrowing megafauna, cobble/stony reef outside of an SAC, rocky reef outside an SAC and Sabellaria reef outside of an SAC) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of procedures in place to prevent invasive species introduction and the already high level of vessel traffic in the area as well as the aversion of invasive species to soft sediment habitats.

Firth of Forth Banks Complex MPA

  1. Overall, the magnitude of the impact is deemed to be low and the sensitivity of the receptors (subtidal sands and gravels, shelf banks and mounds, and ocean quahog) is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of procedures in place to prevent invasive species introduction and the already high level of vessel traffic in the area as well as the aversion of invasive species to soft sediment habitats.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of increased risk of introduction and spread of INNS during the decommissioning phase because the likely effects in the absence of further mitigation (beyond the designed in measures outlined in section 8.10), are not significant in EIA terms.

Alteration of Seabed Habitats Arising from Effects of Physical Processes

  1. Alteration of seabed habitats may arise from the effects of changes to physical processes, including scour effects and changes in the sediment transport and wave regimes resulting in potential effects on benthic receptors. Volume 3, appendix 7.1 provides a full description of the modelling used to inform this assessment.
  2. The relevant MarESA pressures and benchmarks used to inform this assessment of effect are described here.
  • Changes in local water flow (tidal current): change in peak mean spring bed flow velocity between 0.1 m/s to 0.2 m/s for more than one year. The pressure is associated with activities that have the potential to modify hydrological energy flows. This pressure corresponds to the impacts associated with the presence of wind turbine and OSP/Offshore convertor station platform foundations and cable protection.
  • Local wave exposure changes: change in nearshore significant wave height > 3% but < 5% for one year. This pressure corresponds to the impacts associated with the presence of wind turbine and OSP/Offshore convertor station platform foundations and scour protection.
    1. The relevant FeAST pressures and benchmarks used to inform this assessment of effect are described below.
  • Wave exposure changes – local: peak mean spring tide flow change between 0.1 m/s to 0.2 m/s over an area >1 km2 or 50% of width of water body for less than one year.
  • Wave exposure (tidal current) changes – local: change in mean annual nearshore significant wave height >3% but <5%. This considers wind fetch, wind strength, duration of wind, and topography; generally, significant wave height is <1.2 m but can be up to 3 m around UK coast.
    1. These pressures are relevant to the installation of wind turbine and OSP/Offshore convertor station platform into the water column potentially changing the predominant wave and tidal regime on a small scale.
    2. As discussed, in paragraph 40, this assessment has been undertaken on the broad IEFs and separately on the IEFs that comprise features of the FFBC MPA.

Operation and Maintenance Phase

Magnitude of Impact

Subtidal Habitat IEFs

  1. The presence of Proposed Development infrastructure will obstruct tidal flow and alter the wave climate within the benthic subtidal and intertidal ecology study area. The maximum design scenario in terms of hydrographic effects is for the installation of up to 179 wind turbines with four legs at 5.5 m diameter, spaced 60 m apart per unit with scour protection at each 20 m caisson leg foundation of 2 m in height and 80 m diameter covering a total footprint of 12,240 m2. Additional there may be up to five HVAC OSPs/Offshore convertor station platforms each with eight jacket legs comprising suction caissons of 15 m in diameter with associated scour protection of 60 m diameter and a height of 2 m giving rise to 6,346 m2 footprint per unit. The eight legs of 4 m diameter spaced 50 m apart at the seabed were also included within the water column to model associated influence on wave climate and tidal currents. Similarly, two HVDC OSPs/Offshore convertor station platform may also be required each with eight jacket legs comprising suction caissons of 15 m in diameter with associated scour protection of 60 m diameter and a height of 2 m giving rise to 12,559 m2 footprint per unit (including scour protection). The eight legs of 5 m diameter spaced 80 m apart at the seabed were also included ( Table 8.10   Open ▸ ). Additionally, there will be cable protection along up to 15% of the inter-array, OSP/Offshore convertor station platform interconnector and offshore export cables, as well as up to 78 inter-array cable crossings and up to 16 offshore export cable crossings ( Table 8.10   Open ▸ ).
  2. Tidal flow is predicted to accelerate in the immediate vicinity of each structure as it is redirected around the foundation and there may be a zone of reduced speed in the lee of the structure. During peak current speed the flow is redirected in the immediate vicinity of the structures and cable protection at the south of the site. The variation is a maximum of 1 cm/s which constitutes less than 2% of the peak flows within 200 m of the structure and reduces significantly with increased distance from each structure. These changes would also be limited to the immediate the benthic subtidal and intertidal ecology study area and extend a small distance beyond the southern and western boundaries of the Proposed Development array area (volume 3, appendix 7.1). The limited nature of these changes would not influence the hydrodynamic regime which underpins offshore bank morphology and is the supporting process for aspects of the Firth of Forth Banks Complex MPA, in particular Berwick and Marr Banks.
  3. Modelling of the predicted changes to wave climate for a one in one-year storm found the changes will be reductions in the lee of the site and increases where the waves are deflected by the structures. These changes are in the order of 2 cm which represents less than 1% of the baseline significant wave height. For the more severe 1 in 20 year storm event, the changes are predicted to follow the same pattern with decreases in the lee of the benthic subtidal and intertidal ecology study area and increases either side. However, the changes are not significantly increased from the more frequent return period scenario and in the order of 2 cm to 4 cm whereas the baseline wave heights are increased for the greater return period events giving rise to a less marked overall impact on wave climate.
  4. It is important to note that the predicted changes in wave and tidal regime (volume 3, appendix 7.1) are lower than the MarESA benchmarks used to inform the assessment therefore significant effects on communities are not likely to occur. Furthermore, the sensitivities described in the Table 8.29   Open ▸ , Table 8.30   Open ▸ and Table 8.31   Open ▸ are for a much higher magnitude than will result from the Proposed Development.
  5. Sediment transport is driven by a combination of tidal currents and wave conditions, the magnitude of these has been individually quantified as described above. For a one in one year storm from 000° during the flood tide the wave climate is in concert with tidal flow reducing the tidal flow on the lee side of the structure further. However, during the ebb flow, the wave climate and tidal flow are in opposition reducing the magnitude of the littoral current. With the presence of infrastructure, wave climate causes a small reduction in the magnitude of flow whilst there is little difference between the magnitude of littoral current flow and the tidal flows. Changes in magnitude compared to baseline current flow are ±5% (volume 3, appendix 7.1) which would not be sufficient to disrupt beach and offshore bank morphological processes or destabilise coastal features.
  6. Residual currents are effectively the driver of sediment transport and therefore any changes to residual currents would have a direct impact on sediment transport which would persist for the lifecycle of the Proposed Development. However, if the presence of the foundation structures does not have a significant influence on either tide or wave conditions (see assessments of effects presented above for changes in tidal currents and changes to wave climate and littoral current) they cannot therefore have a significant effect on the sediment transport regime. For completeness, the residual current and sediment transport was simulated with the foundations in place. The maximum change in residual current and sediment transport is predicted to be approximately ±15% within close proximity to the structures (less than 300 m elongated in the direction of principal tidal currents). Changes in the residual current and sediment transport reduce with increasing distance from the wind turbines towards baseline levels.
  7. Changes to tides, waves, littoral currents and sediment transport due to the presence of the infrastructure are not predicted to extend to the Barns Ness Coast SSSI or the Berwickshire and North Northumberland Coast SAC.
  8. The impact is predicted to be of local spatial extent, long term duration, continuous and high reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore considered to be low.

Firth of Forth Banks Complex MPA

  1. The magnitude of change in wave and tidal currents as well as sediment transport is consistent across the Proposed Development array area and Proposed Development export cable corridor where there are wind turbines, scour protection and cable protection. The magnitude of impact within the MPA is therefore as described in paragraphs 422 to 426.
  2. The impact is predicted to be of local spatial extent, long term duration, continuous and high reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore considered to be low.

Berwickshire and North Northumberland Coast SAC

  1. The modelling presented in volume 3, appendix 7.1 demonstrates that tidal flows will not be affected in the nearshore. For some wave climates (predominately storms approaching from the northerly sectors), there is predicted to be a very small change at the coast, but these are for specific storm directions and would be imperceptible from natural variation. The combination of the two (littoral currents) and thus the impact on sediment transport is also not predicted to give rise to any discernible change in physical processes at the coast and, therefore, within the Berwickshire and North Northumberland Coast SAC.
  2. The impact is predicted to be of local spatial extent, long term duration, continuous and high reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore considered to be negligible.