Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of increases of SSC and associated sediment deposition during the operation and maintenance 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.

Decommissioning Phase

Magnitude of Impact

Subtidal Habitat IEFs

  1. Decommissioning of the Proposed Development infrastructure may lead to increases in suspended sediment concentrations and associated sediment deposition. The maximum design scenario is represented by the cutting off of piled jacket foundations and the decommissioning of inter-array, OSP/Offshore convertor station platform interconnector and offshore export cables by jet dredging mobilising material from a 3 m deep and 2 m wide trench. Scour protection and cable protection, however, will remain in situ.
  2. Decommissioning of foundations is assumed to result in increases in suspended sediments and associated deposition that are no greater than those produced during construction. For the purpose of this assessment, the impacts of decommissioning activities are therefore predicted to be no greater than those for construction. In actuality the release of sediment in the decommissioning phase will be lower than the construction phase as it doesn’t include activities such as seabed drilling and seabed preparation.
  3. The impact is predicted to be of local spatial extent, short term duration, intermittent and of high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be low.

Firth of Forth Banks Complex MPA

  1. The magnitude of the change in environmental condition due to the impact of increased suspended sediment concentrations and associated sediment deposition is the same across the Proposed Development including in areas which overlap with the FFBC MPA (see paragraphs 227 and 228).
  2. The impact is predicted to be of local spatial extent, short term duration, intermittent and of high reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore considered to be low.

Berwickshire and North Northumberland Coast SAC

  1. The magnitude of the change in environmental condition due to the impact of increased suspended sediment concentrations and associated sediment deposition which may affect the Berwickshire and North Northumberland Coast SAC, should it extend far enough, is as described in paragraphs 227 and 228.
  2. The impact is predicted to be of local spatial extent, short term duration, intermittent and of high reversibility. It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be negligible.
Sensitivity of the Receptor

Subtidal Habitat IEFs

  1. The sensitivity of the subtidal IEFs is as described previously for the construction phase assessment in paragraphs 161 to 170 and in Table 8.21   Open ▸ .

Firth of Forth Banks Complex MPA

  1. The sensitivity of the IEFs is as described previously for the construction phase assessment in paragraphs 176 to 180 and in Table 8.22   Open ▸ .

Berwickshire and North Northumberland Coast SAC

  1. The sensitivity of the IEFs is as described previously for the construction phase assessment in paragraphs 181 to 189 and in Table 8.23   Open ▸ .

 

Significance of the Effect

Subtidal Habitat IEFs

  1. For the cobble/stony reef outside of an SAC IEF, the rocky reef outside a SAC IEF and the moderate energy subtidal rock IEF, the magnitude of the impact is deemed to be low, and the sensitivity of the receptors is considered to be medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms because of the high likelihood of recovery for these IEF to this short-term impact.
  2. For the subtidal sand and muddy sand sediments IEF, and subtidal coarse and mixed sediments 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 high likelihood of recovery for these IEF to this short-term impact.
  3. For the seapens and burrowing megafauna IEF and 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 negligible. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of the high likelihood of recovery for these IEF to this short-term impact.

Intertidal Habitat IEFs

  1. For the intertidal rock IEF and the fucus dominated intertidal rock IEF, the magnitude of the impacts is deemed to be negligible and the sensitivity of the receptors is considered to be medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms because of the high likelihood of recovery for these IEF to this short-term impact.
  2. For the intertidal sands IEF, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptors is considered to be negligible. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms.

Firth of Forth Banks Complex MPA

  1. For the subtidal sands and gravels IEF and shelf banks and mounds 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 high likelihood of recovery for these IEF to this short-term impact.
  2. For the ocean quahog IEF, the magnitude of the impact is deemed to be low and the sensitivity of the receptors is considered to be negligible. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms, because of the high likelihood of recovery for these IEF to this short-term impact.

Berwickshire and North Northumberland Coast SAC

  1. For the mudflats and sandflats not covered by seawater at low tide SAC IEF, the magnitude of the impact is deemed to be negligible, 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.
  2. For the reefs (subtidal and intertidal rocky reef) IEF, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptors is considered to be medium. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms, because of the high likelihood of recovery for these IEFs to this short-term impact and the large distance between this SAC and the Proposed Development.
  3. For the submerged or partially submerged sea caves IEF, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptors is considered to be medium. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms, because of the high likelihood of recovery for these IEF to this short-term impact and the large distance between this SAC and the Proposed Development.
  4. For the large shallow inlets and bays IEF, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptors is considered to be low. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of increases in SSC and associated sediment deposition 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.

Impact to Benthic Invertebrates due to Electromagnetic Fields

  1. The presence and operation of inter-array, OSP/Offshore convertor station platform interconnector and offshore export cables within the Proposed Development array area and Proposed Development export cable corridor may lead to localised EMF affecting benthic subtidal and intertidal receptors.
  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. EMF comprise both the electrical fields, measured in volts per metre (V/m), and the magnetic fields, measured in microtesla (µT) or milligauss (mG). Background measurements of the magnetic field are approximately 50 μT in the North Sea, and the naturally occurring electric field in the North Sea is approximately 25 μV/m (Tasker et al., 2010). It is common practice to block the direct electrical field using conductive sheathing, meaning that the only EMFs that are emitted into the marine environment are the magnetic field (B) and the resultant induced electrical field (iE). It is generally considered impractical to assume that cables can be buried at depths that will reduce the magnitude of the B field, and hence the sediment-sea water interface iE field, to below that at which these fields could be detected by certain marine organisms on or close to the seabed (Gill et al., 2005; Gill et al., 2009). By burying a cable, the magnetic field at the seabed is reduced due to the distance between the cable and the seabed surface as a result of field decay with distance from the cable (CSA, 2019).
  2. A variety of design and installation factors affect EMF levels in the vicinity of the cables. These include current flow, distance between cables, cable insulation, number of conductors, configuration of cable and burial depth. The flow of electricity associated with an alternating current (AC) cable (proposed for the Proposed Development) changes direction (as per the frequency of the AC transmission) and creates a constantly varying electric field in the surrounding marine environment (Huang, 2005).
  3. The strength of the magnetic field (and consequently, induced electrical fields) decreases rapidly horizontally and vertically with distance from source. A recent study conducted by CSA (2019) found that inter-array and offshore export cables buried between depths of 1 m to 2 m reduces the magnetic field at the seabed surface four-fold. For cables that are unburied and instead protected by thick concrete mattresses or rock berms, the field levels were found to be similar to buried cables.
  4. CSA (2019) investigated the link relationship between voltage, current, and burial depth, the results of which are presented in Table 8.24   Open ▸ which shows the magnetic and induced electric field levels expected directly over the undersea power cables and at distance from the cable for varying cable types. Directly above the cable, EMF levels decrease as you move away from the seafloor to 1 m above the cable, while as you move laterally away from the cable, at distances greater than 3 m), the magnetic fields at the seafloor and at 1 m above the seafloor are comparable.

 

Table 8.24:
Typical EMF Levels over AC Undersea Power Cables from Offshore Wind Energy Projects (CSA, 2019)

Table 8.24: Typical EMF Levels over AC Undersea Power Cables from Offshore Wind Energy Projects (CSA, 2019)

 

  1. During the operation phase of the project there will be up to 1,225 km of 66 kV inter-array cables and up to 872 km of 275 kV offshore export cables ( Table 8.10   Open ▸ ). The minimum burial depth for cables will be 0.5 m.
  2. The impact is predicted to be of local spatial extent, long term duration, continuous and high reversibility (when the cables are decommissioned). It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be negligible.

Firth of Forth Banks Complex MPA

  1. The magnitude of the impact on benthic invertebrates due to EMF is consistent across the Proposed Development including in the sections which overlap with the FFBC MPA, therefore for detail on the magnitude refer to paragraphs 251 to 255.
  2. Furthermore, based on the proportion of the FFBC MPA which overlaps with the Proposed Development, for the purposes of this assessment it is assumed that there may be up to 527 km of cables installed within the FFBC MPA. Of which 413 km will be associated with inter-array and interconnector cables, and 114 km will be associated with offshore export cables. For the purposes of this assessment it is assumed that up to 400 km of the cables would be within Berwick Bank and up to 127 km within Scalp and Wee Bankie.
  3. The impact is predicted to be of local spatial extent, long term duration, continuous and high reversibility (when the cables are decommissioned). It is predicted that the impact will affect the receptor directly. The magnitude is therefore considered to be negligible.

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. On the basis that there is no spatial overlap there is no pathway for impact from EMF effects and therefore no further assessment is required for this impact.
Sensitivity of the Receptor

Subtidal Habitat IEFs

  1. Gill and Desender (2020) summarised current research on the impact of EMF emissions on organisms and also acknowledged that relatively little is known about the effects of EMF on invertebrates such as those common in benthic communities. This is supported by a recent evaluation of knowledge of the impacts of EMF on invertebrates which concluded, globally, no direct impact on survival has been identified in the literature (Hervé, 2021). Furthermore, the methods to assess benthic invertebrates are variable therefore creating the same variability in results, as well as, in some cases, contradiction (Hutchinson et al., 2020). Some studies found that benthic communities which grow along cable routes were generally similar to those in the nearby area (Gill and Desender, 2020). These communities however are not exposed to the maximum EMF emissions due to cable burial creating a physical distance between the cable and the seabed surface, although the EMF which reaches the surface is measurable at biologically relevant scales at the seabed and in the water column (Hutchinson et al., 2020).
  2. Experimental evidence has demonstrated that exposure to EMF did not change the distribution of the ragworm Hediste diversicolor, the same result was also found by Jakubowska et al. (2019). Experimental evidence has however demonstrated magnetoreception in marine molluscs and arthropods and biogenic magnetite has been known to occur in marine molluscs for over five decades (Normandeau, 2011). Magneto-receptive and electro-receptive species have evolved to respond to small changes in the Earth’s geomagnetic fields and bioelectric fields making the presence of an EMF more perceivable to receptive species (Hutchinson et al., 2020). Reported sensitivities to electric fields for invertebrates range from around 3 mV/cm to 20 mV/cm (Steullet et al., 2007).
  3. Normandeau (2011) summarises that despite these sensitivities no direct evidence of impacts to invertebrates from undersea cable EMFs exists. What is known about invertebrate sensitivities to EMF does provides some guidance for considering likely significant effects. Likely significant effects would depend on the sensory capabilities of a species, the life functions that its magnetic or electric sensory systems support, and the natural history characteristics of the species. Life functions supported by the electric and magnetic sense indicate that species capable of detecting magnetic fields face likely significant effects different from those that detect electric fields.
  4. Shellfish which also occupy the sea floor, are anticipated to be more sensitive to EMF. Scott et al. (2021), investigated the effects of different strength EMF exposure on the commercially important decapod Cancer pagurus edible crab. This investigation measured stress related parameters as well as behavioural and response parameters over a 24-hour period. The results of this investigation indicated that exposure to 500 µT and 1,000 µT were found to attract crabs, limiting their time spent roaming as well as disrupting the production of chemicals associated with circadian rhythms leading to increased physiological stress when exposed to EMF of 500 µT or above. These results however are not directly applicable to the cables used in the Proposed Development as the magnetic field levels tested by Scott et al. (2021) are an order of magnitude higher than those associated with a buried cable such as those at the Proposed Development. These effects on shellfish receptors are fully considered in volume 2, chapter 9.
  5. Research regarding the impact of EMF on invertebrates still has a number of knowledge gaps which hinder our ability to fully understand the effects. Hervé (2021) identifies that establishing the impact on groups such as Molluscs is highly underdeveloped, the impact on species relative to the strength of the EMF, as well as the impact of different types of cable, are key knowledge gaps.
  6. The subtidal sand and muddy sand sediments IEF, the subtidal coarse and mixed sediments IEF and the moderate energy subtidal rock IEF are deemed to be not sensitive and of regional value. The sensitivity of the IEFs is therefore, considered to be negligible.
  7. The seapens and burrowing megafauna IEF, the cobble/stony reef outside of an SAC IEF, the rocky reef outside an SAC IEF and the Sabellaria reef outside of an SAC IEF are deemed to be not sensitive and of national value. The sensitivity of the IEFs is therefore, considered to be negligible.
  8. As the PMFs are not sensitive to this feature there will be negligible impact on their national status.

Firth of Forth Banks Complex MPA

  1. The IEFs within the FFBC MPA are deemed to be not sensitive and of national value. The sensitivity of the IEFs is therefore, considered to be negligible.
Significance of the Effect

Subtidal Habitat IEFs

  1. For the subtidal sand and muddy sand sediments IEF, the subtidal coarse and mixed sediments IEF and the moderate energy subtidal rock IEF, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptors is considered to be negligible. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms.
  2. For the seapens and burrowing megafauna IEF, the cobble/stony reef outside of an SAC IEF, the rocky reef outside an SAC IEF and the Sabellaria reef outside of an SAC IEF, the magnitude of the impact is deemed to be negligible and the sensitivity of the receptors is considered to be negligible. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms.

Firth of Forth Banks Complex MPA

  1. Overall, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptors (subtidal sands and gravels, shelf banks and mounds, and ocean quahog) is considered to be negligible. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of EMF 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.

Long Term Subtidal Habitat Loss

  1. Long term subtidal habitat loss within the Proposed Development array area and Proposed Development export cable corridor will occur during the construction phase as infrastructure is gradually installed as well as during the operation and maintenance phase ( Table 8.10   Open ▸ ). Long term habitat loss will occur directly under all wind turbine and OSP/Offshore convertor station platform foundation structures (suction caisson and jacket foundations respectively). The installation of scour protection and cable protection (including at cable crossings), where this is required, will also lead to habitat alteration and a physical change to another seabed type under the scour/cable protection material. Magnitude has been considered for both phases combined as the structures will be placed during construction and will be in place during the operation and maintenance phase. The impact of habitat loss occurring during the decommissioning phase has also been considered as the maximum design scenario assumes that scour and cable protection will be left in situ following decommissioning. Although cables and cable protection may be removed where reasonably practicable and appropriate to do so.
  2. The relevant MarESA pressures and their benchmarks which have used to inform this assessment of effect are described here.
  • Physical change (to another seabed type): the benchmark for which is change in sediment type by one Folk class (based on UK SeaMap simplified classification (Long, 2006)) and change from sedimentary or soft rock substrata to hard rock or artificial substrata or vice-versa.
    1. The relevant FeAST pressures and their benchmarks which have used to inform this assessment of effect are described here.
  • Physical change (to another seabed type): the benchmark for which is the permanent change of one marine habitat type to another marine habitat type, through the change in substratum. For instance, a change from sediment to solid substrate including artificial (e.g. concrete mattresses, rock deposition, and moorings), or from one type of sediment to another. This pressure concerns disposal or the deposit of material, whilst the removal of material is covered under abrasion pressures.
    1. These pressures are relevant to the installation of wind turbine and OSP/Offshore convertor station platform foundations, the associated scour protection and the cable protection which will replace the sedimentary seabed with hard structures for the duration of the construction and operation and maintenance phase (35 years). In the decommissioning phase only cable protection and scour protection may remain in situ contributing towards long term habitat loss, whereas wind turbine and OSP/Offshore convertor station platform foundations will be removed.

Construction and Operation and Maintenance Phase

Magnitude of Impact

Subtidal Habitat IEFs

  1. The presence of the Proposed Development infrastructure within the Proposed Development array area and offshore Proposed Development export cable corridor will result in long term habitat loss/alteration. The maximum design scenario is for up to 7,798,856 m2 of long term habitat loss due to the installation of suction caisson jacket foundations and associated scour protection and cable protection associated with wind turbines, OSP/Offshore convertor station platform interconnectors, offshore export cables, inter-array cables, interconnector cables and cable crossings ( Table 8.10   Open ▸ ). Cable protection will also be required for 78 cable crossings for the array cables and 16 crossings for the offshore export cables ( Table 8.10   Open ▸ ). The total long term habitat loss equates to a small proportion (0.54%) of the benthic subtidal and intertidal ecology study area.
  2. Long term subtidal habitat loss impacts will occur during the construction phase and will be continuous throughout the 35 year operation and maintenance phase.
  3. As outlined in Table 8.10   Open ▸ and as discussed previously in paragraph 81, cables will be installed at the landfall via trenchless techniques which means there will be no impact to, or long term loss of, any intertidal IEFs and they have not been considered further in this assessment.
  4. The exit punches out for the selected trenchless technique (e.g. HDD) will be located between 488 m and 1,500 m from MHWS. The seaward installation of the offshore export cables in the nearshore area will therefore be through the nearshore subtidal rock habitat resulting in potential for long term habitat loss. It should however be noted that the cable, if surface laid, would be protected by cable protection and where the cable is installed in a trench, this would be back-filled or protected with cable protection. This would therefore provide substrate for colonisation by benthic organisms after the cessation of construction activities, potentially resulting in habitat alteration rather than total habitat loss. The seaward installation of offshore export cables through the nearshore subtidal rock may cross up to 1,416 m of this habitat per cable with rock protection at a width of 20 m. Of the 7,798,856 m2 of total long term habitat loss discussed in paragraph 278, up to 226,560 m2 may occur within nearshore rock. This equates to approximately 2.8% of this nearshore rock habitat which lies within the Proposed Development export cable corridor (this extent was calculated based on JNCC Annex I reef data for the UK|) and an even smaller proportion of the distribution of this habitat within the regional benthic subtidal and intertidal ecology study area. As outlined in Table 8.16   Open ▸ , pre-construction Annex I reef surveys will be undertaken to determine the location, extent and composition of any geogenic reefs within the Proposed Development. Should reef features be identified appropriate measures will be discussed with the statutory consultees to avoid direct impacts to this feature where reasonably practicable, and on the basis of the extent of these features at the time of construction.
  5. Additionally designed in measures regarding the suitable implementation and monitoring of cable protection will ensure that infrastructure which should be buried will remain so and not impede on the surface sedimentary habitat ( Table 8.16   Open ▸ ).
  6. The impact is predicted to be of local spatial extent, long term duration, continuous and low reversibility during the lifetime of the Proposed Development. 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 some long-term habitat loss may occur within the FFBC MPA. 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 and operation and maintenance phases, up to 1,946,445 m2 of long term subtidal habitat loss may occur within the FFBC MPA, which equates to 0.09% of the total area of the FFBC MPA. This includes up to 1,346,726 m2 within the area of Berwick Bank (0.25% of the area of Berwick Bank) and 599,719 m2 within the area of Scalp and Wee Bankie (0.07% of the area of Scalp and Wee Bankie).
  2. The total area of long term habitat loss represents a very small percentage loss (0.0003%) of the total area of the OSPAR Region II (Greater North Sea) within which ocean quahog is listed as under threat and/or decline. It also represents a very small percentage (0.9%) of the offshore subtidal sands and gravels feature of the MPA, which is also equivalent to the available supporting habitat for ocean quahog.
  3. The impact is predicted to be of local spatial extent, long term duration, continuous and low reversibility during the lifetime of the Proposed Development. 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. On the basis that there is no spatial overlap there is no pathway for impact from long term habitat loss and therefore no further assessment is required for this impact.
Sensitivity of the Receptor

Subtidal Habitat IEFs

  1. Long term habitat loss will affect subtidal IEFs only, including subtidal sand and muddy sand sediments, subtidal coarse and mixed sediments, and Sabellaria reef outside of an SAC.
  2. All subtidal IEFs have high sensitivity to long term habitat loss where a change in seabed type would cause a fundamental change in habitat character ( Table 8.25   Open ▸ ). As outlined previously, this habitat change represents a small proportion of the Proposed Development array area and offshore Proposed Development export cable corridor.
  3. Within the subtidal IEFs all the characterising infaunal species will be affected by long term subtidal habitat loss during the operation and maintenance phase. These species will be removed along with the substratum underneath the offshore structures and scour/cable protection, therefore all the IEFs are considered highly intolerant of, and vulnerable to, complete habitat loss. Given the small spatial scales of the total long term habitat loss outlined above (i.e. 0.54% of the benthic subtidal and intertidal ecology study area) this loss is not expected to undermine regional ecosystem functions or diminish biodiversity. During decommissioning, when the foundations will be removed (although noting this will follow best practice at the time of decommissioning), the impacts will therefore potentially be reversible with the affected habitats likely to recover.
  4. All the nearshore rock and reef habitats (moderate energy subtidal rock, cobble/stony reef outside of an SAC, rocky reef outside of an SAC) have a high sensitivity to a physical change of the seabed. The removal of rock or cobbles would represent a fundamental change to the physical characteristics of this biotope. The physical shift would also result in a change to the associated faunal community, ultimately changing the biotope. By backfilling the trenches for the offshore export cables with the same or similar material, as well as the placement of rock protection, means that this habitat would not be permanently lost, instead the habitat would be altered but still composed of the same physical material allowing the original community to recolonise. For example, Corallina officinalis settled on artificial substrata within one week in the field in summer months in New England (Harlin and Lindbergh, 1977). 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.
  5. Although there is an impact on PMF(s) this will not create significant impact on the national status of these features. This is because of the highly localised nature of the impact only causing habitat loss in discrete locations spread cross the Proposed Development which amounts to 0.54% of the benthic subtidal and intertidal study area. Designed in measures, such as Annex I surveys, aim to avoid impacts to these features where reasonably practicable, and on the basis of the extent of these features at the time of construction.

Table 8.25:
Sensitivity of the Benthic Subtidal IEFs to Long Term Subtidal Habitat Loss

Table 8.25: Sensitivity of the Benthic Subtidal IEFs to Long Term Subtidal Habitat Loss

Firth of Forth Banks Complex MPA

  1. The FeAST determines that the sensitivity of the subtidal sands and gravels IEF to extraction of substratum is high, although this can be reduced to low depending on the species present, as the different species which can occupy a habitat, depending on its location and the physical conditions, can have considerably different sensitivities to the same impact. The MarESA determines the subtidal sands and gravels IEF which occurs within the FFBC MPA to have a high sensitivity to the pressures associated with long term subtidal habitat loss ( Table 8.26   Open ▸ ). The reasons for sensitivity are the same as those outlined in paragraph 290.
  2. The shelf banks and mounds IEF has the same sensitivity as the subtidal sands and gravel IEF as it contains the same biotopes.
  1. With respect to the ocean quahog IEF, both the FeAST Tool and MarESA conclude that a change to hard substratum would remove the sedimentary habitat which is necessary for the species with no resistance and very low resilience to such changes (Tyler-Walters and Sabatini, 2017) resulting in a high sensitivity ( Table 8.26   Open ▸ ).
  1. As discussed in paragraph 106, the presence of the infrastructure associated with the Proposed Development may also have some effects on ocean quahog which could facilitate the recovery following disturbance. Whilst there will be no safety zones enforced during the operation and maintenance phase (except during major maintenance events), a 50 m safe passing distance for logistical and safety reasons (i.e. to account for the offset/drifting of fishing gear that happens as a result of the tide) can be assumed for fishing vessels in the vicinity of wind turbines. The effect of this may be that trawling activity may potentially reduce within the Proposed Development array area. As a result, ocean quahog within the area covered by these safe passing distances will potentially experience a reduced level of disturbance from commercial fishing in the long term (i.e. over the operational lifetime of the Proposed Development and potentially beyond), which may aid with the recovery of the wider population from the direct loss of individuals which may result from the long-term habitat loss impact.
  2. The subtidal sands and gravel 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.
  3. 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.

 

Table 8.26:
Sensitivity of the Benthic Subtidal IEFs found within the FFBC MPA to Long Term Subtidal Habitat Loss

Table 8.26: Sensitivity of the Benthic Subtidal IEFs found within the FFBC MPA to Long Term Subtidal Habitat Loss

 

Significance of the Effect

Subtidal Habitat IEFs

  1. Overall, the magnitude of the impact is deemed to be low, and the sensitivity of the relevant 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 limited extent of this impact as well as the ability of some of these IEFs to colonise infrastructure.

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 extent of this impact within the wider context of the MPA.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary as a result of long term habitat loss during the construction/operation and maintenance phases 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. The potential for Proposed Development infrastructure such as cable and scour protection to remain on the seabed following the decommissioning process and to remain in perpetuity, has been assessed, as permanent habitat alteration on the basis that this habitat will be recolonised over time. The maximum design scenario is for up to 7,562,609 m2 of permanent habitat alteration due to scour protection and cable protection associated with inter-array, OSP/Offshore convertor station platform interconnector and offshore export cables being left in situ after decommissioning. Wind turbine and OSP/Offshore convertor station platform foundations will be removed as part of the decommissioning process. This equates to a small proportion (0.52%) of the benthic subtidal and intertidal ecology study area. In areas of previously soft sediments where the cables and scour protection are left in situ on the seabed, the substrate will not return to soft sediments and therefore there is no potential for recovery in these localised areas. In areas of rock based habitats in the nearshore area, as discussed in paragraph 278, the rock protection in these areas is likely to be colonised by a similar suite of species as present in the surrounding and extensive similar habitat which could effectively lead to recovery in these areas.
  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.

Firth of Forth Banks Complex MPA

  1. The FFBC MPA overlaps with the site boundary for the Proposed Development and therefore some permanent habitat alteration may occur within the FFBC MPA. 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 decommissioning phase, for the purposes of this assessment it is assumed that up to 1,889,581 m2 of permanent subtidal habitat loss may occur within the FFBC MPA, which equates to 0.09% of the FFBC MPA. This includes 1,307,383 m2 within the area of Berwick Bank (0.24% of the area of Berwick Bank) and 582,198 m2 within the area of 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, 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/operation and maintenance phase assessment in paragraphs 288 to 292 and in Table 8.25   Open ▸ .The installation of hard artificial structures may have beneficial effects to some biotopes, as it will increase the structural complexity of the substrata which will provide niche habitats (BioConsult, 2006). However, colonisation of the scour protection and cable protection may also have adverse effects on the baseline communities and habitats due to increased predation on and competition with the existing soft sediment species. Recent published papers and articles have highlighted that the industry does not have a thorough understanding of the effects of artificial hard substrate and the consequences of its removal. These recent publications have added to the scientific knowledge base on the impacts of on marine ecosystems to facilitate the development and discussion around best ecological practice for decommissioning (Cefas, 2020; Birchenough and Degaer, 2020), however, many data gaps still remain.
  2. All of the 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.

Firth of Forth Banks Complex MPA

  1. The sensitivity of the IEFs is as described previously for the construction/operation and maintenance phase assessment in paragraphs 293 to 298 and in Table 8.25   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 relevant receptors (subtidal sand and muddy sand sediments IEF, subtidal coarse and mixed sediments IEF, moderate energy subtidal rock, cobble/stony reef outside of an SAC, rocky reef outside an SAC, 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 limited extent of this impact and permanent infrastructure will not impact IEFs beyond the area it will occupy as well as the ability of some of these IEFs to colonise the remaining infrastructure.

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 extent of this impact within the wider context of the MPA and this extent will not increase as a result of these activities.
Secondary Mitigation and Residual Effect
  1. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact long term habitat loss 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.

Colonisation of Hard Structures

  1. The introduction of infrastructure within the Proposed Development array area and offshore Proposed Development export cable corridor may result in the colonisation of foundations, scour protection and cable protection.
  2. The environmental pressures associated with this impact are the same as those associated with long term subtidal habitat loss because the physical change (to another substratum type) pressure involves the permanent loss of one marine habitat type but has an equal creation of a different marine habitat type component such as the installation of wind turbine foundations and cable protection (Tillin and Tyler-Walters, 2015b; 2014a,b). The pressures are described for the MarESA in paragraph 275 and FeAST in paragraph 276.
  3. 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 maximum design scenario is for up to 10,198,971 m2 of habitat creation due to the installation of jacket foundations, associated scour protection and cable protection associated with inter-array cables, OSP/Offshore convertor station platform interconnector cables and offshore export cables ( Table 8.10   Open ▸ ). This equates to 0.70% of the benthic subtidal and intertidal ecology study area. This value however is likely an over estimation of habitat creation as it has been calculated assuming the foundations were a solid structure. In reality the jacket foundations will have a lattice design rather than a solid surface as has been assumed, which would result in a smaller surface area. It is expected that the foundations and scour and cable protection will be colonised by epifaunal species already occurring in the benthic subtidal and intertidal ecology study area (e.g. tunicates, bryozoans, mussels and barnacles which are typical of temperate seas).
  2. Cables will be installed at the landfall via trenchless techniques which means there will be no impact on any intertidal IEFs as there will be no cable protection and therefore, they have not been considered further in this assessment.
  3. The exit punches out for the selected trenchless technique (e.g. HDD) will be located between 488 m and 1,500 m from MHWS. The seaward installation of the offshore export cables in the nearshore subtidal area will therefore be through the nearshore subtidal rock habitat. It should however be noted that the offshore export cables, if surface laid in the nearshore subtidal, would be protected by cable protection and where the cable is installed in a trench, this would be back-filled or protected with cable protection. This would therefore provide substrate for colonisation by benthic organisms after the cessation of construction activities. This would however effectively replace the previously lost hard substate, noting however that the species colonising this material would likely be similar although not necessarily exactly the same as those species lost. This impact has not been considered to represent new hard substrate habitat creation in this nearshore area.
  4. The effects associated with the colonisation of hard structures are only considered in the operation and maintenance phase and decommissioning phase as it takes time for organisms to colonisation a structure post-installation.
  5. The introduction of new hard substrate will represent a shift in the baseline conditions from soft substrate areas (i.e. muds, sands and gravels) to hard substrate in the areas where infrastructure is present. This may produce some potentially beneficial effects, for example the likely increase in biodiversity and individual abundance of reef species and total number of species over time, as has been observed at the monopile foundations installed at Lysekil research site (a test site for offshore wind-based research, north of Gothenburg, Sweden) (Bender et al., 2020). Additionally, the structural complexity of the substrate may provide refuge as well as increasing feeding opportunities for larger and more mobile species. The presence of mobile benthic organisms is thought to be dependent on sufficient food sources, cover of epibenthic communities and appropriate habitat with shelter opportunities to hide from predators (Langhamer, and Wilhelmsson, 2009). This effect can also be applied to jacket foundations, a study by Lefaible et al. (2019) identified that jacket foundations had higher densities and diversity (species richness) of species in closer vicinity of the wind turbines compared to a control and a monopile foundation. Mavraki et al. (2020), study of gravity based foundations in the Belgian part of the North Sea found that higher food web complexity was associated with zones where high accumulation of organic material such as soft substrate or scour protection, suggesting potential reef effect benefits from the presence of the hard structures.
  6. The reef effect may be enhanced by the deposition of fouling material on the seabed. An investigation conducted at the research platform Forschungsplattformen in Nord- und Ostsee 1 FINO 1 in the south-western German Bight in the North Sea reported that yearly, 878,000 single shell halves from Mytilus edulis sink onto the seabed from the FINO 1 platform, thereby greatly extending the reef effects created by the construction of the offshore platform structure (Krone et al., 2013). Removal of marine growth from the wind turbine foundations may also cause debris to fall within the vicinity of the wind turbine foundation. It is likely that seaweed/algal material would disperse into the water column, with heavier material (e.g. mussels) being deposited within 10 m to 15 m of the foundation. This material has the potential to change the prevailing sediment type in the immediate vicinity of the wind turbines, and therefore extending the reef effect.
  7. The increases biodiversity, species richness and species abundance which has been noted as a feature of colonised infrastructures, such as the jacket foundations of wind turbines, will also provide greater foraging opportunities for some fish species (this has been assessed in volume 2 chapter 9). This is supported by monitoring from Beatrice offshore wind farm (APEM, 2021) which noted fish and shellfish at the base of foundations although no biological material was recorded on the seabed. Material may be rapidly consumed by organisms or relocated due to tidal currents and further monitoring will be required to clarify if biological material builds up over time (APEM, 2021). Any additionally effects up the food chain are considered in relation to marine mammals (volume 2, chapter 10) and ornithology (volume 2, chapter 11) will be considered in their individual chapters.
  8. A review by Degraer et al (2020) explained the process by which wind turbine foundations are colonised and the vertical zonation of species that can occur. In general biofouling communities on offshore installations are dominated by mussels, macroalgae, and barnacles near the water surface, essentially creating a new intertidal zone; filter feeding arthropods at intermediate depths; and anemones in deeper locations (De Mesel et al., 2015). Colonisation by these species will likely represent an increase in biodiversity and a change compared to the situation if no hard substrates were present (Lindeboom et al., 2011).
  9. Additionally, the designed in measures regarding the suitable implementation and monitoring of cable protection will ensure that no more than the than the declared amount of new hard substrate habitat is created and that any buried infrastructure remains so and does not impede upon the surface sedimentary habitat ( Table 8.16   Open ▸ ).
  10. The impact is predicted to be of local spatial extent, long term duration (35-year operation and mainteance 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.

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 will occur within the FFBC MPA. 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 2,715,565 m2 of new habitat for colonisation will be introduced into the FFBC MPA, which equates to 0.13% of the FFBC MPA. For the purposes of this assessment it is assumed that 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).
  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.

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. On the basis that there is no spatial overlap there is no pathway for impact from habitat creation and therefore no further assessment is required for this impact.