8.9.2.    Criteria for Assessment of Effects

53. The process for determining the significance of effects is a two-stage process that involves defining the magnitude of the likely significant effects and the sensitivity of the receptors. This section describes the criteria applied in this chapter to assign values to the magnitude of likely significant effects and the sensitivity of the receptors. The terms used to define magnitude and sensitivity are based on those which are described in further detail in volume 1, chapter 6 of the Offshore EIA Report.
54. The criteria for defining magnitude in this chapter are outlined in Table 8.12   Open ▸ . In determining magnitude within this chapter, each assessment considered the spatial extent, duration, frequency and reversibility of impact and these are outlined within the magnitude section of each assessment of effects (e.g. a duration of hours or days would be considered for most receptors to be of short term duration, which is likely to result in a low magnitude of impact).

Table 8.12: Definition of Terms Relating to the Magnitude of an Impact

55. The Marine Evidence based Sensitivity Assessment (MarESA) and the FeAST have been drawn upon to support the assessment of sensitivity of the benthic subtidal and intertidal ecology IEFs within the benthic subtidal and intertidal ecology study area.
56. The MarESA is a database which has been developed through the Marine Life Information Network (MarLIN) of Britain and Ireland and is maintained by the Marine Biological Association (MBA), supported by statutory organisations in the UK (e.g. Department of Agriculture, Environment and Rural Affairs (DAERA), JNCC, Natural England and NatureScot). This database comprises a detailed review of available evidence on the effects of pressures on marine species or habitats, and a subsequent scoring of sensitivity against a standard list of pressures, and their benchmark levels of effect. The evidence base presented in the MarESA is peer reviewed and represents the largest review undertaken to date on the effects of human activities and natural events on marine species and habitats. It is considered to be one of the best available sources of evidence relating to recovery of seabed species and habitats. The benchmarks for the relevant MarESA pressures which have been used to inform each assessment of effect have also been referenced under each assessment of effect in section 8.11. The process for defining sensitivity in this chapter follows that defined by the MarESA sensitivity assessment, which correlates resistance and recoverability to categorise sensitivity, as set out in Table 8.14   Open ▸ .
57. FeAST allows users to investigate the sensitivity of marine features in Scotland's seas to pressures arising from human activities. This sensitivity assessment considers feature tolerance (ability to absorb or resist change or disturbance) to a pressure and its ability to recover once the pressure stops. These pressures are defined by a benchmark which describes the extent and duration of the pressure but does not consider the intensity, frequency of pressures or any cumulative impacts. The tolerance and recoverability are then compiled into a matrix which provides a final assessment of the effects. Much of the evidence presented within FeAST has been derived from sensitivity assessments originally undertaken by MarLIN and further developed by a number of Scottish organisations such as NatureScot, MSS, Scottish Environment Protection Agency (SEPA) and JNCC. The tool focusses on features of conservation interest such as protected features of MPAs and PMFs. The process for defining sensitivity in this chapter follows that defined by the FeAST sensitivity assessment, which correlates resistance and recoverability to categorise sensitivity, as set out in Table 8.13   Open ▸ .
58. The FeAST is particularly focussed on features relevant to nature conservation MPAs in Scotland and is informed more generally by the MarESA. As a result FeAST doesn’t assess all the relevant IEFs in the required level of detail therefore where the sensitivity differs between the two tools, the tool with the most relevant detail will take precedent, in most scenarios this has been the MarESA.
59. The sensitivities of benthic subtidal and intertidal IEFs presented within this EIA Report have therefore been defined by an assessment of the combined vulnerability (i.e. resistance, following MarESA, or tolerance following FeAST) of the receptor to a given impact and the likely rate of recoverability to pre-impact conditions (consistent with both MarESA and FeAST). Here, vulnerability is defined as the susceptibility of a species to disturbance, damage or death, from a specific external factor. Recoverability is the ability of the same species to return to a state close to that which existed before the activity or event which caused change. Recoverability is dependent on a receptor’s ability to recover or recruit subject to the extent of disturbance/damage incurred. Information on these aspects of sensitivity of the benthic subtidal and intertidal IEFs to given impacts has been informed by the best available evidence following environmental impact or experimental manipulation in the field and evidence from the offshore wind industry and analogous activities such as those associated with aggregate extraction, electrical cabling, and oil and gas industries.

Table 8.13: Definition of Terms Relating to the Sensitivity of the Receptor (Applicable to MarESA and FeAST Sensitivity Assessment)

60. The conclusions of the MarESA and FeAST assessments have been combined with the importance of the relevant IEF(s) as defined in section 8.7 and as presented in Table 8.9   Open ▸ for the benthic subtidal and intertidal IEFs considered in this assessment. The overall sensitivity of a receptor to an impact (based on the combination of vulnerability and recoverability) is then defined as presented in Table 8.14   Open ▸ .

Table 8.14: Definition of Terms Relating to the Overall Sensitivity of the Receptor

61. The significance of the effect upon benthic subtidal and intertidal ecology is determined by correlating the magnitude of the impact and the sensitivity of the receptor. The particular method employed for this assessment is presented in Table 8.15   Open ▸ .
62. In cases where a range is suggested for the significance of effect, there remains the possibility that this may span the significance threshold (i.e. the range is given as minor to moderate). In such cases the final significance conclusion is based upon the author’s professional judgement as to which outcome delineates the most likely effect. Where professional judgement is applied to quantify final significance from a range, the assessment will set out the factors that result in the final assessment of significance. These factors may include the likelihood that an effect will occur, data certainty and relevant information about the wider environmental context.
63. For the purposes of this assessment:

• A level of residual effect of moderate or more will be considered a ‘significant’ effect in terms of the EIA Regulations; and
• A level of residual effect of minor or less will be considered ‘not significant’ in terms of the EIA Regulations.
  64. Effects of moderate significance or above are therefore considered important in the decision-making process, whilst effects of minor significance or less warrant little, if any, weight in the decision-making process.

Table 8.15: Matrix Used for the Assessment of the Significance of the Effect

8.9.3.    Designated Sites

65. Where Natura 2000 sites (i.e. nature conservation sites in Europe designated under the Habitats or Birds Directives[19]) or sites in the UK that comprise the National Site Network (collectively termed ‘European sites’) are considered, this chapter makes an assessment of the likely significant effects in EIA terms on the qualifying interest feature(s) of these sites as described within section 8.7 of this chapter. The assessment of potential impacts on the site itself are deferred to the RIAA (SSER, 2022c) for the Proposed Development. A summary of the outcomes reported in the RIAA is provided in section 8.15 of this chapter.
66. With respect to locally designated sites and national designations (other than European sites), where these sites fall within the boundaries of a European site and where qualifying interest features are the same, only the features of the European site have been taken forward for assessment. This is because potential impacts on the integrity and conservation status of the locally or nationally designated site are assumed to be inherent within the assessment of the features of the European site (i.e. a separate assessment for the local or national site features is not undertaken). However, where a local or nationally designated site falls outside the boundaries of a European site, but within the benthic subtidal and intertidal ecology study area, an assessment of the likely significant effects on the overall site is made in this chapter using the EIA methodology.

8.10. Measures Adopted as part of the Proposed Development

67. As part of the project design process, a number of measures have been proposed to reduce the potential for impacts on benthic subtidal and intertidal ecology (see Table 8.16   Open ▸ ). As there is a commitment to implementing these measures, they are considered inherently part of the design of the Proposed Development) and have therefore been considered in the assessment presented in section 8.11 (i.e. the determination of magnitude and therefore significance assumes implementation of these measures). These measures are considered standard industry practice for this type of development.

Table 8.16: Designed In Measures Adopted as Part of the Proposed Development

8.11. Assessment of Significance

68. The likely significant effects arising from the construction, operation and maintenance and decommissioning phases of the Proposed Development are listed in Table 8.10   Open ▸ , along with the maximum design scenario against which each impact has been assessed.
69. An assessment of the likely significance of the effects of the Proposed Development on benthic subtidal and intertidal ecological receptors caused by each identified impact is given below.

Temporary Habitat Loss/Disturbance

70. Temporary habitat loss/disturbance of subtidal and intertidal habitats within the Proposed Development benthic ecology subtidal and intertidal study area will occur during construction, operation and maintenance, and decommissioning phase ( Table 8.10   Open ▸ ). Temporary habitat loss/disturbance can result from activities including use of jack-up vessels during foundation installation, sand wave and boulder clearance, cable installation and repair as well as anchor placements associated with these activities.
71. The relevant MarESA and FeAST tool pressures and their benchmarks which have used to inform this assessment of effects are described here:

• Habitat structure changes - removal of substratum (extraction): the benchmark for which is the extraction of substratum to 30 cm. This pressure is considered to be analogous to the impacts associated with sand wave and boulder clearance, and the construction of exit punches out associated with trenchless techniques such as HDD.
• Abrasion/disturbance at the surface of the substratum or seabed: the benchmark for which is damage to surface features (e.g. species and physical structures within the habitat). This pressure corresponds to the impacts associated with jack-up vessel operations, anchor placements.
• Penetration and/or disturbance of the substratum subsurface: the benchmark for which is damage to sub-surface features (e.g. species and physical structures within the habitat). This pressure corresponds to the impacts associated with cable installation and jack-up vessel operations.
• Smothering and siltation rate changes (heavy): the benchmark for which is heavy deposition of up to 30 cm of fine material added to the habitat in a single discrete event. This pressure corresponds to impacts associated with the deposition of sand wave material dredged prior to cable installation.
  72. 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, the Berwickshire and North Northumberland Coast SAC and the Barns Ness Coast SSSI.

Construction Phase

Magnitude of Impact

Subtidal Habitat IEFs

73. The installation of the Proposed Development infrastructure within the Proposed Development benthic ecology subtidal and intertidal study area will lead to temporary subtidal habitat loss/disturbance. The maximum design scenario includes for up to 113,974,700 m2 of temporary subtidal habitat loss/disturbance during the construction phase ( Table 8.10   Open ▸ ). This equates to approximately 7.86% of the benthic subtidal and intertidal ecology study area.
74. Seabed preparation activities throughout the construction phase (e.g. sand wave and boulder clearance) will occur in advance of the installation of inter-array cables, OSP/Offshore convertor station platform interconnector cables and offshore export cables. Of the total temporary habitat loss, up to 69,320,500 m2 is predicted to be temporarily lost/disturbed within the benthic subtidal and intertidal ecology study area due to deposition of the material dredged during pre-construction sand wave clearance. Dredged material resulting from the seabed preparation works will be disposed within the Proposed Development array area and Proposed Development export cable corridor. Pre-construction sand wave clearance activities and disposal within the Proposed Development array area and Proposed Development export cable corridor is assumed to result in sediment deposition to a uniform depth of 0.5 m. Any mounds of cleared material will, however, erode over time and displaced material will re-join the natural sedimentary environment, gradually reducing the size of the mounds.
75. Temporary habitat disturbance of up to 42,948,000 m2 may occur as a result of the burial of up to 1,225 km of inter-array cables, 94 km of OSP/Offshore convertor station platform interconnector cables and up to 872 km of offshore export cables. Sand wave clearance may be required for up to 20% of Proposed Development export cable corridor length and up to 30% of inter-array cables and OSP/Offshore convertor station platform interconnector cables. Boulder clearance may be required for up to 20% of offshore export cables length, inter-array cables and OSP/Offshore convertor station platform interconnector cables ( Table 8.10   Open ▸ ). The maximum width of seabed preparation is greater than the disturbance associated with the cable installation itself (i.e. 15 m for cable burial, 25 m for boulder clearance and 25 m for sand wave clearance). Cable burial will therefore occur within the area previously disturbed via sand wave or boulder clearance resulting in localised repeat disturbance within a 15 m wide corridor, within the wider 25 m corridor disturbed during sand wave and boulder clearance.
76. A recent study reviewed the effects of cable installation on subtidal sediments and habitats, drawing on monitoring reports from over 20 UK offshore wind farms (RPS, 2019). This review showed that sandy sediments (e.g. Subtidal Sand and Muddy Sand Sediment IEF and Subtidal Sands and Gravels IEF) recover quickly following cable installation, with trenches infilling quickly following cable installation and little or no evidence of disturbance in the years following cable installation. It also presented evidence that remnant cable trenches in coarse and mixed sediments (e.g. Subtidal Coarse and Mixed Sediment IEF) were conspicuous for several years after installation. However, these shallow depressions were of limited depth (i.e. tens of centimetres) relative to the surrounding seabed, over a horizontal distance of several metres and therefore did not represent a large shift from the baseline environment (RPS, 2019). Remnant trenches (and anchor drag marks) were observed years following cable installation within areas of muddy sand sediments, although these were relatively shallow features (i.e. a few tens of centimetres).
77. There will be anchor footprints from installation vessels, typically one anchor reposition per 500 m of cable may be required, with individual anchors associated with cable installation vessels having a footprint of approximately 100 m2. This area of seabed disturbance will depend on the precise vessel used and in some cases anchor placements may not be required at all (e.g. where the vessel uses dynamic positioning). The maximum design scenario accounts for up to 438,200 m2 from a 100 m2 anchor placed every 500 m during inter-array, OSP/Offshore convertor station platform interconnector and offshore export cables installation.
78. Jack-up footprints associated with foundation installation will result in compression of seabed sediments beneath spud cans where these are placed on the seabed. This is estimated to disturb up to 1,268,000 m2 of seabed habitat. These depressions will infill over time, although may remain on the seabed for a number of years, as demonstrated by monitoring studies of UK offshore wind farms (BOWind, 2008; EGS, 2011). Monitoring at the Barrow offshore wind farm showed depressions were almost entirely infilled 12 months after construction (BOWind, 2008). Monitoring at the Lynn and Inner Dowsing (LID) offshore wind farm also showed some infilling of the footprints, although the depressions were still visible two years post-construction (EGS, 2011). In areas where mobile sands are present, such as in the Proposed Development array area ( Figure 8.2   Open ▸ ), jack-up depressions are likely to be temporary features which will only persist for a period of months to a small number of years.
79. As outlined in Table 8.10   Open ▸ , the maximum design scenario assumes the clearance of up to 14 UXOs from the Proposed Development. The preferred method of removal is for low order clearance methods (only sub sonic combustion, with a single donor charge for each clearance event). These methods allow for the explosive content of a UXO to ignite and burn out but not detonate, these methods result in an 11 times reduction in sound emissions compared to high order detonation of UXO (UK Government, 2020) as well having a localised impact on the seabed. There is a small risk that a low order clearance could result in high order detonation of UXO. In addition, some UXOs may be deemed to be too unstable to warrant a low order approach and therefore for safety reasons would need to be cleared using high order methods.
80. A study undertaken for the Norfolk Vanguard offshore wind farm found the likely diameter of UXO craters for any given charge size in the marine environment following detonation would result in a maximum crater diameter of 21.11 m (Ordteck, 2018). A crater of this size would be within the footprint of sand wave/boulder clearance activities and/or foundation footprints and therefore will not lead to any additional habitat disturbance beyond what has already been considered for these activities. Any craters created during detonation are expected to gradually backfill by natural processes, the speed of which would depend on the sediment transport regimes in the area. The depth of the crater would not increase the amount of temporary habitat disturbance/loss of the characteristic communities of the Proposed Development area as the maximum design scenario assumes the clearance of sand waves with an average height of up to 5 m of sediment in the Proposed Development export cable corridor and 1.5 m in the inter-array/interconnector cable corridor, and Ordtek (2018) estimate the maximum depth of a UXO crater to be 3.30 m. This activity will not result in an increase in habitat disturbance as the infauna in the biotopes found in the Proposed Development are associated with the top 0.5 m of sediment (Tillin and Garrard, 2019; De-Bastos, 2016; De Basto and Hill, 2016; Hill, Tyler and Garrard, 2020; Tillin Marshall, Gibb and Garrard, 2020). Recovery from large scale extraction may occur over two to ten years, however, as the habitat loss due to UXO clearance is small scale, affecting discrete areas and will occur in a limited time scale, recovery is expected to be rapid (at the lower end of the scale) (McLusky et al., 1983). Paragraph 78 provides evidence of how depressions associated with jack-up footprints are likely to infill.
81. In the intertidal area trenchless techniques (e.g. HDD) will be used for cable installation which will not result in any direct habitat disturbance to intertidal habitats. The effect of habitat loss on benthic intertidal receptors is therefore not considered further for this impact.
82. As outlined in Table 8.10   Open ▸ , offshore export cables installation at the landfall will be via trenchless burial techniques only (e.g. HDD) and the associated exit punches out will be located between 488 m and 1,500 m from MHWS. The implication of this is that onward cable installation in the nearshore area will be through the area of nearshore subtidal rock. Temporary habitat disturbance associated with the installation of up to eight exit punches out, at least 488 m from the MHWS mark, is included within the maximum width of disturbance for cable burial including boulder and sand wave clearance (i.e. 25 m wide corridor; see Table 8.10   Open ▸ ). The onward installation of offshore export cables, including any seabed preparation works, through the nearshore subtidal rock may occur over a distance of up to 1,416 m for each cable (the distance from the exit punches out to the nearest sedimentary biotope) with a width of disturbance of 25 m (although noting that the width of disturbance associated with cable installation alone is up to 15 m). Therefore, of the 42,948,000 m2 of temporary disturbance associated with cable installation discussed in paragraph 75, up to 283,200 m2 may occur within nearshore rock. This equates to approximately 3.5% of this nearshore rock habitat within the Proposed Development export cable corridor (this was calculated based on extents taken from 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. This assessment of temporary habitat disturbance primarily considers the impacts associated with abrasion of this habitat during cable installation with the impact associated with the creation of the trench itself considered in the assessment of long-term habitat loss (see paragraph 274 et seq.). 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 these features where reasonably practicable, and on the basis of the extent of these features at the time of construction.
83. Installation of the Proposed Development infrastructure, resulting in the temporary subtidal habitat loss/disturbance will occur intermittently throughout the construction period. The offshore construction phase which includes activities resulting in temporary habitat loss/disturbance will occur over a period of up to 96 months.
84. The impact is predicted to be of local spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore considered to be medium.

Firth of Forth Banks Complex MPA

85. The FFBC MPA overlaps with the site boundary for the Proposed Development and therefore some temporary habitat loss/disturbance may occur within the FFBC MPA. The total area of the FFBC MPA is 2,130 km2, which includes Scalp and Wee Bankie (827.1 km2 which is 39% of the total MPA), Berwick Bank (541 km2 which is 25% of the total MPA) and Montrose Bank (761.8 km2 which is 36% of the total MPA). The Montrose Bank part of the MPA does not however overlap within the Proposed Development and, therefore, will not be affected. The total overlap of the Proposed Development and the FFBC MPA equates to a total of 331.7 km2, of which 316.5 km2 is within the Proposed Development array area (31.33% of the Proposed Development array area), and 15.2 km2 in the Proposed Development export cable corridor (13.08% of the Proposed Development export cable corridor). Overall, within the total area of overlap between the MPA and Proposed Development, 30.81% occurs within Scalp and Wee Bankie and 69.19% occurs within Berwick Bank. The maximum design scenario for the FFBC MPA has therefore been calculated on the assumption that 31.33% of the infrastructure which is to be installed in the Proposed Development array area could be placed in the part of the Proposed Development array area which overlaps with the FFBC MPA. Similarly, it is assumed that 13.08% of the infrastructure which is to be installed in the Proposed Development export cable corridor could be placed in the part of the Proposed Development array area which overlaps with the FFBC MPA.
86. Based on the assumptions outlined above, and the maximum design scenario, for the purposes of this assessment is it assumed that up to 24,697,566 m2 of temporary habitat loss/disturbance may occur within the FFBC MPA (see Table 8.17   Open ▸ ), which equates to 1.16% of the total area of the FFBC MPA. This can be broken down for the composite parts of the MPA as follows: up to 17,088,005 m2 within the area of Berwick Bank (3.16% of the area of Berwick Bank) and up to 7,609,561 m2 within the area of Scalp and Wee Bankie (0.92% of the area of Scalp and Wee Bankie). The Montrose Bank will not be affected by habitat loss/disturbance.
87. The total area of temporary subtidal habitat loss represents a very small percentage loss (0.003%) 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 small percentage (1.16%) of the offshore subtidal sands and gravels feature of the MPA, which is also equivalent to the available supporting habitat for ocean quahog.
88. The impact is predicted to be of local spatial extent, medium term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore considered to be low.

Table 8.17: Area of FFBC MPA Disturbed by Activities During the Proposed Development’s Construction

Berwickshire and North Northumberland Coast SAC

89. 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 for temporary habitat loss/disturbance and therefore no further assessment is required for this impact.

Barns Ness Coast SSSI

90. The Barns Ness Coast SSSI has been designated partially due to the presence of a valuable geological feature. This feature is called the ‘Lower Carboniferous Dinantian-Namurian’ and is composed of a sequence of sedimentary rocks which were formed during the Carboniferous geological period around 340 million years ago, when shallow, tropical seas extended across the lowland central belt area of Scotland (Scottish Natural heritage, 2011). The Applicant is committed to using trenchless techniques (e.g. HDD) in the intertidal zone which will ensure cables run under this feature and not through it. The exit punches out will also be located at least 488 m from MHWS and so will avoid this designated site. The exposed nature of the feature will therefore be preserved which will also ensure that fossils can still be collected from its surface. As a result, there is no further consideration of this feature within this assessment.

Sensitivity of the Receptor

Subtidal Habitat IEFs

91. The key IEFs which are expected to be affected by temporary subtidal habitat loss/disturbance are listed in Table 8.18   Open ▸ . The sensitivity of the IEFs to temporary subtidal habitat loss are presented in Table 8.18   Open ▸ . These sensitivities are based on assessments made by the MarESA and FeAST tool. Most IEFs have low to medium sensitivity to the MarESA pressures associated with temporary subtidal habitat loss/disturbance. All IEFs have a low to medium sensitivity to the FeAST pressures associated with temporary subtidal habitat loss/disturbance based on the related pressures.
92. The subtidal sand and muddy sand sediment IEF has a medium sensitivity to the pressures associated with temporary habitat loss and disturbance. Activities such as sand wave clearance would largely be undertaken in sandy sediments, with fast recovery rates following disturbance. Based on the MarESA sensitivity assessment, recovery of the sand-based habitats following habitat structure changes - removal of substratum (extraction), is likely to occur following the construction phase, aided by wave action and sand mobility (Tillin and Garrard, 2019). As the sediment type deposited to the seabed will be similar to those in surrounding areas, benthic assemblages would be expected to recolonise these areas. Penetration and/or disturbance of the substratum subsurface however is likely to cause the loss/damage of a proportion of characterising species for biotopes such as SS.SMu.CSaMu.ThyNten and SS.SMu.CSaMu.AfilMysAnit, with muddy sand habitats reported as having the longest recovery times. Abrasion/disturbance at the surface of the substratum has a similar effect however burrowing may provide some protection, damage and loss are still expected to occur. It has been reported that benthic communities associated with soft sediments (e.g. muds, sands and gravels) readily recover into areas where disturbance by cable installation has occurred if the sediment type is reflective of the baseline environment (RPS, 2019). Sandy sediments recover over relatively short timescales (e.g. months to one to two years; Newell et al., 2004) and coarse, gravelly and mixed sediments showing longer recovery timescales, usually within five years (Desprez, 2000; Newell et al., 1998; Pearce et al., 2007), but in some cases, recovery has been reported as taking up to nine years following cessation of dredging (Foden et al., 2009).
93. Within the subtidal coarse and mixed sediment IEF, the biotope SS.SMx.CMx.FluHyd is the most sensitive to the pressures associated with temporary habitat loss/disturbance. This is because this biotope is characterised by epifauna such as dahlia anemone Urticina felina and A. digitatum (Connor et al., 2004) which have no resistance to habitat structure change. The resistance to penetration and/or disturbance of the substratum subsurface or abrasion/disturbance of the substratum or seabed is dependent on the duration and magnitude of the pressure. The biotope SS.SMx.OMx.PoVen is most sensitive to heavy smothering and siltation rate changes within this IEF however this is dependent on the character of the smothering (i.e. the depth, small bivalves could migrate was 20 cm in sand for Donax; approximately 40 cm in mud for Tellina sp. and approximately 50 cm in sand (Essink, 1999)), and the type of material. Individuals are more likely to escape from a covering similar to the sediments in which the species is found than a different type (Tillin, 2016).
94. The seapens and burrowing megafauna IEF has a medium sensitivity to the abrasion/disturbance at the surface of the substratum or seabed but have high sensitivity to penetration and habitat structure change MarESA pressures associated with temporary subtidal habitat loss. Habitat structure changes – removal of substratum could remove most of the resident seapens present should it meet the benchmark of the removal of 30 cm of sediment (Hill et al., 2020) and similarly penetrative activities are likely to disturb or lead to mortality of seapens and burrowing megafauna in their burrows making resistance and resilience low and sensitivity high. They are however likely to recover within two years of experiencing pressures from surface abrasion.
95. The Sabellaria reef outside of an SAC IEF has a medium sensitivity to all the identified pressures for temporary habitat loss/disturbance. Sabellaria spinulosa which characterises this IEF is epifaunal and therefore vulnerable to surface abrasion and heavy smothering and siltation rate changes which can damage the tubes of the worms, however their recovery from burial events is high, especially over a short period of time (Tillin et al., 2020). Penetration and/or disturbance of the substratum subsurface is likely to damage and break-up tube aggregations leading to the loss of reef within the footprint of direct impact (Tillin et al., 2020). 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 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 construction.
96. The moderate energy subtidal rock, cobble/stony reef outside of an SAC and rocky reef outside an SAC IEFs may all be affected by offshore export cables installation in the nearshore area including exit punches out for trenchless techniques. These IEFs were all characterised by the CR.MCR.EcCr biotope during the site-specific benthic surveys and the hard nature of the substrate. The construction activities considered within this assessment of temporary habitat loss/disturbance primarily relate to those resulting in abrasion of the surface of this habitat, with the assessment of impacts associated with the construction of the trench itself considered in the long-term habitat loss assessment (see paragraph 274 et seq.). Epifaunal communities on rocky substrates, such as bryozoans, hydroids, soft corals and sponges can be damaged or removed by passing abrasion, and where they occur on mobile substrates such as cobbles the material can be moved or turned leading to further damage (Boulcott and Howell, 2011). The organisms associated with the moderate energy subtidal rock, cobble/stony reef outside of an SAC and rocky reef outside an SAC IEFs are likely to recolonise quickly following abrasion as they are characterised by rapid growth and early reproduction as well as multiple reproductive phases which would allow the biotope to recover quickly (MarLIN, 2011). Ultimately the impact of abrasion on these IEFs will depend on the magnitude and duration of the activity. As noted in paragraph 81 the area of installation within these habitats is small (283,200 m2) representing a similarly small percentage of the total extent of this habitat within the Proposed Development export cable corridor (3.5%, which was calculated based on JNCC Annex I reef data for the UK). Siltation and smothering during cable installation may affect epifaunal communities, especially sessile organisms, by blocking out light or clogging feeding apparatus, however the amount of siltation from the selected trenchless technique and cable installation is likely to be minimal and highly localised to the installation site. There may still be some temporary localised decline of species richness in these IEFs. Additionally, research on the installation of cables through cobble reef habitats has been found to have a very limited spatial footprint (10 to 20 m wide) with no effect on adjacent communities (<50 m from the installed cable) (RPS, 2019). 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 biogenic reefs within the Proposed Development. Should cobble/stony or rocky 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.
97. The subtidal sand and muddy sand sediments IEF, and the subtidal coarse and mixed sediments IEF are deemed to be of medium vulnerability, medium to low recoverability and regional value. The sensitivity of the IEFs is therefore, considered to be medium.
98. The Sabellaria reef outside of an SAC IEF is deemed to be of medium vulnerability, medium recoverability, and national value. The sensitivity of the IEF is therefore, considered to be high.
99. The seapens and burrowing megafauna IEF is deemed to be of high vulnerability, low recoverability and national value. The sensitivity of the IEF is therefore, considered to be high.
100. The moderate energy subtidal rock, cobble/stony reef outside of an SAC and rocky reef outside an SAC IEFs are deemed to be of medium vulnerability and medium recoverability to temporary habitat disturbance (i.e. abrasion effects) and of national value. The sensitivity of the IEFs is therefore, considered to be medium.
101. Although there is an impact on PMF(s), this will not create a significant impact on the national status of these features as only a small proportion of these PMFs will be affected compared to their overall national distribution and the temporary nature of the disturbance will limit the time over which disturbance will occur. Additionally, many will recover fully within a few years of the completion of construction, resulting in no change to their overall national status.
102. The construction activities will result in the displacement and potential mortality of some benthic organisms throughout the Proposed Development array area and Proposed Development export cable corridor. Molluscs and crustaceans will likely provide an increased source of food for some fish and shellfish species. This effect is applicable across all phases of the Proposed Development and the consequences for fish and shellfish receptors is considered in full in volume 2 chapter 9.

Table 8.18: Sensitivity of the Benthic Subtidal IEFs to Temporary Subtidal or Intertidal Habitat Loss/Disturbance

Firth of Forth Banks Complex MPA

103. The FeAST determines that the subtidal sands and gravels IEF has a high sensitivity to surface abrasion and habitat structure change, as well as a medium sensitivity to subsurface penetration and heavy smothering and siltation rate change ( Table 8.19   Open ▸ ). Although for all pressures, the FeAST tool states that this can be reduced to low depending on the species present. The MarESA which assessed the individual biotopes of the IEFs, determines that the subtidal sands and gravels IEF, which occurs within the FFBC MPA, has a medium to low sensitivity to the pressures associated with temporary habitat loss/disturbance ( Table 8.19   Open ▸ ). The biotope SS.SSa.CFiSa.ApriBatPo has a medium sensitivity to this pressure because most of the organisms that occur in this biotope are shallow buried and sediment extraction would remove the assemblage (Tillin, 2016). This range in sensitivity based on the species present is the same for the other pressures. The MarESA assessment for surface abrasion and subsurface penetration gives a sensitivity of low for the relevant biotopes as damage may occur but recovery or high tolerance are likely. Heavy smothering and siltation rate change is assessed by the MarESA to result in a medium sensitivity by this IEF as recovery is dependent on the burrowing capacity of some species. The impact of the Proposed Development on the designated features of the FFBC MPA are also fully considered in the MPA Assessment Report (SSER, 2022b).
104. The shelf banks and mounds IEF has the same sensitivity as the subtidal sands and gravel IEF outlined above as it contains the same biotopes (see Table 8.19   Open ▸ ).
105. Ocean quahog IEF, a designated feature of the FFBC MPA, has high sensitivity to the abrasion, penetration, and habitat structure change MarESA pressures associated with temporary subtidal habitat loss/disturbance but are not sensitive to smothering ( Table 8.19   Open ▸ ). Similarly, to seapens, the extraction of sediment to 30 cm (the benchmark) could remove any ocean quahog present (Tyler-Walters and Sabatini, 2017). Ocean quahog are known to be vulnerable to physical abrasion, but damage is related to their body size. Thorarinsdottir and Jacobson (2005) and Thorarinsdottir et al. (2010) noted that ocean quahog was vulnerable to overfishing due to its long lifespan, slow growth, uncertain recruitment, low productivity, and poor estimates of stock biomass and capture efficiency. Studies based on trawl fishing have shown larger specimens were more affected than smaller specimens (Klein and Witbaard, 1993). This damage can increase the mortality of ocean quahog either through the damage itself, increased vulnerability to predation or high intensity pressures such as the use of hydraulic dredges (Thorarinsdottir et al., 2009). Recovery of ocean quahog populations is also dependant on the age of sexual maturity at which population expansion can begin. Ocean quahogs reach sexual maturity at between 5 and 11 years and may be dependent upon growth rate and locality (Thorarinsdóttir, 1999). Currently within the FFBC MPA demersal trawling is highest in Wee Bankie, which during 2016 recorded a total of over 2,500 hours of dredge fishing, a practice which is known to damage ocean quahogs (JNCC, 2018). These impacts are also attributed to the effect of penetration and disturbance of the substratum as ocean quahog live at the surface of the sediment while feeding but burrows to depths of 14 cm periodically (Strahl et al., 2011) where penetrative activities could damage or lead to mortalities. The recovery of ocean quahog to this kind of disturbance is slow, and a full recovery from activities such as dredge fishing which penetrate the seabed may take decades (Ragnarsson et al., 2015). Heavy smothering or siltation rate change is likely to result negligible effects to ocean quahog as they are able to burrow back to the surface. A study by Powilleit et al. (2006) deposited a till and sand/till mixture up to 1.5 m deep on to existing sediment and found the resident ocean quahogs were ‘almost’ unaffected and the population structure was similar two years later. After initial deposition, 78% and 26% reached the surface under the ‘till’ and ‘sand/till’ mixtures respectively. Finally, the removal of substratum to a depth of 30 cm will remove the substratum occupied by ocean quahog together with any other species in the assemblage (Tyler-Walters and Sabatini, 2017).
106. It is worth noting that 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 be reduced 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 to the impact of temporary habitat disturbance/loss.
107. The subtidal sands and gravel, and shelf banks and mounds IEFs are deemed to be of medium vulnerability, medium recoverability and national value. The sensitivity of the IEF is therefore, considered to be medium.
108. 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 8.19: Sensitivity of the Benthic Subtidal IEFs found within the FFBC MPA to Temporary Subtidal Habitat Loss/Disturbance

Significance of the Effect

Subtidal Habitat IEFs

109. For the subtidal sand and muddy sand sediments IEF, subtidal coarse and mixed sediments IEF, the moderate energy subtidal rock IEF, cobble/stony reef outside of an SAC IEF and rocky reef outside an SAC IEF the magnitude of the impact is deemed to be medium and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of moderate adverse significance in the short term(i.e. within two years of completion of construction activities), with this decreasing to minor adverse significance in the medium to long term as the sediments and communities are predicted to recover. Therefore, minor effects are predicted in the long-term which are not significant in EIA terms.
110. For the seapens and burrowing megafauna IEF and the Sabellaria reef outside of an SAC IEF the magnitude of the impact is deemed to be medium and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of moderate adverse significance in the short term (i.e. within two years of completion of construction), with this decreasing to minor adverse significance in the medium to long term as the sediments and communities are predicted to recover. Therefore, minor effects are predicted in the long-term which are not significant in EIA terms.

Firth of Forth Banks Complex MPA

111. Overall, for the subtidal sands and gravels IEF and the shelf banks and mounds IEF, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.
112. Overall, for ocean quahog IEF, the magnitude of the impact is deemed to be low and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of moderate adverse significance in the medium term (i.e. within ten years of completion of construction activities), with this decreasing to minor adverse significance in the long term as the sediments and ocean quahog populations are predicted to recover. Therefore, minor effects are predicted in the long-term which are not significant in EIA terms.

Secondary Mitigation and Residual Effect

113. No benthic subtidal and intertidal ecology mitigation is considered necessary for the impact of temporary habitat loss/disturbance during the construction phase because the likely effects in the absence of further mitigation (beyond the designed in measures outlined in section 8.10), in the long term, are not significant in EIA terms.

Operation and Maintenance Phase

Magnitude of Impact

Subtidal Habitat IEFs

114. Operation and maintenance activities within the Proposed Development benthic ecology subtidal and intertidal study area will lead to temporary subtidal habitat loss/disturbance. The maximum design scenario is for up to 989,000 m2 of temporary habitat loss/disturbance during the operation and maintenance phase ( Table 8.10   Open ▸ ). This will result from maintenance on each of the wind turbines and substations over the operational life. The maximum design scenario assumes up to seven major component replacements for wind turbines per year, one major component replacement every ten years for OSPs/Offshore convertor station platforms, ten access ladder replacement for wind turbines and seven access ladder replacement for OSP/Offshore convertor station platform over the lifetime of the project, and as well as cable repair and reburial when necessary ( Table 8.10   Open ▸ ). This equates to a very small proportion (0.07%) of the benthic ecology subtidal and intertidal study area. It should also be noted that only a small proportion of the total temporary habitat loss/disturbance is likely to occur at any one time over the 35 year operational lifetime.
115. Temporary habitat loss will occur as a result of the use of jack-up vessels during any component replacement activities (up to 245 major component replacements for wind turbines and up to seven for the OSPs/Offshore convertor station platforms, up to ten access ladder replacements for wind turbines and seven access ladder replacements for OSPs/Offshore convertor station platforms) and during any inter-array, OSP/Offshore convertor station platform interconnector, and offshore export cables repair and reburial events. The impacts of jack-up vessel activities will be similar to those identified for the construction phase above and will be restricted to the immediate area around the wind turbine foundation or cable repair sites, where the spud cans are placed on the seabed, with recovery occurring following removal of spud cans. The spatial extent of this impact is small in relation to the total benthic ecology subtidal and intertidal study area, although there is the potential for repeat disturbance to the habitats in the immediate vicinity of the foundations because of these activities. The repair and reburial of inter-array, OSP/Offshore convertor station platform interconnector and offshore export cables will also affect benthic habitats in the immediate vicinity of these operations, with effects on seabed habitats and associated benthic communities expected to be similar to the construction phase. Activities resulting in the temporary subtidal habitat loss/disturbance will occur intermittently throughout the 35 year operation and maintenance period.
116. Trenchless techniques will be used for cable installation at the landfall and therefore there will be no disturbance to intertidal habitats as a result of operation and maintenance activities to the cable at the landfall. The effect of habitat loss/disturbance on benthic intertidal receptors is therefore not considered further for this impact.
117. The impact is predicted to be of local spatial extent, short term duration, intermittent and high reversibility. 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

118. The FFBC MPA overlaps with the site boundary for the Proposed Development and therefore some temporary habitat loss/disturbance 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 the percentage of overlap and the maximum design scenario for the operation and maintenance phase, up to 287,961 m2 of temporary habitat loss/disturbance may occur within the FFBC MPA, which equates to 0.01% of the total area of the FFBC MPA. This can be broken down for the composite parts of the MPA as follows: up to 199,237 m2 within the area of Berwick Bank (0.04% of the area of Berwick Bank) and up to 88,723 m2 within the area of Scalp and Wee Bankie (0.01% of the area of Scalp and Wee Bankie). The Montrose Bank will not be affected.
119. The total area of temporary subtidal habitat loss represents a very small percentage loss (0.00003%) 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 (0.01%) of the offshore subtidal sands and gravels feature of the MPA, which is also equivalent to the available supporting habitat for ocean quahog.
120. The impact is predicted to be of local spatial extent, short term duration, intermittent and high reversibility. It is predicted that the impact will affect the receptors directly. The magnitude is therefore considered to be negligible.

Sensitivity of the Receptor

Subtidal Habitat IEFs

121. The sensitivity of the IEFs is as described previously for the construction phase assessment in paragraphs 91 to 102 and in Table 8.18   Open ▸ .

Firth of Forth Banks Complex MPA

122. The sensitivity of the IEFs found within the FFBC MPA are as described previously for the construction phase assessment in paragraphs 103 to 107 and in Table 8.19   Open ▸ .

Significance of the Effect

Subtidal Habitat IEFs

123. For the subtidal sand and muddy sand sediments IEF, the subtidal coarse and mixed sediments IEF, the moderate energy subtidal rock IEF, cobble/stony reef outside of an SAC IEF and rocky reef outside an SAC IEF the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms, because of the small scale of the impact and the high rate of recovery for these habitats.
124. For the seapens and burrowing megafauna 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 receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms.

Firth of Forth Banks Complex MPA

125. Overall, for the subtidal sands and gravels IEF and the shelf banks and mounds IEF, the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptor is considered to be medium. The effect will, therefore, be of negligible adverse significance, which is not significant in EIA terms, because of the small scale of the impact and the high rate of recovery for these habitats.
126. Overall, for ocean quahog IEF the magnitude of the impact is deemed to be negligible, and the sensitivity of the receptor is considered to be high. The effect will, therefore, be of minor adverse significance, which is not significant in EIA terms. This has been concluded on the basis that only a very small proportion of the habitat for this species in the south western North Sea is predicted to be affected and, furthermore, as described in section 8.7, with further detail in the Benthic Subtidal and Intertidal Ecology Technical Report (volume 3, appendix 8.1), this species was recorded is very low abundances within the site-specific surveys and predominately as juveniles.