Publication - Publication

Offshore wind energy - draft sectoral marine plan: habitat regulations appraisal

Published: 18 Dec 2019
Directorate:
Marine Scotland Directorate
Part of:
Energy, Marine and fisheries
ISBN:
9781839603754

The habitats regulations appraisal is completed in accordance with the Habitats Regulations that implement the EC Habitats and Birds Directives in UK waters and has been completed for the sectoral marine plan for offshore wind.

Contents
Offshore wind energy - draft sectoral marine plan: habitat regulations appraisal
5 Potential for Adverse Effects on Habitat Features

5 Potential for Adverse Effects on Habitat Features

5.1 Sites Considered

5.1.1 Following the screening process, a total of 468 European/Ramsar sites were identified for which there is a LSE (or the potential for a LSE cannot be excluded) (Table C1).  This large number of European/Ramsar sites were identified as it was not possible to conclude that there would be no LSE from the Draft Plan for some, or all, of the qualifying interest features.

5.1.2 In total there were 267 SACs, SCIs and cSACs, 150 SPAs and pSPAs and a further 51 Ramsar sites with qualifying interest features that were screened in.  The relevant qualifying features within these sites included a range of coastal, intertidal and sublittoral habitats (see Section 2.2).

5.1.3 The habitats within SPAs also warrant consideration and they are encompassed within Section 6 (dealing with the impacts to seabird qualifying features).

5.1.4 Given the broad area covered by the Draft Plan and the large number of sites screened into these assessments, the same method as agreed in previous HRAs [25] [26] [27] has been used where it is not necessary to individually review the full list of all sites and the qualifying seabed interest features that they support within the plan-level HRA. However, the individual European/Ramsar sites that were screened in for each of the 17 DPOs are shown in the screening tables (schedules) (Table D1-D17) and individual maps (Figures E1-E17). The locations of qualifying habitats screened in (either directly as features in their own right or because they support other qualifying species, notably seabirds) during the initial screening stages are provided in Figure 3 to Figure 5.

5.1.5 Some of the SAC and Ramsar sites also contained other interest features (i.e. not habitat) for which it could not be concluded that there was no LSE (e.g. bottlenose dolphin or freshwater pearl mussel). These interest features are reviewed separately within the relevant feature group sections.

5.2 Interest Features Summary

5.2.1 In summary, the screening phase concluded that there is a possibility of a LSE (or that it was not possible to conclude no LSE) for a range of Annex I qualifying habitat features which are listed below. For the purposes of this review they have been divided into five broad categories as follows:

1) Morphological features encompassing a range of habitats:

  • Estuaries (1130) which will encompass sub-feature habitats such as saltmarsh, eelgrass, mussel beds as well as many of the other Annex I habitats that are cited separately below; and
  • Large shallow inlets and bays (1160) which, as with estuaries, encompass a range of other feature and sub-feature habitats.

2) Subtidal habitats with typically soft-sediment habitat:

  • Subtidal sandbanks (i.e. ‘Sandbanks which are slightly covered by seawater at all time’ 1110).

3) Subtidal habitats with typically hard-substratum habitat:

  • Reefs (1170);
  • Submarine structures made by leaking gases (1180); and
  • Submerged or partially submerged sea caves (8330).

4) Intertidal habitats (including saltmarshes):

  • Intertidal mudflats and sandflats (i.e. ‘Mudflats and sandflats not covered by seawater at low tide’ 1140);
  • Annual vegetation of drift lines (1210);
  • Salicornia and other annuals colonising mud and sand (1310);
  • Spartina swards (1320);
  • Atlantic salt meadows (1330); and
  • Mediterranean and thermo-Atlantic halophilous scrubs.

5) Supralittoral habitats:

  • Coastal lagoons (1150);
  • Supralittoral dune habitats encompassing the following
    - 2130 Fixed dunes with herbaceous vegetation (`grey dunes`);
    - 2150 Atlantic decalcified fixed dunes Calluno-Ulicetea;
    - 2170 Dunes with Salix repens spp. argentea Salicion arenariae;
    - 2250 Coastal dunes with Juniperus spp;
    - 2120 Shifting dunes along the shoreline with Ammophila arenaria (`white dunes`);
  • Perennial vegetation of stony banks (1220); and
  • Vegetated sea cliffs (1230).

5.2.2 In addition to these habitats, there are individual habitats that are identified within Ramsar citations (e.g. “sand and shingle spit”) although these individual features are not listed. There are also sub-features of SACs which include a range of habitats and fish species, see below, which have not been cited as qualifying features:

  • Rocky shore communities;
  • Kelp forest communities;
  • Sublittoral faunal turf communities;
  • Mussel bed communities;
  • Eelgrass communities;
  • Intertidal sea cave communities;
  • Subtidal sea cave communities;
  • Rocky and coarse sediment shores;
  • Extensive reedbeds in the inner Firth of Tay;
  • A population of the nationally rare fish ‘smelt’ (or sparling) in the Firth of Tay;
  • Rocky scar communities; and
  • Infralittoral gravel and sand communities.

5.2.3 The impact pathways for these supporting features are considered to be the same as for the qualifying habitat interest features with particular distinctions being possible between soft sediment, hard substratum, intertidal and supralittoral categories as identified above.  Therefore, the impacts to these specific habitats were not considered separately as part of this assessment.

5.2.4 To assess whether there is any adverse effect on the integrity of the European/Ramsar sites that were identified, the following sections review the sensitivities of these habitat features.  Section 1.1 then identifies the conservation objectives for these features and assesses, in tabular format, the effects arising in the context of the proposed additional plan-level mitigation measures.  These plan-level mitigation measures are considered in detail within Section 11.

5.2.5 For the purpose of these reviews the qualifying habitat features and sub-features that are listed above have been divided into four distinct categories (reefs, subtidal sandflats, intertidal (including saltmarsh) and supralittoral habitats) which encompass the impact pathways that are relevant for each of the above-listed qualifying habitat features and sub-features.  Accordingly, the Annex I habitats ‘estuaries’ and ‘large shallow inlets and bays’ are not considered separately as these habitats encompass a range of component features (e.g. saltmarsh, intertidal mudflats, reefs etc.). Hence, the sensitivities of ‘estuaries’ and’ large shallow inlets and bays’ are captured through the consideration of these component features

5.3 Sensitivities of Habitat Interest Features to Sectoral Offshore Wind Plan Activities

5.3.1 This section reviews the sensitivities that are relevant for the habitat interest features.  Initially a generic review of the sensitivities is presented under each of the following impact pathways identified during the screening phase (see Table 2):

  • Physical Loss/Gain of Habitat (loss of onshore or offshore habitat);
  • Physical Damage to Habitat (damage of onshore or offshore habitat);
  • Toxic Contamination (contamination and spillages);
  • Non-Toxic Contamination (elevated turbidity); and
  • Biological Disturbance (introduction of non-native species).

5.3.2 Following this review, the individual characteristics and sensitivities for each of the habitat interest features are presented and reviewed against the relevant Draft Plan activities that could cause a LSE. Information on the relative sensitivities of habitat features have been based on professional judgment and sensitivity assessments available for relevant habitat biotopes on the Marine Life Information Network (MarLIN) website and as presented within the sensitivity matrix that was prepared for Marine Protected Areas and wider marine spatial planning[28].  The interest feature reviews are set out in sections which are representative of the broad categories identified above. The reviews have been used to understand the impact pathways and sensitivities that are pertinent to the full list of habitats screened into this assessment:

  • Reefs (hard-substratum);
  • Subtidal sandbanks (soft subtidal substratum)
  • Intertidal habitats (including mudflats and saltmarshes)
  • Supralittoral habitats

5.4 Physical Loss/Gain of Habitat (Loss of Onshore or Offshore Habitat; Impact Pathway 1)

5.4.1 Intertidal, subtidal and supralittoral interest feature habitats are sensitive to a physical loss or gain of habitat at locations where new structures are introduced to, or removed from, the sea bed or coastal habitats (i.e. within the development ‘footprint’ of these structures).  Thus, the key activities that are relevant are those which introduce permanent or temporary structures that lie on or protrude from the seabed and cause a direct loss (whether permanent or temporary) of habitat.  For the Draft Plan, one of the main activities causing habitat loss or gain would be the installation, presence and then removal of the foundations for the wind devices on the sea bed where these are located within the area of an interest feature habitat. The selection of DPO locations considered direct footprint with designated sites and although several DPOs abut European/Ramsar sites, none have a direct overlap.

5.4.2 Beyond the DPOs consideration needs to be given to the alignment, installation or removal of cables or cable armouring areas which may also result in direct loss (whether permanent or temporary) of offshore or coastal habitat through excavations. However, the alignments of the cables are not known at this stage and therefore it is unclear which cable routes, if any, will pass through the boundaries of a European/Ramsar site. For this reason, all European/Ramsar sites which support coastal or marine habitat features and lie within 100 km of each DPO were initially screened in (see Figure 3 to Figure 5).

5.4.3 However, several SAC sites will clearly not have cable alignments passing through them as a result of a DPO (i.e. because they lie well to seaward of a DPO).  It was therefore possible to screen out these sites from the HRA.  This process screened out SAC sites such as St Kilda; Pisces Reef Complex; North Rona, Darwin Mounds and Wyville Thomson Ridge.

5.4.4 It is recognised that direct loss of habitat can be mitigated, where required, by avoiding habitat interest features within a European/Ramsar site at the project planning and design phase although specific plan-level mitigation measures will be needed to be assured that the relevant considerations are made at a project level (see Section 11).

5.4.5 The sensitivity of the habitats from direct effects (whether from device placement or cabling work) and the magnitude of any effects are dependent on a range of factors such as the habitat type, the extent of habitat affected, the location and the nature of activities (e.g. whether invasive or non-invasive Horizontal Direction Drilling (HDD) approaches can be adopted) and whether the activities are temporary or permanent.  In the future, it will also be dependent on technological advances affecting device or cable installation.

5.4.6 It is recognised that the bases for devices or the armouring of cable, provides potential structures for the settlement of reef forming species and thus there could be impacts from both the initial installation and at the removal phase. During a review of offshore windfarms, Wilson et al.[29] notes that the marine system is able to adjust to new structures in the sea, with these structures even having the potential to benefit their receiving environment. Work has shown how scour protection and towers may create hard substrata and thus act as artificial reefs, thereby increasing production on these ‘reefs’ and creating organic material as enrichment for the local marine environment. However, this potential effect needs to be studied in greater detail, as it may be beneficial or adverse depeding on the receiving ecosystem, in order for it to be taken into consideration when undertaking impact assessments on the benthic community.

5.5 Physical Damage to Habitat (Changes to Coastal and Offshore Habitat; Impact Pathways 4 and 5)

5.5.1 Intertidal and subtidal habitats are sensitive to physical damage from a range of activities associated with turbine and cable installation and removal activities. Damage can also occur during baseline survey work, if activities take place in the vicinity of European/Ramsar site interest features and where they involve the physical retrieval of samples or bed materials, such as borehole surveys or ecological trawl sampling. Where devices require piling, surveys to assess subsurface geological structure and suitability for installation can involve the collection of many cores and the use of drilling equipment from jack-up barges; this all being in addition to activities associated with the installation of the device.

5.5.2 The construction activities will cause damage to the seabed outwith the direct footprint. Such activities could include the use of jack-up legs, piling, and activities involved in cable installation.  They can also include the clearance of algae from areas of the seabed to allow for the construction work.

5.5.3 During the operational phase, the presence of the structures (turbine base, cable armouring, anchorages etc.) have the potential to cause scour effects in soft sediment systems.  The mooring chains associated with anchored turbines also have the potential to cause abrasion of the adjacent substratum.  The magnitude of the scour effects will depend on the size of the structures and the associated risk will depend upon the composition of the seabed substratum, the hydrodynamic conditions, and the distance of the structures from European/Ramsar site interest feature habitats.

5.5.4 A distance of one tidal ellipse away from a DPO (see Section 2.2 and Figure 6) was used to determine the maximum likely distance that water, or any material in suspension or solution it may contain, might be tidally transported from a given location. Evidence from plume studies indicates that even fine particles mobilised from the seabed settle out again to a large extent within the distance of one tidal excursion. Hence, the tidal excursion zone around the DPOs illustrates an area that may be indirectly affected by changes to hydrodynamics and sediment transport, this in turn potentially leading to changes in suspended sediment concentrations and water quality.

5.5.5 The tidal ellipse boundary extends from the edge of a DPO and is shown on the individual figures for each DPO (Figures E1-E17). Due to the uncertainties of cable alignments, only those sites which have been screened out, based on their location being definitively outwith the route of any cabling (see Section 2.2), yet were still within a single tidal excursion, would be screened back in. However, this did not apply to any European/Ramsar sites.

5.5.6 There are also sensitivities to activities associated with maintenance visits because the vessels used may cause small-scale localised damage from shipwash or from chains and anchors. The magnitude of effects will be dependent upon the amount of vessel activity as well as the size and speed of the vessels with the risk being dependent upon the distance of such activities from the European/Ramsar site interest features (which will determine the extent of exposure to any change).

5.5.7 For all the above activities, the rate at which habitats recover from damage will also be a key factor influencing the magnitude of any effects.  Reef features for instance are likely to be more sensitive to impacts and take longer to recover than subtidal sandflats.

5.6 Toxic Contamination (Contamination and Spillages; Impact Pathways 14 and 15)

5.6.1 Intertidal and subtidal interest feature habitats are sensitive to toxic contamination i.e. where concentrations of contaminants exceed sensitivity thresholds for a given feature. Contamination can occur from the release of fuels, oils, construction material into the environment during construction or decommissioning. Where contaminated sediment is released or disturbed during development activities there is also the potential for toxic effects on ecological features.

5.6.2 Spillage of oils and fluids from construction vessels and machinery into the marine environment could adversely affect sediment or water quality potentially impacting upon benthic communities.  In addition, areas of sediment being excavated or disturbed for the installation/removal of turbines or cables will cause an increase in suspended sediment concentrations over the period of the activity.  Where this release of suspended sediments occurs then the potential also exists for the release of sediment-bound contaminants in areas where such contaminants are present.  Sediment contamination is most likely to occur inshore, in the vicinity of ongoing or historic industrial locations, particularly within estuaries.  For offshore activities, then sediment -bound contaminants are less likely to be an issue, therefore disturbance of sediment has less potential to lead to a LSE on relevant interest features.

5.6.3 The likelihood of mobilising sediments and contaminated sediments and the magnitude of any effect is dependent upon the level of contamination; the proximity of the windfarm activity to the European/Ramsar site(s); the type of activity occurring; the manner in which that activity is pursued (including the extent and duration); the particle size of the disturbed sediments and the hydrodynamic conditions.

5.6.4 It has been indicated that settlement of sediment is most likely to occur within 20-200 m of a cable for a wind farm[30]. However, contaminants are almost always associated with fine sediments which could travel further than 200 m in areas where there is a large tidal excursion and strong tidal flows.  However, over greater distances, concentrations of contaminants are less likely to be significant due to increased dilution.

5.7 Non-Toxic Contamination (Elevated Turbidity; Impact Pathway 16)

5.7.1 Increases in suspended sediment concentrations, from construction and decommissioning activities, are typically expected to result in short-term, localised changes in the marine environment. In the event of substantial sediment resuspension, then the potential exists for consequent sediment settlement to cause a smothering effect upon the seabed. In particular, dredging related activities (excavation and disposal) are likely to cause smothering effects seabed features. Settlement of coarse material is most likely to occur within 20-200 m from the point of resuspension[31].  Therefore, the potential for significant smothering effects will reduce at distances beyond 200 m.

5.8 Biological Disturbance (Introduction of Non-Native Species; Impact Pathways 17 and 18)

5.8.1 The introduction of new surfaces such as turbine bases, cable armouring or anchorages (or the clearing of seabed habitats to allow the introduction of these components) has the potential to facilitate the establishment of invasive non-native species through the colonisation of these surfaces.  This assumes that the current spread of such invasive species is limited by the prevailing physical regime and lack of new and suitable substrata for colonisation. Therefore, any development which causes changes in physical processes, provides new space for colonisation or vectors for transportation of non-native species has the potential to result in biological disturbance from this impact pathway. This impact has the greatest potential to occur during the construction and decommissioning phases, where movement of vessels may provide a suitable vector for transportation of invasive non-native species.

5.9 Reef Sensitivity Review

5.9.1 Reefs can be either biogenic concretions or of geogenic origin[32]. They are hard compact substrata on solid and soft bottoms, which arise from the sea floor in the sublittoral and littoral zone. Reefs may support a zonation of benthic communities of algae and animal species as well as concretions of corallogenic organisms. The sensitivities of this Annex I habitat to the relevant draft Plan activities that might affect it are shown in Table 3. The highest sensitivity relates to direct habitat loss because, in instances where turbines or cables are placed on qualifying reef feature habitats, then an effect must occur.

Table 3: Potential sensitivities of reef features to the Draft Plan. Pathway ref no. relates to Table 2.

Sensitivity Category Sensitivities Pathway Ref. No. Leasing Activity as Identified in Sectoral Offshore Wind Plan HRA (Summary Impact Pathway Description) Survey Construction Operation Decommission
PLG Physical Loss/Gain of habitat 1 Loss of coastal and offshore habitat under the footprint of turbines, cables and cable armouring from the installation, operation and decommissioning of these structures. No Impact  No Impact  HS No Impact 
PD Physical Damage to habitat 4 Changes to coastal and offshore habitat as a result of damage from baseline surveys (e.g. boreholes/trawls); from equipment use causing abrasion, damage or smothering during installation and from maintenance and removal of cables/devices (e.g. jack-up legs, vessels, anchors, mooring chain). LS MS LS LS
PD Physical Damage to habitat 5 Changes to coastal and offshore habitat as a result of alterations to the wave climate or hydrodynamic regime from the presence of devices or cable armouring causing physical changes (including changes to sediment transport and/or sediment scour). No Impact  No Impact  LMS No Impact 
TC Toxic Contamination (Reduction in water quality) 14 Spillage of fluids, fuels and/or construction materials during installation or removal of structures (turbines and cables) or during survey/maintenance. LS LS LS LS
TC Toxic Contamination (Reduction in water quality) 15 Release of contaminants associated with the dispersion of suspended sediments during installation or removal of structures (turbines and cables). No Impact  LS No Impact  LS
NTC Non-Toxic Contamination (Elevated turbidity) 16 Increase in turbidity associated with the release of suspended sediments during installation or removal of structures (turbines and cables). No Impact  LMS No Impact  LMS
BD Biological Disturbance (Introduction of non-native species) 17 Introduction of new structures providing new substratum that facilitates the colonisation and ingress of invasive non-native species. No Impact  No Impact  LMS No Impact 
BD Biological Disturbance (Introduction of non-native species) 18 Introduction and ingress of invasive non-native species as biofouling species on the surfaces of vessels or construction plant. LS LS LS LS
In this table, only the estimated sensitivity levels are shown. The level of risk will be dependent upon exposure. For instance, there would be a high degree of exposure for European/Ramsar site habitats were a development to occur within or near to a European/Ramsar site.  However, at the present time, there is uncertainty regarding the degree of exposure and a worst-case assumption has been made.
LS: Low Sensitivity
LMS: Low to Medium Sensitivity
MS: Medium Sensitivity
HS: High Sensitivity

5.10 Subtidal Sandbanks Sensitivity Review

5.10.1 Sandbanks are defined as elevated, elongated, rounded or irregular topographic features, permanently submerged and predominantly surrounded by deeper water[33].  They consist mainly of sandy sediments, but larger grain sizes, including boulders and cobbles, or smaller grain sizes including mud may also be present on a sandbank.  Banks where sandy sediments occur in a layer over hard substrata are classed as sandbanks if the associated biota are dependent on the sand rather than on the underlying hard substrata.  “Slightly covered by sea water all the time” means that above a sandbank the water depth is seldom more than 20 m below chart datum. Sandbanks can, however, extend beneath 20 m below chart datum. It can, therefore, be appropriate to include in designations such areas where they are part of the feature and host its biological assemblages. The sensitivities of this Annex I feature to particular activities that it might be affected by are shown in Table 4.These are very much the same as for reef features although there is a recognition that soft sediment habitats will have a lower sensitivity to sediment smothering events during construction work.

Table 4: Potential sensitivities of the subtidal sandbank feature to the Draft Plan. Pathway ref no. relates to Table 2.

Sensitivity Category Sensitivities Pathway Ref. No. Leasing Activity as Identified in Sectoral Offshore Wind Plan HRA (Summary Impact Pathway Description) Survey Construction Operation Decommission
PLG Physical Loss/Gain of habitat 1 Loss of coastal and offshore habitat under the footprint of turbines, cables and cable armouring from the installation, operation and decommissioning of these structures. No Impact  No Impact  HS No Impact 
PD Physical Damage to habitat 4 Changes to coastal and offshore habitat as result of damage from baseline surveys (e.g. boreholes/trawls); from equipment use causing abrasion, damage or smothering during installation and from maintenance and removal of cables/devices (e.g. jack-up legs, vessels, anchors, mooring chain). LS LS LS LS
PD Physical Damage to habitat 5 Changes to coastal and offshore habitat as a result of alterations to the wave climate or hydrodynamic regime from the presence of devices or cable armouring causing physical changes (including changes to sediment transport and/or sediment scour). No Impact  No Impact  LS No Impact 
TC Toxic Contamination (Reduction in water quality) 14 Spillage of fluids, fuels and/or construction materials during installation or removal of structures (turbines and cables) or during survey/maintenance. LS LS LS LS
TC Toxic Contamination (Reduction in water quality) 15 Release of contaminants associated with the dispersion of suspended sediments during installation or removal of structures (turbines and cables). No Impact  LS No Impact  LS
NTC Non-Toxic Contamination (Elevated turbidity) 16 Increase in turbidity associated with the release of suspended sediments during installation or removal of structures (turbines and cables). No Impact  LS No Impact  LS
BD Biological Disturbance (Introduction of non-native species) 17 Introduction of new structures providing new substratum that facilitates the colonisation and ingress of invasive non-native species. No Impact  No Impact  LMS No Impact 
BD Biological Disturbance (Introduction of non-native species) 18 Introduction and ingress of invasive non-native species as biofouling species on the surfaces of vessels or construction plant. LS LS LS LS
In this table, only the estimated sensitivity levels are shown. The level of risk will be dependent upon exposure.  For instance, there would be a high degree of exposure for European/Ramsar site habitats were a development to occur within or near to a European/Ramsar site.  However, at the present time, there is uncertainty regarding the degree of exposure and a worst-case assumption has been made.
LS: Low Sensitivity
LMS: Low to Medium Sensitivity
MS: Medium Sensitivity
HS: High Sensitivity

5.11 Intertidal Habitats (Including Saltmarshes) Sensitivity Review

5.11.1 Intertidal mudflats and sandflats are defined as the sands and muds of the coasts of the oceans, their connected seas and associated lagoons, not covered by sea water at low tide, devoid of vascular plants, usually coated by blue-green algae and diatoms[34].  They are of particular importance as feeding grounds for wildfowl and waders. Saltmarshes occur in stable intertidal environments typically with fine sediment above the mean high-water neap level where vascular plants can survive and can further stabilise the habitat[35]. Once a cover of vegetation has become established the rate of sedimentation (accretion) often increases as more of the incoming sediment is intercepted and trapped by the increased surface roughness. In addition, the vegetation also reduces the resuspension of deposited material and, at the same time, organic matter is added to the marsh surface.

There is a range of Annex I saltmarsh habitats depending upon the tidal height and vegetation type and these are as listed in Section 2.2.  The sensitivities of these habitats to the activity that might affect it are shown in Table 5. This sensitivities table is similar to those for soft sediment sandbank habitats with the impacts being associated principally with the laying of cables across the intertidal areas.  Again, the highest sensitivity relates to direct habitat loss because, in instances where devices or cables are placed on qualifying intertidal habitats, then an effect must occur.

Table 5: Potential sensitivities of intertidal habitats to the Draft Plan. Pathway ref no. relates to Table 2.

Sensitivity Category Sensitivities Pathway Ref. No. Leasing Activity as Identified in Sectoral Offshore Wind Plan HRA (Summary Impact Pathway Description) Survey Construction Operation Decommission
PLG Physical Loss/Gain of habitat 1 Loss of coastal and offshore habitat under the footprint of turbines, cables and cable armouring from the installation, operation and decommissioning of these structures. No Impact  No Impact  HS No Impact 
PD Physical Damage to habitat 4 Changes to coastal and offshore habitat as result of damage from baseline surveys (e.g. boreholes/trawls); from equipment use causing abrasion, damage or smothering during installation and from maintenance and removal of cables/devices (e.g. jack-up legs, vessels, anchors, mooring chain). LS MS LS MS
PD Physical Damage to habitat 5 Changes to coastal and offshore habitat as a result of alterations to the wave climate or hydrodynamic regime from the presence of devices or cable armouring causing physical changes (including changes to sediment transport and/or sediment scour). No Impact  No Impact  LS No Impact 
TC Toxic Contamination (Reduction in water quality) 14 Spillage of fluids, fuels and/or construction materials during installation or removal of structures (turbines and cables) or during survey/maintenance. LS LS LS LS
TC Toxic Contamination (Reduction in water quality) 15 Release of contaminants associated with the dispersion of suspended sediments during installation or removal of structures (turbines and cables). No Impact  LS No Impact  LS
NTC Non-Toxic Contamination (Elevated turbidity) 16 Increase in turbidity associated with the release of suspended sediments during installation or removal of structures (turbines and cables). No Impact  LS No Impact  LS
BD Biological Disturbance (Introduction of non-native species) 17 Introduction of new structures providing new substratum that facilitates the colonisation and ingress of invasive non-native species. No Impact  No Impact  LS No Impact 
BD Biological Disturbance (Introduction of non-native species) 18 Introduction and ingress of invasive non-native species as biofouling species on the surfaces of vessels or construction plant. LS LS LS LS
In this table, only the estimated sensitivity levels are shown. The level of risk will be dependent upon exposure.  For instance, there would be a high degree of exposure for European/Ramsar site habitats were a development to occur within or near to a European/Ramsar site.  However, at the present time, there is uncertainty regarding the degree of exposure and a worst-case assumption has been made.
LS: Low Sensitivity
LMS: Low to Medium Sensitivity
MS: Medium Sensitivity
HS: High Sensitivity

5.12 Supralittoral Habitat Sensitivity Review

5.12.1 Coastal habitat interest features were scoped into the assessment because they could be affected by cable laying operations or other landside works such as an onshore hydroelectric plant.  The relevant qualifying habitat features include dune habitats, vegetated cliffs and coastal lagoons (see Section 2.2). The sensitivities of these habitats to the activity that might affect them are shown in Table 6.  In each case issues such as the impacts associated with surveys or hydrodynamic effects are not relevant and it is mainly the potential habitat loss/damage from cabling installations. The potential for a construction spillage is relevant at all cable laying locations while the issue of sediment resuspension will also be pertinent for lagoonal habitats.  

Table 6: Potential sensitivities of supralittoral habitats to the draft Plan. Pathway ref no. relates to Table 2

Sensitivity Category Sensitivities Pathway Ref. No. Leasing Activity as Identified in Sectoral Offshore Wind Plan HRA (Summary Impact Pathway Description) Survey Construction Operation Decommission
PLG Physical Loss/Gain of habitat 1 Loss of coastal and offshore habitat under the footprint of turbines, cables and cable armouring from the installation, operation and decommissioning of these structures. No Impact  No Impact  HS No Impact 
PD Physical Damage to habitat 4 Changes to coastal and offshore habitat as result of damage from baseline surveys (e.g. boreholes/trawls); from equipment use causing abrasion; damage or smothering during installation and from maintenance and removal of cables/devices (e.g. jack-up legs, vessels, anchors, mooring chain). No Impact  MS LS MS
TC Toxic Contamination (Reduction in water quality) 14 Spillage of fluids, fuels and/or construction materials during installation or removal of structures (turbines and cables) or during survey/maintenance. LS LS LS LS
TC Toxic Contamination (Reduction in water quality) 15 Release of contaminants associated with the dispersion of suspended sediments during installation or removal of structures (turbines and cables). No Impact  LS No Impact  LS
NTC Non-Toxic Contamination (Elevated turbidity) 16 Increase in turbidity associated with the release of suspended sediments during installation or removal of structures (turbines and cables). No Impact  LS No Impact  LS
In this table, only the estimated sensitivity levels are shown. The level of risk will be dependent upon exposure.  For instance, there would be a high degree of exposure for European/Ramsar site habitats were a development to occur within or near to a European/Ramsar site.  However, at the present time, there is uncertainty regarding the degree of exposure and a worst-case assumption has been made.
LS: Low Sensitivity
LMS: Low to Medium Sensitivity
MS: Medium Sensitivity
HS: High Sensitivity

5.13 Potential Effects on European/Ramsar Sites from the Draft Plan

5.13.1 On the basis of the sensitivities of the relevant interest features the following sections review the generic conservation objectives for these features and the potential effects arising for each of the European/Ramsar sites.

5.13.2 The conservation objectives for the qualifying habitats that are relevant to this HRA will be very similar and in many instances identical for all European/Ramsar sites that have been screened in. The relevant objectives seek to avoid deterioration of the qualifying habitats, ultimately ensuring that the integrity of the site is maintained, and the site makes an appropriate contribution to achieving favourable conservation status for each of the qualifying features. As discussed in Section 2.2, it is appropriate to apply generic objectives for this plan-level HRA.

5.13.3 The conservation objectives ensure that for qualifying habitats the following are maintained in the long term:

  • Extent of the habitat within the site;
  • Distribution of the habitat within the site;
  • Structure and function of the habitat;
  • Processes supporting the habitat;
  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.

5.13.4 Taking account of these conservation objectives and the plan-level activities to which the key interest features are sensitive, this section reviews the effects of the draft Plan on the integrity of the European/Ramsar sites.  The results are presented in Table 7.

Table 7: Assessment of the potential effects of the Draft Plan on habitat features of relevant European/Ramsar sites

Screened-in sites with these qualifying features are provided in Table C1  Is There an Adverse Effect on Integrity on any European/Ramsar sites
Is There an Adverse Effect on Integrity Following Application of
Mitigation Measures?
Qualifying and Supporting Feature Summary Impact Pathway
Pathway Ref. No.  Sensitivity Level(s) Commentary, and Relevant Conservation Objective
  • Morphological Features encompassing a range of habitats
  • Subtidal habitats with typically soft-sediment habitat
  • Subtidal habitats with typically hard-substratum habitat (Reefs)
  • Intertidal habitats (including saltmarshes)
  • Supralittoral habitats

Physical Loss/Gain of habitat

Loss of coastal and offshore habitat under the footprint of devices, cables and cable armouring from the installation, operation and decommissioning of these structures.  

1 Sensitivity Level(s) maximum considered to be high (see Tables 3-6 for detail and colour code)   Possibility of an adverse effect on integrity Further work would be required at project-level to ascertain LSE. However, in advance of considering mitigation measures, it cannot be concluded that there will be no AEOI on any European/Ramsar sites. This is because of the inherent uncertainties such as:
  • the detail of the Plan implementation process;
  • future generation capacities;
  • the location, scale and densities of development;
  • the proposed technologies to be used and future advances in these technologies;
  • the scale of the effects arising via some of the defined impact pathways; and
  • the efficacy of some project-level mitigation options.
No adverse effect on integrity With the application of appropriate and meaningful mitigation measures to accompany the Plan (see Section 11), there will be no AEOI.

Commentary/ Review

None of the DPOs directly overlap with European/Ramsar sites so there would be no direct habitat loss from development within the boundaries of the DPOs. However, it is assumed that cable alignment and landfall have the potential for LSE, as a result of physical loss/gain of qualifying habitat features. It is expected, however, that during the early stages in the design of any development, a primary consideration will be to try and avoid habitats within a European/Ramsar site and minimise exposure and risk.  Effects can be mitigated through careful routeing of cables and choice of landfalls as well as using installation methods such as HDD at the landfall.

Relevant Conservation Objectives (see Section 5.13)

Of the 7 objectives, the majority are considered to be relevant to impacts from the loss/gain during the operational phase of the project with only the objective relating to the processes affecting habitats being less pertinent.  Therefore, the following 6 objectives all need to be considered.

  • Extent of the habitat on site;
  • Distribution of the habitat within site;
  • Structure and function of the habitat;
  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.
  • Morphological Features encompassing a range of habitats
  • Subtidal habitats with typically soft-sediment habitat
  • Subtidal habitats with typically hard-substratum habitat (Reefs)
  • Intertidal habitats (including saltmarshes)
  • Supralittoral habitats

Physical Damage to habitat

Changes to coastal and offshore habitat as result of damage from baseline surveys (e.g. boreholes/trawls); from equipment use causing abrasion, damage or smothering during installation and from maintenance and removal of cables/devices (e.g. jack-up legs, vessels, anchors, mooring chain).

4 Sensitivity Level(s) maximum considered to be medium (see Tables 3-6 for detail and colour code) As above  As above

Commentary/ Review

During the survey phases of a development, for the most part, any changes are likely to be localised and of short-term consequence due to the small amount of material extracted for research and the short duration of activity compared to construction.  The developmental works during installation, maintenance and decommissioning are likely to be more significant but in general, most of the construction activities of concern, such as the use of jack-up legs, piling and activities involved in cable installation, are still likely to result in short-term, localised changes to the marine environment (e.g. increased suspended sediments and turbidity, disturbance of contaminated sediments and direct disturbance).  The disposal of construction material from shoreline installations and piled devices also has the potential to damage habitats if, for example, sediment deposition occurs on habitat features.  The effects of the main construction activities and the cable routeing are likely to be temporary and localised and with careful alignment of cables, unlikely to have any adverse effect on the integrity of a European/Ramsar site.

Relevant Conservation Objectives (see Section 5.13)

Of the 7 objectives, the majority are considered to be relevant to impacts from physical damage during construction and decommissioning work however the following 4 are most pertinent because they relate to the composition and distribution of the habitats and species present rather than the broader extent, structure, function of the habitats and the processes affecting them:

  • Distribution of the habitat within site;
  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.
  • Morphological Features encompassing a range of habitats
  • Subtidal habitats with typically soft-sediment habitat
  • Subtidal habitats with typically hard-substratum habitat (Reefs)
  • Intertidal habitats (including saltmarshes)

Physical Damage to habitat

Changes to coastal and offshore habitat as a result of alterations to the wave climate or hydrodynamic regime from the presence of devices or cable armouring causing physical changes (including changes to sediment transport and/or sediment scour).

5 Sensitivity Level(s) maximum considered to be low-medium (see Tables 3-6 for detail and colour code) As above  As above 

Commentary/ Review

The extent of the effects arising will be greatly influenced by the type and location of the devices that are introduced. Deposition of fine sediments may occur in areas of reduced tidal flow and scouring of benthic communities may result on the seabed around the base of turbines.  Cumulative impacts from multiple devices are likely to be additive. The extent of this effect has been defined within this HRA (based on past work for the R3OWF) as the area that extends to one tidal excursion distance from the DPO.  The effects of scour around devices and their associated moorings is generally of low significance and would be highly localised and therefore unlikely to result in any changes to European/Ramsar sites. Resultant changes in coastal processes and, potentially, sediment transport are likely to have the greatest risks of impact in areas of medium to high energy. Consideration of the potential changes to processes would need understanding during project level HRAs.

Relevant Conservation Objectives (see Section 5.13)

Of the 7 objectives the majority are considered are considered to be relevant to impacts from hydrodynamic changes during the operational phase of the project because the potential exists to alter the balance extent and functionality of habitats and species.  Therefore, all objectives need to be considered:

  • Extent of the habitat on site;
  • Distribution of the habitat within site;
  • Structure and function of the habitat;
  • Processes supporting the habitat;
  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.
  • Morphological Features encompassing a range of habitats
  • Subtidal habitats with typically soft-sediment habitat
  • Subtidal habitats with typically hard-substratum habitat (Reefs)
  • Intertidal habitats (including saltmarshes)
  • Supralittoral habitats

Toxic Contamination (Reduction in water quality)

Spillage of fluids, fuels and/or construction materials during installation or removal of structures (devices and cables) or during survey/maintenance.

14 Sensitivity Level(s) maximum considered to be low (see Tables 3-6 for detail and colour code) As above  As above 

Commentary/ Review

For all stages of the work from the construction to decommissioning and including operational/maintenance works, there is the potential for accidental discharges/spillages from machinery and vessels associated with the development, although the likelihood of spillages occurring is comparatively low.  This is because there are several standard navigational safety measures employed within the marine environment which reduce the likelihood of spillages occurring and limit the effects should they occur. Given the above and acknowledging that none of the DPOs overlap with European/Ramsar sites, with development within European/Ramsar sites limited to cable routeing and landfall activities, the risk from this impact pathway is considered low.

Relevant Conservation Objectives (see Section 5.13)

The conservation objectives are designed to avoid deterioration of the qualifying habitats thus ensuring that the integrity of the site is maintained.  As they are broad-ranging and generic in their scope most activities have the potential to lead to a failure of most, if not all, objectives.  Of the 7 generic objectives listed, the following are considered to be most relevant to impacts from toxic contamination/spillage events because they relate to the composition and distribution of the species present rather than the broader extent, distribution and functionality of habitats and the processes affecting them:

  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.
  • Morphological Features encompassing a range of habitats
  • Subtidal habitats with typically soft-sediment habitat
  • Subtidal habitats with typically hard-substratum habitat (Reefs)
  • Intertidal habitats (including saltmarshes)
  • Supralittoral habitats

Toxic Contamination (Reduction in water quality

Release of contaminants associated with the dispersion of suspended sediments during installation or removal of structures (devices and cables).

15 Sensitivity Level(s) maximum considered to be low (see Tables 3-6 for detail and colour code) As above  As above 

Commentary/ Review

There is a low likelihood of contaminated sediments occurring within the DPOs as these are generally sited away from industrial inputs.  The receiving waterbody will also provide high levels of dilution to any contaminants at locations away from the coast.  Inshore cable routes and landfalls may be located in areas of finer sediments which could have elevated levels of contaminants. Risks can be effectively mitigated through careful routeing of cables and choice of landfalls as well las using installation methods such as HDD at the landfall.

Relevant Conservation Objectives (see Section 5.13)

Of the 7 objectives, the following are considered to be most relevant to impacts from toxic contamination events because they relate to the composition and distribution of the species present rather than the broader extent, distribution and functionality of habitats and the processes affecting them:

  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.
Morphological Features encompassing a range of habitats Subtidal habitats with typically soft-sediment habitat Subtidal habitats with typically hard-substratum habitat (Reefs) Intertidal habitats (including saltmarshes)

Non-Toxic Contamination (Elevated turbidity)

Increase in turbidity associated with the release of suspended sediments during installation or removal of structures (devices and cables).

16 Sensitivity Level(s) maximum considered to be low-medium (see Tables 3-6 for detail and colour code) As above  As above 

Commentary/ Review

Any excavation work associated with the installation of turbines or cables has the potential (depending on the in-situ sediment type) to cause redistribution of sediment and potentially adverse effects on surrounding habitats.  The extent of this effect has been defined within this HRA (based on past plan-level HRA work) as the area that extends to one tidal excursion distance of the DPO. None of the DPOs overlap with European/Ramsar sites, with development within European/Ramsar sites limited to cable routeing and landfall activities. However, the tidal excursion of several DPOs extends into a European/Ramsar site. The disposal of construction material from installations and piled devices also has the potential to increase turbidity levels. The effects from this impact pathway will be temporary and localised and with appropriate site selection unlikely to have any adverse effect on the integrity of a European/Ramsar site.  

Relevant Conservation Objectives (see Section 5.13)

Of the 7 objectives, the following are considered to be most relevant to impacts from non-toxic contamination events because they relate to the composition and distribution of the species present rather than the broader extent, distribution and functionality of habitats and the processes affecting them:

  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.
  • Morphological Features encompassing a range of habitats
  • Subtidal habitats with typically soft-sediment habitat
  • Subtidal habitats with typically hard-substratum habitat (Reefs)
  • Intertidal habitats (including saltmarshes)

Biological Disturbance (Introduction of non-native species)

Introduction of new structures providing new substratum that facilitates the colonisation and ingress of invasive non-native species.

17 Sensitivity Level(s) maximum considered to be low-medium (see Tables 3-6 for detail and colour code) As above  As above 

Commentary/ Review

None of the DPOs overlap with European/Ramsar sites, with development within European/Ramsar sites limited to cable routeing and landfall activities. The placement of structures underwater introduces new, and initially barren, surfaces which have the potential to facilitate the spread of invasive non-native species where, in the absence of competition from indigenous species they are potentially able to colonise these structures.  It is difficult to quantify the risk of introduction of invasive non-native species.  On the assumption that the current spread of such species is limited by the prevailing physical regime and the lack of new colonizing substrate, the options which cause the greatest change in physical processes and provide the greatest colonizing space would be expected to pose the greatest risk.

Relevant Conservation Objectives (see Section 5.13)

Of the 7 objectives listed, the following 3 are considered to be most relevant to impacts from invasive species introductions because they have the potential to affect the balance of species within the habitats:

  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.
  • Morphological Features encompassing a range of habitats
  • Subtidal habitats with typically soft-sediment habitat
  • Subtidal habitats with typically hard-substratum habitat (Reefs)
  • Intertidal habitats (including saltmarshes)

Biological Disturbance (Introduction of non-native species)

Introduction and ingress of invasive non-native species as biofouling species on the surfaces of vessels or construction plant.

18 Sensitivity Level(s) maximum considered to be low (see Tables 3-6 for detail and colour code) As above  As above 

1) Commentary/ Review

The possibility also exists that invasive non-native species could be introduced on the vessels and equipment that are used to construct, maintain or decommission the turbines.  The likelihood of this occurrence is considered to be low because all such equipment is expected to be efficiently maintained and cleaned at regular intervals.  However, it will be dependent upon this inspection regime being in place and on the provenance of the vessels and equipment being used. Any development will require a biosecurity plan which will outline measures to reduce the risk of introduction and spread of invasive non-native species.

1) Relevant Conservation Objectives (see Section 5.13)

Of the 7 objectives listed, the following 3 are considered to be most relevant to impacts from invasive species introductions because they have the potential to affect the balance of species within the habitats:

  • Distribution of typical species of the habitat;
  • Viability of typical species as components of the habitat; and
  • No significant disturbance of typical species of the habitat.

Contact

Email: drew.milne@gov.scot