Operation and maintenance phase

Direct temporary disturbance of subtidal habitat during the operation and maintenance phase may occur within the Firth of Forth Banks Complex MPA as a result of jack-up activities during any component replacement activities and during any inter-array, OSP/Offshore convertor station platforms interconnector, and offshore export cable repair and reburial events. Table 1.39 Open ▸ presents the maximum design scenario for temporary habitat disturbance within the Firth of Forth Banks Complex MPA during the operation and maintenance phase.

Table 1.39: Maximum Design Scenario for Temporary Habitat Disturbance within the Firth of Forth Banks Complex MPA relevant to the Operation and Maintenance Phase

1 For the purposes of replicating the calculations in this table, 31.33% is calculated as 316.5 km2/1010.2 km2 (i.e. overlap between Proposed Development array area / total Proposed Development array area).

2 For the purposes of replicating the calculations in this table, 13.08% is calculated as 114.08 km/872 km (i.e. proportion of total length of offshore export cables that could occur within the part of the Proposed Development export cable corridor that overlaps with the MPA).

The maximum design scenario for temporary habitat disturbance within the Firth of Forth Banks Complex MPA in the operation and maintenance phase assumes that up to 0.29 km2 of temporary seabed disturbance may occur over the lifetime of the Proposed Development. This equates to 0.01% of the total area of the MPA and can be broken down for the composite parts of the MPA as follows: up to 0.2 km2 within the area of the Berwick Bank section of the MPA (0.01% of the MPA area or 0.04% of the area of the Berwick Bank section of the MPA) and up to 0.09 km2 within the area of Scalp and Wee Bankie (0.004% of the MPA area or 0.01% of the area of Scalp and Wee Bankie). The Montrose Bank will not be affected.

Ocean quahog aggregations

On the basis of the assumptions outlined in paragraph 190, and for the purposes of this assessment, it is assumed that all of the temporary habitat disturbance resulting from maintenance activities (i.e. 0.29 km2) could occur within supporting habitat for ocean quahog aggregations, impacting 0.01% of the supporting habitat for this feature.
Activities resulting in temporary habitat disturbance will occur intermittently throughout the operation and maintenance phase which will last up to 35 years, with only a proportion of the total maximum area of temporary habitat disturbance occurring at any one time. Following these activities sediments would be expected to recover to their baseline state through wave and tidal action (volume 2, chapter 7 of the Offshore EIA Report), allowing the associated communities to recover into these areas.
The sensitivity of ocean quahogs to this kind of disturbance is as described in paragraphs 218 to 221 as well as paragraph 224 of the construction phase assessment.
The predictions for the supporting habitats are similar to those made for offshore subtidal sands and gravels feature (see paragraph 203 and 204).
Based on the information presented above, the following can be concluded with respect to the physical attributes of the ocean quahog aggregations feature of the Firth of Forth Banks Complex MPA:

The temporary, intermittent, and small scale (0.01% of the potential habitat) of the effects of this impact in the operation and maintenance phase will have a minimal impact on the extent and distribution of ocean quahog within the Firth of Forth Banks Complex MPA. Additionally, this impact is greatly reduced compared to the construction phase as activities such as sand wave clearance, which directly displace sediment, will not occur. This is consistent with the ‘conserve’ objective of the extent and distribution attribute for this feature.
The structure of the ocean quahogs populations within the Firth of Forth Banks Complex MPA will not impacted due to the small-scale nature of this impact. The deployment of jack up vessels and anchors will result in surface level abrasion and small-scale seabed penetration on a much-reduced scale compared to the construction phase, also reducing the potential for mortality in this phase. Additionally, As noted in paragraph 221, a likely reduction in fishing pressure in the immediate vicinity of the wind turbines will likely aid the recovery of the ocean quahog population within the MPA. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
The operation and maintenance activities will not disrupt the prevailing hydrodynamic regime as there will not be permanent change to the hydrodynamic regime during the construction phase. The maintenance of the prevailing hydrodynamic regime will aid with recovery via the importation of larvae from adjacent sites. Overall, the temporary and intermittent nature of the predicted habitat disturbance will enable recovery where impacts occur and limit large scale damage over the course of the operation and maintenance phase. This is consistent with the ‘conserve’ objective of the supporting processes attribute for this feature.
1. Based on the information presented above, the following can be concluded with respect to the ecological attributes of the protected features of the Firth of Forth Banks Complex MPA:
Ocean quahog aggregations are thought to play a role in carbon cycling and nutrient transport within the MPA, (although there is currently no direct evidence) as well as acting as direct records of climate and environmental change. The temporary and localised nature of the habitat disturbance associated with the maintenance activities make them unlikely to disturb these long term functions. Disturbance to carbon cycling and nutrient transport is unlikely to occur due to the small scale of the disturbance during this phase of the Proposed Development. Sediment disturbance and surface penetration during the operation and maintenance phase will be recoverable, following the completion of activities the baseline will return to its pre-construction levels. Overall, the intermittent and temporary nature of this disturbance is unlikely to cause a disturbance to these functions within the MPA. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
As mentioned in the discussion of the physical attribute of the feature (paragraph 238) the hydrodynamic regime of the MPA is unlikely to be affected by the temporary disturbance during maintenance activities. The stability of these condition therefore will continue to provide the same sediment type and volume to the MPA enabling the maintenance of the supporting habitats of ocean quahog aggregations. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
1. Volume 2, chapter 8 of the Offshore EIA Report concluded that due to the temporary, reversible, and intermittent nature of the impact of temporary habitat disturbance, and the minor proportion of the protected features to be affected during operation and maintenance, the magnitude of the impact on the features of the Firth of Forth Banks Complex MPA was negligible. The ocean quahog protected feature of the Firth of Forth Banks Complex MPA is considered to be of high vulnerability, low recoverability and national importance and therefore was considered to have a high sensitivity. 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 with further detail in the Benthic Subtidal and Intertidal Ecology Technical Report of the Offshore EIA Report (volume 3, appendix 8.1), this species was recorded in very low abundances within the site-specific surveys and predominately as juveniles.
1. Based on the information presented here, it can be concluded that temporary habitat disturbance during the Proposed Development operation and maintenance phase will not lead to a significant risk of hindering the achievement of the overall conservation objective for the ocean quahog aggregations feature of the Firth of Forth Banks Complex MPA (i.e. “recover to favourable condition”) for the following reasons:
Temporary habitat loss is predicted to affect a small proportion of supporting habitat for ocean quahog intermittently during the operation and maintenance phase, but habitats are predicted to recover such that the quality and quantity of ocean quahog habitat is maintained. Whilst some ocean quahog individuals may be directly affected by operation and maintenance activities, this is predicted to be to an extent that will not affect the composition of its population in terms of number, age and sex ratio or its ability to thrive in the future.

Decommissioning phase

Direct temporary disturbance of subtidal habitat in the decommissioning phase within the Proposed Development at the Firth of Forth Banks Complex MPA will occur due to jack-up vessels during foundation decommissioning as well as the decommissioning of inter-array, interconnector and offshore export cables, and the associated anchor placements. Table 1.40 Open ▸ presents the maximum design scenario for temporary habitat disturbance within the Firth of Forth Banks Complex MPA in the decommissioning phase.

Table 1.40: Maximum Design Scenario for Temporary Habitat Disturbance within the Firth of Forth Banks Complex MPA relevant to the Decommissioning Phase

The method used to determine the proportion of temporary habitat disturbance occurring within the Firth of Forth Banks Complex MPA during the decommissioning phase is as outlined in paragraphs 188 to 193.
Up to 8.41 km2 of temporary habitat disturbance is predicted to occur within the Firth of Forth Banks Complex MPA during the decommissioning phase which equates to 0.39% of the total area of the MPA. Of this, up to 2.59 km2 is predicted to occur within the Scalp and Wee Bankie section which equates to 0.12% of its total area of this feature in the MPA (or 0.31% of the area of Scalp and Wee Bankie) and 5.82 km2 within the Berwick Bank section of the MPA section which equates to 0.27% of its total area of this feature in the MPA (or 1.08% of the area of Berwick Bank) ( Table 1.41 Open ▸ ).

Table 1.41: Summary of the Extent of Temporary Habitats /Disturbance within the Firth of Forth Banks Complex MPA (as a Whole, and for the Component Sites) During the Decommissioning Phase

1 Calculated as 30.81% of the 8.41 km2 total on the basis of the overlap with the Scalp and Wee Bankie (see paragraph 170).

2 Calculated as 69.19% of the 8.41 km2 total on the basis of the overlap with the Berwick Bank (see paragraph 188).

3 Calculated as 43.82% of total 2.59 km2 of disturbance within the Scalp and Wee Bankie section (i.e. 43.82% of the total area of Scalp and Wee Bankie that overlaps with the Proposed Development and contains the shelf banks and mounds feature).

4 Calculated as 8.64% of total 5.82 km2 of disturbance within the Berwick Bank section (i.e. 8.64% of the total area of Berwick Bank that overlaps with the Proposed Development and contains the shelf banks and mounds feature).

5 Calculated as 71.59% of total 2.59 km2 of disturbance within the Scalp and Wee Bankie section (i.e.71.59% of the total area of Scalp and Wee Bankie that overlaps with the Proposed Development and contains the moraines feature).

6 Calculated as 0.16% of total 5.82 km2 of disturbance within the Berwick Bank section (i.e. 0.16% of the total area of Berwick Bank that overlaps with the Proposed Development and contains the moraines feature).

Offshore subtidal sands and gravels

On the basis of the assumptions outlined in paragraph 190, and for the purposes of this assessment, it is assumed that all of temporary habitat disturbance predicted during the decommissioning phase (i.e. 8.41 km2) could occur within the offshore subtidal sands and gravels feature (see Table 1.41 Open ▸ ). The maximum design scenario for the decommissioning phase assumes the complete removal of all infrastructure, therefore should any infrastructure be left in situ this will result in a lower area of temporary habitat disturbance during decommissioning.
The description of the activities and sensitivity of the offshore subtidal sands and gravels is discussed in relation to the construction phase in Table 1.40 Open ▸ and paragraphs 203 and 204 (however there is currently no set time period for decommissioning), the effects of decommissioning are expected to be the same or less than construction and therefore these previous statements are applicable to this phase.
Based on the information presented above, the following can be concluded with respect to the physical attributes of the offshore subtidal sands and gravels feature of the Firth of Forth Banks Complex MPA:

Extent and distribution of the offshore subtidal sands and gravels protected habitat feature will be maintained in the long term following the completion of the decommissioning phase, with only a small proportion of the total extent of this feature within the MPA affected (0.39% of the total MPA area will be affected by temporary habitat disturbance in the decommissioning phase). These effects are limited to the northern half of the Berwick Bank section of the MPA (affecting up to 5.82 km2 which equates to 0.27% of the total extent of this feature within the MPA) and a southern/central section of Scalp and Wee Bankie (affecting up to 2.59 km2 which equates to 0.12% of the total extent of the feature within the MPA). In addition, any effects on the offshore subtidal sands and gravels feature will be temporary and reversible with recovery of sediment occurring following the completion of decommissioning. This is consistent with the ‘conserve’ objective of the extent and distribution attribute for this feature.
The hydrodynamic regime of the offshore subtidal sands and gravels protected feature is one of the supporting processes. The temporary and relatively localised scale of the effects for habitat disturbance in the decommissioning phase are unlikely to result in changes to tidal currents and wave exposure, maintaining the regime and its associated processes throughout the Firth of Forth Banks Complex MPA. This is consistent with the ‘conserve’ objective of the supporting processes attribute for this feature.
Unlike the construction phase there will be little removal of sediment, with only a 15 m wide corridor for disturbance associated with the deburial of cables and no new permanent structures added. This will not involve the movement of large amount of sediment, with sediment only being displaced into the immediate vicinity of the cables removed. On this basis there is likely to be little to no effects from this impact on fine scale topographic features and the associated processes which they rely on. This is consistent with the ‘recover’ objective of the structure and function attribute for this feature.
The sediment composition of the offshore subtidal sands and gravels protected feature is unlikely to be affected by the temporary habitat disturbance impact because, there will much less disturbance of sediment than during the construction phase and no large-scale movement of sediment as site preparation activities will not be required. Additionally, the limited change to the hydrodynamic regime is unlikely to lead to any change in the prevailing sediment composition. This is consistent with the ‘recover’ objective of the structure and function attribute for this feature.
1. The ecological attributes which characterise the offshore subtidal sands and gravels protected feature are described in paragraph 203.
2. Based on the information presented above, the following can be concluded with respect to the ecological attributes of the offshore subtidal sands and gravels feature of the Firth of Forth Banks Complex MPA:
The key influential species that have a key role in determining the structure and function of the offshore subtidal sands and gravels feature would not be affected by this impact in the decommissioning phase, with only a small proportion (0.39%) of the total area of this feature within the MPA affected at any one time. The absence of sediment removal and deposition during the decommissioning phase (i.e. as site preparation activities are not required) removes one of the biggest pressures. The reduced area of impact compared to the construction phase as well as the number of pressures may increase recovery time, helping to maintain the presence of key influential species within the offshore subtidal sands and gravels feature. This is consistent with the ‘recover’ objective of the structure and function attribute for this feature.
The presence and spatial distribution of the characteristic communities will be maintained across the Firth of Forth Banks Complex MPA. Only a small proportion of the offshore subtidal sands and gravels feature will be affected in the Berwick Bank section of the MPA (affecting 1.08% of the total area of the Berwick Bank section of the MPA) and a southern/central section of Scalp and Wee Bankie (affecting 0.31% of the total extent of Scalp and Wee Bankie). Biological communities will not be impacted to the same extent as during the construction phase, but the impact will remain intermittent and temporary and therefore improving the likelihood of maintaining the diverse composition of communities in this protected feature. The species associated with this feature have some tolerance to burial, with multiple burrowing species, enabling a rapid recovery of the community. This is consistent with the ‘recover’ objective of the structure and function attribute for this feature.
The function of the offshore subtidal sands and gravels feature will be maintained throughout the decommissioning period due to the localised nature of the impacts and the smaller proportion of the MPA which will be impacted compared to the construction phase. By reducing this area of impact functionality will continue in areas unaffected by decommissioning support those areas which are experiencing disturbance. Coupling this with the negligible impact on the hydrodynamic regime and reduced biological community the function offshore subtidal sands and gravels protected feature will be conserved. This is consistent with the ‘recover’ objective of the structure and function attribute for this feature.
1. Volume 2, chapter 8 of the Offshore EIA Report concluded that due to the temporary, reversible, and intermittent nature of the impact of temporary habitat disturbance, and the relatively small proportion of the protected features to be affected during decommissioning, the magnitude of the impact on the features of the Firth of Forth Banks Complex MPA was low. The offshore subtidal sands and gravels protected feature of the Firth of Forth Banks Complex MPA is considered to be of medium vulnerability, medium recoverability and national importance and therefore was considered to have a medium sensitivity. Therefore, the significance of effect was considered to be minor.
2. Based on the information presented here, it can be concluded that temporary habitat disturbance during the decommissioning phase will not lead to a significant risk of hindering the achievement of the overall conservation objective for this feature of the Firth of Forth Banks Complex MPA (i.e. “recover to favourable condition”) for the following reasons:
Temporary habitat disturbance is predicted to affect a very small proportion of the offshore subtidal sands and gravels feature (0.39%) intermittently during the decommissioning phase, these habitats will recover such that the extent and distribution of the protected feature will remain stable following the decommissioning phase; and
The structures and functions, quality, and the composition of characteristic communities will remain in (or recover to) a condition which is healthy and not deteriorating. Recovery of the seabed sediment will occur in the months following foundation and cable removal, with complete recovery within the areas affected within a few years. The key and influential species are predicted to recolonise disturbed sediment, with full recovery of characteristic communities within months to years of construction. These communities will be supported by an undisturbed hydrodynamic regime which will continue to form the fine scale features of the MPA.

Shelf banks and mounds

On the basis of the assumptions outlined in paragraph 191, and for the purposes of this assessment it is assumed that 19.48% of the maximum temporary habitat disturbance resulting from the decommissioning of the Proposed Development within the MPA could occur in this feature. This would result in temporary disturbance of up to 1.64 km2 or 0.62% of the shelf banks and mound feature within the MPA. Of this temporary habitat disturbance up to 1.14 km2 could occur within Scalp and Wee Bankie (0.43% of the feature within the whole MPA) and 0.50 km2 could occur in the Berwick Bank section of the MPA (0.19% of the feature within the whole MPA) (see Table 1.41 Open ▸ ).
The description of the activities and sensitivity of the shelf banks and mounds is discussed in relation to the construction phase in Table 1.40 Open ▸ and paragraphs 203 and 204 (however there is currently no set time period for decommissioning it has been assumed that it will occur over a similar length of time as construction), the effects of decommissioning are expected to be the same or less than construction and therefore these previous statements are applicable to this phase.
Based on the information presented above, the following can be concluded with respect to the physical attributes of the shelf banks and mounds feature of the Firth of Forth Banks Complex MPA:

As in the construction phase the lack of permanent features on the seabed during the decommissioning phase, along with the highly reduced area of impact, combined with the large scale of this feature means that any potential impact upon the extent and distribution, and the prevailing hydrodynamic regime, which it depends, on will be minimal. The decommissioning activities will not result in any wide scale movement of sediment. Overall, the shelf banks and mounds feature will be conserved throughout the decommissioning phase and following the conclusion of construction the protected feature will quickly recover from the effects of this temporary impact. This is consistent with the ‘conserve’ objective of the extent and distribution attribute for this feature.
As noted above the lack of permanent new infrastructure and without any large-scale movement of sediment, the physical nature of this protected feature is therefore not expected to be affected. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
The previous two points clarify that the hydrodynamic regime and sediment transport systems which support this protected feature will be minimally impacted by this temporary disturbance, therefore maintaining the supporting processes of this protected feature. This is consistent with the ‘conserve’ objective of the supporting processes attribute for this feature.
1. The ecological attributes which characterise the shelf banks and mounds protected features are described in paragraph 203. The following can be concluded with respect to the ecological attributes of the shelf banks and mounds feature of the Firth of Forth Banks Complex MPA:
The role of hydrodynamics in the function of this feature as a spawning ground for commercially important species is noted in the construction phase assessment and has already been established to be negligibly impacted by the temporary habitat disturbance during the decommissioning phase. The ecological functions of this feature will be conserved by the highly limited area of impact, which equates to only 0.62% of the shelf banks and mounds which occur within the Proposed Development. Reducing the impact on spawning grounds which have already been shown to recover from similar damage as well as on the carbon storage capacity of this protected feature conserves the two other primary functions of the feature. The maintenance of these benthic communities demonstrates some tolerance to these kinds of activities, and ensures the continued function of the food web it supports including valuable seabird and marine mammal communities. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
1. Volume 2, chapter 8 of the Offshore EIA Report concluded that due to the temporary, reversible, and intermittent nature of the impact of temporary habitat disturbance, and the minor proportion of the protected features to be affected during decommissioning, the magnitude of the impact on the features of the Firth of Forth Banks Complex MPA was low. The offshore subtidal sands and gravels protected feature of the Firth of Forth Banks Complex MPA is considered to be of medium vulnerability, medium recoverability and national importance and therefore was considered to have a medium sensitivity. Therefore, the significance of effect was considered to be minor.
2. Based on the information presented here, it can be concluded that temporary habitat disturbance during the Proposed Development decommissioning phase will not lead to a significant risk of hindering the achievement of the overall conservation objective for this feature of the Firth of Forth Banks Complex MPA (i.e. “maintain in favourable condition”) for the following reasons:
While the temporary habitat disturbance is predicted to affect a small proportion (0.62%) of the habitat feature intermittently during the construction phase, these habitats will recover with the extent and distribution of the protected feature remaining stable following the completion of the decommissioning phase;
The function will remain in a condition which is healthy and not deteriorating. Recovery of the seabed sediments will occur in the months following cable removal, with complete recovery within the areas affected within a few years. This will ensure that the feature continues to support its characteristic biological communities and their use of the site for feeding, courtship, spawning, or use as nursery ground; and;
The supporting processes which enable the formation of these large features and create the necessary environmental conditions to enable its structure and function will be maintained.

Ocean quahog aggregations

On the basis of the assumptions outlined in paragraph 190, and for the purposes of this assessment, it is assumed that all of the potential temporary habitat disturbance during decommissioning could occur entirely within the ocean quahog aggregations protected feature, this would equate to this temporary habitat disturbance of up to 0.39% of the supporting habitat for this feature within the MPA (see Table 1.41 Open ▸ ).
The description of the activities and sensitivity of the ocean quahog aggregations is discussed in relation to the construction phase in Table 1.37 Open ▸ and paragraph 224 respectively (however there is currently no set time period for decommissioning). The effects of decommissioning are expected to be the same or less than construction and therefore these previous statements are applicable to this phase.
Based on the information presented previously (paragraph 216 et seq.), the following can be concluded with respect to the physical attributes of the ocean quahog aggregations feature of the Firth of Forth Banks Complex MPA:

The activities involved in the decommissioning phase of the Proposed Development will exert only a temporary pressure on the feature and at a reduced extent compared to the construction phase. As previously noted, ocean quahogs in this area are currently being repeatedly exposed to pressures from dredge fishing. The decommissioning activities will not involve the relocation of sediment as will occur in the construction phase, instead disturbance will be much more focussed on the surface within discrete areas (e.g. areas for cable deburial). The decommissioning activities associated with the Proposed Development are therefore unlikely to affect the extent and distribution of ocean quahog and their supporting habitat within the MPA. This is consistent with the ‘conserve’ objective of the extent and distribution attribute for this feature.
Temporary habitat disturbance during decommissioning is unlikely to exceed the impacts of dredge and trawl fishing which already take place in the MPA as well as having a reduced impact compared to the construction phase of the Proposed Development. Discrete areas of impact from anchor and jack ups are unlikely to have a conspicuous effect on the sand and gravel environment that they occupy. The activities will also not disrupt the prevailing hydrodynamic regime. Mortality of all individuals impacted is not predicted and some individuals not directly impacted by decommissioning equipment, such as cable removal tools, could be reasonably expected to survive. It should be noted that whilst the assessment for impacts associated with cable deburial assumes a width of disturbance to the seabed of up to 15 m, the actual width of the trench (i.e. where most direct impacts will occur) will be much smaller than this, at up to 2 m. The scale and extent of activities associated with the decommissioning phase is unlikely to impact upon the structure of ocean quahog aggregations within the MPA. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
The previous points clarify that the hydrodynamic regime, which support the enhancement and health of this protected feature, will be minimally impacted by this temporary disturbance due to a lack of permanent change and the limited extent of activities. This is consistent with the ‘conserve’ objective of the supporting processes attribute for this feature.
1. The ecological attributes which characterise the ocean quahog aggregations protected feature are described in paragraph 218.The following can be concluded with respect to the ecological attributes of the ocean quahog aggregations feature of the Firth of Forth Banks Complex MPA:
The presence and spatial distribution of ocean quahog aggregations may be temporary affected within the discrete locations associated with anchor placements, jack up events and cable deburial. The temporary and localised nature of the decommissioning disturbances however is unlikely to disturb the long term functions associated with this feature. Overall, the limited extent, and the intermittent and temporary nature of this disturbance, is unlikely to cause a disturbance to these functions within the MPA. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
1. The hydrodynamic regime of the MPA is unlikely to be affected by the temporary disturbance of decommissioning. The stability of these condition therefore will continue to provide the same sediment type and volume to the MPA enabling the maintenance of the supporting habitats of ocean quahog aggregations. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature. Volume 2, chapter 8 of the Offshore EIA Report concluded that due to the temporary, reversible, and intermittent nature of the impact of temporary habitat disturbance, and the minor proportion of the protected features to be affected during decommissioning, the magnitude of the impact on the features of the Firth of Forth Banks Complex MPA was low. The ocean quahog protected feature of the Firth of Forth Banks Complex MPA is considered to be of high vulnerability, low recoverability and national importance and therefore was considered to have a high sensitivity. The effect will, therefore, be of moderate adverse significance in the medium term (i.e. within approximately ten years of completion of construction), with this decreasing to minor adverse significance in the long term as the sediments and ocean quahog populations are predicted to recover. Therefore, no significant long term effects are predicted.
2. Based on the information presented here, it can be concluded that temporary habitat disturbance during the Proposed Development decommissioning phase will not lead to a significant risk of hindering the achievement of the overall conservation objective for the ocean quahog aggregations feature of the Firth of Forth Banks Complex MPA (i.e. “recover to favourable condition”) for the following reasons:
Temporary habitat disturbance is predicted to affect a small proportion (0.39%) of supporting habitat for ocean quahog intermittently during the decommissioning phase, but habitats are predicted to recover such that the quality and quantity of ocean quahog habitat is maintained. Whilst some ocean quahog individuals may be directly affected by decommissioning activities, this is predicted to be to an extent that will not affect the composition of its population in terms of number, age and sex ratio or its ability to thrive in the future.

Wee Bankie key geodiversity area (moraines)

On the basis of the assumptions outlined in paragraph 192, and for the purposes of this assessment, it is assumed that 22.17% of the maximum temporary habitat disturbance resulting from the decommissioning of the Proposed Development within the MPA could occur within this feature. This equates to 1.86 km2 or 0.25% of this feature within the MPA, and of this, 1.86 km2 could occur within Scalp and Wee Bankie (0.25% of the feature within the whole MPA) and 0.01 km2 could occur in the Berwick Bank section of the MPA (0.001% of the feature within the whole MPA) (see Table 1.41 Open ▸ ).
The description of the activities is discussed in relation to the construction phase in Table 1.37 Open ▸ (however there is currently no set time period for decommissioning), the effects of decommissioning are expected to be the same or less than construction and therefore these previous statements are applicable to this phase.
Based on the information presented above, the following can be concluded with respect to the physical attributes of the Wee Bankie Key Geodiversity Area feature of the Firth of Forth Banks Complex MPA:

All impacts to the seabed associated with decommissioning activities will be temporary in nature and no sediment will be permanently removed from the system during the construction phase. Whilst material will be removed during sand wave clearance activities, it will be deposited locally such that there will be no overall loss of the feature’s extent or distribution. Disturbance will largely affect the surface sediments as a result of anchor and jack up placements. Only localised areas will be affected by deeper disturbance from cable deburial, and will be those areas, which were originally disturbed during construction 35 years prior. The scale of the potential temporary impacts to this feature are predicted to be minimal, affecting only 1.23% of the total extent of the Wee Bankie Key Geodiversity Area feature in the MPA. This is consistent with the ‘conserve’ objective of the extent and distribution attribute for this feature.
The structures of the moraines in the MPA are characterised by their height above the seabed. This is unlikely to be disturbed by surface level activity and cable deburial where disturbance has already occurred, having a minimal impact on the height of the feature. These activities may inadvertently cause damage to the slopes where anchors or jack-ups are placed on the seabed, but this is unlikely to damage the overall structure due to its large size. The temporary and localised sediment disturbance associated with decommissioning activities are unlikely to result in large scale changes to this feature as the extent of disturbance is predicted to be small (0.25%) in the context of the wider area of the feature. There will be no permanent removal of material. Overall, the structure of this large-scale feature is unlikely to sustain damage from decommissioning. This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
The function of the Wee Bankie Key Geodiversity Area feature is as a valuable site of scientific study as well as contributing to the wider physical and ecological environment. Any disturbance to sediment during the decommissioning phase will be temporary, localised and very small in the context of the wider extent of this feature (i.e. 0.25%) and will not affect the functions provided by this geodiversity feature. The effects on the Wee Bankie Key Geodiversity Area, to the structure and extent of the moraine, will be small with only 1.23% potentially being disturbed, allowing the study of the majority of the undamaged feature. The feature will continue to be an integral part of the offshore subtidal sands and gravels protected feature, supplying substrate that supports the sedimentary biological communities, and it will continue to provide habitat for the ocean quahog aggregations feature This is consistent with the ‘conserve’ objective of the structure and function attribute for this feature.
1. Based on the information presented here, it can be concluded that temporary habitat disturbance during the Proposed Development construction phase will not lead to a significant risk of hindering the achievement of the overall conservation objective for this feature of the Firth of Forth Banks Complex MPA (i.e. “maintain in favourable condition”) for the following reasons:
Temporary habitat disturbance is predicted to affect a very small proportion (0.25%) of the total extent of the protected feature within the MPA during the decommissioning phase. Therefore, its extent, component elements and integrity as a relict feature will be maintained;
The structure and function will remain unimpaired by the activities as only a small proportion of the feature will be affected, and the temporary nature of the impact will not result in any long term changes to the feature; and
The surface of the feature will remain sufficiently unobscured during the decommissioning phase.

Increases in SSC and Associated Sediment Deposition

Construction Phase

Increases in SSC and associated sediment deposition in subtidal habitats during the construction phase of the Proposed Development in the Firth of Forth Banks Complex MPA will occur as a result of drilling for foundation installation, the installation of inter-array, interconnector, and offshore export cables using jet trenching and seabed preparation (i.e. sand wave and boulder clearance) ahead of cable installation. Full detail on the project envelope assumptions and maximum design scenario with respect to foundation and cable installation as well as seabed clearance are provided in section 1.4.
This assessment is equivalent to the following pressures identified by JNCC's Advice on Operations for the Firth of Forth Banks Complex MPA for ‘Renewable Energy: offshore wind’ and ‘Power cables: laying burial and protection’ (JNCC, 2018c):

Changes in suspended solids (water clarity); and
Siltation rate changes (low), including smothering (depth of vertical sediment overburden).
1. FeAST concludes that ocean quahog are not sensitive to changes in SSC and the associated deposition due to their ability to burrow back to the surface following sediment deposition, and this has been found to have no negative effect on growth or population structure (Powilliet et al., 2006; 2009). Ocean quahog are also not directly sensitive to changes in light availability although an increase in turbidity could lead to a release of higher-than-normal levels of nutrients resulting in increased levels of food availability (FeAST, 2013a). As a result of both of these factors, ocean quahog have not been considered further for the impact of increased SSC and sediment deposition.
2. Additionally, as a large-scale geodiversity feature without a biological component, the Wee Bankie Key Geodiversity Area and its moraines feature are not discussed further in relation to this impact as changes to water clarity and light smothering are not relevant to a geodiversity feature (FeAST, 2013d).
3. The disturbance of sediments during foundation installation is likely to result in a temporally and spatially limited plume affecting SSC and associated deposition in close proximity to the point of release. The drilling involved with foundation installation is predicted to have peak suspended sediment concentrations of <5 mg/l, with average values typically less than one fifth of this and dropping to 1 mg/l to 2 mg/l within a very short distance of typically less than 500 m. The sediment plumes are expected to be temporary, returning to background levels within a few tidal cycles. The average sedimentation depth is predicted to be typically 0.05 mm to 0.1 mm during pile installation, with that maximum dropping to <0.003 mm one day following cessation of operations. This demonstrates the dispersive nature of the site, dispersing material the full extent of the tidal excursion, and this settlement would be imperceptible from the background sediment transport activity with plotted sediment depths less than typical grain diameters. The sedimentation beyond the immediate site will be indiscernible due to the low drilling rate.
4. Sand wave clearance also accounts for up to a 25 m wide corridor. The resulting suspended sediment concentrations showed similar characteristics to the offshore export cable clearance. The dredging phase plumes are predicted to be smaller with concentrations <100 mg/l. The release phase plume is slightly larger than the dredging plume with concentrations reaching 2,500 mg/l at the disposal site. The greatest area of increased suspended sediment concentration is also associated with re-mobilisation of the deposited material on subsequent tides with concentrations of 100 mg/l to 250 mg/l extending a tidal excursion circa 10 km from the site, whilst average levels <100 mg/l are predicted. The average sedimentation depth is typically half that resulting from sand wave clearance for the offshore export cables, with maximum sedimentation of 600 mm, which is only reached in very small areas along the corridor, beyond the cable corridor sedimentation as a result of this work is less than 50 mm. The sedimentation one day following the cessation of the clearance activities shows deposited material at the site of release with depth 0.2 m to 0.4 m whilst in the locality lower depths, typically <5 mm, are present at 50 m distance from the release.
5. Sand wave clearance for the offshore export cable installation would involve disturbance of seabed material within a corridor of up to 25 m in width for the 30% of offshore export cables where it may be necessary. Modelling of suspended sediments associated with the site preparation showed that during the dredging phase the plume is very small with concentrations <100 mg/l. Suspended sediment concentration is predicted to reach its peak in the disposal phase with concentrations reaching 2,500 mg/l at the release site, but the plume is predicted to be at its most extensive when the deposited material is redistributed on the successive tides. Under these circumstances’ concentrations of 100 mg/l to 250 mg/l are predicted with average values <100 mg/l extending up to 10 km, corresponding with a tidal excursion. Sedimentation of deposited material is focussed within 100 m of the site of release with a maximum depth 0.5 m to 0.75 m whilst the finer sediment fractions are distributed in the vicinity at much smaller depths circa 5 mm to 10 mm over a maximum distance of 10 km form the site of work. Sedimentation one day following cessation of operation is similar to during operation with a small extension to the area over which sedimentation has occurred but with no increase in maximum sedimentation depth.
6. For the installation of offshore export cables, the modelling outputs predicted average suspended sediment concentrations of up to 500 mg/l at the source whilst more generally the plume is predicted to be one tenth of this value, typically <50 mg/l and extending north and south on the tide. Suspended sediment concentrations are predicted to reduce to background levels on slack tides. Average sedimentation is predicted to be small and typically <1 mm during the works and up to 30 mm one day after cessation of operations.
7. Based on this information, the following can be concluded with respect to all of the physical attributes of all the protected features:

Sediment composition and distribution will not be affected due to increases in SSC and associated deposition, with most of the sediment mobilised during foundation and cable installation as well as seabed preparation falling out of suspension in close proximity to the location of the activity and therefore within the same sediment type. Fine sediments will travel further away from their original location although where they settle, they will not affect the overall sediment composition.
The sedimentation rate will be maintained. As detailed above any effects of sediment mobilisation will be highly localised in extent and of short-term duration, therefore not affecting the natural sedimentation, maintaining the supporting processes and physical nature of these features.
Water turbidity will be affected temporarily during construction activities, although any effects will be limited spatially and temporally, occurring intermittently throughout the construction phase and returning to background levels following the cessation of the works.

Offshore subtidal sands and gravels

Paragraph 276, established the conservation of the physical attributes of the offshore subtidal sands and gravels through the construction phase, which provides some stability to the component biological communities of this feature.
The characteristic biotope with biological components (SS.SSa.CFiSa.ApriBatPo and SS.SSa.CFiSa.EpusOborApri) both have a low sensitivity to the pressures exerted through this impact (changes to water clarity and light smothering). This is due to their preferred habitat being a high energy sedimentary seabed which is sometimes exposed to natural light smothering from storm events (Tillin, 2016a; Tillin, 2016b). The characteristic species groups of these biotopes are polychaetes and bivalves which have been shown to be capable of burrowing and repositioning in the sediment although this can depend on the kind of sediment that is deposited (Tillin, 2016a; Tillin, 2016b). The increase in turbidity may also directly impact upon the phytoplankton, which rely on light, which will indirectly impact upon the bivalves and polychaetes by reducing the amount of food available (Tillin, 2016; Tillin, 2016b).
Ocean quahog is one of the key influential species which characterise this feature, their sensitivity to SSC and associated deposition is detailed in paragraph 270 where it is concluded that they are not sensitive to the pressures which characterise this impact. Other key/influential species include burrowing polychaetas (Spiophanes bombyx, Galathowenia oculata and Owenia fusiformis) and burrowing bivalve molluscs (Abra prismatica and Dosinia exolete). As burrowing species, they are likely to be able to tolerate the levels of deposition associated with the construction phase with the potential exception of directly next to seabed preparation activities where deposition is over 600 mm. This limited area of high deposition is unlikely to result in a change in the distribution of these key/influential species across the protected feature.
Considering the characteristic community of the offshore subtidal sand and gravel protected feature, this is largely defined by the sediment composition which will be maintained through the construction phase. The largely low level, temporary and localised nature of SSC and associated deposition alongside the unaltered hydrodynamic regime leads to an overall conservancy of the environment which will sustain the characteristic community (paragraph 278) of this protected feature. Additionally, the temporary nature of these effects allows for greater level of recovery than the ongoing dredge fishing which currently occurs within the Firth of Forth Banks Complex MPA.
These biological and physical attributes contribute to the high-level function of the site in the context of the environment beyond the MPA. The hydrodynamic regime of the protected feature will not be disturbed as a result of this impact therefore maintaining the internal waves which facilitate nutrient upwelling which make this protected feature an area of high biological productivity. This nutrient productivity feeds into the function of this feature as a spawning ground for a number of species. Volume 2, chapter 9 of the Offshore EIA Report identified that sandeel eggs, a key spawning species in this habitat, are tolerant to some level of sediment deposition due to the nature of this high energy environment. Sediment type however is also a key factor in sandeel spawning, and therefore the settlement of fine sediment on top of preferred sands may temporarily result in avoidance behaviour but only for a short period until the fine material is removed by currents, overall causing no long term changes in spawning. Finally, the short-term nature of the resuspension of sediment is unlikely to reduce the carbon storage potential of this protected feature, especially as the sediments will remain in the same sediment transport cell. Where deeper sediments will be disturbed, as a result of wind turbine foundation installation, these sites will be limited in extent and the sediment will remain in the local environment.
Volume 2, chapter 8 of the Offshore EIA Report concluded that due to the temporary, and limited extent of the impact of increases in SSC and associated deposition, and the relatively small proportion of the protected features to be affected during construction, the magnitude of the impact on the features of the Firth of Forth Banks Complex MPA was low. The offshore subtidal sands and gravels protected feature of the Firth of Forth Banks Complex MPA is considered to be of low vulnerability, high recoverability and national importance and therefore was considered to have a low sensitivity. Therefore, the significance of effect was considered to be minor adverse.
Based on the information presented here, it can be concluded that increases in SSC and associated deposition during the Proposed Development construction phase will not lead to a significant risk of hindering the achievement of the conservation objectives for this feature of the Firth of Forth Banks Complex MPA (i.e. “recover to favourable condition”) for the following reasons:

The increase in SSC and associated deposition is predicted to affect a small proportion of the offshore subtidal sands and gravels feature intermittently during the construction phase. These habitats will recover such that the extent and distribution of the protected feature will remain stable following the construction phase; and
The structures and functions, quality, and the composition of characteristic communities will remain in (or recover to) a condition which is healthy and not deteriorating. Recovery of the seabed sediment will occur within a few tidal cycles following with completion of construction activities. The key and influential species are predicted to recolonise disturbed sediment, with full recovery of characteristic communities also expected. These communities will be supported by an undisturbed hydrodynamic regime which will continue to form the fine scale features of the MPA.

Shelf banks and mounds

The shelf banks and mounds feature contains the same characteristic biotopes as the offshore subtidal sands and gravels feature, therefore for a description of their sensitivity to this impact see paragraph 278.
Paragraph 276, established that the supporting processes which maintain the physical nature of the shelf banks and mounds feature will not be affected. The function of this feature requires the consideration of both physical and biological attributes of the feature. As with the offshore subtidal sands and gravels feature, the biological productivity of this feature is dependent on its internal currents creating an upwelling of nutrients from deeper waters. As the hydrodynamic regime is not affected by this impact this ecosystem function will be preserved throughout the construction phase. Sandeels are the key species which supports numerous protected bird species which forage within this MPA. Elevated SSC may impact upon the ability of birds to see their prey, but this will only occur on a short term and is unlikely to have a widespread or long term impact on these species. As previously discussed in paragraph 281, sandeel eggs have been found to have some tolerance to sediment deposition and any avoidance due to alteration in surface sediment will be temporary (a few tidal cycles) until it is redistributed, and the environment is returned to baseline conditions. As described in paragraph 281 for the offshore subtidal sands and gravels feature, the climate regulation function of this feature is unlikely to be impacted due to the sediment remaining local to the site of resuspension and staying within the sediment transport cell, preventing carbon from being transported out of the MPA.
Volume 2, chapter 8 of the Offshore EIA Report concluded that due to the temporary, and limited extent of the impact of increases in SSC and associated deposition, and the relatively small proportion of the protected features to be affected during construction, the magnitude of the impact on the features of the Firth of Forth Banks Complex MPA was low. The shelf banks and mounds protected feature of the Firth of Forth Banks Complex MPA is considered to be of low vulnerability, high recoverability and national importance and therefore was considered to have a low sensitivity. Therefore, the significance of effect was considered to be minor adverse.
Based on the information presented here, it can be concluded that increases in SSC and associated deposition during the Proposed Development construction phase will not lead to a significant risk of hindering the achievement of the conservation objectives for the shelf banks and mounds feature of the Firth of Forth Banks Complex MPA (i.e. “maintain in favourable condition”) for the following reasons:

While the temporary increase in SSC and associated deposition disturbance is predicted to affect a small proportion of the habitat feature for intermittently during the construction phase, these habitats will recover within a few tidal cycles with the extent and distribution of the protected feature remaining stable following the completion of the construction phase;
The function will remain in a condition which is healthy and not deteriorating. Recovery of the seabed sediments will occur in a few tidal cycles following seabed preparation and cable installation. This will ensure that the feature continues to support its characteristic biological communities and their use of the site for feeding, courtship, spawning, or use as nursery ground; and
The supporting processes which enable the formation of these large features and create the necessary environmental conditions to enable its structure and function will be maintained.

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