Draft Sectoral Marine Plans for Offshore Renewable Energy in Scottish Waters - Environmental Report Appendix C: Assessment of Technologies

SEA Topic Areas

Transmission Infrastructure components - offshore

Subsea Transmission Cables

Landfall and Transition Pit

Transmission Infrastructure components - onshore

Overhead Lines

Onshore AC Substations

Onshore DC/ AC Converter Stations

• Includes offshore AC substations and AC/ DC substations.
• Common designs are based upon experience in offshore oil and gas industry.
• Common designs consist of a 'topside' component housing the main equipment, and a foundation structure ( e.g. steel jacket, monopile, gravity based structure)

• Cables to transfer the power from the AC substation or the offshore AC/ DC convertor station to the shore.
• Installed from a ship or barge, using installation tools to plough, jet or excavate a trench for placement, followed by backfilling of the trench.

• Designed to bring the subsea cables to shore, and connect to buried onshore cables or overhead power lines.
• Can be undertaken from a number of methods ( e.g. Horizontal Directional Drilling ( HDD), trenching) or a combination of them, using drilling rigs or trenching equipment.

• Comprises buried onshore transmission cables and their connections from landfall or transition pit to onshore electricity network.
• Typically undertaken using standard civil engineering equipment performing trench excavations and backfilling.
• Horizontal Directional Drilling ( HDD) may be used in some instances ( e.g. crossing roads, railway lines, rivers, etc.).
• May require additional controls ( e.g. traffic management, etc.) in some instances.

• Installed to transmit electrical power on land via towers and cables.
• Typically undertaken using standard civil engineering equipment excavating and installation foundations for the towers, and placement of infrastructure.
• May require additional controls ( e.g. traffic management, clearing, tree cutting, etc.) in some instances.

• Houses electrical equipment for switching and protection of the electrical system.
• In most cases it also steps up electrical voltages to connect to the onshore electricity transmission system.
• Involves standard civil engineering practices for drainage, foundations, buildings, fences and other structures.

• To convert from HVDC connection from the offshore wind farm to AC for connection to the onshore electricity system. It should be noted that a converter station can be both for converting from AC to DC and vice versa.
• Involves standard civil engineering practices for drainage, foundations, buildings, fences and other structures.

Marine Mammals and fish

Noise from construction from piling ( e.g. behavioural response, lethal effects, displacement from natural habitat and possible feeding areas, physical injury to hearing organs).

Potential habitat loss or disturbance, especially to bottom dwelling species such as sand eels, which are important prey species for birds, marine mammals and fish.

Potential collision risk with submerged structures and associated cabling (if any).

Potential for increased suspended solids during construction and sediment deposition affecting respiration in bottom dwelling and spawning species ( e.g. sand eel).

Potential for EMF effects during operation as part of cable distribution.

Potential creation of artificial rocky habitats due to the presence of submerged infrastructure.

Seabirds

Potential displacement due to disturbance during construction from offshore feeding sites to other areas ( e.g. herring gull, great cormorant, etc.).

Potential loss of feeding grounds for on-passage (migrating) species due to presence of structures ( e.g. dunlin, knot, etc.) and associated with loss of prey species ( e.g. sand eel for migratory species such as Arctic Tern).

Marine and Coastal Habitats

Potential loss or disturbance to especially sensitive/ designated habitats from construction ( e.g. reefs and associated species which may take time to recover).

Potential for increased suspended solids and sediment deposition associated with construction site, and associated effects for epibenthic species, especially filter feeders.

Marine Mammals and fish

Potential habitat loss or disruption to seabed communities during installation.

Potential temporary displacement to other areas and potential collision risk during installation.

Potential EMF from the cable distribution, and potential for impacts such as changes in behaviour and migratory patterns of some fish and mammal species.

Seabirds

Potential loss of prey species in offshore feeding grounds from installation activities.

Marine and Coastal Habitats

Installation can lead to potential increases to suspended solids and deposition, leading to smothering of seabed communities.

Potential habitat loss or disruption to benthic communities during installation.

Potential habitat disturbance due to maintenance and repair activity.

Marine Mammals and fish

Potential habitat loss or disruption to inshore seabed communities from installation.

Potential temporary displacement to other areas during installation.

Potential EMF from the cable distribution, and potential for impacts such as changes in behaviour and migratory patterns of some fish and mammal species.

Seabirds

Possible effects from proximity of landfall sites to protected areas for breeding or wintering birds ( e.g. oystercatcher.)

Potential for loss of prey species in feeding grounds.

Marine and Coastal Habitats

Potential habitat loss or disruption to inshore seabed communities from installation activities.

Potential disruption to intertidal habitats and benthic species.

Potential increase in suspended solids and smothering (deposition) during installation works.

Potential disturbance to seabed and intertidal areas due to maintenance and repair activity.

Onshore Fauna

Potential loss or disturbance of protected or notable species, in particular, water vole, otter, badger, great crested newts, reptiles and breeding birds.

Onshore Habitats

Potential degradation or loss of important habitats ( e.g. ponds, hedgerows, woodland, watercourses, grassland).

Potential adverse effects on designated (statutory and non-statutory) nature conservation sites.

Reinstatement to land from previous condition can include enhancement measures.

Onshore Fauna

Potential collision risk of overhead lines to birds and bats, and disturbance during breeding from noise and light associated with maintenance activities.

Potential loss or disturbance of protected or notable species ( e.g. water vole, otter).

Onshore Habitats

Possible degradation or loss of important habitats ( e.g. ponds, hedgerows).

Potential integrity loss of designed nature conservation sites.

Potential adverse effects and loss of integrity of designated nature conservation sites.

Onshore Fauna

Potential degradation or loss of important habitats such as ponds, hedgerows, woodland, watercourses and grassland.

Onshore Habitats

Potential loss or disturbance of protected or notable species (in particular: water vole, badger, great crested newts, reptiles and breeding birds).

Potential adverse effects on designated (statutory and non-statutory) nature conservation sites.

Additional landscape works and screening may provide habitats and opportunities for biodiversity enhancement.

Onshore Fauna

Potential loss or disturbance of protected or notable species ( e.g. water vole, otter).

Onshore Habitats

Possible degradation or loss of important habitats ( e.g. ponds, hedgerows).

Potential adverse effects on designated (statutory and non-statutory) nature conservation sites.

Additional landscape works and screening may provide habitats and opportunities for biodiversity enhancement.

Construction vessels and helicopter flights may cross other user's transit routes ( e.g. dredging, oil and gas operations and freight).

Potential for increased collision risk, impacts for navigation and displacement of other marine users ( e.g. shipping, recreation, etc.) during construction and maintenance activities.

Potential for displacement of some marine users during construction ( e.g. safety exclusion areas during construction) and operation ( e.g. fishing activities with potential gear interactions with permanent seabed structures).

Potential for collision with cable excavation vessels in transit during installation.

Potential for displacement of other marine users during construction and maintenance activities ( e.g. shipping, recreation, etc.) and operation al periods ( e.g. fishing activities with potential gear interactions with submerged structures, etc.).

Potential interference with communications due to EMF.

Potential for collision with cable excavation vessels in transit during construction.

Potential for displacement of other marine users during construction and maintenance activities ( e.g. shipping, recreation, etc.) and operation al periods ( e.g. fishing activities with potential gear interactions with submerged structures, etc.).

Potential disturbance of previously contaminated land, potential transportation of contaminates (by physical movement, water and air) and the impact on human health and ecology.

Potential noise and vibration from construction traffic and equipment, especially at compounds and drilling locations.

Potential contamination and associated risk to humans and riparian ecology from construction activities ( e.g. activities using oil, bentonite or other harmful substances).

Potential for disruption to communities during construction ( e.g. road closures, diversions, etc.).

Potential for loss of land to existing use ( e.g. agricultural production).

Potential noise and vibration from construction traffic and equipment, especially at compounds and location towers.

Potential for dust generation during construction works.

Potential for disruption to communities during construction ( e.g. road closures, diversions, etc.).

Potential for loss of land to existing use ( e.g. agricultural production).

Potential for dust arising from areas where vegetation has been removed, soils stored, and vehicle tracks, particularly in dry or windy conditions, potential to cause impacts on human health especially where sensitive receptors exist ( e.g. schools, hospitals).

Potential for noise and vibration from construction traffic and equipment, especially at compounds and piling locations and during ground works.

Construction likely to take a significant amount of time in a single location.

Potential for noise from operation from the operation of the substation, in particular a 'humming' associated mainly with the operation of the cooling equipment, particularly in relation to transformers and reactors.

Potential noise and vibration from operation and maintenance activities.

Potential for loss of land to existing use ( e.g. agricultural production).

Potential for dust arising from areas where vegetation has been removed, soils stored, and vehicle tracks, particularly in dry or windy conditions, potential to cause impacts on human health especially where sensitive receptors exist ( e.g. schools, hospitals).

Potential for noise and vibration from construction traffic and equipment, especially at compounds and piling locations and during ground works.

Construction likely to take a significant amount of time in a single location.

Potential for noise from operation from the operation of the substation, in particular a 'humming' associated mainly with the operation of the cooling equipment, particularly in relation to transformers and reactors.

Potential noise and vibration from operation and maintenance activities, and the operation of switchgear.

Potential for loss of land to existing use ( e.g. agricultural production).

Potential re-suspension of sediments and associated hazardous substances during construction.

Potential for accidental spillage from construction vessels and structures during operation.

Potential re-suspension of sediments and hazardous substances due to excavation during installation and during major repair activity.

Potential for accidental spillage from construction and cable repair vessels during operation.

Potential re-suspension of sediments and release of hazardous substances due to excavation.

Potential for accidental spillage from construction equipment.

Potential contamination and associated risk to humans and riparian ecology from construction activities using oil, bentonite or other harmful substances.

Potential sedimentation and increase in turbidity of watercourses during open cut installation or from adjacent soil storage and trench areas, particularly during wet periods.

Potential for accidental spillage from construction equipment entering water courses located near to sites.

Potential water contamination and the associated risks to humans and riparian ecology from construction activities using oil or other harmful substances.

Potential sedimentation and increase in turbidity of watercourses from areas where vegetation has been cleared.

Requirement for significant excavation and potentially pilling may impact on groundwater quality and regimes.

Requirement for de-watering and discharging of water may have potential impacts on water resources ( e.g. abstractions) and riparian ecology.

Potential increase in flood risk to facility itself and to others downstream from increase surface water run-off, especially from large areas of hard standing, for example access tracks and buildings, where sustainable drainage systems are not employed.

Potential water contamination and the associated risks to humans and riparian ecology from construction activities using oil or other harmful substances.

Potential sedimentation and increase in turbidity of watercourses from areas where vegetation has been cleared.

Requirement for significant excavation and potentially pilling may impact on groundwater quality and regimes.

Requirement for de-watering and discharging of water may have potential impacts on water resources ( e.g. abstractions) and riparian ecology.

Potential increase in flood risk to facility itself and to others downstream from increase surface water run-off, especially from large areas of hard standing, for example access tracks and buildings, where sustainable drainage systems are not employed.

Construction vessel emissions have the potential to impact on air quality and contribute to greenhouse emissions.

Construction vessel emissions have the potential to impact on air quality and contribute to greenhouse emissions.

Construction vessel and vehicle emissions have the potential to impact on air quality, and subsequently human health, and contribute to greenhouse emissions.

Construction vehicle emissions have the potential to impact on air quality, and subsequently human health, and contribute to greenhouse emissions.

Construction vehicle emissions have the potential to impact on air quality, and subsequently human health, and contribute to greenhouse emissions.

Construction vehicle emissions have the potential to impact on air quality, and subsequently human health, and contribute to greenhouse emissions.

Construction vehicle emissions have the potential to impact on air quality, and subsequently human health, and contribute to greenhouse emissions.

Scour from seabed foundations ( e.g. piles) and sediment deposition during construction and operation phases have the potential to alter physical processes and sediment structure.

Sediment disturbance during construction has the potential to alter physical processes and sediment structure.

Sediment disturbance during construction has the potential to alter physical processes and sediment structure at landfall.

Potential disturbance of previously contaminated land, potential transportation of contaminates (by physical movement, water and air) and the impact on human health and ecology.

Potential for land contamination from construction activities, in particular the storage and use of oil and the use of bentonite for drilling or filling ducts.

Potential degradation or loss of soil resource, and displacement of land use due to construction activities.

Potential soil heating from electrical cables at full rating, with potential secondary impacts ( e.g. altered crop growth).

Potential loss of land use during construction and operation phases at the tower base and along line routes ( e.g. pylon or overhead lines may obstruct existing agricultural activities).

Potential degradation or loss of soil resource, and displacement of land use due to construction activities.

Potential disturbance of previously contaminated land, potential transportation of contaminants (by physical movement, water and air) and impact on human health and ecology.

Potential degradation or loss of soil resource (construction).

Potential land loss from existing use ( e.g. agricultural production).

Potential disturbance of previously contaminated land, potential transportation of contaminants (by physical movement, water and air) and impact on human health and ecology.

Potential degradation or loss of soil resource (construction).

Potential land loss from existing use ( e.g. agricultural production).

Potential loss of or damage to known and unknown buried heritage in construction activities.

Potential damage to known and unknown buried heritage from maintenance/repair activities ( e.g. vessels anchoring).

Potential loss of or damage to known or unknown buried heritage due to corridor excavation by ploughing or trenching during installation.

Potential damage to known and unknown buried heritage from maintenance/repair activities ( e.g. vessels anchoring).

Potential loss of or damage to known or unknown buried heritage due to corridor excavation by ploughing or trenching during installation.

Potential damage to known and unknown buried heritage from maintenance/repair activities ( e.g. vessels anchoring).

Potential loss of or damage to known or unknown buried heritage.

Potential direct loss of or damage to known and unknown buried heritage.

Potential setting impacts on heritage assets and the historic landscape.

Potential direct loss of, or damage to, known and unknown buried archaeology.

Potential direct loss of, or damage to, designated assets or areas.

Provide opportunities for research and recording previously unknown archaeology.

Potential direct loss of, or damage to, known and unknown buried archaeology.

Potential direct loss of, or damage to, designated assets or areas.

Opportunities for research and recording previously unknown archaeology.

Potential for the seascape to change.

Potential issues of lighting during construction and operation.

Potential issues of temporary lighting during construction.

Potential impacts to landscape/seascape during construction.

Potential impacts to landscape/seascape during construction.

Reinstatement to land from previous condition can include enhancement measures.

The construction of towers, poles and wire are more likely to have an impact on views and landscape character.

Where existing features, such as trees and woodland, are removed, e.g. trees and woodland, there is the potential for the landscape character to change. Screening may be used to mitigate impacts.

Potential alteration and disruption of existing views from infrastructure, particularly if located in or near to designated landscape areas ( e.g. AONB, NSAs, etc.).

Potential change in the character of the landscape and on views particularly if situated within open countryside or residential areas ( e.g. removal of existing ground features).

During construction, areas will be needed for soil storage, site laydown areas, equipment storage, internal access tracks, etc.

Potential for impacts from lighting of compounds.

Potentially tall ( e.g. overhead line gantries and switchgear) and bulky ( e.g. transformers, buildings and converter sheds) equipment may effect landscape character and views of local area.

Additional landscape works and screening may mitigate views of infrastructure.

Potential change in the character of the landscape and on views particularly if situated within open countryside or residential areas ( e.g. removal of existing ground features).

During construction, areas will be needed for soil storage, site laydown areas, equipment storage, internal access tracks, etc.

Potential impacts from lighting of compounds.

Potentially tall ( e.g. overhead line gantries and switchgear) and bulky ( e.g. transformers, buildings and converter sheds) equipment may effect landscape character and views of local area.

Additional landscape works and screening may mitigate views of infrastructure.