Description
The Westray South Tidal Array project consists of a 200MW tidal array which would require the installation and operation of up to 200 tidal turbines. It is anticipated that the project would be built out in stages although the scale of each stage has not yet been determined. The Agreement for Lease (AfL) area covers water depths ranging from 25 – 54m and lies approximately 24km north of Kirkwall which is the closest sizeable port. The proposed area for tidal infrastructure deployment occupies 4.6km2 within the wider AfL area of 12.6km2.
The proposed project consists of the following key components:
- All offshore infrastructure - primarily turbines, support structures and associated electrical infrastructure;
- Export cable(s) to shore;
- Cable landfall(s) and onshore cable to cable transition compound;
- Cable transition compound;
- Onshore control building and compound;
- Temporary works for cable landfall; and
- Access road to cable transition and control building compound.
The project technology envelope requires a degree of flexibility. Support structure type and rotor diameter may vary depending on the location within the development area. All devices selected will, however, fall within the design and operational limits defined for the project design envelope during the EIA .
Based on current understanding and technology evaluation work, devices with a rotor diameter of up to 24m capable of generating at least 1MW will be proposed for installation. Therefore the maximum number of devices proposed may be up to 200.
Westray South Tidal Development Ltd. (WSTDL) is proposing to use:
- Un-shrouded multi-bladed Horizontal Axis Tidal Turbines (HATT) in combination with either a seabed mounted or floating support structure
- Shrouded multi-bladed Horizontal Axis Tidal Turbines (HATT) on a seabed mounted gravity base
Location
The project is located in the Westray Firth off the coasts of Eday, Egilsay and Rousay. The AfL area covers water depths ranging from 25 – 54m and lies adjacent to the European Marine Energy Centre’s (EMEC) Fall of Warness tidal test site, approximately 24km north of Kirkwall.
Coordinates: The coordinates in which the Agreement for Lease area lies are listed below:
- 59° 12’ 19” N 002° 54’ 20” W
- 59° 11’ 20” N 002° 51’ 43” W
- 59° 10’ 06” N 002° 50’ 45” W
- 59° 09’ 02” N 002° 50’ 59” W
- 59° 09’ 14” N 002° 52’ 30” W
- 59° 10’ 29” N 002° 53’ 15” W
- 59° 11’ 02” N 002° 55’ 23” W
Licensing Information
WSTDL proposes to produce a single EIAR covering the assessment of impacts related to the project as outlined above, which includes both offshore and onshore components. Two separate consents and licences will be sought for the various aspects of development.
WSTDL intends to submit one application for the 200MW tidal array. A single ES and Habitats Regulations Appraisal (HRA) will be submitted in support of WSTDL’s applications for both the Marine Licence and Section 36 consent through the regulator, Marine Scotland Licensing Operations Team (MS-LOT), for the offshore and onshore components. Permission will be sought through the determination of a Section 36 Consent under the Electricity Works (Environmental Impact Assessment) (Scotland) Regulations 2017 (as amended).
Two Marine Licences will be required for the offshore project. One Marine Licence application will be submitted for the generating stations (tidal devices) and inter-array cabling whilst a separate Marine Licence application will be submitted for the offshore platform(s) (electrical substations/hubs) and export cabling from the platform to shore.
Where Section 36 consent is required, a statutory provision in the Growth and Infrastructure Act 2013, which amends Section 57 of the Town and Country Planning (Scotland) Act 1997, enables Scottish Ministers to direct that planning permission is deemed to be granted for the ancillary onshore components and related onshore infrastructure. Orkney Islands Council (OIC) will therefore be a statutory consultee for any onshore components and MS-LOT will grant associated works under deemed planning and as part of Section 36.
Formal Pre-Application Consultation is a statutory requirement under the Marine Licensing (Pre-Application Consultation) (Scotland) Regulations 2013 for the construction of a renewable energy structure, where the total area in which the structure is to be located exceeds 10,000 square metres. A Pre-Application Consultation (PAC) Report will therefore accompany the application. A stakeholder engagement plan will be prepared for use by the team to manage WSTDL’s consultation activities and will incorporate the timescales and requirements for PAC consultation to ensure the regulations are met.
Project Progress
In 2010, SSE Renewables (SSER) was awarded an Agreement for Lease (AfL) from The Crown Estate for development rights to support a 200 megawatt (MW) tidal array in the Westray Firth, Orkney. The AfL for the Westray South site was transferred to DP Energy in March 2014.
A Special Purpose Vehicle WSTDL has been set up to progress development of the project.
A pre-scoping exercise was undertaken in April 2011 when a Project Briefing Document (PBD) was issued to a wide range of stakeholders. The objective of the PBD was to provide stakeholders with an introduction to the proposed development in order to provide an early opportunity to engage with the project development process. Feedback received from stakeholders was used to inform the subsequent request for a Scoping Opinion.
A formal request for a Scoping Opinion was made in October 2011 to Marine Scotland Licensing Operations Team (MS-LOT), on behalf of Scottish Ministers, and a Scoping Opinion was received in December 2011. A number of topic-specific consultations and site surveys have since been undertaken to date and these are outlined in Section 4.2 below.
The area was first identified as a potential development opportunity in late 2008 at which point consultation was initiated with a range of stakeholders. Feedback received has influenced a number of areas of the development process including refining the geographical extents.
In 2023, it was announced that a subset of the original lease has been awarded to Orbital Marine Power. The new metadata form for this subset lease is linked here: Orbital Marine Power Westray Firth
Key Environmental Issues
Consultation responses informed baseline data acquisition and following receipt of the scoping opinion a number of EIA and technical studies were undertaken including:
- Two years of bird and marine mammal surveys;
- Seasonal radar surveys to support the Navigational Risk Assessment (NRA) process;
- A full geophysical survey of the development area and cable route corridor;
- Seven ADCP deployments; and
- Onshore and shoreline ecological surveys.
WSTDL now plan to complete the Environmental Impact Assessment (EIA) and Habitats Regulations Appraisal (HRA) in order to support the necessary consent and licence application for the Project.
Project technology envelope
|
Project Component |
Parameter(s) |
Additional Comments |
|---|---|---|
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Tidal turbine generators |
Up to 200 devices (likely range 100 - 200)
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Various device types considered. Potential for a number of different layout scenarios for which work is ongoing. The final layout will be determined post-consent. |
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Turbine support structures |
Up to 200 structures (likely range 100-200)
|
Potential for a range of support structures to be utilised. Some technology types may have more than one option. |
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Offshore electrical infrastructure – subsea or surface-piercing hubs |
Subsea hubs (up to 20)
|
The current technical maturity of such infrastructure is not sufficient to allow a definite description to be made at this point and so all options for offshore electrical infrastructure need to be retained. The final development proposal could require a combination of subsea hubs with large and small surface piercing hubs. |
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Large surface piercing hubs (up to 2)
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Small surface piercing (up to 20)
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Likely to also be utilised as navigation marks. |
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Inter-array cables |
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Number and length of inter-array cables dependent on technology type and array layout. |
|
Export cables |
Range of 2 to 7 required depending on cable voltage rating and staging of construction:
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Landfall and onshore construction compound |
Option 1 - Horizontal Direct Drilling (HDD)
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For landfall using HDD there would be no surface works required within the inter-tidal area. For HDD a temporary onshore construction compound above MHWS of up to 105m wide (parallel to shore) by 60m is estimated to be required. For surface laid or trenched landfall a smaller construction compound ~80m wide by 60m is estimated to be required. A cable corridor of similar width would be required from the inter-tidal zone to the construction compound.
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Option 2 - Surface laid cables at landfall
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HDD layout corridor |
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Temporary layout area for bore hole pipe assembly. Area of land abutting construction compound utilised to assemble conduit for lining HDD bores. |
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Cable joint pits (CJP) and CJP compound |
Up to 7 joint pits
|
For either landfall option it is assumed that the permanent cable joint pits would be located within the footprint of the temporary construction compound as detailed above for landfall works. Ground will be restored post-construction to leave only ground level manhole covers visible within a stockproof fenced compound. |
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Control building and compound |
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Most likely located adjacent to CJP compound with interconnecting underground cables to each cable joint pit. |
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Access road |
Access track(s) from public road to onshore works areas
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Project vessels |
Options include:
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Choice of method for installation and maintenance closely linked to: Risk Assessment; metocean conditions; economics; technology selection; and array design. As the project progresses and technology types are decided, detailed installation methods and procedures will be able to be planned. |
|
Construction and operational maintenance hub |
Kirkwall Harbour identified as preferred hub |
Hydrology, drainage and water quality
|
Topic |
Potentially Significant Impact |
Phase |
Relevant Work to Date/Status |
Next Steps |
|
Hydrology, drainage and water quality |
Pollution of watercourses, groundwater, groundwater dependent terrestrial ecosystems (GWDTE). |
Construction and installation Operation and maintenance Decommissioning |
Desktop assessment and walkover survey undertaken for HDD works. Extended Phase I habitat survey undertaken in August 2012. No further surveys are anticipated.
|
Consultation with SEPA. Assess site for presence of GWDTE (only if required). Undertake EIA. |
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Disruption to drainage and groundwater flow. |
Construction and installation Operation and maintenance Decommissioning |
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Flood risk. |
Construction and installation Operation and maintenance Decommissioning |
Intertidal ecology
|
Topic |
Potentially Significant Impact |
Phase |
Relevant Work to Date/Status |
Next Steps |
|---|---|---|---|---|
|
Intertidal ecology |
Physical disturbance or loss of intertidal habitats during cable landfall installation. |
Construction and installation Operation and maintenance Decommissioning |
Intertidal Phase 1 habitat survey was undertaken in August 2012.
No further surveys are anticipated. |
Follow industry guidance for Ecological Impact Assessment (EcIA) produced by CIEEM. Consultation with SNH and OIC. Undertake EIA. |
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Accidental introduction of invasive species from vessel operations (intertidal effects). |
Construction and installation Operation and maintenance Decommissioning |
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Accidental release of chemical contaminants from devices or vessels (intertidal effects). |
Construction and installation Operation and maintenance Decommissioning |
Coastal and physical processes
|
Topic |
Potentially Significant Impact |
Phase |
Relevant Work to Date/Status |
Next Steps |
|
Geology and physical processes (offshore) |
Changes in suspended sediment concentrations and sediment deposition due to installation activities. |
Construction and installation |
Ground condition desktop assessment undertaken May 2009 (Halcrow). Geophysical survey undertaken in 2012 -13 (Osiris) seabed video survey 2009 and 2012 (SSER and Aquatera). Survey of tidal current speeds with ADCP deployment in 2012 (SSER and Partrac). Hydrodynamic modelling (MIKE21) undertaken 2009 - 2014 (Natural Power, Black & Veatch, SSER and TCE). Method statement issued to and reviewed by MS and SNH in 2015.
No further surveys are anticipated. |
Review of available data and hydrodynamic model. Assessment methodology will follow latest available guidance including COWRIE, BERR etc. Undertake EIA. |
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Changes in morphology due to footprint of project infrastructure. |
Operation and maintenance |
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Changes in suspended sediment concentrations and sediment deposition due to removal activities. |
Operation and maintenance Decommissioning |
Benthic and shellfish ecology
|
Topic |
Potentially Significant Impact |
Phase |
Relevant Work to Date/Status |
Next Steps |
|---|---|---|---|---|
|
Benthic ecology |
Accidental release of chemical contaminants from devices or vessels. |
Construction and installation Operation and maintenance Decommissioning |
Baseline data desktop review undertaken in October 2013 and summary report produced. ROV survey of AfL (2008 and 2009) and cable route (2012) undertaken and survey reports produced. Geophysical (including side scan sonar, SBP and multibeam data acquisition) survey of AfL and cable route corridor plus buffer 2012 - 13 Methodology issued and reviewed by MS and SNH in 2013.
No further surveys are anticipated. |
Review of seabed video data. Review of technical reports for geology and physical processes (containing analysis of ADCP, multi-beam echo sounder, side scan sonar and sub-bottom profiling survey data). Assessment methodology will follow best practice, best available scientific understanding and relevant EIA guidance e.g. Chartered Institute of Ecology and Environmental Management (CIEEM) guidance.
Undertake EIA. |
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Increased suspended sediment and turbidity from installation of subsea infrastructure, cable landfall etc. |
Construction and installation |
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Substrate/habitat loss/damage from installation of subsea infrastructure and cable landfall. |
Construction and installation |
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Seabed scour around subsea infrastructure and vessel moorings. |
Operation and maintenance |
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Colonisation of subsea infrastructure. |
Operation and maintenance |
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Changes in water flow rates leading to downstream change in benthic habitat. |
Operation and maintenance |
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Increased suspended sediment and turbidity from removal of subsea infrastructure. |
Decommissioning |
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Substrate/habitat loss/damage from removal of subsea infrastructure. |
Decommissioning |
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Accidental introduction of invasive species from vessel operations. |
Construction and installation Operation and maintenance Decommissioning |
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Changes to available habitat; shellfish populations. |
Operation and maintenance |
Fish ecology
|
Topic |
Potentially Significant Impact |
Phase |
Relevant Work to Date/Status |
Next Steps |
|---|---|---|---|---|
|
Fish ecology |
Accidental release of chemical contaminants from devices or vessels. |
Construction and installation Operation and maintenance Decommissioning |
EIA and HRA Methodology issued for comment to MS-LOT, MSS and SNH Jan 2015. Comments received during 2015. Approach to salmon collision risk assessment issued and agreed with MSS Dec 2015 and SNH Jan 2016. Marine Mammal (including basking shark) EIA and HRA Position Paper issued to SNH and MS in November 2014. Initial collision risk modelling for basking shark undertaken using the Encounter Rate Model (ERM) and Collision Risk Model (CRM) in 2015.
No further studies required. |
Review of site benthic surveys and underwater noise technical report. Approach to PCoD for basking shark to be agreed with SNH and MSS.
Undertake EIA. |
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Substratum loss at spawning and nursery grounds. |
Construction and installation Decommissioning |
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Smothering of sensitive species during installation and removal of structures and cables. |
Construction and installation Decommissioning |
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Effects of noise and vibration (including auditory injury and disturbance) due to construction and installation activities (vessel, installation activities, etc.). |
Construction and installation Operation and maintenance Decommissioning |
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Electromagnetic fields (EMF) from dynamic, inter-array and export cables (elasmobranchs). |
Operation and maintenance |
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Collision risk (turbines); operational turbines; (basking sharks). |
Operation and maintenance |
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Barrier to movement. |
Operation and maintenance |
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Entanglement with mooring lines and dynamic cables. |
Construction and installation Operation and maintenance |
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Habitat creation. |
Operations and maintenance |
Marine mammals
|
Topic |
Potentially Significant Impact |
Phase |
Relevant Work to Date/Status |
Next Steps |
|---|---|---|---|---|
|
Marine mammals |
Effects of noise and vibration (including auditory injury and disturbance) due to construction and installation activities (vessel, installation activities, etc.). |
Construction and installation Decommissioning |
Marine Mammal EIA and HRA Position Paper issued to SNH and MS in November 2014. Two years of boat-based line transect surveys undertaken from March 2012 to March 2014 using visual observations (MMOs) and a towed passive acoustic monitoring (PAM) array. Initial collision risk modelling undertaken using the Encounter Rate Model (ERM) and Collision Risk Model (CRM), results completed/presented in 2015.
No further surveys are anticipated.
|
Undertake collision risk and PCOD modelling using agreed approach (consultation with SNH and MS required). Review technical underwater noise report. Agree data sources with SNH and MS-LOT. Assessment methodology will follow best practice, best available scientific understanding and relevant EIA guidance e.g. Chartered Institute of Ecology and Environmental Management (CIEEM) guidance. Undertake HRA for Natura 2000 sites. Consultation with Marine Scotland, SNH and OIC.
Undertake EIA. |
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Effects of noise and vibration during device operation. |
Operation and maintenance |
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Barrier effects due to presence and operation of devices. |
Construction and installation Operation and maintenance Decommissioning |
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Disturbance of seals at haul-out sites (vessel activity, landfall works). |
Construction and installation Operation and maintenance Decommissioning |
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Indirect effects on prey species. |
Construction and installation Operation and maintenance |
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Risk of collision of marine mammals with tidal devices. |
Operation and maintenance |
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Entanglement with mooring lines and dynamic cables. |
Construction and installation Operation and maintenance |
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Accidental release of chemical contaminants from devices or vessels. |
Construction and installation Operation and maintenance Decommissioning |
Marine ornithology
|
Topic |
Potentially Significant Impact |
Phase |
Relevant Work to Date/Status |
Next Steps |
|
Marine ornithology |
Direct disturbance (noise and visual) of birds due to vessels. |
Construction and installation Operation and maintenance Decommissioning |
Two years of boat-based surveys (following European Seabirds at Sea (ESAS) protocols) completed in 2014 (covering 2012 - 2014). Approach to assessment issued to and reviewed by MS and SNH in 2013 and revised approach in 2015.
No further surveys are anticipated. |
Collision risk modelling for diving seabirds. Assessment methodology will follow best practice, best available scientific understanding and relevant EIA guidance e.g. Chartered Institute of Ecology and Environmental Management (CIEEM) guidance. Undertake HRA for Natura 2000 sites. Consultation with Marine Scotland, SNH and OIC.
Undertake EIA and HRA. |
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Accidental release of chemical contaminants from devices or vessels. |
Construction and installation Operation and maintenance Decommissioning |
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Risk of collision of diving birds with tidal devices. |
Operation and maintenance |
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Indirect impacts caused by hydrodynamic changes to surrounding seabed habitats and associated prey species. |
Operation and maintenance |
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Direct seabed habitat loss due to project footprint for infrastructure. |
Operation and maintenance |
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Displacement of foraging or loafing birds due to presence and operation of the development. |
Operation and maintenance |
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Habitat creation (roosting platforms). |
Operation and maintenance |
Papers, Reports, Research Studies
Baseline Assessment: Westray South Tidal Project
| Receptor | Study Description | Design and Methods | Results | Status |
|---|---|---|---|---|
| Birds | Disturbance by vessel activity. | Based on SPA studies. | In order to assess this impact the extent and nature of seabird activity will need to be established. An increase in vessel activity will be most apparent during construction and installation works. | Ongoing |
| Human Dimensions | Physical disturbance of submerged historic and prehistoric land surfaces and archaeological finds (known and unknown). | Consultation with Historic Scotland. | Potential known and unknown features within the development footprint may be disturbed during construction activities. | Ongoing |
| Invertebrates | Substratum / habitat loss / damage from placement of devices and other infrastructure on the seabed, cable laying. | Site specific survey and desk based research | Significance of impact not known as will depend on species and habitats within the footprint and surrounding area of any infrastructure placed on the seabed will be considered further. | Ongoing |
| Human Dimensions | Physical disturbance of submerged historic and prehistoric land surfaces and archaeological finds. | Desk reviews, reviews of bathymetric and geophysical data, stakeholder consultation. | As far as possible determine presence of indefinable features within onshore cable corridor, assessing importance of features, assess potential for submerged features within development footprint, landfall(s) and offshore cable route. | Underway |
| Invertebrates | Scour around devices and other subsea infrastructure (including mooring cables as result of movement with wave and tides). | To be determined following outcomes of desk based research, survey and consultation, will be considered when micro siting of devices. | To be determined following outcomes of desk based research, survey and consultation. Review footage taken during installation to validate predictions (operations will most likely be monitored). | Ongoing |
| Reptiles | Device impact to marine reptiles. | Literature review on device impact to sea turtles. | No records of reptiles in Orkney for 14 years, considered very rare and occasional visitor, therefore an interaction of marine reptiles with the proposed development is considered unlikely. | Ongoing |
| Physical Environment, Sediment Transport | Disturbance or loss of features of geological interest, impact on soils. | Desk based study and walkover assessment. | NA | Planned |
| Physical Environment, Water Quality | Pollution of watercourses, groundwater, groundwater dependent terrestrial ecosystems. | Desk based study and walkover assessment. | NA | Planned |
| Marine Mammals | Disturbance to marine mammals from underwater noise generated by DP vessels and devices. | Review of available data. | Dependent on information on species and behaviour in the vicinity of development – further investigation required. | Ongoing |
| Human Dimensions, Fisheries | Loss of access to fishing grounds, during Installation, operation and maintenance. | Desk based study. | There is a significant chance the Westray project will reduce access points for fishermen. It is known that the AfL area and the wider area is actively used by both creel and dive fishermen. | Ongoing |
| Marine Mammals | Marine mammal collision with vessels. | Review of available data. | Dependent on information on species and behavior in the vicinity of development – further investigation required. | Ongoing |
| Human Dimensions, Fisheries | Obstruction to regular fishing vessel transit routes. | Desk based study. | Larger fishing vessels use parts of the AfL as a regular transit route to/from fishing grounds. It is also assumed that smaller vessels transit the AfL area and the adjacent coastal area on a highly regular basis to reach other fishing grounds within and out with Orkney. | Ongoing |
| Marine Mammals | Accidental contamination to marine mammals from vessels or devices. | Literature review. | Industry best practice will be followed. Risk of contamination not deemed to be significant. | Ongoing |
| Human Dimensions, Fisheries | Loss of access to fishing grounds. | Inshore fishery study. | Determine what use is made of key areas. Discuss with local fishers the implications of any disruption to any fishing activity. Establish the relative value of catch for the relevant areas through consultation with local fishermen and OFA. | Underway |
| Fish | Effects on herring and sand eel populations from disturbance to spawning grounds. | Review of available data. | Further information on species present required before assessment can be made regarding disturbance due to noise or physical disturbance of the seabed impacting spawning grounds or species. | Ongoing |
| Human Dimensions, Fisheries | Disruption to regular fishing vessel transit routes. | Inshore fishery study. | Use sea-routing skills, AIS and VMS data to establish options for routing and consult with OFA, local fishermen and navigational experts on potential ways forward. | Underway |
| Birds | Collision risk from underwater turbines (These data were collected in 2010 and cover alternate 2x2km blocks of sea around Orkney and the Pentland Firth). | Based on SPA studies. | Survey and consultation will be required to establish abundance and distribution of species. However there is a general lack of understanding of the behavior of seabirds in the vicinity of turbines and potential collision risks. | Ongoing |
| Human Dimensions, Navigation | Opportunity for expansion of existing port infrastructure. | Statistical analysis. | The main ports (Kirkwall and Hatston) are near capacity with existing users and are likely to reach capacity during busy periods due to increased activity at the EMEC tidal test sites in the coming years. Major upgrade works are about to commence at Hatston which will increase available quayside space considerably which will help to accommodate any additional vessels which will operate out of the area as part of these proposals. There are also plans to increase adjacent onshore space available for project developers in the Hatston Industrial Estate Area. Whilst no decision has been made, it is recognized that the project will require both a loadout and operational base. | Ongoing |