Annex IV distributes metadata forms (questionnaires) to solicit information from developers involved in environmental monitoring around marine renewable energy project sites around the world. This page provides project descriptions, baseline assessment, post-installation monitoring, and links to available data and reports. Content is updated on an annual basis.

Westray South Tidal Project

Project Site Annex IV

Title: Westray South Tidal Project
Technology Type:
Info Updated:
June 26, 2017
Westray South Lease Option Area
Project Status: 
Planned project
Technology neutral
Project Scale: 
Installed Capacity: 
Up to 200MW

The Westray South site was initially developed by SSE Renewables (SSER) who were awarded an Agreement for Lease (AfL) following The Crown Estates Pentland Firth and Orkney Waters Leasing Round in March 2010. However, in April 2014 DP Energy acquired the development rights to the Westray South proposal.


Based on present knowledge of the site it is proposed that a tidal array of up to 200 megawatts (MW) capacity could be installed which equates to approximately 200 devices.


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 which is the closest sizeable port.


The Crown Estate AfL area covers approximately 13km2 (excluding grid connection corridor) within which the proposed development would occupy a smaller area; work on identifying this and related stakeholder consultation is ongoing.


The AfL provides DP Energy with an initial 5 year exclusive development period, in respect of other renewable energy developers, and is not a licence or consent to install tidal energy converters on the site. The Agreement for Lease area is effectively an ‘area of search’ within which DP Energy hopes to identify a development zone or zones suitable for a commercial scale tidal project, built in two distinct phases. It is proposed that Phase I will be within the range of 30 - 45MW with Phase II potentially bringing the total installed capacity up to 200MW. The proposed installed capacity of Phase I has increased since the circulation of the pre-scoping Project Briefing Document of May 2011.

Technology: In the initial scoping report SSER determined that unless required for navigational marking purposes the technology installed will be a non-surface piercing horizontal axis turbine (HAT) type device. Phase I may consist of devices from one or a few technology suppliers with potential differences across these in terms of support structure, tidal energy converter design and rotor diameter. For Phase II it is more likely that the entire phase would be constructed based on one technology supplier but support structure type and rotor diameter may still vary depending on the location within the development area.


Foundations: For each device it is assumed that there are a range of potential support structures. The final choice of structure will be made post-consent, at a more advanced stage of the detailed design process. This approach is analogous to established practice for other offshore renewable energy developments. The range of support structures to be considered in the EIA process is listed below:


  • Monopile foundation (drilled socket in the seabed);
  • Braced monopile (typically three or four legged); and
  • Gravity base structure (pinned or unpinned).


The EIA and NRA processes will describe the potential significant effects associated with the proposed range of support structures, based on a worst case scenario for the predicted likely effects.1


Export cable: The final proposed design for the export to shore cable(s) will be heavily influenced by available technical solutions and seabed conditions. The number of cables required will be informed in technical terms by the tidal technology selected, the voltage of the cables proposed and whether or not an offshore substation is installed. Designs with no offshore substation are likely to require significantly more cables to connect to shore than designs which incorporate an offshore substation. This is because present technology limits the voltages at which devices can be connected subsea which in turn limits the size of cable which can be installed. An offshore platform would bring multiple lower voltage cables together, with the power then being exported to shore on fewer, higher voltage cables. Where multiple cables to shore are proposed, the distance between cables may be substantial depending on the installation method utilised. If a substation is required, Phase 1 will require a single substation and phase two would require up to two. No preferred locations for offshore substations have been identified although it is anticipated that they would need to be within or adjacent to the proposed development areas.


The design and onward route of the grid connection would also influence the preferred location(s) identified. An offshore substation is typically supported on a jacket structure similar to a small offshore rig. The jacket foundation options are typically the same as those for the tidal device support structures i.e. piles and gravity bases. Alternatively a moored floating structure which supports the substation topsides could be utilised. The offshore substation would be a normally unmanned installation with access by helicopter or vessel. All cables would be armoured to protect against abrasion, and where there is a lack of sediment they would be laid directly onto the seabed. In some areas concrete mattresses or a similar form of protection may also be required on top of the cable. In inshore waters and towards landfall points, where there is sufficient sediment, cables may be buried.


Devices will be inter-connected in arrays. A number of factors including turbine choice and available technical solutions will influence the number, length, spacing and configuration of inter-array cables. It is anticipated that the majority of the cables would be laid in line with the prevailing tidal flow directions, although clearly there will be a need to inter-connect within the arrays, with cables running across the prevailing flow directions.1


Onshore infrastructure: The project will require the construction of a 132/33kV onshore substation, which should be located within the vicinity of the site. The development area for this station would take up roughly 90 x 50m of land, within which the following infrastructure would be contained:


  • Compound to house 132/33kV grid transformer and connection terminations;
  • A Control Building compound. This building would be for 33kV switchgear, SCADA etc; and
  • The site would require a welfare/operational compound area. This would contain a building for welfare, workshop, offices etc.

At present the electricity network on Orkney and beyond is not able to accommodate projects of this scale and options for development of new grid connection infrastructure are being investigated.


Vessel spread: Installation methodologies are dependent upon the chosen technology; hence the vessels that will be used have not yet been specified. There are a wide range of installation and removal methodologies currently being trialled in the testing of tidal energy converters and support structures ranging from the use of jack-up barges, moored and tugged barges, anchored crane barges, to dynamically positioned (DP) heavy lift construction vessels. Foundation construction is likely to require either a DP vessel or a jack up barge, however a jack up barge is not likely to be necessary if gravity based structures are used. Construction of the offshore substation would require similar vessels, as would the installation of the actual device. A special cable laying vessel will be required to install the intra array cables and the export cable. Vessels required for the maintenance of that array are likely to be similar to those used in construction, with most expected to be done by a DP vessel.


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: 



Competent Authority


Marine Licence (Marine (Scotland) Act) Consent

Marine Scotland


Section 36 (Electricity Act) Consent

Marine Scotland


Licence to Disturb European Protected Species



Licence to Disturb Basking Shark



Town and County Planning Permission



Process Status: 

Significant investment and progress has been made with an application for consent based on incremental build-out, anticipated to be submitted during 2017. Based on the presently contracted grid connection programme the initial phase of construction is expected to commence in the early 2020’s.


In order to inform the environmental and navigational safety studies a Scoping Report and Preliminary Hazard Analysis were submitted for consultation in 2011. A scoping opinion in response to these was received from Marine Scotland in December 2011 and this, along with subsequent discussions, has guided the environmental and technical assessments which have been carried out thus far.


An Environmental Statement (ES) and Navigational Risk Assessment (NRA) will be submitted at the time an application for consent is lodged. These documents will describe the project and present an assessment of the likely significant effects which may result from it, including any proposed mitigation measures. Further public consultation will be undertaken prior to lodging a formal consent application.


At this stage in order to inform the preparation of the ES and NRA consultation has been undertaken to ensure that the scope and methods utilised for baseline studies will enable a robust Environmental Impact Assessment to be undertaken.

Key Environmental Issues: 

The following impacts were identified in the scoping report, however the potential significance of these impacts was unknown at the time of writing.

  • Collision risk to birds from underwater turbines
  • Displacement of birds from vicinity of underwater turbines
  • Disturbance of birds by vessel activity
  • Disturbance to birds due to onshore construction works mammals
  • Disturbance to marine mammals from underwater noise generated by DP vessels
  • Disturbance to marine mammals from underwater noise generated during potential drilling activities
  • Collision between marine mammals and vessels
  • Disturbance to marine mammals from underwater noise generated by the devices
  • Risk of injury to marine mammals from collision with devices fish and shellfish
  • Effects on herring and sand eel populations from disturbance to spawning grounds
  • Physical disturbance to crustacean and demersal fish species
  • Effects of noise and vibration of increased boat traffic and construction activity on hearing specialists (i.e. herring and sprat)
  • Collision of slow moving larger species such as basking sharks with the devices
  • Effects of Electromagnetic fields on Elasmobranchs
  • Changes in the existing habitat
  • Physical disturbance of Intertidal habitats during cable landfall installation
  • Disturbance of otters during landfall, grid and substation installation
  • Substratum / habitat loss / damage from placement of devices and other infrastructure on the seabed, cable laying;
  • Scour around devices and other subsea infrastructure (including vessel mooring cables as result of movement with wave and tides)
  • Increased suspended sediment and turbidity from installation of subsea infrastructure in inshore waters
  • Decrease in water flow leading to change in benthic habitat downstream of devices
  • Introduction of marine non-natives.
  • Changes to sediment regime as a result of physical structures on the seabed
  • Changes to sediment regime as a result of energy extraction
  • Changes to seabed morphology


Baseline Data Summary:

Ecological surveys were initiated in January 2012 in order to provide baseline data relating to habitats and species which use the proposed development area. The area of survey varies depending on the survey ‘target’ species or habitat, but in general the zone of interest for development and a buffer around this is covered. A key aim of the surveys is to ascertain if there are any species and/or habitats which may be sensitive to the construction, operation and maintenance of the tidal array and associated infrastructure. Although survey work for some species covers all seasons, particular attention has been given to breeding periods (typically April to July) and specifically when seals are pupping (July for common seal, late autumn for grey seal).


Detailed geophysical surveys with additional ROV seabed video footage have been collected and analysed. The AfL area consists largely of exposed bedrock (Devonian sandstone), with thin patchy distribution of sediment cover. There are few pronounced features except in the north where depths of up to 54m are reached. Areas of highest resource generally correlate with bedrock exposure with significantly fewer seabed features found in these areas.


Geophysical data and ROV footage has confirmed a generally even seabed which would suit a range of tidal device options. Ecologically conditions appear comparable to those at similar depths and current velocities elsewhere around Orkney and are not considered to be particularly sensitive.


A resource assessment of the site has been undertaken utilising seven seabed mounted acoustic doppler current profilers (ADCP), and a resource model developed and calibrated based on this measured data. The model enables predictions of resource for specific areas. Mean spring peak tidal velocities have been determined to be in the order of 3.5m/s (msp).


Westray South Tidal Project is located in United Kingdom.

Baseline Assessment: Westray South Tidal Project

ReceptorStudy Description Design and Methods Results Status
  • 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.

  • 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.

  • Infrastructure

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.

  • Archaeology

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.

  • Noise

Disturbance to marine mammals from underwater noise generated by DP vessels and devices.

Based on available data.

Dependent on information on species and behavior in the vicinity of development – further investigation required.

  • Benthos

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.

  • Fish and Fisheries

Effects on herring and sand eel populations from disturbance to spawning grounds.

Based on 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.

  • Marine Mammals

Marine mammal collision with vessels.

Based on available data.

Dependent on information on species and behavior in the vicinity of development – further investigation required.

  • Marine Mammals

Accidental contamination to marine mammals from vessels or devices.


Industry best practice will be followed. Risk of contamination not deemed to be significant.

  • Reptiles

Impact to marine reptiles.

Based on existing reports.

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.

  • 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.

  • 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.

Reports and Papers


Post-Installation Monitoring: Westray South Tidal Project

ReceptorMonitoring Program Description Design and Methods Results Status
  • 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.

  • 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.

  • Archaeology

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.

  • Military

Potential disruption to existing MoD activity.

Based on current military activity maps.

There are no exercise areas in the vicinity of the AfL likely to be affected by the proposals. Therefore, no effect on existing activity is anticipated.

  • Benthos

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).

  • Fish and Fisheries

Effects on herring and sand eel populations.

Based on current data.

Determine the extent of herring and sand eel spawning/nursery.

Reports and Papers
Research N/A
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