Proposed Orkney Caithness Connection 132kV
Consultation Document
October 2011
SCOTTISH HYDRO ELECTRIC TRANSMISSION LIMITED Orkney Caithness Connection 132kV Consultation Document
Scottish Hydro Electric Transmission Limited
Orkney Caithness Connection
Consultation Document
Comments on this document should be sent to:
Lisa Kelly Scottish Hydro Electric Transmission Limited 10 Henderson Road Inverness IV1 1SN
Please submit comments by Friday 2 December 2011
Published by Scottish Hydro Electric Transmission Limited October 2011
SCOTTISH HYDRO ELECTRIC TRANSMISSION LIMITED Orkney Caithness Connection 132kV Consultation Document
CONTENTS 1 INTRODUCTION 1 1.1 Background 1 1.2 The Consultation Document 3 1.3 The next stages 4 1.4 Statutory consents procedure 5 2 PROJECT DESCRIPTION 8 2.1 The Project 8 2.2 Government policy and targets for renewables 8 2.3 Background and Driver for Reinforcement 9 2.4 Design and Construction 13 3 METHODOLOGY 20 3.1 Overview 20 3.2 Substation site selection study- methodology 22 3.3 Landfall site selection study – methodology 23 3.4 Underground cable route selection study – methodology 24 3.5 Subsea cable route selection study - methodology 25 4 ENVIRONMENTAL CHARACTER 27 4.1 Introduction 27 4.2 Key elements of the landward environment 27 4.3 Physical environment 27 4.4 Ecological environment 30 4.5 Human environment 35 4.6 Key elements of the marine enviroment 41 4.7 Marine physical environment 41 4.8 Marine biological environment 44 4.9 Human marine environment 49 5 DETAILED SUBSTATION SITE, LANDFALL SITE, UNDERGROUND CABLE ROUTE AND SUBSEA CABLE ROUTE STUDIES 54 5.1 Introduction 54 5.2 Substation site selection study 54 5.3 Landfall site selection study 57 5.4 Underground cable route selection study 61 5.5 Subsea cable route selection study 63 6 OVERALL PREFERED OPTION 65
APPENDICES Appendix A Nature conservation information
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FIGURES Figure 3.2 Search Area Figure 4.1 Drift Geology Figure 4.2 Designated Sites Figure 4.3 Cultural Heritage Figure 4.4 Landscape Figure 4.5 Subsea Constraints Figure 5.1 Options Summary Figure 6.1 Overall Preferred Route
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1 INTRODUCTION
1.1 Background
1.1.1 The European Union has set a target that 20% of Europe’s energy requirements shall be met from renewable resources by 2020. The UK government’s contribution towards this target is to achieve 15% energy from renewable sources by this date and the Scottish Government aims to exceed this, by achieving 20% energy generated from renewable sources, by 2020. In respect of electricity, the aim of the Scottish Government is that 100% of the demand within Scotland (demand being defined as gross consumption) for electricity should be met from renewable sources by 2020, with a milestone of 31% by 2011 (equivalent to 5,000MW of installed capacity1). Scottish Hydro Electric Transmission Limited (SHETL) is committed to playing its part in ensuring that Scotland takes full advantage of its renewable energy potential.
1.1.2 The existing transmission network in the north of Scotland was originally designed to serve a rural area and the Islands which at that time had a low demand for electricity and generation potential. The Renewables Obligation targets are leading to many renewable generation developers requesting connections to the electricity network in the north of Scotland and this is placing a significant requirement on the transmission system.
1.1.3 The amount of renewable generation that can be exported from Orkney is limited by the capacity of the two existing 33kV subsea cables that connect Orkney to the mainland transmission grid at Thurso. Taking account of the renewable generation that has already been connected or is contracted to be connected on Orkney means that the existing subsea connection has now reached full capacity. Three developers have formally applied for connection to the network on the west coast of mainland Orkney where development of tidal and wave energy generation is proposed and as such, there is now a requirement to reinforce the network between Orkney and mainland Scotland.
1.1.4 SHETL is part of SSE plc and is the transmission licence holder in the north of Scotland. SHETL has a duty, under Section 9 of the Electricity Act 1989, to facilitate competition in the generation and supply of electricity. The company also has obligations to offer non-discriminatory terms for connection to the transmission system, both for new generation and for new sources of electricity demand.
1.1.5 Where there is a requirement to extend, upgrade or reinforce its transmission, SHETL’s aim is to achieve an environmentally appropriate, technically feasible and
1 Energy Policy: An Overview, September 2008, Scottish Government (website only)
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economically viable solution which on balance will cause the least disturbance to the environment including the people who use the area.
1.1.6 SHETL is obliged to provide connections to new renewable generation into the transmission network as part of its general duties as a transmission licensee.
1.1.7 In March 2010 The Crown Estate announced the leased option areas for the Pentland Firth and Orkney Waters Round 1 Development Sites for marine generation totalling a potential 1600MW, which includes a generation potential of up to 1050MW (wave and tidal) around the Orkney isles and 550MW off the Caithness coast. Initial forecasts suggest the earliest developments will start in 2012, growing thereafter up to the full capacity potential by 2020, assuming successful proving of the technology in the early years.
1.1.8 Currently three developers have applied for a connection to the transmission system on the west coast of mainland Orkney. This will ultimately need to connect to the mainland of Scotland as the proposed generation exceeds the demand on Orkney and far exceeds the capability of the existing twin 33kV circuit link to Orkney from the mainland (Thurso) which is already fully committed to connected generation on the islands.
1.1.9 As a result, new transmission infrastructure is required between Orkney and Caithness. This will need to connect into the existing substation at Dounreay which is currently being upgraded to accommodate a number of proposed connections from this project and other developments. A new substation will also be required on the west coast of mainland Orkney to facilitate the connection of the marine generation sites to the network.
1.1.10 Given the geographical location of the connection applications, the only viable connection option for the new infrastructure will be the installation of a subsea cable from the west coast of mainland Orkney to Caithness. There will be a requirement for on-land infrastructure to connect the subsea cable to the proposed substation in Orkney and the existing substation at Dounreay. The starting assumption is that these connections would be made using underground cables given the anticipated proximity for connection.
1.1.11 SHETL’s approach is to develop and explore a range of potential substation sites on Orkney and connecting routes to Dounreay, in an environmentally led manner in order to identify, in the first instance, a ‘preferred option’ for the subsea cable, underground cable, landfall sites and substation site. Following consultation and further environmental studies a ‘proposed option’ will be selected for which consent applications will be made.
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1.2 The Consultation Document
Purpose
1.2.1 This consultation document describes the work undertaken in considering options for connection of the proposed marine wave and tidal generation sites along the west coast of Orkney.
1.2.2 The consultation document outlines the process by which the preferred substation site and cable routes have been selected (including underground cables on land and subsea cables) and gives consultees and other interested parties the opportunity to comment on the proposals.
1.2.3 All comments will then be considered as part of the next stage of the decision-making process, in order to select the proposed route for the new transmission infrastructure and the proposed site for the new substation.
Consultation
1.2.4 Comments on this consultation document have been sought from a wide range of statutory authorities, key consultees, politicians and the general public.
1.2.5 Copies have also been deposited at Council offices in Thurso, Wick, Kirkwall and Stromness and will be available for public consultation from 10 October 2011. The document is also available on the SHETL website, at www.sse.com/OrkneyCaithness
1.2.6 A public consultation exhibition will be held at Harray Community Hall on Thursday 27 October 2011 Between 2pm and 7pm.
1.2.7 Owners of the land through which the preferred route passes, or on which the substation will be constructed, are also being consulted on an individual basis.
Structure of the document
1.2.8 The document is divided into sections that cover the need for the project, the criteria applicable to the routeing of subsea and underground cables and the siting of substations, the route and site options being considered and compared, and the process undertaken in identifying a preferred option for Orkney Caithness Connection. These sections can be summarised as follows:
Section 1: Introduction
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1.2.9 Section 1 reviews the purpose and scope of the consultation document, outlines the subsequent stages of the project and the statutory consents procedure.
Section 2: Project description
1.2.10 Section 2 describes the need for the project and the design, construction and maintenance of of the various components of the project. This section also addresses the alternative options for transmission that have been considered for the Orkney Caithness Connection.
Section 3: Methodology
1.2.11 Section 3 outlines the study methodology and provides a systematic and objective account of the process by which the preferred route and the preferred substation site have been identified.
Section 4: Environmental character
1.2.12 Section 4 reviews the environmental context and character of the study area, including information on topography, soils, geology, hydrology, nature conservation and landscape designations, landscape character, archaeology and cultural heritage, recreation and access, and the policy and development framework.
Section 5: Connection options
1.2.13 Section 5 identifies the route and site options considered for the substation site, underground cable routes, landfall options and subsea cable routes and why details the benefits and constraints of each.
Section 6: Overall preferred option
1.2.14 Section 6 identifies the overall preferred option. Alternative routes options for specific sections of connection are also considered, for which comment is also sought.
1.3 The next stages
Selection of the overall proposed option
1.3.1 On conclusion of the consultation period, all comments and responses made during the period will be considered.
1.3.2 These responses, together with the assessment undertaken as part of the Environmental Appraisal (EA) process, detailed below, will be used to develop and refine the preferred option, in order to minimise the effects of the transmission
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infrastructure on the environment and people of the area, and provide a cost effective solution that meets the technical requirements. It is intended that the result of this will be the selection of the proposed option for which consent applications will be made.
The Environmental Appraisal
1.3.3 The current infrastructure options being considered for the Orkney Caithness Connection do not fall within the requirement to undertake an Environmental Impact Assessment (EIA) as described in The Electricity Works (Environmental Impact Assessment) (Scotland) Regulations 2000, The Town and Country Planning (Environmental Impact Assessment) (Scotland) Regulations 2011 or The Marine Works (Environmental Impact Assessment) Regulations 2007.
1.3.4 Due to the scale of the proposed connection, SHETL is however proposing to undertake a voluntary Environmental Appraisal (EA) that will be prepared for all sections of the proposed option (including the substation site, underground cable routes, landfall locations and the subsea route).
1.3.5 The EA will encompass the findings of desktop information searches, specialist baseline surveys, further consultation where required and technical assessment to provide a robust appraisal of the likely environmental effects of the different components of the proposed development during construction and operation, and the identification of appropriate mitigation measures to eliminate, reduce or offset these effects. Studies would be undertaken in accordance with approved methodologies and/or industry best practice.
1.3.6 In order to define the scope of the EA an informal scoping report will be produced and provided to statutory authorities and selected key consultees to request their opinion as to the information to be provided within the EA. The scoping report will make reference to this consultation document and to the comments received during the consultation process.
1.4 Statutory consents procedure
Planning Permission
1.4.1 The proposed substation development will be undertaken in accordance with the requirements of the Town and Country Planning (Development Management Procedure) (Scotland) Regulations 2008 (as amended). The substation development would be categorised as major development (as the development area would be over 2 hectares) and accordingly there requires to be pre-application discussions and
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consultations, at least 12 weeks in advance of the submission of the application for consent.
1.4.2 In addition, a Design and Access Statement would be prepared and submitted as part of the planning application supporting information. This would set out the design principles and concepts that have been applied to the proposed development, including aspects such as the policies applied to the design concept and in respect of access to the site; the way in which the proposed development has taken the context of its setting into consideration; and the public consultation that has been carried out in respect of the proposed development and the way in which the outcomes of that consultation have influenced the design of the development.
1.4.3 The determination period for major developments is four months (or longer if an extension is agreed), during which time the application is registered and consultations with statutory bodies are undertaken. This period also allows for a pre- determination hearing, if required (generally if the development is significantly contrary to the development plan). The Regulations anticipate that major developments would normally be dealt with by committee, though delegation is not precluded.
1.4.4 Application for planning permission will be made to The Orkney Islands Council for the development of the proposed substation on Orkney. Neighbour notifications will be undertaken by the Local Planning Authority as part of the application process and notice of the application for planning permission will be placed in local newspapers, to provide the opportunity for representations to be made. The planning authority will also carry out a separate consultation exercise as part of the planning application process.
1.4.5 The laying of underground electricity cables is deemed ‘permitted development’ under class 40 of the Town and Country Planning (General Permitted Development) (Scotland) Order 1992 and as such will not require planning permission.
Marine Licensing
1.4.6 The subsea cable component of the proposed option will require consent under the Marine (Scotland) Act 2010 for activities carried out in the Scottish inshore region of UK waters from 0-12 nautical miles (nm).
1.4.7 This new licensing regime simplifies the previous consenting process for subsea cables and incorporates the determination of consents required under the Coast Protection Act 1949 (CPA) and the Food and Environment Protection Act 1985 (FEPA) into one marine licence. Marine Scotland, on behalf of the Scottish Ministers, are responsible for the determination of consents applications under this new regime.
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1.4.8 The determination period for a marine licence is usually in the region of eight weeks (but can take longer if an extension is agreed or further information is required). This determination period also allows for a 28 day period for representations following advertisement and a 4 week period during which Marine Scotland will consult with Statutory Authorities.
1.4.9 The application would include details of the route, what the cable and associated infrastructure to be laid consists of, the quantity of cable and materials to be placed, and how the cable is to be laid. On completion of the works, a return is submitted to details any deviation from the design, so accurate records of cable routes and materials on the sea bed can be made.
Section 37 Application
1.4.10 As all the transmission routes, and connections to the substations are through subsea or underground cables with no installation of overhead transmission lines, this project will not require consent under Section 37 of the Electricity Act 1989.
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2 PROJECT DESCRIPTION
2.1 The Project
2.1.1 The Orkney Caithness Connection is being developed to enable the prompt connection of marine renewable energy generation developments off the west coast of Orkney to the wider transmission network at Dounreay in Caithness.
2.2 Government policy and targets for renewables
Introduction
2.2.1 As outlined in the UK Renewable Energy Strategy 2009, the government is working to a legally-binding target that 15% of energy supplies within the United Kingdom are to be generated from renewable sources by 2020.
2.2.2 In Scotland, the Scottish Government has set a target that 100% of electricity supplies in Scotland should be generated from renewable sources by 2020. Renewable energy will also be an important factor in meeting UK Government’s longer-term target of a 60% reduction in CO2 emissions by 2050. If these targets are to be met, the necessary infrastructure requires to be put in place.
Renewables Obligations
2.2.3 To achieve these targets, the Government introduced a new market support mechanism for renewables – “The Renewables Obligations”. The obligation is imposed upon licensed electricity suppliers to meet, year-on-year, increases of their demand from renewables. The Renewables Obligation Scotland (ROS) was introduced at the same time as an identical obligation on English and Welsh (E&W) suppliers under the Renewables Obligation (RO). The ROS and the RO are collectively referred to as “The Obligations”. Renewable Obligations Certificates (ROCs) will demonstrate compliance with the obligation, and these will be tradable between all suppliers in Great Britain. This means in effect that the location of renewable energy plant is not tied to the demand, which is supplied in pursuit of the obligation. The growth of renewable generation has very significant implications for the electricity transmission system, both in Scotland and in Great Britain as a whole, both in terms of the connection of marine generation and onshore windfarms, and in providing adequate transmission capacity between the north of Scotland and the centres of demand, further south.
Transmission Licensees Statutory and Licence Obligations
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2.2.4 The primary legislation governing the electricity supply industry in Great Britain is the Electricity Act 1989 and the Utilities Act 2000. Under this legislation the Secretary of State and the Gas and Electricity Markets Authority have certain powers and duties in relation to the electricity market. In particular, the Secretary of State or the Authority may grant a licence authorising a person to transmit electricity in an authorised area. The Electricity Act and the Utilities Act also put obligations on a licence holder, termed Statutory and Licence Obligations. These obligations include the requirements:
i. to permit the development, maintenance and operation of an efficient, co- ordinated and economical system for the transmission of electricity;
ii. to facilitate competition in the generation and supply of electricity (and without limiting the foregoing, to facilitate the licensee’s transmission system being made available to persons authorised to supply or generate electricity on terms which neither prevent nor restrict competition in the supply or generation of electricity);
iii. to promote the security and efficiency of the electricity generation, transmission and distribution systems in England and Wales or Scotland, each taken as a whole; and
iv. to have regard for the environment and do what they reasonably can to mitigate any effect any proposals would have on the environment.
2.2.5 SHETL is the holder of the transmission licence for the north of Scotland and In addition, as part of the transmission licence, SHETL has a number of related obligations to offer non-discriminatory terms for connection to the transmission system for both new generation and new sources of electricity demand. SHETL is also obliged to facilitate competition in generation connections.
2.3 Background and Driver for Reinforcement
2.3.1 SHETL, as part of its general duties as a transmission licensee, requires to reinforce the existing connection between Orkney and Caithness.
2.3.2 This reinforcement is required in order to provide a transmission connection and access to the grid, for marine renewable generation situated off the west coast of the Orkney Mainland in accordance with the National Electricity Transmission Security and Quality of Supply Standards (SQSS).
2.3.3 The Crown Estate has leased a number of areas to Developers for the generation of tidal and wave energy under Pentland Firth and Orkney Waters Round 1 – see attached Crown Estate map. The existing connection between Orkney and Caithness, currently provided by two 33kV subsea cables between Thurso and
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Scorradale are at capacity and the potential generation from these new marine developments cannot be transmitted on the existing network.
Figure 2.1
[Source: The Crown Estate] 2.3.4 The significant increase in renewable generation seeking connection in SHETL’s area has resulted in reinforcement proposals to increase the transmission system capability to accommodate the increased power flows.
2.3.5 Potential marine renewable generation off the west coast of Orkney Mainland, with potential to connect into this scheme totals approximately 750MW. A breakdown of this can be seen in table 2.1 below:
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Table 2.1 Summary of generation activity in Penland Firth and Orkney Water – Round 1 Development Project Owner(s) of Tenant Wave/ Potential Potential Tidal Generation Connection to Scheme Costa Head SSE Renewables Developments (UK) Wave 200MW • Ltd Brough Head Aquamarine Power Ltd & SSE Wave 200MW • Renewables Holdings (UK) Ltd Marwick head Scottish Power Renewable UK Ltd Wave 50MW • West Orkney Middle South Wave 50MW •
West Orkney South E.ON Climate & Renewables UK Ltd Wave 50MW • Westray South SSE Renewables Developments (UK) Tidal 200MW • Ltd Farr Point Pelamis Wave Power Limited Wave 50MW Cantick Head SSE Renewables Holdings (UK) Ltd & Tidal 200MW OpenHydro Site Development Ltd Inner Sound Atlantis Resource Corporation Pte Ltd, Tidal 400MW International Power Marine Developemnt Ltd, Morgan Stanley Capital Group Incorporated Ness of Duncansby Scottish Power Renewable UK Ltd Tidal 100MW Brough Ness Marine Current Turbines Limited Tidal 100MW TOTAL 1.6GW 750MW
2.3.6 Connection applications have been received from three Developers off the West coast of Orkney, with a total capacity of 509MW but with varying timescales attached. Due to the uncertainty surrounding the commercial viability of these new technologies and the phased nature of the Developers schemes, SHETL proposes to develop the grid connection in two phases. Phase 1 would consist of a proposed 132kV connection from the Orkney mainland to Caithness, connecting into Dounreay substation. This would accommodate connections up to a total capacity of 180 – 200MW. Phase 2 would then follow and would require High Voltage Direct Current (HVDC) infrastructure in order to connect the full generation potential.
2.3.7 The applications from the Developers led to the establishment of an initial search area for suitable infrastructure. The search areas that are referenced throughout the document are identified in Figure 3.2. Due to the location of the Developer’s lease areas the west and north west coast of Orkney Mainland was accepted as the preferred search area for cable landfalls and siting of a substation facility, providing a relatively short connection route from most of the developments. The only grid connection point in Caithness with suitable capacity is Dounreay Substation (the substation is currently being upgraded and the 275kV line south to Beauly is being reinforced), the other 132kV facility in close proximity is Thurso substation but this facility and the overhead lines connecting it are at capacity and are not due to be upgraded until approximately 2016.
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2.3.8 Throughout the remaining sections of this document, “the project” refers to Phase 1 only.
The preferred transmission connection
2.3.9 Phase 1 of the transmission infrastructure will consist of:
· a new indoor 132/33kV substation located on the Orkney Mainland,
· a section of buried 132kV cable from the substation location to the landfall point,
· a subsea 132kV cable from the landfall in Orkney to the landfall in Caithness,
· a buried 132kV cable from the Caithness landfall to the existing substation at Dounreay.
2.3.10 There is no proposal to connect this infrastructure to the existing Orkney distribution network at present. However this may arise as a result of future applications for connection and will be developed, as appropriate, should such applications be made.
2.3.11 SHETL’s approach is to develop and explore a range of potential sites and routes, in an environmentally led manner that also balances technical and economic requirement, in order to identify in the first instance a ‘preferred’ substation site, cable routes and subsea route. These are identified in subsequent sections of the document. Following this consultation, an indicative proposed route will be identified for the subsea and underground cable sections along with an indicative site for the substation. Further consultation, environmental studies and formal assessment will then take place to refine these further after which SHETL will select a ‘proposed’ substation site, cable routes, and subsea route for which application for consents would be made.
2.3.12 SHETL recognises that the decisions taken at this stage for Phase 1 of the Orkney Caithness Connection project will have knock on considerations for Phase 2 (for example, it is likely that a converter station required for the HVDC connection would be sited adjacent to the 132kV substation proposed for Phase 1) and as a result has and will continue to ensure that the assessment in made with due consideration to Phase 2 of the project.
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Alternative options for transmission reinforcement
2.3.13 Alternatives were considered taking into account the potential volume of marine renewables and potential onshore renewable generation in Orkney and these are briefly outlined below and may be developed further should additional applications be made for connection which justify the additional infrastructure.
2.3.14 Consideration has been given to providing a HVDC solution instead of the initial 132kV connection. This was discounted due to the current applications and build profile submitted by the Developers and can not be justified economically at this stage. It is however being considered for Phase 2 of the development.
2.3.15 Consideration has been given to the provision of separate facilities in South Walls or South Ronaldsay with a subsea cable to Caithness and a new 132kV OHL connection from the west of Orkney. This has been discounted at this stage as no formal applications have been received from Developers in this area (Brough Ness and Cantick Head), and it is not economically justifiable as this would still require a substation on the west coast of Orkney as well as a substation in South Ronaldsay along with a far longer connection within Caithness to a suitable grid connection point.
2.3.16 Connection of the marine renewables directly to the existing Orkney distribution network is not feasible as the existing 33kV cables between Orkney and Caithness are at capacity and there are significant constraints within the distribution network in Orkney which precludes any significant additional generation being connected.
2.4 Design and Construction
2.4.1 This following paragraphs provide details the specific design and construction considerations for each aspect of the project
Substation - Design
2.4.2 A substation is required in order to enable the marine developments to connect to the transmission network.
2.4.3 As the substation on Orkney will be in close proximity to the coast, there is a requirement to house the equipment within a building. This will protect the equipment from possible corrosion caused by salt in the atmosphere. The building or buildings would generally be of similar appearance to large agricultural sheds, based on a steel portal frame with industrial cladding on the exterior.
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2.4.4 The development on Orkney was originally proposed as a substation utilising air insulated switchgear (AIS), but due to sequential increases in the number of 132kV connections required in the design, it became apparent that gas insulated switchgear (GIS) may be a more attractive alternative. As a result a comparison for size and cost was undertaken between an AIS and GIS solution for a typical 132kV substation of the nature proposed for Orkney.
2.4.5 The AIS solution required a building with approximate dimensions of 180 x 80 x 22m at its highest point and a GIS would require a building with approximate dimensions of 50 x 14 x 10m at its highest point, subject to detailed design. The AIS solution is also likely to cost in the region of 25% more than GIS when including the cost of constructing the building to house the infrastructure.
2.4.6 Due to the sensitivity of many environmental receptors on the west coast of mainland Orkney (including the potential for any large development to have adverse impacts on the landscape and visual amenity of the area) and the differential in cost when looking at the overall substation construction, it is proposed that a GIS solution will be utilised in this instance.
2.4.7 The overall footprint of the site being considered is considerably larger, 350 x 350 m than the anticipated 132kV substation building. This size is based on the initial requirements for a 132kV substation, associated access, drainage and SUDS with an allowance for a potential Phase 2 development of an HVDC Converter station at some point in the future.
2.4.8 This overall footprint size will be subject to review and detailed design whereupon the intention would be to reduce the size. The site would be surrounded by a 2.5m high security fence of palisade construction and be fitted with a CCTV system.
2.4.9 Illumination will be provided internally to allow safe working on the installation with limited lighting at access points to allow safe access to the compound and building.
Substation - Construction
2.4.10 In constructing substations, access requirements for long and heavy loads must be taken into account. In some instances improvements to the local road network, such as localised widening at bends in the road, or strengthening of roads or bridges, will be required in advance of the construction works commencing. The largest plant item in a substation is usually the transformer. A 132kV transformer is likely to weigh around 80 tonnes when arranged for transport.
Substation - Maintenance
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2.4.11 Substation plant requires maintenance and inspection at regular intervals. Most substations have a monthly inspection. Maintenance is completed about once every four to six years on each circuit. As the substation would have several circuits, it is likely that some maintenance would be completed most years. This is likely to involve a site presence for about one week with light vehicles. There would be other visits as required for operational duties.
Underground Cable - Design
2.4.12 The connection would consist of a 132kV AC (Alternating Current) single circuit cable. A typical 132kV cable for burial on land will consist of three separate cables (one for each Phase). The three ‘Phase’ cables would normally be bundled together in a trefoil arrangement and directly buried. Alternatively the three cables can be separated and installed in ducts. It is also likely that a fibre optic communications cable will be laid with the 132kV circuit for protection and control purposes.
2.4.13 In order to access and construct the cable trench a Wayleave corridor of 15-20 metres wide is normally required. This corridor width has been used throughout the document to assess the environmental effects.
2.4.14 The length of cable on Orkney will vary between 1km and 3km depending on the landfall and substation site location chosen. The length of cable in Caithness is likely to be between 6km – 10km depending on the chosen landfall.
2.4.15 Various surveys would be completed to identify the ground conditions. This is required for the detailed design of the cable trench. In particular, the ability of the ground to conduct heat away from the cable is critical. If the indigenous ground material cannot conduct heat effectively, or contains large or sharp rock, then a stabilised backfill will be required.
2.4.16 Given the requirement for the Developers generating sites to connect to the substation, it is likely that cables from these sites may follow the same corridor on Orkney. There is a general presumption that a minimum separation of 5 metres would be required between circuits, although this would be further defined during detailed design. This could lead to an extensive cable corridor with disruption over a number of years to meet the individual Developers timescales.
Underground Cable - Construction
2.4.17 The cables would be laid at a depth of approximately 900mm below ground. The burial depth may be reduced in areas of rock or increased in agricultural areas. The most likely installation of the underground cables would be through open cut burial.
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2.4.18 Should stabilised backfill be required, the preferred material would be Cement Bound Sand (CBS). The amount of stabilised backfill would depend on the ground conditions but it is normal to have a minimum of 150mm of backfill around all the cables. Normally CBS would be delivered to site in concrete wagons and installed directly into the trench, to avoid any double handling. Any need for CBS would therefore also require vehicular access to all parts of the cable route.
2.4.19 Excavation through bedrock is very expensive and hazardous. Such excavations usually involve heavy plant breaking up the rock, or explosives. Wherever possible, such excavations would be avoided.
2.4.20 It is possible to lay the cables in the public highway. Again, this is very expensive and can cause significant disruption to traffic flows. As such, laying cables in the public highway would also be avoided where possible.
2.4.21 The cable route would require a haul road along its full length. The haul road would only be used for the installation works. In many areas, an existing road or track can be used for the haul road. In most other areas, the haul road is likely to be formed from prefabricated “Trackway” panels which would be laid immediately prior to the works and removed afterwards. In some areas, where the length between public roads’ access points is too long, or where access may be required on several occasions, it may be preferable to install a temporary stone track.
2.4.22 Traditional excavation of the cable trenches would involve the removal and set aside of the top layer of vegetation for subsequent re-use in reinstatement. The remaining materials would also be set aside, assuming they are suitable for backfill. If the materials are deemed unsuitable, they would be removed from the site. If the ground materials are considered unstable at the depths excavated, then the sides of the trenches may be angled or stepped to reduce the risk of materials falling into the excavation. Where this is not possible or practical, the trench sides may be shored up with timber to ensure the safety of the operatives. The timber shoring would be removed prior to backfilling and reinstatement.
2.4.23 The joint bays would be formed as required and the joints completed once the cables to either side are installed.
2.4.24 The cables would be delivered on drums holding approximately 800m (although this will be dependant on the type of cable specified following detailed design. The cable joints must be formed under clean and dry conditions, which require working areas, known as joint bays, to be constructed with concrete floors. The joint bays would measure in the regions of 10m x 5m. Tents or pre-formed fibre-glass sheds would be used during the jointing in order to provide a controlled environment.
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2.4.25 The cable drums would be set up at one end of the trenches, excavated by conventional excavators and a winch would be used to pull the cables into the trenches. Soil, sand or CBS would be installed around and above the cables. The remainder of the trenches would then be reinstated; this would be done with the material previously set aside, wherever possible.
2.4.26 Cable markers would be installed at regular intervals throughout the length of the route to ensure that third parties are aware of their presence.
2.4.27 A Construction compound would be required in both Orkney and Caithness to facilitate the handling of materials and to provide welfare facilities for the construction workers. The compounds would be around 50m by 50m and surrounded with a temporary “Heras” style security fence. The compounds would contain a small number of portacabins and waste skips, and bunded areas for refuelling. Cable drums and other materials would be off-loaded from low-loaders and transferred to vehicles suitable for use on the site access tracks.
Underground Cable - Maintenance
2.4.28 There is no routine maintenance for an AC cable system. However, it is reasonable to expect a major cable of this nature to experience a number of faults during its lifetime. Fault location is difficult on a buried cable. Test equipment can be used to provide approximate positions of faults. Thereafter, a substantial excavation is often required to cut out and replace the faulted section. As with the initial jointing, this requires clean and dry conditions.
Subsea Cable - Design
2.4.29 Following identification of the indicative proposed route, a detailed cable route survey will be carried out to determine the suitability of the route.
2.4.30 The subsea cable would preferably be a single cable with three cores (one for each ‘Phase’) including fibre optic communication for control purposes within the cable
2.4.31 The required spacing between marine cable circuits is in direct relation to the depth of the water and in general should be three times the water depth, to ensure adequate distance for retrieval at a later stage.
2.4.32 Security of the cable is maximised by burial and therefore the cable would be buried wherever possible. In areas where burial is not possible, or where burial provides insufficient protection against shipping, the requirement for additional protection would be assessed. To facilitate burial, cable lay across sandy or muddy bottoms is preferred. The route survey will provide geophysical information on the nature of the
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terrain to identify all features or items that would pose a risk to the cable during installation and operation.
Subsea Cable - Construction
2.4.33 The general sequence of events for submarine cable installation is as follows:
· cable lay vessel mobilisation;
· transit to the cable storage location and loading onto the vessel. Any required tests are carried out on the cable prior to laying;
· vessel transit to the operational area. All shore end equipment is offloaded and transported by road to the landing points;
· beach anchors are buried in appropriate locations and the cable pull winch is set up and secured;
· the cable lay vessel deploys anchors in a four point mooring formation, assisted by the auxiliary anchor vessel;
· the shore winch begins the cable pull; buoyancy aids may be attached to the cable to float it ashore;
· once sufficient cable has been deployed and the cable is straight, the floats are removed, allowing the cable to sink to the seabed;
· during laying, the cable tension would be adjusted to suit the depth of water;
· wherever possible the cable would be buried during laying; and
· a similar procedure is carried out for the other shore landing point.
2.4.34 The cable lay would be a direct lay with touch down monitoring, to ensure that the cable does not span any rocky outcrops. This requires an ROV (Remotely Operated Vehicle) to travel alongside the laying vessel to allow a camera to continuously supervise the cable as it lands on the seabed. Burial is proposed as a post-lay burial utilising water-jetting technology. An ROV would be used, controlled by a separate vessel. It is intended that burial would be completed as soon as possible following the cable lay.
2.4.35 The subsea cable would be brought onshore at the landing site and, depending on site conditions, would be winched or pulled ashore. If the destination substation was within 1km of the shore (potentially the case in Orkney), the subsea cable could be
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pulled directly into the substation. As this distance is exceeded on this project in Caithness, it is intended to introduce a cable transition joint to allow a change from subsea cable to land cable.
2.4.36 The landfall site may be an open excavation within a bay or directionally drilled through the foreshore. Depending on the landfall method and characteristic of the site it may be necessary to protect the subsea cable in the intertidal area. The protection is likely to be provided by burying the cables in specialised ducts.
2.4.37 Access to the landing site for vehicles, plant and personnel for operation, hauling and maintenance purposes would be required. As part of the hauling operations, it may be necessary to introduce temporary roadways or temporary bridges
2.4.38 It is expected that the works at each landing site would take around four weeks in total. This period is unlikely to be continuous. One cable laying vessel would be able to carry the entire cable associated with one circuit, in one mobilisation. It is likely that the cable would be laid and buried in one summer period but this activity is weather dependent and as such these timescales are only indicative.
Subsea Cable - Maintenance
2.4.39 In general, a subsea cable requires little ongoing maintenance. Inclement weather and direct impact from fishing gear or anchors can cause damage to the cable. Recovery and repair of a subsea cable can be difficult, which can result in a subsea cable having a shorter life span that a cable of comparable distance on land. Increased protection to vulnerable cables is therefore preferred to ongoing maintenance.
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3 METHODOLOGY
3.1 Overview
3.1.1 The project, as described in Sections 1 and 2 includes the construction of a new 132kV substation on the North West coast of mainland Orkney in order to allow grid- connection from marine renewable generators in the region. A new subsea 132kV AC cable would then connect the new Orkney substation to the Dounreay substation on Caithness which will connect the project to the mainland grid infrastructure. All on land transmission and connecting cables that are part of this project are proposed to be buried.
3.1.2 In terms of Section 9 of the Electricity Act 1989, electricity transmission companies are required to install and keep installed an efficient, co-ordinated and economical system of electricity supply.
3.1.3 Paragraph 3 of Schedule 9 to the Act also requires them to:
a) have regard to the desirability of preserving natural beauty, of conserving flora, fauna and geological or physiographical features of special interest and of protecting sites, buildings and objects of architectural, historic or archaeological interest; and
b) do what they reasonably can to mitigate any effect which the proposals would have on the natural beauty of the countryside or on any such flora, fauna, features, sites, buildings or objects.
3.1.4 SHETL are therefore required to consider technical, economic and environmental issues and to achieve a balance between these.
3.1.5 The objective of the consultation document is to identify a ‘preferred overall option’ that has assessed and combined all elements of the overall connection. As a result of the statutory duties referred to above, the preferred overall option must be technically feasible and economically viable whilst causing least disturbance to the environment and to the people who live, work, visit and take recreation within it.
3.1.6 SHETL’s approach is to develop and explore a range of substation sites, landfall locations, and potential route corridors, in an environmentally-led manner, in order to select a ‘preferred overall option’ for the connection. To do this the project was broken down into four components parts:
· Substation site in Orkney, · Landfall sites (both on Orkney and Caithness), · On land cable routes (both on Orkney and Caithness), and
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· Subsea cable routes
3.1.7 Initially, possible substation sites were identified on the west coast of mainland Orkney as this component of the project was seen to be critical in respect to the operational requirements of the scheme but also due to the known sensitivities surrounding any large scale development in this locality within Orkney.
3.1.8 Following identification of possible substation sites, landfall site options were considered for both Orkney and Caithness followed by cable route options between landfalls and the substation sites in Orkney and Caithness, and the identification of subsea route options between the possible landfall sites.
3.1.9 Individual studies were undertaken for each component part of the project to identify the environmental, technical and economic implications of the various route and site options as applicable. These were then reviewed together to identify a ‘preferred overall option’ that balanced these environmental, technical and economic implications across all project components. Figure 3.1 illustrates this process.
Figure 3.1 – Approach to selection of ‘Overall preferred option’
Environment, Substation Landfall site Undergroun Subsea Technical site d cable Cable route Economic studies
Overall Preferred Option
3.1.10 The considerations taken into account for each of the components illustrated above were similar, although variations were allowed for due to the different construction and operational characteristics of the different components. For example, landscape and visual implications featured strongly in the substation site selection study but less so in the subsea cable route study, and tidal currents featured in subsea cable route study but was not considered at all in the underground cable route or substation site studies.
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3.1.11 An overview of the environmental character of the substation and cable route search areas is included in section 4 prior to a detailed description in section 5 of the key findings from each study.
3.2 Substation site selection study- methodology
3.2.1 SHETL has guidelines for the selection of substation sites and these have been applied to the selection of the preferred substation site on the west coast of mainland Orkney. These guidelines set out a framework under which a preferred site should be identified. This requires consideration to be given to the engineering, environmental, technical and operational and economic aspects in a balanced assessment. The guidelines also contain reference to the Holford Rules.
3.2.2 The Holford Rules are broad principles for overhead transmission line routeing and were formulated by the late Lord Holford. These rules have were reviewed by SHETL in 2004 and the review concluded that the rules should continue to be employed as originally formulated, but with NGC’s notes of clarification modified and expanded to meet Scottish circumstances. Although no overhead lines are proposed as part of this project, the Holford Rules also identify guidance for the siting of substation sites and this has been taken into account when assessing the suitability of sites on the west coast of mainland Orkney.
3.2.3 Environmental issues relating to the selection of a substation site are broadly similar to that of an overhead line. Areas of environmental designation should be avoided, as far as possible and areas of local amenity value protected. Ground conditions should be level, dry and firm, wherever possible, with preference given to sites without extensive topographic or drainage constraints, or the presence of near- surface bedrock.
3.2.4 Sites with existing screening features, either from landform or tree cover, are advantageous, as are sites remote from properties, in order to avoid both noise and visual impacts. Areas where children could be expected to congregate should be avoided, for health and safety reasons, as should proximity to watercourses, to eliminate risk of pollution.
3.2.5 The environmental factors considered in the substation site selection study included: Geology/ soils, Hydrolology, Habitats, Protected species, Ornithology, Cultural heritage, Landscape character, Visual amenity, Land use, and Access and recreation.
3.2.6 Technical and operational aspects of the sites relate to issues of health and safety (during construction and operation); the timescales required for the construction of
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the site; the availability of the site; its potential maintenance requirements; and its flexibility in respect of any future developments / connections to the network.
3.2.7 Costs are assessed on the basis of the capital costs associated with the construction of the site, though operational costs can also be relevant. For the economic assessment an indicative cost for construction and commissioning was calculated for each site in order to provide sufficient detail to allow an informed comparison.
3.2.8 The findings form the environmental, technical/ operation and economic scores were then assessed together on an equal basis to identify the preferred substation site location.
3.2.9 The Orkney Substation site was considered to be a highly pertinent component of the development given the landscape and environmental sensitivities in which this large, permanent structure would require to be situated. As a result, a significant amount of survey work was commissioned in order to fully understand the environmental and technical implications of development in specific locations within the search area. This included geology, hydrology, protected species, ornithology, landscape and visual, habitat and cultural heritage/archaeology surveys for all sites taken forward to detailed assessment.
3.3 Landfall site selection study – methodology
3.3.1 The traditional method for pulling a subsea cable ashore is through a ‘direct open cut’ installation technology. This involves excavation of the inter-tidal area to allow the cable to be buried as it is brought ashore. As suitable sites can be limited, their definition can strongly influence onward routes on land and at sea; whatever the technological approach used. It was quickly identified, for both Orkney and Caithness, that only to assess possible landfall sites that were suitable for direct open cut could significantly limit the choice of landfall site due to the natural topography and geology of the search areas.
3.3.2 As a result, for this project, the landfall study was extended to include potential sites for horizontal directional drilling (HDD). HDD requires an establishment area on land from which a borehole would be drilled under the coastline to a specified point on the seabed below mean low water springs. This would be lined by ducts and the cable would then be pulled ashore through the ducts. This method of installation avoids the requirement to find gentle sloping bay with sufficient sediment to allow burial but does carry other associate risks in terms of engineering and cost.
3.3.3 The technical requirements for the two landfall methodologies are vastly different and therefore different criteria were used to assess these. The open cut methodology
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identified key technical requirements including: coast profile; beach type; near shore waters; tidal conditions; weather exposure; and other infrastructure.
3.3.4 The key technical requirements for horizontal directional drilling included: elevation, extent of rock outcrop at sea, distance to the 5m water depth, rock type, and rock structure.
3.3.5 Environmental factors considered and scored for all landfall options included: planning policy; landuse; soils and geology; hydrology; habitats; mammals and ornithology; designated sites (Ecology); landscape and visual; cultural heritage; and proximity to dwellings.
3.3.6 Appropriate landing points and directional drilling sites need to be suitably located, to have necessary physical conditions and to avoid major constraints to onward routeing. These additional constraints include the locality of the marine renewable generation developers and their cable connections to the substation (subsea cables and landfall locations).
3.3.7 Although the results of the landfall study cannot determine a preferred site in isolation to the other component parts of the project, each landfall option was assessed on these criteria and allocated a classification (Very Good; Good; Acceptable; Poor; and Very Poor). These classifications were then used in the overall comparison of all component parts to identify the ‘overall preferred option’.
3.4 Underground cable route selection study – methodology
3.4.1 The underground cable route selection study was undertaken following identification of the substation site and landfall site options. High level route screening was then undertaken to identify possible cable corridors approximately 100m wide between the substation site and landfall options, for Orkney and Caithness. The width of this corridor has been specifically identified to allow the opportunity for further cables to be laid at a later date as part of the possible future HVDC connection or by a Developer connecting to the Orkney substation from a marine renewable generating site(s), should they so wish.
3.4.2 Installation of underground cables can cause effects a variety of environmental receptor, many of which are similar to those of a substation. The environmental factors considered for each cable route option in the comparative study were: planning policy, landuse, habitats, mammals and ornithology, designated sites (Ecology), landscape and visual, cultural heritage, and proximity to dwellings.
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3.4.3 The key technical criterion for which the cable route options were assessed included: rock type, soils, water courses, wetlands, gradient, and accessibility.
3.4.4 The length of underground cables can also have a significant impact on cost. As a result the shortest route is preferred providing it does not have adverse technical or environmental effects.
3.4.5 Although the results of the underground cable study cannot determine a preferred route in isolation to the other component parts of the project, each cable route option was assessed on the criteria above and allocated a classification (Very Good; Good; Acceptable; Poor; and Very Poor). These classifications were then used in the overall comparison of all component parts to identify the ‘overall preferred option’.
3.5 Subsea cable route selection study - methodology
3.5.1 The assessment of the subsea cable route options was undertaken in accordance with SHETL procedures for Subsea Cable Route Selection.
3.5.2 The initial approach to selection of routes for the subsea cable is based on four major factors:
· The route must be secure.
· The route must be financially viable, in terms of both installation and maintenance.
· The route must have the minimum possible effect on the environment, and on users of the waters or landfall areas through which it passes.
· The route should be acceptable to the owners or leaseholders of land/seabed through which it passes.
3.5.3 A high degree of environmental awareness is necessary, both for the routeing of the sub-sea cables, and in their interface to land cables. For this reason, the approach taken by SHETL was to identify broad corridors of interest through which the cables might be run. For this project, due to the number of landfall sites being considered, a ‘lattice’ of corridor options has been identified so the ‘best fit’ subsea cable route can subsequently be selected.
3.5.4 For each possible route corridor identified, an assessment has been made as to their technical, environmental and economic implications for the project.
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3.5.5 The assessment process used for the subsea cable route study was similar to that for the underground cable route study but the criteria differed slightly due to the different technical and environmental requirements for laying a cable on the sea bed.
3.5.6 Technical factors considered in the assessment included: sediment type; sediment depth; gradient; tidal currents; and other infrastructure. Environmental factors considered included: planning policy; sea use (including fisheries, shipping and energy production); Habitats; Protected Species; Designated Sites (Ecology); and Cultural Heritage.
3.5.7 The assessment was made by comparing all criteria equally and assigning a classification from the following range: Very Good; Good; Acceptable; Poor; and Very Poor.
3.5.8 A classification was given for each individual route corridor so that the ‘best fit’ subsea route could be selected once information on preferred landfall sites was known.
3.5.9 The length of subsea cables, the installation method and protection requirements can all have a significant impact on project cost. As a result (providing adequate burial can be achieved) the shortest route is preferred providing it does not have adverse technical or environmental effects.
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4 ENVIRONMENTAL CHARACTER
4.1 Introduction
4.1.1 The information provided in the following section, provides a description of the key environmental sensitivities within the project search area, which are relevant to the study. The significance and relevance of each of the sensitivities to the project are also highlighted where appropriate.
4.2 Key elements of the landward environment
4.2.1 This section of the Consultation Document describes the key features of the landward (terrestrial) environment that may affect, or be affected by, the proposed connection. These are the aspects of the environment which have been taken into account during the preferred route selection process.
4.3 Physical environment
Geology
4.3.1 The search in Orkney is generally characterised and underlain by a solid geology of Stromness flagstone. The search area in Caithness is predominantly underlain by Caithness flagstone.
4.3.2 Both Caithness and Orkney are renowned for their fish fossil beds and there are other fossilised remains in particular rock strata within the sedimentary sequence. Where these are know to outcrop at the surface, or in quarries that have reached these layers geological conservation designations are often applied.
4.3.3 The small catchment areas for streams and rivers mean that sediment burdens are generally relatively low. Therefore, bedrock in both areas is often near to the surface, and although covering soils can be fertile, they are rarely very deep (See paragraph 4.3.11 onwards for further details on soils).
Soils
4.3.4 Soil depth and composition will determine the methods required for excavation during the installation of the substation foundations and when identifying routes for the underground cables from the substation to the selected landfall location. The stability of soils is also important for safety reasons and also with regard to conservation of habitats.
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4.3.5 The soils of the Caithness search area are dominated by peat, sand, gravel and boulders in the western grading into sand, gravels and diamicton in the eastern. The soils in the Orkney search area are dominated by sands, gravels and diamicton throughout.
4.3.6 In both Orkney and Caithness, sand deposits are a coastal feature within the larger bays. They are often associated with dune systems and a machair type hinterland. Many of these areas are designated as national or local conservations areas (see 4.4 below). The key locations within the search area are Birsay Bay, Bay of Skaill, Sandside Bay and Melvich Bay.
4.3.7 Figure 4.1 illustrates the drift geology of the study area.
Geological SSSIs
4.3.8 A number of the SSSIs that fall within the search area have been notified due to their geological/physiographical features of special interest. Some are wholly ‘geological SSSIs’ whilst others are ‘mixed’, where both geological and biological components are of interest.
4.3.9 Within the search area, there are a number of geological and mixed SSSIs. The distribution of these sites is shown in Figure 4.6. The most notable sites from a geological perspective are as follows:
· Strathy Coast SSSI
· Redpoint Coast SSSI
· Sandside Bay SSSI
· Bay of Skaill SSSI
· Stromness Heaths and Coast SSSI
· Cruaday Quarry SSSI
4.3.10 There are a number of Geological Conservation Review (GCR) sites and Regionally Important Geomorphical review sites in the study area and these have also been used in the high level screening process that has been undertaken for the options appraisal.
4.3.11 Geology and soils has played an important role in substation site selection and cable route selection in that areas of peat and shallow soils, and geologically sensitive areas have, as far as possible, been avoided.
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Surface and groundwater
4.3.12 Surface waters commonly have associated habitats rich in species and wildlife diversity, making them particularly sensitive to development and change. Bodies such as lochs, rivers and wetlands can also create physical barriers to development, influencing routeing and site selection.
Rivers
4.3.13 Orkney has no major rivers, so true estuarine habitats are limited. Intermediate salinity water bodies are however present. In the West Mainland, a significant portion of falling water drains into the loch basin systems in Harray and Stenness which are also subject to tidally induced inflows of salt water, particularly during spring tides. Due to their short length and size, the rivers and watercourses within the Orkney study area vary dramatically in terms of their quality. The classification in this area ranges from poor to good.
4.3.14 There are four key rivers within the search area in Caithness; the Halladale River drains into Melvich Bay; the Sandside Burn and Burn of Isauld drain into Sandside Bay; and the Forss Water drains into Crosskirk Bay. Each of these rivers are classified as moderate, good, good and poor respectively in terms of quality status by SEPA.
Lochs
4.3.15 The key freshwater lochs within the Orkney study are Loch of Boardhouse which is currently classified as good status, Loch of Isbister which is also a designated SSSI, SAC and Nature Reserve and is not currently assigned a status, Loch of Harray which is to the very west of the study area and has a classification of moderate, and Loch of Skaill which has a classification of good.
4.3.16 Problems have been encountered in Orkney where excessive nutrient inputs led to an explosion in aquatic vegetation and a subsequent reduction in water quality once this started to decay during the early and mid 1990s. This was particularly in relation to The Loch of Harray.
4.3.17 The Loch of Harry to a lesser extent and its neighbour the Loch of Stenness to a larger extent hold particular interest due to the mixing of salt and fresh water within them. The Loch of Stenness is, in part, designated as an SAC for this reason.
4.3.18 No key lochs are present within the Caithness search area.
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Groundwater
4.3.19 The search area is predominantly comprised of flagstone (see above); largely confining groundwater to dilated joints and bedding planes within the uppermost section of the rock. In Caithness, groundwater is largely confined to a shallow zone of weathered rock, and borehole yields are limited (BGS, 1988). The study area in Caithness falls within the Thurso bedrock and localised sands and gravels aquifer and this has a classification status of good. The Orkney groundwater is also classified as good status.
4.3.20 Surface and groundwaters have both been a critical consideration in the siting of the substation site and the cable route options given the sensitive of specific areas within the study area.
4.4 Ecological environment
Natural heritage conservation designations
4.4.1 In Scotland, there are three levels of designation aimed at protecting areas of high nature conservation and scientific interest: international; national; and local. International designations include Special Protection areas (SPAs), Special Conservation Areas (SACs) and wetlands of international importance (Ramsar sites). National designations include Sites of Special Scientific Interest (SSSIs) and National Nature reserves. The local designations include local wildlife sites and local conservation areas.
4.4.2 Each designation has its own purpose and objectives and the international and national designations are supported by legislation, in some cases enacting the requirements of European Directives. The new Scottish Planning Policy sets out guidance as to the way in which the Scottish Government’s policies for the conservation and enhancement of Scotland’s natural heritage should be reflected in land use planning.
4.4.3 Natura 2000 is the term applied to SPAs and SACs and these areas receive the highest levels of protection. Development that may have the potential for significant effect on these areas must be examined in detail through a process known as ‘appropriate assessment’. Where the development would affect the integrity of a designated Natura 2000 site, or would affect a priority habitat or species, such development will not normally be permitted unless there are overriding reasons of public interest. Such decisions are made by the Scottish Ministers and can be further referred to the European Commission.
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4.4.4 Nature conservation designations applicable within the study are described briefly below and their locations are shown on Figure 4.2. Appendix A provides more detail of the sites referred to below.
Table 4.1 – Nature Conservation designations in the study area International designations Sites in search area Special Special Areas of Conservation (SACs) are protected sites · Loch of Isbister Areas of designated under the EC Habitats Directive. Article 3 of the · Stromness Heaths and Conservation Habitats Directive requires the establishment of a European Coast (SACs) network of important high-quality conservation sites that will · Loch of Stenness make a significant contribution to conserving the 189 habitat · Caithness and types and 788 species identified in Annexes I and II of the Sutherland Peatlands Directive (as amended). The listed habitat types and species are those considered to be most in need of conservation at a European level (excluding birds). Special Special Protection Areas (SPAs) are protected sites classified in · Marwick Head Protection accordance with Article 4 of the EC Directive on the conservation · North Caithness Cliffs Areas of wild birds (79/409/EEC), also known as the Birds Directive, · Caithness and (SPAs) which came into force in April 1979. They are classified for rare Sutherland Peatlands and vulnerable birds, listed in Annex I of the Birds Directive, and · for regularly occurring migratory species. Wetlands of RAMSAR sites are wetlands of international importance · Caithness and international designated under the Convention on Wetlands of International Sutherland Peatlands importance Importance especially as Waterfowl Habitat (RAMSAR, 1971). (RAMSAR "The Convention's mission is the conservation and wise use of all sites) wetlands through local, regional and national actions and international cooperation, as a contribution towards achieving sustainable development throughout the world" (RAMSAR COP8, 2002). National designations Sites of The nature conservation agencies have a duty under the Wildlife · Marwich Head Special and Countryside Act 1981, as amended, to notify any area of · Loch of Isbister and Scientific land which in their opinion is: “of special interest by reason of any the Loons Interest of its flora, fauna, or geological or physiographical features”. · Loch of Banks (SSSIs) Such areas are known as Sites of Special Scientific Interest · Stromness Heaths and (SSSIs). Coast · Lochs of Harray and Stenness · Ushat Head · Sandside Bay · Red Point Coast · Strathy Coast · East Halladale
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· West Halladale
National National Nature Reserves protect a range of wildlife and · None present Nature landscapes, including many rare species and habitats of Reserves international importance. (NNRs) Local and non-statutory designations Local nature A Local Nature Reserve is a place with a special local natural · None present reserves interest, which is set up both to protect nature, and for people to (LNRs) enjoy and appreciate. There are no local nature reserves within the search area. Sites of The Orkney Local Plan identifies a suite of Local Nature · Orkney has area large Local Nature Conservation Sites These areas are not designated, but are number of local nature Conservation deemed to be of key natural heritage interest on a local basis, reserves, of which a Interest merited by their geological, botanical or ornithological interest. key site within the They were selected by locally-based wildlife experts in tandem study area is Loch of with Local Authority planning officers. Skaill.
Caithness and Sutherland have not yet identified a suite of ‘tertiary’ natural heritage sites through their planning process, but they do have important non-designated habitats and areas which would similarly qualify, if such a system was adopted RSPB RSPB nature reserves are selected because of their birds and · The Loons Reserves other wildlife. There are over 150 RSPB nature reserves to visit throughout the UK. They include visitor attractions with full facilities to quieter sites where facilities are minimal.
Scottish These are areas of land owned and managed by the Scottish · None present Wildlife Trust Wildlife Trust. Some of the land within these reserves is covered (SWT) by other designations. Reserves Local This is a document that has been collated by community · There are action plans Biodiversity representatives of an area to catalogue the biodiversity interests for both Orkney and Action Plan of an area and to set out measures that should maintain or Caithness enhance biodiversity interests in the area.
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4.4.5 All designated sites referred to in table 4.1 have been considered throughout the route and site selection process. Detailed assessment work may be necessary to determine whether the proposed development will have a significant adverse effect on these areas and this will be reported in the environmental appraisal that would accompany applications for consent.
Vegetation cover
4.4.6 Habitats of an area are a key factor in determining the sensitivity of an area to development. Construction of a substation or installation of underground cables has the potential to adversely impact upon vegetation within the immediate area of development.
4.4.7 A large proportion of northeast Caithness and west mainland of Orkney, is either cultivated or under permanent pasture. Natural, or semi-natural, rough grassland is not extensive and is largely confined to the lower and middle hill slopes where topography precludes any widespread improvement. Moorland communities are mainly restricted to the west section of the Caithness search area.
4.4.8 Links and dune communities are relatively common along the coastlines of Orkney and Caithness, the majority being underlain by shelly sand and congregating in the larger bays.
4.4.9 There are no significant areas of woodland or forest in the search areas defined.
Key wildlife
Birds
4.4.10 The diversity of habitats which make up the Orkney and Caithness landscapes (moorland, coastal and maritime heath, sea cliffs, loch and marsh, saltmarsh, farmland, wet grassland, wetland, wood/scrub and sheltered sea), provide important breeding and foraging areas for a diverse variety of birds throughout the year and provide cover for many thousands of migratory birds, especially in Orkney. The designated sites provide protection for a number of birds breeding in high concentrations, for example seabird colonies on sea cliffs and inland (for example Arctic terns and Great skuas). They also seek to protect rare, scarce or vulnerable species breeding in lower densities, for example nationally important numbers of Black-throated and Red-throated divers on lochans, raptors and Short-eared owls on moorland, and declining wetland waders.
4.4.11 Many areas outwith designated sites in Orkney and Caithness are very important for breeding, wintering and passage species. In winter, the key habitats for tens of thousands of waders and wildfowl are the lochs and low-lying coastal areas, but
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farmland also supports very large numbers of waders and wildfowl including tens of thousands of geese and waders (for example, Orkney holds 20% of the UK’s wintering Curlew population) and lesser numbers of, for example, Whooper swan and grazing ducks, such as Wigeon.
4.4.12 Many of the habitats in the study area are also very important for migrating birds. The area provides a staging post for passage migrants to/from Greenland, Iceland, Norway, Russia; and their more southerly wintering areas. The area is also renowned for drift migrants, blown off course from their more normal routes.
Mammals
4.4.13 In Orkney, the Orkney Vole is endemic and provides an important food source for Hen harrier and Short-eared owls. Although the vole populations are declining due to habitat loss through agricultural improvement, those which remain are thought to be of reasonably high density despite other pressures such as predation by feral cats.
4.4.14 Otters are more common as an inland species in Caithness, whereas in Orkney, they are most commonly associated with the coast. Although they are rarely seen it is considered that all available territories along the Orkney coast are occupied by Otters.
4.4.15 Brown Hares are particularly prolific across Orkney. The Badger is not found in Orkney but does occur within the Caithness search area. Several species of Bat are found in Caithness and there are two or three populations of Pipistrelle bat in Orkney. In Caithness, the Water vole is a particularly important species, and is prolific along many of the watercourses.
4.4.16 Four species of deer, Red, Roe, Fallow and Sika; Red squirrel and Pine martin have all been recorded in Caithness. Whether these populations are established in the study area will be determined later in the EIA process.
Amphibians and Reptiles
4.4.17 Both Common frog and Common toad breed in Caithness and Orkney. In Orkney, the former is an expanding, introduced species, whereas the latter is a declining, native species. Palmate newts, Slow worms, Viviparous lizards and the Adder snake all occur in Caithness; but in Orkney, despite several introductions, none of these species have become established.
Fish
4.4.18 Three important fish species in the study area are Salmon in Caithness and Trout and Sea trout in Orkney. All support very active fisheries in each region. Trout
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fishing is particularly prevalent of the lochs within Orkney where the local Trout Fishing Association manages an extensive stocking programme.
4.4.19 The consideration of key wildlife species, their sensitivity and the likely impact on these from the proposed operations has formed a critical part of the assessment of all aspects of the project leading to a preferred overall option.
4.5 Human environment
Agriculture, land use and recreation
4.5.1 Land use is an indicator of a number of features all of which have the potential to affect the feasibility of the proposed connection.
Agriculture
4.5.2 The classification is based on the potential productivity, cropping flexibility and ease of management of an area. Factors taken into account in the production of this information include the physical attributes of an area, such as soil, topography, climate, erosion, vegetation, gradient and wetness limitations; together with human resources such as finance and labour management, as well as political considerations.
4.5.3 In the study area for Orkney and Caithness there are few crofts and most farming is restricted to relatively small, owner-occupied farms. Grassland and rough grazing dominate agricultural land use in Orkney and the eastern section of the Caithness search area, whilst rough grazing/moorland dominate significant section of the western section of the Caithness study area.
Recreation and tourism
4.5.4 The scenery, coastline, history and wildlife of the north of Scotland and Orkney are major features in attracting tourists to the area. Much of the recreation, however, tends to be on an informal basis with little infrastructure to support it. There are however key tourist recreation sites within the search area in Orkney and these centre around the wealth of cultural heritage features present, including the UNESCO World Heritage Site. All of these sites are discussed further below.
4.5.5 Seasonal game shooting and fishing is popular in both Orkney and Caithness and can contribute substantially towards the revenue of an estate or land holding. Much of the upland areas and river systems are used in this way. In relation to the search
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areas in both Orkney and Caithness, fishing for salmon and trout is the most likely sporting activity likely to have interaction with the proposals for this connection.
4.5.6 Coastal walks are popular in the Caithness and Orkney search areas predominantly due to the scenic coastlines. There are a number of core paths that traverse the Orkney coastline with associated connecting paths that run inland from the coast. Caithness has a number of core paths and those identified on the wider access network. These are most common along the coast of Caithness but also centre around the inland valleys leading from Sandside Bay.
4.5.7 Temporary impacts on recreation and tourism may occur during the construction phase of the project with any permanent impact coming from the siting and visibility of the substation on Orkney. This has been fully considered in the options assessment described in section 3.
Archaeology and Cultural Heritage
4.5.8 Orkney and Caithness are renowned for their archaeological and cultural heritage. Any disturbance to sites of archaeological and cultural importance has the potential to harm the quality and the significance of these sites. Special care will need to be taken during the detailed route and site planning process and especially during construction to avoid impacts to known and as yet undiscovered sites.
4.5.9 The distribution of historical sites is shown in Figure 4.7. Further details on the main designation categories are provided below.
Archaeological, historical and cultural designations
World Heritage Sites
4.5.10 “The Heart of Neolithic Orkney” was designated as one of UNESCO’s World Heritage Sites in 1999, the fourth in Scotland. The site covers the area of the West Mainland parish of Stenness surrounding the Ring o’ Brodgar, as well as the village of Skara Brae in the neighbouring parish of Sandwick.
4.5.11 The designation includes the area’s major sites such as Maeshowe, the Ring o’ Brodgar and the Stones of Stenness and also the less well-known sites in the area that include the Watch Stone, the Barnhouse Stone and the Barnhouse Settlement. The World Heritage Site designation also protects unexcavated sites that within the viscinity.
4.5.12 The World Heritage Site buffer zone and Skara Brae is located within the search area for Orkney and as such, significant care must be taken when routeing the cables and choosing the substation site.
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4.5.13 There are currently no World Heritage Sites in Caithness or Sutherland.
Scheduled Ancient Monuments
4.5.14 Scheduled Ancient Monuments (SAMs) are designated under the Ancient Monuments and Archaeological Areas Act 1979. These are archaeological sites of national or international importance and SPP states that the purpose of scheduling is to “secure the long term legal protection of the monument in the national interest, in- situ and as far as possible in its existing state and within an appropriate setting” (para 118). Scheduled Monument Consent is required from the Scottish Ministers, through Historic Scotland, for any development affecting the physical fabric of a scheduled monument.
4.5.15 There are numerous SAMs within the Orkney search areas, all of which are important to consider when routeing the underground cable and identifying the substation site and many of which relate directly and indirectly to the World Heritage Site designation. All of these sites should be avoided but careful consideration will also need to be made in relation to setting for these sites for the substation.
4.5.16 There are slightly fewer Scheduled Ancient Monuments in the Caithness search area, the most important in terms of routeing considerations are the Hallidale Bridge Hut Circles to the south of Melvich Bay and the St Mary’s chapel and broch at Crosskirk Bay. Any impact on the SAMs in the Caithness search area will be temporary as the cable will be installed underground.
Non-scheduled sites of national importance
4.5.17 Not all archaeological sites of national importance are scheduled. Highland Council maintains a non-statutory register (NSR) of sites it considers to be of schedulable quality and this is considered in the routeing of the underground cables in Caithness. Such sites should be considered as if they are scheduled..
Listed Buildings
4.5.18 The term ‘building’ is broadly defined and can include other built structures such as monuments and bridges. Buildings of special architectural or historic merit are protected under the Planning (Listed Buildings and Conservation Areas) Act 1997 and are divided into three categories: A, B and C(s) listings. In determining an application for development affecting a listed building or its setting, the planning authority is required to have special regard to the desirability of preserving the building, or its setting, or any features of special architectural or historic merit that it possesses.
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4.5.19 There are 34 Category A buildings in the search area: 18 in Orkney, 15 in Caithness and one in Sutherland.
Gardens and Designed Landscapes
4.5.20 Historic Scotland define ‘Gardens and Designed Landscapes’ as “grounds that are consciously laid out for artistic effect and most often contain architectural features, trees, shrubs, flowers, water features, lawns, woodland and parkland” (www.historic- scotland.gov.uk). There is only one Garden/Designed Landscape in the search area and this is Skaill House, by Bay of Skaill in the Orkney search area.
Conservation Areas
4.5.21 Conservation Areas, including their setting, are protected under Part II of the Planning (Listed Buildings and Conservation Areas) (Scotland) Act 1997, in order to preserve or enhance their special architectural character or historic interest.
4.5.22 There are no consultation areas within the search area.
Other sites of cultural heritage interest in the study area
4.5.23 Highland Council’s Historic Environment Record (HER) and the National Monuments Record of Scotland (NMRS) contain information about numerous other cultural heritage assets that have no statutory designation and are not considered to be of national importance. SPP states that significant assets should be preserved where feasible. Where such preservation is not feasible, preservation by record is likely to be necessary.
4.5.24 There are numerous assets of regional or lesser importance in the study area and these are focused around the key bays in the search area. They are not however just limited to these areas and are distributed throughout.
Landscape character
Introduction
4.5.25 Landscape character can be defined as “a distinct and recognisable pattern of elements that occur consistently in a particular type of landscape”. Character is the result of particular combinations of geology, landform, soils, vegetation, land use, field patterns, human settlement and other activities, making each part of the landscape distinct and creating a sense of place.
4.5.26 For this project underground cable routeing is not considered to be significantly constraint by the landscape character of an area following construction, other than in respect of the potential for removal of, and changes to, the vegetation cover over the
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area of the cable trenches, which could have the potential to alter the landscape character at a local level.
4.5.27 The search areas are covered by SNH’s `Orkney Landscape Character Assessment’ and the `Caithness and Sutherland Landscape Character Assessment’ (LCAs). Within the search areas, there are 10 different landscape character types defined..
Orkney
4.5.28 Orkney has predominantly low and gentle relief, with smooth contours. The land forms a series of low-lying bowls surrounded by higher ridges. The wide vistas that such terrain creates provide long views across the land from many viewpoints and where the viewing position is elevated panoramic views arise. There are a few more enclosed valleys on the Mainland but these are not extensive. The roads network reaches many high points in the Orkney terrain and short walks reach even more. Generally therefore Orkney has a topography that creates high visibility.
4.5.29 The distribution of landscape character types in Orkney is shown in Figure 4.4. A comprehensive guide to each of these landscape character types is given in the Orkney Landscape Character Assessment published by SNH in 1998 in which key sensitivities are described and guidelines for the protection and enhancement of each landscape character type are detailed.
4.5.30 The key landscape character classifications for the Orkney search area are Loch basins, Coastal hills and Heaths, Cliff landscapes, Enclosed bay landscapes and Coastal basins. The majority of the search area consists of Coastal hills and heath character type but there are sections along the coastline of Cliff landscape, Enclosed bay landscapes and Coastal Basin types. Towards the east of the search area, the predominant character type is Loch basins.
Caithness and Sutherland
4.5.31 Eastern Caithness is in some ways similar to Orkney but the relief is somewhat flatter and less organised into ridges and bowls. This means that although there are particular places with long views the frequency and duration of such views when travelling around Caithness is less. Any high points within eastern Caithness are particularly prominent from a number of directions leading to very high visibility. The lower lying land is however much less visible since the roads network and the pattern of dwellings tends to avoid many of the higher places.
4.5.32 Western Caithness is much more undulating and views tend therefore to be more segmented with a long distance vista in a particular direction but much shorter view in another direction. The vertical relief means that roads and dwellings are often
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elevated to some extent. Visibility is generally less extensive than in eastern Caithness than in Orkney.
4.5.33 The distribution of landscape character types in Caithness is shown in Figure 4.4. A comprehensive guide to each of these landscape character types is provided in the Caithness and Sutherland Landscape Character Assessment published by SNH in 1998 and key sensitivities are described and guidelines for the protection and enhancement of each landscape character type are detailed.
4.5.34 The key landscape character types identified in the Caithness search area are Sweeping moorland, High cliffs and sheltered bays, Strath, Long beaches, Open/intensive farmland and mixed agriculture/settlement. Sweeping moorland characterises the majority of the western section of the search area whilst the eastern section is split north to south with Open/intensive farmland and mixed agriculture and settlement respectively.
4.5.35 The routeing of the proposed connection and location of the substation will have regard for the different characteristics of the various landscape character types and this will be considered further at the detailed assessment stage of the project.
Landscape designations
4.5.36 The various landscape designations across the study area are presented in Figure 4.4.
National designations
4.5.37 National Scenic Areas (NSAs) are Scotland’s only national landscape designation enacted under Section 6 of the Natural Heritage (Scotland) Act. They are those areas of land considered of national significance on the basis of their outstanding scenic interest which must be conserved as part of the country’s natural heritage. They have been selected for their characteristic features of scenery, comprising a mixture of richly diverse landscapes, including prominent landforms, coastline, sea, freshwater lochs, rivers, woodlands and moorlands.
4.5.38 Orkney has one National Scenic Area; which falls within the search area. This is an area of 15,000 hectares covering the north end of Hoy, Hoy Sound and the southern West of mainland Orkney. This encroaches into the southern section of the search area and will need to be fully considered, particularly in the selection of a site for the proposed substation.
4.5.39 There are no NSAs in the Caithness search area.
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Local designations
4.5.40 The local landscape designations recognised in the Caithness and Sutherland Local Plans are now identified as Special Landscape Areas (SLAs) and these recognise areas of regional or local landscape importance. The one SLA within the study area is Farr Bay, Strathy and Portskerra although it is unlikely that this will be directly effected as this is on the very western side of the search area and the installation in this area will be underground cable.
4.5.41 Within Orkney there are Local landscape areas identified with the purpose of safeguarding important and locally valued landscapes There are two such areas within the Orkney search area; Bay of Skaill, Sandwick; and Birsay. Consideration of these local landscape areas has assessed, specifically in relation to the proposed substation site assessment. It is predicted that underground cabling is likely to have limited impacts on these area.
4.6 Key elements of the marine enviroment
4.6.1 The following section details the key features of the marine physical, biological and socio-economic environment, that have the potential to be affected by the proposed operations. This baseline information will inform the preferred route selection process by providing the basis for the consideration of environmental, technical and economic viability of the routes.
4.6.2 A search area for possible subsea cable routes was identified early on in the project development and this can be seen in figure 3.1.
4.7 Marine physical environment
4.7.1 The marine physical environment can present limitations for potential routeing options. For example, it is preferable to route cables over regular terrain, where there is no tendency for the cable to ‘free-span’ over deep troughs or irregular high points, in order to minimise stress on the cable.
4.7.2 It is also important to consider the physical marine environment in relation to the operability of the project. For example, laying a subsea cable in swiftly flowing tides may be very difficult or impossible.
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Geology
Offshore geology
4.7.3 The Orkney Islands and inshore waters are underlain by the Shetland platform, which is composed largely of Devonian rocks. These rocks consist of sandstones, flagstones, conglomerates and shales that are comparable to rock sequences found onshore. Offshore, most solid geology is concealed by seabed sediments, but rock outcrops do occur in tide-swept sounds and in shallow water along exposed coasts.
4.7.4 There are bedrock exposures in the study area within the Pentland Firth; off the West coast of Hoy; to the west of Stromness.
Offshore seabed sediment
4.7.5 The type and the depth of sediment overburden are important factors in determining subsea cable routeing and the potential for burial or other forms of protection. Existing bathymetry data has been analysed to provide and indication of the likely makeup of the sediment in the search area. This is presented in figure 4.1 along with baseline information on sediment types from the British Geological Society.
4.7.6 Sediments stretching from the north Caithness coast to the west of the Pentland Firth bedrock platform are predominantly a combination of gravel and sand. There are some dispersed areas of finer more sandy sediments towards the western boundaries of the search area where depths increase and tidal currents decrease. Given the high level of wave exposure, sediments down to at least 100 m can be considered mobile to some extent, under storm conditions, and many areas show sand ripples on the surface as manifestations of this dynamism.
4.7.7 In the northern section of the search area, there are numerous veins of bedrock exposure running north to south. These bedrock areas may have pockets of sediment overlying the rock in hollows or can also be covered by a thin veneer of mobile coarse sediments. The southern section of the search area is dominated by textured sediment and areas of sediment veneer overlying bedrock.
Coastal geology
4.7.8 Orkney’s coastline is dominated by cliffs, rocky shores and sandy bays and inlets. The majority of inshore waters are shallow with most areas of seabed consisting of gently sloping shelves. Very few sites have deep waters adjacent to the coast. Shores in Orkney are largely composed of bedrock or boulders, with sand in the bays. Beaches have clean sediment with a low organic content, as streams in Orkney are small and carry a low burden of sediment to the sea.
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4.7.9 The Caithness coastline is dominated by tall, impressive maritime cliffs and slopes dissected by stony bays and geos (deep incisions at right angles to the cliffs where the sea has excavated along the line of a fault). Rock stacks are prominent although none are present in the defined search area. There are occasional sandy bays which tend to be large or very large and these have been identified in previous sections of the document.
Hydrography
Bathymetry
4.7.10 Bathymetric data shows water depths and is recorded using multibeam sonar. As the resolution of the bathymetry increases, distinct patterns can be seen and good quality bathymetry can be used to translate the submarine ‘terrain’ of an area. This is important because a number of underwater features can influence the suitability of a marine cable route. Generally cable installation is best achieved over flat, gently sloping seabed, where any unusual topographical features such as rock outcrops, relict channels, etc, can be avoided.
4.7.11 The bathymetry within the study area has only been coarsely determined and has been built up from a series of surveys. The surveys conducted in the study area range in date from the 1980s in the south to the late 2000s to the west of Orkney. The later data sets provide a greater detail of resolution with these data sets at 10m res and those towards Caithness at 50m res.
4.7.12 The western Atlantic waters are typically 60-90 m deep offshore and provide a relatively smooth sea bed. More detailed survey data from nearby areas around Orkney suggests that there are likely to be sporadic rocky outcrops but that otherwise the seabed is rather featureless.
4.7.13 The Pentland Firth is essentially a flat shelf of bedrock sitting at approximately 60- 70m deep. The shelf falls away towards the west of the search area, averaging approximately 80-90m deep but with deep holes reaching over 100 m.
4.7.14 Coastal rock debris and bedrock exposures can be expected from depths less than 50 m on the west coast and 30 m on the east coast. Except in sandy bays, this rock and bedrock then continues to shallow towards the shoreline. Coastal faults, promontories, intrusions and caves can be expected to continue underwater in these nearshore zones.
Seabed obstructions
4.7.15 The key seabed obstructions or hazards in the search area are power and communication cables. There are currently two electricity cables that connect Murkle
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Bay to Hoy and two telecommunication cables connecting Caithness to mainland Orkney and the Faroe Islands respectively. These are shown on figure 4.5 and discussed further below.
4.7.16 Archaeologically designated wrecks are discussed in section 4.9.2.
Tidal Currents and circulation
4.7.17 Water movements around Orkney and Caithness are dominated by tidally induced currents. Orkney lies between two separate tidal systems that are out of phase with each other, and this leads to the strong tidal flows through the Pentland Firth and other tidal sounds.
4.7.18 The Pentland Firth is the largest tidal stream in the study area. Charted tidal currents reportedly flow at up to 12 knots (6 m/s) along the south west flank of the Sandy Riddle. Anecdotal evidence suggests that even stronger tides can occur. Through the rest of the Firth, tidal streams of 8 knots are not uncommon.
4.7.19 In relation to the study area, the tides are strongest toward the east, within the Penland Firth. The strength of these tides reduces towards the west of the search area. It is not anticipated that the tides within the search area itself will provide undue constraints on the laying of the subsea cable.
4.8 Marine biological environment
4.8.1 The marine biological environment can present limitations for potential routeing options. Designated sites, locations of protected habitats and known breeding or feeding grounds in the vicinity of, or within a potential route, may impose constraints to the subsea cable installation, or may require an alteration to the route. Wherever possible, all ecologically sensitive marine areas have been avoided during the preferred route selection process.
Plankton
4.8.2 Plankton in the search area is typical of temperate continental shelf seas. The phytoplankton assemblage is dominated by diatoms and dinoflagellates, and the zooplankton, although containing representatives of most marine animal phyla at some stage, is dominated by crustaceans, principally copepods (Barne et al, 1997). Plankton should not be affected significantly by the construction or operation of the proposed cables.
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Seabed communities
4.8.3 Seabed communities are generally determined by the type of seabed and the current speed. The variety of seabed communities present in the area reflects the extreme conditions they are subject to. Much of the area therefore holds seabed communities that are adapted to dynamic seabed conditions. Typically in shallow waters, down to 30 m, with a rocky seabed, kelp forest communities are well developed. These are particularly extensive around Orkney where the shallow coastal rock platform tends to be wider than around Caithness.
4.8.4 In deeper rock areas, faunal rather than seaweed-dominated turf develops. These areas can be dominated by sea urchins in sheltered areas; brittle star beds or dead mans fingers in more tide-swept sounds; and bryozoan turfs in more wave-exposed areas.
4.8.5 Sea life communities in sedimentary areas tend to be more faunal dominated and are characterised by the sediment type.
4.8.6 In muddier areas such as Scapa Flow, communities are dominated by brittle stars, bivalves and worms, or by sea pens. In coarser sediment areas, bivalve dominated communities are most prevalent. These latter sand-based communities are more robust to disturbance than those in muddier sediments.
4.8.7 Special biogenic communities develop where conditions are suitable. Maerl beds arise from the growth of calcareous algae which forms a loose coral like structure. It needs good light and some water currents to develop. The clarity of the waters in the area mean that they can be found deeper here than in other areas. There are also accumulations of dead maerl in deeper waters that still have many of the species that are associated with live maerl beds.
4.8.8 Horse mussels are found in deeper water areas or where water clarity is diminished, but where there are good water currents. In such areas, the accumulation of life and dead shells creates an open matrix that has a rich, associated fauna.
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Intertidal communities
4.8.9 The cables will cross shorelines only briefly at each landfall, but there are certain types of intertidal habitat that may be sensitive to such disturbance. Should horizontal directional drilling be chosen as a preferred landfall it is likely that the reach of the drill will extend beyond the intertidal zone and therefore no impact would occur.
4.8.10 Should the landfall location be chosen using open cut methodologies it is likely that this would be situated in sandy bays rather than over rocky coasts or on more sheltered muddy inlets. Sandy bays are generally more dynamic environments with little particular conservation value. The extent of disturbance in a larger embayment will also generally be rather small and recovery can therefore be expected to be rapid. There are some plants that thrive at the top of the shore in sandy bays and some of the prospective landfall sites are colonised by such species. They include the Oysterplant, Alpine meadow rue and Sand sedge.
4.8.11 The most sensitive intertidal areas are likely to be more sheltered areas with muddy sediments and perhaps areas of saltmarsh. Such habitats are scarce in Orkney and Caithness, but in major bays for example, there may be more sensitive habitats near to the outflow of any streams. Any landfalls should therefore avoid such areas if possible.
Fish
4.8.12 The fish species assemblage around Orkney, the Pentland Firth and the north coast of Scotland, is typical of northern temperate waters. Common species include:
Mackerel Whiting Pollack Herring Haddock Saithe Cod Ling
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4.8.13 It is anticipated that apart from some temporary localised avoidance of marine works, the proposed connection will have no effect on fish species present in the waters of the search area. All of the anticipated marine operations are common activities and will be minimal in duration.
Shellfish
4.8.14 There are exploitable populations of lobster, edible crab, velvet crab and squat lobsters in significant parts of the search area. This is discussed further in section 4.9 below.
Cetaceans
4.8.15 Cetaceans are sensitive to disturbance from vessel activity and underwater noise. Prolonged activity and noise generation can result in indefinite loss of species to a region through direct avoidance.
4.8.16 All cetacean species (whales, dolphins and porpoise) are listed in Annex IV of the EC Habitats Directive, which recognises them as “animal….species of community interest in need of strict protection”. The directive prohibits all forms of deliberate disturbance of these species, particularly during the period of breeding, rearing, hibernation and migration. Cetaceans are also protected under the Wildlife and Countryside Act (1981).
4.8.17 Waters within the search area are relatively rich in cetacean species. Species most commonly observed within the search area are listed in 4.8.18 along with their current status and distribution patterns.
4.8.18 Cetaceans observed within the search area
Common SPECIES STATUS AND DISTRIBUTION name · WIDELY DISTRIBUTED AND COMMON THROUGHOUT ORKNEY WATERS (THE ONLY SPECIES REGULARLY PRESENT IN SCAPA FLOW AND GAIRSAY SOUND) · FAIRLY COMMON IN NEARSHORE HARBOUR PHOCOENA WATERS OF PENTLAND FIRTH PORPOISE PHOCOENA (SCAPA FLOW, DUNNET HEAD, DUNCANSBY AND THE PENTLAND FIRTH) · HIGHEST NUMBERS JULY- OCTOBER · NUMBERS HAVE INCREASED IN RECENT YEARS COMMON DELPHINUS DELPHIS · MOST COMMONLY SIGHTED JULY-
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DOLPHIN OCTOBER IN PENTLAND FIRTH AND OFF SOUTH RONALDSAY · MOST COMMON BALEEN WHALE IN THE SEARCH AREA (WEST COAST OF ORKNEY, SCAPA FLOW AND MINKE BALAENOPTERA PENTLAND FIRTH) · MOST COMMONLY SIGHTED JUNE- WHALE ACUTOROSTRATA OCTOBER; PREDOMINANTLY IN AUGUST · MAY BE RESIDENT ALL YEAR ROUND · USUALLY SIGHTED IN HERDS OF 2- WHITE- 20 LAGENORHYNCHUS BEAKED · MOST COMMONLY SIGHTED JUNE- ALBIROSTRIS SEPTEMBER DOLPHIN · LARGE PERCENTAGE IN THE PENTLAND FIRTH WHITE- · HAS BECOME LESS FREQUENT IN LAGENORHYNCHUS SIDED RECENT YEARS ACUTUS · MOST COMMONLY SIGHTED DOLPHIN MARCH-NOVEMBER · STEADY INCREASE IN NUMBERS OVER RECENT YEARS (MOST KILLER LIKELY RESULTING FROM ORCINUS ORCA INCREASING SEAL POPULATIONS) WHALE · MOST COMMONLY SIGHTED MAY- OCTOBER; REGULARLY IN THE PENTLAND FIRTH LONG- · INFREQUENTLY OBSERVED IN NEARSHORE WATERS; NO FINNED GLOBICEPHALA INDICATION OF PREFERRED PILOT MELAS AREAS WHALE · MOST COMMONLY SIGHTED MAY- AUGUST · MOST COMMON DOLPHIN IN THE PENTLAND FIRTH AREA (AND OFF RISSO’S THE CAITHNESS COAST) GRAMPUS GRISEUS · GROUPS OF 2-6 COMMONLY SEEN DOLPHIN · MOST COMMONLY SIGHTED JULY- OCTOBER (ALSO DECEMBER TO JANUARY) SOURCE: (RGU AND ICIT, 1997)
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Seals
4.8.19 Two species of seal are common within the search area; the common (harbour) seal (Phoca vitulina) and the grey seal (Halichoerus grypus). Both species are particularly common in Orkney and are widely distributed around the coasts.
4.8.20 Both common and grey seals are listed in Annex II of the European Habitats Directive as “animal….species of community interest whose conservation requires the designation of Special Areas of Conservation”. However, no designated sites exist within the search area with seals noted as a qualifying feature.
4.8.21 Important haul-out and breeding sites will be avoided during the preferred route selection process as there are none of importance within the search area.
Seabirds
4.8.22 Orkney is especially important for cliff and island-nesting seabirds, several species occurring in internationally important numbers. The offshore feeding areas associated with breeding seabird colonies are equally important. However, in favourable weather and foraging conditions, most feeding occurs comparatively close inshore.
4.8.23 This region is also one of the most important sea areas for seabirds, outside the breeding season, in Europe. Species such as, gannets, fulmar petrels and gulls feed year round in the rich waters around Orkney and Caithness. In particular, the tidal streams concentrate fish, where turbulence brings more food items to the surface.
4.8.24 Coastal habitats such as sandy and shingle shores provide important breeding habitat for several species of waders and terns.Tens of thousands of waders arrive from their summer breeding grounds in the Arctic, to over-winter in Orkney. The key habitats for over-wintering wader and waterfowl species are the lochs and the rocky and sandy shoreline.
4.9 Human marine environment
4.9.1 There are two main mechanisms of impact between the proposed project and the human environment within the search area. The first is the temporary presence of cable lay and support vessels during cable lay, and the second is the permanent presence of the cable on the seabed.
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Marine archaeology
4.9.2 Marine archaeology includes drowned settlements and charted wrecks. There are no designated War Graves, Scheduled Ancient Monuments or designated wrecks within the search area but there are a number of known wrecks that should be avoided. These are detailed in figure 4.5 .
Commercial fishing
4.9.3 Fishing makes a significant contribution to the culture and economy of both Caithness and Orkney. The number of fishing vessels in Orkney decreased by 6.5%, to 160, between 2002 and 2008. Whitefish landings in Scrabster have also increased significantly over the last few years with 357,300 boxes landed in 2009/10 compared with 301,844 in 2008/09.
4.9.4 Creel fishers operate routinely in the area. Shellfish species targeted by creelers in the area include:
· LOBSTER (HOMARUS GAMMARUS) · BROWN (EDIBLE) CRAB (CANCER PAGARUS) · VELVET CRAB (NECORA PUBER) · WHELKS (BUCCINUM UNDATUM)
4.9.5 Creeling essentially occurs around the majority of Orkney’s coastline and focuses primarily on these species.
4.9.6 Scallops are dredged and had dived in the western Pentland Firth and surrounding waters. The fast-flowing channel generally restricts the development and fishing effort of both demersal and pelagic fish species (RGU and ICIT, 2001).
4.9.7 Commercial fishing vessels may have to avoid certain areas during cable lay, depending on the route selected. It should also be noted that dredging would not necessarily be restricted by the presence of a new cable on the seabed providing adequate burial could be achieved.
Shipping
Commercial shipping
4.9.8 The waters between Orkney and Caithness are used heavily by the shipping industry with the Pentland Firth forming part of the Northern Maritime Corridor. A variety of vessel types pass through the search areas including:
· BULK CARRIERS · STANDBY VESSELS · CARGO VESSELS · SUPPLY VESSELS · FERRIES · CHEMICAL TANKERS
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· LPG/LNG · OIL TANKERS TANKERS · SHUTTLE TANKERS · RO-RO VESSELS · CRUISE LINERS
4.9.9 All cable laying activities will be completed within a short time-frame. Therefore, any disturbance to commercial shipping routes resulting from vessel presence and exclusion zones for operations will be temporary. All operations and exclusion zones would be communicated to vessels through the Notice to Mariners system.
Passenger ferries
4.9.10 Ferries provide commuter and lifeline services between the Orkney Isles, and between the Orkney Mainland and the Scottish Mainland. Therefore, any activity that impinges on these services has the potential to impact upon the operating company and the potential hauliers, tourists, commuters and other passengers.
4.9.11 The only passenger ferry operating within or in close proximity to the search area is the Northlink ferry service connecting Stromness to Scrabster.
4.9.12 Ferries passing through the area may have to alter their routes for the duration of the cable lay depending on the final route selected. Discussions would be held with the operators and the proposed works communicated to the vessels through the Notice to Mariners system, thereby avoiding any navigational issues.
Cruise liners
4.9.13 A large number of Orkney’s tourists are passengers taking daytrips from visiting cruise ships. The industry provides Orkney’s economy with essential income. Is is estimated that up to seventy ship per year berth in Orkne. It is not anticipated that the proposed connection will affect the activity of cruise liners visiting the region.
Recreation and tourism
4.9.14 Both recreation and tourism in the area rely heavily on the marine environment. It is therefore important to identify any activities which may be affected by the proposed connection.
4.9.15 A number of sailing clubs are well established throughout the search area. These clubs have annual regattas and other regular sailing events throughout the year. The area is also popular with visiting yachts. Two marinas have been constructed in or in close proximity to the search area. These are situated at Scrabster and Stromness.
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Water sports
4.9.16 The key water sport activities within the area are likely to include sailing, kayaking, surfing and windsurfing.
· WINDSURFING · CANOEING · JET SKIING · KAYAKING · SAILING · WATER KITING 4.9.17 There are a number of areas along the north coast of Caithness that are popular with surfers and the Bay of Skaill in Orkney is also a popular surfing destination.
4.9.18 As the majority of activities are restricted to the surface of the sea, and are largely located in sheltered waters, there is likely to be little interaction with the proposed connection activities. Any potential interaction would be carefully planned to mitigate any impacts. A number of landfall sites will be located on local shorelines. The visual impact of these will, where possible, be limited.
Marine Infrastructure and Energy
Marine energy
4.9.19 The Crown Estate has leased a number of areas to Developers for the generation of tidal and wave energy. There are three leased areas that fall within the search area and a route will have to be chosen that limits any adverse impact on the ability of these areas to generate renewable energy.
4.9.20 There is also a test site off the west coast of mainland Orkney that lies within the search area and was set up by the European Marine Energy Centre (EMEC) (within the search area), for testing wave energy conversion technologies. This may also be extended in the near future. Locations of the leased areas and the test site area identified in figure 4.5.
Electricity grid
4.9.21 The 33kV grid crosses the Pentland Firth from Murkle Bay in Caithness to Rackwick Bay in Hoy, consisting of two separate cables that follow a similar routeing to each other. These provide a connection to Orkney from the mainland grid and are not buried.
4.9.22 In addition to these grid-related cables, there are four subsea cables extending some 2 km from shore at the EMEC wave energy test centre. These are detailed on figure 4.5.
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Communications cables
4.9.23 There are two telecommunication cables located within the search area. One connects Dunnet Bay to Bay of Skaill on Orkney and was laid in 2008. The other connects Dunnet Bay to the Faeroe Islands. This became operational in 2004. These are detailed in figure 4.5.
Pipelines and outfalls
4.9.24 In Caithness there are a number of short outfalls connected to the Dounreay nuclear facility and a sewer outfall pipe is known to be present to the east of Sandside Bay.
Hazardous areas
Contaminated sites
4.9.25 Routine monitoring around the Dounreay site has indicated that there are a significant number of irradiated particles emanating from an outfall off the coast at Dounreay. The distribution of these particles has been mapped over the seabed and they have also been found on the beach at Sandside and to a lesser extent at other beaches along the north Caithness coast. Discussions have been held with Dounreay Site Restoration Ltd and up to date information of the distribution of offshore particles finds have been used in the route selection process.
Aggregate extraction and sea disposal sites
4.9.26 There are no aggregate extraction sites within the defined search area.
4.9.27 There is one sea disposal site that strays into the eastern edge of the search area. This is the Stromness A disposal site and is currently open. Sea disposal sites are designated purely for the disposal of dredged material from ports, harbours and marinas. This activity is essential to maintain navigation in ports and harbours as well as for the development of new port facilities. Dredged material is assessed for contaminants before disposal to reduce environmental impacts.
4.9.28 In general, dredged material with contaminant levels below a certain threshold can be disposed of at sea. Above this, but below a higher threshold, may require further consideration and testing before a decision can be made, whilst above the higher threshold there is a presumption against disposal at sea.
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5 DETAILED SUBSTATION SITE, LANDFALL SITE, UNDERGROUND CABLE ROUTE AND SUBSEA CABLE ROUTE STUDIES
5.1 Introduction
5.1.1 This section provides information on the detailed studies undertaken for the substation site, landfall site, underground cable route and subsea cable route selection process. The methodologies used in the studies that inform the discussion in this section are identified in section 3 of this report. An overview of the baseline environmental character of the search areas is provided in section 4.
5.2 Substation site selection study
Generally
5.2.1 Initially, the search area was assessed for parcels of land that were suitable for the construction of a substation from an engineering and connectivity perspective. These areas were then visited in order to ‘ground truth’ the desk based assessment.
5.2.2 This provided eight possible substation sites within the limits of the search area and these were discussed with statutory authorities and key consultees to identify which sites should not be considered further. Four sites were selected, in consultation with the statutory authorities and key consultees, to be taken forward for detailed assessment and these sites formed part of the substation site selection study.
5.2.3 The eight initial substation site options and the four identified for further assessment, following the statutory authority and key consultees consultations.
5.2.4 The four sites taken forward for detailed assessment are as follows:
· Site B - Loons West
· Site D - Vestafiold North
· Site E - Vestrafiold South
· Site F – Sands Fiold
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Substation site options
Site B
5.2.5 Site B is located 550m east of the B9056 between Loons Road 350m to the south and Ravie Hill Road to 250m to the north and can be seen in figure 5.1. This site is approximately 1.5km east-northeast of the coast at Mar Wick; 2km west of Twatt; and, 30km northwest of Kirkwall.
5.2.6 From an environmental perspective, a key concern is the close proximity to the loch of Isbister, which is designated as an SAC, SSSI and RSPB nature reserve. There is direct connectivity between site B and the Loch of Isbister through an un-named watercourse that currently flows through the proposed site and there is a concern that construction operations could impact on this burn and as a result the Loch of Isbister. The loch is also designated for ornithological reasons and consideration of the construction activities and construction noise were considered of moderate concern.
5.2.7 As this site is placed in an elevated position above the loch basin, there is the potential for adverse impact from both a landscape and visual impact perspective. There are also a number of scheduled ancient monuments and the setting of these may be impacted on as a result of the development.
5.2.8 In relation to the operational and technical effects, site B performed relatively well for construction and operations although the long cable distance to the landfall point was identified as being of particular note.
5.2.9 This substation was viewed as being the most expensive site to develop, specifically when taking into account the larger underground and subsea cable requirement due to its geographical location on Orkney.
Site D
5.2.10 Site D is located 1km east of Vestrafiold and 27km northwest of Kirkwall as can be seen on figure 5.1. A farm track runs eastward from the southern boundary of the site to the B9056. The site is located 550m inland from Outshore Point.
5.2.11 From an environmental perspective, site D performed relatively well in the majority of topics used to compare the sites but there was one key significant concerns with the development of this site. As the site is located on a steep incline from the coast, there would be a significant excavation required on the topside of the site, with an equivalent requirement to build the land up on the lower side, to create a level platform on which to build the substation.
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5.2.12 The result is that the substation would be clearly visible on the skyline when viewed from the north or south, along the coastline. Given the character of the coastline and the scenic/valued views that are present in the area, this is likely to significantly affect the character and visual enjoyment of the area. The constructed substation would be clearly visible as a silhouette against the skyline from Skara Brae world heritage site in the south and the Kitchener memorial from the north. Views from various residential properties in the vicinity of Marwick Bay would also be affected.
5.2.13 In relation to the operational and technical effects, site B performed least well due to the additional construction timescale and health and safety risks involved with constructing a substation on a site with considerable gradient.
5.2.14 This substation was viewed as being the third most expensive site to develop, due to the significant excavation requirements of the site.
Site E
5.2.15 3.3.1. Site E is located 800m north of Northdyke and 32Km northwest of Kirkwall. A farm track runs southwards from the site to Northdyke Road, which in turn adjoins the B9056, as can be seen on figure 5.1. The site is adjacent to the cliffs at Erens Geo.
5.2.16 From an environmental perspective, site E performed relatively well in the majority of topics used to compare the sites but in contrast to all of the other sites had no key effects that could be regarded as of ‘over-riding’ significance. Site E, although located on the coast like site D, occupies an area of the coastline that has sufficient variances in landform that the constructed site would be hidden from view along the coastline from the north and south.
5.2.17 The placement of the site, within the landform is such that visibility from Skara Brae would be negligible, and there would be no visibility from the north. There would be limited views of the site from the east but these are considerably less compared with all the other sites considered.
5.2.18 As with all other sites, there are scheduled ancient monuments in close vicinity to this site and this would need to be considered in the detailed design to ensure effects on setting are minimised as far as possible.
5.2.19 In relation to the operational and technical effects, site E performed relatively well with no significant issues being raised.
5.2.20 This substation was viewed as being the least expensive overall, when considering the reduced onshore infrastructure requirement to connect the closest landfall to the site.
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Site F
5.2.21 Site F is located 2km south of Quoyloo and 28km northwest of Kirkwall. Quoyloo Road is approximately 100m northeast of the site. Quoyloo Road runs between the B9057 and B9056 and can be seen in figure 5.1. The site is 1.5km east of Bay of Skaill.
5.2.22 From an environmental perspective, site F performed relatively well in the majority of topics used to compare the sites but has a key concern was highlighted in respect to the long term effect on visual amenity. There are a number of properties at close range that overlook the site as well as many more distant views from residential dwelling and main transport routes. This is considered to be significantly more significant than the visual impacts at site E.
5.2.23 As this site would be visible from the north of Skaill Bay, concerns have also been raised in respect to the overall visitor experience on Skara Brae and the indirect effects on the world heritage site area as a whole. This would have to be carefully considered should this site be taken forward.
5.2.24 The landowner at site F has also raised significant concerns regarding the sale of the land and the impact this may have on the larger holding.
5.2.25 There are no significant effects predicted from a technical or operational perspective and site F would not be significantly more expensive to construct than the less expensive, site E.
5.3 Landfall site selection study
Generally
5.3.1 The two search areas (west coast of mainland Orkney and north Caithness coastline) were initially assessed for locations where a subsea cable could be brought ashore. Within both the search areas there are two types of landfall that are envisaged, possible beach based ‘traditional’ landfalls and directionally drilled landfalls, where the cable is pulled ashore through a borehole that has been drilled underneath the coastal section to below mean low water springs.
5.3.2 There are different technical requirements for each of these methods and as such the locations of landfalls are likely to vary depending on the method being considered. Traditional open cut landfall sites ideally have a gentle gradient on the near shore with a suitable depth of sediment to allow conventional burial to be undertaken with an excavator or plough.
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5.3.3 In a lot of ways, the impacts of directional drilling are less pronounced than for open cut landings. However the main limiting factors are the height of the cliff and the rock structure. Another important consideration is the distance the rock outcrop extends offshore. At this stage the assessment has been made on the basis that extending the drill beyond the rock outcrop is desirable but not absolutely essential. If a technical requirement is identified to extend the drill beyond the offshore rock outcrop this could make a number of the directional drilling sites unsuitable and further assessment should be undertaken.
5.3.4 As suitable sites can be limited, their definition can strongly influence onward routes on land and at sea; whatever the technological approach used. Appropriate landing points and directional drilling sites need to be suitably located, to have the necessary characteristics for installation and to avoid major constraints to onward routeing.
5.3.5 On the west coast of mainland Orkney, three sites were identified for traditional open cut landfall options and seven coastal areas were identified for potential directional drilling. These can be seen in figure 5.1.
5.3.6 In Caithness there were a total of four sites identified for traditional open cut landfall options but with a further seven areas identified for directions drilling. These locations are identified on figure 5.1.
Orkney landfall
Traditional open-cut
5.3.7 The three bays identified as possible open cut landfall sites in Orkney are Birsay Bay, Marwick Bay and Bay of Skaill and the results of the study shows that each has its own unique challenges.
5.3.8 The most suitable bay for an open cut cable landfall is Birsay Bay. The other bays are technically and environmentally possible but have a number of restrictions/complexities that Birsay Bay does not.
5.3.9 Bay of Skaill has one possible cable route but this is severely constrained by an existing infrastructure cable that could place very difficult requirements on the installation. There is also only likely to be space for one cable meaning that it would not be of use for future SHETL projects or the developer`s cable landings. It is therefore assessed as ‘very poor’.
5.3.10 Marwick bay has significant constraints in relation to potential impacts on European designated sites including the Marwick Head SPA. It also has challenging geology for a typical open cut installation. These factors contribute to the overall assessment classification of ‘very poor’.
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5.3.11 Although Birsay Bay is classified as ‘acceptable’ the key limiting factor is its geographical location. As the majority of the substation site options are to the south of Birsay Bay, this could mean a significantly longer underground cable route from the landfall location to the substation is required. The influence of an increased length of cable route would need to be considered on environmental, technical and cost grounds when deciding on Birsay Bay’s overall viability should a substation to the south be considered.
Directional drill
5.3.12 Seven possible landfall sites have been identified for further assessment along the west coast of mainland Orkney. These are Birsay Bay, South of Birsay Bay, Marwick Bay, North Vestra Fiold, South Vestra Fiold, North Skaill and Bay of Skaill. These can be seen on figure 5.1.
5.3.13 The surveyed bathymetric data shows that a rock outcrop extends approximately 2km offshore from north of Birsay Bay until you reach the Bay of Skaill. At this point the rock appears to recede landwards, but due to a lack of surveyed data in the area this cannot be proven. Anecdotal evidence shows that this is the case with the rock being closer to shore around the Bay of Skaill.
5.3.14 The initial assessment identifies North Vestra Fiold as the best site for Directional Drilling on the basis of minimal environmental constraints, sufficiently low cliffs and good rock structure. South Vestra Fiold and North Skaill are assessed as ‘good’ sites and Bay of Skaill could be an ‘acceptable’ option. The remaining sites score ‘very poor’ in relation to impacts on European designated sites, height of the cliffs, and the presence of Lamprophyric rock outcrops that could make drilling very challenging.
5.3.15 Although the North Vestra Fiold site is assessed as the best site for directional drilling in isolation, all three sites (North Vestra Fiold, South Vestra Fiold and North Skaill) are possible options that would be feasible.
5.3.16 In fact, if looking at the landfall site selection in conjunction with the preferred substation site, South Vestra Fiold becomes more favourable as at this site there would be no associated impacts from the installation of underground cables. This is because the subsea cable could be pulled ashore immediately adjacent to the substation site.
Caithness landfall
Traditional open cut
5.3.17 The three bays identified as possible open cut landfall sites in Caithness are Melvich Bay, Sandside Bay and Crosskirk Bay. One Geo was also identified as a possible
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open cut landfall location, Gie Uisg Geo. The results of the study show that each has their own unique challenges.
5.3.18 The most suitable location for an open cut cable landfall in Caithness is either Crosskirk Bay or Gie Uisg Geo. The other locations are technically possible (and technically preferable) but have a number of restrictions/complexities from an environmental perspective that Crosskirk Bay and Gie Uisg Geo do not.
5.3.19 Melvich Bay has a number of key environmental constraints. These include the dune, saltmarsh, rocky margins, machair and maritime cliff habitats that are present in an around the bay. As a result the bay is designated as part of the Strathy Coast SSSI for these habitats. Melvich Bay is forms part of the North Caithness Cliffs SPA that is designated for breeding seabird assemblages including, Kittiwake, razorbill, puffin, fulmar, guillemot and peregrine. Given the sensitivities and the designation of this area of coastline a landfall site in this area should be avoided if possible. Melvich Bay was therefore attributed a classification of ‘very poor’.
5.3.20 Sandside Bay also has a number of key environmental constraints and is designated as a SSSI for it’s sand dune habitats. As with Melvich Bay, Sandside Bay also forms part of the North Caithness Cliffs SPA . Given the sensitivities and the designations in this area a landfall site should be avoided if possible. Radioactive particles have also been found in the approaches to and on Sandside Bay itself. This is not expected to significantly limit the potential of this site for landfall but would be likely to require stringent additional safety procedures to be put in place whilst working in the area. Sandside Bay was therefore attributed a classification of ‘very poor’.
5.3.21 Crosskirk Bay and Gie Uisg Geo do have a potential technical limitation in relation to bedrock outcrops in the near shore waters. This could make a traditional open cut landfall challenging due to the associated problems with excavating a trench to lay the cable. It is expected that these could be overcome however. From an environmental perspective Crosskirk Bay and Gie Uisg Geo have very few limitations. The only key limitation for Crosskirk Bay is the presence of the Forss Water that enters the sea at Crosskirk Bay. The Forss Water is a sensitive fishing river but with the adoption of good working practices and the temporary nature of the works in this area, it is expected that the impact on this river system will be minimised. Crosskirk Bay and Gie Uisg Geo have therefore been attributed a classification of ‘good’.
Directional drill
5.3.22 Seven possible landfall sites have been identified for further assessment along the north coast of Caithness. These are West Sandside, East Sandside, Oigin’s Geo, Greeny Geo East, Greeny Geo West, Green Tullochs, and West Crosskirk. These can be seen on figure 5.1.
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5.3.23 The initial assessment identifies Greeny Geo East as the best site for directional drilling on the basis of minimal environmental constraints, sufficiently low cliffs and good rock structure. East Sandside and Greeny Geo West are assessed as ‘good’ sites. The remaining sites score either ‘poor’ or ‘very poor’ in relation to impacts on European designated sites, height of the cliffs, close proximity to cultural heritage and the presence of poor geotechnical structure.
5.3.24 Although the Green Geo East Geo area is assessed as the best site for directional drilling overall, both the East Sandside and Greeny Geo West areas also score relatively well across that majority of criteria. The main constrain being incursion into the North Caithness Cliffs SPA for East Sandside area and slightly more complex geology for Greeny Geo West. These are still options however and all three areas would still be feasible and therefore will be subject to more detailed and intrusive site investigations.
5.4 Underground cable route selection study
Generally
5.4.1 The two search areas (west coast of mainland Orkney and north Caithness coastline) were initially assessed for underground cable routes that would connect the four possible substation sites with the possible landfall sites.
5.4.2 The key technical requirements for the installation of an underground cables includes the requirement for sufficiently deep soils, avoidance of peat where possible and the avoidance of particularly wet areas of ground and steep gradients.
5.4.3 The key environmental implications that are considered include the presence of sensitive habitats and wildlife, archaeology, geology and hydrology. The proximity to local dwellings is also an important consideration.
5.4.4 They key economical consideration relates to the length of route required and if there are no environmental or technical difficulties, the shortest route would be the preferred option.
5.4.5 The route options that were assessed as part of the Orkney underground cable route study are shown in figure 5.1. The options assessed as part of the Caithness study are shown in figure 5.1.
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Orkney underground cable routes
5.4.6 As can be seen in figure 5.1, cable route options were identified between the possible substation sites and landfall sites/areas. Some substation sites had a number of route options identified to the potential landfall areas. To simplify the comparison process and aid the selection of a ‘preferred overall option’, where more than one route was originally identified, only the route with the least technical and environmental sensitivities are represented on the presented figures.
5.4.7 On assessing the route options between the various substation sites and landfall locations on both environmental and technical grounds, it can be seen that there are routes classified as either ‘good’ or ‘very good’ for all cable route requirements. This suggests that there are no significant cable routeing constraints for Orkney. The key consideration will therefore be the length of cable route required to connect the substation to the landfall and this specifically covers the economic implications of different route options.
Caithness underground cable routes
5.4.8 As can be seen in figure 5.1, cable route options were identified between the Dounreay substation and the possible landfall sites/areas. As cable routes to the open cut landfall sites pass in close proximity to all the possible directional drill areas, the assessment and classification of these was considered to be representative of the routes to the possible directional drill areas.
5.4.9 On assessing the route options between Dounreay substation and the various landfall locations on the grounds of technical and environmental considerations it became clear that the routes to the west had significantly greater constraints to the cable route heading eastward. The cable route that extends to Melvich Bay would extend through significant sections of peat and blanket bog and would also be required to cross the Hallidate River that is a sensitive river for salmon and trout. As it approaches Melvich Bay it would also extend into the Strathy Coast SSSI that is designated for the sand dunes, machair and vascular plant assemblages. For these reasons the cable route to Melvich Bay is classified as ‘very poor’.
5.4.10 The route from Dounreay substation to Sandside Bay has less technical and environmental concerns than the route to Mevich Bay but is still constrained by the Sandside Bay SSSI that is designated for its dune and links systems. There is also a high probability that the route may have to pass through an existing golf course that may be of concern. For the reasons identified above, the route to Sandside Bay was classified as ‘Poor’ during the underground cable route selection study.
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5.4.11 The route east of Dounreay substation towards Crosskirk Bay had very few technical or environmental constraints. The key environmental constraint would be if the route was required to cross the Forss Water and any associated impacts this may cause. Should the route need to extend this far, it is expected that appropriate design would be able to mitigation these impacts however (for example, upgrading the existing footbridge to allow the cable to cross over the Forss Water). There are no designated sites or sensitive habitats likely to be impacted by the cable route. For the reasons identified, the route to Crosskirk Bay was classified as ‘Good’.
5.5 Subsea cable route selection study
Generally
5.5.1 The search corridor runs from Orkney (taking in the Brough of Birsay to the North and Yesnaby to the south), to Caithness and Sutherland (incorporating Melvich Bay in the west to Thurso in the east). This area has been selected to incorporate all possible landing sites identified in the sections above.
5.5.2 The corridor contains The Crown Estate lease development areas for E.ON, Scottish Power and Aquamarine Power. Also within the search corridor are sections of the Farice telecommunications cable (which will have to be crossed by any route option), the BT telecommunications cable and two 33kV electricity cables (which can be avoided). Initial discussions with BT, regarding their cable have suggested that a 750m exclusion zone around their cable may be necessary
5.5.3 With regards to other sea users, the corridor is fished with particular note given to creel fishing over the rocky seabed areas along the coastline where lobster and crab were specifically fished. In terms of shipping, the areas to the west of the Orkney mainland and immediately north of the Caithness/Sutherland coastline are infrequently used. As you move towards the west of Hoy and south, shipping levels become very dense with the corridor funnelling multiple ships per day through the Pentland Firth.
5.5.4 The sediments in the area range from gravels at the coarsest scale through to sands at the finest scale. It is believed from surveyed bathymetric data and anecdotal evidence that there is a kilometre wide area of sediment free bedrock following the west Orkney coast line. A visualisation of the predicted seabed features, based on expert interpretation of the bathymetric data is provided in figure 4.5.
5.5.5 For the marine section three principle route corridors have been identified to carry the cable from Orkney to Caithness. These are identified as route corridors 6, 9, and 10
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in figure 5.1. Various route corridors have then been identified towards the landfall locations to give options for the various landfall points also being assessed. There are a total of 21 independent sections identifying all potential route corridors. Where route corridors intersect with an adjacent corridor, an intersection has been identified (A-I).
5.5.6 The assessment in the subsea route selection study has evaluated each route corridor (1-21). This has allowed the identification of a preferred subsea cable route by connecting chosen cable sections at the identified intersections.
Subsea cable route corridors
5.5.7 As with the underground cable route options, the subsea cable routes have been assessed using environmental and technical criteria. These have provided a classification for each section of route. These range from ‘Poor’ to ‘Very good’ and can be seen in figure 5.1.
5.5.8 In general, there are three principle routes connecting the west coast of mainland Orkney to Caithness. These can be described, in general terms, as western, central and eastern.
5.5.9 An eastern route would be the shortest, but would mean crossing the existing BT cable twice and the existing Farice cable. This route would, however, avoid a lot of the rock features identified further west.
5.5.10 A central route would require the cable to pass through more dynamic sediment areas and would be restricted to the west by bedrock ridgelines and to the east by the BT cable. However, it is still relatively short compared to the western route, and follows a proven cable route for much of its length.
5.5.11 A western route would avoid the BT cable completely and once it is far enough west, would avoid the majority of bedrock outcrops and dynamic sedimentary areas. However, it would be long as it would have to pick its way around these bedrock features. There is also the risk that the bedrock features extend beyond the areas that have been identified through the existing bathymetry analysis.
5.5.12 At the north and south of the three principle subsea routes, various connections options have been identified depending on the landfall site chosen. It is clear from the assessment in the subsea cable route selection study that routes to the southern landfall site options in Orkney and eastern landfall site options in Caithness are preferred.
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6 OVERALL PREFERED OPTION
6.1.1 The overall preferred option is selected by comparing the findings of the substation site selection study, landfall site selection study, underground cable route selection study and the subsea cable route selection study. This allows selection of the most appropriate option overall based on environmental, technical and economical grounds.
6.1.2 In relation to the substations selection on Orkney, each of the four sites has potentially adverse effects on the different aspects considered as part of the comparison. Of the four sites however, site B, D, and F are believed, on balance, to have a greater number of significant issues that would be hard to overcome as part of the detailed design. These are considered likely to cause the greatest long term impacts on the people and environment in which they area located and as a result site E would be the preferred substation site.
6.1.3 The landfall site selection for Orkney identifies a number of sites that could be accessed by cable route from substation site E including two open cut sites (Marwick Bay and Birsay Bay) and three possible areas for directional drilling (North Vestra Fiold, South Vestra Fiold and North Skaill). The two bays identified for open cut cable landfalls both have significant constraints in relation to environmental designations and proximity concerns to other infrastructure, respectively. The only acceptable landfall site for open cut installation would be Birsay Bay, but this is a significant distance from site E. This would increase to length of underground and subsea cable required as part of the project and would therefore not be preferred on the grounds of overall project cost or the associated increase in environmental impact on the footprint of the works area.
6.1.4 In term of directional drill locations, all three sites are classified as ‘good’ (South Vestra Fiold and North Skaill) or ‘very good’ (North Vestra Fiold). As substation site E is located immediately adjacent to the South Vestra Fiold directional drill location and this landfall area is assessed as ‘good’, South Vestra Fiold, when assessed in combination with the other project components, would be the preferred landfall option for Orkney. This would eliminate any requirement for an underground cable corridor along the Orkney coastline, reducing any associated environmental impact and addition cost implications.
6.1.5 As both North Vestra Fiold and North Skaill are still classified as ‘very good’ and ‘good’ respectively, these are highlighted as possible alternatives to which comments are welcomed in this consultation process.
6.1.6 Both Melvich Bay and Sandside Bay in Caithness (that are identified as open cut landfalls) both have key constraints in relation to environmentally designated sites.
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The subsequent underground cable routes for both of these sites also have specific constraints confirming that they are not the preferred option. Crosskirk Bay and Gie Uisg Geo have potential for an open-cut landing site but also have specific issues in relation to the geology of the area and difficulty in excavating a cable trench. As a result the preferred landfall site in Caithness is identified as direction drill area Greeny Geo East.Directional drill areas Sandside East and Greeny Geo West and open-cut landfall site Gie Uisg Geo ad Crosskirk Bay are however highlighted as possible alternatives to which comments are welcomed.
6.1.7 The preferred offshore cable route from the preferred directional drill Orkney Landfall at South Vestra Fiold, would follow option route 5, 4, 7, 10, 11, 12 before coming ashore at landfall area D. This route would avoid the Marwick Head (Scottish Power Renewables) leased area, and West Orkney Middle South (E.ON Climate and Renewables) leased area, before heading south to Caithness. Unfortunately it will not be possible to avoid some level of incursion into Brough Head lease area (Aquamarine Power Ltd & SSE Renewables Holdings (UK) Ltd) and discussion with the developers will be required in order to limit any adverse effects in this regard.
6.1.8 This preferred subsea route avoids the main constraints and bedrock features that have been identified as part of the high level bathymetry analysis and screening process but would cut through an area of textured sediment that has the potential to be mobile. Further detailed studies would be undertaken to ensure that this potential constraint would not impact adversely on the installation or operation of the cable.
6.1.9 The final ‘overall preferred route’ is identified in figure 6.1. It should be noted that this route may be changed following feedback from the consultation process or following further detailed studies but any proposed changes will be appropriately communicated to all those concerned.
Aug 2011 Page 66 APPENDIX A NATURE CONSERVATION INFORMATION
NATURE CONSERVATION INFORMATION
Special Protection Areas (SPAs)
Marwick Head SPA (UK9002121) Including Marine Extension Covering a total area of 475.6Ha, The Marwick Head Special Protection Area is a 2 km stretch of sea cliffs, and adjacent coastal waters, along the west coast of Orkney Mainland. The cliffs support large colonies of breeding seabirds.
The boundary of the Special Protection Area overlaps the boundary of Marwick Head SSSI, and the seaward extension extends approximately 1 km into the marine environment to include the seabed, water column and surface.
Marwick Head was classified in 1994 with a marine extension classified in 2009, and qualifies under Article 4.2 by regularly supporting populations of European importance of the migratory species: common guillemot Uria aalge (37,700 individuals 1.1% of the western European biogeographic population). Marwick Head SPA also qualifies under Article 4.2 by regularly supporting in excess of 20,000 individual seabirds. It regularly supports 75,000 seabirds including nationally important populations of the following species: black-legged kittiwake Rissa tridactyla (7,700 pairs, 2% of the GB population) and common guillemot (37,700 individuals, 4% of the GB population).
Hoy SPA (UK9002141) Including Marine Extension Hoy is a mountainous island at the south-western end of the Orkney archipelago. Hoy SPA with an area of 18,122.2Ha covers the northern and western two-thirds of Hoy island, which is formed of Old Red Sandstone and contains Orkney’s highest hills, and adjacent coastal waters. The SPA supports an extremely diverse mixture of mire, heath and alpine vegetation and Britain’s most northerly native woodland. These upland areas and the high sea cliffs at the coast support an important assemblage of moorland breeding birds and breeding seabirds.
The boundary of Hoy SPA overlaps with that of Hoy SSSI, and the seaward extension extends approximately 2 km into the marine environment to include the seabed, water column and surface.
Hoy SPA was classified in 2000 with a marine extension classified in 2009 and qualifies under Article 4.1 by regularly supporting populations of European importance of the Annex 1 species: red-throated diver Gavia stellata (58 territories, 6% of the GB population) and peregrine Falco peregrinus (6 pairs, 0.5% of the GB population). Hoy SPA further qualifies under Article 4.2 by regularly supporting populations of European importance of the migratory species: great skua Stercorarius skua (1,900 pairs, 14% of the world biogeographic population). Hoy SPA also qualifies under Article 4.2 by regularly supporting in excess of 20,000 individual seabirds. It regularly supports 120,000 seabirds including nationally important populations of the following species: Atlantic puffin Fratercula arctica (3,500 pairs, 0.7% of the GB population); black-legged kittiwake Rissa tridactyla (3,000 pairs, 0.6% of the GB population); Arctic skua Stercorarius parasiticus (59 pairs, 2% of the GB population); Northern fulmar Fulmarus glacialis (35,000 pairs, 6% of the GB population); great black-backed gull Larus marinus (570 pairs, 3% of the GB population); common guillemot Uria aalge (13,400 pairs, 2% of the GB population).
North Caithness Cliffs SPA (UK9001181) Including Marine extension Covering an area of 14,621.14Ha North Caithness Cliffs SPA is of special nature conservation and scientific importance within Britain and the European Community for supporting very large populations of breeding seabirds. The site overlaps either partly or wholly with Duncansby Head SSSI, Stroma SSSI, Dunnet Head SSSI, Holborn Head SSSI, and Red Point Coast SSSI. The seaward extension extends approximately 2km into the marine environment to include the seabed, water column and surface.
North Caithness Cliffs SPA was classified in 1996 with a marine extension classified in 2009 and qualifies under Article 4.1 by regularly supporting populations of European importance of the Annex 1 species: peregrine Falco peregrinus (6 pairs, 0.5% of the GB population); and under Article 4.2 by regularly supporting populations of European importance of the migratory species: common guillemot Uria aalge (38,300 individuals, 1% of the North Atlantic biogeographic population). North Caithness Cliffs SPA also qualifies under Article 4.2 by regularly supporting in excess of 20,000 individual seabirds. The site regularly supports 110,000 seabirds including nationally important populations of the following species: Northern fulmarFulmarus glacialis (14,700 pairs; 3% of the GB population); black-legged kittiwake Rissa tridactyla (13,100 pairs, 3% of the GB population); common guillemot (38,300 individuals, 4% of the GB population); razorbill Alca torda (4,000 individuals, 3% of the GB population) and Atlantic puffin Fratercula arctica (1,750 pairs, over 10% of the minimum qualifying assemblage of 20,000 individuals). Special Areas of Conservation (SACs)
Loch of Isbister SAC (Site code 8302) Loch of Isbister SAC was designated for the following qualifying features in March 2005: SCIENTIFIC NAME COMMON NAME Lutra lutra Otter Natural eutrophic lakes with Magnopotamion Naturally nutrient-rich lakes or lochs which or Hydrocharition-type vegetation are often dominated by pondweed Transition mires and quaking bogs Very wet mires often identified by an unstable `quaking` surface
Stromness Heaths and Coast SAC (Site code 8387) Loch of Isbister SAC was designated for the following qualifying in March 2005:
SCIENTIFIC NAME COMMON NAME Alkaline fens Base-rich fens European dry heaths Dry heaths Vegetated sea cliffs of the Atlantic and Baltic Vegetated sea cliffs coasts
Hoy SAC (Site code 8272) Hoy SAC was designated for the following qualifying features in March 2005:
SCIENTIFIC NAME COMMON NAME Alkaline fens Base-rich fens Alpine and Boreal heaths Alpine and subalpine heaths Blanket bogs* Blanket bog Calcareous rocky slopes with chasmophytic Plants in crevices on base-rich rocks vegetation European dry heaths Dry heaths Natural dystrophic lakes and ponds Acid peat-stained lakes and ponds Northern Atlantic wet heaths with Erica Wet heathland with cross-leaved heath tetralix Petrifying springs with tufa formation Hard-water springs depositing lime (Cratoneurion)* Vegetated sea cliffs of the Atlantic and Baltic Vegetated sea cliffs coasts Sites of Special Scientific Interest (SSSIs)
Loch of Isbister and the Loons SSSI (Site code 1031) Covering an area of 104.5HaLoch of Isbister and the Loons Site of Special Scientific Interest (SSSI) is located on the west mainland, between Marwick and Twatt, in the parish of Birsay. The site is a wetland site of national importance for its botanical and ornithological interest. Biological notified natural features include: Fens: Basin fen and Birds: Breeding bird assemblage - Pintail (Anas acuta).
The Loch of Isbister and the Loons has developed into Orkney’s best basin-mire complex as peripheral vegetation has encroached into the open water of Loch of Isbister. The site in particular contains excellent examples of vegetation that forms on the margins of lochs. The variety of bog habitats support a very rich assemblage of wetland plants including autumnal water-starwort, slender-leaved pondweed and the regionally scarce fragrant orchid.
The rich habitat provides a nationally important breeding ground for a range of birds including: wigeon Anas Penelope, mallard Anas platyrhynchos, teal Anas crecca, tufted duck Aythya fuligula, red breasted merganser Mergus serrator, shoveler Anas clypeata and shelduck Tadorna tadorna. The site is also notified for its nationally important breeding population of pintail, supporting on average 6% of the British population.
Marwick Head SSSI (Site code 1131) Covering an area of 8.69Ha, Marwick Head Site of Special Scientific Interest is on the west coast of Orkney Mainland between Bay of Skaill and the Brough of Birsay. The site supports breeding seabirds and its biological notified natural features include Birds: Guillemot (Uria aalge), breeding; Kittiwake (Rissa tridactyla), breeding; and, Breeding Seabird Colony, breeding.
The geology of this site features sandstone cliffs which provide excellent nesting locations for many sea bird species. The site accommodates one of the three largest seabird colonies in Orkney.
The breeding Guillemot Uria aalge and Kittiwake Rissa tridactyla are of national importance with 4% and 2% respectively of the British and Irish breeding populations. The breeding seabird colony is also of national importance and the species in the area include; Fulmar Fulmaris glacialis, Razorbill Alca torda, Puffin Fratercula artica, Shag Phalacrocorax aristotelis, Jackdaw Corvus monedula and Herring Gull Larus argentatus.
Bay of Skail SSSI (Site code 156) Measuring 7.8Ha the Bay of Skaill Site of Special Scientific Interest (SSSI) encompasses the intertidal rock platform at Hangabacks and associated coastal cliffs on the north side of the Bay of Skaill. It is a site of international importance for its fossil plants. Geological notified features include: Palaeontology: Palaeozoic Palaeobotany
The Middle Devonian fish beds of the Orcadian cuvette (basin where sediments accumulated) are characterised by a distinct fossil floral assemblage. The Bay of Skaill site is the best developed example of this flora available. The site still has much research potential, for it has to date received comparatively little attention despite its importance. This is the locality from which Protopteridium thomsonii, the earliest known progymnosperm, was first recorded. It is also noteworthy in being the only known British site to yield Barnandeina. The latter named genus is known from Bohemia and this emphasises the probable affinity of this Orcadian cuvette flora with central European sites.
This key site plays a vital role in our understanding of plant evolution during a period when most land plants were only just appearing.
Stromness Heaths and Coast SSSI (Site code 1499) Covering an Area of 747.74Ha, Stromness Heaths and Coast SSSI covers a long stretch of coast from the southern end of the Bay of Skaill to the golf course in Stromness. This stretch of land is situated on the high exposed cliffs of the west coast and the notified features are of stratigraphy and geomorphology. The maritime cliff habitat is also a notified feature. Almost in the centre of this SSSI coast line is a large area of inshore land which is a habitat notified for its subalpine dry heath. Stomness heaths and Coast SSI is designated for both Geological and Biological notified features.
Geological notified features include;- Geomorphology: Coastal Geomorphology of Scotland; and Stratigraphy: Non-marine Devonian. Biological notified features include;- Coastlands: Maritime cliff; and, Upland habitats: Subalpine dry heath
This part of the west coast of Orkney is important for coastal geomorphology, providing the best examples of the distinctive sandstone and flagstone cliffs and associated features of Orkney. The coast is exposed to high energy Atlantic swell waves and experiences some of the highest levels of incident storm wave energy in Britain. Under these conditions an excellent range of rock coast features has developed, including various types of cliff form, caves, arches, geos, stacks, shore platforms and features of cliff-top scouring.
At Yesnaby and Gaulton good examples of cliff sections of the Lower Old Red Sandstone Yesnaby Group and the Middle Old Red Sandstone Flagstones are exposed, separated by an intervening unconformity. This is important evidence of the regional relationship between these two sets of Devonian sediments typical of the Orcadian basin. The Lower Old Red Sandstone sediments include large-scale aeolian dunes, which are not found elsewhere in the Lower Old Red Sandstone of the Orcadian Basin. This site is important for the study of Lower Old Red Sandstone environments and Middle Old Red Sandstone lake sediments.
The south Stromness coast is the best section through the lower part of the Middle Old Red Sandstone (Stromness Flagstone Group), showing very diverse lake and playa basin sediments. Special features of the lake sediments include: beach gravels at the base of the section, different types of chemical sediments, stromatolitic limestone beds (some of which show heavy-metal enrichment) and fine-grained dolomite and calcite limestones.
Along the clifftops, extreme exposure to wind and salt spray has produced some of the best and most extensive areas of maritime grassland and maritime heath anywhere in the UK. In places where cliff-top communities are strongly influenced by the sea, species such as sea plantain and thrift are co-dominant. These cliff-top communities grade into mosaics of maritime heath and grassland. The coastal heath is often rich in species and is dominated by dwarf shrubs such as heather, crowberry and bell heather. The maritime grassland includes herb-rich sedge dominated vegetation. The nationally scarce Scottish primrose Primula scotica thrives locally in this maritime heathland and grassland mosaic. The largest Primula scotica colonies occur near Yesnaby.
There is a natural landward transition from the more maritime plant communities into areas of wind-pruned acidic heath. Heathland away from the zone of maritime influence is naturally less species-rich. Throughout the heathland there are base-rich flush and mire
Hoy SSSI (Site code 798) Hoy is site is of botanical, ornithological, biological, geological and geomorphological interest covering 9500Ha. Mammals found within the SSSI include mountain hare, which occurs in Orkney only on Hoy, and otter.
The vegetation of Hoy is extremely diverse. Very extensive areas of alpine heath, sub- alpine coastal heath and vegetated sea cliffs are present and the transitions between them are largely natural and well developed. The Northern Atlantic wet heaths are extensively developed on Hoy. These are characterised by abundant lichens and cross-leaved heath Erica tetralix with grasses, sedges and Sphagnum bog mosses. Petrifying tufa springs, characterised by dense yellow-orange mats of the feather moss Cratoneuron commutatum and other lime-loving species such as yellow sedge Carex viridula ssp. Brachyrhyncha, occur throughout the site.
Excellent examples of dwarf shrub heaths, characteristic of mountain environments, occur here at very low altitudes, reflecting the influence of latitude and exposure. The vegetation at the summit of Ward Hill (479 metres) is comparable with that in the Cairngorms at 1000 metres. On the exposed summits fell-field communities have developed. These alpine and sub-alpine heaths comprise arctic-alpine plants including bearberry Arctostaphylos uva-ursi, Alpine bearberry Arctostaphylos alpinus, trailing azalea Loiseleuria procumbens and dwarf willow Salix herbacea. The blanket bog area of Hoy SSSI is in excess of 4000 ha. The mire exhibits a general lack of disturbance by past and on-going management and recovery of the bog surface from localised drainage or cutting is taking place in many areas. The site contains an abundance and variety of microtopic and vegetational features that indicate the bog is of high quality and in a near-natural state. Species indicative of a lack of disturbance include Sphagnum magellanicum and Drosera anglica, and the general abundance of Sphagnum capillifolium and Sphagnum papillosum. Throughout the site the mire communities comprise species indicative of a peatforming capability. Natural surface patterning is widespread and pool and lochan complexes are widely developed above about 200m above sea level. These pools and lochans comprise one of the most diverse groups of dystrophic water bodies in Orkney.
Where the soils are rich in calcium, more species-rich plant communities are found. Cliffs and rocky slopes of calcareous Old Red Sandstone occur on the site, the richest locality being at Quoyawa. This habitat has a montane calcicolous flora that includes a number of rare or uncommon Arctic-alpine plants such as holly fern Polystichum lonchites, Alpine meadow-grass Poa alpina, hoary whitlow grass Draba incana, mountain sorrel Oxyria digyna, mountain avens Dryas octopetala, Alpine saw-wort Saussurea alpina, rose-root Sedum rosea and purple saxifrage Saxifraga oppositifolia. Strongly base-rich small-sedge fens also occur on the site. Their flora includes vascular calcicoles such as Alpine meadow rue Thalictrum alpinum, yellow mountain saxifrage Saxifraga aizoides, starry saxifrage Saxifraga stellaris, purging flax Linum catharticum, few-flowered spike-rush Eleocharis quinqueflora and characteristic mosses such as Scorpidium scorpiodes and Drepanocladus revolvens. The more open flushes are enriched by black bog-rush Schoenus nigricans. Many of these plants, and some of the dwarf shrub heaths, are confined in Orkney to the island of Hoy: others occur only rarely elsewhere in Orkney.
Since 1951 northern Hoy has had very little grazing by domestic stock and no regular burning. This is a rare feature of British moorlands and has led to scrub regeneration and to the widespread occurrence of species vulnerable to grazing and burning, which are normally scarce in moorlands. It has also aided the survival of Orkney’s only indigenous woodland at Berriedale, which is the most northerly natural wood in Britain. Tree species found here include rowan Sorbus aucuparia, downy birch Betula pubescens, aspen Populus tremula, and hazel Corylus avellana.
The Hoy SSSI is the most important area in Orkney for great skua and supports an internationally important breeding population. In 1996 the site supported 1900 Apparently Occupied Territories, representing 22% of the British breeding population and 14% of the total world population, with the densest populations found at The Berry and Bailie Fea. In addition the site is nationally important for Arctic skua with 59 Apparently Occupied Territories present in 1996, representing 2% of the British breeding population and for red- throated diver with a minimum of 58 breeding pairs in 1994, representing approximately 6% of the British breeding population.
The site also supports an internationally important assemblage of breeding seabirds with around 120,000 individuals present comprising 14 different species, including nationally important populations of fulmar, great black-backed gull and guillemot. In addition the site supports a nationally important diverse assemblage of moorland breeding birds including: hen harrier, merlin, peregrine, red grouse, golden plover, dunlin, snipe, wheatear, raven and twite. The peregrine population is exceptionally important as it occurs at a very high density and is at the northern edge of the species’ range in Britain.
The spectacular west coast of Hoy includes St John’s Head (338 metres), one of the highest headlands in Britain, and the Old Man of Hoy, a 137 metre rock stack. In Orkney, rocks of the Upper Old Red Sandstone age are found only in Hoy where they form the greater part of the island. Comprising both Hoy Volcanics and Hoy Sandstones, excellent exposures of these rocks occur forming type-sections and are of high educational and research value.
The entire area has been glaciated and now exhibits a suite of glacial features, including examples of the northernmost corries in the British Isles at Enegars and Dwarfie Hamars. As a consequence of the interaction of freeze-thaw and wind processes a fine assemblage of periglacial features has developed. They include turf-banked terraces, hill dunes, wind stripes and composite stripe/terrace formations, all of which are particularly well developed on the upper slopes of Ward Hill.
Ushat Head SSSI (Site code 1585) Ushat Head Site of Special Scientific Interest (SSSI) is a low exposed headland, approximately 9km northwest of Thurso on the north coast of Caithness. The designated area is 45.32Ha and the site is designated for Botanical and Coastlands (Maritime Cliff) notified natural features. It is of particular botanical importance for its maritime heath, which is a northern, species-rich type of heathland that is found only in Caithness, Sutherland and Orkney.
There is a good representation of species-rich maritime heath communities in a mosaic with maritime grassland. Heathers and creeping willow Salix repens are the main dwarf shrubs. The rare Scottish primrose Primula scotica and small-fruited yellow sedge Carex viridula are found at Ushat Head SSSI. Roseroot Sedum rosea and kidney vetch Anthyllis vulneraria are abundant, along with the maritime species, spring squill Scilla verna, sea campion Silene uniflora and sea plantain Plantago maritima. Sandside Bay SSSI (Site code 1405) Sandside Bay Site of Special Scientific Interest (SSSI) lies just north of Reay, on the north coast of Caithness. The site is in two parts which measure a total of 81.2Ha. The main part of the site includes the foreshore, dunes, dune slacks and the banks of the Burn of Isauld. The second part of the site is an area of herb-rich grassland within the golf course. Sandside Bay SSSI is one of two coastal sites designated to represent dune and links habitats in Caithness.
The dunes are dominated by marram grass Ammophila arenaria, with flowering plants such as Alpine meadow-rue Thalictrum alpinim, yellow rattle Rhinanthus minor, bird’s foot trefoil Lotus corniculatus, and lady’s bedstraw Galium verum on the stabilised back slopes. The links have species-rich short turf with uncommon species including cowslip Primula veris and the nationally scarce curved sedge Carex maritima.
Red Point Coast SSSI (Site code 1338) Red Point Coast Site of Special Scientific Interest (SSSI) is a 6km stretch of coastline between Sandside Bay in Caithness and Melvich Bay in Sutherland, measuring 165.66Ha. The site has been designated for the nationally important geology, coastal vegetation and breeding seabirds. The site contains two geological features: ancient lake margin sediments from the Middle Devonian (around 390 million years ago) and Quaternary sediments deposited by Ice Age glaciers (around 22,000 years ago). The cliff-top vegetation includes large colonies of Scottish primrose Primula scotica and the cliffs themselves support colonies of breeding seabirds.
The geology at Red Point shows the best known example of Middle Devonian lake-margin deposits lying directly on top of ‘Moine’ rocks which are up to 1000 million years old. The ancient Moine rocks had been eroded to form a landscape of hills and hollows by Middle Devonian times. The Middle Devonian sediments formed at the margin of a large lake known as Lake Orcadie. They include unusual algal limestone deposits, small beach ridges of angular gravel derived from the local Moine rock, river deposits formed when the level of the lake was lower, and sandstones and mudstones, including flagstones. These form a unique range of lake-margin deposits which are important to understanding the palaeogeography of the Orcadian Lake basin, and provide an insight into its lake-margin environments.
The Quaternary (Ice Age) sediments are exposed on the coast near Drumhollistan and comprise layers of till (glacial deposits), which are separated in most places by a layer of water-deposited sand and gravel. These deposits provide evidence for the pattern of ice movements in Caithness and the interaction between two separate ice masses of local and external origin during the last glaciation (probably around 22,000 years ago). The lower till was deposited first and contains fragments of rock transported by local ice moving from the south. The upper till forms part of the classic shelly till of Caithness and was deposited by ice flowing from the south-east across the sea floor from the Moray Firth. The till is overlain by up to 1m of periglacial slope deposits - loose weathered rock and soil that moved down slope during a period of cold climate following the melting of the glaciers.
Red Point Coast contains an area of maritime cliff vegetation that is an excellent example of cliff-top habitats in northern Scotland. There is a complex mixture of species-rich maritime grassland and heath communities containing characteristic maritime species such as sea plantain Plantago maritima and spring squill Scilla verna. The maritime communities occur along a narrow zone at the cliff edge, except at Sandside Head where they extend much further inland. Cliff ledge vegetation includes Scots lovage Ligusticum scoticum and roseroot Sedum rosea. Vegetation such as common scurvy grass Cochlearia officinalis and scentless mayweed Tripleurospermum maritimum occurs on cliff ledges and the tops of stacks.
Large colonies of the nationally scarce Scottish primrose Primula scotica grow on this site. This plant grows in Caithness, Sutherland and Orkney, but nowhere else in the world. Red Point Coast SSSI is particularly important for Scottish primrose because the large areas of suitable habitat near Sandside Head hold over 1% of the world population.
The cliffs at Red Point Coast SSSI have large numbers of breeding seabirds, notably guillemots. The breeding guillemot population on Red Point Coast SSSI forms more than 1% of the British population.
Strathy Coast SSSI (Site code 1689) Strathy Coast SSSI covers a section of the north Sutherland coast (675Ha) centred around Strathy Point, 7km to the east of Bettyhill. It comprises north, east and west facing cliffs, interrupted by beach systems at Armadale, Strathy and Melvich. The site is notified for the nationally important maritime cliff, sand dune, machair and salt marsh habitats found along the coast and for the assemblage of rare plants. It is also notified for the Moine rocks around Portskerra.
This nationally important site is crucial to our understanding of the history of deformations that shaped the geology of this part of Scotland. The Moine rocks exposed along 1.5km of coast around Portskerra originated as sands and muds on the seabed around 1.1 billion years ago. Intense heat and pressure within the Earth’s crust first altered the sandstone and mudstone, and then certain minerals separated out to create a banded rock called migmatite. Magma was intruded into these rocks in at least three episodes, forming igneous rocks that were then altered by further heat and pressure. Younger intrusions of the Strath Halladale Granite Complex illustrate a period of folding and shearing around 450 million years ago. The junction between the Moine rocks and overlying Devonian sandstones, and the complex inter-relationships between the many rock types, are superbly exposed in a small area. Areas of machair south of Armadale Bay, Strathy Bay and Melvich are found on the largely calcareous shell sand and support a rich variety of flowering plants. Birds-foot trefoil Lotus corniculatus, wild thyme Thymus polytrichus, common self-heal Prunella vulgaris, frog orchid Coeloglossum viride and cowslip Primula veris are all found within the machair habitat.
The cliff top maritime grasslands of Strathy Coast are both varied and extensive and show complete succession to maritime heaths and sub-maritime grasslands. In the absence of grazing, the rock crevices, cliff ledges and islands support red fescue Festuca rubra and thrift Armeria maritima grassland, with common scurvygrass Cochlearia officinalis and Scots lovage Ligusticum scoticum also abundant. Where there is a degree of shelter, these communities can develop into rich meadows with yarrow Achillea millefolium and occasionally purple oxytropis Oxytropis halleri. The most widespread grassland has a blue- green sward of sedges, including glaucous sedge Carex flacca and carnation sedge Carex panicea. Large populations of the nationally scarce Scottish primrose Primula scotica are found between Kirtomy and Strathy and near Portskerra.
The sand dune habitats of this site are of exceptional quality. They typically show complete succession from pioneering strandline communities with sea sandwort Honckenya peploides and sea rocket Cakile maritima, through mobile dunes with colonising species such as marram grass Ammophila arenaria and sand couch grass Elytrigia juncea, to mature fixed dunes. Field gentian Gentianella campestris, frog orchid Coeloglossum viride and common twayblade Listera ovata are widespread. The nationally rare purple oxytropis and the eyebright Euphrasia rotundifolia also occur in this habitat. An area of saltmarsh has developed in the sheltered intertidal section of the Halladale River behind Melvich beach where silty and gravely muds have accumulated. This is unusually extensive for the north coast and has a typical range of species, including saltmarsh rush Juncus gerardii and sea-milkwort Glaux maritima.
Five nationally scarce or rare plants grow on this site: Scottish primrose, purple oxytropis and three species of eyebright (Euphrasia rotundifolia, E. foulaensis and E. marshallii). Two of these plants – Scottish primrose and Euphrasia rotundifolia – grow in Britain and nowhere else in the world. This site is particularly important for Scottish primrose as this plant grows only in Sutherland, Caithness and Orkney, making the populations on this site some of the largest in the world.
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