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Limekiln Wind Farm 132 kV Grid Connection EIA Report - Volume 1 Non-technical Summary

March 2020

Limekiln Wind Farm 132 kV Grid Connection: Non-Technical Summary Page 1

March 2020

CONTENTS

1. INTRODUCTION 2 2. THE NEED FOR THE PROJECT 4 3. CONSIDERATION OF ALTERNATIVES 5 3.1 “Do-Nothing” Scenario 5 3.2 Alternative Corridors, Routes or Alignments 5 3.3 Alternative Technical Options 5 4. DESCRIPTION OF THE PROPOSED DEVELOPMENT 7 4.1 Phase 1 – Enabling Works 8 4.2 Phase 2 – Construction Works 8 4.3 Phase 3 – Commissioning 9 4.4 Phase 4 – Reinstatement 9 4.5 Construction Environmental Management 9 4.6 Construction Employment and Hours of Work 9 4.7 Construction Traffic 9 4.8 Operation and Management of the Transmission Connection 10 4.9 Decommissioning 10 5. EIA APPROACH, SCOPE AND CONSULTATION 11 6. ENVIRONMENTAL EFFECTS OF THE PROPOSALS 12 6.1 Landscape and Visual Impact 12 6.2 Ecology 12 6.3 Ornithology 13 6.4 Cultural Heritage 13 6.5 Hydrology, Hydrogeology, Geology and Soils 14 6.6 Forestry 15 7. CUMULATIVE EFFECTS 17 8. CONCLUSION 18

FIGURES

Figure 1: Location Plan and Overview

Figure 2: The Proposed Development


March 2020

1. INTRODUCTION

This Non-Technical Summary (NTS) forms part of the Environmental Impact Assessment (EIA) Report

prepared under the Electricity Works (Environmental Impact Assessment) (Scotland) Regulations 2017 on

behalf of Scottish Hydro Electric Transmission plc (SHE Transmission).

SHE Transmission, referred to as ‘the Applicant’ from this point forwards and throughout the EIA Report, owns

and operates the electricity transmission network in the north of Scotland. Under their licence obligations, the

Applicant is obliged to provide a connection to the national electricity network upon request from a developer of

an electricity generation installation.

In June of 2016, an application was submitted to the Scottish Government’s Energy Consents Unit for consent

to build a wind farm at Limekiln Estate in Caithness to the west of Thurso and south of the village of Reay,

hereafter referred to as Limekiln Wind Farm. The Wind Farm was consented in June 2019. The Applicant must

provide a connection between Limekiln Wind Farm and the connection point at the existing Dounreay

substation to the north of Reay (see Figure 1).

It is proposed that this connection be established via an overhead electricity line, supported by wood pole

structures, which would pass through the Limekiln and Broubster forest areas before traversing open

agricultural land to a point south of the A836 road. A sealing end structure would be constructed here to

transfer the overhead line to an underground cable which would cover the remaining kilometre to Dounreay

substation. Some ancillary works, including felling of forestry, provision of temporary and upgraded access

routes and access points, and protective measures for roadways and watercourse crossings, would be required

to create safe clearance for operation and maintenance of the overhead line.

All of these works together, with the exception of the underground cable which would be progressed separately

under the Applicant’s Permitted Development Rights, are referred to through the rest of this NTS, and

throughout the EIA Report, as ‘the Proposed Development’. An overview of the Proposed Development is

shown on Figure 1, whilst more detailed plans are presented in Figure 2.

The full results of the EIA (baseline information, survey findings and technical assessments) that have been

completed for the Proposed Development are presented in the EIA Report. The aim of this NTS is to

summarise the content and the main findings of the EIA Report in a clear and consistent manner to assist the

public in understanding what the environmental effects of the Proposed Development are likely to be. The full

EIA Report (Volume 2: Main Report; Volume 3: Figures; Volume 4: Technical Appendices) provides a more

detailed description of the Proposed Development, and the findings of the EIA.

Due to the current situation with COVID-19, public copies of the EIA cannot be made available. An interim

advert will be issued in appropriate publications to provide a link to the ECU’s online portal, and SHE

Transmission’s website, where the EIA Report may be viewed. When restrictions are finally lifted, the full

newspaper adverts will be placed and the 30-day public consultation period, together with hard copies available

locally, will begin. At that stage, the full EIA Report and supporting Figures and Technical Appendices can be

viewed at the following locations:


March 2020

The Scottish Government Library

Victoria Quay

Edinburgh

EH6 6QQ

Viewing hours generally 9am to 4pm Monday to

Friday, 24 hours’ notice required prior to visit via

[email protected]

The Shop

Reay

Thurso

KW14 7RG

Opening Hours: 7.00am to 6.00pm Monday to Friday

7.00am to 4.00pm Saturday and Sunday

The Highland Council

Thurso Service Point

Council Offices

Rotterdam Street

Thurso

KW14 8AB

Opening Hours: 9.00am to 5.00pm Monday to Friday

The EIA Report can also be viewed at www.energyconsents.scot.

Notice of the application, together with a copy of the Non-Technical Summary, is also provided on the

Applicant's website at: https://www.ssen-transmission.co.uk/projects/limekilns-wind-farm-connection/.

The EIA Report will be available in other formats, if required. For details, including costs, contact:

Lisa Marchi-Grey, Liaison Manager

[email protected]

OR

For the Attention of Lisa Marchi-Grey

Scottish and Southern Electricity Networks

10 Henderson Road

Inverness

IV1 1SN


March 2020

2. THE NEED FOR THE PROJECT

As set out in Section 1: Introduction, the Proposed Development is required due to a request made to the

Applicant for connection of the consented Limekiln Wind Farm to the transmission network. Limekiln Wind

Farm is a 24 turbine, 72 Megawatt (MW) wind farm at Limekiln Estate in Caithness to the west of Thurso.

The Applicant has obligations under the Electricity Act 1989 to develop and maintain an efficient, co-ordinated

and economical system of electricity transmission. As the owner and operator of the local electricity network,

the Applicant is obliged to provide the wind farm with a grid connection following the request. Further details of

the nature and design of the connection are provided in Section 4 of this NTS.


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3. CONSIDERATION OF ALTERNATIVES

The Proposed Development is located in the northern Highlands, west of the town of Thurso and south-east of

Reay. It spans approximately 5 km, connecting the on-site substation of Limekiln Wind Farm to a sealing end

structure approximately 900 m south-east of the substation at Dounreay. The sealing end structure would

transfer the proposed overhead line on an underground cable, which would traverse the last 900 m of the

connection. The underground cable does not form part of the Proposed Development.

As part of early work in designing the project, the Applicant considered alternative options for the connection

route, connection type, and technology to be implemented. This consideration of options also took into account

the requirements of the Electricity Act 1989, which notes that the Applicant must:

• “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

• “do what [it] 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”.

To that end, three main alternative approaches were considered by the Applicant: the “Do Nothing” Scenario,

alternative corridors, routes or alignments, and alternative technical options.

3.1 “Do-Nothing” Scenario

This scenario assumes that no other options are considered and that no connection is made between the

Limekiln Wind Farm and the national electricity network. This scenario was not considered feasible as it would

fail to deliver the connection applied for by the wind farm developer and fail to meet the Applicant’s licence

obligations.

As such, this was considered to be an inappropriate development option and discarded at an early stage.

3.2 Alternative Corridors, Routes or Alignments

As part of the design process, different routes were considered between the Limekiln Wind Farm substation and

the connection point at Dounreay substation. Five alternative routes (A – E) were considered within a defined

area, known as a corridor, and an initial environmental assessment was carried out to compare the on-site

constraints to development and potential effects upon the local environment.

The potential effects of each route option were assigned a red, amber or green (RAG) rating, with red indicating

a greater constraint to development, and green a lesser or no constraint. These ratings were then compared

against each other to determine which had the least potential to impact the environment. The environmental,

physical and amenity constraints were reviewed alongside engineering and cost considerations to determine

the best overall route.

The selected route was marginally the second preference in environmental terms, with only a slight distinction

between it and the first preference, and was favoured due to the reduced engineering implications in regards to

flooding and the need to cross existing overhead lines.

Within this route, an alignment was selected which sought to avoid on-site constraints, such as archaeological

sites, watercourses and sensitive ecology. This alignment was later refined following feedback from Forestry

Commission Scotland in order to minimise the felling of trees which would be required to provide a clear route

for the Proposed Development. This resulted in the alignment displayed on Figure 2.

3.3 Alternative Technical Options

The option of installing an underground cable for the whole route, rather than an overhead line, was considered.

This was discounted due to being a significantly more expensive option, the need to dig through sensitive

ecological habitats, and the likelihood that directional drilling beneath streams would be needed to traverse

them. Given these factors, undergrounding of the full route was not considered further; however, the last 900 m


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of the connection to Dounreay substation would be via underground cable in order to limit the increase of

perception of overhead line infrastructure near the substation. This has had the added benefit of reducing

potential impacts on bird species making use of the open agricultural land.

Use of larger structures, such as steel lattice towers, was also considered. This type of connection would also

entail a significantly increased cost in comparison with wood pole structures and likely give rise to greater

environmental impacts associated with landscape and visual effects and the larger foundations required.

Additional permanent stone tracks would also have to be laid to allow construction and maintenance vehicles to

access the towers. As such, this structure type would not have provided the most economic or efficient option

and was discounted.


March 2020

4. DESCRIPTION OF THE PROPOSED DEVELOPMENT

The Proposed Development consists of construction of a new 132 kilovolt (kV) wood pole overhead line

between the consented Limekiln Wind Farm to an underground cable via a sealing end structure, as illustrated

on Figure 2.

The specific works to be carried out for this would involve:

• installation of approximately 5 km of new overhead line, to be suspended between double wood pole

structures, from the Limekiln Wind Farm on-site substation to a point just south of the A836 road; and

• a sealing end structure which will act as the connecting point between the overhead line and underground

cable which will run the last 1 km to Dounreay substation.

Some ancillary works including tree felling to clear the route through the plantation forest for the overhead line,

protective measures for roads and watercourses, and new access arrangements would be required to facilitate

the Proposed Development.

A typical double wood pole structure supporting an overhead line is shown in Photograph 4.1, and a typical

sealing end structure is shown in Photograph 4.2, below.

Photograph 4.1: Typical Wood Pole Structure and Overhead Line


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Photograph 4.2: Typical Sealing End Structure

The underground cable itself would be installed under the Applicant’s Permitted Development rights, and is thus

not considered under the EIA for the Proposed Development. It will instead be considered under a separate,

proportionate environmental assessment before any works commence to ensure its potential environmental

effects are fully understood and allow for any measures required to protect the environment to be put in place.

The works are anticipated to be carried out between July 2021 and September 2022, subject to the necessary

approvals being granted.

Development would be carried out in four phases, set out as follows.

4.1 Phase 1 – Enabling Works

Enabling works would involve the following:

• works to existing nearby overhead lines to allow for safe working and operating conditions. It is anticipated

that these would also be realigned or undergrounded in places to make way for the Proposed

Development;

• minor improvements to existing tracks to allow safe access by construction and delivery vehicles and laying

of temporary panels to act as a surface for vehicles in areas of boggy or soft ground. Minor improvements

of existing bellmouths off the public road are also anticipated, which would be discussed and agreed with

The Highland Council (THC) beforehand; and

• felling of areas of forestry to allow for safe operation and maintenance of the Proposed Development.

4.2 Phase 2 – Construction Works

The construction works would be broken into three main stages: foundation works, installation of the wood pole

structures, and stringing of the conductors between the wood poles.

Depending on the slope and conditions of the ground, and the type of wood pole (angle or intermediate), the

foundations would comprise an excavation approximately 3 m long and 2 m wide for each pole at a depth of up

to 3 m. The total construction area may extend up to 8 m by 8 m. Some backfilling may require the addition of


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hardcore to provide additional stability. Where very soft ground is present and unavoidable, the use of ‘bog

shoes’ – large sections of timber similar to railway sleepers – may be implemented

The wood pole structures would be assembled and then transported to each pole location then erected using

one or two excavators, depending on their weight. Tensioned lines, called stays, would be added at angle and

terminal poles, and potentially on slopes, for stability. Excavated soils would then be replaced.

The conductors would be delivered to site on wooden drums and pulled between wood poles by stringing

equipment, comprising winches and tensioners. Prior to this, temporary protection measures, usually netted

scaffolds, would be set up where required across public roads and access tracks. In more difficult sections, or

to reduce the need to use temporary access panels, a helicopter may be used to assist with conductor

stringing.

4.3 Phase 3 – Commissioning

This stage would involve an inspection of the completed works to ensure everything has been built and installed

to specification and that the conductors are fit to carry the required voltage. Once inspections are complete and

satisfied, the circuits would be energised from the substations.

4.4 Phase 4 – Reinstatement

Upon completion of the works, all vehicles and machinery would be removed from site, all temporary panels

removed, and any ground disturbed during construction would be reinstated. .

4.5 Construction Environmental Management

All works would be carried out in accordance with the Applicant’s General Environmental Management Plans

(GEMPs) and Species Protection Plans (SPPs), which have been developed by the Applicant to ensure best

practice working methods are adapted to minimise potential environmental effects.

A contractual management requirement of the successful Principal Contractor would be the development and

implementation of a Construction Environmental Management Plan (CEMP). This document would detail how

the successful Principal Contractor would manage the site in accordance with all commitments and mitigation

detailed in the EIA Report, statutory consents and authorisations, and industry best practise and guidance.

4.6 Construction Employment and Hours of Work

The Applicant considers it important to act as a responsible developer with regards to the communities which

host the construction works. The delivery of a major programme of capital investment provides the opportunity

to maximise support of local communities. Employment of construction staff would be the responsibility of the

successful Principal Contractor; however, the Applicant would encourage the successful Principal Contractor to

make use of suitable labour and resources from areas local to the Proposed Development where possible.

Construction activities would in general be undertaken during daytime periods only. For weekdays, this would

involve work between approximately 07:00 to 19:00 in the summer and 07:30 to 17:00 (or as daylight allows) in

the winter. On Saturdays, the working hours would be approximately 07:00 to 17:00 in the summer and 07:30

to 17:00 (or as daylight allows) in the winter. Any variation in these working hours would be agreed in advance

with the THC.

4.7 Construction Traffic

Construction of the Proposed Development would give rise to regular numbers of staff transport movements,

with small work crews travelling to work site areas. It is anticipated that the Principal Contractor would identify a

single main compound area, with a safe area for parking away from the public highway. Obtaining consent or

other authorisations for this compound would be the responsibility of the Principal Contractor.


March 2020

Vehicle movements would be required to construct upgraded access roads; deliver the foundation and pole

components and conductor materials to site; transport the workforce; deliver and setup mobile welfare units;

and deliver and collect materials and construction plant from the main site compound and to individual pole

locations.

The Principal Contractor would determine where access is required, and for which items of plant, and prepare

Traffic Management Plans in consultation with the Applicant and THC as the local roads authority. Traffic

Management Plans would describe all mitigation and signage measures that are proposed on public roads

based on access maps and subsequent site assessments.

It is anticipated that the A9 and A836 roadways would be utilised by construction traffic. In some instances, the

C 1001 minor road may be used for access to the north end of the Proposed Development; however, this would

be kept to a minimum due to the road’s status as a smaller road designed to serve local residences. Some

measures would be put into place to minimise traffic effects, such as debris control and ensuring no obstruction

of public rights of access.

4.8 Operation and Management of the Transmission Connection

In general, an OHL requires very little maintenance. Regular inspections are undertaken to identify any

unacceptable deterioration of components, so that they can be replaced.

4.9 Decommissioning

It is anticipated that the operational lifespan of Limekiln Wind Farm is 25 years. If the wind farm is

decommissioned at the end of this period, the Proposed Development would also be decommissioned. All

components, including wood poles, conductors and fittings, would be removed from the site and either recycled

or disposed of appropriately. Prior to these works being undertaken, the methods to be employed would be

agreed with THC.


March 2020

5. EIA APPROACH, SCOPE AND CONSULTATION

Environmental Impact Assessment (EIA) is a process that considers how a proposed development will change

existing environmental conditions and what the consequences of such changes will be. It therefore informs

both the project design and planning decision making processes.

An important part of the EIA process involves consulting with a variety of organisations and individuals. This

process is important both for allowing interested parties to express their views or concerns about a proposal,

but also to highlight any specific issues to be assessed or reviewed through the EIA. This stakeholder

consultation takes place throughout the design and assessment process.

Initial consultation was undertaken with Scottish Natural Heritage (SNH) in November of 2017 to set out the

nature and extent of bird surveys and agree the approach to be taken. Once the Proposed Development had

undergone further design and was largely finalised, SNH were contacted again for approval of the survey

methods.

During the review of route options for the Proposed Development, a community consultation event was

undertaken in May of 2018, inviting members of the public from the local area to an exhibition to allow them to

comment on the development. 35 members of the public attended, providing feedback for the Applicant.

A Screening Request was also made to the Energy Consents Unit in May of 2018 to determine if the Proposed

Development would be classed as ‘EIA Development’; i.e. whether it should be subject to a full EIA. The

Screening Opinion, received in June of 2018, confirmed that, due to the Proposed Development’s potential

significant landscape and visual effects, it did constitute EIA Development and any application must be

accompanied by a full EIA Report.

Following this, an EIA Scoping Report was issued to the Energy Consents Unit in September of 2018. This

report set out in detail the anticipated works, the environmental assessment methods to be undertaken, and

information on each of the environmental topics to be addressed. The report concluded with a summary of the

particular elements of each topic proposed to be included or excluded from the EIA based on the potential for

significant effects to arise as a result of the Proposed Development.

In March 2019 the Energy Consents Unit issued their Scoping Opinion in response to the EIA Scoping Report.

This set out formal comments and feedback from statutory consultees, such as SNH and the Scottish

Environmental Protection Agency (SEPA), as well as a number of non-statutory consultees consulted as part of

the process. The Scoping responses noted a number of items to be addressed as part of the EIA. These

comments and topics are addressed throughout the EIA Report.

In July 2019, a Gate Check Report was issued to the Energy Consents Unit. The purpose of this report was to

set out the comments and issues raised by consultees in response to the EIA Scoping Report, and set out how

these have been addressed within the EIA Report. A second community consultation event was also carried

out at this time, providing updated information on the status of the project and the preferred route for

connection. No comments were made in relation to the Proposed Development, and one general question was

posed around the planning process and opportunities to make representations.

Throughout the above process, specific consultation was undertaken with a few consultees to further discuss

key issues raised through the consultation process.


March 2020

6. ENVIRONMENTAL EFFECTS OF THE PROPOSALS

The EIA considers the potential for significant effects as a result of the Proposed Development on the following

environmental features:

• landscape and visual impact;

• ecology;

• ornithology;

• cultural heritage;

• hydrology, hydrogeology, geology and soils; and

• forestry.

6.1 Landscape and Visual Impact

The landscape and visual impact (LVIA) assessment considers how the Proposed Development may affect

those living, working and visiting in the area, and the wider landscape. A combination of desk-studies and

surveys in and around the local area were used to determine these potential effects, including production of a

zone of theoretical visibility (ZTV); a computer model based on digital terrain data provided by Ordnance Survey

which sets out where the Proposed Development may be visible from. It assumes a largely ‘bare earth’

scenario, and doesn’t account for visibility being screened by buildings, trees, vegetation or artificial

embankments.

The ZTV formed the basis of the site survey, during which surveyors visited nearby publically accessible

receptors and public routes which may have visibility and assessed the potential impacts of the Proposed

Development. Two visualisations, produced from on-site photography, are included with the EIA Report to

illustrate the appearance of the Proposed Development in situ. While their intended purpose is not to illustrate

visual impacts, they were used to assist the visual impact assessment.

The landscape assessment considers how the Proposed Development may impact upon defined landscape

character areas, as set out by SNH and partner Councils. Considering the likely effects against the particular

characteristics of these landscape character areas, the assessment concludes that no significant impacts upon

the landscape are likely, as there would be no noticeable change or deterioration in their characteristics or

values.

The visual impact assessment considers how the Proposed Development may affect sensitive visual receptors,

such as local residents or those using nearby paths and roads. The assessment concludes that temporary

significant effects are likely for a small number of receptors during construction; however, these effects would

diminish following completion of construction and reinstatement of the site and be of a non-significant level.

Cumulative effects are considered in combination with the Limekiln Wind Farm and the proposed extension to

the Dounreay substation; Dounreay West Substation. It is not considered that the addition of the Proposed

Development to other existing and proposed infrastructure would result in a significant increase in perception of

such developments within the study area.

6.2 Ecology

The ecological assessment considers how the Proposed Development may affect sensitive habitats or

protected species. Desk studies were carried out to identify sites designated for nature conservation and

records of protected species within the vicinity of the Proposed Development, and field surveys undertaken to

identify habitats, plants of significance, and signs of protected species within 250 m.

Several international and national designated sites were identified, including the Caithness and Sutherland

Peatlands Special Area of Conservation (SAC) / RAMSAR, Broubster Leans SAC, Caithness Lochs RAMSAR,

and several Sites of Special Scientific Interest (SSSI). Given the nature and location of the Proposed

Development, and lack of representative features of these designated sites and the development site, it is not

likely that any impacts would occur.


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A variety of habitat types were identified along the route, all of which are of low, very low or negligible ecological

value. Based on the alignment, use of existing tracks and temporary panels, where necessary, and anticipated

land take, no significant impacts are likely to arise on habitats.

Signs of water vole, otter and pine marten were identified during field surveys. No signs of other protected

species were noted, and these were discounted from further assessment. Previous surveys had recorded the

presence of salmon and trout in the Achvarasdal Burn, and it is assumed likely that habitat suitable for these

species is also present in the Dounreay Burn. Of these species, only water vole are likely to experience

significant impacts without the implementation of mitigation measures, which are set out within the Ecology

Chapter of the EIA Report. Observation of the Applicant’s GEMPs and SPPs would ensure no significant

impacts on fish species.

Consequently, all effects on ecology would be reduced to non-significant levels.

Cumulative impacts were considered in relation to Limekiln Wind Farm and Dounreay West Substation. The

addition of effects as a result of the Proposed Development to these would be sufficiently low and no significant

cumulative effects are likely.

6.3 Ornithology

The ornithology assessment considers how the Proposed Development may affect bird species, either

protected or of conservation concern. Desk studies were undertaken to identify sensitive bird species

previously recorded at the site and sites designated for protected bird species. Various bird surveys were also

undertaken, following agreement of methodology with SNH, between April 2018 and March 2019 to collect data

on flights and species present.

Various bird species were recorded, from those with negligible or local value up to international valued species

forming designated features of Special Protection Areas (SPA) within 20 km of the Proposed Development.

Potential effects on bird species are considered in terms of habitat loss, modification of bird habitat,

displacement of bird species, or accidental mortality of bird species through collision or electrocution. The

design of the Proposed Development is such that there should be no risk of electrocution due to the gaps

between conductors.

All impacts on designated sites and high sensitivity species are likely to be low or negligible in magnitude, and

thus not significant. Notwithstanding this, mitigation measures are set out in order to further reduce potential

effects, such as carrying out pre-construction checks for breeding birds and ceasing works should a nest be

discovered during construction until advice is sought from a qualified ornithologist.

Cumulative effects were considered against Limekiln Wind Farm and Dounreay West Substation. The study

areas for these developments overlap with that of the Proposed Development, and their respective

environmental assessments concluded that there were no likely significant impacts on identified bird species.

Consequently, potential cumulative effects with the Proposed Development are not likely to be significant.

6.4 Cultural Heritage

The cultural heritage assessment considers how the Proposed Development may affect archaeology and built

heritage. During desk and field surveys, six Scheduled Monuments (SMs) and a number of lower sensitivity

historic environment records (HERs) were identified within the vicinity.

The assessment considers the potential for direct impacts, which would result in a physical impact or change to

the historic feature, and indirect impacts, which are visual impacts which alter the setting of the feature.

Potential direct impacts are considered within a 200 m corridor, while indirect impacts are considered within 2

km.

No direct impacts are considered likely for any historic features. Indirect impacts are considered for SMs, with

five of the six considered unlikely to experience significant impacts through direct application of the assessment

methodology outlined in Chapter 9: Cultural Heritage. Assessment of the remaining SM, Clac Claid an Tuirc

Standing Stone, derived a moderate level of effect, considered to be significant by the standard methodology.


March 2020

However, on balance with other considerations, such as the existing alteration to its historic setting as a result

of the conifer plantation, effects are likely to be non-significant in reality.

Mitigation measures are proposed to further limit effects, including the application of separation buffers around

historic features to ensure no direct impacts, and limiting the scope of felling to the west of the Proposed

Development as it passes the standing stone to avoid an increase in visual prominence. This mitigation via

felling would be a temporary measure as the forest block in question is planned to be fully felled by the land

owner between 2028 and 2032.

An assessment of cumulative effects with Limekiln Wind Farm and Dounreay West Substation determines that

significant effects are unlikely.

6.5 Hydrology, Hydrogeology, Geology and Soils

This assessment considers how the Proposed Development is likely to affect the soil and water environments.

As effects on these environments can be complex and have wide-ranging effects, the Proposed Development

has been assessed against an array of different legislation, planning policies and guidance documents.

Information for the assessment was drawn from numerous sources, including specific data requests to the

Scottish Environmental Protection Agency and THC.

Assessment of potential effects was carried out in relation to the following aspects of the soil and water

environments:

Peat and Peat Landslide Hazard Risk Assessment

A preliminary peat landslide risk assessment was undertaken by modelling peat depth data collected at various

points during the Proposed Development’s design and digital terrain data to determine instability risk of peat

soils. It was determined that the instability risks for the soils beneath the OHL would be negligible for the

majority of the route, and low for short segments. Consequently, peat slide risk for the Proposed Development

would be minimal, and a full peat landslide hazard risk assessment is not considered necessary.

Notwithstanding this, best practice measures are proposed to further safeguard peat at the site.

No significant earthworks are required; however, best practice measures would be employed in order to

safeguard peat as set out within the Applicant’s GEMP. Consequently, no significant impacts are considered

likely to arise on peat soils.

Soils and Geology

No significant earthworks are required; however, best practice measures would be employed to safeguard soils,

such as managing excavated soils to ensure their value is not degraded, avoiding works during periods of

heavy rain and areas of saturated ground following such, and using ground protection such as temporary

panels for movement of vehicles. These safeguards, in combination with observation of the Applicant’s

GEMPs, would prevent any significant impacts from arising on soils or geology.

Surface Water and Groundwater Quality

Surface water and groundwater quality can be affected by pollutants from development. The Applicant’s

previously mentioned good practice and working control measures are considered sufficient to limit pollution,

and no additional mitigation measures are proposed. Any water required on site, inclusive of site welfare

facilities for personnel, would be provided by a water tanker where a potable supply or water abstraction is not

available, and waste water taken away and disposed of at an appropriately licensed facility.

Flood Risk

Areas of flood risk are highly sensitive, and increases in flood risk can have wide-ranging effects. No new

permanent development would take place within the 1000-year floodplain (i.e. the flood plain of a storm so large

that it has only a 0.1 % chance of occurring in any given year).

Three temporary watercourse crossings are required to facilitate development, and their design will be agreed

with the Scottish Environmental Protection Agency prior to development taking place.


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Surface and Groundwater Flow

Similarly, the good practice and working control measures would serve to ensure surface and groundwater

flows are not impeded, with no difference caused to watercourses or ground conditions. Excavations would be

small in area and depth, with pre-construction ground surveys carried out to identify any further safeguards

required.

Private Water Supplies

No private water supplies were identified within 250 m of the Proposed Development, and thus no impacts are

likely to arise on such.

Designated Sites

No designated sites dependent on water were identified within three kilometres of the Proposed Development.

Good practice and working control measures are thus considered sufficient to prevent any effects upon such

sites.

Summary

With the implementation of best practice mitigation measures, no significant effects are considered likely to

arise on the soil or water environments local to the site.

6.6 Forestry

The forestry assessment considers the potential effects from the Proposed Development on the forest areas at

the development site. Current forest conditions were derived from a combination of desk studies and field

surveys, while the assessment itself is based on the operational corridor (OC), defined as the area required to

be kept clear of vegetation to allow safe operation and maintenance of the overhead line.

As discussed in Section 3, the design of the Proposed Development was revised in order to limit requirements

for felling of forest areas. Furthermore, the Limit of Deviation, defined as the area within which construction of

the overhead line can take place to allow for micrositing to avoid areas of difficult ground or other barriers to

construction, has been refined from an engineering optimum of 80 m to 60 m in order to minimise the potential

for felling of windfirm edges of forest blocks. These edges have grown in such a way as to protect the core of

each forest block from wind effects, and their removal can lead to a situation known as windthrow, where trees

are gradually blown over by wind once exposed.

The forest areas are largely composed of productive conifer plantation, comprising sitka spruce and lodgepole

pine species, and an approved forestry felling plan, devised by Scottish Forestry, is in place. Assessment of

forestry impacts is undertaken through comparison of the loss of woodland to felling against the sensitivity of

the forest itself. The width of the OC has been set at 60 m. Given that the maximum likely height of tree grown

at the site is around 25 m, accounting for the width of the wood pole structures and a safety zone around

conductors, a maximum separation of 30.5 m from the centreline of the Proposed Development would be

required, for a total width of 61 m, rounded down. As noted previously, the alignment has been selected to

avoid the majority of woodland areas, and the Limit of Deviation reduced to minimise potential felling

requirements.

Micrositing would be carried out during construction to limit required felling, where this would not conflict with

other environmental sensitivities; however, based, on the current alignment, the maximum felling requirement

within the OC as defined would be 4.78 hectares. In order to account for windthrow effects, it is proposed that a

further 7.30 hectares of indirect felling be carried out for one of the forest blocks the Proposed Development

would pass through. This would result in a total felling requirement of 12.08 hectares.


March 2020

Given that the Proposed Development is likely to affect coniferous plantation only, which is considered to be

low sensitivity woodland, and that that anticipated felling is small in comparison with the forest areas, impacts

on forestry are not likely to be significant.

Cumulative effects are considered against the Limekiln Wind Farm, which will require more extensive woodland

felling of 53.42 hectares from the total woodland area of 1,122.9 hectares. As the additional loss for the OC

and resulting from indirect felling for the Proposed Development would be negligible in comparison with the

overall area, cumulative effects are not likely to be significant for forestry interests.


March 2020

7. CUMULATIVE EFFECTS

Assessment of cumulative effects requires consideration of how a development is likely to interact with other

similar nearby developments. While each development on its own may not result in any significant effects,

multiple developments affecting the same elements of the environment, such as sensitive habitats or local

residents, may result in significant effects when considered together.

Cumulative effects can also arise through the interaction between different types of effects arising from the

same development on a particular aspect of the environment. For example, the effects of dust, noise, vibration,

light, human presence and visual effects on a nearby protected species may individually be non-significant, but

when considered together may give rise to a significant level of effect.

As described in Section 6, the individual technical chapters within this EIA Report consider the potential

cumulative effects of the Proposed Development with other developments, principally the proposed Limekiln

Wind Farm and the proposed extension to the Dounreay substation, known as Dounreay West Substation. No

significant cumulative effects were identified.


March 2020

8. CONCLUSION

SHE Transmission is proposing to construct and operate a 5 km overhead line grid connection between the

proposed Limkeiln Wind Farm south of Reay and an underground cable south-east of Dounreay to the north.

This would involve installation of wood pole structures to support conductors between the wind farm on-site

substation and a sealing end structure south of the A836. This structure would transfer to an underground

cable running the last 900 m to Dounreay substation, which itself would be considered under SHE

Transmission’s Permitted Development Rights. The construction of the overhead line, sealing end structure

and associated works, including felling of woodland to accommodate the overhead line, protective measures for

roadways and watercourse crossings, and new access arrangements, comprise ‘the Proposed Development’.

The need for the project is driven by the consented Limekiln Wind Farm south of Reay, and the developer’s

request for a connection to the national electricity network. SHE Transmission, as the owner and operator of

the transmission network, is obligated to carry out this connection in the most efficient, cost effective and co-

ordinated manner while minimising potential environmental impacts.

Consultation with statutory and non-statutory consultees was carried out throughout the EIA and Scoping

process, in addition to public engagement, in order to invite comment on the Proposed Development itself and

specific areas of environmental assessment to incorporate into the EIA.

The EIA incorporates assessment of the Proposed Development’s likely significant effects on the following

environmental aspects:

• Landscape and visual impact;

• ecology;

• ornithology;

• cultural heritage;

• hydrology, hydrogeology, geology and soils; and

• forestry.

Subject to implementation of SHE Transmission’s good practice and working control measures, as well as the

identified site-specific mitigation measures outlined in each technical chapter of the EIA Report and

summarised in Chapter 12: Schedule of Environmental Mitigation, the Proposed Development is not considered

likely to give rise to any significant residual effects.

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