CONTENTS...10. HYDROLOGY, HYDROGEOLOGY, GEOLOGY AND SOILS 10.1 Introduction 10.1.1 This Chapter presents an assessment of the potential effects on soils, geology (including peat) and

Creag Riabhach Wind Farm Grid Connection: Environmental Statement Page 10-1

Chapter 10: Hydrology, Hydrogeology, Geology and Soils February 2020

CONTENTS

10. HYDROLOGY, HYDROGEOLOGY, GEOLOGY AND SOILS 10-2 10.1 Introduction 10-2 10.2 Legislation and Guidance 10-2 10.3 Overall Approach 10-9 10.4 Baseline Conditions 10-12 10.5 Summary of Proposed Development 10-30 10.6 Good Practice and Embedded Mitigation by Design 10-34 10.7 Assessment of Potential Effects 10-35 10.8 Summary and Conclusion 10-39

Figures (Volume 3)

Figure 10.1: Local Hydrology

Figure 10.2: Soil Plan

Figure 10.3: Superficial Geology Plan

Figure 10.4: Peatland Classification

Figure 10.5: Bedrock Geology Plan

Figure 10.6: Peat Depth

Figure 10.7: Regional Hydrogeology

Figure 10.8: Groundwater Vulnerability

Appendices (Volume 4)

Appendix 10.1: Peat Management Plan (PMP)

Appendix 10.2: Peat Landslide Hazard Risk Assessment (PLHRA)

Appendix 10.3: Peat Investigation



10. HYDROLOGY, HYDROGEOLOGY, GEOLOGY AND SOILS

10.1 Introduction

10.1.1 This Chapter presents an assessment of the potential effects on soils, geology (including peat) and the water

environment as a result of the Proposed Development.

10.1.2 The assessment is supported by data provided by The Highland Council (THC), Forestry and Land Scotland

(FLS) and the Scottish Environment Protection Agency (SEPA) to characterise current baseline conditions. A

programme of site investigation, which has included peat depth and permeability assessment, has also been

completed and used to inform the design of the Proposed Development and to complete the assessment. The

Chapter discusses the baseline conditions and summarises relevant consultation responses. Industry standard

mitigation measures that would be used as part of the proposed works are detailed and the potential effects of

the Proposed Development on soils (including peat), geology, and the local groundwater and surface water

environments are then identified.

10.1.3 This assessment has considered a buffer of 500 m from the Proposed Development, which includes the

overhead lines (OHL), underground cable alignment, access spur roads, and horizontal directional drill

compounds.

10.1.4 The Proposed Development is located across open moorland and commercial forestry that has been partly

clear felled. Some of the clear felled forestry has been subject to peat restoration. Access is granted from the

A836 public road for much of the route while existing forestry and estate tracks are utilised where possible for

vehicular access.

10.1.5 This assessment has been informed by the following appendices, which should be read in conjunction with this

Chapter:

• Appendix 10.1: Peat Management Plan (PMP);

• Appendix 10.2: Peat Landslide Hazard Risk Assessment (PLHRA); and

• Appendix 10.3: Peat Investigation.

10.1.6 This Chapter has been prepared by SLR Consulting Ltd (SLR) under the supervision of a Technical Director

(FCIWEM). SLR have more than 25 years’ experience in the assessment of electrical transmission

infrastructure, soils, geology and the water environment. This experience includes many sites in Scotland in a

similar setting to this Proposed Development.

10.2 Legislation and Guidance

10.2.1 This assessment has been undertaken with regard to the following environmental legislation, planning policy

and general guidance.

Legislation

• The Water Environment (Controlled Activities) (Scotland) Regulations, 2011 (Controlled Activities

Regulations (CAR)) (as amended);

• EU Water Framework Directive (2000/60/EC);

• EU Drinking Water Directive (98/83/EC);

• The Public Water Supplies (Scotland) Regulations 2014;

• The Flood Risk Management (Scotland) Act 2009;

• Surface Waters (Fishlife) (Classification) (Scotland) Amendment Regulations 2003;

• Water Environment and Water Services (Scotland) Act 2003 (WEWS Act); and

• The Water Intended for Human Consumption (Private Supplies) (Scotland) Regulations 2017.



Planning Policy

10.2.2 In addition to Scottish Planning Policy (SPP) published by The Scottish Government (June 2014), THC

Highland-wide Development Plan (HwDP) (5th April 2012) provides planning guidance on the type and location

of development that can take place in the region. The HwDP presents policies of which the following are

relevant to this assessment:

• Policy 28 - Sustainable Design;

• Policy 30 - Physical Constraints;

• Policy 51 - Trees and Development;

• Policy 52 - Principle of Development in Woodland;

• Policy 53 – Minerals;

• Policy 55 - Peat and Soils;

• Policy 57 - Natural, Built and Cultural Heritage;

• Policy 58 - Protected Species;

• Policy 59 - Other Important Species;

• Policy 60 - Other Important Habitats;

• Policy 62 - Geo-diversity;

• Policy 63 - Water Environment;

• Policy 64 - Flood Risk;

• Policy 69 - Electricity Transmission Infrastructure; and

• Policy 72 – Pollution.

Guidance

10.2.3 The following guidance is also applicable to the assessment.

10.2.4 Planning Advice Notes (PANs) are published by the Scottish Government. Applicable PANs include:

• PAN 50 Controlling the Environmental Effects of Surface Mineral Workings;

• PAN 61 Planning and Sustainable Urban Drainage Systems (SUDS); and

• PAN 69 Planning and Building Standards Advice on Flooding.

10.2.5 SEPA and NetRegs Pollution Prevention Guidelines (PPG) and replacement Guidance for Pollution Prevention

(GPP):

• PPG 1: Understanding your environmental responsibilities - good environmental practices;

• GPP 2: Above ground oil storage tanks;

• GPP 5: Works and maintenance in or near water;

• PPG 6: Working at construction and demolition sites;

• PPG 7: Safe Storage - The safe operation of refuelling facilities;

• GPP 8: Safe storage and disposal of used oils;

• GPP 13: Vehicle washing and cleaning;

• GPP 21: Pollution incident response planning; and

• GPP 22: Dealing with spills.

10.2.6 Construction Industry Research and Information Association (CIRIA) publications:

• C532 Control of Water Pollution from Construction Sites (2001);

• C648 Control of Water Pollution from Linear Construction Projects – Technical Guidance (2006);



• C741 Environmental Good Practice on Site (2015); and

• C753 The SUDS Manual (2015).

10.2.7 SEPA Publications:

• Engineering in the Water Environment: Good Practice Guide – River Crossings (2010);

• Engineering in the Water Environment: Good Practice Guide – Sediment Management (2010);

• Engineering in the Water Environment: Good Practice Guide – Temporary Construction Methods (2009);

• Groundwater Protection Policy for Scotland, Version 3 (2009);

• Land Use Planning System SEPA Guidance Note 4, Issue 9 (September 2017);

• Land Use Planning System SEPA Guidance Note 31, Version 3 (September 2017); and

• Position Statement – Culverting of Watercourses (2015).

10.2.8 Other Guidance:

• Department of Environment, Food and Rural Affairs (DEFRA) Construction Code of Practice for the

Sustainable Use of Soils on Construction Sites (2011);

• DEFRA Good Practice Guide for Handling Soils (Ministry of Agriculture, Fisheries and Food (MAFF) (2000);

and

• Flood Risk and Drainage Impact Assessment: Supplementary Guidance (January 2013).

Information Sources

10.2.9 The following sources of information have been consulted to characterise the soils, geology, hydrogeology and

hydrology of the proposed works and adjacent area:

• Creag Riabhach Wind Farm Environmental Statement, Pegasus Group, January 2014;

• Dalchork 132kV Substation Environmental Appraisal, Ramboll, January 2019;

• Ordnance Survey (OS) 1:50,000 scale mapping data;

• British Geological Survey (BGS) 1:50,000 scale data - superficial deposits, bedrock and linear features

geology1;

• BGS Hydrogeological Map of Scotland, 1988;

• James Hutton Institute National Soil Map of Scotland (1:250,000)2;

• SEPA Groundwater Vulnerability Map of Scotland, SNIFFER, 2004;

• SEPA flood maps3;

• SEPA Water Environment Hub for water body classifications4;

• Scottish Natural Heritage (SNH) Sitelink Online Information Service5;

• SNH Carbon and Peatland 2016 Map6;

• Natural England Magic Map7;

• Joint Nature Conservation Committee The Geological Conservation Review8;

1 British Geological Survey GeoIndex Onshore, http://mapapps2.bgs.ac.uk/geoindex/home.html, accessed April 2019

2 Scotland’s Soils, http://soils.environment.gov.scot/maps/, accessed April 2019

3 Scottish Environment Protection Agency, https://www.sepa.org.uk/environment/water/flooding/flood-maps/ and

http://map.sepa.org.uk/reservoirsfloodmap/Map.htm, accessed April 2019 4 Scottish Environment Protection Agency, Water Classification Hub, https://www.sepa.org.uk/data-visualisation/water-classification-hub/, accessed April

2019 5 Scottish Natural Heritage, Sitelink Inline Information Service, https://gateway.snh.gov.uk/sitelink/searchmap.jsp, accessed April 2019

6 Scottish Natural Heritage, Natural Spaces, https://gateway.snh.gov.uk/natural-spaces/dataset.jsp?dsid=PEAT, accessed April 2019

7 Natural England, Magic Map Application, http://magic.defra.gov.uk/MagicMap.aspx, accessed April 2019

8 JNCC Geological Conservation Review, http://jncc.defra.gov.uk/page-2947, accessed April 2019

http://mapapps2.bgs.ac.uk/geoindex/home.html

http://soils.environment.gov.scot/maps/

http://map.sepa.org.uk/reservoirsfloodmap/Map.htm

https://www.sepa.org.uk/data-visualisation/water-classification-hub/

https://gateway.snh.gov.uk/sitelink/searchmap.jsp

https://gateway.snh.gov.uk/natural-spaces/dataset.jsp?dsid=PEAT

http://magic.defra.gov.uk/MagicMap.aspx

http://jncc.defra.gov.uk/page-2947



• data requests to SEPA regarding details of registered / licensed abstractions and discharges (April 2019);

and

• data requests to THC environmental health department regarding details of historic flooding records and

private water abstractions (April 2019).

Consultation

10.2.10 The consultation process is discussed in detail in Chapter 4 of this EIA Report. Table 10-1 summarises

responses to the consultation responses received that are relevant to soils, geology and the water environment.

Table 10-1: Consultation Responses of Relevance to Hydrology, Hydrogeology, Geology and Soils

Consultee Response Comment

Scoping

Response from

THC

6th June 2019

The proposed route crosses a number of

watercourses and careful consideration of the

siting, design and layout of the overhead line will

be required.

Supplementary Guidance will be important to take

account of within any assessment on development

impact, including the Flood Risk and Drainage

Impact Assessment: Supplementary Guidance

(January 2013).

The design and layout of the

OHL have been considered so

as to minimise impact on

watercourses. Details are set

out in this Chapter.

The noted Supplementary

Guidance has been utilised as

part of this assessment.

Scoping

Response from

SEPA

8th April 2019

The following should be incorporated in the design

of the overhead line, access routes, laydown

areas and construction compounds:

• No OHL poles or construction works should

be located on any watercourse bank;

• Details of groundwater abstractions to be

provided and design of the OHL route should

avoid buffer areas;

• Proposals for temporary watercourse

crossings to be provided; and

• Tree felling waste from works to be removed

from site;

• Proposals for borrow pits should be discussed

with SEPA.

Supporting maps should detail all proposed

upgraded, temporary and permanent site

infrastructure.

The submission must demonstrate how the layout

has been designed to minimise disturbance of

peat and outline the preventative / mitigation

measures to avoid significant drying or oxidation

of peat. The submission must include a detailed

map of peat depths and tabulated excavation

volumes.

Phase 1 habitat wetland areas also known as

Groundwater Dependent Terrestrial Ecosystems

(GWDTE) are protected under the Water

Framework Directive and therefore the layout and

design of the development must avoid impact on

With the exception of where

the proposed OHL crosses

watercourses a 50m buffer

would be applied to

watercourses.

Licensed and private water

abstractions near to the

Proposed Works have been

identified and avoided.

Plans show the location of

proposed upgraded tracks with

relation to watercourses, peat

and GWDTE habitat have

been prepared.

Subject to other development

constraints, areas of deep

peat, potential GWDTE,

flushes and peat instability

have been avoided.

Forestry is assessed in chapter

11.

No borrow pits are required.




such areas. A plan should be provided presenting

the locations of potential GWDTEs and buffer

areas.

A schedule of mitigation for the periods of

construction, operation, maintenance, demolition

and restoration should be prepared.

Gate Check

Response from

SEPA

16th December

2019

Following review of the gate check report and

meeting SEPA requested that:

• Permanent access roads (spurs) are shown

on development drawings and have the peat

depth information overlaid with this. If peat is

to be impacted appropriate proposals for peat

re-use should be made;

• Details of peat depths and any peat re-

use/storage proposals should be clearly

outlined, along with restoration proposals for

temporary infrastructure associated with site

compounds at the proposed Crask crossing;

• The route will cross areas of deep peat and

some of the most difficult ground conditions

have been avoided, but any sensitive wetland

habitats and deep peat areas should have

clear mitigation, outlining how impacts will be

minimised. It was noted that bog matting

might only be appropriate in some locations

depending on topography and that low ground

pressure vehicles are commonly used. We

would ask that a suite of measures be

considered by site contractors to ensure a

precautionary approach is taken to minimising

impacts on peat and wetlands;

• It is welcomed that no felled timber will be left

on site and that trees under a merchantable

size will be utilised for the biomass market.

• It is noted that there will be a Peat

Management Plan produced, and this should

address any re-use of excavated peat that will

not be directly used in backfilling. Due to the

peatland restoration works taking place, the

re-use proposals and working methods should

outline how they will compliment these works.

Methods / approach to ditch blocking should

be outlined etc.

• It is noted that the location of a site compound

/ laydown area will be left to discretion of the

principal contractor at a later stage. As

mentioned in the meeting, we would expect

an indicative location to be identified to ensure

that peat and GWDTE considerations have

been considered, and if the permission for

these is included within this proposed

consent, then we are likely to ask for a

condition to be applied.

The location of permanent

access tracks and recorded

peat depths are shown on the

Proposed Development

drawings.

See PMP (Appendix 10.1).

No peat is recorded at the

proposed compound locations

near the Crask River crossing.

See PMP (Appendix 10.1)

and PLHRA (Appendix 10.2).

Noted.

The PMP (Appendix 10.1)

outlines the general nature of

peat management works given

the information available at this

stage. The Applicant will liaise

directly with FLS and the SNH

Peatland Action Group during

the development of the Stage

2 PMP, and any requirement

for post construction

reinstatement and restoration.

As discussed within Section

3.8 of Chapter 3 of this EIA

Report, the locations of any

temporary site compounds

would be at the discretion of

the Principal Contractor.

Insufficient information is

available at this stage to

determine indicative locations,

and they may be located away




from the site altogether;

however, all available

information relation to peat

soils and GWDTEs would be

made available to the Principal

Contractor in order to ensure

compounds are sited so as to

avoid peat and GWDTE.

Scoping

Response from

Scottish Water

3rd April 2019

No objection to proposals. N/A

Scoping

Response from

Scottish Natural

Heritage (SNH)

3rd May 2019

The EIA report should clearly detail what

mitigation will be implemented to prevent impacts

to the Caithness and Sutherland Peatlands

Special Protection Area (SPA) and Special Area of

Conservation (SAC).

Impacts to the River Naver SAC should be fully

considered within the hydrology section of the EIA

report.

A full NVC survey and peat depth survey should

be undertaken for the OHL section that lies within

the Ben Klibreck Site of Special Scientific Interest

(SSSI). SNH habitat data suggests there may be

pockets of blanket bog within the SSSI and these

should be avoided.

Low ground pressure machines should be used

for all construction within protected areas and

peatland habitats and in order to minimise ground

disturbance poles should not be dragged across

the site.

A detailed construction method statement should

be included as a supporting document within the

EIA.

A restoration plan should also accompany the EIA

detailing what restoration methods will be used

including detail what monitoring and subsequent

actions will be undertaken to ensure restoration is

successful.

A plan should be prepared indication the location

of construction compounds and pulling points,

both of which should avoid protected areas and

Class 1 and 2 priority peatland habitats and Class

5 habitats that have undergone restoration

(Dalchork forest).

The construction methodology should detail how

impacts would be minimised on nationally

important peat habitats.

Mitigation measures required

to safeguard Caithness and

Sutherland Peatlands SPA and

SAC, and the River Naver SAC

have been specified (see

Section 10.6).

A NVC survey has been

undertaken (see Chapter 7:

Ecology). A peat depth survey

has been undertake for the

whole route of the Proposed

Development.

Details of construction

methods are outlined in

Chapter 3 of this EIA Report.

This identifies that low ground

pressure vehicles and

temporary access panels

would be utilised to minimise

impacts on all protected areas

and peatland habitats.

Methods for reinstatement

would be detailed in

construction method

statements, as part of the

CEMP.

The locations of construction

compound(s) and pulling

points for the Proposed

Development would be

identified by the Principal

Contractor, who would seek

any permissions required for

such at the point of detailed

design and mitigation will be

provided via the CEMP.




Gate Check

Response from

SNH

4th December

2019

In response to the gate check report SNH

commented that:

• The proposed line will cross the River Naver

SAC and that impacts to this SAC should be

considered in full within the EIAR. The

qualifying features of the SAC are vulnerable

to pollution and the EIAR should detail what

mitigation will be implemented to avoid

impacts to this protected area.

• Some of the proposed line will pass through

Class 1 and Class 2 Carbon Rich Soils, Deep

Peat and Priority Peatland Habitat and

construction methodology should detail how

minimised on this habitat.

• The proposed line will pas through areas of

restored peat restored through Peatland

Action. These areas should be left in as good

or better condition on completion of

construction of the line. Pre and post

construction surveys should be completed by

a drone survey. Any required restoration

works should be agreed with SNH and FLS.

• The EIAR should detail what mitigation will be

provided to safeguard water quality in the

River Tirry during proposed Horizontal

Directional Drilling (HDD) beneath the river.

SNH advise that a geotechnical survey should

be undertaken prior to any HDD drilling to

ensure bentonite does not leak within the river

bed.

See Good Practice and

Embedded Mitigation by

Design.

See embedded mitigation and

PMP (Appendix 10.1).



Design and the commitment to

undertaken pre and post

development surveys.



Design which includes site

investigation to inform the

HDD programme.

Marine Scotland

Science (MSS)

Information on local fish populations and fisheries

should be sought from the Kyle of Sutherland and

the Brora District Salmon Fishery Boards (DSFB)

and the Kyle of Sutherland Fisheries Trust.

MSS ask that the ES includes the following:

• A description of which fish species are

present and their abundance in the

waterbodies and watercourses which could be

impacted by the development, and whether

they are important for conservation or

supporting fisheries;

• A description of the water quality of

waterbodies which could be impacted and

how the development may impact on these

pre-construction conditions;

• A description of what activities during

construction, post-construction and

decommissioning have the potential to impact

on fish or associated fisheries and what

mitigation measures will be put in place to

avoid and / or reduce this impact;

See Chapter 7 (Ecology) of

this EIA Report for information

on fisheries.

The existing quality of

watercourses and pressures

on these has been identified

(see Section 10.4: Baseline

Conditions).




• Consideration of potential cumulative effects

with adjacent and other developments; and

• Proposals for monitoring during construction,

post-construction and decommissioning.

Kyle of

Sutherland

DSFB

26th April 2019

The Tirry catchment is subject to a salmon

restoration project involving the Kyle of Sutherland

DSFB, SSE and SEPA. Consideration of this

project must be given to protecting the aquatic and

riparian environment.

See Chapter 7 (Ecology) of

this EIA Report.

Safeguards to protect water

quality and flows of water in

the River Tirry have been

specified.

Gate Check

Response from

RSPB

12th December

2019

In response to the gate check report, RSPB

commented that the findings of site works and the

peat investigation work should be undertaken to

inform the new alignment should be included in

the EIA.

See Peat Investigation report

(Appendix 10.3).

10.3 Overall Approach

10.3.1 This assessment has involved the following:

• review of the Creag Riabhach Wind Farm Environmental Statement and Dalchork Substation

Environmental Appraisal;

• a desk study to establish existing soils, geology and hydrogeological and hydrological conditions beneath

and adjacent to the Proposed Development;

• site familiarisation visits by the technical team of this Chapter (14/05/2019 and 16-19/09/2019), which

included a peat investigation, assessing watercourse crossings and a Private Water Supply (PWS) survey;

• identification of the potential effects on the soils, geology and water environment and their significance; and

• identification of additional required mitigation measures and assessment of any residual effects.

Assessment Method

Assessing Significance

10.3.2 The significance of potential effects from the Proposed Development has been assessed by considering two

factors: the sensitivity of the receiving environment and the potential magnitude of effect, should that occur.

10.3.3 The assessment methodology has also been informed by experience of carrying out such assessments for a

range of electrical infrastructure developments, knowledge of the water environment characteristics in Scotland

and cognisance of good practice.

10.3.4 This approach provides a mechanism for identifying the areas where mitigation measures are required and for

identifying mitigation measures appropriate to the significance of potential effects presented by the Proposed

Development.

10.3.5 Criteria for determining the significance of effect are provided in Table 10-2, Table 10-3 and Table 10-4.

Sensitivity of Receptor

10.3.6 The sensitivity of the receiving environment (i.e. the baseline quality of the receiving environment) is defined as

its ability to absorb an effect without a detectable change. It can be considered through a combination of

professional judgement and a set of pre-defined criteria which are set out in Table 10-2. Receptors in the



receiving environment only need to meet one of the defined criteria to be categorised at that associated level of

sensitivity.

Table 10-2: Criteria for Assessing Sensitivity of Receptor

Sensitivity Example

High • SEPA Water Framework Directive Water Body Classification: High-Good or is

close to the boundary of a classification Moderate to Good or Good to High;

• receptor is of high ecological importance or national or international value (e.g.

SSSI, SAC, habitat for protected species or Geological Conservation Review

sites) which may be dependent upon soil, geology or the hydrology of the

development area;

• receptor is at high risk from flooding above 0.5% Annual Exceedance Probability

(AEP) and / or water body acts as an active floodplain or flood defence;

• receptor is used for public and / or private water supply (including Drinking Water

Protected Areas (DWPA);

• groundwater vulnerability is classified as high; and

• if a GWDTE is present and identified as being of high sensitivity.

Moderate • SEPA Water Framework Directive Water Body Classification Moderate or is

close to the boundary of a classification Low to Moderate;

• receptor is at moderate risk from flooding (0.1% AEP to 0.5% AEP) but does not

act as an active floodplain or flood defence; and

• moderate classification of groundwater aquifer vulnerability.

Low • SEPA Water Framework Directive Water Body Classification Poor or Bad;

• receptor is at low risk from flooding (less than 0.1% AEP); and

• receptor not used for water supplies (public or private).

Not Sensitive • receptor would not be affected by the Proposed Development, e.g. lies within a

different and unconnected hydrological or hydrogeological catchment.

Magnitude of Effect

10.3.7 The potential magnitude of an effect would depend upon whether the potential effect would cause a

fundamental, material or detectable change. In addition, the timing, scale, size and duration of the potential

change resulting from the Proposed Development are also determining factors. The criteria that have been

used to assess the magnitude of effect are defined in Table 10-3.

Table 10-3: Criteria for Assessing Magnitude of Effect

Magnitude Criteria Definition

Major Results in loss of

attribute

Fundamental (long term or permanent) changes to the

baseline hydrology, hydrogeology, soils and geology such as:

• wholesale changes to watercourse channel, route,

hydrology or hydrodynamics;

• changes to the site resulting in an increase in runoff with

flood potential and significant changes to erosion and

sedimentation patterns;

• major changes to the water chemistry; and

• major changes to groundwater levels, flow regime and risk

of groundwater flooding.



Magnitude Criteria Definition

Medium Results in effect on

integrity of attribute

or loss of part of

attribute

Material but non-fundamental and short to medium term

changes to baseline soils, geology, hydrology, hydrogeology

and water quality, such as:

• some fundamental changes to watercourses, hydrology or

hydrodynamics. Changes to site resulting in an increase

in runoff within system capacity;

• moderate changes to erosion and sedimentation patterns;

• moderate changes to the water chemistry of surface runoff

and groundwater; and

• moderate changes to groundwater levels, flow regime and

risk of groundwater flooding.

Low Results in minor

effect on attribute

Detectable but non-material and transitory changes to the

baseline soils, geology, hydrology, hydrogeology and water

quality, such as:

• minor or slight changes to the watercourse, hydrology or

hydrodynamics;

• changes to site resulting in slight increase in runoff well

within the drainage system capacity;

• minor changes to erosion and sedimentation patterns;

• minor changes to the water chemistry of surface runoff and

groundwater; and

• minor changes to groundwater levels, flow regime and risk

of groundwater flooding.

Negligible Results in an effect

on attribute but of

insufficient

magnitude to affect

the use / integrity

No perceptible changes to the baseline soils, geology,

hydrology, hydrogeology and water quality such as:

• no alteration or very minor changes with no effect to

watercourses, hydrology, hydrodynamics, erosion and

sedimentation patterns;

• no pollution or change in water chemistry to either

groundwater or surface water; and

• no alteration to groundwater recharge or flow mechanisms.

Potential Effects

10.3.8 The sensitivity of the receptor together with the magnitude of effect determines the significance of the effect,

which can be categorised into a level of significance as identified in Table 10-4. This also takes into account

good practice measures implemented and embedded as part of the design and construction of the Proposed

Development and use of professional judgement where appropriate. Good practice measures (i.e. embedded

mitigation) are discussed later in the Chapter.

10.3.9 The significance of a potential effect provides a guide to assist in decision making. However, it should not be

considered as a substitute for professional judgment and interpretation. In some cases, the potential sensitivity

of the receiving environment or the magnitude of potential effect cannot be quantified with certainty and

therefore, professional judgement remains the most robust method for identifying the predicted significance of a

potential effect.



Table 10-4: Significance of Effect

Magnitude of

Effect

Sensitivity of Receptor

High Moderate Low Not Sensitive

Major Major Major Moderate Negligible

Medium Major Moderate Minor Negligible

Low Moderate Minor Minor Negligible

Negligible Negligible Negligible Negligible Negligible

Mitigation

10.3.10 Potential effects of the Proposed Development on the water environment, soils or geology identified by the

assessment have been addressed and mitigated by the design and application of good practice guidance to be

implemented as standard during construction and operation. As such, a number of mitigation measures would

form an integral part of the construction process and these have been taken into account prior to assessing the

likely effect of the Proposed Development (embedded mitigation). Where appropriate, further tailored mitigation

measures have been identified prior to determining the likely significance of residual effects.

10.3.11 Good practice measures will be applied in relation to pollution risk, sediment management, soils management

and management of surface runoff rates and volumes. This would form part of the Construction and

Environmental Management Plan (CEMP) to be implemented for the Proposed Development and would be

prepared prior to construction.

10.3.12 The final CEMP would include details and responsibilities for environmental management and outline the

necessary surface water management, oil and chemical delivery and storage requirements, waste

management, traffic and transport management and would specify monitoring requirements for waste water,

water supply.

Residual Effects

10.3.13 A statement of residual effects, following consideration of any further specific mitigation measures where

identified, is then given where required.

Statement of Significance

10.3.14 The assessment provides a Statement of Significance associated with the Proposed Development. Effects of

major and moderate significance are considered to be significant in terms of the EIA Regulations.

Cumulative Effect Assessment

10.3.15 Due to the nature of the Proposed Development, in addition to the good practice and mitigation measures set

out at the end of this Chapter, significant cumulative effects on soils, geology or the water environment are not

anticipated, and thus an assessment of cumulative effects has not been included.

10.4 Baseline Conditions

10.4.1 This Section presents information gathered regarding existing soils, geological, hydrogeological and

hydrological conditions (including flood risk). Figure 10.1: Local Hydrology shows the hydrological setting.



Soils

10.4.2 An extract of 1:250,000 National Soil Map of Scotland is presented as Figure 10.2: Soil Plan, review of which

indicates that the route of the Proposed Development and access tracks are underlain by peaty gleys, blanket

peat and peaty podzols:

• peaty gleys have been recorded for much of the OHL route within the River Vagastie catchment (Photograph

10-1) and three sections of the route within the River Tirry catchment. Peaty gleys are described as drifts

derived from schists, gneisses, granulites and quartzites principally of the Moine Series. Landforms generally

associated with this soil type within the study area are undulating lowlands and uplands with gentle and

strong slopes with no-rocky exposures.

• blanket peat is the dominant soil type underlying the OHL route within the River Tirry catchment (Photograph

10-2.

• peaty podzols are recorded toward the south. Landforms associated with the peaty podzols have been

described as hummocky valleys and slope moraines with frequent boulders.

Photograph 10-1 River Vagastie, Looking Northeast towards WX06 and Meall nan Con



Photograph 10-2 Exposure of Blanket Peat near Crask Inn

10.4.3 A comprehensive programme of peat depth probing has been completed and has been used to inform the

alignment of the proposed OHL. The peat depth data and observations gathered during the site surveys have

been used to prepare a peat management plan (PMP) (see Appendix 10.1) and a Peat Landslide Hazard Risk

Assessment (PLHRA) (see Appendix 10.2). Further water level monitoring wells have been advanced in the

peat, permeability data for the peat obtained and the characteristics of the peat recorded by site investigation

(see Peat Investigation, Appendix 10.3).

10.4.4 Much of the area of blanket peat has been used for commercial forestry with large areas having been recently

clear felled (Photograph 10-3) with some areas having undergone restoration work including reprofiling of peat

to remove forestry furrows and drains.

Photograph 10-3 Clear Felled Commercial Forestry With Brash Cover of Blanket Peat Soils



Superficial Geology

10.4.5 An extract of BGS superficial deposits is mapping is presented as Figure 10.3: Superficial Geology Plan.

10.4.6 Till and morainic deposits of Glacial Till, sand and gravel along with large areas of peat have been recorded by

the BGS underlying the Proposed Development with discrete ribbons of alluvium, consisting of clay, silt, sand

and gravel along larger watercourse channels (Photograph 10-4).

Photograph 10-4 Alluvium Exposure along Banks of River Tirry at Crask Inn

10.4.7 It was noted during site visits that peat is typically underlain by low permeability Glacial Till of unsorted sub-

angular boulders, gravel, sand and silts with soil water seepage at the boundary between the peat and Till,

staining the Till orange with organic content and leached metals (Photograph 10-5).

Photograph 10-5 Cut Exposure of Glacial Till Underlying Thin Blanket Peat



10.4.8 Review of Peatland Classification mapping (SNH, 2016) (see Figure 10.4: Peatland Classification) shows

potential Class 1, 2 and 5 peatland across the Proposed Development route. The forested areas (including

areas of clear felling) within the River Tirry catchment are generally classified as Class 5, described as no

peatland habitat recorded and areas that may also include areas of bare soil where soil information has been

prioritised over vegetation data. Soils are carbon-rich and deep peat. Where peaty soils have not been used

for commercial forestry they are generally classified as Class 2, described as nationally important carbon-rich

soils, deep peat and priority peatland habitat. Class 2 peatlands are recorded as areas of potentially high

conservation value and restoration potential. Following the Proposed Development route, areas around the

watercourses Ferith Osdail, Abhainn Sgeamhaidh, the hills Cnoc na Doire and Croc a’ Ghiubhais and north of

the Crask Inn (PWS01) have been classified as Class 1 peatlands. Class 1 peatlands have been described as

nationally important carbon-rich soils, deep peat and priority peatland habitat that are likely to be of high

conservation value.

10.4.9 As part of this assessment peat depth surveys have been completed (Appendix 10.1 and 10.2). Figure 10.6:

Peat Depth shows the recorded peat depths and confirms that the OHL is underlain by peat.

10.4.10 With reference to Figure 10.6: Peat Depth it is evident that the proposed OHL alignment and access tracks

avoid many of the deeper areas of peat and only with the exception of small discrete sections are peat depths

recorded more than 2m. Typically the depth of peat is recorded at or less than 1 m.

10.4.11 The peat depth data has been combined with slope data and observations of underlying substrate condition to

complete an assessment of peat slide risk (Appendix 10.2) which shows that there are no areas of high peat

slide risk, and the proposed access tracks and much of the proposed OHL alignment is underlain by areas of

negligible and low peat slide risk.

10.4.12 As part of the baseline assessment a site investigation was completed to gather additional details of the

properties of the peat in areas at site that have been subject to peatland restoration (see Appendix 10.3). The

investigation included collecting data with regard to water levels in the peat, peat depth and peat permeability

and confirmed that peat deposits are saturated and have a very low bulk permeability typical of blanket peat.

Bedrock Geology

10.4.13 An extract of the BGS bedrock and linear features geology mapping is presented as Figure 10.5: Bedrock

Geology Plan.

10.4.14 The Proposed Development is underlain by metamorphic and metaphophic-igneous units of:

• Altnaharra Psammite Formation of psammites and micaceous psammites. This is the dominant bedrock

unit that underlies the OHL route;

• Lewisianoid Gneiss Complex of orthogneiss;

• Lewisianoid Gneiss Complex of mafic orthogneiss;

• Kilbreck Psammite Formation of migmatitic psammites and migmatitic-micaceous psammites;

• Kilbreck Psammite Formation of gneissose semipelite; and

• Loch Corie Formation of migmatitic pelites.

10.4.15 A number of Inferred faults have been recorded by the BGS, generally trending in a northeast to southwest

orientation.

Hydrogeology

10.4.16 An extract of the BGS 1:625,000 scale Hydrogeological Map of Scotland is presented in Figure 10.8:

Groundwater Vulnerability, review of which collaborates the bedrock and superficial geology records, and that

all of the Proposed Development is underlain by impermeable Precambrian rock. The BGS describe the



Precambrian rock as a low productivity aquifer generally without groundwater except at shallow depth (in the

upper weather surface) with flow almost entirely through fractures and other discontinuities.

10.4.17 Groundwater quality within Scotland is monitored by SEPA and classified annually in accordance with the

requirements of the Water Framework Directive (WFD)9. SEPA record the Proposed Development as underlain

by one groundwater body: Northern Highlands (SEPA ID 150701).

10.4.18 The Northern Highlands groundwater body was classified in 2017 by SEPA as having an overall status of Good

with all sub-parameters also as Good. No pressures have been identified by SEPA for this groundwater

waterbody.

10.4.19 SEPA have confirmed that they do not hold any groundwater water quality data within 10 km of the Proposed

Development.

Groundwater Vulnerability

10.4.20 The SNIFFER groundwater vulnerability map (Figure 10.8: Groundwater Vulnerability) classifies the underlying

aquifer (superficial and bedrock) according to the predominant groundwater flow mechanism (fracture or

intergranular) and the estimated groundwater productivity. Groundwater vulnerability is divided into five classes

(1 to 5) with 1 being least vulnerable and 5 being most vulnerable.

10.4.21 Review of Figure 10.8: Groundwater Vulnerability indicates that the Proposed Development is underlain by

groundwater vulnerability Class 4(b-d) due to the upper weathered surface of the bedrock and thin superficial

cover. This highlights that groundwater is vulnerable to pollution, providing little to no attenuation in the event of

a pollution incident.

Hydrological Site Setting

10.4.22 An extract of Ordnance Survey (OS) mapping illustrating the hydrological setting of the Proposed Development

is presented in Figure 10.1: Local Hydrology and highlights that the Proposed Development straddles the

surface water catchments of the River Vagastie to the north (that sits within the River Naver greater catchment)

and the River Tirry to the south (that sits within the River Shin greater catchment) with a minor length of the

OHL in the very south drain via very small catchments that discharge directly to Loch Shin.

10.4.23 Topography along the Proposed Development route generally falls to the north in the River Vagastie catchment

and south-east within the River Tirry catchment. Elevations range between 115 – 280 m Above Ordnance

Datum (AOD) with the lowest elevations recorded in the south near Dalchork and highest recorded at the

catchment divide of River Vagastie and River Tirry (The Crask) and near the summit of the hill Cnoc na Doire

near the middle of the Proposed Development.

River Vagastie

10.4.24 The River Vagastie (SEPA ID 20609) serves the northern end of the Proposed Development and lies within the

wider River Naver catchment, which ultimately discharges to the North Sea at Bettyhill. The River Vagastie

within the Proposed Development study area is a moderately sized watercourse with a predominantly bedrock

channel with frequent large boulders (Photograph 10-6) and includes the headwater tributary Allt a’Chraisg.

9 SEPA Water Classification Hub available online at https://www.sepa.org.uk/data-visualisation/water-classification-hub. Last accessed 22/04/2019

https://www.sepa.org.uk/data-visualisation/water-classification-hub



Photograph 10-6: River Vagastie

10.4.25 The River Naver and its headwater tributaries are recognised as a SAC statutory designated site for qualifying

features including Atlantic salmon (Salmo salar) and Freshwater pearl mussel (Margaritifera margaritifera), that

both are noted particularly sensitive to pollution, siltation and sedimentation. The River Vagastie has

recognised obstacles to fish migration and at the crossing of the A836 public road and the main River Vagastie

channel a weir has been reported by SEPA (fish barrier ID 2723). Two of the western headwater tributaries

have also been identified to include dams, which divert flow to Loch Shin that pose an obstacle to fish

migration. During the consultation period of the Creag Riabhach Wind Farm EIA the Northern DSFB

(07/02/2014) provided details that electric fishing data on the River Vagastie suggested that autumn flows are

not sufficient to support free access to spawners in every year, probably because of abstraction at the two

dams and diversion to Loch Shin.

River Tirry

10.4.26 The River Tirry (Photograph 10-7 and 10-8) sits within the greater River Shin catchment that ultimately

discharges to the Kyle of Sutherland at Inveran to the south from the Proposed Development.



Photograph 10-7: River Tirry at Crask Inn

Photograph 10-8: River Tirry at Fishery Hatchery and Trapping Site

10.4.27 The River Tirry catchment is large (approximately 161 km2) and includes many headwater sub-catchments:

• Allt Chaiseagail (Photograph 10-9) and its own headwater tributaries Feith Tharsuinn, Alltan Riabhach, Allt

Ruadh and Loch Tigh na Creige;

• Allt a’Bhreac-leathaid (Photograph 10-10) and loch Dubh and Loch Beannach;

• Feith Osdail (Photograph 10-11) and its headwater tributaries Allt a’ Mhadaidh-ruaidh, Allt Geal, Allt Coir’

an Torcain and waterbodies Loch Dail na Copaig, Loch na Fuaralachd and Loch Beag na Fuaralachd. The

Feith Osdail is also connected by canal to the Rover Brora at Strath Bora;

• Abhainn Sgeamhaidh (Photograph 10-12) and its headwater tributaries Feith Ra’fin, Feith Mhearanas,

Abhainn na Bruaiche Duibhe, Allt na Chloiche-muilinn, Allt Coir’ a’ Bheachdachaidh, Feith a’ Chaoruinn, Allt

Meall na Teanga, Allt a’ Mhill Mheadhonaich, Caichan Mor, and Feith a’ Chill;



• Alltan Dubh;

• Allt an Drochaidean Beaga;

• Allt an Fhuaran and Lochan Iain Bhuidhe;

• Feith Dhubh na Caorach;

• Shirink Burn;

• Allt Dubh an Daimh;

• Allt Domhain and its headwater tributaries Allt Leacach and Allt Briste;

• Allt Doir’ a’ Mheathais;

• Loch na Capulich;

• Loch Dubh Cul na Capulich; and

• Loch a’ Ghiubhais.

Photograph 10-9 Allt Chaiseagail



Photograph 10-10 Allt a’Bhreac-leathaid

Photograph 10-11 Feith Osdail



Photograph 10-12 Abhainn Sgeamhaidh

10.4.28 The River Tirry catchment is generally undulating land and steep gradients are absent along main watercourse

corridors.

10.4.29 As illustrated in Photograph 10-8, the River Tirry supports a hatchery (installed by SSE Generation as part of

the salmon fisheries work they undertake in consultation with SEPA and Kyle of Sutherland Fisheries) and

trapping site, which when the hatchery was in operation was restricted to limited stocking on the River Tirry

using fish captured from the River Shin.

10.4.30 The River Shin is dammed at Loch Shin that acts as an obstacle to fish migration (fish barrier ID 2727). Due to

the nature of the dam, Kyle of Sutherland DSFB and SSE operate a “trap and truck” operation on the tributaries

of Loch Shin and the River Shin downstream to maintain migration. Within the minutes of the 2016 Annual

Meeting of the Kyle of Sutherland DSFB10 it is reported that trap figures on the River Tirry were very low in

comparison to normal figures.

Surface Water Quality

10.4.31 SEPA monitor and classify three waterbodies immediately downgradient of the Proposed Development and the

most recent published classification details (2017) are summarised in Table 10-5.

Table 10-5 SEPA Waterbody Classification (2017)

Waterbody ID Overall Status Physico-Chem Biological

Elements

Hydromorphology

River Vagastie

(SEPA ID

20609)

Moderate ecological

potential Good Moderate Moderate

River Tirry –

whole catchment

above Rhian

(SEPA ID

20100)

Poor - Poor Good

10 Kyle of Sutherland DSFB 2016 Annual Meeting minutes, available online at https://kylefisheries.org/wp-content/uploads/2018/08/Mins-of-AMQP-

November-2016.pdf. Last accessed 22/05/2019

https://kylefisheries.org/wp-content/uploads/2018/08/Mins-of-AMQP-November-2016.pdf

https://kylefisheries.org/wp-content/uploads/2018/08/Mins-of-AMQP-November-2016.pdf



Waterbody ID Overall Status Physico-Chem Biological

Elements

Hydromorphology

River Tirry –

Loch Shin to

Rhian

(SEPA ID

20099)

Poor High Poor Good

Allt Chaiseagail

(SEPA ID

20101)

Poor High Poor Good

Feith Osdail

(SEPA ID

20102)

Poor - Poor Good

Loch Beannach

(SEPA ID

100083)

Poor High Poor High

Loch Shin

(SEPA ID

100065)

Poor ecological

potential Moderate Poor Bad

10.4.32 SEPA identified the following pressures on the monitored waterbodies in 2014:

• River Vagastie (SEPA ID 20609): water abstraction and barrier to fish migration (fish barrier ID 3349 and

20074) for hydroelectricity generation;

• River Tirry: whole catchment above Rhian (SEPA ID 20100), River Tirry: Loch Shin to Rhian (SEPA ID

20099), Allt Chaiseagail (SEPA ID 20101), Feith Osdail (SEPA ID 20102), Loch Beannach (SEPA ID 100083)

and Loch Shin (SEPA ID 100065): barrier to fish migration (fish barrier ID 2727) for hydroelectricity

generation;

• Allt Chaiseagail (SEPA ID 20101): in addition to the fish barrier listed above this watercourse also has a

further legacy structure that is an obstacle to fish migration (fish barrier ID 20073); and

• Loch Shin (SEPA ID 100065): in addition to the fish barrier listed above, water quality pressures from elevated

concentrations of nutrients have been recorded however no adverse effects have been reported for plant and

animal communities.

10.4.33 It is noted that River Vagastie received a Good status for Physico-Chem classification due to water temperature

and pH remaining in the Good category while dissolved oxygen was classed as High.

Surface Water Flows

10.4.34 SEPA maintain a rain gauge at Rhian Bridge (ID: 115390) and review of the previous five years data (2014 –

2018) indicates an average annual rainfall of 1,087.84 mm.

10.4.35 SEPA confirmed they hold no recent flow data for the gauging stations downstream of the River Tirry (River

Shin downstream of Loch Shin). Flow data was retrieved from the National River Flow Archive11 for the

gauging station, Apigill, downstream of River Vagastie (River Naver downstream) and correlated with rainfall

data for the Rhian Bridge monitoring station (see Chart 10-1).

11 NRFA Apigill station flow data available online at https://nrfa.ceh.ac.uk/data/station/info/96002. Last accessed 22/05/2019

https://nrfa.ceh.ac.uk/data/station/info/96002



Chart 10-1 River Naver Flow Data (2016)



10.4.36 Review of Chart 10-1 highlights that rainfall at the Proposed Development falls primarily across winter months

while summer is significantly drier. It is noted also that river flow responds quickly during rainfall events and

that the low permeability soils and geology beneath the Proposed Development result in a relatively rapid runoff

response to incident rainfall.

Designated Sites

10.4.37 Review of the Scottish Natural Heritage (SNH) Sitelink12 and Magic Map13 webpages and Joint Nature

Conservation Committee (JNCC) map of Geological Conservation Review (GCR) sites14 indicates that the

following sites are located within 1 km of the Proposed Development (see Figure 10.1: Local Hydrology):

• Ben Klibreck SSSI;

• Caithness and Sutherland Peatlands Ramsar, SAC and SPA;

• Cnoc an Alaskie SSSI; and

• River Naver SAC.

10.4.38 The Ben Kilbreck site has been designated as a SSSI for features including alpine heath, blanket bog, moines

and oligotrophic lochs. The high slopes and summits of Ben Klibreck support a range of alpine heath

communities. At higher elevations, heather is found alongside mountain azalea, a plant that is only found in

short vegetation on mountain tops in Britain while dense low-growing mats of the nationally scarce alpine

bearberry and lichens are also found in this habitat. Ben Klibreck contains one of the largest extents of this rare

dwarf shrub community in Britain. An uncommon combination of deergrass / cotton-sedge (western type) and

cotton-sedge / crowberry (eastern type) blanket-mire vegetation communities is found at this site. Calliergon

trifarium, a very local montane species of moss confined to the Highlands, occurs in a few base-rich flushes,

with lesser clubmoss Selaginella selaginoides. The rocks of the Ben Klibreck area mostly lie within the Moine

Supergroup that were altered by intense heat and pressure deep underground into hard pelites and psammites.

In places, partial melting of certain minerals formed banded rocks called migmatites that this site is particularly

valuable for both historical and current research into the origin of. Loch Choire and Loch a’ Bhealaich are

naturally nutrient-poor lochs, which contain a high diversity of aquatic plants, including the nationally scarce

awlwort. These lochs have clear water, low to moderate levels of nutrients and short underwater vegetation.

10.4.39 The Caithness and Sutherland Peatlands site has been designated as Ramsar, SAC and SPA for features

including acid peat-stained lakes and ponds, blanket bog, clear-water lakes or lochs with aquatic vegetation and

poor to moderate nutrient levels and depressions on peat substrates. The scale and diversity of the peatlands

of Caithness and Sutherland make them unique in Europe and they are three times larger than any other peat

mass in the UK. The site is important because of the considerable abundance of large (several square

kilometres) continuous areas of Sphagnum carpets and hummocks and while not only are these features

usually rare and localised on other bog systems in the UK, but a very high proportion of this ground remains

undisturbed. Caithness and Sutherland Peatlands supports a range of high-quality freshwater loch habitats that

include Oligotrophic to mesotrophic standing waters. The aquatic vegetation is dominated by a very narrow

range of species typical of northern, upland, lochs but there is much local variation in their abundance. The

margins of a few lochs support two nationally scarce plants; bog hair-grass Deschampsia setacea and marsh

clubmoss Lycopodiella inundata. Other notable species include awlwort Subularia aquatica and water sedge

Carex aquatilis. The range of aquatic invertebrates includes the nationally rare water beetle Oreodytes alpinus.

Depressions on peat substrates of the Rhynchosporion occur in complex mosaics with lowland wet heath and

valley mire vegetation, in transition mires, and on the margins of bog pools and hollows in both raised and

blanket bogs. The Nationally scarce species brown beak-sedge Rhynchospora fusca and marsh clubmoss

Lycopodiella inundata also occur in this habitat.

12 SNH SiteLink available online at https://sitelink.nature.scot/home. Last accessed 19/03/2019

13 MAGiC Magic Map available online at https://magic.defra.gov.uk/. Last accessed 19/03/2019

14 JNCC UK map of GCR sites available online at http://jncc.defra.gov.uk/page-4173. Last accessed 19/03/2019

https://sitelink.nature.scot/home

https://magic.defra.gov.uk/

http://jncc.defra.gov.uk/page-4173



10.4.40 The Cnoc an Alaskie site has been designated as a SSSI for features including blanket bog, breeding bird

assemblages and greenshank (Tringa nebularia). The site supports a range of bog types and associated pool

systems including ladder fens. Species of note include marsh clubmoss (Lycopodiella inundata) and the

nationally scarce dwarf birch (Betula nana). This site is notable for the local abundance of the nationally rare

olive bog-moss (Sphagnum majus) and nationally scarce golden bog-moss (Sphagnum pulchrum). The site

supports a nationally important range of breeding upland bird species including red-throated diver, teal, dunlin,

golden eagle, merlin and wood sandpiper. The population of greenshank is particularly important on this site as

this species occurs at a breeding density more than 1.5 times greater than the average in Caithness and

Sutherland.

10.4.41 The River Naver site has been designated as a SAC for features including Atlantic salmon (Salmo salar) and

Freshwater pearl mussel (Margaritifera margaritifera). The site supports a high-quality salmon population and,

along with the Rivers Borgie and Thurso, is representative of the northerly part of the species’ range in the UK.

With the River Borgie, this site in Sutherland represents the northern extreme for freshwater pearl mussels in

the UK while pearl mussels have been recorded throughout much of the length of River Naver.

Flood Risk

10.4.42 SEPA has developed national flood maps15 that present modelled flood extents for river, coastal, surface water

and groundwater flooding. The river, coastal, surface water and groundwater maps were developed using a

consistent methodology to produce outputs for the whole of Scotland, supplemented with more detailed, local

assessments where available and suitable for use. Flood extents are presented in three likelihoods:

• High likelihood: a flood event is likely to occur in the defined area on average more than once in every ten

years (1:10), or a 10% chance of happening in any one year;

• Medium likelihood: a flood event is likely to occur in the defined area on average more than once in every

two hundred years (1:200), or a 0.5% chance of happening in any one year; and

• Low likelihood: a flood event is likely to occur in the defined area on average more than once in every

thousand years (1:1000), or a 0.1% chance of happening in any one year.

10.4.43 A summary of the potential sources of flooding and a review of the potential risks posed by each source is

presented in Table 10-6.

15 SEPA Flood maps available online at http://map.sepa.org.uk/floodmap/map.htm . last accessed 19/03/2019



Table 10-6 Potential Flooding Sources

Potential Source Potential Flood Risk

to Application Site

Justification

Coastal flooding No

Lowest elevations of the Proposed Development are

115 m AOD and therefore the site is not at risk from

tidal or coastal flooding.

River Flooding Yes

SEPA river flood mapping highlights that there is a

High Likelihood of flooding immediately adjacent to

larger watercourses including:

• River Vagastie and its upstream tributaries ;Allt a’

Chraisg and Allt Bealach an Fhuaraun;

• Lochan IIain Bhuidhe;

• River Tirry and its upstream tributaries Feith a’

Chaoruinn and Abhainn Sgeamhaidh;

• Loch Dubh Cul na Capulich;

• Feith Osdail;

• Allt a’ Bhreac-leathaid; and

• Allt Chaiseagail.

The OHL line directly crosses mapped flood extents of

the River Vagastie at watercourse crossing WX06, the

Abhainn Sgeamhaidh at WX04, the Feith Osdail at

WX03, the Allt a’ Bhreac-leathaid at WX02 and Allt

Chaiseagail at WX01 with the underground cable

crossing the River Tirry at WX05.

It is noted that the mapped potential flood extents are

all local to watercourses and never form large areas of

out of bank floodplains.

Small and discrete areas of river or stream flooding

might also be expected immediately adjacent to the

smaller watercourses.

Surface Water Flooding No

SEPA flood mapping does not suggest any

significant, large areas of surface water flooding

beneath the proposed OHL and cable alignment.

The flood maps do present very minor areas of

surface water flooding that have been mapped within

Shin Forest, generally along forestry rides, tracks and

along watercourses and loch bodies.

Groundwater Flooding No

Review of the SEPA mapping and site geology and

hydrogeology confirms that the solid and superficial

geology at and near to site do not contain significant

quantities of groundwater.

Flood Defence Breach

(Failure) No

The application site is remote from any formal flood

defences.

Flooding from artificial

drainage systems No

No drainage systems are present near to the site.

Flooding due to

infrastructure failure No

Review of the SEPA Reservoirs Map highlights that

there is no infrastructure upgradient of the Site.

Private Water Supplies and Licenced Sites (Abstractions / Discharges / Waste)

10.4.44 Consultation with THC and SEPA has been conducted regarding records of registered and licenced water

abstractions and discharges within 500 m of the Proposed Development. Recorded private water supplies



(PWS) and SEPA Controlled Activity Regulation (CAR) registrations / licences are illustrated in Figure 10.1:

Local Hydrology and are discussed below.

10.4.45 THC and review of OS data confirmed that there are four properties served by PWS within a 1 km of the

Proposed Development:

• The Crask Inn (PWS01);

• The Crask Inn House (PWS01);

• Rhian (PWS02); and

• New Log Cabin (PWS03).

10.4.46 During the site visit in April 2019, properties were visited and the source of the PWS confirmed with residents.

10.4.47 Both The Crask Inn and Crask Inn House (both PWS01) abstract surface water from a watercourse discharging

from Lochan Iain Bhuidhe to the north east of the properties (NGR NC 52868 25716). Both the PWS source of

these supplies and the pipeline connecting the properties to the supply are upgradient of the proposed cable

alignment and therefore not considered to be in hydrological connection to the Proposed Development. PWS01

is not considered to be at risk from the Proposed Development.

10.4.48 The property Rhian (PWS02) is supplied by a surface water abstraction from the watercourse Abhainn

Sgeamhaidh. The surface water us collected in a shallow well in adjacent to the watercourse (NGR NC 56295

16598) as illustrated in Photograph 10-13. The proposed OHL alignment lies over 2 km upstream east of the

PWS abstraction point.

Photograph 10-13 Rhian PWS Well

10.4.49 Review of the SEPA CAR authorisations indicated a further property (New Log Cabin, PWS03) that was not

shown on OS mapping also existed in the area to the east of the A836 public road near Rhian. During the site

visit, this property was visited and it was noted that the site has not been developed and that only temporary

structures exist. An intermediate bulk container (IBC) was witnessed that was full with water and it is assumed

that there is no PWS here and that visitors bring their own bottled drinking water and that the IBC is refilled by

tanker and not used for drinking purposes.



10.4.50 SEPA has provided records of five CAR authorisations within 500 m of the Proposed Development. The

locations of the activities are shown on Figure 10.1: Local Hydrology and summary details are given below:

• CAR/R/1113227 & CAR/R/1113228 – Bridging culvert construction;

• CAR/S/1090938 - Croys / Groynes / Flow Deflectors;

• CAR/S/1156545 - Croys / Groynes / Flow Deflectors; and

• CAR/R/1054718 - Sewage (Private) Primary.

Groundwater Dependent Terrestrial Ecosystems (GWDTE)

10.4.51 Potential GWDTEs have been identified within Chapter 7 (Ecology) and discussed therein. National Vegetation

Classification (NVC) mapping has been used to screen for potential highly and moderately dependent GWDTE,

see Figure 7.3: GWDTE and Peatland Habitats, and which review shows that areas of potential GWDTE are

typically associated with stream corridors and forest rides.

10.4.52 It has been shown above that the site receives a high annual rainfall, and that the superficial and solid geology

has little capacity to store or allow the movement of groundwater. It is considered, therefore, that the areas of

potential GWDTE are not sustained by groundwater but rather rainfall and surface water runoff. Stand-offs or

buffers to these habitats specified in the SEPA guidance therefore need not apply.

Summary of Potential Receptors

10.4.53 Table 10-8 summarises the receptors identified as part of the baseline study, and their sensitivity based upon

the criteria contained in Table 10-2. These receptors form the basis of the assessment and are used in

conjunction with an estimate of the magnitude of an effect to determine significance.

Table 10.8: Sensitivity of Receptors

Receptors Sensitivity Reason for Sensitivity

Peat High Much of the Proposed Development crosses proven

deposits of peat and peaty soils of varying condition with

some areas considered to be of high conservation value.

Soils and Geology High The Ben Kilbreck SSSI has been designated for geological

features of the Moine Supergroup however it was noted that

during the site visit, there were no significant exposures of

bedrock along the OHL alingment.

Surface Water High Surface water quality is expected to be good near to and

downstream of the Proposed Development. SEPA

classifications of monitored watercourses show impacts

associaed with existing obstacles to fish migration. The

River Naver SAC that lies downstream on the River

Vagastie catchemtn is designated for species that are

particularly sensitve to pollution.

The Kyle of Sutherland DSFB operate a hatchery on the

River Tirry, downstream its confluce with Allt a’ Bhreac-

leathaid that the proposed OHL crosses the watercourse

(WX02).

Groundwater High Groundwater quality is recorded by SEPA to be good.

Groundwater is also present at relatively shallow depths and

been shown to be vulnerable to pollution.

Groundwater regionally is designated as a Drinking Water

Protection Zone in accordance with the WFD.



Areas of Flood Risk High The OHL and cable alignment has been recorded to pass

over discrete areas of floodplain associated with larger

watercourses and isolated areas of surface water flooding.

Private Water Supplies High The surface water PWS at Rhian (PWS02) has been

identified to abstract from the Abhainn Sgeamhaidh

watercourse that lies approximately 2 km dowsntream from

the OHL crossing of this watercourse (Figure 10.1: Local

Hydrology).

Designated Sites with

Hydraulic Connectivity

to the Proposed

Development

High Designated sites within 1 km from the Proposed

Development are dependent on drainage shed from the site.

Nationally important species and habitats have been

recorded in both the River Vagastie and River Tirry

catchments.

GWDTE Low Potential GWDTE habitats are sustained by incident rainfall

and surface water runoff / ponding rather than by

groundwater.

10.5 Summary of Proposed Development

10.5.1 The construction practices and phasing are detailed within Chapter 3: Description of the Proposed

Development, which includes information on anticipated soil excavation works.

10.5.2 Consent is being sought for:

• approximately 22 km of 132 kV OHL, to be supported by double trident H wood poles, and underground cable

between a proposed on-site substation at Creag Riabhach Wind Farm (NGR NC 52993 27369) and the

proposed Dalchork substation (NGR NC 58204 09565); and

• associated works including tree felling and construction of new temporary and permanent access tracks.

10.5.3 Key tasks during construction of the project would relate to:

• establishment of suitable laydown areas for materials and installation of temporary track solutions (e.g.

Trackway), as necessary;

• upgrades to existing tracks (if required);

• new temporary access track bellmouths to the A836 public road;

• identification and formation (if required) of parking areas for construction workers to ensure safe parking

prior to transfer to tracked All-Terrain Vehicles (ATV);

• formation of Helicopter delivery sites;

• delivery of structures and materials to site;

• excavation of a suitable area for the poles, and backfilling after installation of the pole (backfilling would

generally be carried out the same day as excavation so that no open excavations are left overnight). The

exact area would depend on the ground conditions at each pole;

• in some pole locations, it may be necessary to add imported hardcore backfill around the pole foundations

to provide additional stability in areas where the natural sub soils have poor compaction qualities, this

hardcore will be inert;

• conductors would be installed on the poles using full tension stringing to prevent the conductor coming into

contact with the ground;

• construction of a 1.4 km trenched (0.9-1.6 m deep) section of 132 kV underground cables by the Crask Inn

with sealing end structures of the OHL at either end (details of this process are set out in Chapter 3 of this

EIA Report);

• provision of minor sections of permanent new stone access tracks to retain safe access to commercial

forestry blocks (identified on plans as spur roads); and



• remedial works would be carried out to reinstate the immediate vicinity of the structures, and any ground

disturbed, to pre-existing use. This would be undertaken using excavated material.

10.5.4 Access to the OHL and cable alignment would be afforded from existing tracks where possible and, where

necessary, new temporary access would be set out and removed upon completion of works.

10.5.5 Excavation, other than for the safeguarding of topsoil associated with placement of geo-textile fabric, for the

formation of access tracks is therefore not anticipated. The topsoil would be replaced following use of the

temporary access.

10.5.6 The Proposed Development would require a number of watercourse crossings of the OHL and cable route.

Details of the crossing locations on watercourses with upstream catchment areas greater than 5 km2 are

provided in Table 10-7.

10.5.7 The underground cable in the vicinity of the Crask Inn will require crossing the River Tirry (WX05) which would

be established by Horizontal Directional Drilling (HDD) techniques rather than an open cut technique to isolate

earthwork areas from the water environment. HDD will involve the establishment of temporary entry and exit

pits at either side of the River Tirry. From the entry pit a tracked drilling rig will drill at an angle to provide

enough clearance below the watercourse channel for the drill path. Drilling fluid will be added during operations

to purge cuttings, stabilise the bore hole, and lubricate and cool the drill head.

10.5.8 The entry and exit pits will be developed on temporary areas of ‘hardstanding’ that will constructed using inert

aggregate and be underlain by a low permeability HDPE liner (or similar). The drill rig, drilling fluids, oils and

fuel required to for the HDD technique will be stored on the hardstanding in bunded tanks. Following

completion of the drilling and insertion of the electrical cable all the equipment and hardstanding will be

removed.

10.5.9 Prior to establishment of the entry and exit pits a site investigation will be completed to confirm ground

conditions and the results of which will be used to design the HDD programme. Specifically, the site

investigation will be used to ensure that the HDD does not result in a loss of bentonite to the River Tirry.

10.5.10 Further, the HDD works will require authorisation from SEPA prior to the works being undertaken in accordance

with CAR. The CAR application will include a method statement and details the measures that will be taken to

safeguard the water environment and water quality and flows in the River Tirry.

10.5.11 A buffer of at least 20 m will be maintained at all times from proposed surface works to the River Tirry.

Table 10-7: Schedule of Watercourse Crossings

Crossing ID

Watercourse Name

Notes Photograhy

WX01 Allt Chaiseagail

NGR NC 57829 10777 Top Width: 3 m Channel Depth: 0.75 m Base Width: 2.5 m Water Depth: 0.1 m

View Upstream



View Downstream

WX02 Allt a’ Bhreac-leathaid

NGR NC 58030 12526 Top Width: 2 m Channel Depth: 1 m Base Width: 1.5 m Water Depth: 0.3 m

View Upstream

View Downstream

WX03 Feith Osdail

NGR NC 58308 14497 Top Width: 8 m Channel Depth: 1 m Base Width: 6.5 m Water Depth: 0.5 m

View Upstream

View Downstream



WX04 Abhainn Sgeamhaidh

NGR NC 57792 16833 Top Width: 5 m Channel Depth: 1 m Base Width: 4 m Water Depth: 0.3 m

View Upstream

View Downstream

WX05 River Tirry

NGR NC 52371 24530 (survey conducted approximately 200m downstream) Top Width: 5 m Channel Depth: 1 m Base Width: 4 m Water Depth: 0.2 m

View Upstream

View Downstream

WX06 River Vagastie

NGR NC 53281 27236 Top Width: 4 m Channel Depth: 1 m Base Width: 3 m Water Depth: 0.3 m

View Upstream



View Downstream

10.5.12 Following commissioning of the Proposed Development, all construction sites would be reinstated.

Reinstatement would form part of the contract obligations for the Principal Contractor and would include the

removal of all temporary access panels, all work sites around the pole locations and the re-vegetation of all

construction compounds and Helicopter delivery sites.

10.6 Good Practice and Embedded Mitigation by Design

10.6.1 The Applicant has established best practice construction techniques and procedures that have been agreed

with statutory consultees, including SEPA and SNH. These are set out within the Applicant’s General

Environmental Management Plans (GEMPs), included in Appendix 3.1.

10.6.2 The Proposed Development would be constructed in accordance with these plans.

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

implementation of a comprehensive and site-specific CEMP. This document would detail how the successful

Principal Contractor would manage the works in accordance with all commitments and mitigation detailed in the

Environmental Impact Assessment, SSE’s GEMPs, statutory consents and authorisations, and industry best

practise and guidance.

10.6.4 The CEMP would also outline measures to ensure that the works minimise the risk to soils, peat, geology,

groundwater and surface water and licensed water uses.

10.6.5 It is expected that the following would be included within the CEMP and would ensure the works are undertaken

in accordance with good practice guidance, as detailed in Section 10.2:

• during construction there would be heavy plant and machinery required and as a result it is appropriate to

adopt best working practices and measures to protect the water environment, including those set out in

Pollution Prevention Guidance (PPG1);

• in accordance with PPG2 any above ground on-site fuel and chemical storage would be bunded;

• emergency spill response kits would be maintained during the construction works (GGP21);

• a vehicle management system would be put in place wherever possible to reduce the potential conflicts

between vehicles and thereby reduce the risk of collision (GPP21);

• suitable access routes would be chosen which minimise the potential requirement for either new temporary

access tracks or for tracking across open land which could contribute to the generation of suspended solids

and / or degradation of peat;

• bog matting and / or low load bearing machinery will be used when access is required over deposits of

peat;

• a speed limit would be used to reduce the likelihood and significance of any collisions;

• drip trays would be placed under stationary vehicles which could potentially leak fuel / oils;



• any temporary construction / storage compounds required would be located remote from any sensitive

surface water receptors and will be constructed to manage surface water run-off in accordance with best

practice;

• drilling fluid to be used during the HDD at watercourse crossing beneath the River Tirry will be inorganic

and details of the fluid including any necessary foaming agents will be maintained on site to inform correct

use, treatment and disposal;

• any water contaminated with silt or chemicals would not be discharged directly or indirectly to a

watercourse without prior treatment;

• water for temporary site welfare facilities would be brought to site, and foul water would be collected in a

tank and collected for offsite disposal at an appropriately licensed facility; and

• water quality monitoring requirements for sensitive receptors downstream of work areas.

10.6.6 The implementation of the CEMP would be managed on site by a suitably qualified and experienced

Environmental Clerk of Works (ECoW), with support from other environmental professionals as required. The

ECoW would have authority to stop any works that are or have potential to impair soils, geology or the water

environment.

10.7 Assessment of Potential Effects

10.7.1 The following have the potential to impair the soils, geology, local hydrology (surface water) and hydrogeology

(groundwater):

• the use of and tracking of machinery has the potential to damage soils and peat by compaction or indirectly

by draining water from the peat;

• soil compaction from vehicular movement may cause an increase of local flood risk;

• excavation of soils, peat and shallow geology has the potential to induce local ground instability;

• the use of and tracking of machinery has the potential to generate suspended solids in site runoff;

• the use of machinery has the potential to introduce oils or hydrocarbons;

• inappropriate use of drilling fluids has the potential to contaminate groundwater and without appropriate

controls there could be drilling fluid loss to surface water; and

• new temporary access tracks may change surface drainage paths which might increase flood risk and / or

impair water supplies.

Peat Resources and Peat Slide Risk

10.7.2 An extensive programme of peat depth probing has been completed it has been shown that the areas of

deepest peat have been avoided, where practicable and on balance with other environmental considerations

(see Figure 10.5: Bedrock Geology Plan).

10.7.3 No significant earthworks are required. Notwithstanding this, the following best practice measures would be

detailed in the site CEMP in order to safeguard peat:

• no peat would be excavated to form access tracks to the proposed OHL, low loading bearing access

vehicles would be used, and where required temporary portable tracking would be deployed, so to

safeguard peat below the access routes; and

• works would be undertaken with the Applicant’s GEMP (Working in Sensitive Habitats) which would ensure

peat stripping and excavation is kept to an absolute minimum.

10.7.4 The construction of the OHL does not require permanent excavation of peat, as most excavations to install the

poles and stays are undertaken over short periods of time and the excavated materials replaced generally the

same day. By adopting this approach the volume of peat excavated and stored is minimised.



10.7.5 The method used for pole construction is to remove as large a section of turf to a depth of approximately 300

mm where possible. The turves are laid to the side for re-use and are only used on surface. The turves would

be handled carefully and replaced on the backfilled excavations to replicate the existing conditions. The

required excavation size is stripped in this way and the turves laid to one side.

10.7.6 The excavator operator would then commence excavating the pole foundations that are usually 2 m wide, 2.5 m

deep and 4 m long. The soil is removed in roughly even layers down the excavation depth with different soil

types stacked into separate piles.

10.7.7 With the pole erected or the stay installed, backfilling of the excavation would take place with the soils replaced

in reverse order whilst being compacted with the excavator bucket in approximately 300 mm layers. At this time

it may be necessary to add imported backfill around the pole foundation blocks to ensure stability.

10.7.8 Backfilling would continue until normal ground level is reached. The turfs would then be replaced – using the

excavator – around the structure and deliberately left slightly proud of the surrounding ground level. This is for

two reasons; the subsoils would naturally settle following excavation as a consequence of ‘bulking up’– despite

being compacted as they are replaced – and in time would form a ‘hollow’ around the structure. The second

reason is that with the replaced turf being kept slightly higher it would prevent the excavated materials

‘deteriorating and becoming very soft’ below the turf and aid quicker healing of the turf.

10.7.9 Generally within 12 months of reinstatement the excavated area would return to natural ground levels and no

evidence of the excavation itself visible.

10.7.10 There would be no storage of peat on site, and soils and turves would be handled sensitively to avoid cross

contamination between distinct horizons and to ensure re-use potential is maximised. It is not envisaged that

any excavation would be left open and excavations would be re-instated on the day they are excavated. Based

on experience from similar sites there would be no significant surplus peat generated from these construction

activities identified on site.

10.7.11 Notwithstanding this, a Stage 1 peat management plan (PMP) has been prepared (see Appendix 10.1) and

shows the volume of peat that will be excavated to establish the required poles and how the excavated peat will

be managed, how the integrity of the peat will be maintained how the peat will be reused. The PMP shows that

there will be no surplus peat generated as a consequence of the Proposed Development.

10.7.12 The Principal Contractor will be required to prepare a Stage 2 and Stage 3 peat management plan as part of

the detailed site design. The stage 2 PMP would be developed in consultation with FLS and SNH Peatland

Action, and this would form part of the CEMP agreed with SEPA and THC prior to construction commencing.

10.7.13 It has been shown that the proposed OHL and limit of deviation is mostly underlain by areas of negligible or low

peat slide risk (see Appendix 10.2). The peat slide risk assessment would be revised prior to construction and

incorporate the results of additional site investigation. The risk assessment would also consider the proposed

access routes and track design. Micro-siting would be used to locate the proposed infrastructure in areas of

least peat slide risk and mitigation measures to prevent a peat slide would be identified, if required. The

updated peat landslide risk assessment would form part of the CEMP that would be prepared by the Principal

Contractor and be agreed with SEPA and THC prior to construction commencing.

10.7.14 It is expected that the following controls would form part of the final peat slide risk assessment:

• careful micrositing of proposed pole supports to avoid drainage channels;

• development of detailed construction access plans, including siting of roads, pads and other associated

infrastructure;

• facilitating flow within existing watercourses and drainage features; and



• careful placement of excavation spoil and imported materials to avoid excess surcharging near excavations

or on slopes.

10.7.15 If required, a geotechnical risk register would form part of the updated peat slide risk assessment and part of

the CEMP.

10.7.16 Peat deposits are considered to have a high sensitivity. Given the safeguards detailed above the peat

resources at site would not be degraded nor is peat slide considered a risk. The magnitude of impact is

therefore considered negligible and the resultant significance of effect is likely to be negligible. No further

mitigation, other than monitoring and inspection, is therefore required.

10.7.17 Following pre-application consultation with SNH, the Applicant confirms that drone surveys would be

undertaken where the Proposed Development is within areas that have received grant funding from SNH

peatland action prior to and following construction. This would allow the Applicant, FLS and SNH Peatland

Action to undertake an assessment of the reinstatement and restoration works completed. The assessment

would determine whether works have been completed successfully, or if any further restoration works are

required at specific locations. If SNH determine the restoration works have been unsuccessful further

discussion would be undertaken regarding any requirement for compensation out with the construction area.

Soils and Geology

10.7.18 No significant earthworks are required. Notwithstanding this, the following best practice measures would be

detailed in the site CEMP in order to safeguard soils:

• any soils temporary stockpiled would be managed in accordance with best practice so that their value is not

degraded;

• works would be scheduled to avoid, when possible, periods of heavy rain and vehicular movement shall be

planned to avoid saturated ground conditions;

• soils would be protected from temporary heavy vehicular movement from placement of ground protection

mats or above ground tracks (underlain by a geotextile);

• stationary plant left for long periods would be parked on formal track / compounds so as to avoid potential

of soil compaction;

• all temporary tracks would be removed upon completion of works; and

• localised measures including silt fencing would be used to manage runoff shed from areas where soils are

disrupted so as not to locally impair water resources and protect sensitive receptors.

10.7.19 With careful management of soils and adoption of the above best practice, their value would not be impaired as

a result of the Proposed Development.

10.7.20 With the exception of the Ben Klibreck SSSI, which is considered to have a High sensitivity, the local geology is

considered to have a low sensitivity. The Proposed Development within Ben Klibreck SSSI is limited and not

significant when compared to its overall extent.

10.7.21 Given the safeguards detailed above neither the value of the soils or the geology would be impaired. The

magnitude of impact is therefore considered negligible and the resultant significance of effect is likely to be

negligible. No further mitigation is therefore required.

Surface Water and Groundwater Quality

10.7.22 As stated above, the works would be undertaken in accordance with the Applicant’s GEMPs and relevant

technical guidance, PPG / GPPs and other codes of best practice, to limit the potential for contamination of both

ground and surface waters. In addition, a site-specific CEMP would be prepared by the Principal Contractor

and include a surface and groundwater quality management plan.



10.7.23 The above measures would significantly reduce the likelihood of pollutants, including suspended solids, being

discharged to nearby watercourses or groundwater (including River Naver SAC and the River Tirry).

10.7.24 It is proposed that water required for the site welfare facilities during the construction phase would be provided

by water bowser or tanker. Water from site welfare facilities would be discharged to a sealed tank which would

be routinely emptied and disposed of at an appropriately licensed off-site facility.

10.7.25 Should a need for water abstraction / discharge arise during works (e.g. vehicular / wheel washing), this would

be dealt with through a registration with SEPA as required under the Water Environment (Controlled Activities)

(Scotland) Regulations 2011 (as amended).

10.7.26 Groundwater and surface water is considered to have a high sensitivity. Given the safeguards detailed above

water quality would not be impaired. The magnitude of impact is therefore considered negligible and the

resultant significance of effect is likely to be negligible. No further mitigation is therefore required.

Flood Risk

10.7.27 As part of the detailed site design the Principal Contractor will identify locations for construction compounds and

access routes and prepare a detailed method statement, all of which will have regard to areas of known and

potential flood risk.

10.7.28 No permanent culverts are required. The design and capacity of any temporary watercourse crossings would

be agreed by the Principal Contractor in consultation with SEPA as part of the detailed site design. Any

temporary culverts would be authorised and regulated in accordance with the Controlled Activity Regulations.

10.7.29 The temporary compounds required to establish the entry and exit pits for the HDD would be located outside of

the modelled flood extents of the River Tirry and at least 20 m from the river.

10.7.30 A schedule of temporary watercourse crossings and construction method statements would be specified in the

CEMP.

10.7.31 Flood risk is considered to have a high sensitivity. Given the safeguards detailed above flood risk to the

development would be mitigated and flood risk downstream of the development would not be increased. The



Surface and Groundwater Flow

10.7.32 The works and protection measures for soils would ensure no significant difference to the existing hydrological

characteristics at site. There would, therefore, be no effect on surface water flows or flood risk as there would

be no permanent change to ground conditions.

10.7.33 Surface water flow paths to areas identified as potential GWDTE would be maintained and thus these habitats

would be safeguarded.

10.7.34 The programme of site investigation has shown that the peat has a low bulk permeability (see Appendix 10.3)

and that the proposed foundations to the OHL and cable routes would not result in significant dewatering of the

peat. No permanent dewatering is required and following construction materials used to backfill the cable

trench and pole foundations will saturate and be the same as in the surrounding soils.

10.7.35 To prevent the cable trench forming a preferential flow path, impermeable barriers or ‘plugs’ will be installed in

the trench in accordance with best practice guidance.



10.7.36 As shown by the peat investigation (see Appendix 10.3) the Proposed Development would have no effect on

the quality or water levels within Loch Dubh Cul na Capulich, nor impair the bog pools or habitats present

therein.

10.7.37 Surface and groundwater flow is assessed to have a high sensitivity. Given the safeguards detailed above the

surface and groundwater flows would not be influenced or altered by the Proposed Development. The



Private Water Supplies

10.7.38 PWS02 abstracts directly from the watercourse Abhainn Sgeamhaidh, which the OHL crosses the main channel

approximately 2 km upstream (WX04). The PWS source is considered to have a high sensitivity.

10.7.39 To ensure that the PWS is safeguarded it is proposed that a schedule of monitoring for the abstraction point is

agreed with THC and SEPA as part of the site CEMP.

10.7.40 With these safeguards and proposed monitoring the magnitude of impact is considered negligible and the

resultant significance of effect is likely to be negligible. No further mitigation is therefore required.

Designated Sites

10.7.41 Designated sites including Ben Klibreck SSSI, Caithness and Sutherland Peatlands Ramsar SAC and SPA,

Cnoc an Alaskie SSSI and River Naver SAC are all considered to have a high sensitivity. The safeguards and

embedded mitigation detailed above and used to protect soils, geology, water quality, groundwater and surface

flow detailed above would also afford protection to these sites and thus it is considered that the potential impact

on the designated sites is negligible. The significance of effect is therefore likely to be negligible, and no

further mitigation is required.

10.8 Summary and Conclusion

10.8.1 Existing soils, geological, hydrogeological and hydrological conditions have been identified and used to assess

the potential effects the Proposed Development may have on geology, soils and the water environment.

10.8.2 Best practice construction techniques that would safeguard soils, geology and the water environment and would

be incorporated in the detailed design of the works and during the construction works have been identified.

Subject to the adoption of the best practice peat resources, soils, geology or the water environment can be

safeguarded during and following development. No significant effects are considered likely to arise as a

result of the Proposed Development.

Documents

CONTENTS...10. HYDROLOGY, HYDROGEOLOGY, GEOLOGY AND SOILS 10.1 Introduction 10.1.1 This Chapter presents an assessment of the potential effects on soils, geology (including peat) and