Substation Corridor Assessment - NnG Offshore Wind · 15.06.2012 · substation site located adjacent to the existing Crystal Rig II Wind Farm substation and proposed cable corridor

Neart na Gaoithe Substation and Cable Corridor

Peat Stability Assessment

November 2012

46400082/GLRP0001

Prepared for: Land Use Consultants

UNITED KINGDOM & IRELAND

LUC — Neart na Gaoithe Substation and Cable Corridor, Peat Stability Assessment

LAND USE CONSULTANTS\46400082 NEART NA GAOITHE WINDFARM\GLRP0001/RC/RC

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REVISION SCHEDULE

Rev Date Details Prepared by Reviewed by Approved by

1 15 June 2012 Draft Peat Stability Assessment

Ross Caird

Project Manager

Richard Allan

Engineering Geologist

Russell Scott

Technical Director

2 19 June 2012 Final Issue Ross Caird

Project Manager

Richard Allan

Engineering Geologist

Russell Scott

Technical Director

3 13 August 2012 Final Issue Ross Caird

Project Manager

Johnathon Laing

Senior Geotechnical Engineer

Russell Scott

Technical Director

4 08 November 2012 Final Issue Ross Caird

Project Manager

Johnathon Laing

Senior Geotechnical Engineer

Russell Scott

Technical Director

URS Infrastructure & Environment UK Limited Citypoint 2, 25 Tyndrum Street Glasgow G4 0JY United Kingdom Tel: +44 (0)141 354 5600 Fax: +44 (0)141 354 5601 www.ursglobal.com



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Limitations

URS Infrastructure & Environment UK Limited (“URS”) has prepared this Report for the sole use of LUC (“Client”) in accordance with the Agreement under which our services were performed (03111139). No other warranty, expressed or implied, is made as to the professional advice included in this Report or any other services provided by URS. This Report is confidential and may not be disclosed by the Client nor relied upon by any other party without the prior and express written agreement of URS.

The conclusions and recommendations contained in this Report are based upon information provided by others and upon the assumption that all relevant information has been provided by those parties from whom it has been requested and that such information is accurate. Information obtained by URS has not been independently verified by URS, unless otherwise stated in the Report.

The methodology adopted and the sources of information used by URS in providing its services are outlined in this Report. The field work described in this Report was undertaken between 09th May 2012 and 10th May 2012 and is based on the conditions encountered and the information available during the said period of time. The scope of this Report and the services are accordingly factually limited by these circumstances.

Where assessments of works or costs identified in this Report are made, such assessments are based upon the information available at the time and where appropriate are subject to further investigations or information which may become available.

URS disclaim any undertaking or obligation to advise any person of any change in any matter affecting the Report, which may come or be brought to URS’ attention after the date of the Report.

Certain statements made in the Report that are not historical facts may constitute estimates, projections or other forward-looking statements and even though they are based on reasonable assumptions as of the date of the Report, such forward-looking statements by their nature involve risks and uncertainties that could cause actual results to differ materially from the results predicted. URS specifically does not guarantee or warrant any estimate or projections contained in this Report.

Unless otherwise stated in this Report, the assessments made assume that the sites and facilities will continue to be used for their current purpose without significant changes.

Where field investigations are carried out, these have been restricted to a level of detail required to meet the stated objectives of the services. The results of any measurements taken may vary spatially or with time and further confirmatory measurements should be made after any significant delay in issuing this Report.

Copyright

© This Report is the copyright of URS Infrastructure & Environment UK Limited. Any unauthorised reproduction or usage by any person other than the addressee is strictly prohibited.



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TABLE OF CONTENTS 1 INTRODUCTION ................................................................1

1.1 Objectives..........................................................................1

1.2 Scope of Work...................................................................1

2 METHODOLOGY ...............................................................2

2.1 Documentary Research....................................................2

2.2 Study Area Reconnaissance ...........................................2

3 STUDY AREA DETAILS & ENVIRONMENTAL SETTING3

3.1 Study Area Location.........................................................3

3.2 Study Area Description ....................................................3

3.2.1 Substation Site..................................................................3

3.2.2 Cable Corridor...................................................................3

3.3 Geology..............................................................................4

3.3.1 Bedrock Geology ..............................................................4

3.3.2 Superficial Deposits - Quaternary Geology ...................4

3.4 Hydrology ..........................................................................5

3.5 Hydrogeology....................................................................5

3.6 Scottish Natural Heritage (SNH)......................................5

4 INTRUSIVE PEAT ASSESSMENT FIELDWORK .............6

4.1 Peat Probing......................................................................6

4.2 Peat Coring........................................................................6

4.3 Laboratory Testing ...........................................................6

5 PEAT STABILITY RISK ASSESSMENT...........................7

5.1 General...............................................................................7

5.2 Factors Controlling Peat Stability...................................7

5.3 Consequences of Peat Failure ........................................9

5.4 Study Area Assessment...................................................9

5.4.1 Peat Thickness..................................................................9

5.4.2 Estimate of Peat Volume................................................10

5.4.3 Peat Morphology.............................................................10

5.4.4 Peat Pipes........................................................................11

5.4.5 Historical Failures...........................................................11

5.4.6 Active or Incipient Failures............................................12

5.4.7 Surface Drainage ............................................................12

5.5 Assessments of Risks....................................................12

5.5.1 Risk Rating ......................................................................12

5.5.2 Triggering and Preparatory Factors .............................14



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5.5.3 Study Area Risk Assessment........................................14

6 CONSTRUCTION METHODOLOGIES AND CONTROL MEASURES .....................................................................18

6.1 General.............................................................................18

6.2 Construction Methodologies and Mitigation Measures18

6.3 Peat Handling, Storage and Re-Use .............................19

7 CONCLUSIONS AND RECOMMENDATIONS................21

Appendix A - Site Location Plan, Site Layout Plan and Cross Sections

Appendix B - Indicative Peat Thickness Plan

Appendix C - Assessed Peat Risk Plan

Appendix D - Site Photographs

Appendix E - Peat Probe Data

Appendix F - von Post Scale of Humification Table

Appendix G - Chain of Custody and Lab Certificates

Appendix H - Preliminary Geotechnical Risk Register



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1 INTRODUCTION

URS Infrastructure & Environment UK Limited (URS) has undertaken a Peat Stability Assessment report for the Neart Na Gaoithe Onshore Grid Connection at the request of LUC.

The proposed onshore grid connection scheme comprises a proposed cable corridor of 12km from Thortonloch Beach to a proposed new substation in the vicinity of the operational Crystal Rig II Wind Farm at Friardykes, East Lothian.

In response to LUC’s Scoping Report, the Scottish Environmental Protection Agency (SEPA) requested that the potential effects of the grid connection on peat be addressed. Following an ecological assessment (by LUC), it was reported that the majority of the 12km cable corridor was classed as agricultural land. LUC in discussion with URS, agreed that a Peat Stability Assessment was only required for the upper reaches of the cable corridor, in the vicinity of the proposed new substation and along the proposed cable corridor for 3km from the substation site. These two areas comprise the study site for the Peat Stability Assessment.

The information contained herein details the effects of the construction and operation of the onshore works on peat stability in these areas.

1.1 Objectives

The objectives of this Peat Stability Assessment are to:

• Characterise the surface ground conditions at the study area with consideration of the baseline conditions as well as the proposed development;

• Assess peat thickness and characteristics within the study area by undertaking a hand-held peat probing and coring exercise;

• Identify potential receptors that may be affected by potential failures within the peat;

• Identify possible areas of unstable peat within the study area; and

• Provide recommendations for further work and specific construction methodologies to mitigate against any potential peat instability risks at the study area.

1.2 Scope of Work

The scope of works developed to achieve the above objectives are listed below:

• Desk study;

• Site reconnaissance;

• Intrusive site assessment including peat probing and peat coring;

• Collection of peat samples and scheduling of laboratory testing;

• Peat stability risk assessment; and

• Construction methodologies and mitigation.



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2 METHODOLOGY

2.1 Documentary Research

A desk based assessment of the study area was carried out prior to the site reconnaissance to assess potential peat stability factors at the site, using a variety of information sources as detailed below:

• Topographical information (supplied by LUC);

• Hydrological information;

• Geological information; and

• Aerial photography.

Initial documentary research was carried out prior to the reconnaissance in order to identify any particular areas that might require specific examination during the study area visit. This included a review of baseline ecological, geological, hydrological and hydrogeological information provided by LUC. Further desk-based research was completed after the reconnaissance. The findings of the site reconnaissance and documentary research are discussed in Section 3.

This assessment has been carried out with reference to the following guidance documents:

• SEPA, Developments on Peatland: Guidance on the Assessment of Peat Volumes, Reuse of Excavated Peat and the Minimisation of Waste (January 2012);

• Scottish Executive, Guidance on Developments on Peatland - Site Surveys (July 2011);

• SEPA Regulatory Position Statement – Developments on Peat (2010);

• Scottish Renewables et al, Good Practice during Windfarm Construction (Oct 2010);

• Scottish Executive, Peat Landslide Hazard and Risk Assessments – Best Practice Guide for Proposed Electricity Generation Developments (2007 – presently under review); and

• Forestry Commission Scotland, Guidelines for the Risk Management of Peat Slips on the Construction of Low Volume/Low Cost Roads Over Peat (January 2006).

2.2 Study Area Reconnaissance

An observational site reconnaissance exercise was carried out by URS on 9th May 2012. During this site visit, notes were taken regarding topography, vegetation cover, hydrology, drainage, peat features and evidence of past or potential areas of peat failure.

The weather during the reconnaissance was dry and overcast.

Subsequently, a hand-held peat probing and peat coring exercise was undertaken between 9th and 10th May 2012.



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3 STUDY AREA DETAILS & ENVIRONMENTAL SETTING

3.1 Study Area Location

The study area is located approximately 5km south of the village of Dunbar in the vicinity of the Crystal Rig II Wind Farm at Friardykes within East Lothian Council boundary. The study area for the Peat Stability Assessment includes the proposed substation site located adjacent to the existing Crystal Rig II Wind Farm substation and proposed cable corridor which extends from the northern boundary of the proposed substation site for 3km to Croft Angry (NGR 368483, 671932), along the approximate route of the current access track for the Crystal Rig II Wind Farm.

The baseline ecological, geological, hydrological and hydrogeological information outlined below was provided by LUC for inclusion in the Peat Stability Assessment.

The site location plan is presented in Appendix A. The study area for the Peat Stability Assessment is shown on the Indicative Peat Thickness Plan presented in Appendix B.

A copy of the substation layout plans and associated cross sections are included in Appendix A.

3.2 Study Area Description

3.2.1 Substation Site

The substation site comprises an area of approximately 140,000m2. The permanent area of the proposed substation is a maximum of 33,300m2 and the temporary construction compound area is 6,827m2. The substation site is located adjacent to the Crystal Rig II Wind Farm substation on an upland plateau, with Bransly Hill to the east, Friardykes Dod to the south west and Watch Law to the north west. The topography generally slopes at shallow angles down to the east becoming flat towards the centre of site. Elevations ranged from 312m above Ordnance Datum (AOD) at the lower slopes of Friardykes Dod (at the western site boundary) to 300m AOD beyond the access track (at the eastern site boundary).

Ground conditions were noted to be generally firm with localised soft or boggy ground. The lower slopes of Friardykes Dod and Watch Law at the western site boundary were observed to be generally firm and dry ground. Firm made ground was observed to the immediate west and north of the existing Crystal Rig II Substation, which is likely to be associated with the construction of the existing substation. A localised area of soft ground was observed in the central south east of site on flat ground.

Vegetation cover across the study area was generally grass and / or reeds with sphagnum moss and localised heather in drier areas. A detailed description of habitat types within the study area is found in Environmental Statement Chapter 8 Terrestrial and Inter-tidal Ecology and Ornithology.

3.2.2 Cable Corridor

The cable corridor study area extends from the northern boundary of the substation site for 3km along the approximate route of the current access track for the Crystal Rig II Wind Farm. The width of the cable corridor is 30m at the widest point. Elevations ranged from 300m AOD at the substation site to 210m AOD at the extent of the study area at Croft Angry (NGR 368483, 671932).

From the substation site, the route initially trends approximately north along the valley floor between Watch Law to the west and Bransly Hill to the east. The corridor



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subsequently trends north east up gradient along the contours of Bransly Hill. The topography becomes increasingly steeper to the west of the corridor, sloping steeply down towards Boonslie Burn. To the east the up gradient slope is moderate to steep towards Bransly Hill. Beyond Thorter Cleugh the topography of the corridor increased to a high point located at NGR 367046, 670549. From here the corridor undulated, but was generally observed to slope down. The gradient towards the valley floor to the west and up towards Bransly Hill to the east was observed to decrease as the topography became increasingly flat towards Croft Angry.

Ground conditions along the cable corridor were observed to be generally firm dry ground. Vegetation cover was generally grass with local areas of bracken present on steeper slopes.

Numerous watercourses are located within the cable corridor study area, as discussed in Section 3.4.

A selection of Site Photographs taken during the site reconnaissance is included in Appendix D.

3.3 Geology

3.3.1 Bedrock Geology

Bedrock exposure is restricted due to an extensive cover of superficial deposits. Exposures are confined to within water courses, chiefly Woodhall Burn within the cable corridor study area.

The oldest part of the geological sequence in this area are Lower Palaeozoic (Silurian) age sedimentary rocks deposited between 440 and 430 million years ago (Ma). These rocks are now part of a north-east to south-west trending belt that forms much of the Southern Uplands of Scotland. The rock succession seen here forms part of the Gala Group. This comprises dark grey thick bedded to massive pebbly greywacke, thinner greywacke units and laminated siltstones. Pebbly clasts in the greywacke comprise a range in compositions including coarse and fine-grained granitic rocks, quartzite, vein quartz, spilitic basalt, older sedimentary rocks, and some of metamorphic provenance.

The Devonian (c. 350 Ma) age ‘Lower Old Red Sandstone’ rock outcrop stretches 25 km south-westwards from Dunbar to Duns, and sits unconformably on the underlying Silurian rocks. The Devonian rocks here are mostly of red to purple-red conglomerate with rounded to sub-rounded pebbles and cobbles set in a sparse fine sandy to pea-gravel matrix. Clasts (rock fragments) are largely held together by mainly ferruginous or less commonly calcareous, cement. Clasts are predominantly of greywacke, with some pebbles of leucocratic porphyritic microdiorite, quartzite, jasper and chert. Most of the lithology is poorly sorted, although there are some fine-grained beds of sandstone that show some internal horizontal stratification and crude grading.

3.3.2 Superficial Deposits - Quaternary Geology

The superficial deposits of the study area are characterised by ice sheet deposits in the form of diamictons (e.g. tills and boulder clay). These deposits range in thickness from less than a metre to up to 5 and 10 m (or more) in scoured depressions in the bedrock surface. Deposits comprise sandy and clay-rich stony and boulder diamictons. The colour and composition of the matrix and the dominant clast types reflect the underlying bedrock substrate to the former ice sheet. Hence, tills derived from the Lower Palaeozoic sedimentary rocks are commonly grey and composed of a hard clay matrix with sub-angular to sub-rounded greywacke and siltstone clasts. A gritty sandy diamicton often predominates over the ‘Old Red Sandstone’ bedrock, where the clay



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matrix has a reddish colour, often imparted to the overlying soils. Ice-smoothed and striated pebbles are common within the tills.

3.4 Hydrology

As the cable corridor enters the Crystal Rig site, the catchments change from agricultural to heath, open moorland and hillslopes. The corridor follows the main access road to the existing wind farm, crossing a number of small, upland streams and one larger water course (Weatherly Burn forming the headwaters of Dry Burn). The corridor climbs to the headwaters of Dry Burn, crossing the divide into the catchment of Tay Burn (Bothwell Water) in the last hundred metres of the route as it reaches the site of the Crystal Rig II Substation. The headwaters of the two catchments lie in a relatively flat plateau with blanket peat. A drainage channel parallels the access road and crosses the access road to the west of proposed sub-station.

3.5 Hydrogeology

There is limited publicly accessible borehole information in respect of the glacial till deposits. British Geological Society (BGS) borehole logs from the vicinity of the site indicated that the till deposits were dry. In general the tills and diamictons are impermeable, and hence do not transmit groundwater. Although not established in LUC’s survey or information review, it is possible that parts of these deposits might contain elevated sand content or host glacio-fluvial channel deposits. In these cases there is the possibility of limited, perched groundwater, and flow through that part of the deposit.

Peat has been identified in the vicinity of the proposed substation site. Peat is often saturated and allows groundwater to flow through it, whereas glacial tills are normally classed as a non-aquifer due to their low permeability. However, sand deposits may be present in the study area which may allow limited groundwater flow.

3.6 Scottish Natural Heritage (SNH)

A search on the SNH online database1 was carried out regarding statutory and non-statutory designations on or in close proximity to the study area.

The search confirmed that there are no statutory or non-statutory designations within the study area, however, Woodhall Dean Nature Reserve, a Site of Special Scientific Interest (SSSI), is located approximately 200m (at its closet point) from the cable corridor. The nature reserve contains the largest area of deciduous woodland in East Lothian and is dominated by pure forms of sessile oak.

1 http://www.snh.gov.uk/publications-data-and-research/snhi-information-service/map/



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4 INTRUSIVE PEAT ASSESSMENT FIELDWORK

Intrusive works were undertaken between 9th and 10th May 2012 by Raeburn Drilling and Geotechnical Ltd (Raeburn) under the supervision of URS.

The intrusive works comprised peat probing and peat coring with the aim of assessing the thickness and nature of the peat within the study area. Laboratory testing was subsequently carried out on peat samples recovered during the works.

4.1 Peat Probing

In order to assess the range in thickness of the peat soils, a number of peat probes (using a MacIntosh Probe) were carried out in the study area. Within the substation site probes were undertaken at approximately 50m centres. For the cable corridor, probes were undertaken approximately every 100m along the proposed route.

The depth of peat was assessed by sinking the probe to refusal and the position of each probe was noted using a hand-held Global Positioning System (GPS) with a typical accuracy of ± 10 m.

It should be noted that at peat probing locations, the soils were not exposed in any way. Therefore assessments of ‘peat’ thickness based on this technique may include both peat and any underlying soft soils that may be present. Additionally, refusal at these locations may be the result of the probing rod being obstructed by something (a cobble for example) within the peat preventing the rod from extending to the base.

4.2 Peat Coring

Peat cores logged on-site were undertaken using a ‘Russian sampler’. Within the substation site five peat core locations were selected to provide spatial coverage across the study area. For the cable corridor, peat cores were proposed at approximately every 300m along the route.

Peat coring using a ‘Russian sampler’ involves pushing a rod with a semi-cylindrical head into the ground to the desired depth and turning the ‘T-Handle’, which traps a relatively undisturbed sample in the head of the sampler, which can then be extracted from the ground and examined. This process was repeated at each location until the base of the peat was encountered.

4.3 Laboratory Testing

In order to obtain further information on the properties of the peat soils and underlying material at the site, laboratory tests were scheduled by URS on the peat core samples recovered during the intrusive site works. All tests were carried out in accordance with BS13772 where applicable, in Raeburn’s in-house laboratory.

The following tests were undertaken on peat core samples:

• Moisture Content;

• Bulk Density; and

• Total Organic Carbon (TOC).

2 British Standards Institution, 1990. BS1377: Methods of Test for Soils for Civil Engineering Purposes.



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5 PEAT STABILITY RISK ASSESSMENT

5.1 General

Peat slides can represent a significant hazard to the environment and site users. Such hazards can occur both during the construction phase as well as during its operational life. Construction on an area of peat will inevitably lead to some alteration of the local hydrological regime.

Development in areas of peat accumulation can have an effect on the stability of these soft soils through alteration of the drainage regime, loadings (both temporary loadings during construction and final working loads) and alteration of the topography. Any development planned in such areas require a sufficient peat stability assessment to accurately characterise the area, identify any issues and develop the required construction mitigation measures to reduce the risk of a failure within the peat.

Peat is a biogenic material which, when fully saturated, can comprise up to 90-95% water with 5-10% solid matter. It can be particularly sensitive to changes in rainfall and subsequent surface and groundwater changes. Imbalances in the water content of a peat accumulation can have catastrophic results, due in part to its “immediate impermeability”, meaning that while water can pass through it over time, intense rainfall can allow groundwater to build up locally within the peat increasing pore water pressure and subsequently increasing the risk of failure. Peat slides can occur on slopes with shallow angles (less than 10 degrees) and debris flows (which includes peat slides) in Scotland can be caused by as little rainfall as 10mm to 75mm per hour provided sufficient duration of rainfall is experienced.

The key considerations of this assessment are that:

• Any existing, historical or potential areas of instability are identified; and

• The proposed substation and cable corridor, including construction works, does not result in an unacceptable risk of peat failure.

5.2 Factors Controlling Peat Stability

Peat slides are caused by a combination of factors – triggering factors and preparatory factors. Triggering factors have an immediate or rapid effect on the stability of a peat accumulation whereas preparatory factors can influence peat stability over a much longer period.

The main triggering factors of peat slides that have been identified include:

• High intensity and prolonged rainfall, in particular following dry periods;

• Peat extraction; and

• Peat loading.

The main preparatory factors, which increase the risk of failures occurring, include:

• Deforestation;

• The effects of topography; and

• Alteration of the hydrological regime.

While peat failures are often considered to originate in thick or extensive accumulations, it should be noted that instability could still occur in areas of limited peat thickness. The



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nature of the peat and the interface between the separate layers can also influence its stability. Often the interface between the upper, periodically saturated layer (the acrotelm) and the underlying permanently saturated layer (the catotelm) can contain the plane of failure, or this might be located at the boundary of the peat and underlying material.

Failure can occur due to heavy or prolonged rainfall where groundwater builds up within a peat accumulation exerting an increased pressure on the soil. This can be exacerbated by drying out the peat (in summer months for example) which can encourage the formation of desiccation cracks, and in turn can fill with water during rainfall, which is then concentrated within the soil leading to increased pore pressure and potentially catastrophic failure. However, the influence of rainfall on potential peat failure is generally considered to be heavily dependant on the natural drainage regime within the peat.

Peat extraction can generate new drainage pathways, leading to a concentration of surface and/or groundwater flow and subsequently lead to either increased erosion or concentration of water within localised areas of the accumulation.

Extraction can also have the effect of releasing the confining pressure on peat thus allowing the development of tension cracks in adjacent peat accumulations following the loss in lateral and/or toe support.

Loading of peat can also generate the formation of tension cracks through compression and bulging of underlying or adjacent peat soils. In such a case, depending on the topography, the strength of the peat may be dramatically reduced due to the alteration in loading and rainfall may not be required to initialise a failure. Peat loading can cause catastrophic failure of underlying peat deposits, such as the large failure, which occurred at Derrybrien Wind Farm (developed by a third party) in 2003.

Deforestation in peat areas can have an effect on the stability of a peat accumulation due to the removal of potentially stabilising root systems and a reduction of groundwater extraction by the trees. Over time, the increase in groundwater can lead to an alteration of drainage pathways, localised or potentially extensive erosion of the peat and concentration of localised groundwater pressure. However, given that forest clearance for such developments generally leaves the stump and roots in place, there is an element of soil reinforcement through the roots left in place.

Peat accumulations typically occur in reasonably flat lying areas or topographic hollows where surface and groundwater drainage is often concentrated. In such areas, the likelihood of failure is considered to be low, however, peat can also be present on hillsides and similar sloping ground. Peat failure can occur on gentle slopes just as on steeper slopes depending on the loading and drainage conditions and the condition of the peat structure. Changes in gradient, including subsurface gradient of underlying strata, can also contribute to peat failure due to the potential concentration of porewater pressures within both concave and convex slope profiles and the gravitational effects on the peat mass.

Alteration of the hydrological regime can have long term and far reaching effects on the stability of peat accumulations. Areas of blanket bog have been identified within the site and these generally have limited drainage and as such are considered to represent a greater risk of instability due to the associated high water table and hence such areas are more sensitive to changes in the drainage regime. Alteration by diverting or blocking either man-made or natural surface drainage pathways or development of new ditches can transport and concentrate water into areas of potential instability.



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Within peat accumulations, groundwater will generally flow relatively more readily within the acrotelm than the underlying less permeable catotelm. Excavations within peat soils will influence existing drainage paths and local permeability.

Various factors including topography, assessed peat thickness, hydrology, receptors and others have been used in URS’ consideration of peat stability and have been used to compile the Peat Risk Plans that are discussed further in section 4.5 later in the report.

5.3 Consequences of Peat Failure

A key part of the risk assessment process is to identify the potential scale of peat failure should it occur, and identify the receptors of the consequences. For the study area outlined (substation site and cable corridor), the key potential receptors of a peat failure include:

• Site construction workers and plant (risk of injury/death or damage to plant);

• Woodhall Dean Site of Special Scientific Interest (SSSI);

• Watercourses and aquatic fauna;

• Wildlife (disruption of habitat);

• Visual amenity (scarring of landscape);

• Infrastructure and services associated with the existing Crystal Rig II Wind Farm;

• Farm buildings;

• Site drainage (blocked drains/ditches leading to localised flooding/erosion); and

• Telegraph poles and associated overhead services.

5.4 Study Area Assessment

5.4.1 Peat Thickness

Peat probing was undertaken within the substation site and along the cable corridor study area. Peat Probe/Core Locations are presented on the Indicative Peat Thickness Plan in Appendix B (Sheets 1 to 5). Raw peat probe data is provided in Appendix E and a summary is given in Table 1 below:

TABLE 1:- SUMMARY OF STUDY AREA PEAT PROBE DATA

Substation Site Cable Corridor Recorded Peat Depth Number of

Probes Percentage Number of Probes Percentage

No Peat 3 5% 25 86%

0.0 - � 0.5m 37 66% 3 10%



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as H2 to H3 on the von Post Scale of Humification with a water content of B2 (low moisture content). Peat cores could not be recovered from RC3, RC4 or RC5 due to the presence of clay rather than peat.

Based on the peat cores retrieved only acrotelmic peat was observed on site. Given the thin nature of the peat observed and its fibrous characteristics the amount of catotelmic peat on site is considered to be negligible.

A copy of the von Post Scale of Humification is included in Appendix F.

Results of the laboratory analysis of peat samples RC1 and RC2 are presented in Table 3 below:

TABLE 3:- LABORATORY ANALYSIS OF PEAT SAMPLES

Position Sample Depth (m) Bulk Density (Mg/m3)

Natural Moisture Content (%)

Total Organic Carbon %

RC1

(NGR 366400, 669427) 0.0 1.25 225 17

RC2

(NGR 366362, 669444) 0.2 1.23 387 24

Laboratory results indicate the peat to have high moisture content values and relatively low bulk density values. The TOC values are lower than expected for peat, however this is likely to indicate that some clay content is present within the peat.

A copy of the chain of custody and laboratory certificates are presented in Appendix G.

5.4.4 Peat Pipes

Peat pipes are subsurface drainage pathways that have the potential to transport significant volumes of water through the peat particularly during periods of intense rainfall or snowmelt and can potentially represent a risk of peat failure. Where numerous peat pipes are present, these may form a subsurface drainage network and have the potential to induce peat failure. Collapsed peat pipes can sometimes be identified by circular surface depressions within the peat.

It should be noted that peat pipes can be difficult to find, as they can usually only be viewed in an exposed face of peat or as circular shaped depressions in the peat at ground surface and sometimes they can only be detected by the sound of running water beneath the ground surface.

No evidence of peat pipes or other subsurface watercourses were recorded during the site reconnaissance exercise.

5.4.5 Historical Failures

Where historical failures are present this can indicate areas of potential future risk. This is due to the initially favourable conditions for a failure to occur and because a slip plane may have formed at the base of the feature, which will have lost some of the peat’s natural binding strength and can be lubricated by water within the peat soils.



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No evidence of historical peat failures were encountered during the study area reconnaissance.

However, localised historical soil slips were noted along the cable corridor study area likely to be associated with the steepness of the slopes at these locations. A minor slope failure was observed where the cable corridor crosses a watercourse (Thorter Cleugh) at NGR 366971, 670261. Exposed soils in the failure scar indicated that no peat was present. A number of minor soil slips were also observed along the cable corridor at the lower slopes of Bransly Hill (down gradient of High Wood). Exposed soils here also indicated that no peat was present. Given that peat was not observed at these locations the occurrence of a peat failure is considered negligible.

5.4.6 Active or Incipient Failures

Incipient failures usually indicate where a failure may be due to occur. Tension cracks or bulging can often be precursors to a large failure. However, no evidence of tension cracks, bulges or any other indicators of potential instability was noted during the study area reconnaissance. No active failures were recorded.

5.4.7 Surface Drainage

At the time of the site reconnaissance, it was noted that within the substation site, the lower slopes of Friardykes Dod and Watch Law at the western site boundary were observed to be generally dry. Localised areas of boggy ground with standing water present were observed in the central south east of the substation site on flat ground. Numerous small drainage channels flowing from west to east were observed. A larger drainage channel runs in a north south orientation parallel to the access track.

The ground conditions along the cable corridor study area were generally noted to be dry. Numerous watercourses are located within the cable corridor study area, as discussed in Section 3.4.

5.5 Assessments of Risks

5.5.1 Risk Rating

The level of risk allocated to a particular area relates to the presence of peat, the likelihood of failure occurring (the hazard) and the consequences of such a failure (the exposure). The risk rating for a site or individual area is based on the risk assessment methodology laid out in the Scottish Executive Best Practice Document3 and is summarised below:

Hazard Ranking = Hazard Scale x Exposure Scale

The assessment process uses the following tables to firstly help define the level of hazard and then the exposure:

TABLE 4:- TABLE OF HAZARD SCALE

Scale Hazard Probability of Occurrence

5 Almost certain >1 in 3

3 Peat Landslide Hazard and Risk Assessments – Best Practice Guide for Proposed Electricity Generation Developments (2007).



��Final 13

4 Probable 1 in 10 – 1 in 3

3 Likely 1 in 102 – 1 in 10

2 Unlikely 1 in 107 – 1 in 102

1 Negligible 100% of project / local environment

4 Very high impact 10% - 100%

3 High impact 4% - 10%

2 Low impact 1% - 4%

1 Very low impact



��Final 15

from the west to the east becoming flat towards the eastern centre of the proposed substation site. Ground conditions were noted to be generally firm on the slopes of Friardykes Dod and Watch Law, with localised soft or boggy ground in the central south east of site on flat ground. Information gathered during the intrusive works indicated shallow peat accumulations in this area (generally less than 0.5m). However, localised areas of deeper peat (between 0.5m and 1.0m) were encountered with one probe recording a thickness of 2.0m. Probes located in adjacent grids to the deeper peat assessed the peat to a depth of 0.2m and 0.4m. It is therefore considered that the 2.0m thick layer of peat is a very localised pocket of deeper peat. Peat in the substation area was noted to be fibrous with plant remains. No peat hags, gullies, pipes or historical/active failures within the peat were observed in this area during the site visit.

Potential receptors specific to the proposed substation site include:


• Tay Burn located to the east of site running parallel to the access track;

• Access track to Crystal Rig II Wind Farm;

• Overhead electricity lines and pylons associated with Crystal Rig II Wind Farm;

• Crystal Rig II substation;

• Underground high voltage electricity cable (Array 1) located in the south of the substation site;

• Woodhall Dean SSSI; and

• Site drainage located to the east of site running parallel to the access track.

Although locally thick peat was recorded, it was within a confined area. In view of the generally shallow slope, the typically thin peat accumulations and the fibrous nature of the peat (indicating the peat contains some strength), the baseline hazard scale for this area is considered to be 1 (negligible).

The main receptors in this area are the existing Crystal Rig II substation, the electricity pylons and the watercourses. Although at a steeper gradient than the rest of site, the ground up gradient of the Crystal II Substation on the lower slope of Friardykes Dod was observed to be generally firm made ground with limited peat deposits. The potential for a peat failure impacting the Crystal Rig II Substation is therefore very unlikely. Due to the shallow slope of the ground where the electricity pylons cross the site, it is considered that a potential failure in this vicinity would not have the potential to travel a significant distance. The assessed thickness of peat recorded upslope of the watercourses in this area are generally limited, thus if a potential failure was to occur, not much material would be available to slide into the watercourses. Additionally, due to the shallow topography, it is considered that any failed material would only travel a limited distance and therefore only material in close proximity to the watercourses would affect them. Therefore, a baseline exposure scale of 2 (low impact) is considered appropriate. This results in a baseline hazard rank of 2 (insignificant).

Given that any peat is likely to be removed prior to construction, the hazard scale within this area, considering the proposed development, is therefore only likely to increase minimally to 2 (unlikely), subsequently increasing the hazard rank to 4, which is still ranked as insignificant.



��Final 16

Area B – Cable Corridor

The cable corridor study area extends from the northern boundary of the substation site for 3km along the approximate route of the current access track for the Crystal Rig II Wind Farm.

Topography along the cable corridor varies but generally slopes down gradient to the north east. North of Thorter Cleugh (watercourse) the ground slopes sharply down to the west of the cable corridor towards Boonslie Burn in the valley floor. As the cable corridor approaches Croft Angry the topography becomes increasingly flat.

Ground conditions along the cable corridor were noted to be generally firm. Observed peat deposits were limited to within 400m of the substation site. The ground within this 400m corridor was generally firm with peat thickness ranging from 0.2m to 0.7m. No peat deposits were identified along the remaining cable corridor study area.

Potential receptors specific to the proposed cable corridor study area include:


• Boonslie Burn;

• Wildlife (disruption of habitat);

• Woodhall Dean SSSI;

• Visual amenity (scarring of landscape);

• Access track to Crystal Rig II Wind Farm;

• Overhead electricity lines and pylons associated with Crystal Rig II Wind Farm;

• Farm buildings;

• Site drainage; and

• Telegraph poles and associated overhead services.

Peat deposits were identified along the cable corridor within 400m of the substation site, however given the limited thickness of the peat and the relatively flat topography of the area it is considered unlikely that a peat failure will occur. As peat deposits were not observed along the remainder of the cable corridor study area, it is considered unlikely that a peat failure will occur along the 3km cable corridor from the substation site to Croft Angry. Therefore, the baseline hazard scale is considered to be 1 (negligible). The main receptors in this area are the overhead services, Boonslie Burn and its tributaries and Woodhall Dean SSSI, however due to the relatively thin accumulations assessed, should a potential peat failure occur it is considered that there would be limited material available to affect the receptors. The baseline exposure scale is therefore considered to be 2 (low impact), resulting in a baseline hazard rank of 2, insignificant.

Given the limited peat deposits along the cable corridor, the hazard scale within this area, considering the proposed development, is not likely to increase and therefore the hazard rank of the cable corridor study area considering the proposed development is unlikely to change, i.e. insignificant.



��Final 17

Summary

Table 7 below summarises the assessment of peat stability within the areas detailed above:

TABLE 7:- SUMMARY OF PEAT RISK ASSESSMENT

Area Hazard Rank Considering Baseline Conditions

Hazard Rank Considering Construction Works

Area A – Substation Site Insignificant Insignificant

Area B – Cable Corridor Insignificant Insignificant

With reference to the Scottish Executive Best Practice Document, the above table indicates that works within both areas may proceed with monitoring and mitigation of peat landslide hazards as appropriate (discussed in Section 5 below).



��Final 18

6 CONSTRUCTION METHODOLOGIES AND CONTROL MEASURES

6.1 General

The baseline risk of instability across the site is considered to be generally insignificant, represented by a hazard scale range of 2, which indicates that a failure is unlikely to occur as a result of natural processes.

The risk of instability across the site due to the construction of the proposed substation and cable corridor are higher than the baseline risk due to such factors as loading of the soils from machinery and plant and vehicular movement. However, the aim of the mitigation measures is to minimise the level of risk and where possible/appropriate, reduce it below the baseline hazard. The main receptors for a peat failure on this site are likely to be Woodhall Dean SSSI, the larger watercourses, the existing Crystal Rig II substation, and the electricity pylons, which cross through the area, and the protection of these needs to be carefully considered when planning the construction works. The presence of other small watercourses on-site should also be taken into account during the construction phase.

Any construction activity relating to or undertaken in the vicinity of watercourses (including any water crossings etc.) should be carried out in general accordance with relevant SEPA Pollution Prevention Guidelines, The Water Environment and Water Services (Scotland) Act 2003 (WEWS) and The Water Framework Directive (WFD): Controlled Activities Regulations (CAR) 2011.

6.2 Construction Methodologies and Mitigation Measures

The following examples of working methodologies and mitigation measures can be implemented to reduce the risk of peat instability during construction of the proposed substation and cable corridor are as follows:

• Identification of the localised area (within the substation site) of greater peat thickness, physical demarcation and instruction to site personnel to avoid or minimise activity in this location where practical;

• Design and construction of a suitable drainage system for hardstandings that does not significantly affect the hydrological regime of the peat;

• Side-casting of material during construction only in appropriate areas identified following risk assessment and agreed with all relevant parties (SEPA, SNH, etc.);

• Identification of approved areas for stockpiling of any excavated rock or soils including peat;

• Identification of drainage areas and areas of run-off which could potentially be affected by the development and appropriate stand-off distances established;

• Any excavations in peat should be risk assessed and measures adopted to minimise the risk of failure within excavation side slopes and surrounding materials;

• Monitoring of slope and peat stability in the vicinity of the proposed substation during construction by suitably experienced and qualified personnel;

• Appropriate cable corridor construction methods to take cognisance of local topography and peat thickness (particularly in the cable corridor route within 400m north of the substation site);

• Supervision of all construction work by suitably qualified and experienced personnel;



��Final 19

• Where deep excavations (for hardstanding areas etc.) require dewatering, discharges of the pumped water will require to be controlled in a manner which does not adversely affect habitats on site (due to potential silt content etc.) and does not lead to the creation of over-saturated, and hence very soft, areas of peat;

• Should peat pipes be encountered during construction in the vicinity of the proposed development, consideration should be given to excavating the peat in the areas and backfilling with an appropriate free-draining granular material. In the event of a peat pipe becoming blocked or crushed during construction, this should prevent the water flow from being restricted during high water events, and thus reduce the likelihood of potential failures from occurring;

• Appropriate risk assessment of vehicle and personnel movements on sloping ground where peat is present;

• Development of working methodologies that ensure that any exposed peat is protected to limit the potential for degradation, erosion or failure of the accumulation;

• A site specific Peat Management Plan should be developed for the site which should be followed during construction works; and

• A site specific Geotechnical Risk Register (GRR) should be developed for the site which should be kept on-site and regularly reviewed and updated as the construction works progress (a Preliminary GRR has been produced for the substation and is included in Appendix H, however this will need to be updated by the Principal Contractor and Technical Advisor once construction works are underway).

The above should be considered to represent the minimum requirements for reducing the risk of peat instability during construction works and it is recommended that these are included in the relevant construction method statements.

6.3 Peat Handling, Storage and Re-Use

Guidelines on the reuse of peat is given within the Scottish Renewables and SEPA document ‘Developments on Peatland: Guidance on the Assessment of Peat Volumes, Reuse of Excavated Peat and the Minimisation of Waste’ (January 2012). The following guidance is given:

• Careful handling is essential to retain any existing structure and integrity of the excavated materials and thereby maximise the potential for excavated material to be reused;

• Minimise plant movements and haulage distances in relation to any earthworks activity including peat management;

• Excavation of side slopes within peat should be as shallow an angle as possible and care should be taken to stabilise sides;

• Develop appropriate temporary storage areas for excavated peat close to the excavation (i.e. areas of lower ecological value and lower stability risk);

• Reuse should occur as soon as possible after excavation;

• Peat turfs poorly stored or stored for a long period of time can impact on the quality and time required for the area to fully recover; and

• Valid reuses of excavated peat during construction include:



��Final 20

o Reinstatement of the substation platform using peat to suitably tie in with surrounding area;

o Where a requirement is demonstrated a screening bund using suitable peat may be created;

o Verge reinstatement of access tracks if appropriate; and

o Reinstatement of cable trenches.



��Final 21

7 CONCLUSIONS AND RECOMMENDATIONS

Peat deposits recorded within the study area during this investigation are limited to the substation site and 400m of cable corridor from the substation site on relatively flat ground. Peat probing undertaken generally assessed peat to be relatively thin, with the exception of one localised area of thicker peat accumulation within the substation site. No peat deposits were recorded along the northern section of the cable corridor study area. Peat was noted to be fibrous with plant remains indicating that the peat contains some strength, and is therefore considered to be less susceptible to failure than amorphous peat with decomposed plant structures.

Due to the thickness of the recorded peat, its fibrous nature and the general flat topography observed in areas where peat was recorded (i.e. in the vicinity of the substation site), the baseline hazard rank and subsequent hazard rank considering construction works for the study area (substation site and cable corridor) was assessed to be insignificant.

The potential for a peat slide occurrence is considered unlikely. However, adequate construction methodologies (such as those highlighted in Section 5) should be employed during the development of the substation site and cable corridor.

A Preliminary Geotechnical Risk Register, based on the available information from the investigation, is included in Appendix H. Due to the minimal peat assessed along the proposed cable corridor, an Assessment Sheet has only been produced for the substation area. Once more information relating to the peat at the substation is available, the Assessment Sheet can be used as a starting point for the Geotechnical Risk Register that will require to be produced and maintained, as per the Scottish Executive Best Practice Guide, throughout the works.

Once detailed ground investigations have been undertaken (post-consent) at the detailed design stage, further opportunities for reducing peat impacts may be considered and potentially achieved, in consultation with the appointed Environmental Clerk of Works.


LAND USE CONSULTANTS\46400082 NEART NA GAOITHE WINDFARM\GLRP0001/RC/RC NOVEMBER 2012

Final

Appendix A - Site Location Plan, Site Layout and Cross Sections

Reproduced from Ordnance Survey digital map data © Crown copyright 2012. All rights reserved. Licence numbers 100047514, 0100031673.

0 100 200 MetresLUCGL Fig05-06_5166-0052-r1_SubstationLayout 12/11/2012

Substation Layout

Map Scale: 1:2,500

¯

Figure 5.6

Application BoundaryConstruction CompoundProposed SubstationCrystal Rig access track diversionExisting Crystal Rig II SubstationCut

FillExisting overhead linesExisting hardstandingExisting buildingsExisting turbines

N e a r t n a G a o i t h eOns hore Works

NB: Separate consent is being sought by Scottish Power Transmission to connect Neart na Gaoithe to the National Grid.

#

#

#

#

#

#

299m305m

304m303m

306m307m308m

309m

302m

310m

311m

295m

312m

294m

313m

300m

293m

297m

301m

298m

296m

297m

309m

297m

298m

310m

300m

298m

296m

Y

Z

Y

X

X

Z

Reproduced from Ordnance Survey digital map data © Crown copyright 2012. All rights reserved. Licence numbers 100047514, 0100031673.

0 100 MetresLUCGL Fig05-07_5166-0000-r0_SubstationGradingPlan 22/10/2012

Substation Grading Plan

Map Scale: 1:1,507.65

¯

Figure 5.7

Application BoundaryConstruction CompoundProposed SubstationExisting Crystal Rig II Substation

# Cross Section (See Figure 5.8)Cut

FillExisting hardstandingExisting turbines

N e a r t n a G a o i t h eOnshore Works

NOTES1. CONTOURS GENERATED FROM ELEVATION POINTS PROVIDED BY BALFOUR BEATTY (USING ARCGIS)2. CONTOURS SPACED AT 1m. INTERVALS3. CONTOUR DATA, NOT AVAILABLE FOR THE NORTH SIDE OF THE SUBSTATION HAVE BEEN EXTRAPOLATED FOR CUT / FILL WORKS4. FOR SECTION REFER TO FIGURE 5.8

LUCGL Fig05-07_5166-0000-r0_SubstationGradingPlan 20/09/2012

Example Substation Grading Section

Figure 5.8

N e a r t n a G a o i t h e Ons hore Works

SECTION X-X

292m294m296m298m300m302m304m

SECTION Y-Y

SECTION Z-Z

SUBSTATION COMPOUND

292m294m296m298m300m302m304m306m

SUBSTATION COMPOUND

292m294m296m298m300m302m304m306m

SUBSTATION COMPOUND

EXISTING ROAD

EXISTING ROAD

GABION RETAINING WALL

EXISTING ROAD

GABION RETAINING WALL

COMPOUND PLATFORM LEVEL (298m)

1:8 Backslope

BERM DETAIL (Not to scale)Existing Slope

1:2 Foreslope

CUT

FILL

BERM

EXISTING GROUND

NOTES:

1. CONTOURS GENERATED FROM ELEVATION POINTSPROVIDED BY BALFOUR BEATTY (USING ARCGIS)

2. CONTOURS SPACED AT 1m. INTERVALS

3. CONTOUR DATA, NOT AVAILABLE FOR THE NORTH SIDEOF THE SUBSTATION HAVE BEEN EXTRAPOLATED FORCUT / FILL WORKS

4. FOR PLAN REFER TO FIGURE 5.7

0 12.5 m 25 m 50 m



Final

Appendix B - Indicative Peat Thickness Plan (Drawing Nos 46400082/0002,

46400082/0003, 46400082/0004, 46400082/0005, 46400082/0006)



Final

Appendix C - Assessed Peat Risk Plan (Drawing No 46400082/0012)



Final

Appendix D - Site Photographs

Photograph No: 1 View looking south Description: Substation Site

Photograph No: 2 View looking south

west Description: General ground conditions observed along the cable corridor study area.

Photograph No: 3 View looking south Description: Drainage ditch located east

of the substation study area.

Photograph No: 4 View looking west Description: Thin peat overlying sandy

clay deposits observed in a drainage ditch in the substation study area.

Photograph No: 5 View looking east Description: Lower slopes of Friardykes Dod - photo taken from the western boundary of substation study area (note shallow gradient and dry ground).


west Description: Cable corridor route within 400m of substation site.

Photograph No: 7 View looking north east

Description: Minor slope failure observed along cable corridor at Thorter Cleugh (NGR 366971, 670261). No peat observed in scarring.

Photograph No: 8 View looking south east

Description: Minor soil slips observed along the cable corridor at the lower slopes of Bransly Hill (NGR 368284, 671779). No peat observed in scarring.

Photograph No: 9 Description: Peat core from substation

site (RC1).


west Description: Boundary of cable corridor study area at Croft Angry.



Final

Appendix E - Peat Probe Data

Position Thickness (m) OS X OS YPP01 0.3 366273 669317PP02 0.4 366222 669326PP03 0.4 366158 669332PP04 0.7 366169 669372PP05 0.75 366225 669376PP06 0.55 366273 669372PP07 0.15 366339 669379PP08 No Peat 366400 669369PP09 0.25 366479 669366PP10 0.45 366493 669424PP11 0.5 366421 669425PP12 0.65 366362 669432PP13 1 366313 669429PP14 0.6 366284 669436PP15 0.2 366244 669440PP16 0.5 366262 669499PP17 No Peat 366332 669480PP18 0.7 366369 669469PP19 0.5 366379 669468PP20 1 366449 669466PP21 0.45 366483 669643PP22 0.4 366496 669509PP23 0.9 366467 669513PP24 0.85 366446 669522PP25 0.4 366400 669529PP26 0.15 366344 669539PP27 No Peat 366251 669549PP28 0.1 366249 669576PP29 0.15 366300 669592PP30 0.3 366379 669575PP31 0.2 366428 669566PP32 0.8 366467 669561PP33 0.75 366500 669563PP34 0.3 366480 669609PP35 0.25 366465 669613PP36 0.35 366427 669620PP37 0.35 366365 669636PP38 0.3 366287 669367PP39 0.5 366292 669659PP40 0.3 366333 669656PP41 0.3 366397 669672PP42 0.5 366451 669649PP43 0.2 366500 669645PP44 2 366528 669640PP45 0.4 366513 669701PP46 0.5 366463 669705PP47 0.3 366423 669712PP48 0.3 366403 669718PP49 0.45 366376 669736PP50 0.3 366437 669789PP51 0.2 366467 669765PP52 0.25 366512 669748PP53 0.6 366523 669791PP54 0.3 366501 669816PP55 0.6 366506 669849

Position Thickness (m) OS X OS YPP56 0.3 366528 669844PP57 0.7 366571 669934PP58 0.2 366657 670059PP59 No Peat 366724 670064PP60 0.3 366752 670134PP61 0.2 366831 670174PP62 No Peat 366932 670218PP63 No Peat 366981 670312PP64 No Peat 366998 670424PP65 No Peat 367046 670554PP66 No Peat 367084 670626PP67 No Peat 367116 670711PP68 No Peat 367154 670802PP69 No Peat 367193 670908PP70 No Peat 367230 671030PP71 No Peat 367284 671133PP72 No Peat 367364 671228PP73 No Peat 367424 671330PP74 No Peat 367601 671486PP75 No Peat 367664 671544PP76 No Peat 367767 671549PP77 No Peat 367875 671549PP78 No Peat 367921 671579PP79 No Peat 368053 671647PP80 No Peat 368092 671664PP81 No Peat 368152 671699PP82 No Peat 368252 671699PP83 No Peat 368363 671825PP84 No Peat 368440 671887PP85 No Peat 368463 671923RC1 0.6 366400 669427RC2 0.7 366362 669444RC3 0.3 366452 669563RC4 0.3 366445 669714RC5 0.3 366506 669843

PP = Probe PositionRC = Russian CoreOS = Ordinance Survey



Final

Appendix F - von Post Humification Scale Table

The von Post Scale of Humification

Scale Description

H1 Completely undecomposed peat that, when squeezed, releases almost clear water. Plant remains easily identifiable. No amorphous material present.

H2

Almost entirely undecomposed peat that, when squeezed, releases clear or yellowish water. Plant remains still easily identifiable. No amorphous material present.

H3

Very slightly decomposed peat that, when squeezed, releases muddy brown water, but from which no peat passes between the fingers. Plant remains still identifiable, and no amorphous material present.

H4

Slightly decomposed peat that, when squeezed, releases very muddy dark water. No peat is passed between the fingers but the plant remains are slightly pasty and have lost some of their identifiable features.

H5

Moderately decomposed peat that, when squeezed, releases very muddy water with a very small amount of amorphous granular peat escaping between the fingers. The structure of the plant remains is quite indistinct although it is still possible to recognise certain features. The residue is very pasty.

H6

Moderately highly decomposed peat with a very indistinct plant structure. When squeezed, about one-third of the peat escapes between the fingers. The residue is very pasty but shows the plant structure more distinctly than before squeezing.

H7

Highly decomposed peat. Contains a lot of amorphous material with very faintly recognisable plant structure. When squeezed, about one-half of the peat escapes between the fingers. The water, if any is released, is very dark and almost pasty.

H8

Very highly decomposed peat with a large quantity of amorphous material and very indistinct plant structure. When squeezed, about two-thirds of the peat escapes between the fingers. A small quantity of pasty water may be released. The plant material remaining in the hand consists of residues such as roots and fibres that resist decomposition.

H9 Practically fully decomposed peat in which there is hardly any recognisable plant structure. When squeezed it is a fairly uniform paste.

H10 Completely decomposed peat with no discernible plant structure. When squeezed, all the wet peat escapes between the fingers.

B1 Dry Peat.

B2 Low moisture content.

B3 Moderate moisture content.

B4 High moisture content.

B5 Very high moisture content.



Final

Appendix G - Chain of Custody and Laboratory Certificates

of 1

Report No: RT9989Issue No 01

15/05/201214/05/201216/05/2012

Please find enclosed the results as summarised below

1 2 See Sheets2 2 s/c

Remarks :

Issued by : Date of Issue : 30/05/2012

Approved Signatories :

Project NameDate samples receivedDate written instructions receivedDate testing commenced

RT998922667

Purchase Order

NEART NA GAOITHE PEAT STABILITY

LABORATORY TEST REPORT

TestQuantity

Figure / Table Description

ISO 17025Accredited

Raeburn Drilling & Geotechnical Ltd

Project NumberYour Ref

For the attention of

Whistleberry RoadHamiltonML6 OHP

Craig Ritchie (RDG)

Summary of Geotechnical TestsTotal Organic Carbon

S/C : Testing was sub-contracted

G Wilson (JMD/Laboratories Director), J Murray (Laboratory Manager) , D McGiff (Assistant Laboratory Manager)

30/05/2012

D McGiff

~

Key to symbols used in this report

Only those results indicated in this report are UKAS accredited and any opinions or interpretations expressed are outside the scope of UKAS accreditation.

Feedback on the this report may be left via our website terratek.co.uk/feedback

The results reported relate to samples received in the laboratory only.

This report should not be reproduced except in full without the written approval of the laboratory.

Unless we are notified to the contrary, samples will be disposed after a period of one month from this date.

All results contained in this report are provisional unless signed by an approved signatory

Under multisite accreditation the testing contained in this report may have been performed at another Terra Tek laboratory.The enclosed results remain the property of Terra Tek Limited and we reserve the right to withdraw

our report if we have not received cleared funds in accordance with our standard terms and conditions

Head Office : 62 Rochsolloch Road, Airdrie, ML6 9BG

62 Rochsolloch Road, Airdrie, ML6 9BGTel: +44 (0)1236 747 949 Fax: +44 (0)1236 747 849

[email protected]

Terra Tek Ltd is registered in Scotland No. 121594Offices in Airdrie, Birmingham, Belfast and Chesham

www.terratek.co.uk

Contract No 22667

Lab Project N

o RT9989 : 30/05/2012 08:43:26

TOC

TOC1.25 ~ ~~

62 Rochsolloch R

oad, Airdrie, M

L6 9BG

SUMMARY OF GEOTECHNICAL TESTS

Brown fibrous PEAT 387

~ ~

Dry

Liqu

id L

imit

Pla

stic

Lim

it

Atte

rber

g C

lass

ifica

tion

Par

ticle

Den

sity

Atterberg limits

Mg/m³

She

ar S

treng

th

Other Tests

Total Stress

RC02 0.20

Ang

le o

f She

arin

gR

esis

tanc

e P

hi

Density

Notes

30/05/2012

Originator

SB

Opinions and interpretations are outside the scope of UKAS accreditation Y

App

aren

t Coh

esio

nC

Checked & Approved

Non EngineeringSample Description

Moi

stur

e C

onte

nt

Bul

k

Pla

stic

ity In

dex

Per

cent

age

reta

ined

42

5µm

%

Version 006 - 21/10/2009

RC01 0.00-0.00

RT9989 C

lassification Sum

mary 01.xls

ExploratoryHole

Depthm

Brown fibrous PEAT 225% % Mg/m³ Mg/m³ kPa kPa

~ ~~

~ ~ ~ ~ ~ ~1.23 ~ ~

Y- Y YY Y Y YUKAS Accredited Test Y/N Y

%

~ Indicates test not carried out

Y Y

�Figure C1

Sheet 1 of 1

See individual report sheets

Test details are given on the 'Notes on Laboratory Procedures' sheet

B 105816

B 105817

SampleType

LabSample

ID

Sample Identification

�Site

Client

Engineer

SampleRef


URS Infrastructure & Environment UK Ltd


Lab

Pro

ject

No

RT9

989 Testing carried out by subcontracted lab no. 2653

Contract No 22667

Checked &Approved

KP30/05/2012

SiteHole IDSample RefDepth (m)Sample Type



Rev

isio

n 1.

19 1

6/01

/201

2

�R

T998

9 P

hoto

Fram

e 01

.xls

Engineer

Client

Sheet 1 of 1

Figure 2

�Originator

Total Organic Carbon


No

RDG TTK YesOUR REF No: 22667 * Delete as appropriate

CLIENTS No.: ENGINEER : Site : DATE of SCHEDULE : 14-May-12

CLIENT : DATE RESULTS REQUIRED : 29-May-12

Scheduled prepared by: RC Schedule No: 1 Notes: 1. Standard Triaxial Pressures2. 20m : 200, 400, 800 kN/m²

CLIENTS OR SAMPLE DESCRIPTION

Stores Borehole Depth Sample Lab Moisture Bulk Atterberg Consol. Triaxial Compact. C.B.R M.C.V. pH Sulphate Organic Chloride L.O.I. ENGINEERS

Location or Type Ref No Content Density Limits S.A M.A. Test Test Test Test Test Value Content Matter (as NaCl) TOC INSTRUCTIONS

Trial Pit (m) 100mm (Type) (2.5kg) (Type) (2:1) Content Content COMMENTS

Total No or Cost(£) 2 2 2Rates

10GR RC01 0.00 B 1 1 110GR RC02 0.20 B 1 1 1

Engineer (print) CRAIG RITCHIE

Signed Craig Ritchie

Sample Contamination

AGS Data Required

GEOTECHNICAL LABORATORY TESTING SCHEDULE

SAMPLE

Neart na Gaoithe Peat Stability

CHEMICAL TESTS



Standard pressures and increase at 16% and 18% strain for triaxial test unless statedCarry out MA if >10% passing 0.063mm sieve unless stated.

Particle Size

CLASSIFICATION TESTS TXL / CON EARTHWORK TESTS OTHER TESTS

J:\Glasgow-Jobs\Land Use Consultants\46400082 Neart na Gaoithe Windfarm\Technical\RAEBURN DATA\22667 geotech schedule page 1 of 1



Final

Appendix H - Preliminary Geotechnical Risk Register

Preliminary Geotechnical Risk Register

June 2012 Neart na Gaoithe Substation and Cable Corridor i

Preliminary Geotechnical Risk Register Introduction This Geotechnical Risk Register (GRR) was created as a means of identifying and recording peat conditions at the site and assessing the risk of peat slides to satisfy planning conditions. Following the Derrybrien peat slide of 2003, the Scottish Government’s Energy Consents Unit expect all windfarm applications in Scotland to commit to a system of geotechnical risk management and contain a GRR, to ensure that all identified geotechnical risks are highlighted to those who need to know. The GRR is a dynamic document, which should be updated as construction progresses and as more information relating to peat becomes available. Good communication between the Client, Designer, Contractor and Peat Management Technical Advisor is essential for the GRR to work. Location-specific information relating to the peat is therefore required on a daily basis during the construction works, which can then be fed into the GRR regularly (e.g. following weekly progress meetings).

Responsibility of peat stability ultimately lies with the Contractor during construction and maintenance period, however, as stated above, good communication is required at all levels to make this process work. Due to the minimal peat assessed along the proposed cable corridor, an Assessment Sheet has only been created for the substation area. This Assessment Sheet considers the area in more depth and is explained in further detail below.

Explanation of Risk Assessment Sheets Methodology The following Geotechnical Risk Register (GRR) provides specific risk assessments identified at the location (Position ID) detailed on the attached Assessment Sheet (proposed substation) at the site. This assessment was made by information collected by the Contractor during peat probing / coring works and during the URS site visit. The risk assessment process considers three headings (namely Existing Hazard Assessment, Development Trigger Assessment and Receptor Assessment), identifying the level of hazard associated with each and considers the probability of a slide occurring as a result. The Existing Hazard Assessment is based on baseline conditions at the site, i.e. the site in its natural, undeveloped condition. This assessment includes consideration of the topography, peat thickness and peat classification as well as signs of historical / incipient peat failure, all of which can have an effect on the stability of peat accumulations. The Development Trigger Assessment takes into consideration the works required for the development, and hence what the subsequent potential for failure is as a result of these works. The Receptor Assessment is based on the potential for a failure, if it occurred, to affect receptors such as watercourses or built developments (existing or part of the development). Each assessment table contains the risk assessment criteria in its left-hand column. The remaining three columns contain details which form the basis of the risk assessment, increasing in the level of risk to the right. The particular conditions at the Position ID are highlighted to indicate where they fall in each table. The assessment is determined by identifying which column the majority of the hazard factors fall in. Therefore if the majority of highlighted boxes lie in the left-hand column, this indicates a low probability. However, where hazard factors fall in the right-hand column this is taken into account and the level of probability may be raised. The overall risk assessment concludes with a consideration of the existing risk, the likely increase in risk due to construction activities for the proposed development and the residual risk with the implementation of

appropriate mitigation measures and good practices (as detailed within the report). The existing risk is based on the outcome of the Existing Hazard Assessment together with the outcome of the Receptor Assessment. The risk with development considers the Development Trigger Assessment and Receptor Assessment. The residual risk considers the risk remaining after identified construction methodologies and mitigation measures are employed during the construction phase with the aim of reducing risk as far a practically possible. It is important to note that this GRR is considered to be a dynamic document that should be regularly reviewed and updated with information and data collected during the construction phase of works with input from all necessary parties required.

Preliminary Geotechnical Risk Register

June 2012 Neart na Gaoithe Substation and Cable Corridor Page 1

Assessment Sheet 1 Position ID: (e.g. turbine no, borrow pit no, track chainage, etc) Proposed substation.

Existing Hazard Assessment

Peat depth1 0-500mm 500-1500mm >1500mm

Peat classification2

Fibrous (H1 - H5) Fibrous / Amorphous (H6 - H7)

Amorphous (H8 - H10)

Slope angle3 15° 2° - 10° 10° - 15°

Peat pipes Absent Present Widespread

Historical failure None Present Widespread

Extent of historical failure Minor Moderate Major

Evidence of incipient failure Absent Present Widespread

Natural undercutting of slope Absent Present Widespread

Will any adjacent slope failure subject ground to loading?

Not likely Possible Likely

Surface hydrology Dry Wet Standing water

Probability of slides Not likely Possible Likely

Likely extent of slides Local Medium Large/ extensive

Development Trigger Assessment

Extent of drainage works required Minor Moderate Major

Slope undercutting required Not required Moderate Major

Spoil stockpiling required Negligible Local Widespread

Construction plant loading required Negligible Local Widespread

Vegetation disturbance required Negligible Local Widespread

Blasting required Not required Possible Likely

Trigger assessment Low Medium High

Receptor Assessment

Nature designation area potentially affected

Not likely Possible Likely

Watercourse potentially affected Not likely Possible Likely

Built environment potentially affected Not likely Possible Likely

Receptor assessment Low Medium High

Risk Assessment

Existing risk Insignificant

Risk with development Insignificant

Residual risk with all relevant mitigation employed4] Insignificant

¹ Peat depth based on observations made by URS / Contractor during peat probing / coring works carried out as part of the URS Peat

Stability Assessment, dated June 2012. ² Peat classification based on observations of exposed peat where encountered by URS / Contractor during peat probing / coring works

carried out as part of the URS Peat Stability Assessment, dated June 2012. ³ Slopes of less than 2° are considered to limit the potential for lateral transport of any failed material. Slopes of greater than 15° are

generally considered to be too steep and free-draining to allow the formation of significant peat deposits. 4 Mitigation measures include all those noted in the URS Peat Stability Assessment, dated June 2012.

Document Revision Record

Revision No.

Details of Revisions Revision Date

1 Original document. June 2012

General Notes: (e.g. notes regarding peat, any signs of incipient peat failure, peat pipes, etc. and control measures used to mitigate against a peat failure)

Pre-Construction Notes:- Peat probing / coring carried out as part of the URS Peat Satbility Assessment identified an assessed peat thickness as predominantly less than 0.5m at the substation. However, localised accumulations up to 1m were recorded and at one position (in the northeast of the substation), peat was assessed to be 2m deep. Although no exposed peat was observed at the site, peat coring allowed the peat to be classified as fibrous (ranging from H2 to H3 on the von Post Scale of Humification), with a field estimation of low moisture content (B2 on the von Post Scale). No signs of incipient instability or peat features (such as peat pipes, slumps, etc), were identified at the proposed substation during the site walkover.

During Construction Notes:- This section should be updated to identify any additional peat related information that is obtained during the construction works.

Mitigation Measures and Monitoring:- This section should be updated during construction works to identify mitigation measures and monitoring methods used at this location to reduce the risk of peat failure.

Documents

Substation Corridor Assessment - NnG Offshore Wind · 15.06.2012 · substation site located adjacent to the existing Crystal Rig II Wind Farm substation and proposed cable corridor