good practice during windfarm construction

8/4/2019 Good Practice During Windfarm Construction

http://slidepdf.com/reader/full/good-practice-during-windfarm-construction 1/58

A joint publication by

Scottish Renewables

Scottish Natural HeritageScottish Environment Protection Agency

Forestry Commission Scotland

Version 1, October 2010



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Good practice during windarm construction

Contents

1. Introduction Page 1

2. Pre construction considerations 5

3. Seasonal considerations 10

4. Construction Method Statements 135. Ecological/Environmental Clerk o Works 14

6. Trac Management 17

7. Recreation and access 19

8. Woodland removal 23

9. Drainage 27

10. Construction o Access Tracks 34

11. Site Compound 41

12. Cable trenching/installing 43

13. Turbine oundation and crane pad construction 46

14. Habitat Restoration 50



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Version 1 October 2010

1 Introduction

1.1 Background

Windarm development in Scotland is accelerating rapidly. The Scottish Government,Scottish Environment Protection Agency (SEPA) and Scottish Natural Heritage (SNH) allsupport the development o renewable energy, including windarms, as a key means o tackling climate change.

Considerable experience has been gained during the construction and operationo more than sixty windarms already operating in Scotland. The purpose o thisguidance is to share that experience amongst the industry, planning authorities andthose more broadly involved in the planning and development o windarms. It isocused on pollution prevention, nature conservation, landscape, hydrological andrelated issues. It does not oer guidance on the detailed design or erection o turbines,their components or related inrastructure. It is aimed at the post consent, pre-construction planning phase o development.

This guidance seeks to identiy Good Practice, not necessarily Best Practice, which

is evolving constantly. For example, our knowledge on the management o peat onwindarm sites has increased rapidly during the production o this guidance. It isthereore dicult to oer denitive guidance at this stage. As a result this guidanceaims to ‘raise the bar’. It aims to ensure that all windarm sites are constructed in away which respects the surrounding environment and minimises environmental risksbeyond ensuring compliance with environmental legislation whilst retaining the needto remain cognisant o the practicalities o construction and constraints on developersand contractors rom legislative and commercial sources.

The guidance will be updated as more experience is gained. In particular, ourunderstanding o issues relating to carbon emissions rom windarm sites is evolvingquickly and as a result this guidance will be updated regularly. The guidance boxon page 4 outlines current good practice in relation to peat management on site and

minimising carbon loss.

This guidance is aimed at:

• Windfarmdevelopers

• Constructioncompaniesandcontractorsworkingonwindfarmsites

• Consultantsandadviserssupportingthewindfarmindustry

• Planningofcersworkingonwindfarmapplications

• StatutoryconsulteessuchasSNH,SEPAandotherswithaninterestinwindfarmconstruction, and those responsible or the regulation o wind arms under relevantEnvironmental Protection and Pollution Prevention legislation

• EnvironmentalandEcologicalClerksofWorks

1.2 How to use this guidance

The inormation contained in this guidance has been prepared by a joint workinggroup involving Scottish Renewables, SNH, SEPA, FCS and several representativesrom companies with extensive windarm development experience. It is intended toshare good practice across the industry and to demonstrate what can be achieved onwindarm sites in Scotland. It is not a ‘how to’ guide – the case studies and examplesused are illustrative only and they do not prescribe a specic method, technique orapproach. Better techniques and practices are evolving quickly.

When designing a windarm and planning the construction process, the various issueshighlighted within this guidance will require careul consideration in relation to thesite, it’s location, topography, ground conditions and other actors. It is impossible tooer generic guidance which is relevant to all windarms. Every site is dierent andwill require a tailored approach.



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Within each o the topics included in the guidance key considerations are identied;examples o good practice are provided and the key issues to consider in theConstruction Method Statement are highlighted.

1.3 How this guidance was produced

Recognising the examples o good practice on a number o existing windarm sitesSNH approached Scottish Renewables in summer 2008 to establish a joint project to

promote good practice during windarm construction. As a result a working group wasestablished comprising representatives rom SNH, SEPA, Scottish Renewables, FCS andseveral member companies with extensive windarm development experience. Themembers o the group included:

Jenny Hogan, Scottish RenewablesRosie Vetter, Scottish RenewablesBrendan Turvey, SNHKenny Taylor, SNHLorna Harris, SEPAJohn Burns, SEPAIan Johnson, Morrison ConstructionDavid MacArthur, ScottishPower Renewables

Steve Pears, Natural Power ConsultantsJames Milner-Smith, SSE RenewablesHugh Clayden, Forestry Commission Scotland

Further sta within these organisations have also contributed to the development o theguidance and the working group are grateul or both their time and the considerablecontribution rom the working group.

Some o the examples provided are deliberately ‘disguised’ and not attributed to aparticular company or windarm. The purpose o this guidance is to show what isachievable (and what can go wrong) – not to endorse or criticise a particular windarm,developer or contractor.

The contents o the guidance were also discussed in detail at a Sharing Good Practice

event hosted by SNH on the 7th o May 2009 enabling wider stakeholders and industryrepresentatives to contribute towards the process. It is intended that the guidance wil lbe updated over time as our experience and understanding o windarm constructionimproves. Comments and eedback on the guidance are welcome and should be sent tothe contacts identied in section 1.7 below.

SNH sta on a site visit to a recently completed windarm development



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1.4 Contents

The aim o this guidance is to demonstrate good practice across all aspects o windarm construction, including related inrastructure. Sections are thereoreincluded on:

• Preconstructionplanning

• TheuseofEnvironmentalManagementPlansandConstructionMethodStatements(incorporating a Site Waste Management Plan)

• UsinganEcologicalClerkofWorks(orEnvironmentalClerkofWorksandotherspecialist advisors)

• Accesstracks

• Sitedrainage

• ManagingRecreationalAccess

• Trafcmanagement

• Siteinfrastructure

• Habitatmanagementandrestoration

• Seasonalconsiderations Waste issues are not specically covered within this guidance document. SEPA shouldbe consulted on all aspects o waste management proposed to ensure that all therelevant legislation is ul ly complied with. Advice on how to prepare a Site WasteManagement Plan (SWMP) is available on SEPA’s website at www.sepa.org.uk. Furtheradvice on the reuse o demolition and excavation materials is available rom the Wasteand Resources Action programme (WRAP) at www.aggregain.org.uk. Advice rom SEPAshould be sought at an early stage.

1.5 Carbon emissions

One o the key aims o windarm development is to reduce carbon emissions. Windarm developments, through the materials used, the construction processesemployed and the potential emissions rom disturbed soils and habitats, do resultin carbon emissions. However, these are generally considerably outweighed by thebenets in terms o the carbon ree electricity generated by the windarm over itslietime. In many cases the ‘payback’ will be within the rst ew years o operation.

The Scottish Government published Calculating carbon savings rom wind armson Scottish peat lands - A New Approach in 2008, which provides more detailedguidance on these issues. However, the recommendations contained within thatguidance are very relevant to this guidance on good practice during constructionand these are summarised below. The Scottish Government report recognises thatin some circumstances the payback o windarm development could be signicantly

aected by the construction methods used and the degree o restoration o the site.The recommendations should thereore be considered throughout the guidance thatollows.

1.6 Sources o urther inormation

Key sources o urther inormation include:

www.snh.gov.uk

www.sepa.org.uk

www.scottishrenewables.com

www.orestry.gov.uk/scotland



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Good Practice approach to development on peat and carbonsavings – a summary o recommendations(from page 55 of the Scottish Government Report)

• Whenexcavatingareasofpeat,excavatedpeatturfsshouldbeasintactaspossible,oten it is easiest to achieve this by excavating in large turs or clumps. An intactexcavated block will be less prone to drying out.

• Excavationsshouldbepreventedfromdryingoutordesiccatingasfaraspossible.This can be achieved by minimising disturbance or movement o the excavated peatonce excavated. Consideration should also be given to spraying the peat to keep itmoist in appropriate circumstances.

• Stockpilingofpeatshouldbeinlargeamounts,takingdueregardtopotentialloading eects or peat slide risk. Piles should be bladed o at the side to minimisethe available drying surace area.

• Thepeatshouldberestoredassoonaspossibleafterdisturbance.Whenconstructing tracks, this requires restoration as track construction progresses.However or borrow pits and crane pads it may be more dicult to reinstate beoreconstruction is complete.

• Floatingroadsshouldbeusedinareasofdeeperpeattoavoidcuttingintopeatanddisturbing it leading to drying out.

• Submergedfoundationsshouldbeemployedondeeperareasofpeat,tomaintainhydrology around the turbine base and avoid draining the peat area. Submergedoundations are designed to be larger than normal drained oundations so they canwithstand water pressure liting up the oundation.

• Thedesignoftracksshouldbesuchthattheydonotactasaconduitorchannelforwater or a dam or barrier to water fow. This is a highly site specic consideration,and requires the consideration o track design at the construct ion stage, when allgeotechnical investigations are proceeding, rather than deciding on a nal trackdesign at the planning stage.

• Goodtrackdesignshouldbeemployedwithappropriatecrossdrains,minimisingthecollection o water and ensuring overall catchment characteristics are maintained.

• Developersshouldtakeancillaryopportunitiestoimprovehabitats,byincludingsimple practices such as drain blocking and re wetting o areas. These practices canbe included as mitigation

1.7 Contacts

For urther inormation please contact:

Brendan Turvey, Policy and Advice Manager,SNH: 01738 458622

[email protected]

Rosie Vetter, Planning & Onshore Wind Policy Manager,Scottish Renewables: 0141 353 [email protected]

JohnBurns,OperationsClimateChange&PPCUnitManager, SEPA: 01786 [email protected]



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2 Pre construction considerations

Pre-Construction planning is the incorporation o construction due diligence duringthe Environmental Impact Assessment (EIA) stage o the project development and priorto site mobilisation planning. It is about planning ahead and being proactive in yourconstruction strategy. It involves:

• Thoroughriskassessment

• Baselinemonitoring

• Appropriatesiteinvestigationandappraisalofgroundrisk

• Identicationofpollutionpreventionmeasuresandmitigation

• Wastearisingsandmanagementoptions

• Earlycontractorinvolvement

• AdherencetotheConstruction(DesignandManagement)Regulations2007

• Achievingthebalancebetweenenvironmentalconstraintsandengineeringprocesses.

Getting pre-construction right should prevent pollution o the environment, harm tohuman health, and unnecessary damage to nature conservation interests. It will alsoreduce risk, cost and programme delay, and increase stakeholder condence in theproject.

2.1 Key considerations

The key issues to be considered include:

• Thoroughsiteinvestigation

• Relevantlegislation(Construction(DesignandManagement)Regulations,2007)

• Otherlegislation(e.g.water,wasteandwildlifelegislation)

• Gridconnectionconsiderations

• EnvironmentalProtection

• Wildlifeandhabitatsurveys

• Groundrisk

• Infrastructuredesignandintegratedthinking

• Wastemanagementandsitedrainagestrategy

• Minimisationofpeatarisings

• Justifyingtheneedfor,useandlocationofborrowpits

• Goodconstructionpractice

• Communityengagement

• PublicRoads

• Existingservicesandotherconstraints

2.2 Site inrastructure layout, key questions:

• Arekeytemporaryworks(e.g.sitecompound,laydownareas)andpermanent

works (e.g. sub-station and control building, borrow pits, access tracks and cranehardstandings) situated in areas o suitable gradient, with sucient designseparation rom sensitive receptors (i.e. watercourses, lochs or sensitive wetlands)?

• Areaccesstrackgradientsandradiisuitableforthelargestloadsanticipatedtobedelivered to the site?



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• AresitetracksfollowingdesigntracklinesasidentiedintheEIA?Ifnot,haveproposed alternative track lines and other inrastructure amendments beensuitably assessed?

• Arecriticalpathitems(e.g.sub-station)easytoaccessatanearlystageoftheworks?

• Areborrowpitsproposed?Aretheyproposedinpracticallocations(i.e.closetoproposed construction routes, to minimise haul distances, and available as earlyas they shall be needed (not situated remotely at the ar-side o the site)? Whatis the likely impact on the environment (e.g. impact on the water environmentincluding groundwater, and nature conservation interests)?

(Please, note that this guidance does not deal directly with the issue o wastemanagement, particularly linked to restoration. However excavated material,including peat, rom windarm developments may under some circumstances beclassied as waste and waste activities – recovery and disposal – may requireauthorisation rom SEPA. Please reer to SEPA’s Regulatory Position Statement‘Developments on Peat’ or urther inormation.)

• Haveappropriatearrangementsbeenmadeforthestorageoffuelandoil?Doesthis comply with the The Water Environment (Oil Storage) (Scotland) Regulations2006?

• Canmaintenanceofvehiclesandplantbecarriedoutinimpermeableareaswhere any oil spillage can be contained?

• Hasconsiderationbeengiventotheneedtomaximisetheuseofrecycledmaterial, promote the use o secondary aggregates (sand, gravel and stones etc.),and ensure sucient production o primary materials (excavated material suitableor use)?

• Considerationshouldalsobegiventotherecyclingofwastematerialoriginatingrom elsewhere such as demolition waste. It is recommend that a Site WasteManagement Plan (SWMP) is developed. All imported materials should beadequately assessed or suitable use on site.

2.3 Site Investigation

Good Site Investigation (SI) is essential. SI includes desk study, site walk-oversurveys and more “intrusive” methods which are termed “ground investigation”(GI). SI should begin during the early phases o the EIA design, when other surveys(ornithological, ecological, hydrological, archaeological, hydrogeological) andassessments (e.g. waste management) are being undertaken, such that potentialground risk can be identied and designed or appropriately.

Some ground investigation is likely to be required during the EIA phase (i.e. soil/peat depth surveys, including depth and general characteristics), though the moredetailed GI is typically undertaken “post-consent”.

Any Environmental Statement prepared in support o the planning applicationshould demonstrate that the windarm design has taken into account site hydrologyand habitats. It should ocus on areas o deep peat and intact hydrological units o mire vegetation. Turbines and other inrastructure should be located on the basis o waste minimisation, ecological (species and habitats), hydrological/hydrogeologicalsurvey work and balanced against the other assessments and constraints identiedduring the EIA.

The level o GI required will depend to some extent on the assumed “diculty” o aproject. A rough-guide or gauging approximate costs o the actual GI is between 1%and 3% (or a low to high risk project, respectively) o your estimated “Balance o Plant” (civil and electrical inrastructure, and likely licence and permit) costs.

The scope o GI should include or all the main inrastructure – access trackalignments, watercourse crossings, crane hardstandings and turbine bases, sub-station and construction compounds, laydown areas and borrow pits. A suitablyqualied proessional engineering geologist/geotechnical engineer can advise



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on appropriate methods o GI, which may include (but not be limited to), urtherpeat probing, trial pitting, boreholes, geophysics and appropriate sampling andlaboratory testing and reporting. This is or assessing and quantiying ground risk,hydrogeological impact, risk o peat slide, waste management options, impactson the water environment (especially on peatland) and ecology and to reneconstruction methodology. Some o this assessment will have been completedduring the EIA. I as a result o GI amendments are made to the design it isimportant that this is careully assessed to ensure that the above impacts arereconsidered.

Consider mobilisation and site access or GI Plant – in the absence o anywindarm access tracks existing inrastructure may not permit easy access (i.e. toonarrow gates, bridge parapets, weak ground). Always check or environmentalsensitivities and risks prior to accessing the site. Always reinstate the groundater the GI is completed.

2.4 Planning conditions

Where construction activities could have a signicant detrimental eect on pollutionprevention or nature conservation interests, these will oten be careully controlled

by attaching conditions to the planning consent. Legislation has been written toavoid duplication o eort and regulation i.e. i an activity is controlled through aSEPA permit then planning would not apply conditions. Further guidance on theuse o planning conditions can be ound in Scottish Government Planning Circular4/1998. While there may be restrictive conditions aimed at control, there may alsobe a need to apply or, obtain, and comply with any environmental permissions,licenses or consents.

It is the responsibil ity o the developer o the windarm to ensure that planningconditions are adhered to. It is also the responsibil ity o the author o the planningpermission and conditions to monitor and ensure compliance. SEPA and SNH wil loten advise the determining authority (either the Planning Authority or the ScottishGovernmentEnergyConsentsUnit)ifconditionsarerequiredtomeetpollution

prevention or nature conservation objectives. Conditions should be developed inearly consultation with the developer, SEPA, SNH and the determining authority.There may also be a requirement to obtain other permissions such as a permit orauthorisation rom SEPA, which wil l be monitored and enorced by SEPA.

2.5 CDM Regulations 2007

As part o ullling a Client’s (the Developer’s) responsibilities under the CDMRegulations 2007, a pre-construction inormation pack (PCIP) should be preparedor tendering contractors. In addition, sucient time should be allowed or theappointed contractor to complete any detailed design and mobilisation to the sitewith sucient welare acilities in place or site sta.

2.6 Pre-Construction Monitoring

As a responsible Developer, it is appropriate to ensure that surveys are commencedprior (6-12 months typically, depending on monitoring parameter) to the on-set o the Site Works to establish suitable baseline conditions or such actors as: WaterQuality; Protected Species and Habitat Surveys (fora and auna); background landllsoil/gas, noise and dust levels.



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Peat surveys

Surveying a windarm site’s peat habitats during EIA is essential to allow the statutoryconsultees and appropriate planning authorities to make inormed and sound decisionson proposed workings in the peat environment. Surveys should be carried out in orderto (although not restricted to):

• Remaincompliantwithcurrentandrelevantlegislation

• Gainrealisticvolumes/quantitiesforpeatmanagementonsite

• Makemoreprecisecarbonbudgetingcalculations

• Betterunderstandtheriskofpeatslidesandpeathabitatdynamics

• Increaseknowledgeandawarenessofthesitehydrology

It is recommended that a pre-consent, broad scope survey is carried out, in conjunctionwith a trained ecologist, across the likely construction envelope using a 50m gridstructure. The level o survey eort should be discussed with statutory consultees.Survey at 100m gr ids across the rest o the site that is suitable or development isrecommended. This should identiy both peat depth and habitat characterist ics. Clear justication or areas which are not going to be assessed should be provided.

Particular ocus should be given to areas where known inrastructure is likely to be

located. A urther more detailed study/survey, post consent and pre construction is thenrecommended once the location o site inrastructure and turbines are known. Thiswill provide a better understanding o the site and provide adequate inormation toinorm decisions on micro siting and detailed design. The level o survey eort shouldbe tailored to the sensitivities o the site and proposed engineering solutions o thesite. Full peat depth should be established unless justication is provided or not doingso. Please note that the Scottish Government is currently producing guidance to addurther detail to this process.

2.7 Micro-sitingMicro-siting o wind turbine locations and ancillary inrastructure is commonlyundertaken at this stage. A variety o considerations need to be taken into account,such as:

• Resultsofdetailedhabitatandvegetationsurveys,

• Resultsofsoil/peatsurveys(depthandcharacteristics)

• Geotechnicalassessment

• Hydrology

• Archaeology

• Speciessurveys

Care is required to ensure that the overall eects o micro-siting are taken intoaccount. For example, extensive micro-siting may aect the overall landscape andvisual impact o the development. A level o re-assessment may be required at thisstage to ensure that any negative impacts are minimised. Further consultation may berequired.

2.8 Links/urther inormation/Contacts

SNH Environmental Impact Assessment guidance.

BS 5930 “the code o practice or site investigations”.Scottish Government ”Peat Landslide Hazard and Risk Assessments”.

Construction (Design and Management) Regulations 2007.



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Thorough site investigation, such as detailed peat depth surveys, is essential at the early stages



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3 Seasonal considerations

3.1 Introduction

It is important to consider the time o year and scheduling o windarm construction to

minimise impacts on the surrounding environment. The current turbine supply marketand the availability o specialist contractors will limit the opportunities or a developerto undamentally alter a construction schedule to take account o these issues.

Nonetheless, careul scheduling and an awareness o the dierent issues l ikely to ariseat dierent times o year will be benecial, particularly in the context o planningor drainage and the impact o fooding events, or management o borrow pits eitherduring their operational phase or reinstatement phase.


• Weather-thewintermonthsaregenerallywindierandwetter,makingthe

scheduling o turbine lits dicult and creating additional challenges in terms o managing run o and storm events; generally increased quantities o water on site(especially during snow melts) mean that very careul consideration will need to begiven to drainage and water management on site. Snow and ice cover will restrictaccess and increase risks on site;

• SitedrainageshouldbedesignedtotakeaccountofthelikelyStormEventIntensityor an area and inrastructure appropriately designed or a 1:200 year event. Thishas implications or the size o culverts, settlement ponds, and any other drainageand pollution mitigation techniques. Failure to adequately plan or food events canresult in considerable damage on site, construction delays and pollution o localwatercourses, lochs, sensitive wetlands, and groundwater;1

• Carefuldesignandmaintenanceofdrainage/silttrapstopreventheavysiltrunoff

into the water environment during rainall;

• Floodingonsitemayinhibitsiteoperationsormakesomeareasofasitedifculttoreach. Increased runo rom saturated peat should be considered;

• Thereisanincreasedriskofpeatslidesinverywetweatherandfromtheadditional weight o a snow pack. Appropriate mitigation measures should be put inplace or areas at risk o peat slide and particularly or areas o sensitive habitat,lochs and watercourses;

1. Further inormation is highlighted within Planning Advice Note PAN 69: Planning and Building Standards Advice on Flooding. The assessmentshould take account o the expected impact o climate change. The Flood Estimation Handbook (FEH) published by the Centre or Ecology andHydrology (CEH) should be used to calculate food values. CIRIA and SEPA guidance should also be reerred to.

Winter conditions pose a signicant challenge in allstages o construction.

Storm events can hamper the eectiveness o, andoverwhelm, pollution mitigation measures.



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• Inwetweathersomeexcavatedmaterials(particularlypeat)canquicklyturntosludge making it more dicult to excavate, transport and store;

• Lowvisibilityinblizzardconditionsorheavyfogcanincreasetheriskofaccidentson site;

• Forestry–seasonaltimingoftreefellingshouldbeconsidered(seeForestsand Water Guidelines). Felling near watercourses or lochs increases the risk o highersediment loads, metals and nutrients in runo which can have a negative impacton reshwater ecology. It is important that breeding birds are given considerationwhen planning elling timings. The impact on any nearby sensitive habitat (e.g.good quality blanket bog or other sensitive wetlands) should be minimised wherepossible;

• Dust–extendedperiodsofdryweathercanmakeitdifculttomanagedustfromvehicles and tracks. Vehicle movements may be constrained and suitable mitigationput in place;

• Trafc–patternsofroadusechangethroughouttheyearandtheschedulingofdeliveries, particularly o turbine components should take account o this to avoidconjestion;

• Snowcoverandfrost–duringthewintermonthssnowcoverandfrostmayinhibitactivities such as re-vegetation, restoration work and identication o sensitivefora/habitats on site. Access to some areas may be restricted. Frost may also aectthe eectiveness o temporary drainage/silt traps and road structure;

• Seasonaluseofwatercourses–manysensitivespecies(suchasAtlanticsalmon)which could be aected by watercourse pollution are only present during certainseasons (Oct-May). As a general rule in-stream or near stream works/activitiesshould be avoided as much as practicable and both SNH and SEPA should beconsulted on these matters. Drainage and silt trap maintenance should be careullyundertaken during the salmonid spawning and incubation period (Oct-May). Thepresence o other species (such as lamprey) may require consideration at othertimes o year. Further guidance is provided in the Forests and Water Guidelines (seebelow) and in the SNH Guidance or Competent Authorities (see below);

• Watercrossings–constructingwatercrossingswillbemorechallenginginwinterand will also require particular care i sensitive species such as Atlantic salmon orreshwater pearl mussel are present;

• Breedingbirdseason–manyspeciesofbirdswillonlybepresent/mostatriskduring the main part o the breeding bird season (March-August)2; while otherspecies may be present throughout the year. A Bird Protection Plan should considerthe specic risks to each species on each site. On most sites, a walkover o trackroutes and the locations o site inrastructure by a qualied ornithologist isrecommended prior to construction and at any key stages during the constructionprocess. Please consult SNH or urther inormation;

• Seasonalbirdactivity–somebirdsmayonlybeatriskduringparticularperiods

such as during display behaviour or during migration. Site specic advice may berequired to address impacts and agree appropriate mitigation;

• Otherprotectedspecies,suchasbadger,redsquirrel,otterandbatsarealsomoreactive at dierent times o year and may require consideration i present on site. I licenses are required as derogation then timing and phasing o construction needscareul planning (e.g. oten a year in advance or certain species to record accuratedata, discourage, and mitigate or);

• Deer–managingdeermaynotbepossibleatcertaintimesofyear,forexampleinclosed seasons, and the impact o deer on restoration work should be considered.Known wintering areas or deer require careul consideration. Compensatory cullingmay be required to avoid creating problems or adjacent land managers;

• Habitatmanagement–theeffectivenessofrestorationworkandhabitatmanagement is oten highly dependent on the time o year, especially i livestockare present. Consideration should be given to both seasonality and the need toprovide temporary encing in some circumstances;

Note – SNH intend to produce urther guidance on this later in 2010.



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• Workinghourswillberestrictedatcertaintimesofyearandcarefulconsiderationo site health and saety will be required. The visual impacts o lighting should beconsidered.

• Wastemanagementoptions(whichmayrequireauthorisationfromSEPA)associatedwith any wind arm development may also involve hazards and nuisances ar isingrom waste movement, use o waste, and waste disposal. Bad weather conditionscan increase the risk o pollution and damage to the environment rom theseactivities.

3.3 Key things to address in Construction Method Statement

• Produceaconstructiontimetableandillustrateseasonalconsiderations

• Whatmeasureswi llbeputinplacetodealwithweatherrelatedevents(ashfoods, peat slide, snow melt, dust)?

• Howwillconstructionbescheduledaroundkeysiteconstraints(suchasthebreeding bird season)? Where scheduling is not practical, what other mitigation canbe put in place?


SEPA’s CAR practical guide – http://www.sepa.org.uk/water/water_publications.asp

Pollution Prevention Guidelines relevant to construction (published by SEPA)http://www.netregs.gov.uk/netregs/links/63901.aspx

Forests and Water Guidelines - http://www.orestresearch.gov.uk/PDF/cgl002.pd/$FILE/cgl002.pd

Salmon and Freshwater Fisheries Act (2005)http://www.opsi.gov.uk/legislation/scotland/ssi2005/20050174.htm

CIRIA Control o water pollution rom linear construction projects. Technical guidance

(C648) (2006).http://www.ciria.org/acatalog/C648.html

SNH Guidance or Competent Authoritieshttp://www.snh.org.uk/pds/publications/heritagemanagement/guidanceorcompetentauthorities.pd

Early nightall in winter bringing dark, dicult working conditions



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4 Construction Method Statements

4.1 Introduction

The use o Construction Method Statements (CMS) to guide a development is commonpractice across the construction industry. With the ability to cover a wide range o subjects,

including environmental, hydrological and ecological considerations, Health and Saety onsite, and build procedures, the construction method statement ensures consistency acrossthe site or the duration o a build.

CMS’s are oten required as a condition o Planning Permission. For procedural consistencyand awareness raising, the provision o a useable and clearly laid out document ordevelopers, contractors and statutory consultees to scrutinize makes the development o a CMS with site specic content a necessary and useul tool. Where an environmentalmanagement plan is produced the links between this and the CMS should be made explicit.


• WhatisrequiredtomeetconditionswithingrantedPlanningPermission?• TimelysubmissionanddistributionoftheStatementswilldependontherequirement

and level o consultation and the particular stage o the development. For instance,a more generic CMS may be submitted at a pre-construction or pre-planning stagewhereas specic build CMS’s may require to be written during development as the needarises.

• IslegislationpertainingtoenvironmentissuesandHealthandSafetylegislationincludedin all CMS’s where relevant?

• Avoidfallingintothetrapofinsertingunachievableaims,proceduresanddetailswithinthe CMS. Speak to the appropriate stakeholder or guidance.

• Shouldthemethodstatementtaketheformofasingledocumentcontainingheadingsof

individual works or areas o work (even a dynamic document, a ring binder o segmentsetc) or is it more useul to developers and consultees etc. as individual documentspertaining to a single piece or area o work? Should it be available on-line, usually as apd?

• Areallenvironmentalaspectsassociatedwithaparticularconstructiontopicconsideredand highlighted, or example; water issues and drainage, waste management, noise anddust generation, ecological aspects and habitat management?

• IdentifythereadersandusersofaspecicConstructionMethodStatement(CMS).

• SiteWasteManagementPlansandAccidentManagementPlansshouldalsoformpartofthe CMS.

• ThelevelofdetailandthespeciccontentofaCMSwil lbeimportanttoeachindividualstakeholder depending on their input and involvement with the development i.e. is thesuitability o the CMS targeted at specic audience/consultee? This may have an aecton the layout and structure o the CMS and indeed the timing o their submission.

• Timeframesconsideredi.e.domethodstatementtimingsmatch‘workontheground’timings? Will the content/subject o a particular CMS be aected by seasonality?

• WherewilltheappropriateCMSbelocated?Aretheyavailableonsite,usedonadailybasis or at a central oce location?

• Hasthetemporarystorageofexcavatedmaterialsonsitebeenplannedfor,whererelevant/appropriate? SEPA can advise on this matter.

Statutory agencies have limited resources to engage at these stages in the planningprocess. Developers and consultants can greatly assist by co-ordinating requests ormeetings and channelling requests or advice through the appropriate ocers. GenerallySNH and SEPA will only comment on those aspects o a CMS on which we have specicallyrequested to be consulted on or which have signicant consequences or their statutoryresponsibilities.



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5 Ecological/EnvironmentalClerk o Works (ECoW)

5.1 Introduction

During wind arm construction the developer and contractor have to comply witha number o obligations under both the conditions o the planning consent andenvironmental legislation. To ensure eective implementation and monitoring o theseobligations, an Environmental (or Ecological) Clerk o Works (ECoW) is commonlyrequested as a condition o planning consent. The ECoW role is focused on

providing environmental advice and monitoring compliance – not implementing

measures. An ECoW’s role is to ensure biodiversity is secured and impacts eitheravoided or minimised. They will also advise on relevant wildlie legislation and aidin the development o practical solutions. Environmental Clerks o Works is a termoten used to describe a multi-disciplinary team o individuals covering a diversity o specialist roles e.g. hydrology, landscape and soils.

This section provides details on:

• ThelikelyscopeofworksfortheECoW;

• AdditionalresourcesrequiredtosupporttheECoW;and

• RecommendationsonhowanECoWshouldbeincorporatedwithintheconstructionteam structure.


1. The scope o works and level o resource commitment required o the ECoW needsto be commensurate with the scale o the development, and the complexity o the

ecological and/or environmental issues at a site. This oten requires a variety o skills. For this reason it is oten the case the ECoW position represents a broadmultidisciplinary resource. The scope o the ECoW position is likely to include theollowing aspects:

a) Construction Activities typically Monitored by the ECoW

Installation o site roads, compounds, hard standings, borrow pits, electricalcable installation, turbine oundations, vehicle movements, micro-siting o inrastructure and uel and chemical storage. Monitoring should be undertakenboth beore and during construction on many o the activities listed above.

b) Monitoring o Pollution Prevention and Mitigation undertaken by a developer

This may include: monitoring site pollution prevention plan, advising on requiredpollution prevention measures and monitoring their eectiveness. This will alsoinvolve liaison with SEPA.

c) Breeding bird protection

This may include: monitoring o buers around nest sites identied by pre-construction surveys, spot checks or nesting birds (or liaison with siteornithological consultants), and advice on mitigation measures and monitoringtheir eectiveness.

d) Other protected species

This may include: monitoring buers around protected species structures suchas nests and holts identied during pre-construction surveys and spot checks

or mammals, reptiles and amphibians as appropriate, and providing advicei protected species are ound that were not recorded during previous siteinvestigations.



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e) Environmental RegisterThe ECoW should maintain a register o issues, advice given and action taken bycontractors.

) Reporting

A monthly report should be produced providing a summary o issues on site andtheir status during the relevant month. The report should be issued to the LocalAuthority and relevant statutory consultees, as agreed at the consenting stage.

g) Environmental Induction and Tool Box Talks to contractors and sub-contractors

The ECoW may contribute towards environmental inductions held by theinrastructure contractor. These should be conducted at the same time as Health

and Saety inductions so that all contractors are aware o the environmentalsensitivities and procedures on the site. These may cover protected species to beaware o on site, exclusion zones and sensitive habitats.

h) ECoW Skil ls

As the above scope suggests, the range o skills required by the ECoW is diverse.For this reason, it may be necessary to employ specialists/specialist Clerks o Works or particular tasks that may arise (e.g. hydrologists, hydrogeologists,ecologists (including protected species ecologists), waste managementspecialists, landll engineers and technically competent landll managers).

i) Site Waste Management Plan (SWMP)

It is the developer’s responsibility to monitor compliance with the SWMP. Point o contact should be established with SEPA regarding waste issues.

2. Additional resources required by the ECoW

The ECoW role is ocused on providing environmental advice and monitoringcompliance – not implementing the measures. Generally, or the ECoW’s advice to beeective, appropriate capacity needs to be allocated to environmental protection bythe inrastructure contractor. This may involve a dedicated ‘environmental team’ onsite whose core responsibility is to maintain and monitor environmental protectionmeasures. This team would require access to the necessary capital equipment at alltimes. The size o the ‘environmental team’ required wil l depend on the size andsensitivity o the site. For example during peak construction activity on a 50 turbineupland site, around 3-4 ull t ime sta may be required in addition to the ECoW.

3. Position o ECoW within Construction Team Structure

a) Obligations under planning conditions and environmental legislation are theresponsibility o the developer. These obligations are largely passed onto theinrastructure contractor, via the inrastructure contract, to implement on site.

An ECoW can provide on site advice on protectedhabitats and species, such as this water vole colony.

The ECoW is likely to be involved in the management ohabitat management measures such as drain blocking.



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Trac Management

How best to manage trac fows on approach tothe site is a key consideration. The type o road(trunk road, B-Class, or minor), the typical tracfows (peak times, local domestic, agriculturalor industrial use), and, oten most signicant,proximity to local schools, should al l be considered.The use o trac lights, stop go signals, road

closures and diversions are all possible options,though minimising disruption and inconvenienceto the general public, particularly local residentsor tourists, is o importance. Consider time o year(holiday periods), time o day (rush-hour, schooldrop-o/pick-up times), and typical weather (snowand ice) in your trac management preparations.Plan ahead. Check local dates, such as agricultural/village airs and avoid these periods.

Inormation

Keep the local communities inormed o your

proposed works, key delivery dates and times.Consider door-to-door visits, letter drops, noticesin village post oce, dissemination via community

councils, and newspaper notices. Provide contact details or your Site Manager/Community Liaison Ocer so that concerned individuals may speak with an inormedindividual.

Dry-runs

Always undertake a “dry-run” beore abnormal load deliveries commence. Plan this asar in advance as is practical. Keep communities inormed.

ReinstatementPrior to the on-set o works undertake a pre-condition survey with the local roadsdepartments. Agree areas o existing degradation/damage. Ensure that the publichighway is maintained during your works (either through the use o the localRoads Department contractors, or approved sub-contractors) , and ensure promptreinstatement o damaged verges and inrastructure. Go the extra-mile. Consider theneed or landscaping/planting.

6.4 Key things to address in a Trac Management Plan

• Continueddialoguewithlocalcommunities,includingadvancenoticeofabnormal

load deliveries• Avoidingschoolopeningandclosingtimes,peaktimes,holidayperiods

• Roadsweeperstoclearanyresidueoffpublichighway

• Apre-conditionsurveymaybenecessary

• Includekeycontacts(Police,TrunkRoads,LocalRoadsDepartment,otherkeystakeholders, including local schools/institutions along the proposed transportroute(s))

• Identifyanyspecicenvironmentalrisks

Use o road signs to inorm other road users as well asdrivers approaching site



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7 Outdoor Access and Recreation

7.1 Introduction

Sites which are chosen or windarm development are oten already used or

recreational purposes, because o their rural, upland location, their wildlie, and insome cases due to their location near to centres o population where they can providea valuable outdoor access resource. A windarm’s track network may enhance suchuse, so careul long-term planning is required.

In Scotland, statutory access rights apply on most land, including operationalwindarms and those under construction (with some restrictions). The rights apply toland in general, and are not restricted to paths. Members o the public may use sitesor a wide range o purposes such as walking, cycling, horse-riding, wildlie watching,camping, canoeing and other recreational pursuits, as long as they do so responsibly.Local residents may particularly value these places because o convenience, localknowledge, cultural signicance and amiliarity with the area.

LegislationMaintaining access and managing access saely are thereore key considerationsduring the planning and construction o a windarm, and the site’s track network canprovide a useul resource or recreation users in the long-term. In many locations thenumber o visitors will be small, while some sites may attract considerable numbers o users, depending on existing access arrangements, terrain and location.

Regardless o numbers, or statutory requirements most developers and landownerswill gain signicant benets rom making positive provision or access, includingimproved relations with neighbouring communities.

Access to the outdoors is largely based on the Land Reorm (Scotland) Act 2003, whichestablishes the statutory right or responsible public access to land in Scotland. These

rights are or crossing over land, and or recreational use by non-motorised users, likewalkers, cyclists and horse-riders. The Act also places a legal duty on land managersto manage their land and operations in a way that is responsible in respect o accessrights. The requirements or those accessing the land, and managing land, to act

Site maps can be produced to aid access and reduce risks to the public



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responsibly cannot be overemphasised, and the Scottish Outdoor Access Code providesguidance on responsible behaviour. Construction sites are potentially very dangerous,

with large items o plant machinery moving about requently.

The access rights become suspended on land where building or civi l engineeringwork is being carr ied out, except or routes which are core paths or rights o way.The suspension applies only where building operations are active (rather than, orinstance, to the whole area under the developer’s control).

The Scottish Outdoor Access Code claries that restrictions should be kept to theminimum area, and the minimum duration, that is reasonable and practicable.


Planning phase

• Establishandmaptheexistingpathsandpatternsofaccessonthesite

• Arethereparticularlyheavily-usedpaths,oranyformalcorepathsorrightsofway?

• Consultwithlocalgroups,anduser-representativebodies,todetermineifthereareparticularly popular routes/paths/patterns or types o use (eg. horse-riders, regularevents, access on water etc)

• Arethereanyparticularfeaturesofinterest(eg.viewpoints,hillsummits,lochs)?

• Howcouldaccessopportunitiesbeenhanced(eg.visitorcarparking,byloopandcircular track routes, by connections to external paths)?

• Howcanimpactsonaccessbeminimised?• Co-ordinatedsignagestrategy

• EstablishandmapanyareaswhichmaybeexcludedfromaccessrightsunderSection 6 o the Act

• Ifnewtracksorfootpathsareproposedtoaccommodateaccesstheseshouldbecareully designed to minimise habitat disturbance and maximise recreationalbenets.

Construction phase

• Howwillaccessbemanagedduringtheconstructionprocess?(eg.routesign-posting, alternative paths, training or vehicle drivers, provision o reuge passingplaces)

• Usesitephasing,toensurethatexemptionfromaccessrightsduetobuildingandengineering works is kept to a minimum area, only where works are active

Restrictions on access should be limited as ar aspracticable. In areas where construction is complete,signs restricting access should be removed.

Good signage will help promote responsible access.



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• Informationprovision,includingHealthandSafetyinformation(eg.signsandway-marks, leafets, inormation boards, relevant websites, contacts with representativegroups, community newsletter)

• Willparticularphasesoraspectsoftheconstructionbeproblematic?(e.g.creatingtemporary cul-de-sacs). I so, can suitable alternative routes be provided, indicatedand explained?

• Arethereparticularrisksduringconstruction(eg.blindcornersontracks,unstableground) that users and construction workers need to be made aware o?

Operational phase

• Howwillexistingandnewaccessroutesbemaintained,withadequatesafetymeasures and signage?

• Arethereanyparticularrisksforuserswhichneedassessmentbeforethewindfarmis operational (such as maintenance trac1, or ice throw?2).

• Cansuitableoutdooraccessbeenhancedandpromoted,oncompletionofthewindarm? I so, how? Is there an opportunity to promote access, or exampleor mountain bikers, or horse-riders, or to make new connections to nearbycommunities?

• Caninformationforvisitorstothewindfarmbeprovided,suchassignsexplainingwhat the windarm generates? - who owns it? - how much CO

2it displaces?

7.3 Key things to address in aConstruction Method Statement/Outdoor Access Plan

• Whowillbethekeypointofcontactforlocalresidents/members o the public, or accessissues? How will this be advertised?

• Whatisthecurrentbaselineofaccessuse,andhow will this be aected?

• Howwillanyconictsoveraccessberesolved,and ideas sought (e.g. in liaison with the localauthority access ocer)?

• Arethereanyconditionsrelatingtoaccessintheplanning consent which need to be addressed?

• Whatarrangementswillbeputinplacetomaintain access, as ar as possible?

• Whatsignageisproposedandwhere?

• Whatdesignsofsurfaces/accessarrangements(such as gates and water crossings) will berequired?

• Ifexistingaccessroutesaretobedisturbedduring construction, how will these be restoredaterwards? What temporary alternative routeswill be provided?

• Ifnewaccessistobeprovided,howwillthisbedesigned,andpromoted?

• Whichlocalresidents’andotherrepresentativegroupsshouldbeconsulted?

1. Maintenance trac (and most construction trac) should expect access takers to be using tracks, since this multi-use o tracks is now commonpractice (or instance with orestry tracks). During particularly intensive periods o heavy trac, users can be requested to keep o the track anduse an alternative path, but such periods should be limited. Signs can remind the public to keep a look-out or site trac, and to step aside toallow it to pass saely, while drivers should be trained to operate suitably.2. Modern wind turbines generally have a reduced risk o ice throw. However, on any occasion when icing may present a valid risk, temporarywarning signs at access points should alert the public to this issue, with advice not to stand close below towers, and to take care when nearbyand in-line with turbine blades. Access to the windarm site should not, however, be unnecessarily restricted.

Maintaining access or a wide range o users willincrease the benets o the windarm to the localcommunity.



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Land Reorm (Scotland) Act 2003 (The Stationary Oce).

Scottish Outdoor Access Code. www.outdooraccess-scotland.com

Managing Access – Guidance or Owners and Managers o Land –Scottish Rural Property and Business Association (2004).

The Construction (Design and Management) Regulations 2007.

Countryside Access Design Guide - SNH (2002 with updates).

Management or People – SNH (2004).Public Access and Land Management - SNH (2007).

Signs Guidance or Farmers and other Land Managers – SNH (2006).

Outdoor Access Signage Guidance – Paths or All Partnership (2009).

A Brie Guide to Preparing an Outdoor Access Plan – SNH (2010).

7.4 Case study: Whitelee Windarm

The development o the upland windarm at Whitelee, south o Eaglesham,provided an opportunity to enhance existing access routes and build a ullnetwork o new routes which would increase opportunities to enjoy the wholearea. The local planning authorities and the Scottish Government took thisopportunity to ensure considerable access benets were delivered through

eective consultation and legal agreements.The Whitelee Access Planning Group (WAPG) was set up to secure and improveoutdoor access during the construction and operation o the windarm. The WAPG consists o representatives rom the relevant local planning authoritiesand community groups, Scottish Natural Heritage, Forestry CommissionScotland, Scottish Power Renewables and community groups. An AccessProject Ocer has been appointed, whose salary is paid through EastRenrewshire Council rom money provided by the developer under the Section75 Agreement.

The Access Project Ocer is responsible or establishing a constitution orthe WAPG, implementing their objectives and visions and delivering the

community benets package.This work inluded the publication o a drat Access Action Plan, subject to localconsultation, detailing the strategy and deliverables across the three localauthorities’ administrative areas. Each council will publish its own Core PathsPlan, which will integrate with the Whitelee Access Plan.

SPR also invested in a visitor centre on the site which opened in September2009. This acility provides an insight into how the windarm was built, withspecic emphasis put on education visits. The centre also acts as a hub or allusers o the routes or walking and other outdoor pursuits. Over 30,000 peoplevisited the centre in its rst eight months o opening.



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8 Woodland removal

8.1 Introduction

Wind arm construction has oten involved the removal o signicant areas o

commercial orestry plantation. This has been carried out or a number o reasonsincluding: improving wind yield; reducing turbulence; or habitat mitigation andenhancement. This section deals only with situations where the need or woodlandremoval3 has been agreed and the purpose includes the aims o habitat mitigation orenhancement.

This section provides details on:

• Therequirementforwoodlandremovalandopen-groundhabitatrestoration

• Theaimsofopen-groundhabitatrestoration

• Treeremoval

• Recommendationsforfellingcontract

Habitat restoration is integral to the minimisationo carbon emissions. Further guidance is beingdeveloped by SEPA and SNH on this issue.

8.2 Key Considerations

The requirement or woodland removal andopen-ground habitat restoration

a) Woodland removal and subsequent open-ground habitat restoration may be suggested tocompensate or other actions arising rom thedevelopment that may have a signicant eect(s)identied in the Environmental Statement. Thismay include (or example) impacts on sensitive heathland or blanket bog habitat orimpacts on ornithological interests (such as displacement rom oraging habitat).

b) Open-ground habitat restoration may, however, also be proposed by the developereven though no signicant eect(s) has been identied by the EnvironmentalStatement. This is classed as ‘enhancement’ as it is over and above the requirementso mitigation. The opportunity to deliver substantial positive enhancement measuresmay arise even in cases where woodland removal is planned as part o theconstruction purely or the aim o enhancing wind yield and reducing turbulenceeects.

c) Statutory guidance on woodland removal is contained within paragraph 94 o Scotland’s second National Planning Framework (NPF2). Guidance is also containedin Scotland’s consolidated Scottish Planning Policy and policy direction is set out inthe Scottish Government’s Policy on Control o Woodland Removal (www.orestry.gov.uk/woodlandremoval). One o the key guiding principles is that woodlandremoval should take place only where it would achieve signicant and clearlydened additional public benets. Where woodland is removed in associationwith development NPF2 indicates there wil l be a strong presumption in avour o compensatory planting. However, changes to the type and/or design o woodland, orto the way it is managed, may achieve the required management objectives withoutthe need to resort to woodland removal.

3. Woodland removal, in this context, means the deliberate change o land use rom orestry to another type o land management such as thatassociated with the management o open-ground habitats. Tree elling in itsel does not indicate woodland removal, it is the subsequent atercare o the site that determines whether the site will continue to be woodland or converted to another land use.

On site chipping operations.



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The Aims o open-ground restoration

a) Post-woodland removal habitat restoration can have various ecological aimsdepending on the site-specic circumstances. However, in upland locations the mostcommon aims include blanket bog and heathland restoration to mitigate signicantother development-related eects on these habitats or to compensate or the loss o oraging habitat o sensitive bird species.

b) A detailed Management Plan should be developed. This plan should explain thespecic site aims and objectives and the management prescriptions required toachieve these. When restoring blanket bog, or example, it is essential that measuresto raise the water table and improve hydrological conditions are also included.

Tree Removal

Any tree elling carried out without a elling licence or other valid permission isan oence unless it is covered by an exemption. Prior to undertaking tree ellingit is thereore essential to check that the area to be elled has either been ormallyconsented through the development management process or through a elling licence

issued by Forestry Commission Scotland.

Prior to undertaking woodland removal it is alsoimportant to seek competent advice on whether

the resultant timber will be eligible to be soldas ‘Certied timber’ under the orest certicationschemesoperatingintheUK4.Failuretosecurecertication can have a signicant bearing on thevalue and saleability o timber.

Forestry biomass is utilised in the orm o ‘roundwood’, chips (or energy use or panel products)branchwood (‘brash’) or stumps. In utilising suchbiomass, all orest operations should comply with therequirementsofthelatestversionoftheUKForestryStandard and associated Guidelines.

The harvesting o brash or stumps can pose a numbero particular hazards to the orest environmentthat can threaten sustainable orest management.Accordingly, industry-wide guidance on brash andstump harvesting has been developed to reduce

these risks. On carbon-rich soils such as those commonly associated with wind armdevelopment, such guidance is particularly relevant.

I the util isation o the biomass is not commercially viable, in-situ ‘chipping’ o thetimber and biomass is sometimes suggested as a way o improving subsequent groundand vegetation management. However, this can also have unwanted environmentaland regulatory (waste) consequences which require careul consideration (please reerto Section 14). Whenever such an operation is contemplated it should thereore be

discussed at an early stage o the planning process with SEPA and SNH.All orest operations should comply with the requirements o the latest version o the UKForestry Standard and associated Guidelines5.

a) Generally, two broad techniques may be used to remove trees: commercial timberharvesting and in-situ chipping. Various machines can be used but the mostappropriate technique depends on the size o the crop and site-specic conditions.In all cases it is essential to seek proessional advice in the planning and executiono tree harvesting operations so that saety, environmental, economic and logisticalactors are ully considered, including subsequent atercare/use o the site.

b) Commercial Harvesting: On anything other than the steepest sites this techniquegenerally uses ground-based machines called ‘harvesters’ to ell and process the

timber and orwarders to remove the logs rom the site. The branches are used toorm brash mats or the machinery to move along saely and minimise soil damage

4. Currently the Forestry Stewardship Council (FSC) and the Programme or the Endorsement o Forest Certication Programmes (PEFC).5.Link:www.forestry.gov.uk/ukfs.AsatSeptember2009thecurrentversionoftheUKForestryStandardcanbefoundatwww.forestry.gov.uk/pdf/cc001.pd/$FILE/cc001.pd.

Chipped material may assist with regeneration butcare is required to ensure that both the quality and thequantity is suitable.



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8.3 Case study: Black Law windarm

At Black Law windarm 458Ha o commercial orest plantation was removed as part o an extensive Habitat Management Plan covering 1440Ha. The key objective o removingcommercial orestry was to restore priority blanket bog habitat within this area – a keyUKBiodiversityActionPlanhabitatandimportantcarbonsink.

The Sitka spruce plantations were removed using three techniques depending on thesize o the timber crop and ground conditions. Commercial harvesting was used in areaswhere mature crops existed and immature crops were chipped in-situ using either the‘Bob Little Flail’ or the ‘Gallowtrax’ depending on the ground conditions.

A detailed monitoring programme was implemented to determine the rate and typeo regeneration post woodland removal. The aim o this monitoring is to ascertainwhether the desired blanket bog communities are re-establishing. Since tree removal in2005, monitoring has indicated that some key blanket bog species are successully re-colonising the site.

The percentage cover o Heather and bog cotton species increased on the areas whereblanket bog might be expected to re-develop (peat depth generally > 0.5m). The covero bog mosses (Sphagnum spp.) currently shows a less clear pattern. At the local scale,monitoring indicates that the old ridge and urrow patterns resulting rom the legacyo tree planting determines the distribution o bog mosses within the tree clearanceareas. More generally, the water table across particular parts o the deorested areas isprobably too low to provide the constant waterlogged conditions required or “active”bog to re-develop and persist.

It is thereore considered that successul restoration to “active” blanket bog could requireadditional intervention, which was predicted as part o the Habitat Management Planor the site. Additional hydrological monitoring and drain damming trials are now beingimplemented as part o ongoing research to inorm uture management measures.

and subsequent erosion and diuse pollution. This method is usually used on maturecommercially viable crops. Where the ground is too steep or the sae operation o ground-based machines, aerial extraction systems, known as cable-cranes, areused.

c) In-situ Chipping: On immature crops that are not commercially viable, a numbero techniques can be used which chip the immature timber and branchwood. Atthe time o writing these include: Slash buster fail; Shin systems fail; Bob LittleFlail; and the Gallowtrax. All, except the Gallowtrax, consist o an excavator

mounted with a chipping head. The Gallowtrax chipping head is located beneaththe machine and is usually better suited to dryer habitats where the groundsurace can provide resistance to the chipping head. Reer to section 14 on ‘Habitatmanagement’ or urther detail.

Recommendations or elling Contracts

a) Commercial Harvesting: Methods or commercial removal o timber are welldeveloped and noted within several guidance notes. Competent specialistadvice should always be sought when arranging elling contracts so that saety,environmental and other requirements are ully addressed.

b) In-situ chipping: Contracts should clearly state the specications required or end

products (chips) and post-operation site conditions as well as habitat managementobjectives. This will determine the size and rating o the chip produced. Competent,specialist advice should always be sought when arranging in-situ chippingcontracts so that saety, environmental and all other requirements are ullyaddressed.

Disturbance (including spreading o chips or excavator movements) o areas o vegetation within or adjacent to the orest should be avoided unless absolutelynecessary. These areas can act as important seed sources or restoration o thesurrounding elled areas.

A monitoring programme should be set up during elling operations to ensure that theorestry contractor is meeting the required specications.



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Monitoringa) The ollowing monitoring recommendations should be considered:

i) Long term monitoring is required to inorm site management and atercare.

ii) Monitor elling or in-situ chipping beore, during and ater operations, to ensurethe contractors have achieved the saety and environmental specications agreedwithin the contract;

iii) Monitor the response o vegetation to tree removal and the response o the watertable to actions to improve hydrology. This should ideally be initiated pre-clearance to establish baseline conditions and then continued at an appropriateand pre-agreed requency and duration post-clearance; and

iv) Results rom monitoring programmes should inorm an adaptive managementapproach to allow the dened ecological aims and objectives to be met within thespecied time-scales.

8.4 Links/Further inormation/Contacts

Forestry Commission: Forests and Water Guidelines (Fourth edition).

Scottish Government Policy on the Control o Woodland Removal.

National Planning Framework 2.

Scottish Planning Policy.

Restoring aorested peat bogs (Forestry Commission, 2010).

On site harvesting operations prior to windarmconstruction.

Harvesting adjacent to existing good habitat. Measuresshould be taken to protect areas o good habitat duringelling/chipping.



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9.2 Relevant Legislation

The Water Environment and Water Services (Scotland) Act 2003 (WEWS Act) gaveScottish ministers powers to introduce regulatory controls over water activities,in order to protect, improve and promote sustainable use o Scotland’s waterenvironment. This includes wetlands, rivers, lochs, transitional waters (estuaries),coastal waters and groundwater.

The Water Environment (Controlled Activities) (Scotland) Regulations 2005 are

more commonly known as the Controlled Activity Regulations (CAR). I you intendto carry out any activity which may aect Scotland’s water environment, (thisincludes wetlands, rivers, lochs, transitional waters (estuaries), coastal watersand groundwater) you must be authorised to do so. Discharges, disposal to land,abstractions, impoundments and engineering works are all regulated by SEPA. Earlyengagement with SEPA is recommended.


General Principles

• Dogettoknowyoursite,tounderstanddrainagepaths,downstreamusers,andareas where fows would normally collect and discharge.

• Doconsideroptionsforhabitatenhancementthroughappropriatedrainblockingand other measures.

• Dokeepexistingnaturalhydrologyandhydrogeologyinbalanceasfarasreasonably practical.

• Donotdivertnaturalows,unlessunderprioragreementwithSEPA/SNH

• Dokeepcleanwaterowsclean,bynotallowingmixingwith“construction”drainage. This means that there are lesser volumes o contaminated/ discolouredwater to treat.

• Doallowmanysmall/middiameterofets,ratherthancollectinglargervolumesofdrainage fows to discharge to a smaller number o larger capacity outlet points.

• DousetheRiparian/Bufferzonetoassistwiththepracticallteringoutofsiltyrun-o i appropriate. Please consult with the relevant authority prior to discharge.

• Donotallowdirectditchdischargeintowatercourses,lochsandsensitivewetlands.

9.4 Access Track Drainage

Pre-earthworks drainage

This is the term generally given to cut-o/ diversion ditches that are installed aheado the main earthworks activities to minimise the eects o collected water on thestripped/exposed soils once earthworks commence.

These drainage ditches should be installed on the “high-side” boundary o theareas that will be aected by the access track earthworks operations, and should beinstalled immediately ahead o the main track construction operations commencing.They should generally ollow the natural fow o the ground with a generally constantdepth to ditch invert. They should have shallow longitudinal gradients. Their purposeis to intercept any stormwater surace run-o, and collect it to the existing low pointsin the ground, allowing the clean water fows to be transerred independently throughthe works without mixing with the “construction” drainage.

This can be achieved through dedicated piped culverts and results in a signicant

reduction o the volumes o potentially discoloured run-o that would otherwiserequire to receive urther treatment prior to passing across the riparian zone, andultimately ltering into the existing main watercourses.



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that any collected water is always al lowed to be released to lter across a vegetationbuer zone, or through a settlement area, beore reaching any watercourses, lochs,groundwater or sensitive wetlands.

Culverts/Headwalls/Outlets

The main method o transerring the collected surace waters ‘through’ the track,allowing water fow balance to be maintained, is through the use o culverts, or pipedcrossings. These culverts transer fows rom track side ditches, or are installed to

ensure that existing lowpoints in the groundorm that would have potentially beendrainage paths in periods o high rainall, can continue to ull that purpose.

The culverts are required to be o suitable diameterto allow sucient surace water transer in periodso excessive rainall, and also should have urthercapacity allowed as a actor o saety assuming thatin some cases a build up o deposits in the invertlevel could reduce overall capacity. The culvertsshould be installed in such a way that the invertlevels are slightly lower than the correspondinglevels on the inlet and outlet sides, to al low anatural bed to orm.

Culverts should not be installed with a “hanging”outlet (i.e. signicantly higher than thecorresponding ground level), as this will causeerosion o the ground through the orced actiono the water fows, and also would not provide asuitable path or small mammals to use in periodso drier conditions. Headwalls should be providedaround the inlet and outlet ends o the culverts toretain the track building materials, as well as tominimise any subsequent wash-in o ner materialsrom the track causing potential blockage to theculvert ends.

Where drainage ditches have been installed in materials that may give rise to erosion,silt traps should be installed which take the orm o a ormed pit, which could eitherbe situated at the inlet, or outlet ends or both. It may be necessary to construct aretaining structure (e.g. pre-cast manhole ring units), to ensure that a robust structureis in place to allow uture maintenance to take place without damage or erosion tothe substrate material. A route out should be provided or small mammals that maybecome trapped in these pits.

Track Running Surace Cross-drains

On sections o tracks that have particularly long gradients, surace erosion can beprevalent ollowing periods o persistent rainall. Due to the design specications

that usually limit the amount o track camber or crossall, the surace water tends torun down the roadline, accumulating as it nears the lower sections. This can leadto signicant volumes o fow on the access track that scour out the running surace,causing runnels to orm, that accentuate the problem.

To alleviate this issue, it is recommended to install a series o surace cross-drains tointercept these fows, and divert then into the side ditches, preventing the build-upo fow. These cross-drains can be constructed with channels o various materials butshould be strong enough to withstand the expected trac loadings.

Cross-drain on access track.



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9.5 Additional Protection Measures

During the construction process provision should be made or a combination o some orall o the techniques listed below:-

Silt Traps

Silt traps can be a simple and eective method o controlling sediment laden run-o,but are limited by capacity o what the expected fows are likely to be. These can

be installed either on the inlet or outlet side o culverts, but require to be robust enough to allowor requent clearing out o collected sediments.

Silt Fencing

This system involves the installation o somesemi-permeable geotextile abric, vertically heldon simple timber posts, and is used primarily asan additional means o ltering out sediments romrun-o water. The ences can be installed alongsideany sensitive areas e.g. watercourses, large areaso stripped materials, or downstream rom outletends o culverts, and can usually be arranged in ahorse-shoe style conguration to contain, and allowsettlement o suspended sediments.

Straw Bales

Straw bales can be used to lter out sedimentsrom normal fows in drainage ditches, but theirinstallation positions require to be careullyconsidered, and should allow or potentialovertopping in periods o high fow. They should bepinned securely in position to avoid being washed

down into larger watercourses. Bales can becomesaturated and can become very heavy to manuallymove, so a means o mechanical recovery andreplacement also needs to be considered. These require to be replaced periodically,once they become silt-laden. Bales that become silt-laden, and cease to be eectiverequire to be discarded in an appropriate manner subject to relevant waste legislation.

Settlement lagoons

Any proposed site or large capacity settlement lagoons requires careul planning anda good awareness o the expected volumes o fows that they will be required to copewith. Lagoons are particularly eective where a large run-o volume is expected andsuitable small scale dispersal to existing vegetation would not be successul.

Settlement lagoons normally take the orm o a large contained pool area, eitherpartially dug in to the ground or bunded to act as a barrier to stop the surace run-o escaping. This pool should be urther compartmentalised to allow dierent levelso ltration and settlement to occur, progressively, rom the inlet end through to theeventual discharge end. Care is required to ensure that the sidewalls are strongenough to withstand any potential loadings as an uncontrolled discharge (burst) couldhave serious environmental consequences.

Flocculant dosing

Where all other possibil ities o sediment control have been considered, tried, ordiscounted, another method to increase the rate o settlement would be by the

introduction o liquid, or solid dosed focculants. These work by pulling together nersuspended solids, into larger and thereore heavier particles that settle out quicker.The use o focculant agents should be considered where there are limits on availablespace. Liquid focculants can be dosed into settlement lagoons, and solid focculantblocks can be set in fowing water to slowly dissolve, thereby giving a ‘dose’ to the

Straw bale ‘pinned’ in place.



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suspended sediments in the run-o. Some specialist assistance should be sought i this option is being considered, and approvals rom the statutory agencies may also berequired, prior to use.

Pumping

Where there is a signicant build up o water it may be required to pump this to avoidurther build up, or to allow works to progress in that area. Any required pumpingshould be planned to ensure that the discharge is either entering a sett lement lagoon

or that it can discharge directly over an area o suitable vegetation, an appropriatedistance away rom watercourses, lochs, sensitive wetlands and groundwater in orderto lter out any suspended sediments. Proprietary equipment such as “Siltbuster” typetanks can also be used to assist with the reduction o suspended solids.

It is important that the fows rom the pumping operation do not cause erosion to thevegetation that it is discharging onto. The point o delivery should be alternated tovarious locations to ensure that potential or scouring is minimised. I the fows needto be redistributed more generally over vegetation a connection to the hose end can bemade to discharge the fuid in a spray over a much greater area.

Watercourse Crossings

The location o watercourses should be givencareul consideration in determining the routing o roads and pipelines and the location o temporaryand permanent inrastructure. The crossing o watercourses is to be avoided where possible. Where these do prove a necessity developersshould use bridging structures or bottomless/arched culverts which will not impact on thebottom and banks o the watercourse.

All watercourse crossings must be carried outin accordance with the Controlled ActivityRegulations, controls range rom general binding

rules, through to complex licences. Furtherinormation should be sought rom SEPA. For eachlevel o authorisation, di erent timescales apply,and these timescales require to be allowed or inthe overall Construction Planning.

Maintenance

• Anyinstalledadditionalprotectionmeasuresshouldberegularlyinspected,andprocedures should be put in place to have any collected sediment cleared out toensure maximum capacity can be maintained. It is recommended that clearing outbe done in a period o dry weather, when fows would not aect the disturbedsediment materials.

•Headwallconditionsshouldbecheckedaswellastheinlet,andoutletendsofculverts to ensure no blockages are evident.

•Ifthereareanypermanentsettlementlagoonstheseshouldbecheckedforleakageand, ollowing periods o heavy rainall, i there has been sucient settling o sediments, water levels should be lowered to allow increased containment capacityto be available within the lagoon or the next rainall period.

•Ditchesshouldbecheckedforblockages,andkeptclearandingoodorder.Anygrowing vegetation in ditches should be let as this wil l aid in the ltering o someo the sediments.

Bridge and bank habitat. Steep sides o loose materialcould be washed o in a storm event. Use o splashboards on bridges can prevent contamination owatercourses and is an example o good practice.



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9.6 Key items to address in Construction Method Statement

• Lookcloselyatthelikelytravelpathsofsurfacewaterrun-offandtheeffectthismay have on any downstream receptors, and plan or minimising this potentialeect.

• Pollutionpreventiontechniquesandmitigationmethods or spills o oils and uels, and cementand concrete should be identied.

• Clearlydiscussthepro-activemeasurestobeputin place to prevent uncontrolled surace run-o,including pre-earthworks drainage, silt traps,settlement lagoons, silt encing, etc.

• Discusstheintendedcontrolmeasurestobeconsidered when pumping is required.

• ConsiderdetailsofanEnvironmentalManagement Plan, to look at the pre-construction, construction, and post constructionphase perormance o the intended drainagesystems.

• Identifywhichdrainscouldberestoredattheend o construction.


Forestry Commission: Forests and Water Guidelines (Fourth edition).

CIRIA Publications: Control o Water Pollution rom Linear Construction Projects.Site Guide.

SEPA Pollution Prevention Guidelines.

HSEAvoidingDangertoUndergroundServices.

A well designed and located cement wash out bay canprevent bad practice elsewhere on site. A ticketingsystem to ensure it is used by all drivers has been shownto be useul.



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10 Construction o Access Tracks

10.1 Introduction

The Access Tracks constructed on a windarm are required or our main phases o the

works:1. Initial installation to allow the main construction plant, personnel, and materials to

gain access to the remaining areas o the site to allow the construction o the civiland electrical inrastructure.

2. Sae haulage o the main Wind Turbine Generator component parts, and access orcranes, required or Turbine erection.

3. Long term access or the Operational & Maintenance needs o the windarm, as wellas providing amenity access or landowners and the public.

4. Access or the eventual decommissioning o the windarm.

Getting the track construction correct means that, with properly considered design and

construction methods, you can expect to:• Avoidtrackfailure

• Reducevolumesofsedimentladenrun-offduring,andpost-construction

• Reducequantitiesofroadstoneused

• Minimisewasteproduction

• Avoiddelaysinallowingaccessforwindturbinecomponentdeliveries

• Reducetimescalesforthere-generationofreinstatedverges

• Limitthelongtermrequirementformaintenance

• Minimisetheimpactontheexistinglandscapeandhabitat


Where a windarm is proposed in an upland area then this Section should be read inconjunctionwiththeSNHpublications‘ConstructedtracksintheScottishUplands’and‘Floating Roads on Peat’ (August 2010).

• Drainage (please reer to Drainage section)

• Pre-Constructiontasks

Existing ground conditions analysis

Existing ground surveys/TopographyCatchment/Run-o studies

Construction Planning (including waste management)

Limits o Construction

Existing services and other constraints

• TrackDesign

Alignment Horizontal & Vertical, and consideration o upgrading existing tracks

Peat Stability issues

Specication requirements

• TrackConstruction

Floated Construction (Grid types, structural stability, hydrology, inclusion o existingroots and vegetation).



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Traditional ‘Cut & Fill’ Construction (consider an estimate o the excavated materialthat this technique will generate).

Rock Source; Quantity & Quality

Ditches/Culverts/Catchpits (temporary and permanent)

• Vergereprolingreinstatement(please reer to section 14)

• OperationalMaintenance

10.3 Pre-Construction Tasks

It is essential that there is a ull understanding o the area where the tracks areproposed to be constructed. This understanding should cover the ollowing points :-

Topography o the ground ought to be considered ranging rom detailed reviewso current mapping, right through to detailed ground surveys. This inormationis also important to assess the potential catchment area or expected ground andsurace water run-o, as this will be required when sizing culverts, spacing o-lets,settlement lagoons etc. It is also important that tracks and access to and rom borrowpits are considered.

Results rom a comprehensive ground investigation should also be reviewed tounderstand what the expected ground conditions will be. Important inormation romthe ground investigations or tracks, take the orm o peat/topsoil probing, and trialpitting, in-situ shear vane tests, particle size distributions. This inormation provideskey details to allow ull understanding o the ground make-up.

Initial ly, peat probing should be carried out over a wide corridor, within the limitso construction (set through the Planning Permission) and roughly ollowing theintended track line. The results o detailed probing o sucient intensity (includingcharacterisation o peat and habitats present) could then allow a more detailed xo the tracks’ intended centre-line, avoiding areas o deeper peat, or sloping ground.A series o trial pits could then be commissioned to allow physical cross-checks tocorrelate the probing o the soter materials, and also to provide an inspect ion o thesoil types underlying the “sot” materials.

This is extremely important when considering the types o track construction to beemployed, when assessing the need or additional reinorcement materials and whenconsidering any potential peat stability issues, borrow pits and waste management.

Construction o a cut road.



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10.4 Track Design

During the more detailed track design stages, the specication limits or the intendedtrackconstructionmustbefullyconsidered.Usuallytherearelimitssetbyeitherthe turbine supplier, or delivery contractor, or horizontal, and vertical alignmentgradients, as well as minimum track widths, and load bearing capacities. At thisstage, a Geotechnical Engineer may need to be consulted to ascertain any potentialissues with regard to the intended track construction style, track gradients, temporaryconstruction stages and how this may aect the stability o the existing ground orm,and in particular any potential peat stability issues.

Throughout the construction phase it is also recommended that regular Geotechnicalinspections are made to promote good practice, and provide a orum to review anddiscuss any potential concerns.

Prior to the commencement o construction o a section o track, it is advised that thecentre-line o the track is “set-out”, and a walk over is perormed by the site manageror general oreman, along with the Geotechnical Engineer, and appropriate Clerk o Works (please reer to Section 5). This would be carried out to check that the groundconditions/drainage paths are as expected, and i there are any instances where“ne-tuning” o the alignment is required. This can usually be accommodated withouttoo great an eect on construction progress.

Any requirement to install pre-earthworks drainage can also be carried out at thisstage, once the nal line has been agreed.

10.5 Track Construction

The track construction method generally ollows one o two potential options either:

• A“Floating track” where the vegetation and supporting subsoils remain intact,with a track built o the existing ground surace supported with the introduction o geotextiles and geo-grids to reinorce the track building roadstone. This techniquemay produce less waste due to a reduction in the amount o excavation required.

• Amoretraditional“Cut & Fill track” , is generally constructed where there is arelatively thin layer o vegetation, and sot (soils/subsoils) materials that can beeasily removed to provide a suitable bearing layer to base the track construction, ori the topography is steeper, and foating construction is not considered acceptable.Note that this technique may generate more excavated material.

Choice o track construction will have a bearing on carbon payback times. Sucientdetail on track design wil l thereore be benecial prior to consent to allow areasonably accurate assessment o carbon payback.

Floating tracks

These tracks are commonly constructed across

areas o deep sot materials usually gently rollingpeat, or occasionally sot poor-strength clays. Moredetailed guidance is provided in Floating Roads on

Peat (SNH/FCS August 2010). It is important thatthe topography o the surrounding area is ullyunderstood and that a suitable peat probe surveyhas been carried out to base the decision on thetype o construction on. Floating tracks are notrecommended on areas where the “crossall”, orslope o the virgin ground is o a magnitude thatcould lead to a slip or a circular ailure, or whereit is considered that the strength o the virginmaterials could not support the superimposedloadings o the track construction plant andmaterials, and more signicantly, the weight o the WTG components & vehicles during the deliverystages. Without due consideration, and proessional

Poor foating road construction e.g. attention to detail isrequired at track edges to prevent construction materialspilling onto surrounding vegetation. Please reer to the

Floating roads on Peat guidance.



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opinion, the construction o foating tracks onareas that would not support the ull constructioncycle could lead to catastrophic track ailures withpotentially serious physical and environmentalresults.

For best results or the support o a foating track,the vegetation layer should be let in place, and inthe case o clear-elled orested areas, the tree roots

systems should not be grubbed up, but the stumpremains should be cut/ground to the vegetationlevel. Where easible and appropriate, brash rom awoodland removal undertaking can be re-used toadd support to a foating road.

The rst layer o woven geotextile, and/or geo-gridis careully rolled out across the virgin ground inaccordance with the manuacturer’s instruction. Alayer o rockll is spread evenly and careully acrossthe geogrid to provide the running surace or theconstruction plant to access. This layer can vary inthickness, and can depend on the supportive nature

o the underlying materials, the quality, and size o the rockl l materials used, and even the ski ll and competence o the operators o theplant involved.

I appropriate, some small diameter drainage pipes can be instal led below or withinthe rst layer o rockll, to maintain any natural fow rom one side o the track to theother. This helps to maintain the hydrology o the area.

In many cases once the init ial rockll layer is spread, a second geogrid layer is laidout on top o the levelled rockll, prior to the second rockll layer being spread. Thissecond layer is usually o a slightly ner, crushed ”grading”, to provide a suitabledurable running surace or the construction plant.

It is important that great care is taken to ensure that all minimum lap lengths on the

geogrid sheets are achieved, both along and across the roadlines. Also, the gridsshould extend beyond the intended minimum track width in order to allow additionalweight to be applied to assist the tracks to evenly spread out the applied loads. Careshould be taken however when placing this material not to over-deposit arisings to thedetriment o the works. For example, the provision o high verges can prevent suracewater rom immediately draining o the road where it arises and this can create localponding which can inltrate the road and weaken its construction.

It is not recommended to allow any signicant lengths o cable trenching to remain“open”, or allow drainage ditches to be excavated in close proximity to foating trackareas, as the additional loads imposed through the track could lead to underlying sotmaterials migrating to ll the created void, and potentially causing a weak point to bedeveloped in the track.

Any gathered surace water should be allowed to run o the track edges, at very closeintervals across the verges, and onto the neighbouring vegetation, to avoid any suraceponding. Further guidance is available in Floating Roads on Peat (2010).

Cut & Fill tracks

These tracks are constructed in a more traditional orm, where the vegetation layer(nominally the top 300mm) and remaining underlying “sot” materials are removed,allowing access to construct o the sub-soil or bed-rock, which would usually consisto better bearing capacity material.

Ater the centre-line o the track has been set-out, and any required pre-earthworksdrainage provisions have been made, the corridor o the intended track is markedout to allow the excavators to commence. The vegetation and materials holding theseedbank, (300mm o the top o the soter materials) are stripped, and careully setaside or re-use in the reproling and reinstatement works. Where practical, wholeturves should be set aside and stored vegetation side up, or use in restoration. The

Surveying foating road structural integrity. Note thatexcessive material should not be placed on the sidetracks as shown on the let o this image.



38


sub-soils materials can then be assessed, and in some cases some localised areaso sot-spots may require to be excavated and replaced with imported better qualitymaterials. I the bearing materials are assessed as being “marginal”, it may also benecessary to install some geotextile material reinorcement to spread the track loadover the bearing surace.

On signicantly sloping ground it may be necessary to cut benches into the sub-soillayer to provide suitably proled bearing suraces or the support o the track.

Rockll is then spread over the prepared bearing level, and proled to suit therequired levels. This roadstone is then graded and rolled to provide a well compacteddurable running surace. Any undulations in the bearing level are usually taken out asthe track is proled to suit the specication provided. Care is required to ensure thatthe surace o the tracks do not hold standing water, as this can lead to more extensivemaintenance being required to potholes, ollowing heavy tracking, and can lead topremature localised track ailures.

For best results in constructing the nal running suraces o the tracks it is importantthat a good quality stone which is suitable or the specic task is utilised, as “makingdo“ with a substandard material, that will break down more readily, will lead to :-more silt-laden run-o, more maintenance o the track suraces, and earlier overalltrack deterioration. The source rock should be o good quality either rom an external

quarry, or rom an on-site “Borrow-Pit”. As a guide, rock that can be easily extractedrom the borrow-pit is generally rock that is quicker, or more prone, to deteriorate asa running surace. I the quality o rock is poor then an alternative source should beused.

As either method o track construct ion progresses, whether it is “Floating”, or the moretraditional “Cut & Fill” system, it is strongly advised to install culverts and drainagepipes at regular intervals to alleviate any potential build-up o storm water. Theculverts should be constructed in strong enough materials to withstand the expectedloadings, and should at least be instal led at all low points where o-let points wouldhave existed previously. It makes sense to install all required crossings at an earlystage, as any secondary excavating through a constructed track could lead to moredelays, and an inherent weak point in the track.

Depending on the natural soil types it may be prudent to install silt traps at the inletsto the drainage pipe crossings to reduce the volumes o solids being carried in thedischarged waters. All work associated with any open water should be carr ied out inull accordance with the requirements o the Controlled Activities Regulations (CAR),and all appropriate licences must be obtained rom SEPA.

All ducted crossing points or expected site cabling should be protected and marked asnecessary, and locations or other accesses should also be accommodated at this earlystage.

VergeReinstatements

Once the tracks’ running surace has been installed, the verges can be reinstated.

The main objective with verge reinstatement is to create a good landscape tie-inwith the original ground orm and habitat. To secure the best results, the previouslystripped soils should be brought back over the verges within as short a time period asreasonably possible, as this g ives the seedbank and vegetation the best chance o anearly regeneration. Replacing whole turves is the ideal method o restoration.

The soils should not be spread back on the verges too thinly as the material may thenhave a tendency to dry out and crack (particularly during the summer months) beorethe root system has had a chance to orm, stabilising the surrounding soils. There willbe dierences in the growing perormance depending on season, and altitude, but anearly reinstatement generally provides or the most benecial results.

Construction material should not be placed on track edges unless it is required orre-proling, or to achieve a suitable tie in with the surrounding topography. Not allexcavated materials will be suitable or this use. Only use peat in these instancesto reprole/nish o the edges o tracks and where construction has damaged thesurace. Peat turves should be used where possible.



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11 Site Compound

11.1 Introduction

All wind arms require a site compound during the construction stage o the project.

Typically the compound would include oce and workers welare acil ities, parking,laydown area and storage areas.

UndertheConstruction(DesignandManagement)Regulations2007(CDM)itistheClient’s responsibility to ensure that “contractors have made arrangements or suitablewelare acilities to be provided rom the start and throughout the construction phase”.Thereore there is a legal requirement or developers to consider the welare acilitiesrequired on-site during the construction phase.

The size o the storage, laydown, car parkingand other acilities within the site compound areusually dependant on the size o the project and thetechnical requirements o the turbine supplier andother contractors.

This section provides details on best practice ordesign considerations and construction methods,including possible environmental mitigationmethods. Specically this includes:

• Locationofthesitecompound

• Designofthesitecompoundandconstructionmethods

• Environmentalmitigationmethods

• Reinstatementofsitecompound


a) Location o the site compound

The location o the compound is normally part o the planning consent and anyimpacts, including visual intrusion and ground conditions, should have beenconsidered as part o the Environmental Impact Assessment.

The site compound is normally situated towards the entrance o the site to enablecontrol o material onto the site, ease o access or workers and visitors, and ease o construction at the beginning o the works.

When considering the location o the compound at the construction phase theollowing should be reviewed rom earlier planning stages:

i) Distance rom watercourses, lochs and wetlands.

ii) Topography o the area.

iii) Ground conditions

iv) Hydrology

v) Designated Sites

vi) Visual impact

The results o baseline surveys (and any subsequent survey work) should provide

much o the inormation required.

b) Design o the compound and construction methods

Site compounds are typically large levelled areas constructed o compacted stone.These areas are normally reinstated ollowing construction, except where they

Considerable lay-down areas are required on site.



42


are retained or partially retained or use during the operational phase. During thedesign phase it is desirable to minimise the overall ootprint o the site compound.

Where the compound has been proposed on an incl ined area, the use o split levelareas should be considered to reduce the excavation into the slope and balance thecut and ll required on the area thus minimising haulage o excavated material.

When designing the compound the use o a perimeter drain should be assessed. Where the surace drainage across the compound area could aect the integrity o the compound a perimeter drain should be designed taking into account mitigationor sediment transport. Where surace drainage is unlikely to aect the compound,perimeter drains should be avoided thus preventing impact on the hydrology o thearea and potential o sediment transport.

When construct ing the site compound the peat/topsoil should be stripped andstored in a suitable location even when using geotexti le material. Suitable stoneshould be placed and compacted to create the compound. It is important thatthe content o the stone does not include a high percentage o nes which couldincrease the risk o sediment contamination o the adjacent area and watercourses.

The site acilities wil l include mess and toilet acilities or the site workers. Thedesign o the efuent system, either septic tank and soakaway or contained tank,will depend on the sensitivity o the adjacent area. Where soakaways are proposed

they should be kept as ar away rom watercourses as easibly possible. SEPAlicences may be required.

I compound lighting is required it should be designed to minimise light pollution tothe surrounding area. All lights should ace inwards to reduce overall environmentalimpact.

Normally bulk uel and oil storage will be within the site compound area. Suitablebunded areas should be designed and constructed to meet the requirements o SEPA’s pollution prevention guidelines and oil storage regulations.

c) Environmental Mitigation Methods

The highest risk o pollution is sediment transport rom runo across the compound

area. The use o si lt/sediment traps, settlement ponds and hay/straw bale barriersshould be considered to prevent sediment entering watercourses. Where highpercentages o clays and silts occur, the use o focculants should be considered toreduce settlement time (which may take weeks). Flocculants should only be usedollowing consultation with SEPA and relevant sheries groups.

The contractors on-site should have an emergency procedure or dealing with oiland uel spills. Emergency spill kits should be available within the compound anda contract with a 24 hour response environmental clean up company should be inplace or the construction period.

d) Compound Reinstatement

The compound is required during the whole o the construction period, andwithout appropriate management it is likely that any turves which were strippedwould have decomposed depending on the length o time or which these arestored. The reinstatement o the compound area would normally include a degreeo landscaping ollowed by replacement o the peat/topsoil over the area. Thecompound area will take a number o years to ul ly reinstate, dependant on the typeo adjacent vegetation. The use o reseeding or temporary encing o the area toprotect against grazing animals should be considered to help accelerate vegetation.Careul consideration o the site specic conditions is required to ensure successulregeneration, and in particular the creation o appropriate hydrological conditions.

I the compound is not required during the operational phase o the wind armthe area should be re-graded to match in with the surrounding levels. Suitable

material or reinstatement should be appropriately stored and managed, near to thesite compound but away rom/with suitable buers rom watercourses and othersensitive receptors.



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12 Cable trenching and installation

12.1 Introduction

MostwindfarmswithintheUKinstallthepowerandcommunicationcableswithin

trenches that are excavated and then backlled. Windarm cables on some siteshowever are ploughed in using machines that are capable o dealing with dierentground conditions; laying power and communication cables at the same time asbedding sand and warning tapes. The main dierence between these two methods isthe ability to inspect the cables ollowing them being laid.

It is important to balance land, ecology, economic,drainage requirements and saety actors whendesigning the wind arm electrical collectionsystem.

This section provides advice on good practiceconstruction methods to minimise the impact duringconstruction.

Specically this includes:

• Designingthelocationofcabletrenches

• Designofthecabletrenchesandconstructionmethods

• Timingofconstructionandreinstatementworks


Designing the location o cable trenches

a) Design at planning stage

Typically the location o wind arm cables, as noted within an EnvironmentalStatement (ES), are either not mentioned or reerred to as “generally ollowingthe track routes”. It is oten dicult to identiy the exact cable routes at theplanning stage and it is normally preerable to leave it to be dealt with within theConstruction Method Statement (CMS), as it would normally require more detailedelectrical design than typically undertaken at the ES stage.

Generally it is accepted that wind arm cables should be buried rather than installedas overhead lines on the basis o visual impact and potential impact on birds. Theimpact o a cable trench being constructed adjacent to a site track is likely to be

negligible but a separate cable trench crossing the wind arm area may have a moresignicant impact.

b) Cable route design

When designing the cable route or the wind arm it is important to take theollowing into consideration:

i) The design o the consented turbine and site track layout.

ii) The environmental/ecological sensitivity o the area.

iii) Existing land use.

iv) Archaeological sites.

v) The hydrology o the area.

vi) Ground conditions.

vii) Topography o the area.

Cable trench adjacent to constructed road.



44


viii ) Economics o the cable route.

ix) Ability and speed to repair the cables during the operational phase.

When designing the cable routes it is important to take into account the physicallayout o the turbines and site tracks. Generally it is more convenient to instal lthe cables adjacent to the site tracks to allow easy access or the cable laying andtrenching plant.

The existing land use and habitat should be considered when designing the route to

minimise the impact. Any impact on existing land drainage systems should be takeninto account. Cable trenches can act as water drainage routes; the amount o watertransport dependant on the design o the cable trench.

The hydrology o an area can be aected by a cable trench containing disturbedbackll material, sand bedding and surround. The steeper the cable route thehigher the volume o water is likely to be transported through the cable trench. Itis important to consider the gradient o cable routes and the use o clay plugs andimpermeable barriers within the cable trench to limit water fow.

Ground conditions and topography need to be considered or various practicalreasons. Separate cable routes on steep gradients, especially with sot ground havehigh risks o causing machines to topple and may be more dicult to reinstate andbe subject to erosion by surace water fow. Cables should not be installed in deepsot peat as they will slowly sink adding tension into the cable, which may requirepremature replacement.

It is possible to install cables in nearly all ground conditions, but when planninga route, the possible replacement and repairs o the cables should be considered.Installing cables in areas which require specialist installation equipment or throughdesignated/protected areas, which may require notication, will cause delays torepairs.

Cable routes should avoid areas o potential archaeological interest. Where thismay not be possible mitigation should be proposed, including a written scheme o investigation. Consultation with Historic Scotland or the Local Planning Authoritymay be required.

c) Cable trench design, installation and reinstatement

Cable trenching involves:

i) Stripping and storing separately the topsoil/peat layer.

ii) Excavating the trench through the subsoil.

iii) Laying earth tape/cable in contact with the base o the trench.

iv) Placing sand bedding.

v) Laying power and communication cables and sand surround.

vi) Instal ling marker tapes/tiles and back lling the trench.

vii) Reinstating the topsoil/peat layer.

Where cables are instal led adjacent to foating track sections, trenching in thereinstated track edges should be considered as part o the track design. This canminimise any additional land take area or cable trenching as well as giving supportto the cables preventing them sinking through the peat or sot sub-soils. This hasthe additional benet o not requiring separate cable trenches in virgin ground thusminimising hydrological and ecological impacts.

It is important to consider the timing o other construction activities. Where possibletrench reinstatement works should take into account adjacent activities which maydisturb any reinstatement works already carried out.

Windarms have recently been targeted, due to high metal prices, by thieveswanting to steal cables and earth tapes/cables. It is important that security isconsidered during the construction stage as much o the cable stolen has beenpulled out o the ground. As well as cost o the thet this activity can destroy thereinstated area and reduce the quality o any urther reinstatement attempts.



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Generally the quality o reinstatement o cable instal lation areas is dependent onthe ollowing:

i) The amount o time between the excavation o the trench and the reinstatemento the topsoil/peat. Peat turs poorly stored or stored or a long period o timecan impact on the quality and time required or the area to ully recover. Cabletrenches should not be excavated prior to the electrical contractor havingcables ready on-site or installation. A method should be used which minimisesthe amount o time cable trenches are let open and the time between peat

stripping and reinstatement. Trenches let open or long periods o time tendto act as conduits or water causing erosion and potential sediment pollution o adjacent watercourses and land.

ii) Poor separation o excavated material will lead to mixed soils e.g. contaminatedpeat, thus leading to poor reinstatement. A method should be used whichclearly separates the dierent excavated materials. Consideration should begiven to over stripping or the cable trench areas to prevent mineral soil/sediment contamination o the adjacent vegetated areas. The over strippingmethod will be dependant on the materials excavated rom the trench. Wherecable trench arisings are comprised entirely o peat it may not be worthwhile toover strip. Where cable trench arisings are mineral soil or weathered bedrockover stripping should be considered.

iii) Where the depth o the original topsoil/peat layer is very thin there may beinsucient material or reinstatement. Where the use o peat with little or noseed bank, rom another area o the site is proposed, the method o reseedingshould be agreed with SNH. The use o sand and other materials may beappropriate. Advice should be sought rom SEPA and SNH.

iv) Consider the hydrology at the design stage to ensure the type o vegetation onthe reinstated area does not dier rom the adjacent area.



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13 Turbine Foundationand Crane Pad construction

13.1 Introduction

Beore detailed oundation and crane pad design can be carried out, adequate groundinvestigations are required. Typically this involves: trial pits, boreholes, in-situ testingand laboratory testing o samples.

The type and design o the oundation will typically be based upon the ndingso the ground investigation. Some turbine manuacturers insist on using theirstandard oundation design, which are normally designed or a large range o groundconditions. A key consideration should be waste minimisation and the reduction o carbon emissions. In areas o poor ground conditions greater than 3m in depth, it maybe more appropriate to consider alternative methods such as piling.

As the specic turbine model is unlikely to have been selected prior to the

consent o the wind arm, the size o the oundation and crane pad discussed inthe Environmental Statement (ES) is either generic/typical or based on an actualturbine which could t the wind arm design. The most appropriate type o theoundation (gravity, piled or rock anchored), can only be determined ollowing groundinvestigation works. Ground investigation works (due to their invasive nature andcost) are generally carried out ollowing planning consent, and gravity oundations,as the most common orm, are considered within the ES. However the use o piledoundations should be considered in uture. The results o a peat survey completedduring the EIA stage should inorm whether piling is a easible option.

This section will generally reer to gravity oundations, except where other oundationtypes require particular consideration. Generally gravity oundations are locatedwithin a weathered rock stratum, or on soils that can provide adequate bearing

capacity. Piled oundations are used in sot sediments or deep peat, where the pilesare either driven into underlying bedrock, or the riction o the pile within the sotsediment is sucient to support the turbine or in some cases a combination o both.Rock anchored oundations utilise steel anchors which are drilled and secured into

Liting o nal turbine components. Preparation o turbine oundations.



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strong competent rock. These are less common, but do allow reduced volumes o concrete to be used.

The construction o oundations and crane pads involve heavy civil and earthworks,which have a high risk o sediment pollution and chemical contamination o the waterenvironment. When considering the oundation and crane pad design it is important totake into consideration the ollowing ecological, hydrological and operational actors:

• Minimisingexcavationofmaterial.

• Thepossibleeffectonthewatertable.• Thepossibleeffectofdrainageonthetypeofvegetation.

• Howtodealwithsiltywaterwithintheexcavatedareas.

• Howthetopsoil/peatstrippingshouldbecarriedout.

• Howexcavatedmaterialshouldbestoredtemporarilyorre-used.


a) Turbine and crane pad location

The location o the turbine and crane pad will determine how much earthworkswill be required to enable the civil works. A turbine located on a steep gradient willrequire extensive earthworks to level a large enough area to accommodate both theoundation and crane pad area. Areas o deep peat should be avoided to minimisethe volume o peat excavated.

b) Soil and overburden stripping

When designing the turbine oundation it is essential to understand the existingground conditions. Typically the topsoil/peat is stripped and stored around theperimeter o the oundation excavation.

Where stripped/excavated peat is not suitable or reinstatement it is likely to be

considered to be a waste material and the relevant waste management legislationwill apply (this should be discussed with SEPA). In light o these discussions theCMS should identiy appropriate handling and storage methodologies.

Subject to any waste management control a plan showing areas which are sae orstockpiling should be created prior to works beginning. In areas where stockpilingis not allowed the excavated material should be transported straight away tothe nearest agreed sae area. Where excavated material is not suitable or backlling over the oundation or or reinstatement purposes, i possible it should betransported to its nal agreed location. Double handling o silty material increasesthe risk o pollution and contamination o the adjacent land.

I designed properly the use o a temporary low bund o sub-soil around theperimeter o the excavated area can be a useul mitigation method, to prevent siltrom stockpiles being washed into the adjacent area or watercourses.

Deep excavations should be enced with appropriate warning signs, until suitablyrestored.

c) Drainage

Cut o drains are commonly used on the top side o excavations to prevent suracewater runo entering the excavation. I a cut o drain is to be used they shouldbe designed to prevent high erosion fow rates and include appropriate sedimenttransport mitigation measures.

The amount o water that may accumulate in the bottom o the excavation isdependant on the permeability o the rock, the water table and the weather over theconstruction period. The excavations can produce high amounts o ne sediment,which could have a signicant aect on local watercourses. Each excavationrequires a tailored drainage/mitigation plan which takes in to account its speciccharacteristics.



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I possible the excavation should be designed to allow drainage out through alimited number o controlled outlets, where sediment can be controlled through aseries o settlement ponds or ltering systems. Flocculants should be consideredto assist sediment precipitation. A focculent special ist as well as SEPA should beconsulted prior to use.

Where water collects in the bottom o an excavation it may be necessary to pumpthe water out to allow continued works. I pumping is required it is important toagree locations away rom water courses where discharging or urther treatment

can occur.The turbine oundation design has to consider the water table in the area. I thewater table in the area is higher than the ormation level the oundation will beaected by buoyancy (uplit). The typical solution to this problem is to install adrain around the outside o the oundation (sometimes underneath the oundation)to lower the water table below the ormation level. Alternatively the oundationsize can be increased to account or the buoyancy eect. It is important to assessi localised lowering o the water table will have an undesirable eect on thevegetation or water environment o the local area. Lowering o the water table is notrecommended where these undesirable eects are likely.

d) Crane pad (hardstanding) size and layout

The size o the crane pad is normally directly related to the size o the cranesrequired or installation. The turbine manuacturers also require the crane pads ortemporary storage o turbine components e.g. blades and nacelles. The crane padsare normally designed to accommodate all types o cranes that could possibly beused.

It is possible to reduce the size o the crane hardstanding area by designingseparate pads or the crane outriggers, but only i the precise installation craneis known. Specically designed crane pads also limit the type o crane that canbe used or maintenance during the operational phase. A storage area or turbinecomponents would also be required either on-site or near to site.

e) During construction

Turbine oundations and crane hardstanding involve heavy earthworks and civilworks. It is important that any mitigation measures designed are monitored (bythe contractor and the Environmental/Ecological Clerk o Works) and maintenancecarried out.

) Reinstatement

Within environmental statements crane pad reinstatement is oten either notmentioned or a layer o topsoil/peat is descr ibed as being spread over thehardstanding.

From experience the use o crane pads during the operational period is higher thanpreviously estimated. Where crane pads have been reinstated with a layer o peatollowing construction, the peat is oten stripped o within the rst 2 to 3 years o operation to allow or turbine maintenance.

When the layer o peat is stripped o using an excavator the peat becomes mixedwith the stone rom the hardstanding and is usually not suitable or reuse. Typicallyreinstatement over crane pad areas take 2 to 3 years to establish, but due to thereuse o the hardstanding the reinstatement o these areas rarely reaches a highpercentage o vegetation cover unless reseeding is used.

In the light o operational experience it is recommended that crane pads are notcovered with peat, in particular catotelmic peat, or topsoil or the operational periodo the windarm. It is critical that the area around the crane pads and any exposedbatters are reinstated to reduce visual impact. Long term storage o peat material, in

this circumstance is not a recommended option due to weathering, drying, erosionand run-o. I possible micro-siting o the crane pad should be considered at thedesign stage to reduce excessive excavation and visual impact.



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14 Habitat Restoration

14.1 Introduction

This section provides an overview o habitat restoration measures that may be

required or wind arm developments including case studies and examples. Furtherguidance will be developed on this topic in the near uture.

Management and restoration o habitats that may be impacted by a wind armdevelopment is oten required. This may be to prevent and/or minimise impacts onsensitive habitats (or species dependent on a certain habitat) during the constructionand operational phases o the wind arm. Developers may also be required toimplement restoration measures or certain habitats as compensation or damage, or toimprove the overall carbon balance o the development.

14.2 Habitat Management Plans

Wind arm developers are oten asked to complete Habitat Management Plans (HMP)to ull conditions as part o planning consent. The purpose o the plans is to ensuresuccessul restoration o the site ater construction and mitigate eects on ecology.Restoration during construction should be identied in a Construction MethodStatement and will require due consideration throughout the construction process.Early consideration o the HMP at the preconstruction stage ensures that movementso materials are minimised (e.g. peat or drain blocking), saving money and ensuringsuccessul restoration. In some cases it may be necessary to include land outside thesite to enable long term management o the habitat.

14.3 Restoration o Peatland

I a wind arm is located on degraded peatland it is desirable to implement measuresto restore the peat land or biodiversity and to improve both the overall carbon balanceo the development and wider ecosystem benets. This is oten a requirement o planning consent and the details should be outlined in the HMP.

The aim o peatland restoration should be to restore the original unction (e.g. habitat,carbon store and sequestration) o the peatland, in consultation with a specialist. Thisis oten an approximation o the original condition with the primary aim to avoid theloss o soil carbon and to create the conditions or peat accumulation, or example viarecolonisation o Sphagnum mosses. Consideration should be given to the need tomodiy current land management practices, such as grazing, to achieve restoration.

On operational windarm sites in Scotland the periods o restoration have been too

short to show successul restoration to a ully unctional peatland . Restoration o apeatland can take rom 5 to 30 years depending on the initial condition and primarilythe eectiveness o raising the water table to or near to the surace. Long-termmonitoring is essential to develop cost-eective techniques and methods that work toensure successul restoration.

14.4 Use o excavated peat

Acceptable uses or excavated peat on a windarm site are limited. Give careulconsideration, during the Planning stage, to peat use and depths, as this shouldinfuence the nal location o wind arm inrastructure and material nal use solutions.Guidance on the use o excavated peat is provided below:

• Excavatedpeat(particularlypeatturves)maybeusedfornishingtrackedges,turbine bases and other disturbance rom inrastructure, where this is necessary.

• Alimited amount o peat can be used to restore ditches, by completely inll ing the



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ditch. This process requires timely planning and organisation to ensure eectiverestoration (see below).

• Excesspeatshouldnotbeusedtocreate‘shoulders’onoatingroadsorforcuttracks, or spread on land adjacent to tracks (See Verge Reinstatement section inChapter 10 Construction o Access Tracks).

14.5 Ditch blocking or peatland restoration

Excavated peat may be used to block drainage ditches as part o restoration proposalsor blanket or raised bog. Existing guidance is available (see below) and shouldbe ollowed. Any proposals to use excavated peat to block ditches should considerthe hydrological and ecological conditions o the bog and be planned in advanceo material being excavated. The diculties o transporting material and access toditches are also important considerations.

The aim o ditch blocking is to raise the water table and restore the appropriateconditions or blanket bog habitat. Generally, humied peat that is saturated (andimpermeable) is most suitable or ditch blocking. Dry, unconsolidated peat and suracepeat should not be used to block ditches. The suitabil ity o the peat or the intendeduse should be careully considered. Measures including plastic piling on steeper slopes

or at the end o main ditches or heather brash to inll the ditch may also be required.

The main requirements or successul restoration are:

• Awatertableatornolessthan15cmfromthesurfaceformostoftheyear(requiredto support bog vegetation)

• Targeteddrainblocking

• Forafforestedsites-remnantbogvegetationinforestrides,openareas,oradjacentunplanted bog let undisturbed as these act as a seed source.

Peat dam construction. Blocked drainage ditch using plastic sheet dam.

14.6 Key issues to consider

(a) Creation o peat dams

In some cases it is more appropriate or cost eective to instal l peat dams rather thanplastic piling.

Circumstance where it is benecial or possible to use peat dams:

• Shallowpeat

In some cases particularly on intermediate raised bog the peat thickness reducesto between 50 and 75 cm, oten with a rock substrate below. Plastic pilingwill not provide a watertight seal in the rock substrate, so peat is oten a moresuitable alternative.



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• Extensiveareasofpeat

Some sites have a high density o ditches (every 10 metres) oten over large areas.Installation o plastic piling becomes logistically dicult and expensive.

• Peatwithashallowslope

Peat dams can only successul ly be built on peat with a shallow slope. As the peatdam does not have a spillway, i the gradient is too steep the water fows causeerosion over the top o the dam resulting in ailure. It is thereore advised thatdams at the edges o raised bogs are o plastic construction.

b) Key considerations or ditch blocking using peat:

• Availabilityofsuitablemachinery

Low ground pressure excavators are generally based on peat extraction sites.Currently peat extraction is occurring in the Central Belt and in Aberdeenshire,but the machines can easibly be moved up to 50 miles rom base. In Caithnesswhere large peatland projects have been undertaken contractors have purchased oradapted machinery to work on deeper peat.

• Peatcondition

The peat used or damming must be saturated, as once peat has dried it shrinksand loses the ability to retain water and will not orm a watertight dam. Thereorethe original ditch spoil should not be used and only that taken rom the bottom andwet sides o the ditch is suitable.

To restore the original blanket bog habitat itis acceptable to mulch the trees that are notcommercially viable ollowing elling. The use o mulch or woodchips should be careully consideredduring the Planning stage. Options or commercialuse o the woodchips should be considered and ispreerable to leaving on site particularly i there islikely to be a large quantity o material.

For certain sites it may be an option to spread a verythin layer o mulch/woodchips on the surace o barepeatland as part o restoration eorts. This must beincluded in peat restoration plans in the HMP. This is

very site specic with hydrological conditions beingthe most important actor or successul restoration.The infuence o mulch on blanket mire restorationis unclear, however, use o mulch is not essential orrestoration and quicker restoration.

Peat dam blocking water fow in old orestry drainageditch. The peat may slump and in time the dam becomesineective. In addition, to improve stability, peat turvesshould cover the top.

Good practice: Blocked drainage ditch (plastic sheet damin centre o photo) with Sphagnum sp.

Dense layer o mulch spread across clear elled blanketbog. This is an example o poor practice - the chipsshould be smaller, the layer less dense and the watertable closer to the surace.



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14.7 Case Study: Blawhorn Moss

The ollowing example is taken rom Blawhorn Moss. Whilst this isn’t a wind arm siteit demonstrates the level o restoration which can be achieved and the length o time(comparable to the expected lie o most windarms) which is required.

Blawhorn Moss is a National Nature Reserve in the Central belt o Scotland. It is easilyaccessible and is a demonstration or bog restoration and dierent types o ditchblocking. Please visit the Reserve Website or urther inormation.

The main threat to the hydrology o the mire came rom the continued erosion o thelarger gullies and the lowering o the water table through the ditches.

The main thrust o management has been to try and block the extensive network o drains and reduce the impact o the gullies on the site, particularly the increasedrun-o and ragmentation o the bog edge. Over the years, dierent techniques orditch blocking have been tried. These have included peat, plastic pil ing, heather bales,timber piles and steel piles.

The rst trials or ditch blocking started in 1984, when two surace drains werein-lled with peat sods. The drains retained some water upslope but there was stillconsiderable leakage.

A major programme o ditch blocking took place between 1987 and 1989. All o thesmall section drainage channels were blocked at 12-20 metre intervals and stepwiseup the gradient along their length. One metre corrugated steel sheets, plastic coatedon one side and painted on the other, were tted into cut slots across the drains. Over1000 small dams were installed, achieving almost total drain blockage with onlythree drains on the western boundary remaining unblocked. Six timber pile damsusing elm beams at the southwest corner o the Moss in the over-deepened ditch.Following on rom this tr ial, 61 timber dams were installed the next year on all themain erosion gullies, principally on the north side o the Moss.

The above programme worked reasonably well; all the small drainage channels arenow water lled with new Sphagnum growth covering some o the sheet dams in



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the wettest parts. The timber dams have proven eective at preventing ongoing gullyerosion but are leaky so do not raise the water table ully.

In 2000, mowing and baling heather and rushes or use in ditch blocking was tried.The ollowing year, over 400 mini bales were placed into ditches on two sections o the Moss near the central fush and northern edge o the Moss. The heather bales areeective at slowing down water movement and providing a ramework or Sphagnummoss to grow.

The next phase o ditch blocking came in 2003, when 30 large (3.6m) plastic piledams were built along the central ditch. These dams successully hold water, withdepths o 1.5 metres being maintained in the ditches throughout the year. In addition,water levels are raised in the adjacent ground, encouraging the growth o Sphagnummoss. More dams were instal led on smaller ditches on the south side o the Moss. Thedams were set at a height aimed at raising the water another 15cm above the existingdams. The most recent damming has involved the construction o large steel pilingdams in the largest ditch. This and recent peat damming is seen as the nal stage o damming on the site. The peat dams are being created in areas where the originaldams were set too low and thereore the water levels were not at the surace.

14.7 Key Words

• Acrotelm–Upperlayerofbrouspeatinwhichthewatertablenaturallyuctuates.It is more permeable than the lower layer o peat (catotelm).

• Catotelm – The layer o peat below the acrotelm. It is permanently saturated, mostlyimpermeable, and is typically pseudobrous and/or amorphous in texture.

• Amorphous peat – Highly humied (decomposed) peat with ew visible plantremains. Typical o catotelm layer although conditions or decomposition/humication dependent on hydrology.

• Fibrous peat – Peat composed o densely packed but relatively intact (notdecomposed) plant remains. Typical o acrotelm layer.

• Sphagnum species – species o moss that orms peat bogs.

Acrotelm

Catotelm

Living moss layer

Permanent

Water table



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14.8 Reerences and links to guidance

Anderson, R. (2001). Deoresting and Restoring Peat Bogs – A Review.Forestry Commission Technical Paper 32.

SNH (2006). South o Scotland Bog Scheme Guidance or Land Managers – InstallingPlastic Piling Dams. (available at Installation o Plastic Piling Dams).

SNH Floating Roads on Peat (2010).

Wilkie, N.M. & Thompson, P.S. Identication and Restoration o Damaged Blanket Bog –A Guide to Restoring Drained and Aorested Peatland. LIFE Peatlands Project, SNH.



A joint publication by

Scottish Renewables

Scottish Natural Heritage

Scottish Environment Protection Agency

Forestry Commission Scotland

good practice during windfarm construction

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