ETI Position Paper

Cefas contract report C5748

Position Paper

(Module Two: Provision of Environmental Studies: Final report)

Authors: Daniel Wood1, Freya Goodsir1, Rebecca Walker1 Victoria Bendall1, Ines Martin Grandes1, Sarah Watts1,

Cormac Booth2, Chris Thaxter3 and Paul White4

Issue date: 16 December 2013

Commercial in Confidence

1CentreforEnvironment,FisheriesandAquacultureScience(Cefas),PakefieldRoad,Lowestoft,SuffolkNR330HT2SMRUMarineLtd,NewTechnologyCentre,NorthHaugh,StAndrews,FifeKY169SR3BritishTrustforOrnithology,BTO,TheNunnery,Thetford,NorfolkIP242PU4UniversityofSouthampton,Highfield,SouthamptonSO171BJ

ModuleTwo:ProvisionofEnvironmentalStudies:FinalReport

CefasDocumentControlTitle:PositionPaper

Submittedto: TheGlostenAssociatesDatesubmitted: 16December2013ProjectManager: CharlottePerksReportcompiledby: FreyaGoodsir,DanielWood,VictoriaBendallQualitycontrolby: DanielWoodApprovedby&date: AdrianJudd16 December2013

ModuleTwo:ProvisionofEnvironmentalStudies:FinalReport Pageiii

PositionPaper

ModuleTwo:ProvisionofEnvironmentalStudies:FinalReport

Authors:Daniel Wood, Freya Goodsir, Rebecca Walker Victoria Bendall, Ines Martin Grandes, Sarah Watts,

Cormac Booth, Chris Thaxter and Paul White

Issuedate:16December2013

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Cefas is an executive agency of Defra

ModuleTwo:ProvisionofEnvironmentalStudies:FinalReport Pageiv

Executive Summary

Cefas,incollaborationwiththeSeaMammalResearchUnit(SMRUMarineLtd),theBritishTrustforOrnithology (BTO), and University of Southampton Institute of Sound and Vibration Research(ISVR),hasbeencontractedbyTheGlostenAssociatestoprovideenvironmentalscientificevidenceontheenvironmentaleffectsassociatedwiththePelaStarfloatingtension legplatform(TLP)beingusedaround theUKcoast.Thispaper specifically focusesonenvironmental considerationsofTLPmoorings (anchoring systems), and the environmental interactions of key UK protected speciesincludingmarinemammals,baskingsharksandseabirds.The mooring systems to be utilised in the PelaStar design are different from those used fortraditional fixedturbinessuchasmonopiles.ThePelaStar5armTLP istetheredtotheseafloorbyhighperformancesyntheticropetendonsandhighverticalloadanchors(drivenpileanchorsand/ordrilledandgroutedanchors).Whileanchoring systemsarenew to theoffshorewind sector, theyhavebeenusedformanyyears intheoilandgas industry.Themethodsusedtoplacetheanchors(piledrivenanddrilledandgrouted)arewellknownmethodologies intheoilandgasandthecivilengineeringsectorsandaresimilartoinstallationmethodsalreadyusedinoffshorewindfarms.Twomainenvironmentalimpactshavebeenassessed;seabeddisturbanceandnoise,comparingtheTLPdesignwithmore traditional fixed foundations.ForbothTLPsand traditional foundations, thetype of impact (e.g. loss of habitat) are the same, however the scale of impact differs betweendifferentfoundationtypes.Seabedpreparationactivities intermsoftemporaryhabitat losshavealowtohighimpactintermsofgravitybases,amoderateimpactbysuctioncaissons,alowimpactbymonopiles,multilegand jackets,andnegligibleto low impactforotherfloatingwindturbinesandTLPs. The environmental effects attributable to scour processes are high for monopiles, low tomoderate for floatingwindturbines (otherthanTLPs)and low forgravitybases,multileg, jackets,suction caisson foundations and TLPs. Environmental impacts attributable to blockage effects (ofphysicalprocesses) arehigh for jacketand suction caissons,moderate tohigh,dependingon thediameterof thedesign, forgravitybasesandmultileg foundations,moderate formonopiles,andnegligibleforTLPsandotherfloatingwindturbines.Thetablebelowsummarisestheimpactsontheseabedanddifferentfoundationtypes.Foundationtype Habitatloss Scour NoiseGravityBases Lowtohigh Low LowSuction Moderate Low LowMonopile Low High HighMultileg Low Low LowtoHighJacket Low Low ModerateFloating devices (otherthanTLPs)

Negligibletolow Lowtomoderate Moderatetolow

TLPs Low Moderatetolow

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UnderwaterpilingforTLPanchoringislikelytobeofthesamemagnitudeasforthatexperiencedfortraditionalmonopile foundations.Withpilediametersvarying from2.1m to3.7m,TLPpilenoiseshouldfallsomewherebetweenthenoiseexperiencedfortraditionaljacketpinpilesandmonopiles.Drilling and grouting is significantlyquieter thanpiledriving,butwould take longer to complete,meaningelevatednoiselevelsoveragreaterperiodoftime.Formarinemammals,thebiggestconcernisunderwaternoise.Thenoisegeneratedbydrillingandgrouting may cause a smallscale disturbance around the installation site, and a wide range ofspecies couldencounter thedevicewhere it is likely tobedeployed commercially.However, thenoise levels fromdrillingandgroutingare likely tobe lowand canbeapproximated to thenoisegeneratedfromamediumsizedvessel. It isconcludedthatdrillingnoise ishighlyunlikelytocauseauditoryinjury.Thenoisegeneratedbypiledrivinginstallationwould,however,belikelytohaveanimpactonmarinemammalsinthevicinity.Theimpactranges(auditoryinjury,behaviouralresponse,masking)may be as large as or even greater than those for fixed foundationwind turbines andwould be able to be determined through an EIA. The potential for noise to be generated fromstrumming(causedbywatermovingpasttheundertensiontendonsofthePelaStar)alsoneedstobe considered.During theoperationalphase, theremaybe issuesofwhales interactingwith thetendons,representingacollisionorentrapmentrisk.Aswithmarinemammals,entanglementandconstructionnoiseareconcernsforbaskingsharks,butthereisalsothequestionastohowabaskingsharkmightrespondtoelectromagneticfields(EMFs)from suspendedpowercables.Basking sharkscertainlyhave thecapability todetectand react toanthropogenic EMFs transmitted through electrical cables associated with renewable energydevelopments,but there is currently no literature availableonwhether they actively respond totheseartificialEMFs,norwhethertheremightbeanynegativeimpact.Offshorewind farms have the potential to affect birds through fourmainmechanisms; collision,disturbance,habitatlossandbarriereffects.Theassessmentofcollisionriskisimportantnotjustforbreeding seabirds originating from nearby breeding colonies, but also for those that may passthrough during migration and during the nonbreeding season. There is also a potential risk ofcollision during construction and harbour testing of the turbine. The HVLA tendons may alsoconstituteanadditionalunderwatercollisionriskfordivingspecies.Themainquestionishowbirdsmightrespond/interacttoafloatingturbine(i.e.doseabirdsshowattraction/avoidancebehaviour,resulting in increased or decreased collision risk? Would a heavily biofouled/colonised floatingstructure provide a food source for local diving seabirds, increasing their risk ofcollision/entanglement?).

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Table of contents

1 Introduction ................................................................................................................................ 11.1 Thepurposeofthisdocument................................................................................................31.2 Potentialdevelopmentareas..................................................................................................31.3 Design......................................................................................................................................6

2 Anchoring methods .................................................................................................................... 72.1 Anchoringmethods.................................................................................................................72.2 Examplesofsimilarmoorings.................................................................................................82.3 ComparisonbetweenfixedfoundationsandfloatingTLPanchoring.....................................92.3.1 Seabeddisturbance.......................................................................................................112.3.2 Underwatersound........................................................................................................12

3 Floating TLP turbines and UK protected species .................................................................. 143.1 MarineMammals..................................................................................................................143.1.1 Introduction..................................................................................................................143.1.2 Constructionnoise........................................................................................................153.1.3 Operationalnoise..........................................................................................................163.1.4 Entanglement................................................................................................................173.1.5 Datagaps.......................................................................................................................17

3.2 BaskingSharks.......................................................................................................................183.2.1 Introduction..................................................................................................................183.2.2 Electromagneticfields...................................................................................................193.2.3 Constructionnoise........................................................................................................203.2.4 Entanglement................................................................................................................21

3.3 Seabirds.................................................................................................................................213.3.1 Introduction..................................................................................................................213.3.2 CollisionRisk..................................................................................................................223.3.3 Disturbanceanddisplacement.....................................................................................24

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3.3.4 BarrierEffects................................................................................................................263.3.5..............................................................................................................................................27

3.4 HabitatLossorChange(Includingnoise,sedimentation,electromagneticfields)..............274 Conclusions .............................................................................................................................. 304.1 TLPsedimentdisturbanceandnoise....................................................................................304.2 TLPsandimpactsonmarinemammals................................................................................314.3 TLPsandimpactsonBaskingsharks.....................................................................................314.4 TLPsandimpactsonSeabirds...............................................................................................32

5 References ................................................................................................................................ 336 Annexes .................................................................................................................................... 40

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1 Introduction

Inrecentyearstherehasbeenarapidexpansionoftherenewableenergysectortomeetdemandsfor green energy.Offshorewind farms are viewedbymany, including the Energy TechnologiesInstitute (ETI),as themajorsourceofenergy in thissector for the foreseeable future.Todate,alloffshorewind farms around theUK havehad fixed foundation turbines, andmostusemonopilefoundations,althoughjacketstructuresandgravitybasestructureshavealsobeenusedonoccasion.There is, however, a limited area of theUK continental shelfwhere fixed foundations are costeffective.Theneed forsuitablewindspeedsandshallowwaterhasmeant thatRound3sitesaremany kilometresoffshore. This is particularly true for theDoggerBank,Hornsea and EastAngliazones, Figure1.Asdistanceoffshore increases, sodoes the cost,both in termsof accessing andtransportinghardwaretothesitesandintermsofcablingcosts.The ETI believes that floating offshore wind farms would overcome many of the practical andfinancialchallengesofaccessinghighwindspeedsofftheUKcoast,statingWhilefloatingturbineshaveahighercapitalcost,theycanaccessneartoshore,higherwindsitesofftheWestcoastoftheUK. The studies showed that this access to high winds close to shore means they may be anattractive investment;especially compared to some Round3 siteswhichare locateda longwayfromshore inareasof lowerwind.Thesestudiesalso indicatedthattheglobalmarket for floatingturbinesislikelytobeconsiderable.TheGlostenAssociateshavepartneredwiththeETItodemonstratetheutilityofafloatingoffshorewind turbine termedPelaStar,withadeploymentdateof2016, looks set tobe the first fullscalefloatingwindturbinedeployedofftheUK.


Figure1UKRound3offshorewindfarmsites(Crowncopyright).


1.1 ThepurposeofthisdocumentCefashasbeencontractedbyTheGlostenAssociatestoprovideenvironmentalscientificadvicetoaid inthedesignprocessofthenew floatingwindturbinesystem.CefashassubcontractedSMRUMarine Ltd, theBritishTrust forOrnithology (BTO), andUniversityof Southampton InstituteofSoundandVibrationResearch(ISVR)tocomplement inhouseknowledge,andtogethertheaimofthisphaseof theprocess is tocarryoutadeskbasedstudy toexaminehow thePelaStar floatingturbinemightinteractwithandperhapsimpactthemarineenvironmentaroundtheUKcoast.Thepurposeofthispositionpaperistoformanexternallyfacingscientificevidencebaseandissplitintotwoparts.ThefirstpartfocusesontheenvironmentalconsiderationsofthePelaStaranchoringsystems.ThePelaStarturbineisbasedonatensionlegplatform(TLP),andwhereasTLPshavebeenwidelyusedwithintheoilandgassector,theyremainlargelyunknownwithinthewindindustry.Assuch, regulatorybodies that licenceoffshorewind activities areunfamiliarwith TLP turbines andtheiranchoringmethods.Thesecondpart focusesonkeyUKprotectedmarine faunaandhowtheymight interactwith thePelaStar turbine.Here, keymarine animals are defined asmarinemammals, basking sharks andseabirds,althoughtherearemanyothergroupsofprotectedanimalaroundtheUKcoast,includingfishsuchas lampreys,shadsandeels,marineturtlesandevenbats.However,itisthe larger,morevisibleanimalssuchasmarinemammals,seabirdsandbaskingsharks thatattract themostpublicinterest.Thereisgreaterscientificunderstandingofthelikelyeffectsofoffshoreactivitiesonmarinemammals,andseabirdsthanbaskingsharksandothergroupsofprotectedanimals.ThispaperdoesnotconstituteanEnvironmentalImpactAssessment(EIA),nordoesittaketheformofaScopingReportorEnvironmentalStatement.Inadditiontherehasbeennoconsiderationyetofanycumulativeeffectsofsuchdevices,asthesearedeemedtobeoutsidethescopeofthisreport.1.2 PotentialdevelopmentareasThe flexibilityof the PelaStar TLP designmeans that it canbe deployed in a varietyof locationsaround theUK coast, taking advantage ofwind resources that are currently out of the range ofanchoredwind turbines.Forexample,areason thewestcoastof theUK, inwaterdepthsgreaterthan50m,wheretherearehigherwindspeedscouldpotentiallybeacheaperalternativetocurrentUKproposedRoundthreesites(ETI,2013).Deploymentofsuchdevicesasclosetoshoreaspossiblewouldreducecablingandmaintenancecosts,and it isunderstoodthatseveralcriterianeedtobemet toensure floatingwinddevices are competitivewith competingoffshorewind technologies.Suchcriteria includewindspeed,distancefromgridconnections,andwaterdepth.Ofthese,windspeed (and the regularitywithwhich appropriatewind speeds are encountered) is probably themostcrucial.Windneeds tobeconsistent toensurea regularsupplyofpower.Windspeedsalsoneed to be great enough to drive the turbine efficiently, but not too high to trigger a safetyshutdownoftheturbine.Cablingcostscanformalargecomponentoftheexpenditureofanyoffshorewindfarm.Inordertoremain costeffective, theETIhas advised thatwind farmsneed tobedeployedwithina150 kmradius of a grid connection. Water depth is also key for TLPs; if the depth is too shallow, TLPtechnologybecomes impractical in termsofbothengineeringandof cost competition from fixedwindturbines;howeverwaterdepthsgreaterthan200marenottypicaloftheUKscoastalwaters.BVGassociatesandETIhavedefinedasetofparametersforselectingpotentialsitesfordeployingfloatingwinddevicesaroundtheUK(BVGAssociates,2013).BasedontherecommendationsoftheETI,wehaveconsideredareasaroundtheUKcoastthatmeetthefollowingconditions:


Meanwindspeedabovebetween9ms1 Within100kmofshore Waterdepthsgreaterthan50m

Theseareasareshown inFigure2. IthasalsobeenproposedtotesttheturbineattheWaveHubdemonstratorsiteoffthesouthwesterncoastoftheUK.


Figure2PotentialareasaroundtheUKcoastlineforaPelaStardeployment.Theareaindicatedisa)within100kmofthecoastb)experiencesaveragewindspeedsofmorethan9ms1andc)isatwaterdepthsofgreaterthan50m.


1.3 DesignThePelaStarturbineisastandardhorizontalaxisturbinemountedonatensionlegplatform(TLP).

Figure 3 PelaStar Tension LegPlatform (TLP)with standard tower, nacelle and rotor.Note the fivearmed hull, fiveanchorpointsandthesuspendedpowercable.

Abovethewaterline,thetower,nacelleandrotorsareessentiallythesameaswouldbeusedonafixed turbine (Figure3).Thedifferencesbetween thePelaStarTLPand the traditionallydeployedfixed turbine, however, are the floating platform, the power export cable and the anchoringmethods.ThemaincomponentsthatmakeupthePelaStarTLPdesignarethehull,tendonsandanchors.Thehulldesignhas five arms constructedofhighstrength steel.Attached to these arms are tendonsmadeupofhighperformancesyntheticropefibre.The lowerpartofthetendon isconnectedtoahighverticalload anchoring (HVLA) system. The anchors proposed for the majority of futurecommercial PelaStar deployments around the UK would be drivenpile anchors, and thedemonstratorPelaStarturbineisexpectedtobedeployedattheWaveHubsiteoffCornwallin2016.The substratum there is very different frommany areasof theUKs continental shelf, consistinglargelyofbedrock.Therefore,drilledandgroutedanchorswillbeusedattheWaveHubsiteandforsimilarrockyareasoncommercialdeploymentsinfuture.ThepowerexportcableofthePelaStarTLPissuspendedbelowtheplatforminanSshapebeforeitmeetstheseabed.Thereforeexposedinthewatercolumn,theexposedportionofthecableabovetheseabedwillbefairlyshort,arraycablesarethoughttobeburiedorheldtotheseabedtorestrictmovement.Thisdiffersfromfixedfoundationssuchasmonopilesandgravitybasestructureswherethecableisconcealedwithinthestructureuntilitenterstheseabed.ThePelaStarTLPisdesignedtobedeployedinwaterdeeperthan50m.Thefloatinghullremainsatthesameheightabovetheseabedasaconsequenceofthetension inthetendons, i.e. itdoesnotfollow tidalchanges inwater level.The turbinewould remain largely stationary,and the tendonsprovide a very stable platform in heave, pitch and roll, keeping the tower in a vertical position.Thereforeforthepurposesofthispaper,weconsiderthePelaStartobeastationaryobject.


2 Anchoring methods

ThemooringsystemstobeutilisedinthePelaStardesignareconsiderablydifferentfromthoseusedfor traditional fixed turbines.Herewe aim to highlight themain differences between anchoringproposed forthePelaStarTLPsandthoseusedforthemoretraditional fixedformofturbine.Twoanchoring methods have been proposed for the PelaStar TLP: drilled and grouted anchors, anddrivenpiles.Bothhavebeenusedto installoffshorewind farm foundations (monopiles),buthaverarelybeenusedforanchoringsystemssuchasTLPs.Thepurposeofthischapteristo:

Describethetwoanchoringmethodsproposed. Considerthekeyenvironmentalpressures theseanchoringmethodsare likely to raise, i.e.

seabeddisturbanceandunderwatersound.2.1 AnchoringmethodsAnanchoringsystemconsistsoftheanchor,themooringlinethattransmitsforcesfromthemooredplatform to the anchor, and an attachment pointor tensioning system on themoored vessel orplatform.Thesesystemsneedtobedesignedgeotechnicallyfor installationconditionsandholdingcapacityaswellasforstructuralstrengthand installationandsitespecificconditions(Elaheretal.,2003). Anchoring systems have been utilised extensively in the oil and gas industry to facilitateexploitationofresources indeeperwaters.TherenewableenergysectorisincreasinglyconsideringusinganchoringsystemsforfloatingTLPs,toanchortheirstructurestotheseafloor(seereviewsin(EWEA, 2013; Main(e) International Consulting LLC, 2013). However, to date none have beendeployedwithintheUK.TheuseofTLPmooringsystems isnovel foroffshorewind farms,so it iscrucial that the environmental effects associatedwith thesenewdesigns (where theymaydifferfrom those in the oil and gas industry) have been reviewed to provide an evidence base forregulators.Thiswilldecreasethe likelihoodofdelayduring the licensingprocess.Theuseofhighverticalloadanchors isappropriateforTLPsastheyareabletoholdhighvertical loadsandkeepafloating turbine in position. Anchors, or a combination of anchors, are selected on the basis ofsubstratum.Drilledandgroutedanchorsaremoreappropriateforbedrock,whereasdrivenpilesareutilisedforsoftsubstratasuchassilts,claysandsand.ThePelaStarTLPistobeattachedtotheseabedbyhighverticalloadanchors(HVLA)andtensionedtendons.Twooptions forHVLAshavebeenconsideredwithin this review. TheproposedPelaStardrivenpileanchoringsystemtobeusedformostUKwaters isexpectedtobedeployed insandtogravellysandseabed,buttheseafloorofthedemonstrationlocationproposedinthesouthwesternUK, at the Wave Hub experimental site, consists of bedrock formed by slate and sandstone ofDevonianCarboniferousform(BuscomeandScott,2008).Overall,thecharacteristicsoftheanchorsystem to be used, e.g. size, shape and installation method, depend on the seabed and suchenvironmentalconditionsasseafloortype,wind,waterdepth,wavesandtidalcurrents.

Option1:DrilledandgroutedanchorsDrilled and grouted anchors are more suitable for hard substratum seafloor conditions such asbedrock.Heretherearetwooptionswiththedrillingmethods,thedrillbitcaneitherbeextractedorcanformapartoftheanchorfittedtothetendonconnectionpadeye.Drilledanchorswilltake~40hper anchor to install, equating to ~8.5days in all, assuming a fiveanchordesign. The groutingwould take ~4060hper anchor (~813days), again assuming five anchors. The anchorswillbegroutedintoplacewithtypicalgroutofPortlandcementgrout(Glosten,pers.comm.).


Drilling will be carried out either from barges or subsea equipment. It is assumed that thedemonstratorwillutilisebargemounteddrilling equipment,but commercial installation in futuremayusesubseadrillingequipment.Option2:DrivenpipepileanchorsDrivenpileanchorsare likelytobethemostcommonanchorusedwherethehabitat is i.e.;softersandandgravel.Thepileanchorsaresteeltubeswithadiameterof2.13.7m(712ft)andare~2346m (75150 ft) long.Thepilesaredriven intotheseabedbyanunderwaterhydraulic(suchasaMENCK500or800orsimilar instrument).Whenthepile isdriven,asection is leftprotrudingfromthe substratum,which acts as a connection point to the tendons. For driven pile anchor pointswould likelyprotrudeapproximatelyonemetreabovetheseabed,drilledandgroutedanchorsarelikelytositflushwiththeseabed(subjecttoscour/depositionofsediment).Theinstallationtimeforthepilesisassumedtobe1.75pilesperday,equatingtoabout3daysforafivearmTLP.An alternative to impactpiling is vibropiling. There arehowever,nodata availableon thenoiselevelsofvibropilinginwatersdeeperthanshallownearshorewaters.Therefore,vibropilinghasnotbeenconsideredwithinthispaper.

2.2 ExamplesofsimilarmooringsBothdrivenpileanddrilledandgroutedanchoringmethodshavebeenusedwithintheoilandgassectorandarecommonlyusedtoanchoroilandgasTLPs,alongwithmostotherfoundationtypes.TLPsareaproventechnology,havingbeenusedwithintheoilandgas industryfor>30years,withthe firstoilandgasTLP (theHuttonplatform) installed in theNorthSea in1984 (Randolphetal.,2005). TLPs are now used in deepwater in theNorth Sea, theGulf ofMexico,WestAfrica andIndonesia (Randolphetal.,2005;www.floatec.com/images/posters/Offshore2010TLPPoster)andtogether with other floating and submerged systems have become the principle platforms forextractingoilandgasfromdeepwaterregions(JengandBrandes,2011).TLPsystemsrelyheavilyontheirmooringandanchoringsystems,sotheyhavebeentheobjectofmuch researchand investmentover thepast30years, toensure that thesystemsbeingusedarebothefficientandeffective(JengandBrandes,2011).DuggalandFontenot(2010)reviewedvarioustypesofpermanent (anchor leg)mooringsystems for theoilandgassector,evaluating longtermperformanceandmonitoringtechniques,andtheynoteddevelopmentsand improvements inboththesystemsusedandthemonitoringemployedovertime.Further,theyconcludedthatmostofthemooringsystemshadperformedwelloverthe30years.Drivenpileanchorsarecommonlyused in theoilandgas industry,offering reliableandpreciselylocatedpositioning (Musialetal.,2003;OregonWaveEnergyTrust,2009).However, inhardrock,drilling and grouting is the most effective method of anchor installation (Musial et al., 2003).Underwaterpiledrivingwasdeveloped inthe1980s(Randolphetal.,2005)and itdiffersfromthemoretraditionalvesselpiledriving,onlyintheadditionofamechanismtopileunderwater,e.g.theuseofapowerpackplaceddirectlyon thehammer (www.menck.com).Theuseofapowerpackeliminatestheneedforlonghydraulichosesthattraditionallylinkthehammerwiththepilingvessel.However, the principle of underwater piledriving remains essentially the same as for moretraditionalvesselpiledriving,i.e.thesystemusedcurrentlywithintheoffshorewindfarmsector.Theuseofdrivenpileanddrillandgroutanchoringsystemsisnotlimitedtotheoilandgassector,but isalsoused inotherpermanentmooring systems,e.g.mooringanoffshore ironore shipping


terminal(Gerwick,2007).Similartechnologiesexistwithinthecivilconstruction industry, insimilardepthstooffshorewinddevelopmentsites.Drillandgrouttechniquescanbeusedintheinstallationof bridges, piers, breakwaters and tunnels (www.pelastarwind.com/anchors). There are varioussystemsthatcanbeused,e.g.groutedsockanchoranddrillhollowbarsystems,buttheprinciplesremainthesamewhenusedincivil/onshoreconstructionsandintheoilandgassector.In termsof theoffshorewind industry,mostof the researchon floatingwindplatformshasbeendirectedatplatformdesignandstabilityratherthantheanchoringsystemsthemselves(MusialandButterfield,2004;MusialandRam,2010;ORECCA,2011).Thismaybebecauseanchoringsystemshavebeenused forsome time intheoilandgas industrysohaveaproven trackrecordwith fewchanges/adaptationsbeingrequiredfor implementation.However, it isalsopossiblethatthefocushasbeenplacedontheplatformsbecausemostoftheinnovativedevelopmentsarerequiredtheretoensurethattheturbinesremainafloatinallweatherconditions.Variousfloatingturbinesystemshavebeenproposedandare instagesofconceptualandexperimentaldesign.Alternativetypesoffloating platform (e.g. HyWind Spar design; www.statoil.com) can use different mooring andanchoringsystems(withanchortypedependingonwhethertherearemainlyhorizontalorverticalforcesoracombinationofthetwo).However,theGICONturbineproposestouseaTLP,andtankexperiments have tested a range of anchoring options.Although not detailed, those options arelikelytoincludedpiledrivenanddrillandgroutedanchors(www.gicon.de).Overall,althoughunderwaterpiledrivinganddrillandgroutanchoringsystemshavenotbeenusedextensivelywithintheoffshorewind farm industryyet,vesselbasedpiling (principallythesameasunderwaterpiling)isalreadycommontothesectorandunderwaterpiledrivinganddrillandgroutanchoringsystemsarewidelyusedwithintheoilandgasandcivilengineeringsectors.Floatingwindfarm research isheavily invested inplatformdesignoveranchoringmethods,whichsuggests thatdevelopersarecomfortablewiththetrackrecordoftheseanchoringsystems. 2.3 ComparisonbetweenfixedfoundationsandfloatingTLPanchoringThe aimof this section is todescribe thepotential impacts attributable to thedifferentoffshorewind turbine foundations and to compare them with those likely to be caused by floating TLPanchoring systems. In this section, we describe the major impacts of seabed disturbance andunderwaternoise(otherimpactsaredescribedin(Bremneretal.,2013)).Currently, floatingwind turbinesarestill in theexperimental stage (Lambkinetal.,2009;SanjeevMalhotra,2011;Reachetal.,2012),althoughdevelopmentandtestinghasbeenongoingsincetheearly 1990s (Henderson et al., 2002). Information on the likely effects of anchoring systems forfloatingwind turbineson the seabed anddeepwater is still scarce,and the same applies toTLPmooring systems. Therefore, the information reviewed here considers the PelaStar engineeringdesign details provided by The Glosten Associates (Moon III and Nordstrom, 2010; The GlostenAssociates,v.00andv.01,2012),aswellascurrentguidanceusedtoinformEIAstudiesonpotentialimpactsonthephysicalenvironmentattributabletooffshorewindturbinefoundationsforRound1and Round 2 developments (Lambkin et al., 2009), and relevant published papers and greyliterature.Ingeneral,theprincipaloffshorewindfarmfoundationtypesmaybegroupedasfollows(Lambkinetal.,2009;Reachetal.,2012):Monopilefoundations


Amonopileconsistsofa largediametercylindricalsteel tube (typicalpilediameter47m)withatransition piece connecting the pile to the turbine tower. Depending on the soil characteristics,monopilesarepredominatelydrivenintotheseabedandaresuitableforshallowwaterupto2535mdeep(relatedtoMeanSeaLevel,MSL).Theycanbeinstalledindeeperwater,butthatincreasesthe cost of development. An existing variant of monopile foundations for deep water is guyedmonopile towers, allowing the monopile to be stabilized with tensioned guy wires (SanjeevMalhotra,2011).

Gravitybasefoundations(GBF)Gravitybasefoundationstypicallyconsistofaslendersteelorconcretesubstructuredesignedtobeheldinplacebygravity.Thedesigndependsontheapplication,hydrodynamicregime,waterdepth(normally shallow todeepwater


inthewatercolumnwillfalltotheseabed.Therefore,aseabedsedimentdisturbancezonewillbecreated inahaloaroundthedevicebetweenthe locationswherethecablesarerepeatedlyraisedfromtheseabed(Figure4).Thesizeandshapeofthedisturbancehalowilldependonthenumber/designof thecatenarycablesusedand the frequency,magnitudeanddurationofwaveor tidalevents.

Figure4Schematicpresentationofa catenarymooringdisplaced (fromposition1 to2)bywaveor tidalaction (redarrow).Resultantdisturbanceoftheseabedbyraisingor loweringofcables/chainsystem isshownasa"halo"withintheanchoringsystem.

Todate,monopileandgravitybasefoundationsarethemostcommonlyusedstructuresinoffshorewind developments in the UK; multileg foundations and jacket foundations have been usedextensivelyover thepast40years in theoilandgas industry (Reachetal.,2012)and toa lesserextent inoffshorewinddevelopments.Only the impactsof seabeddisturbanceandnoisewillbereviewed in the following sectionsas theseare themost relevant in the comparisonofTLPsandmore traditional fixed turbines. For a wider evaluation of possible impacts is contained within(Bremneretal.,2013).2.3.1 SeabeddisturbancePotentialimpactsontheseabedassociatedwithfixedfoundationsorfloatingmooringsystemsdifferforthestagesof installation,operationanddecommissioning.Likelyeffectsontheseabedneedingto be assessed during the installation phase are those caused by seabed preparation activities(temporaryhabitatloss),orthosecausedbythetechniquesusedforinstallation(i.e.drilling,suction,jetting or hammering). Those activities, also depending on soil condition, are likely to create anincreaseinsuspendedsedimentconcentration(SSC),formationofsedimentplumesandchangesinseabed level. Duringtheoperationalphase,offshorewindturbineswill leadtoscouringcausedbythe foundations in termsofseabeddisturbanceaswellaspotentialchanges tothehydrodynamicregimeasaresultofblockageeffects.Consequently,potentialvariationsinwaveandtidalcurrentsmay change the sediment transport regime and potentially, (for example) impact the form and


functionof anynearby sandbanks.Changes in the sediment transport regime can impacton theconservation designation associated with Natura 2000 sites and/or Marine Conservation Zones(MCZs).Thepotentialeffectsduringdecommissioningofoffshorewind turbinesmaybesimilar tothosecausedduringinstallation,buttheywillberelatedtothetypeoffoundationusedbecauseoftheinherentdifficultyinremovingtheentirestructurefromtheseabed(i.e.thepiles).The study conducted by Reach et al. (2012), based on a review of marine environmentalconsiderations associated with concrete gravity base foundations (CGBFs) in offshore winddevelopments, provides an overview of the generic effects related to the different foundationoptions.Insummary,seabedpreparationactivitiesintermsoftemporaryhabitatlosshavealowtohigh impact intermsofGBFs,amoderate impactbysuctioncaissons,a low impactbymonopiles,multileg and jacket, and negligible to low impact for floating offshore wind platforms. Theenvironmentaleffectsattributabletoscourprocessesarehighformonopiles, lowtomoderate forfloating wind foundations and low for GBFs, multileg, jacket and suction caisson foundations,because they have the requirement to use scour protection as a mitigation measure. Seabedfootprintassessed intermsofhabitat losshasGBFs,multileg,jacketandsuctioncaissonshavingahighenvironmentalimpact,monopileshavingamoderateimpactandfloatingturbinesalowimpact.Finally, environmental impacts attributable to blockage effects are high for jacket and suctioncaissons, moderate to high, depending on the diameter of the design, for GBFs and multilegfoundations,moderateformonopiles,andnegligibletolowforfloatingwindturbines.With regards to the PelaStar TLPdesign, the installationmethodsdescribed (section 2.1) do notrequireseabedpreparation.FurthermoreaTLPstructuresuchasthiswouldnotrequireacatenarymooring system (eliminating the halo effect described in section 2.3 (Figure 4)), which wouldminimise thepotential impacts to theseafloor.Temporary seabeddisturbance isexpectedduringtheinstallationphaseastheanchorpenetratesthesedimenttotherequireddepth;whichislikelytocause temporary habitat loss and sediment disturbance for sand, gravelly sand, silt and clay soilsubstratumconditions.A5mdiametermonopilehasa20m2footprintontheseabed,comparedto18m2forfive2.1mdiameterpiledanchorsand54m2forfive3.7mdiameteranchors.Assuchthepotential environmental effect attributable to TLP installation are comparable to monopilefoundationsif2.1mdiameterpilesareused,butwillbesignificantlymoreiflargerdiameteranchorpiles areused.During theoperationalphase, scour effects around the anchoringpointsof a TLPwouldbe limited inhardsubstrata;theseabedfootprint intermsofhabitat losswouldbe low. Todate, blockage effects have not been identified. In soft sediments scouring is possible. For thesmallerdiameterpiles(2.1m)potentialscouringaroundthefiveanchorswouldbe lessthana5mdiameter monopile (but higher levels would be expected for five 3.7 m diameter piles). Theenvironmentaleffectsduringdecommissioningwilldependontheanchoringsystemutilised,butwillbesimilartothosecausedduringinstallation.2.3.2 UnderwatersoundTheanchoringpilesoftheTLParenotverydifferenttomonopilesusedintheNorthSeawindfarms.Thesourcelevelassociatedwithdrivingthesepilesislikelytobeintheregionof250dBre1Pa@1mbutwilldependonthesizeofpileused.WithTLPpilediametersvaryingfrom2.1mto3.7m,TLPpilenoiseshouldfallsomewherebetweenthenoiseexperiencedfortraditionaljacketpinpiles(smallerthantheTLPpilesproposed)andmonopiles (biggerthantheTLPpilesproposed).Gravitybase foundationdonot requirepiledriving aspartof their installation, thereforehavenotbeenconsidered but construction noise effects are likely to be significantly lower than TLP, jacket ormonopilefoundations.


Two different methods are proposed for installing the TLP anchoring systems, respectively piledrivingordrillingandgrouting.Theevidence isthatdrilling issignificantlyquieterthanpiledriving.However,whencomparingthetwoprocessescarehastobetakenthatthepilingnoiseisexpressedindifferentquantitiestothatofthedrillingnoise.Therearesomemoresubtleeffects,associatedwith thedrillingprocess,which shouldbeconsidered.Specifically, the tonalqualityof thedrillingnoise issuchthat itmaybeaudibleoversignificantranges.The levelsofsuchsoundswillfallwellbelowany thresholds forbehavioural response currently inuseand sowouldnotbeexpected toelicit a strong reaction. However the longer duration of the installation process associatedwithdrillingwillrequireactivityatthesiteforagreaterperiodoftimeandthesupportvesselscouldwellproducenoise thatexceeds thenoiseof thedrilling itselfacrossmostof the frequency range. Inaddition,thegreaternumberofpilingeventsrequiredforthePelaStardesignmeanthatthenoisemaybeemittedmoreoftenand/orforalongeroveralldurationthanforfixedarrays(fivepilesperturbine,comparedwithoneforamonopileandupto4forjackets).The operational noise from a floating wind turbine is expected to be reduced relative to aconventionalturbineasaconsequenceof itnotbeingrigidlyattachedtotheseabed,soremovingone couplingmechanism.However, there isapotential for strumming (causedbywatermovingpast the undertension tendons of the PelaStar design). Strumming noise is likely to be at a lowfrequencyifatall,Strummingwillbeminimisedduetolowtidalcurrents.Thedecommissioningphaseforthetwoanchoringmethodsislikelytoinducesimilarlevelsofunderwaternoise.


3 Floating TLP turbines and UK protected species

ManyUKmarineanimalsareprotectedbyUKandEuropeanlegislation,e.g.theEuropeanHabitatsDirective (92/43/EEC) and European Birds Directive (2009/147/EC). Animals include marinemammals(whales,dolphinsandseals),seabirdsandseveralspeciesoffish(suchaslampreys,shadsand salmon), sharks such as the basking shark, turtles and bats. Fish, turtles and bats are notconsideredhere.Theeffectsofoffshorewinddevelopmentsonprotectedfishspeciesarestilllargelyunknown(seeGill,etal.,2012,andMuellerBlenkleetal.,2010forfurtherdetail),andtheeffectsonturtles and bats are emerging issueswith very little publishedmaterial. Additionally, the limitedinformationavailableonthepotentialeffectsofoffshorewindturbinesonturtlesandbatsdoesnotsuggest thatanyeffectswouldbeunique to floating turbines (seeAhlnetal.,2009; Ingeretal.,2009).Marinemammals,seabirdsandbaskingsharksareofbothpublicandscientific interest,andmanyquestionsstillremainabouttheirpotentialimpactswithoffshorewindfarms.Formarinemammalsthere is a perceived (as opposed to a proven) concern that certain species might be at risk ofbecomingentangledwithinthetethersofafloatingplatform.Therefore,theavailableliteraturehasbeen reviewed to determinewhether this is simply a perceived concern or a risk supported byevidence.However,formarinemammals,thebiggestconcernisunderwaternoise.Intermsofseabirdsthequestion ishowbirdsmightrespond/interacttoafloatingturbine (i.e.dosea birds show attraction or avoidance behaviour, therefore resulting in increased or decreasedcollisionrisk.Wouldaheavilybiofouled/colonisedfloatingstructureprovideafoodsourceforlocalseabirds?Thisquestionhasbeenconsidered,alongwiththepossibilitythatattractiontoafloatingturbinemightincreasetheriskofcollisionwiththeturbinerotors.Furthertothis,dothetethersoftheTLPposeanyotherthreattodivingbirds?Baskingsharksareahighlymigratorycoastalpelagicspeciesthatiswidelydistributed inUKwatersandoffIrelandandnorthernFrance(Goreetal.,2008).CornishandScottishcoastalregionsarewellknownhotspotsforbaskingsharks,wheretheycanbeobservedatthesurfaceingroupsfeedinganddisplayingcourtship,mostnotablyaround theLizard, the IsleofMan, theHebridesand theClydeSea(Sims,2008;Speedieetal.,2009).Baskingsharkshavebeenincludedherebecausetheproposeddevelopmentareas,bothatWaveHubandatfuturePelaStarcommercialdeployments,arelikelytooverlapwithbaskingsharkmigrationroutes(seeFigure2andFigure5).Aswithmarinemammals,entanglementandconstructionnoiseareperceivedconcerns,but there isalso thequestionas tohowabaskingsharkmightrespondtoelectromagneticfields(EMFs)fromsuspendedpowercables.Inall cases,wehaveonly consideredmarine animals thatare likely tobepresent inornear thepotentialdeploymentareasofaPelaStarturbine(Figure2).3.1 MarineMammals3.1.1 IntroductionAseriesofmappingprojectsdocumentthebroadspatial(and insomecasestemporal)patternsofmarinemammaloccurrencearoundtheUK.(Baxter,etal.,2011;Reid,etal.,2003)Incontributingtotheassessmenthere,thefollowingdatasourceswereexplored: General(Baxter,etal,2011)Cetaceans(Reid,etal,2003).


Seals SCOSReports:ScientificAdvice(www.smru.standrews.ac.uk/sealpopulations) Greyandharboursealusagemaps

(www.scotland.gov.uk/Topics/marine/science/MSInteractive/Themes/sealdensity)BelowisatableofthekeyandmostcommonspeciesthatoccurconsistentlyaroundtheUK.

Speciesname LatinnameGreyseal HalichoerusgrypusHarbour/commonseal PhocavitulinaHarbourporpoise PhocoenaphocoenaShortbeakedcommondolphin DelphinusdelphisBottlenosedolphin TursiopstruncatesWhitebeakeddolphin LagenorhynchusalbirostrisAtlanticwhitesideddolphin LagenorhynchusacutusRissosdolphin GrampusgriseusKillerwhale OrcinusorcaLongfinnedpilotwhale GlobicephalusmelasMinkewhale BalaenopteraacutorostrataHumpbackwhale Megapteranovaengliae

3.1.2 ConstructionnoiseThe issueofunderwaternoisefromconstructionhas longbeenaconcernformarinemammals,sotheriskofunderwaternoiseassociatedwithmarinemammals isrelativelywellstudied. ThemostwidelyadoptedframeworkforassessingtheeffectofnoiseonmarinemammalsisthatproposedbySouthalletal. (2007). Thisworkproposes theuseofweighting functions, in thesame formasCweightingcurvesforhumans.Inparticularthegroupsare:highfrequencycetaceans(e.g.porpoises),midfrequencycetaceans(e.g.dolphins),lowfrequencycetaceans(baleenwhales)andpinnipeds(inairand inwater). WaveHubsitethemostcommonlyencounteredspecieswillbe included inthehighfrequency(hf)cetaceangroupandmidfrequency(mf)cetaceans,alongwithpinnipeds(p).Theweightingcurvescanbeusedtocomputeweightedsoundlevels.Southalletal. (2007)alsoproposedassociatedthresholdcriteria fortheweighted levels for injury(hearinglosspermanentthresholdshift(PTS))andforbehaviouralresponse.Thesethresholdsforexample,forinjuryweightedSELs(soundexposurelevel)of198dBhf,mf,alongwith186dBp,whereasforbehavioural responses the183dBhf,mfand171dBp. Whilst themethodologyofconstructingametrichasgeneralacceptance(althoughmostwouldprobablyacceptitisnotcomplete)thevaluesforthestatedthresholdsarelesswidelyaccepted.InparticularthresholdsforPTSarenotconsistentwith subsequent observed findings that show the (Lucke et al. 2009) temporary threshold shifts(TTS)canoccuratlevelswhichareroughly20dBbelowthoseimpliedbySouthalletal.(2007).An alternative approach is that adopted by the German Government where a threshold for anunweightedSELof160dBre1Pa2sisappliedat750m.Anotherapproachwhichhasbeenapplied,especially within a UK setting, is the dBht. This uses the audiogram of a species to compute aweightedthreshold. However,themethodsuffers froma lackofstandardisationand itsscientificfoundationisnotwidelyaccepted.Asdescribedinsection2.1,twopotentialinstallationmethodswillbeusedinanchoringthePelaStardevice, one using a drilling/grouting technique and another utilising a piledriving approach. Formarinemammals, thenoisegeneratedbydrillingandgroutingmaycause smallscaledisturbance


aroundtheinstallationsite,andawiderangeofspeciescouldencounterthedevicewhereitislikelyto be deployed commercially, ranging from lowfrequency specialists, e.g.minke and humpbackwhales, to highfrequency specialists, e.g. harbour porpoises. However, the noise levels fromdrilling/grouting are likely tobe low (sowouldpropagate lessdistance in thewater) and canbeapproximated to the noise generated from amedium sized vessel (Robinson and Lepper, 2013).Moreover, the noise generated by installation vessel thrustersmay bemore disturbing than thedrillingitself.Also,itislikelythatanydisturbanceordisplacementwouldbeshortterm(installationtends to be fairly swift, albeit longer than is estimated for piling) and small scale (becauseinstallationnoise isnot great). It is thereforequestionablewhether suchnoisewouldbe able tocauseauditoryinjurytomarinemammalspeciesthatarelikelytoencountertheconstructionnoisefield.The noise generated by piledriving installationwould, however, be likely to have an impact onmarinemammalsinthevicinity.BasedonthereportednoiselevelsprovidedbyMenck(e.g.>190dBpeakSPL750m fromthepile),the impactranges (auditory injury,behaviouralresponse,masking)may be as large as or even greater than those for fixed foundation wind turbines. An impactassessmentwouldprobablybeable topredictwithsomeaccuracy the impact ranges forauditoryinjury foreach species/speciesgroup,butbasedon currentunderstanding from fixed installationoffshore wind farms, there is potential for them to be significant. For marine mammals, theinstallationscenariodescribedforPelaStarislikelytocausedisturbanceoversignificantranges.Thisisbecausemarinemammalshave excellentunderwaterhearing and theunderwaternoise levelsgeneratedaspartofthepiledrivinginstallationmethodwillbehigh.Behaviouralavoidanceofsiteswhere piles are being driven has been observed for many species of marine mammal (e.g.Carstensenetal.,2006;Edrenetal.,2010;Brandtetal.,2011).Theextent towhichanimalsaredisturbedorperhapsdisplacedwilldependon factors including (butnot limited to)noise sourcecharacteristics,watercolumnproperties,bottomsedimenttype,thediameterofthepilesandthedurationofpiledrivingoperations.3.1.3 OperationalnoiseThepotentialfornoisetobegeneratedfromstrumming(causedbywatermovingpasttheundertensiontendonsofthePelaStar)requiresconsideration.Asnotedabove,there isthepotential forseveralspeciesofmarinemammaltobefoundadjacenttoPelaStartypeinstallations,rangingfromlow frequency tohigh frequencyspecialists.Strummingnoise is likely tobeata low frequency ifatall,Strumming will be minimised due to low tidal currents. The levels and temporal component of suchsoundswillneedtobeassessedfurther.Thepotential forunderwaternoisetobe introduced intothewatercolumn from fixed foundationwind farms has been assessed before (e.g.Nedwell et al., 2007;Marmo et al., 2013): themaintransmission route for suchoperationalnoise is via the foundation into thewater column. If thenoisetypesgeneratedbyPelaStararesimilar(i.e.fromthegearboxandotherhomologouselementsof the technology), then itmaybepredicted that theoperational turbinewillbeaudible tomostmarinemammalsaboveambientnoise(dependingonthelocationoftheturbineandambientnoiselevels)andinsomecasestherecouldbepotentialforbehaviouralavoidance.Basedonsuchstudiesaroundfixedinstallationsites,itishighlyunlikely,however,thatmarinemammalswouldexperienceauditory injury from the noise levels generated by PelaStar devices. However, the operationaloutputsofafloatingPelaStarunitwouldneedtobeassessedandmonitoredbeforeafullevaluationofthepotentialimpactscouldbeaddressed.


3.1.4 EntanglementMany species of baleen whale have been entangled in the subsea ropes of static fishing gear(Northridgeetal.,2010), thiscauseofmortalityaccounts forapproximately50%ofbaleenwhalemortalityoff Scotland (Northridge et al., 2010). Fishing gear (e.g. lines and traps) tends tobeoflighterconstructionthanthatusedfortetheringTLPs,thoughthe interactionsofmarinemammalswith aquaculture and static fisheries (e.g. creel fishing)may be analogous to thosewith subseastructuresofTLPs.Thecables/tetheringitselfmaybetoolargetoposeanentanglementthreat,butthere could be similar issuesofwhales interactingwith them, representing a collision and/or anentrapmentrisk.3.1.5 DatagapsThe following have been identified as data gaps in terms of what is known about how marinemammalswillinteractwithPelaStardevices:

pollution increasedturbidity/suspendedsediments impactsthedevicesmayhaveonmarinemammalpreyspecies thepotentialforbarriereffects/habitatexclusion whetherthedevicesmayactasFishAggregatingDevice(FADs) sealmortalityfromductedpropellersusedonvesselsattheinstallationorservicingphases

There is the risk that construction activity might increase the turbidity of the water column.Increasedturbiditycanaffectsocialinteractionsandforagingefficiencyofmarinemammalsandmayalso affect the prey species. The potential magnitude of such an impact is, however, currentlyunclearandwilldependonthecharacteristicsofthelocalenvironment(i.e.waterflow,seabedtype,etc)inthedevelopmentarea.However,itisbelievedthattheseimpactswillbeshortlivedandoverasmallspatialscaleonly.Once theunitsare installed, it ispossible that,while smallandbenign, thearraycouldpresentabarrier (either realorperceived) to animalsor result inhabitatexclusion. It isnot clear towhatextent this phenomenon exists at this scale orwhether the TLP technology could cause such aneffect.Anassessmentof thenoisegeneratedby thedevicesonce installedandoperationalcouldinformfutureassessments.Thepotentialforafloatingstructuretoattractpelagicfishiswelldocumented(Castroetal.,2002),soTLPdevicesmaywellserveasaFAD.Thisprocesshasthepotentialtogenerateanenrichedornovel foraginghabitat formarinemammals,and theenhanced attractionofmarinemammals tothe devices may increase their risk by increasing their exposure to collision, entanglement,contamination,etc.ThepotentialbroadscaleimpactsofFADsdoneedtobefurtherconsidered.One emerging issue identified is the interaction seals have with vessels with cowled or ductedpropellers (SCNA,2012).Many sealshavebeenkilledby corkscrew injuries (adescriptionof thewound likely caused by animals being rotated past a propeller; Thompson et al., 2010).Consequently, if the use of vessels with such propellers is planned for the construction andoperational(intermsofmaintenance)phases,thiswillbeanareaoffurtherconsiderationinfutureassessments.


3.2 BaskingSharks3.2.1 IntroductionThebaskingshark(Cetorhinusmaximus)isthelargestfishspeciesinUKwaters,attaininglengthsupto 11m andweights of up to 7 t.During spring and summer, basking sharks tend to aggregatearound the coastsof southwest andnorthwestUK.Within such temperatewatersof continentalshelves, theyareoftenseen baskingat theseasurfaceclose toshore, typicallywith theirsnout,dorsalfin,caudalfinandbackpartlyexposed(BerrowandHeardman1994;Simsetal.,1997).To feed, basking sharks favour transitional waters between stratified and mixed water columns(thermal tidal fronts),actively selectingareas thatcontain thegreatestdensitiesof largecalanoidzooplanktonprey (mainly thecopepodCalanushelgolandicus;SimsandQuayle,1998;Simsetal.,2006). Swimmingwith theirmouths open, they capture prey in thepassive flow across their gillarches,a strategyknownas ram filterfeeding (Sims,1999;Compagno,2001).Ram filterfeedingallowsupto2000tofwatertobefilteredperhour(FAO,2005),socanbehighinpotentialenergycontent;basking sharks thereforeneed toactively selectand remainwithinareasof thegreatestzooplanktonconcentrationstopreventfeedingatanenergeticloss(Sims,1999).Basking sharksarehighlymigratorycoastalpelagicspecies thataredistributedallaround theUK,IrelandandnorthernFrance (Goreetal.,2008).WithinBritishwaterstheyhaveastrongwesterlybiastotheirdistribution,withsightingdensitieshighestoffCornwallandScotland,bothwellknownhotspotswherebaskingsharkscanbeseenatthesurfaceingroupsfeedinganddisplayingcourtship(mostnotablyaroundtheLizardandtheHebridesandintheClydeSea;Simsetal.,2005;Sims,2008;Speedie etal.,2009). Surface sightings areusually recordedbetweenApril andOctober,peakingfrom June toAugust, periods that appear to be correlated significantlywithwarmer sea surfacetemperatures (SST) and the occurrence of theNorth AtlanticOscillation (NAO), an atmosphereoceanclimatephasethoughttocauseanincreasetheabundanceofthepreferredzooplanktonpreyofbaskingsharks (Wittetal.,2012).Literature (Simsetal.,2005;Southalletal.,2005;BloomfieldandSolandt2008;Wittetal.,2012)andFigure5showthatbaskingsharksfavourtheareaaroundtheWaveHubdemonstrationsiteandwillcertainlymigratethroughanyofthepotentialareasforPelaStarcommercialdeploymentonthewesternsideoftheUK.


Figure5a)Thedistributionof9,470individualbaskingsharksightingsaroundtheUKandIreland,plottedassinglereddots,b)samedata,plottedassightingdensityper10km2grid,tohighlightthegreatestdensitiesonthewestcoastofScotland,aroundtheIsleofManandoffsouthwesternEngland(fromBloomfieldandSolandt,2008).

3.2.2 ElectromagneticfieldsElectromagneticfields(EMFs)areproducedbyelectricallychargedobjects.Theyareacombinationofelectrical fields (createdbyvoltageoranelectricalcharge)andamagnetic field (createdbyanelectricalcurrent).EMFsarepresent throughout themarineenvironmentandpresent inall livingorganisms(Kalmijn,1982).SharkshavethegreatestelectricalsensitivityofanyanimalandaregenerallyassumedalsotousetheEarthsmagnetic field fornavigationandtobeabletodetectandrespondtootherbioelectricfieldsencounteredwithintheirmarineenvironment.Usingsmall,poreshapedcanals(theAmpullaeofLorenzini, tinyelectrosensorypores), thatpepper theirsnoutsandheads,sharkscansense thetiniestEMFsemittedbypotentialpreyspecies(Kalmijn,1982).Forbaskingsharks,itisthoughtthatthe spacing and orientation of these pores within their snout enables them to use passiveelectroreception to guide them towards dense zooplankton assemblages (Kempster and Collin,2011).Subsurface marine electrical cables for offshore renewable installations produce EMFs into themarine environment as electrical currents move through the cable. These currents have beenestimatedtoemitEMFs intothesurroundingwaterupto17mperpendicularfromtheaxisofthecable(Gilletal.,2005).TheseanthropogenicEMFscanbealteredbyshieldingthecables,whichwillhelp to contain theelectrical field,butnot themagnetic field componentof theEMF.Therefore,


whenachargedparticle,suchasamarineorganismora tidalmovement,crosses thepathof theresultingmagneticfield,afurthermomentaryelectricfieldcanbegenerated.ForallUKmarinespecies thataresensitive toEMFs, it isevident thatcurrentknowledgeof theirinteractionwith anthropogenic EMFs is limited and highly speculative; knowledge of the use orsensitivity toEMFsofbasking sharks remains largelyunknown.Basking sharks certainlyhave thecapability to detect and react to anthropogenic EMFs transmitted through electrical cablesassociated with new TLP or other renewable energy developments, but there is currently noliterature availableonwhether they actively respond to these artificial EMFs,norwhether theremightbeanynegativeimpact.3.2.3 ConstructionnoisePilingoperationsforTLPsarelikelytobetheprincipalsourcesofnoiseanddisruptionthatmayhaveanimpactonbaskingsharkswithinandadjacenttoconstructionareas.Thisstatementisparticularlyimportantbecause the anticipated installationwindow forTLPs is likely tobebetweenApril andOctober,when theweatherconditionsarebestandbaskingsharksaremostabundantat theseasurfaceoffsouthwesternEnglandforaginganddisplayingcourtship.Few studies have considered the potential impact of piling activities on sharks, and hearingcharacteristics of basking and other shark species remain largely unknown. However, sharks areknown to have welldeveloped hearing and there is evidence that they can and do detect andrespond to sound, with sound playing a major role in their lives (Myrberg 1978, 1990, 2001).Moreover, Casper and Mann (2009) and Casper et al. (2012) recently determined the hearingbandwidths of four species of shark; Atlantic sharpnose (Rhizoprionodon terraenovae), horn(Heterodontusfrancisci),lemon(Negaprionbrevirostris)andnurseshark(Ginglymostomacirratum).Hearing rangesweremeasured from 20 Hz to 1 kHz, despite sharks not having an internal gaschambersuchasaswimbladderorothergasbubbleassociatedwiththeirhearing(commonlyfoundin other fish species). Suchmeasurements give an indication of thepotential hearing range thatbaskingsharksmayexhibit,butcautionneedstobeappliedsincesuchdataarecurrentlytheonlysource for future environmental assessments of TLP construction activities.Note, however, thatgiven the lack of a swimbladder or gas chamber in basking sharks, and other shark species, thepotentialforsignificantphysiologicaleffectsassociatedwithconstructionnoisesuchasbarotrauma(physicaldamagetobodytissuescausedbyadifferenceinpressurebetweenagasspaceinternally)shouldbesubstantiallylessthanforotherfishspecies.Themostimportantconcernforbaskingsharksishowpilingandanchoringoperationscanaltertheirnatural behavioural response or mask other natural marine noise on which they may rely.Constructionnoisecanmasknaturalmarinenoise involved in zooplanktonpreycapture, seasonalcourtshipandeffectivesafenavigationaroundTLPandotherdevelopments.Also,withinthevicinityofTLPs,suchnoisemaydisruptbaskingsharks fromseekingoutand feedinghighdensityareasofzooplanktonwithinthevicinity,forcingthemtofeedinlessproductiveareasatanenergeticlossandultimatelyinfluencingpopulationsurvival.Giventheargumentsabove,carefulconsiderationneedstobegiventotheproposedpositioningofTLPs,toprecludetheirdeploymentinimportanthotspottidalfrontareaswithhighseasonalsurfaceabundanceofbaskingsharkaggregationsaroundtheUKcoasts(notablyaroundtheLizard,thewestcoastoftheIsleofMan,theHebridesandtheClydeSea).


Baskingsharksare,however,highlymobileandadaptiveandhavebeenpreviouslyobservedtoshifttheirhabitatsinresponsetochangesinrelationtootherenvironmentalchangesinzooplanktonpreyabundance(SimsandReid,2002).3.2.4 EntanglementBasking sharks are thought to be particularly susceptible to collision with vessels and marineconstructions.Surfacefeedingsharksrarelyshowareactiontoapproachingvessels,oftenappearingunawareofthepresenceofpotentialsurfaceobstacles (Speedieetal.,2009).Baskingsharkshaverelativelypoorvisionandhavebecomeentangled infishinggear(Valeirasetal.,2001).Theeffectscanrangefromminorscarringtodeath.Entanglementinsetnets(suchasgillnets)iscommon(Doyleetal.,2005),andwithintheCelticSeaalone isthoughttoresult in77120baskingsharksannuallybeingkilled (BerrowandHeardman,1994).However,other static fishinggear suchas lobsterpotheadropeshavealsoentangledandkilledbaskingsharks(BloomfieldandSolandt,2008).Entanglement in TLP anchoring tendons and electrical cables might well increase the levels ofphysical injuryoraccidentalmortality inbaskingsharks.It is importanttostressherethatTLPswillpresent a new obstacle for basking sharks and othermarine species unlike anything theymightpreviouslyhaveencountered.Basking sharksaregenerally slowmovingandbecauseof their sizeandseasonalbaskingbehaviouratthesurface,haverelativelylimitedmanoeuvrability,puttingthemat high risk of collision and entanglement. The potential risk of collision for basking sharks willdependlargelyonthevisibilityandthelevelofnoiseemittedbyTLPs,thebodysizeoftheindividualfish, its levelof social interactionand foragingactivity,and thequantityandqualityof tidal frontconditionspresentatorwithincloseproximitytotheproposedsites.3.3 Seabirds3.3.1 IntroductionOffshorewindfarmshavethepotentialtoaffectbirdsthroughfourmainmechanisms(LangstonandPullan2003;DrewittandLangston2004;Petersonetal.,2006),althoughtheydonotallnecessarilyapplyateachofthephasesofconstruction,operationanddecommissioning:

Collision risk (assumed mortality) with abovesurface structures, especially wind turbineblades(traditionallyonlyduringoperation,butpossiblyalso iftestingofturbines iscarriedoutduringconstruction);

Disturbance and the displacement of birds from favoured habitats,which could result inincreasedmortalityorreducedproductivityofseabirdpopulations(allphases);

Effectsassociatedwithhabitatlossandchange,e.g.changes intheseabedthatwhichmayaffectbirdsthroughchangestopopulationsoftheirpreyorpreyavailability(allphases).

Barriereffectstomigratorybirdsorthosecommutingbetweenbreedingsitesandoffshorefeedingareas,whichcouldpotentiallyresult inelevatedenergycostsandhence increasedmortalityorreducedproductivity.

Keyissuesforconsiderationofeffectsassociatedwitheither(a)or(b)areseabirdspeciessensitivitytotheeffectconsidered(Furnessetal.,2013,TableA1inappendix),thespeciesassemblagespresentatsea,andtheseabirdpopulationsnearbythatarewithinforagingrangeatthetime(s)ofyearthatthevariousphasesof construction,operationanddecommissioning takeplace (Skovetal.,1995;JNCC,2012,2013;Thaxteretal.,2012).


3.3.2 CollisionRiskCollisionriskisthelikelihoodofseabirdscollidingwithabovesurfacestructuressuchaswindturbineblades,withtheoutcomeassumedtobemortality.Calculationofthecollisionriskusesinformationonthenumberofbirds inthesurveyarea,followingthestandardmethodologyof(Camphuysenetal.2004),minusthoseexpectedtoavoidthewindfarm,togetherwithspeciesbiometricdataandturbinespecificdataforawindfarm,toestimatetheprobabilityandhencethenumberofbirdsthatmight be killed through collidingwith a structure. This calculation is traditionally done using theacceptedBandmodel,updatedfortheoffshoreenvironment(Band,2012).Theassessmentofcollisionrisk is importantnot justforbreedingseabirdsoriginatingfromnearbybreedingcolonies,butalso forthosethatmaypassthroughduringmigrationandduring thenonbreeding season.Formigrants, collision risk isbest informed through considering likelymigrationroutes,usingrecentlydevelopedtoolsthatcangeneralisethe likelyareasthroughwhichbirdsofaparticularspeciesmightmigrate(Wrightetal.,2012seeFigure6asanexample)andthenmodelthenumberslikelytopassthroughthewindfarm.

Figure6MigrationzonesofBewicksswansvisitingBritainandIreland(darkblue)andIrelandonly(lightblue)fromWrightetal.(2012).BluedotsshowSpecialProtectedAreas(SPAs)forBewicksswans.

TheTLPturbineissimilarinabovewaterdesigntothatofatraditionalmonopiledesign.Hence,theoverallriskposedtoindividualspeciesislikelytobesimilartothatreportedelsewhereformonopileturbines,andthestandardBandmodel(2000),modifiedforuseintheoffshoreenvironment(Band,2012;Cook etal.,2012), is applicable, assuming thatotherparametersof the TLP andmonopiledesignsaresimilar,forinstancerotationspeed(e.g.upto8.8rpm)andapitchof10degrees.


Thedemonstratorturbinewill likelybetested intheharbourbeforebeing loweredtoahorizontalposition and loaded onto a transporter vessel to be deployed in place at the Wave Hub site.However, the rotation speed of the rotor during testing will be minimised to avoid powergeneration. Despite the rotation speeds being lower, any test undertaken in a harbour wouldconstituteanadditionalcollisionriskforseabirds.Duringthetestingphase(althoughitisnotedthatthisphasewouldbeshortterm),considerationwouldneedtobegiventopopulationsofseabirdsinthevicinityoftheharbour,includinganyprotectedpopulations(includinglocationoftheircoloniesandforagingranges;Figure7).Collisionriskalsoappliestootherwaterbirds(Cooketal.,2012),ofwhich theUK holds internationally important numbers,mainly during their nonbreeding season(Holtetal.,2012).Asaconsequence,informationonimportantwinteringsitesofwaterbirdsnearbyandthepassageofsuchbirdsthroughorovertheharbourwouldneedtobeconsidered.Figure7Exampleoflesserblackbackedgulldistributionfromprotected(SPA,SSSI,Ramsar)breedingsites(seeTableA1inappendixfornumberperspecies),duringthebreedingseason,basedonknowledgeoftheirforagingrange(Thaxteretal.,2012,meanmaximum foraging range=141km) (note thisdoesnotaccount forwintering/migration range).AlsoshownareallrecordsofthespeciesatseafromEuropeanSeabirdsatSeasurveys(conductedusingvariousmethodsindifferentseasons)absenceofadotdoesnotnecessarilymeanthebirdsdidnotusethearea.


Collision risk will also depend on the sensitivity of the species considered at the Wave Hubdemonstratorsite(seeTableA1inAppendix).ThePelaStardevice is likelytohave littlebiofoulingprotection;antifoulingcoatingwillpotentiallybeusedatthetendonconnectionpoints,mainlytoaideasyremovaloftendons inthefuture,andhoweverthismeansthatsomebenthiccolonisationmayoccuronnoncoatedpartsofthetendons.Seabirdsseekingtoaccessthisadditionalpreysourceclosetotheseasurface,maybeattractedtosuch benthic colonisations (see below for more detailed discussion under habitat loss/change),whichmay raise their collision risk as a consequence. Hence this potential impact needs to befactoredintothecalculationofcollisionrisk.The cable carrying thepower to the grid is able tomove aroundunderwater,perhapsbecominganotherhazardfordivingseabirds,butsuchaneffectislikelytobelocalised.ForthedemonstratorTLP, five individualtendonsofthicknessca.200mmextenddown from thePelaStarandareanchored to the seafloor.The fixed tendons thatkeep the turbine inplacemayconstituteanadditionalunderwatercollisionriskfordivingspeciessuchasscoters,divers,auksandcormorants/shags,allofwhich forage forpreyvisuallyunderwater,divingdown fromthesurface.However, plungedivers such as gannets should not be impacted by deployment of the PelaStardevicebecausetheywouldbeunlikelytodiveinthevicinityoftheturbine.With the increased number of turbines at a commercial level of deployment, the potential forunderwater collision risk increases. Moreover, the use of a threearm rather than a fivearmstructure increases thenumberof tendonsper arm to two rather thanone. Such a change at acommercial levelmayposeanincreasedriskofentanglement/collisionofseabirdsbetweendoubletendons,whichwillnotapplytothedemonstrator.Speciesmostatriskintermsofthiseffectarethedivingspeciesnotedpreviously.Giventhelittlepublishedinformationavailabletodeterminetheriskofunderwatercollisionandthefactthatcompetingpressuresmaybeacting indifferentways(e.g.theabsenceofbiofoulingallowing reef constructionand theattractionof foraging seabirds), it isdifficulttosaymorethanthatthethreatposedbyTLPstoseabirdsintermsofcollisionriskishighlyuncertain,butmaywellbegreaterthanfortraditionalmonopileturbines.3.3.3 DisturbanceanddisplacementDisturbanceanddisplacementareinterlinkedand,inessence,reflectdifferentlevelsofseverity.Theeffect of disturbance refers to an effect that causes a direct behavioural reaction of a bird, e.g.increasedvigilanceoraflight/diveresponse.However,prolongeddisturbancecouldresult inmorelongtermdisplacementfromapreviouslyfavouredhabitat,whichmaybecomepermanent ifbirdsareunabletohabituate.Thesensitivityofseabirdstotheseeffectsvariesbetweenspecies(Macleanetal.,2009seeTableA1).Duringtheoperationofawind farm,there ispotential for longtermdisplacement merely because of the longterm presence of moving turbines and the associatedmaintenanceboat traffic.Suchdisplacementconstitutesaneffective lossofhabitat (DesholmandKalhert2005;Langston2010).Behaviouraldisplacementiscommonlyequatedtomacroavoidance,althoughinthecontextofcollisionriskmodellingitreferstofarfieldevasiveactiontakenbyaflyingbird toavoid thewind farm totally (Band,2012).Displacement, incontrast, reflects the longtermlossofallbirdsfromanareaofhabitat.Althoughdifferent,themacroavoidanceratesrecorded instudiesofbird flightpathshasbeen used to informonpotentialdisplacement ratesofdifferentspecies in recentenvironmental impactassessments.Atpresent, there isonlya relatively limitedevidence base on the effects of displacement from offshore wind farms, and it is also unclearwhether therewouldbeanyhabituationover time tonewstructures (LangstonandPullan2003).LongtermhabituationhasbeenrecordedforcommonscoteratHornsRevwindfarmbyLindeboom


etal. (2011),butsuchdataare lacking formostspecies.Theevidencecurrentlyavailablesuggeststhatdifferencesexistintheratesofdisplacement,orattraction,betweendifferentspecies(Zuccoetal.2006Petersenetal.,2006and2011;PetersenandFox,2007;Krijgsveldetal.,2010and2011;APEM, 2011; Rexstad andBuckland, 2012).A classificationdetermined byMaclean et al. (2009),incorporates informationon speciesspecificbehavioural responsesusing indicationsof sensitivitysuggested by Garthe and Hppop (2004), Petersen et al. (2004) and Petersen and Fox (2007).Furnessetal.(2013)usedascoringsystemsimilartothatofMacleanetal.(2009)toestablishthesensitivityofseabirdstodisplacementcausingfactors:1=verylow,2=low,3=medium,4=high,and5=veryhigh(Table1Speciessensitivitytodisturbancefromboats(derivedfromFurnessetal.,2013)).Theworstcaseassumptionofdisplacementoverthelongtermisthatapopulationwilldecreaseasaconsequence of mortality (e.g. direct mortality of the adults because they are unable to findalternative habitat) or suffer reduced breeding success (e.g. McDonald et al., 2012). Longtermfitnessconsequencesofdisplacementneedtobemeasured,buttheycannotbecondensed intoasinglenumber(RexstadandBuckland,2012).Moreover,speciesresponsesarelikelytobevariablydependentonhabitatlossflexibility(Table2Speciessensitivitytohabitatloss(derivedfromFurnessetal.,2013))anddiet(seeBirdlifeInternational,2012),aswellasonthecarryingcapacityofanareaandtheabilityofaspeciestohabituatetoanotherarea(LangstonandPullan,2003).Table1Speciessensitivitytodisturbancefromboats(derivedfromFurnessetal.,2013)

Sensitivity todisturbance

Species/speciesgroup

VeryHigh Common scoter, velvet scoter, redthroated diver, great northern diver, blackthroateddiver

High Commongoldeneye,greatcormorant,greaterscaup

Medium Common eider, longtailed duck, greatcrested grebe, Slavonian grebe, shag,razorbill,blackguillemot,commonguillemot

Low Northerngannet,herringgull,greatblackbackedgull,littletern,littleauk,blackheaded gull, common gull, lesser blackbacked gull, blacklegged kittiwake,Sandwichtern,commontern,roseatetern,Arctictern,Atlanticpuffin

VeryLow Great skua, northern fulmar, sooty shearwater, Manx shearwater, Europeanstormpetrel,Leachsstormpetrel,Arcticskua,littlegull

Table2Speciessensitivitytohabitatloss(derivedfromFurnessetal.,2013)

Sensitivityduetohabitatloss

Species/speciesgroup

VeryHigh RedneckedgrebeHigh Greater scaup, common eider, longtailed duck, common scoter, common

goldeneye, redthroated diver, blackthroated diver, greatcrested grebe,Slavoniangrebe,littletern,blackguillemot

Medium Velvet scoter, great northern diver, great cormorant, shag, Sandwich tern,


common tern, roseate tern, Arctic tern, common guillemot, razorbill, Atlanticpuffin

Low Arcticskua,greatskua,blackheadedgull,commongull,greatblackbackedgull,blackleggedkittiwake,littleauk

VeryLow Northern fulmar, sooty shearwater,Manx shearwater, European stormpetrel,Leachsstormpetrel,northerngannet,lesserblackbackedgull,herringgull

Vesselswillbeusedtotowtheturbine (onaplatform) intoplace.Forboththedemonstratorandthecommercialdeployment,constructionwouldtakeplaceovera24hourperiodandtakebetween3 to 13days. Such towing anddeployment activitymay cause disturbance tobirds preferring toavoidboatsandanyother infrastructure.UnderwateractivitiesassociatedwithdeploymentofthePelaStar (e.g.tendonsbeingdroppedandanchoredtotheseabed,usingdrillingandgrouting)willaffectspeciessuchasdivers,scoters,auksandotherseaducksthataresensitivetothepresenceofboats(Furnessetal.,2013,TableA1inappendix)andmayhavecoloniesnearby(JNCC,2012),withinforagingrangeof thesite (Thaxteretal.,2012).Underwater foragerssuchascommonguillemots,razorbills, and Atlantic puffins are seen at the Wave Hub site (JNCC, 2013) and may show anunderwater disturbance reaction to structures being deployed (see also the section above onunderwatercollision).Therewillbeaneedtocollectfurther informationonprotectedpopulationsnear the area of deployment.However, disturbance should benoworse than the installation oftraditionalmonopilefoundations.Thepresenceofasinglewindturbineisunlikelytocauseconsiderableeffectivehabitatloss,andthepotentialfordisturbance/displacementissimilartothatofatraditionalturbine.Widerscalehabitatlosswouldbeseenatacommercial leveldeploymentoffloatingturbines,however,andtheeffectonseabirdswillbespeciesspecificanddependonthelocationchosenfordevelopments(Skovetal.,1995; JNCC 2012, 2013; Thaxter et al., 2012). Again, the impact will be similar to that from atraditionalmonopileturbinewindfarm.Theeffectofdisturbance/displacementduringdecommissioningislikelytobesimilartothatduringconstructionforbothdemonstratorandlargerscalecommercialdeployment.Theprocessshouldberelativelyquickforfloatingturbinesandlikelymorefavourablethanforthedecommissioningphasesof fixedmonopile turbines, requiring less vessel time at sea.Nevertheless, the activitywill causesomedisturbanceandconsequentlydisplacementofbirdsthroughtheirnegativereactiontoboattraffic,dependingagainonthespeciessensitivity(Furnessetal.,2013)andtheassemblagespresentatseaatthetimeofyearthatdecommissioningisundertaken.Thismayincludeaneffectonspeciesthatmightovertimehavehabituatedtotheeffectofthewindfarm.However,habitatwouldthenbegained from the removalof the turbine.Although it ishard togeneralise theeffectsgiven thevariability inspeciessensitivities, it isanticipatedthatthedurationandextentofdecommissioningactivities forfloatingturbineswillbenoworsethanforexisting fixedwind farms,andagainshortterminnature.3.3.4 BarrierEffectsTraditionalwindfarmsmayposeabarriertomigratorybirdsorthosecommutingbetweenbreedingsitesandoffshorefeedingareas,whichcouldthenresultinelevatedenergyneeds(Speakmanetal.,2009)andevenpotentiallyincreasedmortalityorimpactsonproductivityatthecolonies.Increasesin theenergycostsofdailymovementsof seabirdsorof themovementsofmigratorybirdshavebeenshown inanumberofstudies (Tulpetal.,1999;PetterssonandStalin,2003;Masdenetal.,2009, 2010), although Masden et al (2009), reported changes in the migratory trajectories ofcommon eiders at a Danish offshore wind farm postconstruction, they suggested that this hadminimallikelyeffectonthespeciesenergetics.However,itwasnotedthatcumulativeeffectscould


besignificant,for instance, ifotherwindfarmsorhumandevelopmentsworked incombinationtodisrupttheroutesofbirds.DesholmandKalhert(2005)alsoreportedthatmigrantwildfowldivertedaroundtheNystedwindfarm,andTulpetal.(1999)foundthatcommoneidersdidnotflybetweenwindturbinesplaced200mapartintheKattegat.Duringconstruction,aprogressiveincreaseinthenumberof turbines ata commercial scalewould increasinglypose a greaterbarriereffect.Upondecommissioning, removal of the entire wind farm would remove any barrier to movementpreviouslyimposed,thenconstitutingapositiveeffect.Whilenotanissueforthedemonstratorturbine,atacommercialscaleofdeployment,theextentofthis effectwill depend on the number of turbines eventually installed, the area covered by thedevelopment,andimportantlytheseabirdspeciescompositionsandnumberspresentseasonallyintheareabeingdeveloped.Differentspeciesare lesssensitive toagreateror lesserdegree to thiseffect(seeTableA1inappendix).Theassessmentofbarriereffectsistypicallybestassessedthroughdirectlymonitoring individualbirdsmovingthroughthewindfarmzone,for instanceusingtrackingtelemetryor radar (e.g. Krijgsveldt et al., 2011).However, formany species,particularlymigrantspecies, a lackof informationon trackedbirdsmeans that it is impossible todeterminewhetherindividualstraverseanarea,nor is itpossibletoassessthealtitudeatwhichtheyflyandthereforewhatroutesmightbebeingaffectedbythepresenceofawindfarm(althoughseeKrijgsveldetal.,2011).Analternativemethod is togeneraliseonthe likelyareasthroughwhichbirdsofparticularspeciesmightmigrate (Wrightetal.,2012seeFigure6asanexample, in thiscase forBewicksswans)andthentomodelthenumbersthatarelikelytopassthroughthewindfarm.TherearenodifferencesbetweentraditionalturbinesandfloatingTLPturbinesinthiseffect.3.4 HabitatLossorChange(Includingnoise,sedimentation,electromagneticfields)Duringallphasesofawindfarmsexistence,therearemanywaysbywhichbirdsmaybeimpactedeitherdirectly throughalteringtheirhabitat,or indirectlythroughchangestotheirprey, thatmayimpact the seabirds themselves.Sucheffects includehabitat lossattributable to theexport cablecorridorandwind farm,habitatchangesaffecting theavailabilityofprey speciesby, for instance,duechangingthelevelofsuspendedsediments(whichcanaffectabirdsabilitytodetectandcatchprey aswell as influencing the absolutenumbersofprey),underwaternoise fromdrilling,piling,hammering or other construction activities, electromagnetic frequencies (EMFs), and changes tofishingactivityasaresultofthepresenceofawindfarm(longterm,throughouttheoperationallifeofthefarm).Evidencefromotheroffshoreactivitiessuchasaggregatedredging(CookandBurton,2010)suggeststhoseseabedhabitatsandthebenthic invertebratesandfishfaunaassociatedwiththemmightbealteredbyallwindturbine installationandcablelayingactivities,potentiallyhavingsome impact on bird assemblages, although this is likely to be short term, with recoverycommencingafterconstructionhasbeencompletedTheattractionoffloraandfaunatomanmadestructures,suchasoilplatforms,piersandwrecksiswelldocumented, and includes positive effects on benthic flora and fauna, zooplankton and fish(Wolfson etal.,1979;Baird1990;Wiese etal.,2001;Wilhelmssonetal.,2006b; Langhamer andWilhelmsson,2009;Langhameretal.,2009).Suchchangestofloraandfaunamaythenattracttheprey species of seabirds (Wiese et al., 2001; Wilhelmsson, 2012). For example, species such ascommoneiderand scoters forageon themusselsandshellfish thatestablish themselvesonmanmadestructures,althoughtheseabirdspeciesdotendtoavoidwindturbinesspecifically(Furnessetal.,2013,TableA1inappendix).ThePelaStarfivearmstructurehasindividualarmradiiof31.18m,awidthof3m,andapotentialdepthperarmofuptoca.9m.Fromthis, justacrudecalculation(whichcannotbeexactbecauseof thecomplexityof thecentral structurewhere thearmsmeet)yieldsasurfaceareaperarmof744m2,or3,720m2forfivearms.Hence,evenforasinglePelaStar


turbine, theamountofhabitatcreatedwillbe large,becauseof the largehull.However,seabirdsmayalsobenegatively impactedbychanges inthedistributionsoftheirprey.Attractioncausedbyhabitatbecomingmoresuitablemayalsomeananincreaseintheriskofcollisionforsomespecies,or itmay lessenor reverse the impactofdisplacement causedbydisturbance. Impactsmay alsoeventuateonseabirdsbreedingnearawindfarm.Forexample,Perrowetal.(2011)examinedpreyabundancebeforeandafterassessmentofa30turbinedevelopmentatScrobySands,SEEngland,toassessthe likely impactsonanearbycolonyofbreeding littleterns.Themost importantprey inthe chickdiet,youngoftheyear (0group)herring, showeda significant reduction from2004on,unexplainedbyenvironmental factors, so turbine installationwas suggested tohaveaffected fishreproductionlocally(Perrowetal.,2011).Availabilityofthesepreyspeciesinthetop45cmofwatercausedchangesinlittleternforagingbehaviour,andinturnmayhavecontributedtoincreasedeggabandonment and low hatching success in subsequent years (Perrow et al., 2011). The exampledemonstrates the importance of adopting sensible precautionary approaches to the timing anddurationofpiledrivingactivity(Perrowetal.,2011).Indirecthabitatchangeforseabirdsmayalsoarisethroughreducingthe impactoffisheriesonthehabitats of prey species underwater. Changes to fishing practice may affect fish and shellfishpopulations and hence the seabirds. However, as fishing may cause damage to seabed habitat,disturb sediments, directly removes plants and other organisms and alter habitat structure, areduction in fishingcouldhaveapositiveeffect formarinecommunitiesandseabirdpreyspecies.TheplannedconstructionactivitiesatthedemonstratorWaveHubsitehavethepotentialtocausedirecthabitatlossthroughexportcableconstructionandtheareaaroundthatcableontheseafloor.For seabird prey, the area of seabed potentially affected is likely to be small and unlikely to begreater than for a traditional fixed wind turbine. For all commercial wind farms, changes tocommercialfishingactivityasaresultoftheirestablishmentarelikelyandmaywellhaveanimpactonseabirds,generallythroughforaginghabitatandpreyavailabilitybeingaltered.Wind turbinesmayalsohavepositiveeffects,attractingbirds (increasinghabitat),providing themwithplatforms forperchingand roosting (Petersenetal.,2006;Krijgsveldetal.,2011).Birdsmayalsobeattractedtolightingaroundoffshorestructures,whichmayhelpthemlocatenocturnalprey(Sage,1979;HopeJones,1980;Taskeretal.,1986;Wieseetal.,2001).Agradual increase in thenumberofturbinesinasingleareawillofferincreasedopportunitiesforsomespeciestoperchandroost.Underwaternoisemayaffect theprey speciesof seabirds (see sectionsonmarinemammalsandbaskingsharks formoredetail).Theeffectmaybeseen through lethal/injury toprey for instancefrom auditory system damage, and behavioural changes in swimming and schooling behaviouraffecting spawning which may in turn affect nursery grounds, migration and feeding patterns.Sedimentationhas thepotential toaffectdivingbirds suchasdivers, scoters, seaducks,auksandshags/cormorantsthrougheitherdirectdisruptionofnavigationinthewatercolumnandlocationofprey,orthroughaffectsonthepreythemselves, indirectly impactingtheseabirds.Alossofhabitatmay impact lessmobilespeciesmore,but inparticular itmay impactshellfish,sandeelsandotherfish species thathavehabitatpreferences, aswell as their eggs and larvae, for instance throughreducing the likelihoodof theeggshatching, reduced feedingand survivalpossibilities for larvae,adult suffocation (e.g. of sandeels buried in the seabed), and the temporary loss of spawninggrounds. It isalsopossiblethatchangestothehydrographyduringoperationofthewindfarmcaninfluencethedistributionsofpreyspeciesofseabirds.DuringtheoperationalphaseofaTLP,noisemaybeproducedfromtheunderwatertendons(e.g.bystrumming)andexportcable,howeverthisisthoughtobeverylowifatall.Currently,thepotentialextentofthisdisturbanceanditseffectonseabirdsand/or theirprey isunclear.Thegeneratorwouldbeexpected toproduce justa regularnonintermittentlowdecibellevelofnoise,however,andthatwillnothavemucheffectonseabirds.


Prey distributionsmay also be disrupted as a consequence of the electromagnetic fields (EMFs)around installations throughout all phases of a wind farms life, resulting in changes in seabirdbehaviour (e.g.migrationpatterns and feeding activity).However, thepotential impactsof EMFsfromcablesonfishandseabirdsareveryuncertain(Gilletal.,2005,2009;GillandBartlett,2010).OneissuetonoteisthepotentialforalienhabitatsandnewspeciestobeintroducedwhenaTLP,orlateranextendednumberofTLPs,isdeployed.That,aswithanyothernewdevelopmentinthesea,isakintocolonisation,whichmighthaveknockonandpossiblypositiveconsequencesforseabirds.Thedietsof speciessuchasgullsarediverse (seeBirdlife International,2012),so introducinganyalienspeciesmayactuallyintroduceanewpreysourceforseabirds.Attheconstructionphase,sedimentmaybemobilisedbythedrillingandgroutingprocessapplied,andscouringcanarisearound theanchors.Theknockoneffects toseabirdsand theirprey isstillconsidered tobe localised, intermittent,andshortterm.Finally,changes to the localhydrographyduring operation of a commercial floating turbine wind farm may conceivably influence bothseabirdsandtheirpreybyalteringthemicrohabitat.HoweverthenatureofsuchchangesfromaTLPdesignareunknownatpresent.Table3Summary comparisonofTLP floating turbinesandmonopile turbines fordifferenteffects for seabirdsat thecommercial level,andwhicheffectsarepredicted (basedon information received) tobebetter (+),worse (),ornodifferent(.)fortherespectivedesigns.

Stage Construction Operation DecommissioningTLP Monopile TLP Monopile TLP Monopile

Abovewatercollisionrisk + . . . .Entanglement / underwatercollision

+ Disturbance anddisplacement

+ . . + Barriereffects . . Habitatlossorchange . . + . .Underwaternoise + . . + EMF . . Sedimentation + + Smothering Ballast water issues /pollution

. . . .Scour . . . .


4 Conclusions

The PelaStar floating turbine is a TLP designwith two possible anchoring options dependant onsediment characteristics. This report has shown that TLPs and their anchoring options are wellknownwithin other offshore and onshore sectors, having been used successfully for the last 30years.Floatingwindturbinesareanemergingtechnology,howeverthemajorityoftheresearchtodatehasfocussedontheplatformdesignandstability,possiblybecausedevelopersarecomfortablewiththetrackrecordoftheproposedanchoringsystems.Themajor impacts reviewedwhen comparing TLPs andmore traditional foundations are seabeddisturbance and underwater noise.Overall, the type of impacts for all foundation types are thesame,however,theextentofthe impactchangesdependingonfoundationtype(Error!Referencesourcenotfound.).4.1 TLPsedimentdisturbanceandnoiseThePelaStar installationmethodsdonotrequireseabedpreparation,minimisingpotential impactson the seafloor. Temporary seabed disturbance is expected during the installation/constructionphaseowing to thepenetrationof theanchor into thesediment; this is likely tocause temporaryhabitat loss and sediment disturbancewhere sand, gravelly sand, silt and clay are the dominantsubstrata, (compared with rock at the Wave Hub site). Potential impacts from the installationmethods likely for the anchoring systems are comparable with those caused by monopilefoundations;however,becauseTLPinstallationutilisesfive(albeitsmallerdiameter)anchorpilestheeffectswillatbestbeequivalent toamonopile foundation,but incertaincircumstancescouldbegreater. Scoureffects shouldbe limitedand the seabed footprint in termsofhabitat losswillbelowest for the smallest (2.1 m diameter) anchor piles. Environmental effects duringdecommissioningwilldependontheanchoringsystemutilisedasthepilesaredifficulttoremove.Two different methods are proposed for installing the TLP anchoring systems, respectively piledriving or drilling and grouting. The noise generated by piledriving the anchors are not verydifferent to that generated bymonopiles used inmostNorth Seawind farms. The source levelassociatedwithdriving thesepiles is likely tobe in the regionof250dB re1Pa@1mbutwilldependonthesizeofpileused.Theevidenceisthatdrillingissignificantlyquieterthanpiledriving.The operational noise from a floating wind turbine is expected to be reduced relative to aconventionalturbineasaconsequenceofitnotbeingrigidlyattachedtotheseabed.However,thereis a potential for strumming (caused by water moving past the undertension tendons of thePelaStar). Thedecommissioningphase for the two anchoringmethods is likely to induce similarlevelsofunderwaternoise.Table4Comparisonoffoundationtypewithseabeddisturbanceandnoiseimpacts(adaptedfromReachetal.,2012).

Foundationtype Habitatloss Scour NoiseGravityBases Lowtohigh Low LowSuction Moderate Low LowMonopile Low High High


Multileg Low Low LowtoHighJacket Low Low ModerateFloating devices (otherthanTLPs)

Negligibletolow Lowtomoderate Moderatetolow

TLPs Low Moderatetolow

4.2 TLPsandimpactsonmarinemammalsDuringconstruction,underwaternoise is likelytobethekeymechanism indisturbingtherangeofmarinemammal species likely to encounter the device. Themethod of installation chosen (piledrivingvs.drillingandgrouting)willhaveasignificanteffectontheextentofdisturbanceandcouldcauseauditory injuryout to largedistances from the site.Drillingandgrouting is likely tohaveamorebenigneffectonmarinemammals.Duringtheoperationalphase,themainimpactonmarinemammalsofthePelaStarTLPwillbeaheightenedriskofcollision,entanglementandentrapment,especiallyforlargebaleenwhales.Dependingonthenoisecharacteristicsofanystrumming,theremaybepotentialfordisturbingmarinemammals.There are data gaps in scientific knowledge. Increased turbidity may impact foraging, but thepotentialmagnitude isunknown.Acommercialarraycouldpresentabarrier tomarinemammals,butthereisnoevidencetosuggestwhetherfloatingturbinescouldcausesuchanimpact,andiftheycould,at

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