a scoping study for an environmental impact field programme in tidal current energy

8/13/2019 A Scoping Study for an Environmental Impact Field Programme in Tidal Current Energy

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A SCOPING STUDY FOR AN

ENVIRONMENTAL IMPACT FIELDPROGRAMME IN TIDALCURRENT ENERGY

ETSU T/04/00213/REP

DTI Pub/URN 02/882

Contractor

The Robert Gordon University, AberdeenCentre for Environmental Engineering and Sustainable Energy


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EXECUTIVE SUMMARY

Introduction

The Department of Trade and Industrys (DTI's) renewable energy programmeappointed RGU in December 2001 to conduct a study to define a programmeof work to assess the key potential environmental impacts of tidal currentenergy. This report describes this work and its findings.

The report does not attempt to quantify the environmental impacts of tidal current energy. It merely identifies them with a view to prioritising further research. It should not, therefore, be interpreted as implying that any of theenvironmental consequences listed are either significant or insignificant. At this stage we consider it likely that the environmental impact will beinsignificant but until further research has been carried out no conclusions asto its magnitude can be drawn.

Project Aims and Objectives

The aims of the study were:

(i) To identify the key potential environmental impacts associated withtidal current energy systems.

(ii) To identify and formulate a programme of work to quantify their importance.

In order to achieve these aims, the objectives of the study were as follows:

(i) To identify the principal modes of interaction between tidal currentenergy technology and the marine environment and to discuss theassociated implications.

(ii) To establish consequence models for the principal environmentalinteractions.

(iii) To identify measurables to allow for the quantification of environmental impact for key environmental interactions


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however, that as society increases at an ever-accelerating rate, the need for energy also increases.

Over the years there have been major programmes to develop the use of renewable energy sources, such as wind energy, solar energy and small scalehydro power schemes to name but a few. In total, these renewable sourceshave the potential to meet all the world's energy needs, for the 21 st century and

beyond, cleanly, safely and economically. Developing such energy systems presents a huge challenge, requiring extensive and diligent research and

development effort.The UK Government policy is to stimulate the development effort for new andrenewable energy sources wherever they have prospects of beingeconomically attractive and environmentally acceptable (DTI, 1994). Withthis is mind there is no reason why renewable energy cannot have a major rolein the electricity market (Dacre & Bullen, 2001).

Since 1979, much research has gone into the development of tidal currentenergy technology. Table 1 summarises the growth of such technologicaldevelopment and research (Dacre & Bullen, 2001).

Presently, a series of projects is underway by the tidal energy group at TheRobert Gordon University to determine the potential of economic generationof electricity using the tidal current resource of the Pentland Firth, which lies

between the Scottish mainland and the Orkney Isles. It has been initiallycalculated that using the concept recommended by Marine Current TurbinesLtd. (MCT) electricity could be generated in order of 350MW to 2GW, whichis the equivalent of 1TW and 7TW hours per annum respectively.

In its report Sustainability through diversity: Prospects for the UK Oil and Gas Suppliers Industry , published in 2001, the DTI identified tidal currentenergy as having a close fit with the skills possessed by suppliers to the

offshore oil and gas industry. With this in mind, there is potential for diversification for these and the shipping industries, especially with regard tonumerous areas, such as, design, fabrication, piling, drilling, installation,operations, maintenance etc. Such development would also host a number of employment opportunities and a potential for economic growth (Dacre &Bullen, 2001). All in all, within the UK, tidal current energy has the potential


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concerning tidal current energy. With the installation of the Lynmouth turbineconducted by MCT Ltd., the opportunity has arisen to study suchenvironmental implications in the field. Though this involves the study of oneturbine, it nonetheless provides the opportunity to assess the state of theenvironment before and after installation and establish further understandingof the environmental interactions involved with regard to tidal current energyand the marine environment.

Summary of Methodology Adopted

The identification of impacts and their associated modes of interaction was probably the most critical step towards developing a programme of work.Methodology consisted of the identification of key environment and projectinteractions using a simple list structure, followed by the construction of aninteraction matrix and basic conceptual model. The likelihood, magnitude andlegislative/consultative significance was also considered using an interactionmatrix method. An overall significance matrix was also established. Key

environmental impacts and the sources of impact were noted.

Further development of the identification process and introduction of the process scenarios formed the basis of the consequence model development.Consequence models were formulated for all key impact sources using the

process scenarios, each reflecting broad research areas.

By assessing the overall significance of impacts and using the consequencemodels, research projects were identified and subsequently divided intoappropriate projects and sub-projects. Projects were also prioritised accordingto their potential overall impact significance, current consultative concern and

present state of knowledge.

Project measurables and observables were then identified using the processscenarios and consequence models as a guide. A simplified programme of

work was determined. This consisted of a field monitoring programme and aconcurrent computational and analysis programme.

There is no doubt that the adopted processes are subjective and open tointerpretation, but the methodology employed does establish consistencythrough clear definition. The simplicity of the method also partially deflects


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The main conclusions can be summarised below:

A number of direct and indirect potential environmental impacts wereidentified and included:

(i) A direct disturbance of the seabed and benthic ecology with regard toinstallation of tidal energy devices and overall operation;

(ii) Potential disturbance of seabirds, pinnipeds and cetaceans in theinstallation phase related to equipment activity, both visually and auditory;

(iii) Potential changes in the tidal and wave dynamics in the vicinity of thedevice and on a local level due to the structure itself, the rotor vortices andthe extraction or blockage of tidal energy;

(iv) The potential seabed disturbance and change in sediment dynamics

due to the potential changes of tide and wave dynamics (iii);

(v) The potential changes in water quality and turbidity due to associatedseabed disturbance and chemical leakage from the device and installationequipment;

(vi) The possibility that acoustic emissions from the operating deviceswill be sufficient to disturb migrating or resident cetaceans, pinnipeds andother marine animals and;

(vii) The potential collision risk associated with diving birds and marinemammals.

Throughout the study it has become apparent that such potential impactsare deemed to be highly to moderately significant in terms of their

potential likelihood and magnitude. Such assumptions are very sitespecific and dependant on environmental characteristics. With adequateresearch and suitable mitigation procedures, however, it is expected thatsuch implications could ideally have a low impact potential.

To gain further knowledge of the environmental issues surrounding tidal


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(iii) The effects of the rotor interactions on the water column and thesubsequent effects on seabed morphology;

(iv) The collision risk probability for marine mammals and fish;

(v) The acoustic emissions of the tidal energy device and the potentialimplications involved with respect to marine mammals and other marine ecology, such as fish;

(vi) The vibration and visual characteristics;

(vii) The overall ecological impact of the installation and operation of a tidal energy device, including an assessment of recovery time after decommissioning;

(viii) A comprehensive Life Cycle Analysis (LCA) concentrating onCO 2 emissions and a subsequent comparison to other renewable

energies;

(ix) An assessment into the need for antifoul treatment and a toxiccomparison of each alternative;

(x) The development of a Parametric Model of environmental impact.

The research areas and projects identified have been deemed to have thefollowing benefits:

(i) The ability to enhance knowledge and understanding of theenvironmental issues raised, not only within the realm of tidal currentenergy, but other offshore development industries;(ii) The reduction of uncertainty and the barriers to the development of tidal current energy; and

(iii) The provision of adequate mitigation through technologicaldesign, environmental prediction and modelling.

Though not in the remit of this study, it is recommended that a similar studyshould be conducted concerning the potential socio-economic impacts and the


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CONTENTS

1 INTRODUCTION....................................................................................11.1 Background...........................................................................................1

1.1.1 The Energy and the Environmental Situation................................11.1.2 The Role of Tidal Current Energy .................................................11.1.3 Environmental Impact Research....................................................3

1.2 Benefits of the Study ............................................................................71.3 Aims and Objectives.............................................................................7

1.3.1 Aims...............................................................................................71.3.2 Objectives ......................................................................................72 IDENTIFICATION OF ENVIRONMENTAL IMPACTS......................9

2.1 Environmental Definitions ...................................................................92.2 Considerations ......................................................................................92.3 Identification of Key Deployment Activities .....................................102.4 Identification of Environmental Impacts............................................102.5 Environmental Impact Significance ...................................................11

2.5.1 Likelihood of Environmental Impacts .........................................112.5.2 Magnitude of Environmental Impacts .........................................112.5.3 Legislation and Policy .................................................................162.5.4 Consultative Concerns .................................................................16

2.6 Overall Significance ...........................................................................192.7 Key Environmental Impacts ...............................................................21

3 MODELLING CRITERIA AND QUANTIFICATION ........................233.1 Research and Modelling Development...............................................233.2 Consequence Model Development.....................................................23

3.2.1 Purpose.........................................................................................233.2.2 Development ................................................................................23

3.3 Consequence Models..........................................................................273.3.1 Kinetic Energy Removal..............................................................283.3.2 Rotor and Support Structure Intereference ..................................293.3.3 Ambient Noise and Vibration Levels ..........................................30

3.3.4 Installation/Decommissioning Disturbance.................................333.4 Identification and Formulation of Research Projects .........................36

3.4.1 Identification and Priotisation of Research Projects....................363.4.2 Research Project Measurables and Observables..........................38

4 PROGRAMME OF WORK...................................................................444 1 Monitoring Programme 44


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LIST OF FIGURES

Figure 1: Simplified Conceptual Diagram of Potential Physical andEcological Interactions and Impacts of the Project [ Source: Dacre &Bullen, 2001]............................................................................................14

Figure 2; Research and Model development ..................................................24Figure 3: Impact of Kinetic Energy Removal (CM1).....................................28Figure 4: Support Structure Impacts (CM2(i)) ..............................................31Figure 5: Impacts of Rotor Interference (CM2(ii)) ........................................31

Figure 6: Acoustic and Vibration Impacts (CM3) ..........................................34Figure 7: Installation Impacts (CM4) .............................................................35Figure 8: Gantt Chart Summarising Project Programme................................47

LIST OF TABLES

Table 1: Summary of Tidal Current Development and Research [Source:Dacre & Bullen, 2001] ...............................................................................4

Table 2: Key Stages of Deployment Considered in Report [Source: Dacre &Bullen, 2001]............................................................................................10

Table 3: Determination of likelihood..............................................................11Table 4: Levels of Magnitude [Source: Dacre & Bullen, 2001]....................12Table 5: Environmental Interactions Matrix [Source: Dacre & Bullen, 2001]

..................................................................................................................13Table 6: Likelihood and Magnitude Significance Matrix...............................15

Table 7: Significance of Legislation and Policy .............................................16Table 8: Significance of Consultative Concerns.............................................17Table 9: Legislation/Policy and Consultative Concern Significance .............18Table 10: Overall Significance for Project Interactions [Source: Dacre &

Bullen, 2001]............................................................................................19Table 11: Overall Significance Criteria ..........................................................19Table 12: Overall Significance Matrix ...........................................................20Table 13: Summary of Key Environmental Impact Issues .............................21Table 14: Sources of Impact and Related Environmental Components Likely

to be Affected...........................................................................................22Table 15: Key Environmental Interactions and Process Scenarios ................25Table 16: Key to Environmental Processes Represented in the CMs. ..........27Table 17: Research Projects Identified from the Conceptual Models ............36Table 18: Other Research Projects 36


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1 INTRODUCTION

The Department of Trade and Industrys (DTI's) renewable energy programmeappointed RGU in December 2001 to conduct a study, to define a programmeof work to assess the key potential environmental impacts of tidal currentenergy. This report describes this work and its findings.

The report does not attempt to quantify the environmental impacts of tidal current energy. It merely identifies them with a view to prioritising further

research. It should not, therefore, be interpreted as implying that any of theenvironmental consequences listed are either significant or insignificant. At this stage we consider it likely that the environmental impact will beinsignificant but until further research has been carried out no conclusions asto their magnitude can be drawn.

1.1 Background

1.1.1 The Energy and the Environmental Situation

The bulk of the worlds energy demands are currently met from non-renewable sources. The worlds population is estimated to double by the year 2050 and the worlds energy demand is estimated to increase by at least 70%over the next 30 years (Jennings, 1996). Such estimates for future demand,however are notoriously inaccurate and are subject to extreme change(Charters, 2001). The problem still remains however, that as society increasesat an ever-accelerating rate, the need for energy also increases.

Over the years there have been major programmes to develop the use of renewable energy sources, such as wind energy, solar energy and small scalehydro power schemes to name but a few. In total, these renewable sourceshave the potential to meet all the worlds energy needs for the 21 st century and

beyond, cleanly, safely and economically. Developing such energy systems

presents a huge challenge, requiring extensive and diligent research anddevelopment effort (Dacre & Bullen, 2001).

The UK Government policy is to stimulate that development effort for newand renewable energy sources, wherever they have prospects of beingeconomically attractive and environmentally acceptable (DTI 1994; DTI


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UK Department of Energy (Den) at the 1981 UN Conference on New andRenewable Sources of Energy, held in Nairobi, selected wind and tidal energy

as those thought most likely to provide a substantial contribution to UK electricity production by the early 21 st century (Taylor, 1983).

In the past few decades, tidal current energy technologies have been passedover in the rush to develop other new sources of energy, such as hydro, windand nuclear. All in all, the abundance of tidal current energy has in effectremained predominantly untapped. Therefore it leads to the belief that as theavailable capacity of wind energy becomes fully utilised, tidal current energywill become a more favourable option (Dacre & Bullen, 2001). The most wellknown renewable energies are probably hydro, wind and solar, however, the

basic definition in the Utilities Act 2000 states that sources of renewableenergy are those energies other than fossil fuels and nuclear. It was also statedin the DTI Renewables Obligation Preliminary Consultation, that Governmenttargets for renewable energy can include energy generated from tidal energy(DTI, 2000). The House of Commons Science and Technology Select

Committee has also stated that the UK can no longer afford to neglect the potential of tidal and wave energy (Science and Technology Committee, 2001)and suggested that the UK tidal current energy resource could fall between 31and 58TWh per annum.

Since 1979, much research has gone into the development of tidal currentenergy technology. Table 1 summarises the growth of such technologicaldevelopment and research (Dacre & Bullen, 2001).

Presently, a series of projects is underway conducted by the tidal energyresearch group at The Robert Gordon University (Table 1) to determine the

potential of economic generation of electricity using the tidal current resourceof the Pentland Firth, which lies between the Scottish mainland and theOrkney Isles. It has been initially calculated that using the conceptrecommended by Marine Current Turbines Ltd. (MCT) electricity could be

generated with a rated capacity of 350MW to 2GW, which is the equivalent of 1TW and 7TW hours per annum respectively (Dacre & Bullen, 2001).

In its report Sustainability through diversity: Prospects for the UK Oil and Gas Suppliers Industry , (DTI, 2001), the DTI identified tidal current energy ashaving a close fit with the skills possessed by suppliers to the offshore oil and


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5

Developers/Researchers Date Type CommentsProf. Salter Edinburgh University: UK 1998 Darrieus Rotor diameter of 50m 10.EC Joule Programme(RGU, IT Power, University College Cork [Ireland], Thetis [Italy])

1998-2001Development of a methodology for optimum technical and economic matching of turbines to local flowconditions Opt Current.

EC Joule Programme(IT Power): UK 1998-2002 Horizontal axis

Seaflow. Involves the development of a commercial scale tidal current turbine (300kW) mounted on amonopile support.

Blue Energy: Canada 1998-2000 Davis turbine Vertical Axis Darrieus type turbine. Proposed project originally to be installed at the San Bernando Srait between the two Phillipine Islands of Samar and Leyte 11.

Engineering Business: UK 1997 - present AWCG & StingrayActive Water Column Generator (AWCG) first developed in 1997 and tested at Blyth in 1999. Stingraywas developed later and was based on the original AWCG and plans are underway for a large-scaledemonstration 12.

Present Axial Flow Device based on a numerous small axial flow rotors set into a frame mounted on the seabed. 13

Shetland. Journal of the Society of Underwater Technology . Vol.21 No.2, pp. 21-29, Autumn 1995. Feasibility Study for Tidal Current Power Generation for Coastal Waters: Orkney and Shetland. Final Report. XVII/4 1040/92-41. ICIT and IT Power, 199510 Renewable Energy Workshop (1998) Marine Foresight Workshop: Future Opportunities for Offshore renewable Energy Report. 13th May 1998,Office of Science and Technology, London11International Water Power & Dam Construction (1998) Sink or Swim. International Water Power & Dam Construction , July 1998, pp. 49-5012 Watchorn, M.J. (1997) The EB Ltd. The DTI SMART Feasibility Study Application [Confidential]. Watchorn, M.J. (1999) The EB Ltd. The ActiveWater Column Generator [Commercial in Confidence]. Watchorn - pers comm13 Scottish Executive, (2001) Scotlands Renewable Energy Resource 2001 - Volume II: Context. Prepared by Garrad Hassan and Partners Ltd.


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6

Developers/Researchers Date Type CommentsTidal Hydraulics Ltd., Wales

Hammerfest Stroem AS, Norway Present Axial Flow Developing a seabed mounted axial-flow system of about 300kW 14Teamwork Technology, Netherlands Present Axial Flow Marketing a small floating axial-flow device rated at 25kW, primarily for use on rivers. 15

Enermar, Italy Present Cross-flow Developing a 130kW prototype 16

Aquantis (Enron Wind Corp.), USA Present Process of designing and developing marine current turbine technology 17

J A Consult, London Present Axial Flow Developing a semi-submersible, buoyant axial flow concept. A prototype (1.5 diameter rotor) is currently being tested in the River Thames at Chiswick under DTI contract. 18

Edinburgh University (Prof. S alter) Present Cross-flow Proposal of a large floating cross-flow rotor system at a conceptual stage of development. 19

The Robert Gordon University (TidalCurrent Energy Research Group) 2001-present Axial-flow

Three phase feasibility study to determine the potential of economic generation of electricity in the PentlandFirth. Environmental Impact phase was completed in October 2001. 20

14 Alexander Gas and Oil Connections. Company News Europe, Vol. 4, Issue 19. (1999) Available from:www.gasandoil.com/goc/company/cne94592.htm [Accessed: 15/01/02]15 Scottish Executive (2001), Scotland's Renewable Energy Resource 2001 - Volume II: Context. Prepared by Garrad Hassan and Partners Ltd.16 Scottish Executive, (2001) Scotland's Renewable Energy Resource 2001 - Volume II: Context. Prepared by Garrad Hanssan and Partners Ltd.17 Scottish Executive, (2001) Scotland's Renewable Energy Resource 2001 - Volume II: Context. Prepared by Garrad Hanssan and Partners Ltd.18 Wind and Tidal Stream. Available from: www. windenergy.co.uk/header.htm19 Scottish Executive, (2001) Scotland's Renewable Energy Resource 2001 - Volume II: Context. Prepared by Garrad Hanssan and Partners Ltd.20 Dacre, S.L. and Bullen, C. (2001) Pentland Firth Tidal Energy Feasibility Study - Phase 1, October 2001. RGU, Aberdeen and ICIT, Orkney.[Unpublished Report].


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1.2 Benefits of the Study

With adequate research a greater understanding of highlighted environmentalimpact implications will arise to reduce uncertainty. It is envisaged that theenvironmental impacts discussed in the report will prove, in time, to be withinthe realm of natural variability. It is hoped that future research in this area willaddress any environmental uncertainties and provide a mechanism to ensureadequate mitigation through technological design and environmental

prediction and modelling to reduce such impacts.

Though there are some unique environmental implications associated withtidal current energy, there are commonalities with other offshore and coastalindustries and ventures, such as offshore wind turbine projects. Any researchin this area will inevitably enhance knowledge and understanding of environmental issues that may be common to all.

With the introduction and development of the Environmental Impact

Assessment it is important to assess environmental implications in detail togain a greater understanding of the problems in hand. The more uncertaintythere is of the effects associated with the environment the more controversyheightens. Such lack of understanding only creates barriers to developmentand thus, barriers to the creation of a renewable and sustainable energy future.

1.3 Aims and Objectives

1.3.1 Aims

(i) To identify the key potential environmental impacts associated withtidal current energy systems.

(ii) To identify and formulate a programme of work to quantify their importance.

1.3.2 Objectives

(i) To identify the principal modes of interaction between tidal currentenergy technology and the marine environment and discuss theassociated implications.


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2 IDENTIFICATION OF ENVIRONMENTAL IMPACTS

2.1 Environmental Definitions

The environment in this context can be defined as a system, which is acombination of inter-related attributes that, as a whole, make up the physicaland biological conditions of a tidal current energy device.

Within the context of the report, impacts can be defined as those responsesand changes in behaviour of the environmental system as a result of adevelopment, which are above and beyond any natural variability that mayoccur. The environmental system encompasses the physical and ecologicalconditions in this instance. The physical environment constitutes the physicalcomponents of the air, water and land and the processes that underpin thosecomponents. The ecological environment, therefore, constitutes the biologicalcomponents, such as the fauna and flora that are influenced by the physicalenvironment. The report will not focus on the socio-economic environment as

such, but may briefly discuss impacts concerning commercial and industrialactivities as necessary.

2.2 Considerations

The methodology used was that employed in the Pentland Firth FeasibilityStudy conducted by Dacre and Bullen (2001). However, development of thatmethodology is apparent within the context of this study to fulfil the objectivesthat need to be met.

When considering environmental impact, it was important to use a systematicapproach. This helped in the review of the main principles of potential tidalcurrent energy impacts. It also helped in the process of differentiating theimportant issues, as well as providing consistency (Dacre & Bullen, 2001).The methodology employed was formulated to give a systematic appraisal of

potential impacts using data and knowledge that was currently available and,therefore, enabling gaps within that existing knowledge to be found andfurther research in this area to be considered.

All potential impacts were identified in a generic context and were not sitespecific It must be noted that some impacts for any given development are


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2.3 Identification of Key Deployment Activities

When identifying environmental impacts, it was important to consider thestages involved in the deployment of tidal current energy, whether it is a singledevice or a cluster.

A list of key stages of the deployment process that were considered in thescope of the report is listed below (Table 2).

Table 2: Key Stages of Deployment Considered in Report[Source: Dacre & Bullen, 2001]

Key Stages of Deployment

Transportation Movement of installation equipment Transportation of

foundations/towers/nacelles/blades etc.

Installation

Physical presence of installation equipment Piling foundations (if required) Grouting/cementing of material during

installation Disposal of spoil from drilling (if required) Minor fuel/oil leaks

Installation of Cables

Cable installation (trenching ops/laying onseabed)

Construction activities - land based

Operations andMaintenance

Overall structure presence Rotor effects Kinetic energy removal Routine maintenance/emergency repairs Physical presence and Operation of grid

connections Overall generation of electricity

Decommissioning Physical removal of pile/tower/nacelle/blades etc. Disposal


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input for a research programme. The matrix itself, however, is unable to takeaccount of the fact that environmental components may be affected through

more than one environmental pathway and by more than one aspect of thedevelopment. In reality, potential impacts are a complex web of interactions.Hence, it fails to draw upon the additive, synergistic or neutralising effectsome interactions may have. A simplified conceptual diagram has beenincluded (Figure 1) to illustrate the complexity of potential impacts within themarine natural environment (Dacre & Bullen, 2001).

2.5 Environmental Impact Significance

Having provided an initial identification of the deployment activities and the physical, ecological and socio-economic components such a project mayaffect, it was also necessary to prioritise each mode of interaction and thus

provide a process to establish principal research areas. This was established by applying an overall significance, using the following criteria anddefinitions which related to:

Likelihood of activity leading to environmental impact andMagnitude of predicted potential impact;

Level of legislation and policy requirements associated with each potential impact;

Level of importance expressed by consultative bodies;

2.5.1 Likelihood of Environmental Impacts

In order to determine the likelihood of occurrence, a score between 1 and 5was allocated (Table 3). Scores that are low are thought to most likely occur within the construction and decommissioning phases, where impacts are mostlikely to occur once or twice for a relatively short period of time. Interactionsdesignated a moderate to high level, are those activities that may affect anenvironmental component more than once in a year due to seasonal influences

and breeding sensitivities. Interactions given a level 5 have the potential toinfluence the environment on continuous or near continuous basis.

Table 3: Determination of likelihood

Occurrence Level


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Table 4: Levels of Magnitude [Source: Dacre & Bullen, 2001]

MagnitudeLevel

Definition

5Severe

Impacts in the local environment are considered to belong-term, with poor potential for recovery. OR effectsare unpredictable as yet, but may cause permanent changeto local environment. Protected areas would also beunder threat of such damage and are in the remit of alltypes of designated area.

Long term detrimental effect on infrastructure and local people. High impact on other sea users.

4Major

Impacts are considered medium term, with recoveryexpected to be likely within 2 to 5 years. May have effecton internationally or nationally protected species,designated sites and habitats.Possible effect on infrastructure and local residence.Impact on sea users.

3Moderate

Impacts leading to short-term damage with recoveryexpected within 2 years. May have effect on protectedlocal important sites. Mitigation and remedy possiblewith consultation.Possible nuisance may be caused, but only over the short-term.

2Minor Changes caused by impact are predicted to be within thescope of natural variability, but are potentially detectable

1Negligible

Impacts and changes caused are unlikely to be detected or measurable i.e. no detrimental impact

+Positive

Some aspects of a development may act as anenhancement to the area, whether within a physical,

biological or socio-economic scenario i.e. benefit to thelocal, regional and national economy; tourism etc.

The overall environmental significance for each component, with respect to


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13

Table 5: Environmental Interactions Matrix [Source: Dacre & Bullen, 2001]

PHYSICAL ENVIRONMENT BIOLOGICAL ENVIRONMENT SOCIO-ECONOMIC ENVIRONMENT

C l i m a t e /

A t m

T i d a l c u r r e n t s

W a v e c l

i m a t e

S a l i n i t

T e m e r a t u r e

A m

b i e n

t n o i s e

S e d i m e n

t a t i o n

S e a b e d

W a t e r

C o l u m n

W a t e r u a

l i t

C o a s t a l

D n .

B e n

t h o s

P e l a i c o r .

D e m e r s a

l o r .

P l a n

k t o n

V e e t a t

i o n

S e a b

i r d s

P i n n

i e d s

C e t a c e a n s

D e s

i .

A r e a s

F i s h

i n g

S h i i n / N a v

C a b

l e s /

P i e s

O i l / G a s

f i e l d s

M i l i t a r

M a r

i n e

A r c

h e o

T o u r

i s m

T e c h

B a s e

G r i d

i n f r a s

L o c a

l r e s

i d

O t h e r u s e r s

Environmental Component

Deployment Activity

1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 2 9 3 0 3 1

Movement of installation equips. a

Physical presence of install equip b

Piling foundations c

Grouting/Cementing d

Disposal of spoil e

Minor fuel/oil leaks f

Installation of foundation/tower etc g

Installation of cables h I N S T A L L A T I O N P H A S E

Land based Activities i

Overall structure presence j

Rotor effects k

Extraction of tidal energy l

Routine maintenance/repair m

Physicality/Ops of grid connection n O P E R A T I O N S

P H A S E

Overall generation of elect ricity o

Presence of decomm vessels p

Physical removal of structure q

D E C O M

P H A S E

Disposal r


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14

Figure 1: Simplified Conceptual Diagram of Potential Physicaland Ecological Interactions and Impacts of the Project

Source: Dacre & Bullen, 2001

C o

l l i s i o n

R i s k

TIDAL STREAM ENERGYDEVICE S

Deploymentand Cabling

StructureRotor

Change inSed/Coastal Dyn

WaveModification

Mammal/FishRestriction

Changes inSpawning Grounds

Changes inNut/Part input

Changes inIntertidal Area

Coastal Erosion

Land Implications

Changes in Floraand Fauna

Changes in TidalVelocity/Direction

Siltation

Changes in SedTport/Deposition

Changes in Water Quality/Transparency

Decrease in SusFeeders /

Increase in Sed.Digesters

Water ColumnDisturbance

SeabedScouring/Erosion

Changes in NutrientProductivity

Changes inPhytoplankton Prod

PotentialIncrease in Bacteria

Benthic Anoxia

C o

l l i s i o n

R i s k

AcousticEmission

PossibleInterference withMammals

Rotor BladeVorticity

Extraction of Energy


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15

Table 6: Likelihood and Magnitude Significance Matrix

PHYSICAL ENVIRONMENT BIOLOGICAL ENVIRONMENT SOCIO-ECONOMIC ENVIRONMENT Environmental Component

Project Activity C l i m a t e /

A t m


W a v e c l

i m a t e

S a l i n i t

T e m e r a t u r e

A m

b i e n

t n o i s e

S e d i m e n

t a t i o n

S e a b e d

W a t e r c o

l u m n

W a t e r u a

l i t

C o a s t a l

E n v .

B e n

t h o s

P e l a i c o r .

D e m e r s a

l o r .

P l a n

k t o n

V e e t a t

i o n

S e a b

i r d s

P i n n

i e d s

C e t a c e a n s

D e s

i .

A r e a s

F i s h

i n g

S h i i n / N a v

C a b

l e s /

P i e s

O i l / G a s

f i e l d s

M i l i t a r

M a r

i n e

A r c

h e o

T o u r

i s m

T e c h

B a s e

G r i d

i n f r a s

L o c a

l r e s

i d

O t h e r u s e r s

Movement of installation equips. 1 1 1 1 1 1 1 1 1

Physical presence of install equip1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Piling foundations 1 1 1 1 1 1 1 1 1 1 1

Grouting/Cementing 1 1 1 1 1 1 1 1

Disposal of spoil 1 1 1 1 1 1 1

Minor fuel/oil leaks 1 1 1 1 1 1 1 1 1 1 1

Installation of foundation/tower etc 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Installation of cables 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I N S T A L L A T I O N P H A S E

Land based Activities 1 1 1 1 1 1 1 1 1 1

Overall structure presence 5 5 5 5 5 5 5 4 4 1 4 4 4 5 5 5 2 3 5 2

Rotor effects 5 5 5 5 5 5 5 5 3 3 1 3 3 3 3 2 2 2

Extraction of tidal energy 5 5 5 5 5 5 5 5 5 1

Routine maintenance/repair 3 3 3 3 3 3 3 3 3 3 3 3 3 4 3 3

Physicality/Ops of grid connection 5 5 1 4 5 5 O P E R A T I O N S

P H A S E

Overall generation of electricity 5 5 5 5

Presence of decomm vessels 1 1 1 1 1 1 1 1 1 1 1 1 1 1

Physical removal of structure 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

D E C O M

P H A S E

Disposal 1 1 3 1 1

Severe

Major

Moderate

Minor

Negligible

Positive

MagnitudeLevel

5Continuous

4High

3Moderate

2Minimum

1

1 off even tLikelihoodLevel


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Table 8: Significance of Consultative Concerns

Concern Categories Level

There is a widely held concern, which corresponds to feeling that project activity will have a long-term effect and measures will haveto be taken to mitigate that concern.

a

Local concern, where issues have been raised with moderately to lowimpact potential issues b

Issues that may affect individual people, local businesses that can bemitigated fully. Where concerns have been raised with issues that

are deemed non-impact specific.

c


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18

Table 9: Legislation/Policy and Consultative Concern Significance



A t m


W a v e c l

i m a t e

S a l i n i t

T e m p e r a

t u r e

A m

b i e n

t n o i s e

S e d i m e n

t a t i o n

S e a b e d

W a t e r c o

l u m n

W a t e r q u a l

i t y

C o a s t a l

E n v .

B e n

t h o s

P e l a i c o r .

D e m e r s a

l o r g .

P l a n

k t o n

V e e t a t

i o n

S e a b

i r d s

P i n n

i p e d s

C e t a c e a n s

D e s

i .

A r e a s

F i s h

i n g

S h i p p i n g

/ N a v

C a b

l e s /

P i e s

O i l / G a s

f i e l d s

M i l i t a r

M a r

i n e

A r c

h e o

T o u r

i s m

T e c h

B a s e

G r i d

i n f r a s

L o c a

l r e s

i d

O t h e r u s e r s

Movement of installation equips. b b b b

Physical presence of install equip b b b

Piling foundations

Grouting/Cementing

Disposal of spoil

Minor fuel/oil leaks b b a c c b b b

Installation of foundation/tower etc b c a c c b b b

Installation of cables b I N S T A L L A T I O N P H A S E

Land based Activities

Overall structure presence b a a b b c b c b a b a a c c

Rotor effects a a b b b c c c c b a

Extraction of tidal energy a a a a b c

Routine maintenance/repair c c

Physicality/Ops of grid connection O P E R A T I O N S

P H A S E

Overall generation of electricity

Presence of decomm vessels b b b b

Physical removal of structure b b b b

D E C O M

P H A S E

Disposal


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20

Table 12: Overall Significance Matrix



A t m


W a v e c l

i m a t e

S a l i n i t

T e m p e r a

t u r e

A m

b i e n

t n o i s e

S e d i m e n

t a t i o n

S e a b e d

W a t e r c o

l u m n

W a t e r q u a l

i t y

C o a s t a l

E n v .

B e n

t h o s

P e l a i c o r .

D e m e r s a

l o r g .

P l a n

k t o n

V e e t a t

i o n

S e a b

i r d s

P i n n

i p e d s

C e t a c e a n s

D e s

i .

A r e a s

F i s h

i n g

S h i p p i n g

/ N a v

C a b

l e s /

P i e s

O i l / G a s

f i e l d s

M i l i t a r

M a r

i n e

A r c

h e o

T o u r

i s m

T e c h

B a s e

G r i d

i n f r a s

L o c a

l r e s

i d

O t h e r u s e r s

Movement of installation equips. +

Physical presence of install equip +

Piling foundations

Grouting/Cementing

Disposal of spoil

Minor fuel/oil leaks

Installation of foundation/tower etc

Installation of cables I N S T A L L A T I O N P H A S E

Land based Activities

Overall structure presence

Rotor effects

Extraction of tidal energy

Routine maintenance/repair +

Physicality/Ops of grid connection + O P E R A T I O N S

P H A S E

Overall generation of electricity + + + +

Presence of decomm vessels

Physical removal of structure + D E C O M

P H A S E

Disposal + +


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2.7 Key Environmental Impacts

With respect to the identification process, the key environmental interactionsthat have been recognised as being of particular interest, are summarised inTable 5.12.

Table 13: Summary of Key Environmental Impact Issues

EnvironmentType

Key Interests OtherInterests

Ecological BenthosSeabird disturbancePinniped disturbance

Vegetation

Physical

Ambient noise levelsWater turbidity and qualitySeabed disturbanceOverall impact on coastal dyn.Designated area disturbance

Installation

Socio-EconFishingShipping and navigationconstraints

Impact onother users

Ecological

SeabirdsPinnipedsCetaceansBenthos

Physical

Tidal current movement andintensityWave climateAmbient noise levelsSedimentation/SeabeddisturbancesWater turbidity and qualityOverall effect on coastal

environment

Designated areadisturbanceOperations

andMaintenance

Socio-Econ

FishingShipping and navigationconstraintsGrid Infrastructure

TourismOther Users


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Ambient Noise Levels/Vibration/Visual Installation/Decommissioning Disturbance

These sources of impact, whether directly or indirectly have a potential effecton the following physical and ecological components of the marineenvironment:

Tidal Current Velocity Tidal Current Dynamics Wave Climate Sedimentation and Seabed Disturbance Turbidity and Water Quality Resident or Migratory Cetaceans Marine Ecology

Table 14: Sources of Impact and Related Environmental ComponentsLikely to be Affected.

Impact Source Affected Environmental Components

Kinetic Energy Removal

Tidal Current VelocityWave ClimateSedimentation/TurbidityMarine Ecology

Rotor/StructureInterference

Wave ClimateTidal Current Dynamics

Seabed DisturbanceSedimentation/TurbidityMarine Ecology

Ambient Noise/VibrationResident or Migratory CetaceansMarine Ecology

Installation /Decommissioning

Seabed DisturbanceTurbidityMarine EcologyResident or Migratory Cetaceans


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consequence models. Processes and interactions may also have neutralising,synergistic or additive effects on each other. Each CM does not have the

capacity to reflect these complexities. However, in time such models may beintegrated.

ResearchModels

Identification of Environmental Impacts

Screening of PrincipalResearch Areas through

Matrix Methodology

Define BaseScenario Define ProcessScenario

Define ConceptualModels

MathematicalModels

PhysicalModels

Research andMonitoring

STAGE 1

IDENTIFICATION

STAGE 2

CONSEQUENCEMODELDEVELOPMENT

STAGE 3

RESEARCH/MODELDEVELOPMENT

STAGE 4

MODELLINGSTAGE


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25

Table 15: Key Environmental Interactions and Process ScenariosMatri

x Ref

Environmental Interaction Potential Impacts/Environmental Interrelationships

Processscenario

Influencing ExternalVariable

(Project Activity)

AffectedEnvironmental

Components

Environmental ProcessesInvolved

EnvironmentalImpacts/Consequences

(Level 1)

EnvironmentalImpacts/Consequences

(Level 2)

a1 Manu/Installation Atmosphere Dispersion of gas conc. Local atmospheric pollutionTidal currents Blockage/Obstruction Tidal dynamics disruptionWave climate Blockage/Obstruction Wave dynamics disruption

Ambient noise Sound Propagation > ambient noise Disturbance of marine ecologySeabed Direct seabed disturbance from piling,

disposal of spoil, installation of foundation; cables etc.

Benthic ecology impacts i.e.smothering, crushing etc.

Increased sed. entrainment

Mortality/re-distribution/ < popIncreased turbidity

Water column Sediment entrainment > turbidity Ecological ImplicationsWater quality Chemical diffusion of leaked

substances> local pollution Ecological implications

CoastalEnvironment

Cabling processes/disturbance Habitat destruction Ecological Implications

Benthos Disturbance/smothering/crushing/vibration/sound propagation

Re-distribution/Mortality < population/recolonisation

Pelagic Org. Sed entrainment/Sound propagation

> turbidity/ambientnoise Avoidance/ < population

Demersal Org. Disturbance/smothering/crushingsediment deposition

> turbidity/deposition < population

Seabirds Visual/Physical Intrusion Increased activity/disturbance Temporary avoidancePinnipeds Visual/Phy Intrusion

Sound PropagationIncreased ambient noise/disturbance Temporary avoidance/desertion

Phases b-I p-r

Installation/DecommPhases

Cetaceans Sound propagation Increased ambient noise Avoidance/Chg in migration routes etc. j2 Tidal currents Blockage/Obstruction/Funnelling Tidal dynamics disruption Chg in coastal dynamics j3 Wave climate Blockage/Obstruction Diffraction/reflection Chg in coastal dynamics j5 Temperature Heat Transfer Localised sea temp rise j6 Ambient Noise Sound propagation > ambient noise Disturbance of marine ecology j7 Sedimentation Entrainment/Deposition Scouring/Deposition Chg in Sediment/coastal Dynamics j8 Seabed Direct disturbance/vibration Seabed movement Sedimentation Implications

j11

Structure Presence

Coastal Env Coastal dynamics/Sedimentation Chgs to Intertidal area Ecological Implications


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3.3 Consequence Models

Each consequence model (CM) reflects the broad research areas highlighted insections 2.7 with respect to the key sources of impact and related physical andecological implications. Environmental processes established in Table 15, arealso incorporated into each model, and these are represented as follows:

Table 16: Key to Environmental Processes Represented in the CMs.

Environmental Process CM ReferenceChemical Absorption CAChemical Diffusion CDCollision Risk CDirect Seabed Disturbance DSDEncrustation (artificial reef) EHeat Transfer HTLiquefaction LqOrganism Re-distribution OR Recolonisation (recovery) R Sediment Deposition SDSediment Entrainment SESediment Movement (scouring/erosion) SMSediment Threshold SThSound Propagation SPSurface Distortion Sdist

Tidal Energy Decrease TEDTidal Flow Distortion/Modification TFMTurbidity TbTurbulence TVortex Formation VFVorticity Effects VEWake Effects WAWave Diffraction/Reflection WDR Wave Modifications WM


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3.3.1 Kinetic Energy Removal

Figure 3: Impact of Kinetic Energy Removal (CM1)

Tidal CurrentEnergy Device

Energy Removal

Tidal Flow Tidal Direction

Suspended

Changes in Water Quality

Water Column Seabed Changes

Changes inCoastal

Changes in Ecology;inter-tidal habitats

TEDTFM TFM

SM; WM

Chgs in STh

SD

Tb chgsSM; TFM;WM

CM1a

CM1b

CM1c


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consequence pathways could cause potential impacts with regard to marineecology, whether positively or detrimentally. For example, early depositionmay create new habitat areas and may result in the colonisation by benthiccommunities. Figure 3 summarises the potential impacts due to energyextraction as consequence model 1 (CM1).

3.3.2 Rotor and Support Structure Interference

Figure 4 and Figure 5 summarises the potential impacts of the rotor andsupport structure interference as consequence model 2(i) and 2(ii).

Support Structure

Any structure placed in a marine environment has the potential to change theflow patterns in its surrounding area. Resulting implications include thereduction of current flow; the formation of vortices in front of the structure;the formation of a lee-wake (wake effects) behind the structure; the generationof turbulence and the reflection and diffraction of waves. Liquefaction mayalso occur, allowing sediment material to be carried off by currents and thusmay lead to increased turbidity and changes in water quality. All these

potential processes will inevitably cause changes in local sediment transportand thus lead to scour, which is related to changes in sediment re-suspensionand the potential occurrence of hollows and selective erosion around thestructure. Not only does this serve as an environmental impact, but is also athreat to the stability of the support structure itself.

Entrapment, scour and selective erosion of sediment associated with the presence of structures on the seabed are dependent on seabed characteristicsand sediment type and also the type of structure and the spacing, alignmentand the number of structures imposed.

These issues may also have an added localised effect on the benthos, but sucheffects are assumed to be long term and relatively slow in developing. Theextent of these physical effects on the biological environment is unclear, butcould be beneficial to existing communities with the formation anddevelopment of new seabed habitats. Changes may also encourage thecolonisation of other benthic communities. The structures themselves mayalso serve as an artificial reef, evidence of which can be found on the offshore


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generation of turbulence in the water column and subsequent sedimentationand turbidity issues.

The rotors also represent a collision risk for some marine organisms. Concernhas been expressed for the possible collision risk of fish, but this is thought to

be extremely low. Seabirds are also thought to be at risk, with regard tounderwater shadowing and the mistaken identity as shoals of fish. This againis thought to be a low impact potential. Substantial concern has beenhighlighted, however, for the potential collision risk of marine mammals, suchas pinnipeds and cetaceans. However, it is assumed that the fluid dynamics of

the rotors may aid in the protection of such risk. The physical forces involvedare expected to push any objects through or over the blades clear of anycollision. This does not apply for species larger than the rotor diameter.Avoidance and detection techniques have been witnessed, however, throughcontrolled experiments, whereby such marine mammals have the capacity toavoid oil spills and slicks. Noise emissions may also act as deterrent from theimmediate vicinity of the turbines.

3.3.3 Ambient Noise and Vibration Levels

There are two main sources of noise and vibration within the context of tidalcurrent turbine development. The first is the installation phase which mayinclude the propagation of noise from cable construction and the presence of

boats and other equipment (for example, vessel engine noise; propeller andthruster cavitation; vessel ancillary equipment, both continuous [machinery]

and impulse [hammering]; and piling to secure the structure). Sound fromonshore activities that also propagate into near-shore waters. The secondconcerns the possible noise emissions from the operational characteristics of the device itself.

In terms of impact there are two main sources of consequence. The vibrationof the seabed, and secondly, the influence noise may have on the ecologicalenvironment in terms of its biological components.

Excessive vibration may cause direct effects to the seabed, includingliquefaction, increasing turbidity and disturbing benthic communities.However, this is dependent on the type of seabed and sediment characteristicsand therefore, no significant adverse impacts are expected.


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Figure 4: Support Structure Impacts (CM2(i))

Support Structure

Changes inTidal Flow

WaveModification


Scour/Erosionof Seabed

SeabedStability

EcologicalImplications

TED WDF

T; VF

L DSD

Rotor


Collision Risk

VF; T

T; VE

CM2d

CM2e

CM2f


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The principal fauna affected are likely to be the marine mammals, such as, pinnipeds and cetaceans.

Marine mammals create sounds to communicate about the presence of danger,food, other animals, positioning, identity, territorial and reproductive status(Richardson et al ., 1995). Cetaceans are also known to use echolocation as ameans by which to detect and characterise underwater objects. It is thesesounds and the potential detrimental effect of possible tidal turbine sound onthese activities that raise concern.

Pinnipeds

Short- term installation and cabling works may cause some discomfort andstress, especially in breeding times to such mammals. The extent to whichnoise will impact local colonies of pinnipeds within the surrounding area of adevelopment is also a concern. Usually male pinnipeds use airborne calls tocompete for females and territory. However, females and their pups vocalisein air and water to maintain contact. Underwater calls are also usually used toco-ordinate mating. There is concern with regard to the possible noiseemissions from the operating turbine, but there is evidence to suggest thatseals readily habituate to low level background noise and sounds that becomefamiliar to them. The full extent to which noise interference may impact onseal colonies is unknown.

Cetaceans

Cetaceans rely heavily on sound for many functions necessary for survival andare therefore likely to be affected by any noise produced. Some species of Cetacean also rely on echolocation by sound waves for navigation and socialinteraction and this could also be potentially disrupted by additionalunderwater noise. Some species are more sensitive than others to differentnoise levels and have different adaptations to cope with extensive ambientsound.

The extent of cetacean occurrence does not have to be high, or an areaextensively used for cetacean migration or breeding, to be important withrespect to noise impact. It has been suggested that marine mammals can hear sounds up to 185 Km from source, which could potentially mask any low


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reactions have been evident, such as a decrease in speed, even though thecetaceans may maintain direction.

Whether sounds impair communication in marine mammals is something thathas always been under speculation. It is not necessarily one noise alone thatmay have an effect, but the cumulative effect of all noise present should beconsidered. This can be a very subjective task, as a cumulative effect onmarine mammals of noise from multiple sources has not yet been specificallystudied.

The presence of multiple noise sources in an area may increase the severity of any adverse noise effects resulting from single sources. This in turn createsimplications for tidal farms in critical areas. The long- term consequences of multiple noise sources depend partly on the degree of habituation to repeatednoise exposure. It is expected that habituation would be comparatively fast if various noise sources emit similar sounds. There is evidence of considerabletolerance of repeated exposure to human activities. However, there are casesof reduced numbers of marine mammals in areas with many human activitiesand it is difficult to obtain conclusive evidence about the occurrence andcauses of long-term declines. The consequence model (CM3) describing noiseand vibration impact can be found in Figure 6.

3.3.4 Installation/Decommissioning Disturbance

With any offshore or coastal development, installation and the cabling

involved will inevitably affect the seabed. The installation anddecommissioning phases are assumed to create the most direct adverse impactwith respect to seabed disturbance. Impacts of this nature, however, are

predicted to be short-term and very local, concentrating around the structureand cabling areas. The degree of impact is very dependent on the type of structure, cables and installation methods used.

Installation processes will result in the disturbance of fauna and flora in thearea, especially seabed communities. Such communities will be impactedthrough direct displacement of species located in the immediate vicinity of theinstallation operations and, in-directly, through the re-distribution of anysediment present in the water column and the possible risk of smothering asthe result of re-settlement. Sediments that result from drilling operations and


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Though direct comparison cannot be made, they do provide a preliminaryindication of such rates, which could be in the region of two to three years.

Impacts on sea fish could potentially arise through the disturbance of spawning and nursery grounds and the risk of smothering or direct mortality ishigh for demersal species, such as flat-fish. Indirectly, re-suspension of sediment may possibly increase any food source, especially for pelagicspecies.

Installation and decommissioning may also have an effect on seabird colonies.

Close approach of vessels and the approach of people are effective sources of disturbance. Though such activities seem relatively harmless, they can ineffect cause detrimental impact on bird populations and there is evidence tosuggest that constant or systematic intrusion can lower bird productivity and,in the severest of cases, cause desertion.

Awareness must also be made of the short-term localised impact of contamination. Through the installation and decommissioning phases,contamination may occur through minor oil and fuel leaks from vessels.There is also a minimum risk of the gearbox leaking. Anti-corrosion and anti-fouling agents may also have an influence on the chemical composition of thelocal seawater environment. This is likely to be negligible due to the fact thatmany present agents are less damaging to the environment with regard to their chemical composition and the amount of time it takes for such agents to bereleased into the environment, if at all. Figure 7 summarises installation and

decommissioning impacts.Tidal Current

Ener Device

Installation O erations

AcousticEmittance

AcousticEmittance Vibration

Ambient Noise

Ecolo ical

Seabed Device

LSPSP

DSSM

CM3a

CM3b

CM3c


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35

Figure 7: Installation Impacts (CM4)

Installation Phase

Seabed

Benthic Organisms

ChemicalComposition

TurbidityWater

Quality

Re-colonisation New Species

Increase inPopulation

Decrease in Pop

Inter-tidal/Land

Loss of Habitat(T)

Recolonisation

Demersal OrgPelagic Org

AcousticEmittance

Phy/VisualIntrusion

IncreasedDisturbance/Ambient

Noise

Seabirds M.Mammals

Disturbance/Stress

BreedingInterference

Avoidance/Desertion

change inmigration/Comm

Decreasein Pop

DSD

CD

CA

SECA;CD

Mortality

SE

SP

DSD

CM4a

CM4b

CM4c


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3.4 Identification and Formulation of Research Projects

3.4.1 Identification and Prioritisation of Research Projects

By assessing the importance of the overall impact significance, as summarisedin Table 12, and using the consequence models formulated in section 3.3 anumber of research projects were identified. Some other projects were alsoidentified, though not directly related to the consequence models (Table 18).

All projects were identified with respect to impact source and divided into

sub-projects or stages. Each project was then given a project reference code.It is evident some projects are significantly related to others, in the fact thatsub-projects are likely to be precedents to other sub-projects. For example,

project CM1b cannot be achieved without the results from CM1a. The table below summarises the research projects identified.

Table 17: Research Projects Identified from the Conceptual Models

Research Project Title CM ReferenceKinetic Energy Removal CM1Energy Removal CM1aTidal Flow Interaction CM1bSediment and Seabed Interaction CM1c

Support Structure Interference CM2(i)Support Structure/Tidal Flow Interaction CM2aSupport Structure/Wave Interaction CM2bSupport Structure/Seabed Interaction CM2c

Rotor Interaction CM2(ii)Rotor/Water Column Interaction CM2dRotor/Seabed Interaction CM2eCollision Risk Probability (Ecological) CM2f

Acoustic/Vibration/Visual (AVV) Characteristics CM3Operations Acoustic Emissions CM3a

Ecological Implications CM3bVibration Characteristics CM3cVisual Disturbance Assessment CM4c

Installation/Decommissioning Implications CM4Ecological Comparison CM4a


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From the research prioritisation (Table 20), 16 projects were found to be of ahigh to moderate research level. This indicates that there are not only manyknowledge gaps that need to be closed, but the research issues identified haveassociated impacts that are deemed to be significant with respect to tidalcurrent energy and the environmental implications involved. With this inmind it is evident that a research programme needs to be established in order to accommodate all research areas. Research projects identified have also

been ranked in order of priority (Table 21), which reflects not only theimportance of such research towards the development of tidal current energy,

but also the overall research need and availability of current knowledge.

Some projects are ranked in pairs, which emphasises the fact that some projects are highly dependent upon the results of the relevant preceding project.

3.4.2 Research Project Measurables and Observables

It is apparent that the research projects identified are not only individualsystems, but they are also a series of inter-related scenarios that can beadditive, synergistic and neutralising in nature. Bearing this in mind, it is alsoevident that such projects have similar project measurables and will beaggregated as one, but will be used for a number of different ends and means.Section 4 will discuss this further. Table 22 summarises project measurables.

Kinetic Energy Removal (CM1)

In order to quantify the scale of likely effects associated with the extraction of energy a computational study will need to be formulated. Initially, this shouldinclude measurables associated with the total amount of energy extracted byone turbine in a hypothetical channel using computational modellingtechniques. From these results, tidal and wave influences can then beestablished through further modelling techniques. Sediment interactions, suchas deposition can then be established using a theoretical or modellingapproach. In time, it would be helpful to extend this research to different

numbers of turbines, configurations and channel scenarios.


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40

Research Project CM Ref OverallSig.

Cons.Con

Know.Status

Comments ResearchPriority

Visual AssessmentCM4c M 2 Visual impact is an important factor to assess, not only from an ecological point of view, but also

with respect to human consideration and can be associated with noise impact. All in all it will bea useful exercise to assess the visual amenity of tidal current energy.

2

Install/Decomm CM4EcologicalComparison

CM4a 2 3

Water Monitoring CM4b

H Yes

2

Impacts can be compared to the oil/gas industries and other offshore projects, but there is littledocumentation, especially concerning recovery rates. Monitoring is an essential process in theseareas to ensure minimal impact and to quantify species abundance and density impacts. Oncefully understood, mitigation procedures may be established.

3LCA LCA

Env Releases/CO 2Study LCA(i) n/a 1 2

RE Comparison LCA(ii) n/a

Yes

1/2

Though tidal current energy is a renewable resource, harmful releases will inevitably occur duringthe manufacturing, installation and decommissioning phases of a project. In order to quantify

such releases a Life Cycle Assessment needs to be done. This will also enable the net CO2release to be quantified in order to establish the benefit of a tidal current energy device in thisarea. Comparison of results to other renewables will also be very useful.

2AntifoulingComparison

AC

Antifoul Analysis AC(i) M 3 2ToxicityComparison

AC(ii) MYes

3

A major concern is what effect antifouling and corrosion prevention will have on the local marineenvironment. Much research has gone into establishing the effects of antifoulants, with new

products on the market. Environmentally, toxicity comparisons of different products should beassessed, along with an assessment of the effectiveness of each product on encrustation - animportant factor associated with the efficiency of tidal current energy.

2

Parametric Model PMD n/a n/aParametric modelling development is an important stage to consider with respect to the further development of tidal current energy. Such modelling will allow tidal energy systems to beequated with potential sites and their environmental conditions.

n/a


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h ld d h ll i i d h i h l


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changes could reduce the overall impact, encompassing and enhancing the roleof renewable energy as a clean energy.

Antifouling Comparison

Encrustation is an important issue with respect to tidal energy devices - theeffects can be severe, which include increased drag and lower bladeefficiency; increased inertial and gravity loads due to increased surfaceroughness, area and mass and increased corrosion rates and the possibleabrasion of cables. A comparison of treated and non-treated devices would be

advantageous with respect to increased knowledge in growth rates and theeffects on efficiency. Toxicity comparisons with antifouling treatments shouldalso be taken into consideration to ensure the minimum of impact possible. Adesk study encompassing toxicity, diffusion rates etc. would suffice.

Table 22: Summary of Project Measurables

Required MeasurablesResearch Project Type of Study

Monitoring Programme Comp/Analysis Prog.Kinetic EnergyRemoval

Cp Nm Tide/Wave MmentSediment characteristics

Energy extractedTidal/Wave distortionSed. Interaction

Support StructureDSCp

Nm

Tidal velocityWave mmentSuspended loadSediment characteristicsBed formation

Bed shear stressOscillatory flowSediment transportBed load transport

Rotor InteractionCp

NmTidal velocity/flowSediment characteristicsSeawater characteristics

Tip-vorticity propagation/behaviour Seabed InteractionHydrodynamics of flow

Acoustic, Vibrationand VisualCharacteristics

M NmCpDS

Seawater characteristicsFrequency

Sound power levelAttenuationSeabed characteristicsEcologicalabundance/composition

Propagation path/distanceEcological sensitivities

R i d M blR h P j T f


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Required MeasurablesResearch Project Type of Study Monitoring Programme Comp/Analysis Prog.

AntifoulingComparison

DSM

Encrustation Toxicity analysis

Type of Study Abbrev. Monitoring M Desk

Study/Theoretical DS

Analysis AComputational Cp

Numerical Nm

4 PROGRAMME OF WORK

To achieve the research projects outlined, the programme of work can bedivided into two areas, which can run simultaneously. The first is a fieldmonitoring programme and, the second a programme purely for computationaland analysis purposes. Both are developed to complement each other in termsof real-time monitoring and validation. Such a programme could run for amaximum length of 40 months and a minimum of 28 months, which isdependent on the resources involved. The latter period of time is set at such aminimum in order to maintain an adequate time for baseline surveys andcontinued monitoring. A longer period would inevitably be beneficial in order to maintain valid and unbiased data. An outline of the work that needs to beinitiated can be found in figure 8 in the form of a Gantt chart. The timescaleand duration of each project can be seen as relatively rational. The dates usedare just examples and do not reflect any start or finishing dates.

4.1 Monitoring Programme

The monitoring programme can be divided into three main areas to encompassthe life of the project time and beyond.

4.1.1 Baseline Surveys

shorter period could be initiated It is recommended that the duration be no


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shorter period could be initiated. It is recommended that the duration be noshorter than three months. The spring and summer months are the mostcritical and such studies should be conducted within that time-scale. Theduration of the study is not so critical, as long as samples and data arecollected at the same time of year and then seasonality differences can beruled out. However, defining and monitoring a similar control site near by,concurrently through the operations phase, may be equally beneficial andconsistent as a conventional baseline study. A short baseline and concurrentmonitoring in a similar area may be a further option, not only for theecological studies, but also for the physical parameter monitoring also.

Physical Parameters

There are a number of physical parameters that need to be established. Theseinclude the local tidal velocities, wave height and speed. The sedimentation

parameters, such as, sediment characteristics, suspended load, turbidity andlocal seabed morphology are important baseline parameters.

The chemical composition of the seawater, as well as salinity and temperature profiles will also need to be established. Ambient noise levels are alsoimportant in terms of comparison with acoustic emission results.With respect to baseline study length, duration is less important for the

physical parameters than that of the ecological ones. However, a minimum period of one month is recommended in order to gain a full tidal cycle.Concurrent monitoring in other sites for more generic parameters such asacoustics is reasonable, but not ideal.

4.1.2 Project Monitoring

Project monitoring should be conducted throughout the project lifetime, but itis recommended that a twelve-month period be considered, mainly for thereasons discussed within an ecological context. Any extended amount of time(no shorter than 6 months) is advisable. Data sets for all parameters should be

collected at suitable periods throughout that time, preferably monthly, to gaina comprehensive idea of the changes and influences that may occur.Continuous recording of some parameters would be highly beneficial.

4.1.3 Post Project Monitoring


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4.2 Computational and Analysis Programme

The computational and analysis programme could run parallel to themonitoring programme. With respect to each project, sub-projects rely on the

preceding project to gain results, so any programme of work will need toreflect this. However, most projects will run concurrently and results will notonly reflect the computational and numerical aspects of the programme, butalso the analysis (of the fieldwork) and desk study areas of the overall

programme.


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47

Figure 8: Gantt Chart Summarising Project Programme

ID Tas k Name

1 Baseline Studies2 (CM1a)

3 (CM1b)

4 (CM1c)

5

6 Operation Monitoring

7

8 CM2a/CM2b

9 CM2c

10

11 CM2d

12 CM2e

13 CM2f

14

15 CM3a

16 CM3b

17 CM3c

18 CM4c

19

20 CM4

21

22 LCA

23

24 AC

25

26 PMD

27

2 8 Pos t Mo nitor ing Sur ve ys

Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep2003 2004

CONCLUSIONS AND RECOMMENDATIONS


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The study has highlighted and identified a number of key environmental issuesconcerning tidal current energy development. It is clear that some are wellunderstood within the realm of other offshore industries. Others are, however,relatively unique to this type of development and the need for further researchis evident in these areas to develop a better understanding of theenvironmental implications.

The main conclusions are summarised below:

A number of direct and indirect potential environmental impacts wereidentified and included:

(i) A direct disturbance of the seabed and benthic ecology with regard toinstallation of tidal energy devices and overall operation;

(ii) Potential disturbance of seabirds, pinnipeds and cetaceans during theinstallation phase relating to equipment activity, both visual and auditory;

(iii) Potential changes in the tidal and wave dynamics in the vicinity of thedevice and on a local level due to the structure itself, the rotor vortices andthe extraction or blockage of tidal energy;

(iv) The potential seabed disturbance and change in sediment dynamics

due to the potential changes of tide and wave dynamics (3);

(v) The potential changes in water quality and turbidity due to associatedseabed disturbance and chemical leakage from the device and installationequipment;

(vi) The possibility that acoustic emissions from the operating deviceswill be sufficient to disturb migrating or resident cetaceans, pinnipeds andother marine animals; and

(vii) The potential collision risk associated with diving birds and marinemammals.

(i) The impact of extracting energy through tidal current devices and


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( ) p g gy gthe effects on tidal flow patterns, sedimentation processes and seabedmorphology;

(ii) The effects of the support structures on the wave and tidaldynamics in the area and the possible implications of this on localsedimentation and seabed movement;

(iii) The effects of the rotor interactions with the water column and thesubsequent effects on seabed morphology;

(iv) The collision risk probability for marine mammals and fish;

(v) The acoustic emissions of the tidal energy device and the potentialimplications involved with respect to marine mammals and elsewherein the marine ecology, such as fish;

(vi) The vibration and visual characteristics;

(vii) The overall ecological impact of the installation and operation of a tidal energy device, including an assessment of recovery time after decommissioning;

(viii) A comprehensive Life Cycle Analysis (LCA) concentrating onCO 2 emissions and a subsequent comparison with other renewableenergies;

(ix) An assessment into the need for antifoul prevention and a toxiccomparison of each alternative;

(x) The development of a Parametric Model.

The research areas and projects identified have been deemed to have the

following benefits:

(i) The ability to enhance knowledge and understanding of theenvironmental issues raised, not only, within the realm of tidal currentenergy, but other offshore development industries;


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In conclusion, this study has highlighted that it is a common misconceptionthat renewable energies are without environmental detriments and thatadequate research is required to eradicate uncertainties with respect to themagnitude and likelihood of such impacts. It has identified the presentresearch needs and briefly discussed the implementation of those addressed.


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5 REFERENCES


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Boesch, D.F. and Rabalais, N.N. (Eds.) (1987) Long Term Environmental Effects of Offshore

a scoping study for an environmental impact field programme in tidal current energy

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