Environmental Impact Assessment for Wind farms

Environmental Impact Assessment for Wind farms
Ruth Stevenson, BSc, MSc, PhD
The UK Government has set out Energy, Climate Change and Planning Policy that supports
renewable energy in the attempt to curb CO 2 emissions. These policies were explored in a previous
paper on ‘Planning for Renewables’ (Module 3). As a result of these UK wide policies, Local
Authorities are required to set regional renewable energy targets. Wind power is viewed by many
Authorities to be one of the prime technologies for meeting these targets. However, in order to
implement wind energy projects, planning permission is required, either from the Local Authority
or from the Government through the Secretary of State for Business, Enterprise and Regulatory
Reform ( 50MW by Government). For the majority of windfarm
schemes, planning permission will require the presentation of an Environmental Impact Statement
(EIS), which identifies the environmental, social and economic impacts of the development. This is
used as a decision tool when determining whether planning permission should be granted.
This paper will review the environmental Impact Assessment process, indicating how this fits in to
the planning process but equally how it can be used as design guide for windfarm planning. The
paper will address the following questions:
1. What is an Environmental Impact Statement (EIS)?
2. When is it required?
3. What is the process of an Environmental Impact Assessment (EIA)?
4. What are the environmental, social and economic issues associated with windfarm
developments? How do you assess them and mitigate for them?
5. How does the regulatory body decide whether to grant permission?
6. How does the regulatory body enforce any mitigation requirements following construction?
What is an Environmental Statement?
This is the document containing the EIA that accompanies the Planning Application. It has certain
statutory requirements in terms of its contents. If a full EIA is not required (see below) the
environmental information can be presented in a shorter document without these requirements. The
idea is that enough information is provided so that readers can verify the Statement's conclusions
and to identify the source of the information provided. A Non Technical Summary (NTS) is one of
the requirements of the EIS.
What is an Environmental Impact Assessment?
AN EIA is a predictive tool, where the likely significant effects of a development, both positive and
negative are objectively analysed. This information is used to determine whether the development
should go ahead or not. As the Department for Communities and Local Government (2006) state:
“It is a means of drawing together, in a systematic way, an assessment of a project's likely
significant environmental effects. This helps to ensure that the importance of the predicted effects,
and the scope for reducing them, are properly understood by the public and the relevant competent
authority before it makes its decision.”
I think there are also some important additions to this definition of an EIA. The ‘environment’ in
this case actually covers, not only natural resources, but also environmental quality and impact on
communities, be they environmental, social or economic. The EIA process should enable all of
these factors to be given due weight when an application is being determined.
An EIA is not only a tool for decision makers, it is also a tool for the designers and developers of a
scheme to ensure that they derive maximum benefits from a development (in terms of energy output

and environmental enhancement) whilst minimising local adverse impacts. The EIA process can
throw up design measures that sometimes can enhance certain environments. It is therefore
important to incorporate EIA at the earliest opportunity in any development.
Regulations and Guides
The requirements for an EIA come under the Town and Country Planning Regulations. The primary
legislation is The Town and Country Planning (Assessment of Environmental Effects) Regulations
1988 (“the EIA Regulations”), and equivalent Environmental Impact Assessment (Scotland)
Regulations 1999, which set out the procedural requirements of the EIA process and implements
The European Council Directive No 85/337/EEC (amended by 97/111/EC) on the assessment of the
effects of certain public and private projects on the environment (the EIA Directive).
These regulations are accompanied by the relevant Circulars; DETR Circular 2/99 Environmental
Impact Assessment, (and equivalent Welsh Office Circular 11/99, Scottish Executive Circular
15/1999 which is now being amended and updated. These provide more explanatory information on
the application of EIA regulations (and are an easier read than the T & C Planning Regs!). The
Office of the Deputy Prime Minister(ODPM) has also published a guide: ‘Environmental Impact
Assessment- A Guide to Procedures’ (Office of the Deputy Prime Minister, 2000).
Which Projects Require an EIA? “EIA Applications”
Schedule 1: Always Require an EIA: Tend to be very large projects.
Biomass power station with a heat output of >300 MW or more
Hydro scheme: 10million m 3 reservoir
Section 36 Electricity Act Applications (>50MW onshore/>1MW Offshore)
Schedule 2: Requires EIA if it is likely to have significant effects on the environment by virtue of
factors such as its size, nature or location.
Generally: Hydro >5MW
Wind 5 or more turbines or >5 MMW
Schedule 2 developments require a screening opinion from the Authority (within three weeks) as to
whether an EIA is required.
Permitted Development: some micro renewables (see Permitted Development: Rights for
Householder Micro generation (Communities and Local Government, 2007).
The Process of EIA for Proposed Wind Farms
The figure below sets out the key stages of the EIA process.
Proposal, Scoping and Consultation for Windfarm EIA
The EIA process starts with defining the proposal. This includes size (output), number of turbines,
height of turbines, maintenance tracks, substation and control building, connection to grid etc. It
also includes the various stages of the development: construction, operational decommissioning.
The developer will generally ask the Local Authority for a scoping opinion to determine what
elements of the scheme and what environmental impacts require an assessment i.e. what is required
in the EIS. The Authority is allowed 5 weeks to provide this. This allows the Authority to contact
statutory Consultees and provide a list of issues for which the authority requires information.
The developer may also want to contact the statutory Consultees as part of their own preliminary
surveys and consultations to assess whether the scheme is worth pursuing or not. Consultation

odies are obliged to provide relevant information. The site might be ruled out if the site is in a
particularly sensitive nationally designated area or in the flight line of an airport etc.
Stages in the EIA process
Define proposal
Scoping and consultation
Advise against scheme
Preliminary surveys/ assessments
sensitivity
Identify Impacts
Mitigation.
Design
Changes
Predict impacts
magnitude
significance
Prepare draft ES
Public Inquiry?
Prepare final ES including
Non Technical Summary
Planning policy Appraisal
Reject
Planning Application
and publicity
approve
Monitor
Audit
This is also the stage at which site selection criteria arise. Identification of alternative sites is
considered and it is a requirement of the EIA Regulations to state the reasons for the current choice.
This is often a ‘material consideration’ in deciding an application. In reality, every developer is

likely to look at alternative sites in terms of wind resource and environmental impact prior to
investing thousands of pounds in the planning process.
Schedule 4 of the EIA Regulations sets out the information required for inclusion within
Environmental Statements, and the Companion Guide to Planning Policy 22 (ODPM, 2004) sets out
issues generally required for windfarms. The Government makes clear that it is key issues that are
important rather than information for its own sake (though sometimes planning officers need to be
reminded of this!) Issues for windfarms include:
• Construction and infrastructure Impacts
• Landscape and Visual Impact
• Noise Impact
• Ecological and Ornithological Impacts
• Hydrological impacts, groundwater protection
• Archaeological Impacts
• Electromagnetic Interference and Air Safeguarding
• Public Access, Recreation, Safety
• Shadow Flicker
• Socio – economic effects –positive and negative
• Wider global environmental benefits
In addition to the direct effects of a development, the ES should also cover indirect, secondary,
cumulative, short, medium and long-term, permanent and temporary, positive and negative effects.
Public Consultation
Lack of appropriate public consultation has been blamed for resulting refusals of planning
applications for windfarms e.g. (Toke, 2005). It is advised that consultation should take place at
initial stages of design, and responses be incorporated into design where practicable. It can play an
important role in informing the scope of the EA to ensure local concerns are addressed. The
Scottish Executive’s study “Public Attitudes to Windfarms” (2003) illustrated that issues raised
mirror those above, with visual and noise impact at the top followed by interference with TV,
ecologic effects and house prices.
Assessment of Effects
Critically, for a renewable energy scheme, an EIA informs the decision makers as to whether the
negative local impacts of the development outweigh the positive wider benefits of non fossil fuel
derived energy generation (as set out in climate change and energy policy). It is the significance of
the impact that is therefore important.
In order to assess the impact significance’ a number of steps are required.
1. Firstly the potential structures or construction activities must be identified.
2. Then a base line of existing environment is established.
3. Impact magnitude (of predicted change) is then a measure of the effects of the nature of the
development (size of turbines, number of turbines, access roads etc) on the baseline resource.

4. Mitigation measures are generally put in place to reduce the impact magnitude and a residual
impact magnitude is established. Of course different issues can have conflicting requirements e.g. to
reduce ecological impacts, cabling should be above ground, however this increases visual effects.
The design of a development requires constant revisiting of impacts and designs.
5. Impact significance is then a measure of the sensitivity of the receptor and the impact magnitude.
Impact significance =sensitively of receptor + impact magnitude
A significant impact does not always mean that a proposal is unacceptable. This is partly subjective
but is also influenced by the material considerations of local and Government Policy.
This paper sets out the EIA assessment process for a Windfarm, but could equally well be used for
other technologies.
Wind farm Impact Assessment
Construction Impacts
Compared to the longer term impacts of windfarm developments, construction impacts are
generally considered minor. They include physical effects of the windfarm on highways, land use,
on site access, local resources (used for constructing access tracks) and waste. Traffic movements
are assessed over the period of construction (usually around a year), construction materials are
usually sourced from site if possible and contaminants are minimal (assuming suitable operations
management). Due to the limited magnitude of effects, they are generally considered insignificant.
However, there are particularly sensitive ecological habitats that may suffer from access track
provision (see below).
Landscape and Visual Impacts
Structures to consider:
Modern wind turbines are large structures, around 100m tall, complete with moving elements (the
turbine blades). The landscape and visual assessment is therefore perhaps the most important but
equally most subjective assessment to undertake. The ‘despoliation of the landscape’ is the key
motivation for anti Windfarm campaigners (Burral, 2004, Devine-Wright, 2005, Woods, 2003) and
an EIA must evaluate and set out clearly the potential effects on this resource. There are also access
roads, grid connection and substation facilities to consider, though these are generally considered of
lesser magnitude than the turbines themselves.
Base line:
The first step is the determination of the base line. This takes the form of an assessment of
landscape characteristics (e.g land cover, designations, character areas) to inform the assessor about
its quality and importantly its sensitivity to change. There are standard guidelines for landscape
assessment (e.g. (Landscape Institute and Institute of Environmental Management and Assessment,
2002, Scottish Natural Heritage, 2002).
Assessment of Effects:
This can be divided into
1. An assessment on landscape character and quality (is the landscape character changed and does
this affect its perceived value?)
2. An assessment of the effects on visual amenity (what are the changes in view and how might
these be perceived?)
The significance of impacts on landscaper character are determined by sensitivity of landscape
(from baseline)and magnitude of change (from impact assessment). Similarly the significance of

impacts on visual amenity are determined by sensitivity of receptor (e.g. footpaths, residential
buildings, beauty spots) and the magnitude of change (how many people will see the development).
The graph below illustrates how the impact effects change with these two variables. No effects to
moderate effects are not considered significant. Major to substantial effects are considered
significant.
Landscape / Visual Impact Effects Assessment
high
substantial
effect
MAGNITUDE
OF
CHANGE
medium
low
slight effect
Moderate
effect
no material effect
none low medium high
SENSITIVITY OF LANDSCAPE/RECEPTOR
For the landscape and visual assessments some useful tools include a computer generated Zone of
Theoretical Visibility (ZTV) which identifies those areas from which the windfarm will be visible,
and wire frame and photomontage representations from specified viewpoints illustrating proposed
views.
ZTV off proposed windfarm (extract)
Photomontage of windfarm
Methodologies for assessing the visual impact of wind turbines are quite highly developed (see
references above) but are complicated by the subjectivity of the subject and the emotive nature of
the wind turbine. We also now have the cumulative impact of a number of windfarms to consider
(ETSU, 2000, Scottish Natural Heritage, 2005)
It is true to say that despite approved methodologies, landscape and visual assessment of windfarms
is still an imprecise art and this is why it is so hotly contested at the planning application stage.

Mitigation:
Even at an early stage, design changes can be incorporated into the windfarm design (e.g remove or
moving turbines, reducing turbines heights etc) to address effects on particularly sensitive
viewpoints or landscape areas identified by the baseline. This is a vital part of windfarm planning
and can lead to significantly more sensitive designs. A final assessment of impact magnitude and
significance is then undertaken, based on the final design, having been amended for all
environmental issues. It is the cumulative effects of all the issues that the decision makers will be
interested in.
Acceptability:
It is highly unlikely that a new windfarm proposal in the UK will result in no significant impacts on
landscape and visual amenity. However, significant effects are not necessarily unacceptably adverse.
The acceptability of significant landscape effects of windfarms is a subjective view. There is no
consensus of opinion on the most appropriate types of landscape in which to site the various scales
of wind energy development, nor on the threshold above which significant changes in the view
would have unacceptable effect on visual amenity. This will vary from person to person. Those in
favour of wind energy are more likely to accept greater changes to their visual amenity than those
who do not find wind turbines aesthetically pleasing. Some people will see turbines as
industrialising the landscape. Others will see them as sculptural, as giving expression to a windy
landscape, particularly when their movement is seen to be ‘doing good work’.
These opinions also vary over time, with public opinion surveys consistently concluding that the
majority of people do not think that they are going to like a windfarm when one is proposed, but
consider the development acceptable once it is constructed (British Wind Energy Association, 2005,
Scottish Executive, 2003).
Noise Impact
Elements to assess:
There are two accepted types of noise generated from wind turbines; a) Mechanical noise from the
gearbox, generator etc. and b) aerodynamic noise from the action of the rotating blades. It is
acknowledged that mechanical noise has significantly reduced with new turbine models such that it
is now usually less than or similar to aerodynamic noise. Aerodynamic noise is dealt with in more
detail below 1 .
A third type of noise, low frequency noise (felt as vibrations), has been the cause of some
controversy. The frequency, or 'pitch', of a sound is measured in cycles per second (or 'Hertz' (Hz)).
‘Low frequency noise' describes sound energy in the region below about 200Hz (such as the rumble
of thunder and the throb of a diesel engine both have most of their energy in this low frequency
range). Sensitivity to lower frequency vibration varies considerably between individuals, However,
there appears to be no direct health effects from noise at the level of noise generated by wind
turbines and it is suggested that it even lies below the threshold of perception (BWEA, 2005, ETSU,
1997b).
Wind turbines must be sited to offer a “reasonable degree of protection to wind farm neighbours,
without placing undue restrictions on wind farm development” (ETSU, 1997a). The ETSU guidance
is used in preference to the standard BS 4142 on noise assessment. Some commentators now feel
that this should be updated with turbines being sited increasingly in built up areas, since the
guidance was primarily developed for rural settings.
Baseline:
1 There is an added complication of amplitude modulation due to the blade pass frequency (the number of
blades times the revolution rate), resulting in the characteristic ‘swoosh’. This can increase the annoyance of
the noise. Research is on going.

A ZTV is often used to assess the properties from which noise might be an issue.
The baseline for a noise assessment is measured by background noise measurements. These are
correlated against wind speed and direction at 10 minute intervals. Time history figures are
produced showing sound pressure level against time. The important measurement is the LA90 10
mins, which averages sound levels over a 10 minute interval to remove the effects of individual
transient noises such as aeroplanes, cars etc. graph of (see below). A regression graph is then
generated to indicate how the sound pressure levels change with wind speed.
Noise Impacts Assessment:
Noise from a wind turbine is predicted from manufacturer’s information on source sound pressure
levels based on a reference wind speed at a certain height above the ground (usually 10m). From a
single wind turbine this is usually between 90 and 100 dB(A). At 40m, this translates to a sound
pressure level of 50-60 dB(A), which is about the same level as conversational speech. A number of
attenuating factors e.g. atmospheric absorption and barrier attenuation are then added. The sound
pressure level has the advantage of being an objective yet a handy measure of sound intensity, but it
has the drawback that it is far from being an accurate measure of what is actually perceived. So an
‘A’ weighting is assigned to the sound pressure levels when the background levels are around 40dB
(low).
Some general rules of thumb for noise thresholds: dBA
Threshold of pain 140
Jet aircraft at 250 m 105
Pneumatic drill at 7 m 95
Truck at 30 mph at 100 m 65
Busy general office 60
Car at 40 mph at 100 m 55
Wind farm at 350 m 35–45
Quiet bedroom 20
Rural night-time background 20–40
Threshold of hearing 0
Significance:
In order to determine significance, the A weighted sound pressure levels are assessed against
criteria set out by the ETSU –R-97 guidance which provides advice on noise limits, reiterated by
national Planning Policy PPS 22 and TAN 8 (Wales) etc.
Absolute noise limit: When background noise levels are below 30dB LA90.
Quiet day time: 35-40dBLA90,10mins (depending on number of dwellings, the output of the
windfarm (one turbine causing same amount of noise as 10 turbines would have less planning
merit), duration of exposure.
Night time: 30-35 dBLA9010mins internal (accords with World Health Organisation Guidelines on
Noise (2000). These levels are set to avoid sleep disturbance at neighbouring properties.
Where background noise levels are above 40dB LA90 , then the guidance suggests turbine noise
should not be more than 5dB above the background noise.
The graph below illustrates how the night time noise limits change with windspeed: absolute noise
limits apply up to 40dB background and subsequently, when windspeeds increase the background
noise, limits are set at 5dB above background.

65
Three Moors Wind Farm Turbine Noise Assessment
Whitefield Farm - Predicted Turbine Noise and Background Noise vs Wind
Speed
(Night Hours 2300-0700)
60
55
L90 Sound Pressure Level (dB(A))
50
45
40
35
30
25
20
y = -0.0416x 3 + 0.7653x 2 - 1.5371x + 25.804
15
0 1 2 3 4 5 6 7 8 9 10 11 12
10m Height Wind Speed (m/s)
Measured B/G Noise Night Limit Vestas V80 102.5 Mode Derived Prevailing B/G Noise
So at higher wind speeds (when turbine noise might be high), background noise levels are also
generally higher, so the impact magnitude will be reduced (remember receptor sensitivity +
magnitude = significance). Noise levels are assessed for each property in the vicinity of the
proposed windfarm, or a representative sample. Once again, a substantial effect i.e. a measurement
above ‘absolute noise criteria’ does not mean that a windfarm application should be refused, merely
that the effect must be assessed against all other factors.
With more and more single turbines in residential areas, Local Authorities are having to develop
their own criteria e.g. 100m from residential properties (Powys CC). The DCLG has suggested
limits of 30dB internally and 40dB for neighbouring properties, but this is under review.
Mitigation:
Mitigation will involve reducing turbine numbers, moving turbines away from sensitive properties,
or adapting the turbine specification (e.g. adding baffles and acoustic insulation to generator
housing). A change of turbine manufacturer can also help sometimes.
Ecological and Ornithological Impacts
Factors to consider:
Both the construction and operational phases need to be considered. Construction requires access
roads and on-site access tracks of at least 4m wide, temporary site compounds, and turbine bases,
cabling, grid connection. However, the land between the turbines and access roads is unaffected.
Base line:
The ecological and ornithological merits of a site are surveyed prior to development, with a Phase 1
Habitat survey in the first instance. A level of value is established against which to measure impact,
on the basis of designations, rarity, sensitivity and ecological significance. Habitats and species are
identified, and birds are surveyed at nesting, breeding, over wintering and migration times (these

need to be considered in advance as the surveys are needed over a year’s timescale). Nocturnal
surveys for bats are often necessary.
Low land arable land tends to have minimal ecological value though there may be interesting
hedgerows and bats. The more sensitive environments are the upland peat lands where very
sensitive construction is required to minimise impacts, but some situations may be inappropriate for
development, in particularly wet sites with rare or sensitive species (e.g. protected eagles and hen
harriers). Developments are increasingly seeking existing forestry areas where biodiversity is
already low.
Ecological assessment must refer to various EU Conventions such as RAMSAR Convention on
Wetlands of International importance, EC Council Directive on the Conservation of Wild Birds
(Directive 79/409/EEC) and the Berne Convention on the Conservation of European Wildlife and
Natural habitats. Areas important for birds e.g. (SPA’s, SAC’s and SSSI’s) may constrain
development, though national and local designations do not automatically prevent development.
The value of the site is established at international, national, regional, county/metropolitan/ district
or parish neighbourhood level. Various conservation criteria are established e.g. Wildlife and
Countryside Act (1981), SSSI’s red data book species etc.
Assessment of Effects:
For on shore windfarms, effects may include habitat loss or disturbance, (how much and to what
extent- impact magnitude). This is assessed against the sensitivity of the habitat to measure the
impact significance. Upland moor land tends to be the most sensitive to windfarm development,
since habitats are relatively rare and are easily disturbed. Guidance on the assessment of ecological
assessment is available (Institute of Ecology and Environmental Management, 2006).
Evidence suggests that bird collisions caused by wind turbines (bird strike) cause relatively low
levels of mortality (Drewitt and Langston, 2006). Concern is most likely to occur if the wind
turbines are on a migration path (e.g. Navarra, Spain) or where high concentrations of particular
birds species occur (for e.g. feeding such as the Golden eagles in Altamont pass). Large birds with
poor manoeuvrability (such as swans and geese) and those that habitually fly at dawn and dusk or at
night are generally at greater risk of collision with structures (Drewitt and Langston, 2006). There is
more concern now over offshore windfarms as they consist of greater numbers of turbines and birds
can often hug the coast in flight. There is also concern over wildfowl having to change course
during migration (barrier effects) due to offshore windfarms (ETSU, 2001).
Some disturbance of birds is possible up to about 600m. This can be the prime impact since this can
effectively result in habitat loss.
The effects on bats has also been a concern, but only where there are known concentrations of bat
activity such as summer roosts, swarming sites, and hibernacula (over-wintering sites). Some
fatalities are observed on migration routes.
Some interesting observation by the Sustainable Development Commission (Sustainable
Development Commission, 2004):
- In Orkney there were no differences in the numbers of breeding pairs of ducks, waders, Arctic
Skuas, gulls and small birds as a result of the wind farm being developed..
- At a site close to the Wadden Sea in the Netherlands there were no effects on breeding
Oystercatchers, Lapwings, Blacktailed Godwits or Redshank from the wind farm.
- In a study at Ovenden Moor wind farm in the Yorkshire Pennines the number of breeding Golden
Plover actually increased over a five year period within the wind farm area in contrast to a control
site where numbers remained constant.
- At Bryn Titli in mid-Wales, a study showed that Ravens successfully nested within 60m of a wind
turbine.

Generally those areas that require very careful assessment and may result in significant impact are
areas that support:
(1) a high density of wintering or migratory waterfowl and waders
(2) areas with a high level of raptor activity, especially where a large number of flights to pass
through the wind farm; and
(3) breeding, wintering or migrating populations of less abundant species
Mitigation:
There are many options for mitigation including avoiding construction during breeding bird season,
grouping turbines to avoid alignment perpendicular to main flight paths and within large wind farms,
constructing floating roads on sensitive wet habitats, and restoration of as much of access tracks and
turbine bases as possible. There are also positive management possibilities such as reducing stock
numbers to allow regeneration and providing scrapes or standing water.
These mitigation measures are also suitable for addressing effects on the hydrological regime of a
windfarm site.
Archeologically Impact
Factors to consider: construction activities effects on physical archaeological artefacts and longer
term operational effect on the visual elements and setting of archaeological artefacts.
Baseline; A desk based study and walkover to identify the site’s archaeological artefacts
(archaeological sites and ancient monuments), in conjunction with analysis of recorded history.
This established the sensitivity of each artefact identified and is rated from low (local importance)
to high (Scheduled Ancient Monuments. Grade 1 listed buildings etc).
The setting of the monuments and historic landscapes are also considered important.
Assessment of effects
Impact magnitude will vary between very low (small land take or unimportant part of cultural
feature, no effect on historic integrity or surviving evidence) to high (Loss or physical damage
likely to feature or area which is fundamental to the historic character and integrity of the site).
Significance of impact will be a combination of the sensitivity of the archeologically artefact and
the magnitude of impact by combining the above.
Mitigation:
This usually involves preservation for internationally important monuments. Avoidance can also be
required, for lesser monuments if impact is considered high. For less sensitive sites, excavation and
recording prior to development, is sufficient.
Electromagnetic Interference and Air safeguarding
Elements to consider: Interfering of electromagnetic signal by turbine towers and moving blades.
There is also a potential for the turbines to affect primary radar systems, aircraft landing systems or
aircraft training areas.
Baseline: assessment of line of site radio and microwave signals transmitted through the site by
consultation with various users of EM transmissions e.g. .BT, orange, NTL. These include radio
and TV links to the local transmitter. Also consultation with MOD, National Air traffic Safety )
(NATS) and Civil Aviation Authority.

Assessment of effects: Effects include blocking or scattering of signals. Scattering of signal may
affect domestic TV. Any blocking or scattering of signals is considered significant and requires
mitigation measures. A 100m clearance is generally required for EMI links. If air traffic
safeguarding is put at risk, this is considered significant and will generally stop development in the
UK. Experience is different in Denmark and Holland, where there is more controlled air space and
there is not so much concern about non cooperating aircraft.
Mitigation:
Moving turbines or rerouting electromagnetic signals are both established mitigation measures. For
TV receptors an installation or modification of a local repeater station or cable connection can
alleviate impacts.
Shadow flicker
Elements to consider:
Under certain combinations of geographical position and time of day, the sun may pass behind the
rotors of a wind turbine and cast a shadow over a neighbouring property so that the shadow flicks
on and off.
Baseline: Dwellings within 130 O either side of north relative to a turbine and within 10 rotor
diameters need to be identified.
Assessment of Impact:
The number of hours per year that shadow flicker may occur at a dwelling is calculated from the
relative position of a turbine to a dwelling, the geometry of the wind turbine and the latitude of the
wind farm site. The operating frequency of a wind turbine will be relevant in determining whether
or not shadow flicker can cause health effects in human beings. The frequency at which
photosensitive epilepsy may be triggered is generally between 2.5 and 30 flashes per second (hertz).
Most commercial wind turbines in the UK rotate much more slowly than this, at between 0.3 and
1.0 hertz.
Shadow flicker is more relevant in residential areas with smaller turbines. Here, the window widths,
use of rooms, intervening topography and vegetation will all affect the impact magnitude.
Mitigation:
Local planning authority can impose a planning condition to ensure that wind turbines should
operate in accordance with a shadow flicker mitigation scheme. This involves a control system and
sunlight sensors on the turbines, so that the wind turbine shuts down when a potential shadow
flicker situation arises.
Public Access, Recreation and Safety
This is particularly important on common land or where footpaths cross the site, and can be a result
of both construction and operational phases. These are identified, mapped and the extent of the
physical effects are assessed in terms of total area lost if common land, and cross over of paths or
public roads. Whilst there is no stipulated separation distance, generally turbine ‘fall over’ distance
plus 10m is a rule of thumb to ensure safety to the public. Mitigation measures involve moving
turbines to avoid or move away from public rights of way. Safety plans such as provision of signs
etc are drawn up. Since the turbines will be visible from footpaths, it is sometimes proposed to add
information boards to the paths.
For horse users, design needs to avoid turbines unexpectedly appearing in view. If this is carried out
the turbines can be safely sited 100-200m from a bridleway (British Horse Association suggests
200m). There is no identified safety implications for users of public land where people can walk up

to the base of the turbine. Driver distraction is not considered to be an impact that requires
addressing (PPS 22, Companion Guide).
Socio- Economic and Environmental Benefits
This is an important assessment but strangely usually appears at the back of the ES, following all
the local impact assessments. Economic benefits are considered material considerations in deciding
planning applications (PPS 22) and National Energy Policy (2006) requires that the environmental
benefits of renewable energy schemes are material considerations.
Socio economic Impacts
During construction, this includes civils contracts to local / regional companies, wind turbine supply
contracts (if the UK would increase its manufacturing capabilities!), and grid connection work.
There is also short term work involved in the various local surveys required for the design of the
windfarm and ES work. On going operational work is also required and is usually based locally.
Windfarms can be used as educational resources, and community benefits packages are usually
provided (£750-£3000 per MW installed, depending on developer). Of course community
ownership can improve the local economic impact significantly e.g. Isle of Ghiga.
Property prices: The effects of windfarms on property prices is still uncertain. The Royal Institute
of Chartered Surveyors (2004) found that 60% of respondents to a survey had experience of
negative impacts on house prices, whilst 40% did not. Interestingly, in areas where windfarms are
more prevalent, e.g. Wales and Scotland uplands, the number stating negative impacts was less. A
further survey (Knight Frank LLP on behalf of the BWEA (2004) conceded that there was
insufficient market evidence to determine whether an existing windfarm has affected property
prices
These two reports provide conflicting evidence. Other reports from America and the Netherlands
indicate that house prices increased closer to some windfarms. ! (e.g. (e.g.Sterzinger et al., 2003).
There appears to be no consensus on this subject against which to make an accurate impact
assessment.
Tourism: This again is difficult to quantify and qualify. There is evidence to suggest that tourists
arte attracted to windfarms when they include visitor information e.g. Delabole (Cornwall),
Swaffham (Norfolk). Various surveys (Centre for Sustainable Energy, 2002 , Centre for Sustainable
Energy, 2005 , Mori., 2002) found that a large majority of respondents think that wind turbines
would make no differed to their enjoyment as tourists. The results indicate that there is a largely
positive or neutral effect on tourism. This is of course affected by value judgements associated with
the visual impact of turbines.
This in turn affects public opinion. There are now several studies indicating a favourable response
to windfarm development, both in theory and in practice (see (British Wind Energy Association
(BWEA) For the All-Party Parliamentary Group on Tourism, May 2006,)
Environmental Benefits
Air Quality
CO 2 emissions are one of the major causes of global warming, and about a third of UK’s total
emissions come from generation of fossil fuelled electricity. Renewable energies such as windfarms
can reduce pollution levels. This will affect all issues associated with climate change- rising sea
levels, flood risk, affects on flora and fauna, including loss of habitats for e.g. wading birds. Global
impacts of climate change are also relevant here, as is acid rain.
To quantify this, the pollution saved form displaced conventionally generated electricity is
calculated. The impact magnitude is based on the following savings of pollutants:
860g/MWh for CO2

10kg/MWh for SO2
3kg/MWh for nitrous oxides
(BWEA figures. NB these are slightly lower than Parliamentary Office of Science
and Technology Figures).
The impact significance of this reduction is often represented as the number (or percentage of
homes in a given area) of homes that the windfarm would be able to supply on an annual basis,
based on average consumption of 4,627 kWh per annum.
Energy Balance
The calculation of energy payback in terms of lifecycle costs has no agreed methodology, however
the energy payback period is assessed as between “a few months” (NAW, 2003) and 6 months
(David Milborrow, 1998). Over its operational life, a windfarm will create at least 50 times more
energy than went into its manufacitre.
Final Mitigation and Design
Following the assessments above, the design of the windfarm is amended and a final assessment
made of all the assessments. It is therefore a two stage process (at least!) and takes up to 2 years to
complete.
Weighing up the impacts: how is a Planning decision made?
The decision making body must take into account the results of all of the impact assessment
presented in the EIS, including local impacts and the wider, global impacts. The decisions must be
placed against material considerations such as National Energy Policy and Planning Policy
Statements and Guidelines (PPS’s and PPG’s), regional strategies and Local Development
Frameworks. Weighing up these very different impacts is a difficult process and often depends on
who is on the decision making panel and who in the vicinity is objecting.
Conclusion
Some pointers emerging:
• EIA can be used as a design tool as well as decision tool
• It can aid maximising output whilst minimising negative environmental impact
• Only key impacts need be assessed
• EIA requires objectivity (though some assessments are still subjective!)
• Ensure adequate information is available for decision makers
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