Ministerial guidelines
Wind Energy Development Guidelines
Siting, design, noise and shadow flicker for wind farms. A revised draft was published for consultation in 2019.
Department of the Environment, Heritage and Local Government · June 2006 · 119 pages
Ask this document
Answers come only from the text of Wind Energy Development Guidelines, each claim linked to its page. They are not advice; check the page itself.
Free, with a daily limit.
- Planning Guidelines • The resolution of the Digital Terrain Model used to prepare the Zone of Theoretical Visibility map should be a maximum of 50 by 50 metres to ensure high resolution. • The cumulative effects of a number of different wind energy developments should be clearly represented using Zone of Theoretical Visibility maps. • In addition to a Zone of Theoretical Visibility being based simply on contour data, screening objects such as forestry, buildings, etc., may be introduced to a Zone of Theoretical Visibility map. A very useful exercise at the initial design stage of preparing the wind energy development layout is to carry out a “reverse zone of theoretical visibility” (reverse-ZTV) from locations known to be highly sensitive and from where views of turbines should be avoided. All locations theoretically visible from the sensitive viewpoint can be identified and, if any cross over the wind energy development site, they can be eliminated from the workable area. This effectively means that the wind energy development can be designed thereafter knowing that no turbines will be exposed to viewing from the chosen location. • Selection of viewshed reference points/import viewpoints This stage involves the identification of those locations from where visibility of the proposed wind energy development might be provided. It is helpful to consult with the relevant local authority(s) in identifying and choosing viewshed reference points so that delays owing to omissions can be avoided. The following guidance should be followed in selection of viewshed reference points: 1. They should reflect local designations as might be relevant from the County Development Plan or Local Area Plan, including Views and Prospects and other scenic amenity designations. 95
- 2. They should be located at varying distances from the wind energy development and, where relevant, afford views from all directions so that a good sense of what is proposed can be observed. This might include locations outside the jurisdiction of the planning authority to which the proposal is being lodged. 3. They should always present the worst case (most open) available view from any given location. 4. It is advisable to consult with the relevant planning authority(s) in identifying and choosing viewshed reference points so that delays owing to omissions can be avoided. • Preparation of photomontages of the development Photomontages provide a graphic depiction of the view from each viewshed reference point after introduction of the turbines. The following guidance should be followed in the preparation of photomontages: 1. A camera lens focal length of 50-70mm is recommended for taking photographs for preparation of photomontages. 2. Panoramic photographs included to illustrate the context in which the development might be visible should be prepared by splicing photographs taken with a 50-70mm lens and not by inclusion of views taken with a wide-angle lens. 3. Unless specifically requested to do so by the relevant planning authority or by statutory consultees, the vast majority of photomontages should be prepared from places that do provide views of the proposed wind energy development. The Zone of Theoretical Visibility is prepared to highlight places from where views are not provided and they generally do not need to be considered further thereafter. 96lanning Guidelines
- Planning Guidelines 4. The landscape depicted in the photomontage should represent the most open view possible in the direction of the wind energy development. Care should be taken so as not to place an object such as vegetation or structures between the wind energy development site and the camera. 5. Turbines that are not visible from the viewshed reference point (resulting from intermittent screening) should not be depicted on the photomontages. 6. Related to the above, the photomontage should be accompanied by a wire frame computer generated perspective view of the landscape, or shaded-relief model, illustrating all theoretically visible turbines. These wire frame diagrams may also be used to indicate turbines that are not visible in whole or in part due to screening, simply to prove that point. Wire frames and photomontages should be at the same scale and presented in unison so that direct comparison/correlation can be made. 7. The recommended distance at which the page depicting the photomontage should be held for viewing purposes should be clearly stated (this should not be less than 30cm). 8. The print quality of the photomontages should be highlow resolution or faded colour photocopies are not acceptable. 9. A reference map should be included for orientation purposes, and the longitude and latitude national grid coordinates provided for each camera position used to take the photographs, along with the coordinates of the target point. This will enable the planning authority to test the accuracy of wire frames using their own contour data. • Estimation of likely degree of impact on landscape A structure for this critical part of the Landscape Impact Assessment is proposed below, carried out in respect of each key viewpoint. 97
- 1. Describe the landscape in general, including landform, landcover, structures and features, spatial flow/interconnection and degree of naturalness or human influence. 2. Assess the visual presence of the wind energy development, for example, how spatially dominant it is. (This does not necessarily correspond to the ultimate landscape impact). 3. Assess the aesthetic impact of the wind energy development on the landscape, referring in particular to Chapter 6 of these Guidelines and determining whether the impact might be adverse or positive. 4. Using the results of the earlier estimate of landscape sensitivity from each key viewpoint along with those of visual presence and aesthetic impact, estimate the significance of the impact on the landscape. 98lanning Guidelines
- Planning Guidelines Appendix 4 Best Practice for Wind Energy Development in Peatlands Development of most peatland sites (including upland and lowland bog types, fens and heaths) will generally lead to impacts on natural heritage. Notable exceptions to this would be areas of exploited peatland such as within the extensive milled peat bogs, mainly in Ireland’s midlands, and those that have been converted to farmland. Where wind energy developments are permitted on peatlands, the implementation of the following construction guidelines (along with others that are recommended in the Environmental Impact Statement) may serve to reduce impacts, including minimising habitat disturbance and loss, hydrological disruption and the risk of erosion: 1. A thorough ground investigation, including hydrogeological investigations where appropriate, and a detailed evaluation of the nature of the peat, its geotechnical properties and the associated risk of instability and habitat loss or disturbance during construction and operation of the wind energy development, is to be carried out where the depth of peat is in excess of 50cm. 2. Avoid construction, if possible, on wet areas, flushes and easily eroded soils. 3. Avoid the excavation of drains, where possible, unless it is necessary for geotechnical or hydrological reasons. 4. If drains are unavoidable, ensure that silt traps are constructed and that there is only diffuse discharge of water. 5. Avoid blocking existing drains. 99
- 6. Where blasting is being used in or near a peatland area for borrow pits, foundations etc, the possible effect on the peat stability should be assessed. 7. Avoid stock grazing on any disturbed peat until local peatland vegetation has recovered (e.g., by use of temporary electric fencing). • Construction of Access Tracks/Roads in Peatland Areas 1. Construct roads to take the required vehicular loadings, having due regard to overall site stability. 2. Operate machinery and vehicles used in road construction from the road as it is constructed. 3. Make the road width the minimum compatible with sound engineering practice. 4. Use hard rock to construct the road batters. 5. Culverts should be placed under roads, where appropriate, to preserve existing surface drainage channels. • Construction of Foundations for Turbine Towers 1. A geotechnical analysis must be carried out for each turbine base into the method of excavation and the location for placing and storing excavated material to ensure that these operations do not give rise to slope or site instability. 2. Each tribune base should be assessed on an individual basis for stability purposes. 3. Lay out and store surface vegetated scraghs/turves, for resodding bare areas, off-site and water them in dry weather. 4. If, during excavation, spoil is likely to fall onto the adjacent peatland surface, protect the surface with shuttering boards or geogrid /geotextile. 100lanning Guidelines
- Planning Guidelines 5. Carefully monitor and control any pumping of water from excavated turbine bases to ensure that water is directed into existing water courses, forestry drains or specially constructed drains, all with adequate capacity to deal with the volumes of water encountered. • Installation of High Voltage Cables 1. Cables should be interred alongside the turbine access routes to minimise the degree of ecological impact on site. 2. All machinery and construction methods on-site should be selected with a view to minimising impact on habitat. 3. Specialised low-ground pressure tracked machinery on bog mats should be used if operating on the peatland surface. 4. Place vegetated peatland scraghs on shuttering or geogrid (or on the road) alongside trenches unless backfilling takes place soon after excavation. 5. Place peat spoil alongside the peatland scraghs on shuttering or geogrid or on the road 6. Carefully backfill the trenches with the peat-spoil. 7. Replace the scraghs/surface turves, vegetated side up, and firm them in with the back of the excavator bucket. 101
- Appendix 5 Glossary Alternatives: Description of alternative locations, alternative designs and alternative processes. Anemometer: Equipment fixed on a mast to measure wind speed over a particular site. Anemometry masts are usually slender structures fixed to the ground with guy wires. Ambient Noise: The average noise level over a given period of time, usually composed of sound from many sources, near and far. Background Noise Level: A measurement of the noise level already present within the environment in the absence of wind energy development operation. Baseline Survey: Description of the existing environment against which future changes can be measured. Berm: An extended mound of soils, overburden or structure erected as a barrier to sight, sound or water. Blade Swish: The modulation of broadband noise at blade passing frequency. Borrow Pit: An area of excavation of rock and/or soil material that is used elsewhere within the site development boundaries. Built Environment: Refers to both architectural heritage and archaeological heritage. Commissioning: The making fully operational of a project. Cut-in Wind Speed: The wind speed at which a turbine produces a net power output. This is usually at hub height wind speeds of 4-5 metres per second. 102lanning Guidelines
- Planning Guidelines DAU: Development Applications Unit of the Department of Environment, Heritage and Local Government, which includes the National Parks and Wildlife Service. dB (decibel): Measurement of sound, the scale in which sound pressure level is expressed. When measuring environmental noise, a weighting network is used which filters the frequency of sound, and is expressed as dB(A). dBA or dB(A): An “A-weighted decibel” - a measure of the overall noise level of sound across the audible frequency range (20Hz- 20kHz) with A- frequency weighting (i.e., “A” weighting) to compensate for the varying sensitivity of the human ear to sound at different frequencies. The decibel scale is logarithmic. Every 10 dB(A) increase in sound level represents a doubling of loudness. A change of 3 dB(A) is the minimum perceptible under normal circumstances. Decommissioning: The final closing down of a development or project when it has reached the end of its operational/useful life. Ecology: The study of relationships between living organisms and between organisms and their environment (especially animal and plant communities), their energy flows and their interactions with their surroundings. EIA: Environmental Impact Assessment: An ordered exercise designed to enable the environmental impacts of a proposed development/project to be anticipated before the project is carried out. EIS: Environmental Impact Statement: A statement of results from the ordered exercise which focuses on anticipating all environmental impacts of significance of a proposed development, prior to implementation or construction, and which specifies those measures which should be taken to eliminate or mitigate such impacts to an acceptable level. Environmental Heritage: Includes natural and built, including archaeological, heritage. 103
- Energy Yield: Describes the electrical output from a wind energy project. It is closely related to wind speed; the higher the wind speed, the greater the energy yield. EPA: Environmental Protection Agency. European Site: Designated European site, also known as Natura 2000 Sites and include Special Areas of Conservation (SAC) under Habitats Directive 1992 that is in the listing process, an agreed candidate or designated. Special Protection Areas (SPECIAL PROTECTION AREA) under Birds Directive 1985. Flushes: Areas of vegetation that differ from surrounding vegetation and are influenced by moving ground or surface water. Geology: Science of the earth, including the composition, structure and origin of its rocks. Habitat: Area in which an organism or group of organisms live. Hub height: Height of wind turbine tower from the ground to the centre-line of the turbine rotor. Hydrology: Science concerned with the occurrence and circulation of water in all its phases and modes. Hertz: Hz: Unit of frequency of sound, in cycles per second. Frequency determines pitch of sound. Impact: Degree of change in an environment resulting from a development. Key Viewpoints: Places from which a development can be viewed that are crucial and sensitive with respect to observer numbers and interest. LA90,T,: A-weighted sound pressure level (in decibels, dB) obtained using “Fast” time-weighting that is exceeded for 90% of the given time interval (T), e.g. for background noise level. The given time interval is ten minutes for LA90,10min. 104lanning Guidelines
Source Department of the Environment, Heritage and Local Government: Wind Energy Development Guidelines (June 2006) · Licence the publisher's termsText read from the publisher’s PDF; tables, maps and drawings do not survive as text, and page numbers are the PDF’s (its first page is 1). Check the original before relying on a passage.