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How to Use This Document
The EHS Guidelines for wind energy provide information that is specific to facilities in this industry sector. They are organized according to the following sections.
Section 1.0 — Industry-Specific Impacts and Management
Section 2.0 — Performance Indicators and Monitoring
Section 3.0 — References and Further Information
Annex A — General Description of Industry Activities
They are designed to be jointly used with the General EHS Guidelines document, which provides the user with guidance on common EHS issues potentially applicable to all industry sectors. On complex projects, multiple industry-sector guidelines may be useful. A complete list of industry-sector guidelines can be found at www.ifc.org/ifcext/enviro.nsf/Content/EnvironmentalGuidelines
Applicability
This document includes information relevant to onshore and offshore wind energy project facilities and activities. Annex A contains a full description of industry activities for this sector. EHS issues associated with the operation of transmission lines are addressed in the EHS Guidelines for Electric Transmission and Distribution.
1.0 Industry-Specific Impacts and Management
The following section provides a summary of EHS issues associated with wind energy facilities, along with recommendations for their management.
1.1 Environment
Construction activities for wind energy projects typically include land clearing for site preparation and access routes; excavation, blasting, and filling; transportation of supply materials and fuels; building foundations involving excavations and placement of concrete; operating cranes for unloading and installation of equipment; and commissioning new equipment. Decommissioning activities may include removal of project infrastructure and site rehabilitation.
Environmental issues associated with these construction and decommissioning activities may include, among others, noise and vibration, soil erosion, and threats to biodiversity, including habitat alteration and impacts to wildlife. Due to the typically remote location of wind energy conversion facilities, the transport of equipment and materials during construction and decommissioning may present logistical challenges. Recommendations for the management of these EHS issues are provided in the environmental construction and decommissioning section of the General EHS Guidelines.
Environmental issues specific to wind energy projects and facilities include the following:
• Visual Impacts
• Noise
• Species mortality or injury and disturbance
• Light and illumination issues
• Habitat alteration
• Water quality
Visual Impacts
Depending on the location and local public perception, a wind farm may have an impact on visual resources. There are two primary visual impacts associated with wind energy projects, including impacts relating to the turbines themselves (color, physical structure) and impacts relating to their interaction with the landscape character.
Prevention and control measures to address these impacts include1:
• Consult the community on the location of the wind farm to incorporate community values;
• Consider the landscape character in turbine siting;
• Consider the visual impacts of the turbines from all relevant viewing angles when considering locations;
• Where feasible, limit ancillary structures on the site by avoiding fencing; minimizing roads; burying intraproject power lines; and removing inoperative turbines;
• Avoid steep slopes, control erosion, and promptly revegetate cleared land;
• Maintain uniform size and design of wind turbines (for example, direction of rotation, type of turbine and tower, and height);
• Paint the turbines a uniform color, typically matching the sky (light gray or pale blue), while observing marine and air navigational marking regulations;
• Avoid including lettering, company insignia, advertising, or graphics on the wind turbines.
Noise
Wind turbines produce noise when operating. The noise is generated primarily from mechanical and aerodynamic sources. Mechanical noise may be generated by machinery in the nacelle. Aerodynamic noise emanates from the movement of air around the turbine blades and tower. The types of aerodynamic noise can include low frequency, impulsive low frequency, tonal, and continuous broadband. Also, the amount of noise may increase with increasing rotation speed of the turbine blades, so designs which allow lower rotational speeds in higher winds will limit the amount of noise generated.
Measures to prevent and control noise are mainly related to engineering design standards. For example, broadband noise is generated by air turbulence behind the blades and increases with increasing blade rotational speed. This noise may be controlled through the use of variable speed turbines or pitched blades to lower the rotational speed.
Additional recommended noise management actions include:
• Proper siting of wind farms to avoid locations in close proximity to sensitive noise receptors such as residences, hospitals, and schools;
• Adherence to national or international acoustic design standards for wind turbines (e.g., International Energy Agency, IEC, and American National Standards Institute).
Species Mortality or Injury and Disturbance
Onshore
The operation of onshore wind turbines may result in collisions of birds and bats with wind turbine rotor blades and/or towers potentially causing bird and bat mortality or injury. Potential indirect impacts to birds may include changes in quantity and type of prey species resulting from habitat modification at the wind farm project site, and changes in the type and number of perching and nesting sites due to either natural habitat modification or the use of wind turbines by birds.2
The impact to birds and bats depends on the scale of the project and other factors including technology considerations, such as tower dimension and turbine design, lighting of the wind turbine, and layout of the wind farm. In addition, site characteristics may influence this impact, including physical and landscape features of the wind farm site, such as proximity to habitat that may concentrate birds, bats, or their prey; the numbers of birds and bats moving through the wind farm site; risk behaviors of birds (for example, soaring height) and bats (for example, migration routes); and meteorological considerations.
Prevention and control measures to address these impacts include the following:
• Conduct site selection to account for known migration pathways or areas where birds and bats are highly concentrated. Examples of high-concentration areas include wetlands, designated refuges, staging areas, rookeries, bat hibernation areas, roosts, ridges, river valleys, and riparian areas;
• Configure turbine arrays to avoid potential avian mortality (for example, group turbines rather than spread them widely or orient rows of turbines parallel to known bird movements);
• Implement appropriate stormwater management measures to avoid creating attractions such as small ponds which can attract birds and bats for feeding or nesting near the wind farm.
Offshore
Noise generated during the operation of the offshore wind farms is not likely to displace marine fish and mammals away from the project site. Activities associated with the installation or removal of offshore wind turbines and subsurface cables may result in temporary displacement of fish, marine mammals, sea turtles, and birds. This displacement may result from direct auditory, visual, or vibratory disturbance impacts or indirectly from increased sediment levels in the water column due to disturbance of the seabed.
Measures to address these impacts depend on the characteristics of the local habitat but may include:
• Employ a “soft start” for pile-driving activities to help prevent exposure of fish, marine mammals, and sea turtles to damaging sound levels and provide them an opportunity to leave the area;
• Use of hydraulic jet plowing technology for the installation of cables, which is considered the least environmentally damaging alternative when compared to traditional technology;
• Use of monopole turbine foundation, which results in the least amount of seabed disturbance compared to other foundation types.3 Similar to onshore wind farms, there is a risk of bird mortality and injury due to collisions with offshore wind turbines.
Prevention and control measures to minimize seabird collision risks include:
• Proper siting to avoid high-density bird use areas, including migratory pathways; 3 CWA (2004).
• Maintain turbine tower heights below heights of migratory bird pathways;
• Maintain rotor blades a suitable distance from the ocean surface to avoid strikes with seabird activity close to the ocean surface;
• Employ slower-turning rotor blades to make them more visible.4
Shadow Flicker/Blade Glint
Shadow flicker occurs when the sun passes behind the wind turbine and casts a shadow. As the rotor blades rotate, shadows pass over the same point causing an effect called shadow flicker. Shadow flicker becomes a problem when residences are located near or have a specific orientation to the wind farm.
Similar to shadow flicker, blade or tower glint occurs when the sun strikes a rotor blade or the tower at a particular orientation. This can impact a community, as the reflection of sunlight off the rotor blade may be angled toward nearby residences. Blade glint is a temporary phenomenon for new turbines only, and typically disappears when blades have been soiled after a few months.
Prevention and control measures available to address these impacts include the following:
• Site and orient wind turbines so as to avoid residences located within the narrow bands, generally southwest and southeast of the turbines, where shadow flicker has a high frequency. Commercially available modeling software can be used to identify a “zone” of flicker and the wind farm can then be sited appropriately;
• Paint the wind turbine tower with nonreflective coating to avoid reflections from towers.
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