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Offshore wind projects: Assessing the environmental impact

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An overview of rules and developments in Australia, Germany, Japan, Mexico, the UK and the US

Navigating environmental issues in offshore wind project development

Around the globe, opportunity is on the rise, but regulatory and political challenges persist

Throughout the world, many national and local governments are creating regulatory and commercial environments to encourage developers, lenders and investors to build, finance and invest in offshore wind energy. This has led to an upswing in the number of offshore wind projects being planned and built around the world. Renewable energy generated by offshore wind power is typically consistent with nations' climate change commitments under the Paris Agreement to reduce greenhouse gas emissions. However, offshore wind farms have unique impacts, which are addressed through environmental and natural resource policies and rules.

Governments in many of the key markets for offshore wind investment typically require the environmental and social impacts of a proposed offshore wind project to be assessed and mitigated. The complexity, sophistication and duration of the environmental impact assessment process varies across jurisdictions, and must be carefully evaluated by potential developers and investors. Project proponents also need to be mindful that in most jurisdictions, although to varying degrees, the environmental and social impact assessment
is subject to public scrutiny and comment, and can also be vulnerable to legal challenges.

This report offers an overview of key environmental risks raised by offshore wind projects in six key jurisdictions: Australia; Germany; Japan; Mexico; the UK; and the US. Offshore wind farms operate in many of these jurisdictions. In others, they are increasingly attractive because of higher offshore wind speeds and capacity factors, shallow ocean depths and supportive government policies. We summarize how regulators in these jurisdictions require project proponents to consider impacts to birds, bats, fish and marine mammals during the development process. We also assess how noise associated with the construction and operation of offshore wind projects must be addressed. Finally, we focus on the aesthetic considerations, decommissioning requirements and impacts to fishing, navigation and transportation that arise in the planning, construction and operation of an offshore wind project.


Offshore wind projects face challenges that are not addressed by the regulatory system established for onshore projects


A complex and sophisticated planning and approval process does not prevent opponents from raising environmental challenges—even after project approvals are awarded


Despite strong government support and growing capacity, a lengthy approval process may slow progress


With no offshore precedents, project proponents may find complexity, inconsistency and opportunity

United Kingdom

A global leader in offshore wind power capacity, the UK has seen rapid expansion in the sector

United States

As the offshore wind industry begins to take off, environmental impacts remain key concerns

Offshore wind power gains ground but faces environmental challenges

To maximize its potential, industry players will have to navigate an often-complex web of national, state and local environmental regulation


A complex and sophisticated planning and approval process does not prevent opponents from raising environmental challenges—even after project approvals are awarded

15 min read

Before obtaining the planning approval required to construct and operate an offshore wind farm, the applicant will need to conduct extensive investigations.

The German federal government plans to further expand offshore wind use by 6.5 gigawatts (GWs) by 2020 and by 15 GWs by 2030. However, offshore wind projects in Germany face environmental opposition by, in particular, German nature protection associations regarding construction and operation-related impacts on marine species, protected areas, biotopes and habitats. These aspects are reviewed as part of the complex and lengthy planning and approval process for offshore wind farms. During the review, the project proponent and the approval agency examine whether the project is compatible with public interests. But opponents continue to challenge projects for environmental reasons, even after planning approvals have been awarded for individual projects. For instance, in 2014 and 2015 respectively, the German environmental protection association (NABU) filed suit against the offshore wind farm Butendiek, claiming severe infringements of environmental and species protection law (in particular as to loons and porpoises) and arguing that the project's realization would cause unlawful environmental damage.

While offshore wind projects in territorial waters are governed by federal law (Bundes-Immissionsschutzgesetz) and administered by state authorities, offshore wind farms in the German exclusive economic zone (EEZ) (between 12 and 200 nautical miles off the German coast in the North and Baltic Seas) are administered by the Federal Maritime and Hydrographic Agency (BSH) pursuant to either the Federal Marine Installations Ordinance (SeeAnlV), or for offshore wind farms and related grid connections that start operation after December 31, 2020, pursuant to the Offshore Wind Energy Act (WindSeeG).


Key procedural and permitting prerequisites

The BSH may authorize the erection and operation of an offshore wind farm in the German EEZ if, among other things, the project has no adverse effects on the safety and efficiency of maritime navigation or national defense; poses no risks for the marine environment, including pollution or bird migration risks; and complies with other requirements under the SeeAnlV/WindSeeG or other public law provisions.

Even if an applicant can show that the project meets these prerequisites, the BSH will exercise its discretion by balancing relevant interests and rights. Before obtaining the planning approval required to construct and operate an offshore wind farm, the applicant will need to conduct extensive investigations. EEZ offshore wind projects consisting of more than 20 wind turbines taller than 50 meters must undergo a statutorily specified formal environmental analysis, the Environmental Impact Assessment (EIA), pursuant to the Federal Act on Environmental Impact Assessments (UVPG). An EIA assesses the environmental and other impacts of a contemplated project throughout its lifespan, as well as project alternatives. In an EIA, the project proponent must assess the project's impacts on, in particular, benthos, fish, birds, marine mammals, protected areas and biotopes. Based on this analysis the BSH will, following review and comment of other expert agencies, such as the Federal Agency for Environmental Protection (BfN) and the public, decide whether the project is compatible with protecting the marine environment.

The planning approvals awarded by the BSH for an offshore wind farm impose conditions to ensure that the offshore wind farm meets regulatory prerequisites for approval throughout its lifespan. The BSH planning approvals tend to authorize a project only subject to the condition that construction/installation and operation of the wind farm require further authorizing decisions from the BSH. The BSH grants these further authorizing decisions, called releases (Freigaben), to the extent the project proponent shows compliance with the conditions specified in the planning approval (regarding, for example, technical, engineering, design or monitoring, investigation and reporting requirements) as supplemented by the BSH standards by means of certain expert reports and certifications. The releases function as gatekeepers over the course of an approved wind farm project's implementation. The BSH distinguishes among five principal project phases: (1) development; (2) design; (3) construction; (4) operating; and (5) decommissioning. Typically, three releases must be obtained in addition to the BSH's planning approval.

Given the dynamic character of the regulatory regime, the BSH's planning approvals require environmental impacts of the project to also be assessed following the award of the planning approval. To verify the assumptions made in the EIA underlying the award, operations shall be monitored for a period specified by the BSH (typically, three to five years). Reporting to the BSH shall occur annually through submission of the monitoring data. Based on the monitoring results and other available up-to-date information, the BSH shall determine measures to implement to prevent and mitigate environmental impacts even including, if necessary, the (temporary) shutdown of operations.


of the German EEZ of the North and Baltic Seas are designated as Natura 2000 sites


Impacts to bird and bat species

As part of the EIA, the BSH will review whether offshore wind projects will harm avian species, including birds or bats. To this end, the project proponent will frequently devote significant resources to environmental-technical expert analysis through surveys (e.g., bird and bat species surveys as well as habitat surveys) regarding whether the project area is relevant for specially protected birds and bats as, for example, habitat, resting or nesting ground, and whether these species are likely to collide with wind turbines.

Importantly, where a project is located in or at such a distance from a Natura 2000 site that it may impact the site, an "appropriate assessment" (FFH-Verträglichkeitsprüfung) must be conducted in line with EU legislation to establish whether significant impacts on the Natura 2000 site and protected species, such as birds and bats, can be excluded. Should an exclusion of significant adverse effects be impossible, the project is, in principle, not suitable for approval, unless its proponent can obtain a derogation from the substantive safeguards afforded to protected sites. Notably, approximately 31 percent of the German EEZ of the North and Baltic Seas are designated as Natura 2000 sites (two bird sanctuaries and eight FFH areas). 

Federal Environmental Conservation Law

Offshore wind project proponents prepare assessments and develop related conservation plans to ensure their projects are compatible with the provisions of the German Federal Act on Environmental Conservation (BNatSchG), which transposes the EU Bird and Habitats Directives into national law. Regarding specially protected birds and bats, the BNatSchG generally prohibits: (1) harassing, taking/capture, harming and killing these species as well as capturing, damaging or destroying their eggs; (2) significant disturbance resulting in a deterioration of the conservation status of the local population; and (3) destruction or taking of reproductive or resting places.

Accordingly, the compatibility of a wind farm project with these prohibitions will be reviewed and assessed by the BSH based on technical data such as species surveys. Regarding incidental bird or bat strikes due to animals colliding with wind turbines, the statutory prohibition to harm or kill protected species is not infringed where the wind farm does not significantly increase the collision risk for the affected species, or where such risk can be countered by suitable measures such as light reflectors or special paint. Further, where a project infringes one of the above-mentioned prohibitions, it might, nonetheless, be allowed through an exemption or derogation issued by the BfN on a case-by-case basis. 

Standard planning approval conditions and BSH "Standard Investigation of the Impacts of Offshore Wind Turbines on the Marine Environment (StUK4)"

Given the above-mentioned statutory prohibitions, BSH planning approvals tend to address the risk of bird or bat strikes through the following requirements: First, offshore wind farms must be designed and built to cause as little light emission as possible. Second, six months before the start of operations, the project proponent must submit a monitoring concept to the BSH, which will ensure monitoring of impacts to birds for a period of, in general, three to five years. Third, in case of likely intensive bird migration through the project area, project proponents are required to implement measures monitoring the impacts of the wind farm, in particular the occurrence of bird strikes, and to immediately provide monitoring results to the BSH. The BSH will then determine the appropriate measures to take to protect species based on the monitoring reports and other available data. Importantly, the BSH planning approvals explicitly reserve the BSH's right to order a temporary shutdown of the wind farm.

The StUK4 clarifies the minimum investigations for marine environmental surveys and monitoring required by the BSH for the planning approval procedure, as well as for the monitoring during the construction and operation phase. To obtain the planning approval, the project proponent needs to conduct baseline surveys that establish the pre-construction environmental status of the project site and surrounding environment, identifying the spatial distribution and temporal variability of species. 

The baseline study will determine the distribution and abundance of birds and their behavior to determine the area's importance as a resting, feeding and/or molting ground. For migratory birds, the baseline study will record bird movements during main migration periods March to May and mid‑July to November through radar and visual flight survey periods of seven days per month covering at least 50 survey days (24‑hour days) and 900 total survey hours. Regarding bats, the StUK4 mandates a baseline study of migration to assess the importance of the area as a migratory offshore zone. The surveys should be executed parallel to nighttime flight monitoring of migratory birds on windless nights (up to 3 Bft). The StUK4 provides details on methods, equipment and information on birds and bats to be recorded, and the presentation of results.

Following project approval, construction and operating phase surveys must be conducted to serve as bases for evaluating the project's actual impacts as established by subsequent monitoring to, ideally, verify the EIA's assumptions. The StUK4 therefore, for example, mandates "operation-phase monitoring" to be performed for three to five years once wind turbines become operational. The monitoring data will include documentation on the environmental status both before and after construction. Based on the monitoring result, the BSH will decide on the type and scope of further investigations. While the StUK4 provides recommended timing, scope and technical suggestions for developers, it notes that the avian surveys a developer is required to conduct may vary significantly depending on the scale and/or complexity of a proposed project, and the availability of existing data.


Visual impacts, noise and historic monuments

Under the StUK4, as to visual impacts, a photorealistic simulation of the landscape affected by a wind farm project will be presented as part of the baseline study, unless the project is to be located more than 50 kms from the coast. Due to their locations at significant distances from the coast, EEZ offshore wind farms do not generally create significant visual impacts. Therefore, this aspect tends not to be particularly significant in the permitting process. The same applies for noise in relation to humans (in contrast to drilling noise in relation to marine mammals). Preservation of historic monuments is accommodated in the planning and permitting process. The BSH's planning approval decisions customarily oblige the project developers to investigate the project area for wrecks and cultural heritage, for example. If applicable, the BSH must be informed of any relevant presence and protective measures must be adopted.


Impacts on marine species

Offshore wind farms in the German EEZ have the potential to impact a wide range of marine life, including marine mammals and sea birds. Species of particular relevance in this context are porpoises, seals and loons. As a result, German wind project developers are generally required to ensure that marine species are appropriately considered to avoid significant impacts during construction, operation and decommissioning. According to the BfN, to prevent significant impacts, the following prevention and mitigating measures must be adopted:

  • Selection of suitable locations to prevent or minimize (i) loss of habitats (e.g., resting, molting and/or feeding areas) due to, in particular, construction activities and (ii) barrier effects (e.g., blocking of paths between different resting and/or feeding areas)
  • Selection of the least noise-intense foundation types (e.g., heavy load or bucket foundations) or use of noise-minimizing measures during drilling works (e.g., bubble curtains)
  • Ban of noise-intensive construction works during mating and calving periods
  • Lighting that does not attract birds and installation of equipment effecting shutoff during times of intensive bird migration

Applicable laws

Many marine species are listed as endangered or threatened, and protected by the BNatSchG and underlying EU legislation, such as the Birds and Habitats Directives. The BNatSchG protects all wild animals, including marine mammals, by generally prohibiting their killing or harassment. In addition, specially protected species are subject to the species protection regime outlined above.

To assist the necessary species protection review and assessment of project-related impacts during the planning approval process, the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) issued guidance on methodology to use regarding key species: (1) the Concept for the Protection of Porpoises From Noise Emissions During Construction of Offshore Wind Farms in the German North Sea (Noise Mitigation Concept) and (2) the Position Paper on Cumulative Assessment of Habitat Loss of Loons due to Offshore Wind Farms in the German EEZ of the North and Baltic Seas.

Standard planning approval conditions and StUK4

The StUK4 prescribes fish baseline surveys to be conducted over at least two consecutive pre-construction seasonal cycles describing fish in the project area and reference areas, as well as seasonal spring and autumn conditions. This baseline study shall serve as a reference point for assessing the wind farm's impacts. In addition, surveys shall be conducted during the first, third and fifth year of the operation phase. Regarding marine mammals, the investigations and monitoring shall consist of both visual ship-based and eight to ten annual aircraft-based digital surveys, as well as stationary acoustic (click) detectors to survey abundance and distribution, surveys of habitat use and surveys of noise emission. The StUK4 explicitly provides that, depending on the characteristics of the construction site, additional measures may be prescribed as necessary for conservation and protection, particularly where there are cumulative effects (e.g., several projects and/or shipping and other EEZ uses). Monitoring shall also take place throughout construction and during the operation phase for three to five years. The StUK4 provides details on methods, equipment and information on birds to be recorded, and the presentation of results.

As to porpoises, BSH planning approvals routinely provide that first, installation of the wind farm foundations must be conducted according to state-of-the‑art methods (detonations are prohibited) aiming at minimum noise emissions, with installation to be materially completed within 18 months. Second, the project proponent must implement a noise mitigation concept tailored to the chosen foundation type and installation process, ensuring that sound exposure levels exceed neither 160 dB at a radius of 750 meters nor a peak level of 190 dB. In addition, a detailed plan for implementing noise-minimizing and prevention measures in accordance with the noise mitigation concept must be submitted to the BSH at least three months before installation starts. This plan will also provide a detailed technical description of the relevant measures, including method statements, procedural manuals and a description of how the measures' effectiveness shall be monitored. If not yet tested, identified noise minimizing measures shall be tested in advance and respective testing documentation must be submitted to the BSH at least three months before the scheduled start of installation. Third, the effectiveness of the noise-minimization and prevention measures during installation must also be monitored in accordance with the BSH's "Measuring Instructions for Underwater Sound Monitoring." Monitoring shall pertain to construction-related noise from vessels and pile-driving, with measuring to take place at 750 and 1,500 meters from the pile-driving as well as, if applicable, in any potentially affected protected area. In addition, porpoise detectors or similar equipment shall be employed. In the case of monopiles, pile-driving must be completed within 180 minutes per pile. Further technical details are set forth in the BSH's "Predictions for Underwater Sound Monitoring (Minimum Requirements and Documentation)" and "Measuring Specification for the Quantitative Determination of the Effectiveness of Noise Control Systems."

To verify compliance with the noise-mitigation requirements, reporting to the BSH in accordance with its standards is required during the construction period, with respective specifics to be coordinated with the BSH, at the latest within 24 hours of the completed pile‑driving for the last pile.



Applicable laws

Pursuant to both the SeeAnlV and the WindSeeG, an offshore wind farm shall be dismantled to the extent necessary to protect the marine environment. To ensure dismantling, the BSH may require the project proponent to provide a decommissioning security prior to starting installation works. The amount of this security can be subsequently adjusted to ensure that it provides adequate financial coverage for expected dismantling costs. Typical types of security are lump sum payments, guarantees or corporate group pledges. Under the WindSeeG, in case of a planning approval transfer, the original planning approval holder will remain liable for decommissioning until the transferee provides an adequate substitute security.

Standard planning approval conditions

BSH-issued approvals generally authorize offshore wind farms to operate for up to 25 years. Further, standard auxiliary conditions stipulate that where the planning approval loses its validity for any legal reason, the offshore installations must be dismantled (along with accessory installations and crossing structures) and disposed of onshore. Foundation components installed into the seabed must be dismantled in a way that ensures that any parts remaining in the seabed are deconstructed to at least a depth that avoids risks to shipping and fisheries, even in the case of soil movements. In practice, the project developer tends to be obligated to establish the type, scope and amount of the security, and a calculation of the expected decommissioning costs along with a validation of the cost calculation by a recognized financial auditing firm. Further, it is not uncommon for BSH planning approvals to provide that determinations of type, scope and amount of the security shall be re-verified throughout the project's life.

Projects are required to address decommissioning impacts and to submit a decommissioning concept that includes planned decommissioning activities, resources or activities that could be affected by the proposed decommissioning activities, results of biological surveys and mitigation measures that will be used to protect environmental resources and prevent unauthorized discharge of pollutants. The successful completion of the decommissioning phase must be documented in a certificate of conformity summarizing all the individual inspection reports. This must be submitted to the approval authority. The decommissioning phase ends with the BSH's verification that decommissioning has been fully effected.

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