Proposed Mitigations for Offshore Wind Energy Development

Why is BOEM considering these new or updated measures?  

The pace of offshore wind development – and the size of the turbines – has been increasing over time. BOEM has obligations under the National Environmental Policy Act, the Marine Mammal Protection Act (MMPA), and the Endangered Species Act (ESA) to protect marine species; advancing these new mitigations is critical for striking a balance between wind development and potential impacts to the marine environment. Constructing large offshore wind facilities is known to be a relatively noisy undertaking, so these measures are specifically aimed to reduce acoustic impacts to marine species, many of which are sensitive to underwater sound.  

Why do we want to reduce noise produced during impact pile driving?  

As offshore wind energy development grows in the United States, we need solutions to reduce the underwater noise and substrate vibration generated during fixed-bottom turbine installation to help protect marine life. Monopiles are currently the main turbine foundation type installed globally and are primarily installed by impact hammers driving these large piles into the sea floor. This installation method is a major source of noise and vibration during wind farm construction.  

Using alternative foundation types, installation methods, and innovative noise abatement technologies can help reduce the level of noise that is produced, and/or the propagation of noise through the environment. Some approaches are already widely used in European wind farm development. Additional approaches are also commercially available, and further achievements in noise abatement may be possible through research and development.  

To explore these opportunities, DOE’s Wind Energy Technologies Office (WETO), in collaboration with the Bureau of Ocean Energy Management (BOEM) and the National Oceanic and Atmospheric Administration (NOAA) funded a virtual workshop to gather feedback on noise reduction strategies for the installation of fixed-bottom offshore wind turbines. Workshop results were used to inform a September 2023 Funding Opportunity Announcement from DOE, BOEM, and BSEE to support research, technology, and methods that reduce noise during installation of these turbines. Funding decisions are expected in the fall 2024. 

How do low noise foundations reduce impacts?  

Low noise foundations aim to reduce the level of noise generated during offshore wind turbine foundation installation by using alternatives to traditional monopile, or jacket, foundations. Options such as gravity-based, suction bucket, and shallow-water floating foundations do not require pile driving and can be used in shallow waters. Low noise installation methods can also reduce noise levels. Vibratory piling, gentle driving of piles, and other novel techniques such as bluepiling and vibrojet methods are alternatives to traditional impact hammer pile driving installation. 

What is the difference between low noise foundations and noise abatement systems?  

Low noise foundations and piling methods aim to reduce the amount of noise produced during pile driving (i.e., reducing noise at the source). Noise abatement technologies do not reduce noise at the source, but rather limit the propagation of noise through the water column and substrate once it has been generated.

What types of noise abatement systems are being used?  

Noise abatement technologies focus on limiting noise propagation through the water column and substrate once it has been generated. To date, multiple noise abatement technologies or systems have been deployed in Europe and the United States to reduce noise associated with fixed-bottom offshore wind pile driving. Examples include: bubble curtains and variations; pipe-in-pipe systems; hydro sound dampers; and noise mitigation screens. These may be placed either near-to-pile or far-from-pile. For more information: https://www.bsh.de/EN/TOPICS/Offshore/Environmental_assessments/Underwater_sound/_Anlagen/Downloads/Download_Experience_Report_Underwater.pdf?__blob=publicationFile&v=1

What is a Received Sound Level Limit and what is it meant to do?  

BOEM is committed to requiring developers to reduce noise levels during construction to the maximum extent practicable and to ensure actual noise levels are within the bounds of those analyzed within a project’s environmental review process. The Received Sound Level Limit (RSLL) is a performance-based, predictable, and measurable target from which government and industry can innovate technology and apply flexibilities for meeting the target within each project versus overly prescribing a specific approach.  

BOEM’s Center for Marine Acoustics (CMA) carefully evaluated existing information on modeled noise projections, actual field measurements, and quieting policies worldwide to determine how to reduce noise given the expected increase in impact pile driving noise and the anticipated regulatory drivers under the MMPA and ESA. Part of the effort also included prioritizing species of greatest concern, namely the North Atlantic right whale and other baleen whales (all considered low frequency hearing cetaceans, or LFC).   

By incorporating a weighting function to more accurately reflect the likelihood of inducing hearing loss based on acoustic frequency content, developers can reduce the total noise generated, especially within the bandwidth that is most impactful for LFC. The RSLL not only protects LFC from permanent threshold shift (PTS) (i.e., permanent hearing damage), it also protects other groups of marine mammals, such as mid-frequency cetaceans, pinnipeds, sea turtles, and fish. Application of the Level A LFC RSLL also reduces zones for temporary threshold shift (i.e., temporary hearing impacts) and behavioral impacts to some extent, providing additional environmental protection.  

Within the New York Bight PEIS, BOEM is establishing an RSLL for impact pile driving as follows:   

Sound fields generated during impact pile driving may not exceed NOAA Fisheries’ Level A PTS limits for LFC by the specified date and at the distances below: 

On a case-by-case basis, BOEM may consider an exception to the RSLL if the operator provides sufficient written justification, as deemed by BOEM, of why meeting the RSLL is not technically and commercially practicable. In these cases, compensatory mitigation may be considered, such as operator contributions to research and monitoring (or similar) that reduce noise or contribute to a better understanding of noise reduction.

How is Sound Field Verification done and what is it meant to accomplish?  

Sound field verification (SFV) is the process in which several measurements of the real-world acoustic environment (the sound field) are compared to predicted sound levels. Before implementation of the required RSLL, the lessees will compare the sound field to the sound levels that were predicted via acoustic modeling. After implementation of the RSLL, the sound field will be compared against the RSLL targets listed in the table above.  

To conduct sound field verification, BOEM recommends that lessees place acoustic recorders at several distances and in several radial directions from each pile. Since the propagation of underwater sound is highly influenced by environmental conditions, it is critical to conduct measurements in multiple locations to ensure that some of that variability is captured. This thorough SFV process will be required for the first three foundations that are installed in each calendar year and/or season, as well as any time significant parameters change (e.g., foundation type, hammer size, etc.). To ensure that sound levels remain within allowable levels as the project progresses along, a single SFV measurement at 750m from each pile will also be required. The choice of 750m was deliberate, to be consistent with measurements made at European wind farms. 

What is the difference between real-time Passive Acoustic Monitoring (PAM) and long-term, archival PAM?  

Both real-time and archival PAM systems have underwater microphones (called hydrophones) that record underwater sounds in their vicinity. The key difference between “real-time” and “archival” systems is that real-time systems have onboard software that scans through the acoustic data for specific animal calls, such as the vocalizations of baleen whales. These systems are programmed to send a signal to an onshore analyst when a whale call is detected. The analyst can then verify the detection and notify personnel that a whale is in the vicinity, which usually triggers a mitigative action like a pause in pile driving.  

Archival systems, on the other hand, passively record sounds for the entire deployment duration (usually about 6 months), and the data are retrieved and analyzed after the fact. These systems are very useful for measuring trends in the anthropogenic and biological components of the soundscape. When many archival systems are deployed in a larger area, they can tell a more complete story about animal movements. For example, if whales are detected on several hydrophones in one area, and later in a different area, we may surmise that they moved. Archival systems are often used to look at large-scale, long-term trends over time, like tracking annual whale migrations. 

Why does BOEM believe long-term, archival PAM is needed for at least 10 years of operation?  

Conducting PAM for at least 10 years will reveal trends and patterns in species’ population dynamics, which is critical for detecting temporal trends that shorter studies might miss. PAM can provide insights into the behavioral responses of marine mammals to offshore wind farm construction and operation, such as changes in vocalization rates, calling behavior, or avoidance reactions (Davis et al. 2023). Davis et al. (2020) found that a decade of acoustic observations showed important range shifts for baleen whales, which mirrored known climatic shifts and identifying new habitats that will require further protection from anthropogenic threats. Considering that the Atlantic Ocean is experiencing many environmental changes, including weaking of the Atlantic Meridional Overturning Circulation (AMOC), changes in the Gulf Stream, and intrusion of warm slope water in the Gulf of Maine and Western Scotian shelf (Meyer-Gutbrod et al. 2021), long-term monitoring is essential to discern whether potential impacts to baleen whales can be attributed to offshore wind, another ongoing stressor, or natural climate variability (Kershaw et al. 2023; Meyer-Gutbrod et al. 2021).  

For critically endangered species like the North Atlantic right whale, delayed sexual maturity and low reproductive rates make them even more vulnerable to rapid warming and other anthropogenic stressors (Kraus et al. 2020; Meyer-Gutbrod et al. 2021; O’Brien et al. 2022). Historically, three years was considered a normal healthy interval between right whale births, but now females are having calves every 6 to 10 years on average (NOAA 2023). To discern whether offshore wind impacts North Atlantic right whale reproductive patterns, we must monitor for at least the duration of a full reproductive cycle (i.e., 10 years). Without such long-term monitoring, we could miss critical data during this species’ life cycle, which will leave unanswered questions related to diminishing reproduction rates.  

It is paramount that offshore development is paired with long-term monitoring efforts of at least 10 years. This robust scientific research and monitoring strategy will detect interactions between habitat, marine life, and offshore wind energy infrastructure and other development activities; any resulting impacts; and broader ecosystem-level effects (Kershaw et al. 2023). This is a crucial component of responsible offshore wind energy development. 

How does BOEM plan to build-out a long-term, archival PAM network?  

BOEM and its partners have been developing plans for a large acoustic network for several years now. In FY22, BOEM received funding from the Inflation Reduction Act to advance PAM in the Atlantic ocean; several other stakeholders also have funding for PAM instrumentation and data analysis. The Regional Wildlife Science Collaborative, through its overall science strategy and marine mammal subcommittee, has been serving in a critical role by coordinating the ongoing and planned PAM deployments across many stakeholders, and will continue to do so as the scope of this work expands. BOEM intends to purchase and deploy dozens of archival PAM units in 2024 – both within and in between lease areas – to begin collecting baseline data ahead of construction in certain key areas like the New York Bight.  

BOEM has also been instrumental in urging all stakeholders to submit their acoustic data to a common data repository at the National Centers for Environmental Information, and to submit marine mammal detections to the Passive Acoustic Data Map maintained by NOAA. Data transparency and consistent metadata is absolutely critical to the establishment of this network; as such, BOEM helped write the PAM Data Management and Storage best practices document that is being broadly used in the PAM community.

What is the POWERON initiative?  

The Partnership for an Offshore Wind Energy Regional Observation Network (POWERON) is a public-private partnership between BOEM’s Environmental Studies Program and offshore wind lessees. Conducting long-term PAM is a requirement of COP approval, but lessees have the option to make a monetary contribution to POWERON instead of conducting PAM themselves. Their annual contribution – which is scaled by the size of the lease area – will cover the cost of instrumentation, vessel time, data processing, and analysis. The lessee would make the contribution to BOEM’s ESP program, and BOEM and its partners would conduct the work, thus helping the lessee to meet their COP’s long-term PAM requirements.  

POWERON has several benefits. First and foremost is data consistency: researchers will use similar instrument types, consistent calibration, and standard methods for data processing, which will lead to more robust results. A second benefit is conserving/optimizing resources: the team could save costs (e.g., vessel time) by servicing instruments on neighboring lease areas on the same expedition. Third is a more robust scientific design: data from different locations and across multiple areas could be processed together to tell a more complete story about how whales move through the areas. 

What is the relativistic risk assessment framework used in the PEIS?  

Over the last decade, BOEM has funded the development of a risk assessment framework that can be used to assess the relative risk to marine mammals of acoustic disturbances associated with different development scenarios. This relativistic risk assessment framework is the foundation for the analyses in this section. The framework was used for oil and gas activity in the Gulf of Mexico (Southall et al. 2021a) and, more recently, for potential offshore wind development in New England waters (Southall et al. 2021b). The framework identifies risk to marine mammals based on the exposure – or the spatiotemporal-spectral overlap of noise-generating activities with the marine mammals – and considers numerous contextual variables that define the vulnerability of a species to acoustic disturbances. The framework has been effective in comparing the relative risk of different development scenarios and the relative risk of each scenario between species. The use of this framework does not replace sound field modeling at the project level, which are needed for specific purposes such as informing take estimates and mitigation zones.  

Due to the programmatic nature of this PEIS and the long lead times in the regulatory process, many details needed to fully complete the risk assessment framework for the New York Bight projects are still unknown. Therefore, this assessment draws on thematical findings from a completed hypothetical case study (Southall et al. 2021b) that analyzes the development of two wind farms off New England and serves as the best available proxy for the New York Bight analysis currently. The analysis, therefore, is focused on trade-offs associated with New York Bight alternatives and associated mitigation measures being considered in the PEIS.

Does the PEIS consider the impacts of site characterization surveys on marine mammals?  

Yes, Chapter 3 of the PEIS evaluates the potential impacts of the geophysical and geological (G&G) sound sources used in site characterization surveys. It finds that the likelihood of G&G survey noise from ongoing and planned offshore wind projects to affect mysticetes (including the North Atlantic right whale), odontocetes, and pinnipeds is de minimis in most instances and would be a negligible to minor impact. Minor impacts, such as limited behavioral disturbance or short-term masking, may occur in species with a hearing range that directly overlaps with the sound sources, which will differ depending on the sound source used (e.g., sparker sources may overlap with low-frequency cetacean hearing range, and compressed high intensity radar pulse systems may overlap with mid- and high-frequency cetacean hearing ranges). This finding is consistent with other BOEM analyses (https://www.boem.gov/environment/center-marine-acoustics/characterizing-anthropogenic-sound-sources).

Are there other sections of the New York Bight PEIS that I should read?  

Chapter 3, Appendix J, and Appendix G of the PEIS contain information related to the sound sources, potential impacts, and the selection and description of the noise-related AMMMS.