Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Maryland Offshore Wind Project Offshore of Maryland
Federal RegisterJan 4, 2024
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Part 217
[Docket No. 231206-0289]
RIN 0648-BM32
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Maryland Offshore Wind Project Offshore of Maryland
AGENCY:
National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.
ACTION:
Proposed rule; request for comments.
SUMMARY:
NMFS has received a request from US Wind, Inc., (US Wind) for Incidental Take Regulations (ITR) and an associated Letter of Authorization (LOA) pursuant to the Marine Mammal Protection Act (MMPA). The requested regulations would govern the authorization of take, by Level A harassment and Level B harassment, of small number of marine mammals over the course of 5 years (2025-2029) incidental to construction of the Maryland Offshore Wind Project offshore of Maryland within the Bureau of Ocean Energy Management (BOEM) Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf (OCS) Lease Area OCS-A 0490 (Lease Area) and associated Export Cable Routes. Project activities likely to result in incidental take include impact pile driving and site assessment surveys using high-resolution geophysical (HRG) equipment. NMFS requests comments on its proposed rule. NMFS will consider public comments prior to making any final decision on the promulgation of the requested ITR and issuance of the LOA; agency responses to public comments will be summarized in the final notice of our decision. The proposed regulations, if issued, would be effective January 1, 2025 through December 31, 2029.
DATES:
Comments and information must be received no later than February 5, 2024.
ADDRESSES:
Submit all electronic public comments via the Federal e-Rulemaking Portal. Go to
https://www.regulations.gov
and enter NOAA-NMFS-2023-0110 in the Search box. (note: copying and pasting the FDMS Docket Number directly from this document may not yield search results). Click on the “Comment” icon, complete the required fields, and enter or attach your comments.
Instructions:
Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on
https://www.regulations.gov
without change. All personal identifying information (
e.g.,
name, address), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. NMFS will accept anonymous comments (enter “N/A” in the required fields if you wish to remain anonymous).
FOR FURTHER INFORMATION CONTACT:
Jessica Taylor, Office of Protected Resources, NMFS, (301) 427-8401.
SUPPLEMENTARY INFORMATION:
Availability
A copy of US Wind's Incidental Take Authorization (ITA) application and supporting documents, as well as a list of the references cited in this document, may be obtained online at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-other-energy-activities-renewable.
In case of problems accessing these documents, please call the contact listed above (see
FOR FURTHER INFORMATION CONTACT
).
Purpose and Need for Regulatory Action
This proposed rule would provide a framework under the authority of the MMPA (16 U.S.C. 1361
et seq.
) to allow for the authorization of take of marine mammals incidental to construction of the Maryland Offshore Wind Project (hereafter, “Project”) within the BOEM Renewable Energy Development Lease Area and along export cable corridors to landfall locations in Delaware. NMFS received a request from US Wind for 5-year regulations and a LOA that would authorize take of individuals of 19 species of marine mammals (5 species by Level A harassment and Level B harassment and 14 species by Level B harassment only), comprising 20 stocks, incidental to US Wind's construction activities. No mortality or serious injury is anticipated or proposed for authorization. Please see below for definitions of harassment. Please see the Estimated Take of Marine Mammals section below for definitions of relevant terms.
Legal Authority for the Proposed Action
The MMPA prohibits the “take” of marine mammals, with certain exceptions. Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361
et seq.
) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made, regulations are promulgated (when applicable), and public notice and an opportunity for public comment are provided.
Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, the availability of the species or stocks for taking for certain subsistence uses (referred to as “mitigation”), and requirements pertaining to the mitigation, monitoring and reporting of the takings are set forth.
As noted above, no serious injury or mortality is anticipated or proposed for authorization in this proposed rule. Relevant definitions of MMPA statutory and regulatory terms are included below:
•
Citizen
—individual U.S. citizens or any corporation or similar entity if it is organized under the laws of the United States or any governmental unit defined in 16 U.S.C. 1362(13) (50 CFR 216.103);
•
Take
—to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal (16 U.S.C. 1362; 50 CFR 216.3);
•
Incidental taking
—an accidental taking. This does not mean that the taking is unexpected, but rather it includes those takings that are infrequent, unavoidable, or accidental (50 CFR 216.103);
•
Serious injury
—any injury that will likely result in mortality (50 CFR 216.3);
•
Level A harassment
—any act of pursuit, torment, or annoyance which has the potential to injure a marine mammal or marine mammal stock in the wild (16 U.S.C. 1362); and
•
Level B harassment
—any act of pursuit, torment, or annoyance which has the potential to disturb a marine
mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (16 U.S.C. 1362).
Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50 CFR part 216, subpart I, provide the legal basis for proposing and, if appropriate, issuing 5-year regulations and associated LOA. This proposed rule also establishes required mitigation, monitoring, and reporting requirements for US Wind's activities.
Summary of Major Provisions Within the Proposed Action
The major provisions within this proposed rule are as follows:
• Authorize take of marine mammals by Level A harassment and/or Level B harassment;
• No mortality or serious injury of any marine mammal is proposed to be authorized;
• Establish a seasonal moratorium on pile driving during the months of highest North Atlantic right whale (
Eubalaena glacialis
) presence in the project area (December 1-April 30);
• Require both visual and passive acoustic monitoring by trained, NMFS-approved Protected Species Observers (PSOs) and Passive Acoustic Monitoring (PAM) operators before, during, and after impact pile driving and HRG surveys;
• Require training for all US Wind personnel that would clearly articulate all relevant responsibilities, communication procedures, marine mammal monitoring and mitigation protocols, reporting protocols, safety, operational procedures, and requirements of the ITA and ensure that all requirements are clearly understood by all participating parties;
• Require the use of sound attenuation device(s) during all foundation installation activities to reduce noise levels;
• Delay the start of foundation installation if a North Atlantic right whale is observed at any distance by a PSO or acoustically detected within certain distances;
• Delay the start of foundation installation if other marine mammals are observed entering or within their respective clearance zones;
• Shut down pile driving (if feasible) if a North Atlantic right whale is observed or if other marine mammals enter their respective shut down zones;
• Shut down HRG survey equipment that may impact marine mammals if a marine mammal enters their respective shut down zones;
• Conduct sound field verification during impact pile driving to ensure in situ noise levels are not exceeding those modeled;
• Implement soft starts for impact pile driving;
• Implement ramp-up for HRG site characterization survey equipment;
• Increase awareness of North Atlantic right whale presence through monitoring of the appropriate networks and very high-frequency (VHF) Channel 16, as well as reporting any sightings to the sighting network;
• Implement various vessel strike avoidance measures;
• Implement Best Management Practices (BMPs) during fisheries monitoring surveys, such as removing gear from the water if marine mammals are considered at-risk or are interacting with gear; and
• Require frequent scheduled and situational reporting including, but not limited to, information regarding activities occurring, marine mammal observations and acoustic detections, and sound field verification monitoring results.
Under section 105(a)(1) of the MMPA, failure to comply with these requirements or any other requirements in a regulation or permit implementing the MMPA may result in civil monetary penalties. Pursuant to 50 CFR 216.106, violations may also result in suspension or withdrawal of the LOA for the project. Knowing violations may result in criminal penalties under section 105(b) of the MMPA.
National Environmental Policy Act (NEPA)
To comply with the National Environmental Policy Act of 1969 (NEPA) (42 U.S.C. 4321
et seq.
) and NOAA Administrative Order (NAO) 216-6A, NMFS must evaluate the proposed action (
i.e.,
promulgation of regulations and subsequent issuance of a 5-year LOA) and alternatives with respect to potential impacts on the human environment.
Accordingly, NMFS plans to adopt the BOEM Environmental Impact Statement (EIS), provided our independent evaluation of the document finds that it includes adequate information analyzing the effects of promulgating the proposed regulations and LOA issuance on the human environment. NMFS is a cooperating agency on BOEM's EIS. BOEM's draft EIS, “Maryland Offshore Wind Project Draft Environmental Impact Statement (DEIS) for Commercial Wind Lease OCS-A 0490”, was made available for public comment on October 6, 2023 (88 FR 69658) and is available at
https://www.boem.gov/renewable-energy/state-activities/maryland-offshore-wind.
The DEIS had a 45-day public comment period open from October 6, 2023 to November 20, 2023. Additionally, BOEM held two in-person public meetings on October 24, 2023 in Ocean City, Maryland and October 26, 2023 in Dagsboro, Delaware and two virtual public meetings on October 19, 2023 and October 30, 2023.
Information contained within US Wind's ITA application and this
Federal Register
document provide the environmental information related to these proposed regulations and associated 5-year LOA for public review and comment. NMFS will review all comments submitted in response to this notice of proposed rulemaking prior to concluding the NEPA process or making a final decision on the requested 5-year ITR and LOA.
Fixing America's Surface Transportation Act (FAST-41)
This project is covered under Title 41 of the Fixing America's Surface Transportation Act, or “FAST-41.” FAST-41 includes a suite of provisions designed to expedite the environmental review for covered infrastructure projects, including enhanced interagency coordination as well as milestone tracking on the public-facing Permitting Dashboard. FAST-41 also places a 2-year limitations period on any judicial claim that challenges the validity of a Federal agency decision to issue or deny an authorization for a FAST-41 covered project (42 U.S.C. 4370m-6(a)(1)(A)).
US Wind's proposed project is listed on the Permitting Dashboard. Milestones and schedules related to the environmental review and permitting for the US Wind's Maryland Offshore Wind Project can be found at
https://www.permits.performance.gov/permitting-project/maryland-offshore-wind-project.
Summary of Request
On August 31, 2022, NMFS received a request from US Wind, a Baltimore, Maryland-based company registered in the State of Delaware and subsidiary of Renexia SpA, for the promulgation of regulations and issuance of an associated 5-year LOA to take marine mammals incidental to construction activities associated with implementation of the Project offshore of Maryland in the BOEM Lease Area OCS-A 0490 and associated export cable routes. The request was for the incidental, but not intentional, taking of a small number of 19 marine mammal species (comprising 20 stocks). Neither
US Wind nor NMFS expects serious injury or mortality to result from the specified activities nor is any proposed for authorization.
US Wind is proposing to develop the Project over the course of three construction campaigns. In total, the 3 campaigns would result in a maximum of 114 wind turbine generators (WTGs), 4 offshore substations (OSS) positions, and 1 Meteorological tower (Met tower) within the Lease Area. The initial construction campaign, MarWin, would include installation of approximately 21 WTGs, 1 OSS, and cable landing infrastructure during the first year of activities in the most eastern part of the Lease Area. The second construction campaign, Momentum Wind, would take place during the second year of construction activities and include installation of approximately 55 WTGs, 2 OSSs, and a Met tower immediately to the west of MarWin. The third construction campaign, currently unnamed and referred to as Future Development, would occur during the third year of construction activities and include the installation of approximately 38 WTGs and 1 OSS in the most western portion of the Lease Area. Four offshore export cables would transmit electricity generated by the WTGs from the Lease Area to onshore transmission systems within Delaware Seashore State Park.
In response to our comments and following extensive information exchanges with NMFS, US Wind submitted a final, revised application on March 31, 2023 that NMFS deemed adequate and complete on April 3, 2023. The final version of the application is available on NMFS' website at:
https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-wind-inc-construction-and-operation-maryland-offshore-wind.
On May 2, 2023, NMFS published a notice of receipt (NOR) of the adequate and complete application in the
Federal Register
(88 FR 27463), requesting comments and soliciting information related to US Wind's request during a 30-day public comment period. During the NOR public comment period, NMFS received comment letters from 77 private citizens, 6 non-governmental organizations, and 1 state government organization (Delaware Department of Natural Resources and Environmental Control). NMFS has reviewed all submitted material and has taken these into consideration during the drafting of this proposed rule.
On August 1, 2022, NMFS announced proposed changes to the existing North Atlantic right whale vessel speed regulations (87 FR 46921, August 1, 2022) to further reduce the likelihood of mortalities and serious injuries to endangered right whales from vessel collisions, which are a leading cause of the species' decline and a primary factor in an ongoing Unusual Mortality Event (UME). Should a final vessel speed rule be issued and become effective during the effective period of this ITR (or any other MMPA incidental take authorization), the authorization holder would be required to comply with any and all applicable requirements contained within the final rule. Specifically, where measures in any final vessel speed rule are more protective or restrictive than those in this or any other MMPA authorization, authorization holders would be required to comply with the requirements of the rule. Alternatively, where measures in this or any other MMPA authorization are more restrictive or protective than those in any final vessel speed rule, the measures in the MMPA authorization would remain in place. The responsibility to comply with the applicable requirements of any vessel speed rule would become effective immediately upon the effective date of any final vessel speed rule and when notice is published on the effective date, NMFS would also notify US Wind if the measures in the speed rule were to supersede any of the measures in the MMPA authorization such that they were no longer required.
On September 6, 2023, and September 11, 2023, US Wind submitted supplemental information related to its pilot whale and seal take analyses. The corresponding memos, entitled “US Wind NMFS Request for Information (RFI) Response Memo and Maryland Offshore Wind Project Revised Requested Take Tables” are available on our website.
Description of the Specified Activities
Overview
US Wind has proposed to construct and operate a wind energy facility, the Project, in the Atlantic Ocean in lease area OCS-A 0490, offshore Maryland. The Project would allow the State of Maryland to advance Federal and State offshore wind targets as well as reduce greenhouse gas emissions, increase grid reliability, and support economic development growth in the region. The Project consists of three construction campaigns including MarWin, located in the southeastern portion of the Lease Area with the potential to generate approximately 300 megawatts (MW) of energy, Momentum Wind, located immediately west of MarWin with the potential to generate approximately 808 MW of energy, and Future Development, which encompasses buildout of the remainder of the Lease Area and for which generation capacity has yet to be determined. Once operational, MarWin and Momentum Wind would advance the State of Maryland's renewable energy goals of 50 percent by the year 2030, with the full buildout of the Lease Area further achieving renewable energy targets. US Wind also anticipates completing the Future Development campaign within the effective period of the proposed rule.
The Project would consist of several different types of permanent offshore infrastructure, including up to 114 WTGs (
e.g.,
18-MW model with a 250-meter (m) rotor diameter platform), four OSSs, a Met tower, and inter-array and export cables. The Project is divided into three construction campaigns: MarWin, Momentum Wind, and Future Development (table 1). MarWin would occupy approximately 46.6 km
2
(11,515 acres) which would include approximately 21 WTGs and 1 OSS. The MarWin campaign, as well as subsequent Momentum Wind and Future Development, includes monopiles as the one potential WTG foundation type. For each campaign, the OSS would be supported by monopiles or jacket foundations with skirt piles. Skirt piles are post-piled pin piles. Jacket foundations are placed on the seabed and pin piles are driven into jacket pile guides, which are known as skirts. Table 1 provides a summary of each construction campaign.
Table 1—US Wind's Anticipated Construction Campaign Schedule
Campaigns
Construction
year
Number of 11-m
monopiles for
WTGs
Number 3-m pin piles for OSS jacket foundations
1
Number of
1.8-m pin
piles for
Met tower
Onshore export
cables
Offshore
substations
MarWin
1 (2025)
21
4 (1 jacket)
0
4
1
Momentum
2 (2026)
55
8 (2 jackets)
3
0
2
Future Development
3 (2027)
38
4 (1 jacket)
0
0
1
1
Potential OSS foundations could also include monopile and suction bucket jacket foundations.
Strings of WTGs will connect with the OSS via a submarine inter-array cable transmission system. Up to four high-voltage alternating current (HVAC) offshore export cables would be installed during the MarWin campaign, spanning approximately 65-97 km (40-60 miles (mi)) in length, dependent on the location of the OSS and the final routing. The Export Cable Corridor (ECC) would transmit electricity from the OSS to one or two landfall sites in Delaware Seashore State Park.
The second construction campaign, Momentum Wind, would contain approximately 55 WTGs, 2 OSSs, and 1 Met tower within an area of approximately 142.4 km
2
(35,188 acres). The Met tower would be supported by pin pile foundations. During the third construction campaign, Future Development, approximately 38 WTGs and 1 OSS would be installed within an area of approximately 80.3 km
2
(19,843 acres).
US Wind plans to install all monopile or pin pile foundations via impact pile driving. If suction bucket foundations are selected for OSS jacket foundations, impact pile driving would not be necessary. US Wind would also conduct the following supporting activities: temporary installation and subsequent removal of gravity cells to connect the offshore export cables to onshore facilities; permanently install scour protection around all foundations; permanently install and perform trenching, laying, and burial activities associated with the export cables from the OSSs to shore-based switching and sub-stations and WTG inter-array cables; and, during years 2 and 3, performance of HRG surveys using active acoustic sources with frequencies of less than 180 kilohertz (kHz). Vessels would transit within the project area and anticipated between ports (Port Norris, NJ; Lewes, DE; Ocean City, MD; Baltimore, MD; Hampton Roads, VA; and Cape Charles, VA) and the Lease Area and cable corridors to transport crew, supplies, and materials to support construction activities.
Up to four offshore export cables would be located among up to two corridors from the OSSs and connect to the planned landfall at either 3R's Beach or Tower Road within Delaware Seashore State Park. When the cables reach the landfall site, they would be pulled into a cable duct generated by horizontal directional drilling (HDD), which would route the cables under the existing beach to subterranean transition vaults. All offshore cables would be connected to onshore export cables at the sea-to-shore transition point via trenchless installation (
i.e.,
underground tunneling utilizing micro tunnel boring installation methodologies).
Fishery monitoring surveys, performed via recreational boat-based surveys and a pot-based monitoring approach using ropeless gear technology, would be conducted in conjunction with the University of Maryland Center for Environmental Science (UMCES) to enhance existing data for specific benthic and pelagic species of concern.
Dates and Duration
As described above, US Wind would conduct 3 campaigns over 3 years: MarWin, Momentum Wind, and Future Development (table 1). In case of any delays to any campaign, NMFS is proposing a 5-year effective date of the proposed regulations and LOA; however, no more work in any given year or total over 5 years other than described here would occur. US Wind anticipates that activities with the potential to result in incidental take of marine mammals would occur throughout 3 of the 5 years (2025-2027) of the proposed regulations which, if issued, would be effective from January 1, 2025 through December 31, 2029. Based on US Wind's proposed schedule, the installation of all permanent structures would be completed by the end of November 2027. More specifically, US Wind would install piles only between May 1 and November 30. Also, the installation of WTG foundations and OSS 3-m pin pile jacket foundations is expected to occur during daylight hours between May 1 and November 30 of 2025, 2026, and 2027 (table 2); however, NMFS is proposing to allow nighttime pile driving if US Wind submits, and NMFS approves, an Alternative Monitoring Plan, as discussed below. The single Met tower foundation would be installed in 2026 (table 2).
US Wind anticipates HRG surveys using sparkers and boomers to occur during 2026 and 2027. Up to 14 days of HRG survey activity are planned from April through June 2026 during the Momentum campaign. In addition, up to 14 days of HRG survey activity are planned from April through June 2027 during the Future Development campaign. No HRG surveys using equipment that has the potential to result in the harassment of marine mammals (
e.g.,
sparkers or boomers) are planned for the MarWin campaign during year 1.
Table 2—US Wind's Anticipated Construction and Operations Schedule During the Effective Period of the LOA
1
Project activity
Construction campaign
Expected timing
2
Expected duration
(approximate)
Scour Protection Pre-Installation
MarWin
Year 1:
Q2 through Q3 of 2025
21 days.
Momentum Wind
Year 2:
Q2 through Q3 of 2026
55 days.
Future Development
Year 3:
Q2 through Q3 of 2027
38 days.
WTG Foundation Installation
3 5
MarWin
Year 1:
June through September of 2025
21 days.
Momentum Wind
Year 2:
May through August of 2026
55 days.
Future Development
Year 3:
June through August of 2027
38 days.
Scour Protection Post-Installation
MarWin
Year 1:
Q2 through Q3 of 2025
42 days.
Momentum Wind
Year 2:
Q2 through Q3 of 2026
110 days.
Future Development
Year 3:
Q2 through Q3 of 2027
76 days.
OSS Foundation Installation
3 5
MarWin
Year 1:
July of 2025
1 day.
Momentum Wind
Year 2:
July of 2026
2 days.
Future Development
Year 3:
July of 2027
1 day.
Met Tower Installation
3 4
Momentum Wind
Year 2:
June of 2026
1 day.
HRG Surveys
5
Momentum Wind
Year 2:
Q2 through Q3 of 2026
14 days.
Future Development
Year 3:
Q2 through Q3 of 2027
14 days.
Site Preparation
n/a
Not anticipated
n/a.
Inter-array Cable Installation
Marwin
Year 1:
Q2 through Q4 of 2025
42 days.
Momentum Wind
Year 2:
Q2 through Q4 of 2026
110 days.
Future Development
Year 3:
Q2 through Q4 of 2027
76 days.
Export Cable Installation
MarWin
Year 1:
Q1 through Q4 of 2025
60 days.
Momentum Wind
Year 2:
Q1 through Q4 of 2026
120 days (2 cables).
Future Development
Year 3:
Q1 through Q4 of 2027
60 days.
Fishery Monitoring Surveys
MarWin
Q1 through Q4 Years 1-5
16 days/year for commercial pot surveys.
Momentum Wind
Future Development
12 days/year for recreational surveys.
1
While the effective period of the proposed regulations would extend through December 31, 2029, no activities are proposed to occur in 2028 or 2029 by US Wind so these were not included in this table.
2
Installation timing will depend on vessel availability, contractor selection, weather, and more. Year 1 is anticipated to be 2025, year 2 to be 2026, and year 3 to be 2027, although these are subject to change per the factors identified. Note: “Q1, Q2, Q3, and Q4” each refer to a quarter of the year, starting in January and comprising 3 months each. Therefore, Q1 represents January through March, Q2 represents April through June, Q3 represents July through September, and Q4 represents October through December.
3
The months identified here represent US Wind's planned schedule; however, in case of unanticipated delays, foundation installation may occur between May 1 and November 30 annually.
4
US Wind anticipates that all WTGs, OSS, and Met tower foundations will be installed by November 30, 2027; however, unanticipated delays may require some foundation pile driving to occur in years 4 (2028) or 5 (2029).
5
Represents HRG surveys that may result in take of marine mammals. US Wind plans to conduct HRG surveys that do not have the potential to result in take of marine mammals during Q2 through Q3 of year 1 given those surveys would utilize equipment all operating over 180kHz or have no acoustic output.
Specific Geographic Region
US Wind's specified activities would occur within the Northeast U.S. Continental Shelf Large Marine Ecosystem (NES LME), an area of approximately 260,000 km
2
(64,247,399.2 acres) from Cape Hatteras in the south to the Gulf of Maine in the north. Specifically, the specified geographic region is the Middle-Atlantic Bight (Mid-Atlantic Bight) sub-area of the NES LME. The Mid-Atlantic Bight encompasses waters of the Atlantic Ocean between Cape Hatteras, North Carolina and Martha's Vineyard, Massachusetts, extending westward into the Atlantic to the 100-m isobath. In the Mid-Atlantic Bight, the pattern of sediment distribution is relatively simple. The continental shelf south of New England is broad and flat, dominated by fine grained sediments. Most of the surficial sediments on the continental shelf are sands and gravels. Silts and clays predominate at and beyond the shelf edge, with most of the slope being 70-100 percent mud. Fine sediments are also common in the shelf valleys leading to the submarine canyons. There are some larger materials, left by retreating glaciers, along the coast of Long Island and to the north and east.
Primary productivity is highest in the nearshore and estuarine regions, with coastal phytoplankton blooms initiating in the winter and summer, although the timing and spatial extent of blooms varies from year to year. The relatively productive continental shelf supports a wide variety of fauna and flora, making it important habitat for various benthic and fish species and marine mammals, including but not limited to, fin whales, humpback whales, North Atlantic right whales, and other large whales as they migrate through the area. The Cold Pool, a bottom-trapped cold, nutrient-rich pool and distinct oceanographic feature of the Mid-Atlantic Bight, creates habitat that provides thermal refuge to cold water species in the area (Lentz, 2017). Cold Pool waters, when upwelled to the surface, promote primary productivity within this region (Voynova
et al.,
2013).
The seafloor in the Project Area is dynamic and changes over time due to current, tidal flows, and wave conditions. As the Lease Area is located just south of the mouth of Delaware Bay, the seafloor bedforms and sediments are affected by interactions between storm-driven currents, storm discharges from Delaware Bay, and tidal flows associated with Delaware Bay (US Wind, 2023b). The Lease Area is defined by medium-coarse grained sand at the surface and sub-surface interlays of clay and gravel (Alpine, 2015). The most prominent bathymetric features of the Lease Area are ridges and swales offshore of the Delmarva Peninsula that extend seaward from Delaware Bay (US Wind, 2023b). Sand ripples are present throughout the Project area. Sediment within the onshore export cable corridor is composed of predominantly silt-sand mixed with medium-coarse grained sand (US Wind, 2023b). The bottom habitat of Indian River Bay, through which the export cable route may pass through, is relatively flat in elevation and comprises fine to course-grained sands area.
The benthic habitat of the Project Area contains a variety of seafloor substrates, physical features, and associated benthic organisms. The benthic macrofaunal community of the Lease Area is dominated by polychaetes and oligochaete worms yet may also include sand dollars, sea stars, tube anemones, hermit crabs, rock crabs, moon snails, nassa snails, surf clams, sea scallops, shrimp, and ocean quahog (Guida
et al.,
2017).
Additional information on the underwater environment's physical resources can be found in the COP for the Maryland Offshore Wind Project (US Wind, 2023b) available at:
https://www.boem.gov/renewable-energy/state-activities/maryland-offshore-wind-construction-and-operations-plan.
US Wind would construct the Project in Federal and State waters offshore of Maryland within the BOEM Lease Area OCS-A 0490 and associated export cable routes (figure 1). The Lease Area covers approximately 323.7 square kilometers (km
2
) (80,000 acres) and is located approximately 18.5 km offshore of Maryland. The water depths in the Lease Area range from 13 m along the western lease border to 41.5 m (43 to 136.1 feet (ft)) along the southeast corner of the lease area while depths along the export cable routes range from 10 m to 45 m (33 to 148 ft). Mean sea
surface temperatures range from 42 to 75.8 degrees Fahrenheit (°F; 5.56 to 24.3 degrees Celsius (°C), while the depth-average annual water temperature is 58.2 °F (14.6 °C). Cables would come ashore at 3Rs Beach or Tower Road within Delaware Seashore State Park. The Project Area is defined as the Lease Area and export cable route area.
BILLING CODE 3510-22-P
EP04JA24.000
BILLING CODE 3510-22-C
Detailed Description of the Specified Activity
Below, we provide detailed descriptions of US Wind's planned activities, explicitly noting those that are anticipated to result in the take of marine mammals and for which incidental take authorization is requested. Additionally, a brief explanation is provided for those activities that are not expected to result in the take of marine mammals.
WTG, OSS, and Met Tower Foundations
US Wind proposes to install up to 114 WTGs on monopile foundations, 4 OSSs on 3-m pin pile jacket foundations, and one Met tower on a 1.8-m pin pile foundation. US Wind is also considering monopile foundations and suction bucket jacket foundations for OSSs, although 3-m pin pile jacket foundations are the most likely foundation type. All WTG and OSS foundations would be installed between May 1 and November 30 in 2025 (MarWin), 2026 (Momentum Wind), and 2027 (Future Development) (refer back to table 1). No pile driving would occur December 1-April 30. For purposes of this proposed rule, US Wind assumed all foundations would be installed using an impact hammer, unless US Wind
uses gravity suction bucket-based jacket foundations for OSSs.
A WTG monopile foundation typically consists of a coated single steel tubular section, with several sections of rolled steel plate welded together. Each monopile would have a maximum diameter of 11 m (36 ft). WTGs would be spaced approximately 0.77 nautical miles (nmi; 1.42 km) in an east-west direction and 1.02 nmi (1.89 km) in a north-south direction and driven to a maximum penetration depth of 50 m (164 ft) below the seafloor (US Wind, 2023a). Monopile foundations would consist of a monopile with an integrated or separate transition piece. US Wind would install rock scour protection around the base of the monopile foundations prior to or following installation to minimize scour around the foundation bases (US Wind, 2023). Monopile foundations would be installed using an MHU 4400 impact hammer at a maximum hammer energy of 4,400 kJ. US Wind anticipates that one monopile will be installed per day at a rate of approximately 2 hours of active pile driving time per monopile, though two or more monopile installations per day may be possible depending on operational limitations and environmental conditions (table 3).
Monopile, pin pile jacket, and gravity suction-bucket jacket foundations are technically and economically feasible for OSSs. Up to four OSSs would be installed via impact pile driving (monopile and pin pile jacket foundations) or dewatering process to sink suction buckets to the appropriate depth. Rock scour protection would be applied after foundation installation.
Monopile foundations for the OSSs would have a maximum diameter of 11 m (36 ft) and maximum pile penetration depth of 40 m (131 ft). Monopile foundations would have a separate transition piece with a number of J-tubes to support and protect cables as well as to connect the inter-array cables and the offshore export cable to the OSS. If monopiles are selected for the OSSs, monopiles would be installed through impact pile driving according to the same methods as described for WTG monopile foundations.
Jacket foundations with pin piles, if selected for OSS design, may be pre-piled or post-piled using pin piles with a maximum diameter of 3-m (9.8 ft). A pre-piled jacket would involve pin piles pre-installed in the seabed using a template. A post-piled jacket foundation is formed by a steel lattice construction (comprising tubular steel members and welded joints) secured to the seabed by means of hollow steel pin piles attached to the jacket where the pin piles have been driven through jacket skirts (skirt piles). Each jacket structure may have three, four, or six legs. A four-leg OSS with a post-piled pin pile jacket foundation is the most likely design and was selected for modeling impacts to marine mammals from OSS installation. Each jacket foundation would consist of up to four pin piles. In total, US Wind would install up to 4 OSSs for a total of 16 pin piles. Up to four 3-m pin piles would be installed per day using an impact hammer with a maximum hammer energy 1,500 kJ (table 3). Pin piles would have a maximum diameter of 3 m (9.8 ft) each and would be installed vertically.
US Wind plans to install one Met tower to serve as a permanent metocean monitoring station. The Met tower foundation would be a Braced Caisson design, in which one main steel pile would be supported laterally by two steel supporting (bracing) piles. The main steel pin pile would have a maximum diameter of 1.8 m (72 in) and the two bracing pin piles would have a maximum diameter of 1.5 m (60 in). US Wind assumed bracing pin piles would be 1.8 m in diameter for the purposes of modeling impacts of installation on marine mammals. The main caisson and bracing piles would be installed using an impact hammer with a maximum energy of 500 kJ at a rate of approximately 2 hours per pin over the course of 2 days (table 3). The Met tower would include measurement devices to record weather conditions, such as wind and waves, in the Project Area. US Wind identified three potential locations for placement of the Met tower along the southern edge of the Lease Area, as shown in figure 1-2 of the ITA application.
If US Wind installs suction bucket jacket foundations, they would have a maximum diameter of 15 m (49 ft) and pile penetration depth of 15 m (49 ft). Suction bucket jacket foundations would be installed through a dewatering process which generates pressure that draws the buckets to the desired depth. The process to install a suction bucket foundation does not produce elevated noise levels that could harass marine mammals; therefore, no take from this activity is anticipated to occur or is proposed to be authorized. Installation is not expected to result in take of marine mammals. Suction bucket foundations are not further discussed.
Table 3—Impact Pile Driving Schedule
Pile type
Project
component
Max
hammer
energy
(kJ)
1
Number of
hammer
blows
Piling time
duration
per pile
(min)
Piling time
duration
per day
(min)
Number
piles/day
11-m monopile
WTG
1,100
600
120
120
1
2,200
2,400
3,300
2
1,800
3-m pin pile jacket foundations
OSS
1,500
19,200
120
480
4
1.8-m Steel Bracing Caisson pile
3
Met tower
500
2,988
120
360
1
1.8-m Steel Bracing pile
3
2
1
Assumes MHU 4400 hammer.
2
US Wind has proposed a hammer strike energy progression for impact pile driving of monopiles, beginning at a hammer energy of 1,100 kJ to an energy of 3,300 kJ, although the maximum hammer energy possible (4,400 kJ) was used and scaled in the modeling.
3
A bracing caisson design has one main pile supported laterally by two bracing piles. The bracing caisson pile and bracing piles for the Met tower are pin piles.
While pre-piling preparatory work and post-piling activities could be ongoing at one foundation position as pile driving is occurring at another position, no concurrent/simultaneous pile driving of foundations would occur (see
Dates and Duration
section). Installation of foundations is anticipated to result in the take of marine mammals due to noise generated during pile driving. Proposed mitigation, monitoring, and reporting measures for impact pile driving are described in detail later in this document (see Proposed Mitigation and Proposed Monitoring and Reporting).
US Wind anticipates the 21 WTGs to be installed during the MarWin campaign would become operational by December 31, 2025. The 55 WTGs to be installed during the Momentum Wind
campaign would become operational by December 31, 2026, and the 38 WTGs to be installed during the Future Development campaign would become operational by December 31, 2027 (table 2).
HRG Surveys
US Wind plans on conducting HRG surveys to identify any seabed debris or unexploded ordnance (UXO), confirm previously surveyed site conditions prior to cable installation, meet BOEM or other agency requirements for additional surveys, and to refine or (microsite) locations of construction footprints, WTG and OSS foundations, and cables. US Wind has committed to not detonating any UXOs. US Wind would prepare an avoidance plan for working around UXOs and conduct micro-siting surveys to identify any UXOs in the area. Only the micro-siting surveys have the potential to result in harassment of marine mammals and would be limited to the Lease Area. Pre-construction and UXO HRG surveys would utilize equipment that have operating frequencies that are above relevant marine mammal hearing thresholds or no acoustic output (
e.g.,
magnetometers). Take is not anticipated from the use of this equipment; therefore, pre-construction and UXO HRG surveys are not analyzed further.
HRG micro-siting surveys would occur within the Lease Area, focusing on the inter-array cable layout, as well as along the offshore export cable corridors, if necessary. US Wind estimates approximately 14 days of HRG micro-siting survey effort per year from April through June during years 2 and 3 (Momentum Wind in 2026, Future Development in 2027) and only during daylight hours. HRG micro-siting surveys would be conducted using one vessel at a time. Up to 111.1 km of survey lines would be surveyed per vessel each survey day at approximately 7.4 km/hour (4 knots (kn)) during daylight hours. Acoustic equipment described above (multibeam echosounders, side scan sonars, and marine magnetometers) may be used during micro-siting surveys as well as non-impulsive ultra-short baseline positioning equipment (
i.e.,
Ultra-Short BaseLine (USBL) and other parametric sub-bottom profilers), shallow penetration sub-bottom profilers (SBPs) (
e.g.,
Innomar SES-2000 non-parametric SBP), and medium penetration SBPs (
e.g.,
sparkers and boomers). Take is not anticipated resulting from the use of ultra-short baseline position equipment or the Innomar SBP as these equipment types have a very narrow beam width which limits acoustic propagation, and these sources are not analyzed further.
Of the HRG equipment types proposed for use during micro-siting surveys, the following sources have the potential to result in take of marine mammals:
• Medium penetration SBPs (boomers) to map deeper subsurface stratigraphy as needed. A boomer is a broad-band sound source operating in the 0.2 kHz to 15 kHz frequency range. This system is typically mounted on a sled and towed behind the vessel.
• Medium penetration SBPs (sparkers) to map deeper subsurface stratigraphy as needed. A sparker creates acoustic pulses from 0.05 kHz to 3 kHz omni-directionally from the source that can penetrate several hundred meters into the seafloor. These are typically towed behind the vessel with adjacent hydrophone arrays to receive the return signals.
Table 4 provides a list of the equipment specifications for the medium penetration SBPs that may result in take of marine mammals during HRG micro-siting surveys. Equipment with operating frequencies above 180 kHz are not discussed further because they are outside the general hearing range of marine mammals and therefore do not have the potential to cause harassment. Although US Wind has proposed a beamwidth of 100 degrees for the Geo Spark sparker, NMFS has determined that a 180-degree beamwidth is more appropriate for this analysis, as sparkers are considered omnidirectional sources (Ruppel
et al.,
2022). Additionally, US Wind proposed an RMS source level of 219 decibels (dB), based on a manufacturer specification. Because it was not clear which operating energy, tip configuration, or specific sparker model this source level was based on, and also because the manufacturer-provided source levels are not well-documented, NMFS considers the well-documented measurements for a wide variety of sparker configurations from Crocker and Fratantonio (2016) to be the best-available data for use in deriving appropriate proxy source levels. Further, the RMS source levels are given directly in Crocker and Fratantonio (2016), thus mitigating uncertainty associated with deriving RMS levels from peak levels. For these reasons, we have instead used an RMS source level of 206 dB, based on Crocker and Fratantonio (2016) and a 3 dB adjustment to account for the potential use of two 400 tip decks. Source characteristics and details of the source proxy are found in Table 4, and its footnotes below. The net result of NMFS's changes to the proposed methodology is an increase of the Level B isopleth from 50.1 m to 200 m.
Proposed mitigation, monitoring, and reporting measures for HRG micro-siting surveys are described in detail later in this document (see Proposed Mitigation and Proposed Monitoring and Reporting).
Table 4—Summary of Representative HRG Micro-Siting Survey Equipment That May Result in Take of Marine Mammals
1
HRG system
Representative
survey equipment
Operating
frequencies
(kHz)
Peak
source
level
(dB
peak
)
RMS source
level
(dB
RMS
)
Pulse
duration
(ms)
Repetition
rate
(Hz)
Beamwidth
(degrees)
Medium- penetration SBP
Applied Acoustic S Boomer
2
0.1-5
211
205
0.6
3
80
AA Dura Spark 400 tip (500 J)
3
0.3-4
214
206
2.3
2
180
dB = decibels; Hz = hertz.
1
Of note, NMFS has performed a preliminary review of a report submitted by Rand (2023), that includes measurements of the Geo-Marine Geo-Source 400 sparker (400 tip, 800 J), and suggests that NMFS is assuming lower source and received levels than appropriate in its assessments of HRG impacts. NMFS has determined that the values in our assessment remain appropriate, based on the model methodology (
i.e.,
source level propagated using spherical spreading) here predicting a peak level 3 dB louder than the maximum measured peak levels at the closest measurement range in Rand (2023). NMFS will continue reviewing any available data relevant to these sources.
2
Crocker and Fratantonio (2016) provide Applied Acoustics S Boomer measurements. Frequency and repetition rate of the Applied Acoustics S Boomer verified by survey contractors.
3
AA Dura-Spark 400 tip used as a proxy due to similar configuration and energy to the Geo-spark 2000. See Table 10 in Crocker and Fratantonio (2016) source levels for 500 J setting and 400 tips. Based on previous survey experience, US Wind expects to operate the Geo-spark at 400-500 J per 400 tip deck, with the possibility of one or two total 400 tip decks (
i.e.,
400-1000 J total energy). To account for the potential of two decks, the source level is doubled in energy, which results in the addition of approximately 3 dB (to the 206 dB RMS, as shown in Table 4).
Cable Landfall Construction
US Wind would bring up to four offshore export cables through Indian River Bay to shore to landing locations at 3Rs Beach or Tower Road within the Delaware Seashore State Park (figure 1). The US Wind export cable would be connected to the onshore transmission cable at the landfall locations using horizontal directional drilling (HDD) and a jet plow. Cables would be pulled into cable ducts that would route the cables under the beach to subterranean transition vaults, located in existing developed areas such as parking lots. US Wind evaluated cofferdams at the HDD locations and determined that the use of a gravity cell would be more appropriate for soil conditions as well as avoid the use of a vibratory hammer that would create additional underwater sound. The gravity cell would be lowered onto the seafloor and would not require the walls of the cell to be driven into the seabed (
i.e.,
no pile driving would occur). The HDD drill rig would be set up onshore in an excavated area and the drill would advance to the offshore exit point. The offshore cable would be pulled in through the HDD ducts into the cable jointing/transition vault at the landfall location. The cable installation vessel would then begin laying the cable on the seabed as described in the Cable Laying and Installation section below. Given the work is not expected to produce noise levels that could result in harassment to marine mammals, HDD and gravity cell installation is not expected to result in the take of marine mammals. US Wind did not request, and NMFS is not proposing to authorize, take associated with cable landfall construction; therefore, this activity is not discussed further.
Cable Laying and Installation
Cable burial operations would occur both in the Lease Area and ECCs from the Lease Area to shore. The inter-array cables would connect the WTGs to any one of the OSSs. All WTGs would connect to an OSS in strings of 4-6 WTGs via the inter-array cables. Cables within the ECCs would carry power from the OSSs to shore at the landfall location(s) within Delaware Seashore State Park. The offshore export cables would be buried in the seabed at a target depth of up to 1 m (3.3 ft) to 3 m (9.8 ft), although the exact depth would not exceed 4 m (13.1 ft). Inter-array cable burial operations would be installed to a target depth of 1 m (3.3 ft) to 2 m (6.6 ft), not to exceed 4 m (13.1 ft) in depth and would follow installation of the WTG and OSS foundations as the foundations must be in place to provide connection points. Offshore cable installation may occur concurrently with foundation installation.
Cable laying, cable installation, and cable burial activities planned to occur during the construction of the Project would include the following methods: offshore export cable pull through the HDD duct, simultaneous lay and burial for cable installation through the use of a jet plow, and post-lay burial for cables, as needed. Offshore export cables would be pulled through the HDD duct, as described in the Cable Landfall Construction section above. The inter-array cables would be installed from a dynamically positioned cable installation vessel. US Wind plans to use a jet plow to achieve the target inter-array and offshore cable burial depth. If necessary, post-lay cable burial would be completed through the use of a cable installation support vessel and remotely operated vehicle (ROV) system (US Wind, Inc., 2023a). Areas with cable crossings or hard bottoms may require additional protection measures, such as mattresses, rock placement, or cable protection systems. In shallow areas of cable installation, dredging may be necessary to allow access by the cable lay barge. As the noise levels generated from cable laying and installation work are low, the potential for take of marine mammals to result is discountable. US Wind is not requesting, and NMFS is not proposing, to authorize take associated with cable laying activities. Therefore, cable laying activities are not analyzed further in this document.
Site Preparation and Scour Protection
Site preparation typically includes sand bedform leveling, boulder clearance, pre-lay grapnel runs, and a pre-lay survey to prepare the area for export cable installation. Route clearance activities would be conducted prior to offshore export cable installation. Project activities would include a pre-installation survey and grapnel run along the offshore export cable corridor to remove debris that could impact the cable lay and burial. US Wind does not expect pre-installation seabed preparation, such as leveling, pre-trenching, to be necessary. A pre-lay grapnel run would be conducted along the cable route to remove debris that could impact cable lay and burial.
US Wind would also deposit rock around each foundation as scour protection. Prior to or following the installation of a monopile or jacket foundation for the OSS, a first layer of scour protection rocks will be deployed in a circle around the pile location to stabilize the seabed (US Wind, Inc., 2023a). If suction bucket foundations are selected for OSSs, scour protection would be deployed after buckets reach target penetration depth. A 1-2 m (2-7 ft) thick second layer of larger rocks would be placed for stabilization once the inter-array cables have been pulled into the monopile. Scour protection may also be applied as additional protection for cables after burial.
NMFS does not expect scour protection placement or site preparation work, including pre-lay grapnel runs and pre-lay surveys, to generate noise levels that would cause take of marine mammals. Although not anticipated, any necessary dredging, bedform leveling, or boulder clearance would be extremely localized at any given time, and NMFS expects that any marine mammals would not be exposed at levels or durations likely to disrupt behavioral patterns (
i.e.,
migrating, foraging, calving,
etc.
). Therefore, the potential for the take of marine mammals to result from these activities is so low as to be discountable. US Wind did not request, and NMFS is not proposing, to authorize any takes associated with site preparation and scour protection activities; therefore, they are not analyzed further in this document.
Vessel Operation
US Wind will utilize various types of vessels over the course of the 5-year proposed regulations for surveying, foundation installation, cable installation, WTG and OSS installation, and support activities. US Wind has identified several existing port facilities located in Maryland, Virginia, Delaware, and New Jersey to support offshore construction, assembly and fabrication, crew transfer and logistics, and other operational activities. In addition, some components, materials, and vessels could come from Canadian and European ports. A variety of vessels would be used throughout the construction activities. These range from crew transportation vessels, tugboats, jack-up vessels, cargo ships, and various support vessels (table 5). Details on the vessels, related work, operational speeds, and general trip behavior can be found in table 1-2 of the ITA application and table 4-1 in the COP volume 1.
As part of various vessel-based construction activities, including cable laying and construction material delivery, dynamic positioning thrusters may be utilized to hold vessels in position or move slowly. Sound produced through use of dynamic positioning thrusters is similar to that
produced by transiting vessels, and dynamic positioning thrusters are typically operated either in a similarly predictable manner or used for short durations around stationary activities. Fall pipe vessels may use dynamic positioning thrusters during the installation of scour protection up to 24 hours per day. Jack-up cranes or floating cranes may use dynamic positioning thrusters for up to 4 hours per WTG or OSS installation. Heavy lift and general cargo vessels may use dynamic positioning thrusters for the delivery of Project components from the manufacturing location to the staging/assembly port only while maneuvering in port. Multipurpose offshore supply vessels may also use dynamic positioning thrusters throughout the day during the pre-lay grapnel run boulder clearance and cable burial. Jack-up or accommodation vessels may use dynamic positioning thrusters while constructing housing for offshore works, yet only while maneuvering to the site, which would last approximately 2 hours per WTG or OSS. Dynamic positioning thrusters may also be used by vessels throughout the day for pre-installation, geophysical and geotechnical verification surveys, cable installation, placement of scour protection and concrete mattresses, seabed preparation and leveling, and commissioning activities. Sound produced by dynamic positioning thrusters would be preceded by, and associated with, sound from ongoing vessel noise and would be similar in nature; thus, any marine mammals in the vicinity of the activity would be aware of the vessel's presence. Construction-related vessel activity, including the use of dynamic positioning thrusters, is not expected to result in take of marine mammals. US Wind did not request, and NMFS does not propose to authorize, any take associated with vessel activity.
The total vessels expected for use during the Project are provided in table 5; more details can be found in table 1-2 of the ITA application. Assuming the maximum design scenario, approximately 458 total vessel round trips are expected to occur during the MarWin construction campaign (2025), approximately 1,944 total vessel round trips are expected to occur during the Momentum Wind construction campaign (2026), and approximately 1,587 total vessel round trips are expected to occur during the Future Development construction campaign (2027). Vessels would remain on site during construction activities each year to reduce the number of transits between the Project Area and ports.
For operations and maintenance, US Wind anticipates that up to 10 vessels could be used, although not all vessels would operate at the same time or every year. A fall pipe vessel, jack-up vessel, and multi-role survey vessel only be used for non-routine maintenance activities (table 5). Crew transfer vessels would not be likely to operate on a daily basis year-round, however, to be conservative, US Wind assumed that these vessels would operate on a daily basis (table 5).
Table 5—Type and Number of Vessels Anticipated During Construction and Operations
Project period
Vessel types
Max number
of vessels
Expected
maximum
annual
number
of trips
1
Foundation Installation
Transport, Installation, and Support
5
10
Crew Transfer
1
26
Environmental Monitoring and Mitigation
4
52
WTG Installation
Transport, Installation, and Support
4
26
Crew Transfer Vessel
0
0
Inter-array Cable Installation
Transport, Installation, and Support
4
5
Crew Transfer Vessel
2
136
OSS Installation
Transport, Installation, and Support
9
16
Crew Transfer Vessel
0
0
Offshore Export Cable Installation
Transport, Installation, and Support
6
25
Crew Transfer Vessel
0
0
Operations and Maintenance
2
Fall Pipe Vessel
1
1
Crew Transfer Vessel (refueling)
3
1
20
Jack-up Vessel
1
1
Multi-role Survey Vessel
4
2
13
Sportfisher Vessel
1
100
Crew Transfer Vessel
4
365
5
1
Vessels and trips provided represent the maximum number of year 2 trips for each vessel category for each activity from US Wind's OCS air permit application, appendix A.
2
Potential operation and maintenance ports include Ocean City, MD; Baltimore, MD; and Portsmouth, VA.
3
Only for non-routine maintenance activities
4
One of these vessels would be for non-routine maintenance activities
5
Expected maximum annual number of trips per year for each of the four vessels. Fourth vessel may not be necessary.
While a vessel strike could cause injury or mortality of a marine mammal, NMFS is proposing to require extensive vessel strike avoidance measures that would avoid vessel strikes from occurring (see Proposed Mitigation section). US Wind has not requested, and NMFS is not proposing to authorize, take from vessel strikes.
Fisheries and Benthic Monitoring
Fisheries and benthic monitoring surveys are being designed for the project in collaboration with UMCES. UMCES and US Wind would conduct pot surveys and recreational fishing surveys focusing on evaluating the extent that commercial and recreational fisheries would be impacted due to changes in black sea bass aggregation behaviors during and after Project construction activities. The program includes a trial baseline year to test deployments and collect baseline data in the Project Area as well as a data synthesis year before construction activities would begin. UMCES and US Wind would conduct additional passive acoustic monitoring research for marine mammals.
Pot surveys offshore Ocean City would be conducted monthly from March through November using ropeless fishing gear to collect data on black sea bass relative abundance in the vicinity of the proposed turbine areas. Catches and sizes of other fauna would be assessed as well. US Wind would set strings of 15 pots (six strings, up to 90 pots total) from a commercial fishing vessel, each string with a 1-day duration set period. EdgeTech ropeless gear (EdgeTech, 2023) would allow sets (trawls) of 15 pots without any rope in the water column. Approximately 300-355 m (984-1,165 ft) of
7/16
inch (in) main-line rope would lie on the bottom during the survey. There would also be approximately 1.5 m of
7/16
in line that would form the bridle connecting each pot to the main line. Each string of pots would consist of 15 black sea bass pots, an EdgeTech pot, and an anchor. The EdgeTech pot would be the release pot attached at the end of each trawl. Each survey would consist of six strings deployed for a 1-day soak time (see diagram in Proposed Rule Comment Responses Memo, October 12, 2023). After the 1-day set period, UMCES and US Wind would retrieve the pot trawls by sending a release command from the on-site research vessel to activate an acoustic release on the release pot. Upon activation, the flotation with the attached rope would ascend to the water surface. UMCES and US Wind would recover the floatation connected to the release pot as well as the rest of the pots for that trawl. The pot survey would be conducted under a NMFS Scientific LOA for black sea bass collection research, of which a similar letter was received by UMCES from NMFS Greater Atlantic Regional Fisheries Office (GARFO) for the initial trial baseline year.
UMCES and US Wind would operate the recreational fishing survey off a recreational charter vessel based in Ocean City to compare data on black sea bass and other fauna between two artificial reef/wreck sites and two turbine sites using a Before-After-Control-Impact (BACI) study design. Angling techniques, such as drop bottom fishing and jigging, would be used to collect catch data on black sea bass and other fauna. Six monthly recreational surveys spanning a 2-day window each, would be conducted annually from May through October.
Passive acoustic monitoring research would focus on using rockhopper recorders to determine occurrence and position of large whales and dolphins as well as F-POD (full waveform capture Pod) devices to detect tonal echolocation clicks of small cetaceans in the Lease Area. The goal of the research would be to distinguish changes in marine mammal behavior due to natural inter-annual variation versus behaviors influenced by wind facility operations. US Wind and UMCES would use a before-during-after gradient design involving 2 years of monitoring in each period before, during, and after Project construction, from 2023 to 2029. The Rockhopper recorder would sample at 200 kHz for baleen whales and dolphins while the F-POD would detect echolocation clicks of small cetaceans. Rockhopper recorders would include a localization array with the Lease Area to allow the positions of calling North Atlantic right whales, humpback whales, and dolphins to be detected. Innovasea receivers would also be attached at up to four mooring sites within the Lease Area to examine spatiotemporal patterns of previously tagged fish, such as Atlantic sturgeon, white sharks, and sand tiger sharks.
Given the gear used (ropeless pot and hook and line), the fishery surveys present little risk to marine mammals (although some hook and line entanglement has been documented in marine mammals). To further minimize this already low risk of interaction, US Wind has proposed, and NMFS has included in the proposed rule, mitigation and monitoring measures to avoid taking marine mammals, including, but not limited to, monitoring for marine mammals before and during fishing/survey activities, not deploying, pulling gear, or fishing in certain circumstances, limiting tow times, and fully repairing nets and lines. All vessel captains and crew would also abide by the vessel strike avoidance measures outlined in § 217.344(b) of this rule. A full description of mitigation measures can be found in the Proposed Mitigation section.
With the implementation of these measures, US Wind does not anticipate, and NMFS is not proposing to authorize, take of marine mammals incidental to research pot and recreational surveys. Given no take is anticipated from these surveys, impacts from fishery surveys will not be discussed further in this document (with the exception of the description of measures in the Proposed Mitigation section).
Description of Marine Mammals in the Geographic Area
Thirty-eight marine mammal species under NMFS' jurisdiction have geographic ranges within the western North Atlantic OCS (Hayes
et al.,
2023). However, for reasons described below, US Wind has requested, and NMFS proposes to authorize, take of only 19 species (comprising 20 stocks) of marine mammals. Sections 3 and 4 of US Wind's ITA application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. NMFS fully considered all of this information, and we refer the reader to these descriptions in the application instead of reprinting the information.
Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs;
https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports
) and more general information about these species (
e.g.,
physical and behavioral descriptions) may be found on NMFS' website (
https://www.fisheries.noaa.gov/find-species
).
Of the 38 marine mammal species and/or stocks with geographic ranges that include the Project Area (
i.e.,
found in the coastal and offshore waters of Maryland), 19 species are not expected to be present or are considered rare or unexpected in the Project Area based on sighting and distribution data (see table 3-1 in US Wind's ITA application). Specifically, the following cetacean species are known to occur off of Maryland but are not expected to occur in the Project Area due to the location of preferred habitat outside the Lease Area and ECCs, based on the best available information, and therefore US Wind did not request, and NMFS is not proposing to authorize take, of these species: Blue whale (
Balaenoptera musculus
), Cuvier's beaked whale (
Ziphius cavirostris
), four species of Mesoplodont beaked whales (
Mesoplodon densitostris, M. europaeus, M. mirus,
and
M. bidens
), Atlantic white-sided dolphin (
Lagenorhynchus acutus
), Clymene dolphin (
Stenella clymene
), dwarf sperm whale (
Kogia sima
), false killer whale (
Pseudorca crassidens
), Fraser's dolphin (
Lagenodelphis hosei
), melon-headed whale (
Peponocephala electra
), northern bottlenose whale (
Hyperoodon ampullatus
), pygmy killer whale (
Feresa attenuata
), pygmy sperm whale (
Kogia breviceps
), sperm whale (
Physeter macrocephalus
), spinner dolphin (
Stenella longirostris
), and white-beaked dolphin (
Lagenorhynchus albirostris
). Two species of phocid pinnipeds are also uncommon in the Project Area, including: harp seals (
Pagophilus groenlandica
) and hooded seals (
Cystophora cristata
). However, harp seals are known to strand in coastal Maryland. Therefore, NMFS is
proposing to authorize take of harp seals.
In addition, the Florida manatee (
Trichechus manatus,
a sub-species of the West Indian manatee) has been previously documented as an occasional visitor to the Mid-Atlantic region during summer months (Morgan
et al.,
2002; Cummings
et al.,
2014). However, manatees are managed by the U.S. Fish and Wildlife Service (USFWS) and are not considered further in this document.
Table 6 lists all species or stocks for which take is expected and proposed to be authorized for this action and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined as “the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population” (16 U.S.C. 1362(20)). While no mortality is anticipated or proposed to be authorized, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species or stocks and other threats. Take for 19 species (20 stocks) in table 6 is expected and proposed to be authorized for this activity.
Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock, or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates for most species represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS' U.S. Atlantic and Gulf of Mexico SARs. All values presented in table 6 are the most recent available at the time of publication and, unless noted otherwise, use NMFS' final 2022 SARs (Hayes
et al.,
2023) available online at
https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports
.
Table 6—Marine Mammal Species That May Occur in the Project Area and Be Taken, by Harassment
Common name
1
Scientific name
Stock
ESA/
MMPA
status;
strategic
(Y/N)
2
Stock abundance
(
CV,
Nmin, most recent abundance survey)
3
PBR
Annual
M/SI
4
Order Artiodactyla—Cetacea—Mysticeti (baleen whales)
Family Balaenidae:
North Atlantic right whale
Eubalaena glacialis
Western Atlantic
E, D, Y
338 (0; 332; 2020); 356 (346-363, 2022)
5
0.7
6
31.2
Family Balaenopteridae (rorquals):
Fin whale
Balaenoptera physalus
Western North Atlantic
E, D, Y
6,802 (0.24, 5573, 2016)
11
1.8
Sei whale
Balaenoptera borealis
Nova Scotia
E, D, Y
6,292 (1.02, 3098, 2016)
6.2
0.8
Minke whale
Balaenoptera acutorostrata
Canadian Eastern Coastal
-, -, N
21,968 (0.31, 17,002, 2016)
170
10.6
Humpback whale
Megaptera novaeangliae
Gulf of Maine
-, -, Y
1,396 (0, 1,380, 2016)
22
12.15
Superfamily Odontoceti (toothed whales, dolphins, and porpoises)
Family Delphinidae:
Killer whale
7
Orcinus orca
Western North Atlantic
-, -, N
UNK (UNK, UNK, 2016)
UNK
0
Long-finned pilot whale
Globicephala melas
Western North Atlantic
-, -, N
39,215 (0.3, 30,627, 2016)
306
29
Short-finned pilot whale
Globicephala macrorhynchus
Western North Atlantic
-, -, Y
28,924 (0.24, 23,637, 2016)
236
136
Bottlenose dolphin
Tursiops truncatus
Western North Atlantic Offshore
-, -, N
62,851 (0.23, 51,914, 2016)
519
28
Bottlenose dolphin
Tursiops truncatus
Northern Migratory Coastal
-, -, Y
6,639 (0.41, 4,759, 2016)
48
12.2-21.5
Common dolphin
Delphinus delphis
Western North Atlantic
-, -, N
172,897 (0.21, 145,216, 2016)
1,452
390
Atlantic spotted dolphin
Stenella frontalis
Western North Atlantic
-, -, N
39,921 (0.27, 32,032, 2016)
320
0
Pantropical spotted dolphin
Stenella attenuata
Western North Atlantic
-, D, N
6,593 (0.52, 4,367, 2016)
44
0
Risso's dolphin
Grampus griseus
Western North Atlantic
-, -, N
35,215 (0.19, 30,051, 2016)
301
34
Rough-toothed dolphin
7
Steno bredanensis
Western North Atlantic
-, -, N
136 (1, 67, 2016)
0.7
0
Striped dolphin
7
Stenella coeruleoalba
Western North Atlantic
-, -, N
67,036 (0.29, 52,939, 2016)
529
0
Family Phocoenidae (porpoises):
Harbor porpoise
Phocoena phocoena
Gulf of Maine/Bay of Fundy
-, -, N
95,543 (0.31, 74,034, 2016)
851
164
Order Carnivora—Pinnipedia
Family Phocidae (earless seals):
Harbor seal
Phoca vitulina
Western North Atlantic
-, -, N
61,336 (0.08, 57,637, 2018)
1,729
339
Gray seal
8
Halichoerus grypus
Western North Atlantic
-, -, N
27,300 (0.22, 22,785, 2016)
1,389
4453
Harp seal
Pagophilus groenlandicus
Western North Atlantic
-, -, N
7.6M (UNK, 7.1M, 2019)
426,000
178,573
1
Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy (
https://www.marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/;
Committee on Taxonomy (2022)).
2
ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR, or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.
3
NMFS 2022 marine mammal stock assessment reports online at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments.
CV is the coefficient of variation; Nmin is the minimum estimate of stock abundance.
4
These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (
e.g.,
commercial fisheries, ship strike).
5
The current SAR includes an estimated population (N
best
338) based on sighting history through November 2020 (Hayes
et al.,
2023). In October 2023, NMFS released a technical report identifying that the North Atlantic right whale population size based on sighting history through 2022 was 356 whales, with a 95 percent credible interval ranging from 346 to 363 (Linden, 2023).
6
Total annual average observed North Atlantic right whale mortality during the period 2016-2020 was 8.1 animals and annual average observed fishery mortality was 5.7 animals. Numbers presented in this table (31.2 total mortality and 22 fishery mortality) are 2015-2019 estimated annual means, accounting for undetected mortality and serious injury.
7
US Wind did not request take of these species; however, their exposure analysis demonstrates there is a low risk of harassment. Although these species are rare in the project area, NMFS is proposing to authorize a small amount of Level B harassment in the case of potential presence during pile driving.
8
NMFS' stock abundance estimate (and associated PBR value) applies to the U.S. population only. Total stock abundance (including animals in Canada) is approximately 451,431. The annual M/SI value given is for the total stock.
As indicated above, all 19 species and 20 stocks in table 6 temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur. Three of the marine mammal species for which take is requested are listed as endangered under the ESA, including North Atlantic right, fin, and sei whales. In addition to what is included in sections 3 and 4 of US Wind's ITA application (
https://www.fisheries.noaa.gov/action/incidental-take-authorization-us-wind-inc-construction-and-operation-maryland-offshore-wind
), the SARs (
https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments
), and NMFS' website (
https://www.fisheries.noaa.gov/species-directory/marine-mammals
), we provide further detail below informing the baseline for select species (
e.g.,
information regarding current UME and known important habitat areas, such as Biologically Important Areas (BIAs;
https://oceannoise.noaa.gov/biologically-important-areas
) (Van Parijs, 2015)). There are no ESA-designated critical habitats for any species within the project area (
https://www.fisheries.noaa.gov/resource/map/national-esa-critical-habitat-mapper
).
Under the MMPA, a UME is defined as “a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response” (16 U.S.C. 1421h(6)). As of July 2023, five UMEs are active. Four of these UMEs are occurring along the U.S. Atlantic coast for various marine mammal species. Of these, the most relevant to the project area are the North Atlantic right whale, humpback whale, and harbor and gray seal UMEs given the prevalence of these species in the project area. More information on UMEs, including all active, closed, or pending, can be found on NMFS' website at
https://www.fisheries.noaa.gov/national/marine-life-distress/active-and-closed-unusual-mortality-events.
Below, we include information for a subset of the species that presently have an active or recently closed UME occurring along the Atlantic coast or for which there is information available related to areas of biological significance. For the majority of species potentially present in the specific geographic region, NMFS has designated only a single generic stock (
e.g.,
“western North Atlantic”) for management purposes. This includes the “Canadian east coast” stock of minke whales, which includes all minke whales found in U.S. waters and is also a generic stock for management purposes. For humpback and sei whales, NMFS defines stocks on the basis of feeding locations (
i.e.,
Gulf of Maine and Nova Scotia, respectively). However, references to humpback whales and sei whales in this document refer to any individuals of the species that are found in the project area. Any areas of known biological importance (including the BIAs identified in LaBrecque
et al.,
2015) that overlap spatially (or are adjacent) with the project area are addressed in the species sections below.
North Atlantic Right Whale
The North Atlantic right whale has been listed as Endangered since the ESA's enactment in 1973. The species was recently uplisted from Endangered to Critically Endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (Cooke, 2020). The uplisting was due to a decrease in population size (Pace
et al.,
2017), an increase in vessel strikes and entanglements in fixed fishing gear (Daoust
et al.,
2017; Davis & Brillant, 2019; Knowlton
et al.,
2012; Knowlton
et al.,
2022; Moore
et al.,
2021; Sharp
et al.,
2019), and a decrease in birth rate (Pettis
et al.,
2022; Reed
et al.,
2022). The western Atlantic stock is considered depleted under the MMPA (Hayes
et al.,
2023). There is a recovery plan (NMFS, 2005) for the North Atlantic right whale, and NMFS completed 5-year reviews of the species in 2012, 2017, and 2022 which concluded no change to the listing status is warranted.
Designated by NMFS as a Species in the Spotlight, the North Atlantic right whale is considered among the species with the greatest risk of extinction in the near future (
https://www.fisheries.noaa.gov/topic/endangered-species-conservation/species-in-the-spotlight
).
The North Atlantic right whale population had only a 2.8-percent recovery rate between 1990 and 2011 and an overall abundance decline of 23.5 percent from 2011 to 2019 (Hayes
et al.,
2023). Since 2011, the North Atlantic right whale population has been in decline; however, the sharp decrease observed from 2015 to 2020 appears to have slowed, though the right whale population continues to experience annual mortalities above recovery thresholds (Pace
et al.,
2017; Pace
et al.,
2021; Linden, 2023). North Atlantic right whale calving rates dropped from 2017 to 2020 with zero births recorded during the 2017-2018 season. The 2020-2021 calving season had the first substantial calving increase in 5 years with 20 calves born (including 2 mortalities) followed by 15 calves during the 2021-2022 calving season and 12 births (including 1 mortality) in 2022-2023 calving season. These data demonstrate that birth rates are increasing. However, mortalities continue to outpace births. Best estimates indicate fewer than 70 reproductively active females remain in the population and adult females experience a lower average survival rate than males (Linden, 2023). In 2023, the total annual average observed North Atlantic right whale mortality increased from 8.1 (which represents 2016-2020) to 31.2 (which represents 2015-2019), however, this updated estimate also accounts for undetected mortality and serious injury (Hayes
et al.,
2023). Although the predicted number of deaths from the population are lower in recent years (2021-2022) when compared to the high number of deaths
from 2014 to 2020 suggesting a short-term increase in survival, annual mortality rates still exceed PBR (Linden, 2023).
Critical habitat for North Atlantic right whales is not present in the Project Area. However, the Project Area both spatially and temporally overlaps a portion of the migratory corridor BIA within which North Atlantic right whales migrate south to calving grounds generally in November and December, followed by a northward migration (primarily moms with young calves) into feeding areas far north of the Project Area in March and April (LaBrecque
et al.,
2015; Van Parijs, 2015). North Atlantic right whale foraging may rarely opportunistically occur around the Project Area, yet the region is not considered primary foraging habitat. Engelhaupt
et al.
(2023) documented feeding and socializing behavior off Virginia and North Carolina, just south of the Project Area, suggesting that North Atlantic right whales may use the mid-Atlantic migratory corridor for more than just migration.
NMFS' regulations at 50 CFR 224.105 designated Seasonal Management Areas (SMAs) for North Atlantic right whales in 2008 (73 FR 60173, October 10, 2008). SMAs were developed to reduce the threat of collisions between ships and North Atlantic right whales around their migratory route and calving grounds. The Delaware Bay SMA overlaps with the export cable corridor of the proposed project. This SMA is currently active from November 1 through April 30 of each year and may be used by North Atlantic right whales for migrating and/or feeding. As noted above, NMFS is proposing changes to the North Atlantic right whale speed rule (87 FR 46921, August 1, 2022). Due to the current status of North Atlantic right whales and the spatial proximity overlap of the proposed project with areas of biological significance, (
i.e.,
a migratory corridor, SMA), the potential impacts of the proposed project on North Atlantic right whales warrant particular attention.
During the spring, North Atlantic right whales use the migratory corridor BIA to move north from calving grounds off Georgia and Florida to feeding grounds in New England and Canadian waters (Hayes
et al.,
2023). Right whales feed primarily on the copepod,
Calanus finmarchicus,
a species whose availability and distribution has changed both spatially and temporally over the last decade due to an oceanographic regime shift that has been ultimately linked to climate change (Meyer-Gutbrod
et al.,
2021; Record
et al.,
2019; Sorochan
et al.,
2019). This distribution change in prey availability has led to shifts in right whale habitat-use patterns over the same time period (Davis
et al.,
2020; Meyer-Gutbrod
et al.,
2022; Quintano-Rizzo
et al.,
2021; O'Brien
et al.,
2022; Van Parijs
et al.,
2023) with reduced use of foraging habitats in the Great South Channel and Bay of Fundy and increased use of habitats within Cape Cod Bay and a region south of Martha's Vineyard and Nantucket Islands (Stone
et al.,
2017; Mayo
et al.,
2018; Ganley
et al.,
2019; Record
et al.,
2019; Meyer-Gutbrod
et al.,
2021; Van Parijs
et al.,
2023); these foraging habitats are all located several hundred kilometers north of the project area. In late fall (
i.e.,
November), a portion of the right whale population (including pregnant females) typically departs the feeding grounds in the North Atlantic, moves south along the migratory corridor BIA, including through the Project Area, to right whale calving grounds off Georgia and Florida. Observations of these transitions in right whale habitat use, variability in seasonal presence in identified core habitats, and utilization of habitat outside of previously focused survey effort prompted the formation of a NMFS' Expert Working Group, which identified current data collection efforts, data gaps, and provided recommendations for future survey and research efforts (Oleson
et al.,
2020). Recent research indicates understanding of their movement patterns remains incomplete and not all of the population undergoes a consistent annual migration (Davis
et al.,
2017; Gowan
et al.,
2019; Krzystan
et al.,
2018). Non-calving females may remain in the feeding grounds, during the winter in the years preceding and following the birth of a calf to increase their energy stores (Gowen
et al.,
2019).
Although North Atlantic right whales move seasonally between foraging and calving grounds, Davis
et al.
(2017) acoustically detected right whales along the coast from Cape Hatteras, NC, United States to Nova Scotia, Canada year-round, suggesting that North Atlantic right whale use of the mid-Atlantic and southeast has increased since 2010 (Davis
et al.,
2017). North Atlantic right whale presence in the Project Area is predominately seasonal with individuals likely to be transient and migrating through the area. Bailey
et al.
(2018) acoustically detected the year-round presence of North Atlantic right whales in the vicinity of the Project Area, with a maximum abundance during the late winter and early spring. In addition, a monitoring buoy, deployed by UMCES offshore of Ocean City Maryland in 2022, acoustically detected the presence of North Atlantic right whales in the lease area from November through January, with the highest frequency of confirmed detections occurring during the months of December and January (Woods Hole Oceanographic Institute, 2022). Visual surveys also confirm a maximum abundance of North Atlantic right whales in the vicinity of the Lease Area during the winter (Barco
et al.,
2015; Williams
et al.,
2015). As part of the Mid-Atlantic Baseline Studies Project and Maryland Project, Williams
et al.
(2015) conducted standardized aerial and boat-based surveys of the Delaware, Maryland, Virginia Wind Energy Areas (WEAs), and visually observed North Atlantic right whales in the lease area during the months of February and March. Based upon year-round aerial surveys conducted from 2013 to 2015, Barco
et al.
(2015) observed the largest numbers of North Atlantic right whales in the Maryland WEA during the month of January, suggesting that the area may be a destination for non-breeding individuals and pulses of North Atlantic right whales may travel through the region. Barco
et al.
(2015) also documented North Atlantic right whale open mouth behavior, which is consistent with, though not necessarily indicative of, feeding. As part of the U.S. Navy's Marine Species Monitoring Program, HDR has conducted aerial and vessel-based surveys for large whales off Virginia and North Carolina since 2015. The majority of North Atlantic right whale sightings have occurred in these areas, just south of the Project Area, during the months of January-March (Aschettino
et al.,
2023). The highest density month for North Atlantic right whales in the vicinity of the lease area is February (0.00076 individuals/km (0.54 nmi grid square)) (Roberts
et al.,
2023).
Since 2017, 98 dead, seriously injured, or sublethally injured or ill North Atlantic right whales along the United States and Canadian coasts have been documented, necessitating a UME declaration and investigation. The leading category for the cause of death for this ongoing UME is “human interaction,” specifically from entanglements or vessel strikes. As of October 30, 2023, there have been 36 confirmed mortalities (dead, stranded, or floaters) and 34 seriously injured free-swimming whales for a total of 70 whales. Beginning on October 14, 2022, the UME also considers animals with sublethal injury or illness bringing the total number of whales in the UME to
115. Approximately 42 percent of the population is known to be in reduced health (Hamilton
et al.,
2021) likely contributing to smaller body sizes at maturation, making them more susceptible to threats and reducing fecundity (Moore
et al.,
2021; Reed
et al.,
2022; Stewart
et al.,
2022). More information about the North Atlantic right whale UME is available online at
https://www.fisheries.noaa.gov/national/marine-life-distress/2017-2023-north-atlantic-right-whale-unusual-mortality-event.
Humpback Whale
Humpback whales were listed as endangered under the Endangered Species Conservation Act (ESCA) in June 1970. In 1973, the ESA replaced the ESCA, and humpbacks continued to be listed as endangered. On September 8, 2016, NMFS divided the once single species into 14 distinct population segments (DPS), removed the species-level listing, and, in its place, listed four DPSs as endangered and one DPS as threatened (81 FR 62259, September 8, 2016). The remaining nine DPSs were not listed. The West Indies DPS, which is not listed under the ESA, is the only DPS of humpback whales that is expected to occur in the Project Area. Bettridge
et al.
(2015) estimated the size of the West Indies DPS population at 12,312 (95 percent confidence interval (CI) 8,688-15,954) whales in 2004-2005, which is consistent with previous population estimates of approximately 10,000-11,000 whales (Stevick
et al.,
2003; Smith
et al.,
1999) and the increasing trend for the West Indies DPS (Bettridge
et al.,
2015).
The Project Area does not overlap with any BIAs or other important areas for the humpback whales. A humpback whale feeding BIA extends throughout the Gulf of Maine, Stellwagen Bank, and Great South Channel from May through December, annually (LaBrecque
et al.,
2015). However, this BIA is located approximately 556.2 km (345.6 mi) north of the Project Area, and thus, would not be impacted by project activities.
Humpback whale presence in the mid-Atlantic varies seasonally. Humpback whales are most typically observed in this region during the winter months (Williams
et al.,
2015d; Barco
et al.,
2015) and are known to be migratory off coastal Maryland, moving seasonally between northern feeding grounds in New England and southern calving grounds in the West Indies (Hayes
et al.,
2023). However, not all humpback whales migrate to the Caribbean during the winter as individuals are sighted in mid- to high-latitude areas during this season (Swingle
et al.,
1993; Davis
et al.,
2020). In addition to a migratory pathway, the mid-Atlantic region also represents a supplemental winter feeding ground for juveniles and mature whales (Barco
et al.,
2002). Records of humpback whales off the U.S. mid-Atlantic coast (New Jersey south to North Carolina) suggest that these waters are used as a winter feeding ground from December through March (Mallette
et al.,
2017; Barco
et al.,
2002; LaBrecque
et al.,
2015) and represent important habitat for juveniles, in particular (Swingle
et al.,
1993; Wiley
et al.,
1995).
Acoustic monitoring in the vicinity of the lease area has detected the presence of humpback whales year-round, although detections exhibit similar seasonal trends as visual sightings. Humpback whale detections were lowest during the summer months (June through September), increased through the winter (January through March) and peaked in April (Bailey
et al.,
2018). Davis
et al.
(2020) also found detections of humpback whales off the mid-Atlantic (Virginia) to peak from January through May. Density modeling (Roberts
et al.,
2023) confirms April (0.00187 individuals per 1 km (0.54 nmi) grid cell) as the month of the highest average density of humpback whales in the vicinity of the Project Area.
Since January 2016, elevated humpback whale mortalities along the Atlantic coast from Maine to Florida led to the declaration of a UME. As of October 2, 2023, 209 humpback whales have stranded as part of this UME. Partial or full necropsy examinations have been conducted on approximately 90 of the known cases. Of the whales examined, about 40 percent had evidence of human interaction, either ship strike or entanglement. While a portion of the whales have shown evidence of pre-mortem vessel strike, this finding is not consistent across all whales examined and more research is needed. As the humpback whale population has grown, they are seen more often in the mid-Atlantic. Since January 2023, 34 humpbacks have stranded along the east coast of the United States (1 of these stranded in Maryland). These whales may have been following their prey (small fish) which were reportedly close to shore this past winter. These prey also attract fish that are targeted by recreational and commercial fishermen, which increases the number of boats in these areas. More information is available at
https://www.fisheries.noaa.gov/national/marine-life-distress/active-and-closed-unusual-mortality-events.
Fin Whale
Fin whales frequently occur in the waters of the U.S. Atlantic Exclusive Economic Zone (EEZ), principally from Cape Hatteras, North Carolina northward and are distributed in both continental shelf and deep-water habitats (Hayes
et al.,
2023). Although fin whales are present north of the 35-degree latitude region in every season and are broadly distributed throughout the western North Atlantic for most of the year, densities vary seasonally (Edwards
et al.,
2015; Hayes
et al.,
2023). Fin whales typically feed in the Gulf of Maine and the waters surrounding New England, but their mating and calving (and general wintering) areas are largely unknown (Hain
et al.,
1992; Hayes
et al.,
2023). Acoustic detections of fin whale singers augment and confirm these visual sighting conclusions for males. Recordings from Massachusetts Bay, New York Bight, and deep-ocean areas have detected some level of fin whale singing from September through June (Watkins
et al.,
1987; Clark and Gagnon, 2002; Morano
et al.,
2012). These acoustic observations from both coastal and deep-ocean regions support the conclusion that male fin whales are broadly distributed throughout the western North Atlantic for most of the year (Hayes
et al.,
2022).
Fin whale feeding BIAs occur offshore of Montauk Point, New York from March to October (2,933 km
2
) (Hain
et al.,
1992; LaBrecque
et al.,
2015) and year-round in the southern Gulf of Maine (18,015 km
2
). However, given the more southerly location of the Project Area (located approximately 364.8 km (226.7 mi) and 546.2 km (339.4 mi) away from these BIAs, respectively), there is no spatial overlap from with these BIAs.
Fin whales were among the most frequently observed baleen whale species during the Maryland Wind Energy Area aerial surveys conducted for the Maryland Department of Natural Resources (MD DNR) by the Virginia Aquarium and Marine Science Center Foundation (Barco
et al.,
2015), and the most commonly detected baleen whale species during acoustic monitoring surveys from 2014 to 2017 in the Maryland WEA, although the majority of detections were offshore of the WEA (Bailey
et al.,
2018a). Fin whale abundance in the vicinity of the Project Area peaked during the winter and early spring (Williams
et al.,
2015d; Barco
et al.,
2015), with the lowest occurrence documented during summer and early fall (Bailey
et al.,
2018). Consistent with visual sightings and acoustic detections,
the highest average density of fin whales in the vicinity of the proposed Project Area occurs in January (0.00214 individuals per 1 km (0.54 nmi) grid cell) (Roberts
et al.,
2023). There is no active fin whale UME.
Minke Whale
Minke whales are common and widely distributed throughout the U.S. Atlantic EEZ (Cetacean and Turtle Assessment Program (CETAP), 1982; Hayes
et al.,
2022), although their distribution has a strong seasonal component. Individuals have often been detected acoustically in shelf waters from spring to fall and more often detected in deeper offshore waters from winter to spring (Risch
et al.,
2013). Minke whales are abundant in New England waters from May through September (Pittman
et al.,
2006; Waring
et al.,
2014), yet largely absent from these areas during the winter, suggesting the possible existence of a migratory corridor (LaBrecque
et al.,
2015). A migratory route for minke whales transiting between northern feeding grounds and southern breeding areas may exist to the east of the Project Area, as minke whales may track warmer waters along the continental shelf while migrating (Risch
et al.,
2014). Risch
et al.
(2014) suggests the presence of a minke whale breeding ground offshore of the southeastern US during the winter.
There are two minke whale feeding BIAs identified in the southern and southwestern section of the Gulf of Maine, including Georges Bank, the Great South Channel, Cape Cod Bay and Massachusetts Bay, Stellwagen Bank, Cape Anne, and Jeffreys Ledge from March through November, annually (LaBrecque
et al.,
2015). However, these BIAs are approximately 512.1 km (318.2 mi) and 668.8 km (415.6 mi) northwest of the Project Area, respectively, and would not be impacted by the proposed project activities.
Overall, minke whale use of the Project Area is likely highest during fall, winter, and spring months based upon visual sightings and acoustic detections in the vicinity of the lease area during the months of November, January, February, and April (Bailey
et al.,
2018a; Barco
et al.,
2015; Williams
et al.,
2015b). The highest average density of minke whales in the vicinity of the lease area is expected to occur in May (0.00750 individuals per 1 km (0.54 nmi)).
From 2017 through 2022, elevated minke whale mortalities detected along the Atlantic coast from Maine through South Carolina resulted in the declaration of a UME. As of October 2, 2023, a total of 160 minke whale mortalities have occurred during this UME. Full or partial necropsy examinations were conducted on more than 60 percent of the whales. Preliminary findings in several of the whales have shown evidence of human interactions or infectious disease, but these findings are not consistent across all of the minke whales examined, so more research is needed. More information is available at
https://www.fisheries.noaa.gov/national/marine-life-distress/2017-2022-minke-whale-unusual-mortality-event-along-atlantic-coast.
Sei Whale
The Nova Scotia stock of sei whales can be found in deeper waters of the continental shelf edge of the eastern United States and northeastward to south of Newfoundland (Mitchell, 1975; Hain
et al.,
1985; Hayes
et al.,
2022). During spring and summer, the stock is mainly concentrated in northern feeding areas, including the Scotian Shelf (Mitchell and Chapman, 1977), the Gulf of Maine, Georges Bank, the Northeast Channel, and south of Nantucket (CETAP, 1982; Kraus
et al.,
2016; Roberts
et al.,
2016; Palka
et al.,
2017; Cholewiak
et al.,
2018; Hayes
et al.,
2022). Sei whales have been detected acoustically along the Atlantic Continental Shelf and Slope from south of Cape Hatteras, North Carolina to the Davis Strait, with acoustic occurrence increasing in the mid-Atlantic region since 2010 (Davis
et al.,
2020). Although their migratory movements are not well understood, sei whales are believed to migrate north in June and July to feeding areas and south in September and October to breeding areas (Mitchell, 1975; CETAP, 1982; Davis
et al.,
2020). Sei whales generally occur offshore; however, individuals may also move into shallower, more inshore waters (Payne
et al.,
1990; Halpin
et al.,
2009; Hayes
et al.,
2022).
A sei whale feeding BIA occurs in New England waters from May through November (LaBrecque
et al.,
2015). However, this BIA is located approximately 501.5 km (311.6 mi) north of the Project Area and not likely to be impacted by the Project activities.
Sei whales were sighted infrequently during visual surveys (Williams
et al.,
2015d) and acoustic monitoring (WHOI, 2022; WHOI, 2023) of the Maryland WEA. The highest average density of sei whales in the vicinity of the lease area is expected to occur during the month of April (0.00061 individuals per 1 km (0.54 nmi) (Roberts
et al.,
2023). There is no active sei whale UME.
Phocid Seals
Since June 2022, elevated numbers of harbor seal and gray seal mortalities have occurred across the southern and central coast of Maine. This event has been declared a UME. Preliminary testing of samples has found some harbor and gray seals positive for highly pathogenic avian influenza. While the UME is not occurring in the Project Area, the populations affected by the UME are the same as those potentially affected by the project. Information on this UME is available online at
https://www.fisheries.noaa.gov/2022-2023-pinniped-unusual-mortality-event-along-maine-coast.
The above event was preceded by a different UME, occurring from 2018 to 2020 (closure of the 2018-2020 UME is pending). Beginning in July 2018, elevated numbers of harbor seal and gray seal mortalities occurred across Maine, New Hampshire, and Massachusetts. Additionally, stranded seals have shown clinical signs as far south as Virginia, although not in elevated numbers, therefore the UME investigation encompassed all seal strandings from Maine to Virginia. A total of 3,152 reported strandings (of all species) occurred from July 1, 2018, through March 13, 2020. Full or partial necropsy examinations have been conducted on some of the seals and samples have been collected for testing. Based on tests conducted thus far, the main pathogen found in the seals is phocine distemper virus. NMFS is performing additional testing to identify any other factors that may be involved in this UME, which is pending closure. Information on this UME is available online at:
https://www.fisheries.noaa.gov/new-england-mid-atlantic/marine-life-distress/2018-2020-pinniped-unusual-mortality-event-along.
Marine Mammal Hearing
Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Not all marine mammal species have equal hearing capabilities (
e.g.,
Richardson
et al.,
1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall
et al.
(2007, 2019a) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges
(behavioral response data, anatomical modeling,
etc.
). Note that no direct measurements of hearing ability have been successfully completed for mysticetes (
i.e.,
low-frequency cetaceans). Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65-decibel (dB) threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall
et al.
(2007) retained. Marine mammal hearing groups and their associated hearing ranges are provided in table 7.
Table 7—Marine Mammal Hearing Groups
[NMFS, 2018]
Hearing group
Generalized hearing range *
Low-frequency (LF) cetaceans (baleen whales)
7 Hz to 35 kHz.
Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)
150 Hz to 160 kHz.
High-frequency (HF) cetaceans (true porpoises,
Kogia,
river dolphins, Cephalorhynchid,
Lagenorhynchus cruciger
&
L. australis
)
275 Hz to 160 kHz.
Phocid pinnipeds (PW) (underwater) (true seals)
50 Hz to 86 kHz.
Otariid pinnipeds (OW) (underwater) (sea lions and fur seals)
60 Hz to 39 kHz.
* Represents the generalized hearing range for the entire group as a composite (
i.e.,
all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on ~65-dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans (Southall
et al.,
2007) and PW pinniped (approximation).
The pinniped functional hearing group was modified from Southall
et al.
(2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (Hemilä
et al.,
2006; Kastelein
et al.,
2009; Reichmuth and Holt, 2013). For more detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information.
NMFS notes that in 2019a, Southall
et al.
recommended new names for hearing groups that are widely recognized. However, this new hearing group classification does not change the weighting functions or acoustic thresholds (
i.e.,
the weighting functions and thresholds in Southall
et al.
(2019a) are identical to NMFS 2018 Revised Technical Guidance). When NMFS updates our Technical Guidance, we will be adopting the updated Southall
et al.
(2019a) hearing group classification.
Potential Effects of Specified Activities on Marine Mammals and Their Habitat
This section includes a summary and discussion of the ways that components of the specified activity may impact marine mammals and their habitat. The Estimated Take of Marine Mammals section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Negligible Impact Analysis and Determination section considers the content of this section, the Estimated Take of Marine Mammals section, and the Proposed Mitigation section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and how those impacts on individuals are likely to impact marine mammal species or stocks. General background information on marine mammal hearing was provided previously (see the Description of Marine Mammals in the Geographic Area section). Here, the potential effects of sound on marine mammals are discussed.
US Wind has requested, and NMFS proposes to authorize, the take of marine mammals incidental to the construction activities associated with the project area. In their application, US Wind presented their analyses of potential impacts to marine mammals from the acoustic sources. NMFS both carefully reviewed the information provided by US Wind, as well as independently reviewed applicable scientific research and literature and other information to evaluate the potential effects of the Project's activities on marine mammals.
The proposed activities would result in the construction and placement of up to 119 permanent foundations to support WTGs, OSSs, a Met tower, and seafloor mapping using HRG surveys. There are a variety of types and degrees of effects to marine mammals, prey species, and habitat that could occur as a result of the Project. Below we provide a brief description of the types of sound sources that would be generated by the project, the general impacts from these types of activities, and an analysis of the anticipated impacts on marine mammals from the project, with consideration of the proposed mitigation measures.
Description of Sound Sources
This section contains a brief technical background on sound, on the characteristics of certain sound types, and on metrics used in this proposal inasmuch as the information is relevant to the specified activity and to a discussion of the potential effects of the specified activity on marine mammals found later in this document. For general information on sound and its interaction with the marine environment, please see: Au and Hastings, 2008; Richardson
et al.,
1995; Urick, 1983; as well as the Discovery of Sound in the Sea (DOSITS) website at
https://www.dosits.org.
Sound is a vibration that travels as an acoustic wave through a medium such as a gas, liquid, or solid. Sound waves alternately compress and decompress the medium as the wave travels. These compressions and decompressions are detected as changes in pressure by aquatic life and man-made sound receptors such as hydrophones (underwater microphones). In water, sound waves radiate in a manner similar to ripples on the surface of a pond and may be either directed in a beam (narrow beam or directional sources) or sound beams may radiate in all directions (omnidirectional sources).
Sound travels in water more efficiently than almost any other form of energy, making the use of acoustics ideal for the aquatic environment and its inhabitants. In seawater, sound travels at roughly 1,500 meters per second (m/s). In-air, sound waves travel much more slowly, at about 340 m/s. However, the speed of sound can vary by a small amount based on characteristics of the transmission
medium, such as water temperature and salinity. Sound travels in water more efficiently than almost any other form of energy, making the use of acoustics ideal for the aquatic environment and its inhabitants. In seawater, sound travels at roughly 1,500 m/s. In-air, sound waves travel much more slowly, at about 340 m/s. However, the speed of sound can vary by a small amount based on characteristics of the transmission medium, such as water temperature and salinity.
The basic components of a sound wave are frequency, wavelength, velocity, and amplitude. Frequency is the number of pressure waves that pass by a reference point per unit of time and is measured in hertz (Hz) or cycles per second. Wavelength is the distance between two peaks or corresponding points of a sound wave (length of one cycle). Higher frequency sounds have shorter wavelengths than lower frequency sounds, and typically attenuate (decrease) more rapidly, except in certain cases in shallower water.
The intensity (or amplitude) of sounds is measured in dB, which are a relative unit of measurement that is used to express the ratio of one value of a power or field to another. Decibels are measured on a logarithmic scale, so a small change in dB corresponds to large changes in sound pressure. For example, a 10-dB increase is a ten-fold increase in acoustic power. A 20-dB increase is then a hundred-fold increase in power and a 30-dB increase is a thousand-fold increase in power. However, a ten-fold increase in acoustic power does not mean that the sound is perceived as being 10 times louder. Decibels are a relative unit comparing two pressures; therefore, a reference pressure must always be indicated. For underwater sound, this is 1 microPascal (μPa). For in-air sound, the reference pressure is 20 microPascal (μPa). The amplitude of a sound can be presented in various ways; however, NMFS typically considers three metrics. In this proposed rule, all decibel levels are referenced to (re) 1μPa.
Sound exposure level (SEL) represents the total energy in a stated frequency band over a stated time interval or event and considers both amplitude and duration of exposure (represented as dB re 1 μPa
2
-s). SEL is a cumulative metric; it can be accumulated over a single pulse (for pile driving this is often referred to as single-strike SEL; SEL
ss
) or calculated over periods containing multiple pulses (SEL
cum
). Cumulative SEL represents the total energy accumulated by a receiver over a defined time window or during an event. The SEL metric is useful because it allows sound exposures of different durations to be related to one another in terms of total acoustic energy. The duration of a sound event and the number of pulses, however, should be specified as there is no accepted standard duration over which the summation of energy is measured.
Root mean square (rms) is the quadratic mean sound pressure over the duration of an impulse. Root mean square is calculated by squaring all of the sound amplitudes, averaging the squares, and then taking the square root of the average (Urick, 1983). Root mean square accounts for both positive and negative values; squaring the pressures makes all values positive so that they may be accounted for in the summation of pressure levels (Hastings and Popper, 2005). This measurement is often used in the context of discussing behavioral effects, in part because behavioral effects, which often result from auditory cues, may be better expressed through averaged units than by peak pressures.
Peak sound pressure (also referred to as zero-to-peak sound pressure or 0-pk) is the maximum instantaneous sound pressure measurable in the water at a specified distance from the source and is represented in the same units as the rms sound pressure. Along with SEL, this metric is used in evaluating the potential for PTS (permanent threshold shift) and TTS (temporary threshold shift).
Sounds can be either impulsive or non-impulsive. The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to hearing (
e.g.,
Ward, 1997 in Southall
et al.,
2007). Please see NMFS
et al.
(2018) and Southall
et al.
(2007, 2019a) for an in-depth discussion of these concepts. Impulsive sound sources (
e.g.,
airguns, explosions, gunshots, sonic booms, impact pile driving) produce signals that are brief (typically considered to be less than 1 second), broadband, atonal transients (American National Standards Institute (ANSI), 1986; ANSI, 2005; Harris, 1998; National Institute for Occupational Safety and Health (NIOSH), 1998; International Organization for Standardization (ISO), 2003) and occur either as isolated events or repeated in some succession. Impulsive sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a rapid decay period that may include a period of diminishing, oscillating maximal and minimal pressures, and generally have an increased capacity to induce physical injury as compared with sounds that lack these features. Impulsive sounds are typically intermittent in nature.
Non-impulsive sounds can be tonal, narrowband, or broadband, brief, or prolonged, and may be either continuous or intermittent (ANSI, 1995; NIOSH, 1998). Some of these non-impulsive sounds can be transient signals of short duration but without the essential properties of pulses (
e.g.,
rapid rise time). Examples of non-impulsive sounds include those produced by vessels, aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems. Sounds are also characterized by their temporal component. Continuous sounds are those whose sound pressure level remains above that of the ambient sound with negligibly small fluctuations in level (NIOSH, 1998; ANSI, 2005) while intermittent sounds are defined as sounds with interrupted levels of low or no sound (NIOSH, 1998). NMFS identifies Level B harassment thresholds based on if a sound is continuous or intermittent.
Even in the absence of sound from the specified activity, the underwater environment is typically loud due to ambient sound, which is defined as environmental background sound levels lacking a single source or point (Richardson
et al.,
1995). The sound level of a region is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical (
e.g.,
wind and waves, earthquakes, ice, atmospheric sound), biological (
e.g.,
sounds produced by marine mammals, fish, and invertebrates), and anthropogenic (
e.g.,
vessels, dredging, construction) sound. A number of sources contribute to ambient sound, including wind and waves, which are a main source of naturally occurring ambient sound for frequencies between 200 Hz and 50 kHz (International Council for the Exploration of the Sea (ICES), 1995). In general, ambient sound levels tend to increase with increasing wind speed and wave height. Precipitation can become an important component of total sound at frequencies above 500 Hz and possibly down to 100 Hz during quiet times. Marine mammals can contribute significantly to ambient sound levels as can some fish and snapping shrimp. The frequency band for biological contributions is from approximately 12 Hz to over 100 kHz. Sources of ambient sound related to human activity include transportation (surface vessels), dredging and construction, oil and gas drilling and production, geophysical surveys, sonar, and explosions. Vessel noise typically dominates the total ambient sound for
frequencies between 20 and 300 Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz, and if higher frequency sound levels are created, they attenuate rapidly.
The sum of the various natural and anthropogenic sound sources that comprise ambient sound at any given location and time depends not only on the source levels (as determined by current weather conditions and levels of biological and human activity) but also on the ability of sound to propagate through the environment. In turn, sound propagation is dependent on the spatially and temporally varying properties of the water column and sea floor and is frequency-dependent. As a result of the dependence on a large number of varying factors, ambient sound levels can be expected to vary widely over both coarse and fine spatial and temporal scales. Sound levels at a given frequency and location can vary by 10-20 dB from day to day (Richardson
et al.,
1995). The result is that, depending on the source type and its intensity, sound from the specified activity may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals. Human-generated sound is a significant contributor to the acoustic environment in the project location.
Potential Effects of Underwater Sound on Marine Mammals
Anthropogenic sounds cover a broad range of frequencies and sound levels and can have a range of highly variable impacts on marine life from none or minor to potentially severe responses depending on received levels, duration of exposure, behavioral context, and various other factors. Broadly, underwater sound from active acoustic sources, such as those in the Project, can potentially result in one or more of the following: temporary or permanent hearing impairment, non-auditory physical or physiological effects, behavioral disturbance, stress, and masking (Richardson
et al.,
1995; Gordon
et al.,
2003; Nowacek
et al.,
2007; Southall
et al.,
2007; Götz
et al.,
2009). Non-auditory physiological effects or injuries that theoretically might occur in marine mammals exposed to high level underwater sound or as a secondary effect of extreme behavioral reactions (
e.g.,
change in dive profile as a result of an avoidance reaction) caused by exposure to sound include neurological effects, bubble formation, resonance effects, and other types of organ or tissue damage (Cox
et al.,
2006; Southall
et al.,
2007; Zimmer and Tyack, 2007; Tal
et al.,
2015).
In general, the degree of effect of an acoustic exposure is intrinsically related to the signal characteristics, received level, distance from the source, and duration of the sound exposure, in addition to the contextual factors of the receiver (
e.g.,
behavioral state at time of exposure, age class,
etc.
). In general, sudden, high-level sounds can cause hearing loss as can longer exposures to lower-level sounds. Moreover, any temporary or permanent loss of hearing will occur almost exclusively for noise within an animal's hearing range. We describe below the specific manifestations of acoustic effects that may occur based on the activities proposed by US Wind. Richardson
et al.
(1995) described zones of increasing intensity of effect that might be expected to occur in relation to distance from a source and assuming that the signal is within an animal's hearing range. First (at the greatest distance) is the area within which the acoustic signal would be audible (potentially perceived) to the animal but not strong enough to elicit any overt behavioral or physiological response. The next zone (closer to the receiving animal) corresponds with the area where the signal is audible to the animal and of sufficient intensity to elicit behavioral or physiological responsiveness. The third is a zone within which, for signals of high intensity, the received level is sufficient to potentially cause discomfort or tissue damage to auditory or other systems. Overlaying these zones to a certain extent is the area within which masking (
i.e.,
when a sound interferes with or masks the ability of an animal to detect a signal of interest that is above the absolute hearing threshold) may occur; the masking zone may be highly variable in size.
Below, we provide additional detail regarding potential impacts on marine mammals and their habitat from noise in general, starting with hearing impairment, as well as from the specific activities US Wind plans to conduct, to the degree it is available (noting that there is limited information regarding the impacts of offshore wind construction on marine mammals).
Hearing Threshold Shift
Marine mammals exposed to high-intensity sound or to lower-intensity sound for prolonged periods can experience hearing threshold shift (TS), which NMFS defines as a change, usually an increase, in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level expressed in decibels (NMFS, 2018). Threshold shifts can be permanent, in which case there is an irreversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range or temporary, in which there is reversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range and the animal's hearing threshold would fully recover over time (Southall
et al.,
2019a). Repeated sound exposure that leads to TTS could cause PTS.
When PTS occurs, there can be physical damage to the sound receptors in the ear (
i.e.,
tissue damage) whereas TTS represents primarily tissue fatigue and is reversible (Henderson
et al.,
2008). In addition, other investigators have suggested that TTS is within the normal bounds of physiological variability and tolerance and does not represent physical injury (
e.g.,
Ward, 1997; Southall
et al.,
2019a). Therefore, NMFS does not consider TTS to constitute auditory injury. Relationships between TTS and PTS thresholds have not been studied in marine mammals, and there is no PTS data for cetaceans. However, such relationships are assumed to be similar to those in humans and other terrestrial mammals. Noise exposure can result in either a permanent shift in hearing thresholds from baseline (a 40-dB threshold shift approximates a PTS onset;
e.g.,
Kryter
et al.,
1966; Miller, 1974; Henderson
et al.,
2008) or a temporary, recoverable shift in hearing that returns to baseline (a 6-dB threshold shift approximates a TTS onset;
e.g.,
Southall
et al.,
2019a). Based on data from terrestrial mammals, a precautionary assumption is that the PTS thresholds, expressed in the unweighted peak sound pressure level metric (PK), for impulsive sounds (such as impact pile driving pulses) are at least 6 dB higher than the TTS thresholds and the weighted PTS cumulative sound exposure level thresholds are 15 (impulsive sound) to 20 (non-impulsive sounds) dB higher than TTS cumulative sound exposure level thresholds (Southall
et al.,
2019a). Given the higher level of sound or longer exposure duration necessary to cause PTS as compared with TTS, PTS is less likely to occur as a result of these activities; however, it is possible, and a small amount has been proposed for authorization for several species.
TTS is the mildest form of hearing impairment that can occur during exposure to sound, with a TTS of 6 dB considered the minimum threshold shift clearly larger than any day-to-day or session-to-session variation in a subject's normal hearing ability (Schlundt
et al.,
2000; Finneran
et al.,
2000; Finneran
et al.,
2002). While
experiencing TTS, the hearing threshold rises, and a sound must be at a higher level in order to be heard. In terrestrial and marine mammals, TTS can last from minutes or hours to days (in cases of strong TTS). In many cases, hearing sensitivity recovers rapidly after exposure to the sound ends. There is data on sound levels and durations necessary to elicit mild TTS for marine mammals, but recovery is complicated to predict and dependent on multiple factors.
Marine mammal hearing plays a critical role in communication with conspecifics, and interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration (
i.e.,
recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious depending on the degree of interference of marine mammals hearing. For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that occurs during a time where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical (
e.g.,
for successful mother/calf interactions, consistent detection of prey) could have more serious impacts.
Currently, TTS data only exist for four species of cetaceans (bottlenose dolphin, beluga whale (
Delphinapterus leucas
), harbor porpoise, and Yangtze finless porpoise (
Neophocaena asiaeorientalis
)) and six species of pinnipeds (northern elephant seal (
Mirounga angustirostris
), harbor seal, ring seal, spotted seal, bearded seal, and California sea lion (
Zalophus californianus
)) that were exposed to a limited number of sound sources (
i.e.,
mostly tones and octave-band noise with limited number of exposure to impulsive sources such as seismic airguns or impact pile driving) in laboratory settings (Southall
et al.,
2019a). There is currently no data available on noise-induced hearing loss for mysticetes. For summaries of data on TTS or PTS in marine mammals or for further discussion of TTS or PTS onset thresholds, please see Southall
et al.
(2019a) and NMFS (2018).
Recent studies with captive odontocete species (bottlenose dolphin, harbor porpoise, beluga, and false killer whale) have observed increases in hearing threshold levels when individuals received a warning sound prior to exposure to a relatively loud sound (Nachtigall and Supin, 2013; Nachtigall and Supin, 2015; Nachtigall
et al.,
2016a; Nachtigall
et al.,
2016b; Nachtigall
et al.,
2016c; Finneran, 2018; Nachtigall
et al.,
2018). These studies suggest that captive animals have a mechanism to reduce hearing sensitivity prior to impending loud sounds. Hearing change was observed to be frequency dependent and Finneran (2018) suggests hearing attenuation occurs within the cochlea or auditory nerve. Based on these observations on captive odontocetes, the authors suggest that wild animals may have a mechanism to self-mitigate the impacts of noise exposure by dampening their hearing during prolonged exposures of loud sound or if conditioned to anticipate intense sounds (Finneran, 2018; Nachtigall
et al.,
2018).
Behavioral Effects
Exposure of marine mammals to sound sources can result in, but is not limited to, no response or any of the following observable responses: increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; habitat abandonment (temporary or permanent); and in severe cases, panic, flight, stampede, or stranding, potentially resulting in death (Southall
et al.,
2007). A review of marine mammal responses to anthropogenic sound was first conducted by Richardson (1995). More recent reviews address studies conducted since 1995 and focused on observations where the received sound level of the exposed marine mammal(s) was known or could be estimated (Nowacek
et al.,
2007; DeRuiter
et al.,
2013; Ellison
et al.,
2012; Gomez
et al.,
2016). Gomez
et al.
(2016) conducted a review of the literature considering the contextual information of exposure in addition to received level and found that higher received levels were not always associated with more severe behavioral responses and vice versa. Southall
et al.
(2021) states that results demonstrate that some individuals of different species display clear yet varied responses, some of which have negative implications while others appear to tolerate high levels and that responses may not be fully predictable with simple acoustic exposure metrics (
e.g.,
received sound level). Rather, the authors state that differences among species and individuals along with contextual aspects of exposure (
e.g.,
behavioral state) appear to affect response probability.
Behavioral responses to sound are highly variable and context-specific. Many different variables can influence an animal's perception of and response to (nature and magnitude) an acoustic event. An animal's prior experience with a sound or sound source affects whether it is less likely (habituation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately predisposed to respond to certain sounds in certain ways) (Southall
et al.,
2019a). Related to the sound itself, the perceived nearness of the sound, bearing of the sound (approaching vs. retreating), the similarity of a sound to biologically relevant sounds in the animal's environment (
i.e.,
calls of predators, prey, or conspecifics), and familiarity of the sound may affect the way an animal responds to the sound (Southall
et al.,
2007; DeRuiter
et al.,
2013). Individuals (of different age, gender, reproductive status,
etc.
) among most populations will have variable hearing capabilities, and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Often, specific acoustic features of the sound and contextual variables (
i.e.,
proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors, such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone.
Overall, the variability of responses to acoustic stimuli depends on the species receiving the sound, the sound source, and the social, behavioral, or environmental contexts of exposure (
e.g.,
DeRuiter and Doukara, 2012). For example, Goldbogen
et al.
(2013a) demonstrated that individual behavioral state was critically important in determining response of blue whales to sonar, noting that some individuals engaged in deep (greater than 50 m) feeding behavior had greater dive responses than those in shallow feeding or non-feeding conditions. Some blue whales in the Goldbogen
et al.
(2013a) study that were engaged in shallow feeding behavior demonstrated no clear changes in diving or movement even when received levels were high (~160 dB re 1µPa (microPascal)) for exposures to 3-4 kHz sonar signals, while deep feeding and non-feeding whales showed a clear response at exposures at lower received levels of sonar and pseudorandom noise. Southall
et al.
(2011) found that blue whales had a different response to sonar exposure
depending on behavioral state, more pronounced when deep feeding/travel modes than when engaged in surface feeding.
With respect to distance influencing disturbance, DeRuiter
et al.
(2013) examined behavioral responses of Cuvier's beaked whales to mid-frequency sonar and found that whales responded strongly at low received levels (89-127 dB re 1µPa) by ceasing normal fluking and echolocation, swimming rapidly away, and extending both dive duration and subsequent non-foraging intervals when the sound source was 3.4-9.5 km away. Importantly, this study also showed that whales exposed to a similar range of received levels (78-106 dB re 1µPa) from distant sonar exercises (118 km away) did not elicit such responses, suggesting that context may moderate reactions. Thus, distance from the source is an important variable in influencing the type and degree of behavioral response and this variable is independent of the effect of received levels (
e.g.,
DeRuiter
et al.,
2013; Dunlop
et al.,
2017a; Dunlop
et al.,
2017b; Falcone
et al.,
2017; Dunlop
et al.,
2018; Southall
et al.,
2019a).
Ellison
et al.
(2012) outlined an approach to assessing the effects of sound on marine mammals that incorporates contextual-based factors. The authors recommend considering not just the received level of sound, but also the activity the animal is engaged in at the time the sound is received, the nature and novelty of the sound (
i.e.,
is this a new sound from the animal's perspective), and the distance between the sound source and the animal. They submit that this “exposure context,” as described, greatly influences the type of behavioral response exhibited by the animal. Forney
et al.
(2017) also point out that an apparent lack of response (
e.g.,
no displacement or avoidance of a sound source) may not necessarily mean there is no cost to the individual or population, as some resources or habitats may be of such high value that animals may choose to stay, even when experiencing stress or hearing loss. Forney
et al.
(2017) recommend considering both the costs of remaining in an area of noise exposure such as TTS, PTS, or masking, which could lead to an increased risk of predation or other threats or a decreased capability to forage, and the costs of displacement, including potential increased risk of vessel strike, increased risks of predation or competition for resources, or decreased habitat suitable for foraging, resting, or socializing. This sort of contextual information is challenging to predict with accuracy for ongoing activities that occur over large spatial and temporal expanses. However, distance is one contextual factor for which data exist to quantitatively inform a take estimate, and the method for predicting Level B harassment in this rule does consider distance to the source. Other factors are often considered qualitatively in the analysis of the likely consequences of sound exposure where supporting information is available.
Behavioral change, such as disturbance manifesting in lost foraging time, in response to anthropogenic activities is often assumed to indicate a biologically significant effect on a population of concern. However, individuals may be able to compensate for some types and degrees of shifts in behavior, preserving their health and thus their vital rates and population dynamics. For example, New
et al.
(2013) developed a model simulating the complex social, spatial, behavioral, and motivational interactions of coastal bottlenose dolphins in the Moray Firth, Scotland, to assess the biological significance of increased rate of behavioral disruptions caused by vessel traffic. Despite a modeled scenario in which vessel traffic increased from 70 to 470 vessels a year (a six-fold increase in vessel traffic) in response to the construction of a proposed offshore renewables' facility, the dolphins' behavioral time budget, spatial distribution, motivations, and social structure remained unchanged. Similarly, two bottlenose dolphin populations in Australia were also modeled over 5 years against a number of disturbances (Reed
et al.,
2020) and results indicate that habitat/noise disturbance had little overall impact on population abundances in either location, even in the most extreme impact scenarios modeled. Friedlaender
et al.
(2016) provided the first integration of direct measures of prey distribution and density variables incorporated into across-individual analyses of behavior responses of blue whales to sonar and demonstrated a fivefold increase in the ability to quantify variability in blue whale diving behavior. These results illustrate that responses evaluated without such measurements for foraging animals may be misleading, which again illustrates the context-dependent nature of the probability of response.
The following subsections provide examples of behavioral responses that give an idea of the variability in behavioral responses that would be expected given the differential sensitivities of marine mammal species to sound, contextual factors, and the wide range of potential acoustic sources to which a marine mammal may be exposed. Behavioral responses that could occur for a given sound exposure should be determined from the literature that is available for each species, or extrapolated from closely related species when no information exists, along with contextual factors.
Avoidance and Displacement
Avoidance is the displacement of an individual from an area or migration path as a result of the presence of a sound or other stressors and is one of the most obvious manifestations of disturbance in marine mammals (Richardson
et al.,
1995). For example, gray whales (
Eschrichtius robustus
) and humpback whales are known to change direction—deflecting from customary migratory paths—in order to avoid noise from airgun surveys (Malme
et al.,
1984; Dunlop
et al.,
2018). Avoidance is qualitatively different from the flight response but also differs in the magnitude of the response (
i.e.,
directed movement, rate of travel,
etc.
). Avoidance may be short-term with animals returning to the area once the noise has ceased (
e.g.,
Malme
et al.,
1984; Bowles
et al.,
1994; Goold, 1996; Stone
et al.,
2000; Morton and Symonds, 2002; Gailey
et al.,
2007; Dähne
et al.,
2013; Russel
et al.,
2016). Longer-term displacement is possible, however, which may lead to changes in abundance or distribution patterns of the affected species in the affected region if habituation to the presence of the sound does not occur (
e.g.,
Blackwell
et al.,
2004; Bejder
et al.,
2006; Teilmann
et al.,
2006; Forney
et al.,
2017). Avoidance of marine mammals during the construction of offshore wind facilities (specifically, impact pile driving) has been documented in the literature with some significant variation in the temporal and spatial degree of avoidance and with most studies focused on harbor porpoises as one of the most common marine mammals in European waters (
e.g.,
Tougaard
et al.,
2009; Dähne
et al.,
2013; Thompson
et al.,
2013; Russell
et al.,
2016; Brandt
et al.,
2018).
Available information on impacts to marine mammals from pile driving associated with offshore wind is limited to information on harbor porpoises and seals, as the vast majority of this research has occurred at European offshore wind projects where large whales and other odontocete species are uncommon. Harbor porpoises and harbor seals are considered to be behaviorally sensitive species (
e.g.,
Southall
et al.,
2007) and the effects of wind farm construction in Europe on
these species have been well documented. These species have received particular attention in European waters due to their abundance in the North Sea (Hammond
et al.,
2002; Nachtsheim
et al.,
2021). A summary of the literature on documented effects of wind farm construction on harbor porpoise and harbor seals is described below.
Brandt
et al.
(2016) summarized the effects of the construction of eight offshore wind projects within the German North Sea (
i.e.,
Alpha Ventus, BARD Offshore I, Borkum West II, DanTysk, Global Tech I, Meerwind Süd/Ost, Nordsee Ost, and Riffgat) between 2009 and 2013 on harbor porpoises, combining passive acoustic monitoring (PAM) data from 2010 to 2013 and aerial surveys from 2009 to 2013 with data on noise levels associated with pile driving. Results of the analysis revealed significant declines in porpoise detections during pile driving when compared to 25-48 hours before pile driving began, with the magnitude of decline during pile driving clearly decreasing with increasing distances to the construction site. During the majority of projects, significant declines in detections (by at least 20 percent) were found within at least 5-10 km of the pile driving site, with declines at up to 20-30 km of the pile driving site documented in some cases. Similar results demonstrating the long-distance displacement of harbor porpoises (18-25 km) and harbor seals (up to 40 km) during impact pile driving have also been observed during the construction at multiple other European wind farms (Tougaard
et al.,
2009; Bailey
et al.,
2010; Dähne
et al.,
2013; Lucke
et al.,
2012; Haelters
et al.,
2015).
While harbor porpoises and seals tend to move several kilometers away from wind farm construction activities, the duration of displacement has been documented to be relatively temporary. In two studies at Horns Rev II using impact pile driving, harbor porpoise returned within 1 to 2 days following cessation of pile driving (Tougaard
et al.,
2009; Brandt
et al.,
2011). Similar recovery periods have been noted for harbor seals off England during the construction of four wind farms (Brasseur
et al.,
2012; Carroll
et al.,
2010; Hamre
et al.,
2011; Hastie
et al.,
2015; Russell
et al.,
2016). In some cases, an increase in harbor porpoise activity has been documented inside wind farm areas following construction (
e.g.,
Lindeboom
et al.,
2011). Other studies have noted longer term impacts after impact pile driving. Near Dogger Bank in Germany, harbor porpoises continued to avoid the area for over 2 years after construction began (Gilles
et al.,
2009). Approximately 10 years after construction of the Nysted wind farm, harbor porpoise abundance had not recovered to the original levels previously seen, although the echolocation activity was noted to have been increasing when compared to the previous monitoring period (Teilmann and Carstensen, 2012). However, overall, there are no indications for a population decline of harbor porpoises in European waters (
e.g.,
Brandt
et al.,
2016). Notably, where significant differences in displacement and return rates have been identified for these species, the occurrence of secondary project-specific influences such as use of mitigation measures (
e.g.,
bubble curtains, acoustic deterrent devices (ADDs)), or the manner in which species use the habitat in the project area, are likely the driving factors of this variation.
NMFS notes the aforementioned studies from Europe involve installing much smaller piles than US Wind proposes to install and, therefore, we anticipate noise levels from impact pile driving to be louder. For this reason, we anticipate that the greater distances of displacement observed in harbor porpoise and harbor seals documented in Europe are likely to occur off Maryland. However, we do not anticipate any greater severity of response due to harbor porpoise and harbor seal habitat use off Maryland or population-level consequences similar to European findings. In many cases, harbor porpoises and harbor seals are resident to the areas where European wind farms have been constructed. However, off Maryland, harbor porpoises are transient (with higher abundances in winter when foundation installation would not occur) and a very small percentage of the large harbor seal population are only seasonally present with no rookeries established. In summary, we anticipate that harbor porpoise and harbor seals will likely respond to pile driving by moving several kilometers away from the source but return to typical habitat use patterns when pile driving ceases.
Some avoidance behavior of other marine mammal species has been documented to be dependent on distance from the source. As described above, DeRuiter
et al.
(2013) noted that distance from a sound source may moderate marine mammal reactions in their study of Cuvier's beaked whales (an acoustically sensitive species), which showed the whales swimming rapidly and silently away when a sonar signal was 3.4-9.5 km away while showing no such reaction to the same signal when the signal was 118 km away even though the received levels were similar. Tyack
et al.
(1983) conducted playback studies of Surveillance Towed Array Sensor System (SURTASS) low-frequency active (LFA) sonar in a gray whale migratory corridor off California. Similar to North Atlantic right whales, gray whales migrate close to shore (approximately +2 km) and are low-frequency hearing specialists. The LFA sonar source was placed within the gray whale migratory corridor (approximately 2 km offshore) and offshore of most, but not all, migrating whales (approximately 4 km offshore). These locations influenced received levels and distance to the source. For the inshore playbacks, not unexpectedly, the louder the source level of the playback (
i.e.,
the louder the received level), whale avoided the source at greater distances. Specifically, when the source level was 170 dB rms and 178 dB rms, whales avoided the inshore source at ranges of several hundred meters, similar to avoidance responses reported by Malme
et al.
(1983, 1984). Whales exposed to source levels of 185 dB rms demonstrated avoidance levels at ranges of +1 km. Responses to the offshore source broadcasting at source levels of 185 and 200 dB, avoidance responses were greatly reduced. While there was observed deflection from course, in no case did a whale abandon its migratory behavior.
The signal context of the noise exposure has been shown to play an important role in avoidance responses. In a 2007-2008 Bahamas study, playback sounds of a potential predator—a killer whale—resulted in a similar but more pronounced reaction in beaked whales (an acoustically sensitive species), which included longer inter-dive intervals and a sustained straight-line departure of more than 20 km from the area (Boyd
et al.,
2008; Southall
et al.,
2009; Tyack
et al.,
2011). US Wind does not anticipate, and NMFS is not proposing to authorize take of beaked whales and, moreover, the sounds produced by US Wind do not have signal characteristics similar to predators. Therefore, we would not expect such extreme reactions to occur. Southall
et al.
(2011) found that blue whales had a different response to sonar exposure depending on behavioral state, more pronounced when deep feeding/travel modes than when engaged in surface feeding.
One potential consequence of behavioral avoidance is the altered energetic expenditure of marine mammals because energy is required to move and avoid surface vessels or the
sound field associated with active sonar (Frid and Dill, 2002). Most animals can avoid that energetic cost by swimming away at slow speeds or speeds that minimize the cost of transport (Miksis-Olds, 2006), as has been demonstrated in Florida manatees (Miksis-Olds, 2006). Those energetic costs increase, however, when animals shift from a resting state, which is designed to conserve an animal's energy, to an active state that consumes energy the animal would have conserved had it not been disturbed. Marine mammals that have been disturbed by anthropogenic noise and vessel approaches are commonly reported to shift from resting to active behavioral states, which would imply that they incur an energy cost.
Forney
et al.
(2017) detailed the potential effects of noise on marine mammal populations with high site fidelity, including displacement and auditory masking, noting that a lack of observed response does not imply absence of fitness costs and that apparent tolerance of disturbance may have population-level impacts that are less obvious and difficult to document. Avoidance of overlap between disturbing noise and areas and/or times of particular importance for sensitive species may be critical to avoiding population-level impacts because (particularly for animals with high site fidelity) there may be a strong motivation to remain in the area despite negative impacts. Forney
et al.
(2017) stated that, for these animals, remaining in a disturbed area may reflect a lack of alternatives rather than a lack of effects.
A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. The flight response differs from other avoidance responses in the intensity of the response (
e.g.,
directed movement, rate of travel). Relatively little information on flight responses of marine mammals to anthropogenic signals exist, but observations of flight responses to the presence of predators have occurred (Connor and Heithaus, 1996; Frid and Dill, 2002). The result of a flight response could range from brief, temporary exertion and displacement from the area where the signal provokes flight to, in extreme cases, beaked whale strandings (Cox
et al.,
2006; D'Amico
et al.,
2009). However, it should be noted that response to a perceived predator does not necessarily invoke flight (Ford and Reeves, 2008), and whether individuals are solitary or in groups may influence the response. Flight responses of marine mammals have been documented in response to mobile high intensity active sonar (
e.g.,
Tyack
et al.,
2011; DeRuiter
et al.,
2013; Wensveen
et al.,
2019), and more severe responses have been documented when sources are moving towards an animal or when they are surprised by unpredictable exposures (Watkins, 1986; Falcone
et al.,
2017). Generally speaking, however, marine mammals would be expected to be less likely to respond with a flight response to either stationery pile driving (which they can sense is stationery and predictable) or significantly lower-level HRG surveys, unless they are within the area ensonified above behavioral harassment thresholds at the moment the source is turned on (Watkins, 1986; Falcone
et al.,
2017).
Diving and Foraging
Changes in dive behavior in response to noise exposure can vary widely. They may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive (
e.g.,
Frankel and Clark, 2000; Costa
et al.,
2003; Ng and Leung, 2003; Nowacek
et al.,
2004; Goldbogen
et al.,
2013a; Goldbogen
et al.,
2013b). Variations in dive behavior may reflect interruptions in biologically significant activities (
e.g.,
foraging) or they may be of little biological significance. Variations in dive behavior may also expose an animal to potentially harmful conditions (
e.g.,
increasing the chance of ship-strike) or may serve as an avoidance response that enhances survivorship. The impact of a variation in diving resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure, the type and magnitude of the response, and the context within which the response occurs (
e.g.,
the surrounding environmental and anthropogenic circumstances).
Nowacek
et al.
(2004) reported disruptions of dive behaviors in foraging North Atlantic right whales when exposed to an alerting stimulus, an action, they noted, that could lead to an increased likelihood of ship strike. The alerting stimulus was in the form of an 18-minute exposure that included three 2-minute signals played three times sequentially. This stimulus was designed with the purpose of providing signals distinct to background noise that serve as localization cues. However, the whales did not respond to playbacks of either right whale social sounds or vessel noise, highlighting the importance of the sound characteristics in producing a behavioral reaction. Although source levels for the proposed pile driving activities may exceed the received level of the alerting stimulus described by Nowacek
et al.
(2004), proposed mitigation strategies (further described in the Proposed Mitigation section) will reduce the severity of response to proposed pile driving activities. Converse to the behavior of North Atlantic right whales, Indo-Pacific humpback dolphins have been observed to dive for longer periods of time in areas where vessels were present and/or approaching (Ng and Leung, 2003). In both of these studies, the influence of the sound exposure cannot be decoupled from the physical presence of a surface vessel, thus complicating interpretations of the relative contribution of each stimulus to the response. Indeed, the presence of surface vessels, their approach, and speed of approach, seemed to be significant factors in the response of the Indo-Pacific humpback dolphins (Ng and Leung, 2003). Low-frequency signals of the Acoustic Thermometry of Ocean Climate (ATOC) sound source were not found to affect dive times of humpback whales in Hawaiian waters (Frankel and Clark, 2000) or to overtly affect elephant seal dives (Costa
et al.,
2003). They did, however, produce subtle effects that varied in direction and degree among the individual seals, illustrating the equivocal nature of behavioral effects and consequent difficulty in defining and predicting them.
Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the cessation of secondary indicators of foraging (
e.g.,
bubble nets or sediment plumes), or changes in dive behavior. As for other types of behavioral response, the frequency, duration, and temporal pattern of signal presentation, as well as differences in species sensitivity, are likely contributing factors to differences in response in any given circumstance (
e.g.,
Croll
et al.,
2001; Nowacek
et al.,
2004; Madsen
et al.,
2006; Yazvenko
et al.,
2007; Southall
et al.,
2019b). An understanding of the energetic requirements of the affected individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal can facilitate the assessment of whether foraging disruptions are likely to incur fitness consequences (Goldbogen
et al.,
2013b; Farmer
et al.,
2018; Pirotta
et al.,
2018a; Southall
et al.,
2019a; Pirotta
et al.,
2021).
Impacts on marine mammal foraging rates from noise exposure have been documented, though there is little data regarding the impacts of offshore turbine construction specifically. Several broader examples follow, and it
is reasonable to expect that exposure to noise produced during the 5 years that the proposed rule would be effective could have similar impacts. Visual tracking, passive acoustic monitoring, and movement recording tags were used to quantify sperm whale behavior prior to, during, and following exposure to airgun arrays at received levels in the range 140-160 dB at distances of 7-13 km, following a phase-in of sound intensity and full array exposures at 1-13 km (Madsen
et al.,
2006; Miller
et al.,
2009). Sperm whales did not exhibit horizontal avoidance behavior at the surface. However, foraging behavior may have been affected. The sperm whales exhibited 19 percent less vocal (buzz) rate during full exposure relative to post exposure, and the whale that was approached most closely had an extended resting period and did not resume foraging until the airguns had ceased firing. The remaining
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