Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Revolution Wind Offshore Wind Farm Project Offshore Rhode Island

Federal RegisterDec 23, 2022

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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 217

[Docket No. 221214-0271]

RIN 0648-BL52

Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Revolution Wind Offshore Wind Farm Project Offshore Rhode Island

AGENCY:

National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Commerce.

ACTION:

Proposed rule; proposed incidental take regulations; proposed letter of authorization; request for comments.

SUMMARY:

NMFS has received a request from Revolution Wind, LLC (Revolution Wind), a 50/50 joint venture between Ørsted North America, Inc. (Ørsted) and Eversource Investment, LLC, for Incidental Take Regulations (ITR) and an associated Letter of Authorization (LOA). The requested regulations would govern the authorization of take, by Level A harassment and/or Level B harassment, of small numbers of marine mammals over the course of 5 years (2023-2028) incidental to construction of the Revolution Wind Offshore Wind Farm Project offshore of Rhode Island in a designated lease area on the Outer Continental Shelf (OCS-A-0486), within the Rhode Island-Massachusetts Wind Energy Area (RI/MA WEA). Project activities likely to result in incidental take include pile driving (impact and vibratory), potential unexploded ordnance (UXO/MEC) detonation, and vessel-based 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 would be effective October 5, 2023-October 4, 2028.

DATES:

Comments and information must be received no later than January 23, 2023.

ADDRESSES:

Submit all electronic public comments via the Federal e-Rulemaking Portal. Go to

www.regulations.gov

and enter NOAA-NMFS-2022-0127 in the Search box. 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

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). Attachments to electronic comments will be accepted in Microsoft Word, Excel, or Adobe PDF file formats only.

FOR FURTHER INFORMATION CONTACT:

Carter Esch, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Availability

A copy of Revolution Wind's 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 authority of the Marine Mammal Protection Act (MMPA) (16 U.S.C. 1361

et seq.

) to allow for the authorization of take of marine mammals incidental to construction of the Revolution Wind Farm Project within the Bureau of Ocean Energy Management (BOEM) Renewable Energy lease area OCS-A 0486 and along export cable corridors to landfall locations in Rhode Island. NMFS received a request from Revolution Wind for 5-year regulations and a Letter of Authorization (LOA) that would authorize take of individuals of four species of marine mammals by Level A harassment and Level B harassment and 12 species by only Level B harassment incidental to Revolution Wind's construction activities. No mortality or serious injury is anticipated or proposed for authorization. Please see the

Legal Authority for the Proposed Action

section below for definitions of harassment.

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, 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, and on 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. The definitions of all applicable MMPA statutory terms cited above are included below.

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 this rule containing 5-year regulations and associated LOA. This proposed rule also establishes required mitigation, monitoring, and reporting requirements for Revolution Wind's activities.

Summary of Major Provisions Within the Proposed Rule

The major provisions of this proposed rule include:

• Establishing a seasonal moratorium on impact pile driving during the months of highest North Atlantic right whale (

Eubalaena glacialis

) presence in the project area (January 1-April 30);

• Establishing a seasonal moratorium on any unexploded ordnances or munitions and explosives of concern (UXOs/MECs) detonations during the months of highest North Atlantic right whale present in the project area (January 1-April 30).

• Requiring that any UXO/MEC detonations may only occur during hours of daylight and not during hours of darkness or nighttime.

• Conducting both visual and passive acoustic monitoring by trained, NOAA Fisheries-approved Protected Species Observers (PSOs) and Passive Acoustic Monitoring (PAM) operators before, during, and after the in-water construction activities;

• Requiring the use of sound attenuation device(s) during all impact pile driving and UXO/MEC detonations to reduce noise levels;

• Delaying the start of pile driving if a North Atlantic right whale is observed at any distance by the PSO on the pile driving or dedicated PSO vessels;

• Delaying the start of pile driving if other marine mammals are observed entering or within their respective clearance zones;

• Shutting down pile driving (if feasible) if a North Atlantic right whale is observed or if other marine mammals enter their respective shutdown zones;

• Implementing soft starts for impact pile driving and using the lowest hammer energy possible;

• Implementing ramp-up for high-resolution geophysical (HRG) site characterization survey equipment;

• Requiring PSOs to continue to monitor for 30 minutes after any impact pile driving occurs and for any and all UXO/MEC detonations;

• Increasing awareness of North Atlantic right whale presence through monitoring of the appropriate networks and VHF Channel 16, as well as reporting any sightings to the sighting network;

• Implementing numerous vessel strike avoidance measures;

• A requirement to implement noise abatement system(s) during all impact pile driving and UXO/MEC detonations;

• Sound field verification requirements during impact pile driving and UXO/MEC detonation to measure in situ noise levels for comparison against the model results; and

• Removing gear from the water during fisheries monitoring research surveys if marine mammals are considered at-risk or are interacting with gear.

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 Letter of Authorization (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 proposes to adopt BOEM's 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 (Revolution Wind Draft Environmental Impact Statement (DEIS) for Commercial Wind Lease OCS-A 0486) was made available for public comment on September 2, 2022 (87 FR 54248), beginning the 45-day comment period ending on October 17, 2022. Additionally, BOEM held three in-person public hearings on October 4, 2022, in Aquinnah, MA, October 5, 2022, in East Greenwich, CT, and October 6, 2022, in New Bedford, MA, and two virtual public hearings on September 29 and October 11, 2022.

Information contained within Revolution Wind's incidental take authorization (ITA) application and this

Federal Register

document collectively 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 document prior to concluding the NEPA process or making a final decision on the requested 5-year ITA 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).

Revolution Wind's proposed project is listed on the Permitting Dashboard, where milestones and schedules related to the environmental review and permitting for the project can be found:

https://www.permits.performance.gov/permitting-projects/revolution-wind-farm-project.

Summary of Request

On October 8, 2021, Revolution Wind submitted a request 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 Revolution Wind Offshore Wind Farm Project (herein “the Project”) offshore of Rhode Island, in the BOEM lease area OCS-A-0486.

Revolution Wind's request is for the incidental, but not intentional, taking of a small number of 16 marine mammal species (comprising 16 stocks) by Level A harassment (for four species or stocks) and Level B harassment (for all 16 species or stocks). Neither Revolution Wind nor NMFS expects serious injury or mortality to result from the specified activities based on the implementation of various mitigation measures as described below in the Proposed Mitigation section.

In response to our questions and comments, and following extensive information exchange between Revolution Wind and NMFS, we received subsequent revised applications and/or supplementary materials on January 24, 2022, and February 11, 2022. Revolution Wind submitted a final version of the application on February 23, 2022, which NMFS deemed adequate and complete on February 28, 2022. This final application is available on NMFS' website at:

https://www.fisheries.noaa.gov/action/incidental-take-authorization-revolution-wind-llc-construction-revolution-wind-energy.

On March 21, 2022, a notice of receipt (NOR) of the application was published in the

Federal Register

(87 FR 15942), requesting comments and soliciting information related to Revolution Wind's request during a 30-day public comment period. During the NOR public comment period, NMFS received 27 substantive comments from two environmental non-governmental organizations (ENGO) Oceana and the Rhode Island Saltwater Anglers Association (RISSA). NMFS has reviewed all submitted material and has taken these into consideration during the drafting of this proposed

rulemaking. Subsequently, in June 2022, new scientific information was released regarding marine mammal densities (Robert and Halpin, 2022) and, as such, Revolution Wind submitted an Updated Density and Take Estimation Memo in August that included updated marine mammal densities and take estimates. NMFS posted this memo on the NMFS website on August 26, 2022.

NMFS previously issued four Incidental Harassment Authorizations (IHAs) to Ørsted for the taking of marine mammals incidental to marine site characterization surveys (using HRG equipment) of the Revolution Wind's BOEM lease area (OCS-A 0486) and surrounding BOEM lease areas (OCS-A 0487, OCS-A 0500) (see 84 FR 52464, October 2, 2019; 85 FR 63508, October 8 14, 2020; 87 FR 756, January 6, 2022; and 87 FR 61575, October 12, 2022). To date, Ørsted has complied with all IHA requirements (

e.g.,

mitigation, monitoring, and reporting). Information regarding Ørsted's monitoring results may be found in the Estimated Take section, and the full monitoring reports can be found on NMFS' website:

https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-other-energy-activities-renewable.

On August 1, 2022, NMFS announced proposed changes to the existing North Atlantic right whale vessel speed regulations 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 (87 FR 46921). Should a final vessel speed rule be issued and become effective during the effective period of this ITA (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 of the effective date, NMFS would also notify Revolution 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.

Description of the Specified Activity

Overview

Revolution Wind has proposed to construct and operate a 704 megawatt (MW) wind energy facility (known as Revolution Wind) in State and Federal waters in the Atlantic Ocean in lease area OCS-A-0486, which would provide power to Rhode Island and Connecticut. Revolution Wind's project would consist of several different types of permanent offshore infrastructure, including wind turbine generators (WTGs;

e.g.,

Siemens Gamesa 11 megawatt (MW)) and associated foundations, offshore substations (OSS), offshore substation array cables, and substation interconnector cables. In their application, Revolution Wind indicated they plan to install up to 100 WTGs and two offshore substations (OSS) via impact pile driving; the temporary installation and removal of two cofferdams to assist in the installation of the export cable route by vibratory pile driving; several types of fishery and ecological monitoring surveys; the placement of scour protection; trenching, laying, and burial activities associated with the installation of the export cable route from OSSs to shore-based converter stations and inter-array cables between turbines; HRG vessel-based site characterization surveys using active acoustic sources with frequencies of less than 180 kilohertz (kHz); and the potential detonation of up to 13 UXO/MECs of different charge weights, as necessary. Vessels would transit within the project area, and between ports and the wind farm to transport crew, supplies, and materials to support pile installation. All offshore cables would connect to onshore export cables, substations, and grid connections, which would be located at Quonset Point in North Kingstown, Rhode Island.

Since submission of the application, Revolution Wind has re-evaluated previous survey data and analyzed additional survey data. On October 13, 2022, Revolution Wind informed NMFS that 21 of the 100 WTG positions are not able to be developed due to installation infeasibility. On November 8, 2022, Revolution Wind provided NMFS with a Reduced WTG Foundation Scenario memo that includes revised exposure and take estimates based on the installation of 79 WTG foundations; therefore, for purposes of this proposed rule, we are analyzing take requests associated with the installation of the reduced number of foundations (

i.e.,

79 WTG foundations plus two OSS foundations, for a total of 81 foundations). In addition, the amount of trackline within the lease area that would be surveyed using HRG equipment has been reduced to reflect the shorter overall distance of inter-array cables that would be required for 79 rather than 100 WTG foundations. Revolution Wind now estimates that they would survey 9,559 km over 136.6 days rather than 11,600 km over 165.7 days during construction (Year 1) in the lease area. Following construction (

i.e.,

in Years 2-5), Revolution Wind now plans to survey 2,117 km over 30.2 days per year rather than 2,640 km over 37.7 days per year in the lease area. The amount of survey work that would be conducted in the export cable corridor would not change from what was included in the ITR application, despite installation of fewer WTG foundations. Marine mammals exposed to elevated noise levels during impact and vibratory pile driving, potential detonations of UXOs, or site characterization surveys, may be taken, by Level A harassment and/or Level B harassment, depending on the specified activity.

Dates and Duration

Revolution Wind anticipates that activities with the potential to result in harassment of marine mammals would occur throughout all five years of the proposed regulations which, if promulgated, would be effective from October 5, 2023, through October 4, 2028. Installation of monopile foundations, cable landfall construction, and UXO/MEC detonations in the Revolution Wind Farm (RWF) and Revolution Wind Export Cable (RWEC) corridor would occur over approximately 12 to 18 months, from the third quarter (Q3) of 2023 to the fourth quarter (Q4) of 2024 (Figure 1). Through the end of the 5-year effective period of the requested regulations in Q3 2028, HRG surveys could take place within the RWF and RWEC at any time of year; the timeframe for these post-construction surveys is not included in Figure 1. The general construction schedule in Figure 1 and Table 1 presents all of the major project components, including those that may result in take, and those from which incidental take is not expected (

i.e.,

components in italics in Figure 1 and Table 1).

EP23DE22.000

Table 1—Revolution Wind's Construction and Operations Schedule

Project area

Project component

Expected duration and timing

RWF Construction

WTG foundation installation

~5 months Q2-Q3 2024.

OSS foundation installation

~2-3 days Q2-Q3 2024.

Array cable installation

~5 months Q1-Q3 2024.

HRG surveys

Any time of year Q3 2023-Q4 2024.

In situ

UXO/MEC disposal

~ up to 7 days Q3-Q4 2023.

RWEC Construction

Cable landfall installation (temporary cofferdam or casing pipe installation and removal

~ up to 56 days Q3-Q4 2023.

Offshore export cable installation

~8 months Q4 2023-Q4 2024.

HRG surveys

Any time of year Q3 2023-Q4 2024.

In situ

UXO/MEC disposal

~ up to 6 days Q3-Q4 2023.

Operations

HRG surveys

Any time of year Q4 2024-Q3 2028.

Project components in italics are not expected to result in take.

WTG and OSS Pile Installation (Impact Pile Driving)

The installation of 79 WTG and 2 OSS monopiles foundations would be limited to May through December, given the seasonal restriction on impact pile driving in the RWF from January 1-April 30. As described previously, Revolution Wind intends to install all monopile foundations in a single year. However, it is possible that monopile installation would continue into a second year, depending on construction logistics and local and environmental conditions that may influence Revolution Wind's ability to maintain the planned construction schedule.

Installation of a single WTG monopile foundation is expected to require a maximum of 4 hours of active impact hammering, which can occur either in a continuous 4-hour interval or intermittently over a longer time period. For the purposes of acoustic modeling, it was assumed that installation of a single WTG monopile would require a total of 10,740 hammer strikes over 220 minutes (3.7 hours). Revolution Wind assumes that a maximum of three WTG monopile foundations can be driven into the seabed per day, although fewer installations per day may occur depending on logistics and environmental conditions. Installation of each of the two OSS monopile foundations is expected to require a larger number of hammer strikes (11,564) over a longer period (380 minutes, or 6.3 hours), given that the OSS monopile foundation is larger in diameter than the WTG monopile foundation. Revolution Wind has requested 24-hour pile driving, which would consist of intermittent impact pile driving that could occur anytime within a 24-hour timeframe, amounting to a maximum of 12 hours of active pile driving per day to install up to three monopiles. No concurrent impact pile driving (

i.e.,

installing multiple piles at the same time) is planned for this project.

Revolution Wind anticipates that the first WTG would become operational in Q2 of 2024, after installation is completed and all necessary components, such as array cables, OSSs, export cable routes, and onshore substations are installed. Turbines would be commissioned individually by personnel on location, so the number of commissioning teams would dictate how quickly the process would be achieved. Revolution Wind expects that all turbines would be commissioned by Q4 2024.

Potential UXO/MEC Detonations

Revolution Wind anticipates encountering the potential presence of UXOs/MECs in and around the project area during the 5 years of the proposed rule. These UXOs/MECs are defined as explosive munitions (

e.g.,

shells, mines, bombs, torpedoes,

etc.

) that did not explode or detonate when they were originally deployed or that were intentionally discarded to avoid detonations on land. Typically, these munitions could be left behind following Navy military training, testing, or operations. Revolution Wind primarily plans for avoidance or

relocation of any UXOs/MECs found within the project area, when possible. In some cases, it may also be possible that the UXO/MEC could be cut up to extract the explosive components. However, Revolution Wind notes this may not be possible in all cases and in situ disposal may be required. If in situ disposal is required, all disposals would be performed using low-order methods (deflagration), which are considered less impactful to marine mammals, first and then would be elevated up to high-order removal (detonation), if this approach is determined to be necessary. In the event that high-order removal is needed, all detonations would only occur during daylight hours.

Based on preliminary survey data, Revolution Wind conservatively estimates a maximum of 13 days on which UXO/MEC detonation may occur, with up to one UXO/MEC being detonated per day and a maximum of 13 UXOs/MECs being detonated over the entire 5-year period. NMFS notes that UXOs/MECs may be detonated from May through November in any year; however, no UXOs/MECs would be detonated in Federal waters between December 1 and April 30 of any year during the effective period of the proposed rule.

Cable Landfall Construction

Cable landfall construction is one of the first activities scheduled to occur, sometime within the Q3 2023 to Q4 2023 timeframe. Installation of the RWEC landfall would be accomplished using a horizontal directional drilling (HDD) methodology. The drilling equipment would be located onshore and used to create a borehole, one for each cable, from shore to an exit point on the seafloor approximately 250 m (800 ft) offshore. At the seaward exit site for each borehole, construction activities may include a casing pipe scenario, which involves the temporary installation of two casing pipes, each supported by sheet pile goal posts, to collect drilling mud from the borehole exit point. Alternatively, two temporary cofferdams may be installed to create a dry environment from which drilling mud could be collected. Each cofferdam, if required, may be installed as either a sheet-piled structure into the seafloor or a gravity cell cofferdam placed on the seafloor using ballast weight. Only one of these three landfall construction alternatives (

i.e.,

casing pipe scenario, sheet pile cofferdam, or gravity cell cofferdam) would be installed.

Casing Pipe Installation and Removal

The casing pipes would each require up to 3 hours per day of pneumatic impact hammering to install, over a period of two days for each pipe (6 hours total over 4 days for both), depending on the number of pauses required to weld additional sections onto the casing pipe. Removal of the casing pipe would also involve the use of a pneumatic pipe ramming tool, but the pipe would be pulled out of the seabed while hammering was occurring instead of being pushed into it. The same total of 4 days of pneumatic hammering (6 hours total), may be required for removal of both pipes.

Up to six goal posts may be installed to support each casing pipe (12 goal posts total), which would be located between a barge and the penetration point on the seabed. Each goal post would be composed of two vertical sheet piles installed using a vibratory hammer such as an American Piledriving Equipment (APE) model 300 (or similar). A horizontal cross beam connecting the two sheet piles would then be installed to provide support to the casing pipe. For each casing pipe, installation of six goal posts would require up to three days total of vibratory pile driving, or up to 6 days total for both casing pipes. Removal of the goal posts would also involve the use of a vibratory hammer and would likely require approximately the same amount of time as installation (6 days total for both casing pipes). Thus, use of a vibratory pile driver to install and remove the 12 goal posts may occur on up to 12 days at the landfall location.

Cofferdam Installation and Removal

If Revolution Wind selects this alternative, installation of two 50 m x 10 m x 3 m (164 ft x 33 ft x 10 ft) sheet pile cofferdams at the cable landfall construction location near Quonset Point in Kingstown, Rhode Island, may require up to 14 days of vibratory pile driving per cofferdam (28 days total). After the sheet piles are installed, the inside of each cofferdam would be excavated to approximately 10 ft (3 m). Once HDD operations are complete and the cables installed, the cofferdams would be removed, using vibratory hammering, over the course of up to 14 days per cofferdam. Separate cofferdams would be installed and removed for each of the two export cable bundles, amounting to up to 56 days of vibratory hammering at the landfall location.

If Revolution Wind decides to install the gravity cell cofferdam (which would have the same approximate dimensions as the sheet pile cofferdam), the structure would be fabricated onshore, transported to the site on a barge, and then lifted off the barge and placed on the seafloor using a crane. This process would not involve pile driving or other underwater sound producing activities, and is not expected to result in harassment of marine mammals.

Revolution Wind anticipates that impacts from cofferdam installation and removal using sheet piles would exceed any potential impacts for the use of alternative methods (

i.e.,

gravity cell cofferdam, casing pipe scenario), and therefore the cofferdam estimates using the sheet pile approach ensures that the most conservative values are carried forward in analyses for this proposed action.

HRG Surveys

High-resolution geophysical site characterization surveys would occur annually throughout the 5 years the rule and LOA would be effective. The specific duration would be dependent on the activities occurring in that year (

i.e.,

construction versus non-construction year). HRG surveys would utilize up to a maximum of four vessels working concurrently in different sections of the lease area and RWEC corridor. During the first year of construction (when the majority of foundations and cables would be installed), Revolution Wind estimates that 9,669 km would be surveyed over 136.6 days in the lease area, and 5,748 km would be surveyed along the RWEC corridor over 82.1 days, in water depths ranging from 2 m (6.5 ft) to 50 m (164 ft). During non-construction years (the final 4 years in which the regulations and LOA would be effective), Revolution Wind estimates 2,117 km would be surveyed in the lease area over 30.2 days and 1,642 km would be surveyed over 23.5 days along the RWEC corridor each year. Revolution Wind anticipates that each vessel would survey an average of 70 km (44 miles) per day, assuming a 4 km/hour (2.16 knots) vessel speed and 24-hour operations. Each day that a survey vessel covers 70 km (44 miles) of survey trackline is considered a vessel day. For example, Revolution Wind would consider 2 vessels operating concurrently, with each surveying 70 km (44 miles), two vessel days. In some cases, vessels may conduct daylight-only 12-hour nearshore surveys, covering half that distance (35 km or 22 miles). Over the course of 5 years, HRG surveys would be conducted at any time of year for a total of 30,343 km (18,854 miles) over 433.5 vessel days. In this schedule, Revolution Wind accounted for periods of down-time due to

inclement weather or technical malfunctions.

Specific Geographic Region

Revolution Wind would install the RWF in Federal waters within the designated lease area OCS-A 0486 (Figure 2). The 339 square kilometer (km

) (83,798 acres) lease area is located within the 1,036 km

(256,000 acres) RI/MA WEA. The edge of the lease area closest to land is approximately 15 mi (13 nm, 24 km) southeast of the Rhode Island coast. The RWEC corridor would traverse both federal waters and state territorial waters of Rhode Island, extending up to approximately 50 mi (80 km) from the RWF to the RWEC landfall location at Quonset Point in North Kingstown, Rhode Island. Two temporary cofferdams or casing pipes (with associated goal posts) would be installed at Quonset Point to facilitate the sea-to-shore transition for the export cables. Water depths in the lease area range from 24 to 50 m (78.7 to 164.0 ft), averaging 35 m (114.8 ft), while water depths along the RWEC corridor range from 10 to 45 m (32.8 to 147.6 ft). The cable landfall construction area would be approximately 15 m (49.2 ft) in depth.

Revolution Wind's specified activities would occur in the Northeast U.S. Continental Shelf Large Marine Ecosystem (NES LME), an area of approximately 260,000 km

from Cape Hatteras in the south to the Gulf of Maine in the north. Specifically, the lease area and cable corridor are located within the Mid-Atlantic Bight subarea of the NE LME which extends between Cape Hatteras, North Carolina, and Martha's Vineyard, Massachusetts, extending eastward into the Atlantic to the 100-m isobath. In the Middle 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 gravel. 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, as well as in areas such as the “Mud Patch” south of Rhode Island. There are some larger materials, including boulders and rocks, left on the seabed by retreating glaciers, along the coast of Long Island and to the north and east, including in Rhode Island Sound near where the Revolution Wind lease area is located.

In support of the Rhode Island Ocean Special Area Management Plan development process, Codiga and Ullman (2011) reviewed and summarized the physical oceanography of coastal waters off Rhode Island. Conditions off the coast of Rhode Island are shaped by a complex interplay among wind-driven variability, tidal processes, and density gradients that arise from combined effects of interaction with adjacent estuaries, solar heating, and heat flux through the air-sea interface. In winter and fall, the stratification is minimal and circulation is a weak upwelling pattern, directed offshore at shallow depths and onshore near the seafloor; in spring and summer, strong stratification develops due to an important temperature contribution, and a system of more distinct currents occurs. These include the southern New England shelf flow westward along the offshore area, which bifurcates in the east where a portion moves northward as the RIS Current, a narrow flow that proceeds counterclockwise around the perimeter of RIS, likely in association with a tidal mixing front.

The Revolution Wind lease area, located on Cox Ledge, is dominated by complex habitats that support diverse assemblages of fish and invertebrates. Large contiguous areas of complex habitats are located centrally and throughout the entire southern portion of the lease area. Smaller, patchy areas of complex habitats also occur throughout the northern portion of the lease area. Biogeographic patterns in Rhode Island Sound are persistent from year to year, yet variable by season, reflected by the cross-shelf migration of fish and invertebrate species in the spring and fall (Malek

et al.,

2014).

BILLING CODE 3510-22-P

EP23DE22.001

BILLING CODE 3510-22-C

Detailed Description of Specific Activity

Below, we provide detailed descriptions of Revolution Wind's 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.

Installation of WTG and OSS Monopile Foundations

Revolution Wind plans to install 81 monopile foundations over approximately one year within the 5-year effective period of the proposed rule. To do so, they would use impact pile driving, which is expected to result

in the incidental take of marine mammals. Pile driving would be limited to the months of May through December, annually, and would primarily occur in Year 1 (and potentially Year 2, should significant schedule delays occur). Monopiles are the only foundation type proposed for the project. As mentioned previously, the 81 monopiles installed to support the 79 WTG and two OSSs would have a maximum diameter of 12 m (39.4 ft) and 15 m (49.2 ft), respectively, and would be driven to a maximum penetration depth of 50 m (164 ft) using an IHC-4000 kilojoules (kJ) impact hammer. The monopiles are tapered such that the top diameter is 7 m (for both WTG and OSS foundations), the bottom diameter is 12-m (WTG) or 15-m (OSS), with both sizes tapering near the water line (referred to as 7/12-m and 7/15-m monopiles herein).

A monopile foundation typically consists of a single steel tubular section, with several sections of rolled steel plate welded together. Schematic diagrams showing potential heights and dimensions of the various components of a monopile foundation are shown in Figures 3 and 4 of Revolution Wind's ITA application.

A typical monopile installation sequence begins with the monopiles being transported directly to the lease area for installation, or to the construction staging port by an installation vessel or a feeding barge. At the foundation installation location, the main installation vessel (heavy lift, or jack-up vessel) upends the monopile in a vertical position in the pile gripper mounted on the side of the vessel. The gripper frame, depending upon its design, may be placed on the seabed scour protection materials to stabilize the monopile's vertical alignment before and during piling. Scour protection is included to protect the foundation from scour development, which is the removal of the sediments near structures by hydrodynamic forces, and consists of the placement of stone or rock material around the foundation. Once the monopile is lowered to the seabed, a temporary steel cap called a helmet would be placed on top of the pile to minimize damage to the head during impact driving. The hydraulic impact hammer is then lifted on top of the pile to commence pile driving with a soft start (see Proposed Mitigation section). The largest impact hammer Revolution Wind expects to use for driving monopiles produces up to 4,000 kJ of energy, however, the required energy to install a monopile may ultimately be far less than 4,000 kJ. The intensity (

i.e.,

hammer energy level) of impact hammering would be gradually increased based on resistance from the sediments (see Estimated Take for the potential hammer schedule and strike rate).

Pile installation would occur during daylight hours and could continue into nighttime hours if pile installation is started 1.5 hours prior to civil sunset. Alternatively, if Revolution Wind submits an Alternative Monitoring Plan (as part of the Pile Driving and Marine Mammal Monitoring Plan) that reliably demonstrates to NMFS that Revolution Wind can effectively visually and acoustically monitor marine mammals during nighttime hours, they may initiate pile driving during night (see Proposed Mitigation section). If NMFS approves Revolution Wind's plan and allows pile driving to occur at night, Revolution Wind plans to install three monopiles per day although, given logistical constraints (

e.g.,

sea state limitations for impact pile driving, weather) and the coordination required, it is possible that fewer than three monopiles would be installed per day.

It is estimated that a single foundation installation sequence would require up to approximately nine hours (one hour pre-start clearance, up to four hours of pile driving, and four hours to move to the next location). Again, no concurrent impact pile driving would occur, regardless of the number of piles installed per day. Once construction begins, Revolution Wind would proceed as rapidly as possible, while meeting all required mitigation and monitoring measures, to reduce the total duration of construction such that work is condensed into summer months when right whale occurrence is expected to be lowest in the project area.

UXO/MEC Detonations

Revolution Wind anticipates the potential for construction activities to encounter UXO/MECs on the seabed within the RWF and along the RWEC corridor. The risk of incidental detonation associated with conducting seabed-altering activities such as cable laying and foundation installation in proximity to UXO/MECs jeopardizes the health and safety of project participants (Revolution Wind 2022). Revolution Wind follows an industry standard As Low as Reasonably Practicable (ALARP) process that minimizes the number of potential detonations (Construction and Operations Plan (COP) Appendix G; Revolution-Wind 2022). For UXO/MECs that are positively identified on the seabed in proximity to planned activities, several alternative strategies would be considered prior to in-situ UXO/MEC disposal. These may include (1) relocating the activity away from the UXO/MEC (avoidance), (2) moving the UXO/MEC away from the activity (lift and shift), (3) cutting the UXO/MEC open to apportion large ammunition or deactivate fused munitions, using shaped charges to reduce the net explosive yield of a UXO/MEC (low-order detonation), or (4) using shaped charges to ignite the explosive materials and allow them to burn at a slow rate rather than detonate instantaneously (deflagration) (Revolution Wind 2022). Only after these alternatives are considered would in-situ high-order UXO/MEC detonation be pursued. To detonate a UXO/MEC, a small charge would be placed on the UXO/MEC and ignited, causing the UXO/MEC to then detonate, which could result in the taking of marine mammals.

To better assess the potential UXO/MEC encounter risk, HRG surveys have been and continue to be conducted to identify potential UXO/MECs that have not been previously mapped. As these surveys and analysis of data from them are still underway, the exact number and type of UXO/MECs in the project area are not yet known. As a conservative approach for the purposes of the impact analysis, Revolution Wind assumed that up to 13 UXO/MEC 454-kg (1,000 pounds; lbs) charges (up to seven UXO/MECs in the RWF and up to six UXO/MECs along the RWEC corridor), which is the largest charge that is reasonably expected to be encountered, may require in situ detonation. Although it is highly unlikely that all 13 charges would weigh 454 kg, this approach was determined to be the most conservative for the purposes of impact analysis. If necessary, these detonations would occur on up to 13 different days (

i.e.,

only one detonation would occur per day). In the event that high-order removal (detonation) is determined to be the preferred and safest method of disposal, all detonations would occur during daylight hours. UXO/MEC detonations would be prohibited from December 1 through April 30 to provide protection for right whales during the timeframe they are expected to occur more frequently in the project area.

Export Cable Landfall Construction

Once construction plans are completed, Revolution Wind would determine whether to install gravity cell cofferdam, sheet pile cofferdams, or the casing pipe scenario. Again, only installation of the latter two alternatives are expected to result in the take of marine mammals. As mentioned previously, the amount of take incidental to installation of the casing

pipe alternative is expected to be less than or equal to, and occur over a much shorter duration than, that from installation of sheet pile cofferdams. Installation of sheet pile cofferdams (described below) was carried forward in the take estimation analyses, given the large size of the Level B harassment zone and the longer duration of the activity (see Estimated Take section). Compared to the sheet pile cofferdam alternative, installation of the casing pipe, described below, produced larger Level A harassment (SEL

cum

) zones due to the high hammering rate required for the relatively small hammer to install the pipe. The potential for Level A harassment incidental to casing pipe installation is higher than it is for cofferdam installation, assuming a marine mammal remains within the relevant Level A harassment zone for the duration of the installation. However, the short duration of required pneumatic hammering (see below) coupled with implementation of Revolution Wind's proposed mitigation and monitoring measures (

i.e.,

shutdown zones equivalent to the size of the casing pipe Level A harassment zones) would decrease the likelihood of Level A harassment to the extent that neither Revolution Wind nor NMFS anticipates it would occur, nor is it proposed for authorization.

Installation and Removal of Casing Pipes

Installation of two casing pipes would be completed using pneumatic pipe ramming equipment, while installation of sheet piles for goal posts would be completed using a vibratory pile driving hammer (previously described). Casing pipe and sheet pile installations would not occur simultaneously, and would be limited to daylight hours.

The casing pipe would be installed at a slight upward angle relative to the seabed so that the pipe creates a straight alignment between the point of penetration at the seabed and the construction barge. Casing pipe installation would occur from the construction barge and be accomplished using a pneumatic pipe ramming tool (Gundoram Taurus or similar) with a hammer energy of up to 18 kJ. If necessary, additional sections of casing pipe may be welded together on the barge to extend the length of the casing pipe from the barge to the penetration depth in the seabed. As mentioned previously, installation of each casing pipe would require up to 3 hours per day of pneumatic hammering for 2 days, for a total of 6 hours per pipe. Removal of each casing pipe may require use of the pneumatic hammering tool (during which the pipe is pulled from the seabed) for the same amount of time as installation (3 hours of pneumatic hammering for 2 days for each casing pipe; total of 6 hours per pipe).

Up to six goal posts would be installed for each casing pipe, for a total of twelve goal posts. As described previously, each goal post would be composed of 2 vertical sheet piles installed using a vibratory hammer with a horizontal cross beam connecting the two sheet piles. Up to 10 additional sheet piles may be installed per casing pipe to help anchor the barge and support the construction activities. This results in a total of up to 22 sheet piles per casing pipe, for a total of 44 sheet piles to support both casing pipes. Sheet piles used for the goal posts and supports would be up to 30 m (100 ft) long, 0.6 m (2 ft) wide, and 1 inch thick. Installation of the goal posts would require up to 3 days per casing pipe, or up to 6 days total for both casing pipes. Removal of the goal posts would also involve the use of a vibratory hammer and likely require approximately the same amount of time as installation (6 days total for both casing pipes). Thus, use of a vibratory pile driver to install and remove sheet piles may occur on up to 12 days at the landfall location. All of the sheet pile goal posts would be installed first, followed by installation of the casing pipe.

Installation and Removal of Temporary Cofferdams

As an alternative to the casing pipe/goal post scenario described above, two cofferdams may be installed to allow for a dry environment during construction and manage sediment, contaminated soil, and bentonite (drilling mud used during HDD operations). If required, the cofferdams may be installed as either a sheet-piled structure (driven into the sea floor) or a gravity cell cofferdam placed on the seafloor using ballast weight. Regardless of the type of structure, the cofferdams could each measure up to 50 m x 10 m x 3 m (164 ft x 33 ft x 10 ft). If a gravity cell cofferdam was selected for installation, the structure would be fabricated onshore, transported to the site on a barge, and then lifted off the barge and placed on the seafloor using a crane. This process would not involve pile driving or other underwater sound producing activities so is not carried forward into take analyses. Given that the design process for the HDD is still ongoing, Revolution Wind is not able to commit to a particular landfall construction scenario. As the design matures, Revolution Wind would refine the appropriate HDD export cable landfall methodology based on site conditions and state permit requirements.

If cofferdams are installed using sheet piles, a vibratory hammer such as an APE model 200T (or similar) would be used to drive sheet piles of up to 30 m (100 ft) long, 0.6 m (2 ft) wide, and 1 inch thick. The sidewalls and endwall would be driven to a depth of up to 30 ft (9.1 m); sections of the shore-side endwall would be driven to a depth of up to 6 ft (1.8 m) to facilitate the borehole entering underneath the endwall. Installation of each sheet pile cofferdam may take up to 14 days, as would removal, for a total of 28 days per cofferdam or 56 days of vibratory hammer use (installation and removal) for both cofferdams.

HRG Surveys

HRG surveys would be conducted to identify any seabed debris, and to support micro-siting of the WTG and OSP foundations and cable routes. These surveys may utilize active acoustic equipment such as multibeam echosounders, side scan sonars, shallow penetration sub-bottom profilers (SBPs) (

e.g.,

Compressed High-Intensity Radiated Pulses (CHIRPs) non-parametric SBP), medium penetration sub-bottom profilers (

e.g.,

sparkers and boomers), ultra-short baseline positioning equipment, and marine magnetometers, some of which are expected to result in the take of marine mammals. Surveys would occur annually, with durations dependent on the activities occurring in that year (

i.e.,

construction year versus a non-construction year).

As summarized previously, HRG surveys would be conducted using up to four vessels to survey the RWF and RWEC corridor 12-24 hours/day for a total of 345.8 vessel days, operating at any time of the year over the course of five years. On average, 70-line km would be surveyed per vessel each vessel day at approximately 4 km/hour (2.16 knots). Two 12-hr surveys covering 35 km/per day each would count as one vessel day because one complete vessel day is defined by the total kilometers surveyed (

i.e.,

70 km). While the final survey plans would not be completed until construction contracting commences, approximately 50 percent (218.7 days; 15,307 km (9,511 miles)) of the total survey effort would occur during the construction phase (2023-2024). During non-construction periods, an estimated 3,759 km (2,336 miles) would be surveyed over 53.7 days each year in the RWF and along the RWEC corridor. The purpose of surveying during construction years is to monitor

installation activities, provide third-party verification of contractor's work, and assess seabed levels pre-, during, and post-seabed disturbing activities. The purpose of surveying during non-construction years is to monitor seabed levels and scour protection, identify any risks to inter-array and export cable integrity, and conduct seabed clearance surveys prior to maintenance/repair.

Of the HRG equipment types proposed for use, the following have the potential to result in take:

• Shallow penetration sub-bottom profilers (SBPs) to map the near-surface stratigraphy (top 0 to 5 m (0 to 16 ft) of sediment below seabed). A CHIRP system emits sonar pulses that increase in frequency over time. The pulse length frequency range can be adjusted to meet project variables. These are typically mounted on the hull of the vessel or from a side pole.

• Medium penetration SBPs (boomers) to map deeper subsurface stratigraphy as needed. A boomer is a broad-band sound source operating in the 3.5 Hz to 10 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 50 Hz to 4 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 2 identifies all the representative survey equipment that operates below 180 kilohertz (kHz) (

i.e.,

at frequencies that are audible and have the potential to disturb marine mammals) that may be used in support of planned HRG survey activities, and are likely to be detected by marine mammals given the source level, frequency, and beamwidth of the equipment. Equipment with operating frequencies above 180 kHz (

e.g.,

side-scan sonar (SSS), multibeam echosounder (MBES)) and equipment that does not have an acoustic output (

e.g.,

magnetometer) would also be used, but are not discussed further because they are outside the general hearing range of marine mammals likely to occur in the project area. No harassment exposures can be reasonably expected from the operation of these sources; therefore, they are not considered further in this proposed action.

Table 2—Summary of Representative HRG Survey Equipment

Equipment type

Representative model

Operating

frequency

(kHz)

Source

level

SPL

rms

(dB)

Source

level

0-pk

(dB)

Pulse

duration

(ms)

Repetition rate

(Hz)

Beamwidth

(degrees)

Information source

Sub-bottom Profiler

EdgeTech 216

2-16

195

MAN

EdgeTech 424

4-24

176

3.4

Edgetech 512

0.7-12

179

GeoPulse 5430A

2-17

196

MAN

Teledyn Benthos CHIRP III—TTV 170

2-17

197

100

MAN

Sparker

Applied Acoustics Dura-Spark UHD (400 tips, 500 J)

0.3-1.2

203

1.1

Omni

Boomer

Applied Acoustics triple plate S-Boom (700-1,000 J)

0.1-5

205

0.6

- = not applicable; ET = EdgeTech; J = joule; kHz = kilohertz; dB = decibels; SL = source level; UHD = ultra-high definition; AA = Applied Acoustics; rms = root-mean square; µPa = microPascals; re = referenced to; SPL = sound pressure level; PK = zero-to-peak pressure level; Omni = omnidirectional source.

The Dura-spark measurements and specifications provided in Crocker and Fratantonio (2016) were used for all sparker systems proposed for the survey. These include variants of the Dura-spark sparker system and various configurations of the GeoMarine Geo-Source sparker system. The data provided in Crocker and Fratantonio (2016) represent the most applicable data for similar sparker systems with comparable operating methods and settings when manufacturer or other reliable measurements are not available.

Crocker and Fratantonio (2016) provide S-Boom measurements using two different power sources (CSP-D700 and CSP-N). The CSP-D700 power source was used in the 700 J measurements but not in the 1,000 J measurements. The CSP-N source was measured for both 700 J and 1,000 J operations but resulted in a lower SL; therefore, the single maximum SL value was used for both operational levels of the S-Boom.

Vessel Activity

During construction and development of the project, associated vessels would slightly increase the volume of traffic in the project area, particularly during the first 12-18 months throughout construction of the RWF and installation of the RWEC. The largest size vessels are expected during the monopile installation phase, with floating/jack-up crane barges, DP-equipped cable laying vessels, and associated tugs and barges transporting construction equipment and materials. Up to 60 vessels may be utilized for construction across various components of the Project including installation of the foundations, WTGs, OSSs, inter-array cables, and OSS-Link Cable (Revolution Wind COP Table 3.3-26; Revolution-Wind 2022). The types of vessels Revolution Wind anticipates using during construction activities and operations, as well as the anticipated number of vessels and vessel trips, are summarized in Tables 3 and 4. The actual number of vessels involved in the Project at one time is highly dependent on the final schedule, the final impacts of boulder clearance and in situ UXO/MEC disposal, the final design of the Project's components, and the logistics needed to ensure compliance with the Jones Act, a Federal law that regulates maritime commerce in the U.S (Revolution Wind, 2022).

During construction, the Project would involve the use of temporary construction areas and construction ports. Revolution Wind is considering multiple port locations and any combination of the ports under consideration may be utilized. The ports that may be used during construction are as follows:

•

Construction Hub:

Port of Montauk (New York), Port Jefferson (New York), Port of Brooklyn (New York), Port of Davisville and Quonset Point (Rhode Island), and/or Port of Galilee (Rhode Island).

•

Foundation Marshaling and Advanced Foundation Component Fabrication:

Port of Providence (Rhode Island), Paulsboro Marine Terminal (New Jersey), and/or Sparrows Point (Maryland).

•

WTG Tower, Nacelle, and Blade Storage, Pre-commissioning, and Marshalling:

Port of Providence (Rhode Island), Port of New London (Connecticut), Port of Norfolk (Virginia), and/or New Bedford Marine Commerce Terminal (Massachusetts).

•

Electrical Components:

Port of Providence (Rhode Island).

Vessels not transporting material from the ports listed above may travel with components and equipment directly to the lease area from locations such as the Gulf of Mexico, Europe, or other worldwide ports. Before arriving at the lease area, a port call for inspections,

crew transfers and bunkering may occur (Revolution Wind 2022).

Construction vessel traffic would result in a relatively localized impact which would occur sporadically throughout the approximate 18-month time period of offshore construction in and around the RWF, temporarily increasing the volume and movement of vessels. Large work vessels for foundation and WTG installation would generally transit to the lease area and remain in the area until installation is complete. These large vessels would move slowly over a short distance between work locations within the lease area. Crew transport vessels would travel between several ports and the RWF over the course of the construction period following mandatory vessel speed restrictions, as described in the Proposed Mitigation section below. These vessels would range in size from smaller crew transport vessels, to tug and barge vessels. However, Revolution Wind has confirmed that construction crews would hotel onboard installation vessels at sea, thus limiting the number of crew vessel transits expected (870 round-trips during the construction and 300 round trips during non-construction years) during the effective period of the proposed rule.

Vessels would comply with NMFS' regulations and state regulations as applicable for North Atlantic right whales (hereinafter “right whale,” or “right whales”) and additional measures included in this proposed rule. The total number of estimated round trips for all vessels during the construction (scheduled for Year 1) and non-construction years (Year 2-5) is 1,406 and 444, respectively.

Table 3—Type and Number of Vessels, and Number of Vessel Trips, Anticipated During Construction

[Scheduled for Year 1]

Vessel types

Number of

vessels

Number of

return trips

per vessel type

Wind Turbine Foundation Installation

Heavy Lift Installation Vessel

?Heavy Lift Installation Vessel (secondary steel)

Towing Tug (for fuel barge)

Anchor Handling Tug

Vessel for Bubble Curtain

Heavy Transport Vessel

Crew Transport Vessel

PSO Vessel

Platform Supply Vessel (secondary steel)

Platform Supply Vessel (completions)

Fall Pipe Vessel

Turbine Installation

Jack-up Installation Vessel

Fuel Bunkering Vessel

Towing Tug (for fuel barge)

Array Cable Installation

Pre-Lay Grapnel Run

Boulder Clearance Vessel

Sandwave Clearance Vessel

Cable Laying Vessel

Cable Burial Vessel

Crew Transport Vessel

231

Walk to Work Vessel (SOV)

Survey Vessel

DP2 Construction Vessel

OSS Topside Installation

Heavy Transport Vessel

Offshore Export Cable Installation

Pre-Lay Grapel Run

Boulder Clearance Vessel

Sandwave Clearance Vessel

Cable Lay and Burial Vessel

Cable Burial Vessel—Remedial

Cable Lay Barge

Tug—Small Capacity

Tug—Large Capacity

Crew Transport Vessel

214

Guard Vessel/Scout Vessel

Survey Vessel

DP2 Construction Vessel

Supply Barge

All Construction Activities

Safety Vessel

100

Crew Transport Vessel

395

Supply Vessel

Service Operation Vessel

Helicopter

The vessels included in the “All Construction Activities” section provide general support across all of the activities in Table 3. The vessels listed in each activity (

e.g.,

“Wind Turbine Foundation Installation” are solely utilized for that activity.

Table 4—Type and Number of Vessels, and Number of Vessel Trips, Anticipated During Scheduled Operations and Maintenance Activities

[Years 2-5]

Vessel type

Number of

vessels

Number of return

trips per vessel

type per year

Total number

of return trips

for years 2-5

Service Operation Vessel

104

Crew Transport Vessel

248

Shared Crew Transport Vessel

0.5

Daughter Craft

While marine mammals are known to respond to vessel noise and the presence of vessels in different ways, we do not expect Revolution Wind's vessel operations to result in the take of marine mammals. As existing vessel traffic in the vicinity of the project area off Rhode Island and Massachusetts is relatively high, we expect that marine mammals in the area are likely somewhat habituated to vessel noise. In addition, any construction vessels would be stationary for significant periods of time when on-site and any large vessels would travel to and from the site at relatively low speeds. Project-related vessels would be required to adhere to mitigation measures designed to reduce the potential for marine mammals to be struck by vessels associated with the project; these measures are described further below (see the Proposed Mitigation section). Given the implementation of these measures, vessel strikes are neither anticipated nor proposed to be authorized (see

Potential Effects of Vessel Strike

section).

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. 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, further reducing the potential for harassment. Construction-related vessel activity, including the use of dynamic positioning thrusters, is not expected to result in take of marine mammals and Revolution Wind did not request, and NMFS does not propose to authorize, any take associated with construction vessel activity. However, NMFS acknowledges the aggregate impacts of Revolution Wind's vessel operations on the acoustic habitat of marine mammals and has considered it in the analysis.

Revolution Wind has also included the potential use of an Autonomous Surface Vehicle (ASVs), a small unmanned surface vessel or platform, during HRG surveys. Should an ASV be utilized during surveys, it would be positioned within 800 m (2,625 ft) of the primary vessel while conducting survey operations, operated at a slow speed, and would be monitored by PSOs at all times. Revolution Wind did not request take specific to ASVs and NMFS is not proposing to authorize take associated with ASV operation.

Fisheries and Benthic Habitat Monitoring

As described in section 1.1.7 of Revolution Wind's ITA application, the fisheries and benthic monitoring efforts Revolution Wind plans to conduct throughout the proposed rule's period of effectiveness have been designed for the Project in accordance with recommendations set forth in “Guidelines for Providing Information on Fisheries for Renewable Energy Development on the Atlantic Outer Continental Shelf” (BOEM 2019). In particular, Revolution Wind's Fisheries and Benthic Monitoring Plan includes four elements: trawl surveys, an acoustic telemetry study, ventless trap surveys, and benthic habitat monitoring. Trawl surveys would be focused on sampling the fish and invertebrate community within the Project area. For the acoustic telemetry study, Highly Migratory Species (bluefin tuna, shortfin mako, and blue sharks) would be tagged during the trawl survey, after which Revolution Wind would use a combination of fixed station receivers and active mobile telemetry to assess the movements of these species. Revolution Wind would deploy up to 100 additional acoustic tags opportunistically for cod caught as part of trawl survey. The ventless trap survey would be conducted twice per month between May and November to investigate the relative abundance of

lobster, Jonah crab, and rock crab. Ten trap trawls (6 ventless and 4 vented) would be fished on a five-day soak time. Finally, hard bottom habitat monitoring would occur, during which Revolution Wind would use a remotely operated vehicle (ROV) and video surveying approach to characterize changes from pre-construction conditions. Soft bottom habitat monitoring would be conducted using Sediment Profile and Plan View Imaging (SPI/PV) to document physical (and biological change related to construction of the Project. Because the gear types and equipment used for the acoustic telemetry study and benthic habitat monitoring do not have components with which marine mammals are likely to interact (

i.e.,

become entangled in or hooked by), these activities are unlikely to have any impacts on marine mammals.

Of the activities described, trawl and ventless trap surveys could have the potential to impact marine mammals through interactions with fishing gear (

i.e.,

entanglement). However, Revolution Wind has proposed, and would be required, to implement Best Management Practices (BMPs) that would minimize this risk to the degree that take of marine mammals is not reasonably anticipated. Given these BMPs (included in the Proposed Mitigation section), neither NMFS nor Revolution Wind anticipates that any take is likely to occur incidental to the activities described herein and in section 1.1.7 of the ITA application (Revolution Wind, 2021). Additionally, Revolution Wind has not requested any take of marine mammals incidental to fisheries surveys and benthic habitat monitoring, nor does NMFS propose to authorize any take given the nature of the activities and, for certain gear types, Revolution Wind's planned mitigation measures. Therefore, aside from the mitigation measures provided in the Proposed Mitigation section, these activities are not analyzed further in this document.

Dredging

Dredging may be used to remove materials from the seafloor in preparation of offshore foundation and export cable locations. There are two fundamental types of dredging that could be used by the Project—mechanical and hydraulic. Mechanical dredging refers to crane-operated buckets, grabs (clamshell), or backhoes used to remove seafloor material. Hydraulic (suction) dredging and controlled flow excavation (CFE) dredging involve the use of a suction to either remove sediment from the seabed or relocate sediment from a particular location on the seafloor. There are a variety of hydraulic and CFE dredge types including trailing suction, cutter-suction, auger suction, jet-lift, and air-lift (Kusel

et al.,

2021). The sound produced by hydraulic dredging results from the combination of sounds generated by the impact and abrasion of the sediment passing through the draghead, suction pipe, and pump.

NMFS does not expect dredging to generate noise levels that would cause take of marine mammals. Most of the acoustic energy produced by dredging falls below 1 kHz, and is highly unlikely to cause damage to marine mammal hearing (Todd

et al.,

2015). For example, a study by Reine and Clarke (2014) found that, using a propagation loss coefficient of 15LogR, source levels of dredging operations in the shallow waters (less than 15 m depth) in New York Harbor were measured at and did not exceed 151 dB re 1 μPa, which is not expected to cause hearing shifts in marine mammals. A more recent analysis by McQueen

et al.

(2020) found that, using a maximum sound level of 192 dB re 1 μPa, the resulting isopleths for representative marine mammals (

i.e.,

the harbor seal and harbor porpoise), the resulting isopleths for temporary shifts in hearing would occur less than 20 m and less than 74 m, respectively. Isopleths for permanent shifts occurred at distances of less than 1 m for both marine mammal species.

While NMFS acknowledges the potential for masking or slight behavioral changes to occur during dredging activities (Todd

et al.,

2015), any effects on marine mammals are expected to be short-term, low intensity, and unlikely to qualify as a take. Given the size of the area in which dredging operations would be occurring, as well as the coastal nature of some of these activities for the nearshore sea-to-shore connection points related to temporary cofferdam installation/removal, NMFS expects that any marine mammals would not be exposed at levels or durations likely to disrupt normal life activities (

i.e.,

migrating, foraging, calving, etc.). Therefore, the potential for take of marine mammals to result from these activities is so low as to be discountable. Revolution Wind did not request, and NMFS does not propose to authorize, any take of marine mammals associated with dredging; dredging activities are not analyzed further in this document.

Boulder Clearance

Boulder clearance may occur prior to and during offshore installation construction activities associated with the RWEC, foundation preparation, and the inter-array cable and OSS-Link cable installation, during which a number of different vessels and equipment types would be utilized. The techniques that may be used to remove or relocate surface or partially embedded boulders and debris, primarily during installation of the RWEC, include using a Boulder Grab or a Boulder Plow. The Boulder Grab would be lowered to the seabed over a targeted boulder, then grab the boulder to relocate it to a site away from the RWEC corridor. Alternatively, boulder clearance could be accomplished using a high-bollard pull vessel with a towed plow generally forming an extended V-shaped configuration, splaying from the rear of the main chassis (

i.e.,

Boulder Plow). The V-shaped configuration displaces any boulders to the extremities of the plow, thus clearing the corridor. Multiple iterations of this process may be required to clear a particular section of the corridor. A tracked plow with a front blade similar to a bulldozer may also be used to push boulders away from the corridor. Based on Revolution Wind's review of site-specific geophysical data, it is assumed that a boulder plow may be used in all areas of higher boulder/debris concentrations, conservatively estimated to be up to 60 percent per cable route of the RWEC and 80 percent of the entire inter-array cable network. Both within these areas of higher boulder and debris concentrations and outside of these areas, a boulder grab may be used to remove larger and/or isolated targets. The size of boulders that can be relocated is dependent on a number of factors including the boulder weight, dimensions, embedment, density and ground conditions. Typically, boulders with dimensions less than 8 ft (2.5 m) can be relocated with standard tools and equipment.

NMFS does not expect boulder clearance to generate noise levels that would cause take of marine mammals. Underwater noise associated with boulder clearance is expected to be similar in nature to the sound produced by the dynamic positioning (DP) cable lay vessels used during cable installation activities within the RWEC. Sound produced by DP vessels is considered non-impulsive and is typically more dominant than mechanical or hydraulic noises produced from the cable trenching or boulder removal vessels and equipment. Therefore, noise produced by the high bollard pull vessel with a towed plow or a support vessel carrying a boulder grab would be comparable to or less than the noise produced by DP vessels,

so impacts are also expected to be similar. Boulder clearance is a discrete action occurring over a short duration resulting in short term direct effects. Additionally, sound produced by boulder clearance vessels and equipment 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, further reducing the potential for startle or flight responses on the part of marine mammals. The Revolution Wind DEIS (BOEM, 2022), issued by BOEM on September 2, 2022, discusses boulder clearance in multiple sections, providing summaries of the boulder clearance methodologies described in Revolution Wind's COP. BOEM has deemed boulder clearance activities as a non-noise generating activity; therefore, the DEIS does not describe boulder clearance activities as a source of noise impacts (BOEM, 2022).

While NMFS acknowledges the potential for slight behavioral changes to occur during boulder clearance, any effects on marine mammals are expected to be short-term, low intensity, and unlikely to qualify as a take. Given that boulder clearance is expected to be extremely localized at any given time, NMFS expects that any marine mammals would not be exposed at levels or durations likely to disrupt normal life activities (

i.e.,

migrating, foraging, calving, etc.). Therefore, the potential for take of marine mammals to result from these activities is so low as to be discountable. Revolution Wind did not request, and NMFS does not propose to authorize, any take associated with boulder clearance; therefore, boulder clearance activities are not analyzed further in this document.

Cable Laying and Installation

Cable burial operations would occur both in RWF for the inter-array cables connecting the 79 WTGs to the two OSSs, and in the RWEC corridor for cables carrying power from the OSSs to shore. A single offshore export cable would connect the OSSs to the sea-to-shore transition point in Quonset Point, Rhode Island. All cable burial operations would follow installation of the monopile foundations, as the foundations must be in place to provide connection points for the export cable and inter-array cables.

All cables would be buried below the seabed, when possible, and buried onshore up to the transition joint bays. The targeted burial depths would be determined later by Revolution Wind, following a detailed design and Cable Burial Risk Assessment. This Assessment would note where burial cannot occur, where sufficient depths cannot be achieved, and/or where additional protection is required due to the export cable crossing other cables or pipelines (either related to the Revolution Wind project or not). Burial of cables would be performed by specific vessels, which are described in Table 3.3.10-3 in the Revolution Wind COP, available at:

https://www.boem.gov/renewable-energy/state-activities/revolution-wind-farm-construction-and-operations-plan.

Cable laying, cable installation, and cable burial activities planned to occur during the construction of Revolution Wind may include the following:

• Jetting;

• Vertical injection;

• Leveling;

• Mechanical cutting;

• Plowing (with or without jet-assistance);

• Pre-trenching; and,

• Controlled flow excavation.

Some dredging may be required prior to cable laying due to the presence of sandwaves. Sandwave clearance may be undertaken where cable exposure is predicted over the lifetime of the Project due to seabed mobility. This facilitates cable burial below the reference seabed. Alternatively, sandwave clearance may be undertaken where slopes become greater than approximately 10 degrees (17.6 percent), which could cause instability to the burial tool. The work could be undertaken by traditional dredging methods such as a trailing suction hopper. Alternatively, controlled flow excavation or a sandwave removal plough could be used. In some cases, multiple passes may be required. The method of sandwave clearance Revolution Wind chooses would be based on the results from the site investigation surveys and cable design. More information on cable laying associated with the proposed project is provided in Revolution Wind's COP (Revolution Wind, 2022) available at

https://www.boem.gov/renewable-energy/state-activities/revolution-wind-farm-construction-and-operations-plan.

As the noise levels generated from this activity are low, the potential for take of marine mammals to result is discountable (86 FR 8490; February 5, 2021) and Revolution Wind did not request, and NMFS is not proposing to authorize, marine mammal take associated with cable laying. Therefore, cable laying activities are not analyzed further in this document.

Helicopter Flights

Helicopters may be used during RWF construction and operation phases for crew transfer activities to provide a reduction in the overall transfer time, as well as to reduce the number of vessels on the water. Two of the closest ports to the Revolution Wind lease area are the Port of Davisville at Quonset Point, RI, and New Bedford, MA. Both of these are located approximately 45 km (28 mi) from the nearest portion of the lease area and 70-80 km (44-49 mi) from the most distant parts of the lease area. Assuming a vessel speed of 10 knots, a one-way trip from one of these ports by vessel would require between 2.4 and 4.3 hours. Typical crew transfer helicopters are capable of maximum cruising speeds of approximately 140 knots. Assuming a somewhat slower speed of 120 knots, a one-way trip by helicopter would require 12-22 minutes, thus reducing transit time by 92 percent (Revolution Wind, 2022c).

Without the use of helicopters, all crew transfers to/from offshore locations would be conducted by vessel (either a dedicated crew transfer vessel or other project vessel transiting between a port and the offshore location). Tables 3 and 4 reflect the use of helicopters; therefore, if Revolution Wind did not use helicopters, the amount of crew vessel activity would be higher. Use of helicopters may be limited by many factors, such as logistical constraints (

e.g.,

ability to land on the vessels) and weather conditions that affect flight operations (Revolution Wind, 2022c). Helicopter use also adds significant health, safety and environment (HSE) risk to personnel and, therefore, requires substantially more crew training and additional safety procedures (Revolution Wind, 2022c). These factors can result in significant limitations to helicopter usage. To maintain construction schedules and reliable wind farm operations, the necessity for crew transfers, by vessels or helicopter, would remain a core component of offshore wind farm construction and operations.

Helicopters produce sounds that could be audible to marine mammals. Sound generated by aircraft, both fixed wing and helicopters, is produced in air, but can transmit through the water surface and propagate underwater. In general, underwater sound levels produced by fixed wing aircraft and helicopters are typically low-frequency (16-500 Hz) and range between 84-159 dB re 1 μPa (Richardson

et al.,

1995; Patenaude

et al.,

2002; Erbe

et al.,

2018). However, most sound energy from aircraft reflects off the air-water

interface; only sound radiated downward within a 26-degree cone penetrates below the surface water (Urick, 1972). To the extent noise from helicopters transmits from air through the water surface, there is potential to cause temporary changes in behavior and localized displacement of marine mammals (Richardson

et al.,

1985a; Richardson and Würsig, 1997; Nowacek

et al.,

2007).

Marine mammals tend to react to aircraft noise more often when the aircraft is lower in altitude, closer in lateral distance, and flying over shallow water (Richardson

et al.,

1985b; Patenaude

et al.,

2002). Temporary reactions by marine mammals may include short surfacing, hasty dives, aversion from the aircraft or dispersal from the incoming aircraft (Bel'kovich, 1960; Kleĭnenberg

et al.,

1964; Richardson

et al.,

1985a; Richardson

et al.,

1985b; Luksenburg and Parsons, 2009). The response of marine mammals to aircraft noise largely depends on the species as well as the animal's behavioral state at the time of exposure (

e.g.,

migrating, resting, foraging, socializing) (Würsig

et al.,

1998). A study conducted in the Beaufort Sea in northern Alaska observed a general lack of reaction in bowhead and beluga whales to passing helicopters (Patenaude

et al.,

2002). Patenaude

et al.

(2002) reported behavioral responses by only 17 percent of the observed bowhead whales to passing helicopters at altitudes below 150 m and within a lateral distance of 250 m. Similarly, most observed beluga whales did not show any visible reaction to helicopters passing when flight altitudes were over 150 m (Patenaude

et al.,

2002). Although the sound emitted by aircraft has the potential to result in temporary behavioral responses in marine mammals, project-related aircraft would only occur at low altitudes over water during takeoff and landing at an offshore location where one or more vessels are located. Due to the intermittent nature of helicopter flights, the higher altitude, and the small area potentially ensonified by this sound source, both Revolution Wind and NMFS expect the potential for take of marine mammals incidental to helicopter use to be discountable. The use of helicopters to conduct crew transfers is likely to provide an overall benefit to marine mammals in the form of reduced vessel activity. Revolution Wind did not request, and NMFS is not proposing to authorize, take of marine mammals incidental to Revolution Wind's use of helicopters. This activity is not discussed or analyzed further herein.

Description of Marine Mammals in the Area of Specified Activities

Forty marine mammal species and/or stocks have geographic ranges within the western North Atlantic OCS (Table 5 in Revolution Wind ITA application). However, for reasons described below, Revolution Wind has requested, and NMFS proposes to authorize, take of only 16 species (comprising 16 stocks). Sections 3 and 4 of Revolution Wind's 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, incorporated here by reference, instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS's Stock Assessment Reports (SARs;

https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments

) and more general information about these species (

e.g.,

physical and behavioral descriptions) may be found on NMFS's website (

https://www.fisheries.noaa.gov/find-species

Table 5 lists all species and 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 by the MMPA 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 as described in 16 U.S.C. 1362(20) and as described in NMFS' SARs. While no mortality is anticipated or authorized here, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species and other threats.

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 5 are the most recent available at the time of publication and are available in NMFS' 2021 SARs (Hayes

et al.,

2022), available online at:

https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports.

Table 5—Marine Mammal Species Likely To Occur Near the Project Area That May Be Taken by Revolution Wind's Activities

Common name

Scientific name

Stock

ESA/

MMPA

status;

strategic

(Y/N)

Stock

abundance

(CV, N

min

, most recent

abundance survey)

PBR

Annual

M/SI

Order Artiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)

Family Balaenidae:

North Atlantic right whale

Eubalaena glacialis

Western Atlantic

E, D, Y

368 (0; 364; 2019)

0.7

7.7

Family Balaenopteridae (rorquals):

Blue whale

Balaenoptera musculus

Western North Atlantic

E, D, Y

UNK (UNK; 402; 1980-2008)

0.8

Fin whale

Balaenoptera physalus

Western North Atlantic

E, D, Y

6,802 (0.24; 5,573; 2016)

1.8

Sei whale

Balaenoptera borealis

Nova Scotia

E, D, Y

6,292 (1.02; 3,098; 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)

12.15

Superfamily Odontoceti (toothed whales, dolphins, and porpoises)

Family Physeteridae:

Sperm whale

Physeter macrocephalus

North Atlantic

E, D, Y

4,349 (0.28; 3,451; 2016)

3.9

Family Delphinidae:

Atlantic white-sided dolphin

Lagenorhynchus acutus

Western North Atlantic

-, -, N

93,233 (0.71; 54,433; 2016)

544

Atlantic spotted dolphin

Stenella frontalis

Western North Atlantic

-, -, N

39,921 (0.27; 32,032; 2016)

320

Common bottlenose dolphin

Tursiops truncatus

Western North Atlantic Offshore

-, -, N

62,851 (0.23; 51,914; 2016)

519

Long-finned pilot whales

Globicephala melas

Western North Atlantic

-, -, N

39,215 (0.3; 30,627; 2016)

306

Risso's dolphin

Grampus griseus

Western North Atlantic

-, -, N

35,215 (0.19; 30,051; 2016)

301

Common dolphin (short-beaked)

Delphinus delphis

Western North Atlantic

-, -, N

172,897 (0.21; 145,216; 2016)

1,452

390

Family Phocoenidae (porpoises):

Harbor porpoise

Phocoena phocoena

Gulf of Maine/Bay of Fundy

-, -, N

95,543 (0.31; 74,034; 2016)

851

Order Carnivora—Superfamily Pinnipedia

Family Phocidae (earless seals):

Gray seal

Halichoerus grypus

Western North Atlantic

-, -, N

27,300 (0.22; 22,785; 2016)

1,389

4,453

Harbor seal

Phoca vitulina

Western North Atlantic

-, -, N

61,336 (0.08; 57,637; 2018)

1,729

339

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.

NMFS marine mammal stock assessment reports online at:

www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments

(Hayes et al., 2022). CV is the coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable.

These values, found in NMFS' SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (

e.g.,

commercial fisheries, ship strike).

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.

The draft 2022 SARs have yet to be released; however, NMFS has updated its species web page to recognize the population estimate for right whales is now below 350 animals (

https://www.fisheries.noaa.gov/species/north-atlantic-right-whale

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://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/

; Committee on Taxonomy (2022)).

Of the 40 marine mammal species and/or stocks with geographic ranges that include the western North Atlantic OCS (Table 5 in Revolution Wind ITA application), 24 are not expected to be present or are considered rare or unexpected in the project area based on sighting and distribution data; they are, therefore, not discussed further beyond the explanation provided here. The following species are not expected to occur in the project area due to the location of preferred habitat outside the RWF and RWEC corridor, based on the best available information: dwarf and pygmy sperm whales (

Kogia sima and K breviceps

), northern bottlenose whale (

hyperoodon ampullatus

), cuvier's beaked whale (

Ziphius cavirostris

), four species of Mesoplodont beaked whales (

Mesoplodon densirostris, M. europaeus, M. mirus, and M. bidens

), killer whale (

Orcinus orca

), false killer whale (

Pseudorca crassidens

), pygmy killer whale (

Feresa attenuata

), short-finned pilot whale (

Globicephala Macrohynchus

), melon-headed whale (

Peponocephala electra

), Fraser's dolphin (

Lagenodelphis hosei

), white-beaked dolphin (

Lagenorhynchus albirostris

), pantropical spotted dolphin (

Stenella attenuata

), Clymene dolphin (

Stenella Clymene

), striped dolphin (

Stenella coeruleoalba

), spinner dolphin (

Stenella longirostris

), rough-toothed dolphin (

Steno bredanensis

), and the coastal migratory stock of common bottlenose dolphins (

Tursiops truncatus truncatus

). The following species may occur in the project area, but at such low densities that take is not anticipated: hooded seal (

Cystophora cristata

) and harp seal (

Pagophilus groenlandica

). There are two pilot whale species, long-finned (

Globicephala melas

) and short-finned (

Globicephala macrorhynchus

), with distributions that overlap in the latitudinal range of the RWF (Hayes

et al.,

2020; Roberts

et al.,

2016). Because it is difficult to differentiate between the two species at sea, sightings, and thus the densities calculated from them, are generally reported together as

Globicephala

spp. (Roberts

et al.,

2016; Hayes

et al.,

2020). However, based on the best available information, short-finned pilot whales occur in habitat that is both further offshore on the shelf break and further south than the project area (Hayes

et al.,

2020). Therefore, NMFS assumes that any take of pilot whales would be of long-finned pilot whales.

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 Northeast region during summer months (U.S. Fish and Wildlife Service (USFWS), 2022). However, manatees are managed by the USFWS

and are not considered further in this document. More information on this species can be found at the following website:

https://www.fws.gov/species/manatee-trichechus-manatus.

Between October 2011 and June 2015, a total of 76 aerial surveys were conducted throughout the MA and RI/MA Wind Energy Areas (WEAs) (the RWF is contained within the RI/MA WEA along with several other offshore renewable energy lease areas). Between November 2011 and March 2015, Marine Autonomous Recording Units (MARU; a type of static passive acoustic monitoring (PAM) recorder) were deployed at nine sites in the MA and RI/MA WEAs. The goal of the study was to collect visual and acoustic baseline data on distribution, abundance, and temporal occurrence patterns of marine mammals (Kraus

et al.,

2016). The lack of detections of any of the 24 species listed above reinforces the fact that they are not expected to occur in the project area. In addition, none of these species were observed during HRG surveys conducted by Ørsted from 2018 to 2021. As these species are not expected to occur in the project area during the proposed activities (based on acoustic detection and PSO data), NMFS does not propose to authorize take of these species and they are not discussed further in this document.

As indicated above, all 16 species and stocks in Table 5 temporally and spatially co-occur with the activity to the degree that taking is reasonably likely to occur. Five of the marine mammal species for which take is requested have been designated as ESA-listed, including North Atlantic right, blue, fin, sei, and sperm whales. In addition to what is included in Sections 3 and 4 of Revolution Wind's ITA application (

https://www.fisheries.noaa.gov/action/incidental-take-authorization-revolution-wind-llc-construction-revolution-wind-energy

), 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 Unusual Mortality Events (UME) and known important habitat areas, such as Biologically Important Areas (BIAs) (Van Parijs

et al.,

2015)). There is no ESA-designated critical habitat for any species within the project area.

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 December 2022, seven UMEs in total are considered active, with five of these occurring along the U.S. Atlantic coast for various marine mammal species; of these, the most relevant to the Revolution Wind project are the minke, right, and humpback whale, and phocid 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 UMEs 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 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 specific geographic region. Any areas of known biological importance (including the Biologically Important Areas (BIAs) identified in Van Parijs

et al.,

2015 and LaBrecque

et al.,

2015) that overlap spatially with the project area are addressed in the species sections below.

North Atlantic Right Whale

The North Atlantic right whale has been listed as an Endangered since 1970. They were 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; Davies & Brillant, 2019; Knowlton

et al.,

2012; Sharp

et al.,

2019), and a decrease in birth rate (Pettis

et al.,

2021). The Western Atlantic stock is considered depleted under the MMPA (Hayes

et al.,

2021). There is a recovery plan (NOAA Fisheries 2017) for the North Atlantic right whale, and NMFS completed a 5-year review of the species in 2017 (NOAA Fisheries 2017). In February 2022, NMFS initiated a 5-year review process (

https://www.fisheries.noaa.gov/action/initiation-5-year-review-north-atlantic-right-whale

The right whale population had only a 2.8 percent recovery rate between 1990 and 2011 (Hayes

et al.,

2022). Since 2010, the North Atlantic right whale population has been in decline (Pace

et al.,

2017), with a 40 percent decrease in calving rate (Kraus

et al.,

2016). In 2018, no new right whale calves were documented; this represented the first time since annual NOAA aerial surveys began in 1989 that no new right whale calves were observed within a calving season. Presently, the best available peer-reviewed population estimate for North Atlantic right whales is 368 per the 2021 SARs (Hayes

et al.,

2021) (

https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments

). The draft 2022 SARs have yet to be released; however, NMFS has updated its species web page to acknowledge that the right whale population estimate is now below 350 animals (

https://www.fisheries.noaa.gov/species/north-atlantic-right-whale

). We note that this change in abundance estimate would not change the estimated take of right whales or the take NMFS has proposed to authorize as take estimates are based on the habitat density models (Roberts

et al.,

2016; Roberts and Halpin, 2022).

Right whale presence in the project area is predominately seasonal; however, year-round occurrence is documented (O'Brien

et al.,

2022, Quintano-Rizzo

et al.,

2021). As a result of recent years of aerial surveys and PAM deployments within the RI/MA WEA, we have confidence that right whales are expected in the project area, in higher numbers in winter and spring followed by decreasing abundance into summer and early fall. The project area both spatially and temporally overlaps a portion of the migratory corridor BIA and migratory route Seasonal Management Area (SMA), within which right whales migrate south to calving grounds generally in November and December, followed by a northward migration into feeding areas east and north of the project area in March and April (LaBrecque

et al.,

2015; Van Parijs

et al.,

2015). While the project does not overlap previously identified critical feeding habitat or a feeding BIA, it is located just west of a more recently described important feeding area south of Martha's Vineyard and Nantucket,

along the western side of Nantucket Shoals. Finally, the project overlaps the Block Island SMA, which may be used by right whales for various activities, including feeding and migration. Due to the current status of North Atlantic right whales, and the overlap of the proposed project with areas of biological significance (

i.e.,

a migratory corridor, SMA), the potential impacts of the proposed project on right whales warrant particular attention.

Elevated right whale mortalities have occurred since June 7, 2017, along the U.S. and Canadian coast, with the leading category for the cause of death for this UME determined to be “human interaction,” specifically from entanglements or vessel strikes. As of November 2022, there have been 34 confirmed mortalities (dead stranded or floaters; 21 in Canada; 13 in the United States) and 21 seriously injured free-swimming whales for a total of 55 whales. As of November 15, 2022, the UME also considers animals with sublethal injury or illness bringing the total number of whales in the UME to 92. Approximately 42 percent of the population is known to be in reduced health (Hamilton

et al.,

2021), likely contributing to the smaller body sizes at maturation (Stewart

et al.,

2022) and making them more susceptible to threats. More information about the North Atlantic right whale UME is available online at:

www.fisheries.noaa.gov/national/marine-life-distress/2017-2021-north-atlantic-right-whale-unusual-mortality-event.

North Atlantic right whales may be present in New England waters year-round; however, their presence is limited during summer months. These waters are both a migratory corridor in the spring and early winter and a primary feeding habitat for right whales during late winter through spring. Habitat-use patterns within the region have shifted in relatively recent years (Davis

et al.,

2020; Quintano-Rizzo

et al.,

2021; O'Brien

et al.,

2022). Since 2010, right whales have reduced their use of foraging habitats in the Great South Channel and Bay of Fundy, while increasing their use of habitat within Cape Cod Bay, as well as a region south of Martha's Vineyard and Nantucket Islands, just to the east of the RWF and RWEC corridor (Stone

et al.,

2017; Mayo

et al.,

2018; Ganley

et al.,

2019; Record

et al.,

2019; Meyer-Gutbrod

et al.,

2021). Pendleton

et al.

(2022) found that peak use of right whale foraging habitat in Cape Cod Bay has shifted over the past 20 years to later in the spring, likely due to variations in seasonal conditions. Right whales have recently been observed feeding year-round in the region south of Martha's Vineyard and Nantucket with larger numbers in this area in the winter, making it the only known winter foraging habitat for the species (Quintana-Rizzo

et al.,

2021). Right whale use of habitats such as in the Gulf of St. Lawrence and East Coast mid-Atlantic waters of the have also increased over time (Davis

et al.,

2017; Davis and Brillant, 2019; Crowe

et al.,

2021; Quintana-Rizzo

et al.,

2021). Simard

et al.

(2019) documented the presence of right whales in the southern Gulf of St. Lawrence foraging habitat from late April through mid-January annually from 2010-2018 using passive acoustics, with occurrences peaking in the area from August through November each year (Simard

et al.,

2019). These shifts in foraging habitat use are likely due to changes in oceanographic conditions and food supply as dense patches of zooplankton are necessary for efficient foraging (Mayo and Marx, 1990; Record

et al.,

2019). 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).

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. However, recent research indicates understanding of their movement patterns remains incomplete and not all of the population undergoes a consistent annual migration (

e.g.,

Davis

et al.,

2017; Quintana-Rizzo

et al,

2021). The results of multistate temporary emigration capture-recapture modeling, based on sighting data collected over the past 22 years, indicate that 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).

Within the project area, right whales have primarily been observed during the winter and spring seasons through recent visual surveys (Kraus

et al.,

2016; Quintana-Rizzo

et al.,

2021). During aerial surveys conducted in the RI/MA and MA WEAs from 2011-2015, the highest number of right whale sightings occurred in March (n=21), with sightings also occurring in December (n=4), January (n=7), February (n=14), and April (n=14), and no sightings in any other months (Kraus

et al.,

2016). There was not significant variability in sighting rate among years, indicating consistent annual seasonal use of the area by right whales. Despite the lack of visual detection, right whales were acoustically detected in 30 out of the 36 recorded months (Kraus

et al.,

2016). Since 2017, right whales have been sighted in the southern New England area nearly every month, with peak sighting rates between late winter and spring. Model outputs suggest that 23 percent of the right population is present from December through May, and the mean residence time has tripled to an average of 13 days during these months (Quintano-Rizzo

et al.,

2021). A hotspot analysis analyzing sighting data in southern New England from 2011-2019 indicated that right whale occurrence in the Revolution Wind project area was highest in the spring (March through May), and that few right whales were sighted in the area during that time frame in summer or winter (Quintano-Rizzo

et al.,

2021), a time when right whales distribution shifted to the east and south into other portions of the study area.

North Atlantic right whale distribution can also be derived from acoustic data. A review of passive acoustic monitoring data from 2004 to 2014 collected throughout the western North Atlantic demonstrated nearly continuous year-round right whale presence across their entire habitat range, including in locations previously thought of as migratory corridors, suggesting that not all of the population undergoes a consistent annual migration (Davis

et al.,

2017). Acoustic monitoring data from 2004 to 2014 indicated that the number of right whale vocalizations detected in southern New England were relatively constant throughout the year, with the exception of August through October when detected vocalizations showed an apparent decline (Davis

et al.,

2017).

While density data from Roberts

et al.

(2022) confirm that the highest average density of right whales in the project area (both the lease area and RWEC corridor) occurs in March (0.0060 whales/100km

), which aligns with available sighting and acoustic data, it is clear that that habitat use is changing and right whales are present to some degree in or near the project area throughout the year, most notably south of Martha's Vineyard and Nantucket Islands (Leiter

et al.,

2017; Stone

et al.,

2017; Oleson

et al.,

2020, Quintano-Rizzo

et al.,

2021). Since 2010, right whale abundances have increased in

Southern New England waters, south of Martha's Vineyard and Nantucket Islands. O'Brien

et al.

(2022) detected significant increases in right whale abundance during winter and spring seasons from 2013-2019, likely due to changes in prey availability. Since 2017, right whales were also detected in small numbers during summer and fall, suggesting that these waters provide year-round habitat for right whales (O'Brien

et al.,

2022).

NMFS' regulations at 50 CFR 224.105 designated nearshore waters of the Mid-Atlantic Bight as Mid-Atlantic U.S. Seasonal Management Areas for right whales in 2008. SMAs were developed to reduce the threat of collisions between ships and right whales around their migratory route and calving grounds. As mentioned previously, the Block Island SMA overlaps spatially with the proposed project area (

https://apps-nefsc.fisheries.noaa.gov/psb/surveys/MapperiframeWithText.html

). The SMA is currently active from November 1 through April 30 of each year and may be used by right whales for feeding (although to a lesser extent than the area to the east near Nantucket Shoals) and/or migrating.

Humpback Whale

Humpback whales are a cosmopolitan species found worldwide in all oceans, but 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 CI 8,688-15,954) whales in 2004-05, 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). In New England waters, feeding is the principal activity of humpback whales, and their distribution in this region has been largely correlated to abundance of prey species (Payne

et al.,

1986, 1990). Humpback whales are frequently piscivorous when in New England waters, feeding on herring (

Clupea harengus

), sand lance (

Ammodytes spp.

), and other small fishes, as well as euphausiids in the northern Gulf of Maine (Paquet

et al.,

1997). Kraus

et al.

(2016) observed humpbacks in the RI/MA & MA Wind Energy Areas (WEAs) and surrounding areas during all seasons, but most often during spring and summer months, with a peak from April to June. Acoustic data indicate that this species may be present within the RI/MA WEA year-round, with the highest rates of acoustic detections in the winter and spring (Kraus

et al.,

2016).

A humpback whale feeding BIA extends throughout the Gulf of Maine, Stellwagen Bank, and Great South Channel from May through December, annually (LeBrecque

et al.,

2015). However, this BIA is located further east and north of, and thus does not overlap, the project area. The project area does not overlap any critical habitat for the species.

Since January 2016, elevated humpback whale mortalities along the Atlantic coast from Maine to Florida led to the declaration of a UME. Partial or full necropsy examinations have been conducted on approximately half of the 168 known cases (as of December 6, 2022). Of the whales examined, about 50 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. NOAA is consulting with researchers that are conducting studies on the humpback whale populations, and these efforts may provide information on changes in whale distribution and habitat use that could provide additional insight into how these vessel interactions occurred. More information is available at:

www.fisheries.noaa.gov/national/marine-life-distress/2016-2021-humpback-whale-unusual-mortality-event-along-atlantic-coast.

Fin Whale

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.,

2018). 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.,

2019).

Kraus

et al.

(2016) suggest that, compared to other baleen whale species, fin whales have a high multi-seasonal relative abundance in the RI/MA & MA WEAs and surrounding areas. Fin whales were observed in the MA WEA in spring and summer. This species was observed primarily in the offshore (southern) regions of the RI/MA & MA WEAs during spring and was found closer to shore (northern areas) during the summer months (Kraus

et al.,

2016). Calves were observed three times and feeding was observed nine times during the Kraus

et al.

(2016) study. Although fin whales were largely absent from visual surveys in the RI/MA and MA WEAs in the fall and winter months (Kraus

et al.

2016), acoustic data indicated that this species was present in these areas during all months of the year.

New England waters represent a major feeding ground for fin whales. The proposed project area would overlap spatially and temporally with approximately 11 percent of a relatively small fin whale feeding BIA (2,933 km

) offshore of Montauk Point, from March to October (Hain

et al.,

1992; LaBrecque

et al.,

2015). A separate larger year-round feeding BIA (18,015 km

) to the east in the southern Gulf of Maine does not overlap with the project area, and would thus not be impacted by project activities.

Minke Whale

Minke whale occurrence is common and widespread in New England from spring to fall, although the species is largely absent in the winter (Hayes

et al.,

2021; Risch

et al.,

2013). Surveys conducted in the RI/MA WEA from October 2011 through June 2015 reported 103 minke whale sightings within the area, predominantly in the spring, followed by summer and fall (Kraus

et al.,

2016).

There are two minke whale feeding BIAs in the southern and southwestern section of the Gulf of Maine, including Georges Bank, the Great South Channel, Cape Cod Bay, Massachusetts Bay, Stellwagen Bank, Cape Anne, and Jeffreys Ledge from March through November, annually (LeBrecque

et al.,

2015). However, these BIAs do not overlap the project area, as they are located further east and north. The proposed project area likely serves as a migratory route for minke whales transiting between northern feeding grounds and southern breeding areas.

Since January 2017, elevated minke whale mortalities detected along the

Atlantic coast from Maine through South Carolina resulted in the declaration of a UME. As of December 6, 2022, a total of 135 minke whales have stranded 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 whales examined, so more research is needed. More information is available at:

www.fisheries.noaa.gov/national/marine-life-distress/2017-2021-minke-whale-unusual-mortality-event-along-atlantic-coast.

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 Revolution Wind project area, the populations affected by the UME are the same as those potentially affected by the project.

The above event was preceded by a different UME, occurring from 2018-2020 (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:

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. Current data indicate that 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) recommended that marine mammals be divided into functional hearing groups based on directly measured or estimated hearing ranges on the basis of available behavioral response data, audiograms derived using auditory evoked potential techniques, anatomical modeling, and other data. 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 6.

Table 6—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.

* 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. Sixteen marine mammal species (14 cetacean species (6 mysticetes and 8 odontocetes) and 2 pinniped species (both phocid seals)) have the reasonable potential to co-occur with the proposed project activities (Table 5).

NMFS notes that in 2019, 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.

(2019) are identical to NMFS 2018 Revised Technical Guidance). When NMFS updates our Technical Guidance, we will be adopting the updated Southall

et al.

(2019) hearing group classification.

Potential Effects to 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 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 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 Area of the Specified Activities section). Here, the potential effects of sound on marine mammals are discussed.

Revolution Wind has requested authorization to take marine mammals incidental to construction activities in the Revolution Wind project area. In the ITA application, Revolution Wind presented analyses of potential impacts to marine mammals from use of acoustic and explosive sources. NMFS both carefully reviewed the information provided by Revolution Wind, as well as independently reviewed applicable scientific research and literature and other information, to evaluate the potential effects of Revolution Wind's activities on marine mammals, which are presented in this section.

The proposed activities would result in placement of up to 81 permanent foundations and two temporary cofferdams in the marine environment. Up to 13 UXO/MEC detonations may occur intermittently, only as necessary. There are a variety of effects to marine mammals, prey species, and habitat that could occur as a result of these actions.

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,

e.g.,

Au and Hastings (2008), Richardson

et al.

(1995), and Urick (1983).

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.

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 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 are measured in decibels (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 100-fold increase in power and a 30-dB increase is a 1000-fold increase in power. However, a ten-fold increase in acoustic power does not mean that the sound is perceived as being ten 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 utilizes three metrics.

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

-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

), 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. Sounds are typically classified by their spectral and temporal properties.

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 permanent threshold shift (PTS) and temporary threshold shift (TTS). It is also used to evaluate the potential for gastro-intestinal tract injury (Level A harassment) from explosives.

For explosives, an impulse metric (Pa-s), which is the integral of a transient sound pressure over the duration of the pulse, is used to evaluate the potential for mortality (

i.e.,

severe lung injury) and slight lung injury. These thresholds account for animal mass and depth.

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, 2019) 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 one second), broadband, atonal transients (American National Standards Institute (ANSI), 1986, 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 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. Underwater ambient sound in the Atlantic Ocean southeast of Rhode Island comprises sounds produced by a number of natural and anthropogenic sources. 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 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). Potential effects from explosive sound sources can range in severity from behavioral disturbance or tactile perception to physical discomfort, slight injury of the internal organs and the auditory system, or mortality (Yelverton

et al.,

1973). The degree of effect 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. 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 Revolution 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.

Potential effects from explosive sound sources can range in severity from effects such as behavioral disturbance or tactile perception to physical discomfort, slight injury of the internal organs and the auditory system, or mortality (Yelverton

et al.,

1973). 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).

Below, we provide additional detail regarding potential impacts on marine mammals and their habitat from noise in general, as well as from the specific activities Revolution Wind plans to conduct, to the degree it is available (noting that there is limited information regarding the impacts of offshore wind construction on cetaceans).

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.,

2019). 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.,

2019). 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, but such relationships are assumed to be similar to those in humans and other terrestrial mammals. PTS typically occurs at exposure levels at least several decibels above (a 40 dB threshold shift approximates a PTS onset;

e.g.,

Kryter

et al.,

1966; Miller, 1974; Henderson

et al.,

2008). This can also induce mild TTS (a 6 dB threshold shift approximates a TTS onset;

e.g.,

Southall

et al.,

2019). 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.,

2019). 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, but 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. 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 for successful mother/calf interactions 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 (

Neophocoena 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.,

2019). 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.

(2019), 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, 2015; Nachtigall

et al.,

2016a,b,c; 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 Disturbance

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.,

2019). 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. For example, Goldbogen

et al.

(2013b) 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.

(2013b) 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

) for exposures to 3-4 kHz sonar signals, while others showed a clear response at exposures at lower received levels of sonar and pseudorandom noise.

Studies by DeRuiter

et al.

(2012) indicate that variability of responses to acoustic stimuli depends not only on the species receiving the sound and the sound source, but also on the social, behavioral, or environmental contexts of exposure. Another study by DeRuiter

et al.

(2013) examined behavioral responses of Cuvier's beaked whales to MF 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, it is known that distance from the source can have an effect on behavioral response that 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.

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 five-fold 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.

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 (Nowacek

et al.,

2007; DeRuiter

et al.,

2012, 2013; Ellison

et al.,

2012; Gomez

et al.,

2016) 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. 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. The following subsections provide examples of behavioral responses that provide an idea of the variability in behavioral responses that would be expected given the differential sensitivities of marine mammal species to sound 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 or 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.,

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; Malme

et al.,

1984). 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 for impact pile driving) has been previously noted in the literature, with some significant variation in the effects. Most studies focused on harbor porpoises because it is 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 has 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 porpoises 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 PAM data from 2010-2013 and aerial surveys from 2009-2013 with data on noise levels associated with pile driving. Results of the analysis revealed significant declines in harbor porpoise detections during pile driving when compared to 24-48 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 (Lucke

et al.,

2012; Dähne

et al.,

2013; Tougaard

et al.,

2009; Haelters

et al.,

2015; Bailey

et al.,

2010).

While harbor porpoises and seals tend to move 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 porpoises returned within 1-2 days following cessation of pile driving (Tougaard

et al.,

2009, Brandt

et al.,

2011). Similar recovery periods have been noted for harbor seals off of England during the construction of four wind farms (Carroll

et al.,

2010; Hamre

et al.,

2011; Hastie

et al.,

2015; Russell

et al.,

2016; Brasseur

et al.,

2010). 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 two years after construction began (Gilles

et al.

2009). Approximately ten years after construction of the Nysted wind farm, harbor porpoise abundance had not recovered to the original levels previously observed, although 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 of 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.,

bubb

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