Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the SouthCoast Wind Project Offshore Massachusetts (2024)

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

Proposed rule; proposed letter of authorization; request for comments.

NMFS received a request from SouthCoast Wind Energy LLC (SouthCoast) (formerly Mayflower Wind Energy LLC), for Incidental Take Regulations (ITR) and an associated Letter of Authorization (LOA) pursuant to the Marine Mammal Protection Act (MMPA). The requested regulations would govern the authorization of take, by Level A harassment and Level B harassment, of small numbers of marine mammals over the course of five years (2027-2032) incidental to construction of the SouthCoast Wind Project (SouthCoast Project) offshore of Massachusetts within the Bureau of Ocean Energy Management (BOEM) Commercial Lease of Submerged Lands for Renewable Energy Development on the Outer Continental Shelf (OCS) Lease Area OCS-A 0521 (Lease Area) and associated Export Cable Corridors (ECCs). Specified activities expected to result in incidental take are pile driving (impact and vibratory), unexploded ordnance or munitions and explosives of concern (UXO/MEC) detonation, and site assessment surveys using high-resolution geophysical (HRG) equipment. NMFS requests comments on this 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 rule. The regulations, if promulgated, would be effective April 1, 2027 through March 31, 2032.

Comments and information must be received no later than July 29, 2024.

A plain language summary of this proposed rule is available at https://www.regulations.gov/​docket/​ NOAA-NMFS-2024-0074. Submit all electronic public comments via the Federal e- Portal. Visit https://www.regulations.gov and type NOAA-NMFS-2024-0074 in the Rulemaking 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 https://www.regulations.gov without change. All personal identifying information ( e.g., name, address), confidential business information, or otherwise sensitive information submitted voluntarily by the sender will be publicly accessible. NMFS will accept anonymous comments (enter “N/A” in the required fields if you wish to remain anonymous).

A copy of SouthCoast's Incidental Take Authorization (ITA) application and supporting documents, as well as a list of the references cited in this document, may be obtained online at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​incidental-take-authorizations-other-energy-activities-renewable. In case of problems accessing these documents, please call the contact listed below (see FOR FURTHER INFORMATION CONTACT ).

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

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Purpose and Need for Regulatory Action

This proposed rule, if promulgated, would provide a framework under the authority of the MMPA (16 U.S.C. 1361 et seq.) to allow for the authorization of take of marine mammals incidental to construction of the SouthCoast Project within the Lease Area and along ECCs to landfall locations in Massachusetts. NMFS received a request from SouthCoast for 5-year regulations and a LOA that would authorize take of individuals of 16 species of marine mammals by harassment only (4 species by Level A harassment and Level B harassment and 12 species by Level B harassment only) incidental to SouthCoast'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 relevant definitions.

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). If such findings are made, NMFS must prescribe the permissible methods of taking; 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 monitoring and reporting of such takings.

As noted above, no serious injury or mortality is anticipated or proposed for authorization in this proposed rule. Relevant definitions of MMPA statutory and regulatory terms are included below:

• U.S. Citizen —individual U.S. citizens or any corporation or similar entity if it is organized under the laws of the United States or any governmental unit defined in 16 U.S.C. 1362(13); 50 CFR 216.103);
• Take —to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal (16 U.S.C. 1362(13); 50 CFR 216.3);
• Incidental harassment, Incidental taking, and incidental, but not intentional, taking —an accidental taking. This does not mean that the taking is unexpected, but rather it includes those takings that are infrequent, unavoidable or accidental (50 CFR 216.103);
• Serious Injury —any injury that will likely result in mortality (50 CFR 216.3);
• Level A harassment —any act of pursuit, torment, or annoyance which has the potential to injure a marine mammal or marine mammal stock in the wild (16 U.S.C. 1362(18); 50 CFR 216.3); and
• Level B harassment —any act of pursuit, torment, or annoyance which has the potential to disturb a marine mammal or marine mammal stock in the Start Printed Page 53709 wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (16 U.S.C. 1362(18); 50 CFR 216.3).

Summary of Major Provisions Within the Proposed Rule

The major provisions of this proposed rule are:

• Allowing NMFS to authorize, under a LOA, the take of small numbers of marine mammals by Level A harassment and/or Level B harassment incidental to the SouthCoast Project and prohibiting take of such species or stocks in any manner not permitted (e.g., mortality or serious injury);
• Establishing a seasonal moratorium on foundation installation within 20 kilometers (km) (12.4 miles (mi)) of the 30-m isobath on the western side of Nantucket Shoals which, for purposes of this proposed rule, is hereafter referred to as the North Atlantic Right Whale Enhanced Mitigation Area (NARW EMA), from October 16-May 31, annually;
• Establishing a seasonal moratorium on foundation installation throughout the rest of the Lease Area January 1-May 15 and a restriction on foundation pile driving in December unless Southcoast requests and NMFS approves piling driving in December, which would require SouthCoast to implement enhanced mitigation and monitoring to minimize impacts to North Atlantic right whales (Eubalaena glacialis);
• Establishing enhanced North Atlantic right whale monitoring, clearance, and shutdown procedures SouthCoast must implement in the NARW EMA August 1-October 15, and throughout the rest of the Lease Area May 16-31 and December 1-31;
• Establishing a seasonal moratorium on the detonation of unexploded ordnance or munitions and explosives of concern (UXO/MEC) December 1-April 30 to minimize impacts to North Atlantic right whales;
• Requirements for UXO/MEC detonations to only occur if all other means of removal are exhausted (i.e., As Low As Reasonably Practicable (ALARP) risk mitigation procedure) and conducting UXO/MEC detonations during daylight hours only and limiting detonations to 1 per 24 hour period;
• Conducting both visual and passive acoustic monitoring (PAM) by trained, NMFS-approved Protected Species Observers (PSOs) and PAM operators before, during, and after select in-water construction activities;
• Requiring training for all SouthCoast Project personnel to ensure marine mammal protocols and procedures are understood;
• Establishing clearance and shutdown zones for all in-water construction activities to prevent or reduce the risk of Level A harassment and to minimize the risk of Level B harassment, including a delay or shutdown of foundation impact pile driving and delay to UXO/MEC detonation if a North Atlantic right whale is observed at any distance by PSOs or acoustically detected within certain distances;
• Establishing minimum visibility and PAM monitoring zones during foundation impact pile driving and detonations of UXO/MECs;
• Requiring use of a double bubble curtain during all foundation pile driving installation activities and UXO/MEC detonations to reduce noise levels to those modeled assuming a broadband 10 decibel (dB) attenuation;
• Requiring sound field verification (SFV) monitoring during pile driving of foundation piles and during UXO/MEC detonations to measure in situ noise levels for comparison against the modeled results and ensure noise levels assuming 10 dB attenuation are not exceeded;
• Requiring SFV during the operational phase of the SouthCoast Project;
• Implementing soft-starts during pile driving and ramp-up during the use of high-resolution geophysical (HRG) marine site characterization survey equipment;
• Requiring various vessel strike avoidance measures;
• Requiring various measures during fisheries monitoring surveys, such as immediately removing gear from the water if marine mammals are considered at-risk of interacting with gear;
• Requiring regular and situational reporting, including, but not limited to, information regarding activities occurring, marine mammal observations and acoustic detections, and sound field verification monitoring results; and
• Requiring monitoring of the North Atlantic right whale sighting networks, Channel 16, and PAM data as well as reporting any sightings to NMFS.

Through adaptive management, NMFS Office of Protected Resources may modify ( e.g., remove, revise, or add to) the existing mitigation, monitoring, or reporting measures summarized above and required by the LOA.

NMFS must withdraw or suspend an LOA issued under these regulations, after notice and opportunity for public comment, if it finds the methods of taking or the mitigation, monitoring, or reporting measures are not being substantially complied with (16 U.S.C. 1371(a)(5)(B); 50 CFR 216.106(e)). Additionally, failure to comply with the requirements of the LOA may result in civil monetary penalties and knowing violations may result in criminal penalties (16 U.S.C. 1375; 50 CFR 216.106(g)).

National Environmental Policy Act (NEPA)

On February 15, 2021, SouthCoast submitted a Construction and Operations Plan (COP) to BOEM for approval to construct and operate the SouthCoast Project, which has been updated several times since, as recently as September 2023. On November 1, 2021, BOEM published in the Federal Register a Notice of Intent (NOI) to prepare an Environmental Impact Statement (EIS) for the COP (86 FR 60270). On February 17, 2023, BOEM published and made its SouthCoast Draft Environmental Impact Statement (DEIS) for Commercial Wind Lease OCS-A 0521 available for public comment for 45 days, February 17, 2023 to April 3, 2023 (88 FR 10377). On April 4, 2023, BOEM extended the public comment period by 15 days through April 18, 2023 (88 FR 19986). Additionally, BOEM held three virtual public hearings on March 20, March 22, and March 27, 2023.

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 potential impacts on the human environment of the proposed action ( i.e., promulgating the regulations and subsequently issuing a 5-year LOA to SouthCoast) and alternatives to that action. Accordingly, NMFS is a cooperating agency on BOEM's Environmental Impact Statement (EIS) and proposes to adopt the EIS, provided our independent evaluation of the document finds that it includes adequate information analyzing the effects on the human environment of promulgating the proposed regulations and issuing the LOA.

Information in the SouthCoast ITA application, this proposed rule, and the BOEM EIS mentioned above collectively provide the environmental information related to proposed promulgation of these regulations and associated LOA for public review and comment. NMFS will review all comments submitted in response to this proposed rulemaking prior to concluding the NEPA process or making a final decision on the request for an ITA. Start Printed Page 53710

Fixing America's Surface Transportation Act (FAST-41)

The SouthCoast 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).

SouthCoast'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-project/​southcoast-wind-energy-llc-southcoast-wind.

Summary of Request

On March 18, 2022, Mayflower Wind Energy LLC (Mayflower 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 the Mayflower Wind Project offshore of Massachusetts in the Lease Area OCS-A-0521. On February 1, 2023, Mayflower Wind notified NMFS that it changed its company name and project name to SouthCoast Wind Energy LLC and SouthCoast Wind Project, respectively. SouthCoast's request is for the incidental, but not intentional, taking of a small number of 16 marine mammal species (comprising 16 stocks) by Level B harassment (for all 16 species or stocks) and by Level A harassment (for four species or stocks). No serious injury or mortality is expected to result from the specified activities, nor is any proposed for authorization.

In response to our questions and comments and following extensive information exchange between SouthCoast and NMFS, SouthCoast submitted revised applications on April 23, June 24, and August 16, 2022, and a final revised application on September 14, 2022, which NMFS deemed adequate and complete on September 19, 2022. On October 17, 2022, NMFS published a notice of receipt (NOR) of SouthCoast's adequate and complete application in the Federal Register (87 FR 62793), requesting comments and soliciting information related to SouthCoast's request during a 30-day public comment period. During the NOR public comment period, NMFS received comment letters from one member of the public, Seafreeze, Ltd, and two environmental non-governmental organizations: Conservation Law Foundation and Oceana. NMFS has reviewed all submitted material and has taken the material into consideration during the drafting of this proposed rule.

Following publication of the NOR (87 FR 62793, October 17, 2022), NMFS further assessed potential impacts of SouthCoast's proposed activities on North Atlantic right whales that utilize foraging habitat within and near the Lease Area and consulted with SouthCoast to develop enhanced mitigation and monitoring measures that would reduce the likelihood of these potential impacts. On March 15, 2024, following extensive information exchange, SouthCoast submitted a North Atlantic Right Whale Enhanced Mitigation Plan and Monitoring Plan and revised application on March 15, 2024, which NMFS accepted on March 19, 2024.

NMFS previously issued two Incidental Harassment Authorizations (IHAs) to Mayflower Wind and one IHA to SouthCoast Wind authorizing the taking of marine mammals incidental to marine site characterization surveys (using HRG equipment) of SouthCoast's Lease Area (OCS-A 0521) (see 85 FR 45578, July 29, 2020; 86 FR 38033, July 19, 2021; 88 FR 31678, May 18, 2023). To date, SouthCoast has complied with all IHA requirements ( e.g., mitigation, monitoring, and reporting). Information regarding SouthCoast's monitoring results, which were utilized in take estimation, 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 promulgated and become effective during the effective period of these proposed regulations (or any other MMPA incidental take authorization), the authorization holder would be required to comply with any and all applicable requirements contained within such final vessel speed 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 such 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 SouthCoast if the measures in such speed rule were to supercede any of the measures in the MMPA authorization.

Description of the Specified Activities

Overview

SouthCoast has proposed to construct and operate an up to 2,400 megawatt (MW) offshore wind energy facility (SouthCoast Project) in state and Federal waters in the Atlantic Ocean in Lease Area OCS-A-0521. This lease area is located within the Massachusetts Wind Energy Area (MA WEA), 26 nautical miles (nm, 48 km) south of Martha's Vineyard and 20 nm (37 km) south of Nantucket, Massachusetts. Development of the offshore wind energy facility would be divided into two projects, each of which would be developed in separate years. Project 1 and Project 2 would occupy the northeastern and southwestern halves (approximately) of the Lease Area, respectively. Each Project would have the potential to generate approximately 1,200 MW of renewable energy. Once operational, SouthCoast would allow the State of Massachusetts to advance Federal and State offshore wind targets as well as reduce greenhouse gas emissions, increase grid reliability, and support economic development and growth in the region.

The SouthCoast Project would consist of several different types of permanent offshore infrastructure: wind turbine generators (WTGs), offshore substation platforms (OSPs), associated WTG and OSP foundations, inter-array and ECCs, and offshore cabling. Onshore substation and converter stations, onshore interconnection routes, and operations and maintenance (O&M) facilities are also planned. There are 149 positions in OSP foundations (totaling no more than 149) would be installed. Start Printed Page 53711 The number of WTG foundations installed would vary by project. SouthCoast has not yet determined the exact number of OSPs necessary to support each project, but the total across projects would not exceed five. Project 1 would include up to 85 WTG foundations, and Project 2 would include up to 73 WTG foundations for a maximum of 147 WTG foundations for both Project 1 and Project 2. Project 1 foundations would be installed in two distinct areas. Subject to extensive mitigation, including extended seasonal restrictions and monitoring, SouthCoast would install up to 54 foundations within the NARW EMA, defined as the northeastern portion of the lease area within 20 km (9.3 mi) of the 30-m (98.4 ft) isobath along the western side of Nantucket Shoals (see Figure 2 in the Specified Geographical Area section for more detail). The remaining foundations for Project 1 (out of a maximum of 85) would be installed in positions immediately southwest of the NARW EMA.

SouthCoast is considering three foundation types for WTGs and OSPs: monopile, piled jacket, and suction-bucket jacket. SouthCoast would install up to two different foundation types for WTGs ( i.e., piled jacket and monopiles), and potentially a third concept for OSPs ( e.g., suction bucket jacket). However, due to economic and technical infeasibility, suction-bucket jackets are no longer under consideration for Project 1. Geotechnical investigations at Project 2 foundation locations are ongoing, and SouthCoast will need to assess the data to determine whether it would be feasible to install suction-bucket jacket foundations, rather than monopile or jacket foundations. However, due to predicted installation complexities, this is not the preferred foundation type. If suction bucket foundations are selected for Project 2, pile driving would not be necessary.

SouthCoast is considering multiple installation scenarios for each project, which differ by foundation type and number, and installation method. For Project 1, SouthCoast plans to install either all monopile WTG (Project 1, Scenario 1; P1S1: 71 WTGs) or pin-piled jacket (Project 1, Scenario 2; P1S2: 85 WTGs) foundations by impact pile driving only. For Project 2, unless suction bucket jackets are selected as the preferred type, foundation installation would also include either all monopile or all piled jacket WTG foundations, which would be installed using impact pile driving only (Project 2, Scenario 1; P2S1: 68 WTGs) or a combination of vibratory and impact (Project 2, Scenario 2; P2S2, 73 WTGs; Project 2 Scenario 3; P2S3 62 WTGs) pile driving. Each WTG and OSP would be supported by a single foundation. OSP monopile or piled jacket foundations would be installed using only impact pile driving. SouthCoast is considering three OSP designs: modular, integrated, and DC-converter. Should they elect to install piled jacket foundations to support OSPs, the number of jacket legs and pin piles would vary depending on the OSP design. SouthCoast currently identifies installation of one DC-converter OSP per project, each supported by a piled jacket foundation, as the most realistic scenario.

Inter-array cables will transmit electricity from the WTGs to the OSP. Export cables would transmit electricity from each OSP to a landfall site. All offshore cables will connect to onshore export cables, substations, and grid connections, which would be located at landfall locations. SouthCoast is proposing to develop one preferred ECC for both Project 1 and Project 2, making landfall and interconnecting to the ISO New England Inc. (ISO-NE) grid at Brayton Point, in Somerset, Massachusetts ( i.e., the Brayton Point Export Cable Corridor (Brayton Point ECC)). For Project 2, SouthCoast is proposing an alternative export cable corridor which, if utilized, would make landfall and interconnect to the ISO-NE grid in the town of Falmouth, MA (the Falmouth ECC) in the event that technical, logistical, grid interconnection, or other unforeseen challenges arise during the design and engineering phase that prevent Project 2 from making interconnection at Brayton Point.

Specified activities would also include temporary installation of up to four nearshore gravity-based structures ( e.g., gravity cell or gravity-based cofferdam) and/or dredged exit pits to connect the offshore export cables to onshore facilities; vessel-based site characterization and assessment surveys using high-resolution geophysical active acoustic sources with frequencies of less than 180 kilohertz (kHz) (HRG surveys); detonation of up to 10 unexploded ordnances or Munitions and Explosives of Concern (UXO/MEC) of different charge weights; several types of fishery and ecological monitoring surveys; site preparation work ( e.g., boulder removal); the placement of scour protected; trenching, laying, and burial activities associated with the installation of the export cable from OSPs to shore-based switching and substations and inter-array cables between turbines; transit within the Lease Area and between ports and the Lease Area to transport crew, supplies, and materials to support pile installation via vessels; and WTG operation.

Based on the current project schedule, SouthCoast anticipates WTGs would become operational for Project 1 beginning in approximately Q2 2029 and Project 2 by Q4 2031, after installation is completed and all necessary components, such as array cables, OSPs, ECCs, and onshore substations are installed. Turbines would be commissioned individually by personnel on location, so the number of commissioning teams would dictate how quickly turbines would become operational. SouthCoast expects that all turbines will be commissioned by Q4 2031.

Marine mammals exposed to elevated noise levels during impact and vibratory pile driving during foundation installation, detonations of UXO/MECs, or HRG surveys may be taken by Level A harassment and/or Level B harassment depending on the specified activity. No serious injury or mortality is anticipated or proposed for authorization.

Dates and Duration

The specified activities would occur over approximately 6 years, starting in the fourth quarter of 2026 and continuing through the end of 2031. SouthCoast anticipates that the specified activities with the potential to result in take by harassment of marine mammals would begin in the second quarter of 2027 and occur throughout all 5 years of the proposed regulations which, if issued, would be effective from April 1, 2027-March 31, 2032.

The general schedule provided in table 1 includes all of the major project components, including those that may result in harassment of marine mammals ( i.e., foundation installation, HRG surveys, and UXO/MEC detonation) and those that are not expected to do so (shown in italics). Projects 1 and 2 will be developed in separate years, which may not be consecutive. To allow flexibility in the final design and during the construction period, SouthCoast has not identified specific years in which each Project would be installed. Start Printed Page 53712

Specific Geographical Region

Most of SouthCoast's specified activities would occur in the Northeast U.S. Continental Shelf Large Marine Ecosystem (NES LME), an area of approximately 260,000 km² (64,247,399.2 acres), spanning from Cape Hatteras in the south to the Gulf of Maine in the north. More specifically, the Lease Area and ECC would be located within the Mid-Atlantic Bight subarea of the NES LME, which extends between Cape Hatteras, North Carolina, and Martha's Vineyard, Massachusetts, and eastward into the Atlantic to the 100-m (328.1 ft) isobath.

The Lease Area and ECCs are located within the Southern New England (SNE) sub-region of the Northeast U.S. Shelf Ecosystem, at the northernmost end of the Mid-Atlantic Bight (MAB), which is distinct from other regions based on differences in productivity, species assemblages and structure, and habitat features (Cook and Auster, 2007). Weather-driven surface currents, tidal mixing, and estuarine outflow all contribute to driving water movement through the area (Kaplan, 2011), which is subjected to highly seasonal variation in temperature, stratification, and productivity. The Lease Area, OCS-A 0521, is part of the Massachusetts Wind Energy Area (MA WEA) (3,007 square kilometers (km² ) (742,974 acres)) (Figure 1). Within the MA WEA, the Lease Area covers approximately 516 km² (127, 388 acres) and is located approximately 30 statute miles (mi) (26 nm; 48 km) south of Martha's Vineyard, Massachusetts, and approximately 23 mi (20 nm, 37 km) south of Nantucket, Massachusetts. At its closest point to land, the Lease Area is approximately 45 mi (39 nm, 72 km) south from the mainland at Nobska Point in Falmouth, Massachusetts.

During construction, the Project will require support from temporary construction laydown yard(s) and construction port(s). The operational phase of the Project will require support from onshore O&M facilities. While a final decision has not yet been made, SouthCoast will likely use more than one marshalling port for the SouthCoast Project. The following ports are under consideration: New Bedford, MA; Fall River, MA; South Quay, RI; Salem Harbor, MA; Port of New London, CT; Port of Charleston, SC; Port of Davisville, RI; Sparrows Point Port, Maryland; and Sheet Harbor, Canada.

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The Brayton Point ECC and the Falmouth ECC would traverse Federal and state territorial waters of Massachusetts and Rhode Island, making landfall at Brayton Point in Somerset, Massachusetts or at Falmouth, Massachusetts, respectively. Within the Brayton Point ECC, up to six submarine offshore export cables, including up to four power cables and up to two dedicated communications cables, would be installed from one or more OSPs within the lease area in Federal waters and run through the Sakonnet River, make intermediate landfall on Aquidneck Island in Portsmouth, Rhode Island, which includes an underground onshore export cable route, and then into Mount Hope Bay to make landfall at Brayton Point in Somerset, Massachusetts. Within the Falmouth export cable corridor, up to five submarine offshore export cables, including up to four power cables and up to one dedicated communications cable, would be installed from one or more OSPs within the Lease Area and run through Muskeget Channel into Nantucket Sound in Massachusetts state waters to Start Printed Page 53714 make landfall in Falmouth, Massachusetts.

As described in further detail below, SouthCoast proposed mitigation and monitoring measures that would apply throughout the Lease Area, as well as enhanced measures applicable to a portion of the Lease Area that overlaps with the NARW EMA. The 30-m (98.4 ft)) isobath represents bathymetry defining the edge of Nantucket Shoals and corresponds with the predicted location of tidal mixing fronts in this region (Simpson and Hunter, 1974; Wilkin, 2006) and observations of high productivity and North Atlantic right whale foraging (Leiter et al., 2017; White et al., 2020).

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Water depths in the project area (which includes the lease area, cable corridors, vessel transit lanes and ensonified area above NMFS thresholds) span from less than 1 meter ((m); 3.28 feet (ft)), near the landfall sites, to approximately 64 m at the deepest location in the lease area. Water depths in the lease area, in relation to Mean Lower Low Water (MLLW), range from approximately 37.1 to 63.5 m (121.7-208.3 ft). Of the 149 foundation locations, 101 are located in waters depths less than 54 m (177 ft) and the remaining 48 are located in water Start Printed Page 53716 depths from 54-64 m (177-210 ft). Water depths along the Brayton Point and Falmouth ECCs range from 0-41.5 m (0-136.2 ft) MLLW. The cable landfall construction areas would be approximately 2.0-10.0 m (6.6-32.8 ft) deep in Somerset and 5.0 to 8.0 m (16.4-26.3 ft) deep in Falmouth.

Geological conditions in the project area, including sediment composition, are the result of glacial processes. The pattern of sediment distribution in the Mid-Atlantic Bight is relatively simple. The continental shelf south of New England is broad and flat, dominated by fine-grained sediments. Sediment composition is primarily dominated by sand, but varies by location, comprising various sand grain sizes sand to silt. Seafloor conditions in the Lease Area align with the findings at nearby locations in the RI/MA and MA WEAs showing little relief and low complexity ( i.e., mostly hom*ogeneous) (section 6.6.1.6.1, SouthCoast Wind COP, 2024; Epsilon, 2018). Data collected as part of SouthCoast's benthic surveys indicate varying levels of surficial sediment mobility throughout the Lease Area and ECCs, evidenced by the ubiquitous presence of bedforms (ripples), both large and small. The deeper shelf waters of the Lease Area and ECCs are characterized by predominantly rippled sand and soft bottoms. Where the Falmouth ECC would enter Muskeget Channel and Nantucket Sound, the surface sediments become coarser sand with gravel and hard bottoms. The coarser sediments represent reworked glacial materials. No large-scale seabed topographic features or bedforms were found within the Lease Area (SouthCoast Wind COP, 2024). Moraine deposits related to the formation of Martha's Vineyard and Nantucket Island have resulted in boulder fields along portions of both ECCs (Baldwin et al., 2016; Oldale, 1980). The Brayton Point ECC also crosses moraine features represented by the Southwest Shoal off Martha's Vineyard and Browns Ledge off the Elizabeth Island in Rhode Island Sound (section 3.1, SouthCoast Wind COP, 2024).

The species that inhabit the benthic habitats of the Lease Area and OCS are typically described as infaunal species, those living in the sediments ( e.g., polychaetes, amphipods, mollusks), and epifaunal species, those living on the seafloor surface (mobile, e.g., sea starts, sand dollars, sand shrimp) or attached to substrates (sessile organisms; e.g., barnacles, anemones, tunicates). These organisms are important food sources for several commercially important northern groundfish species.

The SouthCoast Lease Area is located adjacent to Nantucket Shoals, a broad shallow and sandy shelf that extends southeast of Nantucket Island. Waters from the Gulf of Maine, the Great South Channel, and Nantucket Sound converge in this area, creating a well-mixed water column throughout the year (Limeburner and Beardsley, 1982).

The shoals area has an underwater dunelike topography and strong tidal currents (PCCS, 2005). Surface currents become stronger during the spring and summer as heating and stratification increase (Brookes, 1992; PCCS, 2005). Due to wind and tidal mixing, a persistent tidal front occurs along the western edge of Nantucket Shoals, (Chen et al., 1994a; b). This frontal region typically spans approximately 10-20 km (6.2-12.4 mi) (Potter and Lough, 1987; Lough and Manning, 2001; Ullman and Cornillon, 2001; White and Veit, 2020), with its strength and cross-isobath flow potentially influenced by regional winds (Ullman and Cornillon, 2001). The estimated location of this front varies from the 50-m (164-ft) isobath to inshore of the 30-m (98.4-ft) isobath (Ullman and Cornillon, 2001; Wilkin, 2006).

The ecology of the Nantucket Shoals region is unique in that it supports recurring enhanced aggregations of zooplankton that provide prey for North Atlantic right whales and other species migrating to the region to forage (Quintana-Rizzo et al., 2021). The region is characterized by complex hydrodynamics and ecology. The hydrodynamics of this region result from processes at variable spatial scales that extend from oceanic (Gulf Stream warm core rings) to local (tidal mixing) and timescales of seasonal (stratification) to decadal (National Academy of Sciences (NAS), 2023). The physical oceanographic and bathymetric features ( i.e., shallow, well-lit, well-mixed) provide for year-round high phytoplankton biomass. Strong tidal currents create thorough mixing of the water column, distributing nutrients, which enhances and concentrates productivity of phytoplankton and zooplankton (PCCS, 2005; White et al., 2020). High productivity in the area is also stimulated by a local tidal pump generated by the tidal dissipation between Nantucket Sound and the shoals so significantly that this tidal pump creates one of the largest tidal dispensation areas in New England (Chen et al., 2018; Quintana-Rizzo et al., 2021). Hydrographic features, such as circulation patterns and tides, result in the flow of zooplankton into area from source regions outside, rather than increased primary productivity due to upwelling (Kenney and Wishner, 1995; PCCS, 2005). The persistent frontal zone on the western side of Nantucket Shoals, with an estimated location that varies from the 50-m isobath to inshore of the 30-m (98.4-ft) isobath (Ullman and Cornillon, 2001; Wilkin, 2006), aggregates zooplankton prey whose distributions are dependent on hydrodynamics and frontal features (White et al., 2020). These aggregations not only draw North Atlantic right whales but also other marine vertebrates that forage on the resulting dense prey patches, such as schooling fish and sea ducks and white-winged scooters (Scales et al., 2014; White et al., 2020). The frontal zone is also associated with a wide diversity of mollusk, crustacean, and echinoderm species, as well as surf clams, quahogs, and “intense winter aggregations” of Gammarid amphipods (White et al., 2020).

Detailed Description of Specified Activities

Below, we provide detailed descriptions of SouthCoast's specified 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. For more information beyond that provided here, see SouthCoast's ITA application.

WTG and OSP Foundation Installation

SouthCoast proposes to install a maximum of 149 foundations composed of a combination of up to 147 WTG and up to 5 OSP foundations, conforming to spacing on a 1 nm x 1 nm (1.9 km x 1.9 km) grid layout, oriented east-west and north-south). SouthCoast would be restricted from pile driving in the NARW EMA from October 16 through May 31 and January 1 through May 15 in the remainder of the Lease Area. SouthCoast should avoid pile driving in December ( i.e., it should not be planned), and it may only occur with prior approval by NMFS and implementation of enhanced mitigation and monitoring measures. SouthCoast must notify NMFS in writing by September 1 of that year, indicating that circ*mstances are expected to necessitate pile driving in December.

Project 1 would include installation of up to 86 foundations (85 WTG, 1 OSP), including 54 foundations located within the NARW EMA and up to 32 foundations immediately to the southwest of the NARW EMA. Foundation installation would begin in the northeast portion of the Project 1 Start Printed Page 53717 area (Figure 2) no earlier than June 1, 2028, given NMFS' proposed pile driving seasonal restriction. By installing foundations in this portion of the Project 1 area first (beginning June 1), SouthCoast would begin conducting work closest to Nantucket Shoals and then progressing towards the southwest and moving away from Nantucket Shoals. SouthCoast would complete foundation installations in the NARW EMA by October 15, prior to when North Atlantic right whale occurrence is expected to begin increasing in eastern southern New England ( e.g., Davis et al., 2024). The number of WTG foundations available for Project 2 depends on the final footprint for Project 1, but the combined number for both projects would not exceed 147. SouthCoast would install Project 2 foundations in the portion of the Lease Area southwest of Project 1.

SouthCoast would install foundations using impact pile driving only for Project 1 and a combination of impact and vibratory pile driving for Project 2. Vibratory setting, a technique wherein the pile is initially installed with a vibratory hammer until an impact hammer is needed, is particularly useful when soft seabed sediments, such as those previously described for SouthCoast's project area in the Specified Geographic Region section, are not sufficiently stiff to support the weight of the pile during the initial installation, increasing the risk of `pile run' ( i.e., where a pile sinks rapidly through seabed sediments). Piles subject to pile run can be difficult to recover and pose significant safety risks to the personnel and equipment on the construction vessel. The vibratory hammer mitigates this risk by forming a hard connection to the pile using hydraulic clamps, thereby acting as a lifting/handling tool as well as a vibratory hammer. The tool is inserted into the pile on the construction vessel deck, and the connection made. The pile is then lifted, upended, and lowered into position on the seabed using the vessel crane. After the pile is lowered into position, vibratory pile installation will commence, whereby piles are driven into soil using a longitudinal vibration motion. The vibratory hammer installation method can continue until the pile is inserted to a depth that is sufficient to fully support the structure, and then the impact hammer can be positioned and operated to complete the pile installation. This can be accomplished using a single installation vessel equipped with both hammer types or two separate vessels, each equipped with either the vibratory or impact hammer.

For each Project, SouthCoast expects to install foundations within a 6-month period each year for two years. However, it is possible that foundation installation could continue into a second year for either Project, depending on construction logistics and local and environmental conditions that may influence SouthCoast's ability to maintain the planned construction schedule. Regardless of shifts in the construction schedule, the seasonal restrictions on pile driving would apply.

SouthCoast has proposed to initiate pile driving any time of day or night. Once construction begins, SouthCoast would proceed as rapidly as possible while implementing all required mitigation and monitoring measures, to reduce the total duration of construction. NMFS acknowledges the benefits of completing construction quickly during times when North Atlantic right whales are unlikely to be in the area but also recognizes challenges associated with monitoring during reduced visibility conditions, such as at night. SouthCoast is currently conducting a review of available, systematically collected data on the efficacy of technology to monitor (visually and acoustically) marine mammals during nighttime and in reduced visibility conditions during daytime. Should SouthCoast submit, and NMFS approve, an Alternative Monitoring Plan (which includes nighttime pile driving monitoring), pile driving may be initiated at night.

While the majority of foundation installations would be sequential ( i.e., one at a time), SouthCoast proposed concurrent pile driving ( i.e., two installation vessels installing foundations at the same time) for a small number of foundations, limited to the few days on which both OSP and WTG foundations are installed simultaneously. Using a single installation vessel, SouthCoast anticipates that a maximum of two monopile foundations could be sequentially driven into the seabed per day, assuming 24-hour pile driving operations; however, installation of one monopile per day is expected to be more common and the installation schedule assumed for the take estimation analyses reflects this (table 2). For jacket foundation installation, SouthCoast estimates that no more than four pin piles (supporting one jacket foundation) could be installed per 24 hours on days limited to sequential installation. SouthCoast anticipates that, on days with concurrent pile driving using two installation vessels, up to, 1) two WTG monopiles or four WTG pin piles (by one installation vessel) and, 2) four OSP pin piles (by a second vessel, working simultaneously) could be installed in 24 hours.

As described previously, SouthCoast is considering several foundation options. For Project 1, SouthCoast is considering installation of two types of WTG foundations, monopile or pin-piled jacket, which would be installed by impact pile driving only. SouthCoast is also considering these foundation types for Project 2 but may use a combination of vibratory and/or impact pile driving for their installation. Finally, suction-bucket jacket foundations may provide an alternative to monopile and pin-piled jacket foundations to support WTGs for Project 2. However, installing this third foundation type does not require impact or vibratory pile driving, and it is not anticipated to result in noise levels that would cause harassment to marine mammals. Therefore, suction-bucket jacket foundations are not discussed further beyond the brief explanation below.

Although considering three foundation types for Projects 1 and 2, for the purposes of estimating the maximum impacts to marine mammals that could occur incidental to WTG and OSP foundation installation, SouthCoast assumed WTGs would be supported by monopile or pin-piled jacket foundations and that OSPs would be supported by pin-piled jacket foundations. For both Project 1 and Project 2 acoustic and exposure modeling of the potential acoustic impacts resulting from installation of monopiles and pin piles (see Estimated Take section), SouthCoast proposed multiple WTG and OSP foundation installation scenarios for Projects 1 and 2, distinguished by foundation type and number, installation method ( i.e., impact only; vibratory and impact pile driving), order ( i.e., sequential or concurrent) and construction schedule (table 2). Start Printed Page 53718

As described previously, SouthCoast considered two WTG foundation installation scenarios for Project 1 and one scenario for Project 2 that would employ impact pile driving only (I), and two scenarios for Project 2 that would require a combination of vibratory and impact pile driving (V/I):

• Project 1

○ Scenario 1 (I): 71 monopile WTG, 1 pin-piled jacket OSP

○ Scenario 2 (I): 85 pin-piled jacket WTG, 1 pin-piled jacket OSP

• Project 2

○ Scenario 1 (I): 68 monopile WTG, 1 pin-piled jacket OSP

○ Scenario 2 (V/I): 73 monopile WTG, 1 pin-piled jacket OSP

○ Scenario 3 (V/I): 62 pin-piled jacket WTG, 1 pin-piled jacket OSP

For each Project, only one scenario would be implemented. For example, SouthCoast could choose to install Scenario 1 for Project 1 (P1S1; 71 monopile WTG foundations, 1 pin-piled jacket OSP foundation) and Scenario 1 for Project 2 (P2S1; 68 monopile WTG foundations, 1 pin-piled jacket OSP foundation) for a total of 139 WTG monopile and 2 OSP pin-piled jacket foundations, or 141 foundations overall (table 2). Alternatively, SouthCoast could install Scenario 2 for Project 1 (P1S2; 85 WTG pin-piled jacket foundations, and 1 OSP pin-piled jacket) and Scenario 3 for Project 2 (P2S3; 62 pin-piled jacket foundation, 1 pin-piled jacket OSP foundation), for a total of 147 WTG and 2 OSP foundations (or 149 foundations overall). Both of these combinations fall within SouthCoast's PDE, which specifies that SouthCoast would install no more than up to 147 WTG foundations and up to 5 OSP foundations. Given this limitation, there are Project 2 scenarios that can not be combined with scenarios for Project 1 because the total WTG foundation number would exceed 147 ( i.e., the total number of WTG foundations would be 153 should SouthCoast combine the Project 1 Scenario 2 (85 pin-piled jacket WTG foundations) with Project 2 Scenario 1 (68 monopile WTG foundations) or 158 if combined with Project 2 Scenario 2). Thus, SouthCoast's selection of a scenario for Project 2 will depend on their scenario choice for Project 1.

WTG Foundations

Monopile

SouthCoast proposed three scenarios that include monopile installations to support WTGs. A monopile foundation normally consists of a single steel tubular section with several sections of rolled steel plate welded together. Secondary structures on each WTG monopile foundation would include a boat landing or alternative means of safe access, ladders, a crane, and other ancillary components. Figure 3 in SouthCoast's application provides a conceptual example of a monopile. SouthCoast would install up to 147 WTG monopile foundations with a maximum diameter tapering from 9 m (2.7 ft) above the waterline to 16 m (52.5 ft) below the waterline ( 9/16 -m monopile). A typical impact pile driven monopile installation sequence begins with transport of the monopiles either directly to the Lease Area or to the construction staging port by an installation vessel or a feeding barge. At the foundation location, the main installation vessel upends the monopile in a vertical position in the pile gripper mounted on the side of the vessel. The impact hammer is then lifted on top of the pile and pile driving commences with a 20-minute minimum soft-start, where lower hammer energy is used at the beginning of each pile installation to allow marine mammal and prey to move away from the sound source before noise levels increase to the maximum extent. Piles are driven until the target Start Printed Page 53719 embedment depth is met, then the pile hammer is removed and the monopile is released from the pile gripper. SouthCoast would install WTG monopiles using an impact pile driver with a maximum hammer energy of 6,600 kJ (model NNN 6600) for a total of 7,000 strikes (including soft-start hammer strikes) at a rate of 30 strikes per minute to a total maximum penetration depth of 50 m (164 ft). As described previously, for pile installations utilizing vibratory pile driving as well, this impact installation sequence would be preceded by use of a vibratory hammer to drive the pile to a depth that is sufficient to fully support the structure before beginning the soft-start and subsequent impact hammering. For these piles, SouthCoast would use a vibratory hammer (model HX-CV640) followed by a maximum of 5,000 impact hammer strikes (including soft-start) using the same hammer and parameters specified above.

SouthCoast is proposing to install the majority of monopile foundations consecutively using a single vessel and on a small number of days, concurrently with OSP piled jacket pin piles using two vessels (see Dates and Duration section). Under typical conditions, impact installation of a single monopile foundation is estimated to require up to 4 hours of active impact pile driving (7,000 strikes/30 strikes per minute equals approximately 233 minutes, or 3.9 hours), which can occur either in a continuous 4-hour interval or intermittently over a longer time period. For installations requiring vibratory and impact pile driving, the installation duration is also expected to last approximately 4 hours, beginning with 20 minutes of active vibratory driving, followed by short period during which the hammer set-up would be changed from vibratory to impact, after which impact installation would begin with a 20-minute soft-start (5,000 strikes/30 strikes per minute equals approximately 167 minutes, or 2.8 hours). Following monopile installation completion, SouthCoast anticipates it would then take approximately 4 hours to move to the next piling location. Once at the new location, a 1-hour marine mammal monitoring period would occur such that there would be a minimum of 5 hours between pile installations. Based on this schedule, SouthCoast estimates a maximum of two monopiles could be sequentially driven per day using a single installation vessel, assuming a 24-hour pile driving schedule.

For Project 1 Scenario 1, it is assumed that all 71 WTG monopiles would be installed using only an impact hammer ( i.e., no vibratory pile driving), requiring a maximum of 284 hours (71 WTGs × 4 hours each) of active impact pile driving. Similarly, for Project 2 Scenario 1, it is assumed that all 68 monopiles would be installed using the same approach, for a total of 272 hours of impact hammering. However, for Project 2 Scenario 2, it is assumed that 67 (out of a total of 73) monopiles would be installed using a combination of vibratory and impact pile driving, and 6 monopiles would be installed using only impact pile driving. Installation of all WTG foundations for Project 2 Scenario 2 would require a total of approximately 212 hours (6 WTGs × 4 hours plus 67 WTGs × 2.8 hours each) of impact and 23 hours (67 WTGs × 20 minutes each) of vibratory pile driving.

Pin-Piled Jacket

As an alternative to monopiles, SouthCoast proposed one scenario for each Project (P1S2 and P2S3) that, when combined, would include installation of 147 pin-piled jacket foundations to support WTGs. Jackets are large lattice structures made of steel tubes welded together and supported by securing piles ( i.e., pin piles). Figure 4 of SouthCoast's application provides a conceptual example of this type of foundation. For the SouthCoast Project, each WTG piled jacket foundation would have up to four legs supported by one pin pile per leg, for a total of up to 588 pin piles to support 147 WTGs. Each pin pile would have a maximum diameter of 4.5 m (14.7 ft). Pin-piled jacket foundation installation is a multi-stage process, beginning with preparation of the seabed by clearing any debris. The WTG jacket foundations are expected to be pre-piled, meaning that pin piles would be installed first, and the jacket structure would be set on those pre-installed piles. Once the piled-jacket foundation materials are delivered to the Lease Area, a reusable template would be placed on the prepared seabed to ensure accurate positioning of the pin piles that will be installed to support the jacket. Pin piles would be individually lowered into the template and driven to the target penetration depth using the same approach described for monopile installation. For installations requiring only impact pile driving ( e.g., P1S2), SouthCoast would install pin piles using an impact pile driver with a maximum hammer energy of 3,500 kJ (MHU 3500S) for a total of 4,000 strikes (including soft-start hammer strikes) at a rate of 30 strikes per minute to a maximum penetration depth of 70 m (229.6 ft). When installations require both types of pile driving, this impact pile driving sequence would only begin after SouthCoast utilized a vibratory hammer (S-CV640) to set the pile to a depth providing adequate stability. Subsequent impact hammering (using the same hammer specified) above would require fewer strikes (n=2,667) to drive the pile to the final 70-m maximum penetration depth.

Under typical conditions, impact-only installation (applicable to P1S2, and all OSP pin-piled jacket foundations) of each pin pile is estimated to require approximately 2 hours of active impact pile driving (4,000 strikes/30 strikes per minute equals approximately 133 minutes, or 2.2 hours), for a maximum of 8.8 hours total for a single WTG or OSP pin- piled jacket foundation supported by 4 pin piles. For each pin pile requiring vibratory and impact pile driving (applicable to P2S3 WTG pin-piled jacket foundations only), the installation would begin with 90 minutes of vibratory hammering per pin pile, and would require fewer hammer strikes per pile over a shorter duration compared to impact-only installations (2,667 strikes/30 strikes per minute equals approximately 89 minutes, or 1.5 hours), for a total of 6 hours for each installation method (12 hours total). Pile driving would occur continuously or intermittently, with installations requiring both methods of pile driving punctuated by the time required to change from the vibratory to impact hammer. SouthCoast estimates that they could install a maximum of four pin piles per day, assuming use of a single installation vessel and 24-hour pile driving operations. Following pin pile installations, a vessel would install the jacket to the piles, either directly after the piling vessel completes operations or up to one year later.

For Project 1 Scenario 2, it is assumed that all 85 WTG pin-piled jacket foundations (for a total of 340 pin piles) would be installed using only an impact hammer ( i.e., no vibratory pile driving), requiring a maximum of 680 hours (85 WTGs × 8 hours each) of active impact pile driving. For Project 2 Scenario 3, it is assumed that 48 (out of a total of 62) pin-piled jacket foundations (or 192 out of 248 pin piles) would be installed using a combination of vibratory and impact pile driving, and 14 pin-piled jacket foundations (or 56 pin piles) would be installed using only impact pile driving. Installation of all WTG foundations for Project 2 Scenario 3 would require a total of approximately 184 hours (14 WTGs × 8 hours plus 48 WTGs × 1.5 hours each) of impact and 72 hours (48 WTGs × 90 minutes (or 1.5 hours) each) of vibratory pile driving.

Installation of WTG monopile and pin-piled jacket foundations is Start Printed Page 53720 anticipated to result in take of marine mammals due to noise generated during pile driving. Therefore, SouthCoast has requested, and NMFS proposes to authorize, take by Level A harassment and Level B harassment of marine mammals incidental to this activity.

Suction Bucket

Suction bucket jackets have a similar steel lattice design to the piled jacket described previously, but the connection to the seafloor is different (see Figure 5 in SouthCoast's application for a conceptual example of the WTG suction bucket jacket foundation). These substructures use suction-bucket foundations instead of piles to secure the structure to the seabed; thus, no impact driving would be used for installation of WTG suction bucket jackets. Should SouthCoast select this foundation type for Project 2, each of the suction-bucket jacket substructures, including four buckets per foundation (one per leg), would be installed as described below. Similar to monopiles and pin-piled jackets, the number of suction-bucket jacket foundations will depend on the final design for Project 1. For suction-bucket jackets, the jacket is lowered to the seabed, the open bottom of the bucket and weight of the jacket embeds the bottom of the bucket in the seabed. To complete the installation and secure the foundation, water and air are pumped out of the bucket creating a negative pressure within the bucket, which embeds the foundation buckets into the seabed. The jacket can also be leveled at this stage by varying the applied pressure. The pumps will be released from the suction buckets once the jacket reaches its designed penetration. The connection of the required suction hoses is typically completed using a remotely operated vehicle (ROV).

As previously indicated, installation of suction bucket foundations is not expected to result in take of marine mammals; thus, this activity is not further discussed.

Offshore Substation Platform (OSP)

Each construction scenario SouthCoast defined includes installation of a pin-piled jacket foundation to support a single OSP per Projects 1 and 2, However, in the ITA application, SouthCoast indicates that their project design envelope includes the potential installation of up to a total of 5 OSPs, situated on the same 1 nm x 1 nm (1.9 km x 1.9 km) grid layout as the WTG foundation, and describes three OSP designs ( i.e., modular, integrated, or Direct Current (DC) Converter) that are under consideration (see Figures 6, 7, and 8 in SouthCoast's ITA application). The number of OSPs installed would vary based upon design. Based on the COP PDE, SouthCoast could install a minimum of a single modular OSP on a monopile foundation, and a maximum of five DC Converter OSPs, each with nine pin-piled jacket foundations secured by three pin piles each, for a total of 135 pin piles. All OSP monopile and pin-piled jacket foundations would be installed using only impact pile driving.

Installation of an OSP monopile foundation would follow the same parameters ( e.g., pile diameter, hammer energy, penetration depth) and procedure as previously described for WTG monopiles. OSP piled jacket foundations would be similar to that described for WTG piled jacket foundations but would be installed using a post-piling, rather than pre-piling, installation sequence. In this sequence, the seabed is prepared, the jacket is set on the seafloor, and the piles are driven through the jacket legs to the designed penetration depth (dependent upon which OSP design is selected). The piles are connected to the jacket via grouted and/or swaged connections. A second vessel may perform grouting tasks, freeing the installation vessel to continue jacket installation at a subsequent OSP location, if needed. Pin piles for each jacket design would be installed using an impact hammer with a maximum energy of 3,500 kJ. A maximum of four OSP pin piles could be installed per day using a single vessel, assuming 24-hour pile driving operations. All impact pile driving activity of pin piles would include a 20-minute soft-start at the beginning of each pile installation. Installation of a single OSP piled jacket foundation by impact pile driving (the only proposed method) would vary by design and the associated number of supporting pin piles, each of which would require 2 hours of impact hammering.

The “Modular OSP” design would sit on any one of the three types of substructure designs ( i.e., monopile, piled jacket, or suction bucket) similar in size and weight to those described for the WTGs (see Section 1.1.1 in SouthCoast's ITA application), with the topside connected to a transition piece (TP). This Modular OSP design is an AC solution and will likely hold a single transformer with a single export cable. This option is a relatively small design relative to other options and, thus, has benefits related to manufacture, transportation, and installation. An example of the Modular OSP on a jacket substructure is shown in Figure 6 of SouthCoast's ITR application. The Modular OSP design assumes an OSP topside height ranging from 50 m (164 ft) to 73.9 m (242.5 ft). A Modular OSP piled jacket foundation would be the smallest and include three to four legs with one to two pin piles per leg (three to eight total pin piles per piled jacket). Pin piles would have a diameter of up to 4.5 m (14.7 ft) and would be installed using up to a 3,500-kJ hammer to a target penetration depth of 70 m (229.6 ft) below the seabed.

The “Integrated OSP” design would have a jacket substructure and a larger topside than the Modular OSP. This OSP option is also an AC solution and is designed to support a high number of inter-array cable connections as well as the connection of multiple export cables. This design differs from the Modular OSP in that it is expected to contain multiple transformers and export cables integrated into a single topside. The Integrated OSP design assumes the same topside height indicated for the Modular design. Depending on the final weight of the topside and soil conditions, the jacket substructure may be four- or six-legged and require support from one to three piles per leg (up to 16 pin piles). The larger size of the Integrated OSP would provide housing for a greater number of electrical components as compared to smaller designs (such as the Modular OSP), reducing the number of OSPs required to support the proposed Project. An example of the integrated OSP design is shown in Figure 7 of SouthCoast's ITR application.

SouthCoast may install one or more “DC Converter OSPs.” This OSP option would serve as a gathering platform for inter-array cables and then convert power from high-voltage AC to high-voltage DC or it could be connected to one or more AC gathering units (Modular or Integrated OSPs) and serve to convert power from AC to DC prior to transmission on an export cable. The DC Converter OSP would be installed on a piled jacket foundation with four legs, each supported by three to four 3.9-m (12.8-ft) pin piles per leg (up to 16 total pin piles per jacket), installed using a 3,500-kJ hammer to a target penetration depth of 90 m (295.3 ft) below the seabed. Please see Figure 8 in SouthCoast's ITR application for example of a DC jacket OSP design. Although SouthCoast has not yet selected an OSP design or finalized their foundation installation plan, they anticipate that they would only install only two of the five OSPs included in the PDE, one per Project. Each OSP would be supported by a piled jacket foundation with four legs anchored by Start Printed Page 53721 three to four pin piles (for a total of up to 16 pin piles per OSP piled jacket). SouthCoast plans to install a maximum of four OSP jacket pin piles per day, so an OSP jacket foundation requiring 16 pin piles would be installed over four days (intermittently). For all three OSP piled jacket options (modular, integrated and DC-converter), installation of a single pin pile is anticipated to take up to 2 hours of pile driving. It is anticipated that a maximum of eight pin piles could be driven into the seabed per day assuming 24-hour pile driving operation. Pile driving activity will include a soft-start at the beginning of each pin pile installation. Impacts of pile-driving noise incidental to OSP piled jacket foundation installation have been evaluated based on the use of a 3,500 kJ hammer, as this is representative of the maximum hammer energy included in the PDE.

Installation of OSP foundations is anticipated to result in take of marine mammals due to noise generated during pile driving. Therefore, SouthCoast has requested, and NMFS proposes to authorize, take by Level A harassment and Level B harassment of marine mammals incidental to OSP foundation installation.

HRG Surveys

SouthCoast would conduct HRG surveys to identify any seabed debris and to support micrositing of the WTG and OSP foundations and ECCs. These surveys may utilize active acoustic equipment such as multibeam echosounders, side scan sonars, shallow penetration sub-bottom profilers (SBPs) ( e.g., parametric Compressed High-Intensity Radiated Pulses (CHIRP) SBPs and non-parametric SBP), medium penetration sub-bottom profilers ( e.g., sparkers and boomers), and ultra-short baseline positioning equipment, 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 years versus non-construction years).

HRG surveys will be conducted using up to four vessels. On average, 80-line km (49.7-mi) will be surveyed per vessel each survey day at approximately 5.6 km/hour (3 knots) on a 24-hour basis although some vessels may only operate during daylight hours (~12-hour survey vessels).

During the 2-year construction phase, an estimated 4,000 km (2,485 mi) may be surveyed within the Lease Area and 5,000 km (3,106 mi) along the ECCs in water depth ranging from 2 m (6.5 ft) to 62 m (204 ft). A maximum of four vessels will be used concurrently for surveying. While the final survey plans will not be completed until construction contracting commences, HRG surveys are anticipated to operate at any time of year for a maximum of 112.5 survey days per year.

During non-construction periods (3 of the 5 years within the effective period of the regulations), SouthCoast would survey an estimated 2,800 km (1,7398 mi) in the Lease Area and 3,200 km (1,988.4 mi) along the ECCs each year for three years (n=18,000 km total). Using the same estimate of 80 km (49.7 mi) of surveys completed each day per vessel, approximately 75 days of surveys would occur each year, for a total of up to 225 active sound source days over the 3-year operations period.

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

• 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 Projectvariables. 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 3 identifies all the representative survey equipment that operate 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 geophysical survey activities and is 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., SSS, MBES) and equipment that does not have an acoustic output ( e.g., magnetometers) will also be used but are not discussed further because they are outside the general hearing range of marine mammals likely to occur in the Lease Area and ECCs. No take is expected from the operation of these sources; therefore, they are not discussed further.

Based on the operating frequencies of HRG survey equipment in table 3 and the hearing ranges of the marine mammals that have the potential to occur in the Lease Area and ECCs, HRG survey activities have the potential to result in take by Level B harassment of marine mammals. No take by Level A harassment is anticipated as a result of HRG survey activities.

UXO/MEC Detonations

SouthCoast anticipates encountering UXO/MECs during Project construction in the Lease Area and along the ECCs. UXO/MECs include explosive munitions such as bombs, shells, mines, torpedoes, etc., that did not explode when they were originally deployed or were intentionally discarded in offshore munitions dump sites to avoid land-based detonations. SouthCoast plans to remove any UXO/MEC encountered, else, the risk of incidental detonation associated with conducting seabed-altering activities, such as cable laying and foundation installation in proximity to UXO/MECs, would potentially jeopardize the health and safety of Projectparticipants.

SouthCoast would follow an industry standard As Low as Reasonably Practicable (ALARP) process that minimizes the number of detonations, to the extent possible. For UXO/MECs that are positively identified in proximity to specified activities on the seabed, 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) physical UXO/MEC removal (lift and shift); (3) alternative combustive removal technique (low order disposal); (4) cutting the UXO/MEC open to apportion large ammunition or deactivate fused munitions (cut and capture); or (5) using shaped charges to ignite the explosive materials and allow them to burn at a slow rate rather than detonate instantaneously (deflagration). Only after these alternatives are considered and found infeasible would in-situ high-order UXO/MEC detonation be pursued. If detonation is necessary, detonation noise could result in the take of marine mammals by Level A harassment and Level B harassment.

SouthCoast is currently conducting a study to more accurately determine the number of UXO/MECs that may be encountered during the specified activities (see section 1.1.5 in SouthCoast's ITA application). Based on estimates for other offshore wind projects in southern New England, SouthCoast assumes that up to ten UXO/MEC 454-kg (1000 pounds; lbs) charges, which is the largest charge that is reasonably expected to be encountered, may require in situ detonation. Although it is highly unlikely that all ten charges would weigh 454 kg, this approach was determined to be the most conservative for the purposes of impact analysis. All charged detonations would occur on different days ( i.e., only one detonation would occur per day). In the event that high-order detonation is determined to be the preferred and safest method of disposal, all detonations would occur during daylight hours. SouthCoast proposed a seasonal restriction on UXO/MEC detonations from December 1-April 30, annually.

UXO/MEC activities have the potential to result in take by Level A harassment and Level B harassment of marine mammals. No non-auditory take by Level A harassment is anticipated due to proposed mitigation and monitoring measures.

Cable Landfall Construction

Installation of the SouthCoast export cables at the designated landfall sites will be accomplished using horizontal directional drilling (HDD) methodology. HDD is a “trenchless” process for installing cables or pipes which enables the cables to remain buried below the beach and intertidal zone while limiting environmental impact during installation. Drilling activities would occur on land with the borehole extending under the seabed to an exit point offshore, outside of the intertidal zone. There will be up to two ECCs, both exiting the Lease Area in the northwestern corner. These then split, with one making landfall at Brayton Point in Somerset, MA (Brayton Point ECC) and the other in Falmouth, MA (Falmouth ECC). The Brayton Point ECC is anticipated to contain up to six export cables, bundled where practicable, while the Falmouth ECC is anticipated to contain up to five export cables. HDD seaward exit points will be sited within the defined ECCs at the Brayton Point and intermediate Aquidneck Island landfall sites and at the Falmouth landfall site(s). The exit points will be within approximately 3,500 ft (1,069 m) of the shoreline for the Falmouth ECC landfall(s), and within approximately 1,000 ft (305 m) of the shoreline for the Brayton Point landfalls.

At the seaward exit point, construction activities may include installation of either a temporary gravity-based structure ( i.e., gravity cell or gravity-based cofferdam) or a dredged exit pit, neither of which would require pile driving or hammering. Additionally, a conductor pipe may be installed at the exit point to support the drilling activity. Conductor pipe installation would include pushing or jetting rather than pipe ramming.

For the Falmouth landfall locations, the proposed HDD trajectory is anticipated to be approximately 0.9 mi (1.5 km) in length with a cable burial depth of up to approximately 90 ft (27.4 m) below the seabed. HDD boreholes will be separated by a distance of approximately 33 ft (10 m). Each offshore export cable is planned to require a separate HDD, with an individual bore and conduit for each export cable. The number of boreholes per site will be equal to the number of power cables installed. The Falmouth ECC would include up to four power cables with up to four boreholes at each landfall site. There may be up to one additional communications cable; however, the communications cable would be installed within the same bore as one of the power cables, likely within a separate conduit.

For the Brayton Point and Aquidneck Island intermediate landfall locations, the proposed HDD trajectory is anticipated to be approximately 0.3 mi (0.5 km) in length with a cable burial depth of up to approximately 90 ft (27.4 m) below the seabed. HDD bores will be separated by a distance of approximately 33 ft (10 m). It is anticipated the high-voltage DC cables will be unbundled at landfall. Each high-voltage DC power cable is planned to require a separate HDD, with an individual bore and conduit for each power cable. The Brayton Point and Aquidneck Island ECCs will include up to four power cables for a total of up to four boreholes at each landfall site. Each dedicated communications cable may be installed within the same bore as a power cable, likely within a separate conduit.

In collaboration with the HDD contractor, SouthCoast will further assess the potential use of a dredged exit Start Printed Page 53723 pit and/or gravity cell at each landfall location. The specifics of each site will be evaluated in detail, in terms of soil and metocean conditions ( i.e., current), suitability for maintaining a dredged exit pit for the duration of the HDD construction, and other construction planning factors that may affect the HDD operation.

The relatively low noise levels generated by installation and removal of gravity-cell cofferdams, dredged exit pits, and conductor pipe are not expected to result in Level A harassment or Level B harassment of marine mammals. SouthCoast is not requesting, and NMFS is not proposing to authorize, take associated with landfall construction activities. Therefore, these activities are not analyzed further in this document.

Cable Laying and Installation

Cable burial operations would occur both in the Lease Area for the inter-array cables connecting WTGs to OSPs and in the ECCs for cables carrying power from the OSPs to shore. The offshore export cables would be buried in the seabed at a target depth of up to 1.0 to 4.0 m (3.2 to 13.1 ft) while the inter-array cables would be buried at a target depth up to 1.0 to 2.5 m (3.2 to 8.2 ft). Both cable types would be buried onshore up to the transition joint bays. 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. Cable laying, cable installation, and cable burial activities planned to occur during the construction of the SouthCoast Project May include the following: jetting; vertical injection; leveling; mechanical cutting; plowing (with or without jet-assistance); pre-trenching; boulder removal; and controlled flow excavation. Installation of any required protection at the cable ends is typically completed prior to cable installation from the vessel.

Some dredging may be required prior to cable laying due to the presence of sandwaves. Sandwave clearance may be undertaken to provide a level bottom to install the export cable. The work could be undertaken by traditional dredging methods such as a trailing suction hopper. Alternatively, controlled flow excavation or a water-injection dredger could be used. In some cases, multiple passes may be required. The method of sand wave clearance SouthCoast chooses would be based on the results from the site investigation surveys and cable design.

As the noise levels generated from cable laying and installation work are low, the potential for take of marine mammals to result is discountable. SouthCoast is not requesting, and NMFS is not proposing to authorize, take associated with cable laying activities. Therefore, cable laying activities are not analyzed further in this document.

Vessel Operation

SouthCoast will utilize various types of vessels over the course of the 5-year proposed regulations for surveying, foundation installation, cable installation, WTG and OSP installation, UXO/MEC detonation, and support activities. SouthCoast anticipates operating an average of 15 to 35 vessels daily depending on construction phase, with an expected maximum of 50 vessels in the Lease Area at one time during the foundation installation period. Table 4 provides a list of the vessel types, number of each vessel type, number of expected trips, and anticipated years each vessel type will be in use. All vessels will follow the vessel strike avoidance measures as described in the Proposed Mitigation section.

To support offshore construction, assembly and fabrication, crew transfer and logistics, as well as other operational activities, SouthCoast has identified several existing domestic port facilities located in Massachusetts (Ports of Salem, New Bedford, Fall River), Rhode Island (Ports of Providence and Davisville), Connecticut (Port of New London), and to a lesser extent Maryland (Sparrows Point Port), South Carolina (Port of Charleston), and Texas (Port of Corpus Cristi).

The largest vessels are expected to be used during the foundation installation phase with heavy transport vessels, heavy lift crane vessels, cable laying vessels, supply and crew vessels, and associated tugs and barges transporting construction equipment and materials. A large service operation vessel would have the ability to stay in the lease area and house crews overnight. These larger vessels will generally move slowly over a short distance between work locations, within the Lease Area and along ECCs. Smaller vessels would be used to transfer crew and smaller dimension Project materials to and from, as well as within, the Lease Area. Transport vessels will travel between several ports and the Lease Area over the course of the construction period following mandatory vessel speed restrictions (see Proposed Mitigation section). These vessels will range in size from smaller crew transport to tug and barge vessels. Construction crews responsible for assembling the WTGs would hotel onboard installation vessels at sea, thus limiting the number of crew vessel transits expected during the construction period. WTG and OSP foundation installation vessels may include jack-up, DP, or semi-submersible vessels. Jack-up vessels lower their legs into the seabed for stability and then lift out of the water, whereas DP vessels utilize computer-controlled positioning systems and thrusters to maintain their station. SouthCoast is also considering the use of heavy lift vessels, barges, feeder vessels, and roll-on lift-off vessels to transport WTG components to the Lease Area for installation by the WTG installation vessel. Fabrication and installation vessels may include transport vessels, feeder vessels, jack-up vessels, and installation vessels.

Sounds from vessels associated with the proposed Project are anticipated to be similar in frequency to existing levels of commercial traffic present in the region. Vessel sound would be associated with cable installation vessels and operations, piling installation vessels, and general transit to and from WTG or OSP locations during construction. During construction, it is estimated that multiple vessels may operate concurrently at different locations throughout the Lease Area or ECCs. Some of these vessels may maintain their position (using DP thrusters) during pile driving or other construction activities. The dominant underwater sound source on DP vessels arises from cavitation on the propeller blades of the thrusters (Leggat et al., 1981). The noise power from the propellers is proportional to the number of blades, propeller diameter, and propeller tip speed. Sound levels generated by vessels using DP are dependent on the operational state and weather conditions.

All vessels emit sound from propulsion systems while in transit. The SouthCoast Project would be constructed in an area that consistently experiences extensive marine traffic. As such, marine mammals in the general region are regularly subjected to vessel activity and would potentially be habituated to the associated underwater noise as a result of this exposure (BOEM, 2014b). Because noise from vessel traffic associated with construction activities is likely to be similar to background vessel traffic noise, the potential risk of impacts from vessel noise to marine life is expected to be low relative to the risk of impact from pile-driving sound.

Sound produced through use of DP thrusters is considered a continuous sound source and similar to that Start Printed Page 53724 produced by transiting vessels. DP thrusters are typically operated either in a similarly predictable manner or used intermittently for short durations around stationary activities. Sound produced by DP thrusters would be preceded by and associated with sound from ongoing vessel noise and would be similar in nature. Any marine mammals in the vicinity of the activity would be aware of the vessel's presence, thus making it unlikely that the noise source would elicit a startle response. Construction-related vessel activity, including the use of dynamic positioning thrusters, is not expected to result in take of marine mammals. SouthCoast did not request, and NMFS does not propose to authorize, take associated with vessel activity.

During operations, SouthCoast will use crew transfer vessels (CTVs) and service operations vessels (SOVs). The number of each vessel type, number of trips, and potential ports to be used during operations and maintenance are provided in table 4. The operations vessels will follow the vessel strike avoidance measures as described in the Proposed Mitigation section.

While vessel strikes cause injury or mortality of marine mammals, NMFS does not anticipate such taking to occur from the specified activity due to general low probability and proposed extensive vessel strike avoidance measures (see Proposed Mitigation section). SouthCoast has not requested, and NMFS is not proposing to authorize, take from vessel strikes.

Seabed Preparation

Seabed preparations will be the first offshore activity to occur during the construction phase of the SouthCoast Project, and may include scour ( i.e., erosion) protection, sand leveling, sand wave removal, and boulder removal. Scour protection is the placement of materials on the seafloor around the substructures to prevent the development of scour, or erosion, created by the presence of structures. Each substructure used for WTGs and OSPs may require individual scour protection, thus the type and amount utilized will vary depending on the final substructure type selected for installation. For a substructure that utilizes seabed penetration in the form of piles or suction caissons, the use of scour protectant to prevent scour development results in minimized substructure penetration. Scour protection considered for Projects 1 and 2 may include rock (rock bags), concrete mattresses, sandbags, artificial seaweeds/reefs/frond mats, or self-deploying umbrella systems (typically used for suction-bucket jackets). Installation activities and order of events of scour protection will depend on the type and material used. For rock scour protection, a rock placement vessel may be deployed. A thin layer of filter stones would be placed prior to pile driving activity while the armor rock layer would be installed following completion of foundation installation. Frond mats or umbrella-based structures may be pre-attached to the substructure, in which case the pile and scour protection would be installed simultaneously. For all types of scour protection materials considered, the results of detailed geological campaigns and assessments will support the final decision of the extent of scour protection required. Placement of scour protection may result in suspended sediments and a minor conversion of marine mammal prey benthic habitat conversion of the existing sandy bottom habitat to a hard bottom habitat as well as potential beneficial reef effects (see Section 1.3 of the ITA application).

Seabed preparation may also include leveling, sand wave removal, and boulder removal. SouthCoast may utilize equipment to level the seabed locally in order to use seabed operated cable burial tools to ensure consistent Start Printed Page 53725 burial is achieved. If sand waves are present, the tops may be removed to provide a level bottom to install the export cable. Sand wave removal may be conducted using a trailing suction hopper dredger (or similar), a water injection dredge in shallow areas, or a constant flow excavator. Any boulder discovered in the cable route during pre-installation surveys that cannot be easily avoided by micro-routing may be removed using non-explosive methods such as a grab lift or plow. If deemed necessary, a pre-lay grapnel run will be conducted to clear the cable route of buried hazards along the installation route to remove obstacles that could impact cable installation such as abandoned mooring lines, wires, or fishing equipment. Site-specific conditions will be assessed prior to any boulder removal to ensure that boulder removal can safely proceed. Boulder clearance is a discreet action occurring over a short duration resulting in short term direct effects.

Sound produced by Dynamic Positioning (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 a 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 discreet 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. presence, further reducing the potential for startle or flight responses on the part of marine mammals. Monitoring of past projects that entailed use of DP thrusters has shown a lack of observed marine mammal responses as a result of exposure to sound from DP thrusters (NMFS 2018). As DP thrusters are not expected to result in take of marine mammals, these activities are not analyzed further in this document.

NMFS expects that marine mammals would not be exposed to sounds levels or durations from seafloor preparation work that would disrupt behavioral patterns. Therefore, the potential for take of marine mammals to result from these activities is discountable and SouthCoast did not request, and NMFS does not propose to authorize, any takes associated with seafloor preparation work. These activities are not analyzed further in this document.

NMFS does not expect site preparation work, including boulder removal and sand leveling, to generate noise levels that would cause take of marine mammals. Underwater noise associated with these activities is expected to be similar in nature to the non-impulsive sound produced by the DP cable lay vessels used to install inter-array cables in the Lease Area and export cables along the ECCs. Boulder clearance is a discreet action occurring over a short duration resulting in short term direct effects.

Southcoast did not request take of marine mammals incidental to this activity, and based on the activity, NMFS neither expects nor proposes to authorize take of marine mammals incidental to this activity. Thus, this activity will not be discussed further.

Fisheries and Benthic Monitoring

SouthCoast has developed a fisheries monitoring plan (FMP) focusing on the Lease Area, an inshore FMP that focuses on nearshore portions of the Brayton Point ECC ( i.e., the Sakonnet River), and a benthic monitoring plan that covers both offshore and inshore portions of the Lease Area and ECCs. The fisheries and benthic monitoring plans for the SouthCoast Project were developed following guidance outlined in “Guidelines for Providing Information on Fisheries for Renewable Energy Development on the Atlantic Outer Continental Shelf” (BOEM, 2019) and the Responsible Offshore Science Alliance (ROSA) “Offshore Wind Project Monitoring Framework and Guidelines” (2021).

SouthCoast is working with the University of Massachusetts Dartmouth's School for Marine Science and Technology (SMAST) (in partnership with the Massachusetts Lobstermen's Association) and Inspire Environmental to develop and conduct surveys as a cooperative research program using local fishing vessels and knowledge. SouthCoast intends to conduct their research on contracted commercial and recreational fishing vessels whenever practicable.

Offshore fisheries monitoring will likely include the following types of surveys: trawls, ventless trap, drop camera, neuston net, and acoustic telemetry with tagging of highly migratory species ( e.g., blue sharks). Inshore fisheries monitoring surveys will also include acoustic telemetry targeting commercially and recreationally important fish species ( e.g., striped bass) and trap survey targeting whelk. Benthic monitoring plans are under development and may include grab samples and collection of imagery. Because the gear types and equipment used for the acoustic telemetry study, benthic habitat monitoring, and drop camera monitoring surveys 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. Therefore, only trap and trawl surveys, in general, have the potential to result in harassment to marine mammals. However, based on proposed mitigation and monitoring measures, taking marine mammals from this specified activity is not anticipated. A full description of mitigation and monitoring measures can be found in the Proposed Mitigation and Proposed Monitoring sections.

Given the planned implementation of the mitigation and monitoring measures, SouthCoast did not request, and NMFS is not proposing to authorize, take of marine mammals incidental to research trap and trawl surveys. Any lost gear associated with the fishery surveys will be reported to the NOAA Greater Atlantic Regional Fisheries Office Protected Resources Division (GARFO PRD) as soon as possible. Therefore, take from fishery surveys will not be discussed further.

Description of Marine Mammals in the Specified Geographical Region

Thirty-eight marine mammal species and/or stocks under NMFS' jurisdiction have geographic ranges within the western North Atlantic OCS (Hayes et al., 2023). In the ITA application, SouthCoast identified 31 of those species that could potentially occur in the Lease Area and surrounding waters. However, for reasons described below, SouthCoast has requested, and NMFS proposes to authorize, take of only 16 species (comprising 16 stocks) of marine mammals. Section 4 of SouthCoast's ITA application summarizes available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the species included in SouthCoast's take estimation analyses, except for the Atlantic spotted dolphin as it was unintentionally excluded from this section but included in Section 6 Take Estimates for Marine Mammals. Given previous observations of the species in the RI/MA and MA WEAs, SouthCoast included Atlantic spotted dolphins take analyses (and Table 5), and is requesting Level B harassment take of the species incidental to foundation installation, UXO/MEC detonation, and HRG surveys, which NMFS is proposing for authorization. NMFS fully considered all available information for the Start Printed Page 53726 potentially affected species, and we refer the reader to Section 4 of the ITA application for more details about each species (except the Atlantic spotted dolphin) instead of reprinting the information. A description of Atlantic spotted dolphin distribution, population trends, and life history can be found in the NMFS SAR (Hayes et al., 2019) ( https://media.fisheries.bnoaa.gov/​dam-migration/​2019_​sars_​atlantic_​atlanticbspottedbdolphin.pdf).

Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs; https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​draft-marine-mammal-stock-assessment-reports) and more general information about these species ( e.g., physical and behavioral descriptions) may be found on NMFS' website ( https://www.fisheries.noaa.gov/​find-species).

Of the 31 marine mammal species (comprising 31 stocks) SouthCoast determined have geographic ranges that include the project area, 14 are considered rare or unexpected based on the best scientific information available ( i.e., sighting and distribution data, low predicted densities, and lack of preferred habitat) for a given species. SouthCoast did not request, and NMFS is not proposing to authorize, take of these species and they are not discussed further in this proposed rulemaking: Dwarf and pygmy sperm whales ( Kogia sima and K. breviceps), Cuvier's beaked whale ( Ziphius cavirostris), four species of Mesoplodont beaked whales ( Mesoplodon densitostris, M. europaeus, M. mirus, and M. bidens), killer whale ( Orcinus orca), short-finned pilot whale ( Globicephalus macrohynchus), white-beaked dolphin ( Lagenorhynchus albirotris), pantropical spotted dolphin ( Stenella attenuate), and the, striped dolphin ( Stenella coeruleoalba). Two species of phocid pinnipeds are also uncommon in the project area, including: harp seals ( Pagophilus groenlandica) and hooded seals ( Cystophora cristata).

In addition, the Florida manatee ( Trichechus manatus; a sub-species of the West Indian manatee) has been previously documented as a rare 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.

Table 5 lists all species or stocks for which take is likely and proposed for authorization for this action and summarizes information related to the species or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined as “the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population” (16 U.S.C. 1362(20)). While no mortality is anticipated or proposed for authorization, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species or stocks and other threats.

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, unless noted otherwise, use NMFS' draft 2023 SARs (Hayes et al., 2024) available online at https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​draft-marine-mammal-stock-assessment-reports.

As indicated above, all 16 species and stocks in table 5 temporally and spatially co-occur with the activity to the degree that take is likely to occur. Five of the marine mammal species for which take is requested are listed as endangered under the ESA: North Atlantic right, blue, fin, sei, and sperm whales. In addition to what is included in sections 3 and 4 of SouthCoast's ITA application ( https://www.fisheries.noaa.gov/​action/​incidental-take-authorization-southcoast-wind-llc-construction-southcoast-wind-offshore-wind), the SARs ( https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-stock-assessments), and NMFS' website ( https://www.fisheries.noaa.gov/​species-directory/​marine-mammals), we provide further detail below informing the baseline for select species ( e.g., information regarding current UMEs and known important habitat areas, such as Biologically Important Areas (BIAs; https://oceannoise.noaa.gov/​biologically-important-areas) (Van Parijs et al., 2015)). There are no ESA-designated critical habitats 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 May 20, 2024, four UMEs are active. Below we include information for species that are listed under the ESA, have an active or recently closed UME occurring along the Atlantic coast, or for which there is information available related to areas of biological significance within the project area.

North Atlantic Right Whale

The North Atlantic right whale has been listed as Endangered since the ESA's enactment in 1973. The species was recently uplisted from Endangered to Critically Endangered on the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (Cooke, 2020). The uplisting was due to a decrease in population size (Pace et al., 2017), an increase in vessel strikes and entanglements in fixed fishing gear (Daoust et al., 2017; Davis & Brillant, 2019; Knowlton et al., 2012; Knowlton et al., 2022; Moore et al., 2021; Sharp et al., 2019), and a decrease in birth rate (Pettis et al., 2021; Reed et al., 2022). There is a recovery plan (NOAA Fisheries, 2005) for the North Atlantic right whale and, in November 2022, NMFS completed the 5-year review and concluded that no change to this listing status is warranted. ( https://www.fisheries.noaa.gov/​resource/​document/​north-atlantic-right-whale-5-year-review). Designated by NMFS as a Species in the Spotlight, the North Atlantic right whale is considered among the species with the greatest risk of extinction in the near future ( https://www.fisheries.noaa.gov/​topic/​endangered-species-conservation/​species-in-the-spotlight).

The North Atlantic right whale population had only a 2.8-percent recovery rate between 1990 and 2011 and an overall abundance decline of 23.5 percent from 2011-2019 (Hayes et al., 2023). Since 2010, the North Atlantic right whale population has been in decline; however, the sharp decrease observed from 2015 to 2020 appears to have slowed, though the North Atlantic right whale population continues to experience annual mortalities above recovery thresholds (Pace et al., 2017; Pace et al., 2021; Linden, 2023). North Atlantic right whale calving rates dropped from 2017 to 2020 with zero births recorded during the 2017-2018 season. The 2020-2021 calving season had the first substantial calving increase in 5 years with 20 calves born, followed by 15 calves Start Printed Page 53728 during the 2021-2022 calving season and 12 births in the 2022-2023 calving season. As of May 20, 2024, the 2023-2024 calving season includes 19 births. However, mortalities continue to outpace births, including three calf mortalities/presumed mortalities during the 2024 calving season, and the best estimates indicate fewer than 70 reproductively active females remain in the population (Hayes et al., 2024). North Atlantic right whale total annual mortality and serious injury (M/SI) estimates have fluctuated in recent years, as presented in annual stock assessment reports. The estimate for 2022 (31.2) was a marked increase over the previous year. In the 2022 SARs, Hayes et al., (2023) report the total annual North Atlantic right whale mortality increased from 8.1 (which represents 2016-2020) to 31.2 (which represents 2015-2019), however, this updated estimate also accounted for undetected mortality and serious injury (Hayes et al., 2024). Presently, the best available peer-reviewed population estimate for North Atlantic right whales is 340 per the draft 2023 SARs (Hayes et al., 2024). Approximately, 42 percent of the population is known to be in reduced health (Hamilton et al., 2021) likely contributing to smaller body sizes at maturation, making them more susceptible to threats and reducing fecundity (Moore et al., 2021; Reed et al., 2022; Stewart et al., 2022; Pirotta et al., 2024). Body size is generally positively correlated to reproductive potential. Pirrota et al. (2024) found North Atlantic right whale body size was strongly associated with the probability of giving birth to a calf, such that smaller body size was associated with lower reproductive output. In turn, shorter females that do calve tend to produce offspring with a limited maximum size, likely through a combination of genetics and the influence of body condition during gestation and weaning (Pirotta et al., 2024). When combined with other factors ( e.g., health deterioration due to sublethal effects of entanglement), this feedback loop has led to a decrease in overall body length and fecundity over the past 50 years (Pirotta et al., 2023; Pirotta et al., 2024).

Since 2017, dead, seriously injured, sublethally injured, or ill North Atlantic right whales along the United States and Canadian coasts have been documented, necessitating a UME declaration and investigation. The leading category for the cause of death for this ongoing UME is “human interaction,” specifically from entanglements or vessel strikes. As of May 20, 2024, there have been 39 confirmed mortalities (dead, stranded, or floaters), 1 pending mortality, and 34 seriously injured free-swimming whales for a total of 74 whales. The UME also considers animals with sublethal injury or illness ( i.e., “morbidity”; n=51) bringing the total number of whales in the UME from 71 to 122. More information about the North Atlantic right whale UME is available online at https://www.fisheries.noaa.gov/​national/​marine-life-distress/​2017-2023-north-atlantic-right-whale-unusual-mortality-event.

The project area both spatially and temporally overlaps the migratory corridor BIA, within which a portion of the North Atlantic right whale population migrates 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 within a recently described important feeding area south of Martha's Vineyard and Nantucket, primarily along the western side of Nantucket Shoals (Kraus et al., 2016; O'Brien et al., 2022, Quintano-Rizzo et al., 2021). Finally, the Project overlaps the currently established November 1 through April 30th Block Island Seasonal Management Area (SMA) (73 FR 60173, October 10, 2008) and the proposed November 1 through May 30 Atlantic Seasonal Speed Zone (87 FR 46921, August 1, 2022), which may be used by North Atlantic 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, feeding habitat, SMA), the potential impacts of the proposed SouthCoast project on North Atlantic right whales warrant particular attention.

Recent research indicates that the overall understanding of North Atlantic right whale movement patterns remains incomplete, and not all of the population undergoes a consistent annual migration (Davis et al., 2017; Gowan et al., 2019; Krzystan et al., 2018; O'Brien et al., 2022; Estabrook et al., 2022; Davis et al., 2023; van Parijs et al., 2023). The seasonal migration between northern feeding grounds, mating grounds, and southern calving grounds off Florida and Georgia involves a part of the population while the remaining whales overwinter in other widely distributed areas (Morano et al., 2012, Cole et al., 2013, Bort et al., 2015, Davis et al., 2017). 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 habitat during winter in the years preceding and following the birth of a calf to increase their energy stores (Gowen et al., 2019). O' Brien et al. (2022) hypothesized that North Atlantic right whales might gain an energetic advantage by summertime foraging in southern New England on sub-optimal prey patches rather than engaging in the extensive migration required to access more high-quality prey patches in northern feeding habitats ( e.g., Gulf of St. Lawrence). These observations of transitions in North Atlantic 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).

North Atlantic right whale distribution and demography has been shown to depend on the distribution and density of zooplankton, which varies spatially and temporily. North Atlantic right whales feed on high-density patches of different zooplankton species ( e.g., calanoid copepods, Centrophages spp., Pseudocalanus spp.), but primarily on aggregations of late-stage Calanus finmarchicus, a species whose seasonal availability and distribution has changed both spatially and temporally over the last decade due to an oceanographic regime shift that has ultimately been linked to climate change (Meyer-Gutbrod et al., 2021; Meyer-Gutbrod et al., 2023; Record et al., 2019; Sorochan et al., 2019). This distribution change in prey availability has led to shifts in North Atlantic right whale habitat-use patterns over the same time period (Davis et al., 2020; Meyer-Gutbrod et al., 2022; Quintano-Rizzo et al., 2021; O'Brien et al., 2022) with reduced use of foraging habitats in the Great South Channel and Bay of Fundy and increased use of habitat within Cape Cod Bay (Stone et al., 2017; Mayo et al., 2018; Ganley et al., 2019; Record et al., 2019; Meyer-Gutbrod et al., 2021; O'Brien et al., 2022; Davis et al., 2017). North Atlantic right whales have recolonized areas that have not had large numbers of right whales since the whaling era, likely in response to changes in zooplankton distribution ( e.g., Gulf of St. Lawrence, Simard et al.,Start Printed Page 53729 2019; Nantucket Shoals, e.g., Kraus et al., 2016; Quintana-Rizzo et al., 2021; O'Brien et al., 2022; Davis et al., 2023; Ganley et al., 2022; Van Parijs et al., 2023).

Pendleton et al. (2022) found that peak use of North Atlantic right whale foraging habitat in Cape Cod Bay, north of the Lease Area, has shifted over the past 20 years to later in the spring, likely due to variations in seasonal conditions. However, initial yearly sightings of individual North Atlantic right whales in Cape Cod Bay have started earlier in the year concurrent with climate changes, indicating that their migratory movements between habitats may be cued by changes in regional water temperature (Pendleton et al., 2022). These changes have the potential to lead to temporal misalignment between North Atlantic right whale seasonal arrival to this foraging habitat and the availability of the zooplankton prey (Ganley et al., 2022).

North Atlantic right whale use of habitats such as in the Gulf of St. Lawrence and East Coast mid-Atlantic waters of the U.S. have also increased over time (Davis et al., 2017; Davis and Brillant, 2019; Simard et al., 2019; Crowe et al., 2021; Quintana-Rizzo et al., 2021). Using passive acoustic data collected from 2010-2018 throughout the Gulf of St. Lawrence, a foraging habitat more recently exploited by a significant portion of the population, Simard et al. (2019) documented the presence of North Atlantic right whales for an unexpectedly extended period at four out of the eight recording stations, from the end of April through January, and found that occurrence peaked in the area from August through November each year. In 2015, the mean daily occurrence of North Atlantic right whales in the feeding grounds off Gaspé, located on the west side of the upper Gulf of St. Lawrence, quadrupled compared to 2011-2014 (Simard et al., 2019). However, there is concern that prey biomass in the Gulf of St. Lawrence may be insufficient in most years to support successful reproduction of North Atlantic right whales (Gavrilchuk et al., 2021), which could impel whales to seek out alternative foraging habitats. Based on high-resolution climate models, Ross et al., (2021) projected that the redistribution of North Atlantic right whales throughout the western North Atlantic Ocean will continue at least through the year 2050 (Ross et al., 2021).

Within the past decade in southern New England, increasing year-round observations of North Atlantic right whales have occurred and include documentation of social behaviors and foraging in all seasons, making it the only known winter foraging habitat (Kraus et al., 2016; Leiter et al., 2017; Stone et al., 2017; Quintana-Rizzo et al., 2021; O'Brien et al., 2022; Van Parijs et al., 2023; Davis et al., 2023). Both visual and acoustic lines of evidence demonstrate the year-round presence of North Atlantic right whales in southern New England (Kraus et al., 2016; Quintana-Rizzo et al. 2021; Estabrook et al., 2022; O'Brian et al., 2022; Davis et al., 2023; van Parijs et al., 2023). Right whales were sighted in winter and spring during aerial surveys conducted in the RI/MA and MA WEAs from 2011-2015 and 2017-2019 (Kraus et al., 2016; Quintana-Rizzo et al., 2021; O'Brien et al., 2022). There was not significant variability in sighting rates among years, indicating consistent annual seasonal use of the area by North Atlantic right whales. Despite the lack of visual detection in most summer and fall months, right whales were acoustically detected in 30 out of the 36 recorded months (Kraus et al., 2016). Since 2017, whales have been sighted in southern New England nearly every month with peak sighting rates between late winter and spring. Model outputs in Quintana-Rizzo et al. (2021) suggested that 23 percent of the right whale population is present from December through May, and the mean residence time tripled between 2011-2015 and 2017-2019 to an average of 13 days during these same months.

Based on analyses of PAM data collected at recording sites in the RI/MA and MA WEAs from 2011-2015, Estabrook et al. (2022) report that North Atlantic right whale upcall detections occurred throughout both WEAs in all seasons (during 34 of the 37 surveyed months) but predominantly in the late winter and spring, which aligns with visual observations (Kraus et al., 2016; Quintana-Rizzo et al., 2021). Among the recording locations in southern New England, detections were most frequent on acoustic recorders along the eastern side of the MA WEA (Estabrook et al., 2022). December through April had higher presence while June through September had lower presence. Winter (December-April) had the highest presence (75 percent array-days, n = 193), and summer (June-Sep had the lowest presence (10 percent array-days, n = 27). Spring and autumn were similar, where approximately half of the array-days had upcall detections. The mean daily call rate for days upcalls were detected was highest in January, February, and March, accounting for 72 percent of all detected upcalls, and calling rates were significantly different among seasons (Estabrook et al., 2022). Upcalls were detected on 41 percent of the 1,023 recording days in the MA WEA and on only 24 percent of the recording days in the RI-MA WEA. Similarly, both van Parijs et al. (2023) and. Davis et al. (2023) evaluated a 2020-2022 PAM dataset collected using seven acoustic recorders deployed in the RI/MA and MA WEAs, two deployed on Cox Ledge ( i.e., the northwest side of the RI/MA WEA), four along the eastern side of the MA WEA (along a transect approximately parallel to the 30-m isobath on the west side of Nantucket Shoals, the same bathymetric feature used to define the NARW EMA), and one positioned towards the center of Nantucket Shoals, and noted that North Atlantic right whales were acoustically detected at all seven sites from September through May, with sporadic presence in June through August. Upcalls were detected at each location nearly every week, annually, with detections steadily increasing through October, reaching consistently high levels from November through April, steadily declining in May, and remaining low throughout summer. Upcalls were detected nearly 7 days a week December through March at the two locations nearest the Lease Area along the eastern edge of the MA WEA (NS01 and NS02, see Figures 1 and 2 in Davis et al., 2023). Comprehensively, acoustic and visual observations of North Atlantic right whales in southern New England indicate that whales occur year-round but more frequently in winter and spring and in eastern (versus western) southern New England.

While Nantucket Shoals is not designated as critical North Atlantic right whale habitat, its importance as a foraging habitat is well established (Leiter et al., 2017; Quintana-Rizzo et al., 2021; Estabrook et al., 2022; O'Brien et al., 2022). However, studies focusing on the link between right whale habitat use and zooplankton in the Nantucket Shoals region are limited (National Academy of Sciences, 2003). The supply of zooplankton to the Nantucket Shoals region is dependent on advection from sources outside the Shoals via regional circulation, but zooplankton aggregation is presumably dependent on local physical processes and zooplankton behavior (National Academy of Sciences, 2023). Nantucket Shoals' unique oceanographic and bathymetric features, including the persistent tidal front described in the Specified Geographical Area section, help sustain year-round elevated phytoplankton biomass and aggregate zooplankton prey for North Atlantic right whales (White et Start Printed Page 53730 al., 2020; Quintana-Rizzo et al., 2021). O'Brien et al. (2022) hypothesize that North Atlantic right whale southern New England habitat use has increased in recent years ( i.e., over the last decade) as a result of either, or a combination of, a northward shift in prey distribution (thus increasing local prey availability) or a decline in prey in other abandoned feeding areas ( e.g., Gulf of Maine), both induced by climate change. Pendleton et al. (2022) characterize southern New England as a “waiting room” for North Atlantic right whales in the spring, providing sufficient, although sub-optimal, prey choices while North Atlantic right whales wait for Calanus finmarchicus supplies in Cape Cod Bay (and other primary foraging grounds like the Great South Channel) to optimize as seasonal primary and secondary production progresses. Throughout the year, southern New England provides opportunities for North Atlantic right whales to capitalize on C.finmarchicus blooms or alternative prey ( e.g., Pseudocalanus elongatus and Centropages spp., found in greater concentrations than C.finmarchicus in winter), although likely not to the extent provided seasonally in more well-understood feeding habitats like Cape Cod Bay in late spring or the Great South Channel (O'Brien et al., 2022). Although extensive data gaps, highlighted in a recent report by the National Academy of Sciences (NAS, 2023), have prevented development of a thorough understanding of North Atlantic right whale foraging ecology in the Nantucket Shoals region, it is clear that the habitat was historically valuable to the species, given that the whaling industry capitalized on consistent right whale occurrence there and has again become increasingly so over the last decade.

Humpback Whale

Humpback whales were listed as endangered under the Endangered Species Conservation Act (ESCA) in June 1970. In 1973, the ESA replaced the ESCA, and humpbacks continued to be listed as endangered. On September 8, 2016, NMFS divided the once single species into 14 distinct population segments (DPS), removed the species-level listing, and, in its place, listed four DPSs as endangered and one DPS as threatened (81 FR 62259; September 8, 2016). The remaining nine DPSs were not listed. The West Indies DPS, which is not listed under the ESA, is the only DPS of humpback whales that is expected to occur in the project area. Bettridge et al. (2015) estimated the size of the West Indies DPS population at 12,312 (95 percent confidence interval (CI) 8,688-15,954) whales in 2004-2005, which is consistent with previous population estimates of approximately 10,000-11,000 whales (Stevick et al., 2003; Smith et al., 1999) and the increasing trend for the West Indies DPS (Bettridge et al., 2015).

The project area does not overlap any ESA-designated critical habitat, BIAs, or other important areas for the humpback whales. A humpback whale feeding BIA extends throughout the Gulf of Maine, Stellwagen Bank, and Great South Channel from May through December, annually (LeBrecque et al., 2015). However, this BIA is located further east and north of, and thus, does not overlap the project area.

Kraus et al. (2016) visually observed humpback whales in the RI/MA and MA WEAs and surrounding areas during all seasons, but most frequently during spring and summer months, particularly from April to June. Concurrently collected acoustic data (from 2011 through 2015) indicated 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). Analyzing PAM data collected at six acoustic recording locations from January 2020 through November 2022, van Parijs et al. (2023) assessed daily, weekly, and monthly patterns in humpback whale acoustic occurrence within the RI/MA and MA WEAs, and found patterns similar to those described in Kraus et al. (2016). Humpback whale vocalizations were detected in all months, although most commonly from November through June, annually, at recording sites in eastern southern New England (near Nantucket Shoals) (van Parijs et al. 2023). Detections at recorder locations in western southern New England, near Cox Ledge, were even more frequent than at the eastern southern New England recorder locations, indicating humpback whales were present on a nearly daily basis in all months except September and October.

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, although behavior and bathymetry are factors influencing foraging strategy (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). During winter, the majority of humpback whales from North Atlantic feeding areas (including the Gulf of Maine) mate and calve in the West Indies, where spatial and genetic mixing among feeding groups occurs, though significant numbers of animals are found in mid- and high-latitude regions at this time and some individuals have been sighted repeatedly within the same winter season, indicating that not all humpback whales migrate south every winter (Hayes et al., 2018).

Since January 2016, elevated humpback whale mortalities have occurred along the Atlantic coast from Maine to Florida. This event was declared a UME in April 2017. Partial or full necropsy examinations have been conducted on approximately half of the 212 known cases (as of January 5, 2024). Of the whales examined (approximately 90), about 40 percent had evidence of human interaction either from vessel 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: https://www.fisheries.noaa.gov/​national/​marine-life-distress/​active-and-closed-unusual-mortality-events.

Since December 1, 2022, the number of humpback strandings along the mid-Atlantic coast has been elevated. In some cases, the cause of death is not yet known. In others, vessel strike has been deemed the cause of death. As the humpback whale population has grown, they are seen more often in the Mid-Atlantic. These whales may be following their prey (small fish) which were reportedly close to shore in the 2022-2033 winter. Changing distributions of prey impact larger marine species that depend on them and result in changing distribution of whales and other marine life. These prey also attract fish that are targeted by recreational and commercial fishermen, which increases the number of boats and amount of fishing gear in these areas. This nearshore movement increases the potential for anthropogenic interactions, particularly as the increased presence of whales in areas traveled by boats of all sizes increases the risk of vessel strikes.

Minke Whale

Minke whales are common and widely distributed throughout the U.S. Start Printed Page 53731 Atlantic Exclusive Economic Zone (EEZ) (Cetacean and Turtle Assessment Program (CETAP), 1982; Hayes et al., 2022), although their distribution has a strong seasonal component. Individuals have often been detected acoustically in shelf waters from spring to fall and more often detected in deeper offshore waters from winter to spring (Risch et al., 2013). Minke whales are abundant in New England waters from May through September (Pittman et al., 2006; Waring et al., 2014), yet largely absent from these areas during the winter, suggesting the possible existence of a migratory corridor (LaBrecque et al., 2015). A migratory route for minke whales transiting between northern feeding grounds and southern breeding areas may exist to the east of the Lease Area, as minke whales may track warmer waters along the continental shelf while migrating (Risch et al., 2014). Risch et al. (2014) suggests the presence of a minke whale breeding ground offshore of the southeastern U.S. during the winter.

There are two minke whale feeding BIAs from March through November, annually, identified in the southern and southwestern sections of the Gulf of Maine, including multiple habitats: Georges Bank, the Great South Channel, Cape Cod Bay and Massachusetts Bay, Stellwagen Bank, Cape Anne, and Jeffreys Ledge (LeBrecque et al., 2015). However, these BIAs do not overlap the Lease Area or ECCs, as they are located further east and north.

Although minke whales are sighted in every season in southern New England (O'Brien et al., 2022), minke whale use of the area is highest during the months of March through September (Kraus et al., 2016; O'Brien et al., 2023), and the species is largely absent in the winter (Risch et al., 2013; Hayes et al., 2023). Large feeding aggregations of humpback, fin, and minke whales have been observed during the summer (O'Brien et al., 2023), suggesting southern New England may serve as a supplemental feeding grounds for these species. Aerial survey data indicate that minke whales are the most common baleen whale in the RI/MA & MA WEAs (Kraus et al., 2016; Quintana and Kraus, 2019; O'Brien et al., 2021a, b). Surveys also reported a shift in the greatest seasonal abundance of minke whales from spring (2017-2018) (Quintana and Kraus, 2019) to summer (2018-2019 and 2020-2021) (O'Brien et al., 2021a, b). Through analysis of PAM data collected in southern New England from January 2020 through November 2022, Van Parijs et al. (2023) detected minke whales at all seven passive acoustic recorder deployment sites, primarily from March through June and August through early December. Additional detections occurred in January on Cox Ledge and near the northeast portion of the Lease Area.

Elevated minke whale mortalities detected along the Atlantic coast from Maine through South Carolina resulted in the declaration of an on-going UME in 2017. As of May 20, 2024, a total of 169 minke whales have stranded during this UME. Full or partial necropsy examinations were conducted on more than 60 percent of the whales. Preliminary findings show evidence of human interactions or infectious disease, but these findings are not consistent across all of the minke whales examined, so more research is needed. More information is available at: https://www.fisheries.noaa.gov/​national/​marine-life-distress/​2017-2022-minke-whale-unusual-mortality-event-along-atlantic-coast.

Sei Whale

The Nova Scotia stock of sei whales can be found in deeper waters of the continental shelf edge of the eastern United States and northeastward to south of Newfoundland (Mitchell, 1975; Hain et al., 1985; Hayes et al., 2022). Sei whales have been detected acoustically along the Atlantic Continental Shelf and Slope from south of Cape Hatteras, North Carolina to the Davis Strait, and acoustic occurrence has been increasing in the mid-Atlantic region since 2010 (Davis et al., 2020).

Sei whales are largely planktivorous, feeding primarily on euphausiids and copepods (Hayes et al., 2023). Although their migratory movements are not well understood, sei whales are believed to migrate between feeding grounds in temperate and subpolar regions to wintering grounds in lower latitudes (Kenney and Vigness-Raposa, 2010; Hayes et al., 2020). Through an analysis of PAM data collected from X to X, Davis et al. (2020) determined that peak call detections occurred in northern latitudes during summer, ranging from Southern New England through the Scotian Shelf. During spring and summer, the stock is mainly concentrated in these northern feeding areas, including the Scotian Shelf (Mitchell and Chapman, 1977), the Gulf of Maine, Georges Bank, the Northeast Channel, and south of Nantucket (CETAP, 1982; Kraus et al., 2016; Roberts et al., 2016; Palka et al., 2017; Cholewiak et al., 2018; Hayes et al., 2022). While sei whales generally occur offshore, individuals may also move into shallower, more inshore waters to pursue prey (Payne et al., 1990; Halpin et al., 2009; Hayes et al., 2023).

A sei whale feeding BIA occurs in New England waters from May through November (LaBrecque et al., 2015). This BIA is located over 100 km to the east and north of the project area and is not expected to be impacted by the Project activities.

Persistent year-round detections in southern New England and the New York Bight indicate that sei whales may utilize these habitats to a greater extent than previously thought (Hayes et al., 2023). The results of an analysis of acoustic data collected from January 2020 through November 2022 indicate that sei whale acoustic presence in southern New England peaks in late winter and early spring (February to May), and is otherwise sporadic throughout the rest of the year (van Parijs et al., 2023). Fewer detections occurred at the two sites on Cox Ledge to the west compared to the sites located near the eastern edge of the MA WEA, potentially indicating sei whales prefer specific habitat within southern New England (Figure 1 in van Parijs et al., 2023).

Fin Whale

Fin whales frequently occur in the waters of the U.S. Atlantic Exclusive EEZ, principally from Cape Hatteras, North Carolina northward and are distributed in both continental shelf and deep-water habitats (Hayes et al., 2023). Although fin whales are present north of the 35-degree latitude region in every season and are broadly distributed throughout the western North Atlantic for most of the year, densities vary seasonally (Edwards et al., 2015; Hayes et al., 2023). Observations of fin whales indicate that they 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., 2021). Acoustic detections of fin whale singers augment and confirm these conclusions for males drawn from visual sightings. 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).

New England waters represent a major feeding ground for fin whales. A relatively small fin whale feeding BIA (2,933 km² ), active from March through October, is located approximately 34 km Start Printed Page 53732 to the west of the Lease Area, offshore of Montauk Point, New York (Hain et al., 1992; LaBrecque et al. 2015). A portion of the planned Brayton Point ECC route traces the northeast edge of the BIA. Although the Lease Area does not overlap this BIA, should SouthCoast decide to use vibratory pile driving to install foundations for Project 2, it's possible that the resulting Level B harassment zone may extend into the southeastern edge of the BIA during installation of the foundations on the northwest edge of the Lease Area. A separate larger year-round feeding BIA (18,015 km² ) located far to the northeast in the southern Gulf of Maine does not overlap with the project area and would, thus, not be impacted by project activities.

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. 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). Although fin whales were largely absent from visual surveys in the RI/MA & MA WEAs in the fall and winter months (Kraus et al., 2016), acoustic data indicate that this species is present in the RI/MA & MA WEAs during all months of the year, although to a much lesser extent in summer (Morano et al., 2012; Muirhead et al., 2018; Davis et al., 2020). More recent surveys have documented fin whales throughout winter, spring, and summer (O'Brien et al., 2020; 2021; 2022; 2023) with the greatest abundance occurring during the summer and clustered in the western portion of the WEAs (O'Brien et al., 2023). Most recently, from January 2020 through November 2022, van Parijs et al. (2023) fin whales were acoustically detected at all seven recording sites in southern New England, which included two locations on Cox Ledge (western southern New England) and five locations along the east side of the MA WEA (along the western side of Nantucket Shoals). Similar to observations of humpback whale acoustic occurrence, fin whales were detected more frequently near Cox Ledge than at locations closer to Nantucket Shoals (van Paris et al. (2023). Daily acoustic presence occurred for the majority of the year, most intensively in the fall, yet fin whales were essentially acoustically absent at all recorder locations from April through August (van Parijs et al., 2023). Although fin whale distribution is not fully understood, we expect that this period lacking acoustic detections corresponds to fin whale northward movement in late spring towards higher-latitude foraging grounds.

Blue Whale

Much is unknown about the blue whale populations. The last minimum population abundance was estimated at 402, but insufficient data prevent determining population trends (Hayes et al., 2023). The total level of human caused mortality and serious injury is unknown, but it is believed to be insignificant and approaching a zero mortality and serious injury rate (Hayes et al., 2019). There are no blue whale BIAs or ESA-protected critical habitats identified in the project area or along the U.S. Eastern Seaboard. There is no UME for blue whales.

In the North Atlantic Ocean, blue whales range from the subtropics to the Greenland Sea. The North Atlantic Stock includes animals utilizing mid-latitude (North Carolina coastal and open ocean) to Arctic (Newfoundland and Labrador) waters. Blue whales do not regularly occur within the U.S. EEZ, preferring offshore habitat with water depths of 328 ft (100 m) or more (Waring et al., 2011). The most frequent sightings occur at higher latitudes off eastern Canada in the Gulf of St. Lawrence, with the greatest concentration of this species in the St. Lawrence Estuary (Comtois et al., 2010; Lesage et al., 2007; Hayes et al., 2019). They often are found near the continental shelf edge where upwelling produces concentrations of krill, their main prey species (Yochem and Leatherwood, 1985; Fiedler et al., 1998; Gill et al., 2011).

Blue whales are uncommon in New England coastal waters. Visual surveys conducted in 2018-2020, did not result in any sightings of blue whales in MA and RI/MA WEAs (O'Brien et al., 2021a; O'Brien et al., 2021b). However, Kraus et al. (2016) conducted aerial and acoustic surveys between 2011-2015 in the MA and RI/MA WEAs and surrounding areas and, although blue whales were not visually observed, they were infrequently acoustically detected during winter. A 2008 study detected blue whale calls in offshore areas of the New York Bight, south of southern New England, on 28 out of 258 days of recordings (11 percent of recording days), mostly during winter (Muirhead et al., 2018). Van Paris et al. (2023) detected a small number of blue whale calls in southern New England in January and February, although the species was otherwise acoustically absent. Given the long-distance propagation characteristics of low-frequency blue whale vocalizations, it's possible blue whale calls detected in southern New England originated from distant whales. Together, these data suggest that blue whales are rarely present in the MA and RI/MA WEAs.

Sperm Whale

Sperm whales can be found throughout the world's oceans. They can be found near the edge of the ice pack in both hemispheres and are also common along the equator. The North Atlantic stock is distributed mainly along the continental shelf-edge, over the continental slope, and mid-ocean regions, where they prefer water depths of 600 m (1,969 ft) or more and are less common in waters <300 m (984 ft) deep (Waring et al., 2015; Hayes et al., 2020). In the winter, sperm whales are observed east and northeast of Cape Hatteras. In the spring, sperm whales are more widely distributed throughout the Mid-Atlantic Bight and southern portions of George's Bank (Hayes et al., 2020). In the summer, sperm whale distribution is similar to the spring, but they are more widespread in Georges Bank and the Northeast Channel region and are also observed inshore of the 100-m (328-ft) isobath south of New England (Hayes et al., 2020). Sperm whale occurrence on the continental shelf in areas south of New England is at its highest in the fall (Hayes et al., 2020). Between April 2020 and December 2021, there was 1 sighting of 2 individual sperm whales recorded during HRG surveys conducted within the area surrounding the Lease Area and Falmouth ECC.

Kraus et al. (2016) observed sperm whales four times in the RI/MA and MA WEAs and surrounding areas in the summer and fall during the 2011-2015 NLPSC aerial survey. Sperm whales, traveling singly or in groups of three or four, were observed three times in August and September of 2012, and once in June of 2015. Effort-weighted average sighting rates could not be calculated. The frequency of sperm whale clicks exceeded the maximum frequency of PAM equipment used in the Kraus et al. (2016) study, so no acoustic data are available for this species from that study. Sperm whales were observed only once in the MA WEA and nearby waters during the 2010-2017 AMAPPS surveys (NEFSC and SEFSC 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018). This occurred during a summer shipboard survey in 2016. Start Printed Page 53733

Phocid Seals

Harbor and gray seals have experienced two UMEs since 2018, although one was recently closed (2022 Pinniped UME in Maine) and closure of the second, described here, 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 were conducted on some of the seals and samples were collected for testing. Based on tests conducted thus far, the main pathogen found in the seals is phocine distemper virus. NMFS is performing additional testing to identify any other factors that may be involved in this UME, which is pending closure. Information on this UME is available online at: https://www.fisheries.noaa.gov/​new-england-mid-atlantic/​marine-life-distress/​2018-2020-pinniped-unusual-mortality-event-along.

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. 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.

The pinniped functional hearing group was modified from Southall et al. (2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (Hemilä et al., 2006; Kastelein et al., 2009; Reichmuth and Holt, 2013). For more detail concerning these groups and associated frequency ranges, please see NMFS (2018) for a review of available information.

NMFS notes that in 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.

Acoustic Habitat

Acoustic habitat is defined as distinguishable soundscapes inhabited by individual animals or assemblages of species, inclusive of both the sounds they create and those they hear (NOAA, 2016). All of the sound present in a particular location and time, considered as a whole, comprises a “soundscape” (Pijanowski et al., 2011). When examined from the perspective of the animals experiencing it, a soundscape may also be referred to as “acoustic habitat” (Clark et al., 2009, Moore et al., 2012, Merchant et al., 2015). High value acoustic habitats, which vary spectrally, spatially, and temporally, support critical life functions (feeding, breeding, and survival) of their inhabitants. Thus, it is important to consider acute ( e.g., stress or missed feeding/breeding opportunities) and chronic effects ( e.g., masking) of noise on important acoustic habitats. Effects that accumulate over long periods can ultimately result in detrimental impacts on the individual, stability of a population, or ecosystems that they inhabit.

Potential Effects of the Specified Activities on Marine Mammals and Their Habitat

This section includes a summary and discussion of the ways that components of the specified activity may impact marine mammals and their habitat. The Estimated Take 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 Specified Geographical Area section). Here, the potential effects of sound on marine mammals are discussed. Start Printed Page 53734

SouthCoast has requested, and NMFS proposes to authorize, the take of marine mammals incidental to the construction activities associated with the SouthCoast project. In their application, SouthCoast presented their analyses of potential impacts to marine mammals from the specified activities. NMFS carefully reviewed the information provided by SouthCoast and also independently reviewed applicable scientific research and literature and other information to evaluate the potential effects of SouthCoast's specified activities on marine mammals.

The proposed activities would result in the construction and placement of up to 149 permanent foundations (up to 147 WTGs; up to 5 OSPs) in the marine environment. Up to 10 UXO/MEC detonations may occur during construction if any found UXO/MEC cannot be removed by other means. There are a variety of types and degrees of effects to marine mammals, prey species, and habitat that could occur as a result of SouthCoast's specified activities. Below, we provide a brief description of the types of sound sources that would be generated by the project, the general impacts from these types of activities, and an analysis of the anticipated impacts on marine mammals from SouthCoast's specified activities, with consideration of select proposed mitigation measures.

Description of Sound Sources

This section contains a brief technical background on sound, on the characteristics of certain sound types, and on metrics used in this proposal inasmuch as the information is relevant to the specified activity and to a discussion of the potential effects of the specified activity on marine mammals found later in this document. For general information on sound and its interaction with the marine environment, please see Au and Hastings (2008), Richardson et al. (1995), Urick (1983), as well as the Discovery of Sound in the Sea (DOSITS) website at https://dosits.org/​.

Sound is a vibration that travels as an acoustic wave through a medium such as a gas, liquid or solid. Sound waves alternately compress and decompress the medium as the wave travels. These compressions and decompressions are detected as changes in pressure by aquatic life and man-made sound receptors such as hydrophones (underwater microphones). In water, sound waves radiate in a manner similar to ripples on the surface of a pond and may be either directed in a beam (narrow beam or directional sources) or sound beams may radiate in all directions (omnidirectional sources).

Sound travels in water more efficiently than almost any other form of energy, making the use of acoustics ideal for the aquatic environment and its inhabitants. In seawater, sound travels at roughly 1,500 meters per second (m/s). In-air, sound waves travel much more slowly, at about 340 m/s. However, the speed of sound can vary by a small amount based on characteristics of the transmission medium, such as water temperature and salinity.

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 1,000-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 μPa. The amplitude of a sound can be presented in various ways; however, NMFS typically considers three metrics. In this proposed rule, all decibel levels referenced to 1μPa.

Sound exposure level (SEL) represents the total energy in a stated frequency band over a stated time interval or event and considers both amplitude and duration of exposure (represented as dB re 1 μPa² -s). SEL is a cumulative metric; it can be accumulated over a single pulse (for pile driving this is often referred to as single-strike SEL; SEL_ss) or calculated over periods containing multiple pulses (SEL_cum). Cumulative SEL represents the total energy accumulated by a receiver over a defined time window or during an event. The SEL metric is useful because it allows sound exposures of different durations to be related to one another in terms of total acoustic energy. The duration of a sound event and the number of pulses, however, should be specified as there is no accepted standard duration over which the summation of energy is measured.

Sound is generally defined using common metrics. Root mean square (rms) is the quadratic mean sound pressure over the duration of an impulse. Root mean square is calculated by squaring all of the sound amplitudes, averaging the squares, and then taking the square root of the average (Urick, 1983). Root mean square accounts for both positive and negative values; squaring the pressures makes all values positive so that they may be accounted for in the summation of pressure levels (Hastings and Popper, 2005). This measurement is often used in the context of discussing behavioral effects, in part because behavioral effects, which often result from auditory cues, may be better expressed through averaged units than by peak pressures. Peak sound pressure (also referred to as zero-to-peak sound pressure or 0-pk) is the maximum instantaneous sound pressure measurable in the water at a specified distance from the source, and is represented in the same units as the rms sound pressure. Along with SEL, this metric is used in evaluating the potential for PTS (permanent threshold shift) and TTS (temporary threshold shift). Peak pressure 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. Thes impulse metric 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, 2019a) for an in-depth discussion of these concepts. Impulsive sound sources ( e.g., airguns, explosions, gunshots, sonic booms, impact pile driving) produce signals that are brief (typically considered to be less than one second), broadband, atonal transients (American National Standards Institute (ANSI), 1986, 2005; Harris, 1998; National Institute for Occupational Start Printed Page 53735 Safety and Health (NIOSH), 1998; International Organization for Standardization (ISO, 2003)) and occur either as isolated events or repeated in some succession. Impulsive sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a rapid decay period that may include a period of diminishing, oscillating maximal and minimal pressures, and generally have an increased capacity to induce physical injury as compared with sounds that lack these features. Impulsive sounds are typically intermittent in nature.

Non-impulsive sounds can be tonal, narrowband, or broadband, brief or prolonged, and may be either continuous or intermittent (ANSI, 1995; NIOSH, 1998). Some of these non-impulsive sounds can be transient signals of short duration but without the essential properties of pulses ( e.g., rapid rise time). Examples of non-impulsive sounds include those produced by vessels, aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems.

Sounds are also characterized by their temporal component. Continuous sounds are those whose sound pressure level remains above that of the ambient sound with negligibly small fluctuations in level (NIOSH, 1998; ANSI, 2005) while intermittent sounds are defined as sounds with interrupted levels of low or no sound (NIOSH, 1998). NMFS identifies Level B harassment thresholds based on if a sound is continuous or intermittent.

Even in the absence of sound from the specified activity, the underwater environment is typically loud due to ambient sound, which is defined as environmental background sound levels lacking a single source or point (Richardson et al., 1995). The sound level of a region is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical ( e.g., wind and waves, earthquakes, ice, atmospheric sound), biological ( e.g., sounds produced by marine mammals, fish, and invertebrates), and anthropogenic ( e.g., vessels, dredging, construction) sound. A number of sources contribute to ambient sound, including wind and waves, which are a main source of naturally occurring ambient sound for frequencies between 200 Hz and 50 kHz (International Council for the Exploration of the Sea (ICES), 1995). In general, ambient sound levels tend to increase with increasing wind speed and wave height. Precipitation can become an important component of total sound at frequencies above 500 Hz and possibly down to 100 Hz during quiet times. Marine mammals can contribute significantly to ambient sound levels as can some fish and snapping shrimp. The frequency band for biological contributions is from approximately 12 Hz to over 100 kHz. Sources of ambient sound related to human activity include transportation (surface vessels), dredging and construction, oil and gas drilling and production, geophysical surveys, sonar, and explosions. Vessel noise typically dominates the total ambient sound for frequencies between 20 and 300 Hz. In general, the frequencies of anthropogenic sounds are below 1 kHz, and if higher frequency sound levels are created, they attenuate rapidly.

The sum of the various natural and anthropogenic sound sources that comprise ambient sound at any given location and time depends not only on the source levels (as determined by current weather conditions and levels of biological and human activity) but also on the ability of sound to propagate through the environment. In turn, sound propagation is dependent on the spatially and temporally varying properties of the water column and sea floor and is frequency-dependent. As a result of the dependence on a large number of varying factors, ambient sound levels can be expected to vary widely over both coarse and fine spatial and temporal scales. Sound levels at a given frequency and location can vary by 10-20 dB from day to day (Richardson et al., 1995). The result is that, depending on the source type and its intensity, sound from the specified activity may be a negligible addition to the local environment or could form a distinctive signal that may affect marine mammals. Human-generated sound is a significant contributor to the acoustic environment in the Project location.

Potential Effects of Underwater Sound on Marine Mammals

Anthropogenic sounds cover a broad range of frequencies and sound levels and can have a range of highly variable impacts on marine life from none or minor to potentially severe responses depending on received levels, duration of exposure, behavioral context, and various other factors. Broadly, underwater sound from active acoustic sources, such as those that would be produced by SouthCoast's activities, 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; Erbe et al., 2016, 2019). 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). 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; Siebert et al., 2022).

In general, the degree of effect of an acoustic exposure is intrinsically related to the signal characteristics, received level, distance from the source, and duration of the sound exposure, in addition to the contextual factors of the receiver ( e.g., behavioral state at time of exposure, age class, etc.). In general, sudden, high level sounds can cause hearing loss as can longer exposures to lower level sounds. Moreover, any temporary or permanent loss of hearing will occur almost exclusively for noise within an animal's hearing range. We describe below the specific manifestations of acoustic effects that may occur based on the activities proposed by SouthCoast.

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. Start Printed Page 53736

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

Hearing Threshold Shift

Marine mammals exposed to high-intensity sound or to lower-intensity sound for prolonged periods can experience hearing threshold shift (TS), which NMFS defines as a change, usually an increase, in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level expressed in decibels (NMFS, 2018). Threshold shifts can be permanent, in which case there is an irreversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range or temporary, in which there is reversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range and the animal's hearing threshold would fully recover over time (Southall et al., 2019a). Repeated sound exposure that leads to TTS could cause PTS.

When PTS occurs, there can be physical damage to the sound receptors in the ear ( i.e., tissue damage) whereas TTS represents primarily tissue fatigue and is reversible (Henderson et al., 2008). In addition, other investigators have suggested that TTS is within the normal bounds of physiological variability and tolerance and does not represent physical injury ( e.g., Ward, 1997; Southall et al., 2019a). Therefore, NMFS does not consider TTS to constitute auditory injury.

Relationships between TTS and PTS thresholds have not been studied in marine mammals, and there is no PTS data for cetaceans. However, such relationships are assumed to be similar to those in humans and other terrestrial mammals. Noise exposure can result in either a permanent shift in hearing thresholds from baseline (PTS; a 40-dB threshold shift approximates a PTS onset; e.g., Kryter et al., 1966; Miller, 1974; Henderson et al., 2008) or a temporary, recoverable shift in hearing that returns to baseline (a 6-dB threshold shift approximates a TTS onset; e.g., Southall et al., 2019a). Based on data from terrestrial mammals, a precautionary assumption is that the PTS thresholds, expressed in the unweighted peak sound pressure level metric (PK), for impulsive sounds (such as impact pile driving pulses) are at least 6 dB higher than the TTS thresholds and the weighted PTS cumulative sound exposure level thresholds are 15 (impulsive sound) to 20 (non-impulsive sounds) dB higher than TTS cumulative sound exposure level thresholds (Southall et al., 2019a). Given the higher level of sound or longer exposure duration necessary to cause PTS as compared with TTS, PTS is less likely to occur as a result of these activities, 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 a l., 2002). While experiencing TTS, the hearing threshold rises, and a sound must be at a higher level in order to be heard. In terrestrial and marine mammals, TTS can last from minutes or hours to days (in cases of strong TTS). In many cases, hearing sensitivity recovers rapidly after exposure to the sound ends. There is data on sound levels and durations necessary to elicit mild TTS for marine mammals, but recovery is complicated to predict and dependent on multiple factors.

Marine mammal hearing plays a critical role in communication with conspecifics, and interpretation of environmental cues for purposes such as predator avoidance and prey capture. Depending on the degree (elevation of threshold in dB), duration ( i.e., recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious depending on the degree of interference with marine mammals hearing. For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that occurs during a time where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical ( e.g., for successful mother/calf interactions, consistent detection of prey) could have more serious impacts.

Currently, TTS data only exist for four species of cetaceans (bottlenose dolphin, beluga whale ( Delphinapterus leucas), harbor porpoise, and Yangtze finless porpoise ( 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, 2016b, 2016c; Finneran, 2018;, Nachtigall et al., 2018). These studies suggest that captive animals have a mechanism to reduce hearing sensitivity prior to impending loud sounds. Hearing change was observed to be frequency dependent and Finneran (2018) suggests hearing attenuation occurs within the cochlea or auditory nerve. Based on these observations on captive odontocetes, the authors suggest that wild animals may have a mechanism to self-mitigate the impacts of noise exposure by dampening their hearing during prolonged exposures of loud sound, or if conditioned to anticipate intense sounds (Finneran, 2018; Nachtigall et al., 2018).

Behavioral Effects

Exposure of marine mammals to sound sources can result in, but is not limited to, no response or any of the following observable responses: increased alertness; orientation or attraction to a sound source; vocal modifications; cessation of feeding; cessation of social interaction; alteration of movement or diving behavior; habitat abandonment (temporary or permanent); and, in severe cases, panic, flight, stampede, or stranding, potentially resulting in death (Southall et al., 2007). A review of marine mammal responses to anthropogenic sound was first conducted by Richardson (1995). More recent reviews address studies conducted since 1995 and focused on observations where the received sound level of the exposed marine mammal(s) was known or could be estimated Nowacek et al., 2007; DeRuiter et al.,Start Printed Page 53737 2013; Ellison et al., 2012; Gomez et al., 2016; Southall et al., 2021; Gomez et al. 2016). Gomez et al. (2016) conducted a review of the literature considering the contextual information of exposure in addition to received level and found that higher received levels were not always associated with more severe behavioral responses and vice versa. Southall et al. (2021) states that results demonstrate that some individuals of different species display clear yet varied responses, some of which have negative implications while others appear to tolerate high levels and that responses may not be fully predictable with simple acoustic exposure metrics ( e.g., received sound level). Rather, the authors state that differences among species and individuals along with contextual aspects of exposure ( e.g., behavioral state) appear to affect response probability.

Behavioral responses to sound are highly variable and context-specific. Many different variables can influence an animal's perception of and response to (nature and magnitude) an acoustic event. An animal's prior experience with a sound or sound source affects whether it is less likely (habituation) or more likely (sensitization) to respond to certain sounds in the future (animals can also be innately predisposed to respond to certain sounds in certain ways) (Southall et al., 2019a). Related to the sound itself, the perceived nearness of the sound, bearing of the sound (approaching versus retreating), the similarity of a sound to biologically relevant sounds in the animal's environment ( i.e., calls of predators, prey, or conspecifics), and familiarity of the sound may affect the way an animal responds to the sound (Southall et al., 2007, DeRuiter et al., 2013). Individuals (of different age, gender, reproductive status, etc.) among most populations will have variable hearing capabilities, and differing behavioral sensitivities to sounds that will be affected by prior conditioning, experience, and current activities of those individuals. Often, specific acoustic features of the sound and contextual variables ( i.e., proximity, duration, or recurrence of the sound or the current behavior that the marine mammal is engaged in or its prior experience), as well as entirely separate factors such as the physical presence of a nearby vessel, may be more relevant to the animal's response than the received level alone.

Overall, the variability of responses to acoustic stimuli depends on the species receiving the sound, the sound source, and the social, behavioral, or environmental contexts of exposure ( e.g., DeRuiter and Doukara, 2012). For example, Goldbogen et al. (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. (2013a) study that were engaged in shallow feeding behavior demonstrated no clear changes in diving or movement even when received levels were high (~160 dB re 1µPa) for exposures to 3-4 kHz sonar signals, while deep feeding and non-feeding whales showed a clear response at exposures at lower received levels of sonar and pseudorandom noise. Southall et al. (2011) found that blue whales had a different response to sonar exposure depending on behavioral state, more pronounced when deep feeding/travel modes than when engaged in surface feeding.

With respect to distance influencing disturbance, DeRuiter et al. (2013) examined behavioral responses of Cuvier's beaked whales to mid-frequency sonar and found that whales responded strongly at low received levels (89-127 dB re 1m Pa)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 (2.1-5.9 mi) away. Importantly, this study also showed that whales exposed to a similar range of received levels (78-106 dB re 1m Pa) from distant sonar exercises (118 km (73 mi) away) did not elicit such responses, suggesting that context may moderate reactions. Thus, distance from the source is an important variable in influencing the type and degree of behavioral response and this variable is independent of the effect of received levels ( e.g., DeRuiter et al., 2013; Dunlop et al., 2017a, 2017b; Falcone et al., 2017; Dunlop et al., 2018; Southall et al., 2019b).

Ellison et al. (2012) outlined an approach to assessing the effects of sound on marine mammals that incorporates contextual-based factors. The authors recommend considering not just the received level of sound but also the activity the animal is engaged in at the time the sound is received, the nature and novelty of the sound ( i.e., is this a new sound from the animal's perspective), and the distance between the sound source and the animal. They submit that this “exposure context,” as described, greatly influences the type of behavioral response exhibited by the animal. Forney et al. (2017) also point out that an apparent lack of response ( e.g., no displacement or avoidance of a sound source) may not necessarily mean there is no cost to the individual or population, as some resources or habitats may be of such high value that animals may choose to stay, even when experiencing stress or hearing loss. Forney et al. (2017) recommend considering both the costs of remaining in an area of noise exposure such as TTS, PTS, or masking, which could lead to an increased risk of predation or other threats or a decreased capability to forage, and the costs of displacement, including potential increased risk of vessel strike, increased risks of predation or competition for resources, or decreased habitat suitable for foraging, resting, or socializing. This sort of contextual information is challenging to predict with accuracy for ongoing activities that occur over large spatial and temporal expanses. However, distance is one contextual factor for which data exist to quantitatively inform a take estimate, and the method for predicting Level B harassment in this rule does consider distance to the source. Other factors are often considered qualitatively in the analysis of the likely consequences of sound exposure, where supporting information is available.

Behavioral change, such as disturbance manifesting in lost foraging time, in response to anthropogenic activities is often assumed to indicate a biologically significant effect on a population of concern. However, individuals may be able to compensate for some types and degrees of shifts in behavior, preserving their health and thus their vital rates and population dynamics. For example, New et al. (2013) developed a model simulating the complex social, spatial, behavioral and motivational interactions of coastal bottlenose dolphins in the Moray Firth, Scotland, to assess the biological significance of increased rate of behavioral disruptions caused by vessel traffic. Despite a modeled scenario in which vessel traffic increased from 70 to 470 vessels a year (a six-fold increase in vessel traffic) in response to the construction of a proposed offshore renewables' facility, the dolphins' behavioral time budget, spatial distribution, motivations and social structure remained unchanged. Similarly, two bottlenose dolphin populations in Australia were also modeled over 5 years against a number of disturbances (Reed et al., 2020) and results indicate that habitat/noise disturbance had little overall impact on population abundances in either Start Printed Page 53738 location, even in the most extreme impact scenarios modeled.

Friedlaender et al. (2016) provided the first integration of direct measures of prey distribution and density variables incorporated into across-individual analyses of behavior responses of blue whales to sonar, and demonstrated a five-fold increase in the ability to quantify variability in blue whale diving behavior. When the prey field was mapped and used as a covariate in examining how behavioral state of blue whales is influenced by mid-frequency sound, the response in blue whale deep-feeding behavior was even more apparent, reinforcing the need for contextual variables to be included when assessing behavioral responses (Friedlaender et al., 2016). These results illustrate that responses evaluated without such measurements for foraging animals may be misleading, which again illustrates the context-dependent nature of the probability of response.

The following subsections provide examples of behavioral responses that give an idea of the variability in behavioral responses that would be expected given the differential sensitivities of marine mammal species to sound, contextual factors, and the wide range of potential acoustic sources to which a marine mammal may be exposed. Behavioral responses that could occur for a given sound exposure should be determined from the literature that is available for each species, or extrapolated from closely related species when no information exists, along with contextual factors.

Avoidance and Displacement

Avoidance is the displacement of an individual from an area or migration path as a result of the presence of a sound or other stressors and is one of the most obvious manifestations of disturbance in marine mammals (Richardson et al., 1995). For example, gray whales ( Eschrichtius robustus) and humpback whales are known to change direction, deflecting from customary migratory paths, in order to avoid noise from airgun surveys (Malme et al., 1984; Dunlop et al., 2018). Avoidance is qualitatively different from the flight response but also differs in the magnitude of the response ( i.e., directed movement, rate of travel, etc.). Avoidance may be short-term with animals returning to the area once the noise has ceased ( e.g., Malme et al., 1984; Bowles et al., 1994; Goold, 1996; Stone et al., 2000; Morton and Symonds, 2002; Gailey et al., 2007; Dähne et al., 2013; Russel et al., 2016). Longer-term displacement is possible, however, which may lead to changes in abundance or distribution patterns of the affected species in the affected region if habituation to the presence of the sound does not occur ( e.g., Blackwell et al., 2004; Bejder et al., 2006; Teilmann et al., 2006; Forney et al., 2017). Avoidance of marine mammals during the construction of offshore wind facilities (specifically, impact pile driving) has been documented in the literature with some significant variation in the temporal and spatial degree of avoidance and with most studies focused on harbor porpoises as one of the most common marine mammals in European waters ( e.g., Tougaard et al., 2009; Dähne et al., 2013; Thompson et al., 2013; Russell et al., 2016; Brandt et al., 2018).

Available information on impacts to marine mammals from pile driving associated with offshore wind is limited to information on harbor porpoises and seals, as the vast majority of this research has occurred at European offshore wind projects where large whales and other odontocete species are uncommon. Harbor porpoises and harbor seals are considered to be behaviorally sensitive species ( e.g., Southall et al., 2007) and the effects of wind farm construction in Europe on these species 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 porpoise and harbor seals is described below.

Brandt et al. (2016) summarized the effects of the construction of eight offshore wind projects within the German North Sea ( i.e., Alpha Ventus, BARD Offshore I, Borkum West II, DanTysk, Global Tech I, Meerwind Süd/Ost, Nordsee Ost, and Riffgat) between 2009 and 2013 on harbor porpoises, combining 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 porpoise detections during pile driving when compared to 25-48 hours before pile driving began, with the magnitude of decline during pile driving clearly decreasing with increasing distances to the construction site. During the majority of projects, significant declines in detections (by at least 20 percent) were found within at least 5-10 km (3.1-6.2 mi) of the pile driving site, with declines at up to 20-30 km (12.4-18.6 mi) of the pile driving site documented in some cases. Similar results demonstrating the long-distance displacement of harbor porpoises (18-25 km (11.2-15.5 mi)) and harbor seals (up to 40 km (25 mi)) during impact pile driving have also been observed during the construction at multiple other European wind farms (Tougaard et al., 2009; Bailey et al., 2010.; Dähne et al., 2013; Lucke et al., 2012; Haelters et al., 2015).

While harbor porpoises and seals tend to move several kilometers away from wind farm construction activities, the duration of displacement has been documented to be relatively temporary. In two studies at Horns Rev II using impact pile driving, harbor porpoise returned within 1-2 days following cessation of pile driving (Tougaard et al., 2009, Brandt et al., 2011). Similar recovery periods have been noted for harbor seals off England during the construction of four wind farms (Brasseur et al., 2012; Carroll et al., 2010; Hamre et al., 2011; Hastie et al., 2015; Russell et al., 2016). In some cases, an increase in harbor porpoise activity has been documented inside wind farm areas following construction ( e.g., Lindeboom et al., 2011). Other studies have noted longer term impacts after impact pile driving. Near Dogger Bank in Germany, harbor porpoises continued to avoid the area for over 2 years after construction began (Gilles et al. 2009). Approximately 10 years after construction of the Nysted wind farm, harbor porpoise abundance had not recovered to the original levels previously seen, although the echolocation activity was noted to have been increasing when compared to the previous monitoring period (Teilmann and Carstensen, 2012). However, overall, there are no indications for a population decline of harbor porpoises in European waters ( e.g., Brandt et al., 2016). Notably, where significant differences in displacement and return rates have been identified for these species, the occurrence of secondary project-specific influences such as use of mitigation measures ( e.g., bubble curtains, acoustic deterrent devices (ADDs)) or the manner in which species use the habitat in the project area are likely the driving factors of this variation.

NMFS notes the aforementioned studies from Europe involve installing much smaller piles than SouthCoast proposes to install and therefore, we anticipate noise levels from impact pile driving to be louder. For this reason, we anticipate that the greater distances of displacement observed in harbor porpoise and harbor seals documented in Europe are likely to occur off of Massachusetts. However, we do not anticipate any greater severity of Start Printed Page 53739 response due to harbor porpoise and harbor seal habitat use off of Massachusetts or population level consequences similar to European findings. In many cases, harbor porpoises and harbor seals are resident to the areas where European wind farms have been constructed. However, off of Massachusetts, harbor porpoises are transient (with higher abundances in winter when foundation installation would not occur) and a small percentage of the large harbor seal population are only seasonally present with no rookeries established. In summary, we anticipate that harbor porpoise and harbor seals will likely respond to pile driving by moving several kilometers away from the source but return to typical habitat use patterns when pile driving ceases.

Some avoidance behavior of other marine mammal species has been documented to be dependent on distance from the source. As described above, DeRuiter et al. (2013) noted that distance from a sound source may moderate marine mammal reactions in their study of Cuvier's beaked whales (an acoustically sensitive species), which showed the whales swimming rapidly and silently away when a sonar signal was 3.4-9.5 km (2.1-5.9 mi) away while showing no such reaction to the same signal when the signal was 118 km (73 mi) away even though the received levels were similar. Tyack et al. (1983) conducted playback studies of Surveillance Towed Array Sensor System (SURTASS) low-frequency active (LFA) sonar in a gray whale migratory corridor off California. Similar to North Atlantic right whales, gray whales migrate close to shore (approximately 2 km (1.2 mi) from shore) and are low-frequency hearing specialists. The LFA sonar source was placed within the gray whale migratory corridor (approximately 2 km (1.2 mi) offshore) and offshore of most, but not all, migrating whales (approximately 4 km (2.5 mi) offshore). These locations influenced received levels and distance to the source. For the inshore playbacks, not unexpectedly, the louder the source level of the playback ( i.e., the louder the received level), whale avoided the source at greater distances. Specifically, when the source level was 170 dB SPL_rms and 178 dB_rms, whales avoided the inshore source at ranges of several hundred meters, similar to avoidance responses reported by Malme et al. (1983; 1984). Whales exposed to source levels of 185 dB_rm s demonstrated avoidance levels at ranges of +1 km (+0.6 mi). While there was observed deflection from course, in no case did a whale abandon its migratory behavior.

The signal context of the noise exposure has been shown to play an important role in avoidance responses. In a 2007-2008 study in the Bahamas, playback sounds of a potential predator—a killer whale—resulted in a similar but more pronounced reaction in beaked whales (an acoustically sensitive species), which included longer inter-dive intervals and a sustained straight-line departure of more than 20 km (12.4 mi) from the area (Boyd et al., 2008; Southall et al., 2009; Tyack et al., 2011). SouthCoast does not anticipate and NMFS is not proposing to authorize take of beaked whales and, moreover, the sounds produced by SouthCoast do not have signal characteristics similar to predators. Therefore, we would not expect such extreme reactions to occur for similar species.

One potential consequence of behavioral avoidance is the altered energetic expenditure of marine mammals because energy is required to move and avoid surface vessels or the sound field associated with active sonar (Frid and Dill, 2002). Most animals can avoid that energetic cost by swimming away at slow speeds or speeds that minimize the cost of transport (Miksis-Olds, 2006), as has been demonstrated in Florida manatees (Miksis-Olds, 2006). Those energetic costs increase, however, when animals shift from a resting state, which is designed to conserve an animal's energy, to an active state that consumes energy the animal would have conserved had it not been disturbed. Marine mammals that have been disturbed by anthropogenic noise and vessel approaches are commonly reported to shift from resting to active behavioral states, which would imply that they incur an energy cost.

Forney et al. (2017) detailed the potential effects of noise on marine mammal populations with high site fidelity, including displacement and auditory masking, noting that a lack of observed response does not imply absence of fitness costs and that apparent tolerance of disturbance may have population-level impacts that are less obvious and difficult to document. Avoidance of overlap between disturbing noise and areas and/or times of particular importance for sensitive species may be critical to avoiding population-level impacts because (particularly for animals with high site fidelity) there may be a strong motivation to remain in the area despite negative impacts. Forney et al. (2017) stated that, for these animals, remaining in a disturbed area may reflect a lack of alternatives rather than a lack of effects.

A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. The flight response differs from other avoidance responses in the intensity of the response ( e.g., directed movement, rate of travel). Relatively little information on flight responses of marine mammals to anthropogenic signals exist, although observations of flight responses to the presence of predators have occurred (Connor and Heithaus, 1996; Frid and Dill, 2002). The result of a flight response could range from brief, temporary exertion and displacement from the area where the signal provokes flight to, in extreme cases, beaked whale strandings (Cox et al., 2006; D'Amico et al., 2009). However, it should be noted that response to a perceived predator does not necessarily invoke flight (Ford and Reeves, 2008), and whether individuals are solitary or in groups may influence the response. Flight responses of marine mammals have been documented in response to mobile high intensity active sonar ( e.g., Tyack et al., 2011; DeRuiter et al., 2013; Wensveen et al., 2019), and more severe responses have been documented when sources are moving towards an animal or when they are surprised by unpredictable exposures (Watkins 1986; Falcone et al. 2017). Generally speaking, however, marine mammals would be expected to be less likely to respond with a flight response to either stationary pile driving (which they can sense is stationary and predictable) or significantly lower-level HRG surveys unless they are within the area ensonified above behavioral harassment thresholds at the moment the source is turned on (Watkins, 1986; Falcone et al., 2017). A flight response may also be possible in response to UXO/MEC detonation. However, detonations would be restricted to one per day and a maximum of 10 over 5 years, thus, there would be limited opportunities for flight response to be elicited as a result of detonation noise. The proposed mitigation and monitoring would result in any animals being far from the detonation location ( i.e., the clearance zones vary by hearing group and charge weight, but all zones are sized to ensure that marine mammals are beyond the area where PTS could occur prior to detonation) and any flight response would be spatially and temporally limited.

Diving and Foraging

Changes in dive behavior in response to noise exposure can vary widely. They may consist of increased or decreased dive times and surface intervals as well Start Printed Page 53740 as changes in the rates of ascent and descent during a dive ( e.g., Frankel and Clark, 2000; Costa et al., 2003; Ng and Leung, 2003; Nowacek et al.; 2004; Goldbogen et al., 2013a, Goldbogen et al. 2013b). Variations in dive behavior may reflect interruptions in biologically significant activities ( e.g., foraging) or they may be of little biological significance. Variations in dive behavior may also expose an animal to potentially harmful conditions ( e.g., increasing the chance of ship-strike) or may serve as an avoidance response that enhances survivorship. The impact of a variation in diving resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure, the type and magnitude of the response, and the context within which the response occurs ( e.g., the surrounding environmental and anthropogenic circ*mstances).

Nowacek et al. (2004) reported disruptions of dive behaviors in foraging North Atlantic right whales when exposed to an alerting stimulus, an action, they noted, that could lead to an increased likelihood of vessel strike. The alerting stimulus was in the form of an 18 minute exposure that included three 2-minute signals played three times sequentially. This stimulus was designed with the purpose of providing signals distinct to background noise that serve as localization cues. However, the whales did not respond to playbacks of either right whale social sounds or vessel noise, highlighting the importance of the sound characteristics in producing a behavioral reaction. Although source levels for the proposed pile driving activities may exceed the received level of the alerting stimulus described by Nowacek et al. (2004), proposed mitigation strategies (further described in the Proposed Mitigation section) will reduce the severity of any response to proposed pile driving activities. Converse to the behavior of North Atlantic right whales, Indo-Pacific humpback dolphins have been observed to dive for longer periods of time in areas where vessels were present and/or approaching (Ng and Leung, 2003). In both of these studies, the influence of the sound exposure cannot be decoupled from the physical presence of a surface vessel, thus complicating interpretations of the relative contribution of each stimulus to the response. Indeed, the presence of surface vessels, their approach, and speed of approach seemed to be significant factors in the response of the Indo-Pacific humpback dolphins (Ng and Leung, 2003). Low frequency signals of the Acoustic Thermometry of Ocean Climate (ATOC) sound source were not found to affect dive times of humpback whales in Hawaiian waters (Frankel and Clark, 2000) or to overtly affect elephant seal dives (Costa et al., 2003). They did, however, produce subtle effects that varied in direction and degree among the individual seals, illustrating the equivocal nature of behavioral effects and consequent difficulty in defining and predicting them.

Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the cessation of secondary indicators of feeding ( e.g., bubble nets or sediment plumes), or changes in dive behavior. As for other types of behavioral response, the frequency, duration, and temporal pattern of signal presentation as well as differences in species sensitivity are likely contributing factors to differences in response in any given circ*mstance ( e.g., Croll et al., 2001; Nowacek et al.; 2004; Madsen et al., 2006; Yazvenko et al., 2007; Southall et al., 2019b). An understanding of the energetic requirements of the affected individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal can facilitate the assessment of whether foraging disruptions are likely to incur fitness consequences (Goldbogen et al., 2013b; Farmer et al., 2018; Pirotta et al., 2018a; Southall et al., 2019a; Pirotta et al., 2021).

Impacts on marine mammal foraging rates from noise exposure have been documented, though there is little data regarding the impacts of offshore turbine construction specifically. Several broader examples follow, and it is reasonable to expect that exposure to noise produced during the 5-years the proposed rule would be effective could have similar impacts.

Visual tracking, passive acoustic monitoring, and movement recording tags were used to quantify sperm whale behavior prior to, during, and following exposure to airgun arrays at received levels in the range 140-160 dB at distances of 7-13 km (4.3-8.1 mi), following a phase-in of sound intensity and full array exposures at 1-13 km (0.6-8.1 mi) (Madsen et al., 2006; Miller et al., 2009). Sperm whales did not exhibit horizontal avoidance behavior at the surface. However, foraging behavior may have been affected. The sperm whales exhibited 19 percent less vocal (buzz) rate during full exposure relative to post exposure, and the whale that was approached most closely had an extended resting period and did not resume foraging until the airguns had ceased firing. The remaining whales continued to execute foraging dives throughout exposure; however, swimming movements during foraging dives were six percent lower during exposure than control periods (Miller et al., 2009). Miller et al. (2009) noted that more data are required to understand whether the differences were due to exposure or natural variation in sperm whale behavior.

Balaenopterid whales exposed to moderate low-frequency signals similar to the ATOC sound source demonstrated no variation in foraging activity (Croll et al., 2001) whereas five out of six North Atlantic right whales exposed to an acoustic alarm interrupted their foraging dives (Nowacek et al., 2004). Although the received SPLs were similar in the latter two studies, the frequency, duration, and temporal pattern of signal presentation were different. These factors, as well as differences in species sensitivity, are likely contributing factors to the differential response. The source levels of both the proposed construction and HRG activities exceed the source levels of the signals described by Nowacek et al. (2004) and Croll et al. (2001), and noise generated by SouthCoast's activities at least partially overlaps in frequency with the described signals. Blue whales exposed to mid-frequency sonar in the Southern California Bight were less likely to produce low frequency calls usually associated with feeding behavior (Melcón et al., 2012). However, Melcón et al. (2012) were unable to determine if suppression of low-frequency calls reflected a change in their feeding performance or abandonment of foraging behavior and indicated that implications of the documented responses are unknown. Further, it is not known whether the lower rates of calling actually indicated a reduction in feeding behavior or social contact since the study used data from remotely deployed, passive acoustic monitoring buoys. Results from the 2010-2011 field season of a behavioral response study in Southern California waters indicated that, in some cases and at low received levels, tagged blue whales responded to mid-frequency sonar but that those responses were mild and there was a quick return to their baseline activity (Southall et al., 2011; Southall et al., 2012b, Southall et al., 2019b).

Southall et al. (2011) found that blue whales had a different response to sonar exposure depending on behavioral state, which was more pronounced when whales were in deep feeding/travel modes than when engaged in surface Start Printed Page 53741 feeding. Southall et al. (2023) conducted a controlled exposure experiment (CEE) study similar to Southall et al. (2011), but focused on fin whale behavioral responses to different sound sources including mid-frequency active sonar (MFAS), and pseudorandom noise (PRN) signals lacking tonal patterns but having frequency, duration, and source levels similar to sonar. In general, fewer fin whales (33 percent) displayed observable behavioral responses to similar noise stimuli compared to blue whales (66 percent), and fin whale responses were less dependent on the behavioral state of the whale at the time of exposure and more closely associated with the received level ( i.e., loudness) of the signal. Similar to blue whales, some fin whales responded to the sound exposure by lunge feeding and deep diving, particularly at higher received levels, and returned to baseline behaviors ( i.e., as observed prior to sound exposure) relatively quickly following noise exposure. Southall et al. (2023) found no evidence that noise exposure compromised fin whale foraging success, in contrast with observations of noise-exposed foraging blue whales by Friedlander et al. (2016). The baseline acoustic environment appeared to influence the degree of fin whale behavioral responses. The five fin whales that did present observable behavioral responses did so to a greater extent when exposed to PRN than MFAS. Southall et al. (2023) conducted the CEE in fin whale habitat that overlaps with an area in southern California frequently used for military sonar training exercises, thus, whales may be more familiar with sonar signals than PRN, a novel stimulus. The observations by Southall et al. (2023) underscore the importance of considering an animal's exposure history when evaluating behavioral responses to particular noise stimuli.

Foraging strategies may impact foraging efficiency, such as by reducing foraging effort and increasing success in prey detection and capture, in turn promoting fitness and allowing individuals to better compensate for foraging disruptions. Surface feeding blue whales did not show a change in behavior in response to mid-frequency simulated and real sonar sources with received levels between 90 and 179 dB re 1m Pa, but deep feeding and non-feeding whales showed temporary reactions including cessation of feeding, reduced initiation of deep foraging dives, generalized avoidance responses, and changes to dive behavior (DeRuiter et al., 2017; Goldbogen et al.; 2013b; Sivle et al., 2015). Goldbogen et al. (2013b) indicate that disruption of feeding and displacement could impact individual fitness and health. However, for this to be true, we would have to assume that an individual whale could not compensate for this lost feeding opportunity by either immediately feeding at another location, by feeding shortly after cessation of acoustic exposure, or by feeding at a later time. Here, there is no indication that individual fitness and health would be impacted, particularly since unconsumed prey would likely still be available in the environment in most cases following the cessation of acoustic exposure. Seasonal restrictions on pile driving and UXO/MEC detonations would limit temporal and spatial co-occurrence of these activities and foraging North Atlantic right whales (and other marine mammal species) in southern New England, thereby minimizing disturbance during times of year when prey are most abundant.

Similarly, while the rates of foraging lunges decrease in humpback whales due to sonar exposure, there was variability in the response across individuals with one animal ceasing to forage completely and another animal starting to forage during the exposure (Sivle et al., 2016). In addition, almost half of the animals that demonstrated avoidance were foraging before the exposure but the others were not; the animals that avoided while not feeding responded at a slightly lower received level and greater distance than those that were feeding (Wensveen et al., 2017). These findings indicate the behavioral state of the animal and foraging strategies play a role in the type and severity of a behavioral response.

Vocalizations and Auditory Masking

Marine mammals vocalize for different purposes and across multiple modes, such as whistling, production of echolocation clicks, calling, and singing. Changes in vocalization behavior in response to anthropogenic noise can occur for any of these modes and may result directly from increased vigilance or a startle response, or from a need to compete with an increase in background noise (see Erbe et al. (2016)'s review on communication masking), the latter of which is described more below.

For example, in the presence of potentially masking signals, humpback whales and killer whales have been observed to increase the length of their songs (Miller et al., 2000; Fristrup et al., 2003; Foote et al., 2004) and blue whales increased song production (Di Iorio and Clark, 2009) while North Atlantic right whales have been observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks et al., 2007). In some cases, animals may cease or reduce sound production during production of aversive signals (Bowles et al., 1994; Thode et al., 2020; Cerchio et al., (2014); McDonald et al., 1995. Blackwell et al. (2015) showed that whales increased calling rates as soon as airgun signals were detectable before ultimately decreasing calling rates at higher received levels.

Sound can disrupt behavior through masking or interfering with an animal's ability to detect, recognize, or discriminate between acoustic signals of interest ( e.g., those used for intraspecific communication and social interactions, prey detection, predator avoidance, or navigation) (Richardson et al., 1995; Erbe and Farmer, 2000; Tyack, 2000; Erbe et al., 2016). Masking occurs when the receipt of a sound is interfered with by another coincident sound at similar frequencies and at similar or higher intensity and may occur whether the sound is natural ( e.g., snapping shrimp, wind, waves, precipitation) or anthropogenic ( e.g., shipping, sonar, seismic exploration) in origin. The ability of a noise source to mask biologically important sounds depends on the characteristics of both the noise source and the signal of interest ( e.g., signal-to-noise ratio, temporal variability, direction) in relation to each other and to an animal's hearing abilities ( e.g., sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age, or TTS hearing loss), and existing ambient noise and propagation conditions.

Masking these acoustic signals can disturb the behavior of individual animals, groups of animals, or entire populations. Masking can lead to behavioral changes, including vocal changes ( e.g., Lombard effect, increasing amplitude, or changing frequency), cessation of foraging or lost foraging opportunities, and leaving an area, to both signalers and receivers in an attempt to compensate for noise levels (Erbe et al., 2016) or because sounds that would typically have triggered a behavior were not detected. In humans, significant masking of tonal signals occurs as a result of exposure to noise in a narrow band of similar frequencies. As the sound level increases, though, the detection of frequencies above those of the masking stimulus decreases also. This principle is expected to apply to marine mammals as well because of common biomechanical cochlear properties across taxa. Therefore, when the coincident (masking) sound is man- Start Printed Page 53742 made, it may be considered harassment when disrupting behavioral patterns. It is important to distinguish TTS and PTS, which persist after the sound exposure, from masking, which only occurs during the sound exposure. Because masking (without resulting in threshold shift) is not associated with abnormal physiological function, it is not considered a physiological effect, but rather a potential behavioral effect.

The frequency range of the potentially masking sound is important in determining any potential behavioral impacts. For example, low-frequency signals may have less effect on high-frequency echolocation sounds produced by odontocetes but are more likely to affect detection of mysticete communication calls and other potentially important natural sounds such as those produced by surf and some prey species. The masking of communication signals by anthropogenic noise may be considered as a reduction in the communication space of animals ( e.g., Clark et al., 2009; Matthews et al., 2017) and may result in energetic or other costs as animals change their vocalization behavior ( e.g., Miller et al., 2000; Foote et al., 2004; Parks et al., 2007; Di Iorio and Clark, 2009; Holt et al., 2009). Masking can be reduced in situations where the signal and noise come from different directions (Richardson et al., 1995), through amplitude modulation of the signal, or through other compensatory behaviors (Houser and Moore, 2014). Masking can be tested directly in captive species ( e.g., Erbe, 2008), but in wild populations it must be either modeled or inferred from evidence of masking compensation. There are few studies addressing real-world masking sounds likely to be experienced by marine mammals in the wild ( e.g., Branstetter et al., 2013; Cholewiak et al., 2018).

The echolocation calls of toothed whales are subject to masking by high-frequency sound. Human data indicate low-frequency sound can mask high-frequency sounds ( i.e., upward masking). Studies on captive odontocetes by Au et al. (1974, 1985, 1993) indicate that some species may use various processes to reduce masking effects ( e.g., adjustments in echolocation call intensity or frequency as a function of background noise conditions). There is also evidence that the directional hearing abilities of odontocetes are useful in reducing masking at the high-frequencies these cetaceans use to echolocate but not at the low-to-moderate frequencies they use to communicate (Zaitseva et al., 1980). A study by Nachtigall and Supin (2008) showed that false killer whales adjust their hearing to compensate for ambient sounds and the intensity of returning echolocation signals.

Impacts on signal detection, measured by masked detection thresholds, are not the only important factors to address when considering the potential effects of masking. As marine mammals use sound to recognize conspecifics, prey, predators, or other biologically significant sources (Branstetter et al., 2016), it is also important to understand the impacts of masked recognition thresholds (often called “informational masking”). Branstetter et al. (2016) measured masked recognition thresholds for whistle-like sounds of bottlenose dolphins and observed that they are approximately 4 dB above detection thresholds (energetic masking) for the same signals. Reduced ability to recognize a conspecific call or the acoustic signature of a predator could have severe negative impacts. Branstetter et al. (2016) observed that if “quality communication” is set at 90 percent recognition the output of communication space models (which are based on 50 percent detection) would likely result in a significant decrease in communication range.

As marine mammals use sound to recognize predators (Allen et al., 2014; Cummings and Thompson, 1971; Curé et al., 2015; Fish and Vania, 1971), the presence of masking noise may also prevent marine mammals from responding to acoustic cues produced by their predators, particularly if it occurs in the same frequency band. For example, harbor seals that reside in the coastal waters off British Columbia are frequently targeted by mammal-eating killer whales. The seals acoustically discriminate between the calls of mammal-eating and fish-eating killer whales (Deecke et al., 2002), a capability that should increase survivorship while reducing the energy required to attend to all killer whale calls. Similarly, sperm whales (Curé et al., 2016; Isojunno et al., 2016), long-finned pilot whales (Visser et al., 2016), and humpback whales (Curé et al., 2015) changed their behavior in response to killer whale vocalization playbacks; these findings indicate that some recognition of predator cues could be missed if the killer whale vocalizations were masked. The potential effects of masked predator acoustic cues depends on the duration of the masking noise and the likelihood of a marine mammal encountering a predator during the time that detection and recognition of predator cues are impeded.

Redundancy and context can also facilitate detection of weak signals. These phenomena may help marine mammals detect weak sounds in the presence of natural or manmade noise. Most masking studies in marine mammals present the test signal and the masking noise from the same direction. The dominant background noise may be highly directional if it comes from a particular anthropogenic source such as a ship or industrial site. Directional hearing may significantly reduce the masking effects of these sounds by improving the effective signal-to-noise ratio.

Masking affects both senders and receivers of acoustic signals and, at higher levels and longer duration, can potentially have long-term chronic effects on marine mammals at the population level as well as at the individual level. Low-frequency ambient sound levels have increased by as much as 20 dB (more than three times in terms of SPL) in the world's ocean from pre-industrial periods, with most of the increase from distant commercial shipping (Hildebrand, 2009; Cholewiak et al., 2018). All anthropogenic sound sources, but especially chronic and lower-frequency signals ( e.g., from commercial vessel traffic), contribute to elevated ambient sound levels, thus intensifying masking.

In addition to making it more difficult for animals to perceive and recognize acoustic cues in their environment, anthropogenic sound presents separate challenges for animals that are vocalizing. When they vocalize, animals are aware of environmental conditions that affect the “active space” (or communication space) of their vocalizations, which is the maximum area within which their vocalizations can be detected before it drops to the level of ambient noise (Brenowitz, 2004; Brumm et al., 2004; Lohr et al., 2003). Animals are also aware of environmental conditions that affect whether listeners can discriminate and recognize their vocalizations from other sounds, which is more important than simply detecting that a vocalization is occurring (Brenowitz, 1982; Brumm et al., 2004; Dooling, 2004; Marten and Marler, 1977; Patricelli and Blickley, 2006). Most species that vocalize have evolved with an ability to make adjustments to their vocalizations to increase the signal-to-noise ratio, active space, and recognizability/distinguishability of their vocalizations in the face of temporary changes in background noise (Brumm et al., 2004; Patricelli and Blickley, 2006). Vocalizing animals can make adjustments to vocalization characteristics such as the frequency structure, amplitude, temporal Start Printed Page 53743 structure, and temporal delivery (repetition rate), or ceasing to vocalize.

Many animals will combine several of these strategies to compensate for high levels of background noise. Anthropogenic sounds that reduce the signal-to-noise ratio of animal vocalizations, increase the masked auditory thresholds of animals listening for such vocalizations, or reduce the active space of an animal's vocalizations impair communication between animals. Most animals that vocalize have evolved strategies to compensate for the effects of short-term or temporary increases in background or ambient noise on their songs or calls. Although the fitness consequences of these vocal adjustments are not directly known in all instances, like most other trade-offs animals must make, some of these strategies likely come at a cost (Patricelli and Blickley, 2006; Noren et al., 2017; Noren et al., 2020). Shifting songs and calls to higher frequencies may also impose energetic costs (Lambrechts, 1996).

Marine mammals are also known to make vocal changes in response to anthropogenic noise. In cetaceans, vocalization changes have been reported from exposure to anthropogenic noise sources such as sonar, vessel noise, and seismic surveying (see the following for examples: Gordon et al., 2003; Di Iorio and Clark, 2009; Hatch et al., 2012; Holt et al., 2009; Holt et al., 2011; Lesage et al., 1999; McDonald et al., 2009; Parks et al., 2007; Risch et al., 2012; Rolland et al., 2012), as well as changes in the natural acoustic environment (Dunlop et al., 2014). Vocal changes can be temporary or persistent. For example, model simulation suggests that the increase in starting frequency for the North Atlantic right whale upcall over the last 50 years resulted in increased detection ranges between right whales. The frequency shift, coupled with an increase in call intensity by 20 dB, led to a call detectability range of less than 3 km (1.9 mi) to over 9 km (5.6 mi) (Tennessen and Parks, 2016). Holt et al. (2009) measured killer whale call source levels and background noise levels in the 1 to 40 kHz band and reported that the whales increased their call source levels by 1 dB SPL for every one dB SPL increase in background noise level. Similarly, another study on St. Lawrence River belugas reported a similar rate of increase in vocalization activity in response to passing vessels (Scheifele et al., 2005). Di Iorio and Clark (2009) showed that blue whale calling rates vary in association with seismic sparker survey activity, with whales calling more on days with surveys than on days without surveys. They suggested that the whales called more during seismic survey periods as a way to compensate for the elevated noise conditions.

In some cases, these vocal changes may have fitness consequences, such as an increase in metabolic rates and oxygen consumption, as observed in bottlenose dolphins when increasing their call amplitude (Holt et al., 2015). A switch from vocal communication to physical, surface-generated sounds, such as pectoral fin slapping or breaching, was observed for humpback whales in the presence of increasing natural background noise levels indicating that adaptations to masking may also move beyond vocal modifications (Dunlop et al., 2010).

While these changes all represent possible tactics by the sound-producing animal to reduce the impact of masking, the receiving animal can also reduce masking by using active listening strategies such as orienting to the sound source, moving to a quieter location, or reducing self-noise from hydrodynamic flow by remaining still. The temporal structure of noise ( e.g., amplitude modulation) may also provide a considerable release from masking through comodulation masking release (a reduction of masking that occurs when broadband noise, with a frequency spectrum wider than an animal's auditory filter bandwidth at the frequency of interest, is amplitude modulated) (Branstetter and Finneran, 2008; Branstetter et al., 2013). Signal type ( e.g., whistles, burst-pulse, sonar clicks) and spectral characteristics ( e.g., frequency modulated with harmonics) may further influence masked detection thresholds (Branstetter et al., 2016; Cunningham et al., 2014).

Masking is more likely to occur in the presence of broadband, relatively continuous noise sources such as vessels. Several studies have shown decreases in marine mammal communication space and changes in behavior as a result of the presence of vessel noise. For example, right whales were observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks et al., 2007) as well as increasing the amplitude (intensity) of their calls (Parks, 2009; Parks et al., 2011). Clark et al. (2009) observed that right whales' communication space decreased by up to 84 percent in the presence of vessels. Cholewiak et al. (2018) also observed loss in communication space in Stellwagen National Marine Sanctuary for North Atlantic right whales, fin whales, and humpback whales with increased ambient noise and shipping noise. Although humpback whales off Australia did not change the frequency or duration of their vocalizations in the presence of vessel noise, source levels were lower than expected compared to observed source level changes with increased wind noise, potentially indicating some signal masking (Dunlop, 2016). Multiple delphinid species have also been shown to increase the minimum or maximum frequencies of their whistles in the presence of anthropogenic noise and reduced communication space (for examples see: Holt et al., 2009; Holt et al., 2011; Gervaise et al., 2012; Williams et al., 2013; Hermannsen et al., 2014; Papale et al., 2015; Liu et al., 2017). While masking impacts are not a concern from lower intensity, higher frequency HRG surveys, some degree of masking would be expected in the vicinity of turbine pile driving ( e.g., during vibratory pile driving, a continuous acoustic source) and concentrated support vessel operation. However, pile driving is an intermittent sound and would not be continuous throughout the day.

Habituation and Sensitization

Habituation can occur when an animal's response to a stimulus wanes with repeated exposure, usually in the absence of unpleasant associated events (Wartzok et al., 2003). Animals are most likely to habituate to sounds that are predictable and unvarying. It is important to note that habituation is appropriately considered as a “progressive reduction in response to stimuli that are perceived as neither aversive nor beneficial,” rather than as, more generally, moderation in response to human disturbance having a neutral or positive outcome (Bejder et al., 2009). The opposite process is sensitization, when an unpleasant experience leads to subsequent responses, often in the form of avoidance, at a lower level of exposure. Both habituation and sensitization require an ongoing learning process. As noted, behavioral state may affect the type of response. For example, animals that are resting may show greater behavioral change in response to disturbing sound levels than animals that are highly motivated to remain in an area for feeding (Richardson et al., 1995; U.S. National Research Council (NRC), 2003; Wartzok et al., 2003; Southall et al., 2019b). Controlled experiments with captive marine mammals have shown pronounced behavioral reactions, including avoidance of loud sound sources ( e.g., Ridgway et al., 1997; Finneran et al., 2003; Houser et al. (2013a); Houser et al., 2013b; Kastelein Start Printed Page 53744 et al., 2018). Observed responses of wild marine mammals to loud impulsive sound sources (typically airguns or acoustic harassment devices) have been varied but often consist of avoidance behavior or other behavioral changes suggesting discomfort (Morton and Symonds, 2002; see also Richardson et al., 1995; Nowacek et al., 2007; Tougaard et al., 2009; Brandt et al., 2011, Brandt et al., 2012, Dähne et al., 2013; Brandt et al., 2014; Russell et al., 2016; Brandt et al., 2018).

Stone (2015) reported data from at-sea observations during 1,196 airgun surveys from 1994 to 2010. When large arrays of airguns (considered to be 500 in 3 or more) were firing, lateral displacement, more localized avoidance, or other changes in behavior were evident for most odontocetes. However, significant responses to large arrays were found only for the minke whale and fin whale. Behavioral responses observed included changes in swimming or surfacing behavior with indications that cetaceans remained near the water surface at these times. Behavioral observations of gray whales during an airgun survey monitored whale movements and respirations pre-, during-, and post-seismic survey (Gailey et al., 2016). Behavioral state and water depth were the best ‘natural' predictors of whale movements and respiration and after considering natural variation, none of the response variables were significantly associated with survey or vessel sounds. Many delphinids approach low-frequency airgun source vessels with no apparent discomfort or obvious behavioral change ( e.g., Barkaszi et al., 2012), indicating the importance of frequency output in relation to the species' hearing sensitivity.

Physiological Responses

An animal's perception of a threat may be sufficient to trigger stress responses consisting of some combination of behavioral responses, autonomic nervous system responses, neuroendocrine responses, or immune responses ( e.g., Seyle, 1950; Moberg and Mench, 2000). In many cases, an animal's first and sometimes most economical (in terms of energetic costs) response is behavioral avoidance of the potential stressor. Autonomic nervous system responses to stress typically involve changes in heart rate, blood pressure, and gastrointestinal activity. These responses have a relatively short duration and may or may not have a significant long-term effect on an animal's fitness.

Neuroendocrine stress responses often involve the hypothalamus-pituitary-adrenal system. Virtually all neuroendocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction, altered metabolism, reduced immune competence, and behavioral disturbance ( e.g., Moberg, 1987; Blecha, 2000). Increases in the circulation of glucocorticoids are also equated with stress (Romano et al., 2004).

The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and “distress” is the cost of the response. During a stress response, an animal uses glycogen stores that can be quickly replenished once the stress is alleviated. In such circ*mstances, the cost of the stress response would not pose serious fitness consequences. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other functions. This state of distress will last until the animal replenishes its energetic reserves sufficiently to restore normal function.

Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well studied through controlled experiments and for both laboratory and free-ranging animals ( e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003; Krausman et al., 2004; Lankford et al., 2005). Stress responses due to exposure to anthropogenic sounds or other stressors and their effects on marine mammals have also been reviewed (Fair and Becker, 2000; Romano et al., 2002b) and, more rarely, studied in wild populations ( e.g., Lusseau and Bejder, 2007; Romano et al., 2002a; Rolland et al., 2012). For example, Rolland et al. (2012) found that noise reduction from reduced ship traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right whales.

These and other studies lead to a reasonable expectation that some marine mammals will experience physiological stress responses upon exposure to acoustic stressors and that it is possible that some of these would be classified as “distress.” In addition, any animal experiencing TTS would likely also experience stress responses (NRC, 2003, 2017). Respiration naturally varies with different behaviors and variations in respiration rate as a function of acoustic exposure can be expected to co-occur with other behavioral reactions, such as a flight response or an alteration in diving. However, respiration rates in and of themselves may be representative of annoyance or an acute stress response. Mean exhalation rates of gray whales at rest and while diving were found to be unaffected by seismic surveys conducted adjacent to the whale feeding grounds (Gailey et al., 2007). Studies with captive harbor porpoises show increased respiration rates upon introduction of acoustic alarms (Kastelein et al., 2001; Kastelein et al., 2006a) and emissions for underwater data transmission (Kastelein et al., 2005). However, exposure of the same acoustic alarm to a striped dolphin under the same conditions did not elicit a response (Kastelein et al., 2006a), again highlighting the importance in understanding species differences in the tolerance of underwater noise when determining the potential for impacts resulting from anthropogenic sound exposure.

Stranding

The definition for a stranding under title IV of the MMPA is that (A) a marine mammal is dead and is (i) on a beach or shore of the United States; or (ii) in waters under the jurisdiction of the United States (including any navigable waters); or (B) a marine mammal is alive and is (i) on a beach or shore of the United States and is unable to return to the water; (ii) on a beach or shore of the United States and, although able to return to the water, is in need of apparent medical attention; or (iii) in the waters under the jurisdiction of the United States (including any navigable waters), but is unable to return to its natural habitat under its own power or without assistance (16 U.S.C. 1421h).

Marine mammal strandings have been linked to a variety of causes, such as illness from exposure to infectious agents, biotoxins, or parasites; starvation; unusual oceanographic or weather events; or anthropogenic causes including fishery interaction, vessel strike, entrainment, entrapment, sound exposure, or combinations of these stressors sustained concurrently or in series. There have been multiple events worldwide in which marine mammals (primarily beaked whales, or other deep divers) have stranded coincident with relatively nearby activities utilizing loud sound sources (primarily military training events), and five in which mid-frequency active sonar has been more definitively determined to have been a contributing factor.

There are multiple theories regarding the specific mechanisms responsible for marine mammal strandings caused by exposure to loud sounds. One primary Start Printed Page 53745 theme is the behaviorally mediated responses of deep-diving species (odontocetes), in which their startled response to an acoustic disturbance (1) affects ascent or descent rates, the time they stay at depth or the surface, or other regular dive patterns that are used to physiologically manage gas formation and absorption within their bodies, such that the formation or growth of gas bubbles damages tissues or causes other injury, or (2) results in their flight to shallow areas, enclosed bays, or other areas considered “out of habitat,” in which they become disoriented and physiologically compromised. For more information on marine mammal stranding events and potential causes, please see the Mortality and Stranding section of NMFS Proposed Incidental Take Regulations for the Navy's Training and Testing Activities in the Hawaii-Southern California Training and Testing Study Area (50 CFR part 218, Volume 83, No. 123, June 26, 2018).

The construction activities proposed by SouthCoast ( e.g., pile driving) do not inherently have the potential to result in marine mammal strandings. While vessel strikes could kill or injure a marine mammal (which may eventually strand), the required mitigation measures would reduce the potential for take from these activities to de minimus levels (see Proposed Mitigation section for more details). As described above, no mortality or serious injury is anticipated or proposed for authorization from any specified activities.

Of the strandings documented to date worldwide, NMFS is not aware of any being attributed to pile driving or the types of HRG equipment proposed for use during SouthCoast's surveys. Recently, there has been heightened interest in HRG surveys relative to recent marine mammals strandings along the U.S. East Coast. HRG surveys involve the use of certain sources to image the ocean bottom, which are very different from seismic airguns used in oil and gas surveys or tactical military sonar, in that they produce much smaller impact zones. Marine mammals may respond to exposure to these sources by, for example, avoiding the immediate area, which is why offshore wind developers have authorization to allow for Level B (behavioral) harassment, including SouthCoast. However, because of the combination of lower source levels, higher frequency, narrower beam-width (for some sources), and other factors, the area within which a marine mammal might be expected to be behaviorally disturbed by HRG sources is much smaller (by orders of magnitude) than the impact areas for seismic airguns or the military sonar with which a small number of marine mammal have been causally associated. Specifically, estimated harassment zones for HRG surveys are typically less than 200 m (656.2 ft) (such as those associated with the project), while zones for military mid-frequency active sonar or seismic airgun surveys typically extend for several kilometers ranging up to 10s of kilometers. Further, because of this much smaller ensonified area, any marine mammal exposure to HRG sources is reasonably expected to be at significantly lower levels and shorter duration (associated with less severe responses), and there is no evidence suggesting, or reason to speculate, that marine mammals exposed to HRG survey noise are likely to be injured, much less strand, as a result. Last, all but one of the small number of marine mammal stranding events that have been causally associated with exposure to loud sound sources have been deep-diving toothed whale species (not mysticetes), which are known to respond differently to loud sounds. NMFS has performed a thorough review of a report submitted by Rand (2023) that includes measurements of the Geo-Marine Geo-Source 400 sparker and suggests that NMFS is assuming lower source and received levels than is appropriate in its assessments of HRG impacts. NMFS has determined that the values in this proposed rule are appropriate, based on the model methodology ( i.e., the assumed source level propagated using spherical spreading) here predicting a peak level 3 dB louder than the maximum measured peak level at the closest measurement range in Rand (2023).

Also of note, in an assessment of monitoring reports for HRG surveys received from 2021 through 2023, as compared to the takes of marine mammals authorized, an average of fewer than 15 percent have been detected within harassment zones, with no more than 27 percent for any species (common dolphins) and 20 percent or less for all other species. The most common behavioral change observed while the HRG sound source was active was “change direction” ( i.e. a potential behavioral reaction) though detections of “no behavioral change” occurred at least twice as many times as “change direction.”

Potential Effects of Disturbance on Marine Mammal Fitness

The different ways that marine mammals respond to sound are sometimes indicators of the ultimate effect that exposure to a given stimulus will have on the well-being (survival, reproduction, etc.) of an animal. There is numerous data relating the exposure of terrestrial mammals from sound to effects on reproduction or survival, and data for marine mammals continues to accumulate. Several authors have reported that disturbance stimuli may cause animals to abandon nesting and foraging sites (Sutherland and Crockford, 1993); may cause animals to increase their activity levels and suffer premature deaths or reduced reproductive success when their energy expenditures exceed their energy budgets (Daan et al., 1996; Feare, 1976; Mullner et al., 2004); or may cause animals to experience higher predation rates when they adopt risk-prone foraging or migratory strategies (Frid and Dill, 2002). Each of these studies addressed the consequences of animals shifting from one behavioral state ( e.g., resting or foraging) to another behavioral state ( e.g., avoidance or escape behavior) because of human disturbance or disturbance stimuli.

Attention is the cognitive process of selectively concentrating on one aspect of an animal's environment while ignoring other things (Posner, 1994). Because animals (including humans) have limited cognitive resources, there is a limit to how much sensory information they can process at any time. The phenomenon called “attentional capture” occurs when a stimulus (usually a stimulus that an animal is not concentrating on or attending to) “captures” an animal's attention. This shift in attention can occur consciously or subconsciously (for example, when an animal hears sounds that it associates with the approach of a predator) and the shift in attention can be sudden (Dukas, 2002; van Rij, 2007). Once a stimulus has captured an animal's attention, the animal can respond by ignoring the stimulus, assuming a “watch and wait” posture, or treat the stimulus as a disturbance and respond accordingly, which includes scanning for the source of the stimulus or “vigilance” (Cowlishaw et al., 2004).

Vigilance is an adaptive behavior that helps animals determine the presence or absence of predators, assess their distance from conspecifics, or to attend cues from prey (Bednekoff and Lima, 1998; Treves, 2000). Despite those benefits, however, vigilance has a cost of time; when animals focus their attention on specific environmental cues, they are not attending to other activities such as foraging or resting. These effects have generally not been demonstrated for marine mammals, but Start Printed Page 53746 studies involving fish and terrestrial animals have shown that increased vigilance may substantially reduce feeding rates (Saino, 1994; Beauchamp and Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). Animals will spend more time being vigilant, which may translate to less time foraging or resting, when disturbance stimuli approach them more directly, remain at closer distances, have a greater group size ( e.g., multiple surface vessels), or when they co-occur with times that an animal perceives increased risk ( e.g., when they are giving birth or accompanied by a calf).

The primary mechanism by which increased vigilance and disturbance appear to affect the fitness of individual animals is by disrupting an animal's time budget and, as a result, reducing the time they might spend foraging and resting (which increases an animal's activity rate and energy demand while decreasing their caloric intake/energy). In a study of northern resident killer whales off Vancouver Island, exposure to boat traffic was shown to reduce foraging opportunities and increase traveling time (Holt et al., 2021). A simple bioenergetics model was applied to show that the reduced foraging opportunities equated to a decreased energy intake of 18 percent while the increased traveling incurred an increased energy output of 3-4 percent, which suggests that a management action based on avoiding interference with foraging might be particularly effective.

On a related note, many animals perform vital functions, such as feeding, resting, traveling, and socializing, on a diel cycle (24-hr cycle). Behavioral reactions to noise exposure (such as disruption of critical life functions, displacement, or avoidance of important habitat) are more likely to be significant for fitness if they last more than one diel cycle or recur on subsequent days (Southall et al., 2007). Consequently, a behavioral response lasting less than one day and not recurring on subsequent days is not considered particularly severe unless it could directly affect reproduction or survival (Southall et al., 2007). It is important to note the difference between behavioral reactions lasting or recurring over multiple days and anthropogenic activities lasting or recurring over multiple days. For example, just because certain activities last for multiple days does not necessarily mean that individual animals will be either exposed to those activity-related stressors ( i.e., pile driving) for multiple days or further exposed in a manner that would result in sustained multi-day substantive behavioral responses. However, special attention is warranted where longer-duration activities overlay areas in which animals are known to congregate for longer durations for biologically important behaviors.

There are few studies that directly illustrate the impacts of disturbance on marine mammal populations. Lusseau and Bejder (2007) present data from three long-term studies illustrating the connections between disturbance from whale-watching boats and population-level effects in cetaceans. In Shark Bay, Australia, the abundance of bottlenose dolphins was compared within adjacent control and tourism sites over three consecutive 4.5-year periods of increasing tourism levels. Between the second and third time periods, in which tourism doubled, dolphin abundance decreased by 15 percent in the tourism area and did not change significantly in the control area. In Fiordland, New Zealand, two populations (Milford and Doubtful Sounds) of bottlenose dolphins with tourism levels that differed by a factor of seven were observed and significant increases in traveling time and decreases in resting time were documented for both. Consistent short-term avoidance strategies were observed in response to tour boats until a threshold of disturbance was reached (average 68 minutes between interactions), after which the response switched to a longer-term habitat displacement strategy. For one population, tourism only occurred in a part of the home range. However, tourism occurred throughout the home range of the Doubtful Sound population and once boat traffic increased beyond the 68-minute threshold (resulting in abandonment of their home range/preferred habitat), reproductive success drastically decreased (increased stillbirths) and abundance decreased significantly (from 67 to 56 individuals in a short period).

In order to understand how the effects of activities may or may not impact species and stocks of marine mammals, it is necessary to understand not only what the likely disturbances are going to be but how those disturbances may affect the reproductive success and survivorship of individuals and then how those impacts to individuals translate to population-level effects. Following on the earlier work of a committee of the U.S. National Research Council (NRC, 2005); New et al. (2014), in an effort termed the Potential Consequences of Disturbance (PCoD), outline an updated conceptual model of the relationships linking disturbance to changes in behavior and physiology, health, vital rates, and population dynamics. This framework is a four-step process progressing from changes in individual behavior and/or physiology, to changes in individual health, then vital rates, and finally to population-level effects. In this framework, behavioral and physiological changes can have direct (acute) effects on vital rates, such as when changes in habitat use or increased stress levels raise the probability of mother-calf separation or predation; indirect and long-term (chronic) effects on vital rates, such as when changes in time/energy budgets or increased disease susceptibility affect health, which then affects vital rates; or no effect to vital rates (New et al., 2014).

Since the PCoD general framework was outlined and the relevant supporting literature compiled, multiple studies developing state-space energetic models for species with extensive long-term monitoring ( e.g., southern elephant seals, North Atlantic right whales, Ziphiidae beaked whales, and bottlenose dolphins) have been conducted and can be used to effectively forecast longer-term population-level impacts from behavioral changes. While these are very specific models with very specific data requirements that cannot yet be applied broadly to project-specific risk assessments for the majority of species, they are a critical first step towards being able to quantify the likelihood of a population level effect. Since New et al. (2014), several publications have described models developed to examine the long-term effects of environmental or anthropogenic disturbance of foraging on various life stages of selected species ( e.g., sperm whale, Farmer et al. (2018); California sea lion, McHuron et al. (2018); blue whale, Pirotta et al. (2018a); humpback whale, Dunlop et al. (2021)). These models continue to add to refinement of the approaches to the PCoD framework. Such models also help identify what data inputs require further investigation. Pirotta et al. (2018b) provides a review of the PCoD framework with details on each step of the process and approaches to applying real data or simulations to achieve each step.

Despite its simplicity, there are few complete PCoD models available for any marine mammal species due to a lack of data available to parameterize many of the steps. To date, no PCoD model has been fully parameterized with empirical data (Pirotta et al., 2018a) due to the fact they are data intensive and logistically challenging to complete. Therefore, most complete PCoD models include simulations, theoretical modeling, and expert opinion to move through the steps. For example, PCoD models have Start Printed Page 53747 been developed to evaluate the effect of wind farm construction on the North Sea harbor porpoise populations ( e.g., King et al., 2015; Nabe-Nielsen et al., 2018). These models include a mix of empirical data, expert elicitation (King et al., 2015) and simulations of animals' movements, energetics, and/or survival (New et al., 2014; Nabe-Nielsen et a l., 2018).

PCoD models may also be approached in different manners. Dunlop et al. (2021) modeled migrating humpback whale mother-calf pairs in response to seismic surveys using both a forwards and backwards approach. While a typical forwards approach can determine if a stressor would have population-level consequences, Dunlop et al. demonstrated that working backwards through a PCoD model can be used to assess the “worst case” scenario for an interaction of a target species and stressor. This method may be useful for future management goals when appropriate data becomes available to fully support the model. In another example, harbor porpoise PCoD model investigating the impact of seismic surveys on harbor porpoise included an investigation on underlying drivers of vulnerability. Harbor porpoise movement and foraging were modeled for baseline periods and then for periods with seismic surveys as well; the models demonstrated that temporal ( i.e., seasonal) variation in individual energetics and their link to costs associated with disturbances was key in predicting population impacts (Gallagher et al., 2021).

Behavioral change, such as disturbance manifesting in lost foraging time, in response to anthropogenic activities is often assumed to indicate a biologically significant effect on a population of concern. However, as described above, individuals may be able to compensate for some types and degrees of shifts in behavior, preserving their health and thus their vital rates and population dynamics. For example, New et al. (2013) developed a model simulating the complex social, spatial, behavioral and motivational interactions of coastal bottlenose dolphins in the Moray Firth, Scotland, to assess the biological significance of increased rate of behavioral disruptions caused by vessel traffic. Despite a modeled scenario in which vessel traffic increased from 70 to 470 vessels a year (a six-fold increase in vessel traffic) in response to the construction of a proposed offshore renewables' facility, the dolphins' behavioral time budget, spatial distribution, motivations, and social structure remain unchanged. Similarly, two bottlenose dolphin populations in Australia were also modeled over 5 years against a number of disturbances (Reed et al., 2020), and results indicated that habitat/noise disturbance had little overall impact on population abundances in either location, even in the most extreme impact scenarios modeled.

By integrating different sources of data ( e.g., controlled exposure data, activity monitoring, telemetry tracking, and prey sampling) into a theoretical model to predict effects from sonar on a blue whale's daily energy intake, Pirotta et al. (2021) found that tagged blue whales' activity budgets, lunging rates, and ranging patterns caused variability in their predicted cost of disturbance. This method may be useful for future management goals when appropriate data becomes available to fully support the model. Harbor porpoise movement and foraging were modeled for baseline periods and then for periods with seismic surveys as well; the models demonstrated that the seasonality of the seismic activity was an important predictor of impact (Gallagher et al., 2021).

Keen et al. (2021) summarize the emerging themes in PCoD models that should be considered when assessing the likelihood and duration of exposure and the sensitivity of a population to disturbance (see Table 1 from Keen et al., 2021). The themes are categorized by life history traits (movement ecology, life history strategy, body size, and pace of life), disturbance source characteristics (overlap with biologically important areas, duration and frequency, and nature and context), and environmental conditions (natural variability in prey availability and climate change). Keen et al. (2021) then summarize how each of these features influence an assessment, noting, for example, that individual animals with small home ranges have a higher likelihood of prolonged or year-round exposure, that the effect of disturbance is strongly influenced by whether it overlaps with biologically important habitats when individuals are present, and that continuous disruption will have a greater impact than intermittent disruption.

Nearly all PCoD studies and experts agree that infrequent exposures of a single day or less are unlikely to impact individual fitness, let alone lead to population level effects (Booth et al., 2016; Booth et al., 2017; Christiansen and Lusseau 2015; Farmer et al., 2018; Wilson et al., 2020; Harwood and Booth 2016; King et al., 2015; McHuron et al., 2018; National Academies of Sciences, Engineering, and Medicine (NAS) 2017; New et al., 2014; Pirotta et al., 2018a; Southall et al., 2007; Villegas-Amtmann et al., 2015). As described through this proposed rule, NMFS expects that any behavioral disturbance that would occur due to animals being exposed to construction activity would be of a relatively short duration, with behavior returning to a baseline state shortly after the acoustic stimuli ceases or the animal moves far enough away from the source. Given this, and NMFS' evaluation of the available PCoD studies, and the required mitigation discussed later, any such behavioral disturbance resulting from SouthCoast's activities is not expected to impact individual animals' health or have effects on individual animals' survival or reproduction, thus no detrimental impacts at the population level are anticipated. Marine mammals may temporarily avoid the immediate area but are not expected to permanently abandon the area or their migratory or foraging behavior. Impacts to breeding, feeding, sheltering, resting, or migration are not expected nor are shifts in habitat use, distribution, or foraging success.

Potential Effects From Explosive Sources

With respect to the noise from underwater explosives, the same acoustic-related impacts described above apply and are not repeated here. Noise from explosives can cause hearing impairment if an animal is close enough to the sources; however, because noise from an explosion is discrete, lasting less than approximately one second, no behavioral impacts below the TTS threshold are anticipated considering that SouthCoast would not detonate more than one UXO/MEC per day and only ten during the life of the proposed rule. This section focuses on the pressure-related impacts of underwater explosives, including physiological injury and mortality.

Underwater explosive detonations send a shock wave and sound energy through the water and can release gaseous by-products, create an oscillating bubble, or cause a plume of water to shoot up from the water surface. The shock wave and accompanying noise are of most concern to marine animals. Depending on the intensity of the shock wave and size, location, and depth of the animal, an animal can be injured, killed, suffer non-lethal physical effects, experience hearing related effects with or without behavioral responses, or exhibit temporary behavioral responses or tolerance from hearing the blast sound. Generally, exposures to higher levels of impulse and pressure levels would Start Printed Page 53748 result in greater impacts to an individual animal.

Injuries resulting from a shock wave take place at boundaries between tissues of different densities. Different velocities are imparted to tissues of different densities, and this can lead to their physical disruption. Blast effects are greatest at the gas-liquid interface (Landsberg, 2000). Gas-containing organs, particularly the lungs and gastrointestinal tract, are especially susceptible (Goertner, 1982; Hill, 1978; Yelverton et al., 1973). Intestinal walls can bruise or rupture, with subsequent hemorrhage and escape of gut contents into the body cavity. Less severe gastrointestinal tract injuries include contusions, petechiae (small red or purple spots caused by bleeding in the skin), and slight hemorrhaging (Yelverton et al., 1973).

Because the ears are the most sensitive to pressure, they are the organs most sensitive to injury (Ketten, 2000). Sound-related damage associated with sound energy from detonations can be theoretically distinct from injury from the shock wave, particularly farther from the explosion. If a noise is audible to an animal, it has the potential to damage the animal's hearing by causing decreased sensitivity (Ketten, 1995). Lethal impacts are those that result in immediate death or serious debilitation in or near an intense source and are not, technically, pure acoustic trauma (Ketten, 1995). Sublethal impacts include hearing loss, which is caused by exposures to perceptible sounds. Severe damage (from the shock wave) to the ears includes tympanic membrane rupture, fracture of the ossicles, and damage to the cochlea, hemorrhage, and cerebrospinal fluid leakage into the middle ear. Moderate injury implies partial hearing loss due to tympanic membrane rupture and blood in the middle ear. Permanent hearing loss also can occur when the hair cells are damaged by one very loud event as well as by prolonged exposure to a loud noise or chronic exposure to noise. The level of impact from blasts depends on both an animal's location and at outer zones, its sensitivity to the residual noise (Ketten, 1995).

Given the mitigation measures proposed, it is unlikely that any of the more serious injuries or mortality discussed above will result from any UXO/MEC detonation that SouthCoast might need to undertake. PTS, TTS, and brief startle reactions are the most likely impacts to result from this activity, if it occurs (noting detonation is the last method to be chosen for removal).

Potential Effects From Vessel Strike

Vessel collisions with marine mammals, also referred to as vessel strikes or ship strikes, can result in death or serious injury of the animal. The most vulnerable marine mammals are those that spend extended periods of time at the surface in order to restore oxygen levels within their tissues after deep dives ( e.g., the sperm whale). Some baleen whales seem generally unresponsive to vessel sound, making them more susceptible to vessel collisions (Nowacek et al., 2004). Marine mammal responses to vessels may include avoidance and changes in dive pattern (NRC, 2003). Wounds resulting from vessel strike may include massive trauma, hemorrhaging, broken bones, or propeller lacerations (Knowlton and Kraus, 2001). An animal at the surface could be struck directly by a vessel, a surfacing animal could hit the bottom of a vessel, or an animal just below the surface could be cut by a vessel's propeller. Superficial strikes may not kill or result in the death of the animal. Lethal interactions are typically associated with large whales, which are occasionally found draped across the bulbous bow of large commercial ships upon arrival in port. Although smaller cetaceans are more maneuverable in relation to large vessels than are large whales, they may also be susceptible to strike. The severity of injuries typically depends on the size and speed of the vessel (Knowlton and Kraus, 2001; Laist et al., 2001; Vanderlaan and Taggart, 2007; Conn and Silber, 2013). Impact forces increase with speed as does the probability of a strike at a given distance (Silber et al., 2010; Gende et al., 2011).

An examination of all known vessel strikes from all shipping sources (civilian and military) indicates vessel speed is a principal factor in whether a vessel strike occurs and, if so, whether it results in injury, serious injury, or mortality (Knowlton and Kraus, 2001; Laist et al., 2001; Jensen and Silber, 2003; Pace and Silber, 2005; Vanderlaan and Taggart, 2007; Conn and Silber, 2013). In assessing records in which vessel speed was known, Laist et al. (2001) found a direct relationship between the occurrence of a whale strike and the speed of the vessel involved in the collision. The authors concluded that most deaths occurred when a vessel was traveling in excess of 13 knots (15 mph).

Jensen and Silber (2003) detailed 292 records of known or probable vessel strikes of all large whale species from 1975 to 2002. Of these, vessel speed at the time of collision was reported for 58 cases. Of these 58 cases, 39 (or 67 percent) resulted in serious injury or death (19 of those resulted in serious injury as determined by blood in the water, propeller gashes or severed tailstock, and fractured skull, jaw, vertebrae, hemorrhaging, massive bruising or other injuries noted during necropsy and 20 resulted in death). Operating speeds of vessels that struck various species of large whales ranged from 2 to 51 knots (2.3 to 59 mph). The majority (79 percent) of these strikes occurred at speeds of 13 knots (15 mph) or greater. The average speed that resulted in serious injury or death was 18.6 knots (21.4 mph). Pace and Silber (2005) found that the probability of death or serious injury increased rapidly with increasing vessel speed. Specifically, the predicted probability of serious injury or death increased from 45 to 75 percent as vessel speed increased from 10 to 14 knots (11.5 to 16 mph), and exceeded 90 percent at 17 knots (20 mph). Higher speeds during collisions result in greater force of impact and also appear to increase the chance of severe injuries or death. While modeling studies have suggested that hydrodynamic forces pulling whales toward the vessel hull increase with increasing speed (Clyne, 1999; Knowlton et al., 1995), this is inconsistent with Silber et al. (2010), which demonstrated that there is no such relationship ( i.e., hydrodynamic forces are independent of speed).

In a separate study, Vanderlaan and Taggart (2007) analyzed the probability of lethal mortality of large whales at a given speed, showing that the greatest rate of change in the probability of a lethal injury to a large whale as a function of vessel speed occurs between 8.6 and 15 knots (9.9 and 17 mph). The chances of a lethal injury decline from approximately 80 percent at 15 knots (17 mph) to approximately 20 percent at 8.6 knots (10 mph). At speeds below 11.8 knots (13.5 mph), the chances of lethal injury drop below 50 percent, while the probability asymptotically increases toward 100 percent above 15 knots (17 mph).

The Jensen and Silber (2003) report notes that the Large Whale Ship Strike Database represents a minimum number of collisions, because the vast majority go undetected or unreported. In contrast, SouthCoast's personnel are likely to detect any strike that does occur because of the required personnel training and lookouts, along with the inclusion of PSOs as described in the Proposed Mitigation section), and they are required to report all ship strikes involving marine mammals.

There are no known vessel strikes of marine mammals by any offshore wind Start Printed Page 53749 energy vessel in the U.S. Given the extensive mitigation and monitoring measures (see the Proposed Mitigation and Proposed Monitoring and Reporting section) that would be required of SouthCoast, NMFS believes that a vessel strike is not likely to occur.

Potential Effects to Marine Mammal Habitat

SouthCoast's proposed activities could potentially affect marine mammal habitat through the introduction of impacts to the prey species of marine mammals (through noise, oceanographic processes, or reef effects), acoustic habitat (sound in the water column), water quality, and biologically important habitat for marine mammals.

Effects on Prey

Sound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species ( e.g., crustaceans, cephalopods, fish, and zooplankton). Marine mammal prey varies by species, season, and location and, for some, is not well documented. Here, we describe studies regarding the effects of noise on known marine mammal prey.

Fish utilize the soundscape and components of sound in their environment to perform important functions such as foraging, predator avoidance, mating, and spawning ( e.g., Zelick and Mann., 1999; Fay, 2009). The most likely effects on fishes exposed to loud, intermittent, low-frequency sounds are behavioral responses ( i.e., flight or avoidance). Short duration, sharp sounds (such as pile driving or airguns) can cause overt or subtle changes in fish behavior and local distribution. The reaction of fish to acoustic sources depends on the physiological state of the fish, past exposures, motivation ( e.g., feeding, spawning, migration), and other environmental factors. Key impacts to fishes may include behavioral responses, hearing damage, barotrauma (pressure-related injuries), and mortality. While it is clear that the behavioral responses of individual prey, such as displacement or other changes in distribution, can have direct impacts on the foraging success of marine mammals, the effects on marine mammals of individual prey that experience hearing damage, barotrauma, or mortality is less clear, though obviously population scale impacts that meaningfully reduce the amount of prey available could have more serious impacts.

Fishes, like other vertebrates, have a variety of different sensory systems to glean information from ocean around them (Astrup and Mohl, 1993; Astrup, 1999; Braun and Grande, 2008; Carroll et al., 2017; Hawkins and Johnstone, 1978; Ladich and Popper, 2004; Ladich and Schulz-Mirbach, 2016; Mann, 2016; Nedwell et al., 2004; Popper et al., 2003; Popper et al., 2005). Depending on their hearing anatomy and peripheral sensory structures, which vary among species, fishes hear sounds using pressure and particle motion sensitivity capabilities and detect the motion of surrounding water (Fay et al., 2008) (terrestrial vertebrates generally only detect pressure). Most marine fishes primarily detect particle motion using the inner ear and lateral line system while some fishes possess additional morphological adaptations or specializations that can enhance their sensitivity to sound pressure, such as a gas-filled swim bladder (Braun and Grande, 2008; Popper and Fay, 2011).

Hearing capabilities vary considerably between different fish species with data only available for just over 100 species out of the 34,000 marine and freshwater fish species (Eschmeyer and Fong, 2016). In order to better understand acoustic impacts on fishes, fish hearing groups are defined by species that possess a similar continuum of anatomical features, which result in varying degrees of hearing sensitivity (Popper and Hastings, 2009a). There are four hearing groups defined for all fish species (modified from Popper et al., 2014) within this analysis, and they include: fishes without a swim bladder ( e.g., flatfish, sharks, rays, etc.); fishes with a swim bladder not involved in hearing ( e.g., salmon, cod, pollock, etc.); fishes with a swim bladder involved in hearing ( e.g., sardines, anchovy, herring, etc.); and fishes with a swim bladder involved in hearing and high-frequency hearing ( e.g., shad and menhaden). Most marine mammal fish prey species would not be likely to perceive or hear mid- or high-frequency sonars. While hearing studies have not been done on sardines and northern anchovies, it would not be unexpected for them to have hearing similarities to Pacific herring (up to 2-5 kHz) (Mann et al., 2005). Currently, less data are available to estimate the range of best sensitivity for fishes without a swim bladder.

In terms of physiology, multiple scientific studies have documented a lack of mortality or physiological effects to fish from exposure to low- and mid-frequency sonar and other sounds (Halvorsen et al., 2012a; Jørgensen et al., 2005; Juanes et al., 2017; Kane et al., 2010; Kvadsheim and Sevaldsen, 2005; Popper et al., 2007; Popper et al., 2016; Watwood et al., 2016). Techer et al. (2017) exposed carp in floating cages for up to 30 days to low-power 23 and 46 kHz source without any significant physiological response. Other studies have documented either a lack of TTS in species whose hearing range cannot perceive sonar (such as Navy sonar), or for those species that could perceive sonar-like signals, any TTS experienced would be recoverable (Halvorsen et al., 2012a; Ladich and Fay, 2013; Popper and Hastings, 2009a, 2009b; Popper et al., 2014; Smith, 2016). Only fishes that have specializations that enable them to hear sounds above about 2,500 Hz (2.5 kHz), such as herring (Halvorsen et al., 2012a; Mann et al., 2005; Mann, 2016; Popper et al., 2014), would have the potential to receive TTS or exhibit behavioral responses from exposure to mid-frequency sonar. In addition, any sonar induced TTS to fish with a hearing range could perceive sonar would only occur in the narrow spectrum of the source ( e.g., 3.5 kHz) compared to the fish's total hearing range ( e.g., 0.01 kHz to 5 kHz).

In terms of behavioral responses, Juanes et al. (2017) discuss the potential for negative impacts from anthropogenic noise on fish, but the author's focus was on broader based sounds, such as ship and boat noise sources. Watwood et al. (2016) also documented no behavioral responses by reef fish after exposure to mid-frequency active sonar. Doksaeter et al. (2009; 2012) reported no behavioral responses to mid-frequency sonar (such as naval sonar) by Atlantic herring; specifically, no escape reactions (vertically or horizontally) were observed in free swimming herring exposed to mid-frequency sonar transmissions. Based on these results (Doksaeter et al., 2009; Doksaeter et al., 2012; Sivle et al., 2012), Sivle et al. (2014) created a model in order to report on the possible population-level effects on Atlantic herring from active sonar. The authors concluded that the use of sonar poses little risk to populations of herring regardless of season, even when the herring populations are aggregated and directly exposed to sonar. Finally, Bruintjes et al. (2016) commented that fish exposed to any short-term noise within their hearing range might initially startle, but would quickly return to normal behavior.

Pile-driving noise during construction is of particular concern as the very high sound pressure levels could potentially prevent fish from reaching breeding or spawning sites, finding food, and acoustically locating mates. A playback study in West Scotland revealed that there was a significant movement response to the pile-driving stimulus in both species at relatively low received sound pressure levels (sole: 144-156 dB Start Printed Page 53750 re 1μPa Peak; cod: 140-161 dB re 1 μPa Peak, particle motion between 51 × 10 and 62 × 104⁴ m/s² peak) (Mueller-Blenkle et al., 2010). The swimming speed of the sole increased significantly during the playback period compared to before and after playback of construction noise when compared to the playbacks of before and after construction. While not statistically significant, cod also displayed a similar reaction, yet results were not significant. Cod showed a behavioral response during before, during, and after construction playbacks. However, cod demonstrated a specific and significant freezing response at the onset and cessation of the playback recording. Both species displayed indications of directional movements away from the playback source. During wind farm construction in the Eastern Taiwan Strait, Type 1 soniferous fish chorusing showed a relatively lower intensity and longer duration, while Type 2 chorusing exhibited higher intensity and no changes in its duration. Deviation from regular fish vocalization patterns may affect fish reproductive success, cause migration, augmented predation, or physiological alterations.

Occasional behavioral reactions to activities that produce underwater noise sources are unlikely to cause long-term consequences for individual fish or populations. The most likely impact to fish from impact and vibratory pile driving activities at the project areas would be temporary behavioral avoidance of the area. Any behavioral avoidance by fish of the disturbed area would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity. The duration of fish avoidance of an area after pile driving stops is unknown, but a rapid return to normal recruitment, distribution and behavior is anticipated. In general, impacts to marine mammal prey species are expected to be minor and temporary due to the expected short daily duration of individual pile driving events and the relatively small areas being affected.

SPLs of sufficient strength have been known to cause fish auditory impairment, injury, and mortality. Popper et al. (2014) found that fish with or without air bladders could experience TTS at 186 dB SEL_cum. Mortality could occur for fish without swim bladders at >216 dB SEL_cum . Those with swim bladders or at the egg or larvae life stage, mortality was possible at >203 dB SEL_cum . Other studies found that 203 dB SEL_cum or above caused a physiological response in other fish species (Casper et al., 2012; Halvorsen et al., 2012a; Halvorsen et al., 2012b; Casper et al., 2013a; Casper et al., 2013b). However, in most fish species, hair cells in the ear continuously regenerate and loss of auditory function likely is restored when damaged cells are replaced with new cells. Halvorsen et al. (2012a) showed that a TTS of 4-6 dB was recoverable within 24 hours for one species. Impacts would be most severe when the individual fish is close to the source and when the duration of exposure is long. Injury caused by barotrauma can range from slight to severe and can cause death and is most likely for fish with swim bladders. Barotrauma injuries have been documented during controlled exposure to impact pile driving (Halvorsen et al., 2012b; Casper et al., 2013a).

As described in the Proposed Mitigation section below, SouthCoast would utilize a sound attenuation device which would reduce potential for injury to marine mammal prey. Other fish that experience hearing loss as a result of exposure to explosions and impulsive sound sources may have a reduced ability to detect relevant sounds such as predators, prey, or social vocalizations. However, PTS has not been known to occur in fishes and any hearing loss in fish may be as temporary as the timeframe required to repair or replace the sensory cells that were damaged or destroyed (Popper et al., 2005; Popper et al., 2014; Smith et al., 2006). It is not known if damage to auditory nerve fibers could occur, and if so, whether fibers would recover during this process.

It is also possible for fish to be injured or killed by an explosion from UXO/MEC detonation. Physical effects from pressure waves generated by underwater sounds ( e.g., underwater explosions) could potentially affect fish within proximity of the UXO/MEC detonation. The shock wave from an underwater explosion is lethal to fish at close range, causing massive organ and tissue damage and internal bleeding (Keevin and Hempen, 1997). At greater distance from the detonation point, the extent of mortality or injury depends on a number of factors including fish size, body shape, orientation, and species (Keevin and Hempen, 1997; Wright, 1982). At the same distance from the source, larger fish are generally less susceptible to death or injury, elongated forms that are round in cross-section are less at risk than deep-bodied forms, and fish oriented sideways to the blast suffer the greatest impact (Edds-Walton and Finneran, 2006; O'Keeffe, 1984; O'Keeffe and Young, 1984; Wiley et al., 1981; Yelverton et al., 1975). Species with gas-filled organs are more susceptible to injury and mortality than those without them (Gaspin, 1975; Gaspin et al., 1976; Goertner et al., 1994). Barotrauma injuries have been documented during controlled exposure to impact pile driving (an impulsive noise source, as are explosives and air guns) (Halvorsen et al., 2012b; Casper et al., 2013).

Fish not killed or driven from a location by an explosion might change their behavior, feeding pattern, or distribution. Changes in behavior of fish have been observed as a result of sound produced by explosives, with effect intensified in areas of hard substrate (Wright, 1982). Stunning from pressure waves could also temporarily immobilize fish, making them more susceptible to predation. The abundances of various fish (and invertebrates) near the detonation point for explosives could be altered for a few hours before animals from surrounding areas repopulate the area. However, these populations would likely be replenished as waters near the detonation point are mixed with adjacent waters.

UXO/MEC detonations would be dispersed in space and time; therefore, repeated exposure of individual fishes are unlikely. Mortality and injury effects to fishes from explosives would be localized around the area of a given in-water explosion but only if individual fish and the explosive (and immediate pressure field) were co-located at the same time. Repeated exposure of individual fish to sound and energy from underwater explosions is not likely given fish movement patterns, especially schooling prey species. In addition, most acoustic effects, if any, are expected to be short-term and localized. Long-term consequences for fish populations, including key prey species within the project area, would not be expected.

Required soft-starts would allow prey and marine mammals to move away from the impact pile driving source prior to any noise levels that may physically injure prey, and the use of the noise attenuation devices would reduce noise levels to the degree any mortality or injury of prey is also minimized. Use of bubble curtains, in addition to reducing impacts to marine mammals, for example, is a key mitigation measure in reducing injury and mortality of ESA-listed salmon on the U.S. West Coast. However, we recognize some mortality, physical injury and hearing impairment in marine mammal prey may occur, but we anticipate the amount of prey impacted in this manner is minimal compared to overall availability. Any behavioral responses to pile driving by marine Start Printed Page 53751 mammal prey are expected to be brief. We expect that other impacts, such as stress or masking, would occur in fish that serve as marine mammal prey (Popper et al., 2019); however, those impacts would be limited to the duration of impact pile driving and during any UXO/MEC detonations and, if prey were to move out the area in response to noise, these impacts would be minimized.

In addition to fish, prey sources such as marine invertebrates could potentially be impacted by noise stressors as a result of the proposed activities. However, most marine invertebrates' ability to sense sounds is limited. Invertebrates appear to be able to detect sounds (Pumphrey, 1950; Frings and Frings, 1967) and are most sensitive to low-frequency sounds (Packard et al., 1990; Budelmann and Williamson, 1994; Lovell et al., 2005; Mooney et al., 2010). Data on response of invertebrates such as squid, another marine mammal prey species, to anthropogenic sound is more limited (de Soto, 2016; Sole et al., 2017). Data suggest that cephalopods are capable of sensing the particle motion of sounds and detect low frequencies up to 1-1.5 kHz, depending on the species, and so are likely to detect airgun noise (Kaifu et al., 2008; Hu et al., 2009; Mooney et al., 2010; Samson et al., 2014). Sole et al. (2017) reported physiological injuries to cuttlefish in cages placed at-sea when exposed during a controlled exposure experiment to low-frequency sources (315 Hz, 139 to 142 dB re 1m Pa² and 400 Hz, 139 to 141 dB re 1m Pa² ). Fewtrell and McCauley (2012) reported squids maintained in cages displayed startle responses and behavioral changes when exposed to seismic airgun sonar (136-162 re 1m Pa² ·s). Jones et al. (2020) found that when squid ( Doryteuthis pealeii) were exposed to impulse pile driving noise, body pattern changes, inking, jetting, and startle responses were observed and nearly all squid exhibited at least one response. However, these responses occurred primarily during the first eight impulses and diminished quickly, indicating potential rapid, short-term habituation.

Cephalopods have a specialized sensory organ inside the head called a statocyst that may help an animal determine its position in space (orientation) and maintain balance (Budelmann, 1992). Packard et al. (1990) showed that cephalopods were sensitive to particle motion, not sound pressure, and Mooney et al. (2010) demonstrated that squid statocysts act as an accelerometer through which particle motion of the sound field can be detected (Budelmann, 1992). Auditory injuries (lesions occurring on the statocyst sensory hair cells) have been reported upon controlled exposure to low-frequency sounds, suggesting that cephalopods are particularly sensitive to low-frequency sound (Andre et al., 2011; Sole et al., 2013). Behavioral responses, such as inking and jetting, have also been reported upon exposure to low-frequency sound (McCauley et al., 2000; Samson et al., 2014). Squids, like most fish species, are likely more sensitive to low frequency sounds and may not perceive mid- and high-frequency sonars.

With regard to potential impacts on zooplankton, McCauley et al. (2017) found that exposure to airgun noise resulted in significant depletion for more than half the taxa present and that there were two to three times more dead zooplankton after airgun exposure compared with controls for all taxa, within 1 km (0.6 mi) of the airguns. However, the authors also stated that in order to have significant impacts on r -selected species ( i.e., those with high growth rates and that produce many offspring) such as plankton, the spatial or temporal scale of impact must be large in comparison with the ecosystem concerned, and it is possible that the findings reflect avoidance by zooplankton rather than mortality (McCauley et al., 2017). In addition, the results of this study are inconsistent with a large body of research that generally finds limited spatial and temporal impacts to zooplankton as a result of exposure to airgun noise ( e.g., Dalen and Knutsen, 1987; Payne, 2004; Stanley et al., 2011). Most prior research on this topic, which has focused on relatively small spatial scales, has showed minimal effects ( e.g., Kostyuchenko, 1973; Booman et al., 1996; Sætre and Ona, 1996; Pearson et al., 1994; Bolle et al., 2012).

A modeling exercise was conducted as a follow-up to the McCauley et al. (2017) study (as recommended by McCauley et al.), in order to assess the potential for impacts on ocean ecosystem dynamics and zooplankton population dynamics (Richardson et al., 2017). Richardson et al. (2017) found that a full-scale airgun survey would impact copepod abundance within the survey area, but that effects at a regional scale were minimal (2 percent decline in abundance within 150 km of the survey area and effects not discernible over the full region). The authors also found that recovery within the survey area would be relatively quick (3 days following survey completion), and suggest that the quick recovery was due to the fast growth rates of zooplankton, and the dispersal and mixing of zooplankton from both inside and outside of the impacted region. The authors also suggest that surveys in areas with more dynamic ocean circulation in comparison with the study region and/or with deeper waters ( i.e., typical offshore wind locations) would have less net impact on zooplankton.

Notably, a more recent study produced results inconsistent with those of McCauley et al. (2017). Researchers conducted a field and laboratory study to assess if exposure to airgun noise affects mortality, predator escape response, or gene expression of the copepod Calanus finmarchicus (Fields et al., 2019). Immediate mortality of copepods was significantly higher, relative to controls, at distances of 5 m (16.4 ft) or less from the airguns. Mortality one week after the airgun blast was significantly higher in the copepods placed 10 m (32.8 ft) from the airgun but was not significantly different from the controls at a distance of 20 m (65.6 ft) from the airgun. The increase in mortality, relative to controls, did not exceed 30 percent at any distance from the airgun. Moreover, the authors caution that even this higher mortality in the immediate vicinity of the airguns may be more pronounced than what would be observed in free-swimming animals due to increased flow speed of fluid inside bags containing the experimental animals. There were no sublethal effects on the escape performance or the sensory threshold needed to initiate an escape response at any of the distances from the airgun that were tested. Whereas McCauley et al. (2017) reported an SEL of 156 dB at a range of 509-658 m (1,670-2,159 ft), with zooplankton mortality observed at that range, Fields et al. (2019) reported an SEL of 186 dB at a range of 25 m (82 ft), with no reported mortality at that distance.

The presence and operation of wind turbines (both the foundation and WTG) has been shown to impact meso- and sub-meso-scale water column circulation, which can affect the density, distribution, and energy content of zooplankton and thereby, their availability as marine mammal prey. Topside, atmospheric wakes result in wind speed reductions influencing upwelling and downwelling in the ocean, while underwater structures such as WTG and OSP foundations cause turbulent current wakes, which impact circulation, stratification, mixing, turbidity, and sediment resuspension (Daewel et al., 2022). Impacts from the presence of structures and/or operation of wind turbine generators are generally likely to result in certain oceanographic Start Printed Page 53752 effects, such as perturbation of zooplankton aggregation mechanisms through changes to the strength of tidal currents and associated fronts, stratification, the degree of mixing, and primary production in the water column, and these effects may alter the production, distribution, and/or availability of marine mammal zooplankton prey (Chen et al., 2021; Chen et al., 2024, Johnson et al., 2021, Christiansen et al., 2022, Dorrell et al., 2022).

Assessing the ecosystem impacts of offshore wind development has a unique set of challenges, including minimizing uncertainties in the fundamental understanding of how existing physical and biological oceanography might be altered by the presence of a single offshore wind turbine, by an offshore wind farm, or by a region of adjacent offshore wind farms. Physical models can demonstrate, among many things, the extent to which and how a single or large number of operating offshore wind turbine(s) can alter atmospheric and hydrodynamic flow through interruptions of local winds that drive circulation processes and by creating turbulence in the water column surrounding the pile(s). For example, Chen et al., 2024 found that regardless of variations in wind intensity and direction, the downwind wake caused by WTGs, as modeled from a wind farm simulation in a lease area located to the west of the SouthCoast lease area, could consistently produce and enhance offshore water transport of zooplankton (in this case scallop larvae), particularly around the 40 to 50-m isobaths.

However, many physical and biological processes are influenced by cross-scale phenomena ( e.g., aggregation of dense zooplankton patches), necessitating construction of more complex models that tolerate varying degrees of uncertainty. Thus, determining the impacts of offshore wind operations on not only physical processes but trophic connections from phytoplankton to marine mammals and ultimately the ecosystem will require significant data collection, monitoring, modeling, and research effort. Given the limited state of understanding of the entire system in southern New England and the changing oceanography and ecology, identification of substantial impacts on zooplankton, and specifically on right whale prey, that may result from wind energy development in the Nantucket Shoals region is difficult to assess ((National Academy of Sciences (NAS), 2023.

SouthCoast intends to install up to 147 WTGs, up to 85 of which would be operational following completion of Project 1 and the remainder operational following installation of Project 2. SouthCoast may commission turbines in batches ( i.e., not all foundations and WTGs need to be installed per Project before becoming operational). Based on SouthCoast's current schedule (Table 1), commissioning could begin in early 2029, assuming foundations were installed the previous year, thus, it is possible that any influence of operating turbines on local physical and/or biological processes may be observable at that time, depending on latency of effects. Given the proposed sequencing, NMFS anticipates the turbines closest to Nantucket Shoals would be commissioned first. As described above, there is scientific uncertainty around the scale of oceanographic impacts (meters to kilometers) associated with the presence of foundation structures ( e.g., monopile, piled jacket) in the water, as well as operation of the WTGs. Generally speaking and depending on the extent, impacts on prey could influence the distribution of marine mammals in within and among foraging habitats, potentially necessitating additional energy expenditure to find and capture prey, which could lead to fitness consequences. Although studies assessing the impacts of offshore wind development on marine mammals are limited and the results vary, the repopulation of some wind energy areas by harbor porpoises (Brandt et al., 2016; Lindeboom et al., 2011) and harbor seals (Lindeboom et al., 2011; Russell et al., 2016) following the installation of wind turbines indicates that, in some cases, there is evidence that suitable habitat, including prey resources, exists within developed waters.

Reef Effects

The presence of WTG and OSP foundations, scour protection, and cable protection will result in a conversion of the existing sandy bottom habitat to a hard bottom habitat with areas of vertical structural relief. This could potentially alter the existing habitat by creating an “artificial reef effect” that results in colonization by assemblages of both sessile and mobile animals within the new hard-bottom habitat (Wilhelmsson et al., 2006; Reubens et al., 2013; Bergström et al., 2014; Coates et al., 2014). This colonization by marine species, especially hard-substrate preferring species, can result in changes to the diversity, composition, and/or biomass of the area thereby impacting the trophic composition of the site (Wilhelmsson et al., 2010, Krone et al., 2013; Bergström et al., 2014; Hooper et al., 2017; Raoux et al., 2017; Harrison and Rousseau, 2020; Taormina et al., 2020; Buyse et al., 2022a; ter Hofstede et al., 2022).

Artificial structures can create increased habitat heterogeneity important for species diversity and density (Langhamer, 2012). The WTG and OSP foundations will extend through the water column, which may serve to increase settlement of meroplankton or planktonic larvae on the structures in both the pelagic and benthic zones (Boehlert and Gill, 2010). Fish and invertebrate species are also likely to aggregate around the foundations and scour protection which could provide increased prey availability and structural habitat (Boehlert and Gill, 2010; Bonar et al., 2015). Further, instances of species previously unknown, rare, or nonindigenous to an area have been documented at artificial structures, changing the composition of the food web and possibly the attractability of the area to new or existing predators (Adams et al., 2014; de Mesel, 2015; Bishop et al., 2017; Hooper et al., 2017; Raoux et al., 2017; van Hal et al., 2017; Degraer et al., 2020; Fernandez-Betelu et al., 2022). Notably, there are examples of these sites becoming dominated by marine mammal prey species, such as filter-feeding species and suspension-feeding crustaceans (Andersson and Öhman, 2010; Slavik et al., 2019; Hutchison et al., 2020; Pezy et al., 2020; Mavraki et al., 2022).

Numerous studies have documented significantly higher fish concentrations including species like cod and pouting ( Trisopterus luscus), flounder ( Platichthys flesus), eelpout ( Zoarces viviparus), and eel ( Anguilla anguilla) near in-water structures than in surrounding soft bottom habitat (Langhamer and Wilhelmsson, 2009; Bergström et al., 2013; Reubens et al., 2013). In the German Bight portion of the North Sea, fish were most densely congregated near the anchorages of jacket foundations, and the structures extending through the water column were thought to make it more likely that juvenile or larval fish encounter and settle on them (Rhode Island Coastal Resources Management Council (RI-CRMC), 2010; Krone et al., 2013). In addition, fish can take advantage of the shelter provided by these structures while also being exposed to stronger currents created by the structures, which generate increased feeding opportunities and decreased potential for predation (Wilhelmsson et al., 2006). The presence of the foundations and resulting fish aggregations around the foundations is expected to be a long-term habitat impact, but the increase in Start Printed Page 53753 prey availability could potentially be beneficial for some marine mammals.

The most likely impact to marine mammal habitat from the Project is expected to be from pile driving, which may affect marine mammal food sources such as forage fish and zooplankton.

Water Quality

Temporary and localized reduction in water quality will occur as a result of in-water construction activities. Most of this effect will occur during pile driving and installation of the cables, including auxiliary work such as dredging and scour placement. These activities will disturb bottom sediments and may cause a temporary increase in suspended sediment in the Lease Area and ECCs. Indirect effects of explosives and unexploded ordnance to marine mammals via sediment disturbance is possible in the immediate vicinity of the ordnance but through the implementation of the mitigation, is it not anticipated marine mammals would be in the direct area of the explosive source. Currents should quickly dissipate any raised total suspended sediment (TSS) levels, and levels should return to background levels once the Project activities in that area cease.

No direct impacts on marine mammals are anticipated due to increased TSS and turbidity; however, turbidity within the water column has the potential to reduce the level of oxygen in the water and irritate the gills of prey fish species in the Lease Area and ECCs.

Further, contamination of water is not anticipated. Degradation products of Royal Demolition Explosive are not toxic to marine organisms at realistic exposure levels (Rosen and Lotufo, 2010). Relatively low solubility of most explosives and their degradation products means that concentrations of these contaminants in the marine environment are relatively low and readily diluted. Furthermore, while explosives and their degradation products were detectable in marine sediment approximately 6-12 in (0.15-0.3 m) away from degrading ordnance, the concentrations of these compounds were not statistically distinguishable from background beyond 3-6 ft (1-2 m) from the degrading ordnance.

Turbidity plumes associated with the Project would be temporary and localized, and fish in the proposed project area would be able to move away from and avoid the areas where plumes may occur. Therefore, it is expected that the impacts on prey fish species from turbidity, and therefore on marine mammals, would be minimal and temporary.

Equipment used by SouthCoast for the project, including ships and other marine vessels, aircrafts, and other implements, are also potential sources of by-products ( e.g., hydrocarbons, particulate matter, heavy metals). SouthCoast would be required to properly maintain all equipment in accordance with applicable legal requirements such that operating equipment meets Federal water quality standards, where applicable. Given these requirements, impacts to water quality are expected to be minimal.

Acoustic Habitat

Acoustic habitat is the holistic soundscape, encompassing all of the biotic and abiotic sound in a particular location and time, as perceived by an individual. Animals produce sound for and listen for sounds produced by conspecifics (communication during feeding, mating, and other social activities), other animals (finding prey or avoiding predators), and the physical environment (finding suitable habitats, navigating). Together, sounds made by animals and the geophysical environment ( e.g., produced by earthquakes, lightning, wind, rain, waves) comprise the natural contributions to the total soundscape. These acoustic conditions, termed acoustic habitat, are one attribute of an animal's total habitat.

Anthropogenic sound is another facet of the soundscape that influences the overall acoustic habitat. This may include incidental contributions from sources such as vessels or sounds intentionally introduced to the marine environment for data acquisition purposes ( e.g., use of high-resolution geophysical surveys), detonations for munitions disposal or coastal constructions, sonar for Navy training and testing purposes, or pile driving/hammering for construction.projects. Anthropogenic noise varies widely in its frequency, content, duration, and loudness, and these characteristics greatly influence the potential habitat-mediated effects to marine mammals (please also see the previous discussion on Masking), which may range from local effects for brief periods of time to chronic effects over large areas and for long durations. Depending on the extent of effects to their acoustic habitat, animals may alter their communications signals (thereby potentially expending additional energy) or miss acoustic cues (either conspecific or adventitious). Problems arising from a failure to detect cues are more likely to occur when noise stimuli are chronic and overlap with biologically relevant cues used for communication, orientation, and predator/prey detection (Francis and Barber, 2013). For more detail on these concepts see, e.g., Barber et al., 2009; Pijanowski et al., 2011; Francis and Barber, 2013; Lillis et al., 2014.

Communication space describes the area over which an animal's acoustic signal travels and is audible to the intended receiver (Brenowitz, 1982; Janik, 2000; Clark et al., 2009; Havlick et al., 2022). The extent of this area depends on the temporal and spectral structure of the signal, the characteristics of the environment, and the receiver's ability to detect (the detection threshold) and discriminate the signal from background noise (Wiley and Richards, 1978; Clark et al., 2009; Havlick et al., 2022). Large communication spaces are created by acoustic signals that propagate over long distances relative to the distribution of conspecifics, as exemplified by low-frequency baleen whale vocalizations (McGregor and Krebs, 1984; Morton, 1986; Janik, 2000). Conversely, both natural and anthropogenic noise may reduce communication space by increasing background noise, leading to a generalized contraction of the range over which animals would be able to detect signals of biological importance, including eavesdropping on predators and prey (Barber et al., 2009). Any reduction in the communication space, due to increased background noise resulting in masking, may therefore have detrimental effects on the ability of animals to obtain important social and environmental information. Such metrics do not, in and of themselves, document fitness consequences for the marine animals that live in chronically noisy environments. Long-term population-level consequences of acoustic signal interference mediated through changes in the ultimate survival and reproductive success of individuals are difficult to study, and particularly in the marine environment. However, it is increasingly well documented that aquatic species rely on qualities of natural acoustic habitats. For example, researchers have quantified reduced detection of important ecological cues ( e.g., Francis and Barber, 2013; Slabbekoorn et al., 2010) as well as survivorship consequences in several species ( e.g., damselfish; Simpson et al., 2016; larval Atlantic cod, Nedelec et al., 2015a; embryonic sea hare, Nedelec et al., 2015a) following noise exposure.

Although this proposed rulemaking primarily covers the noise produced from construction activities relevant to the SouthCoast offshore wind facility, operational noise was a consideration in NMFS' analysis of the project, as some, and potentially all, turbines would Start Printed Page 53754 become operational within the effective period of the rule (if issued). Once operational, offshore wind turbines are known to produce continuous, non-impulsive underwater noise, primarily below 1 kHz (Tougaard et al., 2020; Stöber and Thomsen, 2021).

In both newer, quieter, direct-drive systems and older generation, geared turbine designs, recent scientific studies indicate that operational noise from turbines is on the order of 110 to 125 dB re 1 μPa root-mean-square sound pressure level (SPL_rms) at an approximate distance of 50 m (164 ft) (Tougaard et al., 2020). Recent measurements of operational sound generated from wind turbines (direct drive, 6 MW, jacket foundations) at Block Island wind farm (BIWF) indicate average broadband levels of 119 dB at 50 m (164 ft) from the turbine, with levels varying with wind speed (HDR, Inc., 2019). Interestingly, measurements from BIWF turbines showed operational sound had less tonal components compared to European measurements of turbines with gear boxes.

Tougaard et al. (2020) further stated that the operational noise produced by WTGs is static in nature and lower than noise produced by passing ships. This is a noise source in this region to which marine mammals are likely already habituated. Furthermore, operational noise levels are likely lower than those ambient levels already present in active shipping lanes, such that operational noise would likely only be detected in very close proximity to the WTG (Thomsen et al., 2006; Tougaard et al., 2020). Similarly, recent measurements from a wind farm (3 MW turbines) in China found at above 300 Hz, turbines produced sound that was similar to background levels (Zhang et al., 2021). Other studies by Jansen and de Jong (2016) and Tougaard et al. (2009) determined that, while marine mammals would be able to detect operational noise from offshore wind farms (again, based on older 2 MW models) for several kilometers, they expected no significant impacts on individual survival, population viability, marine mammal distribution, or the behavior of the animals considered in their study (harbor porpoises and harbor seals). In addition, Madsen et al. (2006) found the intensity of noise generated by operational wind turbines to be much less than the noises present during construction, although this observation was based on a single turbine with a maximum power of 2 MW.

More recently, Stöber and Thomsen (2021) used monitoring data and modeling to estimate noise generated by more recently developed, larger (10 MW) direct-drive WTGs. Their findings, similar to Tougaard et al. (2020), demonstrate that there is a trend that operational noise increases with turbine size. Their study predicts broadband source levels could exceed 170 dB SPL_rms for a 10 MW WTG; however, those noise levels were generated based on geared turbines; newer turbines operate with direct drive technology. The shift from using gear boxes to direct drive technology is expected to reduce the levels by 10 dB. The findings in the Stöber and Thomsen (2021) study have not been experimentally validated, though the modeling (using largely geared turbines parameters) performed by Tougaard et al. (2020) yields similar results for a hypothetical 10 MW WTG.

Recently, Holme et al. (2023) cautioned that Tougaard et al. (2020) and Stöber and Thomsen (2021) extrapolated levels for larger turbines should be interpreted with caution since both studies relied on data from smaller turbines (0.45 to 6.15 MW) collected over a variety of environmental conditions. They demonstrated that the model presented in Tougaard et al. (2020) tends to potentially overestimate levels (up to approximately 8 dB) measured to those in the field, especially with measurements closer to the turbine for larger turbines. Holme et al. (2023) measured operational noise from larger turbines (6.3 and 8.3 MW) associated with three wind farms in Europe and found no relationship between turbine activity (power production, which is proportional to the blade's revolutions per minute) and noise level, though it was noted that this missing relationship may have been masked by the area's relatively high ambient noise sound levels. Sound levels (RMS) of a 6.3 MW direct-drive turbine were measured to be 117.3 dB at a distance of 70 m (229.7 ft). However, measurements from 8.3 MW turbines were inconclusive as turbine noise was deemed to have been largely masked by ambient noise.

Finally, operational turbine measurements are available from the Coastal Virginia Offshore Wind (CVOW) pilot pile project, where two 7.8 m-monopile WTGs were installed (HDR, 2023). Compared to BIWF, levels at CVOW were higher (10-30 dB) below 120 Hz, believed to be caused by the vibrations associated with the monopile structure, while above 120 Hz levels were consistent among the two wind farms.

Overall, noise from operating turbines would raise ambient noise levels in the immediate vicinity of the turbines; however, the spatial extent of increased noise levels would be limited. NMFS proposes to require SouthCoast to measure operational noise levels.

Estimated Take

This section provides an estimate of the number of incidental takes that may be authorized through the proposed regulations, which will inform both NMFS' consideration of “small numbers” and the negligible impact determination. Harassment is the only type of take expected to result from these activities.

Authorized takes would be primarily by Level B harassment, as use of the acoustic sources ( i.e., impact and vibratory pile driving, site characterization surveys, and UXO/MEC detonations) has the potential to result in disruption of marine mammal behavioral patterns due to exposure to elevated noise levels. Impacts such as masking and TTS can contribute to behavioral disturbances. There is also some potential for auditory injury (Level A harassment) to occur in select marine mammal species incidental to the specified activities ( i.e., impact pile driving and UXO/MEC detonations). The required mitigation and monitoring measures, the majority of which are not considered in the estimated take analysis, are expected to reduce the extent of the taking to the lowest level practicable.

While, in general, mortality and serious injury of marine mammals could occur from vessel strikes or UXO/MEC detonation if an animal is close enough to the source, the mitigation and monitoring measures in this proposed rule, when implemented, are expected to minimize the potential for take by mortality or serious injury such that the probability for take is discountable. No other activities have the potential to result in mortality or serious injury, and no serious injury is anticipated or proposed for authorization through this rulemaking.

Generally speaking, we estimate take by considering: (1) thresholds above which the best scientific information available indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment or non-auditory injury; (2) the area or volume of water that will be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and, (4) the number of days of activities. We note that while these factors can contribute to a basic calculation to provide an initial prediction of potential takes; additional information that can qualitatively inform take estimates is also sometimes available ( e.g., previous Start Printed Page 53755 monitoring results or average group size).

Below, we describe NMFS' acoustic and non-auditory injury thresholds, acoustic and exposure modeling methodologies, marine mammal density calculation methodology, occurrence information, and the modeling and methodologies applied to estimate incidental take for each specified activity likely to result in take by harassment.

Marine Mammal Acoustic Thresholds

NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals are likely to be behaviorally harassed (equated to Level B harassment) or to incur PTS of some degree (equated to Level A harassment). Thresholds have also been developed to identify the levels above which animals may incur different types of tissue damage (non-acoustic Level A harassment or mortality) from exposure to pressure waves from explosive detonation. A summary of all NMFS' thresholds can be found at ( https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-acoustic-technical-guidance).

Level B Harassment

Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source or exposure context ( e.g., frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source, ambient noise, and the receiving animals (animal's hearing, motivation, experience, demography, behavior at time of exposure, life stage, depth)) and can be difficult to predict ( e.g., Southall et al., 2007, 2021; Ellison et al., 2012). Based on the best scientific information available and the practical need to use a threshold based on a metric that is both predictable and measurable for most activities, NMFS typically uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS generally predicts that marine mammals are likely to be behaviorally harassed in a manner considered to be Level B harassment when exposed to underwater anthropogenic noise above the received sound pressure levels (SPL_rms) of 120 dB for continuous sources ( e.g., vibratory pile-driving, drilling) and above the received SPL_rms 160 dB for non-explosive impulsive or intermittent sources ( e.g., impact pile driving, scientific sonar). Generally speaking, Level B harassment take estimates based on these behavioral harassment thresholds are expected to include any likely takes by TTS as, in most cases, the likelihood of TTS occurs at distances from the source less than those at which behavioral harassment is likely. TTS of a sufficient degree can manifest as behavioral harassment, as reduced hearing sensitivity and the potential reduced opportunities to detect important signals (conspecific communication, predators, prey) may result in changes in behavior patterns that would not otherwise occur.

Level A Harassment

NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) (NMFS, 2018) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). As dual metrics, NMFS considers onset of PTS (Level A harassment) to have occurred when either one of the two metrics is exceeded ( i.e., metric resulting in the largest isopleth). As described above, SouthCoast's proposed activities include the use of both impulsive and non-impulsive sources.

NMFS' thresholds identifying the onset of PTS are provided in table 7. The references, analysis, and methodology used in the development of the thresholds are described in NMFS' 2018 Technical Guidance, which may be accessed at: www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-acoustic-technical-guidance.

Explosive Source

Based on the best scientific information available, NMFS uses the acoustic and pressure thresholds indicated in tables 8 and 9 to predict the onset of behavioral harassment, TTS, PTS, non-auditory injury, and mortality incidental to explosive detonations. Given SouthCoast would be limited to detonating one UXO/MEC per day, the TTS threshold is used to estimate the potential for Level B (behavioral) harassment ( i.e., individuals exposed above the TTS threshold may also be harassed by behavioral disruption, but we do not anticipate any impacts from exposure to UXO/MEC detonation Start Printed Page 53756 below the TTS threshold would constitute behavioral harassment).

Additional thresholds for non-auditory injury to lung and gastrointestinal (GI) tracts from the blast shock wave and/or onset of high peak pressures are also relevant (at relatively close ranges) (table 9). These criteria have been developed by the U.S. Navy (DoN (U.S. Department of the Navy) 2017a) and are based on the mass of the animal and the depth at which it is present in the water column. Equations predicting the onset of the associated potential effects are included below (table 9).

Modeling and Take Estimation

SouthCoast estimated density-based exposures in two separate ways, depending on the activity. To assess the potential for Level A harassment and Level B harassment resulting from exposure to the underwater sound fields produced during impact and vibratory pile driving, sophisticated sound and animal movement modeling was conducted to account for movement and behavior of marine mammals. For HRG surveys and UXO/MEC detonations, SouthCoast estimated the number of takes by Level B harassment using a simplified “static” method wherein the take estimates are the product of density, area of water ensonified above the NMFS defined threshold ( e.g., unweighted 160 dB SPL_rms) levels, and number of activity days (assuming a maximum of one UXO/MEC detonation per day). For some species, observational data from PSOs aboard HRG survey vessels or group size indicated that the density-based take estimates may be insufficient to account for the number of individuals of a species that may be encountered during the planned activities; thus, adjustments were made to the density-based estimates.

The assumptions and methodologies used to estimate take, in consideration of acoustic thresholds and appropriate marine mammal density and occurrence information, are described in activity-specific subsections below ( i.e., WTG and OSP foundation installation, HRG surveys, and UXO/MEC detonation). Resulting distances to threshold isopleths, densities used, activity-specific exposure estimates (as relevant to the analysis), and take estimates can be found in each activity subsection below. At the end of this section, we present the total annual and 5-year take estimates that NMFS proposes to authorize.

Marine Mammal Density and Occurrence

In this section, we provide information about marine mammal presence, density, or group dynamics that will inform the take calculations for all activities. Depending on the stock and as described in the take estimation section for each activity, take estimates may be based on the Roberts et al. (2023) density estimates, marine mammal monitoring results from HRG surveys, or average group sizes. The density and occurrence information resulting in the highest take estimate Start Printed Page 53757 was considered in subsequent analyses, and the explanation and results for each activity are described in the specific activity sub-sections.

Habitat-based density models produced by the Duke University Marine Geospatial Ecology Laboratory and the Marine-life Data and Analysis Team, based on the best available marine mammal data obtained in a collaboration between Duke University, the Northeast Regional Planning Body, the University of North Carolina Wilmington, the Virginia Aquarium and Marine Science Center, and NOAA (Roberts et al., 2016a, 2016b, 2017, 2018, 2020, 2021a, 2021b, 2023), represent the best available scientific information regarding marine mammal densities in and surrounding the Lease Area and along ECCs. Density data are subdivided into five separate raster data layers for each species, including: Abundance (density), 95 percent Confidence Interval of Abundance, 5 percent Confidence Interval of Abundance, Standard Error of Abundance, and Coefficient of Variation of Abundance.

Modifications to the densities used were necessary for some species. The estimated monthly density of seals provided in Roberts et al. (2016; 2023) includes all seal species present in the region as a single guild. To split the resulting “seal” density estimate by species, SouthCoast multiplied the estimate by the proportion of each species observed by PSOs during SouthCoast's 2020-2021 site characterization surveys (Milne, 2021; 2022). The proportions used were 231/246 (0.939) for gray seals and 15/246 (0.061) for harbor seals. The “seal” density provided by Roberts et al. (2016; 2023) was then multiplied by these proportions to get the species specific densities. While the Roberts et al. (2016; 2023) seals guild includes all phocid seals, as described in the Descriptions of Marine Mammals in the Specified Geographical Region section, harp seal occurrence is considered rare and unexpected in SNE. Given this, harp seals were not included when splitting the seal guild density and SouthCoast did not request take for this species. Monthly densities were unavailable for pilot whales, so SouthCoast applied the annual mean density to estimate take. As described in the Marine Mammal section, species' distributions indicate that the only species of pilot whale expected to occur in SNE is the long-finned pilot whale; therefore, the densities provided in Roberts et al. (2016, 2023) are attributed to this species (and not short-finned pilot whales). Similarly, distribution data for bottlenose dolphins stocks indicate that the only stock likely to occur in SNE is the Western North Atlantic offshore stock, thus all Robert et al. (2016, 2023) densities are attributed to this stock. Below, we describe observational data from monitoring reports and average group size information, both of which are appropriate to inform take estimates for certain activities or species in lieu of density estimates.

For some species and activities, observational data from Protected Species Observers (PSOs) aboard HRG and geotechnical (GT) survey vessels indicate that the density-based exposure estimates may be insufficient to account for the number of individuals of a species that may be encountered during the planned activities. PSO data from geophysical and geotechnical surveys conducted in the area surrounding the Lease Area and ECCs from April 2020 through December 2021 (RPS, 2021) were analyzed to determine the average number of individuals of each species observed per vessel day. For each species, the total number of individuals observed (including the“proportion of unidentified individuals”) was divided by the number of vessel days during which observations were conducted in 2020-2021 HRG surveys (555 survey days) to calculate the number of individuals observed per vessel day, as shown in the final columns of Table 7 in the SouthCoast ITA application.

For other less-common species, the predicted densities from Roberts et al. (2016; 2023) are very low and the resulting density-based exposure estimate is less than a single animal or a typical group size for the species. In such cases, the mean group size was considered as an alternative to the density-based or PSO data-based take estimates to account for potential impacts on a group during an activity. Mean group sizes for each species were calculated from recent aerial and/or vessel-based surveys, as shown in table 10. Additional detail regarding the density and occurrence as well as the methodology used to estimate take for specific activities is included in the activity-specific subsections below.

The estimated exposure and take tables for each activity present the density-based exposure estimates, PSO-date derived take estimate, and mean group size for each species. The number of species-specific takes by Level B harassment that is proposed for authorization is based on the largest of these three values. Although animal Start Printed Page 53758 exposure modeling resulted in Level A harassment exposure estimates for other species, NMFS is not proposing to authorize Level A harassment take for any species other than fin whales, harbor porpoises, and harbor and gray seals. The numbers of takes by Level A harassment proposed for authorization for these species are based strictly on density-based exposure modeling results ( i.e., not on PSO-data derived estimates or group size).

WTG and OSP Foundation Installation

Here, for WTG and OSP monopile and pin-piled jacket foundation installation, we provide summary descriptions of the modeling methodology used to predict sound levels generated from the Project with respect to harassment thresholds and potential exposures using animal movement, the density and/or occurrence information used to support the take estimates for this activity, and the resulting acoustic and exposure ranges, exposures, and authorized takes.

The predominant underwater noise associated with the construction of offshore components of the SouthCoast Project would result from impact and vibratory pile driving of the monopile and jacket foundations. SouthCoast employed JASCO Applied Sciences (USA) Inc. (JASCO) to conduct acoustic modeling to better understand sound fields produced during these activities (Limpert et al., 2024). The basic modeling approach is to characterize the sounds produced by the source, and determine how the sounds propagate within the surrounding water column. For both impact and vibratory pile driving, JASCO conducted sophisticated source and propagation modeling (as described below). JASCO also conducted animal movement modeling to estimate the potential for marine mammal harassment incidental to pile driving. JASCO estimated species-specific exposure probabilities by considering the range- and depth-dependent sound fields in relation to animal movement in simulated representative construction scenarios. More details on these acoustic source modeling, propagation modeling and exposure modeling methods are described below and can be found in Limpert et al. (2024).

Pile Driving Acoustic Source Modeling

To model the sound emissions from the piles, the force of the pile driving hammers had to be modeled first. JASCO used the GRL, Inc. Wave Equation Analysis of Pile Driving wave equation model (GRLWEAP) (Pile Dynamics, 2010) in conjunction with JASCO's Pile Driving Source Model (PDSM), a physical model of pile vibration and near-field sound radiation (MacGillivray, 2014), to predict source levels associated with impact and vibratory pile driving activities. Forcing functions, representing the force of the impact or vibratory hammer at the top of each 9/16-m monopile and 4.5-m jacket foundation pile, were computed using the GRLWEAP 2010 wave equation model (GRLWEAP) (Pile Dynamics, 2010), which includes a large database of simulated impact and vibratory hammers. The GRLWEAP model assumed direct contact between the representative impact and vibratory hammers, helmets, and piles ( i.e., no cushioning material, which provides a more conservative estimate). For monopile and jacket foundations, the piles were assumed to be vertical and driven to a penetration depth of 35 m (115 ft) and 60 m (197 ft), respectively. Modeling assumed jacket foundation piles were either pre- and post-piled. As indicated in the Description of Specified Activitie s section, pre-piling means that the jacket structure will be set on pre-installed piles, as would be the case for SouthCoast's WTG foundations (if jacket foundations are used for WTGs). OSP foundations would be post-piled (using only impact pile driving), meaning that the jacket structure is placed on the seafloor and piles would be subsequently driven through guides at the base of each leg. These jacket foundations (which are separate from the pin piles on which they sit) will also radiate sound as the piles are driven. To account for the additional sound (beyond impact hammering of the OSP pin piles) radiating from the jacket structure, a 2-dB increase in received levels was included in the propagation calculations for OSP post-piling installations, based on a recommendation from Bellman et al. (2020).

Modeling the forcing function for vibratory pile driving required slightly different considerations than for impact pile driving given differences in the way each hammer type interacts with a pile, although the models used are the same for installation methods. Piles deform when driven with impact hammers, creating a bulge that travels down the pile and radiates sound into the surrounding air, water, and seabed. During the vibratory pile driving stage, piles are driven into the substrate due to longitudinal vibration motion at the hammer's operational frequency and corresponding amplitude, which causes the soil to liquefy, allowing the pile to penetrate into the seabed. Using GRLWEAP, one-second long vibratory forcing functions were computed for the 9/16-m monopile and 4.5-m jacket foundations, assuming the use of 32 clamps with total weight of 2102.4 kN for the monopile and 4 clamps with total weight of 213.56 kN for the jacket piles, connecting the hammer to the piles. Non-linearities were introduced to the vibratory forcing functions based on the decay rate observed in data measured during vibratory pile driving of smaller diameter piles (Quijano et al., 2017). Key modeling assumptions can be found in Table B-1 in Appendix B of Limpert et al. (2024). Please see Figures 12 and 13 in Section 4.1.1 of Limpert et al. (2024), for impact pile driving forcing functions, and Figures 18 and 19 in section 4.1.2 for vibratory pile driving forcing functions.

Both the impact and vibratory pile driving forcing functions computed using the GRLWEAP model were used then as inputs to the PDSM model to compute the resulting pile vibrations. These models account for several parameters that describe the operation—pile type, material, size, and length—the pile driving equipment, and approximate pile penetration depth. The PDSM physical model computes the underwater vibration and sound radiation of a pile by solving the theoretical equations of motion for axial and radial vibrations of a cylindrical shell. Piles were modeled assuming vertical installation using a finite-difference structural model of pile vibration based on thin-shell theory. The sound radiating from the pile itself was simulated using a vertical array of discrete point sources. This model is used to estimate the energy distribution per frequency (source spectrum) at a close distance from the source (10 m (32.8 ft)). Please see Appendix E in Limpert et al. (2024), for a more detailed description.

The amount of sound generated during pile driving varies with the energy required to drive piles to a desired depth, and depends on the sediment resistance encountered. Sediment types with greater resistance require hammers that deliver higher energy strikes and/or an increased number of strikes relative to installations in softer sediment. Maximum sound levels usually occur during the last stage of impact pile driving ( i.e., when the pile is approaching full installation depth) where the greatest resistance is encountered (Betke, 2008). Rather than modeling increasing hammer energy with increasing penetration depth, SouthCoast assumed that maximum hammer energy would be used throughout the entire installation of Start Printed Page 53759 monopiles and pin piles (tables 11 and 12). This is a conservative assumption, given the project area includes a predominantly sandy bottom habitat, which is a softer sediment (see Specified Geographical Are a section) that would require less than the maximum hammer energy to penetrate.

Representative hammering schedules for impact installation are shown in table 11 and for installations requiring vibratory followed by impact installation in table 12. For impact installation of 9/16-m WTG monopiles, 7,000 total hammer strikes were assumed, using the maximum hammer energy (6,600 kJ). The smaller 4.5-m pin piles for the WTG and OSP jacket foundations were assumed to require 4,000 total strikes using the maximum hammer energy (3,500 kJ). Modeling vibratory and subsequent impact installation of 9/16-m monopiles assumed 20 minutes of vibratory piling followed by 5,000 strikes of impact hammering. Installation of 4.5-m WTG piles using both vibratory and impact hammering methods assumed 90 minutes of vibratory pile driving followed by 2,667 impact hammer strikes.

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Beyond understanding pile driving source levels (estimated using forcing functions), there are additional factors to consider when determining the degree to which noise would be transmitted through the water column. Noise abatement systems (NAS) are often used to decrease the sound levels in the water near a source by inserting a local impedance change that acts as a barrier to sound transmission. Attenuation by impedance change can be achieved through a variety of technologies, including bubble curtains, evacuated sleeve systems ( e.g., IHC-Noise Mitigation System (NMS)), encapsulated bubble systems ( e.g., HydroSound Dampers (HSD)), or Helmholtz resonators (AdBm NMS). The effectiveness of each system is frequency dependent and may be influenced by local environmental conditions such as current and depth. SouthCoast would employ systems to attenuate noise during all pile driving of monopile and jacket foundations, including, at minimum, a double big bubble curtain (DBBC). Several recent studies summarizing the effectiveness of NAS have shown that broadband sound levels are likely to be reduced by anywhere from 7 to 17 dB, depending on the environment, pile size, and the size, configuration and number of systems used (Buehler et al., 2015; Bellmann et al., 2020). Hence, hypothetical broadband attenuation levels of 0 dB, 6 dB, 10 dB, 15 dB, and 20 dB were incorporated into acoustic modeling to gauge effects on the ranges to thresholds given these levels of attenuation. Although five attenuation levels were evaluated, SouthCoast and NMFS anticipate that the noise attenuation system ultimately chosen will be capable of reliably reducing source levels by 10 dB; therefore, modeling results assuming 10-dB attenuation are carried forward in this analysis for pile driving. See the Proposed Mitigation section for more information regarding the justification for the 10-dB attenuation assumption.

Acoustic Propagation Modeling

To estimate sound propagation during foundation installation, JASCO's used the Full Waveform Range-dependent Acoustic Model (FWRAM) to combine the outputs of the source model with spatial and temporal environmental factors ( e.g., location, oceanographic conditions, and seabed type) to get time-domain representations of the sound signals in the environment and estimate sound field levels ((Limpert et al. (2024), Section F.1 in Appendix F of SouthCoast's ITA application)). Because the foundation pile is represented as a linear array and FWRAM employs the array starter method to accurately model sound propagation from a spatially distributed source (MacGillivray and Chapman, 2012), using FWRAM ensures accurate characterization of vertical directivity effects in the near-field zone. Due to seasonal changes in the temperature and salinity of the water column, sound propagation is likely to vary among different times of the year. To capture this variability, acoustic modeling was conducted using an average sound speed profile for a “summer” period including the months of May through November, and a “winter” period including December through April. FWRAM computes pressure waveforms via Fourier synthesis of the modeled acoustic transfer function in closely spaced frequency bands. This model is used to estimate the energy distribution per frequency (source spectrum) at a close distance from the source (10 m (32.8 ft)). Examples of decidecade spectral levels for each foundation pile type, hammer energy, and modeled location, using average summer sound speed profile are provided in Limpert et al. (2024).

Sounds produced by sequential installation of the 9/16-m WTG monopiles and 4.5-m pin piles were modeled at two locations. Water depths within the Lease Area range from 37 m to 64 m (121 ft to 210 ft). Sound fields produced during both impact and vibratory installation of 9/16-m WTG monopiles and 4.5-m WTG and OSP pin piles were modeled at two locations: L01 in the southwest section of the lease area in 38 m water depth and L02 in the northeast section of the lease area in 53 m (173.9 ft) depth (Figure 2 in Appendix A in Limpert et al., 2024). Propagation modeling did not include water depths between 54 m and 64 m (deepest location) given the majority of foundation locations ( i.e., 101 out of 149) occur in depths less than 54 m (177 ft). The locations were selected to represent the acoustic propagation environment within the Lease Area and may not be actual foundation locations. JASCO selected alternative locations to model the ensonified zones produced during concurrent pile driving because the foundation installation locations would be closer together ( i.e., separated by approximately 2 nm) than those selected for sequential foundation installations.

For impulsive sounds from impact pile driving as well as non-impulsive sounds from vibratory piling, time-domain representations of the pressure waves generated in the water are required for calculating SPL_rms and SPL_peak at various distances from the pile, metrics that are important for characterizing potential impacts of pile driving noise on marine mammals. Furthermore, the pile must be represented as a distributed source to accurately characterize vertical directivity effects in the near-field zone. JASCO used FWRAM to compute synthetic pressure waveforms as a function of range and depth via Fourier synthesis of transfer functions in closely spaced frequency bands, in range-varying marine acoustic environments. Additional modeling details are described in Limpert et al. (2024). Impact and vibratory pile driving source and propagation modeling provides estimates of the distances from the pile Start Printed Page 53761 location to NMFS' Level A harassment and Level B harassment threshold isopleths.

JASCO calculated acoustic ranges, which represent the distance to a harassment threshold based on sound propagation through the environment, independent of movement of a receiver. The use of acoustic ranges (R 95% ) to the Level A harassment SEL_cum metric thresholds to assess the potential for PTS is considered an overly conservative method, as it does not account for animal movement and behavior and, therefore, assumes that animals are essentially stationary at that distance for the entire duration of the pile installation, a scenario that does not reflect realistic animal behavior. However, because NMFS' Level A harassment (SPL_peak) and Level B harassment (SPL_rms) thresholds refer to instantaneous exposures, acoustic ranges are a better representation of distances to these NMFS' instantaneous harassment thresholds. These distances were not applied to exposure estimation but were used to define the Level B harassment zones for all species (see Proposed Mitigation and Monitoring) for WTG and OSP foundation installation in summer and winter, and the minimum visibility zone for installation of foundations in the NARW EMA (see Proposed Mitigation and Monitoring). The following tables present the largest acoustic ranges (R 95% ) among modeling sites (Figure 2 in Limpert et al., 2024) resulting from JASCO's source and propagation models, for both “summer” and “winter.” Table 15 presents the R 95% distances to the Level A harassment (SPL_peak) isopleths. Table 16 provides R 95% distances to the Level A harassment (SEL_cum) thresholds for impact-only and combined method ( i.e., vibratory and impact pile driving) installations, respectively. Finally, table 17 presents R 95% distances for Level B harassment thresholds, for impact (160 dB) and vibratory (120 dB) pile driving.

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To assess the extent to which marine mammal harassment might occur as a result of movement within this acoustic environment, JASCO next conducted animal movement and exposure modeling.

Animal Movement Modeling

To estimate the probability of exposure of animals to sound above NMFS' harassment thresholds to during foundation installation, JASCO's Animal Simulation Model Including Noise Exposure (JASMINE) was used to integrate the sound fields generated from the source and propagation models described above with species-typical behavioral parameters ( e.g., swim speeds dive patterns). The parameters used for forecasting realistic behaviors ( e.g., diving, foraging, and surface times) were determined and interpreted from marine species studies ( e.g., tagging studies) where available, or reasonably extrapolated from related species (Limpert et al., 2024).

Applying animal movement and behavior within the modeled noise fields allows for a more realistic indication of the distances at which PTS acoustic thresholds are reached that considers the accumulation of sound over different durations. Sound exposure models such as JASMINE use simulated animals (animats) to sample the predicted 3-D sound fields with movement derived from animal observations (see Limpert et al., 2024). Animats that exceed NMFS' acoustic thresholds are identified and the range (distance from the noise source) for the exceedances determined. The output of the simulation is the exposure history for each animat accumulated within the simulation. An individual animat's sound exposure levels are summed over a specific duration, (24 hours), to determine its total received acoustic energy (SEL) and maximum received SPL_PK and SPL_rms. These received levels are then compared to the harassment threshold criteria. The combined history of all animats gives a probability density function of exposure above threshold levels. The number of animals expected to exceed the regulatory thresholds is determined by scaling the number of predicted animat exposures by the species-specific density of animals in the area. By programming animats to behave like the 16 marine mammal species that may be exposed to pile driving noise, the sound fields are sampled in a manner similar to that expected for real animals.

Vibratory setting of piles followed by impact pile driving is being considered for Project 2 (Scenarios 2 and 3). Given the qualities of vibratory pile driving noise ( e.g., continuous, lower hammer energy), Level A harassment (PTS) is not an anticipated impact on marine mammals incidental to SouthCoast's use of this method. Although the potential to induce hearing loss is low during vibratory driving, it does introduce some SEL exposure that must be considered in the 24-hour SEL_cum estimates. For this reason, JASCO computed acoustic ranges from the combined sound energy from vibratory and impact pile driving. These results are presented in Appendix G in Limpert et al. (2024). The PTS-onset SEL thresholds are lower for impact piling than for vibratory piling (table 7) so, to be conservative, when estimating acoustic ranges and the number of animats exposed to potentially injurious sound levels from both impact and vibratory pile driving (for those piles that may require both methods), the lower (impulsive) SEL criteria were applied to determine if thresholds were exceeded.

Estimating the number of animats that may be exposed to sound above a behavioral SPL response threshold is simpler because it does not require integrating sound pressure over long time periods. This calculation was done separately for vibratory and impact pile driving because these two sound sources use different thresholds, and they are temporally separated activities ( i.e., impact follows vibratory pile driving). The numbers of animats exposed above the 120 dB (vibratory) and 160 dB (impact) Level B harassment thresholds are calculated individually and then the resulting numbers are combined to get total behavioral exposures from a single pile installed at each representative location when both hammer types are expected to be used on a pile. Individual animats that are exposed above behavioral thresholds for both vibratory and impact pile driving are only counted once to avoid over-estimation.

For modeled animats that have received enough acoustic energy to exceed a given harassment threshold, the exposure range for each animal is defined as the closest point of approach (CPA) to the source made by that animal while it moved throughout the modeled sound field, accumulating received acoustic energy. The CPA for each of the species-specific animats during a simulation is recorded and then the CPA distance that accounts for 95 percent of the animats that exceed an acoustic threshold is determined. The ER 95% (95 percent exposure radial distance) is the horizontal distance that includes 95 percent of the CPAs of animats exceeding a given impact threshold. The ER 95% ranges are species-specific rather than categorized only by any functional hearing group, which allows for the incorporation of more species-specific biological parameters ( e.g., dive durations, swim speeds) for assessing the potential for PTS from pile driving. Furthermore, because these ER 95% ranges are species-specific, they can be used to develop mitigation monitoring or shutdown zones.

As described in the Detailed Description of Specific Activity section, SouthCoast proposed construction schedules that include both sequential and concurrent foundation installations. For sequential installations (both vibratory and/or impact) of two monopiles foundations or four jacket pin piles per day, two sites were used for modeling (see Figures 7 and 8, Section 2.51 of Appendix A in Limpert et al., 2024), both considered representative locations of the Lease Area (one location for each foundation). Animats were exposed to only one sound field at a time. Received levels were accumulated over each animat's track over a 24-hour time window to derive sound exposure levels (SEL). Instantaneous single-exposure metrics ( e.g., SPL_rms and SPL_peak) were recorded at each simulation time step, and the maximum received level was reported.

Concurrent operations were handled slightly differently to capture the effects of installing piles spatially close to each other ( i.e., 2 nm (2.3 mi; 3.7 km)). The sites chosen for exposure modeling for concurrent operations are shown in Figure 9, Section 2.51 in Limpert et al. (2024). When simulating concurrent operations in JASMINE, sound fields from separate piles may be overlapping in time and space. For cumulative metrics (SEL_cum), received energy from each sound field the animat encounters is summed over a 24-hour time window. For SPL, received levels were summed within each simulation time step and the resultant maximum SPL over all time steps was carried forward. For both sequential and concurrent operations, the resulting cumulative or maximum received levels were then compared to the NMFS' thresholds criteria within each analysis period.

Additional assumptions used in modeling for each year of construction are summarized in table 18. As discussed previously, modeling assumed SouthCoast would install Project 1 WTG foundations using only impact pile driving and Project 2 WTG foundations using vibratory and/or impact pile driving. All pin piles supporting OSP jacket foundations would be impact driven. In addition, modeling assumed a seasonal restriction Start Printed Page 53763 on pile driving from January 1 through April 30. However, as previously described, to provide additional North Atlantic right whale protection, SouthCoast would not install foundation in the NARW EMA from October 16 through May 31 or throughout the rest of the Lease Area from January 1 to May 15.

All proposed construction scenarios, including foundation type, installation method, number of monopiles or pin piles installed per day, and the rate of installation were presented in table 2 in the Detailed Description of Specific Activities section.

Tables 19-23 summarize the monthly construction schedules for each scenario assumed for modeling, including installation sequence and method, and the number of pile driving days per month. However, construction schedules cannot be fully predicted due to uncontrollable environmental factors ( e.g., weather) and installation schedules include variability ( e.g., due to drivability). The total number of construction days per month would be dependent on a number of factors, including environmental conditions, planning, construction, and installation logistics. As described previously, SouthCoast assumed that for sequential WTG foundation installations (using a single vessel), a maximum of 2 WTG monopiles or 4 OSP piled jacket pin piles may be driven in 24 hours. For concurrent installation (using two vessels), a maximum of 2 WTG monopiles and 4 OSP piled jacket pin piles or 4 WTG and 4 OSP pin piles may be driven in 24 hours. It is unlikely that these maximum installation rates would be consistently attainable throughout the construction phase, but this schedule was considered to have the greatest potential for Level A harassment (PTS) and was, therefore, carried forward into take estimation.

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By incorporating animal movement into the calculation of ranges to time-dependent thresholds (SEL metrics), ER 95% values provide a more realistic assessment of the distances within which acoustic thresholds may be exceeded. This also means that different species within the same hearing group can have different exposure ranges as a result of species-specific movement patterns. Substantial differences (greater than 500 m (1,640 ft)) between species within the same hearing group occurred for low frequency-cetaceans, so Level A harassment (PTS) ER 95% values are shown separately for those species (tables 24-29). For mid-frequency cetaceans and pinnipeds, the largest value from any single species was selected.

Projects 1 and 2 would include sequential WTG foundation installations using impact pile driving only and both vibratory and impact pile driving (Project 2 only), and concurrent WTG and OSP installations using only impact pile driving, each of which generates different ER 95% distances. The Level A harassment (PTS) ER 95% distances for sequential installation of WTG foundations using only impact pile driving are shown in table 24 for both summer and winter. SouthCoast does not anticipate conducting vibratory or concurrent pile driving in December, thus the Level A harassment (PTS) ER 95% distances for sequential installation of WTG foundations (both monopile and pin-piled jacket) using both vibratory and impact pile driving are shown in table 25 for summer only. Lastly, Level A harassment (PTS) ER 95% distances for potential concurrent installation of WTG and OSP foundations using impact pile driving (also limited to “summer” for modeling) are shown in table 26.

Comparison of the results in table 24 and table 26 show that the case assuming sequential installation of two WTG monopiles per day and concurrent installation of two WTG monopiles and 4 OSP piles per day yield very similar results. This may seem counterintuitive, given the assumed number of piles installed per day for concurrent installations is larger than that assumed for sequential installations, thus it might be expected that Level A harassment (PTS) ER 95% distances would be larger for concurrent installations. However, for that result to occur, animal movement modeling would have to show that animals would routinely occur close enough to one pile driving location ( e.g., WTG monopile) to accumulate enough sound energy without exceeding the Level A harassment SEL_cum threshold, and then also occur at the second pile driving location ( e.g., OSP jacket) at a distance close enough to accumulate the remaining sound energy needed to cross the SEL_cum threshold. The animal movement modeling showed this sequence of events did not happen often enough during concurrent installations of WTG monopile and OSP jacket foundations to cause a consistent increase in the Level A harassment (PTS) ER 95% distances across all species. This sequence of events did occur more often during concurrent installation of WTG jacket and OSP jacket foundation installations, thus the Level A harassment (PTS) ER 95% distances for concurrent installations were consistently larger than for installation of a single WTG jacket foundation on a given day (table 26). This was likely a result of the overall longer duration of pile driving per day required for installing 4 pin piles for each jacket foundation.

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In addition to ER 95% distances to Level A harassment (PTS) thresholds, exposure modeling produced ER 95% distances to the Level B harassment 160 dB SPL_rms (impact pile driving) and 120 dB SPL_rms (vibratory pile driving) thresholds. The following tables provide the Level B harassment ER 95% distances for 1) sequential installation of WTG foundations using only impact pile driving for summer and winter (table 27); 2) summer-only sequential installation of WTG foundations (both monopile and pin-piled jacket) using both vibratory and impact pile driving (table 28); and 3) concurrent installation of WTG monopile and OSP pin-piled jacket foundations (table 29, also limited to “summer”). These ranges were used to define the outer perimeter around the Lease Area from which Roberts et al. (2016, 2023) model data density grid cells were selected for exposure estimation.

SouthCoast modeled potential Level A harassment and Level B harassment density-based exposure estimates for all five foundation installation schedules (P1S1-P2S3), all of which include sequential pile driving and concurrent pile driving. In creating the installation schedules used for exposure modeling, the total number of installations was spread across all potential months in which they might occur (May-December) in order to incorporate the month-to-month variability in species densities. SouthCoast assumed that the OSP jacket foundations would be installed in October for each Project.

For both WTG and OSP foundation installations, mean monthly densities were calculated by first selecting density data from 5 × 5 km (3.1 × 3.1 mi) grid cells (Roberts et al., 2016; 2023) both within the Lease Area and beyond its boundaries to predetermined perimeter distances. The widths of the perimeter (referred to as a “buffer” in SouthCoast's application) around the activity area used to select density data were determined using the ER₉₅% , distances to the isopleths corresponding to Level A harassment (tables 24-26) and Level B harassment (table 27-29) thresholds, assuming 10-dB attenuation, which vary according to sound source (impact/vibratory piling) and season. For each species, foundation type and number, installation method, and season, the most appropriate density perimeter was selected from the predetermined distances ( i.e., 1 km (0.6 mi), 5 km (3.1 mi), 10 km (6.2 mi), 15 km (9.3 mi), 20 km (12.4 mi), 30 km (18.6 mi), 40 km (25 mi), and 50 km (31.1 mi)) by rounding the ER₉₅% up to the nearest predetermined perimeter size. For example, if the Level A harassment (PTS) ER₉₅% was 7.1 km (4.4 mi) for a given species and activity, a 10-km (6.2-mi) perimeter was created around the Lease Area and used to calculate mean monthly densities that were used in foundation installation Level A harassment (PTS) exposure estimates ( e.g., table 30). Similarly, if the 160 dB Level B harassment ER₉₅% was 20.1 km (12.5 mi) for a given species or activity, a 30-km (18.6-mi) perimeter around the Lease Area was created and used to calculate mean monthly densities for exposure estimation. In cases where the ER₉₅% was larger than 50 km (31.1 mi), the 50-km (31.1-mi) perimeter was used. The 50-km (31.1-mi) limit is derived from studies of mysticetes that demonstrate received levels, distance from the source, and behavioral context are known to influence the probability of behavioral response (Dunlop et al., 2017). Please see Figure 10 in SouthCoast's ITA Application for an example of a density map showing the Roberts et al. (2016; 2023) density grid cells overlaid on a map of the Lease Area. Given the extensive number of density tables used for exposure modeling, we do not present them here beyond the example provided in table 30. Please see tables in Section H.2.1.1 of Appendix H in Limpert et al. (2024) for densities within the areas defined by additional perimeter sizes ( i.e., 1 km (0.6 mi), 5 km (3.1 mi), 10 km (6.2 mi), 15 km (9.3 mi), 20 km (12.4 mi), 30 km (18.6 mi), 40 km (25 mi), and 50 km (31.1 mi)).

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As previously discussed, SouthCoast's ITA application includes installation of up to 147 WTG foundations and up to 5 OSP foundations in 149 positions within the Lease Area. However, for the purposes of exposure modeling, SouthCoast assumed installation of two OSPs (one per Project), each supported by a piled jacket foundation secured by 12 to 16 pin piles.

SouthCoast calculated take estimates for all five foundation installation scenarios presented in their application, based on modeled exposures and other relevant data ( e.g., PSO date, mean group sizes). Tables 32-36 provide the results of marine mammal exposure modeling, which assumes 10-dB attenuation and seasonal restrictions, for each scenario. The Level A harassment exposure estimates represent animats that exceeded the PTS SEL _cum thresholds as this metric was exceeded prior to exceeding PTS SPL_peak thresholds The Level B harassment exposure estimates shown for Project 1 Scenarios 1 and 2, and Project 2 Scenario 1 represent animats exceeding the unweighted 160 dB SPL_rms criterion because impact pile driving would be the only installation method in these scenarios. The Level B harassment exposure estimates shown for Project 2 Scenarios 2 and 3 (tables 32-36) represent animats exceeding the unweighted 120 dB SPL_rms and/or 160 dB SPL_rms criteria because these scenarios require both vibratory and impact pile driving. Columns 4 and 5 in tables 32-36 show what the take estimates would be if the PSO data or average group size, respectively, were used to inform the number of proposed takes by Level B harassment in lieu of the density and exposure modeling. The last column represents the total Level B harassment take estimate for each species, based on the highest of the three estimates (density-based exposures, PSO data, or average group size).

Below we present the exposure estimates and the take estimates for these scenarios (Tables 32-36). For Project 1, no single scenario results in a greater amount of take for all species; therefore, the maximum annual and 5-year total amount of take proposed for authorization is a combination of both scenarios depending on species ( i.e., the scenario which resulted in the greatest amount of take was carried forward for each species). For Project 2, Scenario 2 results in the greatest amount of take for all species and is carried forward in the maximum annual and 5-year total amount of take proposed for authorization. Start Printed Page 53770

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The model-based Level A harassment (PTS) exposure estimates are conservative in that they assume no mitigation measures other than 10 dB of sound attenuation and seasonal restrictions. Although the enhanced mitigation and monitoring measures SouthCoast proposed (see Proposed Mitigation and Proposed Monitoring and Reporting sections below) are specifically focused on reducing pile-driving impacts on North Atlantic right whales, other marine mammal species would experience conservation benefits as well ( e.g., extended seasonal restrictions, increased monitoring effort and larger minimum visibility zone improving detectability and mitigation efficacy, extended pile-driving delays (24-48 hrs) if a North Atlantic right whale is detected). When implemented, the additional mitigation measures described in the Proposed Mitigation section, including soft-start and clearance/shutdown processes, would reduce the already very low probability of Level A harassment. Additionally, modeling does not include any avoidance behavior by the animals, yet we know many marine mammals avoid areas of loud sounds. Thus, it is unlikely that an animal would remain within the Level A harassment SEL_cum zone long enough to incur PTS and could potentially redirect their movements away from the pile installation location in response to the soft-start procedure. For these reasons, SouthCoast is not requesting Level A harassment (PTS) take incidental to foundation installation for most marine mammal species, even though animal movement modeling estimated that a small number of PTS exposures could occur for multiple species (as shown in tables 32-36). In the case of North Atlantic right whales, the potential for Level A harassment (PTS) has been determined to be reduced to a de minimis likelihood due to the enhanced mitigation and monitoring measures, which include even larger clearance and shutdown zones (see Proposed Mitigation and Proposed Monitoring and Reporting sections). SouthCoast did not request, and NMFS is not proposing to authorize, take by Level A harassment of North Atlantic right whales.

However, as a precautionary measure, because the WTG and OSP foundation installation Level A harassment ER₉₅% distances for fin whales are, in some cases, substantially larger than for other mysticete whales, Level A harassment take is being requested for this species. The second largest mysticete Level A harassment ER₉₅% distance was selected as the clearance/shutdown zone size for baleen whales to avoid Level A harassment take of other mysticete species. SouthCoast assumed that the large clearance/shutdown zone size along with the soft-start procedure and potential for animal aversion to loud sounds would prevent Level A harassment take of other species. In most installation scenarios, 15-20 percent of the fin whale Level A harassment ER₉₅% zone extends beyond the planned clearance/shutdown distance for non-NARW baleen whales, therefore, the requested Level A take for fin whales incidental to foundation installation is 20 percent of the fin whale Level A exposure estimates produced by the exposure modeling (Project 1 = 14; Project 2 = 15). This results in a request for 3 Level A harassment takes for fin whales for both Project 1 and Project 2 (total of 6 across Projects). Table 37 shows the requested take incidental to foundation installation that is included in the total take NMFS proposes to authorize.

For Project 1, no single scenario resulted in a greater amount of take for all species; therefore, the annual Level B harassment take numbers carried forward in table 37 reflect the maximum take estimate for each species between the two possible foundation installation scenarios (P1S1 and P1S2). Similarly for Project 2, the number of species-specific Level B harassment takes in table 37 reflects the maximum take estimate among the three analyzed scenarios (P2S1, P2S2, P2S3) which, in all cases, resulted from installations of P2S2. However, the 5-year total take incidental to foundation installation proposed for authorization for a given species (shown Start Printed Page 53773 in the last two columns in table 37) is less than the direct sum across Projects 1 and 2 values in the columns to the left. This is because the total number of takes must be based on a realistic construction scenario sequence that does not include take estimates resulting from modeling of installation of more than 149 foundations. For example, the number of estimated sei whale Level B harassment takes in column 3 of table 37 resulted from modeling installation of Project 1 Scenario 2 (85 WTG foundations) and the number in column 5 resulted from modeling installation of Project 2 Scenario 2 (73 WTG foundations), representing take incidental to installation of a number of WTG foundations (158) larger than the maximum in SouthCoast's PDE (147). As described previously, some combinations of Project 1 and 2 scenarios are not possible because they would exceed the number of foundation positions available. However, SouthCoast indicates that the scenario chosen for Project 2 is dependent on the scenario installed for Project 1, which is uncertain at this time. Given this uncertainty, SouthCoast considers each of the five installation scenarios (Project 1, Scenarios 1 or 2; Project 2, Scenarios 1-3) described in table 2 possible. To ensure the total take proposed for authorization is based on a realistic number of foundations, the 5-year total is based on installation of Project 1 Scenario 1 and Project 2 Scenario 2 (146 total foundations). This ensures that the take proposed for authorization for Project 2 represents the maximum possible yearly take among the three scenarios considered for Project 2 as it is estimated using the largest potential ensonified zone (resulting from vibratory pile driving) and that sufficient take is requested for the full buildout. SouthCoast also considers the combination of Project 1 Scenario 2 and Project 2 Scenario 3 (147 total foundations) a realistic construction plan. However, the 5-year take request is based on Project 1 Scenario 1 combined with Project 2 Scenario 2 because it reflects a realistic construction plan that results in the greatest number of estimated takes.

UXO/MEC Detonation

SouthCoast may detonate up to 5 UXO/MECs within the Lease Area and 5 within the ECCs (10 UXOs/MECs total) over the 5-year effective period of the proposed rule. Charge weights of 2.3 kgs (2.2 lbs), 9.1 kgs (20.1 lbs), 45.5 kgs (100 lbs), 227 kgs (500 lbs), and 454 kgs (1,001 lbs), were modeled to determine acoustic ranges to mortality, gastrointestinal injury, lung injury, PTS, and TTS thresholds. To do this, the source pressure function used for estimating peak pressure level and impulse metrics was calculated with an empirical model that approximates the rapid conversion of solid explosive to gaseous form in a small bubble under high pressure, followed by exponential pressure decay as that bubble expands (Hannay and Zykov, 2022). This initial empirical model is only valid close to the source (within tens of meters), so alternative formulas were used beyond those distances to a point where the sound pressure decay with range transitions to the spherical spreading model. The SEL thresholds occur at distances of many water depths in the relatively shallow waters of the Project (Hannay and Zykov, 2022). As a result, the sound field becomes increasingly influenced by the contributions of sound energy reflected from the sea surface and sea bottom multiples times. To account for this, propagation modeling was carried out in decidecade frequency bands using JASCO's MONM. This model applies a parabolic equation approach for frequencies below 4 kHz and a Gaussian beam ray trace model at higher frequencies (Hannay and Zykov, 2022). In SouthCoast project's location, sound speed profiles generally change little with depth, so these environments do not have strong seasonal dependence (see Figure 2 in the SouthCoast Underwater Acoustic Modeling of UXO/MEC report). The propagation modeling for UXO/MEC detonations was performed using an average sound speed profile for “September”, which is slightly downward refracting. Please see Start Printed Page 53774 the supplementary report for SouthCoast's ITA application titled “Underwater Acoustic Modeling of Detonations of Unexploded Ordnance (UXO/MEC removal) for Mayflower Wind Farm Construction,” found on NMFS' website ( https://www.fisheries.noaa.gov/​action/​incidental-take-authorization-SouthCoast-wind-llc-construction-and-operation-SouthCoast-wind) for more technical details about the modeling methods, assumptions and environmental parameters used as inputs (Hannay and Zykov, 2022).

The exact type and net explosive weight of UXO/MECs that may be detonated are not known at this time; however, they are likely to fall into one of the bins identified in table 38. To capture a range of UXO/MECs, five categories or “bins” of net explosive weight, established by the U.S. Navy (2017a), were selected for acoustic modeling (table 38).

These charge weights were modeled at five different locations and associated depths located within the Lease Area and ECCs. Two sites are located in the Lease Area, S1 (60 m (196.9 ft)) and S2 (45 m (147.6 ft)). Three sites are located within the ECCs, one along the western ECC (S3, 30 m) and two along the eastern ECC (S4, 20m (65.6 ft); S5, 10 m (32.8 ft))). Sites 1 and 2 were deemed to be representative of the Lease Area and Sites 3-5 were deemed representative of the ECCs where detonations could occur (see Figure 1 in Hannay and Zykov, 2022). Exact locations for the modeling sites are shown in Figure 1 of Hannay and Zykov (2022).

All distances to isopleths modeled can be found in Hannay and Zykov (2022). It is not currently known how easily SouthCoast would be able to identify the size and charge weights of UXOs/MECs in the field. Therefore, NMFS has proposed to require SouthCoast to implement mitigation measures assuming the largest E12 charge weight as a conservative approach. As such, distances to PTS (tables 39 and 40) and TTS thresholds (tables 41 and 42) for only the 454 kg (1,001 lbs) UXO/MEC are presented, as this size UXO/MEC has the greatest potential for these impacts and is what is used to estimate take. NMFS notes that it is extremely unlikely that all 10 of the UXO/MECs found and requiring detonation for the SouthCoast Project would consist of this 454 kg (1,001 lbs) charge weight. If SouthCoast is able to reliably demonstrate that they can easily and accurately identify charge weights in the field, NMFS will consider mitigation and monitoring zones based on UXO/MEC charge weight for the final rulemaking rather than assuming the largest charge weight in every situation.

To further reduce impacts to marine mammals, SouthCoast would deploy a NAS (a DBBC, at minimum) during every detonation event, similar to that described for foundation installation, with the expectation that their selected system would be able to achieve 10-dB attenuation. This expectation is based on an assessment of UXO/MEC clearance activities in European waters as summarized by Bellman and Betke (2021). NMFS would require SouthCoast to deploy NAS(s) (a dBBC, at minimum) during all denotations, thus it was deemed appropriate to apply attenuation R95% distances to determine the size of the ensonified zone for take estimation.

Given the impact zone sizes and the required mitigation and monitoring measures, neither mortality nor non-auditory injury are considered likely to result from the activity. NMFS does not expect or propose to authorize any non-auditory injury, serious injury, or mortality of marine mammals from UXO/MEC detonation. The modeled distances, assuming 10 dB of sound attenuation, to the mortality threshold for all UXO/MECs sizes for all animal masses for the ECCs and Lease Area are small ( i.e., 28-368 m (91.9 ft-1,207.4 ft); see Tables 40-44 in SouthCoast's supplemental UXO/MEC modeling report; Hannay and Zykov, 2022), as compared to the distance/area that can be effectively monitored. The modeled distances to non-auditory injury thresholds range from 67-694 m (219.8-2,276.9 ft), assuming 10 dB of sound attenuation (see Tables 35-39 in SouthCoast's supplemental UXO/MEC modeling report; Hannay and Zykov, 2022). SouthCoast would be required to conduct extensive monitoring using both PSOs and PAM operators and clear an area of marine mammals prior to any detonation of UXOs/MECs. Given that SouthCoast would be employing multiple platforms to visually monitor marine mammals as well as passive acoustic monitoring, it is reasonable to assume that marine mammals would be reliably detected within approximately 700 m (2,296.59 ft) of the UXO/MEC being detonated, the potential for mortality or non-auditory injury is de minimis. SouthCoast did not request, and NMFS is not proposing to authorize, take by mortality or non-auditory injury. For this reason, we are not presenting all modeling results here; however, they can be found in SouthCoast's UXO/MEC acoustic modeling report (Hannay and Zykov, 2022).

To estimate the maximum ensonified zones that could result from UXO/MEC detonations, the largest acoustic ranges (R₉₅% ; assuming 10-dB attenuation) to PTS and TTS thresholds for the E12 UXO/MEC charge weight were used as radii to calculate the area of a circle (pi × r² ; where r is the range to the threshold level) for each marine mammal hearing group. The largest range for the Lease Area from Sites 1 and 2 (S1 and S2) is shown in tables 39 and 41 and for the ECCs the largest range from Sites 3-5 (S3, S4, and S5) is shown in tables 40 and 42. These results represent the largest area potentially ensonified above the PTS and TTS threshold levels from a single detonation within the SouthCoast ECCs (tables 40 and 42) and Lease Area (tables 39 and 41). Start Printed Page 53775

To avoid any in situ detonations of UXO/MECs during periods when North Atlantic right whale densities are highest in and near the ECCs and Lease Area, this activity would be restricted from December 1 through April 30, annually. Accordingly, for each species, they selected the highest average monthly density between May and November and assumed all 10 UXO/MECs would be detonated in that month to conservatively estimate exposures from UXO/MEC detonation for a given species in any given year. Given UXO/MECs detonations have the potential to occur anywhere within the Lease Area and ECCs, a 15-km (9.3-mi) perimeter was applied around the Lease and, separately, the ECCs to define the area over which densities would be evaluated. As described above, in the case of blue whales and pilot whales, monthly densities were unavailable; therefore, annual densities were used instead.

Table 43 provides those densities and the associated months in which the species-specific densities are highest for the Lease Area and ECCs. Start Printed Page 53776

Based on the available information, up to five UXO/MEC detonations may be necessary in the ECCs and up to five in the Lease Area (10 UXO/MEC detonations total). To estimate take incidental to UXO/MEC detonations in the SouthCoast ECCs, the maximum ensonified areas based on the largest R₉₅% to Level A harassment (PTS) and Level B harassment (TTS) thresholds (assuming 10-dB attenuation) from a single detonation (assuming the largest UXO/MEC charge weight) in the ECC, as shown in tables 40 and 42, were multiplied by three (the maximum number of UXOs/MECs that are expected to be detonated in the SouthCoast ECC in Year 1 of construction) and two (the maximum number of UXOs/MECs that are expected to be detonated in the SouthCoast ECC in Year 2 of construction). The results were then multiplied by the marine mammal densities shown in table 43, resulting in the exposures estimates in table 44. The division of five total detonations within the ECCs across the two years was based on the relative number of foundations to be installed in each year. The same method was applied using the maximum single detonation areas shown in table 39 and table 41 to calculate the potential take from UXO/MEC detonations in the Lease area. The resulting density-based take estimates for all 10 UXO/MEC detonations are summarized in table 44. Table 52 in SouthCoast's application provides annual take estimates separately for each of the two years during which UXO/MEC detonations may occur.

As shown below in table 44, the likelihood of marine mammal exposures above the PTS threshold is low, especially considering the instantaneous nature of the acoustic signal and the fact that there will be no more than 10 UXO/MECs detonated throughout the effective period of the authorization. Further, NMFS is proposing mitigation and monitoring measures intended to minimize the potential for PTS for most marine mammal species, and the extent and severity of behavioral harassment (TTS), including: (1) time of year/seasonal restrictions; (2) time of day restrictions; (3) use of PSOs to visually observe for North Atlantic right whales; (4) use of PAM to acoustically detect North Atlantic right whales; (5) implementation of clearance zones; (6) use of noise mitigation technology; and, (7) post-detonation monitoring visual and acoustic monitoring by PSOs and PAM operators (see Proposed Mitigation and Proposed Monitoring and Reporting sections below). However, given the relatively large distances to the high-frequency cetacean Level A harassment (PTS, SEL_cum) isopleth applicable to harbor porpoises and the difficulty detecting this species at sea, NMFS is proposing to authorize 109 Level A harassment takes of harbor porpoise from UXO/MEC detonations. Similarly, seals are difficult to detect at longer ranges, and although the distances to the phocid hearing group SEL PTS threshold are not as large as those for high-frequency cetaceans, it may not be possible to detect all seals within the PTS threshold distances even with the proposed monitoring measures. Therefore, NMFS is proposing to authorize 40 Level A harassment takes of gray seals and 4 Level A harassment takes of harbor seals incidental to UXO/MEC detonation. Although exposure modeling resulted in small numbers of estimated Level A harassment (PTS) exposures for large whales ( i.e., fin, humpback, minke, North Atlantic, and sei whales), NMFS anticipates that implementation of the mitigation and monitoring measures described above will reduce the potential for Level A harassment to discountable amounts. Start Printed Page 53777

HRG Surveys

SouthCoast's proposed HRG survey activity includes the use of impulsive ( i.e., boomers and sparkers) and non-impulsive ( e.g., CHIRP SBPs) sources (table 45).

Authorized takes would be by Level B harassment only in the form of disruption of behavioral patterns for individual marine mammals resulting from exposure to noise from certain HRG acoustic sources. Based primarily on the characteristics of the signals produced by the acoustic sources planned for use, Level A harassment is neither anticipated, even absent mitigation, nor proposed for authorization. Therefore, the potential for Level A harassment is not evaluated further. Please see SouthCoast's application for details of a quantitative exposure analysis ( i.e., calculated distances to Level A harassment isopleths and Level A harassment exposures). No serious injury or mortality is anticipated to result from HRG survey activities.

In order to better account for the narrower and directional beams of the sources, NMFS has developed a tool, specific to HRG surveys, for determining the sound pressure level (SPL_rms) at the 160-dB isopleth for the purposes of estimating the extent of Level B harassment isopleths associated with HRG survey equipment (NMFS, 2020). This methodology incorporates frequency-dependent absorption and some directionality to refine estimated ensonified zones. SouthCoast used NMFS' methodology with additional modifications to incorporate a seawater absorption formula and account for energy emitted outside of the primary beam of the source. For sources that operate with different beamwidths, the maximum beam width was used, and the lowest frequency of the source was used when calculating the frequency-dependent absorption coefficient.

NMFS considers the data provided by Crocker and Fratantonio (2016) to represent the best scientific information available on source levels associated with HRG equipment and therefore, recommends that source levels provided by Crocker and Fratantonio (2016) be incorporated in the method described above to estimate ranges to the Level A harassment and Level B harassment isopleths. In cases when the source level for a specific type of HRG equipment is not provided in Crocker and Fratantonio (2016), NMFS recommends that either the source levels provided by the manufacturer be used or in instances where source levels provided by the manufacturer are unavailable or unreliable, a proxy from Crocker and Fratantonio (2016) be used instead. SouthCoast utilized the NMFS User Spreadsheet Tool (NMFS, 2018), following these criteria for selecting the appropriate inputs:

(1) For equipment that was measured in Crocker and Fratantonio (2016), the reported SL for the most likely operational parameters was selected. Start Printed Page 53778

(2) For equipment not measured in Crocker and Fratantonio (2016), the best available manufacturer specifications were selected. Use of manufacturer specifications represent the absolute maximum output of any source and do not adequately represent the operational source. Therefore, they should be considered an overestimate of the sound propagation range for that equipment.

(3) For equipment that was not measured in Crocker and Fratantonio (2016) and did not have sufficient manufacturer information, the closest proxy source measured in Crocker and Fratantonio (2016) was used.

The Teledyne Benthos Chirp III has the highest source level, so it was also selected as a representative sub-bottom profiling system in table 45. Crocker and Fratantonio (2016) measured source levels of a device similar to the Teledyne Benthos Chirp III TTV 170 towfish, the Knudsen 3202 Chirp sub-bottom profiler, at several different power settings. The highest power settings measured for the Knudsen 3202 were determined to be applicable to a hull-mounted Teledyne Benthos Chirp III system, while the lowest power settings were determined to be applicable to the towfish version of the Teledyne Benthos Chirp III that may be used by SouthCoast. The EdgeTech Chirp 512i measurements and specifications provided by Crocker and Fratantonio (2016) were used as a proxy for both the Edgetech 3100 with SB-216 towfish and EdgeTech DW-106, given its similar operations settings. The EdgeTech Chirp 424 source levels were used as a proxy for the Knudsen Pinger sub-bottom profiler. The sparker systems that may be used during the HRG surveys, the Applied Acoustics Dura-Spark and the Geomarine Geo-Spark, were measured by Crocker and Fratantonio (2016) but not with an energy setting near 800 Joules (J). A similar alternative system, the SIG ELC 820 sparker,measured with an input voltage of 750 J, was used as a proxy for both the Applied Acoustics Dura-Spark UHD (400 tips, 800 J) and Geomarine Geo-Spark (400 tips, 800 J), and was conservatively assumed to be an omnidirectional source.

Table 46 identifies all the representative survey equipment that operates below 180 kHz ( i.e., at frequencies that are audible and have the potential to disturb marine mammals) that may be used in support of planned survey activities and are likely to be detected by marine mammals given the source level, frequency, and beamwidth of the equipment. This table also provides all operating parameters used to calculate the distances to threshold for marine mammals.

Results of modeling using the methodology described above indicated that, of the HRG equipment planned for use by SouthCoast that has the potential to result in Level B harassment of marine mammals, sound produced by the Geomarine Geo-Spark and Applied Acoustics Dura-Spark would propagate furthest to the Level B harassment isopleth (141 m (462.6 ft); table 47). For the purposes of take estimation, it was conservatively assumed that sparkers would be the dominant acoustic source for all survey days (although, again, this may not always be the case). Thus, the range to the isopleth corresponding to the threshold for Level B harassment for and the boomer and sparkers (141 m (462.6 ft)) was used as the basis of take calculations for all marine mammals. This is a conservative approach as the actual sources used on individual survey days or during a portion of a survey day may produce smaller distances to the Level B harassment isopleth.

To estimate species densities for the HRG surveys occurring both within the Lease Area and within the ECCs based on Roberts et al. (2016; 2023), a 5-km (3.11 mi) perimeter was applied around each area (see Figures 14 and 15 of SouthCoast's application) using GIS (ESRI, 2017). Given that HRG surveys could occur at any point year-round and is likely to be spread out throughout the year, the annual average density for each species was calculated using average monthly densities from January through December (table 48).

The maximum range (141 m (462.6 ft)) to the Level B harassment threshold and the estimated trackline distance traveled per day by a given survey vessel ( i.e., 80 km (50 mi)) were then used to calculate the daily ensonified area or zone of influence (ZOI) around the survey vessel.

The ZOI is a representation of the maximum extent of the ensonified area around a HRG sound source over a 24-hr period. The ZOI for each piece of equipment operating at or below 180 kHz was calculated per the following formula:

ZOI = (Distance/day × 2r) + pi x r²

Where r is the linear distance from the source to the harassment isopleth.

The largest daily ZOI (22.6 km² (8.7 mi² )), associated with the proposed use of sparkers, was applied to all planned survey days.

During construction, SouthCoast estimated approximately a length of 4,000 km (2,485.5 mi) of surveys would occur within the Lease Area and 5,000 km (3,106.8 mi) would occur within the ECCs. Potential Level B density-based harassment exposures were estimated by multiplying the average annual density of each species within the survey area by the daily ZOI. That product was then multiplied by the number of planned survey days in each sector during the approximately 2-year construction timeframe (62.5 days in the ECCs and 50 days in the Lease Area), and the product was rounded to the nearest whole number. This assumed a total ensonified area of 1,130 km² (702.1 mi² ) in the Lease Area and 1,412.5 km² (877.7 mi² ) along the ECCs. The density-based modeled Level B harassment take for HRG surveys during the construction period assumes approximately 60 percent (5,400 km) and 40 percent (3,600 km) of track lines would be surveyed during Year 1 (associated with Project 1) and Year 2 (associated with Project 2), respectively. SouthCoast estimated a conservative number of annual takes by Level B harassment based on the highest predicted value among the density-based, PSO data-derived, or average group size estimates. These results can be found in table 49. Start Printed Page 53780

As mentioned previously, HRG surveys would also routinely be carried out during the period following completion of foundation installations which, for the purposes of exposure modeling, SouthCoast assumed to be three years. Generally, SouthCoast followed the same approach as described above for HRG surveys occurring during the two years of construction activities, modified to account for reduced survey effort following foundation installation. During the three years when construction is not occurring, SouthCoast estimates that HRG surveys would cover 2,800 km (1,739.8 mi) within the Lease Area and 3,200 km (1,988.4 mi) along the ECCs annually. Maintaining that 80 km (50 mi) are surveyed per day, this amounts to 35 days of survey activity in the Lease Area and 40 days of survey activity along the ECCs each year or 225 days total for the three-year timeframe following the two years of construction activities. Similar to the approach outlined above, density-based take was estimated by multiplying the daily ZOI by the annual average densities and the number of survey days planned for the ECCs and SouthCoast Lease Area. Using the same approach described above, SouthCoast estimated a conservative number of annual takes by Level B harassment based on the highest exposures predicted by the density-based, PSO based, or average group size-based estimates. The highest predicted take estimate was multiplied by three to yield the number of takes that is proposed for authorization, as shown in table 50 below.

Start Printed Page 53781

Total Proposed Take Across All Activities

The species-specific numbers of annual take by Level A harassment and Level B harassment NMFS proposes to authorize incidental to all specified activities combined are provided in table 51. Take estimation assumed pile-driving noise will be attenuated by 10 dB and, where applicable, implementation of seasonal restrictions and clearance and shutdown processes to discount the potential for Level A harassment of most species for which it was estimated. NMFS also presents the 5-year total number of takes proposed for authorization for each species in table 52.

Table 51 presents the annual take proposed for authorization, based on the assumption that specific activities would occur in particular years. SouthCoast currently plans to install all permanent structures ( i.e., WTG and OSP foundations) within two of the five years of the proposed effective period, which includes a single year for Project 1 and a single year for Project 2. However, foundation installations may not begin in the first year of the effective period of the rule or occur in sequential years, and NMFS acknowledges that construction schedules may shift. The proposed rule allows for this flexibility; however, the number of takes for each species in any given year must not exceed the maximum annual numbers provided in table 53.

In table 51, years 1 and 2 represent the assumed years (for take estimation) in which SouthCoast would install WTG and OSP foundations. For each species, the Year 1 proposed take includes the highest take estimate between P1S1 and P1S2 for foundation installation, one year of HRG surveys, and five high-order detonations of the heaviest charge weight (E12) UXO/MECs (at a rate of one per day for up to five days). The proposed Level B harassment take for Year 2 is based on P2S2 for foundation installation, given it resulted in the highest Level B harassment take estimates among P2S1, P2S2, and P2S3 for all species because it includes vibratory (in addition to impact) pile driving of monopiles, one year of HRG surveys, and up to five high-order detonations of the heaviest charge weight (E12) UXO/MECs (also at a rate of one per day for up to five days). In table 51, take for years 3-5 is incidental to HRG surveys. All activities with the potential to result in incidental take of marine mammals are expected to be completed by early 2031.

In making the negligible impact determination, NMFS assesses both the maximum annual total number of takes (Level A harassment and Level B harassment) of each marine mammal species or stocks allowable in any one year, which in the case of this proposed rule is in Year 2, and the total taking of each marine mammal species or stock allowable during the 5-year effective period of the rule.

NMFS has carefully considered all information and analysis presented by SouthCoast as well as all other applicable information and, based on the best scientific information available, concurs that the SouthCoast's estimates of the types and number of take for each species and stock are reasonable and, thus, NMFS is proposing to authorize the number requested.

To inform both the negligible impact analysis and the small numbers determination, NMFS assesses the maximum number of takes of marine mammals that could occur within any given year. In this calculation, the maximum number of Level A harassment takes in any one year is summed with the maximum number of Level B harassment takes in any one year for each species to yield the highest number of estimated take that could occur in any year (table 53). Table 53 also depicts the number of takes relative to the abundance of each stock. The takes enumerated here represent daily instances of take, not necessarily individual marine mammals taken. One take represents a day (24-hour period) in which an animal was exposed to noise above the associated harassment threshold at least once. Some takes represent a brief exposure above a threshold, while in some cases takes could represent a longer, or repeated, exposure of one individual animal above a threshold within a 24-hour period. Whether or not every take assigned to a species represents a different individual depends on the daily and seasonal movement patterns of the species in the area. For example, activity areas with continuous activities (all or nearly every day) overlapping known feeding areas (where animals are known to remain for days or weeks on end) or areas where species with small home ranges live ( e.g., some pinnipeds) are more likely to result in repeated takes to some individuals. Alternatively, activities far out in the deep ocean or takes to nomadic species where individuals move over the population's range without spatial or temporal consistency represent circ*mstances where repeat takes of the same individuals are less likely. In other words, for example, 100 takes could represent 100 individuals each taken on 1 day within the year, or it could represent 5 individuals each taken on 20 days within the year, or some other combination depending on the activity, whether there are biologically important areas in the project area, and the daily and seasonal movement patterns of the species of marine mammals exposed. Wherever there is information to better contextualize the enumerated takes for a given species is available, it is discussed in the Preliminary Negligible Impact Analysis and Determination and/or Small Numbers sections, as appropriate. We recognize that certain activities could shift within the 5-year effective period of the rule; however, the rule allows for that flexibility and the takes are not expected to exceed those shown in table 53 in any one year.

Of note, there is significant uncertainty regarding the impacts of turbine foundation presence and operation on the oceanographic conditions that serve to aggregate prey species for North Atlantic right whales and—given SouthCoast's proximity to Nantucket Shoals—it is possible that the expanded analysis of turbine presence and/or operation over the life of the project developed for the ESA biological opinion for the proposed SouthCoast project or additional information received during the public comment period will necessitate modifications to this analysis. For example, it is possible that additional information or analysis could result in a determination that changes in the oceanographic conditions that serve to aggregate North Atlantic right whale prey may result in impacts that would qualify as a take under the MMPA for North Atlantic right whales.

Proposed Mitigation

In order to promulgate a rulemaking under section 101(a)(5)(A) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to the activity and other means of effecting the least practicable adverse impact on the species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance and on the availability of the species or stock for taking for certain subsistence uses (latter not applicable for this action). NMFS' regulations require incidental take authorization applicants to include in their application information about the availability and feasibility ( e.g., economic and technological) of equipment, methods, and manner of conducting the activity or other means of effecting the least practicable adverse impact upon the affected species or stocks and their habitat (50 CFR 216.104(a)(11)).

In evaluating how mitigation may or may not be appropriate to ensure the least practicable adverse impact on species or stocks and their habitat, as well as subsistence uses where applicable, we carefully consider two primary factors:

(1) The manner in which, and the degree to which, the successful implementation of the measure(s) is expected to reduce impacts to marine mammals, marine mammal species or stocks, and their habitat. This considers the nature of the potential adverse impact being mitigated ( e.g., likelihood, scope, range). It further considers the likelihood that the measure will be effective if implemented ( i.e., probability of accomplishing the mitigating result if implemented as planned), the likelihood of effective implementation ( i.e., probability if implemented as planned); and

(2) The practicability of the measures for applicant implementation, which may consider factors, such as: cost, impact on operations, and, in the case of military readiness activities, personnel safety, practicality of implementation, and impact on the effectiveness of the military readiness activity.

The mitigation strategies described below are consistent with those required and successfully implemented under previous incidental take authorizations issued in association with in-water construction activities ( e.g., soft-start, establishing shutdown zones). Additional measures have also been incorporated to account for the fact that the construction activities would occur offshore in an area that includes important marine mammal habitat. Modeling was performed to estimate Level A harassment and Level B harassment zone sizes, which were used to inform mitigation measures for the project's activities to minimize Level A harassment and Level B harassment to the extent practicable. Generally speaking, the proposed mitigation measures considered and required here fall into three categories: temporal ( i.e., seasonal and daily) work restrictions, real-time measures ( e.g., clearance, shutdown, and vessel strike avoidance), and noise attenuation/reduction measures. Temporal work restrictions are designed to avoid operations when marine mammals are concentrated or engaged in behaviors that make them more susceptible or make impacts more likely to occur. When temporal restrictions are in place, both the number and severity of potential takes, as well as both chronic (longer-term) and acute effects are expected to be reduced. Real-time measures, such as clearing an area of marine mammals prior to beginning activities or shutting down an activity if it is occuring, as Start Printed Page 53784 well as vessel strike avoidance measures, are intended to reduce the probability and severity of harassment by taking steps in real time once a higher-risk scenario is identified ( e.g., once animals are detected within a harassment zone). Noise attenuation measures, such as bubble curtains, are intended to reduce the noise at the source, which reduces both acute impacts as well as the contribution to aggregate and cumulative noise that may result in long-term chronic impacts. Soft-starts are another type of noise reduction measure in that animals are warned of the introduction of sound into their environment at lower levels before higher noise levels are produced. As a conservative measure applicable to all project activities and vessels, if a whale is observed or acoustically detected but cannot be confirmed as a species other than a North Atlantic right whale, SouthCoast must assume that it is a North Atlantic right whale and take the appropriate mitigation measures.