Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Alaska LNG Project in Cook Inlet

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 217

[Docket No. 250722-0128]

RIN 0648-BN50

Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Alaska LNG Project in Cook Inlet

AGENCY:

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

ACTION:

Proposed rule; request for comments.

SUMMARY:

NMFS has received a request from 8 Star Alaska, LLC (8 Star Alaska), a subsidiary of Alaska Gasline Development Corporation (AGDC), for authorization to take marine mammals incidental to the Alaska Liquefied Natural Gas (LNG) Project in Cook Inlet, Alaska, over the course of 5 years (2026-2030). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS proposes regulations setting forth permissible methods of taking, other means of effecting the least practicable adverse impact on such marine mammal stocks (

i.e.,

mitigation measures), and requirements pertaining to monitoring and reporting such takes, and requests comments on the proposed regulations. NMFS will consider public comments prior to making any final decision on the promulgation of the requested MMPA regulations, and NMFS' responses to public comments will be summarized in the final notification of our decision.

DATES:

Comments and information must be received no later than August 28, 2025.

ADDRESSES:

A plain language summary of this proposed rule is available at

https://www.regulations.gov/docket/NOAA-NMFS-2025-0141.

You may submit comments on this document, identified by NOAA-NMFS-2025-0141, by any of the following methods:

•

Electronic Submission:

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

https://www.regulations.gov

and type NOAA-NMFS-2025-0141 in the Search box. Click on the “Comment” icon, complete the required fields, and enter or attach your comments.

•

Mail:

Submit written comments to the Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service, 1315 East-West Highway, Silver Spring, MD 20910-3225.

•

Fax:

(301) 713-0376.

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,

etc.

), 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 8 Star Alaska'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-oil-and-gas.

In case of problems accessing these documents, please call the contact listed below.

FOR FURTHER INFORMATION CONTACT:

Kristy Jacobus, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Purpose and Need for Regulatory Action

NMFS received a request from 8 Star Alaska requesting 5-year regulations and a Letter of Authorization (LOA) that would authorize take of marine mammals by Level A and Level B harassment incidental to 8 Star Alaska's activities. No serious injury or mortality is anticipated or proposed to be authorized. Please see below for definitions of relevant terms and the Estimated Take of Marine Mammals section for definitions of harassment.

The proposed rule, promulgated under the authority of the MMPA (16 U.S.C. 1361

et seq.

), would provide a framework for authorizing the take of marine mammals incidental to construction activities associated with 8 Star Alaska's LNG project, including impact and vibratory pile driving and anchor handling.

Legal Authority for the Proposed Action

The MMPA prohibits the “take” of marine mammals, with certain exceptions. Section 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361

et seq.

) directs the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made, regulations are promulgated (when applicable), and public notice and an opportunity for public comment are provided.

Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, the availability of the species or stocks for taking for certain subsistence uses (referred to as “mitigation”), and requirements pertaining to the mitigation, monitoring and reporting of the takings are set forth.

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

•

Citizen

—individual U.S. citizens or any corporation or similar entity if it is organized under the laws of the United States or any governmental unit defined in 16 U.S.C. 1362(13) (50 CFR 216.103);

•

Take

—to harass, hunt, capture, or kill, or attempt to harass, hunt, capture, or kill any marine mammal (16 U.S.C. 1362; 50 CFR 216.3);

•

Incidental taking

—an accidental taking. This does not mean that the taking is unexpected, but rather it includes those takings that are infrequent, unavoidable, or accidental (50 CFR 216.103);

•

Serious injury

—any injury that will likely result in mortality (50 CFR 216.3);

•

Level A harassment

—any act of pursuit, torment, or annoyance which has the potential to injure a marine mammal or marine mammal stock in the wild (16 U.S.C. 1362); and

•

Level B harassment

—any act of pursuit, torment, or annoyance which has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (16 U.S.C. 1362).

Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50 CFR part 216, subpart I, provide the legal basis for proposing and, if appropriate, issuing 5-year regulations and

associated LOA(s). This proposed rule also proposes required mitigation, monitoring, and reporting requirements for 8 Star Alaska's activities.

Summary of Major Provisions Within the Proposed Rule

The major provisions of this proposed rule include:

• Allowing NMFS to authorize, through an LOA, the take of small numbers of marine mammals by Level A harassment and/or Level B harassment;

• No mortality or serious injury of any marine mammal is proposed to be authorized;

• Requiring NMFS-approved protected species observers (PSOs) and delaying commencement of or shutting down select activities should a marine mammal be detected within identified clearance or shutdown zones to minimize the amount and severity of take;

• Requiring time/area closure for beluga whale during summer months in the western portion of Cook Inlet; and

• Requiring soft start for impact pile driving to allow marine mammals the opportunity to leave the area prior to beginning impact pile driving at full power.

National Environmental Policy Act

To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321

et seq.

) and NOAA Administrative Order 216-6A, NMFS must review our proposed action (

i.e.,

promulgation of regulations and subsequent issuance of a 5-year LOA) with respect to potential impacts on the human environment.

NMFS participated as a cooperating agency on the 2020 Alaska LNG Project Environmental Impact Statement (EIS), which was finalized on March 6, 2020, and is available at

https://www.ferc.gov/industries-data/natural-gas/environment/final-environmental-impact-statement-feis.

When acting as a cooperating agency, as is the case with this project, NMFS may satisfy its independent NEPA obligations by either preparing a separate NEPA analysis for its issuance of an incidental take authorization or, if appropriate, by adopting the NEPA analysis prepared by the lead agency. NMFS independently reviewed and evaluated the 2020 Alaska LNG Project EIS and determined it was adequate and sufficient to meet our responsibilities under NEPA for the issuance of the 2020 Alaska LNG Cook Inlet LOA (85 FR 59291, September 21, 2020). NMFS therefore adopted the 2020 Alaska LNG Project EIS and signed a Record of Decision on February 16, 2021.

Consistent with NEPA, applicable NOAA NEPA procedures, and the information and analysis contained in this proposed rule, NMFS has made a preliminary determination that this proposed rule and any subsequent LOAs would not result in significant impacts that were not fully considered in the 2020 Alaska LNG Project EIS. As indicated in this proposed rule, 8 Star Alaska has made no substantial changes to the activities evaluated in the EIS, and NMFS is unaware of any significant new circumstances or information relevant to environmental concerns or their impacts. NMFS will make a final NEPA determination prior to a decision whether to issue a final rule and LOA.

Fixing America's Surface Transportation Act

This project is covered under Title 41 of the Fixing America's Surface Transportation Act, or “FAST-41.” FAST-41 includes a suite of provisions designed to expedite the environmental review for covered infrastructure projects, including enhanced interagency coordination as well as milestone tracking on the public-facing Permitting Dashboard. FAST-41 also places a 2-year limitations period on any judicial claim that challenges the validity of a Federal agency decision to issue or deny an authorization for a FAST-41 covered project. 42 U.S.C. 4370m-6(a)(1)(A).

8 Star Alaska's proposed project is listed on the permitting dashboard. Milestones and schedules related to the environmental review and permitting for the Alaska LNG Project can be found at

https://www.permits.performance.gov/permitting-project/fast-41-covered-projects/alaska-lng-project.

Summary of Request

On December 5, 2024, NMFS received a request from 8 Star Alaska for regulations and a LOA to take marine mammals incidental to construction of LNG facilities in Cook Inlet, Alaska. Following NMFS' review of the application, 8 Star Alaska submitted a revised version on April 3, 2025, which was deemed adequate and complete. On April 8, 2025, NMFS published a notice of receipt (NOR) of application in the

Federal Register

(90 FR 15137), requesting comments and information during a 30-day public comment period related to 8 Star Alaska's request. NMFS received one letter from the Center for Biological Diversity and Cook Inletkeeper providing substantive comments and approximately 14,000 comments from members of the public expressing general opposition to 8 Star Alaska's proposed project but providing no information relevant to the information contained within 8 Star Alaska's application or to NMFS' determination that the application is adequate and complete. The comment letters from members of the public followed a generic template format in which respondents provided comments that were identical or substantively the same. NMFS has reviewed all submitted material and taken the information into consideration during the drafting of this proposed rule.

NMFS is proposing to authorize take of 12 species of marine mammals by Level B harassment, and by Level A harassment for a subset of 3 of these species. Neither 8 Star Alaska nor NMFS expect serious injury or mortality to result from the specified activities and neither are proposed to be authorized.

NMFS previously promulgated regulations and issued an LOA to AGDC for the same work on September 15, 2020 (85 FR 59291, September 21, 2020), effective from January 1, 2021, through December 31, 2025. However, no work has been conducted during the effective period of that LOA and none is planned prior to its expiration.

Description of Proposed Activity

Overview

8 Star Alaska proposes to construct facilities to transport and offload LNG in Cook Inlet, Alaska, for export. Project activities would include the construction of a Marine Terminal comprised of a temporary Marine Terminal Material Offloading Facility (MOF) and a permanent Product Loading Facility (PLF) on the east side of Cook Inlet, near Nikiski; construction of a pipeline (referred to as the Mainline) across Cook Inlet; and construction of a Mainline MOF on the west side of Cook Inlet, north of Tyonek. The components of the proposed construction activities that have the potential to expose marine mammals to sound levels that could result in take are vibratory and impact pile driving of steel sheet piles and 24-, 48-, 60-, and 66-inch (61-, 122-, 152.4-, and 167.6-centimer [cm]) steel pipe piles, as well as the use of anchor handling tugs (AHTs).

Dates and Duration

Planned in-water work would occur over 5 years between January 1, 2026, and December 31, 2030. The construction window is based on the ice-free working window, which is from approximately April 1 through October 31. Pile driving would occur during

daylight hours and is estimated to occur 6 days per week. Work for pipelaying would occur 24 hours per day, 7 days per week, and could occur during periods of low visibility. In-water pile-driving is expected to occur over an estimated 323 nonconsecutive days over the 5-year period, and use of AHTs used for pipelaying in construction of the Mainline is expected to occur over an estimated 55 nonconsecutive days during Years 3 and 4 of the project, for a total of 378 construction days over the 5 year period (See table 1).

Table 1—Estimated Construction Schedule

Construction element

Estimated number of days

Year 1

Marine Terminal MOF

78

Year 2

Marine Terminal MOF

69

Mainline MOF

14

Year 3

PLF

74

Mainline

2

Year 4

Mainline

53

PLF

52

Year 5

PLF

36

Total

378

Specified Geographical Region

The proposed construction activities would occur in Cook Inlet, Alaska. The Marine Terminal, consisting of the temporary marine terminal MOF and PLF, would be constructed adjacent to the proposed onshore liquefaction facility near Nikiski, Alaska. The Mainline would cross the Cook Inlet shoreline on the west side of Cook Inlet south of Beluga Landing, traverse Cook Inlet in a generally southward direction for approximately 26.7 miles (43 kilometers [km]), and cross the east Cook Inlet shoreline near Suneva Lake. An MOF (Mainline MOF) may be constructed on the west side of Cook Inlet near the existing Beluga Landing to support installation of the Cook Inlet shoreline crossing. See figure 1 for a map of 8 Star Alaska's action area (see 8 Star Alaska's application for color legends).

BILLING CODE 3510-22-P

EP29JY25.004

BILLING CODE 3510-22-C

Detailed Description of the Specified Activity

Construction of the Alaska LNG facilities would include construction of a Marine Terminal, comprised of a temporary marine terminal MOF and PLF; a Mainline MOF; and a pipeline (referred to as Mainline) crossing Cook Inlet. Noise generated by impact and vibratory pile driving would be likely to result in take of marine mammals. Additionally, we assume here that noise generated by AHTs conducting anchor handling may result in take of marine mammals.

Temporary Marine Terminal Material Offloading Facility

The temporary Marine Terminal MOF would consist of a quay and two berths, which would be used during construction of the Liquefaction Facility to enable direct deliveries of equipment modules, bulk materials, construction equipment, and other cargo to minimize the transport of large and heavy loads over road infrastructure. See Figure 6 in 8 Star Alaska's application for visual depiction of the Marine Terminal MOF. Construction of the Temporary MOF is expected to occur in Years 1 and 2.

Quay—The quay would be constructed of an outer wall consisting of combi-wall (combination of sheet pile and 66-inch steel pipe piles), tied back to a sheet pile anchor wall, and 11 sheet pile coffer cells, comprised of sheet piles and 24-inch pipe piles, backfilled with granular materials. The 24-inch pipe piles would be removed once coffer cell installation is complete. All pile installation and removal would be conducted with vibratory methods. 8 Star Alaska expects to use two crews during the installation of piles for the combi-wall and coffer cells, and therefore concurrent pile driving is expected to occur during installation of these features. This could result in concurrent vibratory pile driving of two 66-inch sheet piles, 2 sheet piles, 2 24-inch pile piles, a 66-inch pipe pile with a sheet pile, and a 24-inch pipe pile with a sheet pile. Installation of the sheet pile anchor wall is not considered in this analysis because the anchor wall would be installed into fill and would not generate substantial underwater sound.

Berths—Berths at the Marine Terminal MOF would include one Lift-on/Lift-off (Lo-Lo) berth and one Roll-on/Roll-off (Ro-Ro) berth maintained at depths alongside of 32 feet Mean Lower Low Water (MLLW). The berths would be constructed of 24-inch and 48-inch pipe piles using an impact hammer.

The Marine Terminal MOF would be constructed using both land-based (from shore and subsequently from constructed portions of the Marine Terminal MOF) and marine construction methods.

Dredging would be conducted at the Marine Terminal MOF with hydraulic or mechanical dredgers. While marine mammals may behaviorally respond in some small degree to the noise generated by dredging operations, given the slow, predictable movements of these vessels, and absent any other contextual features that would cause enhanced concern, NMFS does not consider it likely that 8 Star Alaska's proposed dredging would result in the take of marine mammals.

Product Loading Facility (PLF)

The proposed PLF would be a permanent facility used to load LNG carriers for export. The PLF would consist of two loading platforms, two berths, a marine operations platform, and an access trestle that supports the piping that delivers LNG from shore. See figure 4 in 8 Star Alaska's application for a visual description. In-water construction for the PLF would occur in Years 3-5. Construction methods would include both overhead construction (conducted with equipment located on a cantilever bridge extending from shore) and marine construction (conducted with equipment located on barges/vessels). All pile driving for the PLF would be conducted with an impact hammer. See figures 3 through 5 in 8 Star Alaska's application for visual depiction of the PLF.

PLF Berth Loading Platforms—The two loading platforms, located at either end of the north-south portion of the trestle would be supported above the seafloor on steel-jacketed structures called quadropods, made of 48-inch steel pipe piles.

PLF Berth Breasting and Mooring Dolphins—Each berth would have four concrete pre-cast breasting dolphins and six concrete pre-cast mooring dolphins that would be supported over the seabed on quadropods, comprised of 48-inch and 60-inch steel pipe piles. A catwalk, supported on two-pile bents comprised of 60-inch steel pipe piles, would connect the mooring dolphins to the loading platforms.

Marine Operations Platform—The platform would be located along the east-west portion of the access trestle and would be supported above the seafloor on four-pile bents, comprised of 60-inch steel pipe piles.

Access Trestle—The access trestle would be T-shaped with a long east-west oriented section and a shorter north-south oriented section. The east-west portion would be supported on three-pile and four-pile bents, comprised of 60-inch steel pipe piles, and the north-south oriented portion would be supported on five-pile quadropods, comprised of 48-inch steel pipe piles.

Mainline MOF

A Mainline MOF may be required on the west side of Cook Inlet to support installation of the Cook Inlet shoreline crossing. The Mainline MOF would consist of a quay, space for tugs, and berths including a Lo-Lo berth for unloading pipe and construction material and Ro-Ro berth and ramp dedicated to Ro-Ro operations. Approximately 1,270 feet (387.1 meters [m]) of sheet pile would be installed with a combination of vibratory and impact methods for construction of the quay and Ro-Ro ramp, and a corresponding length of sheet pile would be installed as anchor wall. However, only 670 feet (204.2 m) of sheet pile would be installed in the water, as the remainder would be installed as anchor wall in fill material or in the intertidal area when the tide is out. Therefore, only the installation of these 670 feet (204.2 m) of sheet pile is likely to result in the take of marine mammals. Construction of the Mainline MOF is expected to occur in Year 2.

Mainline Crossing Cook Inlet

8 Star Alaska proposes to install a 42-inch-diameter natural gas pipeline that would cross Cook inlet from the west side of the inlet south of Beluga Landing in a generally southward direction to the east side of Cook Inlet near Suneva Lake. The pipe would be trenched into the seafloor and buried from the shoreline out to a water depth of approximately 35-45 feet (10.7-13.7 m) MLLW on both sides of the inlet, approximately 8,800 feet from the north landfall and 6,600 feet from the south landfall. Burial depth in these areas would be 3-6 feet (0.9-1.8 m). Seaward of these sections, the pipeline would be placed on the seafloor. The installation methods would vary depending on the distance from shore, as described below. Installation of the Mainline crossing of Cook Inlet would include AHTs engaged in anchor handling (described further below). Construction of the Mainline is expected to occur during Years 3 and 4.

Pre-installation surveys—High-resolution geophysical surveys would be conducted prior to pipeline construction in order to develop a detailed bathymetric profile. The acoustic survey equipment proposed for use includes:

• Single-beam echosounder operating at 200 kilohertz (kHz);

• Multi-beam echosounder operating at 200-400 kHz;

• Side-scan sonar system at 400-900 kHz; and

• Magnetometer, which does not emit underwater sound.

The echosounders and side-scan sonar operate at or above 200 kHz, which are above the range of marine mammals' hearing thresholds, and the magnetometer does not emit sound. Therefore, use of this equipment is not expected to result in take of marine

mammals, and it is not further evaluated in this proposed rule.

Nearshore Trenching, Pipelay, and Burial—In the nearshore portions of the route across Cook Inlet, the pipeline would be trenched and buried. The nearshore portion of the trench (extending from the shoreline to a transition water depth where a dredge vessel can be employed) would be constructed using amphibious or barge-based excavators. From the transition water depth to water depth of the −25 feet or −45 feet MLLW, 8 Star Alaska would use a dredge to excavate a trench for the pipeline. As described above, NMFS does not consider it likely that 8 Star Alaska's proposed dredging would result in the take of marine mammals.

Pipeline joints would be welded together onshore in 1,000 foot-long strings (pipe strings) and laid on the ground surface in an orientation that approximates the offshore alignment. 8 Star Alaska would anchor a pipe pull barge near the seaward end of the trench using AHTs. The barge would be used to pull the pipe strings from their onshore position into the trench. Given the transient and slow, predictable movement of barges, NMFS does not expect any potential for startle responses from individual marine mammals that may be in the vicinity. Similarly, with regard to the characteristics of noise output resulting from use of barges and other, similar industrial activities, NMFS generally assumes that the relative lack of variation in the signal and associated absence of high peak pressure or rapid rise time events (characteristics associated with impulsive and/or intermittent sound sources) significantly limits the likelihood of behavioral responses that might appropriately be considered take.

In addition to these general conclusions related to the physical and acoustic characteristics of the activity, NMFS considers contextual issues that may result in different, case-specific conclusions. For example, when considering relatively loud continuous noise sources, such as use of AHTs or tugging under load, NMFS evaluates the potential for exposure to result in take for sensitive species such as Cook Inlet beluga whales in important habitat is sufficient to justify a determination that some amount of take is likely. Following pipeline installation, the trench is expected to backfill naturally through the movement of seafloor sediments. If manual backfilling is required, the backfill would be placed by reversing the flow of the dredger used offshore or mechanically with the use of excavators.

Trenching, pipelay, and burial would be conducted 24 hours per day, seven days per week. 8 Star Alaska anticipates a pipelay rate of 2,000 (609.6 m) to 2,500 feet (762 m) per 24 hours. Anchor handling is only expected to occur during the initial anchoring of the pull barge, and therefore the AHTs are only expected to be used for a total of two days during nearshore pipelay, one day on the west coast near Beluga and one day on the east coast near Suneva Lake. We note here that AHT activities are not generally dissimilar from dredging, pipe-pulling, etc., in terms of the characteristics of noise output, although AHTs are assumed to be louder than these other similar activities. Given the slow, predictable, and generally straight path (or stationary nature) of tugs engaged in anchor handling activities, the likelihood of disrupting marine mammal behavioral patterns from tug use that would qualify as harassment under the MMPA is considered relatively low. Nevertheless, we have quantified the potential exposures from this activity, assumed that these exposures would equate to take, and analyzed the impacts of the assumed takes, which we propose for authorization. Anchor handling is the only activity assumed to result in take of marine mammals during the nearshore trenching, pipelay, and burial.

Offshore Pipeline Installation—Seaward of the trenched sections, the pipeline would be laid on the seafloor across Cook Inlet using conventional pipelay vessel methods. The pipelay vessel would likely employ 12 anchors to keep it positioned during pipelay and provide resistance as it is winched ahead 80 feet each time an additional 80-foot section of pipe is added/welded on the pipe string. 8 Star Alaska anticipates a pipelay rate of 2,000 to 2,500 feet (609.6-762 m) per 24 hours. 8 Star Alaska would use AHTs to reposition the anchors. Use of the AHTs could potentially result in take of marine mammals and is described in more detail below. Offshore pipelaying would be conducted for 24 hours per day, 7 days per week. 8 Star Alaska anticipates using AHTs about 25 percent of the time (

i.e.,

approximately 6 hours per day).

AHTs—8 Star Alaska would use AHTs and anchor systems to maintain the optimal stability and alignment of a specialized vessel, referred to as a pipelay barge, while laying pipeline on the seafloor. Pipeline activities utilizing pipelay barge methods include support from up to three AHTs that would repeatedly reposition the anchors, thereby maintaining proper position and permitting forward movement.

8 Star Alaska is unable to specify tugging characteristics at this time. However, based on specifications for other similar activities such as Hilcorp Alaska's LLC's Production Drilling Support Activities in Cook Inlet (89 FR 79529; September 30, 2024) and Furie Operating Alaska, LLC Natural Gas Activities in Cook Inlet (89 FR 77836; September 24, 2024), NMFS anticipates that the AHTs would be rated between 4,000 horsepower (hp) and 8,000 hp. Potential tug power output during anchor handling is discussed in further detail in the Estimated Take of Marine Mammals section.

A summary of pile driving activities for the Alaska LNG facilities construction is provided in table 2, and a summary of the use of AHTs for pipelaying is provided in table 3.

Table 2—Anticipated In-Water Pile Driving Schedule

Section

Element

Number of steel pipe piles or length of sheet piles

24-inch steel pipe

48-inch steel pipe

60-inch steel pipe

66-inch steel pipe

Sheet piles

Hammer type

# days

Year 1

Marine Terminal MOF

Combi-wall

70

144

Vibratory

22

Marine Terminal MOF

Coffer cell

48

1,496

Vibratory

56

Year 2

Marine Terminal MOF

Coffer cell

40

1,491

Vibratory

54

Marine Terminal MOF

Ro-Ro/Lo-Lo berths

7

28

Impact

14

Mainline MOF

Quay

205

Vibratory/Impact

10

Mainline MOF

Ro-Ro ramp

87

Vibratory/Impact

4

Year 3

PLF

E-W Trestle

73

Impact

42

PLF

Berth Loading Platforms

40

Impact

16

PLF

N-S Trestle

40

Impact

16

Year 4

PLF

E-W Trestle

28

Impact

14

PLF

Operations Platform

12

Impact

6

PLF

Breasting Dolphin

8

32

Impact

16

PLF

Mooring Dolphin

2

8

Impact

4

PLF

N-S Trestle

30

Impact

12

Year 5

PLF

Mooring Dolphin

10

40

Impact

20

PLF

Catwalk

8

Impact

16

Total

73

158

236

70

3,423

323

Table 3—Schedule of Anchor Handling for Construction of Mainline Across Cook Inlet

Activity

Hours/day

Days

Year 3

Nearshore pipelay

6

2

Year 4

Offshore pipelay

6

53

Proposed mitigation, monitoring, and reporting measures are described in detail later in this document (please see Proposed Mitigation and Proposed Monitoring and Reporting).

Description of Marine Mammals in the Area of Specified Activities

Sections 3 and 4 of the application summarize available information regarding status and trends, distribution and habitat preferences, and behavior and life history of the potentially affected species. NMFS fully considered all of this information, and we refer the reader to these descriptions instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs;

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

) 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).

Table 4 lists all species or stocks for which take is expected and proposed to be authorized for this activity and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (as described in NMFS' SARs). While no serious injury or mortality is anticipated or proposed to be authorized here, PBR and annual serious injury and mortality (M/SI) 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. Alaska and Pacific SARs. All values presented in table 4 are the most recent available at the time of publication (including from the draft 2024 SARs) and are available online at:

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

Table 4—Species

1

With Estimated Take From the Specified Activities

Common name

Scientific name

Stock

ESA/

MMPA

status;

Strategic

(Y/N)

2

Stock abundance (CV, N

min

, most recent abundance

survey)

3

PBR

Annual M/SI

4

Order Artiodactyla—Cetacea—Mysticeti (baleen whales)

Family Eschrichtiidae

:

Gray Whale

Eschrichtius robustus

Eastern North Pacific

-, -, N

26,960 (0.05, 25,849, 2016)

801

131

Family Balaenopteridae (rorquals)

:

Fin Whale

Balaenoptera physalus

Northeast Pacific

E, D, Y

11,065 (0.405 7,970, 2013)

5

UND

0.6

Humpback Whale

Megaptera novaeangliae

Hawai'i

-, -, N

11,278 (0.56, 7,265, 2020)

127

27.09

Humpback Whale

Megaptera novaeangliae

Mexico-North Pacific

T, D, Y

N/A

6

(N/A, N/A, 2006)

UND

0.57

Humpback Whale

Megaptera novaeangliae

Western North Pacific

E, D, Y

1,084 (0.088, 1,007, 2006)

3.4

5.82

Minke Whale

Balaenoptera acutorostrata

Alaska

-, -, N

N/A

7

(N/A, N/A, N/A)

UND

0

Odontoceti (toothed whales, dolphins, and porpoises)

Family Delphinidae

:

Killer Whale

Orcinus orca

Eastern North Pacific Alaska Resident

-, -, N

1,920 (N/A, 1,920, 2019)

19

1.3

Killer Whale

Orcinus orca

Eastern North Pacific Gulf of Alaska, Aleutian Islands and Bering Sea Transient

-, -, N

587 (N/A, 587, 2012)

5.9

0.8

Pacific White-Sided Dolphin

Lagenorhynchus obliquidens

North Pacific

-, -, N

26,880 (N/A, N/A, 1990)

UND

0

Family Monodontidae (white whales)

:

Beluga Whale

Delphinapterus leucas

Cook Inlet

E, D, Y

331 (0.076, 311, 2022)

0

Family Phocoenidae (porpoises):

Dall's Porpoise

Phocoenoides dalli

Alaska

-, -, N

UND

8

(UND, UND, 2015)

UND

37

Harbor Porpoise

Phocoena

Gulf of Alaska

-, -, Y

31,046 (0.21, N/A, 1998)

UND

72

Order Carnivora—Pinnipedia

Family Otariidae (eared seals and sea lions)

:

California Sea Lion

Zalophus californianus

U.S.

-, -, N

257,606 (N/A, 233,515, 2014)

14,011

>321

Steller Sea Lion

Eumetopias jubatus

Western

E, D, Y

49,837

9

(N/A, 49,837, 2022)

299

267

Family Phocidae (earless seals)

:

Harbor Seal

Phoca vitulina

Cook Inlet/Shelikof Strait

-, -, N

28,411 (N/A, 26,907, 2018)

807

107

1

Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy (

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

).

2

Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA as depleted and as a strategic stock.

3

NMFS marine mammal stock assessment reports online at:

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

CV is coefficient of variation; N

min

is the minimum estimate of stock abundance.

4

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

e.g.,

commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range.

5

The best available abundance estimate for this stock is not considered representative of the entire stock as surveys were limited to a small portion of the stock's range.

6

NMFS's abundance estimate for this stock is greater than eight years old and not considered current. PBR is therefore considered undetermined for this stock, as there is no current minimum abundance estimate for use in calculation. We nevertheless present the most recent abundance estimate as the best available information.

7

Reliable population estimates are not available for this stock.

8

The best available abundance estimate is likely an underestimate for the entire stock because it is based upon a survey that covered only a small portion of the stock's range.

9

Nest is best estimate of counts, which have not been corrected for animals at sea during abundance surveys. Estimates provided are for the U.S. only. The overall N

min

is 73,211 and overall PBR is 439.

As indicated above, all 12 species (with 15 managed stocks) in table 4 temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur.

In addition, the northern sea otter may be found in Cook Inlet, Alaska. However, northern sea otters are managed by the U.S. Fish and Wildlife Service and are not considered further in this document.

Gray Whale

The stock structure for gray whales in the Pacific has been studied for a number of years and remains uncertain as of the most recent draft 2024 Pacific SARs (Carretta

et al.,

2025). Gray whale population structure is not determined by simple geography and may be in flux due to evolving migratory dynamics (Carretta

et al.,

2024). Currently, the SARs delineate a western North Pacific (WNP) gray whale stock and an eastern North Pacific (ENP) stock based on genetic differentiation (Carretta

et al.,

2025). WNP gray whales are not known to feed in or travel to upper Cook Inlet (Conant and Lohe, 2023, Weller

et al.,

2023). Therefore, we assume that gray whales near the project area are members of the ENP stock.

An Unusual Mortality Event (UME) for gray whales along the West Coast and in Alaska occurred from December 17, 2018, through November 9, 2023. During that time 690 gray whales stranded in the United States, Mexico, and Canada, 146 of which stranded off the coast of Alaska. The investigative team concluded that the preliminary cause of the UME was localized ecosystem changes in the whale's Subarctic and Arctic feeding areas that led to changes in food, malnutrition, decreased birth rates, and increased mortality (see

https://www.fisheries.noaa.gov/national/marine-life-distress/2019-2023-gray-whale-unusual-mortality-event-along-west-coast-and

for more information).

Gray whales occur infrequently in Cook Inlet, but may be seasonally present during spring and fall in the lower inlet (Bureau of Ocean Energy Management (BOEM), 2022). Migrating gray whales pass through the lower inlet during their spring and fall migrations to and from their primary summer feeding areas in the Bering, Chukchi, and Beaufort seas (Swartz, 2018, Silber

et al.,

2021, Bureau of Ocean Energy Management (BOEM), 2022). Several surveys and monitoring programs have sighted gray whales in lower Cook Inlet (Shelden

et al.,

2013, Owl Ridge, 2014, Lomac-MacNair

et al.,

2013, 2014,

Kendall

et al.,

2015). Gray whales are occasionally seen in mid- and upper Cook Inlet, Alaska, but they are not common. During NMFS aerial surveys conducted in June 1994, 2000, 2001, 2005, and 2009, gray whales were observed in Cook Inlet near Port Graham and Elizabeth Island as well as near Kamishak Bay, with one gray whale observed as far north as the Beluga River (Shelden

et al.,

2013). Gray whales were also observed offshore of Cape Starichkof in 2013 by marine mammal observers monitoring Buccaneer's Cosmopolitan drilling project (Owl Ridge, 2014) and in middle Cook Inlet in 2014 during the 2014 Apache 2D seismic survey (Lomac-MacNair

et al.,

2015). Several projects performed in Cook Inlet in recent years reported no observations of gray whales. These project activities included the SAExploration seismic survey in 2015 (Kendall and Cornick, 2015), the 2018 Cook Inlet Pipeline (CIPL) Extension Project (Sitkiewicz

et al.,

2018), and the 2019 Hilcorp seismic survey in lower Cook Inlet (Fairweather Science, 2020).

In 2020, during the aforementioned UME, a young male gray whale was stranded in the Twentymile River near Girdwood for over a week before swimming back into Turnagain Arm. The whale did not survive and was found dead in west Cook Inlet later that month (NMFS, 2020). One gray whale was sighted in Knik Arm near the Port of Alaska (POA) in Anchorage in upper Cook Inlet in May of 2020 during observations conducted during construction of the Petroleum and Cement Terminal project (61 North Environmental, 2021). The sighting occurred less than a week before the reports of the gray whale stranding in the Twentymile River and was likely the same animal. In 2021, one small gray whale was sighted in Knik Arm near Ship Creek, south of the POA (61 North Environmental, 2022a). Although some sightings have been documented in the middle and upper Inlet, the gray whale range typically only extends into the lower Cook Inlet region.

Humpback Whale

The most comprehensive photo-identification data available suggest that approximately 89 percent of all humpback whales in the Gulf of Alaska are from the Hawaii stock, 11 percent are from the Mexico stock, and less than 1 percent are from the Western North Pacific stock (Wade, 2021). Individuals from different stocks are known to intermix in feeding grounds. There is no designated critical habitat for humpback whales in or near the area where the specified activity is planned to occur (86 FR 21082, April 21, 2021), nor does the project overlap with any known biologically important areas (Wild

et al.,

2023).

Humpback whales are encountered regularly in lower Cook Inlet and occasionally in mid-Cook Inlet; sightings are rare in upper Cook Inlet. Eighty-three groups containing an estimated 187 humpbacks were sighted during Cook Inlet beluga whale aerial surveys conducted by NMFS from 1994 to 2012 (Shelden

et al.,

2013). Surveys conducted north of the forelands have documented small numbers in middle Cook Inlet. During the 2014 Apache seismic surveys in Cook Inlet, five groups (six individuals) were reported, with three groups north of the forelands on the east side of the inlet (Lomac-MacNair

et al.,

2014). In 2015, during the construction of the Furie Operating Alaska, LLC (Furie) platform and pipeline, four groups of humpback whales were documented. Another group of 6 to 10 unidentified whales, thought to be either humpback or gray whales, was sighted approximately 15 km northeast of the Julius R. Platform Large cetaceans were visible near the project (

i.e.,

whales or blows were visible) for 2 hours out of the 1,275 hours of observation conducted (Jacobs Engineering Group Inc., 2015).

Minke Whale

No estimates have been made for the number of minke whales in the entire North Pacific (Young

et al.,

2024). However, some information is available on the number of minke whales in some areas of Alaska. Visual surveys for cetaceans were conducted on the eastern Bering Sea shelf in 2002, 2008, and 2010 in cooperation with research on commercial fisheries (Friday

et al.,

2013). Results of the surveys in 2002, 2008, and 2010 provided provisional abundance estimates of 389 (CV−0.52), 517 (CV = 0.69), and 2,020 (CV = 0.73) minke whales on the eastern Bering Sea shelf, respectively (Friday

et al.,

2013). These estimates are considered provisional because they have not been corrected for animals missed on the trackline, animals submerged when the ship passed, or responsive movement. Additionally, line transect surveys were conducted in shelf and nearshore waters (within 30-45 nautical miles of land) in 2001-2003 from the Kenai Fjords in the Gulf of Alaska to the central Aleutian Islands. Minke whale abundance was estimated to be 1,233 (CV = 0.34) for this area (Zerbini

et al.,

2006). This estimate has also not been corrected for animals missed on the trackline. The majority of the sightings were in the Aleutian Islands, rather than in the Gulf of Alaska, and in water shallower than 200 m. So few minke whales were seen during three offshore Gulf of Alaska surveys for cetaceans in 2009, 2013, and 2015 that a population estimate for the species in this area could not be determined (Rone

et al.,

2017). These estimates cannot be used as an estimate of the entire Alaska stock of minke whales because only a portion of the stock's range was surveyed (Young

et al.,

2024).

Minke whales are most abundant in the Gulf of Alaska during summer and occupy localized feeding areas (Zerbini

et al.,

2006). During the NMFS annual and semiannual surveys of Cook Inlet, minke whales were observed near Anchor Point in 1998, 1999, 2006, and 2021 (Shelden

et al.,

2013, 2015b, 2017, 2022, Shelden and Wade, 2019) and near Ninilchik and the middle of lower Cook Inlet in 2021 (Shelden

et al.,

2022). Minke whales were sighted southeast of Kalgin Island and near Homer during Apache's 2014 survey (Lomac-MacNair

et al.,

2014), and one was observed near Tuxedni Bay in 2015 (Kendall

et al.,

2015 as cited in Weston and SLR 2022). During Hilcorp's seismic survey in lower Cook Inlet in the fall of 2019, eight minke whales were observed (Fairweather Science, 2020). In 2018, no minke whales were observed during observations conducted for the CIPL project near Tyonek (Sitkiewicz

et al.,

2018). Minke whales were also not recorded during Hilcorp's aerial or rig-based monitoring efforts in 2023 (Horsley and Larson, 2023).

Fin Whale

Fin whales' range extends into lower Cook Inlet; however, sightings are infrequent, and they are mostly spotted near the Inlet's entrance. Fin whales are usually observed as individuals traveling alone, although they are sometimes observed in small groups. From 2000 to 2022, 10 sightings of 26 estimated individual fin whales were observed in lower Cook Inlet during NMFS aerial surveys (Shelden

et al.,

2013, 2015b, 2017, 2022, Shelden and Wade, 2019). In the fall of 2019 during Hilcorp's seismic survey in lower Cook Inlet, 8 sightings of 23 fin whales were documented, suggesting greater numbers may use the area in the fall than previously estimated (Fairweather Science, 2020). Hilcorp did not record any sightings of fin whales from their aerial or rig-based monitoring efforts in 2023 (Horsley and Larson, 2023).

Beluga Whale

Five stocks of beluga whales are recognized in Alaska: the Beaufort Sea stock, eastern Chukchi Sea stock,

eastern Bering Sea stock, Bristol Bay stock, and Cook Inlet stock (Young

et al.,

2023). The Cook Inlet stock of beluga whale is the only stock that inhabits the project area. It is geographically and genetically isolated from the other stocks (O'Corry-Crowe

et al.,

1997, Laidre

et al.,

2000) and resides year-round in Cook Inlet (Laidre

et al.,

2000, Castellote

et al.,

2020). Cook Inlet beluga whales (CIBWs) were designated as depleted under the MMPA in 2000 (65 FR 34950, May 31, 2000), and as a distinct population segment (DPS) and listed as endangered under the ESA in October 2008 (73 FR 62919, October 10, 2008) when the species failed to recover following a moratorium on subsistence harvest. Between 2008 and 2018, CIBWs experienced a decline of about 2.3 percent per year (Wade

et al.,

2019). The decline overlapped with the northeast Pacific marine heatwave that occurred from 2014 to 2016 in the Gulf of Alaska, significantly impacting the marine ecosystem (Suryan

et al.,

2021 as cited in Goetz

et al.,

2023).

In June 2023, NMFS released an updated abundance estimate for CIBWs in Alaska that incorporates aerial survey data from June 2021 and 2022 and accounted for visibility bias (Goetz

et al.,

2023). This report estimated that CIBW abundance is between 290 and 386, with a median best estimate of 331. Goetz

et al.

(2023) also present an analysis of population trends for the most recent 10-year period (2012-2022). The addition of data from the 2021 and 2022 survey years in the analysis resulted in a 65.1 percent probability that the CIBW population is now increasing at 0.9 percent per year (95 percent prediction interval of −3 to 5.7 percent). This increase drops slightly to 0.2 percent per year (95 percent prediction interval of −1.8 to 2.6 percent) with a 60 percent probability that the CIBW population is increasing more than 1 percent per year when data from 2021, which had limited survey coverage due to poor weather, are excluded from the analysis.

Threats that have the potential to impact this stock and its habitat include the following: changes in prey availability due to natural environmental variability, ocean acidification, and commercial fisheries; climatic changes affecting habitat; predation by killer whales; contaminants; noise; ship strikes; waste management; urban runoff; construction projects; and physical habitat modifications that may occur as Cook Inlet becomes increasingly urbanized (Moore

et al.,

2000, Hobbs

et al.,

2015, NMFS, 2016). Another source of CIBW mortality in Cook Inlet is predation by transient-type (mammal-eating) killer whales (NMFS, 2016, Shelden

et al.,

2003). No human-caused mortality or serious injury of CIBWs through interactions with commercial, recreational, and subsistence fisheries, takes by subsistence hunters, and or human-caused events (

e.g.,

entanglement in marine debris, ship strikes) has been recently documented (Muto

et al.,

2022) and harvesting of CIBWs has not occurred since 2008 (NMFS, 2008a).

Recovery Plan

In 2010, a recovery team, consisting of a science panel and stakeholder panel, began meeting to develop a recovery plan for the CIBW. The final recovery plan was published in the

Federal Register

on January 5, 2017 (82 FR 1325). In September 2022, NMFS completed the ESA 5-year review for the CIBW DPS and determined that the CIBW DPS should remain listed as endangered (NMFS, 2022a).

In its recovery plan (82 FR 1325, January 5, 2017), NMFS identified several potential threats to CIBWs, including: (1) high concern: catastrophic events (

e.g.,

natural disasters, spills, mass strandings), cumulative effects of multiple stressors, and noise; (2) medium concern: disease agents (

e.g.,

pathogens, parasites, and harmful algal blooms), habitat loss or degradation, reduction in prey, and unauthorized take; and (3) low concern: pollution, predation, and subsistence harvest. The recovery plan did not treat climate change as a distinct threat but rather as a consideration in the threats of high and medium concern. Other potential threats most likely to result in direct human-caused mortality or serious injury of this stock include vessel strikes.

Critical Habitat

On April 11, 2011, NMFS designated two areas of critical habitat for CIBW (76 FR 20179). The designation includes 7,800 square kilometers (km

2

) of marine and estuarine habitat within Cook Inlet, encompassing approximately 1,909 km

2

in Area 1 and 5,891 km

2

in Area 2 (see figure 1 in 76 FR 20179). Area 1 of the CIBW critical habitat encompasses all marine waters of Cook Inlet north of a line connecting Point Possession (lat. 61.04° N, long. 150.37° W) and the mouth of Three Mile Creek (lat. 61.08.55° N, long. 151.04.40° W), including waters of the Susitna, Little Susitna, and Chickaloon Rivers below Mean Higher High Water (MHHW). From spring through fall, Area 1 critical habitat has the highest concentration of CIBWs due to its important foraging and calving habitat. Critical Habitat Area 2, where 8 Star Alaska's proposed construction activities would occur, encompasses some of the fall and winter feeding grounds in middle Cook Inlet. This area has a lower concentration of CIBWs in spring and summer but is used by CIBWs in fall and winter. More information on CIBW critical habitat can be found at

https://www.fisheries.noaa.gov/action/critical-habitat-cook-inlet-beluga-whale.

The designation identified the following Primary Constituent Elements, essential features important to the conservation of the CIBW:

(1) Intertidal and subtidal waters of Cook Inlet with depths of less than 9 m Mean Lower Low Water (MLLW) and within 8 km of high- and medium-flow anadromous fish streams;

(2) Primary prey species, including four of the five species of Pacific salmon (chum (

Oncorhynchus keta

), sockeye (

Oncorhynchus nerka

), Chinook (

Oncorhynchus tshawytscha

), and coho (

Oncorhynchus kisutch

)), Pacific eulachon (

Thaleichthys pacificus

), Pacific cod (

Gadus macrocephalus

), walleye Pollock (

Gadus chalcogrammus

), saffron cod (

Eleginus gracilis

), and yellowfin sole (

Limanda aspera

)

;

(3) The absence of toxins or other agents of a type or amount harmful to CIBWs;

(4) Unrestricted passage within or between the critical habitat areas; and

(5) The absence of in-water noise at levels resulting in the abandonment of habitat by CIBWs.

Biologically Important Areas

Wild

et al.

(2023) delineated a small and resident population Biologically Important Area (BIA) in Cook Inlet that is active year-round and overlaps 8 Star Alaska's proposed project area. The authors assigned the BIA an importance score of 2, an intensity score of 2, a data support score of 3, and a boundary certainty score of 2 (scores range from 1 to 3, with a higher score representing an area of more concentrated or focused use and higher confidence in the data supporting the BIA (Harrison

et al.,

2023)). These scores indicate that the BIA is of moderate importance and intensity, the authors have high confidence that the population is small and resident and in the abundance and range estimates of the population, and the boundary certainty is medium (see Harrison

et al.

(2023) for additional information about the scoring process used to identify BIAs). The boundary of the CIBW BIA is consistent with NMFS' critical habitat designation (Wild

et al.,

2023).

Ecology

Generally, female beluga whales reach sexual maturity at 9 to 12 years old, while males reach maturity later (O'Corry‐Crowe, 2009); however, this can vary between populations. For example, in Greenland, males in a population of beluga whales were found to reach sexual maturity at 6 to 7 years of age and females at 4 to 7 years (Heide-Jørgensen and Teilmann, 1994). Suydam (2009) estimated that 50 percent of females were sexually mature at age 8.25 and the average age at first birth was 8.27 years for belugas sampled near Point Lay. Mating behavior in beluga whales typically occurs between February and June, peaking in March (Burns and Seaman, 1986, Suydam, 2009). In the Chukchi Sea, the gestation period of beluga whales was determined to be 14.9 months, with a calving interval of 2 to 3 years and a pregnancy rate of 0.41, declining after 25 years of age (Suydam, 2009). Calves are born between mid-June and mid-July and typically remain with the mother for up to 2 years of age (Suydam, 2009).

CIBWs feed on a wide variety of prey species, particularly those that are seasonally abundant. From late spring through summer, most CIBW stomachs sampled contained salmon, which corresponded to the timing of fish runs in the area. Anadromous smolt and adult fish aggregate at river mouths and adjacent intertidal mudflats (Calkins, 1989). All five Pacific salmon species (

i.e.,

Chinook, pink (

Oncorhynchus gorbuscha

), coho, sockeye, and chum) spawn in rivers throughout Cook Inlet (Moulton, 1997, Moore

et al.,

2000). Overall, Pacific salmon represent the highest percent frequency of occurrence of prey species in CIBW stomachs. This suggests that their spring feeding in upper Cook Inlet, principally on fat-rich fish such as salmon and eulachon, is important to the energetics of these animals (NMFS, 2016).

The nutritional quality of Chinook salmon in particular is unparalleled, with an energy content four times greater than that of a Coho salmon. It is suggested the decline of the Chinook salmon population has left a nutritional void in the diet of the CIBWs that no other prey species can fill in terms of quality or quantity (Norman

et al.,

2022, Norman

et al.,

2020).

In fall, as anadromous fish runs begin to decline, CIBWs return to consume fish species (cod and bottom fish) found in nearshore bays and estuaries. Stomach samples from CIBWs are not available for winter (December through March), although dive data from CIBWs tagged with satellite transmitters suggest that they feed in deeper waters during winter (Hobbs

et al.,

2005), possibly on such prey species as flatfish, cod, sculpin, and pollock.

Distribution in Cook Inlet

The CIBW stock remains within Cook Inlet throughout the year, showing only small seasonal shifts in distribution (Goetz

et al.,

2012a, Lammers

et al.,

2013, Castellote

et al.,

2015, Shelden

et al.,

2015a, Shelden

et al.,

2018, Lowry

et al.,

2019). The ecological range of CIBWs has contracted significantly since the 1970s. From late spring to fall, nearly the entire population is now found in the upper inlet north of the forelands, with a range reduced to approximately 39 percent of the size documented in the late 1970s (Goetz

et al.,

2023). The recent annual and semiannual aerial surveys (since 2008) found that approximately 83 percent of the population inhabits the area between the Beluga River and Little Susitna River during the survey period, typically conducted in early June. Some aerial survey counts were performed in August, September, and October, finding minor differences in the numbers of belugas in the upper inlet compared to June, reinforcing the importance of the upper inlet habitat area (Young

et al.,

2023). 8 Star Alaska's proposed construction would not occur in this upper inlet habitat area.

During spring and summer, CIBWs generally aggregate near the warmer waters of river mouths along the northern shores of middle and upper Cook Inlet where prey availability is high and predator occurrence is low (Moore

et al.,

2000, Shelden and Wade, 2019, McGuire

et al.,

2020). In particular, CIBW groups are seen in the Susitna River Delta, the Beluga River and along the shore to the Little Susitna River, Knik Arm, and along the shores of Chickaloon Bay. Small groups were recorded farther south in Kachemak Bay, Redoubt Bay (Big River), and Trading Bay (McArthur River) prior to 1996, but rarely thereafter. Since the mid-1990s, most CIBWs (96 to 100 percent) aggregate in shallow areas near river mouths in upper Cook Inlet, and they are only occasionally sighted in the central or southern portions of Cook Inlet during summer (Hobbs

et al.,

2008). Almost the entire population can be found in northern Cook Inlet from late spring through the summer and into the fall (Muto

et al.,

2020), shifting into deeper waters in middle Cook Inlet in winter (Hobbs

et al.,

2008).

Data from tagged whales (14 tags deployed July 2000 through March 2003) show that CIBWs use upper Cook Inlet intensively between summer and late autumn (Hobbs et al., 2005). CIBWs tagged with satellite transmitters continue to use Knik Arm, Turnagain Arm, and Chickaloon Bay as late as October, but some range into lower Cook Inlet to Chinitna Bay, Tuxedni Bay, and Trading Bay (McArthur River) in fall (Hobbs

et al.,

2005, Hobbs

et al.,

2012). From September through November, CIBWs move between Knik Arm, Turnagain Arm, and Chickaloon Bay (Hobbs

et al.,

2005, Goetz

et al.,

2012b). By December, CIBWs are distributed throughout the upper to mid-inlet. From January into March, they move as far south as Kalgin Island and slightly beyond in central offshore waters. CIBWs make occasional excursions into Knik Arm and Turnagain Arm in February and March in spite of ice cover (Hobbs

et al.,

2005). Although tagged CIBWs move widely around Cook Inlet throughout the year, there is no indication of seasonal migration in and out of Cook Inlet (Hobbs

et al.,

2005). Data from NMFS aerial surveys, opportunistic sighting reports, and corrected satellite-tagged CIBWs confirm that they are more widely dispersed throughout Cook Inlet during winter (November-April), with animals found between Kalgin Island and Point Possession. Generally fewer observations of CIBWs are reported from the Anchorage and Knik Arm area from November through April (76 FR 20179, April 11, 2011; Rugh

et al.,

2000, 2004). Later in winter (January into March), belugas were sighted near Kalgin Island and in deeper waters offshore. However, even when ice cover exceeds 90 percent in February and March, belugas travel into Knik Arm and Turnagain Arm (Hobbs

et al.,

2005).

The NMFS Alaska Fisheries Science Center (AFSC) has conducted long-term passive acoustic monitoring demonstrating seasonal shifts in CIBW concentrations throughout Cook Inlet. Castellote

et al.

(2015) conducted long-term acoustic monitoring at 13 locations throughout Cook Inlet between 2008 and 2015: North Eagle Bay, Eagle River Mouth, South Eagle Bay, Six Mile, Point MacKenzie, Cairn Point, Fire Island, Little Susitna, Beluga River, Trading Bay, Kenai River, Tuxedni Bay, and Homer Spit; the former 6 stations being located within Knik Arm. In general, the observed seasonal distribution is in accordance with descriptions based on aerial surveys and satellite telemetry: CIBW detections are higher in the upper inlet during summer, peaking at Little Susitna, Beluga River, and Eagle Bay, followed by fewer detections at those locations during winter. Higher detections in winter at Trading Bay,

Kenai River, and Tuxedni Bay suggest a broader CIBW distribution in the lower inlet during winter.

Goetz

et al.

(2012b) modeled habitat preferences using NMFS' 1994-2008 June abundance survey data. In large areas, such as the Susitna Delta (Beluga to Little Susitna Rivers) and Knik Arm, there was a high probability that CIBWs were in larger groups. CIBW presence and acoustic foraging behavior also increased closer to rivers with Chinook salmon runs, such as the Susitna River (

e.g.,

Castellote

et al.,

2021). Movement has been correlated with the peak discharge of seven major rivers emptying into Cook Inlet. Boat-based surveys from 2005 to the present (McGuire and Stephens, 2017) and results from passive acoustic monitoring across the entire inlet (Castellote

et al.,

2015) also support seasonal patterns observed with other methods. Based on long-term passive acoustic monitoring, foraging behavior was more prevalent during summer, particularly at upper inlet rivers, than during winter. The foraging index was highest at Little Susitna, with a peak in July-August and a secondary peak in May, followed by Beluga River and then Eagle Bay; monthly variation in the foraging index indicates CIBWs shift their foraging behavior among these three locations from April through September. The location of the towing routes are areas of predicted low density in the summer months.

CIBWs are believed to mostly calve in the summer, and breed between late spring and early summer (NMFS, 2016), primarily in upper Cook Inlet. The first neonates encountered during each field season from 2005 through 2015 were always seen in the Susitna River Delta in July. The photographic identification team's documentation of the dates of the first neonate of each year indicate that calving begins in mid-late July/early August, generally coinciding with the observed timing of annual maximum group size. Probable mating behavior of CIBWs was observed in April and May of 2014 in Trading Bay. Young CIBWs are nursed for 2 years and may continue to associate with their mothers for a considerable time thereafter (Colbeck

et al.,

2013). Important calving grounds are thought to be located near the river mouths of upper Cook Inlet.

During Apache's seismic test program in 2011 along the west coast of Redoubt Bay, lower Cook Inlet, a total of 33 CIBWs were sighted during the survey (Lomac-MacNair

et al.,

2013). During Apache's 2012 seismic program in mid-inlet, a total of 151 groups consisting of an estimated 1,463 CIBWs were observed (note individuals were likely observed more than once) (Lomac-MacNair

et al.,

2014). During SAExploration's 2015 seismic program, a total of 8 groups of 33 estimated individual CIBWs were visually observed during this time period and there were two acoustic detections of CIBWs (Kendall

et al.,

2015). During Harvest Alaska's recent CIPL project on the west side of Cook Inlet in between Ladd Landing and Tyonek Platform, a total of 143 CIBW groups (814 individuals) were observed almost daily from May 31 to July 11, even though observations spanned from May 9 through September 15 (Sitkiewicz et al., 2018). There were two CIBW carcasses observed by the project vessels in the 2019 Hilcorp lower Cook Inlet seismic survey in the fall which were reported to the NMFS Marine Mammal Stranding Network (Fairweather Science, 2020). Both carcasses were moderately decomposed when they were sighted by the PSOs. Daily aerial surveys specifically for CIBWs were flown over the lower Cook Inlet region, but no beluga whales were observed. In 2023, Hilcorp recorded 21 groups of more than 125 beluga whales during aerial surveys in middle Cook Inlet, and an additional 21 opportunistic groups which included approximately 81 CIBWs (Horsley and Larson, 2023). Hilcorp did not record any sightings of CIBWs from their rig-based monitoring efforts (Horsley and Larson, 2023).

Killer Whale

Along the west coast of North America, seasonal and year-round occurrence of killer whales has been noted along the entire Alaska coast (Braham and Dahlheim, 1982), in British Columbia and Washington inland waterways (Bigg

et al.,

1990), and along the outer coasts of Washington, Oregon, and California (Green

et al.,

1992, Barlow, 1995, Barlow, 1997, Forney

et al.,

1995). Killer whales from these areas have been labeled as “resident,” “transient,” and “offshore” type killer whales (Bigg

et al.,

1990, Ford

et al.,

2000, Dahlheim

et al.,

2008) based on aspects of morphology, ecology, genetics, and behavior (Ford and Fisher, 1982, Baird and Stacey, 1988, Baird

et al.,

1992, Hoelzel

et al.,

1998, Hoelzel

et al.,

2002, Barrett-Lennard, 2000, Dahlheim

et al.,

2008). Based on data regarding association patterns, acoustics, movements, and genetic differences, eight killer whale stocks are now recognized within the U.S. Pacific, two of which have the potential to be found in the proposed project area: the Eastern North Pacific Alaska Resident stock and the Gulf of Alaska, Aleutian Islands, and the Bering Sea Transient stock. Both stocks occur in lower Cook Inlet, but rarely in middle and upper Cook Inlet (Shelden

et al.,

2013). While these stocks overlap the same geographic area, they maintain social and reproductive isolation and feed on different prey species. Resident killer whales are primarily fish-eaters, while transients primarily hunt and consume marine mammals, such as harbor seals, Dall's porpoises, harbor porpoises, beluga whales and sea lions. Killer whales are not harvested for subsistence in Alaska. Potential threats most likely to result in direct human-caused M/SI of killer whales in this region include oil spills, vessel strikes, and interactions with fisheries.

Killer whales have been sighted near Homer and Port Graham in lower Cook Inlet (Shelden

et al.,

2022, Shelden

et al.,

2003, Rugh

et al.,

2005). Resident killer whales from pods often sighted near Kenai Fjords and Prince William Sound have been occasionally photographed in lower Cook Inlet (Shelden

et al.,

2003). The availability of salmon influences when resident killer whales are more likely to be sighted in Cook Inlet. Killer whales were observed in the Kachemak and English Bay three times during aerial surveys conducted between 1993 and 2004 (Rugh

et al.,

2005). Passive acoustic monitoring efforts throughout Cook Inlet documented killer whales at the Beluga River, Kenai River, and Homer Spit, although they were not encountered within Knik Arm (Castellote

et al.,

2016). These detections were likely resident killer whales. Transient killer whales likely have not been acoustically detected due to their propensity to move quietly through waters to track prey (Small, 2010, Lammers

et al.,

2013). Transient killer whales were increasingly reported to feed on belugas in the middle and upper Cook Inlet in the 1990s.

During the 2015 SAExploration seismic program near the North Foreland, two killer whales were observed (Kendall

et al.,

2015, as cited in Weston and SLR, 2022). Killer whales were observed in lower Cook Inlet in 1994, 1997, 2001, 2005, 2010, 2012, and 2022 during the NMFS aerial surveys (Shelden

et al.,

2013, 2022). Eleven killer whale strandings have been reported in Turnagain Arm: 6 in May 1991 and 5 in August 1993. During the Hilcorp lower Cook Inlet seismic survey in the fall of 2019, 21 killer whales were documented (Fairweather Science, 2020). Throughout 4 months of observation in 2018 during the CIPL project in middle Cook Inlet, no killer whales were observed (Sitkiewicz

et al.,

2018). In September 2021, two killer

whales were documented in Knik Arm in upper Cook Inlet, near the POA (61 North Environmental, 2022a). Hilcorp did not record any sightings of killer whales from their aerial or rig-based monitoring efforts in 2023 (Horsley and Larson, 2023).

Pacific White-Sided Dolphin

The North Pacific stock of Pacific white-sided dolphin is common in the Gulf of Alaska's pelagic waters and Alaska's nearshore areas, British Columbia, and Washington Ferrero and Walker, 1996, as cited in Muto

et al.,

2022). They do not typically occur in Cook Inlet, but in 2019, Castellote

et al.

(2020) documented short durations of Pacific white-sided dolphin presence using passive acoustic recorders near Iniskin Bay (6 minutes) and at an offshore mooring located approximately midway between Port Graham and Iniskin Bay (51 minutes). Detections of vocalizations typically lasted on the order of minutes, suggesting the animals did not remain in the area and/or continue vocalizing for extended durations. Visual monitoring conducted during the same period by marine mammal observers on seismic vessels near the offshore recorder did not detect any Pacific white-sided dolphins (Fairweather Science, 2020). These observational data, combined with anecdotal information, indicate that there is a small potential for Pacific white-sided dolphins to occur in the project area. On May 7, 2014, Apache Alaska observed three Pacific white-sided dolphins during an aerial survey near Kenai. This is one of the only recorded visual observations of Pacific white-sided dolphins in Cook Inlet; they have not been reported in groups as large as those estimated in other parts of Alaska (Muto

et al.,

2022).

Harbor Porpoise

Harbor porpoises in Cook Inlet are assumed to be members of the Gulf of Alaska stock (Young

et al.,

2023). Harbor porpoises occur most frequently in waters less than 100 m deep (Hobbs and Waite, 2010) and are common in nearshore areas of the Gulf of Alaska, Shelikof Strait, and lower Cook Inlet (Dahlheim

et al.,

2000). Harbor porpoises are often observed in lower Cook Inlet in Kachemak Bay and from Cape Douglas to the West Foreland (Rugh

et al.,

2005). They can be opportunistic foragers but consume primarily schooling forage fish (Bowen and Siniff, 1999). Subsistence users have not reported any harvest from the Gulf of Alaska harbor porpoise stock since the early 1900s (Shelden

et al.,

2014). Calving occurs from May to August; however, this can vary by region. Harbor porpoises often travel alone or in small groups of less than 10 individuals (Schmale, 2008).

Harbor porpoises occur throughout Cook Inlet, with passive acoustic detections being more prevalent in lower Cook Inlet. Although harbor porpoises have been frequently observed during aerial surveys in Cook Inlet (Shelden

et al.,

2014), most sightings are of single animals and are concentrated at Chinitna and Tuxedni bays on the west side of lower Cook Inlet (Rugh

et al.,

2005), with smaller numbers observed in upper Cook Inlet between April and October. The occurrence of larger numbers of porpoise in the lower Cook Inlet may be driven by greater availability of preferred prey and possibly less competition with CIBWs, as CIBWs move into upper inlet waters to forage on Pacific salmon during the summer months (Shelden

et al.,

2014).

An increase in harbor porpoise sightings in upper Cook Inlet was observed over recent decades (

e.g.,

61 North Environmental, 2021, 2022a, Shelden

et al.,

2014). Small numbers of harbor porpoises have been consistently reported in upper Cook Inlet between April and October (Prevel-Ramos

et al.,

2008). The reason for the increase in sightings in upper Cook Inlet is unknown, although it may be an artifact of increased monitoring effort in upper Cook Inlet. It is also possible that the contraction in the CIBW's range has opened up previously occupied CIBW range to harbor porpoises (Shelden

et al.,

2014).

During Apache's 2012 seismic program in middle Cook Inlet, 137 groups of harbor porpoises comprising 190 individuals were documented between May and August (Lomac-MacNair

et al.,

2013). In June 2012, Shelden

et al.

(2015b) documented 65 groups of 129 individual harbor porpoises during an aerial survey, none of which were in upper Cook Inlet. Kendall

et al.

(2015, as cited in Weston and SLR, 2022) documented 52 groups comprising 65 individuals north of the Forelands during SAExploration's 2015 seismic survey. Shelden

et al.

(2017, 2019, 2022) also conducted aerial surveys in June and July over Cook Inlet in 2016, 2018, 2021, and 2022 and recorded 65 individuals. Observations occurred in middle and lower Cook Inlet with a majority in Kachemak Bay. There were two sightings of three harbor porpoises observed during the 2019 Hilcorp lower Cook Inlet seismic survey in the fall (Fairweather Science, 2020). A total of 29 groups (44 individuals) were observed north of the Forelands from May to September during the CIPL Extension Project (Sitkiewicz

et al.,

2018). During jack-up rig moves in 2021, a PSO observed two individual harbor porpoises in middle Cook Inlet: one in July and one in October. Four monitoring events were conducted at the POA in Anchorage between April 2020 and August 2022, during which 42 groups of harbor porpoises comprising 50 individual porpoises were documented over 285 days of observation (61 North Environmental, 2021, 2022a, 2022b, 2022c 2022c). One harbor porpoise was observed during Hilcorp's boat-based monitoring efforts in June 2023 (Horsley and Larson, 2023).

Dall's Porpoise

Dall's porpoises in Alaska are of the Alaska stock. This species can be found in offshore, inshore, and nearshore habitat. The most recently updated SAR for the Alaska stock of Dall's porpoise (Muto

et al.,

2021) assess the abundance of Alaska Dall's porpoise only in the northwestern Gulf of Alaska, which is a small portion of the stock's geographic range. Sighting surveys for cetaceans were conducted opportunistically during NMFS' pollock stock assessment surveys in 1999, 2000, 2002, 2004, 2008, and 2010 on the eastern Bering Sea shelf (Moore

et al.,

2002, Friday

et al.,

2012, 2013). The entire study area of the survey, which corresponded to only a fraction of the range of the Alaska stock, was fully covered in three of those years (2002, 2008, and 2010). Dall's porpoise abundance estimates were 35,303 (CV = 0.53) in 2002, 14,543 (CV = 0.32) in 2008, and 11,143 (CV = 0.32) in 2010 (Friday

et al.

2013). Abundance estimates for Dall's porpoise in inland waters of Southeast Alaska were calculated from 19 line-transect vessel surveys from 1991 to 2012 (Jefferson

et al.

2019). Abundance across the whole period was estimated at 5,381 (CV = 0.25), 2,680 (CV = 0.20), and 1,637 (CV = 0.23) in the spring, summer, and fall, respectively (Jefferson

et al.

2019). Vessel surveys were carried out in and around a Navy Maritime Activity/Training Area in the northwestern Gulf of Alaska to document abundance and density of cetaceans in 2013 and 2015 (Rone et al. 2017). The surveys covered different, but partially overlapping, areas in the two years and estimated Dall's porpoise abundance as 15,432 (CV = 0.28) in 2013 and 13,110 (CV = 0.22) in 2015. The minimum population estimate (N

MIN

) for this stock is assumed to correspond to the point estimate of the 2015 vessel-based abundance computed by Rone

et al.

(2017) in the Gulf of Alaska (N = 13,110; CV = 0.22).

The Dall's porpoise range in Alaska includes lower Cook Inlet, but very few sightings have been reported in upper Cook Inlet. Observations have been documented near Kachemak Bay and Anchor Point (Owl Ridge, 2014; BOEM, 2015). Shelden

et al.

(2013). Rugh

et al.

(2005) collated data from aerial surveys conducted between 1994 and 2012 and documented 9 sightings of 25 individuals in the lower Cook Inlet during June and/or July 1997, 1999, and 2000. No Dall's porpoise were observed on subsequent surveys in June and/or July 2014, 2016, 2018, 2021, and 2022 (Shelden

et al.,

2015b, 2017, and 2022; Shelden and Wade, 2019). During Apache's 2014 seismic survey, two groups of three Dall's porpoises were observed in upper and middle Cook Inlet (Lomac-MacNair

et al.,

2014). In August 2015, one Dall's porpoise was reported in north of Nikiski in middle Cook Inlet during SAExploration's seismic program (Kendall

et al.,

2015). During aerial surveys in Cook Inlet, they were observed in Iniskin Bay, Barren Island, Elizabeth Island, and Kamishak Bay (Shelden

et al.,

2013). No Dall's porpoises were observed during the 2018 CIPL Extension Project Acoustic Monitoring Program in middle Cook Inlet (Sitkiewicz

et al.,

2018); however, 30 individuals in 10 groups were sighted during a lower Cook Inlet seismic project in the fall 2019 (Fairweather Science, 2020). Hilcorp recorded three sightings of Dall's porpoises in 2021 and one sighting of a Dall's porpoise in 2023 from their rig-based monitoring efforts in the project area (Korsmo

et al.,

2022, Horsley and Larson, 2023). One Dall's porpoise was observed near the POA during the NES1 project, but it is possible this was misidentified (61 North Environmental, 2025). This higher number of sightings suggests Dall's porpoise may use portions of middle Cook Inlet in greater numbers than previously expected but would still be considered infrequent in middle and upper Cook Inlet.

Steller Sea Lion

Two DPSs of Steller sea lion occur in Alaska: the western DPS and the eastern DPS. The western DPS includes animals that occur west of Cape Suckling, Alaska, and therefore includes individuals within the project area. The western DPS was listed under the ESA as threatened in 1990 (55 FR 49204, November 26, 1990), and its continued population decline resulted in a change in listing status to endangered in 1997 (62 FR 24345, May 5, 1997). Since 2000, studies indicate that the population east of Samalga Pass (

i.e.,

east of the Aleutian Islands) has increased and is potentially stable (Young

et al.,

2023).

There is uncertainty regarding threats currently impeding the recovery of Steller sea lions, particularly in the Aleutian Islands. Many factors have been suggested as causes of the steep decline in abundance of western Steller sea lions observed in the 1980s, including competitive effects of fishing, environmental change, disease, contaminants, killer whale predation, incidental take, and illegal and legal shooting (Atkinson

et al.,

2008, NMFS, 2008b). A number of management actions have been implemented since 1990 to promote the recovery of the Western U.S. stock of Steller sea lions, including 5.6-km (3-nautical mile) no-entry zones around rookeries, prohibition of shooting at or near sea lions, and regulation of fisheries for sea lion prey species (

e.g.,

walleye pollock, Pacific cod, and Atka mackerel (

Pleurogrammus monopterygius

)) (Tollit

et al.,

2017, Sinclair

et al.,

2013). Additionally, potentially deleterious events, such as harmful algal blooms (Lefebvre

et al.,

2016) and disease transmission across the Arctic (VanWormer

et al.,

2019) that have been associated with warming waters, could lead to potentially negative population-level impacts on Steller sea lions.

NMFS designated critical habitat for Steller sea lions on August 27, 1993 (58 FR 45269), including portions of the southern reaches of lower Cook Inlet. The critical habitat designation for the Western DPS was determined to include a 37-km (20-nautical mile) buffer around all major haul-outs and rookeries, and associated terrestrial, atmospheric, and aquatic zones, plus three large offshore foraging areas, none of which occurs in the project area. There is no designated critical habitat for Steller sea lions in the mid- or upper inlet, nor is there habitat of particular importance for Steller sea lions in the project area. Rookeries and haul out sites in lower Cook Inlet include those near the mouth of the inlet, which are approximately 56 km or more south of the closest action area.

Most Steller sea lions in Cook Inlet occur south of Anchor Point on the east side of lower Cook Inlet, with concentrations near haulout sites at Shaw Island and Elizabeth Island and by Chinitna Bay and Iniskin Bay on the west side (Rugh

et al.,

2005). Steller sea lions are rarely seen in upper Cook Inlet (Nemeth

et al.,

2007). About 3,600 sea lions use haulout sites in the lower Cook Inlet area (Sweeney

et al.,

2017), with additional individuals venturing into the area to forage.

Several surveys and monitoring programs have documented Steller sea lions throughout Cook Inlet, including in upper Cook Inlet in 2012 (Lomac-MacNair

et al.,

2013), near Cape Starichkof in 2013 (Owl Ridge, 2014), in middle and lower Cook Inlet in 2015 (Kendall

et al.,

2015, as cited in Weston and SLR, 2022), in middle Cook Inlet in 2018 (Sitkiewicz

et al.,

2018), in lower Cook Inlet in 2019 (Fairweather Science, 2020), and near the POA in Anchorage in 2020, 2021, and 2022 (61 North Environmental, 2021, 2022a, 2022b, and 2022c). During NMFS CIBW aerial surveys from 2000 to 2016, 39 sightings of 769 estimated individual Steller sea lions in lower Cook Inlet were recorded (Shelden

et al.,

2017). Sightings of large congregations of Steller sea lions during NMFS aerial surveys occurred outside the specific geographic region, on land in the mouth of Cook Inlet (

e.g.,

Elizabeth and Shaw Islands). In 2012, during Apache's 3D Seismic surveys, three sightings of approximately four individuals in upper Cook Inlet were recorded (Lomac-MacNair

et al.,

2013). PSOs associated with Buccaneer's drilling project off Cape Starichkof observed seven Steller sea lions in summer 2013 (Owl Ridge, 2014), and another four Steller sea lions were observed in 2015 in Cook Inlet during SAExploration's 3D Seismic Program. Of the three 2015 sightings, one sighting occurred between the West and East Forelands, one occurred near Nikiski, and one occurred northeast of the North Foreland in the center of Cook Inlet (Kendall and Cornick, 2015). Five sightings of five Steller sea lions were recorded during Hilcorp's lower Cook Inlet seismic survey in the fall of 2019 (Fairweather Science, 2020). Additionally, one sighting of two individuals occurred during the CIPL Extension Project in 2018 in middle Cook Inlet (Sitkiewicz

et al.,

2018). At the end of July 2022, while conducting a waterfowl survey an estimated 25 Steller sea lions were observed hauled-out at low tide in the Lewis River, on the west side of Cook Inlet. (K. Lindberg, personal communication, August 15, 2022). Steller sea lions have also been reported near the POA in Anchorage in 2020, 2021, and 2022 (61 North Environmental 2021, 2022a, 2022b, and 2022c). Hilcorp did not record any sightings of Steller sea lions from their aerial or rig-based monitoring efforts in 2023 (Horsley and Larson, 2023).

Harbor Seal

Harbor seals in the proposed project area are of the Cook Inlet/Shelikof stock, which ranges from the southwest tip of

Unimak Island east along the southern coast of the Alaska Peninsula to Elizabeth Island off the southwest tip of the Kenai Peninsula, including Cook Inlet, Knik Arm, and Turnagain Arm. Distribution of the Cook Inlet/Shelikof stock extends from Unimak Island, in the Aleutian Islands archipelago, north through all of upper and lower Cook Inlet (Young

et al.,

2023).

Harbor seals inhabit the coastal and estuarine waters of Cook Inlet and occur in both upper and lower Cook Inlet throughout most of the year (Boveng

et al.,

2012, Shelden

et al.,

2013). High-density areas include Kachemak Bay, Iniskin Bay, Iliamna Bay, Kamishak Bay, Cape Douglas, and Shelikof Strait. Up to a few hundred seals seasonally occur in middle and upper Cook Inlet (Rugh

et al.

2005), with the highest concentrations found near the Susitna River and other tributaries within upper Cook Inlet during eulachon and salmon runs (Nemeth

et al.,

2007; Boveng

et al.,

2012), but most remain south of the forelands (Boveng

et al.,

2012).

The results of past and recent satellite tagging studies in Southeast Alaska, Prince William Sound, Kodiak Island, and Cook Inlet are also consistent with the conclusion that harbor seals are non-migratory (Lowry

et al.,

2001; Small

et al.,

2003; Boveng

et al.,

2012). However, some long-distance movements of tagged animals in Alaska have been recorded (Pitcher and McAllister, 1981, Lowry

et al.,

2001, Small

et al.,

2003, Womble, 2012, Womble and Gende, 2013). Strong fidelity of individuals for haulout sites during the breeding season has been documented in several populations (Härkönen and Harding, 2001), including in Cook Inlet (Small

et al.,

2005, Pitcher and McAllister, 1981, Boveng

et al.,

2012, Womble, 2012, Womble and Gende, 2013). Harbor seals usually give birth to a single pup between May and mid-July; birthing locations are dispersed over several haulout sites and not confined to major rookeries (Klinkhart

et al.,

2008). More than 200 haulout sites are documented in lower Cook Inlet (Montgomery

et al.,

2007) and 18 in middle and upper Cook Inlet (London

et al., 2015).

Of the 18 in middle and upper Cook Inlet, nine are considered “key haulout” locations where aggregations of 50 or more harbor seals have been documented. Seven key haulouts are in the Susitna River delta, and two are near the Chickaloon River.

Recent research on satellite-tagged harbor seals observed several movement patterns within Cook Inlet (Boveng

et al.,

2012), including a strong seasonal pattern of more coastal and restricted spatial use during the spring and summer (breeding, pupping, molting) and more wide-ranging movements within and outside of Cook Inlet during the winter months, with some seals ranging as far as Shumagin Islands. During summer months, movements and distribution were mostly confined to the west side of Cook Inlet and Kachemak Bay, and seals captured in lower Cook Inlet generally exhibited site fidelity by remaining south of the Forelands in lower Cook Inlet after release (Boveng

et al.,

2012). In the fall, a portion of the harbor seals appeared to move out of Cook Inlet and into Shelikof Strait, northern Kodiak Island, and coastal habitats of the Alaska Peninsula. The western coast of Cook Inlet had higher usage by harbor seals than eastern coast habitats, and seals captured in lower Cook Inlet generally exhibited site fidelity by remaining south of the Forelands in lower Cook Inlet after release (south of Nikiski; Boveng

et al.,

2012).

Harbor seals have been sighted in Cook Inlet during every year of the aerial surveys conducted by NMFS and during recent mitigation and monitoring programs in lower, middle, and upper Cook Inlet (61N Environmental, 2021, 2022a, 2022b, and 2022c; Fairweather Science, 2020; Kendall

et al.,

2015 as cited in Weston and SLR, 2022; Lomac-MacNair

et al.,

2013, 2014; Sitkiewicz

et al.,

2018).

California Sea Lion

Few observations of California sea lions have been reported in Alaska, and most observations have been limited to solitary individuals, typically males that are known to migrate long distances. Occasionally, California sea lions occur in small groups of two or more, usually associated with Steller sea lions at their haul outs and rookeries (Maniscalco

et al.,

2004). Sightings in Cook Inlet are rare, with two documented during the Apache 2012 seismic survey (Lomac-MacNair

et al.,

2013) and anecdotal sightings in Kachemak Bay.

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Not all marine mammal species have equal hearing capabilities (Richardson

et al.,

1995, Wartzok and Ketten, 1999, Au and Hastings, 2008). To reflect this, (Southall

et al.,

2007, 2019) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges (behavioral response data, anatomical modeling,

etc.

). Generalized hearing ranges were chosen based on the ~65 decibel (dB) threshold from composite audiograms, previous analyses in NMFS (2018), and/or data from Southall

et al.

(2007) and Southall

et al.

(2019). We note that the names of two hearing groups and the generalized hearing ranges of all marine mammal hearing groups have been recently updated (NMFS, 2024) as reflected below in table 5.

Table 5—Marine Mammal Hearing Groups

[NMFS, 2024]

Hearing group

Generalized hearing range *

Low-frequency (LF) cetaceans (baleen whales)

7 Hz (Hertz) to 36 kHz.

High-frequency (HF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)

150 Hz to 160 kHz.

Very High-frequency (VHF) cetaceans (true porpoises,

Kogia,

river dolphins, Cephalorhynchid,

Lagenorhynchus cruciger

&

L. australis

)

200 Hz to 165 kHz.

Phocid pinnipeds (PW) (underwater) (true seals)

40 Hz to 90 kHz.

Otariid pinnipeds (OW) (underwater) (sea lions and fur seals)

60 Hz to 68 kHz.

* Represents the generalized hearing range for the entire group as a composite (

i.e.,

all species within the group), where individual species' hearing ranges may not be as broad. Generalized hearing range chosen based on ~65 dB threshold from composite audiogram, previous analysis in NMFS (2018), and/or data from Southall

et al.

2007; Southall

et al.

2019. Additionally, animals are able to detect very loud sounds above and below that “generalized” hearing range.

For more detail concerning these groups and associated frequency ranges, please see NMFS (2024) for a review of available information.

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

This section provides a discussion of the ways in which components of the specified activity may impact marine mammals and their habitat. The Estimated Take of Marine Mammals section later in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Negligible Impact Analysis and Determination section considers the content of this section, the Estimated Take of Marine Mammals section, and the Proposed Mitigation section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and whether those impacts are reasonably expected to, or reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.

Description of Sound Sources

The marine soundscape is comprised of both ambient and anthropogenic sounds. Ambient sound is defined as the all-encompassing sound in a given place and is usually a composite of sound from many sources both near and far. The sound level of an area is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical (

e.g.,

waves, wind, precipitation, earthquakes, ice, atmospheric sound), biological (

e.g.,

sounds produced by marine mammals, fish, and invertebrates), and anthropogenic sound (

e.g.,

vessels, dredging, aircraft, construction).

The sum of the various natural and anthropogenic sound sources at any given location and time—which comprise “ambient” or “background” sound—depends not only on the source levels (as determined by current weather conditions and levels of biological and shipping 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.

The proposed project includes impact and vibratory pile driving and use of AHTs to handle anchors during pipelaying. Impact hammers typically operate by repeatedly dropping and/or pushing a heavy piston onto a pile to drive the pile into the substrate. Sound generated by impact hammers is impulsive, characterized by rapid rise times and high peak levels, a potentially injurious combination (Hastings and Popper, 2005). Vibratory hammers install piles by vibrating them and allowing the weight of the hammer to push them into the sediment. Vibratory pile driving produces non-impulsive sound. Non-impulsive sounds typically do not have the high peak sound pressure with rapid rise/decay time that impulsive sounds do (ANSI, 1995, National Institute for Occupational Safety and Health (NIOSH), 1998, NMFS, 2024, ANSI, 2005). Vibratory hammers produce significantly less sound than impact hammers. Peak sound pressure levels (SPLs) may be 180 dB or greater, but are generally 10 to 20 dB lower than SPLs generated during impact pile driving of the same-sized piles (Oestman

et al.,

2009). Rise time is slower, reducing the probability and severity of injury, and sound energy is distributed over a greater amount of time (Nedwell and Edwards, 2002, Carlson

et al.,

2005).

Unlike discrete noise sources with known potential to harass marine mammals (

e.g.,

pile driving), both the noise sources and impacts from the AHTs handling anchors are less well documented. Our assessments of the potential for harassment of marine mammals incidental to 8 Star Alaska's AHTs engaged in anchor handling activities specified here are presented to account for what NMFS concludes is a likely potential for take in context of the generally conservative Level B harassment exposure threshold for continuous noise, and the impact that non-quantitative contextual factors have on the likelihood of Level B harassment occurring (

e.g.,

NMFS considers conservatively the potential for effects of relatively loud continuous noise sources on sensitive species in important habitat, as is the case here for CIBWs), and the nature and duration of the particular tug activities analyzed here.

The likely or possible impacts of 8 Star Alaska's proposed activity on marine mammals could involve both non-acoustic and acoustic stressors. Potential non-acoustic stressors could result from the physical presence of the equipment and personnel; however, any impacts to marine mammals are expected to primarily be acoustic in nature. Acoustic stressors would include effects of heavy equipment operation during pile installation and AHTs engaged in anchor handling during pipelaying.

Acoustic Impacts

The introduction of anthropogenic noise into the aquatic environment from pile driving and AHTs is the primary means by which marine mammals may be harassed from 8 Star Alaska's specified activity. Animals exposed to natural or anthropogenic sound may experience physical and psychological effects, ranging in magnitude from none to severe (Southall

et al.,

2007, Southall

et al.,

2019). Exposure to pile driving and noise from AHTs has the potential to result in auditory threshold shifts (TS) and behavioral disturbance (

e.g.,

avoidance, temporary cessation of foraging and vocalizing, changes in dive behavior). Exposure to anthropogenic noise can also lead to non-observable physiological responses such as an increase in stress hormones. Additional noise in a marine mammal's habitat can mask acoustic cues used by marine mammals to carry out daily functions such as communication and predator and prey detection. The effects of pile driving and AHT noise on marine mammals are influenced by several factors, including, but not limited to, sound type (

e.g.,

impulsive vs. non-impulsive), the species, age and sex class (

e.g.,

adult male vs. mom with calf), duration of exposure, the distance between the pile and the animal, received levels, behavior at time of exposure, and previous history with exposure (Wartzok

et al.,

2004, Southall

et al.,

2007). Here we discuss physical auditory effects (TS) followed by behavioral effects and potential impacts on habitat.

NMFS defines a noise-induced TS 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 (NMFS, 2018). The amount of TS is customarily expressed in dB. TS can be permanent or temporary. As described by NMFS (2024), there are numerous factors to consider when examining the consequence of TS, including, but not limited to, the signal temporal pattern (

e.g.,

impulsive or non-impulsive), likelihood an individual would be exposed for a long enough duration or

to a high enough level to induce a TS, the magnitude of the TS, time to recovery (seconds to minutes or hours to days), the frequency range of the exposure (

i.e.,

spectral content), the hearing and vocalization frequency range of the exposed species relative to the signal's frequency spectrum (

i.e.,

how an animal uses sound within the frequency band of the signal (

e.g.,

Kastelein

et al.,

2014), and the overlap between the animal and the source (

e.g.,

spatial, temporal, and spectral).

Auditory Injury (AUD INJ) and Permanent Threshold Shift (PTS)

NMFS defines auditory injury as “damage to the inner ear that can result in destruction of tissue . . . which may or may not result in PTS” (NMFS, 2024). NMFS defines PTS as a permanent irreversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2024). PTS does not generally affect more than a limited frequency range, and an animal that has incurred PTS has incurred some level of hearing loss at the relevant frequencies; typically, animals with PTS are not functionally deaf (Au and Hastings, 2008, Finneran, 2016). Available data from humans and other terrestrial mammals indicate that a 40 dB threshold shift approximates PTS onset (see Ahroon

et al.,

1996, Kryter

et a

l., 1966, Miller, 1974, Ward

et al.,

1958, 1959, Ward, 1960, Henderson

et al.,

2008). PTS levels for marine mammals are estimates because there are limited empirical data measuring PTS in marine mammals (

e.g.,

Kastak

et al.,

2008), largely due to the fact that, for various ethical reasons, experiments involving anthropogenic noise exposure at levels inducing PTS are not typically pursued or authorized.

Temporary Threshold Shift (TTS)

NMFS defines TTS as a temporary, reversible increase in the threshold of audibility at a specified frequency or portion of an individual's hearing range above a previously established reference level (NMFS, 2018). Based on data from cetacean TTS measurements (see Southall

et al.,

2007, 2019), a TTS of 6 dB is considered the minimum TS clearly larger than any day-to-day or session-to-session variation in a subject's normal hearing ability (Finneran

et al.,

2000, 2022, Schlundt et al., 2000). As described in Finneran (2015), marine mammal studies have shown the amount of TTS increases with cumulative sound exposure level (SELcum) in an accelerating fashion: At low exposures with lower SELcum, the amount of TTS is typically small and the growth curves have shallow slopes. At exposures with higher SELcum, the growth curves become steeper and approach linear relationships with the noise SEL.

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 (similar to those discussed in auditory masking, below). 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 takes place during a time when the animal is traveling through the open ocean, where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical for successful mother/calf interactions could have more serious impacts. We note that reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall

et al.,

2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without cost.

Many studies have examined noise-induced hearing loss in marine mammals (see Finneran (2015) and Southall

et al.,

(2019) for summaries). TTS is the mildest form of hearing impairment that can occur during exposure to sound (Kryter, 2013). 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. For cetaceans, published data on the onset of TTS are limited to captive bottlenose dolphin (

Tursiops truncatus

), beluga whale, harbor porpoise, and Yangtze finless porpoise (

Neophocoena asiaeorientalis

) (Southall

et al.,

2019). For pinnipeds in water, measurements of TTS are limited to harbor seals, elephant seals (

Mirounga angustirostris

), bearded seals (

Erignathus barbatus

) and California sea lions (Kastak

et al.,

1999, Southall et al., 2007, Kastelein

et al.,

2019b, 2019c, 2021, 2022a, 2022b, Reichmuth

et al.,

2019, Sills

et al.,

2020). TTS was not observed in spotted (

Phoca largha

) and ringed (

Pusa hispida

) seals exposed to single airgun impulse sounds at levels matching previous predictions of TTS onset (Reichmuth

et al.,

2016). These studies examine hearing thresholds measured in marine mammals before and after exposure to intense or long-duration sound exposures. The difference between the pre-exposure and post-exposure thresholds can be used to determine the amount of threshold shift at various post-exposure times.

The amount and onset of TTS depends on the exposure frequency. Sounds at low frequencies, well below the region of best sensitivity for a species or hearing group, are less hazardous than those at higher frequencies, near the region of best sensitivity (Finneran and Schlundt, 2013). At low frequencies, onset-TTS exposure levels are higher compared to those in the region of best sensitivity (

i.e.,

a low frequency noise would need to be louder to cause TTS onset when TTS exposure level is higher), as shown for harbor porpoises and harbor seals (Kastelein

et al.,

2020a, Kastelein

et al.,

2020b, Kastelein

et al.,

2019a, Kastelein

et al.,

2019c). Note that in general, harbor seals and harbor porpoises have a lower TTS onset than other measured pinniped or cetacean species (Finneran, 2015). In addition, TTS can accumulate across multiple exposures, but the resulting TTS will be less than the TTS from a single, continuous exposure with the same SEL (Finneran

et al.,

2010, Kastelein

et al.,

2015, Kastelein

et al.,

2014, Mooney

et al.,

2009). This means that TTS predictions based on the total, SELcum will overestimate the amount of TTS from intermittent exposures such as sonars and impulsive sources.

Nachtigall

et al.

(2018) describe measurements of hearing sensitivity of multiple odontocete species (bottlenose dolphin, harbor porpoise, beluga, and false killer whale (

Pseudorca crassidens

)) when a relatively loud sound was preceded by a warning sound. These captive animals were shown to reduce hearing sensitivity when warned of an impending intense sound. Based on these experimental observations of captive animals, the authors suggest that wild animals may dampen their hearing during prolonged exposures or if conditioned to anticipate intense sounds. Another study showed that echolocating animals (including odontocetes) might have anatomical specializations that might allow for conditioned hearing reduction and filtering of low-frequency ambient noise, including increased stiffness and control of middle ear structures and placement of inner ear structures (Ketten

et al.,

2021). Data available on noise-induced hearing loss for mysticetes are currently lacking (NMFS, 2018). Additionally, the existing marine

mammal TTS data come from a limited number of individuals within these species.

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. PTS typically occurs at exposure levels at least several dB above that inducing mild TTS (

e.g.,

a 40-dB threshold shift approximates PTS onset (Kryter

et al.,

1966, Miller, 1974), while a 6-dB threshold shift approximates TTS onset (Southall

et al.,

2007, Southall

et al.,

2019)). Based on data from terrestrial mammals, a precautionary assumption is that the PTS thresholds for impulsive sounds (such as impact pile driving pulses as received close to the source) are at least 6 dB higher than the TTS threshold on a peak-pressure basis, and PTS cumulative sound exposure level thresholds are 15 to 20 dB higher than TTS cumulative sound exposure level thresholds (Southall

et al.,

2007, 2019). Given the higher level of sound or longer exposure duration necessary to cause PTS as compared with TTS, it is considerably less likely that PTS could occur.

8 Star Alaska proposes to conduct vibratory and impact pile driving activities and use AHTs to manage anchors during pipelaying. There would likely be pauses in activities during the day. Given these pauses and the fact that many marine mammals are likely to be moving through the ensonified area and not remaining for extended periods of time, the potential for TS declines.

Behavioral Harassment

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.,

Moberg, 2000, Selye, 1950). 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 circumstances, 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 sufficient to restore normal function.

Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well-studied through controlled experiments for both laboratory and free-ranging animals (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 (Romano

et al.,

2002b, Fair and Becker, 2000) and, more rarely, studied in wild populations (

e.g.,

Romano

et al.,

2002a). For example, Rolland

et al.

(2012) found that noise reduction from reduced vessel traffic in the Bay of Fundy was associated with decreased stress in North Atlantic right whales. In addition, Lemos

et al.

(2022) observed a correlation between higher levels of fecal glucocorticoid metabolite concentrations (indicative of a stress response) and vessel traffic in gray 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 (National Research Council, 2005); however, distress would be an unlikely result of these proposed project activities based on observations of marine mammals during previous, similar projects in the area.

In consideration of the range of potential effects (AUD INJ to behavioral disturbance), we consider the potential exposure scenarios and context in which species would be exposed to pile driving and AHT noise. CIBWs may be present in low numbers during the work; therefore, some individuals may be reasonably expected to be exposed to elevated sound levels, including briefly those that exceed the Level B harassment threshold for continuous or impulsive noise. However, CIBWs would be expected to be transiting through the area, given this work is proposed primarily in middle Cook Inlet (as described in the Description of Marine Mammals in the Area of Specified Activities section), thereby limiting exposure duration, as belugas in the area would be expected to be headed to or from the concentrated foraging areas farther north near the Susitna Delta and Knik and Turnigan Arms. Similarly, humpback whales, fin whales, minke whales, gray whales, killer whales, California sea lion, and Steller sea lions would not be expected to remain in the area of the AHTs. Dall's porpoise, harbor porpoise, and harbor seal have been sighted with more regularity than many other species during oil and gas activities in Cook Inlet, but due to the transitory nature of these species, they would be unlikely to remain at any particular site for the full duration of the noise-producing activity. In fact, during Hilcorp's jack-up rig-based monitoring efforts in 2023, only one Dall's porpoise, two harbor seals, and one harbor porpoise were observed across four different sightings, and observations only lasted 1 to 5 minutes (Horsley and Larson, 2023). Because of this and the relatively low-intensity source levels, the likelihood of AUD INJ over the course of the AHT activities is considered discountable. Harbor seals may linger or haul-out in the area, but they are not known to do so in any large number or for extended periods of time. Here we find there would be a small potential for TTS during the use of AHTs for anchor handling but again, AUD INJ would not be likely due to the nature of the activity. Potential for AUD INJ and TTS due to pile driving is discussed further in the Estimated Take of Marine Mammals section.

Given most marine mammals would likely be transiting through the area, exposure would be expected to be brief but, in combination with the actual presence of the AHTs and pile driving, could result in animals shifting pathways around the work site (

e.g.,

avoidance), increasing speed or dive times, or cessation of vocalizations. The

likelihood of no more than a short-term, localized disturbance response is supported by data indicating belugas regularly pass by industrialized areas such as the Port of Anchorage; therefore, we would not expect abandonment of their transiting route or other disruptions of their behavioral patterns. We also anticipate some animals may respond with such mild reactions to the project that the response would not be detectable.

While in some cases marine mammals have exhibited little to no obviously detectable response to certain common or routine industrialized activity (Cornick and Pinney, 2011), we conservatively assume here that exposure to received levels of sound above the Level B harassment threshold during AHT anchor-handling operations, in conjunction with the nature of AHT operations (

e.g.,

difficult to maneuver, potential need to operate at night) means it is possible that take could occur over the total estimated period of activities.

Masking

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, navigation) (Richardson

et al.,

1995). 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.,

pile driving, 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 of natural sounds can result when human activities produce high levels of background sound at frequencies important to marine mammals. Conversely, if the background level of underwater sound is high (

e.g.,

on a day with strong wind and high waves), an anthropogenic sound source would not be detectable as far away as would be possible under quieter conditions and would itself be masked.

Airborne Acoustic Effects

Pinnipeds that occur near the project site could be exposed to airborne sounds associated with pile driving, depending on their distance from pile driving activities. Cetaceans are not expected to be exposed to airborne sounds that would result in harassment as defined under the MMPA.

There are no known pinniped haulouts near the noise producing project components. Therefore, it is unlikely that pinnipeds would be taken by exposure to in-air noise during construction. We recognize that pinnipeds in the water could be exposed to airborne sound that may result in behavioral harassment when looking with their heads above water. Most likely, airborne sound would cause behavioral responses similar to those discussed above in relation to underwater sound. For instance, anthropogenic sound could cause hauled-out pinnipeds to exhibit changes in their normal behavior, such as reduction in vocalizations, or cause them to temporarily abandon the area and move further from the source. However, these animals would likely previously have been “taken” because of exposure to underwater sound above the behavioral harassment thresholds, which are generally larger than those associated with airborne sound. Thus, the behavioral harassment of these animals is already accounted for in these estimates of potential take. Therefore, we are not proposing to authorize incidental take solely from exposure to airborne sound for pinnipeds, and airborne sound is not discussed further.

Marine Mammal Habitat Effects

8 Star Alaska's proposed activities could have localized, temporary impacts on marine mammal habitat, including prey, by increasing in-water sound pressure levels and, for pile driving, slightly decreasing water quality. Increased noise levels may affect acoustic habitat and adversely affect marine mammal prey in the vicinity of the project area. Elevated levels of underwater noise would ensonify the project areas where both fishes and mammals occur and could affect foraging success.

The total seafloor area likely impacted by the pile driving associated with the project would be relatively small compared to the available habitat in Cook Inlet. Avoidance by potential prey (

i.e.,

fish) of the immediate area due to the temporary loss of this foraging habitat would be possible. The duration of fish and marine mammal avoidance of this area after pile driving stops is unknown, but a rapid return to normal recruitment, distribution, and behavior is anticipated. Any behavioral avoidance by fish or marine mammals of the disturbed area would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity.

Potential Effects on Prey

Sound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species (

e.g.,

crustaceans, cephalopods, fishes, zooplankton). Marine mammal prey varies by species, season, and location and, for some, is not well documented. Studies regarding the effects of noise on known marine mammal prey are described here. Key impacts to fishes may include behavioral responses, hearing damage, barotrauma (pressure-related injuries), and mortality.

Fishes utilize the soundscape and components of sound in their environment to perform important functions such as foraging, predator avoidance, mating, and spawning (Fay, 2009, Zelick

et al.,

1999). 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). The potential effects of noise on fishes depends on the overlapping frequency range, distance from the sound source, water depth of exposure, and species-specific hearing sensitivity, anatomy, and physiology. Reactions also depend on the physiological state of the fish, past exposures, motivation (

e.g.,

feeding, spawning, migration), and other environmental factors.

Fish react to sounds that are especially strong and/or intermittent low-frequency sounds, and behavioral responses such as flight or avoidance are the most likely effects. Short duration, sharp sounds can cause overt or subtle changes in fish behavior and local distribution. The reaction of fish to noise depends on the physiological state of the fish, past exposures, motivation (

e.g.,

feeding, spawning, migration), and other environmental factors. Hastings and Popper (2005) identified several studies that suggest fish may relocate to avoid certain areas of sound energy. Additional studies have documented effects of pile driving on fish; several are based on studies in support of large, multiyear bridge construction projects (

e.g.,

Scholik and Yan, 2002, Scholik and Yan, 2001, Popper and Hastings,

2009). Several studies have demonstrated that impulse sounds might affect the distribution and behavior of some fishes, potentially impacting foraging opportunities or increasing energetic costs (

e.g.,

Fewtrell and McCauley, 2012, Pearson

et al.,

1992, Skalski

et al.,

1992). However, some studies have shown no or slight reaction to impulse sounds (

e.g.,

Peña

et al.,

2013, Wardle

et al.,

2001, Jorgenson and Gyselman, 2009).

SPLs of sufficient strength have been known to cause injury to fishes and fish mortality (Popper

et al.,

2014). 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.

(2012) showed that a TTS of 4 to 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 (Casper

et al.,

2013, Halvorsen

et al.,

2012).

For pile driving, the most likely impact to fishes at the project site would be temporary avoidance of the area, although alarmed responses, including an increase in swimming speed and changes in ventilation and heart rate, could occur. The duration of fish avoidance of this area or an alarm response after pile driving stops is unknown, but a rapid return to normal recruitment, distribution, and behavior is anticipated. In relation to AHT activities, fish have been observed to react when engine and propeller sounds exceed a certain level (Ona and Godø, 1990, Ona, 1988, Olsen, 1983). Avoidance reactions have been observed in fish, including cod and herring, when vessel sound levels were 110 to 130 dB re 1 μPa root-mean-squared (RMS) (Ona and Godø, 1990, Nakken, 1992, Olsen, 1979, Ona and Toresen, 1988). Vessel sound source levels in the audible range for fish are typically 150 to 170 dB re 1 μPa per Hz (Richardson et al., 1995). The AHTs used during the specified activity could be expected to produce levels in this range when in transit. However, much of the tugging would be mobile during anchor handling, and the tugging noise that occurs during anchor handling would be temporary, similar to pile driving. Therefore, based upon the reports in the literature and the predicted sound levels from these vessels, some temporary avoidance by fish in the immediate area may occur.

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, Solé

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 (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 Pascal (Pa)

2

and 400 Hz, 139 to 141 dB re 1m Pa

2

). 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 Pa

2

·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 (André

et al.,

2011, Solé

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 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.,

Bolle

et al.,

2012, Booman

et al.,

1996, Kostyuchenko, 1973, Pearson

et al.,

1994, Saetre and Ona, 1996).

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). 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 feet (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.

In summary, given the relatively small areas potentially affected, the short duration of sound associated with individual pile driving events, and the temporary nature of the use of AHTs for anchor handling activities, any adverse effects from 8 Star Alaska's activities on any prey habitat or prey populations would be expected to be minor and temporary. The most likely impact to fishes at the project site would be temporary 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. Thus, we conclude that the specified activities would not be likely to have more than short-term adverse effects on any prey habitat or

populations of prey species. Further, any impacts to marine mammal habitat would not be expected to result in significant or long-term consequences for individual marine mammals, or to contribute to adverse impacts on their populations.

Estimated Take of Marine Mammals

This section provides an estimate of the number of incidental takes proposed for authorization under the rule, which will inform NMFS' consideration of “small numbers,” the negligible impact determinations, and impacts on subsistence uses.

Harassment is the only type of take expected to result from these activities. Except with respect to certain activities not pertinent here, section 3(18) of the MMPA defines “harassment” as any act of pursuit, torment, or annoyance, which (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment).

Proposed takes would primarily be by Level B harassment, as exposure to sound resulting from use of the acoustic sources (

i.e.,

pile driving and AHT activities) has the potential to result in disruption of behavioral patterns for individual marine mammals. We note here that given the slow, predictable, and generally straight path of tugs towing and positioning, the likelihood of a resulting disruption of marine mammal behavioral patterns that would qualify as harassment is considered relatively low. However, in consideration of the relatively louder sound produced by these tugs and the sensitive context present in Cook Inlet, NMFS cannot consider the likelihood of take to be discountable and here consider it to be sufficiently likely that quantified exposures above the generalized harassment threshold equate to take. Therefore, we have quantified the potential exposures from this activity, assumed that these exposures would equate to take, and analyzed the impacts of the assumed takes, which we propose for authorization. There is also some potential for AUD INJ (Level A harassment) to result due to impact pile driving, primarily for mysticetes, very high frequency species, and phocids because predicted AUD INJ zones are larger than for high-frequency species and otariids. AUD INJ is unlikely to occur for high-frequency species. The proposed mitigation and monitoring measures would be expected to minimize the severity of the taking to the extent practicable.

As described previously, no serious injury or mortality is anticipated or proposed to be authorized for this activity. Below we describe how the proposed take numbers are estimated.

For acoustic impacts, generally speaking, we estimate take by considering: (1) acoustic criteria above which NMFS believes the best available science indicates marine mammals will likely be behaviorally harassed or incur some degree of AUD INJ; (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 monitoring results or average group size). Below, we describe the factors considered here in more detail and present the proposed take estimates.

Acoustic Criteria

NMFS recommends the use of acoustic criteria that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur AUD INJ of some degree (equated to Level A harassment). We note that the criteria for AUD INJ, as well as the names of two hearing groups, have been recently updated (NMFS, 2024) as reflected below in the Level A harassment section.

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), the environment (

e.g.,

bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict (

e.g.,

Southall

et al.,

2007, Southall

et al.,

2021, Ellison

et al.,

2012). Based on what the available science indicates 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 root-mean-squared pressure received levels (RMS SPL) of 120 dB (referenced to 1 micropascal (re 1 μPa)) for continuous (

e.g.,

vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 μPa for non-explosive impulsive (

e.g.,

seismic airguns) or intermittent (

e.g.,

scientific sonar) sources. 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.

8 Star Alaska's proposed activity includes the use of continuous (vibratory pile driving and AHTs engaged in anchor handling) and impulsive (impact pile driving) sources, and therefore the RMS SPL thresholds of 120 and 160 dB re 1 μPa are applicable.

Level A harassment

—NMFS' Updated Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 3.0) (Updated Technical Guidance, 2024) identifies dual criteria to assess AUD INJ (Level A harassment) to five different underwater marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). 8 Star Alaska's proposed activity includes the use of impulsive (impact pile driving) and non-impulsive (vibratory pile driving and use of AHTs) sources.

The 2024 Updated Technical Guidance criteria include both updated thresholds and updated weighting functions for each hearing group. The thresholds are provided in table 6 below. The references, analysis, and methodology used in the development of the criteria are described in NMFS' 2024 Updated Technical Guidance, which may be accessed at:

https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance-other-acoustic-tools.

Table 6—Thresholds Identifying the Onset of Auditory Injury

Hearing group

AUD INJ onset acoustic thresholds *

(received level)

Impulsive

Non-impulsive

Low-Frequency (LF) Cetaceans

Cell 1: L

pk,flat

:

222 dB;

L

E,LF,24h

:

183 dB

Cell 2: L

E,LF,24h

:

197 dB.

High-Frequency (HF) Cetaceans

Cell 3: L

pk,flat

:

230 dB;

L

E,HF,24h

:

193 dB

Cell 4: L

E,HF,24h

:

201 dB.

Very High-Frequency (VHF) Cetaceans

Cell 5: L

pk,flat

:

202 dB;

L

E,VHF,24h

:

159 dB

Cell 6: L

E,VHF,24h:

:

181 dB.

Phocid Pinnipeds (PW) (Underwater)

Cell 7: L

pk,flat

:

223 dB;

L

E,PW,24h

:

183 dB

Cell 8: L

E,PW,24h

:

195 dB.

Otariid Pinnipeds (OW) (Underwater)

Cell 9: L

pk,flat

:

230 dB;

L

E,OW,24h:

:

185 dB

Cell 10: L

E,OW,24h

:

199 dB.

* Dual metric criteria for impulsive sounds: Use whichever criteria results in the larger isopleth for calculating AUD INJ onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level criteria associated with impulsive sounds, the PK SPL criteria are recommended for consideration for non-impulsive sources.

Note:

Peak sound pressure level (

L

p,0-pk

) has a reference value of 1 μPa, and weighted cumulative sound exposure level (

L

E,p

) has a reference value of 1 μPa

2

s. In this Table, criteria are abbreviated to be more reflective of International Organization for Standardization standards (ISO, 2017, ISO, 2020). The subscript “flat” is being included to indicate peak sound pressure are flat weighted or unweighted within the generalized hearing range of marine mammals underwater (

i.e.,

7 Hz to 165 kHz). The subscript associated with cumulative sound exposure level criteria indicates the designated marine mammal auditory weighting function (LF, HF, and VHF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The weighted cumulative sound exposure level criteria could be exceeded in a multitude of ways (

i.e.,

varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these criteria will be exceeded.

Ensonified Area

Here, we describe operational and environmental parameters of the activity that are used in estimating the area ensonified above the acoustic thresholds, including source levels and transmission loss coefficient.

The sound field in the project area is the existing background noise plus additional noise from pile driving and AHTs engaging in anchor handling from the proposed project.

Pile Driving

8 Star Alaska proposes to conduct vibratory pile installation and removal and impact pile installation. Source levels for these activities are based on reviews of measurements of the same or similar types and dimension of piles available in the literature. Source levels for each pile size and activity are presented in table 7. Source levels for vibratory installation and removal of piles of the same diameter are assumed to be the same.

8 Star Alaska proposes to conduct concurrent pile driving during construction of the combi-wall and coffer cells in the Marine Terminal MOF. When two noise sources have overlapping sound fields, the sources are considered additive and combined using the rules of dB addition. For addition of two concurrent sources, the difference between the two sound source levels is calculated, and if that difference is between 0 and 1 dB, 3 dB are added to the higher sound source levels; if the difference is between 2 and 3 dB, 2 dB are added to the highest sound source levels; if the difference is between 4 and 9 dB, 1 db is added to the highest sound source levels; and with differences of 10 or more dB, there is no addition. For two concurrent sources of different type (

i.e.,

impact and vibratory driving), there is no sound source addition. Combinations of concurrent pile driving and the predicted source values are shown in table 8. All concurrent pile driving would consist of two vibratory hammers.

Table 7—Sound Source Levels for Single Hammer Pile Driving

Pile type

Source level (at 10 m)

Peak

(dB re 1 μPa)

SEL

(dB re 1 μPa2 sec)

RMS

(dB re 1 μPa)

Proxy

Source

Impact

Sheet Pile

205

180

190

24-inch (61-cm) AZ Sheet Pile

Caltrans (2015).

24-inch Steel Pipe Pile

203

177

190

24-inch (61-cm) Steel Pipe Pile

Caltrans (2015).

48-inch Steel Pipe Pile

213

179

192

48-inch (121.9-cm) Steel Pipe Pile

Caltrans (2020).

60-inch Steel Pipe Pile

210

185

195

60-inch (152.4 cm) Steel Pipe Pile

Caltrans (2020).

Vibratory

Sheet Pile

N/A

N/A

160

24-inch (61-cm) AZ Sheet Pile

Caltrans (2015).

24-inch Steel Pipe Pile)

N/A

N/A

163

20- to 24-inch (50.8- to 61-cm) Steel Pipe Pile

U.S. Navy (2012, 2013), (Miner, 2020).

66-inch Steel Pipe Pile

N/A

N/A

170

49- to 72-inch (124.5-182.9-cm) to Steel Pipe Piles (average)

Caltrans (2020), Illingworth & Rodkin (2021).

Table 8—Concurrent Pile Driving Scenarios and Predicted Source Levels

[All vibratory hammers]

Concurrent pile driving scenarios

Predicted RMS

(dB re 1 μPa) at 10 m

66-inch Steel Pipe Pile × 2

173

66-inch Steel Pipe Pile with Sheet Pile

170

Sheet Pile × 2

163

24-inch Steel Pipe Pile with Sheet Pile

165

24-inch Steel Pipe Pile × 2

166

Transmission loss (TL) is the decrease in acoustic intensity as an acoustic pressure wave propagates out from a source. TL parameters vary with frequency, temperature, sea conditions, current, source and receiver depth, water depth, water chemistry, and bottom composition topography. The general formula for underwater TL is:

TL = B * Log10 (R

1

/R

2

),

Where:

TL = transmission loss in dB;

B = transmission loss coefficient;

R

1

= the distance of the modeled SPL from the driven pile; and

R

2

= the distance from the driven pile of the initial measurement.

Absent site-specific acoustical monitoring with differing measured transmission loss, a practical spreading value of 15 is used as the transmission loss coefficient in the above formula. Project and site-specific transmission loss data for 8 Star Alaska's project area in Cook Inlet are not available; therefore, the default coefficient of 15 is used to determine the distances to the Level A and Level B harassment thresholds for all pile driving. All Level B harassment isopleths are reported in table 10. However, as discussed in the Proposed Monitoring and Reporting section, 8 Star Alaska would conduct SSV for pile driving. Following the analysis of SSV results, 8 Star Alaska may propose revised estimated Level A and Level B harassment zones (for the purpose of monitoring and reporting) and adjusted shutdown zones accordingly for NMFS review and approval.

The ensonified area associated with Level A harassment is more technically challenging to predict due to the need to account for a duration component. Therefore, NMFS developed an optional User Spreadsheet tool to accompany the 2024 Updated Technical Guidance that can be used to relatively simply predict an isopleth distance for use in conjunction with marine mammal density or occurrence to help predict potential takes. We note that because of some of the assumptions included in the methods underlying this optional tool, we anticipate that the resulting isopleth estimates are typically going to be overestimates of some degree, which may result in an overestimate of potential take by Level A harassment. However, this optional tool offers the best way to estimate isopleth distances when more sophisticated modeling methods are not available or practical. For stationary sources such as impact and vibratory pile driving and AHTs engaged in anchor handling, the optional User Spreadsheet tool predicts the distance at which, if a marine mammal remained at that distance for the duration of the activity, it would be expected to incur AUD INJ. Inputs used in the optional User Spreadsheet tool are provided in table 9, and the resulting estimated isopleths are reported in table 10.

Table 9—User Spreadsheet Input Parameters Used for Calculating Level A Harassment Isopleths

[Source levels provided in Table 7]

Pile

Piles

per day

Strikes

per pile

Duration to

drive pile

(min)

Weighting

factor

adjustment

Impact

Sheet Pile

30

1,000

N/A

2

24-inch Steel Pipe Pile

4

1,000

N/A

2

48-inch Steel Pipe Pile

3

1,000

N/A

2

60-inch Steel Pipe Pile

4

1,000

N/A

2

Vibratory

Sheet Pile

30

N/A

15

2.5

24-inch Steel Pipe Pile

8

N/A

15

2.5

66-inch Steel Pipe Pile

7

N/A

15

2.5

Concurrent Pile Driving With Two Vibratory Hammers

66-inch Steel Pipe Pile × 2

1

N/A

* 105

2.5

66-inch Steel Pipe Pile with Sheet Pile

1

N/A

* 450

2.5

Sheet pile × 2

1

N/A

* 450

2.5

24-inch Steel Pipe Pile with Sheet Pile

1

N/A

* 450

2.5

24-inch Steel Pipe Pile × 2

1

N/A

* 120

2.5

* This value represents the maximum duration of concurrent activity.

Table 10—Calculated Distances to Level A and Level B Harassment Isopleths for Pile Driving

Pile

Level A harassment zone

(m)

LF

cetacean

HF

cetacean

VHF

cetacean

Phocids

Otariids

Level B

harassment zone

(m)

Impact

Sheet Pile

6,061

773

9,380

5,385

2,007

1,000

24-inch Steel Pipe Pile

998

127

1,545

887

331

1,000

48-inch Steel Pipe Pile

1,120

143

1,733

995

371

1,359

60-inch Steel Pipe Pile

3,408

435

5,274

3,028

1,120

2,154

Vibratory

Sheet Pile

30

12

25

39

13

4,642

24-inch Steel Pipe Pile

20

8

16

26

9

7,356

66-inch Steel Pipe Pile

53

21

44

69

23

21,544

Concurrent Pile Driving With Two Vibratory Hammers

66-inch Steel Pipe Pile × 2

85

33

69

109

37

34,146

66-inch Steel Pipe Pile With Sheet Pile

141

54

115

181

61

21,544

Sheet Pile × 2

48

19

39

62

21

7,356

24-inch Steel Pipe Pile With Sheet Pile

32

12

26

41

14

11,659

24-inch Steel Pipe Pile × 2

65

25

53

84

28

10,000

Except for Level B harassment areas of ensonification for the single hammer vibratory installation of 66-inch steel pipe pile, the concurrent vibratory installation of two 66-inch piles, and the concurrent vibratory installation of a 66-inch steel pipe pile with a sheet pile, estimated areas of ensonification were calculated for pile driving using the formula of

1/2

πr

2

, where r is the respective isopleth. For the single hammer vibratory installation of 66-inch steel pipe pile, the concurrent vibratory installation of two 66-inch piles, and the concurrent vibratory installation of a 66-inch steel pipe pile with a sheet pile, the Level B harassment isopleths were truncated by land, and therefore

1/2

πr

2

was not representative of the area of ensonification. Therefore, mapping software was used to draw the estimated area of ensonification. Estimated Level A and Level B harassment areas of ensonification are in table 11.

NMFS used the following formula to estimate the area of ensonification for AHTs engaged in anchor handling, where distance traveled per day is the linear distance that the AHTs would be expected to travel over the course of a day, and r is the radial distance of the Level B harassment isopleth (3.85 km). 8 Star Alaska estimates the pipelay rate to be 2,500 feet/day (0.762 km/day), so 0.762 km was used as the distance traveled per day.

Area of ensonification = (Distance traveled per day × 2r) + πr

2

Table 11—Calculated Level A and B Harassment Areas of Ensonification

Pile

Level A harassment areas of ensonification

(km

2

)

LF

cetacean

HF

cetacean

VHF

cetacean

Phocids

Otariids

Level B

harassment

area of

ensonification

(km

2

)

Impact

Sheet Pile

57.7

0.94

138.21

45.47

6.33

1.57

24-inch Steel Pipe Pile

1.56

0.03

3.75

1.24

0.17

1.57

48-inch Steel Pipe Pile

1.97

0.03

4.72

1.56

0.22

2.9

60-inch Steel Pipe Pile

18.24

0.3

43.69

14.4

2.0

7.29

Vibratory

Sheet Pile

0.00

0.00

0.00

0.00

0.00

33.85

24-inch Steel Pipe Pile

0.00

0.00

0.00

0.00

0.00

24.89

66-inch Steel Pipe Pile

0.00

0.00

0.00

0.00

0.00

62.54

66-inch Steel Pipe Pile × 2

0.01

0.00

0.01

0.02

0.00

1,426.4

66-inch Steel Pipe Pile with Sheet Pile

0.03

0.00

0.02

0.05

0.01

722.5

Sheet Pile × 2

0.00

0.00

0.00

0.01

0.00

85

24-inch Steel Pipe Pile With Sheet Pile

0.01

0.00

0.00

0.01

0.00

157.08

24-inch Steel Pipe Pile × 2

0.00

0.00

0.00

0.00

0.00

213.5

AHTs

Anchor Handling

0.00

0.00

0.00

0.01

0.00

52.4

Level A harassment zones are typically smaller than Level B harassment zones. However, in some cases, the calculated Level A harassment isopleth is greater than the calculated Level B harassment isopleth. Calculation of Level A harassment isopleths include a duration component, which in the case of impact pile driving, is estimated through the total number of daily strikes and the associated pulse duration. For a stationary sound source, we assume here that an animal is exposed to all of the strikes expected within a 24-hour period. Calculation of

a Level B harassment zone does not include a duration component. Depending on the duration included in the calculation, the calculated Level A harassment isopleths can be larger than the calculated Level B harassment isopleth for the same activity.

Mainline Installation

8 Star Alaska intends to use AHTs to position a pipelaying barge in order to install the pipe on the seafloor for the Mainline across Cook Inlet. For the nearshore pipelay, planned for Year 3, an AHT would engage in anchor handling to moor a pull barge, and is expected to be used for two days of work, one day on the west coast near Beluga and one day on the east coast near Suneva Lake. For offshore pipelay, AHTs would be engaged in anchor handling to repeatedly position the barge during the duration of pipelay. Consistent with other tug activities, including those for tugs towing a jack-up rig (Furie Operating Alaska, LLC Natural Gas Activities, 89 FR 77836, September 24, 2024; Hilcorp Alaska, LLC, 89 FR 79529, September 30, 2024), NMFS anticipates that the AHTs would operate at approximately 50 percent power during anchor handling activities.

Because of the similarities to tugging activities planned by Hilcorp in Cook Inlet (89 FR 79529, September 30, 2024), NMFS determined it appropriate to adopt analysis provided for those activities for 8 Star Alaska's planned tugging activities. In addition, we refer here to an existing literature review of available source level data for tugs under load in varying power output scenarios (87 FR 27597, May 9, 2022). Please see that notice for the detailed analysis. While that analysis is for tugs under load towing a jack-up rig, NMFS expects the AHT power output for the proposed anchor handling is to be consistent with that assumed for tugs towing a jack-up rig (Furie Operating Alaska, LLC Natural Gas Activities, 89 FR 77836, September 24, 2024; Hilcorp Alaska, LLC, 89 FR 79529, September 30, 2024), and therefore, NMFS determined that this analysis represents the best scientific evidence available for considering the appropriate source level proxy for 8 Star Alaska's proposed AHT use during anchor handling.

In addition to the literature review referenced above, which indicates that a source level of 180 dB for a single AHT would be appropriate, we also consider other relevant information to adequately consider 8 Star Alaska's planned use of three AHTs to handle anchors. If all three tugs were operating simultaneously at 180 dB RMS, the overall source emission levels would be expected to increase by approximately 5 dB when logarithmically adding the sources (

i.e.,

to 185 dB RMS). To further support this level as an appropriate proxy, a sound source verification (SSV) study performed by JASCO Applied Sciences (JASCO) in Cook Inlet in October 2021 (Lawrence

et al.,

2022) measured the sound source level from three tugs pulling a jack-up rig in Cook Inlet at various power outputs. Lawrence

et al.

(2022) reported a source level of 167.3 dB RMS for the 20 percent-power scenario and a source level of 205.9 dB RMS for the 85 percent-power scenario. Assuming a linear scaling of tug power, a source level of 185 dB RMS was calculated as a single point source level for three tugs operating at 50 percent power output. Therefore, the analyses presented below use a mean tug sound source level scenario of 185 dB RMS to estimate distances to the 120 dB RMS isopleth for three tugs operating at 50 percent power output. In practice, the load condition of the three tugs is unlikely to be identical at all times, so sound emissions would be dominated by the single tug in the group that is working hardest at any point in time. NMFS, therefore, has determined it appropriate to use the source level of 185 dB RMS at 1 m to represent the use of three AHTs. Modeling using this source level resulted in an estimated distance to the 120-dB isopleth of 3,850 m. Please see 89 FR 79529 (September 30, 2024) for full detail.

As noted previously, NMFS determined that Level A harassment would not be a reasonably likely outcome of the use of AHTs. In order to characterize the extent of the Level A harassment isopleths to provide additional quantitative support for this determination, NMFS used the NMFS user spreadsheet to calculate Level A harassment zones for each hearing group for AHTs conducting anchor handling. NMFS used Tab A (Non-Impulse-Stat-Cont) in the spreadsheet and used a WFA of 2, a 6 hour duration of sound production within a 24 hour period, and a propagation loss coefficient of 18.129. Weston and SLR (2022) determined the average 120 dB isopleth was 3,850 meters for a continuous noise source of 185 dB rms SPL across 25 locations in middle Cook Inlet. The coefficient is calculated as (185 dB−120 dB)/Log10(3850/1) = 18.129 dB per decade.)). Estimated Level A and Level B harassment isopleths for AHTs engaged in anchor handling are reported in table 12.

Table 12—Level A and Level B Harassment Isopleths From AHTs Engaged in Anchor Handling

Sound source

Level A harassment isopleths (m)

1

LF

HF

VHF

Phocids

Otariids

Level B

harassment

isopleth

(m)

2

3 AHTs

53

21

28

62

21

3,850

1

Level A harassment isopleths calculated using NMFS User spreadsheet.

2

Level B harassment isopleth determined using results from Hilcorp's modeling.

Marine Mammal Occurrence

In this section we provide information about the occurrence of marine mammals, including density or other relevant information which will inform the take calculations.

8 Star Alaska requested take of humpback whale, killer whale, beluga whale, harbor porpoise, and harbor seal. In addition to those species, NMFS determined that minke whale, gray whale, fin whale, Dall's porpoise, Pacific white-sided dolphin, Steller sea lion, and California sea lion are likely to occur in the project area during 8 Star Alaska's activities and, accordingly, proposes to authorize take for these species.

Densities for marine mammals in Cook Inlet were derived from NMFS AFSC's Marine Mammal Laboratory (MML) aerial surveys, typically flown in June, from 2000 to 2022 (Rugh

et al.,

2005, Shelden

et al.,

2013, 2015b, 2017, 2022, Shelden and Wade, Goetz

et al.,

2023) except for beluga whales, for which other density data exist, or for Steller sea lions, fin whale, Pacific white-sided dolphins, and California sea lions, which occur too rarely to support development of density estimates. Total survey area was not reported for the

2021 or 2022 survey years (Shelden

et al.,

2022, Goetz

et al.,

2023) so total survey area for 2021 and 2022 was estimated as 8,377.2 km

2

for each year based on previous reports. While the surveys are concentrated for a few days in summer annually, which may skew densities for seasonally present species, they represent the best available long-term dataset of marine mammal sightings available in Cook Inlet. To estimate the average density, the maximum number of individuals per species was divided by the area surveyed, and NMFS used the average across all survey years for each species.

CIBW densities estimated from the AFSC surveys across regions are low; however, there is a known effect of seasonality on their distribution. Thus, densities derived directly from these summer surveys might undere

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