Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Port of Alaska Modernization Program Phase 2B: Cargo Terminals Replacement Project in Anchorage, Alaska

DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

50 CFR Part 217

[Docket No. 241018-0276]

RIN 0648-BM30

Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Port of Alaska Modernization Program Phase 2B: Cargo Terminals Replacement Project in Anchorage, Alaska

AGENCY:

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

ACTION:

Proposed rule; request for comments.

SUMMARY:

NMFS received a request from the Don Young Port of Alaska (POA) for authorization to take marine mammals incidental to the Cargo Terminals Replacement Project at the existing port facility in Anchorage, Alaska over the course of 5 construction seasons (2026 through 2030). Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is proposing 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's responses to public comments will be summarized in the final notification of our decision.

DATES:

Comments and information must be received no later than November 27, 2024.

ADDRESSES:

A plain language summary of this proposed rule is available at

https://www.regulations.gov/docket/NOAA-NMFS-2024-0030.

You may submit comments on this document, identified by NOAA-NMFS-2024-0030, by the following method:

•

Electronic Submission:

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

https://www.regulations.gov

and type NOAA-NMFS-2024-0030 in the Search box. Click on the “Comment” icon, complete the required fields, and enter or attach your comments.

Instructions:

Comments sent by any other method, to any other address or individual, or received after the end of the comment period, may not be considered by NMFS. All comments received are a part of the public record and will generally be posted for public viewing on

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).

Electronic copies of the 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/action/incidental-take-authorization-port-alaskas-construction-activities-port-alaska-modernization.

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

FOR FURTHER INFORMATION CONTACT:

Cara Hotchkin, Office of Protected Resources, NMFS, (301) 427-8401.

SUPPLEMENTARY INFORMATION:

Purpose of Regulatory Action

These proposed regulations, 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 the POA's Modernization Program, including impact and vibratory pile driving.

NMFS received an application from the POA requesting 5-year regulations and a letter of authorization issued thereunder to take individuals of seven species, comprising nine stocks of marine mammals by Level A harassment and Level B harassment incidental to the POA's activities. No serious injury or mortality is anticipated or proposed for authorization. Please see Background below for definitions of harassment.

Legal Authority for the Proposed Action

Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) directs the Secretary of Commerce 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 for up to 5 years if, after notice and public comment, the agency makes certain findings and promulgates regulations that set forth permissible methods of taking pursuant to that activity and other means of effecting the “least practicable adverse impact” on the affected species or stocks and their habitat (see the discussion below in the Proposed Mitigation section), as well as monitoring and reporting requirements. Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50 CFR part 216, subpart I provide the legal basis for issuing this proposed rule containing 5-year regulations and for any subsequent Letters of Authorization (LOAs).

Summary of Major Provisions Within the Proposed Rule

Following is a summary of the major provisions of this proposed rule regarding POA's activities. These measures include:

• Prescribing permissible methods of taking of small numbers of marine mammals by Level A harassment and/or Level B harassment incidental to the Cargo Terminals Replacement Project;

• Required monitoring of the construction areas to detect the presence of marine mammals before beginning construction activities;

• Establishment of shutdown zones equivalent to the estimated Level B harassment zone for beluga whales;

• Establishment of shutdown zones equivalent to or greater than the estimated Level A harassment zones for other species;

• Bubble curtains required for all impact and vibratory driving of permanent (72-inch (in) (1.83 meter (m))) piles in more than 3 m of water depth in all months and for vibratory driving of all temporary (24-in (0.61 m) or 36-in (0.91 m)) and permanent (72-in) piles between August and October;

• 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; and

• Submittal of monitoring reports including a summary of marine mammal species and behavioral observations, construction shutdowns or delays, and construction work completed.

Through adaptive management, the proposed regulations would allow NMFS Office of Protected Resources to modify (

e.g.,

remove, revise, or add to) the existing mitigation, monitoring, or reporting measures summarized above and required by the LOA.

Background

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

et seq.

) direct the Secretary of Commerce (as delegated to NMFS) to allow, upon request, the incidental, but not intentional, taking of small numbers of

marine mammals by U.S. citizens who engage in a specified activity (other than commercial fishing) within a specified geographical region if certain findings are made and either regulations are promulgated or an incidental harassment authorization is issued.

Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). If such findings are made, NMFS must prescribe the permissible methods of taking and other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stocks for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and requirements pertaining to the monitoring and reporting of the takings are set forth. The definitions of all applicable MMPA statutory terms cited above are included in the relevant sections below.

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 (NAO) 216-6A, NMFS must evaluate our proposed action's (

i.e.,

promulgation of regulations and subsequent issuance of a LOA thereunder) and alternatives to that action's potential impacts on the human environment.

Accordingly, NMFS has prepared an Environmental Assessment (EA) to evaluate the environmental impacts associated with the issuance of the proposed regulations and LOA. NMFS' EA is available at

https://www.fisheries.noaa.gov/action/incidental-take-authorization-port-alaskas-construction-activities-port-alaska-modernization.

We will review all comments submitted in response to this notice prior to concluding our NEPA process or making a final decision on this request.

Summary of Request

On January 3, 2023, NMFS received a request from the POA for regulations and a subsequent LOA to take marine mammals incidental to construction activities related to the POA Modernization Program (PAMP) Phase 2B: Cargo Terminals Replacement (CTR) at the POA in Anchorage, Alaska. NMFS provided comments on the application on March 3, 2023, April 20, 2023, and May 18, 2023. After POA submitted a revised application on October 13, 2023, and responded to additional questions sent on December 20, 2023, we determined the application was adequate and complete on February 12, 2024.

On March 4, 2024, we published a notice of receipt (NOR) of application in the

Federal Register

(89 FR 15548), requesting comments and information during a 30-day public comment period related to the POA's request. We received one comment letter from the Center for Biological Diversity. NMFS has reviewed all submitted material and taken the information into consideration during the drafting of this proposed rule.

The POA's request is for take of seven species of marine mammals by Level B harassment and for a subset of these species, Level A harassment. Neither POA nor NMFS expect serious injury or mortality to result from the specified activities. If promulgated, the regulations would be effective for the first 5 construction seasons (2026-2030).

NMFS previously issued IHAs to the POA for similar work (85 FR 19294, April 6, 2020; 86 FR 50057, September 7, 2021; 89 FR 2832, January 14, 2024). The POA complied with all the requirements (

e.g.,

mitigation, monitoring, and reporting) of the previous IHAs and information regarding their monitoring results may be found in the Effects of the Specified Activity on Marine Mammals and their Habitat and Estimated Take of Marine Mammals sections of this proposed rule and online at

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

Description of the Specified Activities

Overview

The POA, located on Knik Arm in upper Cook Inlet, provides critical infrastructure for the citizens of Anchorage and a majority of the citizens of Alaska. The POA was constructed primarily in the 1960s and is currently in poor condition and substantially past its initial design life. The existing cargo terminals T1, T2, and T3 are deteriorating and in poor structural condition and present safety and security concerns for human health and the economic stability of the state of Alaska. The PAMP is designed to replace the existing facilities with new infrastructure incorporating modern seismic codes over a 75-year design life. PAMP Phase 2B includes the demolition and replacement of terminals T1 and T2 and the partial demolition of T3. This phase is expected to take approximately 6 years of in-water work to complete. If promulgated, the regulations would be effective for the first 5 construction seasons (2026-2030).

In-water pile installation will include both temporary (24-in (0.61 m) or 36-in (0.91 m)) and permanent (72-in (1.83 m)) steel pipe piles by impact and vibratory hammers. Removal of temporary piles (24- or 35-in) and existing structures (16-in (0.41 m) to 42-in (1.07 m) steel pipe piles) would be primarily by cutting; dead-pull and vibratory extraction methods may also be used. Existing piles may also be left standing in their current positions. In-water work associated with the project would include installation of approximately 275 permanent piles and 450 temporary piles and vibratory extraction of approximately 46 temporary piles over the 5-year period.

Dates and Duration

The POA anticipates that in-water construction activities associated with this proposed rule would begin on April 1, 2026 and extend through November 30, 2030. In-water pile installation and removal associated with the CTR project is anticipated to take place over approximately 689 hours on approximately 337 nonconsecutive days between the months of April and November over the 5 year period (see table 1 for estimated production rates and durations). While the exact sequence of demolition and construction is uncertain, an estimated schedule is shown in table 2. This schedule is based on best available information and is not intended to be a limitation on the number of pile installation or removal hours that may occur in any given month.

The POA has presented the schedule shown in table 2 using the best available information derived from what is known of the existing Cargo Terminals site and the POA's experience with similar construction and demolition projects. A typical construction season at the POA extends from approximately mid-April to mid-October (6 months) and may include November. Exact dates of ice-out in the spring and formation of new ice in the fall vary from year to year and cannot be predicted with accuracy. In-water pile installation and removal cannot occur during the winter months when ice is present because of the hazards associated with moving ice floes that change directions four times a day, preventing the use of tugs, barges, workboats, and other vessels. Ice

movement also prevents accurate placement of piles.

While the POA plans to conduct as much work as possible between April and July, when there is lower Cook Inlet beluga whale (CIBW;

Delphinapterus leucas

) abundance (see the Description of Marine Mammals in the Area of Specified Activities section for details on CIBW presence at the POA), front-loading of work is dependent on construction sequencing. Construction sequencing requires that temporary piles are installed as a template, then larger permanent piles are installed, and then the temporary piles are removed. This required sequence plays out many times, in this order, during the open water construction season. It is not possible to install all of the larger permanent piles during the early season and install temporary piles later in the season; the larger and smaller piles must be alternated. Exact project sequencing and installation and extraction methods are at the discretion of the construction crew. Construction dates may change because of unexpected project delays, ongoing construction activities in other areas of the POA, timing of ice-out and spring breakup, and other factors. Therefore, the estimated schedule (table 2) reflects a realistic scenario for the proposed project, but conditions on the ground may result in slight changes to this estimated schedule.

Table 1—Pile Installation and Removal Methods, Estimated Amounts, and Estimated Durations for Years 1-5

Activity type

Pile size and type

Total

estimated

number of

piles

Estimated number of piles in the water

1

Average

vibratory

duration per pile

(minutes)

Average

impact duration per pile

(minutes)

Estimated impact strikes per pile

Total duration of removal or installation in water (hours)

Average production rate, piles per day (range)

Estimated number of days over 5 years

Temporary pile installation

24- or 36-in (61- or 91-cm) Steel pipe

565

450

30

225 hours

2-4

144.

Temporary pile removal

24- or 36-in (61- or 91-cm) Steel pipe

161

46

45

35 hours

2-4

15.

Permanent pile installation

72-in (182-cm) Steel pipe

310

275

10

86

5,743

440 hours

0.5-3

159.

Total

1,036

771

700 hours

337 days.

Note:

cm = centimeter(s); 1—Piles installed above the mean lower low water line are considered “in the dry” (

i.e.,

not in-water). It is anticipated that the permanent and temporary piles in the three bents nearest the shore for all five trestles would be installed in the dry at low tide levels. An additional bent would be installed in the dry for the northernmost trestle of T1 and for the three trestles of T2. These piles are not considered to have the potential for impact to marine mammals and are thus excluded from the following analyses.

Table 2—Estimated Timing and Duration (in Hours per Month) of Pile Installation and Removal Activities

1

Activity

Duration (hours of activity by month and year)

Apr

Imp

2

Vib

3

May

Imp

Vib

Jun

Imp

Vip

Jul

Imp

Vib

Aug

Imp

Vib

Sep

Imp

Vib

Oct

Imp

Vib

Nov

Imp

Vib

Year 1—2026

24- or 36-in Temporary Pile Installation

2.5

6.0

6.0

6.0

6.0

6.0

3.0

2

24- or 36-in Temporary Pile Removal

0.8

0.8

0.8

0.8

0.8

0.8

0.8

0.8

72-in Permanent Pile Installation

4

7.2

0.8

15.8

1.8

15.8

1.8

15.8

1.8

12.9

1.5

12.9

1.5

12.9

1.5

5.7

0.7

Year 1 total hours

7.2

4.1

15.8

8.6

15.8

8.6

15.8

8.6

12.9

8.3

12.9

8.3

12.9

5.3

5.7

3.4

Year 2—2027

24- or 36-in Temporary Pile Installation

3.0

5.0

5.0

5.0

5.0

5.0

2.5

2

24- or 36-in Temporary Pile Removal

0.8

0.8

0.8

0.8

0.8

0.8

0.8

72-in Permanent Pile Installation

4

7.2

0.8

12.9

1.5

12.9

1.5

12.9

1.5

12.9

1.5

11.5

1.3

11.5

1.3

5.7

0.7

Year 2 total hours

7.2

4.6

12.9

7.3

12.9

7.3

12.9

7.3

12.9

7.3

11.5

7.1

11.5

4.6

5.7

2.7

Year 3—2028

24- or 36-in Temporary Pile Installation

6.5

13.0

13.0

13.0

13.0

13.0

6.5

2

24- or 36-in Temporary Pile Removal

0.8

2.3

2.3

2.3

1.5

1.5

0.8

0.8

72-in Permanent Pile Installation

4

5.7

0.7

5.7

0.7

5.7

0.7

4.3

0.5

4.3

0.5

4.3

0.5

4.3

0.5

4.3

0.5

Year 3 total hours

5.7

7.9

5.7

15.9

5.7

15.9

4.3

15.8

4.3

15.0

4.3

15.0

4.3

7.8

4.3

3.3

Year 4—2029

24- or 36-in Temporary Pile Installation

2.5

5.5

5.5

6.0

5.5

5.5

2.5

2

24- or 36-in Temporary Pile Removal

0.8

0.8

0.8

0.8

0.8

0.8

0.8

72-in Permanent Pile Installation

4

7.2

0.8

12.9

1.5

12.9

1.5

12.9

1.5

12.9

1.5

11.5

1.3

11.5

1.3

5.7

0.7

Year 4 total hours

7.2

4.1

12.9

7.8

12.9

7.8

12.9

8.3

12.9

7.8

11.5

7.6

11.5

4.6

5.7

2.7

Year 5—2030

24- or 36-in Temporary Pile Installation

2.5

6.0

6.0

6.0

6.0

5.5

5.5

2.5

24- or 36-in Temporary Pile Removal

0.8

0.8

1.5

1.5

0.8

0.8

0.8

0.8

72-in Permanent Pile Installation

4

4.3

0.5

12.9

1.5

12.9

1.5

12.9

1.5

11.5

1.3

11.5

1.3

11.5

1.3

4.3

0.5

Year 5 total hours

4.3

3.8

12.9

8.3

12.9

8.3

12.9

8.3

11.5

8.1

11.5

7.6

11.5

7.6

4.3

3.8

1

Duration estimates assume a single hammer active at any time and therefore likely overestimates of actual time needed due to simultaneous pile installation and removal;

2

Impact pile installation;

3

Vibratory pile installation or extraction;

4

To account for piles driven in water less than 3m deep, NMFS has estimated approximately 0.5 unattenuated 72-in piles will be driven (approximately 43 minutes of impact driving and 5 minutes of vibratory driving) each month. Numbers may not add exactly due to rounding.

Specific Geographic Region

The specific geographic region for this action encompasses the land occupied by the POA, as well as the shoreline and waters extending from the POA across Knik Arm, northeast towards Wasilla, and southwest towards Fire Island and the Little Susitna River delta (figure 1).

Northern Cook Inlet bifurcates into Knik Arm to the north and Turnagain Arm to the east. Knik Arm is generally considered to begin at Point Woronzof, 7.4 km southwest of the POA. From Point Woronzof, Knik Arm extends about 48 km in a north-northeasterly direction to the mouths of the Matanuska and Knik rivers. At Cairn Point, just northeast of the POA, Knik Arm narrows to about 2.4 km before widening to as much as 8 km at the tidal flats northwest of Eagle Bay at the mouth of Eagle River.

Knik Arm comprises narrow channels flanked by large tidal flats composed of sand, mud, or gravel, depending upon location. Approximately 60 percent of Knik Arm is exposed at Mean Lower Low Water (MLLW). The intertidal (tidally influenced) areas of Knik Arm are mudflats, both vegetated and unvegetated, which consist primarily of fine, silt-sized glacial flour. Freshwater sources often are glacially born waters, which carry high suspended sediment loads as well as a variety of metals such as zinc, barium, mercury, and cadmium. Surface waters in Cook Inlet typically carry high silt and sediment loads, particularly during summer, making Knik Arm an extremely silty, turbid waterbody with low visibility through the water column. The Matanuska and Knik Rivers contribute the majority of freshwater and suspended sediment into Knik Arm during summer. Smaller rivers and creeks also enter along the sides of Knik Arm (U.S. Department of Transportation and Port of Anchorage, 2008). During winter, sea, beach, and river ice are dominant physical forces within Cook Inlet and Knik Arm. In upper Cook Inlet, sea ice generally forms in October to November and continues to develop through February or March (Moore

et al.,

2000).

Tides in Cook Inlet are semidiurnal, with two unequal high and low tides per tidal day (tidal day = 24 hours, 50 minutes). Due to Knik Arm's predominantly shallow depths and narrow widths, tides near Anchorage are greater than those in the main body of Cook Inlet. The tides at the POA have a mean range of about 8 m, and the maximum water level has been measured at more than 12.5 m at the Anchorage station (NMFS, 2015). Currents throughout Cook Inlet are strong and tidally periodic, with average velocities ranging from 3 to 6 knots (5.6 to 11.1 kilometers (km)/hour (h)) (Sharma and Burrell, 1970). Maximum current speeds in Knik Arm, observed during spring ebb tide, exceed 7 knots (13 km/h). These tides result in strong currents in alternating directions through Knik Arm and a well-mixed water column. The navigation harbor at the POA is a dredged basin in the natural tidal flat. Sediment loads in upper Cook Inlet can be high; spring thaws occur, and accompanying river discharges introduce considerable amounts of sediment into the system (Ebersole and Raad, 2004). Natural sedimentation processes act to continuously infill the dredged basin each spring and summer.

The Municipality of Anchorage is located in the lower reaches of Knik Arm of upper Cook Inlet (see figure 2-1 in the POA's application). The POA sits on the industrial waterfront of Anchorage, just south of Cairn Point and north of Ship Creek (lat. 61°15′ N, long. 149°52′ W; Seward Meridian) (figure 1). The POA's boundaries currently occupy an area of approximately 0.52 km

2

(figure 2). Other commercial and industrial activities related to secured maritime operations are located near the POA on Alaska Railroad Corporation property immediately south of the POA, on approximately 0.45 km

2

at a similar elevation. The POA is located north of Ship Creek, an area that experiences concentrated marine mammal activity during seasonal runs of several salmon species. Ship Creek serves as an important recreational fishing resource and is stocked twice each summer. Ship Creek flows into Knik Arm through the Municipality of Anchorage industrial area. Joint Base Elmendorf-Richardson (JBER) is located east of the POA, approximately 30.5 m higher in elevation. The U.S. Army Defense Fuel Support Point-Anchorage site is located east of the POA, south of JBER, and north of Alaska Railroad Corporation property. The perpendicular distance to the west bank directly across Knik Arm from the POA is approximately 4.2 km. The distance from the POA (east side) to nearby Port MacKenzie (west side) is approximately 4.9 km.

BILLING CODE 3510-22-P

EP28OC24.002

EP28OC24.003

BILLING CODE 3510-22-C

Detailed Description of the Specified Activities

As discussed previously, marine-side infrastructure and facilities at the POA are in need of replacement because they are substantially past their design life and in poor and deteriorating structural condition. Those facilities include three general cargo terminals, two petroleum terminals, a dry barge landing, and an upland sheet-pile-supported storage and work area. To address deficiencies, the POA is modernizing its marine terminals through the PAMP to enable safe, reliable, and cost-effective Port operations. The PAMP will support infrastructure resilience in the event of

a catastrophic natural disaster over a 75-year design life.

The PAMP is critical to maintaining food and fuel security for the state. At the completion of the PAMP, the POA will have modern, safe, resilient, and efficient facilities through which more than 90 percent of Alaskans will continue to obtain food, supplies, tools, vehicles, and fuel. The PAMP is divided into five separate phases; these phases are designed to include projects that have independent utility yet streamline agency permitting. The projects associated with the PAMP include:

•

Phase 1:

Petroleum and Cement Terminal (PCT Phase 1 and 2) and South Floating Dock (SFD) replacement;

•

Phase 2A:

North Extension Stabilization Phase 1 (NES1);

•

Phase 2B:

CTR;

•

Phase 3:

Petroleum, Oil and Lubricants Terminal 2 Replacement;

•

Phase 4:

North Extension Stabilization part 2; and

•

Phase 5:

Demolition of Terminal 3.

Phase 1 of the PAMP was completed in 2022. NMFS issued IHAs for take incidental to the now completed PCT (Phase 1 and Phase 2; 85 FR 19294, April 6, 2020) and SFD projects (86 FR 50057, September 7, 2021). Phase 2A of the PAMP began in 2023; an IHA was issued for phase one of the NES project (89 FR 2832, January 14, 2024) and in-water construction associated with this project is planned for 2024. The project discussed herein, CTR, is Phase 2B of the PAMP and is proposed to begin onshore preparation in 2025 and in-water construction work in 2026.

The purpose of the CTR project is to replace the existing general cargo docks. It would address deteriorating conditions of the existing cargo facilities; improve operational safety and efficiency; accommodate modern (existing and future) shipping operations; and improve the resiliency of the POA to extreme seismic events, all while sustaining ongoing cargo operations. This project is urgently needed due to severe corrosion of the foundation piles and deteriorating structural conditions at Terminals 1, 2, and 3. The existing terminals are more than 50 years old and suffer from severe damage to the foundation piles caused by corrosion and seismic forces. The piles have exceeded their useful service life, and multiple engineering investigations have highlighted the probability of wharf and trestle structure failure during a future major seismic event. The remaining service life of the cargo terminals is unknown. These facilities must be replaced with new resilient terminals for the Port to continue to meet its critical role serving Alaska's general cargo needs as well as supporting national defense and military readiness capabilities.

The geographical isolation of Alaska and the POA's role as the containerized logistic hub and distribution center for much of the state make the cargo terminals a critical lifeline for the southcentral region and Alaska. There are no other ports with the cargo capacity, proximity to Alaska's population centers, and intermodal transportation capabilities that can support the logistic missions sustained by the POA, including commerce, national defense, and earthquake resiliency/disaster response and recovery.

CTR Project Activities

The CTR project includes construction of new terminals T1 and T2, which include planned wharves and access trestles. The two new terminals would be located 140 feet (ft) (42.7 meters (m)) seaward of the existing T1, T2, and T3. It is anticipated that this more seaward location of the new terminals will reduce sedimentation, improve room for handling of berthing ships, and allow construction of the new terminals while the existing terminals remain in use. CTR also includes demolition of the existing Petroleum, Oil, and Lubricants Terminal 1 (POL1) and general cargo terminals (T1, T2, and T3).

The southernmost end of the new T1 and T2 would be approximately 1.4 km (0.9 mile (mi)) north of Ship Creek. Construction of the Project will include completion of the following components:

•

Component 1.

Onshore ground improvement shoreline stabilization (2025)

•

Component 2.

Shoreline expansion and protection (2026)

•

Component 3.

General cargo terminals (new Terminals 1 and 2) construction (2026-2031)

•

Component 4.

Demolition of existing terminals (POL1 and general cargo terminals (existing Terminals 1, 2, and 3)) (2026-2031)

•

Component 5.

Onshore utilities and storm drain outfall replacement (2030-2031)

Of these activities, only Components 3 and 4 include construction work that would occur in the water, and therefore, these would be the only components of the project expected to potentially impact marine mammals.

Landside Activities

Landside activities include work which takes place “in the dry,” either above the high tide line or in the intertidal zone but de-watered. These activities include shoreline stabilization and protection as well as placement of onshore utilities and decking components.

Ground Improvement Shoreline Stabilization—A ground improvement technique, such as deep soil mixing (DSM), or a similar technique would be used to stabilize the shoreline. DSM and similar techniques mechanically mix weak soils with a cement binder causing the soils to behave more like soft rock. This process is used to create foundations for buildings and roads and is used in earthquake-prone areas to prevent soil liquefaction. Soil improvements at trestle abutments, and potentially between the abutments, will mitigate the potential for seismic-induced slope failure that could result in catastrophic structural failure.

The first stage of construction would include installation of soil improvements in the five locations where the access trestles meet the beach to provide geotechnical stability to the embankment. Centered at each of the five trestle abutments, the ground improvement technique would create approximately 200- by 96-ft (61- by 29-m) blocks of treated soil extending from the surface to the top of the clay layer approximately 85-ft (25.9-m) deep (see figure 1-2 of the POA's application). The size of the block is designed to create enough contact area with the clay layer to restrain and significantly reduce the overall ground movements of the liquefiable soils surrounding the trestle abutment. If deemed necessary for geotechnical stability, ground improvements would extend along the embankment in areas between the abutments.

During construction, a temporary soil work pad would be constructed at each of the five trestles to provide a level temporary work surface. The ground improvement panels/columns would extend approximately 100 feet (ft) (30.5-m) seaward and shoreward of the crest of the slope and approximately 30 ft (9-m) to either side of the trestle structure. Temporary armoring will protect the work pad from water forces while in use. After completion of the ground improvement work, the temporary construction work pads will be removed and the foreshore graded and armored.

Shoreline Expansion and Protection—The existing shoreline behind the existing Terminals 1, 2, and 3 is irregular, with two areas where the shoreline is located about 100 ft (30-m) to the east of the typical shoreline (see figure 1-3 of the POA's application). These areas would be excavated to remove deposited silts before the areas

are then filled with more dense, stable materials such as clean gravel and rock. The filled area would provide a consistent shoreline and additional container storage area.

Excavation for the CTR project would be limited to removal of materials that are above the high-water line or below the high-water line in a dewatered state. Sea-based dredging of materials under water will not take place as part of this project.

After ground improvement work and shoreline expansion have been completed, the slope along the shore would be secured with armor stone placed over the clean gravel and rock fill. Placement of armor rock requires good visibility of the shore as each rock is placed carefully to interlock with surrounding armor rock. It is therefore anticipated that placement of most armor rock, filter rock, and granular fill will occur in the dry at low tide levels; however, some placement of armor rock, filter rock, and granular fill may occur in shallow water (

i.e.,

less than 3 m deep). After placement of armor rock, the top of the fill will be paved to match the existing backland pavements.

Onshore utilities and storm drain outfall replacement—The replacement of onshore utilities will involve construction on land and replacement of utilities above the high tide line, on land. Similarly, the storm drain outfall replacement will involve construction on land and replacement of four outfall pipes above the high tide line. No in-water work is proposed as a part of this component.

Ground improvement shoreline stabilization, shoreline expansion and protection, and onshore utilities and storm drain outfall replacement activities would take place on land or in the dry. While a minimal amount of fill and armor rock placement may occur in water, this activity would not be expected to impact marine mammals. Therefore, take of marine mammals related to these activities is not anticipated or proposed to be authorized, and it will not be considered further in this proposed rulemaking.

In-Water Construction

New terminals T1 and T2 would be constructed as seismically resilient adjoining terminals on a continuous berthline with mooring features and appurtenances as required to support safe ship mooring for lift-on/lift-off and roll-on/roll-off related cargo handling operations. The new T1 wharf would be 870 ft x 120 ft (265- x 37-m) with two 36-ft-wide (11-m) trestles of varying length. The new T2 wharf would be 932 ft x 120 ft (284- x 37-m) with two 259-ft- long x 54-ft-wide (79- x 16.5-m) trestles and one 259-ft-long x 76-ft-wide (79- x 23-m) trestle. Both T1 and T2 would be constructed using 48- and 72-in-diameter (121- and 183-centimeter (cm), respectively) steel piles. The 48-in-diameter piles will be installed in the dry.

Both new terminals would be designed to accommodate lift-on/lift-off container operations serviced by rail-mounted ship-to-shore cranes. Structural, in-deck, and surface features to support operational interface for three 100-gauge rail mounted gantry cranes, and associated appurtenances along with an on-terminal combination stevedore-operations building, would be included on the wharf. Additionally, T2 would be designed to support roll-on/roll-off container operations and other multi-purpose cargo functions. The reinforced concrete deck structure for both new terminals and all new access trestles would be designed to 1,000 pound per square foot load capacity. Construction would also include installation of power, lighting, communications, and signal infrastructure to terminal and onshore electrically powered features; potable water service including ship's water; and fire-flow water for terminal-related operations. The on-terminal stevedore-operations building would also be constructed with a connection to the onshore, existing public utility infrastructure.

In addition to these permanent structures, temporary work including temporary pile installation and removal would be required to support construction. Temporary piles would likely be 36-in-diameter (91-cm) steel; however, 24-in (61-cm) steel piles may be used in place of some of the larger temporary piles. Various work boats and barges would be utilized and would be moored at or in the immediate vicinity of the project, but these vessels are not expected to increase overall noise levels at the POA above existing operational levels. No thrusters or other dynamic positioning methods will be used during pile driving activities.

Construction of each terminal would require installation and removal of temporary steel pipe piles, including template piles, and installation of permanent steel pipe piles. Pile installation would occur in water depths that range from a few feet or dry (dewatered) conditions nearest the shore to approximately 20 meters (70 ft) at the outer face of the wharves, depending on tidal stage; the mean diurnal tide range at the POA is approximately 8.0 meters (26 ft; NOAA 2015).

Concurrent Activities—

In-water construction activities would occur at multiple locations across the project site simultaneously; the POA anticipates that two “spreads” (a construction crew with crane and pile driving hammer) would be on site and working throughout the construction season, with a third “spread” present on some days. Of the two regular spreads, one would be designated for permanent (72-in) piles and one for temporary (24-in or 36-in) piles. Each spread would operate a single hammer at a time (impact or vibratory), with no more than two vibratory hammers simultaneously active in-water at any given time. It is not expected that three piles would be driven concurrently, and this scenario is not addressed further in this analysis. The only combinations of vibratory hammers that could be used simultaneously would be for installation of an attenuated (through use of a bubble curtain; see Proposed Mitigation later in this notice) 72-in pile and an attenuated temporary pile, an attenuated 72-in pile and an unattenuated temporary pile, or two temporary piles. There would be no simultaneous driving of unattenuated 72-in piles in water. Simultaneous use of two hammers would increase production rates.

Duration of active hammer use is anticipated to be brief each day (see table 1), and it is, therefore, anticipated that overlap in use of hammers would be uncommon. Pile installation and removal would occur intermittently over the work period, for durations of minutes to hours at a time. Use of two simultaneous hammers would serve to reduce the overall duration of in-water pile installation and removal during each construction season. One construction crane would likely be based on a floating work barge, and one would likely be based on land or on an access trestle. Table 3 provides a summary of concurrent pile driving scenarios.

Table 3—Potential Concurrent Driving Scenarios That Could Occur During CTR Construction

Equipment type and quantity

Pile type and size

Construction months

Vibratory × 2

2 x 36-in steel pipe

1

April-July.

Vibratory, Impact

2 x 72-in steel pipe

2

OR 1 x 72-in steel pipe

2

(impact) and

1 x 36-in steel pipe (vibratory)

April-November.

1

POA may elect to use either 36-in or 24-in temporary piles; as 36-in piles are more likely and estimated to have larger ensonified areas, we have used these piles in our analyses of concurrent activities;

2

All 72-in piles driven concurrently will be attenuated.

Pile Installation and Removal—

Vibratory and impact hammers would be used for the installation of 72-in (182-cm) permanent piles. Vibratory hammers would be used for installation and removal of 24- (61-cm) and or 36-in (91-cm) temporary piles; however, if obstructions are encountered during installation, impact driving may be necessary. Installation and removal of piles in the dry would be maximized as much as feasible, depending on construction sequencing and tide heights. However, the exact number of piles that may be installed and removed in the dry is unknown (see table 1 for estimates and numbers of piles analyzed for in-water construction activities). Impact and vibratory pile driving activities conducted in the dry are not expected to impact marine mammals and therefore, are not discussed further in this rule.

Pile Cutting—

A majority of in-water temporary piles (approximately 90 percent) would be cut off at the mudline and remain in place, removed via direct pulling, or would remain in place intact (without cutting). Temporary piles that conflict with construction or operations or that can be removed in the dry would be removed. Leaving piles in place below the mudline supports stability of the soil. Also, many of the existing T1 and T2 piles are corroded and may break during removal, with the lower part remaining in place. The existing structure is closer to shore than new construction, and many piles can be cut or removed in the dry when their location is dewatered.

The number of piles that would be cut or remain in place would be maximized as feasible; however, the exact number of piles that may be cut or can remain in place is unknown (see table 1 for best estimates of piles to be removed). While the exact method of pile cutting is at the discretion of the construction contractor, any methodology considered for cutting and removing the piles would account for worker safety, constructability, and minimization of potential acoustic impacts that the operation may have on marine mammals. Potential methods of underwater cutting include ultrathermic cutting, pile clippers or wire-saws.

Underwater ultrathermic cutting is performed by commercial divers using hand-held equipment to cut or melt through ferrous and non-ferrous metals. These systems operate through a torch-like process, initiated by applying a melting amperage to a steel tube packed with alloy steel rods, sometimes mixed with aluminum rods to increase the heat output. In the hands of skilled commercial divers, underwater ultrathermic cutting is reputed to be relatively fast and efficient, cutting through approximately 2 to 4 inches (5 to 10 cm) per minute, depending upon the number of divers deployed. This efficacy may be constrained by the requirement to secure the severed piles from falling into the inlet to prevent an extreme hazard to the diver cutting the piles. Tidally driven currents in Cook Inlet may limit dive times to approximately 2 to 3 hours per high- and low-tide event, depending upon the tide cycle and the ability of divers to efficiently perform the cutting task while holding position during high current periods. This activity is not considered to produce sound.

Pile clipping and underwater sawing generate noise that is typically non-impulsive, low-level, and short duration (typically less than 15 seconds per pile) (NAVFAC SW, 2020). Potential pile cutting methodologies are not anticipated to result in incidental take of marine mammals because they are either above water, do not last for sufficient duration to present the reasonable potential for disruption of behavioral patterns, do not produce sound levels likely to result in marine mammal harassment, or some combination of the above. Impacts on marine mammals from pile cutting are therefore considered

de minimis

and NMFS is not proposing to authorize incidental take from this activity.

Demolition of Existing Terminals—

Once the new T1, T2, and petroleum products transfer system are complete and operational, any remaining existing T1, T2, and POL1 platforms, wharves, and trestles would be dismantled (see figure 1-5 of the POA's application). Existing and most temporary piles would be cut and removed, removed via vibratory extraction or direct pull, or left in place. The selection of construction equipment by the contractor, including cranes and barges, would determine the plans and sequencing for demolition. Portions of the existing terminals may be used for construction phasing and as support platforms for ongoing new construction, as feasible.

T3 may be partially demolished during Phase 2B construction of T1 and T2, especially where the existing infrastructure may interfere with new construction. Elements of T3 that remain after Phase 2B is complete would remain in place until Phase 5, when they would be removed at that time.

Demolition would take place above the water, and demolished decking, pipes, and other superstructure materials would be contained before they fall into the water following best management practices. Demolished materials would be removed by barge or truck. Because work would take place out of water with best management practices in place to limit any release of material into Cook Inlet, in addition to cutting off or leaving existing piles in place, impacts on marine mammals from demolition of the existing terminals are considered

de minimis

and NMFS is not proposing to authorize incidental take from this activity.

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 Specified Geographical Region

There are seven species, comprising 9 stocks, of marine mammals that may be found in upper Cook Inlet during the proposed construction and demolition activities. Sections 3 and 4 of the POA's application and request for regulations 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 likely and proposed to be authorized for the specified activities 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” (16 U.S.C. 1362(20)). While no serious injury or mortality is anticipated or proposed to be authorized here, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species or stocks and other threats.

Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates for most species represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS' U.S. Alaska and Pacific SARs (

e.g.,

Carretta,

et al.,

2023; Young

et al.,

2023, 2024). Values presented in table 4 are the most recent available at the time of publication (including from the draft 2023 SARs) and are available online at:

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

The most recent abundance estimate for CIBWs is available from Goetz

et al.

(2023) and available online at

https://www.fisheries.noaa.gov/feature-story/new-abundance-estimate-endangered-cook-inlet-beluga-whales.

Table 4—Species Likely Impacted by the Specified Activities

Common name

Scientific name

MMPA stock

ESA/

MMPA

status;

strategic

(Y/N)

1

Stock abundance

N

best

, (CV, N

min

, most recent

abundance survey)

2

PBR

Annual

M/SI

3

Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales)

Family Eschrichtiidae:

Gray whale

Eschrichtius robustus

Eastern N Pacific

-/-; N

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

801

131

Family Balaenopteridae (rorquals):

Humpback whale

Megaptera novaeangliae

Hawaii

-, -, N

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

127

27.09

Mexico-North Pacific

T, D, Y

N/A (N/A, N/A, 2006)

UND

5

0.57

Order Cetartiodactyla—Superfamily 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

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

-/-; N

587 (N/A, 587, 2012)

5.9

0.8

Family Monodontidae:

Beluga whale

Delphinapterus leucas

Cook Inlet

E/D; Y

331 (0.076, 290, 2022)

4

0.53

0

Family Phocoenidae (porpoises):

Harbor porpoise

Phocoena phocoena

Gulf of Alaska

-/-; Y

31,046 (0.214, N/A, 1998)

UND

5

72

Order Carnivora—Superfamily Pinnipedia

Family Otariidae (eared seals and sea lions):

Steller sea lion

Eumetopias jubatus

Western

E/D; Y

49,837 (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

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.

2

NMFS marine mammal stock assessment reports online at:

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

CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable (N.A.).

3

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

e.g.,

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

4

This abundance estimate is from Goetz

et al.

(2023); which was published after the most recent CIBW SAR (Young et al., 2023).

5

UND means undetermined.

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

Balaenoptera acutorostrata

) and Dall's porpoises (

Phocoenoides dalli

) also occur in Cook Inlet; however, the spatial occurrence of these species is such that take is not likely to occur, and they are not discussed further beyond the explanation provided here. Data from the Alaska Marine Mammal Stranding Network database (NMFS, unpublished data) provide additional support for these determinations. From 2011 to 2020, only one minke whale and one Dall's porpoise were documented as stranded in the portion of Cook Inlet north of Point Possession. Both were dead upon discovery; it is unknown if they were alive upon their entry into upper Cook Inlet or drifted into the area with the tides. With very few exceptions, minke whales and Dall's porpoises do not occur in upper Cook Inlet, and therefore, take of these species is considered unlikely.

In addition to what is included in sections 3 and 4 of the POA's application (

https://www.fisheries.noaa.gov/action/incidental-take-authorization-port-alaskas-construction-activities-port-alaska-modernization

), the SARs (

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

), and NMFS' website, we provide further detail below informing the baseline for species likely to be found in the project area (

e.g.,

information regarding current UMEs and known important habitat areas, such as Biologically Important Areas (BIAs;

https://oceannoise.noaa.gov/biologically-important-areas

) (Van Parijs et al., 2015)).

Gray Whale

Gray whales are infrequent visitors to Cook Inlet but can be seasonally present during spring and fall in the lower inlet (Bureau of Ocean Energy Management (BOEM), 2021). 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; BOEM, 2021). There are no BIAs for gray whales in Cook Inlet.

Gray whales are rarely documented in upper Cook Inlet and in the project area. Gray whales were not documented during POA construction or scientific monitoring from 2005 to 2011 or during 2016 (Prevel-Ramos

et al.,

2006; Markowitz and McGuire, 2007; Cornick and Saxon-Kendall, 2008, 2009; Cornick

et al.,

2010, 2011; Integrated Concepts and Research Corporation (ICRC), 2009, 2010, 2011, 2012; Cornick and Pinney, 2011; Cornick and Seagars, 2016); however, one gray whale was observed near Port MacKenzie during 2020 PCT construction (61 North (61N) Environmental, 2021) and a second whale was observed off of Ship Creek during 2021 PCT construction monitoring (61N Environmental, 2022a, Easley-Appleyard and Leonard, 2022). The whale observed in 2020 is believed to be the same whale that later stranded in the Twentymile River, at the eastern end of Turnagain Arm, approximately 80 km southeast of Knik Arm. There was no indication that work at the PCT had any effect on the animal, which was reported to be in “fair to poor” condition during evaluation (see

https://www.fisheries.noaa.gov/feature-story/alaska-gray-whale-ume-update-twentymile-river-whale-likely-one-twelve-dead-gray-whales

for more information). No gray whales were observed during POA's transitional dredging or SFD construction monitoring from May to August, 2022 (61N Environmental, 2022b, 2022c).

Under the MMPA, a UME is defined as “a stranding that is unexpected; involves a significant die-off of any marine mammal population; and demands immediate response” (16 U.S.C. 1421h(6)). A recently closed UME for gray whales along the West Coast and in Alaska occurred from December 17, 2018 through November 9, 2023. During that time, 146 gray whales 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). Given the changing environment in the polar regions due to climate change, there is potential for changes to gray whale behavior and distribution in the near future.

Humpback Whale

The 2022 Alaska and Pacific SARs described a revised stock structure for humpback whales, which modifies the previous stocks designated under the MMPA to align more closely with the ESA-designated distinct population segments (DPSs) (Carretta

et al.,

2023; Young

et al.,

2023). Specifically, the three previous North Pacific humpback whale stocks (Central and Western North Pacific stocks and a CA/OR/WA stock) were replaced by five stocks, largely corresponding with the ESA-designated DPSs. These include Western North Pacific and Hawaii stocks and a Central America/Southern Mexico-CA/OR/WA stock (which corresponds with the Central America DPS). The remaining two stocks, corresponding with the Mexico DPS, are the Mainland Mexico-CA/OR/WA and Mexico-North Pacific stocks (Carretta

et al.,

2023; Young

et al.,

2023). The former stock is expected to occur along the west coast from California to southern British Columbia, while the latter stock may occur across the Pacific, from northern British Columbia through the Gulf of Alaska and Aleutian Islands/Bering Sea region to Russia.

The Hawaii stock consists of one demographically independent population (DIP) (Hawaii—Southeast Alaska/Northern British Columbia DIP) and the Hawaii—North Pacific unit, which may or may not be composed of multiple DIPs (Wade

et al.,

2021). The DIP and unit are managed as a single stock at this time, due to the lack of data available to separately assess them and lack of compelling conservation benefit to managing them separately (NMFS, 2019, 2022b, 2023). The DIP is delineated based on two strong lines of evidence: genetics and movement data (Wade

et al.,

2021). Whales in the Hawaii—Southeast Alaska/Northern British Columbia DIP winter off Hawaii and largely summer in Southeast Alaska and Northern British Columbia (Wade

et al.,

2021). The group of whales that migrate from Russia, western Alaska (Bering Sea and Aleutian Islands), and central Alaska (Gulf of Alaska excluding Southeast Alaska) to Hawaii have been delineated as the Hawaii-North Pacific unit (Wade

et al.,

2021). There are a small number of whales that migrate between Hawaii and southern British Columbia/Washington, but current data and analyses do not provide a clear understanding of which unit these whales belong to (Wade

et al.,

2021; Carretta

et al.,

2023; Young

et al.,

2023).

The Mexico-North Pacific stock is likely composed of multiple DIPs, based on movement data (Martien

et al.,

2021; Wade, 2021; Wade

et al.,

2021). However, because currently available data and analyses are not sufficient to delineate or assess DIPs within the unit, it was designated as a single stock (NMFS, 2019, 2022c, 2023). Whales in this stock winter off Mexico and the Revillagigedo Archipelago and summer primarily in Alaska waters (Martien

et al.,

2021; Carretta

et al.,

2023; Young

et al.,

2023).

The most comprehensive photo-identification data available suggest that approximately 89 percent of all humpback whales in the Gulf of Alaska are members of the Hawaii stock, 11 percent are from the Mexico-North Pacific stock, and less than 1 percent are from the Western North Pacific stock (Wade, 2021). Members of different stocks are known to intermix in feeding grounds.

On October 9, 2019, NMFS proposed to designate critical habitat for the Western North Pacific, Mexico, and Central America DPSs of humpback whales (84 FR 54354). NMFS issued a final rule on April 21, 2021 to designate critical habitat for ESA-listed humpback whales pursuant to section 4 of the ESA (86 FR 21082). There is no designated critical habitat for humpback whales in or near the Project area (86 FR 21082, April 21, 2021), nor does the project overlap with any known BIAs.

Humpback whales are encountered regularly in lower Cook Inlet and occasionally in mid-Cook Inlet; however, sightings are rare in upper Cook Inlet (

e.g.,

Witteveen

et al.,

2011). During aerial surveys conducted in summers between 2005 and 2012, Shelden

et al.

(2013) reported dozens of sightings in lower Cook Inlet, a handful of sightings in the vicinity of Anchor Point and in lower Cook Inlet, and no sightings north of 60° N latitude. NMFS changed to a biennial survey schedule starting in 2014 after analysis showed there would be little reduction in the ability to detect a trend given the current growth rate of the population (Hobbs, 2013). No survey took place in 2020. Instead, consecutive surveys took place in 2021 and 2022 (Shelden

et al.,

2022). During the 2014-2022 aerial surveys, sightings of humpback whales were recorded in lower Cook Inlet and mid-Cook Inlet, but none were observed in upper Cook Inlet (Shelden

et al.,

2015b, 2017, 2019, 2022). Vessel-based observers participating in the Apache Corporation's 2014 survey operations recorded three humpback whale sightings near Moose Point in upper Cook Inlet and two sightings near Anchor Point, while aerial and land-based observers recorded no humpback whale sightings, including in the upper inlet (Lomac-MacNair

et al.,

2014). Observers monitoring waters between Point Campbell and Fire Island during summer and fall 2011 and spring and summer 2012 recorded no humpback whale sightings (Brueggeman

et al.,

2013). Monitoring of Turnagain Arm during ice-free months between 2006 and 2014 yielded one humpback whale sighting (McGuire, unpublished data, cited in LGL Alaska Research Associates, Inc., and DOWL, 2015).

There have been few sightings of humpback whales in the vicinity of the proposed project area. Humpback whales were not documented during POA construction or scientific monitoring from 2005 to 2011, in 2016, or during 2020 (Prevel-Ramos

et al.,

2006; Markowitz and McGuire, 2007; Cornick and Saxon-Kendall, 2008, 2009; Cornick

et al.,

2010, 2011; ICRC, 2009, 2010, 2011, 2012; Cornick and Pinney, 2011; Cornick and Seagars, 2016; 61N Environmental, 2021). Observers monitoring the Ship Creek Small Boat Launch from August 23 to September 11, 2017 recorded two sightings, each of a single humpback whale, which was presumed to be the same individual (POA, 2017). One other humpback whale sighting has been recorded for the immediate vicinity of the project area. This event involved a stranded whale that was sighted near a number of locations in upper Cook Inlet before washing ashore at Kincaid Park in 2017; it is unclear as to whether the humpback whale was alive or deceased upon entering Cook Inlet waters. Another juvenile humpback stranded in Turnagain Arm in April 2019 near mile 86 of the Seward Highway. One additional humpback whale was observed in July during 2022 transitional dredging monitoring (61N Environmental, 2022c). No humpback whales were observed during the 2020 to 2021 PCT construction monitoring, the NMFS marine mammal monitoring, or the 2022 SFD construction monitoring from April to June (61N Environmental, 2021, 2022a, 2022b, 2022c; Easley-Appleyard and Leonard, 2022).

Killer Whale

Killer whales are rare in Cook Inlet, and there are no known BIAs for this species in Cook Inlet. Most sightings of killer whales in the area are in lower Cook Inlet (Shelden

et al.,

2013). The infrequent sightings of killer whales that are reported in upper Cook Inlet tend to occur when their primary prey (anadromous fish for resident killer whales and beluga whales for transient killer whales) are also in the area (Shelden

et al.,

2003). During CIBW aerial surveys between 1993 and 2012, killer whales were sighted in lower Cook Inlet 17 times, with a total of 70 animals (Shelden

et al.,

2013); no killer whales were observed in upper Cook Inlet during this time. Surveys over 20 years by Shelden

et al.

(2003) documented an increase in CIBW sightings and strandings in upper Cook Inlet beginning in the early 1990s. Several of these sightings and strandings reported evidence of killer whale predation on CIBWs. The pod sizes of killer whales preying on CIBWs ranged from one to six individuals (Shelden

et al.,

2003). 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).

Few killer whales, if any, are expected to approach or be in the vicinity of the proposed project area. No killer whales were spotted in the vicinity of the POA during surveys by Funk

et al.

(2005), Ireland

et al.

(2005), or Brueggeman

et al.

(2007, 2008a, 2008b). Killer whales have also not been documented during any POA construction or scientific monitoring from 2005 to 2011, in 2016, or in 2020 (Prevel-Ramos

et al.,

2006; Markowitz and McGuire, 2007; Cornick and Saxon-Kendall, 2008; ICRC, 2009, 2010, 2011, 2012; Cornick

et al.,

2010, 2011; Cornick and Pinney, 2011; Cornick and Seagars, 2016; 61N Environmental, 2021). Two killer whales, one male and one juvenile of unknown sex, were sighted offshore of Point Woronzof in September 2021 during PCT Phase 2 construction monitoring (61N Environmental, 2022a). The pair of killer whales moved up Knik Arm, reversed direction near Cairn Point, and moved southwest out of Knik Arm toward the open water of Upper Cook Inlet. No killer whales were sighted during the 2021 NMFS marine mammal monitoring or the 2022 transitional dredging and SFD construction monitoring that occurred between May and June 2022 (61N Environmental, 2022b, 2022c; Easley-Appleyard and Leonard, 2022).

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 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). Only the CIBW stock inhabits the proposed project area. CIBWs were designated as a DPS and listed as endangered under the ESA in October 2008 (73 FR 62919, October 10, 2008).

On June 15, 2023, NMFS released an updated abundance estimate for CIBWs (Goetz

et al.,

2023) that incorporates aerial survey data from June 2021 and 2022, which represents an update from the most recent SAR (Young

et al.,

2023) and suggest that the CIBW population is stable or may be slightly increasing. The methodology in the 2023 report is the same as that used for NMFS's SARs (Young

et al.

2023) and incorporates the same time-series of data from previous years. The only change was the inclusion of more recent data from 2021 and 2022 surveys; the 2021 data collection efforts were delayed from 2020 due to COVID-19. Goetz

et al.

(2023) estimated that the population size is currently between 290 and 386, with a median best estimate of 331. We have determined that Goetz

et al.

(2023) represents the most recent and best available science.

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. Median group size estimates in 2021 and 2022 were 34 and 15, respectively (Goetz

et al.,

2023). NMFS has determined that the carrying capacity of Cook Inlet is 1,300 CIBWs (65 FR 34590, May 31, 2000) based on historical CIBW abundance estimated by Calkins (1989). Additional information may be found in NMFS' 2023 report on the abundance and trend of CIBWs in Cook Inlet in June 2021 and June 2022, available online at

https://www.fisheries.noaa.gov/resource/document/abundance-and-trend-belugas-delphinapterus-leucas-cook-inlet-alaska-june-2021-and.

Live stranding events of CIBWs have been regularly observed in upper Cook Inlet. This can occur when an individual or group of individuals strands as the tide recedes. Most live strandings have occurred in Knik Arm and Turnagain Arm, which are shallow and have large tidal ranges, strong currents, and extensive mudflats. Most whales involved in a live stranding event survive, although some associated deaths may not be observed if the whales die later from live-stranding-related injuries (Vos and Shelden, 2005; Burek-Huntington

et al.,

2015). Between 2014 and 2018, there were reports of approximately 79 CIBWs involved in 3 known live stranding events plus 1 suspected live stranding event with two associated deaths reported (NMFS, 2016b; NMFS, unpublished data; Muto

et al.,

2020). In 2014, necropsy results from two whales found in Turnagain Arm suggested that a live stranding event contributed to their deaths as both had aspirated mud and water. No live stranding events were reported prior to the discovery of these dead whales suggesting that not all live stranding events are observed.

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

et al.,

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

e.g.,

entanglement in marine debris, ship strikes) has been recently documented, and subsistence harvesting of CIBWs has not occurred since 2008 (NMFS, 2008b).

Recovery Plan.

The Final Recovery Plan for CIBW was published in the

Federal Register

on January 5, 2017 (82 FR 1325), available online at

https://www.fisheries.noaa.gov/resource/document/recovery-plan-cook-inlet-beluga-whale-delphinapterus-leucas.

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 prohibited take (

e.g.,

entanglements, strikes, poaching or intentional harassment, and close approaches by private vessels); 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 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. From spring through fall, Area 1 critical habitat has the highest concentration of CIBWs due to its important foraging and calving habitat. Area 2 critical habitat has a lower concentration of CIBWs in spring and summer but is used by CIBWs in fall and winter. Critical habitat does not include two areas of military usage: the Eagle River Flats Range on Fort Richardson and military lands of JBER between Mean Higher High Water and MHW. Additionally, the POA, adjacent navigation channel, and turning basin (approximately 6.84 km

2

) were excluded from the critical habitat designation due to national security reasons (76 FR 20180, April 11, 2011). The POA exclusion area is within Area 1, however, marine mammal monitoring results from the POA suggest that this exclusion area is not a particularly important feeding or calving area. CIBWs have been occasionally documented to forage around Ship Creek (south of the POA) but are typically transiting through the area to other, potentially richer, foraging areas to the north (

e.g.,

Six Mile Creek, Eagle River, Eklutna River) (

e.g.,

61N Environmental, 2021, 2022a, 2022b, 2022c, Easley-Appleyard and Leonard, 2022). These locations contain predictable salmon runs, an important food source for CIBWs, and the timing of these runs has been correlated with CIBW movements into the upper reaches of Knik Arm (Ezer

et al.,

2013). 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 (PCE), essential features important to the conservation of the CIBW:

(1) Intertidal and subtidal waters of Cook Inlet with depths of less than 9 m (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.

The area around the POA, while exempted from the Critical Habitat designation due to national security issues, does contain the requisite bathymetric features in the first PCE, as well as the presence of primary prey species. However, given the industrialized nature of the POA and the historical use of the site from the early 1900s, the other physical features are more difficult to confirm. Sediment contamination was examined during a 2008 U.S. Army Corps of Engineers dredging project near the Port, and contaminant levels of volatile and semi-volatile organic compounds, total recoverable petroleum hydrocarbons, PCBs, pesticides, cadmium, mercury, selenium, silver, arsenic, barium, chromium, and lead were found to be suitable for in-water discharge (USACE 2008). Ambient and background noise levels at the POA have been measured and are addressed quantitatively later in this document; briefly, noise levels are elevated due to both anthropogenic activities (

i.e.,

commercial shipping, dredging, and construction) and normal environmental factors (

e.g.,

high current velocity, ice movement, seismic activity). While neither contaminants nor noise have been shown to approach the “harmful” and “habitat abandonment” thresholds described in the PCEs, the concentration of both stressors is highest closer to the POA facilities, within the exemption area, ultimately degrading the habitat at POA relative to the surrounding areas. In total, the exempted area surrounding the POA represents approximately 0.35 percent of the designated Critical Habitat Area 1.

Biologically Important Areas.

Wild

et al.

(2023) delineated portions of Cook Inlet, including near the proposed project area, as a BIA for the small and resident population of CIBWs based on scoring methods outlined by Harrison

et al.

(2023) (see

https://oceannoise.noaa.gov/biologically-important-areas

for more information). The BIA is used year-round by CIBWs for feeding and breeding, and there are limits on food supply such as salmon runs and seasonal movement of other fish species (Wild

et al.,

2023). The boundary of the CIBW BIA is consistent with NMFS' critical habitat designation and does not include the aforementioned exclusion areas (

e.g.,

the POA and surrounding waters) (Wild

et al.,

2023).

Foraging Ecology.

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, 2016b).

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.,

2020, 2022).

In fall, as anadromous fish runs begin to decline, CIBWs 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.

Fish runs in the Anchorage and Matanuska-Susitna area include Chinook (May-August), sockeye (June-September), coho (July-September), pin (July-August), and chum (July-September) salmon, as well as dolly varden, rainbow and lake trout, northern pike, burbot, grayling, smelt, and whitefish. In proximity to the POA, anadromous fish runs occur at Ship Creek, which is heavily used by recreational anglers. On June 26, 2024, the Alaska Department of Fish and Game (ADF&G) issued an emergency closure of recreational fishing on Ship Creek until July 13, 2024, and limited Chinook catching to catch-and-release for the remainder of the season due to low returns of Chinook in the creek. ADF&G anticipates a poor return of this species throughout Knik Arm for 2024, in keeping with a trend of declining Chinook Runs throughout Cook Inlet since 2008 (ADF&G 2019). The Gulf of Alaska Chinook salmon is currently under review for listing under the ESA (89 FR 45815, May 24, 2024).

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; Castallotte

et al.,

2015; Shelden

et al.,

2015a, 2018; Lowery

et al.,

2019). During spring and summer, CIBWs generally aggregate near the warmer waters of river mouths 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 approximately 36 km (23 mi) to the west of the POA across the mouth of Knik arm in Upper Cook Inlet, the Beluga River (approximately 55 km (34 mi) west) and along the shore to the Little Susitna River (21 km (13 mi) west), within all of Knik Arm, and along the shores of Chickaloon Bay to the south of Anchorage, across Turnagain Arm (figure 3). 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).

EP28OC24.004

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, 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 as documented

in the designation of Critical Habitat (76 FR 20179, April 11, 2011; Rugh

et al.,

2000, 2004).

The NMFS Marine Mammal Lab 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, particularly in Tuxedni Bay in the months of September through March (Castellote

et al.,

2015, 2018, 2024; Castellote

et al.

2024).

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, seasonally, foraging behavior was more prevalent during summer, particularly at upper inlet rivers, than during winter. 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.

CIBWs are believed to mostly calve in the summer and concurrently breed between late spring and early summer (NMFS, 2016b), primarily in upper Cook Inlet. McGuire

et al.

(2020) documented three suspected calving events between July and September with no neonates observed during surveys conducted from April to June. The first neonates encountered during each field season from 2005 through 2015 were always seen in the Susitna River Delta in July. Important calving grounds are thought to be located near the river mouths of upper Cook Inlet—both potential births documented in July were at the Susitna River Delta; the third was in Turnagain Arm in September (McGuire

et al.,

2020). 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 during all months of the aerial surveys (McGuire

et al.,

2020). Young CIBWs are nursed for 2 years and may continue to associate with their mothers for a considerable time thereafter (Colbeck

et al.,

2013). Demographic rates were modeled for this population, indicating that low survival of non-breeding (

i.e.,

subadult, male, and non-breeding adult female) CIBWs and general low reproductive rates are likely contributing to the non-recovery of the population (Himes Boor

et al.,

2022).

Presence in Project Area.

Knik Arm is one of three areas in upper Cook Inlet where CIBWs are concentrated during spring, summer, and early fall. Most CIBWs observed in or near the POA are transiting between upper Knik Arm and other portions of Cook Inlet, and the POA itself is not considered high-quality foraging habitat. CIBWs tend to follow their anadromous prey and travel in and out of Knik Arm with the tides. The predictive habitat model derived by Goetz

et al.

(2012a) indicated that the highest predicted densities of CIBWs are in Knik Arm near the mouth of the Susitna River and in Chickaloon Bay. The model suggests that the density of CIBWs ranges from 0 to 1.12 whales per km

2

in Cook Inlet but is lower at the mouth of Knik Arm, near the POA, ranging between approximately 0.013 and 0.062 whales per km

2

. The distribution presented by Goetz

et al.

(2012a) is generally consistent with CIBW distribution documented in upper Cook Inlet throughout ice-free months (NMFS, 2016b).

Several marine mammal monitoring programs and studies have been conducted at or near the POA during the last 17 years. These studies offer some of the best available information on the presence of CIBWs in the proposed project area. Studies that occurred prior to 2020 are summarized in Section 4.5.5 of the POA's application. More recent programs, which most accurately portray current information regarding CIBW presence in the proposed project area, are summarized here.

PCT Construction Monitoring (2020-2021).

A marine mammal monitoring program was implemented during construction of the PCT in 2020 (Phase 1) and 2021 (Phase 2), as required by the NMFS IHAs (85 FR 19294, April 6, 2020). PCT Phase 1 construction included impact installation of 48-in (122-cm) attenuated piles; impact installation of 36-in (91-cm) and 48-in (122-cm) unattenuated piles; vibratory installation of 24-in (61-cm), 36-in (91-cm), and 48-in (122 cm) attenuated and unattenuated piles; and vibratory installation of an unattenuated 72-in (183-cm) casing for a confined bubble curtain across 95 days. PCT Phase 2 construction included vibratory installation of 36-in (91-cm) attenuated piles and impact and vibratory installation of 144-in (366-cm) attenuated breasting and mooring dolphins across 38 days. Marine mammal monitoring in 2020 occurred during 128 non-consecutive days with a total of 1,238.7 hours of monitoring from April 27 to November 24, 2020 (61N Environmental, 2021). Marine mammal monitoring in 2021 occurred during 74 non-consecutive days with a total of 734.9 hours of monitoring from April 26 to June 24 and September 7 to 29, 2021 (61N Environmental, 2022a). A total of 1,504 individual CIBWs across 377 groups were sighted during PCT construction monitoring. Sixty-five and 67 percent of CIBW observations occurred on non-pile driving days or before pile driving occurred on a given day during PCT Phase 1 and PCT Phase 2 construction, respectively.

The monitoring effort and data collection were conducted before, during, and after pile driving activities from four locations as stipulated by the PCT IHAs (85 FR 19294, April 6, 2020): (1) the Anchorage Public Boat Dock by Ship Creek, (2) the Anchorage Downtown Viewpoint near Point Woronzof, (3) the PCT construction site, and (4) the North End (North Extension) at the north end of the POA, near Cairn Point. Marine mammal sighting data from April to September both before, during, and after pile driving indicate that CIBWs swam near the POA and lingered there for periods of time ranging from a few minutes to a few hours. CIBWs were most often seen traveling at a slow or moderate pace, either from the north near Cairn Point or from the south or milling at the

mouth of Ship Creek. Groups of CIBWs were also observed swimming north and south in front of the PCT construction and did not appear to exhibit avoidance behaviors either before, during, or after pile driving activities (61N Environmental, 2021, 2022a). CIBW sightings in June were concentrated on the west side of Knik Arm from the Little Susitna River Delta to Port MacKenzie. From July through September, CIBWs were most often seen milling and traveling on the east side of Knik Arm from Point Woronzof to Cairn Point (61N Environmental, 2021, 2022a).

SFD Construction Monitoring and Transitional Dredging (2022).

In 2022, a marine mammal monitoring program almost identical to that used during PCT construction was implemented during construction of the SFD, as required by the NMFS IHA (86 FR 50057, September 7, 2021). SFD construction included the vibratory installation of ten 36-in (91-cm) attenuated plumb piles and two unattenuated battered piles (61N Environmental, 2022b). Marine mammal monitoring was conducted during 13 non-consecutive days with a total of 108.2 hours of monitoring observation from May 20 through June 11, 2022 (61N Environmental, 2022b). Forty-one individual CIBWs across 9 groups were sighted (61N Environmental, 2022b). One group was observed on a day with no pile-driving, three groups were seen on days before pile driving activities started, and five groups were seen during vibratory pile driving activities (61N Environmental, 2022b).

During SFD construction, the position of the Ship Creek monitoring station was adjusted to allow monitoring of a portion of the shoreline north of Cairn Point that could not be seen by the station at the northern end of the POA (61N Environmental, 2022b). Eleven protected species observers (PSOs) worked from four monitoring stations located along a 9-km (6-mi) stretch of coastline surrounding the POA. The monitoring effort and data collection were conducted at the following four locations: (1) Point Woronzof approximately 6.5 km (4 mi) southwest of the SFD, (2) the promontory near the boat launch at Ship Creek, (3) the SFD project site, and (4) the northern end of the POA (61N Environmental, 2022b).

Ninety groups comprised of 529 CIBWs were also sighted during the transitional dredging monitoring that occurred from May 3 to 15, 2022 and June 27 to August 24, 2022 (61N Environmental, 2022b). Of the nine groups of CIBWs sighted during SFD construction, traveling was recorded as the primary behavior for each group (61N Environmental, 2022b). CIBWs traveled and milled between the SFD construction area, Ship Creek, and areas to the south of the POA for more than an hour at a time, delaying some construction activities.

Harbor Porpoise

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). 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). There are no known BIAs for harbor porpoise in Cook Inlet.

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

e.g.,

61N 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 overall increase in the number of harbor porpoise sightings in upper Cook Inlet is unknown, although it may be an artifact from increased studies and marine mammal monitoring programs in upper Cook Inlet. It is also possible that the apparent contraction in the CIBW's range has opened up previously occupied CIBW range to harbor porpoises (Shelden

et al.,

2014).

Harbor porpoises have been observed within Knik Arm during monitoring efforts from 2005 to 2016. Between April 27 and November 24, 2020, 18 harbor porpoises were observed near the POA during the PCT Phase 1 construction monitoring (61N Environmental, 2021). Twenty-seven harbor porpoises were observed near the POA during the PCT Phase 2 construction monitoring conducted between April 26 and September 29, 2021 (61N Environmental, 2022a). During NMFS marine mammal monitoring conducted in 2021, one harbor porpoise was observed in August and six harbor porpoises were observed in October (Easley-Appleyard and Leonard, 2022). During 2022, five harbor porpoises were sighted during transitional dredging monitoring (61N Environmental, 2022c). No harbor porpoises were sighted at the POA during the 2022 SFD construction monitoring that occurred between May and June 2022 (61N Environmental, 2022b).

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).

NMFS designated critical habitat for Steller sea lions on August 27, 1993 (58 FR 45269). The critical habitat designation for the Western DPS of 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 are no known BIAs for Steller sea lions in Cook Inlet.

Within Cook Inlet, Steller sea lions primarily inhabit lower Cook Inlet. However, they occasionally venture to upper Cook Inlet and Knik Arm and may be attracted to salmon runs in the region. Steller sea lions have not been documented in upper Cook Inlet during CIBW aerial surveys conducted annually in June from 1994 through 2012 and in 2014 (Shelden

et al.,

2013, 2015b, 2017; Shelden and Wade, 2019); however, there has been an increase in individual Steller sea lion sightings near the POA in recent years.

Steller sea lions were observed near the POA in 2009, 2016, and 2019 through 2022 (ICRC, 2009; Cornick and Seagars, 2016; POA, 2019; 61N Environmental, 2021, 2022a, 2022b, 2022c). In 2009, there were three Steller sea lion sightings that were believed to be the same individual (ICRC, 2009). In 2016, Steller sea lions were observed on 2 separate days. On May 2, 2016, one individual was sighted, while on May 25, 2016, there were five Steller Sea lion sightings within a 50-minute period, and these sightings occurred in areas relatively close to one another (Cornick and Seagars, 2016). Given the proximity in time and space, it is believed these five sightings were of the same individual sea lion. In 2019, one Steller sea lion was observed in June at the POA during transitional dredging (POA,

2019). There were six sightings of individual Steller sea lions near the POA during PCT Phase 1 construction monitoring (61N Environmental, 2021). At least two of these sightings may have been re-sights on the same individual. An additional seven unidentified pinnipeds were observed that could have been Steller sea lions or harbor seals (61N Environmental, 2021). In 2021, there were a total of eight sightings of individual Steller sea lions observed near the POA during PCT Phase 2 construction monitoring (61N Environmental, 2022a). During NMFS marine mammal monitoring, one Steller sea lion was observed in August 2021 in the middle of the inlet (Easley-Appleyard and Leonard, 2022). In 2022, there were three Steller sea lion sightings during the transitional dredging monitoring and three during SFD construction monitoring (61N Environmental, 2022b, 2022c). All sightings occurred during summer, when the sea lions were likely attracted to ongoing salmon runs. Sea lion observations near the POA may be increasing due to more consistent observation effort or due to increased presence; observations continue to be occasional.

Harbor Seal

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

et al.,

2012; Shelden

et al.,

2013), though there are no known BIAs for this species in this area. 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).

The presence of harbor seals in upper Cook Inlet is seasonal. Harbor seals are commonly observed along the Susitna River and other tributaries within upper Cook Inlet during eulachon and salmon migrations (NMFS, 2003). The major haulout sites for harbor seals are in lower Cook Inlet; however, there are a few haulout sites in upper Cook Inlet, including near the Little and Big Susitna rivers, Beluga River, Theodore River, and Ivan River (Barbara Mahoney, personal communication, November 16, 2020; Montgomery

et al.,

2007). During CIBW aerial surveys of upper Cook Inlet from 1993 to 2012, harbor seals were observed 24 to 96 km south-southwest of Anchorage at the Chickaloon, Little Susitna, Susitna, Ivan, McArthur, and Beluga rivers (Shelden

et al.,

2013). Harbor seals have been observed in Knik Arm and in the vicinity of the POA (Shelden

et al.,

2013), but they are not known to haul out within the proposed project area.

Harbor seals were observed during construction monitoring at the POA from 2005 through 2011 and in 2016, in groups of one to seven individuals (Prevel-Ramos

et al.,

2006; Markowitz and McGuire, 2007; Cornick and Saxon-Kendall, 2008, 2009; Cornick

et al.,

2010, 2011; Cornick and Seagars, 2016). Harbor seals were also observed near the POA during construction monitoring for PCT Phase 1 in 2020 and PCT Phase 2 in 2021, NMFS marine mammal monitoring in 2021, and transitional dredging monitoring and SFD construction monitoring in 2022 (61N Environmental, 2021, 2022a, 2022b, 2022c, Easley-Appleyard and Leonard, 2022). During the 2020 PCT Phase 1 and 2021 PCT Phase 2 construction monitoring, harbor seals were regularly observed in the vicinity of the POA with frequent observations near the mouth of Ship Creek, located approximately 1,500 m southeast of the CTR location. Harbor seals were observed almost daily during 2020 PCT Phase 1 construction, with 54 individuals documented in July, 66 documented in August, and 44 sighted in September (61N Environmental, 2021). During the 2021 PCT Phase 2 construction, harbor seals were observed with the highest numbers of sightings in June (87 individuals) and in September (124 individuals) (61 N Environmental, 2022a). Over the 13 days of SFD construction monitoring in May and June 2022, 27 harbor seals were observed (61N Environmental, 2022b). Seventy-two groups of 75 total harbor seals (3 groups of 2 individuals) were observed during transitional dredging monitoring in 2022 (61N Environmental, 2022c). Sighting rates of harbor seals have been highly variable and may have increased since 2005. It is unknown whether any potential increase was due to local population increases or habituation to ongoing construction activities. It is possible that increased sighting rates are correlated with more intensive monitoring efforts in 2020 and 2021, when the POA used 11 PSOs spread among four monitoring stations.

Marine Mammal Hearing

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

e.g.,

Richardson

et al.,

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

et al.

(2007, 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.

). Note that no direct measurements of hearing ability have been successfully completed for mysticetes (

i.e.,

low-frequency cetaceans). Subsequently, NMFS (2018, 2024) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 decibel (dB) threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency cetaceans where the lower bound was deemed to be biologically implausible and the lower bound from Southall

et al.

(2007) retained.

On May 3, 2024, NMFS published and solicited public comment on its draft Updated Technical Guidance (89 FR 36762), which includes updated hearing ranges and names for the marine mammal hearing groups and is intended to replace the 2018 Technical Guidance once finalized. The public comment period ended on June 17th, 2024. Because NMFS may finalize the Guidance prior to taking a final agency action on this proposed rulemaking, we considered both the 2018 and 2024 Technical Guidance in our effects and estimated take analysis below. Marine mammal hearing groups and their associated hearing ranges from NMFS (2018) and NMFS (2024) are provided in tables 5 and 6. In the draft Updated

Technical Guidance, mid-frequency cetaceans have been re-classified as high-frequency cetaceans, and high-frequency cetaceans have been updated to very-high-frequency (VHF) cetaceans. Additionally, the draft Updated Technical Guidance includes in-air data for phocid (PA) and otariid (OA) pinnipeds.

Table 5—Marine Mammal Hearing Groups

[NMFS, 2018]

Hearing group

Generalized

hearing range *

Low-frequency (LF) cetaceans (baleen whales)

7 Hz to 35 kHz.

Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)

150 Hz to 160 kHz.

High-frequency (HF) cetaceans (true porpoises,

Kogia,

river dolphins, Cephalorhynchid,

Lagenorhynchus cruciger

&

L. australis

)

275 Hz to 160 kHz.

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

50 Hz to 86 kHz.

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

60 Hz to 39 kHz.

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

i.e.,

all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on ~65 dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans (Southall

et al.

2007) and PW pinniped (approximation).

Table 6—Marine Mammal Hearing Groups

[NMFS 2024]

Hearing group

Generalized

hearing range *

Underwater:

Low-frequency (LF) cetaceans (baleen whales)

7 Hz 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.

In-air:

Phocid pinnipeds (PA) (true seals)

42 Hz to 52 kHz.

Otariid pinnipeds (OA) (sea lions and fur seals)

90 Hz to 40 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 (2018, 2024) for a review of available information.

Potential Effects of the Specified Activity 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 likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival.

Acoustic effects on marine mammals during the specified activities are expected to potentially occur from vibratory pile installation and removal and impact pile installation. The effects of underwater noise from the POA's proposed activities have the potential to result in Level B harassment of marine mammals in the project area and, for some species as a result of certain activities, Level A harassment.

Background on Sound

This section contains a brief technical background on sound, on the characteristics of certain sound types and on metrics used relevant to the specified activity and to a discussion of the potential effects of the specified activities on marine mammals found later in this document. For general information on sound and its interaction with the marine environment, please see: Erbe and Thomas (2022); Au and Hastings (2008); Richardson

et al.

(1995); Urick (1983); as well as the Discovery of Sound in the Sea website at

https://dosits.org/.

Sound is a vibration that travels as an acoustic wave through a medium such as a gas, liquid or solid. Sound waves alternately compress and decompress the medium as the wave travels. In water, sound waves radiate in a manner similar to ripples on the surface of a pond and may be either directed in a beam (narrow beam or directional sources) or sound may radiate in all directions (omnidirectional sources), as is the case for sound produced by the construction activities considered here. The compressions and decompressions associated with sound waves are detected as changes in pressure by marine mammals and human-made sound receptors such as hydrophones.

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

transmission medium such as temperature and salinity.

The basic characteristics of a sound wave are frequency, wavelength, velocity, and amplitude. Frequency is the number of pressure waves that pass by a reference point per unit of time and is measured in hertz (Hz) or cycles per second. Wavelength is the distance between two peaks or corresponding points of a sound wave (length of one cycle). Higher frequency sounds have shorter wavelengths than lower frequency sounds, and typically attenuate (decrease) more rapidly with distance. The amplitude of a sound pressure wave is related to the subjective “loudness” of a sound and is typically expressed in dB, which are a relative unit of measurement that is used to express the ratio of one value of a power or pressure to another. A sound pressure level (SPL) in dB is described as the ratio between a measured pressure and a reference pressure, and is a logarithmic unit that accounts for large variations in amplitude; therefore, a relatively small change in dB corresponds to large changes in sound pressure. For example, a 10-dB increase is a ten-fold increase in acoustic power. A 20-dB increase is then a 100-fold increase in power and a 30-dB increase is a 1,000-fold increase in power. However, a ten-fold increase in acoustic power does not mean that the sound is perceived as being 10 times louder due to the anatomy of mammalian ears. A 10-dB increase in sound is perceived as a doubling of loudness to the human ear, and marine mammal studies of loudness perception are ongoing (Houser

et al.

2017).

The dB is a relative unit comparing two pressures; therefore, a reference pressure must always be indicated. For underwater sound, this is 1 microPascal (μPa). For in-air sound, the reference pressure is 20 microPascal (μPa). The amplitude of a sound can be presented in various ways; however, NMFS typically considers three metrics: sound exposure level (SEL), root-mean-square (RMS) SPL, and peak SPL (defined below). The source level represents the SPL referenced at a standard distance from the source, typically 1 m (Richardson

et al.,

1995; American National Standards Institute (ANSI, 2013), while the received level is the SPL at the receiver's position. For pile driving activities, the SPL is typically referenced at 10 m.

SEL (represented as dB referenced to 1 micropascal squared second (re 1 μPa

2

-s)) represents the total energy in a stated frequency band over a stated time interval or event, and considers both intensity and duration of exposure. The per-pulse SEL (

e.g.,

single strike or single shot SEL) is calculated over the time window containing the entire pulse (

i.e.,

100 percent of the acoustic energy). SEL can also be a cumulative metric; it can be accumulated over a single pulse (for pile driving this is the same as single-strike SEL, above; SEL

ss

), or calculated over periods containing multiple pulses (SEL

cum

). Cumulative SEL (SEL

cum

) represents the total energy accumulated by a receiver over a defined time window or during an event. The SEL metric is useful because it allows sound exposures of different durations to be related to one another in terms of total acoustic energy. The duration of a sound event and the number of pulses, however, should be specified as there is no accepted standard duration over which the summation of energy is measured.

RMS SPL is equal to 10 times the logarithm (base 10) of the ratio of the mean-square sound pressure to the specified reference value, and given in units of dB (International Organization for Standardization (ISO), 2017). RMS is calculated by squaring all of the sound amplitudes, averaging the squares, and then taking the square root of the average (Urick, 1983). RMS accounts for both positive and negative values; squaring the pressures makes all values positive so that they may be accounted for in the summation of pressure levels (Hastings and Popper, 2005). This measurement is often used in the context of discussing behavioral effects, in part because behavioral effects, which often result from auditory cues, may be better expressed through averaged units than by peak SPL. For impulsive sounds, RMS is calculated by the portion of the waveform containing 90 percent of the sound energy from the impulsive event (Madsen, 2005).

Peak SPL (also referred to as zero-to-peak sound pressure or 0-pk) is the maximum instantaneous sound pressure measurable in the water, which can arise from a positive or negative sound pressure, during a specified time, for a specific frequency range at a specified distance from the source, and is represented in the same units as the RMS sound pressure (ISO, 2017). Along with SEL, this metric is used in evaluating the potential for permanent threshold shift (PTS) and temporary threshold shift (TTS) associated with impulsive sound sources.

Sounds are also characterized by their temporal components. Continuous sounds are those whose sound pressure level remains above that of the ambient or background sound with negligibly small fluctuations in level (ANSI, 2005) while intermittent sounds are defined as sounds with interrupted levels of low or no sound (National Institute for Occupational Safety and Health (NIOSH), 1998). A key distinction between continuous and intermittent sound sources is that intermittent sounds have a more regular (predictable) pattern of bursts of sounds and silent periods (

i.e.,

duty cycle), which continuous sounds do not.

Sounds may be either impulsive or non-impulsive (defined below). The distinction between these two sound types is important because they have differing potential to cause physical effects, particularly with regard to noise-induced hearing loss (

e.g.,

Ward, 1997 in Southall

et al.,

2007). Please see NMFS (2018) and Southall

et al.

(2007, 2019) for an in-depth discussion of these concepts.

Impulsive sound sources (

e.g.,

explosions, gunshots, sonic booms, seismic airgun shots, impact pile driving) produce signals that are brief (typically considered to be less than 1 second), broadband, atonal transients (ANSI, 1986, 2005; NIOSH, 1998) and occur either as isolated events or repeated in some succession. Impulsive sounds are all characterized by a relatively rapid rise from ambient pressure to a maximal pressure value followed by a rapid decay period that may include a period of diminishing, oscillating maximal and minimal pressures, and generally have an increased capacity to induce physical injury as compared with sounds that lack these features. Impulsive sounds are intermittent in nature. The duration of such sounds, as received at a distance, can be greatly extended in a highly reverberant environment.

Non-impulsive sounds can be tonal, narrowband, or broadband, brief or prolonged, and may be either continuous or non-continuous (

i.e.,

intermittent) (ANSI, 1995; NIOSH, 1998). Some of these non-impulsive sounds can be transient signals of short duration but without the essential properties of impulses (

e.g.,

rapid rise time). Examples of non-impulsive sounds include those produced by vessels, aircraft, machinery operations such as drilling or dredging, vibratory pile driving, and active sonar systems.

Even in the absence of sound from the specified activity, the underwater environment is characterized by sounds from both natural and anthropogenic sound sources. Ambient sound is defined as a composite of naturally-occurring (

i.e.,

non-anthropogenic) sound from many sources both near and far (ANSI, 1995). Background sound is similar but includes all sounds, including anthropogenic sounds minus

the sound produced by the proposed activities (NMFS, 2012, 2016a). The sound level of a region is defined by the total acoustical energy being generated by known and unknown sources. These sources may include physical (

e.g.,

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

e.g.,

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

e.g.,

vessels, dredging, construction) sound. A number of sources contribute to background and ambient sound, including wind and waves, which are a main source of naturally occurring ambient sound for frequencies between 200 Hz and 50 kilohertz (kHz) (Mitson, 1995). In general, background and ambient sound levels tend to increase with increasing wind speed and wave height. Precipitation can become an important component of total sound at frequencies above 500 Hz, and possibly down to 100 Hz during quiet times. Marine mammals can contribute significantly to background and ambient sound levels, as can some fish and snapping shrimp. The frequency band for biological contributions is from approximately 12 Hz to over 100 kHz. Sources of background sound related to human activity include transportation (surface vessels), dredging and construction, oil and gas drilling and production, geophysical surveys, sonar, and explosions. Vessel noise typically dominates the total background sound for frequencies between 20 and 300 Hz. In general, the frequencies of many anthropogenic sounds, particularly those produced by construction activities, are below 1 kHz (Richardson

et al.,

1995). When sounds at frequencies greater than 1 kHz are produced, they generally attenuate relatively rapidly (Richardson

et al.,

1995), particularly above 20 kHz due to propagation losses and absorption (Urick, 1983).

Transmission loss (

TL

) defines the degree to which underwater sound has spread in space and lost energy after having moved through the environment and reached a receiver. It is defined by the ISO as the reduction in a specified level between two specified points that are within an underwater acoustic field (ISO, 2017). Careful consideration of transmission loss and appropriate propagation modeling is a crucial step in determining the impacts of underwater sound, as it helps to define the ranges (isopleths) to which impacts are expected and depends significantly on local environmental parameters such as seabed type, water depth (bathymetry), and the local speed of sound. Geometric spreading laws are powerful tools which provide a simple means of estimating

TL,

based on the shape of the sound wave front in the water column. For a sound source that is equally loud in all directions and in deep water, the sound field takes the form of a sphere, as the sound extends in every direction uniformly. In this case, the intensity of the sound is spread across the surface of the sphere, and thus we can relate intensity loss to the square of the range (as area = 4*pi*r

2

). This can be expressed logarithmically, where

TL

= 20*Log

10

(range). This situation is known as spherical spreading. In shallow water, the sea surface and seafloor will bound the shape of the sound wave, leading to a more cylindrical shape, as the top and bottom of the sphere is truncated by the largely reflective boundaries. This situation is termed cylindrical spreading, and is given by

TL

= 10*Log

10

(range) (Urick, 1983). An intermediate scenario may be defined by the equation

TL

= 15*Log

10

(range), and is referred to as practical spreading. Though these geometric spreading scenarios do not capture many often important details (scattering, absorption,

etc.

), they offer a reasonable and simple approximation of how sound decreases in intensity as it is transmitted. In the absence of measured data indicating the level of transmission loss at a given site for a specific activity, NMFS recommends practical spreading (

i.e., TL

= 15*Log

10

(range)) to model acoustic propagation for construction activities in most nearshore environments.

The sum of the various natural and anthropogenic sound sources at any given location and time depends not only on the source levels, but also on the propagation of sound through the environment. 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, background and 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 to 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.

Background underwater noise levels in the CTR Project area are both variable and relatively high, primarily because of extreme tidal activity, elevated sediment loads in the water column, periodic high winds, the seasonal presence of ice, and anthropogenic activities. Sources of anthropogenic noise in the CTR Project area consist of dredging operations, boats, ships, oil and gas operations, construction noise, and aircraft overflights from JBER and Ted Stevens International Airport, all of which contribute to high underwater noise levels in upper Cook Inlet (

e.g.,

Blackwell and Greene, 2002; (Knik Arm Bridge and Toll Authority (KABATA), 2011; Castellote

et al.,

2018).

Background sound levels were measured at the POA during the PAMP 2016 Test Pile Program (TPP) in the absence of pile driving at two locations during a 3‐day break in pile installation. Median background noise levels, measured at a location just offshore of the POA SFD and at a second location about 1 km offshore, were 117 and 122.2 dB RMS, respectively (Austin

et al.,

2016). NMFS considers the median sound levels to be most appropriate when considering background noise levels for purposes of evaluating the potential impacts of the proposed project on marine mammals (NMFS, 2012). By using the median value, which is the 50th percentile of the measurements, for background noise levels, one will be able to eliminate the few transient loud identifiable events that do not represent the true ambient condition of the area. This is relevant because during 2 of the 4 days (50 percent) when background measurement data were being collected, the USACE was dredging Terminal 3 (located just north of the Ambient-Offshore hydrophone) for 24 hours per day with two 1-hour breaks for crew change. On the last 2 days of data collection, no dredging occurred. Therefore, the median provides a better representation of background noise levels when the CTR project would be occurring. During the measurements, some typical sound signals were noted, such as noise from current flow and the passage of vessels.

With regard to spatial considerations of the measurements, the offshore location is most applicable to assessing background sound during the CTR project (NMFS, 2012). The median background noise level measured at the offshore hydrophone was 122.2 dB RMS. The measurement location closer to the POA was quieter, with a median of 117 dB; however, that hydrophone was placed very close to a dock. During PCT acoustic monitoring, noise levels in Knik Arm absent pile driving were also collected (Illingworth & Rodkin (I&R), 2021a, 2022b)); however, the PCT IHAs did not require background noise

measurements to be collected in adherence with NMFS (2012) methodological recommendations. Despite this, the noise levels measured during the PCT project were not significantly different from 122.2 dB (I&R, 2021a, 2022b). If additional background data are collected in the future in this region, NMFS may re-evaluate the data to appropriately characterize background sound levels in Knik Arm.

Description of Sound Sources for the Specified Activities

In-water construction activities associated with the project that have the potential to incidentally take marine mammals through exposure to sound would include impact pile installation and vibratory pile installation and removal. 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 hammers typically produce less sound (

i.e.,

lower levels) than impact hammers. Peak 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 pile (Oestman

et al.,

2009; California Department of Transportation (CALTRANS), 2015, 2020). Sounds produced by vibratory hammers are non-impulsive; the rise time is slower, reducing the probability and severity of injury, and the sound energy is distributed over a greater amount of time (Nedwell and Edwards, 2002; Carlson

et al.,

2005).

The likely or possible impacts of the POA's proposed activities 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, given there are no known pinniped haul-out sites in the vicinity of the CTR project site, visual and other non-acoustic stressors would be limited, and any impacts to marine mammals are expected to primarily be acoustic in nature.

Acoustic Impacts

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

et al.,

2007, 2019). Exposure to pile driving noise has the potential to result in auditory threshold shifts and behavioral reactions (

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 noise on marine mammals are dependent on 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 (threshold shifts) followed by behavioral effects and potential impacts on habitat.

NMFS defines a noise-induced threshold shift (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 threshold shift is customarily expressed in dB. A TS can be permanent or temporary. As described in NMFS (2018, 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 frequency range of the exposed species relative to the signal's frequency spectrum (

i.e.,

how 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 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 Ward

et al.,

1958, 1959, 1960; Kryter

et al.,

1966; Miller, 1974; Ahroon

et al.,

1996; Henderson

et al.,

2008). PTS levels for marine mammals are estimates, as with the exception of a single study unintentionally inducing PTS in a harbor seal (Kastak

et al.,

2008), there are no empirical data measuring PTS in marine mammals 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 (NMFS, 2018).

Temporary Threshold Shift (TTS).

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 marine mammal TTS measurements (see Southall

et al.,

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

et al.,

2000, 2002; Schlundt

et al.,

2000). As described in Finneran (2015), marine mammal studies have shown the amount of TTS increases with SEL

cum

in an accelerating fashion: at low exposures with lower SEL

cum

, the amount of TTS is typically small and the growth curves have shallow slopes. At exposures with higher SEL

cum

, 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 (

Zalophus californianus

) (Kastak

et al.,

1999, 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.,

2019a, 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 (Mooney

et al.,

2009; Finneran

et al.,

2010; Kastelein

et al.,

2014, 2015). This means that TTS predictions based on the total, cumulative SEL 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, 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.

Behavioral Harassment.

Exposure to noise also has the potential to behaviorally disturb marine mammals to a level that rises to the definition of harassment under the MMPA. Generally speaking, NMFS considers a behavioral disturbance that rises to the level of harassment under the MMPA a non-minor response—in other words, not every response qualifies as behavioral disturbance, and for responses that do, those of a higher level, or accrued across a longer duration, have the potential to affect foraging, reproduction, or survival. Behavioral disturbance may include a variety of effects, including subtle changes in behavior (

e.g.,

minor or brief avoidance of an area or changes in vocalizations), more conspicuous changes in similar behavioral activities, and more sustained and/or potentially severe reactions, such as displacement from or abandonment of high-quality habitat. Behavioral responses may include changing durations of surfacing and dives; changing direction and/or speed; reducing/increasing vocal activities; changing/cessation of certain behavioral activities (such as socializing or feeding); eliciting a visible startle response or aggressive behavior (such as tail/fin slapping or jaw clapping); avoidance of areas where sound sources are located. Pinnipeds may increase their haul out time, possibly to avoid in-water disturbance (Thorson and Reyff, 2006).

Behavioral responses to sound are highly variable and context-specific and any reactions depend on numerous intrinsic and extrinsic factors (

e.g.,

species, state of maturity, experience, current activity, reproductive state, auditory sensitivity, time of day), as well as the interplay between factors (

e.g.,

Richardson

et al.,

1995; Wartzok

et al.,

2004; Southall

et al.,

2007, 2019; Weilgart, 2007; Archer

et al.,

2010, Erbe

et al.,

2019). Behavioral reactions can vary not only among individuals but also within an individual, depending on previous experience with a sound source, context, and numerous other factors (Ellison

et al.,

2012), and can

vary depending on characteristics associated with the sound source (

e.g.,

whether it is moving or stationary, number of sources, distance from the source). In general, pinnipeds seem more tolerant of, or at least habituate more quickly to, potentially disturbing underwater sound than do cetaceans and generally seem to be less responsive to exposure to industrial sound than most cetaceans. Please see appendices B and C of Southall

et al.

(2007) and Gomez

et al.

(2016) for reviews of studies involving marine mammal behavioral responses to sound.

Habituation can occur when an animal's response to a stimulus wanes with repeated exposure, usually in the absence of unpleasant associated events (Wartzok

et al.,

2004). Animals are most likely to habituate to sounds that are predictable and unvarying. It is important to note that habituation is appropriately considered as a “progressive reduction in response to stimuli that are perceived as neither aversive nor beneficial,” rather than as, more generally, moderation in response to human disturbance (Bejder

et al.,

2009). The opposite process is sensitization, when an unpleasant experience leads to subsequent responses, often in the form of avoidance, at a lower level of exposure.

As noted above, behavioral state may affect the type of response. For example, animals that are resting may show greater behavioral change in response to disturbing sound levels than animals that are highly motivated to remain in an area for feeding (Richardson

et al.,

1995; Wartzok

et al.,

2004; National Research Council (NRC), 2005). Controlled experiments with captive marine mammals have showed pronounced behavioral reactions, including avoidance of loud sound sources (Ridgway

et al.,

1997; Finneran

et al.,

2003). Observed responses of wild marine mammals to loud pulsed sound sources (

e.g.,

seismic airguns) have been varied but often consist of avoidance behavior or other behavioral changes (Richardson

et al.,

1995; Morton and Symonds, 2002; Nowacek

et al.,

2007).

Available studies show wide variation in response to underwater sound; therefore, it is difficult to predict specifically how any given sound in a particular instance might affect marine mammals perceiving the signal (

e.g.,

Erbe

et al.,

2019). If a marine mammal does react briefly to an underwater sound by changing its behavior or moving a small distance, the impacts of the change are unlikely to be significant to the individual, let alone the stock or population. However, if a sound source displaces marine mammals from an important feeding or breeding area for a prolonged period, impacts on individuals and populations could be significant (

e.g.,

Lusseau and Bejder, 2007; Weilgart, 2007; NRC, 2005). However, there are broad categories of potential response, which we describe in greater detail here, that include alteration of dive behavior, alteration of foraging behavior, effects to breathing, interference with or alteration of vocalization, avoidance, and flight.

Changes in dive behavior can vary widely and may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive (

e.g.,

Frankel and Clark, 2000; Costa

et al.,

2003; Ng and Leung, 2003; Nowacek

et al.,

2004; Goldbogen

et al.,

2013a, 2013b, Blair

et al.,

2016). Variations in dive behavior may reflect interruptions in biologically significant activities (

e.g.,

foraging) or they may be of little biological significance. The impact of an alteration to dive behavior resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure and the type and magnitude of the response.

Disruption of feeding behavior can be difficult to correlate with anthropogenic sound exposure, so it is usually inferred by observed displacement from known foraging areas, the appearance of secondary indicators (

e.g.,

bubble nets or sediment plumes) or changes in dive behavior. However, acoustic and movement bio-logging tools have been used in some cases, to infer responses of feeding to anthropogenic noise. For example, Blair

et al.

(2016) reported significant effects on humpback whale foraging behavior in Stellwagen Bank in response to ship noise including slower descent rates, and fewer side-rolling events per dive with increasing ship nose. In addition, Wisniewska

et al.

(2018) reported that tagged harbor porpoises demonstrated fewer prey capture attempts when encountering occasional high-noise levels resulting from vessel noise as well as more vigorous fluking, interrupted foraging, and cessation of echolocation signals observed in response to some high-noise vessel passes.

In response to playbacks of vibratory pile driving sounds, captive bottlenose dolphins showed changes in target detection and number of clicks used for a trained echolocation task (Branstetter

et al.

2018). Similarly, harbor porpoises trained to collect fish during playback of impact pile driving sounds also showed potential changes in behavior and task success, though individual differences were prevalent (Kastelein

et al.

2019d). As for other types of behavioral response, the frequency, duration, and temporal pattern of signal presentation, as well as differences in species sensitivity, are likely contributing factors to differences in response in any given circumstance (

e.g.,

Croll

et al.,

2001; Nowacek

et al.,

2004; Madsen

et al.,

2006; Yazvenko

et al.,

2007). A determination of whether foraging disruptions incur fitness consequences would require information on or estimates of the energetic requirements of the affected individuals and the relationships among prey availability, foraging effort and success, and the life history stage(s) of the animal.

Variations in respiration naturally vary with different behaviors and alterations to breathing rate as a function of acoustic exposure can be expected to co-occur with other behavioral reactions, such as a flight response or an alteration in diving. However, respiration rates in and of themselves may be representative of annoyance or an acute stress response. Various studies have shown that respiration rates may either be unaffected or could increase, depending on the species and signal characteristics, again highlighting the importance in understanding species differences in the tolerance of underwater noise when determining the potential for impacts resulting from anthropogenic sound exposure (

e.g.,

Kastelein

et al.,

2001, 2005, 2006; Gailey

et al.,

2007). For example, harbor porpoise' respiration rate increased in response to pile driving sounds at and above a received broadband SPL of 136 dB (zero-peak SPL: 151 dB re 1 μPa; SEL of a single strike: 127 dB re 1 μPa

2

-s) (Kastelein

et al.,

2013).

Avoidance is the displacement of an individual from an area or migration path as a result of the presence of a sound or other stressors, and is one of the most obvious manifestations of disturbance in marine mammals (Richardson

et al.,

1995). For example, gray whales are known to change direction—deflecting from customary migratory paths—in order to avoid noise from seismic surveys (Malme

et al.,

1984). In response to construction noise from offshore wind farms, harbor porpoises and harbor seals have demonstrated avoidance on the scale of hours to weeks (Brandt et al., 2018; Russell et al., 2016). Avoidance may be short-term, with animals returning to the area once the noise has ceased (

e.g.,

Bowles

et al.,

1994; Goold, 1996; Stone et al., 2000; Morton and Symonds, 2002; Gailey

et al.,

2007). Longer-term displacement is possible, however, which may lead to changes in abundance or distribution patterns of

the affected species in the affected region if habituation to the presence of the sound does not occur (

e.g.,

Blackwell

et al.,

2004; Bejder

et al.,

2006; Teilmann

et al.,

2006).

A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. The flight response differs from other avoidance responses in the intensity of the response (

e.g.,

directed movement, rate of travel). Relatively little information on flight responses of marine mammals to anthropogenic signals exist, although observations of flight responses to the presence of predators have occurred (Connor and Heithaus, 1996; Bowers

et al.,

2018). The result of a flight response could range from brief, temporary exertion and displacement from the area where the signal provokes flight to, in extreme cases, marine mammal strandings (England

et al.,

2001). However, it should be noted that response to a perceived predator does not necessarily invoke flight (Ford and Reeves, 2008), and whether individuals are solitary or in groups may influence the response.

Behavioral disturbance can also impact marine mammals in more subtle ways. Increased vigilance may result in costs related to diversion of focus and attention (

i.e.,

when a response consists of increased vigilance, it may come at the cost of decreased attention to other critical behaviors such as foraging or resting). These effects have generally not been demonstrated for marine mammals, but studies involving fishes and terrestrial animals have shown that increased vigilance may substantially reduce feeding rates (

e.g.,

Beauchamp and Livoreil, 1997; Fritz

et al.,

2002; Purser and Radford, 2011). In addition, chronic disturbance can cause population declines through reduction of fitness (

e.g.,

decline in body condition) and subsequent reduction in reproductive success, survival, or both (

e.g.,

Harrington and Veitch, 1992; Daan

et al.,

1996; Bradshaw

et al.,

1998). However, Ridgway

et al.

(2006) reported that increased vigilance in bottlenose dolphins exposed to sound over a 5-day period did not cause any sleep deprivation or stress effects.

Many animals perform vital functions, such as feeding, resting, traveling, and socializing, on a diel cycle (24-hour cycle). Disruption of such functions resulting from reactions to stressors such as sound exposure are more likely to be significant if they last more than one diel cycle or recur on subsequent days (Southall

et al.,

2007). Consequently, a behavioral response lasting less than 1 day and not recurring on subsequent days is not considered particularly severe unless it could directly affect reproduction or survival (Southall

et al.,

2007). Note that there is a difference between multi-day substantive (

i.e.,

meaningful) behavioral reactions and multi-day anthropogenic activities. For example, just because an activity lasts for multiple days does not necessarily mean that individual animals are either exposed to activity-related stressors for multiple days or, further, exposed in a manner resulting in sustained multi-day substantive behavioral responses.

Behavioral Reactions Observed at the POA.

Specific to recent construction at the POA, behavioral reactions to pile driving have not been reported in non-CIBW species. During POA's PCT construction, 81 harbor seals were observed within estimated Level B harassment zones associated with vibratory and impact installation and removal of 36-in (61-cm) and 144-in (366-cm) piles, and 5 harbor seals were observed within estimated Level A harassment zones during the installation of 144-in (366-cm) piles. No observable behavioral reactions were observed in any of these seals (61N Environmental, 2021, 2022a). One harbor porpoise was observed within the estimated Level B harassment zone during vibratory driving of a 36-in (61-cm) pile in May 2021. The animal was traveling at a moderate pace. No observable reactions to pile driving were noted by the PSOs. Another harbor porpoise near the border of (and may have been within) the estimated Level B harassment zone during the impact installation of 36-in (61-cm) piles in June 2021, but PSOs did not record any behavioral responses of this individual to the pile driving activities. Similarly 13 harbor seals observed within estimated Level B harassment zones associated with pile driving 36-in (61-cm) piles during POA's SFD construction did not exhibit observable behavioral reactions (61N Environmental, 2022b).

Specific to CIBWs, several years of marine mammal monitoring data demonstrate behavioral responses to pile driving at the POA. Previous pile driving activities at the POA include the installation and removal of sheet piles, the vibratory and impact installation of 24-in (61-cm), 36-in (91-cm), 48-in (122-cm), and 144-in (366-cm) pipe piles, and the vibratory installation of 72-in (182-cm) air bubble casings.

Kendall and Cornick (2015) provide a comprehensive overview of 4 years of scientific marine mammal monitoring conducted before (2005-2006) and during the POA's MTRP (2008-2009). These were observations made by biologists at Alaska Pacific University, funded by the POA and other groups but independent of the POA's required monitoring for pile driving activities (

i.e.,

not construction based PSOs). The authors investigated CIBW behavior before and during pile driving activity at the POA. Sighting rates, mean sighting duration, behavior, mean group size, group composition, and group formation were compared between the two periods. A total of about 2,329 hours of sampling effort was completed across 349 days from 2005 to 2009. Overall, 687 whales in 177 groups were documented during the 69 days that whales were sighted. A total of 353 and 1,663 hours of pile driving took place in 2008 and 2009, respectively. There was no relationship between monthly CIBW sighting rates and monthly pile driving rates (

r

= 0.19,

p

= 0.37). Sighting rates before (n = 12; 0.06 ± 0.01) and during (n = 13; 0.01 ± 0.03) pile driving were not significantly different. However, sighting duration of CIBWs decreased significantly during pile driving (39 ± 6 min before and 18 ± 3 min during). There were also significant differences in behavior before versus during pile driving. CIBWs primarily traveled through the study area both before and during pile driving; however, traveling increased relative to other behaviors during pile driving. Documentation of milling was observed on 21 occasions during pile driving. Mean group size decreased during pile driving; however, this difference was not statistically significant. In addition, group composition was significantly different before and during pile driving, with more white (

i.e.,

likely older) animals being present during pile driving (Kendall and Cornick, 2015). CIBWs were primarily observed densely packed before and during pile driving; however, the number of densely packed groups increased by approximately 67 percent during pile driving. There were also significant increases in the number of dispersed groups (approximately 81 percent) and lone white whales (approximately 60 percent) present during pile driving than before pile driving (Kendall and Cornick, 2015).

During PCT and SFD construction monitoring, behaviors of CIBWs groups were compared by month and by construction activity (61N Environmental, 2021, 2022a, 2022b). Little variability was evident in the behaviors recorded from month to month or among sightings that coincided with in-water pile installation and removal and those that did not (61N Environmental, 2021, 2022a). Definitive behavioral reactions to in-water pile

driving or avoidance behaviors were not documented; however, potential reactions (where a group reversed its trajectory shortly after the start of in-water pile driving occurred; a group reversed its trajectory as it got closer to the sound source during active in-water pile driving; or upon an initial sighting, a group was already moving away from in-water pile driving, raising the possibility that it had been moving towards, but was only sighted after they turned away) and instances where CIBWs moved toward active in-water pile driving were recorded. During these instances, impact driving appeared to cause potential behavioral reactions more readily than vibratory hammering (61N Environmental, 2021, 2022a, 2022b). One minor difference documented during PCT construction was a slightly higher incidence of milling behavior and diving during the periods of no pile driving and slightly higher rates of traveling behavior during periods when potential CIBW behavioral reactions to pile driving, as described above, were recorded (61N Environmental, 2021, 2022a). Note, narratives of each CIBW reaction can be found in the appendices of the POA's final monitoring reports (61N Environmental, 2021, 2022a, 2022b).

Acoustically, Saxon-Kendall

et al.

(2013) recorded echolocation clicks (which can be indicative of feeding behavior) during the MTR Project at the POA both while pile driving was occurring and when it was not. This indicates that while feeding is not a predominant behavior that PSOs visually observed in CIBWs sighted near the POA (61N Environmental, 2021, 2022a, 2022b, 2022c; Easley-Appleyard and Leonard, 2022) CIBWs can and still exhibit feeding behaviors during pile driving activities. In addition, Castellote

et al.

(2020) found low echolocation detection rates in lower Knik Arm (

i.e.,

Six Mile, Port MacKenzie, and Cairn Point) and suggested

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