76576 Federal Register / Vol. 88, No. 213 / Monday, November 6, 2023 / Notices 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XD366] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to the Port of 

Alaska’s North Extension Stabilization 

Step 1 (NES1) Project in Anchorage, 

Alaska 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; proposed incidental 

harassment authorization; request for 

comments on proposed authorization 

and possible renewal. 

SUMMARY: NMFS has received a request 

from the Port of Alaska (POA) for 

authorization to take marine mammals 

incidental to the NES1 project at the 

existing port facility in Anchorage, 

Alaska. Pursuant to the Marine Mammal 

Protection Act (MMPA), NMFS is 

requesting comments on its proposal to 

issue an incidental harassment 

authorization (IHA) to incidentally take 

marine mammals during the specified 

activities. NMFS is also requesting 

comments on a possible one-time, 1- 

year renewal that could be issued under 

certain circumstances and if all 

requirements are met, as described in 

the Request for Public Comments 

section at the end of this notice. NMFS 

will consider public comments prior to 

making any final decision on the 

issuance of the requested MMPA 

authorization and agency responses will 

be summarized in the final notice of our 

decision. 

DATES: Comments and information must 

be received no later than December 5, 

2023. 

ADDRESSES: Comments should be 

addressed to Jolie Harrison, Chief, 

Permits and Conservation Division, 

Office of Protected Resources, National 

Marine Fisheries Service and should be 

submitted via email to 

ITP.tyson.moore@noaa.gov. 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/national/ 

marine-mammal-protection/incidentaltake-authorizations-constructionactivities. In case of problems accessing 

these documents, please call the contact 

listed above. 

Instructions: NMFS is not responsible 

for comments sent by any other method, 

to any other address or individual, or 

received after the end of the comment 

period. Comments, including all 

attachments, must not exceed a 25- 

megabyte file size. All comments 

received are a part of the public record 

and will generally be posted online at 

https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

incidental-take-authorizationsconstruction-activities without change. 

All personal identifying information 

(e.g., name, address) voluntarily 

submitted by the commenter may be 

publicly accessible. Do not submit 

confidential business information or 

otherwise sensitive or protected 

information. 

FOR FURTHER INFORMATION CONTACT: 

Reny Tyson Moore, Office of Protected 

Resources, NMFS, (301) 427–8401. 

SUPPLEMENTARY INFORMATION: 

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 

proposed or, if the taking is limited to 

harassment, a notice of a proposed IHA 

is provided to the public for review. 

Authorization for incidental takings 

shall be granted if NMFS finds that the 

taking will have a negligible impact on 

the species or stock(s) and will not have 

an unmitigable adverse impact on the 

availability of the species or stock(s) for 

taking for subsistence uses (where 

relevant). Further, NMFS must prescribe 

the permissible methods of taking and 

other ‘‘means of effecting the least 

practicable adverse impact’’ on the 

affected species or stocks and their 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance, and on the 

availability of the species or stocks for 

taking for certain subsistence uses 

(referred to in shorthand as 

‘‘mitigation’’); and requirements 

pertaining to the mitigation, monitoring 

and reporting of the takings are set forth. 

The definitions of all applicable MMPA 

statutory terms cited above are included 

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 review our 

proposed action (i.e., the issuance of an 

IHA) with respect to potential impacts 

on the human environment. 

Accordingly, NMFS has prepared an 

Environmental Assessment (EA) to 

consider the environmental impacts 

associated with the issuance of the 

proposed IHA. NMFS’ EA is available at 

https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

incidental-take-authorizationsconstruction-activities. We will review 

all comments submitted in response to 

this notice prior to concluding our 

NEPA process or making a final 

decision on the IHA request. 

Summary of Request 

On July 19, 2022, NMFS received a 

request from the POA for an IHA to take 

marine mammals incidental to 

construction activities related to the 

NES1 project in Anchorage, Alaska. 

Following NMFS’ review of the 

application, the POA submitted revised 

versions on December 27, 2022, July 28, 

2023, and August 31, 2023. The 

application was deemed adequate and 

complete on September 7, 2023. The 

POA submitted a final version 

addressing additional minor corrections 

on September 21, 2023. The POA’s 

request is for take of seven species of 

marine mammals by Level B harassment 

and, for a subset of these species (i.e., 

harbor seal (Phoca vitulina) and harbor 

porpoise (Phocoena phocoena)), Level A 

harassment. Neither the POA nor NMFS 

expect serious injury or mortality to 

result from this activity and, therefore, 

an IHA is appropriate. 

NMFS previously issued IHAs to the 

POA for similar work (85 FR 19294, 

April 6, 2020; 86 FR 50057, September 

7, 2021). 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 section of 

this notice and online at https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-constructionactivities. 

This proposed IHA would cover 1 

year of the ongoing Port of Alaska 

Modernization Program (PAMP) for 

which the POA obtained prior IHAs and 

intends to request additional take 

authorization for subsequent facets of 

the program. The PAMP involves 

construction activities related to the 


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Federal Register / Vol. 88, No. 213 / Monday, November 6, 2023 / Notices 76577 

modernization of the POAs marine 

terminals. 

Description of Proposed Activity 

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 North Extension at the 

POA is a failed bulkhead structure that 

was constructed between 2005 and 

2011. Parts of the North Extension 

bulkhead structure and the surrounding 

upland area are unstable and collapsing, 

and some of the sheet piles are visibly 

twisted and buckled. The structure 

presents safety hazards and logistical 

impediments to ongoing Port 

operations, and much of the upland area 

is currently unusable. The NES project 

would result in removal of the failed 

sheet pile structure and reconfiguration 

and realignment of the shoreline within 

the North Extension, including the 

conversion of approximately 0.05 square 

kilometers (km2; 13 acres) of developed 

land back to intertidal and subtidal 

habitat within Knik Arm. The NES 

project would be completed in two 

distinct steps, NES1 and NES2, 

separated by multiple years and 

separate permitting efforts. This notice 

is applicable to a proposed IHA for the 

incidental take of marine mammals 

during in-water construction associated 

with NES1. 

The NES1 project would involve the 

removal of portions of the failed sheet 

pile structure to stabilize the North 

Extension. The POA anticipates this 

project would begin on April 1, 2024 

and extend through November 2024. 

They estimate that work would occur 

over approximately 250 hours on 110 

nonconsecutive days. The NES1 project 

would remove approximately half of the 

North Extension structure extending 

approximately 274 meters (m) north 

from the southern end of the North 

Extension. This project would also 

stabilize the remaining portion of the 

North Extension by creating an end-state 

embankment. In-water construction 

associated with this project includes 

vibratory installation and removal of 81 

24-inch (61-centimeter (cm)) or 36-inch 

(91-cm) temporary steel pipe stability 

template piles and vibratory removal, 

pile splitting and pile cutting (and 

possible impact removal) of 

approximately 4,216 sheet piles from 

the structure tailwalls, cell faces 

(bulkhead), and closure walls. Sound 

produced by these construction 

activities may result in the take of 

marine mammals, by harassment only. 

Dates and Duration 

The POA anticipates that NES1 inwater construction activities would 

begin on April 1, 2024 and extend 

through November 2024. In-water pile 

installation and removal associated with 

the NES1 project is anticipated to take 

place over approximately 246.5 hours 

on 110 nonconsecutive days between 

these dates (see table 1 for estimated 

production rates and durations). While 

the exact sequence of demolition and 

construction is uncertain, an estimated 

schedule of sheet pile removal and 

temporary stability template pile 

installation and removal is shown in 

Table 2. 

TABLE 1—PILE INSTALLATION AND REMOVAL METHODS AND ESTIMATED DURATIONS

Pile type Pile size Structural feature 

Total 

estimated 

number of 

piles 

Estimated 

number of 

piles in 

the water 

Average vibratory and/or 

splitter 

duration 

Maximum 

impact 

strikes 

per day 

Total 

duration of 

removal 

and 

installation 

in water 

(hours) 

Average 

production 

rate, piles 

per day 

(range) 

Estimated 

number of 

days 

PS 27.5 and PS 

31 Sheets.

19.69 inches 

(50 cm).

Tailwalls .......... 3,536 2,267 2 hours/day ..... 150 157 50 (10 to 100) 46 

PS 27.5 and PS 

31 Sheets.

19.69 inches 

(50 cm).

Cell Faces 

(Bulkhead).

568 568 2 hours/day ..... 150 41 30 (10 to 60) 19 

PZC26 Sheets 27.88 inches 

(70 cm).

Closure Walls 110 110 2 hours/day ..... 150 8 50 (10 to 100) 3 

Steel Pipe ........ 24- or 36-inch 

(61- or 91- 

cm) install.

Temporary Stability Templates.81 81 15 min/pile ....... 0 20.25 4 (2 to 10) 21 

Steel Pipe ........ 24- or 36-inch 

(61- or 91- 

cm) removal.

Temporary Stability Templates.81 81 15 min/pile ....... 0 20.25 4 (2 to 10) 21 

Total ......... ......................... ......................... .................... .................... ......................... .................... 246.5 .............................. 110 

Note: cm = centimeter(s). 

TABLE 2—ESTIMATED TIMING AND DURATION BY MONTH OF PILE INSTALLATION AND REMOVAL ACTIVITIES

Activity April May June July August September October November Total 

36-inch (91-cm) or 24-inch (61- 

cm) stability template pile installation: 

Piles ................................... 27 14 14 10 10 3 3 0 81 

Hours .................................. 6.75 3.50 3.50 2.5 2.5 0.75 0.75 0 20.25 

36-inch (91-cm) or 24-inch 

(61.cm) stability template pile 

removal: 

Piles ................................... 0 27 13 13 13 10 4 1 81 

Hours .................................. 0 6.75 3.25 3.25 3.25 2.5 1 0.25 20.25 

Sheet pile vibratory hammer removal: 

Piles ................................... .................... .................... .................... .................... .................... .................... .................... .................... ....................

Hours .................................. 10 45 60 60 13 10 4 2 206 

Total hours .................. 16.75 55.25 66.75 65.75 18.75 15.25 5.75 2.25 246.50 


ddrumheller on DSK120RN23PROD with NOTICES2
76578 Federal Register / Vol. 88, No. 213 / Monday, November 6, 2023 / Notices 

The POA has presented this schedule 

using the best available information 

derived from what is known of the 

North Extension Site and the POA’s 

experience with similar construction 

and demolition projects. The POA plans 

to conduct as much work as possible 

prior to August through October, when 

there is higher Cook Inlet beluga whale 

(CIBW; Delphinapterus leucas) 

abundance. However, as described 

below, due to the instability of the 

North Extension site, it is important that 

the POA attempt to complete the NES1 

in a single construction season, which 

may necessitate work in August through 

October. Potential consequences of 

pausing the construction season (i.e., 

stopping work from August through 

October) include de-rating the structural 

capacity of existing POA docks, a 

shutdown of dock operations due to 

deteriorated conditions, or an actual 

collapse of one or more dock structures. 

The potential for collapse increases with 

schedule delays, due to both worsening 

deterioration and the higher probability 

of a significant seismic event. 

A typical construction season at the 

POA extends from approximately midApril 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. 

Due to the design of the existing sheet 

pile wall, demolition must occur in a 

sequential and uninterrupted manner to 

prevent structural failure of the wall as 

demolition progresses. This safety 

requirement limits the POA’s ability to 

re-sequence in-water sheet pile 

extraction and temporary pile 

installation, as the already compromised 

bulkhead structure may become further 

destabilized. The POA therefore plans to 

complete all work between April and 

November 2024, and requests an IHA for 

the NES1 project for 1 year that is 

effective as of April 1, 2024. All piledriving would occur during daylight 

hours. 

Specific Geographic Region 

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). Knik Arm 

and Turnagain Arm are the two 

branches of upper Cook Inlet, and 

Anchorage is located where the two 

arms join. 

Cook Inlet is a large tidal estuary that 

exchanges waters at its mouth with the 

Gulf of Alaska. The inlet is roughly 

20,000 km2 in area, with approximately 

1,350 linear kilometer (km) of coastline 

(Rugh et al., 2000) and an average depth 

of approximately 100 m. Cook Inlet is 

generally divided into upper and lower 

regions by the East and West Forelands. 

Freshwater input to Cook Inlet comes 

from snowmelt and rivers, many of 

which are glacially fed and carry high 

sediment loads. Currents throughout 

Cook Inlet are strong and tidally 

periodic, with average velocities ranging 

from 3 to 6 knots (Sharma and Burrell, 

1970). Extensive tidal mudflats occur 

throughout Cook Inlet, especially in the 

upper reaches, and are exposed at low 

tides. 

Cook Inlet is a seismically active 

region susceptible to earthquakes and 

has some of the highest tides in North 

America (NOAA, 2015) that drive 

surface circulation. Cook Inlet contains 

substantial quantities of mineral 

resources, including coal, oil, and 

natural gas. During winter, sea, beach, 

and river ice are dominant physical 

forces within Cook Inlet. In upper Cook 

Inlet, sea ice generally forms in October 

to November, and continues to develop 

through February or March (Moore et 

al., 2000). 

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 

fresh water 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). 

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). 

Maximum current speeds in Knik Arm, 

observed during spring ebb tide, exceed 

7 knots. 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 POA’s boundaries currently 

occupy an area of approximately 0.52 

km2. 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 km2 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) 


ddrumheller on DSK120RN23PROD with NOTICES2
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to nearby Port MacKenzie (west side) is 

approximately 4.9 km. 

Detailed Description of the Specified 

Activity 

The POA, located on Knik Arm in 

upper Cook Inlet (Figure 1), provides 

critical infrastructure for the citizens of 

Anchorage and a majority of the citizens 

of Alaska. Marine-side infrastructure 

and facilities at the POA were 

constructed largely in the 1960s and 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. 


ddrumheller on DSK120RN23PROD with NOTICES2
76580 Federal Register / Vol. 88, No. 213 / Monday, November 6, 2023 / Notices 

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: NES1; 

• Phase 2B: General Cargo Terminals 

Replacement (construction planned to 

begin in 2025); 

• Phase 3: Petroleum, Oil and 

Lubricants Terminal 2 Replacement; 

• Phase 4: NES2; and 

• Phase 5: Demolition of Terminal 3. 


ddrumheller on DSK120RN23PROD with NOTICES2EN06NO23.054</GPH>

Figure 1 -- Overview of North Extension Stabilization 1 

__ NES1 Bathymetric Grade of 

Slope in Front of Revetment 

Soil Improvement Area 

LJ NES1 Surface Boundary 

I I I 

0 125 250 Meters 
Federal Register / Vol. 88, No. 213 / Monday, November 6, 2023 / Notices 76581 

Phase 1 of the PAMP was completed 

in 2022. IHAs were issued by NMFS for 

both the PCT (Phase 1 and Phase 2; 85 

FR 19294, April 6, 2020) and SFD 

projects associated with this Phase (86 

FR 50057, September 7, 2021). The NES 

Project would be completed in two 

distinct steps, NES1 and NES2, 

separated by multiple years and 

separate permitting efforts. The project 

discussed herein, NES1, is Phase 2A of 

the PAMP. Ground improvements work 

in preparation for NES1 began in 2023, 

and on-shore and in-water work for 

NES1 is planned to commence in April 

2024. 

The North Extension (the area north 

of the existing general cargo docks) was 

constructed in 2005–2011 under the 

Port Intermodal Expansion Project 

(PIEP), the predecessor effort to the 

PAMP. The POA considers the North 

Extension a failed structure. Parts of the 

North Extension bulkhead structure and 

the surrounding upland area are 

unstable and collapsing, and some of 

the sheet piles are visibly twisted and 

buckled. The structure presents safety 

hazards and logistical impediments to 

ongoing Port operations, and much of 

the upland area is currently unusable. 

The currently proposed NES Project 

overall would result in removal of the 

failed sheet pile structure and 

reconfiguration and realignment of the 

shoreline within the North Extension. 

NES1 would include the conversion of 

approximately 0.05 km2 (13 acres) of 

developed land back to intertidal and 

subtidal habitat within Knik Arm. While 

the majority of the Project will be 

demolition work, the term 

‘‘construction’’ as used herein refers to 

both construction and demolition work. 

The purpose of the NES Project is to 

stabilize the previously failed North 

Extension bulkhead structure and create 

a new shoreline that is structurally and 

seismically stable and balances the 

preservation of uplands created in the 

past while addressing the formation of 

unwanted sedimentation within the 

U.S. Army Corps of Engineers (USACE) 

Anchorage Harbor. The NES Project will 

also improve safety for maneuvering 

vessels at the northern berths. Previous 

establishment of the North Extension 

changed the hydrodynamics of the area 

and resulted in more rapid 

accumulation of sediments at the 

existing cargo dock faces, as well as a 

smaller turning area for vessels. The 

Municipality of Anchorage and the POA 

have identified the NES Project as a 

priority for the PAMP, due to the impact 

of the existing structure’s geometry 

upon the USACE Anchorage Harbor 

Project, mariners’ concerns regarding 

impacts to safe ship-berthing operations, 

and engineering concerns regarding 

structural and geotechnical stability of 

the system. The existing structure poses 

significant risk for continued 

deterioration and could result in 

significant release of impounded fill 

material into the Port’s vessel operating 

and mooring areas, and into the USACE 

Anchorage Harbor Project. Accordingly, 

a significant portion of the NES work 

has been designated for inclusion in 

NES1 as Phase 2A PAMP efforts, 

specifically those portions of the 

existing structure that are closest to the 

north end of the existing cargo 

terminals. Creation of a safe and stable 

uplands area will support POA 

operations while also addressing 

concerns of adverse impacts upon the 

Federal Navigation Channel and 

Dredging Program. 

Existing North Extension Structure 

The existing North Extension 

bulkhead structure is an OPEN CELL 

SHEET PILE (OCSP) design. Demolition 

of the existing OCSP structure will 

include removal and disposal of the 

southerly OCSP bulkhead walls and 

associated backlands. The OCSP 

bulkhead is a retaining structure filled 

with soil that is composed of 29 

interconnected open cells, each 

approximately 8 m wide, with 30 

tailwalls that are up to 61 m long (see 

Figure 1–3 in the POA’s application). 

Each cell is about 20 sheets wide across 

the face, which is along the water. Each 

tailwall consists of approximately 118 

sheet piles that extend landward into 

the filled area, orthogonal to the sheet 

piles along the face (table 1). The sheet 

piles interlock through a series of 

thumb-finger joints or interlocks (where 

two sheet piles are connected along 

their length; see Figure 1–5 in the POA’s 

application) along the cell faces and 

tailwalls. Wye joints occur where three 

sheet piles are connected at the interface 

between two neighboring sheet pile cell 

faces and the adjoining tailwall (see 

Figure 1–6 in the POA’s application). 

Two z-pile closure walls close the gaps 

between structures, one on each end of 

the bulkhead (see Figure 1–4 in the 

POA’s application). The total number of 

sheet piles in the existing structure that 

would be removed is approximately 

4,216, although the exact number of 

sheet piles in the existing structure is 

not known with certainty. 

Demolition of the failed sheet pile 

structure would be accomplished 

through excavation and dredging of 

impounded soils (fill material), and 

cutting and removal of the existing sheet 

piles, most likely through use of a 

splitter and vibratory hammer. 

Demolition of the OCSP cell 

components would not commence until 

ground improvements necessary to 

protect the horizontal to vertical ratio 

(H:V) of 2H:1V embankment slope have 

been completed. Ground improvements 

were scheduled for 2023 and are 

underway. The sequencing of in-water 

events, including how construction 

would proceed while maintaining 

stability among the structure’s cells, is 

unknown. It is anticipated that the 

actual methods, including types of 

equipment and numbers of hours and 

days of each activity, would be 

determined based on the engineering 

specifications for the NES1 project as 

determined by the Construction 

Contractor and the Design Build Team 

designer of record (DOR). The NES1 

DOR and Construction Contractor have 

been selected by the POA, but their 

Construction Work Plan has not yet 

been completed and some actual 

construction techniques are likely to be 

refined adaptively as construction 

advances due to the stability risk of the 

existing impounded materials. The 

following project description is based 

on the best available information at this 

time considering the POA’s knowledge 

of the condition of the North Extension 

and their experience with similar 

marine construction and demolition 

projects, which NMFS has determined 

sufficient for the purposes of the IHA 

application. 

NES1 Project Activities 

The NES1 Project would result in a 

reconfiguration and realignment of the 

shoreline through removal of portions of 

the failed sheet pile structure to 

stabilize the North Extension. Before 

NES1 commences, the upland area 

would be prepared with ground 

improvements to stabilize the existing 

fill. Ground improvements will take 

place in the dry, landward of the 

existing failed sheet pile structure and 

underneath the area where filter rock 

and armor rock would later be placed to 

stabilize the new shoreline. Ground 

improvement work began in 2023. 

Construction of NES1 will include 

completion of the following tasks: 

• Dredging and offshore disposal of 

approximately 1.35 million cubic yards 

(CY) of material down to ¥12 m MLLW; 

• Excavation of 115,000 CY of 

material; 

• Demolition and removal of the 

failed existing sheet pile structure; and 

• Shoreline stabilization including 

placement of granular fill, filter rock, 

and armor rock along the new face of 

the shoreline. 

NES1 would remove approximately 

half of the North Extension structure 

extending approximately 274 m north 


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from the southern end of the North 

Extension. NES1 would also stabilize 

the remaining portion of the North 

Extension by creating an end-state 

embankment with a top elevation of +12 

m MLLW, sloping to a toe elevation of 

approximately ¥12 m MLLW. The 

lower portion of the embankment slope 

from ¥12 m MLLW to approximately 0 

m MLLW would be constructed with a 

6H:1V slope and would be unarmored. 

A grade-break would occur above these 

elevations as the slope will transition to 

a 2H:1V slope armored rock revetment. 

At the cell faces, the depth of the face 

wall sections varies, with most 

extending from a tip elevation of 

approximately ¥60 MLLW to a cutoff 

elevation of approximately +9 m MLLW 

(27 m long). The mudline at the face 

sheets varies but is thought to be at 

approximately ¥11 m MLLW. This 

translates into a requirement to 

demolish sheet piles approximately 25 

m high from the ¥14-m MLLW 

elevation to the top of the containment. 

Demolition of the failed sheet pile 

structure would be accomplished 

through excavation and dredging of 

impounded soils (fill material), and 

cutting and removal of the existing sheet 

piles. Approximately 1,465,000 CY of 

material would be removed. The 

material removed from excavation 

(115,000 CY) would be stockpiled in the 

North Extension area for future use, 

while the dredged material (1,350,000 

CY) would be disposed of offshore into 

the Anchorage Harbor Open Water 

Disposal Site, which is the authorized 

USACE offshore disposal area used by 

the POA under USACE permit POA– 

2003–00503–M20. 

The NES1 Project in-water work 

would begin with landside excavation 

and in-water dredging along the south 

shoreline and south half of the failed 

sheet pile structure. Any methodology 

considered for cutting and removing the 

steel sheet piles would account for 

worker safety, constructability, and 

minimization of potential acoustic 

impacts that the operation may have on 

marine mammals. The first attempt 

would be to extract the sheet piles with 

direct vertical pulling or with a 

vibratory hammer; however, there may 

be complications with the sheet pile 

interlocks, which could become seized, 

and other means of pile removal may be 

required (i.e. shearing or torching). 

Demolition activities would begin with 

the south half of the existing structure, 

followed by the north half of NES1 (see 

Figure 1–8 in the POA’s application). 

The majority of the demolition work 

would occur from the water side to 

eliminate safety hazards from 

unexpected movements of fill material 

or the sheet piles themselves. The 

demolition plan also includes 

stabilization of the face sheets through 

installation of temporary piles and 

dredging back into the cell to relieve 

pressure on the sheet piles and to 

eliminate any release of material into 

Cook Inlet beyond natural tidal forces. 

Safety is a top priority regarding 

planning and executing the work. There 

are several risks at the project site to 

consider when planning demolition 

activities, such as strong currents and 

large tidal swings. Existing sheet piles 

and their interlocks are in poor 

condition. Many of the sheets may be 

damaged and bound up, making 

removal difficult. There are stability 

concerns with the failed OCSP 

structure, where the POA would have to 

closely manage allowable fill 

differentials between adjacent cells and 

loading on the face sheets. In-water 

NES1 activities and quantities are 

summarized in Table 3 (NES1 activities 

to be completed on land are 

summarized in table 1–2 in the POA’s 

application). 

TABLE 3—SUMMARY OF IN-WATER NES1 PROJECT STAGES, ACTIVITIES, AND APPROXIMATE QUANTITIES

Type of activity Size and type Total anticipated amount 

or number 

Dredging of fill material ............................................... Granular fill ................................................................ 1,350,000 CY. 

At-sea transit and disposal of dredged fill .................. Granular fill ................................................................ 1,350,000 CY. 

Cutting piles with sheet splitter (vertical) .................... 19.69-inch (50 cm) sheet piles, cut into vertical ....... Unknown.1

Cutting piles with shears or torch (horizontal) 2 .......... 19.69-inch (50 cm) sheet piles .................................. Unknown.1

Vibratory or direct pull removal of sheet piles 3 .......... 19.69-inch (50 cm) sheet piles, removed in vertical 

panels.

4,216 sheet piles. 

Installation and removal of temporary steel pipe piles 81 24- or 36-inch (61- or 91-cm) piles ...................... 81 installations, 81 removals. 

Slope construction ....................................................... Bedding, filter rock, armor stone ............................... 60,500 CY. 

1The total number of sheet piles to be cut would be a subset of the estimated 4,216 sheet piles needed to be removed. 

2 Deploying divers or underwater shear equipment would be the last resort for removing sheet piles. 

3 Most of the waterside face and tailwall sheets would be cut in the dry to improve operational safety. 

Dredging and Disposal 

Dredging would be performed with a 

derrick barge using a clamshell bucket, 

and would likely take place for 24 hours 

per day for the duration of the project. 

One barge would perform the dredging 

associated with the sheet pile removal, 

working concurrently and in support of 

the crane barge removing the sheets. 

Another barge would perform dredging 

in the remaining proposed project area. 

This barge would start with removing 

the existing armor rock on the south 

slope and work its way north behind the 

OSCP bulkhead. Dredged material 

would be placed on a dump barge and 

taken by tug boat for disposal at the 

Anchorage Harbor Open Water Disposal 

Site. 

Dredging for NES1 will take place in 

an area that has been part of a working 

port for more than 50 years, where 

dredging activities are common. Take of 

marine mammals by dredging is not 

anticipated or proposed to be authorized 

due to the low intensity and stationary 

nature of the sounds produced by 

dredging and its perennial presence 

over many years in the same general 

location near the project site. Further, 

the sounds produced by dredging are 

not meaningfully different and are 

unlikely to exceed sounds produced by 

ongoing normal industrial activities at 

the port. Lastly, mitigation measures 

described in the Proposed Mitigation 

section would ensure that direct 

physical interaction with marine 

mammals during dredging activities 

would be avoided. Therefore, dredging 

will not be considered further in this 

notice. 

Excavation 

Landside excavation would occur 

with loaders and excavators to remove 

the top portion of fill material and open 

up work for initial sheet pile cutting and 

removal. This excavation would begin 

to relieve pressure along the sheet wall 

face and expose the tops of the sheet 

piles to mitigate the risk of damaging 

sheets while dredging with a clamshell 


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bucket. The sheet piles could be more 

easily extracted if undamaged. The 

removal elevation would remain above 

+5 m MLLW in order for the land 

equipment to reach the excavation 

depth with the groundwater and tidal 

elevations and ensure that the removed 

material would be in good condition. 

The material removed would be 

stockpiled at the POA for future use. 

Excavation would occur out of water. 

Therefore, take of marine mammals 

related to excavation activities is not 

anticipated or proposed to be 

authorized, and it will not be 

considered further in this notice. 

Pile Installation and Removal 

The sheet pile removal process would 

begin with the installation of stability 

templates (steel pipe piles) along the 

face of the sheet pile structure, 

following excavation and initial 

dredging work. Once landside 

excavation has removed the top portion 

of fill along the face of the wall, the 

POA would follow behind and begin 

dredging the material within the cells 

while maintaining the allowable fill 

differential between adjacent cells to 

maintain structural integrity. Before 

dredging deeper than the allowable 

elevation determined by the engineer, a 

crane barge would install temporary 

stability templates along the face of the 

sheet pile structure. The addition of 

about 27 temporary stability templates 

would support about one-third of the 

bulkhead sheet pile wall during removal 

of the impounded material. These 

templates would reinforce the sheets as 

material is dredged and hold them 

upright to prohibit any sheet 

deformation and improve the efficiency 

and effectiveness of removal. The 

templates would also minimize the need 

to perform horizontal cuts at multiple 

elevations, including underwater. With 

strong currents and low visibility, 

performing horizontal cuts underwater 

poses significant challenges. After that 

area has been demolished, the 

temporary stability template piles 

would be removed and re-installed 

along the next third of the bulkhead. It 

is anticipated that three sets of 27 

temporary piles would be required for a 

total of 81 installations and 81 removals 

(table 1). The POA anticipates that the 

temporary stability template piles 

would be 24-inch (61-cm) steel pipe 

piles. However, it is possible that 36- 

inch (91-cm) steel pipe piles would be 

used instead. Temporary piles would be 

installed and removed with a vibratory 

hammer. 

The POA would begin on the 

southern end of the sheet pile structure 

and work their way north along the 

sheet wall face, installing templates and 

dredging fill material while managing 

fill elevations from cell to cell (see 

Figure 1–10 in the POA’s application for 

an example section for the proposed 

demolition work). Fill material would 

slide down into the dredge area and 

would continue to be removed until a 

cell has been dredged down to ¥12 m 

MLLW adjacent to the face sheets and 

all pressure of the fill material on the 

face has been relieved. At this point in 

time, the crane barge would begin 

removing the sheet piles, starting with 

the face sheets. 

Some sheet piles from the tailwalls 

would be removed in the dry, 

potentially during excavation, 

depending on construction sequencing 

and tide heights. To minimize potential 

impacts on marine mammals from inwater sheet pile removal with a 

vibratory hammer, removal in the dry 

would be maximized as feasible; 

however, until the Construction 

Contractor and DOR are under contract, 

the exact number of sheet piles that may 

be removed in the dry is unknown. It is 

estimated that approximately 20–30 

percent of sheet piles would be removed 

in the dry. 

Additionally, it is possible that some 

sheet piles may be removed by direct 

pulling. Removal of sheet piles by direct 

pulling where and when possible would 

also be maximized as feasible. Once fill 

material and impounded soils have been 

excavated or dredged from both sides of 

the sheet piles, it may be adequate to 

dislodge the sheet piles out of interlock 

by lifting or direct pulling. 

Although some sheet piles and sheet 

pile sections would be removed by 

direct pulling and/or in the dry, it is 

anticipated that some sheet piles and 

sheet pile sections would need to be 

removed with a vibratory hammer in 

water. Sheet piles may not be extracted 

easily if soil adheres to the sheet piles 

along the embedded length. It is also 

possible that competent portions of the 

interlocks would resist movement, or 

that interlocks that are bent or damaged 

by shearing would be difficult to 

separate and require shaking with a 

vibratory hammer. 

During vibratory removal, a vibratory 

hammer would be suspended from a 

crane and connected to a powerpack. 

The extractor jaw would be 

hydraulically locked onto the web of the 

sheet pile. The pile would be vibrated 

as upward vertical force is applied to 

extract the pile. Ideally, the piles would 

slide within the interlock, separating 

from the adjacent piles. This may not 

always be the case, as the pile may bind, 

and multiple piles may be dislodged 

from the original installed position. 

Another potential outcome of a pile that 

binds up is that the pile web (the thin, 

flat part between the interlocks) may be 

compromised from corrosion or other 

damage, resulting in the web steel 

tearing and partially ripping the pile, 

necessitating the application of vertical 

force to a neighboring pile. 

Vertical cuts to split the sheet piles 

into panels may be made with a sheet 

splitter if the interlocks do not release 

(see Figure 1–10 in the POA’s 

application). The specific tools that 

would be used for pile splitting are not 

known, but it is anticipated that a 

splitter would be used. A pile splitter is 

a stiffened steel H-beam with some of 

the webbing removed. The edges of the 

H-beam webbing are hardened and form 

a large wedge between the flanges. The 

wedge is set on top of the sheet pile 

webbing where a cut is required. The 

splitter is then driven with a hammer 

down the webbing of the sheet pile until 

the tip of the H-beam passes the tip of 

the sheets, cutting the sheet pile all the 

way through and separating it into two 

parts. Multiple cuts split the sheet pile 

wall into tall vertical panels that can be 

removed in smaller pieces. Cuts in the 

sheet piles may be spaced 4 to 6 sheets 

apart and multiple sheets or pieces 

would be removed together. Splitters 

can be used in the air, water, or in soils 

and can be driven with impact or 

vibratory hammers. The splitter would 

be used in conjunction with a vibratory 

hammer and the POA assumed splitting 

would produce the same or similar 

sound levels to a vibratory hammer used 

without the splitter attachment. 

Therefore, the POA combined use of a 

vibratory hammer to remove sheet piles 

and use of a splitter into a single 

category (i.e., vibratory hammer 

removal) and treated them the same for 

time (i.e., table 1) and take estimation 

(see the Estimated Take section). 

The POA estimates that an average of 

approximately 5 minutes of vibratory 

hammer application would be required 

to remove sheet pile sections. It is 

unknown how many sheet piles may be 

included in a section; the POA 

anticipates that this number will vary 

widely. If sheet piles remain seized in 

the sediments and cannot be loosened 

or broken free with a vibratory hammer, 

they may be dislodged with an impact 

hammer. Use of an impact hammer to 

dislodge is expected to be uncommon, 

with up to 150 strikes (an estimated 50 

strikes per pile for up to three piles) on 

any individual day or approximately 5 

percent of active hammer duration for 

each sheet pile. The POA would not use 

two vibratory hammers with or without 

splitters simultaneously. 


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Alternative means of pile removal 

include dredging or excavation to 

reduce further pile embedment, and 

cutting sheet piles using hydraulic 

shears or underwater ultrathermic 

cutting. When feasible, sheet piles 

would be removed in one piece, without 

cutting. Similarly, use of cutting 

methods to cut piles into sections that 

could be more easily removed would 

take place out of water when feasible. 

The POA anticipates that hydraulic 

shears may be used to cut sheet piles 

both in and out of water. The POA 

anticipates that sounds produced by 

hydraulic shears would be brief, low 

level, and intermittent, imparting 

minimal sound energy into the water 

column. A single closure of the shears 

on sheet pile is anticipated to 

successfully sever one or multiple 

sheets depending on the model and jaw 

depth. The POA anticipates that a single 

cut may require up to 2 minutes for the 

shears to close, although the duration of 

a single cut is likely to be less than 2 

minutes. Therefore, take of marine 

mammals associated with hydraulic 

shearing is not anticipated or proposed 

to be authorized. 

Underwater ultrathermic cutting is 

performed by commercial divers using 

hand-held equipment to cut or melt 

through ferrous and non-ferrous metals, 

and could be used to cut the zinc-coated 

OCSP structure. 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. 

Take of marine mammals associated 

with underwater ultrathermic cutting is 

not anticipated or proposed to be 

authorized as this activity is not 

considered to produce sound. 

Once the face sheets have been 

removed, the crane barge would remove 

the stability templates for use on other 

cells. At this point, the tailwalls would 

become independent walls with only fill 

material between them. The crane barge 

would work to extract as many tailwall 

sheets as possible until additional relief 

dredging is required to allow for 

vibratory removal. At this point, the 

crane barge would continue ahead to the 

north while the dredge rig falls back to 

continue dredging between the sheets. 

The POA would continue to remove the 

face wall and tailwall sheets from south 

to north until the OCSP structure has 

been removed. 

A key consideration of the NES1 

project is to avoid rapid release of the 

impounded soils into the inlet. This is 

an important safety issue presenting a 

risk to construction personnel working 

in or near the cells in the immediate 

area of such an event. It is also an 

important operational issue to the POA, 

as releasing large quantities of materials 

into the inlet could quickly foul the 

adjoining cargo terminal berths (see 

Figure 1–7 in the POA’s application). To 

avoid rapid release of the impounded 

soils, the demolition would need to be 

managed to account for the soil pressure 

of the adjacent adjoining cells. Failure 

to properly manage this process would 

likely result in the earth pressure 

generated by adjacent adjoining cells 

exerting lateral forces that would cause 

catastrophic tailwall failures. Also, the 

sheets joined in interlock are 

susceptible to bending in the weak axis, 

which could result in rotational forces 

that may overcome the vertical 

interlocks, causing the interlocks to 

unzip, again resulting in catastrophic 

tailwall failures and or face wall 

failures. Qualified professional 

engineers on the Design Build Team 

would develop the Construction Work 

Plan with the technical details to 

ameliorate these risks. 

The sheet pile interlocks would not 

prevent the flow of seawater into soils 

impounded within the OCSP cells. The 

water infiltration would be most 

prevalent at the face sheets; however, 

dynamic wave forces, the variable sea 

level height of the inlet, and variations 

in the impounded soils and associated 

permeability would make the interface 

elevation between unsaturated and 

saturated soils dynamic. Because 

saturated soils cannot resist shear, landbased excavation could be safely 

accomplished at a height above the 

saturated soil depth to be determined by 

the DOR, lest the equipment weight 

exceed the soil-bearing capacity. 

Shoreline Stabilization 

After the existing sheet pile structure 

has been removed, the sloped shoreline 

would be secured with armor stone 

placed on a layer of filter rock and 

granular fill. Placement of armor rock 

requires good visibility of the shore as 

each rock would be placed carefully to 

interlock with surrounding armor rock. 

The POA therefore anticipates that 

placement of armor rock would occur in 

the dry at low tide levels when feasible; 

however, some placement of armor rock, 

filter rock, and granular fill would occur 

in water. No impacts on marine 

mammals from placement of armor rock, 

filter rock, and granular fill in the dry 

are anticipated and therefore this 

activity will not be discussed further. 

Proposed mitigation, monitoring, and 

reporting measures are described in 

detail later in this document (please see 

Proposed Mitigation and Proposed 

Monitoring and Reporting). 

Description of Marine Mammals in the 

Area of Specified Activities 

There are seven species of marine 

mammals that may be found in upper 

Cook Inlet during the proposed 

construction and demolition activities. 

Sections 3 and 4 of the IHA application 

summarize available information 

regarding status and trends, distribution 

and habitat preferences, and behavior 

and life history of the potentially 

affected species. NMFS fully considered 

all of this information, and we refer the 

reader to these descriptions, instead of 

reprinting the information. Additional 

information regarding population trends 

and threats may be found in NMFS’ 

Stock Assessment Reports (SARs; 

https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

marine-mammal-stock-assessments) 

and more general information about 

these species (e.g., physical and 

behavioral descriptions) may be found 

on NMFS’ website (https://

www.fisheries.noaa.gov/find-species). 

Additional information on CIBWs 

may be found in NMFS’ 2016 Recovery 

Plan for the CIBW, available online at 

https://www.fisheries.noaa.gov/ 

resource/document/recovery-plan-cookinlet-beluga-whale-delphinapterusleucas, and 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-trendbelugas-delphinapterus-leucas-cookinlet-alaska-june-2021-and. 

Table 4 lists all species or stocks for 

which take is expected and proposed to 

be authorized for this activity, and 

summarizes information related to the 

population or stock, including 

regulatory status under the MMPA and 

Endangered Species Act (ESA) and 

potential biological removal (PBR), 

where known. PBR is defined by the 

MMPA as the maximum number of 


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animals, not including natural 

mortalities, that may be removed from a 

marine mammal stock while allowing 

that stock to reach or maintain its 

optimum sustainable population (as 

described in NMFS’ SARs). While no 

serious injury or mortality is anticipated 

or proposed to be authorized here, PBR 

and annual serious injury and mortality 

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). Values presented in Table 4 are 

the most recent available at the time of 

publication and are available online at: 

https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

marine-mammal-stock-assessments. 

The most recent abundance estimate for 

CIBWs, however, is available from Goetz 

et al. (2023) and available online at 

https://www.fisheries.noaa.gov/featurestory/new-abundance-estimateendangered-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 Nbest, (CV, Nmin, 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) ...... 6 UND 0.57 

Order Cetartiodactyla—Superfamily Odontoceti (toothed whales, dolphins, and porpoises) 

Family Delphinidae: 

Beluga whale ...................... Delphinapterus leucas .............. Cook Inlet .................................. E/D; Y 5 331 (0.076, 290, 2022) 0.53 0 

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 Phocoenidae (porpoises): 

Harbor porpoise .................. Phocoena phocoena ................. Gulf of Alaska ........................... -/-; Y 31,046 (0.214, N/A, 

1998).

6 UND 72 

Order Carnivora—Superfamily Pinnipedia 

Family Otariidae (eared seals 

and sea lions): 

Steller sea lion .................... Eumetopias jubatus .................. Western ..................................... E/D; Y 52,932 (N/A, 52,932 

2019).

318 255 

Family Phocidae (earless seals): 

Harbor seal ......................... Phoca vitulina ........................... Cook Inlet/Shelikof Strait .......... -/-; N 28,411 (N/A, 26,907, 

2018).

807 107 

1Endangered 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.). 3These 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. A CV associated with estimated 

mortality due to commercial fisheries is presented in some cases. 4 UNK means unknown. 

5This abundance estimate is from Goetz et al. (2023). 6 UND means undetermined. 

On June 15, 2023, NMFS released an 

updated abundance estimate for 

endangered CIBWs in Alaska (Goetz et 

al., 2023) that incorporates aerial survey 

data from June 2021 and 2022, but 

which is not included in the most recent 

SAR (Young et al., 2023). Data collected 

during NMFS recent aerial survey effort 

suggest that the whale population is 

stable or may be increasing slightly. 

Goetz et al. (2023) estimated that the 

population size is currently between 

290 and 386, with a median best 

estimate of 331. In accordance with the 

MMPA, this population estimate will be 

incorporated into the next draft CIBW 

SAR, which will be reviewed by an 

independent panel of experts, the 

Alaska Scientific Review Group. After 

this review, the SAR will be made 

available as a draft for public review 

before being finalized. We have 

determined that it is appropriate to 

consider the CIBW estimate of 

abundance reported by Goetz et al. 

(2023) in our analysis rather than the 

older estimate currently available from 


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the Alaska SAR (Young et al., 2023) 

because it is based on the most recent 

and best available science. 

As indicated above, all seven species 

(with 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 expected 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, sea otters (Enhydra lutris) 

may be found in Cook Inlet. However, 

sea otters are managed by the U.S. Fish 

and Wildlife Service (USFWS) and are 

not considered further in this document. 

Gray Whale 

The stock structure for gray whales in 

the Pacific has been studied for a 

number of years and remains uncertain 

as of the most recent (2022) Pacific 

SARs (Carretta et al., 2023). Gray whale 

population structure is not determined 

by simple geography and may be in flux 

due to evolving migratory dynamics 

(Carretta et al., 2023). Currently, the 

SARs delineate a western North Pacific 

(WNP) gray whale stock and an eastern 

North Pacific (ENP) stock based on 

genetic differentiation (Carretta et al., 

2023). WNP gray whales are not known 

to feed in or travel to upper Cook Inlet 

(Conant and Lohe, 2023; Weller et al., 

2023). Therefore, we assume that gray 

whales near the project area are 

members of the ENP stock. 

An Unusual Mortality Event (UME) 

along the West Coast and in Alaska was 

declared for gray whales in January 

2019 (NMFS, 2022a). Since 2019, 143 

gray whales have stranded off the coast 

of Alaska. Preliminary findings for 

several of the whales indicate evidence 

of emaciation, but the UME is still 

under investigation, and the cause of the 

mortalities remains unknown (NMFS, 

2022a; see https://

www.fisheries.noaa.gov/national/ 

marine-life-distress/2019-2023-graywhale-unusual-mortality-event-alongwest-coast-and for more information). 

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). 

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 (see 

https://www.fisheries.noaa.gov/featurestory/alaska-gray-whale-ume-updatetwentymile-river-whale-likely-onetwelve-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). 

Humpback Whale 

On September 8, 2016, NMFS divided 

the humpback whales into 14 distinct 

population segments (DPS) under the 

ESA, removed the species-level listing 

as endangered, and, in its place, listed 

four DPSs as endangered and one DPS 

as threatened (81 FR 62259, September 

8, 2016). The remaining nine DPSs were 

not listed. There are four DPSs in the 

North Pacific, including Western North 

Pacific and Central America, which are 

listed as endangered, Mexico, which is 

listed as threatened, and Hawaii, which 

is not listed. 

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 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 


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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 photoidentification 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 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). 

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 landbased 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). 

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 

Cook Inlet stock (CIBWs) 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). 

Shelden and Wade (2019) analyzed 

time-series CIBW abundance data from 

2008 to 2018 and reported that the 

CIBW population was declining at an 

annual rate of 2.3 percent during this 

time. Goetz et al., (2023) suggest that 

this decline could have been part of a 

natural oscillation in the population or 

possibly due to impacts of the 

unprecedented heatwave in the Gulf of 

Alaska during the same time period. 

The CIBW time-series abundance data 

were analyzed using a Bayesian 

statistical method to estimate group size 

for calculating CIBW abundance. This 

method produced an abundance 

estimate of 279 CIBWs, with a 95 

percent probability range of 250 to 317 

whales (Shelden and Wade, 2019). 

In June 2023, NMFS released an 

updated abundance estimate for CIBWs 

in Alaska that incorporates aerial survey 

data from June 2021 and 2022 and 

accounted for visibility bias (i.e., 

availability bias due to diving behavior; 

proximity bias due to individuals 

concealed by another individual in the 

video data; perception bias due to 

individuals not detected because of 

small image size in the video data; and 

individual observer bias in visual 

observer data) (Goetz et al., 2023). This 

report estimated that CIBW abundance 

is between 290 and 386, with a median 

best estimate of 331. Goetz et al. (2023) 

also present an analysis of population 

trends for the most recent 10-year 

period (2012–2022). The addition of 

data from the 2021 and 2022 survey 

years in the analysis resulted in a 65.1 

percent probability that the CIBW 

population is now increasing at 0.9 

percent per year (95 percent prediction 

interval of ¥3 to 5.7 percent). This 

increase drops slightly to 0.2 percent 

per year (95 percent prediction interval 

of ¥1.8 to 2.6 percent) with a 60 

percent probability that the CIBW 

population is increasing more than 1 

percent per year when data from 2021, 

which had limited survey coverage due 

to poor weather, are excluded from the 

analysis. Median group size estimates in 

2021 and 2022 were 34 and 15, 

respectively (Goetz et al., 2023). For 

management purposes, 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). 

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 

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related injuries (Vos and Shelden, 2005; 

Burek-Huntington et al., 2015). Between 

2014 and 2018, there were reports of 

approximately 79 CIBWs involved in 

three known live stranding events, plus 

one 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 humancaused mortality or serious injury of 

CIBWs through interactions with 

commercial, recreational, and 

subsistence fisheries, takes by 

subsistence hunters, and or humancaused events (e.g., entanglement in 

marine debris, ship strikes) has been 

recently documented and harvesting of 

CIBWs has not occurred since 2008 

(NMFS, 2008b). 

Recovery Plan. In 2010, a Recovery 

Team, consisting of a Science Panel and 

Stakeholder Panel, began meeting to 

develop a Recovery Plan for the CIBW. 

The Final Recovery Plan was published 

in the Federal Register on January 5, 

2017 (82 FR 1325). In September 2022, 

NMFS completed the ESA 5-year review 

for the CIBW DPS and determined that 

the CIBW DPS should remain listed as 

endangered (NMFS, 2022d). 

In its Recovery Plan (82 FR 1325, 

January 5, 2017), NMFS identified 

several potential threats to CIBWs, 

including: (1) high concern: catastrophic 

events (e.g., natural disasters, spills, 

mass strandings), cumulative effects of 

multiple stressors, and noise; (2) 

medium concern: disease agents (e.g., 

pathogens, parasites, and harmful algal 

blooms), habitat loss or degradation, 

reduction in prey, and unauthorized 

take; and (3) low concern: pollution, 

predation, and subsistence harvest. The 

recovery plan did not treat climate 

change as a distinct threat but rather as 

a consideration in the threats of high 

and medium concern. Other potential 

threats most likely to result in direct 

human-caused mortality or serious 

injury of this stock include vessel 

strikes. 

Critical Habitat. On April 11, 2011, 

NMFS designated two areas of critical 

habitat for CIBW (76 FR 20179). The 

designation includes 7,800 km2 of 

marine and estuarine habitat within 

Cook Inlet, encompassing 

approximately 1,909 km2 in Area 1 and 

5,891 km2 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 were excluded from 

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/criticalhabitat-cook-inlet-beluga-whale. 

The designation identified the 

following Primary Constituent 

Elements, essential features important to 

the conservation of the CIBW: 

(1) Intertidal and subtidal waters of 

Cook Inlet with depths of less than 9 m 

(MLLW) and within 8 km of high- and 

medium-flow anadromous fish streams; 

(2) Primary prey species, including 

four of the five species of Pacific salmon 

(chum (Oncorhynchus keta), sockeye 

(Oncorhynchus nerka), Chinook 

(Oncorhynchus tshawytscha), and coho 

(Oncorhynchus kisutch)), Pacific 

eulachon (Thaleichthys pacificus), 

Pacific cod (Gadus macrocephalus), 

walleye Pollock (Gadus 

chalcogrammus), saffron cod (Eleginus 

gracilis), and yellowfin sole (Limanda 

aspera); 

(3) The absence of toxins or other 

agents of a type or amount harmful to 

CIBWs; 

(4) Unrestricted passage within or 

between the critical habitat areas; and 

(5) The absence of in-water noise at 

levels resulting in the abandonment of 

habitat by CIBWs. 

Biologically Important Areas. Wild et 

al. (2023) delineated portions of Cook 

Inlet, including near the proposed 

project area, as a Biologically Important 

Area (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 yearround 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 return to consume 

fish species (cod and bottom fish) found 

in nearshore bays and estuaries. 

Stomach samples from CIBWs are not 

available for winter (December through 


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March), although dive data from CIBWs 

tagged with satellite transmitters suggest 

that they feed in deeper waters during 

winter (Hobbs et al., 2005), possibly on 

such prey species as flatfish, cod, 

sculpin, and pollock. 

Distribution in Cook Inlet. The CIBW 

stock remains within Cook Inlet 

throughout the year, showing only small 

seasonal shifts in distribution (Goetz et 

al., 2012a; Lammers et al., 2013; 

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, the 

Beluga River and along the shore to the 

Little Susitna River, Knik Arm, and 

along the shores of Chickaloon Bay. 

Small groups were recorded farther 

south in Kachemak Bay, Redoubt Bay 

(Big River), and Trading Bay (McArthur 

River) prior to 1996, but rarely 

thereafter. Since the mid-1990s, most 

CIBWs (96 to 100 percent) aggregate in 

shallow areas near river mouths in 

upper Cook Inlet, and they are only 

occasionally sighted in the central or 

southern portions of Cook Inlet during 

summer (Hobbs et al., 2008). Almost the 

entire population can be found in 

northern Cook Inlet from late spring 

through the summer and into the fall 

(Muto et al., 2020). 

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 (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 six stations 

being located within Knik Arm. In 

general, the observed seasonal 

distribution is in accordance with 

descriptions based on aerial surveys and 

satellite telemetry: CIBW detections are 

higher in the upper inlet during 

summer, peaking at Little Susitna, 

Beluga River, and Eagle Bay, followed 

by fewer detections at those locations 

during winter. Higher detections in 

winter at Trading Bay, Kenai River, and 

Tuxedni Bay suggest a broader CIBW 

distribution in the lower inlet during 

winter. 

Goetz et al. (2012b) modeled habitat 

preferences using NMFS’ 1994–2008 

June abundance survey data. In large 

areas, such as the Susitna Delta (Beluga 

to Little Susitna Rivers) and Knik Arm, 

there was a high probability that CIBWs 

were in larger groups. CIBW presence 

and acoustic foraging behavior also 

increased closer to rivers with Chinook 

salmon runs, such as the Susitna River 

(e.g., Castellote et al., 2021). Movement 

has been correlated with the peak 

discharge of seven major rivers 

emptying into Cook Inlet. Boat-based 

surveys from 2005 to the present 

(McGuire and Stephens, 2017) and 

results from passive acoustic monitoring 

across the entire inlet (Castellote et al., 

2015) also support seasonal patterns 

observed with other methods. Based on 

long-term passive acoustic monitoring, 

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. The only known observed 

occurrence of calving occurred on July 

20, 2015, in the Susitna Delta area (T. 

McGuire, personal communication, 

March 27, 2017). The first neonates 

encountered during each field season 

from 2005 through 2015 were always 

seen in the Susitna River Delta in July. 

The photographic identification team’s 

documentation of the dates of the first 

neonate of each year indicate that 

calving begins in mid-late July/early 

August, generally coinciding with the 

observed timing of annual maximum 

group size. Probable mating behavior of 

CIBWs was observed in April and May 

of 2014, in Trading Bay. Young CIBWs 

are nursed for 2 years and may continue 

to associate with their mothers for a 

considerable time thereafter (Colbeck et 

al., 2013). Important calving grounds are 

thought to be located near the river 

mouths of upper Cook Inlet. 

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 highquality 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 CIBW 

density ranges from 0 to 1.12 whales per 

km2 in Cook Inlet. 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 at the mouth of Knik Arm, near 

the POA, ranges between approximately 

0.013 and 0.062 whales per km2. 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. 


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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-inch 

(122-cm) attenuated piles; impact 

installation of 36-inch (91-cm) and 48- 

inch (122-cm) unattenuated piles; 

vibratory installation of 24-inch (61-cm), 

36-inch (91-cm), and 48-inch (122 cm) 

attenuated and unattenuated piles; and 

vibratory installation of an unattenuated 

72-inch (183-cm) bubble curtain across 

95 days. PCT Phase 2 construction 

included vibratory installation of 36- 

inch (91-cm) attenuated piles and 

impact and vibratory installation of 144- 

inch (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 sixty-seven 

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-inch (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. 

Killer Whale 

Along the west coast of North 

America, seasonal and year-round 

occurrence of killer whales has been 

noted along the entire Alaska coast 

(Braham and Dahlheim, 1982), in British 

Columbia and Washington inland 

waterways (Bigg et al., 1990), and along 

the outer coasts of Washington, Oregon, 

and California (Green et al., 1992; 

Barlow 1995, 1997; Forney et al., 1995). 

Killer whales from these areas have 

been labeled as ‘‘resident,’’ ‘‘transient,’’ 

and ‘‘offshore’’ type killer whales (Bigg 

et al., 1990; Ford et al., 2000; Dahlheim 

et al., 2008) based on aspects of 

morphology, ecology, genetics, and 

behavior (Ford and Fisher, 1982; Baird 

and Stacey, 1988; Baird et al., 1992; 

Hoelzel et al., 1998, 2002; Barrett 

Lennard, 2000; Dahlheim et al., 2008). 

Based on data regarding association 

patterns, acoustics, movements, and 

genetic differences, eight killer whale 

stocks are now recognized within the 

U.S. Pacific, two of which have the 

potential to be found in the proposed 

project area: the Eastern North Pacific 

Alaska Resident stock and the Gulf of 

Alaska, Aleutian Islands, and the Bering 

Sea Transient stock. Both stocks overlap 

the same geographic area; however, they 

maintain social and reproductive 

isolation and feed on different prey 

species. Resident killer whales are 

primarily fish-eaters, while transients 

primarily hunt and consume marine 

mammals, such as harbor seals, Dall’s 

porpoises, harbor porpoises, beluga 

whales and sea lions. Killer whales are 

not harvested for subsistence in Alaska. 

Potential threats most likely to result in 

direct human-caused mortality or 

serious injury of killer whales in this 

region include oil spills, vessel strikes, 

and interactions with fisheries. 

Killer whales are rare in Cook Inlet, 

and most individuals are observed 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 


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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; EasleyAppleyard and Leonard, 2022). 

Harbor Porpoise 

In the eastern North Pacific Ocean, 

harbor porpoise range from Point 

Barrow, along the Alaska coast, and 

down the west coast of North America 

to Point Conception, California. The 

2022 Alaska SARs describe a revised 

stock structure for harbor porpoises 

(Young et al., 2023). Previously, NMFS 

had designated three stocks of harbor 

porpoises: the Bering Sea stock, the Gulf 

of Alaska stock, and the Southeast 

Alaska stock (Muto et al., 2022; Zerbini 

et al., 2022). The 2022 Alaska SARs 

splits the Southeast Alaska stock into 

three separate stocks, resulting in five 

separate stocks in Alaskan waters for 

this species. This update better aligns 

harbor porpoise stock structure with 

genetics, trends in abundance, and 

information regarding discontinuous 

distribution trends (Young et al., 2023). 

Harbor porpoises found in Cook Inlet 

are assumed to be members of the Gulf 

of Alaska stock (Young et al., 2023). 

Harbor porpoises occur most 

frequently in waters less than 100 m 

deep (Hobbs and Waite, 2010). They can 

be opportunistic foragers but consume 

primarily schooling forage fish (Bowen 

and Siniff, 1999). Given their shallow 

water distribution, harbor porpoise are 

vulnerable to physical modifications of 

nearshore habitats resulting from urban 

and industrial development (including 

waste management and nonpoint source 

runoff) and activities such as 

construction of docks and other overwater structures, filling of shallow areas, 

dredging, and noise (Linnenschmidt et 

al., 2013). Subsistence users have not 

reported any harvest from the Gulf of 

Alaska harbor porpoise stock since the 

early 1900s (Shelden et al., 2014). 

Calving occurs from May to August; 

however, this can vary by region. Harbor 

porpoises are often found traveling 

alone, or in small groups of less than 10 

individuals (Schmale, 2008). 

Harbor porpoises occur throughout 

Cook Inlet, with passive acoustic 

detections being more prevalent in 

lower Cook Inlet. Although harbor 

porpoises have been frequently 

observed during aerial surveys in Cook 

Inlet (Shelden et al., 2014), most 

sightings are of single animals and are 

concentrated at Chinitna and Tuxedni 

bays on the west side of lower Cook 

Inlet (Rugh et al., 2005). The occurrence 

of larger numbers of porpoise in the 

lower Cook Inlet may be driven by 

greater availability of preferred prey and 

possibly less competition with CIBWs, 

as CIBWs move into upper inlet waters 

to forage on Pacific salmon during the 

summer months (Shelden et al., 2014). 

An increase in harbor porpoise 

sightings in upper Cook Inlet was 

observed over recent decades (e.g., 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 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 Distinct Population Segments 

(DPSs) of Steller sea lion occur in 

Alaska: the western DPS and the eastern 

DPS. The western DPS includes animals 

that occur west of Cape Suckling, 

Alaska, and therefore includes 

individuals within the Project area. The 

western DPS was listed under the ESA 

as threatened in 1990 (55 FR 49204, 

November 26, 1990), and its continued 

population decline resulted in a change 

in listing status to endangered in 1997 

(62 FR 24345, May 5, 1997). Since 2000, 

studies indicate that the population east 

of Samalga Pass (i.e., east of the 

Aleutian Islands) has increased and is 

potentially stable (Young et al., 2023). 

There is uncertainty regarding threats 

currently impeding the recovery of 

Steller sea lions, particularly in the 

Aleutian Islands. Many factors have 

been suggested as causes of the steep 

decline in abundance of western Steller 

sea lions observed in the 1980s, 

including competitive effects of fishing, 

environmental change, disease, 

contaminants, killer whale predation, 

incidental take, and illegal and legal 

shooting (Atkinson et al., 2008; NMFS, 

2008a). A number of management 

actions have been implemented since 

1990 to promote the recovery of the 

Western U.S. stock of Steller sea lions, 

including 5.6-km (3-nautical mile) noentry zones around rookeries, 

prohibition of shooting at or near sea 

lions, and regulation of fisheries for sea 

lion prey species (e.g., walleye pollock, 

Pacific cod, and Atka mackerel 

(Pleurogrammus monopterygius)) 

(Sinclair et al., 2013; Tollit et al., 2017). 

Additionally, potentially deleterious 

events, such as harmful algal blooms 


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(Lefebvre et al., 2016) and disease 

transmission across the Arctic 

(VanWormer et al., 2019) that have been 

associated with warming waters, could 

lead to potentially negative populationlevel impacts on Steller sea lions. 

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. 

Steller sea lions are opportunistic 

predators, feeding primarily on a wide 

variety of seasonally abundant fishes 

and cephalopods, including Pacific 

herring (Clupea pallasi), walleye 

pollock, capelin (Mallotus villosus), 

Pacific sand lance (Ammodytes 

hexapterus), Pacific cod, salmon 

(Oncorhynchus spp.), and squid 

(Teuthida spp.); (Jefferson et al., 2008; 

Wynne et al., 2011). Steller sea lions do 

not generally eat every day, but tend to 

forage every 1–2 days and return to 

haulouts to rest between foraging trips 

(Merrick and Loughlin, 1997; Rehberg et 

al., 2009). Steller sea lions feed largely 

on walleye pollock, salmon, and 

arrowtooth flounder during the summer, 

and walleye pollock and Pacific cod 

during the winter (Sinclair and 

Zeppelin, 2002). Except for salmon, 

none of these are found in abundance in 

upper Cook Inlet (Nemeth et al., 2007). 

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 (EasleyAppleyard 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 waters all along 

the western coast of the United States, 

British Columbia, and north through 

Alaska waters to the Pribilof Islands and 

Cape Newenham. NMFS currently 

identifies 12 stocks of harbor seals in 

Alaska based largely on genetic 

structure (Young et al., 2023). Harbor 

seals in the proposed project area are 

members of the Cook Inlet/Shelikof 

stock, which ranges from the southwest 

tip of Unimak Island east along the 

southern coast of the Alaska Peninsula 

to Elizabeth Island off the southwest tip 

of the Kenai Peninsula, including Cook 

Inlet, Knik Arm, and Turnagain Arm. 

Distribution of the Cook Inlet/Shelikof 

stock extends from Unimak Island, in 

the Aleutian Islands archipelago, north 

through all of upper and lower Cook 

Inlet (Young et al., 2023). 

Harbor seals forage in marine, 

estuarine, and occasionally freshwater 

habitat. They are opportunistic feeders 

that adjust their local distribution to 

take advantage of locally and seasonally 

abundant prey (Baird, 2001; Bj<rge, 

2002). In Cook Inlet, harbor seals have 

been documented in higher 

concentrations near steelhead 

(Oncorhynchus mykiss), Chinook, and 

salmon spawning streams during 

summer and may target more offshore 

prey species during winter (Boveng et 

al., 2012). 

Harbor seals haul out on rocks, reefs, 

beaches, and drifting glacial ice (Young 

et al., 2023). Their movements are 

influenced by tides, weather, season, 

food availability, and reproduction, as 

well as individual sex and age class 

(Lowry et al., 2001; Small et al., 2003; 

Boveng et al., 2012). The results of past 

and recent satellite tagging studies in 

Southeast Alaska, Prince William 

Sound, Kodiak Island, and Cook Inlet 

are also consistent with the conclusion 

that harbor seals are non-migratory 

(Lowry et al., 2001; Small et al., 2003; 

Boveng et al., 2012). However, some 

long-distance movements of tagged 

animals in Alaska have been recorded 

(Pitcher and McAllister, 1981; Lowry et 

al., 2001; Small et al., 2003; Womble, 

2012; Womble and Gende, 2013). Strong 

fidelity of individuals for haul-out sites 

during the breeding season has been 

documented in several populations 

(Ha ̈rko ̈nen and Harding, 2001), 

including some regions in Alaska such 

as Kodiak Island, Prince William Sound, 

Glacier Bay/Icy Strait, and Cook Inlet 

(Pitcher and McAllister, 1981; Small et 

al., 2005; Boveng et al., 2012; Womble, 

2012; Womble and Gende, 2013). Harbor 

seals usually give birth to a single pup 

between May and mid-July; birthing 

locations are dispersed over several 

haulout sites and not confined to major 

rookeries (Klinkhart et al., 2008). 

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). Recent research on satellitetagged 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 


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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 

(Prevel-Ramos et al., 2006; Markowitz 

and McGuire, 2007; Cornick and SaxonKendall, 2008, 2009; Cornick et al., 

2010, 2011). Harbor seals were observed 

in groups of one to seven individuals 

(Cornick et al., 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 2,500 

m southeast of the NES1 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) 

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 lowfrequency cetaceans where the lower 

bound was deemed to be biologically 

implausible and the lower bound from 

Southall et al. (2007) retained. Marine 

mammal hearing groups and their 

associated hearing ranges are provided 

in Table 5. Specific to this action, gray 

whales and humpback whales are 

considered low-frequency (LF) 

cetaceans, beluga whales and killer 

whales are considered mid-frequency 

(MF) cetaceans, harbor porpoises are 

considered high-frequency (HF) 

cetaceans, Steller sea lions are otariid 

pinnipeds, and harbor seals are phocid 

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). 

The pinniped functional hearing 

group was modified from Southall et al. 

(2007) on the basis of data indicating 

that phocid species have consistently 

demonstrated an extended frequency 

range of hearing compared to otariids, 

especially in the higher frequency range 

(Hemila ̈ et al., 2006; Kastelein et al., 

2009; Reichmuth and Holt, 2013). This 

division between phocid and otariid 

pinnipeds is now reflected in the 

updated hearing groups proposed in 

Southall et al. (2019). 

For more detail concerning these 

groups and associated frequency ranges, 


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please see NMFS (2018) for a review of 

available information. 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

This section provides a discussion of 

the ways in which components of the 

specified activity may impact marine 

mammals and their habitat. The 

Estimated Take of Marine Mammals 

section later in this document includes 

a quantitative analysis of the number of 

individuals that are expected to be taken 

by this activity. The Negligible Impact 

Analysis and Determination section 

considers the content of this section, the 

Estimated Take section, and the 

Proposed Mitigation section, to draw 

conclusions regarding the likely impacts 

of these activities on the reproductive 

success or survivorship of individuals 

and whether those impacts are 

reasonably expected to, or reasonably 

likely to, adversely affect the species or 

stock through effects on annual rates of 

recruitment or survival. 

Acoustic effects on marine mammals 

during the specified activity are 

expected to potentially occur from 

vibratory pile installation and removal, 

and impact pile removal. 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 action 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 

activity 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, except in certain cases in 

shallower water. The amplitude of a 

sound pressure wave is related to the 

subjective ‘‘loudness’’ of a sound and is 

typically expressed in decibels (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 1000- 

fold increase in power. However, a tenfold increase in acoustic power does not 

mean that the sound is perceived as 

being 10 times louder. The dB is a 

relative unit comparing two pressures; 

therefore, a reference pressure must 

always be indicated. For underwater 

sound, this is 1 microPascal (mPa). For 

in-air sound, the reference pressure is 

20 microPascal (mPa). 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 

mPa2-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; SELss), 

or calculated over periods containing 

multiple pulses (SELcum). Cumulative 

SEL (SELcum) 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-topeak 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 


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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 noiseinduced 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 (ANSI, 

1995; NIOSH, 1998). Some of these nonimpulsive sounds can be transient 

signals of short duration but without the 

essential properties of impulses (e.g., 

rapid rise time). Examples of nonimpulsive 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 naturallyoccurring (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*r2). 

When expressing logarithmically in dB 

as TL, we find that TL = 

20*Log10(range), this situation is known 

as spherical spreading. In shallow 

water, the sea surface and seafloor will 

bound the shape of the sound, 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*Log10(range) (Urick, 1983). An 

intermediate scenario may be defined by 

the equation TL = 15*Log10(range), and 

is referred to as practical spreading. 

Though these geometric spreading laws 

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., 

15*Log10(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 


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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 NES1 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 NES1 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). The lower range of broadband (10 

to 10,000 Hz) background sound levels 

obtained during underwater 

measurements at Port MacKenzie, 

located across Knik Arm from the POA, 

ranged from 115 to 133 dB re 1 mPa RMS 

(Blackwell, 2005). Background sound 

levels measured during the 2007 test 

pile study for the POA’s Marine 

Terminal Redevelopment Project 

(MTRP) site ranged from 105 to 135 dB 

(URS Corporation, 2007). The 

background SPLs obtained in that study 

were highly variable, with most SPL 

recordings exceeding 120 dB RMS. 

Background sound levels measured in 

2008 at the MTRP site ranged from 120 

to 150 dB RMS (Scientific Fishery 

Systems, Inc., 2009). These 

measurements included industrial 

sounds from maritime operations, but 

ongoing USACE maintenance dredging 

and pile driving from construction were 

not underway at the time of the study. 

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 AmbientOffshore hydrophone) for 24 hours per 

day with two 1-hour breaks for crew 

change. On the last 2 days of data 

collection, no dredging was occurring. 

Therefore, the median provides a better 

representation of background noise 

levels when the NES1 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 NES1 

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. These 

measurements were not collected in 

accordance to NMFS (2012) guidance 

for measuring background noise and 

thus cannot be used here for that 

purpose. 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 reevaluate 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 sheet pile 

removal, vibratory pile installation and 

removal, and pile splitting (assumed to 

be similar to 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. For the 

NES1 project, a small number of strikes 

from an impact hammer may be used to 

loosen sheet piles for removal. 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 nonacoustic 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 

NES1 project site, visual and other nonacoustic 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 


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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) 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). 

Permanent Threshold Shift (PTS). 

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, 2018). 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 SELcum in an accelerating 

fashion: at low exposures with lower 

SELcum, the amount of TTS is typically 

small and the growth curves have 

shallow slopes. At exposures with 

higher SELcum, the growth curves 

become steeper and approach linear 

relationships with the noise SEL. 

Depending on the degree (elevation of 

threshold in dB), duration (i.e., recovery 

time), and frequency range of TTS, and 

the context in which it is experienced, 

TTS can have effects on marine 

mammals ranging from discountable to 

serious (similar to those discussed in 

auditory masking, below). For example, 

a marine mammal may be able to readily 

compensate for a brief, relatively small 

amount of TTS in a non-critical 

frequency range that takes place during 

a time when the animal is traveling 

through the open ocean, where ambient 

noise is lower and there are not as many 

competing sounds present. 

Alternatively, a larger amount and 

longer duration of TTS sustained during 

time when communication is critical for 

successful mother/calf interactions 

could have more serious impacts. We 

note that reduced hearing sensitivity as 

a simple function of aging has been 

observed in marine mammals, as well as 

humans and other taxa (Southall et al., 

2007), so we can infer that strategies 

exist for coping with this condition to 

some degree, though likely not without 

cost. 

Many studies have examined noiseinduced 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 longduration 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 


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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, but such 

relationships are assumed to be similar 

to those in humans and other terrestrial 

mammals. PTS typically occurs at 

exposure levels at least several decibels 

above 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 nonminor 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 inwater 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). 

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. 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). 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. 


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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. 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 relationship 

between prey availability, foraging effort 

and success, and the life history stage 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 mPa; SEL of a single 

strike: 127 dB re 1 mPa2-s) (Kastelein et 

al., 2013). 

Marine mammals vocalize for 

different purposes and across multiple 

modes, such as whistling, echolocation 

click production, calling, and singing. 

Changes in vocalization behavior in 

response to anthropogenic noise can 

occur for any of these modes and may 

result from a need to compete with an 

increase in background noise or may 

reflect increased vigilance or a startle 

response. For example, in the presence 

of potentially masking signals, 

humpback whales and killer whales 

have been observed to increase the 

length of their songs (Miller et al., 2000; 

Fristrup et al., 2003) or vocalizations 

(Foote et al., 2004), respectively, while 

North Atlantic right whales (Eubalaena 

glacialis) have been observed to shift the 

frequency content of their calls upward 

while reducing the rate of calling in 

areas of increased anthropogenic noise 

(Parks et al., 2007). In some cases, 

animals may cease sound production 

during production of aversive signals 

(Bowles et al., 1994). 

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). 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 activityrelated 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 nonCIBW species. During POA’s PCT 

construction, 81 harbor seals were 

observed within estimated Level B 

harassment zones associated with 

vibratory and impact installation and or 

removal of 36-inch (61-cm) and 144- 

inch (366-cm) piles, and five harbor 

seals were observed within estimated 

Level A harassment zones during the 

installation of 144-inch (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-inch 

(61-cm) pile in May 2021. The animal 

was travelling at a moderate pace. No 

observable reactions to pile driving were 

noted by the PSOs. Another harbor 

porpoise may have been within the 


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estimated Level B harassment zone 

during the impact installation of 36-inch 

(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-inch (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 the 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-inch (61-cm), 36-inch (91-cm), 48-in 

(122-cm), and 144-inch (366-cm) pipe 

piles, and the vibratory installation of 

72-inch (183-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 MTR Project P (2008– 

2009). These were observations made by 

PSOs independent of the POA and their 

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 between 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 inwater 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 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 that CIBWs moved through 

that area relatively quickly when 

entering or exiting the Arm. No whistles 

or noisy vocalizations were recorded 

during the MTR construction activities; 

however, it is possible that persistent 

noise associated with construction 

activity at the MTR project masked 

beluga vocalizations and or that CIBWs 

did not use these communicative signals 

when they were near the MTR Project 

(Saxon-Kendall et al., 2013). 

Recently, McHuron et al. (2023) 

developed a model to predict general 

patterns related to the movement and 

foraging decisions of pregnant CIBWs in 

Cook Inlet. They found that the effects 

of disturbance from human activities, 

such as pile driving activities occurring 

at the POA assuming no prescribed 

mitigation measures implemented, are 

inextricably linked with prey 

availability. If prey are abundant during 

the summer and early fall, and prey 

during winter is above some critical 

threshold, pregnant CIBWs can likely 

cope with intermittent disruptions, such 

as those produced by pile driving at the 

POA (McHuron et al., 2023). However, 

they stress that more information needs 

to be acquired regarding CIBW prey and 

CIBW body condition, specifically in 

their critical habitat, to better 

understand possible behavioral 

responses to disturbance. 

Stress responses. An animal’s 

perception of a threat may be sufficient 

to trigger stress responses consisting of 

some combination of behavioral 

responses, autonomic nervous system 

responses, neuroendocrine responses, or 

immune responses (e.g., Selye, 1950; 

Moberg, 2000). In many cases, an 

animal’s first and sometimes most 

economical (in terms of energetic costs) 

response is behavioral avoidance of the 

potential stressor. Autonomic nervous 

system responses to stress typically 

involve changes in heart rate, blood 

pressure, and gastrointestinal activity. 

These responses have a relatively short 

duration and may or may not have a 

significant long-term effect on an 

animal’s fitness. 

Neuroendocrine stress responses often 

involve the hypothalamus-pituitaryadrenal system. Virtually all 

neuroendocrine functions that are 

affected by stress—including immune 

competence, reproduction, metabolism, 

and behavior—are regulated by pituitary 

hormones. Stress-induced changes in 


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the secretion of pituitary hormones have 

been implicated in failed reproduction, 

altered metabolism, reduced immune 

competence, and behavioral disturbance 

(e.g., Moberg, 1987; Blecha, 2000). 

Increases in the circulation of 

glucocorticoids are also equated with 

stress (Romano et al., 2004). 

The primary distinction between 

stress (which is adaptive and does not 

normally place an animal at risk) and 

‘‘distress’’ is the cost of the response. 

During a stress response, an animal uses 

glycogen stores that can be quickly 

replenished once the stress is alleviated. 

In such circumstances, the cost of the 

stress response would not pose serious 

fitness consequences. However, when 

an animal does not have sufficient 

energy reserves to satisfy the energetic 

costs of a stress response, energy 

resources must be diverted from other 

functions. This state of distress will last 

until the animal replenishes its 

energetic reserves sufficient to restore 

normal function. 

Relationships between these 

physiological mechanisms, animal 

behavior, and the costs of stress 

responses are well-studied through 

controlled experiments and for both 

laboratory and free-ranging animals 

(e.g., Holberton et al., 1996; Hood et al., 

1998; Jessop et al., 2003; Krausman et 

al., 2004; Lankford et al., 2005). Stress 

responses due to exposure to 

anthropogenic sounds or other stressors 

and their effects on marine mammals 

have also been reviewed (Fair and 

Becker, 2000; Romano et al., 2002b) 

and, more rarely, studied in wild 

populations (e.g., Romano et al., 2002a). 

For example, Rolland et al. (2012) found 

that noise reduction from reduced ship 

traffic in the Bay of Fundy was 

associated with decreased stress in 

North Atlantic right whales. These and 

other studies lead to a reasonable 

expectation that some marine mammals 

will experience physiological stress 

responses upon exposure to acoustic 

stressors and that it is possible that 

some of these would be classified as 

‘‘distress.’’ In addition, any animal 

experiencing TTS would likely also 

experience stress responses (NRC, 

2005), however distress is an unlikely 

result of this project based on 

observations of marine mammals during 

previous, similar construction projects. 

Norman (2011) reviewed 

environmental and anthropogenic 

stressors for CIBWs. Lyamin et al. (2011) 

determined that the heart rate of a 

beluga whale increases in response to 

noise, depending on the frequency and 

intensity. Acceleration of heart rate in 

the beluga whale is the first component 

of the ‘‘acoustic startle response.’’ 

Romano et al. (2004) demonstrated that 

captive beluga whales exposed to highlevel impulsive sounds (i.e., seismic 

airgun and/or single pure tones up to 

201 dB RMS) resembling sonar pings 

showed increased stress hormone levels 

of norepinephrine, epinephrine, and 

dopamine when TTS was reached. 

Thomas et al. (1990) exposed beluga 

whales to playbacks of an oil-drilling 

platform in operation (‘‘Sedco 708,’’ 40 

Hz–20 kHz; source level 153 dB). 

Ambient SPL at ambient conditions in 

the pool before playbacks was 106 dB 

and 134 to 137 dB RMS during 

playbacks at the monitoring hydrophone 

across the pool. All cell and platelet 

counts and 21 different blood 

chemicals, including epinephrine and 

norepinephrine, were within normal 

limits throughout baseline and playback 

periods, and stress response hormone 

levels did not increase immediately 

after playbacks. The difference between 

the Romano et al. (2004) and Thomas et 

al. (1990) studies could be the 

differences in the type of sound (seismic 

airgun and/or tone versus oil drilling), 

the intensity and duration of the sound, 

the individual’s response, and the 

surrounding circumstances of the 

individual’s environment. The 

construction sounds in the Thomas et 

al. (1990) study would be more similar 

to those of pile installation than those 

in the study investigating stress 

response to water guns and pure tones. 

Therefore, no more than short-term, 

low-hormone stress responses, if any, of 

beluga whales or other marine mammals 

are expected as a result of exposure to 

in-water pile installation and removal 

during the NES1 project. 

Auditory Masking. Since many marine 

mammals rely on sound to find prey, 

moderate social interactions, and 

facilitate mating (Tyack, 2008), noise 

from anthropogenic sound sources can 

interfere with these functions, but only 

if the noise spectrum overlaps with the 

hearing sensitivity of the receiving 

marine mammal (Southall et al., 2007; 

Clark et al., 2009; Hatch et al., 2012). 

Chronic exposure to excessive, though 

not high-intensity, noise could cause 

masking at particular frequencies for 

marine mammals that utilize sound for 

vital biological functions (Clark et al., 

2009). Acoustic masking is when other 

noises such as from human sources 

interfere with an animal’s ability to 

detect, recognize, or discriminate 

between acoustic signals of interest (e.g., 

those used for intraspecific 

communication and social interactions, 

prey detection, predator avoidance, 

navigation) (Richardson et al., 1995; 

Erbe et al., 2016). Therefore, under 

certain circumstances, marine mammals 

whose acoustical sensors or 

environment are being severely masked 

could also be impaired from maximizing 

their performance fitness in survival 

and reproduction. The ability of a noise 

source to mask biologically important 

sounds depends on the characteristics of 

both the noise source and the signal of 

interest (e.g., signal-to-noise ratio, 

temporal variability, direction), in 

relation to each other and to an animal’s 

hearing abilities (e.g., sensitivity, 

frequency range, critical ratios, 

frequency discrimination, directional 

discrimination, age or TTS hearing loss), 

and existing ambient noise and 

propagation conditions (Hotchkin and 

Parks, 2013). 

Under certain circumstances, marine 

mammals experiencing significant 

masking could also be impaired from 

maximizing their performance fitness in 

survival and reproduction. Therefore, 

when the coincident (masking) sound is 

human-made, it may be considered 

harassment when disrupting or altering 

critical behaviors. It is important to 

distinguish TTS and PTS, which persist 

after the sound exposure, from masking, 

which occurs during the sound 

exposure. Because masking (without 

resulting in TS) is not associated with 

abnormal physiological function, it is 

not considered a physiological effect, 

but rather a potential behavioral effect 

(though not necessarily one that would 

be associated with harassment). 

The frequency range of the potentially 

masking sound is important in 

determining any potential behavioral 

impacts. For example, low-frequency 

signals may have less effect on highfrequency echolocation sounds 

produced by odontocetes but are more 

likely to affect detection of mysticete 

communication calls and other 

potentially important natural sounds 

such as those produced by surf and 

some prey species. The masking of 

communication signals by 

anthropogenic noise may be considered 

as a reduction in the communication 

space of animals (e.g., Clark et al., 2009) 

and may result in energetic or other 

costs as animals change their 

vocalization behavior (e.g., Miller et al., 

2000; Foote et al., 2004; Parks et al., 

2007; Di Iorio and Clark, 2010; Holt et 

al., 2009). Masking can be reduced in 

situations where the signal and noise 

come from different directions 

(Richardson et al., 1995), through 

amplitude modulation of the signal, or 

through other compensatory behaviors 

(Hotchkin and Parks, 2013). Masking 

can be tested directly in captive species 

(e.g., Erbe, 2008), but in wild 

populations it must be either modeled 


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or inferred from evidence of masking 

compensation. There are few studies 

addressing real-world masking sounds 

likely to be experienced by marine 

mammals in the wild (e.g., Branstetter et 

al., 2013). 

Marine mammals at or near the 

proposed NES1 project site may be 

exposed to anthropogenic noise which 

may be a source of masking. 

Vocalization changes may result from a 

need to compete with an increase in 

background noise and include 

increasing the source level, modifying 

the frequency, increasing the call 

repetition rate of vocalizations, or 

ceasing to vocalize in the presence of 

increased noise (Hotchkin and Parks, 

2013). For example, in response to loud 

noise, beluga whales may shift the 

frequency of their echolocation clicks to 

prevent masking by anthropogenic noise 

(Tyack, 2000; Eickmeier and Vallarta, 

2022). 

Masking is more likely to occur in the 

presence of broadband, relatively 

continuous noise sources such as 

vibratory pile driving. Energy 

distribution of pile driving covers a 

broad frequency spectrum, and sound 

from pile driving would be within the 

audible range of pinnipeds and 

cetaceans present in the proposed action 

area. While some construction during 

the POA’s activities may mask some 

acoustic signals that are relevant to the 

daily behavior of marine mammals, the 

short-term duration and limited areas 

affected make it very unlikely that the 

fitness of individual marine mammals 

would be impacted. 

Airborne Acoustic Effects. Pinnipeds 

that occur near the project site could be 

exposed to airborne sounds associated 

with construction activities that have 

the potential to cause behavioral 

harassment, depending on their distance 

from these activities. Airborne noise 

would primarily be an issue for 

pinnipeds that are swimming or hauled 

out near the project site within the range 

of noise levels elevated above airborne 

acoustic harassment criteria. Although 

pinnipeds are known to haul-out 

regularly on man-made objects, we 

believe that incidents of take resulting 

solely from airborne sound are unlikely 

given there are no known pinniped 

haulout or pupping sites within the 

vicinity of the proposed project area; the 

nearest known pinniped haulout is 

located a minimum of 24 km southsouthwest of Anchorage for harbor seals. 

Cetaceans are not expected to be 

exposed to airborne sounds that would 

result in harassment as defined under 

the MMPA. 

We recognize that pinnipeds in the 

water could be exposed to airborne 

sound that may result in behavioral 

harassment when looking with their 

heads above water. Most likely, airborne 

sound would cause behavioral 

responses similar to those discussed 

above in relation to underwater sound. 

For instance, anthropogenic sound 

could cause hauled-out pinnipeds to 

exhibit changes in their normal 

behavior, such as reduction in 

vocalizations, or cause them to 

temporarily abandon the area and move 

further from the source. However, these 

animals would previously have been 

‘taken’ because of exposure to 

underwater sound above the behavioral 

harassment thresholds, which are in all 

cases larger than those associated with 

airborne sound. Thus, the behavioral 

harassment of these animals is already 

accounted for in these estimates of 

potential take. Therefore, we do not 

believe that authorization of incidental 

take resulting from airborne sound for 

pinnipeds is warranted, and airborne 

sound is not discussed further here. 

Potential Effects on Marine Mammal 

Habitat 

The proposed project will occur 

within the same footprint as existing 

marine infrastructure. The nearshore 

and intertidal habitat where the 

proposed project will occur is an area of 

relatively high marine vessel traffic. 

Temporary, intermittent, and short-term 

habitat alteration may result from 

increased noise levels during the 

proposed construction activities. Effects 

on prey species will be limited in time 

and space. 

Removal of the North Extension 

bulkhead and impounded fill would 

result in restoration of subtidal and 

intertidal habitats that were lost when 

that structure was constructed in 2005– 

2011. Removal of approximately 1.35 

million CY of fill material from below 

the high tide line would re-create 

approximately 0.05 km2 (13 acres) of 

intertidal and subtidal habitat, returning 

them to their approximate original slope 

and shoreline configuration. The 

proposed project area is not considered 

to be high-quality habitat for marine 

mammals or marine mammal prey, such 

as fish, and it is anticipated that the 

removal of the North Extension 

bulkhead would increase the amount of 

available habitat for both marine 

mammals and fish because they would 

be able to swim through the area at 

higher water levels. The area is expected 

to be of higher quality to marine 

mammals and fish as it returns to its 

natural state and is colonized by marine 

organisms. 

Water quality—Temporary and 

localized reduction in water quality 

would occur as a result of in-water 

construction activities. Most of this 

effect would occur during the 

installation and removal of piles when 

bottom sediments are disturbed. The 

installation and removal of piles would 

disturb bottom sediments and may 

cause a temporary increase in 

suspended sediment in the project area. 

During pile removal, sediment attached 

to the pile moves vertically through the 

water column until gravitational forces 

cause it to slough off under its own 

weight. The small resulting sediment 

plume is expected to settle out of the 

water column within a few hours. 

Studies of the effects of turbid water on 

fish (marine mammal prey) suggest that 

concentrations of suspended sediment 

can reach thousands of milligrams per 

liter before an acute toxic reaction is 

expected (Burton, 1993). 

Effects to turbidity and sedimentation 

are expected to be short-term, minor, 

and localized. Since the currents are so 

strong in the area, following the 

completion of sediment-disturbing 

activities, suspended sediments in the 

water column should dissipate and 

quickly return to background levels in 

all construction scenarios. Turbidity 

within the water column has the 

potential to reduce the level of oxygen 

in the water and irritate the gills of prey 

fish species in the proposed project 

area. However, turbidity plumes 

associated with the project would be 

temporary and localized, and fish in the 

proposed project area would be able to 

move away from and avoid the areas 

where plumes may occur. Therefore, it 

is expected that the impacts on prey fish 

species from turbidity, and therefore on 

marine mammals, would be minimal 

and temporary. In general, the area 

likely impacted by the proposed 

construction activities is relatively small 

compared to the available marine 

mammal habitat in Knik Arm. 

Potential Effects on Prey. Sound may 

affect marine mammals through impacts 

on the abundance, behavior, or 

distribution of prey species (e.g., 

crustaceans, cephalopods, fishes, 

zooplankton). Marine mammal prey 

varies by species, season, and location 

and, for some, is not well documented. 

Studies regarding the effects of noise on 

known marine mammal prey are 

described here. 

Fishes utilize the soundscape and 

components of sound in their 

environment to perform important 

functions such as foraging, predator 

avoidance, mating, and spawning (e.g., 

Zelick et al., 1999; Fay, 2009). 

Depending on their hearing anatomy 

and peripheral sensory structures, 

which vary among species, fishes hear 


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sounds using pressure and particle 

motion sensitivity capabilities and 

detect the motion of surrounding water 

(Fay et al., 2008). The potential effects 

of noise on fishes depends on the 

overlapping frequency range, distance 

from the sound source, water depth of 

exposure, and species-specific hearing 

sensitivity, anatomy, and physiology. 

Key impacts to fishes may include 

behavioral responses, hearing damage, 

barotrauma (pressure-related injuries), 

and mortality. 

Fish react to sounds that are 

especially strong and/or intermittent 

low-frequency sounds. Short duration, 

sharp sounds can cause overt or subtle 

changes in fish behavior and local 

distribution. The reaction of fish to 

noise depends on the physiological state 

of the fish, past exposures, motivation 

(e.g., feeding, spawning, migration), and 

other environmental factors. Hastings 

and Popper (2005) identified several 

studies that suggest fish may relocate to 

avoid certain areas of sound energy. 

Additional studies have documented 

effects of pile driving on fishes (e.g. 

Scholik and Yan, 2001, 2002; Popper 

and Hastings, 2009). Several studies 

have demonstrated that impulsive 

sounds might affect the distribution and 

behavior of some fishes, potentially 

impacting foraging opportunities or 

increasing energetic costs (e.g., Fewtrell 

and McCauley, 2012; Pearson et al., 

1992; Skalski et al., 1992; Santulli et al., 

1999; Paxton et al., 2017). However, 

some studies have shown no or slight 

reaction to impulse sounds (e.g., Pen ̃ a et 

al., 2013; Wardle et al., 2001; Jorgenson 

and Gyselman, 2009; Cott et al., 2012). 

More commonly, though, the impacts of 

noise on fishes are temporary. 

During the POA’s MTRP, the effects of 

impact and vibratory installation of 30- 

inch (76-cm) steel sheet piles at the POA 

on 133 caged juvenile coho salmon in 

Knik Arm were studied (Hart Crowser 

Incorporated et al., 2009; Houghton et 

al., 2010). Acute or delayed mortalities, 

or behavioral abnormalities were not 

observed in any of the coho salmon. 

Furthermore, results indicated that the 

pile driving had no adverse effect on 

feeding ability or the ability of the fish 

to respond normally to threatening 

stimuli (Hart Crowser Incorporated et 

al., 2009; Houghton et al., 2010). 

SPLs of sufficient strength have been 

known to cause injury to fishes and fish 

mortality (summarized in Popper et al., 

2014). However, in most fish species, 

hair cells in the ear continuously 

regenerate and loss of auditory function 

likely is restored when damaged cells 

are replaced with new cells. Halvorsen 

et al. (2012b) showed that a TTS of 4 to 

6 dB was recoverable within 24 hours 

for one species. Impacts would be most 

severe when the individual fish is close 

to the source and when the duration of 

exposure is long. Injury caused by 

barotrauma can range from slight to 

severe and can cause death, and is most 

likely for fish with swim bladders. 

Barotrauma injuries have been 

documented during controlled exposure 

to impact pile driving (Halvorsen et al., 

2012a; Casper et al., 2013, 2017). 

Fish populations in the proposed 

project area that serve as marine 

mammal prey could be temporarily 

affected by noise from pile installation 

and removal. The frequency range in 

which fishes generally perceive 

underwater sounds is 50 to 2,000 Hz, 

with peak sensitivities below 800 Hz 

(Popper and Hastings, 2009). Fish 

behavior or distribution may change, 

especially with strong and/or 

intermittent sounds that could harm 

fishes. High underwater SPLs have been 

documented to alter behavior, cause 

hearing loss, and injure or kill 

individual fish by causing serious 

internal injury (Hastings and Popper, 

2005). 

Essential Fish Habitat (EFH) has been 

designated in the estuarine and marine 

waters in the vicinity of the proposed 

project area for all five species of 

salmon (i.e., chum salmon, pink salmon, 

coho salmon, sockeye salmon, and 

Chinook salmon; North Pacific Fishery 

Management Council (NPFMC), 2020, 

2021), which are common prey of 

marine mammals, as well as for other 

species. (NPFMC, 2020). However, there 

are no designated habitat areas of 

particular concern in the vicinity of the 

Port, and therefore, adverse effects on 

EFH in this area are not expected. 

The greatest potential impact to fishes 

during construction would occur during 

impact pile removal. However, the use 

of impact pile driving would be limited 

to situations when sheet piles remain 

seized in the sediments and cannot be 

loosened or broken free with a vibratory 

hammer. Further, use of an impact 

hammer to dislodge piles is expected to 

be uncommon, with a limited number of 

up to 150 strikes (an estimated 50 

strikes per pile for up to three piles) on 

any individual day or approximately 5 

percent of active hammer duration for 

sheet pile. In-water construction 

activities would only occur during 

daylight hours, allowing fish to forage 

and transit the project area in the 

evening. Vibratory pile driving would 

possibly elicit behavioral reactions from 

fishes such as temporary avoidance of 

the area but is unlikely to cause injuries 

to fishes or have persistent effects on 

local fish populations. Construction also 

would have minimal permanent and 

temporary impacts on benthic 

invertebrate species, a marine mammal 

prey source. In addition, it should be 

noted that the area in question is lowquality habitat since it is already highly 

developed and experiences a high level 

of anthropogenic noise from normal 

operations and other vessel traffic at the 

POA. 

Fish species in Knik Arm, including 

those that are prey for marine mammals, 

are expected to benefit from removal of 

the North Extension bulkhead and 

availability of the resulting exposed 

subtidal and intertidal habitat. NES1 is 

not anticipated to impede migration of 

adult or juvenile salmon or to adversely 

affect the health and survival of the 

affected species at the population level. 

Once in-water pile installation and 

removal has ceased and NES1 is 

complete, the newly available habitat is 

expected to transition back to its 

original, more natural condition and 

provide foraging, migrating, and rearing 

habitats to fish and foraging habitat to 

marine mammals. In general, any 

negative impacts on marine mammal 

prey species are expected to be minor 

and temporary. 

In-Water Construction Effects on 

Potential Foraging Habitat 

The NES1 Project area has not been 

considered to be high-quality habitat for 

marine mammals or marine mammal 

prey, such as fish, and it is anticipated 

that the long-term impact on marine 

mammals associated with NES1 would 

be a permanent increase in potential 

habitat because of the removal of the 

North Extension bulkhead, restoring 

access of the area to marine mammals 

and fish. The NES1 project is not 

expected to result in any habitat related 

effects that could cause significant or 

long-term negative consequences for 

individual marine mammals or their 

populations, since installation and 

removal of in-water piles would be 

temporary and intermittent, and the recreation of intertidal and subtidal 

habitats would be permanent. Therefore, 

impacts of the project are not likely to 

have adverse effects on marine mammal 

foraging habitat in the proposed project 

area. 

Estimated Take 

This section provides an estimate of 

the number of incidental takes proposed 

for authorization through the IHA, 

which will inform both NMFS’ 

consideration of ‘‘small numbers,’’ and 

the negligible impact determinations. 

Harassment is the only type of take 

expected to result from these activities. 

Except with respect to certain activities 

not pertinent here, section 3(18) of the 


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MMPA defines ‘‘harassment’’ as any act 

of pursuit, torment, or annoyance, 

which (i) has the potential to injure a 

marine mammal or marine mammal 

stock in the wild (Level A harassment); 

or (ii) has the potential to disturb a 

marine mammal or marine mammal 

stock in the wild by causing disruption 

of behavioral patterns, including, but 

not limited to, migration, breathing, 

nursing, breeding, feeding, or sheltering 

(Level B harassment). 

Authorized takes would primarily be 

by Level B harassment, as use of the 

acoustic sources (i.e., vibratory and 

impact pile driving) has the potential to 

result in disruption of behavioral 

patterns for individual marine 

mammals. There is also some potential 

for auditory injury (Level A harassment) 

to result, primarily for high frequency 

cetaceans and phocids because 

predicted auditory injury zones are 

larger than for mid-frequency cetaceans 

and otariids. Auditory injury is unlikely 

to occur for mysticetes, mid-frequency 

cetaceans, and otariids due to measures 

described in the Proposed Mitigation 

section. The proposed mitigation and 

monitoring measures are expected to 

minimize the severity of the taking to 

the extent practicable. As described 

previously, no serious injury or 

mortality is anticipated or proposed to 

be authorized for this activity. Below we 

describe how the proposed take 

numbers are estimated. 

For acoustic impacts, generally 

speaking, we estimate take by 

considering: (1) acoustic thresholds 

above which NMFS believes the best 

available science indicates marine 

mammals will be behaviorally harassed 

or incur some degree of permanent 

hearing impairment; (2) the area or 

volume of water that will be ensonified 

above these levels in a day; (3) the 

density or occurrence of marine 

mammals within these ensonified areas; 

and, (4) the number of days of activities. 

We note that while these factors can 

contribute to a basic calculation to 

provide an initial prediction of potential 

takes, additional information that can 

qualitatively inform take estimates is 

also sometimes available (e.g., previous 

monitoring results or average group 

size). Below, we describe the factors 

considered here in more detail and 

present the proposed take estimates. 

Acoustic Thresholds 

NMFS recommends the use of 

acoustic thresholds that identify the 

received level of underwater sound 

above which exposed marine mammals 

would be reasonably expected to be 

behaviorally harassed (equated to Level 

B harassment) or to incur PTS of some 

degree (equated to Level A harassment). 

Level B Harassment—Though 

significantly driven by received level, 

the onset of behavioral disturbance from 

anthropogenic noise exposure is also 

informed to varying degrees by other 

factors related to the source or exposure 

context (e.g., frequency, predictability, 

duty cycle, duration of the exposure, 

signal-to-noise ratio, distance to the 

source), the environment (e.g., 

bathymetry, other noises in the area, 

predators in the area), and the receiving 

animals (hearing, motivation, 

experience, demography, life stage, 

depth) and can be difficult to predict 

(e.g., Southall et al., 2007, 2021; Ellison 

et al., 2012). Based on what the 

available science indicates and the 

practical need to use a threshold based 

on a metric that is both predictable and 

measurable for most activities, NMFS 

typically uses a generalized acoustic 

threshold based on received level to 

estimate the onset of behavioral 

harassment. NMFS generally predicts 

that marine mammals are likely to be 

behaviorally harassed in a manner 

considered to be Level B harassment 

when exposed to underwater 

anthropogenic noise above root-meansquared pressure received levels (RMS 

SPL) of 120 dB re 1 mPa for continuous 

(e.g., vibratory pile driving, drilling) and 

above RMS SPL 160 dB re 1 mPa for nonexplosive impulsive (e.g., seismic 

airguns) or intermittent (e.g., scientific 

sonar) sources. Generally speaking, 

Level B harassment take estimates based 

on these behavioral harassment 

thresholds are expected to include any 

likely takes by TTS as, in most cases, 

the likelihood of TTS occurs at 

distances from the source less than 

those at which behavioral harassment is 

likely. TTS of a sufficient degree can 

manifest as behavioral harassment, as 

reduced hearing sensitivity and the 

potential reduced opportunities to 

detect important signals (conspecific 

communication, predators, prey) may 

result in changes in behavior patterns 

that would not otherwise occur. 

The POA’s proposed activity includes 

the use of continuous (vibratory pile 

driving) and intermittent (impact pile 

driving) noise sources, and therefore the 

RMS SPL thresholds of 120 and 160 dB 

re 1 mPa are applicable. 

Level A harassment. NMFS’ Technical 

Guidance for Assessing the Effects of 

Anthropogenic Sound on Marine 

Mammal Hearing (Version 2.0; NMFS, 

2018) identifies dual criteria to assess 

auditory injury (Level A harassment) to 

five different marine mammal groups 

(based on hearing sensitivity) as a result 

of exposure to noise from two different 

types of sources (impulsive or nonimpulsive). The POA’s proposed 

activity includes the use of impulsive 

(impact pile driving) and non-impulsive 

(vibratory driving) sources. 

These thresholds are provided in the 

table below. The references, analysis, 

and methodology used in the 

development of the thresholds are 

described in NMFS’ 2018 Technical 

Guidance, which may be accessed at: 

https://www.fisheries.noaa.gov/ 

national/marine-mammal-protection/ 

marine-mammal-acoustic-technicalguidance. 

TABLE 6—THRESHOLDS IDENTIFYING THE ONSET OF PERMANENT THRESHOLD SHIFT

Hearing Group 

PTS onset acoustic thresholds * 

(received level) 

Impulsive Non-impulsive 

Low-Frequency (LF) Cetaceans ...................................... Cell 1: Lpk,flat: 219 dB; LE,LF,24h: 183 dB ......................... Cell 2: LE,LF,24h: 199 dB. 

Mid-Frequency (MF) Cetaceans ...................................... Cell 3: Lpk,flat: 230 dB; LE,MF,24h: 185 dB ........................ Cell 4: LE,MF,24h: 198 dB. 

High-Frequency (HF) Cetaceans ..................................... Cell 5: Lpk,flat: 202 dB; LE,HF,24h: 155 dB ........................ Cell 6: LE,HF,24h: 173 dB. 

Phocid Pinnipeds (PW) (Underwater) ............................. Cell 7: Lpk,flat: 218 dB; LE,PW,24h: 185 dB ....................... Cell 8: LE,PW,24h: 201 dB. 

Otariid Pinnipeds (OW) (Underwater) ............................. Cell 9: Lpk,flat: 232 dB; LE,OW,24h: 203 dB ....................... Cell 10: LE,OW,24h: 219 dB. 

* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should 

also be considered. 


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Note: Peak sound pressure (Lpk) has a reference value of 1 μPa, and cumulative sound exposure level (LE) has a reference value of 1μPa2s. 

In this Table, thresholds are abbreviated to reflect American National Standards Institute standards (ANSI, 2013). However, peak sound pressure 

is defined by ANSI as incorporating frequency weighting, which is not the intent for NMFS’ 2018 Technical Guidance. Hence, the subscript ‘‘flat’’ 

is being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF 

cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The cumulative sound exposure level 

thresholds could be exceeded in a multitude of ways (i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for 

action proponents to indicate the conditions under which these acoustic thresholds will be exceeded. 

Ensonified Area 

Here, we describe operational and 

environmental parameters of the activity 

that are used in estimating the area 

ensonified above the acoustic 

thresholds, including source levels and 

transmission loss coefficient. 

The sound field in the project area is 

the existing background noise plus 

additional construction noise from the 

proposed project. Marine mammals are 

expected to be affected via sound 

generated by the primary components of 

the project (i.e., impact pile removal and 

vibratory pile installation and removal). 

Calculation of the area ensonified by the 

proposed action is dependent on the 

background sound levels at the project 

site, the source levels of the proposed 

activities, and the estimated 

transmission loss coefficients for the 

proposed activities at the site. These 

factors are addressed in order, below. 

Background Sound Levels at the Port 

of Alaska. As noted in the Potential 

Effects of Specified Activities on Marine 

Mammals and Their Habitat Section of 

this notice, the POA is an industrial 

facility in a location with high levels of 

commercial vessel traffic, port 

operations (including dredging), and 

extreme tidal flow. Previous 

measurements of background noise at 

the POA have recorded a background 

SPL of 122.2 dB RMS (Austin et al., 

2016). NMFS concurs that this SPL 

reasonably represents background noise 

near the proposed project area, and 

therefore we have used 122.2 dB RMS 

as the threshold for Level B harassment 

(instead of 120 dB RMS). 

Sound Source Levels of Proposed 

Activities. The intensity of pile driving 

sounds is greatly influenced by factors 

such as the type of piles (material and 

diameter), hammer type, and the 

physical environment (e.g., sediment 

type) in which the activity takes place. 

In order to calculate the distances to the 

Level A harassment and the Level B 

harassment sound thresholds for the 

methods and piles being used in this 

project, the POA used acoustic 

monitoring data from sound source 

verification studies to develop proxy 

source levels for the various pile types, 

sizes and methods (Table 7). While sitespecific sound source verification 

studies have been conducted at the 

POA, the vast majority of the 

measurements recorded in those studies 

were made when bubble curtains were 

deployed around the sound source, 

which act to attenuate sound levels 

(Austin et al., 2016; I&R, 2021a, 2021b). 

Bubble curtains are not a feasible 

mitigation measure for the NES1 project 

due to the demolition and sequencing 

nature of the project (see the Proposed 

Mitigation section of this notice for 

additional discussion), and therefore the 

majority of the proposed proxy values 

for this project are based on 

measurements recorded from locations 

other than the POA. 

Underwater sound was measured in 

2008 at the POA for the MTRP during 

installation of sheet piles to assess 

potential impacts of sound on marine 

species. Sound levels for installation of 

sheet piles measured at 10 m typically 

ranged from 147 to 161 dB RMS, with 

a mean of approximately 155 dB RMS 

(James Reyff, unpublished data). An SSL 

of 162 dB RMS was reported in 

(CALTRANS, 2020) summary tables for 

24-inch steel sheet piles. This is a more 

rigid type of sheet pile that requires a 

large vibratory driver (James Reyff, 

personal communication, August 26, 

2020). Based on the 2008 measurements 

at the POA and the CALTRANS data, a 

value of 160 dB RMS was assumed for 

vibratory removal of sheet piles. 

NMFS concurs that the source levels 

proposed by the POA for all pile sizes 

during impact hammering activities and 

vibratory installation of all pile types 

are appropriate to use for calculating 

harassment isopleths for the POA’s 

proposed NES1 activities (Table 7). 

However, the source levels proposed by 

the POA for vibratory pile removal were 

based on limited data collected at the 

POA. Therefore, NMFS considered and 

evaluated all data related to 

unattenuated vibratory removal of 24- 

inch (61-cm) and 36-inch (91-cm) steel 

pipe piles available, including sound 

source verification data measured at the 

POA during the PCT project (Reyff et al, 

2021a) and elsewhere (i.e., Coleman, 

2011; U.S. Navy, 2012; I&R, 2017). 

NMFS gathered data from publicly 

available reports that reported driving 

conditions and specified vibratory 

removal for certain piles. If vibratory 

removal was not specifically noted for a 

given pile, we excluded that data from 

the analysis. Mean RMS SPLs reported 

by these studies were converted into 

pressure values, and pressure values for 

piles from each project were averaged to 

give a single SPL for each project. The 

calculated project means were then 

averaged and converted back into dBs to 

give a single recommended SPL for each 

pile type. 

Ten measurements were available for 

unattenuated vibratory removal of 24- 

inch (61-cm) piles: 3 from Columbia 

River Crossing in Oregon (mean RMS 

SPL of 172.4 dB; Coleman, 2011), 5 from 

Joint Expeditionary Base Little Creek in 

Norfolk, Virginia (mean RMS SPL of 

148.2 dB; I&R, 2017), and 2 from the 

PCT project at the POA (mean RMS SPL 

of 168.7 dB; I&R, 2021a, 2023). The 

calculated average SPL for unattenuated 

vibratory removal of 24-inch (61-cm) 

steel pipe piles from these studies was 

168 dB RMS (Table 7). Forty 

measurements were available for 

unattenuated vibratory removal of 36- 

inch (91-cm) piles: 38 from the U.S. 

Navy Test Pile Program at Naval Base 

Kitsap in Bangor, Washington (mean 

RMS SPL of 159.4 dB; U.S. Navy, 2012), 

and 2 from the PCT project at the POA 

(mean RMS SPL of 158.5 dB; I&R, 2021, 

2023). The calculated average SPL for 

unattenuated vibratory removal of 36- 

inch (91-cm) steel pipe piles from these 

studies was 159 dB RMS (Table 7). Note 

that the proxy values in Table 7 

represent SPL referenced at a distance of 

10 m from the source. Interestingly, the 

RMS SPLs for the unattenuated 

vibratory removal of 24-inch (61-cm) 

piles was much louder than the 

unattenuated vibratory removal of 36- 

inch piles (91-cm), and even louder than 

the unattenuated vibratory installation 

of 24-inch piles. I&R (2023) suggest that 

at least for data recorded at the POA, the 

higher 24-inch (61-cm) removal levels 

are likely due to the piles being 

removed at rates of 1,600 to 1,700 

revolutions per minute (rpm), while 36- 

inch (91-cm) piles, which are 

significantly heavier than 24-inch (61- 

cm) piles), were removed at a rate of 

1,900 rpm. The slower rates combined 

with the lighter piles would cause the 

hammer to easily ‘‘jerk’’ or excite the 24- 

inch (61-cm) piles as they were 

extracted, resulting in a louder rattling 

sound and louder sound levels. This did 

not occur for the 36-inch (91-cm) piles, 

which were considerably heavier due to 


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increased diameter, longer length, and 

greater thickness. 

TABLE 7—SUMMARY OF UNATTENUATED IN-WATER PILE DRIVING PROXY LEVELS

[at 10 m] 

Pile type Installation or removal Peak SPL 

(re 1 μPa) 

RMS SPL 

(re 1 μPa) 

SEL 

(re 1 μPa2- 

sec) 

Source 

Impact driving: 

Sheet pile ....................... Removal ................................ 205 189 179 CALTRANS (2020). 

Vibratory driving: 

Sheet pile ....................... Removal (hammer or splitter) NA 160 NA CALTRANS (2015, 2020). 

24-inch (61-cm) steel 

pipe.

Installation ............................. 161 U.S. Navy (2015). 

Removal ................................ 168 Coleman (2011), I&R (2017, 

2021, 2023). 

36-inch (91-cm steel 

pipe).

Installation ............................. 166 U.S. Navy (2015). 

Removal ................................ 159 U.S. Navy (2012), I&R 

(2021, 2023). 

The POA assumes that a pile splitter 

would produce the same or similar 

sound levels as a vibratory hammer 

without the splitter attachment; 

therefore, the POA combined use of a 

vibratory hammer to remove sheet pile 

and use of a splitter into a single 

category (i.e., vibratory hammer 

removal). NMFS is currently unaware of 

any hydroacoustic measurements of pile 

splitting with a vibratory hammer. 

Without additional data, NMFS 

preliminary accepts the POAs proposed 

SPLs and assessments. However, NMFS 

specifically requests comments on the 

proposed SPL values for vibratory pile 

splitting. If available, NMFS requests 

recommendations for available data on 

underwater measurements and potential 

impacts of these construction activities. 

Transmission Loss. For unattenuated 

impact pile driving, the POA proposed 

to use 15 as the TL coefficient, meaning 

they assume practical spreading loss 

(i.e., the POA assumes TL = 

15*Log10(range)); NMFS concurs with 

this value and has used the practical 

spreading loss model for impact driving 

in this analysis. 

The TL coefficient that the POA 

proposed for unattenuated vibratory 

installation and removal of piles is 16.5 

(i.e., TL = 16.5*Log10(range)). This value 

is an average of measurements obtained 

from two 48-in (122-cm) piles installed 

via an unattenuated vibratory hammer 

in 2016 (Austin et al., 2016). To assess 

the appropriateness of this TL 

coefficient to be used for the proposed 

project, NMFS examined and analyzed 

additional TL measurements recorded at 

the POA. This includes a TL coefficient 

of 22 (deep hydrophone measurement) 

from the 2004 unattenuated vibratory 

installation of one 36-inch (91-cm) pile 

in Knik Arm (Blackwell, 2004), as well 

as TL coefficients ranging from 10.3 to 

18.2 from the unattenuated vibratory 

removal of 24-inch (61 cm) and 36-inch 

(91-cm) piles and the unattenuated 

vibratory installation of one 48-in (122- 

cm) pile at the POA in 2021 (I&R 2021, 

2023). To account for statistical 

interdependence due to temporal 

correlations and equipment issues 

across projects, values were averaged 

first within each individual project, and 

then across projects. The mean and 

median value of the measured TL 

coefficients for unattenuated vibratory 

piles in Knik Arm by project are equal 

to 18.9 and 16.5, respectively. NMFS 

proposes the use of the project median 

TL coefficient of 16.5 during 

unattenuated vibratory installation and 

removal of all piles during the NES1 

project. This value is representative of 

all unattenuated vibratory 

measurements in the Knik Arm. Further, 

16.5 is the mean of the 2016 

measurements, which were made closer 

to the NES1 proposed project area than 

other measurements and were 

composed of measurements from 

multiple directions (both north and 

south/southwest). 

Estimated Harassment Isopleths. All 

estimated Level B harassment isopleths 

are reported in Table 9. At POA, Level 

B harassment isopleths from the 

proposed project will be limited by the 

coastline along Knik Arm along and 

across from the project site. The 

maximum predicted isopleth distance is 

5,968 m during vibratory removal of 24- 

inch (61-cm) steel pipe piles. 

The ensonified area associated with 

Level A harassment is more technically 

challenging to predict due to the need 

to account for a duration component. 

Therefore, NMFS developed an optional 

User Spreadsheet tool to accompany the 

Technical Guidance that can be used to 

relatively simply predict an isopleth 

distance for use in conjunction with 

marine mammal density or occurrence 

to help predict potential takes. We note 

that because of some of the assumptions 

included in the methods underlying this 

optional tool, we anticipate that the 

resulting isopleth estimates are typically 

going to be overestimates of some 

degree, which may result in an 

overestimate of potential take by Level 

A harassment. However, this optional 

tool offers the best way to estimate 

isopleth distances when more 

sophisticated modeling methods are not 

available or practical. For stationary 

sources such as pile driving, the 

optional User Spreadsheet tool predicts 

the distance at which, if a marine 

mammal remained at that distance for 

the duration of the activity, it would be 

expected to incur PTS. Inputs used in 

the User Spreadsheet are reported in 

Table 8 and the resulting isopleths and 

ensonified areas are reported in Table 9. 


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TABLE 8—NMFS USER SPREADSHEET INPUTS

Impact pile driving Vibratory pile driving 

Sheet pile Sheet pile 24-inch (61-cm) steel pipe 36-inch (91-cm) steel pipe 

Removal Removal Installation Removal Installation Removal 

Spreadsheet Tab 

Used.

E.1) Impact pile 

driving.

A.1) Non-Impul, 

Stat, Cont.

A.1) Non-Impul, 

Stat, Cont.

A.1) Non-Impul, 

Stat, Cont.

A.1) Non-Impul, 

Stat, Cont.

A.1) Non-Impul, 

Stat, Cont. 

Source Level (SPL) 179 dB SEL ......... 160 dB RMS ....... 161 dB RMS ....... 168 dB RMS ....... 166 dB RMS ....... 159 dB RMS. 

Transmission Loss 

Coefficient.

15 ........................ 16.5 ..................... 16.5 ..................... 16.5 ..................... 16.5 ..................... 16.5. 

Weighting Factor 

Adjustment (kHz).

2 .......................... 2.5 ....................... 2.5 ....................... 2.5 ....................... 2.5 ....................... 2.5. 

Time to install/remove single pile 

(minutes).

............................. 5 .......................... 15 ........................ 15 ........................ 15 ........................ 15. 

Number of strikes 

per pile.

50 

Piles per day .......... 3 .......................... 24 ........................ 12 ........................ 12 ........................ 12 ........................ 12. 

Distance of sound 

pressure level 

measurement (m).

10 ........................ 10 ........................ 10 ........................ 10 ........................ 10 ........................ 10. 

TABLE 9—CALCULATED DISTANCE AND AREAS OF LEVEL A AND LEVEL B HARASSMENT PER PILE TYPE AND PILE DRIVING

METHOD

Activity Pile type/size 

Level A harassment distance 

(m) 

Level B 

harassment 

distance (m) all 

hearing groups 

Level B 

harassment 

area (km2) all 

LF MF HF PW OW hearing groups 

Impact Removal .. Sheet pile ............ 153 6 182 82 6 858 1.44 

Vibratory Installation.24-inch (61-cm) ... 14 2 20 9 1 2,247 8.39 

36-inch (91-cm) ... 28 4 40 18 2 4,514 26.13 

Vibratory or Splitter Removal.Sheet pile ............ 10 1 14 6 1 1,954 6.47 

Vibratory Removal 24-inch (61-cm) ... 37 4 53 24 3 5,968 37.64 

36-inch (91-cm) ... 11 2 15 7 1 1,700 4.99 

Marine Mammal Occurrence and Take 

Estimation 

In this section we provide information 

about the occurrence of marine 

mammals, including density or other 

relevant information which will inform 

the take calculation. We also describe 

how the information provided above is 

synthesized to produce a quantitative 

estimate of the take that is reasonably 

likely to occur and proposed for 

authorization. 

Gray Whale 

Sightings of gray whales in the 

proposed project area are rare. Few, if 

any, gray whales are expected to 

approach the proposed project area. 

However, based on three separate 

sightings of single gray whales near the 

POA in 2020 and 2021 (61N 

Environmental, 2021, 2022a; EasleyAppleyard and Leonard, 2022), the POA 

anticipates that up to six individuals 

could be within estimated harassment 

zones during NES1 project activities. 

Therefore, NMFS proposes to authorize 

six takes by Level B harassment for gray 

whales during the NES1 project. Take 

by Level A harassment is not 

anticipated or proposed to be 

authorized. The Level A harassment 

zones (Table 9) are smaller than the 

required shutdown zones (see the 

Proposed Mitigation section). It is 

unlikely that a gray whale would enter 

and remain within the Level A 

harassment zone long enough to incur 

PTS. 

Humpback Whale 

Sightings of humpback whales in the 

proposed project area are rare, and few, 

if any, humpback whales are expected 

to approach the proposed project area. 

However, there have been a few 

observations of humpback whales near 

the POA as described in the Description 

of Marine Mammals in the Area of 

Specified Activities section of this 

notice. Based on the two sightings in 

2017 of what was likely a single 

individual at the Anchorage Public Boat 

Dock at Ship Creek (ABR, Inc., 2017) 

south of the Project area, the POA 

requested authorization of six takes of 

humpback whales. However, given the 

maximum number of humpback whales 

observed within a single construction 

season was two (in 2017), NMFS instead 

anticipates that only up to four 

humpback whales could be exposed to 

project-related underwater noise during 

the NES1 project. Therefore, NMFS 

proposes to authorize four takes by 

Level B harassment for humpback 

whales during the NES1 project. Take 

by Level A harassment is not 

anticipated or proposed to be 

authorized. The Level A harassment 

zones (Table 9) are smaller than the 

required shutdown zones (see the 

Proposed Mitigation section), therefore, 

it is unlikely that a humpback whale 

would enter and remain within the 

Level A harassment zone long enough to 

incur PTS. 

Killer Whale 

Few, if any, killer whales are expected 

to approach the NES1 project area. No 

killer whales were sighted during 

previous monitoring programs for POA 

construction projects, including the 

2016 TPP, 2020 PCT, and 2022 SFD 

projects (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; 


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Cornick and Seagars, 2016; 61N 

Environmental, 2021, 2022b), until PCT 

construction in 2021, when two killer 

whales were sighted (61N 

Environmental, 2022a). Previous 

sightings of transient killer whales have 

documented pod sizes in upper Cook 

Inlet between one and six individuals 

(Shelden et al., 2003). Therefore, the 

POA conservatively estimates that no 

more than one small pod (assumed to be 

six individuals) could be within 

estimated harassment zones during 

NES1 project activities. 

Take by Level A harassment is not 

anticipated or proposed to be authorized 

due to the implementation of shutdown 

zones, which would be larger than the 

Level A harassment zones (described 

below in the Proposed Mitigation 

section), and the low likelihood that 

killer whales would approach this 

distance for sufficient duration to incur 

PTS. Therefore, NMFS proposes to 

authorize six takes by Level B 

harassment for killer whales. 

Harbor Porpoise 

Monitoring data recorded from 2005 

through 2022 were used to evaluate 

hourly sighting rates for harbor 

porpoises in the proposed NES1 area 

(see Table 4–3 in the POA’s 

application). During most years of 

monitoring, no harbor porpoises were 

observed. However, there has been an 

increase in harbor porpoise sightings in 

upper Cook Inlet in recent decades (e.g., 

61N Environmental, 2021, 2022a; 

Shelden et al., 2014). The highest 

sighting rate for any recorded year 

during in-water pile installation and 

removal was an average of 0.037 harbor 

porpoises per hour during PCT 

construction in 2021, when observations 

occurred across most months. Given the 

uncertainty around harbor porpoise 

occurrence at the POA and potential 

that occurrence is increasing, it is 

estimated that approximately 0.07 

harbor porpoises per hour (the 2021 rate 

of 0.037 harbor porpoises per hour 

doubled) may be observed near the 

proposed NES1 area per hour of 

hammer use. With 246.5 hours of inwater pile installation and removal, we 

estimate that there could be 18 instances 

where harbor porpoises (0.07 harbor 

porpoises per hour * 246.5 hours = 17.3 

harbor porpoises rounded up to 18 

harbor porpoises) could be within 

estimated harassment zones during 

NES1 project activities. 

Harbor porpoises are small, lack a 

visible blow, have low dorsal fins, an 

overall low profile, and a short surfacing 

time, making them difficult to observe 

(Dahlheim et al., 2015). To account for 

the possibility that a harbor porpoise 

could enter a Level A harassment zone 

and remain there for sufficient duration 

to incur PTS before activities were shut 

down, the POA assumed that 5 percent 

of estimated harbor porpoise takes (one 

take of harbor porpoise; 5 percent of 18 

= 0.9, rounded up to 1) could be taken 

by Level A harassment. In its request, 

the POA rounded this estimate up to 

two to account for the average group 

size of this species, However, NMFS has 

determined such adjustments are 

generally unnecessary for purposes of 

estimating potential incidents of Level 

A harassment and does not concur with 

the request. At relatively close 

distances, NMFS believes it unlikely 

that groups will necessarily adhere to 

each other for sufficient duration for the 

entire group to incur PTS. While it is 

unlikely that a harbor porpoise could 

enter a Level A harassment zone for 

sufficient duration to incur PTS given 

the proposed shutdown measures (see 

the Proposed Mitigation section for 

more information) and potential for 

avoidance behavior, this species moves 

quickly and can be difficult to detect 

and track, therefore, NMFS proposes to 

authorize 1 take by Level A harassment 

and 17 takes by Level B harassment for 

harbor porpoises, for a total of 18 

instances of take. 

Steller Sea Lion 

Steller sea lions are anticipated to 

occur in low numbers within the 

proposed NES1 project area as 

summarized in the Description of 

Marine Mammals in the Area of 

Specified Activities section. Similar to 

the approach used above for harbor 

porpoises, the POA used previously 

recorded sighting rates of Steller sea 

lions near the POA to estimate 

requested take for this species. During 

SFD construction in May and June of 

2022, the hourly sighting rate for Steller 

sea lions was 0.028. The hourly sighting 

rate for Steller sea lions in 2021, the 

most recent year with observations 

across most months, was approximately 

0.01. Given the uncertainty around 

Steller sea lion occurrence at the POA 

and potential that occurrence is 

increasing, the POA estimated that 

approximately 0.06 Steller sea lions per 

hour (the May and June 2022 rate of 

0.028 Steller sea lions per hour doubled) 

may be observed near the proposed 

NES1 project areas per hour of hammer 

use. With 246.5 hours of in-water pile 

installation and removal, the POA 

estimates that 15 Steller sea lions (0.06 

sea lions per hour * 246.5 hours = 14.79 

sea lions rounded up to 15) could be 

within estimated harassment zones 

during NES1 project activities. 

However, the highest number of Steller 

sea lions that have been observed during 

the 2020–2022 monitoring efforts at the 

POA was nine individuals (eight during 

PCT Phase 1 monitoring and one during 

NMFS 2021 monitoring). Given the 

POA’s estimate assumes a higher Steller 

sea lion sighting rate (0.06) than has 

been observed at the POA and results in 

an estimate that is much larger than the 

number of Steller sea lions observed in 

a year, NMFS believes that the 15 

estimated takes requested by the POA 

overestimates potential exposures of 

this species. NMFS instead proposed 

that nine Steller sea lions may be taken, 

by Level B harassment only, during the 

NES1 project. 

The largest Level A harassment zone 

for Steller sea lions is 6 m. While it is 

unlikely that a Steller sea lion would 

enter a Level A harassment zone for 

sufficient duration to incur PTS, the 

POA is aware of a Steller sea lion that 

popped up next to a work skiff during 

the TPP in 2016, which was 

documented as a potential take by Level 

A harassment by the PSOs on duty at 

the time. Pile driving, however, was not 

occurring at the time the event was 

recorded and a brief observation of an 

animal within a Level A harassment 

zone does not necessarily mean the 

animal experienced Level A harassment 

(other factors such as duration within 

the harassment zone need to be taken 

into consideration). However, as a result 

of the aforementioned event, the POA 

requested authorization of an additional 

two takes of Steller sea lions by Level 

A harassment. Given the small Level A 

harassment zone (6 m), and proposed 

shutdown zones of ≥ 10 m, NMFS 

believes that it is unlikely that a Steller 

sea lion would be within the Level A 

harassment zone for sufficient duration 

to incur PTS. Therefore, NMFS does not 

propose to authorize take by Level A 

harassment for Steller sea lions. Rather, 

all 9 estimated takes are assumed to 

occur by Level B harassment, and no 

take by Level A harassment is proposed 

for authorization. 

Harbor Seal 

No known harbor seal haulout or 

pupping sites occur in the vicinity of 

the POA. In addition, harbor seals are 

not known to reside in the proposed 

NES1 project area, but they are seen 

regularly near the mouth of Ship Creek 

when salmon are running, from July 

through September. With the exception 

of newborn pups, all ages and sexes of 

harbor seals could occur in the NES1 

project area. Any harassment of harbor 

seals during in-water pile installation 

and removal would involve a limited 

number of individuals that may 


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potentially swim through the NES1 

project area or linger near Ship Creek. 

The POA evaluated marine mammal 

monitoring data to calculate hourly 

sighting rates for harbor seals in the 

NES1 project area (see Table 4–1 in the 

POA’s application). Of the 524 harbor 

seal sightings in 2020 and 2021, 93.7 

percent of the sightings were of single 

individuals; only 5.7 percent of 

sightings were of two individual harbor 

seals, and only 0.6 percent of sightings 

reported three harbor seals. Sighting 

rates of harbor seals were highly 

variable and appeared to have increased 

during monitoring between 2005 and 

2022. It is unknown whether any 

potential increase was due to local 

population increases or habituation to 

ongoing construction activities. The 

highest individual hourly sighting rate 

recorded for a previous year was used 

to quantify take of harbor seals for inwater pile installation and removal 

associated with NES1. This occurred in 

2021 during PCT Phase 2 construction, 

when harbor seals were observed from 

May through September. A total of 220 

harbor seal sightings were observed over 

734.9 hours of monitoring, at an average 

rate of 0.30 harbor seal sightings per 

hour. The maximum monthly sighting 

rate occurred in September 2020 and 

was 0.51 harbor seal sightings per hour. 

Based on these data, the POA estimated 

that approximately one harbor seal (the 

maximum monthly sighting rate (0.51) 

rounded up) may be observed near the 

NES1 project per hour of hammer use. 

This approximate sighting rate of one 

harbor seal per hour was also used to 

calculate potential exposures of harbor 

seals for the SFD project (86 FR 50057, 

September 7, 2021). Therefore, the POA 

estimates that during the 246.5 hours of 

anticipated in-water pile installation 

and removal, up to 247 harbor seals (1 

harbor seal per hour * 246.5 hours = 

246.5 harbor seals, rounded up to 247) 

could be within estimated harassment 

zones. 

Harbor seals often appear curious 

about onshore activities and may 

approach closely. The mouth of Ship 

Creek, where harbor seals linger, is 

about 2,500 m from the southern end of 

the NES1 and is therefore outside of the 

Level A harassment zones calculated for 

harbor seals (Table 9). However, given 

the potential difficulty of tracking 

individual harbor seals along the face of 

the NES1 site and their consistent lowlevel use of the POA area, NMFS 

anticipates the potential for some take 

by Level A harassment for harbor seals. 

For the SFD project, NMFS authorized 

8.6 percent of estimated harbor seal 

takes as potential Level A harassment 

based on the proportion of previous 

harbor seal sightings within the 

estimated Level A harassment zones (86 

FR 50057, September 7, 2021), but the 

NES1 Project is more distant from Ship 

Creek than SFD. NMFS therefore 

anticipates that a smaller proportion of 

takes by Level A harassment may occur 

during the NES1 project, and proposes 

to reduce this percentage to 5 percent. 

Therefore, NMFS proposes to authorize 

13 harbor seal takes (5 percent of 247 

exposures) by Level A harassment and 

234 takes (247 potential exposures 

minus 13) by Level B harassment, for a 

total of 247 takes. 

Beluga Whale 

For the POA’s PCT and SFD projects, 

NMFS used a sighting rate methodology 

to calculate potential exposure (equated 

to take) of CIBWs to sound levels above 

harassment criteria produced by the 

POA’s construction activities (85 FR 

19294, April 6, 2020; 86 FR 50057, 

September 7, 2021, respectively). For 

the PCT project, NMFS used data 

collected during marine mammal 

observations from 2005 to 2009 (Kendall 

and Cornick, 2015) and the total number 

of monthly observation hours during 

these efforts to derive hourly sighting 

rates of CIBWs per month of observation 

(April through November) (85 FR 19294, 

April 6, 2020). For the SFD project, 

observation data from 2020 PCT 

construction were also incorporated into 

the analysis (86 FR 50057, September 7, 

2021; 61N Environmental, 2021). 

The marine mammal monitoring 

programs for the PCT and SFD projects 

produced a unique and comprehensive 

data set of CIBW locations and 

movements (table 10; 61N 

Environmental, 2021, 2022a, 2022b; 

Easley-Appleyard and Leonard, 2022) 

that is the most current data set 

available for Knik Arm. During the PCT 

and SFD projects, the POA’s marine 

mammal monitoring programs included 

11 PSOs working from four elevated, 

specially designed monitoring stations 

located along a 9-km stretch of coastline 

surrounding the POA. The number of 

days data was collected varied among 

years and project, with 128 days during 

PCT Phase 1 in 2020, 74 days during 

PCT Phase 2 in 2021, and 13 days 

during SFD in 2022 (see Table 6–7 in 

the POA’s application for additional 

information regarding CIBW monitoring 

data). PSOs during these projects used 

25-power ‘‘big-eye’’ and hand-held 

binoculars to detect and identify marine 

mammals, and theodolites to track 

movements of CIBW groups over time 

and collect location data while they 

remained in view. 

These POA monitoring programs were 

supplemented in 2021 with a NMFSfunded visual marine mammal 

monitoring project that collected data 

during non-pile driving days during 

PCT Phase 2 (table 10; Easley-Appleyard 

and Leonard, 2022). NMFS replicated 

the POA monitoring efforts, as feasible, 

including use of 2 of the POA’s 

monitoring platforms, equipment (Big 

Eye binoculars, theodolite, 7x50 reticle 

binoculars), data collection software, 

monitoring and data collection protocol, 

and observers; however, the NMFSfunded program utilized only 4 PSOs 

and 2 observation stations along with 

shorter (4- to 8-hour) observation 

periods compared to PCT or SFD data 

collection, which included 11 PSOs, 4 

observation stations, and most 

observation days lasting close to 10 

hours. Despite the differences in effort, 

the NMFS dataset fills in gaps during 

the 2021 season when CIBW presence 

began to increase from low presence in 

July and is thus valuable in this 

analysis. NMFS’ PSO’s monitored for 

231.6 hours on 47 non-consecutive days 

in July, August, September, and 

October. 

Distances from CIBW sightings to the 

project site from the POA and NMFSfunded monitoring programs ranged 

from less than 10 m up to nearly 15 km 

during these monitoring programs. 

These robust marine mammal 

monitoring programs in place from 2020 

through 2022 located, identified, and 

tracked CIBWs at greater distances from 

the proposed project site than previous 

monitoring programs (i.e., Kendall and 

Cornick, 2015), and has contributed to 

a better understanding of CIBW 

movements in upper Cook Inlet (e.g., 

Easley-Appleyard and Leonard, 2022). 

Given the evolution of the best 

available data of CIBW presence in 

upper Cook Inlet, particularly regarding 

the distances at which CIBWs were 

being observed and documented (which 

increased during the PCT and SFD 

compared to earlier monitoring efforts), 

the POA proposes, and NMFS concurs, 

that the original sighting rate 

methodology used for the PCT and SFD 

projects is no longer the best approach 

for calculating potential take of CIBWs 

for the NES1 project. The recent and 

comprehensive data set of CIBW 

locations and movements from the PCT 

and SFD projects (61N Environmental, 

2021, 2022a, 2022b; Easley-Appleyard 

and Leonard, 2022) provides the 

opportunity for refinement of the 

previously used sighting rate 

methodology with updated data. Data 

for 2020, 2021, and 2022 were selected 

for the updated sighting rate analysis for 

the NES1 proposed project because they 

are the most current data available and 

are therefore most likely to accurately 


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represent future CIBW occurrence at the 

proposed project site, which may be 

affected by CIBW population size, CIBW 

movement patterns through Knik Arm, 

environmental change (including 

climate change), differences in salmon 

and other prey abundance among years, 

and other factors (table 10). The data 

from 2005 to 2009 (Kendall and 

Cornick, 2015), which was used by 

NMFS for sighting rate analyses for the 

PCT and SFD IHAs, were not included 

in this analysis due to the changes in 

observation programs and age of the 

data collected. Monitoring data from the 

2016 TPP (Cornick and Seagars, 2016) 

were also not included in the analysis 

because of limited hours observed, 

limited seasonal coverage, and 

differences in the observation programs. 

TABLE 10—MARINE MAMMAL MONITORING DATA USED FOR CIBW SIGHTING RATE CALCULATIONS

Year Monitoring type and 

data source 

Number of CIBW 

group fixes 

Number of CIBW 

groups Number of CIBWs 

2020 .. PCT: POA Construction Monitoring ............................................................

61N Environmental, 2021 ...........................................................................

2,653 245 987 

2021 .. PCT: NMFS Monitoring ..............................................................................

Easley-Appleyard and Leonard, 2022 ........................................................

694 1109 575 

2021 .. PCT: POA Construction Monitoring ............................................................

61N Environmental, 2021, 2022a ...............................................................

1,339 132 517 

2022 .. SFD: POA Construction Monitoring ............................................................

61N Environmental, 2022b .........................................................................

151 9 41 

1This number differs slightly from Table 6–8 in the POA’s application due to our removal of a few duplicate data points in the NMFS data set. 

The sighting rate methodology used 

for the PCT (85 FR 19294, April 6, 2020) 

and SFD (86 FR 50057, September 7, 

2021) projects used observations of 

CIBWs recorded in Knik Arm, regardless 

of observation distance to the POA, to 

produce a single monthly sighting rate 

that was then used to calculate potential 

CIBW take for all activities, regardless of 

the size of the ensonified areas for the 

project activities (i.e., take was 

calculated solely based on the monthly 

sighting rates and the estimated hours of 

proposed activities, and did not 

consider the estimated sizes of the 

ensonified areas). This method may 

have overestimated potential CIBW 

takes when harassment zones were 

small because distant CIBWs would 

have been included in the sighting rate. 

This method also resulted in takes 

estimates that were identical for 

installation and removal of all pile sizes, 

regardless of pile driving method used 

(e.g., vibratory, impact) or 

implementation of attenuation systems, 

since the calculation did not consider 

the size of the ensonified areas. 

NMFS and the POA collaboratively 

developed a new sighting rate 

methodology for the NES1 project that 

incorporates a spatial component for 

CIBW observations, which would allow 

for more accurate estimation of potential 

take of CIBWs for this project. NMFS 

proposes to use this approach to 

estimate potential takes of CIBW for 

authorization. During the POA’s and 

NMFS’ marine mammal monitoring 

programs for the PCT and SFD projects, 

PSOs had an increased ability to detect, 

identify, and track CIBWs groups at 

greater distances from the project work 

site when compared with previous years 

because of the POA’s expanded 

monitoring program as described above. 

This meant that observations of CIBWs 

in the 2020–2022 dataset (table 10) 

include sightings of individuals at 

distances far outside the ensonified 

areas estimated for the NES1 project 

(Table 9). Therefore, it would not be 

appropriate to group all CIBW 

observations from these datasets into a 

single sighting rate as was done for the 

PCT and SFD projects. Rather, we 

propose that CIBW observations should 

be considered in relation to their 

distance to the NES1 project site when 

determining appropriate sighting rates 

to use when estimating take for this 

project. This would help to ensure that 

the sighting rates used to estimate take 

are representative of CIBW presence in 

the proposed ensonified areas. 

To incorporate a spatial component 

into the sighting rate methodology, the 

POA calculated each CIBW group’s 

closest point of approach (CPOA) 

relative to the NES1 proposed project 

site. The 2020–2022 marine mammal 

monitoring programs (table 10) enabled 

the collection, in many cases, of 

multiple locations of CIBW groups as 

they transited through Knik Arm, which 

allowed for track lines to be interpolated 

for many groups. The POA used these 

track lines, or single recorded locations 

in instances where only one sighting 

location was available, to calculate each 

group’s CPOA. CPOAs were calculated 

in ArcGIS software using the GPS 

coordinates provided for documented 

sightings of each group (for details on 

data collection methods, see 61N 

Environmental, 2021, 2022a, 2022b; 

Easley-Appleyard and Leonard, 2022) 

and the NES1 location midpoint, 

centered on the proposed project site. A 

CIBW group was defined as a sighting 

of one or more CIBWs as determined 

during data collection. The most distant 

CPOA location to NES1 was 11,057 m 

and the closest CPOA location was 15 

m. 

The cumulative density distribution 

of CPOA values represents the 

percentage of CIBW observations that 

were within various distances to the 

NES1 action site (Figure 2). This 

distribution shows how CIBW 

observations differed with distances to 

the NES1 site and was used to infer 

appropriate distances within which to 

estimate spatially-derived CIBW 

sighting rates (Figure 2). The POA 

implemented a piecewise regression 

model that detected breakpoints (i.e., 

points within the CPOA data at which 

statistical properties of the sequence of 

observational distances changed) in the 

cumulative density distribution of the 

CPOA locations, which they proposed 

to represent spatially-based sighting rate 

bins for use in calculating CIBW 

sighting rates. The POA used the 

‘‘Segmented’’ package (Muggeo, 2020) in 

the R Statistical Software Package (R 

Core Team, 2022) to determine 

statistically significant breakpoints in 

the linear distances of the CIBW data 

using this regression method (see 

Section 6.5.5.3 of the POA’s application 

for more details regarding this statistical 

analysis). This analysis identified 

breakpoints in the CPOA locations at 74, 

1,651, 2,808, and 7,369 m (Figure 2). 


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Piecewise regression is a common tool 

for modeling ecological thresholds 

(Lopez et al., 2020; Whitehead et al., 

2016; Atwood et al., 2016). In a similar 

scenario to the one outlined above, 

Mayette et al. (2022) used piecewise 

regression methods to model the 

distances between two individual 

CIBWs in a group in a nearshore and a 

far shore environment. For the POA’s 

analysis, the breakpoints (i.e., 74, 1,651, 

2,808, and 7,369 m) detect a change in 

the frequency of CIBW groups sighted 

and the slope of the line between two 

points indicates the magnitude of 

change. A greater positive slope 

indicates a greater accumulation of 

sightings over the linear distance (xaxis) between the defining breakpoints, 

whereas a more level slope (i.e., closer 

to zero) indicates a lower accumulation 

of sightings over that linear distance (xaxis) between those defining 

breakpoints (Figure 2; see Table 6–8 in 

the POA’s application for the slope 

estimates for the empirical cumulative 

distribution function). 

The breakpoints identified by the 

piecewise regression analysis are in 

agreement with what is known about 

CIBW behavior in Knik Arm based on 

recent monitoring efforts (61N 

Environmental, 2021, 2022a, 2022b; 

Easley-Appleyard and Leonard, 2022). 

Observation location data collected 

during POA monitoring programs 

indicate that CIBWs were consistently 

found in higher numbers in the 

nearshore areas, along both shorelines, 

and were found in lower numbers in the 

center of the Arm. Tracklines of CIBW 

group movements collected from 2020 

to 2022 show that CIBWs displayed a 

variety of movement patterns that 

included swimming close to shore past 

the POA on the east side of Knik Arm 

(defined by breakpoint 1 at 74 m), with 

fewer CIBWs swimming in the center of 

Knik Arm (breakpoints 1 to 2, at 74 to 

1,651 m). CIBWs commonly swam past 

the POA close to shore on the west side 

of Knik Arm, with no CIBWs able to 

swim farther from the POA in that area 

than the far shore (breakpoints 2 to 3, 

at 1,651 to 2,808 m). Behaviors and 

locations beyond breakpoint 4 (7,369 m) 

include swimming past the mouth of 

Knik Arm between the Susitna River 

area and Turnagain Arm; milling at the 

mouth of Knik Arm but not entering the 

Arm; and milling to the northwest of the 

POA without exiting Knik Arm. The 

shallowness of slope 5, at distances 

greater than 7,369 m, could be due to 

detection falloff from a proximity 

(distance) bias, which would occur 

when PSOs are less likely to detect 

CIBW groups that are farther away than 

groups that are closer. 

The POA, in collaboration with 

NMFS, used the distances detected by 

the breakpoint analysis to define five 

sighting rate distance bins for CIBWs in 

the NES1 project area. Each breakpoint 

(74, 1,651, 2,808, and 7,369 m, and the 

complete data set of observations [≤ 

7,369 m]) was rounded up to the nearest 

meter and considered the outermost 

limit of each sighting rate bin, resulting 

in five identified bins (table 11). All 

CIBW observations less than each bin’s 

breakpoint distance were used to 

calculated that bin’s respective monthly 

sighting rates (e.g., all sightings from 0 

to 74 m are included in the sighting 

rates calculated for bin number 1, all 

sightings from 0 to 1,651 m are included 

in the sighting rates calculated for bin 

number 2, and so on). NES1 demolition 

is anticipated to take place from April 

through November 2024, therefore 

monthly sighting rates were only 

derived for these months (table 11). 


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Breakpoints by piecewise linear regression 

0 1000 2000 3000 4000 5000 6000 7000 sooo 9000 10000 1'1000 

Distance to NES1 [m] 

Figure 2 -- Percent of CIBW CPOA Observations in Relation to Distance from the 

NESl Project Site and Associated Breakpoints Determined by Piecewise Linear 

Regression 
76612 Federal Register / Vol. 88, No. 213 / Monday, November 6, 2023 / Notices 

TABLE 11—CIBW MONTHLY SIGHTING RATES FOR DIFFERENT SPATIALLY-BASED BIN SIZES

Bin No. Distance 

(m) 

CIBW/hour 1

April May June July August September October November 

1 ................................................ ≤ 74 0.09 0.06 0.10 0.04 0.83 0.62 0.51 0.11 

2 ................................................ ≤ 1,651 0.25 0.14 0.13 0.06 1.43 1.30 1.15 0.70 

3 ................................................ ≤ 2,808 0.36 0.22 0.21 0.07 2.08 1.90 2.04 0.73 

4 ................................................ ≤ 7,369 0.67 0.33 0.29 0.13 2.25 2.19 2.42 0.73 

5 ................................................ > 7,369 0.71 0.39 0.30 0.13 2.29 2.23 2.56 0.73 

1Observation hours have been totaled from the PCT 2020 and 2021 programs, the NMFS 2021 data collection effort, and the SFD 2022 program (61N Environmental 2021, 2022a, 2022b; Easley-Appleyard and Leonard, 2022). 

Potential exposures (equated with 

takes) of CIBWs were calculated by 

multiplying the total number of 

vibratory installation or removal hours 

per month for each sized/shaped pile 

based on the anticipated construction 

schedule (table 2) with the 

corresponding sighting rate month and 

sighting rate distance bin (table 12). For 

example, the Level B harassment 

isopleth distance for the vibratory 

installation of 24-inch (61-cm) piles is 

2,247 m, which falls within bin number 

3 (table 11). Therefore, take for this 

activity is calculated by multiplying the 

total number of hours estimated each 

month to install 24-inch piles via a 

vibratory hammer by the monthly CIBW 

sighting rates calculated for bin number 

3 (table 12). The resulting estimated 

CIBW exposures were totaled for all 

activities in each month (table 13). 

In their calculation of CIBW take, the 

POA assumed that only 24-inch (61-cm) 

template piles would be installed (rather 

than 36-inch, 91-cm) and removed 

during the project due to the vibratory 

removal of 24-inch piles having the 

largest isopleth. If 36-inch (61-cm) piles 

are used for temporary stability template 

piles, it would be assumed that the 

potential impacts of this alternate 

construction scenario and method on 

marine mammals are fungible (i.e., that 

potential impacts of installation and 

removal of 36-inch (91-cm) steel pipe 

piles would be similar to the potential 

impacts of installation and removal of 

24-inch (61-cm) steel pipe piles). Using 

the monthly activity estimates in hours 

(Table 2) and monthly calculated 

sighting rates (CIBWs/hour) for the 

spatially derived distance bins (table 

12), the POA estimates that there could 

be up to 122 (121.1 rounded up to 122) 

instances of CIBW take where during 

the NES1 project (table 13). 

TABLE 12—ALLOCATION OF EACH LEVEL B HARASSMENT ISOPLETH TO A SIGHTING RATE BIN AND CIBW MONTHLY

SIGHTING RATES FOR DIFFERENT PILE SIZES AND HAMMER TYPES

Level B 

harassment 

isopleth 

distance 

(m) 

Sighting 

rate bin 

number and 

distance 

CIBWs/hour 

April May June July August September October November 

24-inch Vibratory 

Installation ...... 2,247 3 

(2,808 m) 

0.36 0.22 0.21 0.07 2.08 1.90 2.04 0.73 

24-inch Vibratory 

Removal ......... 5,968 4 

(7,369 m) 

0.67 0.33 0.29 0.13 2.25 2.19 2.42 0.73 

36-inch Vibratory 

Installation ...... 4,514 4 

(7,369 m) 

0.67 0.33 0.29 0.13 2.25 2.19 2.42 0.73 

36-inch Vibratory 

Removal ......... 1,700 3 

(2,808 m) 

0.36 0.22 0.21 0.07 2.08 1.90 2.04 0.73 

Sheet Pile Vibratory Removal 1,954 3 

(2,808 m) 

0.36 0.22 0.21 0.07 2.08 1.90 2.04 0.73 

Observation 

Hours/ 

Month 1: .. .................... .................... 87.9 615.1 571.6 246.9 224.5 326.2 109.5 132.0 

1Observation hours have been totaled from the PCT 2020 and 2021 programs, the NMFS 2021 data collection effort, and the SFD 2022 program (61N Environmental, 2021, 2022a, 2022b; Easley-Appleyard and Leonard, 2022). 

For the PCT (85 FR 19294, April 6, 

2020) and SFD (86 FR 50057, September 

7, 2021) projects, NMFS accounted for 

the implementation of mitigation 

measures (e.g., shutdown procedures 

implemented when CIBWs entered or 

approached the estimated Level B 

harassment zone) by applying an 

adjustment factor to CIBW take 

estimates. This was based on the 

assumption that some Level B 

harassment takes would likely be 

avoided based on required shutdowns 

for CIBWs at the Level B harassment 

zones (see the Proposed Mitigation 

section for more information). For the 

PCT project, NMFS compared the 

number of realized takes at the POA to 

the number of authorized takes for 

previous projects from 2008 to 2017 and 

found the percentage of realized takes 

ranged from 12 to 59 percent with an 

average of 36 percent (85 FR 19294, 

April 6, 2020). NMFS then applied the 

highest percentage of previous realized 

takes (59 percent during the 2009–2010 

season) to ensure potential takes of 

CIBWs were fully evaluated. In doing 

so, NMFS assumed that approximately 

59 percent of the takes calculated would 

be realized during PCT and SFD 

construction (85 FR 19294, April 6, 

2020; 86 FR 50057, September 7, 2021) 

and that 41 percent of the calculated 

CIBW Level B harassment takes would 

be avoided by successful 


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implementation of required mitigation 

measures. 

The POA calculated the adjustment 

for successful implementation of 

mitigation measures for NES1 using the 

percentage of realized takes for the PCT 

project (see Table 6–12 in the POA’s 

application). The recent data from PCT 

Phase 1 and PCT Phase 2 most 

accurately reflect the current marine 

mammal monitoring program, the 

current program’s effectiveness, and 

CIBW occurrence in the proposed 

project area. Between the two phases of 

the PCT project, 90 total Level B 

harassment takes were authorized and 

53 were potentially realized (i.e., 

number of CIBWs observed within 

estimated Level B harassment zones), 

equating to an overall percentage of 59 

percent. The SFD Project, during which 

only 7 percent of authorized take was 

potentially realized, represents 

installation of only 12 piles during a 

limited time period and does not 

represent the much higher number of 

piles and longer construction season 

anticipated for NES1.2 

NMFS proposes that the 59-percent 

adjustment accurately accounts for the 

efficacy of the POA’s marine mammal 

monitoring program and required 

shutdown protocols. NMFS therefore 

assumes that approximately 59 percent 

of the takes calculated for NES1 may 

actually be realized. This adjusts the 

potential takes by Level B harassment of 

CIBWs proposed for authorization from 

122 to 72 (table 13). Take by Level A 

harassment is not anticipated or 

proposed to be authorized because the 

POA will be required to shutdown 

activities when CIBWs approach and or 

enter the Level B harassment zone (see 

the Proposed Mitigation section for 

more information). 

TABLE 13—POTENTIAL MONTHLY CIBW LEVEL B HARASSMENT EXPOSURES

April May June July August September October November Total 

24-inch Vibratory Installation 

and Removal ......................... 2.5 3.0 1.7 0.6 12.5 6.9 3.9 0.2 31.3 

Sheet Pile Removal .................. 3.6 9.9 12.5 4.4 27.0 22.8 8.1 1.5 89.8 

Total Estimated Level B Harassment Exposures for All Activities (Rounded): 121.1 

Total Estimated Level B Harassment Exposures with 59% Correction Factor (Rounded): 71.5 (72) 

In summary, the total amount of Level 

A harassment and Level B harassment 

proposed to be authorized for each 

marine mammal stock is presented in 

table 14. 

TABLE 14—AMOUNT OF PROPOSED TAKE AS A PERCENTAGE OF STOCK ABUNDANCE, BY STOCK AND HARASSMENT TYPE

Species 

Proposed take 

Stock Percent of 

stock Level A Level B Total 

Gray whale ............................ 0 6 6 Eastern North Pacific ................................... 1 0.02 

Humpback whale ................... 0 4 4 Hawai1i .......................................................... 1 0.04 

Mexico-North Pacific .................................... 2 UNK 

Beluga whale ......................... 0 72 72 Cook Inlet ..................................................... 21.75 

Killer whale ............................ 0 6 6 Eastern North Pacific Alaska Resident ........ 1 0.31 

Eastern North Pacific Gulf of Alaska, Aleutian Islands and Bering Sea Transient.1.021

Harbor porpoise .................... 1 17 18 Gulf of Alaska ............................................... 0.06 

Steller sea lion ...................... 0 9 9 Western ........................................................ 0.02 

Harbor seals .......................... 13 234 247 Cook Inlet/Shelikof Strait .............................. 0.87 

1 NMFS conservatively assumes that all takes occur to each stock. 

2 NMFS does not have an official abundance estimate for this stock and the minimum population estimate is considered to be unknown (Young 

et al., 2023). 

Proposed Mitigation 

In order to issue an IHA under section 

101(a)(5)(D) of the MMPA, NMFS must 

set forth the permissible methods of 

taking pursuant to the activity, and 

other means of effecting the least 

practicable impact on the species or 

stock and its habitat, paying particular 

attention to rookeries, mating grounds, 

and areas of similar significance, and on 

the availability of the species or stock 

for taking for certain subsistence uses 

(latter not applicable for this action). 

NMFS regulations require applicants for 

incidental take authorizations to include 

information about the availability and 

feasibility (economic and technological) 

of equipment, methods, and manner of 

conducting the activity or other means 

of effecting the least practicable adverse 

impact upon the affected species or 

stocks, and their habitat (50 CFR 

216.104(a)(11)). 

In evaluating how mitigation may or 

may not be appropriate to ensure the 

least practicable adverse impact on 

species or stocks and their habitat, as 

well as subsistence uses where 

applicable, NMFS considers two 

primary factors: 

(1) The manner in which, and the 

degree to which, the successful 

implementation of the measure(s) is 

expected to reduce impacts to marine 

mammals, marine mammal species or 

stocks, and their habitat. This considers 

the nature of the potential adverse 

impact being mitigated (likelihood, 

scope, range). It further considers the 

likelihood that the measure will be 

effective if implemented (probability of 

accomplishing the mitigating result if 

implemented as planned), the 

likelihood of effective implementation 

(probability implemented as planned), 

and; 

(2) The practicability of the measures 

for applicant implementation, which 

may consider such things as cost, and 

impact on operations. 


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The POA presented mitigation 

measures in Section 11 of their 

application that were modeled after the 

requirements included in the IHAs 

issued for Phase 1 and Phase 2 PCT 

construction (85 FR 19294, April 6, 

2020) and for SFD construction (86 FR 

50057, September 7, 2021), which were 

designed to minimize the total number, 

intensity, and duration of harassment 

events for CIBWs and other marine 

mammal species during those projects 

(61N Environmental, 2021, 2022a, 

2022b). NMFS concurs that these 

proposed measures reduce the potential 

for CIBWs, and other marine mammals, 

to be adversely impacted by the 

proposed activity. 

The POA must employ the following 

mitigation measures: 

• Ensure that construction 

supervisors and crews, the monitoring 

team and relevant POA staff are trained 

prior to the start of all pile driving, so 

that responsibilities, communication 

procedures, monitoring protocols, and 

operational procedures are clearly 

understood. New personnel joining 

during the project must be trained prior 

to commencing work; 

• Employ PSOs and establish 

monitoring locations as described in 

Section 5 of the IHA and the POA’s 

Marine Mammal Monitoring and 

Mitigation Plan (see Appendix B of the 

POA’s application). The POA must 

monitor the project area to the 

maximum extent possible based on the 

required number of PSOs, required 

monitoring locations, and 

environmental conditions; 

• Monitoring must take place from 30 

minutes prior to initiation of pile 

driving (i.e., pre-clearance monitoring) 

through 30 minutes post-completion of 

pile driving; 

• Pre-start clearance monitoring must 

be conducted during periods of 

visibility sufficient for the lead PSO to 

determine that the shutdown zones 

indicated in table 15 are clear of marine 

mammals. Pile driving may commence 

following 30 minutes of observation 

when the determination is made that the 

shutdown zones are clear of marine 

mammals or when the mitigation 

measures proposed specifically for 

CIBWs (below) are satisfied; 

• For all construction activities, 

shutdown zones must be established 

following table 15. The purpose of a 

shutdown zone is generally to define an 

area within which shutdown of activity 

would occur upon sighting of a marine 

mammal (or in anticipation of an animal 

entering the defined area). In addition to 

the shutdown zones specified in table 

15 and the minimum shutdown zone of 

10-m described above, requirements 

included in NMFS’ proposed IHA, the 

POA plans to implement a minimum 

100-m shutdown zone around the active 

NES1 project work site, including 

around activities other than pile 

installation or removal that NMFS has 

determined do not present a reasonable 

potential to cause take of marine 

mammals. Shutdown zones for pile 

installation and removal would vary 

based on the type of construction 

activity and by marine mammal hearing 

group (table 15). Here, shutdown zones 

are larger than or equal to the calculated 

Level A harassment isopleths shown in 

table 9 for species other than CIBW and 

are equal to the estimated Level B 

harassment isopleths for CIBWs; 

TABLE 15—PROPOSED SHUTDOWN ZONES DURING PROJECT ACTIVITIES

Activity Pile type/size 

Shutdown zone (m) 

PW OW 

LF cetaceans Non-CIBW MF 

cetaceans CIBWs HF cetaceans 

Impact Removal .... Sheet pile ............. 160 10 900 190 90 10 

Vibratory Installation.24-inch (61-cm) .... 20 10 2,300 20 10 10 

36-inch (91-cm) .... 30 10 4,600 40 20 10 

Vibratory Removal Sheet pile ............. 10 10 2,000 20 10 10 

24-inch (61-cm) .... 40 10 6,000 60 30 10 

36-inch (91-cm) .... 20 10 1,700 20 10 10 

Notes: cm = centimeter(s), m = meter(s). 

• Marine mammals observed 

anywhere within visual range of the 

PSO must be tracked relative to 

construction activities. If a marine 

mammal is observed entering or within 

the shutdown zones indicated in table 

15, pile driving must be delayed or 

halted. If pile driving is delayed or 

halted due to the presence of a marine 

mammal, the activity may not 

commence or resume until either the 

animal has voluntarily exited and been 

visually confirmed beyond the 

shutdown zone (table 15, or 15 minutes 

(non-CIBWs) or 30 minutes (CIBWs) 

have passed without re-detection of the 

animal; 

• The POA must use soft start 

techniques when impact pile driving. 

Soft start requires contractors to provide 

an initial set of three strikes at reduced 

energy, followed by a 30-second waiting 

period, then two subsequent reduced 

energy strike sets. A soft start must be 

implemented at the start of each day’s 

impact pile driving and at any time 

following cessation of impact pile 

driving for a period of 30 minutes or 

longer. PSOs shall begin observing for 

marine mammals 30 minutes before 

‘‘soft start’’ or in-water pile installation 

or removal begins; 

• Pile driving activity must be halted 

upon observation of either a species for 

which incidental take is not authorized 

or a species for which incidental take 

has been authorized but the authorized 

number of takes has been met, entering 

or within the harassment zone; and 

• The POA must avoid direct 

physical interaction with marine 

mammals during construction activities. 

If a marine mammal comes within 10 m 

of such activity, operations shall cease. 

Should a marine mammal come within 

10 m of a vessel in transit, the boat 

operator will reduce vessel speed to the 

minimum level required to maintain 

steerage and safe working conditions. If 

human safety is at risk, the in-water 

activity will be allowed to continue 

until it is safe to stop. 

The following additional mitigation 

measures are proposed by NMFS for 

CIBWs: 

• The POA must make all practicable 

efforts to complete construction 

activities between April and July, when 

CIBWs are typically found in lower 

numbers near the proposed site; 

• Prior to the onset of pile driving, 

should a CIBW be observed approaching 

the estimated Level B harassment zone 

(Table 9) (i.e. the CIBWs shutdown zone 

column in Table 15), pile driving must 

not commence until the whale(s) moves 


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at least 100 m past the estimated Level 

B harassment zone and on a path away 

from the zone, or the whale has not been 

re-sighted within 30 minutes; 

• If pile installation or removal has 

commenced, and a CIBW(s) is observed 

within or likely to enter the estimated 

Level B harassment zone, pile 

installation or removal must shut down 

and not re-commence until the whale 

has traveled at least 100 m beyond the 

Level B harassment zone and is on a 

path away from such zone or until no 

CIBW has been observed in the Level B 

harassment zone for 30 minutes; and 

• If during installation and removal of 

piles, PSOs can no longer effectively 

monitor the entirety of the CIBW Level 

B harassment zone due to 

environmental conditions (e.g., fog, rain, 

wind), pile driving may continue only 

until the current segment of the pile is 

driven; no additional sections of pile or 

additional piles may be driven until 

conditions improve such that the Level 

B harassment zone can be effectively 

monitored. If the Level B harassment 

zone cannot be monitored for more than 

15 minutes, the entire Level B 

harassment zone will be cleared again 

for 30 minutes prior to pile driving. 

In addition to these additional 

mitigation measures being proposed by 

NMFS, NMFS requested that the POA 

restrict all pile driving and removal 

work to April to July, when CIBWs are 

typically found in lower numbers. 

However, given the safety and 

environmental concerns of collapse of 

the Northern Extension once removal 

work commences, required sequencing 

of pile installation and removal and fill 

removal, and uncertainties and adaptive 

nature of the work, the POA stated that 

it cannot commit to restricting pile 

driving and removal to April to July. 

Instead, as required in the proposed 

mitigation, NMFS would require the 

POA to complete as much work as is 

practicable in April to July to reduce the 

amount of pile driving and removal 

activities in August through November. 

For previous IHAs issued to the POA 

(PCT: 85 FR 19294, April 6, 2020; SFD: 

86 FR 50057, September 7, 2021), the 

use of a bubble curtain to reduce noise 

has been required as a mitigation 

measure for certain pile driving 

scenarios. The POA did not propose to 

use a bubble curtain system during the 

NES1 project, stating that it is not a 

practicable mitigation measure for this 

demolition project. NMFS concurs with 

this determination. Practicability 

concerns include the following: 

• NES1 construction activities 

includes installation of round, 

temporary, stability template piles to 

shore up the filled NES1 structure while 

fill material and sheet piles are 

removed. Stability template piles that 

would be required for demolition of the 

sheet pile structure are located in 

proximity of the sheet piles. A bubble 

curtain would not physically fit 

between the sheet piles and the 

template piles; 

• Bubble curtains could not be 

installed around the sheet piles as they 

are removed because the structure 

consists of sheet piles that are 

connected to one another and used to 

support fill-material. It would not be 

possible to place a bubble curtain 

system along the sheet pile face for 

similar reasons, including lack of space 

for the bubble curtain and the structures 

and equipment that would be needed to 

install and operate it, and the high 

likelihood that it could not function or 

be retrieved; and 

• NES1 is a failed structure, and has 

been deemed ‘‘globally unstable’’ and 

poses significant risk for continued 

deterioration and structural collapse. If 

the existing structure were to collapse 

during deconstruction and sheet pile 

removal, there is risk of a significant 

release of impounded fill material into 

CIBW habitat, the POA’s vessel 

operating and mooring areas, and the 

USACE Anchorage Harbor Project. Due 

to the stability risk of the existing 

impounded material, it is expected that 

construction and demolition means and 

methods would be highly adaptive once 

actual field work commences, and use 

of a bubble curtain with deconstruction 

would limit operations in the field and 

create significant health and safety 

issues. 

The POA also has efficacy concerns 

about requiring a bubble curtain for 

NES1 construction activities. Adding a 

requirement for a bubble curtain may 

hinder production, due to the time 

required to install and remove the 

bubble curtain itself. This has the 

potential to drive the in-water 

construction schedule further into the 

late summer months, which are known 

for higher CIBW abundance in lower 

Knik Arm, thus lengthening the 

duration of potential interactions 

between CIBW and in-water works. 

Therefore, NMFS is concerned that use 

of a bubble curtain may not be an 

effective measure, given the potential 

that bubble curtain use could ultimately 

result in increased impacts to CIBW, in 

addition to the aforementioned 

practicability issues. 

Based on our evaluation of the 

applicant’s proposed measures, as well 

as other measures considered by NMFS, 

NMFS has preliminarily determined 

that the proposed mitigation measures 

provide the means of effecting the least 

practicable impact on the affected 

species or stocks and their habitat, 

paying particular attention to rookeries, 

mating grounds, and areas of similar 

significance. 

Proposed Monitoring and Reporting 

In order to issue an IHA for an 

activity, section 101(a)(5)(D) of the 

MMPA states that NMFS must set forth 

requirements pertaining to the 

monitoring and reporting of such taking. 

The MMPA implementing regulations at 

50 CFR 216.104(a)(13) indicate that 

requests for authorizations must include 

the suggested means of accomplishing 

the necessary monitoring and reporting 

that will result in increased knowledge 

of the species and of the level of taking 

or impacts on populations of marine 

mammals that are expected to be 

present while conducting the activities. 

Effective reporting is critical both to 

compliance as well as ensuring that the 

most value is obtained from the required 

monitoring. 

Monitoring and reporting 

requirements prescribed by NMFS 

should contribute to improved 

understanding of one or more of the 

following: 

• Occurrence of marine mammal 

species or stocks in the area in which 

take is anticipated (e.g., presence, 

abundance, distribution, density); 

• Nature, scope, or context of likely 

marine mammal exposure to potential 

stressors/impacts (individual or 

cumulative, acute or chronic), through 

better understanding of: (1) action or 

environment (e.g., source 

characterization, propagation, ambient 

noise); (2) affected species (e.g., life 

history, dive patterns); (3) co-occurrence 

of marine mammal species with the 

activity; or (4) biological or behavioral 

context of exposure (e.g., age, calving or 

feeding areas); 

• Individual marine mammal 

responses (behavioral or physiological) 

to acoustic stressors (acute, chronic, or 

cumulative), other stressors, or 

cumulative impacts from multiple 

stressors; 

• How anticipated responses to 

stressors impact either: (1) long-term 

fitness and survival of individual 

marine mammals; or (2) populations, 

species, or stocks; 

• Effects on marine mammal habitat 

(e.g., marine mammal prey species, 

acoustic habitat, or other important 

physical components of marine 

mammal habitat); and, 

• Mitigation and monitoring 

effectiveness. 

The POA would implement a marine 

mammal monitoring and mitigation 

strategy intended to avoid and minimize 


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impacts to marine mammals (see 

Appendix B of the POA’s application for 

their Marine Mammal Monitoring and 

Mitigation Plan). Marine mammal 

monitoring would be conducted at all 

times when in-water pile installation 

and removal is taking place. 

Additionally, PSOs would be on-site 

monitoring for marine mammals during 

in-water cutting of sheet piles with 

shears or an ultrathermic torch. 

The marine mammal monitoring and 

mitigation program that is planned for 

NES1 construction would be modeled 

after the stipulations outlined in the 

IHAs for Phase 1 and Phase 2 PCT 

construction (85 FR 19294, April 6, 

2020) and the IHA for SFD construction 

(86 FR 50057, September 7, 2021). 

Visual Monitoring 

Monitoring must be conducted by 

qualified, NMFS-approved PSOs, in 

accordance with the following: 

• PSOs must be independent of the 

activity contractor (e.g., employed by a 

subcontractor) and have no other 

assigned tasks during monitoring 

periods. At least one PSO must have 

prior experience performing the duties 

of a PSO during construction activity 

pursuant to a NMFS-issued IHA or 

Letter of Concurrence. Other PSOs may 

substitute other relevant experience, 

education (degree in biological science 

or related field), or training for prior 

experience performing the duties of a 

PSO. PSOs must be approved by NMFS 

prior to beginning any activity subject to 

this IHA; 

• The POA must employ PSO stations 

at a minimum of two locations from 

which PSOs can effectively monitor the 

shutdown zones (Table 15). Concerns 

about the stability of the NES1 project 

area preclude determination of the exact 

number and locations of PSO stations 

until the Construction Contractor 

develops their Construction Work Plan. 

PSO stations must be positioned at the 

best practical vantage points that are 

determined to be safe. Likely locations 

include the Anchorage Public Boat Dock 

at Ship Creek to the south of the 

proposed project site, and a location to 

the north of the project site, such as the 

northern end of POA property near 

Cairn Point (see North Extension area on 

Figure 12–1 in the POA’s application) or 

at Port MacKenzie across Knik Arm (see 

Figure 12–1 in the POA’s application for 

potential locations of PSO stations). A 

location near the construction activity 

may not be possible given the risk of 

structural collapse as outlined in the 

POA’s IHA application. Placing a PSO 

on the northernmost portion of 

Terminal 3 would also be considered if 

deemed safe. Areas near Cairn Point or 

Port MacKenzie have safety, security, 

and logistical issues, which would need 

to be considered. Cairn Point proper is 

located on military land and has bear 

presence, and restricted access does not 

allow for the location of an observation 

station at this site. Tidelands along 

Cairn Point are accessible only during 

low tide conditions and have inherent 

safety concerns of being trapped by 

rising tides. Port MacKenzie is a secure 

port that is relatively remote, creating 

safety, logistical, and physical staffing 

limitations due to lack of nearby lodging 

and other facilities. The roadway travel 

time between port sites is approximately 

2–3 hours. An adaptive management 

measure is proposed for a monitoring 

location north of the proposed project 

site, once the Construction Contractor 

has been selected and more detailed 

discussions can occur. Temporary 

staffing of a northerly monitoring station 

during peak marine mammal presence 

time periods and/or when shutdown 

zones are large would be considered. At 

least one PSO station must be able to 

fully observe the shutdown zones (Table 

15); 

• PSOs stations must be elevated 

platforms constructed on top of 

shipping containers or a similar base 

that is at least 8’ 6’’ high (i.e., the 

standard height of a shipping container) 

that can support up to three PSOs and 

their equipment. The platforms must be 

stable enough to support use of a 

theodolite and must be located to 

optimize the PSO’s ability to observe 

marine mammals and the harassment 

zones; 

• Each PSO station must have at least 

two PSOs on watch at any given time; 

one PSO must be observing, one PSO 

would be recording data (and observing 

when there are no data to record). 

Teams of three PSOs would include one 

PSO who would be observing, one PSO 

who would be recording data (and 

observing when there are no data to 

record), and one PSO who would be 

resting. In addition, if POA is 

conducting non-NES1-related in-water 

work that includes PSOs, the NES1 

PSOs must be in real-time contact with 

those PSOs, and both sets of PSOs must 

share all information regarding marine 

mammal sightings with each other; 

• A designated lead PSO must always 

be on site. The lead observer must have 

prior experience performing the duties 

of a PSO during in-water construction 

activities pursuant to a NMFS-issued 

incidental take authorization or Letter of 

Concurrence. Each PSO station must 

also have a designated lead PSO specific 

to that station and shift. These lead 

PSOs must have prior experience 

working as a PSO during in-water 

construction activities; 

• PSOs would use a combination of 

equipment to perform marine mammal 

observations and to verify the required 

monitoring distance from the project 

site, including 7 by 50 binoculars, 20x/ 

40x tripod mounted binoculars, 25 by 

150 ‘‘big eye’’ tripod mounted 

binoculars, and theodolites; 

• PSOs must record all observations 

of marine mammals, regardless of 

distance from the pile being driven. 

PSOs shall document any behavioral 

reactions in concert with distance from 

piles being driven or removed; 

PSOs must have the following 

additional qualifications: 

• Ability to conduct field 

observations and collect data according 

to assigned protocols; 

• Experience or training in the field 

identification of marine mammals, 

including the identification of 

behaviors; 

• Sufficient training, orientation, or 

experience with the construction 

operation to provide for personal safety 

during observations; 

• Writing skills sufficient to record 

required information including but not 

limited to the number and species of 

marine mammals observed; dates and 

times when in-water construction 

activities were conducted; dates, times, 

and reason for implementation of 

mitigation (or why mitigation was not 

implemented when required); and 

marine mammal behavior; and 

• Ability to communicate orally, by 

radio or in person, with project 

personnel to provide real-time 

information on marine mammals 

observed in the area as necessary. 

Reporting 

NMFS would require the POA to 

submit interim weekly and monthly 

monitoring reports (that include raw 

electronic data sheets) during the NES1 

construction season. These reports must 

include a summary of marine mammal 

species and behavioral observations, 

construction shutdowns or delays, and 

construction work completed. They also 

must include an assessment of the 

amount of construction remaining to be 

completed (i.e., the number of estimated 

hours of work remaining), in addition to 

the number of CIBWs observed within 

estimated harassment zones to date. 

A draft summary marine mammal 

monitoring report must be submitted to 

NMFS within 90 days after the 

completion of all construction activities, 

or 60 days prior to a requested date of 

issuance of any future incidental take 

authorization for projects at the same 

location, whichever comes first. The 


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report would include an overall 

description of work completed, a 

narrative regarding marine mammal 

sightings, and associated PSO data 

sheets. Specifically, the report must 

include: 

• Dates and times (begin and end) of 

all marine mammal monitoring; 

• Construction activities occurring 

during each daily observation period, 

including the number and type of piles 

driven or removed and by what method 

(i.e., impact or vibratory, the total 

equipment duration for vibratory 

installation and removal, and the total 

number of strikes for each pile during 

impact driving; 

• PSO locations during marine 

mammal monitoring; 

• Environmental conditions during 

monitoring periods (at beginning and 

end of PSO shift and whenever 

conditions change significantly), 

including Beaufort sea state and any 

other relevant weather conditions 

including cloud cover, fog, sun glare, 

and overall visibility to the horizon, and 

estimated observable distance; 

• Upon observation of a marine 

mammal, the following information: 

name of PSO who sighted the animal(s) 

and PSO location and activity at time of 

sighting; time of sighting; identification 

of the animal(s) (e.g., genus/species, 

lowest possible taxonomic level, or 

unidentified), PSO confidence in 

identification, and the composition of 

the group if there is a mix of species; 

distance and bearing of each marine 

mammal observed relative to the pile 

being driven for each sighting (if pile 

driving was occurring at time of 

sighting); estimated number of animals 

(minimum, maximum, and best 

estimate); estimated number of animals 

by cohort (adults, juveniles, neonates, 

group composition, sex class, etc.); 

animal’s closest point of approach and 

estimated time spent within the 

harassment zone; group spread and 

formation (for CIBWs only); description 

of any marine mammal behavioral 

observations (e.g., observed behaviors 

such as feeding or traveling), including 

an assessment of behavioral responses 

that may have resulted from the activity 

(e.g., no response or changes in 

behavioral state such as ceasing feeding, 

changing direction, flushing, or 

breaching); 

• Number of marine mammals 

detected within the harassment zones 

and shutdown zones, by species; 

• Detailed information about any 

implementation of any mitigation 

triggered (e.g., shutdowns and delays), a 

description of specific actions that 

ensued, and resulting changes in 

behavior of the animal(s), if any; 

If no comments are received from 

NMFS within 30 days, the draft final 

report would constitute the final report. 

If comments are received, a final report 

addressing NMFS comments must be 

submitted within 30 days after receipt of 

comments. 

Reporting Injured or Dead Marine 

Mammals 

In the event that personnel involved 

in the construction activities discover 

an injured or dead marine mammal, the 

IHA-holder must immediately cease the 

specified activities and report the 

incident to the Office of Protected 

Resources, NMFS 

(PR.ITP.MonitoringReports@noaa.gov), 

and to the Alaska Regional Stranding 

Coordinator as soon as feasible. If the 

death or injury was clearly caused by 

the specified activity, the POA must 

immediately cease the specified 

activities until NMFS is able to review 

the circumstances of the incident and 

determine what, if any, additional 

measures are appropriate to ensure 

compliance with the terms of the IHA. 

The POA must not resume their 

activities until notified by NMFS. The 

report must include the following 

information: 

• Time, date, and location (latitude 

and longitude) of the first discovery 

(and updated location information if 

known and applicable); 

• Species identification (if known) or 

description of the animal(s) involved; 

• Condition of the animal(s) 

(including carcass condition if the 

animal is dead); 

• Observed behaviors of the 

animal(s), if alive; 

• If available, photographs or video 

footage of the animal(s); and 

• General circumstances under which 

the animal was discovered. 

Negligible Impact Analysis and 

Determination 

NMFS has defined negligible impact 

as an impact resulting from the 

specified activity that cannot be 

reasonably expected to, and is not 

reasonably likely to, adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival 

(50 CFR 216.103). A negligible impact 

finding is based on the lack of likely 

adverse effects on annual rates of 

recruitment or survival (i.e., populationlevel effects). An estimate of the number 

of takes alone is not enough information 

on which to base an impact 

determination. In addition to 

considering estimates of the number of 

marine mammals that might be ‘‘taken’’ 

through harassment, NMFS considers 

other factors, such as the likely nature 

of any impacts or responses (e.g., 

intensity, duration), the context of any 

impacts or responses (e.g., critical 

reproductive time or location, foraging 

impacts affecting energetics), as well as 

effects on habitat, and the likely 

effectiveness of the mitigation. We also 

assess the number, intensity, and 

context of estimated takes by evaluating 

this information relative to population 

status. Consistent with the 1989 

preamble for NMFS’ implementing 

regulations (54 FR 40338, September 29, 

1989), the impacts from other past and 

ongoing anthropogenic activities are 

incorporated into this analysis via their 

impacts on the baseline (e.g., as 

reflected in the regulatory status of the 

species, population size and growth rate 

where known, ongoing sources of 

human-caused mortality, or ambient 

noise levels). 

To avoid repetition, this introductory 

discussion of our analysis applies to all 

the species listed in Table 14, except 

CIBWs, given that many of the 

anticipated effects of this project on 

different marine mammal stocks are 

expected to be relatively similar in 

nature. For CIBWs, there are meaningful 

differences in anticipated individual 

responses to activities, impact of 

expected take on the population, or 

impacts on habitat; therefore, we 

provide a separate detailed analysis for 

CIBWs following the analysis for other 

species for which we propose take 

authorization. 

NMFS has identified key factors 

which may be employed to assess the 

level of analysis necessary to conclude 

whether potential impacts associated 

with a specified activity should be 

considered negligible. These include 

(but are not limited to) the type and 

magnitude of taking, the amount and 

importance of the available habitat for 

the species or stock that is affected, the 

duration of the anticipated effect to the 

species or stock, and the status of the 

species or stock. The potential effects of 

the specified actions on gray whales, 

humpback whales, killer whales, harbor 

porpoises, Steller sea lions, and harbor 

seals are discussed below. Some of these 

factors also apply to CIBWs; however, a 

more detailed analysis for CIBWs is 

provided in a separate sub-section 

below. 

Pile driving associated with the 

project, as outlined previously, has the 

potential to disturb or displace marine 

mammals. Specifically, the specified 

activities may result in take, in the form 

of Level B harassment and, for some 

species, Level A harassment, from 

underwater sounds generated by pile 

driving. Potential takes could occur if 

marine mammals are present in zones 


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ensonified above the thresholds for 

Level B harassment or Level A 

harassment, identified above, while 

activities are underway. 

The POA’s proposed activities and 

associated impacts would occur within 

a limited, confined area of the stocks’ 

range. The work would occur in the 

vicinity of the NES1 site and sound 

from the proposed activities would be 

blocked by the coastline along Knik 

Arm along the eastern boundaries of the 

site, and for those harassment isopleths 

that extend more than 3,000 m (i.e., the 

vibratory installation of 36-inch (91-cm) 

piles and vibratory removal of 24-inch 

(61-inch) piles), directly across the Arm 

along the western shoreline (see Figure 

6–4 in the POA’s application)). The 

intensity and duration of take by Level 

A and Level B harassment would be 

minimized through use of mitigation 

measures described herein. Further the 

amount of take proposed to be 

authorized is small when compared to 

stock abundance (see Table 14). In 

addition, NMFS does not anticipate that 

serious injury or mortality will occur as 

a result of the POA’s planned activity 

given the nature of the activity, even in 

the absence of required mitigation. 

Exposures to elevated sound levels 

produced during pile driving may cause 

behavioral disturbance of some 

individuals. Behavioral responses of 

marine mammals to pile driving at the 

proposed project site are expected to be 

mild, short term, and temporary. Effects 

on individuals that are taken by Level 

B harassment, as enumerated in the 

Estimated Take section, on the basis of 

reports in the literature as well as 

monitoring from other similar activities 

at the POA and elsewhere, will likely be 

limited to reactions such as increased 

swimming speeds, increased surfacing 

time, or decreased foraging (if such 

activity were occurring; e.g., Ridgway et 

al., 1997; Nowacek et al., 2007; Thorson 

and Reyff, 2006; Kendall and Cornick, 

2015; Goldbogen et al., 2013b; Piwetz et 

al., 2021). Marine mammals within the 

Level B harassment zones may not show 

any visual cues they are disturbed by 

activities or they could become alert, 

avoid the area, leave the area, or display 

other mild responses that are not 

observable such as changes in 

vocalization patterns or increased haul 

out time (e.g., Tougaard et al., 2003; 

Carstensen et al., 2006; Thorson and 

Reyff, 2006; Parks et al., 2007; Brandt et 

al., 2011; Graham et al., 2017). However, 

as described in the Potential Effects of 

Specified Activities on Marine 

Mammals and Their Habitat section of 

this notice, marine mammals, excepting 

CIBWs, observed within Level A and 

Level B harassment zones related to 

recent POA construction activities have 

not shown any acute observable 

reactions to pile driving activities that 

have occurred during the PCT and SFD 

projects (61N Environmental, 2021, 

2022a, 2022b). 

Some of the species present in the 

region will only be present temporarily 

based on seasonal patterns or during 

transit between other habitats. These 

temporarily present species will be 

exposed to even smaller periods of 

noise-generating activity, further 

decreasing the impacts. Most likely, 

individual animals will simply move 

away from the sound source and be 

temporarily displaced from the area. 

Takes may also occur during important 

feeding times. The project area though 

represents a small portion of available 

foraging habitat and impacts on marine 

mammal feeding for all species should 

be minimal. 

The activities analyzed here are 

similar to numerous other construction 

activities conducted in Alaska (e.g., 86 

FR 43190, August 6, 2021; 87 FR 15387, 

March 18, 2022), including the PCT and 

SFD projects within Upper Knik Arm 

(85 FR 19294, April 6, 2020; 86 FR 

50057, September 7, 2021, respectively) 

which have taken place with no known 

long-term adverse consequences from 

behavioral harassment. Any potential 

reactions and behavioral changes are 

expected to subside quickly when the 

exposures cease and, therefore, no such 

long-term adverse consequences should 

be expected (e.g., Graham et al., 2017). 

For example, harbor porpoises returned 

to a construction area between piledriving events within several days 

during the construction of offshore wind 

turbines near Denmark (Carstensen et 

al., 2006). The intensity of Level B 

harassment events would be minimized 

through use of mitigation measures 

described herein, which were not 

quantitatively factored into the take 

estimates. The POA would use PSOs 

stationed strategically to increase 

detectability of marine mammals during 

in-water construction activities, 

enabling a high rate of success in 

implementation of shutdowns to avoid 

or minimize injury for most species. 

Further, given the absence of any major 

rookeries and haulouts within the 

estimated harassment zones, we assume 

that potential takes by Level B 

harassment would have an 

inconsequential short-term effect on 

individuals and would not result in 

population-level impacts. 

As stated in the mitigation section, 

the POA will implement shutdown 

zones that equal or exceed the Level A 

harassment isopleths shown in Table 9. 

Take by Level A harassment is proposed 

for authorization for some species 

(harbor seals and harbor porpoises) to 

account for the potential that an animal 

could enter and remain within the Level 

A harassment zone for a duration long 

enough to incur PTS. Any take by Level 

A harassment is expected to arise from, 

at most, a small degree of PTS because 

animals would need to be exposed to 

higher levels and/or longer duration 

than are expected to occur here in order 

to incur any more than a small degree 

of PTS. 

Due to the levels and durations of 

likely exposure, animals that experience 

PTS will likely only receive slight PTS, 

i.e., minor degradation of hearing 

capabilities within regions of hearing 

that align most completely with the 

frequency range of the energy produced 

by POA’s proposed in-water 

construction activities (i.e., the lowfrequency region below 2 kHz), not 

severe hearing impairment or 

impairment in the ranges of greatest 

hearing sensitivity. If hearing 

impairment does occur, it is most likely 

that the affected animal will lose a few 

dBs in its hearing sensitivity, which in 

most cases is not likely to meaningfully 

affect its ability to forage and 

communicate with conspecifics. There 

are no data to suggest that a single 

instance in which an animal accrues 

PTS (or TTS) and is subject to 

behavioral disturbance would result in 

impacts to reproduction or survival. If 

PTS were to occur, it would be at a 

lower level likely to accrue to a 

relatively small portion of the 

population by being a stationary activity 

in one particular location. Additionally, 

and as noted previously, some subset of 

the individuals that are behaviorally 

harassed could also simultaneously 

incur some small degree of TTS for a 

short duration of time. Because of the 

small degree anticipated, though, any 

PTS or TTS potentially incurred here is 

not expected to adversely impact 

individual fitness, let alone annual rates 

of recruitment or survival. 

Theoretically, repeated, sequential 

exposure to pile driving noise over a 

long duration could result in more 

severe impacts to individuals that could 

affect a population (via sustained or 

repeated disruption of important 

behaviors such as feeding, resting, 

traveling, and socializing; Southall et 

al., 2007). Alternatively, marine 

mammals exposed to repetitious 

construction sounds may become 

habituated, desensitized, or tolerant 

after initial exposure to these sounds 

(reviewed by Richardson et al., 1995; 

Southall et al., 2007). Given that marine 

mammals still frequent and use Knik 

Arm despite being exposed to pile 


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driving activities across many years, 

these severe population level of impacts 

are not anticipated. The absence of any 

pinniped haulouts or other known nonCIBW home-ranges in the proposed 

action area further decreases the 

likelihood of severe population level 

impacts. 

The NES1 project is also not expected 

to have significant adverse effects on 

any marine mammal habitat. The project 

activities would occur within the same 

footprint as existing marine 

infrastructure, and when construction is 

complete, subtidal and intertidal 

habitats previously lost at the project 

site would be restored. Impacts to the 

immediate substrate are anticipated, but 

these would be limited to minor, 

temporary suspension of sediments, 

which could impact water quality and 

visibility for a short amount of time but 

which would not be expected to have 

any effects on individual marine 

mammals. While the area is generally 

not high quality habitat, it is expected 

to be of higher quality to marine 

mammals and fish after NES1 

construction is complete as the site 

returns to its natural state and is 

colonized by marine organisms. Further, 

there are no known BIAs near the 

project zone, except for CIBWs, that will 

be impacted by the POA’s planned 

activities. 

Impacts to marine mammal prey 

species are also expected to be minor 

and temporary and to have, at most, 

short-term effects on foraging of 

individual marine mammals, and likely 

no effect on the populations of marine 

mammals as a whole. Overall, the area 

impacted by the NES1 project is very 

small compared to the available 

surrounding habitat, and does not 

include habitat of particular importance. 

The most likely impact to prey would be 

temporary behavioral avoidance of the 

immediate area. During construction 

activities, it is expected that some fish 

and marine mammals would 

temporarily leave the area of 

disturbance, thus impacting marine 

mammals’ foraging opportunities in a 

limited portion of their foraging range. 

But, because of the relatively small area 

of the habitat that may be affected, and 

lack of any habitat of particular 

importance, the impacts to marine 

mammal habitat are not expected to 

cause significant or long-term negative 

consequences. Further, as described 

above, additional habitat for marine 

mammal prey will be available after the 

completion of the proposed 

construction activities likely providing 

additional foraging, migrating, and 

rearing habitats to fish and foraging 

habitat to marine mammals. 

In summary and as described above, 

the following factors support our 

preliminary negligible impact 

determinations for the affected stocks of 

gray whales, humpback whales, killer 

whales, harbor porpoises, Steller sea 

lions, and harbor seals: 

• No takes by mortality or serious 

injury are anticipated or authorized; 

• Any acoustic impacts to marine 

mammal habitat from pile driving 

(including to prey sources as well as 

acoustic habitat, and including resulting 

behavioral impacts e.g., from masking) 

are expected to be temporary and 

minimal; 

• Take would not occur in places 

and/or times where take would be more 

likely to accrue to impacts on 

reproduction or survival, such as within 

ESA-designated or proposed critical 

habitat, BIAs, or other habitats critical to 

recruitment or survival (e.g., rookery); 

• The project area represents a very 

small portion of the available foraging 

area for all potentially impacted marine 

mammal species; 

• Take will only occur within upper 

Cook Inlet—a limited, confined area of 

any given stock’s home range; 

• Monitoring reports from similar 

work in Knik Arm have documented 

little to no observable effect on 

individuals of the same species 

impacted by the specified activities; 

• The required mitigation measures 

(i.e., soft starts, pre-clearance 

monitoring, shutdown zones) are 

expected to be effective in reducing the 

effects of the specified activity by 

minimizing the numbers of marine 

mammals exposed to injurious levels of 

sound, and by ensuring that any take by 

Level A harassment is, at most, a small 

degree of PTS and of a lower degree that 

would not impact the fitness of any 

animals; and 

• The intensity of anticipated takes 

by Level B harassment is low for all 

stocks consisting of, at worst, temporary 

modifications in behavior, and would 

not be of a duration or intensity 

expected to result in impacts on 

reproduction or survival. 

Cook Inlet Beluga Whales. For CIBWs, 

we further discuss our negligible impact 

findings in the context of potential 

impacts to this endangered stock based 

on our evaluation of the take proposed 

for authorization (Table 14). 

As described in the Recovery Plan for 

the CIBW (NMFS, 2016b), NMFS 

determined the following physical or 

biological features are essential to the 

conservation of this species: (1) 

Intertidal and subtidal waters of Cook 

Inlet with depths less than 9 m mean 

lower low water and within 8 km of 

high and medium flow anadromous fish 

streams; (2) Primary prey species 

consisting of four species of Pacific 

salmon (Chinook, sockeye, chum, and 

coho), Pacific eulachon, Pacific cod, 

walleye pollock, saffron cod, and 

yellowfin sole, (3) Waters free of toxins 

or other agents of a type and amount 

harmful to CIBWs, (4) Unrestricted 

passage within or between the critical 

habitat areas, and (5) Waters with inwater noise below levels resulting in the 

abandonment of critical habitat areas by 

CIBWs. The NES1 project will not 

impact essential features 1–3 listed 

above. All construction will be done in 

a manner implementing best 

management practices to preserve water 

quality, and no work will occur around 

creek mouths or river systems leading to 

prey abundance reductions. In addition, 

no physical structures will restrict 

passage; however, impacts to the 

acoustic habitat are relevant and 

discussed here. 

Monitoring data from the POA suggest 

pile driving does not discourage CIBWs 

from entering Knik Arm and traveling to 

critical foraging grounds such as those 

around Eagle Bay (e.g., 61N 

Environmental, 2021, 2022a, 2022b; 

Easley-Appleyard and Leonard, 2022). 

As described in the Potential Effects of 

Specified Activities on Marine 

Mammals and Their Habitat section of 

this notice, sighting rates were not 

different in the presence or absence of 

pile driving (Kendall and Cornick, 

2015). In addition, large numbers of 

CIBWs have continued to use Knik Arm 

and pass through the area during pile 

driving projects that have taken place at 

the POA during the past two decades 

(Funk et al., 2005; Prevel-Ramos et al., 

2006; Markowitz and McGuire, 2007; 

Cornick and Saxon-Kendall, 2008, 2009; 

ICRC, 2009, 2010, 2011, 2012; Cornick 

et al., 2010, 2011; Cornick and Pinney, 

2011; Cornick and Seagars, 2016; POA, 

2019), including during the recent PCT 

and SFD construction projects (61N 

Environmental, 2021, 2022a, 2022b; 

Easley-Appleyard and Leonard, 2022). 

These findings are not surprising as 

food is a strong motivation for marine 

mammals. As described in Forney et al. 

(2017), animals typically favor 

particular areas because of their 

importance for survival (e.g., feeding or 

breeding), and leaving may have 

significant costs to fitness (reduced 

foraging success, increased predation 

risk, increased exposure to other 

anthropogenic threats). Consequently, 

animals may be highly motivated to 

maintain foraging behavior in historical 

foraging areas despite negative impacts 

(e.g., Rolland et al., 2012). Previous 

monitoring data indicates CIBWs are 


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responding to pile driving noise, but not 

through abandonment of critical habitat, 

including primary foraging areas north 

of the port. Instead, they travel more 

often and faster past the POA, more 

quietly, and in tighter groups (Kendall 

and Cornick, 2015; 61N Environmental, 

2021, 2022a, 2022b). 

During PCT and SFD construction 

monitoring, little variability was evident 

in the behaviors recorded from month to 

month, or between sightings that 

coincided with in-water pile installation 

and removal and those that did not (61N 

Environmental, 2021, 2022a, 2022b; 

Easley-Appleyard and Leonard, 2022). 

Of the 386 CIBWs groups sighted during 

PCT and SFD construction monitoring, 

10 groups were observed during or 

within minutes of in-water impact pile 

installation and 56 groups were 

observed during or within minutes of 

vibratory pile installation or removal 

(61N Environmental, 2021, 2022a, 

2022b). In general, CIBWs were more 

likely to display no reaction or to 

continue to move towards the PCT or 

SFD during pile installation and 

removal. In the situations during which 

CIBWs showed a possible reaction (six 

groups during impact driving and 13 

groups during vibratory driving), CIBWs 

were observed either moving away 

immediately after the pile driving 

activities started or were observed 

increasing their rate of travel. 

NMFS funded a visual marine 

mammal monitoring project in 2021 

(described in the Potential Effects of 

Specified Activities on Marine 

Mammals and Their Habitat) to 

supplement sighting data collected by 

the POA monitoring program during 

non-pile driving days in order to further 

evaluate the impacts of anthropogenic 

activities on CIBWs (Easley-Appleyard 

and Leonard, 2022). Preliminary results 

suggest that group size ranged from 1 to 

34 whales, with an average of 3 to 5.6, 

depending on the month. September 

had the highest sighting rate with 4.08 

whales per hour, followed by October 

and August (3.46 and 3.41, 

respectively). Traveling was recorded as 

the primary behavior for 80 percent of 

the group sightings and milling was the 

secondary behavior most often recorded. 

Sighting duration varied from a single 

surfacing lasting less than 1 minute to 

380 minutes. Preliminary findings 

suggest these results are consistent with 

the results from the POA’s PCT and SFD 

monitoring efforts. For example, group 

sizes ranged from 2.38 to 4.32 

depending on the month and the highest 

sighting rate was observed in September 

(1.75). In addition, traveling was the 

predominant behavior observed for all 

months and categories of construction 

activity (i.e., no pile driving, before pile 

driving, during pile driving, between 

pile driving, or after pile driving), being 

recorded as the primary behavior for 86 

percent of all sightings, and either the 

primary or secondary behavior for 95 

percent of sightings. 

Easley-Appleyard and Leonard (2022) 

also asked PSOs to complete a 

questionnaire post-monitoring that 

provided NMFS with qualitative data 

regarding CIBW behavior during 

observations. Specifically during pile 

driving events, the PSOs noted that 

CIBW behaviors varied; however, 

multiple PSOs noted seeing behavioral 

changes specifically during impact pile 

driving (which would only be used 

when necessary to loosen piles for 

vibratory removal or direct pulling 

during the NES1 project) and not during 

vibratory pile driving. CIBWs were 

observed sometimes changing direction, 

turning around, or changing speed 

during impact pile driving. There were 

numerous instances where CIBWs were 

seen traveling directly towards the POA 

during vibratory pile driving before 

entering the Level B harassment zone 

(POA was required to shutdown prior to 

CIBWs entering the Level B harassment 

zone), which is consistent with findings 

during the POA’s PCT and SFD 

monitoring efforts (61N Environmental, 

2021, 2022a, 2022b). The PSOs also 

reported that it seemed more likely for 

CIBWs to show more cryptic behavior 

during pile driving (e.g., surfacing 

infrequently and without clear 

direction), though this seemed to vary 

across months (Easley-Appleyard and 

Leonard, 2022). 

We anticipate that disturbance to 

CIBWs will manifest in the same 

manner when they are exposed to noise 

during the NES1 project: whales would 

move quickly and silently through the 

area in more cohesive groups. We do not 

believe exposure to elevated noise levels 

during transit past the POA has adverse 

effects on reproduction or survival as 

the whales continue to access critical 

foraging grounds north of the POA, even 

if having shown a potential reaction 

during pile driving, and tight 

associations help to mitigate the 

potential for any contraction of 

communication space for a group. We 

also do not anticipate that CIBWs will 

abandon entering or exiting Knik Arm, 

as this is not evident based on previous 

years of monitoring data (e.g., Kendall 

and Cornick, 2015; 61N Environmental, 

2021, 2022a, 2022b; Easley-Appleyard 

and Leonard, 2022), and the pre-pile 

driving clearance mitigation measure is 

designed to further avoid any potential 

abandonment. Finally, as described 

previously, both telemetry (tagging) and 

acoustic data suggest CIBWs likely stay 

in upper Knik Arm (i.e., north of the 

NES1 project site) for several days or 

weeks before exiting Knik Arm. 

Specifically, a CIBW instrumented with 

a satellite link time/depth recorder 

entered Knik Arm on August 18, 1999 

and remained in Eagle Bay until 

September 12, 1999 (Ferrero et al., 

2000). Further, a recent detailed reanalysis of the satellite telemetry data 

confirms how several tagged whales 

exhibited this same movement pattern: 

whales entered Knik Arm and remained 

there for several days before exiting 

through lower Knik Arm (Shelden et al., 

2018). This longer-term use of upper 

Knik Arm will avoid repetitive 

exposures from pile driving noise. 

There is concern that exposure to pile 

driving at the POA could result in 

CIBWs avoiding Knik Arm and thereby 

not accessing the productive foraging 

grounds north of POA such as Eagle 

River flats thus, impacting essential 

feature number five above. Although the 

data previously presented demonstrate 

CIBWs are not abandoning the area (i.e., 

no significant difference in sighting rate 

with and without pile driving), results 

of an expert elicitation (EE) at a 2016 

workshop, which predicted the impacts 

of noise on CIBW survival and 

reproduction given lost foraging 

opportunities, helped to inform our 

assessment of impacts on this stock. The 

2016 EE workshop used conceptual 

models of an interim population 

consequences of disturbance (PCoD) for 

marine mammals (NRC, 2005; New et 

al., 2014; Tollit et al., 2016) to help in 

understanding how noise-related 

stressors might affect vital rates 

(survival, birth rate and growth) for 

CIBW (King et al., 2015). NMFS (2016b) 

suggests that the main direct effects of 

noise on CIBW are likely to be through 

masking of vocalizations used for 

communication and prey location and 

habitat degradation. The 2016 workshop 

on CIBWs was specifically designed to 

provide regulators with a tool to help 

understand whether chronic and acute 

anthropogenic noise from various 

sources and projects are likely to be 

limiting recovery of the CIBW 

population. The full report can be found 

at https://www.smruconsulting.com/ 

publications/ with a summary of the 

expert elicitation portion of the 

workshop below. 

For each of the noise effect 

mechanisms chosen for EE, the experts 

provided a set of parameters and values 

that determined the forms of a 

relationship between the number of 

days of disturbance a female CIBW 

experiences in a particular period and 

the effect of that disturbance on her 


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energy reserves. Examples included the 

number of days of disturbance during 

the period April, May, and June that 

would be predicted to reduce the energy 

reserves of a pregnant CIBW to such a 

level that she is certain to terminate the 

pregnancy or abandon the calf soon after 

birth, the number of days of disturbance 

in the period April-September required 

to reduce the energy reserves of a 

lactating CIBW to a level where she is 

certain to abandon her calf, and the 

number of days of disturbance where a 

female fails to gain sufficient energy by 

the end of summer to maintain 

themselves and their calves during the 

subsequent winter. Overall, median 

values ranged from 16 to 69 days of 

disturbance depending on the question. 

However, for this elicitation, a ‘‘day of 

disturbance’’ was defined as any day on 

which an animal loses the ability to 

forage for at least one tidal cycle (i.e., it 

forgoes 50–100 percent of its energy 

intake on that day). The day of 

disturbance considered in the context of 

the report is notably more severe than 

the Level B harassment expected to 

result from these activities, which as 

described is expected to be comprised 

predominantly of temporary 

modifications in the behavior of 

individual CIBWs (e.g., faster swim 

speeds, more cohesive group structure, 

decreased sighting durations, cessation 

of vocalizations). Also, NMFS proposes 

to authorize 72 instances of takes, with 

the instances representing disturbance 

events within a day—this means that 

either 72 different individual CIBWs are 

disturbed on no more than 1 day each, 

or some lesser number of individuals 

may be disturbed on more than 1 day, 

but with the product of individuals and 

days not exceeding 72. Given the overall 

anticipated take, it is unlikely that any 

one CIBW will be disturbed on more 

than a few days. Further, the mitigation 

measures NMFS has prescribed for the 

NES1 project are designed to avoid the 

potential that any animal will lose the 

ability to forage for one or more tidal 

cycles should they be foraging in the 

proposed action area, which is not 

known to be a particularly important 

feeding area for CIBWs. While Level B 

harassment (behavioral disturbance) 

would be authorized, the POA’s 

mitigation measures will limit the 

severity of the effects of that Level B 

harassment to behavioral changes such 

as increased swim speeds, tighter group 

formations, and cessation of 

vocalizations, not the loss of foraging 

capabilities. Regardless, this elicitation 

recognized that pregnant or lactating 

females and calves are inherently more 

at risk than other animals, such as 

males. NMFS has determined all CIBWs 

warrant pile driving shutdown to be 

protective of potential vulnerable life 

stages, such as pregnancy, that could 

not be determined from observations, 

and to avoid more severe behavioral 

reaction. 

POA proposed and NMFS has 

prescribed mitigation measures to 

minimize exposure to CIBWs, 

specifically, shutting down pile driving 

should a CIBW approach or enter the 

Level B harassment zone. These 

measures are designed to ensure CIBWs 

will not abandon critical habitat and 

exposure to pile driving noise will not 

result in adverse impacts on the 

reproduction or survival of any 

individuals. The location of the PSOs 

would allow for detection of CIBWs and 

behavioral observations prior to CIBWs 

entering the Level B harassment zone. 

Further, impact driving appeared to 

cause behavioral reactions more readily 

than vibratory hammering (61N 

Environmental, 2021, 2022a, 2022b), 

which would only be used in situations 

where sheet piles remain seized in the 

sediments and cannot be loosened or 

broken free with a vibratory hammer, 

which is expected to be uncommon 

during the NES1 project. If impact 

driving does occur, the POA must 

implement soft starts, which ideally 

allows animals to leave a disturbed area 

before the full-power driving 

commences (Tougaard et al., 2012). 

Although NMFS does not anticipate 

CIBWs will abandon entering Knik Arm 

in the presence of pile driving with the 

required mitigation measures, PSOs will 

be integral to identifying if CIBWs are 

potentially altering pathways they 

would otherwise take in the absence of 

pile driving. Finally, take by mortality, 

serious injury, or Level A harassment of 

CIBWs is not anticipated or proposed to 

be authorized. 

In summary and as described above, 

the following factors primarily support 

our preliminary determination that the 

impacts resulting from this activity are 

not expected to adversely affect the 

CIBWs through effects on annual rates 

of recruitment or survival: 

• No mortality is anticipated or 

proposed to be authorized; 

• The area of exposure would be 

limited to habitat primarily used as a 

travel corridor. Data demonstrates Level 

B harassment of CIBWs typically 

manifests as increased swim speeds past 

the POA, tighter group formations, and 

cessation of vocalizations, rather than 

through habitat abandonment; 

• No critical foraging grounds (e.g., 

Eagle Bay, Eagle River, Susitna Delta) 

would be impacted by pile driving; and 

• While animals could be harassed 

more than once, exposures are not likely 

to exceed more than a few per year for 

any given individual and are not 

expected to occur on sequential days; 

thereby decreasing the likelihood of 

physiological impacts caused by chronic 

stress or masking. 

Based on the analysis contained 

herein of the likely effects of the 

specified activity on marine mammals 

and their habitat, and taking into 

consideration the implementation of the 

required monitoring and mitigation 

measures, NMFS preliminarily finds 

that the total marine mammal take from 

the specified activity will have a 

negligible impact on all affected marine 

mammal species or stocks. 

Small Numbers 

As noted previously, only take of 

small numbers of marine mammals may 

be authorized under sections 

101(a)(5)(A) and (D) of the MMPA for 

specified activities other than military 

readiness activities. The MMPA does 

not define small numbers and so, in 

practice, where estimated numbers are 

available, NMFS compares the number 

of individuals taken to the most 

appropriate estimation of abundance of 

the relevant species or stock in our 

determination of whether an 

authorization is limited to small 

numbers of marine mammals. When the 

predicted number of individuals to be 

taken is fewer than one-third of the 

species or stock abundance, the take is 

considered to be of small numbers. 

Additionally, other qualitative factors 

may be considered in the analysis, such 

as the temporal or spatial scale of the 

activities. 

For all stocks, except for the MexicoNorth Pacific stock of humpback whales 

whose abundance estimate is unknown, 

the amount of taking is less than onethird of the best available population 

abundance estimate (in fact it is less 

than 2 percent for all stocks, except for 

CIBWs whose proposed take is 22 

percent of the stock; Table 14). The 

number of animals proposed for 

authorization to be taken from these 

stocks would be considered small 

relative to the relevant stock’s 

abundances even if each estimated take 

occurred to a new individual. The 

amount of take authorized likely 

represents smaller numbers of 

individual harbor seals and Steller sea 

lions. Harbor seals tend to concentrate 

near Ship Creek and have small home 

ranges. It is possible that a single 

individual harbor seal may linger near 

the POA, especially near Ship Creek, 

and be counted multiple times each day 

as it moves around and resurfaces in 


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different locations. Previous Steller sea 

lion sightings identified that if a Steller 

sea lion is within Knik Arm, it is likely 

lingering to forage on salmon or 

eulachon runs and may be present for 

several days. Therefore, the amount of 

take authorized likely represents repeat 

exposures to the same animals. For all 

species, PSOs would count individuals 

as separate unless they cannot be 

individually identified. 

Abundance estimates for the MexicoNorth Pacific stock of humpback whales 

are based upon data collected more than 

8 years ago and, therefore, current 

estimates are considered unknown 

(Young et al., 2023). The most recent 

minimum population estimates (NMIN) 

for this population include an estimate 

of 2,241 individuals between 2003 and 

2006 (Martinez-Aguilar, 2011) and 766 

individuals between 2004 and 2006 

(Wade, 2021). NMFS’ Guidelines for 

Assessing Marine Mammal Stocks 

suggest that the NMIN estimate of the 

stock should be adjusted to account for 

potential abundance changes that may 

have occurred since the last survey and 

provide reasonable assurance that the 

stock size is at least as large as the 

estimate (NMFS, 2023). The abundance 

trend for this stock is unclear; therefore, 

there is no basis for adjusting these 

estimates (Young et al., 2023). 

Assuming the population has been 

stable, the 4 takes of this stock proposed 

for authorization represents small 

numbers of this stock (0.18 percent of 

the stock assuming a NMIN of 2,241 

individuals and 0.52 percent of the 

stock assuming an NMIN of 766 

individuals). 

Based on the analysis contained 

herein of the proposed activity 

(including the proposed mitigation and 

monitoring measures) and the 

anticipated take of marine mammals, 

NMFS preliminarily finds that small 

numbers of marine mammals would be 

taken relative to the population size of 

the affected species or stocks. 

Unmitigable Adverse Impact Analysis 

and Determination 

In order to issue an IHA, NMFS must 

find that the specified activity will not 

have an ‘‘unmitigable adverse impact’’ 

on the subsistence uses of the affected 

marine mammal species or stocks by 

Alaskan Natives. NMFS has defined 

‘‘unmitigable adverse impact’’ in 50 CFR 

216.103 as an impact resulting from the 

specified activity: (1) That is likely to 

reduce the availability of the species to 

a level insufficient for a harvest to meet 

subsistence needs by: (i) Causing the 

marine mammals to abandon or avoid 

hunting areas; (ii) Directly displacing 

subsistence users; or (iii) Placing 

physical barriers between the marine 

mammals and the subsistence hunters; 

and (2) That cannot be sufficiently 

mitigated by other measures to increase 

the availability of marine mammals to 

allow subsistence needs to be met. 

While no significant subsistence 

activity currently occurs within or near 

the POA, Alaska Natives have 

traditionally harvested subsistence 

resources, including marine mammals, 

in upper Cook Inlet for millennia. 

CIBWs are more than a food source; they 

are important to the cultural and 

spiritual practices of Cook Inlet Native 

communities (NMFS, 2008b). Dena’ina 

Athabascans, currently living in the 

communities of Eklutna, Knik, Tyonek, 

and elsewhere, occupied settlements in 

Cook Inlet for the last 1,500 years and 

have been the primary traditional users 

of this area into the present. 

NMFS estimated that 65 CIBWs per 

year (range 21–123) were killed between 

1994 and 1998, including those 

successfully harvested and those struck 

and lost. NMFS concluded that this 

number was high enough to account for 

the estimated 14 percent annual decline 

in population during this time (Hobbs et 

al., 2008); however, given the difficulty 

of estimating the number of whales 

struck and lost during the hunts, actual 

mortality may have been higher. During 

this same period, population abundance 

surveys indicated a population decline 

of 47 percent, although the reason for 

this decline should not be associated 

solely with subsistence hunting and 

likely began well before 1994 (Rugh et 

al., 2000). 

In 1999, a moratorium was enacted 

(Pub. L. 106–31) prohibiting the 

subsistence harvest of CIBWs except 

through a cooperative agreement 

between NMFS and the affected Alaska 

Native organizations. NMFS began 

working cooperatively with the Cook 

Inlet Marine Mammal Council (CIMMC), 

a group of tribes that traditionally 

hunted CIBWs, to establish sustainable 

harvests. CIMMC voluntarily curtailed 

its harvests in 1999. In 2000, NMFS 

designated the Cook Inlet stock of 

beluga whales as depleted under the 

MMPA (65 FR 34590, May 31, 2000). 

NMFS and CIMMC signed CoManagement of the Cook Inlet Stock of 

Beluga Whales agreements in 2000, 

2001, 2002, 2003, 2005, and 2006. CIBW 

harvests between 1999 and 2006 

resulted in the strike and harvest of five 

whales, including one whale each in 

2001, 2002, and 2003, and two whales 

in 2005 (NMFS, 2008b). No hunt 

occurred in 2004 due to higher-thannormal mortality of CIBWs in 2003, and 

the Native Village of Tyonek agreed to 

not hunt in 2007. Since 2008, NMFS has 

examined how many CIBWs could be 

harvested during 5-year intervals based 

on estimates of population size and 

growth rate and determined that no 

harvests would occur between 2008 and 

2012 and between 2013 and 2017 

(NMFS, 2008b). The CIMMC was 

disbanded by unanimous vote of the 

CIMMC member Tribes’ representatives 

in June 2012, and a replacement group 

of Tribal members has not been formed 

to date. There has been no subsistence 

harvest of CIBWs since 2005 (NMFS, 

2022d). 

Subsistence harvest of other marine 

mammals in upper Cook Inlet is limited 

to harbor seals. Steller sea lions are rare 

in upper Cook Inlet; therefore, 

subsistence use of this species is not 

common. However, Steller sea lions are 

taken for subsistence use in lower Cook 

Inlet. Residents of the Native Village of 

Tyonek are the primary subsistence 

users in the upper Cook Inlet area. 

While harbor seals are hunted for 

subsistence purposes, harvests of this 

for traditional and subsistence uses by 

Native peoples have been low in upper 

Cook Inlet (e.g., 33 harbor seals were 

harvested in Tyonek between 1983 and 

2013; see Table 8–1 in the POA’s 

application), although these data are not 

currently being collected and 

summarized. As the POA’s proposed 

project activities will take place within 

the immediate vicinity of the POA, no 

activities will occur in or near Tyonek’s 

identified traditional subsistence 

hunting areas. As the harvest of marine 

mammals in upper Cook Inlet is 

historically a small portion of the total 

subsistence harvest, and the number of 

marine mammals using upper Cook 

Inlet is proportionately small, the 

number of marine mammals harvested 

in upper Cook Inlet is expected to 

remain low. 

The potential impacts from 

harassment on stocks that are harvested 

in Cook Inlet would be limited to minor 

behavioral changes (e.g., increased swim 

speeds, changes in dive time, temporary 

avoidance near the POA, etc.) within the 

vicinity of the POA. Some PTS may 

occur; however, the shift is likely to be 

slight due to the implementation of 

mitigation measures (e.g., shutdown 

zones, pre-clearance monitoring, soft 

starts) and the shift would be limited to 

lower pile driving frequencies which are 

on the lower end of phocid and otariid 

hearing ranges. In summary, any 

impacts to harbor seals would be 

limited to those seals within Knik Arm 

(outside of any hunting area) and the 

very few takes of Steller sea lions in 

Knik Arm would be far removed in time 

and space from any hunting in lower 

Cook Inlet. 


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The POA will communicate with 

representative Alaska Native 

subsistence users and Tribal members to 

identify and explain the measures that 

have been taken or will be taken to 

minimize any adverse effects of NES1 

on the availability of marine mammals 

for subsistence uses. In addition, the 

POA will adhere to the following 

procedures during Tribal consultation 

regarding marine mammal subsistence 

use within the Project area: 

(1) Send letters to the Kenaitze, 

Tyonek, Knik, Eklutna, Ninilchik, 

Salamatof, and Chickaloon Tribes 

informing them of the proposed project 

(i.e., timing, location, and features). 

Include a map of the proposed project 

area; identify potential impacts to 

marine mammals and mitigation efforts, 

if needed, to avoid or minimize impacts; 

and inquire about possible marine 

mammal subsistence concerns they 

have. 

(2) Follow up with a phone call to the 

environmental departments of the seven 

Tribal entities to ensure that they 

received the letter, understand the 

proposed project, and have a chance to 

ask questions. Inquire about any 

concerns they might have about 

potential impacts to subsistence hunting 

of marine mammals. 

(3) Document all communication 

between the POA and Tribes. 

(4) If any Tribes express concerns 

regarding proposed project impacts to 

subsistence hunting of marine 

mammals, propose a Plan of 

Cooperation between the POA and the 

concerned Tribe(s). 

The proposed project features and 

activities, in combination with a 

number of actions to be taken by the 

POA during project implementation, 

should avoid or mitigate any potential 

adverse effects on the availability of 

marine mammals for subsistence uses. 

Furthermore, although construction will 

occur within the traditional area for 

hunting marine mammals, the proposed 

project area is not currently used for 

subsistence activities. In-water pile 

installation and removal will follow 

mitigation procedures to minimize 

effects on the behavior of marine 

mammals, and impacts will be 

temporary. 

The POA has expressed, if desired, 

regional subsistence representatives 

may support project marine mammal 

biologists during the monitoring 

program by assisting with collection of 

marine mammal observations and may 

request copies of marine mammal 

monitoring reports. 

Based on the description of the 

specified activity, the measures 

described to minimize adverse effects 

on the availability of marine mammals 

for subsistence purposes, and the 

proposed mitigation and monitoring 

measures, NMFS has preliminarily 

determined that there will not be an 

unmitigable adverse impact on 

subsistence uses from the POA’s 

proposed activities. 

Endangered Species Act 

Section 7(a)(2) of the Endangered 

Species Act of 1973 (ESA; 16 U.S.C. 

1531 et seq.) requires that each Federal 

agency insure that any action it 

authorizes, funds, or carries out is not 

likely to jeopardize the continued 

existence of any endangered or 

threatened species or result in the 

destruction or adverse modification of 

designated critical habitat. To ensure 

ESA compliance for the issuance of 

IHAs, NMFS Office of Protected 

Resources (OPR) consults internally 

whenever we propose to authorize take 

for endangered or threatened species, in 

this case with the NMFS Alaska 

Regional Office. 

NMFS OPR is proposing to authorize 

take of Mexico-North Pacific humpback 

whales (including individuals from the 

Mexico DPS), CIBWs, and western DPS 

Steller sea lions, which are listed under 

the ESA. NMFS OPR has requested 

initiation of section 7 consultation with 

the issuance of this IHA. NMFS will 

conclude the ESA consultation prior to 

reaching a determination regarding the 

proposed issuance of the authorization. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to issue 

an IHA to the POA for conducting 

construction and demolition activities 

in Anchorage Alaska from April 1, 2024 

through March 31, 2025, provided the 

previously mentioned mitigation, 

monitoring, and reporting requirements 

are incorporated. A draft of the 

proposed IHA can be found at: https:// 

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/incidentaltake-authorizations-constructionactivities. 

Request for Public Comments 

We request comment on our analyses, 

the proposed authorization, and any 

other aspect of this notice of proposed 

IHA for the proposed construction and 

demolition activities. We also request 

comment on the potential renewal of 

this proposed IHA as described in the 

paragraph below. Please include with 

your comments any supporting data or 

literature citations to help inform 

decisions on the request for this IHA or 

a subsequent renewal IHA. 

On a case-by-case basis, NMFS may 

issue a one-time, 1-year renewal IHA 

following notice to the public providing 

an additional 15 days for public 

comments when (1) up to another year 

of identical or nearly identical activities 

as described in the Description of 

Proposed Activity section of this notice 

is planned or (2) the activities as 

described in the Description of 

Proposed Activity section of this notice 

would not be completed by the time the 

IHA expires and a renewal would allow 

for completion of the activities beyond 

that described in the Dates and Duration 

section of this notice, provided all of the 

following conditions are met: 

• A request for renewal is received no 

later than 60 days prior to the needed 

renewal IHA effective date (recognizing 

that the renewal IHA expiration date 

cannot extend beyond 1 year from 

expiration of the initial IHA). 

• The request for renewal must 

include the following: 

(1) An explanation that the activities 

to be conducted under the requested 

renewal IHA are identical to the 

activities analyzed under the initial 

IHA, are a subset of the activities, or 

include changes so minor (e.g., 

reduction in pile size) that the changes 

do not affect the previous analyses, 

mitigation and monitoring 

requirements, or take estimates (with 

the exception of reducing the type or 

amount of take). 

(2) A preliminary monitoring report 

showing the results of the required 

monitoring to date and an explanation 

showing that the monitoring results do 

not indicate impacts of a scale or nature 

not previously analyzed or authorized. 

Upon review of the request for 

renewal, the status of the affected 

species or stocks, and any other 

pertinent information, NMFS 

determines that there are no more than 

minor changes in the activities, the 

mitigation and monitoring measures 

will remain the same and appropriate, 

and the findings in the initial IHA 

remain valid. 

Dated: October 30, 2023. 

Kimberly Damon-Randall, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2023–24238 Filed 11–3–23; 8:45 am] 

BILLING CODE 3510–22–P 


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