31870 Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Notices 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XA660] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to the Relocation 

of the Port of Alaska’s South Floating 

Dock, 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 pile driving associated 

with the relocation of the POA’s South 

Floating Dock (SFD) in Knik Arm, 

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, oneyear renewal that could be issued under 

certain circumstances and if all 

requirements are met, as described in 

Request for Public Comments at the end 

of this notice. NMFS will consider 

public comments prior to making any 

final decision on the issuance of the 

requested MMPA authorizations and 

agency responses will be summarized in 

the final notice of our decision. 

DATES: Comments and information must 

be received no later than July 15, 2021. 

ADDRESSES: Comments should be 

addressed to Jolie Harrison, Chief, 

Permits and Conservation Division, 

Office of Protected Resources, National 

Marine Fisheries Service. Written 

comments should be submitted via 

email to ITP.tyson.moore@noaa.gov. 

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 

www.fisheries.noaa.gov/permit/ 

incidental-take-authorizations-undermarine-mammal-protection-act 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. 

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/permit/ 

incidental-take-authorizations-undermarine-mammal-protection-act. In case 

of problems accessing these documents, 

please call the contact listed above. 

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 

issued or, if the taking is limited to 

harassment, a notice of a proposed 

incidental take authorization may be 

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 is preparing an 

Environmental Assessment (EA) to 

consider the environmental impacts 

associated with the issuance of the 

proposed IHA. NMFS’ EA will be made 

available at https://www.fisheries.

noaa.gov/permit/incidental-takeauthorizations-under-marine-mammalprotection-act. 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 October 2, 2020, NMFS received a 

request from the POA for an IHA to take 

marine mammals incidental to pile 

driving associated with the relocation of 

the SFD in Knik Arm, Alaska. Revised 

applications were submitted by POA on 

December 15, 2020, January 29, 2021, 

February 5, 2021, and March 5, 2021 

that addressed comments provided by 

NMFS. The application was deemed 

adequate and complete on March 17, 

2021. Additional revised applications 

were submitted on March 26, 2021 and 

May 14, 2021. The POA’s request is for 

take of a small number of six species of 

marine mammals by Level B harassment 

and Level A harassment. Neither the 

POA nor NMFS expects serious injury 

or mortality to result from this activity 

and, therefore, an IHA is appropriate. 

NMFS previously issued IHAs to the 

POA for pile driving (73 FR 41318, July 

18, 2008; 74 FR 35136, July 20, 2009; 81 

FR 15048, March 21, 2016; and 85 FR 

19294, April 06, 2020). The POA has 

complied with the requirements (e.g., 

mitigation, monitoring, and reporting) of 

all 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 sections. 

Description of Proposed Activity 

Overview 

The POA is modernizing its marine 

terminals through the Port of Alaska 

Modernization Program (PAMP). One of 

the first priorities of the PAMP is to 

replace the existing Petroleum Oil 

Lubricants Terminal with a new 

Petroleum Cement Terminal (PCT). 

Phase 1 of the PCT project is complete, 

but for Phase 2 of the project to advance, 

the existing SFD, a small multipurpose 

floating dock constructed in 2004, must 

be relocated south of the PCT near the 

southern portion of the South Backlands 

Stabilization project. The existing 

location of SFD will not allow docking 


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Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Notices 31871 

operations at SFD once the PCT is 

constructed due to the close proximity 

of one of the PCT mooring dolphins (a 

structure for berthing and mooring of 

vessels). Therefore, it must be relocated. 

Relocation of the SFD will include the 

removal of the existing structure, 

including the access trestle and 

gangway, and installation of twelve 

permanent 36-inch steel pipe piles: Ten 

vertical and two battered. Construction 

of the SFD will also require the 

installation and vibratory removal of up 

to six 24- or 36-inch template piles. All 

pile installation will take place from a 

floating work barge and crane with a 

vibratory hammer to the greatest extent 

possible. An impact hammer may be 

used if a pile encounters refusal and 

cannot be advanced to the necessary tip 

elevation with the vibratory hammer. 

An unconfined bubble curtain system 

will be used to reduce in-water noise 

levels for the installation of the sixteen 

vertical piles and removal of the six 

temporary piles but will not be used 

during installation of the two battered 

piles due to the angle of these piles. 

Dates and Duration 

The POA has requested that the IHA 

be valid for one year upon issuance. Inwater pile installation and removal 

associated with SFD removal and 

construction is anticipated to take place 

on up to 24 nonconsecutive days 

between the date of issuance and 

November 2021. Installation of 

permanent and temporary piles is 

anticipated to take 45 minutes per pile 

with 1–3 piles being installed per day 

over 7–18 days. Removal of six 

temporary piles is anticipated to take 75 

minutes per pile with 1–3 piles being 

removed per day over 2–6 days. All 

pile-driving will occur during daylight 

hours. 

Specific Geographic Region 

Cook Inlet is a large tidal estuary that 

exchanges waters at its mouth with the 

Gulf of Alaska. The inlet is roughly 

20,000 square kilometers (km2; 7,700 

square miles (mi2)) in area, with 

approximately 1,350 linear km (840 mi) 

of coastline (Rugh et al., 2000) and an 

average depth of approximately 100 

meters (m) (330 feet (ft)). 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 three to six 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. 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 8.0 

m (26 ft), and the maximum water level 

has been measured at more than 12.5 m 

(41 ft) at the Anchorage station (NOAA, 

2015). Maximum current speeds in Knik 

Arm, observed during spring ebb tide, 

exceed 7 knots (12 feet/second). These 

tides result in strong currents in 

alternating directions through Knik Arm 

and a well-mixed water column. 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. The POA is located in 

the southeastern shoreline of Knik Arm 

in Anchorage, Alaska (Latitude 61°15′ 

N, Longitude 149°52′ W; Seward 

Meridian) (Figure 1). Knik Arm is 

generally considered to begin at Point 

Woronzof, 7.4 km (4.6 mi) southwest of 

the POA. From Point Woronzof, Knik 

Arm extends about 48 km (30 mi) 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 (1.5 mi) before widening to as much 

as 8 km (5 mi) at the tidal flats 

northwest of Eagle Bay at the mouth of 

Eagle River, which are heavily utilized 

by Cook Inlet Beluga Whales (CIBWs). 

Approximately 60 percent of Knik Arm 

is exposed at mean lower low water 

(MLLW). The intertidal (tidally 

influenced) areas of Knik Arm, 

including those at the POA, are 

mudflats, both vegetated and 

unvegetated, which consist primarily of 

fine, silt-sized glacial flour. 

The POA’s boundaries currently 

occupy an area of approximately 129 

acres. Other commercial and industrial 

activities related to secure maritime 

operations are located near the POA on 

Alaska Railroad Corporation (ARRC) 

property immediately south of the POA, 

on approximately 111 acres. The PCT 

footprint spans approximately 0.87 acre 

and is approximately 0.74 km (0.46 m) 

north of Ship Creek, a location of 

concentrated marine mammal activity 

during seasonal runs of several salmon 

species. Ship Creek flows into Knik Arm 

through the Municipality of Anchorage 

industrial area. The perpendicular 

distance to the west bank directly across 

Knik Arm from the POA is 

approximately 4.2 km (2.6 mi). 

BILLING CODE 3510–22–P 


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BILLING CODE 3510–22–C 

Detailed Description of Specific Activity 

Located within the Municipality of 

Anchorage on Knik Arm in upper Cook 

Inlet, the POA (Figure 1) provides 

critical infrastructure for the citizens of 

Anchorage and a majority of the citizens 

of Alaska. The POA’s existing 

infrastructure and support facilities 

were constructed largely in the 1960s. 

Port facilities are substantially past their 

design life, have degraded to levels of 


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149"54'0"W 

61"14'0"N 

149°54'0-W 

149"53'30"W 

Proposed South Floating Dock 

-- SFD Platform 

-- SFD Access Trestle 

South Floating Dock Piles 

o 36 in. Vertical Pile 

o 36 in_ Battered Pile 

PCT Structure 

I 

0 

149°53'30"W 

A 

I 

50 

Meters 

I 

100 

Figure 1. Port of Alaska location within Knik Arm, Alaska. The existing and 

proposed locations for the SFD are included for reference. 

1°14'0"N 
Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Notices 31873 

marginal safety, and are in many cases 

functionally obsolete, especially in 

regard to seismic design criteria and 

condition. To address these 

deficiencies, the POA is modernizing its 

marine terminals through the PAMP. 

Plans for modernization include 

replacing deteriorated pile-supported 

infrastructure with new pile-supported 

infrastructure. One of the first priorities 

of the PAMP is to replace the existing 

Petroleum Oil Lubricants Terminal with 

a new structure that exceeds current 

seismic standards. For the new PCT 

Project to advance, the existing SFD, a 

small multipurpose floating dock 

constructed in 2004, must be relocated 

south of the PCT near the southern 

portion of the South Backlands 

Stabilization project (Figure 1). The 

existing location of SFD will not allow 

docking operations at SFD once the PCT 

is constructed due to close proximity of 

one of the PCT mooring dolphins. 

The purpose of the SFD is to provide 

staging, mooring, and docking of small 

vessels, such as first responder (e.g., 

Anchorage Fire Department, U.S. Coast 

Guard) rescue craft, small work skiffs, 

and occasionally tug boats, in an area 

close to the daily operations at the Port. 

Upper Cook Inlet near Anchorage 

exhibits the largest tide range in the 

United States and one of the largest tide 

ranges in the world, with an average 

daily difference between high and low 

tide of 26.2 feet and an extreme 

difference of up to 41 feet (NOAA, 

2015). The ability of first responders to 

conduct response operations during low 

tide stages requires access to the SFD, as 

the waterline is inaccessible for vessels 

at the Anchorage public boat launch at 

Ship Creek during low tide stages. The 

planned relocation of the SFD south of 

the new PCT structure will provide 

continuous access to the water, and 

relocation is needed to continue to 

provide timely, safe access for rescue 

personnel and vessels in the northern 

portion of Cook Inlet. 

Relocation of the SFD will include the 

removal of the existing structure, 

including the float and gangway, and 

installation of twelve permanent 36- 

inch steel piles: Four for the gangway 

and eight for the floating dock (Table 1). 

Ten of the permanent piles will be 

plumb (i.e., vertical) piles; but two of 

these piles, located at the south corner 

of the floating dock, will be battered 

piles due to lateral ice flow conditions. 

Two of the permanent 36-inch gangway 

piles at Bent B, the bent closest to shore, 

may be installed when the area is dewatered, but will likely be installed in 

water. Temporary template piles may be 

required to assist with permanent pile 

placement and would consist of up to 

six 24- or 36-inch steel pipe piles (Table 

1): 4 For the gangway and 2 for the float. 

To allow for flexibility in design, 

temporary piles may be all of one size 

or a combination of 24- and 36-inch 

steel pipe piles. The piles from the 

existing SFD piles will be left in place 

and will not be removed. 

All piles will be installed with a 

vibratory hammer to the greatest extent 

possible, with each pile requiring 

approximately 45 minutes to install 

(Table 1), based on an analysis of PCT 

Phase 1 data. An impact hammer may 

be required if a pile encounters refusal 

and cannot be advanced to the 

necessary tip elevation with the 

vibratory hammer. Refusal criteria for a 

vibratory hammer is defined by the 

hammer manufacturer and is described 

as the pile not advancing one foot 

within 30 seconds of vibratory hammer 

operation at full speed. Three piles have 

deeper embedment depth than others 

and may reach refusal before the 

specified minimum tip elevation. In 

such a situation, an impact hammer 

would be needed to drive these piles to 

their required depth. A small number of 

total piles, estimated up to five piles, 

may reach refusal before the tip 

elevation is reached, requiring up to 20 

minutes of impact installation each at 

one pile per day. POA estimates that 

each of these piles could require up to 

1,000 strikes, which was the mean 

number of strikes measured for 48-inch 

production piles during the PCT Phase 

1 construction sound source verification 

(SSV) study (Reyff et al., 2021). It is 

likely that the number of strikes will be 

less due to the smaller pile sizes 

associated with SFD. To be 

conservative, 1,000 strikes were used to 

calculate Level A harassment zone sizes. 

It is assumed that if a pile does require 

impact installation, the vibratory 

installation time would be reduced by a 

commensurate amount (i.e., 15 minutes 

of impact installation would replace 15 

minutes of vibratory installation), and 

the overall duration of installation 

would remain the same. 

Temporary template piles (n = 6) will 

be removed with a vibratory hammer 

(Table 1). Based on an analysis of PCT 

Phase 1 data, each temporary pile will 

require approximately 75 minutes of 

vibratory hammer removal. Knik Arm 

soils have demonstrated a strong set up 

and resistance condition on temporary 

piles due to dense clay composition, 

making removal lengthier and more 

difficult than installation. The 

temporary piles for the SFD will be in 

place for only approximately three 

weeks and will not be load-bearing, in 

contrast to the piles used for the PCT 

temporary trestle that were in place for 

approximately five months and subject 

to loads from the construction crane. 

The temporary SFD piles will likely 

require less time for removal than PCT 

piles at approximately two-thirds 

duration. Based on this, the estimated 

removal time is approximately twothirds of the duration required for 

vibratory removal of 36-inch temporary 

trestle piles during PCT Phase 1 

construction. All of the existing SFD 

float and gangway piles will remain in 

place; a vibratory hammer will not be 

required for their removal. 

TABLE 1—PILE DETAILS AND ESTIMATED EFFORT REQUIRED FOR PILE INSTALLATION AND REMOVAL

Pipe pile 

diameter Feature Number of plumb piles 

Number of 

battered 

piles 

Vibratory installation duration per pile 

(minutes) 

Vibratory removal duration 

per pile 

(minutes) 

Potential 

impact 

strikes 

per pile, 

if needed 

(up to 5 

piles; one 

pile per day) 

Production rate 

(piles/day) 

Days of installation Days of removal 

Installation Removal 

36-inch .. Floating 

Dock.

6 2 45 ................... n/a .................. 1,000 1–3 n/a 4–12 n/a 

Gangway 4 0 n/a .................. 1,000 1–3 n/a n/a 

24- or 

36-inch.

Temporary 

Template 

Piles.

6 0 45 ................... 75 ................... 1,000 1–2 1–3 3–6 2–6 

Project Totals 16 2 13.5 hours ...... 7.5 hours ........ .................... ........................ .................... 7–18 2–6 


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31874 Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Notices 

The POA will use an unconfined 

bubble curtain noise attenuation system 

to mitigate noise propagation during 

vibratory installation and potential 

impact installation of the ten permanent 

plumb piles and six temporary plumb 

piles and vibratory removal of the six 

temporary piles when water depth is 

deep enough to deploy a bubble curtain 

(approximately 3 m). Pile installation or 

removal in the dry, which is a 

completely de-watered state, is unlikely 

but, if it occurs, will be conducted 

without a bubble curtain. A bubble 

curtain will not be used with the two 

battered piles due to the angle of 

installation. Use of an unconfined 

bubble curtain is proposed instead of a 

confined bubble curtain in order to 

reduce the need for additional template 

piles that would be required to stabilize 

a confined bubble curtain. 

All pile installation will take place 

from a floating work barge and crane. A 

marine-based operation is required 

because of the extreme tidal range, 

which precludes use of a land-based 

crane in the absence of a temporary 

support trestle. The floating work barge 

will require sufficient water depth for 

support. Opportunities to install piles 

when the project site is dewatered will 

be limited. Piles will be installed in 

water and multiple piles will likely not 

be driven concurrently. 

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 six species of marine 

mammals that may be found in upper 

Cook Inlet during the proposed pile 

driving activities. Sections 3 and 4 of 

the POA’s application summarize 

available information regarding status 

and trends, distribution and habitat 

preferences, and behavior and life 

history, of the potentially affected 

species. 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/marinemammal-stock-assessments), and more 

general information about these species 

(e.g., physical and behavioral 

descriptions) may be found on NMFS’s 

website (https://www.fisheries.

noaa.gov/find-species). Additional 

information on CIBWs may be found in 

NMFS’ 2016 Recovery Plan for the 

CIBW (Delphinapterus leucas), available 

online at https://www.fisheries.

noaa.gov/resource/document/recoveryplan-cook-inlet-beluga-whaledelphinapterus-leucas. 

Table 2 lists all species or stocks for 

which take is expected and proposed to 

be authorized for this action and 

summarizes information related to the 

population or stock, including 

regulatory status under the MMPA and 

Endangered Species Act (ESA) and 

potential biological removal (PBR), 

where known. For taxonomy, we follow 

Committee on Taxonomy (2019). PBR is 

defined by the MMPA as the maximum 

number of animals, not including 

natural mortalities, that may be removed 

from a marine mammal stock while 

allowing that stock to reach or maintain 

its optimum sustainable population (as 

described in NMFS’s SARs). While no 

mortality is anticipated or authorized 

here, PBR and annual serious injury and 

mortality from anthropogenic sources 

are included here as gross indicators of 

the status of the species and other 

threats. 

Marine mammal abundance estimates 

presented in this document represent 

the total number of individuals that 

make up a given stock or the total 

number estimated within a particular 

study or survey area. NMFS’ stock 

abundance estimates for most species 

represent the total estimate of 

individuals within the geographic area, 

if known, that comprises that stock. For 

some species, this geographic area may 

extend beyond U.S. waters. All managed 

stocks in this region are assessed in 

NMFS’ U.S. 2019 SARs (e.g., Muto et al., 

2020a) and 2020 draft SARs (Muto et al., 

2020b). All values presented in Table 2 

are the most recent available at the time 

of publication and are available in the 

2019 SARs (Muto et al., 2020a) and 2020 

draft SARs (Muto et al., 2020b) 

(available online at: https://

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/draftmarine-mammal-stock-assessmentreports). 

TABLE 2—MARINE MAMMAL SPECIES POTENTIALLY OCCURRING IN UPPER COOK INLET, ALASKA

Common name Scientific name Stock 

ESA/ 

MMPA 

status; 

strategic 

(Y/N) 1

Stock 

abundance 

(CV, Nmin, most recent 

abundance survey) 2

PBR Annual 

M/SI 3

Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales) 

Family Balaenopteridae 

(rorquals): 

Humpback whale ................ Megaptera novaeangliae .......... Western North Pacific ............... E/D; Y 1,107 (0.3, 865, 2006) .... 3 2.8 

Central North Pacific ................. -/-; Y 10,103 (0.3, 7890, 2006) 83 26 

Superfamily Odontoceti (toothed whales, dolphins, and porpoises) 

Family Delphinidae: 

Beluga whale ...................... Delphinapterus leucas .............. Cook Inlet .................................. E/D; Y 279 (0.06, 267, 2018) ..... 0.53 0 

Killer whale ......................... Orcinus orca ............................. Alaska Resident ........................ -/-; N 2,347 (N/A, 1102,347, 

2012).

24 1 

Alaska Transient ....................... -/-; N 587 (N/A, 587, 2012) ...... 5.87 0.8 

Family Phocoenidae (porpoises): 

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

1998).

Undet 72 

Order Carnivora—Superfamily Pinnipedia 

Family Otariidae (eared seals 

and sea lions): 

Steller sea lion .................... Eumetopias jubatus .................. Western ..................................... E/D; Y 53,932 (N/A, 52,932 

2013).

318 255 

Family Phocidae (earless seals): 


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I I I 

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Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Notices 31875 

TABLE 2—MARINE MAMMAL SPECIES POTENTIALLY OCCURRING IN UPPER COOK INLET, ALASKA—Continued 

Common name Scientific name Stock 

ESA/ 

MMPA 

status; 

strategic 

(Y/N) 1

Stock 

abundance 

(CV, Nmin, most recent 

abundance survey) 2

PBR Annual 

M/SI 3

Harbor seal ......................... Phoca vitulina ........................... Cook Inlet/Shelikof .................... -/-; 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: www.nmfs.noaa.gov/pr/sars/. CV is coefficient of variation; Nmin is the minimum estimate of stock 

abundance. In some cases, CV is not applicable because it has not been calculated. 3These values, found in NMFS’ SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial fisheries, 

ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases. 

As indicated above, all six species 

(with six managed stocks) in Table 2 

temporally and spatially co-occur with 

the activity to the degree that take is 

reasonably likely to occur, and we have 

proposed authorizing it. Marine 

mammals occurring in Cook Inlet that 

are not expected to be observed in the 

project area and for which take is not 

proposed include gray whales 

(Eschrichtius robustus), minke whales 

(Balaenoptera acutorostrata), and Dall’s 

porpoise (Phocoenoides dalli). Data 

from the Alaska Marine Mammal 

Stranding Network database (NMFS, 

unpublished data) provide additional 

support for the determination that these 

species rarely occur in upper Cook Inlet. 

Since 2011, only one minke whale and 

one Dall’s porpoise have been 

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. No gray 

whales were reported as stranded in 

upper Cook Inlet during this time 

period; however, one juvenile gray 

whale was observed on May 24, 2020 

during PCT Phase 1 construction 

monitoring (61 North Environmental, 

2021). This whale was first observed 

mid-inlet off Port MacKenzie then 

travelled along the southeastern shore of 

Knik Arm until it was last sighted near 

Point Woronzof. On May 27, 2020, there 

were reports that a juvenile gray whale, 

believed to be the same whale, was 

stranded in the Twentymile River, at the 

eastern end of Turnagain Arm, 

approximately 50 mi southeast of Knik 

Arm. The animal remained in the river 

for a week, before swimming out of the 

river. The whale later stranded and died 

about 25 mi away at the mouth of the 

Theodore River on June 12, 2020. No in 

water pile installation occurred on 23 to 

25 May, and there is no indication that 

work at the PCT had any effect on the 

animal. Based on photos and video 

NMFS collected of the whale, 

veterinarians determined the whale was 

in fair to poor condition (see https://

www.fisheries.noaa.gov/feature-story/ 

alaska-gray-whale-ume-updatetwentymile-river-whale-likely-onetwelve-dead-gray-whales for more 

information). With very few exceptions, 

minke whales, gray whales, and Dall’s 

porpoises do not occur in upper Cook 

Inlet; and, therefore, take of these 

species is not requested in this 

application. 

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. 

Humpback Whale 

Currently, three stocks of humpback 

whales are recognized in the North 

Pacific, migrating between their 

respective summer/fall feeding areas 

and winter/spring calving and mating 

areas (Baker et al., 1998; Calambokidis 

et al., 1997): (1) The California/Oregon/ 

Washington and Mexico stock, (2) the 

Central North Pacific stock, and (3) the 

Western North Pacific stock. Humpback 

whales from the Western North Pacific 

breeding stock overlap broadly on 

summer feeding grounds with whales 

from the Central North Pacific breeding 

stock, as well as with whales that winter 

in the Revillagigedo Islands in Mexico 

(Muto et al., 2020a, 2020b). Despite this 

overlap, the whales seasonally found in 

Cook Inlet are probably of the Central 

North Pacific stock (Muto et al., 2020a, 

2020b). The Central North Pacific stock 

winters in Hawaii (Baker et al., 1986) 

and summers from British Columbia to 

the Aleutian Islands (Calambokidis et 

al., 1997), including Cook Inlet. 

The humpback whale ESA listing 

final rule (81 FR 62259, September 8, 

2016) delineated 14 Distinct Population 

Segments (DPSs) with different listing 

statuses. The most comprehensive 

photo-identification data available 

suggest that approximately 89 percent of 

all humpback whales in the Gulf of 

Alaska are members of the Hawaii DPS, 

11 percent are from the Mexico DPS, 

and less than 1 percent are from the 

western North Pacific DPS (Wade et al., 

2016). The Hawaii DPS is not listed 

under the ESA, the Mexico DPS is listed 

as threatened, and the Western North 

Pacific DPS is listed as endangered 

under the ESA. Members of different 

DPSs are known to intermix in feeding 

grounds; therefore, all waters off the 

coast of Alaska should be considered to 

have ESA-listed humpback whales. 

NMFS is in the process of reviewing 

humpback whale stock structure under 

the MMPA in light of the 14 DPSs 

established under the ESA. 

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). 

There have been few sightings of 

humpback whales near the project area. 

Humpback whales were not 

documented during POA construction 

or scientific monitoring from 2005 to 

2011 or during 2016 (Cornick and 

Pinney, 2011; Cornick and SaxonKendall, 2008, 2009; Cornick and 

Seagars, 2016; Cornick et al., 2010, 

2011; ICRC, 2009, 2010a, 2011a, 2012; 

Markowitz and McGuire, 2007; PrevelRamos et al., 2006). 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. 

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. No humpbacks were 

observed from April–November 2020 

during Phase 1 PCT construction 


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monitoring (61 North Environmental, 

2021). 

The Central North Pacific stock is the 

focus of a large whale-watching industry 

in its wintering grounds (Hawaii) and 

summering grounds (Alaska). The 

growth of the whale-watching industry 

is an ongoing concern as preferred 

habitats may be abandoned if 

disturbance levels are too high (Muto et 

al., 2020a, 2020b). Other potential 

impacts include elevated levels of 

sound from anthropogenic sources (e.g., 

shipping, military sonars), harmful algal 

blooms (Geraci et al., 1989), possible 

changes in prey distribution with 

climate change, entanglement in fishing 

gear, ship strikes due to increased vessel 

traffic (e.g., from increased shipping in 

higher latitudes and through the Bering 

Sea with changes in sea-ice coverage), 

and oil and gas activities. An intentional 

unauthorized take of a humpback whale 

by Alaska Natives in Toksook Bay was 

documented in 2016 (Muto et al., 2020a, 

2020b); however, no subsistence use of 

humpback whales occurs in Cook Inlet. 

Humpback whale populations were 

considerably reduced as a result of 

intensive commercial exploitation 

during the 20th century. Currently, the 

overall trend for most humpback whale 

populations found in U. S. waters is 

positive and points toward recovery (81 

FR 62259; September 8, 2016); however, 

this may not be uniform for all breeding 

areas. A sharp decline in observed 

reproduction and encounter rates of 

humpback whales from the Central 

North Pacific stock between 2013 and 

2018 has been related to oceanographic 

anomalies and consequent impacts on 

prey resources (Cartwright et al., 2019), 

suggesting that humpback whales are 

vulnerable to major environmental 

changes. 

Beluga Whale 

The CIBW stock is a small, 

geographically isolated population 

separated from other beluga whale 

populations by the Alaska Peninsula. 

The population is genetically distinct 

from other Alaska populations, 

suggesting the peninsula is an effective 

barrier to genetic exchange (O’CorryCrowe et al., 1997). The CIBW 

population is estimated to have 

declined from 1,300 animals in the 

1970s (Calkins, 1989) to about 340 

animals in 2014 (Shelden et al., 2015), 

and to 279 animals in 2018 (Wade et al., 

2019). The precipitous decline 

documented in the mid-1990s was 

attributed to unsustainable subsistence 

practices by Alaska Native hunters 

(harvest of >50 whales per year) 

(Mahoney and Shelden, 2000). 

Harvesting of CIBWs has not occurred 

since 2008 (NMFS, 2008). 

Despite protection from hunting and 

other threats, this stock has not 

rebounded and continues to decline 

(Wade et al., 2019, Muto et al., 2020b). 

The population was declining at the end 

of the period of unregulated harvest, 

with the relatively steep decline ending 

in 1999, coincident with harvest 

removals dropping from an estimated 42 

in 1998 to just 0 to 2 whales per year 

in 2000 to 2006 (and with no removals 

after 2006). From 1999 to 2016, the rate 

of decline of the population was 

estimated to be 0.4 percent (SE = 0.6 

percent) per year, with a 73 percent 

probability of a population decline. This 

rate increased from 2006 to 2016 to 0.5 

percent per year, (with a 70 percent 

probability of a population decline) 

(Shelden et al., 2017). The latest 

estimates suggest that this rate has 

further increased to 2.3 percent decline 

per year from 2008 to 2018, with a 99.7 

percent probability of population 

decline in the future (Wade et al., 2019, 

Muto et al., 2020b). No human-caused 

mortality or serious injury of CIBWs has 

been recently documented. 

The current best abundance estimate 

of the CIBW population from the aerial 

survey data is 279 (95 percent 

probability interval 250 to 317). This is 

based on the estimate of smoothed 

abundance for 2018, as described in 

Sheldon and Wade (2019). A 

comparison of the population estimates 

over time is presented in Figure 2. 

While Sheldon and Wade (2019) 

provides explanations for the 

differences between model results, 

including inadequacies and biases, the 

authors do not postulate on the reason 

for population decline in general (which 

was evident using both models); 

however, recent literature suggests prey 

reductions may be a critical contributing 

factor (Norman et al., 2019). This is not 

unexpected as reduced prey availability 

has been directly linked to increased 

mortality and reduced health and 

survival of other marine mammals 

populations such as the Southern 

Resident killer whale (e.g., Ward et al., 

2009, Wasser et al., 2017) and California 

sea lion (e.g., McClatchie et al., 2016). 

The CIBW stock was designated as 

depleted under the MMPA in 2000 (65 

FR 34590; May 21, 2000) and listed as 

endangered under the ESA in 2008 (73 

FR 62919; October 22, 2008). Therefore, 

the CIBW stock is considered a strategic 

stock. 


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Mortality related to live stranding 

events, where a CIBW group strands as 

the tide recedes, has been regularly 

observed in upper Cook Inlet. Most 

whales involved in a live stranding 

event survive, although some associated 

deaths may not be observed if the 

whales die later from live-strandingrelated 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, 

2016a; NMFS, unpubl. Data, Muto et al., 

2020b). 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. A CIBW calf that 

stranded alive in 2017 was sent to the 

Alaska SeaLife Center for rehabilitation 

and then transferred to SeaWorld in San 

Antonio, Texas, in 2018. Most live 

strandings occur in Knik Arm and 

Turnagain Arm, which are shallow and 

have large tidal ranges, strong currents, 

and extensive mudflats. Another source 

of CIBW mortality in Cook Inlet is 

predation by transient-type (mammaleating) killer whales (NMFS, 2016a; 

Sheldon et al., 2003). 

In its Recovery Plan (NMFS, 2016a), 

NMFS identified several threats to 

CIBWs. Potential threats include: (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 ship strikes. 

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). 

NMFS designated two areas, consisting 

of 7,809 km2 (3,016 mi2) of marine and 

estuarine environments, considered 

essential for the species’ survival and 

recovery as critical habitat (76 FR 

20180; April 11, 2011). However, in 

recent years the range of the CIBW 

whale has contracted to the upper 

reaches of Cook Inlet because of the 

decline in the population (Rugh et al., 

2010), and almost the entire population 

can be found in northern Cook Inlet 

from late spring through the summer 

and into the fall (Muto et al., 2020b). 

Area 1 of the CIBW critical habitat 

encompasses all marine waters of Cook 

Inlet north of a line connecting Point 

Possession (61.04° N, 150.37° W) and 

the mouth of Three Mile Creek 

(61.08.55° N, 151.04.40° W), including 

waters of the Susitna, Little Susitna, and 

Chickaloon Rivers below mean higher 

high water. This area provides 

important habitat during ice-free 

months and is used intensively by 

CIBWs between April and November 

(NMFS, 2016a). The POA, the adjacent 

navigation channel, and the turning 

basin were excluded from critical 

habitat designation due to national 


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8 

■ 

eHobbsN 

BoydN 

400 --------------------------

■ 

1---~---~---

i / 

1------r--+-------~- ! ■ 

■ 

250 ---------------------■--·----

■ 

200 ----------------------------..... 2004 2005 2008 2007 2008 2009 2010 2011 2012 2013 2014 2015 2018 2017 2018 

Survey year 

Figure 2. Annual estimates of abundance for both group size estimation methods. 

The moving average of each set of estimates is also plotted. Taken from Sheldon and 

Wade (2019). 
31878 Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Notices 

security reasons (76 FR 20180; April 11, 

2011). More information on CIBW 

critical habitat can be found at https:// 

www.fisheries.noaa.gov/action/criticalhabitat-cook-inlet-beluga-whale. 

Aerial surveys were conducted by 

NMFS each year during from 1994 to 

2012 (Rugh et al., 2000, 2005; Shelden 

et al., 2013, 2019) to document 

distribution and abundance of CIBWs. 

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). The collective survey 

results show that CIBWs have been 

consistently found near or in river 

mouths along the northern shores of 

upper Cook Inlet (i.e., north of East and 

West Foreland). In particular, CIBW 

groups are seen in the Susitna River 

Delta, Knik Arm, and along the shores 

of Chickaloon Bay. Small groups have 

also been recorded farther south in 

Kachemak Bay, Redoubt Bay (Big River), 

and Trading Bay (McArthur River) prior 

to 1996 but very rarely thereafter. Since 

the mid-1990s, most (96 to 100 percent) 

CIBWs in upper Cook Inlet have been 

concentrated in shallow areas near river 

mouths (Sheldon et al., 2015), no longer 

occurring in the central or southern 

portions of Cook Inlet (Hobbs et al., 

2008). Based on these aerial surveys, the 

concentration of CIBWs in the 

northernmost portion of Cook Inlet 

appears to be consistent from June to 

October (Rugh et al., 2000, 2004a, 

2004b, 2005, 2006, 2007). Research 

reports generated from the surveys can 

be found at https://www.fisheries.

noaa.gov/alaska/endangered-speciesconservation/research-reports-andpublications-cook-inlet-beluga-whales. 

Though CIBWs can be found 

throughout the inlet at any time of year, 

they spend the ice-free months generally 

in the upper Cook Inlet, shifting into the 

middle and lower Inlet in winter (Hobbs 

et al., 2005). In 1999, one CIBW was 

tagged with a satellite transmitter, and 

its movements were recorded from June 

through September of that year. Since 

1999, 18 CIBWs in upper Cook Inlet 

have been captured and fitted with 

satellite tags to provide information on 

their movements during late summer, 

fall, winter, and spring (Goetz et al., 

2012a; Shelden et al., 2015a, 2018). All 

tagged CIBWs remained in Cook Inlet 

(Shelden et al., 2015a, 2018). Most 

tagged whales were in the lower to 

middle inlet (70 to 100 percent of tagged 

whales) during January through March, 

near the Susitna River Delta from April 

to July (60 to 90 percent of tagged 

whales) and in the Knik and Turnagain 

Arms from August to December (Ezer et 

al., 2013). More recently, the Marine 

Mammal Lab has conducted long-term 

passive acoustic monitoring 

demonstrating seasonal shifts in CIBW 

concentrations throughout Cook Inlet. 

Castellote et al. (2015) conducted longterm 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. 

CIBWs are generally concentrated 

near the warmer waters of river mouths 

during the spring and summer because 

that is where prey availability is high 

and predator occurrence is low (Moore 

et al., 2000). 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 

group sizes. CIBW presence also 

increased closer to rivers with Chinook 

salmon (Oncorhynchus tshawytscha) 

runs, such as the Susitna River. 

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 in Cook Inlet are believed to 

mostly calve between mid-May and 

mid-July, and concurrently breed 

between late spring and early summer 

(NMFS, 2016a), primarily in upper Cook 

Inlet. The only known observed 

occurrence of calving occurred on July 

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

McGuire, pers. comm. 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 midlate 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 two 

years and may continue to associate 

with their mothers for a considerable 

time thereafter (Colbeck et al., 2013). 

The POA conducted dedicated 

monitoring during PCT Phase 1 

construction between April and 

November 2020 (61 North 

Environmental, 2021). In total, protected 

species observers (PSOs) observed 245 

groups of approximately 987 CIBWs 

near the POA (group sizes ranged from 

1 to 53 individuals), with the most 

number of individuals and groups being 

seen in August (N = 56 groups of 274 

individuals) and September (N = 73 

groups of 276 individuals). CIBWs were 

observed in every month of the project 

(except during October, which only 

included three project and monitoring 

days) with the highest sightings per unit 

effort, measured as CIBWs per hour of 

observation, occurring at the end of 

August and beginning of September. 

Killer Whale 

Killer whales are found throughout 

the North Pacific Ocean. Along the west 

coast of North America, seasonal and 

year-round occurrence of killer whales 

occur 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). Two stocks of 

killer whales may be present in upper 

Cook Inlet: The Eastern North Pacific 

Alaska Resident stock and the Gulf of 

Alaska, Aleutian Islands, and Bering Sea 


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Transient stock. Both ecotypes overlap 

in the same geographic area; however, 

they maintain social and reproductive 

isolation and feed on different prey 

species. 

While there have been some anecdotal 

reports of killer whales feeding on 

CIBWs in upper Cook Inlet, sightings in 

this region and near the POA are rare 

(e.g., NMFS, 2016a; Sheldon et al., 

2003). During aerial surveys conducted 

between 1993 and 2004 in Cook Inlet, 

killer whales were only observed on 

three flights, and all sightings were 

located in the Kachemak and English 

Bay area, south of the POA (Rugh et al., 

2005). Acoustic monitoring carried out 

by Castellote et al. (2016) between 2008 

and 2013 only detected one transient 

killer whale at Beluga River, located 

along the western shore of Cook Inlet, 

west of the POA. Surveys conducted by 

Funk et al., (2005), Ireland et al., (2005), 

Brueggeman et al., (2007, 2008a, 2008b), 

and McGuire et al., (2020) did not 

observe killer whales in the vicinity of 

or north of the POA. Lastly, killer 

whales were not observed during POA 

construction or scientific monitoring 

from 2005 to 2011, during the 2016 Test 

Pile Program (TPP), or during Phase 1 of 

the PCT project carried out between 

April–November 2020 (61 North 

Environmental, 2021). Therefore, very 

few killer whales, if any, are expected 

to approach or be near the project area 

during construction of the SFD. 

Killer whales are not harvested for 

subsistence in Alaska. Potential threats 

most likely to result in direct humancaused mortality or serious injury of 

killer whales in this region include oil 

spills, vessel strikes, and interactions 

with fisheries. Based on currently 

available data, a minimum estimate of 

the mean annual mortality and serious 

injury rate for both the Alaska Residents 

and Gulf of Alaska, Aleutian Islands, 

and Bering Sea Transient stocks due to 

U.S. commercial fisheries is less than 10 

percent of the PBR and, therefore, is 

considered to be insignificant and 

approaching zero mortality and serious 

injury rate. Therefore, neither stock is 

classified as a strategic stock (Muto et 

al., 2020b). 

Harbor Porpoise 

Harbor porpoises primarily frequent 

the coastal waters of the Gulf of Alaska 

and Southeast Alaska (Dahlheim et al., 

2000, 2009), typically occurring in 

waters less than 100 m deep (Hobbs and 

Waite, 2010). Harbor porpoise prefer 

nearshore areas, bays, tidal areas, and 

river mouths (Dahlheim et al., 2000, 

2009, 2015; Hobbs and Waite, 2010). In 

Alaskan waters, NMFS has designated 

three stocks of harbor porpoises for 

management purposes: Southeast 

Alaska, Gulf of Alaska, and Bering Sea 

Stocks (Muto et al., 2020b). Porpoises 

found in Cook Inlet belong to the Gulf 

of Alaska Stock, which is distributed 

from Cape Suckling to Unimak Pass. 

Although harbor porpoises have been 

frequently observed during aerial 

surveys in Cook Inlet (Shelden et al., 

2014), most sightings are of single 

animals and are concentrated at 

Chinitna and Tuxedni bays on the west 

side of lower Cook Inlet (Rugh et al., 

2005). The occurrence of larger numbers 

of porpoise in the lower Cook Inlet may 

be driven by greater availability of 

preferred prey and possibly less 

competition with CIBWs, as CIBWs 

move into upper inlet waters to forage 

on Pacific salmon during the summer 

months (Shelden et al., 2014). 

There has been an increase in harbor 

porpoise sightings in upper Cook Inlet 

over the past two decades (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). Harbor porpoises have been 

observed within Knik Arm during 

monitoring efforts since 2005. During 

POA construction from 2005 through 

2011 and in 2016, harbor porpoises 

were reported in 2009, 2010, and 2011 

(Cornick and Saxon-Kendall, 2008, 

2009; Cornick and Seagars, 2016; 

Cornick et al., 2010, 2011; Markowitz 

and McGuire, 2007; Prevel-Ramos et al., 

2006). In 2009, 20 harbor porpoises 

were observed during construction 

monitoring, with sightings in June, July, 

August, October, and November. Harbor 

porpoises were observed twice in 2010, 

once in July and again in August. In 

2011, POA monitoring efforts 

documented harbor porpoises five 

times, with a total of six individuals, in 

August, October, and November at the 

POA (Cornick et al., 2011). During other 

monitoring efforts conducted in Knik 

Arm, there were four sightings of harbor 

porpoises in 2005 (Shelden et al., 2014), 

and a single harbor porpoise was 

observed within the vicinity of the POA 

in October 2007. More recent 

monitoring conducted during Phase 1 

PCT construction documented 15 

groups (18 individuals) of harbor 

porpoises near the POA between April 

and November 2020 (group sizes ranged 

1–2 individuals) (61 North 

Environmental, 2021). 

Estimates of human-caused mortality 

and serious injury from stranding data 

and fisherman self-reports are 

underestimates because not all animals 

strand or are self-reported nor are all 

stranded animals found, reported, or 

have the cause of death determined. In 

addition, the trend of this stock is 

unknown given existing data is more 

than eight years old. NMFS considers 

this stock strategic because the level of 

mortality and serious injury would 

likely exceed the PBR level if we had 

accurate information on stock structure, 

a newer abundance estimate, and 

complete fisheries observer coverage. 

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). 

Steller Sea Lion 

Steller sea lions inhabiting Cook Inlet 

belong to the Western distinct 

population segment (WDPS), and this is 

the stock considered in this analysis. 

NMFS defines the Steller sea lion WDPS 

as all populations west of longitude 

144° W to the western end of the 

Aleutian Islands. The most recent 

comprehensive aerial photographic and 

land-based surveys of WDPS Steller sea 

lions in Alaska were conducted during 

the 2018 (Aleutian Islands west of 

Shumagin Islands) and 2019 (Southeast 

Alaska and Gulf of Alaska east of 

Shumagin Islands) breeding seasons 

(Sweeney et al., 2018, 2019). The WDPS 

of Steller sea lions is currently listed as 

endangered under the ESA (55 FR 

49204, November 26, 1990) and 

designated as depleted under the 

MMPA. NMFS designated critical 

habitat on August 27, 1993 (58 FR 

45269). The critical habitat designation 

for the WDPS of Steller sea lions was 

determined to include a 37 km (20 nm) 

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 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 been 


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observed near the POA in 2009 (ICRC 

2009), 2016 (Cornick and Seagars, 2016), 

and in 2020 during Phase 1 PCT 

construction monitoring (61 North 

Environmental, 2021). During POA 

construction monitoring in June of 2009, 

a Steller sea lion was documented three 

times (within the same day) in Knik 

Arm and was believed to be the same 

individual (ICRC, 2009). In 2016, Steller 

sea lions were observed on two separate 

days. On May 2, 2016, one individual 

was sighted. 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 suggesting they 

were likely the same animal (Cornick 

and Seagars, 2016). Most recently, up to 

six Steller sea lions were sighted across 

four days between May 29 and June 24, 

2020 during Phase PCT 1 construction 

monitoring (61 North 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 (61 North Environmental, 

2021). 

The minimum estimated mean annual 

level of human-caused mortality and 

serious injury for Western U.S. Steller 

sea lions between 2014 and 2018 is 255 

sea lions: 38 in U.S. commercial 

fisheries, 0.8 in unknown (commercial, 

recreational, or subsistence) fisheries, 

3.2 in marine debris, 3.6 due to other 

causes (arrow strike, entangled in 

hatchery net, illegal shooting, mortality 

incidental to Marine Mammal 

Protection Act (MMPA) authorized 

research), and 209 in the Alaska Native 

subsistence harvest (Muto et al., 2020b). 

However, there are multiple nearshore 

commercial fisheries which are not 

observed; thus, there is likely to be 

unreported fishery-related mortality and 

serious injury of Steller sea lions. 

Several factors may have been 

important drivers of the decline of the 

stock. However, there is uncertainty 

about threats currently impeding their 

recovery, 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 3-nmi no-entry zones around 

rookeries, prohibition of shooting at or 

near sea lions, and regulation of 

fisheries for sea lion prey species (e.g., 

walleye pollock, Pacific cod, and Atka 

mackerel) (Sinclair et al., 2013, Tollit et 

al., 2017). Additionally, potentially 

deleterious events, such as harmful algal 

blooms (Lefebvre et al., 2016) and 

disease transmission across the Arctic 

(VanWormer et al., 2019) that have been 

associated with warming waters, could 

lead to potentially negative populationlevel impacts on Steller sea lions. 

Harbor Seal 

Harbor seals inhabit coastal and 

estuarine waters off Baja California, 

north along the western coasts of the 

United States, British Columbia, and 

Southeast Alaska, west through the Gulf 

of Alaska and Aleutian Islands, and in 

the Bering Sea north to Cape Newenham 

and the Pribilof Islands. They haul out 

on rocks, reefs, beaches, and drifting 

glacial ice and feed in marine, estuarine, 

and occasionally fresh waters. Harbor 

seals generally are non-migratory, with 

local movements associated with such 

factors as tides, weather, season, food 

availability, and reproduction (Scheffer 

and Slipp, 1944; Fisher, 1952; Bigg, 

1969, 1981; Hastings et al., 2004). NMFS 

currently identifies twelve stocks of 

harbor seals based largely on genetic 

structure (Muto et al., 2020a). Harbor 

seals from the Cook Inlet/Shelikof Strait 

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, 

are considered in this analysis. 

Harbor seals belonging to this stock 

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). Research on 

satellite-tagged harbor seals conducted 

between 2004 and 2006 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 Shumigan 

Islands. During summer months, 

movements and distribution was 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). 

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 located 

in lower Cook Inlet with fewer sites in 

upper Cook Inlet (Montgomery et al., 

2007). In the project area (Knik Arm), 

harbor seals tend to congregate near the 

mouth of Ship Creek (Cornick et al., 

2011; Shelden et al., 2013), likely 

foraging on salmon and eulachon runs. 

Approximately 138 harbor seals were 

observed during POA monitoring prior 

to 2020, with sightings ranging from 

three individuals in 2008 to 59 

individuals in 2011. During 2020 PCT 

Phase 1 construction monitoring, harbor 

seals were regularly observed in the 

vicinity of the POA with frequent 

observations near the mouth of Ship 

Creek, located approximately 700 m 

southeast of the SFD location. From 27 

April through 24 November 2020, a total 

of 340 individual harbor seals were 

observed (61 North Environmental, 

2021). An additional seven unidentified 

pinnipeds were observed that could 

have been Steller sea lions or harbor 

seals. Harbor seals were observed almost 

daily during construction, with 54 

individuals documented in July, 66 

documented in August, and 44 sighted 

in September (61North Environmental, 

2021). 

The most current population trend 

estimate of the Cook Inlet/Shelikof 

Strait stock is approximately –111 seals 

per year, with a probability that the 

stock is decreasing of 0.609 (Muto et al., 

2020a). The estimated level of humancaused mortality and serious injury for 

this stock is 234 seals, of which 233 

seals are taken for subsistence uses. 

Between 2013 and 2017, there were two 

reports of Cook Inlet/Shelikof Strait 

harbor seal mortality and serious injury 

due to entanglements in fishing gear, 

including one in a Cook Inlet salmon set 

gillnet in 2014 and one in an 

unidentified net in 2017, resulting in a 

mean annual mortality and serious 

injury rate of 0.4 harbor seals from this 

stock due to interactions with unknown 

(commercial, recreational, or 

subsistence) fisheries (Muto et al., 

2020a). Additional potential threats 

most likely to result in direct humancaused mortality or serious injury for all 

stocks of harbor seals in Alaska include 

unmonitored subsistence harvests, 

incidental takes in commercial fisheries, 

illegal shooting, and entanglements in 

marine debris (Delean et al., 2020, Muto 

et al., 2020a). Disturbance by cruise 

vessels is an additional threat for harbor 

seal stocks that occur in glacial fjords 

(Jansen et al., 2010, 2015; Matthews et 


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al., 2016). The average annual harvest of 

this stock of harbor seals between 2004 

and 2008 was 233 seals per year. The 

annual harvest in 2014 was 104 seals 

(Muto et al., 2020a). This stock is not 

designated as depleted under the 

MMPA or listed as threatened or 

endangered under the ESA, and the 

minimum estimate of the mean annual 

level of human-caused mortality and 

serious injury does not exceed PBR; 

therefore, the Cook Inlet/Shelikof Strait 

stock of harbor seals is not classified as 

a strategic stock (Muto et al., 2020a). 

Marine Mammal Hearing 

Hearing is the most important sensory 

modality for marine mammals 

underwater, and exposure to 

anthropogenic sound can have 

deleterious effects. To appropriately 

assess the potential effects of exposure 

to sound, it is necessary to understand 

the frequency ranges marine mammals 

are able to hear. Current data indicate 

that not all marine mammal species 

have equal hearing capabilities (e.g., 

Richardson et al., 1995; Wartzok and 

Ketten, 1999; Au and Hastings, 2008). 

To reflect this, Southall et al., (2007) 

recommended that marine mammals be 

divided into functional hearing groups 

based on directly measured or estimated 

hearing ranges on the basis of available 

behavioral response data, audiograms 

derived using auditory evoked potential 

techniques, anatomical modeling, and 

other data. Note that no direct 

measurements of hearing ability have 

been successfully completed for 

mysticetes (i.e., low-frequency 

cetaceans). Subsequently, NMFS (2018) 

described generalized hearing ranges for 

these marine mammal hearing groups. 

Generalized hearing ranges were chosen 

based on the approximately 65 decibel 

(dB) threshold from the normalized 

composite audiograms, with the 

exception for lower limits for 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 3. 

TABLE 3—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). 

For more detail concerning these 

groups and associated frequency ranges, 

please see NMFS (2018) for a review of 

available information. Six marine 

mammal species (four cetacean and two 

pinniped (one otariid and one phocid) 

species) have the reasonable potential to 

co-occur with the proposed construction 

activities. Please refer to Table 2. Of the 

cetacean species that may be present, 

one is classified as low-frequency 

cetaceans (i.e., all mysticete species), 

two are classified as mid-frequency 

cetaceans (i.e., all delphinid and ziphiid 

species and the sperm whale), and one 

is classified as high-frequency cetaceans 

(i.e., harbor porpoise and Kogia spp.). 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

This section includes a summary and 

discussion of the ways that components 

of the specified activity may impact 

marine mammals and their habitat. The 

Estimated Take section later in this 

document includes a quantitative 

analysis of the number of individuals 

that are expected to be taken by this 

activity. The Negligible Impact Analysis 

and Determination section considers the 

content of this section, the Estimated 

Take section, and the Proposed 

Mitigation section, to draw conclusions 

regarding the likely impacts of these 

activities on the reproductive success or 

survivorship of individuals and how 

those impacts on individuals are likely 

to impact marine mammal species or 

stocks. 

Description of Sound Sources 

The primary relevant stressor to 

marine mammals from the proposed 

activity is the introduction of noise into 

the aquatic environment; therefore, we 

focus our impact analysis on the effects 

of anthropogenic noise on marine 

mammals. To better understand the 

potential impacts of exposure to pile 

driving noise, we describe sound source 

characteristics below. Specifically, we 

look at the following two ways to 

characterize sound: by its temporal (i.e., 

continuous or intermittent) and its pulse 

(i.e., impulsive or non-impulsive) 

properties. Continuous sounds are those 

whose sound pressure level remains 

above that of the ambient sound, with 

negligibly small fluctuations in level 

(NIOSH, 1998; ANSI, 2005), while 

intermittent sounds are defined as 

sounds with interrupted levels of low or 

no sound (NIOSH, 1998). Impulsive 

sounds, such as those generated by 

impact pile driving, are typically 

transient, brief (<1 sec), broadband, and 

consist of a high peak pressure with 

rapid rise time and rapid decay (ANSI, 

1986; NIOSH, 1998). The majority of 

energy in pile impact pulses is at 

frequencies below 500 hertz (Hz). 

Impulsive sounds, by definition, are 

intermittent. Non-impulsive sounds, 

such as those generated by vibratory 

pile driving, can be broadband, 

narrowband or tonal, brief or prolonged, 

and typically do not have a high peak 

sound pressure with rapid rise/decay 

time that impulsive sounds do (ANSI, 

1995; NIOSH, 1998). Non-impulsive 

sounds can be intermittent or 

continuous. Similar to impact pile 

driving, vibratory pile driving generates 

low frequency sounds. Vibratory pile 

driving is considered a non-impulsive, 

continuous source. Discussion on the 

appropriate harassment threshold 

associated with these types of sources 


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based on these characteristics can be 

found in the Estimated Take section. 

Potential Effects of Pile Driving—In 

general, the effects of sounds from pile 

driving to marine mammals might result 

in one or more of the following: 

Temporary or permanent hearing 

impairment, non-auditory physical or 

physiological effects, behavioral 

disturbance, and masking (Richardson 

et al., 1995; Nowacek et al., 2007; 

Southall et al., 2007). The potential for 

and magnitude of these effects are 

dependent on several factors, including 

receiver characteristics (e.g., age, size, 

depth of the marine mammal receiving 

the sound during exposure); the energy 

needed to drive the pile (usually related 

to pile size, depth driven, and 

substrate), the standoff distance between 

the pile and receiver; and the sound 

propagation properties of the 

environment. 

Impacts to marine mammals from pile 

driving activities are expected to result 

primarily from acoustic pathways. As 

such, the degree of effect is intrinsically 

related to the received level and 

duration of the sound exposure, which 

are in turn influenced by the distance 

between the animal and the source. The 

further away from the source, the less 

intense the exposure should be. The 

type of pile driving also influences the 

type of impacts, for example, exposure 

to impact pile driving may result in 

temporary or permanent hearing 

impairment, while auditory impacts are 

unlikely to result from exposure to 

vibratory pile driving. The substrate and 

depth of the habitat affect the sound 

propagation properties of the 

environment. Shallow environments are 

typically more structurally complex, 

which leads to rapid sound attenuation. 

In addition, substrates that are soft (e.g., 

sand) absorb or attenuate the sound 

more readily than hard substrates (e.g., 

rock) which may reflect the acoustic 

wave. Soft porous substrates also likely 

require less time to drive the pile, and 

possibly less forceful equipment, which 

ultimately decrease the intensity of the 

acoustic source. 

Richardson et al., (1995) described 

zones of increasing intensity of effect 

that might be expected to occur, in 

relation to distance from a source and 

assuming that the signal is within an 

animal’s hearing range. First is the area 

within which the acoustic signal would 

be audible (potentially perceived) to the 

animal, but not strong enough to elicit 

any overt behavioral or physiological 

response. The next zone corresponds 

with the area where the signal is audible 

to the animal and of sufficient intensity 

to elicit behavioral or physiological 

responsiveness. Third is a zone within 

which, for signals of high intensity, the 

received level is sufficient to potentially 

cause discomfort or tissue damage to 

auditory or other systems. Overlaying 

these zones to a certain extent is the 

area within which masking (i.e., when a 

sound interferes with or masks the 

ability of an animal to detect a signal of 

interest that is above the absolute 

hearing threshold) may occur; the 

masking zone may be highly variable in 

size. 

We describe the more severe effects 

(i.e., permanent hearing impairment, 

certain non-auditory physical or 

physiological effects) only briefly as we 

do not expect that there is a reasonable 

likelihood that POA’s activities would 

result in such effects (see below for 

further discussion). 

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, 2016b). The amount of 

threshold shift is customarily expressed 

in dB (ANSI 1995, Yost 2007). A TS can 

be permanent (PTS) or temporary (TTS). 

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 nonimpulsive), likelihood an individual 

would be exposed for a long enough 

duration or to a high enough level to 

induce a TS, the magnitude of the TS, 

time to recovery (seconds to minutes or 

hours to days), the frequency range of 

the exposure (i.e., spectral content), the 

hearing and vocalization frequency 

range of the exposed species relative to 

the signal’s frequency spectrum (i.e., 

how 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). When 

analyzing the auditory effects of noise 

exposure, it is often helpful to broadly 

categorize sound as either impulsive— 

noise with high peak sound pressure, 

short duration, fast rise-time, and broad 

frequency content—or non-impulsive. 

When considering auditory effects, 

vibratory pile driving is considered a 

non-impulsive source while impact pile 

driving is treated as an impulsive 

source. 

Permanent Threshold Shift—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). Available data from 

humans and other terrestrial mammals 

indicate that a 40 dB threshold shift 

approximates PTS onset (see NMFS 

2018 for review). 

Temporary Threshold Shift—NMFS 

defines TTS as a temporary, reversible 

increase in the threshold of audibility at 

a specified frequency or portion of an 

individual’s hearing range above a 

previously established reference level 

(NMFS, 2018). Based on data from 

cetacean TTS measurements (see 

Finneran 2015 for a review), 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 (Schlundt et al., 2000; Finneran 

et al., 2000; Finneran et al., 2002). 

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. 

Schlundt et al. (2000) performed a 

study exposing five bottlenose dolphins 

and two beluga whales (same 

individuals as Finneran’s studies) to 

intense one second tones at different 

frequencies. The resulting levels of 

fatiguing stimuli necessary to induce 6 

dB or larger masked TTSs were 

generally between 192 and 201 dB re: 1 

microPascal (mPa). Dolphins began to 

exhibit altered behavior at levels of 178– 

193 dB re: 1mPa and above; beluga 

whales displayed altered behavior at 

180–196 dB re: 1 mPa and above. At the 

conclusion of the study, all thresholds 

were at baseline values. 

There are a limited number of studies 

investigating the potential for cetacean 

TTS from pile driving and only one has 

elicited a small amount of TTS in a 

single harbor porpoise individual 

(Kastelein et al., 2015). However, 


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captive bottlenose dolphins and beluga 

whales have exhibited changes in 

behavior when exposed to pulsed 

sounds (Finneran et al., 2000, 2002, 

2005). The animals tolerated high 

received levels of sound before 

exhibiting aversive behaviors. 

Experiments on a beluga whale showed 

that exposure to a single watergun 

impulse at a received level of 207 

kiloPascal (kPa) (30 psi) p-p, which is 

equivalent to 228 dB p-p, resulted in a 

7 and 6 dB TTS in the beluga whale at 

0.4 and 30 kHz, respectively. 

Thresholds returned to within 2 dB of 

the pre-exposure level within four 

minutes of the exposure (Finneran et al., 

2002). Although the source level of pile 

driving from one hammer strike is 

expected to be lower than the single 

watergun impulse cited here, animals 

being exposed for a prolonged period to 

repeated hammer strikes could receive 

more sound exposure in terms of SEL 

than from the single watergun impulse 

(estimated at 188 dB re 1 mPa2-s) in the 

aforementioned experiment (Finneran et 

al., 2002). Results of these studies 

suggest odontocetes are susceptible to 

TTS from pile driving, but that they 

seem to recover quickly from at least 

small amounts of TTS. 

Behavioral Responses—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. 

Disturbance may result in changing 

durations of surfacing and dives, 

number of blows per surfacing, or 

moving direction and/or speed; 

reduced/increased vocal activities; 

changing/cessation of certain behavioral 

activities (such as socializing or 

feeding); visible startle response or 

aggressive behavior (such as tail/fluke 

slapping or jaw clapping); avoidance of 

areas where sound sources are located. 

Pinnipeds may increase their haul-out 

time, possibly to avoid in-water 

disturbance (Thorson and Reyff, 2006). 

Behavioral responses to sound are 

highly variable and context-specific and 

any reactions depend on numerous 

intrinsic and extrinsic factors (e.g., 

species, state of maturity, experience, 

current activity, reproductive state, 

auditory sensitivity, time of day), as 

well as the interplay between factors 

(e.g., Richardson et al., 1995; Wartzok et 

al., 2003; Southall et al., 2007; 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–C of Southall 

et al. (2007) for a review 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., 2003). Animals are most 

likely to habituate to sounds that are 

predictable and unvarying. It is 

important to note that habituation is 

appropriately considered as a 

‘‘progressive reduction in response to 

stimuli that are perceived as neither 

aversive nor beneficial,’’ rather than as, 

more generally, moderation in response 

to human disturbance (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; NRC, 2003; Wartzok et al., 2003). 

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 (typically seismic airguns or 

acoustic harassment devices) have been 

varied but often consist of avoidance 

behavior or other behavioral changes 

suggesting discomfort (Morton and 

Symonds 2002; see also Richardson et 

al., 1995; Nowacek et al., 2007). 

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,b). 

Variations in dive behavior may reflect 

interruptions in biologically significant 

activities (e.g., foraging) or they may be 

of little biological significance. The 

impact of an alteration to dive behavior 

resulting from an acoustic exposure 

depends on what the animal is doing at 

the time of the exposure and the type 

and magnitude of the response. 

Disruption of feeding behavior can be 

difficult to correlate with anthropogenic 

sound exposure, so it is usually inferred 

by observed displacement from known 

foraging areas, the appearance of 

secondary indicators (e.g., bubble nets 

or sediment plumes), or changes in dive 

behavior. 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 


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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, 

2005b, 2006; Gailey et al., 2007). 

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; Foote et al., 2004), 

while 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 (Eschrictius robustus) 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). 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 (Evans and 

England, 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 fish 

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 fiveday 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 one day and not 

recurring on subsequent days is not 

considered particularly severe unless it 

could directly affect reproduction or 

survival (Southall et al., 2007). Note that 

there is a difference between multi-day 

substantive behavioral reactions and 

multi-day anthropogenic activities. For 

example, just because an activity lasts 

for multiple days does not necessarily 

mean that individual animals are either 

exposed to activity-related stressors for 

multiple days or, further, exposed in a 

manner resulting in sustained multi-day 

substantive behavioral responses. 

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., Seyle, 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 

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, 

Wright et al., 2007) and, more rarely, 

studied in wild populations (e.g., 


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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, 2003). 

Specific to CIBWs, we have several 

years of marine mammal monitoring 

data demonstrating the behavioral 

responses to pile driving at the POA. 

Previous pile driving activities range 

from the installation and removal of 

sheet pile driving to installation of 48- 

in pipe piles with both vibratory and 

impact hammers, and vibratory 

installation of 72-inch air bubble 

casings. Kendall and Cornick (2015) 

provide a comprehensive overview of 

four years of scientific marine mammal 

monitoring conducted during the POA’s 

Expansion Project. These were 

observations made independent of pile 

driving activities (i.e., not construction 

based PSOs). The authors investigated 

CIBWs 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 h of sampling effort was 

completed across 349 d 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. Suspected feeding decreased 

during pile driving although the sample 

size was low as feeding was observed on 

only two occasions before pile driving 

and on zero occasions during pile 

driving. Documentation of milling began 

in 2008 and was observed on 21 

occasions. No acute behavioral 

responses were documented. Mean 

group size decreased during pile 

driving; however, this difference was 

not statistically significant. There were 

significant differences in group 

composition before and during pile 

driving between monthly CIBW sighting 

rates and monthly pile driving rates 

with more white (i.e., older) animals 

being present during pile driving. 

During PCT construction monitoring, 

behaviors of CIBWs groups were 

compared by month and by construction 

activity (61 North Environmental, 2021). 

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. One 

minor difference was a slightly higher 

incidence of milling behavior during the 

periods of no pile driving and slightly 

higher rates of traveling behavior during 

periods when CIBWs were potential 

disturbed by pile driving. 

Acoustically, Kendall et al. (2013) 

only recorded echolocation clicks and 

no whistles or noisy vocalizations near 

construction activity at the POA. CIBWs 

have been occasionally documented to 

forage around Ship Creek (south of the 

POA) but, during pile driving, may 

choose to move past the POA to other, 

potentially richer, feeding areas further 

into Knik Arm (e.g., Six Mile Creek, 

Eagle River, Eklutna River). These 

locations contain predictable salmon 

runs (ADF&G, 2010), 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). 

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 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 animal detection 

of acoustic signals such as 

communication calls, echolocation 

sounds, and environmental sounds 

important to marine mammals. 

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. 

Masking, which can occur over large 

temporal and spatial scales, can 

potentially affect the species at 

population, community, or even 

ecosystem levels, as well as individual 

levels. Masking affects both senders and 

receivers of the signals and could have 

long-term chronic effects on marine 

mammal species and populations. 

Masking occurs at the frequency band 

which the animals utilize so the 

frequency range of the potentially 

masking sound is important in 

determining any potential behavioral 

impacts. Pile driving generates low 

frequency sounds; therefore, mysticete 

foraging is likely more affected than 

odontocetes given very high frequency 

echolocation clicks (typically associated 

with odontocete foraging) are likely 

unmasked to any significant degree. 

However, lower frequency man-made 

sounds may affect communication 

signals when they occur near the sound 

band and thus reduce the 

communication space of animals (e.g., 

Clark et al., 2009) and cause increased 

stress levels (e.g., Foote et al., 2004; Holt 

et al., 2009). 

Moreover, even within a given 

species, different types of man-made 

noises may results in varying degrees of 

masking. For example, Erbe (1997) and 

Erbe and Farmer (1998) analyzed the 

effect of masking of beluga calls by 

exposing a trained beluga to icebreaker 

propeller noise, an icebreaker’s bubbler 

system, and ambient Arctic ice cracking 

noise, and found that the latter was the 

least problematic for the whale 

detecting the calls. Sheifele et al. (2005) 

studied a population of belugas in the 

St. Lawrence River Estuary to determine 

whether beluga vocalizations showed 

intensity changes in response to 

shipping noise. This type of behavior 

has been observed in humans and is 

known as the Lombard vocal response 

(Lombard, 1911). Sheifele et al. (2005) 

demonstrated that shipping noise did 

cause belugas to vocalize louder. The 

acoustic behavior of this same 

population of belugas was studied in the 

presence of ferry and small boat noise. 

Lesage et al. (1999) described more 

persistent vocal responses when whales 

were exposed to the ferry than to the 

small-boat noise. These included a 

progressive reduction in calling rate 

while vessels were approaching, an 

increase in the repetition of specific 

calls, and a shift to higher frequency 

bands used by vocalizing animals when 

vessels were close to the whales. The 

authors concluded that these changes, 


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and the reduction in calling rate to 

almost silence, may reduce 

communication efficiency which is 

critical for a species of a gregarious 

nature. However, the authors also stated 

that because of the gregarious nature of 

belugas, this ‘‘would not pose a serious 

problem for intraherd communication’’ 

of belugas given the short distance 

between group members, and concluded 

a noise source would have to be very 

close to potentially limit any 

communication within the beluga group 

(Lesage et al., 1999). However, 

increasing the intensity or repetition 

rate, or shifting to higher frequencies 

when exposed to shipping noise (from 

merchant, whale watching, ferry and 

small boats), is indicative of an increase 

of energy costs (Bradbury and 

Vehrencamp, 1998). 

Marine mammals in Cook Inlet are 

continuously exposed to anthropogenic 

noise which may lead to some 

habituation but is also a source of 

masking (Castellote et al., 2019, Mooney 

et al., 2020). A subsample (8756 hours) 

of the acoustic recordings collected by 

the Cook Inlet Beluga Acoustics 

research program in Cook Inlet, Alaska, 

from July 2008 to May 2013, were 

analyzed to describe anthropogenic 

sources of underwater noise, acoustic 

characteristics, and frequency of 

occurrence and evaluate the potential 

for acoustic impact to CIBWs. As 

described in Castellote et al., (2016), a 

total of 13 sources of noise were 

identified: commercial ship, dredging, 

helicopter, jet aircraft (commercial or 

non-fighter), jet aircraft (military 

fighter), outboard engine (small skiffs, 

rafts), pile driving, propeller aircraft, 

sub-bottom profiler, unclassified 

machinery (continuous mechanical 

sound; e.g., engine), unidentified ‘clank’ 

or ‘bang’ (impulsive mechanical sound; 

e.g., barge dumping), unidentified 

(unclassifiable anthropogenic sound), 

unknown up- or down-sweep 

(modulated tone of mechanical origin; 

e.g., hydraulics). A total of 6263 

anthropogenic acoustic events were 

detected and classified, which had a 

total duration of 1025 hours and 

represented 11.7 percent of the sound 

recordings analyzed. There was strong 

variability in source diversity, loudness, 

distribution, and seasonal occurrence of 

noise, which reflects the many different 

activities within the Cook Inlet. Cairn 

Point was the location where the 

loudness and duration of commercial 

ship noise events were most 

concentrated, due to activities at the 

POA. This specific source of 

anthropogenic noise was present in the 

recordings from all months analyzed, 

with highest levels in August. In 

addition to the concentrated shipping 

noise at Cairn Point, a combination of 

unknown noise classes occurred in this 

area, particularly during summer. 

Specifically, unknown up or down 

sweeps, unidentified, unclassed 

machinery, and unidentified clank or 

bang noise classes were all documented. 

In contrast, Eagle River (north of the 

POA and where CIBWs concentrate to 

forage) was the quietest of all sampled 

locations. 

Sensitivity in CIBW hearing may 

make them more susceptible to masking. 

The first empirical hearing data of a 

CIBW was recently obtained by Mooney 

et al., (2020), who used auditory evoked 

potentials to measure the hearing of a 

wild, stranded CIBW as part of its 

rehabilitation assessment. The CIBW 

exhibited broadband (4–128 kHz) and 

sensitive hearing (<80 dB) for a wide 

range of frequencies (16–80 kHz), with 

the audiogram shape and waveforms 

generally reflective of a sensitive 

odontocete’s auditory system without 

substantial hearing loss (Mooney et al., 

2020). This sensitivity suggests that 

CIBWs are susceptible to masking from 

a variety of anthropogenic sources in 

Cook Inlet. 

Potential Pile Driving Effects on 

Prey—Pile driving produces continuous, 

non-impulsive (i.e., vibratory pile 

driving) sounds and intermittent, pulsed 

(i.e., impact driving) sounds. 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. Hastings and 

Popper (2005) identified several studies 

that suggest fish may relocate to avoid 

certain areas of sound energy. 

Additional studies have documented 

effects of pile driving on fish, although 

several are based on studies in support 

of large, multiyear bridge construction 

projects (e.g., Scholik and Yan, 2001, 

2002; Popper and Hastings, 2009). 

Sound pressure levels (SPLs) of 

sufficient strength have been known to 

cause injury to fish and fish mortality 

(summarized in Popper et al., 2014). 

The most likely impact to fish from pile 

driving activities at the project area 

would be temporary behavioral 

avoidance of the area. The duration of 

fish avoidance of this area after pile 

driving stops is unknown, but a rapid 

return to normal recruitment, 

distribution and behavior is anticipated. 

As discussed in the Marine Mammal 

section above, NMFS designated CIBW 

critical habitat in Knik Arm. Knik Arm 

is Type 1 habitat for the CIBWs, which 

means it is the most valuable, used 

intensively by CIBWs from spring 

through fall for foraging and nursery 

habitat. However, the POA, the adjacent 

navigation channel, and the turning 

basin were excluded from critical 

habitat designation due to national 

security concerns (76 FR 20180; April 

11, 2011). Foraging primarily occurs at 

river mouths (e.g., Susitna Delta, Eagle 

River flats) which are unlikely to be 

influenced by pile driving activities. 

The Susitna Delta is more than 20 km 

from the POA and Cairn Point is likely 

to impede any pile driving noise from 

propagating into northern Knik Arm. Of 

the 245 CIBW groups observed during 

PCT construction monitoring, only two 

groups were suspected to be feeding (61 

North Environmental, 2021). One of 

these groups (n = 4 CIBWs) was 

observed on May 7, 2020, a non-pile 

driving day, approximately 142 m away 

from the PCT. The other group (n = 3 

CIBWs) was observed on July 14, 2020 

during impact installation of an 

attenuated 48-inch pile. These CIBWs 

were suspected to be foraging in 

Bootleggers Cove, approximately 1,399 

m way from the PCT and outside the 

respective Level B harassment zone (824 

m). It was unclear whether or not 

feeding occurred during pile driving 

activities (61 North Environmental, 

2021). 

Acoustic habitat is the soundscape 

which encompasses all of the sound 

present in a particular location and 

time, as a whole, when considered from 

the perspective of the animals 

experiencing it. Animals produce sound 

for, or listen for sounds produced by, 

conspecifics (communication during 

feeding, mating, and other social 

activities), other animals (finding prey 

or avoiding predators) and the physical 

environment (finding suitable habitats, 

navigating). Together, sounds made by 

animals and the geophysical 

environment (e.g., produced by 

earthquakes, lightning, wind, rain, 

waves) make up the natural 

contributions to the total acoustics of a 

place. These acoustic conditions, 

termed acoustic habitat, are one 

attribute of an animal’s total habitat. 

Soundscapes are also defined by, and 

acoustic habitat influenced by, the total 

contribution of anthropogenic sound. 

This may include incidental emissions 

from sources such as vessel traffic or 

may be intentionally introduced to the 

marine environment for data acquisition 

purposes (as in the use of airgun arrays 

or other sources). Anthropogenic noise 

varies widely in its frequency content, 

duration, and loudness and these 

characteristics greatly influence the 

potential habitat-mediated effects to 

marine mammals (please see also the 


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previous discussion on masking under 

‘‘Acoustic Effects’’), which may range 

from local effects for brief periods of 

time to chronic effects over large areas 

and for long durations. Depending on 

the extent of effects to habitat, animals 

may alter their communications signals 

(thereby potentially expending 

additional energy) or miss acoustic cues 

(either conspecific or adventitious). For 

more detail on these concepts see, e.g., 

Barber et al., 2010; Pijanowski et al., 

2011; Francis and Barber, 2013; Lillis et 

al., 2014. 

CIBW foraging habitat is limited at the 

POA given the highly industrialized 

area. However, foraging habitat exists 

near the POA, including Ship Creek and 

to the north of Cairn Point. Potential 

impacts to foraging habitat include 

increased turbidity and elevation in 

noise levels during pile driving. While 

the POA is building a new dock, it is 

removing the float and gangway of the 

existing dock and permanent impacts 

from the presence of the new dock are 

negligible. Here, we focus on 

construction impacts such as increased 

turbidity and reference the section on 

acoustic habitat impacts above. 

Pile installation may temporarily 

increase turbidity resulting from 

suspended sediments. Any increases 

would be temporary, localized, and 

minimal. POA must comply with state 

water quality standards during these 

operations by limiting the extent of 

turbidity to the immediate project area. 

In general, turbidity associated with pile 

installation is localized to about a 25- 

foot (7.6 m) radius around the pile 

(Everitt et al., 1980). Cetaceans are not 

expected to be close enough to the 

project activity areas to experience 

effects of turbidity, and any small 

cetaceans and pinnipeds could avoid 

localized areas of turbidity. Therefore, 

the impact from increased turbidity 

levels is expected to be discountable to 

marine mammals. No turbidity impacts 

to Ship Creek or critical CIBW foraging 

habitats are anticipated. 

In summary, activities associated with 

the proposed SFD project are not likely 

to have a permanent, adverse effect on 

marine mammal habitat or populations 

of fish species or on the quality of 

acoustic habitat. Marine mammals may 

choose to not forage in close proximity 

to the SFD site during pile driving; 

however, the POA is not a critical 

foraging location for any marine 

mammal species. As discussed above, 

harbor seals primarily use Ship Creek as 

foraging habitat within Knik Arm. 

CIBWs utilize Eagle Bay and rivers 

north of the POA which are not 

expected to be ensonified by the SFD 

project. Therefore, no impacts to critical 

foraging grounds are anticipated. 

Estimated Take 

This section provides an estimate of 

the number of incidental takes proposed 

for authorization through this IHA, 

which will inform both NMFS’ 

consideration of ‘‘small numbers’’ and 

the negligible impact determination. 

Harassment is the only type of take 

expected to result from these activities. 

Except with respect to certain activities 

not pertinent here, section 3(18) of the 

MMPA defines ‘‘harassment’’ as any act 

of pursuit, torment, or annoyance, 

which (i) has the potential to injure a 

marine mammal or marine mammal 

stock in the wild (Level A harassment); 

or (ii) has the potential to disturb a 

marine mammal or marine mammal 

stock in the wild by causing disruption 

of behavioral patterns, including, but 

not limited to, migration, breathing, 

nursing, breeding, feeding, or sheltering 

(Level B harassment). 

Authorized takes would primarily be 

by Level B harassment, as pile driving 

has the potential to result in disruption 

of behavioral patterns for individual 

marine mammals, either directly or as a 

result of TTS. There is also some 

potential for auditory injury (Level A 

harassment) to result, primarily for 

mysticetes, high frequency species, and 

phocids because predicted auditory 

injury zones are larger than for midfrequency species and otariids. Auditory 

injury is unlikely to occur for midfrequency species and otariids. The 

proposed mitigation and monitoring 

measures are expected to minimize the 

severity of the taking to the extent 

practicable. 

As described previously, no mortality 

is anticipated or proposed to be 

authorized for this activity. Below we 

describe how the take is estimated. 

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) and the number of days of 

activities. We note that while these 

basic factors can contribute to a basic 

calculation to provide an initial 

prediction of 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 estimate. 

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 for non-explosive 

sources—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 (e.g., frequency, predictability, 

duty cycle), the environment (e.g., 

bathymetry), and the receiving animals 

(hearing, motivation, experience, 

demography, behavioral context) and 

can be difficult to predict (Southall et 

al., 2007, Ellison et al., 2012). Based on 

what the available science indicates and 

the practical need to use a threshold 

based on a factor that is both predictable 

and measurable for most activities, 

NMFS uses a generalized acoustic 

threshold based on received level to 

estimate the onset of behavioral 

harassment. NMFS predicts that marine 

mammals are likely to be behaviorally 

harassed in a manner we consider Level 

B harassment when exposed to 

underwater anthropogenic noise above 

received levels of 120 dB re 1 mPa (root 

mean square; rms) for continuous (e.g., 

vibratory pile-driving, drilling) and 

above 160 dB re 1 mPa (rms) for nonexplosive impulsive (e.g., seismic 

airguns) or intermittent (e.g., scientific 

sonar) sources. This take estimation 

includes disruption of behavioral 

patterns resulting directly in response to 

noise exposure (e.g., avoidance), as well 

as that resulting indirectly from 

associated impacts such as TTS or 

masking. However, ambient noise levels 

within Knik Arm are above the 120-dB 

threshold, and therefore, for purposes of 

this analysis, NMFS considers received 

levels above those of the measured 

ambient noise (122.2 dB) to constitute 

Level B harassment of marine mammals 

incidental to continuous noise, 

including vibratory pile driving. 

Results from recent acoustic 

monitoring conducted at the port are 

presented in Austin et al. (2016) and 

Denes et al. (2016) wherein noise levels 

were measured in absence of pile 

driving from May 27 through May 30, 

2016 at two locations: Ambient-Dock 

and Ambient-Offshore. NMFS considers 

the median sound levels to be most 

appropriate when considering 

background noise levels for purposes of 


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evaluating the potential impacts of the 

POA’s SFD Project on marine mammals 

(NMFS, 2012). By using the median 

value, which is the 50th percentile of 

the measurements, for ambient noise 

level, 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 two of the four days (50 

percent) when background 

measurement data were being collected, 

the U.S. Army Corps of Engineers was 

dredging Terminal 3 (located just north 

of the Ambient-Offshore hydrophone) 

for 24 hours per day with two 1-hour 

breaks for crew change. On the last two 

days of data collection, no dredging was 

occurring. Therefore, the median 

provides a better representation of 

background noise levels when the SFD 

project would be occurring. With regard 

to spatial considerations of the 

measurements, the Ambient-Offshore 

location is most applicable to this 

discussion (NMFS, 2012). The median 

ambient noise level collected over four 

days at the end of May at the AmbientOffshore hydrophone was 122.2 dB. We 

note the Ambient-Dock location was 

quieter, with a median of 117 dB; 

however, that hydrophone was placed 

very close to the dock and not where we 

would expect Level B harassment to 

occur given mitigation measures (e.g., 

shut downs). We also recognize that 

during Phase 1 PCT acoustic 

monitoring, noise levels in Knik Arm 

absent pile driving were collected (Reyff 

et al., 2021); however, the Phase 1 PCT 

IHA did not require ambient noise 

measurements to be collected. These 

measurements were not collected in 

accordance to NMFS (2012) guidance 

for measuring ambient noise and thus 

cannot be used here for that purpose. If 

additional data collected in the future 

warrant revisiting this issue, NMFS may 

adjust the 122.2 dB rms Level B 

harassment threshold. 

Level A harassment for non-explosive 

sources—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 nonimpulsive (vibratory pile driving) 

sources. 

These thresholds are provided in 

Table 4 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 4—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. 

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 this 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 will feed into identifying the area 

ensonified above the acoustic 

thresholds, which include source levels 

and transmission loss coefficient. 

The estimated sound source levels 

(SSL) proposed by the POA and used in 

this assessment for vibratory installation 

of attenuated piles are based on sound 

levels of 24-inch and 36-inch piles 

measured during a sound source 

verification (SSV) study conducted 

during Phase 1 of the POA’s 2020 PCT 

project (Reyff et al., 2021). For the 24- 

inch template piles, SSLs measured for 

24-inch PCT template piles by Reyff et 

al. (2021) were selected for use as a 

proxy for 24-inch SFD template piles 

based on anticipated pile function 

(Table 5). These piles were driven for 

19.2 to 25.6 minutes, using an APE 200– 

6 vibratory hammer and a confined 

bubble curtain (Reyff et al., 2021). For 

the 36-inch template piles, SSLs are 

assumed to be similar to the SSLs 

measured for 36-inch trestle piles 

installed during PCT construction (note 

no 36-inch template piles were 

measured in Reyffe et al., 2021) (Table 

5). These piles were installed with a 

confined bubble curtain using an APE 

300–6 vibratory hammer; driving times 

ranged from 22.1 to 36.4 minutes. It is 

assumed that SLLs during pile 

installation and removal for both pile 

sizes will be similar. 

No unattenuated 24-inch or 36-inch 

piles were installed during either the 

TPP (Austin et al., 2016) or PCT SSV 

projects (Reyeff et al., 2021). Instead, 

SSL measurements collected during 

marine construction projects conducted 

by the U.S. Navy for the Naval Base 

Kitsap at Bangor EHW–2 Project (U.S. 

Navy, 2015), which were installed at 

similar depths and in a similar marine 

environment, were used as proxies for 

vibratory and impact installation of 

unattenuated piles for the SFD project 

(Table 5). It is assumed that SSLs during 

vibratory pile installation and removal 

will be similar. 

SSLs measurements for attenuated 24- 

inch and 36-inch piles driven with an 

impact hammer also were not measured 

during either the TPP (Austin et al., 

2016) or PCT SSV projects (Reyeff et al., 

2021). SSL measurements for impact 


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installation made by Ryeff et al. (2021) 

were on piles using a confined bubble 

curtain system with 48-inch piles; 

whereas, an unconfined system is 

proposed with smaller piles for the SFD. 

In a confined bubble curtain system, the 

bubbles are confined to the area around 

the pile with a flexible material or rigid 

pipe; however, in an unconfined bubble 

curtain system, there is no such system 

for restraining the bubbles (NAVFAC 

SW, 2020). Unconfined bubble curtain 

performance is highly variable and 

effectiveness depends on the system 

design and on-site conditions such as 

water depth, water current velocity, 

substrate and underlying geology. The 

unconfined systems typically consist of 

vertically stacked bubble rings, while 

the confined systems are a single ring at 

the bottom placed inside a casing that 

encompasses the pile. The U.S. Navy 

(2015) summarized several studies 

which demonstrated that unconfined 

bubble curtains performance can be 

effective in attenuating underwater 

noise from impact pile installation. 

They found bubble curtain performance 

to be highly variable, but based on 

information from the Bangor Naval Base 

Test Pile Program, found an average 

peak SPL reduction of 8 dB to 10 dB at 

10 m would be an achievable level of 

attenuation for steel pipe piles of 36- 

and 48-inches in diameter. The 

efficiency of bubble curtains with 24- 

inch piles was not examined by the U.S. 

Navy (2015). Based on these analyses, 

and the effect that local currents may 

have on the distribution of bubbles and 

thus effectiveness of an unconfined 

bubble curtain, NMFS conservatively 

applies a 7 dB reduction to the U.S. 

Navy (2015) unattenuated SSLs (Table 

5) for attenuated 24-inch and 36-inch 

piles during impact pile driving (Table 

5). These SSLs are consistent with SSLs 

previously proposed and authorized by 

NMFS for POA impact pile driving of 

24-inch and 36-inch piles (e.g., PCT 

Final IHA [85 FR 19294]). Rationale for 

using a 7 dB reduction has further been 

provided on June 19, 2019, in 84 FR 

28474 and on November 25, 2019, in 84 

FR 64833. This reduction is more 

conservative than the confined bubble 

curtain efficacy reported by Reyff et al. 

(2021), which ranged from 9 to 11 dB for 

peak, rms, and SEL single strike 

measurements. 

The TL coefficients reported in the 

PCT SSV are highly variable and are 

generally lower than values previously 

reported and used in the region. For 

example, Reyff et al. (2021) reported 

unweighted transmission loss 

coefficients ranging from 8.9 to 16.3 dB 

SEL and 7.0 to 16.7 dB rms for impact 

driving 48-inch attenuated piles. In the 

PCT Final IHA (85 FR 19294), the POA 

proposed, and NMFS applied, a TL rate 

of 16.85 dB SEL for assessing potential 

for Level A harassment from impact pile 

driving and a TL rate of 18.35 dB rms 

when assessing potential for Level B 

harassment from impact pile driving for 

based on Austin et al. (2016) 

measurements recorded during the TPP 

on 48-in piles. Higher TL rates in Knik 

Arm are supported by additional 

studies, such as by Sˇirovic ́ and Kendall 

(2009), who reported a TL of 16.4 dB 

during impact hammer driving during 

passive acoustic monitoring of the POA 

Marine Terminal Redevelopment 

Project, and by Blackwell (2005) who 

reported TLs ranging from 16—18 dB 

SEL and 21.8 dB rms for impact and 

vibratory installation of 36-inch piles, 

respectively, during modifications made 

to the Port MacKenzie dock. After 

careful inspection of the data presented 

in the Reyff et al., study (including 

relevant spectrograms), NMFS is 

concerned that flow noise in the far 

field measurements is negatively biasing 

the regressions derived to infer TL rates. 

While Reyff et al. (2021) discuss 

attempts they made to remove flow 

noise from their calculations, NMFS 

could not conclude that these attempts 

adequately removed flow noise from 

their measurements. Relevant to the 

SFD, the TL calculations of individual 

vibratory installation of 24-inch 

template piles and 36-inch trestle piles 

reported by Reyff et al. (2021) were also 

highly variable ranging from 12.5 to 16.6 

dB rms and 14.4 to 17.2 dB rms, 

respectively. Given this variability and 

previous data suggesting higher TL 

rates, NMFS has preliminarily 

determined that applying a practical 

spreading loss model (15logR) to 

ensonified area calculations is most 

likely the representative scenario in 

Knik Arm (Table 5). The 15 TL 

coefficient also falls within the range of 

TL coefficients reported in Reyff et al. 

(2021). We note the POA will conduct 

additional acoustic monitoring during 

Phase II of the PCT in 2021 (prior to 

when the SFD project will commence) 

and, if warranted, these assumptions 

may be adjusted and resulting 

harassment isopleths modified. 

TABLE 5—ESTIMATED SOUND SOURCE LEVELS AND TRANSMISSION LOSS COEFFICIENTS WITH AND WITHOUT A BUBBLE

CURTAIN

Method and pile size Unattenuated Bubble curtain 

Vibratory Sound level at 10 m TL coefficient Sound level at 10 m TL coefficient 

(dB rms) (dB rms) (dB rms) (dB rms) 

36-inch ....................................................... a 166.0 c 15.0 b 161.4 c 15.0 

24-inch ....................................................... a 161.0 c 15.0 b 158.5 c 15.0 

Impact Unattenuated Bubble curtain 

Sound level at 10 m TL coefficient Sound level at 10 m TL coefficient 

dB rms dB SEL dB Peak dB rms dB SEL dB rms dB SEL dB peak dB rms dB SEL 

36-inch ....................................................... a 194.0 a 184.0 a 211.0 c 15.0 c 15.0 a 187.0 a 177.0 a 204.0 c 15.0 c 15.0 

24-inch ....................................................... a 193.0 a 181.0 a 210.0 c 15.0 c 15.0 a 186.0 a 174.0 a 203.0 c 15.0 c 15.0 

a U.S. Navy 2015. 

b Reyff et al., 2021. cPractical spreading loss model. 

When the NMFS Technical Guidance 

(2016) was published, in recognition of 

the fact that ensonified area/volume 

could be more technically challenging 

to predict because of the duration 

component in the new thresholds, we 

developed a User Spreadsheet that 

includes tools to help predict a simple 

isopleth that can be used in conjunction 

with marine mammal density or 

occurrence to help predict takes. We 

note that because of some of the 

assumptions included in the methods 

used for these tools, we anticipate that 

isopleths produced are typically going 


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to be overestimates of some degree, 

which may result in some degree of 

overestimate of Level A harassment 

take. However, these tools offer the best 

way to predict appropriate isopleths 

when more sophisticated 3D modeling 

methods are not available, and NMFS 

continues to develop ways to 

quantitatively refine these tools, and 

will qualitatively address the output 

where appropriate. For stationary 

sources (such as pile driving), NMFS 

User Spreadsheet predicts the distance 

at which, if a marine mammal remained 

at that distance the whole duration of 

the activity, it would incur PTS. Inputs 

used in the User Spreadsheet, and the 

resulting isopleths are reported below in 

Table 6. 

TABLE 6—NMFS USER SPREADSHEET INPUTS

24-Inch 

(unattenuated) 

24-Inch 

(bubble curtain) 

36-Inch 

(unattenuated) 

36-Inch 

(bubble curtain) 

User Spreadsheet Input: Vibratory Pile Driving 

Spreadsheet Tab Used ............ 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 RMS) ........ 161 ........................................... 158.5 ........................................ 166 ........................................... 161.4. 

Transmission Loss Coefficient 15 ............................................. 15 ............................................. 15 ............................................. 15. 

Weighting Factor Adjustment 

(kHz).

2.5 ............................................ 2.5 ............................................ 2.5 ............................................ 2.5. 

Time to install/remove single 

pile (minutes).

45/75 ........................................ 45/75 ........................................ 45/75 ........................................ 45/75. 

Piles to install/remove per day 1/1 ............................................ 1–2/1–3 .................................... 1/1 ............................................ 1–3/1–3. 

User Spreadsheet Input: Impact Pile Driving 

Spreadsheet Tab Used ............ E.1) Impact pile driving ............ E.1) Impact pile driving ............ E.1) Impact pile driving ............ E.1) Impact pile driving. 

Source Level (Single Strike/ 

shot SEL).

181 ........................................... 174 ........................................... 184 ........................................... 177. 

Transmission Loss Coefficient 15 ............................................. 15 ............................................. 15 ............................................. 15. 

Weighting Factor Adjustment 

(kHz).

2 ............................................... 2 ............................................... 2 ............................................... 2. 

Number of strikes pile .............. 1000 ......................................... 1000 ......................................... 1000 ......................................... 1000. 

Piles per day ............................ 1 ............................................... 1 ............................................... 1 ............................................... 1. 

To calculate the Level B harassment 

isopleths, NMFS considered SPLrms 

source levels and the corresponding TL 

coefficients (dB rms; Table 5) for impact 

and vibratory pile driving, respectively. 

The resulting Level A harassment and 

Level B harassment isopleths are 

presented in Table 7. 

TABLE 7—DISTANCES TO LEVEL A HARASSMENT, BY HEARING GROUP, AND LEVEL B HARASSMENT THRESHOLDS PER

PILE TYPE AND INSTALLATION METHOD

Pile size Attenuation Hammer type 

(installation/removal) 

Piles 

per day 

Level A harassment 

(m) 

Level A 

harassment 

areas 

(km2) 

all hearing 

groups 

Level B 

harassment 

(m) LF MF HF PW OW 

24-inch .......... Bubble Curtain ..................... Vibratory (Installation) .......... 1 4 1 6 3 1 <0.01 2,631 

2 7 1 9 4 1 

Vibratory (Removal) ............. 1 6 1 8 4 1 

3 12 1 17 7 1 

Impact (Installation) ............. 1 251 9 299 135 10 <0.19 542 

Unattenuated ....................... Vibratory (Installation) .......... 1 6 1 9 4 1 <0.01 3,861 

Vibratory (Removal) ............. 1 8 1 12 5 1 

Impact (Installation) ............. 1 735 27 876 394 29 <1.34 1,585 

36-inch .......... Bubble Curtain ..................... Vibratory (Installation) .......... 1 6 1 9 4 1 <0.01 4,106 

2 10 1 15 6 1 

3 13 2 19 8 1 

Vibratory (Removal) ............. 1 9 1 13 6 1 

3 18 2 26 11 1 

Impact (Installation) ............. 1 398 15 474 213 16 <0.76 631 

Unattenuated ....................... Vibratory (Installation) .......... 1 13 2 18 8 1 <0.01 8,318 

Vibratory (Removal) ............. 1 18 2 26 11 1 

Impact (Installation) ............. 1 1,165 42 1,387 624 46 <3.14 1,848 

Marine Mammal Occurrence and Take 

Estimation 

In this section we provide the 

information about the presence, density, 

or group dynamics of marine mammals 

that will inform the take calculations. 

For all species of cetaceans other than 

CIBWs, density data is not available for 

upper Cook Inlet. Therefore, the POA 

relied on marine mammal monitoring 

data collected during past POA projects. 

These data cover the POAs construction 

season (April through November) across 

multiple years. Calculations used to 

estimate exposure from pile installation 

for all marine mammals is described 

below. 

Humpback Whales 

Sightings of humpback whales in the 

project area are rare, and the potential 

risk of exposure of a humpback whale 

to sounds exceeding the Level B 

harassment threshold is low. Few, if 

any, humpback whales are expected to 

approach the project area. However, 

there were two sightings in 2017 of what 


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was likely a single individual at the 

Ship Creek Boat Launch (ABR Inc., 

2017) which is located south of the 

project area. Based on these data, the 

POA conservatively estimates that up to 

two individuals could be behaviorally 

harassed during the 24 days of pile 

driving for the SFD. This could include 

sighting a cow-calf pair on multiple 

days or multiple sightings of single 

humpback whales. No Level A 

harassment take of humpback whales is 

anticipated or proposed to be 

authorized. 

Killer Whales 

Few, if any, killer whales are expected 

to approach the project area. No killer 

whales were sighted during previous 

monitoring programs for the Knik Arm 

Crossing and POA construction projects, 

including the 2016 TPP or during Phase 

1 of the PCT project in 20202. 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 CIBWs for transient killer 

whales) are also in the area (Shelden et 

al., 2003). Previous sightings of 

transient killer whales have 

documented pod sizes in upper Cook 

Inlet between one and six individuals 

(Shelden et al., 2003). The potential for 

exposure of killer whales within the 

Level B harassment isopleths is 

anticipated to be extremely low. Level B 

harassment take is conservatively 

estimated at no more than one small 

pod (6 individuals). No Level A 

harassment take for killer whales is 

anticipated or proposed to be authorized 

due to the small Level A harassment 

zones (Table 7) and implementation of 

a 100 m shutdown which is larger than 

Level A harassment isopleths, and 

described below in the Proposed 

Mitigation section. 

Harbor Porpoise 

Previous monitoring data at the POA 

were used to evaluate daily sighting 

rates for harbor porpoises in the project 

area. During most years of monitoring, 

no harbor porpoises were observed; 

however, during Phase 1 of the PCT 

project (2020), 18 individuals (15 

groups) were observed near the POA, 

with group sizes ranging from 1–2 

individuals. The highest daily sighting 

rate for any recorded year during pile 

installation and removal associated with 

the PCT was an average of 0.09 harbor 

porpoise per day during 2009 

construction monitoring, but this value 

may not account for increased sightings 

in Upper Cook Inlet or range extensions 

(Shelden et al., 2014). Therefore, the 

POA estimates that one harbor porpoise 

could be observed every 2 days of pile 

driving. Based on this assumption, the 

POA has requested, and NMFS is 

proposing to authorize, twelve Level B 

harassment exposures during the 24 

days of pile driving. 

Harbor porpoises are relatively small 

cetaceans that move at high velocities, 

which can make their detection and 

identification at great distances difficult. 

Despite this, PSOs during Phase 1 PCT 

construction monitoring (2020) were 

able to detect harbor porpoises as far as 

6,486 m from the PCT, indicating that 

the monitoring methods detailed in the 

Final IHAs for Phase 1 and Phase 2 PCT 

construction (85 FR 19294), (and 

described below in the Proposed 

Mitigation section for the SFD) allowed 

for harbor porpoises to be detected at 

great distances. Therefore, no Level A 

harassment take for harbor porpoises is 

anticipated or proposed to be authorized 

for the SFD. The POA anticipates that 

the majority of piles will be driven 

using vibratory methods. Using the 

NMFS User Spreadsheet, vibratory 

driving 24-inch and 36-inch piles 

results in Level A harassment isopleths 

that are smaller than the proposed 100 

m shutdown zone, described below in 

the Proposed Mitigation section (≤26 m; 

Table 7). The Level A harassment 

isopleths calculated using the NMFS 

User Spreadsheet for impact driving 24- 

inch and 36-inch piles are larger than 

this 100-m shutdown zone (≤1,387 m; 

Table 7); however, Level A harassment 

isopleths consider long durations and 

harbor porpoise are likely moving 

through the area, if present, not 

lingering. Further few harbor porpoises 

are expected to approach the project 

area and are likely to be sighted prior to 

entering the Level A harassment zone. 

During Phase 1 PCT construction 

monitoring (2020) only five harbor 

porpoises were observed near the PCT 

and within the largest Level A 

harassment zone for SFD (1,387 m; 

Table 7). Given that the POA anticipates 

that only a small number of piles (up to 

five), may be driven with an impact 

hammer (requiring up to 20 minutes of 

impact installation each at 1 pile per 

day), the likelihood that harbor 

porpoises will be in these larger zones 

is minimized. Accounting for measures 

described below in the Proposed 

Mitigation section below and the low 

likelihood that individual harbor 

porpoises would appear undetected 

within the Level A harassment zones, 

we agree with the POA and do not 

authorize any Level A harassment takes 

of harbor porpoises during the 

construction of the SFD. 

Steller Sea Lion 

Steller sea lions are anticipated to be 

encountered in low numbers, if at all, 

within the project area. Three sightings 

of what was likely a single individual 

occurred in the project area in 2009, two 

sightings occurred in 2016, one 

occurred in 2019, and up to six 

individuals were observed in 2020 (4 in 

May and 2 in June). Based on 

observations in 2016, the POA 

anticipates an exposure rate of two 

individuals every 19 days during SFD 

pile installation and removal. Based on 

this rate, the POA anticipates that there 

could be up to four harassment 

exposures of Steller sea lions during the 

24 days of SFD pile installation and 

removal. 

Sea lions are known to travel at high 

speeds, in rapidly changing directions, 

and have the potential to be counted 

multiple times. Because of this the POA 

anticipates that, despite all precautions, 

sea lions could enter the Level A 

harassment zone before a shutdown 

could be fully implemented. For 

example, in 2016 during the POA Test 

Pile Program, a Steller sea lion was first 

sighted next to a work boat and within 

the Level A harassment zone. Nine 

PSOs had been monitoring for the 

presence of marine mammals near the 

construction activities at this time, but 

they did not observe the approaching 

sea lion. Sea lions are known to be 

curious and willing to approach human 

activity closely, and they can swim with 

a low profile. The incident was recorded 

as a Level A harassment take and raises 

concern for the POA that a sighting of 

a Steller sea lion within the Level A 

harassment zones, while unlikely, could 

occur. While Level A harassment takes 

are unlikely given the low likelihood of 

sea lions in the project area, the small 

Level A harassment isopleths (<46 m; 

Table 7), and the proposed mitigation 

measures, including the implementation 

of shutdown zones and the use of PSOs, 

we propose to authorize the POA’s 

request that a small number of Steller 

sea lions could be exposed to Level A 

harassment levels. Therefore, we 

propose that two Steller sea lions could 

be exposed to Level A harassment levels 

and 2 Steller sea lions could be exposed 

to Level B harassment levels. 

Harbor Seals 

No known harbor seal haulout or 

pupping sites occur in the vicinity of 

the POA; therefore, exposure of harbor 

seals to in-air noise is not considered in 

this application, and no take for in-air 

exposure is requested. Harbor seals are 

not known to reside in the project area, 

but they are seen regularly near the 


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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 project area during 

construction of the SFD. Any 

harassment of harbor seals during pile 

installation would involve a limited 

number of individuals that may 

potentially swim through the project 

area or linger near Ship Creek. 

Marine mammal monitoring data were 

used to examine hourly sighting rates 

for harbor seals in the project area. 

Sighting rates of harbor seals were 

highly variable and appeared to have 

increased during monitoring between 

2005 and 2020 (See Table 4–1 in POA’s 

application). It is unknown whether any 

potential increase was due to local 

population increases or habituation to 

ongoing construction activities. The 

highest monthly hourly sighting rate 

(rounded) observed during previous 

monitoring at the POA was used to 

quantify take of harbor seals for pile 

installation associated with the SFD. 

This occurred in 2020 during Phase 1 

PCT construction monitoring, when 

harbor seals were observed from May 

through September. A total of 340 

harbor seals were observed over 1,237.7 

hours of monitoring, at a rate of 0.3 

harbor seals per hour. The maximum 

monthly hourly sighting rate occurred 

in September and was 0.51 harbor seals 

per hour. Based on these data, the POA 

estimates that approximately 1 harbor 

seal may be observed near the project 

per hour of hammer use. During the 21 

hours of anticipated pile installation 

and removal, the POA estimates that up 

21 harbor seals will be exposed to inwater noise levels exceeding harassment 

thresholds for pile installation and 

removal during SFD construction. 

All efforts will be taken to shut down 

prior to a harbor seal entering the 100- 

m shutdown zone and prior to a harbor 

seal entering the Level A harassment 

zones. However, harbor seals often are 

curious of onshore activities, and 

previous monitoring suggests that this 

species may mill at the mouth of Ship 

Creek. It is important to note that the 

mouth of Ship Creek is about 700 m 

from the southern end of the SFD and 

is outside the Level A harassment zones 

for harbor seals during both 

unattenuated and attenuated vibratory 

and impact pile installation and 

removal (Table 7). While exposure is 

anticipated to be minimized because 

pile installation and removal will occur 

intermittently over the short 

construction period, the POA is 

requesting Level A harassment take for 

a small number of harbor seals, given 

the potential difficulty of detecting 

harbor seals and their consistent use of 

the area. Given that 30 harbor seals (8.6 

percent) of all harbor seals and 

unidentified pinnipeds were detected 

within 624 m, the largest Level A 

harassment zone for SFD, during PCT 

Phase 1 construction monitoring (61 

North Environmental, 2021), POA 

requests and NMFS proposes to 

authorize that two harbor seals (8.6 

percent of 21 exposures rounded up) 

could be exposed to Level A harassment 

levels and 19 harbor seals could be 

exposed to Level B harassment levels. 

Beluga Whales 

For CIBWs, we looked at several 

sources of information on marine 

mammal occurrence in upper Cook Inlet 

to determine how best to estimate the 

potential for exposure to pile driving 

noise from the SFD Project. In their 

application, the POA estimated Level B 

harassment take following methods 

outlined in the PCT final IHA (85 FR 

19294), which relies on monitoring data 

of CIBWs published in Kendall and 

Cornick (2015). For the SFD application, 

POA also considered monitoring data of 

CIBWs collected during Phase 1 of the 

PCT project (61 North Environmental, 

2021). These data sets (Kendall and 

Cornick, 2015, and 61 North 

Environmental, 2021) cover all months 

the POA may be conducting pile driving 

for the SFD and they are based on all 

animals observed during scientific 

monitoring within the proximity of the 

SFD regardless of distance. Hourly 

sighting rates for CIBWs for each 

calendar month were calculated using 

documented hours of observation and 

CIBW sightings from April through 

November for 2005, 2006, 2008 and 

2009 (Kendall and Cornick, 2015) and 

2020 (61 North Environmental, 2021) 

(Table 8). The highest calculated 

monthly hourly sighting rate of 0.94 

whales per hour was used to calculate 

potential CIBW exposures (21 hours of 

pile installation and removal multiplied 

by 0.94 whales/hour). Using this 

method, the POA estimated that 20 

CIBWs (rounded from 19.75) could be 

exposed to the Level B harassment level 

during pile installation and removal 

associated with the construction of the 

SFD. These calculations assume no 

mitigation and that all animals observed 

would enter a given Level B harassment 

zone during pile driving. 

TABLE 8—SUMMARY OF CIBWS SIGHTING DATA FROM APRIL–NOVEMBER 2005–2009 AND APRIL–NOVEMBER 2020 

Month Total hours Total groups Total whales Whales/hour 

April .................................................................................................................. 52.50 13 35 0.67 

May .................................................................................................................. 457.40 53 208 0.45 

June ................................................................................................................. 597.77 37 122 0.20 

July ................................................................................................................... 552.67 14 27 0.05 

August .............................................................................................................. 577.30 120 543 0.94 

September ....................................................................................................... 533.03 124 445 0.83 

October ............................................................................................................ 450.70 9 22 0.05 

November ........................................................................................................ 346.63 52 272 0.78 

Data compiled from Kendall and Cornick (2015) and (61 North Environmental, 2021). 

To more accurately estimate potential 

exposures than simply using the 

monthly sighting rate data, which does 

not account for any mitigation, POA 

followed methods described by NMFS 

for the PCT Final IHA (85 FR 19294), 

which looked at previous monitoring 

results at the POA in relation to 

authorized take numbers. Between 2008 

and 2012, NMFS authorized 34 CIBW 

takes per year to POA, with mitigation 

measures similar to the measures 

proposed here. The percent of the 

authorized takes documented during 

this time period ranged from 12 to 59 

percent with an average of 36 percent 

(Table 9). In 2020, NMFS authorized 55 

CIBW takes in Phase 1 of the PCT 

project, with mitigation and monitoring 

measures that are consistent with those 

proposed for the SFD and described 

below in the Proposed Mitigation 

section. The percent of the authorized 

takes that were documented was 47 

percent (26 out of 55 exposures; 61 

North Environmental, 2021; Table 9). 

Given that there was extensive 

monitoring occurring across all IHAs 

(with effort intensified in 2020), we 


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believe there is little potential that 

animals were taken but not observed. 

TABLE 9—AUTHORIZED AND REPORTED CIBW TAKES DURING POA ACTIVITIES FROM 2009–2012 AND 2020 

ITA effective dates Reported 

takes 

Authorized 

takes 

Percent of 

authorized 

takes 

15 July 2008–14 July 2009 ......................................................................................................... 12 34 35 

15 July 2009–14 July 2010 ......................................................................................................... 20 34 59 

15 July 2010–14 July 2011 ......................................................................................................... 13 34 38 

15 July 2011–14 July 2012 ......................................................................................................... 4 34 12 

1 April 2020–31 March 2021 ....................................................................................................... 26 55 47 

As described in the POA’s application 

and in more detail in the Proposed 

Mitigation section, mitigation measures 

have been designed to reduce Level B 

harassment take as well avoid Level A 

harassment take. We recognize that in 

certain situations, pile driving may not 

be able to be shut down prior to whales 

entering the Level B harassment zone 

due to safety concerns. During previous 

monitoring, sometimes CIBWs were 

initially sighted outside of the 

harassment zone and shutdown was 

called, but the CIBWs swam into the 

harassment zone before activities could 

be halted, and exposure within the 

harassment zone occurred. For example, 

on September 14, 2009, a construction 

observer sighted a CIBW just outside the 

harassment zone, moving quickly 

towards the 1,300 m Level B harassment 

zone during vibratory pile driving. The 

animal entered the harassment zone 

before construction activity could be 

shut down (ICRC, 2010). On other 

occasions, CIBWs were initially 

observed when they surfaced within the 

harassment zone. For example, on 

November 4, 2009, 15 CIBWs were 

initially sighted approximately 950 m 

north of the project site near the shore, 

and then they surfaced in the Level B 

harassment zone during vibratory pile 

driving (ICRC, 2010). Construction 

activities were immediately shut down, 

but the 15 CIBWs were nevertheless 

exposed within the Level B harassment 

zone. During Phase 1 of the PCT project 

all of the recorded takes (n = 26) were 

instances where the whales were first 

sighted within the Level B harassment 

zone, prompting shutdown procedures. 

Most of these exposures (21 of 26) 

occurred when the CIBWs first appeared 

near the northern station, just south of 

Cairn Point (61 North Environmental, 

2021). For example, on November 21, 

2020 one CIBW was sighted in front of 

the north PSO station, located just south 

of Cairn Point, traveling south during 

vibratory removal of an attenuated 36- 

inch pile and a shutdown was called 

immediately (61 North Environmental, 

2021). In 2020, the northern station did 

not have visibility of the near shoreline 

north of Cairn Point. As a result, CIBWs 

traveling south during ebb tides around 

Cairn Point were often inside of the 

Level B harassment zone upon first 

sighting (61 North Environmental, 

2021). As described below in the 

Proposed Monitoring and Reporting 

section, mitigation and monitoring 

approaches for the SFD project are 

modeled after the stipulations outlined 

in the Final IHAs for Phase 1 and Phase 

2 PCT construction (85 FR 19294), but 

one of the PSO stations will be moved 

to enhance visibility to the north, 

especially near Cairn point. Therefore, 

we believe the ability to detect whales 

and shut down prior to them entering 

the Level B harassment zones will be 

better or consistent with previous years. 

To account for these mitigation 

measures, the POA then applied the 

highest percentage of previous takes (59 

percent) to ensure potential impacts to 

CIBWs are adequately evaluated. After 

applying this adjustment to account for 

potential exposures of CIBWs that 

would be avoided by shutting down, the 

POA estimated that 12 CIBWs (20 

whales * 0.59 = 11.80 whales; 12 

rounded up) may be exposed to Level B 

harassment during pile installation and 

removal. The POA and NMFS are 

concerned, however, that this approach 

does not accurately reflect the reality 

that CIBWs can travel in large groups. 

Large groups of CIBWs have been seen 

swimming through the POA vicinity 

during POA monitoring efforts. For 

example, during Phase 1 of the PCT, the 

mean group size was 4.34 whales; 

however, 52 percent of observations 

were of groups greater than the mean 

group size, with 5 percent of those 119 

groups being larger than 12 individuals, 

the number of exposures proposed by 

POA (61 North Environmental, 2021). 

To ensure that a large group of CIBWs 

would not result in the POA using the 

majority or all of their take in one or two 

sightings, POA buffered the exposure 

estimate detailed in the preceding by 

adding the estimated size of a notional 

large group of CIBWs. The 95th 

percentile is commonly used in 

statistics to evaluate risk. Therefore, to 

determine the most appropriate size of 

a large group, the POA calculated the 95 

percentile group size of CIBWs observed 

during Kendall and Cornick (2015) and 

2020 Phase 1 PCT construction 

monitoring (61 North Environmental, 

2021); the same data used above to 

derive hourly sighting rates (Table 8 and 

Figure 3). In this case, the 95th 

percentile provides a conservative value 

that reduces the risk to the POA of 

taking a large group of CIBWs and 

exceeding authorized take levels. The 

95th percentile of group size for the 

Kendall and Cornick (2015) and the PCT 

Phase 1 monitoring data (61 North 

Environmental, 2021) is 12.0. This 

means that, of the 422 documented 

CIBW groups in these data sets, 95 

percent consisted of fewer than 12.0 

whales; 5 percent of the groups 

consisted of more than 12.0. 

Considering large group size, the POA 

requests and we propose to authorize 24 

takes (accounting for the 12 takes 

calculated following the methods 

outlined for the PCT project that 

accounts for mitigation plus a group size 

of 12) of CIBWs incidental to pile 

driving for the SFD. Incorporation of 

large groups into the CIBW exposure 

estimate is intended to reduce risk to 

the POA of the unintentional take of a 

larger number of belugas than would be 

authorized by using the proposed 

methods alone and thus improve our 

estimate of exposure. No Level A 

harassment is expected or proposed 

given the small Level A harassment 

zones for CIBWs (Table 7) and the 

additional mitigation measures 

described in the Proposed Mitigation 

section below specific to CIBWs, 

including the measure that pile driving 

activities must shut down when any 

CIBW enters the relevant Level B 

harassment zone. 


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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 10. 

TABLE 10—PROPOSED AMOUNT OF TAKE, BY STOCK AND HARASSMENT TYPE

Species Stock 

Proposed authorized take Percent of 

stock Level A Level B 

Humpback whale ............................................ Western N Pacific .......................................... 0 2 0.19 

Beluga whale .................................................. Cook Inlet ....................................................... 0 24 8.60 

Killer whale ...................................................... Transient/Alaska Resident ............................. 0 6 1.02/0.26 

Harbor porpoise .............................................. Gulf of Alaska ................................................. 0 12 0.04 

Steller sea lion ................................................ Western .......................................................... 2 2 <0.01 

Harbor seal ..................................................... Cook Inlet/Shelikof ......................................... 2 19 0.07 

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, we carefully consider two 

primary factors: 

(1) The manner in which, and the 

degree to which, the successful 

implementation of the measure(s) is 

expected to reduce impacts to marine 

mammals, marine mammal species or 

stocks, and their habitat. This considers 

the nature of the potential adverse 

impact being mitigated (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, 

impact on operations, and, in the case 

of a military readiness activity, 

personnel safety, practicality of 

implementation, and impact on the 

effectiveness of the military readiness 

activity. 

The POA presented mitigation 

measures in Section 11 of their 


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(/) 

C: 

0 

I 

Cl) 

90 

~ 60 .. 

0 

0 

0 

0 

I 

I 

I 

I i --

' I 

20 40 

Group Size 

Figure 3. CIBW sighting data from Kendall and Cornick (2015) and Phase 1 of the 

PCT (61 North Environmental, 2021). The dashed vertical line represents the 95th 

percentile of group size (i.e., 12 CIBWs) 
Federal Register / Vol. 86, No. 113 / Tuesday, June 15, 2021 / Notices 31895 

application that were modeled after the 

stipulations outlined in the Final IHAs 

for Phase 1 and Phase 2 PCT 

construction (85 FR 19294), which were 

successful in minimizing the total 

number and duration of Level B 

harassment exposures for endangered 

CIBWs during Phase 1 PCT Construction 

(61 North Environmental, 2021). These 

measures both reduce noise into the 

aquatic environment and reduce the 

potential for CIBWs to be adversely 

impacted from any unavoidable noise 

exposure. 

A key mitigation measure NMFS 

considered for this project is reducing 

noise levels propagating into the 

environment. The POA will deploy an 

unconfined bubble curtain system 

during installation and removal of 

plumb (vertical) 24- and 36-inch piles 

with a vibratory or impact hammer. An 

unconfined bubble curtain is composed 

of an air compressor(s), supply lines to 

deliver the air, distribution manifolds or 

headers, perforated aeration pipe, and a 

frame. The frame facilitates transport 

and placement of the system, keeps the 

aeration pipes stable, and provides 

ballast to counteract the buoyancy of the 

aeration pipes in operation. The air is 

released through a series of vertically 

distributed bubble rings that create a 

cloud of bubbles that act to impede and 

scatter sound, lowering the sound 

velocity. A compressor provides a 

continuous supply of compressed air, 

which is distributed among the layered 

bubble rings. Air is released from small 

holes in the bubble rings to create a 

curtain of air bubbles surrounding the 

pile. The curtain of air bubbles floating 

to the surface inhibits the transmission 

of pile installation sounds into the 

surrounding water column. The final 

design of the bubble curtain will be 

determined by the Construction 

Contractor based on factors such as 

water depth, current velocities, and pile 

sizes. However, the proposed IHA 

requires the bubble curtain be operated 

in a manner consistent with the 

following performance standards: 

• The aeration pipe system will 

consist of multiple layers of perforated 

pipe rings, stacked vertically in 

accordance with the following depths: 

Two layers for water depths <5 m; four 

layers for water depths 5 m to <10 m; 

seven layers for water depths 10 m to 

<15 m; ten layers for water depths 15 m 

to <20 m; and thirteen layers for water 

depths 20 m to <25 m; 

• The pipes in all layers will be 

arranged in a geometric pattern that will 

allow for the pile being driven to be 

completely enclosed by bubbles for the 

full depth of the water column and with 

a radial dimension such that the rings 

are no more than 0.5 m from the outside 

surface of the pile; 

• The lowest layer of perforated 

aeration pipe will be designed to ensure 

contact with the substrate without 

burial and will accommodate sloped 

conditions; 

• Air holes will be 1.6 millimeters 

(1⁄16 inch) in diameter and will be 

spaced approximately 20 millimeters 

(3⁄4 inch) apart. Air holes with this size 

and spacing will be placed in four 

adjacent rows along the pipe to provide 

uniform bubble flux; 

• The system will provide a bubble 

flux of 3 cubic meters (m3) per minute 

per linear meter of pipe in each layer 

(32.91 cubic feet (ft3) per minute per 

linear foot of pipe in each layer). The 

total volume of air per layer is the 

product of the bubble flux and the 

circumference of the ring using the 

formula: Vt = 3.0 m3/min/m * 

Circumference of the aeration ring in 

meters or Vt = 32.91 ft3/min/ft * 

Circumference of the aeration ring in 

feet; and 

• Meters must be provided as follows: 

Æ Pressure meters must be installed at 

all inlets to aeration pipelines and at 

points of lowest pressure in each branch 

of the aeration pipeline; 

Æ Flow meters must be installed in 

the main line at each compressor and at 

each branch of the aeration pipelines at 

each inlet. In applications where the 

feed line from the compressor is 

continuous from the compressor to the 

aeration pipe inlet, the flow meter at the 

compressor can be eliminated; and 

Æ Flow meters must be installed 

according to the manufacturer’s 

recommendation based on either 

laminar flow or non-laminar flow. 

The bubble curtain will be used 

during installation and removal of all 

plumb piles when water depth is great 

enough (approximately 3 m) to deploy 

the bubble curtain. A bubble curtain 

will not be used with the two battered 

piles due to the angle of installation. It 

is important to note that a small number 

of piles could be installed or removed 

when the pile location is de-watered (no 

water present) or when the water is too 

shallow (≤3 m) to deploy the bubble 

curtain. The tides at the POA have a 

mean range of about 8.0 m (26 ft) 

(NOAA, 2015), and low water levels 

will prevent proper deployment and 

function of the bubble curtain system. 

Piles that are driven at a location that is 

de-watered will not use a bubble 

curtain, and marine mammal 

harassment zones will not be monitored. 

When piles are installed or removed in 

water without a bubble curtain because 

the pile orientation is battered, or if 

water is too shallow (≤3 m) to deploy 

the bubble curtain, the unattenuated 

Level A and Level B harassment zones 

for that hammer type and pile size will 

be implemented. 

In addition to noise attenuation 

devices, POA and NMFS considered 

practicable work restrictions. Given the 

extensive Level B harassment zone 

generated from the installation of the 

two unattenuated battered piles, 

vibratory driving these large piles 

during peak CIBW season poses an 

amount of risk and uncertainty to the 

degree that it should be minimized. This 

August and September peak is 

confirmed through acoustic monitoring 

(Castellote et al., 2020) and Phase 1 PCT 

construction monitoring (61 North 

Environmental, 2021). Castellote et al. 

(2020) for example indicate CIBWs 

appeared concentrated in the upper 

inlet year-round, but particularly 

feeding in river mouths from AprilDecember, shifting their geographical 

foraging preferences from the Susitna 

River region towards Knik Arm in midAugust, and dispersing towards the mid 

inlet throughout the winter. Further, 

hourly sighting rates calculated from 

monitoring data from Kendall and 

Cornick (2015) and Phase 1 of the PCT 

(61 North Environmental, 2021) were 

highest in August and September (0.94 

and 0.83, respectively; Table 8). 

Therefore, vibratory driving 

unattenuated battered piles (which 

have, by far, the largest Level B 

harassment zones) will not occur during 

August or September. Further, to 

minimize the potential for overlapping 

sound fields from multiple stressors, the 

POA will not simultaneously operate 

two vibratory hammers for either pile 

installation or removal. This measure is 

designed to reduce simultaneous inwater noise exposure. Because impact 

hammers will not likely be dropping at 

the same time, and to expedite 

construction of the project to minimize 

pile driving during peak CIBW 

abundance periods, NMFS is not 

proposing to restrict the operation of 

two impact hammers at the same time. 

Given the small size of the project and 

the plan to primarily drive hammers 

with a vibratory hammer, the POA has 

indicated that it is highly unlikely that 

an impact hammer and vibratory 

hammer or two impact hammers would 

operate simultaneously during the SFD 

project. 

Additional mitigation measures 

include the following, modeled after the 

stipulations outlined in the Final IHAs 

for Phase 1 and Phase 2 PCT 

construction (85 FR 19294): 

For in-water construction involving 

heavy machinery activities other than 

pile driving (e.g., use of barge-mounted 


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excavators), the POA will cease 

operations and reduce vessel speed to 

the minimum level required to maintain 

steerage and safe working conditions if 

a marine mammal approaches within 10 

m of the equipment or vessel. 

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 thirty-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 thirty minutes or 

longer. Soft starts will not be used for 

vibratory pile installation and removal. 

PSOs shall begin observing for marine 

mammals 30 minutes before ‘‘soft start’’ 

or in-water pile installation or removal 

begins. 

The POA will conduct briefings for 

construction supervisors and crews, the 

monitoring team, and POA staff prior to 

the start of all pile installation and 

removal, and when new personnel join 

the work in order to explain 

responsibilities, communication 

procedures, the marine mammal 

monitoring protocol, and operational 

procedures. 

The POA will employ PSOs per the 

Marine Mammal Monitoring Plan (see 

Appendix A in the POA’s application). 

Marine mammal monitoring will take 

place from 30 minutes prior to initiation 

of pile installation and removal through 

30 minutes post-completion of pile 

installation and removal. The Level B 

harassment zone must be fully visible 

for 30 minutes before the zone can be 

considered clear. Pile driving will 

commence when observers have 

declared the shutdown zone clear of 

marine mammals or the mitigation 

measures developed specifically for 

CIBWs (below) are satisfied. In the event 

of a delay or shutdown of activity, 

marine mammal behavior will be 

monitored and documented until the 

marine mammals leave the shutdown 

zone of their own volition, at which 

point pile installation or removal will 

begin. Further, NMFS requires that if 

pile driving has ceased for more than 30 

minutes within a day and monitoring is 

not occurring during this break, another 

30-minute pre-pile driving observation 

period is required before pile driving 

may commence. 

If a marine mammal is entering or is 

observed within an established Level A 

harassment zone or shutdown zone, pile 

installation and removal will be halted 

or delayed. Pile driving will not 

commence or resume until either the 

animal has voluntarily left and been 

visually confirmed 100 m beyond the 

shutdown zone and on a path away 

from such zone, or 15 minutes (nonCIBWs) or 30 minutes (CIBWs) have 

passed without subsequent detections. 

If a species for which authorization 

has not been granted, or a species for 

which authorization has been granted 

but the authorized takes are met, is 

observed approaching or within the 

Level B harassment zone, pile 

installation and removal will shut down 

immediately. Pile driving will not 

resume until the animal has been 

confirmed to have left the area or the 30 

minute observation period has elapsed. 

In addition to these measures which 

greatly reduce the potential for 

harassment of all marine mammals and 

establish shutdown zones that 

realistically reflect non-CIBW whale 

detectability, the following additional 

mitigation measures have been 

proposed which would ensure valuable 

protection and conservation of CIBWs: 

Prior to the onset of pile driving, 

should a CIBW be observed approaching 

the mouth of Knik Arm, pile driving 

will be delayed. An in-bound preclearance line extends from Point 

Woronzof to approximately 2.5 kms 

west of Point McKenzie. Pile driving 

may commence once the whale(s) 

moves at least 100 m past the Level B 

harassment zone or pre-clearance zone 

(whichever is larger) and on a path away 

from the zone. A similar pre-pile driving 

clearance zone will be established to the 

north of the POA (from Cairn Point to 

the opposite bank), allowing whales to 

leave Knik Arm undisturbed. Similar to 

the in-bound whale clearance zone, pile 

driving may not commence until a 

whale(s) moves at least 100 m past the 

Level B harassment zone or preclearance zone (whichever is larger) and 

on a path away from the zone. If nonCIBW whale species are observed 

within or likely to enter the Level B 

harassment zone prior to pile driving, 

the POA may commence pile driving 

but only if those animals are outside the 

100 m shutdown zone and Level B 

harassment takes have not been 

exceeded. 

If pile installation or removal has 

commenced, and a CIBW(s) is observed 

within or likely to enter the Level B 

harassment zone, pile installation or 

removal will shut down and not recommence 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. 

There may be situations where it is 

not possible to monitor the entire Level 

B harassment zone (e.g., during 

vibratory hammering of two 

unattenuated battered piles). In these 

cases, the pre-clearance zone remains 

applicable. 

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 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. 

Based on our evaluation of the 

applicant’s proposed measures, NMFS 

has preliminarily determined that the 

proposed mitigation measures provide 

the means 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 in the proposed action area. 

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 


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action; 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 will implement a marine 

mammal monitoring and mitigation 

strategy intended to avoid and minimize 

impacts to marine mammals (see 

Appendix A in the POA’s application). 

The marine mammal monitoring and 

mitigation program that is planned for 

SFD construction will be modeled after 

the stipulations outlined in the Final 

IHAs for Phase 1 and Phase 2 PCT 

construction (85 FR 19294). The POA 

will collect electronic data on marine 

mammal sightings and any behavioral 

responses to in-water pile installation or 

removal for species observed during pile 

installation and removal associated with 

the SFD Project. Four PSO teams will 

work concurrently to provide full 

coverage for marine mammal 

monitoring in rotating shifts during inwater pile installation and removal. All 

PSOs will be trained in marine mammal 

identification and behaviors. NMFS will 

review submitted PSO CVs and indicate 

approval as warranted. 

All PSOs will also undergo projectspecific training, which will include 

training in monitoring, data collection, 

theodolite operation, and mitigation 

procedures specific to the SFD Project. 

This training will also include sitespecific health and safety procedures, 

communication protocols, and 

supplemental training in marine 

mammal identification and data 

collection specific to the SFD Project. 

Training will include hands-on use of 

required field equipment to ensure that 

all equipment is working and PSOs 

know how to use the equipment. 

The POA proposes that eleven PSOs 

will be distributed at four stations: 

Anchorage Downtown Viewpoint near 

Point Woronzof, the Anchorage Public 

Boat Dock at Ship Creek, the SFD 

Project site, and the north end of POA 

property. These locations were chosen 

to maximize CIBW detection outside of 

Knik Arm and the mouth of Knik Arm. 

Specifically, PSOs at Port Woronzof will 

have unencumbered views of the 

entrance to Knik Arm and can provide 

information on CIBW group dynamics 

(e.g., group size, demographics, etc.) and 

behavior of animals approaching Knik 

Arm in the absence of and during pile 

driving. During the time since the POA 

submitted their final application, 

observers for the 2020 PCT Phase 1 

project have recommended, and NMFS 

has included in the proposed IHA, that 

the Ship Creek station be moved about 

40 m to the end of the promontory to 

enhance visibility to the north, 

especially near Cairn point. The POA 

also considered moving a station from 

the POA property to Port MacKenzie for 

an improved view of CIBWs moving 

from north to south within Knik Arm. 

However, Port MacKenzie is not an 

available option due to logistical 

reasons; therefore, the northern station 

will remain located on POA property. 

Each of the PSO stations will be 

outfitted with a cargo container with an 

observation platform constructed on 

top. This additional elevation provides 

better viewing conditions for seeing 

distant marine mammals than from 

ground level and provides the PSOs 

with protection from weather. At least 

two PSOs will be on watch at any given 

time at each station; one PSO will be 

observing, one PSO will be recording 

data (and observing when there are no 

data to record). The station at the SFD 

site will have at least two PSOs. The 

northern and southern observations 

stations will have PSOs who will work 

in three- to four-person teams. Teams of 

three will include one PSO who will be 

observing, one PSO who will be 

recording data (and observing when 

there are no data to record), and one 

PSO who will be resting. When 

available, a fourth PSO will assist with 

scanning, increasing scan intensity and 

the likelihood of detecting marine 

mammals. PSOs will work on a 60 

minute rotation cycle and may observe 

for no more than 4 hours at time and no 

more than 12 hours per day. In addition, 

if POA is conducting non-PCT-related 

in-water work that includes PSOs, the 

PCT 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. 

Trained PSOs will have no other 

construction-related tasks or 

responsibilities while conducting 

monitoring for marine mammals. 

Observations will be carried out using 

combinations of equipment that include 

7 by 50 binoculars, 20x/40x tripod 

mounted binoculars, 25 by 150 ‘‘big 

eye’’ tripod mounted binoculars (North 

End, Ship Creek, and Woronzof), and 

theodolites. PSOs will be responsible for 

monitoring the 100 m shutdown zone, 

the Level A harassment zones, the Level 

B harassment zones, and the preclearance zones, as well as effectively 

documenting Level A and Level B 

harassment take. They will also (1) 

report on the frequency at which marine 

mammals are present in the project area, 

(2) report on behavior and group 

composition near the POA, (3) record all 

construction activities, and (4) report on 

observed reactions (changes in behavior 

or movement) of marine mammals 

during each sighting. Observers will 

monitor for marine mammals during all 

in-water pile installation and removal 

associated with the SFD Project. Once 

pile installation and removal are 

completed for the day, marine mammal 

observations will continue for 30 

minutes. Observers will work in 

collaboration with the POA to 

immediately communicate the presence 

of marine mammals prior to or during 

pile installation or removal. 

A draft report, including all electronic 

data collected and summarized from all 

monitoring locations, must be submitted 

to NMFS’ MMPA program within 90 

days of the completion of monitoring 

efforts. The report must include: Dates 

and times (begin and end) of all marine 

mammal monitoring; a description of 

daily construction activities, weather 

parameters and water conditions during 

each monitoring period; number of 

marine mammals observed, by species, 

distances and bearings of each marine 

mammal observed to the pile being 

driven or removed, age and sex class, if 

possible; number of individuals of each 

species (differentiated by month as 

appropriate) detected within the Level 

A harassment zones, the Level B 

harassment zones, and the shutdown 

zones, and estimates of number of 

marine mammals taken, by species (a 

correction factor may be applied); 

description of mitigation implemented, 

and description of attempts to 

distinguish between the number of 

individual animals taken and the 

number of incidences of take. A final 

marine mammal monitoring report will 

be prepared and submitted to NMFS 

within 30 days following receipt of 

comments on the draft report from 

NMFS. 

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 


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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 responses (e.g., intensity, 

duration), the context of any responses 

(e.g., critical reproductive time or 

location, migration), 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 environmental 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, the discussion of 

our analyses applies to all the species 

listed in Table 10 for which we 

authorized take, other than CIBWs, as 

the anticipated effects the POAs 

activities on marine mammals 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 CIBWs, or impacts on 

habitat; therefore, we provide a 

supplemental analysis for CIBWs, 

independent of the other species for 

which we authorize take. 

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 following factors 

support negligible impact 

determinations for the affected stocks of 

humpback whales, killer whales, harbor 

porpoise, harbor seals, and Steller sea 

lions. The potential effects of the 

proposed actions on these species are 

discussed above. Some of these factors 

also apply to CIBWs; however, a more 

detailed analysis for CIBWs is provided 

below. 

• No takes by mortality or serious 

injury are anticipated or authorized; 

• The number of total takes (by Level 

A and Level B harassment) are less than 

2 percent of the best available 

abundance estimates for all stocks; 

• 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, biologically important areas 

(BIA), or other habitats critical to 

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

• Take would occur over a short 

timeframe (i.e., up to 21 total hours 

spread over nine to 24 non-consecutive 

days), and would be limited to the short 

duration a marine mammal would likely 

be present within a Level B harassment 

zone during pile driving. This short 

timeframe minimizes the probability of 

multiple exposures on individuals, and 

any repeated exposures that do occur 

are not expected to occur on sequential 

days, decreasing the likelihood of 

physiological impacts caused by chronic 

stress or sustained energetic impacts 

that might affect survival or 

reproductive success; 

• Any impacts to marine mammal 

habitat from pile driving (including to 

prey sources as well as acoustic habitat, 

e.g., from masking) are expected to be 

temporary and minimal; and 

• Take would only occur within 

upper Cook Inlet—a limited, confined 

area of any given stock’s home range. 

For CIBWs, we further discuss our 

negligible impact findings in the context 

of potential impacts to this endangered 

stock. As described in the Recovery Plan 

for the CIBW (NMFS, 2016a), 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 30 feet mean 

lower low water (9.1 m) and within 5 mi 

(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 in-water noise below levels 

resulting in the abandonment of critical 

habitat areas by CIBWs. The SFD would 

not impact essential features 1–3 listed 

above. All construction would be done 

in a manner implementing best 

management practices to preserve water 

quality, and no work would occur 

around creek mouths or river systems 

leading to prey abundance reductions. 

In addition, no physical structures 

would restrict passage; however, 

impacts to the acoustic habitat are of 

concern. Previous marine mammal 

monitoring data at the POA demonstrate 

CIBWs indeed pass by the POA during 

pile driving (e.g., 61 North 

Environmental, 2021). As described 

above, there was no significant 

difference in CIBW sighting rate with 

and in the absence of pile driving 

(Kendall and Cornick, 2015). However, 

CIBWs do swim faster and in tighter 

formation in the presence of pile driving 

(Kendall and Cornick, 2015). 

Previously there has been 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 based on 

the proposed project and mitigation 

measures—thus, impacting essential 

feature number 5 above (85 FR 19294). 

Although the data previously presented 

demonstrate whales are not abandoning 

the area (i.e., no significant difference in 

sighting rate with and without pile 

driving), results of a recent 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 (2015, 

section IX.D—CI Beluga Hearing, 

Vocalization, and Noise Supplement) 

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 http://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 expert 

elicitation, the experts provided a set of 


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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 

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 be comprised 

predominantly of temporary 

modifications in the behavior of 

individual CIBWs (e.g., faster swim 

speeds, more cohesive group structure, 

avoidance, and increased foraging). 

Also, NMFS anticipates and has 

proposed to authorized 24 instances of 

takes, with the instances representing 

disturbance events within a day—this 

means that either 24 different individual 

beluga whales are disturbed on no more 

than one day each, or some lesser 

number of individuals may be disturbed 

on more than one day, but with the 

product of individuals and days not 

exceeding 24. Given the overall 

anticipated take, it is very unlikely that 

any one beluga would be disturbed on 

more than a few days. Further, the 

mitigation measures NMFS has 

prescribed for the SFD project are 

designed to avoid the potential that any 

animal would lose the ability to forage 

for one or more tidal cycles. While Level 

B harassment (behavioral disturbance) is 

authorized, our mitigation measures 

would 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 first considered proposing 

the POA shutdown based on more 

vulnerable life stages (e.g., calf 

presence) but ultimately determined all 

CIBWs warranted 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. 

Monitoring data from the POA suggest 

pile driving does not discourage CIBWs 

from entering Knik Arm and travelling 

to critical foraging grounds such as 

those around Eagle Bay. As previously 

described, sighting rates were not 

different in the presence or absence of 

pile driving (Kendall and Cornick, 

2015). In addition, CIBWs continued to 

use Knik Arm in 2020 during the 

duration of the PCT Phase 1 

construction project (61 North 

Environmental, 2021). 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 responding to pile 

driving noise, but not through 

abandonment of critical habitat, 

including primary foraging areas north 

of the port. Instead, they travel faster 

past the POA, more quietly, and in 

tighter groups (which may be linked to 

the decreased communication patterns). 

During PCT Phase 1 construction 

monitoring, no definitive behavioral 

reactions to the in-water activity or 

avoidance behaviors were documented 

in CIBW. Little variability was evident 

in CIBW behaviors recorded by PSOs 

from month to month, or between 

sightings that coincided with in-water 

pile installation or removal and those 

that did not (61 North Environmental, 

2021). Of the 245 CIBWs groups sighted 

during PCT Phase 1 construction 

monitoring, seven groups were observed 

during or within minutes of in-water 

impact pile installation and 37 groups 

were observed during or within minutes 

of vibratory pile installation or removal 

(61 North Environmental, 2021). During 

impact installation, three of these 

groups of CIBWs showed no reaction, 

three showed a potential reaction, and 

one group continued moving towards 

impact pile installation. Of the 37 

vibratory events monitored, nine groups 

of CIBWs displayed a potential reaction, 

16 displayed no reaction, and 12 

continued a trajectory towards the PCT 

(61N Environmental 2021). In general, 

CIBWs were more likely to display no 

reaction or to continue to move towards 

the PCT during pile installation and 

removal. In the situations during which 

CIBWs showed a possible reaction 

(three groups during impact driving and 

nine groups during vibratory driving), 

CIBWs were observed either moving 

away immediately after the pile driving 

activities started or observed increasing 

their rate of travel. This traveling 

behavior past the POA has also been 

verified by acoustic monitoring. 

Castellote et al. (2020) found low 

echolocation detection rates in lower 

Knik Arm indicating CIBWs moved 

through that area relatively quickly 

when entering or exiting the Arm. We 

anticipate that disturbance to CIBWs 

would manifest in the same manner 

when they are exposed to noise during 

the SFD project: Whales 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, 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), 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 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 18th and 

remained in Eagle Bay until September 

12th (Ferrero et al., 2000). Further, a 

recent detailed re-analysis 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 

would avoid repetitive exposures from 

pile driving noise. 


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POA proposed and NMFS has 

prescribed mitigation measures to 

minimize exposure to CIBWs, 

specifically, shutting down pile driving 

if CIBWs are observed approaching the 

mouth of Knik Arm, shutting down pile 

driving should a CIBW approach or 

enter the Level B harassment zone, 

stationing PSOs at Point Woronzof and 

Ship Creek, and not vibratory pile 

driving unattenuated battered piles 

during August or September (peak 

CIBW season). 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 PSOs at Point Woronzof 

allows for detection of CIBWs and 

behavioral observations prior to CIBWs 

entering Knik Arm. Although NMFS 

does not anticipate CIBWs would 

abandon entering Knik Arm in the 

presence of pile driving with the 

required mitigation measures, these 

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 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 

authorized; 

• Area of exposure would be limited 

to travel corridors. Data demonstrates 

Level B harassment manifests as 

increased swim speeds past the POA 

and tight group formations and not 

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. 

We also considered our negligible 

impact analysis with respect to NMFS’ 

technical report released in January 

2020 regarding the abundance and 

status of CIBWs (Sheldon and Wade, 

2019). As described in the marine 

mammal section, new analysis indicates 

the CIBW stock is smaller and declining 

faster than previously recognized. While 

this is concerning, NMFS continues to 

believe the taking authorized (allowed 

for in the cases where shutdowns 

cannot occur in time to avoid Level B 

harassment take) will not impact the 

reproduction or survival of any 

individuals, much less the stock, and 

will thereby have a negligible impact. 

The monitoring measures (four stations 

each equipped with two PSOs 

simultaneously on watch at each 

station) are extensive, such that we find 

it unlikely whales would go undetected. 

The mitigation measures reduce noise 

entering the water column (a benefit for 

all marine mammals) through the use of 

an unconfined bubble curtain. Further, 

the exposure risk to CIBWs is greatly 

minimized through the incorporation of 

in-bound and out-bound whale pre-pile 

driving clearance zones. Finally, should 

pile driving be occurring at the same 

time a whale is detected, pile driving 

would shut down prior to its entering 

the Level B harassment zone. All these 

measures, as well as other required 

measures such as soft-starts, greatly 

reduce the risk of animals not accessing 

important foraging areas north of the 

POA, which could result in impacts to 

individual fitness or annual rates of 

recruitment or survival. For these 

reasons, the new status of CIBWs does 

not ultimately change our findings with 

respect to the specified activities. 

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 

proposed monitoring and mitigation 

measures, NMFS preliminarily finds 

that the total marine mammal take from 

the proposed activity will have a 

negligible impact on all affected marine 

mammal species or stocks. 

Small Numbers 

As noted above, only small numbers 

of incidental take 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, the amount of 

taking is less than one-third of the best 

available population abundance 

estimate (in fact it is less than 9 percent 

for all stocks considered here; Table 10). 

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 will 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 a 

specified activity that is likely to reduce 

the availability of the species to a level 

insufficient for a harvest to meet 

subsistence needs by either causing the 

marine mammals to abandon or avoid 

hunting areas, directly displacing 

subsistence users, or placing physical 

barriers between the marine mammals 

and the subsistence hunters. An 

‘‘unmitigable adverse impact’’ can also 

results from a specified activity that 

cannot be sufficiently mitigated by other 

measures to increase the availability of 

marine mammals to allow subsistence 

needs to be met. 

No subsistence use of CIBWs occurs 

and 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. In 2013 and 2014, the Alaska 

Department of Fish and Game 

conducted studies to document the 

harvest and use of wild resources by 

residents of four tribal communities in 

Cook Inlet: Tyonek, Nanwalek, Port 

Graham, and Seldovia (Jones and 

Kostick, 2016). Tyonek is the 

community in closest proximity to Knik 

Arm while the other communities are 

located lower in Cook Inlet. The only 

marine mammal species taken by the 

Tyonek community was harbor seals 

(from the McArthur River Flats north to 

the Beluga River (Jones et al., 2015) 

south of Knik Arm) while communities 

lower in the inlet relied on harbor seals, 

Steller sea lions and sea otters (we note 

the sea otter is under the jurisdiction of 

the USFWS; therefore, it is not a part of 

our analysis). 


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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) 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. 

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 consults internally 

whenever we propose to authorize take 

for endangered or threatened species, in 

this case with the Alaska Region 

Protected Resources Division Office. 

NMFS is proposing to authorize take 

of CIBWs, humpback whales from the 

Mexico DPS stock or Western North 

Pacific Stock, and Steller sea lions from 

the western DPS, which are listed under 

the ESA. The Permit and Conservation 

Division has requested initiation of 

Section 7 consultation with the Alaska 

Region Protected Resources Division 

Office for 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 pile 

driving associated with the relocation of 

SFD in Knik Arm, Alaska, 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/permit/ 

incidental-take-authorizations-undermarine-mammal-protection-act. 

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 pile driving 

associated with the relocation of the 

SFD in Knik Arm, Alaska. We also 

request at this time 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, one-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, or nearly 

identical, activities as described in the 

Description of Proposed Activities 

section of this notice is planned or (2) 

the activities as described in the 

Description of Proposed Activities 

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 one 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); and 

(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: June 10, 2021. 

Catherine Marzin, 

Acting Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2021–12551 Filed 6–14–21; 8:45 am] 

BILLING CODE 3510–22–P 


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