1066 Federal Register / Vol. 89, No. 6 / Tuesday, January 9, 2024 / Notices 

Registered participants joining inperson will be emailed instructions on 

accessing the designated meeting space. 

SUPPLEMENTARY INFORMATION: 

Background: The Secretary of 

Commerce established the REEEAC 

pursuant to discretionary authority and 

in accordance with the Federal 

Advisory Committee Act, as amended (5 

U.S.C. 1001 et seq.), on July 14, 2010. 

The REEEAC was re-chartered most 

recently on May 27, 2022. The REEEAC 

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with advice from the private sector on 

the development and administration of 

programs and policies to expand the 

export competitiveness of U.S. 

renewable energy and energy efficiency 

products and services. More information 

about the REEEAC, including the list of 

appointed members for this charter, is 

published online at http://trade.gov/ 

reeeac. 

On January 25, 2024, the REEEAC will 

hold the sixth meeting of its current 

charter term. The Committee will 

deliberate on approval of several 

recommendations. The REEEAC will 

also be briefed on recent ITA 

accomplishments of relevance to the 

U.S. renewable energy and energy 

efficiency industries, including the 

delegation to COP28, the launch of the 

Clean Tech Top Export Markets website, 

and the establishment of the Supply 

Chain Center. The agenda will be made 

available by January 22, 2024 upon 

request to Cora Dickson, and the most 

current version of the agenda will also 

be made available on the REEEAC 

website. 

The meeting will be open to the 

public and will be accessible to people 

with disabilities. All guests are required 

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Cora Dickson using the contact 

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submit written comments concerning 

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submitted via email to the Renewable 

Energy and Energy Efficiency Advisory 

Committee, c/o: Cora Dickson, 

Designated Federal Officer, Office of 

Energy and Environmental Industries, 

U.S. Department of Commerce; 

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Copies of REEEAC meeting minutes 

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following the meeting. 

Dated: January 3, 2024. 

Man K. Cho, 

Deputy Director, Office of Energy and 

Environmental Industries. 

[FR Doc. 2024–00194 Filed 1–8–24; 8:45 am] 

BILLING CODE 3510–DR–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XD284] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to the Hydaburg 

Seaplane Base Refurbishment Project 

in Hydaburg, Alaska 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Issuance of an incidental 

harassment authorization. 

SUMMARY: In accordance with the 

regulations implementing the Marine 

Mammal Protection Act (MMPA) as 

amended, notification is hereby given 

that NMFS has issued an incidental 

harassment authorization (IHA) to the 

Alaska Department of Transportation 

and Public Facilities (DOT&PF) to 

incidentally harass marine mammals 

during construction associated with the 

Hydaburg Seaplane Base Refurbishment 

Project in Hydaburg, Alaska. 

DATES: This authorization is effective 

from September 15, 2024 through 

September 14, 2025. 

ADDRESSES: Electronic copies of the 

application and supporting documents, 

as well as a list of the references cited 

in this document, may be obtained 

online at: https://www.fisheries.noaa.

gov/national/marine-mammalprotection/incidental-takeauthorizations-construction-activities. 

In case of problems accessing these 

documents, please call the contact listed 

below. 

FOR FURTHER INFORMATION CONTACT: 

Reny Tyson Moore, Office of Protected 

Resources, NMFS, (301) 427–8401. 

SUPPLEMENTARY INFORMATION: 

Background 

The MMPA prohibits the ‘‘take’’ of 

marine mammals, with certain 

exceptions. Sections 101(a)(5)(A) and 

(D) of the MMPA (16 U.S.C. 1361 et 

seq.) direct the Secretary of Commerce 

(as delegated to NMFS) to allow, upon 

request, the incidental, but not 

intentional, taking of small numbers of 

marine mammals by U.S. citizens who 

engage in a specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

proposed or, if the taking is limited to 

harassment, a notice of a proposed IHA 

is provided to the public for review. 

Authorization for incidental takings 

shall be granted if NMFS finds that the 

taking will have a negligible impact on 

the species or stock(s) and will not have 

an unmitigable adverse impact on the 

availability of the species or stock(s) for 

taking for subsistence uses (where 

relevant). Further, NMFS must prescribe 

the permissible methods of taking and 

other ‘‘means of effecting the least 

practicable adverse impact’’ on the 

affected species or stocks and their 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance, and on the 

availability of the species or stocks for 

taking for certain subsistence uses 

(referred to in shorthand as 

‘‘mitigation’’); and requirements 

pertaining to the mitigation, monitoring 

and reporting of the takings are set forth. 

The definitions of all applicable MMPA 

statutory terms cited above are included 

in the relevant sections below. 


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Federal Register / Vol. 89, No. 6 / Tuesday, January 9, 2024 / Notices 1067 

Summary of Request 

On June 28, 2022, NMFS received a 

request from DOT&PF for an IHA to take 

marine mammals incidental to the 

Hydaburg Seaplane Base Refurbishment 

Project in Hydaburg, Alaska. Following 

NMFS’ review of the application, and 

multiple discussions between DOT&PF 

and NMFS, DOT&PF submitted 

responses to NMFS questions on 

December 15, 2022 and a revised 

application on February 22, 2023. The 

application was deemed adequate and 

complete on March 13, 2023. DOT&PF’s 

request is for take of nine species of 

marine mammals by Level B harassment 

and, for a subset of 6 of these species, 

Level A harassment. Neither DOT&PF 

nor NMFS expect serious injury or 

mortality to result from this activity 

and, therefore, an IHA is appropriate. 

Description of Activity 

Overview 

DOT&PF, in cooperation with the 

Federal Aviation Administration, is 

planning maintenance improvements to 

the existing Hydaburg Seaplane Base as 

part of the Hydaburg Seaplane Base 

Refurbishment Project. The existing 

facility has experienced deterioration in 

recent years, and DOT&PF has 

conducted several repair projects. The 

facility is near the end of its useful life, 

and replacement of the existing float 

structures is required to continue safe 

operation in the future. The in-water 

portion of the project will include the 

removal of five existing steel piles and 

installation of eight permanent steel 

piles to support replacement of the 

floating dock structure (Table 1). Up to 

10 temporary steel piles will be 

installed to support permanent pile 

installation and will be removed 

following completion of permanent pile 

installation (Table 1). Activities 

included as part of the project with 

potential to affect marine mammals 

include vibratory removal, down-thehole (DTH) installation, and vibratory 

and impact installation of steel pipe 

piles. Pile installation and removal will 

occur intermittently over 26 

nonconsecutive days within a 2-month 

construction window, and is anticipated 

to begin in fall 2024. 

TABLE 1—SUMMARY OF PILES TO BE INSTALLED AND REMOVED

Pile diameter 

and type 

Number 

of piles 

Number 

of rock 

sockets 

Number 

of 

tension 

anchors 

Impact 

strikes 

per pile 

Vibratory 

duration 

per pile 

(minutes) 

Rock socket 

DTH pile 

installation, 

duration per 

pile, minutes 

(range) 

Tension 

anchor 

DTH pile 

installation, 

duration per 

pile, minutes 

(range) 

Total 

duration of 

activity per 

pile, hours 

Typical 

production 

rate in 

piles per 

day 

(range) 

Days of 

installation 

or removal 

Pile Installation 

24′′ Steel Plumb 

Piles (Permanent) ................... 4 4 4 50 15 240 (60–480) 120 (60–240) 6.75 0.5 (0–1) 8 

20′′ Steel Plumb 

Piles (Permanent) ................... 4 2 2 50 15 240 (60–480) 120 (60–240) 1 0.75/6.75 0.5 (0–1) 8 

24′′ Steel Piles 

(Temporary) ....... 10 5 N/A N/A 15 240 (60–480) N/A 4.25 2.5 (1–10) 4 

Pile Removal 

16′′ Steel Cantilevered Piles ...... 5 N/A N/A N/A 30 N/A N/A 0.5 2.5 (2–4) 2 

24′′ Steel Piles 

(Temporary) ....... 10 N/A N/A N/A 30 N/A N/A 0.5 2.5 (2–4) 4 

Totals ............. 23 11 6 N/A N/A N/A N/A N/A N/A 26 

1Two of the 20-inch plumb piles will include vibratory and impact installation in addition to rock sockets and tension anchors, estimated at 6.75 hours duration total, 

and two will only use vibratory and impact, estimated at 0.75 hours duration total. 

A detailed description of the planned 

construction project is provided in the 

Federal Register notice for the proposed 

IHA (88 FR 45774, June 17, 2023). Since 

that time, no changes have been made 

to the planned activities. Therefore, a 

detailed description is not provided 

here. Please refer to that Federal 

Register notice for the description of the 

specific activity. 

Mitigation, monitoring, and reporting 

measures are described in detail later in 

this document (please see Mitigation 

and Monitoring and Reporting). 

Comments and Responses 

A notice of NMFS’ proposal to issue 

an IHA to the DOT&PF was published 

in the Federal Register on July 17, 2023 

(88 FR 45774). That notice described, in 

detail, the DOT&PF’s activities, the 

marine mammal species that may be 

affected by the activities, and the 

anticipated effects on marine mammals. 

In that notice, we requested public 

input on the request for authorization 

described therein, our analyses, the 

proposed authorization, and any other 

aspect of the notice of proposed IHA, 

and requested that interested persons 

submit relevant information, 

suggestions, and comments. This 

proposed notice was available for a 30- 

day public comment period. 

In the Federal Register notice of the 

proposed IHA, NMFS presented our 

assessment of DTH systems, which 

differed from DOT&PF’s assessment. 

Specifically, the DOT&PF and NMFS 

disagreed about some of the source 

levels and transmission loss (TL) 

coefficients that should be used as 

proxies to estimate the ensonified area 

resulting from certain DTH activities. 

NMFS also disagreed with the 

DOT&PF’s assessment that sounds 

resulting from the DTH installation of 8 

inch anchor piles should only be 

considered as continuous sound sources 

when calculating Level A and Level B 

harassment rather than as having both 

impulsive and continuous components 

as recommended by NMFS (2022) 

(https://media.fisheries.noaa.gov/2022- 

11/PUBLIC%20DTH%20Basic%20

Guidance_November%202022.pdf). 

Available data does not support 

DOT&PF’s evaluation. NMFS’ 

recommendations regarding analysis of 

sound produced through use of DTH 

techniques is based on the best available 

science and interpretation of available 

data by subject matter experts, and is 

publicly available online. NMFS 

explained these issues in the notice of 

the proposed IHA, and specifically 


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1068 Federal Register / Vol. 89, No. 6 / Tuesday, January 9, 2024 / Notices 

requested public comment on its DTHrelated recommendations in context of 

DOT&PF’s alternative interpretation. 

During the 30-day public comment 

period, NMFS received comments from 

the Marine Mammal Commission 

(MMC). The MMC expressed support for 

NMFS’ assessment and evaluation of 

DTH systems. Specifically, the MMC 

agrees with NMFS that DTH installation 

of all sized piles, including 8-inch 

tension anchors, should be considered 

an impulsive, continuous source and 

that NMFS should the use proxy source 

levels recommended by NMFS (2022) 

instead of those proposed by the 

DOT&PF to estimate associated 

ensonified areas. In addition, the MMC 

agrees with NMFS’ determination that 

applying proxy TL coefficients 

measured in other locations in 

Hydaburg is inappropriate, because 

transmission loss is dependent on 

sediment characteristics, bathymetry/ 

water depth, and sound speed profiles 

in a given area. The MMC supports 

NMFS’ decision to require the DOT&PF 

to use practical spreading loss models 

(i.e., 15 log R) when calculating 

ensonified areas resulting from DTH 

pile installation at Hydaburg, and 

recommends that NMFS continue to 

require action proponents to use 

practical spreading unless site-specific 

transmission loss data are available from 

the proposed project site. The comments 

and recommendations are available 

online at: https://www.fisheries.noaa.

gov/national/marine-mammalprotection/incidental-takeauthorizations-construction-activities. 

Please see the comment submission for 

full details regarding the 

recommendations and supporting 

rationale. 

Changes From the Proposed IHA to 

Final IHA 

Since the Federal Register notice of 

the proposed IHA was published (88 FR 

45774, July 17, 2023), NMFS published 

the 2022 Alaska and Pacific Stock 

Assessment Reports (SARs), which 

provide updates to the humpback whale 

stock structure and Southeast Alaska 

harbor porpoise stock structure (Carretta 

et al., 2023; Young et al, 2023). Updates 

have been made to the species 

descriptions for these species (see 

Description of Marine Mammals in the 

Area of Specified Activities) as well as 

to our analysis of take (see Estimated 

Take) and small numbers 

determinations (see Small Numbers). 

In addition, based on the comment 

letter received from the MMC in support 

of NMFS’ assessment of DTH systems, 

the Estimated Take section in this notice 

only considers source levels and 

transmission loss coefficients 

recommended by NMFS (2022) for DTH 

systems as proxies to estimate 

associated ensonified areas (in contrast 

to including a discussion regarding the 

DOT&PF’s assessment of DTH systems). 

Specifically, DTH installation of all 

sized piles are considered to be an 

impulsive, continuous source; proxy 

source levels follow NMFS’s 

recommendations for DTH systems 

(NMFS, 2022); and transmission loss of 

sounds produced by DTH systems in the 

Hydaburg project area are modelled 

assuming practical spreading loss. 

Lastly, a typographical error 

identified in Table 1 in the Federal 

Register notice of the proposed IHA has 

been corrected in this Federal Register 

notice. Specifically, the number of 

estimated days of installation and 

removal of 24-inch steel piles included 

in the Table was incorrect. No other 

changes have been made from the 

proposed IHA to the final IHA. 

Description of Marine Mammals in the 

Area of Specified Activities 

Sections 3 and 4 of the DOT&PF’s 

application summarize available 

information regarding status and trends, 

distribution and habitat preferences, 

and behavior and life history of the 

potentially affected species. NMFS fully 

considered all of this information, and 

we refer the reader to these descriptions, 

referenced here, instead of reprinting 

the information. Additional information 

regarding population trends and threats 

may be found in NMFS’ Stock 

Assessment Reports (SARs; 

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’ 

website (https://www.fisheries.noaa.

gov/find-species). 

Table 2 lists all species or stocks for 

which take is expected and authorized 

for this activity, and summarizes 

information related to the population or 

stock, including regulatory status under 

the MMPA and Endangered Species Act 

(ESA) and potential biological removal 

(PBR), where known. PBR is defined by 

the MMPA as the maximum number of 

animals, not including natural 

mortalities, that may be removed from a 

marine mammal stock while allowing 

that stock to reach or maintain its 

optimum sustainable population (as 

described in NMFS’ SARs). While no 

serious injury or mortality is expected to 

occur, PBR and annual serious injury 

and mortality from anthropogenic 

sources are included here as gross 

indicators of the status of the species or 

stocks and other threats. 

Marine mammal abundance estimates 

presented in this document represent 

the total number of individuals that 

make up a given stock or the total 

number estimated within a particular 

study or survey area. NMFS’ stock 

abundance estimates for most species 

represent the total estimate of 

individuals within the geographic area, 

if known, that comprises that stock. For 

some species, this geographic area may 

extend beyond U.S. waters. All stocks 

managed under the MMPA in this 

region are assessed in NMFS’ U.S. 

Alaska and Pacific SARs (e.g., Carretta, 

et al., 2023; Young et al., 2023). All 

values presented in Table 2 are the most 

recent available at the time of 

publication and are available online at: 

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/marinemammal-stock-assessments. 

TABLE 2—SPECIES 4 LIKELY IMPACTED BY THE SPECIFIED ACTIVITIES

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 Artiodactyla—Cetacea—Mysticeti (baleen whales) 

Family Balaenopteridae 

(rorquals): 

Humpback Whale ............... Megaptera novaeangliae .......... Hawaii ....................................... -, -, N 11,278 (0.56, 7,265, 

2020).

127 27.09 

Mexico-North Pacific ................. T, D, Y 918 (0.217, UNK, 2006) UND 0.57 

Minke Whale ....................... Balaenoptera acutorostrata ...... Alaska ....................................... -, -, N N/A (N/A, N/A, N/A) ........ UND 0 


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Federal Register / Vol. 89, No. 6 / Tuesday, January 9, 2024 / Notices 1069 

TABLE 2—SPECIES 4 LIKELY IMPACTED BY THE SPECIFIED ACTIVITIES—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

Odontoceti (toothed whales, dolphins, and porpoises) 

Family Delphinidae: 

Killer Whale ........................ Orcinus orca ............................. Eastern North Pacific Alaska 

Resident.

-, -, N 1,920 (N/A, 1,920, 2019) 19 1.3 

Killer Whale ........................ Orcinus orca ............................. Eastern Northern Pacific Northern Resident.-, -, N 302 (N/A, 302, 2018) ...... 2.2 0.2 

Killer Whale ........................ Orcinus orca ............................. West Coast Transient ............... -, -, N 349 (N/A, 349, 2018) ...... 3.5 0.4 

Pacific White-Sided Dolphin Lagenorhynchus obliquidens .... N Pacific .................................... -, -, N 26,880 (N/A, N/A, 1990) UND 0 

Family Phocoenidae (porpoises): 

Dall’s Porpoise .................... Phocoenoides dalli .................... Alaska ....................................... -, -, N UND (UND, UND, 2015) UND 37 

Harbor Porpoise ......................... Phocoena phocoena ................. Southern Southeast Alaska Inland Waters.-, -, Y 890 (0.37, 610, 2019) ..... 6.1 7.4 

Order Carnivora—Pinnipedia 

Family Otariidae (eared seals 

and sea lions): 

Steller Sea Lion .................. Eumetopias jubatus .................. Eastern ...................................... -, -, N 43,201 (N/A, 43,201, 

2017).

2,592 112 

Family Phocidae (earless seals): 

Harbor Seal ........................ Phoca vitulina ........................... Dixon/Cape Decision ................ -, -, N 23,478 (N/A, 21,453, 

2015).

644 69 

Northern Elephant Seal ...... Mirounga angustirostris ............ CA Breeding ............................. -, -, N 187,386 (N/A, 85,369, 

2013).

5,122 13.7 

1ESA status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or which is determined to be 

declining and likely to be listed under the ESA within the foreseeable future. Any species or stock listed under the ESA is automatically designated under the MMPA 

as depleted and as a strategic stock. 2 NMFS marine mammal stock assessment reports online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessmentreports-region/. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable (N/A). 3These values, found in NMFS’s SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (e.g., commercial fisheries, ship strike). Annual human caused mortality and serious injury (M/SI) often cannot be determined precisely and is in some cases presented as a minimum 

value or range. 4 Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy’s Committee on Taxonomy 

(https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/; Committee on Taxonomy (2022)). 

A detailed description of the species 

likely to be affected by the construction 

project, including a brief introduction to 

the affected stock as well as available 

information regarding population trends 

and threats, and information regarding 

local occurrence, were provided in the 

Federal Register notice for the proposed 

IHA (88 FR 41920, June 28, 2023). Since 

that time, the structure of the harbor 

porpoise and humpback whale stocks 

have been updated; therefore, a detailed 

description of those species updated 

stock structure is provided here. Please 

refer to the Federal Register notice of 

the proposed IHA (88 FR 41920, June 

28, 2023) for the full description for all 

species. Please also refer to NMFS’ 

website (https://www.fisheries.noaa

.gov/find-species) for generalized 

species accounts. 

Harbor Porpoise 

In the 2022 Alaska SAR, stock 

structure was revised for the Southeast 

Alaska harbor porpoise stock, which 

was split into three stocks: the Northern 

Southeast Alaska Inland Waters, 

Southern Southeast Alaska Inland 

Waters, and Yakutat/Southeast Alaska 

Offshore Waters harbor porpoise stocks 

(Young et al., 2023). This update better 

aligns harbor porpoise stock structure 

with genetics, trends in abundance, and 

information regarding discontinuous 

distribution trends (Young et al., 2023). 

Harbor porpoises found in Hydaburg are 

assumed to be members of the Southern 

Southeast Alaska Inland Waters stock 

based on the geographical range of the 

stock, which encompasses Sumner 

Strait, including areas around Wrangell 

and Zarembo Islands, Clarence Strait, 

and adjacent inlets and channels within 

the inland waters of Southeast Alaska 

north-northeast of Dixon Entrance. 

Humpback Whale 

The 2022 Alaska and Pacific SARs 

include an update to the humpback 

whale stock structure which modifies 

the previously MMPA-designated 

humpback stocks to align more closely 

with the ESA-designated distinct 

population segments (DPSs) (Caretta et 

al., 2023; Young et al., 2023). 

Specifically, the three existing North 

Pacific humpback whale stocks (Central 

and Western North Pacific stocks and a 

CA/OR/WA stock) were replaced by five 

stocks, largely corresponding with the 

ESA-designated DPSs. These include 

Western North Pacific and Hawaii 

stocks and a Central America/Southern 

Mexico-CA/OR/WA stock (which 

corresponds with the Central America 

DPS). The remaining two stocks, 

corresponding with the Mexico DPS, are 

the Mainland Mexico-CA/OR/WA and 

Mexico-North Pacific stocks (Carretta et 

al., 2023; Young et al., 2023). In the 

notice of the proposed IHA, NMFS 

assumed that humpbacks in the 

proposed action area were members of 

the Central North Pacific Stock. Based 

on these new delineations, humpback 

whales in the proposed action area are 

now assumed to be members of either 

the Hawaii stock or the Mexico-North 

Pacific stock. 

The Hawaii stock consists of one 

demographically independent 

population (DIP) (Hawaii-Southeast 

Alaska/Northern British Columbia DIP) 

and the Hawaii-North Pacific unit, 

which may or may not be composed of 

multiple DIPs (Wade et al., 2021). The 

DIP and unit are managed as a single 

stock at this time, due to the lack of data 

available to separately assess them and 

lack of compelling conservation benefit 

to managing them separately (NMFS, 

2019; NMFS, 2022b; NMFS 2023). The 


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DIP is delineated based on two strong 

lines of evidence: genetics and 

movement data (Wade et al., 2021). 

Whales in the Hawaii-Southeast Alaska/ 

Northern British Columbia DIP winter 

off Hawaii and largely summer in 

Southeast Alaska and Northern British 

Columbia (Wade et al., 2021). The group 

of whales that migrate from Russia, 

western Alaska (Bering Sea and 

Aleutian Islands), and central Alaska 

(Gulf of Alaska excluding Southeast 

Alaska) to Hawaii have been delineated 

as the Hawaii-North Pacific unit (Wade 

et al., 2021). There are a small number 

of whales that migrate between Hawaii 

and southern British Columbia/ 

Washington, but current data and 

analyses do not provide a clear 

understanding of which unit these 

whales belong to (Wade et al., 2021; 

Caretta et al., 2023; Young et al., 2023) 

The Hawaii stock of humpback 

whales is equivalent to the Hawaii DPS 

of humpback whales, which is not listed 

under the ESA (Bettridge et al., 2015; 

Wade et al., 2021). Humpback whales 

were previously considered to be 

depleted species-wide under the MMPA 

solely on the basis of the species’ ESA 

listing. After the evaluation of the listing 

status of DPSs of humpback whales, 

humpback whale DPSs that are not 

listed as threatened or endangered were 

not considered to have depleted status 

under the MMPA (81 FR 62259, 

September 8, 2016). However, because 

the Central North Pacific stock, which is 

what humpback whales in Hydaburg 

were presumed to be members of in the 

notice of the proposed IHA, included 

some whales from the ESA-listed 

Mexico and Western North Pacific 

DPSs, the stock was considered to be 

endangered and depleted, and as a 

result, was classified as a strategic stock. 

The newly defined Hawaii stock of 

humpback whales does not include 

whales from any listed DPSs and, 

therefore, is not currently considered 

depleted under the MMPA, and is also 

not a strategic stock due to its ESA 

status. 

The Mexico-North Pacific unit is 

likely composed of multiple DIPs, based 

on movement data (Martien et al., 2021; 

Wade, 2021, Wade et al., 2021). 

However, because currently available 

data and analyses are not sufficient to 

delineate or assess DIPs within the unit, 

it was designated as a single stock 

(NMFS, 2019; NMFS, 2022c; NMFS, 

2023a). Whales in this stock winter off 

Mexico and the Revillagigedo 

Archipelago and summer primarily in 

Alaska waters (Martien et al., 2021) 

(Carretta et al., 2023; Young et al., 

2023). The Mexico-North Pacific stock 

of humpback whales is one of two 

stocks that make up the ‘‘Mexico DPS’’ 

of humpback whales, which are listed as 

threatened under the ESA (Bettridge et 

al. 2015; Martien et al., 2021), and is 

therefore considered ‘‘depleted’’ and 

‘‘strategic’’ under the MMPA. 

Marine Mammal Hearing 

Hearing is the most important sensory 

modality for marine mammals 

underwater, and exposure to 

anthropogenic sound can have 

deleterious effects. To appropriately 

assess the potential effects of exposure 

to sound, it is necessary to understand 

the frequency ranges marine mammals 

are able to hear. Not all marine mammal 

species have equal hearing capabilities 

or hear over the same frequency range 

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

and Ketten, 1999; Au and Hastings, 

2008). To reflect this, Southall et al. 

(2007, 2019) recommended that marine 

mammals be divided into hearing 

groups based on directly measured 

(behavioral or auditory evoked potential 

techniques) or estimated hearing ranges 

(behavioral response data, anatomical 

modeling, etc.). Note that no direct 

measurements of hearing ability have 

been successfully completed for 

mysticetes (i.e., low-frequency 

cetaceans). Subsequently, NMFS (2018) 

described generalized hearing ranges for 

these marine mammal hearing groups. 

Generalized hearing ranges were chosen 

based on the approximately 65 decibel 

(dB) threshold from the normalized 

composite audiograms, with the 

exception for lower limits for lowfrequency cetaceans where the lower 

bound was deemed to be biologically 

implausible and the lower bound from 

Southall et al. (2007) retained. Marine 

mammal hearing groups and their 

associated hearing ranges are provided 

in Table 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 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 

et al., 2013). 

For more detail concerning these 

groups and associated generalized 

hearing ranges, please see NMFS (2018) 

for a review of available information. 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

The underwater noise produced by 

the DOT&PF’s construction activities 

has the potential to result in behavioral 

harassment of marine mammals in the 

vicinity of the survey area. The Federal 

Register notice of the proposed IHA (88 

FR 45774, July 17, 2023) included a 

discussion of the effects of 

anthropogenic noise on marine 

mammals and the potential effects of 

underwater noise from the DOT&PF’ 

construction activities on marine 

mammals and their habitat. That 

information and analysis is incorporated 

by reference into this final IHA 

determination and is not repeated here; 

please refer to the notice of the 

proposed IHA (88 FR 45774, July 17, 

2023). 


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Estimated Take 

This section provides an estimate of 

the number of incidental takes 

authorized through the IHA, which will 

inform both NMFS’ consideration of 

‘‘small numbers,’’ and the negligible 

impact determinations. 

Harassment is the only type of take 

expected to result from these activities. 

Except with respect to certain activities 

not pertinent here, section 3(18) of the 

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 will primarily be by 

Level B harassment, as use of the 

acoustic source (i.e., vibratory pile 

driving, impact pile driving, and DTH 

systems) has the potential to result in 

disruption of behavioral patterns for 

individual marine mammals. There is 

also some potential for auditory (Level 

A harassment) to result, primarily for 

mysticetes and 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 or otariids. The 

mitigation and monitoring measures are 

expected to minimize the severity of the 

taking to the extent practicable. As 

described previously, no serious injury 

or mortality is anticipated or authorized 

for this activity. Below we describe how 

the take numbers are estimated. 

For acoustic impacts, generally 

speaking, we estimate take by 

considering: (1) acoustic thresholds 

above which NMFS believes the best 

available science indicates marine 

mammals will be behaviorally harassed 

or incur some degree of permanent 

hearing impairment; (2) the area or 

volume of water that will be ensonified 

above these levels in a day; (3) the 

density or occurrence of marine 

mammals within these ensonified areas; 

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

We note that while these factors can 

contribute to a basic calculation to 

provide an initial prediction of potential 

takes, additional information that can 

qualitatively inform take estimates is 

also sometimes available (e.g., previous 

monitoring results or average group 

size). Below, we describe the factors 

considered here in more detail and 

present the take estimates. 

Acoustic Thresholds 

NMFS recommends the use of 

acoustic thresholds that identify the 

received level of underwater sound 

above which exposed marine mammals 

would be reasonably expected to be 

behaviorally harassed (equated to Level 

B harassment) or to incur PTS of some 

degree (equated to Level A harassment). 

Level B Harassment—Though 

significantly driven by received level, 

the onset of behavioral disturbance from 

anthropogenic noise exposure is also 

informed to varying degrees by other 

factors related to the source or exposure 

context (e.g., frequency, predictability, 

duty cycle, duration of the exposure, 

signal-to-noise ratio, distance to the 

source), the environment (e.g., 

bathymetry, other noises in the area, 

predators in the area), and the receiving 

animals (hearing, motivation, 

experience, demography, life stage, 

depth) and can be difficult to predict 

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

et al., 2012). Based on what the 

available science indicates and the 

practical need to use a threshold based 

on a metric that is both predictable and 

measurable for most activities, NMFS 

typically uses a generalized acoustic 

threshold based on received level to 

estimate the onset of behavioral 

harassment. NMFS generally predicts 

that marine mammals are likely to be 

behaviorally harassed in a manner 

considered to be Level B harassment 

when exposed to underwater 

anthropogenic noise above root-meansquared pressure received levels (RMS 

SPL) of 120 dB re 1 mPa for continuous 

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

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

airguns) or intermittent (e.g., scientific 

sonar) sources. Generally speaking, 

Level B harassment take estimates based 

on these behavioral harassment 

thresholds are expected to include any 

likely takes by TTS as, in most cases, 

the likelihood of TTS occurs at 

distances from the source less than 

those at which behavioral harassment is 

likely. TTS of a sufficient degree can 

manifest as behavioral harassment, as 

reduced hearing sensitivity and the 

potential reduced opportunities to 

detect important signals (conspecific 

communication, predators, prey) may 

result in changes in behavior patterns 

that would not otherwise occur. 

The DOT&PF’s activity includes the 

use of continuous (vibratory pile 

driving) and intermittent (impact pile 

driving) sources, and therefore the RMS 

SPL thresholds of 120 and 160 dB re 1 

mPa are applicable. DTH systems have 

both continuous, non-impulsive, and 

impulsive components. When 

evaluating Level B harassment, NMFS 

recommends treating DTH as a 

continuous source and applying the 

RMS SPL thresholds of 120 dB re 1 mPa. 

Level A harassment—NMFS’ 

Technical Guidance for Assessing the 

Effects of Anthropogenic Sound on 

Marine Mammal Hearing (Version 2.0) 

(Technical Guidance, 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 DOT&PF’s construction 

includes the use of impulsive (impact 

pile driving) and non-impulsive 

(vibratory pile driving) sources. As 

described above, DTH includes both 

impulsive and non-impulsive 

characteristics. When evaluating Level 

A harassment, NMFS recommends 

treating DTH as an impulsive source. 

The thresholds used to identify the 

onset of PTS are provided in Table 4. 

The references, analysis, and 

methodology used in the development 

of the thresholds are described in 

NMFS’ 2018 Technical Guidance, which 

may be accessed at: 

www.fisheries.noaa.gov/national/ 

marine-mammal-protection/marinemammal-acoustic-technical-guidance. 

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. 


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TABLE 4—THRESHOLDS IDENTIFYING THE ONSET OF PERMANENT THRESHOLD SHIFT—Continued 

Hearing group 

PTS onset acoustic thresholds * 

(received level) 

Impulsive Non-impulsive 

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 NMFS’ 2018 Technical Guidance. Hence, the subscript ‘‘flat’’ 

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

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

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

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

Ensonified Area 

Here, we describe operational and 

environmental parameters of the activity 

that are used in estimating the area 

ensonified above the acoustic 

thresholds, including source levels and 

transmission loss coefficient. 

The sound field in the project area is 

the existing background noise plus 

additional construction noise from the 

project. Marine mammals are expected 

to be affected via sound generated by 

the primary components of the project 

(i.e., impact pile installation, vibratory 

pile installation, vibratory pile removal, 

and DTH). 

Sound Source Levels of Construction 

Activities—The intensity of pile driving 

sounds is greatly influenced by factors 

such as the type of piles (material and 

diameter), hammer type, and the 

physical environment (e.g., sediment 

type) in which the activity takes place 

(Table 5). A description of the 

assessment and appropriateness of 

proxy sound source levels and TL 

measurements for the DOT&PF’s 

activities can be found in the notice of 

proposed IHA (88 FR 45774, July 17, 

2023). This includes a discussion 

regarding the analyses of noise from 

DTH systems that follows NMFS’ 

recommendations (i.e., https://media.

fisheries.noaa.gov/2022-11/PUBLIC%20

DTH%20Basic%20Guidance_

November%202022.pdf; NMFS, 2022a). 

Please refer to the notice of the 

proposed IHA (88 FR 45774, July 17, 

2023) for full details. 

TABLE 5—SUMMARY OF UNATTENUATED IN-WATER PILE DRIVING PROXY LEVELS

[At 10 m] 

Pile type Installation method Peak SPL 

(dB re 1 μPa) 

RMS SPL 

(dB re 1 μPa) 

SELss

(dB re 1 μPa2 sec) 

Reference 

(levels) 

16-inch steel piles ............... Vibratory hammer .............. NA 158 NA CALTRANS (2020). 

20-inch steel piles ............... Vibratory hammer .............. NA 161 NA Navy (2015). 

24-inch steel piles ............... Vibratory hammer .............. NA 161 NA Navy (2015). 

20-inch steel piles ............... Impact hammer .................. 208 187 176 CALTRANS (2020). 

24-inch steel piles ............... Impact hammer .................. 208 193 178 CALTRANS (2020). 

8-inch tension anchors ....... DTH system ....................... 170 156 144 Reyff and Heyvaert (2019); 

Reyff (2020). 

20-inch rock sockets ........... DTH system ....................... 184 167 159 Heyvaert and Reyff (2021). 

24-inch rock sockets ........... DTH system ....................... 184 167 159 Heyvaert and Reyff (2021). 

Notes: NMFS conservatively assumes that noise levels during vibratory pile removal are the same as those during installation for the same 

type and size pile; all SPLs are unattenuated and represent the SPL referenced at a distance of 10 m from the source; NA = Not applicable; dB 

re 1 μPa = decibels (dB) referenced to a pressure of 1 micropascal. 

Estimated Harassment Isopleths—All 

Level B harassment isopleths are 

reported in Table 7 considering RMS 

SPLs and the default TL coefficient for 

practical spreading loss (i.e., 

15*Log10(range)). Land forms 

(including causeways, breakwaters, 

islands, and other land masses) impede 

the transmission of underwater sound 

and create shadows behind them where 

sound from construction is not audible. 

At Hydaburg, Level B harassment 

isopleths from the project will be 

blocked by Sukkwan Island, Spook 

Island, Mushroom Island, and the 

coastline along Prince of Wales Island 

both southeast and northwest of the 

project site. The maximum distance that 

a harassment isopleth can extend due to 

these land masses is 5,162 m. 

The ensonified area associated with 

Level A harassment is technically 

challenging to predict due to the need 

to account for a duration component. 

Therefore, NMFS developed an optional 

User Spreadsheet tool to accompany the 

Technical Guidance (2018) that can be 

used to relatively simply predict an 

isopleth distance for use in conjunction 

with marine mammal density or 

occurrence to help predict potential 

takes. We note that because of some of 

the assumptions included in the 

methods underlying this optional tool, 

we anticipate that the resulting isopleth 

estimates are typically going to be 

overestimates of some degree, which 

may result in an overestimate of 

potential take by Level A harassment. 

However, this optional tool offers the 

best way to estimate isopleth distances 

when more sophisticated modeling 

methods are not available or practical. 

For stationary sources (such as from 

impact pile driving, vibratory pile 

driving, and DTH), the optional User 

Spreadsheet tool predicts the distance at 

which, if a marine mammal remained at 

that distance for the duration of the 

activity, it would be expected to incur 

PTS. Inputs used in the optional User 


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Spreadsheet tool are reported in Table 6 and the resulting estimated isopleths are 

reported in Table 7. 

TABLE 6—NMFS USER SPREADSHEET INPUTS

Vibratory pile driving Impact pile driving DTH 

16-inch steel 

piles 

20-inch steel 

piles 24-inch steel piles 

20-inch steel 

piles 

24-inch steel 

piles 

20- and 24-inch 

rock socket 

8-inch tension 

anchor 

Removal 

Installation/ 

removal Installation Removal Installation Installation Installation Installation 

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.

E.1) Impact pile 

driving.

E.1) Impact pile 

driving.

E.2) DTH Systems.A.1) DTH Systems. 

Source Level 

(SPL).

158 dB RMS ... 161 dB RMS .......... 161 dB RMS ... 161 dB RMS ... 176 dB SEL .... 178 dB SEL .... 159 dB RMS ... 144 dB RMS. 

Transmission 

Loss Coefficient.

15 .................... 15 ........................... 15 .................... 15 .................... 15 .................... 15 .................... 15 .................... 15. 

Weighting Factor Adjustment (kHz).2.5 ................... 2.5 .......................... 2.5 ................... 2.5 ................... 2 ...................... 2 ...................... 2 ...................... 2. 

Time to install/ 

remove single pile (minutes).

30 .................... 15/30 1 ................... 15/30 1 ............. 30 .................... ......................... ......................... 60–480 2 .......... 60–240.2

Number of 

strikes per 

pile.

......................... ................................ ......................... ......................... 50 .................... 50 .................... 15 .................... 15. 

Piles per day ... 2 ...................... 2/10 1 ..................... 2/10 1 ............... 2 ...................... 1/2 1 ................. 1/2 1 ................. 1 ...................... 1. 

Distance of 

sound pressure level 

measurement 

(m).

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

1A maximum scenario was calculated for this activity. 

2A range of scenarios was calculated for this activity. 

TABLE 7—DISTANCES TO LEVEL A HARASSMENT, BY HEARING GROUP, AND DISTANCES AND AREAS OF LEVEL B 

HARASSMENT THRESHOLDS PER PILE TYPE AND PILE DRIVING METHOD

Activity Pile size Minutes (min) 

or strikes per pile 

Piles 

per day 

Level A harassment distance (m) Level B 

harassment 

distance 

(m) all 

hearing 

groups 

Level B 

harassment area 

(km2) all 

hearing 

groups 

LF MF HF PW OW 

Vibratory Installation ..... 20- and 24-inch ............ 15 min ........................... 2 5 1 7 3 1 3 5,412 4 4.34 

30 1 min ........................ 1 10 20 2 30 13 1 

Vibratory Removal ........ 16-inch .......................... 30 min ........................... 2 5 1 7 3 1 3,415 3.90 

24-inch .......................... 30 min ........................... 2 7 1 11 5 1 3 5,412 4 4.34 

Impact Installation ......... 20-inch .......................... 50 strikes ...................... 1 47 2 56 25 2 1,585 2.14 

50 1 strikes .................... 1 2 74 3 88 40 3 

24-inch .......................... 50 strikes ...................... 1 63 3 75 34 3 631 0.65 

50 1 strikes .................... 1 2 100 4 119 54 4 

DTH (Rock Socket) 2 ..... 20- and 24-inch ............ 60 min ........................... 1 359 13 427 192 14 3 13,594 4 4.34 

120 min ......................... 1 569 21 678 305 23 

80 min ........................... 1 746 27 888 399 29 

240 min ......................... 1 903 33 1,076 484 36 

300 min ......................... 1 1,048 38 1,249 561 41 

360 min ......................... 1 1,184 43 1,410 634 47 

420 min ......................... 1 1,312 47 1,563 702 52 

480 min ......................... 1 1,434 51 1,708 768 56 

DTH (Tension Anchor) 2 8-inch ............................ 60 min ........................... 1 36 2 43 20 2 2,512 3.07 

120 min ......................... 1 57 2 68 31 3 

180 min ......................... 1 75 3 89 40 3 

240 min ......................... 1 91 4 108 4 4 

300 min ......................... 1 105 4 125 57 5 

360 min ......................... 1 119 5 141 64 5 

420 min ......................... 1 132 5 157 71 6 

480 min ......................... 1 144 6 171 77 6 

1A maximum scenario was calculated for this activity. 

2A range of scenarios was calculated for this activity. 

3 Harassment distances will be truncated where appropriate to account for land masses, to a maximum distance of 5,162 m. 

4 Harassment areas are truncated where appropriate to account for land masses, to a maximum area of 4.34 km2. 


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Marine Mammal Occurrence and Take 

Estimation 

In this section we provide information 

about the occurrence of marine 

mammals, including density or other 

relevant information that will inform 

the take calculations. We also describe 

how this information is synthesized to 

produce a quantitative estimate of the 

take that is reasonably likely to occur 

and is authorized. Although 

construction is currently planned to 

begin in fall 2023, unexpected delays 

associated with construction can occur. 

To account for this uncertainty, the 

following exposure estimates assume 

that construction will occur during the 

periods of peak abundance for those 

species for which abundance varies 

seasonally. 

Steller Sea Lion 

No density or abundance numbers 

exist for Steller sea lions in the action 

area, and they are not known to 

regularly occur near Hydaburg. 

However, in context of a lack of local 

data, the DOT&PF conservatively 

estimated that during peak salmon runs, 

6 groups of 10 individuals could be 

exposed to project-related underwater 

noise each week during pile installation 

and removal activities, for a total of 240 

exposures (4 weeks * 60 sea lions per 

week = 240 total exposures). 

The largest Level A harassment zone 

for Steller sea lions is 59 m (Table 7). 

Due to the small Level A harassment 

zones (Table 7) and the implementation 

of shutdown zones, which will be larger 

than Level A harassment zones 

(described below in the Mitigation 

section), NMFS has determined that 

take by Level A harassment is not 

anticipated for Steller sea lions. 

Therefore, NMFS authorizes all 240 

estimated exposures as takes by Level B 

harassment. Takes by Level A 

harassment for Steller sea lions are not 

authorized. 

Harbor Seal 

Up to six known harbor seal haulouts 

are located near the project area; 

however, they are all located outside of 

the estimated harassment zones, with 

the closest haulout located just over 4.5 

km southeast of the project site, but 

blocked by a land shadow (see Figure 4– 

2 in the DOT&PF’s application). Within 

the project area, harbor seals remain 

relatively rare as described by local 

residents. The DOT&PF conservatively 

estimated that up to 8 harbor seals could 

be within estimated harassment zones 

each day during pile installation and 

removal activities, for a total of 208 

exposures (26 days * 8 seals per day = 

208 total exposures). 

The largest Level A harassment zone 

for harbor seals is 768 m (Table 7). 

There are no known harbor seal 

haulouts within this distance, however, 

it is possible that harbor seals may 

approach and enter within this distance 

for sufficient duration to incur PTS. 

Further, the largest practicable 

shutdown zone that the DOT&PF can 

implement for harbor seals is 400 m 

(described below in the Mitigation 

section). To account for this difference, 

NMFS authorizes additional takes by 

Level A harassment, as compared with 

the DOT&PF’s request of 48 takes by 

Level A harassment, which assumed 

smaller Level A harassment isopleths 

based on their assessment of DTH 

systems. Additional takes were 

determined by calculating the ratio of 

the largest Level A harassment area for 

20- and 24-inch (50.8- and 60.96-cm) 

DTH activities (i.e., 0.89 km2 for a Level 

A harassment distance of 768 m) minus 

the area of the shutdown zone for harbor 

seals (i.e., 0.27 km2 for a shutdown zone 

distance of 400 m) to the area of the 

Level B harassment isopleth (4.34 km2

for a Level B harassment distance of 

5,162 m) (i.e., (0.89 km2¥0.27 km2)/ 

4.34 km2 = 0.14). We then multiplied 

this ratio by the total number of 

estimated harbor seal exposures to 

determine additional take by Level A 

harassment (i.e., 0.14 * 208 exposures = 

29.12 takes, rounded up to 30 takes). 

The total take by Level A harassment 

was then calculated as the take 

originally requested by the DOT&PF 

plus the additional take calculated by 

NMFS (i.e., 48 + 30), for a total of 78 

takes by Level A harassment. Takes by 

Level B harassment were calculated as 

the number of estimated harbor seal 

exposures minus the amount of take by 

Level A harassment (i.e., 208¥78). 

Therefore, NMFS authorizes 78 takes by 

Level A harassment and 130 takes by 

Level B harassment for harbor seals, for 

a total of 208 takes. 

Northern Elephant Seal 

Northern elephant seal abundance 

throughout coastal southeast Alaska is 

low, and anecdotal reports have not 

included northern elephant seals near 

the project area. However, northern 

elephant seals have been observed 

elsewhere in southeast Alaska; 

therefore, this species could occur near 

the project area. To account for this 

possibility, the DOT&PF estimated that 

one northern elephant seal could be 

within estimated harassment zones each 

week during pile installation and 

removal activities, for a total of four 

exposures (4 weeks * 1 northern 

elephant seal each week = 4 total 

exposures). 

The largest practicable shutdown 

zone the DOT&PF can implement for 

northern elephant seals (400 m) 

(described below in the Mitigation 

section) is smaller than the Level A 

harassment isopleths that result from 

240 or minutes more of 20- and 24-inch 

(50.8- and 60.96-cm) DTH rock socket 

installation (Table 7). To account for 

this difference, NMFS followed the 

same method as described above for 

harbor seals to calculate take by Level 

A harassment for northern elephant 

seals. This was achieved by calculating 

the ratio of the largest Level A 

harassment area for 20- and 24-inch 

(50.8- and 60.96-cm) DTH activities (i.e., 

0.89 km2 for a Level A harassment 

distance of 768 m) minus the area of the 

shutdown zone for elephant seals (i.e., 

0.27 km2 for a shutdown zone distance 

of 400 m) to the area of the Level B 

harassment isopleth (4.34 km2 for a 

Level B harassment distance of 5,162 m) 

(i.e., (0.89 km2¥0.27 km2)/4.34 km2 = 

0.14), and by multiplying this ratio by 

the total number of estimated northern 

elephant seal exposures (i.e., 0.14 * 4 

exposures = 0.56 takes, rounded up to 

1 take by Level A harassment). Takes by 

Level B harassment were calculated as 

the number of estimated northern 

elephant exposures minus the amount 

of authorized take by Level A 

harassment (i.e., 4¥1). Therefore, 

NMFS authorizes one take by Level A 

harassment and three takes by Level B 

harassment for northern elephant seals, 

for a total of four takes. 

Harbor Porpoise 

There have been no systematic studies 

or observations of harbor porpoises 

specific to Hydaburg or Sukkwan Strait, 

and sightings of harbor porpoises have 

not been described in this region by 

local residents. As such, there is limited 

potential for them to occur in the project 

area, but they could occur in low 

numbers as individuals have been 

observed in southern inland waters of 

southeast Alaska. Therefore, the 

DOT&PF estimated that up to two 

harbor porpoises could be within 

estimated harassment zones each day 

during pile installation and removal 

activities, for a total of 52 exposures (26 

days * 2 porpoises per day = 52 

exposures). 

Harbor porpoises are small, lack a 

visible blow, have low dorsal fins, an 

overall low profile, and a short surfacing 

time, making them difficult to observe 

(Dahlheim et al., 2015). These 

characteristics likely reduce the 

identification and reporting of this 

species. For these reasons, and based off 


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of their assessment of DTH systems, the 

DOT&PF requested that eight takes by 

Level A harassment be authorized for 

harbor porpoises (4 weeks * 2 harbor 

porpoise per week = 8 takes by Level A 

harassment). 

The maximum Level A harassment 

isopleth estimated by NMFS for harbor 

porpoises is 1,708 m, which is larger 

than what the DOT&PF analyzed. The 

largest practicable shutdown zone that 

the DOT&PF can implement for harbor 

porpoises is 500 m (described below in 

the Mitigation section). To account for 

this difference and the increased 

possibility of harbor porpoises occurring 

outside of the shutdown zone and in the 

Level A harassment zone long enough to 

incur PTS, NMFS authorizes additional 

takes by Level A harassment, as 

compared with the DOT&PF’s request. 

Additional takes were determined by 

calculating the ratio of the largest Level 

A harassment area for 20- and 24-inch 

(50.8- and 60.96-cm) DTH activities (i.e., 

2.25 km2 for a Level A harassment 

distance of 1,708 m minus the area of 

the shutdown zone for harbor porpoises 

(i.e., 0.42 km2 for a shutdown zone 

distance of 500 m) to the area of the 

Level B harassment isopleth (4.34 km2

for a Level B harassment distance of 

5,162 m) (i.e., (2.25 km2¥0.42 km2)/ 

4.34 km2 = 0.42). We then multiplied 

this ratio by the total number of 

estimated harbor porpoise exposures to 

determine additional take by Level A 

harassment (i.e., 0.42 * 8 exposures = 

3.36 takes, rounded up to 4 takes). The 

total take by Level A harassment was 

then calculated as the take originally 

requested by the DOT&PF plus the 

additional take calculated by NMFS 

(i.e., 8 + 4), for a total of 12 takes by 

Level A harassment. Takes by Level B 

harassment were calculated as the 

number of estimated harbor porpoise 

exposures minus the amount of take by 

Level A harassment (i.e., 52¥12). 

Therefore, NMFS authorizes 12 takes by 

Level A harassment and 40 takes by 

Level B harassment for harbor seals, for 

a total of 52 takes. 

Dall’s Porpoise 

Dall’s porpoises are not expected to 

occur in Sukkwan Strait because the 

shallow water habitat of the bay is 

atypical of areas where Dall’s porpoises 

usually occur. However, recent research 

indicates that Dall’s porpoises may 

opportunistically exploit nearshore 

habitats where predators, such as killer 

whales, are absent. Therefore, the 

DOT&PF anticipates that one large 

Dall’s porpoise pod (15 individuals) 

could be within the estimated 

harassment zones during in-water 

construction, for a total of 15 possible 

exposures. 

Dall’s porpoises typically appear in 

larger groups and exhibit behaviors that 

make them more visible and thus easier 

to observe at distance. Based on this 

assumption, the DOT&PF did not 

request any takes by Level A harassment 

for this species. However, the maximum 

Level A harassment zone is 1,708 m, 

which is larger than what the DOT&PF 

analyzed. The largest practicable 

shutdown zone that the DOT&PF can 

implement for Dall’s porpoises during 

this project is 500 m (described below 

in the Mitigation section). To account 

for this difference and the increased 

possibility of Dall’s porpoises occurring 

outside of the shutdown zone and in the 

Level A harassment zones for sufficient 

duration to incur PTS, NMFS adds takes 

by Level A harassment, as compared 

with the DOT&PF’s request. Because 

Dall’s porpoises typically occur in 

groups, NMFS authorizes 15 takes (i.e., 

one large pod) by Level A harassment in 

addition to the 15 takes by Level B 

harassment that the DOT&PF requested, 

for a total of 30 takes. This will help to 

ensure that the DOT&PF have enough 

takes to account for the possibility of 

one large pod occurring in either the 

Level A or the Level B harassment zone. 

Pacific White-Sided Dolphin 

Pacific white-sided dolphins do not 

generally occur in the shallow, inland 

waterways of southeast Alaska. There 

are no records of this species occurring 

in Sukkwan Strait, and it is uncommon 

for individuals to occur in the project 

area. However, recent fluctuations in 

distribution and abundance decrease the 

certainty in this prediction. Therefore, 

the DOT&PF conservatively estimated 

that one large group (92 individuals) of 

Pacific white-sided dolphins could be 

within estimated harassment zones 

during the in-water construction. 

The largest Level A harassment zone 

estimated by NMFS for Pacific whitesided dolphins is 51 m. Due to the small 

Level A harassment zones (Table 7) and 

the implementation of shutdown zones, 

which will be larger than Level A 

harassment zones (described below in 

the Mitigation section), take by Level A 

harassment is not anticipated for Pacific 

white-sided dolphins. Therefore, NMFS 

authorizes all 92 estimated exposures as 

takes by Level B harassment. Takes by 

Level A harassment for Pacific whitesided dolphins are not authorized. 

Killer Whale 

Killer whales are observed 

infrequently throughout Sukkwan Strait, 

and their presence near Hydaburg is 

unlikely. However, anecdotal local 

information suggests that a pod may be 

seen in the project area every few 

months. Therefore, the DOT&PF 

estimate that one killer whale pod of up 

to 15 individuals may be within 

estimated harassment zones once during 

the pile installation and removal 

activities (15 total exposures). 

The largest Level A harassment zone 

for killer whales is 51 m (Table 7). 

Because killer whales are unlikely to 

enter Sukkwan Strait and are relatively 

conspicuous, it is unlikely they will 

approach this distance for sufficient 

duration to incur PTS. Due to the small 

Level A harassment zones (Table 7) and 

the implementation of shutdown zones, 

which will be larger than Level A 

harassment zones (described below in 

the Mitigation section), take by Level A 

harassment is not anticipated for killer 

whales. Therefore, NMFS authorizes all 

15 estimated exposures as takes by 

Level B harassment. Takes by Level A 

harassment for killer whales are not 

authorized. 

Humpback Whale 

Use of Sukkwan Strait by humpback 

whales is common but intermittent and 

dependent on the presence of prey fish. 

Based on anecdotal evidence from local 

residents, the DOT&PF predicts that 

four groups of two whales, up to eight 

individuals per week, may be within 

estimated harassment zones each week 

during the 4 weeks of the pile 

installation and removal activities, for a 

total of 32 exposures (8 per week * 4 

weeks = 32 total exposures). Wade 

(2021) estimated that approximately 2.4 

percent of humpback whales in 

southeast Alaska are members of the 

Mexico-North Pacific stock, while all 

others are members of the Hawaii stock. 

Therefore, the DOT&PF estimates that 1 

of the exposures (32 whales * 0.024 = 

0.77 rounded up to 1) will be of an 

individual from the Mexico stock 

individuals and 31 exposures will be of 

individuals from the Hawaii stock. 

Due to the long duration of DTH 

piling that is anticipated, and the 

potential for humpback whales to enter 

the Level A harassment zones from 

around obstructions or landforms near 

the project area, the DOT&PF requested 

that NMFS authorize 4 takes by Level A 

harassment (equivalent to two groups of 

two individuals) of humpback whales. 

Due to the small percentage of 

humpback whales that may belong to 

the Mexico-North Pacific stock in 

southeast Alaska, the DOT&PF assumes 

that all takes by Level A harassment will 

be attributed to Hawaii DPS whales. 

The largest Level A harassment zone 

for humpback whales is 1,435 m (Table 

7), which is larger than what the 


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DOT&PF analyzed. The largest 

practicable shutdown zone that the 

DOT&PF can implement for humpback 

whales during this project is 1,000 m 

(described below in the Mitigation 

section). To account for this difference 

and the increased possibility of 

humpback whales occurring outside of 

the shutdown zone and in the Level A 

harassment zone long enough to incur 

PTS, NMFS added additional takes by 

Level A harassment, compared with the 

DOT&PF’s request. 

NMFS calculated additional takes by 

Level A harassment by determining the 

ratio of the largest Level A harassment 

area for 20- and 24-inch (50.8- and 

60.96-cm) DTH activities (i.e., 2.01 km2

for a Level A harassment distance of 

1,435 m) minus the area of the 

shutdown zone for humpback whales 

(i.e., 1.34 km2 for a shutdown zone 

distance of 1,000 m) to the area of the 

Level B harassment isopleth (4.34 km2

for a Level B harassment distance of 

5,162 m) (i.e., (2.01 km2¥1.34 km2)/ 

4.34 km2 = 0.15). We then multiplied 

this ratio by the total number of 

estimated humpback whales exposures 

to determine additional take by Level A 

harassment (i.e., 0.15 * 32 exposures = 

4.80 takes, rounded up to 5 takes). The 

total take by Level A harassment was 

then calculated as the take originally 

requested by the DOT&PF plus the 

additional take calculated by NMFS 

(i.e., 4 + 5), for a total of 9 takes by Level 

A harassment. Takes by Level B 

harassment were calculated as the 

number of estimated humpback whale 

exposures minus the amount of take by 

Level A harassment (i.e., 32¥9). 

Therefore, NMFS authorizes 9 takes by 

Level A harassment and 23 takes by 

Level B harassment for humpback 

whales, for a total of 32 takes. Given that 

approximately 2.4 percent of humpback 

whales in southeast Alaska are members 

of the Mexico-North Pacific stock, 

NMFS assumes that one of the takes by 

Level B harassment may be attributed to 

a humpback whale from the MexicoNorth Pacific stock (32 * 2.4 percent = 

0.77, rounded up to 1 take). All other 

takes by Level B harassment and all 

takes by Level A harassment (i.e., 31) are 

assumed to be attributed to humpback 

whales from the Hawaii stock. 

Minke Whale 

Minke whale abundance throughout 

southeast Alaska is low, and anecdotal 

reports have not included minke whales 

near the project area. However, minke 

whales are distributed throughout a 

wide variety of habitats and have been 

observed elsewhere in southeast Alaska; 

therefore, this species could occur near 

the project area. NMFS has previously 

estimated that three individual minke 

whales could occur near Metlakatla 

every 4 months during a similar activity 

(86 FR 43190, August 6, 2021). 

Therefore, DOT&PF conservatively 

estimated that up to three minke whales 

may be exposed to project-related 

underwater noise during the pile 

installation and removal activities. 

Due to the low likelihood of minke 

whale occurrence near the project site, 

the DOT&PF did not request any takes 

by Level A harassment for this species. 

However, the maximum Level A 

harassment isopleth estimated by NMFS 

for minke whales is 1,435 m, which is 

larger than what the DOT&PF analyzed. 

The largest practicable shutdown zone 

that the DOT&PF can implement for 

minke whales during this project is 

1,000 m (described below in the 

Mitigation section). To account for this 

difference and the increased possibility 

of minke whales occurring outside of 

the shutdown zone and within the Level 

A harassment zone long enough to incur 

PTS, NMFS added takes by Level A 

harassment to the DOT&PF’s request. 

NMFS calculated additional takes by 

Level A harassment by determining the 

ratio of the largest Level A harassment 

area for 20- and 24-inch (50.8- and 

60.69-cm) DTH activities (i.e., 2.01 km2

for a Level A harassment distance of 

1,435 m) minus the area of the 

shutdown zone for minke whales (i.e., 

1.34 km2 for a shutdown zone distance 

of 1,000 m) to the area of the Level B 

harassment isopleth (4.34 km2) for a 

Level B harassment distance of 5,162 m) 

(i.e., (2.01 km2¥1.34 km2)/4.34 km2 = 

0.15). We then multiplied this ratio by 

the total number of estimated minke 

whales exposures to determine take by 

Level A harassment (i.e., 0.15 * 3 

exposures = 0.45 takes, rounded up to 

1 take by Level A harassment). Takes by 

Level B harassment were calculated as 

the number of estimated minke whale 

exposures minus the amount of take by 

Level A harassment (i.e., 3¥1). 

Therefore, NMFS authorizes one take by 

Level A harassment and two takes by 

Level B harassment for minke whales, 

for a total of three takes. 

In summary, the total amount of takes 

by Level A harassment and Level B 

harassment authorized for each marine 

mammal stock is presented in Table 8. 

TABLE 8—AMOUNT OF AUTHORIZED TAKE AS A PERCENTAGE OF STOCK ABUNDANCE, BY STOCK AND HARASSMENT TYPE

Species Stock or DPS 

Authorized take Percent 

of stock Level A Level B Total 

Steller sea lion .................................. Eastern ............................................. 0 240 240 0.56 

Harbor seals ...................................... Dixon/Cape Decision ........................ 78 130 208 0.89 

Northern elephant seals .................... CA Breeding ..................................... 1 3 4 <0.01 

Harbor porpoises .............................. Southern Southeast Alaska Inland 

Waters.

12 40 52 5.84 

Dall’s porpoises ................................. Alaska ............................................... 15 15 30 1 UNK 

Pacific white-sided dolphins .............. N Pacific ........................................... 0 92 92 0.34 

Killer whales ...................................... Eastern North Pacific Alaska Resident.0 15 15 2 0.78 

Eastern Northern Pacific Northern 

Resident. 

2 4.97 

West Coast Transient. 3 4.30 

Humpback whales ............................. Hawaii ............................................... 9 23 32 2 0.28 

Mexico-North Pacific. 1 2 UNK 

Minke whales .................................... Alaska ............................................... 1 2 3 ........................

1 NMFS does not have an official abundance estimate for this stock; please refer to the Small Numbers section of this notice for a discussion 

regarding the percentage of this stock authorized for take. 2 NMFS conservatively assumes that all takes occur to each stock. 


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Mitigation 

In order to issue an IHA under section 

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

set forth the permissible methods of 

taking pursuant to the activity, and 

other means of effecting the least 

practicable impact on the species or 

stock and its habitat, paying particular 

attention to rookeries, mating grounds, 

and areas of similar significance, and on 

the availability of the species or stock 

for taking for certain subsistence uses 

(latter not applicable for this action). 

NMFS regulations require applicants for 

incidental take authorizations to include 

information about the availability and 

feasibility (economic and technological) 

of equipment, methods, and manner of 

conducting the activity or other means 

of effecting the least practicable adverse 

impact upon the affected species or 

stocks, and their habitat (50 CFR 

216.104(a)(11)). 

In evaluating how mitigation may or 

may not be appropriate to ensure the 

least practicable adverse impact on 

species or stocks and their habitat, as 

well as subsistence uses where 

applicable, NMFS considers two 

primary factors: 

(1) The manner in which, and the 

degree to which, the successful 

implementation of the measure(s) is 

expected to reduce impacts to marine 

mammals, marine mammal species or 

stocks, and their habitat. This considers 

the nature of the potential adverse 

impact being mitigated (likelihood, 

scope, range). It further considers the 

likelihood that the measure will be 

effective if implemented (probability of 

accomplishing the mitigating result if 

implemented as planned), the 

likelihood of effective implementation 

(probability implemented as planned); 

and 

(2) The practicability of the measures 

for applicant implementation, which 

may consider such things as cost, and 

impact on operations. 

The DOT&PF must employ the 

following standard mitigation measures, 

as included in the IHA: 

• Ensure that construction 

supervisors and crews, the monitoring 

team and relevant DOT&PF staff are 

trained prior to the start of all pile 

driving and DTH activity, so that 

responsibilities, communication 

procedures, monitoring protocols, and 

operational procedures are clearly 

understood. New personnel joining 

during the project must be trained prior 

to commencing work; 

• Avoid direct physical interaction 

with marine mammals during 

construction activity. If a marine 

mammal comes within 10 m of such 

activity, operations shall cease. Should 

a marine mammal come within 10 m of 

a vessel in transit, the boat operator will 

reduce vessel speed to the minimum 

level required to maintain steerage and 

safe working conditions. If human safety 

is at risk, the in-water activity will be 

allowed to continue until it is safe to 

stop; 

• Employ PSOs and establish 

monitoring locations as described in 

Section 5 of the IHA. The DOT&PF must 

monitor the project area to the 

maximum extent possible based on the 

required number of PSOs, required 

monitoring locations, and 

environmental conditions. For all pile 

driving and DTH activities at least two 

PSOs must be used; 

• For all pile driving/removal 

activities, a minimum 30 m shutdown 

zone must be established. The purpose 

of a shutdown zone is generally to 

define an area within which shutdown 

of activity will occur upon sighting of a 

marine mammal (or in anticipation of an 

animal entering the defined area). 

Shutdown zones will vary based on the 

type of driving/removal activity type 

and by marine mammal hearing group 

(see Table 9). Here, shutdown zones are 

larger than or equivalent to the 

calculated Level A harassment isopleths 

shown in Table 7, except when 

indicated due to practicability and 

effectiveness concerns. These concerns 

include the limited viewpoints available 

to station PSOs along Sukkwan Strait, 

the presence of landmasses that may 

obstruct viewpoints, and decreased 

effectiveness in sighting marine 

mammals at increased distances. 

Further, shutdown zones at greater 

distances than those in Table 9 will 

likely result in the DOT&PFs activities 

being shut down more frequently than 

is practicable for them to maintain their 

project schedule; 

TABLE 9—SHUTDOWN ZONES DURING PROJECT ACTIVITIES

Activity Pile size Minutes (min) 

or strikes per pile 

Piles 

per day 

Shutdown zone (m) 

LF MF HF PW OW 

Vibratory Installation ............. 20- and 24-inch ................... ≤30 min ................................ ≤10 30 30 30 30 30 

Vibratory Removal ................ 16- and 24-inch ................... 30 min .................................. 2 30 30 30 30 30 

Impact Installation ................. 20-inch ................................. 50 strikes ............................. 1 50 30 60 30 30 

50 strikes ............................. 2 80 30 90 1 40 30 

24-inch ................................. 50 strikes ............................. 1 70 30 80 40 30 

50 strikes ............................. 2 1 100 30 120 60 30 

DTH (Rock Socket) .............. 20- and 24-inch ................... 60 min .................................. 1 360 30 430 200 30 

120 min ................................ 1 570 30 2 500 310 30 

180 min ................................ 1 750 30 2 500 400 30 

240 min ................................ 1 1,000 40 2 500 2 400 40 

300 min ................................ 1 2 1,000 40 2 500 2 400 50 

360 min ................................ 1 2 1,000 50 2 500 2 400 50 

420 min ................................ 1 2 1,000 50 2 500 2 400 60 

480 min ................................ 1 2 1,000 60 2 500 2 400 60 

DTH (Tension Anchor) .......... 8-inch ................................... 60 min .................................. 1 40 30 50 30 30

120 min ................................ 1 60 30 70 40 30 

180 min ................................ 1 80 30 90 1 40 30 

240 min ................................ 1 100 30 110 30 30 

300 min ................................ 1 110 30 130 60 30 

360 min ................................ 1 120 30 150 70 30 

420 min ................................ 1 140 30 160 80 30 

480 min ................................ 1 150 30 180 80 30 

1The shutdown zone is equivalent to the Level A harassment distance. 

2The shutdown is smaller than the Level A harassment distance. 

• DOT&PF anticipates that the 

maximum number of piles to be 

installed and or the daily duration of 

pile driving or DTH use may vary 

significantly, with large differences in 

maximum zone sizes possible 


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depending on the work planned for a 

given day (Table 7). Given this 

uncertainty, DOT&PF will utilize a 

tiered system to identify and monitor 

the appropriate Level A harassment 

zones and shutdown zones on a daily 

basis, based on the maximum expected 

number of piles to be installed (impact 

or vibratory pile driving) or the 

maximum expected DTH duration for 

each day. At the start of each work day, 

DOT&PF will determine the maximum 

scenario for that day (according to the 

defined duration intervals in Tables 7 

and 9), which will determine the 

appropriate Level A harassment isopleth 

and associated shutdown zone for that 

day. This Level A harassment zone 

(Table 7) and associated shutdown zone 

(Table 9) must be observed by PSO(s) for 

the entire work day, regardless of 

whether DOT&&PF ultimately meets the 

anticipated scenario parameters for that 

day; 

• Marine mammals observed 

anywhere within visual range of the 

PSO will be tracked relative to 

construction activities. If a marine 

mammal is observed entering or within 

the shutdown zones indicated in Table 

9, pile driving or DTH activities must be 

delayed or halted. If pile driving or DTH 

activities are delayed or halted due to 

the presence of a marine mammal, the 

activity may not commence or resume 

until either the animal has voluntarily 

exited and been visually confirmed 

beyond the shutdown zone (Table 9) or 

15 minutes have passed without redetection of the animal; 

• Monitoring must take place from 30 

minutes prior to initiation of pile 

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

through 30 minutes post-completion of 

pile driving or DTH activity; 

• Pre-start clearance monitoring must 

be conducted during periods of 

visibility sufficient for the lead PSO to 

determine that the shutdown zones 

indicated in Table 9 are clear of marine 

mammals. Pile driving may commence 

following 30 minutes of observation 

when the determination is made that the 

shutdown zones are clear of marine 

mammals; 

• The DOT&PF must use soft start 

techniques when impact pile driving. 

Soft start requires contractors to provide 

an initial set of three strikes at reduced 

energy, followed by a 30-second waiting 

period, then two subsequent reduced 

energy strike sets. A soft start must be 

implemented at the start of each day’s 

impact pile driving and at any time 

following cessation of impact pile 

driving for a period of 30 minutes or 

longer. Soft starts will not be used for 

vibratory pile installation and removal 

or for DTH activities. PSOs shall begin 

observing for marine mammals 30 

minutes before ‘‘soft start’’ or in-water 

pile installation or removal begins; and 

• Pile driving activity must be halted 

upon observation of either a species for 

which incidental take is not authorized 

or a species for which incidental take 

has been authorized but the authorized 

number of takes has been met, entering 

or within the harassment zone. 

Based on our evaluation of the 

applicant’s mitigation measures, as well 

as other measures considered by NMFS, 

NMFS has determined that the 

mitigation measures provide the means 

of effecting the least practicable impact 

on the affected species or stocks and 

their habitat, paying particular attention 

to rookeries, mating grounds, areas of 

similar significance, and on the 

availability of such species or stock for 

subsistence uses. 

Monitoring and Reporting 

In order to issue an IHA for an 

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

MMPA states that NMFS must set forth 

requirements pertaining to the 

monitoring and reporting of such taking. 

The MMPA implementing regulations at 

50 CFR 216.104(a)(13) indicate that 

requests for authorizations must include 

the suggested means of accomplishing 

the necessary monitoring and reporting 

that will result in increased knowledge 

of the species and of the level of taking 

or impacts on populations of marine 

mammals that are expected to be 

present while conducting the activities. 

Effective reporting is critical both to 

compliance as well as ensuring that the 

most value is obtained from the required 

monitoring. 

Monitoring and reporting 

requirements prescribed by NMFS 

should contribute to improved 

understanding of one or more of the 

following: 

• Occurrence of marine mammal 

species or stocks in the area in which 

take is anticipated (e.g., presence, 

abundance, distribution, density); 

• Nature, scope, or context of likely 

marine mammal exposure to potential 

stressors/impacts (individual or 

cumulative, acute or chronic), through 

better understanding of: (1) action or 

environment (e.g., source 

characterization, propagation, ambient 

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

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

of marine mammal species with the 

activity; or (4) biological or behavioral 

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

feeding areas); 

• Individual marine mammal 

responses (behavioral or physiological) 

to acoustic stressors (acute, chronic, or 

cumulative), other stressors, or 

cumulative impacts from multiple 

stressors; 

• How anticipated responses to 

stressors impact either: (1) long-term 

fitness and survival of individual 

marine mammals; or (2) populations, 

species, or stocks; 

• Effects on marine mammal habitat 

(e.g., marine mammal prey species, 

acoustic habitat, or other important 

physical components of marine 

mammal habitat); and 

• Mitigation and monitoring 

effectiveness. 

Visual Monitoring 

Monitoring must be conducted by 

qualified, NMFS-approved PSOs, in 

accordance with the following: 

• PSOs must be independent of the 

activity contractor (e.g., employed by a 

subcontractor) and have no other 

assigned tasks during monitoring 

periods. At least one PSO must have 

prior experience performing the duties 

of a PSO during construction activity 

pursuant to a NMFS-issued IHA or 

Letter of Concurrence. Other PSOs may 

substitute other relevant experience, 

education (degree in biological science 

or related field), or training for prior 

experience performing the duties of a. 

PSOs must be approved by NMFS prior 

to beginning any activity subject to 

these IHAs; 

• DOT&PF must employ at least two 

PSOs during all pile driving and DTH 

activities. A minimum of one PSO must 

be assigned to the active pile driving or 

DTH location to monitor for marine 

mammals and implement shutdown/ 

delay procedures when applicable by 

calling for the shutdown to the hammer 

operator. At least one additional PSO is 

also required, and should be placed at 

the best practical vantage point(s) to 

ensure that the shutdown zones are 

fully monitored and as much as the 

Level B harassment zones are monitored 

as practicable; though the observation 

points may vary depending on the 

construction activity and location of the 

piles; 

• Where a team of three or more PSOs 

is required, a lead observer or 

monitoring coordinator must be 

designated. The lead observer must have 

prior experience performing the duties 

of a PSO during construction activity 

pursuant to a NMFS-issued incidental 

take authorization; 

• PSOs will use a hand-held GPS 

device, rangefinder, or reticle binoculars 

to verify the required monitoring 

distance from the project site; and 

• PSOs must record all observations 

of marine mammals, regardless of 

distance from the pile being driven. 

PSOs shall document any behavioral 


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reactions in concert with distance from 

piles being driven or removed. 

PSOs must have the following 

additional qualifications: 

• Ability to conduct field 

observations and collect data according 

to assigned protocols; 

• Experience or training in the field 

identification of marine mammals, 

including the identification of 

behaviors; 

• Sufficient training, orientation, or 

experience with the construction 

operation to provide for personal safety 

during observations; 

• Writing skills sufficient to record 

required information including but not 

limited to the number and species of 

marine mammals observed; dates and 

times when in-water construction 

activities were conducted; dates, times, 

and reason for implementation of 

mitigation (or why mitigation was not 

implemented when required); and 

marine mammal behavior; and 

• Ability to communicate orally, by 

radio or in person, with project 

personnel to provide real-time 

information on marine mammals 

observed in the area as necessary. 

Reporting 

A draft marine mammal monitoring 

report will be submitted to NMFS 

within 90 days after the completion of 

pile driving and DTH activities, or 60 

days prior to a requested date of 

issuance of any future IHAs for projects 

at the same location, whichever comes 

first. The reports will include an overall 

description of work completed, a 

narrative regarding marine mammal 

sightings, and associated PSO data 

sheets. Specifically, the reports must 

include: 

• Dates and times (begin and end) of 

all marine mammal monitoring; 

• Construction activities occurring 

during each daily observation period, 

including the number and type of piles 

driven or removed and by what method 

(i.e., impact, vibratory, or DTH) and the 

total equipment duration for vibratory 

installation, removal and DTH for each 

pile or total number of strikes for each 

pile (impact driving); 

• PSO locations during marine 

mammal monitoring; 

• Environmental conditions during 

monitoring periods (at beginning and 

end of PSO shift and whenever 

conditions change significantly), 

including Beaufort sea state and any 

other relevant weather conditions 

including cloud cover, fog, sun glare, 

and overall visibility to the horizon, and 

estimated observable distance; 

• Upon observation of a marine 

mammal, the following information: 

name of PSO who sighted the animal(s) 

and PSO location and activity at time of 

sighting; time of sighting; identification 

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

lowest possible taxonomic level, or 

unidentified), PSO confidence in 

identification, and the composition of 

the group if there is a mix of species; 

distance and bearing of each marine 

mammal observed relative to the pile 

being driven for each sighting (if pile 

driving was occurring at time of 

sighting); estimated number of animals 

(minimum, maximum, and best 

estimate); estimated number of animals 

by cohort (adults, juveniles, neonates, 

group composition, sex class, etc.); 

animal’s closest point of approach and 

estimated time spent within the 

harassment zone; description of any 

marine mammal behavioral observations 

(e.g., observed behaviors such as feeding 

or traveling), including an assessment of 

behavioral responses thought to have 

resulted from the activity (e.g., no 

response or changes in behavioral state 

such as ceasing feeding, changing 

direction, flushing, or breaching); 

• Number of marine mammals 

detected within the harassment zones 

and shutdown zones, by species; and 

• Detailed information about any 

implementation of any mitigation 

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

description of specific actions that 

ensued, and resulting changes in 

behavior of the animal(s), if any. 

If no comments are received from 

NMFS within 30 days, the draft final 

reports will constitute the final reports. 

If comments are received, a final report 

addressing NMFS comments must be 

submitted within 30 days after receipt of 

comments. 

Reporting Injured or Dead Marine 

Mammals 

In the event that personnel involved 

in the construction activities discover 

an injured or dead marine mammal, the 

IHA-holder must immediately cease the 

specified activities and report the 

incident to the Office of Protected 

Resources, NMFS 

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

and to the Alaska Regional Stranding 

Coordinator as soon as feasible. If the 

death or injury was clearly caused by 

the specified activity, the DOT&PF must 

immediately cease the specified 

activities until NMFS is able to review 

the circumstances of the incident and 

determine what, if any, additional 

measures are appropriate to ensure 

compliance with the terms of the IHAs. 

The DOT&PF must not resume their 

activities until notified by NMFS. The 

report must include the following 

information: 

• Time, date, and location (latitude 

and longitude) of the first discovery 

(and updated location information if 

known and applicable); 

• Species identification (if known) or 

description of the animal(s) involved; 

• Condition of the animal(s) 

(including carcass condition if the 

animal is dead); 

• Observed behaviors of the 

animal(s), if alive; 

• If available, photographs or video 

footage of the animal(s); and 

• General circumstances under which 

the animal was discovered. 

Negligible Impact Analysis and 

Determination 

NMFS has defined negligible impact 

as an impact resulting from the 

specified activity that cannot be 

reasonably expected to, and is not 

reasonably likely to, adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival 

(50 CFR 216.103). A negligible impact 

finding is based on the lack of likely 

adverse effects on annual rates of 

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

of takes alone is not enough information 

on which to base an impact 

determination. In addition to 

considering estimates of the number of 

marine mammals that might be ‘‘taken’’ 

through harassment, NMFS considers 

other factors, such as the likely nature 

of any impacts or responses (e.g., 

intensity, duration), the context of any 

impacts or responses (e.g., critical 

reproductive time or location, foraging 

impacts affecting energetics), as well as 

effects on habitat, and the likely 

effectiveness of the mitigation. We also 

assess the number, intensity, and 

context of estimated takes by evaluating 

this information relative to population 

status. Consistent with the 1989 

preamble for NMFS’ implementing 

regulations (54 FR 40338, September 29, 

1989), the impacts from other past and 

ongoing anthropogenic activities are 

incorporated into this analysis via their 

impacts on the baseline (e.g., as 

reflected in the regulatory status of the 

species, population size and growth rate 

where known, ongoing sources of 

human-caused mortality, or ambient 

noise levels). 

To avoid repetition, the majority of 

our analysis applies to all the species 

listed in Table 2, given that many of the 

anticipated effects of the DOT&PFs 

construction activities on different 

marine mammal stocks are expected to 

be relatively similar in nature. Where 

there are meaningful differences 

between species or stocks, or groups of 

species, in anticipated individual 


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responses to activities, impact of 

expected take on the population due to 

differences in population status, or 

impacts on habitat, they are described 

independently in the analysis below. 

Pile driving and DTH activities 

associated with the project, as outlined 

previously, have the potential to disturb 

or displace marine mammals. 

Specifically, the specified activities may 

result in take, in the form of Level B 

harassment and, for some species Level 

A harassment, from underwater sounds 

generated by pile driving and DTH 

systems. Potential takes could occur if 

marine mammals are present in zones 

ensonified above the thresholds for 

Level B harassment or Level A 

harassment, identified above, while 

activities are underway. 

The DOT&PF’s construction activities 

and associated impacts will occur 

within a limited, confined area of the 

stocks’ range. The work will occur in 

the vicinity of the seaplane dock 

immediately adjacent to Hydaburg and 

sound from the construction activities 

will be blocked by Sukkwan Island, 

Spook Island, Mushroom Island, and the 

coastline along Prince of Wales Island 

both southeast and northwest of the 

project site (see Figure 1–2 in the 

DOT&PF’s application) to a maximum 

distance of 5,162 m and area of 4.34 

km2. The intensity and duration of take 

by Level A harassment and Level B 

harassment will be minimized through 

use of mitigation measures described 

herein. Further the amount of take 

authorized is small when compared to 

stock abundance. In addition, NMFS 

does not anticipate that serious injury or 

mortality will occur as a result of the 

DOT&PF’s construction activities given 

the nature of the activity, even in the 

absence of required mitigation. 

Exposures to elevated sound levels 

produced during pile driving and DTH 

may cause behavioral disturbance of 

some individuals. Behavioral responses 

of marine mammals to pile driving, pile 

removal, and DTH systems at the project 

site are expected to be mild, short term, 

and temporary. Effects on individuals 

that are taken by Level B harassment, as 

enumerated in the Estimated Take 

section, on the basis of reports in the 

literature as well as monitoring from 

other similar activities, will likely be 

limited to reactions such as increased 

swimming speeds, increased surfacing 

time, or decreased foraging (if such 

activity were occurring) (e.g., Thorson 

and Reyff, 2006). Marine mammals 

within the Level B harassment zones 

may not show any visual cues they are 

disturbed by activities or they could 

become alert, avoid the area, leave the 

area, or display other mild responses 

that are not observable such as changes 

in vocalization patterns or increased 

haul out time (Thorson and Reyff, 2006). 

Additionally, some of the species 

present in the region will only be 

present temporarily based on seasonal 

patterns or during transit between other 

habitats. These temporarily present 

species will be exposed to even smaller 

periods of noise-generating activity, 

further decreasing the impacts. Most 

likely, individual animals will simply 

move away from the sound source and 

be temporarily displaced from the area, 

although even this reaction has been 

observed primarily only in association 

with impact pile driving. Because 

DOT&PF’s activities could occur during 

any season, takes may occur during 

important feeding times. The project 

area though represents a small portion 

of available foraging habitat and impacts 

on marine mammal feeding for all 

species should be minimal. 

The activities analyzed here are 

similar to numerous other construction 

activities conducted along southeastern 

Alaska (e.g., 86 FR 43190, August 6, 

2021; 87 FR 15387, March 18, 2022), 

which have taken place with no known 

long-term adverse consequences from 

behavioral harassment. These reactions 

and behavioral changes are expected to 

subside quickly when the exposures 

cease and, therefore, no such long-term 

adverse consequences should be 

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

intensity of Level B harassment events 

will be minimized through use of 

mitigation measures described herein, 

which were not quantitatively factored 

into the take estimates. The DOT&PF 

will use at least two PSOs stationed 

strategically to increase detectability of 

marine mammals during in-water pile 

driving and DTH activities, enabling a 

high rate of success in implementation 

of shutdowns to avoid or minimize 

injury for most species. Further, given 

the absence of any major rookeries and 

haulouts within the estimated 

harassment zones, we assume that 

potential takes by Level B harassment 

will have an inconsequential short-term 

effect on individuals and will not result 

in population-level impacts. 

As stated in the mitigation section, 

DOT&PF will implement shutdown 

zones that equal or exceed many of the 

Level A harassment isopleths shown in 

Table 9. Take by Level A harassment is 

authorized for some species (harbor 

seals, northern elephant seals, harbor 

porpoises, Dall’s porpoises, humpback 

whales, and minke whales) to account 

for the potential that an animal could 

enter and remain within the Level A 

harassment zone for a duration long 

enough to incur PTS. Any take by Level 

A harassment is expected to arise from, 

at most, a small degree of PTS because 

animals will need to be exposed to 

higher levels and/or longer duration 

than are expected to occur here in order 

to incur any more than a small degree 

of PTS. 

Due to the levels and durations of 

likely exposure, animals that experience 

PTS will likely only receive slight PTS, 

i.e., minor degradation of hearing 

capabilities within regions of hearing 

that align most completely with the 

frequency range of the energy produced 

by DOT&PF’s in-water construction 

activities (i.e., the low-frequency region 

below 2 kHz), not severe hearing 

impairment or impairment in the reigns 

of greatest hearing sensitivity. If hearing 

impairment does occur, it is most likely 

that the affected animal will lose a few 

dBs in its hearing sensitivity, which in 

most cases is not likely to meaningfully 

affect its ability to forage and 

communicate with conspecifics. There 

are no data to suggest that a single 

instance in which an animal accrues 

PTS (or TTS) and is subject to 

behavioral disturbance will result in 

impacts to reproduction or survival. If 

PTS were to occur, it will be at a lower 

level likely to accrue to a relatively 

small portion of the population by being 

a stationary activity in one particular 

location. Additionally, and as noted 

previously, some subset of the 

individuals that are behaviorally 

harassed could also simultaneously 

incur some small degree of TTS for a 

short duration of time. Because of the 

small degree anticipated, though, any 

PTS or TTS potentially incurred here is 

not expected to adversely impact 

individual fitness, let alone annual rates 

of recruitment or survival. 

Theoretically, repeated, sequential 

exposure to pile driving noise over a 

long duration could result in more 

severe impacts to individuals that could 

affect a population. However, the 

limited number of non-consecutive pile 

driving days for this project and the 

absence of any pinniped haulouts or 

other known cetacean residency 

patterns in the action area means that 

these types of impacts are not 

anticipated. 

For all species except humpback 

whales, there are no known BIAs near 

the project zone that will be impacted 

by DOT&PF’s planned activities. For 

humpback whales, the whole of 

southeast Alaska is a seasonal feeding 

BIA from May through September (Wild 

et al., 2023), however, Sukkwan Strait is 

a small passageway and represents a 

very small portion of the total available 

habitat. Also, while southeast Alaska is 

considered an important area for feeding 


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humpback during this time, it is not 

currently designated as critical habitat 

for humpback whales (86 FR 21082, 

April 21, 2021). 

The project is also not expected to 

have significant adverse effects on any 

marine mammal habitat. The project 

activities will not modify existing 

marine mammal habitat since the 

project will occur within the same 

footprint as existing marine 

infrastructure. Impacts to the immediate 

substrate are anticipated, but these will 

be limited to minor, temporary 

suspension of sediments, which could 

impact water quality and visibility for a 

short amount of time but which will not 

be expected to have any effects on 

individual marine mammals. 

In addition, impacts to marine 

mammal prey species are expected to be 

minor and temporary and to have, at 

most, short-term effects on foraging of 

individual marine mammals, and likely 

no effect on the populations of marine 

mammals as a whole. Overall, the area 

impacted by the project is very small 

compared to the available surrounding 

habitat, and does not include habitat of 

particular importance. The most likely 

impact to prey will be temporary 

behavioral avoidance of the immediate 

area. During construction activities, it is 

expected that some fish and marine 

mammals will temporarily leave the 

area of disturbance, thus impacting 

marine mammals’ foraging 

opportunities in a limited portion of the 

foraging range. But, because of the 

relatively small area of the habitat that 

may be affected, and lack of any habitat 

of particular importance, the impacts to 

marine mammal habitat are not 

expected to cause significant or longterm negative consequences. 

In summary and as described above, 

the following factors primarily support 

our determination that the impacts 

resulting from this activity are not 

expected to adversely affect any of the 

species or stocks through effects on 

annual rates of recruitment or survival: 

• No serious injury or mortality is 

anticipated or authorized; 

• Level A harassment authorized is 

expected to be of a lower degree that 

will not impact the fitness of any 

animals; 

• Anticipated incidents of Level B 

harassment consist of, at worst, 

temporary modifications in behavior; 

• The required mitigation measures 

(i.e., soft starts, shutdown zones) are 

expected to be effective in reducing the 

effects of the specified activity by 

minimizing the numbers of marine 

mammals exposed to injurious levels of 

sound, and by ensuring that any take by 

Level A harassment is, at most, a small 

degree of PTS; 

• The intensity of anticipated takes 

by Level B harassment is low for all 

stocks and will not be of a duration or 

intensity expected to result in impacts 

on reproduction or survival; 

• Minimal impacts to marine 

mammal habitat/prey are expected; 

• The only known area of specific 

biological importance covers a broad 

area of southeast Alaska for humpback 

whales, and the project area is a very 

small portion of that BIA. No other 

known areas of particular biological 

importance to any of the affected 

species or stocks are impacted by the 

activity, including ESA-designated 

critical habitat; 

• The project area represents a very 

small portion of the available foraging 

area for all potentially impacted marine 

mammal species and stocks and 

anticipated habitat impacts are minor; 

and 

• Monitoring reports from similar 

work in southeast Alaska have 

documented little to no effect on 

individuals of the same species 

impacted by 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 

monitoring and mitigation measures, 

NMFS finds that the total marine 

mammal take from the activity will have 

a negligible impact on all affected 

marine mammal species or stocks. 

Small Numbers 

As noted previously, only small 

numbers of incidental take may be 

authorized under section 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. 

The maximum annual amount of take 

NMFS proposes to authorize for five 

marine mammal stocks is below onethird of the estimated stock abundance 

for all species (in fact, take of 

individuals is less than six percent of 

the abundance of all affected stocks, see 

Table 8). The number of animals 

authorized to be taken from these stocks 

will be considered small relative to the 

relevant stock’s abundances even if each 

estimated take occurred to a new 

individual. Some individuals may 

return multiple times in a day, but PSOs 

will count them as separate individuals 

if they cannot be individually 

identified. 

The Alaska stock of Dall’s porpoise 

has no official NMFS abundance 

estimate for this area, as the most recent 

estimate is greater than eight years old. 

Abundance estimates for Dall’s porpoise 

in inland waters of southeast Alaska 

were calculated from 19 line-transect 

vessel surveys from 1991 to 2012 

(Jefferson et al., 2019). Abundance 

across the whole period was estimated 

at 5,381 (CV = 0.25), 2,680 (CV = 0.20), 

and 1,637 (CV = 0.23) in the spring, 

summer, and fall, respectively (Jefferson 

et al., 2019). The minimum population 

estimate (NMIN) for the entire Alaska 

stock is assumed to correspond to the 

point estimate of a 2015 vessel-based 

abundance computed by Rone et al. 

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

CV = 0.22) (Muto et al., 2022); however, 

the study area of this survey 

corresponds to a small fraction of the 

range of the stock and, thus it is 

reasonable to assume that the stock size 

is equal to or greater than that estimate 

(Muto et al., 2022). Therefore, the 22 

takes of this stock authorized clearly 

represent small numbers of this stock. 

The abundance estimate for the 

Mexico-North Pacific stock of 

humpback whales is also considered to 

be unknown as estimates are based on 

data collected more than 15 years ago 

(Young et al., 2023). A multi-strata 

mark-recapture analysis of data from 

2004 through 2006 resulted in an 

abundance estimate of 5,890 (CV = 

0.075) humpbacks for Southeast Alaska 

and northern British Columbia (Wade 

2021); however, this estimate represents 

a mixture of whales from up to three 

winter areas (the western North Pacific 

(Asia), Hawaii, and Mexico), and thus 

does not represent the abundance of just 

the Mexico-North Pacific stock in its 

summer areas. The number of animals 

in the feeding areas belonging to the 

Mexico-North Pacific stock was 

determined by multiplying the 

abundance estimate for each feeding 

area (i.e., Bering Sea and Aleutian 

Islands, Gulf of Alaska, and Southeast 

Alaska and northern British Columbia) 

by the probability of movement between 

that feeding area and the Mexican 

wintering area, as estimated by Wade 


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(2021), and then adding those estimates 

together. This resulted in an estimate of 

918 animals (CV = 0.217) and an NMIN

estimate of 766 animals for this stock 

(Young et al., 2023). While the 

abundance trend for this stock is 

unclear; the 32 takes authorized 

represent small numbers of this stock 

based on this available data. 

There is also no current or historical 

estimate of the Alaska minke whale 

stock, but minke whale abundance has 

been estimated to be over 1,000 whales 

in portions of Alaska (Muto et al., 2022) 

so the 3 takes authorized represent 

small numbers of this stock. 

Additionally, the range of the Alaska 

stock of minke whales is extensive, 

stretching from the Canadian Pacific 

coast to the Chukchi Sea, and DOT&PF’s 

project area impacts a small portion of 

this range. Therefore, the three takes of 

minke whale authorized is small 

relative to estimated survey abundance, 

even if each authorized take occurred to 

a new individual. 

Based on the analysis contained 

herein of the construction activity 

(including the mitigation and 

monitoring measures) and the 

anticipated take of marine mammals, 

NMFS 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 the 

specified activity: (1) that is likely to 

reduce the availability of the species to 

a level insufficient for a harvest to meet 

subsistence needs by: (i) causing the 

marine mammals to abandon or avoid 

hunting areas; (ii) directly displacing 

subsistence users; or (iii) placing 

physical barriers between the marine 

mammals and the subsistence hunters; 

and (2) that cannot be sufficiently 

mitigated by other measures to increase 

the availability of marine mammals to 

allow subsistence needs to be met. 

Alaska Natives have traditionally 

harvested subsistence resources in 

southeast Alaska for many hundreds of 

years, particularly large terrestrial 

mammals, marine mammals, salmon, 

and other fish (Alaska Department of 

Fish and Game (ADF&G), 1997). Harbor 

seals and sea otters are reported to be 

the marine mammal species most 

regularly harvested for subsistence in 

the waters surrounding Hydaburg 

(NOAA, 2013). An estimated 14.4 

harbor seals were harvested by 

Hydaburg residents every year from 

2000 through 2008 (ADF&G, 2009a, 

2009b). Hunting usually occurs in the 

late fall and winter (ADF&G, 2009a). 

The ADF&G has not recorded harvest of 

cetaceans from Hydaburg (ADF&G, 

2022). There are no subsistence 

activities near the project that target 

humpback whales, and subsistence 

hunters rarely target Steller sea lions 

near the project area. 

Approximately 93 percent of 

Hydaburg residents identified as Alaska 

Native (Sill and Koster, 2017) in 2012. 

Nearly half of all households harvested 

wild resources in 2012, with nearly all 

Hydaburg households using salmon, 

non-salmon fish, marine invertebrates, 

and vegetation (Sill and Koster, 2017). 

Only six percent of Hydaburg 

households participated in the hunting, 

use, or receiving of harbor seals in 2012, 

whereas up to eight percent used sea 

otters (Sill and Koster, 2017). Based on 

data from 2012, marine mammals 

account for approximately one percent 

(1,666 pounds or 756 kg) of all 

subsistence harvest in Hydaburg (Sill 

and Koster, 2017). 

All pile driving and DTH activities 

will take place in the vicinity of 

seaplane dock immediately adjacent to 

Hydaburg where subsistence activities 

do not generally occur. The project will 

not have an adverse impact on the 

availability of marine mammals for 

subsistence use at locations farther 

away. Some minor, short-term 

disturbance of the harbor seals or sea 

otters could occur, but this is not likely 

to have any measurable effect on 

subsistence harvest activities in the 

region. No changes to availability of 

subsistence resources will result from 

the specified activities. Additionally, 

DOT&PF is working with Haida Elders 

on the project to raise awareness and 

collaborate on the project within the 

local community. 

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 

mitigation and monitoring measures, 

NMFS has determined that there will 

not be an unmitigable adverse impact on 

subsistence uses from the DOT&PF’s 

construction activities. 

Endangered Species Act 

Section 7(a)(2) of the 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 NMFS’ Alaska Regional 

Office (AKRO). 

There is one marine mammal species 

(Mexico DPS humpback whales) with 

confirmed occurrence in the project area 

that is listed as threatened under the 

ESA. AKRO issued a Biological Opinion 

on December 19, 2023 under section 7 

of the ESA, on the issuance of an IHA 

to the DOT&PF under section 

101(a)(5)(D) of the MMPA by the NMFS 

Office of Protected Resources. The 

Biological Opinion concluded that the 

proposed action is not likely to 

jeopardize the continued existence of 

Mexico DPS humpback whales. 

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 action 

(i.e., the issuance of an IHA) with 

respect to potential impacts on the 

human environment. 

This action is consistent with 

categories of activities identified in 

Categorical Exclusion B4 (IHAs with no 

anticipated serious injury or mortality) 

of the Companion Manual for NAO 216– 

6A, which do not individually or 

cumulatively have the potential for 

significant impacts on the quality of the 

human environment and for which we 

have not identified any extraordinary 

circumstances that will preclude this 

categorical exclusion. Accordingly, 

NMFS has determined that the issuance 

of the IHA qualifies to be categorically 

excluded from further NEPA review. 

Authorization 

NMFS has issued an IHA to the 

DOT&PF for the potential harassment of 

small numbers of nine marine mammal 

species incidental to the Hydaburg 

Seaplane Base Refurbishment Project in 

Hydaburg, Alaska, that includes the 

previously explained mitigation, 

monitoring and reporting requirements. 

Dated: January 3, 2024. 

Kimberly Damon-Randall, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2024–00189 Filed 1–8–24; 8:45 am] 

BILLING CODE 3510–22–P 


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