Federal Register / Vol. 87, No. 53 / Friday, March 18, 2022 / Notices 15387 

Additional Access to Materials 

You may request a CD of the Draft RP/ 

EA #8 (see FOR FURTHER INFORMATION

CONTACT above). Copies of the Draft RP/ 

EA #8 are also available during the 

public comment period at the following 

locations: 

Library Address City Zip code 

St. Tammany Parish Library .................................. 310 W. 21st Avenue .............................................. Covington ....................... 70433 

New Orleans Public Library, Louisiana Division .... 219 Loyola Avenue ................................................ New Orleans .................. 70112 

St. Bernard Parish Library ...................................... 1125 E. St. Bernard Highway ................................ Chalmette ....................... 70043 

Plaquemines Parish Library ................................... 8442 Highway 23 ................................................... Belle Chasse .................. 70037 

Jefferson Parish Library, East Bank Regional Library.4747 W. Napoleon Avenue .................................... Metairie .......................... 70001 

Jefferson Parish Library, West Bank Regional Library.2751 Manhattan Boulevard .................................... Harvey ............................ 70058 

Terrebonne Parish Library ..................................... 151 Library Drive .................................................... Houma ........................... 70360 

Martha Sowell Utley Memorial Library ................... 314 St. Mary Street ................................................ Thibodaux ...................... 70301 

South Lafourche Public Library .............................. 16241 E. Main Street ............................................. Cut Off ........................... 70345 

East Baton Rouge Parish Library .......................... 7711 Goodwood Boulevard ................................... Baton Rouge .................. 70806 

Alex P. Allain Library .............................................. 206 Iberia Street .................................................... Franklin .......................... 70538 

St. Martin Parish Library ........................................ 201 Porter Street .................................................... St. Martinville ................. 70582 

Iberia Parish Library ............................................... 445 E. Main Street ................................................. New Iberia ...................... 70560 

Vermilion Parish Library ......................................... 405 E. St. Victor Street .......................................... Abbeville ........................ 70510 

Mark Shirley, LSU AgCenter .................................. 1105 West Port Street ........................................... Abbeville ........................ 70510 

Calcasieu Parish Public Library Central Branch .... 301 W. Claude Street ............................................ Lake Charles .................. 70605 

Translation Opportunities 

Vietnamese translated materials 

including the Executing Summary and 

project fact sheets are posted in the 

‘‘News’’ section of the Louisiana TIG’s 

website: http://

www.gulfspillrestoration.noaa.gov/ 

restoration-areas/louisiana. 

Administrative Record 

The documents comprising the 

Administrative Record for the Draft RP/ 

EA #8 can be viewed electronically at 

http://www.doi.gov/deepwaterhorizon/ 

adminrecord. 

Authority 

The authority of this action is the Oil 

Pollution Act of 1990 (33 U.S.C. 2701 et 

seq.) and its implementing Oil Pollution 

Act Natural Resource Damage 

Assessment regulations found at 15 CFR 

part 990 and the National 

Environmental Policy Act of 1969 (42 

U.S.C. 4321 et seq.). 

Dated: March 11, 2022. 

Carrie Diane Robinson, 

Director, Office of Habitat Conservation, 

National Marine Fisheries Service. 

[FR Doc. 2022–05553 Filed 3–17–22; 8:45 am] 

BILLING CODE 3510–22–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XB799] 

Takes of Marine Mammals Incidental to 

Specified Activities; Taking Marine 

Mammals Incidental to Ferry Berth 

Improvements in Tongass Narrows in 

Ketchikan, Alaska 

AGENCY: National Marine Fisheries 

Service (NMFS), National Oceanic and 

Atmospheric Administration (NOAA), 

Commerce. 

ACTION: Notice; 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 (ADOT) to 

incidentally harass, by Level A 

harassment and Level B harassment 

only, marine mammals during 

construction activities associated with 

construction of four ferry berth facilities 

in Tongass Narrows in Ketchikan, 

Alaska. 

DATES: This authorization is effective 

from March 5, 2022 through March 4, 

2023. 

FOR FURTHER INFORMATION CONTACT: 

Leah Davis, Office of Protected 

Resources, NMFS, (301) 427–8401. 

Electronic copies of the application and 

supporting documents, as well as a list 

of the references cited in this document, 

may be obtained online at: https://

www.fisheries.noaa.gov/permit/ 

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

of problems accessing these documents, 

please call the contact listed above. 

SUPPLEMENTARY INFORMATION: 

Background 

The MMPA prohibits the ‘‘take’’ of 

marine mammals, with certain 

exceptions. sections 101(a)(5)(A) and (D) 

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

direct the Secretary of Commerce (as 

delegated to NMFS) to allow, upon 

request, the incidental, but not 

intentional, taking of small numbers of 

marine mammals by U.S. citizens who 

engage in a specified activity (other than 

commercial fishing) within a specified 

geographical region if certain findings 

are made and either regulations are 

issued or, if the taking is limited to 

harassment, a notice of a proposed 

incidental take authorization may be 

provided to the public for review. 

Authorization for incidental takings 

shall be granted if NMFS finds that the 

taking will have a negligible impact on 

the species or stock(s) and will not have 

an unmitigable adverse impact on the 

availability of the species or stock(s) for 

taking for subsistence uses (where 

relevant). Further, NMFS must prescribe 

the permissible methods of taking and 

other ‘‘means of effecting the least 

practicable adverse impact’’ on the 

affected species or stocks and their 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance, and on the 

availability of the species or stocks for 

taking for certain subsistence uses 

(referred to in shorthand as 


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‘‘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. 

Summary of Request 

On August 19, 2021, NMFS received 

a request from the ADOT for an IHA to 

take marine mammals incidental to the 

construction of two ferry berth facilities 

in Tongass Narrows in Ketchikan, 

Alaska: The Gravina Airport Ferry 

Layup Facility and the Gravina Freight 

Facility. On December 17, 2021 we 

received a revised request that included 

additional work components associated 

with the Revilla New Ferry Berth and 

Upland Improvements and the New 

Gravina Island Shuttle Ferry Berth and 

Related Terminal Improvements in the 

same region. The application was 

deemed adequate and complete on 

January 4, 2022. ADOT’s request is for 

take of a small number of eight species 

of marine mammals, by Level B 

harassment and Level A harassment. Of 

those eight species, five (Steller sea lion 

(Eumetopias jubatus), harbor seal 

(Phoca vitulina richardii), harbor 

porpoise (Phocoena phocoena), Dall’s 

porpoise (Phocoenoides dalli) and 

minke whale (Balaenoptera 

acutorostrata)) may also be taken by 

Level A harassment. Neither ADOT nor 

NMFS expects serious injury or 

mortality to result from this activity 

and, therefore, an IHA is appropriate. 

NMFS previously issued two 

consecutive IHAs and a Renewal IHA to 

ADOT for this work (85 FR 673, January 

7, 2020; 86 FR 23938, May 05, 2021). 

ADOT complied with all the 

requirements (e.g., mitigation, 

monitoring, and reporting) of the 

previous IHAs and information 

regarding their monitoring results may 

be found in the Description of Marine 

Mammals in the Area of Specified 

Activities and Marine Mammal 

Occurrence and Take Calculation and 

Estimation sections. An IHA for the first 

phase of construction of the KetchikanGravina Access Project was issued to 

ADOT on December 20, 2019 (85 FR 

673, January 7, 2020). Complete 

construction of two of those 

components, the Revilla New Ferry 

Berth and Upland Improvements and 

Gravina Island Shuttle Ferry Berth 

Facility/Related Terminal 

Improvements, did not occur within the 

timeframe authorized by the Phase 1 

IHA and will not be finished before the 

expiration of the subsequent one-year 

renewal (86 FR 23938, May 05, 2021). 

Therefore, ADOT requested a new IHA 

for incidental take associated with the 

continued marine construction of these 

facilities. 

Description of the Specified Activity 

ADOT is making improvements to 

existing ferry berths and constructing 

new ferry berths on Gravina Island and 

Revillagigedo (Revilla) Island in 

Tongass Narrows, near Ketchikan in 

southeast Alaska (Figure 1 of proposed 

IHA; 87 FR 5980; February 2, 2022). 

These ferry facilities provide the only 

public access between the city of 

Ketchikan, AK on Revilla Island, and 

the Ketchikan International Airport on 

Gravina Island. The project’s planned 

activities that have the potential to take 

marine mammals, by Level A 

harassment and Level B harassment, 

include vibratory and impact pile 

driving, down-the-hole (DTH) 

operations for pile installation (rock 

socketing of piles and tension anchors 

to secure piles), and vibratory pile 

removal. The marine construction 

associated with the activities is planned 

to occur over 91 non-consecutive days 

over one year beginning March 2022. 

A detailed description of the planned 

construction project is provided in the 

Federal Register notice for the proposed 

IHA (87 FR 5980; February 2, 2022). 

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. 

Comments and Responses 

A notice of NMFS’ proposal to issue 

an IHA to ADOT was published in the 

Federal Register on February 2, 2022 

(87 FR 5980). That notice described, in 

detail, ADOT’s activity, the marine 

mammal species that may be affected by 

the activity, and the anticipated effects 

on marine mammals. During the 30-day 

public comment period, NMFS did not 

receive any public comments. 

Description of Marine Mammals in the 

Area of Specified Activities 

Sections 3 and 4 of the application 

summarize available information 

regarding status and trends, distribution 

and habitat preferences, and behavior 

and life history, of the potentially 

affected species. Additional information 

regarding population trends and threats 

may be found in NMFS’ Stock 

Assessment Reports (SARs; https://

www.fisheries.noaa .gov/national/ 

marine-mammal-protection/marinemammal-stock-assessments) and more 

general information about these species 

(e.g., physical and behavioral 

descriptions) may be found on NMFS’ 

website (https://www.fisheries.noaa 

.gov/find-species). 

Table 1 lists all species or stocks for 

which take is expected and proposed to 

be authorized for this specified 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. For taxonomy, we follow 

Committee on Taxonomy (2021). 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 

mortality is anticipated or authorized 

here, PBR and annual serious injury and 

mortality from anthropogenic sources 

are included here as gross indicators of 

the status of the species and other 

threats. 

Marine mammal abundance estimates 

presented in this document represent 

the total number of individuals that 

make up a given stock or the total 

number estimated within a particular 

study or survey area. NMFS’ stock 

abundance estimates for most species 

represent the total estimate of 

individuals within the geographic area, 

if known, that comprises that stock. For 

some species, this geographic area may 

extend beyond U.S. waters. All managed 

stocks in this region are assessed in 

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

al. 2021). All values presented in Table 

1 are the most recent available at the 

time of publication and are available in 

the draft 2021 SARs (Muto et al. 2021; 

available online at: https://

www.fisheries.noaa.gov/national/ 

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


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TABLE 1—MARINE MAMMAL SPECIES OR STOCKS FOR WHICH TAKE IS EXPECTED AND AUTHORIZED

Common name Scientific name MMPA stock 

ESA/ 

MMPA 

status; 

strategic 

(Y/N) 1

Stock 

abundance 

Nbest, 

(CV; Nmin; most recent 

abundance survey) 2

PBR Annual 

M/SI 3

Order Cetartiodactyla—Cetacea—Superfamily Mysticeti (baleen whales) 

Family Balaenidae: 

Humpback whale ................ Megaptera novaeangliae .......... Central North Pacific ................. E, D, Y 10,103 (0.3; 7,890; 2006) 83 26 

Minke whale ........................ Balaenoptera acutorostrata ...... Alaska ....................................... -, N N.A. (See SAR; N.A.; 

see SAR).

UND 0 

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

Family Delphinidae: 

Killer whale ......................... Orcinus orca ............................. Alaska Resident ........................ -, N 2,347 (N.A.; 2,347; 2012) 24 1 

West Coast Transient ............... -, N 349 (N.A, 349; 2018) ...... 3.5 *0.4 

Northern Resident ..................... -, N 302 (N.A.; 302; 2018 ...... 2.2 0.2 

Pacific white-sided dolphin Lagenorhynchus obliquidens .... North Pacific ............................. -,-; N 26,880 (N.A.; N.A.; 1990) UND 0 

Family Phocoenidae: 

Harbor porpoise .................. Phocoena phocoena ................. Southeast Alaska ...................... -, Y See SAR (see SAR; see 

SAR; 2012).

See SAR 34 

Dall’s porpoise .................... Phocoenoides dalli .................... Alaska ....................................... -, N See SAR (see SAR; see 

SAR; 2015).

See SAR 37 

Order Carnivora—Superfamily Pinnipedia 

Family Otariidae (eared seals 

and sea lions): 

Steller sea lion .................... Eumetopias jubatus .................. Eastern U.S. ............................. -,-, N 43,201 (see SAR; 

43,201; 2017).

2,592 112 

Family Phocidae (earless seals): 

Harbor seal ......................... Phoca vitulina richardii .............. Clarence Strait .......................... -, N 27,659 (See SAE; 

24,854; 2015).

746 40 

1Endangered Species Act (ESA) status: Endangered (E), Threatened (T)/MMPA status: Depleted (D). A dash (-) indicates that the species is not listed under the 

ESA or designated as depleted under the MMPA. Under the MMPA, a strategic stock is one for which the level of direct human-caused mortality exceeds PBR or 

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

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

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

All species that could potentially 

occur in the project area are included in 

Table 3–1 of ADOT’s IHA application. 

However, the spatial occurrence of gray 

whale and fin whale is such that take is 

not expected to occur, and they are not 

discussed further beyond the 

explanation provided here. Gray whales 

have not been reported by any local 

experts or recorded in monitoring 

reports and it would be extremely 

unlikely for a gray whale to enter 

Tongass Narrows or the small portions 

of Revillagigedo Channel this project 

will impact. Similarly for fin whale, 

sightings have not been reported and it 

would be unlikely for a fin whale to 

enter the project area as they are 

generally associated with deeper, more 

offshore waters. The eight species (with 

10 managed stocks) in Table 1 

temporally and spatially co-occur with 

the activity to the degree that take is 

reasonably likely to occur, and we have 

authorized it. 

A detailed description of the of the 

species likely to be affected by ADOT’s 

project, including brief introductions to 

the species and relevant stocks 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 (87 FR 

5980; February 2, 2022); since that time, 

we are not aware of any changes in the 

status of these species and stocks; 

therefore, detailed descriptions are not 

provided here. Please refer to that 

Federal Register notice for these 

descriptions. Please also refer to NMFS’ 

website (https://www.fisheries.noaa 

.gov/find-species) for generalized 

species accounts. 

Marine Mammal Hearing 

Hearing is the most important sensory 

modality for marine mammals 

underwater, and exposure to 

anthropogenic sound can have 

deleterious effects. To appropriately 

assess the potential effects of exposure 

to sound, it is necessary to understand 

the frequency ranges marine mammals 

are able to hear. Current data indicate 

that not all marine mammal species 

have equal hearing capabilities (e.g., 

Richardson et al. 1995; Wartzok and 

Ketten, 1999; Au and Hastings, 2008). 

To reflect this, Southall et al. (2007) 

recommended that marine mammals be 

divided into functional hearing groups 

based on directly measured or estimated 

hearing ranges on the basis of available 

behavioral response data, audiograms 

derived using auditory evoked potential 

techniques, anatomical modeling, and 

other data. Note that no direct 

measurements of hearing ability have 

been successfully completed for 

mysticetes (i.e., low-frequency 

cetaceans). Subsequently, NMFS (2018) 

described generalized hearing ranges for 

these marine mammal hearing groups. 

Generalized hearing ranges were chosen 

based on the approximately 65 decibel 

(dB) threshold from the normalized 

composite audiograms, with the 

exception for lower limits for lowfrequency cetaceans where the lower 

bound was deemed to be biologically 

implausible and the lower bound from 

Southall et al. (2007) retained. Marine 

mammal hearing groups and their 

associated hearing ranges are provided 

in Table 2. 


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TABLE 2—MARINE MAMMAL HEARING GROUPS

[NMFS, 2018] 

Hearing group Generalized hearing 

range * 

Low-frequency (LF) cetaceans (baleen whales) ..................................................................................................................... 7 Hz to 35 kHz. 

Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales) ........................................... 150 Hz to 160 kHz. 

High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, cephalorhynchid, Lagenorhynchus cruciger & L. 

australis).

275 Hz to 160 kHz. 

Phocid pinnipeds (PW) (underwater) (true seals) ................................................................................................................... 50 Hz to 86 kHz. 

Otariid pinnipeds (OW) (underwater) (sea lions and fur seals) .............................................................................................. 60 Hz to 39 kHz. 

* Represents the generalized hearing range for the entire group as a composite (i.e., all species within the group), where individual species’ 

hearing ranges are typically not as broad. Generalized hearing range chosen based on ∼65 dB threshold from normalized composite audiogram, 

with the exception for lower limits for LF cetaceans (Southall et al. 2007) and PW pinniped (approximation). 

The pinniped functional hearing 

group was modified from Southall et al. 

(2007) on the basis of data indicating 

that phocid species have consistently 

demonstrated an extended frequency 

range of hearing compared to otariids, 

especially in the higher frequency range 

(Hemila ̈ et al. 2006; Kastelein et al. 

2009; Reichmuth and Holt, 2013). 

For more detail concerning these 

groups and associated frequency ranges, 

please see NMFS (2018) for a review of 

available information. Eight marine 

mammal species (six cetacean and two 

pinniped (one otariid and one phocid) 

species) have the reasonable potential to 

co-occur with the planned activities. 

Please refer to Table 1. Of the cetacean 

species that may be present, two are 

classified as low-frequency cetaceans 

(i.e., all mysticete species), two are 

classified as mid-frequency cetaceans 

(i.e., all delphinid and ziphiid species 

and the sperm whale), and two are 

classified as high-frequency cetaceans 

(i.e., harbor porpoise, Dall’s porpoise 

and Kogia spp.). 

Potential Effects of Specified Activities 

on Marine Mammals and Their Habitat 

The effects of underwater noise from 

the ADOT’s activities have the potential 

to result in take of marine mammals by 

Level B harassment and Level A 

harassment in the vicinity of the survey 

area. The notice of proposed IHA (87 FR 

5980; February 2, 2022) included a 

discussion of the effects of 

anthropogenic noise on marine 

mammals and the potential effects of 

underwater noise from ADOT’s 

construction activities on marine 

mammals and their habitat. That 

information and analysis is incorporated 

by reference into this final IHA and is 

not repeated here; please refer to the 

notice of the proposed IHA (87 FR 5980; 

February 2, 2022). 

The Estimated Take section in this 

document includes a quantitative 

analysis of the number of individuals 

that are expected to be taken by this 

activity. The Negligible Impact Analysis 

and Determination section considers the 

content of this section, the Estimated 

Take section, and the Mitigation 

Measures section, to draw conclusions 

regarding the likely impacts of these 

activities on the reproductive success or 

survivorship of individuals and how 

those impacts on individuals are likely 

to impact marine mammal species or 

stocks. We also provided additional 

description of sound sources in our 

notice of proposed IHA (87 FR 5980; 

February 2, 2022). 

Estimated Take 

This section provides an estimate of 

the number of incidental takes 

authorized through this IHA, which will 

inform both NMFS’ consideration of 

‘‘small numbers’’ and the negligible 

impact determination. 

Harassment is the only type of take 

expected to result from these activities. 

Except with respect to certain activities 

not pertinent here, section 3(18) of the 

MMPA defines ‘‘harassment’’ as any act 

of pursuit, torment, or annoyance, 

which (i) has the potential to injure a 

marine mammal or marine mammal 

stock in the wild (Level A harassment); 

or (ii) has the potential to disturb a 

marine mammal or marine mammal 

stock in the wild by causing disruption 

of behavioral patterns, including, but 

not limited to, migration, breathing, 

nursing, breeding, feeding, or sheltering 

(Level B harassment). 

Authorized takes will primarily be by 

Level B harassment, as use of the 

acoustic sources (i.e., impact and 

vibratory pile driving and DTH) have 

the potential to result in disruption of 

behavioral patterns for individual 

marine mammals. There is also some 

potential for auditory injury (Level A 

harassment) to result, primarily for 

mysticetes, high frequency species and 

phocids because predicted auditory 

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

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

required mitigation and monitoring 

measures are expected to minimize the 

severity of such taking to the extent 

practicable. 

As described previously, no mortality 

is anticipated or authorized for this 

activity. Below we describe how the 

take is estimated. 

Generally speaking, we estimate take 

by considering: (1) Acoustic thresholds 

above which NMFS believes the best 

available science indicates marine 

mammals will be behaviorally harassed 

or incur some degree of permanent 

hearing impairment; (2) the area or 

volume of water that will be ensonified 

above these levels in a day; (3) the 

density or occurrence of marine 

mammals within these ensonified areas; 

and, (4) and the number of days of 

activities. We note that while these 

basic factors can contribute to a basic 

calculation to provide an initial 

prediction of takes, additional 

information that can qualitatively 

inform take estimates is also sometimes 

available (e.g., previous monitoring 

results or average group size). Below, we 

describe the factors considered here in 

more detail and present the take 

estimate. 

Acoustic Thresholds 

NMFS recommends the use of 

acoustic thresholds that identify the 

received level of underwater sound 

above which exposed marine mammals 

would be reasonably expected to be 

behaviorally harassed (equated to Level 

B harassment) or to incur PTS of some 

degree (equated to Level A harassment). 

Level B Harassment for non-explosive 

sources—Though significantly driven by 

received level, the onset of behavioral 

disturbance from anthropogenic noise 

exposure is also informed to varying 

degrees by other factors related to the 

source (e.g., frequency, predictability, 

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

bathymetry), and the receiving animals 

(hearing, motivation, experience, 

demography, behavioral context) and 


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can be difficult to predict (Southall et al. 

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

the available science indicates and the 

practical need to use a threshold based 

on a factor that is both predictable and 

measurable for most activities, NMFS 

uses a generalized acoustic threshold 

based on received level to estimate the 

onset of behavioral harassment. NMFS 

predicts that marine mammals are likely 

to be behaviorally harassed in a manner 

we consider Level B harassment when 

exposed to underwater anthropogenic 

noise above received levels of 120 dB re 

1 microPascal (mPa) (root mean square 

(rms)) for continuous (e.g., vibratory 

pile-driving, DTH) and above 160 dB re 

1 mPa (rms) for non-explosive impulsive 

(e.g., seismic airguns) or intermittent 

(e.g., scientific sonar) sources. This take 

estimation includes disruption of 

behavioral patterns resulting directly in 

response to noise exposure (e.g., 

avoidance), as well as that resulting 

indirectly from associated impacts such 

as TTS or masking. ADOT’s planned 

activity includes the use of continuous 

(vibratory pile driving/removal and 

DTH) and impulsive (impact pile 

driving and DTH) sources, and therefore 

both the 120 and 160 dB re 1 mPa (rms) 

thresholds are applicable. 

Level A harassment for non-explosive 

sources—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). ADOT’s planned activity 

includes the use of impulsive (impact 

pile driving and DTH) and nonimpulsive (vibratory pile driving/ 

removal and DTH) sources. 

These thresholds are provided in 

Table 3 below. The references, analysis, 

and methodology used in the 

development of the thresholds are 

described in NMFS 2018 Technical 

Guidance, which may be accessed at 

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

national/marine-mammal-protection/ 

marine-mammal-acoustic-technicalguidance. 

TABLE 3—THRESHOLDS IDENTIFYING THE ONSET OF PERMANENT THRESHOLD SHIFT

Hearing group 

PTS onset acoustic thresholds * 

(received level) 

Impulsive Non-impulsive 

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

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

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

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

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

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

also be considered. 

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

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

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

included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated 

with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF 

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

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

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

Ensonified Area 

Here, we describe operational and 

environmental parameters of the activity 

that will feed into identifying the area 

ensonified above the acoustic 

thresholds, which include source levels 

and transmission loss coefficient. 

The 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 driving, vibratory pile 

driving, vibratory pile removal, and 

DTH). 

In order to calculate distances to the 

Level A harassment and Level B 

harassment sound thresholds for the 

methods and piles being used in this 

project, NMFS used acoustic monitoring 

data from other locations to develop 

source levels for the various pile types, 

sizes and methods (Table 4). Note that 

piles of differing sizes have different 

sound source levels (SSLs). 

Empirical data from recent ADOT 

sound source verification (SSV) studies 

at Ketchikan were used to estimate SSLs 

for vibratory and impact driving of 30- 

inch steel pipe piles (Denes et al. 2016). 

Data from Ketchikan was used because 

of its proximity to this project in 

Tongass Narrows. However, the use of 

data from Alaska sites was not 

appropriate in all instances. Details are 

described below. 

For vibratory driving of 24-inch steel 

piles, data from a Navy pile driving 

project in the Puget Sound, WA was 

reviewed (Navy 2015). From this 

review, ADOT determined the Navy’s 

suggested source value of 161 decibels 

(dB) root mean squared (rms) was an 

appropriate proxy source value, and 

NMFS concurs. Because the source 

value of smaller piles of the same 

general type (steel in this case) are not 

expected to exceed a larger pile, the 

same 161 dB rms source value was used 

for 20-inch steel piles. This assumption 

conforms with source values presented 

in Navy (2015) for a project using 16- 

inch steel piles at Naval Base Kitsap in 

Bangor, WA. 

ADOT used source values of 177 dB 

sound exposure level (SEL) and 190 dB 

rms for impact driving of 24-inch and 

20-inch steel piles. These values were 

determined based on summary values 

presented in Caltrans (2015) for impact 

driving of 24-inch steel piles. NMFS 

concurs that the same source value was 

an acceptable proxy for impact driving 

of 20-inch steel piles. 

Sound pressure levels in the water 

column resulting from DTH are not well 

studied. Because DTH hole creation 

includes both impulsive and continuous 

components, NMFS guidance currently 

recommends that it be treated as a 

continuous sound for Level B 

calculations and as an impulsive sound 

for Level A calculations (Table 10). In 

the absence of data specific to different 

hole sizes, current NMFS guidance 


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recommends that calculation of Level B 

zones for DTH use the same continuous 

SSL of 167 dB SEL for all hole sizes 

(Heyvaert and Reyff 2021). 

Recommended SSLs for 30-inch and 24- 

inch holes as well as 8-inch holes for 

tension anchors and micropiles for use 

in the calculation of Level A harassment 

thresholds are provided by current 

NMFS guidance and in Table 4. 

TABLE 4—ESTIMATES OF MEAN UNDERWATER SOUND LEVELS GENERATED DURING VIBRATORY AND IMPACT PILE

INSTALLATION, DTH, AND VIBRATORY PILE REMOVAL

Method and pile type SSL at 10 m Literature source 

Vibratory hammer ................................... dB rms 

30-inch steel piles .................................. 162 Denes et al. 2016. 

24-inch steel piles .................................. 161 Navy 2015. 

20-inch steel piles .................................. 161 Navy 2015. 

DTH of rock sockets and tension anchors.dB rms 

All pile diameters .................................... 167 Heyvaert and Reyff 2021. 

DTH of rock sockets and tension anchors.dB SELss dB peak 

30-inch rock socket ................................ 164 194 Reyff and Heyvaert 2019; Reyff 2020; 

Denes et al. 2016. 

24-inch rock socket ................................ 159 184 Heyvaert and Reyff 2021. 

8-inch tension anchor/micropile ............. 144 170 Reyff 2020. 

Impact Hammer dB rms dB SEL dB peak 

30-inch steel piles ................................. 195 181 209 Denes et al. 2016. 

24-inch steel piles ................................. 190 177 203 Caltrans 2015. 

20-inch steel piles ................................. 190 177 202 Caltrans 2015. 

Note: It is assumed that noise levels during pile installation and removal are similar. SEL = sound exposure level; dB peak = peak sound level; 

rms = root mean square. 

Simultaneous use of two impact, 

vibratory, or DTH hammers, or any 

combination of those equipment, could 

occur. Such occurrences are anticipated 

to be infrequent, will be for short 

durations on any given day, and ADOT 

anticipates that no more than two 

hammers will be operated concurrently. 

Simultaneous use of two hammers or 

DTH systems could occur at the same 

project site, or at two different, but 

nearby project sites. Simultaneous use 

of hammers could result in increased 

SPLs and harassment zone sizes given 

the proximity of the component driving 

sites and the physical rules of decibel 

addition. ADOT anticipates that 

concurrent use of two hammers 

producing continuous noise could occur 

on 44 days, which is half the anticipated 

number of days of construction (91 

days) and represents complete overlap 

between the two contracts and/or 

represents use of two hammers by a 

single contractor. Although it is unlikely 

that overlap will be complete, ADOT 

anticipates, and NMFS concurs, this 

scenario represents the potential worst 

case scenario, given that a more accurate 

estimate is not possible, and concurrent 

operation of hammers will be 

incidental. Given that the use of more 

than one hammer for pile installation on 

the same day (whether simultaneous or 

not) will increase the number of piles 

installed per day, this is anticipated to 

result in a reduction of the total number 

of days of pile installation. Table 5 

shows how potential scenarios would 

reduce the total number of pile driving 

days and weeks. However, as described 

in the Marine Mammal Occurrence and 

Take Calculation and Estimation 

section below, ADOT has conservatively 

calculated take with the assumption that 

pile driving will occur on all 91 days. 

TABLE 5—CALCULATED REDUCTION OF PILE DRIVING DAYS BASED ON PERCENTAGE OF PROJECT DAYS WITH TWO

HAMMERS IN USE

Percent overlap Days of 

overlap 

Days of work 

completed 

during overlap 

(2 hammers) 

Remaining 

days of work 

with single 

hammer 

Total number 

of days of 

work 

Weeks of work 

0 ........................................................................................... 0.0 0.0 91.0 91.0 15.2 

10 ......................................................................................... 9.1 18.2 72.8 81.9 13.7 

20 ......................................................................................... 18.2 36.4 54.6 72.8 12.1 

30 ......................................................................................... 27.3 54.6 36.4 63.7 10.6 


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TABLE 5—CALCULATED REDUCTION OF PILE DRIVING DAYS BASED ON PERCENTAGE OF PROJECT DAYS WITH TWO

HAMMERS IN USE—Continued 

Percent overlap Days of 

overlap 

Days of work 

completed 

during overlap 

(2 hammers) 

Remaining 

days of work 

with single 

hammer 

Total number 

of days of 

work 

Weeks of work 

40 ......................................................................................... 36.4 72.8 18.2 54.6 9.1 

50 ......................................................................................... 45.5 91.0 0.0 45.5 7.6 

NMFS (2018b) handles overlapping 

sound fields created by the use of more 

than one hammer differently for 

impulsive (impact hammer and Level A 

harassment zones for drilling with a 

DTH hammer) and continuous sound 

sources (vibratory hammer and Level B 

harassment zones for drilling with a 

DTH hammer; Table 6) and differently 

for impulsive sources with rapid 

impulse rates of multiple strikes per 

second (DTH) and slow impulse rates 

(impact hammering) (NMFS 2021). It is 

unlikely that the two impact hammers 

will strike at the same instant, and 

therefore, the SPLs will not be adjusted 

regardless of the distance between 

impact hammers. In this case, each 

impact hammer will be considered to 

have its own independent Level A 

harassment and Level B harassment 

zones. 

When two DTH hammers operate 

simultaneously their continuous sound 

components overlap completely in time. 

When the Level B isopleth of one DTH 

sound source encompasses the isopleth 

of another DTH sound source, the 

sources are considered additive and 

combined using the following rules 

(Table 7). The method described below 

was based on one created by 

Washington State Department of 

Transportation (WSDOT) and has been 

updated and modified by NMFS 

(WSDOT 2020). For addition of two 

simultaneous DTH hammers, the 

difference between the two SSLs is 

calculated, and if that difference is 

between 0 and 1 dB, 3 dB are added to 

the higher SSL; if difference is between 

2 or 3 dB, 2 dB are added to the highest 

SSL; if the difference is between 4 to 9 

dB, 1 dB is added to the highest SSL; 

and with differences of 10 or more 

decibels, there is no addition. 

When two continuous noise sources, 

such as vibratory hammers, have 

overlapping sound fields, there is 

potential for higher sound levels than 

for non-overlapping sources. 

When two or more vibratory hammers 

are used simultaneously, and the 

isopleth of one sound source 

encompasses the isopleth of another 

sound source, the sources are 

considered additive and source levels 

are combined using the rules in Table 6, 

similar to that described above for DTH. 

TABLE 6—RULES FOR COMBINING SOUND SOURCE LEVELS GENERATED DURING PILE INSTALLATION

Hammer types Difference in SSL Level A zones Level B zones 

Vibratory, Impact ........................................... Any ........................ Use impact zones ............................. Use largest zone. 

Impact, Impact ............................................... Any ........................ Use zones for each pile size and 

number of strikes.

Use zone for each pile size. 

Vibratory, Vibratory or DTH, DTH ................. 0 or 1 dB ...............

2 or 3 dB ...............

Add 3 dB to the higher source level

Add 2 dB to the higher source level. 

Add 3 dB to the higher source level 

Add 2 dB to the higher source level. 

4 to 9 dB ............... Add 1 dB to the higher source level Add 1 dB to the higher source level. 

10 dB or more ....... Add 0 dB to the higher source level Add 0 dB to the higher source level. 

During pile driving, it is common for 

pile installation to start and stop 

multiple times as each pile is adjusted 

and its progress is measured and 

documented, though as stated above, for 

short durations, it is anticipated that 

multiple hammers could be in use 

simultaneously. Following an approach 

modified from WSDOT in their 

Biological Assessment manual (WSDOT 

2020) and described in Table 7, decibel 

addition calculations were carried out 

for possible combinations of pile driving 

and DTH throughout the project area. 

The source levels included in Table 7 

are used to estimate the Level A 

harassment zones and the Level B 

harassment zones. 

TABLE 7—COMBINED SSLS (dB AT 10 m) GENERATED DURING PILE INSTALLATION AND REMOVAL FOR COMBINATIONS OF

TWO PIECES OF EQUIPMENT: IMPACT HAMMER, VIBRATORY HAMMER, AND DOWN-THE-HOLE DRILL

Method Vibratory (RMS) DTH (RMS) DTH (SEL) 

Pile diameter 20 24 30 8 24 30 8 24 30 

SSL 161 161 162 167 167 167 144 159 164 

Vibratory (RMS) .................... 20 161 164 164 165 168 168 168 ................ ................ ................

24 161 164 164 165 168 168 168 ................ ................ ................

30 162 165 165 165 168 168 168 ................ ................ ................

DTH (RMS) ........................... 8 167 168 168 168 170 170 170 ................ ................ ................

24 167 168 168 168 170 170 170 ................ ................ ................

30 167 168 168 168 170 170 170 ................ ................ ................

DTH (SEL) ............................. 8 144 ................ ................ ................ ................ ................ ................ 147 159 164 

24 159 ................ ................ ................ ................ ................ ................ 159 162 165 

30 164 ................ ................ ................ ................ ................ ................ 164 165 167 


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No addition is warranted for impact 

pile driving in combination with 

vibratory or impact pile driving or DTH 

(NMFS 2021). 

Level B Harassment Zones 

Transmission loss (TL) is the decrease 

in acoustic intensity as an acoustic 

pressure wave propagates out from a 

source. TL parameters vary with 

frequency, temperature, sea conditions, 

current, source and receiver depth, 

water depth, water chemistry, and 

bottom composition and topography. 

The general formula for underwater TL 

is: 

TL = B * Log10 (R1/R2), 

Where: 

TL = transmission loss in dB 

B = transmission loss coefficient; for practical 

spreading equals 15 

R1 = the distance of the modeled SPL from 

the driven pile, and 

R2 = the distance from the driven pile of the 

initial measurement 

The recommended TL coefficient for 

most nearshore environments is the 

practical spreading value of 15. This 

value results in an expected propagation 

environment that will lie between 

spherical and cylindrical spreading loss 

conditions, which is the most 

appropriate assumption for ADOT’s 

planned activity in the absence of 

specific modelling. 

All Level B harassment isopleths are 

reported in Table 8 and Table 9 below. 

It should be noted that based on the 

geography of Tongass Narrows and the 

surrounding islands, sound will not 

reach the full distance of the Level B 

harassment isopleth in most directions. 

Generally, due to interaction with land, 

only a thin slice of the possible area is 

ensonified to the full distance of the 

Level B harassment isopleth. 

The size of the Level B harassment 

zone during concurrent operation of two 

vibratory or DTH hammers will depend 

on the combination of sound sources 

and the decibel addition of two 

hammers producing continuous noise. 

Table 8 shows the distances to Level B 

harassment isopleths during 

simultaneous hammering from two 

sources, based on the combined SSL. 

Because the calculated Level B 

harassment isopleths for two sources are 

dependent upon the combined SSL, the 

Level B harassment zone for each 

combined sound source level included 

in Table 8 is consistent, regardless of the 

equipment combination. Please refer to 

Table 7 to determine which sound 

sources apply to each combined SSL. 

As noted previously, pile installation 

often involves numerous stops and 

starts of the hammer for each pile. 

Therefore, decibel addition is applied 

only when the adjacent continuous 

sound sources experience overlapping 

sound fields, which generally requires 

close proximity of driving locations. 

TABLE 8—LEVEL B HARASSMENT

ISOPLETHS FOR MULTIPLE VIBRATORY HAMMER ADDITIONS

Combined SSL 

(dB) 

Level B 

harassment 

isopleth 

(m) a

164 ............................................ 8,577 

165 ............................................ 10,000 

166 ............................................ 11,659 

167 ............................................ 13,594 

168 ............................................ 15,849 

169 ............................................ 18,478 

170 ............................................ 21,544 

aThese larger zones are truncated to the 

southeast by islands, which prevent propagation of sound in that direction beyond the confines of Tongass Narrows. To the northwest of 

Tongass Narrows, combined sound levels that 

exceed 167 dB rms extend into Clarence 

Strait before attenuating to sound levels that 

are anticipated to be below 120 dB rms. 

TABLE 9—LEVEL B HARASSMENT ISOPLETHS FOR SINGLE HAMMER USE BY ACTIVITY AND PILE SIZE

Activity Pile diameter 

Level B 

harassment 

isopleth 

(m) 

Vibratory Installation ..................................................................... 30-inch .......................................................................................... 6,310 

24-inch .......................................................................................... 5,412 

20-inch.

Vibratory Removal ........................................................................ 24-inch.

DTH Rock Sockets ....................................................................... 30-inch .......................................................................................... 13,594 

24-inch.

DTH Tension Anchor/Micropile .................................................... 8-inch.

Impact Installation ......................................................................... 30-inch .......................................................................................... 2,154 

24-inch .......................................................................................... 1,000 

20-inch .......................................................................................... 1,000 

Level A Harassment Zones 

When the NMFS Technical Guidance 

(2016) was published, in recognition of 

the fact that ensonified area/volume 

could be more technically challenging 

to predict because of the duration 

component in the new thresholds, we 

developed a User Spreadsheet that 

includes tools to help predict a simple 

isopleth that can be used in conjunction 

with marine mammal density or 

occurrence to help predict takes. We 

note that because of some of the 

assumptions included in the methods 

used for these tools, we anticipate that 

isopleths produced are typically going 

to be overestimates of some degree, 

which may result in some degree of 

overestimate of takes by Level A 

harassment. However, these tools offer 

the best way to predict appropriate 

isopleths when more sophisticated 3D 

modeling methods are not available, and 

NMFS continues to develop ways to 

quantitatively refine these tools, and 

will qualitatively address the output 

where appropriate. For stationary 

sources such as pile driving or removal 

and DTH using any of the methods 

discussed above, NMFS’ User 

Spreadsheet predicts the closest 

distance at which, if a marine mammal 

remained at that distance the whole 

duration of the activity, it will incur 

PTS. Inputs used in the User 

Spreadsheet are reported in Table 10 

and Table 11, and the resulting 

isopleths are reported below in Table 12 

and Table 13. Pile installation and 

removal can occur at variable rates, from 

a few minutes one day to many hours 

the next. ADOT anticipates that one 

permanent pile will be installed per day 

on 27 non-consecutive days, two 

temporary piles will be installed per day 

on 10 non-consecutive days, and two 

temporary piles will be removed per day 

on 10 days. 


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TABLE 10—NMFS USER SPREADSHEET INPUTS FOR SINGLE HAMMER USE

Equipment type 

Vibratory 

pile driver 

(installation 

of 30-inch 

steel piles) 

Vibratory 

pile driver 

(installation 

and removal 

of 24-inch 

steel piles) 

Vibratory 

pile driver 

(installation 

of 20-inch 

steel piles) 

DTH rock 

sockets 

(30-inch) 

DTH rock 

sockets 

(24-inch) 

DTH tension 

anchor 

(8-inch) 

Impact pile 

driver 

(30-inch 

steel piles) 

Impact pile 

driver 

(24-inch 

steel piles) 

Impact pile 

driver 

(20-inch 

steel piles) 

Spreadsheet tab used (A.1) 

vibratory 

pile driving 

(A.1) 

vibratory 

pile driving 

(A.1) 

vibratory 

pile driving 

(E.2) 

DTH pile 

driving 

(E.2) 

DTH pile 

driving 

(E.2) 

DTH pile 

driving 

(E.1) 

impact pile 

driving 

(E.1) 

impact pile 

driving 

(E.1) 

impact pile 

driving 

Weighting Factor Adjustment 

(kHz) ...................................... 2.5 2.5 2.5 2 2 2 2 2 2 

SSL ............................................ a 162 a 161 a 161 b 164 b 159 b 144 b 181 b 177 b 177 

Activity duration (hours) within 

24 hours ................................. 1 1 1 1–10 1–10 2–4 .................... .................... ....................

Number of piles per day ........... 1 1 1 1 1 1 1 1 1 

Strike rate strikes per second ... .................... .................... .................... 15 15 25.83 .................... .................... ....................

Number of strikes per pile ......... .................... .................... .................... .................... .................... .................... 50 50 50 

Notes: Propagation loss coefficient in all cases is 15. Duration estimates for DTH are based on assumption of multiple rock sockets and tension anchors being installed each day, with the maximum duration time for installation per day predicted to be 10 hours for rock socket DTH and 4 hours for tension anchor DTH. For specifics regarding the number of strikes and number of piles that will be used in a given situation, please refer to Table 1 in the notice of proposed IHA (87 FR 5980; 

February 2, 2022). a dB rms at 10m. 

b dB SEL at 10m. 

Regarding implications for Level A 

harassment zones when two vibratory 

hammers are operating concurrently, 

given the small size of the estimated 

Level A harassment isopleths for all 

hearing groups during vibratory pile 

driving, the zones of any two hammers 

are not expected to overlap. Therefore, 

compounding effects of multiple 

vibratory hammers operating 

concurrently are not anticipated, and 

NMFS has treated each source 

independently. 

Regarding implications for Level A 

harassment zones when one vibratory 

hammer and one DTH hammer are 

operating concurrently, combining 

isopleths for these sources is difficult 

for a variety of reasons. First, vibratory 

pile driving relies upon non-impulsive 

PTS thresholds, while DTH/rock 

hammers use impulsive thresholds. 

Second, vibratory pile driving account 

for the duration to drive a pile, while 

DTH account for strikes per pile. Thus, 

it is difficult to measure sound on the 

same scale and combine isopleths from 

these impulsive and non-impulsive, 

continuous sources. Therefore, NMFS 

has treated each source independently 

at this time. 

Regarding the operation of two DTH 

hammers concurrently, since DTH 

hammers are capable of multiple strikes 

per second, there is potential for 

multiple DTH/rock hammer sources’ 

isopleths to overlap in space and time 

(a higher strike rate indicates a greater 

potential for overlap). Therefore, NMFS 

has calculated distances to Level A 

harassment isopleths, by hearing group 

for simultaneous use of two DTH 

hammers (Table 13), using NMFS’ User 

Spreadsheet. The inputs for these 

calculations are outlined in Table 11. 

When the Level A isopleth of one DTH 

sound source encompasses the isopleth 

of another DTH sound source, the 

sources are considered additive and 

combined using the rules in Table 7 as 

described above. The number of piles 

per day is altered to reflect only a single 

pile for all those that overlap in space 

and time (i.e., no double counting of 

overlapping piles). The maximum strike 

rate and duration of the two DTH 

systems is used in the User Spreadsheet 

calculations. 

TABLE 11—NMFS USER SPREADSHEET INPUTS FOR SIMULTANEOUS

USE OF TWO DTH HAMMERS

Spreadsheet tab used (E.2) DTH pile 

driving 

Weighting Factor Adjustment (kHz).2. 

SSL(dB SEL at 10m) a

8-in pile/8-in pile ......... 147. 

8-in pile, 24-in pile ...... 159. 

8-in pile, 30-in pile ...... 164. 

24-in pile, 24-in pile .... 162. 

24-in pile, 30-in pile .... 165. 

30-in pile, 30-in pile .... 167. 

Activity duration (minutes) 

within 24 hours b.

60, 120, 180 or 

240 c. 

Number of piles per day b .. 1. 

Strike rate (strikes per second).15 or 25.83 d. 

aSSL reflects the combined SSLs calculated 

in Table 7. 

bADOT anticipates that DTH could occur at 

one site for up to 10 hours (600 minutes) per 

day, and overlap between two sites could 

occur for up to 4 hours (240 minutes) per day. 

Since the potential overlap in sources is accounted for in the SSL adjustment, and the 

total potential duration (even with two hammers) is accounted for in the ‘‘Activity duration 

(minutes) within 24 hours,’’ the ‘‘Number of 

piles per day’’ is assumed to be 1. c Duration will vary. 

d 25.83 for combinations that include 8-in 

piles. 15 for all other combinations. 

Level A harassment thresholds for 

impulsive sound sources (impact pile 

driving and DTH) are defined for both 

SELcum and Peak SPL with the 

threshold that results in the largest 

modeled isopleth for each marine 

mammal hearing group used to establish 

the Level A harassment isopleth. In this 

project, Level A harassment isopleths 

based on cumulative sound exposure 

level (SELcum) were always larger than 

those based on Peak SPL (for both single 

hammer use and simultaneous use of 

two hammers). It should be noted that 

there is a duration component when 

calculating the Level A harassment 

isopleth based on SELcum, and this 

duration depends on the number of 

piles that will be driven in a day and 

strikes per pile. For some activities, 

ADOT plans to drive variable numbers 

of piles per day throughout the project 

(See ‘‘Average Piles per Day (Range)’’ in 

Table 1 in the notice of proposed IHA 

(87 FR 5980; February 2, 2022)), and 

determine at the beginning of each pile 

driving day, the maximum number or 

duration piles will be driven that day. 

Here, this flexibility has been accounted 

for by modeling multiple durations for 

the activity, and determining the 

relevant isopleths. 


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TABLE 12—DISTANCES TO LEVEL A HARASSMENT ISOPLETHS, BY HEARING GROUP, AND AREA OF LEVEL A HARASSMENT

ZONES, FOR SINGLE HAMMER USE DURING PILE INSTALLATION AND REMOVAL

Activity Pile diameter(s) Minutes per pile or 

strikes per pile 

Level A harassment isopleth 

(m) 

Level A 

harassment areas 

(km 2) all hearing 

groups LF MF HF PW OW a

Vibratory Installation ........ 30-inch .................. 60 minutes ............ 8 1 12 5 1 <0.1 

24-inch b ............... 60 minutes ............ 7 1 11 5 1 <0.1 

20-inch .................. 60 minutes ............ 7 1 11 5 1 <0.1 

Vibratory Removal ........... 24-inch .................. 60 minutes ............ 7 1 11 5 1 <0.1 

DTH Rock Sockets .......... 30-inch .................. 60 minutes ............ 773 28 920 414 31 <0.9 

300 minutes .......... 2,258 81 2,690 1,209 88 <3.5 

600 minutes .......... 3,584 128 4,269 1,918 140 <6.6 

24-inch .................. 60 minutes ............ 359 13 427 192 15 <0.2 

300 minutes .......... 1,048 38 1,249 561 41 <1.4 

600 minutes .......... 1,664 60 1,982 891 65 <2.4 

DTH Tension Anchor ....... 8-inch .................... 120 minutes .......... 82 3 98 44 4 <0.1 

240 minutes .......... 130 5 155 70 6 <0.1 

Impact Installation ........... 30-inch .................. 50 strikes .............. 100 4 119 54 4 <0.1 

24-inch .................. 50 strikes .............. 54 2 65 29 3 <0.1 

20-inch .................. 50 strikes .............. 54 2 65 29 3 <0.1 

aPlease refer to Table 6–4 of ADOT’s IHA application for hearing group-specific areas. 

b Includes vibratory installation and removal. 

TABLE 13—DISTANCES TO LEVEL A HARASSMENT ISOPLETHS, BY HEARING GROUP FOR SIMULTANEOUS USE OF TWO

DTH HAMMERS

Activity combination Duration 

Level A harassment isopleth (m) 

LF MF HF PW OW 

8-in pile, 8-in pile ..................................... 60 82 3 98 44 3 

120 130 5 155 70 5 

180 170 6 202 91 7 

240 206 7 245 110 8 

8-in pile, 24-in pile ................................... 60 515 18 613 276 20 

120 817 29 974 437 32 

180 1,071 38 1,276 573 42 

240 1,297 46 1,545 694 51 

8-in pile, 30-in pile ................................... 60 1,109 40 1,321 594 43 

120 1,761 63 2,097 942 69 

180 2,307 82 2,748 1,235 90 

240 2,796 99 3,329 1,496 109 

24-in pile, 24-in pile ................................. 60 568 20 677 304 22 

120 902 32 1,074 483 35 

180 1,181 42 1,407 632 46 

240 1,431 51 1,705 766 56 

24-in pile, 30-in ........................................ 60 900 32 1,072 482 35 

120 1,429 51 1,702 765 56 

180 1,873 67 2,230 1,002 73 

240 2,268 81 2,702 1,214 88 

30-in pile, 30-in pile ................................. 60 1,224 44 1,458 655 48 

120 1,943 69 2,314 1,040 76 

180 2,545 91 3,032 1,362 99 

240 3,084 110 3,673 1,650 120 

Regarding implications for impact 

hammers used in combination with a 

vibratory hammer or DTH drill, the 

likelihood of these multiple sources’ 

isopleths to completely overlap in time 

is slim primarily because impact pile 

driving is intermittent. Furthermore, 

non-impulsive, continuous sources rely 

upon non-impulsive TTS/PTS 

thresholds, while impact pile driving 

uses impulsive thresholds, making it 

difficult to calculate isopleths that may 

overlap from impact driving and the 

simultaneous action of a non-impulsive 

continuous source or one with multiple 

strikes per second. Thus, with such slim 

potential for multiple different sources’ 

isopleths to overlap in space and time, 

specifications should be entered as 

‘‘normal’’ into the User Spreadsheet for 

each individual source separately. 

Marine Mammal Occurrence and Take 

Calculation and Estimation 

In this section we provide the 

information about the presence, density, 

or group dynamics of marine mammals 

that will inform the take calculations. 

Additionally, we describe how the 

occurrence information is brought 

together to produce a quantitative take 

estimate for each phase. A summary of 

the estimated take, including as a 

percentage of population for each of the 

species, is shown in Table 14. 

Steller Sea Lion 

Steller sea lion abundance in the 

Tongass Narrows area is not well 

known. No systematic studies of Steller 

sea lions have been conducted in or 

near the Tongass Narrows area. Steller 

sea lions are known to occur year-round 

and local residents report observing 

Steller sea lions approximately once or 

twice per week (based on 

communication outlined in Section 6 of 

ADOT’s IHA application). Abundance 


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appears to increase during herring runs 

(March to May) and salmon runs (July 

to September). Group sizes may reach 

up to 6 to 10 individuals (Freitag 2017 

as cited in 83 FR 37473; August 1, 

2018), though groups of up to 80 

individuals have been observed (HDR, 

Inc. 2003). 

ADOT conservatively estimates that 

one group of 10 Steller sea lions may be 

present in the project area each day, but 

this occurrence rate may as much as 

double (20 Steller sea lions per day) 

during periods of increased abundance 

associated with the herring and salmon 

runs (March to May and July to 

September). Therefore, ADOT 

anticipates that two large groups (20 

individuals) may be taken by Level B 

harassment each day during these 

months. To be conservative, we assume 

all 91 days of work could be completed 

during these months of increased 

abundance and thus estimate 1,820 

potential takes by Level B harassment of 

Steller sea lions in Tongass Narrows 

(i.e., 2 groups of 10 sea lions per day × 

91 construction days = 1,820 takes by 

Level B harassment; Table 14). 

ADOT estimates that simultaneous 

use of two hammers (any combination) 

could occur on up to 44 days during the 

project. On those days, Level B 

harassment zones will extend into 

Clarence Strait. Steller sea lions are 

known to swim across Clarence Strait 

and to use offshore areas with deeper 

waters, although no estimates of at-sea 

density or abundance in Clarence Strait 

are available. Therefore, ADOT has 

conservatively estimated, and NMFS 

concurs, that during the 44 days with 

potential simultaneous use of two 

hammers, a group of 10 Steller sea lions 

may occur in the portion of the Level B 

harassment zone in Clarence Strait each 

day (one group of 10 sea lions per day 

× 44 days = 440 individuals). Therefore, 

the preliminary sum of estimated takes 

by Level B harassment of Steller sea 

lions between Tongass Narrows and 

Clarence Strait is 2,260 (1,820 + 440 = 

2,260 takes by Level B harassment). 

The largest Level A harassment zone 

for otariid pinnipeds could extend 140 

m from the noise source for 10 hours of 

DTH using a single hammer, or 120m 

from the noise source for 4 hours of 

DTH using two hammers for 30-in piles 

simultaneously. (As noted previously, 

ADOT estimates that simultaneous use 

of any two hammer types will occur on 

no more than 44 days). Zones for shorter 

durations and other activities will be 

smaller (Table 12). For some DTH 

activities, the estimated Level A 

harassment zone is larger than the 

shutdown zone, and therefore, some 

Level A harassment could occur. 

Further, while unlikely, it is possible 

that a Steller sea lion could enter a 

shutdown zone without detection given 

the various obstructions along the 

shoreline, and remain in the zone long 

enough to be taken by Level A 

harassment before being observed and a 

shutdown occurring. ADOT therefore 

requested, and NMFS authorized, one 

take by Level A harassment on each of 

the 91 construction days (91 takes by 

Level A harassment). Authorized take 

by Level B harassment was calculated as 

the total calculated Steller sea lion takes 

by Level B harassment minus the takes 

by Level A harassment (2,260 takes¥91 

takes by Level A harassment) for a total 

of 2,169 takes by Level B harassment. 

Therefore, ADOT requested, and NMFS 

authorized, 91 takes of Steller sea lion 

by Level A harassment and 2,169 takes 

of Steller sea lion by Level B harassment 

(2,260 total takes of Steller sea lion; 

Table 14). 

Harbor Seal 

Harbor seal densities in the Tongass 

Narrows area are not well known. No 

systematic studies of harbor seals have 

been conducted in or near Tongass 

Narrows. They are known to occur yearround with little seasonal variation in 

abundance (Freitag 2017 as cited in 83 

FR 37473; August 1, 2018) and local 

experts estimate that there are about 1 

to 3 harbor seals in Tongass Narrows 

every day, in addition to those that 

congregate near the seafood processing 

plants and fish hatcheries. NMFS has 

indicated that the maximum group size 

in Tongass Narrows is three individuals 

(83 FR 22009; May 11, 2018); however, 

ADOT monitoring in March 2021 

observed several groups of up to 5 

individuals. Based on this knowledge, 

the expected maximum group size in 

Tongass Narrows is five individuals. 

Harbor seals are known to be curious 

and may approach novel activity. For 

these reasons ADOT conservatively 

estimates that up to two groups of 5 

harbor seals per group could be taken by 

Level B harassment due to projectrelated underwater noise each 

construction day for a total of 910 takes 

by Level B harassment of harbor seal in 

Tongass Narrows (i.e., 2 groups of 5 

harbor seals per day × 91 construction 

days = 910 total takes by Level B 

harassment of harbor seal; Table 14). 

As noted above, ADOT estimates that 

simultaneous use of two hammers (any 

combination) could occur on up to 44 

days during the project. On those days, 

Level B harassment zones will extend 

into Clarence Strait. Harbor seals are 

known to swim across Clarence Strait, 

although no estimates of at-sea density 

or abundance in Clarence Strait are 

available. It is likely that harbor seal 

abundance in Clarence Strait is lower 

than in Tongass Narrows, as harbor 

seals generally prefer nearshore waters. 

Therefore, ADOT has conservatively 

estimated, and NMFS concurs, that 

during the 44 days with potential 

simultaneous use of two hammers, a 

group of 5 harbor seals may occur in the 

portion of the Level B harassment zone 

in Clarence Strait each day (one group 

of 5 harbor seals per day × 44 days = 220 

individuals). Therefore, the sum of total 

estimated takes by Level B harassment 

of harbor seals between Tongass 

Narrows and Clarence Strait is 1,130 

(910 + 220 = 1,130 takes by Level B 

harassment). 

The largest Level A harassment zone 

for harbor seals could extend 1,918 m 

from the noise source for 10 hours of 

DTH using a single hammer, or 1,640 m 

from the noise source for 4 hours of 

DTH using two hammers for 30-in piles 

simultaneously. (As noted previously, 

ADOT estimates that simultaneous use 

of any two hammer types will occur on 

no more than 44 days). Zones for shorter 

durations and other activities will be 

smaller (Table 12). Due to practicability 

concerns, NMFS is requiring a 200 m 

shutdown zone for harbor seals during 

24-in and 30-in DTH activities (Table 

15). Therefore, for some DTH activities, 

the estimated Level A harassment zone 

is larger than the shutdown zone, and 

therefore, some Level A harassment 

could occur. Harbor seals may enter and 

remain within the area between the 

Level A harassment zone and the 

shutdown zone for a duration long 

enough to be taken by Level A 

harassment. Additionally, while 

unlikely, it is possible that a harbor seal 

could enter a shutdown zone without 

detection given the various obstructions 

along the shoreline, and remain in the 

zone for a duration long enough to be 

taken by Level A harassment before 

being observed and a shutdown 

occurring. 

To calculate take by Level A 

harassment, ADOT first calculated the 

ratio of the maximum Level A 

harassment isopleth for 30-in DTH using 

a single hammer minus the shutdown 

zone isopleth (1,918 m¥200 m 

shutdown zone = 1,718 m) to the Level 

B harassment zone isopleth (13,594 m; 

1,718 m/13,594 m = 0.1264). ADOT 

multiplied the resulting ratio by the 

total potential take in Tongass Narrows, 

resulting in 116 takes by Level A 

harassment (i.e., 910 takes by Level B 

harassment × 0.1264 = 116 takes by 

Level A harassment). NMFS reviewed, 

and concurs with and adopts this 

method. (Potential operation of two 

DTH hammers for 24-in/30-in or 30-in/ 


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30-in pile combinations would result in 

larger Level A harassment isopleths 

than 1,918 m, however, such concurrent 

work will rarely occur, if at all, and 

therefore, NMFS expects that 

calculating Level A harassment take 

using those zones would be overly 

conservative and unrealistic. Moreover, 

since the method used above assumes 

30-inch DTH on all days it provided a 

precautionary cushion since activities 

with smaller Level A harassment zone 

sizes will occur on many days.) 

Authorized take by Level B harassment 

was calculated as the total calculated 

harbor seal takes by Level B harassment 

minus the takes by Level A harassment 

(1,130 takes¥116 takes by Level A 

harassment) for a total of 1,014 takes by 

Level B harassment. ADOT therefore 

requested, and NMFS authorized, 116 

takes of harbor seal by Level A 

harassment and 1,014 takes of harbor 

seal by Level B harassment (1,130 total 

takes of harbor seal; Table 14). 

Harbor Porpoise 

Harbor porpoises are non-migratory; 

therefore, our occurrence estimates are 

not dependent on season. Freitag (2017 

as cited in 83 FR 37473; August 1, 2018) 

observed harbor porpoises in Tongass 

Narrows zero to one time per month. 

Harbor porpoises observed in the project 

vicinity typically occur in groups of one 

to five animals with an estimated 

maximum group size of eight animals 

(83 FR 37473, August 1, 2018, Solstice 

2018). ADOT’s 2020 and 2021 

monitoring program in Tongass Narrows 

did not result in sightings of this 

species; however, ADOT assumes an 

occurrence rate of one group per month 

in the following take estimations. For 

our analysis, we are considering a group 

to consist of five animals. Based on 

Freitag (2017), and supported by the 

reports of knowledgeable locals as 

described in ADOT’s application, ADOT 

estimates that one group of five harbor 

porpoises could enter Tongass Narrows 

and potentially taken by Level B 

harassment due to project-related noise 

each month for a total of 15 potential 

harbor porpoise takes by Level B 

harassment in Tongass Narrows (i.e., 1 

group of 5 individuals × 3 months (91 

days) = 15 harbor porpoises). 

As noted above, ADOT estimates that 

simultaneous use of two hammers (any 

combination) could occur on up to 44 

days during the project. On those days, 

the Level B harassment zone will extend 

into Clarence Strait. Harbor porpoises 

are known to swim across Clarence 

Strait and to use other areas of deep, 

open waters. Dahlheim et al. (2015) 

estimated a density of 0.02 harbor 

porpoises/km2 in an area that 

encompasses Clarence Strait. ADOT 

estimates, and NMFS concurs that 

during the 44 days with potential 

simultaneous use of two hammers, 17 

harbor porpoises (0.02 harbor porpoises/ 

km2 × 18.5 km2 × 44 days = 17 harbor 

porpoises) may occur in the portion of 

the Level B harassment zone in Clarence 

Strait during the project (though ADOT 

and NMFS anticipate that this is a 

conservative estimate, given the entire 

18.5 km2 area will rarely be ensonified 

above the Level B harassment 

threshold). Therefore, the sum of total 

estimated takes by Level B harassment 

of harbor porpoise between Tongass 

Narrows and Clarence Strait is 32 (15 + 

17 = 32 takes by Level B harassment). 

The largest Level A harassment zone 

for harbor porpoises extends 4,269 m 

from the noise source for 10 hours of 

DTH using a single hammer, and 3,673 

m from the noise source for 4 hours of 

DTH using two hammers for 30-in piles 

simultaneously. (As noted previously, 

ADOT estimates that simultaneous use 

of any two hammer types will occur on 

no more than 44 days). Zones for shorter 

durations and other activities will be 

smaller (Table 12). Due to practicability 

concerns, NMFS is requiring a 500 m 

shutdown zone for high frequency 

cetaceans during 24-in and 30-in DTH 

activities. Therefore, for some DTH 

activities, the estimated Level A 

harassment zone is larger than the 

shutdown zone, and therefore, some 

Level A harassment could occur. Harbor 

porpoises may enter and remain within 

the area between the Level A 

harassment zone and the shutdown 

zone for a duration long enough to be 

taken by Level A harassment. 

Additionally, given the large size of 

required shutdown zones for some 

activities and the cryptic nature of 

harbor porpoises, it is possible that a 

harbor porpoise could enter a shutdown 

zone without detection and remain in 

the zone for a duration long enough to 

be taken by Level A harassment before 

being observed and a shutdown 

occurring. 

To calculate take by Level A 

harassment, ADOT first calculated the 

ratio of the maximum Level A 

harassment isopleth for 30-in DTH using 

a single hammer minus the shutdown 

zone isopleth (4,269 m¥500 m = 3,769 

m) to the Level B harassment zone 

isopleth (13,594 m; 3,769/13,594 = 

0.2773). ADOT multiplied the resulting 

ratio by the total potential take in 

Tongass Narrows, resulting in 5 takes by 

Level A harassment (i.e., 15 takes by 

Level B harassment × 0.2773 = 5 takes 

by Level A harassment). NMFS 

reviewed and concurs with this method. 

(Potential operation of two DTH 

hammers for 24-in/30-in or 30-in/30-in 

pile combinations would result in larger 

Level A harassment isopleths than 4,269 

m, however, such concurrent work 

would rarely occur, if at all, and 

therefore, as described above, NMFS 

expects that calculating Level A 

harassment take using those zones is 

unnecessary.) Authorized take by Level 

B harassment was calculated as the total 

calculated harbor porpoise takes by 

Level B harassment minus the takes by 

Level A harassment (32 takes¥5 takes 

by Level A harassment) for a total of 27 

takes by Level B harassment. ADOT 

therefore requested and NMFS 

authorized 5 takes by Level A 

harassment and 27 takes by Level B 

harassment (32 total takes of harbor 

porpoise; Table 14). 

Dall’s Porpoise 

Dall’s porpoises are expected to only 

occur in the project area a few times per 

year. Their relative rarity is supported 

by Jefferson et al.’s (2019) presentation 

of historical survey data showing very 

few sightings in the Ketchikan area and 

conclusion that Dall’s porpoise 

generally are rare in narrow waterways, 

like the Tongass Narrows. ADOT’s 

monitoring program from 2020 and 2021 

recorded one sighting of 6 individuals 

over 23 days of observation, 16 days of 

observations with no sightings, and two 

sightings of 10 individuals in 14 days of 

observation; this equates to one sighting 

every approximately 17 days (DOT&PF 

2020, 2021a, 2021b, 2021c, 2021d) or 

approximately two sightings per month. 

This species is non-migratory; therefore, 

the occurrence estimates are not 

dependent on season. ADOT anticipates 

that one large Dall’s porpoise pod (12 

individuals) may be present in the 

project area and exposed to project 

related underwater noise twice each 

month during 3 months of construction 

(91 days rounded to 3 months) for a 

total of 72 potential takes by Level B 

harassment in Tongass Narrows (i.e., 2 

groups of 12 Dall’s porpoises per month 

× 3 months = 72 potential takes by Level 

B harassment). 

As noted above, ADOT estimates that 

simultaneous use of two hammers (any 

combination) could occur on up to 44 

days during the project. On those days, 

the Level B harassment zone will extend 

into Clarence Strait, where Dall’s 

porpoises are known to occur. Jefferson 

et al. (2019) estimated an average 

density of 0.19 Dall’s porpoises/km2 in 

Southeast Alaska. ADOT estimates, and 

NMFS concurs, that during the 44 days 

with potential simultaneous use of two 

hammers, 155 Dall’s porpoises (0.19 

Dall’s porpoises/km2 × 18.5 km2 × 44 

days = 155 Dall’s porpoises) may occur 


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in the portion of the Level B harassment 

zone in Clarence Strait during the 

project (though ADOT and NMFS 

anticipate that this is a conservative 

estimate, given the entire 18.5 km2 area 

will rarely be ensonified above the Level 

B harassment threshold). Therefore, the 

sum of total estimated takes by Level B 

harassment of harbor porpoise between 

Tongass Narrows and Clarence Strait is 

227 (72 + 155= 227 takes by Level B 

harassment). 

The largest Level A harassment zone 

for Dall’s porpoises extends 4,269 m 

from the noise source for 10 hours of 

DTH using a single hammer, and 3,673 

m from the noise source for 4 hours of 

DTH using two hammers for 30-in piles 

simultaneously. (As noted previously, 

ADOT estimates that simultaneous use 

of any two hammer types will occur on 

no more than 44 days.) Zones for shorter 

durations and other activities will be 

smaller (Table 12). Due to practicability 

concerns, NMFS proposes to require a 

500 m shutdown zone for high 

frequency cetaceans during 24-in and 

30-in DTH activities. Therefore, for 

some DTH activities, the estimated 

Level A harassment zone is larger than 

the shutdown zone, and therefore, some 

Level A harassment could occur. Dall’s 

porpoises may enter and remain within 

the area between the Level A 

harassment zone and the shutdown 

zone and be exposed to sound levels for 

a duration long enough to be taken by 

Level A harassment. Additionally, given 

the large size of the required shutdown 

zones for some activities, it is possible 

that a Dall’s porpoise could enter a 

shutdown zone without detection and 

remain in the zone for a duration long 

enough to taken by Level A harassment 

before being observed and a shutdown 

occurring. 

To calculate take by Level A 

harassment, ADOT first calculated the 

ratio of the maximum Level A 

harassment isopleth for 30-in DTH using 

a single hammer minus the shutdown 

zone isopleth (4,269 m¥500 m = 3,769 

m) to the Level B harassment zone 

isopleth (13,594 m; 3,769/13,594 = 

0.2773). ADOT multiplied the resulting 

ratio by the total potential take in 

Tongass Narrows, resulting in 20 takes 

by Level A harassment (i.e., 72 takes by 

Level B harassment × 0.2773 = 20 takes 

by Level A harassment). NMFS revised 

and concurs with this method. 

(Potential operation of two DTH 

hammers for 24-in/30-in or 30-in/30-in 

pile combinations would result in larger 

Level A harassment isopleths than 4,269 

m, however, such concurrent work 

would rarely occur, if at all, and 

therefore, as described above, NMFS 

expects that calculating Level A 

harassment take using those zones is 

unnecessary.) Authorized take by Level 

B harassment was calculated as the total 

calculated Dall’s porpoise takes by Level 

B harassment minus the takes by Level 

A harassment (227 takes¥20 takes by 

Level A harassment) for a total of 207 

takes by Level B harassment. ADOT 

therefore requested and NMFS 

authorized 20 takes by Level A 

harassment, and 207 takes by Level B 

harassment (227 total takes of Dall’s 

porpoise; Table 14). 

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 Tongass Narrows, and it is 

uncommon for individuals to occur in 

the project area. However, historical 

sightings in nearby areas (Dahlheim and 

Towell 1994; Muto et al. 2018) and 

recent fluctuations in distribution and 

abundance mean it is possible the 

species could be present. 

To account for the possibility that this 

species could be present in the project 

area, ADOT conservatively estimates, 

and NMFS concurs, that one large group 

(92 individuals) of Pacific white-sided 

dolphins may be taken by Level B 

harassment in Tongass Narrows during 

the activity. 

As noted above, ADOT estimates that 

simultaneous use of two hammers (any 

combination) could occur on up to 44 

days during the project. On those days, 

the Level B harassment zone will extend 

into Clarence Strait. However, no 

additional takes of Pacific white-sided 

dolphin are anticipated to occur due to 

simultaneous use of two hammers, 

given that Pacific white-sided dolphins 

are uncommon in the project area. 

Therefore, NMFS authorized 92 takes by 

Level B harassment of Pacific whitesided dolphins. 

ADOT did not request, nor did NMFS 

authorize take by Level A harassment 

for this activity given that Pacific whitesided dolphins are uncommon in the 

project area. Further, considering the 

small Level A harassment zones for 

mid-frequency cetaceans (Table 12 and 

Table 13) in comparison to the required 

shutdown zones, it is unlikely that a 

Pacific white-sided dolphin will enter 

and remain within the area between the 

Level A harassment zone and the 

shutdown zone for a duration long 

enough to be taken by Level A 

harassment. 

Killer Whale 

Killer whales are observed in Tongass 

Narrows irregularly with peaks in 

abundance between May and July. 

During 7 months of intermittent marine 

mammal monitoring (October 2020– 

February 2021; May–June 2021), there 

were five killer whale sightings in 4 

months (November, February, May, 

June) totaling 22 animals; sightings 

occurred on 5 out of 88 days of 

monitoring (DOT&PF 2020, 2021a, 

2021b, 2021c, 2021d). Pod sizes ranged 

from two to eight animals (DOT&PF 

2020, 2021a, 2021b, 2021c, 2021d). 

Previous incidental take authorizations 

in the Ketchikan area have estimated 

killer whale occurrence in Tongass 

Narrows at one pod per month, except 

during the peak period of May to July 

when estimates have included two pods 

per month (Freitag 2017 as cited in 83 

FR 37473; August 1, 2018 and 83 FR 

34134; July 17, 2019). 

As noted above, ADOT estimates that 

simultaneous use of two hammers (any 

combination) could occur on up to 44 

days during the project. On those days, 

the Level B harassment zone will extend 

into Clarence Strait. In estimating take 

by Level B harassment, ADOT assumed 

a pod size of 12 killer whales, that all 

91 days of work will occur between May 

and July during the peaks in abundance, 

and that therefore, 2 pods may occur 

within the Level B harassment zone 

(including both Tongass Narrows and 

Clarence Strait) during each month of 

work, for a total of 72 takes by Level B 

harassment (2 groups × 12 individuals × 

3 months = 72 killer whales). Therefore, 

ADOT estimates that a total of 72 killer 

whales may be taken by Level B 

harassment (i.e., 2 pods of 12 

individuals per month × 3 months (91 

days) = 72 takes by Level B harassment). 

NMFS reviewed and concurs with this 

method, and authorized 72 takes by 

Level B harassment of killer whale. 

ADOT did not request, nor did NMFS 

authorize take by Level A harassment of 

killer whales for this activity. 

Considering the small Level A 

harassment zones for mid-frequency 

cetaceans (Table 12 and Table 13) in 

comparison to the required shutdown 

zones, it is unlikely that a killer whale 

will enter and remain within the area 

between the Level A harassment zone 

and the shutdown zone for a duration 

long enough to be taken by Level A 

harassment. 

Humpback Whale 

As discussed in the Description of 

Marine Mammals in the Area of 

Specified Activities section, locals have 

observed humpback whales an average 

of about once per week in Tongass 

Narrows, but there is evidence to 

suggest occurrence may be higher 

during some periods of the year. The 

December 19, 2019 Biological Opinion 


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stated that based on observations by 

local experts, approximately one group 

of two individuals will occur in Tongass 

Narrows during ADOT’s activity two 

times per seven days during pile 

driving, pile removal, and DTH 

activities throughout the year. The 

assumption was based on differences in 

abundance throughout the year, recent 

observations of larger groups of whales 

present during summer, and a higher 

than average frequency of occurrence in 

recent months (NMFS 2019). ADOT’s 

2020 and 2021 monitoring program 

documented a similar sighting rate, with 

30 humpback whale sightings over 53 

days of in-water pile driving; some of 

the sightings were believed to be 

repeated sightings of the same 

individual (DOT&PF 2020, 2021a, 

2021b, 2021c, 2021d). ADOT therefore 

predicts, and NMFS concurs, that one 

group of two individuals may occur 

within the Level B harassment zones 

twice per week during the planned 

activities. As noted previously, ADOT 

estimates that pile driving will occur 

over the course of 91 days (13 weeks). 

Therefore, ADOT estimates, and NMFS 

concurs that 52 takes by Level B 

harassment of humpback whales (1 

group of 2 individuals × 2 groups per 

week × 13 weeks = 52 takes by Level B 

harassment) from the Central North 

Pacific stock may occur in Tongass 

Narrows. 

As noted above, ADOT estimates that 

simultaneous use of two hammers (any 

combination) could occur on up to 44 

days during the project. On those days, 

the Level B harassment zone will extend 

into Clarence Strait. Local specialists 

estimated that approximately four 

humpback whales could pass through or 

near the portion of the Level B 

harassment zone in Clarence Strait each 

day. Therefore, ADOT estimates, and 

NMFS concurs, that during the 44 days 

with potential simultaneous use of two 

hammers, 176 takes by Level B 

harassment of humpback whale could 

occur in Clarence Strait (4 humpback 

whales × 44 days = 176 takes by Level 

B harassment). Therefore, the sum of 

total estimated takes by Level B 

harassment of humpback whale between 

Tongass Narrows and Clarence Strait is 

228 (52 + 176 = 228 takes by Level B 

harassment), and NMFS authorized 228 

takes by Level B harassment of 

humpback whale. 

As noted previously, Wade et al. 

(2021) estimates that approximately 2 

percent of all humpback whales in 

Southeast Alaska and northern British 

Columbia are of the Mexico DPS, while 

all others are of the Hawaii DPS. 

However, NMFS has conservatively 

assumed here that 6.1 percent of the 

total humpback population in Southeast 

Alaska is from the Mexico DPS (Wade 

et al. 2016). Therefore, of the 228 takes 

of humpback whale authorized, NMFS 

expects that a total of 14 takes will be 

of individuals from the Mexico DPS. 

NMFS expects that all other instances of 

take will be from the non-listed Hawaii 

DPS. 

Take by Level A harassment of 

humpback whales is neither anticipated 

nor authorized because of the expected 

effectiveness of the required monitoring 

and mitigation measures (see Mitigation 

Measures section below for more 

details). For all pile driving and DTH 

activities, the shutdown zone exceeds 

the calculated Level A harassment zone. 

Humpbacks are usually readily visible, 

and therefore, we expect protected 

species observers (PSOs) to be able to 

effectively implement the required 

shutdown measures prior to any 

humpback whales incurring PTS within 

Level A harassment zones. 

Minke Whales 

Minke whales may be present in 

Tongass Narrows year-round. Their 

abundance throughout Southeast Alaska 

is very low, and anecdotal reports have 

not included minke whales near the 

project area. ADOT’s monitoring 

program in Tongass Narrows also did 

not report any minke whale sightings. 

However, minke whales are distributed 

throughout a wide variety of habitats 

and could occur near the project area. 

Minke whales are generally sighted as 

solo individuals (Dahlheim et al. 2009). 

As noted above, ADOT estimates that 

simultaneous use of two hammers (any 

combination) could occur on up to 44 

days during the project. On those days, 

the Level B harassment zone will extend 

into Clarence Strait. Based on Freitag 

(2017; as cited in 83 FR 37473; August 

1, 2018 and 83 FR 34134; July 17, 2019), 

ADOT estimates that three individual 

minke whales may occur near or within 

the Level B harassment zone (including 

both Tongass Narrows and Clarence 

Strait) every four months. Based on that 

estimated occurrence rate, NMFS 

estimates that 3 minke whales may 

occur in the Level B harassment zone 

during the planned activities (occurring 

over approximately 3 months), and 

authorized 3 takes by Level B 

harassment of minke whales (Table 14). 

The largest Level A harassment zone 

for minke whale extends 3,584 m from 

the noise source for 10 hours of DTH 

using a single hammer, and 3,084 m 

from the noise source for 4 hours of 

DTH using two hammers for 30-in piles 

simultaneously. (As noted previously, 

ADOT estimates that simultaneous use 

of any two hammer types will occur on 

no more than 44 days.) Zones for shorter 

durations and other activities will be 

smaller (Table 13). NMFS required a 

1,500 m shutdown zone for minke 

whales during 24-in and 30-in DTH 

activities. Therefore, for some DTH 

activities, the estimated Level A 

harassment zone is larger than the 

required shutdown zone, and Level A 

harassment could occur. 

To calculate take by Level A 

harassment, ADOT first calculated the 

ratio of the maximum Level A 

harassment isopleth for 30-in DTH using 

a single hammer minus the shutdown 

zone isopleth (3,584 m¥1,500 m = 

2,084 m) to the Level B harassment zone 

isopleth (13,594 m; 2,084 m/13,594 m = 

0.1533). ADOT multiplied the resulting 

ratio by the total potential take by Level 

B harassment, resulting in 1 take by 

Level A harassment (i.e., 3 takes by 

Level B harassment × 0.1533 = 1 take by 

Level A harassment). NMFS reviewed 

and concurs with this method. 

(Potential operation of two DTH 

hammers for 24-in/30-in or 30-in/30-in 

pile combinations would result in larger 

Level A harassment isopleths than 

4,269 m, however, such concurrent 

work would rarely occur, if at all, and 

therefore, as described above NMFS 

expects that calculating Level A 

harassment take using those zones is 

unnecessary.) Take by Level B 

harassment was calculated as the total 

potential minke whale takes by Level B 

harassment minus the takes by Level A 

harassment. ADOT therefore requested, 

and NMFS authorized 1 take by Level A 

harassment and 2 takes by Level B 

harassment (3 total takes of minke 

whale; Table 14). 


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

Species DPS/stock 

Authorized take 

Percent 

Level A of stock 

harassment 

Level B 

harassment Total 

Steller sea lion .................................. Eastern U.S. ..................................... 91 2,169 2,260 5.2 

Harbor seal ....................................... Clarence Strait ................................. 116 1,014 1,130 4.1 

Harbor porpoise ................................ Southeast Alaska ............................. 5 27 32 2.5 

Dall’s porpoise .................................. Alaska ............................................... 20 207 227 1.7 

Pacific white-sided dolphin ............... North Pacific ..................................... 0 92 92 0.3 

Killer whale ........................................ Alaska Resident ............................... 0 72 72 a 3.1 

West Coast Transient a 20.1 

Northern Resident a 23.8 

Humpback whale .............................. Central North Pacific ........................ 0 228 228 2.3 

Minke whale ...................................... Alaska ............................................... 1 2 3 N/A 

a Conservatively assumes that all 72 takes occur to each stock. 

Mitigation Measures 

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. 

NMFS regulations require applicants for 

incidental take authorizations to include 

information about the availability and 

feasibility (economic and technological) 

of equipment, methods, and manner of 

conducting the activity or other means 

of effecting the least practicable adverse 

impact upon the affected species or 

stocks and their habitat (50 CFR 

216.104(a)(11)). 

In evaluating how mitigation may or 

may not be appropriate to ensure the 

least practicable adverse impact on 

species or stocks and their habitat, as 

well as subsistence uses where 

applicable, we carefully consider two 

primary factors: 

(1) The manner in which, and the 

degree to which, the successful 

implementation of the measure(s) is 

expected to reduce impacts to marine 

mammals, marine mammal species or 

stocks, and their habitat. This considers 

the nature of the potential adverse 

impact being mitigated (likelihood, 

scope, range). It further considers the 

likelihood that the measure will be 

effective if implemented (probability of 

accomplishing the mitigating result if 

implemented as planned), the 

likelihood of effective implementation 

(probability implemented as planned), 

and; 

(2) The practicability of the measures 

for applicant implementation, which 

may consider such things as cost, 

impact on operations, and, in the case 

of a military readiness activity, 

personnel safety, practicality of 

implementation, and impact on the 

effectiveness of the military readiness 

activity. 

Because of the need for an ESA 

Section 7 consultation for effects of the 

project on ESA listed humpback whales, 

there are a number of mitigation 

measures that go beyond, or are in 

addition to, typical mitigation measures 

we would otherwise require for this sort 

of project. However, these measures are 

typical for actions in the Ketchikan area. 

The mitigation measures included 

herein include measures that align with 

the 2019 Biological Opinion. ADOT 

must employ the following mitigation 

measures as included in the proposed 

IHA: 

• Avoid direct physical interaction 

with marine mammals during 

construction activity. If a marine 

mammal comes within 10 m of such 

activity, operations must cease and 

vessels must reduce speed to the 

minimum level required to maintain 

steerage and safe working conditions 

(note that NMFS expects that a 10 m 

shutdown zone is sufficient to avoid 

direct physical interaction with marine 

mammals, but ADOT conservatively 

proposed a 20 m shutdown zone to 

avoid physical interaction for in-water 

other than vessel transit); 

• Ensure that construction 

supervisors and crews, the monitoring 

team and relevant ADOT 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; 

• 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; 

• For any marine mammal species for 

which take by Level B harassment has 

not been requested or authorized, inwater pile installation/removal and DTH 

will shut down immediately when the 

animals are sighted; 

• Employ PSOs and establish 

monitoring locations as described in the 

Marine Mammal Monitoring Plan and 

Section 5 of the IHA. The Holder 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 removal at least three PSOs 

must be used; 

• The placement of the PSOs during 

all pile driving and removal and DTH 

activities will ensure that the entire 

shutdown zone is visible during pile 

installation; 

• Monitoring must take place from 30 

minutes prior to initiation of pile 

driving or DTH activity (i.e., preclearance monitoring) through 30 

minutes post-completion of pile driving 

or DTH activity; 

• If in-water work ceases for more 

than 30 minutes, ADOT will conduct 

pre-clearance monitoring of both the 

Level B harassment zone and shutdown 

zone; 

• Pre-start clearance monitoring must 

be conducted during periods of 

visibility sufficient for the lead PSO to 

determine that the shutdown zones 

indicated in Table 15 are clear of marine 

mammals. Pile driving may commence 

following 30 minutes of observation 

when the determination is made that the 

shutdown zones are clear of marine 

mammals; 

• If a marine mammal is observed 

entering or within the shutdown zones 


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indicated in Table 15, pile driving must 

be delayed or halted. If pile driving is 

delayed or halted due to the presence of 

a marine mammal, the activity may not 

commence or resume until either the 

animal has voluntarily exited and been 

visually confirmed beyond the 

shutdown zone (Table 15) or 15 minutes 

have passed without re-detection of the 

animal (30 minutes for humpback 

whales); 

• As required by the 2019 Biological 

Opinion, if waters exceed a sea state 

that restricts the PSOs’ ability to make 

observations within the shutdown zone, 

in-water pile installation and removal 

will cease. Pile installation and removal 

will not be initiated or continue until 

the appropriate shutdown zone is 

visible in its entirety; 

• For humpback whales, if the 

boundaries of the harassment zone have 

not been monitored continuously during 

a work stoppage, the entire harassment 

zone will be surveyed again to ensure 

that no humpback whales have entered 

the harassment zone that were not 

previously accounted for; 

• In-water activities will take place 

only: Between civil dawn and civil dusk 

when PSOs can effectively monitor for 

the presence of marine mammals; 

during conditions with a Beaufort Sea 

State of 4 or less; when the entire 

shutdown zone and adjacent waters are 

visible (e.g., monitoring effectiveness is 

not reduced due to rain, fog, snow, etc.). 

Pile driving may continue for up to 30 

minutes after sunset during evening 

civil twilight, as necessary to secure a 

pile for safety prior to demobilization 

for the evening. PSO(s) will continue to 

observe shutdown and monitoring zones 

during this time. The length of the postactivity monitoring period may be 

reduced if darkness precludes visibility 

of the shutdown and monitoring zones; 

• Vessel operators will implement the 

following required measures: Maintain a 

watch for marine mammals at all times 

while underway; remain at least and at 

least 91 m (100 yards (yd)) from all 

other listed marine mammals, travel at 

less than 5 knots (9 km/hr) when within 

274 m (300 yd) of a whale; avoid 

changes in direction and speed when 

within 274 m (300 yd) of whales, unless 

doing so is necessary for maritime 

safety; not position vessel(s) in the path 

of whales, and will not cut in front of 

whales in a way or at a distance that 

causes the whales to change their 

direction of travel or behavior 

(including breathing/surfacing pattern); 

check the waters immediately adjacent 

to the vessel(s) to ensure that no whales 

will be injured when the propellers are 

engaged; adhere to the Alaska 

Humpback Whale Approach 

Regulations when transiting to and from 

the project site (see 50 CFR 216.18, 

223.214, and 224.103(b)); not allow 

lines to remain in the water, and not 

throw trash or other debris overboard, 

thereby reducing the potential for 

marine mammal entanglement; follow 

established transit routes and travel <10 

knots while in the harassment zones; 

follow the speed limit within Tongass 

Narrows (7 knots for vessels over 23 ft 

in length). If a whale’s course and speed 

are such that it will likely cross in front 

of a vessel that is underway, or 

approach within 91 m (100 yards (yd)) 

of the vessel, and if maritime conditions 

safely allow, the engine will be put in 

neutral and the whale will be allowed 

to pass beyond the vessel, except that 

vessels will remain 460 m (500 yd) from 

North Pacific right whales; if a 

humpback whale comes within 10 m 

(32.8 ft) of a vessel during construction, 

the vessel will reduce speed to the 

minimum level required to maintain 

safe steerage and working conditions 

until the humpback whale is at least 10 

m (32.8 ft) away from the vessel; vessels 

are prohibited from disrupting the 

normal behavior or prior activity of a 

whale by any other act or omission. 

• ADOT 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 reducedenergy 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; and 

• If take by Level B harassment 

reaches the authorized limit for an 

authorized species, pile installation will 

be stopped as these species approach 

the Level B harassment zone to avoid 

additional take of them. 

Further, on days when simultaneous 

use of two hammers producing 

continuous noise (two DTH hammers, 

one DTH and one vibratory hammer, or 

two vibratory hammers) is expected: 

• When combinations of one DTH 

hammer with a vibratory hammer or two 

DTH hammers are used simultaneously, 

each PSO of the two contractors will 

have three PSOs working and the PSO 

teams will work together to monitor the 

entire area; 

• One or more PSOs will be present 

at each construction site during in-water 

pile installation and removal so that 

Level A harassment zones and 

shutdown zones are monitored by a 

dedicated PSO at all times. 

• The ADOT environmental 

coordinator for the project will 

implement coordination between or 

among the PSO contractors. ADOT will 

include in the contracts that PSOs must 

coordinate, collaborate, and otherwise 

work together to ensure compliance 

with project permits and authorizations. 

The following specific mitigation 

measures will also apply to ADOT’s inwater construction activities: 

Establishment of Level A Harassment 

Zones and Shutdown Zones—For all 

pile driving/removal and DTH activities, 

ADOT will establish a shutdown zone 

(Table 15). 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 vary based on the activity type 

and duration and marine mammal 

hearing group (Table 15). For vibratory 

installation and removal and impact 

installation, shutdown zones will be 

based on the Level A harassment 

isopleth distances for each hearing 

group. 

ADOT anticipates that the daily 

duration of DTH use may vary 

significantly, with large differences in 

maximum zones sizes possible 

depending on the work planned for a 

given day. Given this uncertainty and 

concerns related to ESA-listed 

humpback whales, ADOT will utilize a 

tiered system to identify and monitor 

the appropriate Level A harassment 

zones and shutdown zones, based on 

the maximum expected DTH duration. 

At the start of any work involving DTH, 

ADOT will first determine whether DTH 

may occur at two sites concurrently or 

just at one site. If DTH may occur at two 

sites concurrently, then ADOT will 

implement the Level A harassment 

zones and shutdown zones associated 

with simultaneous DTH use of the 

relevant pile sizes (Table 13 and Table 

15). If DTH may only occur at one site, 

ADOT will then determine the 

maximum duration of DTH possible that 

day (according to the defined duration 

intervals in Table 15), which will 

determine the appropriate Level A 

harassment isopleth for that day (Table 

12 and Table 13). This Level A 

harassment zone and associated 

shutdown zone must be observed by 

PSO(s) for the entire work day or until 

it is determined that, given the duration 

of activity for the day, the Level A 

harassment isopleth cannot exceed the 

next lower Level A harassment isopleth 

size in Table 12. 

Due to practicability concerns, 

shutdown zones for some species during 

some activities may be smaller than the 

Level A harassment isopleths (Table 15). 

The placement of PSOs during all pile 


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driving, pile removal, and DTH 

activities (described in detail in the 

Monitoring and Reporting section) will 

ensure that the entire shutdown zones 

are visible during pile installation. 

TABLE 15—SHUTDOWN ZONES AND LEVEL B HARASSMENT ISOPLETHS FOR EACH ACTIVITY

Activity Pile size 

(in) 

Minutes per 

pile or 

strikes per 

pile 

Shutdown distances 

(m) Level B 

harassment 

isopleth 

(m) 

LF 

(humpback 

whales) 

LF 

(minke 

whales) 

MF HF PW OW 

Vibratory Installation ................. 30 60 min ........ 50 20 6,310 

24 60 min 5,412 

20 60 min 

Vibratory Removal .................... 24 60 min 

DTH of Rock Sockets ............... 30 60 min ........ 780 1,500 30 500 200 40 13,594 

120 min ...... 1,300 50 50 

180 min ...... 1,700 60 70 

240 min ...... 2,000 70 80 

300 min ...... 2,300 90 90 

360 min ...... 2,600 100 100 

420 min ...... 2,900 

480 min ...... 3,100 

540 min ...... 3,400 

600 min ...... 3,600 130 100 

24 60 min ........ 360 1,500 20 500 200 20 

120 min ...... 570 30 30 

180 min ...... 750 30 30 

240 min ...... 910 40 40 

300 min ...... 1,100 40 50 

360 min ...... 1,200 50 50 

420 min ...... 1,400 50 60 

480 min ...... 1,500 60 60 

540 min ...... 1,600 60 70 

600 min ...... 1,700 60 70 

DTH of Tension Anchor ............ 8 120 min ...... 90 90 20 100 50 20 

240 min ...... 130 130 160 70 

Impact Installation ..................... 30 50 strikes .... 100 100 20 120 60 20 2,154 

24 50 strikes .... 60 60 70 30 1,000 

20 50 strikes 

TABLE 16—SHUTDOWN ZONES, BY HEARING GROUP FOR SIMULTANEOUS USE OF TWO DTH HAMMERS

Activity combination Duration 

(minutes) 

Level A harassment isopleth 

(m) 

LF MF HF PW OW 

8-in pile, 8-in pile ..................................... 60 90 20 100 50 20 

120 130 160 70 

180 170 200 100 

240 210 250 110 

8-in pile, 24-in pile ................................... 60 520 20 500 200 20 

120 820 30 40 

180 1,080 40 50 

240 1,300 50 60 

8-in pile, 30-in pile ................................... 60 1,110 40 50 

120 1,770 70 70 

180 2,310 90 90 

240 2,800 100 110 

24-in pile, 24-in pile ................................. 60 570 20 30 

120 910 32 40 

180 1,190 42 50 

240 1,440 60 60 

24-in pile, 30-in ........................................ 60 900 40 40 

120 1,430 60 60 

180 1,880 70 80 

240 2,270 90 90 

30-in pile, 30-in pile ................................. 60 1,230 50 50 

120 1,950 70 80 


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TABLE 16—SHUTDOWN ZONES, BY HEARING GROUP FOR SIMULTANEOUS USE OF TWO DTH HAMMERS—Continued 

Activity combination Duration 

(minutes) 

Level A harassment isopleth 

(m) 

LF MF HF PW OW 

180 2,550 100 100 

240 3,090 110 120 

ADOT also must abide by the terms 

and conditions of the December 19, 

2019 Biological Opinion and Incidental 

Take Statement issued by NMFS 

pursuant to section 7 of the Endangered 

Species Act. 

Based on our evaluation of the 

applicant’s proposed measures, as well 

as other measures considered by NMFS, 

NMFS has determined that the required 

mitigation measures provide the means 

effecting the least practicable impact on 

the affected species or stocks and their 

habitat, paying particular attention to 

rookeries, mating grounds, and areas of 

similar significance. 

Monitoring and Reporting 

In order to issue an IHA for an 

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

MMPA states that NMFS must set forth 

requirements pertaining to the 

monitoring and reporting of such taking. 

The MMPA implementing regulations at 

50 CFR 216.104 (a)(13) indicate that 

requests for authorizations must include 

the suggested means of accomplishing 

the necessary monitoring and reporting 

that will result in increased knowledge 

of the species and of the level of taking 

or impacts on populations of marine 

mammals that are expected to be 

present in the project area. Effective 

reporting is critical both to compliance 

as well as ensuring that the most value 

is obtained from the required 

monitoring. 

Monitoring and reporting 

requirements prescribed by NMFS 

should contribute to improved 

understanding of one or more of the 

following: 

• Occurrence of marine mammal 

species or stocks in the area in which 

take is anticipated (e.g., presence, 

abundance, distribution, density). 

• Nature, scope, or context of likely 

marine mammal exposure to potential 

stressors/impacts (individual or 

cumulative, acute or chronic), through 

better understanding of: (1) Action or 

environment (e.g., source 

characterization, propagation, ambient 

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

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

of marine mammal species with the 

action; or (4) biological or behavioral 

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

feeding areas). 

• Individual marine mammal 

responses (behavioral or physiological) 

to acoustic stressors (acute, chronic, or 

cumulative), other stressors, or 

cumulative impacts from multiple 

stressors. 

• How anticipated responses to 

stressors impact either: (1) Long-term 

fitness and survival of individual 

marine mammals; or (2) populations, 

species, or stocks. 

• Effects on marine mammal habitat 

(e.g., marine mammal prey species, 

acoustic habitat, or other important 

physical components of marine 

mammal habitat). 

• Mitigation and monitoring 

effectiveness. 

Visual Monitoring 

Monitoring must be conducted by 

qualified, NMFS-approved PSOs, in 

accordance with the following: 

• PSOs must be independent (i.e., not 

construction personnel) 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. Other 

PSOs may substitute other relevant 

experience, education (degree in 

biological science or related field), or 

training for prior experience performing 

the duties of a PSO during construction 

activity pursuant to a NMFS-issued 

IHA. 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 must be 

approved by NMFS prior to beginning 

any activity subject to this IHA; and 

• PSOs must record all observations 

of marine mammals as described in the 

Section 5 of the IHA and the Marine 

Mammal Monitoring Plan, regardless of 

distance from the pile being driven. 

PSOs shall document any behavioral 

reactions in concert with distance from 

piles being driven or removed; 

PSOs must have the following 

additional qualifications: 

• Ability to conduct field 

observations and collect data according 

to assigned protocols; 

• Experience or training in the field 

identification of marine mammals, 

including the identification of 

behaviors; 

• Sufficient training, orientation, or 

experience with the construction 

operation to provide for personal safety 

during observations; 

• Writing skills sufficient to prepare a 

report of observations 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; 

Additionally, as required by NMFS’ 

December 2019 Biological Opinion, 

each PSO will be trained and provided 

with reference materials to ensure 

standardized and accurate observations 

and data collection. 

ADOT must employ three PSOs 

during all pile driving and DTH. A 

minimum of one PSO (the lead PSO) 

must be assigned to the active pile 

driving or DTH location to monitor the 

shutdown zones and as much of the 

Level B harassment zones as possible. 

Two additional PSOs are also required, 

though the observation points may vary 

depending on the construction activity 

and location of the piles. To select the 

best observation locations, prior to start 

of construction, the lead PSO will stand 

at the construction site to monitor the 

Level A harassment zones while two or 

more PSOs travel in opposite directions 

from the project site along Tongass 

Narrows until they have reached the 

edge of the appropriate Level B 

harassment zone, where they will 

identify suitable observation points 

from which to observe. When needed, 

an additional PSO will be stationed on 

the north end of Revilla Island 

observing to the northwest. See Figure 

2–11 of ADOT’s Marine Mammal 


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Monitoring and Mitigation Plan for a 

map of planned PSO locations. If 

visibility deteriorates so that the entire 

width of Tongass Narrows at the 

harassment zone boundary is not 

visible, additional PSOs may be 

positioned so that the entire width is 

visible, or work will be halted until the 

entire width is visible to ensure that any 

humpback whales entering or within the 

harassment zone are detected by PSOs. 

When DTH use occurs, or 

simultaneous use of one DTH with a 

vibratory hammer or two DTH systems 

occurs, creating Level B harassment 

zones that exceed 13 km and 21 km, 

respectively, and Level A harassment 

zones that extend over 6 km, one 

additional PSO will be stationed at the 

northernmost land-based location at the 

entrance to Tongass Narrows (at least 

two PSOs total at that location, four 

PSOs on duty across all PSO locations). 

One of these PSO will focus on Tongass 

Narrows, specifically watching for 

marine mammals that could approach or 

enter Tongass Narrows and the project 

area. The second PSO will look out into 

Clarence Strait, watching for marine 

mammals that could swim through the 

ensonified area. No additional PSOs 

will be required at the southern-most 

monitoring location because the Level B 

harassment zones are truncated to the 

southeast by islands, which prevent 

propagation of sound in that direction 

beyond the confines of Tongass 

Narrows. Takes by Level B harassment 

will be recorded by PSOs and 

extrapolated based upon the number of 

observed takes and the percentage of the 

Level B harassment zone that was not 

visible. 

Each construction contractor 

managing an active construction site 

and on-going in-water pile installation 

or removal will provide qualified, 

independent PSOs for their specific 

contract. The ADOT environmental 

coordinator for the project will 

implement coordination between or 

among the PSO contractors. It will be a 

required component of their contracts 

that PSOs coordinate, collaborate, and 

otherwise work together to ensure 

compliance with project permits and 

authorizations. 

Reporting 

A draft marine mammal monitoring 

report will be submitted to NMFS 

within 90 days after the completion of 

pile driving and removal 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 report will include an overall 

description of work completed, a 

narrative regarding marine mammal 

sightings, and associated PSO data 

sheets. Specifically, the report must 

include: 

• Dates and times (begin and end) of 

all marine mammal monitoring; 

• Construction activities occurring 

during each daily observation period, 

including the number and type of piles 

driven or removed and by what method 

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

total equipment duration for vibratory 

removal or DTH for each pile or hole 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 

(min/max/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; 

• Table summarizing any incidents 

resulting in take of ESA-listed species; 

• Detailed information about any 

implementation of any mitigation 

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

description of specific actions that 

ensued, and resulting changes in 

behavior of the animal(s), if any; 

• Description of other human activity 

within each monitoring period; 

• Description of any deviation from 

initial proposal in pile numbers, pile 

types, average driving times, etc.; 

• Brief description of any 

impediments to obtaining reliable 

observations during construction 

period; 

• Description of any impediments to 

complying with these mitigation 

measures; and 

• If visibility degrades to where the 

PSO(s) cannot view the entire impact or 

vibratory harassment zones, take of 

humpback whales will be extrapolated 

based on the estimated percentage of the 

monitoring zone that remains visible 

and the number of marine mammals 

observed. 

If no comments are received from 

NMFS within 30 days, the draft final 

report will constitute the final report. If 

comments are received, a final report 

addressing NMFS comments must be 

submitted within 30 days after receipt of 

comments. 

Reporting Injured or Dead Marine 

Mammals 

In the event that personnel involved 

in the construction activities discover 

an injured or dead marine mammal, the 

IHA-holder must immediately cease the 

specified activities and report the 

incident to the Office of Protected 

Resources (OPR) 

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

NMFS and to the Alaska Regional 

Stranding Coordinator as soon as 

feasible. If the death or injury was 

clearly caused by the specified activity, 

ADOT must immediately cease the 

specified activities until NMFS is able 

to review the circumstances of the 

incident and determine what, if any, 

additional measures are appropriate to 

ensure compliance with the terms of the 

IHA. The IHA-holder must not resume 

their activities until notified by NMFS. 

The report must include the following 

information: 

• Time, date, and location (latitude/ 

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. 


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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 responses (e.g., intensity, 

duration), the context of any responses 

(e.g., critical reproductive time or 

location, migration), as well as effects 

on habitat, and the likely effectiveness 

of the mitigation. We also assess the 

number, intensity, and context of 

estimated takes by evaluating this 

information relative to population 

status. Consistent with the 1989 

preamble for NMFS’ implementing 

regulations (54 FR 40338; September 29, 

1989), the impacts from other past and 

ongoing anthropogenic activities are 

incorporated into this analysis via their 

impacts on the environmental baseline 

(e.g., as reflected in the regulatory status 

of the species, population size and 

growth rate where known, ongoing 

sources of human-caused mortality, or 

ambient noise levels). 

To avoid repetition, our analysis 

applies to all species listed in Table 1 

for which take could occur, given that 

NMFS expects the anticipated effects of 

the planned pile driving/removal and 

DTH on different marine mammal 

stocks to be similar in nature. Where 

there are meaningful differences 

between species or stocks, or groups of 

species, in anticipated individual 

responses to activities, impact of 

expected take on the population due to 

differences in population status, or 

impacts on habitat, NMFS has identified 

species-specific factors to inform the 

analysis. 

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. 

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. 

NMFS does not anticipate that serious 

injury or mortality will occur as a result 

of ADOT’s planned activity given the 

nature of the activity, even in the 

absence of required mitigation. Further, 

no take by Level A harassment is 

anticipated for Pacific white-sided 

dolphin, killer whale, or humpback 

whale, due to the likelihood of 

occurrence and/or required mitigation 

measures. As stated in the mitigation 

section, ADOT will implement 

shutdown zones that equal or exceed 

many of the Level A harassment 

isopleths shown in Table 12. Take by 

Level A harassment is authorized for 

some species (Steller sea lions, harbor 

seals, harbor porpoises, Dall’s porpoises, 

and minke whales) to account for the 

potential that an animal could enter and 

remain within the area between a Level 

A harassment zone and the shutdown 

zone for a duration long enough to be 

taken by Level A harassment, and in 

some cases, to account for the 

possibility that an animal could enter a 

shutdown zone without detection given 

the various obstructions along the 

shoreline, and remain in the Level A 

harassment zone for a duration long 

enough to be taken by Level A 

harassment before being observed and a 

shutdown occurring. Any take by Level 

A harassment is expected to arise from, 

at most, a small degree of PTS because 

animals would need to be exposed to 

higher levels and/or longer duration 

than are expected to occur here in order 

to incur any more than a small degree 

of PTS. 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. 

For all species and stocks, take will 

occur within a limited, confined area 

(adjacent to the project site) of the 

stock’s range. Take by Level A 

harassment and Level B harassment will 

be reduced to the level of least 

practicable adverse impact through use 

of mitigation measures described herein. 

Further the amount of take authorized is 

small when compared to stock 

abundance. 

Behavioral responses of marine 

mammals to pile driving, pile removal, 

and DTH at the sites in Tongass 

Narrows are expected to be mild, short 

term, and temporary. 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. Given that pile 

driving, pile removal, and DTH will 

occur for only a portion of the project’s 

duration and often on nonconsecutive 

days, any harassment will be temporary. 

Additionally, many of the species 

present in Tongass Narrows or Clarence 

Strait 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. 

For all species except humpback 

whales, there are no known Biologically 

Important Areas (BIAs) near the project 

zone that will be impacted by ADOT’s 

planned activities. For humpback 

whales, the whole of Southeast Alaska 

is a seasonal BIA from spring through 

late fall (Ferguson et al. 2015), however, 

Tongass Narrows and Clarence Strait are 

not important portions of this habitat 

due to development and human 

presence. Tongass Narrows is also 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 

humpback whales between March and 

May (Ellison et al. 2012), it is not 

currently designated as critical habitat 

for humpback whales (86 FR 21082; 

April 21, 2021). 

More generally, there are no known 

calving or rookery grounds within the 

project area, but anecdotal evidence 

from local experts shows that marine 

mammals are more prevalent in Tongass 

Narrows and Clarence Strait during 

spring and summer associated with 

feeding on aggregations of fish, meaning 

the area may play a role in foraging. 

Because ADOT’s activities could occur 

during any season, takes may occur 

during important feeding times. 

However, the project area represents a 

small portion of available foraging 

habitat and impacts on marine mammal 

feeding for all species, including 

humpback whales, should be minimal. 

Any impacts on marine mammal prey 

that occur during ADOT’s planned 

activity will 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. Indirect effects on marine 

mammal prey during the construction 

are expected to be minor, and these 


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effects are unlikely to cause substantial 

effects on marine mammals at the 

individual level, with no expected effect 

on annual rates of recruitment or 

survival. 

In addition, it is unlikely that minor 

noise effects in a small, localized area of 

habitat will have any effect on the 

reproduction or survival of any 

individuals, much less the stocks’ 

annual rates of recruitment or survival. 

In combination, we believe that these 

factors, as well as the available body of 

evidence from other similar activities, 

demonstrate that the potential effects of 

the specified activities will have only 

minor, short-term effects on individuals. 

The specified activities are not expected 

to impact rates of recruitment or 

survival and will, therefore, not result in 

population-level impacts. 

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 the species 

or stock through effects on annual rates 

of recruitment or survival: 

• No serious injury or mortality is 

anticipated or authorized; 

• Take by Level A harassment of 

Pacific white-sided dolphin, killer 

whale, and humpback whale is not 

anticipated or authorized; 

• ADOT will implement mitigation 

measures including soft-starts for 

impact pile driving and shutdown zones 

to minimize the numbers of marine 

mammals exposed to injurious levels of 

sound, and to ensure 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 relatively low 

for all stocks and will not be of a 

duration or intensity expected to result 

in impacts on reproduction or survival; 

• 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 Tongass Narrows 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 

required monitoring and mitigation 

measures, NMFS finds that the total 

marine mammal take from the planned 

activity will have a negligible impact on 

all affected marine mammal species or 

stocks. 

Small Numbers 

As noted above, only small numbers 

of incidental take may be authorized 

under sections 101(a)(5)(A) and (D) of 

the MMPA for specified activities other 

than military readiness activities. The 

MMPA does not define small numbers 

and so, in practice, where estimated 

numbers are available, NMFS compares 

the number of individuals taken to the 

most appropriate estimation of 

abundance of the relevant species or 

stock in our determination of whether 

an authorization is limited to small 

numbers of marine mammals. When the 

predicted number of individuals to be 

taken is fewer than one third of the 

species or stock abundance, the take is 

considered to be of small numbers. 

Additionally, other qualitative factors 

may be considered in the analysis, such 

as the temporal or spatial scale of the 

activities. 

The instances of take NMFS 

authorized are below one third of the 

estimated stock abundance for all stocks 

(see Table 14). The number of animals 

that we expect to authorize to be taken 

from these stocks is considered small 

relative to the relevant stocks’ 

abundances even if each estimated 

taking occurred to a new individual, 

which is an unlikely scenario. Some 

individuals may return multiple times 

in a day, but PSOs will count them as 

separate takes 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. 

The most recent estimate was 13,110 

animals for just a portion of the stock’s 

range. Therefore, the 227 authorized 

takes of this stock clearly represent 

small numbers of this stock. 

Likewise, the Southeast Alaska stock 

of harbor porpoise has no official NMFS 

abundance estimate as the most recent 

estimate is greater than 8 years old. The 

most recent estimate was 11,146 

animals (Muto et al. 2021) and it is 

highly unlikely this number has 

drastically declined. Therefore, the 32 

authorized takes of this stock clearly 

represent small numbers of this stock. 

There is no current or historical 

estimate of the Alaska minke whale 

stock, but there are known to be over 

1,000 minke whales in the Gulf of 

Alaska (Muto et al. 2018), so the 3 

authorized takes clearly 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 ADOT’s project area impacts a 

small portion of this range. 

Based on the analysis contained 

herein of the planned activity (including 

the required 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 

Alaska 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. 

Harbor seals are the marine mammal 

species most regularly harvested for 

subsistence by households in Ketchikan 

and Saxman (a community a few miles 

south of Ketchikan, on the Tongass 

Narrows). Eighty harbor seals were 

harvested by Ketchikan residents in 

2007, which ranked fourth among all 

communities in Alaska that year for 

harvest of harbor seals. Thirteen harbor 

seals were harvested by Saxman 

residents in 2007. In 2008, two Steller 

sea lions were harvested by Ketchikanbased subsistence hunters, but this is 

the only record of sea lion harvest by 

residents of either Ketchikan or Saxman. 

In 2012, the community of Ketchikan 

had an estimated subsistence take of 22 

harbor seals and 0 Steller sea lion (Wolf 

et al. 2013). NMFS is not aware of more 

recent data. Hunting usually occurs in 

October and November (ADF&G 2009), 

but there are also records of relatively 

high harvest in May (Wolfe et al. 2013). 

The Alaska Department of Fish and 


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Game (ADF&G) has not recorded harvest 

of cetaceans from Ketchikan or Saxman 

(ADF&G 2018). 

All project activities will take place 

within the industrial area of Tongass 

Narrows immediately adjacent to 

Ketchikan where subsistence activities 

do not generally occur. Both the harbor 

seal and the Steller sea lion may be 

temporarily displaced from the project 

area. The project will also not have an 

adverse impact on the availability of 

marine mammals for subsistence use at 

locations farther away, where these 

construction activities are not expected 

to take place. Some minor, short-term 

harassment of the harbor seals could 

occur, but given the information above, 

we do not expect such harassment to 

have effects on subsistence hunting 

activities. 

Based on the description of the 

specified activity and the required 

mitigation and monitoring measures, 

NMFS has determined that there will 

not be an unmitigable adverse impact on 

subsistence uses from ADOT’s planned 

activities. 

National Environmental Policy Act 

To comply with the National 

Environmental Policy Act of 1969 

(NEPA; 42 U.S.C. 4321 et seq.) and 

NOAA Administrative Order (NAO) 

216–6A, NMFS must evaluate our 

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

IHA) and alternatives with respect to 

potential impacts on the human 

environment. This action is consistent 

with categories of activities identified in 

Categorical Exclusion B4 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 would preclude this 

categorical exclusion. Accordingly, 

NMFS has determined that this action 

qualifies to be categorically excluded 

from further NEPA review. 

Endangered Species Act 

Section 7(a)(2) of the Endangered 

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

1531 et seq.) requires that each Federal 

agency insure that any action it 

authorizes, funds, or carries out is not 

likely to jeopardize the continued 

existence of any endangered or 

threatened species or result in the 

destruction or adverse modification of 

designated critical habitat. To ensure 

ESA compliance for the issuance of 

IHAs, NMFS’ Office of Protected 

Resources (OPR) consults internally 

whenever we propose to authorize take 

for endangered or threatened species, in 

this case with NMFS’ Alaska Regional 

Office (AKRO). 

NMFS OPR is proposing to authorize 

take of the Central North Pacific stock 

of humpback whales, of which a portion 

belong to the Mexico DPS of humpback 

whales, which are ESA-listed. On 

February 6, 2019, NMFS AKRO 

completed consultation with NMFS for 

the Tongass Narrows Project and issued 

a Biological Opinion. Reinitiation of 

formal consultation was required to 

analyze changes to the action that were 

not considered in the February 2019 

opinion (PCTS# AKR–2018–9806/ECO# 

AKRO–2018–01287). The original 

opinion considered the effects of only 

one project component being 

constructed at a time and did not 

analyze potential effects of concurrent 

pile driving that may cause effects to the 

listed species that were not considered 

in the original opinion; therefore, 

reinitiation of formal consultation was 

required. NMFS’ AKRO issued a revised 

Biological Opinion to NMFS’ OPR on 

December 19, 2019 that concluded that 

issuance of IHAs to ADOT is not likely 

to jeopardize the continued existence of 

Mexico DPS humpback whales. The 

effects of this Federal action were 

adequately analyzed in NMFS’ 

Endangered Species Act (ESA) Section 

7(a)(2) Biological Opinion for 

Construction of the Tongass Narrows 

Project (Gravina Access), revised 

December 19, 2019, which concluded 

that the take NMFS proposes to 

authorize through this IHA would not 

jeopardize the continued existence of 

any endangered or threatened species or 

destroy or adversely modify any 

designated critical habitat. NMFS has 

determined that issuance of this IHA 

does not require reinitiation of the 

December 2019 Biological Opinion. 

Authorization 

NMFS has issued an IHA to ADOT for 

the potential harassment of small 

numbers of eight marine mammal 

species incidental to construction of 

four facilities in the channel between 

Gravina Island and Revillagigedo 

(Revilla) Island in Ketchikan, Alaska, 

that includes the previously explained 

mitigation, monitoring and reporting 

requirements. 

Dated: March 11, 2022. 

Kimberly Damon-Randall, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2022–05561 Filed 3–17–22; 8:45 am] 

BILLING CODE 3510–22–P 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[Docket ID No.: NOAA–NOS–2022–0033] 

Deep Seabed Hard Minerals; Request 

for Extension of Exploration Licenses; 

Comments Request 

AGENCY: Office for Coastal Management 

(OCM), National Ocean Service (NOS), 

National Oceanic and Atmospheric 

Administration (NOAA), Department of 

Commerce (DOC). 

ACTION: Notice of receipt of application 

to extend Deep Seabed Mineral 

Exploration Licenses USA–1 and USA– 

4; request for comments. 

SUMMARY: NOS has received from the 

Lockheed Martin Corporation 

(‘‘Lockheed Martin’’ or ‘‘Licensee’’) a 

request to extend to 2027 two deep 

seabed hard mineral exploration 

licenses issued pursuant to the Deep 

Seabed Hard Mineral Resources Act 

(DSHMRA). Lockheed Martin’s 

extension request includes an updated 

exploration plan for activities 

conducted under the licenses. Lockheed 

Martin’s request and accompanying 

exploration plan are available for public 

review and comment on whether the 

Licensee has met the criteria for the 

issuance of extensions specified in 

DSHMRA. 

DATES: Comments may be submitted on 

or before May 17, 2022. 

ADDRESSES: To access and review all 

documents related to the extension 

request under consideration, please use 

http://www.regulations.gov by searching 

the Docket ID number NOAA–NOS– 

2022–0033. Comments submitted in 

response to this notice should be 

submitted electronically through the 

Federal eRulemaking Portal at http://

www.regulations.gov by selecting the 

Docket ID number. 

FOR FURTHER INFORMATION CONTACT: 

Kerry Kehoe, Federal Consistency 

Specialist, NOAA Office of Coastal 

Management, at kerry.kehoe@noaa.gov, 

or at 240–560–8515. 

SUPPLEMENTARY INFORMATION: NOAA has 

received an application from Lockheed 

Martin for a five-year extension of its 

two Deep Seabed Hard Mineral 

Exploration Licenses, USA–1 and USA– 

4. Lockheed Martin’s application 

includes a single revised exploration 

plan for both licenses that sets forth the 

activities to be conducted during the 

extension. 

DSHMRA exploration licenses USA–1 

and USA–4 were issued in 1984 and 

both are presently held by Lockheed 


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