5980 Federal Register / Vol. 87, No. 22 / Wednesday, February 2, 2022 / Notices 

DEPARTMENT OF COMMERCE 

National Oceanic and Atmospheric 

Administration 

[RTID 0648–XB709] 

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; proposed incidental 

harassment authorization; request for 

comments on proposed authorization 

and possible renewal. 

SUMMARY: NMFS has received a request 

from the Alaska Department of 

Transportation and Public Facilities 

(ADOT) for an Incidental Harassment 

Authorization (IHA) to take marine 

mammals incidental to the construction 

of four ferry berth facilities in Tongass 

Narrows in Ketchikan, Alaska: The 

Gravina Airport Ferry Layup Facility, 

the Gravina Freight Facility, the Revilla 

New Ferry Berth, and the Gravina Island 

Shuttle Ferry Berth Facility. Pursuant to 

the Marine Mammal Protection Act 

(MMPA), NMFS is requesting comments 

on its proposal to issue an IHA to 

incidentally take marine mammals 

during the specified activities. NMFS is 

also requesting comments on a possible 

one-time, one-year renewal that could 

be issued under certain circumstances 

and if all requirements are met, as 

described in Request for Public 

Comments at the end of this notice. 

NMFS will consider public comments 

prior to making any final decision on 

the issuance of the requested MMPA 

authorizations and agency responses 

will be summarized in the final notice 

of our decision. 

DATES: Comments and information must 

be received no later than March 4, 2022. 

ADDRESSES: Comments should be 

addressed to Jolie Harrison, Chief, 

Permits and Conservation Division, 

Office of Protected Resources, National 

Marine Fisheries Service. Written 

comments should be submitted via 

email to ITP.Davis@noaa.gov. 

Instructions: NMFS is not responsible 

for comments sent by any other method, 

to any other address or individual, or 

received after the end of the comment 

period. Comments, including all 

attachments, must not exceed a 25- 

megabyte file size. All comments 

received are a part of the public record 

and will generally be posted online at 

www.fisheries.noaa.gov/permit/ 

incidental-take-authorizations-undermarine-mammal-protection-act without 

change. All personal identifying 

information (e.g., name, address) 

voluntarily submitted by the commenter 

may be publicly accessible. Do not 

submit confidential business 

information or otherwise sensitive or 

protected information. 

FOR FURTHER INFORMATION CONTACT: 

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 

‘‘mitigation’’); and requirements 

pertaining to the mitigation, monitoring 

and reporting of the takings are set forth. 

The definitions of all applicable MMPA 

statutory terms cited above are included 

in the relevant sections below. 

National Environmental Policy Act 

To comply with the National 

Environmental Policy Act of 1969 

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

NOAA Administrative Order (NAO) 

216–6A, NMFS must review our 

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

IHA) with respect to potential impacts 

on the human environment. 

This action is consistent with 

categories of activities identified in 

Categorical Exclusion B4 (IHAs with no 

anticipated serious injury or mortality) 

of the Companion Manual for NOAA 

Administrative Order 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 

preliminarily determined that the 

issuance of the proposed IHA qualifies 

to be categorically excluded from 

further NEPA review. 

We will review all comments 

submitted in response to this notice 

prior to concluding our NEPA process 

or making a final decision on the IHA 

request. 

Summary of Request 

On 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 the 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). 


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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 is requesting a new 

IHA for incidental take associated with 

the continued marine construction of 

these facilities. This proposed IHA 

would be valid for one year. 

Description of Proposed Activity 

Overview 

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). 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 

(Figure 1). The project’s proposed 

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 proposed activities 

is planned to occur over 91 nonconsecutive days over one year 

beginning March 2022. 

Improvement and construction of 

facilities is important to provide reliable 

access to the airport and facilitate 

growth and development in the region. 

Some of the existing ferry facilities are 

aging and periodically out-of-service for 

repairs or maintenance, and this project 

would provide redundant ferry berths to 

increase reliability. Ketchikan is 

Alaska’s fifth largest city, with a 

population of approximately 8,125 

(DCCED 2017), and has numerous 

marine facilities including fishing 

infrastructure, cruise and ferry 

terminals, and shipyards. 

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Dates and Duration 

In-water construction is scheduled to 

begin on March 1, 2022, upon 

expiration of the current Phase I IHA (86 

FR 23938; May 5, 2021). ADOT 

anticipates that construction would 

occur during daylight hours only with 

in-water construction occurring 6 days 

per week. ADOT anticipates that the 

project would require approximately 91 

days of pile installation and removal 


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over the course of 7 or 8 months. 

Although it is anticipated that the 

project would be completed sooner, 

ADOT requests that the IHA be valid for 

a full year, from March 1, 2022 to 

February 28, 2023, to accommodate 

scheduling unknowns or delays. 

ADOT plans to implement the 

Essential Fish Habitat (EFH) 

Conservation Recommendations 

developed by NMFS. No in-water work 

would occur between March 1 and June 

15 for three project components: The 

Revilla New Ferry Berth and Upland 

Improvements, Gravina Airport Ferry 

Layup Facility, and Revilla Refurbish 

Existing Ferry Berth Facility. 

Specific Geographic Region 

The proposed construction project is 

located in Ketchikan, Alaska (Figure 1). 

Improvements to the Gravina Airport 

Ferry Layup Facility construction would 

occur in the same location as the 

existing layup dock facility. The new 

Gravina Freight Facility would be 

constructed in the same location as the 

existing barge offload facility. The New 

Gravina Island Shuttle Ferry Berth 

construction would occur slightly North 

of the Airport Ferry Layup Facility. 

Improvements and construction on 

Revilla Island would occur 

approximately 4 kilometers (km; 2.5 

miles (mi)) north of downtown 

Ketchikan. The new Revilla Island 

Airport Shuttle Ferry Berth would be 

constructed immediately adjacent to the 

existing Revilla Island Ferry Berth. 

Tongass Narrows is an approximately 

13-mile-long, north-south-oriented 

marine channel situated between 

Revilla Island to the east and Gravina 

Island to the west. In the vicinity of the 

proposed project, Tongass Narrows is as 

little as 300 meters (m; 984 feet; ft) 

wide. Tongass Narrows is generally 

characterized by strong tidal currents 

and by steep bedrock or coarse gravelcobble-boulder shoreline. Lower 

intertidal and shallow subtidal areas are 

often sandy or mixed gravel, sand, and 

shell, with varied amounts of silt. At 

other areas, however, such as at rocky 

points and along the northwestern shore 

of Pennock Island (which is located in 

the south end of Tongass Narrows, 

between Gravina and Revilla Islands), 

bedrock slopes steeply to subtidal 

depths. Subtidal habitats are a mix of 

bedrock outcrops or ledges, bouldercobble slopes, and, where lower slopes 

permit, sandy gravel bottoms, often 

mixed with significant amounts of shell 

debris, similar to intertidal habitats. 

Several small natural coves and areas 

protected by constructed breakwaters 

provide wave and current protection for 

marine habitats with sand or gravel 

bottoms with some areas of eelgrass 

(Zostera marina) beds. Extensive areas 

of riprap bank protection and fill occur 

along the northeastern shoreline of the 

City of Ketchikan. Construction of 

numerous buildings and docks on 

pilings over the intertidal and shallow 

subtidal zone has significantly modified 

the shorelines in these areas. Shoreline 

protection activities have similarly 

modified approximately 1 mile of the 

shoreline of Gravina Island in the 

vicinity of the airport and airport ferry 

terminal. 

Water depths reach approximately 49 

m (160 ft) in the middle of the Tongass 

Narrows between the airport and town, 

but generally do not exceed 18 m (60 ft) 

where piles would be installed. The 

channel bottom slopes at about 2:1 

(horizontal: vertical) from opposite 

shores. Geological conditions in the 

vicinity of the project were recently 

evaluated (CH2M 2018). The substrate 

consists of approximately 18 to 23 m (60 

to 75 ft) of very loose to very dense 

granular deltaic or alluvial sand and 

gravel. At approximately 18 to 23 m (60 

to 75 ft) below the mudline, the 

substrate transitions to phyllite bedrock 

(CH2M 2018). Pile installation would 

occur in waters ranging in depth from 

less than 1 m (3.3 ft) nearshore to 

approximately 20 m (66 ft), depending 

on the structure and location. 

Ongoing vessel activities throughout 

Tongass Narrows, land-based industrial 

and commercial activities, and regular 

aircraft operations result in elevated inair and underwater sound conditions in 

the project area that increase with 

proximity to the proposed project 

component sites. Sound levels likely 

vary seasonally, with elevated levels 

during summer when the tourism and 

fishing industries are at their peaks. 

Detailed Description of Specific Activity 

Planned construction includes the 

installation and continued construction 

of new ferry facilities and the 

renovation of existing structures. As 

stated above, the four proposed 

construction components include: The 

Gravina Airport Ferry Layup Facility, 

the Gravina Freight Facility, the Revilla 

New Ferry Berth and Upland 

Improvements, and the New Gravina 

Island Shuttle Ferry Berth and Related 

Terminal Improvements. ADOT 

anticipates that work may occur at 

multiple sites concurrently, and that 

two hammers or DTH equipment could 

be used concurrently (discussed further 

in the Estimated Take section). 

Gravina Airport Ferry Layup Facility 

The new ferry layup dock and transfer 

bridge would support layup and 

maintenance of the airport ferry system. 

The current layup dock at the Gravina 

Airport Ferry Layup Facility is in 

disrepair and needs to be replaced. 

ADOT would remove the existing 265- 

ft (80.1-m)-long floating dock, mooring 

structures, and transfer bridge and 

construct a new 250-ft by 85-ft (76.2 m 

by 25.9 m) concrete or steel floating 

dock in its place. The floating dock 

would be restrained by two siderestraint float dolphins and three 

corner/mid-restraint float dolphins. A 

new 20-ft by 140-ft (6.1 m by 42.6 m) 

steel transfer bridge would provide 

access to the floating dock. It would be 

necessary to remove, relocate, and 

replenish the existing rock slope, 

demolish the existing concrete 

abutment, and construct a new pilesupported bridge abutment. The Gravina 

Airport Ferry Layup Facility 

construction and Gravina Freight 

Facility construction is anticipated to 

require a total of 47 days of in-water pile 

installation and removal. 

Gravina Freight Facility 

The new Gravina Freight Facility, 

located approximately 100 m from the 

Gravina Airport Ferry Layup Facility 

(Figure 1), would be constructed in the 

same location as the existing barge 

offload facility. This facility would 

provide improved access to Gravina 

Island for highway loads that cannot be 

accommodated by the shuttle ferry. The 

existing ramp would be widened and regraded both above and below the high 

tide line. A new concrete plank or 

asphalt pavement ramp would be 

constructed in its place. Five breasting 

dolphins and one mooring dolphin 

would be constructed to support barge 

docking and would include pedestrian 

walkways for access by personnel. In 

addition, two new pile-supported 

mooring structures would be 

constructed above the high tide line. As 

stated above, the Gravina Airport Ferry 

Layup Facility construction and Gravina 

Freight Facility construction is 

anticipated to require a total of 47 days 

of in-water pile installation and 

removal. 

Revilla New Ferry Berth and Upland 

Improvements 

The new Revilla Island airport shuttle 

ferry berth is the only project 

component that would occur on Revilla 

Island, and is currently under 

construction immediately adjacent to 

the existing Revilla Island Ferry Berth 

(Figure 1). The new ferry berth consists 

of a 7,400 square ft (ft2; 687.4 m2) pilesupported approach trestle at the shore 

side of the ferry terminal and a 1,500 ft2

(139.4 m) pile-supported approach 


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trestle extension located landside and 

north of the new approach trestle. A 25- 

ft by 142-ft (7.6 m by 43.2 m) steel 

transfer bridge with vehicle traffic lane 

and separated pedestrian walkway 

extends from the trestle to a new 2,200 

ft2 (204.3 m2) steel float and apron. The 

steel float is supported by three guide 

pile dolphins. A bulkhead retaining 

wall is being constructed at the 

transition from uplands to the approach 

trestle. Two new stern berth dolphins 

with fixed hanging fenders and three 

new floating fender dolphins are being 

constructed to moor vessels. The new 

apron would be supported by three new 

guide pile dolphins. Water depths at the 

dolphins reach approximately 60 ft 

(18.2 m). 

While construction on the Revilla 

New Ferry Berth is already underway, 

ADOT anticipates that it would not be 

complete before ADOT’s current IHA 

(86 FR 23938; May 5, 2021) expires. 

Therefore, ADOT has requested take 

associated with the portion of the 

project that it anticipates may remain, 

which consists of installation of up to 

five tension anchors. 

Upland improvements associated 

with the Revilla New Ferry Berth 

include reconstruction of terminal 

facilities, installation of utilities, and 

construction of improvements to 

existing staging/parking areas. Upland 

improvements are not anticipated to 

harass marine mammals, and therefore, 

are not discussed further in this 

document. 

Gravina Island Shuttle Ferry Berth and 

Related Terminal Improvements 

The new Gravina Island Airport 

Shuttle Ferry Berth is currently under 

construction (86 FR 23938; May 5, 2021) 

immediately adjacent to the existing 

Gravina Island Ferry Berth (Figure 1). 

The new facility consists of an 

approximately 7,000 ft2 (650.3 m2) pilesupported approach trestle at the shore 

side of the ferry terminal. A 25-ft by 

142-ft (7.6 m by 43.2 m) steel transfer 

bridge with vehicle traffic lane and 

separated pedestrian walkway leads to a 

new 2,200 ft2 (204.3 m2) steel float and 

apron. The steel float is supported by 

three new guide pile dolphins. Ferry 

berthing is supported by two new stern 

berth dolphins and three new floating 

fender dolphins. To support the new 

facility, a new bulkhead retaining wall 

is being constructed between the 

existing ferry berth and the new 

approach trestle. A new fill slope 

measuring approximately 21,200 ft2

(1,969.5 m2) is being constructed west of 

the approach trestle. Upland 

improvements include widening of the 

ferry approach road, retrofits to the 

existing pedestrian walkway, 

installation of utilities, and construction 

of a new employee access walkway. Due 

to unforeseen construction delays 

encountered during the Phase 1 IHA 

construction period, ADOT anticipates 

that construction on the Gravina Island 

Shuttle Ferry Berth would not be 

completed before the expiration of the 

current IHA (86 FR 23938; May 5, 2021). 

Therefore, ADOT has requested take 

associated with the portion of the 

project that it anticipates may remain, 

which consists of up to 35 piles (both 

plumb and battered), 17–21 rock 

sockets, 28 tension anchors, and up to 

4 micropile anchors (Table 1). 

Across the four project sites, three 

methods of pile installation are 

anticipated. These include vibratory and 

impact hammers, use of DTH systems to 

make holes for rock sockets and tension 

and micropile anchors at some locations 

(Figure 1–3 of ADOT’s IHA 

Application). Installation of steel piles 

through the sediment layer would be 

accomplished using vibratory or impact 

methods. Depending on the location, the 

pile would be advanced to refusal at 

bedrock. Where sediments are deep and 

rock socketing or anchoring (described 

below) is not required, the final 

approximately 10 ft (3 m) of driving 

would be conducted using an impact 

hammer so that the structural capacity 

of the pile embedment can be verified 

or proofed. Proofing is expected to 

require approximately 50 strikes over 15 

minutes. Where sediments are shallow, 

an impact hammer would be used to 

seat the piles into competent bedrock 

before a DTH system is used to create 

holes for the rock sockets and/or tension 

anchors. The pile installation methods 

used would depend on sediment depth 

and conditions at each pile location. 

Rock sockets are holes made in the 

bedrock where overlying sediments are 

too shallow to adequately secure the 

bottom portion of a pile using other 

methods. Rock sockets are constructed 

utilizing a DTH device which uses both 

rotary and percussion-type drill action. 

These devices consist of a drill bit that 

drills through the bedrock using both 

rotary and pulse impact mechanisms. 

This breaks up the rock to allow 

removal of the fragments, creating a hole 

that allows for insertion of the pile. The 

socket holes are just large enough for the 

pile to fit down in to provide lateral 

strength for the pile. The pile is usually 

advanced at the same time that drilling 

occurs (the bit has a flexible tip that can 

be retracted and pulled back up through 

the center of a pile). Rock socket holes 

would be up to 15 ft (4.6 m) into the 

bedrock. Drill cuttings are expelled from 

the top of the pile using compressed air 

and/or other fluids. It is estimated that 

use of DTH for rock sockets into the 

bedrock would take approximately 4–8 

hours per pile. Some piles would be 

seated in rock sockets as well as 

anchored with tension anchors. 

Tension anchors are comprised of a 

threaded steel rod grouted into the 

bedrock strata at a specified depth 

below the pile tip. The rod is tested and 

anchored to the top of the pile to resist 

uplift forces in the associated structure. 

Tension anchors are installed within 

piles that are DTH drilled or hammered 

into the bedrock below the elevation of 

the pile tip, after the pile has been 

driven through the sediment layer to 

refusal. A 6- or 8-inch-diameter steel 

pipe casing is inserted inside the largerdiameter production pile. A DTH 

hammer and bit is inserted into the 

casing, and a 6- to 8-inch-diameter hole 

is made into bedrock. The typical depth 

of the hole varies, but 20–30 ft (6.1–9.1 

m) is common to meet engineering 

needs. Rock fragments would be 

removed through the top of the casing 

with compressed air. A steel rebar rod 

is then grouted into the drilled hole and 

affixed to the top of the pile. 

Micropiles have a casing diameter of 

approximately 3 to 10 in. A DTH 

hammer device is used to create a hole 

in a manner identical to the rock sockets 

as described above. The micropile 

casing is inserted to depth and a steel 

reinforcement bar is inserted in the 

casing, and then grout is pumped into 

the casing. The construction of the 

Gravina Island Shuttle Ferry Berth 

could potentially utilize up to four 

micropiles. Because both tension 

anchors and micropiles require drilling 

an 8-inch-diameter hole, they are 

discussed together throughout this 

document. 

Vibratory methods would also be used 

to remove temporary steel pipe piles. 

These proposed activities and the noise 

they produce have the potential to take 

marine mammals, by Level A 

harassment and Level B harassment of 

marine mammals. 

Each of the project components would 

include installation of steel pipe piles 

that are 20, 24, or 30 inches in diameter 

(Table 1). Temporary piles would be 

installed and removed with a vibratory 

hammer. Some permanent piles would 

be battered (i.e., installed at an angle). 

Approximately 50 impact strikes would 

be required for proofing each permanent 

pile, requiring approximately 15 

minutes of active impact hammering per 

pile. 

The estimated average installation 

rate for the project is one to one and a 

half permanent or two temporary pipe 

piles per day (Table 1). On some days, 


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more or fewer piles or partial piles may 

be installed. It would likely not be 

possible to install an individual 

permanent pile to refusal with a 

vibratory hammer, use DTH methods for 

the rock socket, impact proof, and 

install the tension anchor on the same 

day. The construction crew may use a 

single installation method for multiple 

piles on a single day or find other 

efficiencies to increase production; the 

anticipated ranges of possible values are 

provided in Table 1. The estimated 

removal rate for temporary piles is two 

steel pipe piles per day. On some days, 

more or fewer piles may be removed. It 

is estimated that the 40 temporary piles 

would be removed in 36 days. 

In sum, approximately 91 days of pile 

installation and removal are anticipated 

(Table 1), and of the 102 piles which 

ADOT anticipates it will install, 40 of 

them will be installed and removed (for 

a total of 142 pile installations and 

removals). 

Above-water work would consist of 

the installation of a concrete float, a 

transfer bridge and transition ramp, 

dock-mounted fenders, and utility lines. 

A utility and storage building would be 

constructed on top of the concrete float. 

No in-water noise is anticipated in 

association with above-water and 

upland construction activities, and no 

associated take of marine mammals is 

anticipated from the noise or visual 

disturbance. Therefore, above-water and 

upland construction activities are not 

discussed further in this document. 

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BILLING CODE 3510–22–C 

Proposed mitigation, monitoring, and 

reporting measures are described in 

detail later in this document (please see 

Proposed Mitigation and Proposed 

Monitoring and Reporting). 

Description of Marine Mammals in the 

Area of Specified Activities 

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’s Stock 

Assessment Reports (SARs; https://

www.fisheries.noaa.gov/national/ 

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

general information about these species 

(e.g., physical and behavioral 

descriptions) may be found on NMFS’s 

website (https://

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

Table 2 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’s SARs). While no 

mortality is anticipated or authorized 

here, PBR and annual serious injury and 

mortality from anthropogenic sources 

are included here as gross indicators of 

the status of the species and other 

threats. 

Marine mammal abundance estimates 

presented in this document represent 

the total number of individuals that 

make up a given stock or the total 

number estimated within a particular 

study or survey area. NMFS’s 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’s U.S. Alaska SARs (e.g., Muto et 

al. 2021). All values presented in Table 

2 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). 

TABLE 2—MARINE MAMMAL SPECIES OR STOCKS FOR WHICH TAKE IS EXPECTED AND PROPOSED TO BE 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’s 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 proposed survey areas are 

included in Table 3–1 of the IHA 

application. However, the spatial 

occurrence of gray whale and fin whale 

is such that take is not expected to 


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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 would 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 

remaining eight species (with 10 

managed stocks) in Table 2 temporally 

and spatially co-occur with the activity 

to the degree that take is reasonably 

likely to occur, and we have proposed 

authorizing it. 

Humpback Whale 

Humpback whales are found 

throughout Southeast Alaska in a 

variety of marine environments, 

including open-ocean, near-shore 

waters, and areas with strong tidal 

currents (Dahlheim et al. 2009). Most 

humpback whales are migratory and 

spend winters in the breeding grounds 

off either Hawaii or Mexico. Humpback 

whales generally arrive in Southeast 

Alaska in March and return to their 

wintering grounds in November. Some 

humpback whales depart late or arrive 

early to feeding grounds, and therefore 

the species occurs in Southeast Alaska 

year-round (Straley 1990; Straley et al. 

2018). Current threats to humpback 

whales include vessel strikes, spills, 

climate change, and commercial fishing 

operations (Muto et al. 2021). 

Humpback whales worldwide were 

designated as ‘‘endangered’’ under the 

Endangered Species Conservation Act in 

1970, and were listed under the ESA at 

its inception in 1973. However, on 

September 8, 2016, NMFS published a 

final decision that changed the status of 

humpback whales under the ESA (81 FR 

62259), effective October 11, 2016. The 

decision recognized the existence of 14 

DPSs based on distinct breeding areas in 

tropical and temperate waters. Five of 

the 14 DPSs were classified under the 

ESA (4 endangered and 1 threatened), 

while the other 9 DPSs were delisted. 

Humpback whales found in the project 

area are predominantly members of the 

Hawaii DPS, which is not listed under 

the ESA. However, based on a 

comprehensive photo-identification 

study, members of the Mexico DPS, 

which is listed as threatened, are known 

to occur in Southeast Alaska. Members 

of different DPSs are known to intermix 

on feeding grounds; therefore, all waters 

off the coast of Alaska should be 

considered to have ESA-listed 

humpback whales. Approximately 2 

percent of all humpback whales in 

Southeast Alaska and northern British 

Columbia are members of the Mexico 

DPS, while all others are members of the 

Hawaii DPS (Wade et al. 2021). 

The DPSs of humpback whales that 

were identified through the ESA listing 

process do not necessarily equate to the 

existing MMPA stocks. The stock 

delineations of humpback whales under 

the MMPA are currently under review. 

Until this review is complete, NMFS 

considers humpback whales in 

Southeast Alaska to be part of the 

Central North Pacific stock, with a 

status of endangered under the ESA and 

designations of strategic and depleted 

under the MMPA (Muto et al. 2021). 

Southeast Alaska is considered a 

biologically important area for feeding 

humpback whales between March and 

May (Ellison et al. 2012), though not 

currently designated as critical habitat 

(86 FR 21082; April 21, 2021). Most 

humpback whales migrate to other 

regions during the winter to breed, but 

rare events of over-wintering 

humpbacks have been noted, and may 

be attributable to staggered migration 

(Straley, 1990; Straley et al. 2018). It is 

thought that those humpbacks that 

remain in Southeast Alaska do so in 

response to the availability of winter 

schools of fish prey, which primarily 

includes overwintering herring (Straley 

et al. 2018). In Alaska, humpback 

whales filter feed on tiny crustaceans, 

plankton, and small fish such as walleye 

pollock, Pacific sand lance, herring, 

eulachon, and capelin (Witteveen et al. 

2012). It is common to observe groups 

of humpback whales cooperatively 

bubble feeding. Group sizes in 

Southeast Alaska generally range from 

one to four individuals (Dahlheim et al. 

2009). 

No systematic studies have 

documented humpback whale 

abundance near Ketchikan. Anecdotal 

information (See Section 4 of IHA 

Application) suggests that this species is 

present in low numbers year-round in 

Tongass Narrows, with the highest 

abundance during summer and fall. 

Anecdotal reports suggest that 

humpback whales are seen only once or 

twice per month, while more recently it 

has been suggested that the occurrence 

is more regular, such as once per week 

on average, and more seasonal. 

Humpbacks observed in Tongass 

Narrows are generally alone or in groups 

of one to three individuals. Most 

humpback whales depart Alaska for 

their breeding grounds in October and 

November, and return in March and 

April. In August 2017, a group of six 

individuals was observed passing 

through Tongass Narrows several times 

per day, for several days in a row. Local 

residents reported that such high 

abundance is common in August and 

September. NMFS reported that in 2018 

airport ferry personnel observed a lone 

humpback whale in the area every few 

days for several months and a group of 

two humpback whales every other week 

(Muto et al. 2019). 

In the Biological Opinion for this 

project, NMFS assumed the occurrence 

of humpback whales in the project area 

to be one two individuals twice per 

week, year-round. 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. 

The City of Ketchikan (COK) Rock 

Pinnacle project, which was located 

approximately 4 km southeast of the 

proposed project site, reported one 

humpback whale sighting of one 

individual during the project (December 

2019 through January 2020) (Sitkiewicz 

2020). During the Ward Cove Cruise 

Ship Dock Construction, located 

approximately 5 km northwest of the 

proposed project site, protected species 

observers (PSOs) observed 28 sightings 

of humpbacks on eighteen days of in 

water work that occurred between 

February and September 2020, with at 

least one humpback being recorded 

every month. A total of 42 individuals 

were recorded and group sizes ranged 

from solo whales to pods of up to six 

(Power Systems & Supplies of Alaska 

2020). Humpbacks were recorded in 

each month of construction, with the 

most individuals (10) being recorded in 

May, 2020. 

Humpback whales were sighted on 17 

days out of 88 days of monitoring in 

Tongass Narrows in 2020 and 2021 

(DOT&PF 2020, 2021a, 2021b, 2021c, 

2021d). There were no sightings in 

January or February, but humpback 

whales were observed each month from 

October to December 2020 and May to 

June 2021 (DOT&PF 2020, 2021a, 2021b, 

2021c, 2021d). There was only 1 day in 

June in which humpback whales were 

observed, but on that day there were 

four groups of whales—three pairs and 

one group of four (DOT&PF 2021d). In 

other months, humpback whale 

sightings were mostly individual 

animals and occasionally pairs. During 

November 2020, a single known 

individual (by fluke pattern) was 

observed repeatedly, accounting for 14 

of the 26 sighting events that month 

(DOT&PF 2020). During monitoring, 

humpback whales were observed on 

average once a week. 


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Minke Whale 

Minke whales are found throughout 

the northern hemisphere in polar, 

temperate, and tropical waters. The 

population status of minke whales is 

considered stable throughout most of 

their range. Historically, commercial 

whaling reduced the population size of 

this species, but given their small size, 

they were never a primary target of 

whaling and did not experience the 

severe population declines as did larger 

cetaceans. 

The International Whaling 

Commission has identified a less 

concentrated stock throughout the 

eastern Pacific. NOAA further splits this 

stock between Alaska whales and 

resident whales of California, Oregon, 

and Washington (Muto et al., 2021). 

Minke whales are found in all Alaska 

waters. There are no population 

estimates for minke whales in Alaska. 

Surveys in Southeast Alaska have 

consistently identified individuals 

throughout inland waters in low 

numbers (Dahlheim et al. 2009). 

Minke whales in Southeast Alaska are 

part of the Alaska stock (Muto et al. 

2021). Dedicated surveys for cetaceans 

in Southeast Alaska found that minke 

whales were scattered throughout 

inland waters from Glacier Bay and Icy 

Strait to Clarence Strait, with small 

concentrations near the entrance of 

Glacier Bay (Dahlheim et al. 2009). All 

sightings were of single minke whales, 

except for a single sighting of multiple 

minke whales. Surveys took place in 

spring, summer, and fall, and minke 

whales were present in low numbers in 

all seasons and years. No information 

appears to be available on the winter 

occurrence of minke whales in 

Southeast Alaska. 

In Alaska, the minke whale diet 

consists primarily of euphausiids and 

walleye pollock. Minke whales are 

generally found in shallow, coastal 

waters within 200 m of shore (Zerbini 

et al. 2006) and are almost always 

solitary or in small groups of 2 to 3. In 

Alaska, seasonal movements are 

associated with feeding areas that are 

generally located at the edge of the pack 

ice (NMFS 2014). 

There are no known occurrences of 

minke whales within the project area. 

Since their ranges extend into the 

project area and they have been 

observed in southeast Alaska, including 

in Clarence Strait (Dahlheim et al., 

2009), it is possible the species could 

occur near the project area. During the 

surveys by Dalheim et al. (2009), all but 

one encounter was with a single whale 

and, although infrequent, minke whales 

were observed during all seasons 

surveyed (spring, summer and fall). No 

minke whales where reported during 

the COK Rock Pinnacle Blasting Project 

(Sitkiewicz 2020). During marine 

mammal monitoring of Tongass 

Narrows in 2020 and 2021, there were 

no minke whales observed on 88 days 

of observations across 7 months 

(October 2020–February 2021; May– 

June 2021) (DOT&PF 2020, 2021a, 

2021b, 2021c, 2021d). Future 

observations of minke whale in the 

project area are expected to be rare. 

Killer Whale 

Killer whales have been observed in 

all the world’s oceans, but the highest 

densities occur in colder and more 

productive waters found at high 

latitudes (NMFS 2016). Killer whales 

occur along the entire Alaska coast, in 

British Columbia and Washington 

inland waterways, and along the outer 

coasts of Washington, Oregon, and 

California (NMFS 2016). 

Based on data regarding association 

patterns, acoustics, movements, and 

genetic differences, eight killer whale 

stocks are now recognized within the 

Pacific U.S. Exclusive Economic Zone. 

This proposed IHA considers only the 

Eastern North Pacific Alaska Resident 

stock (Alaska Resident stock), Eastern 

North Pacific Northern Resident stock 

(Northern Resident stock), and West 

Coast Transient stock, because all other 

stocks occur outside the geographic area 

under consideration (Muto et al., 2021). 

There are three distinct ecotypes, or 

forms, of killer whales recognized: 

Resident, Transient, and Offshore. The 

three ecotypes differ morphologically, 

ecologically, behaviorally, and 

genetically. Surveys between 1991 and 

2007 encountered resident killer whales 

during all seasons throughout Southeast 

Alaska. Both residents and transients 

were common in a variety of habitats 

and all major waterways, including 

protected bays and inlets. There does 

not appear to be strong seasonal 

variation in abundance or distribution 

of killer whales, but there was 

substantial variability between years 

during this study (Dahlheim et al., 

2009). Spatial distribution has been 

shown to vary among the different 

ecotypes, with resident and, to a lesser 

extent, transient killer whales more 

commonly observed along the 

continental shelf, and offshore killer 

whales more commonly observed in 

pelagic waters (Rice et al., 2021). 

No systematic studies of killer whales 

have been conducted in or around 

Tongass Narrows. Killer whales have 

been observed in Tongass Narrows yearround and are most common during the 

summer Chinook salmon run (MayJuly). During the Chinook salmon run, 

Ketchikan residents have reported pods 

of 20–30 whales and during the 2016/ 

2017 winter a pod of 5 whales was 

observed in Tongass Narrows (84 FR 

36891; July 30, 2019). Typical pod sizes 

observed within the project vicinity 

range from 1 to 10 animals and the 

frequency of killer whales passing 

through the action area is estimated to 

be once per month (Frietag 2017). 

Anecdotal reports suggest that large 

pods of killer whales (as many as 80 

individuals, but generally between 25 

and 40 individuals) are not uncommon 

in May, June, and July when the king 

salmon are running. During the rest of 

the year, killer whales occur irregularly 

in pods of 6 to 12 or more individuals. 

Large pods would be indicative of the 

Alaska resident population, which 

travels and hunts in large social groups. 

Transient killer whales are often 

found in long-term stable social units 

(pods) of 1 to 16 whales. Average pod 

sizes in Southeast Alaska were 6.0 in 

spring, 5.0 in summer, and 3.9 in fall. 

Pod sizes of transient whales are 

generally smaller than those of resident 

social groups. Resident killer whales 

occur in larger pods, ranging from 7 to 

70 whales that are seen in association 

with one another more than 50 percent 

of the time (Dahlheim et al., 2009; 

NMFS 2016b). In Southeast Alaska, 

resident killer whale mean pod size was 

approximately 21.5 in spring, 32.3 in 

summer, and 19.3 in fall (Dahlheim et 

al., 2009). 

Although killer whales may occur in 

large numbers, they generally form large 

pods and would incur fewer work 

stoppages than their numbers suggest. 

Killer whales tend to transit through 

Tongass Narrows, and do not linger in 

the project area. 

Marine mammal observations in 

Tongass Narrows during 2020 and 2021 

support an estimate of approximately 

one group of killer whales a month in 

the project area. During 7 months of 

monitoring (October 2020–February 

2021; May–June 2021), there were five 

killer whale sightings in 4 months 

(November, February, May, June) 

totaling 22 animals and 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). 

During the COK’s monitoring for the 

Rock Pinnacle Removal project in 

December 2019 and January 2020, no 

killer whales were observed (Sitkiewicz 

2020). Over 8 months of monitoring at 

the Ward Cove Cruise Ship Dock in 

2020, killer whales were only observed 

on two days in March (Power Systems 


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and Supplies of Alaska, 2020). These 

observations included a sighting of one 

pod of two killer whales and a second 

pod of five individuals travelling 

through the project area. 

Pacific White-Sided Dolphin 

Pacific white-sided dolphins are a 

pelagic species inhabiting temperate 

waters of the North Pacific Ocean and 

along the coasts of California, Oregon, 

Washington, and Alaska (Muto et al., 

2021). Despite their distribution mostly 

in deep, offshore waters, they may also 

be found over the continental shelf and 

near shore waters, including inland 

waters of Southeast Alaska (Ferrero and 

Walker 1996). The North Pacific stock is 

found within the project area. The 

Pacific white-sided dolphin is 

distributed throughout the temperate 

North Pacific Ocean, north of Baja 

California to Alaska’s southern coastline 

and Aleutian Islands. The North Pacific 

Stock ranges from Canada into Alaska 

(Muto et al., 2021). 

Pacific white-sided dolphins prey on 

squid and small schooling fish such as 

capelin, sardines, and herring (Morton 

2006). They are known to work in 

groups to herd schools of fish and can 

dive underwater for up to 6 minutes to 

feed (Morton 2006). Group sizes have 

been reported to range from 40 to over 

1,000 animals, but groups of between 10 

and 100 individuals (Stacey and Baird 

1991) occur most commonly. Seasonal 

movements of Pacific white-sided 

dolphins are not well understood, but 

there is evidence of both north-south 

seasonal movement (Leatherwood et al. 

1984) and inshore-offshore seasonal 

movement (Stacey and Baird 1991). 

Scientific studies and data are lacking 

relative to the presence or abundance of 

Pacific white-sided dolphins in or near 

Tongass Narrows. Although they 

generally prefer deeper and moreoffshore waters, anecdotal reports 

suggest that Pacific white-sided 

dolphins have previously been observed 

in Tongass Narrows, although they have 

not been observed entering Tongass 

Narrows or nearby inter-island 

waterways in 15–20 years. 

Pacific white-sided dolphins are rare 

in the inside passageways of Southeast 

Alaska. Most observations occur off the 

outer coast or in inland waterways near 

entrances to the open ocean. According 

to Muto et al. (2018), aerial surveys in 

1997 sighted one group of 164 Pacific 

white-sided dolphins in Dixon entrance 

to the south of Tongass Narrows. 

Surveys in April and May from 1991 to 

1993 identified Pacific white-sided 

dolphins in Revillagigedo Channel, 

Behm Canal, and Clarence Strait 

(Dahlheim and Towell 1994). These 

areas are contiguous with the open 

ocean waters of Dixon Entrance. 

Dalheim et al. (2009) frequently 

encountered Pacific white-sided 

dolphin in Clarence Strait with 

significant differences in mean group 

size and rare enough encounters to limit 

the seasonality investigation to a 

qualitative note that spring featured the 

highest number of animals observed. 

These observations were noted most 

typically in open strait environments, 

near the open ocean. Mean group size 

was over 20, with no recorded winter 

observations nor observations made in 

the Nichols Passage or Behm Canal, 

located on either side of the Tongass 

Narrows. Though generally preferring 

more pelagic, open-water environments, 

Pacific white-sided dolphin could be 

present within the action area during 

the construction period. This 

observational data, combined with 

anecdotal information, indicates there is 

a rare, however, slight potential for 

Pacific white-sided dolphins to occur in 

the project area. 

During marine mammal monitoring of 

Tongass Narrows in 2020 and 2021, no 

Pacific white-sided dolphins were 

observed on 88 days of observations 

across 7 months (October 2020– 

February 2021; May–June 2021), which 

supports the anecdotal evidence that 

sightings of this species are rare 

(DOT&PF 2020, 2021a, 2021b, 2021c, 

2021d). There were also no sightings of 

Pacific white-sided dolphins during the 

COK Rock Pinnacle Blasting Project 

during monitoring surveys conducted in 

December 2019 and January 2020 

(Sitkiewicz 2020) or during monitoring 

surveys conducted between February 

and September 2020 as part of the Ward 

Cove Cruise Ship Dock (Power Systems 

and Supplies of Alaska, 2020). 

Harbor Porpoise 

In the eastern North Pacific Ocean, 

the harbor porpoise ranges from Point 

Barrow, along the Alaska coast, and 

down the west coast of North America 

to Point Conception, California. In 

Alaska, harbor porpoises are currently 

divided into three stocks, based 

primarily on geography: The Bering Sea 

stock, the Southeast Alaska stock, and 

the Gulf of Alaska stock. The Southeast 

Alaska stock ranges from Cape Suckling 

to the Canadian border (Muto et al. 

2021). Harbor porpoises frequent 

primarily coastal waters in Southeast 

Alaska (Dahlheim et al. 2009) and occur 

most frequently in waters less than 100 

m (328 ft) deep (Hobbs and Waite 2010; 

Dahlheim et al. 2015). 

Abundance data for harbor porpoises 

in Southeast Alaska were collected 

during 18 seasonal surveys spanning 22 

years, from 1991 to 2012 (Dahlheim et 

al. 2015). The project area and Tongass 

Narrows fall within the Clarence Strait 

to Ketchikan region, as identified by this 

study for the survey effort. Harbor 

porpoise densities in this region in 

summer were low, ranging from 0.01 to 

0.02 harbor porpoises/km2. 

Studies of harbor porpoises reported 

no evidence of seasonal changes in 

distribution for the inland waters of 

Southeast Alaska (Dahlheim et al. 2009). 

Their small overall size, lack of a visible 

blow, low dorsal fins and overall low 

profile, and short surfacing time make 

them difficult to observe (Dahlheim et 

al. 2015), likely reducing identification 

and reporting of this species, and these 

estimates therefore may be low. 

Calving occurs from May to August; 

however, this can vary by region. Harbor 

porpoises are often found traveling 

alone, or in small groups less than 10 

individuals (Schmale 2008). According 

to aerial surveys of harbor porpoise 

abundance in Alaska conducted in 

1991–1993, mean group size in 

Southeast Alaska was calculated to be 

1.2 animals (Dahlheim et al. 2000). 

Anecdotal reports (see Section 3 of 

the IHA Application) specific to 

Tongass Narrows indicate that harbor 

porpoises are rarely observed in the 

project area, and actual sightings are 

less common than those suggested by 

Dahlheim et al. (2015). Harbor porpoises 

prefer shallower waters (Dahlheim et al. 

2015) and generally are not attracted to 

areas with elevated levels of vessel 

activity and noise such as Tongass 

Narrows. Harbor porpoises are expected 

to be present in the project area only a 

few times per year. Freitag (2017 as 

cited in 83 FR 22009; May 11, 2018) 

observed harbor porpoises in Tongass 

Narrows zero to one time per month and 

NMFS (83 FR 22009; May 11, 2018) has 

estimated that one group of harbor 

porpoises would enter Tongass Narrows 

each month. 

Harbor porpoises were sighted on 3 

days of in-water work during 

monitoring associated with the Ward 

Cove Cruise Ship Dock, with three 

sightings of 15 individuals sighted in 

March and April, 2020 (Power Systems 

and Supplies of Alaska, 2020). Solo 

individuals and pods of up to 10 were 

identified as swimming and travelling 

2,500 m to 2,800 m from in-water work. 

During marine mammal monitoring of 

Tongass Narrows in 2020 and 2021, no 

harbor porpoises were observed on 88 

days of observations across 7 months 

(October 2020–February 2021; May– 

June 2021), which supports the 

anecdotal evidence that harbor porpoise 

sightings are rare (DOT&PF 2020, 2021a, 

2021b, 2021c, 2021d). Marine mammal 


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monitoring associated with the COK 

Rock Pinnacle Removal project also did 

not observe any harbor porpoise during 

surveys conducted in December 2019 

and January 2020 (Sitkiewicz 2020). 

Dall’s Porpoise 

Dall’s porpoises are found throughout 

the North Pacific, from southern Japan 

to southern California north to the 

Bering Sea. Dall’s porpoises are not 

listed as endangered or threatened 

under the ESA. All Dall’s porpoises in 

Alaska are members of the Alaska stock, 

and those off California, Oregon, and 

Washington are part of a separate stock. 

This species can be found in offshore, 

inshore, and nearshore habitat, but 

prefer waters more than 600 ft (180 m) 

deep (Jefferson 2009). 

No systematic studies of Dall’s 

porpoise abundance or distribution have 

occurred in Tongass Narrows; however, 

surveys for cetaceans throughout 

Southeast Alaska were conducted 

between 1991 and 2007 (Dahlheim et al. 

2009). The species is generally found in 

waters in excess of 600 ft (183 m) deep 

(Dahlheim et al. 2009, Jefferson 2009), 

which do not occur in Tongass Narrows. 

Jefferson et al. (2019) presents historical 

survey data showing few sightings in 

the Ketchikan area, and based on these 

occurrence patterns, concludes that 

Dall’s porpoise rarely come into narrow 

waterways, like Tongass Narrows. 

Anecdotal reports suggest that Dall’s 

porpoises are found northwest of 

Ketchikan near the Guard Islands, 

where waters are deeper, as well as in 

deeper waters to the southeast of 

Tongass Narrows. Should Dall’s 

porpoises occur in the project area, they 

would likely be present in March or 

April, given past observations in the 

region. Despite generalized water depth 

preferences, Dall’s porpoises may occur 

in shallower waters. This species has a 

tendency to bow-ride with vessels and 

may occur in the project area 

incidentally a few times per year. 

The mean group size in Southeast 

Alaska is estimated at approximately 

three individuals (Dahlheim et al. 2009; 

Jefferson 2019). However, in the 

Ketchikan vicinity, Dall’s porpoises are 

reported to typically occur in groups of 

10–15 animals, with an estimated 

maximum group size of 20 animals 

(Freitag 2017, 83 FR 37473; August 1, 

2018). 

Dall’s porpoises were positively 

identified on 2 days of in-water work 

during monitoring associated with the 

Ward Cove Cruise Ship Dock (Power 

Systems and Supplies of Alaska, 2020). 

A pod of three and a pod of five were 

recorded travelling at least 3,000 m from 

the construction site in April and May, 

respectively. During marine mammal 

monitoring of Tongass Narrows in 2020 

and 2021, there were sightings of Dall’s 

porpoises on 2 out of 88 days of 

observations across 7 months (October 

2020–February 2021; May–June 2021)— 

once in November 2020 and once in 

February 2021. The pod sighted in 

November contained six animals; the 

pod observed in February had 10. Based 

on this recent data, there is no known 

pattern to their attendance in the project 

area, but they do occur rarely (DOT&PF 

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

Steller Sea Lion 

Steller sea lions were listed as 

threatened range-wide under the ESA 

on November 26, 1990 (55 FR 49204). 

Steller sea lions were subsequently 

partitioned into the western and eastern 

DPSs (and MMPA stocks) in 1997 (62 

FR 24345; May 5, 1997). The eastern 

DPS remained classified as threatened 

until it was delisted in November 2013. 

The current minimum abundance 

estimate for the eastern DPS of Steller 

sea lions is 43,201 individuals (Muto et 

al. 2021). The western DPS (those 

individuals west of 144° W longitude or 

Cape Suckling, Alaska) was upgraded to 

endangered status following separation 

of the DPSs, and it remains endangered 

today. There is regular movement of 

both DPSs across this 144° W longitude 

boundary (Jemison et al. 2013), 

however, due to the distance from this 

DPS boundary, it is likely that only 

eastern DPS Steller sea lions are present 

in the project area. Therefore, animals 

potentially affected by the project are 

assumed to be part of the eastern DPS. 

There are several mapped and 

regularly monitored long-term Steller 

sea lion haulouts surrounding 

Ketchikan, such as West Rocks (36 

miles/58 km) or Nose Point (37 miles/ 

60 km), but none are known to occur 

within Tongass Narrows (Fritz et al. 

2015). The nearest known Steller sea 

lion haulout is located approximately 20 

miles (58 km) west/northwest of 

Ketchikan on Grindall Island (Figure 4– 

1 in application). Summer counts of 

adult and juvenile sea lions at this 

haulout since 2000 have averaged 

approximately 191 individuals, with a 

range from 6 in 2009 to 378 in 2008. 

Only two winter surveys of this haulout 

have occurred. In March 1993, a total of 

239 individuals were recorded, and in 

December 1994, a total of 211 

individuals were recorded. No sea lion 

pups have been observed at this haulout 

during surveys. Although this is a 

limited and dated sample, it suggests 

that abundance may be consistent yearround at the Grindall Island haulout. 

No systematic studies of sea lion 

abundance or distribution have 

occurred in Tongass Narrows. 

Anecdotal reports suggest that Steller 

sea lions may be found in Tongass 

Narrows year-round, with an increase in 

abundance from March to early May 

during the herring spawning season, 

and another increase in late summer 

associated with salmon runs. Overall 

sea lion presence in Tongass Narrows 

tends to be lower in summer than in 

winter (FHWA 2017). During summer, 

Steller sea lions may aggregate outside 

the project area, at rookery and haulout 

sites. Monitoring during construction of 

the Ketchikan Ferry Terminal in 

summer (July 16 through August 17, 

2016) did not record any Steller sea 

lions (ADOT&PF 2015); however, 

monitoring during construction of the 

Ward Cove Dock, located approximately 

6 km northwest of the Project site, 

recorded 181 individual sea lions on 44 

days between February and September 

2020 (Power Systems & Supplies of 

Alaska, 2020). Most sightings occurred 

in February (45 sightings of 88 sea lions) 

and March (34 sightings of 45 sea lions); 

the fewest number of sightings were 

observed in May (1 sighting of 1 sea 

lion) (Power Systems & Supplies of 

Alaska, 2020). Sightings were of single 

individuals, pairs, and herds of up to 10 

individuals. 

Sea lions are known to transit through 

Tongass Narrows while pursuing prey. 

Steller sea lions are also known to 

follow fishing vessels, and may 

congregate in small numbers at seafood 

processing facilities and hatcheries or at 

the mouths of rivers and creeks 

containing hatcheries, where large 

numbers of salmon congregate in late 

summer. Three seafood processing 

facilities are located east of the 

proposed berth location on Revilla 

Island, and two salmon hatcheries 

operated by the Alaska Department of 

Fish & Game (ADF&G) are located east 

of the project area. Steller sea lions may 

aggregate near the mouth of Ketchikan 

Creek, where a hatchery upstream 

supports a summer salmon run. The 

Creek mouth is more than 4 km (2.5 mi) 

from both ferry berth sites, and is 

positioned behind the cruise ship 

terminal and within the small boat 

harbor. In addition to these locations, 

anecdotal information from a local 

kayaking company suggests that there 

are Steller sea lions present at Gravina 

Point, near the southwest entrance to 

Tongass Narrows. 

A total of 181 Steller sea lions were 

sighted on 44 separate days during all 

months of Ward Cove Cruise Ship Dock 

construction (February through 

September, 2020) (Power Systems and 


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Supplies of Alaska, 2020). Most 

sightings occurred in February and 

March and the fewest sightings were in 

May. Sightings were of single 

individuals, pairs, and herds of up to 10 

individuals. 

The DOT&PF implemented a marine 

mammal monitoring program in 

Tongass Narrows for recent previous 

construction components of the Tongass 

Narrows Project (84 FR 34134; July 17, 

2019). Monitoring took place from 

October 2020 through February 2021 

and May through June 2021, and results 

indicated that Steller sea lion numbers 

were highest in January and February 

(DOT&PF 2020, 2021a, 2021b, 2021c, 

2021d). Steller sea lions were observed 

in the Tongass Narrows Project area on 

49 of 88 days between October 2020 and 

June 2021 (DOT&PF 2020, 2021a, 2021b, 

2021c, 2021d). They were observed in 

every month that observations took 

place (DOT&PF 2020, 2021a, 2021b, 

2021c, 2021d). Over the course of the 7 

months of monitoring, there were 77 

sightings of 92 individual animals 

(DOT&PF 2020, 2021a, 2021b, 2021c, 

2021d). Sightings of Steller sea lions 

were most frequent in January and 

February and least common in May and 

June (DOT&PF 2020, 2021a, 2021b, 

2021c, 2021d). Sightings were primarily 

of single animals, but animals were also 

present in pairs and groups up to five 

sea lions (DOT&PF 2020, 2021a, 2021b, 

2021c, 2021d). This is consistent with 

Freitag (2017 as cited in 83 FR 22009; 

May 11, 2018), though groups of up to 

80 individuals have been observed 

(HDR, Inc. 2003). On average over the 

course of a year, Steller sea lions occur 

in Tongass Narrows approximately three 

or four times per week (DOT&PF 2020, 

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

Harbor Seal 

Harbor seals range from Baja 

California north along the west coasts of 

Washington, Oregon, California, British 

Columbia, and Southeast Alaska; west 

through the Gulf of Alaska, Prince 

William Sound, and the Aleutian 

Islands; and north in the Bering Sea to 

Cape Newenham and the Pribilof 

Islands. In 2010, harbor seals in Alaska 

were partitioned into 12 separate stocks 

based largely on genetic structure (Allen 

and Angliss 2010). Harbor seals in 

Tongass Narrows are recognized as part 

of the Clarence Strait stock. Distribution 

of the Clarence Strait stock ranges from 

the east coast of Prince of Wales Island 

from Cape Chacon north through 

Clarence Strait to Point Baker and along 

the east coast of Mitkof and Kupreanof 

Islands north to Bay Point, including 

Ernest Sound, Behm Canal, and Pearse 

Canal (Muto et al. 2021). The latest 

stock assessment analysis indicates that 

the current 8-year estimate of the 

Clarence Strait population trend is +138 

seals per year, with a probability that 

the stock is decreasing of 0.413 (Muto et 

al. 2021). Harbor seals haul out on 

rocks, reefs, beaches, and drifting glacial 

ice, and feed in marine, estuarine, and 

occasionally fresh waters. Harbor seals 

are generally non-migratory, with local 

movements associated with such factors 

as tides, weather, season, food 

availability, and reproduction (Muto, et 

al. 2021). 

No systematic studies of harbor seal 

abundance or distribution have 

occurred in Tongass Narrows. Aerial 

surveys conducted in August 2011 did 

not record any harbor seal haulouts in 

Tongass Narrows, but several haulouts 

were located on the outer shores of 

Gravina Island (London et al. 2015). 

There is no known harbor seal haulout 

in Tongass Narrows although seals have 

been observed hauled out on docks in 

Ketchikan Harbor. The closest listed 

haulout is located off the tip of Gravina 

Island, approximately 8 km (5 mi) 

northwest of Ward Cove (AFSC 2018). 

Anecdotal observations indicate that 

harbor seals are common in Tongass 

Narrows, although no data exist to 

quantify abundance. Two salmon 

hatcheries operated by ADF&G are 

located east of the project area. Like 

Steller sea lions, harbor seals may 

aggregate near the mouth of Ketchikan 

Creek when salmon are running in 

summer. The creek mouth is more than 

4 km (2.5 mi) from the project 

component sites, and is positioned 

behind both the cruise ship terminal 

and within the small boat harbor. In the 

project area, they tend to be more 

abundant during spring, summer and 

fall months when salmon are present in 

Ward Creek. Anecdotal evidence 

indicates that harbor seals typically 

occur in groups of 1–3 animals in Ward 

Cove (Spokely 2019). They were not 

observed in Tongass Narrows during a 

combined 63.5 hours of marine mammal 

monitoring that took place in 2001 and 

2016 (OSSA 2001, Turnagain 2016). The 

COK conducted pinnacle rock blasting 

in December 2019 and January 2020 

near the vicinity of the proposed project 

and recorded a total of 21 harbor seal 

sightings of 24 individuals over 76.2 

hours of pre- and post-blast monitoring 

(Sitkiewicz 2020). 

Harbor seals were sighted during 

every month of construction (February 

through September, 2020) associated 

with the Ward Cove Cruise Ship Dock, 

with most sightings in February and 

March and the fewest in July (Power 

Systems and Supplies of Alaska, 2020). 

There were 247 sighting events of 271 

individuals. Sighting events were of 

solo individuals, pairs, and the 

occasional group of three. 

Marine mammal monitoring occurred 

near the project site from October 2020 

to February 2021 and resumed in May 

2021 during Phase 1 of the previously 

issued IHA (85 FR 673; January 7, 2020). 

Harbor seals were observed in the 

Tongass Narrows Project area in every 

month in which observations took 

place, except during October 2020 when 

only 3 days of monitoring occurred 

(DOT&PF 2020, 2021a, 2021b, 2021c, 

2021d). Harbor seals were sighted on 68 

days out of 88 days of monitoring 

(DOT&PF 2020, 2021a, 2021b, 2021c, 

2021d). They were mostly sightings of 

single animals, but animals were also 

present in pairs and groups up to five 

seals (DOT&PF 2020, 2021a, 2021b, 

2021c, 2021d). Sightings of harbor seals 

were consistent over the course of 7 

months of intermittent monitoring; they 

were observed 5 to 6 days per week on 

average (DOT&PF 2020, 2021a, 2021b, 

2021c, 2021d). 

Marine Mammal Hearing 

Hearing is the most important sensory 

modality for marine mammals 

underwater, and exposure to 

anthropogenic sound can have 

deleterious effects. To appropriately 

assess the potential effects of exposure 

to sound, it is necessary to understand 

the frequency ranges marine mammals 

are able to hear. Current data indicate 

that not all marine mammal species 

have equal hearing capabilities (e.g., 

Richardson et al. 1995; Wartzok and 

Ketten, 1999; Au and Hastings, 2008). 

To reflect this, Southall et al. (2007) 

recommended that marine mammals be 

divided into functional hearing groups 

based on directly measured or estimated 

hearing ranges on the basis of available 

behavioral response data, audiograms 

derived using auditory evoked potential 

techniques, anatomical modeling, and 

other data. Note that no direct 

measurements of hearing ability have 

been successfully completed for 

mysticetes (i.e., low-frequency 

cetaceans). Subsequently, NMFS (2018) 

described generalized hearing ranges for 

these marine mammal hearing groups. 

Generalized hearing ranges were chosen 

based on the approximately 65 decibel 

(dB) threshold from the normalized 

composite audiograms, with the 

exception for lower limits for lowfrequency cetaceans where the lower 

bound was deemed to be biologically 

implausible and the lower bound from 

Southall et al. (2007) retained. Marine 

mammal hearing groups and their 

associated hearing ranges are provided 

in Table 3. 


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TABLE 3—MARINE MAMMAL HEARING GROUPS

[NMFS, 2018] 

Hearing group Generalized hearing 

range* 

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

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

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

australis).

275 Hz to 160 kHz. 

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

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

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

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

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

The pinniped functional hearing 

group was modified from Southall et al. 

(2007) on the basis of data indicating 

that phocid species have consistently 

demonstrated an extended frequency 

range of hearing compared to otariids, 

especially in the higher frequency range 

(Hemila ̈ et al. 2006; Kastelein et al. 

2009; Reichmuth and Holt, 2013). 

For more detail concerning these 

groups and associated frequency ranges, 

please see NMFS (2018) for a review of 

available information. Eight marine 

mammal species (six cetacean and two 

pinniped (one otariid and one phocid) 

species) have the reasonable potential to 

co-occur with the proposed survey 

activities. Please refer to Table 2. 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 

This section includes a summary and 

discussion of the ways that components 

of the specified activity may impact 

marine mammals and their habitat. The 

Estimated Take section later in this 

document includes a quantitative 

analysis of the number of individuals 

that are expected to be taken by this 

activity. The Negligible Impact Analysis 

and Determination section considers the 

content of this section, the Estimated 

Take section, and the Proposed 

Mitigation section, to draw conclusions 

regarding the likely impacts of these 

activities on the reproductive success or 

survivorship of individuals and how 

those impacts on individuals are likely 

to impact marine mammal species or 

stocks. 

Acoustic effects on marine mammals 

during the specified activity can occur 

from impact and vibratory pile driving 

and removal and use of DTH equipment. 

The effects of underwater noise from 

ADOT’s proposed activities have the 

potential to result in Level A or Level 

B harassment of marine mammals in the 

action area. 

Description of Sound Sources 

The marine soundscape is comprised 

of both ambient and anthropogenic 

sounds. Ambient sound is defined as 

the all-encompassing sound in a given 

place and is usually a composite of 

sound from many sources both near and 

far (ANSI 1995). The sound level of an 

area is defined by the total acoustical 

energy being generated by known and 

unknown sources. These sources may 

include physical (e.g., waves, wind, 

precipitation, earthquakes, ice, 

atmospheric sound), biological (e.g., 

sounds produced by marine mammals, 

fish, and invertebrates), and 

anthropogenic sound (e.g., vessels, 

dredging, aircraft, construction). 

The sum of the various natural and 

anthropogenic sound sources at any 

given location and time—which 

comprise ‘‘ambient’’ or ‘‘background’’ 

sound—depends not only on the source 

levels (as determined by current 

weather conditions and levels of 

biological and shipping activity) but 

also on the ability of sound to propagate 

through the environment. In turn, sound 

propagation is dependent on the 

spatially and temporally varying 

properties of the water column and sea 

floor, and is frequency-dependent. As a 

result of the dependence on a large 

number of varying factors, ambient 

sound levels can be expected to vary 

widely over both coarse and fine spatial 

and temporal scales. Sound levels at a 

given frequency and location can vary 

by 10–20 dB from day to day 

(Richardson et al. 1995). The result is 

that, depending on the source type and 

its intensity, sound from the specified 

activity may be a negligible addition to 

the local environment or could form a 

distinctive signal that may affect marine 

mammals. 

In-water construction activities 

associated with the project would 

include impact pile driving, vibratory 

pile driving and removal, and use of 

DTH equipment. The sounds produced 

by these activities fall into one of two 

general sound types: Impulsive and 

non-impulsive. Impulsive sounds (e.g., 

explosions, gunshots, sonic booms, 

impact pile driving) are typically 

transient, brief (less than 1 second), 

broadband, and consist of high peak 

sound pressure with rapid rise time and 

rapid decay (ANSI 1986; NIOSH 1998; 

NMFS 2018). Non-impulsive sounds 

(e.g. aircraft, machinery operations such 

as drilling or dredging, vibratory pile 

driving, and active sonar systems) can 

be broadband, narrowband or tonal, 

brief or prolonged (continuous or 

intermittent), and typically do not have 

the high peak sound pressure with rapid 

rise/decay time that impulsive sounds 

do (ANSI 1995; NIOSH 1998; NMFS 

2018). The distinction between these 

two sound types is important because 

they have differing potential to cause 

physical effects, particularly with regard 

to hearing (e.g., Ward 1997 in Southall 

et al. 2007). 

Three types of hammers would be 

used on this project: Impact, vibratory, 

and DTH. Impact hammers operate by 

repeatedly dropping and/or pushing a 

heavy piston onto a pile to drive the pile 

into the substrate. Sound generated by 

impact hammers is characterized by 

rapid rise times and high peak levels, a 

potentially injurious combination 

(Hastings and Popper 2005). Vibratory 

hammers install piles by vibrating them 

and allowing the weight of the hammer 

to push them into the sediment. 

Vibratory hammers produce 

significantly less sound than impact 

hammers. Peak Sound Pressure Levels 

(SPLs) may be 180 dB or greater, but are 

generally 10 to 20 dB lower than SPLs 

generated during impact pile driving of 

the same-sized pile (Oestman et al. 


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2009). Rise time is slower, reducing the 

probability and severity of injury, and 

sound energy is distributed over a 

greater amount of time (Nedwell and 

Edwards 2002; Carlson et al. 2005). 

A DTH hammer is essentially a drill 

bit that drills through the bedrock using 

a rotating function like a normal drill, 

in concert with a hammering 

mechanism operated by a pneumatic (or 

sometimes hydraulic) component 

integrated into to the DTH hammer to 

increase speed of progress through the 

substrate (i.e., it is similar to a ‘‘hammer 

drill’’ hand tool). The sounds produced 

by the DTH method contain both a 

continuous non-impulsive component 

from the drilling action and an 

impulsive component from the 

hammering effect. Therefore, we treat 

DTH systems as both impulsive and 

continuous, non-impulsive sound 

source types simultaneously. 

The likely or possible impacts of 

ADOT’s proposed activity on marine 

mammals could involve both nonacoustic and acoustic stressors. 

Potential non-acoustic stressors could 

result from the physical presence of the 

equipment and personnel; however, any 

impacts to marine mammals are 

expected to primarily be acoustic in 

nature. Acoustic stressors include 

effects of heavy equipment operation 

during pile installation and removal and 

use of DTH. 

Acoustic Impacts 

The introduction of anthropogenic 

noise into the aquatic environment from 

pile driving and removal and DTH is the 

primary means by which marine 

mammals may be harassed from ADOT’s 

specified activity. In general, animals 

exposed to natural or anthropogenic 

sound may experience physical and 

psychological effects, ranging in 

magnitude from none to severe 

(Southall et al. 2007, 2019). In general, 

exposure to pile driving and DTH noise 

has the potential to result in auditory 

threshold shifts and behavioral 

reactions (e.g., avoidance, temporary 

cessation of foraging and vocalizing, 

changes in dive behavior). Exposure to 

anthropogenic noise can also lead to 

non-observable physiological responses 

such an increase in stress hormones. 

Additional noise in a marine mammal’s 

habitat can mask acoustic cues used by 

marine mammals to carry out daily 

functions such as communication and 

predator and prey detection. The effects 

of pile driving and DTH noise on marine 

mammals are dependent on several 

factors, including, but not limited to, 

sound type (e.g., impulsive vs. nonimpulsive), the species, age and sex 

class (e.g., adult male vs. mom with 

calf), duration of exposure, the distance 

between the pile and the animal, 

received levels, behavior at time of 

exposure, and previous history with 

exposure (Wartzok et al. 2004; Southall 

et al. 2007). Here we discuss physical 

auditory effects (threshold shifts) 

followed by behavioral effects and 

potential impacts on habitat. 

NMFS defines a noise-induced 

threshold shift (TS) as a change, usually 

an increase, in the threshold of 

audibility at a specified frequency or 

portion of an individual’s hearing range 

above a previously established reference 

level (NMFS 2018). The amount of 

threshold shift is customarily expressed 

in dB. A TS can be permanent or 

temporary. As described in NMFS 

(2018), there are numerous factors to 

consider when examining the 

consequence of TS, including, but not 

limited to, the signal temporal pattern 

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

likelihood an individual would be 

exposed for a long enough duration or 

to a high enough level to induce a TS, 

the magnitude of the TS, time to 

recovery (seconds to minutes or hours to 

days), the frequency range of the 

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

hearing and vocalization frequency 

range of the exposed species relative to 

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

how animal uses sound within the 

frequency band of the signal; e.g., 

Kastelein et al. 2014), and the overlap 

between the animal and the source (e.g., 

spatial, temporal, and spectral). 

Permanent Threshold Shift (PTS)— 

NMFS defines PTS as a permanent, 

irreversible increase in the threshold of 

audibility at a specified frequency or 

portion of an individual’s hearing range 

above a previously established reference 

level (NMFS 2018). Available data from 

humans and other terrestrial mammals 

indicate that a 40 dB threshold shift 

approximates PTS onset (see Ward et al. 

1958, 1959; Ward 1960; Kryter et al. 

1966; Miller 1974; Ahroon et al. 1996; 

Henderson et al. 2008). PTS levels for 

marine mammals are estimates, as with 

the exception of a single study 

unintentionally inducing PTS in a 

harbor seal (Kastak et al. 2008), there are 

no empirical data measuring PTS in 

marine mammals largely due to the fact 

that, for various ethical reasons, 

experiments involving anthropogenic 

noise exposure at levels inducing PTS 

are not typically pursued or authorized 

(NMFS 2018). 

Temporary Threshold Shift (TTS)—A 

temporary, reversible increase in the 

threshold of audibility at a specified 

frequency or portion of an individual’s 

hearing range above a previously 

established reference level (NMFS 

2018). Based on data from cetacean TTS 

measurements (see Southall et al. 2007), 

a TTS of 6 dB is considered the 

minimum threshold shift clearly larger 

than any day-to-day or session-tosession variation in a subject’s normal 

hearing ability (Schlundt et al. 2000; 

Finneran et al. 2000, 2002). As 

described in Finneran (2015), marine 

mammal studies have shown the 

amount of TTS increases with 

cumulative sound exposure level 

(SELcum) in an accelerating fashion: At 

low exposures with lower SELcum, the 

amount of TTS is typically small and 

the growth curves have shallow slopes. 

At exposures with higher SELcum, the 

growth curves become steeper and 

approach linear relationships with the 

noise SEL. 

Depending on the degree (elevation of 

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

time), and frequency range of TTS, and 

the context in which it is experienced, 

TTS can have effects on marine 

mammals ranging from discountable to 

serious (similar to those discussed in 

auditory masking, below). For example, 

a marine mammal may be able to readily 

compensate for a brief, relatively small 

amount of TTS in a non-critical 

frequency range that takes place during 

a time when the animal is traveling 

through the open ocean, where ambient 

noise is lower and there are not as many 

competing sounds present. 

Alternatively, a larger amount and 

longer duration of TTS sustained during 

time when communication is critical for 

successful mother/calf interactions 

could have more serious impacts. We 

note that reduced hearing sensitivity as 

a simple function of aging has been 

observed in marine mammals, as well as 

humans and other taxa (Southall et al. 

2007), so we can infer that strategies 

exist for coping with this condition to 

some degree, though likely not without 

cost. 

Currently, TTS data only exist for four 

species of cetaceans (bottlenose dolphin 

(Tursiops truncatus), beluga whale 

(Delphinapterus leucas), harbor 

porpoise, and Yangtze finless porpoise 

(Neophocoena asiaeorientalis)) and five 

species of pinnipeds exposed to a 

limited number of sound sources (i.e., 

mostly tones and octave-band noise) in 

laboratory settings (Finneran 2015). TTS 

was not observed in trained spotted 

(Phoca largha) and ringed (Pusa 

hispida) seals exposed to impulsive 

noise at levels matching previous 

predictions of TTS onset (Reichmuth et 

al. 2016). In general, harbor seals and 

harbor porpoises have a lower TTS 

onset than other measured pinniped or 

cetacean species (Finneran 2015). 

Additionally, the existing marine 


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mammal TTS data come from a limited 

number of individuals within these 

species. No data are available on noiseinduced hearing loss for mysticetes. For 

summaries of data on TTS in marine 

mammals or for further discussion of 

TTS onset thresholds, please see 

Southall et al. (2007), Finneran and 

Jenkins (2012), Finneran (2015), and 

Table 5 in NMFS (2018). 

Installing piles requires a combination 

of impact pile driving, vibratory pile 

driving, and DTH. For the project, these 

activities may occur at the same time 

(up to two hammers of any combination 

of hammer/drill type), though such an 

occurrence is anticipated to be 

infrequent and for short durations on 

any given day, given that pile 

installation and removal occurs 

intermittently to allow for adjusting 

piles and measuring and documenting 

progress. Therefore, there would likely 

be pauses in activities producing the 

sound during each day. Given these 

pauses and that many marine mammals 

are likely moving through the project 

area and not remaining for extended 

periods of time, the potential for TS 

declines. 

Behavioral Harassment—Exposure to 

noise from pile driving and removal and 

DTH also has the potential to 

behaviorally disturb marine mammals. 

Available studies show wide variation 

in response to underwater sound; 

therefore, it is difficult to predict 

specifically how any given sound in a 

particular instance might affect marine 

mammals perceiving the signal. If a 

marine mammal does react briefly to an 

underwater sound by changing its 

behavior or moving a small distance, the 

impacts of the change are unlikely to be 

significant to the individual, let alone 

the stock or population. However, if a 

sound source displaces marine 

mammals from an important feeding or 

breeding area for a prolonged period, 

impacts on individuals and populations 

could be significant (e.g., Lusseau and 

Bejder 2007; Weilgart 2007; NRC 2005). 

Disturbance may result in changing 

durations of surfacing and dives, 

number of blows per surfacing, or 

moving direction and/or speed; 

reduced/increased vocal activities; 

changing/cessation of certain behavioral 

activities (such as socializing or 

feeding); visible startle response or 

aggressive behavior (such as tail/fluke 

slapping or jaw clapping); avoidance of 

areas where sound sources are located. 

Pinnipeds may increase their haul out 

time, possibly to avoid in-water 

disturbance (Thorson and Reyff 2006). 

Behavioral responses to sound are 

highly variable and context-specific and 

any reactions depend on numerous 

intrinsic and extrinsic factors (e.g., 

species, state of maturity, experience, 

current activity, reproductive state, 

auditory sensitivity, time of day), as 

well as the interplay between factors 

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

al. 2003; Southall et al. 2007; Weilgart 

2007; Archer et al. 2010). Behavioral 

reactions can vary not only among 

individuals but also within an 

individual, depending on previous 

experience with a sound source, 

context, and numerous other factors 

(Ellison et al. 2012), and can vary 

depending on characteristics associated 

with the sound source (e.g., whether it 

is moving or stationary, number of 

sources, distance from the source). In 

general, pinnipeds seem more tolerant 

of, or at least habituate more quickly to, 

potentially disturbing underwater sound 

than do cetaceans, and generally seem 

to be less responsive to exposure to 

industrial sound than most cetaceans. 

Please see Appendices B and C of 

Southall et al. (2007) for a review of 

studies involving marine mammal 

behavioral responses to sound. 

Disruption of feeding behavior can be 

difficult to correlate with anthropogenic 

sound exposure, so it is usually inferred 

by observed displacement from known 

foraging areas, the appearance of 

secondary indicators (e.g., bubble nets 

or sediment plumes), or changes in dive 

behavior. As for other types of 

behavioral response, the frequency, 

duration, and temporal pattern of signal 

presentation, as well as differences in 

species sensitivity, are likely 

contributing factors to differences in 

response in any given circumstance 

(e.g., Croll et al. 2001; Nowacek et al. 

2004; Madsen et al. 2006; Yazvenko et 

al. 2007). A determination of whether 

foraging disruptions incur fitness 

consequences would require 

information on or estimates of the 

energetic requirements of the affected 

individuals and the relationship 

between prey availability, foraging effort 

and success, and the life history stage of 

the animal. 

In 2016, ADOT documented 

observations of marine mammals during 

construction activities (i.e., pile driving 

and DTH) at the Kodiak Ferry Dock 

(ABR 2016) in the Gulf of Alaska. In the 

marine mammal monitoring report for 

that project, 1,281 Steller sea lions were 

observed within the estimated Level B 

harassment zone during pile driving or 

DTH (i.e., documented as potential take 

by Level B harassment). Of these, 19 

individuals demonstrated an alert 

behavior, 7 were fleeing, and 19 swam 

away from the project site. All other 

animals (98 percent) were engaged in 

activities such as milling, foraging, or 

fighting and did not change their 

behavior. In addition, two sea lions 

approached within 20 m of active 

vibratory pile driving activities. Three 

harbor seals were observed within the 

disturbance zone during pile driving 

activities; none of them displayed 

disturbance behaviors. Fifteen killer 

whales and three harbor porpoise were 

also observed within the Level B 

harassment zone during pile driving. 

The killer whales were travelling or 

milling while all harbor porpoises were 

travelling. No signs of disturbance were 

noted for either of these species. Given 

the similarities in species, activities, 

and habitat, we expect similar 

behavioral responses of marine 

mammals to the ADOT’s specified 

activity. That is, disturbance, if any, is 

likely to be temporary and localized 

(e.g., small area movements). 

Monitoring reports from other recent 

pile driving and DTH projects in Alaska 

have observed similar behaviors, for 

example, the Biorka Island Dock 

Replacement Project (https://

www.fisheries.noaa.gov/action/ 

incidental-take-authorization-faabiorka-island-dock-replacement-projectsitka-ak). 

Stress responses—An animal’s 

perception of a threat may be sufficient 

to trigger stress responses consisting of 

some combination of behavioral 

responses, autonomic nervous system 

responses, neuroendocrine responses, or 

immune responses (e.g., Seyle 1950; 

Moberg 2000). In many cases, an 

animal’s first and sometimes most 

economical (in terms of energetic costs) 

response is behavioral avoidance of the 

potential stressor. Autonomic nervous 

system responses to stress typically 

involve changes in heart rate, blood 

pressure, and gastrointestinal activity. 

These responses have a relatively short 

duration and may or may not have a 

significant long-term effect on an 

animal’s fitness. 

Neuroendocrine stress responses often 

involve the hypothalamus-pituitaryadrenal system. Virtually all 

neuroendocrine functions that are 

affected by stress—including immune 

competence, reproduction, metabolism, 

and behavior—are regulated by pituitary 

hormones. Stress-induced changes in 

the secretion of pituitary hormones have 

been implicated in failed reproduction, 

altered metabolism, reduced immune 

competence, and behavioral disturbance 

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

Increases in the circulation of 

glucocorticoids are also equated with 

stress (Romano et al. 2004). 

The primary distinction between 

stress (which is adaptive and does not 

normally place an animal at risk) and 


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

During a stress response, an animal uses 

glycogen stores that can be quickly 

replenished once the stress is alleviated. 

In such circumstances, the cost of the 

stress response would not pose serious 

fitness consequences. However, when 

an animal does not have sufficient 

energy reserves to satisfy the energetic 

costs of a stress response, energy 

resources must be diverted from other 

functions. This state of distress will last 

until the animal replenishes its 

energetic reserves sufficient to restore 

normal function. 

Relationships between these 

physiological mechanisms, animal 

behavior, and the costs of stress 

responses are well-studied through 

controlled experiments and for both 

laboratory and free-ranging animals 

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

1998; Jessop et al. 2003; Krausman et al. 

2004; Lankford et al. 2005). Stress 

responses due to exposure to 

anthropogenic sounds or other stressors 

and their effects on marine mammals 

have also been reviewed (Fair and 

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

more rarely, studied in wild populations 

(e.g., Romano et al. 2002a). For example, 

Rolland et al. (2012) found that noise 

reduction from reduced ship traffic in 

the Bay of Fundy was associated with 

decreased stress in North Atlantic right 

whales. These and other studies lead to 

a reasonable expectation that some 

marine mammals will experience 

physiological stress responses upon 

exposure to acoustic stressors and that 

it is possible that some of these would 

be classified as ‘‘distress.’’ In addition, 

any animal experiencing TTS would 

likely also experience stress responses 

(NRC 2003), however distress is an 

unlikely result of this project based on 

observations of marine mammals during 

previous, similar projects in the area. 

Masking—Sound can disrupt behavior 

through masking, or interfering with, an 

animal’s ability to detect, recognize, or 

discriminate between acoustic signals of 

interest (e.g., those used for intraspecific 

communication and social interactions, 

prey detection, predator avoidance, 

navigation) (Richardson et al. 1995). 

Masking occurs when the receipt of a 

sound is interfered with by another 

coincident sound at similar frequencies 

and at similar or higher intensity, and 

may occur whether the sound is natural 

(e.g., snapping shrimp, wind, waves, 

precipitation) or anthropogenic (e.g., 

pile driving, shipping, sonar, seismic 

exploration) in origin. The ability of a 

noise source to mask biologically 

important sounds depends on the 

characteristics of both the noise source 

and the signal of interest (e.g., signal-tonoise ratio, temporal variability, 

direction), in relation to each other and 

to an animal’s hearing abilities (e.g., 

sensitivity, frequency range, critical 

ratios, frequency discrimination, 

directional discrimination, age or TTS 

hearing loss), and existing ambient 

noise and propagation conditions. 

Masking of natural sounds can result 

when human activities produce high 

levels of background sound at 

frequencies important to marine 

mammals. Conversely, if the 

background level of underwater sound 

is high (e.g., on a day with strong wind 

and high waves), an anthropogenic 

sound source would not be detectable as 

far away as would be possible under 

quieter conditions and would itself be 

masked. 

Airborne Acoustic Effects—Pinnipeds 

that occur near the project site could be 

exposed to airborne sounds associated 

with pile driving and removal and DTH 

that have the potential to cause 

behavioral harassment, depending on 

their distance from these activities. 

Cetaceans are not expected to be 

exposed to airborne sounds that would 

result in harassment as defined under 

the MMPA. 

Airborne noise would primarily be an 

issue for pinnipeds that are swimming 

or hauled out near the project site 

within the range of noise levels elevated 

above the acoustic criteria. We 

recognize that pinnipeds in the water 

could be exposed to airborne sound that 

may result in behavioral harassment 

when looking with their heads above 

water. Most likely, airborne sound 

would cause behavioral responses 

similar to those discussed above in 

relation to underwater sound. For 

instance, anthropogenic sound could 

cause hauled-out pinnipeds to exhibit 

changes in their normal behavior, such 

as reduction in vocalizations, or cause 

them to temporarily abandon the area 

and move further from the source. 

However, these animals would 

previously have been ‘taken’ because of 

exposure to underwater sound above the 

behavioral harassment thresholds, 

which are in all cases larger than those 

associated with airborne sound. Thus, 

the behavioral harassment of these 

animals is already accounted for in 

these estimates of potential take. 

Therefore, we do not believe that 

authorization of incidental take 

resulting from airborne sound for 

pinnipeds is warranted, and airborne 

sound is not discussed further here. 

Marine Mammal Habitat Effects 

ADOT’s proposed activities at the 

project area would not result in 

permanent negative impacts to habitats 

used directly by marine mammals, but 

may have potential short-term impacts 

to food sources such as forage fish and 

may affect acoustic habitat (see masking 

discussion above). There are no known 

foraging hotspots or other ocean bottom 

structure of significant biological 

importance to marine mammals present 

in the marine waters of the project area 

during the construction window, but 

there are times of increased foraging 

during periods of forage fish and 

salmonid spawning. ADOT’s 

construction activities in Tongass 

Narrows could have localized, 

temporary impacts on marine mammal 

habitat and their prey by increasing inwater sound pressure levels and slightly 

decreasing water quality. Increased 

noise levels may affect acoustic habitat 

(see masking discussion above) and 

adversely affect marine mammal prey in 

the vicinity of the project area (see 

discussion below). During DTH, impact 

and vibratory pile driving or removal, 

elevated levels of underwater noise 

would ensonify a portion of Tongass 

Narrows and nearby waters where both 

fishes and mammals occur and could 

affect foraging success. Additionally, 

marine mammals may avoid the area 

during construction, however, 

displacement due to noise is expected to 

be temporary and is not expected to 

result in long-term effects to the 

individuals or populations. 

Construction activities are of short 

duration and would likely have 

temporary impacts on marine mammal 

habitat through increases in underwater 

and airborne sound. 

The area likely impacted by the 

project includes much of Tongass 

Narrows, but overall this area is 

relatively small compared to the 

available habitat in the surrounding area 

including Revillagigedo Channel, Behm 

Canal, and Clarence Strait. Pile 

installation/removal and DTH may 

temporarily increase turbidity resulting 

from suspended sediments. Any 

increases would be temporary, 

localized, and minimal. In general, 

turbidity associated with pile 

installation is localized to about a 25-ft 

radius around the pile (Everitt et al. 

1980). Cetaceans are not expected to be 

close enough to the project pile driving 

areas to experience effects of turbidity, 

and pinnipeds could avoid localized 

areas of turbidity. Therefore, the impact 

from increased turbidity levels is 

expected to minimal for marine 

mammals. Furthermore, pile driving 

and removal at the project site would 

not obstruct movements or migration of 

marine mammals. 

In-water Construction Effects on 

Potential Prey—Construction activities 


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would produce continuous (i.e., 

vibratory pile driving and DTH) and 

intermittent (i.e. impact driving and 

DTH) sounds. Sound may affect marine 

mammals through impacts on the 

abundance, behavior, or distribution of 

prey species (e.g., crustaceans, 

cephalopods, fish, zooplankton). Marine 

mammal prey varies by species, season, 

and location. Here, we describe studies 

regarding the effects of noise on known 

marine mammal prey. 

Fish utilize the soundscape and 

components of sound in their 

environment to perform important 

functions such as foraging, predator 

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

Zelick and Mann 1999; Fay 2009). 

Depending on their hearing anatomy 

and peripheral sensory structures, 

which vary among species, fishes hear 

sounds using pressure and particle 

motion sensitivity capabilities and 

detect the motion of surrounding water 

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

noise on fishes depends on the 

overlapping frequency range, distance 

from the sound source, water depth of 

exposure, and species-specific hearing 

sensitivity, anatomy, and physiology. 

Key impacts to fishes may include 

behavioral responses, hearing damage, 

barotrauma (pressure-related injuries), 

and mortality. 

Fish react to sounds that are 

especially strong and/or intermittent 

low-frequency sounds. Short duration, 

sharp sounds can cause overt or subtle 

changes in fish behavior and local 

distribution. The reaction of fish to 

noise depends on the physiological state 

of the fish, past exposures, motivation 

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

other environmental factors. Hastings 

and Popper (2005) identified several 

studies that suggest fish may relocate to 

avoid certain areas of sound energy. 

Additional studies have documented 

effects of pile driving on fish; several are 

based on studies in support of large, 

multiyear bridge construction projects 

(e.g., Scholik and Yan 2001, 2002; 

Popper and Hastings 2009). Several 

studies have demonstrated that impulse 

sounds might affect the distribution and 

behavior of some fishes, potentially 

impacting foraging opportunities or 

increasing energetic costs (e.g., Fewtrell 

and McCauley, 2012; Pearson et al. 

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

1999; Paxton et al. 2017). However, 

some studies have shown no or slight 

reaction to impulse sounds (e.g., Pena et 

al. 2013; Wardle et al. 2001; Jorgenson 

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

SPLs of sufficient strength have been 

known to cause injury to fish and fish 

mortality. However, in most fish 

species, hair cells in the ear 

continuously regenerate and loss of 

auditory function likely is restored 

when damaged cells are replaced with 

new cells. Halvorsen et al. (2012a) 

showed that a TTS of 4–6 dB was 

recoverable within 24 hours for one 

species. Impacts would be most severe 

when the individual fish is close to the 

source and when the duration of 

exposure is long. Injury caused by 

barotrauma can range from slight to 

severe and can cause death, and is most 

likely for fish with swim bladders. 

Barotrauma injuries have been 

documented during controlled exposure 

to impact pile driving (Halvorsen et al. 

2012b; Casper et al. 2013). 

The most likely impact to fish from 

pile driving and removal and DTH 

activities at the project area would be 

temporary behavioral avoidance of the 

area. The duration of fish avoidance of 

this area after pile driving stops is 

unknown, but a rapid return to normal 

recruitment, distribution and behavior 

is anticipated. Any behavioral 

avoidance by fish of the disturbed area 

would still leave significantly large 

areas of fish and marine mammal 

foraging habitat in the nearby vicinity in 

Revillagigedo Channel, Behm Canal, 

and Clarence Strait. Additionally, the 

City of Ketchikan within Tongass 

Narrows has a busy industrial water 

front, and human impact lessens the 

value of the area as foraging habitat. 

There are times of known seasonal 

marine mammal foraging in Tongass 

Narrows around fish processing/ 

hatchery infrastructure or when fish are 

congregating, but the impacted areas of 

Tongass Narrows are a small portion of 

the total foraging habitat available in the 

region. In general, impacts to marine 

mammal prey species are expected to be 

minor and temporary due to the short 

timeframe of the project. 

Construction activities, in the form of 

increased turbidity, have the potential 

to adversely affect eulachon, herring, 

and juvenile salmonid outmigratory 

routes in the project area. Salmon and 

forage fish, like eulachon and herring, 

form a significant prey base for Steller 

sea lions and are major components of 

the diet of many other marine mammal 

species that occur in the project area. 

Increased turbidity is expected to occur 

only in the immediate vicinity of 

construction activities and to dissipate 

quickly with tidal cycles. Given the 

limited area affected and high tidal 

dilution rates any effects on fish are 

expected to be minor. 

Additionally, the presence of 

transient killer whales means some 

marine mammal species are also 

possible prey (harbor seals, harbor 

porpoises). ADOT’s pile driving, pile 

removal and DTH activities are expected 

to result in limited instances of take by 

Level B and Level A harassment on 

these smaller marine mammals. That, as 

well as the fact that ADOT is impacting 

a small portion of the total available 

marine mammal habitat means that 

there would be minimal impact on these 

marine mammals as prey. 

In summary, given the short daily 

duration of sound associated with 

individual pile driving and DTH events 

and the small area being affected 

relative to available nearby habitat, pile 

driving and DTH activities associated 

with the proposed action are not likely 

to have a permanent, adverse effect on 

any fish habitat, or populations of fish 

species or other prey. Thus, we 

conclude that impacts of the specified 

activity are not likely to have more than 

short-term adverse effects on any prey 

habitat or populations of prey species. 

Further, any impacts to marine mammal 

habitat are not expected to result in 

significant or long-term consequences 

for individual marine mammals, or to 

contribute to adverse impacts on their 

populations. 

Estimated Take 

This section provides an estimate of 

the number of incidental takes proposed 

for authorization through this IHA, 

which will inform both NMFS’ 

consideration of ‘‘small numbers’’ and 

the negligible impact determination. 

Harassment is the only type of take 

expected to result from these activities. 

Except with respect to certain activities 

not pertinent here, section 3(18) of the 

MMPA defines ‘‘harassment’’ as any act 

of pursuit, torment, or annoyance, 

which (i) has the potential to injure a 

marine mammal or marine mammal 

stock in the wild (Level A harassment); 

or (ii) has the potential to disturb a 

marine mammal or marine mammal 

stock in the wild by causing disruption 

of behavioral patterns, including, but 

not limited to, migration, breathing, 

nursing, breeding, feeding, or sheltering 

(Level B harassment). 

Authorized takes would primarily be 

by Level B harassment, as 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 for midfrequency species and otariids. The 

proposed mitigation and monitoring 


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measures are expected to minimize the 

severity of such taking to the extent 

practicable. 

As described previously, no mortality 

is anticipated or proposed to be 

authorized for this activity. Below we 

describe how the take is estimated. 

Generally speaking, we estimate take 

by considering: (1) Acoustic thresholds 

above which NMFS believes the best 

available science indicates marine 

mammals will be behaviorally harassed 

or incur some degree of permanent 

hearing impairment; (2) the area or 

volume of water that will be ensonified 

above these levels in a day; (3) the 

density or occurrence of marine 

mammals within these ensonified areas; 

and, (4) and the number of days of 

activities. We note that while these 

basic factors can contribute to a basic 

calculation to provide an initial 

prediction of takes, additional 

information that can qualitatively 

inform take estimates is also sometimes 

available (e.g., previous monitoring 

results or average group size). Below, we 

describe the factors considered here in 

more detail and present the proposed 

take estimate. 

Acoustic Thresholds 

NMFS recommends the use of 

acoustic thresholds that identify the 

received level of underwater sound 

above which exposed marine mammals 

would be reasonably expected to be 

behaviorally harassed (equated to Level 

B harassment) or to incur PTS of some 

degree (equated to Level A harassment). 

Level B Harassment for non-explosive 

sources—Though significantly driven by 

received level, the onset of behavioral 

disturbance from anthropogenic noise 

exposure is also informed to varying 

degrees by other factors related to the 

source (e.g., frequency, predictability, 

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

bathymetry), and the receiving animals 

(hearing, motivation, experience, 

demography, behavioral context) and 

can be difficult to predict (Southall et al. 

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

the available science indicates and the 

practical need to use a threshold based 

on a factor that is both predictable and 

measurable for most activities, NMFS 

uses a generalized acoustic threshold 

based on received level to estimate the 

onset of behavioral harassment. NMFS 

predicts that marine mammals are likely 

to be behaviorally harassed in a manner 

we consider Level B harassment when 

exposed to underwater anthropogenic 

noise above received levels of 120 dB re 

1 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 proposed 

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 proposed 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 4 below. The references, analysis, 

and methodology used in the 

development of the thresholds are 

described in NMFS 2018 Technical 

Guidance, which may be accessed at 

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

national/marine-mammal-protection/ 

marine-mammal-acoustic-technicalguidance. 

TABLE 4—THRESHOLDS IDENTIFYING THE ONSET OF PERMANENT THRESHOLD SHIFT

Hearing group 

PTS onset acoustic thresholds * 

(received level) 

Impulsive Non-impulsive 

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

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

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

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

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

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

also be considered. 

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

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

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

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

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

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

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

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

Ensonified Area 

Here, we describe operational and 

environmental parameters of the activity 

that will feed into identifying the area 

ensonified above the acoustic 

thresholds, which include source levels 

and transmission loss coefficient. 

The sound field in the project area is 

the existing background noise plus 

additional construction noise from the 

proposed project. Marine mammals are 

expected to be affected via sound 

generated by the primary components of 

the project (i.e., impact pile 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, 


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sizes and methods (Table 5). 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 proposed 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 dB 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 

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 11). In 

the absence of data specific to different 

hole sizes, current NMFS guidance 

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 5. 

TABLE 5—ESTIMATES OF MEAN UNDERWATER SOUND LEVELS GENERATED DURING VIBRATORY AND IMPACT PILE

INSTALLATION, DTH, AND VIBRATORY PILE REMOVAL

Method and pile type 

Vibratory hammer 

SSL at 10 m 

dB rms Literature source 

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, would be for short 

durations on any given day, and ADOT 

anticipates that no more than two 

hammers would 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 

would 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 would be 

incidental. Given that the use of more 

than one hammer for pile installation on 

the same day (whether simultaneous or 

not) would increase the number of piles 

installed per day, this would be 

anticipated to result in a reduction of 

the total number of days of pile 

installation. Table 6 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 would occur on all 91 days. 


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TABLE 6—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 

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 7) 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 

would strike at the same instant, and 

therefore, the SPLs would not be 

adjusted regardless of the distance 

between impact hammers. In this case, 

each impact hammer would 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 7, 

similar to described above for DTH. 

TABLE 7—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 ...............

10 dB or more .......

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

Add 0 dB to the higher source level ....

Add 1 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 8, decibel 

addition calculations were carried out 

for possible combinations of pile driving 

and DTH throughout the project area. 

The source levels included in Table 8 

are used to estimate the Level A 

harassment zones and the Level B 

harassment zones. 

TABLE 8—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 ............ ............ ............


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TABLE 8—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—Continued 

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 

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 

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 would lie between 

spherical and cylindrical spreading loss 

conditions, which is the most 

appropriate assumption for ADOT’s 

proposed activity in the absence of 

specific modelling. 

All Level B harassment isopleths are 

reported in Table 9 and Table 10 below. 

It should be noted that based on the 

geography of Tongass Narrows and the 

surrounding islands, sound would 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 would 

depend on the combination of sound 

sources and the decibel addition of two 

hammers producing continuous noise. 

Table 9 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 9 is consistent, regardless of the 

equipment combination. Please refer to 

Table 8 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 9— 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 10—LEVEL B HARASSMENT ISOPLETHS FOR SINGLE HAMMER USE BY ACTIVITY AND PILE SIZE

Activity Pile diameter 

(inch) 

Level B 

harassment 

isopleth 

(m) 

Vibratory Installation ................................................................................................................................................ 30 6,310 

24 5,412 

.................................................................................................................................................................................. 20 ........................

Vibratory Removal ................................................................................................................................................... 24 ........................

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


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TABLE 10—LEVEL B HARASSMENT ISOPLETHS FOR SINGLE HAMMER USE BY ACTIVITY AND PILE SIZE—Continued 

Activity Pile diameter 

(inch) 

Level B 

harassment 

isopleth 

(m) 

24 ........................

DTH Tension Anchor/Micropile ................................................................................................................................ 8 ........................

Impact Installation .................................................................................................................................................... 30 2,154 

24 1,000 

20 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 would incur 

PTS. Inputs used in the User 

Spreadsheet are reported in Table 11 

and Table 12, and the resulting 

isopleths are reported below in Table 13 

and Table 14. 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 would be installed per 

day on 27 non-consecutive days, two 

temporary piles would be installed per 

day on 10 non-consecutive days, and 

two temporary piles would be removed 

per day on 10 days. 

BILLING CODE 3510–22–P 


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BILLING CODE 3510–22–C 

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 zone of any two hammers 

would not be 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 


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for simultaneous use of two DTH 

hammers (Table 14), using NMFS’ User 

Spreadsheet. The inputs for these 

calculations are outlined in Table 12. 

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 12—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 ....................................................................................................................................... 240 

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

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

aSSL reflects the combined SSLs calculated in Table 8. 

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 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 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 would be driven in 

a day and strikes per pile. For some 

activities, ADOT has proposed to drive 

variable numbers of piles per day 

throughout the project (See ‘‘Average 

Piles per Day (Range)’’ in Table 1), and 

determine at the beginning of each pile 

driving day, the maximum number or 

duration piles would be driven that day. 

Here, this flexibility has been accounted 

for by modeling multiple durations for 

the activity, and determining the 

relevant isopleths. 

TABLE 13—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 (km2) 

all hearing 

groups LF MF HF PW OW a

Vibratory Installation ................ 30 60 minutes ..... 8 1 12 5 1 <0.1 b 24 60 minutes ..... 7 1 11 5 1 <0.1 

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

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

DTH Rock Sockets .................. 30 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 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 ............... 8 120 minutes ... 82 3 98 44 4 <0.1 

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

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

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

20 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. 


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TABLE 14—DISTANCES TO LEVEL A HARASSMENT ISOPLETHS, BY HEARING GROUP FOR SIMULTANEOUS USE OF TWO

DTH HAMMERS

Activity combination 

Level A harassment isopleth (m) 

LF MF HF PW OW 

8-in pile, 8-in pile ................................................................. 206 7 245 110 8 

8-in pile, 24-in pile ............................................................... 1,297 46 1,545 694 51 

8-in pile, 30-in pile ............................................................... 2,796 99 3,329 1,496 109 

24-in pile, 24-in pile ............................................................. 1,431 51 1,705 766 56 

24-in pile, 30-in .................................................................... 2,268 81 2,702 1,214 88 

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

proposed take, including as a percentage 

of population for each of the species, is 

shown in Table 15. 

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 

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 15). 

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 would 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 120 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 would occur 

on no more than 44 days). Zones for 

shorter durations and other activities 

would be smaller (Table 13). For some 

DTH activities, the estimated Level A 

harassment zone is larger than the 

proposed 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 

requests, and NMFS proposes to 

authorize, one take by Level A 

harassment on each of the 91 

construction days (91 takes by Level A 

harassment). Take by Level B 

harassment proposed for authorization 

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 requests, and NMFS proposes to 

authorize, 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 15). 

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 


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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 15). 

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 would 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 would occur 

on no more than 44 days). Zones for 

shorter durations and other activities 

would be smaller (Table 13). Due to 

practicability concerns, NMFS proposes 

to require a 200 m shutdown zone for 

harbor seals during 24-in and 30-in DTH 

activities (Table 16). Therefore, for some 

DTH activities, the estimated Level A 

harassment zone is larger than the 

proposed 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/ 

30-in pile combinations would result in 

larger Level A harassment isopleths 

than 1,918 m, however, such concurrent 

work would 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.) Take by 

Level B harassment proposed for 

authorization 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 requests, and NMFS proposes 

to authorize, 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 

15). 

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 would 

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 would 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 would occur 

on no more than 44 days). Zones for 

shorter durations and other activities 

would be smaller (Table 13). 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 proposed 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 


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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.) Take by Level B 

harassment proposed for authorization 

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 

requests and NMFS proposes to 

authorize 5 takes by Level A harassment 

and 27 takes by Level B harassment (32 

total takes of harbor porpoise, Table 15). 

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 would 

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 

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 

would 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 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 would occur 

on no more than 44 days). Zones for 

shorter durations and other activities 

would be smaller (Table 13). 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 proposed 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.) Take by Level B 

harassment proposed for authorization 

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 requests and NMFS proposes 

to authorize 20 takes by Level A 

harassment, and 207 takes by Level B 

harassment (227 total takes of Dall’s 

porpoise, Table 15). 

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 proposed 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 proposed 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 would 


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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 is proposing to 

authorize 92 takes by Level B 

harassment of Pacific white-sided 

dolphins. 

ADOT did not request, nor does 

NMFS propose to authorize take by 

Level A harassment for this activity 

given that Pacific white-sided dolphins 

are uncommon in the project area. 

Further, considering the small Level A 

harassment zones for mid-frequency 

cetaceans (Table 13 and Table 14) in 

comparison to the required shutdown 

zones, it is unlikely that a Pacific whitesided dolphin would 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 would 

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 would 

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 proposes 

to authorize 72 takes by Level B 

harassment of killer whale. 

ADOT did not request, nor does 

NMFS propose to authorize take by 

Level A harassment of killer whales for 

this activity. Considering the small 

Level A harassment zones for midfrequency cetaceans (Table 13 and Table 

14) in comparison to the required 

shutdown zones, it is unlikely that a 

killer whale would 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 

stated that based on observations by 

local experts, approximately one group 

of two individuals would 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 proposed 

activities. As noted previously, ADOT 

estimates that pile driving would 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 would 

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 proposes to 

authorize 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 proposed for 

authorization, NMFS expects that a total 

of 14 takes would be of individuals from 

the Mexico DPS. NMFS expects that all 

other instances of proposed take would 

be from the non-listed Hawaii DPS. 

Take by Level A harassment of 

humpback whales is neither anticipated 

nor proposed to be authorized because 

of the expected effectiveness of the 

required monitoring and mitigation 

measures (see Proposed Mitigation 

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 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. 


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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 would 

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 three minke 

whales may occur in the Level B 

harassment zone during the proposed 

activities (occurring over approximately 

3 months), and proposes to authorize 3 

takes by Level B harassment of minke 

whales (Table 15). 

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 would occur 

on no more than 44 days.) Zones for 

shorter durations and other activities 

would be smaller (Table 14). NMFS 

proposes to require 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 proposed 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 requests, 

and NMFS proposes to authorize 1 take 

by Level A harassment and 2 takes by 

Level B harassment (3 total takes of 

minke whale, Table 15). 

TABLE 15—PROPOSED AMOUNT OF TAKE AS A PERCENTAGE OF STOCK ABUNDANCE, BY STOCK AND HARASSMENT TYPE

Species DPS/stock 

Proposed authorized take 

Percent of 

Level A 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 ............................... ........................ ........................ ........................ a 3.1 

West Coast Transient ...................... 0 72 72 a 20.1 

Northern Resident ............................ ........................ ........................ ........................ a 23.8 

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

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

Proposed Mitigation 

In order to issue an IHA under section 

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

set forth the permissible methods of 

taking pursuant to the activity, and 

other means of effecting the least 

practicable impact on the species or 

stock and its habitat, paying particular 

attention to rookeries, mating grounds, 

and areas of similar significance, and on 

the availability of the species or stock 

for taking for certain subsistence uses. 

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. The proposed measures are 

however typical for actions in the 

Ketchikan area. The mitigation 

measures included herein include 

measures that align with the 2019 

Biological Opinion, and are subject to 

change, as required by NMFS’ ESA 

Section 7 consultation. If Section 7 

consultation warrants changes to these 

measures, NMFS expects that the new 

measures would align closely with those 

included in the recent proposed IHA for 

construction at the NOAA Port Facility 


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Project in Ketchikan, Alaska (86 FR 

68223; December 1, 2021). 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 has 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 16 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 

indicated in Table 16, 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 16) 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: 


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• 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 16). The purpose of a shutdown 

zone is generally to define an area 

within which shutdown of activity 

would occur upon sighting of a marine 

mammal (or in anticipation of an animal 

entering the defined area). Shutdown 

zones vary based on the activity type 

and duration and marine mammal 

hearing group (Table 16). 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 would 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 would 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 would implement the Level 

A harassment zones and shutdown 

zones associated with simultaneous 

DTH use of the relevant pile sizes (Table 

14 and Table 16). If DTH may only 

occur at one site, ADOT would then 

determine the maximum duration of 

DTH possible that day (according to the 

defined duration intervals in Table 16), 

which would determine the appropriate 

Level A harassment isopleth for that day 

(Table 13 and Table 14). 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 13. 

Due to practicability concerns, 

shutdown zones for some species during 

some activities may be smaller than the 

Level A harassment isopleths (Table 16). 

The placement of PSOs during all pile 

driving, pile removal, and DTH 

activities (described in detail in the 

Proposed Monitoring and Reporting 

Section) will ensure that the entire 

shutdown zones are visible during pile 

installation. 

TABLE 16—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 

24 

20 

60 min 

60 min 

60 min 

50 20 6,310 

5,412 

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

Activity combination 

Level A harassment isopleth (m) 

LF MF HF PW OW 

8-in pile, 8-in pile ..................................................................................... 210 20 250 110 20 


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TABLE 17—SHUTDOWN ZONES, BY HEARING GROUP FOR SIMULTANEOUS USE OF TWO DTH HAMMERS—Continued 

Activity combination 

Level A harassment isopleth (m) 

LF MF HF PW OW 

8-in pile, 24-in pile ................................................................................... 1,300 50 500 200 60 

8-in pile, 30-in pile ................................................................................... 2,800 100 110 

24-in pile, 24-in pile ................................................................................. 1,440 60 60 

24-in pile, 30-in ........................................................................................ 2,270 90 90 

30-in pile, 30-in pile ................................................................................. 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 preliminarily determined 

that the proposed mitigation measures 

provide the means effecting the least 

practicable impact on the affected 

species or stocks and their habitat, 

paying particular attention to rookeries, 

mating grounds, and areas of similar 

significance. 

Proposed Monitoring and Reporting 

In order to issue an IHA for an 

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

MMPA states that NMFS must set forth 

requirements pertaining to the 

monitoring and reporting of such taking. 

The MMPA implementing regulations at 

50 CFR 216.104 (a)(13) indicate that 

requests for authorizations must include 

the suggested means of accomplishing 

the necessary monitoring and reporting 

that will result in increased knowledge 

of the species and of the level of taking 

or impacts on populations of marine 

mammals that are expected to be 

present in the proposed action area. 

Effective reporting is critical both to 

compliance as well as ensuring that the 

most value is obtained from the required 

monitoring. 

Monitoring and reporting 

requirements prescribed by NMFS 

should contribute to improved 

understanding of one or more of the 

following: 

• Occurrence of marine mammal 

species or stocks in the area in which 

take is anticipated (e.g., presence, 

abundance, distribution, density). 

• Nature, scope, or context of likely 

marine mammal exposure to potential 

stressors/impacts (individual or 

cumulative, acute or chronic), through 

better understanding of: (1) Action or 

environment (e.g., source 

characterization, propagation, ambient 

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

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

of marine mammal species with the 

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 


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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 

Monitoring and Mitigation Plan for a 

map of proposed 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 would 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 would include an 

overall description of work completed, 

a narrative regarding marine mammal 

sightings, and associated PSO data 

sheets. Specifically, the report must 

include: 

• Dates and times (begin and end) of 

all marine mammal monitoring; 

• Construction activities occurring 

during each daily observation period, 

including the number and type of piles 

driven or removed and by what method 

(i.e., impact, 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 would 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 would constitute the final report. 

If comments are received, a final report 

addressing NMFS comments must be 

submitted within 30 days after receipt of 

comments. 

Reporting Injured or Dead Marine 

Mammals 

In the event that personnel involved 

in the construction activities discover 

an injured or dead marine mammal, the 

IHA-holder must immediately cease the 

specified activities and report the 

incident to the Office of Protected 

Resources (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 


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• General circumstances under which 

the animal was discovered. 

Negligible Impact Analysis and 

Determination 

NMFS has defined negligible impact 

as an impact resulting from the 

specified activity that cannot be 

reasonably expected to, and is not 

reasonably likely to, adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival 

(50 CFR 216.103). A negligible impact 

finding is based on the lack of likely 

adverse effects on annual rates of 

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

of takes alone is not enough information 

on which to base an impact 

determination. In addition to 

considering estimates of the number of 

marine mammals that might be ‘‘taken’’ 

through harassment, NMFS considers 

other factors, such as the likely nature 

of any 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’s 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 2 

for which take could occur, given that 

NMFS expects the anticipated effects of 

the proposed 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. 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 would 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 would implement 

shutdown zones that equal or exceed 

many of the Level A harassment 

isopleths shown in Table 13. 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 

would not be expected to adversely 

impact individual fitness, let alone 

annual rates of recruitment or survival. 

For all species and stocks, take would 

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 

would be reduced to the level of least 

practicable adverse impact through use 

of mitigation measures described herein. 

Further the amount of take proposed to 

be 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 would 

occur for only a portion of the project’s 

duration and often on nonconsecutive 

days, any harassment occurring would 

be temporary. Additionally, many of the 

species present in Tongass Narrows or 

Clarence Strait would only be present 

temporarily based on seasonal patterns 

or during transit between other habitats. 

These temporarily present species 

would 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 would 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 would occur during ADOT’s 

planned activity would 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 


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construction are expected to be minor, 

and these 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 would have any effect on 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 would have only minor, shortterm effects on individuals. The 

specified activities are not expected to 

impact rates of recruitment or survival 

and would, therefore, not result in 

population-level impacts. 

In summary and as described above, 

the following factors primarily support 

our preliminary determination that the 

impacts resulting from this activity are 

not expected to adversely affect the 

species or stock through effects on 

annual rates of recruitment or survival: 

• No serious injury or mortality is 

anticipated or proposed for 

authorization; 

• Take by Level A harassment of 

Pacific white-sided dolphin, killer 

whale, and humpback whale is not 

anticipated or proposed for 

authorization; 

• ADOT would 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 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 would 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 

proposed monitoring and mitigation 

measures, NMFS preliminarily finds 

that the total marine mammal take from 

the proposed activity will have a 

negligible impact on all affected marine 

mammal species or stocks. 

Small Numbers 

As noted above, only small numbers 

of incidental take may be authorized 

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

the MMPA for specified activities other 

than military readiness activities. The 

MMPA does not define small numbers 

and so, in practice, where estimated 

numbers are available, NMFS compares 

the number of individuals taken to the 

most appropriate estimation of 

abundance of the relevant species or 

stock in our determination of whether 

an authorization is limited to small 

numbers of marine mammals. When the 

predicted number of individuals to be 

taken is fewer than one third of the 

species or stock abundance, the take is 

considered to be of small numbers. 

Additionally, other qualitative factors 

may be considered in the analysis, such 

as the temporal or spatial scale of the 

activities. 

The instances of take NMFS proposes 

to authorize is below one third of the 

estimated stock abundance for all stocks 

(see Table 15). The number of animals 

that we expect to authorize to be taken 

from these stocks would be 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 would 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 takes of this 

stock proposed for authorization 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 eight 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 

takes of this stock proposed for 

authorization 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 takes 

proposed for authorization 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. Therefore, the 3 takes of 

minke whale proposed for authorization 

is small relative to estimated survey 

abundance, even if each proposed take 

occurred to a new individual. 

Based on the analysis contained 

herein of the proposed activity 

(including the proposed mitigation and 

monitoring measures) and the 

anticipated take of marine mammals, 

NMFS preliminarily finds that small 

numbers of marine mammals will be 

taken relative to the population size of 

the affected species or stocks. 

Unmitigable Adverse Impact Analysis 

and Determination 

In order to issue an IHA, NMFS must 

find that the specified activity will not 

have an ‘‘unmitigable adverse impact’’ 

on the subsistence uses of the affected 

marine mammal species or stocks by 

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 


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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 

Game (ADF&G) has not recorded harvest 

of cetaceans from Ketchikan or Saxman 

(ADF&G 2018). 

All project activities would 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 also would 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 would not expect such harassment 

to have effects on subsistence hunting 

activities. 

Based on the description of the 

specified activity and the proposed 

mitigation and monitoring measures, 

NMFS has preliminarily determined 

that there will not be an unmitigable 

adverse impact on subsistence uses from 

ADOT’s proposed activities. 

Endangered Species Act 

Section 7(a)(2) of the Endangered 

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

1531 et seq.) requires that each Federal 

agency insure that any action it 

authorizes, funds, or carries out is not 

likely to jeopardize the continued 

existence of any endangered or 

threatened species or result in the 

destruction or adverse modification of 

designated critical habitat. To ensure 

ESA compliance for the issuance of 

IHAs, NMFS’ Office of Protected 

Resources (OPR) consults internally 

whenever we propose to authorize take 

for endangered or threatened species, in 

this case with 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 ADOT for 

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 which 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 which concluded that issuance 

of IHAs to ADOT is not likely to 

jeopardize the continued existence of 

Mexico DPS humpback whales. The 

effects of this proposed 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. Because the 

currently proposed take of Mexico DPS 

of humpback whales exceeds that 

authorized in the 2019 Biological 

Opinion, NMFS will need to reinitiate 

consultation on this project. 

Proposed Authorization 

As a result of these preliminary 

determinations, NMFS proposes to issue 

an IHA to ADOT for the construction of 

four facilities in the channel between 

Gravina Island and Revillagigedo 

(Revilla) Island in Ketchikan, Alaska: 

The Gravina Airport Ferry Layup 

Facility, the Gravina Freight Facility, 

the Revilla New Ferry Berth, and the 

Gravina Island Shuttle Ferry Berth 

Facility in Tongass Narrows, Alaska 

beginning in March 2022, provided the 

previously mentioned mitigation, 

monitoring, and reporting requirements 

are incorporated. A draft of the 

proposed IHA can be found at https:// 

www.fisheries.noaa.gov/permit/ 

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

Request for Public Comments 

We request comment on our analyses, 

the proposed authorization, and any 

other aspect of this notice of proposed 

IHA for the proposed construction 

activities. We also request at this time 

comment on the potential Renewal of 

this proposed IHA as described in the 

paragraph below. Please include with 

your comments any supporting data or 

literature citations to help inform 

decisions on the request for this IHA or 

a subsequent Renewal IHA. 

On a case-by-case basis, NMFS may 

issue a one-time, one-year Renewal IHA 

following notice to the public providing 

an additional 15 days for public 

comments when (1) up to another year 

of identical or nearly identical activities 

as described in the Description of 

Proposed Activities section of this 

notice is planned or (2) the activities as 

described in the Description of 

Proposed Activities section of this 

notice would not be completed by the 

time the IHA expires and a Renewal 

would allow for completion of the 

activities beyond that described in the 

Dates and Duration section of this 

notice, provided all of the following 

conditions are met: 

• A request for renewal is received no 

later than 60 days prior to the needed 

Renewal IHA effective date (recognizing 

that the Renewal IHA expiration date 

cannot extend beyond one year from 

expiration of the initial IHA). 

• The request for renewal must 

include the following: 

(1) An explanation that the activities 

to be conducted under the requested 

Renewal IHA are identical to the 

activities analyzed under the initial 

IHA, are a subset of the activities, or 

include changes so minor (e.g., 

reduction in pile size) that the changes 

do not affect the previous analyses, 

mitigation and monitoring 

requirements, or take estimates (with 

the exception of reducing the type or 

amount of take). 

(2) A preliminary monitoring report 

showing the results of the required 

monitoring to date and an explanation 

showing that the monitoring results do 

not indicate impacts of a scale or nature 

not previously analyzed or authorized. 

Upon review of the request for 

Renewal, the status of the affected 

species or stocks, and any other 

pertinent information, NMFS 

determines that there are no more than 

minor changes in the activities, the 

mitigation and monitoring measures 

will remain the same and appropriate, 

and the findings in the initial IHA 

remain valid. 

Dated: January 27, 2022. 

Kimberly Damon-Randall, 

Director, Office of Protected Resources, 

National Marine Fisheries Service. 

[FR Doc. 2022–02035 Filed 2–1–22; 8:45 am] 

BILLING CODE 3510–22–P 


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