# Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Relocation of National Oceanic and Atmospheric Administration Research Vessels at Naval Station Newport, Rhode Island

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2022-23775

## Record

- **Collection:** Federal Register
- **Document type:** Notice
- **Published:** November 2, 2022
- **Citation:** 87 FR 66133

## Text

DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
[RTID 0648-XC247]
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Relocation of National Oceanic and Atmospheric Administration Research Vessels at Naval Station Newport, Rhode Island

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 U.S. Navy on behalf of NOAA Office of Marine and Aviation Operations (OMAO) for authorization to take marine mammals incidental to construction activities associated with the relocation of NOAA research vessels at Naval Station Newport in Rhode Island. Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting comments on its proposal to issue an incidental harassment authorization (IHA) to incidentally take marine mammals during the specified activities. NMFS is also requesting comments on a possible one-time, 1-year renewal that could be issued under certain circumstances and if all requirements are met, as described in 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 authorization and agency responses will be summarized in the final notice of our decision.

DATES:

Comments and information must be received no later than December 2, 2022.

ADDRESSES:

Comments should be addressed to Jolie Harrison, Chief, Permits and Conservation Division, Office of Protected Resources, National Marine Fisheries Service and should be submitted via email to
ITP.taylor@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 would generally be posted online at
www.fisheries.noaa.gov/permit/incidental-take-authorizations-under-marine-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:

Jessica Taylor, 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/national/marine-mammal-protection/incidental-take-authorizations-construction-activities.
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 proposed or, if the taking is limited to harassment, a notice of a proposed incidental harassment authorization is provided to the public for review.

Authorization for incidental takings shall be granted if NMFS finds that the taking will have a negligible impact on the species or stock(s) and will not have an unmitigable adverse impact on the availability of the species or stock(s) for taking for subsistence uses (where relevant). Further, NMFS must prescribe the permissible methods of taking and other “means of effecting the least practicable adverse impact” on the affected species or stocks and their habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stocks for taking for certain subsistence uses (referred to in shorthand as “mitigation”); and requirements pertaining to the mitigation, monitoring and reporting of the takings are set forth. The definitions of all applicable MMPA statutory terms cited above are included in the relevant sections below.

National Environmental Policy Act

To comply with the National Environmental Policy Act of 1969 (NEPA; 42 U.S.C. 4321
et seq.
) and NOAA Administrative Order (NAO) 216-6A, NMFS must review our proposed action (
i.e.,
the issuance of an IHA) with respect to potential impacts on the human environment.

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 May 6, 2022, NMFS received a request from the U.S. Navy on behalf of OMAO for an IHA to take marine mammals incidental to construction activities associated with the relocation of NOAA research vessels to the Naval Station Newport in Rhode Island. NMFS reviewed the Navy's application and the Navy provided a revised application on July 14, 2022. The application was deemed adequate and complete on October 5, 2022. OMAO's request is for take of 7 species of marine mammals, by Level B harassment and, for a subset of these species, Level A harassment. Neither OMAO nor NMFS expect serious injury or mortality to result from this activity and, therefore, an IHA is appropriate. OMAO plans to commence in-water construction activities on February 1, 2024 yet has requested the IHA in advance due to OMAO's NEPA requirements.

Description of Proposed Activity

Overview

OMAO proposes to establish adequate pier, shore side, and support facilities for four NOAA research vessels in Coddington Cove at Naval Station (NAVSTA) Newport in Newport, Rhode Island. As part of the proposed activity, a new pier, trestle, small boat floating dock, and bulkhead would be constructed in Coddington Cove in order to meet NOAA docking/berthing requirements for these four vessels. These construction activities would involve the use of impact and vibratory pile driving, vibratory pile extraction, rotary drilling, and down-the-hole (DTH) mono-hammer excavation events, which have the potential to take marine mammals, by Level A and Level B harassment. The project would also include shore side administrative, warehouse, and other support facilities.

Currently two of the four Rhode Island NOAA research vessels are located at Pier 2 at NAVSTA Newport; however, Pier 2 does not provide adequate docking and berthing for these vessels to meet NOAA requirements. The two other NOAA Atlantic Fleet vessels are located in New Hampshire, Virginia, South Carolina, or Mississippi. As many of the NOAA research cruises are conducted in the northeast, relocating four vessels to the project area provides logistical advantages and operational efficiencies.

Coddington Cove, which opens to Narragansett Bay, covers an area of approximately 395 acres (1.6 square kilometers) and is located near the southeast corner of NAVSTA Newport. Construction activities would last for approximately 1 year from February 1, 2024 to January 31, 2025 of which in-water work would take place over 343 non-consecutive days.

Dates and Duration

In-water construction activities are estimated to occur over 343 non-consecutive days from February 1, 2024 to January 31, 2025. OMAO anticipates that all work would be limited to daylight hours. Specific construction activities may occur concurrently over a period of approximately 138 days. Table 1 provides a summary of proposed scenarios in which equipment may be used concurrently.

Table 1—Summary of Multiple Equipment Scenarios

Structure
Activity
Equipment and quantity

Bulkhead
Template installation (16-inch steel) and steel pipe pile installation (18-inch)

Vibratory Hammer (2).
Vibratory Hammer (1), Impact Hammer (1).

Vibratory Hammer (2), DTH Mono-hammer (1).

Bulkhead and Trestle
Template extraction from Bulkhead (16-inch steel), Install sheet piles Bulkhead (Z26-700), Install steel pipe piles at Trestle (18-inch)

Vibratory Hammer (3).
Vibratory Hammer (1), Impact Hammer (1), Rotary Drill (1).

Vibratory Hammer (2), Impact Hammer (1), Rotary Drill (1).

Pier
Template Install (16-inch steel) and Install steel pipe piles (30-inch) at Pier

Vibratory Hammer (2).
Vibratory Hammer (1), Impact Hammer (1)

Vibratory Hammer (1), Impact Hammer (1), Rotary Drill (1).

Pier fender piles, gangway, and floating dock
Install pipe piles (16-inch) at Pier and install steel pipe piles at Small Boat Floating Dock (18-Inch)

Vibratory Hammer (2)
Vibratory Hammer (1), Impact Hammer (1).

Template Extraction from Pier (16-inch steel) and install shafts (36-inch) at Small Boat Floating Dock

Vibratory Hammer (2), Impact Hammer (1).
Vibratory Hammer (1), Impact Hammer (1).

Vibratory (2), DTH Mono-hammer (1).

Specific Geographic Region

NAVSTA Newport encompasses 1,399 acres (5.66 (square kilometers) km
2
) extending 6-7 miles (9.7-11.3 kilometers (km)) along the western shore of Aquidneck Island in the towns of Portsmouth and Middletown, Rhode Island and the city of Newport, Rhode Island. The base footprint also includes the northern third of Gould Island in the town of Jamestown, Rhode Island. The base is located in the southern part of the state where Narragansett Bay adjoins the Atlantic Ocean. Figure 1 shows the site of where the proposed action would occur in Coddington Cove.

Coddington Cove covers an area of approximately 395 acres (1.6 km
2
) and is partially protected by Coddington Point to the south and a breakwater to the north. The northwest section of the cove opens to Narragansett Bay. Water depths in the proposed project area of Coddington Cove are less than 34 ft (10.4 m) mean lower low water. The proposed project area experiences semi-diurnal tides, an average water temperature of 36-68 °F (2.2-20 °C), and salinity of 31 parts per thousand. Narragansett Bay is approximately 22 nautical miles (nm) (40 km) long and 7 nm (16 km) wide. Narragansett Bay's most prominent bathymetric feature is a submarine valley that runs between Conanicut and Aquidneck Islands to Rhode Island Sound, and defines the East Passage of Narragansett Bay. The shipping channel in the East Passage serves as the primary shipping channel for the rest of Narragansett Bay and is generally 100 ft (30.5 m) deep. The shipping channel from the lower East Passage splits just south of Gould Island with the western shipping channel heading to Quonset Point and the eastern shipping channel heading to Providence and Fall River (Navy, 2008). Vessel noise from commercial shipping and recreational activities contribute to the ambient underwater soundscape in the proposed project area. Based upon underwater noise data collected at the Naval Undersea Warfare Center (NUWC) and the shallow depth of nearshore water, the ambient underwater noise in the proposed project area is expected to be approximately 120 dB RMS.

BILLING CODE 3510-22-P

EN02NO22.000

BILLING CODE 3510-22-C
Figure 1. Proposed NAVSTA Project Area

Detailed Description of the Specified Activity

The proposed activity would establish adequate pier, shore side, and support facilities to support the relocation of four NOAA Atlantic Fleet research vessels at NAVSTA Newport, RI. This includes the construction of a new pier, trestle, small boat floating dock, bulkhead, and shore side facilities in Coddington Cove for which the in-water schedule is shown in Table 2. Upland construction at the Pier landing and parking facilities near Building 11 (Figure 1) would not involve any in-water work and is not expected to result in any takes of marine mammals; these activities are therefore not further discussed.

Table 2—Proposed In-Water Work Schedule

Facility

Construction
period

Pile type and
diameter
(in)

Number
of piles

Method of
pile
driving/extraction

Daily
production
rate

Minutes to
drive/
extract/
drill a
single pile

Number of
impact
strikes/pile

Total
production

days
1

Abandoned guide piles along bulkhead
February 2024
12″ steel
3
Vibratory extraction
3 piles/day
30
N/A
1

Floating dock demolition
February 2024
12″ timber
4
Vibratory extraction
4 piles/day
30
N/A
1

Bulkhead Construction
February-April 2024
18″ steel
115
Vibratory/impact
8 piles/day
30
1,000
15

12

DTH Mono-hammer
2

3

1 hole/day
300
13
12

Steel sheet pile Z26-700, 18″ deep
230 (115 pairs)
Vibratory
8 pairs/day
30
N/A
15

16 template steel pile
60 (4x 15 moves)
Vibratory installation/extraction
4 piles/day
30
N/A
30

Trestle
April-June 2024 *
18″ steel pipe pile
36
Vibratory/impact
2 piles/day
30
1,500
18

bents 1-18

4

Rotary drilling
4

1 hole/day
300
N/A
4

16″ template steel pipe pile
72 (4x 18 moves)
Vibratory installation/extraction
4 piles/day
30
N/A
36

Trestle
June 2024
30″ steel pipe pile
2
Vibratory/impact
2 piles/day
45
2,000
1

bent 19

16″ template steel pipe pile
4 (4x 1 moves)
Vibratory installation/extraction
4 piles/day
30
N/A
2

Pier
June-December 2024 **
30″ steel pipe pile
120
Vibratory/impact
4 piles/day
45
2,000
30

12

Rotary drilling
4

1 hole/day
300
N/A
12

16″ template steel pipe pile
120 (4x 30 moves)
Vibratory installation/extraction
4 piles/day
30
N/A
60

Fender Piles
September 2024-January 2025 **
16″ steel pipe pile
201
Vibratory
4 piles/day
20
N/A
50

16″ template steel pipe pile
96 (4x 24 moves)
Vibratory installation/extraction
4 piles/day
30
N/A
48

Gangway support piles for small boat floating dock
January 2025 **
18″ steel pipe piles
4
Vibratory/impact
2 piles/day
30
1,000
2

Small floating dock
January 2025 **
36″ steel casing shaft with rock socket (guide pile)
2
Vibratory/impact
1 pile/day
60
1,000
2

2

DTH Mono-hammer
2

3

5

1 hole/day
300
13 strikes/second
2

16″ template steel pipe pile
4 (4x 1 moves)
Vibratory installation/extraction
4 piles/day
30
N/A
2

* Pile installation at Bulkhead and Trestle may be concurrent.
** Pile installation of Fender piles, Gangway, and Floating Dock may be concurrent.

1
Total production days for template piles includes the time to install and the time to extract the piles.

2
“Down-the-hole” (DTH) mono-hammer excavation may be used to clear boulders and other hard driving conditions for pipe piling at the bulkhead. DTH mono-hammer would only be used when obstructions or refusal (hard driving) occurs that prevents the pile from being advanced to the required tip elevation using vibratory/impact driving. The DTH mono-hammer is placed inside of the steel pipe pile and operates at the bottom of the hole to clear through rock obstructions, hammer does not “drive” the pile but rather cleans the pile and removes obstructions such that the piles may be installed to “minimum” tip elevation.

3
DTH mono-hammer uses both impulsive (strikes/second) and continuous methods (minutes).

4
Rotary drilling may be used to clear boulders/obstructions for trestle and pier. Core barrel would be lowered through the pile and advanced using rotary methods to clear the obstruction. After the obstruction is cleared, the piling would be advanced to the required tip elevation using impact driving methods.

5
DTH mono-hammer would be used to create a rock socket at each of the 36-inch shafts for the floating dock.

Pier and Trestle:
A new pile supported concrete pier would be constructed approximately 450 ft (137.1 m) north of the existing T-pier in Coddington Cover (Figure 1). The new pier would be approximately 62 ft (18.9 m) wide and and 587 ft (178.9 m) long, encompassing an area of 36,400 square ft (ft
2
, 3,381.6 m
2
). Structural support piles for the new pier would consist of 120 30″ steel pipe piles. These piles would be driven by vibratory and impact hammers to a depth required to achieve bearing capacity. A rotary drill may be used to clear any obstructions, such as glacial boulders. Fender piles would be installed and consist of 201 16″ diameter steel pipe piles.

In order to access the pier, a 28 ft (8.5 m) wide by 525 ft (160 m) long pile-supported trestle would be constructed. The trestle would cover an area of approximately 14,200 ft
2
(1,319.2 m
2
) over the water. The entrance to the trestle would be located upland and span over two existing bulkheads, a sheet pile bulkhead, and a new bulkhead connected to the pier. Structural support piles for the trestle concrete deck would include 36 18″ steel pipe piles and 2 30″ steel pipe piles. The piles would be driven by impact and vibratory hammers to depths required to achieve bearing capacity. If construction crews encounter obstructions, such as glacial boulders, a rotary drill may be used.

Trestle and pier piles would be installed using a template that would be secured by 4 16″ steel pipe piles. Once the pier or trestle piles are installed in the template, the template would be removed and relocated to the next section of the pier/trestle construction. The template piles would be installed and removed by vibratory installation and extraction. Use of the template would require the driving and removal of the template piles approximately 19 times for the trestle and 30 times for the pier, for a total of 196 installation/extraction moves of the pipe piles.

Small Boat Floating Dock:
A small boat floating dock would be constructed northwest of the pier and trestle structure. The dock would be approximately 20 ft (6.1 m) wide by 66 ft (20.1 m) long, and provide berthing on two sides. The floating system would consist of a single heavy duty 20 ft (6.1 m) by 66 ft (20.1 m) concrete float of approximately 1,300 ft
2
(120.8 m
2
) and two 5.5 ft (1.7 m) wide by 80 ft (24.3 m) long gangway segments of approximately 440 ft
2
(40.9 m
2
) each. The gangway would be supported by 4 18″ steel pipe piles. These piles would be driven by vibratory installation followed by impact installation to achieve bearing capacity. Two 36″ steel pipe guide piles would provide lateral support to the floating dock. The guide piles would be rock socketed into the bedrock. Shafts would be installed using vibratory and impact driving methods, then set into rock socket anchors and filled with concrete. DTH excavation using a mono-hammer would be used to

create the rock sockets. Additionally, an abandoned dock currently exists at the proposed site of the floating dock. Demolition of the abandoned dock involving the vibratory extraction of 3 12″ steel pipe piles and 4 12″ timber piles would take place before the small boat floating dock would be installed.

Bulkhead:
In order to reinforce and stabilize an existing deteriorating bulkhead, a new bulkhead of approximately 728 ft (221.9 m) in length would be constructed near the proposed new pier location. A combination of approximately 115 18″ steel pipe piles and 230 steel Z-shaped sheet piles (55″ long and 8″ deep) would be installed along the face of the existing bulkhead using vibratory and impact driving. If obstructions, such as solid bedrock, boulders, or debris are encountered, pile installation may require the use of DTH mono-hammer excavation to break up rock or moving the obstruction aside using mechanical means. Piles would be installed using a template that would be secured by 4 16″ steel pipe piles. The use of the template would require the vibratory driving and extraction of the 4 template piles approximately 15 times for a total of 60 installation/extraction moves of the pipe template piles.

Pile installation and removal would occur using barge-mounted cranes and land-based cranes equipped with vibratory and impact hammers. Piles would initially be installed using vibratory methods, then finished with impact hammers as necessary. Impact hammers would also be used where obstructions or sediment conditions do not permit the efficient use of vibratory hammers. Rotary drilling may be used to clear obstructions during pile driving. DTH mono-hammer excavation combines the use of rotary drilling and percussive hammering to fracture rock. This method may also be used to clear obstructions in addition to set piles in rock sockets. Piles would be driven using a vibratory pile driver whenever possible in order to reduce impacts.

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. NMFS fully considered all of this information, and we refer the reader to these descriptions, incorporated here by reference, instead of reprinting the information. Additional information regarding population trends and threats may be found in NMFS' Stock Assessment Reports (SARs;
www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments
) and more general information about these species (
e.g.,
physical and behavioral descriptions) may be found on NMFS' website (
https://www.fisheries.noaa.gov/find-species
).

Table 3 lists all species or stocks for which take is expected and proposed to be authorized for these activities, and summarizes information related to the population or stock, including regulatory status under the MMPA and Endangered Species Act (ESA) and potential biological removal (PBR), where known. PBR is defined by the MMPA as the maximum number of animals, not including natural mortalities, that may be removed from a marine mammal stock while allowing that stock to reach or maintain its optimum sustainable population (as described in NMFS' SARs). While no serious injury or mortality is anticipated or authorized here, PBR and annual serious injury and mortality from anthropogenic sources are included here as gross indicators of the status of the species and other threats.

Marine mammal abundance estimates presented in this document represent the total number of individuals that make up a given stock or the total number estimated within a particular study or survey area. NMFS' stock abundance estimates represent the total estimate of individuals within the geographic area, if known, that comprises that stock. For some species, this geographic area may extend beyond U.S. waters. All managed stocks in this region are assessed in NMFS' U.S. Atlantic and Gulf of Mexico SARs (
e.g.,
Hayes
et al.,
2022). All values presented in Table 3 are the most recent available at the time of publication (available online at:
https://www.fisheries.noaa.gov/national/marine-mammal-protection/draft-marine-mammal-stock-assessment-reports
).

Table 3—Marine Mammal Species

4

Likely Impacted by the Specified Activities

Common name
Scientific name
Stock

ESA/
MMPA
status;
strategic

(Y/N)
1

Stock abundance
(CV, Nmin, most recent

abundance survey)
2

PBR

Annual M/SI
3

Order Artiodactyla—Infraorder Cetacea—Odontoceti (toothed whales, dolphins, and porpoises)

Family Delphinidae:

Atlantic white-sided dolphins

Lagenorhynchus acutus

Western North Atlantic
-, -, N
93,233 (0.71, 54,443, 2016)
544
27

Common dolphins

Delphinus delphis

Western North Atlantic
-, -, N
172,974 (0.21, 145,216, 2016)
1,452
390

Family Phocoenidae (porpoises):

Harbor Porpoise

Phocoena phocoena

Gulf of Maine/Bay of Fundy
-, -, N
95,543 (0.31, 74,034, 2016)
851
164

Order Carnivora—Pinnipedia

Family Phocidae (earless seals):

Harbor Seal

Phoca vitulina

Western North Atlantic
-, -, N
61,336 (0.08, 57,637, 2018)
1,729
339

Gray Seal

Halichoerus grypus

Western North Atlantic
-, -, N
27,300 (0.22, 22,785, 2016)
1,389
4,453

Harp Seal

Pagophilus groenlandicus

Western North Atlantic
-, -, N
7.6 M (UNK, 7.1, 2019)
426,000
178,573

Hooded Seal

Cystophora cristata

Western North Atlantic
-, -, N
593,500 (UNK, UNK, 2005)
UNK
1,680

1
Endangered 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.

3
These values, found in NMFS's SARs, represent annual levels of human-caused mortality plus serious injury from all sources combined (
e.g.,
commercial fisheries, ship strike). Annual M/SI often cannot be determined precisely and is in some cases presented as a minimum value or range. A CV associated with estimated mortality due to commercial fisheries is presented in some cases.

4
Information on the classification of marine mammal species can be found on the web page for The Society for Marine Mammalogy's Committee on Taxonomy (
https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/;
Committee on Taxonomy (2022)).

As indicated above, all seven species (with seven managed stocks) in Table 3 temporally and spatially co-occur with the activity to the degree that take is reasonably likely to occur. While several species of whales have been documented seasonally in New England waters, the spatial occurrence of these species is such that take is not expected to occur, and they are not discussed further beyond the explanation provided here. The humpback (
Megaptera novaeangliae
), fin (
Balaenoptera physalus
), sei (
Balaenoptera borealis
), sperm (
Physeter macrocephalus
) and North Atlantic right whales (
Eubaleana glacialis
) occur seasonally in the Atlantic Ocean, offshore of Rhode Island. However, due to the depths of Narragansett Bay and near shore location of the project area, these marine mammals are unlikely to occur in the project area. Therefore, OMAO did not request, and NMFS is not proposing to authorize takes of these species.

Atlantic White-Sided Dolphin

Atlantic white-sided dolphins occur in the temperate waters of the North Atlantic and specifically off the coast of North Carolina to Maine in U.S. waters (Hayes
et al.,
2022). The Gulf of Maine population of white-sided dolphin primarily occurs in continental shelf waters from Hudson Canyon to Georges Bank, and in the Gulf of Maine and lower Bay of Fundy. From January to May, this population occurs in low numbers from Georges Bank to Jeffreys Ledge (off New Hampshire) with even lower numbers south of Georges Bank. They are most common from June through September from Georges Bank to lower Bay of Fundy, with densities declining from October through December (Payne and Heinemann, 1990; Hayes
et al.,
2022).

Since stranding recordings for the Atlantic white-sided dolphin began in Rhode Island in the late 1960s, this species has become the third most frequently recorded small cetacean. There are occasional unconfirmed opportunistic reports of white-sided dolphins in Narragansett Bay, typically in fall and winter. Atlantic white-sided dolphins in Rhode Island inhabit the continental shelf, with a slight tendency to occur in shallower water in the spring when they are most common (approximately 64 percent of records). Seasonal occurrence of Atlantic white-sided dolphins decreases significantly following spring with 21 percent of records in summer, 10 percent in winter, and 7.6 percent in fall (Kenny and Vigness-Raposa, 2010).

Mass strandings of up to 100 animals or more is common for this species. In an analysis of stranded marine mammals in Cape Cod and southeastern Massachusetts, Bogomolni
et al.
(2010) found that 69 percent of stranded white-sided dolphins were involved in mass stranding events with no significant cause determined, and 21 percent were classified as disease-related. Impacts from contaminants and pesticides, as well as climate-related changes, pose the greatest threats for Atlantic white-sided dolphins.

Common Dolphin

The common dolphin is one of the most widely distributed species of cetaceans, found world-wide in temperate and subtropical seas. In the North Atlantic, they are common along the shoreline of Massachusetts and at sea sightings have been concentrated over the continental shelf between the 100-meter (m) and 2000-m isobaths over prominent underwater topography and east to the mid-Atlantic Ridge. The common dolphin occurs from Cape Hatteras northeast to Georges Bank from mid-January to May and in the Gulf of Maine from mid-summer to autumn (Hayes
et al.,
2022).

Strandings occur year-round. In the stranding record for Rhode Island, common dolphins are the second most frequently stranded cetacean (exceeded only by harbor porpoises) and the most common delphinid. There were 23 strandings in Rhode Island between 1972 and 2005 (Kenny and Vigness-Raposa, 2010). A short-beaked common dolphin was most recently recorded in Narragansett Bay in October of 2016 (Hayes
et al.,
2022). There are no recent records of common dolphins far up rivers, however such occurrences would only show up in the stranding database if the stranding network responded, and there is no centralized clearinghouse for opportunistic sightings of that type. In Rhode Island, there are occasional opportunistic reports of common dolphins in Narragansett Bay up as far as the Providence River, usually in winter. The greatest threats for common dolphins include impacts from contaminants, anthropogenic sound, and climate change (Hayes
et al.,
2022).

Harbor Porpoise

Harbor porpoises occur in northern temperate and subarctic coastal and offshore waters in both the Atlantic and Pacific Oceans. In the western North Atlantic, harbor porpoises occur in the northern Gulf of Maine and southern Bay of Fundy region in waters generally less than 150 m deep, primarily during the summer (July to September). During fall (October to December) and spring (April to June), harbor porpoises are widely dispersed between New Jersey and Maine. Lower densities of harbor porpoise occur during the winter (January to March) in waters off New York to New Brunswick, Canada (Hayes
et al.,
2022).

Harbor porpoises are the most stranded cetacean in Rhode Island. Their occurrence is strongly seasonal and the highest occurrence is in spring at approximately 70 percent of all

records. Harbor porpoises may occur in Narragansett Bay during the winter, but reports are second- and third-hand anecdotal reports (Kenny, 2013). As harbor porpoises spend a significant amount of time in nearshore areas, harbor porpoises are vulnerable to contaminants, ship traffic, and physical habitat modifications in addition to fishery bycatch and sources of anthropogenic underwater noise (Hall
et al.,
2006; Todd
et al.,
2015; Oakley
et al.,
2017; Hayes
et al.,
2022).

Harbor Seal

Harbor seals occur in all nearshore waters of the North Atlantic and North Pacific Oceans and adjoining seas above approximately 30°N (Burns, 2009). They are year-round residents in the coastal waters of eastern Canada and Maine (Katona
et al.,
1993), occurring seasonally from southern New England to New Jersey from September through late May (Schneider and Payne, 1983; Schroeder, 2000; Rees
et al.,
2016, Toth
et al.,
2018). Harbor seals' northern movement occurs prior to pupping season that takes place from May through June along the Maine coast. In autumn to early winter, harbor seals move southward from the Bay of Fundy to southern New England and mid-Atlantic waters (Rosenfeld
et al.,
1988; Whitman and Payne, 1990; Jacobs and Terhune, 2000; Hayes
et al.,
2022). Overall, there are five recognized subspecies of harbor seal, two of which occur in the Atlantic Ocean. The western Atlantic harbor seal is the subspecies likely to occur in the proposed project area. There is some uncertainly about the overall population stock structure of harbor seals in the western North Atlantic Ocean. However, it is theorized that harbor seals along the eastern U.S. and Canada are all from a single population (Temte
et al.,
1991; Anderson and Olsen, 2010).

Harbor seals are regularly observed around all coastal areas throughout Rhode Island, and occasionally well inland up bays, rivers, and streams. In general, rough estimates indicate that approximately 100,000 harbor seals occur in New England waters (DeAngelis, 2020). Seals are very difficult to detect during surveys, since they tend to be solitary and the usual sighting cue is only the seal's head above the surface. Available data on harbor seals in New England are strongly dominated by stranding records, which comprise 446 of 507 total records for harbor seals (88 percent) (Kenny and Vigness-Raposa, 2010). Of the available records, 52.5 percent are in spring, 31.2 percent in winter, 9.5 percent in summer, and 6.9 percent in fall. In Rhode Island, there are no records offshore of the 90-meter isobath. Based upon seasonal monitoring in Rhode Island, seals begin to arrive in Narragansett Bay in September, with numbers slowly increasing in March before dropping off sharply in April. By May, seals have left the Bay (DeAngelis, 2020).

Seasonal nearshore marine mammal surveys were conducted at NAVSTA Newport between May 2016 and February 2017. The surveys were conducted along the western shoreline of Coasters Harbor Island northward to Coggeshall Point and eastward to include Gould Island. The only species that was sighted during the survey was harbor seal. During the spring survey of 2016, one live harbor seal was sighted on May 12 and one harbor seal carcass was observed and reported to the Mystic Aquarium Stranding Network (Moll,
et al.,
2016, 2017; Navy, 2017b). A group of three harbor seals was sighted on February 1 2017, during the winter survey.

In Rhode Island waters, harbor seals prefer to haul out on isolated intertidal rock ledges and outcrops. Numerous Naval Station employees have reported seals hauled out on an intertidal rock ledge named “The Sisters,” which is north-northwest of Coddington Point and approximately 3,500 ft (1,066.8 m) from the proposed project area (see Figure 4-1 of the application) (NUWC Division, 2011). This haulout site has been studied by the NUWC Division Newport since 2011 and has demonstrated a steady increase in use during winter months when harbor seals are present in the Bay. Harbor seals are rarely observed at “The Sisters” haulout in the early fall (September-October) but sighted in consistent numbers in mid-November (0-10 animals), and are regularly observed with a gradual increase of more than 20 animals until numbers peak in the upper 40s during March, typically at low tide. The number of harbor seals begin to drop off in April and by mid-May, they are not observed hauled out at all (DeAngelis, 2020). Haulout spaces at “The Sisters” haulout site is primarily influenced by tide level, swell, and wind direction (Moll
et al.,
2017; DeAngelis, 2020).

In addition to “The Sisters” haul out, there are 22 haulout sites in Narragansett Bay (see Figure 4-1 in the application). During a 1 day Narragansett Bay-wide count in 2018, there were at least 423 seals observed and all 22 haulout sites were represented. Preliminary results from the Bay-wide count for 2019 recorded 572 harbor seals, which also included counts from Block Island (DeAngelis, 2020).

Gray Seal

Gray seals within U.S. waters are from the western North Atlantic stock and are expected to be part of the eastern Canadian population. The western North Atlantic stock is centered in Canadian waters, including the Gulf of St. Lawrence and the Atlantic coasts of Nova Scotia, Newfoundland, and Labrador, Canada, and the northeast U.S. continental shelf (Hayes
et al.,
2022). In U.S. waters, year-round breeding of approximately 400 animals has been documented on areas of outer Cape Cod and Muskeget Island in Massachusetts.

Gray seal occurrences in Rhode Island are mostly represented by stranding records—155 of 193 total records (80 percent). Gray seal records in the region are primarily from the spring (approximately 87 percent), with much smaller numbers in all other seasons. Kenney and Vigness-Raposa (2010) found strandings to be broadly distributed along ocean-facing beaches in Long Island and Rhode Island, with a few spring records in Connecticut. Habitat use by gray seals in Rhode Island is poorly understood. They are seen mainly when stranded or hauled out, and are infrequently observed at sea. There are very few observations of gray seals in Rhode Island other than strandings. The annual numbers of gray seal strandings in the Rhode Island study area since 1993 have fluctuated markedly, from a low of 1 in 1999 to a high of 24 in 2011 (Kenney, 2020). The very strong seasonality of gray seal occurrence in Rhode Island between March and June is linked to the timing of pupping in January and February. Most stranded individuals encountered in Rhode Island area appear to be post-weaning juveniles and starved or starving juveniles (Nawojchik, 2002; Kenney, 2005). Annual informal surveys conducted since 1994 observed a small number of gray seals in Narragansett Bay in 2016, although the majority of seals observed were harbor seals (ecoRI News, 2016).

Harp Seal

The harp seal is a highly migratory species, and its range can extend from the Canadian Arctic to New Jersey (Sergeant, 1965; Stenson and Sjare, 1997; Hayes
et al.,
2021). Harp seals are classified into three stocks, which coincide with specific pupping sites on pack ice. These pupping sites are as follows: (1) Eastern Canada, including the areas off the coast of Newfoundland and Labrador and the area near the

Magdalen Islands in the Gulf of St. Lawrence; (2) the West Ice off eastern Greenland, and (3) the ice in the White Sea off the coast of Russia ((Lavigne and Kovacs, 1988; Bonner, 1990; Hayes
et al.,
2021). In U.S. waters, the species has an increasing presence in the coastal waters between Maine and New Jersey with a general presence from January through May (Hayes
et al.,
2021).

Harp seals in Rhode Island are known almost exclusively from strandings (approximately 98 percent). Strandings are widespread on ocean-facing beaches throughout Long Island and Rhode Island and the records occur almost entirely during spring (approximately 68 percent) and winter (approximately 30 percent). Harp seals are nearly absent in summer and fall. Harp seals also make occasional appearances well inland up rivers (Kenny and Vigness-Raposa, 2010). During late winter of 2020, a healthy harp seal was observed hauled out and resting near “The Sisters” haulout site (DeAngelis, 2020).

Hooded Seal

The hooded seal is a highly migratory species, and its range can extend from the Canadian Arctic to as far south as Puerto Rico (Mignucci-Giannoni and Odell, 2001; Hayes
et al.,
2019). In U.S. waters, the species has an increasing presence in the coastal waters between Maine and Florida. Hooded seals in the U.S. are considered members of the western North Atlantic stock and generally occur in New England waters from January through May and further south off the southeast U.S. coast and in the Caribbean in the summer and fall seasons (McAlpine
et al.,
1999; Harris
et al.,
2001; and Mignucci-Giannoni and Odell, 2001; Hayes
et al.,
2019).

Hooded seal occurrences in Rhode Island are predominately from stranding records (approximately 99 percent). They are rare in summer and fall but most common in the area during spring and winter (45 percent and 36 percent of all records, respectively) (Kenney, 2005; Kenny and Vigness-Raposa, 2010). Hooded seal strandings are broadly distributed across ocean-facing beaches in Rhode Island and they occasionally occur well up rivers, but less often than harp seals. Hooded seals have been recorded in Narragansett Bay but are considered occasional visitors and are expected to be the least encountered seal species in the Bay (RICRMC, 2010).

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. Not all marine mammal species have equal hearing capabilities (
e.g.,
Richardson
et al.,
1995; Wartzok and Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall
et al.
(2007, 2019) recommended that marine mammals be divided into hearing groups based on directly measured (behavioral or auditory evoked potential techniques) or estimated hearing ranges (behavioral response data, anatomical modeling,
etc.
). Note that no direct measurements of hearing ability have been successfully completed for mysticetes (
i.e.,
low-frequency cetaceans). Subsequently, NMFS (2018) described generalized hearing ranges for these marine mammal hearing groups. Generalized hearing ranges were chosen based on the approximately 65 decibel (dB) threshold from the normalized composite audiograms, with the exception for lower limits for low-frequency 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 4.

Table 4—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 (Hemilä
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.

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

This section provides a 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 whether those impacts are reasonably expected to, or reasonably likely to, adversely affect the species or stock through effect on annual rates of recruitment or survival.

Acoustic effects on marine mammals during the specified activities can occur from vibratory and impact pile driving as well as rotary drilling and DTH mono-hammer events. The effects of underwater noise from OMAO's proposed activities have the potential to result in Level A and Level B harassment of marine mammals in the proposed 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 decibels (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 activities 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 and vibratory pile driving, vibratory removal, and rotary drilling and DTH mono-hammer excavation events. The sounds produced by these activities fall into one of two general sound types: impulsive and non-impulsive. Impulsive sounds (
e.g.,
explosions, 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.,
machinery operations such as drilling or dredging, vibratory pile driving, underwater chainsaws, 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 raid rise/decay time that impulsive sounds do (ANSI 1995; NIOSH 1998; NMFS 2018). DTH mono-hammer excavation includes the use of rotary drilling (non-impulsive sound source) and percussive hammering (impulsive sound source). The distinction between impulsive and non-impulsive sound sources 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 mono-hammer. 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 considered impulsive. Vibratory hammers install piles by vibrating them and allowing the weight of the hammer to push them into the sediment. Vibratory hammers produce non-impulsive, continuous sounds. Vibratory hammering generally produces sounds pressure levels (SPLs) 10 to 20 dB lower than impact pile driving of the same-sized pile (Oestman
et al.,
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).

DTH systems, involving both mono-hammers and cluster-hammers, and rotary drills will also be used during the proposed construction. In rotary drilling, the drill bit rotates on the rock while the drill rig applies pressure. The bit rotates and grinds continuously to fracture the rock and create a hole. Rotary drilling is considered an intermittent, non-impulsive noise source. 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). Rock socketing involves using DTH equipment to create a hole in the bedrock inside which the pile is placed to give it lateral and longitudinal strength. The sounds produced by the DTH methods 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 OMAO's proposed activities on marine mammals could be generated from both non-acoustic and acoustic stressors. Potential non-acoustic stressors include the physical presence of the equipment, vessels, and personnel; however, we expect that any animals that approach the project site(s) close enough to be harassed due to the presence of equipment or personnel would be within the Level A or Level B harassment zones from pile driving/removal and would already be subject to harassment from the in-water activities. Therefore, any impacts to marine mammals are expected to primarily be acoustic in nature. Acoustic stressors include heavy equipment operation during pile installation and removal (
i.e.,
impact and vibratory pile driving and removal, rotary drilling, and DTH mono-hammer excavation).

Acoustic Impacts

The introduction of anthropogenic noise into the aquatic environment from pile driving and removal equipment is the primary means by which marine mammals may be harassed from OMAO's specified activities. 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). Generally, exposure to pile driving and removal and other construction noise has the potential to result in auditory threshold shifts and behavioral reactions (
e.g.,
avoidance, temporary cessation of foraging and vocalizing, changes in dive behavior). Exposure to anthropogenic noise can also lead to non-observable physiological responses such as an increase in stress hormones. Additional noise in a marine mammal's habitat can mask acoustic cues used by marine mammals to carry out daily functions such as communication and predator and prey detection. The effects of pile driving and demolition noise on marine mammals are dependent on several factors, including, but not limited to, sound type (
e.g.,
impulsive vs. non-impulsive), the species, age and sex class (
e.g.,
adult male vs. mother 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.,
2003; 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; Henderson
et al.,
2008). PTS levels for marine mammals are estimates, because there are limited empirical data measuring PTS in marine mammals (
e.g.,
Kastak
et al.,
2008), 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)
—TTS is 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-to-session variation in a subject's normal hearing ability (Schlundt
et al.,
2000; Finneran
et al.,
2000, 2002). As described in Finneran (2016), marine mammal studies have shown the amount of TTS increases with cumulative sound exposure level (SEL
cum
) in an accelerating fashion: At low exposures with lower SEL
cum,
the amount of TTS is typically small and the growth curves have shallow slopes. At exposures with higher SEL
cum
, the growth curves become steeper and approach linear relationships with the noise SEL.

Depending on the degree (elevation of threshold in dB), duration (
i.e.,
recovery time), and frequency range of TTS, and the context in which it is experienced, TTS can have effects on marine mammals ranging from discountable to serious (similar to those discussed in
Auditory Masking,
below). For example, a marine mammal may be able to readily compensate for a brief, relatively small amount of TTS in a non-critical frequency range that takes place during a time when the animal is traveling through the open ocean, where ambient noise is lower and there are not as many competing sounds present. Alternatively, a larger amount and longer duration of TTS sustained during time when communication is critical for successful mother/calf interactions could have more serious impacts. We note that reduced hearing sensitivity as a simple function of aging has been observed in marine mammals, as well as humans and other taxa (Southall
et al.,
2007), so we can infer that strategies exist for coping with this condition to some degree, though likely not without cost.

Many studies have examined noise-induced hearing loss in marine mammals (see Finneran (2015) and Southall
et al.
(2019) for summaries). For cetaceans, published data on the onset of TTS are limited to the captive bottlenose dolphin (
Tursiops truncatus
), beluga whale (
Delphinapterus leucas
), harbor porpoise, and Yangtze finless porpoise (
Neophocoena asiaeorientalis
), and for pinnipeds in water, measurements of TTS are limited to harbor seals, elephant seals (
Mirounga angustirostris
), and California sea lions (
Zalophus californianus
). These studies examine hearing thresholds measured in marine mammals before and after exposure to intense sounds. The difference between the pre-exposure and post-exposure thresholds can be used to determine the amount of threshold shift at various post-exposure times. The amount and onset of TTS depends on the exposure frequency. Sounds at low frequencies, well below the region of best sensitivity, are less hazardous than those at higher frequencies, near the region of best sensitivity (Finneran and Schlundt, 2013). At low frequencies, onset-TTS exposure levels are higher compared to those in the region of best sensitivity (
i.e.,
a low frequency noise would need to be louder to cause TTS onset when TTS exposure level is higher), as shown for harbor porpoises and harbor seals (Kastelein
et al.,
2019a, 2019b, 2020a, 2020b). In addition, TTS can accumulate across multiple exposures, but the resulting TTS will be less than the TTS from a single, continuous exposure with the same SEL (Finneran
et al.,
2010; Kastelein
et al.,
2014; Kastelein
et al.,
2015a; Mooney
et al.,
2009). This means that TTS predictions based on the total, cumulative SEL will overestimate the amount of TTS from intermittent exposures such as sonars and impulsive sources. Nachtigall
et al.
(2018) and Finneran (2018) describe the measurements of hearing sensitivity of multiple odontocete species (bottlenose dolphin, harbor porpoise, beluga, and false killer whale (
Pseudorca crassidens
)) when a relatively loud sound was preceded by a warning sound. These captive animals were shown to reduce hearing sensitivity when warned of an impending intense sound. Based on these experimental observations of captive animals, the authors suggest that wild animals may dampen their hearing during prolonged exposures or if conditioned to anticipate intense sounds. Another study showed that echolocating animals (including odontocetes) might have anatomical specializations that might allow for conditioned hearing reduction and filtering of low-frequency ambient noise, including increased stiffness and control of middle ear structures and placement of inner ear structures (Ketten
et al.,
2021). Data available on noise-induced hearing loss for mysticetes are currently lacking (NMFS, 2018).

Activities for this project include impact and vibratory pile driving, vibratory pile removal, rotary drilling, and DTH mono-hammer excavation. There would likely be pauses in activities producing the sound during each day. Given these pauses and the fact that many marine mammals are likely moving through the project areas and not remaining for extended periods of time, the potential for threshold shift declines.

Behavioral harassment
—Exposure to noise from pile driving and removal also has the potential to behaviorally disturb marine mammals. 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; Southall
et al.,
2021). 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).

The following subsections provide examples of behavioral responses that provide an idea of the variability in behavioral responses that would be expected given the differential sensitivities of marine mammal species to sound and the wide range of potential acoustic sources to which a marine mammal may be exposed. Behavioral responses that could occur for a given sound exposure should be determined from the literature that is available for each species, or extrapolated from closely related species when no information exists, along with contextual factors. 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. There are broad categories of potential response, which we describe in greater detail here, that include alteration of dive behavior, alteration of foraging behavior, effects to respiration, interference with or alteration of vocalization, avoidance, and flight.

Pinnipeds may increase their haul out time, possibly to avoid in-water disturbance (Thorson and Reyff, 2006). 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.

Alteration of Dive Behavior
—Changes in dive behavior can vary widely, and may consist of increased or decreased dive times and surface intervals as well as changes in the rates of ascent and descent during a dive (
e.g.,
Frankel and Clark, 2000; Costa
et al.,
2003; Ng and Leung, 2003; Nowacek
et al.,
2004; Goldbogen
et al.,
2013). Seals exposed to non-impulsive sources with a received sound pressure level within the range of calculated exposures (142-193 dB re 1 μPa), have been shown to change their behavior by modifying diving activity and avoidance of the sound source (Götz
et al.,
2010; Kvadsheim
et al.,
2010). Variations in dive behavior may reflect interruptions in biologically significant activities (
e.g.,
foraging) or they may be of little biological significance. The impact of an alteration to dive behavior resulting from an acoustic exposure depends on what the animal is doing at the time of the exposure and the type and magnitude of the response.

Alteration of Feeding Behavior
—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; Melcón
et al.,
2012). In addition, behavioral state of the animal plays a role in the type and severity of a behavioral response, such as disruption to foraging (
e.g.,
Silve
et al.,
2016; Wensveen
et al.,
2017). 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. Goldbogen
et al.
(2013) indicate that disruption of feeding and displacement could impact individual fitness and health. However, for this to be true, we would have to assume that an individual could not compensate for this lost feeding opportunity by either immediately feeding at another location, by feeding shortly after cessation of acoustic exposure, or by feeding at a later time. There is no indication this is the case, particularly since unconsumed prey would likely still be available in the environment in most cases following the cessation of acoustic exposure. Information on or estimates of the energetic requirements of the individuals and the relationship between prey availability, foraging effort and success, and the life history stage of the animal will help better inform a determination of whether foraging disruptions incur fitness consequences.

Respiration
—Respiration naturally varies with different behaviors, and variations in respiration rate as a function of acoustic exposure can be expected to co-occur with other behavioral reactions, such as a flight response or an alteration in diving. However, respiration rates in and of themselves may be representative of annoyance or an acute stress response. Studies with captive harbor porpoises showed increased respiration rates upon introduction of acoustic alarms (Kastelein
et al.,
2001; Kastelein
et al.,
2006a) and emissions for underwater data transmission (Kastelein
et al.,
2005). Various studies also have shown that species and signal characteristics are important factors in whether respiration rates are unaffected or change, again highlighting the importance in understanding species differences in the tolerance of underwater noise when determining the potential for impacts resulting from anthropogenic sound exposure (
e.g.,
Kastelein
et al.,
2005, 2006, 2018; Gailey
et al.,
2007; Isojunno
et al.,
2018).

Vocalization
—Marine mammals vocalize for different purposes and across multiple modes, such as whistling, echolocation click production, calling, and singing. Changes in vocalization behavior in response to anthropogenic noise can occur for any of these modes and may result from a need to compete with an increase in background noise or may reflect increased vigilance or a startle response. For example, in the presence of potentially masking signals, humpback whales and killer whales (
Orcinus orca
) have been observed to increase the length of their songs (Miller
et al.,
2000; Fristrup
et al.,
2003; Foote
et al.,
2004), while right whales have been observed to shift the frequency content of their calls upward while reducing the rate of calling in areas of increased anthropogenic noise (Parks
et al.,
2007; Rolland
et al.,
2012). Killer whales off the northwestern coast of the United States have been observed to increase the duration of primary calls once a threshold in observing vessel density (
e.g.,
whale watching) was reached, which has been suggested as a response to increased masking noise produced by the vessels (Foote
et al.,
2004; NOAA, 2014). In some cases, however, animals may cease or alter sound production in response to underwater sound (
e.g.,
Bowles
et al.,
1994; Castellote
et al.,
2012; Cerchio
et al.,
2014). Studies also demonstrate that even low levels of noise received far from the noise source can induce changes in vocalization and/or

behavioral responses (Blackwell
et al.,
2013, 2015).

Avoidance
—Avoidance is the displacement of an individual from an area or migration path as a result of the presence of a sound or other stressors, and is one of the most obvious manifestations of disturbance in marine mammals (Richardson
et al.,
1995). Avoidance is qualitatively different from the flight response, but also differs in the magnitude of the response (
i.e.,
directed movement, rate of travel,
etc.
). Often avoidance is temporary, and animals return to the area once the noise has ceased. Acute avoidance responses have been observed in captive porpoises and pinnipeds exposed to a number of different sound sources (Kastelein
et al.,
2001; Finneran
et al.,
2003; Kastelein
et al.,
2006a; Kastelein
et al.,
2006b; Kastelein
et al.,
2015b; Kastelein
et al.,
2015c; Kastelein
et al.,
2018). Short-term avoidance of seismic surveys, low frequency emissions, and acoustic deterrents have also been noted in wild populations of odontocetes (Bowles
et al.,
1994; Goold, 1996; Goold and Fish, 1998; Morton and Symonds, 2002; Hiley
et al.,
2021) and to some extent in mysticetes (Malme
et al.,
1984; McCauley
et al.,
2000; Gailey
et al.,
2007). Longer-term displacement is possible, however, which may lead to changes in abundance or distribution patterns of the affected species in the affected region if habituation to the presence of the sound does not occur (
e.g.,
Blackwell
et al.,
2004; Bejder
et al.,
2006; Teilmann
et al.,
2006).

Forney
et al.
(2017) described the potential effects of noise on marine mammal populations with high site fidelity, including displacement and auditory masking. In cases of Western gray whales (
Eschrichtius robustus
) (Weller
et al.,
2006) and beaked whales (
Ziphius cavirostris
), anthropogenic effects in areas where they are resident or exhibit site fidelity could cause severe biological consequences, in part because displacement may adversely affect foraging rates, reproduction, or health, while an overriding instinct to remain in the area could lead to more severe acute effects. Avoidance of overlap between disturbing noise and areas and/or times of particular importance for sensitive species may be critical to avoiding population-level impacts because (particularly for animals with high site fidelity) there may be a strong motivation to remain in the area despite negative impacts.

Flight Response
—A flight response is a dramatic change in normal movement to a directed and rapid movement away from the perceived location of a sound source. The flight response differs from other avoidance responses in the intensity of the response (
e.g.,
directed movement, rate of travel). Relatively little information on flight responses of marine mammals to anthropogenic signals exist, although observations of flight responses to the presence of predators have occurred (Connor and Heithaus, 1996). The result of a flight response could range from brief, temporary exertion and displacement from the area where the signal provokes flight to, in extreme cases, marine mammal strandings (Evans and England, 2001). There are limited data on flight response for marine mammals in water; however, there are examples of this response in species on land. For instance, the probability of flight responses in Dall's sheep
Ovis dalli dalli
(Frid, 2003), hauled out ringed seals (
Phoca hispida
) (Born
et al.,
1999), Pacific brant (
Branta bernicla nigricans
), and Canada geese (
B. canadensis
) increased as a helicopter or fixed-wing aircraft more directly approached groups of these animals (Ward
et al.,
1999). However, it should be noted that response to a perceived predator does not necessarily invoke flight (Ford and Reeves, 2008), and whether individuals are solitary or in groups may influence the response.

Behavioral disturbance can also impact marine mammals in more subtle ways. Increased vigilance may result in costs related to diversion of focus and attention (
i.e.,
when a response consists of increased vigilance, it may come at the cost of decreased attention to other critical behaviors such as foraging or resting). These effects have generally not been observed in marine mammals, but studies involving fish and terrestrial animals have shown that increased vigilance may substantially reduce feeding rates and efficiency (
e.g.,
Beauchamp and Livoreil, 1997; Fritz
et al.,
2002; Purser and Radford, 2011). In addition, chronic disturbance can cause population declines through reduction of fitness (
e.g.,
decline in body condition) and subsequent reduction in reproductive success, survival, or both (
e.g.,
Harrington and Veitch, 1992; Daan
et al.,
1996; Bradshaw
et al.,
1998).

Many animals perform vital functions, such as feeding, resting, traveling, and socializing, on a diel cycle (24-hour cycle). Disruption of such functions resulting from reactions to stressors such as sound exposure are more likely to be significant if they last more than one diel cycle or recur on subsequent days (Southall
et al.,
2007). Consequently, a behavioral response lasting less than one day and not recurring on subsequent days is not considered particularly severe unless it could directly affect reproduction or survival (Southall
et al.,
2007). Note that there is a difference between multi-day substantive behavioral reactions and multi-day anthropogenic activities. For example, just because an activity lasts for multiple days does not necessarily mean that individual animals are either exposed to activity-related stressors for multiple days or, further, exposed in a manner resulting in sustained multi-day substantive behavioral responses.

Many of the contextual factors resulting from the behavioral response studies (
e.g.,
close approaches by multiple vessels or tagging) would not occur during the proposed action. In 2016, the Alaska Department of Transportation and Public Facilities (ADOT&PF) documented observations of marine mammals during construction activities (
i.e.,
pile driving) at the Kodiak Ferry Dock (see 80 FR 60636, October 7, 2015). In the marine mammal monitoring report for that project (ABR, 2016), 1,281 Steller sea lions were observed within the Level B disturbance zone during pile driving or drilling (
i.e.,
documented as Level B harassment take). 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. 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. The proposed action involves impact and vibratory pile driving, vibratory pile removal, rotary drilling, and DTH mono-hammer excavation. Given the similarities in activities and habitat (
e.g.,
cool-temperate waters, industrialized area), we expect similar behavioral responses from the same and similar species affected by OMAO's proposed action. That is, disturbance, if any, is likely to be temporary and localized (
e.g.,
small area movements).

To assess the strength of behavioral changes and responses to external sounds and SPLs associated with changes in behavior, Southall
et al.,
(2007) developed and utilized a severity scale, which is a 10 point scale ranging from no effect (labeled 0), effects not likely to influence vital rates (low; labeled from 1 to 3), effects that could affect vital rates (moderate; labeled 4 to

6), to effects that were thought likely to influence vital rates (high; labeled 7 to 9). Southall
et al.,
(2021) updated the severity scale by integrating behavioral context (
i.e.,
survival, reproduction, and foraging) into severity assessment. For non-impulsive sounds (
i.e.,
similar to the sources used during the proposed action), data suggest that exposures of pinnipeds to sources between 90 and 140 dB re 1 μPa do not elicit strong behavioral responses; no data were available for exposures at higher received levels for Southall
et al.,
(2007) to include in the severity scale analysis. Reactions of harbor seals were the only available data for which the responses could be ranked on the severity scale. For reactions that were recorded, the majority (17 of 18 individuals/groups) were ranked on the severity scale as a 4 (defined as moderate change in movement, brief shift in group distribution, or moderate change in vocal behavior) or lower; the remaining response was ranked as a 6 (defined as minor or moderate avoidance of the sound source).

Habituation
—Habituation can occur when an animal's response to a stimulus wanes with repeated exposure, usually in the absence of unpleasant associated events (Wartzok
et al.,
2003). Animals are most likely to habituate to sounds that are predictable and unvarying. It is important to note that habituation is appropriately considered as a “progressive reduction in response to stimuli that are perceived as neither aversive nor beneficial,” rather than as, more generally, moderation in response to human disturbance (Bejder
et al.,
2009). The opposite process is sensitization, when an unpleasant experience leads to subsequent responses, often in the form of avoidance, at a lower level of exposure. As noted, behavioral state may affect the type of response. For example, animals that are resting may show greater behavioral change in response to disturbing sound levels than animals that are highly motivated to remain in an area for feeding (Richardson
et al.,
1995; NRC, 2003; Wartzok
et al.,
2003). Controlled experiments with captive marine mammals have showed pronounced behavioral reactions, including avoidance of loud sound sources (Ridgway
et al.,
1997; Finneran
et al.,
2003). Observed responses of wild marine mammals to loud impulsive sound sources (typically seismic airguns or acoustic harassment devices) have been varied but often consist of avoidance behavior or other behavioral changes suggesting discomfort (Morton and Symonds, 2002; see also Richardson
et al.,
1995; Nowacek
et al.,
2007).

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-pituitary-adrenal system. Virtually all neuroendocrine functions that are affected by stress—including immune competence, reproduction, metabolism, and behavior—are regulated by pituitary hormones. Stress-induced changes in the secretion of pituitary hormones have been implicated in failed reproduction, altered metabolism, reduced immune competence, and behavioral disturbance (
e.g.,
Moberg, 1987; Blecha, 2000). Increases in the circulation of glucocorticoids are also equated with stress (Romano
et al.,
2004).

The primary distinction between stress (which is adaptive and does not normally place an animal at risk) and “distress” is the cost of the response. During a stress response, an animal uses glycogen stores that can be quickly replenished once the stress is alleviated. In such circumstances, the cost of the stress response would not pose serious fitness consequences. However, when an animal does not have sufficient energy reserves to satisfy the energetic costs of a stress response, energy resources must be diverted from other functions. This state of distress will last until the animal replenishes its energetic reserves sufficient to restore normal function.

Relationships between these physiological mechanisms, animal behavior, and the costs of stress responses are well-studied through controlled experiments and for both laboratory and free-ranging animals (
e.g.,
Holberton
et al.,
1996; Hood
et al.,
1998; Jessop
et al.,
2003; Krausman
et al.,
2004; Lankford
et al.,
2005). Stress responses due to exposure to anthropogenic sounds or other stressors and their effects on marine mammals have also been reviewed (Fair and Becker 2000; Romano
et al.,
2002b) 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 these projects based on observations of marine mammals during previous, similar projects.

Auditory 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-to-noise ratio, temporal variability, direction), in relation to each other and to an animal's hearing abilities (
e.g.,
sensitivity, frequency range, critical ratios, frequency discrimination, directional discrimination, age or TTS hearing loss), and existing ambient noise and propagation conditions. 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. Narragansett Bay supports cargo vessel traffic as well as numerous recreational and fishing vessels, and background sound levels in the proposed project area are already elevated.

Airborne Acoustic Effects
—Pinnipeds that occur near the project site could be

exposed to airborne sounds associated with pile driving and removal that have the potential to cause behavioral harassment, depending on their distance from pile driving 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 likely previously have been `taken' because of exposure to underwater sound above the behavioral harassment thresholds, which are generally 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.

Marine Mammal Habitat Effects

OMAO's proposed construction activities could have localized, temporary impacts on marine mammal habitat, including prey, by increasing in-water 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 areas (see discussion below). Elevated levels of underwater noise would ensonify the project areas 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.

A temporary and localized increase in turbidity near the seafloor would occur in the immediate area surrounding the area where piles are installed or removed. In general, turbidity associated with pile installation is localized to about a 25-ft (7.6 m) radius around the pile (Everitt
et al.,
1980). Turbidity and sedimentation effects are expected to be short-term, minor, and localized. Re-suspended sediments in Coddington Cove are expected to remain in Coddington Cove due to the circular nature of the currents with ambient conditions returning a few hours after completion of construction. Cetaceans are not expected to be close enough to the pile driving areas to experience effects of turbidity, and any pinnipeds could avoid localized areas of turbidity. Therefore, we expect the impact from increased turbidity levels to be discountable to marine mammals and do not discuss it further.

In-Water Construction Effects on Potential Foraging Habitat

The area likely impacted by the project is relatively small compared to the available habitat in Narragansett Bay. In addition, the area is highly influenced by anthropogenic activities and habitat in this area has been previously disturbed by as a part of offshore remediation activities. The total seafloor area affected by pile installation and removal is a small area compared to the vast amount of habitat available to marine mammals in the area. All marine mammal species using habitat near the proposed project area are primarily transiting the area. There are no known foraging or haulout areas within one half mile of the proposed project area. Furthermore, pile driving and removal at the project site would not obstruct long-term movements or migration of marine mammals.

Avoidance by potential prey (
i.e.,
fish) of the immediate area due to the temporary loss of this foraging habitat is also possible. The duration of fish and marine mammal 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 or marine mammals of the disturbed area would still leave significantly large areas of fish and marine mammal foraging habitat in the nearby vicinity.

Effects on Potential Prey

Sound may affect marine mammals through impacts on the abundance, behavior, or distribution of prey species (
e.g.,
fish). 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 which are especially strong and/or intermittent low-frequency sounds, and behavioral responses such as flight or avoidance are the most likely effects. 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).

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 fishes from pile driving and removal and construction 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.

Construction activities have the potential to have adverse impacts on forage fish in the project area in the form of increased turbidity. Forage fish form a significant prey base for many marine mammal species that occur in the project area. Increased turbidity is expected to occur in the immediate vicinity (on the order of 10 ft (3 m) or less) of construction activities. Turbidity within the water column has the potential to reduce the level of oxygen in the water and irritate the gills of prey fish in the proposed project area. However, fish in the proposed project area would be able to move away from and avoid the areas where increase turbidity may occur. Given the limited area affected and ability of fish to move to other areas, any effects on forage fish are expected to be minor or negligible.

In summary, given the short daily duration of sound associated with individual pile driving and removal events and the relatively small areas being affected, pile driving and removal activities associated with the proposed actions are not likely to have a permanent, adverse effect on any fish habitat, or populations of fish species. 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. Thus, we conclude that impacts of the specified activities 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 determinations.

Harassment is the only type of take expected to result from these activities. Except with respect to certain activities not pertinent here, section 3(18) of the MMPA defines “harassment” as any act of pursuit, torment, or annoyance, which (i) has the potential to injure a marine mammal or marine mammal stock in the wild (Level A harassment); or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (Level B harassment).

Authorized takes would primarily be by Level B harassment, as use of the acoustic sources (
i.e.,
pile driving and removal, DTH, and rotary drilling) has the potential to result in disruption of behavioral patterns for individual marine mammals. There is also some potential for auditory injury (Level A harassment) to result, primarily for high frequency species and phocids because predicted auditory injury zones are larger than for mid-frequency species. Auditory injury is unlikely to occur for mid-frequency species. The proposed mitigation and monitoring measures are expected to minimize the severity of the taking to the extent practicable.

As described previously, no serious injury or mortality is anticipated or proposed to be authorized for this activity. Below we describe how the proposed take numbers are estimated.

For acoustic impacts, generally speaking, we estimate take by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment; (2) the area or volume of water that will be ensonified above these levels in a day; (3) the density or occurrence of marine mammals within these ensonified areas; and, (4) the number of days of activities. We note that while these factors can contribute to a basic calculation to provide an initial prediction of potential takes, additional information that can qualitatively inform take estimates is also sometimes available (
e.g.,
previous monitoring results or average group size). Below, we describe the factors considered here in more detail and present the proposed take estimates.

Acoustic Thresholds

NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur PTS of some degree (equated to Level A harassment). Thresholds have also been developed identifying the received level of in-air sound above which exposed pinnipeds would likely be behaviorally harassed.

Level B Harassment
—Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source or exposure context (
e.g.,
frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source), the environment (
e.g.,
bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict (
e.g.,
Southall
et al.,
2007, 2021, Ellison
et al.,
2012). Based on what the available science indicates and the practical need to use a threshold based on a metric that is both predictable and measurable for most activities, NMFS typically uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS generally predicts that marine mammals are likely to be behaviorally harassed in a manner considered to be Level B harassment when exposed to underwater anthropogenic noise above root-mean-squared pressure received levels (RMS SPL) of 120 dB (referenced to 1 micropascal (re 1 μPa)) for continuous (
e.g.,
vibratory pile-driving, drilling) and above RMS SPL 160 dB re 1 μPa for non-explosive impulsive (
e.g.,
seismic airguns) or intermittent (
e.g.,
scientific sonar) sources. Generally speaking, Level B harassment take estimates based on these behavioral harassment thresholds are expected to include any likely takes by TTS as, in most cases, the likelihood of TTS occurs at distances from the source less than those at which behavioral harassment is likely. TTS of a sufficient degree can manifest as behavioral harassment, as reduced hearing sensitivity and the potential reduced opportunities to detect important signals (conspecific communication, predators, prey) may result in changes in behavior patterns that would not otherwise occur.

OMAO's proposed activities includes the use of continuous (vibratory hammer/rotary drill/DTH mono-hammer) and impulsive (impact hammer/DTH mono-hammer) sources, and therefore the RMS SPL thresholds of 120 and 160 dB re 1 μPa are applicable.

Level A Harassment
—NMFS' Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing (Version 2.0) (Technical Guidance, 2018) identifies dual criteria to assess auditory injury (Level A harassment) to five different marine mammal groups (based on hearing sensitivity) as a result of exposure to noise from two different types of sources (impulsive or non-impulsive). OMAO's proposed activity includes the use of impulsive (impact hammer/DTH mono-hammer) and non-impulsive (vibratory hammer/rotary drill/DTH mono-hammer) sources.

These thresholds are provided in the table below. The references, analysis, and methodology used in the development of the thresholds are described in NMFS' 2018 Technical Guidance, which may be accessed at:
www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance.

Table 5—Thresholds Identifying the Onset of Permanent Threshold Shift

Hearing group

PTS onset thresholds *
(received level)

Impulsive
Non-impulsive

Low-Frequency (LF) Cetaceans

Cell 1:

L
p,0-pk,flat
:
219 dB;
L
E,p,LF,24h
:
183 dB

Cell 2:

L
E,p,LF,24h:
199 dB.

Mid-Frequency (MF) Cetaceans

Cell 3:

L
p,0-pk,flat
:
230 dB;
L
E,p,MF,24h
:
185 dB

Cell 4:

L
E,p,MF,24h:
198 dB.

High-Frequency (HF) Cetaceans

Cell 5:

L
p,0-pk,flat
:
202 dB;
L
E,p,HF,24h
:
155 dB

Cell 6:

L
E,p,HF,24h:
173 dB.

Phocid Pinnipeds (PW) (Underwater)

Cell 7:

L
p,0-pk.flat
:
218 dB;
L
E,p,PW,24h
: 185 dB

Cell 8:

L
E,p,PW,24h
:
201 dB.

Otariid Pinnipeds (OW) (Underwater)

Cell 9:

L
p,0-pk,flat
:
232 dB;
L
E,p,OW,24h
: 203 dB

Cell 10:

L
E,p,OW,24h
:
219 dB.

* Dual metric 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 are recommended for consideration.

Note:
Peak sound pressure level (
L
p,0-pk
) has a reference value of 1 μPa, and weighted cumulative sound exposure level (
L
E,p
) has a reference value of 1μPa
2
s. In this Table, thresholds are abbreviated to be more reflective of International Organization for Standardization standards (ISO 2017). The subscript “flat” is being included to indicate peak sound pressure are flat weighted or unweighted within the generalized hearing range of marine mammals (
i.e.,
7 Hz to 160 kHz). 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 weighted 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 thresholds will be exceeded.

Ensonified Area

Here, we describe operational and environmental parameters of the activity that are used in estimating the area ensonified above the acoustic thresholds, including source levels and transmission loss coefficient.

The sound field in the project area is the existing background noise plus additional construction noise from the proposed project. Marine mammals are expected to be affected via sound generated by the primary components of the project (
i.e.,
impact pile driving, vibratory pile driving, vibratory pile removal, rotary drilling, and DTH).

The intensity of underwater sound is greatly influenced by factors such as the size and type of piles, type of driver or drill, and the physical environment in which the activity takes place. In order to calculate distances to the Level A harassment and Level B harassment thresholds for the methods and piles being used in this project, NMFS used representative source levels (Table 6) from acoustic monitoring at other locations.

Table 6—Source Levels for Proposed Activities

Method
Pile type
Pile diameter

Peak
(dB re 1 μPa)

RMS
(dB re 1 μPa)

SEL
(dB re 1 μPa 2-sec sec)

Reference

Vibratory Extraction

Steel pipe
1

12″
171
155
155
Caltrans 2020, Table 1.2-1d.

Timber
12″
NA
152
NA
NMFS 2021a, Table 4.

Vibratory Installation
Steel pipe
18″
NA

162
2

162
NAVFAC Mid-Atlantic 2019, Table 6-4.

Sheet pile

Z26-700
3

NA
156
NA
NMFS 2019, p.37846.

Steel pipe
30″
NA
167
167
Navy 2015, p.14.

Casing/shaft for steel pipe
36″
NA
175
175
NAVFAC Mid-Atlantic 2019, Table 6-4.

DTH Mono-hammer
Steel pipe
18″
172
167
146
Egger, 2021; Guan and Miner 2020; Heyvaert and Reyff, 2021.

Casing/shaft for steel pipe

36″
4

194
167
164
Reyff and Heyvaert 2019; Reyff 2020; and Denes et al. 2019.

Rotary Drilling
Steel pipe
18″ and 30″
NA
154
NA
Dazey et al. 2012.

Impact Install

Steel pipe
5

18″
208
187
176
Caltrans 2020, Table 1.2-1a.

Steel pipe
30″
211
196
181
NAVFAC Southwest 2020, p.A-4.

Vibratory Installation/Extraction
Steel pipe
16″
NA
162
162
NAVFAC Mid-Atlantic 2019, Table 6-4.

1
13-inch steel pipe used as proxy because data were not available for vibratory install/extract of 12-inch steel pipe.

2
Although conservative, this 162 dB RMS is consistent with source level value used for 18-inch steel pipe in for Dry Dock 1 at Portsmouth Naval Shipyard (84 FR 13252, April 4, 2019).

3
30-inch steel pipe pile used as the proxy source for vibratory driving of steel sheet piles because data were not available for Z26-700 (Navy 2015 [p. 14]).

4
Guidance from NMFS states: For each metric, select the highest SL provided among these listed references (Reyff and Heyvaert, 2019); (Reyff J., 2020); (Denes
et al.,
2019).

5
Impact install of 20-inch steel pipe used as proxy because data were not available for 18-inch.

Notes:
All SPLs are unattenuated; dB = decibels; NA = Not applicable/Not available; RMS = root mean square; SEL = sound exposure level; Caltrans = California Department of Transportation; NAVFAC = Naval Facilities Engineering Systems Command; dB re 1 μPa = dB referenced to a pressure of 1 microPascal, measures underwater SPL. dB re 1 μPa2-sec = dB referenced to a pressure of 1 microPascal squared per second, measures underwater SEL.

Single strike SEL are the proxy source levels presented for impact pile driving and were used to calculate distances to PTS. All data referenced at 10 meters.

NMFS recommends treating DTH systems as both impulsive and continuous, non-impulsive sound source types simultaneously. Thus, impulsive thresholds are used to evaluate Level A harassment, and continuous thresholds are used to evaluate Level B harassment. With regards to DTH mono-hammers, NMFS recommends proxy levels for Level A harassment based on available data regarding DTH systems of similar sized piles and holes (Denes
et al.,
2019; Guan and Miner, 2020; Reyff and Heyvaert, 2019; Reyff, 2020; Heyvaert and Reyff, 2021) (Table 1 includes number of piles and duration; Table 6 includes sound pressure levels for each pile type). At the time of the Navy's application submission, NMFS recommended that the RMS sound pressure level at 10 m should be 167 dB when evaluating Level B harassment (Heyvaert and Reyff, 2021 as cited in NMFS 2021b) for all DTH pile/hole sizes. However, since that time, NMFS has received additional clarifying information regarding DTH data presented in Reyff and Heyvaert (2019) and Reyff (2020) that allows for different RMS sound pressure levels at 10 m to be recommended for piles/holes of varying diameters. Therefore, NMFS proposes to use the following proxy RMS sound pressure levels at 10 m to evaluate Level B harassment from this sound source in this analysis (Table 6): 167 dB RMS for the 18-inch steel pipe piles (Heyvaert and Reyff, 2021) and 174 dB RMS for the 36 inch steel shafts (Reyff and Heyvaert, 2019; Reyff, 2020).

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 * log
10
(R
1
/R
2
),

Where:

TL = transmission loss in dB

B = transmission loss coefficient; for practical spreading equals 15

R
1
= the distance of the modeled SPL from the driven pile, and

R
2
= 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, known as practical spreading. As is common practice in coastal waters, here we assume practical spreading (4.5 dB reduction in sound level for each doubling of distance). Practical spreading was used to determine sound propagation for this project.

The TL model described above was used to calculate the expected noise propagation from vibratory pile driving/extracting, impact pile driving, rotary drilling, and DTH mono-hammer excavation using representative source levels to estimate the harassment zones or area exceeding the noise criteria. Utilizing the described practical spreading model, NMFS calculated the Level B isopleths shown in Tables 7 and 8. The largest calculated Level B isopleth, with the exception of concurrent activities, discussed below, is 46,416 m for the vibratory installation of the 36″ steel casing/shaft guide piles with rock socket to build the small boat floating dock; however, this distance is truncated by shoreline in all directions, so sound would not reach the full distance of the calculated Level B harassment isopleth. This activity would generate a maximum ensonified area of 3.31 km
2
(Table 8).

Level A Harassment Zones

The ensonified area associated with Level A harassment is technically more challenging to predict due to the need to account for a duration component. Therefore, NMFS developed an optional User Spreadsheet tool to accompany the Technical Guidance that can be used to relatively simply predict an isopleth distance for use in conjunction with marine mammal density or occurrence to help predict potential takes. We note that because of some of the assumptions included in the methods underlying this optional tool, we anticipate that the resulting isopleth estimates are typically going to be overestimates of some degree, which may result in an overestimate of potential take by Level A harassment. However, this optional tool offers the best way to estimate isopleth distances when more sophisticated modeling methods are not available or practical. For stationary sources such as pile driving, the optional User Spreadsheet tool predicts the distance at which, if a marine mammal remained at that distance for the duration of the activity, it would be expected to incur PTS. Inputs used in the optional User Spreadsheet tool are reported in Tables 1 (number piles/day and duration to drive a single pile) and 6 (source levels/distance to source levels). The resulting estimated isopleths are reported below in Tables 7 and 8. The largest Level A isopleth would be generated by the impact driving of the 30″ steel pipe pile at the proposed pier for high-frequency cetaceans (3,500.3 m; Table 7). This activity would have a maximum ensonified area of 6.49 km
2
(Table 7). Excluding concurrent activities, described below, the largest calculated Level B isopleth would be generated by the vibratory installation of the 36″ steel casing/shaft guide piles at the proposed small boat floating dock (46,416 m; Table 8), though as noted above, this distance would be truncated by shoreline in all directions, so sound would not reach the full distance of the calculated Level B harassment isopleth. This activity would have a maximum ensonified area of 3.31 km
2
(Table 8).

Table 7—Maximum Distances to Level A Harassment and Level B Harassment Thresholds for Impulsive Sound
[Impact Hammer and DTH Mono-Hammer]

Structure
Pile size and type
Activity
Level A (PTS onset) harassment

Maximum

distance to 185 dB SEL
cum
threshold(m)/area of

harassment zone (km
2
)

Maximum

distance to 155 dB SEL
cum
threshold(m)/area of

harassment zone (km
2
)

Maximum

distance to 185 dB SEL
cum
threshold(m)/area of

harassment zone (km
2
)

Level B (behavioral) harassment

Maximum

distance 160 dB RMS SPL (120 dB DTH) threshold (m)/area of harassment zone (km
2
)

MF cetacean
HF cetacean
Phocid
All Marine Mammals

Bulkhead construction (Combination Pipe/Z-pile)
18″ steel pipe
Impact Install
48.5/0.0037
1,624.7/0.66
729.9/0.21
631/0.16

DTH Mono-Hammer
4.6/0.000033
154.2/0.028
69.3/0.0075
13,594/3.31

Trestle (Bents 1-18)
18″ steel pipe
Impact Install
25.2/0.0020
844.9/1.21
379.6/0.38
631/0.82

Trestle (Bent 19)
30″ steel pipe
Impact Install
65.8/0.014
2,205.0/3.72
990.7/1.47
2,512/4.44

Pier
30″ steel pipe
Impact Install
104.5/0.034
3,500.3/6.49
1,572.6/2.50
2,512/4.44

Gangway support piles (small boat floating dock)
18″ steel pipe
Impact Install
19.3/0.00058
644.8/0.17
289.7/0.049
631/0.16

Small Boat Floating Dock
36″ Steel Casing/Shaft with Rock Socket (Guide Pile)
Impact Install
35.5/0.002
1,189.5/0.45
534.4/0.12
3,415/2.14

DTH Mono-Hammer
73/0.0084
2,444.5/1.21
1,098.2/0.42
13,594/3.31

Notes:
dB = decibel; DTH = down-the-hole; dB RMS SPL = decibel root mean square sound pressure. level; dB SEL
cum
= cumulative sound exposure level; m = meter; PTS = Permanent Threshold Shift; km
2
= square kilometer.

Table 8—Maximum Distances to Level A Harassment and Level B Harassment Thresholds for Continuous
[Vibratory Hammer/Rotary Drill]

Structure
Pile size and type
Activity
Level A (PTS onset) harassment

Maximum

distance to 198 dB SEL
cum
threshold(m)/area of harassment zone (km
2
)

Maximum

distance to 173 dB SEL
cum
threshold(m)/area of harassment zone (km
2
)

Maximum

distance to 201 dB SEL
cum
threshold(m)/area of harassment zone (km
2
)

Level B (behavioral) harassment

Maximum

distance 120 dB RMS SPL (120 dB DTH) threshold (m)/area of harassment zone (km
2
)

MF cetacean
HF cetacean
Phocid
All Marine Mammals

Abandoned guide piles along bulkhead
12″ steel pipe
Vibratory Extract
0.3/0
5.3/0.000044
2.2/0.000008
2,514/1.26

Floating dock demolition (Timber Guide Piles)
12″ timber
Vibratory Extract
0.2/0
4/0.000025
1.7/0.000005
1,359/0.53

Bulkhead construction (Combination Pipe/Z-pile)
18″ steel pipe
Vibratory Install
1.8/0.000005
29.7/0.0014
12.2/0.00023
6,310/3.31

Steel sheet Z26-700
Vibratory Install
0.7/0.000001
11.8/0.00022
4.9/0.000038
2,512/1.26

16″ steel pipe template piles
Vibratory Install/Extract
1.1/0.000002
18.7/0.00055
7.7/0.000093
6,310/3.31

Trestle (Bents 1-18)
18″ steel pipe
Vibratory Install
0.7/0.000002
11.8/0.00044
4.8/0.000072
6,310/8.53

18″ steel pipe hole
Rotary Drill
0.0/0
0.6/0.000001
0.4/0.000001
1,848/2.98

16″ steel pipe template piles
Vibratory Install/Extract
1.1/0.000004
18.7/0.0011
7.7/0.00019
6,310/8.53

Trestle (Bent 19)
30″ steel pipe
Vibratory Install
2.0/0.000013
33.2/0.0034
13.7/0.00059
13,594/8.53

16″ steel pipe template piles
Vibratory Install/Extract
1.1/0.000004
18.7/0.0011
7.7/0.00019
6,310/8.53

Pier
30″ steel pipe
Vibratory Install
3.2/0.000032
52.8/0.0087
21.7/0.0015
13,594/8.53

30″ hole
Rotary Drill
0.0/0
0.6/0.000001
0.4/0.000001
1,848/2.98

16″ steel pipe template piles
Vibratory Install/Extract
1.1/0.000004
18.7/0.0011
7.7/0.00019
6,310/8.53

Fender Piles
16″ steel pipe
Vibratory Install
0.9/0.000003
14.3/0.00064
5.9/0.00011
6,310/8.53

16″ steel pipe template piles
Vibratory Install/Extract
1.1/0.000004
18.7/0.0011
7.7/0.00019
6,310/8.53

Gangway support piles (small boat floating dock)
18″ steel pipe
Vibratory Install
0.7/0.000001
11.8/0.00022
4.8/0.000036
6,310/3.31

Small Boat Floating Dock
36″ Steel Casing/Shaft Guide Piles with Rock Socket
Vibratory Install
5.2/0.000042
86.6/0.012
35.6/0.002
46,416/3.31

16″ steel pipe template piles
Vibratory Install/Extract
1.1/0.000002
18.7/0.00055
7.7/0.000093
6,310/3.31

Notes:
dB = decibel; dB RMS SPL = decibel root mean square sound pressure level; dB SELcum = cumulative sound exposure level; m = meter; PTS = Permanent Threshold Shift; km
2
= square kilometer.

Concurrent Activities

Simultaneous use of two or three impact, vibratory, or DTH hammers, or rotary drills, could occur (potential combinations described in Table 1) and may result in increased sound source levels and harassment zone sizes, given the proximity of the structure sites and the rules of decibel addition (Table 9).

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, rotary drill, and Level B harassment zones for drilling with a DTH hammer (Table 9) and differently for impulsive sources with rapid impulse rates of multiple strikes per second (DTH) and slow impulse rates (impact hammering) (NMFS 2021). It is unlikely that the two impact hammers will strike at the same instant, and therefore, the SPLs will not be adjusted regardless of the distance between impact hammers. In this case, each impact hammer will be considered to have its own independent Level A harassment and Level B harassment zones.

When two DTH hammers operate simultaneously their continuous sound components overlap completely in time. When the Level B isopleth of one DTH sound source encompasses the isopleth of another DTH sound source, the sources are considered additive and combined using the rules for combining sound source levels generated during pile installation, described in Table 9.

Table 9—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 Rotary drill, or DTH, DTH
0 or 1 dB
Add 3 dB to the higher source level
Add 3 dB to the higher source level.

2 or 3 dB
Add 2 dB to the higher source level
Add 2 dB to the higher source level.

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

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

Note:
The method is based on a method created by Washington State Department of Transportation (WSDOT 2020) and has been updated and modified by NMFS.

When two continuous noise sources have overlapping sound fields, there is potential for higher sound levels than for non-overlapping sources. When two or more continuous noise sources 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 of decibel addition (Table 9; NMFS 2021c).

For simultaneous use of three or more continuous sound sources, NMFS first identifies the three overlapping sources with the highest sound source level. Then, using the rules for combining sound source levels generated during pile installation (Table 9), NMFS determines the difference between the lower two source levels, and adds the appropriate number of decibels to the higher source level of the two. Then, NMFS calculates the difference between the newly calculated source level and the highest source level of the three identified in the first step, and again, adds the appropriate number of decibels to the highest source level of the three.

For example, with overlapping isopleths from 24″, 36″, and 42″ diameter steel pipe piles with sound source levels of 161, 167, and 168 dB RMS respectively, NMFS would first calculate the difference between the 24″ and 36″ source levels (167 dB−161 dB = 6 dB. Then, given that the difference is 6 dB, as described in Table 9, NMFS would then add 1 dB to the highest of the two sound source levels (167 dB), for a combined noise level of 168 dB. Next, NMFS calculates the difference between the newly calculated 168 dB and the sound source level of the 42″ steel pile (168 dB). Since 168 dB−168 dB = 0 dB, 3 dB is added to the highest value (168 dB + 3 dB = 171 dB). Therefore, for the combination of 24″, 36″, and 42″ steel pipe piles, zones would be calculated using a combined sound source level of 171 dB.

If an impact hammer and a vibratory hammer are used concurrently, the largest Level B harassment zone generated by either hammer would apply, and the Level A harassment zone generated by the impact hammer would apply. Simultaneous use of two or more impact hammers does not require source level additions as it is unlikely that two hammers would strike at the same exact instant. Thus, sound source levels are not adjusted regardless of distance, and the zones for each individual activity apply.

For activity combinations that do require sound source level adjustment, Table 10 shows the revised proxy source levels for concurrent activities based upon the rules for combining sound source levels generated during pile installation, described in Table 9. Resulting Level A harassment and Level B harassment zones for concurrent activities are summarized in Table 11. The maximum Level A harassment isopleth would be 2,444.5 m for high-frequency cetaceans generated by concurrent use of two vibratory pile drivers and DTH mono-hammer during installation of 36″ shafts for the small boat floating dock (Table 11). The maximum Level B harassment isopleth would be 54,117 m for the concurrent use of DTH mono-hammer and two vibratory pile drivers for installation of 36″ shafts for the small boat floating dock (Table 11).

Table 10—Proxy Values for Simultaneous Use of Non-Impulsive Sources

Structure
Activity and proxy
New proxy

Bulkhead
Vibratory Inst

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2022-23775. Public record. Not legal advice.