2024-27342. Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Gary Paxton Industrial Park Vessel Haulout Project in Sitka, Alaska

Table 1—Marine Mammal Species ¹ Likely To Occur Near the Project Area That May Be Taken by CBS's Activities

Common name	Scientific name	Stock	ESA/ MMPA status; strategic (Y/N) 2	Stock abundance ( CV, Nmin , most recent abundance survey) 3	PBR	Annual M/S1 4
Order Artiodactyla—Cetacea—Mysticeti (baleen whales)
Family Eschrichtiidae:
Gray Whale	Eschrichtius robustus	Eastern N Pacific	-, -, N	26,960 (0.05, 25,849, 2016)	801	131
Family Balaenopteridae (rorquals):
Humpback Whale	Megaptera novaeangliae	Hawai'i	-, -, N	11,278 (0.56, 7,265, 2020)	127	27.09
		Mexico-North Pacific	T, D, Y	N/A (N/A, N/A, 2006)  5	UND	0.57
Family Delphinidae:
Killer Whale	Orcinus orca	Eastern North Pacific Alaska Resident	-, -, N	1,920 (N/A, 1,920, 2019) 6	19	1.3
		Eastern North Pacific Gulf of Alaska, Aleutian Islands and Bering Sea Transient	-, -, N	587 (N/A, 587, 2012) 6	5.9	0.8
		Eastern Northern Pacific Northern Resident	-, -, N	302 (N/A, 302, 2018) 6	2.2	0.2
		West Coast Transient	-, -, N	349 (N/A, 349, 2018) 6	3.5	0.4
Pacific White-Sided Dolphin	Lagenorhynchus obliquidens	N Pacific	-, -, N	26,880 (N/A, N/A, 1990)	UND	0
Family Phocoenidae (porpoises):
Harbor Porpoise	Phocoena phocoena	Yakutat/Southeast Alaska Offshore Waters	-, -, N	N/A (N/A, N/A, 1997) 7	UND	22.2
Order Carnivora—Pinnipedia
Family Otariidae (eared seals and sea lions):
CA Sea Lion	Zalophus californianus	U.S.	-, -, N	257,606 (N/A, 233,515, 2014)	14,011	>321
Northern Fur Seal	Callorhinus ursinus	Eastern Pacific	-, D, Y	626,618 (0.2, 530,376, 2019)	11,403	373
Steller Sea Lion	Eumetopias jubatus	Western	E, D, Y	49,837 (N/A, 49,837, 2022) 8	299	267
		Eastern	-, -, N	36,308 (N/A, 36,308, 2022) 9	2,178	93.2
Family Phocidae (earless seals):
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Harbor Seal	Phoca vitulina	Sitka/Chatham Strait	-, -, N	13,289 (N/A, 11,883, 2015)	356	77
1  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).
2  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.
3  NMFS marine mammal SARs online at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-stock-assessment-reports-region. CV is coefficient of variation; Nmin is the minimum estimate of stock abundance. In some cases, CV is not applicable [explain if this is the case]
4  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.
5  Abundance estimates are based upon data collected more than 8 years ago and, therefore, current estimates are considered unknown.
6   Nest is based upon counts of individuals identified from photo-ID catalogs.
7  New stock split from Southeast Alaska stock.
8   Nest is best estimate of counts, which have not been corrected for animals at sea during abundance surveys. Estimates provided are for the United States only. The overall Nmin is 73,211 and overall PBR is 439.
9   Nest is best estimate of counts, which have not been corrected for animals at sea during abundance surveys. Estimates provided are for the United States only.

A detailed description of the species likely to be affected by CBS's GPIP vessel haulout project, including brief introductions to the species and relevant stocks as well as available information regarding population trends and threats, and information regarding local occurrence, were provided in the Federal Register notice for the proposed IHA (89 FR 56317; July 9, 2024); since that time, we are not aware of any changes in the status of these species and stocks; therefore, detailed descriptions are not provided here. Please refer to that Federal Register notice for these descriptions. Please also refer to NMFS' website ( https://www.fisheries.noaa.gov/​find-species) for generalized species accounts.

Marine Mammal Hearing

Hearing is the most important sensory modality for marine mammals underwater, and exposure to anthropogenic sound can have deleterious effects. To appropriately assess the potential effects of exposure to sound, it is necessary to understand the frequency ranges marine mammals are able to hear. 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.). Subsequently, NMFS (2018, 2024) 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. Note that between the proposed FRN (89 FR 56317, July 9, 2024) and the issuance of the final IHA, NMFS' 2024 Technical Guidance was finalized (89 FR 84872, 24 October 2024) and has been incorporated into this analysis. The marine mammal hearing groups and their associated hearing ranges included in the proposed FRN (89 FR 56317, July 9, 2024) are provided in table 2. The re-named marine mammal hearing groups that have been incorporated into this final IHA are presented in table 3. The references, analysis, and methodology used in the development of the thresholds are described in the 2024 Technical Guidance, which may be accessed at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-acoustic-technical-guidance.

Table 2—Marine Mammal Hearing Groups

[NMFS, 2018]

Hearing group	Generalized hearing range *
Low-frequency (LF) cetaceans (baleen whales)	7 Hz to 35 kHz.
Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)	150 Hz to 160 kHz.
High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchids, 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).

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Table 3—Marine Mammal Hearing Groups

[NMFS 2024]

Hearing group	Generalized hearing range *
Low-frequency (LF) cetaceans (baleen whales)	7 Hz to 36 kHz.
High-frequency (HF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)	150 Hz to 160 kHz.
Very High-frequency (VHF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus cruciger & L. australis)	200 Hz to 165 kHz.
Phocid pinnipeds (PW) (underwater) (true seals)	40 Hz to 90 kHz.
Otariid pinnipeds (OW) (underwater) (sea lions and fur seals)	60 Hz to 68 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 may not be as broad. Generalized hearing range chosen based on ~65 dB threshold from composite audiogram, previous analysis in NMFS 2018, and/or data from Southall et al. 2007; Southall et al. 2019. Additionally, animals are able to detect very loud sounds above and below that “generalized” hearing range.

For more detail concerning these groups and associated frequency ranges, please see NMFS (2024) for a review of available information.

Potential Effects of Specified Activities on Marine Mammals and Their Habitat

The effects of underwater noise from CBS's construction activities have the potential to result in the harassment of marine mammals in the vicinity of the project area. The notice of proposed IHA (89 FR 56317; July 9, 2024) included a discussion of the effects of anthropogenic noise on marine mammals and the potential effects of underwater noise from CBS's construction on marine mammals and their habitat. That information and analysis is referenced in this final IHA determination and is not repeated here; please refer to the notice of proposed IHA (89 FR 56317; July 9, 2024).

Estimated Take of Marine Mammals

This section provides an estimate of the number of incidental takes authorized through the IHA, which informed NMFS' consideration of “small numbers,” the negligible impact determinations, and impacts on subsistence uses.

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 are primarily by Level B harassment, as use of the acoustic sources ( i.e., pile driving) has the potential to result in disruption of behavioral patterns for individual marine mammals. There is also some potential for AUD INJ (Level A harassment) to result, for all hearing groups because, after applying the 2024 Technical Guidance, the predicted AUD INJ zones have increased such that Protected Species Observers (PSO) may be unable to observe most of these species during impact pile driving. The mitigation and monitoring measures are expected to minimize the severity of the taking to the extent practicable.

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

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

Acoustic Thresholds

NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed (equated to Level B harassment) or to incur AUD INJ of some degree (equated to Level A harassment).

Level B Harassment —Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source or exposure context ( e.g., frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source), the environment ( e.g., bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict ( e.g., Southall et al., 2007, 2021; Ellison et al., 2012). Based on what the available science indicates and the practical need to use a threshold based on a metric that is both predictable and measurable for most activities, NMFS typically uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS generally predicts that marine mammals are likely to be behaviorally harassed in a manner considered to be Level B harassment when exposed to underwater anthropogenic noise above root-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 temporary threshold shift (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 ( print page 92632) communication, predators, prey) may result in changes in behavior patterns that would not otherwise occur.

CBS's activity includes the use of continuous (vibratory pile driving) and impulsive (impact pile driving) sources, and therefore the RMS SPL thresholds of 120 and 160 dB re 1 μPa are applicable.

Level A Harassment —NMFS' 2024 Technical Guidance (NMFS, 2024) identifies dual criteria to assess AUD INJ (Level A harassment) to 5 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). Note that between the proposed FRN (89 FR 56317, July 9, 2024) and the issuance of the final IHA, NMFS' 2024 Technical Guidance was finalized (89 FR 84872, 24 October 2024) and has been incorporated into this analysis. CBS's activity includes the use of impulsive (impact pile driving) and non-impulsive (continuous pile driving) sources.

The thresholds identifying the onset of Permanent Threshold Shift (PTS) based on 2018 Technical Guidance and included in the proposed FRN (89 FR 56317, July 9, 2024) are provided in table 4. The references, analysis, and methodology used in the development of the thresholds used in the proposed IHA are described in NMFS' 2018 Technical Guidance, which may be accessed at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-acoustic-technical-guidance. The updated thresholds, which identify the Onset of AUD INJ based on the 2024 Technical Guidance, have been incorporated in this final IHA are presented in table 5. The references, analysis, and methodology used in the development of the thresholds are described in the 2024 Technical Guidance, which may be accessed at: https://www.fisheries.noaa.gov/​national/​marine-mammal-protection/​marine-mammal-acoustic-technical-guidance. NMFS defines AUD INJ as “damage to the inner ear that can result in destruction of tissue . . . which may or may not result in PTS” (NMFS 2024). NMFS defined 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, 2024).

Table 4—Thresholds Identifying the Onset of PTS based on 2018 Technical Guidance

Hearing group	PTS onset acoustic thresholds * (received level)
	Impulsive	Non-impulsive
Low-Frequency (LF) Cetaceans	Cell 1: Lpk,flat : 219 dB; LE, LF,24h : 183 dB	Cell 2: LE, LF,24h : 199 dB.
Mid-Frequency (MF) Cetaceans	Cell 3: Lpk,flat : 230 dB; LE, MF,24h : 185 dB	Cell 4: LE, MF,24h : 198 dB.
High-Frequency (HF) Cetaceans	Cell 5: Lpk,flat : 202 dB; LE, HF,24h : 155 dB	Cell 6: LE, HF,24h : 173 dB.
Phocid Pinnipeds (PW) (Underwater)	Cell 7: Lpk,flat : 218 dB; LE, PW,24h : 185 dB	Cell 8: LE, PW,24h : 201 dB.
Otariid Pinnipeds (OW) (Underwater)	Cell 9: Lpk,flat : 232 dB; LE, OW,24h : 203 dB	Cell 10: LE, OW,24h : 219 dB.
* Dual metric acoustic thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating PTS onset. If a non-impulsive sound has the potential of exceeding the peak sound pressure level thresholds associated with impulsive sounds, these thresholds should also be considered.
Note: Peak sound pressure ( Lpk ) has a reference value of 1 µPa, and cumulative sound exposure level ( LE ) has a reference value of 1µPa2 s. In this table, thresholds are abbreviated to reflect ANSI standards (ANSI, 2013). However, peak sound pressure is defined by ANSI as incorporating frequency weighting, which is not the intent for this Technical Guidance. Hence, the subscript “flat” is being included to indicate peak sound pressure should be flat weighted or unweighted within the generalized hearing range. The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, MF, and HF cetaceans, and PW and OW pinnipeds) and that the recommended accumulation period is 24 hours. The cumulative sound exposure level thresholds could be exceeded in a multitude of ways ( i.e., varying exposure levels and durations, duty cycle). When possible, it is valuable for action proponents to indicate the conditions under which these acoustic thresholds will be exceeded.

Table 5—Thresholds Identifying the Onset of Auditory Injury Based on 2024 Technical Guidance

Hearing group	AUD INJ onset thresholds * (received level)
	Impulsive	Non-impulsive
Hearing group
Low-Frequency (LF) Cetaceans	Cell 1: Lp, 0-pk,flat : 222 dB; LE, p, LF,24h: 183 dB	Cell 2: LE, p, LF,24h : 197 dB.
High-Frequency (HF) Cetaceans	Cell 3: Lp, 0-pk,flat : 230 dB; LE, p, HF,24h: 193 dB	Cell 4: LE, p, , HF,24h : 201 dB.
Very High-Frequency (VHF) Cetaceans	Cell 5: Lp, 0-pk,flat : 202 dB; LE, p, VHF,24h: 159 dB	Cell 6: LE, p, VHF,24h : 181 dB.
Phocid Pinnipeds (PW) (Underwater)	Cell 7: Lp, 0-pk.flat : 223 dB; LE, p, PW,24h: 183 dB	Cell 8: LE, p, PW,24h : 195 dB.
Otariid Pinnipeds (OW) (Underwater)	Cell 9: Lp, 0-pk,flat : 230 dB; LE, p, OW,24h: 185 dB	Cell 10: LE, p, OW,24h : 199 dB.
* Dual metric thresholds for impulsive sounds: Use whichever results in the largest isopleth for calculating AUD INJ 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 ( Lp, 0-pk ) has a reference value of 1 µPa, and weighted cumulative sound exposure level ( LE, p ) has a reference value of 1µPa2 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 165 kHz). The subscript associated with cumulative sound exposure level thresholds indicates the designated marine mammal auditory weighting function (LF, HF, and VHF 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.

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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 planned project. Marine mammals are expected to be affected via sound generated by the primary components of the project ( i.e., pile driving and removal).

The project includes vibratory pile installation and removal, and impact pile driving. Source levels for these activities are based on reviews of measurements of the same or similar types and dimensions of piles available in the literature. Source levels for each pile size and activity each year are presented in table 6. Source levels for vibratory installation and removal of piles of the same diameter are assumed to be the same.

Table 6—Estimates of Mean Underwater Sound Levels * Generated During Vibratory and Impact Pile Installation and Vibratory Pile Removal

Pile driving method	Pile type	Pile size	dB RMS	dB peak	dB SEL	Reference
Impact	Steel Pipe Support Pile	36-in	193	210	183	Caltrans 2015, 2020.
	Steel Pipe Batter Pile
Vibratory Installation and Extraction	Steel Pipe Support	36-in	166	N/A	N/A	NMFS 2023 Calculations.
	Steel Pipe Batter
	Steel Pipe Fender	24-in	163	N/A	N/A	NMFS 2023 Calculations
	Steel Pipe Template
Note: dB peak = peak sound level; rms = root mean square; SEL = sound exposure level.
* All sound levels are referenced at 10 m.

TL is the decrease in acoustic intensity as an acoustic pressure wave propagates out from a source. TL parameters vary with frequency, temperature, sea conditions, current, source and receiver depth, water depth, water chemistry, and bottom composition and topography. The general formula for underwater TL is:

TL = B × Log10 ( R₁ / R₂ ),

where

TL = transmission loss in dB

B = transmission loss coefficient

R₁ = the distance of the modeled SPL from the driven pile, and

R₂ = the distance from the driven pile of the initial measurement

Absent site-specific acoustical monitoring with differing measured TL, a practical spreading value of 15 is used as the TL coefficient in the above formula. Site-specific TL data for the Sitka Sound are not available; therefore, the default coefficient of 15 is used to determine the distances to the Level A harassment and Level B harassment thresholds.

The ensonified area associated with Level A harassment is more technically challenging to predict due to the need to account for a duration component. Therefore, NMFS developed an optional User Spreadsheet tool to accompany the 2024 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 AUD INJ, which includes, but is not limited to, PTS. Inputs used in the optional User Spreadsheet tool, and the resulting estimated isopleths, are reported below. Table 8 provides the calculated Level A isopleths that are based on the 2018 Technical Guidance, which were presented in the proposed FRN (89 FR 56317, July 9, 2024) while table 9 provides the updated Level A isopleths using the 2024 Technical Guidance.

Table 7—User Spreadsheet Inputs

	Vibratory				Impact
	36-in haulout pier support pile	36-in haulout pier batter pile	24-in haulout pier fender pile	24-in template pile	36-in haulout pier support pile	36-in haulout pier batter pile
	Installation			Installation or removal	Installation
Spreadsheet Tab Used	A.1) Vibratory pile driving				E.1) Impact pile driving
Source Level (SPL)	166 RMS		163 RMS		183 SEL
Transmission Loss Coefficient	15
Weighting Factor Adjustment (kHz)	2.5				2
Activity Duration per day (minutes)	60	120	30	20
( print page 92634)
Number of strikes per pile					2,000	3,000
Number of piles per day	2		4	8	2
Distance of sound pressure level measurement	10

Table 8—Level A Harassment and Level B Harassment Isopleths and Associated Areas From Vibratory and Impact Pile Driving and Vibratory Removal, Using the 2018 Technical Guidance

Pile size/type	Method	Level A harassment: isopleths (m), areas (km2 )					Level B harassment: isopleth (m), areas (km2 )
		LF	MF	HF	PW	OW
Haulout Pier Support Pile
36-in Steel Pipe Pile	Vibratory Installation	23.4, ( 0.006)	2.1, ( 0.001)	34.5, ( 0.009)	14.2, ( 0.004)	1.0, ( 0.001)	11,659, ( 9.41)
	Impact Installation	2,516, ( 3.13)	89.5, ( 0.022)	2,997, ( 3.64)	1,347, ( 1.49)	98, ( 0.024)	1,585, ( 1.94)
Haulout Pier Batter Pile
36-in Steel Pipe Pile	Vibratory Installation	37.1, ( 0.010)	3.3, ( 0.003)	54.8, ( 0.013)	22.5, ( 0.006)	1.6, ( 0.001)	11,659, ( 9.41)
	Impact Installation	3,297, (3.97)	117.3, ( 0.029)	3,928, ( 4.64)	1,765, ( 2.24)	128, ( 0.032)	1,585, ( 1.94)
Haulout Pier Fender Pile
24-in Steel Pipe Pile	Vibratory Installation	14.7, ( 0.004)	1.3, ( 0.001)	21.8, ( 0.006)	9.0, ( 0.003)	0.6, ( 0.001)	7,356, ( 7.61)
Template Pile
24-in Steel Pipe Pile	Vibratory Installation and Removal	17.9, ( 0.005)	1.6, ( 0.001)	26.4, ( 0.008)	10.9, ( 0.003)	0.8, ( 0.001)	7,356, ( 7.61)

Table 9—Level A Harassment and Level B Harassment Isopleths and Associated Areas * From Vibratory and Impact Pile Driving and Vibratory Removal, Using the 2024 Technical Guidance

Pile size/type	Method	Level A harassment: isopleths (m), areas (km2 )					Level B harassment: isopleth (m), areas (km2 )
		LF	HF 1	VHF 2	PW	OW
Haulout Pier Support Pile
36-in Steel Pipe Pile	Vibratory Installation	31.5	12.1	25.8	40.6	13.7	11,659, ( 9.41)
	Impact Installation	2,507	319.9	3,880, ( 4.59)	2,227.3, ( 2.86)	830.3, ( 0.62)	1,585, ( 1.94)
Haulout Pier Batter Pile
36-in Steel Pipe Pile	Vibratory Installation	50.1	19.2	40.9	64.4	21.7	11,659, ( 9.41)
	Impact Installation	3,285.4	419.2	5,084.2 ( 5.73)	2,918.6 ( 3.55)	1,087.9 ( 1.01)	1,585, ( 1.94)
Haulout Pier Fender Pile
24-in Steel Pipe Pile	Vibratory Installation	19.9	7.6	16.3	25.6	8.6	7,356, ( 7.61)
Template Pile
24-in Steel Pipe Pile	Vibratory Installation and Removal	24.1	9.3	19.7	31.0	10.4	7,356, ( 7.61)
* Level A harassment areas (km2 ) have been presented only in cases where they are necessary to calculate updates to take by Level A harassment based on the 2024 Technical Guidance and methodology used in the Proposed IHA (89 FR 56317, July 9, 2024). In cases where the shutdown zone meets or exceeds the Level A harassment isopleth, take by Level A harassment was not reanalyzed.
1  Species that were considered Mid-Frequency cetaceans under the NMFS 2018 Technical Guidance are now considered High Frequency cetaceans.
2  Species that were considered High-Frequency cetaceans under the NMFS 2018 Technical Guidance are now considered Very High Frequency cetaceans.

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Marine Mammal Occurrence and Take Estimation

In this section we provide information about the occurrence of marine mammals, including density or other relevant information which will inform the take calculations.

Additionally, we describe how the occurrence information is synthesized to produce a quantitative estimate of the take that is reasonably likely to occur and authorized. Available information regarding marine mammal occurrence in the vicinity of the project area includes site-specific and nearby survey information and historic data sets. Prior data sets consulted included: (1) PSO monitoring completed at the project site on 8 days between September 20 and 29, 2023 during the geotechnical investigation preceding this project (Solstice, 2023), (2) PSO monitoring completed at the project site on 22 days between October and November 2017 during the Multipurpose Dock Project (TMC, 2017), (3) PSO monitoring completed at O'Connell Bridge (approximately 7 km to the east of the project site) on 4 days in June 2019 (CBS, 2019); (4) Land-based surveys conducted at Sitka's Whale Park completed weekly between September and May 1995—2000 (Straley and Pendell (2017)); and, (5) data available on the Global Biodiversity Information Facility (see CBS's application for further details).

To estimate take, CBS referred to the above referenced data sets to estimate total (Level A and Level B combined) takes per day for each species and multiplied this factor by the total number of construction days. NMFS finds it more appropriate to describe the take estimate inputs according to a daily occurrence probability in which groups per day and group size are estimated for each species and multiplied by the number of days of each type of pile driving activity. The equation used to estimate take by Level B harassment for all species is:

Exposure Estimate = group size × groups per day × days of pile driving activity.

CBS initially planned to implement shutdown zones for mid-frequency cetaceans and otariids (except Steller sea lions) that met or exceeded the Level A harassment isopleths for all activities. Using the 2018 Technical Guidance, the calculated Level A harassment zones during impact installation of 36-in steel piles, planned to occur on 30 construction days, exceeded the shutdown zones for phocids, high frequency cetaceans, and low frequency cetaceans. After applying the 2024 Technical Guidance, the calculated Level A harassment zones for this activity exceeded the shutdown zones for all species except killer whale. The best available abundance estimates for these species cover the general region of Sitka Sound and Silver Bay; therefore, we used proportional comparisons of predicted harassment areas to estimate predicted take by Level A harassment. In the absence of density data, best available monitoring data for the general area were used to estimate take by Level A harassment. Specifically, to calculate estimated take by Level A harassment for all species except California sea lion and Northern fur seal, which are expected to be very rare for the area) we proportionally compared, by hearing group, the portion of the largest Level A harassment area square kilometers (km² ) that exceeds the planned shutdown zone area (km² ) to the area (km² ) of the largest Level B harassment zone across that pile type (typically from vibratory pile driving). This ratio was then multiplied by the group size, daily sightings, and number of construction days, according to the equation below. For LF cetaceans, there was no meaningful change to the calculated Level A harassment isopleths after applying the 2024 Technical Guidance. For killer whales, the shutdown zone still exceeds the calculated Level A harassment isopleths. Therefore, the take estimates for these species (LF cetaceans and killer whale) have not changed. The estimated take by Level A harassment has been updated for all other species to account for larger Level A harassment isopleths which exceed the shutdown zone.

Take by Level A harassment = Level A harassment area (km² )/maximum Level B harassment area (km² ) × group size × groups per day × days of pile driving.

For Steller sea lions, during impact pile driving of 36-in steel pipe piles (batter and support), the shutdown zone will be established at 60 meters (m) rather than the larger Level A harassment isopleths due to practicability; local monitoring data suggests that Steller sea lions frequently occur within close proximity of the project site. The method described above did not produce an estimate of take by Level A harassment consistent with the best available data for this species at the project location. Therefore, recent monitoring data collected at this site (Solstice, 2023), were used to calculate take by Level A harassment. The proportion of Steller sea lions detected between 60 m and the largest level A zone (130 m based on 2018 Technical Guidance, updated to 1,087 m based on the 2024 Technical Guidance) was multiplied by group size, number of daily sightings, and the number of construction days when impact pile driving would occur according to this equation:

Take by Level A harassment = group size × groups per day × days of impact pile driving activity × proportion of Steller sea lions observed occurring between 60 m and the largest level A zone during geotechnical drilling.

Take estimates were rounded up to the nearest whole number in table 10.

Gray Whale

CBS requested take by Level B harassment of 31 gray whales, based on an estimated 1 gray whale every 2 days for 62 construction days. However, during weekly surveys conducted from September to May between 1995 and 2000, gray whales were infrequently observed in groups of 3 from Whale Park. As such, NMFS proposed 1 group of 3 gray whales every 14 construction days (62/14 construction days = 4.4 2-week construction week periods), resulting in 14 takes by Level B harassment (1 group × 3 gray whales × 4.4 construction periods = 13.2 takes by Level B harassment).

The shutdown zone exceeds the calculated Level A harassment zone except during impact pile driving of 36-in steel piles (support and battered), estimated across 30 construction days. As such, it is possible that gray whales may occur in the Level A harassment zone and stay long enough to incur AUD INJ before exiting during those 30 days. For 36-in support piles, the ratio of the Level A harassment area (km² ) that exceeds the shutdown zone to the maximum predicted Level B harassment area (km² ) is 0.06. This activity is estimated to take place on 20 construction days. For 36-in batter piles, the ratio of the Level A harassment area (km² ) that exceeds the shutdown zone to the Level B harassment area is 0.16. This activity is estimated to take place on 10 construction days. As such, 3 takes by Level A harassment are estimated [(0.06 × 4.4 construction periods × 1 group × 3 gray whales) + (0.16 × 4.4 construction periods × 1 group × 3 gray whales) = 2.9 takes by Level A harassment].

Any individuals exposed to the higher levels associated with the potential for AUD INJ closer to the source might also be behaviorally disturbed, however, for the purposes of quantifying take we do not count those exposures of one individual as a take by both Level A and ( print page 92636) Level B harassment. Therefore, takes by Level B harassment calculated as described above were further modified to deduct the authorized amount of take by Level A harassment. Therefore, NMFS has authorized 3 takes by Level A harassment and 11 takes by Level B harassment for gray whale, for a total of 14 takes. When allocating take across stocks, take estimates are rounded up to the nearest whole number.

Humpback Whale

CBS requested take by Level B harassment of 248 humpback whales, based on an estimated 4 humpback whales occurring every 1 construction day for 62 construction days. NMFS concurred with this take estimate, acknowledging that 2 groups of 2 humpback whales occurring each construction day is reasonable based on previous monitoring data (2 groups × 2 humpback whales × 62 construction days = 248 takes by Level B harassment of humpback whale).

The shutdown zone exceeds the calculated Level A harassment zone except during impact pile driving of 36-in steel piles (support and battered), estimated across 30 construction days. As such, it is possible that humpback whales may occur in the Level A harassment zone and stay long enough to incur AUD INJ before exiting. For 36-in support piles, the ratio of the Level A harassment area (km² ) that exceeds the shutdown zone to the maximum predicted Level B harassment area (km² ) is 0.06. This activity is estimated to take place on 20 construction days. For 36-in batter piles, the ratio of the Level A harassment area (km² ) that exceeds the shutdown zone to the Level B harassment area is 0.16. This activity is estimated to take place on 10 construction days. As such, 12 takes by Level A harassment are estimated [(0.06 × 20 construction days × 2 groups × 2 humpback whales) + (0.16 × 10 construction days × 2 groups × 2 humpback whales) = 11.2 takes by Level A harassment].

Any individuals exposed to the higher levels associated with the potential for AUD INJ closer to the source might also be behaviorally disturbed, however, for the purposes of quantifying take we do not count those exposures of one individual as a take by both Level A and Level B harassment. Therefore, takes by Level B harassment calculated as described above were further modified to deduct the amount of take by Level A harassment. Therefore, NMFS has authorized 12 takes by Level A harassment and 236 takes by Level B harassment for humpback whale, for a total of 248 takes. When allocating take across stocks, take estimates are rounded up to the nearest whole number.

Killer Whale

CBS requested take by Level B harassment of 31 killer whales, based on an estimated 1 killer whale occurring every 2 construction days for 62 construction days. However, because killer whales were unpredictably observed from Whale Park in groups of 4-8 during weekly surveys conducted from September to May between 1995 and 2000, NMFS found it more appropriate to propose 1 group of 8 killer whales every 7 construction days (62/7 construction days = 8.9 construction weeks), and has authorized the resulting 71 takes by Level B harassment (1 group × 8 killer whales × 8.9 construction weeks = 71 takes by Level B harassment). No takes by Level A harassment were requested or are authorized.

Pacific White-Sided Dolphin

CBS requested take by Level B harassment of 16 Pacific white-sided dolphin, based on an estimated 1 Pacific white-sided dolphin occurring every 4 construction days for 62 construction days. However, although a rare occurrence, Pacific white-sided dolphin were observed in groups averaging 4 individuals when sighted from Whale Park during weekly surveys conducted from September to May between 1995 and 2000. As such, NMFS finds it more appropriate to authorize 1 group of 4 Pacific white-sided dolphin every 14 construction days (62 ÷ 14 = 4.4 2-week construction periods), resulting in 18 authorized takes by Level B harassment (1 group × 4 Pacific white-sided dolphin × construction 4.4 periods = 17.6 takes by Level B harassment). No takes by Level A harassment were requested or proposed for authorization (89 FR 56317, July 9, 2024).

However, using the 2024 Technical Guidance, the re-calculated Level A harassment zone exceeds the planned shutdown zone during impact installation of 36-in steel piles (estimated to occur on 30 construction days). NMFS therefore finds it appropriate to authorize 4 takes by Level A harassment of Pacific white-sided dolphin, which is derived from the following: For 36-in support piles, the ratio of the Level A harassment area (km² ) that exceeds the shutdown zone to the maximum predicted Level B harassment area (km² ) is 0.003. This activity is estimated to take place on 20 construction days (20 construction days ÷ 14 days = 1.43 2-week construction periods). For 36-in batter piles, the ratio of the Level A harassment area (km² ) that exceeds the shutdown zone to the Level B harassment area is 0.01. This activity is estimated to take place on 10 construction days (10 construction days ÷ 14 days = 0.71 2-week periods). As such, 0.05 takes by Level A harassment are estimated [(0.0 × 1.43 construction days × 1 group × 4 Pacific white-sided dolphin) + (0.01 × 0.71 construction days × 1 group × 4 pacific white-sided dolphin) = 0.05 takes by Level A harassment]. The take by Level A harassment estimate was then increased to the minimum estimated group size of 4 for Pacific white-sided dolphin.

Any individuals exposed to the higher levels associated with the potential for AUD INJ closer to the source might also be behaviorally disturbed, however, for the purposes of quantifying take we do not count those exposures of one individual as a take by both Level A and Level B harassment. Therefore, takes by Level B harassment calculated as described above were further modified to deduct the amount of take by Level A harassment. Thus, NMFS has authorized 4 takes by Level A harassment and 14 takes by Level B harassment for Pacific white-sided dolphin, for a total of 18 takes. When allocating take across stocks, take estimates are rounded up to the nearest whole number.

Harbor Porpoise

CBS requested take by Level B harassment of 16 harbor porpoise, based on an estimated 1 harbor porpoise occurring every 4 construction days for 62 construction days. However, harbor porpoise were rarely observed from Whale Park in groups of five during weekly surveys conducted from September to May between 1995 and 2000. As such, NMFS finds it more appropriate to authorize 1 group of 5 harbor porpoise every 14 construction days (62 ÷ 14 construction days = 4.4 2-week construction week periods), resulting in 22 takes by Level B harassment (1 group × 5 harbor porpoises × 4.4 construction periods = 22 takes by Level B harassment).

During impact pile driving of 36-in steel piles, estimated across 30 construction days, the expected Level A harassment zone is larger than the planned shutdown zone (see Figure 1 of the Marine Mammal Mitigation and Monitoring Plan). As such, it is possible that harbor porpoise may enter the Level A harassment zone and stay long enough to incur AUD INJ before exiting. For 36-in support piles, the ratio of the Level A harassment area (km² ) that exceeds the shutdown zone to the maximum predicted Level B harassment ( print page 92637) area (km² ) is 0.49 after applying the 2024 Technical Guidance (increased from 0.38). This activity is estimated to take place on 20 construction days (20 construction days ÷ 14 days = 1.43 2-week construction periods). For 36-in batter piles, the ratio of the portion of the Level A harassment area that exceeds the shutdown zone area (km² ) to the maximum predicted Level B harassment area is 0.60 after applying the 2024 Technical Guidance (increased from 0.48). This activity is estimated to take place on 10 construction days (10 construction days ÷ 14 days = 0.71 2-week construction periods). As such, six instead of five takes by Level A harassment are authorized [(0.49 × 1 group × 5 harbor porpoise × 1.43 2-week construction periods) + (0.60 × 1 group × 5 harbor porpoises × 0.71 2-week construction periods) = 5.6 takes by Level A harassment].

Any individuals exposed to the higher levels associated with the potential for AUD INJ closer to the source might also be behaviorally disturbed; however, for the purposes of quantifying take we do not count those exposures of one individual as a take by both Level A and Level B harassment. Therefore, takes by Level B harassment calculated as described above were further modified to deduct the amount of take by Level A harassment. Thus, NMFS has authorized 6 takes by Level A harassment and 16 takes by Level B harassment for harbor porpoise, for a total of 22 takes.

Steller Sea Lion

CBS requested take by Level B harassment of 496 Steller sea lions, based on an estimated 8 Steller sea lions occurring every 1 construction day for 62 construction days. NMFS concurs with this take estimate, acknowledging that four groups of two Steller sea lions occurring each construction day is reasonable based on previous monitoring data (2 groups × 4 Steller sea lion × 62 construction days = 496 takes by Level B harassment of Steller sea lion).

During impact pile driving of 36-in steel piles, estimated across 30 construction days, the expected Level A harassment zone is larger than the shutdown zone. As such, it is possible that Steller sea lion may enter the Level A harassment zone and stay long enough to incur AUD INJ before exiting. For 36-in support piles, the ratio of the Level A harassment area that exceeds the planned shutdown zone (km² ) to the maximum predicted Level B harassment area (km² ) for is 0.07 after applying the 2024 Technical Guidance (increased from 0.001). This activity is estimated to take place on 20 construction days. For 36-in batter piles, the ratio of the Level A harassment area (km² ) to the maximum predicted Level B harassment area is 0.1 after applying the 2024 Technical Guidance (increased from 0.002). This activity is estimated to take place on 10 construction days. As such, one take by Level A harassment was estimated [(0.07 × 20 construction days × 2 groups × 4 Steller sea lion × 20 construction days) + (0.1 × 10 construction days × 2 groups × 4 Steller sea lion × 10 construction days) = 19.2 takes by Level A harassment].

However, the 19.2 takes by Level A harassment estimated using the method described above likely does not reflect the true occurrence of Steller sea lion in the project area. Based on monitoring data collected during geotechnical survey conducted to inform CBS's IHA application, Steller sea lions are expected to disproportionally occur within close proximity to the project site. All (100 percent) Steller sea lions documented during that survey were observed between 60 m and 1,087.9 m, which corresponds to the Level A zones during impact pile driving of 36-in piles after applying the 2024 Technical Guidance. These scenarios may occur on up to 30 construction days. Therefore 240 additional takes by Level A harassment are anticipated (2 groups of 4 Steller sea lion × 30 construction days × 1 = 240 takes by Level A harassment).

Any individuals exposed to the higher levels associated with the potential for AUD INJ closer to the source might also be behaviorally disturbed, however, for the purposes of quantifying take we do not count those exposures of one individual as a take by both Level A and Level B harassment. Therefore takes by Level B harassment calculated as described above are further modified to deduct the authorized amount of take by Level A harassment. Thus, NMFS has authorized 240 takes by Level A harassment and 256 takes by Level B harassment for Steller sea lion, for a total of 496 takes.

California Sea Lion

CBS requested take by Level B harassment of five California sea lions, based on an estimated one California sea lion occurring every month that construction is planned (October to March = 5 months) to account for the unlikely but small possibility that California sea lion could occur in the project area. However, NMFS finds it more appropriate to estimate take by Level B harassment according to duration of in-water work (62 construction days/30 days in 1 month = 2.06 construction months). As such, NMFS authorized take by Level B harassment of three California sea lion (1 group × 1 California sea lion × 2.06 construction months = 2.06 takes by Level B harassment of California sea lion). After applying the 2024 Technical Guidance, calculated Level A harassment isopleths increased to 830 m and 1,087 m during impact pile driving activities, which is much further than the distances at which we estimate this species can reliably be observed by PSOs. As such NMFS has authorized a maximum total of 3 takes by either Level B or Level A harassment.

Northern Fur Seal

CBS requested take by Level B harassment of five northern fur seals, based on an estimated one northern fur seal occurring every month that construction is planned (October-March = 5 months) to account for the unlikely but small possibility that northern fur seals could occur in the project area. However, NMFS finds it more appropriate to estimate take by Level B harassment according to the duration of in-water work (62 construction days/30 days in 1 month = 2.06 months). As such, NMFS authorized take by Level B harassment of three northern fur seals (1 group × 1 northern fur seal × 2.06 construction months = 2.06 takes by Level B harassment of northern fur seal). After applying the 2024 Technical Guidance, calculated Level A harassment isopleths increased to 830 m and 1,087 m during impact pile driving activities, which is much further than the distances at which we estimate this species can reliably be observed by PSOs. As such, NMFS has authorized a maximum total of 3 takes by either Level B or Level A harassment.

Harbor Seal

CBS requested take by Level B harassment of 124 harbor seals, based on an estimated 2 harbor seals occurring every 2 construction days for 62 construction days. However, because harbor seals are frequently documented in the project area, NMFS finds it more appropriate to authorize 186 takes by Level B harassment of harbor seal, based on the maximum groups size of 3 documented at the project site in 2017 (1 group × 3 harbor seal × 62 construction days = 186 takes by Level B harassment).

During impact pile driving of 36-in steel piles, estimated across 30 construction days, the expected Level A harassment zone is larger than the planned shutdown zone. As such, it is possible that harbor seal may enter the Level A harassment zone and stay long enough to incur AUD INJ before exiting. ( print page 92638) For 36-in support piles, the ratio of the Level A harassment area (km² ) that exceeds the planned shutdown zone to the Level B harassment area (km² ) is 0.27 after applying the 2024 Technical Guidance (increased from 0.16). This activity is estimated to take place on 20 construction days. For 36-in batter piles, the ratio of the Level A harassment area that exceeds the shutdown zone area (km² ) to the maximum predicted Level B harassment area is 0.24 after applying the 2024 Technical Guidance (increased from 0.23). This activity is estimated to take place on 10 construction days. As such, 34 takes by Level A harassment are estimated [(0.27 × 20 construction days × 1 group × 3 harbor seals) + (0.34 × 10 construction days × 1 group × 3 harbor seals) = 52.8 takes by Level A harassment].

Any individuals exposed to the higher levels associated with the potential for AUD INJ closer to the source might also be behaviorally disturbed, however, for the purposes of quantifying take we do not count those exposures of one individual as a take by both Level A and Level B harassment. Therefore, takes by Level B harassment calculated as described above are further modified to deduct the amount of take by Level A harassment. Thus, NMFS has authorized 53 takes by Level A harassment and 133 takes by Level B harassment for harbor seal, for a total of 186 takes.

The total takes authorized for all species are summarized in table 10 below, which reflects changes incorporated after applying the 2024 Technical Guidance. Take by Level A harassment is authorized for a total of 3 individuals for gray whale, 12 individuals for humpback whale, 4 individuals for Pacific white-sided dolphin (increased from 0), 6 individuals for harbor porpoise (increased from 5), 240 individuals for Steller sea lion (increased from 88), 53 (increased from 34) individuals for harbor seal, 3 individuals of California sea lion (increased from 0), and 3 individuals of Northern fur seal (increased from 0).

Table 10—Take by Stock and Harassment Type and as a Percentage of Stock Abundance Presented in Proposed FRN (89 FR 56317, July 9, 2024) and as Authorized Based on the Updated 2024 Technical Guidance

Species	Stock	Proposed authorized take 1		Authorized take 1		Authorized take as a percentage of stock abundance
		Level B harassment	Level A harassment	Level B harassment	Level A harassment
Gray Whale	Eastern N. Pacific	11	3	11	3	<1
Humpback Whale 2	Mexico—North Pacific	5	1	5	1	<1
	Hawai'i	231	11	231	11	2.2
Killer Whale 3	ENP Alaska Resident	44	0	44	0	2.3
	ENP Northern Resident	7	0	7	0	2.3
	ENP Gulf of Alaska, Aleutian Islands, and Bering Sea	14	0	14	0	2.4
	West Coast Transient	8	0	8	0	2.3
Pacific white-sided dolphin	North Pacific	18	0	14	4	<1
Harbor Porpoise	Yakutat/Southeast Alaska Offshore Waters	17	5	16	6	(4 )
Steller sea lion 5	Western DPS	5	1	4	3	<1
	Eastern DPS	402	88	252	237	1.3
California sea lion	United States	3	0	3		<1
Northern fur seal	Eastern Pacific	3	0	3		<1
Harbor Seal	Sitka/Chatham Strait	152	34	133	53	1.4
1  When allocating take across stocks, take estimates are rounded up to the nearest whole number.
2  2 percent of take by Level A and Level B harassment of humpback whales are allocated to the Mexico DPS according to NMFS, 2021.
3  Take by level B harassment of killer whale is allocated across stocks according to the proportion of the stock compared to total number of animals in all four stocks that could occur in the project area: Alaska Residents, 60.7 percent; Northern Residents, 9.6 percent; Gulf of Alaska, Aleutian Islands, and Bering Sea: 18.6 percent ; West Coast Transient, 11.1 percent.
4  A reliable abundance estimate for this stock is currently unavailable.
5  1.2 percent take by Level A and Level B harassment of Steller sea lions are allocated to the Western DPS according to Hastings et al. (2020).

Mitigation

In order to issue an IHA under section 101(a)(5)(D) of the MMPA, NMFS must set forth the permissible methods of taking pursuant to the activity, and other means of effecting the least practicable impact on the species or stock and its habitat, paying particular attention to rookeries, mating grounds, and areas of similar significance, and on the availability of the species or stock for taking for certain subsistence uses (latter not applicable for this action). NMFS regulations require applicants for incidental take authorizations to include information about the availability and feasibility (economic and technological) of equipment, methods, and manner of conducting the activity or other means of effecting the least practicable adverse impact upon the affected species or stocks, and their habitat (50 CFR 216.104(a)(11)).

In evaluating how mitigation may or may not be appropriate to ensure the least practicable adverse impact on ( print page 92639) species or stocks and their habitat, as well as subsistence uses where applicable, NMFS considers two primary factors:

(1) The manner in which, and the degree to which, the successful implementation of the measure(s) is expected to reduce impacts to marine mammals, marine mammal species or stocks, and their habitat, as well as subsistence uses. This considers the nature of the potential adverse impact being mitigated (likelihood, scope, range). It further considers the likelihood that the measure will be effective if implemented (probability of accomplishing the mitigating result if implemented as planned), the likelihood of effective implementation (probability implemented as planned); and

(2) The practicability of the measures for applicant implementation, which may consider such things as cost, and impact on operations.

Mitigation for Marine Mammals and Their Habitat

Shutdown Zones —For all pile driving activities, CBS plans to implement shutdowns within designated zones. The purpose of a shutdown zone is generally to define an area within which shutdown of the activity will occur upon sighting of a marine mammal (or in anticipation of an animal entering the defined area). Shutdown zones vary based on the activity type and marine mammal species or hearing group (table 11 and table 12). In most cases, the shutdown zones are based on the estimated Level A harassment isopleth distances for each hearing group. However, in cases where it would be challenging to detect marine mammals at the Level A harassment isopleth ( e.g., for all species during impact pile driving except killer whale, after application of the 2024 Technical Guidance) and/or frequent shutdowns would create practicability concerns ( e.g., Steller sea lions during impact pile driving), smaller shutdown zones are planned (table 12).

Construction supervisors and crews, PSOs, and relevant CBS staff must avoid direct physical interaction with marine mammals during construction activity. If a marine mammal comes within 10 m of such activity, operations must cease and vessels must reduce speed to the minimum level required to maintain steerage and safe working conditions, as necessary to avoid direct physical interaction. If an activity is delayed or halted due to the presence of a marine mammal, the activity may not commence or resume until, either the animal has voluntarily exited and been visually confirmed beyond the shutdown zone indicated in table 11, or 15 minutes have passed without re-detection of the animal.

Finally, construction activities must be halted upon observation of a species for which incidental take is not authorized or a species for which incidental take has been authorized but the authorized number of takes has been met entering or within any harassment zone. If a marine mammal species not covered under this IHA enters a harassment zone, all in-water activities will cease until the animal leaves the zone or has not been observed for at least 15 minutes, and NMFS would be notified about species and precautions taken. Pile driving will proceed if the unauthorized species is observed leaving the harassment zone or if 15 minutes have passed since the last observation.

Table 11—Shutdown Zones Presented in the Proposed FRN

[89 FR 56317, July 9, 2024]

Pile size/type	Method	Shutdown zones (m)
		LF	MF	HF	PW	OW
						Steller sea lion	Other OW
Haulout Pier Support Pile
36-in Steel Pipe Pile	Vibratory Installation	30	10	40	20	10	10
	Impact Installation	2,000	90	300	130	60	100
Haulout Pier Batter Pile
36-in Steel Pipe Pile	Vibratory Installation	40	10	60	30	10	10
	Impact Installation	2,000	120	300	130	60	130
Haulout Pier Fender Pile
24-in Steel Pipe Pile	Vibratory Installation	20	10	30	10	10	10
Template Pile
24-in Steel Pipe Pile	Vibratory Installation and removal	20	10	30	20	10	10

Table 12—Final Shutdown zones based on the 2024 Technical Guidance

Pile size/type	Method	Shutdown zones (m)
		LF	HF 1		VHF 2	PW	OW
			Killer whale	Other HF			Steller sea lion	Other OW
Haulout Pier Support Pile
36-in Steel Pipe Pile	Vibratory Installation	3  40	3  20	3  20	40	3  50	3  20	3  20
	Impact Installation	2,000	3  320	4  300	300	130	60	4  130
Haulout Pier Batter Pile
36-in Steel Pipe Pile	Vibratory Installation	3  60	3  20	3  20	60	3  70	3  30	3  30
( print page 92640)
	Impact Installation	2,000	3  420	4  300	300	130	60	130
Haulout Pier Fender Pile
24-in Steel Pipe Pile	Vibratory Installation	20	10	10	30	3  30	10	10
Template Pile
24-in Steel Pipe Pile	Vibratory Installation and removal	3  30	10	10	30	40	20	20
1  Species that were considered Mid-Frequency cetaceans under the NMFS 2018 Technical Guidance are now considered High Frequency cetaceans.
2  Species that were considered High-Frequency cetaceans under the NMFS 2018 Technical Guidance are now considered Very High Frequency cetaceans.
3  Shutdown zones have been increased to meet the calculated Level A harassment isopleths using the 2024 Technical Guidance.
4  Shutdown zones have been increased to the extent that this hearing group is expected to be reliably observable.