2024-15859. Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to the Pillar Point Harbor Johnson Pier Expansion and Dock Replacement Project in Princeton, California

Table 1—Species 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 Carnivora—Superfamily Pinnipedia
Family Otariidae (eared seals and sea lions):
California Sea Lion	Zalophus californianus	United States	-/-, N	257,606 (N/A, 233,515, 2014)	14,011	>321
Family Phocidae (earless seals):
Harbor Seal	Phoca vitulina	California	-/-, N	30,968 (N/A, 27,348, 2012)	1,641	43
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: www.nmfs.noaa.gov/​pr/​sars/​. 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.

A detailed description of the of the species likely to be affected by the Johnson Pier 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 (88 FR 12334, February 27, 2023); 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) 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 2.

Table 2—Marine Mammal Hearing Groups

[NMFS, 2018]

Hearing group	Generalized hearing range *
Low-frequency (LF) cetaceans (baleen whales)	7 Hz to 35 kHz.
Mid-frequency (MF) cetaceans (dolphins, toothed whales, beaked whales, bottlenose whales)	150 Hz to 160 kHz.
High-frequency (HF) cetaceans (true porpoises, Kogia, river dolphins, Cephalorhynchid, Lagenorhynchus cruciger & L. australis)	275 Hz to 160 kHz.
Phocid pinnipeds (PW) (underwater) (true seals)	50 Hz to 86 kHz.
Otariid pinnipeds (OW) (underwater) (sea lions and fur seals)	60 Hz to 39 kHz.
* Represents the generalized hearing range for the entire group as a composite ( i.e., all species within the group), where individual species' hearing ranges are typically not as broad. Generalized hearing range chosen based on ~65 dB threshold from normalized composite audiogram, with the exception for lower limits for LF cetaceans (Southall et al., 2007) and PW pinniped (approximation).

The pinniped functional hearing group was modified from Southall et al. (2007) on the basis of data indicating that phocid species have consistently demonstrated an extended frequency range of hearing compared to otariids, especially in the higher frequency range (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

The effects of underwater noise from SMCHD's construction activities have the potential to result in behavioral harassment of marine mammals in the vicinity of the construction area. The notice of proposed IHA (88 FR 12334, February 27, 2023) included a discussion of the effects of anthropogenic noise on marine mammals and the potential effects of underwater noise from impact and vibratory pile driving on marine mammals and their habitat. That information and analysis is incorporated by reference into this final IHA determination and is not repeated here; please refer to the notice of proposed IHA (88 FR 12334, February 27, 2023).

Estimated Take of Marine Mammals

This section provides an estimate of the number of incidental takes authorized through this IHA, which informs both NMFS' consideration of “small numbers,” and the negligible impact determinations.

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

Authorized takes will primarily be by Level B harassment, as noise generated during construction activities ( i.e., impact and vibratory pile driving) 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. The mitigation and monitoring measures are expected to minimize the severity of the taking to the extent practicable.

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

For acoustic impacts, generally speaking, we estimate take by considering: (1) acoustic thresholds above which NMFS believes the best available science indicates marine mammals would be behaviorally harassed or incur some degree of permanent hearing impairment; (2) the area or volume of water that would 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 permanent threshold shift (PTS) of some degree (equated to Level A harassment).

Level B Harassment —Though significantly driven by received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source or exposure context ( e.g., frequency, predictability, duty cycle, duration of the exposure, signal-to-noise ratio, distance to the source), the environment ( e.g., bathymetry, other noises in the area, predators in the area), and the receiving animals (hearing, motivation, experience, demography, life stage, depth) and can be difficult to predict ( e.g., Southall et al., 2007, 2021; Ellison et al., 2012). Based on what the available science indicates and the practical need to use a threshold based on a metric that is both predictable and measurable for most activities, NMFS typically uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS generally predicts that marine mammals are likely to be behaviorally harassed in a manner considered to be Level B harassment when exposed to underwater anthropogenic noise above root-mean-squared pressure received levels (RMS SPL) of 120 dB (referenced to 1 micropascal (re 1 μPa)) for continuous non-impulsive ( e.g., vibratory pile driving, drilling) and above RMS SPL 160 dB re 1 μPa for non-explosive impulsive ( e.g., impact pile driving) 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 communication, predators, prey) may result in changes in behavior patterns that would not otherwise occur.

SMCHD's planned activity includes the use of continuous non-impulsive (vibratory pile installation and extraction) 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' 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). SMCHD's planned activity includes the use of non-impulsive (vibratory pile installation and extraction) and impulsive (impact pile driving) sources.

These thresholds are provided in Table 3. 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 3—Thresholds Identifying the Onset of Permanent Threshold Shift

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

Ensonified Area

Here, we describe operational and environmental parameters of the activity that 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. Pile driving generates underwater noise that can potentially result in disturbance to marine mammals in the project area. The maximum (underwater) area ensonified is determined by the topography of the Pillar Point inner harbor, including hard structure breakwaters that bound the inner harbor and preclude sound from transmitting into the outer harbor. Additionally, vessel traffic and other commercial and industrial activities in the project area may contribute to elevated background noise levels, which may mask sounds produced by the project.

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

TL = B * Log₁₀ (R₁ /R₂), where

TL = transmission loss in dB

B = transmission loss coefficient; for practical spreading equals 15

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

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

This formula neglects loss due to scattering and absorption, which is assumed to be zero here. The degree to which underwater sound propagates away from a sound source is dependent on a variety of factors, most notably the water bathymetry and presence or absence of reflective or absorptive conditions including in-water structures and sediments. Spherical spreading occurs in a perfectly unobstructed (free-field) environment not limited by depth or water surface, resulting in a 6 dB reduction in sound level for each doubling of distance from the source (20*log[range]). Cylindrical spreading occurs in an environment in which sound propagation is bounded by the water surface and sea bottom, resulting in a reduction of 3 dB in sound level for each doubling of distance from the source (10*log[range]). A practical spreading value of 15 is often used under conditions, such as the project site, where water increases with depth as the receiver moves away from the shoreline, resulting in an expected propagation environment that would lie between spherical and cylindrical spreading loss conditions. Practical spreading loss is assumed here.

The intensity of pile driving sounds is greatly influenced by factors such as the type of piles, hammers, and the physical environment in which the activity takes place. In order to calculate the distances to the Level A harassment and the Level B harassment sound thresholds for the methods and piles being used in this project, NMFS used acoustic monitoring data from other locations to develop proxy source levels for the various pile types, sizes and methods (Table 4). Generally, we choose source levels from similar pile types from locations ( e.g., geology, bathymetry) similar to the project. At this time, NMFS is not aware of reliable source levels available for fiberglass piles using vibratory pile installation; therefore, source levels for timber pile driving were used as a proxy. While vibratory extraction of concrete piles has been measured only for 20-in piles, NMFS has conservatively applied this source level to vibratory extraction of 14-in concrete piles.

For this project, one impact and one vibratory hammer may operate simultaneously. Because an impact hammer is not a continuous source, there is no adjustment needed in the source levels needed to calculate the Level A harassment or Level B harassment zones. In the event of concurrent activities, the Level A harassment zones would be equivalent to those produced by the impact hammer alone, and the Level B harassment zone would be the largest zone. Due to the confined nature of the Project Area, these zones are sometimes identical. Therefore, no separate analysis of concurrent activities was conducted for this project.

Table 4—Project Sound Source Levels Normalized to 10 Meters

Pile type	Pile size (inch)	Method	Peak SPL (re 1 μPa (rms))	RMS SPL (re 1 μPa (rms))	SEL (re 1 μPa (rms))	Source
Concrete	16	Impact	193	168	160	Caltrans 2020.
Concrete	24	Impact	188	176	166	Caltrans 2020.
Fiberglass	16	Vibratory	NA	162	NA	Caltrans 2020.
Concrete or Timber	14	Vibratory extraction	NA	162	NA	NAVFAC SW 2022.

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 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 like 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. The resulting isopleths are reported in Table 5, below.

Table 5—Calculated Level A Harassment and Level B Harassment Isopleths for Impact Pile Driving

Method	Source	Level A harassment— radius to isopleth (m)		Level B Harassment— radius to isopleth (m)
		Phocids	Otariids
Impact	16-in Concrete	96	7	35
	24-in Concrete	290	22	117
Vibratory	16-in Fiberglass	23	2	* 6,265
	14-in Concrete or Timber	23	2	* 6,265
* The calculated distance to the Level B harassment threshold of 120 dB is 6,265m. However, sound propagation will be limited by the solid breakwaters surrounding the inner harbor and therefore the harassment zone will be limited to the area within the inner harbor breakwaters.

The maximum Level A harassment zones are expected to occur during impact driving of 24-in concrete piles, extending out to 290 m from the source pile for harbor seals, and out to 22 m from the source pile for sea lions. The 290 m zone fills the inner harbor area surrounded by the breakwaters, as shown in Figure 7 of the IHA application. The largest Level B harassment zone would occur during vibratory pile driving and extraction, and would encompass the entire inner harbor basin.

Marine Mammal Occurrence and Take Calculation and Estimation

In this section, we provide information about the occurrence of marine mammals, including density or other relevant information that informs the take calculations, and describe how the information provided is synthesized to produce a quantitative estimate of the take that is reasonably likely to occur.

California Sea Lion

California sea lions regularly occur on rocks, buoys, and other structures. California sea lions were observed within the Project area during the field survey (Rincon, 2021). Breeding and pupping are not known to occur in the Project area. Based on anecdotal statements from Pillar Point Harbor operations staff, California sea lions could occur within the inner harbor area on a daily basis. Past observations indicate that sea lions rarely haul out within the Project area (Meyers, 2022). Because no density estimates are available for the species in this area, the SMCHD estimated that two California sea lions could be present within the Pillar Point Inner Harbor each day. Based on this information, NMFS has similarly estimated that two California sea lions may be taken by Level B harassment each day of pile driving. This equates to 260 Level B harassment takes over 130 project days. Therefore, the SMCHD requested, and NMFS has authorized, 260 takes by Level B harassment of California sea lion (Table 6).

The largest Level A harassment zone for otariids extends approximately 23 m from the source during impact driving of a 24-in concrete pile (Table 5). SMCHD has conservatively assumed that 1 sea lion may occur within the 23 m zone for a duration long enough to be taken by Level A harassment every 2 days of impact pile driving, equating to 40 takes over 80 project days. Therefore, the SMCHD requested, and NMFS has authorized, 40 takes by Level A harassment of California sea lion (Table 6).

Harbor Seal

Harbor seals were observed within the Project area during the field survey and have been frequently documented within Pillar Point Harbor (Rincon, 2021). Breeding and pupping are not known to occur in the Project area. Based on anecdotal statements from Pillar Point Harbor operations staff, harbor seals could occur within the inner harbor area on a daily basis. Past observations indicate that harbor seals rarely haul out within the Project area (Meyers, 2022). Because no density estimates are available for the species in this area, the SMCHD estimated that two harbor seals could be present within the Pillar Point Inner Harbor each day. Based on this information, NMFS has similarly estimated that two harbor seals may be taken by Level B harassment each day of vibratory pile driving, and up to 10 percent of those individuals may be taken by Level A harassment each day. On days with impact driving, up to two harbor seals may be taken by Level A harassment, with no Level B harassment due to the Level A harassment zone extending to the boundaries of the inner harbor. This equates to 90 Level B harassment takes and 170 Level A harassment takes over 130 project days. Therefore, SMCHD requested, and NMFS has authorized, 90 takes by Level B harassment, and 170 takes by Level A harassment of harbor seals (Table 6).

Table 6—Authorized Amount of Taking, by Level A Harassment and Level B Harassment, by Species and Stock and as a Percentage of Stock Abundance

Common name	Stock	Level A harassment	Level B harassment	Total	Percent of stock
California sea lion	United States	40	260	300	0.12
Harbor seal	California	170	90	260	0.84