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Federal Register / Vol. 86, No. 86 / Thursday, May 6, 2021 / Rules and Regulations
For more detail concerning these groups and associated frequency ranges, please see NMFS 2018 for a review of available information. Five marine mammal species three cetacean and two phocid pinniped species have the reasonable potential to co-occur with the planned construction activities.
Please refer to Table 1. Of the cetacean species that may be present, one is classified as a LF cetacean i.e., humpback whale one is classified as a mid-frequency cetacean i.e., bottlenose dolphin, and one is classified as a highfrequency cetacean i.e., harbor porpoise.

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Potential Effects of Specified Activities on Marine Mammals and Their Habitat The effects of underwater noise from the Navys activities have the potential to result in behavioral harassment of marine mammals in the vicinity of the survey area. The proposed rule 85 FR
83001; December 21, 2020 included a discussion of the effects of anthropogenic noise on marine mammals and the potential effects of underwater noise from the Navys construction activities on marine mammals and their habitat. That information and analysis is incorporated by reference into this final rule and is not repeated here; please refer to the proposed rule 85 FR 83001; December 21, 2020.
The Estimated Take section in this document includes a quantitative analysis of the number of individuals that are expected to be taken by this activity. The Negligible Impact Analysis and Determination section considers the content of this section, the Estimated Take section, and the Mitigation Measures section, to draw conclusions regarding the likely impacts of these activities on the reproductive success or survivorship of individuals and how those impacts on individuals are likely to impact marine mammal species or stocks. We also provided additional description of sound sources in our proposed rule 85 FR 83001; December 21, 2020.
Estimated Take This section provides an estimate of the number of incidental takes that may be authorized, which will inform both NMFS consideration of small numbers and the negligible impact determination.
Harassment is the only type of take expected to result from these activities.
Except with respect to certain activities
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not pertinent here, section 318 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 be by Level B
harassment only, in the form of disruption of behavioral patterns and potential TTS for individual marine mammals resulting from exposure to pile driving and removal. Based on the nature of the activity and the anticipated effectiveness of the mitigation measures i.e., shutdown zones discussed in detail below in the Mitigation Measures section, Level A
harassment is neither anticipated nor will be authorized.
As described previously, mortality is neither anticipated nor will be authorized for this activity. Below we describe how the take is estimated.
Generally speaking, we estimate take by considering: 1 Acoustic thresholds above which NMFS believes the best available science indicates marine mammals will be behaviorally harassed or incur some degree of permanent hearing impairment; 2 the area or volume of water that will be ensonified above these levels in a day; 3 the density or occurrence of marine mammals within these ensonified areas;
and, 4 the number of days of activities.
We note that while these factors can contribute to a basic calculation to provide an initial prediction of takes, additional information that can qualitatively inform take estimates is also sometimes available e.g., previous monitoring results or average group size. Below, we describe the factors considered here in more detail and present the take estimate.
Acoustic Thresholds NMFS recommends the use of acoustic thresholds that identify the received level of underwater sound above which exposed marine mammals would be reasonably expected to be behaviorally harassed equated to Level B harassment or to incur PTS of some degree equated to Level A harassment.
Level B Harassment for non-explosive sourcesThough significantly driven by
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received level, the onset of behavioral disturbance from anthropogenic noise exposure is also informed to varying degrees by other factors related to the source e.g., frequency, predictability, duty cycle, the environment e.g., bathymetry, and the receiving animals hearing, motivation, experience, demography, behavioral context and can be difficult to predict Southall et al.
2007, Ellison et al. 2012. Based on what the available science indicates and the practical need to use a threshold based on a factor that is both predictable and measurable for most activities, NMFS
uses a generalized acoustic threshold based on received level to estimate the onset of behavioral harassment. NMFS
predicts that marine mammals are likely to be behaviorally harassed in a manner we consider Level B harassment when exposed to underwater anthropogenic noise above received levels of 120 dB re 1 mPa rms microPascal, root mean square for continuous e.g., vibratory pile-driving, drilling and above 160 dB
re 1 mPa rms for non-explosive impulsive e.g., seismic airguns or intermittent e.g., scientific sonar sources.
The Navys construction includes the use of continuous vibratory pile driving and impulsive impact pile driving sources, and therefore the 120
and 160 dB re 1 mPa rms are applicable.
Level A harassment for non-explosive sourcesNMFS Technical Guidance for Assessing the Effects of Anthropogenic Sound on Marine Mammal Hearing Version 2.0
Technical Guidance, 2018 identifies dual criteria to assess auditory injury Level A harassment to five different marine mammal groups based on hearing sensitivity as a result of exposure to noise from two different types of sources impulsive or nonimpulsive. The Navys planned construction includes the use of impulsive impact pile driving and non-impulsive vibratory pile driving 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 https www.fisheries.noaa.gov/
national/marine-mammal-protection/
marine-mammal-acoustic-technicalguidance.

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