Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Hilcorp Alaska, LLC Production Drilling Support in Cook Inlet, Alaska, 79529-79557 [2024-22293]

Agencies

• DEPARTMENT OF COMMERCE
• National Oceanic and Atmospheric Administration

[Federal Register Volume 89, Number 189 (Monday, September 30, 2024)]
[Notices]
[Pages 79529-79557]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-22293]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[RTID 0648-XE199]


Takes of Marine Mammals Incidental to Specified Activities; 
Taking Marine Mammals Incidental to Hilcorp Alaska, LLC Production 
Drilling Support in Cook Inlet, Alaska

AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION: Notice; issuance of an incidental harassment authorization.

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SUMMARY: In accordance with the regulations implementing the Marine 
Mammal Protection Act (MMPA) as amended, notification is hereby given 
that NMFS has issued an incidental harassment authorization (IHA) to 
Hilcorp Alaska, LLC (Hilcorp) to incidentally harass marine mammals 
during production drilling support activities in Cook Inlet, Alaska.

DATES: This authorization is effective from September 24, 2024 through 
September 23, 2025.

ADDRESSES: 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-oil-and-gas. In 
case of problems accessing these documents, please call the contact 
listed below.

FOR FURTHER INFORMATION CONTACT: Reny Tyson Moore, Office of Protected 
Resources, NMFS, (301) 427-8401.

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 IHA 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

[[Page 79530]]

``mitigation''); and requirements pertaining to the monitoring and 
reporting of the takings. The definitions of all applicable MMPA 
statutory terms cited above are included in the relevant sections 
below.

Summary of Request

    On August 2, 2023, NMFS received a request from Hilcorp for an IHA 
to take marine mammals incidental to production drilling support 
activities in Cook Inlet, Alaska. Following NMFS' review of the 
application, Hilcorp submitted revised versions on September 29, 2023, 
December 27, 2023, February 29, 2024, and April 8, 2024. The 
application was deemed adequate and complete on April 12, 2024, and the 
notice for the proposed IHA was published in the Federal Register on 
July 24, 2024 (89 FR 60164). Hilcorp's request is for take of 12 
species of marine mammals, by Level B harassment. Neither Hilcorp nor 
NMFS expect serious injury or mortality to result from this activity 
and, therefore, an IHA is appropriate.
    NMFS previously issued two consecutive IHAs to Hilcorp for similar 
work (87 FR 62364, October 1, 2022). Hilcorp complied with all the 
requirements (e.g., mitigation, monitoring, and reporting) of the 
previous IHAs, and information regarding their monitoring results may 
be found in the Potential Effects of Specified Activities on Marine 
Mammals and their Habitat section of this notice.
    There are no changes from the proposed IHA to the final IHA other 
than the addition of some clarifying language and some minor 
typographical corrections.

Description of Specified Activity

    Hilcorp plans to use three tug boats to tow and hold, and up to 
four tug boats to position, a jack-up rig to support production 
drilling at existing platforms on 6 non-consecutive days during a 1-
year period, in middle Cook Inlet and Trading Bay Alaska. Tug 
activities will include one demobilization effort of a jack-up rig 
(Spartan 151 or equivalent rig) from an existing platform to Rig 
Tenders Dock in Nikiski, one jack-up rig relocation between existing 
platforms, and one remobilization effort of the jack-up rig from Rig 
Tenders Dock in Nikiski to middle Cook Inlet. Noise produced by tugs 
under load with a jack-up rig may result in take, by Level B 
harassment, of 12 marine mammal species. References to tugging 
activities herein refer to activities where tugs are under load with 
the rig (i.e., tugs towing, holding, and or positioning a jack-up rig).
    A detailed description of the planned tugging activities is 
provided in the Federal Register notice for the proposed IHA (89 FR 
60164, July 24, 2024). Since that time, no changes have been made to 
the planned activities. Therefore, a detailed description is not 
provided here. Please refer to that Federal Register notice for the 
description of the specific activity.

Comments and Responses

    A notice of NMFS' proposal to issue an IHA to Hilcorp was published 
in the Federal Register on July 24, 2024 (89 FR 60164). That notice 
described, in detail, Hilcorp's activity, the marine mammal species 
that may be affected by the activity, and the anticipated effects on 
marine mammals. In that notice, we requested public input on the 
request for authorization described therein, our analyses, the proposed 
authorization, and any other aspect of the notice of proposed IHA, and 
requested that interested persons submit relevant information, 
suggestions, and comments.
    During the 30-day public comment period, NMFS received comments 
from Hilcorp, the Center for Biological Diversity (CBD), and Cook 
Inletkeeper. All relevant, substantive comments, and NMFS' responses, 
are provided below and are organized by topic. The comments and 
recommendations are available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities. Please see the comment 
submissions for full details regarding the recommendations and 
supporting rationale.
    Comment 1: Hilcorp requests that NMFS provide context for the term 
``serious'' as used in the description of effects that temporary 
threshold shifts (TTS) can have on marine mammals included in the 
Federal Register notice for the proposed IHA (89 FR 60164, July 24, 
2024) and/or edit for better accuracy.
    Response: NMFS reviewed the referenced text provided in the 
Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat of the notice of proposed IHA, which is referenced in this 
notice. We determined the discussion was sufficiently clear as 
originally written.
    Comment 2: Hilcorp requests that NMFS clarify that NMFS has found 
permanent threshold shifts (PTS) to not be likely based on the modeling 
results provided in the Federal Register notice for the proposed IHA 
(89 FR 60164, July 24, 2024).
    Response: NMFS concurs that PTS resulting from Hilcorp's tugging 
activities is unlikely. As described in the Federal Register notice for 
the proposed IHA (89 FR 60164, July 24, 2024), Hilcorp contracted SLR 
Consulting to model the extent of the harassment isopleths for tugs 
under load with a jack-up rig during their planned activities. The 
modeling efforts used detailed propagation calculations that accounted 
for local bathymetry and specific sound source locations and frequency-
dependent propagation effects in an attempt to improve the 
representation of the influence of relevant environmental variables on 
the propagation of sound from Hilcorp's planned activities. The results 
of these modeling efforts estimated distances to PTS thresholds under 
the mobile tug scenarios that are smaller than the overall size of the 
tug and rig configuration (i.e., less than or equal to 8 meters (m)), 
making it unlikely an animal would remain close enough to the tug 
engines to incur PTS. For stationary positioning of the jack up rig, 
the PTS isopleths for both the 3-tug and 4-tug scenarios were estimated 
to be up to 749 m for high frequency (HF) cetaceans and up to 102 m for 
all other species, but calculated on the assumption that an animal 
would remain within several hundred meters of the jack-up rig for the 
full 5 hours of noise-producing activity. Given the location of the 
activity is not in an area known to be essential habitat for any marine 
mammal species with extreme site fidelity, in addition to the mobile 
nature of marine mammals and the likelihood of avoidance, NMFS concurs 
that the occurrence of PTS is unlikely and thus, Level A harassment was 
not proposed or authorized for any species.
    Comment 3: Hilcorp requests that NMFS clarify that the required 
mitigation measures will reduce Level B harassment as well as the 
already insignificant potential for Level A harassment as a result of 
the specified activity.
    Response: As described in NMFS' response to Comment 2, there is a 
discountable potential for marine mammals to incur PTS from the 
project. Source levels from Hicorp's tugging activities are anticipated 
to be relatively low, non-impulsive, and animals would have to remain 
at very close distances for multiple hours to accumulate acoustic 
energy at levels that could damage hearing. We agree that mitigation 
measures required by NMFS are expected to be effective in further 
reducing the potential for Level A and Level B harassment and 
minimizing impacts of the specified activity. These

[[Page 79531]]

measures include the employment of multiple protected species observers 
(PSOs), vessel maneuvering restrictions, pre-clearance monitoring prior 
to commencing activities (which includes a measure that Hilcorp must 
delay any tugging activities should Cook Inlet beluga whales (CIBWs) be 
observed at any distance or if other marine mammals are observed within 
a 1.5 kilometer (km) clearance zone) as well as a requirement that 
Hilcorp must conduct tugging activities with a favorable tide to reduce 
noise output. These required measures should reduce any effects of the 
specified activity on marine mammals by minimizing the numbers of 
marine mammals exposed to sound and by minimizing the intensity of any 
exposures. Please see the Mitigation section of this notice for a full 
description of the required mitigation measures.
    Comment 4: Hilcorp notes that some of the densities reported in the 
Federal Register notice for the proposed IHA (89 FR 60164, July 24, 
2024) did not match those included in the Hilcorp application.
    Response: Hilcorp correctly identified a typo in table 10 of the 
notice of proposed IHA (89 FR 60164, July 24, 2024) regarding the 
density of minke whales. The table included a density of 0.0004 
individuals per kilometers squared (km\2\), whereas Hilcorp's 
application included a density of 0.00003 individuals per km\2\. That 
table (table 9 in this notice) has been corrected to include the 
correct density estimate of 0.00003 individuals per km\2\ for this 
species.
    Hilcorp also commented that the density value for CIBWs based on 
MML annual surveys for the entire Cook Inlet reported in table 10 in 
the notice for the proposed IHA (89 FR 60164, July 24, 2024) (i.e., 
0.07166 individuals per km\2\) does not align with other numbers 
provided in that table for CIBWs. This value was calculated as the 
average density of CIBWs in the entire Cook Inlet from 2000 through 
2022 as indicated by table 16 in Hilcorp's application and is included 
in table 9 of this notice.
    Comment 5: Hilcorp requests that NMFS specify that Hilcorp's 
activity will not cause repeated, sequential exposure or repetitious 
sounds. They also state that the best available information shows no 
potential for any population level impacts.
    Response: As described in the Negligible Impact Analysis and 
Determination section of the notice for the proposed IHA (89 FR 60164, 
July 24, 2024) and this notice, we describe how repeated, sequential 
exposure to elevated noise or repetitious sounds from tugs under load 
with a jack-up rig over a long duration could result in more 
significant impacts to individuals that could affect a population (via 
sustained or repeated disruption of important behaviors such as 
feeding, resting, traveling, and socializing; Southall et al., 2007). 
It is unlikely that any individual would be exposed to repeated, 
sequential exposures or repetitious sounds from Hilcop's activities 
given the short duration of Hilcorp's tugging activities (i.e., 6 non-
consecutive days over a 1-year period), and the low densities of marine 
mammals in the planned action area (see tables 10 in the notice for the 
proposed IHA (89 FR 60164, July 24, 2024) and table 9 in this notice). 
However, the potential for some repeat, sequential exposure or 
repetitious sounds from Hilcorp's tugging activities, though limited, 
does exist given that NMFS does not know with certainty that any 
individuals would not be exposed to Hilcorp's activity more than once.
    Despite the small potential for limited repeated, sequential 
exposure or repetitive sounds from Hilcorp's tugging activities, NMFS 
concurs with Hilcorp that the best available science supports the 
notion that exposure to tugging activities would not have impacts on 
the fitness or reproductive success of any individual marine mammals, 
much less population level impacts. Marine mammals, including CIBWs, 
frequent and use Cook Inlet despite being exposed to anthropogenic 
sounds such as those produced by tug boats and other vessels across 
many years. The absence of any pinniped haul outs or other known home-
ranges in the planned action area further decreases the likelihood of 
any population level impacts. As described in the Description of Sound 
Sources for the Specified Activities section of the notice for the 
proposed IHA (89 FR 60164, July 24, 2024), while marine mammals may be 
present in low numbers during Hilcorp's tugging activities, most 
individuals, including CIBWs, are anticipated to be transiting through 
the area, limiting exposure duration. CIBWs in the area are expected to 
be headed to or from the concentrated foraging areas farther north near 
the Beluga River, Susitna Delta, and Knik and Turnigan Arms. Similarly, 
humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera 
physalus), minke whales (Balaenoptera acutorostrata), gray whales 
(Eschrichtius robustus), killer whales (Orcinus orca), California sea 
lion (Zalophus californianus), and Steller sea lions (Eumetopias 
jubatus) are not expected to remain in the area of the tugs. Dall's 
porpoise (Phocoenoides dalli), harbor porpoise (Phocoena phocoena), and 
harbor seal (Phoca vitulina) have been sighted with more regularity 
than many other species during oil and gas activities in Cook Inlet, 
but due to the transitory nature of these species, they are unlikely to 
remain close to a tug under load for the full duration of the noise-
producing activity. Further, previous observations of marine mammals 
sighted near Hilcorp's planned activities have shown little to no 
observable reactions to tugs under load with a jack-up rig (e.g., 
Horsley and Larson, 2023).
    Lastly, no serious injury or mortality is anticipated to result 
from this activity. Take by Level A harassment (injury) is considered 
unlikely and is not authorized because of the small estimated Level A 
harassment zones resulting from tugs under load with a jack-up rig 
(i.e., <=8 m during mobile tugging activities and <=749 m for 
stationary tugging activities), the mobile nature of both the activity 
itself and marine mammals in the project area, and the required 
mitigation and monitoring program. Any take that may potentially occur 
would be in the form of Level B harassment, likely in the form of 
avoidance of the vessels and the noise they produce. Please see the 
Negligible Impact Analysis and Determination section of the notice for 
the proposed IHA (89 FR 60164, July 24, 2024) and this notice for more 
detailed information regarding why population level impacts resulting 
from the additional noise produced by tugs under load with a jack-up 
rig are not anticipated.
    Comment 6: Hilcorp suggests that because the MMPA requires NMFS to 
use the ``best scientific information available'', NMFS should use the 
CIBW abundance estimate of 331 from Goetz et al. (2003) as described in 
the footnote of table 12 of the Federal Register notice for the 
proposed IHA (89 FR 60164, July 24, 2024) rather than 271 from the most 
recent Stock Assessment Report (Young et al., 2023) when considering 
the percentage of the stock proposed to be authorized for taking.
    Response: As noted by Hilcorp, the abundance estimate provided by 
Goetz et al. (2023) is the most recent CIBW abundance estimate 
available. Footnotes 8 and 4 in tables 2 and 12, respectively, of the 
notice of the proposed IHA (and table 1 and table 11 in this notice) 
also state that ``in accordance with the MMPA, this population estimate 
will be incorporated into the CIBW SAR, which will be reviewed by an 
independent

[[Page 79532]]

panel of experts, the Alaska Scientific Review Group. After this 
review, the SAR will be made available as a draft for public review 
before being finalized.'' Even when more recent abundance estimates are 
available, NMFS typically considers abundance estimates from the SARs 
to be the best available given the rigorous SAR review process. 
However, in this case, regardless of whether the number of instances of 
takes is compared to the abundance estimate in the current CIBW SAR or 
the Goetz et al. (2023) abundance estimate, the number of instances of 
take as a percent of the stock abundance is less than 6 percent and is 
considered to be small numbers even if each instance of take represents 
a different CIBW.
    Comment 7: Hilcorp requests that NMFS delete the requirement of the 
proposed IHA that they must monitor the project area to the maximum 
extent possible based on the required number of PSOs, required 
monitoring locations, and environmental conditions. They state that 
Hilcorp is not required to ``monitor the project area to the maximum 
extent possible,'' but rather is required to monitor certain zones, 
according to the terms of the IHA.
    Response: NMFS has revised the IHA to make clear that the 
requirement to ``monitor the project area to the maximum extent 
possible'' does not refer to mitigation clearance zones but is rather a 
monitoring requirement that applies once operations commence. 
Specifically, we moved that requirement, which Hilcorp included in its 
application, to item 5(a) of the IHA, which addresses monitoring 
requirements during tug operations (in acknowledgement of the fact that 
Hilcorp will not be able to shut down activities once the tugs are 
under-load with the jack-up rig). We have also clarified in the final 
IHA that the maximum extent possible is the maximum distance possible.
    The monitoring requirement during operations is distinguished from 
the mitigation-related pre-clearance zones identified in item 4 of the 
IHA, which identifies the clearance zones that must be monitored as 
part of a pre-operational mitigation requirement. See the Mitigation 
section of this final notice for additional details.
    Comment 8: Hilcorp requests that NMFS delete and/or modify language 
that describes NMFS' purpose and alternatives considered in the 
agency's Environmental Assessment (EA). Specifically they state that 
language included in the draft EA incorrectly states NMFS' purpose, and 
that NMFS does not have the authority to require Hilcorp to use 
alternative technologies.
    Response: NMFS believes the referenced paragraph regarding NMFS' 
purpose in the EA appropriately describes our intent (which includes 
evaluating the information in Hilcorp's application). Therefore, NMFS 
has not deleted the referenced text as requested by Hilcorp. NMFS has 
revised the language referring to alternatives considered but 
eliminated from further consideration to clarify that NMFS does not 
have authority under the MMPA to prescribe that an applicant use 
alternative technologies to accomplish their objectives (i.e., an IHA 
does not authorize an activity, rather take of marine mammals 
incidental to an activity).
    Comment 9: CBD states that NMFS failed to seriously evaluate the 
assertion that noise from tugboats is the highest noise threat to CIBWs 
according to NMFS' Recovery Plan for CIBWs (NMFS, 2016).
    Response: NMFS' Recovery Plan (NMFS, 2016) ranks noise from 
tugboats as the most important source that could potentially interfere 
with CIBW recovery based on signal characteristics and spatio-temporal 
acoustic footprint. Specifically, NMFS (2016) identified propeller 
cavitation (the formation of bubbles in a liquid) and engine noise 
including azimuth/bow thruster noise from tug boats as concerning. 
However, notably, the Recovery Plan is referencing tugboat noise as a 
whole across all vessels and the entirety of Cook Inlet, not Hilcorp's 
specified activity in the specified location and geographic region, 
which is likely a small portion of overall tugboat use in Cook Inlet 
throughout the year. The NMFS Alaska Regional Office (AKRO) issued a 
Biological Opinion on September 4, 2024, under section 7 of the 
Endangered Species Act (ESA), on the issuance of an IHA to Hilcorp 
under section 101(a)(5)(D) of the MMPA by the NMFS Office of Protected 
Resources, which addressed the impacts of the CIBW take NMFS is 
authorizing in the context of both the environmental baseline and the 
cumulative effects (including tugboats) and found that it is not likely 
to jeopardize the continued existence of CIBWs or to destroy or 
adversely modify their designated Critical Habitat.
    NMFS acknowledges that the sounds produced by Hilcorp's tugging 
activities may potentially result in take, by Level B harassment 
(behavioral disturbance), of some marine mammals, most likely in the 
form of avoidance of the vessels and the noise they produce. As 
described in the Estimated Take section of the notice for the proposed 
IHA (89 FR 60164, July 24, 2024) and this notice, the sound source 
levels of tugging activities range widely according to the level of 
operational effort, with full power output and higher speeds generating 
more propeller cavitation and hence greater sound source levels than 
lower power output and lower speeds. As such, Hilcorp will implement 
mitigation measures intended to reduce the sound source levels from the 
tugs under load. First, the IHA requires that Hilcorp must conduct tug 
towing rig operations with a favorable tide unless human safety or 
equipment integrity are at risk. This is in an effort to reduce the 
operational effort of the tugs under load and to minimize source levels 
from Hilcorp's activities. Further, Hilcorp will only use bow thrusters 
occasionally for a short duration (20 to 30 seconds) to either push or 
pull a vessel in or away from a dock or platform, and the total tugging 
activities will be limited to (at most) 6 days of operations out to an 
estimated maximum distance of 4,453 m around the noise source. Last, 
the IHA prohibits Hilcorp from initiating tugging activities if a CIBW 
is observed at any distance within the pre-clearance monitoring period. 
If a CIBW(s) is observed during those 30 minutes, operations may not 
commence until the CIBW(s) is no longer detected at any range or 30 
minutes have elapsed without any observations of CIBWs. Therefore, NMFS 
anticipates that Hilcorp would not initiate a tow (which would include 
the use of bow thrusters) if a CIBW is within the portion of the Level 
B harassment zone that is closer to the activity, and thus more likely 
to disturb a CIBW. Lastly, it is important to note that there are 
multiple contextual factors (including the signal characteristics and 
the spatio-temporal (space and time) acoustic footprint of Hilcorp's 
activity as well as bearing and distance, predictability of source 
movement, and likelihood of habituation to routine vessel traffic) that 
minimize this potential and the likelihood of behavioral disturbance 
even if a marine mammal is exposed above the Level B harassment 
threshold. Based on this analysis, NMFS has made the determinations 
required by the MMPA and authorized take accordingly.
    Comment 10: CBD asserts that NMFS should defer issuance of 
incidental take of CIBWs unless and until NMFS has a better 
understanding of the reasons the species is failing to recover. They 
state that until it does so, NMFS has no rational basis for concluding 
that any amount of take constitutes a ``negligible impact'' to the 
species. Cook Inletkeeper also comments that NMFS should not authorize 
any take of CIBWs due to

[[Page 79533]]

uncertainty regarding trends in their population and the impacts that 
anthropogenic noise may have on this species.
    Response: NMFS shares the commenter's concern regarding the impacts 
of human activities on CIBWs and is committed to supporting the 
conservation and recovery of the species. Under section 101(a)(5)(D) of 
the MMPA, NMFS considers the at-risk status of CIBWs (and other 
species) in both the negligible impact analysis and through our 
consideration of impact minimization measures that support the least 
practicable adverse impact on those species. For example, the IHA 
includes a requirement for Hilcorp to delay the commencement of tugging 
activities should CIBWs be observed at any distance during the pre-
clearance monitoring period and requires that tug operations occur with 
favorable tides. However, section 101(a)(5)(D) also mandates that NMFS 
``shall issue'' an IHA, provided the necessary findings are made for 
the specified activity for which incidental take is requested.
    In accordance with our implementing regulations at 50 CFR 
216.104(c), we use the best available scientific evidence to determine 
whether the taking by the specified activity within the specified 
geographic region will have a negligible impact on the species or stock 
and will not have an unmitigable adverse impact on the availability of 
such species or stock for subsistence uses. Based on the scientific 
evidence available, NMFS determined that the take, by Level B 
harassment only, incidental to Hilcorp's tugging of the jack-up rig, 
which is primarily acoustic in nature, transient, and of a low level, 
would have a negligible impact on CIBWs. Moreover, Hilcorp proposed and 
NMFS has required in the IHA a rigorous mitigation plan to further 
reduce potential impacts to CIBWs (and other marine mammal species/
stocks) to the lowest level practicable. Additionally, the ESA 
Biological Opinion determined that the issuance of the IHA is not 
likely to jeopardize the continued existence of CIBWs, the Mexico 
Distinct Population Segment (DPS) of humpback whales, the Western DPS 
of Steller sea lions, and the Northeast Pacific stock of fin whales, or 
to destroy or adversely modify CIBW critical habitat. The Biological 
Opinion also outlined Terms and Conditions and Reasonable and Prudent 
Measures to reduce impacts, which have been incorporated into the IHA. 
Therefore, based on the analysis of potential effects, the parameters 
of the activity, and the rigorous mitigation and monitoring program, 
NMFS determined that the taking from the specified activity would have 
a negligible impact on the CIBW stock.
    Cook Inletkeeper stated that recent changes in survey methods calls 
into question the reliability of using the most recent aerial survey 
data to identify trends in population status, and that based upon this 
potential uncertainty and the impact that anthropogenic noise may have 
on this species, NMFS should not authorize any take of CIBWs. Cook 
Inletkeeper is incorrect in that survey methods for detecting trends in 
CIBW population have changed; the survey field methods are essentially 
unchanged since 2004 (Paul Wade, personal communication, December 11, 
2023). The analysis methods used to detect trends in the CIBW 
population have been updated and implemented in recent studies 
examining the CIBW population, notably Sheldon and Wade (2019) and 
Goetz et al. (2023).
    Results of recent studies provide evidence that the CIBW population 
increased between 2004 and 2010, declined after 2010, and increased 
again from 2016 to 2022 (Jacobsen et al., 2020; Shelden and Wade, 2019; 
Warlick et al., 2023; Goetz et al., 2023). While there is some 
uncertainty around CIBW population trend analyses, the results of these 
four studies are consistent in showing general trends. Thus, while Cook 
Inletkeeper is correct that some studies confirm a declining trend in 
CIBW abundance, recent studies, which NMFS considers the best 
scientific information available, suggest the population may now be 
increasing (see Goetz et al., 2023). Additional data in the coming 
years will help to inform whether the recent positive trend in the CIBW 
population will continue.
    Beyond the requirements in this IHA to minimize the impact of any 
taking from Hilcorp's activity, NMFS is taking several proactive steps 
to help protect and better understand the species. For example, NMFS is 
supporting the development of a population consequences of disturbance 
(PCoD) model, currently being developed by NMFS researchers, to 
quantitatively assess the degree to which anthropogenic disturbance, 
and in particular noise, may impact survival and reproduction of CIBWs. 
Results of Phase 1 of the model were published in 2023 (McHuron et al., 
2023) and the Phase 2 analysis is underway. NMFS also continues to 
conduct outreach and education to various stakeholders to minimize the 
potential for unauthorized take of CIBWs. NMFS also issued Cook Inlet 
and Kodiak Marine Mammal Disaster Response Guidelines in 2019 (NMFS, 
2019b) and a stranding response plan specific to CIBWs in 2009 (NMFS, 
2009), which could inform responses and further reduce impacts to 
CIBWs. NMFS initiated efforts to update the 2009 stranding response 
plan in 2021, and those efforts are ongoing. For more information, see 
NMFS' 5-year Priority Action Plan (2021-2025) for CIBWs as part of its 
Species in the Spotlight initiative to provide immediate, targeted 
efforts to halt declines and stabilize populations of the species most 
at-risk of extinction in the near future (see https://www.fisheries.noaa.gov/resource/document/species-spotlight-priority-actions-2021-2025-cook-inlet-beluga-whale).
    Comment 11: CBD and Cook Inletkeeper comment that NMFS cannot issue 
``Renewed'' IHAs under the MMPA. CBD further comments that NMFS cannot 
issue ``successive'' IHAs without a comprehensive analysis and must 
analyze and mitigate the total take it is proposing to authorize across 
all two years. CBD states that the 15-day comment period proposed for 
renewals is also unlawful and places a burden on interested members of 
the public to review not only the original authorization and supporting 
documents but also the draft monitoring reports, the renewal request, 
and the proposed renewed authorization and then to formulate comments, 
all within 15 calendar days. They assert that NMFS should set forth, 
via proposed regulation or policy document, its rationale for the 
Renewal process and to allow public comment.
    Response: The process of issuing a renewal IHA does not bypass the 
public notice and comment requirements of the MMPA. The notice of the 
proposed IHA initiated a 30-day public comment period and expressly 
notifies the public that under certain, limited conditions an applicant 
could seek a renewal IHA for an additional year. The notice describes 
the conditions under which such a renewal request could be considered 
and expressly seeks public comment in the event such a renewal is 
sought. Importantly, any such renewals (if issued) would be limited to 
where the activities are identical or nearly identical to those 
analyzed in the proposed IHA, monitoring does not indicate impacts that 
were not previously analyzed and authorized, and the mitigation and 
monitoring requirements remain the same, all of which allow the public 
to comment on the appropriateness and effects of a renewal at the same 
time the public provides comments on the initial IHA.
    Importantly, renewal IHAs are evaluated by NMFS on a case-by-case 
basis and are not an automatic matter of right. Each 1-year IHA must

[[Page 79534]]

independently satisfy the negligible impact standard for the authorized 
taking and include the means of effecting the least practicable adverse 
impact on the species or stock and its habitat and, where relevant, on 
the availability of such species or stock for taking for subsistence 
uses (i.e., mitigation). Moreover, NMFS is not proposing to issue a 
``successive'' IHA for a second year. For these reasons a comprehensive 
analysis of the impacts of potential take across two years is not 
appropriate under the MMPA. Any renewal request would be evaluated 
under the appropriate statutes (e.g., MMPA, National Environmental 
Policy Act (EPA), and ESA) for compliance with relevant standards. 
These analyses would consider the environmental baseline at that time, 
including any impacts of the IHA we have issued.
    Should a renewal request be made, additional documentation would be 
required from Hilcorp that NMFS would make publicly available and would 
use to verify that the activities are identical to those in the initial 
IHA, are nearly identical such that the changes would have either no 
effect on impacts to marine mammals or decrease those impacts, or are a 
subset of activities already analyzed and authorized but not completed 
under the initial IHA. NMFS would also confirm, among other things, 
that the activities would occur in the same location; involve the same 
species and stocks; provide for continuation of the same mitigation, 
monitoring, and reporting requirements; and that no new information had 
been received that would alter the prior analysis. If new information 
has been received that would alter the prior analysis, that information 
would be analyzed in the notice of the proposed renewal IHA. A renewal 
request would also contain a preliminary monitoring report, 
specifically to verify that effects from the activities do not indicate 
impacts of a scale or nature not previously analyzed. Any renewal 
request is subject to an additional 15-day public comment period that 
provides the public an opportunity to review these few documents, 
provide any additional pertinent information and comment on whether 
they think the criteria for a renewal have been met. Between the 
initial 30-day comment period on these same activities and the 
additional 15 days, the total comment period for a Renewal is 45 days.
    In addition to the IHA renewal process being consistent with all 
requirements under section 101(a)(5)(D), it is also consistent with 
Congress' intent for issuance of IHAs to the extent reflected in 
statements in the legislative history of the MMPA. Through the 
provision for renewals in the implementing regulations, description of 
the process and express invitation to comment on specific potential 
renewals in the Request for Public Comments section of each proposed 
IHA, the description of the process on NMFS' website, further 
elaboration on the process through responses to comments such as these, 
posting of substantive documents on the agency's website, and provision 
of 30 or 45 days for public review and comment on all proposed initial 
IHAs and renewals respectively, NMFS has ensured that the public has 
full opportunity to meaningfully participate in the agency's decision-
making process.
    Comment 12: CBD states that NMFS' small numbers determination is 
arbitrary, unlawful, unreasonable, and improper. They comment that 
NMFS' determination is based on a patently unlawful interpretation of 
what constitutes a small number and fails to consider that even a 
relatively small number of takes of critical endangered CIBWs can be 
more than small considering the species' highly imperiled status.
    In support of NMFS' small numbers determination, Hilcorp recommends 
that NMFS expressly reference the Federal Register notice where the 
standard for small numbers is identified and fully explained, include 
that reference in the record, and summarize that explanation in this 
final notice of IHA issuance. They also request that NMFS clearly 
express its finding that the proposed incidental harassment levels 
constitutes a ``small number'' for each marine mammal stock, 
independent of NMFS's ``one-third'' standard.
    Response: Our notice of the proposed IHA referenced an earlier 
rulemaking in which we provided a full explanation of the agency's 
interpretation of ``small numbers.'' (86 FR 5322, 5438, January 19, 
2021). NMFS makes its small numbers findings based on an analysis of 
whether the number of individuals authorized to be taken annually from 
a specified activity is small relative to the stock or population size. 
This relative approach is consistent with the statement from the 
legislative history that ``[small numbers] is not capable of being 
expressed in absolute numerical limits'' (H.R. Rep. No. 97-228, at 19 
(September 16, 1981)), and relevant case law (Center for Biological 
Diversity v. Salazar, 695 F.3d 893, 907 (9th Cir. 2012) (holding that 
the U.S. Fish and Wildlife Service reasonably interpreted ``small 
numbers'' by analyzing take in relative or proportional terms)). Using 
such a simple approach that establishes equal bins corresponding to 
small, medium, and large proportions of the population abundance, when 
the predicted number of individuals to be taken is fewer than one-third 
of the species or stock abundance, the take is considered to be of 
small numbers. (86 FR 5322, 5438, January 19, 2021).
    As described in the Small Numbers section of the Federal Register 
notice of the proposed IHA (89 FR 60164, July 24, 2024) and this notice 
of issuance, NMFS is authorizing take of less than 2 percent for all 
stocks, except for CIBWs whose authorized take is 5.38 percent of the 
stock; see tables 12 and 11 in the notice for the proposed IHA (89 FR 
60164, July 24, 2024) and this notice, respectively). Here, NMFS finds 
the taking of 5.38 percent of CIBWs, and 2 percent of other 14 other 
stocks of marine mammals constitutes small numbers of marine mammals 
taken relative to the population size of the affected species or 
stocks. As Hilcorp's comment letter points out, these percentages also 
fall under the amount upheld as small numbers by the U.S. District 
Court for the District of Alaska in Native Village of Chickaloon v. 
NMFS, 947 F. Supp. 2d 1031 (D. Alaska 2013) (concluding that NMFS' 
authorization of 10 percent of CIBWs constituted small numbers relative 
to the affected population size). This is well below NMFS' upper limit 
of one-third as described above. Further, using the take numbers (which 
actually represent instances of take) to compare to the population 
abundance conservatively assumes (for small numbers purposes) that each 
take represents a different individual (rather than a few individuals 
experiencing multiple instances of take). Therefore, NMFS has deemed 
the taking to be of small numbers of marine mammals (relative to the 
relevant species or stock abundances).
    Finally, we disagree with CBD's assertion that NMFS' small number 
determination for CIBWs should consider the highly imperiled status of 
the species. The argument to establish a small numbers threshold on the 
basis of stock-specific context is unnecessarily duplicative of the 
required negligible impact finding, in which relevant biological and 
contextual factors are considered in conjunction with the amount of 
take, and would risk conflating the two standards. See Ctr. for 
Biological Diversity v. Salazar, 695 F.3d at 907 (cautioning the U.S. 
Fish and Wildlife Service to ``keep[] the standards distinct'').
    Comment 13: CBD comments that NMFS' negligible impact determination 
is improper and arbitrary. They state

[[Page 79535]]

that it overlooks that CIBWs are among the most highly endangered 
animals under the agency's jurisdiction to protect. They state that 
NMFS has no rational basis for concluding that additional harassment by 
noise has a negligible impact on the species.
    Response: NMFS disagrees with the comment. In the Negligible Impact 
Analysis and Determination section of the notice of the proposed IHA 
(89 FR 60164, July 24, 2024) and again in this notice, we describe how 
the take estimated and authorized for Hilcorp's tugging activity will 
have a negligible impact on all of the affected species or stocks, 
including CIBWs. We discuss how this determination is based upon, among 
other things, the low number of takes of each stock that might be 
exposed briefly during 6 days of activity over the course of the 1-year 
IHA, the comparatively low level of behavioral harassment that might 
result from an instance of take that could occur within that year, and 
the likelihood that the mitigation measures required further lessen the 
likelihood, magnitude, or severity of exposures. NMFS also considered 
the status of each stock in its analysis.
    NMFS' negligible impact finding considers a number of parameters 
including, but not limited to, the nature of the activities (e.g., 
duration, sound source), effects/intensity of the taking, the context 
of takes, and mitigation. For CIBWs, NMFS considered data from previous 
similar tugging activities. Hilcorp's most recent annual marine mammal 
monitoring report indicates that it did not record any sightings of 
CIBWs from their rig-based monitoring efforts (Horsley and Larson, 
2023), and the most recent monthly monitoring report that describes 
monitoring results from the May 2024 rig transiting also indicates no 
recorded sightings of CIBWs during transit (Weston Solutions, 2024). 
Any disturbance that may occur is anticipated to be limited to 
behavioral changes such as increased swim speeds, changes in diving and 
surfacing behaviors, and alterations to communication signals, not the 
loss of foraging capabilities or the abandonment of critical habitat. 
Given these anticipated impacts, none of which would be expected to 
impact the fitness or reproduction of any individual marine mammals, 
much less adversely impact annual rates of recruitment or survival of 
CIBWs, NMFS' independent evaluation of the best scientific evidence in 
this case supports our negligible impact determination. Further, the 
ESA Biological Opinion concluded that the proposed action is not likely 
to jeopardize the continued existence of CIBWs or to destroy or 
adversely modify designated CIBW critical habitat.
    Comment 14: CBD asserts that NMFS discounts the best available 
science for CIBWs. CBD claims that NMFS incorrectly stated that CIBWs 
are not known to engage in critical behaviors in the area where 
Hilcorp's project is planned.
    Response: NMFS acknowledges observation of two potential but 
unconfirmed incidences of mating behavior in the Trading Bay area in 
2014, but the extent to which critical behaviors occur in Hilcorp's 
project area is still unknown (Lomac-Macnair et al., 2016). Such 
behaviors have not been reported since. Surveys by NMFS or McGuire et 
al. (2020) with concentrated effort on the western coast of Cook Inlet 
have not yielded a comparable sighting. Other key behaviors, such as 
calving and feeding, are described in more detail below but are thought 
to occur primarily in other concentrated areas outside of Hilcorp's 
action area.
    We are unaware of any information regarding areas where CIBWs are 
more likely to engage in mating behavior, however, what is known about 
calving suggests that it is most concentrated in the upper Inlet, north 
of Hilcorp's project area. McGuire et al. (2020) characterizes habitat 
use by age class in northern Cook Inlet and documented the majority of 
calves in the northernmost parts of Cook Inlet (e.g., Susitna Delta) 
despite concentrated survey effort in areas along the west part of the 
Inlet heading south toward the Forelands. NMFS acknowledges that CIBWs 
use the area, especially in spring and fall months, but their habitat 
range at those times is not nearly as constricted as their summer 
habitat, which is concentrated in a small area with high anthropogenic 
activity.
    CIBWs may well occur in the project area, which is why a small 
amount of take by Level B harassment is authorized for this species 
incidental to Hilcorp's jack-up rig towing. Tagging data, acoustic 
studies, and opportunistic sightings indicate that CIBWs continue to 
occur in the upper inlet throughout the winter months, in particular 
the coastal areas from Trading Bay to Little Susitna River, with 
foraging behavior detected in lower Knik Arm and Chickaloon Bay, and 
also detected in several areas of the lower inlet such as the Kenai 
River, Tuxedni Bay, Big River, and NW Kalgin Island (e.g., Castellote 
et al., 2020, 2021; C. Garner, pers. comm.; Shelden et al., 2015a, 
2018). CIBWs were historically seen in and around the Kenai and Kasilof 
rivers during June aerial surveys conducted by ADFG in the late 1970s 
and early 1980s and by NMFS starting in 1993 (Shelden et al., 2015b), 
and throughout the summer by other researchers and local observers. In 
recent years, sightings in and near these rivers have been more typical 
in the spring and fall (Ovitz, 2019). It is unknown if this is due to 
increased monitoring efforts in the area or an increase in CIBWs using 
this area. While visual sightings indicate peaks in spring and fall, 
acoustic detections indicate that CIBWs can be present in the Kenai 
River throughout the winter (Castellote et al., 2016). Despite the 
historic sightings (1970s-1990s) of CIBWs throughout the summer (June-
August) in the area, recent acoustic detections and visual sightings 
indicate that there appears to be a steep decline in CIBWs presence in 
the Kenai River during the summer, despite an annual return in recent 
years of 1-1.8 million sockeye salmon, which are important CIBW prey. 
Further, while feeding behaviors may occur in Hilcorp's project area, 
there are no known foraging hot spots near the project area. CIBWs are 
expected to be transiting through the area, headed to or from the 
concentrated foraging areas farther north near the Beluga River, 
Susitna Delta, and Knik and Turnigan Arms. Therefore, any exposures are 
likely to be limited in duration during the 6 days of tugging activity 
and would take place in a small portion of available foraging habitat. 
Any impacts on feeding are expected to be minimal.
    As described above, we have no reason to expect CIBWs to be 
concentrated in the path of Hilcorp's tug boats for the purposes of 
reproductive or feeding behaviors, but even if one or more of the 15 
instances in which noise from tugboat operations briefly intersects 
with an individual CIBW engaged in these behaviors, the anticipated 
short duration and low level disturbance of any such encounter would 
not be likely to impact reproductive or foraging success of any 
individuals.
    The commenter further asserts that NMFS' negligible impact 
conclusion is particularly arbitrary considering the project will occur 
within a year-round Biologically Important Area (BIA) for CIBWs and 
also in CIWB critical habitat. While exposure to elevated noise levels 
associated with Hilcorp's activities may result in low-level behavioral 
changes in marine mammals, NMFS' review of the best available 
scientific evidence, as summarized and cited herein, demonstrates that 
these responses do not rise to the level of having adverse effects on 
the reproduction or survival of any marine mammals, much less on

[[Page 79536]]

rates of recruitment or survival of any species or stock, and the 
commenter has provided no evidence to the contrary. Further, while 
Hilcorp's project area does overlap ESA-designated critical habitat for 
CIBWs and the CIBW small and resident BIA (Wild et al., 2023), the 
impacts from the project are not expected to occur in areas that are 
specifically important for feeding or reproduction for any species, 
including CIBWs, nor are they anticipated to result in a loss of prey 
or habitat. Monitoring data from Hilcorp's past activities suggest that 
tugging activities do not discourage CIBWs from transiting throughout 
Cook Inlet and between critical habitat areas and that the whales do 
not abandon critical habitat areas (Horsley and Larson, 2023). In 
addition, large numbers of CIBWs have continued to use Cook Inlet and 
pass through the area, likely traveling to critical foraging grounds 
found in upper Cook Inlet (i.e., outside of the project area), while 
noise-producing anthropogenic activities, including vessel use, have 
taken place during the past two decades (e.g., Shelden et al., 2013, 
2015b, 2017, 2022; Shelden and Wade, 2019; Geotz et al., 2023).
    Comment 15: CBD asserts that NMFS negligible impact determination 
for all species relies on mitigation measures that rely nearly 
exclusively on visual monitoring measures that it claims are ``known to 
be ineffective and inadequate'' to protect marine mammals.
    Response: NMFS disagrees with the comment. Our discussion in the 
Negligible Impact Analysis and Determination section below contains the 
factors NMFS considered in reaching its negligible impact 
determinations. Although NMFS' implementing regulations at 50 CFR 
216.104(c) state that NMFS may incorporate successful implementation of 
mitigation measures to arrive at a negligible impact determination, for 
issuance of the IHA for Hilcorp's tug towing activities, NMFS did not 
rely upon an assumption of set level of effectiveness in mitigation to 
make our negligible impact determinations. While NMFS acknowledges that 
visual observations can be difficult in Cook Inlet due to the extreme 
tidal range, harsh weather, turbid waters, and seasonal ice presence 
(e.g., Castellote et al., 2020; Lammers et al., 2013), prior monitoring 
efforts by Hilcorp have shown that it is clearly possible to detect and 
identify marine mammals to the species several km away from the source, 
including CIBWs, acknowledging that visibility depends on several 
factors such as visual acuity, sea state, glare, light, animal 
behavior/body type, speed of travel for vessel and animal, etc. 
(Horsley and Larson, 2023). NMFS does not assume total effectiveness of 
monitoring, but the demonstrated record of PSO sightings for activities 
in Cook Inlet illustrate that visual monitoring is appropriate for 
implementing mitigation in this case.
    Comment 16: CBD and Cook Inletkeeper comment that NMFS fails to 
ensure the least practicable adverse impact on CIBWs, the other species 
or stocks to be taken, and their habitats because NMFS failed to 
consider requiring several practicable mitigation measures, such as the 
use of passive acoustic monitors (PAM) and drones to help detect the 
presence of marine mammals, time-area restrictions, and requiring the 
use of noise-quieting engines. Cook Inletkeeper recommended that NMFS 
should require improved look-outs for marine mammals and additional 
monitoring.
    Response: We disagree with the commenter's claims. NMFS has 
included measures designed to effect the least practicable adverse 
impact on marine mammals species and their habitat, and has also 
included appropriate monitoring and reporting requirements. For 
example, during tugging activities, Hilcorp must conduct pre-clearance 
monitoring prior to commencing activities and must delay the start of 
activities if marine mammals are within designated pre-clearance zones 
(1,500 m for non-CIBW species and at any distance for CIBWs). Hilcorp 
must also conduct tugging activities with a favorable tide to reduce 
noise output. Please see the Mitigation section of this notice for a 
full description of the required mitigation measures.
    The CBD states that NMFS should require PAM for marine mammals. The 
use of PAM for real-time mitigation purposes has been used in Cook 
Inlet for some studies. These efforts have generally not resulted in 
successful deployment of PAM or useful detections of marine mammals to 
inform mitigation and monitoring during the activities due to the 
environmental conditions of the region (Austin and Zeddies, 2012; 
Kendall et al., 2015). For example, background acoustic conditions, 
including flow noise from strong currents, large tidal changes, and 
weather along with additional noise from the project (e.g., vessel 
noise, noise from project equipment) made it difficult to detect marine 
mammals from a real-time PAM system implemented as part of the 2012 
Apache 3D seismic survey program in lower- and mid-Cook Inlet (Austin 
and Zeddies, 2012; Lomac-MacNair et al., 2013) and during the 2015 
SAExploration Cook Inlet 3D seismic survey program (Kendall et al., 
2015). Further, environmental conditions restricted the type of PAM 
systems that could be deployed during these programs to a single omni-
directional hydrophone lowered from the side of a vessel, which 
restricted the possible range of detections. These factors suggest that 
effective PAM monitoring in Cook Inlet can be challenging (Austin and 
Zeddies, 2012).
    As CBD notes, academic researchers have begun to implement more 
effective passive acoustic monitors for research purposes at several 
places in Cook Inlet (e.g., Lammers et al., 2013 and Castellote et al., 
2020 as cited by CBD). However, the framework used by those researchers 
is not practicable for Hilcorp's planned activity. An article on NOAA's 
website (https://www.fisheries.noaa.gov/science-blog/beluga-whale-acoustic-monitoring-survey-post-3) illustrates the level of 
customization, expertise, and difficulty required to assemble a passive 
acoustic mooring to then deploy in the Inlet. Additionally, these 
instruments are stationary, which means to effectively use these 
monitors as a means of avoiding harassment of marine mammals during 
Hilcorp's tugging activities, Hilcorp would need to build and 
successfully deploy dozens (or more) stationary monitors along a route 
of travel that is subject to change depending upon weather or other 
environmental and shipping restrictions. Additionally, the data stored 
on these types of moorings is not accessible until they are retrieved 
by the researcher who deployed them. In the future, if an established 
network of passive acoustic monitors with shared access to the data is 
available, this could be a useful tool for implementing mitigation 
measures, but is currently not practicable.
    Contrary to CBD's assertion, NMFS did consider a time-area 
restriction; both the IHA and resulting ESA Biological Opinion require 
that Hilcorp maintain a distance of at least 2.4 km from the mean 
lower-low water line of the Susitna River Delta (Beluga River to the 
Little Susitna River) between April 15 and November 15, as this is an 
area where CIBWs can aggregate for feeding. CBD suggested further 
restrictions could include, for example, a prohibition on activities in 
April and May at Trading Bay where and when CIBWs have been observed 
engaged in probable mating behavior (Lomac-MacNair et al., 2016); or a 
prohibition on activities from July through September when CIBWs have 
been observed feeding in the area. Hilcorp's activity in Trading Bay 
would

[[Page 79537]]

be either a single day of transit or several hours of positioning the 
jack-up rig at an existing well site. As discussed in our above comment 
response, there has been one published observation of potential (not 
confirmed) mating behavior of CIBWs in Trading Bay in 2014. Surveys by 
NMFS or McGuire et al. (2020) with concentrated effort on the western 
coast of Cook Inlet have not yielded a comparable sighting. Closure of 
the entire area for two months is not practicable as Hilcorp would not 
be able to access the well sites that are part of the intended 
activity. As discussed above and in the species-specific section of the 
proposed IHA, CIBWs are highly concentrated in the upper Cook Inlet 
especially in the summer months (Goetz et al., 2012; McGuire et al., 
2020). In the past, CIBWs used the Kenai area in summer months but that 
trend has shifted in recent decades to occasional spring and fall 
sightings (Ovitz, 2019). Throughout the Inlet, mean group sizes during 
the summer and fall were largest in July and smallest in October, with 
the largest groups seen during mid-July and early August in the Susitna 
River Delta, while the smallest group sizes were in the Kenai River 
Delta. These patterns of high seasonal concentrations have continued to 
be documented since 2012 (e.g., McGuire et al., 2020). In reflection of 
this information, NMFS, as described above, has imposed time area 
restrictions in the Susitna River Delta from April to November to 
reduce effects of Hilcorp's activity to the greatest extent 
practicable. A closure in the middle Inlet during the summer months, in 
the season with longest daylight hours and best conditions for visual 
observations to implement mitigation and monitoring, is not warranted 
under the least practicable adverse impact standard.
    CBD states that NMFS failed to consider requiring noise-quieting 
engines, such as electric tugboats, which would have the added benefit 
of reducing air pollution and greenhouse gas emissions from tugs. NMFS 
is not aware of any commercially available seaworthy tug vessels that 
are used in tandem (e.g., three tug configuration) with effective 
quieting technologies or of any company or entity with electric tug 
fleets able to use them in tandem as required for Hilcorp's activities. 
The eWolf, and electronic tug boat, was christened in San Francisco Bay 
in June 2024 and was the first of its kind in U.S. waters. NMFS is also 
not aware of alternative technologies available that would allow 
Hilcorp to move the jack-up rig to various well sites without 
generating noise, which is the primary activity that has the potential 
to take marine mammals by harassment. Further, as described in our 
response to Comment 8, NMFS does not have the authority under the MMPA 
or ESA to prescribe that an applicant use alternative technologies to 
accomplish their objectives.
    CBD also commented that NMFS failed to consider an alternative that 
would require the use of drones, in addition to PSOs, to detect the 
presence of marine mammals. Cook Inletkeeper similarly suggested that 
NMFS should require a combination of drone and visual monitoring at all 
times. While unmanned aerial vehicles (UAVs; i.e., drones) have been 
used in some instances to observe marine mammals, there are logistical 
reasons (including limited berthing availability) that this measure is 
not practicable for Hilcorp to implement for this project. For these 
reasons, NMFS has not required that Hilcorp use drones or other UASs to 
assist in detecting marine mammals during their planned tugging 
activities.
    CBD correctly notes that the 1,500 m pre-clearance zone for non-
CIBWs is smaller than the Level B harassment zone (<=4,453 m). However, 
as mentioned in the response to Comment 7 above, NMFS has prescribed a 
requirement for this IHA (not included in previous IHAs issued to 
Hilcorp for take of marine mammals incidental to tugging activities; 87 
FR 62364, October 14, 2022) that Hilcorp establish a pre-clearance zone 
whereby they delay new operational activities should CIBWs be observed 
at any distance. This measure provides additional protection for CIBWs 
by further limiting the potential that tugging activities will commence 
while CIBWs are nearby. Further, using the Level B harassment zone as 
the clearance zone would not be practicable for some non-CIBW species 
(e.g., pinnipeds, harbor species) whose smaller size and often cryptic 
behavior may make accurate identification difficult at greater 
distances in Cook Inlet's environmental conditions. While underway, 
PSOs will observe for marine mammals to the greatest distance possible 
(they are not limited to observing within 1,500 m of the vessel). Any 
marine mammal sighted by PSOs at any distance is noted and reported to 
NMFS, per the reporting requirements of the IHAs.
    Cook Inletkeeper recommended that NMFS require improved look-outs 
(i.e., additional observers) and additional monitoring to better inform 
about the marine mammal populations and distributions as well as 
impacts from the proposed activities to better inform future 
activities. Hilcorp has informed NMFS that stationing additional PSOs 
on the tug boats or jack-up rig is not a practicable option for this 
project due to the limited berthing areas on the vessels. Cook 
Inletkeeper did not provide any recommendations for what additional 
monitoring would entail; however, the IHA does require that Hilcorp 
monitor and carefully record all observations of marine mammals, 
regardless of distance from the activity, as well as additional data 
such the group composition of any species observations, their distance 
and bearing from the source, their closest approach and time spent in 
estimated harassment zones, and any behavioral observations, including 
an assessment of behavioral responses thought to have resulted from the 
tugging activities. This information will be used to inform any future 
decisions regarding the issuance of IHAs for tugging activities, 
similarly as details documented by Hilcorp in their reports (e.g., 
Horsley and Larson, 2023) informed the decisions made herein.
    Lastly, Cook Inletkeeper recommended that NMFS not permit tug 
towing rig activities during periods of low visibility or at night, 
even to accommodate a favorable tide. Hilcorp's ability to move the 
jack-up rig is limited by several factors, including the presence of 
favorable environmental conditions for safe operations, crew 
availability, and the availability of the tug boats, which is limited 
by other scheduled work. Hilcorp must balance these factors with the 
timing of their planned actions. Despite this, Hilcorp will only begin 
operations in low light or night conditions if necessary for safety 
purposes (e.g., incoming inclement weather or ice) or to accommodate a 
favorable tide. Tugs may work at up to 80 percent power for much longer 
durations of time when pulling against the strong tides in Cook Inlet. 
As sound is the primary potential stressor from the proposed activity, 
limiting the sound output is preferred and tugs moving with the tide 
will reduce engine load by as much as 60 percent. Additionally, limited 
daylight, particularly in the shoulder seasons, results in at least a 
portion of activity occurring in low light or night conditions. As the 
ice-free season is already limited to roughly half the year, in order 
to maximize the ice-free season, operations in low-light or night 
conditions may be necessary. To mitigate this and enhance PSO's 
visibility, PSOs are required to use NMFS-approved night vision devices 
(NVDs) (e.g., PVS-7s, or equivalent) and have magnifying lenses 
available for use.

[[Page 79538]]

    Comment 17: Cook Inletkeeper asserts that NMFS must consider 
whether the cumulative impacts from Hilcorp's proposed activities in 
Cook Inlet will have a negligible impact on the area's marine mammals. 
Specifically, NMFS must consider the cumulative impacts of noise in 
Cook Inlet, including noise impacts from vessels and nearby 
construction, and determine what activities or combinations of 
activities would exceed a cumulative negligible impact threshold. Cook 
Inletkeeper urges NMFS to perform such an analysis before authorizing 
any ITAs for take of CIBWs.
    Response: Neither the MMPA nor NMFS' codified implementing 
regulations call for consideration of the take resulting from other 
activities in the negligible impact analysis. The preamble for NMFS' 
implementing regulations (54 FR 40338, September 29, 1989) states, in 
response to comments, that the impacts from other past and ongoing 
anthropogenic activities are to be incorporated into the negligible 
impact analysis via their impacts on the baseline. Consistent with that 
direction, NMFS has factored into its negligible impact analysis the 
impacts of other past and ongoing anthropogenic activities via their 
impacts on the baseline (e.g., as reflected in the density/distribution 
and status of the species, population size and growth rate, and other 
relevant stressors (such as incidental mortality in commercial 
fisheries, Unusual Mortality Events (UMEs), and subsistence hunting); 
see the Negligible Impact Analyses and Determinations section of this 
notice of issuance). The 1989 final rule for the MMPA implementing 
regulations also addressed public comments regarding cumulative effects 
from future, unrelated activities. There, NMFS stated that such effects 
are not considered in making findings under section 101(a)(5) 
concerning negligible impact. In this case, this IHA as well as other 
incidental take authorizations (ITAs) currently in effect or proposed 
within the specified geographic region, are appropriately considered an 
unrelated activity relative to the others. The ITAs are unrelated in 
the sense that they are discrete actions under section 101(a)(5)(D) 
issued to discrete applicants.
    Through the response to public comments in the 1989 implementing 
regulations, NMFS also indicated (1) that we would consider cumulative 
effects that are reasonably foreseeable when preparing a National 
Environmental Policy Act (NEPA) analysis, and (2) that reasonably 
foreseeable cumulative effects would also be considered under section 7 
of the Endangered Species Act (ESA) for ESA-listed species, as 
appropriate. Accordingly, NMFS has prepared an EA that considers 
cumulative effects. Additionally, under the ESA, NMFS' Biological 
Opinion independently considered the reasonably foreseeable cumulative 
effects of activities on ESA-listed species.
    Comment 18: Cook Inletkeeper raises concerns with Hilcorp's record 
of safety and environmental compliance. They state that according to 
the Alaska Oil and Gas Conservation Commission (AOGCC), Hilcorp has a 
documented pattern of accidents and safety violations and disregard for 
compliance with the law in Alaska. They assert that NMFS must consider 
Hilcorp's record and provide rigorous oversight.
    Response: It is the responsibility of the applicants to comply with 
all applicable laws and regulations, and to work with the state to 
obtain approval of their Oil Discharge Prevention and Contingency Plans 
(ODPCP). Hilcorp complied with the mitigation, monitoring, and 
reporting requirements of previously issued LOAs and IHAs under the 
MMPA (Fairweather Science, LLC, 2020; Korsmo et al., 2022; Horsley and 
Larson, 2023; Weston Solutions, 2024), thus we have no reason to 
believe that the requirements of the current IHA will not be upheld.

Changes From the Proposed IHA to Final IHA

    There are no changes from the proposed IHA to the final IHA other 
than the addition of some clarifying language and some minor 
typographical corrections.

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, instead of reprinting the information. Additional 
information regarding population trends and threats may be found in 
NMFS' Stock Assessment Reports (SARs; https://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 1 lists all species or stocks for which take is expected and 
authorized for this activity and summarizes information related to the 
population or stock, including regulatory status under the MMPA and 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 in table 1 
as gross indicators of the status of the species or stocks 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 for most species represent the total 
estimate of individuals within the geographic area, if known, that 
comprises that stock. For some species, this geographic area may extend 
beyond U.S. waters. All managed stocks in this region are assessed in 
NMFS' U.S. 2022 SARs. All values presented in table 1 are the most 
recent available at the time of publication (including from the draft 
2023 SARs) and are available online at: https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments.

[[Page 79539]]



                                         Table 1--Species \1\ With Estimated Take From the Specified Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                         ESA/MMPA status;    Stock abundance (CV,
             Common name                  Scientific name               Stock             strategic (Y/N)      Nmin, most recent       PBR     Annual M/
                                                                                                \2\          abundance survey) \3\               SI \4\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                 Order Artiodactyla--Cetacea--Mysticeti (baleen whales)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Eschrichtiidae:
    Gray Whale......................  Eschrichtius robustus..  Eastern N Pacific......  -, -, N             26,960 (0.05, 25,849,         801        131
                                                                                                             2016).
Family Balaenidae:
Family Balaenopteridae (rorquals):
    Fin Whale.......................  Balaenoptera physalus..  Northeast Pacific......  E, D, Y             UND \5\ (UND, UND,            UND        0.6
                                                                                                             2013).
    Humpback Whale..................  Megaptera novaeangliae.  Hawai[revaps]i.........  -, -, N             11,278 (0.56, 7,265,          127      27.09
                                                                                                             2020).
                                                               Mexico-North Pacific...  T, D, Y             N/A \6\ (N/A, N/A,            UND       0.57
                                                                                                             2006).
                                                               Western North Pacific..  E, D, Y             1,084 (0.088, 1,007,          3.4       5.82
                                                                                                             2006).
    Minke Whale.....................  Balaenoptera             Alaska.................  -, -, N             N/A \7\ (N/A, N/A, N/         UND          0
                                       acutorostrata.                                                        A).
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                  Odontoceti (toothed whales, dolphins, and porpoises)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Delphinidae:
    Killer Whale....................  Orcinus orca...........  Eastern North Pacific    -, -, N             1,920 (N/A, 1,920,             19        1.3
                                                                Alaska Resident.                             2019).
                                                               Eastern North Pacific    -, -, N             587 (N/A, 587, 2012)..        5.9        0.8
                                                                Gulf of Alaska,
                                                                Aleutian Islands and
                                                                Bering Sea Transient.
    Pacific White-Sided Dolphin.....  Lagenorhynchus           North Pacific..........  -, -, N             26,880 (N/A, N/A,             UND          0
                                       obliquidens.                                                          1990).
Family Monodontidae (white whales):
    Beluga Whale....................  Delphinapterus leucas..  Cook Inlet.............  E, D, Y             279 \8\ (0.061, 267,         0.53          0
                                                                                                             2018).
Family Phocoenidae (porpoises):
    Dall's Porpoise.................  Phocoenoides dalli.....  Alaska.................  -, -, N             UND \9\ (UND, UND,            UND         37
                                                                                                             2015).
    Harbor Porpoise.................  Phocoena phocoena......  Gulf of Alaska.........  -, -, Y             31,046 (0.21, N/A,            UND         72
                                                                                                             1998).
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                               Order Carnivora--Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals and
 sea lions):
    CA Sea Lion.....................  Zalophus californianus.  U.S....................  -, -, N             257,606 (N/A, 233,515,     14,011       >321
                                                                                                             2014).
    Steller Sea Lion................  Eumetopias jubatus.....  Western................  E, D, Y             49,837 \10\ (N/A,             299        267
                                                                                                             49,837, 2020).
Family Phocidae (earless seals):
    Harbor Seal.....................  Phoca vitulina.........  Cook Inlet/Shelikof      -, -, N             28,411 (N/A, 26,907,          807        107
                                                                Strait.                                      2018).
--------------------------------------------------------------------------------------------------------------------------------------------------------
\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\ 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.
\3\ NMFS marine mammal stock assessment reports 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.
\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\ The best available abundance estimate for this stock is not considered representative of the entire stock as surveys were limited to a small portion
  of the stock's range. Based upon this estimate and the Nmin, the PBR value is likely negatively biased for the entire stock.
\6\ Abundance estimates are based upon data collected more than 8 years ago and, therefore, current estimates are considered unknown.
\7\ Reliable population estimates are not available for this stock. Please see Friday et al. (2013) and Zerbini et al. (2006) for additional information
  on numbers of minke whales in Alaska.
\8\ On June 15, 2023, NMFS released an updated abundance estimate for endangered Cook Inlet beluga whales (CIBWs) in Alaska (Goetz et al., 2023). Data
  collected during NOAA Fisheries' 2022 aerial survey suggest that the whale population is stable or may be increasing slightly. Scientists estimated
  that the population size is between 290 and 386, with a median best estimate of 331. In accordance with the MMPA, this population estimate will be
  incorporated into the CIBW SAR, which will be reviewed by an independent panel of experts, the Alaska Scientific Review Group. After this review, the
  SAR will be made available as a draft for public review before being finalized.
\9\ The best available abundance estimate is likely an underestimate for the entire stock because it is based upon a survey that covered only a small
  portion of the stock's range.
\10\ Nest is best estimate of counts, which have not been corrected for animals at sea during abundance surveys.

    As indicated above, all 12 species (with 15 managed stocks) in 
table 1 temporally and spatially co-occur with the activity to the 
degree that take could occur. In addition, the northern sea otter may 
be found in Cook Inlet, Alaska. However, northern sea otters are 
managed by the U.S. Fish and Wildlife Service and are not considered 
further in this document.
    A detailed description of the species likely to be affected by 
Hilcorp's tugging activities, including a brief introduction to the 
affected stock as well as available information regarding population 
trends and threats, and information regarding local occurrence, were 
provided in the Federal Register notice of the proposed IHA (89 FR 
60164, July 24, 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

[[Page 79540]]

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. 
Specific to this action, gray whales, fin whales, minke whales, and 
humpback whales are considered low-frequency (LF) cetaceans, beluga 
whales, pacific white-sided dolphins, and killer whales are considered 
mid-frequency (MF) cetaceans, harbor porpoises and Dall's porpoises are 
considered high-frequency (HF) cetaceans, Steller sea lions and 
California sea lions are otariid pinnipeds (OW), and harbor seals are 
phocid pinnipeds (PW).

                  Table 2--Marine Mammal Hearing Groups
                              [NMFS, 2018]
------------------------------------------------------------------------
               Hearing group                 Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen         7 Hz to 35 kHz.
 whales).
Mid-frequency (MF) cetaceans (dolphins,      150 Hz to 160 kHz.
 toothed whales, beaked whales, bottlenose
 whales).
High-frequency (HF) cetaceans (true          275 Hz to 160 kHz.
 porpoises, Kogia, river dolphins,
 Cephalorhynchid, Lagenorhynchus cruciger &
 L. australis).
Phocid pinnipeds (PW) (underwater) (true     50 Hz to 86 kHz.
 seals).
Otariid pinnipeds (OW) (underwater) (sea     60 Hz to 39 kHz.
 lions and fur seals).
------------------------------------------------------------------------
* 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).

    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 Hilcorp's tugging activities 
have the potential to result in harassment of marine mammals in the 
vicinity of the project area. The notice of proposed IHA (89 FR 60164, 
July 24, 2024) included a discussion of the effects of anthropogenic 
noise on marine mammals and the potential effects of underwater noise 
from tugging activities 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 60164, July 24, 2024).

Estimated Take of Marine Mammals

    This section provides an estimate of the number of incidental takes 
authorized through the IHA, which will inform 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 will be by Level B harassment only, as use of the 
acoustic sources (i.e., tugging activities) may result in disruption of 
behavioral patterns of individual marine mammals. We note here that 
given the slow, predictable, and generally straight path of tug towing, 
holding, and positioning, the likelihood of a resulting disruption of 
marine mammal behavioral patterns that would qualify as harassment is 
considered relatively low; however, at the request of the applicant, we 
have quantified the potential take from this activity, analyzed the 
impacts, and authorized take. The required mitigation and monitoring 
measures are expected to minimize the potential for take and, if take 
were to occur, the severity of the taking to the extent practicable. 
Based on the nature of the activity (e.g., the very small area 
ensonified above the Level A harassment threshold), Level A harassment 
is neither anticipated nor authorized.
    No serious injury or mortality is anticipated or authorized for 
this activity. Below we describe how the take numbers are estimated.
    To determine whether Level B harassment is expected to result from 
acoustic exposure, NMFS considers the received levels a marine mammal 
is expected to be exposed to as compared to the relevant NMFS Level B 
harassment thresholds, as well as multiple contextual factors that can 
impact whether a marine mammal's behavioral patterns are likely to be 
disrupted (e.g., bearing and distance, predictability of source 
movement, whether habituation in a noisier/busy area is likely); 
specifically, whether any contextual factors would be expected to lower 
the likelihood of behavioral disturbance even when a marine mammal is 
exposed above the Level B harassment threshold. Where the take of 
marine mammals is considered likely or is requested by the applicant, 
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 (absent relevant 
contextual factors) or incur some degree of permanent hearing 
impairment where relevant; (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

[[Page 79541]]

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 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., Richardson et al., 1995; 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 support the 
estimation of the onset of Level B harassment and to quantify likely 
Level B harassment. Acknowledging the consideration of contextual 
factors noted above, NMFS generally predicts that marine mammals are 
likely to be behaviorally disturbed in a manner considered to be Level 
B harassment when exposed to underwater anthropogenic noise above root-
mean-squared pressure received levels (root mean square [RMS] sound 
pressure level [SPL]) of 120 dB (referenced to 1 micropascal (re 1 
[mu]Pa)) for continuous sources (e.g., tugging, vibratory pile driving, 
drilling) and above RMS SPL 160 dB re 1 [mu]Pa 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 thresholds are expected to include any likely takes by 
TTS as, in most cases, the likelihood of TTS occurs at distances from 
the source smaller 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.
    Hilcorp's planned activity includes the use of continuous sources 
(tugging activities), and therefore the RMS SPL threshold of 120 dB is 
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). Hilcorp's 
planned activity includes the use of non-impulsive sources (i.e., 
tugging activities).
    The thresholds identifying the onset of PTS are provided in table 3 
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-technical-guidance. Take by Level A harassment is considered unlikely for this 
action because of the small estimated Level A harassment zones 
resulting from tugs under load with a jack-up rig (i.e., <1 m) (as 
described below), the mobile nature of both the activity itself and 
marine mammals in the project area, and the required mitigation and 
monitoring program (see the Mitigation and Monitoring sections of this 
notice).

                                Table 3--Thresholds Identifying the Onset of PTS
----------------------------------------------------------------------------------------------------------------
                                                     PTS onset acoustic thresholds * (received level)
             Hearing group              ------------------------------------------------------------------------
                                                  Impulsive                         Non-impulsive
----------------------------------------------------------------------------------------------------------------
Low-Frequency (LF) Cetaceans...........  Cell 1: Lpk,flat: 219 dB;   Cell 2: LE,LF,24h: 199 dB.
                                          LE,LF,24h: 183 dB.
Mid-Frequency (MF) Cetaceans...........  Cell 3: Lpk,flat: 230 dB;   Cell 4: LE,MF,24h: 198 dB.
                                          LE,MF,24h: 185 dB.
High-Frequency (HF) Cetaceans..........  Cell 5: Lpk,flat: 202 dB;   Cell 6: LE,HF,24h: 173 dB.
                                          LE,HF,24h: 155 dB.
Phocid Pinnipeds (PW) (Underwater).....  Cell 7: Lpk,flat: 218 dB;   Cell 8: LE,PW,24h: 201 dB.
                                          LE,PW,24h: 185 dB.
Otariid Pinnipeds (OW) (Underwater)....  Cell 9: Lpk,flat: 232 dB;   Cell 10: LE,OW,24h: 219 dB.
                                          LE,OW,24h: 203 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 [micro]Pa, and cumulative sound exposure level (LE)
  has a reference value of 1[micro]Pa\2\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 (TL) 
coefficient.
    The sound field in the project area is the existing background 
noise plus additional noise resulting from the planned project. Marine 
mammals are expected to be affected via sound generated by the primary 
components of the project (i.e., tugging activities). Calculation of 
the area ensonified by the planned action is dependent on the 
background sound levels at the project

[[Page 79542]]

site, the source levels of the planned activities, and the estimated TL 
coefficients for the planned activities at the site. These factors are 
addressed below.
    Sound Source Levels of Tugging Activities. The project includes 
three to four tugs under load with a jack-up rig. Hilcorp conducted a 
literature review of underwater sound emissions of tugs under various 
loading efforts. The sound source levels for tugs of various horsepower 
(2,000 to 8,200) under load can range from approximately 164 dB RMS to 
202 dB RMS. This range largely relates to the level of operational 
effort, with full power output and higher speeds generating more 
propeller cavitation and hence greater sound source levels than lower 
power output and lower speeds. Tugs under tow produce higher source 
levels than tugs transiting with no load because of the higher power 
output necessary to pull the load. The amount of power the tugs expend 
while operating is the best predictor of relative sound source level. 
Several factors will determine the duration that the tugboats are 
towing the jack-up rig, including the origin and destination of the 
towing route (e.g., Rig Tenders Dock, an existing platform) and the 
tidal conditions. The power output will be variable and influenced by 
the prevailing wind direction and velocity, the current velocity, and 
the tidal stage. Unless human safety or equipment integrity are at 
risk, transport will be timed with the tide to minimize towing duration 
and power output.
    Hilcorp's literature review identified no existing data on sound 
source levels of tugs towing jack-up rigs. Accordingly, for this 
analysis, Hilcorp considered data from tug-under-load activities, 
including berthing and towing activities. Austin and Warner (2013) 
measured 167 dB RMS for tug towing barge activity in Cook Inlet. 
Blackwell and Greene (2002) reported berthing activities in the POA 
with a source level of 179 dB RMS. Laurinolli et al. (2005) measured a 
source level of 200 dB RMS for anchor towing activities by a tugboat in 
the Strait of Juan de Fuca, WA. The Roberts Bank Terminal 2 study 
(2014) repeated measurements of the same tug operating under different 
speeds and loading conditions. Broadband measurements from this study 
ranged from approximately 162 dB RMS up to 200 dB RMS.
    The rig manager for Hilcorp, who is experienced with towing jack-up 
rigs in Cook Inlet, described operational conditions wherein the tugs 
generally operate at half power or less for the majority of the time 
they are under load (pers. Comm., Durham, 2021). Transits with the tide 
(lower power output) are preferred for safety reasons, and effort is 
made to reduce or eliminate traveling against the tide (higher power 
output). The Roberts Bank Terminal 2 study (2014) allowed for a 
comparison of source levels from the same vessel (Seaspan Resolution 
tug) at half power versus full power. Seaspan Resolution's half-power 
(i.e., 50 percent) berthing scenario had a sound source level of 180 dB 
RMS. In addition, the Roberts Bank Terminal 2 Study (2014) reported a 
mean tug source level of 179.3 dB RMS from 650 tug transits under 
varying load and speed conditions.
    The 50 percent (or less) power output scenario will occur during 
the vast majority of tug towing jack-up rig activity. Therefore, based 
on Hilcorp's literature review, a source level of 180 dB RMS was found 
to be an appropriate proxy source level for a single tug under load 
based on the Roberts Bank Terminal 2 study. If all three tugs were 
operating simultaneously at 180 dB RMS, the overall source emission 
levels will be expected to increase by approximately 5 dB when 
logarithmically adding the sources (i.e., to 185 dB RMS). To further 
support this level as an appropriate proxy, a sound source verification 
(SSV) study performed by JASCO Applied Sciences (JASCO) in Cook Inlet 
in October 2021 (Lawrence et al., 2022) measured the sound source level 
from three tugs pulling a jack-up rig in Cook Inlet at various power 
outputs. Lawrence et al. (2022) reported a source level of 167.3 dB RMS 
for the 20 percent-power scenario and a source level of 205.9 dB RMS 
for the 85 percent-power scenario. Assuming a linear scaling of tug 
power, a source level of 185 dB RMS was calculated as a single point 
source level for three tugs operating at 50 percent power output. 
Because the 2021 Cook Inlet SSV measurements by JASCO represent the 
most recent best available data, and because multiple tugs may be 
operating simultaneously, the analyses presented below use a mean tug 
sound source level scenario of 185 dB RMS to calculate the 120-dB 
isopleths for three tugs operating at 50 percent power output. In 
practice, the load condition of the three tugs is unlikely to be 
identical at all times, so sound emissions will be dominated by the 
single tug in the group that is working hardest at any point in time.
    Further modeling was done to account for one additional tug working 
for 1 hour at 50 percent power during jack-up rig positioning, a 
stationary activity. This is equivalent in terms of acoustic energy to 
three tugs operating at 180.0 dB RMS (each of them) for 4 hours, joined 
by a fourth tug for 1 hour, increasing the source level to 186.0 dB RMS 
only during the 1-hour period (the logarithmic sum of four tugs working 
together at 180.0 dB RMS). A sound exposure level (SEL) of 185.1 dB was 
used to account for the cumulative sound exposure when calculating 
Level A harassment by adding a 4th tug operating at 50 percent power 
for 20 percent of the 5-hour period. This is equivalent in terms of 
acoustic energy to three tugs operating at 185.0 dB for 4 hours, joined 
by a fourth tug for 1 hour, increasing the source level to 186.0 dB 
only during the 1-hour period. The use of the 20 percent duty cycle was 
a computational requirement and, although equal in terms of overall 
energy and determination of impacts, should not be confused with the 
actual instantaneous SPL (see section 6.2.1.1 of Hilcorp's application 
for additional computational details).
    In summary, Hilcorp proposed to use a source level of 185.0 dB RMS 
to calculate the stationary 120-dB isopleth where three tugs were under 
load for 4 hours with a 50 percent power output and a source level of 
186.0 dB RMS to calculate the stationary 120-dB isopleth where four 
tugs were under load for 1 hour with a 50 percent power output. 
Further, Hilcorp proposed to use a source level of 185.1 dB SEL to 
calculate the stationary Level A harassment isopleths where three tugs 
were underload for 4 hours and then one tug joined for 1 additional 
hour. Lastly, Hilcorp proposed to use the 185.0 dB RMS level to model 
the mobile Level A harassment isopleths for three tugs under load with 
a 50 percent power output. NMFS concurs that Hilcorp's proposed source 
levels are appropriate.
    Underwater Sound Propagation Modeling. Hilcorp contracted SLR 
Consulting to model the extent of the harassment isopleths for tugs 
under load with a jack-up rig during their planned activities. Cook 
Inlet is a particularly complex acoustic environment with strong 
currents, large tides, variable sea floor and generally changing 
conditions. Accordingly, Hilcorp applied a more detailed propagation 
model than the ``practical spreading loss'' approach that uses a factor 
of 15. The objective of a more detailed propagation calculation is to 
improve the representation of the influence of some environmental 
variables, in particular by accounting for bathymetry and specific 
sound source locations and frequency-dependent propagation effects.
    Modeling was conducted using the dBSea software package. The fluid 
parabolic equation modeling algorithm was used with 5 Pad[eacute] terms 
to calculate

[[Page 79543]]

the TL between the source and the receiver at low frequencies (1/3-
octave bands, 31.5 Hz up to 1 kHz). For higher frequencies (1 kHz up to 
8 kHz) the ray tracing model was used with 1,000 reflections for each 
ray. Sound sources were assumed to be omnidirectional and modeled as 
points. The received sound levels for the project were calculated as 
follows: (1) One-third octave source spectral levels were obtained via 
reference spectral curves with subsequent corrections based on their 
corresponding overall source levels; (2) TL was modeled at one-third 
octave band central frequencies along 100 radial paths at regular 
increments around each source location, out to the maximum range of the 
bathymetry data set or until constrained by land; (3) The bathymetry 
variation of the vertical plane along each modeling path was obtained 
via interpolation of the bathymetry dataset which has 83 m grid 
resolution; (4) The one-third octave source levels and transmission 
loss were combined to obtain the received levels as a function of 
range, depth, and frequency; and (5) The overall received levels were 
calculated at a 1-m depth resolution along each propagation path by 
summing all frequency band spectral levels.
    Model Inputs. Bathymetry data used in the model was collected from 
the NOAA National Centers for Environmental Information (AFSC, 2019). 
Using NOAA's temperature and salinity data, sound speed profiles were 
computed for depths from 0 to 100 m for May, July, and October to 
capture the range of possible sound speed depending on the time of year 
Hilcorp's work could be conducted. These sound speed profiles were 
compiled using the Mackenzie Equation (1981) and are presented in table 
8 of Hilcorp's application (available at https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llc-oil-and-gas-activities-cook-inlet-alaska-0). Geoacoustic 
parameters were also incorporated into the model. The parameters were 
based on substrate type and their relation to depth. These parameters 
are presented in table 9 of Hilcorp's application (available at https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llc-oil-and-gas-activities-cook-inlet-alaska-0).
    Detailed broadband sound transmission loss modeling in dBSea used 
the source level of 185 dB RMS calculated in one-third octave band 
levels (31.5 Hz to 64,000 Hz) for frequency dependent solutions. The 
frequencies associated with tug sound sources occur within the hearing 
range of marine mammals in Cook Inlet. Received levels for each hearing 
marine mammal group based on one-third octave auditory weighting 
functions were also calculated and integrated into the modeling 
scenarios of dBSea. For modeling the distances to relevant PTS 
thresholds, a weighting factor adjustment was not used; instead, the 
data on the spectrum associated with their source was used and 
incorporated the full auditory weighting function for each marine 
mammal hearing group.
    The tugs towing the jack-up rig represent a mobile sound source, 
while tugs holding and positioning the jack-up rig on a platform are 
more akin to a stationary sound source. In addition, three tugs will be 
used for towing (mobile) and holding and positioning (stationary) and 
up to four tugs could be used for positioning (stationary). 
Consequently, sound TL modeling was undertaken for the various 
stationary and mobile scenarios for three and four tugs to generate the 
distances to the 120-dB (relevant Level B) and Level A harassment 
isopleths.
    For acoustic modeling of the stationary Level A harassment 
isopleths, two locations representative of where tugs will be 
stationary while they position the jack-up rig were selected in middle 
Cook Inlet near the Tyonek platform and in lower Trading Bay where the 
production platforms are located. To account for the mobile scenarios, 
the acoustic model calculated the Level A harassment isopleths along a 
representative route from the Rig Tenders dock in Nikiski to the Tyonek 
platform, the northernmost platform in Cook Inlet (representing middle 
Cook Inlet), as well as from the Tyonek Platform to the Dolly Varden 
platform in lower Trading Bay, then from the Dolly Varden platform back 
to the Rig Tenders Dock in Nikiski. Note that this route is 
representative of a typical route the tugs may take; the specific route 
is not yet known, as the order in which platforms will be drilled with 
the jack-up rig is not yet known. The locations represent a range of 
water depths from 18 to 77 m found throughout the project area.
    For mobile Level B harassment and stationary Level B harassment 
with three tugs, the average distance to the 120 dB RMS threshold was 
based on the assessment of 100 radials at 25 locations across seasons 
(May, July, and October) and represented the average 120-dB isopleth 
for each season and location (table 4). The result is a mobile and 
stationary 120-dB isopleth of 3,850 m when three tugs are used (table 
4). For four stationary tugs, the average distance to the 120 dB 
threshold was based on 100 radials at two locations, one in Trading Bay 
and one in middle Cook Inlet, across seasons (May, July, and October) 
and represents the average 120-dB isopleth for each season and 
location. The result is a stationary 120-dB isopleth of 4,453 m when 
four tugs are in use (table 5). NMFS concurs that 3,850 m and 4,453 m 
are appropriate estimates for the extent of the 120-dB isopleths for 
Hilcorp's towing, holding, and positioning activities when using three 
and four tugs, respectively, for the purpose of predicting the number 
of potential takes by Level B harassment.

  Table 4--Average Distances to the 120-dB Threshold for Three Tugs Towing (Mobile) and Holding and Positioning
                                            for 4 Hours (Stationary)
----------------------------------------------------------------------------------------------------------------
                                                     Average distance to 120-dB threshold (m)     Season average
                                                 ------------------------------------------------   distance to
                    Location                                                                          120-dB
                                                        May            July           October      threshold (m)
----------------------------------------------------------------------------------------------------------------
M1..............................................           4,215           3,911           4,352           4,159
M2..............................................           3,946           3,841           4,350           4,046
M3..............................................           4,156           3,971           4,458           4,195
M4..............................................           4,040           3,844           4,364           4,083
M5..............................................           4,053           3,676           4,304           4,011
M6..............................................           3,716           3,445           3,554           3,572
M7..............................................           2,947           2,753           2,898           2,866
M8..............................................           3,270           3,008           3,247           3,175

[[Page 79544]]

 
M9..............................................           3,567           3,359           3,727           3,551
M10.............................................           3,600           3,487           3,691           3,593
M11.............................................           3,746           3,579           4,214           3,846
M12.............................................           3,815           3,600           3,995           3,803
M13.............................................           4,010           3,831           4,338           4,060
M14.............................................           3,837           3,647           4,217           3,900
M15.............................................           3,966           3,798           4,455           4,073
M16.............................................           3,873           3,676           4,504           4,018
M18.............................................           5,562           3,893           4,626           4,694
M20.............................................           5,044           3,692           4,320           4,352
M22.............................................           4,717           3,553           4,067           4,112
M24.............................................           4,456           3,384           4,182           4,007
M25.............................................           3,842           3,686           4,218           3,915
M26.............................................           3,690           3,400           3,801           3,630
M27.............................................           3,707           3,497           3,711           3,638
M28.............................................           3,546           3,271           3,480           3,432
M29.............................................           3,618           3,279           3,646           3,514
                                                 ---------------------------------------------------------------
Average.........................................           3,958           3,563           4,029           3,850
----------------------------------------------------------------------------------------------------------------


      Table 5--Average Distances to the 120-dB Threshold for Four Tugs Positioning (Stationary) for 1 Hour
----------------------------------------------------------------------------------------------------------------
                                                     Average distance to 120-dB threshold (m)     Season average
                                                 ------------------------------------------------   distance to
                    Location                                                                          120-dB
                                                        May            July           October      threshold (m)
----------------------------------------------------------------------------------------------------------------
Trading Bay.....................................           4,610           3,850           4,810           4,423
Middle CI.......................................           4,820           4,130           4,500           4,483
                                                 ---------------------------------------------------------------
Average.........................................           4,715           3,990           4,655           4,453
----------------------------------------------------------------------------------------------------------------

    The average Level A harassment distances for the stationary, four 
tug scenario were calculated assuming a SEL of 185.1 dB for a 5-hour 
exposure duration (table 6). For the mobile, three tug scenario, the 
average Level A harassment distances were calculated assuming a SEL of 
185.0 dB with an 18-second exposure period (table 7). This 18-second 
exposure was derived using the standard TL equation (Source Level-TL = 
Received Level) for determining threshold distance (R [m]), where TL = 
15Log10. In this case, the equation was 185.0 dB-15Log10 = 173 dB. 
Solving for threshold distance (R) yields a distance of approximately 6 
m, which was then used as the preliminary ensonified radius to 
determine the duration of time it would take for the ensonified area of 
the sound source traveling at a speed of 2.06 m/s (4 knots) to pass a 
marine mammal. The duration (twice the radius divided by speed of the 
source) that the ensonified area of a single tug would take to pass a 
marine mammal under these conditions is 6 seconds. An 18-second 
exposure was used in the model to reflect the time it would take for 
three ensonified areas (from three consecutive individual tugs) to pass 
a single point that represents a marine mammal (6 seconds + 6 seconds + 
6 seconds = 18 seconds).

           Table 6--Average Distances to the Level A Harassment Thresholds for Four Stationary Tugs Under Load With a Jack-Up Rig for 5 Hours
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                            Average distance (m) to Level A harassment threshold by functional hearing
                                                                                                               group
                 Location                              Season            -------------------------------------------------------------------------------
                                                                                LF              MF              HF              PW            OW \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Trading Bay...............................  May.........................             107              77             792              64  ..............
Trading Bay...............................  July........................             132              80             758              66  ..............
Trading Bay...............................  October.....................             105              75             784              79  ..............
Middle Cook Inlet.........................  May.........................              86              85             712              78  ..............
Middle Cook Inlet.........................  July........................              95              89             718              80  ..............
Middle Cook Inlet.........................  October.....................              82              86             730              80  ..............
                                                                         -------------------------------------------------------------------------------

[[Page 79545]]

 
Average...................................  ............................             102              82             749              75               0
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ The Level A harassment distances are smaller than the footprint of the tugs.


   Table 7--Average Distances to the Level A Harassment Thresholds for Three Mobile Tugs Under Load With a Jack-Up Rig Assuming an 18-Second Exposure
                                                                        Duration
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                               Average distance (m) to Level A threshold by functional hearing group
                 Location                              Season            -------------------------------------------------------------------------------
                                                                              LF \1\          MF \1\            HF            PW \1\          OW \1\
--------------------------------------------------------------------------------------------------------------------------------------------------------
M2........................................  May.........................  ..............  ..............              10  ..............  ..............
M2........................................  July........................  ..............  ..............               5  ..............  ..............
M2........................................  October.....................  ..............  ..............              10  ..............  ..............
M11.......................................  May.........................  ..............  ..............              10  ..............  ..............
M11.......................................  July........................  ..............  ..............               5  ..............  ..............
M11.......................................  October.....................  ..............  ..............              10  ..............  ..............
M22.......................................  May.........................  ..............  ..............              10  ..............  ..............
M22.......................................  July........................  ..............  ..............               5  ..............  ..............
M22.......................................  October.....................  ..............  ..............              10  ..............  ..............
                                                                         -------------------------------------------------------------------------------
Average...................................  ............................               0               0               8               0               0
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ The Level A harassment distances are smaller than the footprint of the tugs.

    Tugs are anticipated to be towing the jack-up rig between platforms 
and considered a mobile sound source for 6 hours in a single day per 
jack-up rig move. Tugs are anticipated to be towing the jack-up rig and 
considered a mobile source during demobilization and mobilization to/
from Rig Tenders Dock in Nikiski for 9 hours. One jack-up rig move 
between platforms is planned during the IHA period. Tugs are 
anticipated to be holding or positioning the jack-up rig at the 
platforms or Rig Tenders Dock during demobilization and mobilization 
and are considered a stationary sound source for 5 hours in the first 
day and 5 hours in the second day if a second attempt to pin the jack-
up rig is required due to the first pinning event being unsuccessful. A 
second attempt was built into the exposure estimate for each pinning 
event; three total pinning events are anticipated during the IHA period 
for production drilling.
    The ensonified area for a location-to-location transport for 
production drilling represents a rig move between two production 
platforms in middle Cook Inlet and/or Trading Bay and includes 6 mobile 
hours over an average distance of 16.77 km in a single day and 5 
stationary hours on the first day and 5 stationary hours on a second 
day. The 5 stationary hours are further broken into 4 hours with three 
tugs under load and 1 hour with four tugs under load. One location-to-
location jack-up rig move is planned for the IHA period.
    The ensonified area for production drilling demobilization and 
mobilization represents a rig move from a production platform in middle 
Cook Inlet to Rig Tenders Dock in Nikiski and reverse for mobilization 
and includes 9 mobile hours over a distance of up to 64.34 km in a 
single day and 5 stationary hours on the first day and 5 stationary 
hours on a second day, which are further broken into the same three 
tugs working for 4 hours and four tugs working for 1 hour as mentioned 
above. A summary of the estimated Level A and Level B harassment 
distances and areas for the various tugging scenarios is provided in 
table 8.

 Table 8--Average Distances and Areas to the Estimated Level A and Level B Harassment Thresholds for the Various
                                                Tugging Scenarios
----------------------------------------------------------------------------------------------------------------
                                        Level A harassment distance (m)/area (km\2\)                Level B
                             -----------------------------------------------------------------     harassment
          Activity                                                                             distance (m)/area
                                   LF           MF           HF           PW           OW           (km\2\)
----------------------------------------------------------------------------------------------------------------
                                           Demobilization/Mobilization
----------------------------------------------------------------------------------------------------------------
3 Tugs Towing a Jack-Up Rig--       (\1\)        (\1\)       8/1.07        (\1\)        (\1\)       3,850/541.96
 Mobile.....................
3 Tugs Towing a Jack-Up Rig--    102/0.03      82/0.02     749/1.76      75/0.02        (\1\)        3,850/46.56
 Stationary for up to 4
 hours......................
4 Tugs Towing a Jack-Up Rig--    102/0.03      82/0.02     749/1.76      75/0.02        (\1\)        4,453/62.30
 Stationary for up to 1 hour
----------------------------------------------------------------------------------------------------------------
                                              Location-to-Location
----------------------------------------------------------------------------------------------------------------
3 Tugs Towing a Jack-Up Rig--       (\1\)        (\1\)       8/0.28        (\1\)        (\1\)        3,850/175.6
 Mobile.....................
3 Tugs Towing a Jack-Up Rig--    102/0.03      82/0.02     749/1.76      75/0.02        (\1\)        3,850/46.56
 Stationary for up to 4
 hours......................
4 Tugs Towing a Jack-Up Rig--    102/0.03      82/0.02     749/1.76      75/0.02        (\1\)        4,453/62.30
 Stationary for up to 1 hour
----------------------------------------------------------------------------------------------------------------
\1\ The Level A harassment distances are smaller than the footprint of the tugs.


[[Page 79546]]

Marine Mammal Occurrence

    In this section we provide information about the occurrence of 
marine mammals, including density or other relevant information that 
informed the take calculations.
    Densities for marine mammals in Cook Inlet were derived from NMFS' 
Marine Mammal Laboratory (MML) aerial surveys, typically flown in June, 
from 2000 to 2022 (Rugh et al., 2005; Shelden et al., 2013, 2015b, 
2017, 2019, 2022; Goetz, et al. 2023). While the surveys are 
concentrated for a few days in summer annually, which may skew 
densities for seasonally present species, they represent the best 
available long-term dataset of marine mammal sightings available in 
Cook Inlet. Densities were calculated by summing the total number of 
animals observed during the MML surveys and dividing the number sighted 
by the approximate area of Cook Inlet. For CIBWs, several correction 
factors were applied to the density estimates to address perception, 
availability, and proximity bias; correction factors were not applied 
to the non-CIBW density estimates. For CIBWs, densities were derived 
for the entirety of Cook Inlet as well as for middle and lower Cook 
Inlet; for non-CIBW marine mammals densities account for both lower and 
upper Cook Inlet. There are no density estimates available for 
California sea lions and Pacific white-sided dolphins in Cook Inlet, as 
they were so infrequently sighted. Average densities across survey 
years are presented in table 9.

  Table 9--Average Densities of Marine Mammal Species in Cook Inlet \1\
------------------------------------------------------------------------
                                                   Density (individuals
                    Species                             per km\2\)
------------------------------------------------------------------------
Humpback whale.................................                  0.00185
Minke whale....................................                  0.00003
Gray whale.....................................                  0.00007
Fin whale......................................                  0.00028
Killer whale...................................                  0.00061
Beluga whale (Entire Cook Inlet)...............                  0.07166
Beluga whale (Middle Cook Inlet)...............                  0.00658
Beluga whale (Lower Cook Inlet)................                  0.00003
Beluga whale (North Cook Inlet) \2\............                  0.00166
Beluga whale (Lower Cook Inlet) \2\............                  0.00000
Beluga whale (Trading Bay) \2\.................                  0.01505
Dall's porpoise................................                  0.00014
Harbor porpoise................................                  0.00380
Pacific white-sided dolphin....................                  \3\ N/A
Harbor seal....................................                  0.26819
Steller sea lion...............................                  0.00669
California sea lion............................                  \3\ N/A
------------------------------------------------------------------------
\1\ Density estimates are derived from MML surveys unless otherwise
  identified.
\2\ Density estimates are derived from the Goetz et al. (2012a) habitat-
  based model.
\3\ Density estimates are not available in Cook Inlet for this species.

    CIBW densities estimated from the MML surveys across regions are 
low, however, there is a known effect of seasonality on their 
distribution. Thus, densities derived directly from these summer 
surveys might underestimate the density of CIBWs in lower Cook Inlet at 
other ice-free times of the year. Therefore, additional CIBW densities 
were considered as a comparison of available data. The other mechanism 
for arriving at CIBW density considered here is the Goetz et al. 
(2012a) habitat-based model. This model is derived from sightings and 
incorporates depth soundings, coastal substrate type, environmental 
sensitivity index, anthropogenic disturbance, and anadromous fish 
streams to predict densities throughout Cook Inlet. The output of this 
model is a density map of Cook Inlet, which predicts spatially explicit 
density estimates for CIBW. Using the resulting grid densities, average 
densities were calculated for two regions applicable to Hilcorp's 
operations (table 9). The densities applicable to the area of activity 
(i.e., the North Cook Inlet Unit density for middle Cook Inlet 
activities and the Trading Bay density for activities in Trading Bay) 
are provided in table 9 above and were carried forward to the exposure 
estimates as they were deemed to likely be the most representative 
estimates available. Likewise, when a range is given, the higher end of 
the range was used out of caution to calculate exposure estimates 
(i.e., Trading Bay in the Goetz model has a range of 0.004453 to 
0.015053; 0.015053 was used for the exposure estimates).

Take Estimation

    Here we describe how the information provided above was synthesized 
to produce a quantitative estimate of the take that could occur and is 
authorized.
    As described above, Hilcorp's tugging activity considers a total of 
three rig moves across 6 days (one 2-day location-to-location jack-up 
rig move, one 2-day demobilization effort, and one 2-day mobilization 
effort). For the location-to-location move, Hilcorp assumed 6 hours of 
mobile (towing) and 5 hours of stationary (holding and positioning) 
activities on the first day, and 5 hours of the stationary activity (4 
hours with three tugs and 1 hour with four tugs) on the second day to 
account for two positioning attempts (across 2 days). For the 
demobilization and mobilization efforts, Hilcorp assumed 9 hours of 
mobile and 5 hours of stationary (4 hours with three tugs and 1 hour 
with four tugs) activities on the first day, and 5 hours of stationary 
(4 hours with three tugs and 1 hour with four tugs) activities on the 
second day (across 2 days for each effort, for a total of 4 days of 
tugs under load with a jack-up rigs).
    Potential take by Level A harassment was quantified by multiplying 
the ensonified Level A harassment areas per tugging activity scenario 
for each functional hearing group (table 8) by the estimated marine 
mammal densities (table 9) to get an estimate of exposures per day. 
This value was then multiplied by the number of days per move and the 
number of moves of that type of activity scenario. The estimated 
exposures by activity scenario were then summed to result in a number 
of exposures for all tugging activities. Based on this

[[Page 79547]]

analysis, only Dall's porpoise, harbor porpoise, and harbor seals had 
potential estimated take by Level A harassment that was greater than 
zero: 0.001, 0.018, and 0.006, respectively. For mobile tugging, the 
distances to the PTS thresholds for HF cetaceans and phocids are 
smaller than the overall size of the tug and rig configuration (i.e., 8 
m and 0 m, respectively), making it unlikely an animal will remain 
close enough to the tug engines to incur PTS. For stationary 
positioning of the jack up rig, the PTS isopleths for both the 3-tug 
and 4-tug scenarios are up to 749 m for HF cetaceans and up to 102 m 
for all other species, but calculated on the assumption that an animal 
would remain within several hundred meters of the jack-up rig for the 
full 5 hours of noise-producing activity. Given the location of the 
activity is not in an area known to be essential habitat for any marine 
mammal species with extreme site fidelity over the course of 2 days, in 
addition to the low exposure estimates for take by Level A harassment 
(i.e., <=0.18 for all species), the mobile nature of marine mammals, 
and the general tendencies of most marine mammals to avoid loud noises, 
the occurrence of PTS is unlikely and thus not authorized for any 
species.
    The ensonified Level B harassment areas calculated per activity 
scenario (three tug stationary, four tug stationary, and three tug 
mobile for the location-to-location move and the demobilization and 
mobilization efforts) for a single day (see table 8) were multiplied by 
marine mammal densities to estimate takes by Level B harassment per 
day, acknowledging that there are contextual factors that make take 
less likely to result from this activity. This was then multiplied by 
the number of days per move and the number of moves of that type of 
activity scenario to arrive at the number of estimated exposures above 
120 dB per activity type. These exposures by activity scenario were 
then summed to result in a number of exposures for all Hilcorp's 
tugging activities during the IHA period (table 10). As exposure 
estimates were calculated based on specific potential rig moves or well 
locations, the density value for CIBWs that was carried through the 
estimate was the higher density value for that particular location 
(table 9; i.e., 0.00658 for locations in middle Cook Inlet and 0.01505 
for locations in Trading Bay). There are no estimated exposures based 
on this method of calculation for California sea lions and Pacific 
white-sided dolphins because the assumed density of these species in 
the project area is 0.00 animals per km\2\. Table 10 also indicates the 
number of takes, by Level B harassment, authorized. For species where 
the total calculated exposures above the Level B harassment threshold 
is less than the estimated group size for that species, NMFS adjusted 
the take authorized up to the anticipated group size. Explanations for 
species for which take authorized is greater than the calculated take 
are included below.

         Table 10--Calculated Exposures and Total Authorized Take by Level B Harassment, by Species and Stock, for Hilcorp's Tugging Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                         Location-to-location                 Demobilization/mobilization          Total        Total
                                               --------------------------------------------------------------------------------  calculated   authorized
                   Scenario                                                                                                       Level B      take by
                                                 3 Mobile   3 Stationary  4 Stationary   3 Mobile   3 Stationary  4 Stationary   harassment    Level B
                                                   tugs         tugs          tugs         tugs         tugs          tugs       exposures    harassment
--------------------------------------------------------------------------------------------------------------------------------------------------------
Level B Harassment Area (km\2\)...............      175.67         46.56         62.30      541.96         46.56         62.30
-------------------------------------------------------------------------------------------------------------------------------
Species                                                   Calculated Exposures above the Level B Harassment threshold
--------------------------------------------------------------------------------------------------------------------------------------------------------
Humpback whale................................       0.324         0.029         0.010       2.001         0.057         0.019        2.440            3
Minke whale...................................       0.005         0.000         0.000       0.031         0.001         0.000        0.037            3
Gray whale....................................       0.012         0.001         0.000       0.072         0.002         0.001        0.088            3
Fin whale.....................................       0.048         0.004         0.001       0.299         0.009         0.003        0.364            2
Killer whale..................................       0.108         0.009         0.003       0.663         0.019         0.006        0.808           10
Beluga whale..................................       1.900         0.168         0.056       7.133         0.204         0.068        9.529           15
Dall's porpoise...............................       0.024         0.002         0.001       0.148         0.004         0.001        0.180            6
Harbor porpoise...............................       0.667         0.059         0.020       4.117         0.118         0.039        5.020           12
Pacific white-sided dolphin...................       0.000         0.000         0.000       0.000         0.000         0.000        0.000            3
Harbor seal...................................      47.112         4.163         1.392     290.699         8.325         2.785      354.476          355
Steller sea lion..............................       1.175         0.104         0.035       7.253         0.208         0.069        8.844            9
California sea lion...........................       0.000         0.000         0.000       0.000         0.000         0.000        0.000            2
--------------------------------------------------------------------------------------------------------------------------------------------------------

    During annual aerial surveys conducted in Cook Inlet from 2000 to 
2016, humpback group sizes ranged from 1 to 12 individuals, with most 
groups comprised of 1 to 3 individuals (Shelden et al., 2013). Three 
humpback whales were observed in Cook Inlet during SAExploration's 
seismic study in 2015: two near the Forelands and one in Kachemak Bay 
(Kendall and Cornick, 2015). In total, 14 sightings of 38 humpback 
whales (ranging in group size from 1 to 14) were recorded in the 2019 
Hilcorp lower Cook Inlet seismic survey in the fall (Fairweather 
Science, 2020). Two sightings totaling three individual humpback whales 
were recorded near Ladd Landing north of the Forelands on the recent 
Harvest Alaska CIPL Extension Project (Sitkiewicz et al., 2018). Based 
on documented observations from the CIPL Extension Project, which is 
the data closest to the specific geographic region, NMFS has 
authorized, three takes by Level B harassment for humpback whales, 
which is slightly greater than the calculated exposures using the 
methods described above (0.2440 takes by Level B harassment, table 10).
    Minke whales usually travel in groups of two to three individuals 
(NMFS, 2023b). During Cook Inlet-wide aerial surveys conducted from 
1993 to 2004, minke whales were encountered three times (1998, 1999, 
and 2006), all were observed off Anchor Point (Shelden et al., 2013, 
2015b, and 2017). Several minke whales were recorded off Cape 
Starichkof in early summer 2013 during exploratory drilling (Owl Ridge, 
2014), suggesting this location is regularly used by minke whales year-
round. During Apache's 2014 survey, a total of two minke whale groups 
(three individuals) were observed. One sighting occurred southeast of 
Kalgin Island while the other sighting occurred near Homer (Lomac-
MacNair et al., 2014). SAExploration noted one minke whale near Tuxedni 
Bay in 2015 (Kendall and Cornick, 2015). Eight sightings of eight minke 
whales were recorded in the 2019 Hilcorp lower Cook Inlet seismic 
survey

[[Page 79548]]

(Fairweather Science, 2020). Based on these observations of group size 
and consistency of sightings in Cook Inlet, NMFS has authorized three 
takes by Level B harassment for minke whales (table 10). This is higher 
than the exposure estimate (i.e., 0.037, table 10) to allow for the 
potential occurrence of a group, or several individuals, during the 
project period.
    During Apache's 2012 seismic program, nine sightings of a total of 
nine gray whales were observed in June and July (Lomac-MacNair et al., 
2013). In 2014, one gray whale was observed during Apache's seismic 
program (Lomac-MacNair et al., 2014) and in 2015, no gray whales were 
observed during SAExploration's seismic survey (Kendall and Cornick, 
2015). No gray whales were observed during the 2018 CIPL Extension 
Project (Sitkiewicz et al., 2018) or during the 2019 Hilcorp seismic 
survey in lower Cook Inlet (Fairweather Science, 2020). The greatest 
densities of gray whales in Cook Inlet occur from November through 
January and March through May; the former are southbound, the latter 
are northbound (Ferguson et al., 2015). Based on this information, NMFS 
has authorized three takes by Level B harassment for gray whales. This 
is higher than the exposure estimate (i.e., 0.088, table 10) to allow 
for the potential occurrence of a group, or several individuals, 
particularly during the fall shoulder season during the higher density 
periods mentioned above.
    Fin whales most often travel alone, although they are sometimes 
seen in groups of two to seven individuals. During migration they may 
be in groups of 50 to 300 individuals (NMFS, 2010). During the NMFS 
aerial surveys in Cook Inlet from 2000 to 2018, 10 sightings of 26 
estimated individual fin whales were recorded in lower Cook Inlet 
(Shelden et al., 2013, 2015b, and 2017; Shelden and Wade, 2019). Wild 
et al. (2023) identified areas south of the mouth of Cook Inlet as a 
fin whale feeding BIA from June to September with an importance score 
of 1 and an intensity score of 1 (see Harrison et al. 2023 for more 
details regarding BIA scoring). As such, the potential for fin whales 
to occupy waters adjacent to the BIA during that time period and near 
the specified area may be higher. Acoustic detections of fin whales 
were recorded during passive acoustic monitoring in the fall of 2019 
(Castellote et al., 2020) Additionally, during seismic surveys 
conducted in 2019 by Hilcorp in lower Cook Inlet, 8 sightings of 23 fin 
whales were recorded in groups ranging in size from 1 to 15 individuals 
(Fairweather Science, 2020). The higher number of sightings in a single 
year relative to the multi-year NMFS aerial surveys flown earlier in 
season each year suggests fin whales may be present in greater numbers 
in the fall. Given the possible presence of fin whales in the project 
area, NMFS has authorized two takes by Level B harassment for fin 
whales during Hilcorp's planned activities.
    Killer whale pods typically consist of a few to 20 or more animals 
(NMFS, 2023c). During seismic surveys conducted in 2019 by Hilcorp in 
lower Cook Inlet, 21 killer whales were observed. Although also 
observed as single individuals, killer whales were recorded during this 
survey in groups ranging in size from two to five individuals 
(Fairweather Science, 2020). One killer whale group of two individuals 
was observed during the 2015 SAExploration seismic program near the 
North Foreland (Kendall and Cornick, 2015). Based on recent documented 
sightings, observed group sizes, and the established presence of killer 
whales in Cook Inlet, NMFS has authorized 10 takes by Level B 
harassment for killer whales. This will account for two sightings with 
a group size of five individuals, which represents the upper end of 
recorded group size in recent surveys conducted in Cook Inlet.
    The total calculated exposures for CIBW was calculated to be 9.529 
individuals based on recorded densities and estimated durations that 
tugs will be under load with a jack-up rig (table 10). The 2018 MML 
aerial survey (Shelden and Wade, 2019) reported a median beluga group 
size estimate of approximately 11 whales, although estimated group 
sizes were highly variable (ranging from 2 to 147 whales) as was the 
case in previous survey years (Boyd et al., 2019). The median group 
size during 2021 and 2022 MML aerial surveys was 34 and 15, 
respectively, with variability between 1 and 174 between the years 
(Goetz et al., 2023). Additionally, vessel-based surveys in 2019 found 
CIBW groups in the Susitna River Delta (roughly 24 km north of the 
Tyonek Platform) that ranged from 5 to 200 animals (McGuire et al., 
2022). Based on these observations, NMFS increased the estimated take 
calculated above and has authorized 15 takes by Level B harassment for 
CIBWs to account for 1 group of 15 individuals, the lower end of the 
2022 median group size, or 2 observations of smaller-sized groups. 
While large groups of CIBWs have been seen in the Susitna River Delta 
region, they are not expected near Hilcorp's specified activity because 
groups of this size have not been observed or documented outside river 
deltas in upper Cook Inlet; however, smaller groups (i.e., around the 
2022 median group size) could be traveling through to access the 
Susitna River Delta and other nearby coastal locations.
    Dall's porpoises are usually found in groups averaging between 2 
and 12 individuals (NMFS, 2023d). During seismic surveys conducted in 
2019 by Hilcorp in lower Cook Inlet, Dall's porpoises were recorded in 
groups ranging from two to seven individuals (Fairweather Science, 
2020). The 2012 Apache survey recorded two groups of three individual 
Dall's porpoises (Lomac-MacNair et al., 2014). NMFS has authorized six 
takes by Level B harassment for Dall's porpoises. This is greater than 
the estimated exposure estimate for this species (0.180, table 10), but 
will allow for at least one group at the higher end of documented group 
size or a combination of small groups plus individuals.
    Harbor porpoises are most often seen in groups of two to three 
(NMFS, 2023e); however, based on observations during project-based 
marine mammal monitoring, they can also occur in larger group sizes. 
Shelden et al. (2014) compiled historical sightings of harbor porpoises 
from lower to upper Cook Inlet that spanned from a few animals to 92 
individuals. The 2018 CIPL Extension Project that occurred in middle 
Cook Inlet reported 29 sightings of 44 individuals (Sitkiewicz et al., 
2018). NMFS has authorized 12 takes by Level B harassment for harbor 
porpoises to allow for multiple group sightings during the specified 
activity. These authorized takes are greater than the exposure estimate 
calculated (5.020, table 10) but will account for the possibility of a 
couple sightings of small groups of harbor porpoises during Hilcorp's 6 
days of tugging activity.
    Recent data specific to Pacific white-sided dolphins within Cook 
Inlet are lacking, and the calculated exposure estimate is zero based 
on the paucity of sightings of this species in this region (table 10). 
However, Pacific-white sided dolphins have been observed in Cook Inlet. 
During an aerial survey in May 2014, Apache observed three Pacific 
white-sided dolphins near Kenai. No large groups of Pacific white-sided 
dolphins have been reported within Cook Inlet, although acoustic 
detections of several Pacific white-sided dolphins were recorded near 
Iniskin Bay during Hilcorp's 3D seismic survey in 2020. Prior to this, 
only one other survey in the last 20 years noted the presence of 
Pacific white-sided dolphins (three animals) within Cook Inlet. As a 
result of the dearth of current data on this species, an accurate 
density for Pacific

[[Page 79549]]

white-sided dolphins in the specific project region has not been 
generated. However, based on the possibility of this species in the 
project area, NMFS has authorized three takes by Level B harassment for 
Pacific white-sided dolphins, the maximum number of Pacific white-sided 
dolphins that have been recorded in the somewhat recent past are 
present in Cook Inlet. This is consistent with NMFS' IHA for Hilcorp's 
previous tugging activities (87 FR 62364, October 14, 2022).
    Harbor seals are often solitary in water but can haul out in groups 
of a few to thousands (Alaska Department of Fish and Game (ADF&G), 
2022). Given their presence in the study region, NMFS has authorized 
355 takes by Level B harassment for harbor seals, which is commensurate 
with the calculated exposure estimate based on harbor seal densities 
and Hilcorp's estimated durations for tugging activities (table 10).
    Steller sea lions tend to forage individually or in small groups 
(Fiscus and Baines, 1966) but have been documented feeding in larger 
groups when schooling fish were present (Gende et al., 2001). Steller 
sea lions have been observed during marine mammal surveys conducted in 
Cook Inlet. In 2012, during Apache's 3D Seismic survey, three sightings 
of approximately four individuals in upper Cook Inlet were reported 
(Lomac-MacNair et al., 2013). Marine mammal observers associated with 
Buccaneer's drilling project off Cape Starichkof observed seven Steller 
sea lions during the summer of 2013 (Owl Ridge, 2014). During 
SAExploration's 3D Seismic Program in 2015, four Steller sea lions were 
observed in Cook Inlet. One sighting occurred between the West and East 
Forelands, one occurred near Nikiski, and one occurred northeast of the 
North Foreland in the center of Cook Inlet (Kendall and Cornick, 2015). 
During NMFS CIWB aerial surveys from 2000 to 2016, 39 sightings of 769 
estimated individual Steller sea lions in lower Cook Inlet were 
reported (Shelden et al., 2017). During a waterfowl survey in upper 
Cook Inlet, an observer documented an estimated 25 Steller sea lions 
hauled out at low tide in the Lewis River on the west side of Cook 
Inlet (K. Lindberg, pers. comm., August 15, 2022). Hilcorp reported one 
sighting of two Steller sea lions while conducting pipeline work in 
upper Cook Inlet (Sitkiewicz et al., 2018). Commensurate with exposure 
estimates shown in table 10, NMFS has authorized nine takes by Level B 
harassment for Steller sea lions.
    While California sea lions are uncommon in the specific geographic 
region, two were seen during the 2012 Apache seismic survey in Cook 
Inlet (Lomac-MacNair et al., 2013). California sea lions in Alaska are 
typically alone but may be seen in small groups usually associated with 
Steller sea lions at their haulouts and rookeries (Maniscalco et al., 
2004). Despite the estimated exposure estimate being zero due to the 
lack of sightings during aerial surveys, NMFS has authorized two takes 
by Level B harassment for California sea lions to account for the 
potential to see up to two animals over the course of the season. This 
is consistent with NMFS authorization for Hilcorp's previous tugging 
activities (87 FR 62364, October 14, 2022).

Mitigation

    In order to issue an IHA under section 101(a)(5)(D) of the MMPA, 
NMFS must set forth the permissible methods of taking pursuant to the 
activity, and other means of effecting the least practicable impact on 
the species or stock and its habitat, paying particular attention to 
rookeries, mating grounds, and areas of similar significance, and on 
the availability of the species or stock for taking for certain 
subsistence uses. NMFS regulations require applicants for ITAs to 
include information about the availability and feasibility (economic 
and technological) of equipment, methods, and manner of conducting the 
activity or other means of effecting the least practicable adverse 
impact upon the affected species or stocks, and their habitat (50 CFR 
216.104(a)(11)).
    In evaluating how mitigation may or may not be appropriate to 
ensure the least practicable adverse impact on species or stocks and 
their habitat, as well as subsistence uses where applicable, 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.
    There is a discountable potential for marine mammals to incur PTS 
from the project, as source levels are relatively low, non-impulsive, 
and animals would have to remain at very close distances for multiple 
hours to accumulate acoustic energy at levels that could damage 
hearing. Therefore, we do not believe there is reasonable potential for 
Level A harassment and we are not authorizing it. Hilcorp will 
implement a number of mitigation and related monitoring measures 
designed to reduce the potential for and severity of Level B harassment 
and further reduce the already insignificant potential for Level A 
harassment.
    The tugs towing a jack-up rig are not able to shut down while 
transiting, holding, or positioning the rig. Hilcorp will maneuver the 
tugs towing the jack-up rig such that they maintain a consistent speed 
(approximately 4 knots [7 km/hr]) and avoid multiple changes of speed 
and direction to make the course of the vessels as predictable as 
possible to marine mammals in the surrounding environment, 
characteristics that are expected to be associated with a lower 
likelihood of disturbance.
    Hilcorp will use two NMFS-approved PSOs to observe and implement 
clearance zone procedures as described below (i.e., pre-clearance 
monitoring). If a marine mammal(s) is observed within the relevant 
clearance zone during the pre-clearance monitoring period, tugging 
activities will be delayed, unless the delay interferes with the safety 
of working conditions. The pre-clearance zones include a distance of 
1.5 km for non-CIBWs and any distance for CIBWs (note: transitioning 
from towing to positioning without shutting down will not be considered 
commencing a new operational activity). The 1.5 km clearance zone is 
consistent with previous authorizations for tugging activities (87 FR 
62364, October 14, 2022), and was determined to be appropriate as it is 
approximately twice as large as the largest Level A harassment zone 
(table 9) and is a reasonable distance within which cryptic species 
(e.g., porpoises, pinnipeds) could be observed. The larger clearance 
zone for CIBWs is a new measure aimed to further minimize any potential 
impacts from tugs under load with a jack-up rig on this species.
    During daylight hours, for 30 minutes prior to commencing new 
operational activities, or if there is a 30-minute lapse in operational 
activities, two PSOs will observe and implement clearance zones 
procedures as described below (i.e., pre-clearance monitoring); Note: 
transitioning from towing to positioning

[[Page 79550]]

without shutting down will not be considered commencing a new 
operational activity. If no marine mammals are observed within the 
relevant clearance zones described above during this 30 minute pre-
clearance monitoring period, tugging activities may commence. If a 
CIBW(s) is observed at any distance during those 30 minutes, operations 
may not commence until the PSO(s) confirm that the CIBW(s) or any other 
CIBW(s) has not been observed for 30 minutes, unless the delay 
interferes with the safety of working conditions. If a non-CIBW marine 
mammal(s) is observed within the relevant clearance zone (i.e., 1.5 km) 
during the 30 minute pre-clearance monitoring period, tugging 
activities will not commence until the PSO(s) observe that the non-CIBW 
animal(s) is outside of and on a path away from the clearance zone, or 
30 minutes have elapsed without observing the non-CIBW marine mammal.
    During nighttime hours or low/no-light conditions, NVDs shown to be 
effective at detecting marine mammals in low-light conditions (e.g., 
Portable Visual Search-7 model, or similar) will be provided to PSOs to 
aid in their monitoring of marine mammals. Every effort will be made to 
observe that the relevant clearance zone is free of marine mammals by 
using night-vision devices and or the naked eye, however it may not 
always be possible to see and clear the entire clearance zones prior to 
nighttime transport. Prior to commencing new operational activities 
during nighttime hours or if there is a 30-minute lapse in operational 
activities in low/no-light conditions, the two PSOs will observe and 
implement clearance zone procedures as described below while using NVDs 
(i.e., pre-clearance monitoring). If a marine mammal(s) is observed 
during the 30 minute pre-clearance monitoring period, operations may 
not commence until the PSO(s) observe that one of the following 
conditions is met, unless the delay interferes with the safely of 
working conditions: (1) the animal(s) is outside of the observable 
area; or (2) 30 minutes have elapsed without observing the marine 
mammal. If no marine mammals are observed during the 30 minute pre-
clearance monitoring period, tugs may commence towing, positioning, or 
holding the jack-up rig.
    Hilcorp will operate with the tide, resulting in a low power output 
from the tugs towing the jack-up rig, unless human safety or equipment 
integrity are at risk. Due to the nature of tidal cycles in Cook Inlet, 
it is possible that the most favorable tide for the towing operation 
will occur during nighttime hours. Hilcorp will only operate the tugs 
towing the jack-up rigs at night if the nighttime operations result in 
a lower power output from the tugs by operating with a favorable tide.
    Out of concern for potential disturbance to CIBWs in sensitive and 
essential habitat, Hilcorp will maintain a distance of 2.4 km from the 
mean lower-low water (MLLW) line of the Susitna River Delta (Beluga 
River to the Little Susitna River) between April 15 and November 15. 
The dates of applicability of this exclusion area have been expanded 
based on new available science, including visual surveys and acoustic 
studies, which indicate that substantial numbers of CIBWs continue to 
occur in the Susitna Delta area through at least mid-November (M. 
Castellote, pers. comm., T. McGuire, pers. comm.). In addition, Hilcorp 
will coordinate with local Tribes as described in its Stakeholder 
Engagement Plan (see appendix C in Hilcorp's application), notify the 
communities of any changes in the operation, and take action to avoid 
or mitigate impacts to subsistence harvests.
    For transportation of a jack-up rig to or from the Tyonek platform, 
in addition to the two PSOs stationed on the rig during towing, one 
additional PSO will be stationed on the Tyonek platform to monitor for 
marine mammals. The PSO will be on-watch for at least 1 hour before 
tugs are expected to arrive (scheduled to approach the estimated 120-dB 
isopleth).
    Based on our evaluation of our proposed measures and consideration 
of public comments, NMFS has determined that the required mitigation 
and related monitoring measures (see below for additional descriptions) 
provide the means of effecting the least practicable impact on the 
affected species or stocks and their habitat, paying particular 
attention to rookeries, mating grounds, and areas of similar 
significance, and on the availability of such species or stock for 
subsistence uses.

Monitoring and Reporting

    In order to issue an IHA for an activity, section 101(a)(5)(D) of 
the MMPA states that NMFS must set forth requirements pertaining to the 
monitoring and reporting of such taking. The MMPA implementing 
regulations at 50 CFR 216.104(a)(13) indicate that requests for 
authorizations must include the suggested means of accomplishing the 
necessary monitoring and reporting that will result in increased 
knowledge of the species and of the level of taking or impacts on 
populations of marine mammals that are expected to be present while 
conducting the activities. Effective reporting is critical both to 
compliance as well as ensuring that the most value is obtained from the 
required monitoring.
    Monitoring and reporting requirements prescribed by NMFS should 
contribute to improved understanding of one or more of the following:
     Occurrence of marine mammal species or stocks in the area 
in which take is anticipated (e.g., presence, abundance, distribution, 
density);
     Nature, scope, or context of likely marine mammal exposure 
to potential stressors/impacts (individual or cumulative, acute or 
chronic), through better understanding of: (1) action or environment 
(e.g., source characterization, propagation, ambient noise); (2) 
affected species (e.g., life history, dive patterns); (3) co-occurrence 
of marine mammal species with the activity; or (4) biological or 
behavioral context of exposure (e.g., age, calving or feeding areas);
     Individual marine mammal responses (behavioral or 
physiological) to acoustic stressors (acute, chronic, or cumulative), 
other stressors, or cumulative impacts from multiple stressors;
     How anticipated responses to stressors impact either: (1) 
long-term fitness and survival of individual marine mammals; or (2) 
populations, species, or stocks;
     Effects on marine mammal habitat (e.g., marine mammal prey 
species, acoustic habitat, or other important physical components of 
marine mammal habitat); and,
     Mitigation and monitoring effectiveness.
    Hilcorp will abide by all monitoring and reporting measures 
contained within the IHA and their Marine Mammal Monitoring and 
Mitigation Plan (see appendix D of Hilcorp's application). A summary of 
those measures and additional requirements from NMFS is provided below.
    Hilcorp must monitor the project area once tugging activities are 
underway to the maximum distance possible based on the required number 
of PSOs, required monitoring locations, and environmental conditions. 
PSOs must also conduct monitoring for marine mammals during the pre-
clearance monitoring periods, through 30 minutes post-completion of any 
tugging activity each day, and after each stoppage of 30 minutes or 
greater.
    A minimum of two NMFS-approved PSOs must be stationed on the tug or 
jack-up rig for monitoring purposes for the entirety of jack-up rig 
towing,

[[Page 79551]]

holding, and positioning operations and pre-clearance monitoring. PSOs 
must be independent of the activity contractor (for example, employed 
by a subcontractor) and have no other assigned tasks during monitoring 
periods. At least one PSO must have prior experience performing the 
duties of a PSO during an activity pursuant to a NMFS-issued ITA or 
Letter of Concurrence. Other PSOs may substitute other relevant 
experience (including relevant Alaska Native traditional knowledge), 
education (degree in biological science or related field), or training 
for prior experience performing the duties of a PSO.
    PSOs must also have the following additional qualifications:
    (a) The ability to conduct field observations and collect data 
according to assigned protocols;
    (b) Experience or training in the field identification of marine 
mammals, including the identification of behaviors;
    (c) Sufficient training, orientation, or experience with the 
tugging operation to provide for personal safety during observations;
    (d) Sufficient writing skills to record required information 
including but not limited to the number and species of marine mammals 
observed; dates and times when tugs were under load with the jack-up 
rig; dates, times, and reason for implementation of mitigation (or why 
mitigation was not implemented when required); and marine mammal 
behavior; and
    (e) The ability to communicate orally, by radio or in person, with 
project personnel to provide real-time information on marine mammals 
observed in the area as necessary.
    PSOs must be positioned aboard the tug or the jack-up-rig at the 
best practical vantage points that are determined to be safe, ideally 
an elevated stable platform from which a single PSO would have an 
unobstructed 360-degree view of the water or a total 360-degree view 
between all PSOs on-watch. Generally, one PSO will be on the port side 
and one PSO will be on the starboard side. Additionally, when towing 
the jack-up rig to the Tyonek platform, an additional PSO must be 
stationed on the Tyonek platform 1 hour before tugs are expected to 
arrive (i.e., scheduled to approach the estimated 120-dB isopleth) to 
monitor for marine mammals. PSOs may use a combination of equipment to 
scan the monitoring area and to verify the required monitoring distance 
from the project site, including the naked eye, 7 by 50 binoculars, and 
NMFS approved NVDs for low light and nighttime operations. PSOs must be 
in communication with all vessel captains via VHF radio and/or cell 
phones at all times and alert vessel captains to all marine mammal 
sightings relative to the vessel location.
    Hilcorp must submit interim monthly reports for all months in which 
tugging activities occur. Monthly reports will be due 14 days after the 
conclusion of each calendar month, and must include a summary of marine 
mammal species and behavioral observations, delays, and tugging 
activities completed (i.e., tugs towing, holding, or positioning the 
jack-up rig). They also must include an assessment of the amount of 
tugging remaining to be completed, in addition to the number of CIBWs 
observed within estimated harassment zones to date.
    A draft final summary marine mammal monitoring report must be 
submitted to NMFS within 90 days after the completion of the tug towing 
jack-up rig activities for the year or 60 calendar days prior to the 
requested issuance of any subsequent IHA for similar activity at the 
same location, whichever comes first. The draft summary report must 
include an overall description of all work completed, a narrative 
regarding marine mammal sightings, and associated marine mammal 
observation data sheets (data must be submitted electronically in a 
format that can be queried such as a spreadsheet or database). 
Specifically, the summary report must include:
     Date and time that monitored activity begins or ends;
     Activities occurring during each observation period, 
including (a) the type of activity (towing, holding, positioning), (b) 
the total duration of each type of activity, (c) the number of attempts 
required for positioning, (d) when nighttime operations were required, 
and (e) whether towing against the tide was required;
     PSO locations during marine mammal monitoring;
     Environmental conditions during monitoring periods (at the 
beginning and end of the PSO shift and whenever conditions change 
significantly), including Beaufort sea state, tidal state, and any 
other relevant weather conditions including cloud cover, fog, sun 
glare, overall visibility to the horizon, and estimated observable 
distance;
     Upon observation of a marine mammal, the following 
information:
    [cir] Name of PSO who sighted the animal(s) and PSO location and 
activity at time of sighting;
    [cir] Time of sighting;
    [cir] Identification of the animal(s) (e.g., genus/species, lowest 
possible taxonomic level, or unidentified), PSO confidence in 
identification, and the composition of the group if there is a mix of 
species;
    [cir] Distance and location of each observed marine mammal relative 
to the tug boats for each sighting;
    [cir] Estimated number of animals (min/max/best estimate);
    [cir] Estimated number of animals by cohort (adults, juveniles, 
neonates, group composition, etc.);
    [cir] Animal's closest point of approach and estimated time spent 
within the harassment zone;
    [cir] Description of any marine mammal behavioral observations 
(e.g., observed behaviors such as feeding or traveling), including an 
assessment of behavioral responses thought to have resulted from the 
activity (e.g., no response or changes in behavioral state such as 
ceasing feeding, changing direction, flushing, or breaching);
     Number of marine mammals detected within the harassment 
zones, by species; and
     Detailed information about implementation of any 
mitigation (e.g., delays), a description of specific actions that 
ensued, and resulting changes in behavior of the animal(s), if any.
    If no comments are received from NMFS within 30 days, the draft 
summary report will constitute the final report. If comments are 
received, a final report addressing NMFS comments must be submitted 
within 30 days after receipt of comments.
    In the event that personnel involved in Hilcorp's tugging 
activities discover an injured or dead marine mammal, Hilcorp must 
report the incident to the Office of Protected Resources, NMFS 
([email protected], [email protected]), and to 
the Alaska Regional Stranding Coordinator as soon as feasible. If the 
death or injury was clearly caused by the specified activity, Hilcorp 
must immediately cease the specified activities until NMFS is able to 
review the circumstances of the incident and determine what, if any, 
additional measures are appropriate to ensure compliance with the IHA. 
Hilcorp must not resume their activities until notified by NMFS. The 
report must include the following information:
     Time, date, and location (latitude and longitude) of the 
first discovery (and updated location information if known and 
applicable);
     Species identification (if known) or description of the 
animal(s) involved;
     Condition of the animal(s) (including carcass condition if 
the animal is dead);

[[Page 79552]]

     Observed behaviors of the animal(s), if alive;
     If available, photographs or video footage of the 
animal(s); and
     General circumstances under which the animal was 
discovered.

Negligible Impact Analysis and Determination

    NMFS has defined negligible impact as an impact resulting from the 
specified activity that cannot be reasonably expected to, and is not 
reasonably likely to, adversely affect the species or stock through 
effects on annual rates of recruitment or survival (50 CFR 216.103). A 
negligible impact finding is based on the lack of likely adverse 
effects on annual rates of recruitment or survival (i.e., population-
level effects). An estimate of the number of takes alone is not enough 
information on which to base an impact determination. In addition to 
considering estimates of the number of marine mammals that might be 
``taken'' through harassment, NMFS considers other factors, such as the 
likely nature of any impacts or responses (e.g., intensity, duration), 
the context of any impacts or responses (e.g., critical reproductive 
time or location, foraging impacts affecting energetics), as well as 
effects on habitat, and the likely effectiveness of the mitigation. We 
also assess the number, intensity, and context of estimated takes by 
evaluating this information relative to population status. Consistent 
with the 1989 preamble for NMFS' implementing regulations (54 FR 40338, 
September 29, 1989), the impacts from other past and ongoing 
anthropogenic activities are incorporated into this analysis via their 
impacts on the baseline (e.g., as reflected in the regulatory status of 
the species, population size and growth rate where known, ongoing 
sources of human-caused mortality, or ambient noise levels).
    To avoid repetition, the discussion of our analysis applies to all 
the species listed in table 10, except CIBWs, given that many of the 
anticipated effects of this project on different marine mammal stocks 
are expected to be relatively similar in nature. For CIBWs, there are 
potentially meaningful differences in anticipated responses to 
activities, impact of expected take on the population, or impacts on 
habitat; therefore, we provide a separate independent detailed analysis 
for CIBWs following the analysis for other species for which we 
authorize take.
    NMFS has identified several key factors to assess whether potential 
impacts associated with a specified activity should be considered 
negligible. These include (but are not limited to) the type and 
magnitude of taking, the amount and importance of the available habitat 
for the species or stock that is affected, the duration of the 
anticipated effect on the individuals, and the status of the species or 
stock. The potential effects of the specified activity on humpback 
whales, minke whales, gray whales, fin whales, killer whales, Dall's 
porpoises, harbor porpoises, Pacific white-sided dolphins, Steller sea 
lions, harbor seals, and California sea lions are discussed below. 
These factors also apply to CIBWs; however, an additional analysis for 
CIBWs is provided in a separate sub-section below.
    Tugs under load with the jack-up rig, as outlined previously, have 
the potential to disturb or displace marine mammals, and the number of 
authorized takes that could potentially result from Hilcorp's 
activities have been identified above in the Estimated Take section. 
Hilcorp's planned activities and associated impacts will occur within a 
limited, confined area of the affected species or stocks' range over a 
total of 6 days between September 24, 2024, and September 23, 2025. The 
intensity and duration of take by Level B harassment will be minimized 
through use of mitigation measures described herein. In addition, NMFS 
does not anticipate that serious injury or mortality will occur as a 
result of Hilcorp's planned activity given the nature of the activity, 
even in the absence of required mitigation.
    Exposures to elevated sound levels produced during tugs under load 
with the jack-up rig may cause behavioral disturbance of some 
individuals within the vicinity of the sound source. Behavioral 
responses of marine mammals to tugs under load with the jack-up rig are 
expected to be mild, short term, and temporary. Effects on individuals 
that are taken by Level B harassment, as enumerated in the Estimated 
Take of Marine Mammals section, on the basis of reports in the 
literature as well as monitoring from other similar activities 
conducted by Hilcorp (Horsley and Larson, 2023), will likely be limited 
to behavioral response such as increased swimming speeds, changing in 
directions of travel and diving and surfacing behaviors, increased 
respiration rates, or decreased foraging (if such activity were 
occurring) (Ridgway et al., 1997; Nowacek et al., 2007; Thorson and 
Reyff, 2006; Kendall and Cornick, 2015; Goldbogen et al., 2013b; Blair 
et al., 2016; Wisniewska et al., 2018; Piwetz et al., 2021). Marine 
mammals within the 120-dB isopleths may not present any visual cues 
they are disturbed by activities, or they could become alert, avoid the 
area, leave the area, or have other mild responses that are not 
observable such as increased stress levels (e.g., Rolland et al. 2012; 
Bejder et al., 2006; Rako et al., 2013; Pirotta et al., 2015; 
P[eacute]rez-Jorge et al., 2016). They may also exhibit increased 
vocalization rates (e.g., Dahlheim, 1987; Dahlheim and Castellote, 
2016), louder vocalizations (e.g., Frankel and Gabriele, 2017; Fournet 
et al., 2018), alterations in the spectral features of vocalizations 
(e.g., Castellote et al., 2012), or a cessation of communication 
signals (e.g., Tsujii et al., 2018). However, as described in the 
Potential Effects of Specified Activities on Marine Mammals and Their 
Habitat section of the Federal Register notice of the proposed IHA (89 
FR 60164, July 24, 2024), marine mammals observed near Hilcorp's 
planned activities have shown little to no observable reactions to tugs 
under load with a jack-up rig (Horsley and Larson, 2023).
    Tugs towing, holding, and positioning a jack-up rig are slow-moving 
as compared to typical recreational and commercial vessel traffic. 
Assuming an animal is stationary, exposure from the moving tug 
configuration (which comprises most of the tug activity being 
considered) will be on the order of minutes in any particular location. 
The slow, predictable, and generally straight path of this activity is 
expected to further lessen the likelihood that sound exposures at the 
expected levels will result in the harassment of marine mammals, though 
the potential takes based on straight calculations have nonetheless 
been considered in the analysis. Also, this slow transit along a 
predictable path is planned in an area of routine vessel traffic where 
many large vessels move in slow straight-line paths, and some 
individuals are expected to be habituated to these sorts of sounds. 
While it is possible that animals may swim around the project area, 
avoiding closer approaches to the boats, we do not expect them to 
abandon any intended path. Further, most animals present in the region 
will likely be transiting through the area; therefore, any potential 
exposure is expected to be brief. Based on the characteristics of the 
sound source and the other activities regularly encountered in the 
area, it is unlikely Hilcorp's planned activities will be of a duration 
or intensity expected to result in impacts on reproduction or survival.
    Further, most of the species present in the region will only be 
present temporarily based on seasonal patterns or during transit 
between other habitats. These temporarily present species will be 
exposed to even shorter periods of

[[Page 79553]]

noise-generating activity, further decreasing the impacts. Most likely, 
individual animals will simply move away from the sound source and be 
temporarily displaced from the area. Takes also have the potential to 
occur during important feeding times. However, the project area 
represents a small portion of available foraging habitat and impacts on 
marine mammal feeding for all species should be minimal.
    We anticipate that any potential reactions and behavioral changes 
are expected to subside quickly when the exposures cease and, 
therefore, we do not expect long-term adverse consequences from 
Hilcorp's planned activities for individuals of any species. The 
intensity of Level B harassment events will be minimized through use of 
mitigation measures described herein, which were not quantitatively 
factored into the take estimates. Hilcorp will use PSOs to monitor for 
marine mammals before commencing any tugging activity, which will 
minimize the potential for marine mammals to be present within the 120-
dB isopleth when tugs are under load, further reducing the likely 
amount of any potential Level B harassment. Further, given the absence 
of any major rookeries or areas of known biological significance for 
marine mammals (e.g., foraging hot spots) within the estimated 
harassment zones (other than critical habitat and a BIA for CIBWs as 
described below), we predict that potential takes by Level B harassment 
will have an inconsequential short-term effect on individuals and will 
not result in population-level impacts.
    Theoretically, repeated, sequential exposure to elevated noise from 
tugs under load with a jack-up rig over a long duration could result in 
more severe impacts to individuals that could affect individual fitness 
or reproductive success (via sustained or repeated disruption of 
important behaviors such as feeding, resting, traveling, and 
socializing; Southall et al., 2007). Alternatively, marine mammals 
exposed to repetitious sounds may become habituated, desensitized, or 
tolerant after initial exposure to these sounds (reviewed by Richardson 
et al., 1995; Southall et al., 2007). Cook Inlet is a regional hub of 
marine transportation and is used by various classes of vessels, 
including containerships, bulk cargo freighters, tankers, commercial 
and sport-fishing vessels, and recreational vessels. Off-shore vessels, 
tug vessels, and tour boats represent 86 percent of the total operating 
days for vessels in Cook Inlet (BOEM, 2016). Given that marine mammals 
still frequent and use Cook Inlet despite being exposed to 
anthropogenic sounds such as those produced by tug boats and other 
vessels across many years, and that it is unlikely that any individual 
would be exposed to repeated, sequential exposures or repetitious 
sounds from Hilcop's activities, no impacts to the reproduction or 
survival of any marine mammal individuals from the additional noise 
produced by tugs under load with a jack-up rig are anticipated. The 
absence of any pinniped haul outs or other known home-ranges in the 
planned action area further decreases the likelihood of any more severe 
energetic impacts that might affect reproduction or survival.
    Hilcorp's planned activities are also not expected to have 
significant adverse effects on any marine mammal habitat as no physical 
impacts to habitat are anticipated to result from the specified 
activities and any impacts to marine mammal habitat (i.e., elevated 
sound levels) will be temporary. In addition to being temporary and 
short in overall duration, the acoustic footprint of the planned 
activity is small relative to the overall distribution of the animals 
in the area and their use of the area. Additionally, the habitat within 
the estimated acoustic footprint is not known to be heavily used by 
marine mammals.
    Impacts to marine mammal prey species are also expected to be minor 
and temporary and to have, at most, short-term effects on foraging of 
individual marine mammals, and likely no effect on the populations of 
marine mammals as a whole. Overall, as described above, the area 
anticipated to be impacted by Hilcorp's planned activities is very 
small compared to the available surrounding habitat and does not 
include habitat of particular importance to marine mammals. The most 
likely impact to prey will be temporary behavioral avoidance of the 
immediate area. When tugs are under load with the jack-up rig, it is 
expected that some fish will temporarily leave the area of disturbance 
(e.g., Nakken, 1992; Olsen, 1979; Ona and Godo, 1990; Ona and Toresen, 
1988), thus impacting marine mammals' foraging opportunities in a 
limited portion of their foraging range. But, because of the relatively 
small area of the habitat that may be affected, and lack of any 
foraging habitat of particular importance, the impacts to marine mammal 
habitat are not expected to cause significant or long-term negative 
consequences.
    Finally, Hilcorp will minimize potential exposure of marine mammals 
to elevated noise levels by delaying tugging activities if CIBWs are 
observed at any distance or if non-CIBW marine mammals are observed 
within 1.5 km during the pre-clearance monitoring period. Hilcorp will 
also implement vessel maneuvering measures to reduce the likelihood of 
disturbing marine mammals during any periods when marine mammals may be 
present near the vessels. Lastly, Hilcorp will also reduce the impact 
of their activity by conducting tugging operations with favorable tides 
whenever feasible.
    In summary and as described above, the following factors (with 
additional analyses for CIBWs included below) primarily support our 
determinations that the impacts resulting from the activities described 
for this IHA are not expected to affect any individual marine mammal's 
fitness for survival or reproduction, and thus is not expected to 
adversely affect the species or stocks through effects on annual rates 
of recruitment or survival:
     No takes by mortality, serious injury, or Level A 
harassment are anticipated or authorized;
     Exposure, and resulting impacts, will likely be brief 
given the short duration of the specified activity and the transiting 
behavior of marine mammals in the action area;
     Marine mammal densities are low in the project area; 
therefore, there will not be substantial numbers of marine mammals 
exposed to the noise from the project compared to the affected 
population sizes;
     Take will not occur in places and/or times where take is 
more likely to accrue to impacts on reproduction or survival, such as 
within ESA-designated or proposed critical habitat, BIAs (other than 
for CIBWs as described below), or other habitats critical to 
recruitment or survival (e.g., rookery);
     The project area represents a very small portion of the 
available foraging area for all potentially impacted marine mammal 
species;
     Take will only occur within middle Cook Inlet and Trading 
Bay--a limited, confined area of any given stock's home range;
     Monitoring reports from previous projects where tugs were 
under load with a jack-up rig in Cook Inlet have documented little to 
no observable effect on individuals of the same species impacted by the 
specified activities;
     The required mitigation is expected to be effective in 
reducing the effects of the specified activity by minimizing the 
numbers of marine mammals exposed to sound and the intensity of the 
exposures; and
     The intensity of anticipated takes by Level B harassment 
is low for all stocks consisting of, at worst, temporary

[[Page 79554]]

modifications in behavior, and will not be of a duration or intensity 
expected to result in impacts on reproduction or survival.
    Cook Inlet Beluga Whales. For CIBWs, we further discuss our 
negligible impact findings in addition to the findings discussed above 
for all species in the context of potential impacts to this endangered 
stock based on our evaluation of the take authorized (table 10).
    All tugging activities will be done in a manner implementing best 
management practices to preserve water quality, and no work will occur 
around creek mouths or river systems leading to prey abundance 
reductions. In addition, no physical structures will restrict passage, 
though impacts to the acoustic habitat are relevant and discussed here. 
While the specified activity will occur within CIBW Critical Habitat 
Area 2, and the CIBW small and resident BIA (see the Description of 
Marine Mammals in the Area of Specified Activities section in the 
notice for the proposed IHA; 89 FR 60164, July 24, 2024), monitoring 
data from Hilcorp's activities suggest that the presence of tugs under 
load with a jack-up rig do not discourage CIBWs from transiting 
throughout Cook Inlet and between critical habitat areas and that the 
whales do not abandon critical habitat areas (Horsley and Larson, 
2023). In addition, large numbers of CIBWs have continued to use Cook 
Inlet and pass through the area, likely traveling to critical foraging 
grounds found in upper Cook Inlet, while noise-producing anthropogenic 
activities, including vessel use, have taken place during the past two 
decades (e.g., Shelden et al., 2013, 2015b, 2017, 2022; Shelden and 
Wade, 2019; Geotz et al., 2023). These findings are not surprising as 
food is a strong motivation for marine mammals. As described in Forney 
et al. (2017), animals typically favor particular areas because of 
their importance for survival (e.g., feeding or breeding), and leaving 
may have significant costs to fitness (reduced foraging success, 
increased predation risk, increased exposure to other anthropogenic 
threats). Consequently, animals may be highly motivated to maintain 
foraging behavior in historical foraging areas despite negative impacts 
(e.g., Rolland et al., 2012).
    Generation of sound may result in avoidance behaviors that will be 
limited in time and space relative to the larger availability of 
important habitat areas in Cook Inlet; however, the area ensonified by 
sound from the specified activity is anticipated to be small compared 
to the overall available critical habitat for CIBWs to feed and travel. 
Therefore, the specified activity will not create a barrier to movement 
through or within important areas. We anticipate that disturbance to 
CIBWs will manifest in the same manner as other marine mammals 
described above (i.e., increased swimming speeds, changes in the 
direction of travel and dive behaviors, increased respiration rates, 
decreased foraging (if such activity were occurring), or alterations to 
communication signals). We do not believe exposure to elevated noise 
levels during transit past tugging activity will have adverse effects 
on individuals' fitness for reproduction or survival.
    Although data demonstrate that CIBWs are not abandoning the planned 
project area during anthropogenic activities, results of an expert 
elicitation (EE) at a 2016 workshop, which predicted the impacts of 
noise on CIBW survival and reproduction given a specific amount of lost 
foraging opportunities, helped to inform our assessment of impacts on 
this stock. The 2016 EE workshop used conceptual models of an interim 
population consequences of disturbance (PCoD) for marine mammals (NRC, 
2005; New et al., 2014; Tollit et al., 2016) to help in understanding 
how noise-related stressors might affect vital rates (survival, birth 
rate and growth) for CIBW (King et al., 2015). NMFS (2016b) suggests 
that the main direct effects of noise on CIBWs are likely to be through 
masking of vocalizations used for communication and prey location and 
habitat degradation. The 2016 workshop on CIBWs was specifically 
designed to provide regulators with a tool to help understand whether 
chronic and acute anthropogenic noise from various sources and projects 
are likely to be limiting recovery of the CIBW population. The full 
report can be found at https://www.smruconsulting.com/publications/ 
with a summary of the expert elicitation portion of the workshop below.
    For each of the noise effect mechanisms chosen for the EE, the 
experts provided a set of parameters and values that determined the 
forms of a relationship between the number of days of disturbance a 
female CIBW experiences in a particular period and the effect of that 
disturbance on her energy reserves. Examples included the number of 
days of disturbance during the period April, May, and June that would 
be predicted to reduce the energy reserves of a pregnant CIBW to such a 
level that she is certain to terminate the pregnancy or abandon the 
calf soon after birth, the number of days of disturbance in the period 
April-September required to reduce the energy reserves of a lactating 
CIBW to a level where she is certain to abandon her calf, and the 
number of days of disturbance where a female fails to gain sufficient 
energy by the end of summer to maintain herself and her calf during the 
subsequent winter. Overall, median values ranged from 16 to 69 days of 
disturbance depending on the question. However, for this elicitation, a 
``day of disturbance'' was defined as any day on which an animal loses 
the ability to forage for at least one tidal cycle (i.e., it forgoes 
50-100 percent of its energy intake on that day). The day of 
disturbance considered in the context of the report is notably more 
severe than any Level B harassment expected to result from these 
activities, which as described is expected to be comprised 
predominantly of temporary modifications in the behavior of individual 
CIBWs (e.g., faster swim speeds, longer dives, decreased sighting 
durations, alterations in communication). Also, NMFS has authorized 15 
instances of take, with the instances representing disturbance events 
within a day--this means that either 15 different individual CIBWs are 
disturbed on no more than 1 day each, or some lesser number of 
individuals may be disturbed on more than 1 day, but with the product 
of individuals and days not exceeding 15. Given the overall authorized 
take, and the short duration of the specified activities (i.e., 6 
days), it is unlikely that any one CIBW will be disturbed on more than 
a couple of days. Lastly, even if a CIBW was exposed every day of 
Hilcorp's planned activities, these activities are only planned for 6 
days, and thus do not fall into the expected range of days of 
disturbance expected to elicit an effect on energy reserves as 
determined by the experts as described above (i.e., 16 to 19 days). 
Further, Hilcorp will implement mitigation measures specific to CIBWs 
whereby they will not begin tugging activities should a CIBW be 
observed at any distance. While Level B harassment (behavioral 
disturbance) is authorized, this measure, along with other mitigation 
measures described herein, will limit the severity of the effects of 
that Level B harassment to behavioral changes such as increased swim 
speeds, changes in diving and surfacing behaviors, and alterations to 
communication signals, not the loss of foraging capabilities. Finally, 
take by mortality, serious injury, or Level A harassment of CIBWs is 
not anticipated or authorized.
    In summary and as described above, the additional following factors 
primarily support our determination

[[Page 79555]]

that the impacts resulting from this activity are not expected to 
adversely affect the CIBWs through effects on annual rates of 
recruitment or survival:
     The area of exposure will be limited to habitat primarily 
used for transiting, and not areas known to be of particular importance 
for feeding or reproduction;
     The activities are not expected to result in CIBWs 
abandoning critical habitat nor are they expected to restrict passage 
of CIBWs within or between critical habitat areas; and
     Any disturbance to CIBWs is expected to be limited to 
temporary modifications in behavior, and will not be of a duration or 
intensity expected to result in impacts on reproduction or survival.
    Based on the analysis contained herein of the likely effects of the 
specified activity on marine mammals and their habitat, and taking into 
consideration the implementation of the required monitoring and 
mitigation measures, NMFS finds that the total marine mammal take from 
the planned specified activity will have a negligible impact on all 
affected marine mammal species or stocks.

Small Numbers

    As noted previously, only take of small numbers of marine mammals 
may be authorized under section 101(a)(5)(D) of the MMPA for specified 
activities other than military readiness activities. The MMPA does not 
define small numbers and so, in practice, where estimated numbers are 
available, NMFS compares the number of individuals taken to the most 
appropriate estimation of abundance of the relevant species or stock in 
our determination of whether an authorization is limited to small 
numbers of marine mammals. When the predicted number of individuals to 
be taken is fewer than one-third of the species or stock abundance, the 
take is considered to be of small numbers (see 86 FR 5322, January 19, 
2021). Additionally, other qualitative factors may be considered in the 
analysis, such as the temporal or spatial scale of the activities.
    For all stocks whose abundance estimate is known, the amount of 
authorized taking is less than one-third of the best available 
population abundance estimate (in fact it is less than 2 percent for 
all stocks, except for CIBWs whose authorized take is for up to 5.38 
percent of the stock; see table 11). The numbers of animals authorized 
to be taken are small relative to the relevant species or stock 
abundances even if each estimated take occurred to a new individual.

                          Table 11--Authorized Take as a Percentage of Stock Abundance
----------------------------------------------------------------------------------------------------------------
                                            Total amount
                  Species                      of take                Stock              Abundance    Percent of
                                             authorized                                 (Nbest \1\)     stock
----------------------------------------------------------------------------------------------------------------
Humpback whale............................             3  Hawaii (Hawaii DPS).........       11,278         0.03
                                                          Mexico-North Pacific (Mexico      \1\ N/A          N/A
                                                           DPS).
                                                          Western North Pacific.......        1,084         0.28
Minke whale...............................             3  Alaska......................      \2\ N/A          N/A
Gray whale................................             3  Eastern Pacific.............       26,960         0.01
Fin whale.................................             2  Northeast Pacific...........      \3\ UND          N/A
Killer whale..............................            10  Eastern North Pacific Alaska        1,920         0.52
                                                           Resident.
                                                          Eastern North Pacific Gulf            587          1.7
                                                           of Alaska, Aleutian
                                                           Islands, and Bering Sea
                                                           Transient.
Beluga whale..............................            15  Cook Inlet..................      \4\ 279         5.38
Dall's porpoise...........................             6  Alaska......................      \5\ UND          N/A
Harbor porpoise...........................            12  Gulf of Alaska..............       31,046         0.04
Pacific white-sided dolphin...............             3  North Pacific...............       26,880         0.01
Harbor seal...............................           365  Cook Inlet/Shelikof.........       28,411         1.29
Steller sea lion..........................             9  Western U.S.................   \6\ 49,932         0.02
California sea lion.......................             2  U.S.........................      257,606        <0.01
----------------------------------------------------------------------------------------------------------------
\1\ Abundance estimates are based upon data collected more than 8 years ago and, therefore, current estimates
  are considered unknown.
\2\ Reliable population estimates are not available for this stock. Please see Friday et al. (2013) and Zerbini
  et al. (2006) for additional information on numbers of minke whales in Alaska.
\3\ The best available abundance estimate for this stock is not considered representative of the entire stock as
  surveys were limited to a small portion of the stock's range.
\4\ On June 15, 2023, NMFS released an updated abundance estimate for endangered CIBWs in Alaska (Goetz et al.,
  2023). Data collected during NOAA Fisheries' 2022 aerial survey suggest that the whale population is stable or
  may be increasing slightly. Scientists estimated that the population size is between 290 and 386, with a
  median best estimate of 331. In accordance with the MMPA, this population estimate will be incorporated into
  the CIBW SAR, which will be reviewed by an independent panel of experts, the Alaska Scientific Review Group.
  After this review, the SAR will be made available as a draft for public review before being finalized. When
  the number of instances of takes is compared to this median abundance, the percent of the stock authorized is
  4.53 percent.
\5\ The best available abundance estimate is likely an underestimate for the entire stock because it is based
  upon a survey that covered only a small portion of the stock's range.
\6\ Nest is the best estimate of counts, which have not been corrected for Steller sea lions at sea during
  abundance surveys.

    Abundance estimates for the Mexico-North Pacific stock of humpback 
whales are based upon data collected more than 8 years ago and, 
therefore, current estimates are considered unknown (Young et al., 
2023). The most recent minimum population estimates (NMIN) 
for this population include an estimate of 2,241 individuals between 
2003 and 2006 (Martinez-Aguilar, 2011) and 766 individuals between 2004 
and 2006 (Wade, 2021). NMFS' Guidelines for Assessing Marine Mammal 
Stocks suggest that the NMIN estimate of the stock should be 
adjusted to account for potential abundance changes that may have 
occurred since the last survey and provide reasonable assurance that 
the stock size is at least as large as the estimate (NMFS, 2023a). The 
abundance trend for this stock is unclear; therefore, there is no basis 
for adjusting these estimates (Young et al., 2023). Assuming the 
population has been stable, and that the 4 authorized takes of humpback 
whale will all be of the Mexico-North Pacific stock, this represents 
small numbers of this stock (0.18 percent of the stock assuming a 
NMIN of 2,241 individuals and 0.52 percent of the stock 
assuming an NMIN of 766 individuals).

[[Page 79556]]

    A lack of an accepted stock abundance value for the Alaska stock of 
minke whale did not allow for the calculation of an expected percentage 
of the population that will be affected. The most relevant estimate of 
partial stock abundance is 1,233 minke whales in coastal waters of the 
Alaska Peninsula and Aleutian Islands (Zerbini et al., 2006). Given 
three authorized takes by Level B harassment for the stock, comparison 
to the best estimate of stock abundance shows, at most, less than 1 
percent of the stock is expected to be impacted.
    There is no stock-wide abundance estimate for Northeast Pacific fin 
whales. However, Young et al. (2022) estimate the minimum stock size 
for the areas surveyed is 2,554. Given two authorized takes by Level B 
harassment for the stock, comparison to the minimum population estimate 
shows, at most, less than 1 percent of the stock is expected to be 
impacted.
    The Alaska stock of Dall's porpoise has no official NMFS abundance 
estimate for this area, as the most recent estimate is greater than 8 
years old. As described in the 2022 Alaska SAR (Young et al., 2023) the 
minimum population estimate is assumed to correspond to the point 
estimate of the 2015 vessel-based abundance computed by Rone et al. 
(2017) in the Gulf of Alaska (N = 13,110; CV = 0.22). Given six 
authorized takes by Level B harassment for the stock, comparison to the 
minimum population estimate shows, at most, less than 1 percent of the 
stock is expected to be impacted.
    Based on the analysis contained herein of the planned activity 
(including the required mitigation and monitoring measures) and the 
anticipated take of marine mammals, NMFS finds that small numbers of 
marine mammals will be taken relative to the population sizes of the 
affected species or stocks.

Unmitigable Adverse Impact Analysis and Determination

    In order to issue an IHA, NMFS must find that the specified 
activity will not have an ``unmitigable adverse impact'' on the 
subsistence uses of the affected marine mammal species or stocks by 
Alaskan Natives. NMFS has defined ``unmitigable adverse impact'' in 50 
CFR 216.103 as an impact resulting from the specified activity: (1) 
That is likely to reduce the availability of the species to a level 
insufficient for a harvest to meet subsistence needs by: (i) Causing 
the marine mammals to abandon or avoid hunting areas; (ii) Directly 
displacing subsistence users; or (iii) Placing physical barriers 
between the marine mammals and the subsistence hunters; and (2) That 
cannot be sufficiently mitigated by other measures to increase the 
availability of marine mammals to allow subsistence needs to be met.
    Hilcorp's tugging activities will occur offshore and north of Kenai 
and the Village of Salmatof. The last ADF&G subsistence survey 
conducted in Kenai was in 1998 (Fall et al., 2000). In the greater 
Kenai area, an estimated 13 harbor seals and no sea lions were 
harvested in 1988 by an estimated 10 households. In the Kenai area, 
estimated harbor seal harvest has ranged between 13 (1998) and 35 
(1997) animals. In 1996, two sea lions and six harbor seals were 
harvested. No sea otters have been reported harvested in Kenai. ADF&G 
Community Subsistence Information System harvest data are not available 
for Salamatof, so Hilcorp assumes the subsistence harvest patterns are 
similar to other communities along the road system on the southern 
Kenai Peninsula, namely Kenai.
    Tugging activities at the Tyonek platform in the North Cook Inlet 
Unit in middle Cook Inlet will occur approximately 10 km from the 
Native Village of Tyonek. Tyonek, on the western side of middle Cook 
Inlet, has a subsistence harvest area that extends south from the 
Susitna River to Tuxedni Bay (Stanek et al., 2007). Moose and salmon 
are the most important subsistence resources measured by harvested 
weight (Stanek, 1994). In Tyonek, harbor seals were harvested between 
June and September by 6 percent of the households (Jones et al., 2015). 
Seals were harvested in several areas, encompassing an area stretching 
32 km along the Cook Inlet coastline from the McArthur Flats north to 
the Beluga River. Seals were searched for or harvested in the Trading 
Bay areas as well as from the beach adjacent to Tyonek (Jones et al., 
2015).
    Seal hunting occurs opportunistically among Alaska Natives who may 
be fishing or traveling in upper Cook Inlet near the mouths of the 
Susitna River, Beluga River, and Little Susitna River. Hilcorp's 
tugging activities may overlap with subsistence hunting of seals. 
However, these activities typically occur along the shoreline or very 
close to shore near river mouths, whereas most of Hilcorps's tugging is 
in the middle of the Inlet and rarely near the shoreline or river 
mouths.
    Any harassment to marine mammals will be limited to minor 
behavioral changes (e.g., increased swim speeds, changes in dive 
behaviors and communication signals, temporary avoidance near the tugs) 
and is anticipated to be short-term, mild, and not result in any 
abandonment or behaviors that would make the animals unavailable to 
Alaska Natives.
    To further minimize any potential effects of their action on 
subsistence activities, Hilcorp has outlined their communication plan 
for engaging with subsistence users in their Stakeholder Engagement 
Plan (see appendix C of Hilcorp's application). This includes using 
traditional/subsistence knowledge to inform planning for the activity. 
Hilcorp is required to abide by this plan and update the plan 
accordingly.
    Based on the description of the specified activity, the measures 
described to minimize adverse effects on the availability of marine 
mammals for subsistence purposes, and the required mitigation and 
monitoring measures, NMFS has determined that the authorized harassment 
will not have an unmitigable adverse impact on the availability of 
marine mammal species or stocks for taking for subsistence uses.

Endangered Species Act

    Section 7(a)(2) of the ESA of 1973 (16 U.S.C. 1531 et seq.) 
requires that each Federal agency insure that any action it authorizes, 
funds, or carries out is not likely to jeopardize the continued 
existence of any endangered or threatened species or result in the 
destruction or adverse modification of designated critical habitat. To 
ensure ESA compliance for the issuance of IHAs, NMFS consults 
internally whenever we propose to authorize take for endangered or 
threatened species, in this case with the NMFS AKRO.
    Four marine mammal species (fin whale, humpback whale (Mexico DPS), 
beluga whale (Cook Inlet), and Steller sea lion (Western DPS)) occur in 
the project area and are listed as threatened or endangered under the 
ESA. The NMFS AKRO issued a Biological Opinion under section 7 of the 
ESA on the issuance of an IHA to Hilcorp under section 101(a)(5)(D) of 
the MMPA by NMFS Office of Protected Resources. The Biological Opinion 
concluded that the action is not likely to jeopardize the continued 
existence of these species and is not likely to destroy or adversely 
modify their critical habitat.

National Environmental Policy Act

    To comply with the NEPA of 1969 (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. NMFS prepared an EA and analyzed the potential 
impacts to marine mammals that would result from Hilcorp's planned 
activities. A Finding of No Significant Impact

[[Page 79557]]

(FONSI) was signed on September 4, 2024. Copies of the EA and FONSI are 
available at https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-oil-and-gas.

Authorization

    NMFS has issued an IHA to Hilcorp for the potential harassment of 
small numbers of 12 marine mammal species incidental to Hilcorp's use 
of tugs to tow, hold, and position a jack-up rig in support of their 
oil and gas activities in Cook Inlet, Alaska from September 24, 2024 
through September 23, 2025, that includes the previously explained 
mitigation, monitoring and reporting requirements.

    Dated: September 24, 2024.
Kimberly Damon-Randall,
Director, Office of Protected Resources, National Marine Fisheries 
Service.
[FR Doc. 2024-22293 Filed 9-27-24; 8:45 am]
BILLING CODE 3510-22-P