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Notice2024-22293

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

Primary source

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Published

September 30, 2024

Effective

September 24, 2024

Issuing agencies

Commerce DepartmentNational Oceanic and Atmospheric Administration

Abstract

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.

Full Text

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<title>Federal Register, Volume 89 Issue 189 (Monday, September 30, 2024)</title>
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[Federal Register Volume 89, Number 189 (Monday, September 30, 2024)]
[Notices]
[Pages 79529-79557]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[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: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-oil-and-gas">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-oil-and-gas</a>. 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: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities">https://www.fisheries.noaa.gov/national/marine-mammal-protection/incidental-take-authorizations-construction-activities</a>. 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 <a href="https://www.fisheries.noaa.gov/resource/document/species-spotlight-priority-actions-2021-2025-cook-inlet-beluga-whale">https://www.fisheries.noaa.gov/resource/document/species-spotlight-priority-actions-2021-2025-cook-inlet-beluga-whale</a>).
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 (<a href="https://www.fisheries.noaa.gov/science-blog/beluga-whale-acoustic-monitoring-survey-post-3">https://www.fisheries.noaa.gov/science-blog/beluga-whale-acoustic-monitoring-survey-post-3</a>) 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; <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>) and
more general information about these species (e.g., physical and
behavioral descriptions) may be found on NMFS' website (<a href="https://www.fisheries.noaa.gov/find-species">https://www.fisheries.noaa.gov/find-species</a>).
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: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessments</a>.

[[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
(<a href="https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/">https://marinemammalscience.org/science-and-publications/list-marine-mammal-species-subspecies/</a>; 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: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-stock-assessment-reports-region</a>. 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 (<a href="https://www.fisheries.noaa.gov/find-species">https://www.fisheries.noaa.gov/find-species</a>) 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: <a href="https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance">https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-acoustic-technical-guidance</a>. 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 <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llc-oil-and-gas-activities-cook-inlet-alaska-0">https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llc-oil-and-gas-activities-cook-inlet-alaska-0</a>). 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 <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llc-oil-and-gas-activities-cook-inlet-alaska-0">https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llc-oil-and-gas-activities-cook-inlet-alaska-0</a>).
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:
<bullet> Occurrence of marine mammal species or stocks in the area
in which take is anticipated (e.g., presence, abundance, distribution,
density);
<bullet> 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);
<bullet> Individual marine mammal responses (behavioral or
physiological) to acoustic stressors (acute, chronic, or cumulative),
other stressors, or cumulative impacts from multiple stressors;
<bullet> How anticipated responses to stressors impact either: (1)
long-term fitness and survival of individual marine mammals; or (2)
populations, species, or stocks;
<bullet> Effects on marine mammal habitat (e.g., marine mammal prey
species, acoustic habitat, or other important physical components of
marine mammal habitat); and,
<bullet> 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:
<bullet> Date and time that monitored activity begins or ends;
<bullet> 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;
<bullet> PSO locations during marine mammal monitoring;
<bullet> 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;
<bullet> 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);
<bullet> Number of marine mammals detected within the harassment
zones, by species; and
<bullet> 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
(<a href="/cdn-cgi/l/email-protection#cb9b99e5829f9be586a4a5a2bfa4b9a2a5ac99aebba4b9bfb88ba5a4aaaae5aca4bd"><span class="__cf_email__" data-cfemail="0252502c4b56522c4f6d6c6b766d706b6c655067726d707671426c6d63632c656d74">[email&#160;protected]</span></a>, <a href="/cdn-cgi/l/email-protection#afc6dbdf81dbd6dcc0c181c2c0c0ddcaefc1c0cece81c8c0d9"><span class="__cf_email__" data-cfemail="c8a1bcb8e6bcb1bba7a6e6a5a7a7baad88a6a7a9a9e6afa7be">[email&#160;protected]</span></a>), 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:
<bullet> Time, date, and location (latitude and longitude) of the
first discovery (and updated location information if known and
applicable);
<bullet> Species identification (if known) or description of the
animal(s) involved;
<bullet> Condition of the animal(s) (including carcass condition if
the animal is dead);

[[Page 79552]]

<bullet> Observed behaviors of the animal(s), if alive;
<bullet> If available, photographs or video footage of the
animal(s); and
<bullet> 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:
<bullet> No takes by mortality, serious injury, or Level A
harassment are anticipated or authorized;
<bullet> 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;
<bullet> 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;
<bullet> 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);
<bullet> The project area represents a very small portion of the
available foraging area for all potentially impacted marine mammal
species;
<bullet> Take will only occur within middle Cook Inlet and Trading
Bay--a limited, confined area of any given stock's home range;
<bullet> 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;
<bullet> 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
<bullet> 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 <a href="https://www.smruconsulting.com/publications/">https://www.smruconsulting.com/publications/</a>
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:
<bullet> 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;
<bullet> 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
<bullet> 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 e

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