Proposed Rule2025-13973
Takes of Marine Mammals Incidental to Specified Activities; Taking Marine Mammals Incidental to Hilcorp Alaska, LLC Oil and Gas Activities in Cook Inlet, Alaska
Primary source
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Published
July 24, 2025
Issuing agencies
Commerce DepartmentNational Oceanic and Atmospheric Administration
Abstract
NMFS has received a request from Hilcorp Alaska, LLC (Hilcorp) for regulations allowing for the take of marine mammals incidental to activities conducted in support of oil and gas exploration, development, production, and decommissioning in Cook Inlet, Alaska, over the course of 5 years (2025-2030). As required by the Marine Mammal Protection Act (MMPA), NMFS is proposing regulations to govern the requested take, and requests comments on the proposed regulations. NMFS will consider public comments prior to making any final decision on the requested MMPA regulations. Agency responses to received comments will be summarized in the final rule, if issued.
Full Text
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[Federal Register Volume 90, Number 140 (Thursday, July 24, 2025)]
[Proposed Rules]
[Pages 34974-35031]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-13973]
[[Page 34973]]
Vol. 90
Thursday,
No. 140
July 24, 2025
Part II
Department of Commerce
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National Oceanic and Atmospheric Administration
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50 CFR Part 217
Takes of Marine Mammals Incidental to Specified Activities; Taking
Marine Mammals Incidental to Hilcorp Alaska, LLC Oil and Gas Activities
in Cook Inlet, Alaska; Proposed Rule
Federal Register / Vol. 90 , No. 140 / Thursday, July 24, 2025 /
Proposed Rules
[[Page 34974]]
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DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
50 CFR Part 217
[Docket No. 250721-0127]
RIN 0648-BN57
Takes of Marine Mammals Incidental to Specified Activities;
Taking Marine Mammals Incidental to Hilcorp Alaska, LLC Oil and Gas
Activities in Cook Inlet, Alaska
AGENCY: National Marine Fisheries Service (NMFS), National Oceanic and
Atmospheric Administration (NOAA), Commerce.
ACTION: Proposed rule; request for comments.
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SUMMARY: NMFS has received a request from Hilcorp Alaska, LLC (Hilcorp)
for regulations allowing for the take of marine mammals incidental to
activities conducted in support of oil and gas exploration,
development, production, and decommissioning in Cook Inlet, Alaska,
over the course of 5 years (2025-2030). As required by the Marine
Mammal Protection Act (MMPA), NMFS is proposing regulations to govern
the requested take, and requests comments on the proposed regulations.
NMFS will consider public comments prior to making any final decision
on the requested MMPA regulations. Agency responses to received
comments will be summarized in the final rule, if issued.
DATES: Comments and information must be received no later than August
25, 2025.
ADDRESSES: A plain language summary of this proposed rule is available
at <a href="https://www.regulations.gov/docket/NOAA-NMFS-2025-0052">https://www.regulations.gov/docket/NOAA-NMFS-2025-0052</a>. Submit all
electronic public comments via the Federal e-Rulemaking Portal. Go to
<a href="https://www.regulations.gov">https://www.regulations.gov</a> and type NOAA-NMFS-2025-0052 in the Search
box (note: copying and pasting the FDMS Docket Number directly from
this document may not yield search results). Click on the ``Comment''
icon, complete the required fields, and enter or attach your comments.
Comments sent by any other method, to any other address or individual,
or received after the end of the comment period, may not be considered
by NMFS. All comments received are a part of the public record and will
generally be posted for public viewing on <a href="https://www.regulations.gov">https://www.regulations.gov</a>
without change. All personal identifying information (e.g., name,
address, etc.), confidential business information, or otherwise
sensitive information submitted voluntarily by the sender will be
publicly accessible. NMFS will accept anonymous comments (enter ``N/A''
in the required fields if you wish to remain anonymous).
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: Jaclyn Daly, 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 promulgated and a Letter of Authorization (LOA) is issued or an
incidental harassment authorization (IHA) is issued.
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). If such findings are made, 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 ``mitigation''); and set forth requirements
pertaining to the monitoring and reporting of the takings. The
definitions of applicable MMPA statutory terms are provided directly
below or included in the relevant sections of this proposed rule.
<bullet> U.S. citizen--individual U.S. citizens or any corporation
or similar entity if it is organized under the laws of the United
States or any governmental unit defined in 16 U.S.C. 1362(13); 50 CFR
216.103);
<bullet> Take--to harass, hunt, capture, or kill, or attempt to
harass, hunt, capture, or kill any marine mammal (16 U.S.C. 1362(13);
<bullet> Incidental harassment, incidental taking, and incidental,
but not intentional, taking--an accidental taking. This does not mean
that the taking is unexpected, but rather it includes those takings
that are infrequent, unavoidable or accidental (50 CFR 216.103);
<bullet> Level A harassment--any act of pursuit, torment, or
annoyance which has the potential to injure a marine mammal or marine
mammal stock in the wild (16 U.S.C. 1362(18); 50 CFR 216.3); and
<bullet> Level B harassment--any act of pursuit, torment, or
annoyance which 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 (16 U.S.C. 1362(18); 50 CFR 216.3).
Purpose of Regulatory Action
NMFS received an application from Hilcorp requesting 5-year
regulations and a letter of authorization (LOA) that would authorize
the take of 12 marine mammal species, comprising 15 stocks, by Level B
harassment, and take by Level A harassment of 9 of those 12 species,
comprising 12 stocks, incidental to activities conducted by Hilcorp in
support of oil and gas exploration, development, production, and
decommissioning. No serious injury or mortality is anticipated or
proposed for authorization.
The proposed regulations would provide a framework for authorizing
the take of marine mammals incidental to specified activities
associated with Hilcorp's oil and gas exploration, development,
production, and decommissioning activities in Cook Inlet, Alaska.
Legal Authority for the Proposed Action
Section 101(a)(5)(A) of the MMPA (16 U.S.C. 1371(a)(5)(A)) directs
the Secretary of Commerce 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 for up to 5 years if,
after notice and public comment, the agency makes certain findings and
promulgates regulations that set forth permissible methods of taking
pursuant to that activity and other means of effecting the ``least
practicable adverse impact'' on the affected species or
[[Page 34975]]
stocks and their habitat (see the discussion below in the Proposed
Mitigation section), as well as monitoring and reporting requirements.
Section 101(a)(5)(A) of the MMPA and the implementing regulations at 50
CFR part 216, subpart I provide the legal basis for issuing this
proposed rule containing 5-year regulations and for any subsequent
Letter(s) of Authorization (LOA).
Summary of Major Provisions Within the Proposed Rule
The major provisions of this proposed rule are:
<bullet> Allowing NMFS to authorize, through an LOA, the take of
small numbers of marine mammals by Level A harassment and/or Level B
harassment incidental to Hilcorp's specified activities (no mortality
or serious injury of any marine mammal would be authorized);
<bullet> Avoiding activities that may result in take of Cook Inlet
beluga whales (CIBWs) within 16 kilometers (km) (10 miles, mi) of the
Mean Higher High Water (MHHW) line of the Susitna Delta (Beluga River
to the Little Susitna River) between April 15 and November 15 to avoid
and minimize impacts when CIBWs are more likely engaging in foraging
behavior;
<bullet> Requiring NMFS-approved protected species observers (PSOs)
and delaying commencement of or shutting down certain activities should
a marine mammal be detected within identified clearance or shutdown
zones to minimize the amount and severity of take;
<bullet> Requiring a soft start for impact pile driving to allow
marine mammals the opportunity to leave the area prior to being exposed
to higher noise levels; and
<bullet> Requiring submission of monitoring reports including, but
not limited to, a summary of marine mammal species and behavioral
observations, construction shutdowns or delays, and construction work
completed.
National Environmental Policy Act
To comply with the National Environmental Policy Act of 1969 (NEPA;
42 U.S.C. 4321 et seq.) and NOAA Administrative Order (NAO) 216-6A,
NMFS must review our proposed action (i.e., promulgation of regulations
and subsequent issuance of an LOA thereunder) with respect to potential
impacts on the human environment. Accordingly, NMFS has prepared a
draft Environmental Assessment (EA) to evaluate the environmental
impacts associated with the proposed issuance of the regulations and
LOA. NMFS' draft EA is available 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>. NMFS will review all comments submitted in response to this
notice prior to concluding our NEPA process or making a final decision
on this request.
Summary of Request
On October 30, 2024, NMFS received an application from Hilcorp
requesting authorization to take marine mammals incidental to oil and
gas exploration, development, production, and decommissioning
activities in Cook Inlet, Alaska. Specifically, Hilcorp plans to
conduct necessary work, including use of tugs towing, holding, or
positioning a jack-up rig, pile driving, and pipeline replacement/
installation activities. NMFS requested additional information from
Hilcorp regarding their request on November 19, 2024, which Hilcorp
provided on January 2, 2025. A final request from NMFS for information
was sent to Hilcorp on January 22, 2025. Hilcorp provided all necessary
information on February 10, 2025, and NMFS deemed Hilcorp's application
adequate and complete on February 18, 2025 (note that NMFS' Notice of
Receipt of Hilcorp's application erroneously described this date as
being February 10, 2025). On March 13, 2025, NMFS published a notice of
receipt (NOR) of Hilcorp's adequate and complete application in the
Federal Register (90 FR 11951), requesting comments and soliciting
information related to Hilcorp's request during a 30-day public comment
period. NMFS did not receive public comments. Subsequently, on March
14, 2025, Hilcorp submitted a revised application that corrected minor
details but did not substantively modify the description of the
specified activities or the type or amount of take requested incidental
to those activities. This revised application is available at: <a href="https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llcs-oil-and-gas-activities-cook-inlet-alaska">https://www.fisheries.noaa.gov/action/incidental-take-authorization-hilcorp-alaska-llcs-oil-and-gas-activities-cook-inlet-alaska</a>.
The requested regulations, if promulgated, would be valid for 5
years, from approximately September 23, 2025, through September 22,
2030. The exposure of marine mammals occurring in the vicinity to
underwater noise generated by the activities could result in incidental
take of marine mammals by Level A and/or Level B harassment. Therefore,
Hilcorp requests authorization to incidentally take marine mammals.
Hilcorp's Incidental Take Authorization (ITA) History
NMFS previously issued multiple ITAs to Hilcorp. Initially, NMFS
issued 5-year Incidental Take Regulations (ITR) to Hilcorp for a suite
of oil and gas activities in Cook Inlet, Alaska (84 FR 37442, July 31,
2019) and three 1-year Letters of Authorization (LOAs) under the ITR.
The 2019 ITR allowed for the take of marine mammals incidental to two-
dimensional (2D) and three-dimensional (3D) geophysical surveys,
vibratory sheet pile driving, and drilling of exploratory wells.
On September 17, 2019, Cook Inletkeeper and the Center for
Biological Diversity filed suit in Federal district court in Alaska
challenging the 2019 ITR and LOAs and supporting documents (the EA and
Endangered Species Act (ESA) Biological Opinion). In a decision issued
on March 30, 2021, the court ruled largely in NMFS' favor, but found a
lack of adequate support in NMFS' record for the agency's determination
that tug towing of drill rigs in connection with production activity
would not cause take of CIBWs and remanded the rulemaking back to NMFS
for further analysis of tug use under the MMPA, ESA, and NEPA. Hilcorp
notified NMFS that all activities covered by the 2019 ITR had already
been completed or would not be completed in the remaining effective
period of the ITR. As a result, the only remaining activity was the use
of tugs towing a jack-up rig. NMFS considered the specific
circumstances relating to Hilcorp's request for take authorization for
tug towing of a jack-up rig, which had not been covered under the 2019
ITR, and issued two sequential Incidental Harassment Authorizations
(IHAs) (87 FR 62364, October 14, 2022). In 2024, NMFS issued an
additional IHA to Hilcorp, at its request and in consideration of the
specific circumstances, for production drilling support in Cook Inlet,
Alaska, which included the use of tugs towing, holding, and positioning
a jack-up rig (89 FR 79529, September 30, 2024). Hilcorp complied with
all the requirements (e.g., mitigation, monitoring, and reporting) of
the previous LOAs and 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.
Description of Proposed Activity
Overview
Hilcorp plans to continue oil and gas exploration, development,
production,
[[Page 34976]]
and decommissioning activities in Cook Inlet, Alaska, for the
reasonably foreseeable future. Over the course of the five years
considered here, this work includes up to 54 days of tugs towing,
holding, or positioning a jack-up rig in support of production drilling
at existing platforms in middle Cook Inlet and Trading Bay; up to 70
days of pile driving in support of production well development at the
Tyonek Platform in middle Cook Inlet; up to 6 days of tugs towing,
holding, or positioning a jack-up rig and up to 18 days of pile driving
in support of exploration drilling at two locations in the Middle
Ground Shoal Unit in middle Cook Inlet and one location between the
Anna and Bruce platforms on the northern border of Trading Bay; and up
to 22 days of pipeline replacement/installation, involving either pipe
pulling or anchor handling or a combination of both, at up to two
locations in middle Cook Inlet and/or Trading Bay. Hilcorp requests
authorization of take by Level B harassment for 12 marine mammal
species (including CIBWs (Delphinapterus leucas)), and additionally by
Level A harassment for a subset of 9 of these species.
Dates and Duration
The specified activities analyzed in this proposed rule are
anticipated to begin in September 2025 and extend through December
2029. However, the proposed rule and LOA, if issued, would be effective
through September 2030 (5 years) to allow for any delays in project
activities. Table 1 provides a summary of Hilcorp's anticipated timings
and durations for their planned activities; however, the schedule may
shift such that actual activities occur in different years than
specified below.
Table 1--Summary of Hilcorp's Planned Activities
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Anticipated duration
Project activity Cook Inlet region Seasonal timing Year(s) planned \1\ of sound-producing Anticipated sound
activity sources
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Tugs under Load with a Jack-Up Rig Middle Cook Inlet..... April--December....... Years 1, 3, and 5 12 days (2 days each: 3 to 4 tugs towing,
in support of Production Drilling. (2025, 2027, 2029). 1 mobilization, 4 holding, and
location-location positioning a jack-
moves, 1 up rig.
demobilization, up
to 12 total pinning
events).
Year 2 (2026)........ 10 days (2 days each:
1 mobilization, 3
location-location
moves, 1
demobilization, up
to 10 total pinning
events).
Year 4 (2028)........ 8 days (2 days each:
1 mobilization, 2
location-location
moves, 1
demobilization, up
to 8 total pinning
events).
Pile Driving in Support of Middle Cook Inlet..... Mid-November--Mid- Year 1-Year 5 (2025- 14 days (7 days per Impact pile driving.
Production Well Development at the April. 2029). pile (intermittent);
Tyonek Platform. 8 hour (hr) per day;
2 piles per year).
Tugs under Load with a Jack-Up Rig Trading Bay (between April--December....... Year 2 (2026)........ 2 days tugs under Impact pile driving,
and Pile Driving in Support of Anna and Bruce load with a jack-up 3 to 4 tugs towing,
Exploratory Drilling\2\. platforms). rig (1 location- holding, and
location move, up to positioning a jack-
2 total pinning up rig.
events); 6 days
intermittent pile
driving (1 well, 1
pile each well).
Middle Cook Inlet (MGS Unit)....... April--December....... Year 4 (2028)......... 4 days tugs under Impact pile driving,
load with a jack-up 3 to 4 tugs towing,
rig (2 location- holding, and
location moves, up positioning a jack-
to 4 total pinning up rig.
events); 12 days
intermittent pile
driving (2 wells, 1
pile each well).
Pipeline Replacement/Installation Middle Cook Inlet/ April--November....... Year 2 (2026)........ Scenario 1: 11 days Scenario 1: Anchor
\3\. Trading Bay. using lay barge handling.
methods. Scenario 2: Anchor
Scenario 2: 22 days handling.
using lay barge
methods (11 days per
project, 2 projects).
April--November....... Year 4 (2028)........ Scenario 1: 8 days Scenario 1: 2 tugs
using pipe pull engaged in pipe
methods. pulling, bottom
Scenario 2: no impact sounds of
pipeline replacement/ pipe connecting with
installation. seafloor.
Scenario 2: none.
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\1\ The specific years activities are planned to occur may or may not coincide with the actual year of execution.
\2\ One exploratory well between Anna and Bruce is analyzed to occur in Year 2 and two exploratory wells in the Middle Ground Shoal Unit are analyzed to
occur in Year 4; however, the exploratory wells may be developed in any separate years during the proposed authorization period.
\3\ Two pipeline scenarios are analyzed to occur: Scenario 1 comprises one project using lay barge methods in Year 2 and one project using pipe pull
methods in Year 4; Scenario 2 comprises two projects using lay barge methods in Year 2 and no additional projects thereafter. A maximum of two
pipeline projects will occur during the proposed authorization period. Pipeline projects may occur simultaneously in any one year or in separate years
during the proposed authorization period. However, only lay barge methodology can be utilized in the same year (i.e., Scenario 2).
Specified Geographical Region
Hilcorp's planned activities would occur in Cook Inlet, Alaska,
which is the specified geographical region. Specifically, activities
would occur in middle Cook Inlet and Trading Bay, Alaska (figure 1)
from a point on the eastern shoreline approximately 12 km (7.5 mi)
south of the East Foreland to a
[[Page 34977]]
point approximately 16 km (10 mi) south of Point Possession on the west
side, to the northernmost production platform in middle Cook Inlet
(Tyonek, located in the North Cook Inlet Unit) to a point that is 3.5
km (2.2 mi) north of the village of Tyonek near the mouth of the
Chuitna River. From there the area extends south to a point along the
western shoreline approximately 15 km (9.3 mi) south of the West
Foreland, and across the inlet back to a point on the eastern shoreline
approximately 12 km (7.5 mi) south of the East Foreland. The geographic
area of all activity covers a total of approximately 1,865 square
kilometers (km\2\) (460,850 acres) (within Cook Inlet in State of
Alaska waters). For the purpose of this proposed rule, middle Cook
Inlet refers to waters north of the East and West Forelands and south
of Threemile River in the west and Point Possession in the east, and
Trading Bay refers to waters from approximately Granite Point in the
north to the West Foreland in the south. Upper Cook Inlet refers to
waters north and east of Beluga River in the west and Point Possession
in the east.
BILLING CODE 3510-22-P
[[Page 34978]]
[GRAPHIC] [TIFF OMITTED] TP24JY25.001
BILLING CODE 3510-22-C
[[Page 34979]]
Detailed Description of the Specified Activity
Hilcorp's ITR petition includes four stages of oil and gas
activities: production, exploration, development, and decommissioning.
Production Drilling and Well Development--Hilcorp routinely
conducts production drilling activities at offshore platforms to meet
production needs; all Hilcorp platforms have the potential for
production drilling activity. Drilling activities are accomplished
using conventional drilling equipment from a variety of rig
configurations and occur through existing well slots or wellbores
located in legs of the existing platforms. Hilcorp plans to conduct
production drilling in middle Cook Inlet and Trading Bay during the
open water season, which generally runs from April to November but may
extend into December depending on ice conditions. Drilling activities
would span up to 240 days (table 1), with tugboats towing, holding, or
positioning a jack-up rig for a total of up to 54 days across the 5-
year proposed authorization period (table 1). In addition to production
drilling activities, 10 drilling conductor pipes (piles) would be
driven into the sediment to support future well slots for production
well development on the Tyonek Platform at an installation rate not to
exceed two per year (table 1). Pile driving would occur intermittently
between mid-November and mid-April. Hilcorp has requested, and NMFS
proposes to authorize, take associated with tug use (to tow, hold, and
position a jack-up rig) and pile driving at the Tyonek Platform to
support production drilling and well development.
Tugs under load with a jack-up rig in support of production
drilling. Some platforms in Cook Inlet have permanent drilling rigs
installed that operate using power provided by the platform power
generation systems; other platforms do not have drill rigs or the
platform drill rig is not sufficient for the work needing to be done,
and the use of a mobile drill rig is required. Mobile offshore drill
rigs may be powered by the platform power generation system (if
compatible with the platform power generation system) or may self-
generate power with the use of diesel-powered generators.
Hilcorp proposes to conduct production drilling using the Spartan
151 jack-up drill rig (or similar). A jack-up rig is a type of mobile
offshore drill unit used in offshore oil and gas drilling activities.
It is comprised of a buoyant mobile platform or hull with moveable legs
that are adjusted to raise and lower the hull over the surface of the
water. Spartan 151 is a 150 H class independent-leg, cantilevered jack-
up drill rig with a drilling depth capability of 7,620 meters (m)
(25,000 feet (ft)) that can operate in maximum water depths up to 46 m
(151 ft). To maintain safety and work efficiency, the jack-up rig would
be equipped with the following:
<bullet> Either a 5,000-, 10,000-, or 15,000-pound-per-square-inch
(psi) blowout preventer (BOP) stack for drilling in higher pressure
formations found at greater depths in Cook Inlet;
<bullet> Sufficient variable deck load to accommodate the increased
drilling loads, tubular frame for deeper drilling;
<bullet> Reduced draft characteristics to enable the rig to easily
access shallow water locations;
<bullet> Riser tensioning system to adequately deal with the
extreme tides and currents in up to 46 m (151 ft) water depth;
<bullet> Steel hull designed according to United States Coast Guard
(USCG) specifications (inspected by USCG prior to entering the water);
and
<bullet> Ability to cantilever over existing platforms for working
on development wells.
The jack-up rig would be stocked with most of the drilling supplies
required to complete a full summer program each year, including both
production and exploratory drilling. Deliveries of the remaining items,
including crew transfers, would be performed by support vessels and
helicopters. The majority of the oilfield support services contractors
have offices, shops, and additional equipment located in Anchorage,
Kenai, and Nikiski that would support their remote field operations.
Tugs would be used to mobilize or move the jack-up rig and would be
released once the rig is in place.
Jack-up rig equipment would use diesel fuel or electricity from
generators. Personnel associated with fuel delivery, transfer, and
handling would be knowledgeable of industry Best Management Practices
(BMPs) related to fuel transfer and handling, drum labeling, secondary
containment guidelines, and the use of liners/drip trays. The jack-up
rig would take on a maximum fuel load prior to operations to reduce
fuel transfers during production or exploratory drilling. T
The jack-up rig would have a diesel burn rate of approximately
9,464 liters (2,500 gallons) per day. The jack-up rig would need to be
refueled on location one time per well via an International
Organization for Standardization (ISO) tank or directly from a supply
boat. Commercial tank farms in the Nikiski or Kenai area would supply
fuel transported by workboats as needed. The Rig Barge Master would
oversee re-fueling and fluid transfers between the rig and fuel
workboats, and subsequent transfers between tanks on the rig.
Three ocean-going tugs would be used to safely pull the Spartan-151
(or similar jack-up rig) to drilling locations and to position the
jack-up rig to appropriately secure it on the sea floor. The most
common configuration while traveling with the jack-up rig during the
proposed moves is two tugs positioned side by side (approximately 30 to
60 m apart [98 to 197 ft]), pulling from the front of the jack-up rig,
and one tug approximately 200 m (656 ft) behind the front tugs
positioned behind the jack-up rig, applying tension on the line as
needed for steering and straightening. While positioning the jack-up
rig on a platform, the tugs may be fanned out around the jack-up rig to
provide the finer control of movement necessary to safely position the
jack-up rig on the platform. A fourth tug would be available on standby
in the event that mechanical issues occur with one of the tugs.
Additionally, the fourth tug may be used minimally (for approximately 1
hr) to help with positioning the jack-up rig. The horsepower (hp) of
each of the tugs may range between 4,000 and 8,000. Details of the
proposed tugs, or similar, are provided in table 2.
Table 2--Description of Tugs (or Similar) Planned for Use for Towing, Holding, and Positioning the Jack-Up Rig
----------------------------------------------------------------------------------------------------------------
Gross
Vessel \1\ Activity Length (m) Width (m) tonnage
----------------------------------------------------------------------------------------------------------------
Bering Wind (or similar)................ Towing, holding, and 22 10 144
positioning the jack-up rig.
Stellar Wind (or similar)............... Towing, holding, and 32 11 160
positioning the jack-up rig.
Glacial Wind (or similar)............... Towing, holding, and 37 11 196
positioning the jack-up rig.
[[Page 34980]]
Dr. Hank Kaplan (or similar)............ Standby tug used only for 23 11 196
positioning the jack-up rig,
if needed.
----------------------------------------------------------------------------------------------------------------
\1\ This is not intended to be a specific list of tugs. Rather, tugs would be the same or similar such that
potential effects of their use would be equivalent to what is analyzed herein.
The jack-up rig would be moved in a manner to minimize any
potential safety risks as well as cultural or environmental impacts.
While under tow to a well site, rig operations would be monitored by
Hilcorp and the drilling contractor. Very high frequency (VHF) radio,
satellite, and cellular phone communication systems would also be used
while the jack-up rig is under tow. Helicopter transport would be
available to move personnel to and from the rig and platforms.
The amount of time that tugs would be under load transiting and
holding or positioning the jack-up rig in Cook Inlet would be tide-
dependent. The amount of operational effort (i.e., power output) the
tugs use for transiting would depend on whether the tugs are towing
with or against the tide and could vary across a tide cycle as the
current increases or decreases in speed over time. Hilcorp would make
every effort to maximize transit with the tide (which would require
lower power output) and minimize transit against the tide (which would
require higher power output). See the Estimated Take of Marine Mammals
section of this proposed notice of issuance for more detail on
assumptions related to power output.
To mobilize the jack-up rig each year, a high slack tide is
necessary for the tugs to approach close enough to shore to attach and
pull the jack-up rig off Rig Tenders Dock. The same conditions would be
required for demobilization when the jack-up rig is returned to Rig
Tenders Dock at the end of the open water season and to position the
jack-up rig on existing platforms or well sites. The relatively slow
current and calm conditions at a slack tide would enable the tugs to
perform the fine movements necessary to safely position the jack-up rig
within several feet of the platform. Additionally, positioning and
securing the jack-up rig at high slack tide rather than low slack tide
would allow for the legs to be pinned down (jack the legs down onto the
sea floor) at an adequate height to ensure that the hull of the jack-up
rig remains above the water level of the subsequent incoming high tide.
Because 12 hrs elapse between each high slack tide, tugs are generally
under load for those 12 hrs, even if the towed distance is small, as
high slack tides are preferred to both attach and detach the jack-up
rig from the tugs. Once the tugs are on location with the jack-up rig
at high slack tide (12 hours from the previous departure), there is a 1
to 2-hour window when the tide is slow enough (e.g., 1 to 2 knots [kt])
for the tugs to initiate positioning the jack-up rig and pin the legs
to the seafloor on location. The tugs are estimated to be under load,
generally at half-power conditions or less, for up to 14 hours from the
time of departure through the initial positioning attempt of the jack-
up rig. An additional fourth tug, may engage during positioning
activities to assist with fine movements necessary to place the jack-up
rig. The fourth tug would engage with the three tugs during a
positioning attempt for up to approximately 1 hour at half power.
If the first positioning attempt takes longer than anticipated, the
increasing current speed (approximately 3 to 4 kt) would prevent the
tugs from safely positioning the jack-up rig on location. If the first
positioning attempt is not successful, the jack-up rig would be pinned
down at a nearby location and the tugs would be released from the jack-
up rig and no longer be under load. The tugs would remain nearby,
generally floating with the current. Approximately one hour before the
next high slack tide, the tugs would re-attach to the jack-up rig and
reattempt positioning over a period of 2 to 3 hours. Positioning
activities would generally be performed at half power. If a second
attempt is needed, the tugs would be under load holding or positioning
the jack-up rig on a second day for up to 5 hours. Typically, the jack-
up rig can be successfully positioned over the platform in one or two
attempts.
During a location-to-location transport (e.g., platform-to-
platform), the tugs would transport the jack-up rig, traveling with the
tide in nearly all circumstances except in situations that threaten the
safety of humans and/or infrastructure integrity. In a north-to-south
transit, the tugs would tow the jack-up rig with the outgoing tide and
would typically arrive at their next location to position the jack-up
rig on the low slack tide, requiring half power or a lower power output
during the transport. In a south-to-north transit, Hilcorp would prefer
to pull the jack-up rig from the platform on a low slack tide to begin
transiting north following the incoming tide. This would maximize their
control over the jack-up rig and would require half power or a lower
power output. There may be a situation where the tugs pulling the jack-
up rig begin transiting with the tide to their next location, miss the
tide window to safely set the jack-up rig on the platform or pin it
nearby, and so have to transport the jack-up rig against the tide to a
safe harbor. Tugs may also need to transport the jack-up rig against
the tide if large pieces of ice or extreme wind events threaten the
stability of the jack-up rig on the platform. All tug towing, holding,
or positioning would be done in a manner implementing best management
practices to preserve water quality, and no work would occur around
creek mouths or river systems where prey abundance could be affected.
Although the variability in power output from the tugs can range
from an estimated 20 to 90 percent when they are under load with the
jack-up rig, as described above, the majority of the hours (spent
transiting, holding, and positioning) would occur at half power (i.e.,
50 percent) or less. Scenarios in which power output may be greater
than 50 percent could include small periods of time (i.e., minutes
during positioning to counteract the tide (up to 90 percent power
output); Durham, pers. comm. 2022).
Production Well Development at Tyonek Platform. Hilcorp plans to
install ten 76.2-centimeter (cm; 30-inch [in]) diameter (or smaller)
steel piles immediately adjacent to three of the four existing legs of
the Tyonek Platform in middle Cook Inlet during the proposed 5-year
authorization period. The piles would be delivered to the platform via
a supply vessel from Nikiski and pile driving operations would be
conducted using an existing crane on the Tyonek platform. Each pile
would be arranged in a concentric configuration around the outside of
legs 1, 2, and 3. Each leg would have up to
[[Page 34981]]
four piles with a maximum of 10 piles total between all three legs.
Pile driving would be intermittent to weld additional pile sections
onto the driven pile approximately every 12.2 m (40 ft). Once
installation is complete, each pile would extend approximately 53 m
(175 ft) or 91 m (300 ft) below the mudline. The piles would be driven
to target depth using an APE 20-5 hydraulic impact hammer with a ram
weight of 18,144 kilograms (kg; 40,000 pounds [lb]) or an APE D80-42
single acting diesel impact hammer with a ram weight of 18,144 kg
(40,000 lb) or a similar impact hammer. Impact hammering is anticipated
to occur intermittently over weeks for 8 hours per day for up to seven
days per pile, and a total of up to 14 days per season. Pile driving at
the Tyonek Platform would occur between mid-November and mid-April.
Exploration Drilling-Hilcorp plans to drill one exploratory well
between the Anna and Bruce platforms near the northern border of
Trading Bay and two exploratory wells in the MGS Unit in middle Cook
Inlet, based on mapping of subsurface structures from previously
collected two-dimensional (2D) and three-dimensional (3D) seismic data
and historical well information (table 1). For all three wells,
drilling would begin after the jack-up rig has already mobilized to
middle Cook Inlet and before it has demobilized back to Rig Tenders
Dock. The exact start dates for drilling the wells are currently
unknown and would be dependent upon availability of the jack-up rig.
Hilcorp anticipates that each well would take approximately 40 to 60
days to drill and test with 2 days of tugs towing a jack-up rig, and 6
days of impact pile driving. After testing, the wells would undergo
plug and abandonment (P&A) for the following 14 to 90 days.
Tugs under load with a jack-up rig in support of exploration
drilling--Tugging activity in support of exploratory drilling is the
same as described above for production drilling. In Year 2, tugs would
tow, hold, or position the jack-up rig for up to 2 days at one
exploratory well site between the Anna and Bruce platforms. In Year 4,
tugs would tow, hold, or position the jack-up rig for up to 4 days at
two exploratory well sites within the MGS Unit.
Drilling Program and Well Operations--A drive pipe is a relatively
short, large-diameter pipe driven into the sediment prior to the
drilling of oil wells. The drive pipe serves to support the initial
sedimentary part of the well, preventing the loose surface layer from
collapsing and obstructing the wellbore. Drive pipes (piles) for each
well would be installed using impact pile driving techniques. At each
well site, Hilcorp proposes to drive a 76.2-cm (30-in) diameter pile to
approximately 120 m (394 ft) using an APE Model 15-4 hydraulic impact
hammer (or similar) with a ram weight of 13,608 kg (30,001 lb). Pile
driving would be discontinuous and average 0.3 m (1 ft) per min with a
1-hour break for cooling and maintenance after approximately every 40
min. For each well, the assumed maximum impact hammering in one 24-hour
period is 12 hours and is anticipated to last up to 6 days at each well
site, although actual hammering of the pile would occur intermittently
over the whole period.
Once piles are installed and ready for drilling, smaller diameter
conductor pipes would be inserted into the 76.2-cm (30-in) diameter
piles to transport drill cuttings to the surface. These small diameter
pipes would be drilled and not hammered, and the drilling sounds would
not be in direct contact with the water column. As a result, no take is
expected to result from this activity.
The drilling program for one exploratory well between the Anna and
Bruce platforms and for two wells in the MGS Unit would be described in
detail in the request for a permit to drill submitted to the Alaska Oil
and Gas Conservation Commission (AOGCC). When planned and permitted
operations are completed, the wells would be suspended according to
State of Alaska regulations. All drilling waste, wastewater,
recyclables, hazardous waste, and municipal solid waste would be
stored, transported, and disposed of in accordance with local, state,
and Federal regulations. Drilling waste from each well including
drilling fluids, mud, and rock cuttings would be circulated from
downhole to the jack-up mud pit system. Non-hydrocarbon-based drilling
wastes would be discharged to Cook Inlet under an approved Alaska
Pollutant Discharge Elimination System general permit or sent to an
approved waste disposal facility. Hydrocarbon-based drilling wastes
which would be delivered to an onshore permitted location for disposal.
Hilcorp would follow BMPs and all stipulations of the applicable
permits for this activity. More information on oil production can be
found in Hilcorp's application.
Pipeline Installation and/or Replacement. Hilcorp proposes to
execute two pipeline replacement or installation projects in any year.
The acoustic sources associated with pipeline replacement/installation
activities for which Hilcorp has requested incidental take
authorization include tugs engaged in anchor handling and/or pipe
pulling activities (table 3). The project timelines are subject to
weather conditions and equipment readiness. Each project's scope
entails the installation or replacement of pipeline in either middle
Cook Inlet or Trading Bay or a combination of both. The specific
methodology of the pipeline replacement or installation is pending
finalization, with both methods--pipe pulling and lay barge
positioning--under consideration for implementation. Both methods
include replacing or installing approximately 2,286 m (7,500 ft) of
pipeline. Pipeline replacement and installation is driven by the need
to mitigate corrosion, pipeline fatigue, and abrasion leaks, ensuring
alignment with requirements of the Pipeline and Hazardous Materials
Safety Administration. Installation of new gas pipelines would also
address the growing consumer demand for natural gas in Southcentral
Alaska by allowing larger quantities of natural gas to be extracted for
use.
Table 3--Summary of Pipeline Activities, Purposes, Durations, and Anticipated Sound Sources
----------------------------------------------------------------------------------------------------------------
Anticipated sound
Activity Purpose Duration per project sources
----------------------------------------------------------------------------------------------------------------
Lay Barge Method
----------------------------------------------------------------------------------------------------------------
Anchor Setting...................... Set 8-point anchor 2 days................... 2 AHTs*, 1 assist tug.
system.
Pipelay............................. Lay out 2,286 (7,500 8 days................... 2 AHTs.
ft) of pipeline.
Anchor Recovery..................... Recover 8 Anchors...... 1 day.................... 2 AHTs.
----------------------------------------------------------------------------------------------------------------
[[Page 34982]]
Pipe Pull Method
----------------------------------------------------------------------------------------------------------------
Pipelay............................. Pull out 2,286 m (7,500 8 days................... 1 installation tug, 1
ft) of pipeline. assist tug, seafloor
bottom impact sounds.
----------------------------------------------------------------------------------------------------------------
* Note: AHT is an acronym for anchor handling tugs.
Pipeline Replacement Activities Using Lay Barge Methodology.
Hilcorp is considering employing lay barge methods for pipeline
replacement/installation. This approach would involve the use of anchor
handling tugs (AHTs) and anchor systems to maintain the optimal
stability and alignment of a specialized vessel, referred to as a lay
barge, while laying pipeline on the seafloor. Additional pre-
mobilization needs for replacement/installation activities using lay
barge methods include procurement and transport to the worksite of
project materials and vessels. All activities involving sound
generation in the day-to-day activities, such as anchor handling and
pipelaying, would follow uniform procedures for both pipeline
replacement and installation as detailed in the subsequent sections.
Subsea Pipeline Operations. Pipeline activities utilizing lay barge
methods require support from two AHTs, a pipelay barge, and one assist
tug (see table 4 for examples of anticipated vessel specifications).
The pipelay barge would be towed by an AHT to the initial anchor
setting location. To anchor the barge, eight anchors would be set, one
at a time using one AHT during slack tide. During anchor setting, a tug
would handle each anchor, one at a time. Setting each anchor during
slack tide may require 1 hour each, intermittently, over a 2-day period
(i.e., 4 hours per day for all eight anchors). During an incoming or
outgoing tide, anchors would not be set, rather one AHT and one assist
tug would hold the pipelay barge in a stationary position until the
next slack tide (i.e., 4 to 5 hours).
Table 4--Example Types of Tugs and Barges Used in Lay Barge Operations
----------------------------------------------------------------------------------------------------------------
Length Beam \2\
Vessel \1\ Operational Use \2\ (m) (m) hp
----------------------------------------------------------------------------------------------------------------
Barge
----------------------------------------------------------------------------------------------------------------
Ninilchik........................ Lay barge to be positioned and anchored by 79 22 N/A
tugs using up to eight anchors and serve as
an above-water work platform.
----------------------------------------------------------------------------------------------------------------
Assist Tug \3\
----------------------------------------------------------------------------------------------------------------
Bering Wind...................... Assist tug used to assist the AHTs in 22 10 5,080
holding the pipelay barge in place against
an incoming or outgoing tide during initial
barge positioning.
Dr. Hank Kaplan.................. ............................................ 24 11 5,380
----------------------------------------------------------------------------------------------------------------
Anchor Handling Tugs \3\
----------------------------------------------------------------------------------------------------------------
Denise Foss...................... AHTs used to hold the barge in place during 37 12 7,268
incoming or outgoing tides when anchor
setting or retrieving; re-position anchors
along the pipeline route; and operate in
tandem during pipelay.
Resolve Pioneer.................. ............................................ 63 12 5,750
----------------------------------------------------------------------------------------------------------------
\1\This is not intended to be a specific list of tugs. Rather, tugs would be the same or similar such that
potential effects of their use would be equivalent to what is analyzed herein.
\2\ Vessel length and beam width are rounded to the nearest whole number.
\3\ Tugs may range in power from 2,000 to 8,000 horsepower (hp).
Pipeline segments would be installed approximately every 305 m
(1,000 ft) from the pipelay barge along the proposed routes. To lay the
pipeline in place, the pipelay barge would be moved in a sequence along
the pipeline route by moving the eight anchors one at a time to shift
the position of the barge forward. To move anchors, two AHTs would
operate one at a time in sequence and move a single anchor at a time
(i.e., a single tug would move an individual anchor).
Laying pipe from the lay barge would engage a U-shaped stinger
roller assembly that would be affixed to the pipelay barge to guide the
pipeline into the water. This assembly is specifically engineered to
regulate the curvature of the pipeline during the laying process and
safely lay pipe while preventing damage from excessive bending. On the
deck of the pipelay barge, segments of pipeline would be inspected and
hydrotested and coatings would be verified prior to installation in the
water.
Anchor Setting. To secure the pipelay barge, each of the eight
anchors would be set one at a time using one tug (C. Burvee, Blackfin,
Pers. comm., March 13, 2023). Setting one anchor would take
approximately 1 hour during slack tide. There are four slack tides per
day; therefore, four anchors would be set in 1 day. Setting all eight
anchors is expected to take 2 days (i.e., during each of the four slack
tides per day). There are approximately 4 to 5 hours between slack
tides (i.e., between low tide and high tide).
During an incoming or outgoing tide, an assist tug would work
simultaneously with an AHT to hold the pipelay barge in place against
the tide. During this 4-to-5-hour period, the two tugs would average 50
percent power output (C. Burvee, Blackfin, Pers.
[[Page 34983]]
comm., March 13, 2023). During an incoming or outgoing tide, the other
AHT would be idle. Therefore, during a 24-hour period of setting four
anchors, a single AHT would operate at an average of 50 percent power
for 4 hours (during each slack tide) to set anchors, followed by a 4-
to-5-hour period when the assist tug and the second AHT would operate
at an average of 50 percent power holding the barge between each slack
tide. This pattern would continue until all eight anchors are set over
2 days. During anchor setting, only one tug would be anchor handling at
a time, operating at 50 percent power. Once all eight anchors are set,
the assist tug would depart the pipelay site, leaving only the two AHTs
for pipelay. Setting an anchor requires the tug captain to aim for an
X, Y coordinate on the seafloor. Due to the strong tides and currents
in Cook Inlet and the need to aim for a specific location, setting
anchors is more complex and requires more time than anchor retrieval.
Pipelaying. Once all eight anchors are set, the barge would be
moved approximately every 305 m (1,000 ft) along the pipeline route.
Each time that the barge needs to be repositioned, a single tug would
be used at half power (50 percent) for anchor handling. Each of the
eight anchors would be repositioned in the new location, one anchor at
a time. Two bow anchors would typically be repositioned first (one at a
time), then each set of port and starboard anchors (i.e., two on each
side) would be repositioned one at a time, finishing with the two stern
anchors one at a time to move the barge. The two tugs would work in
sequence to relocate a single anchor at a time to ``crawl'' the barge
into the new position approximately 305 m (1,000 ft) from the previous
position. To execute this, the bow anchor cables of the pipelay barge
would be tightened to slowly pull it to the new position as the stern
anchors are slowly released. It is estimated it will take 8 days to
complete the pipelaying portion of replacement/installation activity
using the lay barge method.
Each anchor weighs 9,071 kg (20,000 lb) and has approximately 4.6 m
(15 ft) of chain and 915 m (3,002 ft) of wire cable. All wire cables
would be under tension when in the water. During pipelay, each anchor
move would take about 15 minutes and would be an intermittent process
as each anchor is moved individually.
Anchor Retrieval. Anchor retrieval is only possible during slack
tides. The process would involve pulling eight anchors one by one using
a single tug from a fixed, stationary position. While one tug is
engaged in retrieving an anchor, the second tug would remain idle.
Between slack tides, when the tide is either incoming or outgoing, both
AHTs would hold the barge in place for approximately 4 to 5 hours,
operating at an average power output of 50 percent. The process of
retrieving anchors would be swifter compared to the initial anchoring
procedure due to the relative ease of lifting the anchor from its fixed
position on the seafloor as detailed in the previous section. Within
one slack tide period, two anchors could be successfully retrieved.
Consequently, all eight anchors could be pulled up within a 24-hr span.
Vessels for Pipeline Replacement/Installation Activities. Pipeline
activities utilizing lay barge methods would require support from two
AHTs, a pipelay barge, and one assist tug as shown in table 4. The two
AHTs would be involved in replacement/installation operations,
specifically during anchor handling. An assist tug from within Cook
Inlet (Bering Wind or Dr. Hank Kaplan, or similar) would hold the barge
between slack tides along with one of the AHTs. It is important to note
their availability may not be guaranteed once project timelines are
finalized. In such cases, a comparable vessel would be chosen for the
intended activity.
Pipeline Replacement Activities Using Pipe Pull Methodology.
Hilcorp is also considering implementing a pipe pull method for
pipeline replacement/installation during the proposed ITR period. For
this approach, the pipeline would be assembled on land in 305-m (1000-
ft) sections and subsequently towed to sea one section at a time along
the seafloor. This process would be executed by an installation tug
with assistance from an assist tug. A large tug will tow the project
spools into position.
During the initial phases of pipe-pulling, a pull wire would be
connected to the winch on the installation tug; the tug would then pull
the pipe towards its stern while remaining on anchor. As the towing of
the pull wire begins, buoyancy assemblies would be installed from shore
along the pull wire to lift the wire out of the mud. This added
buoyancy would act to reduce drag and would also reduce the pull force
required by the installation tug. Onshore, the pull wire would be
attached to the buoyed pull head of the first pipeline spool and the
first pipeline segment would be pulled into the water during high tide.
After the installation tug has pulled the pipeline, placing the
tailhead about 91 m (300 ft) offshore, it would stop pulling and
continue to release wire as it moves to a specified location farther
offshore. Once it reached this new location, the tug would resume
pulling the pipeline segment using the attached pull wire and remove
the buoyancy assemblies as the pull wire is reeled in. Next, the
pipeline segment would be guided into position within a predetermined 3
m by 3 m (10 ft by 10 ft) target area near the platform; the
installation vessel would then detach the pull wire and attach a buoy
to a 45.7-m (150-ft) pennant secured at the front of the pipeline.
Following positioning of the first pipeline spool, the process
would be repeated by pulling the second spool within a 3 m by 3 m (10
ft by 10 ft) target area at the tailhead of the first spool, and then
pull the third spool within a 3 m by 3 m (10 ft by 10 ft) target area
at the tailhead of the second spool and so on until all spools are laid
out 2,286 m (7,500 ft). The assist tug would help keep the installation
tug on the correct bearing throughout each pull and will assist in
final positioning of the spools. The estimated duration to position all
the spools is approximately 8 days, with one spool being pulled per
day. The total anticipated tug operation time, operating at 50 percent
to 85 percent power, is expected to be 3 hours per day.
A separate tugboat would help the installation tug maintain the
planned route during tidal changes. A shallow-water support vessel
would ferry the messenger rope from the installation tug to the beach
and assist in any onshore to offshore operations. The messenger rope is
a wire used to transfer the larger pull wire from/to the floating asset
to/from the beach. This is a light, usually floating line that can be
messengered by a small craft. Messenger wire would only be needed if
the weight, due to length or required diameter, of the actual pulling
wire would be unmanageable by a small craft. Divers would remove the
45.7-m (150-ft) pennant wire and buoy from the pull head, flood each
pipeline segment, and assist with post tie-in operations. See table 5
for examples of vessel sizes and function details for this activity.
[[Page 34984]]
Table 5--Example Types of Tugs and Barges Used in Pipe Pull Operations
--------------------------------------------------------------------------------------------------------------------------------------------------------
Vessel \1\ Operational Use Length \2\ m Beam \2\ m Horsepower
--------------------------------------------------------------------------------------------------------------------------------------------------------
Installation Tug \3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Resolve Pioneer..................... Main tug for installation and is responsible 63.................... 12.................... 5,750
for pulling spools into position.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Assist Tug \3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Steller Wind........................ Assist tug supports the Resolve Pioneer, or 26.................... 9..................... 3,500
similar, in maneuvering the spool of pipe to
its designated seabed position, particularly
when contending with tidal currents.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\ This is not intended to be a specific list of tugs. Rather, tugs would be the same or similar such that potential effects of their use would be
commensurate with what is analyzed herein.
\2\ Vessel length and beam width are rounded to the nearest whole number.
\3\ Tugs may range in power from 2,000 to 8,000 hp.
The risk of interaction or entanglement with gear or equipment
during pipeline replacement/installation activities is avoided due to
the small area occupied by the cables relative to the marine mammals'
habitat in Cook Inlet, use of taut lines, and mitigation and monitoring
measures described in the Proposed Mitigation and Proposed Monitoring
and Reporting sections of this notice. Vessel strikes or other
encounters are also not anticipated as a result of anchor handling
activities. No other interactions are anticipated.
Proposed mitigation, monitoring, and reporting measures are
described in detail later in this document (please see Proposed
Mitigation and Proposed Monitoring and Reporting).
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 6 lists all species or stocks for which take is expected and
proposed to be 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 mortality
or serious injury (M/SI) is anticipated or proposed to be authorized
here, PBR and M/SI rates from anthropogenic sources are included here
as gross indicators of the status of the species or stocks and other
threats.
Marine mammal abundance estimates presented in table 6 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 values presented in table 6 are the most recent available
at the time of publication (including from the draft 2024 SARs; 90 FR
13344, March 21, 2025) 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>.
Table 6--Species With Estimated Take From the Specified Activities
--------------------------------------------------------------------------------------------------------------------------------------------------------
ESA/MMPA status; Stock abundance (CV,
Common name Scientific name \1\ 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 3,168 (0.26, 2,554, UND 0.6
2013)\ 5\.
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/A) UND 0
acutorostrata.
--------------------------------------------------------------------------------------------------------------------------------------------------------
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).
[[Page 34985]]
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 331 (0.076, 311, 2022) 0.62 0
Family Phocoenidae (porpoises):
Dall's Porpoise................. Phocoenoides dalli..... Alaska................. -, -, N UND \8\ (UND, UND, UND 37
2015).
Harbor Porpoise................. Phocoena............... Gulf of Alaska......... -, -, Y 31,046 (0.21, N/A, UND 72
1998).
--------------------------------------------------------------------------------------------------------------------------------------------------------
Order Carnivora--Pinnipedia
--------------------------------------------------------------------------------------------------------------------------------------------------------
Family Otariidae (eared seals and
sea lions):
California 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 \9\ (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>).
\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' 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 values presented here based on the 2020 SAR and are an underestimate for the entire stock because it is based on surveys which covered only a
small portion of the stock's range.
\6\ Abundance estimates are currently 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\ 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.
\9\ 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 6 temporally and spatially co-occur with the activity to the
degree that take is reasonably likely to 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 rulemaking.
Gray Whale
The stock structure for gray whales in the Pacific has been studied
for a number of years and remains uncertain as of the most recent
(2022) Pacific SARs (Carretta et al., 2023). Gray whale population
structure is not determined by simple geography and may be in flux due
to evolving migratory dynamics (Carretta et al., 2023). Currently, the
SARs delineate a western North Pacific (WNP) gray whale stock and an
eastern North Pacific (ENP) stock based on genetic differentiation
(Carretta et al., 2023). WNP gray whales are not known to feed in or
travel to upper Cook Inlet (Conant and Lohe, 2023; Weller et al.,
2023). Therefore, we assume that gray whales near the project area are
members of the ENP stock.
An Unusual Mortality Event (UME) for gray whales along the U.S.
West Coast and in Alaska occurred from December 17, 2018, through
November 9, 2023. During that time, 146 gray whales stranded off the
coast of Alaska. The investigative team concluded that the preliminary
cause of the UME was localized ecosystem changes in the whale's
Subarctic and Arctic feeding areas that led to changes in food,
malnutrition, decreased birth rates, and increased mortality (see
<a href="https://www.fisheries.noaa.gov/national/marine-life-distress/2019-2023-gray-whale-unusual-mortality-event-along-west-coast-and">https://www.fisheries.noaa.gov/national/marine-life-distress/2019-2023-gray-whale-unusual-mortality-event-along-west-coast-and</a> for more
information).
Gray whales are infrequent visitors to Cook Inlet, but may be
seasonally present during spring and fall in the lower inlet (Bureau of
Ocean Energy Management (BOEM), 2021). Migrating gray whales pass
through the lower inlet during their spring and fall migrations to and
from their primary summer feeding areas in the Bering, Chukchi, and
Beaufort seas (Swartz, 2018; Silber et al., 2021; BOEM, 2021). Several
surveys and monitoring programs have sighted gray whales in lower Cook
Inlet (Shelden et al., 2013; Owl Ridge, 2014; Lomac-MacNair et al.,
2013, 2014; Kendall et al., 2015, as cited in Weston and SLR, 2022).
Gray whales are occasionally seen in mid- and upper Cook Inlet, Alaska,
but they are not common. During NMFS aerial surveys conducted in June
1994, 2000, 2001, 2005, and 2009 gray whales were observed in Cook
Inlet near Port Graham and Elizabeth Island as well as near Kamishak
Bay, with one gray whale observed as far north as the Beluga River
(Shelden et al., 2013). Gray whales were also observed offshore of Cape
Starichkof in 2013 by marine mammal observers monitoring Buccaneer's
Cosmopolitan drilling project (Owl Ridge, 2014) and in middle Cook
Inlet in 2014 during the 2014 Apache 2D seismic survey (Lomac-MacNair
et al., 2015). Several projects performed in Cook Inlet in recent years
reported no observations of gray whales. These project activities
included the SAExploration seismic survey in 2015
[[Page 34986]]
(Kendall and Cornick, 2015), the 2018 Cook Inlet Pipeline (CIPL)
Extension Project (Sitkiewicz et al., 2018), the 2019 Hilcorp seismic
survey in lower Cook Inlet (Fairweather Science, 2020), Hilcorp's 2022,
2023, and 2024 aerial and rig-based monitoring efforts (Horsley and
Larson, 2023, 2024).
In 2020, a young male gray whale was stranded in the Twentymile
River near Girdwood for over a week before swimming back into Turnagain
Arm. The whale did not survive and was found dead in west Cook Inlet
later that month (NMFS, 2020). One gray whale was sighted in Knik Arm
near the Don Young Port of Alaska (POA) in Anchorage in upper Cook
Inlet in May of 2020 during observations conducted during construction
of the Petroleum and Cement Terminal project (61N Environmental, 2021).
The sighting occurred less than a week before the reports of the gray
whale stranding in the Twentymile River and was likely the same animal.
In 2021, one small gray whale was sighted in Knik Arm near Ship Creek,
south of the POA (61N Environmental, 2022a). Although some sightings
have been documented in the middle and upper Inlet, the gray whale
range typically only extends into the lower Cook Inlet region.
Humpback Whale
The 2022 NMFS Alaska and Pacific SARs described a revised stock
structure for humpback whales which modifies the previous designated
stocks to align more closely with the ESA-designated Distinct
Population Segments (DPSs) (Carretta et al., 2023; Young et al., 2023).
Specifically, the three previous North Pacific humpback whale stocks
(Central and Western North Pacific stocks and a CA/OR/WA stock) were
replaced by five stocks, largely corresponding with the ESA-designated
DPSs. These include Western North Pacific and Hawaii stocks and a
Central America/Southern Mexico-California (CA)/Oregon (OR)/Washington
(WA) stock (which corresponds with the Central America DPS). The
remaining two stocks, corresponding with the Mexico DPS, are the
Mainland Mexico-CA/OR/WA and Mexico-North Pacific stocks (Carretta et
al., 2023; Young et al., 2023). The former stock is expected to occur
along the west coast from California to southern British Columbia,
while the latter stock may occur across the Pacific, from northern
British Columbia through the Gulf of Alaska and Aleutian Islands/Bering
Sea region to Russia.
The Hawaii stock consists of one demographically independent
population (DIP) (Hawaii-Southeast Alaska/Northern British Columbia
DIP) and the Hawaii-North Pacific unit, which may or may not be
composed of multiple DIPs (Wade et al., 2021). The DIP and unit are
managed as a single stock at this time, due to the lack of data
available to separately assess them and lack of compelling conservation
benefit to managing them separately (Martien et al., 2021, NMFS 2019,
2023a). The DIP is delineated based on two strong lines of evidence:
genetics and movement data (Wade et al., 2021). Whales in the Hawaii-
Southeast Alaska/Northern British Columbia DIP winter off Hawaii and
largely summer in Southeast Alaska and Northern British Columbia (Wade
et al., 2021). The group of whales that migrate from Russia, western
Alaska (Bering Sea and Aleutian Islands), and central Alaska (Gulf of
Alaska excluding Southeast Alaska) to Hawaii have been delineated as
the Hawaii-North Pacific unit (Wade et al., 2021). There are a small
number of whales that migrate between Hawaii and southern British
Columbia/Washington, but current data and analyses do not provide a
clear understanding of which unit these whales belong to (Wade et al.,
2021; Carretta et al., 2023; Young et al., 2023).
The Mexico-North Pacific stock is likely composed of multiple DIPs,
based on movement data (Martien et al., 2021, Wade 2021, Wade et al.,
2021). However, because currently available data and analyses are not
sufficient to delineate or assess DIPs within the unit, it was
designated as a single stock (NMFS 2019, 2022d, 2023a). Whales in this
stock winter off Mexico and the Revillagigedo Archipelago and summer
primarily in Alaska waters (Martien et al., 2021; Carretta et al.,
2023; Young et al., 2023).
The Western North Pacific stock consists of two units--the
Philippines/Okinawa-North Pacific unit and the Marianas/Ogasawara-North
Pacific unit. The units are managed as a single stock at this time, due
to a lack of data available to separately assess them (NMFS 2019,
2022d, 2023a). Recognition of these units is based on movements and
genetic data (Oleson et al., 2022). Whales in the Philippines/Okinawa-
North Pacific unit winter near the Philippines and in the Ryukyu
Archipelago and migrate to summer feeding areas primarily off the
Russian mainland (Oleson et al., 2022). Whales that winter off the
Mariana Archipelago, Ogasawara, and other areas not yet identified and
then migrate to summer feeding areas off the Commander Islands, and to
the Bering Sea and Aleutian Islands comprise the Marianas/Ogasawara-
North Pacific unit.
The most comprehensive photo-identification data available suggest
that approximately 89 percent of all humpback whales in the Gulf of
Alaska are from the Hawaii stock, 11 percent are from the Mexico stock,
and less than 1 percent are from the Western North Pacific stock (Wade,
2021). Individuals from different stocks are known to intermix in
feeding grounds. There is no designated critical habitat for humpback
whales in or near the project area (86 FR 21082, April 21, 2021), nor
does the project overlap with any known biologically important areas.
Humpback whales are encountered regularly in lower Cook Inlet and
occasionally in mid-Cook Inlet; sightings are rare in upper Cook Inlet.
Eighty-three groups containing an estimated 187 humpbacks were sighted
during the CIBW aerial surveys conducted by NMFS from 1994 to 2012
(Shelden et al., 2013). Surveys conducted north of the forelands have
documented small numbers in middle Cook Inlet. During the 2014 Apache
seismic surveys in Cook Inlet, five groups (six individuals) were
reported, with three groups north of the forelands on the east side of
the inlet (Lomac-MacNair et al., 2014). In 2015, during the
construction of the Furie Operating Alaska, LLC (Furie) platform and
pipeline, four groups of humpback whales were documented. Another group
of 6 to 10 unidentified whales, thought to be either humpback or gray
whales, was sighted approximately 15 km (9 mi) northeast of the Julius
R. Platform. Large cetaceans were visible near the project (i.e.,
whales or blows were visible) for 2 hours out of the 1,275 hours of
observation conducted (Jacobs, 2015). During SAExploration's 2015
seismic program, three humpback whales were observed in Cook Inlet,
including two near the Forelands and one in lower Cook Inlet (Kendall
et al., 2015 as cited in Weston and SLR, 2022). Hilcorp did not record
any sightings of humpback whales in middle Cook Inlet from their aerial
or rig-based monitoring efforts in 2022, 2023, or 2024 (Horsley and
Larson, 2023, 2024). The POA has observed humpbacks in Knik Arm (2
sightings of likely the same individual near Ship Creek in 2017 (ABR
2017) and 1 at the POA in 2022 (61N Environmental 2022b). Based on
these observations, humpback whales may be infrequent visitors to
middle Cook Inlet.
Minke Whale
Two stocks of minke whales occur within U.S. waters: Alaska and
California/Oregon/Washington (Muto et al., 2022). The Alaskan stock of
minke whales is considered migratory, as they
[[Page 34987]]
are speculated to migrate seasonally from the Bering and Chukchi Seas
in fall to areas of the central North Pacific Ocean (Delarue et al.,
2013). Although they are likely migratory in Alaska, minke whales have
been observed off Cape Starichkof and Anchor Point year-round (Muto et
al., 2017).
Minke whales are most abundant in the Gulf of Alaska during summer
and occupy localized feeding areas (Zerbini et al., 2006). During the
NMFS annual and semiannual surveys of Cook Inlet, minke whales were
observed near Anchor Point in 1998, 1999, 2006, and 2021 (Shelden et
al., 2013, 2015b, 2017, 2022; Shelden and Wade, 2019) and near
Ninilchik and the middle of lower Cook Inlet in 2021 (Shelden et al.,
2022). Minkes were sighted southeast of Kalgin Island and near Homer
during Apache's 2014 survey (Lomac-MacNair et al., 2014), and one was
observed near Tuxedni Bay in 2015 (Kendall et al., 2015, as cited in
Weston and SLR, 2022). During Hilcorp's seismic survey in lower Cook
Inlet in the fall of 2019, eight minke whales were observed
(Fairweather Science, 2020). In 2018, no minke whales were observed
during observations conducted for the CIPL project near Tyonek
(Sitkiewicz et al., 2018). Minke whales were also not recorded during
Hilcorp's aerial or rig-based monitoring efforts in 2022, 2023, or 2024
(Horsley and Larson, 2023, 2024), however, one sighting of one minke
whale was recorded during Hilcorp's spring marine vibroseis seismic
survey offshore from Anchor Point in April 2024 (Hanks et al., 2024).
Fin Whale
In U.S. Pacific waters, fin whales are seasonally found in the Gulf
of Alaska, and Bering Sea and as far north as the northern Chukchi Sea
(Muto et al., 2021). Several surveys have been conducted to assess the
distribution and habitat preferences of fin whales within parts of
their range in the North Pacific. In coastal waters of the Aleutians
and the Alaska Peninsula, they were found primarily from the Kenai
Peninsula to the Shumagin Islands, with a higher abundance near the
Semidi Islands and Kodiak Island (Zerbini et al., 2006). An
opportunistic survey in the Gulf of Alaska revealed that fin whales
were concentrated west of Kodiak Island, in Shelikof Strait, and in the
southern Cook Inlet region, with smaller numbers observed over the
shelf east of Kodiak to Prince William Sound (Alaska Fisheries Science
Center [AFSC], 2003). Muto et al. (2021) reported visual sightings and
acoustic detections in the northeastern Chukchi Sea have been
increasing, suggesting that the stock may be re-occupying habitat used
prior to large-scale commercial whaling. Delarue et al. (2013) also
detected fin whale calls in the northeastern Chukchi Sea from July
through October in a 3-year acoustic study.
Fin whales' range extends into lower Cook Inlet; however, their
sightings are infrequent, and they are mostly spotted near the inlet's
entrance. Fin whales are usually observed as individuals traveling
alone, although they are sometimes observed in small groups. Rarely,
large groups of 50 to 300 fin whales can travel together during
migrations (NMFS, 2010). Fin whales in Cook Inlet have only been
observed as individuals or in small groups. From 2000 to 2022, 10
sightings of 26 estimated individual fin whales in lower Cook Inlet
were observed during NMFS aerial surveys (Shelden et al., 2013, 2015b,
2017, 2022; Shelden and Wade, 2019). No fin whales were observed during
the 2018 Harvest's CIPL Extension Project Acoustic Monitoring Program
in middle Cook Inlet (Sitkiewicz et al., 2018). In September and
October 2019, Castellote et al. (2020) detected fin whales acoustically
in lower Cook Inlet during three-dimensional (3D) seismic surveys,
which coincided with the Hilcorp lower Cook Inlet seismic survey.
During this period, 8 sightings of 23 individual fin whales were
reported, indicating the offshore waters of lower Cook Inlet may be
more heavily used than previously believed, especially during the fall
season (Fairweather Science, 2020). Hilcorp did not record any
sightings of fin whales from their aerial or rig-based monitoring
efforts in 2022, 2023, or 2024 (Horsley and Larson, 2023, 2024).
Beluga Whale
Five stocks of beluga whales are recognized in Alaska: the Beaufort
Sea stock, eastern Chukchi Sea stock, eastern Bering Sea stock, Bristol
Bay stock, and Cook Inlet stock (Young et al., 2023). The Cook Inlet
stock is geographically and genetically isolated from the other stocks
(O'Corry-Crowe et al., 1997; Laidre et al., 2000) and resides year-
round in Cook Inlet (Laidre et al., 2000; Castellote et al., 2020).
Only the Cook Inlet stock inhabits the area where Hilcorp would conduct
activities. CIBWs were designated as depleted under the MMPA in 2000
(65 FR 34950, May 31, 2000), and as a DPS and listed as endangered
under the ESA in October 2008 (73 FR 62919, October 10, 2008) when the
species failed to recover following a moratorium on subsistence
harvest. Between 2008 and 2018, CIBWs experienced a decline of about
2.3 percent per year (Wade et al., 2019). The decline partially
overlapped with the northeast Pacific marine heatwave that occurred
from 2014 to 2016 in the Gulf of Alaska, significantly impacting the
marine ecosystem (Suryan et al., 2021, as cited in Goetz et al., 2023).
In June 2023, NMFS released an updated abundance estimate for CIBWs
in Alaska that incorporates aerial survey data from June 2021 and 2022
and accounted for visibility bias (Goetz et al., 2023). This report
estimated that CIBW abundance is between 290 and 386, with a median
best estimate of 331. Goetz et al. (2023) also present an analysis of
population trends for the most recent 10-year period (2012-2022). The
addition of data from the 2021 and 2022 survey years in the analysis
resulted in a 65.1 percent probability that the CIBW population is now
increasing at 0.9 percent per year (95 percent prediction interval of -
3 to 5.7 percent). This increase drops slightly to 0.2 percent per year
(95 percent prediction interval of -1.8 to 2.6 percent) with a 60
percent probability that the CIBW population is increasing more than 1
percent per year when data from 2021, which had limited survey coverage
due to poor weather, are excluded from the analysis.For management
purposes, NMFS has determined that the carrying capacity of Cook Inlet
is 1,300 CIBWs (65 FR 34590, May 31, 2000) based on historical CIBW
abundance estimated by Calkins (1989).
Threats that have the potential to impact this stock and its
habitat include the following: catastrophic events (e.g., natural
disasters, spills, mass strandings); disease agents (e.g., pathogens,
parasites, and harmful algal blooms), habitat loss or degradation,
reduction in prey, changes in prey availability due to natural
environmental variability, ocean acidification, and commercial
fisheries; climatic changes affecting habitat; predation by killer
whales; contaminants; noise; ship strikes; waste management; urban
runoff; construction projects; and physical habitat modifications that
may occur as Cook Inlet becomes increasingly urbanized (Moore et al.,
2000; Hobbs et al., 2015; NMFS, 2016b). Another source of CIBW
mortality in Cook Inlet is predation by transient-type (mammal-eating)
killer whales (NMFS, 2016b; Shelden et al., 2003). No human-caused
mortality or serious injury of CIBWs through interactions with
commercial, recreational, and subsistence fisheries, takes by
subsistence hunters, and or human-caused events (e.g., entanglement in
marine debris, ship strikes) has been recently documented,
[[Page 34988]]
and harvesting of CIBWs has not occurred since 2008 (NMFS, 2008b).
Critical Habitat. On April 11, 2011, NMFS designated two areas of
critical habitat for CIBW (76 FR 20179). The designation includes 7,800
km\2\ (3012 square mi, mi\2\) of marine and estuarine habitat within
Cook Inlet, encompassing approximately 1,909 km\2\ (737 mi\2\) in Area
1 and 5,891 km\2\ (2275 mi\2\) in Area 2 (see figure 1 in 76 FR 20179).
Area 1 of the CIBW critical habitat encompasses all marine waters of
Cook Inlet north of a line connecting Point Possession and the mouth of
Three Mile Creek, including waters of the Susitna, Little Susitna, and
Chickaloon Rivers below Mean Higher High Water (MHHW). From spring
through fall, Area 1 critical habitat has the highest concentration of
CIBWs due to its important foraging and calving habitat. Critical
Habitat Area 2 encompasses some of the fall and winter feeding grounds
in middle Cook Inlet. This area has a lower concentration of CIBWs in
spring and summer but is used by CIBWs in fall and winter. More
information on CIBW critical habitat can be found at <a href="https://www.fisheries.noaa.gov/action/critical-habitat-cook-inlet-beluga-whale">https://www.fisheries.noaa.gov/action/critical-habitat-cook-inlet-beluga-whale</a>.
The designation identified the following Primary Constituent
Elements, essential features important to the conservation of the CIBW:
(1) Intertidal and subtidal waters of Cook Inlet with depths of
less than 9 m (30 ft) Mean Lower-Low Water (MLLW) and within 8 km (5
mi) of high- and medium-flow anadromous fish streams;
(2) Primary prey species, including four of the five species of
Pacific salmon (chum (Oncorhynchus keta), sockeye (Oncorhynchus nerka),
Chinook (Oncorhynchus tshawytscha), and coho (Oncorhynchus kisutch)),
Pacific eulachon (Thaleichthys pacificus), Pacific cod (Gadus
macrocephalus), walleye Pollock (Gadus chalcogrammus), saffron cod
(Eleginus gracilis), and yellowfin sole (Limanda aspera);
(3) The absence of toxins or other agents of a type or amount
harmful to CIBWs;
(4) Unrestricted passage within or between the critical habitat
areas; and
(5) The absence of in-water noise at levels resulting in the
abandonment of habitat by CIBWs.
Biologically Important Areas. Wild et al. (2023) delineated a Small
and Resident Population Biologically Important Area (BIA) in Cook Inlet
that is active year-round and overlaps where Hilcorp would conduct the
specified activities. The authors assigned the BIA an importance score
of 2, an intensity score of 2, a data support score of 3, and a
boundary certainty score of 2 (scores range from 1 to 3, with a higher
score representing an area of more concentrated or focused use and
higher confidence in the data supporting the BIA; Harrison et al.,
2023). These scores indicate that the BIA is of moderate importance and
intensity, the authors have high confidence that the population is
small and resident and in the abundance and range estimates of the
population, and the boundary certainty is medium (see Harrison et al.
(2023) for additional information about the scoring process used to
identify BIAs). The boundary of the CIBW BIA is consistent with NMFS'
critical habitat designation (Wild et al., 2023).
Foraging ecology
CIBWs feed on a wide variety of prey species, particularly those
that are seasonally abundant. From late spring through summer, most
CIBW stomachs sampled contained salmon, which corresponded to the
timing of fish runs in the area. Anadromous smolt and adult fish
aggregate at river mouths and adjacent intertidal mudflats (Calkins,
1989). All five Pacific salmon species (i.e., Chinook, pink
(Oncorhynchus gorbuscha), coho, sockeye, and chum) spawn in rivers
throughout Cook Inlet (Moulton, 1997; Moore et al., 2000). Overall,
Pacific salmon represent the highest percent frequency of occurrence of
prey species in CIBW stomachs. This suggests that their spring feeding
in upper Cook Inlet, principally on fat-rich fish such as salmon and
eulachon, is important to the energetics of these animals (NMFS,
2016b).
The nutritional quality of Chinook salmon in particular is
unparalleled, with an energy content four times greater than that of a
Coho salmon. It is suggested the decline of the Chinook salmon
population has left a nutritional void in the diet of the CIBWs that no
other prey species can fill in terms of quality or quantity (Norman et
al., 2020, 2022).
In fall, as anadromous fish runs begin to decline, CIBWs return to
consume fish species (cod and bottom fish) found in nearshore bays and
estuaries. Stomach samples from CIBWs are not available for winter
(December through March), although dive data from CIBWs tagged with
satellite transmitters suggest that they feed in deeper waters during
winter (Hobbs et al., 2005), possibly on such prey species as flatfish,
cod, sculpin, and pollock.
Habitat Use
The CIBW stock remains within Cook Inlet throughout the year,
showing only small seasonal shifts in distribution (Goetz et al.,
2012a; Lammers et al., 2013; Castellotte et al., 2015; Shelden et al.,
2015a, 2018; Lowry et al., 2019). The ecological range of CIBWs has
contracted significantly since the 1970s. From late spring to fall,
nearly the entire population is now found in the upper inlet north of
the forelands, with a range reduced to approximately 39 percent of the
size documented in the late 1970s (Goetz et al., 2023). The recent
annual and semiannual aerial surveys (since 2008) found that
approximately 83 percent of the population inhabits the area between
the Beluga River and Little Susitna River during the survey period,
typically conducted in early June. Some aerial survey counts were
performed in August, September, and October, finding minor differences
in the numbers of belugas in the upper inlet compared to June,
reinforcing the importance of the upper inlet habitat area (Young et
al., 2023).
During spring and summer, CIBWs generally aggregate near the warmer
waters of river mouths along the northern shores of middle and upper
Cook Inlet where prey availability is high and predator occurrence is
low (Moore et al., 2000; Shelden and Wade, 2019; McGuire et al., 2020).
In particular, CIBW groups are seen in the Susitna River Delta, the
Beluga River and along the shore to the Little Susitna River, Knik Arm,
and along the shores of Chickaloon Bay. Large groups of CIBWs have been
observed in the Susitna River Delta, with sizes ranging from 200 to 300
individuals and including a mix of adults, juveniles, and neonates
(McGuire et al., 2014, 2020). Small groups have been recorded farther
south in Kachemak Bay, Redoubt Bay (Big River), and Trading Bay
(McArthur River) prior to 1996, but rarely thereafter. Since the mid-
1990s, most CIBWs (96 to 100 percent) aggregate in shallow areas near
river mouths in upper Cook Inlet, and they are only occasionally
sighted in the central or southern portions of Cook Inlet during summer
(Hobbs et al., 2008). Almost the entire population can be found in
northern Cook Inlet from late spring through the summer and into the
fall (Muto et al., 2020), shifting into deeper waters in middle Cook
Inlet in winter (Hobbs et al., 2008).
Data from tagged whales (14 tags deployed July 2000 through March
2003) show that CIBWs use upper Cook Inlet intensively between summer
and late autumn (Hobbs et al., 2005). CIBWs tagged with satellite
transmitters continue to use Knik Arm, Turnagain Arm, and Chickaloon
Bay as late as October, but some range into lower
[[Page 34989]]
Cook Inlet to Chinitna Bay, Tuxedni Bay, and Trading Bay (McArthur
River) in fall (Hobbs et al., 2005, 2012). From September through
November, CIBWs move between Knik Arm, Turnagain Arm, and Chickaloon
Bay (Hobbs et al., 2005; Goetz et al., 2012b). By December, CIBWs are
distributed throughout the upper to mid-inlet. Data from recent
monitoring suggests lower Cook Inlet (e.g., Tuxedni Bay and Kenai and
Kasilof waters) may also be important spring, fall, and/or winter
habitat (Castellote et al., 2023, 2024; Kumar, 2024). From January into
March, they move as far south as Kalgin Island and slightly beyond in
central offshore waters. However, CIBWs make occasional excursions into
Knik Arm and Turnagain Arm in February and March in spite of ice cover
(Hobbs et al., 2005). Although tagged CIBWs move widely around Cook
Inlet throughout the year, there is no indication of seasonal migration
in and out of Cook Inlet (Hobbs et al., 2005). Data from NMFS aerial
surveys, opportunistic sighting reports, and corrected satellite-tagged
CIBWs confirm that they are more widely dispersed throughout Cook Inlet
during winter (November-April), with animals found between Kalgin
Island and Point Possession. Generally fewer observations of CIBWs are
reported from the Anchorage and Knik Arm area from November through
April (76 FR 20179, April 11, 2011; Rugh et al., 2000, 2004). Later in
winter (January into March), belugas were sighted near Kalgin Island
and in deeper waters offshore. However, even when ice cover exceeds 90
percent in February and March, belugas travel into Knik Arm and
Turnagain Arm (Hobbs et al., 2005).
The NMFS AFSC has conducted long-term passive acoustic monitoring
demonstrating seasonal shifts in CIBW concentrations throughout Cook
Inlet. Castellote et al. (2015) conducted long-term acoustic monitoring
at 13 locations throughout Cook Inlet between 2008 and 2015: North
Eagle Bay, Eagle River Mouth, South Eagle Bay, Six Mile, Point
MacKenzie, Cairn Point, Fire Island, Little Susitna, Beluga River,
Trading Bay, Kenai River, Tuxedni Bay, and Homer Spit; the former 6
stations being located within Knik Arm. In general, the observed
seasonal distribution is in accordance with descriptions based on
aerial surveys and satellite telemetry: CIBW detections are higher in
the upper inlet during summer, peaking at Little Susitna, Beluga River,
and Eagle Bay, followed by fewer detections at those locations during
winter. Higher detections in winter at Trading Bay, Kenai River, and
Tuxedni Bay suggest a broader CIBW distribution in the lower inlet
during winter. That is, CIBWs spend a considerable amount of time
outside of middle Cook Inlet where Hilcorp project activities would
occur (Castellote et al., 2024). Acoustic studies also provide evidence
that the Susitna Delta is a crucial habitat for CIBWs, especially
during the summer and fall months. An acoustic recorder in the Little
Susitna River detected peak CIBW activity from late May to early June
and again from July through August (Castellote et al., 2016). In the
Beluga River, three peaks in activity were recorded: the first from
mid-February to early April, the strongest peak from June to mid-July,
and a third peak from mid-November to mid-December. The bimodal
distribution of these detections is thought to be related to the known
availability of the two main anadromous summer prey species for CIBWs,
eulachon and Pacific salmon.
Goetz et al. (2012b) modeled habitat preferences using NMFS' 1994-
2008 June abundance survey data. In large areas, such as the Susitna
Delta (Beluga to Little Susitna Rivers) and Knik Arm, there was a high
probability that CIBWs were in larger groups. CIBW presence and
acoustic foraging behavior also increased closer to rivers with Chinook
salmon runs, such as the Susitna River (e.g., Castellote et al., 2021).
Movement has been correlated with the peak discharge of seven major
rivers emptying into Cook Inlet. Boat-based surveys (McGuire and
Stephens, 2017) and results from passive acoustic monitoring across the
entire inlet (Castellote et al., 2015) also support seasonal patterns
observed with other methods. Based on long-term passive acoustic
monitoring, foraging behavior was more prevalent during summer,
particularly at upper inlet rivers, than during winter. The foraging
index was highest at Little Susitna, with a peak in July[hyphen]August
and a secondary peak in May, followed by Beluga River and then Eagle
Bay; monthly variation in the foraging index indicates CIBWs shift
their foraging behavior among these three locations from April through
September. The location of the towing routes are areas of predicted low
density in the summer months.
CIBWs are believed to mostly calve in the summer, and breed between
late spring and early summer (NMFS, 2016b), primarily in upper Cook
Inlet. The only known observed occurrence of calving occurred on July
20, 2015, in the Susitna Delta area (T. McGuire, pers. comm., March 27,
2017). The first neonates encountered during each field season from
2005 through 2015 were always seen in the Susitna River Delta in July.
The photographic identification team's documentation of the dates of
the first neonate of each year indicate that calving begins in mid-late
July/early August, generally coinciding with the observed timing of
annual maximum group size. Probable mating behavior of CIBWs was
observed in April and May of 2014, in Trading Bay. Young CIBWs are
nursed for 2 years and may continue to associate with their mothers for
a considerable time thereafter (Colbeck et al., 2013). Important
calving grounds are thought to be located near the river mouths of
upper Cook Inlet.
CIBWs have been observed during marine mammal monitoring efforts in
support of industry and research projects. During Apache's seismic test
program in 2011 along the west coast of Redoubt Bay, lower Cook Inlet,
a total of 33 CIBWs were sighted during the survey (Lomac-MacNair et
al., 2013). During Apache's 2012 seismic program in mid-inlet, a total
of 151 groups consisting of an estimated 1,463 CIBWs were observed
(note individuals were likely observed more than once) (Lomac-MacNair
et al., 2014). During SAExploration's 2015 seismic program, a total of
eight groups of 33 estimated individual CIBWs were visually observed
during this time period and there were two acoustic detections of CIBWs
in upper Cook Inlet (Kendall et al., 2015). During Harvest Alaska's
CIPL project on the west side of Cook Inlet in between Ladd Landing and
Tyonek Platform, a total of 143 CIBW groups (814 individuals) were
observed almost daily from May 31 to July 11, even though observations
spanned from May 9 through September 15 (Sitkiewicz et al., 2018).
There were two CIBW carcasses observed by the project vessels in the
2019 Hilcorp lower Cook Inlet seismic survey in the fall which were
reported to the NMFS Marine Mammal Stranding Network (Fairweather
Science, 2020). Both carcasses were moderately decomposed when they
were sighted by the PSOs. Daily aerial surveys specifically for CIBWs
were flown over the lower Cook Inlet region, but no CIBWs were
observed. Aerial surveys during Hilcorp rig moves in June 2021, and
June and September 2022 reported sightings of 11, more than 25, and 20
individual CIBWs, respectively; some were within the aerial survey area
and some outside. Rig moves also occurred in June and July of 2023;
aerial observers reported 37 sightings of 281 individuals observed both
in and out of the survey area (Horsley and Larson, 2023). No CIBWs were
sighted from vessel-based PSOs during these rig moves. In May 2024
[[Page 34990]]
during Hilcorp's jack-up rig move, two opportunistic sightings of
approximately 25 CIBWs were recorded outside of the designated aerial
survey area. No additional observations were recorded by aerial or
vessel-based PSOs (Horsley and Larson, 2024). Furthermore, three
additional CIBWs were observed near the Tyonek Platform by vessel-based
PSOs during the pre-clearance monitoring period for Hilcorp's October
2024 jack-up rig move (Horsley et al,. 2024). In November 2024, no
sightings of CIBWs were reported during the rig move conducted under
the operatorship of Furie Operating Alaska, LLC (S. Vercelline, pers.
comm., December 9, 2024).
Killer Whale
Along the west coast of North America, seasonal and year-round
occurrence of killer whales has been noted along the entire Alaska
coast (Braham and Dahlheim, 1982), in British Columbia and Washington
inland waterways (Bigg et al., 1990), and along the outer coasts of
Washington, Oregon, and California (Green et al., 1992; Barlow 1995,
1997; Forney et al., 1995). Killer whales from these areas have been
labeled as ``resident,'' ``transient,'' and ``offshore'' type killer
whales (Bigg et al., 1990; Ford et al., 2000; Dahlheim et al., 2008)
based on aspects of morphology, ecology, genetics, and behavior (Ford
and Fisher, 1982; Baird and Stacey, 1988; Baird et al., 1992; Hoelzel
et al., 1998, 2002; Barrett-Lennard, 2000; Dahlheim et al., 2008).
Based on data regarding association patterns, acoustics, movements, and
genetic differences, eight killer whale stocks are now recognized
within the U.S. Pacific, two of which have the potential to be found in
Cook Inlet: the Eastern North Pacific Alaska Resident stock and the
Gulf of Alaska, Aleutian Islands, and the Bering Sea Transient stock.
Both stocks occur in lower Cook Inlet, but rarely in middle and upper
Cook Inlet (Shelden et al., 2013). While stocks overlap the same
geographic area, they maintain social and reproductive isolation and
feed on different prey species. Resident killer whales are primarily
fish-eaters, while transients primarily hunt and consume marine
mammals, such as harbor seals, Dall's porpoises, harbor porpoises,
CIBWs and sea lions. Killer whales are not harvested for subsistence in
Alaska. Potential threats most likely to result in direct human-caused
mortality or serious injury of killer whales in this region include oil
spills, vessel strikes, and interactions with fisheries.
Killer whales have been sighted near Homer and Port Graham in lower
Cook Inlet (Shelden et al., 2003, 2022; Rugh et al., 2005). Resident
killer whales from pods often sighted near Kenai Fjords and Prince
William Sound have been occasionally photographed in lower Cook Inlet
(Shelden et al., 2003). The availability of salmon influences when
resident killer whales are more likely to be sighted in Cook Inlet.
Killer whales were observed in the Kachemak and English Bay three times
during aerial surveys conducted between 1993 and 2004 (Rugh et al.,
2005). Passive acoustic monitoring efforts throughout Cook Inlet
documented killer whales at the Beluga River, Kenai River, and Homer
Spit, although they were not encountered within Knik Arm (Castellote et
al., 2016). These detections were likely resident killer whales.
Transient killer whales likely have not been acoustically detected due
to their propensity to move quietly through waters to track prey
(Small, 2010; Lammers et al., 2013). Transient killer whales were
increasingly reported to feed on belugas in the middle and upper Cook
Inlet in the 1990s.
During the 2015 SAExploration seismic program near the North
Foreland, two killer whales were observed (Kendall et al., 2015, as
cited in Weston and SLR, 2022). Killer whales were observed in lower
Cook Inlet in 1994, 1997, 2001, 2005, 2010, 2012, and 2022 during the
NMFS aerial surveys (Shelden et al., 2013, 2022). Eleven killer whale
strandings have been reported in Turnagain Arm: 6 in May 1991 and 5 in
August 1993. During the Hilcorp lower Cook Inlet seismic survey in the
fall of 2019, 21 killer whales were documented (Fairweather Science,
2020). Throughout 4 months of observation in 2018 during the CIPL
project in middle Cook Inlet, no killer whales were observed
(Sitkiewicz et al., 2018). In September 2021, two killer whales were
documented in Knik Arm in upper Cook Inlet, near the POA (61N
Environmental, 2022a). One killer whale was observed during Hilcorp's
pilot marine vibroseis seismic survey in lower Cook Inlet in October of
2023. During the 2024 marine vibroseis seismic survey, a group of four
individuals was recorded nearshore Clam Gulch (Hanks et al., 2024).
Hilcorp did not record any sightings of killer whales from their aerial
or rig-based monitoring efforts in 2022, 2023, or 2024 (Horsley and
Larson, 2023, 2024).
Pacific White-Sided Dolphin
The Pacific white-sided dolphin is divided into three stocks within
U.S. waters. The North Pacific stock includes the coast of Alaska,
including the project area. Pacific white-sided dolphins are common in
the Gulf of Alaska's pelagic waters and Alaska's nearshore areas,
British Columbia, and Washington (Ferrero and Walker, 1996, as cited in
Muto et al., 2022). They do not typically occur in Cook Inlet, but in
2019, Castellote et al. (2020) documented short durations of Pacific
white-sided dolphin presence using passive acoustic recorders near
Iniskin Bay (6 minutes) and at an offshore mooring located
approximately midway between Port Graham and Iniskin Bay (51 minutes).
Detections of vocalizations typically lasted on the order of minutes,
suggesting the animals did not remain in the area and/or continue
vocalizing for extended durations. Visual monitoring conducted during
the same period by marine mammal observers on seismic vessels near the
offshore recorder did not detect any Pacific white-sided dolphins
(Fairweather Science, 2020). These observational data, combined with
anecdotal information, indicate that there is a small potential for
Pacific white-sided dolphins to occur in the Project area. On May 7,
2014, Apache Alaska observed three Pacific white-sided dolphins during
an aerial survey near Kenai. This is one of the only recorded visual
observations of Pacific white-sided dolphins in Cook Inlet; they have
not been reported in groups as large as those estimated in other parts
of Alaska (Muto et al., 2022).
Harbor Porpoise
In the eastern North Pacific Ocean, harbor porpoise range from
Point Barrow, along the Alaska coast, and down the west coast of North
America to Point Conception, California. The 2022 Alaska SARs describe
a revised stock structure for harbor porpoises (Young et al., 2023).
Previously, NMFS had designated three stocks of harbor porpoises: the
Bering Sea stock, the Gulf of Alaska stock, and the Southeast Alaska
stock (Muto et al., 2022; Zerbini et al., 2022). The 2022 Alaska SARs
splits the Southeast Alaska stock into three separate stocks, resulting
in five separate stocks in Alaskan waters for this species. This update
better aligns harbor porpoise stock structure with genetics, trends in
abundance, and information regarding discontinuous distribution trends
(Young et al., 2023). Harbor porpoises found in Cook Inlet are likely
to be members of the Gulf of Alaska stock (Young et al., 2023).
Harbor porpoises occur most frequently in waters less than 100 m
deep (Hobbs and Waite, 2010) and are common in nearshore areas of the
Gulf of Alaska, Shelikof Strait, and lower Cook Inlet (Dahlheim et al.,
2000).
[[Page 34991]]
Harbor porpoises are often observed in lower Cook Inlet in Kachemak Bay
and from Cape Douglas to the West Foreland (Rugh et al., 2005). They
can be opportunistic foragers but consume primarily schooling forage
fish (Bowen and Siniff, 1999). Given their shallow water distribution,
harbor porpoise are vulnerable to physical modifications of nearshore
habitats resulting from urban and industrial development (including
waste management and nonpoint source runoff) and activities such as
construction of docks and other over-water structures, filling of
shallow areas, dredging, and noise (Linnenschmidt et al., 2013).
Subsistence users have not reported any harvest from the Gulf of Alaska
harbor porpoise stock since the early 1900s (Shelden et al., 2014).
Calving occurs from May to August; however, this can vary by region.
Harbor porpoises are often found traveling alone, or in small groups of
less than 10 individuals (Schmale, 2008).
Harbor porpoises occur throughout Cook Inlet, with passive acoustic
detections being more prevalent in lower Cook Inlet. Although harbor
porpoises have been frequently observed during aerial surveys in Cook
Inlet (Shelden et al., 2014), most sightings are of single animals and
are concentrated at Chinitna and Tuxedni bays on the west side of lower
Cook Inlet (Rugh et al., 2005), with smaller numbers observed in upper
Cook Inlet between April and October. The occurrence of larger numbers
of porpoise in the lower Cook Inlet may be driven by greater
availability of preferred prey and possibly less competition with
CIBWs, as CIBWs move into upper inlet waters to forage on Pacific
salmon during the summer months (Shelden et al., 2014).
An increase in harbor porpoise sightings in upper Cook Inlet was
observed over recent decades (e.g., 61N Environmental, 2021, 2022a;
Shelden et al., 2014). Small numbers of harbor porpoises have been
consistently reported in upper Cook Inlet between April and October
(Prevel-Ramos et al., 2008). The overall increase in the number of
harbor porpoise sightings in upper Cook Inlet is unknown, although it
may be an artifact of increased studies and marine mammal monitoring
programs in upper Cook Inlet. It is also possible that the contraction
in the CIBW's range has opened up previously occupied CIBW range to
harbor porpoises (Shelden et al., 2014).
During Apache's 2012 seismic program in middle Cook Inlet, 137
groups of harbor porpoises comprising 190 individuals were documented
between May and August (Lomac-MacNair et al., 2013). Lomac-MacNair et
al. (2014) identified 13 groups of harbor porpoises totaling 77
individuals during Apache's 2014 Cook Inlet seismic survey, both from
vessels and aircraft, in May. In June 2012, Shelden et al. (2015b)
documented 65 groups of 129 individual harbor porpoises during an
aerial survey, none of which were in upper Cook Inlet. Kendall et al.
(2015, as cited in Weston and SLR, 2022) documented 52 groups
comprising 65 individuals north of the Forelands during SAExploration's
2015 seismic survey. Shelden et al. (2017, 2019, and 2022) also
conducted aerial surveys in June and July over Cook Inlet in 2016,
2018, 2021, and 2022 and recorded 65 individuals. Observations occurred
in middle and lower Cook Inlet with a majority in Kachemak Bay. A total
of 29 groups (44 individuals) were observed north of the Forelands from
May to September during the CIPL Extension Project (Sitkiewicz et al.,
2018). There were two sightings of three harbor porpoises observed
during the 2019 Hilcorp lower Cook Inlet seismic survey in the fall
(Fairweather Science, 2020). Four monitoring events were conducted at
the POA in Anchorage between April 2020 and August 2022, during which
42 groups of harbor porpoises comprising 50 individual porpoises were
documented over 285 days of observation (61N Environmental 2021, 2022a,
2022b, and 2022c). An additional 16 harbor porpoises were observed near
the POA during their North Extension Stabilization--Step 1 (NES1)
project (61N Environmental 2025). During jack-up rig moves in 2021, a
PSO observed an individual harbor porpoise in middle Cook Inlet in July
and another in October (Horsley and Larson 2023). During a jack-up rig
move in June 2023, a PSO also observed an individual harbor porpoise in
middle Cook Inlet (Horsley and Larson 2023). In 2023 Hilcorp conducted
a pilot marine vibroseis seismic survey in October where two sightings
of two harbor porpoises were recorded offshore from Clam Gulch. In
April, the survey was conducted once again and one harbor seal sighting
of one individual was reported in the same area (Hanks et al., 2024).
Recent passive acoustic research in Cook Inlet by Alaska Department of
Fish and Game (ADF&G) and AFSC have indicated harbor porpoises occur
more frequently than expected, particularly in the West Foreland area
in spring, although overall numbers are unknown at this time
(Castellote et al., 2016).
Dall's Porpoise
Dall's porpoises are found throughout the North Pacific, from
southern Japan to southern California north to the Bering Sea. All
Dall's porpoises in Alaska are of the Alaska stock. This species can be
found in offshore, inshore, and nearshore habitat. The Dall's porpoise
range in Alaska includes lower Cook Inlet, but very few sightings have
been reported in upper Cook Inlet. Observations have been documented
near Kachemak Bay and Anchor Point (Owl Ridge, 2014; BOEM, 2015).
Shelden et al. (2013) and Rugh et al. (2005) collated data from aerial
surveys conducted between 1994 and 2012 and documented 9 sightings of
25 individuals in the lower Cook Inlet during June and/or July 1997,
1999, and 2000. No Dall's porpoise were observed on subsequent surveys
in June and/or July 2014, 2016, 2018, 2021, and 2022 (Shelden et al.,
2015b, 2017, and 2022; Shelden and Wade, 2019). During Apache's 2014
seismic survey, two groups of three Dall's porpoises were observed in
Upper and middle Cook Inlet (Lomac-MacNair et al., 2014). In August
2015, one Dall's porpoise was reported in the mid-inlet north of
Nikiski in middle Cook Inlet during SAExploration's seismic program
(Kendall et al., 2015). During aerial surveys in Cook Inlet, they were
observed in Iniskin Bay, Barren Island, Elizabeth Island, and Kamishak
Bay (Shelden et al., 2013). No Dall's porpoises were observed during
the 2018 CIPL Extension Project Acoustic Monitoring Program in middle
Cook Inlet (Sitkiewicz et al., 2018); however, 30 individuals in 10
groups were sighted during a lower Cook Inlet seismic project in the
fall 2019 (Fairweather Science, 2020). Hilcorp recorded three sightings
of Dall's porpoises in 2021 and one sighting of a Dall's porpoise in
2023 from their rig-based monitoring efforts in the project area
(Korsmo et al., 2022; Horsley and Larson, 2023). One Dall's porpoise
was observed near the POA during the NES1 project, but it is possible
this was misidentified (61N Environmental 2025). This higher number of
sightings suggests Dall's porpoise may use portions of middle Cook
Inlet in greater numbers than previously expected but would still be
considered infrequent in middle and upper Cook Inlet.
Steller Sea Lion
Two DPSs of Steller sea lion occur in Alaska: the western DPS and
the eastern DPS. The western DPS includes animals that occur west of
Cape Suckling, Alaska, and therefore includes
[[Page 34992]]
individuals within the project area. The western DPS was listed under
the ESA as threatened in 1990 (55 FR 49204, November 26, 1990), and its
continued population decline resulted in a change in listing status to
endangered in 1997 (62 FR 24345, May 5, 1997). Since 2000, studies
indicate that the population east of Samalga Pass (i.e., east of the
Aleutian Islands) has increased and is potentially stable (Young et
al., 2023).
There is uncertainty regarding threats currently impeding the
recovery of Steller sea lions, particularly in the Aleutian Islands.
Many factors have been suggested as causes of the steep decline in
abundance of western Steller sea lions observed in the 1980s, including
competitive effects of fishing, environmental change, disease,
contaminants, killer whale predation, incidental take, and illegal and
legal shooting (Atkinson et al., 2008; NMFS, 2008a). A number of
management actions have been implemented since 1990 to promote the
recovery of the Western U.S. stock of Steller sea lions, including 5.6-
km (3-nautical mile) no-entry zones around rookeries, prohibition of
shooting at or near sea lions, and regulation of fisheries for sea lion
prey species (e.g., walleye pollock, Pacific cod, and Atka mackerel
(Pleurogrammus monopterygius)) (Sinclair et al., 2013; Tollit et al.,
2017). Additionally, potentially deleterious events, such as harmful
algal blooms (Lefebvre et al., 2016) and disease transmission across
the Arctic (VanWormer et al., 2019) that have been associated with
warming waters, could lead to potentially negative population-level
impacts on Steller sea lions.
NMFS designated critical habitat for Steller sea lions on August
27, 1993 (58 FR 45269), including portions of the southern reaches of
lower Cook Inlet. The critical habitat designation for the Western DPS
of was determined to include a 37-km (20-nautical mile) buffer around
all major haul-outs and rookeries, and associated terrestrial,
atmospheric, and aquatic zones, plus three large offshore foraging
areas, none of which occurs in the project area. There is no designated
critical habitat for Steller sea lions in the mid- or upper inlet, nor
are there any known BIAs for Steller sea lions within the project area.
Rookeries and haul out sites in lower Cook Inlet include those near the
mouth of the inlet, which are approximately 56 km or more south of the
closest action area.
Steller sea lions are opportunistic predators, feeding primarily on
a wide variety of seasonally abundant fishes and cephalopods, including
Pacific herring (Clupea pallasi), walleye pollock, capelin (Mallotus
villosus), Pacific sand lance (Ammodytes hexapterus), Pacific cod,
salmon (Oncorhynchus spp.), and squid (Teuthida spp.); (Jefferson et
al., 2008; Wynne et al., 2011). Steller sea lions do not generally eat
every day, but tend to forage every 1-2 days and return to haulouts to
rest between foraging trips (Merrick and Loughlin, 1997; Rehberg et
al., 2009). Steller sea lions feed largely on walleye pollock, salmon,
and arrowtooth flounder during the summer, and walleye pollock and
Pacific cod during the winter (Sinclair and Zeppelin, 2002).
Most Steller sea lions in Cook Inlet occur south of Anchor Point on
the east side of lower Cook Inlet, with concentrations near haulout
sites at Shaw Island and Elizabeth Island and by Chinitna Bay and
Iniskin Bay on the west side (Rugh et al., 2005). Steller sea lions are
rarely seen in upper Cook Inlet (Nemeth et al., 2007). About 3,600 sea
lions use haulout sites in the lower Cook Inlet area (Sweeney et al.,
2017), with additional individuals venturing into the area to forage.
Several surveys and monitoring programs have documented Steller sea
lions throughout Cook Inlet, including in upper Cook Inlet in 2012
(Lomac-MacNair et al., 2013), near Cape Starichkof in 2013 (Owl Ridge,
2014), in middle and lower Cook Inlet in 2015 (Kendall et al., 2015, as
cited in Weston and SLR, 2022), in middle Cook Inlet in 2018
(Sitkiewicz et al., 2018), in lower Cook Inlet in 2019 (Fairweather
Science, 2020), and near the POA in Anchorage in 2020, 2021, 2022, and
2025 (61N Environmental, 2021, 2022a, 2022b, and 2022c, 2025). During
NMFS CIBW aerial surveys from 2000 to 2016, 39 sightings of 769
estimated individual Steller sea lions in lower Cook Inlet were
recorded (Shelden et al., 2017). Sightings of large congregations of
Steller sea lions during NMFS aerial surveys occurred outside the
specific geographic region, on land in the mouth of Cook Inlet (e.g.,
Elizabeth and Shaw Islands). In 2012, during Apache's 3D seismic
surveys, three sightings of approximately four individuals in upper
Cook Inlet were recorded (Lomac-MacNair et al., 2013). PSOs associated
with Buccaneer's drilling project off Cape Starichkof observed seven
Steller sea lions in summer 2013 (Owl Ridge, 2014), and another four
Steller sea lions were observed in 2015 in Cook Inlet during
SAExploration's 3D Seismic Program. Of the three 2015 sightings, 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). One sighting of two
individuals occurred during the CIPL Extension Project in 2018 in
middle Cook Inlet (Sitkiewicz et al., 2018). Additionally, five
sightings of five Steller sea lions were recorded during Hilcorp's
lower Cook Inlet seismic survey in the fall of 2019 (Fairweather
Science, 2020). At the end of July 2022, while conducting a waterfowl
survey an estimated 25 Steller sea lions were observed hauled-out at
low tide in the Lewis River, on the west side of Cook Inlet. (K.
Lindberg, pers. comm., August 15, 2022). Hilcorp did not record any
sightings of Steller sea lions from their aerial or rig-based
monitoring efforts in 2022, 2023, or 2024 (Horsley and Larson, 2023,
2024).
Harbor Seal
Harbor seals inhabit waters all along the western coast of the
United States, British Columbia, and north through Alaska waters to the
Pribilof Islands and Cape Newenham. NMFS currently identifies 12 stocks
of harbor seals in Alaska based largely on genetic structure (Young et
al., 2023). Harbor seals potentially affected by Hilcorp's specified
activities are members of the Cook Inlet/Shelikof stock, which ranges
from the southwest tip of Unimak Island east along the southern coast
of the Alaska Peninsula to Elizabeth Island off the southwest tip of
the Kenai Peninsula, including Cook Inlet, Knik Arm, and Turnagain Arm.
Distribution of the Cook Inlet/Shelikof stock extends from Unimak
Island, in the Aleutian Islands archipelago, north through all of upper
and lower Cook Inlet (Young et al., 2023).
Harbor seals inhabit the coastal and estuarine waters of Cook Inlet
and are observed in both upper and lower Cook Inlet throughout most of
the year (Boveng et al., 2012; Shelden et al., 2013). High-density
areas include Kachemak Bay, Iniskin Bay, Iliamna Bay, Kamishak Bay,
Cape Douglas, and Shelikof Strait. Up to a few hundred seals seasonally
occur in middle and upper Cook Inlet (Rugh et al. 2005), with the
highest concentrations found near the Susitna River and other
tributaries within upper Cook Inlet during eulachon and salmon runs
(Nemeth et al., 2007; Boveng et al., 2012), but most remain south of
the forelands (Boveng et al., 2012).
Harbor seals haul out on rocks, reefs, beaches, and drifting
glacial ice (Young et al., 2023). Their movements are influenced by
tides, weather, season, food availability, and reproduction, as well as
individual sex and age class (Lowry et al., 2001; Small et al., 2003;
[[Page 34993]]
Boveng et al., 2012). The results of past and recent satellite tagging
studies in Southeast Alaska, Prince William Sound, Kodiak Island, and
Cook Inlet are also consistent with the conclusion that harbor seals
are non-migratory (Lowry et al., 2001; Small et al., 2003; Boveng et
al., 2012). However, some long-distance movements of tagged animals in
Alaska have been recorded (Pitcher and McAllister, 1981; Lowry et al.,
2001; Small et al., 2003; Womble, 2012; Womble and Gende, 2013). Strong
fidelity of individuals for haulout sites during the breeding season
has been documented in several populations (H[auml]rk[ouml]nen and
Harding, 2001), including in Cook Inlet (Pitcher and McAllister, 1981;
Small et al., 2005; Boveng et al., 2012; Womble, 2012; Womble and
Gende, 2013). Harbor seals usually give birth to a single pup between
May and mid-July; birthing locations are dispersed over several haulout
sites and not confined to major rookeries (Klinkhart et al., 2008).
More than 200 haulout sites are documented in lower Cook Inlet
(Montgomery et al., 2007) and 18 in middle and upper Cook Inlet (London
et al., 2015). Of the 18 in middle and upper Cook Inlet, nine are
considered ``key haulout'' locations where aggregations of 50 or more
harbor seals have been documented. Seven key haulouts are in the
Susitna River delta, and two are near the Chickaloon River.
Recent research on satellite-tagged harbor seals observed several
movement patterns within Cook Inlet (Boveng et al., 2012), including a
strong seasonal pattern of more coastal and restricted spatial use
during the spring and summer (breeding, pupping, molting) and more
wide-ranging movements within and outside of Cook Inlet during the
winter months, with some seals ranging as far as Shumagin Islands.
During summer months, movements and distribution were mostly confined
to the west side of Cook Inlet and Kachemak Bay, and seals captured in
lower Cook Inlet generally exhibited site fidelity by remaining south
of the Forelands in lower Cook Inlet after release (Boveng et al.,
2012). In the fall, a portion of the harbor seals appeared to move out
of Cook Inlet and into Shelikof Strait, northern Kodiak Island, and
coastal habitats of the Alaska Peninsula. The western coast of Cook
Inlet had higher usage by harbor seals than eastern coast habitats, and
seals captured in lower Cook Inlet generally exhibited site fidelity by
remaining south of the Forelands in lower Cook Inlet after release
(south of Nikiski; Boveng et al., 2012).
Harbor seals have been sighted in Cook Inlet during every year of
the aerial surveys conducted by NMFS and during all recent mitigation
and monitoring programs in lower, middle, and upper Cook Inlet (61N
Environmental, 2021, 2022a, 2022b, 2022c, 2025; Fairweather Science,
2020; Kendall et al., 2015 as cited in Weston and SLR, 2022; Lomac-
MacNair et al., 2013, 2014; Sitkiewicz et al., 2018). In 2018 Harvest
Alaska conducted marine mammal monitoring in middle Cook Inlet within
the same geographic area as Hilcorp's proposed action area and reported
313 sightings comprised of 316 harbor seal individuals (Sitkiewicz et
al., 2018). During Hilcorp's June 2023 jack-up rig move, PSOs observed
two separate sightings of harbor seals in middle Cook Inlet: one just
north of Nikiski, and the other closer to the Tyonek Platform (Horsley
and Larson, 2023). Two separate sightings of harbor seals in middle
Cook Inlet also occurred during Hilcorp's May 2024 jack-up rig move,
one occurring near the Tyonek Platform and the other approximately
halfway between the Tyonek Platform and OSK Dock (Horsley and Larson,
2024).
California Sea Lion
California sea lions live along the Pacific coastline spanning an
area from central Mexico to Southeast Alaska and typically breed on
islands located in southern California, western Baja California, and
the Gulf of California (Carretta et al., 2020). Five genetically
distinct geographic populations are known to exist: Pacific Temperate,
Pacific Subtropical, Southern Gulf of California, Central Gulf of
California, and Northern Gulf of California (Schramm et al., 2009).
Few observations of California sea lions have been reported in
Alaska and most observations have been limited to solitary individuals,
typically males that are known to migrate long distances. Occasionally,
California sea lions can be found in small groups of two or more and
are usually associated with Steller sea lions at their haul outs and
rookeries (Maniscalco et al., 2004). The few California sea lions
observed in Alaska typically do not travel further north than Southeast
Alaska. They are often associated with Steller sea lion haulouts and
rookeries (Maniscalco et al., 2004). Sightings in Cook Inlet are rare,
with two documented during the Apache 2012 seismic survey (Lomac-
MacNair et al., 2013) and anecdotal sightings in Kachemak Bay. No
California sea lions were sighted during the 2019 Hilcorp lower Cook
Inlet seismic survey (Fairweather Science, 2020), the CIPL project in
2018 (Sitkiewicz et al., 2018), or the 2022, 2023, or 2024 Hilcorp
aerial or rig-based monitoring efforts (Horsley and Larson, 2023,
2024).
Marine Mammal Hearing
Hearing is the most important sensory modality for marine mammals
underwater, and exposure to anthropogenic sound can have deleterious
effects. To appropriately assess the potential effects of exposure to
sound, it is necessary to understand the frequency ranges marine
mammals are able to hear. Not all marine mammal species have equal
hearing capabilities (e.g., Richardson et al., 1995; Wartzok and
Ketten, 1999; Au and Hastings, 2008). To reflect this, Southall et al.
(2007, 2019) recommended that marine mammals be divided into hearing
groups based on directly measured (behavioral or auditory evoked
potential techniques) or estimated hearing ranges (behavioral response
data, anatomical modeling, etc.). Subsequently, NMFS (2018, 2024)
described generalized hearing ranges for these marine mammal hearing
groups. Generalized hearing ranges were chosen based on the ~65-decibel
(dB) threshold from 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. Frequency is expressed in hertz (Hz) or kilohertz
(kHz). We note that the names of two hearing groups and the generalized
hearing ranges of all marine mammal hearing groups were recently
updated (NMFS 2024) as reflected below in table 7. Of the species
potentially present in the action area, gray whales, fin whales, minke
whales, and humpback whales are considered low-frequency (LF)
cetaceans, CIBWs, 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).
[[Page 34994]]
Table 7--Marine Mammal Hearing Groups (NMFS, 2024)
------------------------------------------------------------------------
Hearing group Generalized hearing range *
------------------------------------------------------------------------
Low-frequency (LF) cetaceans (baleen 7 Hz to 36 kHz.
whales).
High-frequency (HF) cetaceans (dolphins, 150 Hz to 160 kHz.
toothed whales, beaked whales, bottlenose
whales).
Very high-frequency (VHF) cetaceans (true 200 Hz to 165 kHz.
porpoises, Kogia, river dolphins,
Cephalorhynchid, Lagenorhynchus cruciger &
L. australis).
Phocid pinnipeds (PW) (underwater) (true 40 Hz to 90 kHz.
seals).
Otariid pinnipeds (OW) (underwater) (sea 60 Hz to 68 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 may not be as broad. Generalized hearing range
chosen based on ~65 dB threshold from composite audiogram, previous
analysis in NMFS 2018, and/or data from Southall et al., 2007;
Southall et al., 2019. Additionally, animals are able to detect very
loud sounds above and below that ``generalized'' hearing range.
For more detail concerning these groups and associated frequency
ranges, please see NMFS (2024) for a review of available information.
Potential Effects of Specified Activities on Marine Mammals and Their
Habitat
This section provides a discussion of the ways in which components
of the specified activity may impact marine mammals and their habitat.
The Estimated Take of Marine Mammals section later in this document
includes a quantitative analysis of the number of individuals that are
expected to be taken by this activity. The Negligible Impact Analysis
and Determination section considers the content of this section, the
Estimated Take of Marine Mammals section, and the Proposed Mitigation
section, to draw conclusions regarding the likely impacts of these
activities on the reproductive success or survivorship of individuals
and whether those impacts are reasonably expected to, or reasonably
likely to, adversely affect the species or stock through effects on
annual rates of recruitment or survival.
There are a variety of types and degrees of effects to marine
mammals, prey species, and habitat that could occur as a result of
Hilcorp's specified activities. In this section, NMFS provides a brief
description of the types of sound sources that would be generated by
the specified activities of the project, and a description of the ways
marine mammals may be generally affected by these activities including
in the form of mortality, physical injury, sensory impairment
(permanent threshold shifts (PTS), TTS, acoustic masking),
physiological responses (particular stress responses), behavioral
disturbance, and habitat effects. The Estimated Take of Marine Mammals
section also discusses how the potential effects on marine mammals from
non-impulsive and impulsive sources relate to the MMPA definitions of
Level A harassment and Level B harassment, and quantifies those effects
that rise to the level of a take. The Preliminary Analysis and
Negligible Impact Determination section assesses whether the proposed
authorized take would have a negligible impact on the affected species
and stocks.
Background on Sound
This section contains a brief technical background on sound, on the
characteristics of certain sound types, on metrics used relevant to the
specified activity, and to a discussion of the potential effects of the
specified activity on marine mammals found later in this document. For
general information on sound and its interaction with the marine
environment, please see: Erbe and Thomas (2022); Au and Hastings
(2008); Richardson et al. (1995); Urick (1983); as well as the
Discovery of Sound in the Sea website at <a href="https://dosits.org/">https://dosits.org/</a>.
Sound is a vibration that travels as an acoustic wave through a
medium such as a gas, liquid, or solid. Sound waves alternately
compress and decompress the medium as the wave travels. In water, sound
waves radiate in a manner similar to ripples on the surface of a pond
and may be either directed in a beam (narrow beam or directional
sources) or sound may radiate in all directions (omnidirectional
sources), as is the case for sound produced by tugs under load with a
jack-up rig considered here. The compressions and decompressions
associated with sound waves are detected as changes in pressure by
marine mammals and human-made sound receptors such as hydrophones.
Sound travels more efficiently in water than almost any other form
of energy, making the use of sound as a primary sensory modality ideal
for inhabitants of the aquatic environment. In seawater, sound travels
at roughly 1,500 meters per second (m/s). In air, sound waves travel
much more slowly at about 340 m/s. However, the speed of sound in water
can vary by a small amount based on characteristics of the transmission
medium such as temperature and salinity.
The basic characteristics of a sound wave are frequency,
wavelength, velocity, and amplitude. Frequency is the number of
pressure waves that pass by a reference point per unit of time and is
measured in Hz or cycles per second. Wavelength is the distance between
two peaks or corresponding points of a sound wave (length of one
cycle). Higher frequency sounds have shorter wavelengths than lower
frequency sounds, and typically attenuate (decrease) more rapidly with
distance, except in certain cases in shallower water. The amplitude of
a sound pressure wave is related to the subjective ``loudness'' of a
sound and is typically expressed in dB, which are a relative unit of
measurement that is used to express the ratio of one value of a power
or pressure to another. A sound pressure level (SPL) in dB is described
as the ratio between a measured pressure and a reference pressure, and
is a logarithmic unit that accounts for large variations in amplitude;
therefore, a relatively small change in dB corresponds to large changes
in sound pressure. For example, a 10-dB increase is a 10-fold increase
in acoustic power. A 20-dB increase is then a 100-fold increase in
power and a 30-dB increase is a 1,000-fold increase in power. However,
a 10-fold increase in acoustic power does not mean that the sound is
perceived as being 10 times louder. The dB is a relative unit comparing
two pressures; therefore, a reference pressure must always be
indicated. For underwater sound, this is 1 microPascal ([mu]Pa). For
in-air sound, the reference pressure is 20 [mu]Pa. The amplitude of a
sound can be presented in various ways; however, NMFS typically
considers three metrics: sound exposure level (SEL), root-mean-square
(RMS) SPL, and peak SPL (defined below). The source level represents
the SPL referenced at a standard distance from the source, typically 1
m (Richardson et al., 1995; American National Standards Institute
(ANSI), 2013), while the received level is the SPL at the receiver's
position. For
[[Page 34995]]
tugging activities, the SPL is typically referenced at 1 m.
SEL (represented as dB referenced to 1 micropascal squared second
(re 1 [mu]Pa\2\-s)) represents the total energy in a stated frequency
band over a stated time interval or event, and considers both intensity
and duration of exposure. SEL can also be a cumulative metric; it can
be accumulated over a single pulse (i.e., during activities such as
impact pile driving) or calculated over periods containing multiple
pulses. Cumulative SEL (SEL<INF>cum</INF>) represents the total energy
accumulated by a receiver over a defined time window or during an
event. The SEL metric is useful because it allows sound exposures of
different durations to be related to one another in terms of total
acoustic energy. The duration of a sound event and the number of
pulses, however, should be specified as there is no accepted standard
duration over which the summation of energy is measured.
RMS SPL is equal to 10 times the logarithm (base 10) of the ratio
of the mean-square sound pressure to the specified reference value, and
given in units of dB (International Organization for Standardization
(ISO), 2017). RMS is calculated by squaring all of the sound
amplitudes, averaging the squares, and then taking the square root of
the average (Urick, 1983). RMS accounts for both positive and negative
values; squaring the pressures makes all values positive so that they
may be accounted for in the summation of pressure levels (Hastings and
Popper, 2005). This measurement is often used in the context of
discussing behavioral effects, in part because behavioral effects,
which often result from auditory cues, may be better expressed through
averaged units than by peak SPL. For impulsive sounds, RMS is
calculated by the portion of the waveform containing 90 percent of the
sound energy from the impulsive event (Madsen, 2005).
Peak SPL (also referred to as zero-to-peak sound pressure or 0-pk)
is the maximum instantaneous sound pressure measurable in the water,
which can arise from a positive or negative sound pressure, during a
specified time, for a specific frequency range at a specified distance
from the source, and is represented in the same units as the RMS sound
pressure (ISO, 2017). Along with SEL, this metric is used in evaluating
the potential for permanent threshold shift (PTS) and temporary
threshold shift (TTS) associated with impulsive sound sources.
Sounds are also characterized by their temporal components.
Continuous sounds are those whose sound pressure level remains above
that of the ambient or background sound with negligibly small
fluctuations in level (ANSI, 2005) while intermittent sounds are
defined as sounds with interrupted levels of low or no sound (National
Institute for Occupational Safety and Health (NIOSH), 1998). A key
distinction between continuous and intermittent sound sources is that
intermittent sounds have a more regular (predictable) pattern of bursts
of sounds and silent periods (i.e., duty cycle), which continuous
sounds do not. Tugs under load are considered sources of continuous
sound.
Sounds may be either impulsive or non-impulsive (defined below).
The distinction between these two sound types is important because they
have differing potential to cause physical effects, particularly with
regard to noise-induced hearing loss (e.g., Ward, 1997 in Southall et
al., 2007). Please see NMFS (2018) and Southall et al. (2007, 2019) for
an in-depth discussion of these concepts.
Impulsive sound sources (e.g., explosions, gunshots, sonic booms,
seismic airgun shots, impact pile driving) produce signals that are
brief (typically considered to be less than 1 second), broadband,
atonal transients (ANSI, 1986, 2005; NIOSH, 1998) and occur either as
isolated events or repeated in some succession. Impulsive sounds are
all characterized by a relatively rapid rise from ambient pressure to a
maximal pressure value followed by a rapid decay period that may
include a period of diminishing, oscillating maximal and minimal
pressures, and generally have an increased capacity to induce physical
injury as compared with sounds that lack these features. Impulsive
sounds are intermittent in nature. The duration of such sounds, as
received at a distance, can be greatly extended in a highly reverberant
environment.
Non-impulsive sounds can be tonal, narrowband, or broadband, brief
or prolonged, and may be either continuous or non-continuous (ANSI,
1995; NIOSH, 1998). Some of these non-impulsive sounds can be transient
signals of short duration but without the essential properties of
impulses (e.g., rapid rise time). Examples of non-impulsive sounds
include those produced by vessels (including tugs under load),
aircraft, machinery operations, such as drilling or dredging, and
vibratory pile driving, and active sonar systems.
Even in the absence of sound from the specified activity, the
underwater environment is characterized by sounds from both natural and
anthropogenic sound sources. Ambient sound is defined as a composite of
naturally-occurring (i.e., non-anthropogenic) sound from many sources
both near and far (ANSI, 1995). Background sound is similar, but
includes all sounds, including anthropogenic sounds, minus the sound
produced by the proposed activities (NMFS, 2012, 2016a). The sound
level of a region is defined by the total acoustical energy being
generated by known and unknown sources. These sources may include
physical (e.g., wind and waves, earthquakes, ice, atmospheric sound),
biological (e.g., sounds produced by marine mammals, fish, and
invertebrates), and anthropogenic (e.g., vessels, dredging,
construction) sound.
A number of sources contribute to background and ambient sound,
including wind and waves, which are a main source of naturally
occurring ambient sound for frequencies between 200 Hz and 50 kHz
(Mitson, 1995). In general, background and ambient sound levels tend to
increase with increasing wind speed and wave height. Precipitation can
become an important component of total sound at frequencies above 500
Hz, and possibly down to 100 Hz during quiet times. Marine mammals can
contribute significantly to background and ambient sound levels, as can
some fish and snapping shrimp. The frequency band for biological
contributions is from approximately 12 Hz to over 100 kHz. Sources of
background sound related to human activity include transportation
(surface vessels), dredging and construction, oil and gas drilling and
production, geophysical surveys, sonar, and explosions. Vessel noise
typically dominates the total background sound for frequencies between
20 and 300 Hz. In general, the frequencies of many anthropogenic
sounds, particularly those produced by construction activities, are
below 1 kHz (Richardson et al., 1995). When sounds at frequencies
greater than 1 kHz are produced, they generally attenuate relatively
rapidly (Richardson et al., 1995), particularly above 20 kHz due to
propagation losses and absorption (Urick, 1983).
Transmission loss (TL) defines the degree to which underwater sound
has spread in space and lost energy after having moved through the
environment and reached a receiver. It is defined as the reduction in a
specified level between two specified points that are within an
underwater acoustic field (ISO, 2017). Careful consideration of TL and
appropriate propagation modeling is a crucial step in determining the
impacts of underwater sound, as it helps to define the ranges
(isopleths) to which
[[Page 34996]]
impacts are expected and depends significantly on local environmental
parameters such as seabed type, water depth (bathymetry), and the local
speed of sound. Geometric spreading laws are powerful tools, which
provide a simple means of estimating TL, based on the shape of the
sound wave front in the water column. For a sound source that is
equally loud in all directions and in deep water, the sound field takes
the form of a sphere, as the sound extends in every direction
uniformly. In this case, the intensity of the sound is spread across
the surface of the sphere, and thus we can relate intensity loss to the
square of the range (as area = 4\*\pi\*\r\2\). When TL =
20\*\Log<INF>10</INF>(range), this situation is known as spherical
spreading. In shallow water, the sea surface and seafloor will bound
the shape of the sound, leading to a more cylindrical shape, as the top
and bottom of the sphere is truncated by the largely reflective
boundaries. This situation is termed cylindrical spreading, and is
given by TL = 10\*\Log<INF>10</INF>(range) (Urick, 1983). An
intermediate scenario may be defined by the equation TL =
15\*\Log<INF>10</INF>(range), and is referred to as practical
spreading. Though these geometric spreading laws do not capture many
often important details (scattering, absorption, etc.), they offer a
reasonable and simple approximation of how sound decreases in intensity
as it is transmitted. Cook Inlet is a particularly complex acoustic
environment with strong currents, large tides, variable sea floor and
generally changing conditions.
The sum of the various natural and anthropogenic sound sources at
any given location and time depends not only on the source levels, but
also on the propagation of sound through the environment. Sound
propagation is dependent on the spatially and temporally varying
properties of the water column and sea floor, and is frequency-
dependent. As a result of the dependence on a large number of varying
factors, background and ambient sound levels can be expected to vary
widely over both coarse and fine spatial and temporal scales. Sound
levels at a given frequency and location can vary by 10 to 20 dB from
day to day (Richardson et al., 1995). The result is that, depending on
the source type and its intensity, sound from a specified activity may
be a negligible addition to the local environment or could form a
distinctive signal that may affect marine mammals.
Description of Sound Sources for the Specified Activities
In-water activities associated with the project that have the
potential to incidentally take marine mammals through exposure to sound
include impact pile driving, tugs under load with a jack-up rig, and
tugs involved in anchor handling and pipe pulling. Impact hammers
typically operate by repeatedly dropping and/or pushing a heavy piston
onto a pile to drive the pile into the substrate. Sound generated by
impact hammers is impulsive, characterized by rapid rise times and high
peak levels, a potentially injurious combination (Hastings and Popper,
2005). Sound energy associated with tug use is produced by vessel
propeller cavitation, a non-impulsive sound source. Bow thrusters, also
a non-impulsive sound source, would be occasionally used for a short
duration (20 to 30 seconds) to either push or pull a vessel in or away
from a dock or platform. Other sound sources include onboard diesel
generators and sound from the main engine, but both are subordinate to
the thruster and main propeller blade rate harmonics (Gray and Greeley,
1980). The various tug scenarios that may occur during this project
include tugs in a stationary mode positioning the drill rig and pulling
the jack-up rig at nearly full power against strong tides, and tugs
engaged in anchor handling and pipe pulling activities. Our assessments
of the likelihood for harassment of marine mammals incidental to
Hilcorp's tug activities specified here and in its take authorization
request are conservative in light of the general Level B harassment
exposure thresholds, the fact that NMFS is still in the process of
developing analyses of the impact that non-quantitative contextual
factors have on the likelihood of Level B harassment occurring, and the
nature and duration of the particular tug activities analyzed here.
Potential non-acoustic stressors could result from the physical
presence of the equipment and personnel; however, given there are no
known pinniped haul-out sites in the vicinity of the specified
activity, visual and other non-acoustic stressors would be limited, and
any impacts to marine mammals are expected to primarily be acoustic in
nature.
Potential Effects of Underwater Sound on Marine Mammals
The introduction of underwater anthropogenic noise into the aquatic
environment from impact pile driving and tugs towing, holding, and
positioning a jack-up rig or engaging in pipe pulling or anchor
handling is the primary means by which marine mammals may be disturbed
from Hilcorp's specified activity. In general, animals exposed to
natural or anthropogenic sound may experience physical and
psychological effects, ranging in magnitude from none to severe
(Southall et al., 2007, 2019). Exposure to anthropogenic noise has the
potential to result in auditory threshold shifts and behavioral
reactions (e.g., avoidance, temporary cessation of foraging and
vocalizing, changes in dive behavior). In addition to auditory
implications, there exists the potential for non-auditory physical
effects. Prolonged exposure to intense underwater sound associated with
industrial activities may trigger physiological responses in marine
mammals that are not observable to the eye, including stress,
neurological effects, bubble formation, resonance effects, and various
forms of organ or tissue damage (Richardson et al., 1995). Additional
noise in a marine mammal's habitat can mask acoustic cues used to carry
out daily functions, such as communication and predator and prey
detection. The effects of noise on marine mammals are dependent on
several factors, including but not limited to sound type (e.g.,
impulsive vs. non-impulsive), the species, age and sex class (e.g.,
adult male vs. mother with calf), duration of exposure, the distance
between the vessel and the animal, received levels, behavior at time of
exposure, and previous history with exposure (Wartzok et al., 2004;
Southall et al., 2007). Here we provide additional detail regarding
potential impacts on marine mammals and their habitat from noise in
general, starting with hearing impairment, as well as from Hilcorp's
specified activities, to the degree available.
Hearing Threshold Shifts
Marine mammals, like all mammals, develop increased hearing
thresholds over time due to age-related degeneration of auditory
pathways and sensory cells of the inner ear. This natural, age-related
hearing loss is contrasted with noise-induced hearing loss
(M[oslash]ller, 2013). Marine mammals exposed to high-intensity sound
or to lower-intensity sound for prolonged periods can experience a
noise-induced hearing threshold shift (TS), which NMFS defines as a
change, usually an increase, in the threshold of audibility at a
specified frequency or portion of an individual's hearing range above a
previously established reference level as a result of noise exposure
(NMFS, 2018, 2024). The amount of threshold shift is customarily
expressed in dB. Noise-induced hearing TS can be temporary (TTS) or
permanent (PTS), with higher-energy sound exposures (which considers
both intensity and duration)
[[Page 34997]]
are more likely to cause PTS or other auditory injury. As described in
NMFS (2018, 2024) there are numerous factors to consider when examining
the consequence of TS, including but not limited to the signal temporal
pattern (e.g., impulsive or non-impulsive), likelihood an individual
would be exposed for a long enough duration or to a high enough level
to induce a TS, the magnitude of the TS, time to recovery (seconds to
minutes or hours to days), the frequency range of the exposure (i.e.,
spectral content), the hearing frequency range of the exposed species
relative to the signal's frequency spectrum (i.e., how animal uses
sound within the frequency band of the signal; e.g., Kastelein et al.,
2014), and the overlap between the animal and the source (e.g.,
spatial, temporal, and spectral).
Auditory Injury (AUD INJ). NMFS (2024) defines AUD INJ as damage to
the inner ear that can result in destruction of tissue, such as the
loss of cochlear neuron synapses or auditory neuropathy (Houser, 2021;
Finneran, 2024). AUD INJ may or may not result in a PTS. PTS is defined
as a permanent, irreversible increase in the threshold of audibility at
a specified frequency or portion of an individual's hearing range above
a previously established reference level (NMFS, 2024). PTS does not
generally affect more than a limited frequency range, and an animal
that has incurred PTS has some level of hearing loss at the relevant
frequencies; thus typically animals with PTS or other AUD INJ are not
functionally deaf (Au and Hastings, 2008; Finneran, 2016). For marine
mammals, AUD INJ is considered possible when sound exposures are
sufficient to produce 40 dB of TTS measured after exposure (Southall et
al., 2007, 1019). AUD INJ levels for marine mammals are estimates, as
with the exception of a single study unintentionally inducing PTS in a
harbor seal (Kastak et al., 2008; Reichmuth et al., 2019), there are no
empirical data measuring AUD INJ in marine mammals largely due to the
fact that, for various ethical reasons, experiments involving
anthropogenic noise exposure at levels inducing AUD INJ are not
typically pursued or authorized (NMFS, 2024).
Temporary Threshold Shift (TTS). TTS is the mildest form of hearing
impairment that can occur during exposure to sound. TTS is a temporary,
reversible increase in the threshold of audibility at a specified
frequency or portion of an individual's hearing range above a
previously established reference level (NMFS, 2024) that represents
primarily tissue fatigue (Henderson et al., 2008), and is not
considered an AUD INJ. Based on data from marine mammal TTS
measurements (see Southall et al., 2007, 2019), a TTS of 6 dB is
considered the minimum threshold shift clearly larger than any day-to-
day or session-to-session variation in a subject's normal hearing
ability (Finneran et al., 2000, 2002; Schlundt et al., 2000). While
experiencing TTS, the hearing threshold rises, meaning that a sound
must be at a higher level in order to be heard. As described in
Finneran (2015), marine mammal studies have shown the amount of TTS
increases with SEL<INF>cum</INF> in an accelerating fashion: at low
exposures with lower SEL<INF>cum</INF>, the amount of TTS is typically
small and the growth curves have shallow slopes. At exposures with
higher SEL<INF>cum</INF>, the growth curves become steeper and approach
linear relationships with the noise SEL.
In terrestrial and marine mammals, TTS can last from minutes or
hours to days (i.e., there is recovery back to baseline/pre-exposure
levels), can occur within a specific frequency range (i.e., an animal
might only have a temporary loss of hearing sensitivity within a
limited frequency band of its auditory range), and can be of varying
amounts (e.g., an animal's hearing sensitivity might be reduced by only
6 dB or reduced by 30 dB). In many cases, hearing sensitivity recovers
rapidly after exposure to the sound ends. While there are data on sound
levels and durations necessary to elicit mild TTS for marine mammals,
recovery is complicated to predict and dependent on multiple factors.
Depending on the degree (elevation of threshold in dB), duration
(i.e., recovery time), and frequency range of TTS, and the context in
which it is experienced, TTS can have effects on marine mammals ranging
from discountable to serious (similar to those discussed in auditory
masking, below). For example, a marine mammal may be able to readily
compensate for a brief, relatively small amount of TTS in a non-
critical frequency range that takes place during a time when the animal
is traveling through the open ocean, where ambient noise is lower and
there are not as many competing sounds present. Alternatively, a larger
amount and longer duration of TTS sustained during time when
communication is critical for successful mother/calf interactions could
have more serious impacts. We note that reduced hearing sensitivity as
a simple function of aging has been observed in marine mammals, as well
as humans and other taxa (Southall et al., 2007), so we can infer that
strategies exist for coping with this condition to some degree, though
likely not without cost.
Many studies have examined noise-induced hearing loss in marine
mammals (see Finneran (2015) and Southall et al. (2019) for summaries).
TTS is the mildest form of hearing impairment that can occur during
exposure to sound (Kryter, 2013). While experiencing TTS, the hearing
threshold rises, and a sound must be at a higher level in order to be
heard. In terrestrial and marine mammals, TTS can last from minutes or
hours to days (in cases of strong TTS). In many cases, hearing
sensitivity recovers rapidly after exposure to the sound ends. For
cetaceans, published data on the onset of TTS are limited to captive
bottlenose dolphin (Tursiops truncatus), beluga whale, harbor porpoise,
and Yangtze finless porpoise (Neophocoena asiaeorientalis) (Southall et
al., 2019). For pinnipeds in water, measurements of TTS are limited to
harbor seals, elephant seals (Mirounga angustirostris), bearded seals
(Erignathus barbatus), and California sea lions (Kastak et al., 1999,
2007; Kastelein et al., 2019b, 2019c, 2021, 2022a, 2022b; Reichmuth et
al., 2019; Sills et al., 2020). TTS was not observed in spotted (Phoca
largha) and ringed (Pusa hispida) seals exposed to single airgun
impulse sounds at levels matching previous predictions of TTS onset
(Reichmuth et al., 2016). These studies examine hearing thresholds
measured in marine mammals before and after exposure to intense or
long-duration sound exposures. The difference between the pre-exposure
and post-exposure thresholds can be used to determine the amount of
threshold shift at various post-exposure times.
The amount and onset of TTS depends on the exposure frequency.
Sounds below the region of best sensitivity for a species or hearing
group are less hazardous than those near the region of best sensitivity
(Finneran and Schlundt, 2013). At low frequencies, onset-TTS exposure
levels are higher compared to those in the region of best sensitivity
(i.e., a low frequency noise would need to be louder to cause TTS onset
when TTS exposure level is higher), as shown for harbor porpoises and
harbor seals (Kastelein et al., 2019a, 2019c). Note that in general,
harbor seals and harbor porpoises have a lower TTS onset than other
measured pinniped and cetacean species (Finneran, 2015). In addition,
TTS can accumulate across multiple exposures, but the resulting TTS
will be less than the TTS from a single, continuous exposure with the
same SEL (Mooney et al., 2009; Finneran et al., 2010;
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Kastelein et al., 2014, 2015). This means that TTS predictions based on
the total, cumulative SEL will overestimate the amount of TTS from
intermittent exposures, such as sonars and impulsive sources.
Nachtigall et al. (2018) describe measurements of hearing sensitivity
of multiple odontocete species (bottlenose dolphin, harbor porpoise,
beluga, and false killer whale (Pseudorca crassidens)) when a
relatively loud sound was preceded by a warning sound. These captive
animals were shown to reduce hearing sensitivity when warned of an
impending intense sound. Based on these experimental observations of
captive animals, the authors suggest that wild animals may dampen their
hearing during prolonged exposures or if conditioned to anticipate
intense sounds. Another study showed that echolocating animals
(including odontocetes) might have anatomical specializations that
might allow for conditioned hearing reduction and filtering of low-
frequency ambient noise, including increased stiffness and control of
middle ear structures and placement of inner ear structures (Ketten et
al., 2021). Data available on noise-induced hearing loss for mysticetes
are currently lacking (NMFS, 2018). Additionally, the existing marine
mammal TTS data come from a limited number of individuals within these
species.
Relationships between TTS and PTS thresholds have not been studied
in marine mammals, and there is no PTS data for cetaceans, but such
relationships are assumed to be similar to those in humans and other
terrestrial mammals. PTS typically occurs at exposure levels at least
several decibels above that inducing mild TTS (e.g., a 40-dB threshold
shift approximates PTS onset (Kryter et al., 1966; Miller, 1974), while
a 6-dB threshold shift approximates TTS onset (Southall et al., 2007,
2019). Based on data from terrestrial mammals, a precautionary
assumption is that the PTS thresholds for impulsive sounds are at least
6 dB higher than the TTS threshold on a peak-pressure basis and PTS
cumulative sound exposure level thresholds are 15 to 20 dB higher than
TTS cumulative sound exposure level thresholds (Southall et al., 2007,
2019). Given the higher level of sound or longer exposure duration
necessary to cause PTS as compared with TTS, it is considerably less
likely that PTS could occur.
Non-acoustic Stressors. Hilcorp's specified activities could also
involve non-acoustic stressors. Potential non-acoustic stressors could
result from the physical presence of the equipment (e.g., tug and
vessel configuration, pile driving equipment) and personnel; however,
given there are no known pinniped haul-out sites in the vicinity of the
project site, visual and other non-acoustic stressors would be limited,
and any impacts to marine mammals are expected to primarily be acoustic
in nature.
Behavioral Disturbance. Exposure to noise also has the potential to
behaviorally disturb marine mammals to a level that rises to the
definition of Level B harassment under the MMPA. Behavioral disturbance
may include a variety of effects, including subtle changes in behavior
(e.g., minor or brief avoidance of an area or changes in
vocalizations), more conspicuous changes in similar behavioral
activities, and more sustained and/or potentially severe reactions,
such as displacement from or abandonment of high-quality habitat.
Behavioral responses may include changing durations of surfacing and
dives, changing direction and/or speed; reducing/increasing vocal
activities; changing/cessation of certain behavioral activities (such
as socializing or feeding); eliciting a visible startle response or
aggressive behavior (such as tail/fin slapping or jaw clapping); and
avoidance of areas where sound sources are located (Erbe et al., 2019).
In addition, pinnipeds may increase their haul out time, possibly to
avoid in-water disturbance (Thorson and Reyff, 2006).
Behavioral responses to sound are highly variable and context-
specific and any reactions depend on numerous intrinsic and extrinsic
factors (e.g., species, state of maturity, experience, current
activity, reproductive state, auditory sensitivity, time of day), as
well as the interplay between factors (e.g., Richardson et al., 1995;
Wartzok et al., 2004; Southall et al., 2007, 2019; Weilgart, 2007;
Archer et al., 2010; Erbe et al., 2019). Behavioral reactions can vary
not only among individuals but also within an individual, depending on
previous experience with a sound source, context, and numerous other
factors (Ellison et al., 2012), and can vary depending on
characteristics associated with the sound source (e.g., whether it is
moving or stationary, number of sources, distance from the source). For
example, animals that are resting may show greater behavioral change in
response to disturbing sound levels than animals that are highly
motivated to remain in an area for feeding (Richardson et al., 1995;
Wartzok et al., 2004; National Research Council (NRC), 2005). In
general, pinnipeds seem more tolerant of, or at least habituate more
quickly to, potentially disturbing underwater sound than do cetaceans,
and generally seem to be less responsive to exposure to industrial
sound than most cetaceans. The biological significance of many of
behavioral disturbances is difficult to predict, especially if the
detected disturbances appear minor. However, the consequences of
behavioral modification could be biologically significant if the change
affects growth, survival, and/or reproduction, which depends on the
severity, duration, and context of the effects. Please see appendices B
and C of Southall et al. (2007) and Gomez et al. (2016) for reviews of
studies involving marine mammal behavioral responses to sound.
Habituation can occur when an animal's response to a stimulus wanes
with repeated exposure, usually in the absence of unpleasant associated
events (Wartzok et al., 2004). Animals are most likely to habituate to
sounds that are predictable and unvarying. It is important to note that
habituation is appropriately considered as a ``progressive reduction in
response to stimuli that are perceived as neither aversive nor
beneficial,'' rather than as, more generally, moderation in response to
human disturbance (Bejder et al., 2009). The opposite process is
sensitization, when an unpleasant experience leads to subsequent
responses, often in the form of avoidance, at a lower level of
exposure.
Available studies show wide variation in response to underwater
sound; therefore, it is difficult to predict specifically how any given
sound in a particular instance might affect marine mammals perceiving
the signal (e.g., Erbe et al., 2019). If a marine mammal does react
briefly to an underwater sound by changing its behavior or moving a
small distance, the impacts of the change are unlikely to be
significant to the individual, let alone the stock or population. If a
sound source displaces marine mammals from an important feeding or
breeding area for a prolonged period, impacts on individuals and
populations could be significant (e.g., Lusseau and Bejder, 2007;
Weilgart, 2007; NRC, 2005). However, there are broad categories of
potential response, which we describe in greater detail here, that
include alteration of dive behavior, alteration of foraging behavior,
effects to breathing, interference with or alteration of vocalization,
avoidance, and flight.
Changes in dive behavior can vary widely and may consist of
increased or decreased dive times and surface intervals as well as
changes in the rates of ascent and descent during a dive (e.g., Frankel
and Clark, 2000; Costa et al., 2003; Ng and Leung, 2003; Nowacek et
al., 2004; Goldbogen et al., 2013a, 2013b, Blair et al., 2016).
Variations in
[[Page 34999]]
dive behavior may reflect interruptions in biologically significant
activities (e.g., foraging) or they may be of little biological
significance. The impact of an alteration to dive behavior resulting
from an acoustic exposure depends on what the animal is doing at the
time of the exposure and the type and magnitude of the response.
Disruption of feeding behavior from anthropogenic sound exposure is
usually inferred by observed displacement from known foraging areas,
the appearance of secondary indicators (e.g., bubble nets or sediment
plumes), or changes in dive behavior. Acoustic and movement bio-logging
tools also have been used in some cases to infer responses to
anthropogenic noise. For example, Blair et al. (2016) reported
significant effects on humpback whale foraging behavior in Stellwagen
Bank in response to ship noise including slower descent rates, and
fewer side-rolling events per dive with increasing ship nose. In
addition, Wisniewska et al. (2018) reported that tagged harbor
porpoises demonstrated fewer prey capture attempts when encountering
occasional high-noise levels resulting from vessel noise as well as
more vigorous fluking, interrupted foraging, and cessation of
echolocation signals observed in response to some high-noise vessel
passes. In addition, harbor porpoises trained to collect fish during
playback of impact pile driving sounds also showed potential changes in
behavior and task success, though individual differences were prevalent
(Kastelein et al., 2019d). As for other types of behavioral response,
the frequency, duration, and temporal pattern of signal presentation,
as well as differences in species sensitivity, are likely contributing
factors to differences in response in any given circumstance (e.g.,
Croll et al., 2001; Nowacek et al., 2004; Madsen et al., 2006; Yazvenko
et al., 2007). A determination of whether foraging disruptions incur
fitness consequences would require information on or estimates of the
energetic requirements of the affected individuals and the
relationships among prey availability, foraging effort and success, and
the life history stage(s) of the animal.
Variations in respiration naturally vary with different behaviors
and alterations to breathing rate as a function of acoustic exposure
can be expected to co-occur with other behavioral reactions, such as a
flight response or an alteration in diving. However, respiration rates
in and of themselves may be representative of annoyance or an acute
stress response. Various studies have shown that respiration rates may
either be unaffected or could increase, depending on the species and
signal characteristics, again highlighting the importance in
understanding species differences in the tolerance of underwater noise
when determining the potential for impacts resulting from anthropogenic
sound exposure (e.g., Kastelein et al., 2001, 2005, 2006; Gailey et
al., 2007). For example, harbor porpoise respiration rate increased in
response to pile driving sounds at and above a received broadband SPL
of 136 dB (zero-peak SPL: 151 dB re 1 [mu]Pa; SEL of a single strike:
127 dB re 1 [mu]Pa\2\-s) (Kastelein et al., 2013).
Avoidance is the displacement of an individual from an area or
migration path as a result of the presence of a sound or other
stressors, and is one of the most obvious manifestations of disturbance
in marine mammals (Richardson et al., 1995). For example, gray whales
are known to change direction--deflecting from customary migratory
paths--in order to avoid noise from seismic surveys (Malme et al.,
1984). Harbor porpoises, Atlantic white-sided dolphins (Lagenorhynchus
actusus), and minke whales have demonstrated avoidance in response to
vessels during line transect surveys (Palka and Hammond, 2001). In
addition, beluga whales in the St. Lawrence Estuary in Canada have been
reported to increase levels of avoidance with increased boat presence
by way of increased dive durations and swim speeds, decreased surfacing
intervals, and by bunching together into groups (Blane and Jaakson,
1994). Possible avoidance of pile driving activities has also been
documented in species such as harbor porpoises (e.g., D[auml]hne et
al., 2013, Kastelein et al., 2013, Degraer et al., 2022) and harbor
seals (e.g., Russel et al., 2016). Avoidance may be short-term, with
animals returning to the area once the noise has ceased (e.g., Bowles
et al., 1994; Goold, 1996; Stone et al., 2000; Morton and Symonds,
2002; Gailey et al., 2007). Longer-term displacement is possible,
however, which may lead to changes in abundance or distribution
patterns of the affected species in the affected region if habituation
to the presence of the sound does not occur (e.g., Blackwell et al.,
2004; Bejder et al., 2006; Teilmann et al., 2006).
A flight response is a dramatic change in normal movement to a
directed and rapid movement away from the perceived location of a sound
source. The flight response differs from other avoidance responses in
the intensity of the response (e.g., directed movement, rate of
travel). Relatively little information on flight responses of marine
mammals to anthropogenic signals exists, although observations of
flight responses to the presence of predators have occurred (Connor and
Heithaus, 1996; Bowers et al., 2018). The result of a flight response
could range from brief, temporary exertion and displacement from the
area where the signal provokes flight to, in extreme cases, marine
mammal strandings (England et al., 2001). However, it should be noted
that response to a perceived predator does not necessarily invoke
flight (Ford and Reeves, 2008), and whether individuals are solitary or
in groups may influence the response.
Behavioral disturbance can also impact marine mammals in more
subtle ways. Increased vigilance may result in costs related to
diversion of focus and attention (i.e., when a response consists of
increased vigilance, it may come at the cost of decreased attention to
other critical behaviors such as foraging or resting). Studies
involving fishes and terrestrial animals have shown that increased
vigilance may substantially reduce feeding rates (e.g., Beauchamp and
Livoreil, 1997; Fritz et al., 2002; Purser and Radford, 2011). Ridgway
et al. (2006) reported that increased vigilance in bottlenose dolphins
exposed to sound over a 5-day period did not cause any sleep
deprivation or stress effects.
Many animals perform vital functions, such as feeding, resting,
traveling, and socializing, on a diel cycle (24-hour cycle). Disruption
of such functions resulting from reactions to stressors such as sound
exposure are more likely to be significant if they last more than one
diel cycle or recur on subsequent days (Southall et al., 2007). That
is, chronic disturbance can cause population declines through reduction
of fitness (e.g., decline in body condition) and subsequent reduction
in reproductive success, survival, or both (e.g., Harrington and
Veitch, 1992; Daan et al., 1996; Bradshaw et al., 1998). Consequently,
a behavioral response lasting less than 1 day and not recurring on
subsequent days is not considered particularly severe unless it could
directly affect reproduction or survival (Southall et al., 2007). Note
that there is a difference between multi-day substantive (i.e.,
meaningful) behavioral reactions and multi-day anthropogenic
activities. For example, just because an activity lasts for multiple
days does not necessarily mean that individual animals are either
exposed to activity-related stressors for multiple days or, further,
exposed in a manner resulting in sustained multi-day substantive
behavioral responses.
[[Page 35000]]
Stress Responses. An animal's perception of a threat may be
sufficient to trigger stress responses consisting of some combination
of behavioral responses, autonomic nervous system responses,
neuroendocrine responses, or immune responses (e.g., Selye, 1950;
Moberg, 2000). In many cases, an animal's first and sometimes most
economical (in terms of energetic costs) response is behavioral
avoidance of the potential stressor. Autonomic nervous system responses
to stress typically involve changes in heart rate, blood pressure, and
gastrointestinal activity. These responses have a relatively short
duration and may or may not have a significant long-term effect on an
animal's fitness.
Neuroendocrine stress responses often involve the hypothalamus-
pituitary-adrenal system. Virtually all neuroendocrine functions that
are affected by stress--including immune competence, reproduction,
metabolism, and behavior--are regulated by pituitary hormones. Stress-
induced changes in the secretion of pituitary hormones have been
implicated in failed reproduction, altered metabolism, reduced immune
competence, and behavioral disturbance (e.g., Moberg, 1987; Blecha,
2000). Increases in the circulation of glucocorticoids are also equated
with stress (Romano et al., 2004).
The primary distinction between stress (which is adaptive and does
not normally place an animal at risk) and ``distress'' is the cost of
the response. During a stress response, an animal uses glycogen stores
that can be quickly replenished once the stress is alleviated. In such
circumstances, the cost of the stress response would not pose serious
fitness consequences. However, when an animal does not have sufficient
energy reserves to satisfy the energetic costs of a stress response,
energy resources must be diverted from other functions. This state of
distress will last until the animal replenishes its energetic reserves
sufficient to restore normal function.
Relationships between these physiological mechanisms, animal
behavior, and the costs of stress responses are well-studied through
controlled experiments and for both laboratory and free-ranging animals
(e.g., Holberton et al., 1996; Hood et al., 1998; Jessop et al., 2003;
Krausman et al., 2004; Lankford et al., 2005). Stress responses due to
exposure to anthropogenic sounds or other stressors and their effects
on marine mammals have also been reviewed (Fair and Becker, 2000;
Romano et al., 2002b) and, more rarely, studied in wild populations
(e.g., Romano et al., 2002a). For example, Rolland et al. (2012) found
that noise reduction from reduced ship traffic in the Bay of Fundy was
associated with decreased stress in North Atlantic right whales. In
addition, Lemos et al. (2022) observed a correlation between higher
levels of fecal glucocorticoid metabolite concentrations (indicative of
a stress response) and vessel traffic in gray whales. These and other
studies lead to a reasonable expectation that some marine mammals will
experience physiological stress responses upon exposure to acoustic
stressors and that it is possible that some of these would be
classified as ``distress.'' In addition, any animal experiencing TTS
would likely also experience stress responses (NRC, 2005). Based on
marine mammal behavior observed during pile driving projects in Cook
Inlet and previous monitoring by Hilcorp and other ITA holders, marine
mammals exposed to noise from Hilcorp's activities are unlikely to
experience a high degree of stress.
Norman (2011) reviewed environmental and anthropogenic stressors
for CIBWs. Lyamin et al. (2011) determined that the heart rate of a
beluga whale increases in response to noise, depending on the frequency
and intensity. Acceleration of heart rate in the beluga whale is the
first component of the ``acoustic startle response.'' Romano et al.
(2004) demonstrated that captive beluga whales exposed to high-level
impulsive sounds (i.e., seismic airgun and/or single pure tones up to
201 dB RMS) resembling sonar pings showed increased stress hormone
levels of norepinephrine, epinephrine, and dopamine when TTS was
reached. Thomas et al. (1990) exposed beluga whales to playbacks of an
oil-drilling platform in operation (``Sedco 708,'' 40 Hz-20 kHz; source
level 153 dB). Ambient SPL at ambient conditions in the pool before
playbacks was 106 dB and 134 to 137 dB RMS during playbacks at the
monitoring hydrophone across the pool. All cell and platelet counts and
21 different blood chemicals, including epinephrine and norepinephrine,
were within normal limits throughout baseline and playback periods, and
stress response hormone levels did not increase immediately after
playbacks. The difference between the Romano et al. (2004) and Thomas
et al. (1990) studies could be the differences in the type of sound
(seismic airgun and/or tone versus oil drilling), the intensity and
duration of the sound, the individual's response, and the surrounding
circumstances of the individual's environment. The sounds in the Thomas
et al. (1990) study would be more similar to those anticipated by
Hilcorp's tugs under load with a jack-up rig; therefore, no more than
short-term, low-hormone stress responses, if any, of CIBWs or other
marine mammals are expected as a result of exposure to noise during
tugs under load with a jack-up rig during Hilcorp's planned activities.
Auditory Masking. Acoustic masking is when other noises such as
from human sources interfere with an animal's ability to detect,
recognize, or discriminate between acoustic signals of interest (e.g.,
those used for intraspecific communication and social interactions,
prey detection, predator avoidance, navigation) (Richardson et al.,
1995; Erbe et al., 2016). Since many marine mammals rely on sound to
find prey, moderate social interactions, and facilitate mating (Tyack,
2008), noise from anthropogenic sound sources can interfere with these
functions, but only if the noise spectrum overlaps with the hearing
sensitivity of the receiving marine mammal (Southall et al., 2007;
Clark et al., 2009; Hatch et al., 2012). For example, Brewer et al.
(2023) investigated masking of CIBW calls in the 0-12 kHz range by
commercial ship noise and found that all seven of the most common call
types in the CIBW repertoire were partially masked by distant
commercial ship noise and completely masked by close commercial ship
noise in the 0-12 kHz range. Chronic exposure to excessive, though not
high-intensity, noise could cause masking at particular frequencies for
marine mammals that utilize sound for vital biological functions (Clark
et al., 2009). Therefore, under certain circumstances, marine mammals
whose acoustical sensors or environment are being severely masked could
also be impaired from maximizing their performance fitness for survival
and reproduction. The ability of a noise source to mask biologically
important sounds depends on the characteristics of both the noise
source and the signal of interest (e.g., signal-to-noise ratio,
temporal variability, direction), in relation to each other and to an
animal's hearing abilities (e.g., sensitivity, frequency range,
critical ratios, frequency discrimination, directional discrimination,
age or TTS hearing loss), and existing ambient noise and propagation
conditions (Hotchkin and Parks, 2013).
Marine mammals vocalize for different purposes and across multiple
modes, such as whistling, echolocation click production, calling, and
singing. Changes in vocalization behavior in response to anthropogenic
noise can occur for any of these modes and may
[[Page 35001]]
result from a need to compete with an increase in background noise or
may reflect increased vigilance or a startle response. For example, in
the presence of potentially masking signals, humpback whales and killer
whales have been observed to increase the length of their songs (Miller
et al., 2000; Fristrup et al., 2003) or vocalizations (Foote et al.,
2004), respectively, while North Atlantic right whales (Eubalaena
glacialis) have been observed to shift the frequency content of their
calls upward while reducing the rate of calling in areas of increased
anthropogenic noise (Parks et al., 2007). Blue whales in California
have been observed to shift their call frequencies downward by 31
percent since the 1960s to effectively communicate below the sound
frequency generated by propeller cavitation from ships (McDonald et
al., 1995). Fin whales have also been documented lowering the
bandwidth, peak frequency, and center frequency of their vocalizations
under increased levels of background noise from large vessels
(Castellote et al., 2012) and reducing their calling rate in response
to sound from boats (Watkins, 1986). Other alterations to communication
signals have also been observed. For example, gray whales, in response
to playback experiments exposing them to vessel noise, have been
observed increasing their vocalization rate and producing louder
signals at times of increased outboard engine noise (Dahlheim and
Castellote, 2016). Alternatively, in some cases, animals may cease
sound production during production of aversive signals (Bowles et al.,
1994; Wisniewska et al., 2018).
Under certain circumstances, marine mammals experiencing
significant masking could also be impaired from maximizing their
performance fitness in survival and reproduction. Therefore, when the
coincident (masking) sound is human-made, it may be considered
harassment when disrupting or altering critical behaviors. It is
important to distinguish TTS and PTS, which persist after the sound
exposure, from masking, which occurs only during the sound exposure.
Because masking (without resulting in TS) is not associated with
abnormal physiological function, it is not considered a physiological
effect, but rather a potential behavioral effect (though not
necessarily one that would be considered harassment).
The frequency range of the potentially masking sound is important
in determining any potential behavioral impacts
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