# Marine Mammals; Incidental Take During Specified Activities: Cook Inlet, Alaska

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URL: https://www.frixlaw.com/law-library/documents/fr%3A2019-16279

## Record

- **Collection:** Federal Register
- **Document type:** Rule
- **Published:** August 1, 2019
- **Citation:** 84 FR 37716

## Text

DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 18
[Docket No. FWS-R7-ES-2019-0012; FXES111607MRG01-190-FF07CAMM00]
RIN 1018-BD63
Marine Mammals; Incidental Take During Specified Activities: Cook Inlet, Alaska

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Final rule.

SUMMARY:

We, the U.S. Fish and Wildlife Service, in response to a request from Hilcorp Alaska, LLC, Harvest Alaska, LLC, and the Alaska Gasline Development Corporation, finalize regulations authorizing the nonlethal, incidental take by harassment of small numbers of northern sea otters in State and Federal waters (Alaska and the Outer Continental Shelf) within Cook Inlet, Alaska, as well as all adjacent rivers, estuaries, and coastal lands. Take may result from oil and gas exploration, development, production, and transportation activities occurring for a period of 5 years. This rule authorizes take by harassment only; no lethal take is authorized. We will issue Letters of Authorization, upon request, for specific proposed activities in accordance with these regulations. Additionally, the Office of Management and Budget has approved a revision of the existing Information Collection control number 1018-0070, for incidental take of marine mammals in the Beaufort and Chukchi Seas, to include oil and gas activities in Cook Inlet.

DATES:

This rule is effective August 1, 2019, and remains effective through August 1, 2024.

ADDRESSES:

Document availability:
You may view this rule, the original and updated application packages, supporting information, final environmental assessment and U.S. Fish and Wildlife Service finding of no significant impact (FONSI), and the list of references cited herein at
http://www.regulations.gov
under Docket No. FWS-R7-ES-2019-0012, or these documents may be requested as described under
FOR FURTHER INFORMATION CONTACT
.

FOR FURTHER INFORMATION CONTACT:

Mr. Christopher Putnam, U.S. Fish and Wildlife Service, MS 341, 1011 East Tudor Road, Anchorage, Alaska 99503, by email at
fw7_ak_marine_mammals@fws.gov,
or by telephone at 1-800-362-5148. Persons who use a telecommunications device for the deaf (TDD) may call the Federal Relay Service (FRS) at 1-800-877-8339, 24 hours a day, 7 days a week.

For information on Information Collection control number 1018-0070, contact the Service Information Collection Clearance Officer, U.S. Fish and Wildlife Service, MS: BPHC, 5275 Leesburg Pike, Falls Church, VA 22041-3803 (mail); 703-358-2503 (telephone), or
info_coll@fws.gov
(email). Please include “1018-0070” in the subject line of your email request.

SUPPLEMENTARY INFORMATION:

Immediate Promulgation

In accordance with 5 U.S.C. 553(d)(3), we find that we have good cause to make this rule effective less than 30 days after publication. Immediate promulgation of the rule will ensure that the applicant will implement mitigation measures and monitoring programs in the geographic region that reduce the risk of any lethal and nonlethal effects to sea otters by their activities.

Background

Section 101(a)(5)(A) of the Marine Mammal Protection Act of 1972 (16 U.S.C. 1361(a)(5)(A)) (MMPA), gives the Secretary of the Interior (Secretary) the authority to allow the incidental, but not intentional, taking of small numbers of marine mammals in response to requests by U.S. citizens engaged in a specified activity in a specified region. The Secretary has delegated authority for implementation of the MMPA to the U.S. Fish and Wildlife Service (Service). According to the MMPA, the Service shall allow this incidental taking for a period of up to 5 years if we make findings that such taking: (1) Will affect only small numbers of individuals of these species or stocks; (2) will have no more than a negligible impact on these species or stocks; (3) will not have an unmitigable adverse impact on the availability of these species or stocks for taking for subsistence use by Alaska Natives; and (4) we issue an incidental take regulation (ITR) setting forth: (a) The permissible methods of taking, (b) the means of effecting the least practicable adverse impact on the species, their habitat, and the availability of the species for subsistence uses, and (c) the requirements for monitoring and reporting. If final regulations allowing such incidental taking are issued, we may then subsequently issue a letter of authorization (LOA), upon request, to authorize incidental take during the specified activities.

The term “take,” as defined by the MMPA, means to harass, hunt, capture, or kill, or to attempt to harass, hunt, capture, or kill any marine mammal (16 U.S.C. 1362(13)). Harassment, as defined by the MMPA for non-military readiness activities, means any act of pursuit, torment, or annoyance that (i) has the potential to injure a marine mammal or marine mammal stock in the wild (the MMPA calls this “Level A harassment”), or (ii) has the potential to disturb a marine mammal or marine mammal stock in the wild by causing disruption of behavioral patterns, including, but not limited to, migration, breathing, nursing, breeding, feeding, or sheltering (the MMPA calls this “Level B harassment”).

The terms “negligible impact,” “small numbers,” “unmitigable adverse impact,” and “U.S. citizens,” among others, are defined in title 50 of the Code of Federal Regulations at 50 CFR 18.27, the Service's regulations governing take of small numbers of marine mammals incidental to specified activities. “Negligible impact” is defined as an impact resulting from the specified activity that cannot be reasonably expected to, and is not reasonably likely to, adversely affect the species or stock through effects on annual rates of recruitment or survival. “Small numbers” is defined as a portion of a marine mammal species or stock whose taking would have a negligible impact on that species or stock. However, we do not rely on that definition here, as it conflates the terms “small numbers” and “negligible impact,” which we recognize as two separate and distinct requirements. Instead, in our small numbers determination, we evaluate whether the number of marine mammals likely to be taken is small relative to the size of the overall stock.

“Unmitigable adverse impact” is defined as an impact resulting from the specified activity (1) that is likely to reduce the availability of the species to a level insufficient for a harvest to meet subsistence needs by (i) causing the marine mammals to abandon or avoid hunting areas, (ii) directly displacing subsistence users, or (iii) placing physical barriers between the marine mammals and the subsistence hunters; and (2) that cannot be sufficiently mitigated by other measures to increase the availability of marine mammals to allow subsistence needs to be met. The term “least practicable adverse impact” is not defined in the MMPA or its enacting regulations. We ensure the least practicable adverse impact by

requiring mitigation measures that are effective in reducing the impacts of the proposed activities, but are not so restrictive as to make conducting the activities unduly burdensome or impossible to undertake and complete.

Implementation of the ITR will require information collection activities. The Office of Management and Budget has approved a revision of the existing Information Collection control number 1018-0070, for incidental take of marine mammals in the Beaufort and Chukchi Seas, to include oil and gas activities in Cook Inlet.

Summary of Request

On May 3, 2018, Hilcorp Alaska, LLC (Hilcorp), Harvest Alaska, LLC (Harvest), and the Alaska Gasline Development Corporation (AGDC), hereinafter referred to as the “applicant,” petitioned the Service to promulgate regulations pursuant to section 101(a)(5)(A) of the MMPA for the nonlethal, unintentional taking of small numbers of northern sea otters (
Enhydra lutris kenyoni;
hereafter “sea otters” or “otters,” unless otherwise indicated) incidental to oil and gas exploration, development, production, and transportation activities in Cook Inlet, Alaska, for a period of 5 years. On June 28, 2018, the applicant submitted an amended request providing additional project details. In March 2019, Hilcorp and Harvest notified the Service that three-dimensional (3D) seismic survey activities originally planned to begin in April 2019 would be delayed until fall 2019. In June 2019, AGDC, Hilcorp, and Harvest also provided an updated application package at the request of the Service. The updated application clarified project details and provided additional information where necessary to respond to questions and concerns raised by comments received during the public review of the proposed ITR. These updates and clarifications were minor and did not significantly change the analysis of effects or the estimates of take, and did not alter the conclusions regarding whether the planned activities would have a negligible impact on the stocks, would affect subsistence use, or would affect more than a small number of animals.

Summary of Changes From the Proposed ITR

In preparing this final regulation for the incidental take of sea otters, we reviewed and considered comments and information from the public on our proposed rule published in the
Federal Register
on March 19, 2019 (84 FR 10224), for which the comment period was extended by notice in the
Federal Register
on April 5, 2019 (84 FR 13603). We also reviewed and considered comments and information from the public for our draft Environmental Assessment (EA). Based on those considerations, and the new information provided by the applicant, we are finalizing these regulations with the following changes from our proposed rule:

• Table 1 and table 3 were updated to reflect the most recent project details available from the applicant.

• The Description of Specified Activities and table 1 were appended to include redevelopment of existing wells at Granite Point.

• Mitigation measures were added or modified in § 18.137(b)(1)(ii), (b)(4)(ii), (b)(7)(ii), (b)(9), (c)(2), (c)(3), (e)(4), and § 18.140(b) of this final rule.

• The total estimated number of Level B takes was adjusted from 1,663 to 1,684 after the analysis was updated to reflect updates in the project plans.

• The duration of activities used in the estimation of take was adjusted to reflect the maximum number of days during which underwater work may generate noise above thresholds for take. The following adjustments were made: Vibratory sheet pile driving was adjusted from 5 to 20 days, Lower Cook Inlet (LCI) pipe driving was revised from 3 to 12 days, Trading Bay (TB) pipe driving was revised from 1.5 to 6 days, vertical seismic profiling (VSP) in LCI was changed from 2 to 8 days, VSP in TB was adjusted from 1 to 4 days, and use of water jets was increased from 10.5 to 21 days.

• The analyses of take tables were updated to remove tugs towing rigs and use of hydraulic grinders at the request of the applicant and after analysis of take using the updated duration for these sources indicated that take was unlikely.

• Field verifications of sound production during two-dimensional (2D) and 3D seismic surveys have been added to the required mitigation measures.

• A discussion of the alternative mitigation measures evaluated but not required has been added.

• Use of a mitigation gun was changed from required mitigation for 2D and 3D seismic surveys to a measure that may be required in LOAs issued under this ITR.

• Table 9 was added to clarify allocation of sea otter take by location of activity relative to the appropriate stock boundary.

• Total estimated Level A take was adjusted from three takes from the southcentral Alaska stock to one take from the southwest Alaska stock and two takes from the southcentral Alaska stock. This change was made to correct an error in the proposed ITR.

• A mitigation measure was added requiring an applicant for an LOA to evaluate alternatives to pile-supported facilities and establishing that the Service may require sound-attenuation devices or alternatives to pile-supported designs.

• The Estimated Incidental Take section was updated to reflect changes to the analysis due to the updated project details and to provide additional clarity in the analysis methods used.

• The evaluation of impacts of the specified activities was modified throughout the document to focus on the total numbers of takes rather than the numbers of individual sea otters taken. This change was needed to ensure the estimates from the analysis were accurate and did not underestimate take.

Description of the Regulation

This regulation does not authorize the specified activities to be conducted by the applicant. Rather, it authorizes the nonlethal incidental, unintentional take of small numbers of sea otters associated with those planned activities based on standards set forth in the MMPA. The ITR includes: Permissible amounts and methods of nonlethal taking; measures to ensure the least practicable adverse impact on sea otters and their habitat; measures to avoid and reduce impacts to subsistence uses; and requirements for monitoring and reporting.

Description of the ITR Geographic Area

The geographic region of the ITR encompasses Cook Inlet, Alaska, south of a line from the Susitna River Delta to Point Possession (approximately 61°15′54″ N, 150°41′07″ W, to 61°02′19″ N, 150°23′48″ W, WGS 1984) and north of a line from Rocky Cove to Coal Cove (at approximately 59°25′56″ N, 153°44′25″ W and 59°23′48″ N, 151°54′28″ W WGS 1984), excluding Ursus Cove, Iniskin Bay, Iliamna Bay, and Tuxedni Bay (see Regulation Promulgation, § 18.131 Specified geographic region where this subpart applies). The ITR area includes all Alaska State waters and Outer Continental Shelf (OCS) Federal waters within this area as well as all adjacent rivers, estuaries, and coastal lands where sea otters may occur, unless explicitly excluded.

The geographical extent of the Cook Inlet ITR region is approximately 1.1 million hectares (ha) (2.7 million acres (ac)). For descriptive purposes, the specified area is organized into two

marine areas within Cook Inlet: LCI (south of the Forelands to Homer) and middle Cook Inlet (MCI; north of the Forelands to the Susitna River and Point Possession). Project sites within these general areas include TB, Granite Point, and the North Cook Inlet unit (NCI) in the MCI, and the Iniskin Peninsula and the OCS waters of LCI.

Description of Specified Activities

The specified activities (also “project activities” or “planned activities”) include work related to oil and gas exploration, development, production, transport, and the decommissioning of existing facilities conducted by the applicant within a 5-year period. Hilcorp and Harvest jointly plan to conduct the following activities: 2D and 3D seismic surveys in LCI; routine operations of, maintenance of, redevelopment of, and production drilling from existing oil and gas facilities in MCI; geophysical and geohazard surveys in both regions; drilling of two to four exploration wells in OCS waters of LCI and one to three wells in MCI; construction of a dock facility in Chinitna Bay; and decommissioning of an existing facility at the Drift River Terminal in MCI. The following support activities will be conducted: Pipe and pile driving using both vibratory and impact hammers; VSP; and pipeline and platform maintenance. AGDC plans to install a natural gas pipeline from the west side of MCI to the east side of LCI and to construct processing and loading facilities on either side. These include a product loading facility (PLF) and temporary and mainline materials offloading facilities (TMOF, MMOF, MOF). Support activities for AGDC will include pile driving, dredging, geophysical surveys, trenching, fill placement, and anchor handling. Hilcorp, Harvest, and AGDC will use vessels and aircraft to support the activities. Detailed descriptions of the planned work are provided in the applicant's updated petition for incidental take regulations for oil and gas activities in Cook Inlet (June 2019), the stakeholder engagement plan (April 2018), and the marine mammal monitoring and mitigation plan (May 2018). These documents can be obtained from the locations described above in
ADDRESSES
. Table 1 summarizes the planned activities.

Table 1—Summary of Planned Activities Included in Incidental Take Regulation Petition

Project component
name & location

Geographic region

Year(s)
planned

Seasonal timing

Total anticipated duration
(2019-2024)

Anchor Point 2D seismic survey
LCI, Anchor Point to Kasilof
2021 or 2022
April-October
30 days (10 days in water seismic).

OCS 3D seismic survey
LCI OCS
2019 or 2020
April-October
45-60 days.

OCS geohazard survey
LCI OCS
2019-2021
April-October
28 days.

OCS exploratory wells
LCI OCS
2020-2022
February-November
40-60 days per well, 2-4 wells per year.

Iniskin Peninsula exploration and development
LCI, west side
2020-2022
April-October
180 days.

Platform & pipeline maintenance
MCI
2019-2024
April-October
180 days per year.

NCI subsea well geohazard survey
MCI
2020
April-October
7 days.

NCI well abandonment activity
MCI
2020
April-October
90 days.

TB area geohazard survey
MCI
2020
April-October
14 days.

Granite Point development drilling
MCI
2019
June-October
120-150 days.

Drift River terminal decommissioning
LCI, west side
2020-2023
April-October
120 days.

Product loading facility pile driving
MCI
2021-2023
April-October
162 days.

Material offloading facilities dredging
MCI
2021-2022
April-October
360 days.

Material offloading facilities pile driving
MCI
2021-2022
April-October
482 days.

Trenching, pipelay, burial
MCI
2023-2024
April-October
360 days.

Pipelay anchor handling
MCI
2023-2024
April-October
76 days.

LCI = Lower Cook Inlet, MCI = Middle Cook Inlet, NCI = North Cook Inlet, TB = Trading Bay.

Description of Marine Mammals in the Specified Area

The northern sea otter is the only marine mammal under the Service's jurisdiction that normally occupies Cook Inlet, Alaska. Sea otters in Alaska are composed of three stocks. Those in Cook Inlet belong to either the southwest Alaska stock or the southcentral Alaska stock, depending on whether they occur west or east of the center of Cook Inlet, respectively. A third stock occurs in southeast Alaska.

The southwest Alaska stock of the northern sea otter is the southwest distinct population segment (DPS), which was listed as threatened under the Endangered Species Act of 1973 (ESA; 16 U.S.C. 1531,
et seq.
) on August 9, 2005 (70 FR 46366). On October 8, 2009 (74 FR 51988), the Service finalized designation of 15,164 square kilometers (km
2
) (or 5,855 square miles (mi
2
)) of critical habitat for the Southwest DPS of sea otters. Critical habitat occurs in nearshore marine waters ranging from the mean high-tide line seaward for a distance of 100 meters (m), or to a water depth of 20 m. Detailed information about the biology and conservation status of the listed DPS can be found at
https://www.fws.gov/alaska/fisheries/mmm/seaotters/otters.htm.
Stock assessment reports for each of the three stocks are available at
https://www.fws.gov/alaska/pages/marine-mammal-management.

Sea otters may occur anywhere within the specified project area, other than upland areas, but are not usually found north of about 60°23′30″ N. The number of sea otters in Cook Inlet was estimated from an aerial survey conducted by the Service in cooperation with the U.S. Geological Survey (USGS) in May 2017 (Garlich-Miller
et al.
2018). The sea otter survey was conducted in all areas of Cook Inlet south of approximately 60°16′30″ N within the 40-m (131-feet (ft)) depth contour, including Kachemak Bay in southeastern Cook Inlet and Kamishak Bay in southwestern Cook Inlet. This survey was designed to estimate abundance in Cook Inlet while accounting for the variable densities and observability of sea otters in the region. Total abundance was estimated to be 19,889 sea otters (standard error = 2,988). Within the project area, the highest densities of sea otters were found in the outer Kamishak Bay area, with 3.5 otters per km
2
, followed by the eastern shore of Cook Inlet with 1.7 otters per km
2
.

Sea otters generally occur in shallow water near the shoreline. They are most commonly observed within the 40-m (131-ft) depth contour (USFWS 2014a, b), although they can be found in areas with deeper water. Depth is generally correlated with distance to shore, and sea otters typically remain within 1 to 2 kilometers (km) or 0.62 to 1.24 miles (mi) of shore (Riedman and Estes 1990). They tend to remain closer to shore

during storms, and they venture farther out during calm seas (Lensink 1962; Kenyon 1969).

Sea otters are non-migratory and generally do not disperse over long distances (Garshelis and Garshelis 1984). They usually remain within a few kilometers of their established feeding grounds (Kenyon 1981). Breeding males remain for all or part of the year in a breeding territory covering up to 1 km (0.62 mi) of coastline. Adult females have home ranges of approximately 8 to 16 km (5 to 10 mi), which may include one or more male territories. Juveniles move greater distances between resting and foraging areas (Lensink 1962; Kenyon 1969; Riedman and Estes 1990; Tinker and Estes 1996).

Although sea otters generally remain local to an area, they may shift home ranges seasonally, and are capable of long-distance travel. Otters in Alaska have shown daily movement distances greater than 3 km (1.9 mi) at speeds up to 5.5 km/hr (3.4 mi per hour) (Garshelis and Garshelis 1984). In eastern Cook Inlet, large numbers of sea otters have been observed riding the incoming tide northward and returning on the outgoing tide, especially in August. They are presumably feeding along the eastern shoreline of Cook Inlet during the slack tides when the seas are calm, and they remain in Kachemak Bay during periods of less favorable weather (Gill
et al.
2009; BlueCrest 2013). In western Cook Inlet, otters appear to move in and out of Kamishak Bay in response to seasonal changes in the presence of sea ice (Larned 2006).

Potential Effects of the Activities

Effects of Noise

The operations outlined in the Description of Specified Activities and described in the applicant's updated petition have the potential to result in take of sea otters by harassment from noise. Here we characterize “noise” as sound released into the environment from human activities that exceeds ambient levels or interferes with normal sound production or reception by sea otters. The terms “acoustic disturbance” or “acoustic harassment” are disturbances or harassment events resulting from noise exposure. Potential effects of noise exposure are likely to depend on the distance of the otter from the sound source and the level of sound received by the otter. Project components most likely to cause acoustic disturbance are shown in table 2. Temporary disturbance or localized displacement reactions are the most likely to occur. With implementation of the mitigation and monitoring measures described in § 18.137 Mitigation, § 18.138 Monitoring, and § 18.139 Reporting requirements, no lethal take is anticipated, and take by harassment (Level A and Level B) is expected to be minimized to the greatest extent practicable.

Table 2—Project Components Planned by Hilcorp, Harvest, and Alaska Gasline Development Corporation That Produce Noise Capable of Causing Incidental Take by Harassment of Northern Sea Otters

Project component name & location
Anticipated noise sources

Anchor Point 2D seismic survey
Marine: 1 source vessel with airgun, 1 node vessel; Onshore/Intertidal: Shot holes, tracked vehicles, helicopters.

OCS 3D seismic survey
1 source vessel with airguns, 1 support vessel, 1 or 2 chase vessels to maintain security around streamers, 1 or 2 mitigation vessels.

OCS geohazard survey
1 vessel with echosounders and/or subbottom profilers.

OCS exploratory wells
1 jack-up rig, drive pipe installation, support vessels, helicopters.

Iniskin Peninsula exploration and development
Construction of causeway, dredging, vessels.

Platform & pipeline maintenance
Vessels, water jets, helicopters, and/or sub-bottom profilers.

NCI subsea well geohazard survey
1 vessel with echosounders and/or subbottom profilers.

NCI well abandonment activity
1 jack-up rig, support vessel, helicopters.

TB area geohazard survey
1 vessel with echosounders and/or subbottom profilers.

TB area exploratory wells
1 jack-up rig, drive pipe installation, support vessels, helicopters.

Drift River terminal decommissioning
Vessels.

OCS = outer continental shelf, NCI = North Cook Inlet, TB = Trading Bay.

Noise Levels

Whether a specific noise source will affect a sea otter depends on several factors, including the distance between the animal and the sound source, the sound intensity, background noise levels, the noise frequency, the noise duration, and whether the noise is pulsed or continuous. The actual noise level perceived by individual sea otters will depend on distance to the source, whether the animal is above or below water, atmospheric and environmental conditions, as well as aspects of the noise emitted.

Noise levels herein are given in decibels referenced to 1 μPa (dB re: 1 μPa) for underwater sound. All dB levels are dB
RMS
unless otherwise noted; dB
RMS
refers to the root-mean-squared dB level, the square root of the average of the squared sound pressure level (SPL) typically measured over 1 second. Other important metrics include the sound exposure level (SEL; represented as dB re: 1 μPa
2
-s), which represents the total energy contained within a pulse and considers both intensity and duration of exposure, and the peak sound pressure (also referred to as the zero-to-peak sound pressure or 0-p). Peak sound pressure is the maximum instantaneous sound pressure measurable in the water at a specified distance from the source and is represented in the same units as the RMS sound pressure. See Richardson
et al.
(1995), Götz
et al.
(2009), Hopp
et al.
(2012), Navy (2014), for descriptions of acoustical terms and measurement units in the context of ecological impact assessment. A summary of the noises produced by the various components of the planned activities is provided in tables 3 and 4.

Table 3—Summary of Sound Source Levels for the Planned Oil and Gas Activities by Hilcorp/Harvest Alaska and Alaska Gasline Development Corporation (AGDC)

Applicant
Activity

Sound pressure levels
(dB re 1 µPa)

Frequency
Reference

Hilcorp/Harvest Alaska, AGDC
General vessel operations
145-175 dB rms at 1 m
10-1,500 Hz

Richardson
et al.
1995; Blackwell and Greene 2003; Ireland and Bisson 2016.

Hilcorp/Harvest Alaska, AGDC
General aircraft operations
100-124 dB rms at 1 m
<500 Hz

Richardson
et al.
1995.

Hilcorp/Harvest Alaska
2D seismic survey (1,945 cui airgun)

217 dB peak at 100 m
185 dB SEL at 100 m
197 dB rms at 100 m

<300 Hz
Austin and Warner 2013; 81 FR 47240 (July 20, 2016).

Hilcorp/Harvest Alaska
3D seismic survey (1,945 cui airgun)

217 dB peak at 100 m
185 dB SEL at 100 m
197 dB rms at 100 m

<300 Hz
Austin and Warner 2013; 81 FR 47240 (July 20, 2016).

Hilcorp/Harvest Alaska
Geohazard surveys
210-220 dB rms at 1 m

Echosounders & side scan sonar: >200 kHz
High-resolution sub-bottom profiler: 2-24 kHz
Low-resolution sub-bottom profiler: 1-4 kHz

Manufacturer specifications.

Hilcorp/Harvest Alaska
Exploratory drilling rig
137 dB rms at 1 m
<200 Hz
Marine Acoustics Inc. 2011.

Hilcorp/Harvest Alaska
Drive pipe installation
190 dB rms at 55 m
<500 Hz
Illingworth & Rodkin 2014.

Hilcorp/Harvest Alaska
Vertical seismic profiling
227 dB rms at 1 m
<500 Hz
Illingworth & Rodkin 2014.

Hilcorp/Harvest Alaska
Sub-bottom profiling
212 dB rms at 1 m
1-24 kHz
Manufacturer specifications.

Hilcorp/Harvest Alaska
Rock laying for Iniskin Peninsula causeway
136-141 dB rms at 12-19 m
<500 Hz
URS 2007.

Hilcorp/Harvest Alaska
Vibratory sheet pile driving for Iniskin Peninsula causeway

175 dB peak at 10 m
160 dB SEL at 10 m
160 dB rms at 10 m

<100-2,500 Hz
Illingworth & Rodkin 2007.

Hilcorp/Harvest Alaska
Offshore production platforms
97-111 dB rms at 0.3-19 km
<500 Hz
Blackwell and Greene 2003.

Hilcorp/Harvest Alaska
Water jet
176 dB rms at 1 m
500 Hz-2 kHz
Austin 2017.

Hilcorp/Harvest Alaska
Pingers
192 dB rms at 1 m
4-14 kHz
Manufacturer specifications.

AGDC
Dredging: Including Clamshell dredge, Winching in/out, Dumping into barge, Empty barge at placement site
107-142.6 dB rms at 10 m
<2.5 kHz, broadband

Dickerson
et al.
2001; URS 2007.

AGDC
Underwater trenching with backhoe in shallow water
145 dB @10 m
<2.5 kHz, broadband

Greene
et al.
2008.

AGDC
Anchor handling
188 dB rms @1 m
<2.5 kHz, broadband
LGL/JASCO/Greeneridge 2014.

SEL = sound exposure level.

Table 4—Summary of Sound Sources of Pile-Driving Activities for Alaska Gasline Development Corporation (AGDC) From Illingworth & Rodkin (2007).

Representative pile type and size

Hammer
type

Sound pressure level
(dB re 1 µPa)

Peak
RMS
SEL

Project pile type
and size

24-inch sheet pile
Impact
205
190
180
Sheet pile.

24-inch sheet pile
Vibratory
175
160
160
Sheet pile.

24-inch steel pipe pile
Impact
207
194
178
18- and 24-inch piles.

60-inch steel shell pile
Impact
210
195
185
48- and 60-inch piles.

72-inch steel pipe piles
Vibratory
183
170
170
All size piles.

Sea Otter Hearing

Sound frequencies produced by the applicant's survey and construction activities will fall within the hearing range of sea otters and therefore will be audible to animals. Controlled sound exposure trials on southern sea otters (
E. l. nereis
) indicate that hearing ability spans frequencies between 125 hertz (Hz) and 38 kilohertz (kHz) with best sensitivity between 1.2 and 27 kHz (Ghoul and Reichmuth 2014). Aerial and underwater audiograms for a captive adult male southern sea otter in the presence of ambient noise suggest the sea otter's hearing was less sensitive to high-frequency (greater than 22 kHz) and low-frequency (less than 2 kHz) sounds than terrestrial mustelids but similar to that of a sea lion (
e.g., Zalophus californianus
). Dominant frequencies of southern sea otter vocalizations are between 3 and 8 kHz, with some energy extending above 60 kHz (McShane
et al.
1995; Ghoul and Reichmuth 2012a).

Exposure to high levels of sound may cause changes in behavior, masking of communications, temporary changes in hearing sensitivity, discomfort, and physical or auditory injury. Species-specific criteria for preventing harmful exposures to sound have not been identified for sea otters. Thresholds have been developed for other marine mammals, above which exposure is likely to cause behavioral disturbance and injuries (Southall
et al.
2007; Finneran and Jenkins 2012; NMFS 2018a). Because sea otter hearing abilities and sensitivities have not been fully evaluated, we relied on the closest related proxy, California sea lions, to evaluate the potential effects of noise exposure. The California sea lion, an otariid pinniped, has a frequency range of hearing most similar to that of the southern sea otter (Ghoul and Reichmuth 2014) and provides the closest related proxy for which data are available. Sea otters and pinnipeds

share a common mammalian aural physiology (Echteler
et al.
1994; Solntseva 2007). Both are adapted to amphibious hearing, and both use sound in the same way (primarily for communication rather than feeding).

Exposure Criteria

Noise exposure criteria have been established by the National Marine Fisheries Service (NMFS) for identifying underwater noise levels capable of causing Level A harassment (injury) of certain marine mammals, including otariid pinnipeds (NMFS 2018a). Sea otter-specific criteria have not been determined; however, because of their biological similarities, we assume that noise criteria developed by NMFS for injury for otariid pinnipeds will be a suitable surrogate for sea otter impacts as well. Those criteria are based on estimated levels of sound exposure capable of causing a permanent shift in sensitivity of hearing (
e.g.,
a permanent threshold shift (PTS) (NMFS 2018a)). PTS occurs when noise exposure causes hairs within the inner ear system to die.

NMFS' (2018a) criteria for sound exposure incorporate two metrics of exposure: The peak level of instantaneous exposure likely to cause PTS, and the cumulative sound exposure level during a 24-hour period (SEL
cum
). They also include weighting adjustments for the sensitivity of different species to varying frequencies. PTS-based injury criteria were developed from theoretical extrapolation of observations of temporary threshold shifts (TTS) detected in lab settings during sound exposure trials. Studies were summarized by Finneran (2015). For otariid pinnipeds, PTS is predicted to occur at 232 dB peak or 203 dB SEL
cum
for impulsive sound, or 219 dB SEL
cum
for non-impulsive (continuous) sound.

NMFS' criteria for take by Level A harassment represents the best available information for predicting injury from exposure to underwater sound among pinnipeds, and in the absence of data specific to otters, we assume these criteria also represent appropriate exposure limits for Level A take of sea otters.

NMFS (2018a) criteria do not identify thresholds for avoidance of Level B take. For pinnipeds, NMFS has adopted a 160-dB threshold for Level B take from exposure to impulse noise and a 120-dB threshold for continuous noise (NMFS 1998; HESS 1999; NMFS undated). These thresholds were developed from observations of mysticete (baleen) whales responding to airgun operations (
e.g.,
Malme
et al.
1983a, b; Richardson
et al.
1986, 1995) and from equating Level B take with noise levels capable of causing TTS in lab settings.

We have evaluated these thresholds and determined that the Level B threshold of 120 dB for non-impulsive noise is not applicable to sea otters. The 120-dB threshold is based on studies conducted by Malme
et al.
in the 1980s, during which gray whales were exposed to experimental playbacks of industrial noise. Based on the behavioral responses of gray whales to the playback of drillship noise during a study at St. Lawrence Island, Alaska, Malme
et al.
(1988) concluded that “exposure to levels of 120 dB or more would probably cause avoidance of the area by more than one-half of the gray whales.” Sea otters do not usually occur at St. Lawrence Island, Alaska, but similar playback studies conducted off the coast of California (Malme 1983a, 1984) included a southern sea otter monitoring component (Riedman 1983, 1984). The 1983 and 1984 studies detected probabilities of avoidance in gray whales comparable to those reported in Malme
et al.
(1988), but there was no evidence of disturbance reactions or avoidance in southern sea otters.

The applicable Level B thresholds may also depend on the levels of background noise present and the frequencies generated. NMFS acknowledges that the 120-dB threshold may not be applicable if background noise levels are high (NMFS undated), which is the case in Cook Inlet, where ambient levels can often exceed 120 dB (Blackwell and Greene 2003).

Thresholds developed for one species may not be appropriate for another due to differences in their frequency sensitivities. Continuous sound sources associated with the planned activities include vibratory pile driving, vessel activities, use of a water jet, dredging, trenching, and anchor handling. These are expected to produce low-frequency broadband noise. For example, vibratory pile driving will generate sound with frequencies that are predominantly lower than 2 kHz, and with the greatest pressure spectral densities at frequencies below 1 kHz (Dahl
et al.
2015). Sea otters are capable of hearing down to 125 Hz, but have relatively poor hearing sensitivity at frequencies below 2 kHz (Ghoul and Reichmuth 2014). During a project that occurred in Elkhorn Slough, California, sound levels ranging from approximately 135 to 165 dB during vibratory pile driving elicited no clear pattern of disturbance or avoidance among southern sea otters in areas exposed to these levels of underwater sound (ESNERR 2011). In contrast, gray whales are in the group of marine mammals believed to be most sensitive to low-frequency sounds, with an estimated audible frequency range of approximately 10 Hz to 30 kHz (Finneran 2015). Given the different range of frequencies to which sea otters and gray whales are sensitive, the NMFS 120-dB threshold based on gray whale behavior is not useful for predicting sea otter behavioral responses to low-frequency sound.

Although no specific thresholds have been developed for sea otters, several alternative behavioral response thresholds have been developed for pinnipeds. Southall
et al.
(2007, 2019) assessed behavioral response studies, found considerable variability among pinnipeds, and determined that exposures between approximately 90 to 140 dB generally do not appear to induce strong behavioral responses in pinnipeds in water, but behavioral effects, including avoidance, become more likely in the range between 120 to 160 dB, and most marine mammals showed some, albeit variable, responses to sound between 140 to 180 dB. Wood
et al.
(2012) later adapted the approach identified in Southall
et al.
(2007) to develop a probabilistic scale for marine mammal taxa at which 10 percent, 50 percent, and 90 percent of individuals exposed are assumed to produce a behavioral response. For many marine mammals, including pinnipeds, these response rates were set at sound pressure levels of 140, 160, and 180 dB respectively.

Thresholds based on TTS have been used as a proxy for Level B harassment (
i.e.,
70 FR 1871, January 11, 2005; 71 FR 3260, January 20, 2006; and 73 FR 41318, July 18, 2008). Southall
et al.
(2007) derived TTS thresholds for pinnipeds based on 212 dB peak and 171-dB SEL
cum.
Kastak
et al.
(2005) found exposures resulting in TTS in pinnipeds ranging from 152 to 174 dB (183-206 dB SEL). Kastak
et al.
(2008) demonstrated a persistent TTS, if not a PTS, after 60 seconds of 184 dB SEL. Kastelein
et al.
(2012) found small but statistically significant TTSs at approximately 170 dB SEL (136 dB, 60 min) and 178 dB SEL (148 dB, 15 min). Finneran (2015) summarized these and other studies, and NMFS (2018a) has used the data to develop TTS threshold for otariid pinnipeds of 188 dB SEL
cum
for impulsive sounds and 199 dB SEL
cum
for non-impulsive sounds.

Based on the lack of a disturbance response or any other reaction by sea otters to the 1980s playback studies and the absence of a clear pattern of disturbance or avoidance behaviors attributable to underwater sound levels up to about 160 dB resulting from

vibratory pile driving and other sources of similar low-frequency broadband noise, we assume 120 dB is not an appropriate behavioral response threshold for sea otters exposed to continuous underwater noise. We assume, based on the work of NMFS (2018a), Southall
et al.
(2007, 2019), and others described here, that either a 160-dB threshold or a 199-dB SEL
cum
threshold is likely to be the best predictor of Level B take of sea otters for continuous noise exposure, using southern sea otters and pinnipeds as a proxy, and based on the best available data. When behavioral observations during vibratory pile driving (ESNERR 2011) and results of behavioral response modelling (Wood
et al.
2012) are considered, the application of a 160-dB rms threshold is most appropriate.

Exposure to impulsive sound levels greater than 160 dB can elicit behavioral changes in marine mammals that might be detrimental to health and long-term survival where it disrupts normal behavioral routines. Thus, using information available for other marine mammals as a surrogate, and taking into consideration the best available information about sea otters, the Service has set the received sound level under water of 160 dB as a threshold for Level B take by disturbance for sea otters for this ITR based on the work of Ghoul and Reichmuth (2012a, b), McShane
et al.
(1995), NOAA (2005), Riedman (1983), Richardson
et al.
(1995), and others. Exposure to unmitigated in-water noise levels between 125 Hz and 38 kHz that are greater than 160 dB—for both impulsive and non-impulsive sound sources—will be considered by the Service as Level B take; thresholds for potentially injurious Level A take will be 232 dB peak or 203 dB SEL for impulsive sounds and 219 dB SEL for continuous sounds (table 5).

The area in which underwater noise in the frequency range of sea otter hearing will exceed thresholds, is termed the “area of ensonification” or “zone of ensonification.” The ensonification zone in which noise levels exceed thresholds for Level A take is often referred to as the Level A harassment zone. The Level B harassment zone likewise includes areas ensonified to thresholds for Level B take of sea otters.

Table 5—Summary of Thresholds for Predicting Level A and Level B Take of Northern Sea Otters From Underwater Sound Exposure in the Frequency Range 125

Marine mammals
Injury (Level A) threshold

Impulsive
1

Non-impulsive
1

Disturbance (Level B) threshold
All

Sea otters

232 dB peak; 203 dB SEL
CUM

219 dB SEL
CUM

160 dB rms.

1
Based on National Marine Fisheries Service acoustic exposure criteria for take of otariid pinnipeds (NMFS 2018a).

SEL
CUM
= cumulative sound exposure level.

Noise-Generating Activities

The components of the specified activities that have the greatest likelihood of exposing sea otters to underwater noise capable of causing Level A or Level B take include geophysical surveys, pile driving, drilling activities, and anchor handling associated with pipeline construction. Vessel and aircraft operations also have the ability to expose otters to sound that may cause disturbance. A brief description of potential impacts follows.

Geophysical Surveys
—Airgun arrays used in seismic surveys to locate potential hydrocarbon-bearing geologic formations typically produce most noise energy in the 10- to 120-Hertz (Hz) range, with some energy extending to 1,000 Hz (Richardson
et al.
1995). There is no empirical evidence that exposure to pulses of airgun sound is likely to cause serious injury or death in any marine mammal, even with large arrays of airguns (Southall
et al.
2007). But high-level noise exposure has been implicated in mass stranding events among whales (
e.g.,
see Cox
et al.
2006), and with source levels of up to 260 dB, the potential of seismic airgun arrays to acoustically injure marine mammals at close proximity must be considered.

In addition to seismic surveys for hydrocarbon-bearing formations, geophysical surveys are conducted to produce imagery of sea-floor surfaces and substrates on a finer spatial scale. Sounds produced by the instruments used for these surveys vary in terms of frequency bands, source levels, repetition rates, and beam widths. Operating frequencies range from roughly 300 Hz to several hundred kHz with peak-to-peak source levels ranging from 170 to 240 dB (Crocker and Fratantonio 2016).

Pipe/Pile Driving—
During the course of pile driving, a portion of the kinetic energy from the hammer is lost to the water column in the form of sound. Levels of underwater sounds produced during pile driving are dependent upon the size and composition of the pile, the substrate into which the pile is driven, bathymetry, physical and chemical characteristics of the surrounding waters, and pile installation method (impact versus vibratory hammer) (Illingworth and Rodkin 2007, 2014; Denes
et al.
2016).

Both impact and vibratory pile installation produce underwater sounds of frequencies predominantly lower than 2.5 kHz, with the highest intensity of pressure spectral density at or below 1 kHz (Denes
et al.
2016; Dahl
et al.
2015; Illingworth and Rodkin 2007). Source levels of underwater sounds produced by impact pile driving tend to be higher than for vibratory pile driving; however, both methods of installation can generate underwater sound levels capable of causing behavioral disturbance or hearing threshold shift in marine mammals, and both methods will be used in Cook Inlet.

Drilling Operations—
For drilling operations, two project components have the potential to disturb sea otters: Installing the drive pipe at each well prior to drilling; and VSP operations that may occur at the completion of each well drilling. The types of underwater sounds generated by these activities are discussed in “Pile Driving” and “Geophysical Surveys,” respectively. Drilling and the associated noise from pumps and generators on the drill rig is not expected to produce underwater noise levels that will affect sea otters (
e.g.,
see Richardson
et al.
1995; Spence
et al.
2007; Marine Acoustics, Inc. 2011; Illingworth and Rodkin 2014).

Aircraft Overflights—
Richardson
et al.
(1995) presented analyses of recordings of sounds produced by a Bell 212 helicopter. The estimated source levels for two of the flights were 149 and 151 dB re 1 µPa-m, and underwater received levels were 109 dB when the aircraft flew at an altitude of 152 m (500 ft) and

107 dB at a flight altitude of 305 m (1,000 ft). Received sound levels in air at the water surface would be 81 and 75 dB re 20 µPa for flights at 152 and 305 m (500 and 1,000 ft), respectively.

Anchor Handling
—The characteristics of sounds produced by vessels are a product of several variables pertaining to the specifications of the vessel, including the number and type of engines, propeller shape and size, and the mechanical condition of these components. Operational status of the vessel, such as towing heavy loads or using bow thrusters, can significantly affect the levels of sounds emitted by the same vessel at different times (Richardson
et al.
1995). Manipulation of anchors for the laying of the AGDC pipeline will involve vessel operations that are likely to be substantially louder than normal transit. Data from recent exploratory drilling activities in the Chukchi and Beaufort Seas indicate that anchor handling can intermittently produce sounds likely greater than 190 dB; the source level of the anchor-handling vessel was estimated to be 188 dB (LGL/JASCO/Greeneridge 2014). It is not known whether anchor handling will produce similar noise levels in Cook Inlet, but it will occur in areas where sea otters are uncommon and unlikely to be affected.

Airborne Sounds

The NMFS (2018a) guidance neither addresses thresholds for preventing injury or disturbance from airborne noise, nor provides thresholds for avoidance of Level B take. However, a review of literature by Southall
et al.
(2007) suggested thresholds for PTS and TTS for sea lions exposed to non-pulsed airborne noise of 172.5 and 159 dB re (20 µPa)
2
-s SEL. Behavioral responses to overflights are addressed in
Responses to Activities.

Conveyance of underwater noise into the air is of little concern since the effects of pressure release and interference at the water's surface, which scatter and reflect sound, reduce underwater noise transmission into the air. For activities that create both in-air and underwater sounds, such as pile driving, we will estimate take based on parameters for underwater noise transmission. Because sound energy travels more efficiently through water than through air, this estimation will also account for exposures to animals at the surface.

Aircraft are the most significant source of airborne sounds. Proposed flights are to be conducted at an altitude of 305 m (1,000 ft) except during takeoff and landing. At the surface of the water, the received sound level from a helicopter flown at this altitude is roughly 75 dB re 20 µPa (see “Noise-Generating Activities”), and so threshold shift is extremely unlikely.

Loud screams are used to communicate between pups and mothers at the surface (McShane
et al.
1995), but sea otters do not appear to communicate vocally under water, and they do not use sound to detect prey. Although masking of these crucial airborne calls is possible, the duration of sound from aircraft will be brief and therefore unlikely to result in separation of females from pups.

Effects on Habitat and Prey

Habitat areas of significance for sea otters exist in the project area. Sea otter critical habitat was designated under the ESA (74 FR 51988, October 8, 2009). In Cook Inlet, critical habitat occurs along the western shoreline south of approximately Redoubt Point. It extends from mean high-tide line out to 100 m (328.1 ft) from shore or to the 20-m (65.6-ft) depth contour. Physical and biological features of critical habitat essential to the conservation of sea otters include the benthic invertebrates (
e.g.,
red sea urchins (
Mesocentrotus franciscanus
), blue mussels (
Mytilus spp.
), butter clams (
Saxidomus giganteus
), etc.) eaten by otters and the shallow rocky areas and kelp (
e.g.,
bull kelp (
Nereocystis luetkeana
) and dragon kelp (
Eualaria fistulosa
)) beds that provide cover from predators. Other important habitat in the applicant's project area includes outer Kamishak Bay between Augustine Island and Iniskin Bay within the 40-m (131-ft) depth contour where high densities of otters have been detected.

The applicant's planned activities include drilling, dredging, trenching, pile driving, and dock construction. These activities would change the physical characteristics of localized areas of habitat. Construction would result in seafloor disturbance. Docks can increase seafloor shading, which affects the amount of light penetration on the seafloor. Water quality may be affected by drilling-related discharges within limits permitted by the State of Alaska.

Sampling efforts at borrow and disposal areas before and after dredging activity have produced mixed results in terms of whether dredging causes significant changes to the productivity and diversity of infaunal benthic and epibenthic invertebrate communities (Fraser
et al.
2017; Angonesi
et al.
2006). The areas where dredging activities are proposed include a materials loading facility at Nikiski and along the planned AGDC pipeline route between Nikiski and Beluga; the proposed disposal area is just west of Nikiski. This is beyond the northern limit of sea otter distribution in Cook Inlet, so effects of dredging upon invertebrate communities would not affect availability of prey to sea otters.

In addition to the disturbances outlined above to sea otters or their designated critical habitat, survey and construction activities could affect sea otter habitat in the form of impacts to prey species. The primary prey species for sea otters are sea urchins, abalone, clams, mussels, crabs, and squid (Tinker and Estes 1999). When preferential prey are scarce, otters will also eat kelp, turban snails (
Tegula spp.
), octopuses (
e.g., Octopus spp.
), barnacles (
Balanus spp.
), sea stars (
e.g., Pycnopodia helianthoides),
scallops (
e.g., Patinopecten caurinus),
rock oysters (
Saccostrea spp.
), worms (
e.g., Eudistylia spp.
), and chitons (
e.g., Mopalia spp.
) (Riedman and Estes 1990).

Limited research has been conducted on the effects of noise on invertebrates (Normandeau Associates, Inc. 2012). Christian
et al.
(2003) concluded that there were no obvious effects from seismic signals on crab behavior and no significant effects on the health of adult crabs. Pearson
et al.
(1994) had previously found no effects of seismic signals upon crab larvae for exposures as close as 1 m (3.3 ft) from the array, or for mean sound pressure as high as 231 dB. Pearson
et al.
(1994) did not observe any statistically significant effects on Dungeness crab (
Cancer magister
) larvae shot as close as 1 m from a 231-dB source. Further, Christian
et al.
(2004) did not find any behavioral or significant health impacts to snow crabs (
Chionoecetes opilio
) exposed to seismic noise. The only effect noted was a reduction in the speed of egg development after exposure to noise levels (221 dB at 2 m), far higher than what bottom-dwelling crabs could be exposed to by seismic guns. Invertebrates such as mussels, clams, and crabs do not have auditory systems or swim bladders that could be affected by sound pressure. Squid and other cephalopod species have complex statocysts (Nixon and Young 2003) that resemble the otolith organs of fish that may allow them to detect sounds (Budelmann 1992).

Some species of invertebrates have shown temporary behavioral changes in the presence of increased sound levels. Fewtrell and McCauley (2012) reported increases in alarm behaviors in wild-caught captive reef squid (
Sepioteuthis australis
) exposed to seismic airguns at noise levels between 156-161 dB. Additionally, captive crustaceans have

changed behaviors when exposed to simulated sounds consistent with those emitted during seismic exploration and pile-driving activities (Tidau and Briffa 2016).

In general, there is little knowledge regarding effects of sound in marine invertebrates or how invertebrates are affected by high noise levels (Hawkins and Popper 2012). A review of literature pertaining to effects of seismic surveys on fish and invertebrates (Carroll
et al.
2016) noted that there is a wide disparity between results obtained in field and laboratory settings. Some of the reviewed studies indicate the potential for noise-induced physiological and behavioral changes in a number of invertebrates. However, changes were observed only when animals were housed in enclosed tanks and many were exposed to prolonged bouts of continuous, pure tones. We would not expect similar results in open marine conditions. Given the short-term duration of sounds produced by each component of the proposed work, it is unlikely that noises generated by survey and construction activities will have any lasting effect on sea otter prey.

Potential Impacts From an Oil Spill or Unpermitted Discharge

We provided discussion of relevant impacts to sea otters from oil spills and unpermitted discharges in our
Federal Register
notice of proposed rulemaking (84 FR 10224, March 19, 2019) and do not repeat that information here. Adverse impacts of exposure to oil is well documented for sea otters (
e.g.,
Kooyman
et al.
1976; Baker
et al.
1981; Costa and Kooyman 1982, 1984; Engelhardt 1983; Lipscomb 1996; Bickham 1998; Monson 2000; Albers 2003; Peterson 2003). An oil spill or unpermitted discharge is an illegal act, and ITRs do not authorize take of sea otters caused by illegal or unpermitted activities. Typical spills that may result from the proposed activities are relatively small in scale and are not likely to affect otters. A large spill could affect large numbers of otters, but these events are rare. We do not anticipate effects to sea otters as a result of oil spills from this activity.

Collisions

Vessel collisions with marine mammals can result in death or serious injury. Wounds resulting from ship strike may include massive trauma, hemorrhaging, broken bones, or propeller lacerations (Knowlton and Kraus 2001). An animal at the surface may be struck directly by a vessel, a surfacing animal may hit the bottom of a vessel, or an animal just below the surface may be cut by a vessel's propeller. Mortality associated with boat strike has been identified from recovery of carcasses with lacerations indicative of propeller injuries (
e.g.,
Wild and Ames 1974; Morejohn
et al.
1975). From 1998 to 2001, boat strike was identified as the cause of death for 5 of 105 southern sea otter mortalities (Kreuder
et al.
2003). From 2006 through 2010, evidence indicates that 11 southern sea otters were likely struck by boats (USGS and California Department of Fish and Game, unpublished data cited in 77 FR 59211-59220, September 26, 2012). From January 2003 to May 2013, researchers recovered 35 southern sea otters with trauma consistent with impact from a boat hull or propeller. These data suggest a rate of boat-strike mortality in California of 2.6 otters per year, or about 0.1 percent of the population size.

Boat strike has been documented as a cause of death across all three stocks of northern sea otters in Alaska. Since 2002, the Service has undertaken a health and disease study of sea otters in Alaska in which the Service conducts necropsies on sea otter carcasses to determine cause of death, disease incidence, and status of general health parameters. Of 1,433 necropsies conducted during 24 years, boat strike or blunt trauma was identified as a definitive or presumptive cause of death in 64 cases (4 percent) (USFWS unpublished data). It has been determined in most of these cases that, while trauma was the ultimate cause of death, there was a contributing factor, such as disease or biotoxin exposure, which incapacitated the animal and made it more vulnerable to boat strike (USFWS 2014).

In Alaska, the annual rate of documented mortality from boat strike was similar to that reported for California: 2.7 otters per year (USFWS unpublished data). However, compared to otters in California, Alaska otters belong to much larger and more dispersed populations where carcass recovery is lower. Instances of vessel collision are likely to be underreported, and the probability of collision is unknown.

Likelihood of vessel strikes involving sea otters appears to be primarily related to vessel speed. Most collision reports have come from small, fast-moving vessels (NMFS 2003). The severity of injuries to marine mammals during a boat strike also depends on vessel speed, with the probability of death or serious injury increasing as vessel speed increases (Laist
et al.
2001; Vanderlaan and Taggart 2007). Because sea otters spend a considerable portion of their time at the surface of the water, they are typically visually aware of approaching boats and are able to move away if a vessel is not traveling too quickly.

The probability of the specified activities in Cook Inlet causing a sea otter/vessel collision is very low for three reasons: First, most of the work will occur in lower-density regions of Cook Inlet; second, the project work will involve slow-moving, noisy vessels that sea otters can more easily avoid; and third, the specified activities will constitute only a small fraction of the total level of vessel traffic in the region, which increases the likelihood that otters in the project area are accustomed to avoiding vessels and will successfully avoid collisions with project vessels.

The AGDC pipeline work and work by Hilcorp and Harvest on maintenance of existing facilities will be conducted in MCI, in areas that are outside of the normal range of sea otters. The unusual occurrence of otters in MCI makes vessel collisions extremely unlikely. Hilcorp and Harvest will conduct their 3D seismic work in offshore areas of LCI where otter densities are also low. They will conduct 2D seismic work along the eastern shoreline of LCI where densities are higher, but vessel speeds during the specified activities will be slow. Hilcorp/Harvest's seismic vessels would travel at approximately 4 knots (kn) or 7.4 km per hour (km/hr) while towing seismic survey gear and a maximum of 4.5 kn (8.3 km/hr) while conducting geophysical surveys. Vessel speed during rig towing will generally be less than 5 kn. AGDC's pipeline construction operations will proceed at similar slow speeds. Anchor handling will occur at about 3 kn. For comparison, freighters in Cook Inlet travel at 20 to 24 kn (Eley 2006), and small recreational vessels may travel at 40 kn.

The applicant's support vessels and vessels in transit will travel at faster speeds; for example, Hilcorp/Harvest's maintenance activities will require the use of dive vessels, typically ranging up to 21 m (70 ft) in length and capable of approximately 7 kn (13 km/hr). The risk of collision is thus reduced, but not eliminated, by the predominance of slow-moving vessel work in areas of low density.

Commercial and recreational vessels are much more common in both space and time than are geophysical survey activities, drilling support operations, and pipeline work. Based on U.S. Coast Guard records and other local sources of information compiled by Eley (2006), 704 large vessels, other than fuel barges in domestic trade, called at Cook Inlet ports from January 1, 2005, through July 15, 2006. Almost two-thirds (65 percent)

of the calls were made by container vessels, cargo, or ferries. Twenty-nine percent (29 percent) of the vessel traffic was gas or liquid tankships calling primarily at Nikiski. Bulk carriers and general cargo ships represented 6 percent. Tugs and fishing and passenger vessels combined represented 2 percent of the Cook Inlet vessel traffic. Tugs made approximately 150 fuel barge transits a year, assisted in docking and undocking ships in Nikiski and Anchorage, and moved miscellaneous deck and gravel barges in and out of the Port of Anchorage. Although small vessels are less common than larger ships, they are the most likely source of collision due to faster speeds and their presence in shallow water where sea otters are common. In 2005, there were 570 commercial fishing vessels registered in the Cook Inlet salmon/groundfish fleet. Of these, 86 percent were 31-40 ft in length. Vessels in this size class typically travel at up to 30 kn while in transit. The high level of ship traffic in Cook Inlet allows many sea otters in Cook Inlet to habituate to vessels. This will reduce risk of collision for the project activities when vessels are in transit.

Although the likelihood of a project vessel striking a sea otter is low, we intend to require mitigation measures to reduce the risk of ship strike in all LOAs. We anticipate that vessel collisions involving a seismic-data-acquisition vessel towing gear or vessels conducting geophysical operations are unlikely given the rarity of documented collisions, the low densities of otters in most of the project areas, the frequent vessel traffic to which otters have become accustomed, and the slow vessel speeds. Vessels in transit and support vessels travelling at greater rates of speed are more likely to cause collisions.

Mitigation measures for reducing the probability of ship strike include speed reductions during periods of low visibility, required separation distances from observed otters, avoidance of nearshore travel, and use of navigation channels, when practicable. We believe these measures will further reduce the risk of collision. Given the required mitigation measures, the relatively slow speed of most of the project vessels, the presence of marine mammal observers, and the short duration of many of the activities, we believe that the possibility of ship strike is discountable. No incidental take resulting from ship strike is anticipated, and this potential effect of the specified activity will not be discussed further in the following analysis.

Characterizing Take

In the previous section, we discussed the components of the project activities that have the potential to affect sea otters. Here we describe and categorize the physiological and behavioral effects that can be expected based on documented responses to human activities observed during sea otter studies. We also discuss how these behaviors are characterized under the MMPA.

An individual sea otter's reaction to a human activity will depend on its prior exposure to the activity, its need to be in the particular area, its physiological status, or other intrinsic factors. The location, timing, frequency, intensity, and duration of the encounter are among the external factors that will also influence the animal's response.

Relatively minor reactions such as increased vigilance or a short-term change in direction of travel are not likely to disrupt biologically important behavioral patterns and are not considered take by harassment. These types of responses typify the most likely reactions of the majority of sea otters that will be exposed to the applicant's activities.

Reactions capable of causing injury are characterized as Level A harassment events. Examples include separation of mothers from young or repeatedly flushing sea otters from a haulout. Exposure to noise capable of causing PTS is also considered take by Level A harassment.

Intermediate reactions that disrupt biologically significant behaviors are considered Level B harassment under the MMPA. The Service has identified the following sea otter behaviors as indicating possible Level B take:

• Swimming away at a fast pace on belly (
i.e.,
porpoising);

• Repeatedly raising the head vertically above the water to get a better view (spyhopping) while apparently agitated or while swimming away;

• In the case of a pup, repeatedly spyhopping while hiding behind and holding onto its mother's head;

• Abandoning prey or feeding area;

• Ceasing to nurse and/or rest (applies to dependent pups);

• Ceasing to rest (applies to independent animals);

• Ceasing to use movement corridors along the shoreline;

• Ceasing mating behaviors;

• Shifting/jostling/agitation in a raft so that the raft disperses;

• Sudden diving of an entire raft;

• Flushing animals off a haulout.

This list is not meant to encompass all possible behaviors; other situations may also indicate Level B take. It is also important to note that, depending on the duration and severity of the above-described behaviors, such responses could constitute take by Level A harassment,
e.g.,
repeatedly flushing sea otters from a haulout versus a single flushing event.

Direct and Indirect Effects

The reactions of wildlife to disturbance can range from short-term behavioral changes to long-term impacts that affect survival and reproduction. Most sea otters will respond to human disturbance with nonlethal reactions that are similar to antipredator responses (Frid and Dill 2002). Sea otters are susceptible to predation, particularly from killer whales and eagles, and have a well-developed antipredator response to perceived threats. Sea otters will swim away, dive, or hide among rocks or kelp, and will sometimes spyhop (vertically raise its head out of the water, presumably to look around) or splash when threatened. Limbaugh (1961) reported that sea otters were apparently undisturbed by the presence of a harbor seal (
Phoca vitulina
), but they were quite concerned with the appearance of a California sea lion. They demonstrated their fear by actively looking above and beneath the water when a sea lion was swimming nearby.

Although an increase in vigilance or a flight response is nonlethal, a tradeoff occurs between risk avoidance and energy conservation (Frid and Dill 2002). For example, southern sea otters in areas with heavy recreational boat traffic demonstrated changes in behavioral time budgeting showing decreased time resting and changes in haulout patterns and distribution (Benham 2006; Maldini
et al.
2012). In an example described by Pavez
et al.
(2015), South American sea lions (
Otaria byronia
) visited by tourists exhibited an increase in the state of alertness and a decrease in maternal attendance and resting time on land, thereby potentially reducing population size. In another example, killer whales (
Orcinus orca
) that lost feeding opportunities due to boat traffic faced a substantial (18 percent) estimated decrease in energy intake (Williams
et al.
2006). Such disturbance effects can have population-level consequences. Increased disturbance rates have been associated with a decline in abundance of bottlenose dolphins (
Tursiops
sp.) (Bejder
et al.
2006; Lusseau
et al.
2006).

These examples illustrate direct effects on survival and reproductive success, but disturbances can also have indirect effects. When disturbed by

noise, animals may respond behaviorally (
e.g.,
escape response), as well as physiologically (
e.g.,
increased heart rate, hormonal response) (Harms
et al.
1997; Tempel and Gutierrez 2003). In the absence of an apparent behavioral response, an animal exposed to noise disturbance may still experience stress and direct energy away from fitness-enhancing activities such as feeding and mating. The energy expense and physiological effects could ultimately lead to reduced survival and reproduction (Gill and Sutherland 2000; Frid and Dill 2002). Changes in behavior from anthropogenic disturbance can also include latent agonistic interactions between individuals (Barton
et al.
1998). Chronic stress can lead to weakened reflexes, lowered learning responses (Welch and Welch 1970; van Polanen Petel
et al.
2006), compromised immune function, decreased body weight, and abnormal thyroid function (Selye 1979).

The type and extent of response may be influenced by intensity of the disturbance (Cevasco
et al.
2001), the extent of previous exposure to humans (Holcomb
et al.
2009), the type of disturbance (Andersen
et al.
2012), and the age and/or sex of the individuals (Shaughnessy
et al.
2008; Holcomb
et al.
2009). Despite the importance of understanding the effects of disturbance, few controlled experiments or field observations have been conducted on sea otters to address this topic.

Responses to Activities

The available studies of sea otter behavior suggest that sea otters may be more resistant to the effects of sound disturbance and other human activities than some other marine mammals. For example, at Soberanes Point, California, Riedman (1983) examined changes in the behavior, density, and distribution of southern sea otters that were exposed to recorded noises associated with oil and gas activity. The underwater sound sources were played at a level of 110 dB and a frequency range of 50 to 20,000 Hz and included production platform activity, drillship, helicopter, and semi-submersible sounds. Riedman (1983) also observed the sea otters during seismic airgun shots fired at decreasing distances from the nearshore environment (50, 20, 8, 3.8, 3, 1, and 0.5 nautical miles) at a firing rate of 4 shots per minute and a maximum air volume of 4,070 cubic inches (in
3
). Riedman (1983) observed no changes in the presence, density, or behavior of sea otters as a result of underwater sounds from recordings or airguns, even at the closest distance of 0.5 nautical miles (<1 km or 0.6 mi). However, otters did display slight reactions to airborne engine noise. Riedman (1983, 1984) also monitored the behavior of sea otters along the California coast while they were exposed to a single 100-in
3
airgun and a 4,089-in
3
airgun array. Sea otters did not respond noticeably to the single airgun, and no disturbance reactions were evident when the airgun array was as close as 0.9 km (0.6 mi).

Sea otters spend from 30 to 80 percent of their time each day at the surface of the water resting and grooming (Riedman 1983, 1984; Bodkin
et al.
2004; Wolt
et al.
2012). While at the surface, turbulence from wind and waves attenuate noise more quickly than in deeper water, reducing potential noise exposure (Greene and Richardson 1988; Richardson
et al.
1995). Additionally, turbulence at the water's surface limits the transference of sound from water to air. A sea otter with its head above water will be exposed to only a small fraction of the sound energy travelling through the water beneath it. Thus, the amount of total time spent at the surface may help limit sea otters' exposure during noise-generating operations.

Sea otters do not rely on sound to orient themselves, locate prey, or communicate underwater. Sea otters use sound for communication in air (especially mothers and pups; McShane
et al.
1995) and may avoid predators by monitoring underwater sound. Davis
et al.
(1987) documented sea otters retreating from simulated killer whale vocalizations. Otters are not known to vocalize underwater and do not echolocate; therefore, masking of communications by anthropogenic sound is less of a concern than for other marine mammals.

Sea otters generally show a high degree of tolerance to noise. In another study using prerecorded sounds, Davis
et al.
(1988) exposed both northern sea otters in Simpson Bay, Alaska, and southern sea otters in Morro Bay, California, to a variety of airborne and underwater sounds, including a warble tone, sea otter pup calls, killer whale calls, airhorns, and an underwater noise harassment system designed to drive marine mammals away from crude oil spills. The sounds were projected at a variety of frequencies, decibel levels, and intervals. The authors noted that certain noises could cause a startle response and result in dispersal. However, the disturbance effects were limited in range (no responses were observed for otters approximately 100-200 m (328-656 ft) from the source of the stimuli), and habituation to the stimuli was generally very quick (within hours or, at most, 3 to 4 days).

Southern sea otters in an area with frequent railroad noise appeared to be relatively undisturbed by pile-driving activities, many showing no response and generally reacting more strongly to passing vessels than to the sounds of pile-driving equipment (ESNERR 2011; ESA 2016). Additionally, many of the otters who displayed a reaction behavior during pile driving did so while their heads were above the surface of the water, suggesting that airborne noise was as important as, and possibly more important than underwater noise in prompting the animals' reactions. When sea otters have displayed behavioral reactions in response to noise, these responses were often short-lived; the otters resumed normal activities soon after a new sound was introduced (Davis
et al.
1987, 1988).

Stimuli from shoreline construction activities, aircraft, and vessel traffic, including noise, are likely to cause some level of disturbance. Populations of sea otters in Alaska have been known to avoid areas with heavy boat traffic but return to those same areas during seasons with less traffic (Garshelis and Garshelis 1984). Sea otters in Alaska have shown signs of disturbance (escape behaviors) in response to the presence and approach of survey vessels, including: otters diving and/or actively swimming away from a boat; hauled-out otters entering the water; and groups of otters disbanding and swimming in multiple different directions (Udevitz
et al.
1995).

In Cook Inlet, otters were observed riding the tides past a new offshore drilling platform while drilling was being conducted. Otters drifting on a trajectory that would have taken them within 500 m (0.3 mi) of the rig tended to swim to change their angle of drift to avoid a close approach, although noise levels from the work were near the ambient level of underwater noise (BlueCrest 2013).

Sea otter behavior is suggestive of a dynamic response to disturbance, influenced by the intensity and duration of the source. Otters initially abandon areas when disturbed and return when the disturbance ceases. Groups of sea otters in two locations in California showed markedly different responses to kayakers approaching to within specific distances, suggesting a different level of tolerance between the groups (Gunvalson 2011). Benham (2006) found evidence that the otters exposed to high levels of recreational activity may have become more tolerant than individuals in less-disturbed areas.

Some individual otters will habituate to the presence of project vessels, noise, and activity. Sea otters often seem quite tolerant of boats or humans nearby (
e.g.,
Calkins 1979). Sea otters off the California coast showed only mild interest in boats passing within hundreds of meters and appeared to have habituated to boat traffic (Riedman 1983; Curland 1997). Boat traffic, commercial and recreational, is common in Cook Inlet. However, there are seasonal (
i.e.,
temporal) and spatial components to vessel traffic. Both recreational and commercial vessel traffic in Kachemak Bay is much higher than in western Cook Inlet, and all traffic is much higher in summer than in other months. Some sea otters in the area of activity are likely to have already become habituated to vessel traffic and noise caused by vessels, whereas for others, the specified activities will be a novel experience and will elicit a more intense response.

Some degree of disturbance is also possible from unmitigated aircraft activities. Individual sea otters in Cook Inlet will show a range of responses to noise from low-flying aircraft. Some may abandon the flightpath area and return when the disturbance has ceased. Based on the observed movement patterns of wild sea otters (
i.e.,
Lensink 1962; Kenyon 1969, 1981; Garshelis and Garshelis 1984; Riedman and Estes 1990; Tinker and Estes 1996; and others), we expect that some individuals, independent juveniles, for example, will respond to the project activities by dispersing to areas of suitable habitat nearby, while others, especially breeding-age adult males, will not be displaced by overflights. Mitigation measures will stipulate a minimum of 305 m (1,000 ft) flight altitude to minimize harassment of otters.

Given the observed responses of sea otters to sources of disturbance, it is likely that some degree of take by harassment will occur due to underwater noise stimuli associated with the specified activities. Some otters will likely show startle responses, change direction of travel, disperse from the area, or dive. Sea otters reacting to project activities may expend energy and divert time and attention from biologically important behaviors, such as feeding. Some effects may be undetectable in observations of behavior, especially the physiological effects of chronic and cumulative noise exposure. Air and vessel traffic, commercial and recreational, is routine in Cook Inlet. Construction activities are common. Some sea otters in the area of activity may become habituated to the project noise or may already be habituated to noise due to previous and ongoing exposure to frequent air traffic and other activities in the area and will have little, if any, reaction to project activities.

Mitigation and Monitoring

When the Service issues an ITR, we specify means for effecting the least practicable adverse impact on sea otters and their habitat, paying particular attention to habitat areas of significance, and on the availability of sea otters for taking for subsistence uses by coastal-dwelling Alaska Natives. These measures are stipulated in § 18.137 Mitigation.

In evaluating what mitigation measures are appropriate to ensure the least practicable adverse impact on species or stocks and their habitat, as well as subsistence uses, we considered the manner in which, and the degree to which, the successful implementation of the measures are expected to reduce impacts to sea otters, stocks, and their habitat, as well as subsistence uses. We considered the nature of the potential adverse impact being mitigated (likelihood, scope, range), the likelihood the measures will be effective, and the likelihood the measures will be implemented. We also considered the practicability of the measures for applicant implementation (
e.g.,
cost, impact on operations).

To reduce the potential for disturbance from noise associated with the activities, the following mitigation measures are required:

• Development of marine mammal monitoring and mitigation plans;

• Establishment of an exclusion zone (EZ) and safety zone (SZ) during noise-generating work;

• Visual mitigation monitoring by designated protected species observers (PSOs);

• Site clearance before startup;

• Shutdown procedures;

• Ramp-up procedures; and

• Vessel strike avoidance measures.

This ITR establishes the process for evaluating specific activities in specific project areas and determining the appropriate mitigation measures to be included in an LOA. A marine mammal mitigation and monitoring plan (4MP) is required for all LOAs. The 4MP identifies the specific avoidance and minimization measures an applicant will take to reduce effects to otters. It describes the project in detail, assesses the effects, identifies effective means to avoid effects, and describes specific methods for limiting effects when they cannot be avoided.

During “noise-generating work” (work that creates underwater sound louder than 160 dB and within the frequency hearing range of sea otters), an applicant will establish and monitor an EZ. The EZ is defined as the area surrounding a sound source in which all operations must be shut down in the event a sea otter enters or is about to enter this zone based on distances to Level A thresholds. Any otter detected within this zone will be exposed to sound levels likely to cause take by Level A harassment. The SZ is an area larger than the EZ and is defined as the area in which otters may experience noise above the Level B exposure threshold. Sea otters observed inside the SZ are likely to be disturbed by underwater noise, and each otter within the SZ will be counted as one Level B take. In the event a sea otter is in or about to enter the zone, operations will be powered down, when practicable, to minimize take. Radii of each SZ and EZ will be specified in each LOA issued under this ITR. The methodology for calculation of the radii will be described in each LOA and is identified in § 18.137 Mitigation. Sound source levels will be monitored and evaluated in the field prior to conducting 2D and 3D seismic surveys. This on-site sound source verification (SSV) testing will be used to determine the size of the SZ and EZ for these activities. A minimum 10-m (33-ft) shutdown zone will be observed for all in-water construction and heavy machinery.

PSOs will be stationed on the source vessel or at a suitable vantage point with maximum view of the SZ and EZ. The PSOs will determine that the EZ is clear of sea otters prior to the start of daily activities or if activities have been stopped for longer than a 30-minute period. The PSOs will ensure that no sea otters are observed in the EZ for a period of 30 minutes prior to work commencing.

For the 2D survey, PSOs will be stationed on the source vessel during all seismic operations and geohazard surveys when the sub-bottom profilers are used. Because of the proximity to land, PSOs may also be stationed on land to augment the viewing area. For the 3D survey, PSOs will be stationed on at least two of the project vessels: The source vessel and the chase vessel. For the vertical seismic profiling, PSOs will be stationed on the drilling rig. For geohazard surveys, PSOs will be stationed on the survey vessel. The viewing area may be augmented by placing PSOs on a vessel specifically for mitigation purposes or using an unmanned aircraft system (drone). If drones will be used in areas with sea

otters, mitigation measures will be required to ensure drone use does not disturb otters. These measures may include maintaining a minimum altitude and horizontal distance no less than 100 m away from otters, conducting continuous visual monitoring by PSOs, and ceasing activities in response to sea otter behaviors indicating any reaction to drones.

A power-down procedure will be in place during seismic work. It will provide the option of reducing the number of airguns in use, which reduces the EZ or SZ radius. Alternatively, a shutdown procedure may be necessary, during which all airgun activity is suspended immediately. During a power-down, a single airgun (“mitigation gun”) may be operated, maintaining a sound source with a much-reduced EZ. If a sea otter is detected outside of either the SZ or EZ but is likely to enter that zone, the airguns may be powered down before the animal is within the radius, as an alternative to a complete shutdown. Likewise, if a sea otter is already within the SZ when first detected, the airguns may be powered down if this is a reasonable alternative to an immediate shutdown. If a sea otter is already within the EZ when first detected, the airguns will be shut down immediately. All power-down events will be at the discretion of the operator in cooperation with the PSOs. The applicant has determined that it is not practicable to power down in response to all sea otters within the SZ, and that to do so would incapacitate the 2D and 3D seismic operations. Because power-down events will be discretionary, all otters within the SZ will be assumed to experience Level B take regardless of whether a power-down is conducted. Although there is no calculated reduction of take estimated for this mitigation measure due to uncertainty in its application, it is expected that some unquantified benefits to sea otters will be realized whenever the operator powers down to reduce or avoid sea otter noise exposures.

A shutdown will occur when all underwater sound generation that is louder than 160 dB and within the frequency hearing range of sea otters is suspended. The sound source will be shut down completely if a sea otter approaches the EZ or appears to be in distress due to the noise-generating work. The shutdown procedure will be accomplished as soon as practicable upon the determination that a sea otter is either in or about to enter the EZ, and generally within several seconds. Following a shutdown, noise-generating work will not resume until the sea otter has cleared the EZ. Any shutdown due to a sea otter sighting within the EZ must be followed by a 30-minute all-clear period and then a standard, full ramp-up. Any shutdown for other reasons resulting in the cessation of the sound source for a period greater than 30 minutes must also be followed by full ramp-up procedures.

A “ramp-up” procedure will be in place to gradually increase sound volume at a specified rate. Ramp-up is used at the start of airgun operations, including after a power-down, shutdown, or any period greater than 10 minutes in duration without airgun operations. The rate of ramp-up will be no more than 6 dB per 5-minute period. Ramp-up will begin with the smallest gun in the array that is being used for all airgun array configurations. The ramp-up procedure for pipe/pile driving involves initially starting with soft strikes or a reduced level of energy. If the complete EZ has not been visible for at least 30 minutes prior to the start of operations, operation of a mitigation gun may be required during the interruption of seismic survey operations prior to commencing ramp-up procedures. It will not be permissible to ramp up the full array from a complete shutdown in thick fog or at other times when the outer part of the Level A EZ is not visible. Ramp-up of the airguns will not be initiated if a sea otter is sighted within the EZ at any time.

A speed or course alteration is appropriate if a sea otter is detected outside the EZ and, based on its position and relative motion, is likely to enter the EZ, and a vessel's speed and/or direct course may, when practical and safe, be changed. This technique can be used in coordination with a power-down procedure. The sea otter activities and movements relative to the seismic and support vessels will be closely monitored to ensure that the sea otter does not approach within the EZ. If the sea otter appears likely to enter the EZ, further mitigative actions will be taken,
i.e.,
further course alterations, power-down, or shutdown of the airguns.

This ITR establishes the stakeholder engagement process that the applicant is required to undertake in order to obtain an LOA for incidental take of sea otters. This process is an ongoing collaborative process between the applicant, the Service, and subsistence users of sea otters. Stakeholder engagement efforts for the specified activities have been ongoing since mid-2018 and have indicated that a plan of cooperation (POC) is necessary for the Hilcorp and Harvest 3D seismic work. The POC must include a schedule for meeting with the affected communities, both prior to and while conducting the activities, a plan for resolving any conflicts, suggested means for resolving conflict, and process for notifying the communities of any changes in the operations.

The measures described here and required in § 18.137 through § 18.140, Mitigation, Monitoring, Reporting Requirements, and Measures to Reduce Impacts to Subsistence Users, are those determined to achieve the least practicable adverse impact to northern sea otters and their availability for subsistence use. These mitigation measures were evaluated against a suite of possible alternatives to determine whether they would effect the least practicable adverse impact on the species, their habitat, and the availability of the species for subsistence uses.

Alternative mitigation measures were evaluated but ultimately rejected as either not feasible, not practicable, not likely to be implemented effectively, or no more likely to be successful in reducing the impacts of the applicant's project. We considered requiring work to be paused or stopped to prevent exposure of northern sea otters to levels of noise exceeding a 160-dB Level B take threshold. The distances to the 160-dB sound isopleths for several of the specified activities are greater than 1 km (0.6 mi). Avoiding all northern sea otters within these distances would require work to shut down or power down for prolonged and repeated periods, which the applicant has determined would incapacitate the project. Therefore, this is not a practicable mitigation measure.

The Service considered alternative mitigation measures based on observing and interpreting northern sea otter behaviors for preventing Level B harassment. Presently, mitigation protocols use sound exposure to predict behavioral responses rather than observing behavior directly. While direct observation of injury or the disruption of a behavioral pattern is the definitive criteria for identifying take once it has occurred, at present there is insufficient data to develop observation-based criteria for preventing harassment. Thus, monitoring of behavioral responses is useful for identifying take after it occurs, but not for preventing or mitigating it. As such, effectiveness of monitoring protocols based on behavior cannot be ascertained. Therefore, behavior-based mitigation was not a feasible alternative.

We considered requiring the use of alternative technologies such as marine vibroseis to reduce or eliminate the

need for seismic airguns. Hilcorp and Harvest have requested takes of marine mammals incidental to the seismic survey operations described in the petition, which identified airgun arrays as the preferred data acquisition tool. It would be inappropriate for the Service to require the applicant to change the specified activity unless it was necessary to make the findings established for issuance of incidental take under the MMPA or necessary for achieving the least practicable adverse impact to the marine mammal stock. Currently, no alternative technology scaled for industrial use is reliable enough to meet the environmental challenges of operating in Cook Inlet. Many prototypes are currently in development and may ultimately become important for achieving the least practicable level of effect on marine mammals, but none of these technologies are currently practicable for use on a large scale in Cook Inlet.

The option of designating seasonal exclusion areas within the specified geographic area was considered. However, no activities are planned in areas of Cook Inlet known to provide important habitat. Kachemak Bay, Kamishak Bay, and the designated critical habitat along the western shoreline of LCI and MCI are known areas of important habitat, but have not been identified as the target location of any planned activity in this rule. There is some information that suggests that the east coast of Cook Inlet along the Kenai Peninsula may be used seasonally by sea otters in late summer (BlueCrest 2013). Restrictions on seismic survey operations in this area during this time period might reduce the probability of disturbance of sea otters. However, there is currently insufficient information to support a seasonal restriction in eastern Cook Inlet. Little is known about the extent or duration of the use of the area by sea otters or what life-history functions the area supports. The benefit such a designation might offer is entirely unknown and, until additional information is available, remains speculative.

Compensatory mitigation was considered. Some environmental laws allow compensatory mitigation, such as habitat restoration projects, to be used by the applicant to offset effects of the project activities that cannot otherwise be avoided. The Service is issuing an authorization for incidental take of sea otters under the MMPA. The MMPA requires that impacts be reduced to the least practicable level, but does not require offsets. The Service must consider the practicability of implementation of measures to reduce impacts, as well as proven or likely effectiveness of those measures. The impacts to sea otters and their habitat in Cook Inlet will be primarily acoustic and temporary in nature. We are not currently aware of literature demonstrating the effectiveness of habitat restoration for mitigating the effects of underwater noise. Additionally, we are not aware of any practicable habitat improvement projects in Cook Inlet that would have demonstrable benefits for the affected stocks.

In order to issue an LOA for an activity, section 101(a)(5)(A) of the MMPA states that the Service must set forth “requirements pertaining to the monitoring and reporting of such taking.” The Service's implementing regulations at § 18.27(d)(vii) stipulate that requests for authorizations must include the suggested means of accomplishing the necessary monitoring and reporting. Effective reporting is critical to compliance as well as ensuring that the most value is obtained from the required monitoring. The applicant will employ PSOs to conduct visual project monitoring. SSV monitoring will be conducted to document sound levels produced by the work. During 2D and 3D seismic surveys, Hilcorp and Harvest have agreed to conduct aerial overflights for avoidance of other marine mammal species, which will improve monitoring of sea otters. Additional monitoring and reporting requirements are at § 18.138 Monitoring and § 18.139 Reporting requirements.

Alternative monitoring measures were considered, but they were not incorporated in this rule. Passive acoustic monitoring is appropriate for some species of marine mammals but is not indicated for sea otters, which are not known to vocalize extensively underwater. Visual monitoring during all times of day and night was rejected because limited visibility during periods of darkness would prevent the detection of animals. Thermal monitoring or monitoring of sea otters with unmanned aircraft systems (drones) has not yet been fully tested and evaluated for use in Cook Inlet, but may prove useful in the future. Requiring visual observation and PSO monitoring of 100 percent of all spatial areas within the 160-dB ensonification area was also considered, but for 2D and 3D seismic surveys in particular, this was not expected to be achievable. We instead accounted for all sea otter exposures to 160 dB or greater in our estimation of take, and we did not reduce this number to attempt to account for some proportion of the total that might be avoided when detected by PSO monitoring.

Estimated Incidental Take

This section provides the number of incidental takes estimated to occur because of the planned activities. The number of takes were analyzed to make the required small numbers and negligible impact determinations.

Estimating Exposure Rates

The Service anticipates that incidental take of sea otters may occur during the project activities in Cook Inlet. Noise, aircraft, vessels, and human activities could temporarily interrupt feeding, resting, and movement patterns. Elevated underwater noise levels from seismic surveys may cause short-term, nonlethal, but biologically significant changes in behavior that the Service considers harassment. Pile-driving and other construction activities along the shoreline may have similar effects and could cause behavioral disturbance leading to take. Harassment (Level A or B) is the only type of take expected to result from these activities; no lethal take is expected.

The number of animals affected will be determined by the distribution of animals and their location in proximity to the project work. Although we cannot predict the outcome of each encounter, it is possible to consider the most likely reactions, given observed responses of sea otters to various stimuli.

Sound exposure criteria provide the best available proxy for estimation of exposure to harassment. The behavioral response of sea otters to shoreline construction and vessel activities is related to the distance between the activity and the animals. Underwater sound is generated in tandem with other airborne visual, olfactory, or auditory signals from the specified activities, and travels much farther. Therefore, estimating exposure to underwater sound can be used to estimate the take from project activities.

No separate exposure evaluation was done for activities that do not generate underwater sound. Nearly all of the planned activities that may disturb sea otters will occur simultaneously with in-water activities that do generate sound. For example, operation of heavy equipment along the shoreline will facilitate underwater pile driving. The otters affected by the equipment operations are the same as those affected by the pile driving. Sound exposure and behavioral disturbances are accumulated over a 24-hour period, resulting in estimation of one exposure from all in-water sources rather than one each from equipment operations

and pile-driving noise. Aircraft support activities will be conducted without a corresponding underwater sound component, but no take is expected from this source of disturbance; see “Airborne Sounds.”

To estimate the exposure of sea otters to take, we first calculated the number of otters in Cook Inlet that occur within the project area. The number of otters was calculated from density multiplied by project area. Density was estimated according to region in Cook Inlet.

Density data for Kamishak and the East side of Cook Inlet along the shore of the Kenai Peninsula was derived from aerial surveys conducted in May 2017 (Garlich-Miller
et al.
2018). Surveys were not conducted for central Cook Inlet in 2017, and the 2017 surveys for western Cook Inlet north of Kamishak did not yield useful results. Therefore, the density for those regions was derived from the 2002 surveys conducted by Bodkin
et al.
(2003) and corrected for population growth proportional to the growth rate of Cook Inlet as a whole, as determined from comparison of the 2002 and 2017 surveys. Density values (in otters per km
2
) were 1.7 in East Cook Inlet (excluding Kachemak Bay and the outer Coast of Kenai Peninsula south and east of Seldovia), 3.53 in Kamishak Bay, and 0.026 in West and Central Cook Inlet. There are no density data for sea otters in the MCI region north of approximately 60°14′ N (the latitude of Clam Gulch), and otters are uncommon north of about 60°24′ N. Therefore, densities north of Clam Gulch were conservatively assumed to equal the 2002 mid-Cook Inlet survey region density of 0.01 per km
2
from Bodkin
et al.
(2003).

The geographic area of activity covers approximately 11,084 km
2
(4,280 mi
2
) in Cook Inlet. Of this area, 1,572 km
2
(607 mi
2
) is in East Cook Inlet, 725 km
2
(280 mi
2
) in Kamishak Bay, 4,341 km
2
(1,676 mi
2
) in West and Central Cook Inlet, and 4,445 km
2
(1,716 mi
2
) in Cook Inlet north of the normal range of sea otters. The total number of otters within the project area was calculated to be 5,389 otters ((1,572 × 1.7) + (725 × 3.53) + (4,341 × 0.026) + (4,445 × 0.01) ≉ 5,389).

Not all otters in the project area will be exposed to noise levels capable of causing take from project activities. Many activities associated with oil and gas exploration, development, production, and transportation may result in underwater sounds that do not meet Levels A and B acoustic harassment criteria. The acoustic characteristics of the different project activities are described in table 3. Only those specific activities with the likelihood of meeting the acoustic exposure criteria and occurring in the normal range of sea otters were evaluated for estimation of potential Levels A and B harassment. Specifically, Hilcorp and Harvest's activities include 2D and 3D seismic surveys, vibratory driving of sheet piles at the Iniskin Peninsula causeway in Chinitna Bay, sub-bottom profilers used in high- and low-resolution geohazard surveys, drive-pipe installation, vertical seismic profiling, plug-and-abandon activities, and use of water jets during routine maintenance. AGDC's activities include pile driving and anchor handling.

The number of exposures to underwater sound levels capable of causing take by Level A harassment from specific project elements was estimated using the thresholds recommended by NMFS (2018a,b) for otariid pinnipeds (232 dB peak and 203 dB SEL
cum
). For Level B harassment we used a 160-dB threshold. We multiplied the estimated area of ensonification (km
2
), by the density of sea otters in that area (number (#) of otters per km
2
) to estimate the number of otters in the ensonified area. This value was then multiplied by the maximum duration of the activity (# of days) over the course of the 5-year regulatory period to get the total number of exposures to sound above the thresholds for take.

Predicting Behavioral Response Rates

Although we cannot predict the outcome of each encounter between a sea otter and the equipment and vessels used for the planned activities, it is possible to consider the most likely reactions. Sea otters do not appear highly reactive to underwater sounds, but the presence of vessels may elicit stronger behavioral responses (see
Responses to Activities
). Whether an individual animal responds behaviorally to the presence of vessels and equipment is dependent upon several variables, including the activity of the animal prior to stimulus, whether the animal is habituated to similar disturbances, whether the animal is in a state of heightened awareness due to recent disturbances or the presence of predators, group size, the presence of pups, and the temperament of the individual animals. We assumed all animals exposed to underwater sound levels that meet the acoustic exposure criteria shown in table 5 would experience Level A or Level B take.

Calculating Take

The total take of sea otters from these oil and gas activities in Cook Inlet was estimated by calculating the number of otters in the ensonified area during the full duration (the maximum number of days) of each project activity. After publication of the proposed ITR in the
Federal Register
, the applicant provided updates and minor modifications to their project plans. Changes included an increase in the 3D seismic survey line length from 74 km (46 mi) to 127 km (79 mi), an adjustment to account for the proportion of line length actively surveyed with the airgun array each day, use of a boomer rather than chirper sub-bottom profiler, and changes to the total duration (number of days) of pile driving and vertical seismic profiling in TB and LCI. The changes are reflected in the analysis presented here. Details of the project activities and calculations of take are included in the applicant's updated petition (June 2019) available at
www.regulations.gov
under docket number FWS-R7-ES-2019-0012. Methods used for calculating take did not change, but the resulting estimates have been updated. The total take increased from 1,666 to 1,687.

Distances to Thresholds

To calculate the ensonified area, we first estimated the distances that underwater sound will travel before attenuating to levels below thresholds for take by Level A and Level B harassment. The distances to the Level A thresholds were calculated using the NMFS Acoustical Guidance Spreadsheets (NMFS 2018b) using thresholds for otariid pinnipeds as a proxy for sea otters. Distances to the 160-dB Level B threshold were calculated using a practical spreading transmission loss model (15 LogR). The only exceptions to the use of the practical spreading model were made when data was available from a site-specific sound source verification of substantially similar equipment used and powered in a similar manner to that proposed by the applicant.

Model estimates incorporated operational and environmental parameters for each activity. For example, sound levels at the source are shown in table 3, and characteristics of the sound produced are shown in table 6. Weighting factor adjustments were used for SEL (sound exposure level) calculations based on NMFS Technical Guidance (2018b). Operational parameters were estimated from the updated description of activities.

The distances to the modelled Level A and Level B thresholds are shown in table 7. Each estimate represents the radial distance away from the sound source within which a sea otter exposed to the sound of the activity is expected

to experience take by Level A or Level B harassment.

Table 6—Assumptions Used in Calculating Distances to Level A and Level B Thresholds

Activity
Type of source

Source level
1

WFA
2

Source
velocity

Pulse
duration

Repetition rate
Duration per day

2D/3D seismic
Mobile impulsive

217 @100 m (185 dB
SEL
@100 m)

1 kHz
2.05 m/s
N/A
every 6 s

3D: 10 hrs/day.
2D: 2 hrs/day.

Sub bottom profiler
Mobile impulsive
212 @1 m
4 kHz
2.05 m/s
0.02 s
every 0.30 s
N/A.

Impact pile driving
Stationary impulsive
≤195 @10 m
2 kHz
N/A
N/A
1,560 strikes/hr
≤5.5 hrs/day.

Pipe driving
Stationary impulsive
≤195 @55 m
2 kHz
N/A
0.02 s
≤1,560 strikes/hr
≤4.8 hrs/day.

Vertical seismic profiling
Stationary impulsive
227 @1 m
1 kHz
N/A
0.02 s
every 6 s
4 hrs/day.

Impact sheet piling
Stationary impulsive
190 @10 m
2 kHz
N/A
0.02 s
1,560 strikes/hr
3 hrs/day.

Vibratory sheet piling
Stationary non-impulsive
160 @10 m
2.5 kHz
N/A
N/A
N/A
≤4.8.

Water jet
Stationary non-impulsive
176 @1 m
2 kHz
N/A
N/A
N/A
0.5 hrs/day.

Anchor handling
Mobile non-impulsive
179 @1 m
1.5 kHz
1.54 m/s
N/A
N/A
3 hrs/day.

1
Source level is given in dBrms, unless otherwise indicated, as measured at the given distance from the source in meters.

WFA = Weighting Factor Adjustment, SEL = sound exposure level.

Table 7—Calculated Distance in Meters
(m)
to Level A and Level B Thresholds

Activity
Level A—NMFS otariid
Impulsive
232 dB peak
203 dB SEL
Non-impulsive
219 dB SEL
Level B
Both
160 dB rms

2D/3D seismic
10
1.32
N/A
7,330

Sub-bottom profiler
0.05
1
N/A
2,929

Pipe driving, Chinitna Bay
0.19
39.48
N/A
1,630

VSP
0.46
284.84
N/A
2,470

Vibratory sheet pile driving
N/A
N/A
0.46
10

Water jet
N/A
N/A
0.54
11.66

18- and 24-inch pipe, impact
0.22
50.53
N/A
1,874.85

48- and 60-inch pipe, impact
0.34
147.99
N/A
2,154.43

all sizes pipe, vibratory
N/A
N/A
3.30
46.42

Sheet pile, impact
0.16
68.69
NA
1,000

Sheet pile, vibratory
N/A
N/A
0.71
10

Anchor handling
N/A
N/A
0.00
0.00

SEL = sound exposure level.

Area and Duration

The area of ensonification is the area in which an animal exposed to underwater sound is expected to experience take from Level A or Level B harassment based on the distance to the Level A and Level B thresholds. The area of a circle (A = πr
2
) where r is the distance to the Level A or Level B threshold was used to calculate the area of ensonification for impulsive stationary sources (pipe driving, vertical seismic profiling), non-impulsive stationary sources (water jets, vibratory pile driving). For impulsive mobile sources (2D/3D seismic, sub-bottom profiler), the radial area was then multiplied by the distance of the line to be surveyed each day to get the total area of ensonification. Otters spend most of their time at the water's surface or below their last surface location, so a circle with the sound source at its center is a reasonable representation of the ensonified area. For shoreline activities, the area of the circle is divided by two to remove the area that lies above the shoreline. The daily area of ensonification was then multiplied by the duration of the activity in number of days and the density of otters in the applicable region of Cook Inlet to estimate the number of otters that might be taken. In total, 1,687 instances of take are expected. The total Level A take of sea otters in Cook Inlet over the 5-year course of this ITR is anticipated to be 3. The total number of takes from each project activity is presented in table 8.

For some projects, like the 3D seismic survey, the design of the project is well developed; therefore, the duration is well defined. However, for other projects, the duration is not well developed, such as activities around the LCI well sites. In each case, the calculations are based on the applicant's best forecast of activities in the 5-year ITR period. The assumptions regarding duration of these activities are presented in the applicant's updated petition (June 2019). The durations used for each activity are provided in table 8. For Level B take, we assumed one take per otter per day regardless of duration of work within a day. The resulting estimate of the total number of Level B takes expected from planned oil and gas activities in Cook Inlet from 2019 through the date 5 years from the effective date of the final rule is 1,684.

The proposed ITR included calculation of the numbers of individual otters taken. Those estimates have been removed from this ITR because the methodology used to calculate take of individuals led to substantial uncertainty in the accuracy of the estimates. We here rely instead on the number of takes to determine the likely effects to the stock. The total number of takes is expected to be higher than the number of otters taken because, for example, a resident otter may be taken on each day of noise-generating activity.

Table 8—Estimate of Total Take for Each Activity

Applicant
Activity

Density

(#/km
2
)

Duration
(days)

Level A
Impulsive
232 pk
203 SEL
Non-impulsive
219 SEL
Level B

160 rms

Hilcorp/Harvest Alaska
2D seismic
1.705
10.000
1.023
0.135

749.859

3D seismic
0.026
60
1.155
0.152

846.896

Vibratory sheet pile driving
0.026
20

0.000
0.000

Sub-bottom profiler-LCI
0.026
28
0.001
0.014

46.291

Sub-bottom profiler-NCI
0.010
7
0.000
0.001

4.740

Sub-bottom profiler-TB
0.010
14
0.000
0.003

9.479

Sub-bottom profiler-MCI
0.010
3
0.000
0.000

2.031

Pipe driving-LCI
0.026
12
0.000
0.002

2.604

Pipe driving-TB
0.010
6
0.000
0.000

0.501

VSP-LCI
0.026
8
0.000
0.040

3.987

VSP-TB
0.010
4
0.000
0.008

0.767

AGDC
Product Loading Facility
0.010

48-inch impact

56
0.000
0.019

4.083

60-inch impact
0.010
106
0.000
0.036

7.728

Temporary MOF
0.010

18- and 24-inch vibratory

301

0.000
0.010

18- and 24-inch impact
0.010
7
0.000
0.000

0.510

48-inch impact
0.010
7
0.000
0.002

0.510

60-inch vibratory
0.010
11

0.000
0.000

sheet vibratory
0.010
66

0.000
0.000

Mainline MOF
0.010

sheet vibratory

7

0.000
0.000

sheet impact
0.010
7
0.000
0.001

0.110

Anchor handling
0.010
76

0.000
0.000

Total

2.18
0.42
0.00
1,683.108

SEL = sound exposure level, LCI = Lower Cook Inlet, MCI = Middle Cook Inlet, NCI = North Cook Inlet, TB = Trading Bay, MOF = material offloading facility, VSP = vertical seismic profiling.

The number of takes from each stock was estimated by categorizing each activity by its location relative to sea otter stock boundaries. Some activities will occur within both the southcentral Alaska and southwest Alaska stock boundaries. For these, take was assigned in proportion to the area of the activity within each stock region. Table 9 shows the activities in relation to the sea otter stock boundaries as they were assigned for this analysis. The total number of takes of sea otters from the southwest Alaska stock is 418. The take number from the southcentral Alaska stock is 1,269.

The total number of takes by Level A harassment is estimated to be 2.6. When the total take from each activity (table 8) is multiplied by the proportion of that activity occurring within each stock boundary (table 9), the sum of take is 0.6 and 2 within the southwest Alaska and southcentral Alaska stocks, respectively. Because the number of takes from the southwest Alaska stock is 0.6, and take cannot occur unless it affects an animal, we rounded the number of takes from the southwest Alaska stock from 0.6 to 1. The total take is summarized in table 10.

Table 9—Percent of Each Activity Occurring Within Each Stock Boundary

Applicant
Activity

Southwest
Alaska
stock
(%)

Southcentral
Alaska
stock
(%)

Hilcorp & Harvest Alaska
2D seismic

100

3D seismic
44
56

Vibratory sheet pile driving
100

Sub-bottom profiler—LCI
44
56

Sub-bottom profiler—NCI
100

Sub-bottom profiler—TB
100

Sub-bottom profiler—MCI
100

Pipe driving—LCI
50
50

Pipe driving—TB
100

VSP—LCI
50
50

VSP—TB
100

Hydraulic grinder
100

Water jet
100

AGDC

Product Loading Facility

48-inch impact

100

60-inch impact

100

Temporary MOF:

18-inch vibratory

100

24-inch impact

100

48-inch impact

100

60-inch vibratory

100

sheet vibratory

100

Mainline MOF:

sheet vibratory

100

sheet impact

100

Anchor handling
50
50

LCI = Lower Cook Inlet, MCI = Middle Cook Inlet, NCI = North Cook Inlet, TB = Trading Bay, MOF = material offloading facility.

Table 10—Summary of Estimates of Sea Otter Take by Level A and Level B Harassment and Stock

Type
Unit of take

Southwest
Alaska stock

Southcentral
Alaska stock

Sum

Level A
Number of takes
1
2
3

Level B
Number of takes
417
1,267
1,684

Total
Number of takes
418
1,269
1,687

Annual Estimates of Take

The estimates of exposures by activity and location discussed in the previous section are not representative of the estimated exposures per year (
i.e.,
annual takes). It is difficult to characterize each year accurately because many of the activities are progressive (
i.e.,
they depend on results and/or completion of the previous activity). This results in much uncertainty in the timing, duration, and complete scope of work. Each year, each applicant will submit an application for an LOA with the specific details of the planned work for that year and estimated take numbers. Table 11 summarizes the activities according to a scenario presented in the applicant's updated petition (June 2019). This scenario combines the most realistic progression by Hilcorp and Harvest with an optimistic scenario for AGDC. In the first season, Hilcorp and Harvest plan to conduct 3D seismic surveys. In the second season, in LCI they plan to conduct activities for one well; in MCI, they plan to conduct plugging and abandonment activities in the NCI and two wells in the TB area. In the third season, activities include drilling two wells in LCI. The final well in LCI is planned for the fourth season.

The timing of AGDC's activities will depend on final authorizations and funding and may begin in 2020 rather than 2019. Season 1 will be the first year of project work regardless of year, followed by season 2 during the second year, etc. Work will generally occur from April through October. Material offloading facilities will be constructed in the first and second season, and a product loading facility will be installed during seasons 2, 3, and 4. Installation of the gas pipeline is planned for seasons 3 and 4 as well.

The number of sea otters takes by year was then estimated by allocating the total expected take by proportion of each project component occurring in each year. For example, the 2D seismic surveys are planned for year 3, so all takes during 2D seismic surveys were assigned to year 3. The resulting estimates of total Level B take by year are shown in table 12.

Table 11—Noise-Generating Activities by Year. Activities Are Those With Source Levels Above 160
dB rms
Within Frequencies Heard by Sea Otters

Year
Applicant
Activity
Area

2019: Season 1
Hilcorp/Harvest
3D seismic
LCI

NCI geohazard surveys
LCI

Pipeline maintenance (geohazard, water jet)
MCI

2020: Season 2
Hilcorp/Harvest
2D seismic
LCI

Drilling activities (geohazard, pipe driving, VSP) at 1 well
LCI

Drilling activities (geohazard, pipe driving, VSP) at 2 wells in TB
MCI

Plug and abandon activities (geohazard) at 1 well in the NCI
MCI

Pipeline maintenance (geohazard, water jet)
MCI

AGDC
Sheet pile driving at TMOF
MCI

2021: Season 3
Hilcorp/Harvest
Drilling activities (geohazard, pipe driving, VSP) at 2 wells
LCI

Sheet pile driving in Chinitna Bay
LCI

AGDC
Pipeline maintenance (geohazard, water jet)
MCI

Sheet pile driving at MMOF
MCI

Sheet pile driving at MMOF
MCI

2022: Season 4
Hilcorp/Harvest
Drilling activities (tugs, geohazard, pipe driving, VSP) at 1 well
LCI

AGDC
Pipeline maintenance (geohazard, water jet)
MCI

Impact pile driving at PLF: 80 48-inch piles, 63 60-inch piles
LCI

Anchor handling for pipeline installation
MCI

2023-2024: Season 5
Hilcorp/Harvest
Pipeline maintenance (geohazard, water jet)
MCI

AGDC
Impact pile driving at PLF: 40 48-inch piles, 80 60-inch piles
LCI

Impact pile driving at PLF: 10 48-inch piles, 48 60-inch piles
LCI

Anchor handling for pipeline installation
MCI

LCI = Lower Cook Inlet, MCI = Middle Cook Inlet, NCI = North Cook Inlet, TB = Trading Bay, PLF = product loading facility, TMOF = temporary material offloading facility, MMOF = mainline material offloading facility, VSP = vertical seismic profiling.

Table 12—Estimates of Total Number of Takes by Level B Harassment by Year (or Project Season)

Take

Year
(Project season)

2019
(Season 1)

2020
(Season 2)

2021
(Season 3)

2022
(Season 4)

2023
(Season 5)

Takes by year (season)
877
800
2
3
2

% takes by year (season)
52%
48%
0%
0%
0%

Critical Assumptions

In order to conduct this analysis and estimate the potential amount of take, several critical assumptions were made. Here we discuss these assumptions, the potential sources of bias or error inherent in them, and their effects on the analysis. Take by harassment is equated herein with exposure to noise meeting or exceeding the specified criteria. We assume all otters exposed to these noise levels will exhibit behavioral responses that indicate harassment or disturbance. There are likely to be a proportion of animals that respond in ways that indicate some level of disturbance but do not experience significant biological consequences. A correction factor was not applied. This may result in overestimation in take calculations from exposure to underwater noise, while our separate assumption that sea otters exposed to noise in the air but not in the water do not independently experience harassment may result in underestimation of take. The net effect is unknown.

Our estimates do not account for variable responses by age and sex. Females with dependent pups and with pups that have recently weaned are physiologically the most sensitive (Thometz
et al.
2014) and most likely to experience take from disturbance. There is not enough information on composition of the Cook Inlet sea otter population in the applicant's project area to incorporate individual variability based on age and sex or to predict its influence on take estimates. We therefore assume the response rates are uniform throughout the population. The degree of over- or under-estimation of take is unknown.

The estimates of behavioral response presented here do not account for the individual movements of animals away from the project area due to avoidance or habituation. Our assessment of density does not change. There is not enough information about the movement of sea otters in response to specific disturbances to refine these assumptions. While otters do have res

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Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2019-16279. Public record. Not legal advice.